1 . /////////////////////////////////////////////////////////////////////////////
2 . This is the primary source of the Exim Manual. It is an xfpt document that is
3 . converted into DocBook XML for subsequent conversion into printable and online
4 . formats. The markup used herein is "standard" xfpt markup, with some extras.
5 . The markup is summarized in a file called Markup.txt.
7 . WARNING: When you use the .new macro, make sure it appears *before* any
8 . adjacent index items; otherwise you get an empty "paragraph" which causes
9 . unwanted vertical space.
10 . /////////////////////////////////////////////////////////////////////////////
15 . /////////////////////////////////////////////////////////////////////////////
16 . This outputs the standard DocBook boilerplate.
17 . /////////////////////////////////////////////////////////////////////////////
21 . /////////////////////////////////////////////////////////////////////////////
22 . These lines are processing instructions for the Simple DocBook Processor that
23 . Philip Hazel has developed as a less cumbersome way of making PostScript and
24 . PDFs than using xmlto and fop. They will be ignored by all other XML
26 . /////////////////////////////////////////////////////////////////////////////
30 foot_right_recto="&chaptertitle; (&chapternumber;)"
31 foot_right_verso="&chaptertitle; (&chapternumber;)"
32 toc_chapter_blanks="yes,yes"
33 table_warn_overflow="overprint"
37 . /////////////////////////////////////////////////////////////////////////////
38 . This generates the outermost <book> element that wraps the entire document.
39 . /////////////////////////////////////////////////////////////////////////////
43 . /////////////////////////////////////////////////////////////////////////////
44 . These definitions set some parameters and save some typing.
45 . Update the Copyright year (only) when changing content.
46 . /////////////////////////////////////////////////////////////////////////////
48 .set previousversion "4.91"
49 .include ./local_params
51 .set ACL "access control lists (ACLs)"
52 .set I " "
58 . /////////////////////////////////////////////////////////////////////////////
59 . Additional xfpt markup used by this document, over and above the default
60 . provided in the xfpt library.
61 . /////////////////////////////////////////////////////////////////////////////
63 . --- Override the &$ flag to automatically insert a $ with the variable name.
65 .flag &$ $& "<varname>$" "</varname>"
67 . --- Short flags for daggers in option headings. They will always be inside
68 . --- an italic string, but we want the daggers to be in Roman.
70 .flag &!! "</emphasis>†<emphasis>"
71 .flag &!? "</emphasis>‡<emphasis>"
73 . --- A macro for an Exim option definition heading, generating a one-line
74 . --- table with four columns. For cases when the option name is given with
75 . --- a space, so that it can be split, a fifth argument is used for the
85 .itable all 0 0 4 8* left 6* center 6* center 6* right
86 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
90 . --- A macro for the common 2-column tables. The width of the first column
91 . --- is suitable for the many tables at the start of the main options chapter;
92 . --- a small number of other 2-column tables override it.
94 .macro table2 196pt 254pt
95 .itable none 0 0 2 $1 left $2 left
98 . --- A macro that generates .row, but puts &I; at the start of the first
99 . --- argument, thus indenting it. Assume a minimum of two arguments, and
100 . --- allow up to four arguments, which is as many as we'll ever need.
104 .row "&I;$1" "$2" "$3" "$4"
108 .row "&I;$1" "$2" "$3"
116 . --- Macros for option, variable, and concept index entries. For a "range"
117 . --- style of entry, use .scindex for the start and .ecindex for the end. The
118 . --- first argument of .scindex and the only argument of .ecindex must be the
119 . --- ID that ties them together.
122 &<indexterm role="concept">&
123 &<primary>&$1&</primary>&
125 &<secondary>&$2&</secondary>&
131 &<indexterm role="concept" id="$1" class="startofrange">&
132 &<primary>&$2&</primary>&
134 &<secondary>&$3&</secondary>&
140 &<indexterm role="concept" startref="$1" class="endofrange"/>&
144 &<indexterm role="option">&
145 &<primary>&$1&</primary>&
147 &<secondary>&$2&</secondary>&
153 &<indexterm role="variable">&
154 &<primary>&$1&</primary>&
156 &<secondary>&$2&</secondary>&
162 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
164 . ////////////////////////////////////////////////////////////////////////////
167 . ////////////////////////////////////////////////////////////////////////////
168 . The <bookinfo> element is removed from the XML before processing for ASCII
170 . ////////////////////////////////////////////////////////////////////////////
174 <title>Specification of the Exim Mail Transfer Agent</title>
175 <titleabbrev>The Exim MTA</titleabbrev>
179 <author><firstname>Exim</firstname><surname>Maintainers</surname></author>
180 <authorinitials>EM</authorinitials>
181 <revhistory><revision>
183 <authorinitials>EM</authorinitials>
184 </revision></revhistory>
187 </year><holder>University of Cambridge</holder></copyright>
192 . /////////////////////////////////////////////////////////////////////////////
193 . This chunk of literal XML implements index entries of the form "x, see y" and
194 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
195 . at the top level, so we have to put the .chapter directive first.
196 . /////////////////////////////////////////////////////////////////////////////
198 .chapter "Introduction" "CHID1"
201 <indexterm role="variable">
202 <primary>$1, $2, etc.</primary>
203 <see><emphasis>numerical variables</emphasis></see>
205 <indexterm role="concept">
206 <primary>address</primary>
207 <secondary>rewriting</secondary>
208 <see><emphasis>rewriting</emphasis></see>
210 <indexterm role="concept">
211 <primary>Bounce Address Tag Validation</primary>
212 <see><emphasis>BATV</emphasis></see>
214 <indexterm role="concept">
215 <primary>Client SMTP Authorization</primary>
216 <see><emphasis>CSA</emphasis></see>
218 <indexterm role="concept">
219 <primary>CR character</primary>
220 <see><emphasis>carriage return</emphasis></see>
222 <indexterm role="concept">
223 <primary>CRL</primary>
224 <see><emphasis>certificate revocation list</emphasis></see>
226 <indexterm role="concept">
227 <primary>delivery</primary>
228 <secondary>failure report</secondary>
229 <see><emphasis>bounce message</emphasis></see>
231 <indexterm role="concept">
232 <primary>dialup</primary>
233 <see><emphasis>intermittently connected hosts</emphasis></see>
235 <indexterm role="concept">
236 <primary>exiscan</primary>
237 <see><emphasis>content scanning</emphasis></see>
239 <indexterm role="concept">
240 <primary>failover</primary>
241 <see><emphasis>fallback</emphasis></see>
243 <indexterm role="concept">
244 <primary>fallover</primary>
245 <see><emphasis>fallback</emphasis></see>
247 <indexterm role="concept">
248 <primary>filter</primary>
249 <secondary>Sieve</secondary>
250 <see><emphasis>Sieve filter</emphasis></see>
252 <indexterm role="concept">
253 <primary>ident</primary>
254 <see><emphasis>RFC 1413</emphasis></see>
256 <indexterm role="concept">
257 <primary>LF character</primary>
258 <see><emphasis>linefeed</emphasis></see>
260 <indexterm role="concept">
261 <primary>maximum</primary>
262 <seealso><emphasis>limit</emphasis></seealso>
264 <indexterm role="concept">
265 <primary>monitor</primary>
266 <see><emphasis>Exim monitor</emphasis></see>
268 <indexterm role="concept">
269 <primary>no_<emphasis>xxx</emphasis></primary>
270 <see>entry for xxx</see>
272 <indexterm role="concept">
273 <primary>NUL</primary>
274 <see><emphasis>binary zero</emphasis></see>
276 <indexterm role="concept">
277 <primary>passwd file</primary>
278 <see><emphasis>/etc/passwd</emphasis></see>
280 <indexterm role="concept">
281 <primary>process id</primary>
282 <see><emphasis>pid</emphasis></see>
284 <indexterm role="concept">
285 <primary>RBL</primary>
286 <see><emphasis>DNS list</emphasis></see>
288 <indexterm role="concept">
289 <primary>redirection</primary>
290 <see><emphasis>address redirection</emphasis></see>
292 <indexterm role="concept">
293 <primary>return path</primary>
294 <seealso><emphasis>envelope sender</emphasis></seealso>
296 <indexterm role="concept">
297 <primary>scanning</primary>
298 <see><emphasis>content scanning</emphasis></see>
300 <indexterm role="concept">
301 <primary>SSL</primary>
302 <see><emphasis>TLS</emphasis></see>
304 <indexterm role="concept">
305 <primary>string</primary>
306 <secondary>expansion</secondary>
307 <see><emphasis>expansion</emphasis></see>
309 <indexterm role="concept">
310 <primary>top bit</primary>
311 <see><emphasis>8-bit characters</emphasis></see>
313 <indexterm role="concept">
314 <primary>variables</primary>
315 <see><emphasis>expansion, variables</emphasis></see>
317 <indexterm role="concept">
318 <primary>zero, binary</primary>
319 <see><emphasis>binary zero</emphasis></see>
325 . /////////////////////////////////////////////////////////////////////////////
326 . This is the real start of the first chapter. See the comment above as to why
327 . we can't have the .chapter line here.
328 . chapter "Introduction"
329 . /////////////////////////////////////////////////////////////////////////////
331 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
332 Unix-like operating systems. It was designed on the assumption that it would be
333 run on hosts that are permanently connected to the Internet. However, it can be
334 used on intermittently connected hosts with suitable configuration adjustments.
336 Configuration files currently exist for the following operating systems: AIX,
337 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
338 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
339 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
340 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and UnixWare.
341 Some of these operating systems are no longer current and cannot easily be
342 tested, so the configuration files may no longer work in practice.
344 There are also configuration files for compiling Exim in the Cygwin environment
345 that can be installed on systems running Windows. However, this document does
346 not contain any information about running Exim in the Cygwin environment.
348 The terms and conditions for the use and distribution of Exim are contained in
349 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
350 Public Licence, a copy of which may be found in the file &_LICENCE_&.
352 The use, supply, or promotion of Exim for the purpose of sending bulk,
353 unsolicited electronic mail is incompatible with the basic aims of Exim,
354 which revolve around the free provision of a service that enhances the quality
355 of personal communications. The author of Exim regards indiscriminate
356 mass-mailing as an antisocial, irresponsible abuse of the Internet.
358 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
359 experience of running and working on the Smail 3 code, I could never have
360 contemplated starting to write a new MTA. Many of the ideas and user interfaces
361 were originally taken from Smail 3, though the actual code of Exim is entirely
362 new, and has developed far beyond the initial concept.
364 Many people, both in Cambridge and around the world, have contributed to the
365 development and the testing of Exim, and to porting it to various operating
366 systems. I am grateful to them all. The distribution now contains a file called
367 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
371 .section "Exim documentation" "SECID1"
372 . Keep this example change bar when updating the documentation!
375 .cindex "documentation"
376 This edition of the Exim specification applies to version &version() of Exim.
377 Substantive changes from the &previousversion; edition are marked in some
378 renditions of this document; this paragraph is so marked if the rendition is
379 capable of showing a change indicator.
382 This document is very much a reference manual; it is not a tutorial. The reader
383 is expected to have some familiarity with the SMTP mail transfer protocol and
384 with general Unix system administration. Although there are some discussions
385 and examples in places, the information is mostly organized in a way that makes
386 it easy to look up, rather than in a natural order for sequential reading.
387 Furthermore, this manual aims to cover every aspect of Exim in detail, including
388 a number of rarely-used, special-purpose features that are unlikely to be of
391 .cindex "books about Exim"
392 An &"easier"& discussion of Exim which provides more in-depth explanatory,
393 introductory, and tutorial material can be found in a book entitled &'The Exim
394 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
395 (&url(https://www.uit.co.uk/exim-book/)).
397 The book also contains a chapter that gives a general introduction to SMTP and
398 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
399 with the latest release of Exim. (Note that the earlier book about Exim,
400 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
402 .cindex "Debian" "information sources"
403 If you are using a Debian distribution of Exim, you will find information about
404 Debian-specific features in the file
405 &_/usr/share/doc/exim4-base/README.Debian_&.
406 The command &(man update-exim.conf)& is another source of Debian-specific
409 .cindex "&_doc/NewStuff_&"
410 .cindex "&_doc/ChangeLog_&"
412 As Exim develops, there may be features in newer versions that have not
413 yet made it into this document, which is updated only when the most significant
414 digit of the fractional part of the version number changes. Specifications of
415 new features that are not yet in this manual are placed in the file
416 &_doc/NewStuff_& in the Exim distribution.
418 Some features may be classified as &"experimental"&. These may change
419 incompatibly while they are developing, or even be withdrawn. For this reason,
420 they are not documented in this manual. Information about experimental features
421 can be found in the file &_doc/experimental.txt_&.
423 All changes to Exim (whether new features, bug fixes, or other kinds of
424 change) are noted briefly in the file called &_doc/ChangeLog_&.
426 .cindex "&_doc/spec.txt_&"
427 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
428 that it can easily be searched with a text editor. Other files in the &_doc_&
432 .row &_OptionLists.txt_& "list of all options in alphabetical order"
433 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
434 .row &_exim.8_& "a man page of Exim's command line options"
435 .row &_experimental.txt_& "documentation of experimental features"
436 .row &_filter.txt_& "specification of the filter language"
437 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
438 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
439 .row &_openssl.txt_& "installing a current OpenSSL release"
442 The main specification and the specification of the filtering language are also
443 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
444 &<<SECTavail>>& below tells you how to get hold of these.
448 .section "FTP site and websites" "SECID2"
451 The primary site for Exim source distributions is the &%exim.org%& FTP site,
452 available over HTTPS, HTTP and FTP. These services, and the &%exim.org%&
453 website, are hosted at the University of Cambridge.
457 As well as Exim distribution tar files, the Exim website contains a number of
458 differently formatted versions of the documentation. A recent addition to the
459 online information is the Exim wiki (&url(https://wiki.exim.org)),
460 which contains what used to be a separate FAQ, as well as various other
461 examples, tips, and know-how that have been contributed by Exim users.
462 The wiki site should always redirect to the correct place, which is currently
463 provided by GitHub, and is open to editing by anyone with a GitHub account.
466 An Exim Bugzilla exists at &url(https://bugs.exim.org). You can use
467 this to report bugs, and also to add items to the wish list. Please search
468 first to check that you are not duplicating a previous entry.
469 Please do not ask for configuration help in the bug-tracker.
472 .section "Mailing lists" "SECID3"
473 .cindex "mailing lists" "for Exim users"
474 The following Exim mailing lists exist:
477 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
478 .row &'exim-users@exim.org'& "General discussion list"
479 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
480 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
483 You can subscribe to these lists, change your existing subscriptions, and view
484 or search the archives via the mailing lists link on the Exim home page.
485 .cindex "Debian" "mailing list for"
486 If you are using a Debian distribution of Exim, you may wish to subscribe to
487 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
490 &url(https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-exim4-users)
492 Please ask Debian-specific questions on that list and not on the general Exim
495 .section "Bug reports" "SECID5"
496 .cindex "bug reports"
497 .cindex "reporting bugs"
498 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
499 via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
500 whether some behaviour is a bug or not, the best thing to do is to post a
501 message to the &'exim-dev'& mailing list and have it discussed.
505 .section "Where to find the Exim distribution" "SECTavail"
507 .cindex "HTTPS download site"
508 .cindex "distribution" "FTP site"
509 .cindex "distribution" "https site"
510 The master distribution site for the Exim distribution is
512 &url(https://downloads.exim.org/)
514 The service is available over HTTPS, HTTP and FTP.
515 We encourage people to migrate to HTTPS.
517 The content served at &url(https://downloads.exim.org/) is identical to the
518 content served at &url(https://ftp.exim.org/pub/exim) and
519 &url(ftp://ftp.exim.org/pub/exim).
521 If accessing via a hostname containing &'ftp'&, then the file references that
522 follow are relative to the &_exim_& directories at these sites.
523 If accessing via the hostname &'downloads'& then the subdirectories described
524 here are top-level directories.
526 There are now quite a number of independent mirror sites around
527 the world. Those that I know about are listed in the file called &_Mirrors_&.
529 Within the top exim directory there are subdirectories called &_exim3_& (for
530 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
531 distributions), and &_Testing_& for testing versions. In the &_exim4_&
532 subdirectory, the current release can always be found in files called
536 &_exim-n.nn.tar.bz2_&
538 where &'n.nn'& is the highest such version number in the directory. The three
539 files contain identical data; the only difference is the type of compression.
540 The &_.xz_& file is usually the smallest, while the &_.gz_& file is the
541 most portable to old systems.
543 .cindex "distribution" "signing details"
544 .cindex "distribution" "public key"
545 .cindex "public key for signed distribution"
546 The distributions will be PGP signed by an individual key of the Release
547 Coordinator. This key will have a uid containing an email address in the
548 &'exim.org'& domain and will have signatures from other people, including
549 other Exim maintainers. We expect that the key will be in the "strong set" of
550 PGP keys. There should be a trust path to that key from the Exim Maintainer's
551 PGP keys, a version of which can be found in the release directory in the file
552 &_Exim-Maintainers-Keyring.asc_&. All keys used will be available in public keyserver pools,
553 such as &'pool.sks-keyservers.net'&.
555 At the time of the last update, releases were being made by Jeremy Harris and signed
556 with key &'0xBCE58C8CE41F32DF'&. Other recent keys used for signing are those
557 of Heiko Schlittermann, &'0x26101B62F69376CE'&,
558 and of Phil Pennock, &'0x4D1E900E14C1CC04'&.
560 The signatures for the tar bundles are in:
562 &_exim-n.nn.tar.xz.asc_&
563 &_exim-n.nn.tar.gz.asc_&
564 &_exim-n.nn.tar.bz2.asc_&
566 For each released version, the log of changes is made available in a
567 separate file in the directory &_ChangeLogs_& so that it is possible to
568 find out what has changed without having to download the entire distribution.
570 .cindex "documentation" "available formats"
571 The main distribution contains ASCII versions of this specification and other
572 documentation; other formats of the documents are available in separate files
573 inside the &_exim4_& directory of the FTP site:
575 &_exim-html-n.nn.tar.gz_&
576 &_exim-pdf-n.nn.tar.gz_&
577 &_exim-postscript-n.nn.tar.gz_&
578 &_exim-texinfo-n.nn.tar.gz_&
580 These tar files contain only the &_doc_& directory, not the complete
581 distribution, and are also available in &_.bz2_& and &_.xz_& forms.
584 .section "Limitations" "SECID6"
586 .cindex "limitations of Exim"
587 .cindex "bang paths" "not handled by Exim"
588 Exim is designed for use as an Internet MTA, and therefore handles addresses in
589 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
590 simple two-component bang paths can be converted by a straightforward rewriting
591 configuration. This restriction does not prevent Exim from being interfaced to
592 UUCP as a transport mechanism, provided that domain addresses are used.
594 .cindex "domainless addresses"
595 .cindex "address" "without domain"
596 Exim insists that every address it handles has a domain attached. For incoming
597 local messages, domainless addresses are automatically qualified with a
598 configured domain value. Configuration options specify from which remote
599 systems unqualified addresses are acceptable. These are then qualified on
602 .cindex "transport" "external"
603 .cindex "external transports"
604 The only external transport mechanisms that are currently implemented are SMTP
605 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
606 transport is available, and there are facilities for writing messages to files
607 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
608 to send messages to other transport mechanisms such as UUCP, provided they can
609 handle domain-style addresses. Batched SMTP input is also catered for.
611 Exim is not designed for storing mail for dial-in hosts. When the volumes of
612 such mail are large, it is better to get the messages &"delivered"& into files
613 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
616 Although Exim does have basic facilities for scanning incoming messages, these
617 are not comprehensive enough to do full virus or spam scanning. Such operations
618 are best carried out using additional specialized software packages. If you
619 compile Exim with the content-scanning extension, straightforward interfaces to
620 a number of common scanners are provided.
624 .section "Runtime configuration" "SECID7"
625 Exim's runtime configuration is held in a single text file that is divided
626 into a number of sections. The entries in this file consist of keywords and
627 values, in the style of Smail 3 configuration files. A default configuration
628 file which is suitable for simple online installations is provided in the
629 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
632 .section "Calling interface" "SECID8"
633 .cindex "Sendmail compatibility" "command line interface"
634 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
635 can be a straight replacement for &_/usr/lib/sendmail_& or
636 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
637 about Sendmail in order to run Exim. For actions other than sending messages,
638 Sendmail-compatible options also exist, but those that produce output (for
639 example, &%-bp%&, which lists the messages in the queue) do so in Exim's own
640 format. There are also some additional options that are compatible with Smail
641 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
642 documents all Exim's command line options. This information is automatically
643 made into the man page that forms part of the Exim distribution.
645 Control of messages in the queue can be done via certain privileged command
646 line options. There is also an optional monitor program called &'eximon'&,
647 which displays current information in an X window, and which contains a menu
648 interface to Exim's command line administration options.
652 .section "Terminology" "SECID9"
653 .cindex "terminology definitions"
654 .cindex "body of message" "definition of"
655 The &'body'& of a message is the actual data that the sender wants to transmit.
656 It is the last part of a message and is separated from the &'header'& (see
657 below) by a blank line.
659 .cindex "bounce message" "definition of"
660 When a message cannot be delivered, it is normally returned to the sender in a
661 delivery failure message or a &"non-delivery report"& (NDR). The term
662 &'bounce'& is commonly used for this action, and the error reports are often
663 called &'bounce messages'&. This is a convenient shorthand for &"delivery
664 failure error report"&. Such messages have an empty sender address in the
665 message's &'envelope'& (see below) to ensure that they cannot themselves give
666 rise to further bounce messages.
668 The term &'default'& appears frequently in this manual. It is used to qualify a
669 value which is used in the absence of any setting in the configuration. It may
670 also qualify an action which is taken unless a configuration setting specifies
673 The term &'defer'& is used when the delivery of a message to a specific
674 destination cannot immediately take place for some reason (a remote host may be
675 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
678 The word &'domain'& is sometimes used to mean all but the first component of a
679 host's name. It is &'not'& used in that sense here, where it normally refers to
680 the part of an email address following the @ sign.
682 .cindex "envelope, definition of"
683 .cindex "sender" "definition of"
684 A message in transit has an associated &'envelope'&, as well as a header and a
685 body. The envelope contains a sender address (to which bounce messages should
686 be delivered), and any number of recipient addresses. References to the
687 sender or the recipients of a message usually mean the addresses in the
688 envelope. An MTA uses these addresses for delivery, and for returning bounce
689 messages, not the addresses that appear in the header lines.
691 .cindex "message" "header, definition of"
692 .cindex "header section" "definition of"
693 The &'header'& of a message is the first part of a message's text, consisting
694 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
695 &'Subject:'&, etc. Long header lines can be split over several text lines by
696 indenting the continuations. The header is separated from the body by a blank
699 .cindex "local part" "definition of"
700 .cindex "domain" "definition of"
701 The term &'local part'&, which is taken from RFC 2822, is used to refer to the
702 part of an email address that precedes the @ sign. The part that follows the
703 @ sign is called the &'domain'& or &'mail domain'&.
705 .cindex "local delivery" "definition of"
706 .cindex "remote delivery, definition of"
707 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
708 delivery to a file or a pipe on the local host from delivery by SMTP over
709 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
710 host it is running on are &'remote'&.
712 .cindex "return path" "definition of"
713 &'Return path'& is another name that is used for the sender address in a
716 .cindex "queue" "definition of"
717 The term &'queue'& is used to refer to the set of messages awaiting delivery
718 because this term is in widespread use in the context of MTAs. However, in
719 Exim's case, the reality is more like a pool than a queue, because there is
720 normally no ordering of waiting messages.
722 .cindex "queue runner" "definition of"
723 The term &'queue runner'& is used to describe a process that scans the queue
724 and attempts to deliver those messages whose retry times have come. This term
725 is used by other MTAs and also relates to the command &%runq%&, but in Exim
726 the waiting messages are normally processed in an unpredictable order.
728 .cindex "spool directory" "definition of"
729 The term &'spool directory'& is used for a directory in which Exim keeps the
730 messages in its queue &-- that is, those that it is in the process of
731 delivering. This should not be confused with the directory in which local
732 mailboxes are stored, which is called a &"spool directory"& by some people. In
733 the Exim documentation, &"spool"& is always used in the first sense.
740 . ////////////////////////////////////////////////////////////////////////////
741 . ////////////////////////////////////////////////////////////////////////////
743 .chapter "Incorporated code" "CHID2"
744 .cindex "incorporated code"
745 .cindex "regular expressions" "library"
748 A number of pieces of external code are included in the Exim distribution.
751 Regular expressions are supported in the main Exim program and in the
752 Exim monitor using the freely-distributable PCRE library, copyright
753 © University of Cambridge. The source to PCRE is no longer shipped with
754 Exim, so you will need to use the version of PCRE shipped with your system,
755 or obtain and install the full version of the library from
756 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
758 .cindex "cdb" "acknowledgment"
759 Support for the cdb (Constant DataBase) lookup method is provided by code
760 contributed by Nigel Metheringham of (at the time he contributed it) Planet
761 Online Ltd. The implementation is completely contained within the code of Exim.
762 It does not link against an external cdb library. The code contains the
763 following statements:
766 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
768 This program is free software; you can redistribute it and/or modify it under
769 the terms of the GNU General Public License as published by the Free Software
770 Foundation; either version 2 of the License, or (at your option) any later
772 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
773 the spec and sample code for cdb can be obtained from
774 &url(https://cr.yp.to/cdb.html). This implementation borrows
775 some code from Dan Bernstein's implementation (which has no license
776 restrictions applied to it).
779 .cindex "SPA authentication"
780 .cindex "Samba project"
781 .cindex "Microsoft Secure Password Authentication"
782 Client support for Microsoft's &'Secure Password Authentication'& is provided
783 by code contributed by Marc Prud'hommeaux. Server support was contributed by
784 Tom Kistner. This includes code taken from the Samba project, which is released
788 .cindex "&'pwcheck'& daemon"
789 .cindex "&'pwauthd'& daemon"
790 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
791 by code taken from the Cyrus-SASL library and adapted by Alexander S.
792 Sabourenkov. The permission notice appears below, in accordance with the
793 conditions expressed therein.
796 Copyright © 2001 Carnegie Mellon University. All rights reserved.
798 Redistribution and use in source and binary forms, with or without
799 modification, are permitted provided that the following conditions
803 Redistributions of source code must retain the above copyright
804 notice, this list of conditions and the following disclaimer.
806 Redistributions in binary form must reproduce the above copyright
807 notice, this list of conditions and the following disclaimer in
808 the documentation and/or other materials provided with the
811 The name &"Carnegie Mellon University"& must not be used to
812 endorse or promote products derived from this software without
813 prior written permission. For permission or any other legal
814 details, please contact
816 Office of Technology Transfer
817 Carnegie Mellon University
819 Pittsburgh, PA 15213-3890
820 (412) 268-4387, fax: (412) 268-7395
821 tech-transfer@andrew.cmu.edu
824 Redistributions of any form whatsoever must retain the following
827 &"This product includes software developed by Computing Services
828 at Carnegie Mellon University (&url(https://www.cmu.edu/computing/)."&
830 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
831 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
832 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
833 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
834 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
835 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
836 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
841 .cindex "Exim monitor" "acknowledgment"
844 The Exim Monitor program, which is an X-Window application, includes
845 modified versions of the Athena StripChart and TextPop widgets.
846 This code is copyright by DEC and MIT, and their permission notice appears
847 below, in accordance with the conditions expressed therein.
850 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
851 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
855 Permission to use, copy, modify, and distribute this software and its
856 documentation for any purpose and without fee is hereby granted,
857 provided that the above copyright notice appear in all copies and that
858 both that copyright notice and this permission notice appear in
859 supporting documentation, and that the names of Digital or MIT not be
860 used in advertising or publicity pertaining to distribution of the
861 software without specific, written prior permission.
863 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
864 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
865 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
866 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
867 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
868 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
873 .cindex "opendmarc" "acknowledgment"
874 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
875 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
876 derived code are indicated in the respective source files. The full OpenDMARC
877 license is provided in the LICENSE.opendmarc file contained in the distributed
881 Many people have contributed code fragments, some large, some small, that were
882 not covered by any specific license requirements. It is assumed that the
883 contributors are happy to see their code incorporated into Exim under the GPL.
890 . ////////////////////////////////////////////////////////////////////////////
891 . ////////////////////////////////////////////////////////////////////////////
893 .chapter "How Exim receives and delivers mail" "CHID11" &&&
894 "Receiving and delivering mail"
897 .section "Overall philosophy" "SECID10"
898 .cindex "design philosophy"
899 Exim is designed to work efficiently on systems that are permanently connected
900 to the Internet and are handling a general mix of mail. In such circumstances,
901 most messages can be delivered immediately. Consequently, Exim does not
902 maintain independent queues of messages for specific domains or hosts, though
903 it does try to send several messages in a single SMTP connection after a host
904 has been down, and it also maintains per-host retry information.
907 .section "Policy control" "SECID11"
908 .cindex "policy control" "overview"
909 Policy controls are now an important feature of MTAs that are connected to the
910 Internet. Perhaps their most important job is to stop MTAs from being abused as
911 &"open relays"& by misguided individuals who send out vast amounts of
912 unsolicited junk and want to disguise its source. Exim provides flexible
913 facilities for specifying policy controls on incoming mail:
916 .cindex "&ACL;" "introduction"
917 Exim 4 (unlike previous versions of Exim) implements policy controls on
918 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
919 series of statements that may either grant or deny access. ACLs can be used at
920 several places in the SMTP dialogue while receiving a message from a remote
921 host. However, the most common places are after each RCPT command, and at the
922 very end of the message. The sysadmin can specify conditions for accepting or
923 rejecting individual recipients or the entire message, respectively, at these
924 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
927 An ACL is also available for locally generated, non-SMTP messages. In this
928 case, the only available actions are to accept or deny the entire message.
930 When Exim is compiled with the content-scanning extension, facilities are
931 provided in the ACL mechanism for passing the message to external virus and/or
932 spam scanning software. The result of such a scan is passed back to the ACL,
933 which can then use it to decide what to do with the message.
935 When a message has been received, either from a remote host or from the local
936 host, but before the final acknowledgment has been sent, a locally supplied C
937 function called &[local_scan()]& can be run to inspect the message and decide
938 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
939 is accepted, the list of recipients can be modified by the function.
941 Using the &[local_scan()]& mechanism is another way of calling external scanner
942 software. The &%SA-Exim%& add-on package works this way. It does not require
943 Exim to be compiled with the content-scanning extension.
945 After a message has been accepted, a further checking mechanism is available in
946 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
947 runs at the start of every delivery process.
952 .section "User filters" "SECID12"
953 .cindex "filter" "introduction"
954 .cindex "Sieve filter"
955 In a conventional Exim configuration, users are able to run private filters by
956 setting up appropriate &_.forward_& files in their home directories. See
957 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
958 configuration needed to support this, and the separate document entitled
959 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
960 of filtering are available:
963 Sieve filters are written in the standard filtering language that is defined
966 Exim filters are written in a syntax that is unique to Exim, but which is more
967 powerful than Sieve, which it pre-dates.
970 User filters are run as part of the routing process, described below.
974 .section "Message identification" "SECTmessiden"
975 .cindex "message ids" "details of format"
976 .cindex "format" "of message id"
977 .cindex "id of message"
982 Every message handled by Exim is given a &'message id'& which is sixteen
983 characters long. It is divided into three parts, separated by hyphens, for
984 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
985 normally encoding numbers in base 62. However, in the Darwin operating
986 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
987 (avoiding the use of lower case letters) is used instead, because the message
988 id is used to construct filenames, and the names of files in those systems are
989 not always case-sensitive.
991 .cindex "pid (process id)" "re-use of"
992 The detail of the contents of the message id have changed as Exim has evolved.
993 Earlier versions relied on the operating system not re-using a process id (pid)
994 within one second. On modern operating systems, this assumption can no longer
995 be made, so the algorithm had to be changed. To retain backward compatibility,
996 the format of the message id was retained, which is why the following rules are
1000 The first six characters of the message id are the time at which the message
1001 started to be received, to a granularity of one second. That is, this field
1002 contains the number of seconds since the start of the epoch (the normal Unix
1003 way of representing the date and time of day).
1005 After the first hyphen, the next six characters are the id of the process that
1006 received the message.
1008 There are two different possibilities for the final two characters:
1010 .oindex "&%localhost_number%&"
1011 If &%localhost_number%& is not set, this value is the fractional part of the
1012 time of reception, normally in units of 1/2000 of a second, but for systems
1013 that must use base 36 instead of base 62 (because of case-insensitive file
1014 systems), the units are 1/1000 of a second.
1016 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1017 the fractional part of the time, which in this case is in units of 1/200
1018 (1/100) of a second.
1022 After a message has been received, Exim waits for the clock to tick at the
1023 appropriate resolution before proceeding, so that if another message is
1024 received by the same process, or by another process with the same (re-used)
1025 pid, it is guaranteed that the time will be different. In most cases, the clock
1026 will already have ticked while the message was being received.
1029 .section "Receiving mail" "SECID13"
1030 .cindex "receiving mail"
1031 .cindex "message" "reception"
1032 The only way Exim can receive mail from another host is using SMTP over
1033 TCP/IP, in which case the sender and recipient addresses are transferred using
1034 SMTP commands. However, from a locally running process (such as a user's MUA),
1035 there are several possibilities:
1038 If the process runs Exim with the &%-bm%& option, the message is read
1039 non-interactively (usually via a pipe), with the recipients taken from the
1040 command line, or from the body of the message if &%-t%& is also used.
1042 If the process runs Exim with the &%-bS%& option, the message is also read
1043 non-interactively, but in this case the recipients are listed at the start of
1044 the message in a series of SMTP RCPT commands, terminated by a DATA
1045 command. This is called &"batch SMTP"& format,
1046 but it isn't really SMTP. The SMTP commands are just another way of passing
1047 envelope addresses in a non-interactive submission.
1049 If the process runs Exim with the &%-bs%& option, the message is read
1050 interactively, using the SMTP protocol. A two-way pipe is normally used for
1051 passing data between the local process and the Exim process.
1052 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1053 example, the ACLs for SMTP commands are used for this form of submission.
1055 A local process may also make a TCP/IP call to the host's loopback address
1056 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1057 does not treat the loopback address specially. It treats all such connections
1058 in the same way as connections from other hosts.
1062 .cindex "message sender, constructed by Exim"
1063 .cindex "sender" "constructed by Exim"
1064 In the three cases that do not involve TCP/IP, the sender address is
1065 constructed from the login name of the user that called Exim and a default
1066 qualification domain (which can be set by the &%qualify_domain%& configuration
1067 option). For local or batch SMTP, a sender address that is passed using the
1068 SMTP MAIL command is ignored. However, the system administrator may allow
1069 certain users (&"trusted users"&) to specify a different sender addresses
1070 unconditionally, or all users to specify certain forms of different sender
1071 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1072 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1073 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1074 users to change sender addresses.
1076 Messages received by either of the non-interactive mechanisms are subject to
1077 checking by the non-SMTP ACL if one is defined. Messages received using SMTP
1078 (either over TCP/IP or interacting with a local process) can be checked by a
1079 number of ACLs that operate at different times during the SMTP session. Either
1080 individual recipients or the entire message can be rejected if local policy
1081 requirements are not met. The &[local_scan()]& function (see chapter
1082 &<<CHAPlocalscan>>&) is run for all incoming messages.
1084 Exim can be configured not to start a delivery process when a message is
1085 received; this can be unconditional, or depend on the number of incoming SMTP
1086 connections or the system load. In these situations, new messages wait on the
1087 queue until a queue runner process picks them up. However, in standard
1088 configurations under normal conditions, delivery is started as soon as a
1089 message is received.
1095 .section "Handling an incoming message" "SECID14"
1096 .cindex "spool directory" "files that hold a message"
1097 .cindex "file" "how a message is held"
1098 When Exim accepts a message, it writes two files in its spool directory. The
1099 first contains the envelope information, the current status of the message, and
1100 the header lines, and the second contains the body of the message. The names of
1101 the two spool files consist of the message id, followed by &`-H`& for the
1102 file containing the envelope and header, and &`-D`& for the data file.
1104 .cindex "spool directory" "&_input_& sub-directory"
1105 By default, all these message files are held in a single directory called
1106 &_input_& inside the general Exim spool directory. Some operating systems do
1107 not perform very well if the number of files in a directory gets large; to
1108 improve performance in such cases, the &%split_spool_directory%& option can be
1109 used. This causes Exim to split up the input files into 62 sub-directories
1110 whose names are single letters or digits. When this is done, the queue is
1111 processed one sub-directory at a time instead of all at once, which can improve
1112 overall performance even when there are not enough files in each directory to
1113 affect file system performance.
1115 The envelope information consists of the address of the message's sender and
1116 the addresses of the recipients. This information is entirely separate from
1117 any addresses contained in the header lines. The status of the message includes
1118 a list of recipients who have already received the message. The format of the
1119 first spool file is described in chapter &<<CHAPspool>>&.
1121 .cindex "rewriting" "addresses"
1122 Address rewriting that is specified in the rewrite section of the configuration
1123 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1124 both in the header lines and the envelope, at the time the message is accepted.
1125 If during the course of delivery additional addresses are generated (for
1126 example, via aliasing), these new addresses are rewritten as soon as they are
1127 generated. At the time a message is actually delivered (transported) further
1128 rewriting can take place; because this is a transport option, it can be
1129 different for different forms of delivery. It is also possible to specify the
1130 addition or removal of certain header lines at the time the message is
1131 delivered (see chapters &<<CHAProutergeneric>>& and
1132 &<<CHAPtransportgeneric>>&).
1136 .section "Life of a message" "SECID15"
1137 .cindex "message" "life of"
1138 .cindex "message" "frozen"
1139 A message remains in the spool directory until it is completely delivered to
1140 its recipients or to an error address, or until it is deleted by an
1141 administrator or by the user who originally created it. In cases when delivery
1142 cannot proceed &-- for example when a message can neither be delivered to its
1143 recipients nor returned to its sender, the message is marked &"frozen"& on the
1144 spool, and no more deliveries are attempted.
1146 .cindex "frozen messages" "thawing"
1147 .cindex "message" "thawing frozen"
1148 An administrator can &"thaw"& such messages when the problem has been
1149 corrected, and can also freeze individual messages by hand if necessary. In
1150 addition, an administrator can force a delivery error, causing a bounce message
1153 .oindex "&%timeout_frozen_after%&"
1154 .oindex "&%ignore_bounce_errors_after%&"
1155 There are options called &%ignore_bounce_errors_after%& and
1156 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1157 The first applies only to frozen bounces, the second to all frozen messages.
1159 .cindex "message" "log file for"
1160 .cindex "log" "file for each message"
1161 While Exim is working on a message, it writes information about each delivery
1162 attempt to its main log file. This includes successful, unsuccessful, and
1163 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1164 lines are also written to a separate &'message log'& file for each message.
1165 These logs are solely for the benefit of the administrator and are normally
1166 deleted along with the spool files when processing of a message is complete.
1167 The use of individual message logs can be disabled by setting
1168 &%no_message_logs%&; this might give an improvement in performance on very busy
1171 .cindex "journal file"
1172 .cindex "file" "journal"
1173 All the information Exim itself needs to set up a delivery is kept in the first
1174 spool file, along with the header lines. When a successful delivery occurs, the
1175 address is immediately written at the end of a journal file, whose name is the
1176 message id followed by &`-J`&. At the end of a delivery run, if there are some
1177 addresses left to be tried again later, the first spool file (the &`-H`& file)
1178 is updated to indicate which these are, and the journal file is then deleted.
1179 Updating the spool file is done by writing a new file and renaming it, to
1180 minimize the possibility of data loss.
1182 Should the system or Exim crash after a successful delivery but before
1183 the spool file has been updated, the journal is left lying around. The next
1184 time Exim attempts to deliver the message, it reads the journal file and
1185 updates the spool file before proceeding. This minimizes the chances of double
1186 deliveries caused by crashes.
1190 .section "Processing an address for delivery" "SECTprocaddress"
1191 .cindex "drivers" "definition of"
1192 .cindex "router" "definition of"
1193 .cindex "transport" "definition of"
1194 The main delivery processing elements of Exim are called &'routers'& and
1195 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1196 number of them is provided in the source distribution, and compile-time options
1197 specify which ones are included in the binary. Runtime options specify which
1198 ones are actually used for delivering messages.
1200 .cindex "drivers" "instance definition"
1201 Each driver that is specified in the runtime configuration is an &'instance'&
1202 of that particular driver type. Multiple instances are allowed; for example,
1203 you can set up several different &(smtp)& transports, each with different
1204 option values that might specify different ports or different timeouts. Each
1205 instance has its own identifying name. In what follows we will normally use the
1206 instance name when discussing one particular instance (that is, one specific
1207 configuration of the driver), and the generic driver name when discussing
1208 the driver's features in general.
1210 A &'router'& is a driver that operates on an address, either determining how
1211 its delivery should happen, by assigning it to a specific transport, or
1212 converting the address into one or more new addresses (for example, via an
1213 alias file). A router may also explicitly choose to fail an address, causing it
1216 A &'transport'& is a driver that transmits a copy of the message from Exim's
1217 spool to some destination. There are two kinds of transport: for a &'local'&
1218 transport, the destination is a file or a pipe on the local host, whereas for a
1219 &'remote'& transport the destination is some other host. A message is passed
1220 to a specific transport as a result of successful routing. If a message has
1221 several recipients, it may be passed to a number of different transports.
1223 .cindex "preconditions" "definition of"
1224 An address is processed by passing it to each configured router instance in
1225 turn, subject to certain preconditions, until a router accepts the address or
1226 specifies that it should be bounced. We will describe this process in more
1227 detail shortly. First, as a simple example, we consider how each recipient
1228 address in a message is processed in a small configuration of three routers.
1230 To make this a more concrete example, it is described in terms of some actual
1231 routers, but remember, this is only an example. You can configure Exim's
1232 routers in many different ways, and there may be any number of routers in a
1235 The first router that is specified in a configuration is often one that handles
1236 addresses in domains that are not recognized specifically by the local host.
1237 Typically these are addresses for arbitrary domains on the Internet. A precondition
1238 is set up which looks for the special domains known to the host (for example,
1239 its own domain name), and the router is run for addresses that do &'not'&
1240 match. Typically, this is a router that looks up domains in the DNS in order to
1241 find the hosts to which this address routes. If it succeeds, the address is
1242 assigned to a suitable SMTP transport; if it does not succeed, the router is
1243 configured to fail the address.
1245 The second router is reached only when the domain is recognized as one that
1246 &"belongs"& to the local host. This router does redirection &-- also known as
1247 aliasing and forwarding. When it generates one or more new addresses from the
1248 original, each of them is routed independently from the start. Otherwise, the
1249 router may cause an address to fail, or it may simply decline to handle the
1250 address, in which case the address is passed to the next router.
1252 The final router in many configurations is one that checks to see if the
1253 address belongs to a local mailbox. The precondition may involve a check to
1254 see if the local part is the name of a login account, or it may look up the
1255 local part in a file or a database. If its preconditions are not met, or if
1256 the router declines, we have reached the end of the routers. When this happens,
1257 the address is bounced.
1261 .section "Processing an address for verification" "SECID16"
1262 .cindex "router" "for verification"
1263 .cindex "verifying address" "overview"
1264 As well as being used to decide how to deliver to an address, Exim's routers
1265 are also used for &'address verification'&. Verification can be requested as
1266 one of the checks to be performed in an ACL for incoming messages, on both
1267 sender and recipient addresses, and it can be tested using the &%-bv%& and
1268 &%-bvs%& command line options.
1270 When an address is being verified, the routers are run in &"verify mode"&. This
1271 does not affect the way the routers work, but it is a state that can be
1272 detected. By this means, a router can be skipped or made to behave differently
1273 when verifying. A common example is a configuration in which the first router
1274 sends all messages to a message-scanning program unless they have been
1275 previously scanned. Thus, the first router accepts all addresses without any
1276 checking, making it useless for verifying. Normally, the &%no_verify%& option
1277 would be set for such a router, causing it to be skipped in verify mode.
1282 .section "Running an individual router" "SECTrunindrou"
1283 .cindex "router" "running details"
1284 .cindex "preconditions" "checking"
1285 .cindex "router" "result of running"
1286 As explained in the example above, a number of preconditions are checked before
1287 running a router. If any are not met, the router is skipped, and the address is
1288 passed to the next router. When all the preconditions on a router &'are'& met,
1289 the router is run. What happens next depends on the outcome, which is one of
1293 &'accept'&: The router accepts the address, and either assigns it to a
1294 transport or generates one or more &"child"& addresses. Processing the
1295 original address ceases
1296 .oindex "&%unseen%&"
1297 unless the &%unseen%& option is set on the router. This option
1298 can be used to set up multiple deliveries with different routing (for example,
1299 for keeping archive copies of messages). When &%unseen%& is set, the address is
1300 passed to the next router. Normally, however, an &'accept'& return marks the
1303 Any child addresses generated by the router are processed independently,
1304 starting with the first router by default. It is possible to change this by
1305 setting the &%redirect_router%& option to specify which router to start at for
1306 child addresses. Unlike &%pass_router%& (see below) the router specified by
1307 &%redirect_router%& may be anywhere in the router configuration.
1309 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1310 requests that the address be passed to another router. By default, the address
1311 is passed to the next router, but this can be changed by setting the
1312 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1313 must be below the current router (to avoid loops).
1315 &'decline'&: The router declines to accept the address because it does not
1316 recognize it at all. By default, the address is passed to the next router, but
1317 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1318 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1319 &'decline'& into &'fail'&.
1321 &'fail'&: The router determines that the address should fail, and queues it for
1322 the generation of a bounce message. There is no further processing of the
1323 original address unless &%unseen%& is set on the router.
1325 &'defer'&: The router cannot handle the address at the present time. (A
1326 database may be offline, or a DNS lookup may have timed out.) No further
1327 processing of the address happens in this delivery attempt. It is tried again
1328 next time the message is considered for delivery.
1330 &'error'&: There is some error in the router (for example, a syntax error in
1331 its configuration). The action is as for defer.
1334 If an address reaches the end of the routers without having been accepted by
1335 any of them, it is bounced as unrouteable. The default error message in this
1336 situation is &"unrouteable address"&, but you can set your own message by
1337 making use of the &%cannot_route_message%& option. This can be set for any
1338 router; the value from the last router that &"saw"& the address is used.
1340 Sometimes while routing you want to fail a delivery when some conditions are
1341 met but others are not, instead of passing the address on for further routing.
1342 You can do this by having a second router that explicitly fails the delivery
1343 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1344 facility for this purpose.
1347 .section "Duplicate addresses" "SECID17"
1348 .cindex "case of local parts"
1349 .cindex "address duplicate, discarding"
1350 .cindex "duplicate addresses"
1351 Once routing is complete, Exim scans the addresses that are assigned to local
1352 and remote transports and discards any duplicates that it finds. During this
1353 check, local parts are treated case-sensitively. This happens only when
1354 actually delivering a message; when testing routers with &%-bt%&, all the
1355 routed addresses are shown.
1359 .section "Router preconditions" "SECTrouprecon"
1360 .cindex "router" "preconditions, order of processing"
1361 .cindex "preconditions" "order of processing"
1362 The preconditions that are tested for each router are listed below, in the
1363 order in which they are tested. The individual configuration options are
1364 described in more detail in chapter &<<CHAProutergeneric>>&.
1367 .cindex affix "router precondition"
1368 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1369 the local parts handled by the router may or must have certain prefixes and/or
1370 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1371 skipped. These conditions are tested first. When an affix is present, it is
1372 removed from the local part before further processing, including the evaluation
1373 of any other conditions.
1375 Routers can be designated for use only when not verifying an address, that is,
1376 only when routing it for delivery (or testing its delivery routing). If the
1377 &%verify%& option is set false, the router is skipped when Exim is verifying an
1379 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1380 &%verify_recipient%&, which independently control the use of the router for
1381 sender and recipient verification. You can set these options directly if
1382 you want a router to be used for only one type of verification.
1383 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1385 If the &%address_test%& option is set false, the router is skipped when Exim is
1386 run with the &%-bt%& option to test an address routing. This can be helpful
1387 when the first router sends all new messages to a scanner of some sort; it
1388 makes it possible to use &%-bt%& to test subsequent delivery routing without
1389 having to simulate the effect of the scanner.
1391 Routers can be designated for use only when verifying an address, as
1392 opposed to routing it for delivery. The &%verify_only%& option controls this.
1393 Again, cutthrough delivery counts as a verification.
1395 Individual routers can be explicitly skipped when running the routers to
1396 check an address given in the SMTP EXPN command (see the &%expn%& option).
1398 If the &%domains%& option is set, the domain of the address must be in the set
1399 of domains that it defines.
1401 .vindex "&$local_part_prefix$&"
1402 .vindex "&$local_part$&"
1403 .vindex "&$local_part_suffix$&"
1404 .cindex affix "router precondition"
1405 If the &%local_parts%& option is set, the local part of the address must be in
1406 the set of local parts that it defines. If &%local_part_prefix%& or
1407 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1408 part before this check. If you want to do precondition tests on local parts
1409 that include affixes, you can do so by using a &%condition%& option (see below)
1410 that uses the variables &$local_part$&, &$local_part_prefix$&, and
1411 &$local_part_suffix$& as necessary.
1413 .vindex "&$local_user_uid$&"
1414 .vindex "&$local_user_gid$&"
1416 If the &%check_local_user%& option is set, the local part must be the name of
1417 an account on the local host. If this check succeeds, the uid and gid of the
1418 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1419 user's home directory is placed in &$home$&; these values can be used in the
1420 remaining preconditions.
1422 If the &%router_home_directory%& option is set, it is expanded at this point,
1423 because it overrides the value of &$home$&. If this expansion were left till
1424 later, the value of &$home$& as set by &%check_local_user%& would be used in
1425 subsequent tests. Having two different values of &$home$& in the same router
1426 could lead to confusion.
1428 If the &%senders%& option is set, the envelope sender address must be in the
1429 set of addresses that it defines.
1431 If the &%require_files%& option is set, the existence or non-existence of
1432 specified files is tested.
1434 .cindex "customizing" "precondition"
1435 If the &%condition%& option is set, it is evaluated and tested. This option
1436 uses an expanded string to allow you to set up your own custom preconditions.
1437 Expanded strings are described in chapter &<<CHAPexpand>>&.
1441 Note that &%require_files%& comes near the end of the list, so you cannot use
1442 it to check for the existence of a file in which to lookup up a domain, local
1443 part, or sender. However, as these options are all expanded, you can use the
1444 &%exists%& expansion condition to make such tests within each condition. The
1445 &%require_files%& option is intended for checking files that the router may be
1446 going to use internally, or which are needed by a specific transport (for
1447 example, &_.procmailrc_&).
1451 .section "Delivery in detail" "SECID18"
1452 .cindex "delivery" "in detail"
1453 When a message is to be delivered, the sequence of events is as follows:
1456 If a system-wide filter file is specified, the message is passed to it. The
1457 filter may add recipients to the message, replace the recipients, discard the
1458 message, cause a new message to be generated, or cause the message delivery to
1459 fail. The format of the system filter file is the same as for Exim user filter
1460 files, described in the separate document entitled &'Exim's interfaces to mail
1462 .cindex "Sieve filter" "not available for system filter"
1463 (&*Note*&: Sieve cannot be used for system filter files.)
1465 Some additional features are available in system filters &-- see chapter
1466 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1467 filter only once per delivery attempt, however many recipients it has. However,
1468 if there are several delivery attempts because one or more addresses could not
1469 be immediately delivered, the system filter is run each time. The filter
1470 condition &%first_delivery%& can be used to detect the first run of the system
1473 Each recipient address is offered to each configured router, in turn, subject to
1474 its preconditions, until one is able to handle it. If no router can handle the
1475 address, that is, if they all decline, the address is failed. Because routers
1476 can be targeted at particular domains, several locally handled domains can be
1477 processed entirely independently of each other.
1479 .cindex "routing" "loops in"
1480 .cindex "loop" "while routing"
1481 A router that accepts an address may assign it to a local or a remote
1482 transport. However, the transport is not run at this time. Instead, the address
1483 is placed on a list for the particular transport, which will be run later.
1484 Alternatively, the router may generate one or more new addresses (typically
1485 from alias, forward, or filter files). New addresses are fed back into this
1486 process from the top, but in order to avoid loops, a router ignores any address
1487 which has an identically-named ancestor that was processed by itself.
1489 When all the routing has been done, addresses that have been successfully
1490 handled are passed to their assigned transports. When local transports are
1491 doing real local deliveries, they handle only one address at a time, but if a
1492 local transport is being used as a pseudo-remote transport (for example, to
1493 collect batched SMTP messages for transmission by some other means) multiple
1494 addresses can be handled. Remote transports can always handle more than one
1495 address at a time, but can be configured not to do so, or to restrict multiple
1496 addresses to the same domain.
1498 Each local delivery to a file or a pipe runs in a separate process under a
1499 non-privileged uid, and these deliveries are run one at a time. Remote
1500 deliveries also run in separate processes, normally under a uid that is private
1501 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1502 run in parallel. The maximum number of simultaneous remote deliveries for any
1503 one message is set by the &%remote_max_parallel%& option.
1504 The order in which deliveries are done is not defined, except that all local
1505 deliveries happen before any remote deliveries.
1507 .cindex "queue runner"
1508 When it encounters a local delivery during a queue run, Exim checks its retry
1509 database to see if there has been a previous temporary delivery failure for the
1510 address before running the local transport. If there was a previous failure,
1511 Exim does not attempt a new delivery until the retry time for the address is
1512 reached. However, this happens only for delivery attempts that are part of a
1513 queue run. Local deliveries are always attempted when delivery immediately
1514 follows message reception, even if retry times are set for them. This makes for
1515 better behaviour if one particular message is causing problems (for example,
1516 causing quota overflow, or provoking an error in a filter file).
1518 .cindex "delivery" "retry in remote transports"
1519 Remote transports do their own retry handling, since an address may be
1520 deliverable to one of a number of hosts, each of which may have a different
1521 retry time. If there have been previous temporary failures and no host has
1522 reached its retry time, no delivery is attempted, whether in a queue run or
1523 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1525 If there were any permanent errors, a bounce message is returned to an
1526 appropriate address (the sender in the common case), with details of the error
1527 for each failing address. Exim can be configured to send copies of bounce
1528 messages to other addresses.
1530 .cindex "delivery" "deferral"
1531 If one or more addresses suffered a temporary failure, the message is left on
1532 the queue, to be tried again later. Delivery of these addresses is said to be
1535 When all the recipient addresses have either been delivered or bounced,
1536 handling of the message is complete. The spool files and message log are
1537 deleted, though the message log can optionally be preserved if required.
1543 .section "Retry mechanism" "SECID19"
1544 .cindex "delivery" "retry mechanism"
1545 .cindex "retry" "description of mechanism"
1546 .cindex "queue runner"
1547 Exim's mechanism for retrying messages that fail to get delivered at the first
1548 attempt is the queue runner process. You must either run an Exim daemon that
1549 uses the &%-q%& option with a time interval to start queue runners at regular
1550 intervals or use some other means (such as &'cron'&) to start them. If you do
1551 not arrange for queue runners to be run, messages that fail temporarily at the
1552 first attempt will remain in your queue forever. A queue runner process works
1553 its way through the queue, one message at a time, trying each delivery that has
1554 passed its retry time.
1555 You can run several queue runners at once.
1557 Exim uses a set of configured rules to determine when next to retry the failing
1558 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1559 should give up trying to deliver to the address, at which point it generates a
1560 bounce message. If no retry rules are set for a particular host, address, and
1561 error combination, no retries are attempted, and temporary errors are treated
1566 .section "Temporary delivery failure" "SECID20"
1567 .cindex "delivery" "temporary failure"
1568 There are many reasons why a message may not be immediately deliverable to a
1569 particular address. Failure to connect to a remote machine (because it, or the
1570 connection to it, is down) is one of the most common. Temporary failures may be
1571 detected during routing as well as during the transport stage of delivery.
1572 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1573 is on a file system where the user is over quota. Exim can be configured to
1574 impose its own quotas on local mailboxes; where system quotas are set they will
1577 If a host is unreachable for a period of time, a number of messages may be
1578 waiting for it by the time it recovers, and sending them in a single SMTP
1579 connection is clearly beneficial. Whenever a delivery to a remote host is
1581 .cindex "hints database" "deferred deliveries"
1582 Exim makes a note in its hints database, and whenever a successful
1583 SMTP delivery has happened, it looks to see if any other messages are waiting
1584 for the same host. If any are found, they are sent over the same SMTP
1585 connection, subject to a configuration limit as to the maximum number in any
1590 .section "Permanent delivery failure" "SECID21"
1591 .cindex "delivery" "permanent failure"
1592 .cindex "bounce message" "when generated"
1593 When a message cannot be delivered to some or all of its intended recipients, a
1594 bounce message is generated. Temporary delivery failures turn into permanent
1595 errors when their timeout expires. All the addresses that fail in a given
1596 delivery attempt are listed in a single message. If the original message has
1597 many recipients, it is possible for some addresses to fail in one delivery
1598 attempt and others to fail subsequently, giving rise to more than one bounce
1599 message. The wording of bounce messages can be customized by the administrator.
1600 See chapter &<<CHAPemsgcust>>& for details.
1602 .cindex "&'X-Failed-Recipients:'& header line"
1603 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1604 failed addresses, for the benefit of programs that try to analyse such messages
1607 .cindex "bounce message" "recipient of"
1608 A bounce message is normally sent to the sender of the original message, as
1609 obtained from the message's envelope. For incoming SMTP messages, this is the
1610 address given in the MAIL command. However, when an address is expanded via a
1611 forward or alias file, an alternative address can be specified for delivery
1612 failures of the generated addresses. For a mailing list expansion (see section
1613 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1618 .section "Failures to deliver bounce messages" "SECID22"
1619 .cindex "bounce message" "failure to deliver"
1620 If a bounce message (either locally generated or received from a remote host)
1621 itself suffers a permanent delivery failure, the message is left in the queue,
1622 but it is frozen, awaiting the attention of an administrator. There are options
1623 that can be used to make Exim discard such failed messages, or to keep them
1624 for only a short time (see &%timeout_frozen_after%& and
1625 &%ignore_bounce_errors_after%&).
1631 . ////////////////////////////////////////////////////////////////////////////
1632 . ////////////////////////////////////////////////////////////////////////////
1634 .chapter "Building and installing Exim" "CHID3"
1635 .scindex IIDbuex "building Exim"
1637 .section "Unpacking" "SECID23"
1638 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1639 creates a directory with the name of the current release (for example,
1640 &_exim-&version()_&) into which the following files are placed:
1643 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1644 .irow &_CHANGES_& "contains a reference to where changes are &&&
1646 .irow &_LICENCE_& "the GNU General Public Licence"
1647 .irow &_Makefile_& "top-level make file"
1648 .irow &_NOTICE_& "conditions for the use of Exim"
1649 .irow &_README_& "list of files, directories and simple build &&&
1653 Other files whose names begin with &_README_& may also be present. The
1654 following subdirectories are created:
1657 .irow &_Local_& "an empty directory for local configuration files"
1658 .irow &_OS_& "OS-specific files"
1659 .irow &_doc_& "documentation files"
1660 .irow &_exim_monitor_& "source files for the Exim monitor"
1661 .irow &_scripts_& "scripts used in the build process"
1662 .irow &_src_& "remaining source files"
1663 .irow &_util_& "independent utilities"
1666 The main utility programs are contained in the &_src_& directory and are built
1667 with the Exim binary. The &_util_& directory contains a few optional scripts
1668 that may be useful to some sites.
1671 .section "Multiple machine architectures and operating systems" "SECID24"
1672 .cindex "building Exim" "multiple OS/architectures"
1673 The building process for Exim is arranged to make it easy to build binaries for
1674 a number of different architectures and operating systems from the same set of
1675 source files. Compilation does not take place in the &_src_& directory.
1676 Instead, a &'build directory'& is created for each architecture and operating
1678 .cindex "symbolic link" "to build directory"
1679 Symbolic links to the sources are installed in this directory, which is where
1680 the actual building takes place. In most cases, Exim can discover the machine
1681 architecture and operating system for itself, but the defaults can be
1682 overridden if necessary.
1683 .cindex compiler requirements
1684 .cindex compiler version
1685 A C99-capable compiler will be required for the build.
1688 .section "PCRE library" "SECTpcre"
1689 .cindex "PCRE library"
1690 Exim no longer has an embedded PCRE library as the vast majority of
1691 modern systems include PCRE as a system library, although you may need to
1692 install the PCRE package or the PCRE development package for your operating
1693 system. If your system has a normal PCRE installation the Exim build
1694 process will need no further configuration. If the library or the
1695 headers are in an unusual location you will need to either set the PCRE_LIBS
1696 and INCLUDE directives appropriately,
1697 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1698 If your operating system has no
1699 PCRE support then you will need to obtain and build the current PCRE
1700 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1701 More information on PCRE is available at &url(https://www.pcre.org/).
1703 .section "DBM libraries" "SECTdb"
1704 .cindex "DBM libraries" "discussion of"
1705 .cindex "hints database" "DBM files used for"
1706 Even if you do not use any DBM files in your configuration, Exim still needs a
1707 DBM library in order to operate, because it uses indexed files for its hints
1708 databases. Unfortunately, there are a number of DBM libraries in existence, and
1709 different operating systems often have different ones installed.
1711 .cindex "Solaris" "DBM library for"
1712 .cindex "IRIX, DBM library for"
1713 .cindex "BSD, DBM library for"
1714 .cindex "Linux, DBM library for"
1715 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1716 Linux distribution, the DBM configuration should happen automatically, and you
1717 may be able to ignore this section. Otherwise, you may have to learn more than
1718 you would like about DBM libraries from what follows.
1720 .cindex "&'ndbm'& DBM library"
1721 Licensed versions of Unix normally contain a library of DBM functions operating
1722 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1723 versions of Unix seem to vary in what they contain as standard. In particular,
1724 some early versions of Linux have no default DBM library, and different
1725 distributors have chosen to bundle different libraries with their packaged
1726 versions. However, the more recent releases seem to have standardized on the
1727 Berkeley DB library.
1729 Different DBM libraries have different conventions for naming the files they
1730 use. When a program opens a file called &_dbmfile_&, there are several
1734 A traditional &'ndbm'& implementation, such as that supplied as part of
1735 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1737 .cindex "&'gdbm'& DBM library"
1738 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1739 compatibility interface it makes two different hard links to it with names
1740 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1741 filename is used unmodified.
1743 .cindex "Berkeley DB library"
1744 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1745 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1746 programmer exactly the same as the traditional &'ndbm'& implementation.
1748 If the Berkeley package is used in its native mode, it operates on a single
1749 file called &_dbmfile_&; the programmer's interface is somewhat different to
1750 the traditional &'ndbm'& interface.
1752 To complicate things further, there are several very different versions of the
1753 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1754 2.&'x'& and 3.&'x'& were current for a while, but the latest versions when Exim last revamped support were numbered 4.&'x'&.
1755 Maintenance of some of the earlier releases has ceased. All versions of
1756 Berkeley DB could be obtained from
1757 &url(http://www.sleepycat.com/), which is now a redirect to their new owner's
1758 page with far newer versions listed.
1759 It is probably wise to plan to move your storage configurations away from
1760 Berkeley DB format, as today there are smaller and simpler alternatives more
1761 suited to Exim's usage model.
1763 .cindex "&'tdb'& DBM library"
1764 Yet another DBM library, called &'tdb'&, is available from
1765 &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
1766 operates on a single file.
1770 .cindex "DBM libraries" "configuration for building"
1771 Exim and its utilities can be compiled to use any of these interfaces. In order
1772 to use any version of the Berkeley DB package in native mode, you must set
1773 USE_DB in an appropriate configuration file (typically
1774 &_Local/Makefile_&). For example:
1778 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1779 error is diagnosed if you set more than one of these.
1781 At the lowest level, the build-time configuration sets none of these options,
1782 thereby assuming an interface of type (1). However, some operating system
1783 configuration files (for example, those for the BSD operating systems and
1784 Linux) assume type (4) by setting USE_DB as their default, and the
1785 configuration files for Cygwin set USE_GDBM. Anything you set in
1786 &_Local/Makefile_&, however, overrides these system defaults.
1788 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1789 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1790 in one of these lines:
1795 Settings like that will work if the DBM library is installed in the standard
1796 place. Sometimes it is not, and the library's header file may also not be in
1797 the default path. You may need to set INCLUDE to specify where the header
1798 file is, and to specify the path to the library more fully in DBMLIB, as in
1801 INCLUDE=-I/usr/local/include/db-4.1
1802 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1804 There is further detailed discussion about the various DBM libraries in the
1805 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1809 .section "Pre-building configuration" "SECID25"
1810 .cindex "building Exim" "pre-building configuration"
1811 .cindex "configuration for building Exim"
1812 .cindex "&_Local/Makefile_&"
1813 .cindex "&_src/EDITME_&"
1814 Before building Exim, a local configuration file that specifies options
1815 independent of any operating system has to be created with the name
1816 &_Local/Makefile_&. A template for this file is supplied as the file
1817 &_src/EDITME_&, and it contains full descriptions of all the option settings
1818 therein. These descriptions are therefore not repeated here. If you are
1819 building Exim for the first time, the simplest thing to do is to copy
1820 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1822 There are three settings that you must supply, because Exim will not build
1823 without them. They are the location of the runtime configuration file
1824 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1825 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1826 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1827 a colon-separated list of filenames; Exim uses the first of them that exists.
1829 There are a few other parameters that can be specified either at build time or
1830 at runtime, to enable the same binary to be used on a number of different
1831 machines. However, if the locations of Exim's spool directory and log file
1832 directory (if not within the spool directory) are fixed, it is recommended that
1833 you specify them in &_Local/Makefile_& instead of at runtime, so that errors
1834 detected early in Exim's execution (such as a malformed configuration file) can
1837 .cindex "content scanning" "specifying at build time"
1838 Exim's interfaces for calling virus and spam scanning software directly from
1839 access control lists are not compiled by default. If you want to include these
1840 facilities, you need to set
1842 WITH_CONTENT_SCAN=yes
1844 in your &_Local/Makefile_&. For details of the facilities themselves, see
1845 chapter &<<CHAPexiscan>>&.
1848 .cindex "&_Local/eximon.conf_&"
1849 .cindex "&_exim_monitor/EDITME_&"
1850 If you are going to build the Exim monitor, a similar configuration process is
1851 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1852 your installation and saved under the name &_Local/eximon.conf_&. If you are
1853 happy with the default settings described in &_exim_monitor/EDITME_&,
1854 &_Local/eximon.conf_& can be empty, but it must exist.
1856 This is all the configuration that is needed in straightforward cases for known
1857 operating systems. However, the building process is set up so that it is easy
1858 to override options that are set by default or by operating-system-specific
1859 configuration files, for example, to change the C compiler, which
1860 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1865 .section "Support for iconv()" "SECID26"
1866 .cindex "&[iconv()]& support"
1868 The contents of header lines in messages may be encoded according to the rules
1869 described RFC 2047. This makes it possible to transmit characters that are not
1870 in the ASCII character set, and to label them as being in a particular
1871 character set. When Exim is inspecting header lines by means of the &%$h_%&
1872 mechanism, it decodes them, and translates them into a specified character set
1873 (default is set at build time). The translation is possible only if the operating system
1874 supports the &[iconv()]& function.
1876 However, some of the operating systems that supply &[iconv()]& do not support
1877 very many conversions. The GNU &%libiconv%& library (available from
1878 &url(https://www.gnu.org/software/libiconv/)) can be installed on such
1879 systems to remedy this deficiency, as well as on systems that do not supply
1880 &[iconv()]& at all. After installing &%libiconv%&, you should add
1884 to your &_Local/Makefile_& and rebuild Exim.
1888 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1889 .cindex "TLS" "including support for TLS"
1890 .cindex "encryption" "including support for"
1891 .cindex "SUPPORT_TLS"
1892 .cindex "OpenSSL" "building Exim with"
1893 .cindex "GnuTLS" "building Exim with"
1894 Exim can be built to support encrypted SMTP connections, using the STARTTLS
1895 command as per RFC 2487. It can also support legacy clients that expect to
1896 start a TLS session immediately on connection to a non-standard port (see the
1897 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1900 If you want to build Exim with TLS support, you must first install either the
1901 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1904 If OpenSSL is installed, you should set
1907 TLS_LIBS=-lssl -lcrypto
1909 in &_Local/Makefile_&. You may also need to specify the locations of the
1910 OpenSSL library and include files. For example:
1913 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1914 TLS_INCLUDE=-I/usr/local/openssl/include/
1916 .cindex "pkg-config" "OpenSSL"
1917 If you have &'pkg-config'& available, then instead you can just use:
1920 USE_OPENSSL_PC=openssl
1922 .cindex "USE_GNUTLS"
1923 If GnuTLS is installed, you should set
1927 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1929 in &_Local/Makefile_&, and again you may need to specify the locations of the
1930 library and include files. For example:
1934 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1935 TLS_INCLUDE=-I/usr/gnu/include
1937 .cindex "pkg-config" "GnuTLS"
1938 If you have &'pkg-config'& available, then instead you can just use:
1942 USE_GNUTLS_PC=gnutls
1945 You do not need to set TLS_INCLUDE if the relevant directory is already
1946 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1947 given in chapter &<<CHAPTLS>>&.
1952 .section "Use of tcpwrappers" "SECID27"
1954 .cindex "tcpwrappers, building Exim to support"
1955 .cindex "USE_TCP_WRAPPERS"
1956 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1957 .cindex "tcp_wrappers_daemon_name"
1958 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1959 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1960 alternative to Exim's own checking facilities for installations that are
1961 already making use of &'tcpwrappers'& for other purposes. To do this, you
1962 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1963 &_tcpd.h_& to be available at compile time, and also ensure that the library
1964 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1965 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1968 USE_TCP_WRAPPERS=yes
1969 CFLAGS=-O -I/usr/local/include
1970 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1972 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1973 files is &"exim"&. For example, the line
1975 exim : LOCAL 192.168.1. .friendly.domain.example
1977 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1978 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1979 All other connections are denied. The daemon name used by &'tcpwrappers'&
1980 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1981 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1982 configure file. Consult the &'tcpwrappers'& documentation for
1986 .section "Including support for IPv6" "SECID28"
1987 .cindex "IPv6" "including support for"
1988 Exim contains code for use on systems that have IPv6 support. Setting
1989 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1990 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1991 where the IPv6 support is not fully integrated into the normal include and
1994 Two different types of DNS record for handling IPv6 addresses have been
1995 defined. AAAA records (analogous to A records for IPv4) are in use, and are
1996 currently seen as the mainstream. Another record type called A6 was proposed
1997 as better than AAAA because it had more flexibility. However, it was felt to be
1998 over-complex, and its status was reduced to &"experimental"&.
2000 have a compile option for including A6 record support but this has now been
2005 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
2006 .cindex "lookup modules"
2007 .cindex "dynamic modules"
2008 .cindex ".so building"
2009 On some platforms, Exim supports not compiling all lookup types directly into
2010 the main binary, instead putting some into external modules which can be loaded
2012 This permits packagers to build Exim with support for lookups with extensive
2013 library dependencies without requiring all users to install all of those
2015 Most, but not all, lookup types can be built this way.
2017 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2018 installed; Exim will only load modules from that directory, as a security
2019 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2020 for your OS; see &_OS/Makefile-Linux_& for an example.
2021 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2022 see &_src/EDITME_& for details.
2024 Then, for each module to be loaded dynamically, define the relevant
2025 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2026 For example, this will build in lsearch but load sqlite and mysql support
2035 .section "The building process" "SECID29"
2036 .cindex "build directory"
2037 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2038 created, run &'make'& at the top level. It determines the architecture and
2039 operating system types, and creates a build directory if one does not exist.
2040 For example, on a Sun system running Solaris 8, the directory
2041 &_build-SunOS5-5.8-sparc_& is created.
2042 .cindex "symbolic link" "to source files"
2043 Symbolic links to relevant source files are installed in the build directory.
2045 If this is the first time &'make'& has been run, it calls a script that builds
2046 a make file inside the build directory, using the configuration files from the
2047 &_Local_& directory. The new make file is then passed to another instance of
2048 &'make'&. This does the real work, building a number of utility scripts, and
2049 then compiling and linking the binaries for the Exim monitor (if configured), a
2050 number of utility programs, and finally Exim itself. The command &`make
2051 makefile`& can be used to force a rebuild of the make file in the build
2052 directory, should this ever be necessary.
2054 If you have problems building Exim, check for any comments there may be in the
2055 &_README_& file concerning your operating system, and also take a look at the
2056 FAQ, where some common problems are covered.
2060 .section 'Output from &"make"&' "SECID283"
2061 The output produced by the &'make'& process for compile lines is often very
2062 unreadable, because these lines can be very long. For this reason, the normal
2063 output is suppressed by default, and instead output similar to that which
2064 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2065 each module that is being compiled or linked. However, it is still possible to
2066 get the full output, by calling &'make'& like this:
2070 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2071 command reflection in &'make'&. When you ask for the full output, it is
2072 given in addition to the short output.
2076 .section "Overriding build-time options for Exim" "SECToverride"
2077 .cindex "build-time options, overriding"
2078 The main make file that is created at the beginning of the building process
2079 consists of the concatenation of a number of files which set configuration
2080 values, followed by a fixed set of &'make'& instructions. If a value is set
2081 more than once, the last setting overrides any previous ones. This provides a
2082 convenient way of overriding defaults. The files that are concatenated are, in
2085 &_OS/Makefile-Default_&
2086 &_OS/Makefile-_&<&'ostype'&>
2088 &_Local/Makefile-_&<&'ostype'&>
2089 &_Local/Makefile-_&<&'archtype'&>
2090 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2091 &_OS/Makefile-Base_&
2093 .cindex "&_Local/Makefile_&"
2094 .cindex "building Exim" "operating system type"
2095 .cindex "building Exim" "architecture type"
2096 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2097 architecture type. &_Local/Makefile_& is required to exist, and the building
2098 process fails if it is absent. The other three &_Local_& files are optional,
2099 and are often not needed.
2101 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2102 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2103 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2104 values are used, thereby providing a means of forcing particular settings.
2105 Otherwise, the scripts try to get values from the &%uname%& command. If this
2106 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2107 of &'ad hoc'& transformations are then applied, to produce the standard names
2108 that Exim expects. You can run these scripts directly from the shell in order
2109 to find out what values are being used on your system.
2112 &_OS/Makefile-Default_& contains comments about the variables that are set
2113 therein. Some (but not all) are mentioned below. If there is something that
2114 needs changing, review the contents of this file and the contents of the make
2115 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2119 .cindex "building Exim" "overriding default settings"
2120 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2121 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2122 need to change the original files. Instead, you should make the changes by
2123 putting the new values in an appropriate &_Local_& file. For example,
2124 .cindex "Tru64-Unix build-time settings"
2125 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2126 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2127 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2128 called with the option &%-std1%&, to make it recognize some of the features of
2129 Standard C that Exim uses. (Most other compilers recognize Standard C by
2130 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2131 containing the lines
2136 If you are compiling for just one operating system, it may be easier to put
2137 these lines directly into &_Local/Makefile_&.
2139 Keeping all your local configuration settings separate from the distributed
2140 files makes it easy to transfer them to new versions of Exim simply by copying
2141 the contents of the &_Local_& directory.
2144 .cindex "NIS lookup type" "including support for"
2145 .cindex "NIS+ lookup type" "including support for"
2146 .cindex "LDAP" "including support for"
2147 .cindex "lookup" "inclusion in binary"
2148 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2149 lookup, but not all systems have these components installed, so the default is
2150 not to include the relevant code in the binary. All the different kinds of file
2151 and database lookup that Exim supports are implemented as separate code modules
2152 which are included only if the relevant compile-time options are set. In the
2153 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2159 and similar settings apply to the other lookup types. They are all listed in
2160 &_src/EDITME_&. In many cases the relevant include files and interface
2161 libraries need to be installed before compiling Exim.
2162 .cindex "cdb" "including support for"
2163 However, there are some optional lookup types (such as cdb) for which
2164 the code is entirely contained within Exim, and no external include
2165 files or libraries are required. When a lookup type is not included in the
2166 binary, attempts to configure Exim to use it cause runtime configuration
2169 .cindex "pkg-config" "lookups"
2170 .cindex "pkg-config" "authenticators"
2171 Many systems now use a tool called &'pkg-config'& to encapsulate information
2172 about how to compile against a library; Exim has some initial support for
2173 being able to use pkg-config for lookups and authenticators. For any given
2174 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2175 variable with the &`_PC`& suffix in the name and assign as the value the
2176 name of the package to be queried. The results of querying via the
2177 &'pkg-config'& command will be added to the appropriate Makefile variables
2178 with &`+=`& directives, so your version of &'make'& will need to support that
2179 syntax. For instance:
2182 LOOKUP_SQLITE_PC=sqlite3
2184 AUTH_GSASL_PC=libgsasl
2185 AUTH_HEIMDAL_GSSAPI=yes
2186 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2189 .cindex "Perl" "including support for"
2190 Exim can be linked with an embedded Perl interpreter, allowing Perl
2191 subroutines to be called during string expansion. To enable this facility,
2195 must be defined in &_Local/Makefile_&. Details of this facility are given in
2196 chapter &<<CHAPperl>>&.
2198 .cindex "X11 libraries, location of"
2199 The location of the X11 libraries is something that varies a lot between
2200 operating systems, and there may be different versions of X11 to cope
2201 with. Exim itself makes no use of X11, but if you are compiling the Exim
2202 monitor, the X11 libraries must be available.
2203 The following three variables are set in &_OS/Makefile-Default_&:
2206 XINCLUDE=-I$(X11)/include
2207 XLFLAGS=-L$(X11)/lib
2209 These are overridden in some of the operating-system configuration files. For
2210 example, in &_OS/Makefile-SunOS5_& there is
2213 XINCLUDE=-I$(X11)/include
2214 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2216 If you need to override the default setting for your operating system, place a
2217 definition of all three of these variables into your
2218 &_Local/Makefile-<ostype>_& file.
2221 If you need to add any extra libraries to the link steps, these can be put in a
2222 variable called EXTRALIBS, which appears in all the link commands, but by
2223 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2224 command for linking the main Exim binary, and not for any associated utilities.
2226 .cindex "DBM libraries" "configuration for building"
2227 There is also DBMLIB, which appears in the link commands for binaries that
2228 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2229 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2230 binary, and which can be used, for example, to include additional X11
2233 .cindex "configuration file" "editing"
2234 The make file copes with rebuilding Exim correctly if any of the configuration
2235 files are edited. However, if an optional configuration file is deleted, it is
2236 necessary to touch the associated non-optional file (that is,
2237 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2240 .section "OS-specific header files" "SECID30"
2242 .cindex "building Exim" "OS-specific C header files"
2243 The &_OS_& directory contains a number of files with names of the form
2244 &_os.h-<ostype>_&. These are system-specific C header files that should not
2245 normally need to be changed. There is a list of macro settings that are
2246 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2247 are porting Exim to a new operating system.
2251 .section "Overriding build-time options for the monitor" "SECID31"
2252 .cindex "building Eximon"
2253 A similar process is used for overriding things when building the Exim monitor,
2254 where the files that are involved are
2256 &_OS/eximon.conf-Default_&
2257 &_OS/eximon.conf-_&<&'ostype'&>
2258 &_Local/eximon.conf_&
2259 &_Local/eximon.conf-_&<&'ostype'&>
2260 &_Local/eximon.conf-_&<&'archtype'&>
2261 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2263 .cindex "&_Local/eximon.conf_&"
2264 As with Exim itself, the final three files need not exist, and in this case the
2265 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2266 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2267 variables of the same name, preceded by EXIMON_. For example, setting
2268 EXIMON_LOG_DEPTH in the environment overrides the value of
2269 LOG_DEPTH at runtime.
2273 .section "Installing Exim binaries and scripts" "SECID32"
2274 .cindex "installing Exim"
2275 .cindex "BIN_DIRECTORY"
2276 The command &`make install`& runs the &(exim_install)& script with no
2277 arguments. The script copies binaries and utility scripts into the directory
2278 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2279 .cindex "setuid" "installing Exim with"
2280 The install script copies files only if they are newer than the files they are
2281 going to replace. The Exim binary is required to be owned by root and have the
2282 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2283 install`& as root so that it can set up the Exim binary in this way. However, in
2284 some special situations (for example, if a host is doing no local deliveries)
2285 it may be possible to run Exim without making the binary setuid root (see
2286 chapter &<<CHAPsecurity>>& for details).
2288 .cindex "CONFIGURE_FILE"
2289 Exim's runtime configuration file is named by the CONFIGURE_FILE setting
2290 in &_Local/Makefile_&. If this names a single file, and the file does not
2291 exist, the default configuration file &_src/configure.default_& is copied there
2292 by the installation script. If a runtime configuration file already exists, it
2293 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2294 alternative files, no default is installed.
2296 .cindex "system aliases file"
2297 .cindex "&_/etc/aliases_&"
2298 One change is made to the default configuration file when it is installed: the
2299 default configuration contains a router that references a system aliases file.
2300 The path to this file is set to the value specified by
2301 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2302 If the system aliases file does not exist, the installation script creates it,
2303 and outputs a comment to the user.
2305 The created file contains no aliases, but it does contain comments about the
2306 aliases a site should normally have. Mail aliases have traditionally been
2307 kept in &_/etc/aliases_&. However, some operating systems are now using
2308 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2309 Exim's configuration if necessary.
2311 The default configuration uses the local host's name as the only local domain,
2312 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2313 running as the local user. System aliases and &_.forward_& files in users' home
2314 directories are supported, but no NIS or NIS+ support is configured. Domains
2315 other than the name of the local host are routed using the DNS, with delivery
2318 It is possible to install Exim for special purposes (such as building a binary
2319 distribution) in a private part of the file system. You can do this by a
2322 make DESTDIR=/some/directory/ install
2324 This has the effect of pre-pending the specified directory to all the file
2325 paths, except the name of the system aliases file that appears in the default
2326 configuration. (If a default alias file is created, its name &'is'& modified.)
2327 For backwards compatibility, ROOT is used if DESTDIR is not set,
2328 but this usage is deprecated.
2330 .cindex "installing Exim" "what is not installed"
2331 Running &'make install'& does not copy the Exim 4 conversion script
2332 &'convert4r4'&. You will probably run this only once if you are
2333 upgrading from Exim 3. None of the documentation files in the &_doc_&
2334 directory are copied, except for the info files when you have set
2335 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2337 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2338 to their names. The Exim binary itself, however, is handled differently. It is
2339 installed under a name that includes the version number and the compile number,
2340 for example, &_exim-&version()-1_&. The script then arranges for a symbolic link
2341 called &_exim_& to point to the binary. If you are updating a previous version
2342 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2343 from the directory (as seen by other processes).
2345 .cindex "installing Exim" "testing the script"
2346 If you want to see what the &'make install'& will do before running it for
2347 real, you can pass the &%-n%& option to the installation script by this
2350 make INSTALL_ARG=-n install
2352 The contents of the variable INSTALL_ARG are passed to the installation
2353 script. You do not need to be root to run this test. Alternatively, you can run
2354 the installation script directly, but this must be from within the build
2355 directory. For example, from the top-level Exim directory you could use this
2358 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2360 .cindex "installing Exim" "install script options"
2361 There are two other options that can be supplied to the installation script.
2364 &%-no_chown%& bypasses the call to change the owner of the installed binary
2365 to root, and the call to make it a setuid binary.
2367 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2371 INSTALL_ARG can be used to pass these options to the script. For example:
2373 make INSTALL_ARG=-no_symlink install
2375 The installation script can also be given arguments specifying which files are
2376 to be copied. For example, to install just the Exim binary, and nothing else,
2377 without creating the symbolic link, you could use:
2379 make INSTALL_ARG='-no_symlink exim' install
2384 .section "Installing info documentation" "SECTinsinfdoc"
2385 .cindex "installing Exim" "&'info'& documentation"
2386 Not all systems use the GNU &'info'& system for documentation, and for this
2387 reason, the Texinfo source of Exim's documentation is not included in the main
2388 distribution. Instead it is available separately from the FTP site (see section
2391 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2392 source of the documentation is found in the source tree, running &`make
2393 install`& automatically builds the info files and installs them.
2397 .section "Setting up the spool directory" "SECID33"
2398 .cindex "spool directory" "creating"
2399 When it starts up, Exim tries to create its spool directory if it does not
2400 exist. The Exim uid and gid are used for the owner and group of the spool
2401 directory. Sub-directories are automatically created in the spool directory as
2407 .section "Testing" "SECID34"
2408 .cindex "testing" "installation"
2409 Having installed Exim, you can check that the runtime configuration file is
2410 syntactically valid by running the following command, which assumes that the
2411 Exim binary directory is within your PATH environment variable:
2415 If there are any errors in the configuration file, Exim outputs error messages.
2416 Otherwise it outputs the version number and build date,
2417 the DBM library that is being used, and information about which drivers and
2418 other optional code modules are included in the binary.
2419 Some simple routing tests can be done by using the address testing option. For
2422 &`exim -bt`& <&'local username'&>
2424 should verify that it recognizes a local mailbox, and
2426 &`exim -bt`& <&'remote address'&>
2428 a remote one. Then try getting it to deliver mail, both locally and remotely.
2429 This can be done by passing messages directly to Exim, without going through a
2430 user agent. For example:
2432 exim -v postmaster@your.domain.example
2433 From: user@your.domain.example
2434 To: postmaster@your.domain.example
2435 Subject: Testing Exim
2437 This is a test message.
2440 The &%-v%& option causes Exim to output some verification of what it is doing.
2441 In this case you should see copies of three log lines, one for the message's
2442 arrival, one for its delivery, and one containing &"Completed"&.
2444 .cindex "delivery" "problems with"
2445 If you encounter problems, look at Exim's log files (&'mainlog'& and
2446 &'paniclog'&) to see if there is any relevant information there. Another source
2447 of information is running Exim with debugging turned on, by specifying the
2448 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2449 with debugging turned on by a command of the form
2451 &`exim -d -M`& <&'exim-message-id'&>
2453 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2454 produces rather a lot of output, but you can cut this down to specific areas.
2455 For example, if you use &%-d-all+route%& only the debugging information
2456 relevant to routing is included. (See the &%-d%& option in chapter
2457 &<<CHAPcommandline>>& for more details.)
2459 .cindex '&"sticky"& bit'
2460 .cindex "lock files"
2461 One specific problem that has shown up on some sites is the inability to do
2462 local deliveries into a shared mailbox directory, because it does not have the
2463 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2464 writing to a mailbox file, and if it cannot create the lock file, the delivery
2465 is deferred. You can get round this either by setting the &"sticky bit"& on the
2466 directory, or by setting a specific group for local deliveries and allowing
2467 that group to create files in the directory (see the comments above the
2468 &(local_delivery)& transport in the default configuration file). Another
2469 approach is to configure Exim not to use lock files, but just to rely on
2470 &[fcntl()]& locking instead. However, you should do this only if all user
2471 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2472 see chapter &<<CHAPappendfile>>&.
2474 One thing that cannot be tested on a system that is already running an MTA is
2475 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2476 &%-oX%& option can be used to run an Exim daemon that listens on some other
2477 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2478 &'exim_checkaccess'& utility can be used to check out policy controls on
2481 Testing a new version on a system that is already running Exim can most easily
2482 be done by building a binary with a different CONFIGURE_FILE setting. From
2483 within the runtime configuration, all other file and directory names
2484 that Exim uses can be altered, in order to keep it entirely clear of the
2488 .section "Replacing another MTA with Exim" "SECID35"
2489 .cindex "replacing another MTA"
2490 Building and installing Exim for the first time does not of itself put it in
2491 general use. The name by which the system's MTA is called by mail user agents
2492 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2493 operating system), and it is necessary to make this name point to the &'exim'&
2494 binary in order to get the user agents to pass messages to Exim. This is
2495 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2496 or &_/usr/lib/sendmail_&
2497 .cindex "symbolic link" "to &'exim'& binary"
2498 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2499 privilege and executable status from the old MTA. It is then necessary to stop
2500 and restart the mailer daemon, if one is running.
2502 .cindex "FreeBSD, MTA indirection"
2503 .cindex "&_/etc/mail/mailer.conf_&"
2504 Some operating systems have introduced alternative ways of switching MTAs. For
2505 example, if you are running FreeBSD, you need to edit the file
2506 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2507 described. A typical example of the contents of this file for running Exim is
2510 sendmail /usr/exim/bin/exim
2511 send-mail /usr/exim/bin/exim
2512 mailq /usr/exim/bin/exim -bp
2513 newaliases /usr/bin/true
2515 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2516 your Exim installation is &"live"&. Check it by sending a message from your
2517 favourite user agent.
2519 You should consider what to tell your users about the change of MTA. Exim may
2520 have different capabilities to what was previously running, and there are
2521 various operational differences such as the text of messages produced by
2522 command line options and in bounce messages. If you allow your users to make
2523 use of Exim's filtering capabilities, you should make the document entitled
2524 &'Exim's interface to mail filtering'& available to them.
2528 .section "Upgrading Exim" "SECID36"
2529 .cindex "upgrading Exim"
2530 If you are already running Exim on your host, building and installing a new
2531 version automatically makes it available to MUAs, or any other programs that
2532 call the MTA directly. However, if you are running an Exim daemon, you do need
2533 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2534 new binary. You do not need to stop processing mail in order to install a new
2535 version of Exim. The install script does not modify an existing runtime
2541 .section "Stopping the Exim daemon on Solaris" "SECID37"
2542 .cindex "Solaris" "stopping Exim on"
2543 The standard command for stopping the mailer daemon on Solaris is
2545 /etc/init.d/sendmail stop
2547 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2548 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2549 for the text &"sendmail"&; this is not present because the actual program name
2550 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2551 solution is to replace the line that finds the process id with something like
2553 pid=`cat /var/spool/exim/exim-daemon.pid`
2555 to obtain the daemon's pid directly from the file that Exim saves it in.
2557 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2558 still be received from local processes, and if automatic delivery is configured
2559 (the normal case), deliveries will still occur.
2564 . ////////////////////////////////////////////////////////////////////////////
2565 . ////////////////////////////////////////////////////////////////////////////
2567 .chapter "The Exim command line" "CHAPcommandline"
2568 .scindex IIDclo1 "command line" "options"
2569 .scindex IIDclo2 "options" "command line"
2570 Exim's command line takes the standard Unix form of a sequence of options,
2571 each starting with a hyphen character, followed by a number of arguments. The
2572 options are compatible with the main options of Sendmail, and there are also
2573 some additional options, some of which are compatible with Smail 3. Certain
2574 combinations of options do not make sense, and provoke an error if used.
2575 The form of the arguments depends on which options are set.
2578 .section "Setting options by program name" "SECID38"
2580 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2581 were present before any other options.
2582 The &%-bp%& option requests a listing of the contents of the mail queue on the
2584 This feature is for compatibility with some systems that contain a command of
2585 that name in one of the standard libraries, symbolically linked to
2586 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2589 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2590 were present before any other options, for compatibility with Smail. The
2591 &%-bS%& option is used for reading in a number of messages in batched SMTP
2595 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2596 &%-oee%& options were present before any other options, for compatibility with
2597 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2600 .cindex "queue runner"
2601 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2602 were present before any other options, for compatibility with Smail. The &%-q%&
2603 option causes a single queue runner process to be started.
2605 .cindex "&'newaliases'&"
2606 .cindex "alias file" "building"
2607 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2608 If Exim is called under the name &'newaliases'& it behaves as if the option
2609 &%-bi%& were present before any other options, for compatibility with Sendmail.
2610 This option is used for rebuilding Sendmail's alias file. Exim does not have
2611 the concept of a single alias file, but can be configured to run a given
2612 command if called with the &%-bi%& option.
2615 .section "Trusted and admin users" "SECTtrustedadmin"
2616 Some Exim options are available only to &'trusted users'& and others are
2617 available only to &'admin users'&. In the description below, the phrases &"Exim
2618 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2619 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2620 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2623 .cindex "trusted users" "definition of"
2624 .cindex "user" "trusted definition of"
2625 The trusted users are root, the Exim user, any user listed in the
2626 &%trusted_users%& configuration option, and any user whose current group or any
2627 supplementary group is one of those listed in the &%trusted_groups%&
2628 configuration option. Note that the Exim group is not automatically trusted.
2630 .cindex '&"From"& line'
2631 .cindex "envelope sender"
2632 Trusted users are always permitted to use the &%-f%& option or a leading
2633 &"From&~"& line to specify the envelope sender of a message that is passed to
2634 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2635 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2636 users to set envelope senders.
2638 .cindex "&'From:'& header line"
2639 .cindex "&'Sender:'& header line"
2640 .cindex "header lines" "From:"
2641 .cindex "header lines" "Sender:"
2642 For a trusted user, there is never any check on the contents of the &'From:'&
2643 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2644 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2646 Trusted users may also specify a host name, host address, interface address,
2647 protocol name, ident value, and authentication data when submitting a message
2648 locally. Thus, they are able to insert messages into Exim's queue locally that
2649 have the characteristics of messages received from a remote host. Untrusted
2650 users may in some circumstances use &%-f%&, but can never set the other values
2651 that are available to trusted users.
2653 .cindex "user" "admin definition of"
2654 .cindex "admin user" "definition of"
2655 The admin users are root, the Exim user, and any user that is a member of the
2656 Exim group or of any group listed in the &%admin_groups%& configuration option.
2657 The current group does not have to be one of these groups.
2659 Admin users are permitted to list the queue, and to carry out certain
2660 operations on messages, for example, to force delivery failures. It is also
2661 necessary to be an admin user in order to see the full information provided by
2662 the Exim monitor, and full debugging output.
2664 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2665 Exim to attempt delivery of messages on its queue is restricted to admin users.
2666 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2667 option false (that is, specifying &%no_prod_requires_admin%&).
2669 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2670 is restricted to admin users unless &%queue_list_requires_admin%& is set
2675 &*Warning*&: If you configure your system so that admin users are able to
2676 edit Exim's configuration file, you are giving those users an easy way of
2677 getting root. There is further discussion of this issue at the start of chapter
2683 .section "Command line options" "SECID39"
2684 Exim's command line options are described in alphabetical order below. If none
2685 of the options that specifies a specific action (such as starting the daemon or
2686 a queue runner, or testing an address, or receiving a message in a specific
2687 format, or listing the queue) are present, and there is at least one argument
2688 on the command line, &%-bm%& (accept a local message on the standard input,
2689 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2690 outputs a brief message about itself and exits.
2692 . ////////////////////////////////////////////////////////////////////////////
2693 . Insert a stylized XML comment here, to identify the start of the command line
2694 . options. This is for the benefit of the Perl script that automatically
2695 . creates a man page for the options.
2696 . ////////////////////////////////////////////////////////////////////////////
2699 <!-- === Start of command line options === -->
2706 .cindex "options" "command line; terminating"
2707 This is a pseudo-option whose only purpose is to terminate the options and
2708 therefore to cause subsequent command line items to be treated as arguments
2709 rather than options, even if they begin with hyphens.
2712 .oindex "&%--help%&"
2713 This option causes Exim to output a few sentences stating what it is.
2714 The same output is generated if the Exim binary is called with no options and
2717 .vitem &%--version%&
2718 .oindex "&%--version%&"
2719 This option is an alias for &%-bV%& and causes version information to be
2726 These options are used by Sendmail for selecting configuration files and are
2729 .vitem &%-B%&<&'type'&>
2731 .cindex "8-bit characters"
2732 .cindex "Sendmail compatibility" "8-bit characters"
2733 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2734 clean; it ignores this option.
2739 .cindex "SMTP" "listener"
2740 .cindex "queue runner"
2741 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2742 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2743 that the daemon should also initiate periodic queue runs.
2745 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2746 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2747 disconnect from the controlling terminal. When running this way, it can be
2748 stopped by pressing ctrl-C.
2750 By default, Exim listens for incoming connections to the standard SMTP port on
2751 all the host's running interfaces. However, it is possible to listen on other
2752 ports, on multiple ports, and only on specific interfaces. Chapter
2753 &<<CHAPinterfaces>>& contains a description of the options that control this.
2755 When a listening daemon
2756 .cindex "daemon" "process id (pid)"
2757 .cindex "pid (process id)" "of daemon"
2758 is started without the use of &%-oX%& (that is, without overriding the normal
2759 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2760 in Exim's spool directory. This location can be overridden by setting
2761 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2764 When &%-oX%& is used on the command line to start a listening daemon, the
2765 process id is not written to the normal pid file path. However, &%-oP%& can be
2766 used to specify a path on the command line if a pid file is required.
2770 .cindex "daemon" "restarting"
2771 can be used to cause the daemon to re-execute itself. This should be done
2772 whenever Exim's configuration file, or any file that is incorporated into it by
2773 means of the &%.include%& facility, is changed, and also whenever a new version
2774 of Exim is installed. It is not necessary to do this when other files that are
2775 referenced from the configuration (for example, alias files) are changed,
2776 because these are reread each time they are used.
2780 This option has the same effect as &%-bd%& except that it never disconnects
2781 from the controlling terminal, even when no debugging is specified.
2785 .cindex "testing" "string expansion"
2786 .cindex "expansion" "testing"
2787 Run Exim in expansion testing mode. Exim discards its root privilege, to
2788 prevent ordinary users from using this mode to read otherwise inaccessible
2789 files. If no arguments are given, Exim runs interactively, prompting for lines
2790 of data. Otherwise, it processes each argument in turn.
2792 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2793 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2794 used without command line arguments. If successful, it uses the &[readline()]&
2795 function, which provides extensive line-editing facilities, for reading the
2796 test data. A line history is supported.
2798 Long expansion expressions can be split over several lines by using backslash
2799 continuations. As in Exim's runtime configuration, white space at the start of
2800 continuation lines is ignored. Each argument or data line is passed through the
2801 string expansion mechanism, and the result is output. Variable values from the
2802 configuration file (for example, &$qualify_domain$&) are available, but no
2803 message-specific values (such as &$message_exim_id$&) are set, because no message
2804 is being processed (but see &%-bem%& and &%-Mset%&).
2806 &*Note*&: If you use this mechanism to test lookups, and you change the data
2807 files or databases you are using, you must exit and restart Exim before trying
2808 the same lookup again. Otherwise, because each Exim process caches the results
2809 of lookups, you will just get the same result as before.
2811 Macro processing is done on lines before string-expansion: new macros can be
2812 defined and macros will be expanded.
2813 Because macros in the config file are often used for secrets, those are only
2814 available to admin users.
2816 .vitem &%-bem%&&~<&'filename'&>
2818 .cindex "testing" "string expansion"
2819 .cindex "expansion" "testing"
2820 This option operates like &%-be%& except that it must be followed by the name
2821 of a file. For example:
2823 exim -bem /tmp/testmessage
2825 The file is read as a message (as if receiving a locally-submitted non-SMTP
2826 message) before any of the test expansions are done. Thus, message-specific
2827 variables such as &$message_size$& and &$header_from:$& are available. However,
2828 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2829 recipients are read from the headers in the normal way, and are shown in the
2830 &$recipients$& variable. Note that recipients cannot be given on the command
2831 line, because further arguments are taken as strings to expand (just like
2834 .vitem &%-bF%&&~<&'filename'&>
2836 .cindex "system filter" "testing"
2837 .cindex "testing" "system filter"
2838 This option is the same as &%-bf%& except that it assumes that the filter being
2839 tested is a system filter. The additional commands that are available only in
2840 system filters are recognized.
2842 .vitem &%-bf%&&~<&'filename'&>
2844 .cindex "filter" "testing"
2845 .cindex "testing" "filter file"
2846 .cindex "forward file" "testing"
2847 .cindex "testing" "forward file"
2848 .cindex "Sieve filter" "testing"
2849 This option runs Exim in user filter testing mode; the file is the filter file
2850 to be tested, and a test message must be supplied on the standard input. If
2851 there are no message-dependent tests in the filter, an empty file can be
2854 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2855 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2856 filter and a user filter in the same run. For example:
2858 exim -bF /system/filter -bf /user/filter </test/message
2860 This is helpful when the system filter adds header lines or sets filter
2861 variables that are used by the user filter.
2863 If the test filter file does not begin with one of the special lines
2868 it is taken to be a normal &_.forward_& file, and is tested for validity under
2869 that interpretation. See sections &<<SECTitenonfilred>>& to
2870 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2873 The result of an Exim command that uses &%-bf%&, provided no errors are
2874 detected, is a list of the actions that Exim would try to take if presented
2875 with the message for real. More details of filter testing are given in the
2876 separate document entitled &'Exim's interfaces to mail filtering'&.
2878 When testing a filter file,
2879 .cindex "&""From""& line"
2880 .cindex "envelope sender"
2881 .oindex "&%-f%&" "for filter testing"
2882 the envelope sender can be set by the &%-f%& option,
2883 or by a &"From&~"& line at the start of the test message. Various parameters
2884 that would normally be taken from the envelope recipient address of the message
2885 can be set by means of additional command line options (see the next four
2888 .vitem &%-bfd%&&~<&'domain'&>
2890 .vindex "&$qualify_domain$&"
2891 This sets the domain of the recipient address when a filter file is being
2892 tested by means of the &%-bf%& option. The default is the value of
2895 .vitem &%-bfl%&&~<&'local&~part'&>
2897 This sets the local part of the recipient address when a filter file is being
2898 tested by means of the &%-bf%& option. The default is the username of the
2899 process that calls Exim. A local part should be specified with any prefix or
2900 suffix stripped, because that is how it appears to the filter when a message is
2901 actually being delivered.
2903 .vitem &%-bfp%&&~<&'prefix'&>
2905 .cindex affix "filter testing"
2906 This sets the prefix of the local part of the recipient address when a filter
2907 file is being tested by means of the &%-bf%& option. The default is an empty
2910 .vitem &%-bfs%&&~<&'suffix'&>
2912 .cindex affix "filter testing"
2913 This sets the suffix of the local part of the recipient address when a filter
2914 file is being tested by means of the &%-bf%& option. The default is an empty
2917 .vitem &%-bh%&&~<&'IP&~address'&>
2919 .cindex "testing" "incoming SMTP"
2920 .cindex "SMTP" "testing incoming"
2921 .cindex "testing" "relay control"
2922 .cindex "relaying" "testing configuration"
2923 .cindex "policy control" "testing"
2924 .cindex "debugging" "&%-bh%& option"
2925 This option runs a fake SMTP session as if from the given IP address, using the
2926 standard input and output. The IP address may include a port number at the end,
2927 after a full stop. For example:
2929 exim -bh 10.9.8.7.1234
2930 exim -bh fe80::a00:20ff:fe86:a061.5678
2932 When an IPv6 address is given, it is converted into canonical form. In the case
2933 of the second example above, the value of &$sender_host_address$& after
2934 conversion to the canonical form is
2935 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2937 Comments as to what is going on are written to the standard error file. These
2938 include lines beginning with &"LOG"& for anything that would have been logged.
2939 This facility is provided for testing configuration options for incoming
2940 messages, to make sure they implement the required policy. For example, you can
2941 test your relay controls using &%-bh%&.
2945 You can test features of the configuration that rely on ident (RFC 1413)
2946 information by using the &%-oMt%& option. However, Exim cannot actually perform
2947 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2950 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2951 are also skipped when testing using &%-bh%&. If you want these callouts to
2952 occur, use &%-bhc%& instead.
2954 Messages supplied during the testing session are discarded, and nothing is
2955 written to any of the real log files. There may be pauses when DNS (and other)
2956 lookups are taking place, and of course these may time out. The &%-oMi%& option
2957 can be used to specify a specific IP interface and port if this is important,
2958 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2959 session were authenticated.
2961 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2962 output just states whether a given recipient address from a given host is
2963 acceptable or not. See section &<<SECTcheckaccess>>&.
2965 Features such as authentication and encryption, where the client input is not
2966 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2967 specialized SMTP test program such as
2968 &url(https://www.jetmore.org/john/code/swaks/,swaks).
2970 .vitem &%-bhc%&&~<&'IP&~address'&>
2972 This option operates in the same way as &%-bh%&, except that address
2973 verification callouts are performed if required. This includes consulting and
2974 updating the callout cache database.
2978 .cindex "alias file" "building"
2979 .cindex "building alias file"
2980 .cindex "Sendmail compatibility" "&%-bi%& option"
2981 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2982 Exim does not have the concept of a single alias file, and so it cannot mimic
2983 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2984 tend to appear in various scripts such as NIS make files, so the option must be
2987 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2988 configuration option is run, under the uid and gid of the caller of Exim. If
2989 the &%-oA%& option is used, its value is passed to the command as an argument.
2990 The command set by &%bi_command%& may not contain arguments. The command can
2991 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2992 if this is required. If the &%bi_command%& option is not set, calling Exim with
2995 . // Keep :help first, then the rest in alphabetical order
2997 .oindex "&%-bI:help%&"
2998 .cindex "querying exim information"
2999 We shall provide various options starting &`-bI:`& for querying Exim for
3000 information. The output of many of these will be intended for machine
3001 consumption. This one is not. The &%-bI:help%& option asks Exim for a
3002 synopsis of supported options beginning &`-bI:`&. Use of any of these
3003 options shall cause Exim to exit after producing the requested output.
3006 .oindex "&%-bI:dscp%&"
3007 .cindex "DSCP" "values"
3008 This option causes Exim to emit an alphabetically sorted list of all
3009 recognised DSCP names.
3011 .vitem &%-bI:sieve%&
3012 .oindex "&%-bI:sieve%&"
3013 .cindex "Sieve filter" "capabilities"
3014 This option causes Exim to emit an alphabetically sorted list of all supported
3015 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3016 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3017 &`SIEVE`& capability response line. As the precise list may depend upon
3018 compile-time build options, which this option will adapt to, this is the only
3019 way to guarantee a correct response.
3023 .cindex "local message reception"
3024 This option runs an Exim receiving process that accepts an incoming,
3025 locally-generated message on the standard input. The recipients are given as the
3026 command arguments (except when &%-t%& is also present &-- see below). Each
3027 argument can be a comma-separated list of RFC 2822 addresses. This is the
3028 default option for selecting the overall action of an Exim call; it is assumed
3029 if no other conflicting option is present.
3031 If any addresses in the message are unqualified (have no domain), they are
3032 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3033 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3034 suppressing this for special cases.
3036 Policy checks on the contents of local messages can be enforced by means of
3037 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3039 .cindex "return code" "for &%-bm%&"
3040 The return code is zero if the message is successfully accepted. Otherwise, the
3041 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3044 .cindex "message" "format"
3045 .cindex "format" "message"
3046 .cindex "&""From""& line"
3047 .cindex "UUCP" "&""From""& line"
3048 .cindex "Sendmail compatibility" "&""From""& line"
3049 of the message must be as defined in RFC 2822, except that, for
3050 compatibility with Sendmail and Smail, a line in one of the forms
3052 From sender Fri Jan 5 12:55 GMT 1997
3053 From sender Fri, 5 Jan 97 12:55:01
3055 (with the weekday optional, and possibly with additional text after the date)
3056 is permitted to appear at the start of the message. There appears to be no
3057 authoritative specification of the format of this line. Exim recognizes it by
3058 matching against the regular expression defined by the &%uucp_from_pattern%&
3059 option, which can be changed if necessary.
3061 .oindex "&%-f%&" "overriding &""From""& line"
3062 The specified sender is treated as if it were given as the argument to the
3063 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3064 preference to the address taken from the message. The caller of Exim must be a
3065 trusted user for the sender of a message to be set in this way.
3067 .vitem &%-bmalware%&&~<&'filename'&>
3068 .oindex "&%-bmalware%&"
3069 .cindex "testing", "malware"
3070 .cindex "malware scan test"
3071 This debugging option causes Exim to scan the given file or directory
3072 (depending on the used scanner interface),
3073 using the malware scanning framework. The option of &%av_scanner%& influences
3074 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3075 the expansion should have defaults which apply to this invocation. ACLs are
3076 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3077 will never be populated and &%-bmalware%& will fail.
3079 Exim will have changed working directory before resolving the filename, so
3080 using fully qualified pathnames is advisable. Exim will be running as the Exim
3081 user when it tries to open the file, rather than as the invoking user.
3082 This option requires admin privileges.
3084 The &%-bmalware%& option will not be extended to be more generally useful,
3085 there are better tools for file-scanning. This option exists to help
3086 administrators verify their Exim and AV scanner configuration.
3090 .cindex "address qualification, suppressing"
3091 By default, Exim automatically qualifies unqualified addresses (those
3092 without domains) that appear in messages that are submitted locally (that
3093 is, not over TCP/IP). This qualification applies both to addresses in
3094 envelopes, and addresses in header lines. Sender addresses are qualified using
3095 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3096 defaults to the value of &%qualify_domain%&).
3098 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3099 being used to re-submit messages that originally came from remote hosts after
3100 content scanning, you probably do not want to qualify unqualified addresses in
3101 header lines. (Such lines will be present only if you have not enabled a header
3102 syntax check in the appropriate ACL.)
3104 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3105 messages that originate on the local host. When this is used, unqualified
3106 addresses in the envelope provoke errors (causing message rejection) and
3107 unqualified addresses in header lines are left alone.
3112 .cindex "configuration options" "extracting"
3113 .cindex "options" "configuration &-- extracting"
3114 If this option is given with no arguments, it causes the values of all Exim's
3115 main configuration options to be written to the standard output. The values
3116 of one or more specific options can be requested by giving their names as
3117 arguments, for example:
3119 exim -bP qualify_domain hold_domains
3121 .cindex "hiding configuration option values"
3122 .cindex "configuration options" "hiding value of"
3123 .cindex "options" "hiding value of"
3124 However, any option setting that is preceded by the word &"hide"& in the
3125 configuration file is not shown in full, except to an admin user. For other
3126 users, the output is as in this example:
3128 mysql_servers = <value not displayable>
3130 If &%config%& is given as an argument, the config is
3131 output, as it was parsed, any include file resolved, any comment removed.
3133 If &%config_file%& is given as an argument, the name of the runtime
3134 configuration file is output. (&%configure_file%& works too, for
3135 backward compatibility.)
3136 If a list of configuration files was supplied, the value that is output here
3137 is the name of the file that was actually used.
3139 .cindex "options" "hiding name of"
3140 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3141 name will not be output.
3143 .cindex "daemon" "process id (pid)"
3144 .cindex "pid (process id)" "of daemon"
3145 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3146 directories where log files and daemon pid files are written are output,
3147 respectively. If these values are unset, log files are written in a
3148 sub-directory of the spool directory called &%log%&, and the pid file is
3149 written directly into the spool directory.
3151 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3153 exim -bP +local_domains
3155 it searches for a matching named list of any type (domain, host, address, or
3156 local part) and outputs what it finds.
3158 .cindex "options" "router &-- extracting"
3159 .cindex "options" "transport &-- extracting"
3160 .cindex "options" "authenticator &-- extracting"
3161 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3162 followed by the name of an appropriate driver instance, the option settings for
3163 that driver are output. For example:
3165 exim -bP transport local_delivery
3167 The generic driver options are output first, followed by the driver's private
3168 options. A list of the names of drivers of a particular type can be obtained by
3169 using one of the words &%router_list%&, &%transport_list%&, or
3170 &%authenticator_list%&, and a complete list of all drivers with their option
3171 settings can be obtained by using &%routers%&, &%transports%&, or
3174 .cindex "environment"
3175 If &%environment%& is given as an argument, the set of environment
3176 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3179 .cindex "options" "macro &-- extracting"
3180 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3181 are available, similarly to the drivers. Because macros are sometimes used
3182 for storing passwords, this option is restricted.
3183 The output format is one item per line.
3184 For the "-bP macro <name>" form, if no such macro is found
3185 the exit status will be nonzero.
3189 .cindex "queue" "listing messages in"
3190 .cindex "listing" "messages in the queue"
3191 This option requests a listing of the contents of the mail queue on the
3192 standard output. If the &%-bp%& option is followed by a list of message ids,
3193 just those messages are listed. By default, this option can be used only by an
3194 admin user. However, the &%queue_list_requires_admin%& option can be set false
3195 to allow any user to see the queue.
3197 Each message in the queue is displayed as in the following example:
3199 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3200 red.king@looking-glass.fict.example
3203 .cindex "message" "size in queue listing"
3204 .cindex "size" "of message"
3205 The first line contains the length of time the message has been in the queue
3206 (in this case 25 minutes), the size of the message (2.9K), the unique local
3207 identifier for the message, and the message sender, as contained in the
3208 envelope. For bounce messages, the sender address is empty, and appears as
3209 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3210 the default sender address, the user's login name is shown in parentheses
3211 before the sender address.
3213 .cindex "frozen messages" "in queue listing"
3214 If the message is frozen (attempts to deliver it are suspended) then the text
3215 &"*** frozen ***"& is displayed at the end of this line.
3217 The recipients of the message (taken from the envelope, not the headers) are
3218 displayed on subsequent lines. Those addresses to which the message has already
3219 been delivered are marked with the letter D. If an original address gets
3220 expanded into several addresses via an alias or forward file, the original is
3221 displayed with a D only when deliveries for all of its child addresses are
3227 This option operates like &%-bp%&, but in addition it shows delivered addresses
3228 that were generated from the original top level address(es) in each message by
3229 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3235 .cindex "queue" "count of messages on"
3236 This option counts the number of messages in the queue, and writes the total
3237 to the standard output. It is restricted to admin users, unless
3238 &%queue_list_requires_admin%& is set false.
3243 This option operates like &%-bp%&, but the output is not sorted into
3244 chronological order of message arrival. This can speed it up when there are
3245 lots of messages in the queue, and is particularly useful if the output is
3246 going to be post-processed in a way that doesn't need the sorting.
3250 This option is a combination of &%-bpr%& and &%-bpa%&.
3254 This option is a combination of &%-bpr%& and &%-bpu%&.
3259 This option operates like &%-bp%& but shows only undelivered top-level
3260 addresses for each message displayed. Addresses generated by aliasing or
3261 forwarding are not shown, unless the message was deferred after processing by a
3262 router with the &%one_time%& option set.
3267 .cindex "testing" "retry configuration"
3268 .cindex "retry" "configuration testing"
3269 This option is for testing retry rules, and it must be followed by up to three
3270 arguments. It causes Exim to look for a retry rule that matches the values
3271 and to write it to the standard output. For example:
3273 exim -brt bach.comp.mus.example
3274 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3276 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3277 argument, which is required, can be a complete address in the form
3278 &'local_part@domain'&, or it can be just a domain name. If the second argument
3279 contains a dot, it is interpreted as an optional second domain name; if no
3280 retry rule is found for the first argument, the second is tried. This ties in
3281 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3282 rule is found that matches the host, one that matches the mail domain is
3283 sought. Finally, an argument that is the name of a specific delivery error, as
3284 used in setting up retry rules, can be given. For example:
3286 exim -brt haydn.comp.mus.example quota_3d
3287 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3292 .cindex "testing" "rewriting"
3293 .cindex "rewriting" "testing"
3294 This option is for testing address rewriting rules, and it must be followed by
3295 a single argument, consisting of either a local part without a domain, or a
3296 complete address with a fully qualified domain. Exim outputs how this address
3297 would be rewritten for each possible place it might appear. See chapter
3298 &<<CHAPrewrite>>& for further details.
3302 .cindex "SMTP" "batched incoming"
3303 .cindex "batched SMTP input"
3304 This option is used for batched SMTP input, which is an alternative interface
3305 for non-interactive local message submission. A number of messages can be
3306 submitted in a single run. However, despite its name, this is not really SMTP
3307 input. Exim reads each message's envelope from SMTP commands on the standard
3308 input, but generates no responses. If the caller is trusted, or
3309 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3310 believed; otherwise the sender is always the caller of Exim.
3312 The message itself is read from the standard input, in SMTP format (leading
3313 dots doubled), terminated by a line containing just a single dot. An error is
3314 provoked if the terminating dot is missing. A further message may then follow.
3316 As for other local message submissions, the contents of incoming batch SMTP
3317 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3318 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3319 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3321 Some other SMTP commands are recognized in the input. HELO and EHLO act
3322 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3323 QUIT quits, ignoring the rest of the standard input.
3325 .cindex "return code" "for &%-bS%&"
3326 If any error is encountered, reports are written to the standard output and
3327 error streams, and Exim gives up immediately. The return code is 0 if no error
3328 was detected; it is 1 if one or more messages were accepted before the error
3329 was detected; otherwise it is 2.
3331 More details of input using batched SMTP are given in section
3332 &<<SECTincomingbatchedSMTP>>&.
3336 .cindex "SMTP" "local input"
3337 .cindex "local SMTP input"
3338 This option causes Exim to accept one or more messages by reading SMTP commands
3339 on the standard input, and producing SMTP replies on the standard output. SMTP
3340 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3341 Some user agents use this interface as a way of passing locally-generated
3342 messages to the MTA.
3345 .cindex "sender" "source of"
3346 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3347 set, the senders of messages are taken from the SMTP MAIL commands.
3348 Otherwise the content of these commands is ignored and the sender is set up as
3349 the calling user. Unqualified addresses are automatically qualified using
3350 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3351 &%-bnq%& option is used.
3355 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3356 using a listening daemon. Exim can distinguish the two cases by checking
3357 whether the standard input is a TCP/IP socket. When Exim is called from
3358 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3359 above concerning senders and qualification do not apply. In this situation,
3360 Exim behaves in exactly the same way as it does when receiving a message via
3361 the listening daemon.
3365 .cindex "testing" "addresses"
3366 .cindex "address" "testing"
3367 This option runs Exim in address testing mode, in which each argument is taken
3368 as a recipient address to be tested for deliverability. The results are
3369 written to the standard output. If a test fails, and the caller is not an admin
3370 user, no details of the failure are output, because these might contain
3371 sensitive information such as usernames and passwords for database lookups.
3373 If no arguments are given, Exim runs in an interactive manner, prompting with a
3374 right angle bracket for addresses to be tested.
3376 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3377 &[readline()]& function, because it is running as &'root'& and there are
3380 Each address is handled as if it were the recipient address of a message
3381 (compare the &%-bv%& option). It is passed to the routers and the result is
3382 written to the standard output. However, any router that has
3383 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3384 genuine routing tests if your first router passes everything to a scanner
3387 .cindex "return code" "for &%-bt%&"
3388 The return code is 2 if any address failed outright; it is 1 if no address
3389 failed outright but at least one could not be resolved for some reason. Return
3390 code 0 is given only when all addresses succeed.
3392 .cindex "duplicate addresses"
3393 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3394 addresses after routing is complete, so that only one delivery takes place.
3395 This does not happen when testing with &%-bt%&; the full results of routing are
3398 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3399 routers in the configuration makes any tests on the sender address of a
3401 .oindex "&%-f%&" "for address testing"
3402 you can use the &%-f%& option to set an appropriate sender when running
3403 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3404 default qualifying domain. However, if you have set up (for example) routers
3405 whose behaviour depends on the contents of an incoming message, you cannot test
3406 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3411 .cindex "version number of Exim"
3412 This option causes Exim to write the current version number, compilation
3413 number, and compilation date of the &'exim'& binary to the standard output.
3414 It also lists the DBM library that is being used, the optional modules (such as
3415 specific lookup types), the drivers that are included in the binary, and the
3416 name of the runtime configuration file that is in use.
3418 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3419 configuration file. However, this is a static check only. It cannot check
3420 values that are to be expanded. For example, although a misspelt ACL verb is
3421 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3422 alone to discover (for example) all the typos in the configuration; some
3423 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3424 dynamic testing facilities.
3428 .cindex "verifying address" "using &%-bv%&"
3429 .cindex "address" "verification"
3430 This option runs Exim in address verification mode, in which each argument is
3431 taken as a recipient address to be verified by the routers. (This does
3432 not involve any verification callouts). During normal operation, verification
3433 happens mostly as a consequence processing a &%verify%& condition in an ACL
3434 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3435 including callouts, see the &%-bh%& and &%-bhc%& options.
3437 If verification fails, and the caller is not an admin user, no details of the
3438 failure are output, because these might contain sensitive information such as
3439 usernames and passwords for database lookups.
3441 If no arguments are given, Exim runs in an interactive manner, prompting with a
3442 right angle bracket for addresses to be verified.
3444 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3445 &[readline()]& function, because it is running as &'exim'& and there are
3448 Verification differs from address testing (the &%-bt%& option) in that routers
3449 that have &%no_verify%& set are skipped, and if the address is accepted by a
3450 router that has &%fail_verify%& set, verification fails. The address is
3451 verified as a recipient if &%-bv%& is used; to test verification for a sender
3452 address, &%-bvs%& should be used.
3454 If the &%-v%& option is not set, the output consists of a single line for each
3455 address, stating whether it was verified or not, and giving a reason in the
3456 latter case. Without &%-v%&, generating more than one address by redirection
3457 causes verification to end successfully, without considering the generated
3458 addresses. However, if just one address is generated, processing continues,
3459 and the generated address must verify successfully for the overall verification
3462 When &%-v%& is set, more details are given of how the address has been handled,
3463 and in the case of address redirection, all the generated addresses are also
3464 considered. Verification may succeed for some and fail for others.
3467 .cindex "return code" "for &%-bv%&"
3468 return code is 2 if any address failed outright; it is 1 if no address
3469 failed outright but at least one could not be resolved for some reason. Return
3470 code 0 is given only when all addresses succeed.
3472 If any of the routers in the configuration makes any tests on the sender
3473 address of a message, you should use the &%-f%& option to set an appropriate
3474 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3475 calling user at the default qualifying domain.
3479 This option acts like &%-bv%&, but verifies the address as a sender rather
3480 than a recipient address. This affects any rewriting and qualification that
3487 .cindex "inetd" "wait mode"
3488 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3489 similarly to the &%-bd%& option. All port specifications on the command-line
3490 and in the configuration file are ignored. Queue-running may not be specified.
3492 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3493 listening for connections. This permits the system to start up and have
3494 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3495 each port only when the first connection is received.
3497 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3498 which the daemon will exit, which should cause inetd to listen once more.
3500 .vitem &%-C%&&~<&'filelist'&>
3502 .cindex "configuration file" "alternate"
3503 .cindex "CONFIGURE_FILE"
3504 .cindex "alternate configuration file"
3505 This option causes Exim to find the runtime configuration file from the given
3506 list instead of from the list specified by the CONFIGURE_FILE
3507 compile-time setting. Usually, the list will consist of just a single filename,
3508 but it can be a colon-separated list of names. In this case, the first
3509 file that exists is used. Failure to open an existing file stops Exim from
3510 proceeding any further along the list, and an error is generated.
3512 When this option is used by a caller other than root, and the list is different
3513 from the compiled-in list, Exim gives up its root privilege immediately, and
3514 runs with the real and effective uid and gid set to those of the caller.
3515 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3516 file contains a list of full pathnames, one per line, for configuration files
3517 which are trusted. Root privilege is retained for any configuration file so
3518 listed, as long as the caller is the Exim user (or the user specified in the
3519 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3520 not writeable by inappropriate users or groups.
3522 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3523 configuration using &%-C%& right through message reception and delivery,
3524 even if the caller is root. The reception works, but by that time, Exim is
3525 running as the Exim user, so when it re-executes to regain privilege for the
3526 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3527 test reception and delivery using two separate commands (one to put a message
3528 in the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3530 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3531 prefix string with which any file named in a &%-C%& command line option
3532 must start. In addition, the filename must not contain the sequence &`/../`&.
3533 However, if the value of the &%-C%& option is identical to the value of
3534 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3535 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3536 unset, any filename can be used with &%-C%&.
3538 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3539 to a directory to which only root has access. This prevents someone who has
3540 broken into the Exim account from running a privileged Exim with an arbitrary
3543 The &%-C%& facility is useful for ensuring that configuration files are
3544 syntactically correct, but cannot be used for test deliveries, unless the
3545 caller is privileged, or unless it is an exotic configuration that does not
3546 require privilege. No check is made on the owner or group of the files
3547 specified by this option.
3550 .vitem &%-D%&<&'macro'&>=<&'value'&>
3552 .cindex "macro" "setting on command line"
3553 This option can be used to override macro definitions in the configuration file
3554 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3555 unprivileged caller, it causes Exim to give up its root privilege.
3556 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3557 completely disabled, and its use causes an immediate error exit.
3559 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3560 colon-separated list of macros which are considered safe and, if &%-D%& only
3561 supplies macros from this list, and the values are acceptable, then Exim will
3562 not give up root privilege if the caller is root, the Exim run-time user, or
3563 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3564 to be removed in the future. Acceptable values for the macros satisfy the
3565 regexp: &`^[A-Za-z0-9_/.-]*$`&
3567 The entire option (including equals sign if present) must all be within one
3568 command line item. &%-D%& can be used to set the value of a macro to the empty
3569 string, in which case the equals sign is optional. These two commands are
3575 To include spaces in a macro definition item, quotes must be used. If you use
3576 quotes, spaces are permitted around the macro name and the equals sign. For
3579 exim '-D ABC = something' ...
3581 &%-D%& may be repeated up to 10 times on a command line.
3582 Only macro names up to 22 letters long can be set.
3585 .vitem &%-d%&<&'debug&~options'&>
3587 .cindex "debugging" "list of selectors"
3588 .cindex "debugging" "&%-d%& option"
3589 This option causes debugging information to be written to the standard
3590 error stream. It is restricted to admin users because debugging output may show
3591 database queries that contain password information. Also, the details of users'
3592 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3593 writes an error message to the standard error stream and exits with a non-zero
3596 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3597 standard debugging data is output. This can be reduced, or increased to include
3598 some more rarely needed information, by directly following &%-d%& with a string
3599 made up of names preceded by plus or minus characters. These add or remove sets
3600 of debugging data, respectively. For example, &%-d+filter%& adds filter
3601 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3602 no spaces are allowed in the debug setting. The available debugging categories
3605 &`acl `& ACL interpretation
3606 &`auth `& authenticators
3607 &`deliver `& general delivery logic
3608 &`dns `& DNS lookups (see also resolver)
3609 &`dnsbl `& DNS black list (aka RBL) code
3610 &`exec `& arguments for &[execv()]& calls
3611 &`expand `& detailed debugging for string expansions
3612 &`filter `& filter handling
3613 &`hints_lookup `& hints data lookups
3614 &`host_lookup `& all types of name-to-IP address handling
3615 &`ident `& ident lookup
3616 &`interface `& lists of local interfaces
3617 &`lists `& matching things in lists
3618 &`load `& system load checks
3619 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3620 &<<CHAPlocalscan>>&)
3621 &`lookup `& general lookup code and all lookups
3622 &`memory `& memory handling
3623 &`noutf8 `& modifier: avoid UTF-8 line-drawing
3624 &`pid `& modifier: add pid to debug output lines
3625 &`process_info `& setting info for the process log
3626 &`queue_run `& queue runs
3627 &`receive `& general message reception logic
3628 &`resolver `& turn on the DNS resolver's debugging output
3629 &`retry `& retry handling
3630 &`rewrite `& address rewriting
3631 &`route `& address routing
3632 &`timestamp `& modifier: add timestamp to debug output lines
3634 &`transport `& transports
3635 &`uid `& changes of uid/gid and looking up uid/gid
3636 &`verify `& address verification logic
3637 &`all `& almost all of the above (see below), and also &%-v%&
3639 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3640 for &`-all`&. The reason for this is that &`+all`& is something that people
3641 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3642 is included, an awful lot of output that is very rarely of interest is
3643 generated, so it now has to be explicitly requested. However, &`-all`& does
3644 turn everything off.
3646 .cindex "resolver, debugging output"
3647 .cindex "DNS resolver, debugging output"
3648 The &`resolver`& option produces output only if the DNS resolver was compiled
3649 with DEBUG enabled. This is not the case in some operating systems. Also,
3650 unfortunately, debugging output from the DNS resolver is written to stdout
3653 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3654 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3655 However, the &`pid`& selector is forced when debugging is turned on for a
3656 daemon, which then passes it on to any re-executed Exims. Exim also
3657 automatically adds the pid to debug lines when several remote deliveries are
3660 The &`timestamp`& selector causes the current time to be inserted at the start
3661 of all debug output lines. This can be useful when trying to track down delays
3665 .cindex debugging "UTF-8 in"
3666 .cindex UTF-8 "in debug output"
3667 The &`noutf8`& selector disables the use of
3668 UTF-8 line-drawing characters to group related information.
3669 When disabled. ascii-art is used instead.
3670 Using the &`+all`& option does not set this modifier,
3673 If the &%debug_print%& option is set in any driver, it produces output whenever
3674 any debugging is selected, or if &%-v%& is used.
3676 .vitem &%-dd%&<&'debug&~options'&>
3678 This option behaves exactly like &%-d%& except when used on a command that
3679 starts a daemon process. In that case, debugging is turned off for the
3680 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3681 behaviour of the daemon without creating as much output as full debugging does.
3684 .oindex "&%-dropcr%&"
3685 This is an obsolete option that is now a no-op. It used to affect the way Exim
3686 handled CR and LF characters in incoming messages. What happens now is
3687 described in section &<<SECTlineendings>>&.
3691 .cindex "bounce message" "generating"
3692 This option specifies that an incoming message is a locally-generated delivery
3693 failure report. It is used internally by Exim when handling delivery failures
3694 and is not intended for external use. Its only effect is to stop Exim
3695 generating certain messages to the postmaster, as otherwise message cascades
3696 could occur in some situations. As part of the same option, a message id may
3697 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3698 new message contains the id, following &"R="&, as a cross-reference.
3701 .oindex "&%-e%&&'x'&"
3702 There are a number of Sendmail options starting with &%-oe%& which seem to be
3703 called by various programs without the leading &%o%& in the option. For
3704 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3705 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3707 .vitem &%-F%&&~<&'string'&>
3709 .cindex "sender" "name"
3710 .cindex "name" "of sender"
3711 This option sets the sender's full name for use when a locally-generated
3712 message is being accepted. In the absence of this option, the user's &'gecos'&
3713 entry from the password data is used. As users are generally permitted to alter
3714 their &'gecos'& entries, no security considerations are involved. White space
3715 between &%-F%& and the <&'string'&> is optional.
3717 .vitem &%-f%&&~<&'address'&>
3719 .cindex "sender" "address"
3720 .cindex "address" "sender"
3721 .cindex "trusted users"
3722 .cindex "envelope sender"
3723 .cindex "user" "trusted"
3724 This option sets the address of the envelope sender of a locally-generated
3725 message (also known as the return path). The option can normally be used only
3726 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3729 Processes running as root or the Exim user are always trusted. Other
3730 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3731 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3732 of a local message is set to the caller's login name at the default qualify
3735 There is one exception to the restriction on the use of &%-f%&: an empty sender
3736 can be specified by any user, trusted or not, to create a message that can
3737 never provoke a bounce. An empty sender can be specified either as an empty
3738 string, or as a pair of angle brackets with nothing between them, as in these
3739 examples of shell commands:
3741 exim -f '<>' user@domain
3742 exim -f "" user@domain
3744 In addition, the use of &%-f%& is not restricted when testing a filter file
3745 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3748 Allowing untrusted users to change the sender address does not of itself make
3749 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3750 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3751 though this can be overridden by setting &%no_local_from_check%&.
3754 .cindex "&""From""& line"
3755 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3756 given as two arguments or one combined argument). The sender of a
3757 locally-generated message can also be set (when permitted) by an initial
3758 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3759 if &%-f%& is also present, it overrides &"From&~"&.
3763 .cindex "submission fixups, suppressing (command-line)"
3764 This option is equivalent to an ACL applying:
3766 control = suppress_local_fixups
3768 for every message received. Note that Sendmail will complain about such
3769 bad formatting, where Exim silently just does not fix it up. This may change
3772 As this affects audit information, the caller must be a trusted user to use
3775 .vitem &%-h%&&~<&'number'&>
3777 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3778 This option is accepted for compatibility with Sendmail, but has no effect. (In
3779 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3784 .cindex "Solaris" "&'mail'& command"
3785 .cindex "dot" "in incoming non-SMTP message"
3786 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3787 line by itself should not terminate an incoming, non-SMTP message. I can find
3788 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3789 command in Solaris 2.4 uses it. See also &%-ti%&.
3791 .vitem &%-L%&&~<&'tag'&>
3793 .cindex "syslog" "process name; set with flag"
3794 This option is equivalent to setting &%syslog_processname%& in the config
3795 file and setting &%log_file_path%& to &`syslog`&.
3796 Its use is restricted to administrators. The configuration file has to be
3797 read and parsed, to determine access rights, before this is set and takes
3798 effect, so early configuration file errors will not honour this flag.
3800 The tag should not be longer than 32 characters.
3802 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3804 .cindex "forcing delivery"
3805 .cindex "delivery" "forcing attempt"
3806 .cindex "frozen messages" "forcing delivery"
3807 This option requests Exim to run a delivery attempt on each message in turn. If
3808 any of the messages are frozen, they are automatically thawed before the
3809 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3810 and &%hold_domains%& are ignored.
3813 .cindex "hints database" "overriding retry hints"
3814 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3815 the normal retry time has not yet been reached. This option requires the caller
3816 to be an admin user. However, there is an option called &%prod_requires_admin%&
3817 which can be set false to relax this restriction (and also the same requirement
3818 for the &%-q%&, &%-R%&, and &%-S%& options).
3820 The deliveries happen synchronously, that is, the original Exim process does
3821 not terminate until all the delivery attempts have finished. No output is
3822 produced unless there is a serious error. If you want to see what is happening,
3823 use the &%-v%& option as well, or inspect Exim's main log.
3825 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3827 .cindex "message" "adding recipients"
3828 .cindex "recipient" "adding"
3829 This option requests Exim to add the addresses to the list of recipients of the
3830 message (&"ar"& for &"add recipients"&). The first argument must be a message
3831 id, and the remaining ones must be email addresses. However, if the message is
3832 active (in the middle of a delivery attempt), it is not altered. This option
3833 can be used only by an admin user.
3835 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3836 &~<&'message&~id'&>"
3838 .cindex "SMTP" "passed connection"
3839 .cindex "SMTP" "multiple deliveries"
3840 .cindex "multiple SMTP deliveries"
3841 This option is not intended for use by external callers. It is used internally
3842 by Exim to invoke another instance of itself to deliver a waiting message using
3843 an existing SMTP connection, which is passed as the standard input. Details are
3844 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3845 must be root or the Exim user in order to use it.
3849 This option is not intended for use by external callers. It is used internally
3850 by Exim in conjunction with the &%-MC%& option. It signifies that the
3851 connection to the remote host has been authenticated.
3855 This option is not intended for use by external callers. It is used internally
3856 by Exim in conjunction with the &%-MC%& option. It signifies that the
3857 remote host supports the ESMTP &_DSN_& extension.
3859 .vitem &%-MCG%&&~<&'queue&~name'&>
3861 This option is not intended for use by external callers. It is used internally
3862 by Exim in conjunction with the &%-MC%& option. It signifies that an
3863 alternate queue is used, named by the following argument.
3867 This option is not intended for use by external callers. It is used internally
3868 by Exim in conjunction with the &%-MC%& option. It signifies that a
3869 remote host supports the ESMTP &_CHUNKING_& extension.
3873 This option is not intended for use by external callers. It is used internally
3874 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3875 which Exim is connected supports pipelining.
3877 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3879 This option is not intended for use by external callers. It is used internally
3880 by Exim in conjunction with the &%-MC%& option when the original delivery was
3881 started by a queue runner. It passes on the process id of the queue runner,
3882 together with the file descriptor number of an open pipe. Closure of the pipe
3883 signals the final completion of the sequence of processes that are passing
3884 messages through the same SMTP connection.
3888 This option is not intended for use by external callers. It is used internally
3889 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3890 SMTP SIZE option should be used on messages delivered down the existing
3895 This option is not intended for use by external callers. It is used internally
3896 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3897 host to which Exim is connected supports TLS encryption.
3899 .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
3901 This option is not intended for use by external callers. It is used internally
3902 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3903 connection is being proxied by a parent process for handling TLS encryption.
3904 The arguments give the local address and port being proxied, and the TLS cipher.
3906 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3908 .cindex "hints database" "not overridden by &%-Mc%&"
3909 .cindex "delivery" "manually started &-- not forced"
3910 This option requests Exim to run a delivery attempt on each message, in turn,
3911 but unlike the &%-M%& option, it does check for retry hints, and respects any
3912 that are found. This option is not very useful to external callers. It is
3913 provided mainly for internal use by Exim when it needs to re-invoke itself in
3914 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3915 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3916 respects retry times and other options such as &%hold_domains%& that are
3917 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3918 If you want to run a specific delivery as if in a queue run, you should use
3919 &%-q%& with a message id argument. A distinction between queue run deliveries
3920 and other deliveries is made in one or two places.
3922 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3924 .cindex "message" "changing sender"
3925 .cindex "sender" "changing"
3926 This option requests Exim to change the sender address in the message to the
3927 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3928 &"edit sender"&). There must be exactly two arguments. The first argument must
3929 be a message id, and the second one an email address. However, if the message
3930 is active (in the middle of a delivery attempt), its status is not altered.
3931 This option can be used only by an admin user.
3933 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3935 .cindex "freezing messages"
3936 .cindex "message" "manually freezing"
3937 This option requests Exim to mark each listed message as &"frozen"&. This
3938 prevents any delivery attempts taking place until the message is &"thawed"&,
3939 either manually or as a result of the &%auto_thaw%& configuration option.
3940 However, if any of the messages are active (in the middle of a delivery
3941 attempt), their status is not altered. This option can be used only by an admin
3944 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3946 .cindex "giving up on messages"
3947 .cindex "message" "abandoning delivery attempts"
3948 .cindex "delivery" "abandoning further attempts"
3949 This option requests Exim to give up trying to deliver the listed messages,
3950 including any that are frozen. However, if any of the messages are active,
3951 their status is not altered. For non-bounce messages, a delivery error message
3952 is sent to the sender, containing the text &"cancelled by administrator"&.
3953 Bounce messages are just discarded. This option can be used only by an admin
3956 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3958 .cindex "delivery" "cancelling all"
3959 This option requests Exim to mark all the recipient addresses in the messages
3960 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3961 message is active (in the middle of a delivery attempt), its status is not
3962 altered. This option can be used only by an admin user.
3964 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3966 .cindex "delivery" "cancelling by address"
3967 .cindex "recipient" "removing"
3968 .cindex "removing recipients"
3969 This option requests Exim to mark the given addresses as already delivered
3970 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3971 the remaining ones must be email addresses. These are matched to recipient
3972 addresses in the message in a case-sensitive manner. If the message is active
3973 (in the middle of a delivery attempt), its status is not altered. This option
3974 can be used only by an admin user.
3976 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3978 .cindex "removing messages"
3979 .cindex "abandoning mail"
3980 .cindex "message" "manually discarding"
3981 This option requests Exim to remove the given messages from the queue. No
3982 bounce messages are sent; each message is simply forgotten. However, if any of
3983 the messages are active, their status is not altered. This option can be used
3984 only by an admin user or by the user who originally caused the message to be
3985 placed in the queue.
3990 . .cindex REQUIRETLS
3991 . This option is used to request REQUIRETLS processing on the message.
3992 . It is used internally by Exim in conjunction with -E when generating
3996 .vitem &%-Mset%&&~<&'message&~id'&>
3998 .cindex "testing" "string expansion"
3999 .cindex "expansion" "testing"
4000 This option is useful only in conjunction with &%-be%& (that is, when testing
4001 string expansions). Exim loads the given message from its spool before doing
4002 the test expansions, thus setting message-specific variables such as
4003 &$message_size$& and the header variables. The &$recipients$& variable is made
4004 available. This feature is provided to make it easier to test expansions that
4005 make use of these variables. However, this option can be used only by an admin
4006 user. See also &%-bem%&.
4008 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4010 .cindex "thawing messages"
4011 .cindex "unfreezing messages"
4012 .cindex "frozen messages" "thawing"
4013 .cindex "message" "thawing frozen"
4014 This option requests Exim to &"thaw"& any of the listed messages that are
4015 &"frozen"&, so that delivery attempts can resume. However, if any of the
4016 messages are active, their status is not altered. This option can be used only
4019 .vitem &%-Mvb%&&~<&'message&~id'&>
4021 .cindex "listing" "message body"
4022 .cindex "message" "listing body of"
4023 This option causes the contents of the message body (-D) spool file to be
4024 written to the standard output. This option can be used only by an admin user.
4026 .vitem &%-Mvc%&&~<&'message&~id'&>
4028 .cindex "message" "listing in RFC 2822 format"
4029 .cindex "listing" "message in RFC 2822 format"
4030 This option causes a copy of the complete message (header lines plus body) to
4031 be written to the standard output in RFC 2822 format. This option can be used
4032 only by an admin user.
4034 .vitem &%-Mvh%&&~<&'message&~id'&>
4036 .cindex "listing" "message headers"
4037 .cindex "header lines" "listing"
4038 .cindex "message" "listing header lines"
4039 This option causes the contents of the message headers (-H) spool file to be
4040 written to the standard output. This option can be used only by an admin user.
4042 .vitem &%-Mvl%&&~<&'message&~id'&>
4044 .cindex "listing" "message log"
4045 .cindex "message" "listing message log"
4046 This option causes the contents of the message log spool file to be written to
4047 the standard output. This option can be used only by an admin user.
4051 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
4052 treats it that way too.
4056 .cindex "debugging" "&%-N%& option"
4057 .cindex "debugging" "suppressing delivery"
4058 This is a debugging option that inhibits delivery of a message at the transport
4059 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4060 it just doesn't actually transport the message, but instead behaves as if it
4061 had successfully done so. However, it does not make any updates to the retry
4062 database, and the log entries for deliveries are flagged with &"*>"& rather
4065 Because &%-N%& discards any message to which it applies, only root or the Exim
4066 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4067 words, an ordinary user can use it only when supplying an incoming message to
4068 which it will apply. Although transportation never fails when &%-N%& is set, an
4069 address may be deferred because of a configuration problem on a transport, or a
4070 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4071 the message, and applies to any subsequent delivery attempts that may happen
4076 This option is interpreted by Sendmail to mean &"no aliasing"&.
4077 For normal modes of operation, it is ignored by Exim.
4078 When combined with &%-bP%& it makes the output more terse (suppresses
4079 option names, environment values and config pretty printing).
4081 .vitem &%-O%&&~<&'data'&>
4083 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4086 .vitem &%-oA%&&~<&'file&~name'&>
4088 .cindex "Sendmail compatibility" "&%-oA%& option"
4089 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4090 alternative alias filename. Exim handles &%-bi%& differently; see the
4093 .vitem &%-oB%&&~<&'n'&>
4095 .cindex "SMTP" "passed connection"
4096 .cindex "SMTP" "multiple deliveries"
4097 .cindex "multiple SMTP deliveries"
4098 This is a debugging option which limits the maximum number of messages that can
4099 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4100 transport. If <&'n'&> is omitted, the limit is set to 1.
4104 .cindex "background delivery"
4105 .cindex "delivery" "in the background"
4106 This option applies to all modes in which Exim accepts incoming messages,
4107 including the listening daemon. It requests &"background"& delivery of such
4108 messages, which means that the accepting process automatically starts a
4109 delivery process for each message received, but does not wait for the delivery
4110 processes to finish.
4112 When all the messages have been received, the reception process exits,
4113 leaving the delivery processes to finish in their own time. The standard output
4114 and error streams are closed at the start of each delivery process.
4115 This is the default action if none of the &%-od%& options are present.
4117 If one of the queueing options in the configuration file
4118 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4119 overrides it if &%queue_only_override%& is set true, which is the default
4120 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4124 .cindex "foreground delivery"
4125 .cindex "delivery" "in the foreground"
4126 This option requests &"foreground"& (synchronous) delivery when Exim has
4127 accepted a locally-generated message. (For the daemon it is exactly the same as
4128 &%-odb%&.) A delivery process is automatically started to deliver the message,
4129 and Exim waits for it to complete before proceeding.
4131 The original Exim reception process does not finish until the delivery
4132 process for the final message has ended. The standard error stream is left open
4135 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4136 false and one of the queueing options in the configuration file is in effect.
4138 If there is a temporary delivery error during foreground delivery, the
4139 message is left in the queue for later delivery, and the original reception
4140 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4141 restricted configuration that never queues messages.
4146 This option is synonymous with &%-odf%&. It is provided for compatibility with
4151 .cindex "non-immediate delivery"
4152 .cindex "delivery" "suppressing immediate"
4153 .cindex "queueing incoming messages"
4154 This option applies to all modes in which Exim accepts incoming messages,
4155 including the listening daemon. It specifies that the accepting process should
4156 not automatically start a delivery process for each message received. Messages
4157 are placed in the queue, and remain there until a subsequent queue runner
4158 process encounters them. There are several configuration options (such as
4159 &%queue_only%&) that can be used to queue incoming messages under certain
4160 conditions. This option overrides all of them and also &%-odqs%&. It always
4165 .cindex "SMTP" "delaying delivery"
4166 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4167 However, like &%-odb%& and &%-odi%&, this option has no effect if
4168 &%queue_only_override%& is false and one of the queueing options in the
4169 configuration file is in effect.
4171 When &%-odqs%& does operate, a delivery process is started for each incoming
4172 message, in the background by default, but in the foreground if &%-odi%& is
4173 also present. The recipient addresses are routed, and local deliveries are done
4174 in the normal way. However, if any SMTP deliveries are required, they are not
4175 done at this time, so the message remains in the queue until a subsequent queue
4176 runner process encounters it. Because routing was done, Exim knows which
4177 messages are waiting for which hosts, and so a number of messages for the same
4178 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4179 configuration option has the same effect for specific domains. See also the
4184 .cindex "error" "reporting"
4185 If an error is detected while a non-SMTP message is being received (for
4186 example, a malformed address), the error is reported to the sender in a mail
4189 .cindex "return code" "for &%-oee%&"
4191 this error message is successfully sent, the Exim receiving process
4192 exits with a return code of zero. If not, the return code is 2 if the problem
4193 is that the original message has no recipients, or 1 for any other error.
4194 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4198 .cindex "error" "reporting"
4199 .cindex "return code" "for &%-oem%&"
4200 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4201 return code, whether or not the error message was successfully sent.
4202 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4206 .cindex "error" "reporting"
4207 If an error is detected while a non-SMTP message is being received, the
4208 error is reported by writing a message to the standard error file (stderr).
4209 .cindex "return code" "for &%-oep%&"
4210 The return code is 1 for all errors.
4214 .cindex "error" "reporting"
4215 This option is supported for compatibility with Sendmail, but has the same
4220 .cindex "error" "reporting"
4221 This option is supported for compatibility with Sendmail, but has the same
4226 .cindex "dot" "in incoming non-SMTP message"
4227 This option, which has the same effect as &%-i%&, specifies that a dot on a
4228 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4229 single dot does terminate, though Exim does no special processing for other
4230 lines that start with a dot. This option is set by default if Exim is called as
4231 &'rmail'&. See also &%-ti%&.
4234 .oindex "&%-oitrue%&"
4235 This option is treated as synonymous with &%-oi%&.
4237 .vitem &%-oMa%&&~<&'host&~address'&>
4239 .cindex "sender" "host address, specifying for local message"
4240 A number of options starting with &%-oM%& can be used to set values associated
4241 with remote hosts on locally-submitted messages (that is, messages not received
4242 over TCP/IP). These options can be used by any caller in conjunction with the
4243 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4244 other circumstances, they are ignored unless the caller is trusted.
4246 The &%-oMa%& option sets the sender host address. This may include a port
4247 number at the end, after a full stop (period). For example:
4249 exim -bs -oMa 10.9.8.7.1234
4251 An alternative syntax is to enclose the IP address in square brackets,
4252 followed by a colon and the port number:
4254 exim -bs -oMa [10.9.8.7]:1234
4256 The IP address is placed in the &$sender_host_address$& variable, and the
4257 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4258 are present on the command line, the sender host IP address is taken from
4259 whichever one is last.
4261 .vitem &%-oMaa%&&~<&'name'&>
4263 .cindex "authentication" "name, specifying for local message"
4264 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4265 option sets the value of &$sender_host_authenticated$& (the authenticator
4266 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4267 This option can be used with &%-bh%& and &%-bs%& to set up an
4268 authenticated SMTP session without actually using the SMTP AUTH command.
4270 .vitem &%-oMai%&&~<&'string'&>
4272 .cindex "authentication" "id, specifying for local message"
4273 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4274 option sets the value of &$authenticated_id$& (the id that was authenticated).
4275 This overrides the default value (the caller's login id, except with &%-bh%&,
4276 where there is no default) for messages from local sources. See chapter
4277 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4279 .vitem &%-oMas%&&~<&'address'&>
4281 .cindex "authentication" "sender, specifying for local message"
4282 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4283 option sets the authenticated sender value in &$authenticated_sender$&. It
4284 overrides the sender address that is created from the caller's login id for
4285 messages from local sources, except when &%-bh%& is used, when there is no
4286 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4287 specified on a MAIL command overrides this value. See chapter
4288 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4290 .vitem &%-oMi%&&~<&'interface&~address'&>
4292 .cindex "interface" "address, specifying for local message"
4293 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4294 option sets the IP interface address value. A port number may be included,
4295 using the same syntax as for &%-oMa%&. The interface address is placed in
4296 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4298 .vitem &%-oMm%&&~<&'message&~reference'&>
4300 .cindex "message reference" "message reference, specifying for local message"
4301 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4302 option sets the message reference, e.g. message-id, and is logged during
4303 delivery. This is useful when some kind of audit trail is required to tie
4304 messages together. The format of the message reference is checked and will
4305 abort if the format is invalid. The option will only be accepted if exim is
4306 running in trusted mode, not as any regular user.
4308 The best example of a message reference is when Exim sends a bounce message.
4309 The message reference is the message-id of the original message for which Exim
4310 is sending the bounce.
4312 .vitem &%-oMr%&&~<&'protocol&~name'&>
4314 .cindex "protocol, specifying for local message"
4315 .vindex "&$received_protocol$&"
4316 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4317 option sets the received protocol value that is stored in
4318 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4319 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4320 SMTP protocol names (see the description of &$received_protocol$& in section
4321 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4322 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4323 be set by &%-oMr%&. Repeated use of this option is not supported.
4325 .vitem &%-oMs%&&~<&'host&~name'&>
4327 .cindex "sender" "host name, specifying for local message"
4328 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4329 option sets the sender host name in &$sender_host_name$&. When this option is
4330 present, Exim does not attempt to look up a host name from an IP address; it
4331 uses the name it is given.
4333 .vitem &%-oMt%&&~<&'ident&~string'&>
4335 .cindex "sender" "ident string, specifying for local message"
4336 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4337 option sets the sender ident value in &$sender_ident$&. The default setting for
4338 local callers is the login id of the calling process, except when &%-bh%& is
4339 used, when there is no default.
4343 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4344 In Sendmail, this option means &"me too"&, indicating that the sender of a
4345 message should receive a copy of the message if the sender appears in an alias
4346 expansion. Exim always does this, so the option does nothing.
4350 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4351 This option is ignored. In Sendmail it specifies &"old style headers"&,
4352 whatever that means.
4354 .vitem &%-oP%&&~<&'path'&>
4356 .cindex "pid (process id)" "of daemon"
4357 .cindex "daemon" "process id (pid)"
4358 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4359 value. The option specifies the file to which the process id of the daemon is
4360 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4361 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4362 because in those cases, the normal pid file is not used.
4364 .vitem &%-or%&&~<&'time'&>
4366 .cindex "timeout" "for non-SMTP input"
4367 This option sets a timeout value for incoming non-SMTP messages. If it is not
4368 set, Exim will wait forever for the standard input. The value can also be set
4369 by the &%receive_timeout%& option. The format used for specifying times is
4370 described in section &<<SECTtimeformat>>&.
4372 .vitem &%-os%&&~<&'time'&>
4374 .cindex "timeout" "for SMTP input"
4375 .cindex "SMTP" "input timeout"
4376 This option sets a timeout value for incoming SMTP messages. The timeout
4377 applies to each SMTP command and block of data. The value can also be set by
4378 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4379 for specifying times is described in section &<<SECTtimeformat>>&.
4383 This option has exactly the same effect as &%-v%&.
4385 .vitem &%-oX%&&~<&'number&~or&~string'&>
4387 .cindex "TCP/IP" "setting listening ports"
4388 .cindex "TCP/IP" "setting listening interfaces"
4389 .cindex "port" "receiving TCP/IP"
4390 This option is relevant only when the &%-bd%& (start listening daemon) option
4391 is also given. It controls which ports and interfaces the daemon uses. Details
4392 of the syntax, and how it interacts with configuration file options, are given
4393 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4394 file is written unless &%-oP%& is also present to specify a pid filename.
4398 .cindex "Perl" "starting the interpreter"
4399 This option applies when an embedded Perl interpreter is linked with Exim (see
4400 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4401 option, forcing the starting of the interpreter to be delayed until it is
4406 .cindex "Perl" "starting the interpreter"
4407 This option applies when an embedded Perl interpreter is linked with Exim (see
4408 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4409 option, forcing the starting of the interpreter to occur as soon as Exim is
4412 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4414 For compatibility with Sendmail, this option is equivalent to
4416 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4418 It sets the incoming protocol and host name (for trusted callers). The
4419 host name and its colon can be omitted when only the protocol is to be set.
4420 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4421 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4422 or &`s`& using this option (but that does not seem a real limitation).
4423 Repeated use of this option is not supported.
4427 .cindex "queue runner" "starting manually"
4428 This option is normally restricted to admin users. However, there is a
4429 configuration option called &%prod_requires_admin%& which can be set false to
4430 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4431 and &%-S%& options).
4433 .cindex "queue runner" "description of operation"
4434 If other commandline options do not specify an action,
4435 the &%-q%& option starts one queue runner process. This scans the queue of
4436 waiting messages, and runs a delivery process for each one in turn. It waits
4437 for each delivery process to finish before starting the next one. A delivery
4438 process may not actually do any deliveries if the retry times for the addresses
4439 have not been reached. Use &%-qf%& (see below) if you want to override this.
4442 .cindex "SMTP" "passed connection"
4443 .cindex "SMTP" "multiple deliveries"
4444 .cindex "multiple SMTP deliveries"
4445 the delivery process spawns other processes to deliver other messages down
4446 passed SMTP connections, the queue runner waits for these to finish before
4449 When all the queued messages have been considered, the original queue runner
4450 process terminates. In other words, a single pass is made over the waiting
4451 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4452 this to be repeated periodically.
4454 Exim processes the waiting messages in an unpredictable order. It isn't very
4455 random, but it is likely to be different each time, which is all that matters.
4456 If one particular message screws up a remote MTA, other messages to the same
4457 MTA have a chance of getting through if they get tried first.
4459 It is possible to cause the messages to be processed in lexical message id
4460 order, which is essentially the order in which they arrived, by setting the
4461 &%queue_run_in_order%& option, but this is not recommended for normal use.
4463 .vitem &%-q%&<&'qflags'&>
4464 The &%-q%& option may be followed by one or more flag letters that change its
4465 behaviour. They are all optional, but if more than one is present, they must
4466 appear in the correct order. Each flag is described in a separate item below.
4470 .cindex "queue" "double scanning"
4471 .cindex "queue" "routing"
4472 .cindex "routing" "whole queue before delivery"
4473 An option starting with &%-qq%& requests a two-stage queue run. In the first
4474 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4475 every domain. Addresses are routed, local deliveries happen, but no remote
4478 .cindex "hints database" "remembering routing"
4479 The hints database that remembers which messages are waiting for specific hosts
4480 is updated, as if delivery to those hosts had been deferred. After this is
4481 complete, a second, normal queue scan happens, with routing and delivery taking
4482 place as normal. Messages that are routed to the same host should mostly be
4483 delivered down a single SMTP
4484 .cindex "SMTP" "passed connection"
4485 .cindex "SMTP" "multiple deliveries"
4486 .cindex "multiple SMTP deliveries"
4487 connection because of the hints that were set up during the first queue scan.
4488 This option may be useful for hosts that are connected to the Internet
4491 .vitem &%-q[q]i...%&
4493 .cindex "queue" "initial delivery"
4494 If the &'i'& flag is present, the queue runner runs delivery processes only for
4495 those messages that haven't previously been tried. (&'i'& stands for &"initial
4496 delivery"&.) This can be helpful if you are putting messages in the queue using
4497 &%-odq%& and want a queue runner just to process the new messages.
4499 .vitem &%-q[q][i]f...%&
4501 .cindex "queue" "forcing delivery"
4502 .cindex "delivery" "forcing in queue run"
4503 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4504 message, whereas without &'f'& only those non-frozen addresses that have passed
4505 their retry times are tried.
4507 .vitem &%-q[q][i]ff...%&
4509 .cindex "frozen messages" "forcing delivery"
4510 If &'ff'& is present, a delivery attempt is forced for every message, whether
4513 .vitem &%-q[q][i][f[f]]l%&
4515 .cindex "queue" "local deliveries only"
4516 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4517 be done. If a message requires any remote deliveries, it remains in the queue
4520 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4523 .cindex "named queues"
4524 .cindex "queue" "delivering specific messages"
4525 If the &'G'& flag and a name is present, the queue runner operates on the
4526 queue with the given name rather than the default queue.
4527 The name should not contain a &'/'& character.
4528 For a periodic queue run (see below)
4529 append to the name a slash and a time value.
4531 If other commandline options specify an action, a &'-qG<name>'& option
4532 will specify a queue to operate on.
4535 exim -bp -qGquarantine
4537 exim -qGoffpeak -Rf @special.domain.example
4540 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4541 When scanning the queue, Exim can be made to skip over messages whose ids are
4542 lexically less than a given value by following the &%-q%& option with a
4543 starting message id. For example:
4545 exim -q 0t5C6f-0000c8-00
4547 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4548 second message id is given, messages whose ids are lexically greater than it
4549 are also skipped. If the same id is given twice, for example,
4551 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4553 just one delivery process is started, for that message. This differs from
4554 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4555 that it counts as a delivery from a queue run. Note that the selection
4556 mechanism does not affect the order in which the messages are scanned. There
4557 are also other ways of selecting specific sets of messages for delivery in a
4558 queue run &-- see &%-R%& and &%-S%&.
4560 .vitem &%-q%&<&'qflags'&><&'time'&>
4561 .cindex "queue runner" "starting periodically"
4562 .cindex "periodic queue running"
4563 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4564 starting a queue runner process at intervals specified by the given time value
4565 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4566 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4567 single daemon process handles both functions. A common way of starting up a
4568 combined daemon at system boot time is to use a command such as
4570 /usr/exim/bin/exim -bd -q30m
4572 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4573 process every 30 minutes.
4575 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4576 pid file is written unless one is explicitly requested by the &%-oP%& option.
4578 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4580 This option is synonymous with &%-R%&. It is provided for Sendmail
4583 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4585 This option is synonymous with &%-S%&.
4587 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4589 .cindex "queue runner" "for specific recipients"
4590 .cindex "delivery" "to given domain"
4591 .cindex "domain" "delivery to"
4592 The <&'rsflags'&> may be empty, in which case the white space before the string
4593 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4594 which are the possible values for <&'rsflags'&>. White space is required if
4595 <&'rsflags'&> is not empty.
4597 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4598 perform a single queue run, except that, when scanning the messages on the
4599 queue, Exim processes only those that have at least one undelivered recipient
4600 address containing the given string, which is checked in a case-independent
4601 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4602 regular expression; otherwise it is a literal string.
4604 If you want to do periodic queue runs for messages with specific recipients,
4605 you can combine &%-R%& with &%-q%& and a time value. For example:
4607 exim -q25m -R @special.domain.example
4609 This example does a queue run for messages with recipients in the given domain
4610 every 25 minutes. Any additional flags that are specified with &%-q%& are
4611 applied to each queue run.
4613 Once a message is selected for delivery by this mechanism, all its addresses
4614 are processed. For the first selected message, Exim overrides any retry
4615 information and forces a delivery attempt for each undelivered address. This
4616 means that if delivery of any address in the first message is successful, any
4617 existing retry information is deleted, and so delivery attempts for that
4618 address in subsequently selected messages (which are processed without forcing)
4619 will run. However, if delivery of any address does not succeed, the retry
4620 information is updated, and in subsequently selected messages, the failing
4621 address will be skipped.
4623 .cindex "frozen messages" "forcing delivery"
4624 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4625 all selected messages, not just the first; frozen messages are included when
4628 The &%-R%& option makes it straightforward to initiate delivery of all messages
4629 to a given domain after a host has been down for some time. When the SMTP
4630 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4631 effect is to run Exim with the &%-R%& option, but it can be configured to run
4632 an arbitrary command instead.
4636 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4638 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4640 .cindex "delivery" "from given sender"
4641 .cindex "queue runner" "for specific senders"
4642 This option acts like &%-R%& except that it checks the string against each
4643 message's sender instead of against the recipients. If &%-R%& is also set, both
4644 conditions must be met for a message to be selected. If either of the options
4645 has &'f'& or &'ff'& in its flags, the associated action is taken.
4647 .vitem &%-Tqt%&&~<&'times'&>
4649 This is an option that is exclusively for use by the Exim testing suite. It is not
4650 recognized when Exim is run normally. It allows for the setting up of explicit
4651 &"queue times"& so that various warning/retry features can be tested.
4655 .cindex "recipient" "extracting from header lines"
4656 .cindex "&'Bcc:'& header line"
4657 .cindex "&'Cc:'& header line"
4658 .cindex "&'To:'& header line"
4659 When Exim is receiving a locally-generated, non-SMTP message on its standard
4660 input, the &%-t%& option causes the recipients of the message to be obtained
4661 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4662 from the command arguments. The addresses are extracted before any rewriting
4663 takes place and the &'Bcc:'& header line, if present, is then removed.
4665 .cindex "Sendmail compatibility" "&%-t%& option"
4666 If the command has any arguments, they specify addresses to which the message
4667 is &'not'& to be delivered. That is, the argument addresses are removed from
4668 the recipients list obtained from the headers. This is compatible with Smail 3
4669 and in accordance with the documented behaviour of several versions of
4670 Sendmail, as described in man pages on a number of operating systems (e.g.
4671 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4672 argument addresses to those obtained from the headers, and the O'Reilly
4673 Sendmail book documents it that way. Exim can be made to add argument addresses
4674 instead of subtracting them by setting the option
4675 &%extract_addresses_remove_arguments%& false.
4677 .cindex "&%Resent-%& header lines" "with &%-t%&"
4678 If there are any &%Resent-%& header lines in the message, Exim extracts
4679 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4680 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4681 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4682 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4684 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4685 message is resent several times). The RFC also specifies that they should be
4686 added at the front of the message, and separated by &'Received:'& lines. It is
4687 not at all clear how &%-t%& should operate in the present of multiple sets,
4688 nor indeed exactly what constitutes a &"set"&.
4689 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4690 are often added at the end of the header, and if a message is resent more than
4691 once, it is common for the original set of &%Resent-%& headers to be renamed as
4692 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4696 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4697 compatibility with Sendmail.
4699 .vitem &%-tls-on-connect%&
4700 .oindex "&%-tls-on-connect%&"
4701 .cindex "TLS" "use without STARTTLS"
4702 .cindex "TLS" "automatic start"
4703 This option is available when Exim is compiled with TLS support. It forces all
4704 incoming SMTP connections to behave as if the incoming port is listed in the
4705 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4706 &<<CHAPTLS>>& for further details.
4711 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4712 Sendmail uses this option for &"initial message submission"&, and its
4713 documentation states that in future releases, it may complain about
4714 syntactically invalid messages rather than fixing them when this flag is not
4715 set. Exim ignores this option.
4719 This option causes Exim to write information to the standard error stream,
4720 describing what it is doing. In particular, it shows the log lines for
4721 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4722 dialogue is shown. Some of the log lines shown may not actually be written to
4723 the log if the setting of &%log_selector%& discards them. Any relevant
4724 selectors are shown with each log line. If none are shown, the logging is
4729 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4730 National Language Support extended characters in the body of the mail item"&).
4731 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4734 .vitem &%-X%&&~<&'logfile'&>
4736 This option is interpreted by Sendmail to cause debug information to be sent
4737 to the named file. It is ignored by Exim.
4739 .vitem &%-z%&&~<&'log-line'&>
4741 This option writes its argument to Exim's logfile.
4742 Use is restricted to administrators; the intent is for operational notes.
4743 Quotes should be used to maintain a multi-word item as a single argument,
4751 . ////////////////////////////////////////////////////////////////////////////
4752 . Insert a stylized DocBook comment here, to identify the end of the command
4753 . line options. This is for the benefit of the Perl script that automatically
4754 . creates a man page for the options.
4755 . ////////////////////////////////////////////////////////////////////////////
4758 <!-- === End of command line options === -->
4765 . ////////////////////////////////////////////////////////////////////////////
4766 . ////////////////////////////////////////////////////////////////////////////
4769 .chapter "The Exim runtime configuration file" "CHAPconf" &&&
4770 "The runtime configuration file"
4772 .cindex "runtime configuration"
4773 .cindex "configuration file" "general description"
4774 .cindex "CONFIGURE_FILE"
4775 .cindex "configuration file" "errors in"
4776 .cindex "error" "in configuration file"
4777 .cindex "return code" "for bad configuration"
4778 Exim uses a single runtime configuration file that is read whenever an Exim
4779 binary is executed. Note that in normal operation, this happens frequently,
4780 because Exim is designed to operate in a distributed manner, without central
4783 If a syntax error is detected while reading the configuration file, Exim
4784 writes a message on the standard error, and exits with a non-zero return code.
4785 The message is also written to the panic log. &*Note*&: Only simple syntax
4786 errors can be detected at this time. The values of any expanded options are
4787 not checked until the expansion happens, even when the expansion does not
4788 actually alter the string.
4790 The name of the configuration file is compiled into the binary for security
4791 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4792 most configurations, this specifies a single file. However, it is permitted to
4793 give a colon-separated list of filenames, in which case Exim uses the first
4794 existing file in the list.
4797 .cindex "EXIM_GROUP"
4798 .cindex "CONFIGURE_OWNER"
4799 .cindex "CONFIGURE_GROUP"
4800 .cindex "configuration file" "ownership"
4801 .cindex "ownership" "configuration file"
4802 The runtime configuration file must be owned by root or by the user that is
4803 specified at compile time by the CONFIGURE_OWNER option (if set). The
4804 configuration file must not be world-writeable, or group-writeable unless its
4805 group is the root group or the one specified at compile time by the
4806 CONFIGURE_GROUP option.
4808 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4809 to root, anybody who is able to edit the runtime configuration file has an
4810 easy way to run commands as root. If you specify a user or group in the
4811 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4812 who are members of that group will trivially be able to obtain root privileges.
4814 Up to Exim version 4.72, the runtime configuration file was also permitted to
4815 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4816 since it offered a simple privilege escalation for any attacker who managed to
4817 compromise the Exim user account.
4819 A default configuration file, which will work correctly in simple situations,
4820 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4821 defines just one filename, the installation process copies the default
4822 configuration to a new file of that name if it did not previously exist. If
4823 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4824 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4829 .section "Using a different configuration file" "SECID40"
4830 .cindex "configuration file" "alternate"
4831 A one-off alternate configuration can be specified by the &%-C%& command line
4832 option, which may specify a single file or a list of files. However, when
4833 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4834 unless the argument for &%-C%& is identical to the built-in value from
4835 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4836 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4837 is useful mainly for checking the syntax of configuration files before
4838 installing them. No owner or group checks are done on a configuration file
4839 specified by &%-C%&, if root privilege has been dropped.
4841 Even the Exim user is not trusted to specify an arbitrary configuration file
4842 with the &%-C%& option to be used with root privileges, unless that file is
4843 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4844 testing a configuration using &%-C%& right through message reception and
4845 delivery, even if the caller is root. The reception works, but by that time,
4846 Exim is running as the Exim user, so when it re-execs to regain privilege for
4847 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4848 can test reception and delivery using two separate commands (one to put a
4849 message in the queue, using &%-odq%&, and another to do the delivery, using
4852 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4853 prefix string with which any file named in a &%-C%& command line option must
4854 start. In addition, the filename must not contain the sequence &"&`/../`&"&.
4855 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any
4856 filename can be used with &%-C%&.
4858 One-off changes to a configuration can be specified by the &%-D%& command line
4859 option, which defines and overrides values for macros used inside the
4860 configuration file. However, like &%-C%&, the use of this option by a
4861 non-privileged user causes Exim to discard its root privilege.
4862 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4863 completely disabled, and its use causes an immediate error exit.
4865 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4866 to declare certain macro names trusted, such that root privilege will not
4867 necessarily be discarded.
4868 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4869 considered safe and, if &%-D%& only supplies macros from this list, and the
4870 values are acceptable, then Exim will not give up root privilege if the caller
4871 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4872 transition mechanism and is expected to be removed in the future. Acceptable
4873 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4875 Some sites may wish to use the same Exim binary on different machines that
4876 share a file system, but to use different configuration files on each machine.
4877 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4878 looks for a file whose name is the configuration filename followed by a dot
4879 and the machine's node name, as obtained from the &[uname()]& function. If this
4880 file does not exist, the standard name is tried. This processing occurs for
4881 each filename in the list given by CONFIGURE_FILE or &%-C%&.
4883 In some esoteric situations different versions of Exim may be run under
4884 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4885 help with this. See the comments in &_src/EDITME_& for details.
4889 .section "Configuration file format" "SECTconffilfor"
4890 .cindex "configuration file" "format of"
4891 .cindex "format" "configuration file"
4892 Exim's configuration file is divided into a number of different parts. General
4893 option settings must always appear at the start of the file. The other parts
4894 are all optional, and may appear in any order. Each part other than the first
4895 is introduced by the word &"begin"& followed by at least one literal
4896 space, and the name of the part. The optional parts are:
4899 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4902 .cindex "AUTH" "configuration"
4903 &'authenticators'&: Configuration settings for the authenticator drivers. These
4904 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4906 &'routers'&: Configuration settings for the router drivers. Routers process
4907 addresses and determine how the message is to be delivered (see chapters
4908 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4910 &'transports'&: Configuration settings for the transport drivers. Transports
4911 define mechanisms for copying messages to destinations (see chapters
4912 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4914 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4915 If there is no retry section, or if it is empty (that is, no retry rules are
4916 defined), Exim will not retry deliveries. In this situation, temporary errors
4917 are treated the same as permanent errors. Retry rules are discussed in chapter
4920 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4921 when new addresses are generated during delivery. Rewriting is discussed in
4922 chapter &<<CHAPrewrite>>&.
4924 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4925 want to use this feature, you must set
4927 LOCAL_SCAN_HAS_OPTIONS=yes
4929 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4930 facility are given in chapter &<<CHAPlocalscan>>&.
4933 .cindex "configuration file" "leading white space in"
4934 .cindex "configuration file" "trailing white space in"
4935 .cindex "white space" "in configuration file"
4936 Leading and trailing white space in configuration lines is always ignored.
4938 Blank lines in the file, and lines starting with a # character (ignoring
4939 leading white space) are treated as comments and are ignored. &*Note*&: A
4940 # character other than at the beginning of a line is not treated specially,
4941 and does not introduce a comment.
4943 Any non-comment line can be continued by ending it with a backslash. Note that
4944 the general rule for white space means that trailing white space after the
4945 backslash and leading white space at the start of continuation
4946 lines is ignored. Comment lines beginning with # (but not empty lines) may
4947 appear in the middle of a sequence of continuation lines.
4949 A convenient way to create a configuration file is to start from the
4950 default, which is supplied in &_src/configure.default_&, and add, delete, or
4951 change settings as required.
4953 The ACLs, retry rules, and rewriting rules have their own syntax which is
4954 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4955 respectively. The other parts of the configuration file have some syntactic
4956 items in common, and these are described below, from section &<<SECTcos>>&
4957 onwards. Before that, the inclusion, macro, and conditional facilities are
4962 .section "File inclusions in the configuration file" "SECID41"
4963 .cindex "inclusions in configuration file"
4964 .cindex "configuration file" "including other files"
4965 .cindex "&`.include`& in configuration file"
4966 .cindex "&`.include_if_exists`& in configuration file"
4967 You can include other files inside Exim's runtime configuration file by
4970 &`.include`& <&'filename'&>
4971 &`.include_if_exists`& <&'filename'&>
4973 on a line by itself. Double quotes round the filename are optional. If you use
4974 the first form, a configuration error occurs if the file does not exist; the
4975 second form does nothing for non-existent files.
4976 The first form allows a relative name. It is resolved relative to
4977 the directory of the including file. For the second form an absolute filename
4980 Includes may be nested to any depth, but remember that Exim reads its
4981 configuration file often, so it is a good idea to keep them to a minimum.
4982 If you change the contents of an included file, you must HUP the daemon,
4983 because an included file is read only when the configuration itself is read.
4985 The processing of inclusions happens early, at a physical line level, so, like
4986 comment lines, an inclusion can be used in the middle of an option setting,
4989 hosts_lookup = a.b.c \
4992 Include processing happens after macro processing (see below). Its effect is to
4993 process the lines of the included file as if they occurred inline where the
4998 .section "Macros in the configuration file" "SECTmacrodefs"
4999 .cindex "macro" "description of"
5000 .cindex "configuration file" "macros"
5001 If a line in the main part of the configuration (that is, before the first
5002 &"begin"& line) begins with an upper case letter, it is taken as a macro
5003 definition, and must be of the form
5005 <&'name'&> = <&'rest of line'&>
5007 The name must consist of letters, digits, and underscores, and need not all be
5008 in upper case, though that is recommended. The rest of the line, including any
5009 continuations, is the replacement text, and has leading and trailing white
5010 space removed. Quotes are not removed. The replacement text can never end with
5011 a backslash character, but this doesn't seem to be a serious limitation.
5013 Macros may also be defined between router, transport, authenticator, or ACL
5014 definitions. They may not, however, be defined within an individual driver or
5015 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
5017 .section "Macro substitution" "SECID42"
5018 Once a macro is defined, all subsequent lines in the file (and any included
5019 files) are scanned for the macro name; if there are several macros, the line is
5020 scanned for each, in turn, in the order in which the macros are defined. The
5021 replacement text is not re-scanned for the current macro, though it is scanned
5022 for subsequently defined macros. For this reason, a macro name may not contain
5023 the name of a previously defined macro as a substring. You could, for example,
5026 &`ABCD_XYZ = `&<&'something'&>
5027 &`ABCD = `&<&'something else'&>
5029 but putting the definitions in the opposite order would provoke a configuration
5030 error. Macro expansion is applied to individual physical lines from the file,
5031 before checking for line continuation or file inclusion (see above). If a line
5032 consists solely of a macro name, and the expansion of the macro is empty, the
5033 line is ignored. A macro at the start of a line may turn the line into a
5034 comment line or a &`.include`& line.
5037 .section "Redefining macros" "SECID43"
5038 Once defined, the value of a macro can be redefined later in the configuration
5039 (or in an included file). Redefinition is specified by using &'=='& instead of
5044 MAC == updated value
5046 Redefinition does not alter the order in which the macros are applied to the
5047 subsequent lines of the configuration file. It is still the same order in which
5048 the macros were originally defined. All that changes is the macro's value.
5049 Redefinition makes it possible to accumulate values. For example:
5053 MAC == MAC and something added
5055 This can be helpful in situations where the configuration file is built
5056 from a number of other files.
5058 .section "Overriding macro values" "SECID44"
5059 The values set for macros in the configuration file can be overridden by the
5060 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5061 used, unless called by root or the Exim user. A definition on the command line
5062 using the &%-D%& option causes all definitions and redefinitions within the
5067 .section "Example of macro usage" "SECID45"
5068 As an example of macro usage, consider a configuration where aliases are looked
5069 up in a MySQL database. It helps to keep the file less cluttered if long
5070 strings such as SQL statements are defined separately as macros, for example:
5072 ALIAS_QUERY = select mailbox from user where \
5073 login='${quote_mysql:$local_part}';
5075 This can then be used in a &(redirect)& router setting like this:
5077 data = ${lookup mysql{ALIAS_QUERY}}
5079 In earlier versions of Exim macros were sometimes used for domain, host, or
5080 address lists. In Exim 4 these are handled better by named lists &-- see
5081 section &<<SECTnamedlists>>&.
5084 .section "Builtin macros" "SECTbuiltinmacros"
5085 Exim defines some macros depending on facilities available, which may
5086 differ due to build-time definitions and from one release to another.
5087 All of these macros start with an underscore.
5088 They can be used to conditionally include parts of a configuration
5091 The following classes of macros are defined:
5093 &` _HAVE_* `& build-time defines
5094 &` _DRIVER_ROUTER_* `& router drivers
5095 &` _DRIVER_TRANSPORT_* `& transport drivers
5096 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5097 &` _LOG_* `& log_selector values
5098 &` _OPT_MAIN_* `& main config options
5099 &` _OPT_ROUTERS_* `& generic router options
5100 &` _OPT_TRANSPORTS_* `& generic transport options
5101 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5102 &` _OPT_ROUTER_*_* `& private router options
5103 &` _OPT_TRANSPORT_*_* `& private transport options
5104 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5107 Use an &"exim -bP macros"& command to get the list of macros.
5110 .section "Conditional skips in the configuration file" "SECID46"
5111 .cindex "configuration file" "conditional skips"
5112 .cindex "&`.ifdef`&"
5113 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5114 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5115 portions of the configuration file. The processing happens whenever the file is
5116 read (that is, when an Exim binary starts to run).
5118 The implementation is very simple. Instances of the first four directives must
5119 be followed by text that includes the names of one or macros. The condition
5120 that is tested is whether or not any macro substitution has taken place in the
5124 message_size_limit = 50M
5126 message_size_limit = 100M
5129 sets a message size limit of 50M if the macro &`AAA`& is defined
5130 (or &`A`& or &`AA`&), and 100M
5131 otherwise. If there is more than one macro named on the line, the condition
5132 is true if any of them are defined. That is, it is an &"or"& condition. To
5133 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5135 Although you can use a macro expansion to generate one of these directives,
5136 it is not very useful, because the condition &"there was a macro substitution
5137 in this line"& will always be true.
5139 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5140 to clarify complicated nestings.
5144 .section "Common option syntax" "SECTcos"
5145 .cindex "common option syntax"
5146 .cindex "syntax of common options"
5147 .cindex "configuration file" "common option syntax"
5148 For the main set of options, driver options, and &[local_scan()]& options,
5149 each setting is on a line by itself, and starts with a name consisting of
5150 lower-case letters and underscores. Many options require a data value, and in
5151 these cases the name must be followed by an equals sign (with optional white
5152 space) and then the value. For example:
5154 qualify_domain = mydomain.example.com
5156 .cindex "hiding configuration option values"
5157 .cindex "configuration options" "hiding value of"
5158 .cindex "options" "hiding value of"
5159 Some option settings may contain sensitive data, for example, passwords for
5160 accessing databases. To stop non-admin users from using the &%-bP%& command
5161 line option to read these values, you can precede the option settings with the
5162 word &"hide"&. For example:
5164 hide mysql_servers = localhost/users/admin/secret-password
5166 For non-admin users, such options are displayed like this:
5168 mysql_servers = <value not displayable>
5170 If &"hide"& is used on a driver option, it hides the value of that option on
5171 all instances of the same driver.
5173 The following sections describe the syntax used for the different data types
5174 that are found in option settings.
5177 .section "Boolean options" "SECID47"
5178 .cindex "format" "boolean"
5179 .cindex "boolean configuration values"
5180 .oindex "&%no_%&&'xxx'&"
5181 .oindex "&%not_%&&'xxx'&"
5182 Options whose type is given as boolean are on/off switches. There are two
5183 different ways of specifying such options: with and without a data value. If
5184 the option name is specified on its own without data, the switch is turned on;
5185 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5186 boolean options may be followed by an equals sign and one of the words
5187 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5188 the following two settings have exactly the same effect:
5193 The following two lines also have the same (opposite) effect:
5198 You can use whichever syntax you prefer.
5203 .section "Integer values" "SECID48"
5204 .cindex "integer configuration values"
5205 .cindex "format" "integer"
5206 If an option's type is given as &"integer"&, the value can be given in decimal,
5207 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5208 number is assumed. Otherwise, it is treated as an octal number unless it starts
5209 with the characters &"0x"&, in which case the remainder is interpreted as a
5212 If an integer value is followed by the letter K, it is multiplied by 1024; if
5213 it is followed by the letter M, it is multiplied by 1024x1024;
5214 if by the letter G, 1024x1024x1024.
5216 of integer option settings are output, values which are an exact multiple of
5217 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5218 and M. The printing style is independent of the actual input format that was
5222 .section "Octal integer values" "SECID49"
5223 .cindex "integer format"
5224 .cindex "format" "octal integer"
5225 If an option's type is given as &"octal integer"&, its value is always
5226 interpreted as an octal number, whether or not it starts with the digit zero.
5227 Such options are always output in octal.
5230 .section "Fixed point numbers" "SECID50"
5231 .cindex "fixed point configuration values"
5232 .cindex "format" "fixed point"
5233 If an option's type is given as &"fixed-point"&, its value must be a decimal
5234 integer, optionally followed by a decimal point and up to three further digits.
5238 .section "Time intervals" "SECTtimeformat"
5239 .cindex "time interval" "specifying in configuration"
5240 .cindex "format" "time interval"
5241 A time interval is specified as a sequence of numbers, each followed by one of
5242 the following letters, with no intervening white space:
5252 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5253 intervals are output in the same format. Exim does not restrict the values; it
5254 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5258 .section "String values" "SECTstrings"
5259 .cindex "string" "format of configuration values"
5260 .cindex "format" "string"
5261 If an option's type is specified as &"string"&, the value can be specified with
5262 or without double-quotes. If it does not start with a double-quote, the value
5263 consists of the remainder of the line plus any continuation lines, starting at
5264 the first character after any leading white space, with trailing white space
5265 removed, and with no interpretation of the characters in the string. Because
5266 Exim removes comment lines (those beginning with #) at an early stage, they can
5267 appear in the middle of a multi-line string. The following two settings are
5268 therefore equivalent:
5270 trusted_users = uucp:mail
5271 trusted_users = uucp:\
5272 # This comment line is ignored
5275 .cindex "string" "quoted"
5276 .cindex "escape characters in quoted strings"
5277 If a string does start with a double-quote, it must end with a closing
5278 double-quote, and any backslash characters other than those used for line
5279 continuation are interpreted as escape characters, as follows:
5282 .irow &`\\`& "single backslash"
5283 .irow &`\n`& "newline"
5284 .irow &`\r`& "carriage return"
5286 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5287 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5291 If a backslash is followed by some other character, including a double-quote
5292 character, that character replaces the pair.
5294 Quoting is necessary only if you want to make use of the backslash escapes to
5295 insert special characters, or if you need to specify a value with leading or
5296 trailing spaces. These cases are rare, so quoting is almost never needed in
5297 current versions of Exim. In versions of Exim before 3.14, quoting was required
5298 in order to continue lines, so you may come across older configuration files
5299 and examples that apparently quote unnecessarily.
5302 .section "Expanded strings" "SECID51"
5303 .cindex "expansion" "definition of"
5304 Some strings in the configuration file are subjected to &'string expansion'&,
5305 by which means various parts of the string may be changed according to the
5306 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5307 is as just described; in particular, the handling of backslashes in quoted
5308 strings is done as part of the input process, before expansion takes place.
5309 However, backslash is also an escape character for the expander, so any
5310 backslashes that are required for that reason must be doubled if they are
5311 within a quoted configuration string.
5314 .section "User and group names" "SECID52"
5315 .cindex "user name" "format of"
5316 .cindex "format" "user name"
5317 .cindex "groups" "name format"
5318 .cindex "format" "group name"
5319 User and group names are specified as strings, using the syntax described
5320 above, but the strings are interpreted specially. A user or group name must
5321 either consist entirely of digits, or be a name that can be looked up using the
5322 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5325 .section "List construction" "SECTlistconstruct"
5326 .cindex "list" "syntax of in configuration"
5327 .cindex "format" "list item in configuration"
5328 .cindex "string" "list, definition of"
5329 The data for some configuration options is a list of items, with colon as the
5330 default separator. Many of these options are shown with type &"string list"& in
5331 the descriptions later in this document. Others are listed as &"domain list"&,
5332 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5333 are all the same; however, those other than &"string list"& are subject to
5334 particular kinds of interpretation, as described in chapter
5335 &<<CHAPdomhosaddlists>>&.
5337 In all these cases, the entire list is treated as a single string as far as the
5338 input syntax is concerned. The &%trusted_users%& setting in section
5339 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5340 in a list, it must be entered as two colons. Leading and trailing white space
5341 on each item in a list is ignored. This makes it possible to include items that
5342 start with a colon, and in particular, certain forms of IPv6 address. For
5345 local_interfaces = 127.0.0.1 : ::::1
5347 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5349 &*Note*&: Although leading and trailing white space is ignored in individual
5350 list items, it is not ignored when parsing the list. The space after the first
5351 colon in the example above is necessary. If it were not there, the list would
5352 be interpreted as the two items 127.0.0.1:: and 1.
5354 .section "Changing list separators" "SECTlistsepchange"
5355 .cindex "list separator" "changing"
5356 .cindex "IPv6" "addresses in lists"
5357 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5358 introduced to allow the separator character to be changed. If a list begins
5359 with a left angle bracket, followed by any punctuation character, that
5360 character is used instead of colon as the list separator. For example, the list
5361 above can be rewritten to use a semicolon separator like this:
5363 local_interfaces = <; 127.0.0.1 ; ::1
5365 This facility applies to all lists, with the exception of the list in
5366 &%log_file_path%&. It is recommended that the use of non-colon separators be
5367 confined to circumstances where they really are needed.
5369 .cindex "list separator" "newline as"
5370 .cindex "newline" "as list separator"
5371 It is also possible to use newline and other control characters (those with
5372 code values less than 32, plus DEL) as separators in lists. Such separators
5373 must be provided literally at the time the list is processed. For options that
5374 are string-expanded, you can write the separator using a normal escape
5375 sequence. This will be processed by the expander before the string is
5376 interpreted as a list. For example, if a newline-separated list of domains is
5377 generated by a lookup, you can process it directly by a line such as this:
5379 domains = <\n ${lookup mysql{.....}}
5381 This avoids having to change the list separator in such data. You are unlikely
5382 to want to use a control character as a separator in an option that is not
5383 expanded, because the value is literal text. However, it can be done by giving
5384 the value in quotes. For example:
5386 local_interfaces = "<\n 127.0.0.1 \n ::1"
5388 Unlike printing character separators, which can be included in list items by
5389 doubling, it is not possible to include a control character as data when it is
5390 set as the separator. Two such characters in succession are interpreted as
5391 enclosing an empty list item.
5395 .section "Empty items in lists" "SECTempitelis"
5396 .cindex "list" "empty item in"
5397 An empty item at the end of a list is always ignored. In other words, trailing
5398 separator characters are ignored. Thus, the list in
5400 senders = user@domain :
5402 contains only a single item. If you want to include an empty string as one item
5403 in a list, it must not be the last item. For example, this list contains three
5404 items, the second of which is empty:
5406 senders = user1@domain : : user2@domain
5408 &*Note*&: There must be white space between the two colons, as otherwise they
5409 are interpreted as representing a single colon data character (and the list
5410 would then contain just one item). If you want to specify a list that contains
5411 just one, empty item, you can do it as in this example:
5415 In this case, the first item is empty, and the second is discarded because it
5416 is at the end of the list.
5421 .section "Format of driver configurations" "SECTfordricon"
5422 .cindex "drivers" "configuration format"
5423 There are separate parts in the configuration for defining routers, transports,
5424 and authenticators. In each part, you are defining a number of driver
5425 instances, each with its own set of options. Each driver instance is defined by
5426 a sequence of lines like this:
5428 <&'instance name'&>:
5433 In the following example, the instance name is &(localuser)&, and it is
5434 followed by three options settings:
5439 transport = local_delivery
5441 For each driver instance, you specify which Exim code module it uses &-- by the
5442 setting of the &%driver%& option &-- and (optionally) some configuration
5443 settings. For example, in the case of transports, if you want a transport to
5444 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5445 a local file you would use the &(appendfile)& driver. Each of the drivers is
5446 described in detail in its own separate chapter later in this manual.
5448 You can have several routers, transports, or authenticators that are based on
5449 the same underlying driver (each must have a different instance name).
5451 The order in which routers are defined is important, because addresses are
5452 passed to individual routers one by one, in order. The order in which
5453 transports are defined does not matter at all. The order in which
5454 authenticators are defined is used only when Exim, as a client, is searching
5455 them to find one that matches an authentication mechanism offered by the
5458 .cindex "generic options"
5459 .cindex "options" "generic &-- definition of"
5460 Within a driver instance definition, there are two kinds of option: &'generic'&
5461 and &'private'&. The generic options are those that apply to all drivers of the
5462 same type (that is, all routers, all transports or all authenticators). The
5463 &%driver%& option is a generic option that must appear in every definition.
5464 .cindex "private options"
5465 The private options are special for each driver, and none need appear, because
5466 they all have default values.
5468 The options may appear in any order, except that the &%driver%& option must
5469 precede any private options, since these depend on the particular driver. For
5470 this reason, it is recommended that &%driver%& always be the first option.
5472 Driver instance names, which are used for reference in log entries and
5473 elsewhere, can be any sequence of letters, digits, and underscores (starting
5474 with a letter) and must be unique among drivers of the same type. A router and
5475 a transport (for example) can each have the same name, but no two router
5476 instances can have the same name. The name of a driver instance should not be
5477 confused with the name of the underlying driver module. For example, the
5478 configuration lines:
5483 create an instance of the &(smtp)& transport driver whose name is
5484 &(remote_smtp)&. The same driver code can be used more than once, with
5485 different instance names and different option settings each time. A second
5486 instance of the &(smtp)& transport, with different options, might be defined
5492 command_timeout = 10s
5494 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5495 these transport instances from routers, and these names would appear in log
5498 Comment lines may be present in the middle of driver specifications. The full
5499 list of option settings for any particular driver instance, including all the
5500 defaulted values, can be extracted by making use of the &%-bP%& command line
5508 . ////////////////////////////////////////////////////////////////////////////
5509 . ////////////////////////////////////////////////////////////////////////////
5511 .chapter "The default configuration file" "CHAPdefconfil"
5512 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5513 .cindex "default" "configuration file &""walk through""&"
5514 The default configuration file supplied with Exim as &_src/configure.default_&
5515 is sufficient for a host with simple mail requirements. As an introduction to
5516 the way Exim is configured, this chapter &"walks through"& the default
5517 configuration, giving brief explanations of the settings. Detailed descriptions
5518 of the options are given in subsequent chapters. The default configuration file
5519 itself contains extensive comments about ways you might want to modify the
5520 initial settings. However, note that there are many options that are not
5521 mentioned at all in the default configuration.
5525 .section "Macros" "SECTdefconfmacros"
5526 All macros should be defined before any options.
5528 One macro is specified, but commented out, in the default configuration:
5530 # ROUTER_SMARTHOST=MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
5532 If all off-site mail is expected to be delivered to a "smarthost", then set the
5533 hostname here and uncomment the macro. This will affect which router is used
5534 later on. If this is left commented out, then Exim will perform direct-to-MX
5535 deliveries using a &(dnslookup)& router.
5537 In addition to macros defined here, Exim includes a number of built-in macros
5538 to enable configuration to be guarded by a binary built with support for a
5539 given feature. See section &<<SECTbuiltinmacros>>& for more details.
5542 .section "Main configuration settings" "SECTdefconfmain"
5543 The main (global) configuration option settings section must always come first
5544 in the file, after the macros.
5545 The first thing you'll see in the file, after some initial comments, is the line
5547 # primary_hostname =
5549 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5550 to know the official, fully qualified name of your host, and this is where you
5551 can specify it. However, in most cases you do not need to set this option. When
5552 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5554 The first three non-comment configuration lines are as follows:
5556 domainlist local_domains = @
5557 domainlist relay_to_domains =
5558 hostlist relay_from_hosts = 127.0.0.1
5560 These are not, in fact, option settings. They are definitions of two named
5561 domain lists and one named host list. Exim allows you to give names to lists of
5562 domains, hosts, and email addresses, in order to make it easier to manage the
5563 configuration file (see section &<<SECTnamedlists>>&).
5565 The first line defines a domain list called &'local_domains'&; this is used
5566 later in the configuration to identify domains that are to be delivered
5569 .cindex "@ in a domain list"
5570 There is just one item in this list, the string &"@"&. This is a special form
5571 of entry which means &"the name of the local host"&. Thus, if the local host is
5572 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5573 be delivered locally. Because the local host's name is referenced indirectly,
5574 the same configuration file can be used on different hosts.
5576 The second line defines a domain list called &'relay_to_domains'&, but the
5577 list itself is empty. Later in the configuration we will come to the part that
5578 controls mail relaying through the local host; it allows relaying to any
5579 domains in this list. By default, therefore, no relaying on the basis of a mail
5580 domain is permitted.
5582 The third line defines a host list called &'relay_from_hosts'&. This list is
5583 used later in the configuration to permit relaying from any host or IP address
5584 that matches the list. The default contains just the IP address of the IPv4
5585 loopback interface, which means that processes on the local host are able to
5586 submit mail for relaying by sending it over TCP/IP to that interface. No other
5587 hosts are permitted to submit messages for relaying.
5589 Just to be sure there's no misunderstanding: at this point in the configuration
5590 we aren't actually setting up any controls. We are just defining some domains
5591 and hosts that will be used in the controls that are specified later.
5593 The next two configuration lines are genuine option settings:
5595 acl_smtp_rcpt = acl_check_rcpt
5596 acl_smtp_data = acl_check_data
5598 These options specify &'Access Control Lists'& (ACLs) that are to be used
5599 during an incoming SMTP session for every recipient of a message (every RCPT
5600 command), and after the contents of the message have been received,
5601 respectively. The names of the lists are &'acl_check_rcpt'& and
5602 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5603 section of the configuration. The RCPT ACL controls which recipients are
5604 accepted for an incoming message &-- if a configuration does not provide an ACL
5605 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5606 contents of a message to be checked.
5608 Two commented-out option settings are next:
5610 # av_scanner = clamd:/tmp/clamd
5611 # spamd_address = 127.0.0.1 783
5613 These are example settings that can be used when Exim is compiled with the
5614 content-scanning extension. The first specifies the interface to the virus
5615 scanner, and the second specifies the interface to SpamAssassin. Further
5616 details are given in chapter &<<CHAPexiscan>>&.
5618 Three more commented-out option settings follow:
5620 # tls_advertise_hosts = *
5621 # tls_certificate = /etc/ssl/exim.crt
5622 # tls_privatekey = /etc/ssl/exim.pem
5624 These are example settings that can be used when Exim is compiled with
5625 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5626 first one specifies the list of clients that are allowed to use TLS when
5627 connecting to this server; in this case, the wildcard means all clients. The
5628 other options specify where Exim should find its TLS certificate and private
5629 key, which together prove the server's identity to any clients that connect.
5630 More details are given in chapter &<<CHAPTLS>>&.
5632 Another two commented-out option settings follow:
5634 # daemon_smtp_ports = 25 : 465 : 587
5635 # tls_on_connect_ports = 465
5637 .cindex "port" "465 and 587"
5638 .cindex "port" "for message submission"
5639 .cindex "message" "submission, ports for"
5640 .cindex "submissions protocol"
5641 .cindex "smtps protocol"
5642 .cindex "ssmtp protocol"
5643 .cindex "SMTP" "submissions protocol"
5644 .cindex "SMTP" "ssmtp protocol"
5645 .cindex "SMTP" "smtps protocol"
5646 These options provide better support for roaming users who wish to use this
5647 server for message submission. They are not much use unless you have turned on
5648 TLS (as described in the previous paragraph) and authentication (about which
5649 more in section &<<SECTdefconfauth>>&).
5650 Mail submission from mail clients (MUAs) should be separate from inbound mail
5651 to your domain (MX delivery) for various good reasons (eg, ability to impose
5652 much saner TLS protocol and ciphersuite requirements without unintended
5654 RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
5655 which uses STARTTLS, so this is the &"submission"& port.
5656 RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
5657 which should be used in preference to 587.
5658 You should also consider deploying SRV records to help clients find
5660 Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
5662 Two more commented-out options settings follow:
5665 # qualify_recipient =
5667 The first of these specifies a domain that Exim uses when it constructs a
5668 complete email address from a local login name. This is often needed when Exim
5669 receives a message from a local process. If you do not set &%qualify_domain%&,
5670 the value of &%primary_hostname%& is used. If you set both of these options,
5671 you can have different qualification domains for sender and recipient
5672 addresses. If you set only the first one, its value is used in both cases.
5674 .cindex "domain literal" "recognizing format"
5675 The following line must be uncommented if you want Exim to recognize
5676 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5677 (an IP address within square brackets) instead of a named domain.
5679 # allow_domain_literals
5681 The RFCs still require this form, but many people think that in the modern
5682 Internet it makes little sense to permit mail to be sent to specific hosts by
5683 quoting their IP addresses. This ancient format has been used by people who
5684 try to abuse hosts by using them for unwanted relaying. However, some
5685 people believe there are circumstances (for example, messages addressed to
5686 &'postmaster'&) where domain literals are still useful.
5688 The next configuration line is a kind of trigger guard:
5692 It specifies that no delivery must ever be run as the root user. The normal
5693 convention is to set up &'root'& as an alias for the system administrator. This
5694 setting is a guard against slips in the configuration.
5695 The list of users specified by &%never_users%& is not, however, the complete
5696 list; the build-time configuration in &_Local/Makefile_& has an option called
5697 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5698 contents of &%never_users%& are added to this list. By default
5699 FIXED_NEVER_USERS also specifies root.
5701 When a remote host connects to Exim in order to send mail, the only information
5702 Exim has about the host's identity is its IP address. The next configuration
5707 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5708 in order to get a host name. This improves the quality of the logging
5709 information, but if you feel it is too expensive, you can remove it entirely,
5710 or restrict the lookup to hosts on &"nearby"& networks.
5711 Note that it is not always possible to find a host name from an IP address,
5712 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5715 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5716 1413 (hence their names):
5719 rfc1413_query_timeout = 0s
5721 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5722 Few hosts offer RFC1413 service these days; calls have to be
5723 terminated by a timeout and this needlessly delays the startup
5724 of an incoming SMTP connection.
5725 If you have hosts for which you trust RFC1413 and need this
5726 information, you can change this.
5728 This line enables an efficiency SMTP option. It is negotiated by clients
5729 and not expected to cause problems but can be disabled if needed.
5734 When Exim receives messages over SMTP connections, it expects all addresses to
5735 be fully qualified with a domain, as required by the SMTP definition. However,
5736 if you are running a server to which simple clients submit messages, you may
5737 find that they send unqualified addresses. The two commented-out options:
5739 # sender_unqualified_hosts =
5740 # recipient_unqualified_hosts =
5742 show how you can specify hosts that are permitted to send unqualified sender
5743 and recipient addresses, respectively.
5745 The &%log_selector%& option is used to increase the detail of logging
5748 log_selector = +smtp_protocol_error +smtp_syntax_error \
5749 +tls_certificate_verified
5752 The &%percent_hack_domains%& option is also commented out:
5754 # percent_hack_domains =
5756 It provides a list of domains for which the &"percent hack"& is to operate.
5757 This is an almost obsolete form of explicit email routing. If you do not know
5758 anything about it, you can safely ignore this topic.
5760 The next two settings in the main part of the default configuration are
5761 concerned with messages that have been &"frozen"& on Exim's queue. When a
5762 message is frozen, Exim no longer continues to try to deliver it. Freezing
5763 occurs when a bounce message encounters a permanent failure because the sender
5764 address of the original message that caused the bounce is invalid, so the
5765 bounce cannot be delivered. This is probably the most common case, but there
5766 are also other conditions that cause freezing, and frozen messages are not
5767 always bounce messages.
5769 ignore_bounce_errors_after = 2d
5770 timeout_frozen_after = 7d
5772 The first of these options specifies that failing bounce messages are to be
5773 discarded after 2 days in the queue. The second specifies that any frozen
5774 message (whether a bounce message or not) is to be timed out (and discarded)
5775 after a week. In this configuration, the first setting ensures that no failing
5776 bounce message ever lasts a week.
5778 Exim queues it's messages in a spool directory. If you expect to have
5779 large queues, you may consider using this option. It splits the spool
5780 directory into subdirectories to avoid file system degradation from
5781 many files in a single directory, resulting in better performance.
5782 Manual manipulation of queued messages becomes more complex (though fortunately
5785 # split_spool_directory = true
5788 In an ideal world everybody follows the standards. For non-ASCII
5789 messages RFC 2047 is a standard, allowing a maximum line length of 76
5790 characters. Exim adheres that standard and won't process messages which
5791 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5792 In particular, the Exim maintainers have had multiple reports of
5793 problems from Russian administrators of issues until they disable this
5794 check, because of some popular, yet buggy, mail composition software.
5796 # check_rfc2047_length = false
5799 If you need to be strictly RFC compliant you may wish to disable the
5800 8BITMIME advertisement. Use this, if you exchange mails with systems
5801 that are not 8-bit clean.
5803 # accept_8bitmime = false
5806 Libraries you use may depend on specific environment settings. This
5807 imposes a security risk (e.g. PATH). There are two lists:
5808 &%keep_environment%& for the variables to import as they are, and
5809 &%add_environment%& for variables we want to set to a fixed value.
5810 Note that TZ is handled separately, by the $%timezone%$ runtime
5811 option and by the TIMEZONE_DEFAULT buildtime option.
5813 # keep_environment = ^LDAP
5814 # add_environment = PATH=/usr/bin::/bin
5818 .section "ACL configuration" "SECID54"
5819 .cindex "default" "ACLs"
5820 .cindex "&ACL;" "default configuration"
5821 In the default configuration, the ACL section follows the main configuration.
5822 It starts with the line
5826 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5827 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5828 and &%acl_smtp_data%& above.
5830 .cindex "RCPT" "ACL for"
5831 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5832 RCPT command specifies one of the message's recipients. The ACL statements
5833 are considered in order, until the recipient address is either accepted or
5834 rejected. The RCPT command is then accepted or rejected, according to the
5835 result of the ACL processing.
5839 This line, consisting of a name terminated by a colon, marks the start of the
5844 This ACL statement accepts the recipient if the sending host matches the list.
5845 But what does that strange list mean? It doesn't actually contain any host
5846 names or IP addresses. The presence of the colon puts an empty item in the
5847 list; Exim matches this only if the incoming message did not come from a remote
5848 host, because in that case, the remote hostname is empty. The colon is
5849 important. Without it, the list itself is empty, and can never match anything.
5851 What this statement is doing is to accept unconditionally all recipients in
5852 messages that are submitted by SMTP from local processes using the standard
5853 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5856 deny message = Restricted characters in address
5857 domains = +local_domains
5858 local_parts = ^[.] : ^.*[@%!/|]
5860 deny message = Restricted characters in address
5861 domains = !+local_domains
5862 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5864 These statements are concerned with local parts that contain any of the
5865 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5866 Although these characters are entirely legal in local parts (in the case of
5867 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5868 in Internet mail addresses.
5870 The first three have in the past been associated with explicitly routed
5871 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5872 option). Addresses containing these characters are regularly tried by spammers
5873 in an attempt to bypass relaying restrictions, and also by open relay testing
5874 programs. Unless you really need them it is safest to reject these characters
5875 at this early stage. This configuration is heavy-handed in rejecting these
5876 characters for all messages it accepts from remote hosts. This is a deliberate
5877 policy of being as safe as possible.
5879 The first rule above is stricter, and is applied to messages that are addressed
5880 to one of the local domains handled by this host. This is implemented by the
5881 first condition, which restricts it to domains that are listed in the
5882 &'local_domains'& domain list. The &"+"& character is used to indicate a
5883 reference to a named list. In this configuration, there is just one domain in
5884 &'local_domains'&, but in general there may be many.
5886 The second condition on the first statement uses two regular expressions to
5887 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5888 or &"|"&. If you have local accounts that include these characters, you will
5889 have to modify this rule.
5891 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5892 allows them because they have been encountered in practice. (Consider the
5893 common convention of local parts constructed as
5894 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5895 the author of Exim, who has no second initial.) However, a local part starting
5896 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5897 filename (for example, for a mailing list). This is also true for local parts
5898 that contain slashes. A pipe symbol can also be troublesome if the local part
5899 is incorporated unthinkingly into a shell command line.
5901 The second rule above applies to all other domains, and is less strict. This
5902 allows your own users to send outgoing messages to sites that use slashes
5903 and vertical bars in their local parts. It blocks local parts that begin
5904 with a dot, slash, or vertical bar, but allows these characters within the
5905 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5906 and &"!"& is blocked, as before. The motivation here is to prevent your users
5907 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5909 accept local_parts = postmaster
5910 domains = +local_domains
5912 This statement, which has two conditions, accepts an incoming address if the
5913 local part is &'postmaster'& and the domain is one of those listed in the
5914 &'local_domains'& domain list. The &"+"& character is used to indicate a
5915 reference to a named list. In this configuration, there is just one domain in
5916 &'local_domains'&, but in general there may be many.
5918 The presence of this statement means that mail to postmaster is never blocked
5919 by any of the subsequent tests. This can be helpful while sorting out problems
5920 in cases where the subsequent tests are incorrectly denying access.
5922 require verify = sender
5924 This statement requires the sender address to be verified before any subsequent
5925 ACL statement can be used. If verification fails, the incoming recipient
5926 address is refused. Verification consists of trying to route the address, to
5927 see if a bounce message could be delivered to it. In the case of remote
5928 addresses, basic verification checks only the domain, but &'callouts'& can be
5929 used for more verification if required. Section &<<SECTaddressverification>>&
5930 discusses the details of address verification.
5932 accept hosts = +relay_from_hosts
5933 control = submission
5935 This statement accepts the address if the message is coming from one of the
5936 hosts that are defined as being allowed to relay through this host. Recipient
5937 verification is omitted here, because in many cases the clients are dumb MUAs
5938 that do not cope well with SMTP error responses. For the same reason, the
5939 second line specifies &"submission mode"& for messages that are accepted. This
5940 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5941 messages that are deficient in some way, for example, because they lack a
5942 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5943 probably add recipient verification here, and disable submission mode.
5945 accept authenticated = *
5946 control = submission
5948 This statement accepts the address if the client host has authenticated itself.
5949 Submission mode is again specified, on the grounds that such messages are most
5950 likely to come from MUAs. The default configuration does not define any
5951 authenticators, though it does include some nearly complete commented-out
5952 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5953 fact authenticate until you complete the authenticator definitions.
5955 require message = relay not permitted
5956 domains = +local_domains : +relay_to_domains
5958 This statement rejects the address if its domain is neither a local domain nor
5959 one of the domains for which this host is a relay.
5961 require verify = recipient
5963 This statement requires the recipient address to be verified; if verification
5964 fails, the address is rejected.
5966 # deny message = rejected because $sender_host_address \
5967 # is in a black list at $dnslist_domain\n\
5969 # dnslists = black.list.example
5971 # warn dnslists = black.list.example
5972 # add_header = X-Warning: $sender_host_address is in \
5973 # a black list at $dnslist_domain
5974 # log_message = found in $dnslist_domain
5976 These commented-out lines are examples of how you could configure Exim to check
5977 sending hosts against a DNS black list. The first statement rejects messages
5978 from blacklisted hosts, whereas the second just inserts a warning header
5981 # require verify = csa
5983 This commented-out line is an example of how you could turn on client SMTP
5984 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5989 The final statement in the first ACL unconditionally accepts any recipient
5990 address that has successfully passed all the previous tests.
5994 This line marks the start of the second ACL, and names it. Most of the contents
5995 of this ACL are commented out:
5998 # message = This message contains a virus \
6001 These lines are examples of how to arrange for messages to be scanned for
6002 viruses when Exim has been compiled with the content-scanning extension, and a
6003 suitable virus scanner is installed. If the message is found to contain a
6004 virus, it is rejected with the given custom error message.
6006 # warn spam = nobody
6007 # message = X-Spam_score: $spam_score\n\
6008 # X-Spam_score_int: $spam_score_int\n\
6009 # X-Spam_bar: $spam_bar\n\
6010 # X-Spam_report: $spam_report
6012 These lines are an example of how to arrange for messages to be scanned by
6013 SpamAssassin when Exim has been compiled with the content-scanning extension,
6014 and SpamAssassin has been installed. The SpamAssassin check is run with
6015 &`nobody`& as its user parameter, and the results are added to the message as a
6016 series of extra header line. In this case, the message is not rejected,
6017 whatever the spam score.
6021 This final line in the DATA ACL accepts the message unconditionally.
6024 .section "Router configuration" "SECID55"
6025 .cindex "default" "routers"
6026 .cindex "routers" "default"
6027 The router configuration comes next in the default configuration, introduced
6032 Routers are the modules in Exim that make decisions about where to send
6033 messages. An address is passed to each router, in turn, until it is either
6034 accepted, or failed. This means that the order in which you define the routers
6035 matters. Each router is fully described in its own chapter later in this
6036 manual. Here we give only brief overviews.
6039 # driver = ipliteral
6040 # domains = !+local_domains
6041 # transport = remote_smtp
6043 .cindex "domain literal" "default router"
6044 This router is commented out because the majority of sites do not want to
6045 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
6046 you uncomment this router, you also need to uncomment the setting of
6047 &%allow_domain_literals%& in the main part of the configuration.
6049 Which router is used next depends upon whether or not the ROUTER_SMARTHOST
6050 macro has been defined, per
6052 .ifdef ROUTER_SMARTHOST
6061 If ROUTER_SMARTHOST has been defined, either at the top of the file or on the
6062 command-line, then we route all non-local mail to that smarthost; otherwise, we'll
6063 perform DNS lookups for direct-to-MX lookup. Any mail which is to a local domain will
6064 skip these routers because of the &%domains%& option.
6068 driver = manualroute
6069 domains = ! +local_domains
6070 transport = smarthost_smtp
6071 route_data = ROUTER_SMARTHOST
6072 ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
6075 This router only handles mail which is not to any local domains; this is
6076 specified by the line
6078 domains = ! +local_domains
6080 The &%domains%& option lists the domains to which this router applies, but the
6081 exclamation mark is a negation sign, so the router is used only for domains
6082 that are not in the domain list called &'local_domains'& (which was defined at
6083 the start of the configuration). The plus sign before &'local_domains'&
6084 indicates that it is referring to a named list. Addresses in other domains are
6085 passed on to the following routers.
6087 The name of the router driver is &(manualroute)& because we are manually
6088 specifying how mail should be routed onwards, instead of using DNS MX.
6089 While the name of this router instance is arbitrary, the &%driver%& option must
6090 be one of the driver modules that is in the Exim binary.
6092 With no pre-conditions other than &%domains%&, all mail for non-local domains
6093 will be handled by this router, and the &%no_more%& setting will ensure that no
6094 other routers will be used for messages matching the pre-conditions. See
6095 &<<SECTrouprecon>>& for more on how the pre-conditions apply. For messages which
6096 are handled by this router, we provide a hostname to deliver to in &%route_data%&
6097 and the macro supplies the value; the address is then queued for the
6098 &(smarthost_smtp)& transport.
6103 domains = ! +local_domains
6104 transport = remote_smtp
6105 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
6108 The &%domains%& option behaves as per smarthost, above.
6110 The name of the router driver is &(dnslookup)&,
6111 and is specified by the &%driver%& option. Do not be confused by the fact that
6112 the name of this router instance is the same as the name of the driver. The
6113 instance name is arbitrary, but the name set in the &%driver%& option must be
6114 one of the driver modules that is in the Exim binary.
6116 The &(dnslookup)& router routes addresses by looking up their domains in the
6117 DNS in order to obtain a list of hosts to which the address is routed. If the
6118 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6119 specified by the &%transport%& option. If the router does not find the domain
6120 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6121 the address fails and is bounced.
6123 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6124 be entirely ignored. This option is present because a number of cases have been
6125 encountered where MX records in the DNS point to host names
6126 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6127 Completely ignoring these IP addresses causes Exim to fail to route the
6128 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6129 continue to try to deliver the message periodically until the address timed
6136 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6138 file_transport = address_file
6139 pipe_transport = address_pipe
6141 Control reaches this and subsequent routers only for addresses in the local
6142 domains. This router checks to see whether the local part is defined as an
6143 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6144 data that it looks up from that file. If no data is found for the local part,
6145 the value of the &%data%& option is empty, causing the address to be passed to
6148 &_/etc/aliases_& is a conventional name for the system aliases file that is
6149 often used. That is why it is referenced by from the default configuration
6150 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6151 &_Local/Makefile_& before building Exim.
6156 # local_part_suffix = +* : -*
6157 # local_part_suffix_optional
6158 file = $home/.forward
6163 file_transport = address_file
6164 pipe_transport = address_pipe
6165 reply_transport = address_reply
6167 This is the most complicated router in the default configuration. It is another
6168 redirection router, but this time it is looking for forwarding data set up by
6169 individual users. The &%check_local_user%& setting specifies a check that the
6170 local part of the address is the login name of a local user. If it is not, the
6171 router is skipped. The two commented options that follow &%check_local_user%&,
6174 # local_part_suffix = +* : -*
6175 # local_part_suffix_optional
6177 .vindex "&$local_part_suffix$&"
6178 show how you can specify the recognition of local part suffixes. If the first
6179 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6180 by any sequence of characters, is removed from the local part and placed in the
6181 variable &$local_part_suffix$&. The second suffix option specifies that the
6182 presence of a suffix in the local part is optional. When a suffix is present,
6183 the check for a local login uses the local part with the suffix removed.
6185 When a local user account is found, the file called &_.forward_& in the user's
6186 home directory is consulted. If it does not exist, or is empty, the router
6187 declines. Otherwise, the contents of &_.forward_& are interpreted as
6188 redirection data (see chapter &<<CHAPredirect>>& for more details).
6190 .cindex "Sieve filter" "enabling in default router"
6191 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6192 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6193 is commented out by default), the contents of the file are interpreted as a set
6194 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6195 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6196 separate document entitled &'Exim's interfaces to mail filtering'&.
6198 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6199 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6200 There are two reasons for doing this:
6203 Whether or not a local user has a &_.forward_& file is not really relevant when
6204 checking an address for validity; it makes sense not to waste resources doing
6207 More importantly, when Exim is verifying addresses or handling an EXPN
6208 command during an SMTP session, it is running as the Exim user, not as root.
6209 The group is the Exim group, and no additional groups are set up.
6210 It may therefore not be possible for Exim to read users' &_.forward_& files at
6214 The setting of &%check_ancestor%& prevents the router from generating a new
6215 address that is the same as any previous address that was redirected. (This
6216 works round a problem concerning a bad interaction between aliasing and
6217 forwarding &-- see section &<<SECTredlocmai>>&).
6219 The final three option settings specify the transports that are to be used when
6220 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6221 auto-reply, respectively. For example, if a &_.forward_& file contains
6223 a.nother@elsewhere.example, /home/spqr/archive
6225 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6231 # local_part_suffix = +* : -*
6232 # local_part_suffix_optional
6233 transport = local_delivery
6235 The final router sets up delivery into local mailboxes, provided that the local
6236 part is the name of a local login, by accepting the address and assigning it to
6237 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6238 routers, so the address is bounced. The commented suffix settings fulfil the
6239 same purpose as they do for the &(userforward)& router.
6242 .section "Transport configuration" "SECID56"
6243 .cindex "default" "transports"
6244 .cindex "transports" "default"
6245 Transports define mechanisms for actually delivering messages. They operate
6246 only when referenced from routers, so the order in which they are defined does
6247 not matter. The transports section of the configuration starts with
6251 Two remote transports and four local transports are defined.
6255 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6257 dnssec_request_domains = *
6264 This transport is used for delivering messages over SMTP connections.
6265 The list of remote hosts comes from the router.
6266 The &%message_size_limit%& usage is a hack to avoid sending on messages
6267 with over-long lines. The built-in macro _HAVE_DANE guards configuration
6268 to try to use DNSSEC for all queries and to use DANE for delivery;
6269 see section &<<SECDANE>>& for more details.
6271 The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
6272 negotiated between client and server and not expected to cause problems
6273 but can be disabled if needed. The built-in macro _HAVE_PRDR guards the
6274 use of the &%hosts_try_prdr%& configuration option.
6276 The other remote transport is used when delivering to a specific smarthost
6277 with whom there must be some kind of existing relationship, instead of the
6278 usual federated system.
6283 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6287 # Comment out any of these which you have to, then file a Support
6288 # request with your smarthost provider to get things fixed:
6289 hosts_require_tls = *
6290 tls_verify_hosts = *
6291 # As long as tls_verify_hosts is enabled, this won't matter, but if you
6292 # have to comment it out then this will at least log whether you succeed
6294 tls_try_verify_hosts = *
6296 # The SNI name should match the name which we'll expect to verify;
6297 # many mail systems don't use SNI and this doesn't matter, but if it does,
6298 # we need to send a name which the remote site will recognize.
6299 # This _should_ be the name which the smarthost operators specified as
6300 # the hostname for sending your mail to.
6301 tls_sni = ROUTER_SMARTHOST
6303 .ifdef _HAVE_OPENSSL
6304 tls_require_ciphers = HIGH:!aNULL:@STRENGTH
6307 tls_require_ciphers = SECURE192:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1
6314 After the same &%message_size_limit%& hack, we then specify that this Transport
6315 can handle messages to multiple domains in one run. The assumption here is
6316 that you're routing all non-local mail to the same place and that place is
6317 happy to take all messages from you as quickly as possible.
6318 All other options depend upon built-in macros; if Exim was built without TLS support
6319 then no other options are defined.
6320 If TLS is available, then we configure "stronger than default" TLS ciphersuites
6321 and versions using the &%tls_require_ciphers%& option, where the value to be
6322 used depends upon the library providing TLS.
6323 Beyond that, the options adopt the stance that you should have TLS support available
6324 from your smarthost on today's Internet, so we turn on requiring TLS for the
6325 mail to be delivered, and requiring that the certificate be valid, and match
6326 the expected hostname. The &%tls_sni%& option can be used by service providers
6327 to select an appropriate certificate to present to you and here we re-use the
6328 ROUTER_SMARTHOST macro, because that is unaffected by CNAMEs present in DNS.
6329 You want to specify the hostname which you'll expect to validate for, and that
6330 should not be subject to insecure tampering via DNS results.
6332 For the &%hosts_try_prdr%& option see the previous transport.
6334 All other options are defaulted.
6338 file = /var/mail/$local_part
6345 This &(appendfile)& transport is used for local delivery to user mailboxes in
6346 traditional BSD mailbox format. By default it runs under the uid and gid of the
6347 local user, which requires the sticky bit to be set on the &_/var/mail_&
6348 directory. Some systems use the alternative approach of running mail deliveries
6349 under a particular group instead of using the sticky bit. The commented options
6350 show how this can be done.
6352 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6353 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6354 similarly-named options above.
6360 This transport is used for handling deliveries to pipes that are generated by
6361 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6362 option specifies that any output on stdout or stderr generated by the pipe is to
6363 be returned to the sender.
6371 This transport is used for handling deliveries to files that are generated by
6372 redirection. The name of the file is not specified in this instance of
6373 &(appendfile)&, because it comes from the &(redirect)& router.
6378 This transport is used for handling automatic replies generated by users'
6383 .section "Default retry rule" "SECID57"
6384 .cindex "retry" "default rule"
6385 .cindex "default" "retry rule"
6386 The retry section of the configuration file contains rules which affect the way
6387 Exim retries deliveries that cannot be completed at the first attempt. It is
6388 introduced by the line
6392 In the default configuration, there is just one rule, which applies to all
6395 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6397 This causes any temporarily failing address to be retried every 15 minutes for
6398 2 hours, then at intervals starting at one hour and increasing by a factor of
6399 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6400 is not delivered after 4 days of temporary failure, it is bounced. The time is
6401 measured from first failure, not from the time the message was received.
6403 If the retry section is removed from the configuration, or is empty (that is,
6404 if no retry rules are defined), Exim will not retry deliveries. This turns
6405 temporary errors into permanent errors.
6408 .section "Rewriting configuration" "SECID58"
6409 The rewriting section of the configuration, introduced by
6413 contains rules for rewriting addresses in messages as they arrive. There are no
6414 rewriting rules in the default configuration file.
6418 .section "Authenticators configuration" "SECTdefconfauth"
6419 .cindex "AUTH" "configuration"
6420 The authenticators section of the configuration, introduced by
6422 begin authenticators
6424 defines mechanisms for the use of the SMTP AUTH command. The default
6425 configuration file contains two commented-out example authenticators
6426 which support plaintext username/password authentication using the
6427 standard PLAIN mechanism and the traditional but non-standard LOGIN
6428 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6429 to support most MUA software.
6431 The example PLAIN authenticator looks like this:
6434 # driver = plaintext
6435 # server_set_id = $auth2
6436 # server_prompts = :
6437 # server_condition = Authentication is not yet configured
6438 # server_advertise_condition = ${if def:tls_in_cipher }
6440 And the example LOGIN authenticator looks like this:
6443 # driver = plaintext
6444 # server_set_id = $auth1
6445 # server_prompts = <| Username: | Password:
6446 # server_condition = Authentication is not yet configured
6447 # server_advertise_condition = ${if def:tls_in_cipher }
6450 The &%server_set_id%& option makes Exim remember the authenticated username
6451 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6452 &%server_prompts%& option configures the &(plaintext)& authenticator so
6453 that it implements the details of the specific authentication mechanism,
6454 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6455 when Exim offers authentication to clients; in the examples, this is only
6456 when TLS or SSL has been started, so to enable the authenticators you also
6457 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6459 The &%server_condition%& setting defines how to verify that the username and
6460 password are correct. In the examples it just produces an error message.
6461 To make the authenticators work, you can use a string expansion
6462 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6464 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6465 usercode and password are in different positions.
6466 Chapter &<<CHAPplaintext>>& covers both.
6468 .ecindex IIDconfiwal
6472 . ////////////////////////////////////////////////////////////////////////////
6473 . ////////////////////////////////////////////////////////////////////////////
6475 .chapter "Regular expressions" "CHAPregexp"
6477 .cindex "regular expressions" "library"
6479 Exim supports the use of regular expressions in many of its options. It
6480 uses the PCRE regular expression library; this provides regular expression
6481 matching that is compatible with Perl 5. The syntax and semantics of
6482 regular expressions is discussed in
6483 online Perl manpages, in
6484 many Perl reference books, and also in
6485 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6486 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6487 . --- the http: URL here redirects to another page with the ISBN in the URL
6488 . --- where trying to use https: just redirects back to http:, so sticking
6489 . --- to the old URL for now. 2018-09-07.
6491 The documentation for the syntax and semantics of the regular expressions that
6492 are supported by PCRE is included in the PCRE distribution, and no further
6493 description is included here. The PCRE functions are called from Exim using
6494 the default option settings (that is, with no PCRE options set), except that
6495 the PCRE_CASELESS option is set when the matching is required to be
6498 In most cases, when a regular expression is required in an Exim configuration,
6499 it has to start with a circumflex, in order to distinguish it from plain text
6500 or an &"ends with"& wildcard. In this example of a configuration setting, the
6501 second item in the colon-separated list is a regular expression.
6503 domains = a.b.c : ^\\d{3} : *.y.z : ...
6505 The doubling of the backslash is required because of string expansion that
6506 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6507 of this issue, and a way of avoiding the need for doubling backslashes. The
6508 regular expression that is eventually used in this example contains just one
6509 backslash. The circumflex is included in the regular expression, and has the
6510 normal effect of &"anchoring"& it to the start of the string that is being
6513 There are, however, two cases where a circumflex is not required for the
6514 recognition of a regular expression: these are the &%match%& condition in a
6515 string expansion, and the &%matches%& condition in an Exim filter file. In
6516 these cases, the relevant string is always treated as a regular expression; if
6517 it does not start with a circumflex, the expression is not anchored, and can
6518 match anywhere in the subject string.
6520 In all cases, if you want a regular expression to match at the end of a string,
6521 you must code the $ metacharacter to indicate this. For example:
6523 domains = ^\\d{3}\\.example
6525 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6528 domains = ^\\d{3}\\.example\$
6530 if you want &'example'& to be the top-level domain. The backslash before the
6531 $ is needed because string expansion also interprets dollar characters.
6535 . ////////////////////////////////////////////////////////////////////////////
6536 . ////////////////////////////////////////////////////////////////////////////
6538 .chapter "File and database lookups" "CHAPfdlookup"
6539 .scindex IIDfidalo1 "file" "lookups"
6540 .scindex IIDfidalo2 "database" "lookups"
6541 .cindex "lookup" "description of"
6542 Exim can be configured to look up data in files or databases as it processes
6543 messages. Two different kinds of syntax are used:
6546 A string that is to be expanded may contain explicit lookup requests. These
6547 cause parts of the string to be replaced by data that is obtained from the
6548 lookup. Lookups of this type are conditional expansion items. Different results
6549 can be defined for the cases of lookup success and failure. See chapter
6550 &<<CHAPexpand>>&, where string expansions are described in detail.
6551 The key for the lookup is specified as part of the string expansion.
6553 Lists of domains, hosts, and email addresses can contain lookup requests as a
6554 way of avoiding excessively long linear lists. In this case, the data that is
6555 returned by the lookup is often (but not always) discarded; whether the lookup
6556 succeeds or fails is what really counts. These kinds of list are described in
6557 chapter &<<CHAPdomhosaddlists>>&.
6558 The key for the lookup is given by the context in which the list is expanded.
6561 String expansions, lists, and lookups interact with each other in such a way
6562 that there is no order in which to describe any one of them that does not
6563 involve references to the others. Each of these three chapters makes more sense
6564 if you have read the other two first. If you are reading this for the first
6565 time, be aware that some of it will make a lot more sense after you have read
6566 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6568 .section "Examples of different lookup syntax" "SECID60"
6569 It is easy to confuse the two different kinds of lookup, especially as the
6570 lists that may contain the second kind are always expanded before being
6571 processed as lists. Therefore, they may also contain lookups of the first kind.
6572 Be careful to distinguish between the following two examples:
6574 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6575 domains = lsearch;/some/file
6577 The first uses a string expansion, the result of which must be a domain list.
6578 No strings have been specified for a successful or a failing lookup; the
6579 defaults in this case are the looked-up data and an empty string, respectively.
6580 The expansion takes place before the string is processed as a list, and the
6581 file that is searched could contain lines like this:
6583 192.168.3.4: domain1:domain2:...
6584 192.168.1.9: domain3:domain4:...
6586 When the lookup succeeds, the result of the expansion is a list of domains (and
6587 possibly other types of item that are allowed in domain lists).
6589 In the second example, the lookup is a single item in a domain list. It causes
6590 Exim to use a lookup to see if the domain that is being processed can be found
6591 in the file. The file could contains lines like this:
6596 Any data that follows the keys is not relevant when checking that the domain
6597 matches the list item.
6599 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6600 Consider a file containing lines like this:
6602 192.168.5.6: lsearch;/another/file
6604 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6605 first &%domains%& setting above generates the second setting, which therefore
6606 causes a second lookup to occur.
6608 The rest of this chapter describes the different lookup types that are
6609 available. Any of them can be used in any part of the configuration where a
6610 lookup is permitted.
6613 .section "Lookup types" "SECID61"
6614 .cindex "lookup" "types of"
6615 .cindex "single-key lookup" "definition of"
6616 Two different types of data lookup are implemented:
6619 The &'single-key'& type requires the specification of a file in which to look,
6620 and a single key to search for. The key must be a non-empty string for the
6621 lookup to succeed. The lookup type determines how the file is searched.
6623 .cindex "query-style lookup" "definition of"
6624 The &'query-style'& type accepts a generalized database query. No particular
6625 key value is assumed by Exim for query-style lookups. You can use whichever
6626 Exim variables you need to construct the database query.
6629 The code for each lookup type is in a separate source file that is included in
6630 the binary of Exim only if the corresponding compile-time option is set. The
6631 default settings in &_src/EDITME_& are:
6636 which means that only linear searching and DBM lookups are included by default.
6637 For some types of lookup (e.g. SQL databases), you need to install appropriate
6638 libraries and header files before building Exim.
6643 .section "Single-key lookup types" "SECTsinglekeylookups"
6644 .cindex "lookup" "single-key types"
6645 .cindex "single-key lookup" "list of types"
6646 The following single-key lookup types are implemented:
6649 .cindex "cdb" "description of"
6650 .cindex "lookup" "cdb"
6651 .cindex "binary zero" "in lookup key"
6652 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6653 string without a terminating binary zero. The cdb format is designed for
6654 indexed files that are read frequently and never updated, except by total
6655 re-creation. As such, it is particularly suitable for large files containing
6656 aliases or other indexed data referenced by an MTA. Information about cdb and
6657 tools for building the files can be found in several places:
6659 &url(https://cr.yp.to/cdb.html)
6660 &url(http://www.corpit.ru/mjt/tinycdb.html)
6661 &url(https://packages.debian.org/stable/utils/freecdb)
6662 &url(https://github.com/philpennock/cdbtools) (in Go)
6664 . --- 2018-09-07: corpit.ru http:-only
6665 A cdb distribution is not needed in order to build Exim with cdb support,
6666 because the code for reading cdb files is included directly in Exim itself.
6667 However, no means of building or testing cdb files is provided with Exim, so
6668 you need to obtain a cdb distribution in order to do this.
6670 .cindex "DBM" "lookup type"
6671 .cindex "lookup" "dbm"
6672 .cindex "binary zero" "in lookup key"
6673 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6674 DBM file by looking up the record with the given key. A terminating binary
6675 zero is included in the key that is passed to the DBM library. See section
6676 &<<SECTdb>>& for a discussion of DBM libraries.
6678 .cindex "Berkeley DB library" "file format"
6679 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6680 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6681 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6682 the DB_UNKNOWN option. This enables it to handle any of the types of database
6683 that the library supports, and can be useful for accessing DBM files created by
6684 other applications. (For earlier DB versions, DB_HASH is always used.)
6686 .cindex "lookup" "dbmjz"
6687 .cindex "lookup" "dbm &-- embedded NULs"
6689 .cindex "dbmjz lookup type"
6690 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6691 interpreted as an Exim list; the elements of the list are joined together with
6692 ASCII NUL characters to form the lookup key. An example usage would be to
6693 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6694 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6695 &(cram_md5)& authenticator.
6697 .cindex "lookup" "dbmnz"
6698 .cindex "lookup" "dbm &-- terminating zero"
6699 .cindex "binary zero" "in lookup key"
6701 .cindex "&_/etc/userdbshadow.dat_&"
6702 .cindex "dbmnz lookup type"
6703 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6704 is not included in the key that is passed to the DBM library. You may need this
6705 if you want to look up data in files that are created by or shared with some
6706 other application that does not use terminating zeros. For example, you need to
6707 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6708 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6709 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6710 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6712 .cindex "lookup" "dsearch"
6713 .cindex "dsearch lookup type"
6714 &(dsearch)&: The given file must be a directory; this is searched for an entry
6715 whose name is the key by calling the &[lstat()]& function. The key may not
6716 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6717 the lookup is the name of the entry, which may be a file, directory,
6718 symbolic link, or any other kind of directory entry. An example of how this
6719 lookup can be used to support virtual domains is given in section
6720 &<<SECTvirtualdomains>>&.
6722 .cindex "lookup" "iplsearch"
6723 .cindex "iplsearch lookup type"
6724 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6725 terminated by a colon or white space or the end of the line. The keys in the
6726 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6727 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6728 being interpreted as a key terminator. For example:
6730 1.2.3.4: data for 1.2.3.4
6731 192.168.0.0/16: data for 192.168.0.0/16
6732 "abcd::cdab": data for abcd::cdab
6733 "abcd:abcd::/32" data for abcd:abcd::/32
6735 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6736 file is searched linearly, using the CIDR masks where present, until a matching
6737 key is found. The first key that matches is used; there is no attempt to find a
6738 &"best"& match. Apart from the way the keys are matched, the processing for
6739 &(iplsearch)& is the same as for &(lsearch)&.
6741 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6742 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6743 lookup types support only literal keys.
6745 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6746 the implicit key is the host's IP address rather than its name (see section
6747 &<<SECThoslispatsikey>>&).
6749 .cindex "linear search"
6750 .cindex "lookup" "lsearch"
6751 .cindex "lsearch lookup type"
6752 .cindex "case sensitivity" "in lsearch lookup"
6753 &(lsearch)&: The given file is a text file that is searched linearly for a
6754 line beginning with the search key, terminated by a colon or white space or the
6755 end of the line. The search is case-insensitive; that is, upper and lower case
6756 letters are treated as the same. The first occurrence of the key that is found
6757 in the file is used.
6759 White space between the key and the colon is permitted. The remainder of the
6760 line, with leading and trailing white space removed, is the data. This can be
6761 continued onto subsequent lines by starting them with any amount of white
6762 space, but only a single space character is included in the data at such a
6763 junction. If the data begins with a colon, the key must be terminated by a
6768 Empty lines and lines beginning with # are ignored, even if they occur in the
6769 middle of an item. This is the traditional textual format of alias files. Note
6770 that the keys in an &(lsearch)& file are literal strings. There is no
6771 wildcarding of any kind.
6773 .cindex "lookup" "lsearch &-- colons in keys"
6774 .cindex "white space" "in lsearch key"
6775 In most &(lsearch)& files, keys are not required to contain colons or #
6776 characters, or white space. However, if you need this feature, it is available.
6777 If a key begins with a doublequote character, it is terminated only by a
6778 matching quote (or end of line), and the normal escaping rules apply to its
6779 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6780 quoted keys (exactly as for unquoted keys). There is no special handling of
6781 quotes for the data part of an &(lsearch)& line.
6784 .cindex "NIS lookup type"
6785 .cindex "lookup" "NIS"
6786 .cindex "binary zero" "in lookup key"
6787 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6788 the given key, without a terminating binary zero. There is a variant called
6789 &(nis0)& which does include the terminating binary zero in the key. This is
6790 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6791 aliases; the full map names must be used.
6794 .cindex "wildlsearch lookup type"
6795 .cindex "lookup" "wildlsearch"
6796 .cindex "nwildlsearch lookup type"
6797 .cindex "lookup" "nwildlsearch"
6798 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6799 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6800 the file may be wildcarded. The difference between these two lookup types is
6801 that for &(wildlsearch)&, each key in the file is string-expanded before being
6802 used, whereas for &(nwildlsearch)&, no expansion takes place.
6804 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6805 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6806 file that are regular expressions can be made case-sensitive by the use of
6807 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6809 . ==== As this is a nested list, any displays it contains must be indented
6810 . ==== as otherwise they are too far to the left.
6813 The string may begin with an asterisk to mean &"ends with"&. For example:
6815 *.a.b.c data for anything.a.b.c
6816 *fish data for anythingfish
6819 The string may begin with a circumflex to indicate a regular expression. For
6820 example, for &(wildlsearch)&:
6822 ^\N\d+\.a\.b\N data for <digits>.a.b
6824 Note the use of &`\N`& to disable expansion of the contents of the regular
6825 expression. If you are using &(nwildlsearch)&, where the keys are not
6826 string-expanded, the equivalent entry is:
6828 ^\d+\.a\.b data for <digits>.a.b
6830 The case-insensitive flag is set at the start of compiling the regular
6831 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6832 For example, to make the entire pattern case-sensitive:
6834 ^(?-i)\d+\.a\.b data for <digits>.a.b
6837 If the regular expression contains white space or colon characters, you must
6838 either quote it (see &(lsearch)& above), or represent these characters in other
6839 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6840 colon. This may be easier than quoting, because if you quote, you have to
6841 escape all the backslashes inside the quotes.
6843 &*Note*&: It is not possible to capture substrings in a regular expression
6844 match for later use, because the results of all lookups are cached. If a lookup
6845 is repeated, the result is taken from the cache, and no actual pattern matching
6846 takes place. The values of all the numeric variables are unset after a
6847 &((n)wildlsearch)& match.
6850 Although I cannot see it being of much use, the general matching function that
6851 is used to implement &((n)wildlsearch)& means that the string may begin with a
6852 lookup name terminated by a semicolon, and followed by lookup data. For
6855 cdb;/some/file data for keys that match the file
6857 The data that is obtained from the nested lookup is discarded.
6860 Keys that do not match any of these patterns are interpreted literally. The
6861 continuation rules for the data are the same as for &(lsearch)&, and keys may
6862 be followed by optional colons.
6864 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6865 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6866 lookup types support only literal keys.
6869 .cindex "lookup" "spf"
6870 If Exim is built with SPF support, manual lookups can be done
6871 (as opposed to the standard ACL condition method.
6872 For details see section &<<SECSPF>>&.
6876 .section "Query-style lookup types" "SECTquerystylelookups"
6877 .cindex "lookup" "query-style types"
6878 .cindex "query-style lookup" "list of types"
6879 The supported query-style lookup types are listed below. Further details about
6880 many of them are given in later sections.
6883 .cindex "DNS" "as a lookup type"
6884 .cindex "lookup" "DNS"
6885 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6886 are given in the supplied query. The resulting data is the contents of the
6887 records. See section &<<SECTdnsdb>>&.
6889 .cindex "InterBase lookup type"
6890 .cindex "lookup" "InterBase"
6891 &(ibase)&: This does a lookup in an InterBase database.
6893 .cindex "LDAP" "lookup type"
6894 .cindex "lookup" "LDAP"
6895 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6896 returns attributes from a single entry. There is a variant called &(ldapm)&
6897 that permits values from multiple entries to be returned. A third variant
6898 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6899 any attribute values. See section &<<SECTldap>>&.
6901 .cindex "MySQL" "lookup type"
6902 .cindex "lookup" "MySQL"
6903 &(mysql)&: The format of the query is an SQL statement that is passed to a
6904 MySQL database. See section &<<SECTsql>>&.
6906 .cindex "NIS+ lookup type"
6907 .cindex "lookup" "NIS+"
6908 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6909 the field to be returned. See section &<<SECTnisplus>>&.
6911 .cindex "Oracle" "lookup type"
6912 .cindex "lookup" "Oracle"
6913 &(oracle)&: The format of the query is an SQL statement that is passed to an
6914 Oracle database. See section &<<SECTsql>>&.
6916 .cindex "lookup" "passwd"
6917 .cindex "passwd lookup type"
6918 .cindex "&_/etc/passwd_&"
6919 &(passwd)& is a query-style lookup with queries that are just user names. The
6920 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6921 success, the result string is the same as you would get from an &(lsearch)&
6922 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6923 password value. For example:
6925 *:42:42:King Rat:/home/kr:/bin/bash
6928 .cindex "PostgreSQL lookup type"
6929 .cindex "lookup" "PostgreSQL"
6930 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6931 PostgreSQL database. See section &<<SECTsql>>&.
6934 .cindex "Redis lookup type"
6935 .cindex lookup Redis
6936 &(redis)&: The format of the query is either a simple get or simple set,
6937 passed to a Redis database. See section &<<SECTsql>>&.
6940 .cindex "sqlite lookup type"
6941 .cindex "lookup" "sqlite"
6942 &(sqlite)&: The format of the query is a filename followed by an SQL statement
6943 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6946 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6947 not likely to be useful in normal operation.
6949 .cindex "whoson lookup type"
6950 .cindex "lookup" "whoson"
6951 . --- still http:-only, 2018-09-07
6952 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6953 allows a server to check whether a particular (dynamically allocated) IP
6954 address is currently allocated to a known (trusted) user and, optionally, to
6955 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6956 at one time for &"POP before SMTP"& authentication, but that approach has been
6957 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6958 &"POP before SMTP"& checking using ACL statements such as
6960 require condition = \
6961 ${lookup whoson {$sender_host_address}{yes}{no}}
6963 The query consists of a single IP address. The value returned is the name of
6964 the authenticated user, which is stored in the variable &$value$&. However, in
6965 this example, the data in &$value$& is not used; the result of the lookup is
6966 one of the fixed strings &"yes"& or &"no"&.
6971 .section "Temporary errors in lookups" "SECID63"
6972 .cindex "lookup" "temporary error in"
6973 Lookup functions can return temporary error codes if the lookup cannot be
6974 completed. For example, an SQL or LDAP database might be unavailable. For this
6975 reason, it is not advisable to use a lookup that might do this for critical
6976 options such as a list of local domains.
6978 When a lookup cannot be completed in a router or transport, delivery
6979 of the message (to the relevant address) is deferred, as for any other
6980 temporary error. In other circumstances Exim may assume the lookup has failed,
6981 or may give up altogether.
6985 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6986 .cindex "wildcard lookups"
6987 .cindex "lookup" "default values"
6988 .cindex "lookup" "wildcard"
6989 .cindex "lookup" "* added to type"
6990 .cindex "default" "in single-key lookups"
6991 In this context, a &"default value"& is a value specified by the administrator
6992 that is to be used if a lookup fails.
6994 &*Note:*& This section applies only to single-key lookups. For query-style
6995 lookups, the facilities of the query language must be used. An attempt to
6996 specify a default for a query-style lookup provokes an error.
6998 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6999 and the initial lookup fails, the key &"*"& is looked up in the file to
7000 provide a default value. See also the section on partial matching below.
7002 .cindex "*@ with single-key lookup"
7003 .cindex "lookup" "*@ added to type"
7004 .cindex "alias file" "per-domain default"
7005 Alternatively, if &"*@"& is added to a single-key lookup type (for example
7006 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
7007 character, a second lookup is done with everything before the last @ replaced
7008 by *. This makes it possible to provide per-domain defaults in alias files
7009 that include the domains in the keys. If the second lookup fails (or doesn't
7010 take place because there is no @ in the key), &"*"& is looked up.
7011 For example, a &(redirect)& router might contain:
7013 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
7015 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
7016 looks up these keys, in this order:
7022 The data is taken from whichever key it finds first. &*Note*&: In an
7023 &(lsearch)& file, this does not mean the first of these keys in the file. A
7024 complete scan is done for each key, and only if it is not found at all does
7025 Exim move on to try the next key.
7029 .section "Partial matching in single-key lookups" "SECTpartiallookup"
7030 .cindex "partial matching"
7031 .cindex "wildcard lookups"
7032 .cindex "lookup" "partial matching"
7033 .cindex "lookup" "wildcard"
7034 .cindex "asterisk" "in search type"
7035 The normal operation of a single-key lookup is to search the file for an exact
7036 match with the given key. However, in a number of situations where domains are
7037 being looked up, it is useful to be able to do partial matching. In this case,
7038 information in the file that has a key starting with &"*."& is matched by any
7039 domain that ends with the components that follow the full stop. For example, if
7040 a key in a DBM file is
7042 *.dates.fict.example
7044 then when partial matching is enabled this is matched by (amongst others)
7045 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
7046 by &'dates.fict.example'&, if that does not appear as a separate key in the
7049 &*Note*&: Partial matching is not available for query-style lookups. It is
7050 also not available for any lookup items in address lists (see section
7051 &<<SECTaddresslist>>&).
7053 Partial matching is implemented by doing a series of separate lookups using
7054 keys constructed by modifying the original subject key. This means that it can
7055 be used with any of the single-key lookup types, provided that
7056 partial matching keys
7057 beginning with a special prefix (default &"*."&) are included in the data file.
7058 Keys in the file that do not begin with the prefix are matched only by
7059 unmodified subject keys when partial matching is in use.
7061 Partial matching is requested by adding the string &"partial-"& to the front of
7062 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
7063 is done, the subject key is first looked up unmodified; if that fails, &"*."&
7064 is added at the start of the subject key, and it is looked up again. If that
7065 fails, further lookups are tried with dot-separated components removed from the
7066 start of the subject key, one-by-one, and &"*."& added on the front of what
7069 A minimum number of two non-* components are required. This can be adjusted
7070 by including a number before the hyphen in the search type. For example,
7071 &%partial3-lsearch%& specifies a minimum of three non-* components in the
7072 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
7073 subject key is &'2250.dates.fict.example'& then the following keys are looked
7074 up when the minimum number of non-* components is two:
7076 2250.dates.fict.example
7077 *.2250.dates.fict.example
7078 *.dates.fict.example
7081 As soon as one key in the sequence is successfully looked up, the lookup
7084 .cindex "lookup" "partial matching &-- changing prefix"
7085 .cindex "prefix" "for partial matching"
7086 The use of &"*."& as the partial matching prefix is a default that can be
7087 changed. The motivation for this feature is to allow Exim to operate with file
7088 formats that are used by other MTAs. A different prefix can be supplied in
7089 parentheses instead of the hyphen after &"partial"&. For example:
7091 domains = partial(.)lsearch;/some/file
7093 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
7094 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
7095 components is unchanged). The prefix may consist of any punctuation characters
7096 other than a closing parenthesis. It may be empty, for example:
7098 domains = partial1()cdb;/some/file
7100 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
7101 &`a.b.c`&, &`b.c`&, and &`c`&.
7103 If &"partial0"& is specified, what happens at the end (when the lookup with
7104 just one non-wild component has failed, and the original key is shortened right
7105 down to the null string) depends on the prefix:
7108 If the prefix has zero length, the whole lookup fails.
7110 If the prefix has length 1, a lookup for just the prefix is done. For
7111 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
7113 Otherwise, if the prefix ends in a dot, the dot is removed, and the
7114 remainder is looked up. With the default prefix, therefore, the final lookup is
7115 for &"*"& on its own.
7117 Otherwise, the whole prefix is looked up.
7121 If the search type ends in &"*"& or &"*@"& (see section
7122 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
7123 this implies happens after all partial lookups have failed. If &"partial0"& is
7124 specified, adding &"*"& to the search type has no effect with the default
7125 prefix, because the &"*"& key is already included in the sequence of partial
7126 lookups. However, there might be a use for lookup types such as
7127 &"partial0(.)lsearch*"&.
7129 The use of &"*"& in lookup partial matching differs from its use as a wildcard
7130 in domain lists and the like. Partial matching works only in terms of
7131 dot-separated components; a key such as &`*fict.example`&
7132 in a database file is useless, because the asterisk in a partial matching
7133 subject key is always followed by a dot.
7138 .section "Lookup caching" "SECID64"
7139 .cindex "lookup" "caching"
7140 .cindex "caching" "lookup data"
7141 Exim caches all lookup results in order to avoid needless repetition of
7142 lookups. However, because (apart from the daemon) Exim operates as a collection
7143 of independent, short-lived processes, this caching applies only within a
7144 single Exim process. There is no inter-process lookup caching facility.
7146 For single-key lookups, Exim keeps the relevant files open in case there is
7147 another lookup that needs them. In some types of configuration this can lead to
7148 many files being kept open for messages with many recipients. To avoid hitting
7149 the operating system limit on the number of simultaneously open files, Exim
7150 closes the least recently used file when it needs to open more files than its
7151 own internal limit, which can be changed via the &%lookup_open_max%& option.
7153 The single-key lookup files are closed and the lookup caches are flushed at
7154 strategic points during delivery &-- for example, after all routing is
7160 .section "Quoting lookup data" "SECID65"
7161 .cindex "lookup" "quoting"
7162 .cindex "quoting" "in lookups"
7163 When data from an incoming message is included in a query-style lookup, there
7164 is the possibility of special characters in the data messing up the syntax of
7165 the query. For example, a NIS+ query that contains
7169 will be broken if the local part happens to contain a closing square bracket.
7170 For NIS+, data can be enclosed in double quotes like this:
7172 [name="$local_part"]
7174 but this still leaves the problem of a double quote in the data. The rule for
7175 NIS+ is that double quotes must be doubled. Other lookup types have different
7176 rules, and to cope with the differing requirements, an expansion operator
7177 of the following form is provided:
7179 ${quote_<lookup-type>:<string>}
7181 For example, the safest way to write the NIS+ query is
7183 [name="${quote_nisplus:$local_part}"]
7185 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
7186 operator can be used for all lookup types, but has no effect for single-key
7187 lookups, since no quoting is ever needed in their key strings.
7192 .section "More about dnsdb" "SECTdnsdb"
7193 .cindex "dnsdb lookup"
7194 .cindex "lookup" "dnsdb"
7195 .cindex "DNS" "as a lookup type"
7196 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7197 of a record type and a domain name, separated by an equals sign. For example,
7198 an expansion string could contain:
7200 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7202 If the lookup succeeds, the result is placed in &$value$&, which in this case
7203 is used on its own as the result. If the lookup does not succeed, the
7204 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7205 &<<SECTforexpfai>>& for an explanation of what this means.
7207 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7208 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7209 If no type is given, TXT is assumed.
7211 For any record type, if multiple records are found, the data is returned as a
7212 concatenation, with newline as the default separator. The order, of course,
7213 depends on the DNS resolver. You can specify a different separator character
7214 between multiple records by putting a right angle-bracket followed immediately
7215 by the new separator at the start of the query. For example:
7217 ${lookup dnsdb{>: a=host1.example}}
7219 It is permitted to specify a space as the separator character. Further
7220 white space is ignored.
7221 For lookup types that return multiple fields per record,
7222 an alternate field separator can be specified using a comma after the main
7223 separator character, followed immediately by the field separator.
7225 .cindex "PTR record" "in &(dnsdb)& lookup"
7226 When the type is PTR,
7227 the data can be an IP address, written as normal; inversion and the addition of
7228 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7230 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7232 If the data for a PTR record is not a syntactically valid IP address, it is not
7233 altered and nothing is added.
7235 .cindex "MX record" "in &(dnsdb)& lookup"
7236 .cindex "SRV record" "in &(dnsdb)& lookup"
7237 For an MX lookup, both the preference value and the host name are returned for
7238 each record, separated by a space. For an SRV lookup, the priority, weight,
7239 port, and host name are returned for each record, separated by spaces.
7240 The field separator can be modified as above.
7242 .cindex "TXT record" "in &(dnsdb)& lookup"
7243 .cindex "SPF record" "in &(dnsdb)& lookup"
7244 For TXT records with multiple items of data, only the first item is returned,
7245 unless a field separator is specified.
7246 To concatenate items without a separator, use a semicolon instead.
7248 default behaviour is to concatenate multiple items without using a separator.
7250 ${lookup dnsdb{>\n,: txt=a.b.example}}
7251 ${lookup dnsdb{>\n; txt=a.b.example}}
7252 ${lookup dnsdb{spf=example.org}}
7254 It is permitted to specify a space as the separator character. Further
7255 white space is ignored.
7257 .cindex "SOA record" "in &(dnsdb)& lookup"
7258 For an SOA lookup, while no result is obtained the lookup is redone with
7259 successively more leading components dropped from the given domain.
7260 Only the primary-nameserver field is returned unless a field separator is
7263 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7266 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7267 .cindex "dnsdb modifiers"
7268 .cindex "modifiers" "dnsdb"
7269 .cindex "options" "dnsdb"
7270 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7271 each followed by a comma,
7272 that may appear before the record type.
7274 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7275 temporary DNS error for any of them, the behaviour is controlled by
7276 a defer-option modifier.
7277 The possible keywords are
7278 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7279 With &"strict"& behaviour, any temporary DNS error causes the
7280 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7281 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7282 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7283 error causes the whole lookup to defer only if none of the other lookups
7284 succeed. The default is &"lax"&, so the following lookups are equivalent:
7286 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7287 ${lookup dnsdb{a=one.host.com:two.host.com}}
7289 Thus, in the default case, as long as at least one of the DNS lookups
7290 yields some data, the lookup succeeds.
7292 .cindex "DNSSEC" "dns lookup"
7293 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7294 The possible keywords are
7295 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7296 With &"strict"& or &"lax"& DNSSEC information is requested
7298 With &"strict"& a response from the DNS resolver that
7299 is not labelled as authenticated data
7300 is treated as equivalent to a temporary DNS error.
7301 The default is &"never"&.
7303 See also the &$lookup_dnssec_authenticated$& variable.
7305 .cindex timeout "dns lookup"
7306 .cindex "DNS" timeout
7307 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7308 The form is &"retrans_VAL"& where VAL is an Exim time specification
7310 The default value is set by the main configuration option &%dns_retrans%&.
7312 Retries for the dnsdb lookup can be controlled by a retry modifier.
7313 The form if &"retry_VAL"& where VAL is an integer.
7314 The default count is set by the main configuration option &%dns_retry%&.
7316 .cindex caching "of dns lookup"
7317 .cindex TTL "of dns lookup"
7319 Dnsdb lookup results are cached within a single process (and its children).
7320 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7321 value of the set of returned DNS records.
7324 .section "Pseudo dnsdb record types" "SECID66"
7325 .cindex "MX record" "in &(dnsdb)& lookup"
7326 By default, both the preference value and the host name are returned for
7327 each MX record, separated by a space. If you want only host names, you can use
7328 the pseudo-type MXH:
7330 ${lookup dnsdb{mxh=a.b.example}}
7332 In this case, the preference values are omitted, and just the host names are
7335 .cindex "name server for enclosing domain"
7336 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7337 records on the given domain, but if none are found, it removes the first
7338 component of the domain name, and tries again. This process continues until NS
7339 records are found or there are no more components left (or there is a DNS
7340 error). In other words, it may return the name servers for a top-level domain,
7341 but it never returns the root name servers. If there are no NS records for the
7342 top-level domain, the lookup fails. Consider these examples:
7344 ${lookup dnsdb{zns=xxx.quercite.com}}
7345 ${lookup dnsdb{zns=xxx.edu}}
7347 Assuming that in each case there are no NS records for the full domain name,
7348 the first returns the name servers for &%quercite.com%&, and the second returns
7349 the name servers for &%edu%&.
7351 You should be careful about how you use this lookup because, unless the
7352 top-level domain does not exist, the lookup always returns some host names. The
7353 sort of use to which this might be put is for seeing if the name servers for a
7354 given domain are on a blacklist. You can probably assume that the name servers
7355 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7358 .cindex "CSA" "in &(dnsdb)& lookup"
7359 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7360 records according to the CSA rules, which are described in section
7361 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7362 not sufficient because of the extra parent domain search behaviour of CSA. The
7363 result of a successful lookup such as:
7365 ${lookup dnsdb {csa=$sender_helo_name}}
7367 has two space-separated fields: an authorization code and a target host name.
7368 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7369 authorization required but absent, or &"?"& for unknown.
7371 .cindex "A+" "in &(dnsdb)& lookup"
7372 The pseudo-type A+ performs an AAAA
7373 and then an A lookup. All results are returned; defer processing
7374 (see below) is handled separately for each lookup. Example:
7376 ${lookup dnsdb {>; a+=$sender_helo_name}}
7380 .section "Multiple dnsdb lookups" "SECID67"
7381 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7382 However, you can specify a list of domains or IP addresses in a single
7383 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7384 the default separator, but with the ability to change this. For example:
7386 ${lookup dnsdb{one.domain.com:two.domain.com}}
7387 ${lookup dnsdb{a=one.host.com:two.host.com}}
7388 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7390 In order to retain backwards compatibility, there is one special case: if
7391 the lookup type is PTR and no change of separator is specified, Exim looks
7392 to see if the rest of the string is precisely one IPv6 address. In this
7393 case, it does not treat it as a list.
7395 The data from each lookup is concatenated, with newline separators by default,
7396 in the same way that multiple DNS records for a single item are handled. A
7397 different separator can be specified, as described above.
7402 .section "More about LDAP" "SECTldap"
7403 .cindex "LDAP" "lookup, more about"
7404 .cindex "lookup" "LDAP"
7405 .cindex "Solaris" "LDAP"
7406 The original LDAP implementation came from the University of Michigan; this has
7407 become &"Open LDAP"&, and there are now two different releases. Another
7408 implementation comes from Netscape, and Solaris 7 and subsequent releases
7409 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7410 the lookup function level, their error handling is different. For this reason
7411 it is necessary to set a compile-time variable when building Exim with LDAP, to
7412 indicate which LDAP library is in use. One of the following should appear in
7413 your &_Local/Makefile_&:
7415 LDAP_LIB_TYPE=UMICHIGAN
7416 LDAP_LIB_TYPE=OPENLDAP1
7417 LDAP_LIB_TYPE=OPENLDAP2
7418 LDAP_LIB_TYPE=NETSCAPE
7419 LDAP_LIB_TYPE=SOLARIS
7421 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7422 same interface as the University of Michigan version.
7424 There are three LDAP lookup types in Exim. These behave slightly differently in
7425 the way they handle the results of a query:
7428 &(ldap)& requires the result to contain just one entry; if there are more, it
7431 &(ldapdn)& also requires the result to contain just one entry, but it is the
7432 Distinguished Name that is returned rather than any attribute values.
7434 &(ldapm)& permits the result to contain more than one entry; the attributes
7435 from all of them are returned.
7439 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7440 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7441 the data returned by a successful lookup is described in the next section.
7442 First we explain how LDAP queries are coded.
7445 .section "Format of LDAP queries" "SECTforldaque"
7446 .cindex "LDAP" "query format"
7447 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7448 the configuration of a &(redirect)& router one might have this setting:
7450 data = ${lookup ldap \
7451 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7452 c=UK?mailbox?base?}}
7454 .cindex "LDAP" "with TLS"
7455 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7456 secure (encrypted) LDAP connections. The second of these ensures that an
7457 encrypted TLS connection is used.
7459 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7460 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7461 See the &%ldap_start_tls%& option.
7463 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7464 controlled. Every part of the TLS configuration can be configured by settings in
7465 &_exim.conf_&. Depending on the version of the client libraries installed on
7466 your system, some of the initialization may have required setting options in
7467 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7468 certificates. This revealed a nuance where the current UID that exim was
7469 running as could affect which config files it read. With Exim 4.83, these
7470 methods become optional, only taking effect if not specifically set in
7474 .section "LDAP quoting" "SECID68"
7475 .cindex "LDAP" "quoting"
7476 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7477 and the second because the LDAP query is represented as a URL. Furthermore,
7478 within an LDAP query, two different kinds of quoting are required. For this
7479 reason, there are two different LDAP-specific quoting operators.
7481 The &%quote_ldap%& operator is designed for use on strings that are part of
7482 filter specifications. Conceptually, it first does the following conversions on
7490 in accordance with RFC 2254. The resulting string is then quoted according
7491 to the rules for URLs, that is, all non-alphanumeric characters except
7495 are converted to their hex values, preceded by a percent sign. For example:
7497 ${quote_ldap: a(bc)*, a<yz>; }
7501 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7503 Removing the URL quoting, this is (with a leading and a trailing space):
7505 a\28bc\29\2A, a<yz>;
7507 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7508 base DN specifications in queries. Conceptually, it first converts the string
7509 by inserting a backslash in front of any of the following characters:
7513 It also inserts a backslash before any leading spaces or # characters, and
7514 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7515 is then quoted according to the rules for URLs. For example:
7517 ${quote_ldap_dn: a(bc)*, a<yz>; }
7521 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7523 Removing the URL quoting, this is (with a trailing space):
7525 \ a(bc)*\, a\<yz\>\;\
7527 There are some further comments about quoting in the section on LDAP
7528 authentication below.
7531 .section "LDAP connections" "SECID69"
7532 .cindex "LDAP" "connections"
7533 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7534 is in use, via a Unix domain socket. The example given above does not specify
7535 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7538 ldap://<hostname>:<port>/...
7540 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7541 used. When no server is specified in a query, a list of default servers is
7542 taken from the &%ldap_default_servers%& configuration option. This supplies a
7543 colon-separated list of servers which are tried in turn until one successfully
7544 handles a query, or there is a serious error. Successful handling either
7545 returns the requested data, or indicates that it does not exist. Serious errors
7546 are syntactical, or multiple values when only a single value is expected.
7547 Errors which cause the next server to be tried are connection failures, bind
7548 failures, and timeouts.
7550 For each server name in the list, a port number can be given. The standard way
7551 of specifying a host and port is to use a colon separator (RFC 1738). Because
7552 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7553 doubled. For example
7555 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7557 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7558 to the LDAP library with no server name, and the library's default (normally
7559 the local host) is used.
7561 If you are using the OpenLDAP library, you can connect to an LDAP server using
7562 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7563 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7564 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7567 For this type of connection, instead of a host name for the server, a pathname
7568 for the socket is required, and the port number is not relevant. The pathname
7569 can be specified either as an item in &%ldap_default_servers%&, or inline in
7570 the query. In the former case, you can have settings such as
7572 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7574 When the pathname is given in the query, you have to escape the slashes as
7575 &`%2F`& to fit in with the LDAP URL syntax. For example:
7577 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7579 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7580 a pathname, it uses the Unix domain socket code, even if the query actually
7581 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7582 socket connection. This behaviour means that you can use a setting of
7583 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7584 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7585 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7588 If an explicit &`ldapi`& type is given in a query when a host name is
7589 specified, an error is diagnosed. However, if there are more items in
7590 &%ldap_default_servers%&, they are tried. In other words:
7593 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7596 Using &`ldapi`& with a host name causes an error.
7600 Using &`ldapi`& with no host or path in the query, and no setting of
7601 &%ldap_default_servers%&, does whatever the library does by default.
7605 .section "LDAP authentication and control information" "SECID70"
7606 .cindex "LDAP" "authentication"
7607 The LDAP URL syntax provides no way of passing authentication and other control
7608 information to the server. To make this possible, the URL in an LDAP query may
7609 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7610 spaces. If a value contains spaces it must be enclosed in double quotes, and
7611 when double quotes are used, backslash is interpreted in the usual way inside
7612 them. The following names are recognized:
7614 &`DEREFERENCE`& set the dereferencing parameter
7615 &`NETTIME `& set a timeout for a network operation
7616 &`USER `& set the DN, for authenticating the LDAP bind
7617 &`PASS `& set the password, likewise
7618 &`REFERRALS `& set the referrals parameter
7619 &`SERVERS `& set alternate server list for this query only
7620 &`SIZE `& set the limit for the number of entries returned
7621 &`TIME `& set the maximum waiting time for a query
7623 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7624 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7625 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7626 library from trying to follow referrals issued by the LDAP server.
7628 .cindex LDAP timeout
7629 .cindex timeout "LDAP lookup"
7630 The name CONNECT is an obsolete name for NETTIME, retained for
7631 backwards compatibility. This timeout (specified as a number of seconds) is
7632 enforced from the client end for operations that can be carried out over a
7633 network. Specifically, it applies to network connections and calls to the
7634 &'ldap_result()'& function. If the value is greater than zero, it is used if
7635 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7636 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7637 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7638 Netscape SDK; for OpenLDAP no action is taken.
7640 The TIME parameter (also a number of seconds) is passed to the server to
7641 set a server-side limit on the time taken to complete a search.
7643 The SERVERS parameter allows you to specify an alternate list of ldap servers
7644 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7645 default list of ldap servers, and a single lookup can specify a single ldap
7646 server to use. But when you need to do a lookup with a list of servers that is
7647 different than the default list (maybe different order, maybe a completely
7648 different set of servers), the SERVERS parameter allows you to specify this
7649 alternate list (colon-separated).
7651 Here is an example of an LDAP query in an Exim lookup that uses some of these
7652 values. This is a single line, folded to fit on the page:
7655 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7656 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7659 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7660 any of the auxiliary data. Exim configuration settings that include lookups
7661 which contain password information should be preceded by &"hide"& to prevent
7662 non-admin users from using the &%-bP%& option to see their values.
7664 The auxiliary data items may be given in any order. The default is no
7665 connection timeout (the system timeout is used), no user or password, no limit
7666 on the number of entries returned, and no time limit on queries.
7668 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7669 removes any URL quoting that it may contain before passing it LDAP. Apparently
7670 some libraries do this for themselves, but some do not. Removing the URL
7671 quoting has two advantages:
7674 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7675 DNs as with DNs inside actual queries.
7677 It permits spaces inside USER= DNs.
7680 For example, a setting such as
7682 USER=cn=${quote_ldap_dn:$1}
7684 should work even if &$1$& contains spaces.
7686 Expanded data for the PASS= value should be quoted using the &%quote%&
7687 expansion operator, rather than the LDAP quote operators. The only reason this
7688 field needs quoting is to ensure that it conforms to the Exim syntax, which
7689 does not allow unquoted spaces. For example:
7693 The LDAP authentication mechanism can be used to check passwords as part of
7694 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7699 .section "Format of data returned by LDAP" "SECID71"
7700 .cindex "LDAP" "returned data formats"
7701 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7702 as a sequence of values, for example
7704 cn=manager,o=University of Cambridge,c=UK
7706 The &(ldap)& lookup type generates an error if more than one entry matches the
7707 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7708 the result between the data from different entries. It is possible for multiple
7709 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7710 you know that whatever values are returned all came from a single entry in the
7713 In the common case where you specify a single attribute in your LDAP query, the
7714 result is not quoted, and does not contain the attribute name. If the attribute
7715 has multiple values, they are separated by commas. Any comma that is
7716 part of an attribute's value is doubled.
7718 If you specify multiple attributes, the result contains space-separated, quoted
7719 strings, each preceded by the attribute name and an equals sign. Within the
7720 quotes, the quote character, backslash, and newline are escaped with
7721 backslashes, and commas are used to separate multiple values for the attribute.
7722 Any commas in attribute values are doubled
7723 (permitting treatment of the values as a comma-separated list).
7724 Apart from the escaping, the string within quotes takes the same form as the
7725 output when a single attribute is requested. Specifying no attributes is the
7726 same as specifying all of an entry's attributes.
7728 Here are some examples of the output format. The first line of each pair is an
7729 LDAP query, and the second is the data that is returned. The attribute called
7730 &%attr1%& has two values, one of them with an embedded comma, whereas
7731 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7732 (they have SUP &%attr%& in their schema definitions).
7735 ldap:///o=base?attr1?sub?(uid=fred)
7738 ldap:///o=base?attr2?sub?(uid=fred)
7741 ldap:///o=base?attr?sub?(uid=fred)
7742 value1.1,value1,,2,value two
7744 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7745 attr1="value1.1,value1,,2" attr2="value two"
7747 ldap:///o=base??sub?(uid=fred)
7748 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7751 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7752 results of LDAP lookups.
7753 The &%extract%& operator in string expansions can be used to pick out
7754 individual fields from data that consists of &'key'&=&'value'& pairs.
7755 The &%listextract%& operator should be used to pick out individual values
7756 of attributes, even when only a single value is expected.
7757 The doubling of embedded commas allows you to use the returned data as a
7758 comma separated list (using the "<," syntax for changing the input list separator).
7763 .section "More about NIS+" "SECTnisplus"
7764 .cindex "NIS+ lookup type"
7765 .cindex "lookup" "NIS+"
7766 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7767 and field name. If this is given, the result of a successful query is the
7768 contents of the named field; otherwise the result consists of a concatenation
7769 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7770 values containing spaces are quoted. For example, the query
7772 [name=mg1456],passwd.org_dir
7774 might return the string
7776 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7777 home=/home/mg1456 shell=/bin/bash shadow=""
7779 (split over two lines here to fit on the page), whereas
7781 [name=mg1456],passwd.org_dir:gcos
7787 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7788 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7789 operator is to double any quote characters within the text.
7793 .section "SQL lookups" "SECTsql"
7794 .cindex "SQL lookup types"
7795 .cindex "MySQL" "lookup type"
7796 .cindex "PostgreSQL lookup type"
7797 .cindex "lookup" "MySQL"
7798 .cindex "lookup" "PostgreSQL"
7799 .cindex "Oracle" "lookup type"
7800 .cindex "lookup" "Oracle"
7801 .cindex "InterBase lookup type"
7802 .cindex "lookup" "InterBase"
7803 .cindex "Redis lookup type"
7804 .cindex lookup Redis
7805 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
7807 databases. Queries for these databases contain SQL statements, so an example
7810 ${lookup mysql{select mailbox from users where id='userx'}\
7813 If the result of the query contains more than one field, the data for each
7814 field in the row is returned, preceded by its name, so the result of
7816 ${lookup pgsql{select home,name from users where id='userx'}\
7821 home=/home/userx name="Mister X"
7823 Empty values and values containing spaces are double quoted, with embedded
7824 quotes escaped by a backslash. If the result of the query contains just one
7825 field, the value is passed back verbatim, without a field name, for example:
7829 If the result of the query yields more than one row, it is all concatenated,
7830 with a newline between the data for each row.
7833 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
7834 .cindex "MySQL" "lookup type"
7835 .cindex "PostgreSQL lookup type"
7836 .cindex "lookup" "MySQL"
7837 .cindex "lookup" "PostgreSQL"
7838 .cindex "Oracle" "lookup type"
7839 .cindex "lookup" "Oracle"
7840 .cindex "InterBase lookup type"
7841 .cindex "lookup" "InterBase"
7842 .cindex "Redis lookup type"
7843 .cindex lookup Redis
7844 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
7845 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
7846 or &%redis_servers%&
7847 option (as appropriate) must be set to a colon-separated list of server
7849 (For MySQL and PostgreSQL, the global option need not be set if all
7850 queries contain their own server information &-- see section
7851 &<<SECTspeserque>>&.)
7853 each item in the list is a slash-separated list of four
7854 items: host name, database name, user name, and password. In the case of
7855 Oracle, the host name field is used for the &"service name"&, and the database
7856 name field is not used and should be empty. For example:
7858 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7860 Because password data is sensitive, you should always precede the setting with
7861 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7862 option. Here is an example where two MySQL servers are listed:
7864 hide mysql_servers = localhost/users/root/secret:\
7865 otherhost/users/root/othersecret
7867 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7868 because this is a colon-separated list, the colon has to be doubled. For each
7869 query, these parameter groups are tried in order until a connection is made and
7870 a query is successfully processed. The result of a query may be that no data is
7871 found, but that is still a successful query. In other words, the list of
7872 servers provides a backup facility, not a list of different places to look.
7874 For Redis the global option need not be specified if all queries contain their
7875 own server information &-- see section &<<SECTspeserque>>&.
7876 If specified, the option must be set to a colon-separated list of server
7878 Each item in the list is a slash-separated list of three items:
7879 host, database number, and password.
7881 The host is required and may be either an IPv4 address and optional
7882 port number (separated by a colon, which needs doubling due to the
7883 higher-level list), or a Unix socket pathname enclosed in parentheses
7885 The database number is optional; if present that number is selected in the backend
7887 The password is optional; if present it is used to authenticate to the backend
7890 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7891 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7892 respectively, and the characters single-quote, double-quote, and backslash
7893 itself are escaped with backslashes.
7895 The &%quote_redis%& expansion operator
7896 escapes whitespace and backslash characters with a backslash.
7898 .section "Specifying the server in the query" "SECTspeserque"
7899 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
7900 it is possible to specify a list of servers with an individual query. This is
7901 done by starting the query with
7903 &`servers=`&&'server1:server2:server3:...'&&`;`&
7905 Each item in the list may take one of two forms:
7907 If it contains no slashes it is assumed to be just a host name. The appropriate
7908 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7909 of the same name, and the remaining parameters (database, user, password) are
7912 If it contains any slashes, it is taken as a complete parameter set.
7914 The list of servers is used in exactly the same way as the global list.
7915 Once a connection to a server has happened and a query has been
7916 successfully executed, processing of the lookup ceases.
7918 This feature is intended for use in master/slave situations where updates
7919 are occurring and you want to update the master rather than a slave. If the
7920 master is in the list as a backup for reading, you might have a global setting
7923 mysql_servers = slave1/db/name/pw:\
7927 In an updating lookup, you could then write:
7929 ${lookup mysql{servers=master; UPDATE ...} }
7931 That query would then be sent only to the master server. If, on the other hand,
7932 the master is not to be used for reading, and so is not present in the global
7933 option, you can still update it by a query of this form:
7935 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7939 .section "Special MySQL features" "SECID73"
7940 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7941 causes a connection to the server on the local host by means of a Unix domain
7942 socket. An alternate socket can be specified in parentheses.
7943 An option group name for MySQL option files can be specified in square brackets;
7944 the default value is &"exim"&.
7945 The full syntax of each item in &%mysql_servers%& is:
7947 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
7948 <&'database'&>/<&'user'&>/<&'password'&>
7950 Any of the four sub-parts of the first field can be omitted. For normal use on
7951 the local host it can be left blank or set to just &"localhost"&.
7953 No database need be supplied &-- but if it is absent here, it must be given in
7956 If a MySQL query is issued that does not request any data (an insert, update,
7957 or delete command), the result of the lookup is the number of rows affected.
7959 &*Warning*&: This can be misleading. If an update does not actually change
7960 anything (for example, setting a field to the value it already has), the result
7961 is zero because no rows are affected.
7964 .section "Special PostgreSQL features" "SECID74"
7965 PostgreSQL lookups can also use Unix domain socket connections to the database.
7966 This is usually faster and costs less CPU time than a TCP/IP connection.
7967 However it can be used only if the mail server runs on the same machine as the
7968 database server. A configuration line for PostgreSQL via Unix domain sockets
7971 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7973 In other words, instead of supplying a host name, a path to the socket is
7974 given. The path name is enclosed in parentheses so that its slashes aren't
7975 visually confused with the delimiters for the other server parameters.
7977 If a PostgreSQL query is issued that does not request any data (an insert,
7978 update, or delete command), the result of the lookup is the number of rows
7981 .section "More about SQLite" "SECTsqlite"
7982 .cindex "lookup" "SQLite"
7983 .cindex "sqlite lookup type"
7984 SQLite is different to the other SQL lookups because a filename is required in
7985 addition to the SQL query. An SQLite database is a single file, and there is no
7986 daemon as in the other SQL databases. The interface to Exim requires the name
7987 of the file, as an absolute path, to be given at the start of the query. It is
7988 separated from the query by white space. This means that the path name cannot
7989 contain white space. Here is a lookup expansion example:
7991 ${lookup sqlite {/some/thing/sqlitedb \
7992 select name from aliases where id='userx';}}
7994 In a list, the syntax is similar. For example:
7996 domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \
7997 select * from relays where ip='$sender_host_address';
7999 The only character affected by the &%quote_sqlite%& operator is a single
8000 quote, which it doubles.
8002 .cindex timeout SQLite
8003 .cindex sqlite "lookup timeout"
8004 The SQLite library handles multiple simultaneous accesses to the database
8005 internally. Multiple readers are permitted, but only one process can
8006 update at once. Attempts to access the database while it is being updated
8007 are rejected after a timeout period, during which the SQLite library
8008 waits for the lock to be released. In Exim, the default timeout is set
8009 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
8012 .section "More about Redis" "SECTredis"
8013 .cindex "lookup" "Redis"
8014 .cindex "redis lookup type"
8015 Redis is a non-SQL database. Commands are simple get and set.
8018 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
8019 ${lookup redis{get keyname}}
8022 As of release 4.91, "lightweight" support for Redis Cluster is available.
8023 Requires &%redis_servers%& list to contain all the servers in the cluster, all
8024 of which must be reachable from the running exim instance. If the cluster has
8025 master/slave replication, the list must contain all the master and slave
8028 When the Redis Cluster returns a "MOVED" response to a query, Exim does not
8029 immediately follow the redirection but treats the response as a DEFER, moving on
8030 to the next server in the &%redis_servers%& list until the correct server is
8037 . ////////////////////////////////////////////////////////////////////////////
8038 . ////////////////////////////////////////////////////////////////////////////
8040 .chapter "Domain, host, address, and local part lists" &&&
8041 "CHAPdomhosaddlists" &&&
8042 "Domain, host, and address lists"
8043 .scindex IIDdohoadli "lists of domains; hosts; etc."
8044 A number of Exim configuration options contain lists of domains, hosts,
8045 email addresses, or local parts. For example, the &%hold_domains%& option
8046 contains a list of domains whose delivery is currently suspended. These lists
8047 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
8048 arguments to expansion conditions such as &%match_domain%&.
8050 Each item in one of these lists is a pattern to be matched against a domain,
8051 host, email address, or local part, respectively. In the sections below, the
8052 different types of pattern for each case are described, but first we cover some
8053 general facilities that apply to all four kinds of list.
8055 Note that other parts of Exim use a &'string list'& which does not
8056 support all the complexity available in
8057 domain, host, address and local part lists.
8061 .section "Expansion of lists" "SECTlistexpand"
8062 .cindex "expansion" "of lists"
8063 Each list is expanded as a single string before it is used.
8065 &'Exception: the router headers_remove option, where list-item
8066 splitting is done before string-expansion.'&
8069 expansion must be a list, possibly containing empty items, which is split up
8070 into separate items for matching. By default, colon is the separator character,
8071 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
8072 &<<SECTempitelis>>& for details of the list syntax; the second of these
8073 discusses the way to specify empty list items.
8076 If the string expansion is forced to fail, Exim behaves as if the item it is
8077 testing (domain, host, address, or local part) is not in the list. Other
8078 expansion failures cause temporary errors.
8080 If an item in a list is a regular expression, backslashes, dollars and possibly
8081 other special characters in the expression must be protected against
8082 misinterpretation by the string expander. The easiest way to do this is to use
8083 the &`\N`& expansion feature to indicate that the contents of the regular
8084 expression should not be expanded. For example, in an ACL you might have:
8086 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
8087 ${lookup{$domain}lsearch{/badsenders/bydomain}}
8089 The first item is a regular expression that is protected from expansion by
8090 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
8091 senders based on the receiving domain.
8096 .section "Negated items in lists" "SECID76"
8097 .cindex "list" "negation"
8098 .cindex "negation" "in lists"
8099 Items in a list may be positive or negative. Negative items are indicated by a
8100 leading exclamation mark, which may be followed by optional white space. A list
8101 defines a set of items (domains, etc). When Exim processes one of these lists,
8102 it is trying to find out whether a domain, host, address, or local part
8103 (respectively) is in the set that is defined by the list. It works like this:
8105 The list is scanned from left to right. If a positive item is matched, the
8106 subject that is being checked is in the set; if a negative item is matched, the
8107 subject is not in the set. If the end of the list is reached without the
8108 subject having matched any of the patterns, it is in the set if the last item
8109 was a negative one, but not if it was a positive one. For example, the list in
8111 domainlist relay_to_domains = !a.b.c : *.b.c
8113 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
8114 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
8115 list is positive. However, if the setting were
8117 domainlist relay_to_domains = !a.b.c
8119 then all domains other than &'a.b.c'& would match because the last item in the
8120 list is negative. In other words, a list that ends with a negative item behaves
8121 as if it had an extra item &`:*`& on the end.
8123 Another way of thinking about positive and negative items in lists is to read
8124 the connector as &"or"& after a positive item and as &"and"& after a negative
8129 .section "File names in lists" "SECTfilnamlis"
8130 .cindex "list" "filename in"
8131 If an item in a domain, host, address, or local part list is an absolute
8132 filename (beginning with a slash character), each line of the file is read and
8133 processed as if it were an independent item in the list, except that further
8134 filenames are not allowed,
8135 and no expansion of the data from the file takes place.
8136 Empty lines in the file are ignored, and the file may also contain comment
8140 For domain and host lists, if a # character appears anywhere in a line of the
8141 file, it and all following characters are ignored.
8143 Because local parts may legitimately contain # characters, a comment in an
8144 address list or local part list file is recognized only if # is preceded by
8145 white space or the start of the line. For example:
8147 not#comment@x.y.z # but this is a comment
8151 Putting a filename in a list has the same effect as inserting each line of the
8152 file as an item in the list (blank lines and comments excepted). However, there
8153 is one important difference: the file is read each time the list is processed,
8154 so if its contents vary over time, Exim's behaviour changes.
8156 If a filename is preceded by an exclamation mark, the sense of any match
8157 within the file is inverted. For example, if
8159 hold_domains = !/etc/nohold-domains
8161 and the file contains the lines
8166 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
8167 any domain matching &`*.b.c`& is not.
8171 .section "An lsearch file is not an out-of-line list" "SECID77"
8172 As will be described in the sections that follow, lookups can be used in lists
8173 to provide indexed methods of checking list membership. There has been some
8174 confusion about the way &(lsearch)& lookups work in lists. Because
8175 an &(lsearch)& file contains plain text and is scanned sequentially, it is
8176 sometimes thought that it is allowed to contain wild cards and other kinds of
8177 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
8178 always fixed strings, just as for any other single-key lookup type.
8180 If you want to use a file to contain wild-card patterns that form part of a
8181 list, just give the filename on its own, without a search type, as described
8182 in the previous section. You could also use the &(wildlsearch)& or
8183 &(nwildlsearch)&, but there is no advantage in doing this.
8188 .section "Named lists" "SECTnamedlists"
8189 .cindex "named lists"
8190 .cindex "list" "named"
8191 A list of domains, hosts, email addresses, or local parts can be given a name
8192 which is then used to refer to the list elsewhere in the configuration. This is
8193 particularly convenient if the same list is required in several different
8194 places. It also allows lists to be given meaningful names, which can improve
8195 the readability of the configuration. For example, it is conventional to define
8196 a domain list called &'local_domains'& for all the domains that are handled
8197 locally on a host, using a configuration line such as
8199 domainlist local_domains = localhost:my.dom.example
8201 Named lists are referenced by giving their name preceded by a plus sign, so,
8202 for example, a router that is intended to handle local domains would be
8203 configured with the line
8205 domains = +local_domains
8207 The first router in a configuration is often one that handles all domains
8208 except the local ones, using a configuration with a negated item like this:
8212 domains = ! +local_domains
8213 transport = remote_smtp
8216 The four kinds of named list are created by configuration lines starting with
8217 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8218 respectively. Then there follows the name that you are defining, followed by an
8219 equals sign and the list itself. For example:
8221 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8222 addresslist bad_senders = cdb;/etc/badsenders
8224 A named list may refer to other named lists:
8226 domainlist dom1 = first.example : second.example
8227 domainlist dom2 = +dom1 : third.example
8228 domainlist dom3 = fourth.example : +dom2 : fifth.example
8230 &*Warning*&: If the last item in a referenced list is a negative one, the
8231 effect may not be what you intended, because the negation does not propagate
8232 out to the higher level. For example, consider:
8234 domainlist dom1 = !a.b
8235 domainlist dom2 = +dom1 : *.b
8237 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8238 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8239 means it matches the second list as well. The effect is not the same as
8241 domainlist dom2 = !a.b : *.b
8243 where &'x.y'& does not match. It's best to avoid negation altogether in
8244 referenced lists if you can.
8246 Named lists may have a performance advantage. When Exim is routing an
8247 address or checking an incoming message, it caches the result of tests on named
8248 lists. So, if you have a setting such as
8250 domains = +local_domains
8252 on several of your routers
8253 or in several ACL statements,
8254 the actual test is done only for the first one. However, the caching works only
8255 if there are no expansions within the list itself or any sublists that it
8256 references. In other words, caching happens only for lists that are known to be
8257 the same each time they are referenced.
8259 By default, there may be up to 16 named lists of each type. This limit can be
8260 extended by changing a compile-time variable. The use of domain and host lists
8261 is recommended for concepts such as local domains, relay domains, and relay
8262 hosts. The default configuration is set up like this.
8266 .section "Named lists compared with macros" "SECID78"
8267 .cindex "list" "named compared with macro"
8268 .cindex "macro" "compared with named list"
8269 At first sight, named lists might seem to be no different from macros in the
8270 configuration file. However, macros are just textual substitutions. If you
8273 ALIST = host1 : host2
8274 auth_advertise_hosts = !ALIST
8276 it probably won't do what you want, because that is exactly the same as
8278 auth_advertise_hosts = !host1 : host2
8280 Notice that the second host name is not negated. However, if you use a host
8283 hostlist alist = host1 : host2
8284 auth_advertise_hosts = ! +alist
8286 the negation applies to the whole list, and so that is equivalent to
8288 auth_advertise_hosts = !host1 : !host2
8292 .section "Named list caching" "SECID79"
8293 .cindex "list" "caching of named"
8294 .cindex "caching" "named lists"
8295 While processing a message, Exim caches the result of checking a named list if
8296 it is sure that the list is the same each time. In practice, this means that
8297 the cache operates only if the list contains no $ characters, which guarantees
8298 that it will not change when it is expanded. Sometimes, however, you may have
8299 an expanded list that you know will be the same each time within a given
8300 message. For example:
8302 domainlist special_domains = \
8303 ${lookup{$sender_host_address}cdb{/some/file}}
8305 This provides a list of domains that depends only on the sending host's IP
8306 address. If this domain list is referenced a number of times (for example,
8307 in several ACL lines, or in several routers) the result of the check is not
8308 cached by default, because Exim does not know that it is going to be the
8309 same list each time.
8311 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8312 cache the result anyway. For example:
8314 domainlist_cache special_domains = ${lookup{...
8316 If you do this, you should be absolutely sure that caching is going to do
8317 the right thing in all cases. When in doubt, leave it out.
8321 .section "Domain lists" "SECTdomainlist"
8322 .cindex "domain list" "patterns for"
8323 .cindex "list" "domain list"
8324 Domain lists contain patterns that are to be matched against a mail domain.
8325 The following types of item may appear in domain lists:
8328 .cindex "primary host name"
8329 .cindex "host name" "matched in domain list"
8330 .oindex "&%primary_hostname%&"
8331 .cindex "domain list" "matching primary host name"
8332 .cindex "@ in a domain list"
8333 If a pattern consists of a single @ character, it matches the local host name,
8334 as set by the &%primary_hostname%& option (or defaulted). This makes it
8335 possible to use the same configuration file on several different hosts that
8336 differ only in their names.
8338 .cindex "@[] in a domain list"
8339 .cindex "domain list" "matching local IP interfaces"
8340 .cindex "domain literal"
8341 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8342 in square brackets (as in an email address that contains a domain literal), but
8343 only if that IP address is recognized as local for email routing purposes. The
8344 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8345 control which of a host's several IP addresses are treated as local.
8346 In today's Internet, the use of domain literals is controversial.
8349 .cindex "@mx_primary"
8350 .cindex "@mx_secondary"
8351 .cindex "domain list" "matching MX pointers to local host"
8352 If a pattern consists of the string &`@mx_any`& it matches any domain that
8353 has an MX record pointing to the local host or to any host that is listed in
8354 .oindex "&%hosts_treat_as_local%&"
8355 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8356 are similar, except that the first matches only when a primary MX target is the
8357 local host, and the second only when no primary MX target is the local host,
8358 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8359 preference value &-- there may of course be more than one of them.
8361 The MX lookup that takes place when matching a pattern of this type is
8362 performed with the resolver options for widening names turned off. Thus, for
8363 example, a single-component domain will &'not'& be expanded by adding the
8364 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8365 options of the &(dnslookup)& router for a discussion of domain widening.
8367 Sometimes you may want to ignore certain IP addresses when using one of these
8368 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8369 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8370 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8371 on a router). For example:
8373 domains = @mx_any/ignore=127.0.0.1
8375 This example matches any domain that has an MX record pointing to one of
8376 the local host's IP addresses other than 127.0.0.1.
8378 The list of IP addresses is in fact processed by the same code that processes
8379 host lists, so it may contain CIDR-coded network specifications and it may also
8380 contain negative items.
8382 Because the list of IP addresses is a sublist within a domain list, you have to
8383 be careful about delimiters if there is more than one address. Like any other
8384 list, the default delimiter can be changed. Thus, you might have:
8386 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8387 an.other.domain : ...
8389 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8390 involved, it is easiest to change the delimiter for the main list as well:
8392 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8393 an.other.domain ? ...
8396 .cindex "asterisk" "in domain list"
8397 .cindex "domain list" "asterisk in"
8398 .cindex "domain list" "matching &""ends with""&"
8399 If a pattern starts with an asterisk, the remaining characters of the pattern
8400 are compared with the terminating characters of the domain. The use of &"*"& in
8401 domain lists differs from its use in partial matching lookups. In a domain
8402 list, the character following the asterisk need not be a dot, whereas partial
8403 matching works only in terms of dot-separated components. For example, a domain
8404 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8408 .cindex "regular expressions" "in domain list"
8409 .cindex "domain list" "matching regular expression"
8410 If a pattern starts with a circumflex character, it is treated as a regular
8411 expression, and matched against the domain using a regular expression matching
8412 function. The circumflex is treated as part of the regular expression.
8413 Email domains are case-independent, so this regular expression match is by
8414 default case-independent, but you can make it case-dependent by starting it
8415 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8416 are given in chapter &<<CHAPregexp>>&.
8418 &*Warning*&: Because domain lists are expanded before being processed, you
8419 must escape any backslash and dollar characters in the regular expression, or
8420 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8421 it is not to be expanded (unless you really do want to build a regular
8422 expression by expansion, of course).
8424 .cindex "lookup" "in domain list"
8425 .cindex "domain list" "matching by lookup"
8426 If a pattern starts with the name of a single-key lookup type followed by a
8427 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8428 must be a filename in a suitable format for the lookup type. For example, for
8429 &"cdb;"& it must be an absolute path:
8431 domains = cdb;/etc/mail/local_domains.cdb
8433 The appropriate type of lookup is done on the file using the domain name as the
8434 key. In most cases, the data that is looked up is not used; Exim is interested
8435 only in whether or not the key is present in the file. However, when a lookup
8436 is used for the &%domains%& option on a router
8437 or a &%domains%& condition in an ACL statement, the data is preserved in the
8438 &$domain_data$& variable and can be referred to in other router options or
8439 other statements in the same ACL.
8442 Any of the single-key lookup type names may be preceded by
8443 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8445 domains = partial-dbm;/partial/domains
8447 This causes partial matching logic to be invoked; a description of how this
8448 works is given in section &<<SECTpartiallookup>>&.
8451 .cindex "asterisk" "in lookup type"
8452 Any of the single-key lookup types may be followed by an asterisk. This causes
8453 a default lookup for a key consisting of a single asterisk to be done if the
8454 original lookup fails. This is not a useful feature when using a domain list to
8455 select particular domains (because any domain would match), but it might have
8456 value if the result of the lookup is being used via the &$domain_data$&
8459 If the pattern starts with the name of a query-style lookup type followed by a
8460 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8461 pattern must be an appropriate query for the lookup type, as described in
8462 chapter &<<CHAPfdlookup>>&. For example:
8464 hold_domains = mysql;select domain from holdlist \
8465 where domain = '${quote_mysql:$domain}';
8467 In most cases, the data that is looked up is not used (so for an SQL query, for
8468 example, it doesn't matter what field you select). Exim is interested only in
8469 whether or not the query succeeds. However, when a lookup is used for the
8470 &%domains%& option on a router, the data is preserved in the &$domain_data$&
8471 variable and can be referred to in other options.
8473 .cindex "domain list" "matching literal domain name"
8474 If none of the above cases apply, a caseless textual comparison is made
8475 between the pattern and the domain.
8478 Here is an example that uses several different kinds of pattern:
8480 domainlist funny_domains = \
8483 *.foundation.fict.example : \
8484 \N^[1-2]\d{3}\.fict\.example$\N : \
8485 partial-dbm;/opt/data/penguin/book : \
8486 nis;domains.byname : \
8487 nisplus;[name=$domain,status=local],domains.org_dir
8489 There are obvious processing trade-offs among the various matching modes. Using
8490 an asterisk is faster than a regular expression, and listing a few names
8491 explicitly probably is too. The use of a file or database lookup is expensive,
8492 but may be the only option if hundreds of names are required. Because the
8493 patterns are tested in order, it makes sense to put the most commonly matched
8498 .section "Host lists" "SECThostlist"
8499 .cindex "host list" "patterns in"
8500 .cindex "list" "host list"
8501 Host lists are used to control what remote hosts are allowed to do. For
8502 example, some hosts may be allowed to use the local host as a relay, and some
8503 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8504 two different ways, by name or by IP address. In a host list, some types of
8505 pattern are matched to a host name, and some are matched to an IP address.
8506 You need to be particularly careful with this when single-key lookups are
8507 involved, to ensure that the right value is being used as the key.
8510 .section "Special host list patterns" "SECID80"
8511 .cindex "empty item in hosts list"
8512 .cindex "host list" "empty string in"
8513 If a host list item is the empty string, it matches only when no remote host is
8514 involved. This is the case when a message is being received from a local
8515 process using SMTP on the standard input, that is, when a TCP/IP connection is
8518 .cindex "asterisk" "in host list"
8519 The special pattern &"*"& in a host list matches any host or no host. Neither
8520 the IP address nor the name is actually inspected.
8524 .section "Host list patterns that match by IP address" "SECThoslispatip"
8525 .cindex "host list" "matching IP addresses"
8526 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8527 the incoming address actually appears in the IPv6 host as
8528 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8529 list, it is converted into a traditional IPv4 address first. (Not all operating
8530 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8533 The following types of pattern in a host list check the remote host by
8534 inspecting its IP address:
8537 If the pattern is a plain domain name (not a regular expression, not starting
8538 with *, not a lookup of any kind), Exim calls the operating system function
8539 to find the associated IP address(es). Exim uses the newer
8540 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8541 This typically causes a forward DNS lookup of the name. The result is compared
8542 with the IP address of the subject host.
8544 If there is a temporary problem (such as a DNS timeout) with the host name
8545 lookup, a temporary error occurs. For example, if the list is being used in an
8546 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8547 temporary SMTP error code. If no IP address can be found for the host name,
8548 what happens is described in section &<<SECTbehipnot>>& below.
8551 .cindex "@ in a host list"
8552 If the pattern is &"@"&, the primary host name is substituted and used as a
8553 domain name, as just described.
8556 If the pattern is an IP address, it is matched against the IP address of the
8557 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8558 IPv6 addresses can be given in colon-separated format, but the colons have to
8559 be doubled so as not to be taken as item separators when the default list
8560 separator is used. IPv6 addresses are recognized even when Exim is compiled
8561 without IPv6 support. This means that if they appear in a host list on an
8562 IPv4-only host, Exim will not treat them as host names. They are just addresses
8563 that can never match a client host.
8566 .cindex "@[] in a host list"
8567 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8568 the local host. For example, if the local host is an IPv4 host with one
8569 interface address 10.45.23.56, these two ACL statements have the same effect:
8571 accept hosts = 127.0.0.1 : 10.45.23.56
8575 .cindex "CIDR notation"
8576 If the pattern is an IP address followed by a slash and a mask length (for
8577 example 10.11.42.0/24), it is matched against the IP address of the subject
8578 host under the given mask. This allows, an entire network of hosts to be
8579 included (or excluded) by a single item. The mask uses CIDR notation; it
8580 specifies the number of address bits that must match, starting from the most
8581 significant end of the address.
8583 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8584 of a range of addresses. It is the number of bits in the network portion of the
8585 address. The above example specifies a 24-bit netmask, so it matches all 256
8586 addresses in the 10.11.42.0 network. An item such as
8590 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8591 32 for an IPv4 address is the same as no mask at all; just a single address
8594 Here is another example which shows an IPv4 and an IPv6 network:
8596 recipient_unqualified_hosts = 192.168.0.0/16: \
8597 3ffe::ffff::836f::::/48
8599 The doubling of list separator characters applies only when these items
8600 appear inline in a host list. It is not required when indirecting via a file.
8603 recipient_unqualified_hosts = /opt/exim/unqualnets
8605 could make use of a file containing
8610 to have exactly the same effect as the previous example. When listing IPv6
8611 addresses inline, it is usually more convenient to use the facility for
8612 changing separator characters. This list contains the same two networks:
8614 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8617 The separator is changed to semicolon by the leading &"<;"& at the start of the
8623 .section "Host list patterns for single-key lookups by host address" &&&
8624 "SECThoslispatsikey"
8625 .cindex "host list" "lookup of IP address"
8626 When a host is to be identified by a single-key lookup of its complete IP
8627 address, the pattern takes this form:
8629 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8633 hosts_lookup = net-cdb;/hosts-by-ip.db
8635 The text form of the IP address of the subject host is used as the lookup key.
8636 IPv6 addresses are converted to an unabbreviated form, using lower case
8637 letters, with dots as separators because colon is the key terminator in
8638 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8639 quoting the keys, but this is a facility that was added later.] The data
8640 returned by the lookup is not used.
8642 .cindex "IP address" "masking"
8643 .cindex "host list" "masked IP address"
8644 Single-key lookups can also be performed using masked IP addresses, using
8645 patterns of this form:
8647 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8651 net24-dbm;/networks.db
8653 The IP address of the subject host is masked using <&'number'&> as the mask
8654 length. A textual string is constructed from the masked value, followed by the
8655 mask, and this is used as the lookup key. For example, if the host's IP address
8656 is 192.168.34.6, the key that is looked up for the above example is
8657 &"192.168.34.0/24"&.
8659 When an IPv6 address is converted to a string, dots are normally used instead
8660 of colons, so that keys in &(lsearch)& files need not contain colons (which
8661 terminate &(lsearch)& keys). This was implemented some time before the ability
8662 to quote keys was made available in &(lsearch)& files. However, the more
8663 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8664 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8665 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8666 converted using colons and not dots. In all cases, full, unabbreviated IPv6
8667 addresses are always used.
8669 Ideally, it would be nice to tidy up this anomalous situation by changing to
8670 colons in all cases, given that quoting is now available for &(lsearch)&.
8671 However, this would be an incompatible change that might break some existing
8674 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8675 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8676 the former case the key strings include the mask value, whereas in the latter
8677 case the IP address is used on its own.
8681 .section "Host list patterns that match by host name" "SECThoslispatnam"
8682 .cindex "host" "lookup failures"
8683 .cindex "unknown host name"
8684 .cindex "host list" "matching host name"
8685 There are several types of pattern that require Exim to know the name of the
8686 remote host. These are either wildcard patterns or lookups by name. (If a
8687 complete hostname is given without any wildcarding, it is used to find an IP
8688 address to match against, as described in section &<<SECThoslispatip>>&
8691 If the remote host name is not already known when Exim encounters one of these
8692 patterns, it has to be found from the IP address.
8693 Although many sites on the Internet are conscientious about maintaining reverse
8694 DNS data for their hosts, there are also many that do not do this.
8695 Consequently, a name cannot always be found, and this may lead to unwanted
8696 effects. Take care when configuring host lists with wildcarded name patterns.
8697 Consider what will happen if a name cannot be found.
8699 Because of the problems of determining host names from IP addresses, matching
8700 against host names is not as common as matching against IP addresses.
8702 By default, in order to find a host name, Exim first does a reverse DNS lookup;
8703 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
8704 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
8705 are done can be changed by setting the &%host_lookup_order%& option. For
8706 security, once Exim has found one or more names, it looks up the IP addresses
8707 for these names and compares them with the IP address that it started with.
8708 Only those names whose IP addresses match are accepted. Any other names are
8709 discarded. If no names are left, Exim behaves as if the host name cannot be
8710 found. In the most common case there is only one name and one IP address.
8712 There are some options that control what happens if a host name cannot be
8713 found. These are described in section &<<SECTbehipnot>>& below.
8715 .cindex "host" "alias for"
8716 .cindex "alias for host"
8717 As a result of aliasing, hosts may have more than one name. When processing any
8718 of the following types of pattern, all the host's names are checked:
8721 .cindex "asterisk" "in host list"
8722 If a pattern starts with &"*"& the remainder of the item must match the end of
8723 the host name. For example, &`*.b.c`& matches all hosts whose names end in
8724 &'.b.c'&. This special simple form is provided because this is a very common
8725 requirement. Other kinds of wildcarding require the use of a regular
8728 .cindex "regular expressions" "in host list"
8729 .cindex "host list" "regular expression in"
8730 If the item starts with &"^"& it is taken to be a regular expression which is
8731 matched against the host name. Host names are case-independent, so this regular
8732 expression match is by default case-independent, but you can make it
8733 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
8734 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
8739 is a regular expression that matches either of the two hosts &'a.c.d'& or
8740 &'b.c.d'&. When a regular expression is used in a host list, you must take care
8741 that backslash and dollar characters are not misinterpreted as part of the
8742 string expansion. The simplest way to do this is to use &`\N`& to mark that
8743 part of the string as non-expandable. For example:
8745 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
8747 &*Warning*&: If you want to match a complete host name, you must include the
8748 &`$`& terminating metacharacter in the regular expression, as in the above
8749 example. Without it, a match at the start of the host name is all that is
8756 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
8757 .cindex "host" "lookup failures, permanent"
8758 While processing a host list, Exim may need to look up an IP address from a
8759 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
8760 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
8761 behaviour when it fails to find the information it is seeking is the same.
8763 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
8764 apply to temporary DNS errors, whose handling is described in the next section.
8766 .cindex "&`+include_unknown`&"
8767 .cindex "&`+ignore_unknown`&"
8768 Exim parses a host list from left to right. If it encounters a permanent
8769 lookup failure in any item in the host list before it has found a match,
8770 Exim treats it as a failure and the default behavior is as if the host
8771 does not match the list. This may not always be what you want to happen.
8772 To change Exim's behaviour, the special items &`+include_unknown`& or
8773 &`+ignore_unknown`& may appear in the list (at top level &-- they are
8774 not recognized in an indirected file).
8777 If any item that follows &`+include_unknown`& requires information that
8778 cannot found, Exim behaves as if the host does match the list. For example,
8780 host_reject_connection = +include_unknown:*.enemy.ex
8782 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
8783 any hosts whose name it cannot find.
8786 If any item that follows &`+ignore_unknown`& requires information that cannot
8787 be found, Exim ignores that item and proceeds to the rest of the list. For
8790 accept hosts = +ignore_unknown : friend.example : \
8793 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8794 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8795 name can be found for 192.168.4.5, it is rejected.
8798 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8799 list. The effect of each one lasts until the next, or until the end of the
8802 .section "Mixing wildcarded host names and addresses in host lists" &&&
8804 .cindex "host list" "mixing names and addresses in"
8806 This section explains the host/ip processing logic with the same concepts
8807 as the previous section, but specifically addresses what happens when a
8808 wildcarded hostname is one of the items in the hostlist.
8811 If you have name lookups or wildcarded host names and
8812 IP addresses in the same host list, you should normally put the IP
8813 addresses first. For example, in an ACL you could have:
8815 accept hosts = 10.9.8.7 : *.friend.example
8817 The reason you normally would order it this way lies in the
8818 left-to-right way that Exim processes lists. It can test IP addresses
8819 without doing any DNS lookups, but when it reaches an item that requires
8820 a host name, it fails if it cannot find a host name to compare with the
8821 pattern. If the above list is given in the opposite order, the
8822 &%accept%& statement fails for a host whose name cannot be found, even
8823 if its IP address is 10.9.8.7.
8826 If you really do want to do the name check first, and still recognize the IP
8827 address, you can rewrite the ACL like this:
8829 accept hosts = *.friend.example
8830 accept hosts = 10.9.8.7
8832 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8833 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
8834 &`+ignore_unknown`&, which was discussed in depth in the first example in
8839 .section "Temporary DNS errors when looking up host information" &&&
8841 .cindex "host" "lookup failures, temporary"
8842 .cindex "&`+include_defer`&"
8843 .cindex "&`+ignore_defer`&"
8844 A temporary DNS lookup failure normally causes a defer action (except when
8845 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8846 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
8847 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8848 section. These options should be used with care, probably only in non-critical
8849 host lists such as whitelists.
8853 .section "Host list patterns for single-key lookups by host name" &&&
8854 "SECThoslispatnamsk"
8855 .cindex "unknown host name"
8856 .cindex "host list" "matching host name"
8857 If a pattern is of the form
8859 <&'single-key-search-type'&>;<&'search-data'&>
8863 dbm;/host/accept/list
8865 a single-key lookup is performed, using the host name as its key. If the
8866 lookup succeeds, the host matches the item. The actual data that is looked up
8869 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8870 keys in the file, not IP addresses. If you want to do lookups based on IP
8871 addresses, you must precede the search type with &"net-"& (see section
8872 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8873 two items in the same list, one doing an address lookup and one doing a name
8874 lookup, both using the same file.
8878 .section "Host list patterns for query-style lookups" "SECID81"
8879 If a pattern is of the form
8881 <&'query-style-search-type'&>;<&'query'&>
8883 the query is obeyed, and if it succeeds, the host matches the item. The actual
8884 data that is looked up is not used. The variables &$sender_host_address$& and
8885 &$sender_host_name$& can be used in the query. For example:
8887 hosts_lookup = pgsql;\
8888 select ip from hostlist where ip='$sender_host_address'
8890 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8891 can use the &%sg%& expansion item to change this if you need to. If you want to
8892 use masked IP addresses in database queries, you can use the &%mask%& expansion
8895 If the query contains a reference to &$sender_host_name$&, Exim automatically
8896 looks up the host name if it has not already done so. (See section
8897 &<<SECThoslispatnam>>& for comments on finding host names.)
8899 Historical note: prior to release 4.30, Exim would always attempt to find a
8900 host name before running the query, unless the search type was preceded by
8901 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8902 still recognized for query-style lookups, but its presence or absence has no
8903 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8904 See section &<<SECThoslispatsikey>>&.)
8910 .section "Address lists" "SECTaddresslist"
8911 .cindex "list" "address list"
8912 .cindex "address list" "empty item"
8913 .cindex "address list" "patterns"
8914 Address lists contain patterns that are matched against mail addresses. There
8915 is one special case to be considered: the sender address of a bounce message is
8916 always empty. You can test for this by providing an empty item in an address
8917 list. For example, you can set up a router to process bounce messages by
8918 using this option setting:
8922 The presence of the colon creates an empty item. If you do not provide any
8923 data, the list is empty and matches nothing. The empty sender can also be
8924 detected by a regular expression that matches an empty string,
8925 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8927 Non-empty items in an address list can be straightforward email addresses. For
8930 senders = jbc@askone.example : hs@anacreon.example
8932 A certain amount of wildcarding is permitted. If a pattern contains an @
8933 character, but is not a regular expression and does not begin with a
8934 semicolon-terminated lookup type (described below), the local part of the
8935 subject address is compared with the local part of the pattern, which may start
8936 with an asterisk. If the local parts match, the domain is checked in exactly
8937 the same way as for a pattern in a domain list. For example, the domain can be
8938 wildcarded, refer to a named list, or be a lookup:
8940 deny senders = *@*.spamming.site:\
8941 *@+hostile_domains:\
8942 bozo@partial-lsearch;/list/of/dodgy/sites:\
8943 *@dbm;/bad/domains.db
8945 .cindex "local part" "starting with !"
8946 .cindex "address list" "local part starting with !"
8947 If a local part that begins with an exclamation mark is required, it has to be
8948 specified using a regular expression, because otherwise the exclamation mark is
8949 treated as a sign of negation, as is standard in lists.
8951 If a non-empty pattern that is not a regular expression or a lookup does not
8952 contain an @ character, it is matched against the domain part of the subject
8953 address. The only two formats that are recognized this way are a literal
8954 domain, or a domain pattern that starts with *. In both these cases, the effect
8955 is the same as if &`*@`& preceded the pattern. For example:
8957 deny senders = enemy.domain : *.enemy.domain
8960 The following kinds of more complicated address list pattern can match any
8961 address, including the empty address that is characteristic of bounce message
8965 .cindex "regular expressions" "in address list"
8966 .cindex "address list" "regular expression in"
8967 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8968 done against the complete address, with the pattern as the regular expression.
8969 You must take care that backslash and dollar characters are not misinterpreted
8970 as part of the string expansion. The simplest way to do this is to use &`\N`&
8971 to mark that part of the string as non-expandable. For example:
8973 deny senders = \N^.*this.*@example\.com$\N : \
8974 \N^\d{8}.+@spamhaus.example$\N : ...
8976 The &`\N`& sequences are removed by the expansion, so these items do indeed
8977 start with &"^"& by the time they are being interpreted as address patterns.
8980 .cindex "address list" "lookup for complete address"
8981 Complete addresses can be looked up by using a pattern that starts with a
8982 lookup type terminated by a semicolon, followed by the data for the lookup. For
8985 deny senders = cdb;/etc/blocked.senders : \
8986 mysql;select address from blocked where \
8987 address='${quote_mysql:$sender_address}'
8989 Both query-style and single-key lookup types can be used. For a single-key
8990 lookup type, Exim uses the complete address as the key. However, empty keys are
8991 not supported for single-key lookups, so a match against the empty address
8992 always fails. This restriction does not apply to query-style lookups.
8994 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8995 cannot be used, and is ignored if specified, with an entry being written to the
8997 .cindex "*@ with single-key lookup"
8998 However, you can configure lookup defaults, as described in section
8999 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
9000 default. For example, with this lookup:
9002 accept senders = lsearch*@;/some/file
9004 the file could contains lines like this:
9006 user1@domain1.example
9009 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
9012 nimrod@jaeger.example
9016 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
9017 would mean that every address matches, thus rendering the test useless.
9019 &*Warning 2*&: Do not confuse these two kinds of item:
9021 deny recipients = dbm*@;/some/file
9022 deny recipients = *@dbm;/some/file
9024 The first does a whole address lookup, with defaulting, as just described,
9025 because it starts with a lookup type. The second matches the local part and
9026 domain independently, as described in a bullet point below.
9030 The following kinds of address list pattern can match only non-empty addresses.
9031 If the subject address is empty, a match against any of these pattern types
9036 .cindex "@@ with single-key lookup"
9037 .cindex "address list" "@@ lookup type"
9038 .cindex "address list" "split local part and domain"
9039 If a pattern starts with &"@@"& followed by a single-key lookup item
9040 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
9041 split into a local part and a domain. The domain is looked up in the file. If
9042 it is not found, there is no match. If it is found, the data that is looked up
9043 from the file is treated as a colon-separated list of local part patterns, each
9044 of which is matched against the subject local part in turn.
9046 .cindex "asterisk" "in address list"
9047 The lookup may be a partial one, and/or one involving a search for a default
9048 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
9049 patterns that are looked up can be regular expressions or begin with &"*"&, or
9050 even be further lookups. They may also be independently negated. For example,
9053 deny senders = @@dbm;/etc/reject-by-domain
9055 the data from which the DBM file is built could contain lines like
9057 baddomain.com: !postmaster : *
9059 to reject all senders except &%postmaster%& from that domain.
9061 .cindex "local part" "starting with !"
9062 If a local part that actually begins with an exclamation mark is required, it
9063 has to be specified using a regular expression. In &(lsearch)& files, an entry
9064 may be split over several lines by indenting the second and subsequent lines,
9065 but the separating colon must still be included at line breaks. White space
9066 surrounding the colons is ignored. For example:
9068 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
9071 As in all colon-separated lists in Exim, a colon can be included in an item by
9074 If the last item in the list starts with a right angle-bracket, the remainder
9075 of the item is taken as a new key to look up in order to obtain a continuation
9076 list of local parts. The new key can be any sequence of characters. Thus one
9077 might have entries like
9079 aol.com: spammer1 : spammer 2 : >*
9080 xyz.com: spammer3 : >*
9083 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
9084 local parts for all domains, in addition to the specific local parts listed for
9085 each domain. Of course, using this feature costs another lookup each time a
9086 chain is followed, but the effort needed to maintain the data is reduced.
9088 .cindex "loop" "in lookups"
9089 It is possible to construct loops using this facility, and in order to catch
9090 them, the chains may be no more than fifty items long.
9093 The @@<&'lookup'&> style of item can also be used with a query-style
9094 lookup, but in this case, the chaining facility is not available. The lookup
9095 can only return a single list of local parts.
9098 &*Warning*&: There is an important difference between the address list items
9099 in these two examples:
9102 senders = *@+my_list
9104 In the first one, &`my_list`& is a named address list, whereas in the second
9105 example it is a named domain list.
9110 .section "Case of letters in address lists" "SECTcasletadd"
9111 .cindex "case of local parts"
9112 .cindex "address list" "case forcing"
9113 .cindex "case forcing in address lists"
9114 Domains in email addresses are always handled caselessly, but for local parts
9115 case may be significant on some systems (see &%caseful_local_part%& for how
9116 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
9117 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
9118 blocking lists should be done in a case-independent manner. Since most address
9119 lists in Exim are used for this kind of control, Exim attempts to do this by
9122 The domain portion of an address is always lowercased before matching it to an
9123 address list. The local part is lowercased by default, and any string
9124 comparisons that take place are done caselessly. This means that the data in
9125 the address list itself, in files included as plain filenames, and in any file
9126 that is looked up using the &"@@"& mechanism, can be in any case. However, the
9127 keys in files that are looked up by a search type other than &(lsearch)& (which
9128 works caselessly) must be in lower case, because these lookups are not
9131 .cindex "&`+caseful`&"
9132 To allow for the possibility of caseful address list matching, if an item in
9133 an address list is the string &"+caseful"&, the original case of the local
9134 part is restored for any comparisons that follow, and string comparisons are no
9135 longer case-independent. This does not affect the domain, which remains in
9136 lower case. However, although independent matches on the domain alone are still
9137 performed caselessly, regular expressions that match against an entire address
9138 become case-sensitive after &"+caseful"& has been seen.
9142 .section "Local part lists" "SECTlocparlis"
9143 .cindex "list" "local part list"
9144 .cindex "local part" "list"
9145 Case-sensitivity in local part lists is handled in the same way as for address
9146 lists, as just described. The &"+caseful"& item can be used if required. In a
9147 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
9148 set false, the subject is lowercased and the matching is initially
9149 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
9150 matching in the local part list, but not elsewhere in the router. If
9151 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
9152 option is case-sensitive from the start.
9154 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
9155 comments are handled in the same way as address lists &-- they are recognized
9156 only if the # is preceded by white space or the start of the line.
9157 Otherwise, local part lists are matched in the same way as domain lists, except
9158 that the special items that refer to the local host (&`@`&, &`@[]`&,
9159 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
9160 Refer to section &<<SECTdomainlist>>& for details of the other available item
9162 .ecindex IIDdohoadli
9167 . ////////////////////////////////////////////////////////////////////////////
9168 . ////////////////////////////////////////////////////////////////////////////
9170 .chapter "String expansions" "CHAPexpand"
9171 .scindex IIDstrexp "expansion" "of strings"
9172 Many strings in Exim's runtime configuration are expanded before use. Some of
9173 them are expanded every time they are used; others are expanded only once.
9175 When a string is being expanded it is copied verbatim from left to right except
9176 when a dollar or backslash character is encountered. A dollar specifies the
9177 start of a portion of the string that is interpreted and replaced as described
9178 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
9179 escape character, as described in the following section.
9181 Whether a string is expanded depends upon the context. Usually this is solely
9182 dependent upon the option for which a value is sought; in this documentation,
9183 options for which string expansion is performed are marked with † after
9184 the data type. ACL rules always expand strings. A couple of expansion
9185 conditions do not expand some of the brace-delimited branches, for security
9190 .section "Literal text in expanded strings" "SECTlittext"
9191 .cindex "expansion" "including literal text"
9192 An uninterpreted dollar can be included in an expanded string by putting a
9193 backslash in front of it. A backslash can be used to prevent any special
9194 character being treated specially in an expansion, including backslash itself.
9195 If the string appears in quotes in the configuration file, two backslashes are
9196 required because the quotes themselves cause interpretation of backslashes when
9197 the string is read in (see section &<<SECTstrings>>&).
9199 .cindex "expansion" "non-expandable substrings"
9200 A portion of the string can specified as non-expandable by placing it between
9201 two occurrences of &`\N`&. This is particularly useful for protecting regular
9202 expressions, which often contain backslashes and dollar signs. For example:
9204 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
9206 On encountering the first &`\N`&, the expander copies subsequent characters
9207 without interpretation until it reaches the next &`\N`& or the end of the
9212 .section "Character escape sequences in expanded strings" "SECID82"
9213 .cindex "expansion" "escape sequences"
9214 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9215 expanded string is recognized as an escape sequence for the character newline,
9216 carriage return, or tab, respectively. A backslash followed by up to three
9217 octal digits is recognized as an octal encoding for a single character, and a
9218 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9221 These escape sequences are also recognized in quoted strings when they are read
9222 in. Their interpretation in expansions as well is useful for unquoted strings,
9223 and for other cases such as looked-up strings that are then expanded.
9226 .section "Testing string expansions" "SECID83"
9227 .cindex "expansion" "testing"
9228 .cindex "testing" "string expansion"
9230 Many expansions can be tested by calling Exim with the &%-be%& option. This
9231 takes the command arguments, or lines from the standard input if there are no
9232 arguments, runs them through the string expansion code, and writes the results
9233 to the standard output. Variables based on configuration values are set up, but
9234 since no message is being processed, variables such as &$local_part$& have no
9235 value. Nevertheless the &%-be%& option can be useful for checking out file and
9236 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9239 Exim gives up its root privilege when it is called with the &%-be%& option, and
9240 instead runs under the uid and gid it was called with, to prevent users from
9241 using &%-be%& for reading files to which they do not have access.
9244 If you want to test expansions that include variables whose values are taken
9245 from a message, there are two other options that can be used. The &%-bem%&
9246 option is like &%-be%& except that it is followed by a filename. The file is
9247 read as a message before doing the test expansions. For example:
9249 exim -bem /tmp/test.message '$h_subject:'
9251 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9252 Exim message identifier. For example:
9254 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9256 This loads the message from Exim's spool before doing the test expansions, and
9257 is therefore restricted to admin users.
9260 .section "Forced expansion failure" "SECTforexpfai"
9261 .cindex "expansion" "forced failure"
9262 A number of expansions that are described in the following section have
9263 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9264 (which are sometimes called &"curly brackets"&). Which of the two strings is
9265 used depends on some condition that is evaluated as part of the expansion. If,
9266 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9267 the entire string expansion fails in a way that can be detected by the code
9268 that requested the expansion. This is called &"forced expansion failure"&, and
9269 its consequences depend on the circumstances. In some cases it is no different
9270 from any other expansion failure, but in others a different action may be
9271 taken. Such variations are mentioned in the documentation of the option that is
9277 .section "Expansion items" "SECTexpansionitems"
9278 The following items are recognized in expanded strings. White space may be used
9279 between sub-items that are keywords or substrings enclosed in braces inside an
9280 outer set of braces, to improve readability. &*Warning*&: Within braces,
9281 white space is significant.
9284 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9285 .cindex "expansion" "variables"
9286 Substitute the contents of the named variable, for example:
9291 The second form can be used to separate the name from subsequent alphanumeric
9292 characters. This form (using braces) is available only for variables; it does
9293 &'not'& apply to message headers. The names of the variables are given in
9294 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9295 given, the expansion fails.
9297 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9298 .cindex "expansion" "operators"
9299 The string is first itself expanded, and then the operation specified by
9300 <&'op'&> is applied to it. For example:
9304 The string starts with the first character after the colon, which may be
9305 leading white space. A list of operators is given in section &<<SECTexpop>>&
9306 below. The operator notation is used for simple expansion items that have just
9307 one argument, because it reduces the number of braces and therefore makes the
9308 string easier to understand.
9310 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9311 This item inserts &"basic"& header lines. It is described with the &%header%&
9312 expansion item below.
9315 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9316 .cindex "expansion" "calling an acl"
9317 .cindex "&%acl%&" "call from expansion"
9318 The name and zero to nine argument strings are first expanded separately. The expanded
9319 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9320 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9321 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9322 and may use the variables; if another acl expansion is used the values
9323 are restored after it returns. If the ACL sets
9324 a value using a "message =" modifier and returns accept or deny, the value becomes
9325 the result of the expansion.
9326 If no message is set and the ACL returns accept or deny
9327 the expansion result is an empty string.
9328 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9331 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
9332 .cindex authentication "results header"
9333 .cindex headers "authentication-results:"
9334 .cindex authentication "expansion item"
9335 This item returns a string suitable for insertion as an
9336 &'Authentication-Results"'&
9338 The given <&'authserv-id'&> is included in the result; typically this
9339 will be a domain name identifying the system performing the authentications.
9340 Methods that might be present in the result include:
9349 Example use (as an ACL modifier):
9351 add_header = :at_start:${authresults {$primary_hostname}}
9353 This is safe even if no authentication results are available.
9356 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9357 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9358 .cindex "expansion" "extracting certificate fields"
9359 .cindex "&%certextract%&" "certificate fields"
9360 .cindex "certificate" "extracting fields"
9361 The <&'certificate'&> must be a variable of type certificate.
9362 The field name is expanded and used to retrieve the relevant field from
9363 the certificate. Supported fields are:
9367 &`subject `& RFC4514 DN
9368 &`issuer `& RFC4514 DN
9373 &`subj_altname `& tagged list
9377 If the field is found,
9378 <&'string2'&> is expanded, and replaces the whole item;
9379 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9380 variable &$value$& contains the value that has been extracted. Afterwards, it
9381 is restored to any previous value it might have had.
9383 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9384 key is not found. If {<&'string2'&>} is also omitted, the value that was
9387 Some field names take optional modifiers, appended and separated by commas.
9389 The field selectors marked as "RFC4514" above
9390 output a Distinguished Name string which is
9392 parseable by Exim as a comma-separated tagged list
9393 (the exceptions being elements containing commas).
9394 RDN elements of a single type may be selected by
9395 a modifier of the type label; if so the expansion
9396 result is a list (newline-separated by default).
9397 The separator may be changed by another modifier of
9398 a right angle-bracket followed immediately by the new separator.
9399 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9401 The field selectors marked as "time" above
9402 take an optional modifier of "int"
9403 for which the result is the number of seconds since epoch.
9404 Otherwise the result is a human-readable string
9405 in the timezone selected by the main "timezone" option.
9407 The field selectors marked as "list" above return a list,
9408 newline-separated by default,
9409 (embedded separator characters in elements are doubled).
9410 The separator may be changed by a modifier of
9411 a right angle-bracket followed immediately by the new separator.
9413 The field selectors marked as "tagged" above
9414 prefix each list element with a type string and an equals sign.
9415 Elements of only one type may be selected by a modifier
9416 which is one of "dns", "uri" or "mail";
9417 if so the element tags are omitted.
9419 If not otherwise noted field values are presented in human-readable form.
9421 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9422 {*&<&'arg'&>&*}...}*&"
9424 This expansion dynamically loads and then calls a locally-written C function.
9425 This functionality is available only if Exim is compiled with
9429 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9430 object so that it doesn't reload the same object file in the same Exim process
9431 (but of course Exim does start new processes frequently).
9433 There may be from zero to eight arguments to the function. When compiling
9434 a local function that is to be called in this way, &_local_scan.h_& should be
9435 included. The Exim variables and functions that are defined by that API
9436 are also available for dynamically loaded functions. The function itself
9437 must have the following type:
9439 int dlfunction(uschar **yield, int argc, uschar *argv[])
9441 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9442 function should return one of the following values:
9444 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9445 into the expanded string that is being built.
9447 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9448 from &'yield'&, if it is set.
9450 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9451 taken from &'yield'& if it is set.
9453 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9455 When compiling a function that is to be used in this way with gcc,
9456 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9457 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9460 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9461 .cindex "expansion" "extracting value from environment"
9462 .cindex "environment" "values from"
9463 The key is first expanded separately, and leading and trailing white space
9465 This is then searched for as a name in the environment.
9466 If a variable is found then its value is placed in &$value$&
9467 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9469 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9470 appear, for example:
9472 ${env{USER}{$value} fail }
9474 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9475 {<&'string1'&>} must be present for &"fail"& to be recognized.
9477 If {<&'string2'&>} is omitted an empty string is substituted on
9479 If {<&'string1'&>} is omitted the search result is substituted on
9482 The environment is adjusted by the &%keep_environment%& and
9483 &%add_environment%& main section options.
9486 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9487 {*&<&'string3'&>&*}}*&"
9488 .cindex "expansion" "extracting substrings by key"
9489 .cindex "&%extract%&" "substrings by key"
9490 The key and <&'string1'&> are first expanded separately. Leading and trailing
9491 white space is removed from the key (but not from any of the strings). The key
9492 must not be empty and must not consist entirely of digits.
9493 The expanded <&'string1'&> must be of the form:
9495 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9498 where the equals signs and spaces (but not both) are optional. If any of the
9499 values contain white space, they must be enclosed in double quotes, and any
9500 values that are enclosed in double quotes are subject to escape processing as
9501 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9502 for the value that corresponds to the key. The search is case-insensitive. If
9503 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9504 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9505 variable &$value$& contains the value that has been extracted. Afterwards, it
9506 is restored to any previous value it might have had.
9508 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9509 key is not found. If {<&'string2'&>} is also omitted, the value that was
9510 extracted is used. Thus, for example, these two expansions are identical, and
9513 ${extract{gid}{uid=1984 gid=2001}}
9514 ${extract{gid}{uid=1984 gid=2001}{$value}}
9516 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9517 appear, for example:
9519 ${extract{Z}{A=... B=...}{$value} fail }
9521 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9522 {<&'string2'&>} must be present for &"fail"& to be recognized.
9525 .vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9526 {*&<&'string3'&>&*}}*&"
9527 .cindex "expansion" "extracting from JSON object"
9528 .cindex JSON expansions
9529 The key and <&'string1'&> are first expanded separately. Leading and trailing
9530 white space is removed from the key (but not from any of the strings). The key
9531 must not be empty and must not consist entirely of digits.
9532 The expanded <&'string1'&> must be of the form:
9534 { <&'"key1"'&> : <&'value1'&> , <&'"key2"'&> , <&'value2'&> ... }
9537 The braces, commas and colons, and the quoting of the member name are required;
9538 the spaces are optional.
9539 Matching of the key against the member names is done case-sensitively.
9540 . XXX should be a UTF-8 compare
9542 The results of matching are handled as above.
9546 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9547 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9548 .cindex "expansion" "extracting substrings by number"
9549 .cindex "&%extract%&" "substrings by number"
9550 The <&'number'&> argument must consist entirely of decimal digits,
9551 apart from leading and trailing white space, which is ignored.
9552 This is what distinguishes this form of &%extract%& from the previous kind. It
9553 behaves in the same way, except that, instead of extracting a named field, it
9554 extracts from <&'string1'&> the field whose number is given as the first
9555 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9556 <&'string3'&> as before.
9558 The fields in the string are separated by any one of the characters in the
9559 separator string. These may include space or tab characters.
9560 The first field is numbered one. If the number is negative, the fields are
9561 counted from the end of the string, with the rightmost one numbered -1. If the
9562 number given is zero, the entire string is returned. If the modulus of the
9563 number is greater than the number of fields in the string, the result is the
9564 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9565 provided. For example:
9567 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9571 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9573 yields &"99"&. Two successive separators mean that the field between them is
9574 empty (for example, the fifth field above).
9578 .vitem "&*${extract json{*&<&'number'&>&*}}&&&
9579 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9580 .cindex "expansion" "extracting from JSON array"
9581 .cindex JSON expansions
9582 The <&'number'&> argument must consist entirely of decimal digits,
9583 apart from leading and trailing white space, which is ignored.
9585 Field selection and result handling is as above;
9586 there is no choice of field separator.
9590 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9591 .cindex "list" "selecting by condition"
9592 .cindex "expansion" "selecting from list by condition"
9594 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9595 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
9597 in this list, its value is place in &$item$&, and then the condition is
9598 evaluated. If the condition is true, &$item$& is added to the output as an
9599 item in a new list; if the condition is false, the item is discarded. The
9600 separator used for the output list is the same as the one used for the
9601 input, but a separator setting is not included in the output. For example:
9603 ${filter{a:b:c}{!eq{$item}{b}}}
9605 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9606 to what it was before. See also the &*map*& and &*reduce*& expansion items.
9609 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9610 .cindex "hash function" "textual"
9611 .cindex "expansion" "textual hash"
9612 This is a textual hashing function, and was the first to be implemented in
9613 early versions of Exim. In current releases, there are other hashing functions
9614 (numeric, MD5, and SHA-1), which are described below.
9616 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9617 <&'n'&>. If you are using fixed values for these numbers, that is, if
9618 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9619 use the simpler operator notation that avoids some of the braces:
9621 ${hash_<n>_<m>:<string>}
9623 The second number is optional (in both notations). If <&'n'&> is greater than
9624 or equal to the length of the string, the expansion item returns the string.
9625 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9626 function to the string. The new string consists of characters taken from the
9627 first <&'m'&> characters of the string
9629 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9631 If <&'m'&> is not present the value 26 is used, so that only lower case
9632 letters appear. For example:
9634 &`$hash{3}{monty}} `& yields &`jmg`&
9635 &`$hash{5}{monty}} `& yields &`monty`&
9636 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9639 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9640 &*$h_*&<&'header&~name'&>&*:*&" &&&
9641 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9642 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9643 "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9644 &*$lh_*&<&'header&~name'&>&*:*&"
9645 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9646 &*$rh_*&<&'header&~name'&>&*:*&"
9647 .cindex "expansion" "header insertion"
9648 .vindex "&$header_$&"
9649 .vindex "&$bheader_$&"
9650 .vindex "&$lheader_$&"
9651 .vindex "&$rheader_$&"
9652 .cindex "header lines" "in expansion strings"
9653 .cindex "header lines" "character sets"
9654 .cindex "header lines" "decoding"
9655 Substitute the contents of the named message header line, for example
9659 The newline that terminates a header line is not included in the expansion, but
9660 internal newlines (caused by splitting the header line over several physical
9661 lines) may be present.
9663 The difference between the four pairs of expansions is in the way
9664 the data in the header line is interpreted.
9667 .cindex "white space" "in header lines"
9668 &%rheader%& gives the original &"raw"& content of the header line, with no
9669 processing at all, and without the removal of leading and trailing white space.
9672 .cindex "list" "of header lines"
9673 &%lheader%& gives a colon-separated list, one element per header when there
9674 are multiple headers with a given name.
9675 Any embedded colon characters within an element are doubled, so normal Exim
9676 list-processing facilities can be used.
9677 The terminating newline of each element is removed; in other respects
9678 the content is &"raw"&.
9681 .cindex "base64 encoding" "in header lines"
9682 &%bheader%& removes leading and trailing white space, and then decodes base64
9683 or quoted-printable MIME &"words"& within the header text, but does no
9684 character set translation. If decoding of what looks superficially like a MIME
9685 &"word"& fails, the raw string is returned. If decoding
9686 .cindex "binary zero" "in header line"
9687 produces a binary zero character, it is replaced by a question mark &-- this is
9688 what Exim does for binary zeros that are actually received in header lines.
9691 &%header%& tries to translate the string as decoded by &%bheader%& to a
9692 standard character set. This is an attempt to produce the same string as would
9693 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
9694 returned. Translation is attempted only on operating systems that support the
9695 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
9696 a system Makefile or in &_Local/Makefile_&.
9699 In a filter file, the target character set for &%header%& can be specified by a
9700 command of the following form:
9702 headers charset "UTF-8"
9704 This command affects all references to &$h_$& (or &$header_$&) expansions in
9705 subsequently obeyed filter commands. In the absence of this command, the target
9706 character set in a filter is taken from the setting of the &%headers_charset%&
9707 option in the runtime configuration. The value of this option defaults to the
9708 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
9711 Header names follow the syntax of RFC 2822, which states that they may contain
9712 any printing characters except space and colon. Consequently, curly brackets
9713 &'do not'& terminate header names, and should not be used to enclose them as
9714 if they were variables. Attempting to do so causes a syntax error.
9716 Only header lines that are common to all copies of a message are visible to
9717 this mechanism. These are the original header lines that are received with the
9718 message, and any that are added by an ACL statement or by a system
9719 filter. Header lines that are added to a particular copy of a message by a
9720 router or transport are not accessible.
9722 For incoming SMTP messages, no header lines are visible in
9723 ACLs that are obeyed before the data phase completes,
9724 because the header structure is not set up until the message is received.
9725 They are visible in DKIM, PRDR and DATA ACLs.
9726 Header lines that are added in a RCPT ACL (for example)
9727 are saved until the message's incoming header lines are available, at which
9728 point they are added.
9729 When any of the above ACLs ar
9730 running, however, header lines added by earlier ACLs are visible.
9732 Upper case and lower case letters are synonymous in header names. If the
9733 following character is white space, the terminating colon may be omitted, but
9734 this is not recommended, because you may then forget it when it is needed. When
9735 white space terminates the header name, this white space is included in the
9736 expanded string. If the message does not contain the given header, the
9737 expansion item is replaced by an empty string. (See the &%def%& condition in
9738 section &<<SECTexpcond>>& for a means of testing for the existence of a
9741 If there is more than one header with the same name, they are all concatenated
9742 to form the substitution string, up to a maximum length of 64K. Unless
9743 &%rheader%& is being used, leading and trailing white space is removed from
9744 each header before concatenation, and a completely empty header is ignored. A
9745 newline character is then inserted between non-empty headers, but there is no
9746 newline at the very end. For the &%header%& and &%bheader%& expansion, for
9747 those headers that contain lists of addresses, a comma is also inserted at the
9748 junctions between headers. This does not happen for the &%rheader%& expansion.
9751 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
9752 .cindex "expansion" "hmac hashing"
9754 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
9755 shared secret and some text into a message authentication code, as specified in
9756 RFC 2104. This differs from &`${md5:secret_text...}`& or
9757 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
9758 cryptographic hash, allowing for authentication that is not possible with MD5
9759 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
9760 present. For example:
9762 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
9764 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
9767 dd97e3ba5d1a61b5006108f8c8252953
9769 As an example of how this might be used, you might put in the main part of
9770 an Exim configuration:
9772 SPAMSCAN_SECRET=cohgheeLei2thahw
9774 In a router or a transport you could then have:
9777 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
9778 ${hmac{md5}{SPAMSCAN_SECRET}\
9779 {${primary_hostname},${message_exim_id},$h_message-id:}}
9781 Then given a message, you can check where it was scanned by looking at the
9782 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
9783 this header line is authentic by recomputing the authentication code from the
9784 host name, message ID and the &'Message-id:'& header line. This can be done
9785 using Exim's &%-be%& option, or by other means, for example, by using the
9786 &'hmac_md5_hex()'& function in Perl.
9789 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9790 .cindex "expansion" "conditional"
9791 .cindex "&%if%&, expansion item"
9792 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
9793 item; otherwise <&'string2'&> is used. The available conditions are described
9794 in section &<<SECTexpcond>>& below. For example:
9796 ${if eq {$local_part}{postmaster} {yes}{no} }
9798 The second string need not be present; if it is not and the condition is not
9799 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
9800 be present instead of the second string (without any curly brackets). In this
9801 case, the expansion is forced to fail if the condition is not true (see section
9802 &<<SECTforexpfai>>&).
9804 If both strings are omitted, the result is the string &`true`& if the condition
9805 is true, and the empty string if the condition is false. This makes it less
9806 cumbersome to write custom ACL and router conditions. For example, instead of
9808 condition = ${if >{$acl_m4}{3}{true}{false}}
9812 condition = ${if >{$acl_m4}{3}}
9817 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
9818 .cindex expansion "imap folder"
9819 .cindex "&%imapfolder%& expansion item"
9820 This item converts a (possibly multilevel, or with non-ASCII characters)
9821 folder specification to a Maildir name for filesystem use.
9822 For information on internationalisation support see &<<SECTi18nMDA>>&.
9826 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9827 .cindex "expansion" "string truncation"
9828 .cindex "&%length%& expansion item"
9829 The &%length%& item is used to extract the initial portion of a string. Both
9830 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
9831 you are using a fixed value for the number, that is, if <&'string1'&> does not
9832 change when expanded, you can use the simpler operator notation that avoids
9835 ${length_<n>:<string>}
9837 The result of this item is either the first <&'n'&> bytes or the whole
9838 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
9839 &%strlen%&, which gives the length of a string.
9840 All measurement is done in bytes and is not UTF-8 aware.
9843 .vitem "&*${listextract{*&<&'number'&>&*}&&&
9844 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9845 .cindex "expansion" "extracting list elements by number"
9846 .cindex "&%listextract%&" "extract list elements by number"
9847 .cindex "list" "extracting elements by number"
9848 The <&'number'&> argument must consist entirely of decimal digits,
9849 apart from an optional leading minus,
9850 and leading and trailing white space (which is ignored).
9852 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9853 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
9855 The first field of the list is numbered one.
9856 If the number is negative, the fields are
9857 counted from the end of the list, with the rightmost one numbered -1.
9858 The numbered element of the list is extracted and placed in &$value$&,
9859 then <&'string2'&> is expanded as the result.
9861 If the modulus of the
9862 number is zero or greater than the number of fields in the string,
9863 the result is the expansion of <&'string3'&>.
9867 ${listextract{2}{x:42:99}}
9871 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
9873 yields &"result: 42"&.
9875 If {<&'string3'&>} is omitted, an empty string is used for string3.
9876 If {<&'string2'&>} is also omitted, the value that was
9878 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
9881 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
9882 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9883 This is the first of one of two different types of lookup item, which are both
9884 described in the next item.
9886 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
9887 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9888 .cindex "expansion" "lookup in"
9889 .cindex "file" "lookups"
9890 .cindex "lookup" "in expanded string"
9891 The two forms of lookup item specify data lookups in files and databases, as
9892 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
9893 lookups, and the second is used for query-style lookups. The <&'key'&>,
9894 <&'file'&>, and <&'query'&> strings are expanded before use.
9896 If there is any white space in a lookup item which is part of a filter command,
9897 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
9898 other place where white space is significant, the lookup item must be enclosed
9899 in double quotes. The use of data lookups in users' filter files may be locked
9900 out by the system administrator.
9903 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
9904 During its expansion, the variable &$value$& contains the data returned by the
9905 lookup. Afterwards it reverts to the value it had previously (at the outer
9906 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
9907 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
9908 string on failure. If <&'string2'&> is provided, it can itself be a nested
9909 lookup, thus providing a mechanism for looking up a default value when the
9910 original lookup fails.
9912 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
9913 data for the outer lookup while the parameters of the second lookup are
9914 expanded, and also while <&'string2'&> of the second lookup is expanded, should
9915 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
9916 appear, and in this case, if the lookup fails, the entire expansion is forced
9917 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
9918 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
9919 successful lookup, and nothing in the case of failure.
9921 For single-key lookups, the string &"partial"& is permitted to precede the
9922 search type in order to do partial matching, and * or *@ may follow a search
9923 type to request default lookups if the key does not match (see sections
9924 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
9926 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
9927 If a partial search is used, the variables &$1$& and &$2$& contain the wild
9928 and non-wild parts of the key during the expansion of the replacement text.
9929 They return to their previous values at the end of the lookup item.
9931 This example looks up the postmaster alias in the conventional alias file:
9933 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
9935 This example uses NIS+ to look up the full name of the user corresponding to
9936 the local part of an address, forcing the expansion to fail if it is not found:
9938 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
9943 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9944 .cindex "expansion" "list creation"
9946 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9947 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
9949 in this list, its value is place in &$item$&, and then <&'string2'&> is
9950 expanded and added to the output as an item in a new list. The separator used
9951 for the output list is the same as the one used for the input, but a separator
9952 setting is not included in the output. For example:
9954 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
9956 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
9957 value of &$item$& is restored to what it was before. See also the &*filter*&
9958 and &*reduce*& expansion items.
9960 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9961 .cindex "expansion" "numeric hash"
9962 .cindex "hash function" "numeric"
9963 The three strings are expanded; the first two must yield numbers. Call them
9964 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9965 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9966 can use the simpler operator notation that avoids some of the braces:
9968 ${nhash_<n>_<m>:<string>}
9970 The second number is optional (in both notations). If there is only one number,
9971 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
9972 processed by a div/mod hash function that returns two numbers, separated by a
9973 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
9976 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
9978 returns the string &"6/33"&.
9982 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
9983 .cindex "Perl" "use in expanded string"
9984 .cindex "expansion" "calling Perl from"
9985 This item is available only if Exim has been built to include an embedded Perl
9986 interpreter. The subroutine name and the arguments are first separately
9987 expanded, and then the Perl subroutine is called with those arguments. No
9988 additional arguments need be given; the maximum number permitted, including the
9989 name of the subroutine, is nine.
9991 The return value of the subroutine is inserted into the expanded string, unless
9992 the return value is &%undef%&. In that case, the expansion fails in the same
9993 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
9994 Whatever you return is evaluated in a scalar context. For example, if you
9995 return the name of a Perl vector, the return value is the size of the vector,
9998 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
9999 with the error message that was passed to &%die%&. More details of the embedded
10000 Perl facility are given in chapter &<<CHAPperl>>&.
10002 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
10003 out the use of this expansion item in filter files.
10006 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
10007 .cindex "&%prvs%& expansion item"
10008 The first argument is a complete email address and the second is secret
10009 keystring. The third argument, specifying a key number, is optional. If absent,
10010 it defaults to 0. The result of the expansion is a prvs-signed email address,
10011 to be typically used with the &%return_path%& option on an &(smtp)& transport
10012 as part of a bounce address tag validation (BATV) scheme. For more discussion
10013 and an example, see section &<<SECTverifyPRVS>>&.
10015 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
10016 {*&<&'string'&>&*}}*&"
10017 .cindex "&%prvscheck%& expansion item"
10018 This expansion item is the complement of the &%prvs%& item. It is used for
10019 checking prvs-signed addresses. If the expansion of the first argument does not
10020 yield a syntactically valid prvs-signed address, the whole item expands to the
10021 empty string. When the first argument does expand to a syntactically valid
10022 prvs-signed address, the second argument is expanded, with the prvs-decoded
10023 version of the address and the key number extracted from the address in the
10024 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
10026 These two variables can be used in the expansion of the second argument to
10027 retrieve the secret. The validity of the prvs-signed address is then checked
10028 against the secret. The result is stored in the variable &$prvscheck_result$&,
10029 which is empty for failure or &"1"& for success.
10031 The third argument is optional; if it is missing, it defaults to an empty
10032 string. This argument is now expanded. If the result is an empty string, the
10033 result of the expansion is the decoded version of the address. This is the case
10034 whether or not the signature was valid. Otherwise, the result of the expansion
10035 is the expansion of the third argument.
10037 All three variables can be used in the expansion of the third argument.
10038 However, once the expansion is complete, only &$prvscheck_result$& remains set.
10039 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
10041 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
10042 .cindex "expansion" "inserting an entire file"
10043 .cindex "file" "inserting into expansion"
10044 .cindex "&%readfile%& expansion item"
10045 The filename and end-of-line string are first expanded separately. The file is
10046 then read, and its contents replace the entire item. All newline characters in
10047 the file are replaced by the end-of-line string if it is present. Otherwise,
10048 newlines are left in the string.
10049 String expansion is not applied to the contents of the file. If you want this,
10050 you must wrap the item in an &%expand%& operator. If the file cannot be read,
10051 the string expansion fails.
10053 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
10054 locks out the use of this expansion item in filter files.
10058 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
10059 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
10060 .cindex "expansion" "inserting from a socket"
10061 .cindex "socket, use of in expansion"
10062 .cindex "&%readsocket%& expansion item"
10063 This item inserts data from a Unix domain or TCP socket into the expanded
10064 string. The minimal way of using it uses just two arguments, as in these
10067 ${readsocket{/socket/name}{request string}}
10068 ${readsocket{inet:some.host:1234}{request string}}
10070 For a Unix domain socket, the first substring must be the path to the socket.
10071 For an Internet socket, the first substring must contain &`inet:`& followed by
10072 a host name or IP address, followed by a colon and a port, which can be a
10073 number or the name of a TCP port in &_/etc/services_&. An IP address may
10074 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
10077 ${readsocket{inet:[::1]:1234}{request string}}
10079 Only a single host name may be given, but if looking it up yields more than
10080 one IP address, they are each tried in turn until a connection is made. For
10081 both kinds of socket, Exim makes a connection, writes the request string
10082 unless it is an empty string; and no terminating NUL is ever sent)
10083 and reads from the socket until an end-of-file
10084 is read. A timeout of 5 seconds is applied. Additional, optional arguments
10085 extend what can be done. Firstly, you can vary the timeout. For example:
10087 ${readsocket{/socket/name}{request string}{3s}}
10090 The third argument is a list of options, of which the first element is the timeout
10091 and must be present if the argument is given.
10092 Further elements are options of form &'name=value'&.
10093 Two option types is currently recognised: shutdown and tls.
10094 The first defines whether (the default)
10095 or not a shutdown is done on the connection after sending the request.
10096 Example, to not do so (preferred, eg. by some webservers):
10098 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
10101 The second, tls, controls the use of TLS on the connection. Example:
10103 ${readsocket{/socket/name}{request string}{3s:tls=yes}}
10105 The default is to not use TLS.
10106 If it is enabled, a shutdown as descripbed above is never done.
10109 A fourth argument allows you to change any newlines that are in the data
10110 that is read, in the same way as for &%readfile%& (see above). This example
10111 turns them into spaces:
10113 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
10115 As with all expansions, the substrings are expanded before the processing
10116 happens. Errors in these sub-expansions cause the expansion to fail. In
10117 addition, the following errors can occur:
10120 Failure to create a socket file descriptor;
10122 Failure to connect the socket;
10124 Failure to write the request string;
10126 Timeout on reading from the socket.
10129 By default, any of these errors causes the expansion to fail. However, if
10130 you supply a fifth substring, it is expanded and used when any of the above
10131 errors occurs. For example:
10133 ${readsocket{/socket/name}{request string}{3s}{\n}\
10136 You can test for the existence of a Unix domain socket by wrapping this
10137 expansion in &`${if exists`&, but there is a race condition between that test
10138 and the actual opening of the socket, so it is safer to use the fifth argument
10139 if you want to be absolutely sure of avoiding an expansion error for a
10140 non-existent Unix domain socket, or a failure to connect to an Internet socket.
10142 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
10143 locks out the use of this expansion item in filter files.
10146 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10147 .cindex "expansion" "reducing a list to a scalar"
10148 .cindex "list" "reducing to a scalar"
10149 .vindex "&$value$&"
10151 This operation reduces a list to a single, scalar string. After expansion,
10152 <&'string1'&> is interpreted as a list, colon-separated by default, but the
10153 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10154 Then <&'string2'&> is expanded and
10155 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
10156 list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
10157 them. The result of that expansion is assigned to &$value$& before the next
10158 iteration. When the end of the list is reached, the final value of &$value$& is
10159 added to the expansion output. The &*reduce*& expansion item can be used in a
10160 number of ways. For example, to add up a list of numbers:
10162 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
10164 The result of that expansion would be &`6`&. The maximum of a list of numbers
10167 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
10169 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
10170 restored to what they were before. See also the &*filter*& and &*map*&
10173 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
10174 This item inserts &"raw"& header lines. It is described with the &%header%&
10175 expansion item in section &<<SECTexpansionitems>>& above.
10177 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
10178 {*&<&'string2'&>&*}}*&"
10179 .cindex "expansion" "running a command"
10180 .cindex "&%run%& expansion item"
10181 The command and its arguments are first expanded as one string. The string is
10182 split apart into individual arguments by spaces, and then the command is run
10183 in a separate process, but under the same uid and gid. As in other command
10184 executions from Exim, a shell is not used by default. If the command requires
10185 a shell, you must explicitly code it.
10187 Since the arguments are split by spaces, when there is a variable expansion
10188 which has an empty result, it will cause the situation that the argument will
10189 simply be omitted when the program is actually executed by Exim. If the
10190 script/program requires a specific number of arguments and the expanded
10191 variable could possibly result in this empty expansion, the variable must be
10192 quoted. This is more difficult if the expanded variable itself could result
10193 in a string containing quotes, because it would interfere with the quotes
10194 around the command arguments. A possible guard against this is to wrap the
10195 variable in the &%sg%& operator to change any quote marks to some other
10198 The standard input for the command exists, but is empty. The standard output
10199 and standard error are set to the same file descriptor.
10200 .cindex "return code" "from &%run%& expansion"
10201 .vindex "&$value$&"
10202 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
10203 and replaces the entire item; during this expansion, the standard output/error
10204 from the command is in the variable &$value$&. If the command fails,
10205 <&'string2'&>, if present, is expanded and used. Once again, during the
10206 expansion, the standard output/error from the command is in the variable
10209 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
10210 can be the word &"fail"& (not in braces) to force expansion failure if the
10211 command does not succeed. If both strings are omitted, the result is contents
10212 of the standard output/error on success, and nothing on failure.
10214 .vindex "&$run_in_acl$&"
10215 The standard output/error of the command is put in the variable &$value$&.
10216 In this ACL example, the output of a command is logged for the admin to
10219 warn condition = ${run{/usr/bin/id}{yes}{no}}
10220 log_message = Output of id: $value
10222 If the command requires shell idioms, such as the > redirect operator, the
10223 shell must be invoked directly, such as with:
10225 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
10228 .vindex "&$runrc$&"
10229 The return code from the command is put in the variable &$runrc$&, and this
10230 remains set afterwards, so in a filter file you can do things like this:
10232 if "${run{x y z}{}}$runrc" is 1 then ...
10233 elif $runrc is 2 then ...
10237 If execution of the command fails (for example, the command does not exist),
10238 the return code is 127 &-- the same code that shells use for non-existent
10241 &*Warning*&: In a router or transport, you cannot assume the order in which
10242 option values are expanded, except for those preconditions whose order of
10243 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
10244 by the expansion of one option, and use it in another.
10246 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
10247 out the use of this expansion item in filter files.
10250 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
10251 .cindex "expansion" "string substitution"
10252 .cindex "&%sg%& expansion item"
10253 This item works like Perl's substitution operator (s) with the global (/g)
10254 option; hence its name. However, unlike the Perl equivalent, Exim does not
10255 modify the subject string; instead it returns the modified string for insertion
10256 into the overall expansion. The item takes three arguments: the subject string,
10257 a regular expression, and a substitution string. For example:
10259 ${sg{abcdefabcdef}{abc}{xyz}}
10261 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
10262 if any $, } or \ characters are required in the regular expression or in the
10263 substitution string, they have to be escaped. For example:
10265 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
10267 yields &"defabc"&, and
10269 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
10271 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
10272 the regular expression from string expansion.
10274 The regular expression is compiled in 8-bit mode, working against bytes
10275 rather than any Unicode-aware character handling.
10278 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
10279 .cindex sorting "a list"
10280 .cindex list sorting
10281 .cindex expansion "list sorting"
10282 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10283 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10284 The <&'comparator'&> argument is interpreted as the operator
10285 of a two-argument expansion condition.
10286 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
10287 The comparison should return true when applied to two values
10288 if the first value should sort before the second value.
10289 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
10290 the element being placed in &$item$&,
10291 to give values for comparison.
10293 The item result is a sorted list,
10294 with the original list separator,
10295 of the list elements (in full) of the original.
10299 ${sort{3:2:1:4}{<}{$item}}
10301 sorts a list of numbers, and
10303 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10305 will sort an MX lookup into priority order.
10308 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10309 .cindex "&%substr%& expansion item"
10310 .cindex "substring extraction"
10311 .cindex "expansion" "substring extraction"
10312 The three strings are expanded; the first two must yield numbers. Call them
10313 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10314 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10315 can use the simpler operator notation that avoids some of the braces:
10317 ${substr_<n>_<m>:<string>}
10319 The second number is optional (in both notations).
10320 If it is absent in the simpler format, the preceding underscore must also be
10323 The &%substr%& item can be used to extract more general substrings than
10324 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10325 length required. For example
10327 ${substr{3}{2}{$local_part}}
10329 If the starting offset is greater than the string length the result is the
10330 null string; if the length plus starting offset is greater than the string
10331 length, the result is the right-hand part of the string, starting from the
10332 given offset. The first byte (character) in the string has offset zero.
10334 The &%substr%& expansion item can take negative offset values to count
10335 from the right-hand end of its operand. The last byte (character) is offset -1,
10336 the second-last is offset -2, and so on. Thus, for example,
10338 ${substr{-5}{2}{1234567}}
10340 yields &"34"&. If the absolute value of a negative offset is greater than the
10341 length of the string, the substring starts at the beginning of the string, and
10342 the length is reduced by the amount of overshoot. Thus, for example,
10344 ${substr{-5}{2}{12}}
10346 yields an empty string, but
10348 ${substr{-3}{2}{12}}
10352 When the second number is omitted from &%substr%&, the remainder of the string
10353 is taken if the offset is positive. If it is negative, all bytes (characters) in the
10354 string preceding the offset point are taken. For example, an offset of -1 and
10355 no length, as in these semantically identical examples:
10358 ${substr{-1}{abcde}}
10360 yields all but the last character of the string, that is, &"abcd"&.
10362 All measurement is done in bytes and is not UTF-8 aware.
10366 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10367 {*&<&'replacements'&>&*}}*&"
10368 .cindex "expansion" "character translation"
10369 .cindex "&%tr%& expansion item"
10370 This item does single-character (in bytes) translation on its subject string. The second
10371 argument is a list of characters to be translated in the subject string. Each
10372 matching character is replaced by the corresponding character from the
10373 replacement list. For example
10375 ${tr{abcdea}{ac}{13}}
10377 yields &`1b3de1`&. If there are duplicates in the second character string, the
10378 last occurrence is used. If the third string is shorter than the second, its
10379 last character is replicated. However, if it is empty, no translation takes
10382 All character handling is done in bytes and is not UTF-8 aware.
10388 .section "Expansion operators" "SECTexpop"
10389 .cindex "expansion" "operators"
10390 For expansion items that perform transformations on a single argument string,
10391 the &"operator"& notation is used because it is simpler and uses fewer braces.
10392 The substring is first expanded before the operation is applied to it. The
10393 following operations can be performed:
10396 .vitem &*${address:*&<&'string'&>&*}*&
10397 .cindex "expansion" "RFC 2822 address handling"
10398 .cindex "&%address%& expansion item"
10399 The string is interpreted as an RFC 2822 address, as it might appear in a
10400 header line, and the effective address is extracted from it. If the string does
10401 not parse successfully, the result is empty.
10403 The parsing correctly handles SMTPUTF8 Unicode in the string.
10406 .vitem &*${addresses:*&<&'string'&>&*}*&
10407 .cindex "expansion" "RFC 2822 address handling"
10408 .cindex "&%addresses%& expansion item"
10409 The string (after expansion) is interpreted as a list of addresses in RFC
10410 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10411 operative address (&'local-part@domain'&) is extracted from each item, and the
10412 result of the expansion is a colon-separated list, with appropriate
10413 doubling of colons should any happen to be present in the email addresses.
10414 Syntactically invalid RFC2822 address items are omitted from the output.
10416 It is possible to specify a character other than colon for the output
10417 separator by starting the string with > followed by the new separator
10418 character. For example:
10420 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10422 expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
10423 first, so if the expanded string starts with >, it may change the output
10424 separator unintentionally. This can be avoided by setting the output
10425 separator explicitly:
10427 ${addresses:>:$h_from:}
10430 Compare the &*address*& (singular)
10431 expansion item, which extracts the working address from a single RFC2822
10432 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
10435 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10436 a strict interpretation of header line formatting. Exim parses the bare,
10437 unquoted portion of an email address and if it finds a comma, treats it as an
10438 email address separator. For the example header line:
10440 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10442 The first example below demonstrates that Q-encoded email addresses are parsed
10443 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10444 It does not see the comma because it's still encoded as "=2C". The second
10445 example below is passed the contents of &`$header_from:`&, meaning it gets
10446 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10447 The third example shows that the presence of a comma is skipped when it is
10448 quoted. The fourth example shows SMTPUTF8 handling.
10450 # exim -be '${addresses:From: \
10451 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10453 # exim -be '${addresses:From: Last, First <user@example.com>}'
10454 Last:user@example.com
10455 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10457 # exim -be '${addresses:フィル <フィリップ@example.jp>}'
10461 .vitem &*${base32:*&<&'digits'&>&*}*&
10462 .cindex "&%base32%& expansion item"
10463 .cindex "expansion" "conversion to base 32"
10464 The string must consist entirely of decimal digits. The number is converted to
10465 base 32 and output as a (empty, for zero) string of characters.
10466 Only lowercase letters are used.
10468 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10469 .cindex "&%base32d%& expansion item"
10470 .cindex "expansion" "conversion to base 32"
10471 The string must consist entirely of base-32 digits.
10472 The number is converted to decimal and output as a string.
10474 .vitem &*${base62:*&<&'digits'&>&*}*&
10475 .cindex "&%base62%& expansion item"
10476 .cindex "expansion" "conversion to base 62"
10477 The string must consist entirely of decimal digits. The number is converted to
10478 base 62 and output as a string of six characters, including leading zeros. In
10479 the few operating environments where Exim uses base 36 instead of base 62 for
10480 its message identifiers (because those systems do not have case-sensitive
10481 filenames), base 36 is used by this operator, despite its name. &*Note*&: Just
10482 to be absolutely clear: this is &'not'& base64 encoding.
10484 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10485 .cindex "&%base62d%& expansion item"
10486 .cindex "expansion" "conversion to base 62"
10487 The string must consist entirely of base-62 digits, or, in operating
10488 environments where Exim uses base 36 instead of base 62 for its message
10489 identifiers, base-36 digits. The number is converted to decimal and output as a
10492 .vitem &*${base64:*&<&'string'&>&*}*&
10493 .cindex "expansion" "base64 encoding"
10494 .cindex "base64 encoding" "in string expansion"
10495 .cindex "&%base64%& expansion item"
10496 .cindex certificate "base64 of DER"
10497 This operator converts a string into one that is base64 encoded.
10499 If the string is a single variable of type certificate,
10500 returns the base64 encoding of the DER form of the certificate.
10503 .vitem &*${base64d:*&<&'string'&>&*}*&
10504 .cindex "expansion" "base64 decoding"
10505 .cindex "base64 decoding" "in string expansion"
10506 .cindex "&%base64d%& expansion item"
10507 This operator converts a base64-encoded string into the un-coded form.
10510 .vitem &*${domain:*&<&'string'&>&*}*&
10511 .cindex "domain" "extraction"
10512 .cindex "expansion" "domain extraction"
10513 The string is interpreted as an RFC 2822 address and the domain is extracted
10514 from it. If the string does not parse successfully, the result is empty.
10517 .vitem &*${escape:*&<&'string'&>&*}*&
10518 .cindex "expansion" "escaping non-printing characters"
10519 .cindex "&%escape%& expansion item"
10520 If the string contains any non-printing characters, they are converted to
10521 escape sequences starting with a backslash. Whether characters with the most
10522 significant bit set (so-called &"8-bit characters"&) count as printing or not
10523 is controlled by the &%print_topbitchars%& option.
10525 .vitem &*${escape8bit:*&<&'string'&>&*}*&
10526 .cindex "expansion" "escaping 8-bit characters"
10527 .cindex "&%escape8bit%& expansion item"
10528 If the string contains and characters with the most significant bit set,
10529 they are converted to escape sequences starting with a backslash.
10530 Backslashes and DEL characters are also converted.
10533 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
10534 .cindex "expansion" "expression evaluation"
10535 .cindex "expansion" "arithmetic expression"
10536 .cindex "&%eval%& expansion item"
10537 These items supports simple arithmetic and bitwise logical operations in
10538 expansion strings. The string (after expansion) must be a conventional
10539 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
10540 logical operators, and parentheses. All operations are carried out using
10541 integer arithmetic. The operator priorities are as follows (the same as in the
10542 C programming language):
10544 .irow &'highest:'& "not (~), negate (-)"
10545 .irow "" "multiply (*), divide (/), remainder (%)"
10546 .irow "" "plus (+), minus (-)"
10547 .irow "" "shift-left (<<), shift-right (>>)"
10548 .irow "" "and (&&)"
10550 .irow &'lowest:'& "or (|)"
10552 Binary operators with the same priority are evaluated from left to right. White
10553 space is permitted before or after operators.
10555 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
10556 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
10557 decimal, even if they start with a leading zero; hexadecimal numbers are not
10558 permitted. This can be useful when processing numbers extracted from dates or
10559 times, which often do have leading zeros.
10561 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
10563 respectively. Negative numbers are supported. The result of the computation is
10564 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
10567 &`${eval:1+1} `& yields 2
10568 &`${eval:1+2*3} `& yields 7
10569 &`${eval:(1+2)*3} `& yields 9
10570 &`${eval:2+42%5} `& yields 4
10571 &`${eval:0xc&5} `& yields 4
10572 &`${eval:0xc|5} `& yields 13
10573 &`${eval:0xc^5} `& yields 9
10574 &`${eval:0xc>>1} `& yields 6
10575 &`${eval:0xc<<1} `& yields 24
10576 &`${eval:~255&0x1234} `& yields 4608
10577 &`${eval:-(~255&0x1234)} `& yields -4608
10580 As a more realistic example, in an ACL you might have
10582 deny message = Too many bad recipients
10585 {>{$rcpt_count}{10}} \
10588 {$recipients_count} \
10589 {${eval:$rcpt_count/2}} \
10593 The condition is true if there have been more than 10 RCPT commands and
10594 fewer than half of them have resulted in a valid recipient.
10597 .vitem &*${expand:*&<&'string'&>&*}*&
10598 .cindex "expansion" "re-expansion of substring"
10599 The &%expand%& operator causes a string to be expanded for a second time. For
10602 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
10604 first looks up a string in a file while expanding the operand for &%expand%&,
10605 and then re-expands what it has found.
10608 .vitem &*${from_utf8:*&<&'string'&>&*}*&
10610 .cindex "UTF-8" "conversion from"
10611 .cindex "expansion" "UTF-8 conversion"
10612 .cindex "&%from_utf8%& expansion item"
10613 The world is slowly moving towards Unicode, although there are no standards for
10614 email yet. However, other applications (including some databases) are starting
10615 to store data in Unicode, using UTF-8 encoding. This operator converts from a
10616 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
10617 converted to underscores. The input must be a valid UTF-8 string. If it is not,
10618 the result is an undefined sequence of bytes.
10620 Unicode code points with values less than 256 are compatible with ASCII and
10621 ISO-8859-1 (also known as Latin-1).
10622 For example, character 169 is the copyright symbol in both cases, though the
10623 way it is encoded is different. In UTF-8, more than one byte is needed for
10624 characters with code values greater than 127, whereas ISO-8859-1 is a
10625 single-byte encoding (but thereby limited to 256 characters). This makes
10626 translation from UTF-8 to ISO-8859-1 straightforward.
10629 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10630 .cindex "hash function" "textual"
10631 .cindex "expansion" "textual hash"
10632 The &%hash%& operator is a simpler interface to the hashing function that can
10633 be used when the two parameters are fixed numbers (as opposed to strings that
10634 change when expanded). The effect is the same as
10636 ${hash{<n>}{<m>}{<string>}}
10638 See the description of the general &%hash%& item above for details. The
10639 abbreviation &%h%& can be used when &%hash%& is used as an operator.
10643 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
10644 .cindex "base64 encoding" "conversion from hex"
10645 .cindex "expansion" "hex to base64"
10646 .cindex "&%hex2b64%& expansion item"
10647 This operator converts a hex string into one that is base64 encoded. This can
10648 be useful for processing the output of the various hashing functions.
10652 .vitem &*${hexquote:*&<&'string'&>&*}*&
10653 .cindex "quoting" "hex-encoded unprintable characters"
10654 .cindex "&%hexquote%& expansion item"
10655 This operator converts non-printable characters in a string into a hex
10656 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
10657 as is, and other byte values are converted to &`\xNN`&, for example, a
10658 byte value 127 is converted to &`\x7f`&.
10661 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
10662 .cindex "&%ipv6denorm%& expansion item"
10663 .cindex "IP address" normalisation
10664 This expands an IPv6 address to a full eight-element colon-separated set
10665 of hex digits including leading zeroes.
10666 A trailing ipv4-style dotted-decimal set is converted to hex.
10667 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10669 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
10670 .cindex "&%ipv6norm%& expansion item"
10671 .cindex "IP address" normalisation
10672 .cindex "IP address" "canonical form"
10673 This converts an IPv6 address to canonical form.
10674 Leading zeroes of groups are omitted, and the longest
10675 set of zero-valued groups is replaced with a double colon.
10676 A trailing ipv4-style dotted-decimal set is converted to hex.
10677 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10680 .vitem &*${lc:*&<&'string'&>&*}*&
10681 .cindex "case forcing in strings"
10682 .cindex "string" "case forcing"
10683 .cindex "lower casing"
10684 .cindex "expansion" "case forcing"
10685 .cindex "&%lc%& expansion item"
10686 This forces the letters in the string into lower-case, for example:
10690 Case is defined per the system C locale.
10692 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
10693 .cindex "expansion" "string truncation"
10694 .cindex "&%length%& expansion item"
10695 The &%length%& operator is a simpler interface to the &%length%& function that
10696 can be used when the parameter is a fixed number (as opposed to a string that
10697 changes when expanded). The effect is the same as
10699 ${length{<number>}{<string>}}
10701 See the description of the general &%length%& item above for details. Note that
10702 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
10703 when &%length%& is used as an operator.
10704 All measurement is done in bytes and is not UTF-8 aware.
10707 .vitem &*${listcount:*&<&'string'&>&*}*&
10708 .cindex "expansion" "list item count"
10709 .cindex "list" "item count"
10710 .cindex "list" "count of items"
10711 .cindex "&%listcount%& expansion item"
10712 The string is interpreted as a list and the number of items is returned.
10715 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
10716 .cindex "expansion" "named list"
10717 .cindex "&%listnamed%& expansion item"
10718 The name is interpreted as a named list and the content of the list is returned,
10719 expanding any referenced lists, re-quoting as needed for colon-separation.
10720 If the optional type is given it must be one of "a", "d", "h" or "l"
10721 and selects address-, domain-, host- or localpart- lists to search among respectively.
10722 Otherwise all types are searched in an undefined order and the first
10723 matching list is returned.
10726 .vitem &*${local_part:*&<&'string'&>&*}*&
10727 .cindex "expansion" "local part extraction"
10728 .cindex "&%local_part%& expansion item"
10729 The string is interpreted as an RFC 2822 address and the local part is
10730 extracted from it. If the string does not parse successfully, the result is
10732 The parsing correctly handles SMTPUTF8 Unicode in the string.
10735 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
10736 .cindex "masked IP address"
10737 .cindex "IP address" "masking"
10738 .cindex "CIDR notation"
10739 .cindex "expansion" "IP address masking"
10740 .cindex "&%mask%& expansion item"
10741 If the form of the string to be operated on is not an IP address followed by a
10742 slash and an integer (that is, a network address in CIDR notation), the
10743 expansion fails. Otherwise, this operator converts the IP address to binary,
10744 masks off the least significant bits according to the bit count, and converts
10745 the result back to text, with mask appended. For example,
10747 ${mask:10.111.131.206/28}
10749 returns the string &"10.111.131.192/28"&. Since this operation is expected to
10750 be mostly used for looking up masked addresses in files, the result for an IPv6
10751 address uses dots to separate components instead of colons, because colon
10752 terminates a key string in lsearch files. So, for example,
10754 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
10758 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
10760 Letters in IPv6 addresses are always output in lower case.
10763 .vitem &*${md5:*&<&'string'&>&*}*&
10765 .cindex "expansion" "MD5 hash"
10766 .cindex certificate fingerprint
10767 .cindex "&%md5%& expansion item"
10768 The &%md5%& operator computes the MD5 hash value of the string, and returns it
10769 as a 32-digit hexadecimal number, in which any letters are in lower case.
10771 If the string is a single variable of type certificate,
10772 returns the MD5 hash fingerprint of the certificate.
10775 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10776 .cindex "expansion" "numeric hash"
10777 .cindex "hash function" "numeric"
10778 The &%nhash%& operator is a simpler interface to the numeric hashing function
10779 that can be used when the two parameters are fixed numbers (as opposed to
10780 strings that change when expanded). The effect is the same as
10782 ${nhash{<n>}{<m>}{<string>}}
10784 See the description of the general &%nhash%& item above for details.
10787 .vitem &*${quote:*&<&'string'&>&*}*&
10788 .cindex "quoting" "in string expansions"
10789 .cindex "expansion" "quoting"
10790 .cindex "&%quote%& expansion item"
10791 The &%quote%& operator puts its argument into double quotes if it
10792 is an empty string or
10793 contains anything other than letters, digits, underscores, dots, and hyphens.
10794 Any occurrences of double quotes and backslashes are escaped with a backslash.
10795 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
10796 respectively For example,
10804 The place where this is useful is when the argument is a substitution from a
10805 variable or a message header.
10807 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
10808 .cindex "&%quote_local_part%& expansion item"
10809 This operator is like &%quote%&, except that it quotes the string only if
10810 required to do so by the rules of RFC 2822 for quoting local parts. For
10811 example, a plus sign would not cause quoting (but it would for &%quote%&).
10812 If you are creating a new email address from the contents of &$local_part$&
10813 (or any other unknown data), you should always use this operator.
10815 This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
10816 will likely use the quoting form.
10817 Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
10820 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
10821 .cindex "quoting" "lookup-specific"
10822 This operator applies lookup-specific quoting rules to the string. Each
10823 query-style lookup type has its own quoting rules which are described with
10824 the lookups in chapter &<<CHAPfdlookup>>&. For example,
10826 ${quote_ldap:two * two}
10832 For single-key lookup types, no quoting is ever necessary and this operator
10833 yields an unchanged string.
10836 .vitem &*${randint:*&<&'n'&>&*}*&
10837 .cindex "random number"
10838 This operator returns a somewhat random number which is less than the
10839 supplied number and is at least 0. The quality of this randomness depends
10840 on how Exim was built; the values are not suitable for keying material.
10841 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
10842 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
10843 for versions of GnuTLS with that function.
10844 Otherwise, the implementation may be arc4random(), random() seeded by
10845 srandomdev() or srandom(), or a custom implementation even weaker than
10849 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
10850 .cindex "expansion" "IP address"
10851 This operator reverses an IP address; for IPv4 addresses, the result is in
10852 dotted-quad decimal form, while for IPv6 addresses the result is in
10853 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
10854 for DNS. For example,
10856 ${reverse_ip:192.0.2.4}
10857 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
10862 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
10866 .vitem &*${rfc2047:*&<&'string'&>&*}*&
10867 .cindex "expansion" "RFC 2047"
10868 .cindex "RFC 2047" "expansion operator"
10869 .cindex "&%rfc2047%& expansion item"
10870 This operator encodes text according to the rules of RFC 2047. This is an
10871 encoding that is used in header lines to encode non-ASCII characters. It is
10872 assumed that the input string is in the encoding specified by the
10873 &%headers_charset%& option, which gets its default at build time. If the string
10874 contains only characters in the range 33&--126, and no instances of the
10877 ? = ( ) < > @ , ; : \ " . [ ] _
10879 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
10880 string, using as many &"encoded words"& as necessary to encode all the
10884 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
10885 .cindex "expansion" "RFC 2047"
10886 .cindex "RFC 2047" "decoding"
10887 .cindex "&%rfc2047d%& expansion item"
10888 This operator decodes strings that are encoded as per RFC 2047. Binary zero
10889 bytes are replaced by question marks. Characters are converted into the
10890 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
10891 not recognized unless &%check_rfc2047_length%& is set false.
10893 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
10894 access a header line, RFC 2047 decoding is done automatically. You do not need
10895 to use this operator as well.
10899 .vitem &*${rxquote:*&<&'string'&>&*}*&
10900 .cindex "quoting" "in regular expressions"
10901 .cindex "regular expressions" "quoting"
10902 .cindex "&%rxquote%& expansion item"
10903 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
10904 characters in its argument. This is useful when substituting the values of
10905 variables or headers inside regular expressions.
10908 .vitem &*${sha1:*&<&'string'&>&*}*&
10909 .cindex "SHA-1 hash"
10910 .cindex "expansion" "SHA-1 hashing"
10911 .cindex certificate fingerprint
10912 .cindex "&%sha1%& expansion item"
10913 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
10914 it as a 40-digit hexadecimal number, in which any letters are in upper case.
10916 If the string is a single variable of type certificate,
10917 returns the SHA-1 hash fingerprint of the certificate.
10920 .vitem &*${sha256:*&<&'string'&>&*}*&
10921 .cindex "SHA-256 hash"
10922 .cindex certificate fingerprint
10923 .cindex "expansion" "SHA-256 hashing"
10924 .cindex "&%sha256%& expansion item"
10925 The &%sha256%& operator computes the SHA-256 hash value of the string
10927 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10929 If the string is a single variable of type certificate,
10930 returns the SHA-256 hash fingerprint of the certificate.
10933 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
10934 &*${sha3_<n>:*&<&'string'&>&*}*&
10935 .cindex "SHA3 hash"
10936 .cindex "expansion" "SHA3 hashing"
10937 .cindex "&%sha3%& expansion item"
10938 The &%sha3%& operator computes the SHA3-256 hash value of the string
10940 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10942 If a number is appended, separated by an underbar, it specifies
10943 the output length. Values of 224, 256, 384 and 512 are accepted;
10944 with 256 being the default.
10946 The &%sha3%& expansion item is only supported if Exim has been
10947 compiled with GnuTLS 3.5.0 or later,
10948 or OpenSSL 1.1.1 or later.
10949 The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
10952 .vitem &*${stat:*&<&'string'&>&*}*&
10953 .cindex "expansion" "statting a file"
10954 .cindex "file" "extracting characteristics"
10955 .cindex "&%stat%& expansion item"
10956 The string, after expansion, must be a file path. A call to the &[stat()]&
10957 function is made for this path. If &[stat()]& fails, an error occurs and the
10958 expansion fails. If it succeeds, the data from the stat replaces the item, as a
10959 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
10960 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
10961 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
10962 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
10963 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
10964 can extract individual fields using the &%extract%& expansion item.
10966 The use of the &%stat%& expansion in users' filter files can be locked out by
10967 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
10968 systems for files larger than 2GB.
10970 .vitem &*${str2b64:*&<&'string'&>&*}*&
10971 .cindex "&%str2b64%& expansion item"
10972 Now deprecated, a synonym for the &%base64%& expansion operator.
10976 .vitem &*${strlen:*&<&'string'&>&*}*&
10977 .cindex "expansion" "string length"
10978 .cindex "string" "length in expansion"
10979 .cindex "&%strlen%& expansion item"
10980 The item is replace by the length of the expanded string, expressed as a
10981 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
10982 All measurement is done in bytes and is not UTF-8 aware.
10985 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
10986 .cindex "&%substr%& expansion item"
10987 .cindex "substring extraction"
10988 .cindex "expansion" "substring expansion"
10989 The &%substr%& operator is a simpler interface to the &%substr%& function that
10990 can be used when the two parameters are fixed numbers (as opposed to strings
10991 that change when expanded). The effect is the same as
10993 ${substr{<start>}{<length>}{<string>}}
10995 See the description of the general &%substr%& item above for details. The
10996 abbreviation &%s%& can be used when &%substr%& is used as an operator.
10997 All measurement is done in bytes and is not UTF-8 aware.
10999 .vitem &*${time_eval:*&<&'string'&>&*}*&
11000 .cindex "&%time_eval%& expansion item"
11001 .cindex "time interval" "decoding"
11002 This item converts an Exim time interval such as &`2d4h5m`& into a number of
11005 .vitem &*${time_interval:*&<&'string'&>&*}*&
11006 .cindex "&%time_interval%& expansion item"
11007 .cindex "time interval" "formatting"
11008 The argument (after sub-expansion) must be a sequence of decimal digits that
11009 represents an interval of time as a number of seconds. It is converted into a
11010 number of larger units and output in Exim's normal time format, for example,
11013 .vitem &*${uc:*&<&'string'&>&*}*&
11014 .cindex "case forcing in strings"
11015 .cindex "string" "case forcing"
11016 .cindex "upper casing"
11017 .cindex "expansion" "case forcing"
11018 .cindex "&%uc%& expansion item"
11019 This forces the letters in the string into upper-case.
11020 Case is defined per the system C locale.
11022 .vitem &*${utf8clean:*&<&'string'&>&*}*&
11023 .cindex "correction of invalid utf-8 sequences in strings"
11024 .cindex "utf-8" "utf-8 sequences"
11025 .cindex "incorrect utf-8"
11026 .cindex "expansion" "utf-8 forcing"
11027 .cindex "&%utf8clean%& expansion item"
11028 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
11030 In versions of Exim before 4.92, this did not correctly do so for a truncated
11031 final codepoint's encoding, and the character would be silently dropped.
11032 If you must handle detection of this scenario across both sets of Exim behavior,
11033 the complexity will depend upon the task.
11034 For instance, to detect if the first character is multibyte and a 1-byte
11035 extraction can be successfully used as a path component (as is common for
11036 dividing up delivery folders), you might use:
11038 condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
11040 (which will false-positive if the first character of the local part is a
11041 literal question mark).
11044 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
11045 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
11046 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
11047 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
11048 .cindex expansion UTF-8
11049 .cindex UTF-8 expansion
11051 .cindex internationalisation
11052 .cindex "&%utf8_domain_to_alabel%& expansion item"
11053 .cindex "&%utf8_domain_from_alabel%& expansion item"
11054 .cindex "&%utf8_localpart_to_alabel%& expansion item"
11055 .cindex "&%utf8_localpart_from_alabel%& expansion item"
11056 These convert EAI mail name components between UTF-8 and a-label forms.
11057 For information on internationalisation support see &<<SECTi18nMTA>>&.
11065 .section "Expansion conditions" "SECTexpcond"
11066 .scindex IIDexpcond "expansion" "conditions"
11067 The following conditions are available for testing by the &%${if%& construct
11068 while expanding strings:
11071 .vitem &*!*&<&'condition'&>
11072 .cindex "expansion" "negating a condition"
11073 .cindex "negation" "in expansion condition"
11074 Preceding any condition with an exclamation mark negates the result of the
11077 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11078 .cindex "numeric comparison"
11079 .cindex "expansion" "numeric comparison"
11080 There are a number of symbolic operators for doing numeric comparisons. They
11086 &`>= `& greater or equal
11088 &`<= `& less or equal
11092 ${if >{$message_size}{10M} ...
11094 Note that the general negation operator provides for inequality testing. The
11095 two strings must take the form of optionally signed decimal integers,
11096 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
11097 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
11098 As a special case, the numerical value of an empty string is taken as
11101 In all cases, a relative comparator OP is testing if <&'string1'&> OP
11102 <&'string2'&>; the above example is checking if &$message_size$& is larger than
11103 10M, not if 10M is larger than &$message_size$&.
11106 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
11107 {*&<&'arg2'&>&*}...}*&
11108 .cindex "expansion" "calling an acl"
11109 .cindex "&%acl%&" "expansion condition"
11110 The name and zero to nine argument strings are first expanded separately. The expanded
11111 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
11112 Any unused are made empty. The variable &$acl_narg$& is set to the number of
11113 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
11114 and may use the variables; if another acl expansion is used the values
11115 are restored after it returns. If the ACL sets
11116 a value using a "message =" modifier the variable $value becomes
11117 the result of the expansion, otherwise it is empty.
11118 If the ACL returns accept the condition is true; if deny, false.
11119 If the ACL returns defer the result is a forced-fail.
11121 .vitem &*bool&~{*&<&'string'&>&*}*&
11122 .cindex "expansion" "boolean parsing"
11123 .cindex "&%bool%& expansion condition"
11124 This condition turns a string holding a true or false representation into
11125 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
11126 (case-insensitively); also integer numbers map to true if non-zero,
11128 An empty string is treated as false.
11129 Leading and trailing whitespace is ignored;
11130 thus a string consisting only of whitespace is false.
11131 All other string values will result in expansion failure.
11133 When combined with ACL variables, this expansion condition will let you
11134 make decisions in one place and act on those decisions in another place.
11137 ${if bool{$acl_m_privileged_sender} ...
11141 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
11142 .cindex "expansion" "boolean parsing"
11143 .cindex "&%bool_lax%& expansion condition"
11144 Like &%bool%&, this condition turns a string into a boolean state. But
11145 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
11146 loose definition that the Router &%condition%& option uses. The empty string
11147 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
11148 true. Leading and trailing whitespace is ignored.
11150 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
11152 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11153 .cindex "expansion" "encrypted comparison"
11154 .cindex "encrypted strings, comparing"
11155 .cindex "&%crypteq%& expansion condition"
11156 This condition is included in the Exim binary if it is built to support any
11157 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
11158 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
11159 included in the binary.
11161 The &%crypteq%& condition has two arguments. The first is encrypted and
11162 compared against the second, which is already encrypted. The second string may
11163 be in the LDAP form for storing encrypted strings, which starts with the
11164 encryption type in curly brackets, followed by the data. If the second string
11165 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
11166 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
11167 Typically this will be a field from a password file. An example of an encrypted
11168 string in LDAP form is:
11170 {md5}CY9rzUYh03PK3k6DJie09g==
11172 If such a string appears directly in an expansion, the curly brackets have to
11173 be quoted, because they are part of the expansion syntax. For example:
11175 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
11177 The following encryption types (whose names are matched case-independently) are
11182 .cindex "base64 encoding" "in encrypted password"
11183 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
11184 printable characters to compare with the remainder of the second string. If the
11185 length of the comparison string is 24, Exim assumes that it is base64 encoded
11186 (as in the above example). If the length is 32, Exim assumes that it is a
11187 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
11191 .cindex "SHA-1 hash"
11192 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
11193 printable characters to compare with the remainder of the second string. If the
11194 length of the comparison string is 28, Exim assumes that it is base64 encoded.
11195 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
11196 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
11199 .cindex "&[crypt()]&"
11200 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
11201 only the first eight characters of the password. However, in modern operating
11202 systems this is no longer true, and in many cases the entire password is used,
11203 whatever its length.
11206 .cindex "&[crypt16()]&"
11207 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
11208 use up to 16 characters of the password in some operating systems. Again, in
11209 modern operating systems, more characters may be used.
11211 Exim has its own version of &[crypt16()]&, which is just a double call to
11212 &[crypt()]&. For operating systems that have their own version, setting
11213 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
11214 operating system version instead of its own. This option is set by default in
11215 the OS-dependent &_Makefile_& for those operating systems that are known to
11216 support &[crypt16()]&.
11218 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
11219 it was not using the same algorithm as some operating systems' versions. It
11220 turns out that as well as &[crypt16()]& there is a function called
11221 &[bigcrypt()]& in some operating systems. This may or may not use the same
11222 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
11224 However, since there is now a move away from the traditional &[crypt()]&
11225 functions towards using SHA1 and other algorithms, tidying up this area of
11226 Exim is seen as very low priority.
11228 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
11229 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
11230 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
11231 default is &`{crypt}`&. Whatever the default, you can always use either
11232 function by specifying it explicitly in curly brackets.
11234 .vitem &*def:*&<&'variable&~name'&>
11235 .cindex "expansion" "checking for empty variable"
11236 .cindex "&%def%& expansion condition"
11237 The &%def%& condition must be followed by the name of one of the expansion
11238 variables defined in section &<<SECTexpvar>>&. The condition is true if the
11239 variable does not contain the empty string. For example:
11241 ${if def:sender_ident {from $sender_ident}}
11243 Note that the variable name is given without a leading &%$%& character. If the
11244 variable does not exist, the expansion fails.
11246 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
11247 &~&*def:h_*&<&'header&~name'&>&*:*&"
11248 .cindex "expansion" "checking header line existence"
11249 This condition is true if a message is being processed and the named header
11250 exists in the message. For example,
11252 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
11254 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
11255 the header name must be terminated by a colon if white space does not follow.
11257 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11258 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11259 .cindex "string" "comparison"
11260 .cindex "expansion" "string comparison"
11261 .cindex "&%eq%& expansion condition"
11262 .cindex "&%eqi%& expansion condition"
11263 The two substrings are first expanded. The condition is true if the two
11264 resulting strings are identical. For &%eq%& the comparison includes the case of
11265 letters, whereas for &%eqi%& the comparison is case-independent, where
11266 case is defined per the system C locale.
11268 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
11269 .cindex "expansion" "file existence test"
11270 .cindex "file" "existence test"
11271 .cindex "&%exists%&, expansion condition"
11272 The substring is first expanded and then interpreted as an absolute path. The
11273 condition is true if the named file (or directory) exists. The existence test
11274 is done by calling the &[stat()]& function. The use of the &%exists%& test in
11275 users' filter files may be locked out by the system administrator.
11277 .vitem &*first_delivery*&
11278 .cindex "delivery" "first"
11279 .cindex "first delivery"
11280 .cindex "expansion" "first delivery test"
11281 .cindex "&%first_delivery%& expansion condition"
11282 This condition, which has no data, is true during a message's first delivery
11283 attempt. It is false during any subsequent delivery attempts.
11286 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
11287 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
11288 .cindex "list" "iterative conditions"
11289 .cindex "expansion" "&*forall*& condition"
11290 .cindex "expansion" "&*forany*& condition"
11292 These conditions iterate over a list. The first argument is expanded to form
11293 the list. By default, the list separator is a colon, but it can be changed by
11294 the normal method (&<<SECTlistsepchange>>&).
11295 The second argument is interpreted as a condition that is to
11296 be applied to each item in the list in turn. During the interpretation of the
11297 condition, the current list item is placed in a variable called &$item$&.
11299 For &*forany*&, interpretation stops if the condition is true for any item, and
11300 the result of the whole condition is true. If the condition is false for all
11301 items in the list, the overall condition is false.
11303 For &*forall*&, interpretation stops if the condition is false for any item,
11304 and the result of the whole condition is false. If the condition is true for
11305 all items in the list, the overall condition is true.
11307 Note that negation of &*forany*& means that the condition must be false for all
11308 items for the overall condition to succeed, and negation of &*forall*& means
11309 that the condition must be false for at least one item. In this example, the
11310 list separator is changed to a comma:
11312 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
11314 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
11315 being processed, to enable these expansion items to be nested.
11317 To scan a named list, expand it with the &*listnamed*& operator.
11320 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11321 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11322 .cindex "string" "comparison"
11323 .cindex "expansion" "string comparison"
11324 .cindex "&%ge%& expansion condition"
11325 .cindex "&%gei%& expansion condition"
11326 The two substrings are first expanded. The condition is true if the first
11327 string is lexically greater than or equal to the second string. For &%ge%& the
11328 comparison includes the case of letters, whereas for &%gei%& the comparison is
11330 Case and collation order are defined per the system C locale.
11332 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11333 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11334 .cindex "string" "comparison"
11335 .cindex "expansion" "string comparison"
11336 .cindex "&%gt%& expansion condition"
11337 .cindex "&%gti%& expansion condition"
11338 The two substrings are first expanded. The condition is true if the first
11339 string is lexically greater than the second string. For &%gt%& the comparison
11340 includes the case of letters, whereas for &%gti%& the comparison is
11342 Case and collation order are defined per the system C locale.
11344 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11345 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11346 .cindex "string" "comparison"
11347 .cindex "list" "iterative conditions"
11348 Both strings are expanded; the second string is treated as a list of simple
11349 strings; if the first string is a member of the second, then the condition
11351 For the case-independent &%inlisti%& condition, case is defined per the system C locale.
11353 These are simpler to use versions of the more powerful &*forany*& condition.
11354 Examples, and the &*forany*& equivalents:
11356 ${if inlist{needle}{foo:needle:bar}}
11357 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11358 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11359 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11362 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11363 &*isip4&~{*&<&'string'&>&*}*& &&&
11364 &*isip6&~{*&<&'string'&>&*}*&
11365 .cindex "IP address" "testing string format"
11366 .cindex "string" "testing for IP address"
11367 .cindex "&%isip%& expansion condition"
11368 .cindex "&%isip4%& expansion condition"
11369 .cindex "&%isip6%& expansion condition"
11370 The substring is first expanded, and then tested to see if it has the form of
11371 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11372 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11374 For an IPv4 address, the test is for four dot-separated components, each of
11375 which consists of from one to three digits. For an IPv6 address, up to eight
11376 colon-separated components are permitted, each containing from one to four
11377 hexadecimal digits. There may be fewer than eight components if an empty
11378 component (adjacent colons) is present. Only one empty component is permitted.
11380 &*Note*&: The checks used to be just on the form of the address; actual numerical
11381 values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
11383 This is no longer the case.
11385 The main use of these tests is to distinguish between IP addresses and
11386 host names, or between IPv4 and IPv6 addresses. For example, you could use
11388 ${if isip4{$sender_host_address}...
11390 to test which IP version an incoming SMTP connection is using.
11392 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11393 .cindex "LDAP" "use for authentication"
11394 .cindex "expansion" "LDAP authentication test"
11395 .cindex "&%ldapauth%& expansion condition"
11396 This condition supports user authentication using LDAP. See section
11397 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11398 queries. For this use, the query must contain a user name and password. The
11399 query itself is not used, and can be empty. The condition is true if the
11400 password is not empty, and the user name and password are accepted by the LDAP
11401 server. An empty password is rejected without calling LDAP because LDAP binds
11402 with an empty password are considered anonymous regardless of the username, and
11403 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11404 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11408 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11409 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11410 .cindex "string" "comparison"
11411 .cindex "expansion" "string comparison"
11412 .cindex "&%le%& expansion condition"
11413 .cindex "&%lei%& expansion condition"
11414 The two substrings are first expanded. The condition is true if the first
11415 string is lexically less than or equal to the second string. For &%le%& the
11416 comparison includes the case of letters, whereas for &%lei%& the comparison is
11418 Case and collation order are defined per the system C locale.
11420 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11421 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11422 .cindex "string" "comparison"
11423 .cindex "expansion" "string comparison"
11424 .cindex "&%lt%& expansion condition"
11425 .cindex "&%lti%& expansion condition"
11426 The two substrings are first expanded. The condition is true if the first
11427 string is lexically less than the second string. For &%lt%& the comparison
11428 includes the case of letters, whereas for &%lti%& the comparison is
11430 Case and collation order are defined per the system C locale.
11433 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11434 .cindex "expansion" "regular expression comparison"
11435 .cindex "regular expressions" "match in expanded string"
11436 .cindex "&%match%& expansion condition"
11437 The two substrings are first expanded. The second is then treated as a regular
11438 expression and applied to the first. Because of the pre-expansion, if the
11439 regular expression contains dollar, or backslash characters, they must be
11440 escaped. Care must also be taken if the regular expression contains braces
11441 (curly brackets). A closing brace must be escaped so that it is not taken as a
11442 premature termination of <&'string2'&>. The easiest approach is to use the
11443 &`\N`& feature to disable expansion of the regular expression.
11446 ${if match {$local_part}{\N^\d{3}\N} ...
11448 If the whole expansion string is in double quotes, further escaping of
11449 backslashes is also required.
11451 The condition is true if the regular expression match succeeds.
11452 The regular expression is not required to begin with a circumflex
11453 metacharacter, but if there is no circumflex, the expression is not anchored,
11454 and it may match anywhere in the subject, not just at the start. If you want
11455 the pattern to match at the end of the subject, you must include the &`$`&
11456 metacharacter at an appropriate point.
11457 All character handling is done in bytes and is not UTF-8 aware,
11458 but we might change this in a future Exim release.
11460 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11461 At the start of an &%if%& expansion the values of the numeric variable
11462 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11463 succeeds causes them to be reset to the substrings of that condition and they
11464 will have these values during the expansion of the success string. At the end
11465 of the &%if%& expansion, the previous values are restored. After testing a
11466 combination of conditions using &%or%&, the subsequent values of the numeric
11467 variables are those of the condition that succeeded.
11469 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11470 .cindex "&%match_address%& expansion condition"
11471 See &*match_local_part*&.
11473 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11474 .cindex "&%match_domain%& expansion condition"
11475 See &*match_local_part*&.
11477 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11478 .cindex "&%match_ip%& expansion condition"
11479 This condition matches an IP address to a list of IP address patterns. It must
11480 be followed by two argument strings. The first (after expansion) must be an IP
11481 address or an empty string. The second (not expanded) is a restricted host
11482 list that can match only an IP address, not a host name. For example:
11484 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
11486 The specific types of host list item that are permitted in the list are:
11489 An IP address, optionally with a CIDR mask.
11491 A single asterisk, which matches any IP address.
11493 An empty item, which matches only if the IP address is empty. This could be
11494 useful for testing for a locally submitted message or one from specific hosts
11495 in a single test such as
11496 . ==== As this is a nested list, any displays it contains must be indented
11497 . ==== as otherwise they are too far to the left. This comment applies to
11498 . ==== the use of xmlto plus fop. There's no problem when formatting with
11499 . ==== sdop, with or without the extra indent.
11501 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
11503 where the first item in the list is the empty string.
11505 The item @[] matches any of the local host's interface addresses.
11507 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
11508 even if &`net-`& is not specified. There is never any attempt to turn the IP
11509 address into a host name. The most common type of linear search for
11510 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
11511 masks. For example:
11513 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
11515 It is of course possible to use other kinds of lookup, and in such a case, you
11516 do need to specify the &`net-`& prefix if you want to specify a specific
11517 address mask, for example:
11519 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
11521 However, unless you are combining a &%match_ip%& condition with others, it is
11522 just as easy to use the fact that a lookup is itself a condition, and write:
11524 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
11528 Note that <&'string2'&> is not itself subject to string expansion, unless
11529 Exim was built with the EXPAND_LISTMATCH_RHS option.
11531 Consult section &<<SECThoslispatip>>& for further details of these patterns.
11533 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11534 .cindex "domain list" "in expansion condition"
11535 .cindex "address list" "in expansion condition"
11536 .cindex "local part" "list, in expansion condition"
11537 .cindex "&%match_local_part%& expansion condition"
11538 This condition, together with &%match_address%& and &%match_domain%&, make it
11539 possible to test domain, address, and local part lists within expansions. Each
11540 condition requires two arguments: an item and a list to match. A trivial
11543 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
11545 In each case, the second argument may contain any of the allowable items for a
11546 list of the appropriate type. Also, because the second argument
11547 is a standard form of list, it is possible to refer to a named list.
11548 Thus, you can use conditions like this:
11550 ${if match_domain{$domain}{+local_domains}{...
11552 .cindex "&`+caseful`&"
11553 For address lists, the matching starts off caselessly, but the &`+caseful`&
11554 item can be used, as in all address lists, to cause subsequent items to
11555 have their local parts matched casefully. Domains are always matched
11558 Note that <&'string2'&> is not itself subject to string expansion, unless
11559 Exim was built with the EXPAND_LISTMATCH_RHS option.
11561 &*Note*&: Host lists are &'not'& supported in this way. This is because
11562 hosts have two identities: a name and an IP address, and it is not clear
11563 how to specify cleanly how such a test would work. However, IP addresses can be
11564 matched using &%match_ip%&.
11566 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
11567 .cindex "PAM authentication"
11568 .cindex "AUTH" "with PAM"
11569 .cindex "Solaris" "PAM support"
11570 .cindex "expansion" "PAM authentication test"
11571 .cindex "&%pam%& expansion condition"
11572 &'Pluggable Authentication Modules'&
11573 (&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
11574 available in the latest releases of Solaris and in some GNU/Linux
11575 distributions. The Exim support, which is intended for use in conjunction with
11576 the SMTP AUTH command, is available only if Exim is compiled with
11580 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
11581 in some releases of GNU/Linux &%-ldl%& is also needed.
11583 The argument string is first expanded, and the result must be a
11584 colon-separated list of strings. Leading and trailing white space is ignored.
11585 The PAM module is initialized with the service name &"exim"& and the user name
11586 taken from the first item in the colon-separated data string (<&'string1'&>).
11587 The remaining items in the data string are passed over in response to requests
11588 from the authentication function. In the simple case there will only be one
11589 request, for a password, so the data consists of just two strings.
11591 There can be problems if any of the strings are permitted to contain colon
11592 characters. In the usual way, these have to be doubled to avoid being taken as
11593 separators. If the data is being inserted from a variable, the &%sg%& expansion
11594 item can be used to double any existing colons. For example, the configuration
11595 of a LOGIN authenticator might contain this setting:
11597 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
11599 For a PLAIN authenticator you could use:
11601 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
11603 In some operating systems, PAM authentication can be done only from a process
11604 running as root. Since Exim is running as the Exim user when receiving
11605 messages, this means that PAM cannot be used directly in those systems.
11606 . --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that
11609 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
11610 .cindex "&'pwcheck'& daemon"
11612 .cindex "expansion" "&'pwcheck'& authentication test"
11613 .cindex "&%pwcheck%& expansion condition"
11614 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
11615 This is one way of making it possible for passwords to be checked by a process
11616 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
11617 deprecated. Its replacement is &'saslauthd'& (see below).
11619 The pwcheck support is not included in Exim by default. You need to specify
11620 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
11621 building Exim. For example:
11623 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
11625 You do not need to install the full Cyrus software suite in order to use
11626 the pwcheck daemon. You can compile and install just the daemon alone
11627 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
11628 access to the &_/var/pwcheck_& directory.
11630 The &%pwcheck%& condition takes one argument, which must be the user name and
11631 password, separated by a colon. For example, in a LOGIN authenticator
11632 configuration, you might have this:
11634 server_condition = ${if pwcheck{$auth1:$auth2}}
11636 Again, for a PLAIN authenticator configuration, this would be:
11638 server_condition = ${if pwcheck{$auth2:$auth3}}
11640 .vitem &*queue_running*&
11641 .cindex "queue runner" "detecting when delivering from"
11642 .cindex "expansion" "queue runner test"
11643 .cindex "&%queue_running%& expansion condition"
11644 This condition, which has no data, is true during delivery attempts that are
11645 initiated by queue runner processes, and false otherwise.
11648 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
11650 .cindex "expansion" "Radius authentication"
11651 .cindex "&%radius%& expansion condition"
11652 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
11653 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
11654 the Radius client configuration file in order to build Exim with Radius
11657 With just that one setting, Exim expects to be linked with the &%radiusclient%&
11658 library, using the original API. If you are using release 0.4.0 or later of
11659 this library, you need to set
11661 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
11663 in &_Local/Makefile_& when building Exim. You can also link Exim with the
11664 &%libradius%& library that comes with FreeBSD. To do this, set
11666 RADIUS_LIB_TYPE=RADLIB
11668 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
11669 You may also have to supply a suitable setting in EXTRALIBS so that the
11670 Radius library can be found when Exim is linked.
11672 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
11673 Radius client library, which calls the Radius server. The condition is true if
11674 the authentication is successful. For example:
11676 server_condition = ${if radius{<arguments>}}
11680 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
11681 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
11682 .cindex "&'saslauthd'& daemon"
11684 .cindex "expansion" "&'saslauthd'& authentication test"
11685 .cindex "&%saslauthd%& expansion condition"
11686 This condition supports user authentication using the Cyrus &'saslauthd'&
11687 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
11688 Using this daemon is one way of making it possible for passwords to be checked
11689 by a process that is not running as root.
11691 The saslauthd support is not included in Exim by default. You need to specify
11692 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
11693 building Exim. For example:
11695 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
11697 You do not need to install the full Cyrus software suite in order to use
11698 the saslauthd daemon. You can compile and install just the daemon alone
11699 from the Cyrus SASL library.
11701 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
11702 two are mandatory. For example:
11704 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
11706 The service and the realm are optional (which is why the arguments are enclosed
11707 in their own set of braces). For details of the meaning of the service and
11708 realm, and how to run the daemon, consult the Cyrus documentation.
11713 .section "Combining expansion conditions" "SECID84"
11714 .cindex "expansion" "combining conditions"
11715 Several conditions can be tested at once by combining them using the &%and%&
11716 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
11717 conditions on their own, and precede their lists of sub-conditions. Each
11718 sub-condition must be enclosed in braces within the overall braces that contain
11719 the list. No repetition of &%if%& is used.
11723 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11724 .cindex "&""or""& expansion condition"
11725 .cindex "expansion" "&""or""& of conditions"
11726 The sub-conditions are evaluated from left to right. The condition is true if
11727 any one of the sub-conditions is true.
11730 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
11732 When a true sub-condition is found, the following ones are parsed but not
11733 evaluated. If there are several &"match"& sub-conditions the values of the
11734 numeric variables afterwards are taken from the first one that succeeds.
11736 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11737 .cindex "&""and""& expansion condition"
11738 .cindex "expansion" "&""and""& of conditions"
11739 The sub-conditions are evaluated from left to right. The condition is true if
11740 all of the sub-conditions are true. If there are several &"match"&
11741 sub-conditions, the values of the numeric variables afterwards are taken from
11742 the last one. When a false sub-condition is found, the following ones are
11743 parsed but not evaluated.
11745 .ecindex IIDexpcond
11750 .section "Expansion variables" "SECTexpvar"
11751 .cindex "expansion" "variables, list of"
11752 This section contains an alphabetical list of all the expansion variables. Some
11753 of them are available only when Exim is compiled with specific options such as
11754 support for TLS or the content scanning extension.
11757 .vitem "&$0$&, &$1$&, etc"
11758 .cindex "numerical variables (&$1$& &$2$& etc)"
11759 When a &%match%& expansion condition succeeds, these variables contain the
11760 captured substrings identified by the regular expression during subsequent
11761 processing of the success string of the containing &%if%& expansion item.
11762 In the expansion condition case
11763 they do not retain their values afterwards; in fact, their previous
11764 values are restored at the end of processing an &%if%& item. The numerical
11765 variables may also be set externally by some other matching process which
11766 precedes the expansion of the string. For example, the commands available in
11767 Exim filter files include an &%if%& command with its own regular expression
11768 matching condition.
11770 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
11771 Within an acl condition, expansion condition or expansion item
11772 any arguments are copied to these variables,
11773 any unused variables being made empty.
11775 .vitem "&$acl_c...$&"
11776 Values can be placed in these variables by the &%set%& modifier in an ACL. They
11777 can be given any name that starts with &$acl_c$& and is at least six characters
11778 long, but the sixth character must be either a digit or an underscore. For
11779 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
11780 variables persist throughout the lifetime of an SMTP connection. They can be
11781 used to pass information between ACLs and between different invocations of the
11782 same ACL. When a message is received, the values of these variables are saved
11783 with the message, and can be accessed by filters, routers, and transports
11784 during subsequent delivery.
11786 .vitem "&$acl_m...$&"
11787 These variables are like the &$acl_c...$& variables, except that their values
11788 are reset after a message has been received. Thus, if several messages are
11789 received in one SMTP connection, &$acl_m...$& values are not passed on from one
11790 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
11791 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
11792 message is received, the values of these variables are saved with the message,
11793 and can be accessed by filters, routers, and transports during subsequent
11796 .vitem &$acl_narg$&
11797 Within an acl condition, expansion condition or expansion item
11798 this variable has the number of arguments.
11800 .vitem &$acl_verify_message$&
11801 .vindex "&$acl_verify_message$&"
11802 After an address verification has failed, this variable contains the failure
11803 message. It retains its value for use in subsequent modifiers. The message can
11804 be preserved by coding like this:
11806 warn !verify = sender
11807 set acl_m0 = $acl_verify_message
11809 You can use &$acl_verify_message$& during the expansion of the &%message%& or
11810 &%log_message%& modifiers, to include information about the verification
11813 .vitem &$address_data$&
11814 .vindex "&$address_data$&"
11815 This variable is set by means of the &%address_data%& option in routers. The
11816 value then remains with the address while it is processed by subsequent routers
11817 and eventually a transport. If the transport is handling multiple addresses,
11818 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
11819 for more details. &*Note*&: The contents of &$address_data$& are visible in
11822 If &$address_data$& is set when the routers are called from an ACL to verify
11823 a recipient address, the final value is still in the variable for subsequent
11824 conditions and modifiers of the ACL statement. If routing the address caused it
11825 to be redirected to just one address, the child address is also routed as part
11826 of the verification, and in this case the final value of &$address_data$& is
11827 from the child's routing.
11829 If &$address_data$& is set when the routers are called from an ACL to verify a
11830 sender address, the final value is also preserved, but this time in
11831 &$sender_address_data$&, to distinguish it from data from a recipient
11834 In both cases (recipient and sender verification), the value does not persist
11835 after the end of the current ACL statement. If you want to preserve
11836 these values for longer, you can save them in ACL variables.
11838 .vitem &$address_file$&
11839 .vindex "&$address_file$&"
11840 When, as a result of aliasing, forwarding, or filtering, a message is directed
11841 to a specific file, this variable holds the name of the file when the transport
11842 is running. At other times, the variable is empty. For example, using the
11843 default configuration, if user &%r2d2%& has a &_.forward_& file containing
11845 /home/r2d2/savemail
11847 then when the &(address_file)& transport is running, &$address_file$&
11848 contains the text string &`/home/r2d2/savemail`&.
11849 .cindex "Sieve filter" "value of &$address_file$&"
11850 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
11851 then up to the transport configuration to generate an appropriate absolute path
11852 to the relevant file.
11854 .vitem &$address_pipe$&
11855 .vindex "&$address_pipe$&"
11856 When, as a result of aliasing or forwarding, a message is directed to a pipe,
11857 this variable holds the pipe command when the transport is running.
11859 .vitem "&$auth1$& &-- &$auth3$&"
11860 .vindex "&$auth1$&, &$auth2$&, etc"
11861 These variables are used in SMTP authenticators (see chapters
11862 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
11864 .vitem &$authenticated_id$&
11865 .cindex "authentication" "id"
11866 .vindex "&$authenticated_id$&"
11867 When a server successfully authenticates a client it may be configured to
11868 preserve some of the authentication information in the variable
11869 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
11870 user/password authenticator configuration might preserve the user name for use
11871 in the routers. Note that this is not the same information that is saved in
11872 &$sender_host_authenticated$&.
11874 When a message is submitted locally (that is, not over a TCP connection)
11875 the value of &$authenticated_id$& is normally the login name of the calling
11876 process. However, a trusted user can override this by means of the &%-oMai%&
11877 command line option.
11878 This second case also sets up information used by the
11879 &$authresults$& expansion item.
11881 .vitem &$authenticated_fail_id$&
11882 .cindex "authentication" "fail" "id"
11883 .vindex "&$authenticated_fail_id$&"
11884 When an authentication attempt fails, the variable &$authenticated_fail_id$&
11885 will contain the failed authentication id. If more than one authentication
11886 id is attempted, it will contain only the last one. The variable is
11887 available for processing in the ACL's, generally the quit or notquit ACL.
11888 A message to a local recipient could still be accepted without requiring
11889 authentication, which means this variable could also be visible in all of
11893 .vitem &$authenticated_sender$&
11894 .cindex "sender" "authenticated"
11895 .cindex "authentication" "sender"
11896 .cindex "AUTH" "on MAIL command"
11897 .vindex "&$authenticated_sender$&"
11898 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
11899 SMTP MAIL command if it believes the sender is sufficiently trusted, as
11900 described in section &<<SECTauthparamail>>&. Unless the data is the string
11901 &"<>"&, it is set as the authenticated sender of the message, and the value is
11902 available during delivery in the &$authenticated_sender$& variable. If the
11903 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
11905 .vindex "&$qualify_domain$&"
11906 When a message is submitted locally (that is, not over a TCP connection), the
11907 value of &$authenticated_sender$& is an address constructed from the login
11908 name of the calling process and &$qualify_domain$&, except that a trusted user
11909 can override this by means of the &%-oMas%& command line option.
11912 .vitem &$authentication_failed$&
11913 .cindex "authentication" "failure"
11914 .vindex "&$authentication_failed$&"
11915 This variable is set to &"1"& in an Exim server if a client issues an AUTH
11916 command that does not succeed. Otherwise it is set to &"0"&. This makes it
11917 possible to distinguish between &"did not try to authenticate"&
11918 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
11919 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
11920 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
11921 negative response to an AUTH command, including (for example) an attempt to use
11922 an undefined mechanism.
11924 .vitem &$av_failed$&
11925 .cindex "content scanning" "AV scanner failure"
11926 This variable is available when Exim is compiled with the content-scanning
11927 extension. It is set to &"0"& by default, but will be set to &"1"& if any
11928 problem occurs with the virus scanner (specified by &%av_scanner%&) during
11929 the ACL malware condition.
11931 .vitem &$body_linecount$&
11932 .cindex "message body" "line count"
11933 .cindex "body of message" "line count"
11934 .vindex "&$body_linecount$&"
11935 When a message is being received or delivered, this variable contains the
11936 number of lines in the message's body. See also &$message_linecount$&.
11938 .vitem &$body_zerocount$&
11939 .cindex "message body" "binary zero count"
11940 .cindex "body of message" "binary zero count"
11941 .cindex "binary zero" "in message body"
11942 .vindex "&$body_zerocount$&"
11943 When a message is being received or delivered, this variable contains the
11944 number of binary zero bytes (ASCII NULs) in the message's body.
11946 .vitem &$bounce_recipient$&
11947 .vindex "&$bounce_recipient$&"
11948 This is set to the recipient address of a bounce message while Exim is creating
11949 it. It is useful if a customized bounce message text file is in use (see
11950 chapter &<<CHAPemsgcust>>&).
11952 .vitem &$bounce_return_size_limit$&
11953 .vindex "&$bounce_return_size_limit$&"
11954 This contains the value set in the &%bounce_return_size_limit%& option, rounded
11955 up to a multiple of 1000. It is useful when a customized error message text
11956 file is in use (see chapter &<<CHAPemsgcust>>&).
11958 .vitem &$caller_gid$&
11959 .cindex "gid (group id)" "caller"
11960 .vindex "&$caller_gid$&"
11961 The real group id under which the process that called Exim was running. This is
11962 not the same as the group id of the originator of a message (see
11963 &$originator_gid$&). If Exim re-execs itself, this variable in the new
11964 incarnation normally contains the Exim gid.
11966 .vitem &$caller_uid$&
11967 .cindex "uid (user id)" "caller"
11968 .vindex "&$caller_uid$&"
11969 The real user id under which the process that called Exim was running. This is
11970 not the same as the user id of the originator of a message (see
11971 &$originator_uid$&). If Exim re-execs itself, this variable in the new
11972 incarnation normally contains the Exim uid.
11974 .vitem &$callout_address$&
11975 .vindex "&$callout_address$&"
11976 After a callout for verification, spamd or malware daemon service, the
11977 address that was connected to.
11979 .vitem &$compile_number$&
11980 .vindex "&$compile_number$&"
11981 The building process for Exim keeps a count of the number
11982 of times it has been compiled. This serves to distinguish different
11983 compilations of the same version of Exim.
11985 .vitem &$config_dir$&
11986 .vindex "&$config_dir$&"
11987 The directory name of the main configuration file. That is, the content of
11988 &$config_file$& with the last component stripped. The value does not
11989 contain the trailing slash. If &$config_file$& does not contain a slash,
11990 &$config_dir$& is ".".
11992 .vitem &$config_file$&
11993 .vindex "&$config_file$&"
11994 The name of the main configuration file Exim is using.
11996 .vitem &$dkim_verify_status$&
11997 Results of DKIM verification.
11998 For details see section &<<SECDKIMVFY>>&.
12000 .vitem &$dkim_cur_signer$& &&&
12001 &$dkim_verify_reason$& &&&
12002 &$dkim_domain$& &&&
12003 &$dkim_identity$& &&&
12004 &$dkim_selector$& &&&
12006 &$dkim_canon_body$& &&&
12007 &$dkim_canon_headers$& &&&
12008 &$dkim_copiedheaders$& &&&
12009 &$dkim_bodylength$& &&&
12010 &$dkim_created$& &&&
12011 &$dkim_expires$& &&&
12012 &$dkim_headernames$& &&&
12013 &$dkim_key_testing$& &&&
12014 &$dkim_key_nosubdomains$& &&&
12015 &$dkim_key_srvtype$& &&&
12016 &$dkim_key_granularity$& &&&
12017 &$dkim_key_notes$& &&&
12018 &$dkim_key_length$&
12019 These variables are only available within the DKIM ACL.
12020 For details see section &<<SECDKIMVFY>>&.
12022 .vitem &$dkim_signers$&
12023 .vindex &$dkim_signers$&
12024 When a message has been received this variable contains
12025 a colon-separated list of signer domains and identities for the message.
12026 For details see section &<<SECDKIMVFY>>&.
12028 .vitem &$dnslist_domain$& &&&
12029 &$dnslist_matched$& &&&
12030 &$dnslist_text$& &&&
12032 .vindex "&$dnslist_domain$&"
12033 .vindex "&$dnslist_matched$&"
12034 .vindex "&$dnslist_text$&"
12035 .vindex "&$dnslist_value$&"
12036 .cindex "black list (DNS)"
12037 When a DNS (black) list lookup succeeds, these variables are set to contain
12038 the following data from the lookup: the list's domain name, the key that was
12039 looked up, the contents of any associated TXT record, and the value from the
12040 main A record. See section &<<SECID204>>& for more details.
12043 .vindex "&$domain$&"
12044 When an address is being routed, or delivered on its own, this variable
12045 contains the domain. Uppercase letters in the domain are converted into lower
12046 case for &$domain$&.
12048 Global address rewriting happens when a message is received, so the value of
12049 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
12050 is set during user filtering, but not during system filtering, because a
12051 message may have many recipients and the system filter is called just once.
12053 When more than one address is being delivered at once (for example, several
12054 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
12055 have the same domain. Transports can be restricted to handling only one domain
12056 at a time if the value of &$domain$& is required at transport time &-- this is
12057 the default for local transports. For further details of the environment in
12058 which local transports are run, see chapter &<<CHAPenvironment>>&.
12060 .oindex "&%delay_warning_condition%&"
12061 At the end of a delivery, if all deferred addresses have the same domain, it is
12062 set in &$domain$& during the expansion of &%delay_warning_condition%&.
12064 The &$domain$& variable is also used in some other circumstances:
12067 When an ACL is running for a RCPT command, &$domain$& contains the domain of
12068 the recipient address. The domain of the &'sender'& address is in
12069 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
12070 normally set during the running of the MAIL ACL. However, if the sender address
12071 is verified with a callout during the MAIL ACL, the sender domain is placed in
12072 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
12073 the &(smtp)& transport.
12076 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12077 &$domain$& contains the domain portion of the address that is being rewritten;
12078 it can be used in the expansion of the replacement address, for example, to
12079 rewrite domains by file lookup.
12082 With one important exception, whenever a domain list is being scanned,
12083 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
12084 a &%sender_domains%& condition in an ACL is being processed, the subject domain
12085 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
12086 that, in a RCPT ACL, the sender domain list can be dependent on the
12087 recipient domain (which is what is in &$domain$& at this time).
12090 .cindex "ETRN" "value of &$domain$&"
12091 .oindex "&%smtp_etrn_command%&"
12092 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
12093 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
12097 .vitem &$domain_data$&
12098 .vindex "&$domain_data$&"
12099 When the &%domains%& option on a router matches a domain by
12100 means of a lookup, the data read by the lookup is available during the running
12101 of the router as &$domain_data$&. In addition, if the driver routes the
12102 address to a transport, the value is available in that transport. If the
12103 transport is handling multiple addresses, the value from the first address is
12106 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
12107 domain by means of a lookup. The data read by the lookup is available during
12108 the rest of the ACL statement. In all other situations, this variable expands
12111 .vitem &$exim_gid$&
12112 .vindex "&$exim_gid$&"
12113 This variable contains the numerical value of the Exim group id.
12115 .vitem &$exim_path$&
12116 .vindex "&$exim_path$&"
12117 This variable contains the path to the Exim binary.
12119 .vitem &$exim_uid$&
12120 .vindex "&$exim_uid$&"
12121 This variable contains the numerical value of the Exim user id.
12123 .vitem &$exim_version$&
12124 .vindex "&$exim_version$&"
12125 This variable contains the version string of the Exim build.
12126 The first character is a major version number, currently 4.
12127 Then after a dot, the next group of digits is a minor version number.
12128 There may be other characters following the minor version.
12130 .vitem &$header_$&<&'name'&>
12131 This is not strictly an expansion variable. It is expansion syntax for
12132 inserting the message header line with the given name. Note that the name must
12133 be terminated by colon or white space, because it may contain a wide variety of
12134 characters. Note also that braces must &'not'& be used.
12135 See the full description in section &<<SECTexpansionitems>>& above.
12137 .vitem &$headers_added$&
12138 .vindex "&$headers_added$&"
12139 Within an ACL this variable contains the headers added so far by
12140 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
12141 The headers are a newline-separated list.
12145 When the &%check_local_user%& option is set for a router, the user's home
12146 directory is placed in &$home$& when the check succeeds. In particular, this
12147 means it is set during the running of users' filter files. A router may also
12148 explicitly set a home directory for use by a transport; this can be overridden
12149 by a setting on the transport itself.
12151 When running a filter test via the &%-bf%& option, &$home$& is set to the value
12152 of the environment variable HOME, which is subject to the
12153 &%keep_environment%& and &%add_environment%& main config options.
12157 If a router assigns an address to a transport (any transport), and passes a
12158 list of hosts with the address, the value of &$host$& when the transport starts
12159 to run is the name of the first host on the list. Note that this applies both
12160 to local and remote transports.
12162 .cindex "transport" "filter"
12163 .cindex "filter" "transport filter"
12164 For the &(smtp)& transport, if there is more than one host, the value of
12165 &$host$& changes as the transport works its way through the list. In
12166 particular, when the &(smtp)& transport is expanding its options for encryption
12167 using TLS, or for specifying a transport filter (see chapter
12168 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
12171 When used in the client part of an authenticator configuration (see chapter
12172 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
12173 client is connected.
12176 .vitem &$host_address$&
12177 .vindex "&$host_address$&"
12178 This variable is set to the remote host's IP address whenever &$host$& is set
12179 for a remote connection. It is also set to the IP address that is being checked
12180 when the &%ignore_target_hosts%& option is being processed.
12182 .vitem &$host_data$&
12183 .vindex "&$host_data$&"
12184 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
12185 result of the lookup is made available in the &$host_data$& variable. This
12186 allows you, for example, to do things like this:
12188 deny hosts = net-lsearch;/some/file
12189 message = $host_data
12191 .vitem &$host_lookup_deferred$&
12192 .cindex "host name" "lookup, failure of"
12193 .vindex "&$host_lookup_deferred$&"
12194 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
12195 message comes from a remote host and there is an attempt to look up the host's
12196 name from its IP address, and the attempt is not successful, one of these
12197 variables is set to &"1"&.
12200 If the lookup receives a definite negative response (for example, a DNS lookup
12201 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
12204 If there is any kind of problem during the lookup, such that Exim cannot
12205 tell whether or not the host name is defined (for example, a timeout for a DNS
12206 lookup), &$host_lookup_deferred$& is set to &"1"&.
12209 Looking up a host's name from its IP address consists of more than just a
12210 single reverse lookup. Exim checks that a forward lookup of at least one of the
12211 names it receives from a reverse lookup yields the original IP address. If this
12212 is not the case, Exim does not accept the looked up name(s), and
12213 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
12214 IP address (for example, the existence of a PTR record in the DNS) is not
12215 sufficient on its own for the success of a host name lookup. If the reverse
12216 lookup succeeds, but there is a lookup problem such as a timeout when checking
12217 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
12218 &"1"&. See also &$sender_host_name$&.
12220 .cindex authentication "expansion item"
12221 Performing these checks sets up information used by the
12222 &$authresults$& expansion item.
12225 .vitem &$host_lookup_failed$&
12226 .vindex "&$host_lookup_failed$&"
12227 See &$host_lookup_deferred$&.
12229 .vitem &$host_port$&
12230 .vindex "&$host_port$&"
12231 This variable is set to the remote host's TCP port whenever &$host$& is set
12232 for an outbound connection.
12234 .vitem &$initial_cwd$&
12235 .vindex "&$initial_cwd$&
12236 This variable contains the full path name of the initial working
12237 directory of the current Exim process. This may differ from the current
12238 working directory, as Exim changes this to "/" during early startup, and
12239 to &$spool_directory$& later.
12242 .vindex "&$inode$&"
12243 The only time this variable is set is while expanding the &%directory_file%&
12244 option in the &(appendfile)& transport. The variable contains the inode number
12245 of the temporary file which is about to be renamed. It can be used to construct
12246 a unique name for the file.
12248 .vitem &$interface_address$&
12249 .vindex "&$interface_address$&"
12250 This is an obsolete name for &$received_ip_address$&.
12252 .vitem &$interface_port$&
12253 .vindex "&$interface_port$&"
12254 This is an obsolete name for &$received_port$&.
12258 This variable is used during the expansion of &*forall*& and &*forany*&
12259 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
12260 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
12264 .vindex "&$ldap_dn$&"
12265 This variable, which is available only when Exim is compiled with LDAP support,
12266 contains the DN from the last entry in the most recently successful LDAP
12269 .vitem &$load_average$&
12270 .vindex "&$load_average$&"
12271 This variable contains the system load average, multiplied by 1000 so that it
12272 is an integer. For example, if the load average is 0.21, the value of the
12273 variable is 210. The value is recomputed every time the variable is referenced.
12275 .vitem &$local_part$&
12276 .vindex "&$local_part$&"
12277 When an address is being routed, or delivered on its own, this
12278 variable contains the local part. When a number of addresses are being
12279 delivered together (for example, multiple RCPT commands in an SMTP
12280 session), &$local_part$& is not set.
12282 Global address rewriting happens when a message is received, so the value of
12283 &$local_part$& during routing and delivery is the value after rewriting.
12284 &$local_part$& is set during user filtering, but not during system filtering,
12285 because a message may have many recipients and the system filter is called just
12288 .vindex "&$local_part_prefix$&"
12289 .vindex "&$local_part_suffix$&"
12290 .cindex affix variables
12291 If a local part prefix or suffix has been recognized, it is not included in the
12292 value of &$local_part$& during routing and subsequent delivery. The values of
12293 any prefix or suffix are in &$local_part_prefix$& and
12294 &$local_part_suffix$&, respectively.
12296 When a message is being delivered to a file, pipe, or autoreply transport as a
12297 result of aliasing or forwarding, &$local_part$& is set to the local part of
12298 the parent address, not to the filename or command (see &$address_file$& and
12301 When an ACL is running for a RCPT command, &$local_part$& contains the
12302 local part of the recipient address.
12304 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12305 &$local_part$& contains the local part of the address that is being rewritten;
12306 it can be used in the expansion of the replacement address, for example.
12308 In all cases, all quoting is removed from the local part. For example, for both
12311 "abc:xyz"@test.example
12312 abc\:xyz@test.example
12314 the value of &$local_part$& is
12318 If you use &$local_part$& to create another address, you should always wrap it
12319 inside a quoting operator. For example, in a &(redirect)& router you could
12322 data = ${quote_local_part:$local_part}@new.domain.example
12324 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
12325 to process local parts in a case-dependent manner in a router, you can set the
12326 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
12328 .vitem &$local_part_data$&
12329 .vindex "&$local_part_data$&"
12330 When the &%local_parts%& option on a router matches a local part by means of a
12331 lookup, the data read by the lookup is available during the running of the
12332 router as &$local_part_data$&. In addition, if the driver routes the address
12333 to a transport, the value is available in that transport. If the transport is
12334 handling multiple addresses, the value from the first address is used.
12336 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
12337 matches a local part by means of a lookup. The data read by the lookup is
12338 available during the rest of the ACL statement. In all other situations, this
12339 variable expands to nothing.
12341 .vitem &$local_part_prefix$&
12342 .vindex "&$local_part_prefix$&"
12343 .cindex affix variables
12344 When an address is being routed or delivered, and a
12345 specific prefix for the local part was recognized, it is available in this
12346 variable, having been removed from &$local_part$&.
12348 .vitem &$local_part_suffix$&
12349 .vindex "&$local_part_suffix$&"
12350 When an address is being routed or delivered, and a
12351 specific suffix for the local part was recognized, it is available in this
12352 variable, having been removed from &$local_part$&.
12354 .vitem &$local_scan_data$&
12355 .vindex "&$local_scan_data$&"
12356 This variable contains the text returned by the &[local_scan()]& function when
12357 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
12359 .vitem &$local_user_gid$&
12360 .vindex "&$local_user_gid$&"
12361 See &$local_user_uid$&.
12363 .vitem &$local_user_uid$&
12364 .vindex "&$local_user_uid$&"
12365 This variable and &$local_user_gid$& are set to the uid and gid after the
12366 &%check_local_user%& router precondition succeeds. This means that their values
12367 are available for the remaining preconditions (&%senders%&, &%require_files%&,
12368 and &%condition%&), for the &%address_data%& expansion, and for any
12369 router-specific expansions. At all other times, the values in these variables
12370 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
12372 .vitem &$localhost_number$&
12373 .vindex "&$localhost_number$&"
12374 This contains the expanded value of the
12375 &%localhost_number%& option. The expansion happens after the main options have
12378 .vitem &$log_inodes$&
12379 .vindex "&$log_inodes$&"
12380 The number of free inodes in the disk partition where Exim's
12381 log files are being written. The value is recalculated whenever the variable is
12382 referenced. If the relevant file system does not have the concept of inodes,
12383 the value of is -1. See also the &%check_log_inodes%& option.
12385 .vitem &$log_space$&
12386 .vindex "&$log_space$&"
12387 The amount of free space (as a number of kilobytes) in the disk
12388 partition where Exim's log files are being written. The value is recalculated
12389 whenever the variable is referenced. If the operating system does not have the
12390 ability to find the amount of free space (only true for experimental systems),
12391 the space value is -1. See also the &%check_log_space%& option.
12394 .vitem &$lookup_dnssec_authenticated$&
12395 .vindex "&$lookup_dnssec_authenticated$&"
12396 This variable is set after a DNS lookup done by
12397 a dnsdb lookup expansion, dnslookup router or smtp transport.
12398 .cindex "DNS" "DNSSEC"
12399 It will be empty if &(DNSSEC)& was not requested,
12400 &"no"& if the result was not labelled as authenticated data
12401 and &"yes"& if it was.
12402 Results that are labelled as authoritative answer that match
12403 the &%dns_trust_aa%& configuration variable count also
12404 as authenticated data.
12406 .vitem &$mailstore_basename$&
12407 .vindex "&$mailstore_basename$&"
12408 This variable is set only when doing deliveries in &"mailstore"& format in the
12409 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
12410 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
12411 contains the basename of the files that are being written, that is, the name
12412 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
12415 .vitem &$malware_name$&
12416 .vindex "&$malware_name$&"
12417 This variable is available when Exim is compiled with the
12418 content-scanning extension. It is set to the name of the virus that was found
12419 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12421 .vitem &$max_received_linelength$&
12422 .vindex "&$max_received_linelength$&"
12423 .cindex "maximum" "line length"
12424 .cindex "line length" "maximum"
12425 This variable contains the number of bytes in the longest line that was
12426 received as part of the message, not counting the line termination
12428 It is not valid if the &%spool_files_wireformat%& option is used.
12430 .vitem &$message_age$&
12431 .cindex "message" "age of"
12432 .vindex "&$message_age$&"
12433 This variable is set at the start of a delivery attempt to contain the number
12434 of seconds since the message was received. It does not change during a single
12437 .vitem &$message_body$&
12438 .cindex "body of message" "expansion variable"
12439 .cindex "message body" "in expansion"
12440 .cindex "binary zero" "in message body"
12441 .vindex "&$message_body$&"
12442 .oindex "&%message_body_visible%&"
12443 This variable contains the initial portion of a message's body while it is
12444 being delivered, and is intended mainly for use in filter files. The maximum
12445 number of characters of the body that are put into the variable is set by the
12446 &%message_body_visible%& configuration option; the default is 500.
12448 .oindex "&%message_body_newlines%&"
12449 By default, newlines are converted into spaces in &$message_body$&, to make it
12450 easier to search for phrases that might be split over a line break. However,
12451 this can be disabled by setting &%message_body_newlines%& to be true. Binary
12452 zeros are always converted into spaces.
12454 .vitem &$message_body_end$&
12455 .cindex "body of message" "expansion variable"
12456 .cindex "message body" "in expansion"
12457 .vindex "&$message_body_end$&"
12458 This variable contains the final portion of a message's
12459 body while it is being delivered. The format and maximum size are as for
12462 .vitem &$message_body_size$&
12463 .cindex "body of message" "size"
12464 .cindex "message body" "size"
12465 .vindex "&$message_body_size$&"
12466 When a message is being delivered, this variable contains the size of the body
12467 in bytes. The count starts from the character after the blank line that
12468 separates the body from the header. Newlines are included in the count. See
12469 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
12471 If the spool file is wireformat
12472 (see the &%spool_files_wireformat%& main option)
12473 the CRLF line-terminators are included in the count.
12475 .vitem &$message_exim_id$&
12476 .vindex "&$message_exim_id$&"
12477 When a message is being received or delivered, this variable contains the
12478 unique message id that is generated and used by Exim to identify the message.
12479 An id is not created for a message until after its header has been successfully
12480 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
12481 line; it is the local id that Exim assigns to the message, for example:
12482 &`1BXTIK-0001yO-VA`&.
12484 .vitem &$message_headers$&
12485 .vindex &$message_headers$&
12486 This variable contains a concatenation of all the header lines when a message
12487 is being processed, except for lines added by routers or transports. The header
12488 lines are separated by newline characters. Their contents are decoded in the
12489 same way as a header line that is inserted by &%bheader%&.
12491 .vitem &$message_headers_raw$&
12492 .vindex &$message_headers_raw$&
12493 This variable is like &$message_headers$& except that no processing of the
12494 contents of header lines is done.
12496 .vitem &$message_id$&
12497 This is an old name for &$message_exim_id$&. It is now deprecated.
12499 .vitem &$message_linecount$&
12500 .vindex "&$message_linecount$&"
12501 This variable contains the total number of lines in the header and body of the
12502 message. Compare &$body_linecount$&, which is the count for the body only.
12503 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
12504 number of lines received. Before delivery happens (that is, before filters,
12505 routers, and transports run) the count is increased to include the
12506 &'Received:'& header line that Exim standardly adds, and also any other header
12507 lines that are added by ACLs. The blank line that separates the message header
12508 from the body is not counted.
12510 As with the special case of &$message_size$&, during the expansion of the
12511 appendfile transport's maildir_tag option in maildir format, the value of
12512 &$message_linecount$& is the precise size of the number of newlines in the
12513 file that has been written (minus one for the blank line between the
12514 header and the body).
12516 Here is an example of the use of this variable in a DATA ACL:
12518 deny message = Too many lines in message header
12520 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
12522 In the MAIL and RCPT ACLs, the value is zero because at that stage the
12523 message has not yet been received.
12525 This variable is not valid if the &%spool_files_wireformat%& option is used.
12527 .vitem &$message_size$&
12528 .cindex "size" "of message"
12529 .cindex "message" "size"
12530 .vindex "&$message_size$&"
12531 When a message is being processed, this variable contains its size in bytes. In
12532 most cases, the size includes those headers that were received with the
12533 message, but not those (such as &'Envelope-to:'&) that are added to individual
12534 deliveries as they are written. However, there is one special case: during the
12535 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
12536 doing a delivery in maildir format, the value of &$message_size$& is the
12537 precise size of the file that has been written. See also
12538 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
12540 .cindex "RCPT" "value of &$message_size$&"
12541 While running a per message ACL (mail/rcpt/predata), &$message_size$&
12542 contains the size supplied on the MAIL command, or -1 if no size was given. The
12543 value may not, of course, be truthful.
12545 .vitem &$mime_$&&'xxx'&
12546 A number of variables whose names start with &$mime$& are
12547 available when Exim is compiled with the content-scanning extension. For
12548 details, see section &<<SECTscanmimepart>>&.
12550 .vitem "&$n0$& &-- &$n9$&"
12551 These variables are counters that can be incremented by means
12552 of the &%add%& command in filter files.
12554 .vitem &$original_domain$&
12555 .vindex "&$domain$&"
12556 .vindex "&$original_domain$&"
12557 When a top-level address is being processed for delivery, this contains the
12558 same value as &$domain$&. However, if a &"child"& address (for example,
12559 generated by an alias, forward, or filter file) is being processed, this
12560 variable contains the domain of the original address (lower cased). This
12561 differs from &$parent_domain$& only when there is more than one level of
12562 aliasing or forwarding. When more than one address is being delivered in a
12563 single transport run, &$original_domain$& is not set.
12565 If a new address is created by means of a &%deliver%& command in a system
12566 filter, it is set up with an artificial &"parent"& address. This has the local
12567 part &'system-filter'& and the default qualify domain.
12569 .vitem &$original_local_part$&
12570 .vindex "&$local_part$&"
12571 .vindex "&$original_local_part$&"
12572 When a top-level address is being processed for delivery, this contains the
12573 same value as &$local_part$&, unless a prefix or suffix was removed from the
12574 local part, because &$original_local_part$& always contains the full local
12575 part. When a &"child"& address (for example, generated by an alias, forward, or
12576 filter file) is being processed, this variable contains the full local part of
12577 the original address.
12579 If the router that did the redirection processed the local part
12580 case-insensitively, the value in &$original_local_part$& is in lower case.
12581 This variable differs from &$parent_local_part$& only when there is more than
12582 one level of aliasing or forwarding. When more than one address is being
12583 delivered in a single transport run, &$original_local_part$& is not set.
12585 If a new address is created by means of a &%deliver%& command in a system
12586 filter, it is set up with an artificial &"parent"& address. This has the local
12587 part &'system-filter'& and the default qualify domain.
12589 .vitem &$originator_gid$&
12590 .cindex "gid (group id)" "of originating user"
12591 .cindex "sender" "gid"
12592 .vindex "&$caller_gid$&"
12593 .vindex "&$originator_gid$&"
12594 This variable contains the value of &$caller_gid$& that was set when the
12595 message was received. For messages received via the command line, this is the
12596 gid of the sending user. For messages received by SMTP over TCP/IP, this is
12597 normally the gid of the Exim user.
12599 .vitem &$originator_uid$&
12600 .cindex "uid (user id)" "of originating user"
12601 .cindex "sender" "uid"
12602 .vindex "&$caller_uid$&"
12603 .vindex "&$originator_uid$&"
12604 The value of &$caller_uid$& that was set when the message was received. For
12605 messages received via the command line, this is the uid of the sending user.
12606 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
12609 .vitem &$parent_domain$&
12610 .vindex "&$parent_domain$&"
12611 This variable is similar to &$original_domain$& (see
12612 above), except that it refers to the immediately preceding parent address.
12614 .vitem &$parent_local_part$&
12615 .vindex "&$parent_local_part$&"
12616 This variable is similar to &$original_local_part$&
12617 (see above), except that it refers to the immediately preceding parent address.
12620 .cindex "pid (process id)" "of current process"
12622 This variable contains the current process id.
12624 .vitem &$pipe_addresses$&
12625 .cindex "filter" "transport filter"
12626 .cindex "transport" "filter"
12627 .vindex "&$pipe_addresses$&"
12628 This is not an expansion variable, but is mentioned here because the string
12629 &`$pipe_addresses`& is handled specially in the command specification for the
12630 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
12631 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
12632 It cannot be used in general expansion strings, and provokes an &"unknown
12633 variable"& error if encountered.
12635 .vitem &$primary_hostname$&
12636 .vindex "&$primary_hostname$&"
12637 This variable contains the value set by &%primary_hostname%& in the
12638 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
12639 a single-component name, Exim calls &[gethostbyname()]& (or
12640 &[getipnodebyname()]& where available) in an attempt to acquire a fully
12641 qualified host name. See also &$smtp_active_hostname$&.
12644 .vitem &$proxy_external_address$& &&&
12645 &$proxy_external_port$& &&&
12646 &$proxy_local_address$& &&&
12647 &$proxy_local_port$& &&&
12649 These variables are only available when built with Proxy Protocol
12651 For details see chapter &<<SECTproxyInbound>>&.
12653 .vitem &$prdr_requested$&
12654 .cindex "PRDR" "variable for"
12655 This variable is set to &"yes"& if PRDR was requested by the client for the
12656 current message, otherwise &"no"&.
12658 .vitem &$prvscheck_address$&
12659 This variable is used in conjunction with the &%prvscheck%& expansion item,
12660 which is described in sections &<<SECTexpansionitems>>& and
12661 &<<SECTverifyPRVS>>&.
12663 .vitem &$prvscheck_keynum$&
12664 This variable is used in conjunction with the &%prvscheck%& expansion item,
12665 which is described in sections &<<SECTexpansionitems>>& and
12666 &<<SECTverifyPRVS>>&.
12668 .vitem &$prvscheck_result$&
12669 This variable is used in conjunction with the &%prvscheck%& expansion item,
12670 which is described in sections &<<SECTexpansionitems>>& and
12671 &<<SECTverifyPRVS>>&.
12673 .vitem &$qualify_domain$&
12674 .vindex "&$qualify_domain$&"
12675 The value set for the &%qualify_domain%& option in the configuration file.
12677 .vitem &$qualify_recipient$&
12678 .vindex "&$qualify_recipient$&"
12679 The value set for the &%qualify_recipient%& option in the configuration file,
12680 or if not set, the value of &$qualify_domain$&.
12682 .vitem &$queue_name$&
12683 .vindex &$queue_name$&
12684 .cindex "named queues"
12685 .cindex queues named
12686 The name of the spool queue in use; empty for the default queue.
12688 .vitem &$rcpt_count$&
12689 .vindex "&$rcpt_count$&"
12690 When a message is being received by SMTP, this variable contains the number of
12691 RCPT commands received for the current message. If this variable is used in a
12692 RCPT ACL, its value includes the current command.
12694 .vitem &$rcpt_defer_count$&
12695 .vindex "&$rcpt_defer_count$&"
12696 .cindex "4&'xx'& responses" "count of"
12697 When a message is being received by SMTP, this variable contains the number of
12698 RCPT commands in the current message that have previously been rejected with a
12699 temporary (4&'xx'&) response.
12701 .vitem &$rcpt_fail_count$&
12702 .vindex "&$rcpt_fail_count$&"
12703 When a message is being received by SMTP, this variable contains the number of
12704 RCPT commands in the current message that have previously been rejected with a
12705 permanent (5&'xx'&) response.
12707 .vitem &$received_count$&
12708 .vindex "&$received_count$&"
12709 This variable contains the number of &'Received:'& header lines in the message,
12710 including the one added by Exim (so its value is always greater than zero). It
12711 is available in the DATA ACL, the non-SMTP ACL, and while routing and
12714 .vitem &$received_for$&
12715 .vindex "&$received_for$&"
12716 If there is only a single recipient address in an incoming message, this
12717 variable contains that address when the &'Received:'& header line is being
12718 built. The value is copied after recipient rewriting has happened, but before
12719 the &[local_scan()]& function is run.
12721 .vitem &$received_ip_address$&
12722 .vindex "&$received_ip_address$&"
12723 As soon as an Exim server starts processing an incoming TCP/IP connection, this
12724 variable is set to the address of the local IP interface, and &$received_port$&
12725 is set to the local port number. (The remote IP address and port are in
12726 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
12727 the port value is -1 unless it has been set using the &%-oMi%& command line
12730 As well as being useful in ACLs (including the &"connect"& ACL), these variable
12731 could be used, for example, to make the filename for a TLS certificate depend
12732 on which interface and/or port is being used for the incoming connection. The
12733 values of &$received_ip_address$& and &$received_port$& are saved with any
12734 messages that are received, thus making these variables available at delivery
12736 For outbound connections see &$sending_ip_address$&.
12738 .vitem &$received_port$&
12739 .vindex "&$received_port$&"
12740 See &$received_ip_address$&.
12742 .vitem &$received_protocol$&
12743 .vindex "&$received_protocol$&"
12744 When a message is being processed, this variable contains the name of the
12745 protocol by which it was received. Most of the names used by Exim are defined
12746 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
12747 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
12748 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
12749 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
12750 connection and the client was successfully authenticated.
12752 Exim uses the protocol name &"smtps"& for the case when encryption is
12753 automatically set up on connection without the use of STARTTLS (see
12754 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
12755 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
12756 where the client initially uses EHLO, sets up an encrypted connection using
12757 STARTTLS, and then uses HELO afterwards.
12759 The &%-oMr%& option provides a way of specifying a custom protocol name for
12760 messages that are injected locally by trusted callers. This is commonly used to
12761 identify messages that are being re-injected after some kind of scanning.
12763 .vitem &$received_time$&
12764 .vindex "&$received_time$&"
12765 This variable contains the date and time when the current message was received,
12766 as a number of seconds since the start of the Unix epoch.
12768 .vitem &$recipient_data$&
12769 .vindex "&$recipient_data$&"
12770 This variable is set after an indexing lookup success in an ACL &%recipients%&
12771 condition. It contains the data from the lookup, and the value remains set
12772 until the next &%recipients%& test. Thus, you can do things like this:
12774 &`require recipients = cdb*@;/some/file`&
12775 &`deny `&&'some further test involving'& &`$recipient_data`&
12777 &*Warning*&: This variable is set only when a lookup is used as an indexing
12778 method in the address list, using the semicolon syntax as in the example above.
12779 The variable is not set for a lookup that is used as part of the string
12780 expansion that all such lists undergo before being interpreted.
12782 .vitem &$recipient_verify_failure$&
12783 .vindex "&$recipient_verify_failure$&"
12784 In an ACL, when a recipient verification fails, this variable contains
12785 information about the failure. It is set to one of the following words:
12788 &"qualify"&: The address was unqualified (no domain), and the message
12789 was neither local nor came from an exempted host.
12792 &"route"&: Routing failed.
12795 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
12796 or before the MAIL command (that is, on initial connection, HELO, or
12800 &"recipient"&: The RCPT command in a callout was rejected.
12803 &"postmaster"&: The postmaster check in a callout was rejected.
12806 The main use of this variable is expected to be to distinguish between
12807 rejections of MAIL and rejections of RCPT.
12809 .vitem &$recipients$&
12810 .vindex "&$recipients$&"
12811 This variable contains a list of envelope recipients for a message. A comma and
12812 a space separate the addresses in the replacement text. However, the variable
12813 is not generally available, to prevent exposure of Bcc recipients in
12814 unprivileged users' filter files. You can use &$recipients$& only in these
12818 In a system filter file.
12820 In the ACLs associated with the DATA command and with non-SMTP messages, that
12821 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
12822 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
12823 &%acl_not_smtp_mime%&.
12825 From within a &[local_scan()]& function.
12829 .vitem &$recipients_count$&
12830 .vindex "&$recipients_count$&"
12831 When a message is being processed, this variable contains the number of
12832 envelope recipients that came with the message. Duplicates are not excluded
12833 from the count. While a message is being received over SMTP, the number
12834 increases for each accepted recipient. It can be referenced in an ACL.
12837 .vitem &$regex_match_string$&
12838 .vindex "&$regex_match_string$&"
12839 This variable is set to contain the matching regular expression after a
12840 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
12842 .vitem "&$regex1$&, &$regex2$&, etc"
12843 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
12844 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
12845 these variables contain the
12846 captured substrings identified by the regular expression.
12849 .vitem &$reply_address$&
12850 .vindex "&$reply_address$&"
12851 When a message is being processed, this variable contains the contents of the
12852 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
12853 contents of the &'From:'& header line. Apart from the removal of leading
12854 white space, the value is not processed in any way. In particular, no RFC 2047
12855 decoding or character code translation takes place.
12857 .vitem &$return_path$&
12858 .vindex "&$return_path$&"
12859 When a message is being delivered, this variable contains the return path &--
12860 the sender field that will be sent as part of the envelope. It is not enclosed
12861 in <> characters. At the start of routing an address, &$return_path$& has the
12862 same value as &$sender_address$&, but if, for example, an incoming message to a
12863 mailing list has been expanded by a router which specifies a different address
12864 for bounce messages, &$return_path$& subsequently contains the new bounce
12865 address, whereas &$sender_address$& always contains the original sender address
12866 that was received with the message. In other words, &$sender_address$& contains
12867 the incoming envelope sender, and &$return_path$& contains the outgoing
12870 .vitem &$return_size_limit$&
12871 .vindex "&$return_size_limit$&"
12872 This is an obsolete name for &$bounce_return_size_limit$&.
12874 .vitem &$router_name$&
12875 .cindex "router" "name"
12876 .cindex "name" "of router"
12877 .vindex "&$router_name$&"
12878 During the running of a router this variable contains its name.
12881 .cindex "return code" "from &%run%& expansion"
12882 .vindex "&$runrc$&"
12883 This variable contains the return code from a command that is run by the
12884 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
12885 assume the order in which option values are expanded, except for those
12886 preconditions whose order of testing is documented. Therefore, you cannot
12887 reliably expect to set &$runrc$& by the expansion of one option, and use it in
12890 .vitem &$self_hostname$&
12891 .oindex "&%self%&" "value of host name"
12892 .vindex "&$self_hostname$&"
12893 When an address is routed to a supposedly remote host that turns out to be the
12894 local host, what happens is controlled by the &%self%& generic router option.
12895 One of its values causes the address to be passed to another router. When this
12896 happens, &$self_hostname$& is set to the name of the local host that the
12897 original router encountered. In other circumstances its contents are null.
12899 .vitem &$sender_address$&
12900 .vindex "&$sender_address$&"
12901 When a message is being processed, this variable contains the sender's address
12902 that was received in the message's envelope. The case of letters in the address
12903 is retained, in both the local part and the domain. For bounce messages, the
12904 value of this variable is the empty string. See also &$return_path$&.
12906 .vitem &$sender_address_data$&
12907 .vindex "&$address_data$&"
12908 .vindex "&$sender_address_data$&"
12909 If &$address_data$& is set when the routers are called from an ACL to verify a
12910 sender address, the final value is preserved in &$sender_address_data$&, to
12911 distinguish it from data from a recipient address. The value does not persist
12912 after the end of the current ACL statement. If you want to preserve it for
12913 longer, you can save it in an ACL variable.
12915 .vitem &$sender_address_domain$&
12916 .vindex "&$sender_address_domain$&"
12917 The domain portion of &$sender_address$&.
12919 .vitem &$sender_address_local_part$&
12920 .vindex "&$sender_address_local_part$&"
12921 The local part portion of &$sender_address$&.
12923 .vitem &$sender_data$&
12924 .vindex "&$sender_data$&"
12925 This variable is set after a lookup success in an ACL &%senders%& condition or
12926 in a router &%senders%& option. It contains the data from the lookup, and the
12927 value remains set until the next &%senders%& test. Thus, you can do things like
12930 &`require senders = cdb*@;/some/file`&
12931 &`deny `&&'some further test involving'& &`$sender_data`&
12933 &*Warning*&: This variable is set only when a lookup is used as an indexing
12934 method in the address list, using the semicolon syntax as in the example above.
12935 The variable is not set for a lookup that is used as part of the string
12936 expansion that all such lists undergo before being interpreted.
12938 .vitem &$sender_fullhost$&
12939 .vindex "&$sender_fullhost$&"
12940 When a message is received from a remote host, this variable contains the host
12941 name and IP address in a single string. It ends with the IP address in square
12942 brackets, followed by a colon and a port number if the logging of ports is
12943 enabled. The format of the rest of the string depends on whether the host
12944 issued a HELO or EHLO SMTP command, and whether the host name was verified by
12945 looking up its IP address. (Looking up the IP address can be forced by the
12946 &%host_lookup%& option, independent of verification.) A plain host name at the
12947 start of the string is a verified host name; if this is not present,
12948 verification either failed or was not requested. A host name in parentheses is
12949 the argument of a HELO or EHLO command. This is omitted if it is identical to
12950 the verified host name or to the host's IP address in square brackets.
12952 .vitem &$sender_helo_dnssec$&
12953 .vindex "&$sender_helo_dnssec$&"
12954 This boolean variable is true if a successful HELO verification was
12955 .cindex "DNS" "DNSSEC"
12956 done using DNS information the resolver library stated was authenticated data.
12958 .vitem &$sender_helo_name$&
12959 .vindex "&$sender_helo_name$&"
12960 When a message is received from a remote host that has issued a HELO or EHLO
12961 command, the argument of that command is placed in this variable. It is also
12962 set if HELO or EHLO is used when a message is received using SMTP locally via
12963 the &%-bs%& or &%-bS%& options.
12965 .vitem &$sender_host_address$&
12966 .vindex "&$sender_host_address$&"
12967 When a message is received from a remote host using SMTP,
12968 this variable contains that
12969 host's IP address. For locally non-SMTP submitted messages, it is empty.
12971 .vitem &$sender_host_authenticated$&
12972 .vindex "&$sender_host_authenticated$&"
12973 This variable contains the name (not the public name) of the authenticator
12974 driver that successfully authenticated the client from which the message was
12975 received. It is empty if there was no successful authentication. See also
12976 &$authenticated_id$&.
12978 .vitem &$sender_host_dnssec$&
12979 .vindex "&$sender_host_dnssec$&"
12980 If an attempt to populate &$sender_host_name$& has been made
12981 (by reference, &%hosts_lookup%& or
12982 otherwise) then this boolean will have been set true if, and only if, the
12983 resolver library states that both
12984 the reverse and forward DNS were authenticated data. At all
12985 other times, this variable is false.
12987 .cindex "DNS" "DNSSEC"
12988 It is likely that you will need to coerce DNSSEC support on in the resolver
12989 library, by setting:
12994 Exim does not perform DNSSEC validation itself, instead leaving that to a
12995 validating resolver (e.g. unbound, or bind with suitable configuration).
12997 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
12998 mechanism in the list, then this variable will be false.
13000 This requires that your system resolver library support EDNS0 (and that
13001 DNSSEC flags exist in the system headers). If the resolver silently drops
13002 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
13003 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
13006 .vitem &$sender_host_name$&
13007 .vindex "&$sender_host_name$&"
13008 When a message is received from a remote host, this variable contains the
13009 host's name as obtained by looking up its IP address. For messages received by
13010 other means, this variable is empty.
13012 .vindex "&$host_lookup_failed$&"
13013 If the host name has not previously been looked up, a reference to
13014 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
13015 A looked up name is accepted only if it leads back to the original IP address
13016 via a forward lookup. If either the reverse or the forward lookup fails to find
13017 any data, or if the forward lookup does not yield the original IP address,
13018 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
13020 .vindex "&$host_lookup_deferred$&"
13021 However, if either of the lookups cannot be completed (for example, there is a
13022 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
13023 &$host_lookup_failed$& remains set to &"0"&.
13025 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
13026 host name again if there is a subsequent reference to &$sender_host_name$&
13027 in the same Exim process, but it does try again if &$host_lookup_deferred$&
13030 Exim does not automatically look up every calling host's name. If you want
13031 maximum efficiency, you should arrange your configuration so that it avoids
13032 these lookups altogether. The lookup happens only if one or more of the
13033 following are true:
13036 A string containing &$sender_host_name$& is expanded.
13038 The calling host matches the list in &%host_lookup%&. In the default
13039 configuration, this option is set to *, so it must be changed if lookups are
13040 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
13042 Exim needs the host name in order to test an item in a host list. The items
13043 that require this are described in sections &<<SECThoslispatnam>>& and
13044 &<<SECThoslispatnamsk>>&.
13046 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
13047 In this case, the host name is required to compare with the name quoted in any
13048 EHLO or HELO commands that the client issues.
13050 The remote host issues a EHLO or HELO command that quotes one of the
13051 domains in &%helo_lookup_domains%&. The default value of this option is
13052 . ==== As this is a nested list, any displays it contains must be indented
13053 . ==== as otherwise they are too far to the left.
13055 helo_lookup_domains = @ : @[]
13057 which causes a lookup if a remote host (incorrectly) gives the server's name or
13058 IP address in an EHLO or HELO command.
13062 .vitem &$sender_host_port$&
13063 .vindex "&$sender_host_port$&"
13064 When a message is received from a remote host, this variable contains the port
13065 number that was used on the remote host.
13067 .vitem &$sender_ident$&
13068 .vindex "&$sender_ident$&"
13069 When a message is received from a remote host, this variable contains the
13070 identification received in response to an RFC 1413 request. When a message has
13071 been received locally, this variable contains the login name of the user that
13074 .vitem &$sender_rate_$&&'xxx'&
13075 A number of variables whose names begin &$sender_rate_$& are set as part of the
13076 &%ratelimit%& ACL condition. Details are given in section
13077 &<<SECTratelimiting>>&.
13079 .vitem &$sender_rcvhost$&
13080 .cindex "DNS" "reverse lookup"
13081 .cindex "reverse DNS lookup"
13082 .vindex "&$sender_rcvhost$&"
13083 This is provided specifically for use in &'Received:'& headers. It starts with
13084 either the verified host name (as obtained from a reverse DNS lookup) or, if
13085 there is no verified host name, the IP address in square brackets. After that
13086 there may be text in parentheses. When the first item is a verified host name,
13087 the first thing in the parentheses is the IP address in square brackets,
13088 followed by a colon and a port number if port logging is enabled. When the
13089 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
13092 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
13093 was used and its argument was not identical to the real host name or IP
13094 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
13095 all three items are present in the parentheses, a newline and tab are inserted
13096 into the string, to improve the formatting of the &'Received:'& header.
13098 .vitem &$sender_verify_failure$&
13099 .vindex "&$sender_verify_failure$&"
13100 In an ACL, when a sender verification fails, this variable contains information
13101 about the failure. The details are the same as for
13102 &$recipient_verify_failure$&.
13104 .vitem &$sending_ip_address$&
13105 .vindex "&$sending_ip_address$&"
13106 This variable is set whenever an outgoing SMTP connection to another host has
13107 been set up. It contains the IP address of the local interface that is being
13108 used. This is useful if a host that has more than one IP address wants to take
13109 on different personalities depending on which one is being used. For incoming
13110 connections, see &$received_ip_address$&.
13112 .vitem &$sending_port$&
13113 .vindex "&$sending_port$&"
13114 This variable is set whenever an outgoing SMTP connection to another host has
13115 been set up. It contains the local port that is being used. For incoming
13116 connections, see &$received_port$&.
13118 .vitem &$smtp_active_hostname$&
13119 .vindex "&$smtp_active_hostname$&"
13120 During an incoming SMTP session, this variable contains the value of the active
13121 host name, as specified by the &%smtp_active_hostname%& option. The value of
13122 &$smtp_active_hostname$& is saved with any message that is received, so its
13123 value can be consulted during routing and delivery.
13125 .vitem &$smtp_command$&
13126 .vindex "&$smtp_command$&"
13127 During the processing of an incoming SMTP command, this variable contains the
13128 entire command. This makes it possible to distinguish between HELO and EHLO in
13129 the HELO ACL, and also to distinguish between commands such as these:
13134 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
13135 command, the address in &$smtp_command$& is the original address before any
13136 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
13137 the address after SMTP-time rewriting.
13139 .vitem &$smtp_command_argument$&
13140 .cindex "SMTP" "command, argument for"
13141 .vindex "&$smtp_command_argument$&"
13142 While an ACL is running to check an SMTP command, this variable contains the
13143 argument, that is, the text that follows the command name, with leading white
13144 space removed. Following the introduction of &$smtp_command$&, this variable is
13145 somewhat redundant, but is retained for backwards compatibility.
13147 .vitem &$smtp_command_history$&
13148 .cindex SMTP "command history"
13149 .vindex "&$smtp_command_history$&"
13150 A comma-separated list (with no whitespace) of the most-recent SMTP commands
13151 received, in time-order left to right. Only a limited number of commands
13154 .vitem &$smtp_count_at_connection_start$&
13155 .vindex "&$smtp_count_at_connection_start$&"
13156 This variable is set greater than zero only in processes spawned by the Exim
13157 daemon for handling incoming SMTP connections. The name is deliberately long,
13158 in order to emphasize what the contents are. When the daemon accepts a new
13159 connection, it increments this variable. A copy of the variable is passed to
13160 the child process that handles the connection, but its value is fixed, and
13161 never changes. It is only an approximation of how many incoming connections
13162 there actually are, because many other connections may come and go while a
13163 single connection is being processed. When a child process terminates, the
13164 daemon decrements its copy of the variable.
13166 .vitem "&$sn0$& &-- &$sn9$&"
13167 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
13168 that were current at the end of the system filter file. This allows a system
13169 filter file to set values that can be tested in users' filter files. For
13170 example, a system filter could set a value indicating how likely it is that a
13171 message is junk mail.
13173 .vitem &$spam_$&&'xxx'&
13174 A number of variables whose names start with &$spam$& are available when Exim
13175 is compiled with the content-scanning extension. For details, see section
13176 &<<SECTscanspamass>>&.
13178 .vitem &$spf_header_comment$& &&&
13179 &$spf_received$& &&&
13181 &$spf_result_guessed$& &&&
13182 &$spf_smtp_comment$&
13183 These variables are only available if Exim is built with SPF support.
13184 For details see section &<<SECSPF>>&.
13186 .vitem &$spool_directory$&
13187 .vindex "&$spool_directory$&"
13188 The name of Exim's spool directory.
13190 .vitem &$spool_inodes$&
13191 .vindex "&$spool_inodes$&"
13192 The number of free inodes in the disk partition where Exim's spool files are
13193 being written. The value is recalculated whenever the variable is referenced.
13194 If the relevant file system does not have the concept of inodes, the value of
13195 is -1. See also the &%check_spool_inodes%& option.
13197 .vitem &$spool_space$&
13198 .vindex "&$spool_space$&"
13199 The amount of free space (as a number of kilobytes) in the disk partition where
13200 Exim's spool files are being written. The value is recalculated whenever the
13201 variable is referenced. If the operating system does not have the ability to
13202 find the amount of free space (only true for experimental systems), the space
13203 value is -1. For example, to check in an ACL that there is at least 50
13204 megabytes free on the spool, you could write:
13206 condition = ${if > {$spool_space}{50000}}
13208 See also the &%check_spool_space%& option.
13211 .vitem &$thisaddress$&
13212 .vindex "&$thisaddress$&"
13213 This variable is set only during the processing of the &%foranyaddress%&
13214 command in a filter file. Its use is explained in the description of that
13215 command, which can be found in the separate document entitled &'Exim's
13216 interfaces to mail filtering'&.
13218 .vitem &$tls_in_bits$&
13219 .vindex "&$tls_in_bits$&"
13220 Contains an approximation of the TLS cipher's bit-strength
13221 on the inbound connection; the meaning of
13222 this depends upon the TLS implementation used.
13223 If TLS has not been negotiated, the value will be 0.
13224 The value of this is automatically fed into the Cyrus SASL authenticator
13225 when acting as a server, to specify the "external SSF" (a SASL term).
13227 The deprecated &$tls_bits$& variable refers to the inbound side
13228 except when used in the context of an outbound SMTP delivery, when it refers to
13231 .vitem &$tls_out_bits$&
13232 .vindex "&$tls_out_bits$&"
13233 Contains an approximation of the TLS cipher's bit-strength
13234 on an outbound SMTP connection; the meaning of
13235 this depends upon the TLS implementation used.
13236 If TLS has not been negotiated, the value will be 0.
13238 .vitem &$tls_in_ourcert$&
13239 .vindex "&$tls_in_ourcert$&"
13240 .cindex certificate variables
13241 This variable refers to the certificate presented to the peer of an
13242 inbound connection when the message was received.
13243 It is only useful as the argument of a
13244 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13245 or a &%def%& condition.
13247 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
13248 when a list of more than one
13249 file is used for &%tls_certificate%&, this variable is not reliable.
13251 .vitem &$tls_in_peercert$&
13252 .vindex "&$tls_in_peercert$&"
13253 This variable refers to the certificate presented by the peer of an
13254 inbound connection when the message was received.
13255 It is only useful as the argument of a
13256 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13257 or a &%def%& condition.
13258 If certificate verification fails it may refer to a failing chain element
13259 which is not the leaf.
13261 .vitem &$tls_out_ourcert$&
13262 .vindex "&$tls_out_ourcert$&"
13263 This variable refers to the certificate presented to the peer of an
13264 outbound connection. It is only useful as the argument of a
13265 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13266 or a &%def%& condition.
13268 .vitem &$tls_out_peercert$&
13269 .vindex "&$tls_out_peercert$&"
13270 This variable refers to the certificate presented by the peer of an
13271 outbound connection. It is only useful as the argument of a
13272 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13273 or a &%def%& condition.
13274 If certificate verification fails it may refer to a failing chain element
13275 which is not the leaf.
13277 .vitem &$tls_in_certificate_verified$&
13278 .vindex "&$tls_in_certificate_verified$&"
13279 This variable is set to &"1"& if a TLS certificate was verified when the
13280 message was received, and &"0"& otherwise.
13282 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
13283 except when used in the context of an outbound SMTP delivery, when it refers to
13286 .vitem &$tls_out_certificate_verified$&
13287 .vindex "&$tls_out_certificate_verified$&"
13288 This variable is set to &"1"& if a TLS certificate was verified when an
13289 outbound SMTP connection was made,
13290 and &"0"& otherwise.
13292 .vitem &$tls_in_cipher$&
13293 .vindex "&$tls_in_cipher$&"
13294 .vindex "&$tls_cipher$&"
13295 When a message is received from a remote host over an encrypted SMTP
13296 connection, this variable is set to the cipher suite that was negotiated, for
13297 example DES-CBC3-SHA. In other circumstances, in particular, for message
13298 received over unencrypted connections, the variable is empty. Testing
13299 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
13300 non-encrypted connections during ACL processing.
13302 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
13303 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
13304 becomes the same as &$tls_out_cipher$&.
13306 .vitem &$tls_out_cipher$&
13307 .vindex "&$tls_out_cipher$&"
13309 cleared before any outgoing SMTP connection is made,
13310 and then set to the outgoing cipher suite if one is negotiated. See chapter
13311 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
13312 details of the &(smtp)& transport.
13314 .vitem &$tls_out_dane$&
13315 .vindex &$tls_out_dane$&
13316 DANE active status. See section &<<SECDANE>>&.
13318 .vitem &$tls_in_ocsp$&
13319 .vindex "&$tls_in_ocsp$&"
13320 When a message is received from a remote client connection
13321 the result of any OCSP request from the client is encoded in this variable:
13323 0 OCSP proof was not requested (default value)
13324 1 No response to request
13325 2 Response not verified
13326 3 Verification failed
13327 4 Verification succeeded
13330 .vitem &$tls_out_ocsp$&
13331 .vindex "&$tls_out_ocsp$&"
13332 When a message is sent to a remote host connection
13333 the result of any OCSP request made is encoded in this variable.
13334 See &$tls_in_ocsp$& for values.
13336 .vitem &$tls_in_peerdn$&
13337 .vindex "&$tls_in_peerdn$&"
13338 .vindex "&$tls_peerdn$&"
13339 .cindex certificate "extracting fields"
13340 When a message is received from a remote host over an encrypted SMTP
13341 connection, and Exim is configured to request a certificate from the client,
13342 the value of the Distinguished Name of the certificate is made available in the
13343 &$tls_in_peerdn$& during subsequent processing.
13344 If certificate verification fails it may refer to a failing chain element
13345 which is not the leaf.
13347 The deprecated &$tls_peerdn$& variable refers to the inbound side
13348 except when used in the context of an outbound SMTP delivery, when it refers to
13351 .vitem &$tls_out_peerdn$&
13352 .vindex "&$tls_out_peerdn$&"
13353 When a message is being delivered to a remote host over an encrypted SMTP
13354 connection, and Exim is configured to request a certificate from the server,
13355 the value of the Distinguished Name of the certificate is made available in the
13356 &$tls_out_peerdn$& during subsequent processing.
13357 If certificate verification fails it may refer to a failing chain element
13358 which is not the leaf.
13360 .vitem &$tls_in_sni$&
13361 .vindex "&$tls_in_sni$&"
13362 .vindex "&$tls_sni$&"
13363 .cindex "TLS" "Server Name Indication"
13364 When a TLS session is being established, if the client sends the Server
13365 Name Indication extension, the value will be placed in this variable.
13366 If the variable appears in &%tls_certificate%& then this option and
13367 some others, described in &<<SECTtlssni>>&,
13368 will be re-expanded early in the TLS session, to permit
13369 a different certificate to be presented (and optionally a different key to be
13370 used) to the client, based upon the value of the SNI extension.
13372 The deprecated &$tls_sni$& variable refers to the inbound side
13373 except when used in the context of an outbound SMTP delivery, when it refers to
13376 .vitem &$tls_out_sni$&
13377 .vindex "&$tls_out_sni$&"
13378 .cindex "TLS" "Server Name Indication"
13380 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
13383 .vitem &$tls_out_tlsa_usage$&
13384 .vindex &$tls_out_tlsa_usage$&
13385 Bitfield of TLSA record types found. See section &<<SECDANE>>&.
13387 .vitem &$tod_bsdinbox$&
13388 .vindex "&$tod_bsdinbox$&"
13389 The time of day and the date, in the format required for BSD-style mailbox
13390 files, for example: Thu Oct 17 17:14:09 1995.
13392 .vitem &$tod_epoch$&
13393 .vindex "&$tod_epoch$&"
13394 The time and date as a number of seconds since the start of the Unix epoch.
13396 .vitem &$tod_epoch_l$&
13397 .vindex "&$tod_epoch_l$&"
13398 The time and date as a number of microseconds since the start of the Unix epoch.
13400 .vitem &$tod_full$&
13401 .vindex "&$tod_full$&"
13402 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
13403 +0100. The timezone is always given as a numerical offset from UTC, with
13404 positive values used for timezones that are ahead (east) of UTC, and negative
13405 values for those that are behind (west).
13408 .vindex "&$tod_log$&"
13409 The time and date in the format used for writing Exim's log files, for example:
13410 1995-10-12 15:32:29, but without a timezone.
13412 .vitem &$tod_logfile$&
13413 .vindex "&$tod_logfile$&"
13414 This variable contains the date in the format yyyymmdd. This is the format that
13415 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
13418 .vitem &$tod_zone$&
13419 .vindex "&$tod_zone$&"
13420 This variable contains the numerical value of the local timezone, for example:
13423 .vitem &$tod_zulu$&
13424 .vindex "&$tod_zulu$&"
13425 This variable contains the UTC date and time in &"Zulu"& format, as specified
13426 by ISO 8601, for example: 20030221154023Z.
13428 .vitem &$transport_name$&
13429 .cindex "transport" "name"
13430 .cindex "name" "of transport"
13431 .vindex "&$transport_name$&"
13432 During the running of a transport, this variable contains its name.
13435 .vindex "&$value$&"
13436 This variable contains the result of an expansion lookup, extraction operation,
13437 or external command, as described above. It is also used during a
13438 &*reduce*& expansion.
13440 .vitem &$verify_mode$&
13441 .vindex "&$verify_mode$&"
13442 While a router or transport is being run in verify mode or for cutthrough delivery,
13443 contains "S" for sender-verification or "R" for recipient-verification.
13446 .vitem &$version_number$&
13447 .vindex "&$version_number$&"
13448 The version number of Exim.
13450 .vitem &$warn_message_delay$&
13451 .vindex "&$warn_message_delay$&"
13452 This variable is set only during the creation of a message warning about a
13453 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13455 .vitem &$warn_message_recipients$&
13456 .vindex "&$warn_message_recipients$&"
13457 This variable is set only during the creation of a message warning about a
13458 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13464 . ////////////////////////////////////////////////////////////////////////////
13465 . ////////////////////////////////////////////////////////////////////////////
13467 .chapter "Embedded Perl" "CHAPperl"
13468 .scindex IIDperl "Perl" "calling from Exim"
13469 Exim can be built to include an embedded Perl interpreter. When this is done,
13470 Perl subroutines can be called as part of the string expansion process. To make
13471 use of the Perl support, you need version 5.004 or later of Perl installed on
13472 your system. To include the embedded interpreter in the Exim binary, include
13477 in your &_Local/Makefile_& and then build Exim in the normal way.
13480 .section "Setting up so Perl can be used" "SECID85"
13481 .oindex "&%perl_startup%&"
13482 Access to Perl subroutines is via a global configuration option called
13483 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
13484 no &%perl_startup%& option in the Exim configuration file then no Perl
13485 interpreter is started and there is almost no overhead for Exim (since none of
13486 the Perl library will be paged in unless used). If there is a &%perl_startup%&
13487 option then the associated value is taken to be Perl code which is executed in
13488 a newly created Perl interpreter.
13490 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
13491 need backslashes before any characters to escape special meanings. The option
13492 should usually be something like
13494 perl_startup = do '/etc/exim.pl'
13496 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
13497 use from Exim. Exim can be configured either to start up a Perl interpreter as
13498 soon as it is entered, or to wait until the first time it is needed. Starting
13499 the interpreter at the beginning ensures that it is done while Exim still has
13500 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
13501 fact used in a particular run. Also, note that this does not mean that Exim is
13502 necessarily running as root when Perl is called at a later time. By default,
13503 the interpreter is started only when it is needed, but this can be changed in
13507 .oindex "&%perl_at_start%&"
13508 Setting &%perl_at_start%& (a boolean option) in the configuration requests
13509 a startup when Exim is entered.
13511 The command line option &%-ps%& also requests a startup when Exim is entered,
13512 overriding the setting of &%perl_at_start%&.
13515 There is also a command line option &%-pd%& (for delay) which suppresses the
13516 initial startup, even if &%perl_at_start%& is set.
13519 .oindex "&%perl_taintmode%&"
13520 .cindex "Perl" "taintmode"
13521 To provide more security executing Perl code via the embedded Perl
13522 interpreter, the &%perl_taintmode%& option can be set. This enables the
13523 taint mode of the Perl interpreter. You are encouraged to set this
13524 option to a true value. To avoid breaking existing installations, it
13528 .section "Calling Perl subroutines" "SECID86"
13529 When the configuration file includes a &%perl_startup%& option you can make use
13530 of the string expansion item to call the Perl subroutines that are defined
13531 by the &%perl_startup%& code. The operator is used in any of the following
13535 ${perl{foo}{argument}}
13536 ${perl{foo}{argument1}{argument2} ... }
13538 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
13539 arguments may be passed. Passing more than this results in an expansion failure
13540 with an error message of the form
13542 Too many arguments passed to Perl subroutine "foo" (max is 8)
13544 The return value of the Perl subroutine is evaluated in a scalar context before
13545 it is passed back to Exim to be inserted into the expanded string. If the
13546 return value is &'undef'&, the expansion is forced to fail in the same way as
13547 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
13548 by obeying Perl's &%die%& function, the expansion fails with the error message
13549 that was passed to &%die%&.
13552 .section "Calling Exim functions from Perl" "SECID87"
13553 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
13554 is available to call back into Exim's string expansion function. For example,
13557 my $lp = Exim::expand_string('$local_part');
13559 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
13560 Note those are single quotes and not double quotes to protect against
13561 &$local_part$& being interpolated as a Perl variable.
13563 If the string expansion is forced to fail by a &"fail"& item, the result of
13564 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
13565 expansion string, the Perl call from the original expansion string fails with
13566 an appropriate error message, in the same way as if &%die%& were used.
13568 .cindex "debugging" "from embedded Perl"
13569 .cindex "log" "writing from embedded Perl"
13570 Two other Exim functions are available for use from within Perl code.
13571 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
13572 debugging is enabled. If you want a newline at the end, you must supply it.
13573 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
13574 timestamp. In this case, you should not supply a terminating newline.
13577 .section "Use of standard output and error by Perl" "SECID88"
13578 .cindex "Perl" "standard output and error"
13579 You should not write to the standard error or output streams from within your
13580 Perl code, as it is not defined how these are set up. In versions of Exim
13581 before 4.50, it is possible for the standard output or error to refer to the
13582 SMTP connection during message reception via the daemon. Writing to this stream
13583 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
13584 error streams are connected to &_/dev/null_& in the daemon. The chaos is
13585 avoided, but the output is lost.
13587 .cindex "Perl" "use of &%warn%&"
13588 The Perl &%warn%& statement writes to the standard error stream by default.
13589 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
13590 you have no control. When Exim starts up the Perl interpreter, it arranges for
13591 output from the &%warn%& statement to be written to the Exim main log. You can
13592 change this by including appropriate Perl magic somewhere in your Perl code.
13593 For example, to discard &%warn%& output completely, you need this:
13595 $SIG{__WARN__} = sub { };
13597 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
13598 example, the code for the subroutine is empty, so it does nothing, but you can
13599 include any Perl code that you like. The text of the &%warn%& message is passed
13600 as the first subroutine argument.
13604 . ////////////////////////////////////////////////////////////////////////////
13605 . ////////////////////////////////////////////////////////////////////////////
13607 .chapter "Starting the daemon and the use of network interfaces" &&&
13608 "CHAPinterfaces" &&&
13609 "Starting the daemon"
13610 .cindex "daemon" "starting"
13611 .cindex "interface" "listening"
13612 .cindex "network interface"
13613 .cindex "interface" "network"
13614 .cindex "IP address" "for listening"
13615 .cindex "daemon" "listening IP addresses"
13616 .cindex "TCP/IP" "setting listening interfaces"
13617 .cindex "TCP/IP" "setting listening ports"
13618 A host that is connected to a TCP/IP network may have one or more physical
13619 hardware network interfaces. Each of these interfaces may be configured as one
13620 or more &"logical"& interfaces, which are the entities that a program actually
13621 works with. Each of these logical interfaces is associated with an IP address.
13622 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
13623 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
13624 knowledge about the host's interfaces for use in three different circumstances:
13627 When a listening daemon is started, Exim needs to know which interfaces
13628 and ports to listen on.
13630 When Exim is routing an address, it needs to know which IP addresses
13631 are associated with local interfaces. This is required for the correct
13632 processing of MX lists by removing the local host and others with the
13633 same or higher priority values. Also, Exim needs to detect cases
13634 when an address is routed to an IP address that in fact belongs to the
13635 local host. Unless the &%self%& router option or the &%allow_localhost%&
13636 option of the smtp transport is set (as appropriate), this is treated
13637 as an error situation.
13639 When Exim connects to a remote host, it may need to know which interface to use
13640 for the outgoing connection.
13644 Exim's default behaviour is likely to be appropriate in the vast majority
13645 of cases. If your host has only one interface, and you want all its IP
13646 addresses to be treated in the same way, and you are using only the
13647 standard SMTP port, you should not need to take any special action. The
13648 rest of this chapter does not apply to you.
13650 In a more complicated situation you may want to listen only on certain
13651 interfaces, or on different ports, and for this reason there are a number of
13652 options that can be used to influence Exim's behaviour. The rest of this
13653 chapter describes how they operate.
13655 When a message is received over TCP/IP, the interface and port that were
13656 actually used are set in &$received_ip_address$& and &$received_port$&.
13660 .section "Starting a listening daemon" "SECID89"
13661 When a listening daemon is started (by means of the &%-bd%& command line
13662 option), the interfaces and ports on which it listens are controlled by the
13666 &%daemon_smtp_ports%& contains a list of default ports
13668 (For backward compatibility, this option can also be specified in the singular.)
13670 &%local_interfaces%& contains list of interface IP addresses on which to
13671 listen. Each item may optionally also specify a port.
13674 The default list separator in both cases is a colon, but this can be changed as
13675 described in section &<<SECTlistsepchange>>&. When IPv6 addresses are involved,
13676 it is usually best to change the separator to avoid having to double all the
13677 colons. For example:
13679 local_interfaces = <; 127.0.0.1 ; \
13682 3ffe:ffff:836f::fe86:a061
13684 There are two different formats for specifying a port along with an IP address
13685 in &%local_interfaces%&:
13688 The port is added onto the address with a dot separator. For example, to listen
13689 on port 1234 on two different IP addresses:
13691 local_interfaces = <; 192.168.23.65.1234 ; \
13692 3ffe:ffff:836f::fe86:a061.1234
13695 The IP address is enclosed in square brackets, and the port is added
13696 with a colon separator, for example:
13698 local_interfaces = <; [192.168.23.65]:1234 ; \
13699 [3ffe:ffff:836f::fe86:a061]:1234
13703 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
13704 default setting contains just one port:
13706 daemon_smtp_ports = smtp
13708 If more than one port is listed, each interface that does not have its own port
13709 specified listens on all of them. Ports that are listed in
13710 &%daemon_smtp_ports%& can be identified either by name (defined in
13711 &_/etc/services_&) or by number. However, when ports are given with individual
13712 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
13716 .section "Special IP listening addresses" "SECID90"
13717 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
13718 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
13719 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
13720 instead of setting up separate listening sockets for each interface. The
13721 default value of &%local_interfaces%& is
13723 local_interfaces = 0.0.0.0
13725 when Exim is built without IPv6 support; otherwise it is:
13727 local_interfaces = <; ::0 ; 0.0.0.0
13729 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
13733 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
13734 The &%-oX%& command line option can be used to override the values of
13735 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
13736 instance. Another way of doing this would be to use macros and the &%-D%&
13737 option. However, &%-oX%& can be used by any admin user, whereas modification of
13738 the runtime configuration by &%-D%& is allowed only when the caller is root or
13741 The value of &%-oX%& is a list of items. The default colon separator can be
13742 changed in the usual way (&<<SECTlistsepchange>>&) if required.
13743 If there are any items that do not
13744 contain dots or colons (that is, are not IP addresses), the value of
13745 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
13746 items that do contain dots or colons, the value of &%local_interfaces%& is
13747 replaced by those items. Thus, for example,
13751 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
13754 -oX 192.168.34.5.1125
13756 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
13757 (However, since &%local_interfaces%& now contains no items without ports, the
13758 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
13762 .section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
13763 .cindex "submissions protocol"
13764 .cindex "ssmtp protocol"
13765 .cindex "smtps protocol"
13766 .cindex "SMTP" "ssmtp protocol"
13767 .cindex "SMTP" "smtps protocol"
13768 Exim supports the use of TLS-on-connect, used by mail clients in the
13769 &"submissions"& protocol, historically also known as SMTPS or SSMTP.
13770 For some years, IETF Standards Track documents only blessed the
13771 STARTTLS-based Submission service (port 587) while common practice was to support
13772 the same feature set on port 465, but using TLS-on-connect.
13773 If your installation needs to provide service to mail clients
13774 (Mail User Agents, MUAs) then you should provide service on both the 587 and
13777 If the &%tls_on_connect_ports%& option is set to a list of port numbers or
13778 service names, connections to those ports must first establish TLS, before
13779 proceeding to the application layer use of the SMTP protocol.
13781 The common use of this option is expected to be
13783 tls_on_connect_ports = 465
13786 There is also a command line option &%-tls-on-connect%&, which forces all ports
13787 to behave in this way when a daemon is started.
13789 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
13790 daemon to listen on those ports. You must still specify them in
13791 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
13792 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
13793 connections via the daemon.)
13798 .section "IPv6 address scopes" "SECID92"
13799 .cindex "IPv6" "address scopes"
13800 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
13801 can, in principle, have the same link-local IPv6 address on different
13802 interfaces. Thus, additional information is needed, over and above the IP
13803 address, to distinguish individual interfaces. A convention of using a
13804 percent sign followed by something (often the interface name) has been
13805 adopted in some cases, leading to addresses like this:
13807 fe80::202:b3ff:fe03:45c1%eth0
13809 To accommodate this usage, a percent sign followed by an arbitrary string is
13810 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
13811 to convert a textual IPv6 address for actual use. This function recognizes the
13812 percent convention in operating systems that support it, and it processes the
13813 address appropriately. Unfortunately, some older libraries have problems with
13814 &[getaddrinfo()]&. If
13816 IPV6_USE_INET_PTON=yes
13818 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
13819 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
13820 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
13821 function.) Of course, this means that the additional functionality of
13822 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
13824 .section "Disabling IPv6" "SECID93"
13825 .cindex "IPv6" "disabling"
13826 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
13827 run on a host whose kernel does not support IPv6. The binary will fall back to
13828 using IPv4, but it may waste resources looking up AAAA records, and trying to
13829 connect to IPv6 addresses, causing delays to mail delivery. If you set the
13830 .oindex "&%disable_ipv6%&"
13831 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
13832 activities take place. AAAA records are never looked up, and any IPv6 addresses
13833 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
13834 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13835 to handle IPv6 literal addresses.
13837 On the other hand, when IPv6 is in use, there may be times when you want to
13838 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
13839 option to globally suppress the lookup of AAAA records for specified domains,
13840 and you can use the &%ignore_target_hosts%& generic router option to ignore
13841 IPv6 addresses in an individual router.
13845 .section "Examples of starting a listening daemon" "SECID94"
13846 The default case in an IPv6 environment is
13848 daemon_smtp_ports = smtp
13849 local_interfaces = <; ::0 ; 0.0.0.0
13851 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
13852 Either one or two sockets may be used, depending on the characteristics of
13853 the TCP/IP stack. (This is complicated and messy; for more information,
13854 read the comments in the &_daemon.c_& source file.)
13856 To specify listening on ports 25 and 26 on all interfaces:
13858 daemon_smtp_ports = 25 : 26
13860 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
13862 local_interfaces = <; ::0.25 ; ::0.26 \
13863 0.0.0.0.25 ; 0.0.0.0.26
13865 To listen on the default port on all IPv4 interfaces, and on port 26 on the
13866 IPv4 loopback address only:
13868 local_interfaces = 0.0.0.0 : 127.0.0.1.26
13870 To specify listening on the default port on specific interfaces only:
13872 local_interfaces = 10.0.0.67 : 192.168.34.67
13874 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
13878 .section "Recognizing the local host" "SECTreclocipadd"
13879 The &%local_interfaces%& option is also used when Exim needs to determine
13880 whether or not an IP address refers to the local host. That is, the IP
13881 addresses of all the interfaces on which a daemon is listening are always
13884 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
13885 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
13886 available interfaces from the operating system, and extracts the relevant
13887 (that is, IPv4 or IPv6) addresses to use for checking.
13889 Some systems set up large numbers of virtual interfaces in order to provide
13890 many virtual web servers. In this situation, you may want to listen for
13891 email on only a few of the available interfaces, but nevertheless treat all
13892 interfaces as local when routing. You can do this by setting
13893 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
13894 &"all"& wildcard values. These addresses are recognized as local, but are not
13895 used for listening. Consider this example:
13897 local_interfaces = <; 127.0.0.1 ; ::1 ; \
13899 3ffe:2101:12:1:a00:20ff:fe86:a061
13901 extra_local_interfaces = <; ::0 ; 0.0.0.0
13903 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
13904 address, but all available interface addresses are treated as local when
13907 In some environments the local host name may be in an MX list, but with an IP
13908 address that is not assigned to any local interface. In other cases it may be
13909 desirable to treat other host names as if they referred to the local host. Both
13910 these cases can be handled by setting the &%hosts_treat_as_local%& option.
13911 This contains host names rather than IP addresses. When a host is referenced
13912 during routing, either via an MX record or directly, it is treated as the local
13913 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
13914 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
13918 .section "Delivering to a remote host" "SECID95"
13919 Delivery to a remote host is handled by the smtp transport. By default, it
13920 allows the system's TCP/IP functions to choose which interface to use (if
13921 there is more than one) when connecting to a remote host. However, the
13922 &%interface%& option can be set to specify which interface is used. See the
13923 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
13929 . ////////////////////////////////////////////////////////////////////////////
13930 . ////////////////////////////////////////////////////////////////////////////
13932 .chapter "Main configuration" "CHAPmainconfig"
13933 .scindex IIDconfima "configuration file" "main section"
13934 .scindex IIDmaiconf "main configuration"
13935 The first part of the runtime configuration file contains three types of item:
13938 Macro definitions: These lines start with an upper case letter. See section
13939 &<<SECTmacrodefs>>& for details of macro processing.
13941 Named list definitions: These lines start with one of the words &"domainlist"&,
13942 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
13943 section &<<SECTnamedlists>>&.
13945 Main configuration settings: Each setting occupies one line of the file
13946 (with possible continuations). If any setting is preceded by the word
13947 &"hide"&, the &%-bP%& command line option displays its value to admin users
13948 only. See section &<<SECTcos>>& for a description of the syntax of these option
13952 This chapter specifies all the main configuration options, along with their
13953 types and default values. For ease of finding a particular option, they appear
13954 in alphabetical order in section &<<SECTalomo>>& below. However, because there
13955 are now so many options, they are first listed briefly in functional groups, as
13956 an aid to finding the name of the option you are looking for. Some options are
13957 listed in more than one group.
13959 .section "Miscellaneous" "SECID96"
13961 .row &%bi_command%& "to run for &%-bi%& command line option"
13962 .row &%debug_store%& "do extra internal checks"
13963 .row &%disable_ipv6%& "do no IPv6 processing"
13964 .row &%keep_malformed%& "for broken files &-- should not happen"
13965 .row &%localhost_number%& "for unique message ids in clusters"
13966 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
13967 .row &%message_body_visible%& "how much to show in &$message_body$&"
13968 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
13969 .row &%print_topbitchars%& "top-bit characters are printing"
13970 .row &%spool_wireformat%& "use wire-format spool data files when possible"
13971 .row &%timezone%& "force time zone"
13975 .section "Exim parameters" "SECID97"
13977 .row &%exim_group%& "override compiled-in value"
13978 .row &%exim_path%& "override compiled-in value"
13979 .row &%exim_user%& "override compiled-in value"
13980 .row &%primary_hostname%& "default from &[uname()]&"
13981 .row &%split_spool_directory%& "use multiple directories"
13982 .row &%spool_directory%& "override compiled-in value"
13987 .section "Privilege controls" "SECID98"
13989 .row &%admin_groups%& "groups that are Exim admin users"
13990 .row &%commandline_checks_require_admin%& "require admin for various checks"
13991 .row &%deliver_drop_privilege%& "drop root for delivery processes"
13992 .row &%local_from_check%& "insert &'Sender:'& if necessary"
13993 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
13994 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
13995 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
13996 .row &%never_users%& "do not run deliveries as these"
13997 .row &%prod_requires_admin%& "forced delivery requires admin user"
13998 .row &%queue_list_requires_admin%& "queue listing requires admin user"
13999 .row &%trusted_groups%& "groups that are trusted"
14000 .row &%trusted_users%& "users that are trusted"
14005 .section "Logging" "SECID99"
14007 .row &%event_action%& "custom logging"
14008 .row &%hosts_connection_nolog%& "exemption from connect logging"
14009 .row &%log_file_path%& "override compiled-in value"
14010 .row &%log_selector%& "set/unset optional logging"
14011 .row &%log_timezone%& "add timezone to log lines"
14012 .row &%message_logs%& "create per-message logs"
14013 .row &%preserve_message_logs%& "after message completion"
14014 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
14015 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
14016 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
14017 .row &%syslog_facility%& "set syslog &""facility""& field"
14018 .row &%syslog_pid%& "pid in syslog lines"
14019 .row &%syslog_processname%& "set syslog &""ident""& field"
14020 .row &%syslog_timestamp%& "timestamp syslog lines"
14021 .row &%write_rejectlog%& "control use of message log"
14026 .section "Frozen messages" "SECID100"
14028 .row &%auto_thaw%& "sets time for retrying frozen messages"
14029 .row &%freeze_tell%& "send message when freezing"
14030 .row &%move_frozen_messages%& "to another directory"
14031 .row &%timeout_frozen_after%& "keep frozen messages only so long"
14036 .section "Data lookups" "SECID101"
14038 .row &%ibase_servers%& "InterBase servers"
14039 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
14040 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
14041 .row &%ldap_cert_file%& "client cert file for LDAP"
14042 .row &%ldap_cert_key%& "client key file for LDAP"
14043 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
14044 .row &%ldap_default_servers%& "used if no server in query"
14045 .row &%ldap_require_cert%& "action to take without LDAP server cert"
14046 .row &%ldap_start_tls%& "require TLS within LDAP"
14047 .row &%ldap_version%& "set protocol version"
14048 .row &%lookup_open_max%& "lookup files held open"
14049 .row &%mysql_servers%& "default MySQL servers"
14050 .row &%oracle_servers%& "Oracle servers"
14051 .row &%pgsql_servers%& "default PostgreSQL servers"
14052 .row &%sqlite_lock_timeout%& "as it says"
14057 .section "Message ids" "SECID102"
14059 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
14060 .row &%message_id_header_text%& "ditto"
14065 .section "Embedded Perl Startup" "SECID103"
14067 .row &%perl_at_start%& "always start the interpreter"
14068 .row &%perl_startup%& "code to obey when starting Perl"
14069 .row &%perl_taintmode%& "enable taint mode in Perl"
14074 .section "Daemon" "SECID104"
14076 .row &%daemon_smtp_ports%& "default ports"
14077 .row &%daemon_startup_retries%& "number of times to retry"
14078 .row &%daemon_startup_sleep%& "time to sleep between tries"
14079 .row &%extra_local_interfaces%& "not necessarily listened on"
14080 .row &%local_interfaces%& "on which to listen, with optional ports"
14081 .row &%pid_file_path%& "override compiled-in value"
14082 .row &%queue_run_max%& "maximum simultaneous queue runners"
14087 .section "Resource control" "SECID105"
14089 .row &%check_log_inodes%& "before accepting a message"
14090 .row &%check_log_space%& "before accepting a message"
14091 .row &%check_spool_inodes%& "before accepting a message"
14092 .row &%check_spool_space%& "before accepting a message"
14093 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
14094 .row &%queue_only_load%& "queue incoming if load high"
14095 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14096 .row &%queue_run_max%& "maximum simultaneous queue runners"
14097 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14098 .row &%smtp_accept_max%& "simultaneous incoming connections"
14099 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14100 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14101 .row &%smtp_accept_max_per_connection%& "messages per connection"
14102 .row &%smtp_accept_max_per_host%& "connections from one host"
14103 .row &%smtp_accept_queue%& "queue mail if more connections"
14104 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14106 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14107 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14108 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14109 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
14110 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14115 .section "Policy controls" "SECID106"
14117 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
14118 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
14119 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
14120 .row &%acl_smtp_auth%& "ACL for AUTH"
14121 .row &%acl_smtp_connect%& "ACL for connection"
14122 .row &%acl_smtp_data%& "ACL for DATA"
14123 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
14124 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
14125 .row &%acl_smtp_etrn%& "ACL for ETRN"
14126 .row &%acl_smtp_expn%& "ACL for EXPN"
14127 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
14128 .row &%acl_smtp_mail%& "ACL for MAIL"
14129 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
14130 .row &%acl_smtp_mime%& "ACL for MIME parts"
14131 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
14132 .row &%acl_smtp_predata%& "ACL for start of data"
14133 .row &%acl_smtp_quit%& "ACL for QUIT"
14134 .row &%acl_smtp_rcpt%& "ACL for RCPT"
14135 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
14136 .row &%acl_smtp_vrfy%& "ACL for VRFY"
14137 .row &%av_scanner%& "specify virus scanner"
14138 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14140 .row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
14141 .row &%dns_csa_search_limit%& "control CSA parent search depth"
14142 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
14143 .row &%header_maxsize%& "total size of message header"
14144 .row &%header_line_maxsize%& "individual header line limit"
14145 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
14146 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
14147 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
14148 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
14149 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
14150 .row &%host_lookup%& "host name looked up for these hosts"
14151 .row &%host_lookup_order%& "order of DNS and local name lookups"
14152 .row &%hosts_proxy%& "use proxy protocol for these hosts"
14153 .row &%host_reject_connection%& "reject connection from these hosts"
14154 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
14155 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
14156 .row &%message_size_limit%& "for all messages"
14157 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14158 .row &%spamd_address%& "set interface to SpamAssassin"
14159 .row &%strict_acl_vars%& "object to unset ACL variables"
14164 .section "Callout cache" "SECID107"
14166 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
14168 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
14170 .row &%callout_negative_expire%& "timeout for negative address cache item"
14171 .row &%callout_positive_expire%& "timeout for positive address cache item"
14172 .row &%callout_random_local_part%& "string to use for &""random""& testing"
14177 .section "TLS" "SECID108"
14179 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
14180 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
14181 .row &%openssl_options%& "adjust OpenSSL compatibility options"
14182 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14183 .row &%tls_certificate%& "location of server certificate"
14184 .row &%tls_crl%& "certificate revocation list"
14185 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
14186 .row &%tls_dhparam%& "DH parameters for server"
14187 .row &%tls_eccurve%& "EC curve selection for server"
14188 .row &%tls_ocsp_file%& "location of server certificate status proof"
14189 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
14190 .row &%tls_pre_flight_checks%& "control TLS checks during process startup"
14191 .row &%tls_privatekey%& "location of server private key"
14192 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
14193 .row &%tls_require_ciphers%& "specify acceptable ciphers"
14194 .row &%tls_try_verify_hosts%& "try to verify client certificate"
14195 .row &%tls_verify_certificates%& "expected client certificates"
14196 .row &%tls_verify_hosts%& "insist on client certificate verify"
14201 .section "Local user handling" "SECID109"
14203 .row &%finduser_retries%& "useful in NIS environments"
14204 .row &%gecos_name%& "used when creating &'Sender:'&"
14205 .row &%gecos_pattern%& "ditto"
14206 .row &%max_username_length%& "for systems that truncate"
14207 .row &%unknown_login%& "used when no login name found"
14208 .row &%unknown_username%& "ditto"
14209 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
14210 .row &%uucp_from_sender%& "ditto"
14215 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
14217 .row &%header_maxsize%& "total size of message header"
14218 .row &%header_line_maxsize%& "individual header line limit"
14219 .row &%message_size_limit%& "applies to all messages"
14220 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14221 .row &%received_header_text%& "expanded to make &'Received:'&"
14222 .row &%received_headers_max%& "for mail loop detection"
14223 .row &%recipients_max%& "limit per message"
14224 .row &%recipients_max_reject%& "permanently reject excess recipients"
14230 .section "Non-SMTP incoming messages" "SECID111"
14232 .row &%receive_timeout%& "for non-SMTP messages"
14239 .section "Incoming SMTP messages" "SECID112"
14240 See also the &'Policy controls'& section above.
14243 .row &%dkim_verify_signers%& "DKIM domain for which DKIM ACL is run"
14244 .row &%host_lookup%& "host name looked up for these hosts"
14245 .row &%host_lookup_order%& "order of DNS and local name lookups"
14246 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
14247 .row &%rfc1413_hosts%& "make ident calls to these hosts"
14248 .row &%rfc1413_query_timeout%& "zero disables ident calls"
14249 .row &%sender_unqualified_hosts%& "may send unqualified senders"
14250 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
14251 .row &%smtp_accept_max%& "simultaneous incoming connections"
14252 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14253 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14254 .row &%smtp_accept_max_per_connection%& "messages per connection"
14255 .row &%smtp_accept_max_per_host%& "connections from one host"
14256 .row &%smtp_accept_queue%& "queue mail if more connections"
14257 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14259 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14260 .row &%smtp_active_hostname%& "host name to use in messages"
14261 .row &%smtp_banner%& "text for welcome banner"
14262 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14263 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14264 .row &%smtp_enforce_sync%& "of SMTP command/responses"
14265 .row &%smtp_etrn_command%& "what to run for ETRN"
14266 .row &%smtp_etrn_serialize%& "only one at once"
14267 .row &%smtp_load_reserve%& "only reserve hosts if this load"
14268 .row &%smtp_max_unknown_commands%& "before dropping connection"
14269 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
14270 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
14271 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
14272 .row &%smtp_receive_timeout%& "per command or data line"
14273 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14274 .row &%smtp_return_error_details%& "give detail on rejections"
14279 .section "SMTP extensions" "SECID113"
14281 .row &%accept_8bitmime%& "advertise 8BITMIME"
14282 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
14283 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
14284 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
14285 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
14286 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
14287 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
14288 .row &%prdr_enable%& "advertise PRDR to all hosts"
14289 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
14290 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14295 .section "Processing messages" "SECID114"
14297 .row &%allow_domain_literals%& "recognize domain literal syntax"
14298 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
14299 .row &%allow_utf8_domains%& "in addresses"
14300 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14302 .row &%delivery_date_remove%& "from incoming messages"
14303 .row &%envelope_to_remove%& "from incoming messages"
14304 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
14305 .row &%headers_charset%& "default for translations"
14306 .row &%qualify_domain%& "default for senders"
14307 .row &%qualify_recipient%& "default for recipients"
14308 .row &%return_path_remove%& "from incoming messages"
14309 .row &%strip_excess_angle_brackets%& "in addresses"
14310 .row &%strip_trailing_dot%& "at end of addresses"
14311 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
14316 .section "System filter" "SECID115"
14318 .row &%system_filter%& "locate system filter"
14319 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
14321 .row &%system_filter_file_transport%& "transport for delivery to a file"
14322 .row &%system_filter_group%& "group for filter running"
14323 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
14324 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
14325 .row &%system_filter_user%& "user for filter running"
14330 .section "Routing and delivery" "SECID116"
14332 .row &%disable_ipv6%& "do no IPv6 processing"
14333 .row &%dns_again_means_nonexist%& "for broken domains"
14334 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
14335 .row &%dns_dnssec_ok%& "parameter for resolver"
14336 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
14337 .row &%dns_retrans%& "parameter for resolver"
14338 .row &%dns_retry%& "parameter for resolver"
14339 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
14340 .row &%dns_use_edns0%& "parameter for resolver"
14341 .row &%hold_domains%& "hold delivery for these domains"
14342 .row &%local_interfaces%& "for routing checks"
14343 .row &%queue_domains%& "no immediate delivery for these"
14344 .row &%queue_only%& "no immediate delivery at all"
14345 .row &%queue_only_file%& "no immediate delivery if file exists"
14346 .row &%queue_only_load%& "no immediate delivery if load is high"
14347 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14348 .row &%queue_only_override%& "allow command line to override"
14349 .row &%queue_run_in_order%& "order of arrival"
14350 .row &%queue_run_max%& "of simultaneous queue runners"
14351 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
14352 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14353 .row &%remote_sort_domains%& "order of remote deliveries"
14354 .row &%retry_data_expire%& "timeout for retry data"
14355 .row &%retry_interval_max%& "safety net for retry rules"
14360 .section "Bounce and warning messages" "SECID117"
14362 .row &%bounce_message_file%& "content of bounce"
14363 .row &%bounce_message_text%& "content of bounce"
14364 .row &%bounce_return_body%& "include body if returning message"
14365 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
14366 .row &%bounce_return_message%& "include original message in bounce"
14367 .row &%bounce_return_size_limit%& "limit on returned message"
14368 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
14369 .row &%dsn_from%& "set &'From:'& contents in bounces"
14370 .row &%errors_copy%& "copy bounce messages"
14371 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
14372 .row &%delay_warning%& "time schedule"
14373 .row &%delay_warning_condition%& "condition for warning messages"
14374 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
14375 .row &%smtp_return_error_details%& "give detail on rejections"
14376 .row &%warn_message_file%& "content of warning message"
14381 .section "Alphabetical list of main options" "SECTalomo"
14382 Those options that undergo string expansion before use are marked with
14385 .option accept_8bitmime main boolean true
14387 .cindex "8-bit characters"
14388 .cindex "log" "selectors"
14389 .cindex "log" "8BITMIME"
14390 This option causes Exim to send 8BITMIME in its response to an SMTP
14391 EHLO command, and to accept the BODY= parameter on MAIL commands.
14392 However, though Exim is 8-bit clean, it is not a protocol converter, and it
14393 takes no steps to do anything special with messages received by this route.
14395 Historically Exim kept this option off by default, but the maintainers
14396 feel that in today's Internet, this causes more problems than it solves.
14397 It now defaults to true.
14398 A more detailed analysis of the issues is provided by Dan Bernstein:
14400 &url(https://cr.yp.to/smtp/8bitmime.html)
14403 To log received 8BITMIME status use
14405 log_selector = +8bitmime
14408 .option acl_not_smtp main string&!! unset
14409 .cindex "&ACL;" "for non-SMTP messages"
14410 .cindex "non-SMTP messages" "ACLs for"
14411 This option defines the ACL that is run when a non-SMTP message has been
14412 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
14415 .option acl_not_smtp_mime main string&!! unset
14416 This option defines the ACL that is run for individual MIME parts of non-SMTP
14417 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
14420 .option acl_not_smtp_start main string&!! unset
14421 .cindex "&ACL;" "at start of non-SMTP message"
14422 .cindex "non-SMTP messages" "ACLs for"
14423 This option defines the ACL that is run before Exim starts reading a
14424 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
14426 .option acl_smtp_auth main string&!! unset
14427 .cindex "&ACL;" "setting up for SMTP commands"
14428 .cindex "AUTH" "ACL for"
14429 This option defines the ACL that is run when an SMTP AUTH command is
14430 received. See chapter &<<CHAPACL>>& for further details.
14432 .option acl_smtp_connect main string&!! unset
14433 .cindex "&ACL;" "on SMTP connection"
14434 This option defines the ACL that is run when an SMTP connection is received.
14435 See chapter &<<CHAPACL>>& for further details.
14437 .option acl_smtp_data main string&!! unset
14438 .cindex "DATA" "ACL for"
14439 This option defines the ACL that is run after an SMTP DATA command has been
14440 processed and the message itself has been received, but before the final
14441 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
14443 .option acl_smtp_data_prdr main string&!! accept
14444 .cindex "PRDR" "ACL for"
14445 .cindex "DATA" "PRDR ACL for"
14446 .cindex "&ACL;" "PRDR-related"
14447 .cindex "&ACL;" "per-user data processing"
14448 This option defines the ACL that,
14449 if the PRDR feature has been negotiated,
14450 is run for each recipient after an SMTP DATA command has been
14451 processed and the message itself has been received, but before the
14452 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
14454 .option acl_smtp_dkim main string&!! unset
14455 .cindex DKIM "ACL for"
14456 This option defines the ACL that is run for each DKIM signature
14457 (by default, or as specified in the dkim_verify_signers option)
14458 of a received message.
14459 See section &<<SECDKIMVFY>>& for further details.
14461 .option acl_smtp_etrn main string&!! unset
14462 .cindex "ETRN" "ACL for"
14463 This option defines the ACL that is run when an SMTP ETRN command is
14464 received. See chapter &<<CHAPACL>>& for further details.
14466 .option acl_smtp_expn main string&!! unset
14467 .cindex "EXPN" "ACL for"
14468 This option defines the ACL that is run when an SMTP EXPN command is
14469 received. See chapter &<<CHAPACL>>& for further details.
14471 .option acl_smtp_helo main string&!! unset
14472 .cindex "EHLO" "ACL for"
14473 .cindex "HELO" "ACL for"
14474 This option defines the ACL that is run when an SMTP EHLO or HELO
14475 command is received. See chapter &<<CHAPACL>>& for further details.
14478 .option acl_smtp_mail main string&!! unset
14479 .cindex "MAIL" "ACL for"
14480 This option defines the ACL that is run when an SMTP MAIL command is
14481 received. See chapter &<<CHAPACL>>& for further details.
14483 .option acl_smtp_mailauth main string&!! unset
14484 .cindex "AUTH" "on MAIL command"
14485 This option defines the ACL that is run when there is an AUTH parameter on
14486 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
14487 &<<CHAPSMTPAUTH>>& for details of authentication.
14489 .option acl_smtp_mime main string&!! unset
14490 .cindex "MIME content scanning" "ACL for"
14491 This option is available when Exim is built with the content-scanning
14492 extension. It defines the ACL that is run for each MIME part in a message. See
14493 section &<<SECTscanmimepart>>& for details.
14495 .option acl_smtp_notquit main string&!! unset
14496 .cindex "not-QUIT, ACL for"
14497 This option defines the ACL that is run when an SMTP session
14498 ends without a QUIT command being received.
14499 See chapter &<<CHAPACL>>& for further details.
14501 .option acl_smtp_predata main string&!! unset
14502 This option defines the ACL that is run when an SMTP DATA command is
14503 received, before the message itself is received. See chapter &<<CHAPACL>>& for
14506 .option acl_smtp_quit main string&!! unset
14507 .cindex "QUIT, ACL for"
14508 This option defines the ACL that is run when an SMTP QUIT command is
14509 received. See chapter &<<CHAPACL>>& for further details.
14511 .option acl_smtp_rcpt main string&!! unset
14512 .cindex "RCPT" "ACL for"
14513 This option defines the ACL that is run when an SMTP RCPT command is
14514 received. See chapter &<<CHAPACL>>& for further details.
14516 .option acl_smtp_starttls main string&!! unset
14517 .cindex "STARTTLS, ACL for"
14518 This option defines the ACL that is run when an SMTP STARTTLS command is
14519 received. See chapter &<<CHAPACL>>& for further details.
14521 .option acl_smtp_vrfy main string&!! unset
14522 .cindex "VRFY" "ACL for"
14523 This option defines the ACL that is run when an SMTP VRFY command is
14524 received. See chapter &<<CHAPACL>>& for further details.
14526 .option add_environment main "string list" empty
14527 .cindex "environment" "set values"
14528 This option allows to set individual environment variables that the
14529 currently linked libraries and programs in child processes use.
14530 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
14532 .option admin_groups main "string list&!!" unset
14533 .cindex "admin user"
14534 This option is expanded just once, at the start of Exim's processing. If the
14535 current group or any of the supplementary groups of an Exim caller is in this
14536 colon-separated list, the caller has admin privileges. If all your system
14537 programmers are in a specific group, for example, you can give them all Exim
14538 admin privileges by putting that group in &%admin_groups%&. However, this does
14539 not permit them to read Exim's spool files (whose group owner is the Exim gid).
14540 To permit this, you have to add individuals to the Exim group.
14542 .option allow_domain_literals main boolean false
14543 .cindex "domain literal"
14544 If this option is set, the RFC 2822 domain literal format is permitted in
14545 email addresses. The option is not set by default, because the domain literal
14546 format is not normally required these days, and few people know about it. It
14547 has, however, been exploited by mail abusers.
14549 Unfortunately, it seems that some DNS black list maintainers are using this
14550 format to report black listing to postmasters. If you want to accept messages
14551 addressed to your hosts by IP address, you need to set
14552 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
14553 domains (defined in the named domain list &%local_domains%& in the default
14554 configuration). This &"magic string"& matches the domain literal form of all
14555 the local host's IP addresses.
14558 .option allow_mx_to_ip main boolean false
14559 .cindex "MX record" "pointing to IP address"
14560 It appears that more and more DNS zone administrators are breaking the rules
14561 and putting domain names that look like IP addresses on the right hand side of
14562 MX records. Exim follows the rules and rejects this, giving an error message
14563 that explains the misconfiguration. However, some other MTAs support this
14564 practice, so to avoid &"Why can't Exim do this?"& complaints,
14565 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
14566 recommended, except when you have no other choice.
14568 .option allow_utf8_domains main boolean false
14569 .cindex "domain" "UTF-8 characters in"
14570 .cindex "UTF-8" "in domain name"
14571 Lots of discussion is going on about internationalized domain names. One
14572 camp is strongly in favour of just using UTF-8 characters, and it seems
14573 that at least two other MTAs permit this. This option allows Exim users to
14574 experiment if they wish.
14576 If it is set true, Exim's domain parsing function allows valid
14577 UTF-8 multicharacters to appear in domain name components, in addition to
14578 letters, digits, and hyphens. However, just setting this option is not
14579 enough; if you want to look up these domain names in the DNS, you must also
14580 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
14581 suitable setting is:
14583 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
14584 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
14586 Alternatively, you can just disable this feature by setting
14588 dns_check_names_pattern =
14590 That is, set the option to an empty string so that no check is done.
14593 .option auth_advertise_hosts main "host list&!!" *
14594 .cindex "authentication" "advertising"
14595 .cindex "AUTH" "advertising"
14596 If any server authentication mechanisms are configured, Exim advertises them in
14597 response to an EHLO command only if the calling host matches this list.
14598 Otherwise, Exim does not advertise AUTH.
14599 Exim does not accept AUTH commands from clients to which it has not
14600 advertised the availability of AUTH. The advertising of individual
14601 authentication mechanisms can be controlled by the use of the
14602 &%server_advertise_condition%& generic authenticator option on the individual
14603 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
14605 Certain mail clients (for example, Netscape) require the user to provide a name
14606 and password for authentication if AUTH is advertised, even though it may
14607 not be needed (the host may accept messages from hosts on its local LAN without
14608 authentication, for example). The &%auth_advertise_hosts%& option can be used
14609 to make these clients more friendly by excluding them from the set of hosts to
14610 which Exim advertises AUTH.
14612 .cindex "AUTH" "advertising when encrypted"
14613 If you want to advertise the availability of AUTH only when the connection
14614 is encrypted using TLS, you can make use of the fact that the value of this
14615 option is expanded, with a setting like this:
14617 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
14619 .vindex "&$tls_in_cipher$&"
14620 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
14621 the expansion is empty, thus matching no hosts. Otherwise, the result of the
14622 expansion is *, which matches all hosts.
14625 .option auto_thaw main time 0s
14626 .cindex "thawing messages"
14627 .cindex "unfreezing messages"
14628 If this option is set to a time greater than zero, a queue runner will try a
14629 new delivery attempt on any frozen message, other than a bounce message, if
14630 this much time has passed since it was frozen. This may result in the message
14631 being re-frozen if nothing has changed since the last attempt. It is a way of
14632 saying &"keep on trying, even though there are big problems"&.
14634 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
14635 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
14636 thought to be very useful any more, and its use should probably be avoided.
14639 .option av_scanner main string "see below"
14640 This option is available if Exim is built with the content-scanning extension.
14641 It specifies which anti-virus scanner to use. The default value is:
14643 sophie:/var/run/sophie
14645 If the value of &%av_scanner%& starts with a dollar character, it is expanded
14646 before use. See section &<<SECTscanvirus>>& for further details.
14649 .option bi_command main string unset
14651 This option supplies the name of a command that is run when Exim is called with
14652 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
14653 just the command name, it is not a complete command line. If an argument is
14654 required, it must come from the &%-oA%& command line option.
14657 .option bounce_message_file main string unset
14658 .cindex "bounce message" "customizing"
14659 .cindex "customizing" "bounce message"
14660 This option defines a template file containing paragraphs of text to be used
14661 for constructing bounce messages. Details of the file's contents are given in
14662 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
14665 .option bounce_message_text main string unset
14666 When this option is set, its contents are included in the default bounce
14667 message immediately after &"This message was created automatically by mail
14668 delivery software."& It is not used if &%bounce_message_file%& is set.
14670 .option bounce_return_body main boolean true
14671 .cindex "bounce message" "including body"
14672 This option controls whether the body of an incoming message is included in a
14673 bounce message when &%bounce_return_message%& is true. The default setting
14674 causes the entire message, both header and body, to be returned (subject to the
14675 value of &%bounce_return_size_limit%&). If this option is false, only the
14676 message header is included. In the case of a non-SMTP message containing an
14677 error that is detected during reception, only those header lines preceding the
14678 point at which the error was detected are returned.
14679 .cindex "bounce message" "including original"
14681 .option bounce_return_linesize_limit main integer 998
14682 .cindex "size" "of bounce lines, limit"
14683 .cindex "bounce message" "line length limit"
14684 .cindex "limit" "bounce message line length"
14685 This option sets a limit in bytes on the line length of messages
14686 that are returned to senders due to delivery problems,
14687 when &%bounce_return_message%& is true.
14688 The default value corresponds to RFC limits.
14689 If the message being returned has lines longer than this value it is
14690 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
14692 The option also applies to bounces returned when an error is detected
14693 during reception of a message.
14694 In this case lines from the original are truncated.
14696 The option does not apply to messages generated by an &(autoreply)& transport.
14699 .option bounce_return_message main boolean true
14700 If this option is set false, none of the original message is included in
14701 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
14702 &%bounce_return_body%&.
14705 .option bounce_return_size_limit main integer 100K
14706 .cindex "size" "of bounce, limit"
14707 .cindex "bounce message" "size limit"
14708 .cindex "limit" "bounce message size"
14709 This option sets a limit in bytes on the size of messages that are returned to
14710 senders as part of bounce messages when &%bounce_return_message%& is true. The
14711 limit should be less than the value of the global &%message_size_limit%& and of
14712 any &%message_size_limit%& settings on transports, to allow for the bounce text
14713 that Exim generates. If this option is set to zero there is no limit.
14715 When the body of any message that is to be included in a bounce message is
14716 greater than the limit, it is truncated, and a comment pointing this out is
14717 added at the top. The actual cutoff may be greater than the value given, owing
14718 to the use of buffering for transferring the message in chunks (typically 8K in
14719 size). The idea is to save bandwidth on those undeliverable 15-megabyte
14722 .option bounce_sender_authentication main string unset
14723 .cindex "bounce message" "sender authentication"
14724 .cindex "authentication" "bounce message"
14725 .cindex "AUTH" "on bounce message"
14726 This option provides an authenticated sender address that is sent with any
14727 bounce messages generated by Exim that are sent over an authenticated SMTP
14728 connection. A typical setting might be:
14730 bounce_sender_authentication = mailer-daemon@my.domain.example
14732 which would cause bounce messages to be sent using the SMTP command:
14734 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
14736 The value of &%bounce_sender_authentication%& must always be a complete email
14739 .option callout_domain_negative_expire main time 3h
14740 .cindex "caching" "callout timeouts"
14741 .cindex "callout" "caching timeouts"
14742 This option specifies the expiry time for negative callout cache data for a
14743 domain. See section &<<SECTcallver>>& for details of callout verification, and
14744 section &<<SECTcallvercache>>& for details of the caching.
14747 .option callout_domain_positive_expire main time 7d
14748 This option specifies the expiry time for positive callout cache data for a
14749 domain. See section &<<SECTcallver>>& for details of callout verification, and
14750 section &<<SECTcallvercache>>& for details of the caching.
14753 .option callout_negative_expire main time 2h
14754 This option specifies the expiry time for negative callout cache data for an
14755 address. See section &<<SECTcallver>>& for details of callout verification, and
14756 section &<<SECTcallvercache>>& for details of the caching.
14759 .option callout_positive_expire main time 24h
14760 This option specifies the expiry time for positive callout cache data for an
14761 address. See section &<<SECTcallver>>& for details of callout verification, and
14762 section &<<SECTcallvercache>>& for details of the caching.
14765 .option callout_random_local_part main string&!! "see below"
14766 This option defines the &"random"& local part that can be used as part of
14767 callout verification. The default value is
14769 $primary_hostname-$tod_epoch-testing
14771 See section &<<CALLaddparcall>>& for details of how this value is used.
14774 .option check_log_inodes main integer 100
14775 See &%check_spool_space%& below.
14778 .option check_log_space main integer 10M
14779 See &%check_spool_space%& below.
14781 .oindex "&%check_rfc2047_length%&"
14782 .cindex "RFC 2047" "disabling length check"
14783 .option check_rfc2047_length main boolean true
14784 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
14785 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
14786 word; strings to be encoded that exceed this length are supposed to use
14787 multiple encoded words. By default, Exim does not recognize encoded words that
14788 exceed the maximum length. However, it seems that some software, in violation
14789 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
14790 set false, Exim recognizes encoded words of any length.
14793 .option check_spool_inodes main integer 100
14794 See &%check_spool_space%& below.
14797 .option check_spool_space main integer 10M
14798 .cindex "checking disk space"
14799 .cindex "disk space, checking"
14800 .cindex "spool directory" "checking space"
14801 The four &%check_...%& options allow for checking of disk resources before a
14802 message is accepted.
14804 .vindex "&$log_inodes$&"
14805 .vindex "&$log_space$&"
14806 .vindex "&$spool_inodes$&"
14807 .vindex "&$spool_space$&"
14808 When any of these options are nonzero, they apply to all incoming messages. If you
14809 want to apply different checks to different kinds of message, you can do so by
14810 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
14811 &$spool_space$& in an ACL with appropriate additional conditions.
14814 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
14815 either value is greater than zero, for example:
14817 check_spool_space = 100M
14818 check_spool_inodes = 100
14820 The spool partition is the one that contains the directory defined by
14821 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
14824 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
14825 files are written if either is greater than zero. These should be set only if
14826 &%log_file_path%& and &%spool_directory%& refer to different partitions.
14828 If there is less space or fewer inodes than requested, Exim refuses to accept
14829 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
14830 error response to the MAIL command. If ESMTP is in use and there was a
14831 SIZE parameter on the MAIL command, its value is added to the
14832 &%check_spool_space%& value, and the check is performed even if
14833 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
14835 The values for &%check_spool_space%& and &%check_log_space%& are held as a
14836 number of kilobytes (though specified in bytes).
14837 If a non-multiple of 1024 is specified, it is rounded up.
14839 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
14840 failure a message is written to stderr and Exim exits with a non-zero code, as
14841 it obviously cannot send an error message of any kind.
14843 There is a slight performance penalty for these checks.
14844 Versions of Exim preceding 4.88 had these disabled by default;
14845 high-rate installations confident they will never run out of resources
14846 may wish to deliberately disable them.
14848 .option chunking_advertise_hosts main "host list&!!" *
14849 .cindex CHUNKING advertisement
14850 .cindex "RFC 3030" "CHUNKING"
14851 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
14853 Hosts may use the BDAT command as an alternate to DATA.
14855 .option commandline_checks_require_admin main boolean &`false`&
14856 .cindex "restricting access to features"
14857 This option restricts various basic checking features to require an
14858 administrative user.
14859 This affects most of the &%-b*%& options, such as &%-be%&.
14861 .option debug_store main boolean &`false`&
14862 .cindex debugging "memory corruption"
14863 .cindex memory debugging
14864 This option, when true, enables extra checking in Exim's internal memory
14865 management. For use when a memory corruption issue is being investigated,
14866 it should normally be left as default.
14868 .option daemon_smtp_ports main string &`smtp`&
14869 .cindex "port" "for daemon"
14870 .cindex "TCP/IP" "setting listening ports"
14871 This option specifies one or more default SMTP ports on which the Exim daemon
14872 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
14873 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
14875 .option daemon_startup_retries main integer 9
14876 .cindex "daemon startup, retrying"
14877 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
14878 the daemon at startup when it cannot immediately bind a listening socket
14879 (typically because the socket is already in use): &%daemon_startup_retries%&
14880 defines the number of retries after the first failure, and
14881 &%daemon_startup_sleep%& defines the length of time to wait between retries.
14883 .option daemon_startup_sleep main time 30s
14884 See &%daemon_startup_retries%&.
14886 .option delay_warning main "time list" 24h
14887 .cindex "warning of delay"
14888 .cindex "delay warning, specifying"
14889 .cindex "queue" "delay warning"
14890 When a message is delayed, Exim sends a warning message to the sender at
14891 intervals specified by this option. The data is a colon-separated list of times
14892 after which to send warning messages. If the value of the option is an empty
14893 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
14894 message has been in the queue for longer than the last time, the last interval
14895 between the times is used to compute subsequent warning times. For example,
14898 delay_warning = 4h:8h:24h
14900 the first message is sent after 4 hours, the second after 8 hours, and
14901 the third one after 24 hours. After that, messages are sent every 16 hours,
14902 because that is the interval between the last two times on the list. If you set
14903 just one time, it specifies the repeat interval. For example, with:
14907 messages are repeated every six hours. To stop warnings after a given time, set
14908 a very large time at the end of the list. For example:
14910 delay_warning = 2h:12h:99d
14912 Note that the option is only evaluated at the time a delivery attempt fails,
14913 which depends on retry and queue-runner configuration.
14914 Typically retries will be configured more frequently than warning messages.
14916 .option delay_warning_condition main string&!! "see below"
14917 .vindex "&$domain$&"
14918 The string is expanded at the time a warning message might be sent. If all the
14919 deferred addresses have the same domain, it is set in &$domain$& during the
14920 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
14921 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
14922 &"false"& (the comparison being done caselessly) then the warning message is
14923 not sent. The default is:
14925 delay_warning_condition = ${if or {\
14926 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
14927 { match{$h_precedence:}{(?i)bulk|list|junk} }\
14928 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
14931 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
14932 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
14933 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
14934 &"auto-replied"& in an &'Auto-Submitted:'& header.
14936 .option deliver_drop_privilege main boolean false
14937 .cindex "unprivileged delivery"
14938 .cindex "delivery" "unprivileged"
14939 If this option is set true, Exim drops its root privilege at the start of a
14940 delivery process, and runs as the Exim user throughout. This severely restricts
14941 the kinds of local delivery that are possible, but is viable in certain types
14942 of configuration. There is a discussion about the use of root privilege in
14943 chapter &<<CHAPsecurity>>&.
14945 .option deliver_queue_load_max main fixed-point unset
14946 .cindex "load average"
14947 .cindex "queue runner" "abandoning"
14948 When this option is set, a queue run is abandoned if the system load average
14949 becomes greater than the value of the option. The option has no effect on
14950 ancient operating systems on which Exim cannot determine the load average.
14951 See also &%queue_only_load%& and &%smtp_load_reserve%&.
14954 .option delivery_date_remove main boolean true
14955 .cindex "&'Delivery-date:'& header line"
14956 Exim's transports have an option for adding a &'Delivery-date:'& header to a
14957 message when it is delivered, in exactly the same way as &'Return-path:'& is
14958 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
14959 should not be present in incoming messages, and this option causes them to be
14960 removed at the time the message is received, to avoid any problems that might
14961 occur when a delivered message is subsequently sent on to some other recipient.
14963 .option disable_fsync main boolean false
14964 .cindex "&[fsync()]&, disabling"
14965 This option is available only if Exim was built with the compile-time option
14966 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
14967 a runtime configuration generates an &"unknown option"& error. You should not
14968 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
14969 really, really, really understand what you are doing. &'No pre-compiled
14970 distributions of Exim should ever make this option available.'&
14972 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
14973 updated files' data to be written to disc before continuing. Unexpected events
14974 such as crashes and power outages may cause data to be lost or scrambled.
14975 Here be Dragons. &*Beware.*&
14978 .option disable_ipv6 main boolean false
14979 .cindex "IPv6" "disabling"
14980 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
14981 activities take place. AAAA records are never looked up, and any IPv6 addresses
14982 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
14983 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14984 to handle IPv6 literal addresses.
14987 .option dkim_verify_signers main "domain list&!!" $dkim_signers
14988 .cindex DKIM "controlling calls to the ACL"
14989 This option gives a list of DKIM domains for which the DKIM ACL is run.
14990 It is expanded after the message is received; by default it runs
14991 the ACL once for each signature in the message.
14992 See section &<<SECDKIMVFY>>&.
14995 .option dns_again_means_nonexist main "domain list&!!" unset
14996 .cindex "DNS" "&""try again""& response; overriding"
14997 DNS lookups give a &"try again"& response for the DNS errors
14998 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
14999 keep trying to deliver a message, or to give repeated temporary errors to
15000 incoming mail. Sometimes the effect is caused by a badly set up name server and
15001 may persist for a long time. If a domain which exhibits this problem matches
15002 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
15003 This option should be used with care. You can make it apply to reverse lookups
15004 by a setting such as this:
15006 dns_again_means_nonexist = *.in-addr.arpa
15008 This option applies to all DNS lookups that Exim does. It also applies when the
15009 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
15010 since these are most likely to be caused by DNS lookup problems. The
15011 &(dnslookup)& router has some options of its own for controlling what happens
15012 when lookups for MX or SRV records give temporary errors. These more specific
15013 options are applied after this global option.
15015 .option dns_check_names_pattern main string "see below"
15016 .cindex "DNS" "pre-check of name syntax"
15017 When this option is set to a non-empty string, it causes Exim to check domain
15018 names for characters that are not allowed in host names before handing them to
15019 the DNS resolver, because some resolvers give temporary errors for names that
15020 contain unusual characters. If a domain name contains any unwanted characters,
15021 a &"not found"& result is forced, and the resolver is not called. The check is
15022 done by matching the domain name against a regular expression, which is the
15023 value of this option. The default pattern is
15025 dns_check_names_pattern = \
15026 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
15028 which permits only letters, digits, slashes, and hyphens in components, but
15029 they must start and end with a letter or digit. Slashes are not, in fact,
15030 permitted in host names, but they are found in certain NS records (which can be
15031 accessed in Exim by using a &%dnsdb%& lookup). If you set
15032 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
15035 .option dns_csa_search_limit main integer 5
15036 This option controls the depth of parental searching for CSA SRV records in the
15037 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
15039 .option dns_csa_use_reverse main boolean true
15040 This option controls whether or not an IP address, given as a CSA domain, is
15041 reversed and looked up in the reverse DNS, as described in more detail in
15042 section &<<SECTverifyCSA>>&.
15045 .option dns_cname_loops main integer 1
15046 .cindex DNS "CNAME following"
15047 This option controls the following of CNAME chains, needed if the resolver does
15048 not do it internally.
15049 As of 2018 most should, and the default can be left.
15050 If you have an ancient one, a value of 10 is likely needed.
15052 The default value of one CNAME-follow is needed
15053 thanks to the observed return for an MX request,
15054 given no MX presence but a CNAME to an A, of the CNAME.
15058 .option dns_dnssec_ok main integer -1
15059 .cindex "DNS" "resolver options"
15060 .cindex "DNS" "DNSSEC"
15061 If this option is set to a non-negative number then Exim will initialise the
15062 DNS resolver library to either use or not use DNSSEC, overriding the system
15063 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
15065 If the resolver library does not support DNSSEC then this option has no effect.
15068 .option dns_ipv4_lookup main "domain list&!!" unset
15069 .cindex "IPv6" "DNS lookup for AAAA records"
15070 .cindex "DNS" "IPv6 lookup for AAAA records"
15071 .cindex DNS "IPv6 disabling"
15072 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
15073 looks for IPv6 address records (AAAA records) as well as IPv4 address records
15074 (A records) when trying to find IP addresses for hosts, unless the host's
15075 domain matches this list.
15077 This is a fudge to help with name servers that give big delays or otherwise do
15078 not work for the AAAA record type. In due course, when the world's name
15079 servers have all been upgraded, there should be no need for this option.
15082 .option dns_retrans main time 0s
15083 .cindex "DNS" "resolver options"
15084 .cindex timeout "dns lookup"
15085 .cindex "DNS" timeout
15086 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
15087 retransmission and retry parameters for DNS lookups. Values of zero (the
15088 defaults) leave the system default settings unchanged. The first value is the
15089 time between retries, and the second is the number of retries. It isn't
15090 totally clear exactly how these settings affect the total time a DNS lookup may
15091 take. I haven't found any documentation about timeouts on DNS lookups; these
15092 parameter values are available in the external resolver interface structure,
15093 but nowhere does it seem to describe how they are used or what you might want
15095 See also the &%slow_lookup_log%& option.
15098 .option dns_retry main integer 0
15099 See &%dns_retrans%& above.
15102 .option dns_trust_aa main "domain list&!!" unset
15103 .cindex "DNS" "resolver options"
15104 .cindex "DNS" "DNSSEC"
15105 If this option is set then lookup results marked with the AA bit
15106 (Authoritative Answer) are trusted the same way as if they were
15107 DNSSEC-verified. The authority section's name of the answer must
15108 match with this expanded domain list.
15110 Use this option only if you talk directly to a resolver that is
15111 authoritative for some zones and does not set the AD (Authentic Data)
15112 bit in the answer. Some DNS servers may have an configuration option to
15113 mark the answers from their own zones as verified (they set the AD bit).
15114 Others do not have this option. It is considered as poor practice using
15115 a resolver that is an authoritative server for some zones.
15117 Use this option only if you really have to (e.g. if you want
15118 to use DANE for remote delivery to a server that is listed in the DNS
15119 zones that your resolver is authoritative for).
15121 If the DNS answer packet has the AA bit set and contains resource record
15122 in the answer section, the name of the first NS record appearing in the
15123 authority section is compared against the list. If the answer packet is
15124 authoritative but the answer section is empty, the name of the first SOA
15125 record in the authoritative section is used instead.
15127 .cindex "DNS" "resolver options"
15128 .option dns_use_edns0 main integer -1
15129 .cindex "DNS" "resolver options"
15130 .cindex "DNS" "EDNS0"
15131 .cindex "DNS" "OpenBSD
15132 If this option is set to a non-negative number then Exim will initialise the
15133 DNS resolver library to either use or not use EDNS0 extensions, overriding
15134 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
15137 If the resolver library does not support EDNS0 then this option has no effect.
15139 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
15140 means that DNSSEC will not work with Exim on that platform either, unless Exim
15141 is linked against an alternative DNS client library.
15144 .option drop_cr main boolean false
15145 This is an obsolete option that is now a no-op. It used to affect the way Exim
15146 handled CR and LF characters in incoming messages. What happens now is
15147 described in section &<<SECTlineendings>>&.
15149 .option dsn_advertise_hosts main "host list&!!" unset
15150 .cindex "bounce messages" "success"
15151 .cindex "DSN" "success"
15152 .cindex "Delivery Status Notification" "success"
15153 DSN extensions (RFC3461) will be advertised in the EHLO message to,
15154 and accepted from, these hosts.
15155 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
15156 and RET and ORCPT options on MAIL FROM commands.
15157 A NOTIFY=SUCCESS option requests success-DSN messages.
15158 A NOTIFY= option with no argument requests that no delay or failure DSNs
15161 .option dsn_from main "string&!!" "see below"
15162 .cindex "&'From:'& header line" "in bounces"
15163 .cindex "bounce messages" "&'From:'& line, specifying"
15164 This option can be used to vary the contents of &'From:'& header lines in
15165 bounces and other automatically generated messages (&"Delivery Status
15166 Notifications"& &-- hence the name of the option). The default setting is:
15168 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
15170 The value is expanded every time it is needed. If the expansion fails, a
15171 panic is logged, and the default value is used.
15173 .option envelope_to_remove main boolean true
15174 .cindex "&'Envelope-to:'& header line"
15175 Exim's transports have an option for adding an &'Envelope-to:'& header to a
15176 message when it is delivered, in exactly the same way as &'Return-path:'& is
15177 handled. &'Envelope-to:'& records the original recipient address from the
15178 message's envelope that caused the delivery to happen. Such headers should not
15179 be present in incoming messages, and this option causes them to be removed at
15180 the time the message is received, to avoid any problems that might occur when a
15181 delivered message is subsequently sent on to some other recipient.
15184 .option errors_copy main "string list&!!" unset
15185 .cindex "bounce message" "copy to other address"
15186 .cindex "copy of bounce message"
15187 Setting this option causes Exim to send bcc copies of bounce messages that it
15188 generates to other addresses. &*Note*&: This does not apply to bounce messages
15189 coming from elsewhere. The value of the option is a colon-separated list of
15190 items. Each item consists of a pattern, terminated by white space, followed by
15191 a comma-separated list of email addresses. If a pattern contains spaces, it
15192 must be enclosed in double quotes.
15194 Each pattern is processed in the same way as a single item in an address list
15195 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
15196 the bounce message, the message is copied to the addresses on the list. The
15197 items are scanned in order, and once a matching one is found, no further items
15198 are examined. For example:
15200 errors_copy = spqr@mydomain postmaster@mydomain.example :\
15201 rqps@mydomain hostmaster@mydomain.example,\
15202 postmaster@mydomain.example
15204 .vindex "&$domain$&"
15205 .vindex "&$local_part$&"
15206 The address list is expanded before use. The expansion variables &$local_part$&
15207 and &$domain$& are set from the original recipient of the error message, and if
15208 there was any wildcard matching in the pattern, the expansion
15209 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
15210 variables &$0$&, &$1$&, etc. are set in the normal way.
15213 .option errors_reply_to main string unset
15214 .cindex "bounce message" "&'Reply-to:'& in"
15215 By default, Exim's bounce and delivery warning messages contain the header line
15217 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
15219 .oindex &%quota_warn_message%&
15220 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
15221 A warning message that is generated by the &%quota_warn_message%& option in an
15222 &(appendfile)& transport may contain its own &'From:'& header line that
15223 overrides the default.
15225 Experience shows that people reply to bounce messages. If the
15226 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
15227 and warning messages. For example:
15229 errors_reply_to = postmaster@my.domain.example
15231 The value of the option is not expanded. It must specify a valid RFC 2822
15232 address. However, if a warning message that is generated by the
15233 &%quota_warn_message%& option in an &(appendfile)& transport contain its
15234 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
15238 .option event_action main string&!! unset
15240 This option declares a string to be expanded for Exim's events mechanism.
15241 For details see chapter &<<CHAPevents>>&.
15244 .option exim_group main string "compile-time configured"
15245 .cindex "gid (group id)" "Exim's own"
15246 .cindex "Exim group"
15247 This option changes the gid under which Exim runs when it gives up root
15248 privilege. The default value is compiled into the binary. The value of this
15249 option is used only when &%exim_user%& is also set. Unless it consists entirely
15250 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
15251 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
15255 .option exim_path main string "see below"
15256 .cindex "Exim binary, path name"
15257 This option specifies the path name of the Exim binary, which is used when Exim
15258 needs to re-exec itself. The default is set up to point to the file &'exim'& in
15259 the directory configured at compile time by the BIN_DIRECTORY setting. It
15260 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
15262 &*Warning*&: Do not use a macro to define the value of this option, because
15263 you will break those Exim utilities that scan the configuration file to find
15264 where the binary is. (They then use the &%-bP%& option to extract option
15265 settings such as the value of &%spool_directory%&.)
15268 .option exim_user main string "compile-time configured"
15269 .cindex "uid (user id)" "Exim's own"
15270 .cindex "Exim user"
15271 This option changes the uid under which Exim runs when it gives up root
15272 privilege. The default value is compiled into the binary. Ownership of the run
15273 time configuration file and the use of the &%-C%& and &%-D%& command line
15274 options is checked against the values in the binary, not what is set here.
15276 Unless it consists entirely of digits, the string is looked up using
15277 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
15278 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
15279 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
15282 .option extra_local_interfaces main "string list" unset
15283 This option defines network interfaces that are to be considered local when
15284 routing, but which are not used for listening by the daemon. See section
15285 &<<SECTreclocipadd>>& for details.
15288 . Allow this long option name to split; give it unsplit as a fifth argument
15289 . for the automatic .oindex that is generated by .option.
15291 .option "extract_addresses_remove_arguments" main boolean true &&&
15292 extract_addresses_remove_arguments
15294 .cindex "command line" "addresses with &%-t%&"
15295 .cindex "Sendmail compatibility" "&%-t%& option"
15296 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
15297 are present on the command line when the &%-t%& option is used to build an
15298 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
15299 line addresses are removed from the recipients list. This is also how Smail
15300 behaves. However, other Sendmail documentation (the O'Reilly book) states that
15301 command line addresses are added to those obtained from the header lines. When
15302 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
15303 argument headers. If it is set false, Exim adds rather than removes argument
15307 .option finduser_retries main integer 0
15308 .cindex "NIS, retrying user lookups"
15309 On systems running NIS or other schemes in which user and group information is
15310 distributed from a remote system, there can be times when &[getpwnam()]& and
15311 related functions fail, even when given valid data, because things time out.
15312 Unfortunately these failures cannot be distinguished from genuine &"not found"&
15313 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
15314 many extra times to find a user or a group, waiting for one second between
15317 .cindex "&_/etc/passwd_&" "multiple reading of"
15318 You should not set this option greater than zero if your user information is in
15319 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
15320 search the file multiple times for non-existent users, and also cause delay.
15324 .option freeze_tell main "string list, comma separated" unset
15325 .cindex "freezing messages" "sending a message when freezing"
15326 On encountering certain errors, or when configured to do so in a system filter,
15327 ACL, or special router, Exim freezes a message. This means that no further
15328 delivery attempts take place until an administrator thaws the message, or the
15329 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
15330 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
15331 warning message whenever it freezes something, unless the message it is
15332 freezing is a locally-generated bounce message. (Without this exception there
15333 is the possibility of looping.) The warning message is sent to the addresses
15334 supplied as the comma-separated value of this option. If several of the
15335 message's addresses cause freezing, only a single message is sent. If the
15336 freezing was automatic, the reason(s) for freezing can be found in the message
15337 log. If you configure freezing in a filter or ACL, you must arrange for any
15338 logging that you require.
15341 .option gecos_name main string&!! unset
15343 .cindex "&""gecos""& field, parsing"
15344 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
15345 password file to hold other information in addition to users' real names. Exim
15346 looks up this field for use when it is creating &'Sender:'& or &'From:'&
15347 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
15348 of the field are used unchanged, except that, if an ampersand is encountered,
15349 it is replaced by the user's login name with the first character forced to
15350 upper case, since this is a convention that is observed on many systems.
15352 When these options are set, &%gecos_pattern%& is treated as a regular
15353 expression that is to be applied to the field (again with && replaced by the
15354 login name), and if it matches, &%gecos_name%& is expanded and used as the
15357 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
15358 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
15359 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
15360 name terminates at the first comma, the following can be used:
15362 gecos_pattern = ([^,]*)
15366 .option gecos_pattern main string unset
15367 See &%gecos_name%& above.
15370 .option gnutls_compat_mode main boolean unset
15371 This option controls whether GnuTLS is used in compatibility mode in an Exim
15372 server. This reduces security slightly, but improves interworking with older
15373 implementations of TLS.
15376 .option gnutls_allow_auto_pkcs11 main boolean unset
15377 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
15378 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
15381 &url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
15386 .option headers_charset main string "see below"
15387 This option sets a default character set for translating from encoded MIME
15388 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
15389 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
15390 ultimate default is ISO-8859-1. For more details see the description of header
15391 insertions in section &<<SECTexpansionitems>>&.
15395 .option header_maxsize main integer "see below"
15396 .cindex "header section" "maximum size of"
15397 .cindex "limit" "size of message header section"
15398 This option controls the overall maximum size of a message's header
15399 section. The default is the value of HEADER_MAXSIZE in
15400 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
15401 sections are rejected.
15404 .option header_line_maxsize main integer 0
15405 .cindex "header lines" "maximum size of"
15406 .cindex "limit" "size of one header line"
15407 This option limits the length of any individual header line in a message, after
15408 all the continuations have been joined together. Messages with individual
15409 header lines that are longer than the limit are rejected. The default value of
15410 zero means &"no limit"&.
15415 .option helo_accept_junk_hosts main "host list&!!" unset
15416 .cindex "HELO" "accepting junk data"
15417 .cindex "EHLO" "accepting junk data"
15418 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
15419 mail, and gives an error response for invalid data. Unfortunately, there are
15420 some SMTP clients that send syntactic junk. They can be accommodated by setting
15421 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
15422 if you want to do semantic checking.
15423 See also &%helo_allow_chars%& for a way of extending the permitted character
15427 .option helo_allow_chars main string unset
15428 .cindex "HELO" "underscores in"
15429 .cindex "EHLO" "underscores in"
15430 .cindex "underscore in EHLO/HELO"
15431 This option can be set to a string of rogue characters that are permitted in
15432 all EHLO and HELO names in addition to the standard letters, digits,
15433 hyphens, and dots. If you really must allow underscores, you can set
15435 helo_allow_chars = _
15437 Note that the value is one string, not a list.
15440 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
15441 .cindex "HELO" "forcing reverse lookup"
15442 .cindex "EHLO" "forcing reverse lookup"
15443 If the domain given by a client in a HELO or EHLO command matches this
15444 list, a reverse lookup is done in order to establish the host's true name. The
15445 default forces a lookup if the client host gives the server's name or any of
15446 its IP addresses (in brackets), something that broken clients have been seen to
15450 .option helo_try_verify_hosts main "host list&!!" unset
15451 .cindex "HELO verifying" "optional"
15452 .cindex "EHLO" "verifying, optional"
15453 By default, Exim just checks the syntax of HELO and EHLO commands (see
15454 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
15455 to do more extensive checking of the data supplied by these commands. The ACL
15456 condition &`verify = helo`& is provided to make this possible.
15457 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
15458 to force the check to occur. From release 4.53 onwards, this is no longer
15459 necessary. If the check has not been done before &`verify = helo`& is
15460 encountered, it is done at that time. Consequently, this option is obsolete.
15461 Its specification is retained here for backwards compatibility.
15463 When an EHLO or HELO command is received, if the calling host matches
15464 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
15465 EHLO command either:
15468 is an IP literal matching the calling address of the host, or
15470 .cindex "DNS" "reverse lookup"
15471 .cindex "reverse DNS lookup"
15472 matches the host name that Exim obtains by doing a reverse lookup of the
15473 calling host address, or
15475 when looked up in DNS yields the calling host address.
15478 However, the EHLO or HELO command is not rejected if any of the checks
15479 fail. Processing continues, but the result of the check is remembered, and can
15480 be detected later in an ACL by the &`verify = helo`& condition.
15482 If DNS was used for successful verification, the variable
15483 .cindex "DNS" "DNSSEC"
15484 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
15486 .option helo_verify_hosts main "host list&!!" unset
15487 .cindex "HELO verifying" "mandatory"
15488 .cindex "EHLO" "verifying, mandatory"
15489 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
15490 backwards compatibility. For hosts that match this option, Exim checks the host
15491 name given in the HELO or EHLO in the same way as for
15492 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
15493 rejected with a 550 error, and entries are written to the main and reject logs.
15494 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
15497 .option hold_domains main "domain list&!!" unset
15498 .cindex "domain" "delaying delivery"
15499 .cindex "delivery" "delaying certain domains"
15500 This option allows mail for particular domains to be held in the queue
15501 manually. The option is overridden if a message delivery is forced with the
15502 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
15503 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
15504 item in &%hold_domains%&, no routing or delivery for that address is done, and
15505 it is deferred every time the message is looked at.
15507 This option is intended as a temporary operational measure for delaying the
15508 delivery of mail while some problem is being sorted out, or some new
15509 configuration tested. If you just want to delay the processing of some
15510 domains until a queue run occurs, you should use &%queue_domains%& or
15511 &%queue_smtp_domains%&, not &%hold_domains%&.
15513 A setting of &%hold_domains%& does not override Exim's code for removing
15514 messages from the queue if they have been there longer than the longest retry
15515 time in any retry rule. If you want to hold messages for longer than the normal
15516 retry times, insert a dummy retry rule with a long retry time.
15519 .option host_lookup main "host list&!!" unset
15520 .cindex "host name" "lookup, forcing"
15521 Exim does not look up the name of a calling host from its IP address unless it
15522 is required to compare against some host list, or the host matches
15523 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
15524 option (which normally contains IP addresses rather than host names). The
15525 default configuration file contains
15529 which causes a lookup to happen for all hosts. If the expense of these lookups
15530 is felt to be too great, the setting can be changed or removed.
15532 After a successful reverse lookup, Exim does a forward lookup on the name it
15533 has obtained, to verify that it yields the IP address that it started with. If
15534 this check fails, Exim behaves as if the name lookup failed.
15536 .vindex "&$host_lookup_failed$&"
15537 .vindex "&$sender_host_name$&"
15538 After any kind of failure, the host name (in &$sender_host_name$&) remains
15539 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
15540 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
15541 &`verify = reverse_host_lookup`& in ACLs.
15544 .option host_lookup_order main "string list" &`bydns:byaddr`&
15545 This option specifies the order of different lookup methods when Exim is trying
15546 to find a host name from an IP address. The default is to do a DNS lookup
15547 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
15548 if that fails. You can change the order of these lookups, or omit one entirely,
15551 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
15552 multiple PTR records in the DNS and the IP address is not listed in
15553 &_/etc/hosts_&. Different operating systems give different results in this
15554 case. That is why the default tries a DNS lookup first.
15558 .option host_reject_connection main "host list&!!" unset
15559 .cindex "host" "rejecting connections from"
15560 If this option is set, incoming SMTP calls from the hosts listed are rejected
15561 as soon as the connection is made.
15562 This option is obsolete, and retained only for backward compatibility, because
15563 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
15564 connections immediately.
15566 The ability to give an immediate rejection (either by this option or using an
15567 ACL) is provided for use in unusual cases. Many hosts will just try again,
15568 sometimes without much delay. Normally, it is better to use an ACL to reject
15569 incoming messages at a later stage, such as after RCPT commands. See
15570 chapter &<<CHAPACL>>&.
15573 .option hosts_connection_nolog main "host list&!!" unset
15574 .cindex "host" "not logging connections from"
15575 This option defines a list of hosts for which connection logging does not
15576 happen, even though the &%smtp_connection%& log selector is set. For example,
15577 you might want not to log SMTP connections from local processes, or from
15578 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
15579 the daemon; you should therefore strive to restrict its value to a short inline
15580 list of IP addresses and networks. To disable logging SMTP connections from
15581 local processes, you must create a host list with an empty item. For example:
15583 hosts_connection_nolog = :
15585 If the &%smtp_connection%& log selector is not set, this option has no effect.
15589 .option hosts_proxy main "host list&!!" unset
15590 .cindex proxy "proxy protocol"
15591 This option enables use of Proxy Protocol proxies for incoming
15592 connections. For details see section &<<SECTproxyInbound>>&.
15595 .option hosts_treat_as_local main "domain list&!!" unset
15596 .cindex "local host" "domains treated as"
15597 .cindex "host" "treated as local"
15598 If this option is set, any host names that match the domain list are treated as
15599 if they were the local host when Exim is scanning host lists obtained from MX
15601 or other sources. Note that the value of this option is a domain list, not a
15602 host list, because it is always used to check host names, not IP addresses.
15604 This option also applies when Exim is matching the special items
15605 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
15606 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
15607 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
15608 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
15609 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
15610 interfaces and recognizing the local host.
15613 .option ibase_servers main "string list" unset
15614 .cindex "InterBase" "server list"
15615 This option provides a list of InterBase servers and associated connection data,
15616 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
15617 The option is available only if Exim has been built with InterBase support.
15621 .option ignore_bounce_errors_after main time 10w
15622 .cindex "bounce message" "discarding"
15623 .cindex "discarding bounce message"
15624 This option affects the processing of bounce messages that cannot be delivered,
15625 that is, those that suffer a permanent delivery failure. (Bounce messages that
15626 suffer temporary delivery failures are of course retried in the usual way.)
15628 After a permanent delivery failure, bounce messages are frozen,
15629 because there is no sender to whom they can be returned. When a frozen bounce
15630 message has been in the queue for more than the given time, it is unfrozen at
15631 the next queue run, and a further delivery is attempted. If delivery fails
15632 again, the bounce message is discarded. This makes it possible to keep failed
15633 bounce messages around for a shorter time than the normal maximum retry time
15634 for frozen messages. For example,
15636 ignore_bounce_errors_after = 12h
15638 retries failed bounce message deliveries after 12 hours, discarding any further
15639 failures. If the value of this option is set to a zero time period, bounce
15640 failures are discarded immediately. Setting a very long time (as in the default
15641 value) has the effect of disabling this option. For ways of automatically
15642 dealing with other kinds of frozen message, see &%auto_thaw%& and
15643 &%timeout_frozen_after%&.
15646 .option ignore_fromline_hosts main "host list&!!" unset
15647 .cindex "&""From""& line"
15648 .cindex "UUCP" "&""From""& line"
15649 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
15650 the headers of a message. By default this is treated as the start of the
15651 message's body, which means that any following headers are not recognized as
15652 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
15653 match those hosts that insist on sending it. If the sender is actually a local
15654 process rather than a remote host, and is using &%-bs%& to inject the messages,
15655 &%ignore_fromline_local%& must be set to achieve this effect.
15658 .option ignore_fromline_local main boolean false
15659 See &%ignore_fromline_hosts%& above.
15661 .option keep_environment main "string list" unset
15662 .cindex "environment" "values from"
15663 This option contains a string list of environment variables to keep.
15664 You have to trust these variables or you have to be sure that
15665 these variables do not impose any security risk. Keep in mind that
15666 during the startup phase Exim is running with an effective UID 0 in most
15667 installations. As the default value is an empty list, the default
15668 environment for using libraries, running embedded Perl code, or running
15669 external binaries is empty, and does not not even contain PATH or HOME.
15671 Actually the list is interpreted as a list of patterns
15672 (&<<SECTlistexpand>>&), except that it is not expanded first.
15674 WARNING: Macro substitution is still done first, so having a macro
15675 FOO and having FOO_HOME in your &%keep_environment%& option may have
15676 unexpected results. You may work around this using a regular expression
15677 that does not match the macro name: ^[F]OO_HOME$.
15679 Current versions of Exim issue a warning during startup if you do not mention
15680 &%keep_environment%& in your runtime configuration file and if your
15681 current environment is not empty. Future versions may not issue that warning
15684 See the &%add_environment%& main config option for a way to set
15685 environment variables to a fixed value. The environment for &(pipe)&
15686 transports is handled separately, see section &<<SECTpipeenv>>& for
15690 .option keep_malformed main time 4d
15691 This option specifies the length of time to keep messages whose spool files
15692 have been corrupted in some way. This should, of course, never happen. At the
15693 next attempt to deliver such a message, it gets removed. The incident is
15697 .option ldap_ca_cert_dir main string unset
15698 .cindex "LDAP", "TLS CA certificate directory"
15699 .cindex certificate "directory for LDAP"
15700 This option indicates which directory contains CA certificates for verifying
15701 a TLS certificate presented by an LDAP server.
15702 While Exim does not provide a default value, your SSL library may.
15703 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
15704 and constrained to be a directory.
15707 .option ldap_ca_cert_file main string unset
15708 .cindex "LDAP", "TLS CA certificate file"
15709 .cindex certificate "file for LDAP"
15710 This option indicates which file contains CA certificates for verifying
15711 a TLS certificate presented by an LDAP server.
15712 While Exim does not provide a default value, your SSL library may.
15713 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
15714 and constrained to be a file.
15717 .option ldap_cert_file main string unset
15718 .cindex "LDAP" "TLS client certificate file"
15719 .cindex certificate "file for LDAP"
15720 This option indicates which file contains an TLS client certificate which
15721 Exim should present to the LDAP server during TLS negotiation.
15722 Should be used together with &%ldap_cert_key%&.
15725 .option ldap_cert_key main string unset
15726 .cindex "LDAP" "TLS client key file"
15727 .cindex certificate "key for LDAP"
15728 This option indicates which file contains the secret/private key to use
15729 to prove identity to the LDAP server during TLS negotiation.
15730 Should be used together with &%ldap_cert_file%&, which contains the
15731 identity to be proven.
15734 .option ldap_cipher_suite main string unset
15735 .cindex "LDAP" "TLS cipher suite"
15736 This controls the TLS cipher-suite negotiation during TLS negotiation with
15737 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
15738 cipher-suite options with OpenSSL (as used by LDAP client libraries).
15741 .option ldap_default_servers main "string list" unset
15742 .cindex "LDAP" "default servers"
15743 This option provides a list of LDAP servers which are tried in turn when an
15744 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
15745 details of LDAP queries. This option is available only when Exim has been built
15749 .option ldap_require_cert main string unset.
15750 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
15751 This should be one of the values "hard", "demand", "allow", "try" or "never".
15752 A value other than one of these is interpreted as "never".
15753 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
15754 Although Exim does not set a default, the LDAP library probably defaults
15758 .option ldap_start_tls main boolean false
15759 .cindex "LDAP" "whether or not to negotiate TLS"
15760 If set, Exim will attempt to negotiate TLS with the LDAP server when
15761 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
15762 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
15764 In the event of failure to negotiate TLS, the action taken is controlled
15765 by &%ldap_require_cert%&.
15766 This option is ignored for &`ldapi`& connections.
15769 .option ldap_version main integer unset
15770 .cindex "LDAP" "protocol version, forcing"
15771 This option can be used to force Exim to set a specific protocol version for
15772 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
15773 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
15774 the LDAP headers; otherwise it is 2. This option is available only when Exim
15775 has been built with LDAP support.
15779 .option local_from_check main boolean true
15780 .cindex "&'Sender:'& header line" "disabling addition of"
15781 .cindex "&'From:'& header line" "disabling checking of"
15782 When a message is submitted locally (that is, not over a TCP/IP connection) by
15783 an untrusted user, Exim removes any existing &'Sender:'& header line, and
15784 checks that the &'From:'& header line matches the login of the calling user and
15785 the domain specified by &%qualify_domain%&.
15787 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
15788 locally submitted message is automatically qualified by Exim, unless the
15789 &%-bnq%& command line option is used.
15791 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
15792 on the local part. If the &'From:'& header line does not match, Exim adds a
15793 &'Sender:'& header with an address constructed from the calling user's login
15794 and the default qualify domain.
15796 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
15797 and no &'Sender:'& header is ever added. If, in addition, you want to retain
15798 &'Sender:'& header lines supplied by untrusted users, you must also set
15799 &%local_sender_retain%& to be true.
15801 .cindex "envelope sender"
15802 These options affect only the header lines in the message. The envelope sender
15803 is still forced to be the login id at the qualify domain unless
15804 &%untrusted_set_sender%& permits the user to supply an envelope sender.
15806 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
15807 request similar header line checking. See section &<<SECTthesenhea>>&, which
15808 has more details about &'Sender:'& processing.
15813 .option local_from_prefix main string unset
15814 When Exim checks the &'From:'& header line of locally submitted messages for
15815 matching the login id (see &%local_from_check%& above), it can be configured to
15816 ignore certain prefixes and suffixes in the local part of the address. This is
15817 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
15818 appropriate lists, in the same form as the &%local_part_prefix%& and
15819 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
15822 local_from_prefix = *-
15824 is set, a &'From:'& line containing
15826 From: anything-user@your.domain.example
15828 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
15829 matches the actual sender address that is constructed from the login name and
15833 .option local_from_suffix main string unset
15834 See &%local_from_prefix%& above.
15837 .option local_interfaces main "string list" "see below"
15838 This option controls which network interfaces are used by the daemon for
15839 listening; they are also used to identify the local host when routing. Chapter
15840 &<<CHAPinterfaces>>& contains a full description of this option and the related
15841 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
15842 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
15843 &%local_interfaces%& is
15845 local_interfaces = 0.0.0.0
15847 when Exim is built without IPv6 support; otherwise it is
15849 local_interfaces = <; ::0 ; 0.0.0.0
15852 .option local_scan_timeout main time 5m
15853 .cindex "timeout" "for &[local_scan()]& function"
15854 .cindex "&[local_scan()]& function" "timeout"
15855 This timeout applies to the &[local_scan()]& function (see chapter
15856 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
15857 the incoming message is rejected with a temporary error if it is an SMTP
15858 message. For a non-SMTP message, the message is dropped and Exim ends with a
15859 non-zero code. The incident is logged on the main and reject logs.
15863 .option local_sender_retain main boolean false
15864 .cindex "&'Sender:'& header line" "retaining from local submission"
15865 When a message is submitted locally (that is, not over a TCP/IP connection) by
15866 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
15867 do not want this to happen, you must set &%local_sender_retain%&, and you must
15868 also set &%local_from_check%& to be false (Exim will complain if you do not).
15869 See also the ACL modifier &`control = suppress_local_fixups`&. Section
15870 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
15875 .option localhost_number main string&!! unset
15876 .cindex "host" "locally unique number for"
15877 .cindex "message ids" "with multiple hosts"
15878 .vindex "&$localhost_number$&"
15879 Exim's message ids are normally unique only within the local host. If
15880 uniqueness among a set of hosts is required, each host must set a different
15881 value for the &%localhost_number%& option. The string is expanded immediately
15882 after reading the configuration file (so that a number can be computed from the
15883 host name, for example) and the result of the expansion must be a number in the
15884 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
15885 systems). This is available in subsequent string expansions via the variable
15886 &$localhost_number$&. When &%localhost_number is set%&, the final two
15887 characters of the message id, instead of just being a fractional part of the
15888 time, are computed from the time and the local host number as described in
15889 section &<<SECTmessiden>>&.
15893 .option log_file_path main "string list&!!" "set at compile time"
15894 .cindex "log" "file path for"
15895 This option sets the path which is used to determine the names of Exim's log
15896 files, or indicates that logging is to be to syslog, or both. It is expanded
15897 when Exim is entered, so it can, for example, contain a reference to the host
15898 name. If no specific path is set for the log files at compile or runtime,
15899 or if the option is unset at runtime (i.e. &`log_file_path = `&)
15900 they are written in a sub-directory called &_log_& in Exim's spool directory.
15901 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
15902 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
15903 used. If this string is fixed at your installation (contains no expansion
15904 variables) it is recommended that you do not set this option in the
15905 configuration file, but instead supply the path using LOG_FILE_PATH in
15906 &_Local/Makefile_& so that it is available to Exim for logging errors detected
15907 early on &-- in particular, failure to read the configuration file.
15910 .option log_selector main string unset
15911 .cindex "log" "selectors"
15912 This option can be used to reduce or increase the number of things that Exim
15913 writes to its log files. Its argument is made up of names preceded by plus or
15914 minus characters. For example:
15916 log_selector = +arguments -retry_defer
15918 A list of possible names and what they control is given in the chapter on
15919 logging, in section &<<SECTlogselector>>&.
15922 .option log_timezone main boolean false
15923 .cindex "log" "timezone for entries"
15924 .vindex "&$tod_log$&"
15925 .vindex "&$tod_zone$&"
15926 By default, the timestamps on log lines are in local time without the
15927 timezone. This means that if your timezone changes twice a year, the timestamps
15928 in log lines are ambiguous for an hour when the clocks go back. One way of
15929 avoiding this problem is to set the timezone to UTC. An alternative is to set
15930 &%log_timezone%& true. This turns on the addition of the timezone offset to
15931 timestamps in log lines. Turning on this option can add quite a lot to the size
15932 of log files because each line is extended by 6 characters. Note that the
15933 &$tod_log$& variable contains the log timestamp without the zone, but there is
15934 another variable called &$tod_zone$& that contains just the timezone offset.
15937 .option lookup_open_max main integer 25
15938 .cindex "too many open files"
15939 .cindex "open files, too many"
15940 .cindex "file" "too many open"
15941 .cindex "lookup" "maximum open files"
15942 .cindex "limit" "open files for lookups"
15943 This option limits the number of simultaneously open files for single-key
15944 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
15945 Exim normally keeps these files open during routing, because often the same
15946 file is required several times. If the limit is reached, Exim closes the least
15947 recently used file. Note that if you are using the &'ndbm'& library, it
15948 actually opens two files for each logical DBM database, though it still counts
15949 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
15950 open files"& errors with NDBM, you need to reduce the value of
15951 &%lookup_open_max%&.
15954 .option max_username_length main integer 0
15955 .cindex "length of login name"
15956 .cindex "user name" "maximum length"
15957 .cindex "limit" "user name length"
15958 Some operating systems are broken in that they truncate long arguments to
15959 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
15960 this option is set greater than zero, any attempt to call &[getpwnam()]& with
15961 an argument that is longer behaves as if &[getpwnam()]& failed.
15964 .option message_body_newlines main bool false
15965 .cindex "message body" "newlines in variables"
15966 .cindex "newline" "in message body variables"
15967 .vindex "&$message_body$&"
15968 .vindex "&$message_body_end$&"
15969 By default, newlines in the message body are replaced by spaces when setting
15970 the &$message_body$& and &$message_body_end$& expansion variables. If this
15971 option is set true, this no longer happens.
15974 .option message_body_visible main integer 500
15975 .cindex "body of message" "visible size"
15976 .cindex "message body" "visible size"
15977 .vindex "&$message_body$&"
15978 .vindex "&$message_body_end$&"
15979 This option specifies how much of a message's body is to be included in the
15980 &$message_body$& and &$message_body_end$& expansion variables.
15983 .option message_id_header_domain main string&!! unset
15984 .cindex "&'Message-ID:'& header line"
15985 If this option is set, the string is expanded and used as the right hand side
15986 (domain) of the &'Message-ID:'& header that Exim creates if a
15987 locally-originated incoming message does not have one. &"Locally-originated"&
15988 means &"not received over TCP/IP."&
15989 Otherwise, the primary host name is used.
15990 Only letters, digits, dot and hyphen are accepted; any other characters are
15991 replaced by hyphens. If the expansion is forced to fail, or if the result is an
15992 empty string, the option is ignored.
15995 .option message_id_header_text main string&!! unset
15996 If this variable is set, the string is expanded and used to augment the text of
15997 the &'Message-id:'& header that Exim creates if a locally-originated incoming
15998 message does not have one. The text of this header is required by RFC 2822 to
15999 take the form of an address. By default, Exim uses its internal message id as
16000 the local part, and the primary host name as the domain. If this option is set,
16001 it is expanded, and provided the expansion is not forced to fail, and does not
16002 yield an empty string, the result is inserted into the header immediately
16003 before the @, separated from the internal message id by a dot. Any characters
16004 that are illegal in an address are automatically converted into hyphens. This
16005 means that variables such as &$tod_log$& can be used, because the spaces and
16006 colons will become hyphens.
16009 .option message_logs main boolean true
16010 .cindex "message logs" "disabling"
16011 .cindex "log" "message log; disabling"
16012 If this option is turned off, per-message log files are not created in the
16013 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
16014 Exim, by reducing the number of files involved in handling a message from a
16015 minimum of four (header spool file, body spool file, delivery journal, and
16016 per-message log) to three. The other major I/O activity is Exim's main log,
16017 which is not affected by this option.
16020 .option message_size_limit main string&!! 50M
16021 .cindex "message" "size limit"
16022 .cindex "limit" "message size"
16023 .cindex "size" "of message, limit"
16024 This option limits the maximum size of message that Exim will process. The
16025 value is expanded for each incoming connection so, for example, it can be made
16026 to depend on the IP address of the remote host for messages arriving via
16027 TCP/IP. After expansion, the value must be a sequence of decimal digits,
16028 optionally followed by K or M.
16030 &*Note*&: This limit cannot be made to depend on a message's sender or any
16031 other properties of an individual message, because it has to be advertised in
16032 the server's response to EHLO. String expansion failure causes a temporary
16033 error. A value of zero means no limit, but its use is not recommended. See also
16034 &%bounce_return_size_limit%&.
16036 Incoming SMTP messages are failed with a 552 error if the limit is
16037 exceeded; locally-generated messages either get a stderr message or a delivery
16038 failure message to the sender, depending on the &%-oe%& setting. Rejection of
16039 an oversized message is logged in both the main and the reject logs. See also
16040 the generic transport option &%message_size_limit%&, which limits the size of
16041 message that an individual transport can process.
16043 If you use a virus-scanner and set this option to to a value larger than the
16044 maximum size that your virus-scanner is configured to support, you may get
16045 failures triggered by large mails. The right size to configure for the
16046 virus-scanner depends upon what data is passed and the options in use but it's
16047 probably safest to just set it to a little larger than this value. E.g., with a
16048 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
16049 some problems may result.
16051 A value of 0 will disable size limit checking; Exim will still advertise the
16052 SIZE extension in an EHLO response, but without a limit, so as to permit
16053 SMTP clients to still indicate the message size along with the MAIL verb.
16056 .option move_frozen_messages main boolean false
16057 .cindex "frozen messages" "moving"
16058 This option, which is available only if Exim has been built with the setting
16060 SUPPORT_MOVE_FROZEN_MESSAGES=yes
16062 in &_Local/Makefile_&, causes frozen messages and their message logs to be
16063 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
16064 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
16065 standard utilities for handling such moved messages, and they do not show up in
16066 lists generated by &%-bp%& or by the Exim monitor.
16069 .option mua_wrapper main boolean false
16070 Setting this option true causes Exim to run in a very restrictive mode in which
16071 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
16072 contains a full description of this facility.
16076 .option mysql_servers main "string list" unset
16077 .cindex "MySQL" "server list"
16078 This option provides a list of MySQL servers and associated connection data, to
16079 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
16080 option is available only if Exim has been built with MySQL support.
16083 .option never_users main "string list&!!" unset
16084 This option is expanded just once, at the start of Exim's processing. Local
16085 message deliveries are normally run in processes that are setuid to the
16086 recipient, and remote deliveries are normally run under Exim's own uid and gid.
16087 It is usually desirable to prevent any deliveries from running as root, as a
16090 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
16091 list of users that must not be used for local deliveries. This list is fixed in
16092 the binary and cannot be overridden by the configuration file. By default, it
16093 contains just the single user name &"root"&. The &%never_users%& runtime option
16094 can be used to add more users to the fixed list.
16096 If a message is to be delivered as one of the users on the fixed list or the
16097 &%never_users%& list, an error occurs, and delivery is deferred. A common
16100 never_users = root:daemon:bin
16102 Including root is redundant if it is also on the fixed list, but it does no
16103 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
16107 .option openssl_options main "string list" "+no_sslv2 +single_dh_use +no_ticket"
16108 .cindex "OpenSSL "compatibility options"
16109 This option allows an administrator to adjust the SSL options applied
16110 by OpenSSL to connections. It is given as a space-separated list of items,
16111 each one to be +added or -subtracted from the current value.
16113 This option is only available if Exim is built against OpenSSL. The values
16114 available for this option vary according to the age of your OpenSSL install.
16115 The &"all"& value controls a subset of flags which are available, typically
16116 the bug workaround options. The &'SSL_CTX_set_options'& man page will
16117 list the values known on your system and Exim should support all the
16118 &"bug workaround"& options and many of the &"modifying"& options. The Exim
16119 names lose the leading &"SSL_OP_"& and are lower-cased.
16121 Note that adjusting the options can have severe impact upon the security of
16122 SSL as used by Exim. It is possible to disable safety checks and shoot
16123 yourself in the foot in various unpleasant ways. This option should not be
16124 adjusted lightly. An unrecognised item will be detected at startup, by
16125 invoking Exim with the &%-bV%& flag.
16127 The option affects Exim operating both as a server and as a client.
16129 Historical note: prior to release 4.80, Exim defaulted this value to
16130 "+dont_insert_empty_fragments", which may still be needed for compatibility
16131 with some clients, but which lowers security by increasing exposure to
16132 some now infamous attacks.
16136 # Make both old MS and old Eudora happy:
16137 openssl_options = -all +microsoft_big_sslv3_buffer \
16138 +dont_insert_empty_fragments
16140 # Disable older protocol versions:
16141 openssl_options = +no_sslv2 +no_sslv3
16144 Possible options may include:
16148 &`allow_unsafe_legacy_renegotiation`&
16150 &`cipher_server_preference`&
16152 &`dont_insert_empty_fragments`&
16156 &`legacy_server_connect`&
16158 &`microsoft_big_sslv3_buffer`&
16160 &`microsoft_sess_id_bug`&
16162 &`msie_sslv2_rsa_padding`&
16164 &`netscape_challenge_bug`&
16166 &`netscape_reuse_cipher_change_bug`&
16170 &`no_session_resumption_on_renegotiation`&
16184 &`safari_ecdhe_ecdsa_bug`&
16188 &`single_ecdh_use`&
16190 &`ssleay_080_client_dh_bug`&
16192 &`sslref2_reuse_cert_type_bug`&
16194 &`tls_block_padding_bug`&
16198 &`tls_rollback_bug`&
16201 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
16202 all clients connecting using the MacOS SecureTransport TLS facility prior
16203 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
16204 to negotiate TLS then this option value might help, provided that your OpenSSL
16205 release is new enough to contain this work-around. This may be a situation
16206 where you have to upgrade OpenSSL to get buggy clients working.
16209 .option oracle_servers main "string list" unset
16210 .cindex "Oracle" "server list"
16211 This option provides a list of Oracle servers and associated connection data,
16212 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
16213 The option is available only if Exim has been built with Oracle support.
16216 .option percent_hack_domains main "domain list&!!" unset
16217 .cindex "&""percent hack""&"
16218 .cindex "source routing" "in email address"
16219 .cindex "address" "source-routed"
16220 The &"percent hack"& is the convention whereby a local part containing a
16221 percent sign is re-interpreted as a new email address, with the percent
16222 replaced by @. This is sometimes called &"source routing"&, though that term is
16223 also applied to RFC 2822 addresses that begin with an @ character. If this
16224 option is set, Exim implements the percent facility for those domains listed,
16225 but no others. This happens before an incoming SMTP address is tested against
16228 &*Warning*&: The &"percent hack"& has often been abused by people who are
16229 trying to get round relaying restrictions. For this reason, it is best avoided
16230 if at all possible. Unfortunately, a number of less security-conscious MTAs
16231 implement it unconditionally. If you are running Exim on a gateway host, and
16232 routing mail through to internal MTAs without processing the local parts, it is
16233 a good idea to reject recipient addresses with percent characters in their
16234 local parts. Exim's default configuration does this.
16237 .option perl_at_start main boolean false
16239 This option is available only when Exim is built with an embedded Perl
16240 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16243 .option perl_startup main string unset
16245 This option is available only when Exim is built with an embedded Perl
16246 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16248 .option perl_startup main boolean false
16250 This Option enables the taint mode of the embedded Perl interpreter.
16253 .option pgsql_servers main "string list" unset
16254 .cindex "PostgreSQL lookup type" "server list"
16255 This option provides a list of PostgreSQL servers and associated connection
16256 data, to be used in conjunction with &(pgsql)& lookups (see section
16257 &<<SECID72>>&). The option is available only if Exim has been built with
16258 PostgreSQL support.
16261 .option pid_file_path main string&!! "set at compile time"
16262 .cindex "daemon" "pid file path"
16263 .cindex "pid file, path for"
16264 This option sets the name of the file to which the Exim daemon writes its
16265 process id. The string is expanded, so it can contain, for example, references
16268 pid_file_path = /var/log/$primary_hostname/exim.pid
16270 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
16272 The value set by the option can be overridden by the &%-oP%& command line
16273 option. A pid file is not written if a &"non-standard"& daemon is run by means
16274 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
16277 .option pipelining_advertise_hosts main "host list&!!" *
16278 .cindex "PIPELINING" "suppressing advertising"
16279 This option can be used to suppress the advertisement of the SMTP
16280 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
16281 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
16282 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
16283 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
16284 that clients will use it; &"out of order"& commands that are &"expected"& do
16285 not count as protocol errors (see &%smtp_max_synprot_errors%&).
16288 .option prdr_enable main boolean false
16289 .cindex "PRDR" "enabling on server"
16290 This option can be used to enable the Per-Recipient Data Response extension
16291 to SMTP, defined by Eric Hall.
16292 If the option is set, PRDR is advertised by Exim when operating as a server.
16293 If the client requests PRDR, and more than one recipient, for a message
16294 an additional ACL is called for each recipient after the message content
16295 is received. See section &<<SECTPRDRACL>>&.
16297 .option preserve_message_logs main boolean false
16298 .cindex "message logs" "preserving"
16299 If this option is set, message log files are not deleted when messages are
16300 completed. Instead, they are moved to a sub-directory of the spool directory
16301 called &_msglog.OLD_&, where they remain available for statistical or debugging
16302 purposes. This is a dangerous option to set on systems with any appreciable
16303 volume of mail. Use with care!
16306 .option primary_hostname main string "see below"
16307 .cindex "name" "of local host"
16308 .cindex "host" "name of local"
16309 .cindex "local host" "name of"
16310 .vindex "&$primary_hostname$&"
16311 This specifies the name of the current host. It is used in the default EHLO or
16312 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
16313 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
16314 The value is also used by default in some SMTP response messages from an Exim
16315 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
16317 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
16318 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
16319 contains only one component, Exim passes it to &[gethostbyname()]& (or
16320 &[getipnodebyname()]& when available) in order to obtain the fully qualified
16321 version. The variable &$primary_hostname$& contains the host name, whether set
16322 explicitly by this option, or defaulted.
16325 .option print_topbitchars main boolean false
16326 .cindex "printing characters"
16327 .cindex "8-bit characters"
16328 By default, Exim considers only those characters whose codes lie in the range
16329 32&--126 to be printing characters. In a number of circumstances (for example,
16330 when writing log entries) non-printing characters are converted into escape
16331 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
16332 is set, code values of 128 and above are also considered to be printing
16335 This option also affects the header syntax checks performed by the
16336 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
16337 the user's full name when constructing From: and Sender: addresses (as
16338 described in section &<<SECTconstr>>&). Setting this option can cause
16339 Exim to generate eight bit message headers that do not conform to the
16343 .option process_log_path main string unset
16344 .cindex "process log path"
16345 .cindex "log" "process log"
16346 .cindex "&'exiwhat'&"
16347 This option sets the name of the file to which an Exim process writes its
16348 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
16349 utility script. If this option is unset, the file called &_exim-process.info_&
16350 in Exim's spool directory is used. The ability to specify the name explicitly
16351 can be useful in environments where two different Exims are running, using
16352 different spool directories.
16355 .option prod_requires_admin main boolean true
16356 .cindex "restricting access to features"
16360 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
16361 admin user unless &%prod_requires_admin%& is set false. See also
16362 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
16365 .option qualify_domain main string "see below"
16366 .cindex "domain" "for qualifying addresses"
16367 .cindex "address" "qualification"
16368 This option specifies the domain name that is added to any envelope sender
16369 addresses that do not have a domain qualification. It also applies to
16370 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
16371 are accepted by default only for locally-generated messages. Qualification is
16372 also applied to addresses in header lines such as &'From:'& and &'To:'& for
16373 locally-generated messages, unless the &%-bnq%& command line option is used.
16375 Messages from external sources must always contain fully qualified addresses,
16376 unless the sending host matches &%sender_unqualified_hosts%& or
16377 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
16378 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
16379 necessary. Internally, Exim always works with fully qualified envelope
16380 addresses. If &%qualify_domain%& is not set, it defaults to the
16381 &%primary_hostname%& value.
16384 .option qualify_recipient main string "see below"
16385 This option allows you to specify a different domain for qualifying recipient
16386 addresses to the one that is used for senders. See &%qualify_domain%& above.
16390 .option queue_domains main "domain list&!!" unset
16391 .cindex "domain" "specifying non-immediate delivery"
16392 .cindex "queueing incoming messages"
16393 .cindex "message" "queueing certain domains"
16394 This option lists domains for which immediate delivery is not required.
16395 A delivery process is started whenever a message is received, but only those
16396 domains that do not match are processed. All other deliveries wait until the
16397 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
16400 .option queue_list_requires_admin main boolean true
16401 .cindex "restricting access to features"
16403 The &%-bp%& command-line option, which lists the messages that are on the
16404 queue, requires the caller to be an admin user unless
16405 &%queue_list_requires_admin%& is set false.
16406 See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
16409 .option queue_only main boolean false
16410 .cindex "queueing incoming messages"
16411 .cindex "message" "queueing unconditionally"
16412 If &%queue_only%& is set, a delivery process is not automatically started
16413 whenever a message is received. Instead, the message waits in the queue for the
16414 next queue run. Even if &%queue_only%& is false, incoming messages may not get
16415 delivered immediately when certain conditions (such as heavy load) occur.
16417 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
16418 and &%-odi%& command line options override &%queue_only%& unless
16419 &%queue_only_override%& is set false. See also &%queue_only_file%&,
16420 &%queue_only_load%&, and &%smtp_accept_queue%&.
16423 .option queue_only_file main string unset
16424 .cindex "queueing incoming messages"
16425 .cindex "message" "queueing by file existence"
16426 This option can be set to a colon-separated list of absolute path names, each
16427 one optionally preceded by &"smtp"&. When Exim is receiving a message,
16428 it tests for the existence of each listed path using a call to &[stat()]&. For
16429 each path that exists, the corresponding queueing option is set.
16430 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
16431 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
16433 queue_only_file = smtp/some/file
16435 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
16436 &_/some/file_& exists.
16439 .option queue_only_load main fixed-point unset
16440 .cindex "load average"
16441 .cindex "queueing incoming messages"
16442 .cindex "message" "queueing by load"
16443 If the system load average is higher than this value, incoming messages from
16444 all sources are queued, and no automatic deliveries are started. If this
16445 happens during local or remote SMTP input, all subsequent messages received on
16446 the same SMTP connection are queued by default, whatever happens to the load in
16447 the meantime, but this can be changed by setting &%queue_only_load_latch%&
16450 Deliveries will subsequently be performed by queue runner processes. This
16451 option has no effect on ancient operating systems on which Exim cannot
16452 determine the load average. See also &%deliver_queue_load_max%& and
16453 &%smtp_load_reserve%&.
16456 .option queue_only_load_latch main boolean true
16457 .cindex "load average" "re-evaluating per message"
16458 When this option is true (the default), once one message has been queued
16459 because the load average is higher than the value set by &%queue_only_load%&,
16460 all subsequent messages received on the same SMTP connection are also queued.
16461 This is a deliberate choice; even though the load average may fall below the
16462 threshold, it doesn't seem right to deliver later messages on the same
16463 connection when not delivering earlier ones. However, there are special
16464 circumstances such as very long-lived connections from scanning appliances
16465 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
16466 should be set false. This causes the value of the load average to be
16467 re-evaluated for each message.
16470 .option queue_only_override main boolean true
16471 .cindex "queueing incoming messages"
16472 When this option is true, the &%-od%&&'x'& command line options override the
16473 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
16474 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
16475 to override; they are accepted, but ignored.
16478 .option queue_run_in_order main boolean false
16479 .cindex "queue runner" "processing messages in order"
16480 If this option is set, queue runs happen in order of message arrival instead of
16481 in an arbitrary order. For this to happen, a complete list of the entire queue
16482 must be set up before the deliveries start. When the queue is all held in a
16483 single directory (the default), a single list is created for both the ordered
16484 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
16485 single list is not created when &%queue_run_in_order%& is false. In this case,
16486 the sub-directories are processed one at a time (in a random order), and this
16487 avoids setting up one huge list for the whole queue. Thus, setting
16488 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
16489 when the queue is large, because of the extra work in setting up the single,
16490 large list. In most situations, &%queue_run_in_order%& should not be set.
16494 .option queue_run_max main integer&!! 5
16495 .cindex "queue runner" "maximum number of"
16496 This controls the maximum number of queue runner processes that an Exim daemon
16497 can run simultaneously. This does not mean that it starts them all at once,
16498 but rather that if the maximum number are still running when the time comes to
16499 start another one, it refrains from starting another one. This can happen with
16500 very large queues and/or very sluggish deliveries. This option does not,
16501 however, interlock with other processes, so additional queue runners can be
16502 started by other means, or by killing and restarting the daemon.
16504 Setting this option to zero does not suppress queue runs; rather, it disables
16505 the limit, allowing any number of simultaneous queue runner processes to be
16506 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
16507 the daemon's command line.
16509 .cindex queues named
16510 .cindex "named queues"
16511 To set limits for different named queues use
16512 an expansion depending on the &$queue_name$& variable.
16514 .option queue_smtp_domains main "domain list&!!" unset
16515 .cindex "queueing incoming messages"
16516 .cindex "message" "queueing remote deliveries"
16517 When this option is set, a delivery process is started whenever a message is
16518 received, routing is performed, and local deliveries take place.
16519 However, if any SMTP deliveries are required for domains that match
16520 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
16521 message waits in the queue for the next queue run. Since routing of the message
16522 has taken place, Exim knows to which remote hosts it must be delivered, and so
16523 when the queue run happens, multiple messages for the same host are delivered
16524 over a single SMTP connection. The &%-odqs%& command line option causes all
16525 SMTP deliveries to be queued in this way, and is equivalent to setting
16526 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
16530 .option receive_timeout main time 0s
16531 .cindex "timeout" "for non-SMTP input"
16532 This option sets the timeout for accepting a non-SMTP message, that is, the
16533 maximum time that Exim waits when reading a message on the standard input. If
16534 the value is zero, it will wait forever. This setting is overridden by the
16535 &%-or%& command line option. The timeout for incoming SMTP messages is
16536 controlled by &%smtp_receive_timeout%&.
16538 .option received_header_text main string&!! "see below"
16539 .cindex "customizing" "&'Received:'& header"
16540 .cindex "&'Received:'& header line" "customizing"
16541 This string defines the contents of the &'Received:'& message header that is
16542 added to each message, except for the timestamp, which is automatically added
16543 on at the end (preceded by a semicolon). The string is expanded each time it is
16544 used. If the expansion yields an empty string, no &'Received:'& header line is
16545 added to the message. Otherwise, the string should start with the text
16546 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
16547 header lines. The default setting is:
16550 received_header_text = Received: \
16551 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
16552 {${if def:sender_ident \
16553 {from ${quote_local_part:$sender_ident} }}\
16554 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
16555 by $primary_hostname \
16556 ${if def:received_protocol {with $received_protocol}} \
16557 ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\
16558 (Exim $version_number)\n\t\
16559 ${if def:sender_address \
16560 {(envelope-from <$sender_address>)\n\t}}\
16561 id $message_exim_id\
16562 ${if def:received_for {\n\tfor $received_for}}
16565 The reference to the TLS cipher is omitted when Exim is built without TLS
16566 support. The use of conditional expansions ensures that this works for both
16567 locally generated messages and messages received from remote hosts, giving
16568 header lines such as the following:
16570 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
16571 by marley.carol.example with esmtp (Exim 4.00)
16572 (envelope-from <bob@carol.example>)
16573 id 16IOWa-00019l-00
16574 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
16575 Received: by scrooge.carol.example with local (Exim 4.00)
16576 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
16578 Until the body of the message has been received, the timestamp is the time when
16579 the message started to be received. Once the body has arrived, and all policy
16580 checks have taken place, the timestamp is updated to the time at which the
16581 message was accepted.
16584 .option received_headers_max main integer 30
16585 .cindex "loop" "prevention"
16586 .cindex "mail loop prevention"
16587 .cindex "&'Received:'& header line" "counting"
16588 When a message is to be delivered, the number of &'Received:'& headers is
16589 counted, and if it is greater than this parameter, a mail loop is assumed to
16590 have occurred, the delivery is abandoned, and an error message is generated.
16591 This applies to both local and remote deliveries.
16594 .option recipient_unqualified_hosts main "host list&!!" unset
16595 .cindex "unqualified addresses"
16596 .cindex "host" "unqualified addresses from"
16597 This option lists those hosts from which Exim is prepared to accept unqualified
16598 recipient addresses in message envelopes. The addresses are made fully
16599 qualified by the addition of the &%qualify_recipient%& value. This option also
16600 affects message header lines. Exim does not reject unqualified recipient
16601 addresses in headers, but it qualifies them only if the message came from a
16602 host that matches &%recipient_unqualified_hosts%&,
16603 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
16604 option was not set.
16607 .option recipients_max main integer 0
16608 .cindex "limit" "number of recipients"
16609 .cindex "recipient" "maximum number"
16610 If this option is set greater than zero, it specifies the maximum number of
16611 original recipients for any message. Additional recipients that are generated
16612 by aliasing or forwarding do not count. SMTP messages get a 452 response for
16613 all recipients over the limit; earlier recipients are delivered as normal.
16614 Non-SMTP messages with too many recipients are failed, and no deliveries are
16617 .cindex "RCPT" "maximum number of incoming"
16618 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
16619 RCPT commands in a single message.
16622 .option recipients_max_reject main boolean false
16623 If this option is set true, Exim rejects SMTP messages containing too many
16624 recipients by giving 552 errors to the surplus RCPT commands, and a 554
16625 error to the eventual DATA command. Otherwise (the default) it gives a 452
16626 error to the surplus RCPT commands and accepts the message on behalf of the
16627 initial set of recipients. The remote server should then re-send the message
16628 for the remaining recipients at a later time.
16631 .option remote_max_parallel main integer 2
16632 .cindex "delivery" "parallelism for remote"
16633 This option controls parallel delivery of one message to a number of remote
16634 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
16635 does all the remote deliveries for a message one by one. Otherwise, if a single
16636 message has to be delivered to more than one remote host, or if several copies
16637 have to be sent to the same remote host, up to &%remote_max_parallel%&
16638 deliveries are done simultaneously. If more than &%remote_max_parallel%&
16639 deliveries are required, the maximum number of processes are started, and as
16640 each one finishes, another is begun. The order of starting processes is the
16641 same as if sequential delivery were being done, and can be controlled by the
16642 &%remote_sort_domains%& option. If parallel delivery takes place while running
16643 with debugging turned on, the debugging output from each delivery process is
16644 tagged with its process id.
16646 This option controls only the maximum number of parallel deliveries for one
16647 message in one Exim delivery process. Because Exim has no central queue
16648 manager, there is no way of controlling the total number of simultaneous
16649 deliveries if the configuration allows a delivery attempt as soon as a message
16652 .cindex "number of deliveries"
16653 .cindex "delivery" "maximum number of"
16654 If you want to control the total number of deliveries on the system, you
16655 need to set the &%queue_only%& option. This ensures that all incoming messages
16656 are added to the queue without starting a delivery process. Then set up an Exim
16657 daemon to start queue runner processes at appropriate intervals (probably
16658 fairly often, for example, every minute), and limit the total number of queue
16659 runners by setting the &%queue_run_max%& parameter. Because each queue runner
16660 delivers only one message at a time, the maximum number of deliveries that can
16661 then take place at once is &%queue_run_max%& multiplied by
16662 &%remote_max_parallel%&.
16664 If it is purely remote deliveries you want to control, use
16665 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
16666 doing the SMTP routing before queueing, so that several messages for the same
16667 host will eventually get delivered down the same connection.
16670 .option remote_sort_domains main "domain list&!!" unset
16671 .cindex "sorting remote deliveries"
16672 .cindex "delivery" "sorting remote"
16673 When there are a number of remote deliveries for a message, they are sorted by
16674 domain into the order given by this list. For example,
16676 remote_sort_domains = *.cam.ac.uk:*.uk
16678 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
16679 then to those in the &%uk%& domain, then to any others.
16682 .option retry_data_expire main time 7d
16683 .cindex "hints database" "data expiry"
16684 This option sets a &"use before"& time on retry information in Exim's hints
16685 database. Any older retry data is ignored. This means that, for example, once a
16686 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
16690 .option retry_interval_max main time 24h
16691 .cindex "retry" "limit on interval"
16692 .cindex "limit" "on retry interval"
16693 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
16694 intervals between delivery attempts for messages that cannot be delivered
16695 straight away. This option sets an overall limit to the length of time between
16696 retries. It cannot be set greater than 24 hours; any attempt to do so forces
16700 .option return_path_remove main boolean true
16701 .cindex "&'Return-path:'& header line" "removing"
16702 RFC 2821, section 4.4, states that an SMTP server must insert a
16703 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
16704 The &'Return-path:'& header preserves the sender address as received in the
16705 MAIL command. This description implies that this header should not be present
16706 in an incoming message. If &%return_path_remove%& is true, any existing
16707 &'Return-path:'& headers are removed from messages at the time they are
16708 received. Exim's transports have options for adding &'Return-path:'& headers at
16709 the time of delivery. They are normally used only for final local deliveries.
16712 .option return_size_limit main integer 100K
16713 This option is an obsolete synonym for &%bounce_return_size_limit%&.
16716 .option rfc1413_hosts main "host list&!!" @[]
16718 .cindex "host" "for RFC 1413 calls"
16719 RFC 1413 identification calls are made to any client host which matches
16720 an item in the list.
16721 The default value specifies just this host, being any local interface
16724 .option rfc1413_query_timeout main time 0s
16725 .cindex "RFC 1413" "query timeout"
16726 .cindex "timeout" "for RFC 1413 call"
16727 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
16728 no RFC 1413 calls are ever made.
16731 .option sender_unqualified_hosts main "host list&!!" unset
16732 .cindex "unqualified addresses"
16733 .cindex "host" "unqualified addresses from"
16734 This option lists those hosts from which Exim is prepared to accept unqualified
16735 sender addresses. The addresses are made fully qualified by the addition of
16736 &%qualify_domain%&. This option also affects message header lines. Exim does
16737 not reject unqualified addresses in headers that contain sender addresses, but
16738 it qualifies them only if the message came from a host that matches
16739 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
16740 using TCP/IP), and the &%-bnq%& option was not set.
16742 .option set_environment main "string list" empty
16743 .cindex "environment"
16744 This option allows to set individual environment variables that the
16745 currently linked libraries and programs in child processes use. The
16746 default list is empty,
16749 .option slow_lookup_log main integer 0
16750 .cindex "logging" "slow lookups"
16751 .cindex "dns" "logging slow lookups"
16752 This option controls logging of slow lookups.
16753 If the value is nonzero it is taken as a number of milliseconds
16754 and lookups taking longer than this are logged.
16755 Currently this applies only to DNS lookups.
16759 .option smtp_accept_keepalive main boolean true
16760 .cindex "keepalive" "on incoming connection"
16761 This option controls the setting of the SO_KEEPALIVE option on incoming
16762 TCP/IP socket connections. When set, it causes the kernel to probe idle
16763 connections periodically, by sending packets with &"old"& sequence numbers. The
16764 other end of the connection should send an acknowledgment if the connection is
16765 still okay or a reset if the connection has been aborted. The reason for doing
16766 this is that it has the beneficial effect of freeing up certain types of
16767 connection that can get stuck when the remote host is disconnected without
16768 tidying up the TCP/IP call properly. The keepalive mechanism takes several
16769 hours to detect unreachable hosts.
16773 .option smtp_accept_max main integer 20
16774 .cindex "limit" "incoming SMTP connections"
16775 .cindex "SMTP" "incoming connection count"
16777 This option specifies the maximum number of simultaneous incoming SMTP calls
16778 that Exim will accept. It applies only to the listening daemon; there is no
16779 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
16780 value is set to zero, no limit is applied. However, it is required to be
16781 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
16782 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
16784 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
16785 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
16786 that limit has not been reached for the client host, &%smtp_accept_reserve%&
16787 and &%smtp_load_reserve%& are then checked before accepting the connection.
16790 .option smtp_accept_max_nonmail main integer 10
16791 .cindex "limit" "non-mail SMTP commands"
16792 .cindex "SMTP" "limiting non-mail commands"
16793 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
16794 the connection if there are too many. This option defines &"too many"&. The
16795 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
16796 client looping sending EHLO, for example. The check is applied only if the
16797 client host matches &%smtp_accept_max_nonmail_hosts%&.
16799 When a new message is expected, one occurrence of RSET is not counted. This
16800 allows a client to send one RSET between messages (this is not necessary,
16801 but some clients do it). Exim also allows one uncounted occurrence of HELO
16802 or EHLO, and one occurrence of STARTTLS between messages. After
16803 starting up a TLS session, another EHLO is expected, and so it too is not
16804 counted. The first occurrence of AUTH in a connection, or immediately
16805 following STARTTLS is not counted. Otherwise, all commands other than
16806 MAIL, RCPT, DATA, and QUIT are counted.
16809 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
16810 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
16811 check by setting this option. The default value makes it apply to all hosts. By
16812 changing the value, you can exclude any badly-behaved hosts that you have to
16816 . Allow this long option name to split; give it unsplit as a fifth argument
16817 . for the automatic .oindex that is generated by .option.
16818 . We insert " &~&~" which is both pretty nasty visually and results in
16819 . non-searchable text. HowItWorks.txt mentions an option for inserting
16820 . zero-width-space, which would be nicer visually and results in (at least)
16821 . html that Firefox will split on when it's forced to reflow (rather than
16822 . inserting a horizontal scrollbar). However, the text is still not
16823 . searchable. NM changed this occurrence for bug 1197 to no longer allow
16824 . the option name to split.
16826 .option "smtp_accept_max_per_connection" main integer 1000 &&&
16827 smtp_accept_max_per_connection
16828 .cindex "SMTP" "limiting incoming message count"
16829 .cindex "limit" "messages per SMTP connection"
16830 The value of this option limits the number of MAIL commands that Exim is
16831 prepared to accept over a single SMTP connection, whether or not each command
16832 results in the transfer of a message. After the limit is reached, a 421
16833 response is given to subsequent MAIL commands. This limit is a safety
16834 precaution against a client that goes mad (incidents of this type have been
16838 .option smtp_accept_max_per_host main string&!! unset
16839 .cindex "limit" "SMTP connections from one host"
16840 .cindex "host" "limiting SMTP connections from"
16841 This option restricts the number of simultaneous IP connections from a single
16842 host (strictly, from a single IP address) to the Exim daemon. The option is
16843 expanded, to enable different limits to be applied to different hosts by
16844 reference to &$sender_host_address$&. Once the limit is reached, additional
16845 connection attempts from the same host are rejected with error code 421. This
16846 is entirely independent of &%smtp_accept_reserve%&. The option's default value
16847 of zero imposes no limit. If this option is set greater than zero, it is
16848 required that &%smtp_accept_max%& be non-zero.
16850 &*Warning*&: When setting this option you should not use any expansion
16851 constructions that take an appreciable amount of time. The expansion and test
16852 happen in the main daemon loop, in order to reject additional connections
16853 without forking additional processes (otherwise a denial-of-service attack
16854 could cause a vast number or processes to be created). While the daemon is
16855 doing this processing, it cannot accept any other incoming connections.
16859 .option smtp_accept_queue main integer 0
16860 .cindex "SMTP" "incoming connection count"
16861 .cindex "queueing incoming messages"
16862 .cindex "message" "queueing by SMTP connection count"
16863 If the number of simultaneous incoming SMTP connections being handled via the
16864 listening daemon exceeds this value, messages received by SMTP are just placed
16865 in the queue; no delivery processes are started automatically. The count is
16866 fixed at the start of an SMTP connection. It cannot be updated in the
16867 subprocess that receives messages, and so the queueing or not queueing applies
16868 to all messages received in the same connection.
16870 A value of zero implies no limit, and clearly any non-zero value is useful only
16871 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
16872 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
16873 various &%-od%&&'x'& command line options.
16876 . See the comment on smtp_accept_max_per_connection
16878 .option "smtp_accept_queue_per_connection" main integer 10 &&&
16879 smtp_accept_queue_per_connection
16880 .cindex "queueing incoming messages"
16881 .cindex "message" "queueing by message count"
16882 This option limits the number of delivery processes that Exim starts
16883 automatically when receiving messages via SMTP, whether via the daemon or by
16884 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
16885 and the number of messages received in a single SMTP session exceeds this
16886 number, subsequent messages are placed in the queue, but no delivery processes
16887 are started. This helps to limit the number of Exim processes when a server
16888 restarts after downtime and there is a lot of mail waiting for it on other
16889 systems. On large systems, the default should probably be increased, and on
16890 dial-in client systems it should probably be set to zero (that is, disabled).
16893 .option smtp_accept_reserve main integer 0
16894 .cindex "SMTP" "incoming call count"
16895 .cindex "host" "reserved"
16896 When &%smtp_accept_max%& is set greater than zero, this option specifies a
16897 number of SMTP connections that are reserved for connections from the hosts
16898 that are specified in &%smtp_reserve_hosts%&. The value set in
16899 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
16900 restricted to this number of connections; the option specifies a minimum number
16901 of connection slots for them, not a maximum. It is a guarantee that this group
16902 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
16903 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
16906 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
16907 set to 5, once there are 45 active connections (from any hosts), new
16908 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
16909 provided the other criteria for acceptance are met.
16912 .option smtp_active_hostname main string&!! unset
16913 .cindex "host" "name in SMTP responses"
16914 .cindex "SMTP" "host name in responses"
16915 .vindex "&$primary_hostname$&"
16916 This option is provided for multi-homed servers that want to masquerade as
16917 several different hosts. At the start of an incoming SMTP connection, its value
16918 is expanded and used instead of the value of &$primary_hostname$& in SMTP
16919 responses. For example, it is used as domain name in the response to an
16920 incoming HELO or EHLO command.
16922 .vindex "&$smtp_active_hostname$&"
16923 The active hostname is placed in the &$smtp_active_hostname$& variable, which
16924 is saved with any messages that are received. It is therefore available for use
16925 in routers and transports when the message is later delivered.
16927 If this option is unset, or if its expansion is forced to fail, or if the
16928 expansion results in an empty string, the value of &$primary_hostname$& is
16929 used. Other expansion failures cause a message to be written to the main and
16930 panic logs, and the SMTP command receives a temporary error. Typically, the
16931 value of &%smtp_active_hostname%& depends on the incoming interface address.
16934 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
16935 {cox.mydomain}{box.mydomain}}
16938 Although &$smtp_active_hostname$& is primarily concerned with incoming
16939 messages, it is also used as the default for HELO commands in callout
16940 verification if there is no remote transport from which to obtain a
16941 &%helo_data%& value.
16943 .option smtp_banner main string&!! "see below"
16944 .cindex "SMTP" "welcome banner"
16945 .cindex "banner for SMTP"
16946 .cindex "welcome banner for SMTP"
16947 .cindex "customizing" "SMTP banner"
16948 This string, which is expanded every time it is used, is output as the initial
16949 positive response to an SMTP connection. The default setting is:
16951 smtp_banner = $smtp_active_hostname ESMTP Exim \
16952 $version_number $tod_full
16954 Failure to expand the string causes a panic error. If you want to create a
16955 multiline response to the initial SMTP connection, use &"\n"& in the string at
16956 appropriate points, but not at the end. Note that the 220 code is not included
16957 in this string. Exim adds it automatically (several times in the case of a
16958 multiline response).
16961 .option smtp_check_spool_space main boolean true
16962 .cindex "checking disk space"
16963 .cindex "disk space, checking"
16964 .cindex "spool directory" "checking space"
16965 When this option is set, if an incoming SMTP session encounters the SIZE
16966 option on a MAIL command, it checks that there is enough space in the
16967 spool directory's partition to accept a message of that size, while still
16968 leaving free the amount specified by &%check_spool_space%& (even if that value
16969 is zero). If there isn't enough space, a temporary error code is returned.
16972 .option smtp_connect_backlog main integer 20
16973 .cindex "connection backlog"
16974 .cindex "SMTP" "connection backlog"
16975 .cindex "backlog of connections"
16976 This option specifies a maximum number of waiting SMTP connections. Exim passes
16977 this value to the TCP/IP system when it sets up its listener. Once this number
16978 of connections are waiting for the daemon's attention, subsequent connection
16979 attempts are refused at the TCP/IP level. At least, that is what the manuals
16980 say; in some circumstances such connection attempts have been observed to time
16981 out instead. For large systems it is probably a good idea to increase the
16982 value (to 50, say). It also gives some protection against denial-of-service
16983 attacks by SYN flooding.
16986 .option smtp_enforce_sync main boolean true
16987 .cindex "SMTP" "synchronization checking"
16988 .cindex "synchronization checking in SMTP"
16989 The SMTP protocol specification requires the client to wait for a response from
16990 the server at certain points in the dialogue. Without PIPELINING these
16991 synchronization points are after every command; with PIPELINING they are
16992 fewer, but they still exist.
16994 Some spamming sites send out a complete set of SMTP commands without waiting
16995 for any response. Exim protects against this by rejecting a message if the
16996 client has sent further input when it should not have. The error response &"554
16997 SMTP synchronization error"& is sent, and the connection is dropped. Testing
16998 for this error cannot be perfect because of transmission delays (unexpected
16999 input may be on its way but not yet received when Exim checks). However, it
17000 does detect many instances.
17002 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
17003 If you want to disable the check selectively (for example, only for certain
17004 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
17005 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
17009 .option smtp_etrn_command main string&!! unset
17010 .cindex "ETRN" "command to be run"
17011 .vindex "&$domain$&"
17012 If this option is set, the given command is run whenever an SMTP ETRN
17013 command is received from a host that is permitted to issue such commands (see
17014 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
17015 are independently expanded. The expansion variable &$domain$& is set to the
17016 argument of the ETRN command, and no syntax checking is done on it. For
17019 smtp_etrn_command = /etc/etrn_command $domain \
17020 $sender_host_address
17022 A new process is created to run the command, but Exim does not wait for it to
17023 complete. Consequently, its status cannot be checked. If the command cannot be
17024 run, a line is written to the panic log, but the ETRN caller still receives
17025 a 250 success response. Exim is normally running under its own uid when
17026 receiving SMTP, so it is not possible for it to change the uid before running
17030 .option smtp_etrn_serialize main boolean true
17031 .cindex "ETRN" "serializing"
17032 When this option is set, it prevents the simultaneous execution of more than
17033 one identical command as a result of ETRN in an SMTP connection. See
17034 section &<<SECTETRN>>& for details.
17037 .option smtp_load_reserve main fixed-point unset
17038 .cindex "load average"
17039 If the system load average ever gets higher than this, incoming SMTP calls are
17040 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
17041 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
17042 the load is over the limit. The option has no effect on ancient operating
17043 systems on which Exim cannot determine the load average. See also
17044 &%deliver_queue_load_max%& and &%queue_only_load%&.
17048 .option smtp_max_synprot_errors main integer 3
17049 .cindex "SMTP" "limiting syntax and protocol errors"
17050 .cindex "limit" "SMTP syntax and protocol errors"
17051 Exim rejects SMTP commands that contain syntax or protocol errors. In
17052 particular, a syntactically invalid email address, as in this command:
17054 RCPT TO:<abc xyz@a.b.c>
17056 causes immediate rejection of the command, before any other tests are done.
17057 (The ACL cannot be run if there is no valid address to set up for it.) An
17058 example of a protocol error is receiving RCPT before MAIL. If there are
17059 too many syntax or protocol errors in one SMTP session, the connection is
17060 dropped. The limit is set by this option.
17062 .cindex "PIPELINING" "expected errors"
17063 When the PIPELINING extension to SMTP is in use, some protocol errors are
17064 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
17065 Exim assumes that PIPELINING will be used if it advertises it (see
17066 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
17067 not count towards the limit.
17071 .option smtp_max_unknown_commands main integer 3
17072 .cindex "SMTP" "limiting unknown commands"
17073 .cindex "limit" "unknown SMTP commands"
17074 If there are too many unrecognized commands in an incoming SMTP session, an
17075 Exim server drops the connection. This is a defence against some kinds of abuse
17078 into making connections to SMTP ports; in these circumstances, a number of
17079 non-SMTP command lines are sent first.
17083 .option smtp_ratelimit_hosts main "host list&!!" unset
17084 .cindex "SMTP" "rate limiting"
17085 .cindex "limit" "rate of message arrival"
17086 .cindex "RCPT" "rate limiting"
17087 Some sites find it helpful to be able to limit the rate at which certain hosts
17088 can send them messages, and the rate at which an individual message can specify
17091 Exim has two rate-limiting facilities. This section describes the older
17092 facility, which can limit rates within a single connection. The newer
17093 &%ratelimit%& ACL condition can limit rates across all connections. See section
17094 &<<SECTratelimiting>>& for details of the newer facility.
17096 When a host matches &%smtp_ratelimit_hosts%&, the values of
17097 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
17098 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
17099 respectively. Each option, if set, must contain a set of four comma-separated
17103 A threshold, before which there is no rate limiting.
17105 An initial time delay. Unlike other times in Exim, numbers with decimal
17106 fractional parts are allowed here.
17108 A factor by which to increase the delay each time.
17110 A maximum value for the delay. This should normally be less than 5 minutes,
17111 because after that time, the client is liable to timeout the SMTP command.
17114 For example, these settings have been used successfully at the site which
17115 first suggested this feature, for controlling mail from their customers:
17117 smtp_ratelimit_mail = 2,0.5s,1.05,4m
17118 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
17120 The first setting specifies delays that are applied to MAIL commands after
17121 two have been received over a single connection. The initial delay is 0.5
17122 seconds, increasing by a factor of 1.05 each time. The second setting applies
17123 delays to RCPT commands when more than four occur in a single message.
17126 .option smtp_ratelimit_mail main string unset
17127 See &%smtp_ratelimit_hosts%& above.
17130 .option smtp_ratelimit_rcpt main string unset
17131 See &%smtp_ratelimit_hosts%& above.
17134 .option smtp_receive_timeout main time&!! 5m
17135 .cindex "timeout" "for SMTP input"
17136 .cindex "SMTP" "input timeout"
17137 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
17138 input, including batch SMTP. If a line of input (either an SMTP command or a
17139 data line) is not received within this time, the SMTP connection is dropped and
17140 the message is abandoned.
17141 A line is written to the log containing one of the following messages:
17143 SMTP command timeout on connection from...
17144 SMTP data timeout on connection from...
17146 The former means that Exim was expecting to read an SMTP command; the latter
17147 means that it was in the DATA phase, reading the contents of a message.
17149 If the first character of the option is a &"$"& the option is
17150 expanded before use and may depend on
17151 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
17155 The value set by this option can be overridden by the
17156 &%-os%& command-line option. A setting of zero time disables the timeout, but
17157 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
17158 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
17159 timeout is controlled by &%receive_timeout%& and &%-or%&.
17162 .option smtp_reserve_hosts main "host list&!!" unset
17163 This option defines hosts for which SMTP connections are reserved; see
17164 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
17167 .option smtp_return_error_details main boolean false
17168 .cindex "SMTP" "details policy failures"
17169 .cindex "policy control" "rejection, returning details"
17170 In the default state, Exim uses bland messages such as
17171 &"Administrative prohibition"& when it rejects SMTP commands for policy
17172 reasons. Many sysadmins like this because it gives away little information
17173 to spammers. However, some other sysadmins who are applying strict checking
17174 policies want to give out much fuller information about failures. Setting
17175 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
17176 example, instead of &"Administrative prohibition"&, it might give:
17178 550-Rejected after DATA: '>' missing at end of address:
17179 550 failing address in "From" header is: <user@dom.ain
17183 .option smtputf8_advertise_hosts main "host list&!!" *
17184 .cindex "SMTPUTF8" "advertising"
17185 When Exim is built with support for internationalised mail names,
17186 the availability thereof is advertised in
17187 response to EHLO only to those client hosts that match this option. See
17188 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
17191 .option spamd_address main string "127.0.0.1 783"
17192 This option is available when Exim is compiled with the content-scanning
17193 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
17194 See section &<<SECTscanspamass>>& for more details.
17198 .option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
17199 This option is available when Exim is compiled with SPF support.
17200 See section &<<SECSPF>>& for more details.
17204 .option split_spool_directory main boolean false
17205 .cindex "multiple spool directories"
17206 .cindex "spool directory" "split"
17207 .cindex "directories, multiple"
17208 If this option is set, it causes Exim to split its input directory into 62
17209 subdirectories, each with a single alphanumeric character as its name. The
17210 sixth character of the message id is used to allocate messages to
17211 subdirectories; this is the least significant base-62 digit of the time of
17212 arrival of the message.
17214 Splitting up the spool in this way may provide better performance on systems
17215 where there are long mail queues, by reducing the number of files in any one
17216 directory. The msglog directory is also split up in a similar way to the input
17217 directory; however, if &%preserve_message_logs%& is set, all old msglog files
17218 are still placed in the single directory &_msglog.OLD_&.
17220 It is not necessary to take any special action for existing messages when
17221 changing &%split_spool_directory%&. Exim notices messages that are in the
17222 &"wrong"& place, and continues to process them. If the option is turned off
17223 after a period of being on, the subdirectories will eventually empty and be
17224 automatically deleted.
17226 When &%split_spool_directory%& is set, the behaviour of queue runner processes
17227 changes. Instead of creating a list of all messages in the queue, and then
17228 trying to deliver each one, in turn, it constructs a list of those in one
17229 sub-directory and tries to deliver them, before moving on to the next
17230 sub-directory. The sub-directories are processed in a random order. This
17231 spreads out the scanning of the input directories, and uses less memory. It is
17232 particularly beneficial when there are lots of messages in the queue. However,
17233 if &%queue_run_in_order%& is set, none of this new processing happens. The
17234 entire queue has to be scanned and sorted before any deliveries can start.
17237 .option spool_directory main string&!! "set at compile time"
17238 .cindex "spool directory" "path to"
17239 This defines the directory in which Exim keeps its spool, that is, the messages
17240 it is waiting to deliver. The default value is taken from the compile-time
17241 configuration setting, if there is one. If not, this option must be set. The
17242 string is expanded, so it can contain, for example, a reference to
17243 &$primary_hostname$&.
17245 If the spool directory name is fixed on your installation, it is recommended
17246 that you set it at build time rather than from this option, particularly if the
17247 log files are being written to the spool directory (see &%log_file_path%&).
17248 Otherwise log files cannot be used for errors that are detected early on, such
17249 as failures in the configuration file.
17251 By using this option to override the compiled-in path, it is possible to run
17252 tests of Exim without using the standard spool.
17254 .option spool_wireformat main boolean false
17255 .cindex "spool directory" "file formats"
17256 If this option is set, Exim may for some messages use an alternative format
17257 for data-files in the spool which matches the wire format.
17258 Doing this permits more efficient message reception and transmission.
17259 Currently it is only done for messages received using the ESMTP CHUNKING
17262 The following variables will not have useful values:
17264 $max_received_linelength
17269 Users of the local_scan() API (see &<<CHAPlocalscan>>&),
17270 and any external programs which are passed a reference to a message data file
17271 (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
17272 will need to be aware of the different formats potentially available.
17274 Using any of the ACL conditions noted will negate the reception benefit
17275 (as a Unix-mbox-format file is constructed for them).
17276 The transmission benefit is maintained.
17278 .option sqlite_lock_timeout main time 5s
17279 .cindex "sqlite lookup type" "lock timeout"
17280 This option controls the timeout that the &(sqlite)& lookup uses when trying to
17281 access an SQLite database. See section &<<SECTsqlite>>& for more details.
17283 .option strict_acl_vars main boolean false
17284 .cindex "&ACL;" "variables, handling unset"
17285 This option controls what happens if a syntactically valid but undefined ACL
17286 variable is referenced. If it is false (the default), an empty string
17287 is substituted; if it is true, an error is generated. See section
17288 &<<SECTaclvariables>>& for details of ACL variables.
17290 .option strip_excess_angle_brackets main boolean false
17291 .cindex "angle brackets, excess"
17292 If this option is set, redundant pairs of angle brackets round &"route-addr"&
17293 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
17294 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
17295 passed on to another MTA, the excess angle brackets are not passed on. If this
17296 option is not set, multiple pairs of angle brackets cause a syntax error.
17299 .option strip_trailing_dot main boolean false
17300 .cindex "trailing dot on domain"
17301 .cindex "dot" "trailing on domain"
17302 If this option is set, a trailing dot at the end of a domain in an address is
17303 ignored. If this is in the envelope and the message is passed on to another
17304 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
17305 domain causes a syntax error.
17306 However, addresses in header lines are checked only when an ACL requests header
17310 .option syslog_duplication main boolean true
17311 .cindex "syslog" "duplicate log lines; suppressing"
17312 When Exim is logging to syslog, it writes the log lines for its three
17313 separate logs at different syslog priorities so that they can in principle
17314 be separated on the logging hosts. Some installations do not require this
17315 separation, and in those cases, the duplication of certain log lines is a
17316 nuisance. If &%syslog_duplication%& is set false, only one copy of any
17317 particular log line is written to syslog. For lines that normally go to
17318 both the main log and the reject log, the reject log version (possibly
17319 containing message header lines) is written, at LOG_NOTICE priority.
17320 Lines that normally go to both the main and the panic log are written at
17321 the LOG_ALERT priority.
17324 .option syslog_facility main string unset
17325 .cindex "syslog" "facility; setting"
17326 This option sets the syslog &"facility"& name, used when Exim is logging to
17327 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
17328 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
17329 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
17330 details of Exim's logging.
17333 .option syslog_pid main boolean true
17334 .cindex "syslog" "pid"
17335 If &%syslog_pid%& is set false, the PID on Exim's log lines are
17336 omitted when these lines are sent to syslog. (Syslog normally prefixes
17337 the log lines with the PID of the logging process automatically.) You need
17338 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
17339 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
17343 .option syslog_processname main string &`exim`&
17344 .cindex "syslog" "process name; setting"
17345 This option sets the syslog &"ident"& name, used when Exim is logging to
17346 syslog. The value must be no longer than 32 characters. See chapter
17347 &<<CHAPlog>>& for details of Exim's logging.
17351 .option syslog_timestamp main boolean true
17352 .cindex "syslog" "timestamps"
17353 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
17354 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
17355 details of Exim's logging.
17358 .option system_filter main string&!! unset
17359 .cindex "filter" "system filter"
17360 .cindex "system filter" "specifying"
17361 .cindex "Sieve filter" "not available for system filter"
17362 This option specifies an Exim filter file that is applied to all messages at
17363 the start of each delivery attempt, before any routing is done. System filters
17364 must be Exim filters; they cannot be Sieve filters. If the system filter
17365 generates any deliveries to files or pipes, or any new mail messages, the
17366 appropriate &%system_filter_..._transport%& option(s) must be set, to define
17367 which transports are to be used. Details of this facility are given in chapter
17368 &<<CHAPsystemfilter>>&.
17369 A forced expansion failure results in no filter operation.
17372 .option system_filter_directory_transport main string&!! unset
17373 .vindex "&$address_file$&"
17374 This sets the name of the transport driver that is to be used when the
17375 &%save%& command in a system message filter specifies a path ending in &"/"&,
17376 implying delivery of each message into a separate file in some directory.
17377 During the delivery, the variable &$address_file$& contains the path name.
17380 .option system_filter_file_transport main string&!! unset
17381 .cindex "file" "transport for system filter"
17382 This sets the name of the transport driver that is to be used when the &%save%&
17383 command in a system message filter specifies a path not ending in &"/"&. During
17384 the delivery, the variable &$address_file$& contains the path name.
17386 .option system_filter_group main string unset
17387 .cindex "gid (group id)" "system filter"
17388 This option is used only when &%system_filter_user%& is also set. It sets the
17389 gid under which the system filter is run, overriding any gid that is associated
17390 with the user. The value may be numerical or symbolic.
17392 .option system_filter_pipe_transport main string&!! unset
17393 .cindex "&(pipe)& transport" "for system filter"
17394 .vindex "&$address_pipe$&"
17395 This specifies the transport driver that is to be used when a &%pipe%& command
17396 is used in a system filter. During the delivery, the variable &$address_pipe$&
17397 contains the pipe command.
17400 .option system_filter_reply_transport main string&!! unset
17401 .cindex "&(autoreply)& transport" "for system filter"
17402 This specifies the transport driver that is to be used when a &%mail%& command
17403 is used in a system filter.
17406 .option system_filter_user main string unset
17407 .cindex "uid (user id)" "system filter"
17408 If this option is set to root, the system filter is run in the main Exim
17409 delivery process, as root. Otherwise, the system filter runs in a separate
17410 process, as the given user, defaulting to the Exim run-time user.
17411 Unless the string consists entirely of digits, it
17412 is looked up in the password data. Failure to find the named user causes a
17413 configuration error. The gid is either taken from the password data, or
17414 specified by &%system_filter_group%&. When the uid is specified numerically,
17415 &%system_filter_group%& is required to be set.
17417 If the system filter generates any pipe, file, or reply deliveries, the uid
17418 under which the filter is run is used when transporting them, unless a
17419 transport option overrides.
17422 .option tcp_nodelay main boolean true
17423 .cindex "daemon" "TCP_NODELAY on sockets"
17424 .cindex "Nagle algorithm"
17425 .cindex "TCP_NODELAY on listening sockets"
17426 If this option is set false, it stops the Exim daemon setting the
17427 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
17428 turns off the &"Nagle algorithm"&, which is a way of improving network
17429 performance in interactive (character-by-character) situations. Turning it off
17430 should improve Exim's performance a bit, so that is what happens by default.
17431 However, it appears that some broken clients cannot cope, and time out. Hence
17432 this option. It affects only those sockets that are set up for listening by the
17433 daemon. Sockets created by the smtp transport for delivering mail always set
17437 .option timeout_frozen_after main time 0s
17438 .cindex "frozen messages" "timing out"
17439 .cindex "timeout" "frozen messages"
17440 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
17441 message of any kind that has been in the queue for longer than the given time
17442 is automatically cancelled at the next queue run. If the frozen message is a
17443 bounce message, it is just discarded; otherwise, a bounce is sent to the
17444 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
17445 If you want to timeout frozen bounce messages earlier than other kinds of
17446 frozen message, see &%ignore_bounce_errors_after%&.
17448 &*Note:*& the default value of zero means no timeouts; with this setting,
17449 frozen messages remain in the queue forever (except for any frozen bounce
17450 messages that are released by &%ignore_bounce_errors_after%&).
17453 .option timezone main string unset
17454 .cindex "timezone, setting"
17455 .cindex "environment" "values from"
17456 The value of &%timezone%& is used to set the environment variable TZ while
17457 running Exim (if it is different on entry). This ensures that all timestamps
17458 created by Exim are in the required timezone. If you want all your timestamps
17459 to be in UTC (aka GMT) you should set
17463 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
17464 or, if that is not set, from the value of the TZ environment variable when Exim
17465 is built. If &%timezone%& is set to the empty string, either at build or run
17466 time, any existing TZ variable is removed from the environment when Exim
17467 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
17468 unfortunately not all, operating systems.
17471 .option tls_advertise_hosts main "host list&!!" *
17472 .cindex "TLS" "advertising"
17473 .cindex "encryption" "on SMTP connection"
17474 .cindex "SMTP" "encrypted connection"
17475 When Exim is built with support for TLS encrypted connections, the availability
17476 of the STARTTLS command to set up an encrypted session is advertised in
17477 response to EHLO only to those client hosts that match this option. See
17478 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
17479 Note that the default value requires that a certificate be supplied
17480 using the &%tls_certificate%& option. If TLS support for incoming connections
17481 is not required the &%tls_advertise_hosts%& option should be set empty.
17484 .option tls_certificate main string list&!! unset
17485 .cindex "TLS" "server certificate; location of"
17486 .cindex "certificate" "server, location of"
17487 The value of this option is expanded, and must then be a list of absolute paths to
17488 files which contains the server's certificates. Commonly only one file is
17490 The server's private key is also
17491 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
17492 &<<CHAPTLS>>& for further details.
17494 &*Note*&: The certificates defined by this option are used only when Exim is
17495 receiving incoming messages as a server. If you want to supply certificates for
17496 use when sending messages as a client, you must set the &%tls_certificate%&
17497 option in the relevant &(smtp)& transport.
17499 &*Note*&: If you use filenames based on IP addresses, change the list
17500 separator in the usual way (&<<SECTlistsepchange>>&) >to avoid confusion under IPv6.
17502 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
17503 when a list of more than one
17504 file is used, the &$tls_in_ourcert$& variable is unreliable.
17506 &*Note*&: OCSP stapling is not usable under OpenSSL
17507 when a list of more than one file is used.
17509 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
17510 if the OpenSSL build supports TLS extensions and the TLS client sends the
17511 Server Name Indication extension, then this option and others documented in
17512 &<<SECTtlssni>>& will be re-expanded.
17514 If this option is unset or empty a fresh self-signed certificate will be
17515 generated for every connection.
17517 .option tls_crl main string&!! unset
17518 .cindex "TLS" "server certificate revocation list"
17519 .cindex "certificate" "revocation list for server"
17520 This option specifies a certificate revocation list. The expanded value must
17521 be the name of a file that contains CRLs in PEM format.
17523 Under OpenSSL the option can specify a directory with CRL files.
17525 &*Note:*& Under OpenSSL the option must, if given, supply a CRL
17526 for each signing element of the certificate chain (i.e. all but the leaf).
17527 For the file variant this can be multiple PEM blocks in the one file.
17529 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17532 .option tls_dh_max_bits main integer 2236
17533 .cindex "TLS" "D-H bit count"
17534 The number of bits used for Diffie-Hellman key-exchange may be suggested by
17535 the chosen TLS library. That value might prove to be too high for
17536 interoperability. This option provides a maximum clamp on the value
17537 suggested, trading off security for interoperability.
17539 The value must be at least 1024.
17541 The value 2236 was chosen because, at time of adding the option, it was the
17542 hard-coded maximum value supported by the NSS cryptographic library, as used
17543 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
17545 If you prefer more security and are willing to break some clients, raise this
17548 Note that the value passed to GnuTLS for *generating* a new prime may be a
17549 little less than this figure, because GnuTLS is inexact and may produce a
17550 larger prime than requested.
17553 .option tls_dhparam main string&!! unset
17554 .cindex "TLS" "D-H parameters for server"
17555 The value of this option is expanded and indicates the source of DH parameters
17556 to be used by Exim.
17558 &*Note: The Exim Maintainers strongly recommend using a filename with site-generated
17559 local DH parameters*&, which has been supported across all versions of Exim. The
17560 other specific constants available are a fallback so that even when
17561 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
17563 If &%tls_dhparam%& is a filename starting with a &`/`&,
17564 then it names a file from which DH
17565 parameters should be loaded. If the file exists, it should hold a PEM-encoded
17566 PKCS#3 representation of the DH prime. If the file does not exist, for
17567 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
17568 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
17569 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
17570 and treated as though the &%tls_dhparam%& were set to "none".
17572 If this option expands to the string "none", then no DH parameters will be
17575 If this option expands to the string "historic" and Exim is using GnuTLS, then
17576 Exim will attempt to load a file from inside the spool directory. If the file
17577 does not exist, Exim will attempt to create it.
17578 See section &<<SECTgnutlsparam>>& for further details.
17580 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
17581 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
17583 In older versions of Exim the default was the 2048 bit prime described in section
17584 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
17585 in IKE is assigned number 23.
17587 Otherwise, the option must expand to the name used by Exim for any of a number
17588 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
17589 sources. As names, Exim uses a standard specified name, else "ike" followed by
17590 the number used by IKE, or "default" which corresponds to
17591 &`exim.dev.20160529.3`&.
17593 The available standard primes are:
17594 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
17595 &`ike1`&, &`ike2`&, &`ike5`&,
17596 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
17597 &`ike22`&, &`ike23`& and &`ike24`&.
17599 The available additional primes are:
17600 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
17602 Some of these will be too small to be accepted by clients.
17603 Some may be too large to be accepted by clients.
17604 The open cryptographic community has suspicions about the integrity of some
17605 of the later IKE values, which led into RFC7919 providing new fixed constants
17606 (the "ffdhe" identifiers).
17608 At this point, all of the "ike" values should be considered obsolete;
17609 they're still in Exim to avoid breaking unusual configurations, but are
17610 candidates for removal the next time we have backwards-incompatible changes.
17612 The TLS protocol does not negotiate an acceptable size for this; clients tend
17613 to hard-drop connections if what is offered by the server is unacceptable,
17614 whether too large or too small, and there's no provision for the client to
17615 tell the server what these constraints are. Thus, as a server operator, you
17616 need to make an educated guess as to what is most likely to work for your
17619 Some known size constraints suggest that a bit-size in the range 2048 to 2236
17620 is most likely to maximise interoperability. The upper bound comes from
17621 applications using the Mozilla Network Security Services (NSS) library, which
17622 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
17623 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
17624 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
17625 acceptable bound from 1024 to 2048.
17628 .option tls_eccurve main string&!! &`auto`&
17629 .cindex TLS "EC cryptography"
17630 This option selects a EC curve for use by Exim when used with OpenSSL.
17631 It has no effect when Exim is used with GnuTLS.
17633 After expansion it must contain a valid EC curve parameter, such as
17634 &`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
17635 for valid selections.
17637 For OpenSSL versions before (and not including) 1.0.2, the string
17638 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
17639 &`auto`& tells the library to choose.
17641 If the option expands to an empty string, no EC curves will be enabled.
17644 .option tls_ocsp_file main string&!! unset
17645 .cindex TLS "certificate status"
17646 .cindex TLS "OCSP proof file"
17648 must if set expand to the absolute path to a file which contains a current
17649 status proof for the server's certificate, as obtained from the
17650 Certificate Authority.
17652 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
17654 For GnuTLS 3.5.6 or later the expanded value of this option can be a list
17655 of files, to match a list given for the &%tls_certificate%& option.
17656 The ordering of the two lists must match.
17659 .option tls_on_connect_ports main "string list" unset
17662 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
17663 operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
17664 set up without waiting for the client to issue a STARTTLS command. For
17665 further details, see section &<<SECTsupobssmt>>&.
17669 .option tls_pre_flight_checks main boolean true
17670 .cindex TLS "pre flight checks"
17671 .cindex TLS "startup"
17672 This option controls, if, during process startup, speculative tests are
17673 done in a suprocess. Disabling this tests may delay TLS errors and may
17674 make them harder to debug. This is an advanced option. This option is
17675 experimental and may be removed or renamed without further notice.
17679 .option tls_privatekey main string list&!! unset
17680 .cindex "TLS" "server private key; location of"
17681 The value of this option is expanded, and must then be a list of absolute paths to
17682 files which contains the server's private keys.
17683 If this option is unset, or if
17684 the expansion is forced to fail, or the result is an empty string, the private
17685 key is assumed to be in the same file as the server's certificates. See chapter
17686 &<<CHAPTLS>>& for further details.
17688 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17691 .option tls_remember_esmtp main boolean false
17692 .cindex "TLS" "esmtp state; remembering"
17693 .cindex "TLS" "broken clients"
17694 If this option is set true, Exim violates the RFCs by remembering that it is in
17695 &"esmtp"& state after successfully negotiating a TLS session. This provides
17696 support for broken clients that fail to send a new EHLO after starting a
17700 .option tls_require_ciphers main string&!! unset
17701 .cindex "TLS" "requiring specific ciphers"
17702 .cindex "cipher" "requiring specific"
17703 This option controls which ciphers can be used for incoming TLS connections.
17704 The &(smtp)& transport has an option of the same name for controlling outgoing
17705 connections. This option is expanded for each connection, so can be varied for
17706 different clients if required. The value of this option must be a list of
17707 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
17708 in somewhat different ways. If GnuTLS is being used, the client controls the
17709 preference order of the available ciphers. Details are given in sections
17710 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
17713 .option tls_try_verify_hosts main "host list&!!" unset
17714 .cindex "TLS" "client certificate verification"
17715 .cindex "certificate" "verification of client"
17716 See &%tls_verify_hosts%& below.
17719 .option tls_verify_certificates main string&!! system
17720 .cindex "TLS" "client certificate verification"
17721 .cindex "certificate" "verification of client"
17722 The value of this option is expanded, and must then be either the
17724 or the absolute path to
17725 a file or directory containing permitted certificates for clients that
17726 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
17728 The "system" value for the option will use a
17729 system default location compiled into the SSL library.
17730 This is not available for GnuTLS versions preceding 3.0.20,
17731 and will be taken as empty; an explicit location
17734 The use of a directory for the option value is not available for GnuTLS versions
17735 preceding 3.3.6 and a single file must be used.
17737 With OpenSSL the certificates specified
17739 either by file or directory
17740 are added to those given by the system default location.
17742 These certificates should be for the certificate authorities trusted, rather
17743 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
17744 the value is a file then the certificates are sent by Exim as a server to
17745 connecting clients, defining the list of accepted certificate authorities.
17746 Thus the values defined should be considered public data. To avoid this,
17747 use the explicit directory version.
17749 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17751 A forced expansion failure or setting to an empty string is equivalent to
17755 .option tls_verify_hosts main "host list&!!" unset
17756 .cindex "TLS" "client certificate verification"
17757 .cindex "certificate" "verification of client"
17758 This option, along with &%tls_try_verify_hosts%&, controls the checking of
17759 certificates from clients. The expected certificates are defined by
17760 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
17761 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
17762 &%tls_verify_certificates%& is not set.
17764 Any client that matches &%tls_verify_hosts%& is constrained by
17765 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
17766 present one of the listed certificates. If it does not, the connection is
17767 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
17768 the host to use TLS. It can still send SMTP commands through unencrypted
17769 connections. Forcing a client to use TLS has to be done separately using an
17770 ACL to reject inappropriate commands when the connection is not encrypted.
17772 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
17773 matches this option (but not &%tls_verify_hosts%&), Exim requests a
17774 certificate and checks it against &%tls_verify_certificates%&, but does not
17775 abort the connection if there is no certificate or if it does not match. This
17776 state can be detected in an ACL, which makes it possible to implement policies
17777 such as &"accept for relay only if a verified certificate has been received,
17778 but accept for local delivery if encrypted, even without a verified
17781 Client hosts that match neither of these lists are not asked to present
17785 .option trusted_groups main "string list&!!" unset
17786 .cindex "trusted groups"
17787 .cindex "groups" "trusted"
17788 This option is expanded just once, at the start of Exim's processing. If this
17789 option is set, any process that is running in one of the listed groups, or
17790 which has one of them as a supplementary group, is trusted. The groups can be
17791 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
17792 details of what trusted callers are permitted to do. If neither
17793 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
17796 .option trusted_users main "string list&!!" unset
17797 .cindex "trusted users"
17798 .cindex "user" "trusted"
17799 This option is expanded just once, at the start of Exim's processing. If this
17800 option is set, any process that is running as one of the listed users is
17801 trusted. The users can be specified numerically or by name. See section
17802 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
17803 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
17804 Exim user are trusted.
17806 .option unknown_login main string&!! unset
17807 .cindex "uid (user id)" "unknown caller"
17808 .vindex "&$caller_uid$&"
17809 This is a specialized feature for use in unusual configurations. By default, if
17810 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
17811 gives up. The &%unknown_login%& option can be used to set a login name to be
17812 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
17813 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
17814 is used for the user's real name (gecos field), unless this has been set by the
17817 .option unknown_username main string unset
17818 See &%unknown_login%&.
17820 .option untrusted_set_sender main "address list&!!" unset
17821 .cindex "trusted users"
17822 .cindex "sender" "setting by untrusted user"
17823 .cindex "untrusted user setting sender"
17824 .cindex "user" "untrusted setting sender"
17825 .cindex "envelope sender"
17826 When an untrusted user submits a message to Exim using the standard input, Exim
17827 normally creates an envelope sender address from the user's login and the
17828 default qualification domain. Data from the &%-f%& option (for setting envelope
17829 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
17830 is used) is ignored.
17832 However, untrusted users are permitted to set an empty envelope sender address,
17833 to declare that a message should never generate any bounces. For example:
17835 exim -f '<>' user@domain.example
17837 .vindex "&$sender_ident$&"
17838 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
17839 other envelope sender addresses in a controlled way. When it is set, untrusted
17840 users are allowed to set envelope sender addresses that match any of the
17841 patterns in the list. Like all address lists, the string is expanded. The
17842 identity of the user is in &$sender_ident$&, so you can, for example, restrict
17843 users to setting senders that start with their login ids
17844 followed by a hyphen
17845 by a setting like this:
17847 untrusted_set_sender = ^$sender_ident-
17849 If you want to allow untrusted users to set envelope sender addresses without
17850 restriction, you can use
17852 untrusted_set_sender = *
17854 The &%untrusted_set_sender%& option applies to all forms of local input, but
17855 only to the setting of the envelope sender. It does not permit untrusted users
17856 to use the other options which trusted user can use to override message
17857 parameters. Furthermore, it does not stop Exim from removing an existing
17858 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
17859 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
17860 overriding these actions. The handling of the &'Sender:'& header is also
17861 described in section &<<SECTthesenhea>>&.
17863 The log line for a message's arrival shows the envelope sender following
17864 &"<="&. For local messages, the user's login always follows, after &"U="&. In
17865 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
17866 envelope sender address, the user's login is shown in parentheses after the
17870 .option uucp_from_pattern main string "see below"
17871 .cindex "&""From""& line"
17872 .cindex "UUCP" "&""From""& line"
17873 Some applications that pass messages to an MTA via a command line interface use
17874 an initial line starting with &"From&~"& to pass the envelope sender. In
17875 particular, this is used by UUCP software. Exim recognizes such a line by means
17876 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
17877 matches, the sender address is constructed by expanding the contents of
17878 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
17879 default pattern recognizes lines in the following two forms:
17881 From ph10 Fri Jan 5 12:35 GMT 1996
17882 From ph10 Fri, 7 Jan 97 14:00:00 GMT
17884 The pattern can be seen by running
17886 exim -bP uucp_from_pattern
17888 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
17889 year in the second case. The first word after &"From&~"& is matched in the
17890 regular expression by a parenthesized subpattern. The default value for
17891 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
17892 (&"ph10"& in the example above) as the message's sender. See also
17893 &%ignore_fromline_hosts%&.
17896 .option uucp_from_sender main string&!! &`$1`&
17897 See &%uucp_from_pattern%& above.
17900 .option warn_message_file main string unset
17901 .cindex "warning of delay" "customizing the message"
17902 .cindex "customizing" "warning message"
17903 This option defines a template file containing paragraphs of text to be used
17904 for constructing the warning message which is sent by Exim when a message has
17905 been in the queue for a specified amount of time, as specified by
17906 &%delay_warning%&. Details of the file's contents are given in chapter
17907 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
17910 .option write_rejectlog main boolean true
17911 .cindex "reject log" "disabling"
17912 If this option is set false, Exim no longer writes anything to the reject log.
17913 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
17914 .ecindex IIDconfima
17915 .ecindex IIDmaiconf
17920 . ////////////////////////////////////////////////////////////////////////////
17921 . ////////////////////////////////////////////////////////////////////////////
17923 .chapter "Generic options for routers" "CHAProutergeneric"
17924 .scindex IIDgenoprou1 "options" "generic; for routers"
17925 .scindex IIDgenoprou2 "generic options" "router"
17926 This chapter describes the generic options that apply to all routers.
17927 Those that are preconditions are marked with ‡ in the &"use"& field.
17929 For a general description of how a router operates, see sections
17930 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
17931 which the preconditions are tested. The order of expansion of the options that
17932 provide data for a transport is: &%errors_to%&, &%headers_add%&,
17933 &%headers_remove%&, &%transport%&.
17937 .option address_data routers string&!! unset
17938 .cindex "router" "data attached to address"
17939 The string is expanded just before the router is run, that is, after all the
17940 precondition tests have succeeded. If the expansion is forced to fail, the
17941 router declines, the value of &%address_data%& remains unchanged, and the
17942 &%more%& option controls what happens next. Other expansion failures cause
17943 delivery of the address to be deferred.
17945 .vindex "&$address_data$&"
17946 When the expansion succeeds, the value is retained with the address, and can be
17947 accessed using the variable &$address_data$& in the current router, subsequent
17948 routers, and the eventual transport.
17950 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
17951 that runs a user's filter file, the contents of &$address_data$& are accessible
17952 in the filter. This is not normally a problem, because such data is usually
17953 either not confidential or it &"belongs"& to the current user, but if you do
17954 put confidential data into &$address_data$& you need to remember this point.
17956 Even if the router declines or passes, the value of &$address_data$& remains
17957 with the address, though it can be changed by another &%address_data%& setting
17958 on a subsequent router. If a router generates child addresses, the value of
17959 &$address_data$& propagates to them. This also applies to the special kind of
17960 &"child"& that is generated by a router with the &%unseen%& option.
17962 The idea of &%address_data%& is that you can use it to look up a lot of data
17963 for the address once, and then pick out parts of the data later. For example,
17964 you could use a single LDAP lookup to return a string of the form
17966 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
17968 In the transport you could pick out the mailbox by a setting such as
17970 file = ${extract{mailbox}{$address_data}}
17972 This makes the configuration file less messy, and also reduces the number of
17973 lookups (though Exim does cache lookups).
17975 .vindex "&$sender_address_data$&"
17976 .vindex "&$address_data$&"
17977 The &%address_data%& facility is also useful as a means of passing information
17978 from one router to another, and from a router to a transport. In addition, if
17979 &$address_data$& is set by a router when verifying a recipient address from an
17980 ACL, it remains available for use in the rest of the ACL statement. After
17981 verifying a sender, the value is transferred to &$sender_address_data$&.
17985 .option address_test routers&!? boolean true
17987 .cindex "router" "skipping when address testing"
17988 If this option is set false, the router is skipped when routing is being tested
17989 by means of the &%-bt%& command line option. This can be a convenience when
17990 your first router sends messages to an external scanner, because it saves you
17991 having to set the &"already scanned"& indicator when testing real address
17996 .option cannot_route_message routers string&!! unset
17997 .cindex "router" "customizing &""cannot route""& message"
17998 .cindex "customizing" "&""cannot route""& message"
17999 This option specifies a text message that is used when an address cannot be
18000 routed because Exim has run out of routers. The default message is
18001 &"Unrouteable address"&. This option is useful only on routers that have
18002 &%more%& set false, or on the very last router in a configuration, because the
18003 value that is used is taken from the last router that is considered. This
18004 includes a router that is skipped because its preconditions are not met, as
18005 well as a router that declines. For example, using the default configuration,
18008 cannot_route_message = Remote domain not found in DNS
18010 on the first router, which is a &(dnslookup)& router with &%more%& set false,
18013 cannot_route_message = Unknown local user
18015 on the final router that checks for local users. If string expansion fails for
18016 this option, the default message is used. Unless the expansion failure was
18017 explicitly forced, a message about the failure is written to the main and panic
18018 logs, in addition to the normal message about the routing failure.
18021 .option caseful_local_part routers boolean false
18022 .cindex "case of local parts"
18023 .cindex "router" "case of local parts"
18024 By default, routers handle the local parts of addresses in a case-insensitive
18025 manner, though the actual case is preserved for transmission with the message.
18026 If you want the case of letters to be significant in a router, you must set
18027 this option true. For individual router options that contain address or local
18028 part lists (for example, &%local_parts%&), case-sensitive matching can be
18029 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
18032 .vindex "&$local_part$&"
18033 .vindex "&$original_local_part$&"
18034 .vindex "&$parent_local_part$&"
18035 The value of the &$local_part$& variable is forced to lower case while a
18036 router is running unless &%caseful_local_part%& is set. When a router assigns
18037 an address to a transport, the value of &$local_part$& when the transport runs
18038 is the same as it was in the router. Similarly, when a router generates child
18039 addresses by aliasing or forwarding, the values of &$original_local_part$&
18040 and &$parent_local_part$& are those that were used by the redirecting router.
18042 This option applies to the processing of an address by a router. When a
18043 recipient address is being processed in an ACL, there is a separate &%control%&
18044 modifier that can be used to specify case-sensitive processing within the ACL
18045 (see section &<<SECTcontrols>>&).
18049 .option check_local_user routers&!? boolean false
18050 .cindex "local user, checking in router"
18051 .cindex "router" "checking for local user"
18052 .cindex "&_/etc/passwd_&"
18054 When this option is true, Exim checks that the local part of the recipient
18055 address (with affixes removed if relevant) is the name of an account on the
18056 local system. The check is done by calling the &[getpwnam()]& function rather
18057 than trying to read &_/etc/passwd_& directly. This means that other methods of
18058 holding password data (such as NIS) are supported. If the local part is a local
18059 user, &$home$& is set from the password data, and can be tested in other
18060 preconditions that are evaluated after this one (the order of evaluation is
18061 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
18062 overridden by &%router_home_directory%&. If the local part is not a local user,
18063 the router is skipped.
18065 If you want to check that the local part is either the name of a local user
18066 or matches something else, you cannot combine &%check_local_user%& with a
18067 setting of &%local_parts%&, because that specifies the logical &'and'& of the
18068 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
18069 setting to achieve this. For example:
18071 local_parts = passwd;$local_part : lsearch;/etc/other/users
18073 Note, however, that the side effects of &%check_local_user%& (such as setting
18074 up a home directory) do not occur when a &(passwd)& lookup is used in a
18075 &%local_parts%& (or any other) precondition.
18079 .option condition routers&!? string&!! unset
18080 .cindex "router" "customized precondition"
18081 This option specifies a general precondition test that has to succeed for the
18082 router to be called. The &%condition%& option is the last precondition to be
18083 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
18084 result is a forced failure, or an empty string, or one of the strings &"0"& or
18085 &"no"& or &"false"& (checked without regard to the case of the letters), the
18086 router is skipped, and the address is offered to the next one.
18088 If the result is any other value, the router is run (as this is the last
18089 precondition to be evaluated, all the other preconditions must be true).
18091 This option is unusual in that multiple &%condition%& options may be present.
18092 All &%condition%& options must succeed.
18094 The &%condition%& option provides a means of applying custom conditions to the
18095 running of routers. Note that in the case of a simple conditional expansion,
18096 the default expansion values are exactly what is wanted. For example:
18098 condition = ${if >{$message_age}{600}}
18100 Because of the default behaviour of the string expansion, this is equivalent to
18102 condition = ${if >{$message_age}{600}{true}{}}
18105 A multiple condition example, which succeeds:
18107 condition = ${if >{$message_age}{600}}
18108 condition = ${if !eq{${lc:$local_part}}{postmaster}}
18112 If the expansion fails (other than forced failure) delivery is deferred. Some
18113 of the other precondition options are common special cases that could in fact
18114 be specified using &%condition%&.
18116 Historical note: We have &%condition%& on ACLs and on Routers. Routers
18117 are far older, and use one set of semantics. ACLs are newer and when
18118 they were created, the ACL &%condition%& process was given far stricter
18119 parse semantics. The &%bool{}%& expansion condition uses the same rules as
18120 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
18121 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
18122 Router rules processing behavior.
18124 This is best illustrated in an example:
18126 # If used in an ACL condition will fail with a syntax error, but
18127 # in a router condition any extra characters are treated as a string
18129 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
18132 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
18135 In each example above, the &%if%& statement actually ends after
18136 &"{google.com}}"&. Since no true or false braces were defined, the
18137 default &%if%& behavior is to return a boolean true or a null answer
18138 (which evaluates to false). The rest of the line is then treated as a
18139 string. So the first example resulted in the boolean answer &"true"&
18140 with the string &" {yes} {no}}"& appended to it. The second example
18141 resulted in the null output (indicating false) with the string
18142 &" {yes} {no}}"& appended to it.
18144 In fact you can put excess forward braces in too. In the router
18145 &%condition%&, Exim's parser only looks for &"{"& symbols when they
18146 mean something, like after a &"$"& or when required as part of a
18147 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
18150 Thus, in a Router, the above expansion strings will both always evaluate
18151 true, as the result of expansion is a non-empty string which doesn't
18152 match an explicit false value. This can be tricky to debug. By
18153 contrast, in an ACL either of those strings will always result in an
18154 expansion error because the result doesn't look sufficiently boolean.
18157 .option debug_print routers string&!! unset
18158 .cindex "testing" "variables in drivers"
18159 If this option is set and debugging is enabled (see the &%-d%& command line
18160 option) or in address-testing mode (see the &%-bt%& command line option),
18161 the string is expanded and included in the debugging output.
18162 If expansion of the string fails, the error message is written to the debugging
18163 output, and Exim carries on processing.
18164 This option is provided to help with checking out the values of variables and
18165 so on when debugging router configurations. For example, if a &%condition%&
18166 option appears not to be working, &%debug_print%& can be used to output the
18167 variables it references. The output happens after checks for &%domains%&,
18168 &%local_parts%&, and &%check_local_user%& but before any other preconditions
18169 are tested. A newline is added to the text if it does not end with one.
18170 The variable &$router_name$& contains the name of the router.
18174 .option disable_logging routers boolean false
18175 If this option is set true, nothing is logged for any routing errors
18176 or for any deliveries caused by this router. You should not set this option
18177 unless you really, really know what you are doing. See also the generic
18178 transport option of the same name.
18180 .option dnssec_request_domains routers "domain list&!!" unset
18181 .cindex "MX record" "security"
18182 .cindex "DNSSEC" "MX lookup"
18183 .cindex "security" "MX lookup"
18184 .cindex "DNS" "DNSSEC"
18185 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
18186 the dnssec request bit set.
18187 This applies to all of the SRV, MX, AAAA, A lookup sequence.
18189 .option dnssec_require_domains routers "domain list&!!" unset
18190 .cindex "MX record" "security"
18191 .cindex "DNSSEC" "MX lookup"
18192 .cindex "security" "MX lookup"
18193 .cindex "DNS" "DNSSEC"
18194 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
18195 the dnssec request bit set. Any returns not having the Authenticated Data bit
18196 (AD bit) set will be ignored and logged as a host-lookup failure.
18197 This applies to all of the SRV, MX, AAAA, A lookup sequence.
18200 .option domains routers&!? "domain list&!!" unset
18201 .cindex "router" "restricting to specific domains"
18202 .vindex "&$domain_data$&"
18203 If this option is set, the router is skipped unless the current domain matches
18204 the list. If the match is achieved by means of a file lookup, the data that the
18205 lookup returned for the domain is placed in &$domain_data$& for use in string
18206 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
18207 a list of the order in which preconditions are evaluated.
18211 .option driver routers string unset
18212 This option must always be set. It specifies which of the available routers is
18216 .option dsn_lasthop routers boolean false
18217 .cindex "DSN" "success"
18218 .cindex "Delivery Status Notification" "success"
18219 If this option is set true, and extended DSN (RFC3461) processing is in effect,
18220 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
18221 instead send a success DSN as if the next hop does not support DSN.
18222 Not effective on redirect routers.
18226 .option errors_to routers string&!! unset
18227 .cindex "envelope sender"
18228 .cindex "router" "changing address for errors"
18229 If a router successfully handles an address, it may assign the address to a
18230 transport for delivery or it may generate child addresses. In both cases, if
18231 there is a delivery problem during later processing, the resulting bounce
18232 message is sent to the address that results from expanding this string,
18233 provided that the address verifies successfully. The &%errors_to%& option is
18234 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
18236 The &%errors_to%& setting associated with an address can be overridden if it
18237 subsequently passes through other routers that have their own &%errors_to%&
18238 settings, or if the message is delivered by a transport with a &%return_path%&
18241 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
18242 the expansion fails to verify, the errors address associated with the incoming
18243 address is used. At top level, this is the envelope sender. A non-forced
18244 expansion failure causes delivery to be deferred.
18246 If an address for which &%errors_to%& has been set ends up being delivered over
18247 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
18248 any bounces that are generated by other MTAs on the delivery route are also
18249 sent there. You can set &%errors_to%& to the empty string by either of these
18255 An expansion item that yields an empty string has the same effect. If you do
18256 this, a locally detected delivery error for addresses processed by this router
18257 no longer gives rise to a bounce message; the error is discarded. If the
18258 address is delivered to a remote host, the return path is set to &`<>`&, unless
18259 overridden by the &%return_path%& option on the transport.
18261 .vindex "&$address_data$&"
18262 If for some reason you want to discard local errors, but use a non-empty
18263 MAIL command for remote delivery, you can preserve the original return
18264 path in &$address_data$& in the router, and reinstate it in the transport by
18265 setting &%return_path%&.
18267 The most common use of &%errors_to%& is to direct mailing list bounces to the
18268 manager of the list, as described in section &<<SECTmailinglists>>&, or to
18269 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
18273 .option expn routers&!? boolean true
18274 .cindex "address" "testing"
18275 .cindex "testing" "addresses"
18276 .cindex "EXPN" "router skipping"
18277 .cindex "router" "skipping for EXPN"
18278 If this option is turned off, the router is skipped when testing an address
18279 as a result of processing an SMTP EXPN command. You might, for example,
18280 want to turn it off on a router for users' &_.forward_& files, while leaving it
18281 on for the system alias file.
18282 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18285 The use of the SMTP EXPN command is controlled by an ACL (see chapter
18286 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
18287 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
18291 .option fail_verify routers boolean false
18292 .cindex "router" "forcing verification failure"
18293 Setting this option has the effect of setting both &%fail_verify_sender%& and
18294 &%fail_verify_recipient%& to the same value.
18298 .option fail_verify_recipient routers boolean false
18299 If this option is true and an address is accepted by this router when
18300 verifying a recipient, verification fails.
18304 .option fail_verify_sender routers boolean false
18305 If this option is true and an address is accepted by this router when
18306 verifying a sender, verification fails.
18310 .option fallback_hosts routers "string list" unset
18311 .cindex "router" "fallback hosts"
18312 .cindex "fallback" "hosts specified on router"
18313 String expansion is not applied to this option. The argument must be a
18314 colon-separated list of host names or IP addresses. The list separator can be
18315 changed (see section &<<SECTlistsepchange>>&), and a port can be specified with
18316 each name or address. In fact, the format of each item is exactly the same as
18317 defined for the list of hosts in a &(manualroute)& router (see section
18318 &<<SECTformatonehostitem>>&).
18320 If a router queues an address for a remote transport, this host list is
18321 associated with the address, and used instead of the transport's fallback host
18322 list. If &%hosts_randomize%& is set on the transport, the order of the list is
18323 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
18324 transport for further details.
18327 .option group routers string&!! "see below"
18328 .cindex "gid (group id)" "local delivery"
18329 .cindex "local transports" "uid and gid"
18330 .cindex "transport" "local"
18331 .cindex "router" "setting group"
18332 When a router queues an address for a transport, and the transport does not
18333 specify a group, the group given here is used when running the delivery
18335 The group may be specified numerically or by name. If expansion fails, the
18336 error is logged and delivery is deferred.
18337 The default is unset, unless &%check_local_user%& is set, when the default
18338 is taken from the password information. See also &%initgroups%& and &%user%&
18339 and the discussion in chapter &<<CHAPenvironment>>&.
18343 .option headers_add routers list&!! unset
18344 .cindex "header lines" "adding"
18345 .cindex "router" "adding header lines"
18346 This option specifies a list of text headers,
18347 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
18348 that is associated with any addresses that are accepted by the router.
18349 Each item is separately expanded, at routing time. However, this
18350 option has no effect when an address is just being verified. The way in which
18351 the text is used to add header lines at transport time is described in section
18352 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
18353 message is in the process of being transported. This means that references to
18354 header lines in string expansions in the transport's configuration do not
18355 &"see"& the added header lines.
18357 The &%headers_add%& option is expanded after &%errors_to%&, but before
18358 &%headers_remove%& and &%transport%&. If an item is empty, or if
18359 an item expansion is forced to fail, the item has no effect. Other expansion
18360 failures are treated as configuration errors.
18362 Unlike most options, &%headers_add%& can be specified multiple times
18363 for a router; all listed headers are added.
18365 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
18366 router that has the &%one_time%& option set.
18368 .cindex "duplicate addresses"
18369 .oindex "&%unseen%&"
18370 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
18371 additions are deleted when the address is passed on to subsequent routers.
18372 For a &%redirect%& router, if a generated address is the same as the incoming
18373 address, this can lead to duplicate addresses with different header
18374 modifications. Exim does not do duplicate deliveries (except, in certain
18375 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
18376 which of the duplicates is discarded, so this ambiguous situation should be
18377 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
18381 .option headers_remove routers list&!! unset
18382 .cindex "header lines" "removing"
18383 .cindex "router" "removing header lines"
18384 This option specifies a list of text headers,
18385 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
18386 that is associated with any addresses that are accepted by the router.
18387 Each item is separately expanded, at routing time. However, this
18388 option has no effect when an address is just being verified. The way in which
18389 the text is used to remove header lines at transport time is described in
18390 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
18391 the message is in the process of being transported. This means that references
18392 to header lines in string expansions in the transport's configuration still
18393 &"see"& the original header lines.
18395 The &%headers_remove%& option is expanded after &%errors_to%& and
18396 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
18397 the item has no effect. Other expansion failures are treated as configuration
18400 Unlike most options, &%headers_remove%& can be specified multiple times
18401 for a router; all listed headers are removed.
18403 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
18404 router that has the &%one_time%& option set.
18406 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
18407 removal requests are deleted when the address is passed on to subsequent
18408 routers, and this can lead to problems with duplicates -- see the similar
18409 warning for &%headers_add%& above.
18411 &*Warning 3*&: Because of the separate expansion of the list items,
18412 items that contain a list separator must have it doubled.
18413 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
18417 .option ignore_target_hosts routers "host list&!!" unset
18418 .cindex "IP address" "discarding"
18419 .cindex "router" "discarding IP addresses"
18420 Although this option is a host list, it should normally contain IP address
18421 entries rather than names. If any host that is looked up by the router has an
18422 IP address that matches an item in this list, Exim behaves as if that IP
18423 address did not exist. This option allows you to cope with rogue DNS entries
18426 remote.domain.example. A 127.0.0.1
18430 ignore_target_hosts = 127.0.0.1
18432 on the relevant router. If all the hosts found by a &(dnslookup)& router are
18433 discarded in this way, the router declines. In a conventional configuration, an
18434 attempt to mail to such a domain would normally provoke the &"unrouteable
18435 domain"& error, and an attempt to verify an address in the domain would fail.
18436 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
18437 router declines if presented with one of the listed addresses.
18439 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
18440 means of the first or the second of the following settings, respectively:
18442 ignore_target_hosts = 0.0.0.0/0
18443 ignore_target_hosts = <; 0::0/0
18445 The pattern in the first line matches all IPv4 addresses, whereas the pattern
18446 in the second line matches all IPv6 addresses.
18448 This option may also be useful for ignoring link-local and site-local IPv6
18449 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
18450 is expanded before use as a list, it is possible to make it dependent on the
18451 domain that is being routed.
18453 .vindex "&$host_address$&"
18454 During its expansion, &$host_address$& is set to the IP address that is being
18457 .option initgroups routers boolean false
18458 .cindex "additional groups"
18459 .cindex "groups" "additional"
18460 .cindex "local transports" "uid and gid"
18461 .cindex "transport" "local"
18462 If the router queues an address for a transport, and this option is true, and
18463 the uid supplied by the router is not overridden by the transport, the
18464 &[initgroups()]& function is called when running the transport to ensure that
18465 any additional groups associated with the uid are set up. See also &%group%&
18466 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
18470 .option local_part_prefix routers&!? "string list" unset
18471 .cindex affix "router precondition"
18472 .cindex "router" "prefix for local part"
18473 .cindex "prefix" "for local part, used in router"
18474 If this option is set, the router is skipped unless the local part starts with
18475 one of the given strings, or &%local_part_prefix_optional%& is true. See
18476 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
18479 The list is scanned from left to right, and the first prefix that matches is
18480 used. A limited form of wildcard is available; if the prefix begins with an
18481 asterisk, it matches the longest possible sequence of arbitrary characters at
18482 the start of the local part. An asterisk should therefore always be followed by
18483 some character that does not occur in normal local parts.
18484 .cindex "multiple mailboxes"
18485 .cindex "mailbox" "multiple"
18486 Wildcarding can be used to set up multiple user mailboxes, as described in
18487 section &<<SECTmulbox>>&.
18489 .vindex "&$local_part$&"
18490 .vindex "&$local_part_prefix$&"
18491 During the testing of the &%local_parts%& option, and while the router is
18492 running, the prefix is removed from the local part, and is available in the
18493 expansion variable &$local_part_prefix$&. When a message is being delivered, if
18494 the router accepts the address, this remains true during subsequent delivery by
18495 a transport. In particular, the local part that is transmitted in the RCPT
18496 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
18497 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
18498 the relevant transport.
18500 When an address is being verified, &%local_part_prefix%& affects only the
18501 behaviour of the router. If the callout feature of verification is in use, this
18502 means that the full address, including the prefix, will be used during the
18505 The prefix facility is commonly used to handle local parts of the form
18506 &%owner-something%&. Another common use is to support local parts of the form
18507 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
18508 to tell a user their forwarding is broken &-- by placing a router like this one
18509 immediately before the router that handles &_.forward_& files:
18513 local_part_prefix = real-
18515 transport = local_delivery
18517 For security, it would probably be a good idea to restrict the use of this
18518 router to locally-generated messages, using a condition such as this:
18520 condition = ${if match {$sender_host_address}\
18521 {\N^(|127\.0\.0\.1)$\N}}
18524 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
18525 both conditions must be met if not optional. Care must be taken if wildcards
18526 are used in both a prefix and a suffix on the same router. Different
18527 separator characters must be used to avoid ambiguity.
18530 .option local_part_prefix_optional routers boolean false
18531 See &%local_part_prefix%& above.
18535 .option local_part_suffix routers&!? "string list" unset
18536 .cindex "router" "suffix for local part"
18537 .cindex "suffix for local part" "used in router"
18538 This option operates in the same way as &%local_part_prefix%&, except that the
18539 local part must end (rather than start) with the given string, the
18540 &%local_part_suffix_optional%& option determines whether the suffix is
18541 mandatory, and the wildcard * character, if present, must be the last
18542 character of the suffix. This option facility is commonly used to handle local
18543 parts of the form &%something-request%& and multiple user mailboxes of the form
18547 .option local_part_suffix_optional routers boolean false
18548 See &%local_part_suffix%& above.
18552 .option local_parts routers&!? "local part list&!!" unset
18553 .cindex "router" "restricting to specific local parts"
18554 .cindex "local part" "checking in router"
18555 The router is run only if the local part of the address matches the list.
18556 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18558 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
18559 string is expanded, it is possible to make it depend on the domain, for
18562 local_parts = dbm;/usr/local/specials/$domain
18564 .vindex "&$local_part_data$&"
18565 If the match is achieved by a lookup, the data that the lookup returned
18566 for the local part is placed in the variable &$local_part_data$& for use in
18567 expansions of the router's private options. You might use this option, for
18568 example, if you have a large number of local virtual domains, and you want to
18569 send all postmaster mail to the same place without having to set up an alias in
18570 each virtual domain:
18574 local_parts = postmaster
18575 data = postmaster@real.domain.example
18579 .option log_as_local routers boolean "see below"
18580 .cindex "log" "delivery line"
18581 .cindex "delivery" "log line format"
18582 Exim has two logging styles for delivery, the idea being to make local
18583 deliveries stand out more visibly from remote ones. In the &"local"& style, the
18584 recipient address is given just as the local part, without a domain. The use of
18585 this style is controlled by this option. It defaults to true for the &(accept)&
18586 router, and false for all the others. This option applies only when a
18587 router assigns an address to a transport. It has no effect on routers that
18588 redirect addresses.
18592 .option more routers boolean&!! true
18593 The result of string expansion for this option must be a valid boolean value,
18594 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
18595 result causes an error, and delivery is deferred. If the expansion is forced to
18596 fail, the default value for the option (true) is used. Other failures cause
18597 delivery to be deferred.
18599 If this option is set false, and the router declines to handle the address, no
18600 further routers are tried, routing fails, and the address is bounced.
18602 However, if the router explicitly passes an address to the following router by
18603 means of the setting
18607 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
18608 does not affect the behaviour if one of the precondition tests fails. In that
18609 case, the address is always passed to the next router.
18611 Note that &%address_data%& is not considered to be a precondition. If its
18612 expansion is forced to fail, the router declines, and the value of &%more%&
18613 controls what happens next.
18616 .option pass_on_timeout routers boolean false
18617 .cindex "timeout" "of router"
18618 .cindex "router" "timeout"
18619 If a router times out during a host lookup, it normally causes deferral of the
18620 address. If &%pass_on_timeout%& is set, the address is passed on to the next
18621 router, overriding &%no_more%&. This may be helpful for systems that are
18622 intermittently connected to the Internet, or those that want to pass to a smart
18623 host any messages that cannot immediately be delivered.
18625 There are occasional other temporary errors that can occur while doing DNS
18626 lookups. They are treated in the same way as a timeout, and this option
18627 applies to all of them.
18631 .option pass_router routers string unset
18632 .cindex "router" "go to after &""pass""&"
18633 Routers that recognize the generic &%self%& option (&(dnslookup)&,
18634 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
18635 routing to continue, and overriding a false setting of &%more%&. When one of
18636 these routers returns &"pass"&, the address is normally handed on to the next
18637 router in sequence. This can be changed by setting &%pass_router%& to the name
18638 of another router. However (unlike &%redirect_router%&) the named router must
18639 be below the current router, to avoid loops. Note that this option applies only
18640 to the special case of &"pass"&. It does not apply when a router returns
18641 &"decline"& because it cannot handle an address.
18645 .option redirect_router routers string unset
18646 .cindex "router" "start at after redirection"
18647 Sometimes an administrator knows that it is pointless to reprocess addresses
18648 generated from alias or forward files with the same router again. For
18649 example, if an alias file translates real names into login ids there is no
18650 point searching the alias file a second time, especially if it is a large file.
18652 The &%redirect_router%& option can be set to the name of any router instance.
18653 It causes the routing of any generated addresses to start at the named router
18654 instead of at the first router. This option has no effect if the router in
18655 which it is set does not generate new addresses.
18659 .option require_files routers&!? "string list&!!" unset
18660 .cindex "file" "requiring for router"
18661 .cindex "router" "requiring file existence"
18662 This option provides a general mechanism for predicating the running of a
18663 router on the existence or non-existence of certain files or directories.
18664 Before running a router, as one of its precondition tests, Exim works its way
18665 through the &%require_files%& list, expanding each item separately.
18667 Because the list is split before expansion, any colons in expansion items must
18668 be doubled, or the facility for using a different list separator must be used
18669 (&<<SECTlistsepchange>>&).
18670 If any expansion is forced to fail, the item is ignored. Other expansion
18671 failures cause routing of the address to be deferred.
18673 If any expanded string is empty, it is ignored. Otherwise, except as described
18674 below, each string must be a fully qualified file path, optionally preceded by
18675 &"!"&. The paths are passed to the &[stat()]& function to test for the
18676 existence of the files or directories. The router is skipped if any paths not
18677 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
18680 If &[stat()]& cannot determine whether a file exists or not, delivery of
18681 the message is deferred. This can happen when NFS-mounted filesystems are
18684 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
18685 options, so you cannot use it to check for the existence of a file in which to
18686 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
18687 full list of the order in which preconditions are evaluated.) However, as
18688 these options are all expanded, you can use the &%exists%& expansion condition
18689 to make such tests. The &%require_files%& option is intended for checking files
18690 that the router may be going to use internally, or which are needed by a
18691 transport (e.g., &_.procmailrc_&).
18693 During delivery, the &[stat()]& function is run as root, but there is a
18694 facility for some checking of the accessibility of a file by another user.
18695 This is not a proper permissions check, but just a &"rough"& check that
18696 operates as follows:
18698 If an item in a &%require_files%& list does not contain any forward slash
18699 characters, it is taken to be the user (and optional group, separated by a
18700 comma) to be checked for subsequent files in the list. If no group is specified
18701 but the user is specified symbolically, the gid associated with the uid is
18704 require_files = mail:/some/file
18705 require_files = $local_part:$home/.procmailrc
18707 If a user or group name in a &%require_files%& list does not exist, the
18708 &%require_files%& condition fails.
18710 Exim performs the check by scanning along the components of the file path, and
18711 checking the access for the given uid and gid. It checks for &"x"& access on
18712 directories, and &"r"& access on the final file. Note that this means that file
18713 access control lists, if the operating system has them, are ignored.
18715 &*Warning 1*&: When the router is being run to verify addresses for an
18716 incoming SMTP message, Exim is not running as root, but under its own uid. This
18717 may affect the result of a &%require_files%& check. In particular, &[stat()]&
18718 may yield the error EACCES (&"Permission denied"&). This means that the Exim
18719 user is not permitted to read one of the directories on the file's path.
18721 &*Warning 2*&: Even when Exim is running as root while delivering a message,
18722 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
18723 without root access. In this case, if a check for access by a particular user
18724 is requested, Exim creates a subprocess that runs as that user, and tries the
18725 check again in that process.
18727 The default action for handling an unresolved EACCES is to consider it to
18728 be caused by a configuration error, and routing is deferred because the
18729 existence or non-existence of the file cannot be determined. However, in some
18730 circumstances it may be desirable to treat this condition as if the file did
18731 not exist. If the filename (or the exclamation mark that precedes the filename
18732 for non-existence) is preceded by a plus sign, the EACCES error is treated
18733 as if the file did not exist. For example:
18735 require_files = +/some/file
18737 If the router is not an essential part of verification (for example, it
18738 handles users' &_.forward_& files), another solution is to set the &%verify%&
18739 option false so that the router is skipped when verifying.
18743 .option retry_use_local_part routers boolean "see below"
18744 .cindex "hints database" "retry keys"
18745 .cindex "local part" "in retry keys"
18746 When a delivery suffers a temporary routing failure, a retry record is created
18747 in Exim's hints database. For addresses whose routing depends only on the
18748 domain, the key for the retry record should not involve the local part, but for
18749 other addresses, both the domain and the local part should be included.
18750 Usually, remote routing is of the former kind, and local routing is of the
18753 This option controls whether the local part is used to form the key for retry
18754 hints for addresses that suffer temporary errors while being handled by this
18755 router. The default value is true for any router that has &%check_local_user%&
18756 set, and false otherwise. Note that this option does not apply to hints keys
18757 for transport delays; they are controlled by a generic transport option of the
18760 The setting of &%retry_use_local_part%& applies only to the router on which it
18761 appears. If the router generates child addresses, they are routed
18762 independently; this setting does not become attached to them.
18766 .option router_home_directory routers string&!! unset
18767 .cindex "router" "home directory for"
18768 .cindex "home directory" "for router"
18770 This option sets a home directory for use while the router is running. (Compare
18771 &%transport_home_directory%&, which sets a home directory for later
18772 transporting.) In particular, if used on a &(redirect)& router, this option
18773 sets a value for &$home$& while a filter is running. The value is expanded;
18774 forced expansion failure causes the option to be ignored &-- other failures
18775 cause the router to defer.
18777 Expansion of &%router_home_directory%& happens immediately after the
18778 &%check_local_user%& test (if configured), before any further expansions take
18780 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18782 While the router is running, &%router_home_directory%& overrides the value of
18783 &$home$& that came from &%check_local_user%&.
18785 When a router accepts an address and assigns it to a local transport (including
18786 the cases when a &(redirect)& router generates a pipe, file, or autoreply
18787 delivery), the home directory setting for the transport is taken from the first
18788 of these values that is set:
18791 The &%home_directory%& option on the transport;
18793 The &%transport_home_directory%& option on the router;
18795 The password data if &%check_local_user%& is set on the router;
18797 The &%router_home_directory%& option on the router.
18800 In other words, &%router_home_directory%& overrides the password data for the
18801 router, but not for the transport.
18805 .option self routers string freeze
18806 .cindex "MX record" "pointing to local host"
18807 .cindex "local host" "MX pointing to"
18808 This option applies to those routers that use a recipient address to find a
18809 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
18810 and &(manualroute)& routers.
18811 Certain configurations of the &(queryprogram)& router can also specify a list
18813 Usually such routers are configured to send the message to a remote host via an
18814 &(smtp)& transport. The &%self%& option specifies what happens when the first
18815 host on the list turns out to be the local host.
18816 The way in which Exim checks for the local host is described in section
18817 &<<SECTreclocipadd>>&.
18819 Normally this situation indicates either an error in Exim's configuration (for
18820 example, the router should be configured not to process this domain), or an
18821 error in the DNS (for example, the MX should not point to this host). For this
18822 reason, the default action is to log the incident, defer the address, and
18823 freeze the message. The following alternatives are provided for use in special
18828 Delivery of the message is tried again later, but the message is not frozen.
18830 .vitem "&%reroute%&: <&'domain'&>"
18831 The domain is changed to the given domain, and the address is passed back to
18832 be reprocessed by the routers. No rewriting of headers takes place. This
18833 behaviour is essentially a redirection.
18835 .vitem "&%reroute: rewrite:%& <&'domain'&>"
18836 The domain is changed to the given domain, and the address is passed back to be
18837 reprocessed by the routers. Any headers that contain the original domain are
18842 .vindex "&$self_hostname$&"
18843 The router passes the address to the next router, or to the router named in the
18844 &%pass_router%& option if it is set. This overrides &%no_more%&. During
18845 subsequent routing and delivery, the variable &$self_hostname$& contains the
18846 name of the local host that the router encountered. This can be used to
18847 distinguish between different cases for hosts with multiple names. The
18853 ensures that only those addresses that routed to the local host are passed on.
18854 Without &%no_more%&, addresses that were declined for other reasons would also
18855 be passed to the next router.
18858 Delivery fails and an error report is generated.
18861 .cindex "local host" "sending to"
18862 The anomaly is ignored and the address is queued for the transport. This
18863 setting should be used with extreme caution. For an &(smtp)& transport, it
18864 makes sense only in cases where the program that is listening on the SMTP port
18865 is not this version of Exim. That is, it must be some other MTA, or Exim with a
18866 different configuration file that handles the domain in another way.
18871 .option senders routers&!? "address list&!!" unset
18872 .cindex "router" "checking senders"
18873 If this option is set, the router is skipped unless the message's sender
18874 address matches something on the list.
18875 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18878 There are issues concerning verification when the running of routers is
18879 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
18880 setting, it sets the sender to the null string. When using the &%-bt%& option
18881 to check a configuration file, it is necessary also to use the &%-f%& option to
18882 set an appropriate sender. For incoming mail, the sender is unset when
18883 verifying the sender, but is available when verifying any recipients. If the
18884 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
18888 .option translate_ip_address routers string&!! unset
18889 .cindex "IP address" "translating"
18890 .cindex "packet radio"
18891 .cindex "router" "IP address translation"
18892 There exist some rare networking situations (for example, packet radio) where
18893 it is helpful to be able to translate IP addresses generated by normal routing
18894 mechanisms into other IP addresses, thus performing a kind of manual IP
18895 routing. This should be done only if the normal IP routing of the TCP/IP stack
18896 is inadequate or broken. Because this is an extremely uncommon requirement, the
18897 code to support this option is not included in the Exim binary unless
18898 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
18900 .vindex "&$host_address$&"
18901 The &%translate_ip_address%& string is expanded for every IP address generated
18902 by the router, with the generated address set in &$host_address$&. If the
18903 expansion is forced to fail, no action is taken.
18904 For any other expansion error, delivery of the message is deferred.
18905 If the result of the expansion is an IP address, that replaces the original
18906 address; otherwise the result is assumed to be a host name &-- this is looked
18907 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
18908 produce one or more replacement IP addresses. For example, to subvert all IP
18909 addresses in some specific networks, this could be added to a router:
18911 translate_ip_address = \
18912 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
18915 The file would contain lines like
18917 10.2.3.128/26 some.host
18918 10.8.4.34/26 10.44.8.15
18920 You should not make use of this facility unless you really understand what you
18925 .option transport routers string&!! unset
18926 This option specifies the transport to be used when a router accepts an address
18927 and sets it up for delivery. A transport is never needed if a router is used
18928 only for verification. The value of the option is expanded at routing time,
18929 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
18930 and result must be the name of one of the configured transports. If it is not,
18931 delivery is deferred.
18933 The &%transport%& option is not used by the &(redirect)& router, but it does
18934 have some private options that set up transports for pipe and file deliveries
18935 (see chapter &<<CHAPredirect>>&).
18939 .option transport_current_directory routers string&!! unset
18940 .cindex "current directory for local transport"
18941 This option associates a current directory with any address that is routed
18942 to a local transport. This can happen either because a transport is
18943 explicitly configured for the router, or because it generates a delivery to a
18944 file or a pipe. During the delivery process (that is, at transport time), this
18945 option string is expanded and is set as the current directory, unless
18946 overridden by a setting on the transport.
18947 If the expansion fails for any reason, including forced failure, an error is
18948 logged, and delivery is deferred.
18949 See chapter &<<CHAPenvironment>>& for details of the local delivery
18955 .option transport_home_directory routers string&!! "see below"
18956 .cindex "home directory" "for local transport"
18957 This option associates a home directory with any address that is routed to a
18958 local transport. This can happen either because a transport is explicitly
18959 configured for the router, or because it generates a delivery to a file or a
18960 pipe. During the delivery process (that is, at transport time), the option
18961 string is expanded and is set as the home directory, unless overridden by a
18962 setting of &%home_directory%& on the transport.
18963 If the expansion fails for any reason, including forced failure, an error is
18964 logged, and delivery is deferred.
18966 If the transport does not specify a home directory, and
18967 &%transport_home_directory%& is not set for the router, the home directory for
18968 the transport is taken from the password data if &%check_local_user%& is set for
18969 the router. Otherwise it is taken from &%router_home_directory%& if that option
18970 is set; if not, no home directory is set for the transport.
18972 See chapter &<<CHAPenvironment>>& for further details of the local delivery
18978 .option unseen routers boolean&!! false
18979 .cindex "router" "carrying on after success"
18980 The result of string expansion for this option must be a valid boolean value,
18981 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
18982 result causes an error, and delivery is deferred. If the expansion is forced to
18983 fail, the default value for the option (false) is used. Other failures cause
18984 delivery to be deferred.
18986 When this option is set true, routing does not cease if the router accepts the
18987 address. Instead, a copy of the incoming address is passed to the next router,
18988 overriding a false setting of &%more%&. There is little point in setting
18989 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
18990 the value of &%unseen%& contains expansion items (and therefore, presumably, is
18991 sometimes true and sometimes false).
18993 .cindex "copy of message (&%unseen%& option)"
18994 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
18995 qualifier in filter files. It can be used to cause copies of messages to be
18996 delivered to some other destination, while also carrying out a normal delivery.
18997 In effect, the current address is made into a &"parent"& that has two children
18998 &-- one that is delivered as specified by this router, and a clone that goes on
18999 to be routed further. For this reason, &%unseen%& may not be combined with the
19000 &%one_time%& option in a &(redirect)& router.
19002 &*Warning*&: Header lines added to the address (or specified for removal) by
19003 this router or by previous routers affect the &"unseen"& copy of the message
19004 only. The clone that continues to be processed by further routers starts with
19005 no added headers and none specified for removal. For a &%redirect%& router, if
19006 a generated address is the same as the incoming address, this can lead to
19007 duplicate addresses with different header modifications. Exim does not do
19008 duplicate deliveries (except, in certain circumstances, to pipes -- see section
19009 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
19010 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
19011 &%redirect%& router may be of help.
19013 Unlike the handling of header modifications, any data that was set by the
19014 &%address_data%& option in the current or previous routers &'is'& passed on to
19015 subsequent routers.
19018 .option user routers string&!! "see below"
19019 .cindex "uid (user id)" "local delivery"
19020 .cindex "local transports" "uid and gid"
19021 .cindex "transport" "local"
19022 .cindex "router" "user for filter processing"
19023 .cindex "filter" "user for processing"
19024 When a router queues an address for a transport, and the transport does not
19025 specify a user, the user given here is used when running the delivery process.
19026 The user may be specified numerically or by name. If expansion fails, the
19027 error is logged and delivery is deferred.
19028 This user is also used by the &(redirect)& router when running a filter file.
19029 The default is unset, except when &%check_local_user%& is set. In this case,
19030 the default is taken from the password information. If the user is specified as
19031 a name, and &%group%& is not set, the group associated with the user is used.
19032 See also &%initgroups%& and &%group%& and the discussion in chapter
19033 &<<CHAPenvironment>>&.
19037 .option verify routers&!? boolean true
19038 Setting this option has the effect of setting &%verify_sender%& and
19039 &%verify_recipient%& to the same value.
19042 .option verify_only routers&!? boolean false
19043 .cindex "EXPN" "with &%verify_only%&"
19045 .cindex "router" "used only when verifying"
19046 If this option is set, the router is used only when verifying an address,
19047 delivering in cutthrough mode or
19048 testing with the &%-bv%& option, not when actually doing a delivery, testing
19049 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
19050 restricted to verifying only senders or recipients by means of
19051 &%verify_sender%& and &%verify_recipient%&.
19053 &*Warning*&: When the router is being run to verify addresses for an incoming
19054 SMTP message, Exim is not running as root, but under its own uid. If the router
19055 accesses any files, you need to make sure that they are accessible to the Exim
19059 .option verify_recipient routers&!? boolean true
19060 If this option is false, the router is skipped when verifying recipient
19062 delivering in cutthrough mode
19063 or testing recipient verification using &%-bv%&.
19064 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19066 See also the &$verify_mode$& variable.
19069 .option verify_sender routers&!? boolean true
19070 If this option is false, the router is skipped when verifying sender addresses
19071 or testing sender verification using &%-bvs%&.
19072 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19074 See also the &$verify_mode$& variable.
19075 .ecindex IIDgenoprou1
19076 .ecindex IIDgenoprou2
19083 . ////////////////////////////////////////////////////////////////////////////
19084 . ////////////////////////////////////////////////////////////////////////////
19086 .chapter "The accept router" "CHID4"
19087 .cindex "&(accept)& router"
19088 .cindex "routers" "&(accept)&"
19089 The &(accept)& router has no private options of its own. Unless it is being
19090 used purely for verification (see &%verify_only%&) a transport is required to
19091 be defined by the generic &%transport%& option. If the preconditions that are
19092 specified by generic options are met, the router accepts the address and queues
19093 it for the given transport. The most common use of this router is for setting
19094 up deliveries to local mailboxes. For example:
19098 domains = mydomain.example
19100 transport = local_delivery
19102 The &%domains%& condition in this example checks the domain of the address, and
19103 &%check_local_user%& checks that the local part is the login of a local user.
19104 When both preconditions are met, the &(accept)& router runs, and queues the
19105 address for the &(local_delivery)& transport.
19112 . ////////////////////////////////////////////////////////////////////////////
19113 . ////////////////////////////////////////////////////////////////////////////
19115 .chapter "The dnslookup router" "CHAPdnslookup"
19116 .scindex IIDdnsrou1 "&(dnslookup)& router"
19117 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
19118 The &(dnslookup)& router looks up the hosts that handle mail for the
19119 recipient's domain in the DNS. A transport must always be set for this router,
19120 unless &%verify_only%& is set.
19122 If SRV support is configured (see &%check_srv%& below), Exim first searches for
19123 SRV records. If none are found, or if SRV support is not configured,
19124 MX records are looked up. If no MX records exist, address records are sought.
19125 However, &%mx_domains%& can be set to disable the direct use of address
19128 MX records of equal priority are sorted by Exim into a random order. Exim then
19129 looks for address records for the host names obtained from MX or SRV records.
19130 When a host has more than one IP address, they are sorted into a random order,
19131 except that IPv6 addresses are sorted before IPv4 addresses. If all the
19132 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
19133 generic option, the router declines.
19135 Unless they have the highest priority (lowest MX value), MX records that point
19136 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
19137 are discarded, together with any other MX records of equal or lower priority.
19139 .cindex "MX record" "pointing to local host"
19140 .cindex "local host" "MX pointing to"
19141 .oindex "&%self%&" "in &(dnslookup)& router"
19142 If the host pointed to by the highest priority MX record, or looked up as an
19143 address record, is the local host, or matches &%hosts_treat_as_local%&, what
19144 happens is controlled by the generic &%self%& option.
19147 .section "Problems with DNS lookups" "SECTprowitdnsloo"
19148 There have been problems with DNS servers when SRV records are looked up.
19149 Some misbehaving servers return a DNS error or timeout when a non-existent
19150 SRV record is sought. Similar problems have in the past been reported for
19151 MX records. The global &%dns_again_means_nonexist%& option can help with this
19152 problem, but it is heavy-handed because it is a global option.
19154 For this reason, there are two options, &%srv_fail_domains%& and
19155 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
19156 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
19157 an attempt to look up an SRV or MX record causes one of these results, and the
19158 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
19159 such record"&. In the case of an SRV lookup, this means that the router
19160 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
19161 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
19162 case routing fails.
19165 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
19166 .cindex "&(dnslookup)& router" "declines"
19167 There are a few cases where a &(dnslookup)& router will decline to accept
19168 an address; if such a router is expected to handle "all remaining non-local
19169 domains", then it is important to set &%no_more%&.
19171 The router will defer rather than decline if the domain
19172 is found in the &%fail_defer_domains%& router option.
19174 Reasons for a &(dnslookup)& router to decline currently include:
19176 The domain does not exist in DNS
19178 The domain exists but the MX record's host part is just "."; this is a common
19179 convention (borrowed from SRV) used to indicate that there is no such service
19180 for this domain and to not fall back to trying A/AAAA records.
19182 Ditto, but for SRV records, when &%check_srv%& is set on this router.
19184 MX record points to a non-existent host.
19186 MX record points to an IP address and the main section option
19187 &%allow_mx_to_ip%& is not set.
19189 MX records exist and point to valid hosts, but all hosts resolve only to
19190 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
19192 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
19193 &%dns_check_names_pattern%& for handling one variant of this)
19195 &%check_secondary_mx%& is set on this router but the local host can
19196 not be found in the MX records (see below)
19202 .section "Private options for dnslookup" "SECID118"
19203 .cindex "options" "&(dnslookup)& router"
19204 The private options for the &(dnslookup)& router are as follows:
19206 .option check_secondary_mx dnslookup boolean false
19207 .cindex "MX record" "checking for secondary"
19208 If this option is set, the router declines unless the local host is found in
19209 (and removed from) the list of hosts obtained by MX lookup. This can be used to
19210 process domains for which the local host is a secondary mail exchanger
19211 differently to other domains. The way in which Exim decides whether a host is
19212 the local host is described in section &<<SECTreclocipadd>>&.
19215 .option check_srv dnslookup string&!! unset
19216 .cindex "SRV record" "enabling use of"
19217 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
19218 addition to MX and address records. The support is disabled by default. To
19219 enable SRV support, set the &%check_srv%& option to the name of the service
19220 required. For example,
19224 looks for SRV records that refer to the normal smtp service. The option is
19225 expanded, so the service name can vary from message to message or address
19226 to address. This might be helpful if SRV records are being used for a
19227 submission service. If the expansion is forced to fail, the &%check_srv%&
19228 option is ignored, and the router proceeds to look for MX records in the
19231 When the expansion succeeds, the router searches first for SRV records for
19232 the given service (it assumes TCP protocol). A single SRV record with a
19233 host name that consists of just a single dot indicates &"no such service for
19234 this domain"&; if this is encountered, the router declines. If other kinds of
19235 SRV record are found, they are used to construct a host list for delivery
19236 according to the rules of RFC 2782. MX records are not sought in this case.
19238 When no SRV records are found, MX records (and address records) are sought in
19239 the traditional way. In other words, SRV records take precedence over MX
19240 records, just as MX records take precedence over address records. Note that
19241 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
19242 defined it. It is apparently believed that MX records are sufficient for email
19243 and that SRV records should not be used for this purpose. However, SRV records
19244 have an additional &"weight"& feature which some people might find useful when
19245 trying to split an SMTP load between hosts of different power.
19247 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
19248 when there is a DNS lookup error.
19253 .option fail_defer_domains dnslookup "domain list&!!" unset
19254 .cindex "MX record" "not found"
19255 DNS lookups for domains matching &%fail_defer_domains%&
19256 which find no matching record will cause the router to defer
19257 rather than the default behaviour of decline.
19258 This maybe be useful for queueing messages for a newly created
19259 domain while the DNS configuration is not ready.
19260 However, it will result in any message with mistyped domains
19264 .option ipv4_only "string&!!" unset
19265 .cindex IPv6 disabling
19266 .cindex DNS "IPv6 disabling"
19267 The string is expanded, and if the result is anything but a forced failure,
19268 or an empty string, or one of the strings “0” or “no” or “false”
19269 (checked without regard to the case of the letters),
19270 only A records are used.
19272 .option ipv4_prefer "string&!!" unset
19273 .cindex IPv4 preference
19274 .cindex DNS "IPv4 preference"
19275 The string is expanded, and if the result is anything but a forced failure,
19276 or an empty string, or one of the strings “0” or “no” or “false”
19277 (checked without regard to the case of the letters),
19278 A records are sorted before AAAA records (inverting the default).
19280 .option mx_domains dnslookup "domain list&!!" unset
19281 .cindex "MX record" "required to exist"
19282 .cindex "SRV record" "required to exist"
19283 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
19284 record in order to be recognized. (The name of this option could be improved.)
19285 For example, if all the mail hosts in &'fict.example'& are known to have MX
19286 records, except for those in &'discworld.fict.example'&, you could use this
19289 mx_domains = ! *.discworld.fict.example : *.fict.example
19291 This specifies that messages addressed to a domain that matches the list but
19292 has no MX record should be bounced immediately instead of being routed using
19293 the address record.
19296 .option mx_fail_domains dnslookup "domain list&!!" unset
19297 If the DNS lookup for MX records for one of the domains in this list causes a
19298 DNS lookup error, Exim behaves as if no MX records were found. See section
19299 &<<SECTprowitdnsloo>>& for more discussion.
19304 .option qualify_single dnslookup boolean true
19305 .cindex "DNS" "resolver options"
19306 .cindex "DNS" "qualifying single-component names"
19307 When this option is true, the resolver option RES_DEFNAMES is set for DNS
19308 lookups. Typically, but not standardly, this causes the resolver to qualify
19309 single-component names with the default domain. For example, on a machine
19310 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
19311 &'thesaurus.ref.example'& inside the resolver. For details of what your
19312 resolver actually does, consult your man pages for &'resolver'& and
19317 .option rewrite_headers dnslookup boolean true
19318 .cindex "rewriting" "header lines"
19319 .cindex "header lines" "rewriting"
19320 If the domain name in the address that is being processed is not fully
19321 qualified, it may be expanded to its full form by a DNS lookup. For example, if
19322 an address is specified as &'dormouse@teaparty'&, the domain might be
19323 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
19324 occur as a result of setting the &%widen_domains%& option. If
19325 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
19326 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
19327 header lines of the message are rewritten with the full domain name.
19329 This option should be turned off only when it is known that no message is
19330 ever going to be sent outside an environment where the abbreviation makes
19333 When an MX record is looked up in the DNS and matches a wildcard record, name
19334 servers normally return a record containing the name that has been looked up,
19335 making it impossible to detect whether a wildcard was present or not. However,
19336 some name servers have recently been seen to return the wildcard entry. If the
19337 name returned by a DNS lookup begins with an asterisk, it is not used for
19341 .option same_domain_copy_routing dnslookup boolean false
19342 .cindex "address" "copying routing"
19343 Addresses with the same domain are normally routed by the &(dnslookup)& router
19344 to the same list of hosts. However, this cannot be presumed, because the router
19345 options and preconditions may refer to the local part of the address. By
19346 default, therefore, Exim routes each address in a message independently. DNS
19347 servers run caches, so repeated DNS lookups are not normally expensive, and in
19348 any case, personal messages rarely have more than a few recipients.
19350 If you are running mailing lists with large numbers of subscribers at the same
19351 domain, and you are using a &(dnslookup)& router which is independent of the
19352 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
19353 lookups for identical domains in one message. In this case, when &(dnslookup)&
19354 routes an address to a remote transport, any other unrouted addresses in the
19355 message that have the same domain are automatically given the same routing
19356 without processing them independently,
19357 provided the following conditions are met:
19360 No router that processed the address specified &%headers_add%& or
19361 &%headers_remove%&.
19363 The router did not change the address in any way, for example, by &"widening"&
19370 .option search_parents dnslookup boolean false
19371 .cindex "DNS" "resolver options"
19372 When this option is true, the resolver option RES_DNSRCH is set for DNS
19373 lookups. This is different from the &%qualify_single%& option in that it
19374 applies to domains containing dots. Typically, but not standardly, it causes
19375 the resolver to search for the name in the current domain and in parent
19376 domains. For example, on a machine in the &'fict.example'& domain, if looking
19377 up &'teaparty.wonderland'& failed, the resolver would try
19378 &'teaparty.wonderland.fict.example'&. For details of what your resolver
19379 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
19381 Setting this option true can cause problems in domains that have a wildcard MX
19382 record, because any domain that does not have its own MX record matches the
19387 .option srv_fail_domains dnslookup "domain list&!!" unset
19388 If the DNS lookup for SRV records for one of the domains in this list causes a
19389 DNS lookup error, Exim behaves as if no SRV records were found. See section
19390 &<<SECTprowitdnsloo>>& for more discussion.
19395 .option widen_domains dnslookup "string list" unset
19396 .cindex "domain" "partial; widening"
19397 If a DNS lookup fails and this option is set, each of its strings in turn is
19398 added onto the end of the domain, and the lookup is tried again. For example,
19401 widen_domains = fict.example:ref.example
19403 is set and a lookup of &'klingon.dictionary'& fails,
19404 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
19405 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
19406 and &%search_parents%& options can cause some widening to be undertaken inside
19407 the DNS resolver. &%widen_domains%& is not applied to sender addresses
19408 when verifying, unless &%rewrite_headers%& is false (not the default).
19411 .section "Effect of qualify_single and search_parents" "SECID119"
19412 When a domain from an envelope recipient is changed by the resolver as a result
19413 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
19414 corresponding address in the message's header lines unless &%rewrite_headers%&
19415 is set false. Exim then re-routes the address, using the full domain.
19417 These two options affect only the DNS lookup that takes place inside the router
19418 for the domain of the address that is being routed. They do not affect lookups
19419 such as that implied by
19423 that may happen while processing a router precondition before the router is
19424 entered. No widening ever takes place for these lookups.
19425 .ecindex IIDdnsrou1
19426 .ecindex IIDdnsrou2
19436 . ////////////////////////////////////////////////////////////////////////////
19437 . ////////////////////////////////////////////////////////////////////////////
19439 .chapter "The ipliteral router" "CHID5"
19440 .cindex "&(ipliteral)& router"
19441 .cindex "domain literal" "routing"
19442 .cindex "routers" "&(ipliteral)&"
19443 This router has no private options. Unless it is being used purely for
19444 verification (see &%verify_only%&) a transport is required to be defined by the
19445 generic &%transport%& option. The router accepts the address if its domain part
19446 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
19447 router handles the address
19451 by setting up delivery to the host with that IP address. IPv4 domain literals
19452 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
19453 are similar, but the address is preceded by &`ipv6:`&. For example:
19455 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
19457 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
19458 grounds that sooner or later somebody will try it.
19460 .oindex "&%self%&" "in &(ipliteral)& router"
19461 If the IP address matches something in &%ignore_target_hosts%&, the router
19462 declines. If an IP literal turns out to refer to the local host, the generic
19463 &%self%& option determines what happens.
19465 The RFCs require support for domain literals; however, their use is
19466 controversial in today's Internet. If you want to use this router, you must
19467 also set the main configuration option &%allow_domain_literals%&. Otherwise,
19468 Exim will not recognize the domain literal syntax in addresses.
19472 . ////////////////////////////////////////////////////////////////////////////
19473 . ////////////////////////////////////////////////////////////////////////////
19475 .chapter "The iplookup router" "CHID6"
19476 .cindex "&(iplookup)& router"
19477 .cindex "routers" "&(iplookup)&"
19478 The &(iplookup)& router was written to fulfil a specific requirement in
19479 Cambridge University (which in fact no longer exists). For this reason, it is
19480 not included in the binary of Exim by default. If you want to include it, you
19483 ROUTER_IPLOOKUP=yes
19485 in your &_Local/Makefile_& configuration file.
19487 The &(iplookup)& router routes an address by sending it over a TCP or UDP
19488 connection to one or more specific hosts. The host can then return the same or
19489 a different address &-- in effect rewriting the recipient address in the
19490 message's envelope. The new address is then passed on to subsequent routers. If
19491 this process fails, the address can be passed on to other routers, or delivery
19492 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
19493 must not be specified for it.
19495 .cindex "options" "&(iplookup)& router"
19496 .option hosts iplookup string unset
19497 This option must be supplied. Its value is a colon-separated list of host
19498 names. The hosts are looked up using &[gethostbyname()]&
19499 (or &[getipnodebyname()]& when available)
19500 and are tried in order until one responds to the query. If none respond, what
19501 happens is controlled by &%optional%&.
19504 .option optional iplookup boolean false
19505 If &%optional%& is true, if no response is obtained from any host, the address
19506 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
19507 delivery to the address is deferred.
19510 .option port iplookup integer 0
19511 .cindex "port" "&(iplookup)& router"
19512 This option must be supplied. It specifies the port number for the TCP or UDP
19516 .option protocol iplookup string udp
19517 This option can be set to &"udp"& or &"tcp"& to specify which of the two
19518 protocols is to be used.
19521 .option query iplookup string&!! "see below"
19522 This defines the content of the query that is sent to the remote hosts. The
19525 $local_part@$domain $local_part@$domain
19527 The repetition serves as a way of checking that a response is to the correct
19528 query in the default case (see &%response_pattern%& below).
19531 .option reroute iplookup string&!! unset
19532 If this option is not set, the rerouted address is precisely the byte string
19533 returned by the remote host, up to the first white space, if any. If set, the
19534 string is expanded to form the rerouted address. It can include parts matched
19535 in the response by &%response_pattern%& by means of numeric variables such as
19536 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
19537 whether or not a pattern is in use. In all cases, the rerouted address must end
19538 up in the form &'local_part@domain'&.
19541 .option response_pattern iplookup string unset
19542 This option can be set to a regular expression that is applied to the string
19543 returned from the remote host. If the pattern does not match the response, the
19544 router declines. If &%response_pattern%& is not set, no checking of the
19545 response is done, unless the query was defaulted, in which case there is a
19546 check that the text returned after the first white space is the original
19547 address. This checks that the answer that has been received is in response to
19548 the correct question. For example, if the response is just a new domain, the
19549 following could be used:
19551 response_pattern = ^([^@]+)$
19552 reroute = $local_part@$1
19555 .option timeout iplookup time 5s
19556 This specifies the amount of time to wait for a response from the remote
19557 machine. The same timeout is used for the &[connect()]& function for a TCP
19558 call. It does not apply to UDP.
19563 . ////////////////////////////////////////////////////////////////////////////
19564 . ////////////////////////////////////////////////////////////////////////////
19566 .chapter "The manualroute router" "CHID7"
19567 .scindex IIDmanrou1 "&(manualroute)& router"
19568 .scindex IIDmanrou2 "routers" "&(manualroute)&"
19569 .cindex "domain" "manually routing"
19570 The &(manualroute)& router is so-called because it provides a way of manually
19571 routing an address according to its domain. It is mainly used when you want to
19572 route addresses to remote hosts according to your own rules, bypassing the
19573 normal DNS routing that looks up MX records. However, &(manualroute)& can also
19574 route to local transports, a facility that may be useful if you want to save
19575 messages for dial-in hosts in local files.
19577 The &(manualroute)& router compares a list of domain patterns with the domain
19578 it is trying to route. If there is no match, the router declines. Each pattern
19579 has associated with it a list of hosts and some other optional data, which may
19580 include a transport. The combination of a pattern and its data is called a
19581 &"routing rule"&. For patterns that do not have an associated transport, the
19582 generic &%transport%& option must specify a transport, unless the router is
19583 being used purely for verification (see &%verify_only%&).
19586 In the case of verification, matching the domain pattern is sufficient for the
19587 router to accept the address. When actually routing an address for delivery,
19588 an address that matches a domain pattern is queued for the associated
19589 transport. If the transport is not a local one, a host list must be associated
19590 with the pattern; IP addresses are looked up for the hosts, and these are
19591 passed to the transport along with the mail address. For local transports, a
19592 host list is optional. If it is present, it is passed in &$host$& as a single
19595 The list of routing rules can be provided as an inline string in
19596 &%route_list%&, or the data can be obtained by looking up the domain in a file
19597 or database by setting &%route_data%&. Only one of these settings may appear in
19598 any one instance of &(manualroute)&. The format of routing rules is described
19599 below, following the list of private options.
19602 .section "Private options for manualroute" "SECTprioptman"
19604 .cindex "options" "&(manualroute)& router"
19605 The private options for the &(manualroute)& router are as follows:
19607 .option host_all_ignored manualroute string defer
19608 See &%host_find_failed%&.
19610 .option host_find_failed manualroute string freeze
19611 This option controls what happens when &(manualroute)& tries to find an IP
19612 address for a host, and the host does not exist. The option can be set to one
19613 of the following values:
19622 The default (&"freeze"&) assumes that this state is a serious configuration
19623 error. The difference between &"pass"& and &"decline"& is that the former
19624 forces the address to be passed to the next router (or the router defined by
19627 overriding &%no_more%&, whereas the latter passes the address to the next
19628 router only if &%more%& is true.
19630 The value &"ignore"& causes Exim to completely ignore a host whose IP address
19631 cannot be found. If all the hosts in the list are ignored, the behaviour is
19632 controlled by the &%host_all_ignored%& option. This takes the same values
19633 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
19635 The &%host_find_failed%& option applies only to a definite &"does not exist"&
19636 state; if a host lookup gets a temporary error, delivery is deferred unless the
19637 generic &%pass_on_timeout%& option is set.
19640 .option hosts_randomize manualroute boolean false
19641 .cindex "randomized host list"
19642 .cindex "host" "list of; randomized"
19643 If this option is set, the order of the items in a host list in a routing rule
19644 is randomized each time the list is used, unless an option in the routing rule
19645 overrides (see below). Randomizing the order of a host list can be used to do
19646 crude load sharing. However, if more than one mail address is routed by the
19647 same router to the same host list, the host lists are considered to be the same
19648 (even though they may be randomized into different orders) for the purpose of
19649 deciding whether to batch the deliveries into a single SMTP transaction.
19651 When &%hosts_randomize%& is true, a host list may be split
19652 into groups whose order is separately randomized. This makes it possible to
19653 set up MX-like behaviour. The boundaries between groups are indicated by an
19654 item that is just &`+`& in the host list. For example:
19656 route_list = * host1:host2:host3:+:host4:host5
19658 The order of the first three hosts and the order of the last two hosts is
19659 randomized for each use, but the first three always end up before the last two.
19660 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
19661 randomized host list is passed to an &(smtp)& transport that also has
19662 &%hosts_randomize set%&, the list is not re-randomized.
19665 .option route_data manualroute string&!! unset
19666 If this option is set, it must expand to yield the data part of a routing rule.
19667 Typically, the expansion string includes a lookup based on the domain. For
19670 route_data = ${lookup{$domain}dbm{/etc/routes}}
19672 If the expansion is forced to fail, or the result is an empty string, the
19673 router declines. Other kinds of expansion failure cause delivery to be
19677 .option route_list manualroute "string list" unset
19678 This string is a list of routing rules, in the form defined below. Note that,
19679 unlike most string lists, the items are separated by semicolons. This is so
19680 that they may contain colon-separated host lists.
19683 .option same_domain_copy_routing manualroute boolean false
19684 .cindex "address" "copying routing"
19685 Addresses with the same domain are normally routed by the &(manualroute)&
19686 router to the same list of hosts. However, this cannot be presumed, because the
19687 router options and preconditions may refer to the local part of the address. By
19688 default, therefore, Exim routes each address in a message independently. DNS
19689 servers run caches, so repeated DNS lookups are not normally expensive, and in
19690 any case, personal messages rarely have more than a few recipients.
19692 If you are running mailing lists with large numbers of subscribers at the same
19693 domain, and you are using a &(manualroute)& router which is independent of the
19694 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
19695 lookups for identical domains in one message. In this case, when
19696 &(manualroute)& routes an address to a remote transport, any other unrouted
19697 addresses in the message that have the same domain are automatically given the
19698 same routing without processing them independently. However, this is only done
19699 if &%headers_add%& and &%headers_remove%& are unset.
19704 .section "Routing rules in route_list" "SECID120"
19705 The value of &%route_list%& is a string consisting of a sequence of routing
19706 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
19707 entered as two semicolons. Alternatively, the list separator can be changed as
19708 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
19709 Empty rules are ignored. The format of each rule is
19711 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
19713 The following example contains two rules, each with a simple domain pattern and
19717 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
19718 thes.ref.example mail-3.ref.example:mail-4.ref.example
19720 The three parts of a rule are separated by white space. The pattern and the
19721 list of hosts can be enclosed in quotes if necessary, and if they are, the
19722 usual quoting rules apply. Each rule in a &%route_list%& must start with a
19723 single domain pattern, which is the only mandatory item in the rule. The
19724 pattern is in the same format as one item in a domain list (see section
19725 &<<SECTdomainlist>>&),
19726 except that it may not be the name of an interpolated file.
19727 That is, it may be wildcarded, or a regular expression, or a file or database
19728 lookup (with semicolons doubled, because of the use of semicolon as a separator
19729 in a &%route_list%&).
19731 The rules in &%route_list%& are searched in order until one of the patterns
19732 matches the domain that is being routed. The list of hosts and then options are
19733 then used as described below. If there is no match, the router declines. When
19734 &%route_list%& is set, &%route_data%& must not be set.
19738 .section "Routing rules in route_data" "SECID121"
19739 The use of &%route_list%& is convenient when there are only a small number of
19740 routing rules. For larger numbers, it is easier to use a file or database to
19741 hold the routing information, and use the &%route_data%& option instead.
19742 The value of &%route_data%& is a list of hosts, followed by (optional) options.
19743 Most commonly, &%route_data%& is set as a string that contains an
19744 expansion lookup. For example, suppose we place two routing rules in a file
19747 dict.ref.example: mail-1.ref.example:mail-2.ref.example
19748 thes.ref.example: mail-3.ref.example:mail-4.ref.example
19750 This data can be accessed by setting
19752 route_data = ${lookup{$domain}lsearch{/the/file/name}}
19754 Failure of the lookup results in an empty string, causing the router to
19755 decline. However, you do not have to use a lookup in &%route_data%&. The only
19756 requirement is that the result of expanding the string is a list of hosts,
19757 possibly followed by options, separated by white space. The list of hosts must
19758 be enclosed in quotes if it contains white space.
19763 .section "Format of the list of hosts" "SECID122"
19764 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
19765 always separately expanded before use. If the expansion fails, the router
19766 declines. The result of the expansion must be a colon-separated list of names
19767 and/or IP addresses, optionally also including ports.
19768 If the list is written with spaces, it must be protected with quotes.
19769 The format of each item
19770 in the list is described in the next section. The list separator can be changed
19771 as described in section &<<SECTlistsepchange>>&.
19773 If the list of hosts was obtained from a &%route_list%& item, the following
19774 variables are set during its expansion:
19777 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
19778 If the domain was matched against a regular expression, the numeric variables
19779 &$1$&, &$2$&, etc. may be set. For example:
19781 route_list = ^domain(\d+) host-$1.text.example
19784 &$0$& is always set to the entire domain.
19786 &$1$& is also set when partial matching is done in a file lookup.
19789 .vindex "&$value$&"
19790 If the pattern that matched the domain was a lookup item, the data that was
19791 looked up is available in the expansion variable &$value$&. For example:
19793 route_list = lsearch;;/some/file.routes $value
19797 Note the doubling of the semicolon in the pattern that is necessary because
19798 semicolon is the default route list separator.
19802 .section "Format of one host item" "SECTformatonehostitem"
19803 Each item in the list of hosts is either a host name or an IP address,
19804 optionally with an attached port number. When no port is given, an IP address
19805 is not enclosed in brackets. When a port is specified, it overrides the port
19806 specification on the transport. The port is separated from the name or address
19807 by a colon. This leads to some complications:
19810 Because colon is the default separator for the list of hosts, either
19811 the colon that specifies a port must be doubled, or the list separator must
19812 be changed. The following two examples have the same effect:
19814 route_list = * "host1.tld::1225 : host2.tld::1226"
19815 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
19818 When IPv6 addresses are involved, it gets worse, because they contain
19819 colons of their own. To make this case easier, it is permitted to
19820 enclose an IP address (either v4 or v6) in square brackets if a port
19821 number follows. For example:
19823 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
19827 .section "How the list of hosts is used" "SECThostshowused"
19828 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
19829 the hosts is tried, in the order specified, when carrying out the SMTP
19830 delivery. However, the order can be changed by setting the &%hosts_randomize%&
19831 option, either on the router (see section &<<SECTprioptman>>& above), or on the
19834 Hosts may be listed by name or by IP address. An unadorned name in the list of
19835 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
19836 interpreted as an indirection to a sublist of hosts obtained by looking up MX
19837 records in the DNS. For example:
19839 route_list = * x.y.z:p.q.r/MX:e.f.g
19841 If this feature is used with a port specifier, the port must come last. For
19844 route_list = * dom1.tld/mx::1225
19846 If the &%hosts_randomize%& option is set, the order of the items in the list is
19847 randomized before any lookups are done. Exim then scans the list; for any name
19848 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
19849 be an interface on the local host and the item is not the first in the list,
19850 Exim discards it and any subsequent items. If it is the first item, what
19851 happens is controlled by the
19852 .oindex "&%self%&" "in &(manualroute)& router"
19853 &%self%& option of the router.
19855 A name on the list that is followed by &`/MX`& is replaced with the list of
19856 hosts obtained by looking up MX records for the name. This is always a DNS
19857 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
19858 below) are not relevant here. The order of these hosts is determined by the
19859 preference values in the MX records, according to the usual rules. Because
19860 randomizing happens before the MX lookup, it does not affect the order that is
19861 defined by MX preferences.
19863 If the local host is present in the sublist obtained from MX records, but is
19864 not the most preferred host in that list, it and any equally or less
19865 preferred hosts are removed before the sublist is inserted into the main list.
19867 If the local host is the most preferred host in the MX list, what happens
19868 depends on where in the original list of hosts the &`/MX`& item appears. If it
19869 is not the first item (that is, there are previous hosts in the main list),
19870 Exim discards this name and any subsequent items in the main list.
19872 If the MX item is first in the list of hosts, and the local host is the
19873 most preferred host, what happens is controlled by the &%self%& option of the
19876 DNS failures when lookup up the MX records are treated in the same way as DNS
19877 failures when looking up IP addresses: &%pass_on_timeout%& and
19878 &%host_find_failed%& are used when relevant.
19880 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
19881 whether obtained from an MX lookup or not.
19885 .section "How the options are used" "SECThowoptused"
19886 The options are a sequence of words, space-separated.
19887 One of the words can be the name of a transport; this overrides the
19888 &%transport%& option on the router for this particular routing rule only. The
19889 other words (if present) control randomization of the list of hosts on a
19890 per-rule basis, and how the IP addresses of the hosts are to be found when
19891 routing to a remote transport. These options are as follows:
19894 &%randomize%&: randomize the order of the hosts in this list, overriding the
19895 setting of &%hosts_randomize%& for this routing rule only.
19897 &%no_randomize%&: do not randomize the order of the hosts in this list,
19898 overriding the setting of &%hosts_randomize%& for this routing rule only.
19900 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
19901 find IP addresses. This function may ultimately cause a DNS lookup, but it may
19902 also look in &_/etc/hosts_& or other sources of information.
19904 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
19905 no address records are found. If there is a temporary DNS error (such as a
19906 timeout), delivery is deferred.
19908 &%ipv4_only%&: in direct DNS lookups, look up only A records.
19910 &%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
19915 route_list = domain1 host1:host2:host3 randomize bydns;\
19916 domain2 host4:host5
19918 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
19919 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
19920 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
19921 or &[gethostbyname()]&, and the result of the lookup is the result of that
19924 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
19925 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
19926 instead of TRY_AGAIN. That is why the default action is to try a DNS
19927 lookup first. Only if that gives a definite &"no such host"& is the local
19930 &*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
19931 inadvertent constraint that a transport name as an option had to be the last
19936 If no IP address for a host can be found, what happens is controlled by the
19937 &%host_find_failed%& option.
19940 When an address is routed to a local transport, IP addresses are not looked up.
19941 The host list is passed to the transport in the &$host$& variable.
19945 .section "Manualroute examples" "SECID123"
19946 In some of the examples that follow, the presence of the &%remote_smtp%&
19947 transport, as defined in the default configuration file, is assumed:
19950 .cindex "smart host" "example router"
19951 The &(manualroute)& router can be used to forward all external mail to a
19952 &'smart host'&. If you have set up, in the main part of the configuration, a
19953 named domain list that contains your local domains, for example:
19955 domainlist local_domains = my.domain.example
19957 You can arrange for all other domains to be routed to a smart host by making
19958 your first router something like this:
19961 driver = manualroute
19962 domains = !+local_domains
19963 transport = remote_smtp
19964 route_list = * smarthost.ref.example
19966 This causes all non-local addresses to be sent to the single host
19967 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
19968 they are tried in order
19969 (but you can use &%hosts_randomize%& to vary the order each time).
19970 Another way of configuring the same thing is this:
19973 driver = manualroute
19974 transport = remote_smtp
19975 route_list = !+local_domains smarthost.ref.example
19977 There is no difference in behaviour between these two routers as they stand.
19978 However, they behave differently if &%no_more%& is added to them. In the first
19979 example, the router is skipped if the domain does not match the &%domains%&
19980 precondition; the following router is always tried. If the router runs, it
19981 always matches the domain and so can never decline. Therefore, &%no_more%&
19982 would have no effect. In the second case, the router is never skipped; it
19983 always runs. However, if it doesn't match the domain, it declines. In this case
19984 &%no_more%& would prevent subsequent routers from running.
19987 .cindex "mail hub example"
19988 A &'mail hub'& is a host which receives mail for a number of domains via MX
19989 records in the DNS and delivers it via its own private routing mechanism. Often
19990 the final destinations are behind a firewall, with the mail hub being the one
19991 machine that can connect to machines both inside and outside the firewall. The
19992 &(manualroute)& router is usually used on a mail hub to route incoming messages
19993 to the correct hosts. For a small number of domains, the routing can be inline,
19994 using the &%route_list%& option, but for a larger number a file or database
19995 lookup is easier to manage.
19997 If the domain names are in fact the names of the machines to which the mail is
19998 to be sent by the mail hub, the configuration can be quite simple. For
20002 driver = manualroute
20003 transport = remote_smtp
20004 route_list = *.rhodes.tvs.example $domain
20006 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
20007 whose names are the same as the mail domains. A similar approach can be taken
20008 if the host name can be obtained from the domain name by a string manipulation
20009 that the expansion facilities can handle. Otherwise, a lookup based on the
20010 domain can be used to find the host:
20013 driver = manualroute
20014 transport = remote_smtp
20015 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
20017 The result of the lookup must be the name or IP address of the host (or
20018 hosts) to which the address is to be routed. If the lookup fails, the route
20019 data is empty, causing the router to decline. The address then passes to the
20023 .cindex "batched SMTP output example"
20024 .cindex "SMTP" "batched outgoing; example"
20025 You can use &(manualroute)& to deliver messages to pipes or files in batched
20026 SMTP format for onward transportation by some other means. This is one way of
20027 storing mail for a dial-up host when it is not connected. The route list entry
20028 can be as simple as a single domain name in a configuration like this:
20031 driver = manualroute
20032 transport = batchsmtp_appendfile
20033 route_list = saved.domain.example
20035 though often a pattern is used to pick up more than one domain. If there are
20036 several domains or groups of domains with different transport requirements,
20037 different transports can be listed in the routing information:
20040 driver = manualroute
20042 *.saved.domain1.example $domain batch_appendfile; \
20043 *.saved.domain2.example \
20044 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
20047 .vindex "&$domain$&"
20049 The first of these just passes the domain in the &$host$& variable, which
20050 doesn't achieve much (since it is also in &$domain$&), but the second does a
20051 file lookup to find a value to pass, causing the router to decline to handle
20052 the address if the lookup fails.
20055 .cindex "UUCP" "example of router for"
20056 Routing mail directly to UUCP software is a specific case of the use of
20057 &(manualroute)& in a gateway to another mail environment. This is an example of
20058 one way it can be done:
20064 command = /usr/local/bin/uux -r - \
20065 ${substr_-5:$host}!rmail ${local_part}
20066 return_fail_output = true
20071 driver = manualroute
20073 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
20075 The file &_/usr/local/exim/uucphosts_& contains entries like
20077 darksite.ethereal.example: darksite.UUCP
20079 It can be set up more simply without adding and removing &".UUCP"& but this way
20080 makes clear the distinction between the domain name
20081 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
20083 .ecindex IIDmanrou1
20084 .ecindex IIDmanrou2
20093 . ////////////////////////////////////////////////////////////////////////////
20094 . ////////////////////////////////////////////////////////////////////////////
20096 .chapter "The queryprogram router" "CHAPdriverlast"
20097 .scindex IIDquerou1 "&(queryprogram)& router"
20098 .scindex IIDquerou2 "routers" "&(queryprogram)&"
20099 .cindex "routing" "by external program"
20100 The &(queryprogram)& router routes an address by running an external command
20101 and acting on its output. This is an expensive way to route, and is intended
20102 mainly for use in lightly-loaded systems, or for performing experiments.
20103 However, if it is possible to use the precondition options (&%domains%&,
20104 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
20105 be used in special cases, even on a busy host. There are the following private
20107 .cindex "options" "&(queryprogram)& router"
20109 .option command queryprogram string&!! unset
20110 This option must be set. It specifies the command that is to be run. The
20111 command is split up into a command name and arguments, and then each is
20112 expanded separately (exactly as for a &(pipe)& transport, described in chapter
20113 &<<CHAPpipetransport>>&).
20116 .option command_group queryprogram string unset
20117 .cindex "gid (group id)" "in &(queryprogram)& router"
20118 This option specifies a gid to be set when running the command while routing an
20119 address for deliver. It must be set if &%command_user%& specifies a numerical
20120 uid. If it begins with a digit, it is interpreted as the numerical value of the
20121 gid. Otherwise it is looked up using &[getgrnam()]&.
20124 .option command_user queryprogram string unset
20125 .cindex "uid (user id)" "for &(queryprogram)&"
20126 This option must be set. It specifies the uid which is set when running the
20127 command while routing an address for delivery. If the value begins with a digit,
20128 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
20129 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
20130 not set, a value for the gid also.
20132 &*Warning:*& Changing uid and gid is possible only when Exim is running as
20133 root, which it does during a normal delivery in a conventional configuration.
20134 However, when an address is being verified during message reception, Exim is
20135 usually running as the Exim user, not as root. If the &(queryprogram)& router
20136 is called from a non-root process, Exim cannot change uid or gid before running
20137 the command. In this circumstance the command runs under the current uid and
20141 .option current_directory queryprogram string /
20142 This option specifies an absolute path which is made the current directory
20143 before running the command.
20146 .option timeout queryprogram time 1h
20147 If the command does not complete within the timeout period, its process group
20148 is killed and the message is frozen. A value of zero time specifies no
20152 The standard output of the command is connected to a pipe, which is read when
20153 the command terminates. It should consist of a single line of output,
20154 containing up to five fields, separated by white space. The maximum length of
20155 the line is 1023 characters. Longer lines are silently truncated. The first
20156 field is one of the following words (case-insensitive):
20159 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
20162 &'Decline'&: the router declines; pass the address to the next router, unless
20163 &%no_more%& is set.
20165 &'Fail'&: routing failed; do not pass the address to any more routers. Any
20166 subsequent text on the line is an error message. If the router is run as part
20167 of address verification during an incoming SMTP message, the message is
20168 included in the SMTP response.
20170 &'Defer'&: routing could not be completed at this time; try again later. Any
20171 subsequent text on the line is an error message which is logged. It is not
20172 included in any SMTP response.
20174 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
20176 &'Pass'&: pass the address to the next router (or the router specified by
20177 &%pass_router%&), overriding &%no_more%&.
20179 &'Redirect'&: the message is redirected. The remainder of the line is a list of
20180 new addresses, which are routed independently, starting with the first router,
20181 or the router specified by &%redirect_router%&, if set.
20184 When the first word is &'accept'&, the remainder of the line consists of a
20185 number of keyed data values, as follows (split into two lines here, to fit on
20188 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
20189 LOOKUP=byname|bydns DATA=<text>
20191 The data items can be given in any order, and all are optional. If no transport
20192 is included, the transport specified by the generic &%transport%& option is
20193 used. The list of hosts and the lookup type are needed only if the transport is
20194 an &(smtp)& transport that does not itself supply a list of hosts.
20196 The format of the list of hosts is the same as for the &(manualroute)& router.
20197 As well as host names and IP addresses with optional port numbers, as described
20198 in section &<<SECTformatonehostitem>>&, it may contain names followed by
20199 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
20200 (see section &<<SECThostshowused>>&).
20202 If the lookup type is not specified, Exim behaves as follows when trying to
20203 find an IP address for each host: First, a DNS lookup is done. If this yields
20204 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
20205 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
20206 result of the lookup is the result of that call.
20208 .vindex "&$address_data$&"
20209 If the DATA field is set, its value is placed in the &$address_data$&
20210 variable. For example, this return line
20212 accept hosts=x1.y.example:x2.y.example data="rule1"
20214 routes the address to the default transport, passing a list of two hosts. When
20215 the transport runs, the string &"rule1"& is in &$address_data$&.
20216 .ecindex IIDquerou1
20217 .ecindex IIDquerou2
20222 . ////////////////////////////////////////////////////////////////////////////
20223 . ////////////////////////////////////////////////////////////////////////////
20225 .chapter "The redirect router" "CHAPredirect"
20226 .scindex IIDredrou1 "&(redirect)& router"
20227 .scindex IIDredrou2 "routers" "&(redirect)&"
20228 .cindex "alias file" "in a &(redirect)& router"
20229 .cindex "address redirection" "&(redirect)& router"
20230 The &(redirect)& router handles several kinds of address redirection. Its most
20231 common uses are for resolving local part aliases from a central alias file
20232 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
20233 files, but it has many other potential uses. The incoming address can be
20234 redirected in several different ways:
20237 It can be replaced by one or more new addresses which are themselves routed
20240 It can be routed to be delivered to a given file or directory.
20242 It can be routed to be delivered to a specified pipe command.
20244 It can cause an automatic reply to be generated.
20246 It can be forced to fail, optionally with a custom error message.
20248 It can be temporarily deferred, optionally with a custom message.
20250 It can be discarded.
20253 The generic &%transport%& option must not be set for &(redirect)& routers.
20254 However, there are some private options which define transports for delivery to
20255 files and pipes, and for generating autoreplies. See the &%file_transport%&,
20256 &%pipe_transport%& and &%reply_transport%& descriptions below.
20258 If success DSNs have been requested
20259 .cindex "DSN" "success"
20260 .cindex "Delivery Status Notification" "success"
20261 redirection triggers one and the DSN options are not passed any further.
20265 .section "Redirection data" "SECID124"
20266 The router operates by interpreting a text string which it obtains either by
20267 expanding the contents of the &%data%& option, or by reading the entire
20268 contents of a file whose name is given in the &%file%& option. These two
20269 options are mutually exclusive. The first is commonly used for handling system
20270 aliases, in a configuration like this:
20274 data = ${lookup{$local_part}lsearch{/etc/aliases}}
20276 If the lookup fails, the expanded string in this example is empty. When the
20277 expansion of &%data%& results in an empty string, the router declines. A forced
20278 expansion failure also causes the router to decline; other expansion failures
20279 cause delivery to be deferred.
20281 A configuration using &%file%& is commonly used for handling users'
20282 &_.forward_& files, like this:
20287 file = $home/.forward
20290 If the file does not exist, or causes no action to be taken (for example, it is
20291 empty or consists only of comments), the router declines. &*Warning*&: This
20292 is not the case when the file contains syntactically valid items that happen to
20293 yield empty addresses, for example, items containing only RFC 2822 address
20298 .section "Forward files and address verification" "SECID125"
20299 .cindex "address redirection" "while verifying"
20300 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
20301 &_.forward_& files, as in the example above. There are two reasons for this:
20304 When Exim is receiving an incoming SMTP message from a remote host, it is
20305 running under the Exim uid, not as root. Exim is unable to change uid to read
20306 the file as the user, and it may not be able to read it as the Exim user. So in
20307 practice the router may not be able to operate.
20309 However, even when the router can operate, the existence of a &_.forward_& file
20310 is unimportant when verifying an address. What should be checked is whether the
20311 local part is a valid user name or not. Cutting out the redirection processing
20312 saves some resources.
20320 .section "Interpreting redirection data" "SECID126"
20321 .cindex "Sieve filter" "specifying in redirection data"
20322 .cindex "filter" "specifying in redirection data"
20323 The contents of the data string, whether obtained from &%data%& or &%file%&,
20324 can be interpreted in two different ways:
20327 If the &%allow_filter%& option is set true, and the data begins with the text
20328 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
20329 &'filtering'& instructions in the form of an Exim or Sieve filter file,
20330 respectively. Details of the syntax and semantics of filter files are described
20331 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
20332 document is intended for use by end users.
20334 Otherwise, the data must be a comma-separated list of redirection items, as
20335 described in the next section.
20338 When a message is redirected to a file (a &"mail folder"&), the filename given
20339 in a non-filter redirection list must always be an absolute path. A filter may
20340 generate a relative path &-- how this is handled depends on the transport's
20341 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
20342 for the &(appendfile)& transport.
20346 .section "Items in a non-filter redirection list" "SECTitenonfilred"
20347 .cindex "address redirection" "non-filter list items"
20348 When the redirection data is not an Exim or Sieve filter, for example, if it
20349 comes from a conventional alias or forward file, it consists of a list of
20350 addresses, filenames, pipe commands, or certain special items (see section
20351 &<<SECTspecitredli>>& below). The special items can be individually enabled or
20352 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
20353 depending on their default values. The items in the list are separated by
20354 commas or newlines.
20355 If a comma is required in an item, the entire item must be enclosed in double
20358 Lines starting with a # character are comments, and are ignored, and # may
20359 also appear following a comma, in which case everything between the # and the
20360 next newline character is ignored.
20362 If an item is entirely enclosed in double quotes, these are removed. Otherwise
20363 double quotes are retained because some forms of mail address require their use
20364 (but never to enclose the entire address). In the following description,
20365 &"item"& refers to what remains after any surrounding double quotes have been
20368 .vindex "&$local_part$&"
20369 &*Warning*&: If you use an Exim expansion to construct a redirection address,
20370 and the expansion contains a reference to &$local_part$&, you should make use
20371 of the &%quote_local_part%& expansion operator, in case the local part contains
20372 special characters. For example, to redirect all mail for the domain
20373 &'obsolete.example'&, retaining the existing local part, you could use this
20376 data = ${quote_local_part:$local_part}@newdomain.example
20380 .section "Redirecting to a local mailbox" "SECTredlocmai"
20381 .cindex "routing" "loops in"
20382 .cindex "loop" "while routing, avoidance of"
20383 .cindex "address redirection" "to local mailbox"
20384 A redirection item may safely be the same as the address currently under
20385 consideration. This does not cause a routing loop, because a router is
20386 automatically skipped if any ancestor of the address that is being processed
20387 is the same as the current address and was processed by the current router.
20388 Such an address is therefore passed to the following routers, so it is handled
20389 as if there were no redirection. When making this loop-avoidance test, the
20390 complete local part, including any prefix or suffix, is used.
20392 .cindex "address redirection" "local part without domain"
20393 Specifying the same local part without a domain is a common usage in personal
20394 filter files when the user wants to have messages delivered to the local
20395 mailbox and also forwarded elsewhere. For example, the user whose login is
20396 &'cleo'& might have a &_.forward_& file containing this:
20398 cleo, cleopatra@egypt.example
20400 .cindex "backslash in alias file"
20401 .cindex "alias file" "backslash in"
20402 For compatibility with other MTAs, such unqualified local parts may be
20403 preceded by &"\"&, but this is not a requirement for loop prevention. However,
20404 it does make a difference if more than one domain is being handled
20407 If an item begins with &"\"& and the rest of the item parses as a valid RFC
20408 2822 address that does not include a domain, the item is qualified using the
20409 domain of the incoming address. In the absence of a leading &"\"&, unqualified
20410 addresses are qualified using the value in &%qualify_recipient%&, but you can
20411 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
20413 Care must be taken if there are alias names for local users.
20414 Consider an MTA handling a single local domain where the system alias file
20419 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
20420 messages in the local mailbox, and also forward copies elsewhere. He creates
20423 Sam.Reman, spqr@reme.elsewhere.example
20425 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
20426 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
20427 second time round, because it has previously routed it,
20428 and the following routers presumably cannot handle the alias. The forward file
20429 should really contain
20431 spqr, spqr@reme.elsewhere.example
20433 but because this is such a common error, the &%check_ancestor%& option (see
20434 below) exists to provide a way to get round it. This is normally set on a
20435 &(redirect)& router that is handling users' &_.forward_& files.
20439 .section "Special items in redirection lists" "SECTspecitredli"
20440 In addition to addresses, the following types of item may appear in redirection
20441 lists (that is, in non-filter redirection data):
20444 .cindex "pipe" "in redirection list"
20445 .cindex "address redirection" "to pipe"
20446 An item is treated as a pipe command if it begins with &"|"& and does not parse
20447 as a valid RFC 2822 address that includes a domain. A transport for running the
20448 command must be specified by the &%pipe_transport%& option.
20449 Normally, either the router or the transport specifies a user and a group under
20450 which to run the delivery. The default is to use the Exim user and group.
20452 Single or double quotes can be used for enclosing the individual arguments of
20453 the pipe command; no interpretation of escapes is done for single quotes. If
20454 the command contains a comma character, it is necessary to put the whole item
20455 in double quotes, for example:
20457 "|/some/command ready,steady,go"
20459 since items in redirection lists are terminated by commas. Do not, however,
20460 quote just the command. An item such as
20462 |"/some/command ready,steady,go"
20464 is interpreted as a pipe with a rather strange command name, and no arguments.
20466 Note that the above example assumes that the text comes from a lookup source
20467 of some sort, so that the quotes are part of the data. If composing a
20468 redirect router with a &%data%& option directly specifying this command, the
20469 quotes will be used by the configuration parser to define the extent of one
20470 string, but will not be passed down into the redirect router itself. There
20471 are two main approaches to get around this: escape quotes to be part of the
20472 data itself, or avoid using this mechanism and instead create a custom
20473 transport with the &%command%& option set and reference that transport from
20474 an &%accept%& router.
20477 .cindex "file" "in redirection list"
20478 .cindex "address redirection" "to file"
20479 An item is interpreted as a path name if it begins with &"/"& and does not
20480 parse as a valid RFC 2822 address that includes a domain. For example,
20482 /home/world/minbari
20484 is treated as a filename, but
20486 /s=molari/o=babylon/@x400gate.way
20488 is treated as an address. For a filename, a transport must be specified using
20489 the &%file_transport%& option. However, if the generated path name ends with a
20490 forward slash character, it is interpreted as a directory name rather than a
20491 filename, and &%directory_transport%& is used instead.
20493 Normally, either the router or the transport specifies a user and a group under
20494 which to run the delivery. The default is to use the Exim user and group.
20496 .cindex "&_/dev/null_&"
20497 However, if a redirection item is the path &_/dev/null_&, delivery to it is
20498 bypassed at a high level, and the log entry shows &"**bypassed**"&
20499 instead of a transport name. In this case the user and group are not used.
20502 .cindex "included address list"
20503 .cindex "address redirection" "included external list"
20504 If an item is of the form
20506 :include:<path name>
20508 a list of further items is taken from the given file and included at that
20509 point. &*Note*&: Such a file can not be a filter file; it is just an
20510 out-of-line addition to the list. The items in the included list are separated
20511 by commas or newlines and are not subject to expansion. If this is the first
20512 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
20513 the alias name. This example is incorrect:
20515 list1 :include:/opt/lists/list1
20517 It must be given as
20519 list1: :include:/opt/lists/list1
20522 .cindex "address redirection" "to black hole"
20523 .cindex "delivery" "discard"
20524 .cindex "delivery" "blackhole"
20525 .cindex "black hole"
20526 .cindex "abandoning mail"
20527 Sometimes you want to throw away mail to a particular local part. Making the
20528 &%data%& option expand to an empty string does not work, because that causes
20529 the router to decline. Instead, the alias item
20533 can be used. It does what its name implies. No delivery is
20534 done, and no error message is generated. This has the same effect as specifying
20535 &_/dev/null_& as a destination, but it can be independently disabled.
20537 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
20538 delivery is done for the original local part, even if other redirection items
20539 are present. If you are generating a multi-item list (for example, by reading a
20540 database) and need the ability to provide a no-op item, you must use
20544 .cindex "delivery" "forcing failure"
20545 .cindex "delivery" "forcing deferral"
20546 .cindex "failing delivery" "forcing"
20547 .cindex "deferred delivery, forcing"
20548 .cindex "customizing" "failure message"
20549 An attempt to deliver a particular address can be deferred or forced to fail by
20550 redirection items of the form
20555 respectively. When a redirection list contains such an item, it applies
20556 to the entire redirection; any other items in the list are ignored. Any
20557 text following &':fail:'& or &':defer:'& is placed in the error text
20558 associated with the failure. For example, an alias file might contain:
20560 X.Employee: :fail: Gone away, no forwarding address
20562 In the case of an address that is being verified from an ACL or as the subject
20564 .cindex "VRFY" "error text, display of"
20565 VRFY command, the text is included in the SMTP error response by
20567 .cindex "EXPN" "error text, display of"
20568 The text is not included in the response to an EXPN command. In non-SMTP cases
20569 the text is included in the error message that Exim generates.
20571 .cindex "SMTP" "error codes"
20572 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
20573 &':fail:'&. However, if the message starts with three digits followed by a
20574 space, optionally followed by an extended code of the form &'n.n.n'&, also
20575 followed by a space, and the very first digit is the same as the default error
20576 code, the code from the message is used instead. If the very first digit is
20577 incorrect, a panic error is logged, and the default code is used. You can
20578 suppress the use of the supplied code in a redirect router by setting the
20579 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
20582 .vindex "&$acl_verify_message$&"
20583 In an ACL, an explicitly provided message overrides the default, but the
20584 default message is available in the variable &$acl_verify_message$& and can
20585 therefore be included in a custom message if this is desired.
20587 Normally the error text is the rest of the redirection list &-- a comma does
20588 not terminate it &-- but a newline does act as a terminator. Newlines are not
20589 normally present in alias expansions. In &(lsearch)& lookups they are removed
20590 as part of the continuation process, but they may exist in other kinds of
20591 lookup and in &':include:'& files.
20593 During routing for message delivery (as opposed to verification), a redirection
20594 containing &':fail:'& causes an immediate failure of the incoming address,
20595 whereas &':defer:'& causes the message to remain in the queue so that a
20596 subsequent delivery attempt can happen at a later time. If an address is
20597 deferred for too long, it will ultimately fail, because the normal retry
20601 .cindex "alias file" "exception to default"
20602 Sometimes it is useful to use a single-key search type with a default (see
20603 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
20604 for exceptions to the default. These can be handled by aliasing them to
20605 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
20606 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
20607 results in an empty redirection list has the same effect.
20611 .section "Duplicate addresses" "SECTdupaddr"
20612 .cindex "duplicate addresses"
20613 .cindex "address duplicate, discarding"
20614 .cindex "pipe" "duplicated"
20615 Exim removes duplicate addresses from the list to which it is delivering, so as
20616 to deliver just one copy to each address. This does not apply to deliveries
20617 routed to pipes by different immediate parent addresses, but an indirect
20618 aliasing scheme of the type
20620 pipe: |/some/command $local_part
20624 does not work with a message that is addressed to both local parts, because
20625 when the second is aliased to the intermediate local part &"pipe"& it gets
20626 discarded as being the same as a previously handled address. However, a scheme
20629 localpart1: |/some/command $local_part
20630 localpart2: |/some/command $local_part
20632 does result in two different pipe deliveries, because the immediate parents of
20633 the pipes are distinct.
20637 .section "Repeated redirection expansion" "SECID128"
20638 .cindex "repeated redirection expansion"
20639 .cindex "address redirection" "repeated for each delivery attempt"
20640 When a message cannot be delivered to all of its recipients immediately,
20641 leading to two or more delivery attempts, redirection expansion is carried out
20642 afresh each time for those addresses whose children were not all previously
20643 delivered. If redirection is being used as a mailing list, this can lead to new
20644 members of the list receiving copies of old messages. The &%one_time%& option
20645 can be used to avoid this.
20648 .section "Errors in redirection lists" "SECID129"
20649 .cindex "address redirection" "errors"
20650 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
20651 error is skipped, and an entry is written to the main log. This may be useful
20652 for mailing lists that are automatically managed. Otherwise, if an error is
20653 detected while generating the list of new addresses, the original address is
20654 deferred. See also &%syntax_errors_to%&.
20658 .section "Private options for the redirect router" "SECID130"
20660 .cindex "options" "&(redirect)& router"
20661 The private options for the &(redirect)& router are as follows:
20664 .option allow_defer redirect boolean false
20665 Setting this option allows the use of &':defer:'& in non-filter redirection
20666 data, or the &%defer%& command in an Exim filter file.
20669 .option allow_fail redirect boolean false
20670 .cindex "failing delivery" "from filter"
20671 If this option is true, the &':fail:'& item can be used in a redirection list,
20672 and the &%fail%& command may be used in an Exim filter file.
20675 .option allow_filter redirect boolean false
20676 .cindex "filter" "enabling use of"
20677 .cindex "Sieve filter" "enabling use of"
20678 Setting this option allows Exim to interpret redirection data that starts with
20679 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
20680 are some features of Exim filter files that some administrators may wish to
20681 lock out; see the &%forbid_filter_%&&'xxx'& options below.
20683 It is also possible to lock out Exim filters or Sieve filters while allowing
20684 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
20687 The filter is run using the uid and gid set by the generic &%user%& and
20688 &%group%& options. These take their defaults from the password data if
20689 &%check_local_user%& is set, so in the normal case of users' personal filter
20690 files, the filter is run as the relevant user. When &%allow_filter%& is set
20691 true, Exim insists that either &%check_local_user%& or &%user%& is set.
20695 .option allow_freeze redirect boolean false
20696 .cindex "freezing messages" "allowing in filter"
20697 Setting this option allows the use of the &%freeze%& command in an Exim filter.
20698 This command is more normally encountered in system filters, and is disabled by
20699 default for redirection filters because it isn't something you usually want to
20700 let ordinary users do.
20704 .option check_ancestor redirect boolean false
20705 This option is concerned with handling generated addresses that are the same
20706 as some address in the list of redirection ancestors of the current address.
20707 Although it is turned off by default in the code, it is set in the default
20708 configuration file for handling users' &_.forward_& files. It is recommended
20709 for this use of the &(redirect)& router.
20711 When &%check_ancestor%& is set, if a generated address (including the domain)
20712 is the same as any ancestor of the current address, it is replaced by a copy of
20713 the current address. This helps in the case where local part A is aliased to B,
20714 and B has a &_.forward_& file pointing back to A. For example, within a single
20715 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
20716 &_&~jb/.forward_& contains:
20718 \Joe.Bloggs, <other item(s)>
20720 Without the &%check_ancestor%& setting, either local part (&"jb"& or
20721 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
20722 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
20723 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
20724 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
20725 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
20726 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
20727 original address. See also the &%repeat_use%& option below.
20730 .option check_group redirect boolean "see below"
20731 When the &%file%& option is used, the group owner of the file is checked only
20732 when this option is set. The permitted groups are those listed in the
20733 &%owngroups%& option, together with the user's default group if
20734 &%check_local_user%& is set. If the file has the wrong group, routing is
20735 deferred. The default setting for this option is true if &%check_local_user%&
20736 is set and the &%modemask%& option permits the group write bit, or if the
20737 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
20741 .option check_owner redirect boolean "see below"
20742 When the &%file%& option is used, the owner of the file is checked only when
20743 this option is set. If &%check_local_user%& is set, the local user is
20744 permitted; otherwise the owner must be one of those listed in the &%owners%&
20745 option. The default value for this option is true if &%check_local_user%& or
20746 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
20749 .option data redirect string&!! unset
20750 This option is mutually exclusive with &%file%&. One or other of them must be
20751 set, but not both. The contents of &%data%& are expanded, and then used as the
20752 list of forwarding items, or as a set of filtering instructions. If the
20753 expansion is forced to fail, or the result is an empty string or a string that
20754 has no effect (consists entirely of comments), the router declines.
20756 When filtering instructions are used, the string must begin with &"#Exim
20757 filter"&, and all comments in the string, including this initial one, must be
20758 terminated with newline characters. For example:
20760 data = #Exim filter\n\
20761 if $h_to: contains Exim then save $home/mail/exim endif
20763 If you are reading the data from a database where newlines cannot be included,
20764 you can use the &${sg}$& expansion item to turn the escape string of your
20765 choice into a newline.
20768 .option directory_transport redirect string&!! unset
20769 A &(redirect)& router sets up a direct delivery to a directory when a path name
20770 ending with a slash is specified as a new &"address"&. The transport used is
20771 specified by this option, which, after expansion, must be the name of a
20772 configured transport. This should normally be an &(appendfile)& transport.
20775 .option file redirect string&!! unset
20776 This option specifies the name of a file that contains the redirection data. It
20777 is mutually exclusive with the &%data%& option. The string is expanded before
20778 use; if the expansion is forced to fail, the router declines. Other expansion
20779 failures cause delivery to be deferred. The result of a successful expansion
20780 must be an absolute path. The entire file is read and used as the redirection
20781 data. If the data is an empty string or a string that has no effect (consists
20782 entirely of comments), the router declines.
20784 .cindex "NFS" "checking for file existence"
20785 If the attempt to open the file fails with a &"does not exist"& error, Exim
20786 runs a check on the containing directory,
20787 unless &%ignore_enotdir%& is true (see below).
20788 If the directory does not appear to exist, delivery is deferred. This can
20789 happen when users' &_.forward_& files are in NFS-mounted directories, and there
20790 is a mount problem. If the containing directory does exist, but the file does
20791 not, the router declines.
20794 .option file_transport redirect string&!! unset
20795 .vindex "&$address_file$&"
20796 A &(redirect)& router sets up a direct delivery to a file when a path name not
20797 ending in a slash is specified as a new &"address"&. The transport used is
20798 specified by this option, which, after expansion, must be the name of a
20799 configured transport. This should normally be an &(appendfile)& transport. When
20800 it is running, the filename is in &$address_file$&.
20803 .option filter_prepend_home redirect boolean true
20804 When this option is true, if a &(save)& command in an Exim filter specifies a
20805 relative path, and &$home$& is defined, it is automatically prepended to the
20806 relative path. If this option is set false, this action does not happen. The
20807 relative path is then passed to the transport unmodified.
20810 .option forbid_blackhole redirect boolean false
20811 .cindex "restricting access to features"
20812 .cindex "filter" "locking out certain features"
20813 If this option is true, the &':blackhole:'& item may not appear in a
20817 .option forbid_exim_filter redirect boolean false
20818 .cindex "restricting access to features"
20819 .cindex "filter" "locking out certain features"
20820 If this option is set true, only Sieve filters are permitted when
20821 &%allow_filter%& is true.
20826 .option forbid_file redirect boolean false
20827 .cindex "restricting access to features"
20828 .cindex "delivery" "to file; forbidding"
20829 .cindex "filter" "locking out certain features"
20830 .cindex "Sieve filter" "forbidding delivery to a file"
20831 .cindex "Sieve filter" "&""keep""& facility; disabling"
20832 If this option is true, this router may not generate a new address that
20833 specifies delivery to a local file or directory, either from a filter or from a
20834 conventional forward file. This option is forced to be true if &%one_time%& is
20835 set. It applies to Sieve filters as well as to Exim filters, but if true, it
20836 locks out the Sieve's &"keep"& facility.
20839 .option forbid_filter_dlfunc redirect boolean false
20840 .cindex "restricting access to features"
20841 .cindex "filter" "locking out certain features"
20842 If this option is true, string expansions in Exim filters are not allowed to
20843 make use of the &%dlfunc%& expansion facility to run dynamically loaded
20846 .option forbid_filter_existstest redirect boolean false
20847 .cindex "restricting access to features"
20848 .cindex "filter" "locking out certain features"
20849 .cindex "expansion" "statting a file"
20850 If this option is true, string expansions in Exim filters are not allowed to
20851 make use of the &%exists%& condition or the &%stat%& expansion item.
20853 .option forbid_filter_logwrite redirect boolean false
20854 .cindex "restricting access to features"
20855 .cindex "filter" "locking out certain features"
20856 If this option is true, use of the logging facility in Exim filters is not
20857 permitted. Logging is in any case available only if the filter is being run
20858 under some unprivileged uid (which is normally the case for ordinary users'
20859 &_.forward_& files).
20862 .option forbid_filter_lookup redirect boolean false
20863 .cindex "restricting access to features"
20864 .cindex "filter" "locking out certain features"
20865 If this option is true, string expansions in Exim filter files are not allowed
20866 to make use of &%lookup%& items.
20869 .option forbid_filter_perl redirect boolean false
20870 .cindex "restricting access to features"
20871 .cindex "filter" "locking out certain features"
20872 This option has an effect only if Exim is built with embedded Perl support. If
20873 it is true, string expansions in Exim filter files are not allowed to make use
20874 of the embedded Perl support.
20877 .option forbid_filter_readfile redirect boolean false
20878 .cindex "restricting access to features"
20879 .cindex "filter" "locking out certain features"
20880 If this option is true, string expansions in Exim filter files are not allowed
20881 to make use of &%readfile%& items.
20884 .option forbid_filter_readsocket redirect boolean false
20885 .cindex "restricting access to features"
20886 .cindex "filter" "locking out certain features"
20887 If this option is true, string expansions in Exim filter files are not allowed
20888 to make use of &%readsocket%& items.
20891 .option forbid_filter_reply redirect boolean false
20892 .cindex "restricting access to features"
20893 .cindex "filter" "locking out certain features"
20894 If this option is true, this router may not generate an automatic reply
20895 message. Automatic replies can be generated only from Exim or Sieve filter
20896 files, not from traditional forward files. This option is forced to be true if
20897 &%one_time%& is set.
20900 .option forbid_filter_run redirect boolean false
20901 .cindex "restricting access to features"
20902 .cindex "filter" "locking out certain features"
20903 If this option is true, string expansions in Exim filter files are not allowed
20904 to make use of &%run%& items.
20907 .option forbid_include redirect boolean false
20908 .cindex "restricting access to features"
20909 .cindex "filter" "locking out certain features"
20910 If this option is true, items of the form
20912 :include:<path name>
20914 are not permitted in non-filter redirection lists.
20917 .option forbid_pipe redirect boolean false
20918 .cindex "restricting access to features"
20919 .cindex "filter" "locking out certain features"
20920 .cindex "delivery" "to pipe; forbidding"
20921 If this option is true, this router may not generate a new address which
20922 specifies delivery to a pipe, either from an Exim filter or from a conventional
20923 forward file. This option is forced to be true if &%one_time%& is set.
20926 .option forbid_sieve_filter redirect boolean false
20927 .cindex "restricting access to features"
20928 .cindex "filter" "locking out certain features"
20929 If this option is set true, only Exim filters are permitted when
20930 &%allow_filter%& is true.
20933 .cindex "SMTP" "error codes"
20934 .option forbid_smtp_code redirect boolean false
20935 If this option is set true, any SMTP error codes that are present at the start
20936 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
20937 the default codes (451 and 550, respectively) are always used.
20942 .option hide_child_in_errmsg redirect boolean false
20943 .cindex "bounce message" "redirection details; suppressing"
20944 If this option is true, it prevents Exim from quoting a child address if it
20945 generates a bounce or delay message for it. Instead it says &"an address
20946 generated from <&'the top level address'&>"&. Of course, this applies only to
20947 bounces generated locally. If a message is forwarded to another host, &'its'&
20948 bounce may well quote the generated address.
20951 .option ignore_eacces redirect boolean false
20953 If this option is set and an attempt to open a redirection file yields the
20954 EACCES error (permission denied), the &(redirect)& router behaves as if the
20955 file did not exist.
20958 .option ignore_enotdir redirect boolean false
20960 If this option is set and an attempt to open a redirection file yields the
20961 ENOTDIR error (something on the path is not a directory), the &(redirect)&
20962 router behaves as if the file did not exist.
20964 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
20965 router that has the &%file%& option set discovers that the file does not exist
20966 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
20967 against unmounted NFS directories. If the parent can not be statted, delivery
20968 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
20969 is set, because that option tells Exim to ignore &"something on the path is not
20970 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
20971 that some operating systems give ENOENT where others give ENOTDIR.
20975 .option include_directory redirect string unset
20976 If this option is set, the path names of any &':include:'& items in a
20977 redirection list must start with this directory.
20980 .option modemask redirect "octal integer" 022
20981 This specifies mode bits which must not be set for a file specified by the
20982 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
20985 .option one_time redirect boolean false
20986 .cindex "one-time aliasing/forwarding expansion"
20987 .cindex "alias file" "one-time expansion"
20988 .cindex "forward file" "one-time expansion"
20989 .cindex "mailing lists" "one-time expansion"
20990 .cindex "address redirection" "one-time expansion"
20991 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
20992 files each time it tries to deliver a message causes a problem when one or more
20993 of the generated addresses fails be delivered at the first attempt. The problem
20994 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
20995 but of what happens when the redirection list changes during the time that the
20996 message is on Exim's queue. This is particularly true in the case of mailing
20997 lists, where new subscribers might receive copies of messages that were posted
20998 before they subscribed.
21000 If &%one_time%& is set and any addresses generated by the router fail to
21001 deliver at the first attempt, the failing addresses are added to the message as
21002 &"top level"& addresses, and the parent address that generated them is marked
21003 &"delivered"&. Thus, redirection does not happen again at the next delivery
21006 &*Warning 1*&: Any header line addition or removal that is specified by this
21007 router would be lost if delivery did not succeed at the first attempt. For this
21008 reason, the &%headers_add%& and &%headers_remove%& generic options are not
21009 permitted when &%one_time%& is set.
21011 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
21012 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
21013 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
21015 &*Warning 3*&: The &%unseen%& generic router option may not be set with
21018 The original top-level address is remembered with each of the generated
21019 addresses, and is output in any log messages. However, any intermediate parent
21020 addresses are not recorded. This makes a difference to the log only if
21021 &%all_parents%& log selector is set. It is expected that &%one_time%& will
21022 typically be used for mailing lists, where there is normally just one level of
21026 .option owners redirect "string list" unset
21027 .cindex "ownership" "alias file"
21028 .cindex "ownership" "forward file"
21029 .cindex "alias file" "ownership"
21030 .cindex "forward file" "ownership"
21031 This specifies a list of permitted owners for the file specified by &%file%&.
21032 This list is in addition to the local user when &%check_local_user%& is set.
21033 See &%check_owner%& above.
21036 .option owngroups redirect "string list" unset
21037 This specifies a list of permitted groups for the file specified by &%file%&.
21038 The list is in addition to the local user's primary group when
21039 &%check_local_user%& is set. See &%check_group%& above.
21042 .option pipe_transport redirect string&!! unset
21043 .vindex "&$address_pipe$&"
21044 A &(redirect)& router sets up a direct delivery to a pipe when a string
21045 starting with a vertical bar character is specified as a new &"address"&. The
21046 transport used is specified by this option, which, after expansion, must be the
21047 name of a configured transport. This should normally be a &(pipe)& transport.
21048 When the transport is run, the pipe command is in &$address_pipe$&.
21051 .option qualify_domain redirect string&!! unset
21052 .vindex "&$qualify_recipient$&"
21053 If this option is set, and an unqualified address (one without a domain) is
21054 generated, and that address would normally be qualified by the global setting
21055 in &%qualify_recipient%&, it is instead qualified with the domain specified by
21056 expanding this string. If the expansion fails, the router declines. If you want
21057 to revert to the default, you can have the expansion generate
21058 &$qualify_recipient$&.
21060 This option applies to all unqualified addresses generated by Exim filters,
21061 but for traditional &_.forward_& files, it applies only to addresses that are
21062 not preceded by a backslash. Sieve filters cannot generate unqualified
21065 .option qualify_preserve_domain redirect boolean false
21066 .cindex "domain" "in redirection; preserving"
21067 .cindex "preserving domain in redirection"
21068 .cindex "address redirection" "domain; preserving"
21069 If this option is set, the router's local &%qualify_domain%& option must not be
21070 set (a configuration error occurs if it is). If an unqualified address (one
21071 without a domain) is generated, it is qualified with the domain of the parent
21072 address (the immediately preceding ancestor) instead of the global
21073 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
21074 this applies whether or not the address is preceded by a backslash.
21077 .option repeat_use redirect boolean true
21078 If this option is set false, the router is skipped for a child address that has
21079 any ancestor that was routed by this router. This test happens before any of
21080 the other preconditions are tested. Exim's default anti-looping rules skip
21081 only when the ancestor is the same as the current address. See also
21082 &%check_ancestor%& above and the generic &%redirect_router%& option.
21085 .option reply_transport redirect string&!! unset
21086 A &(redirect)& router sets up an automatic reply when a &%mail%& or
21087 &%vacation%& command is used in a filter file. The transport used is specified
21088 by this option, which, after expansion, must be the name of a configured
21089 transport. This should normally be an &(autoreply)& transport. Other transports
21090 are unlikely to do anything sensible or useful.
21093 .option rewrite redirect boolean true
21094 .cindex "address redirection" "disabling rewriting"
21095 If this option is set false, addresses generated by the router are not
21096 subject to address rewriting. Otherwise, they are treated like new addresses
21097 and are rewritten according to the global rewriting rules.
21100 .option sieve_subaddress redirect string&!! unset
21101 The value of this option is passed to a Sieve filter to specify the
21102 :subaddress part of an address.
21104 .option sieve_useraddress redirect string&!! unset
21105 The value of this option is passed to a Sieve filter to specify the :user part
21106 of an address. However, if it is unset, the entire original local part
21107 (including any prefix or suffix) is used for :user.
21110 .option sieve_vacation_directory redirect string&!! unset
21111 .cindex "Sieve filter" "vacation directory"
21112 To enable the &"vacation"& extension for Sieve filters, you must set
21113 &%sieve_vacation_directory%& to the directory where vacation databases are held
21114 (do not put anything else in that directory), and ensure that the
21115 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
21116 needs their own directory; Exim will create it if necessary.
21120 .option skip_syntax_errors redirect boolean false
21121 .cindex "forward file" "broken"
21122 .cindex "address redirection" "broken files"
21123 .cindex "alias file" "broken"
21124 .cindex "broken alias or forward files"
21125 .cindex "ignoring faulty addresses"
21126 .cindex "skipping faulty addresses"
21127 .cindex "error" "skipping bad syntax"
21128 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
21129 non-filter redirection data are skipped, and each failing address is logged. If
21130 &%syntax_errors_to%& is set, a message is sent to the address it defines,
21131 giving details of the failures. If &%syntax_errors_text%& is set, its contents
21132 are expanded and placed at the head of the error message generated by
21133 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
21134 be the same address as the generic &%errors_to%& option. The
21135 &%skip_syntax_errors%& option is often used when handling mailing lists.
21137 If all the addresses in a redirection list are skipped because of syntax
21138 errors, the router declines to handle the original address, and it is passed to
21139 the following routers.
21141 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
21142 error in the filter causes filtering to be abandoned without any action being
21143 taken. The incident is logged, and the router declines to handle the address,
21144 so it is passed to the following routers.
21146 .cindex "Sieve filter" "syntax errors in"
21147 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
21148 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
21149 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
21151 &%skip_syntax_errors%& can be used to specify that errors in users' forward
21152 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
21153 option, used with an address that does not get redirected, can be used to
21154 notify users of these errors, by means of a router like this:
21160 file = $home/.forward
21161 file_transport = address_file
21162 pipe_transport = address_pipe
21163 reply_transport = address_reply
21166 syntax_errors_to = real-$local_part@$domain
21167 syntax_errors_text = \
21168 This is an automatically generated message. An error has\n\
21169 been found in your .forward file. Details of the error are\n\
21170 reported below. While this error persists, you will receive\n\
21171 a copy of this message for every message that is addressed\n\
21172 to you. If your .forward file is a filter file, or if it is\n\
21173 a non-filter file containing no valid forwarding addresses,\n\
21174 a copy of each incoming message will be put in your normal\n\
21175 mailbox. If a non-filter file contains at least one valid\n\
21176 forwarding address, forwarding to the valid addresses will\n\
21177 happen, and those will be the only deliveries that occur.
21179 You also need a router to ensure that local addresses that are prefixed by
21180 &`real-`& are recognized, but not forwarded or filtered. For example, you could
21181 put this immediately before the &(userforward)& router:
21186 local_part_prefix = real-
21187 transport = local_delivery
21189 For security, it would probably be a good idea to restrict the use of this
21190 router to locally-generated messages, using a condition such as this:
21192 condition = ${if match {$sender_host_address}\
21193 {\N^(|127\.0\.0\.1)$\N}}
21197 .option syntax_errors_text redirect string&!! unset
21198 See &%skip_syntax_errors%& above.
21201 .option syntax_errors_to redirect string unset
21202 See &%skip_syntax_errors%& above.
21203 .ecindex IIDredrou1
21204 .ecindex IIDredrou2
21211 . ////////////////////////////////////////////////////////////////////////////
21212 . ////////////////////////////////////////////////////////////////////////////
21214 .chapter "Environment for running local transports" "CHAPenvironment" &&&
21215 "Environment for local transports"
21216 .scindex IIDenvlotra1 "local transports" "environment for"
21217 .scindex IIDenvlotra2 "environment" "local transports"
21218 .scindex IIDenvlotra3 "transport" "local; environment for"
21219 Local transports handle deliveries to files and pipes. (The &(autoreply)&
21220 transport can be thought of as similar to a pipe.) Exim always runs transports
21221 in subprocesses, under specified uids and gids. Typical deliveries to local
21222 mailboxes run under the uid and gid of the local user.
21224 Exim also sets a specific current directory while running the transport; for
21225 some transports a home directory setting is also relevant. The &(pipe)&
21226 transport is the only one that sets up environment variables; see section
21227 &<<SECTpipeenv>>& for details.
21229 The values used for the uid, gid, and the directories may come from several
21230 different places. In many cases, the router that handles the address associates
21231 settings with that address as a result of its &%check_local_user%&, &%group%&,
21232 or &%user%& options. However, values may also be given in the transport's own
21233 configuration, and these override anything that comes from the router.
21237 .section "Concurrent deliveries" "SECID131"
21238 .cindex "concurrent deliveries"
21239 .cindex "simultaneous deliveries"
21240 If two different messages for the same local recipient arrive more or less
21241 simultaneously, the two delivery processes are likely to run concurrently. When
21242 the &(appendfile)& transport is used to write to a file, Exim applies locking
21243 rules to stop concurrent processes from writing to the same file at the same
21246 However, when you use a &(pipe)& transport, it is up to you to arrange any
21247 locking that is needed. Here is a silly example:
21251 command = /bin/sh -c 'cat >>/some/file'
21253 This is supposed to write the message at the end of the file. However, if two
21254 messages arrive at the same time, the file will be scrambled. You can use the
21255 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
21256 file using the same algorithm that Exim itself uses.
21261 .section "Uids and gids" "SECTenvuidgid"
21262 .cindex "local transports" "uid and gid"
21263 .cindex "transport" "local; uid and gid"
21264 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
21265 overrides any group that the router set in the address, even if &%user%& is not
21266 set for the transport. This makes it possible, for example, to run local mail
21267 delivery under the uid of the recipient (set by the router), but in a special
21268 group (set by the transport). For example:
21271 # User/group are set by check_local_user in this router
21275 transport = group_delivery
21278 # This transport overrides the group
21280 driver = appendfile
21281 file = /var/spool/mail/$local_part
21284 If &%user%& is set for a transport, its value overrides what is set in the
21285 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
21286 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
21289 .oindex "&%initgroups%&"
21290 When the uid is taken from the transport's configuration, the &[initgroups()]&
21291 function is called for the groups associated with that uid if the
21292 &%initgroups%& option is set for the transport. When the uid is not specified
21293 by the transport, but is associated with the address by a router, the option
21294 for calling &[initgroups()]& is taken from the router configuration.
21296 .cindex "&(pipe)& transport" "uid for"
21297 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
21298 is set and &%user%& is not set, the uid of the process that called Exim to
21299 receive the message is used, and if &%group%& is not set, the corresponding
21300 original gid is also used.
21302 This is the detailed preference order for obtaining a gid; the first of the
21303 following that is set is used:
21306 A &%group%& setting of the transport;
21308 A &%group%& setting of the router;
21310 A gid associated with a user setting of the router, either as a result of
21311 &%check_local_user%& or an explicit non-numeric &%user%& setting;
21313 The group associated with a non-numeric &%user%& setting of the transport;
21315 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
21316 the uid is the creator's uid;
21318 The Exim gid if the Exim uid is being used as a default.
21321 If, for example, the user is specified numerically on the router and there are
21322 no group settings, no gid is available. In this situation, an error occurs.
21323 This is different for the uid, for which there always is an ultimate default.
21324 The first of the following that is set is used:
21327 A &%user%& setting of the transport;
21329 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
21331 A &%user%& setting of the router;
21333 A &%check_local_user%& setting of the router;
21338 Of course, an error will still occur if the uid that is chosen is on the
21339 &%never_users%& list.
21345 .section "Current and home directories" "SECID132"
21346 .cindex "current directory for local transport"
21347 .cindex "home directory" "for local transport"
21348 .cindex "transport" "local; home directory for"
21349 .cindex "transport" "local; current directory for"
21350 Routers may set current and home directories for local transports by means of
21351 the &%transport_current_directory%& and &%transport_home_directory%& options.
21352 However, if the transport's &%current_directory%& or &%home_directory%& options
21353 are set, they override the router's values. In detail, the home directory
21354 for a local transport is taken from the first of these values that is set:
21357 The &%home_directory%& option on the transport;
21359 The &%transport_home_directory%& option on the router;
21361 The password data if &%check_local_user%& is set on the router;
21363 The &%router_home_directory%& option on the router.
21366 The current directory is taken from the first of these values that is set:
21369 The &%current_directory%& option on the transport;
21371 The &%transport_current_directory%& option on the router.
21375 If neither the router nor the transport sets a current directory, Exim uses the
21376 value of the home directory, if it is set. Otherwise it sets the current
21377 directory to &_/_& before running a local transport.
21381 .section "Expansion variables derived from the address" "SECID133"
21382 .vindex "&$domain$&"
21383 .vindex "&$local_part$&"
21384 .vindex "&$original_domain$&"
21385 Normally a local delivery is handling a single address, and in that case the
21386 variables such as &$domain$& and &$local_part$& are set during local
21387 deliveries. However, in some circumstances more than one address may be handled
21388 at once (for example, while writing batch SMTP for onward transmission by some
21389 other means). In this case, the variables associated with the local part are
21390 never set, &$domain$& is set only if all the addresses have the same domain,
21391 and &$original_domain$& is never set.
21392 .ecindex IIDenvlotra1
21393 .ecindex IIDenvlotra2
21394 .ecindex IIDenvlotra3
21402 . ////////////////////////////////////////////////////////////////////////////
21403 . ////////////////////////////////////////////////////////////////////////////
21405 .chapter "Generic options for transports" "CHAPtransportgeneric"
21406 .scindex IIDgenoptra1 "generic options" "transport"
21407 .scindex IIDgenoptra2 "options" "generic; for transports"
21408 .scindex IIDgenoptra3 "transport" "generic options for"
21409 The following generic options apply to all transports:
21412 .option body_only transports boolean false
21413 .cindex "transport" "body only"
21414 .cindex "message" "transporting body only"
21415 .cindex "body of message" "transporting"
21416 If this option is set, the message's headers are not transported. It is
21417 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
21418 or &(pipe)& transports, the settings of &%message_prefix%& and
21419 &%message_suffix%& should be checked, because this option does not
21420 automatically suppress them.
21423 .option current_directory transports string&!! unset
21424 .cindex "transport" "current directory for"
21425 This specifies the current directory that is to be set while running the
21426 transport, overriding any value that may have been set by the router.
21427 If the expansion fails for any reason, including forced failure, an error is
21428 logged, and delivery is deferred.
21431 .option disable_logging transports boolean false
21432 If this option is set true, nothing is logged for any
21433 deliveries by the transport or for any
21434 transport errors. You should not set this option unless you really, really know
21435 what you are doing.
21438 .option debug_print transports string&!! unset
21439 .cindex "testing" "variables in drivers"
21440 If this option is set and debugging is enabled (see the &%-d%& command line
21441 option), the string is expanded and included in the debugging output when the
21443 If expansion of the string fails, the error message is written to the debugging
21444 output, and Exim carries on processing.
21445 This facility is provided to help with checking out the values of variables and
21446 so on when debugging driver configurations. For example, if a &%headers_add%&
21447 option is not working properly, &%debug_print%& could be used to output the
21448 variables it references. A newline is added to the text if it does not end with
21450 The variables &$transport_name$& and &$router_name$& contain the name of the
21451 transport and the router that called it.
21453 .option delivery_date_add transports boolean false
21454 .cindex "&'Delivery-date:'& header line"
21455 If this option is true, a &'Delivery-date:'& header is added to the message.
21456 This gives the actual time the delivery was made. As this is not a standard
21457 header, Exim has a configuration option (&%delivery_date_remove%&) which
21458 requests its removal from incoming messages, so that delivered messages can
21459 safely be resent to other recipients.
21462 .option driver transports string unset
21463 This specifies which of the available transport drivers is to be used.
21464 There is no default, and this option must be set for every transport.
21467 .option envelope_to_add transports boolean false
21468 .cindex "&'Envelope-to:'& header line"
21469 If this option is true, an &'Envelope-to:'& header is added to the message.
21470 This gives the original address(es) in the incoming envelope that caused this
21471 delivery to happen. More than one address may be present if the transport is
21472 configured to handle several addresses at once, or if more than one original
21473 address was redirected to the same final address. As this is not a standard
21474 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
21475 its removal from incoming messages, so that delivered messages can safely be
21476 resent to other recipients.
21479 .option event_action transports string&!! unset
21481 This option declares a string to be expanded for Exim's events mechanism.
21482 For details see chapter &<<CHAPevents>>&.
21485 .option group transports string&!! "Exim group"
21486 .cindex "transport" "group; specifying"
21487 This option specifies a gid for running the transport process, overriding any
21488 value that the router supplies, and also overriding any value associated with
21489 &%user%& (see below).
21492 .option headers_add transports list&!! unset
21493 .cindex "header lines" "adding in transport"
21494 .cindex "transport" "header lines; adding"
21495 This option specifies a list of text headers,
21496 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
21497 which are (separately) expanded and added to the header
21498 portion of a message as it is transported, as described in section
21499 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
21500 routers. If the result of the expansion is an empty string, or if the expansion
21501 is forced to fail, no action is taken. Other expansion failures are treated as
21502 errors and cause the delivery to be deferred.
21504 Unlike most options, &%headers_add%& can be specified multiple times
21505 for a transport; all listed headers are added.
21508 .option headers_only transports boolean false
21509 .cindex "transport" "header lines only"
21510 .cindex "message" "transporting headers only"
21511 .cindex "header lines" "transporting"
21512 If this option is set, the message's body is not transported. It is mutually
21513 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
21514 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
21515 checked, since this option does not automatically suppress them.
21518 .option headers_remove transports list&!! unset
21519 .cindex "header lines" "removing"
21520 .cindex "transport" "header lines; removing"
21521 This option specifies a list of header names,
21522 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&);
21523 these headers are omitted from the message as it is transported, as described
21524 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
21526 Each list item is separately expanded.
21527 If the result of the expansion is an empty string, or if the expansion
21528 is forced to fail, no action is taken. Other expansion failures are treated as
21529 errors and cause the delivery to be deferred.
21531 Unlike most options, &%headers_remove%& can be specified multiple times
21532 for a transport; all listed headers are removed.
21534 &*Warning*&: Because of the separate expansion of the list items,
21535 items that contain a list separator must have it doubled.
21536 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
21540 .option headers_rewrite transports string unset
21541 .cindex "transport" "header lines; rewriting"
21542 .cindex "rewriting" "at transport time"
21543 This option allows addresses in header lines to be rewritten at transport time,
21544 that is, as the message is being copied to its destination. The contents of the
21545 option are a colon-separated list of rewriting rules. Each rule is in exactly
21546 the same form as one of the general rewriting rules that are applied when a
21547 message is received. These are described in chapter &<<CHAPrewrite>>&. For
21550 headers_rewrite = a@b c@d f : \
21553 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
21554 &'w@z'& in all address-bearing header lines. The rules are applied to the
21555 header lines just before they are written out at transport time, so they affect
21556 only those copies of the message that pass through the transport. However, only
21557 the message's original header lines, and any that were added by a system
21558 filter, are rewritten. If a router or transport adds header lines, they are not
21559 affected by this option. These rewriting rules are &'not'& applied to the
21560 envelope. You can change the return path using &%return_path%&, but you cannot
21561 change envelope recipients at this time.
21564 .option home_directory transports string&!! unset
21565 .cindex "transport" "home directory for"
21567 This option specifies a home directory setting for a local transport,
21568 overriding any value that may be set by the router. The home directory is
21569 placed in &$home$& while expanding the transport's private options. It is also
21570 used as the current directory if no current directory is set by the
21571 &%current_directory%& option on the transport or the
21572 &%transport_current_directory%& option on the router. If the expansion fails
21573 for any reason, including forced failure, an error is logged, and delivery is
21577 .option initgroups transports boolean false
21578 .cindex "additional groups"
21579 .cindex "groups" "additional"
21580 .cindex "transport" "group; additional"
21581 If this option is true and the uid for the delivery process is provided by the
21582 transport, the &[initgroups()]& function is called when running the transport
21583 to ensure that any additional groups associated with the uid are set up.
21586 .option max_parallel transports integer&!! unset
21587 .cindex limit "transport parallelism"
21588 .cindex transport "parallel processes"
21589 .cindex transport "concurrency limit"
21590 .cindex "delivery" "parallelism for transport"
21591 If this option is set and expands to an integer greater than zero
21592 it limits the number of concurrent runs of the transport.
21593 The control does not apply to shadow transports.
21595 .cindex "hints database" "transport concurrency control"
21596 Exim implements this control by means of a hints database in which a record is
21597 incremented whenever a transport process is being created. The record
21598 is decremented and possibly removed when the process terminates.
21599 Obviously there is scope for
21600 records to get left lying around if there is a system or program crash. To
21601 guard against this, Exim ignores any records that are more than six hours old.
21603 If you use this option, you should also arrange to delete the
21604 relevant hints database whenever your system reboots. The names of the files
21605 start with &_misc_& and they are kept in the &_spool/db_& directory. There
21606 may be one or two files, depending on the type of DBM in use. The same files
21607 are used for ETRN and smtp transport serialization.
21610 .option message_size_limit transports string&!! 0
21611 .cindex "limit" "message size per transport"
21612 .cindex "size" "of message, limit"
21613 .cindex "transport" "message size; limiting"
21614 This option controls the size of messages passed through the transport. It is
21615 expanded before use; the result of the expansion must be a sequence of decimal
21616 digits, optionally followed by K or M. If the expansion fails for any reason,
21617 including forced failure, or if the result is not of the required form,
21618 delivery is deferred. If the value is greater than zero and the size of a
21619 message exceeds this limit, the address is failed. If there is any chance that
21620 the resulting bounce message could be routed to the same transport, you should
21621 ensure that &%return_size_limit%& is less than the transport's
21622 &%message_size_limit%&, as otherwise the bounce message will fail to get
21627 .option rcpt_include_affixes transports boolean false
21628 .cindex "prefix" "for local part, including in envelope"
21629 .cindex "suffix for local part" "including in envelope"
21630 .cindex "local part" "prefix"
21631 .cindex "local part" "suffix"
21632 When this option is false (the default), and an address that has had any
21633 affixes (prefixes or suffixes) removed from the local part is delivered by any
21634 form of SMTP or LMTP, the affixes are not included. For example, if a router
21637 local_part_prefix = *-
21639 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
21642 RCPT TO:<xyz@some.domain>
21644 This is also the case when an ACL-time callout is being used to verify a
21645 recipient address. However, if &%rcpt_include_affixes%& is set true, the
21646 whole local part is included in the RCPT command. This option applies to BSMTP
21647 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
21648 &(lmtp)& and &(smtp)& transports.
21651 .option retry_use_local_part transports boolean "see below"
21652 .cindex "hints database" "retry keys"
21653 When a delivery suffers a temporary failure, a retry record is created
21654 in Exim's hints database. For remote deliveries, the key for the retry record
21655 is based on the name and/or IP address of the failing remote host. For local
21656 deliveries, the key is normally the entire address, including both the local
21657 part and the domain. This is suitable for most common cases of local delivery
21658 temporary failure &-- for example, exceeding a mailbox quota should delay only
21659 deliveries to that mailbox, not to the whole domain.
21661 However, in some special cases you may want to treat a temporary local delivery
21662 as a failure associated with the domain, and not with a particular local part.
21663 (For example, if you are storing all mail for some domain in files.) You can do
21664 this by setting &%retry_use_local_part%& false.
21666 For all the local transports, its default value is true. For remote transports,
21667 the default value is false for tidiness, but changing the value has no effect
21668 on a remote transport in the current implementation.
21671 .option return_path transports string&!! unset
21672 .cindex "envelope sender"
21673 .cindex "transport" "return path; changing"
21674 .cindex "return path" "changing in transport"
21675 If this option is set, the string is expanded at transport time and replaces
21676 the existing return path (envelope sender) value in the copy of the message
21677 that is being delivered. An empty return path is permitted. This feature is
21678 designed for remote deliveries, where the value of this option is used in the
21679 SMTP MAIL command. If you set &%return_path%& for a local transport, the
21680 only effect is to change the address that is placed in the &'Return-path:'&
21681 header line, if one is added to the message (see the next option).
21683 &*Note:*& A changed return path is not logged unless you add
21684 &%return_path_on_delivery%& to the log selector.
21686 .vindex "&$return_path$&"
21687 The expansion can refer to the existing value via &$return_path$&. This is
21688 either the message's envelope sender, or an address set by the
21689 &%errors_to%& option on a router. If the expansion is forced to fail, no
21690 replacement occurs; if it fails for another reason, delivery is deferred. This
21691 option can be used to support VERP (Variable Envelope Return Paths) &-- see
21692 section &<<SECTverp>>&.
21694 &*Note*&: If a delivery error is detected locally, including the case when a
21695 remote server rejects a message at SMTP time, the bounce message is not sent to
21696 the value of this option. It is sent to the previously set errors address.
21697 This defaults to the incoming sender address, but can be changed by setting
21698 &%errors_to%& in a router.
21702 .option return_path_add transports boolean false
21703 .cindex "&'Return-path:'& header line"
21704 If this option is true, a &'Return-path:'& header is added to the message.
21705 Although the return path is normally available in the prefix line of BSD
21706 mailboxes, this is commonly not displayed by MUAs, and so the user does not
21707 have easy access to it.
21709 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
21710 the delivery SMTP server makes the final delivery"&. This implies that this
21711 header should not be present in incoming messages. Exim has a configuration
21712 option, &%return_path_remove%&, which requests removal of this header from
21713 incoming messages, so that delivered messages can safely be resent to other
21717 .option shadow_condition transports string&!! unset
21718 See &%shadow_transport%& below.
21721 .option shadow_transport transports string unset
21722 .cindex "shadow transport"
21723 .cindex "transport" "shadow"
21724 A local transport may set the &%shadow_transport%& option to the name of
21725 another local transport. Shadow remote transports are not supported.
21727 Whenever a delivery to the main transport succeeds, and either
21728 &%shadow_condition%& is unset, or its expansion does not result in the empty
21729 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
21730 passed to the shadow transport, with the same delivery address or addresses. If
21731 expansion fails, no action is taken except that non-forced expansion failures
21732 cause a log line to be written.
21734 The result of the shadow transport is discarded and does not affect the
21735 subsequent processing of the message. Only a single level of shadowing is
21736 provided; the &%shadow_transport%& option is ignored on any transport when it
21737 is running as a shadow. Options concerned with output from pipes are also
21738 ignored. The log line for the successful delivery has an item added on the end,
21741 ST=<shadow transport name>
21743 If the shadow transport did not succeed, the error message is put in
21744 parentheses afterwards. Shadow transports can be used for a number of different
21745 purposes, including keeping more detailed log information than Exim normally
21746 provides, and implementing automatic acknowledgment policies based on message
21747 headers that some sites insist on.
21750 .option transport_filter transports string&!! unset
21751 .cindex "transport" "filter"
21752 .cindex "filter" "transport filter"
21753 This option sets up a filtering (in the Unix shell sense) process for messages
21754 at transport time. It should not be confused with mail filtering as set up by
21755 individual users or via a system filter.
21756 If unset, or expanding to an empty string, no filtering is done.
21758 When the message is about to be written out, the command specified by
21759 &%transport_filter%& is started up in a separate, parallel process, and
21760 the entire message, including the header lines, is passed to it on its standard
21761 input (this in fact is done from a third process, to avoid deadlock). The
21762 command must be specified as an absolute path.
21764 The lines of the message that are written to the transport filter are
21765 terminated by newline (&"\n"&). The message is passed to the filter before any
21766 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
21767 lines beginning with a dot, and also before any processing implied by the
21768 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
21769 &(pipe)& transports.
21771 The standard error for the filter process is set to the same destination as its
21772 standard output; this is read and written to the message's ultimate
21773 destination. The process that writes the message to the filter, the
21774 filter itself, and the original process that reads the result and delivers it
21775 are all run in parallel, like a shell pipeline.
21777 The filter can perform any transformations it likes, but of course should take
21778 care not to break RFC 2822 syntax. Exim does not check the result, except to
21779 test for a final newline when SMTP is in use. All messages transmitted over
21780 SMTP must end with a newline, so Exim supplies one if it is missing.
21782 .cindex "content scanning" "per user"
21783 A transport filter can be used to provide content-scanning on a per-user basis
21784 at delivery time if the only required effect of the scan is to modify the
21785 message. For example, a content scan could insert a new header line containing
21786 a spam score. This could be interpreted by a filter in the user's MUA. It is
21787 not possible to discard a message at this stage.
21789 .cindex "SMTP" "SIZE"
21790 A problem might arise if the filter increases the size of a message that is
21791 being sent down an SMTP connection. If the receiving SMTP server has indicated
21792 support for the SIZE parameter, Exim will have sent the size of the message
21793 at the start of the SMTP session. If what is actually sent is substantially
21794 more, the server might reject the message. This can be worked round by setting
21795 the &%size_addition%& option on the &(smtp)& transport, either to allow for
21796 additions to the message, or to disable the use of SIZE altogether.
21798 .vindex "&$pipe_addresses$&"
21799 The value of the &%transport_filter%& option is the command string for starting
21800 the filter, which is run directly from Exim, not under a shell. The string is
21801 parsed by Exim in the same way as a command string for the &(pipe)& transport:
21802 Exim breaks it up into arguments and then expands each argument separately (see
21803 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
21804 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
21805 of arguments, one for each address that applies to this delivery. (This isn't
21806 an ideal name for this feature here, but as it was already implemented for the
21807 &(pipe)& transport, it seemed sensible not to change it.)
21810 .vindex "&$host_address$&"
21811 The expansion variables &$host$& and &$host_address$& are available when the
21812 transport is a remote one. They contain the name and IP address of the host to
21813 which the message is being sent. For example:
21815 transport_filter = /some/directory/transport-filter.pl \
21816 $host $host_address $sender_address $pipe_addresses
21819 Two problems arise if you want to use more complicated expansion items to
21820 generate transport filter commands, both of which due to the fact that the
21821 command is split up &'before'& expansion.
21823 If an expansion item contains white space, you must quote it, so that it is all
21824 part of the same command item. If the entire option setting is one such
21825 expansion item, you have to take care what kind of quoting you use. For
21828 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
21830 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
21831 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
21832 stripped by Exim when it read the option's value. When the value is used, if
21833 the single quotes were missing, the line would be split into two items,
21834 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
21835 Exim tried to expand the first one.
21837 Except for the special case of &$pipe_addresses$& that is mentioned above, an
21838 expansion cannot generate multiple arguments, or a command name followed by
21839 arguments. Consider this example:
21841 transport_filter = ${lookup{$host}lsearch{/a/file}\
21842 {$value}{/bin/cat}}
21844 The result of the lookup is interpreted as the name of the command, even
21845 if it contains white space. The simplest way round this is to use a shell:
21847 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
21848 {$value}{/bin/cat}}
21852 The filter process is run under the same uid and gid as the normal delivery.
21853 For remote deliveries this is the Exim uid/gid by default. The command should
21854 normally yield a zero return code. Transport filters are not supposed to fail.
21855 A non-zero code is taken to mean that the transport filter encountered some
21856 serious problem. Delivery of the message is deferred; the message remains on
21857 the queue and is tried again later. It is not possible to cause a message to be
21858 bounced from a transport filter.
21860 If a transport filter is set on an autoreply transport, the original message is
21861 passed through the filter as it is being copied into the newly generated
21862 message, which happens if the &%return_message%& option is set.
21865 .option transport_filter_timeout transports time 5m
21866 .cindex "transport" "filter, timeout"
21867 When Exim is reading the output of a transport filter, it applies a timeout
21868 that can be set by this option. Exceeding the timeout is normally treated as a
21869 temporary delivery failure. However, if a transport filter is used with a
21870 &(pipe)& transport, a timeout in the transport filter is treated in the same
21871 way as a timeout in the pipe command itself. By default, a timeout is a hard
21872 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
21873 becomes a temporary error.
21876 .option user transports string&!! "Exim user"
21877 .cindex "uid (user id)" "local delivery"
21878 .cindex "transport" "user, specifying"
21879 This option specifies the user under whose uid the delivery process is to be
21880 run, overriding any uid that may have been set by the router. If the user is
21881 given as a name, the uid is looked up from the password data, and the
21882 associated group is taken as the value of the gid to be used if the &%group%&
21885 For deliveries that use local transports, a user and group are normally
21886 specified explicitly or implicitly (for example, as a result of
21887 &%check_local_user%&) by the router or transport.
21889 .cindex "hints database" "access by remote transport"
21890 For remote transports, you should leave this option unset unless you really are
21891 sure you know what you are doing. When a remote transport is running, it needs
21892 to be able to access Exim's hints databases, because each host may have its own
21894 .ecindex IIDgenoptra1
21895 .ecindex IIDgenoptra2
21896 .ecindex IIDgenoptra3
21903 . ////////////////////////////////////////////////////////////////////////////
21904 . ////////////////////////////////////////////////////////////////////////////
21906 .chapter "Address batching in local transports" "CHAPbatching" &&&
21908 .cindex "transport" "local; address batching in"
21909 The only remote transport (&(smtp)&) is normally configured to handle more than
21910 one address at a time, so that when several addresses are routed to the same
21911 remote host, just one copy of the message is sent. Local transports, however,
21912 normally handle one address at a time. That is, a separate instance of the
21913 transport is run for each address that is routed to the transport. A separate
21914 copy of the message is delivered each time.
21916 .cindex "batched local delivery"
21917 .oindex "&%batch_max%&"
21918 .oindex "&%batch_id%&"
21919 In special cases, it may be desirable to handle several addresses at once in a
21920 local transport, for example:
21923 In an &(appendfile)& transport, when storing messages in files for later
21924 delivery by some other means, a single copy of the message with multiple
21925 recipients saves space.
21927 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
21928 a single copy saves time, and is the normal way LMTP is expected to work.
21930 In a &(pipe)& transport, when passing the message
21931 to a scanner program or
21932 to some other delivery mechanism such as UUCP, multiple recipients may be
21936 These three local transports all have the same options for controlling multiple
21937 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
21938 repeating the information for each transport, these options are described here.
21940 The &%batch_max%& option specifies the maximum number of addresses that can be
21941 delivered together in a single run of the transport. Its default value is one
21942 (no batching). When more than one address is routed to a transport that has a
21943 &%batch_max%& value greater than one, the addresses are delivered in a batch
21944 (that is, in a single run of the transport with multiple recipients), subject
21945 to certain conditions:
21948 .vindex "&$local_part$&"
21949 If any of the transport's options contain a reference to &$local_part$&, no
21950 batching is possible.
21952 .vindex "&$domain$&"
21953 If any of the transport's options contain a reference to &$domain$&, only
21954 addresses with the same domain are batched.
21956 .cindex "customizing" "batching condition"
21957 If &%batch_id%& is set, it is expanded for each address, and only those
21958 addresses with the same expanded value are batched. This allows you to specify
21959 customized batching conditions. Failure of the expansion for any reason,
21960 including forced failure, disables batching, but it does not stop the delivery
21963 Batched addresses must also have the same errors address (where to send
21964 delivery errors), the same header additions and removals, the same user and
21965 group for the transport, and if a host list is present, the first host must
21969 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
21970 both when the file or pipe command is specified in the transport, and when it
21971 is specified by a &(redirect)& router, but all the batched addresses must of
21972 course be routed to the same file or pipe command. These two transports have an
21973 option called &%use_bsmtp%&, which causes them to deliver the message in
21974 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
21975 &%check_string%& and &%escape_string%& options are forced to the values
21978 escape_string = ".."
21980 when batched SMTP is in use. A full description of the batch SMTP mechanism is
21981 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
21982 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
21984 .cindex "&'Envelope-to:'& header line"
21985 If the generic &%envelope_to_add%& option is set for a batching transport, the
21986 &'Envelope-to:'& header that is added to the message contains all the addresses
21987 that are being processed together. If you are using a batching &(appendfile)&
21988 transport without &%use_bsmtp%&, the only way to preserve the recipient
21989 addresses is to set the &%envelope_to_add%& option.
21991 .cindex "&(pipe)& transport" "with multiple addresses"
21992 .vindex "&$pipe_addresses$&"
21993 If you are using a &(pipe)& transport without BSMTP, and setting the
21994 transport's &%command%& option, you can include &$pipe_addresses$& as part of
21995 the command. This is not a true variable; it is a bit of magic that causes each
21996 of the recipient addresses to be inserted into the command as a separate
21997 argument. This provides a way of accessing all the addresses that are being
21998 delivered in the batch. &*Note:*& This is not possible for pipe commands that
21999 are specified by a &(redirect)& router.
22004 . ////////////////////////////////////////////////////////////////////////////
22005 . ////////////////////////////////////////////////////////////////////////////
22007 .chapter "The appendfile transport" "CHAPappendfile"
22008 .scindex IIDapptra1 "&(appendfile)& transport"
22009 .scindex IIDapptra2 "transports" "&(appendfile)&"
22010 .cindex "directory creation"
22011 .cindex "creating directories"
22012 The &(appendfile)& transport delivers a message by appending it to an existing
22013 file, or by creating an entirely new file in a specified directory. Single
22014 files to which messages are appended can be in the traditional Unix mailbox
22015 format, or optionally in the MBX format supported by the Pine MUA and
22016 University of Washington IMAP daemon, &'inter alia'&. When each message is
22017 being delivered as a separate file, &"maildir"& format can optionally be used
22018 to give added protection against failures that happen part-way through the
22019 delivery. A third form of separate-file delivery known as &"mailstore"& is also
22020 supported. For all file formats, Exim attempts to create as many levels of
22021 directory as necessary, provided that &%create_directory%& is set.
22023 The code for the optional formats is not included in the Exim binary by
22024 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
22025 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
22028 .cindex "quota" "system"
22029 Exim recognizes system quota errors, and generates an appropriate message. Exim
22030 also supports its own quota control within the transport, for use when the
22031 system facility is unavailable or cannot be used for some reason.
22033 If there is an error while appending to a file (for example, quota exceeded or
22034 partition filled), Exim attempts to reset the file's length and last
22035 modification time back to what they were before. If there is an error while
22036 creating an entirely new file, the new file is removed.
22038 Before appending to a file, a number of security checks are made, and the
22039 file is locked. A detailed description is given below, after the list of
22042 The &(appendfile)& transport is most commonly used for local deliveries to
22043 users' mailboxes. However, it can also be used as a pseudo-remote transport for
22044 putting messages into files for remote delivery by some means other than Exim.
22045 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
22050 .section "The file and directory options" "SECTfildiropt"
22051 The &%file%& option specifies a single file, to which the message is appended;
22052 the &%directory%& option specifies a directory, in which a new file containing
22053 the message is created. Only one of these two options can be set, and for
22054 normal deliveries to mailboxes, one of them &'must'& be set.
22056 .vindex "&$address_file$&"
22057 .vindex "&$local_part$&"
22058 However, &(appendfile)& is also used for delivering messages to files or
22059 directories whose names (or parts of names) are obtained from alias,
22060 forwarding, or filtering operations (for example, a &%save%& command in a
22061 user's Exim filter). When such a transport is running, &$local_part$& contains
22062 the local part that was aliased or forwarded, and &$address_file$& contains the
22063 name (or partial name) of the file or directory generated by the redirection
22064 operation. There are two cases:
22067 If neither &%file%& nor &%directory%& is set, the redirection operation
22068 must specify an absolute path (one that begins with &`/`&). This is the most
22069 common case when users with local accounts use filtering to sort mail into
22070 different folders. See for example, the &(address_file)& transport in the
22071 default configuration. If the path ends with a slash, it is assumed to be the
22072 name of a directory. A delivery to a directory can also be forced by setting
22073 &%maildir_format%& or &%mailstore_format%&.
22075 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
22076 used to determine the file or directory name for the delivery. Normally, the
22077 contents of &$address_file$& are used in some way in the string expansion.
22081 .cindex "Sieve filter" "configuring &(appendfile)&"
22082 .cindex "Sieve filter" "relative mailbox path handling"
22083 As an example of the second case, consider an environment where users do not
22084 have home directories. They may be permitted to use Exim filter commands of the
22089 or Sieve filter commands of the form:
22091 require "fileinto";
22092 fileinto "folder23";
22094 In this situation, the expansion of &%file%& or &%directory%& in the transport
22095 must transform the relative path into an appropriate absolute filename. In the
22096 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
22097 is used as a result of a &"keep"& action in the filter. This example shows one
22098 way of handling this requirement:
22100 file = ${if eq{$address_file}{inbox} \
22101 {/var/mail/$local_part} \
22102 {${if eq{${substr_0_1:$address_file}}{/} \
22104 {$home/mail/$address_file} \
22108 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
22109 location, absolute paths are used without change, and other folders are in the
22110 &_mail_& directory within the home directory.
22112 &*Note 1*&: While processing an Exim filter, a relative path such as
22113 &_folder23_& is turned into an absolute path if a home directory is known to
22114 the router. In particular, this is the case if &%check_local_user%& is set. If
22115 you want to prevent this happening at routing time, you can set
22116 &%router_home_directory%& empty. This forces the router to pass the relative
22117 path to the transport.
22119 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
22120 the &%file%& or &%directory%& option is still used if it is set.
22125 .section "Private options for appendfile" "SECID134"
22126 .cindex "options" "&(appendfile)& transport"
22130 .option allow_fifo appendfile boolean false
22131 .cindex "fifo (named pipe)"
22132 .cindex "named pipe (fifo)"
22133 .cindex "pipe" "named (fifo)"
22134 Setting this option permits delivery to named pipes (FIFOs) as well as to
22135 regular files. If no process is reading the named pipe at delivery time, the
22136 delivery is deferred.
22139 .option allow_symlink appendfile boolean false
22140 .cindex "symbolic link" "to mailbox"
22141 .cindex "mailbox" "symbolic link"
22142 By default, &(appendfile)& will not deliver if the path name for the file is
22143 that of a symbolic link. Setting this option relaxes that constraint, but there
22144 are security issues involved in the use of symbolic links. Be sure you know
22145 what you are doing if you set this. Details of exactly what this option affects
22146 are included in the discussion which follows this list of options.
22149 .option batch_id appendfile string&!! unset
22150 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22151 However, batching is automatically disabled for &(appendfile)& deliveries that
22152 happen as a result of forwarding or aliasing or other redirection directly to a
22156 .option batch_max appendfile integer 1
22157 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22160 .option check_group appendfile boolean false
22161 When this option is set, the group owner of the file defined by the &%file%&
22162 option is checked to see that it is the same as the group under which the
22163 delivery process is running. The default setting is false because the default
22164 file mode is 0600, which means that the group is irrelevant.
22167 .option check_owner appendfile boolean true
22168 When this option is set, the owner of the file defined by the &%file%& option
22169 is checked to ensure that it is the same as the user under which the delivery
22170 process is running.
22173 .option check_string appendfile string "see below"
22174 .cindex "&""From""& line"
22175 As &(appendfile)& writes the message, the start of each line is tested for
22176 matching &%check_string%&, and if it does, the initial matching characters are
22177 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
22178 a literal string, not a regular expression, and the case of any letters it
22179 contains is significant.
22181 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
22182 are forced to &"."& and &".."& respectively, and any settings in the
22183 configuration are ignored. Otherwise, they default to &"From&~"& and
22184 &">From&~"& when the &%file%& option is set, and unset when any of the
22185 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
22187 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
22188 suitable for traditional &"BSD"& mailboxes, where a line beginning with
22189 &"From&~"& indicates the start of a new message. All four options need changing
22190 if another format is used. For example, to deliver to mailboxes in MMDF format:
22191 .cindex "MMDF format mailbox"
22192 .cindex "mailbox" "MMDF format"
22194 check_string = "\1\1\1\1\n"
22195 escape_string = "\1\1\1\1 \n"
22196 message_prefix = "\1\1\1\1\n"
22197 message_suffix = "\1\1\1\1\n"
22199 .option create_directory appendfile boolean true
22200 .cindex "directory creation"
22201 When this option is true, Exim attempts to create any missing superior
22202 directories for the file that it is about to write. A created directory's mode
22203 is given by the &%directory_mode%& option.
22205 The group ownership of a newly created directory is highly dependent on the
22206 operating system (and possibly the file system) that is being used. For
22207 example, in Solaris, if the parent directory has the setgid bit set, its group
22208 is propagated to the child; if not, the currently set group is used. However,
22209 in FreeBSD, the parent's group is always used.
22213 .option create_file appendfile string anywhere
22214 This option constrains the location of files and directories that are created
22215 by this transport. It applies to files defined by the &%file%& option and
22216 directories defined by the &%directory%& option. In the case of maildir
22217 delivery, it applies to the top level directory, not the maildir directories
22220 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
22221 &"belowhome"&. In the second and third cases, a home directory must have been
22222 set for the transport. This option is not useful when an explicit filename is
22223 given for normal mailbox deliveries. It is intended for the case when filenames
22224 are generated from users' &_.forward_& files. These are usually handled
22225 by an &(appendfile)& transport called &%address_file%&. See also
22226 &%file_must_exist%&.
22229 .option directory appendfile string&!! unset
22230 This option is mutually exclusive with the &%file%& option, but one of &%file%&
22231 or &%directory%& must be set, unless the delivery is the direct result of a
22232 redirection (see section &<<SECTfildiropt>>&).
22234 When &%directory%& is set, the string is expanded, and the message is delivered
22235 into a new file or files in or below the given directory, instead of being
22236 appended to a single mailbox file. A number of different formats are provided
22237 (see &%maildir_format%& and &%mailstore_format%&), and see section
22238 &<<SECTopdir>>& for further details of this form of delivery.
22241 .option directory_file appendfile string&!! "see below"
22243 .vindex "&$inode$&"
22244 When &%directory%& is set, but neither &%maildir_format%& nor
22245 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
22246 whose name is obtained by expanding this string. The default value is:
22248 q${base62:$tod_epoch}-$inode
22250 This generates a unique name from the current time, in base 62 form, and the
22251 inode of the file. The variable &$inode$& is available only when expanding this
22255 .option directory_mode appendfile "octal integer" 0700
22256 If &(appendfile)& creates any directories as a result of the
22257 &%create_directory%& option, their mode is specified by this option.
22260 .option escape_string appendfile string "see description"
22261 See &%check_string%& above.
22264 .option file appendfile string&!! unset
22265 This option is mutually exclusive with the &%directory%& option, but one of
22266 &%file%& or &%directory%& must be set, unless the delivery is the direct result
22267 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
22268 specifies a single file, to which the message is appended. One or more of
22269 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
22272 .cindex "NFS" "lock file"
22273 .cindex "locking files"
22274 .cindex "lock files"
22275 If you are using more than one host to deliver over NFS into the same
22276 mailboxes, you should always use lock files.
22278 The string value is expanded for each delivery, and must yield an absolute
22279 path. The most common settings of this option are variations on one of these
22282 file = /var/spool/mail/$local_part
22283 file = /home/$local_part/inbox
22286 .cindex "&""sticky""& bit"
22287 In the first example, all deliveries are done into the same directory. If Exim
22288 is configured to use lock files (see &%use_lockfile%& below) it must be able to
22289 create a file in the directory, so the &"sticky"& bit must be turned on for
22290 deliveries to be possible, or alternatively the &%group%& option can be used to
22291 run the delivery under a group id which has write access to the directory.
22295 .option file_format appendfile string unset
22296 .cindex "file" "mailbox; checking existing format"
22297 This option requests the transport to check the format of an existing file
22298 before adding to it. The check consists of matching a specific string at the
22299 start of the file. The value of the option consists of an even number of
22300 colon-separated strings. The first of each pair is the test string, and the
22301 second is the name of a transport. If the transport associated with a matched
22302 string is not the current transport, control is passed over to the other
22303 transport. For example, suppose the standard &(local_delivery)& transport has
22306 file_format = "From : local_delivery :\
22307 \1\1\1\1\n : local_mmdf_delivery"
22309 Mailboxes that begin with &"From"& are still handled by this transport, but if
22310 a mailbox begins with four binary ones followed by a newline, control is passed
22311 to a transport called &%local_mmdf_delivery%&, which presumably is configured
22312 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
22313 is assumed to match the current transport. If the start of a mailbox doesn't
22314 match any string, or if the transport named for a given string is not defined,
22315 delivery is deferred.
22318 .option file_must_exist appendfile boolean false
22319 If this option is true, the file specified by the &%file%& option must exist.
22320 A temporary error occurs if it does not, causing delivery to be deferred.
22321 If this option is false, the file is created if it does not exist.
22324 .option lock_fcntl_timeout appendfile time 0s
22325 .cindex "timeout" "mailbox locking"
22326 .cindex "mailbox" "locking, blocking and non-blocking"
22327 .cindex "locking files"
22328 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
22329 when locking an open mailbox file. If the call fails, the delivery process
22330 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
22331 Non-blocking calls are used so that the file is not kept open during the wait
22332 for the lock; the reason for this is to make it as safe as possible for
22333 deliveries over NFS in the case when processes might be accessing an NFS
22334 mailbox without using a lock file. This should not be done, but
22335 misunderstandings and hence misconfigurations are not unknown.
22337 On a busy system, however, the performance of a non-blocking lock approach is
22338 not as good as using a blocking lock with a timeout. In this case, the waiting
22339 is done inside the system call, and Exim's delivery process acquires the lock
22340 and can proceed as soon as the previous lock holder releases it.
22342 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
22343 timeout, are used. There may still be some retrying: the maximum number of
22346 (lock_retries * lock_interval) / lock_fcntl_timeout
22348 rounded up to the next whole number. In other words, the total time during
22349 which &(appendfile)& is trying to get a lock is roughly the same, unless
22350 &%lock_fcntl_timeout%& is set very large.
22352 You should consider setting this option if you are getting a lot of delayed
22353 local deliveries because of errors of the form
22355 failed to lock mailbox /some/file (fcntl)
22358 .option lock_flock_timeout appendfile time 0s
22359 This timeout applies to file locking when using &[flock()]& (see
22360 &%use_flock%&); the timeout operates in a similar manner to
22361 &%lock_fcntl_timeout%&.
22364 .option lock_interval appendfile time 3s
22365 This specifies the time to wait between attempts to lock the file. See below
22366 for details of locking.
22369 .option lock_retries appendfile integer 10
22370 This specifies the maximum number of attempts to lock the file. A value of zero
22371 is treated as 1. See below for details of locking.
22374 .option lockfile_mode appendfile "octal integer" 0600
22375 This specifies the mode of the created lock file, when a lock file is being
22376 used (see &%use_lockfile%& and &%use_mbx_lock%&).
22379 .option lockfile_timeout appendfile time 30m
22380 .cindex "timeout" "mailbox locking"
22381 When a lock file is being used (see &%use_lockfile%&), if a lock file already
22382 exists and is older than this value, it is assumed to have been left behind by
22383 accident, and Exim attempts to remove it.
22386 .option mailbox_filecount appendfile string&!! unset
22387 .cindex "mailbox" "specifying size of"
22388 .cindex "size" "of mailbox"
22389 If this option is set, it is expanded, and the result is taken as the current
22390 number of files in the mailbox. It must be a decimal number, optionally
22391 followed by K or M. This provides a way of obtaining this information from an
22392 external source that maintains the data.
22395 .option mailbox_size appendfile string&!! unset
22396 .cindex "mailbox" "specifying size of"
22397 .cindex "size" "of mailbox"
22398 If this option is set, it is expanded, and the result is taken as the current
22399 size the mailbox. It must be a decimal number, optionally followed by K or M.
22400 This provides a way of obtaining this information from an external source that
22401 maintains the data. This is likely to be helpful for maildir deliveries where
22402 it is computationally expensive to compute the size of a mailbox.
22406 .option maildir_format appendfile boolean false
22407 .cindex "maildir format" "specifying"
22408 If this option is set with the &%directory%& option, the delivery is into a new
22409 file, in the &"maildir"& format that is used by other mail software. When the
22410 transport is activated directly from a &(redirect)& router (for example, the
22411 &(address_file)& transport in the default configuration), setting
22412 &%maildir_format%& causes the path received from the router to be treated as a
22413 directory, whether or not it ends with &`/`&. This option is available only if
22414 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
22415 &<<SECTmaildirdelivery>>& below for further details.
22418 .option maildir_quota_directory_regex appendfile string "See below"
22419 .cindex "maildir format" "quota; directories included in"
22420 .cindex "quota" "maildir; directories included in"
22421 This option is relevant only when &%maildir_use_size_file%& is set. It defines
22422 a regular expression for specifying directories, relative to the quota
22423 directory (see &%quota_directory%&), that should be included in the quota
22424 calculation. The default value is:
22426 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
22428 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
22429 (directories whose names begin with a dot). If you want to exclude the
22431 folder from the count (as some sites do), you need to change this setting to
22433 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
22435 This uses a negative lookahead in the regular expression to exclude the
22436 directory whose name is &_.Trash_&. When a directory is excluded from quota
22437 calculations, quota processing is bypassed for any messages that are delivered
22438 directly into that directory.
22441 .option maildir_retries appendfile integer 10
22442 This option specifies the number of times to retry when writing a file in
22443 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
22446 .option maildir_tag appendfile string&!! unset
22447 This option applies only to deliveries in maildir format, and is described in
22448 section &<<SECTmaildirdelivery>>& below.
22451 .option maildir_use_size_file appendfile&!! boolean false
22452 .cindex "maildir format" "&_maildirsize_& file"
22453 The result of string expansion for this option must be a valid boolean value.
22454 If it is true, it enables support for &_maildirsize_& files. Exim
22455 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
22456 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
22457 value is zero. See &%maildir_quota_directory_regex%& above and section
22458 &<<SECTmaildirdelivery>>& below for further details.
22460 .option maildirfolder_create_regex appendfile string unset
22461 .cindex "maildir format" "&_maildirfolder_& file"
22462 .cindex "&_maildirfolder_&, creating"
22463 The value of this option is a regular expression. If it is unset, it has no
22464 effect. Otherwise, before a maildir delivery takes place, the pattern is
22465 matched against the name of the maildir directory, that is, the directory
22466 containing the &_new_& and &_tmp_& subdirectories that will be used for the
22467 delivery. If there is a match, Exim checks for the existence of a file called
22468 &_maildirfolder_& in the directory, and creates it if it does not exist.
22469 See section &<<SECTmaildirdelivery>>& for more details.
22472 .option mailstore_format appendfile boolean false
22473 .cindex "mailstore format" "specifying"
22474 If this option is set with the &%directory%& option, the delivery is into two
22475 new files in &"mailstore"& format. The option is available only if
22476 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
22477 below for further details.
22480 .option mailstore_prefix appendfile string&!! unset
22481 This option applies only to deliveries in mailstore format, and is described in
22482 section &<<SECTopdir>>& below.
22485 .option mailstore_suffix appendfile string&!! unset
22486 This option applies only to deliveries in mailstore format, and is described in
22487 section &<<SECTopdir>>& below.
22490 .option mbx_format appendfile boolean false
22491 .cindex "locking files"
22492 .cindex "file" "locking"
22493 .cindex "file" "MBX format"
22494 .cindex "MBX format, specifying"
22495 This option is available only if Exim has been compiled with SUPPORT_MBX
22496 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
22497 the message is appended to the mailbox file in MBX format instead of
22498 traditional Unix format. This format is supported by Pine4 and its associated
22499 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
22501 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
22502 automatically changed by the use of &%mbx_format%&. They should normally be set
22503 empty when using MBX format, so this option almost always appears in this
22510 If none of the locking options are mentioned in the configuration,
22511 &%use_mbx_lock%& is assumed and the other locking options default to false. It
22512 is possible to specify the other kinds of locking with &%mbx_format%&, but
22513 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
22514 interworks with &'c-client'&, providing for shared access to the mailbox. It
22515 should not be used if any program that does not use this form of locking is
22516 going to access the mailbox, nor should it be used if the mailbox file is NFS
22517 mounted, because it works only when the mailbox is accessed from a single host.
22519 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
22520 the standard version of &'c-client'&, because as long as it has a mailbox open
22521 (this means for the whole of a Pine or IMAP session), Exim will not be able to
22522 append messages to it.
22525 .option message_prefix appendfile string&!! "see below"
22526 .cindex "&""From""& line"
22527 The string specified here is expanded and output at the start of every message.
22528 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
22529 in which case it is:
22531 message_prefix = "From ${if def:return_path{$return_path}\
22532 {MAILER-DAEMON}} $tod_bsdinbox\n"
22534 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22535 &`\n`& to &`\r\n`& in &%message_prefix%&.
22537 .option message_suffix appendfile string&!! "see below"
22538 The string specified here is expanded and output at the end of every message.
22539 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
22540 in which case it is a single newline character. The suffix can be suppressed by
22545 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22546 &`\n`& to &`\r\n`& in &%message_suffix%&.
22548 .option mode appendfile "octal integer" 0600
22549 If the output file is created, it is given this mode. If it already exists and
22550 has wider permissions, they are reduced to this mode. If it has narrower
22551 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
22552 if the delivery is the result of a &%save%& command in a filter file specifying
22553 a particular mode, the mode of the output file is always forced to take that
22554 value, and this option is ignored.
22557 .option mode_fail_narrower appendfile boolean true
22558 This option applies in the case when an existing mailbox file has a narrower
22559 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
22560 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
22561 continues with the delivery attempt, using the existing mode of the file.
22564 .option notify_comsat appendfile boolean false
22565 If this option is true, the &'comsat'& daemon is notified after every
22566 successful delivery to a user mailbox. This is the daemon that notifies logged
22567 on users about incoming mail.
22570 .option quota appendfile string&!! unset
22571 .cindex "quota" "imposed by Exim"
22572 This option imposes a limit on the size of the file to which Exim is appending,
22573 or to the total space used in the directory tree when the &%directory%& option
22574 is set. In the latter case, computation of the space used is expensive, because
22575 all the files in the directory (and any sub-directories) have to be
22576 individually inspected and their sizes summed. (See &%quota_size_regex%& and
22577 &%maildir_use_size_file%& for ways to avoid this in environments where users
22578 have no shell access to their mailboxes).
22580 As there is no interlock against two simultaneous deliveries into a
22581 multi-file mailbox, it is possible for the quota to be overrun in this case.
22582 For single-file mailboxes, of course, an interlock is a necessity.
22584 A file's size is taken as its &'used'& value. Because of blocking effects, this
22585 may be a lot less than the actual amount of disk space allocated to the file.
22586 If the sizes of a number of files are being added up, the rounding effect can
22587 become quite noticeable, especially on systems that have large block sizes.
22588 Nevertheless, it seems best to stick to the &'used'& figure, because this is
22589 the obvious value which users understand most easily.
22591 The value of the option is expanded, and must then be a numerical value
22592 (decimal point allowed), optionally followed by one of the letters K, M, or G,
22593 for kilobytes, megabytes, or gigabytes, optionally followed by a slash
22594 and further option modifiers. If Exim is running on a system with
22595 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
22598 The option modifier &%no_check%& can be used to force delivery even if the over
22599 quota condition is met. The quota gets updated as usual.
22601 &*Note*&: A value of zero is interpreted as &"no quota"&.
22603 The expansion happens while Exim is running as root, before it changes uid for
22604 the delivery. This means that files that are inaccessible to the end user can
22605 be used to hold quota values that are looked up in the expansion. When delivery
22606 fails because this quota is exceeded, the handling of the error is as for
22607 system quota failures.
22609 By default, Exim's quota checking mimics system quotas, and restricts the
22610 mailbox to the specified maximum size, though the value is not accurate to the
22611 last byte, owing to separator lines and additional headers that may get added
22612 during message delivery. When a mailbox is nearly full, large messages may get
22613 refused even though small ones are accepted, because the size of the current
22614 message is added to the quota when the check is made. This behaviour can be
22615 changed by setting &%quota_is_inclusive%& false. When this is done, the check
22616 for exceeding the quota does not include the current message. Thus, deliveries
22617 continue until the quota has been exceeded; thereafter, no further messages are
22618 delivered. See also &%quota_warn_threshold%&.
22621 .option quota_directory appendfile string&!! unset
22622 This option defines the directory to check for quota purposes when delivering
22623 into individual files. The default is the delivery directory, or, if a file
22624 called &_maildirfolder_& exists in a maildir directory, the parent of the
22625 delivery directory.
22628 .option quota_filecount appendfile string&!! 0
22629 This option applies when the &%directory%& option is set. It limits the total
22630 number of files in the directory (compare the inode limit in system quotas). It
22631 can only be used if &%quota%& is also set. The value is expanded; an expansion
22632 failure causes delivery to be deferred. A value of zero is interpreted as
22635 The option modifier &%no_check%& can be used to force delivery even if the over
22636 quota condition is met. The quota gets updated as usual.
22638 .option quota_is_inclusive appendfile boolean true
22639 See &%quota%& above.
22642 .option quota_size_regex appendfile string unset
22643 This option applies when one of the delivery modes that writes a separate file
22644 for each message is being used. When Exim wants to find the size of one of
22645 these files in order to test the quota, it first checks &%quota_size_regex%&.
22646 If this is set to a regular expression that matches the filename, and it
22647 captures one string, that string is interpreted as a representation of the
22648 file's size. The value of &%quota_size_regex%& is not expanded.
22650 This feature is useful only when users have no shell access to their mailboxes
22651 &-- otherwise they could defeat the quota simply by renaming the files. This
22652 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
22653 the file length to the filename. For example:
22655 maildir_tag = ,S=$message_size
22656 quota_size_regex = ,S=(\d+)
22658 An alternative to &$message_size$& is &$message_linecount$&, which contains the
22659 number of lines in the message.
22661 The regular expression should not assume that the length is at the end of the
22662 filename (even though &%maildir_tag%& puts it there) because maildir MUAs
22663 sometimes add other information onto the ends of message filenames.
22665 Section &<<SECID136>>& contains further information.
22668 .option quota_warn_message appendfile string&!! "see below"
22669 See below for the use of this option. If it is not set when
22670 &%quota_warn_threshold%& is set, it defaults to
22672 quota_warn_message = "\
22673 To: $local_part@$domain\n\
22674 Subject: Your mailbox\n\n\
22675 This message is automatically created \
22676 by mail delivery software.\n\n\
22677 The size of your mailbox has exceeded \
22678 a warning threshold that is\n\
22679 set by the system administrator.\n"
22683 .option quota_warn_threshold appendfile string&!! 0
22684 .cindex "quota" "warning threshold"
22685 .cindex "mailbox" "size warning"
22686 .cindex "size" "of mailbox"
22687 This option is expanded in the same way as &%quota%& (see above). If the
22688 resulting value is greater than zero, and delivery of the message causes the
22689 size of the file or total space in the directory tree to cross the given
22690 threshold, a warning message is sent. If &%quota%& is also set, the threshold
22691 may be specified as a percentage of it by following the value with a percent
22695 quota_warn_threshold = 75%
22697 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
22698 percent sign is ignored.
22700 The warning message itself is specified by the &%quota_warn_message%& option,
22701 and it must start with a &'To:'& header line containing the recipient(s) of the
22702 warning message. These do not necessarily have to include the recipient(s) of
22703 the original message. A &'Subject:'& line should also normally be supplied. You
22704 can include any other header lines that you want. If you do not include a
22705 &'From:'& line, the default is:
22707 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
22709 .oindex &%errors_reply_to%&
22710 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
22713 The &%quota%& option does not have to be set in order to use this option; they
22714 are independent of one another except when the threshold is specified as a
22718 .option use_bsmtp appendfile boolean false
22719 .cindex "envelope sender"
22720 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
22721 format, with the envelope sender and recipient(s) included as SMTP commands. If
22722 you want to include a leading HELO command with such messages, you can do
22723 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
22724 for details of batch SMTP.
22727 .option use_crlf appendfile boolean false
22728 .cindex "carriage return"
22730 This option causes lines to be terminated with the two-character CRLF sequence
22731 (carriage return, linefeed) instead of just a linefeed character. In the case
22732 of batched SMTP, the byte sequence written to the file is then an exact image
22733 of what would be sent down a real SMTP connection.
22735 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
22736 (which are used to supply the traditional &"From&~"& and blank line separators
22737 in Berkeley-style mailboxes) are written verbatim, so must contain their own
22738 carriage return characters if these are needed. In cases where these options
22739 have non-empty defaults, the values end with a single linefeed, so they must be
22740 changed to end with &`\r\n`& if &%use_crlf%& is set.
22743 .option use_fcntl_lock appendfile boolean "see below"
22744 This option controls the use of the &[fcntl()]& function to lock a file for
22745 exclusive use when a message is being appended. It is set by default unless
22746 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
22747 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
22748 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
22751 .option use_flock_lock appendfile boolean false
22752 This option is provided to support the use of &[flock()]& for file locking, for
22753 the few situations where it is needed. Most modern operating systems support
22754 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
22755 each other. Exim uses &[fcntl()]& locking by default.
22757 This option is required only if you are using an operating system where
22758 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
22759 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
22760 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
22762 .cindex "Solaris" "&[flock()]& support"
22763 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
22764 have it (and some, I think, provide a not quite right version built on top of
22765 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
22766 the ability to use it, and any attempt to do so will cause a configuration
22769 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
22770 is just being mapped onto &[fcntl()]& by the OS).
22773 .option use_lockfile appendfile boolean "see below"
22774 If this option is turned off, Exim does not attempt to create a lock file when
22775 appending to a mailbox file. In this situation, the only locking is by
22776 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
22777 sure that every MUA that is ever going to look at your users' mailboxes uses
22778 &[fcntl()]& rather than a lock file, and even then only when you are not
22779 delivering over NFS from more than one host.
22781 .cindex "NFS" "lock file"
22782 In order to append to an NFS file safely from more than one host, it is
22783 necessary to take out a lock &'before'& opening the file, and the lock file
22784 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
22787 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
22788 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
22789 except when &%mbx_format%& is set.
22792 .option use_mbx_lock appendfile boolean "see below"
22793 This option is available only if Exim has been compiled with SUPPORT_MBX
22794 set in &_Local/Makefile_&. Setting the option specifies that special MBX
22795 locking rules be used. It is set by default if &%mbx_format%& is set and none
22796 of the locking options are mentioned in the configuration. The locking rules
22797 are the same as are used by the &'c-client'& library that underlies Pine and
22798 the IMAP4 and POP daemons that come with it (see the discussion below). The
22799 rules allow for shared access to the mailbox. However, this kind of locking
22800 does not work when the mailbox is NFS mounted.
22802 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
22803 &%use_flock_lock%& to control what kind of locking is used in implementing the
22804 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
22805 without &%use_fcntl_lock%& or &%use_flock_lock%&.
22810 .section "Operational details for appending" "SECTopappend"
22811 .cindex "appending to a file"
22812 .cindex "file" "appending"
22813 Before appending to a file, the following preparations are made:
22816 If the name of the file is &_/dev/null_&, no action is taken, and a success
22820 .cindex "directory creation"
22821 If any directories on the file's path are missing, Exim creates them if the
22822 &%create_directory%& option is set. A created directory's mode is given by the
22823 &%directory_mode%& option.
22826 If &%file_format%& is set, the format of an existing file is checked. If this
22827 indicates that a different transport should be used, control is passed to that
22831 .cindex "file" "locking"
22832 .cindex "locking files"
22833 .cindex "NFS" "lock file"
22834 If &%use_lockfile%& is set, a lock file is built in a way that will work
22835 reliably over NFS, as follows:
22838 Create a &"hitching post"& file whose name is that of the lock file with the
22839 current time, primary host name, and process id added, by opening for writing
22840 as a new file. If this fails with an access error, delivery is deferred.
22842 Close the hitching post file, and hard link it to the lock filename.
22844 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
22845 Unlink the hitching post name.
22847 Otherwise, use &[stat()]& to get information about the hitching post file, and
22848 then unlink hitching post name. If the number of links is exactly two, creation
22849 of the lock file succeeded but something (for example, an NFS server crash and
22850 restart) caused this fact not to be communicated to the &[link()]& call.
22852 If creation of the lock file failed, wait for &%lock_interval%& and try again,
22853 up to &%lock_retries%& times. However, since any program that writes to a
22854 mailbox should complete its task very quickly, it is reasonable to time out old
22855 lock files that are normally the result of user agent and system crashes. If an
22856 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
22857 it before trying again.
22861 A call is made to &[lstat()]& to discover whether the main file exists, and if
22862 so, what its characteristics are. If &[lstat()]& fails for any reason other
22863 than non-existence, delivery is deferred.
22866 .cindex "symbolic link" "to mailbox"
22867 .cindex "mailbox" "symbolic link"
22868 If the file does exist and is a symbolic link, delivery is deferred, unless the
22869 &%allow_symlink%& option is set, in which case the ownership of the link is
22870 checked, and then &[stat()]& is called to find out about the real file, which
22871 is then subjected to the checks below. The check on the top-level link
22872 ownership prevents one user creating a link for another's mailbox in a sticky
22873 directory, though allowing symbolic links in this case is definitely not a good
22874 idea. If there is a chain of symbolic links, the intermediate ones are not
22878 If the file already exists but is not a regular file, or if the file's owner
22879 and group (if the group is being checked &-- see &%check_group%& above) are
22880 different from the user and group under which the delivery is running,
22881 delivery is deferred.
22884 If the file's permissions are more generous than specified, they are reduced.
22885 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
22886 is set false, in which case the delivery is tried using the existing
22890 The file's inode number is saved, and the file is then opened for appending.
22891 If this fails because the file has vanished, &(appendfile)& behaves as if it
22892 hadn't existed (see below). For any other failures, delivery is deferred.
22895 If the file is opened successfully, check that the inode number hasn't
22896 changed, that it is still a regular file, and that the owner and permissions
22897 have not changed. If anything is wrong, defer delivery and freeze the message.
22900 If the file did not exist originally, defer delivery if the &%file_must_exist%&
22901 option is set. Otherwise, check that the file is being created in a permitted
22902 directory if the &%create_file%& option is set (deferring on failure), and then
22903 open for writing as a new file, with the O_EXCL and O_CREAT options,
22904 except when dealing with a symbolic link (the &%allow_symlink%& option must be
22905 set). In this case, which can happen if the link points to a non-existent file,
22906 the file is opened for writing using O_CREAT but not O_EXCL, because
22907 that prevents link following.
22910 .cindex "loop" "while file testing"
22911 If opening fails because the file exists, obey the tests given above for
22912 existing files. However, to avoid looping in a situation where the file is
22913 being continuously created and destroyed, the exists/not-exists loop is broken
22914 after 10 repetitions, and the message is then frozen.
22917 If opening fails with any other error, defer delivery.
22920 .cindex "file" "locking"
22921 .cindex "locking files"
22922 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
22923 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
22924 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
22925 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
22926 file, and an exclusive lock on the file whose name is
22928 /tmp/.<device-number>.<inode-number>
22930 using the device and inode numbers of the open mailbox file, in accordance with
22931 the MBX locking rules. This file is created with a mode that is specified by
22932 the &%lockfile_mode%& option.
22934 If Exim fails to lock the file, there are two possible courses of action,
22935 depending on the value of the locking timeout. This is obtained from
22936 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
22938 If the timeout value is zero, the file is closed, Exim waits for
22939 &%lock_interval%&, and then goes back and re-opens the file as above and tries
22940 to lock it again. This happens up to &%lock_retries%& times, after which the
22941 delivery is deferred.
22943 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
22944 &[flock()]& are used (with the given timeout), so there has already been some
22945 waiting involved by the time locking fails. Nevertheless, Exim does not give up
22946 immediately. It retries up to
22948 (lock_retries * lock_interval) / <timeout>
22950 times (rounded up).
22953 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
22954 and/or &[flock()]& locks) and then deletes the lock file if one was created.
22957 .section "Operational details for delivery to a new file" "SECTopdir"
22958 .cindex "delivery" "to single file"
22959 .cindex "&""From""& line"
22960 When the &%directory%& option is set instead of &%file%&, each message is
22961 delivered into a newly-created file or set of files. When &(appendfile)& is
22962 activated directly from a &(redirect)& router, neither &%file%& nor
22963 &%directory%& is normally set, because the path for delivery is supplied by the
22964 router. (See for example, the &(address_file)& transport in the default
22965 configuration.) In this case, delivery is to a new file if either the path name
22966 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
22968 No locking is required while writing the message to a new file, so the various
22969 locking options of the transport are ignored. The &"From"& line that by default
22970 separates messages in a single file is not normally needed, nor is the escaping
22971 of message lines that start with &"From"&, and there is no need to ensure a
22972 newline at the end of each message. Consequently, the default values for
22973 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
22974 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
22976 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
22977 the files in the delivery directory by default. However, you can specify a
22978 different directory by setting &%quota_directory%&. Also, for maildir
22979 deliveries (see below) the &_maildirfolder_& convention is honoured.
22982 .cindex "maildir format"
22983 .cindex "mailstore format"
22984 There are three different ways in which delivery to individual files can be
22985 done, controlled by the settings of the &%maildir_format%& and
22986 &%mailstore_format%& options. Note that code to support maildir or mailstore
22987 formats is not included in the binary unless SUPPORT_MAILDIR or
22988 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
22990 .cindex "directory creation"
22991 In all three cases an attempt is made to create the directory and any necessary
22992 sub-directories if they do not exist, provided that the &%create_directory%&
22993 option is set (the default). The location of a created directory can be
22994 constrained by setting &%create_file%&. A created directory's mode is given by
22995 the &%directory_mode%& option. If creation fails, or if the
22996 &%create_directory%& option is not set when creation is required, delivery is
23001 .section "Maildir delivery" "SECTmaildirdelivery"
23002 .cindex "maildir format" "description of"
23003 If the &%maildir_format%& option is true, Exim delivers each message by writing
23004 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
23005 directory that is defined by the &%directory%& option (the &"delivery
23006 directory"&). If the delivery is successful, the file is renamed into the
23007 &_new_& subdirectory.
23009 In the filename, <&'stime'&> is the current time of day in seconds, and
23010 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
23011 Exim checks that the time-of-day clock has moved on by at least one microsecond
23012 before terminating the delivery process. This guarantees uniqueness for the
23013 filename. However, as a precaution, Exim calls &[stat()]& for the file before
23014 opening it. If any response other than ENOENT (does not exist) is given,
23015 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
23017 Before Exim carries out a maildir delivery, it ensures that subdirectories
23018 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
23019 do not exist, Exim tries to create them and any superior directories in their
23020 path, subject to the &%create_directory%& and &%create_file%& options. If the
23021 &%maildirfolder_create_regex%& option is set, and the regular expression it
23022 contains matches the delivery directory, Exim also ensures that a file called
23023 &_maildirfolder_& exists in the delivery directory. If a missing directory or
23024 &_maildirfolder_& file cannot be created, delivery is deferred.
23026 These features make it possible to use Exim to create all the necessary files
23027 and directories in a maildir mailbox, including subdirectories for maildir++
23028 folders. Consider this example:
23030 maildir_format = true
23031 directory = /var/mail/$local_part\
23032 ${if eq{$local_part_suffix}{}{}\
23033 {/.${substr_1:$local_part_suffix}}}
23034 maildirfolder_create_regex = /\.[^/]+$
23036 If &$local_part_suffix$& is empty (there was no suffix for the local part),
23037 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
23038 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
23039 not match this name, so Exim will not look for or create the file
23040 &_/var/mail/pimbo/maildirfolder_&, though it will create
23041 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
23043 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
23044 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
23045 does match &%maildirfolder_create_regex%&. In this case, Exim will create
23046 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
23047 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
23049 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
23050 not inadvertently match the toplevel maildir directory, because a
23051 &_maildirfolder_& file at top level would completely break quota calculations.
23053 .cindex "quota" "in maildir delivery"
23054 .cindex "maildir++"
23055 If Exim is required to check a &%quota%& setting before a maildir delivery, and
23056 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
23057 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
23058 Exim assumes the directory is a maildir++ folder directory, which is one level
23059 down from the user's top level mailbox directory. This causes it to start at
23060 the parent directory instead of the current directory when calculating the
23061 amount of space used.
23063 One problem with delivering into a multi-file mailbox is that it is
23064 computationally expensive to compute the size of the mailbox for quota
23065 checking. Various approaches have been taken to reduce the amount of work
23066 needed. The next two sections describe two of them. A third alternative is to
23067 use some external process for maintaining the size data, and use the expansion
23068 of the &%mailbox_size%& option as a way of importing it into Exim.
23073 .section "Using tags to record message sizes" "SECID135"
23074 If &%maildir_tag%& is set, the string is expanded for each delivery.
23075 When the maildir file is renamed into the &_new_& sub-directory, the
23076 tag is added to its name. However, if adding the tag takes the length of the
23077 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
23078 the tag is dropped and the maildir file is created with no tag.
23081 .vindex "&$message_size$&"
23082 Tags can be used to encode the size of files in their names; see
23083 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
23084 happens after the message has been written. The value of the &$message_size$&
23085 variable is set to the number of bytes actually written. If the expansion is
23086 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
23087 be deferred. The expanded tag may contain any printing characters except &"/"&.
23088 Non-printing characters in the string are ignored; if the resulting string is
23089 empty, it is ignored. If it starts with an alphanumeric character, a leading
23090 colon is inserted; this default has not proven to be the path that popular
23091 maildir implementations have chosen (but changing it in Exim would break
23092 backwards compatibility).
23094 For one common implementation, you might set:
23096 maildir_tag = ,S=${message_size}
23098 but you should check the documentation of the other software to be sure.
23100 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
23101 as this allows Exim to extract the size from your tag, instead of having to
23102 &[stat()]& each message file.
23105 .section "Using a maildirsize file" "SECID136"
23106 .cindex "quota" "in maildir delivery"
23107 .cindex "maildir format" "&_maildirsize_& file"
23108 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
23109 storing quota and message size information in a file called &_maildirsize_&
23110 within the toplevel maildir directory. If this file does not exist, Exim
23111 creates it, setting the quota from the &%quota%& option of the transport. If
23112 the maildir directory itself does not exist, it is created before any attempt
23113 to write a &_maildirsize_& file.
23115 The &_maildirsize_& file is used to hold information about the sizes of
23116 messages in the maildir, thus speeding up quota calculations. The quota value
23117 in the file is just a cache; if the quota is changed in the transport, the new
23118 value overrides the cached value when the next message is delivered. The cache
23119 is maintained for the benefit of other programs that access the maildir and
23120 need to know the quota.
23122 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
23123 file is maintained (with a zero quota setting), but no quota is imposed.
23125 A regular expression is available for controlling which directories in the
23126 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
23127 See the description of the &%maildir_quota_directory_regex%& option above for
23131 .section "Mailstore delivery" "SECID137"
23132 .cindex "mailstore format" "description of"
23133 If the &%mailstore_format%& option is true, each message is written as two
23134 files in the given directory. A unique base name is constructed from the
23135 message id and the current delivery process, and the files that are written use
23136 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
23137 contains the message's envelope, and the &_.msg_& file contains the message
23138 itself. The base name is placed in the variable &$mailstore_basename$&.
23140 During delivery, the envelope is first written to a file with the suffix
23141 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
23142 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
23143 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
23144 file before accessing either of them. An alternative approach is to wait for
23145 the absence of a &_.tmp_& file.
23147 The envelope file starts with any text defined by the &%mailstore_prefix%&
23148 option, expanded and terminated by a newline if there isn't one. Then follows
23149 the sender address on one line, then all the recipient addresses, one per line.
23150 There can be more than one recipient only if the &%batch_max%& option is set
23151 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
23152 appended to the file, followed by a newline if it does not end with one.
23154 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
23155 failure, it is ignored. Other expansion errors are treated as serious
23156 configuration errors, and delivery is deferred. The variable
23157 &$mailstore_basename$& is available for use during these expansions.
23160 .section "Non-special new file delivery" "SECID138"
23161 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
23162 file is created directly in the named directory. For example, when delivering
23163 messages into files in batched SMTP format for later delivery to some host (see
23164 section &<<SECTbatchSMTP>>&), a setting such as
23166 directory = /var/bsmtp/$host
23168 might be used. A message is written to a file with a temporary name, which is
23169 then renamed when the delivery is complete. The final name is obtained by
23170 expanding the contents of the &%directory_file%& option.
23171 .ecindex IIDapptra1
23172 .ecindex IIDapptra2
23179 . ////////////////////////////////////////////////////////////////////////////
23180 . ////////////////////////////////////////////////////////////////////////////
23182 .chapter "The autoreply transport" "CHID8"
23183 .scindex IIDauttra1 "transports" "&(autoreply)&"
23184 .scindex IIDauttra2 "&(autoreply)& transport"
23185 The &(autoreply)& transport is not a true transport in that it does not cause
23186 the message to be transmitted. Instead, it generates a new mail message as an
23187 automatic reply to the incoming message. &'References:'& and
23188 &'Auto-Submitted:'& header lines are included. These are constructed according
23189 to the rules in RFCs 2822 and 3834, respectively.
23191 If the router that passes the message to this transport does not have the
23192 &%unseen%& option set, the original message (for the current recipient) is not
23193 delivered anywhere. However, when the &%unseen%& option is set on the router
23194 that passes the message to this transport, routing of the address continues, so
23195 another router can set up a normal message delivery.
23198 The &(autoreply)& transport is usually run as the result of mail filtering, a
23199 &"vacation"& message being the standard example. However, it can also be run
23200 directly from a router like any other transport. To reduce the possibility of
23201 message cascades, messages created by the &(autoreply)& transport always have
23202 empty envelope sender addresses, like bounce messages.
23204 The parameters of the message to be sent can be specified in the configuration
23205 by options described below. However, these are used only when the address
23206 passed to the transport does not contain its own reply information. When the
23207 transport is run as a consequence of a
23209 or &%vacation%& command in a filter file, the parameters of the message are
23210 supplied by the filter, and passed with the address. The transport's options
23211 that define the message are then ignored (so they are not usually set in this
23212 case). The message is specified entirely by the filter or by the transport; it
23213 is never built from a mixture of options. However, the &%file_optional%&,
23214 &%mode%&, and &%return_message%& options apply in all cases.
23216 &(Autoreply)& is implemented as a local transport. When used as a result of a
23217 command in a user's filter file, &(autoreply)& normally runs under the uid and
23218 gid of the user, and with appropriate current and home directories (see chapter
23219 &<<CHAPenvironment>>&).
23221 There is a subtle difference between routing a message to a &(pipe)& transport
23222 that generates some text to be returned to the sender, and routing it to an
23223 &(autoreply)& transport. This difference is noticeable only if more than one
23224 address from the same message is so handled. In the case of a pipe, the
23225 separate outputs from the different addresses are gathered up and returned to
23226 the sender in a single message, whereas if &(autoreply)& is used, a separate
23227 message is generated for each address that is passed to it.
23229 Non-printing characters are not permitted in the header lines generated for the
23230 message that &(autoreply)& creates, with the exception of newlines that are
23231 immediately followed by white space. If any non-printing characters are found,
23232 the transport defers.
23233 Whether characters with the top bit set count as printing characters or not is
23234 controlled by the &%print_topbitchars%& global option.
23236 If any of the generic options for manipulating headers (for example,
23237 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
23238 of the original message that is included in the generated message when
23239 &%return_message%& is set. They do not apply to the generated message itself.
23241 .vindex "&$sender_address$&"
23242 If the &(autoreply)& transport receives return code 2 from Exim when it submits
23243 the message, indicating that there were no recipients, it does not treat this
23244 as an error. This means that autoreplies sent to &$sender_address$& when this
23245 is empty (because the incoming message is a bounce message) do not cause
23246 problems. They are just discarded.
23250 .section "Private options for autoreply" "SECID139"
23251 .cindex "options" "&(autoreply)& transport"
23253 .option bcc autoreply string&!! unset
23254 This specifies the addresses that are to receive &"blind carbon copies"& of the
23255 message when the message is specified by the transport.
23258 .option cc autoreply string&!! unset
23259 This specifies recipients of the message and the contents of the &'Cc:'& header
23260 when the message is specified by the transport.
23263 .option file autoreply string&!! unset
23264 The contents of the file are sent as the body of the message when the message
23265 is specified by the transport. If both &%file%& and &%text%& are set, the text
23266 string comes first.
23269 .option file_expand autoreply boolean false
23270 If this is set, the contents of the file named by the &%file%& option are
23271 subjected to string expansion as they are added to the message.
23274 .option file_optional autoreply boolean false
23275 If this option is true, no error is generated if the file named by the &%file%&
23276 option or passed with the address does not exist or cannot be read.
23279 .option from autoreply string&!! unset
23280 This specifies the contents of the &'From:'& header when the message is
23281 specified by the transport.
23284 .option headers autoreply string&!! unset
23285 This specifies additional RFC 2822 headers that are to be added to the message
23286 when the message is specified by the transport. Several can be given by using
23287 &"\n"& to separate them. There is no check on the format.
23290 .option log autoreply string&!! unset
23291 This option names a file in which a record of every message sent is logged when
23292 the message is specified by the transport.
23295 .option mode autoreply "octal integer" 0600
23296 If either the log file or the &"once"& file has to be created, this mode is
23300 .option never_mail autoreply "address list&!!" unset
23301 If any run of the transport creates a message with a recipient that matches any
23302 item in the list, that recipient is quietly discarded. If all recipients are
23303 discarded, no message is created. This applies both when the recipients are
23304 generated by a filter and when they are specified in the transport.
23308 .option once autoreply string&!! unset
23309 This option names a file or DBM database in which a record of each &'To:'&
23310 recipient is kept when the message is specified by the transport. &*Note*&:
23311 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
23313 If &%once%& is unset, or is set to an empty string, the message is always sent.
23314 By default, if &%once%& is set to a non-empty filename, the message
23315 is not sent if a potential recipient is already listed in the database.
23316 However, if the &%once_repeat%& option specifies a time greater than zero, the
23317 message is sent if that much time has elapsed since a message was last sent to
23318 this recipient. A setting of zero time for &%once_repeat%& (the default)
23319 prevents a message from being sent a second time &-- in this case, zero means
23322 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
23323 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
23324 greater than zero, it changes the way Exim implements the &%once%& option.
23325 Instead of using a DBM file to record every recipient it sends to, it uses a
23326 regular file, whose size will never get larger than the given value.
23328 In the file, Exim keeps a linear list of recipient addresses and the times at
23329 which they were sent messages. If the file is full when a new address needs to
23330 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
23331 means that a given recipient may receive multiple messages, but at
23332 unpredictable intervals that depend on the rate of turnover of addresses in the
23333 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
23336 .option once_file_size autoreply integer 0
23337 See &%once%& above.
23340 .option once_repeat autoreply time&!! 0s
23341 See &%once%& above.
23342 After expansion, the value of this option must be a valid time value.
23345 .option reply_to autoreply string&!! unset
23346 This specifies the contents of the &'Reply-To:'& header when the message is
23347 specified by the transport.
23350 .option return_message autoreply boolean false
23351 If this is set, a copy of the original message is returned with the new
23352 message, subject to the maximum size set in the &%return_size_limit%& global
23353 configuration option.
23356 .option subject autoreply string&!! unset
23357 This specifies the contents of the &'Subject:'& header when the message is
23358 specified by the transport. It is tempting to quote the original subject in
23359 automatic responses. For example:
23361 subject = Re: $h_subject:
23363 There is a danger in doing this, however. It may allow a third party to
23364 subscribe your users to an opt-in mailing list, provided that the list accepts
23365 bounce messages as subscription confirmations. Well-managed lists require a
23366 non-bounce message to confirm a subscription, so the danger is relatively
23371 .option text autoreply string&!! unset
23372 This specifies a single string to be used as the body of the message when the
23373 message is specified by the transport. If both &%text%& and &%file%& are set,
23374 the text comes first.
23377 .option to autoreply string&!! unset
23378 This specifies recipients of the message and the contents of the &'To:'& header
23379 when the message is specified by the transport.
23380 .ecindex IIDauttra1
23381 .ecindex IIDauttra2
23386 . ////////////////////////////////////////////////////////////////////////////
23387 . ////////////////////////////////////////////////////////////////////////////
23389 .chapter "The lmtp transport" "CHAPLMTP"
23390 .cindex "transports" "&(lmtp)&"
23391 .cindex "&(lmtp)& transport"
23392 .cindex "LMTP" "over a pipe"
23393 .cindex "LMTP" "over a socket"
23394 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
23396 or by interacting with a Unix domain socket.
23397 This transport is something of a cross between the &(pipe)& and &(smtp)&
23398 transports. Exim also has support for using LMTP over TCP/IP; this is
23399 implemented as an option for the &(smtp)& transport. Because LMTP is expected
23400 to be of minority interest, the default build-time configure in &_src/EDITME_&
23401 has it commented out. You need to ensure that
23405 .cindex "options" "&(lmtp)& transport"
23406 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
23407 included in the Exim binary. The private options of the &(lmtp)& transport are
23410 .option batch_id lmtp string&!! unset
23411 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23414 .option batch_max lmtp integer 1
23415 This limits the number of addresses that can be handled in a single delivery.
23416 Most LMTP servers can handle several addresses at once, so it is normally a
23417 good idea to increase this value. See the description of local delivery
23418 batching in chapter &<<CHAPbatching>>&.
23421 .option command lmtp string&!! unset
23422 This option must be set if &%socket%& is not set. The string is a command which
23423 is run in a separate process. It is split up into a command name and list of
23424 arguments, each of which is separately expanded (so expansion cannot change the
23425 number of arguments). The command is run directly, not via a shell. The message
23426 is passed to the new process using the standard input and output to operate the
23429 .option ignore_quota lmtp boolean false
23430 .cindex "LMTP" "ignoring quota errors"
23431 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
23432 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
23433 in its response to the LHLO command.
23435 .option socket lmtp string&!! unset
23436 This option must be set if &%command%& is not set. The result of expansion must
23437 be the name of a Unix domain socket. The transport connects to the socket and
23438 delivers the message to it using the LMTP protocol.
23441 .option timeout lmtp time 5m
23442 The transport is aborted if the created process or Unix domain socket does not
23443 respond to LMTP commands or message input within this timeout. Delivery
23444 is deferred, and will be tried again later. Here is an example of a typical
23449 command = /some/local/lmtp/delivery/program
23453 This delivers up to 20 addresses at a time, in a mixture of domains if
23454 necessary, running as the user &'exim'&.
23458 . ////////////////////////////////////////////////////////////////////////////
23459 . ////////////////////////////////////////////////////////////////////////////
23461 .chapter "The pipe transport" "CHAPpipetransport"
23462 .scindex IIDpiptra1 "transports" "&(pipe)&"
23463 .scindex IIDpiptra2 "&(pipe)& transport"
23464 The &(pipe)& transport is used to deliver messages via a pipe to a command
23465 running in another process. One example is the use of &(pipe)& as a
23466 pseudo-remote transport for passing messages to some other delivery mechanism
23467 (such as UUCP). Another is the use by individual users to automatically process
23468 their incoming messages. The &(pipe)& transport can be used in one of the
23472 .vindex "&$local_part$&"
23473 A router routes one address to a transport in the normal way, and the
23474 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
23475 contains the local part of the address (as usual), and the command that is run
23476 is specified by the &%command%& option on the transport.
23478 .vindex "&$pipe_addresses$&"
23479 If the &%batch_max%& option is set greater than 1 (the default is 1), the
23480 transport can handle more than one address in a single run. In this case, when
23481 more than one address is routed to the transport, &$local_part$& is not set
23482 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
23483 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
23484 that are routed to the transport.
23486 .vindex "&$address_pipe$&"
23487 A router redirects an address directly to a pipe command (for example, from an
23488 alias or forward file). In this case, &$address_pipe$& contains the text of the
23489 pipe command, and the &%command%& option on the transport is ignored unless
23490 &%force_command%& is set. If only one address is being transported
23491 (&%batch_max%& is not greater than one, or only one address was redirected to
23492 this pipe command), &$local_part$& contains the local part that was redirected.
23496 The &(pipe)& transport is a non-interactive delivery method. Exim can also
23497 deliver messages over pipes using the LMTP interactive protocol. This is
23498 implemented by the &(lmtp)& transport.
23500 In the case when &(pipe)& is run as a consequence of an entry in a local user's
23501 &_.forward_& file, the command runs under the uid and gid of that user. In
23502 other cases, the uid and gid have to be specified explicitly, either on the
23503 transport or on the router that handles the address. Current and &"home"&
23504 directories are also controllable. See chapter &<<CHAPenvironment>>& for
23505 details of the local delivery environment and chapter &<<CHAPbatching>>&
23506 for a discussion of local delivery batching.
23509 .section "Concurrent delivery" "SECID140"
23510 If two messages arrive at almost the same time, and both are routed to a pipe
23511 delivery, the two pipe transports may be run concurrently. You must ensure that
23512 any pipe commands you set up are robust against this happening. If the commands
23513 write to a file, the &%exim_lock%& utility might be of use.
23514 Alternatively the &%max_parallel%& option could be used with a value
23515 of "1" to enforce serialization.
23520 .section "Returned status and data" "SECID141"
23521 .cindex "&(pipe)& transport" "returned data"
23522 If the command exits with a non-zero return code, the delivery is deemed to
23523 have failed, unless either the &%ignore_status%& option is set (in which case
23524 the return code is treated as zero), or the return code is one of those listed
23525 in the &%temp_errors%& option, which are interpreted as meaning &"try again
23526 later"&. In this case, delivery is deferred. Details of a permanent failure are
23527 logged, but are not included in the bounce message, which merely contains
23528 &"local delivery failed"&.
23530 If the command exits on a signal and the &%freeze_signal%& option is set then
23531 the message will be frozen in the queue. If that option is not set, a bounce
23532 will be sent as normal.
23534 If the return code is greater than 128 and the command being run is a shell
23535 script, it normally means that the script was terminated by a signal whose
23536 value is the return code minus 128. The &%freeze_signal%& option does not
23537 apply in this case.
23539 If Exim is unable to run the command (that is, if &[execve()]& fails), the
23540 return code is set to 127. This is the value that a shell returns if it is
23541 asked to run a non-existent command. The wording for the log line suggests that
23542 a non-existent command may be the problem.
23544 The &%return_output%& option can affect the result of a pipe delivery. If it is
23545 set and the command produces any output on its standard output or standard
23546 error streams, the command is considered to have failed, even if it gave a zero
23547 return code or if &%ignore_status%& is set. The output from the command is
23548 included as part of the bounce message. The &%return_fail_output%& option is
23549 similar, except that output is returned only when the command exits with a
23550 failure return code, that is, a value other than zero or a code that matches
23555 .section "How the command is run" "SECThowcommandrun"
23556 .cindex "&(pipe)& transport" "path for command"
23557 The command line is (by default) broken down into a command name and arguments
23558 by the &(pipe)& transport itself. The &%allow_commands%& and
23559 &%restrict_to_path%& options can be used to restrict the commands that may be
23562 .cindex "quoting" "in pipe command"
23563 Unquoted arguments are delimited by white space. If an argument appears in
23564 double quotes, backslash is interpreted as an escape character in the usual
23565 way. If an argument appears in single quotes, no escaping is done.
23567 String expansion is applied to the command line except when it comes from a
23568 traditional &_.forward_& file (commands from a filter file are expanded). The
23569 expansion is applied to each argument in turn rather than to the whole line.
23570 For this reason, any string expansion item that contains white space must be
23571 quoted so as to be contained within a single argument. A setting such as
23573 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
23575 will not work, because the expansion item gets split between several
23576 arguments. You have to write
23578 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
23580 to ensure that it is all in one argument. The expansion is done in this way,
23581 argument by argument, so that the number of arguments cannot be changed as a
23582 result of expansion, and quotes or backslashes in inserted variables do not
23583 interact with external quoting. However, this leads to problems if you want to
23584 generate multiple arguments (or the command name plus arguments) from a single
23585 expansion. In this situation, the simplest solution is to use a shell. For
23588 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
23591 .cindex "transport" "filter"
23592 .cindex "filter" "transport filter"
23593 .vindex "&$pipe_addresses$&"
23594 Special handling takes place when an argument consists of precisely the text
23595 &`$pipe_addresses`& (no quotes).
23596 This is not a general expansion variable; the only
23597 place this string is recognized is when it appears as an argument for a pipe or
23598 transport filter command. It causes each address that is being handled to be
23599 inserted in the argument list at that point &'as a separate argument'&. This
23600 avoids any problems with spaces or shell metacharacters, and is of use when a
23601 &(pipe)& transport is handling groups of addresses in a batch.
23603 If &%force_command%& is enabled on the transport, Special handling takes place
23604 for an argument that consists of precisely the text &`$address_pipe`&. It
23605 is handled similarly to &$pipe_addresses$& above. It is expanded and each
23606 argument is inserted in the argument list at that point
23607 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
23608 the only item in the argument; in fact, if it were then &%force_command%&
23609 should behave as a no-op. Rather, it should be used to adjust the command
23610 run while preserving the argument vector separation.
23612 After splitting up into arguments and expansion, the resulting command is run
23613 in a subprocess directly from the transport, &'not'& under a shell. The
23614 message that is being delivered is supplied on the standard input, and the
23615 standard output and standard error are both connected to a single pipe that is
23616 read by Exim. The &%max_output%& option controls how much output the command
23617 may produce, and the &%return_output%& and &%return_fail_output%& options
23618 control what is done with it.
23620 Not running the command under a shell (by default) lessens the security risks
23621 in cases when a command from a user's filter file is built out of data that was
23622 taken from an incoming message. If a shell is required, it can of course be
23623 explicitly specified as the command to be run. However, there are circumstances
23624 where existing commands (for example, in &_.forward_& files) expect to be run
23625 under a shell and cannot easily be modified. To allow for these cases, there is
23626 an option called &%use_shell%&, which changes the way the &(pipe)& transport
23627 works. Instead of breaking up the command line as just described, it expands it
23628 as a single string and passes the result to &_/bin/sh_&. The
23629 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
23630 with &%use_shell%&, and the whole mechanism is inherently less secure.
23634 .section "Environment variables" "SECTpipeenv"
23635 .cindex "&(pipe)& transport" "environment for command"
23636 .cindex "environment" "&(pipe)& transport"
23637 The environment variables listed below are set up when the command is invoked.
23638 This list is a compromise for maximum compatibility with other MTAs. Note that
23639 the &%environment%& option can be used to add additional variables to this
23640 environment. The environment for the &(pipe)& transport is not subject
23641 to the &%add_environment%& and &%keep_environment%& main config options.
23643 &`DOMAIN `& the domain of the address
23644 &`HOME `& the home directory, if set
23645 &`HOST `& the host name when called from a router (see below)
23646 &`LOCAL_PART `& see below
23647 &`LOCAL_PART_PREFIX `& see below
23648 &`LOCAL_PART_SUFFIX `& see below
23649 &`LOGNAME `& see below
23650 &`MESSAGE_ID `& Exim's local ID for the message
23651 &`PATH `& as specified by the &%path%& option below
23652 &`QUALIFY_DOMAIN `& the sender qualification domain
23653 &`RECIPIENT `& the complete recipient address
23654 &`SENDER `& the sender of the message (empty if a bounce)
23655 &`SHELL `& &`/bin/sh`&
23656 &`TZ `& the value of the &%timezone%& option, if set
23657 &`USER `& see below
23659 When a &(pipe)& transport is called directly from (for example) an &(accept)&
23660 router, LOCAL_PART is set to the local part of the address. When it is
23661 called as a result of a forward or alias expansion, LOCAL_PART is set to
23662 the local part of the address that was expanded. In both cases, any affixes are
23663 removed from the local part, and made available in LOCAL_PART_PREFIX and
23664 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
23665 same value as LOCAL_PART for compatibility with other MTAs.
23668 HOST is set only when a &(pipe)& transport is called from a router that
23669 associates hosts with an address, typically when using &(pipe)& as a
23670 pseudo-remote transport. HOST is set to the first host name specified by
23674 If the transport's generic &%home_directory%& option is set, its value is used
23675 for the HOME environment variable. Otherwise, a home directory may be set
23676 by the router's &%transport_home_directory%& option, which defaults to the
23677 user's home directory if &%check_local_user%& is set.
23680 .section "Private options for pipe" "SECID142"
23681 .cindex "options" "&(pipe)& transport"
23685 .option allow_commands pipe "string list&!!" unset
23686 .cindex "&(pipe)& transport" "permitted commands"
23687 The string is expanded, and is then interpreted as a colon-separated list of
23688 permitted commands. If &%restrict_to_path%& is not set, the only commands
23689 permitted are those in the &%allow_commands%& list. They need not be absolute
23690 paths; the &%path%& option is still used for relative paths. If
23691 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
23692 in the &%allow_commands%& list, or a name without any slashes that is found on
23693 the path. In other words, if neither &%allow_commands%& nor
23694 &%restrict_to_path%& is set, there is no restriction on the command, but
23695 otherwise only commands that are permitted by one or the other are allowed. For
23698 allow_commands = /usr/bin/vacation
23700 and &%restrict_to_path%& is not set, the only permitted command is
23701 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
23702 &%use_shell%& is set.
23705 .option batch_id pipe string&!! unset
23706 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23709 .option batch_max pipe integer 1
23710 This limits the number of addresses that can be handled in a single delivery.
23711 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23714 .option check_string pipe string unset
23715 As &(pipe)& writes the message, the start of each line is tested for matching
23716 &%check_string%&, and if it does, the initial matching characters are replaced
23717 by the contents of &%escape_string%&, provided both are set. The value of
23718 &%check_string%& is a literal string, not a regular expression, and the case of
23719 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
23720 of &%check_string%& and &%escape_string%& are forced to values that implement
23721 the SMTP escaping protocol. Any settings made in the configuration file are
23725 .option command pipe string&!! unset
23726 This option need not be set when &(pipe)& is being used to deliver to pipes
23727 obtained directly from address redirections. In other cases, the option must be
23728 set, to provide a command to be run. It need not yield an absolute path (see
23729 the &%path%& option below). The command is split up into separate arguments by
23730 Exim, and each argument is separately expanded, as described in section
23731 &<<SECThowcommandrun>>& above.
23734 .option environment pipe string&!! unset
23735 .cindex "&(pipe)& transport" "environment for command"
23736 .cindex "environment" "&(pipe)& transport"
23737 This option is used to add additional variables to the environment in which the
23738 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
23739 a string which is expanded, and then interpreted as a colon-separated list of
23740 environment settings of the form <&'name'&>=<&'value'&>.
23743 .option escape_string pipe string unset
23744 See &%check_string%& above.
23747 .option freeze_exec_fail pipe boolean false
23748 .cindex "exec failure"
23749 .cindex "failure of exec"
23750 .cindex "&(pipe)& transport" "failure of exec"
23751 Failure to exec the command in a pipe transport is by default treated like
23752 any other failure while running the command. However, if &%freeze_exec_fail%&
23753 is set, failure to exec is treated specially, and causes the message to be
23754 frozen, whatever the setting of &%ignore_status%&.
23757 .option freeze_signal pipe boolean false
23758 .cindex "signal exit"
23759 .cindex "&(pipe)& transport", "signal exit"
23760 Normally if the process run by a command in a pipe transport exits on a signal,
23761 a bounce message is sent. If &%freeze_signal%& is set, the message will be
23762 frozen in Exim's queue instead.
23765 .option force_command pipe boolean false
23766 .cindex "force command"
23767 .cindex "&(pipe)& transport", "force command"
23768 Normally when a router redirects an address directly to a pipe command
23769 the &%command%& option on the transport is ignored. If &%force_command%&
23770 is set, the &%command%& option will used. This is especially
23771 useful for forcing a wrapper or additional argument to be added to the
23772 command. For example:
23774 command = /usr/bin/remote_exec myhost -- $address_pipe
23778 Note that &$address_pipe$& is handled specially in &%command%& when
23779 &%force_command%& is set, expanding out to the original argument vector as
23780 separate items, similarly to a Unix shell &`"$@"`& construct.
23783 .option ignore_status pipe boolean false
23784 If this option is true, the status returned by the subprocess that is set up to
23785 run the command is ignored, and Exim behaves as if zero had been returned.
23786 Otherwise, a non-zero status or termination by signal causes an error return
23787 from the transport unless the status value is one of those listed in
23788 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
23790 &*Note*&: This option does not apply to timeouts, which do not return a status.
23791 See the &%timeout_defer%& option for how timeouts are handled.
23794 .option log_defer_output pipe boolean false
23795 .cindex "&(pipe)& transport" "logging output"
23796 If this option is set, and the status returned by the command is
23797 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
23798 and any output was produced on stdout or stderr, the first line of it is
23799 written to the main log.
23802 .option log_fail_output pipe boolean false
23803 If this option is set, and the command returns any output on stdout or
23804 stderr, and also ends with a return code that is neither zero nor one of
23805 the return codes listed in &%temp_errors%& (that is, the delivery
23806 failed), the first line of output is written to the main log. This
23807 option and &%log_output%& are mutually exclusive. Only one of them may
23811 .option log_output pipe boolean false
23812 If this option is set and the command returns any output on stdout or
23813 stderr, the first line of output is written to the main log, whatever
23814 the return code. This option and &%log_fail_output%& are mutually
23815 exclusive. Only one of them may be set.
23818 .option max_output pipe integer 20K
23819 This specifies the maximum amount of output that the command may produce on its
23820 standard output and standard error file combined. If the limit is exceeded, the
23821 process running the command is killed. This is intended as a safety measure to
23822 catch runaway processes. The limit is applied independently of the settings of
23823 the options that control what is done with such output (for example,
23824 &%return_output%&). Because of buffering effects, the amount of output may
23825 exceed the limit by a small amount before Exim notices.
23828 .option message_prefix pipe string&!! "see below"
23829 The string specified here is expanded and output at the start of every message.
23830 The default is unset if &%use_bsmtp%& is set. Otherwise it is
23833 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
23837 .cindex "&%tmail%&"
23838 .cindex "&""From""& line"
23839 This is required by the commonly used &_/usr/bin/vacation_& program.
23840 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
23841 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
23846 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23847 &`\n`& to &`\r\n`& in &%message_prefix%&.
23850 .option message_suffix pipe string&!! "see below"
23851 The string specified here is expanded and output at the end of every message.
23852 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
23853 The suffix can be suppressed by setting
23857 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23858 &`\n`& to &`\r\n`& in &%message_suffix%&.
23861 .option path pipe string&!! "/bin:/usr/bin"
23862 This option is expanded and
23863 specifies the string that is set up in the PATH environment
23864 variable of the subprocess.
23865 If the &%command%& option does not yield an absolute path name, the command is
23866 sought in the PATH directories, in the usual way. &*Warning*&: This does not
23867 apply to a command specified as a transport filter.
23870 .option permit_coredump pipe boolean false
23871 Normally Exim inhibits core-dumps during delivery. If you have a need to get
23872 a core-dump of a pipe command, enable this command. This enables core-dumps
23873 during delivery and affects both the Exim binary and the pipe command run.
23874 It is recommended that this option remain off unless and until you have a need
23875 for it and that this only be enabled when needed, as the risk of excessive
23876 resource consumption can be quite high. Note also that Exim is typically
23877 installed as a setuid binary and most operating systems will inhibit coredumps
23878 of these by default, so further OS-specific action may be required.
23881 .option pipe_as_creator pipe boolean false
23882 .cindex "uid (user id)" "local delivery"
23883 If the generic &%user%& option is not set and this option is true, the delivery
23884 process is run under the uid that was in force when Exim was originally called
23885 to accept the message. If the group id is not otherwise set (via the generic
23886 &%group%& option), the gid that was in force when Exim was originally called to
23887 accept the message is used.
23890 .option restrict_to_path pipe boolean false
23891 When this option is set, any command name not listed in &%allow_commands%& must
23892 contain no slashes. The command is searched for only in the directories listed
23893 in the &%path%& option. This option is intended for use in the case when a pipe
23894 command has been generated from a user's &_.forward_& file. This is usually
23895 handled by a &(pipe)& transport called &%address_pipe%&.
23898 .option return_fail_output pipe boolean false
23899 If this option is true, and the command produced any output and ended with a
23900 return code other than zero or one of the codes listed in &%temp_errors%& (that
23901 is, the delivery failed), the output is returned in the bounce message.
23902 However, if the message has a null sender (that is, it is itself a bounce
23903 message), output from the command is discarded. This option and
23904 &%return_output%& are mutually exclusive. Only one of them may be set.
23908 .option return_output pipe boolean false
23909 If this option is true, and the command produced any output, the delivery is
23910 deemed to have failed whatever the return code from the command, and the output
23911 is returned in the bounce message. Otherwise, the output is just discarded.
23912 However, if the message has a null sender (that is, it is a bounce message),
23913 output from the command is always discarded, whatever the setting of this
23914 option. This option and &%return_fail_output%& are mutually exclusive. Only one
23915 of them may be set.
23919 .option temp_errors pipe "string list" "see below"
23920 .cindex "&(pipe)& transport" "temporary failure"
23921 This option contains either a colon-separated list of numbers, or a single
23922 asterisk. If &%ignore_status%& is false
23923 and &%return_output%& is not set,
23924 and the command exits with a non-zero return code, the failure is treated as
23925 temporary and the delivery is deferred if the return code matches one of the
23926 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
23927 codes are treated as permanent errors. The default setting contains the codes
23928 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
23929 compiled on a system that does not define these macros, it assumes values of 75
23930 and 73, respectively.
23933 .option timeout pipe time 1h
23934 If the command fails to complete within this time, it is killed. This normally
23935 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
23936 specifies no timeout. In order to ensure that any subprocesses created by the
23937 command are also killed, Exim makes the initial process a process group leader,
23938 and kills the whole process group on a timeout. However, this can be defeated
23939 if one of the processes starts a new process group.
23941 .option timeout_defer pipe boolean false
23942 A timeout in a &(pipe)& transport, either in the command that the transport
23943 runs, or in a transport filter that is associated with it, is by default
23944 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
23945 is set true, both kinds of timeout become temporary errors, causing the
23946 delivery to be deferred.
23948 .option umask pipe "octal integer" 022
23949 This specifies the umask setting for the subprocess that runs the command.
23952 .option use_bsmtp pipe boolean false
23953 .cindex "envelope sender"
23954 If this option is set true, the &(pipe)& transport writes messages in &"batch
23955 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
23956 commands. If you want to include a leading HELO command with such messages,
23957 you can do so by setting the &%message_prefix%& option. See section
23958 &<<SECTbatchSMTP>>& for details of batch SMTP.
23960 .option use_classresources pipe boolean false
23961 .cindex "class resources (BSD)"
23962 This option is available only when Exim is running on FreeBSD, NetBSD, or
23963 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
23964 resource limits when a &(pipe)& transport is run to perform a delivery. The
23965 limits for the uid under which the pipe is to run are obtained from the login
23969 .option use_crlf pipe boolean false
23970 .cindex "carriage return"
23972 This option causes lines to be terminated with the two-character CRLF sequence
23973 (carriage return, linefeed) instead of just a linefeed character. In the case
23974 of batched SMTP, the byte sequence written to the pipe is then an exact image
23975 of what would be sent down a real SMTP connection.
23977 The contents of the &%message_prefix%& and &%message_suffix%& options are
23978 written verbatim, so must contain their own carriage return characters if these
23979 are needed. When &%use_bsmtp%& is not set, the default values for both
23980 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
23981 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
23984 .option use_shell pipe boolean false
23985 .vindex "&$pipe_addresses$&"
23986 If this option is set, it causes the command to be passed to &_/bin/sh_&
23987 instead of being run directly from the transport, as described in section
23988 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
23989 where the command is expected to be run under a shell and cannot easily be
23990 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
23991 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
23992 command is expanded as a single string, and handed to &_/bin/sh_& as data for
23997 .section "Using an external local delivery agent" "SECID143"
23998 .cindex "local delivery" "using an external agent"
23999 .cindex "&'procmail'&"
24000 .cindex "external local delivery"
24001 .cindex "delivery" "&'procmail'&"
24002 .cindex "delivery" "by external agent"
24003 The &(pipe)& transport can be used to pass all messages that require local
24004 delivery to a separate local delivery agent such as &%procmail%&. When doing
24005 this, care must be taken to ensure that the pipe is run under an appropriate
24006 uid and gid. In some configurations one wants this to be a uid that is trusted
24007 by the delivery agent to supply the correct sender of the message. It may be
24008 necessary to recompile or reconfigure the delivery agent so that it trusts an
24009 appropriate user. The following is an example transport and router
24010 configuration for &%procmail%&:
24015 command = /usr/local/bin/procmail -d $local_part
24019 check_string = "From "
24020 escape_string = ">From "
24029 transport = procmail_pipe
24031 In this example, the pipe is run as the local user, but with the group set to
24032 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
24033 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
24034 user to supply a correct sender address. If you do not specify either a
24035 &%group%& or a &%user%& option, the pipe command is run as the local user. The
24036 home directory is the user's home directory by default.
24038 &*Note*&: The command that the pipe transport runs does &'not'& begin with
24042 as shown in some &%procmail%& documentation, because Exim does not by default
24043 use a shell to run pipe commands.
24046 The next example shows a transport and a router for a system where local
24047 deliveries are handled by the Cyrus IMAP server.
24050 local_delivery_cyrus:
24052 command = /usr/cyrus/bin/deliver \
24053 -m ${substr_1:$local_part_suffix} -- $local_part
24065 local_part_suffix = .*
24066 transport = local_delivery_cyrus
24068 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
24069 &%return_output%& to cause any text written by Cyrus to be returned to the
24071 .ecindex IIDpiptra1
24072 .ecindex IIDpiptra2
24075 . ////////////////////////////////////////////////////////////////////////////
24076 . ////////////////////////////////////////////////////////////////////////////
24078 .chapter "The smtp transport" "CHAPsmtptrans"
24079 .scindex IIDsmttra1 "transports" "&(smtp)&"
24080 .scindex IIDsmttra2 "&(smtp)& transport"
24081 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
24082 or LMTP protocol. The list of hosts to try can either be taken from the address
24083 that is being processed (having been set up by the router), or specified
24084 explicitly for the transport. Timeout and retry processing (see chapter
24085 &<<CHAPretry>>&) is applied to each IP address independently.
24088 .section "Multiple messages on a single connection" "SECID144"
24089 The sending of multiple messages over a single TCP/IP connection can arise in
24093 If a message contains more than &%max_rcpt%& (see below) addresses that are
24094 routed to the same host, more than one copy of the message has to be sent to
24095 that host. In this situation, multiple copies may be sent in a single run of
24096 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
24097 does when it has too many addresses to send in one message also depends on the
24098 value of the global &%remote_max_parallel%& option. Details are given in
24099 section &<<SECToutSMTPTCP>>&.)
24101 .cindex "hints database" "remembering routing"
24102 When a message has been successfully delivered over a TCP/IP connection, Exim
24103 looks in its hints database to see if there are any other messages awaiting a
24104 connection to the same host. If there are, a new delivery process is started
24105 for one of them, and the current TCP/IP connection is passed on to it. The new
24106 process may in turn send multiple copies and possibly create yet another
24111 For each copy sent over the same TCP/IP connection, a sequence counter is
24112 incremented, and if it ever gets to the value of &%connection_max_messages%&,
24113 no further messages are sent over that connection.
24117 .section "Use of the $host and $host_address variables" "SECID145"
24119 .vindex "&$host_address$&"
24120 At the start of a run of the &(smtp)& transport, the values of &$host$& and
24121 &$host_address$& are the name and IP address of the first host on the host list
24122 passed by the router. However, when the transport is about to connect to a
24123 specific host, and while it is connected to that host, &$host$& and
24124 &$host_address$& are set to the values for that host. These are the values
24125 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
24126 &%serialize_hosts%&, and the various TLS options are expanded.
24129 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
24130 .vindex &$tls_bits$&
24131 .vindex &$tls_cipher$&
24132 .vindex &$tls_peerdn$&
24133 .vindex &$tls_sni$&
24134 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
24135 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
24136 are the values that were set when the message was received.
24137 These are the values that are used for options that are expanded before any
24138 SMTP connections are made. Just before each connection is made, these four
24139 variables are emptied. If TLS is subsequently started, they are set to the
24140 appropriate values for the outgoing connection, and these are the values that
24141 are in force when any authenticators are run and when the
24142 &%authenticated_sender%& option is expanded.
24144 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
24145 and will be removed in a future release.
24148 .section "Private options for smtp" "SECID146"
24149 .cindex "options" "&(smtp)& transport"
24150 The private options of the &(smtp)& transport are as follows:
24153 .option address_retry_include_sender smtp boolean true
24154 .cindex "4&'xx'& responses" "retrying after"
24155 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
24156 is the combination of sender and recipient that is delayed in subsequent queue
24157 runs until the retry time is reached. You can delay the recipient without
24158 reference to the sender (which is what earlier versions of Exim did), by
24159 setting &%address_retry_include_sender%& false. However, this can lead to
24160 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
24162 .option allow_localhost smtp boolean false
24163 .cindex "local host" "sending to"
24164 .cindex "fallback" "hosts specified on transport"
24165 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
24166 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
24167 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
24168 the delivery anyway. This should be used only in special cases when the
24169 configuration ensures that no looping will result (for example, a differently
24170 configured Exim is listening on the port to which the message is sent).
24173 .option authenticated_sender smtp string&!! unset
24175 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
24176 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
24177 overriding any existing authenticated sender value. If the string expansion is
24178 forced to fail, the option is ignored. Other expansion failures cause delivery
24179 to be deferred. If the result of expansion is an empty string, that is also
24182 The expansion happens after the outgoing connection has been made and TLS
24183 started, if required. This means that the &$host$&, &$host_address$&,
24184 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
24185 particular connection.
24187 If the SMTP session is not authenticated, the expansion of
24188 &%authenticated_sender%& still happens (and can cause the delivery to be
24189 deferred if it fails), but no AUTH= item is added to MAIL commands
24190 unless &%authenticated_sender_force%& is true.
24192 This option allows you to use the &(smtp)& transport in LMTP mode to
24193 deliver mail to Cyrus IMAP and provide the proper local part as the
24194 &"authenticated sender"&, via a setting such as:
24196 authenticated_sender = $local_part
24198 This removes the need for IMAP subfolders to be assigned special ACLs to
24199 allow direct delivery to those subfolders.
24201 Because of expected uses such as that just described for Cyrus (when no
24202 domain is involved), there is no checking on the syntax of the provided
24206 .option authenticated_sender_force smtp boolean false
24207 If this option is set true, the &%authenticated_sender%& option's value
24208 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
24209 authenticated as a client.
24212 .option command_timeout smtp time 5m
24213 This sets a timeout for receiving a response to an SMTP command that has been
24214 sent out. It is also used when waiting for the initial banner line from the
24215 remote host. Its value must not be zero.
24218 .option connect_timeout smtp time 5m
24219 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
24220 to a remote host. A setting of zero allows the system timeout (typically
24221 several minutes) to act. To have any effect, the value of this option must be
24222 less than the system timeout. However, it has been observed that on some
24223 systems there is no system timeout, which is why the default value for this
24224 option is 5 minutes, a value recommended by RFC 1123.
24227 .option connection_max_messages smtp integer 500
24228 .cindex "SMTP" "passed connection"
24229 .cindex "SMTP" "multiple deliveries"
24230 .cindex "multiple SMTP deliveries"
24231 This controls the maximum number of separate message deliveries that are sent
24232 over a single TCP/IP connection. If the value is zero, there is no limit.
24233 For testing purposes, this value can be overridden by the &%-oB%& command line
24237 .option dane_require_tls_ciphers smtp string&!! unset
24238 .cindex "TLS" "requiring specific ciphers for DANE"
24239 .cindex "cipher" "requiring specific"
24240 .cindex DANE "TLS ciphers"
24241 This option may be used to override &%tls_require_ciphers%& for connections
24242 where DANE has been determined to be in effect.
24243 If not set, then &%tls_require_ciphers%& will be used.
24244 Normal SMTP delivery is not able to make strong demands of TLS cipher
24245 configuration, because delivery will fall back to plaintext. Once DANE has
24246 been determined to be in effect, there is no plaintext fallback and making the
24247 TLS cipherlist configuration stronger will increase security, rather than
24248 counter-intuitively decreasing it.
24249 If the option expands to be empty or is forced to fail, then it will
24250 be treated as unset and &%tls_require_ciphers%& will be used instead.
24253 .option data_timeout smtp time 5m
24254 This sets a timeout for the transmission of each block in the data portion of
24255 the message. As a result, the overall timeout for a message depends on the size
24256 of the message. Its value must not be zero. See also &%final_timeout%&.
24259 .option dkim_canon smtp string&!! unset
24260 .option dkim_domain smtp string list&!! unset
24261 .option dkim_hash smtp string&!! sha256
24262 .option dkim_identity smtp string&!! unset
24263 .option dkim_private_key smtp string&!! unset
24264 .option dkim_selector smtp string&!! unset
24265 .option dkim_strict smtp string&!! unset
24266 .option dkim_sign_headers smtp string&!! "per RFC"
24267 .option dkim_timestamps smtp string&!! unset
24268 DKIM signing options. For details see section &<<SECDKIMSIGN>>&.
24271 .option delay_after_cutoff smtp boolean true
24272 .cindex "final cutoff" "retries, controlling"
24273 .cindex retry "final cutoff"
24274 This option controls what happens when all remote IP addresses for a given
24275 domain have been inaccessible for so long that they have passed their retry
24278 In the default state, if the next retry time has not been reached for any of
24279 them, the address is bounced without trying any deliveries. In other words,
24280 Exim delays retrying an IP address after the final cutoff time until a new
24281 retry time is reached, and can therefore bounce an address without ever trying
24282 a delivery, when machines have been down for a long time. Some people are
24283 unhappy at this prospect, so...
24285 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
24286 addresses are past their final cutoff time, Exim tries to deliver to those
24287 IP addresses that have not been tried since the message arrived. If there are
24288 none, of if they all fail, the address is bounced. In other words, it does not
24289 delay when a new message arrives, but immediately tries those expired IP
24290 addresses that haven't been tried since the message arrived. If there is a
24291 continuous stream of messages for the dead hosts, unsetting
24292 &%delay_after_cutoff%& means that there will be many more attempts to deliver
24296 .option dns_qualify_single smtp boolean true
24297 If the &%hosts%& or &%fallback_hosts%& option is being used,
24298 and the &%gethostbyname%& option is false,
24299 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
24300 in chapter &<<CHAPdnslookup>>& for more details.
24303 .option dns_search_parents smtp boolean false
24304 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
24305 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
24306 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
24310 .option dnssec_request_domains smtp "domain list&!!" unset
24311 .cindex "MX record" "security"
24312 .cindex "DNSSEC" "MX lookup"
24313 .cindex "security" "MX lookup"
24314 .cindex "DNS" "DNSSEC"
24315 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
24316 the dnssec request bit set.
24317 This applies to all of the SRV, MX, AAAA, A lookup sequence.
24321 .option dnssec_require_domains smtp "domain list&!!" unset
24322 .cindex "MX record" "security"
24323 .cindex "DNSSEC" "MX lookup"
24324 .cindex "security" "MX lookup"
24325 .cindex "DNS" "DNSSEC"
24326 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
24327 the dnssec request bit set. Any returns not having the Authenticated Data bit
24328 (AD bit) set will be ignored and logged as a host-lookup failure.
24329 This applies to all of the SRV, MX, AAAA, A lookup sequence.
24333 .option dscp smtp string&!! unset
24334 .cindex "DCSP" "outbound"
24335 This option causes the DSCP value associated with a socket to be set to one
24336 of a number of fixed strings or to numeric value.
24337 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
24338 Common values include &`throughput`&, &`mincost`&, and on newer systems
24339 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
24341 The outbound packets from Exim will be marked with this value in the header
24342 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
24343 that these values will have any effect, not be stripped by networking
24344 equipment, or do much of anything without cooperation with your Network
24345 Engineer and those of all network operators between the source and destination.
24348 .option fallback_hosts smtp "string list" unset
24349 .cindex "fallback" "hosts specified on transport"
24350 String expansion is not applied to this option. The argument must be a
24351 colon-separated list of host names or IP addresses, optionally also including
24352 port numbers, though the separator can be changed, as described in section
24353 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
24354 item in a &%route_list%& setting for the &(manualroute)& router, as described
24355 in section &<<SECTformatonehostitem>>&.
24357 Fallback hosts can also be specified on routers, which associate them with the
24358 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
24359 &%fallback_hosts%& specified on the transport is used only if the address does
24360 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
24361 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
24362 However, &%hosts_randomize%& does apply to fallback host lists.
24364 If Exim is unable to deliver to any of the hosts for a particular address, and
24365 the errors are not permanent rejections, the address is put on a separate
24366 transport queue with its host list replaced by the fallback hosts, unless the
24367 address was routed via MX records and the current host was in the original MX
24368 list. In that situation, the fallback host list is not used.
24370 Once normal deliveries are complete, the fallback queue is delivered by
24371 re-running the same transports with the new host lists. If several failing
24372 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
24373 copy of the message is sent.
24375 The resolution of the host names on the fallback list is controlled by the
24376 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
24377 both to cases when the host list comes with the address and when it is taken
24378 from &%hosts%&. This option provides a &"use a smart host only if delivery
24382 .option final_timeout smtp time 10m
24383 This is the timeout that applies while waiting for the response to the final
24384 line containing just &"."& that terminates a message. Its value must not be
24387 .option gethostbyname smtp boolean false
24388 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
24389 being used, names are looked up using &[gethostbyname()]&
24390 (or &[getipnodebyname()]& when available)
24391 instead of using the DNS. Of course, that function may in fact use the DNS, but
24392 it may also consult other sources of information such as &_/etc/hosts_&.
24394 .option gnutls_compat_mode smtp boolean unset
24395 This option controls whether GnuTLS is used in compatibility mode in an Exim
24396 server. This reduces security slightly, but improves interworking with older
24397 implementations of TLS.
24399 .option helo_data smtp string&!! "see below"
24400 .cindex "HELO" "argument, setting"
24401 .cindex "EHLO" "argument, setting"
24402 .cindex "LHLO argument setting"
24403 The value of this option is expanded after a connection to a another host has
24404 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
24405 command that starts the outgoing SMTP or LMTP session. The default value of the
24410 During the expansion, the variables &$host$& and &$host_address$& are set to
24411 the identity of the remote host, and the variables &$sending_ip_address$& and
24412 &$sending_port$& are set to the local IP address and port number that are being
24413 used. These variables can be used to generate different values for different
24414 servers or different local IP addresses. For example, if you want the string
24415 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
24416 interface address, you could use this:
24418 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
24419 {$primary_hostname}}
24421 The use of &%helo_data%& applies both to sending messages and when doing
24424 .option hosts smtp "string list&!!" unset
24425 Hosts are associated with an address by a router such as &(dnslookup)&, which
24426 finds the hosts by looking up the address domain in the DNS, or by
24427 &(manualroute)&, which has lists of hosts in its configuration. However,
24428 email addresses can be passed to the &(smtp)& transport by any router, and not
24429 all of them can provide an associated list of hosts.
24431 The &%hosts%& option specifies a list of hosts to be used if the address being
24432 processed does not have any hosts associated with it. The hosts specified by
24433 &%hosts%& are also used, whether or not the address has its own hosts, if
24434 &%hosts_override%& is set.
24436 The string is first expanded, before being interpreted as a colon-separated
24437 list of host names or IP addresses, possibly including port numbers. The
24438 separator may be changed to something other than colon, as described in section
24439 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
24440 item in a &%route_list%& setting for the &(manualroute)& router, as described
24441 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
24442 of the &(manualroute)& router is not available here.
24444 If the expansion fails, delivery is deferred. Unless the failure was caused by
24445 the inability to complete a lookup, the error is logged to the panic log as
24446 well as the main log. Host names are looked up either by searching directly for
24447 address records in the DNS or by calling &[gethostbyname()]& (or
24448 &[getipnodebyname()]& when available), depending on the setting of the
24449 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
24450 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
24453 During delivery, the hosts are tried in order, subject to their retry status,
24454 unless &%hosts_randomize%& is set.
24457 .option hosts_avoid_esmtp smtp "host list&!!" unset
24458 .cindex "ESMTP, avoiding use of"
24459 .cindex "HELO" "forcing use of"
24460 .cindex "EHLO" "avoiding use of"
24461 .cindex "PIPELINING" "avoiding the use of"
24462 This option is for use with broken hosts that announce ESMTP facilities (for
24463 example, PIPELINING) and then fail to implement them properly. When a host
24464 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
24465 start of the SMTP session. This means that it cannot use any of the ESMTP
24466 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
24469 .option hosts_avoid_pipelining smtp "host list&!!" unset
24470 .cindex "PIPELINING" "avoiding the use of"
24471 Exim will not use the SMTP PIPELINING extension when delivering to any host
24472 that matches this list, even if the server host advertises PIPELINING support.
24475 .option hosts_avoid_tls smtp "host list&!!" unset
24476 .cindex "TLS" "avoiding for certain hosts"
24477 Exim will not try to start a TLS session when delivering to any host that
24478 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
24480 .option hosts_verify_avoid_tls smtp "host list&!!" unset
24481 .cindex "TLS" "avoiding for certain hosts"
24482 Exim will not try to start a TLS session for a verify callout,
24483 or when delivering in cutthrough mode,
24484 to any host that matches this list.
24487 .option hosts_max_try smtp integer 5
24488 .cindex "host" "maximum number to try"
24489 .cindex "limit" "number of hosts tried"
24490 .cindex "limit" "number of MX tried"
24491 .cindex "MX record" "maximum tried"
24492 This option limits the number of IP addresses that are tried for any one
24493 delivery in cases where there are temporary delivery errors. Section
24494 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
24497 .option hosts_max_try_hardlimit smtp integer 50
24498 This is an additional check on the maximum number of IP addresses that Exim
24499 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
24504 .option hosts_nopass_tls smtp "host list&!!" unset
24505 .cindex "TLS" "passing connection"
24506 .cindex "multiple SMTP deliveries"
24507 .cindex "TLS" "multiple message deliveries"
24508 For any host that matches this list, a connection on which a TLS session has
24509 been started will not be passed to a new delivery process for sending another
24510 message on the same connection. See section &<<SECTmulmessam>>& for an
24511 explanation of when this might be needed.
24513 .option hosts_noproxy_tls smtp "host list&!!" *
24514 .cindex "TLS" "passing connection"
24515 .cindex "multiple SMTP deliveries"
24516 .cindex "TLS" "multiple message deliveries"
24517 For any host that matches this list, a TLS session which has
24518 been started will not be passed to a new delivery process for sending another
24519 message on the same session.
24521 The traditional implementation closes down TLS and re-starts it in the new
24522 process, on the same open TCP connection, for each successive message
24523 sent. If permitted by this option a pipe to to the new process is set up
24524 instead, and the original process maintains the TLS connection and proxies
24525 the SMTP connection from and to the new process and any subsequents.
24526 The new process has no access to TLS information, so cannot include it in
24531 .option hosts_override smtp boolean false
24532 If this option is set and the &%hosts%& option is also set, any hosts that are
24533 attached to the address are ignored, and instead the hosts specified by the
24534 &%hosts%& option are always used. This option does not apply to
24535 &%fallback_hosts%&.
24538 .option hosts_randomize smtp boolean false
24539 .cindex "randomized host list"
24540 .cindex "host" "list of; randomized"
24541 .cindex "fallback" "randomized hosts"
24542 If this option is set, and either the list of hosts is taken from the
24543 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
24544 were not obtained from MX records (this includes fallback hosts from the
24545 router), and were not randomized by the router, the order of trying the hosts
24546 is randomized each time the transport runs. Randomizing the order of a host
24547 list can be used to do crude load sharing.
24549 When &%hosts_randomize%& is true, a host list may be split into groups whose
24550 order is separately randomized. This makes it possible to set up MX-like
24551 behaviour. The boundaries between groups are indicated by an item that is just
24552 &`+`& in the host list. For example:
24554 hosts = host1:host2:host3:+:host4:host5
24556 The order of the first three hosts and the order of the last two hosts is
24557 randomized for each use, but the first three always end up before the last two.
24558 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
24560 .option hosts_require_auth smtp "host list&!!" unset
24561 .cindex "authentication" "required by client"
24562 This option provides a list of servers for which authentication must succeed
24563 before Exim will try to transfer a message. If authentication fails for
24564 servers which are not in this list, Exim tries to send unauthenticated. If
24565 authentication fails for one of these servers, delivery is deferred. This
24566 temporary error is detectable in the retry rules, so it can be turned into a
24567 hard failure if required. See also &%hosts_try_auth%&, and chapter
24568 &<<CHAPSMTPAUTH>>& for details of authentication.
24571 .option hosts_request_ocsp smtp "host list&!!" *
24572 .cindex "TLS" "requiring for certain servers"
24573 Exim will request a Certificate Status on a
24574 TLS session for any host that matches this list.
24575 &%tls_verify_certificates%& should also be set for the transport.
24577 .option hosts_require_dane smtp "host list&!!" unset
24578 .cindex DANE "transport options"
24579 .cindex DANE "requiring for certain servers"
24580 If built with DANE support, Exim will require that a DNSSEC-validated
24581 TLSA record is present for any host matching the list,
24582 and that a DANE-verified TLS connection is made.
24583 There will be no fallback to in-clear communication.
24584 See section &<<SECDANE>>&.
24586 .option hosts_require_ocsp smtp "host list&!!" unset
24587 .cindex "TLS" "requiring for certain servers"
24588 Exim will request, and check for a valid Certificate Status being given, on a
24589 TLS session for any host that matches this list.
24590 &%tls_verify_certificates%& should also be set for the transport.
24592 .option hosts_require_tls smtp "host list&!!" unset
24593 .cindex "TLS" "requiring for certain servers"
24594 Exim will insist on using a TLS session when delivering to any host that
24595 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
24596 &*Note*&: This option affects outgoing mail only. To insist on TLS for
24597 incoming messages, use an appropriate ACL.
24599 .option hosts_try_auth smtp "host list&!!" unset
24600 .cindex "authentication" "optional in client"
24601 This option provides a list of servers to which, provided they announce
24602 authentication support, Exim will attempt to authenticate as a client when it
24603 connects. If authentication fails, Exim will try to transfer the message
24604 unauthenticated. See also &%hosts_require_auth%&, and chapter
24605 &<<CHAPSMTPAUTH>>& for details of authentication.
24607 .option hosts_try_chunking smtp "host list&!!" *
24608 .cindex CHUNKING "enabling, in client"
24609 .cindex BDAT "SMTP command"
24610 .cindex "RFC 3030" "CHUNKING"
24611 This option provides a list of servers to which, provided they announce
24612 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
24613 BDAT will not be used in conjunction with a transport filter.
24615 .option hosts_try_dane smtp "host list&!!" unset
24616 .cindex DANE "transport options"
24617 .cindex DANE "attempting for certain servers"
24618 If built with DANE support, Exim will lookup a
24619 TLSA record for any host matching the list.
24620 If found and verified by DNSSEC,
24621 a DANE-verified TLS connection is made to that host;
24622 there will be no fallback to in-clear communication.
24623 See section &<<SECDANE>>&.
24625 .option hosts_try_fastopen smtp "host list&!!" unset
24626 .cindex "fast open, TCP" "enabling, in client"
24627 .cindex "TCP Fast Open" "enabling, in client"
24628 .cindex "RFC 7413" "TCP Fast Open"
24629 This option provides a list of servers to which, provided
24630 the facility is supported by this system, Exim will attempt to
24631 perform a TCP Fast Open.
24632 No data is sent on the SYN segment but, if the remote server also
24633 supports the facility, it can send its SMTP banner immediately after
24634 the SYN,ACK segment. This can save up to one round-trip time.
24636 The facility is only active for previously-contacted servers,
24637 as the initiator must present a cookie in the SYN segment.
24639 On (at least some) current Linux distributions the facility must be enabled
24640 in the kernel by the sysadmin before the support is usable.
24641 There is no option for control of the server side; if the system supports
24642 it it is always enabled. Note that lengthy operations in the connect ACL,
24643 such as DNSBL lookups, will still delay the emission of the SMTP banner.
24645 .option hosts_try_prdr smtp "host list&!!" *
24646 .cindex "PRDR" "enabling, optional in client"
24647 This option provides a list of servers to which, provided they announce
24648 PRDR support, Exim will attempt to negotiate PRDR
24649 for multi-recipient messages.
24650 The option can usually be left as default.
24652 .option interface smtp "string list&!!" unset
24653 .cindex "bind IP address"
24654 .cindex "IP address" "binding"
24656 .vindex "&$host_address$&"
24657 This option specifies which interface to bind to when making an outgoing SMTP
24658 call. The value is an IP address, not an interface name such as
24659 &`eth0`&. Do not confuse this with the interface address that was used when a
24660 message was received, which is in &$received_ip_address$&, formerly known as
24661 &$interface_address$&. The name was changed to minimize confusion with the
24662 outgoing interface address. There is no variable that contains an outgoing
24663 interface address because, unless it is set by this option, its value is
24666 During the expansion of the &%interface%& option the variables &$host$& and
24667 &$host_address$& refer to the host to which a connection is about to be made
24668 during the expansion of the string. Forced expansion failure, or an empty
24669 string result causes the option to be ignored. Otherwise, after expansion, the
24670 string must be a list of IP addresses, colon-separated by default, but the
24671 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
24674 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
24676 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
24677 connection. If none of them are the correct type, the option is ignored. If
24678 &%interface%& is not set, or is ignored, the system's IP functions choose which
24679 interface to use if the host has more than one.
24682 .option keepalive smtp boolean true
24683 .cindex "keepalive" "on outgoing connection"
24684 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
24685 connections. When set, it causes the kernel to probe idle connections
24686 periodically, by sending packets with &"old"& sequence numbers. The other end
24687 of the connection should send a acknowledgment if the connection is still okay
24688 or a reset if the connection has been aborted. The reason for doing this is
24689 that it has the beneficial effect of freeing up certain types of connection
24690 that can get stuck when the remote host is disconnected without tidying up the
24691 TCP/IP call properly. The keepalive mechanism takes several hours to detect
24695 .option lmtp_ignore_quota smtp boolean false
24696 .cindex "LMTP" "ignoring quota errors"
24697 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
24698 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
24699 has advertised support for IGNOREQUOTA in its response to the LHLO command.
24701 .option max_rcpt smtp integer 100
24702 .cindex "RCPT" "maximum number of outgoing"
24703 This option limits the number of RCPT commands that are sent in a single
24704 SMTP message transaction. Each set of addresses is treated independently, and
24705 so can cause parallel connections to the same host if &%remote_max_parallel%&
24709 .option multi_domain smtp boolean&!! true
24710 .vindex "&$domain$&"
24711 When this option is set, the &(smtp)& transport can handle a number of
24712 addresses containing a mixture of different domains provided they all resolve
24713 to the same list of hosts. Turning the option off restricts the transport to
24714 handling only one domain at a time. This is useful if you want to use
24715 &$domain$& in an expansion for the transport, because it is set only when there
24716 is a single domain involved in a remote delivery.
24718 It is expanded per-address and can depend on any of
24719 &$address_data$&, &$domain_data$&, &$local_part_data$&,
24720 &$host$&, &$host_address$& and &$host_port$&.
24722 .option port smtp string&!! "see below"
24723 .cindex "port" "sending TCP/IP"
24724 .cindex "TCP/IP" "setting outgoing port"
24725 This option specifies the TCP/IP port on the server to which Exim connects.
24726 &*Note:*& Do not confuse this with the port that was used when a message was
24727 received, which is in &$received_port$&, formerly known as &$interface_port$&.
24728 The name was changed to minimize confusion with the outgoing port. There is no
24729 variable that contains an outgoing port.
24731 If the value of this option begins with a digit it is taken as a port number;
24732 otherwise it is looked up using &[getservbyname()]&. The default value is
24734 but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"&
24735 and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
24736 If the expansion fails, or if a port number cannot be found, delivery
24740 Note that at least one Linux distribution has been seen failing
24741 to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
24746 .option protocol smtp string smtp
24747 .cindex "LMTP" "over TCP/IP"
24748 .cindex "ssmtp protocol" "outbound"
24749 .cindex "TLS" "SSL-on-connect outbound"
24751 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
24752 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
24753 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
24754 deliveries into closed message stores. Exim also has support for running LMTP
24755 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
24757 If this option is set to &"smtps"&, the default value for the &%port%& option
24758 changes to &"smtps"&, and the transport initiates TLS immediately after
24759 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
24761 The Internet standards bodies used to strongly discourage use of this mode,
24762 but as of RFC 8314 it is perferred over STARTTLS for message submission
24763 (as distinct from MTA-MTA communication).
24767 .option retry_include_ip_address smtp boolean&!! true
24768 Exim normally includes both the host name and the IP address in the key it
24769 constructs for indexing retry data after a temporary delivery failure. This
24770 means that when one of several IP addresses for a host is failing, it gets
24771 tried periodically (controlled by the retry rules), but use of the other IP
24772 addresses is not affected.
24774 However, in some dialup environments hosts are assigned a different IP address
24775 each time they connect. In this situation the use of the IP address as part of
24776 the retry key leads to undesirable behaviour. Setting this option false causes
24777 Exim to use only the host name.
24778 Since it is expanded it can be made to depend on the host or domain.
24781 .option serialize_hosts smtp "host list&!!" unset
24782 .cindex "serializing connections"
24783 .cindex "host" "serializing connections"
24784 Because Exim operates in a distributed manner, if several messages for the same
24785 host arrive at around the same time, more than one simultaneous connection to
24786 the remote host can occur. This is not usually a problem except when there is a
24787 slow link between the hosts. In that situation it may be helpful to restrict
24788 Exim to one connection at a time. This can be done by setting
24789 &%serialize_hosts%& to match the relevant hosts.
24791 .cindex "hints database" "serializing deliveries to a host"
24792 Exim implements serialization by means of a hints database in which a record is
24793 written whenever a process connects to one of the restricted hosts. The record
24794 is deleted when the connection is completed. Obviously there is scope for
24795 records to get left lying around if there is a system or program crash. To
24796 guard against this, Exim ignores any records that are more than six hours old.
24798 If you set up this kind of serialization, you should also arrange to delete the
24799 relevant hints database whenever your system reboots. The names of the files
24800 start with &_misc_& and they are kept in the &_spool/db_& directory. There
24801 may be one or two files, depending on the type of DBM in use. The same files
24802 are used for ETRN serialization.
24804 See also the &%max_parallel%& generic transport option.
24807 .option size_addition smtp integer 1024
24808 .cindex "SMTP" "SIZE"
24809 .cindex "message" "size issue for transport filter"
24810 .cindex "size" "of message"
24811 .cindex "transport" "filter"
24812 .cindex "filter" "transport filter"
24813 If a remote SMTP server indicates that it supports the SIZE option of the
24814 MAIL command, Exim uses this to pass over the message size at the start of
24815 an SMTP transaction. It adds the value of &%size_addition%& to the value it
24816 sends, to allow for headers and other text that may be added during delivery by
24817 configuration options or in a transport filter. It may be necessary to increase
24818 this if a lot of text is added to messages.
24820 Alternatively, if the value of &%size_addition%& is set negative, it disables
24821 the use of the SIZE option altogether.
24824 .option socks_proxy smtp string&!! unset
24825 .cindex proxy SOCKS
24826 This option enables use of SOCKS proxies for connections made by the
24827 transport. For details see section &<<SECTproxySOCKS>>&.
24830 .option tls_certificate smtp string&!! unset
24831 .cindex "TLS" "client certificate, location of"
24832 .cindex "certificate" "client, location of"
24834 .vindex "&$host_address$&"
24835 The value of this option must be the absolute path to a file which contains the
24836 client's certificate, for possible use when sending a message over an encrypted
24837 connection. The values of &$host$& and &$host_address$& are set to the name and
24838 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
24841 &*Note*&: This option must be set if you want Exim to be able to use a TLS
24842 certificate when sending messages as a client. The global option of the same
24843 name specifies the certificate for Exim as a server; it is not automatically
24844 assumed that the same certificate should be used when Exim is operating as a
24848 .option tls_crl smtp string&!! unset
24849 .cindex "TLS" "client certificate revocation list"
24850 .cindex "certificate" "revocation list for client"
24851 This option specifies a certificate revocation list. The expanded value must
24852 be the name of a file that contains a CRL in PEM format.
24855 .option tls_dh_min_bits smtp integer 1024
24856 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
24857 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
24858 key agreement is negotiated, the server will provide a large prime number
24859 for use. This option establishes the minimum acceptable size of that number.
24860 If the parameter offered by the server is too small, then the TLS handshake
24863 Only supported when using GnuTLS.
24866 .option tls_privatekey smtp string&!! unset
24867 .cindex "TLS" "client private key, location of"
24869 .vindex "&$host_address$&"
24870 The value of this option must be the absolute path to a file which contains the
24871 client's private key. This is used when sending a message over an encrypted
24872 connection using a client certificate. The values of &$host$& and
24873 &$host_address$& are set to the name and address of the server during the
24874 expansion. If this option is unset, or the expansion is forced to fail, or the
24875 result is an empty string, the private key is assumed to be in the same file as
24876 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
24879 .option tls_require_ciphers smtp string&!! unset
24880 .cindex "TLS" "requiring specific ciphers"
24881 .cindex "cipher" "requiring specific"
24883 .vindex "&$host_address$&"
24884 The value of this option must be a list of permitted cipher suites, for use
24885 when setting up an outgoing encrypted connection. (There is a global option of
24886 the same name for controlling incoming connections.) The values of &$host$& and
24887 &$host_address$& are set to the name and address of the server during the
24888 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
24889 is used in different ways by OpenSSL and GnuTLS (see sections
24890 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
24891 ciphers is a preference order.
24895 .option tls_sni smtp string&!! unset
24896 .cindex "TLS" "Server Name Indication"
24897 .vindex "&$tls_sni$&"
24898 If this option is set then it sets the $tls_out_sni variable and causes any
24899 TLS session to pass this value as the Server Name Indication extension to
24900 the remote side, which can be used by the remote side to select an appropriate
24901 certificate and private key for the session.
24903 See &<<SECTtlssni>>& for more information.
24905 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
24911 .option tls_tempfail_tryclear smtp boolean true
24912 .cindex "4&'xx'& responses" "to STARTTLS"
24913 When the server host is not in &%hosts_require_tls%&, and there is a problem in
24914 setting up a TLS session, this option determines whether or not Exim should try
24915 to deliver the message unencrypted. If it is set false, delivery to the
24916 current host is deferred; if there are other hosts, they are tried. If this
24917 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
24918 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
24919 TLS negotiation fails, Exim closes the current connection (because it is in an
24920 unknown state), opens a new one to the same host, and then tries the delivery
24924 .option tls_try_verify_hosts smtp "host list&!!" *
24925 .cindex "TLS" "server certificate verification"
24926 .cindex "certificate" "verification of server"
24927 This option gives a list of hosts for which, on encrypted connections,
24928 certificate verification will be tried but need not succeed.
24929 The &%tls_verify_certificates%& option must also be set.
24930 Note that unless the host is in this list
24931 TLS connections will be denied to hosts using self-signed certificates
24932 when &%tls_verify_certificates%& is matched.
24933 The &$tls_out_certificate_verified$& variable is set when
24934 certificate verification succeeds.
24937 .option tls_verify_cert_hostnames smtp "host list&!!" *
24938 .cindex "TLS" "server certificate hostname verification"
24939 .cindex "certificate" "verification of server"
24940 This option give a list of hosts for which,
24941 while verifying the server certificate,
24942 checks will be included on the host name
24943 (note that this will generally be the result of a DNS MX lookup)
24944 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
24945 limited to being the initial component of a 3-or-more component FQDN.
24947 There is no equivalent checking on client certificates.
24950 .option tls_verify_certificates smtp string&!! system
24951 .cindex "TLS" "server certificate verification"
24952 .cindex "certificate" "verification of server"
24954 .vindex "&$host_address$&"
24955 The value of this option must be either the
24957 or the absolute path to
24958 a file or directory containing permitted certificates for servers,
24959 for use when setting up an encrypted connection.
24961 The "system" value for the option will use a location compiled into the SSL library.
24962 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
24963 is taken as empty and an explicit location
24966 The use of a directory for the option value is not available for GnuTLS versions
24967 preceding 3.3.6 and a single file must be used.
24969 With OpenSSL the certificates specified
24971 either by file or directory
24972 are added to those given by the system default location.
24974 The values of &$host$& and
24975 &$host_address$& are set to the name and address of the server during the
24976 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
24978 For back-compatibility,
24979 if neither tls_verify_hosts nor tls_try_verify_hosts are set
24980 (a single-colon empty list counts as being set)
24981 and certificate verification fails the TLS connection is closed.
24984 .option tls_verify_hosts smtp "host list&!!" unset
24985 .cindex "TLS" "server certificate verification"
24986 .cindex "certificate" "verification of server"
24987 This option gives a list of hosts for which, on encrypted connections,
24988 certificate verification must succeed.
24989 The &%tls_verify_certificates%& option must also be set.
24990 If both this option and &%tls_try_verify_hosts%& are unset
24991 operation is as if this option selected all hosts.
24994 .option utf8_downconvert smtp integer!! unset
24995 .cindex utf8 "address downconversion"
24996 .cindex i18n "utf8 address downconversion"
24997 If built with internationalization support,
24998 this option controls conversion of UTF-8 in message addresses
25000 For details see section &<<SECTi18nMTA>>&.
25006 .section "How the limits for the number of hosts to try are used" &&&
25008 .cindex "host" "maximum number to try"
25009 .cindex "limit" "hosts; maximum number tried"
25010 There are two options that are concerned with the number of hosts that are
25011 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
25012 &%hosts_max_try_hardlimit%&.
25015 The &%hosts_max_try%& option limits the number of hosts that are tried
25016 for a single delivery. However, despite the term &"host"& in its name, the
25017 option actually applies to each IP address independently. In other words, a
25018 multihomed host is treated as several independent hosts, just as it is for
25021 Many of the larger ISPs have multiple MX records which often point to
25022 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
25023 created as a result of routing one of these domains.
25025 Trying every single IP address on such a long list does not seem sensible; if
25026 several at the top of the list fail, it is reasonable to assume there is some
25027 problem that is likely to affect all of them. Roughly speaking, the value of
25028 &%hosts_max_try%& is the maximum number that are tried before deferring the
25029 delivery. However, the logic cannot be quite that simple.
25031 Firstly, IP addresses that are skipped because their retry times have not
25032 arrived do not count, and in addition, addresses that are past their retry
25033 limits are also not counted, even when they are tried. This means that when
25034 some IP addresses are past their retry limits, more than the value of
25035 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
25036 that all IP addresses are considered before timing out an email address (but
25037 see below for an exception).
25039 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
25040 list to see if there is a subsequent host with a different (higher valued) MX.
25041 If there is, that host is considered next, and the current IP address is used
25042 but not counted. This behaviour helps in the case of a domain with a retry rule
25043 that hardly ever delays any hosts, as is now explained:
25045 Consider the case of a long list of hosts with one MX value, and a few with a
25046 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
25047 hosts at the top of the list are tried at first. With the default retry rule,
25048 which specifies increasing retry times, the higher MX hosts are eventually
25049 tried when those at the top of the list are skipped because they have not
25050 reached their retry times.
25052 However, it is common practice to put a fixed short retry time on domains for
25053 large ISPs, on the grounds that their servers are rarely down for very long.
25054 Unfortunately, these are exactly the domains that tend to resolve to long lists
25055 of hosts. The short retry time means that the lowest MX hosts are tried every
25056 time. The attempts may be in a different order because of random sorting, but
25057 without the special MX check, the higher MX hosts would never be tried until
25058 all the lower MX hosts had timed out (which might be several days), because
25059 there are always some lower MX hosts that have reached their retry times. With
25060 the special check, Exim considers at least one IP address from each MX value at
25061 every delivery attempt, even if the &%hosts_max_try%& limit has already been
25064 The above logic means that &%hosts_max_try%& is not a hard limit, and in
25065 particular, Exim normally eventually tries all the IP addresses before timing
25066 out an email address. When &%hosts_max_try%& was implemented, this seemed a
25067 reasonable thing to do. Recently, however, some lunatic DNS configurations have
25068 been set up with hundreds of IP addresses for some domains. It can
25069 take a very long time indeed for an address to time out in these cases.
25071 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
25072 Exim never tries more than this number of IP addresses; if it hits this limit
25073 and they are all timed out, the email address is bounced, even though not all
25074 possible IP addresses have been tried.
25075 .ecindex IIDsmttra1
25076 .ecindex IIDsmttra2
25082 . ////////////////////////////////////////////////////////////////////////////
25083 . ////////////////////////////////////////////////////////////////////////////
25085 .chapter "Address rewriting" "CHAPrewrite"
25086 .scindex IIDaddrew "rewriting" "addresses"
25087 There are some circumstances in which Exim automatically rewrites domains in
25088 addresses. The two most common are when an address is given without a domain
25089 (referred to as an &"unqualified address"&) or when an address contains an
25090 abbreviated domain that is expanded by DNS lookup.
25092 Unqualified envelope addresses are accepted only for locally submitted
25093 messages, or for messages that are received from hosts matching
25094 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
25095 appropriate. Unqualified addresses in header lines are qualified if they are in
25096 locally submitted messages, or messages from hosts that are permitted to send
25097 unqualified envelope addresses. Otherwise, unqualified addresses in header
25098 lines are neither qualified nor rewritten.
25100 One situation in which Exim does &'not'& automatically rewrite a domain is
25101 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
25102 such a domain should be rewritten using the &"canonical"& name, and some MTAs
25103 do this. The new RFCs do not contain this suggestion.
25106 .section "Explicitly configured address rewriting" "SECID147"
25107 This chapter describes the rewriting rules that can be used in the
25108 main rewrite section of the configuration file, and also in the generic
25109 &%headers_rewrite%& option that can be set on any transport.
25111 Some people believe that configured address rewriting is a Mortal Sin.
25112 Others believe that life is not possible without it. Exim provides the
25113 facility; you do not have to use it.
25115 The main rewriting rules that appear in the &"rewrite"& section of the
25116 configuration file are applied to addresses in incoming messages, both envelope
25117 addresses and addresses in header lines. Each rule specifies the types of
25118 address to which it applies.
25120 Whether or not addresses in header lines are rewritten depends on the origin of
25121 the headers and the type of rewriting. Global rewriting, that is, rewriting
25122 rules from the rewrite section of the configuration file, is applied only to
25123 those headers that were received with the message. Header lines that are added
25124 by ACLs or by a system filter or by individual routers or transports (which
25125 are specific to individual recipient addresses) are not rewritten by the global
25128 Rewriting at transport time, by means of the &%headers_rewrite%& option,
25129 applies all headers except those added by routers and transports. That is, as
25130 well as the headers that were received with the message, it also applies to
25131 headers that were added by an ACL or a system filter.
25134 In general, rewriting addresses from your own system or domain has some
25135 legitimacy. Rewriting other addresses should be done only with great care and
25136 in special circumstances. The author of Exim believes that rewriting should be
25137 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
25138 Although it can sometimes be used as a routing tool, this is very strongly
25141 There are two commonly encountered circumstances where rewriting is used, as
25142 illustrated by these examples:
25145 The company whose domain is &'hitch.fict.example'& has a number of hosts that
25146 exchange mail with each other behind a firewall, but there is only a single
25147 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
25148 &'hitch.fict.example'& when sending mail off-site.
25150 A host rewrites the local parts of its own users so that, for example,
25151 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
25156 .section "When does rewriting happen?" "SECID148"
25157 .cindex "rewriting" "timing of"
25158 .cindex "&ACL;" "rewriting addresses in"
25159 Configured address rewriting can take place at several different stages of a
25160 message's processing.
25162 .vindex "&$sender_address$&"
25163 At the start of an ACL for MAIL, the sender address may have been rewritten
25164 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
25165 ordinary rewrite rules have yet been applied. If, however, the sender address
25166 is verified in the ACL, it is rewritten before verification, and remains
25167 rewritten thereafter. The subsequent value of &$sender_address$& is the
25168 rewritten address. This also applies if sender verification happens in a
25169 RCPT ACL. Otherwise, when the sender address is not verified, it is
25170 rewritten as soon as a message's header lines have been received.
25172 .vindex "&$domain$&"
25173 .vindex "&$local_part$&"
25174 Similarly, at the start of an ACL for RCPT, the current recipient's address
25175 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
25176 rewrite rules have yet been applied to it. However, the behaviour is different
25177 from the sender address when a recipient is verified. The address is rewritten
25178 for the verification, but the rewriting is not remembered at this stage. The
25179 value of &$local_part$& and &$domain$& after verification are always the same
25180 as they were before (that is, they contain the unrewritten &-- except for
25181 SMTP-time rewriting &-- address).
25183 As soon as a message's header lines have been received, all the envelope
25184 recipient addresses are permanently rewritten, and rewriting is also applied to
25185 the addresses in the header lines (if configured). This happens before adding
25186 any header lines that were specified in MAIL or RCPT ACLs, and
25187 .cindex "&[local_scan()]& function" "address rewriting; timing of"
25188 before the DATA ACL and &[local_scan()]& functions are run.
25190 When an address is being routed, either for delivery or for verification,
25191 rewriting is applied immediately to child addresses that are generated by
25192 redirection, unless &%no_rewrite%& is set on the router.
25194 .cindex "envelope sender" "rewriting at transport time"
25195 .cindex "rewriting" "at transport time"
25196 .cindex "header lines" "rewriting at transport time"
25197 At transport time, additional rewriting of addresses in header lines can be
25198 specified by setting the generic &%headers_rewrite%& option on a transport.
25199 This option contains rules that are identical in form to those in the rewrite
25200 section of the configuration file. They are applied to the original message
25201 header lines and any that were added by ACLs or a system filter. They are not
25202 applied to header lines that are added by routers or the transport.
25204 The outgoing envelope sender can be rewritten by means of the &%return_path%&
25205 transport option. However, it is not possible to rewrite envelope recipients at
25211 .section "Testing the rewriting rules that apply on input" "SECID149"
25212 .cindex "rewriting" "testing"
25213 .cindex "testing" "rewriting"
25214 Exim's input rewriting configuration appears in a part of the runtime
25215 configuration file headed by &"begin rewrite"&. It can be tested by the
25216 &%-brw%& command line option. This takes an address (which can be a full RFC
25217 2822 address) as its argument. The output is a list of how the address would be
25218 transformed by the rewriting rules for each of the different places it might
25219 appear in an incoming message, that is, for each different header and for the
25220 envelope sender and recipient fields. For example,
25222 exim -brw ph10@exim.workshop.example
25224 might produce the output
25226 sender: Philip.Hazel@exim.workshop.example
25227 from: Philip.Hazel@exim.workshop.example
25228 to: ph10@exim.workshop.example
25229 cc: ph10@exim.workshop.example
25230 bcc: ph10@exim.workshop.example
25231 reply-to: Philip.Hazel@exim.workshop.example
25232 env-from: Philip.Hazel@exim.workshop.example
25233 env-to: ph10@exim.workshop.example
25235 which shows that rewriting has been set up for that address when used in any of
25236 the source fields, but not when it appears as a recipient address. At the
25237 present time, there is no equivalent way of testing rewriting rules that are
25238 set for a particular transport.
25241 .section "Rewriting rules" "SECID150"
25242 .cindex "rewriting" "rules"
25243 The rewrite section of the configuration file consists of lines of rewriting
25246 <&'source pattern'&> <&'replacement'&> <&'flags'&>
25248 Rewriting rules that are specified for the &%headers_rewrite%& generic
25249 transport option are given as a colon-separated list. Each item in the list
25250 takes the same form as a line in the main rewriting configuration (except that
25251 any colons must be doubled, of course).
25253 The formats of source patterns and replacement strings are described below.
25254 Each is terminated by white space, unless enclosed in double quotes, in which
25255 case normal quoting conventions apply inside the quotes. The flags are single
25256 characters which may appear in any order. Spaces and tabs between them are
25259 For each address that could potentially be rewritten, the rules are scanned in
25260 order, and replacements for the address from earlier rules can themselves be
25261 replaced by later rules (but see the &"q"& and &"R"& flags).
25263 The order in which addresses are rewritten is undefined, may change between
25264 releases, and must not be relied on, with one exception: when a message is
25265 received, the envelope sender is always rewritten first, before any header
25266 lines are rewritten. For example, the replacement string for a rewrite of an
25267 address in &'To:'& must not assume that the message's address in &'From:'& has
25268 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
25269 that the envelope sender has already been rewritten.
25271 .vindex "&$domain$&"
25272 .vindex "&$local_part$&"
25273 The variables &$local_part$& and &$domain$& can be used in the replacement
25274 string to refer to the address that is being rewritten. Note that lookup-driven
25275 rewriting can be done by a rule of the form
25279 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
25280 refer to the address that is being rewritten.
25283 .section "Rewriting patterns" "SECID151"
25284 .cindex "rewriting" "patterns"
25285 .cindex "address list" "in a rewriting pattern"
25286 The source pattern in a rewriting rule is any item which may appear in an
25287 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
25288 single-item address list, which means that it is expanded before being tested
25289 against the address. As always, if you use a regular expression as a pattern,
25290 you must take care to escape dollar and backslash characters, or use the &`\N`&
25291 facility to suppress string expansion within the regular expression.
25293 Domains in patterns should be given in lower case. Local parts in patterns are
25294 case-sensitive. If you want to do case-insensitive matching of local parts, you
25295 can use a regular expression that starts with &`^(?i)`&.
25297 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
25298 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
25299 depending on the type of match which occurred. These can be used in the
25300 replacement string to insert portions of the incoming address. &$0$& always
25301 refers to the complete incoming address. When a regular expression is used, the
25302 numerical variables are set from its capturing subexpressions. For other types
25303 of pattern they are set as follows:
25306 If a local part or domain starts with an asterisk, the numerical variables
25307 refer to the character strings matched by asterisks, with &$1$& associated with
25308 the first asterisk, and &$2$& with the second, if present. For example, if the
25311 *queen@*.fict.example
25313 is matched against the address &'hearts-queen@wonderland.fict.example'& then
25315 $0 = hearts-queen@wonderland.fict.example
25319 Note that if the local part does not start with an asterisk, but the domain
25320 does, it is &$1$& that contains the wild part of the domain.
25323 If the domain part of the pattern is a partial lookup, the wild and fixed parts
25324 of the domain are placed in the next available numerical variables. Suppose,
25325 for example, that the address &'foo@bar.baz.example'& is processed by a
25326 rewriting rule of the form
25328 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
25330 and the key in the file that matches the domain is &`*.baz.example`&. Then
25336 If the address &'foo@baz.example'& is looked up, this matches the same
25337 wildcard file entry, and in this case &$2$& is set to the empty string, but
25338 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
25339 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
25340 whole domain. For non-partial domain lookups, no numerical variables are set.
25344 .section "Rewriting replacements" "SECID152"
25345 .cindex "rewriting" "replacements"
25346 If the replacement string for a rule is a single asterisk, addresses that
25347 match the pattern and the flags are &'not'& rewritten, and no subsequent
25348 rewriting rules are scanned. For example,
25350 hatta@lookingglass.fict.example * f
25352 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
25355 .vindex "&$domain$&"
25356 .vindex "&$local_part$&"
25357 If the replacement string is not a single asterisk, it is expanded, and must
25358 yield a fully qualified address. Within the expansion, the variables
25359 &$local_part$& and &$domain$& refer to the address that is being rewritten.
25360 Any letters they contain retain their original case &-- they are not lower
25361 cased. The numerical variables are set up according to the type of pattern that
25362 matched the address, as described above. If the expansion is forced to fail by
25363 the presence of &"fail"& in a conditional or lookup item, rewriting by the
25364 current rule is abandoned, but subsequent rules may take effect. Any other
25365 expansion failure causes the entire rewriting operation to be abandoned, and an
25366 entry written to the panic log.
25370 .section "Rewriting flags" "SECID153"
25371 There are three different kinds of flag that may appear on rewriting rules:
25374 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
25377 A flag that specifies rewriting at SMTP time: S.
25379 Flags that control the rewriting process: Q, q, R, w.
25382 For rules that are part of the &%headers_rewrite%& generic transport option,
25383 E, F, T, and S are not permitted.
25387 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
25389 .cindex "rewriting" "flags"
25390 If none of the following flag letters, nor the &"S"& flag (see section
25391 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
25392 and to both the sender and recipient fields of the envelope, whereas a
25393 transport-time rewriting rule just applies to all headers. Otherwise, the
25394 rewriting rule is skipped unless the relevant addresses are being processed.
25396 &`E`& rewrite all envelope fields
25397 &`F`& rewrite the envelope From field
25398 &`T`& rewrite the envelope To field
25399 &`b`& rewrite the &'Bcc:'& header
25400 &`c`& rewrite the &'Cc:'& header
25401 &`f`& rewrite the &'From:'& header
25402 &`h`& rewrite all headers
25403 &`r`& rewrite the &'Reply-To:'& header
25404 &`s`& rewrite the &'Sender:'& header
25405 &`t`& rewrite the &'To:'& header
25407 "All headers" means all of the headers listed above that can be selected
25408 individually, plus their &'Resent-'& versions. It does not include
25409 other headers such as &'Subject:'& etc.
25411 You should be particularly careful about rewriting &'Sender:'& headers, and
25412 restrict this to special known cases in your own domains.
25415 .section "The SMTP-time rewriting flag" "SECTrewriteS"
25416 .cindex "SMTP" "rewriting malformed addresses"
25417 .cindex "RCPT" "rewriting argument of"
25418 .cindex "MAIL" "rewriting argument of"
25419 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
25420 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
25421 before any other processing; even before syntax checking. The pattern is
25422 required to be a regular expression, and it is matched against the whole of the
25423 data for the command, including any surrounding angle brackets.
25425 .vindex "&$domain$&"
25426 .vindex "&$local_part$&"
25427 This form of rewrite rule allows for the handling of addresses that are not
25428 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
25429 input). Because the input is not required to be a syntactically valid address,
25430 the variables &$local_part$& and &$domain$& are not available during the
25431 expansion of the replacement string. The result of rewriting replaces the
25432 original address in the MAIL or RCPT command.
25435 .section "Flags controlling the rewriting process" "SECID155"
25436 There are four flags which control the way the rewriting process works. These
25437 take effect only when a rule is invoked, that is, when the address is of the
25438 correct type (matches the flags) and matches the pattern:
25441 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
25442 unqualified local part. It is qualified with &%qualify_recipient%&. In the
25443 absence of &"Q"& the rewritten address must always include a domain.
25445 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
25446 even if no rewriting actually takes place because of a &"fail"& in the
25447 expansion. The &"q"& flag is not effective if the address is of the wrong type
25448 (does not match the flags) or does not match the pattern.
25450 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
25451 address, up to ten times. It can be combined with the &"q"& flag, to stop
25452 rewriting once it fails to match (after at least one successful rewrite).
25454 .cindex "rewriting" "whole addresses"
25455 When an address in a header is rewritten, the rewriting normally applies only
25456 to the working part of the address, with any comments and RFC 2822 &"phrase"&
25457 left unchanged. For example, rewriting might change
25459 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
25463 From: Ford Prefect <prefectf@hitch.fict.example>
25466 Sometimes there is a need to replace the whole address item, and this can be
25467 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
25468 causes an address in a header line to be rewritten, the entire address is
25469 replaced, not just the working part. The replacement must be a complete RFC
25470 2822 address, including the angle brackets if necessary. If text outside angle
25471 brackets contains a character whose value is greater than 126 or less than 32
25472 (except for tab), the text is encoded according to RFC 2047. The character set
25473 is taken from &%headers_charset%&, which gets its default at build time.
25475 When the &"w"& flag is set on a rule that causes an envelope address to be
25476 rewritten, all but the working part of the replacement address is discarded.
25480 .section "Rewriting examples" "SECID156"
25481 Here is an example of the two common rewriting paradigms:
25483 *@*.hitch.fict.example $1@hitch.fict.example
25484 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
25485 {$value}fail}@hitch.fict.example bctfrF
25487 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
25488 the string expansion to fail if the lookup does not succeed. In this context it
25489 has the effect of leaving the original address unchanged, but Exim goes on to
25490 consider subsequent rewriting rules, if any, because the &"q"& flag is not
25491 present in that rule. An alternative to &"fail"& would be to supply &$1$&
25492 explicitly, which would cause the rewritten address to be the same as before,
25493 at the cost of a small bit of processing. Not supplying either of these is an
25494 error, since the rewritten address would then contain no local part.
25496 The first example above replaces the domain with a superior, more general
25497 domain. This may not be desirable for certain local parts. If the rule
25499 root@*.hitch.fict.example *
25501 were inserted before the first rule, rewriting would be suppressed for the
25502 local part &'root'& at any domain ending in &'hitch.fict.example'&.
25504 Rewriting can be made conditional on a number of tests, by making use of
25505 &${if$& in the expansion item. For example, to apply a rewriting rule only to
25506 messages that originate outside the local host:
25508 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
25509 {$1@hitch.fict.example}fail}"
25511 The replacement string is quoted in this example because it contains white
25514 .cindex "rewriting" "bang paths"
25515 .cindex "bang paths" "rewriting"
25516 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
25517 an address it treats it as an unqualified local part which it qualifies with
25518 the local qualification domain (if the source of the message is local or if the
25519 remote host is permitted to send unqualified addresses). Rewriting can
25520 sometimes be used to handle simple bang paths with a fixed number of
25521 components. For example, the rule
25523 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
25525 rewrites a two-component bang path &'host.name!user'& as the domain address
25526 &'user@host.name'&. However, there is a security implication in using this as
25527 a global rewriting rule for envelope addresses. It can provide a backdoor
25528 method for using your system as a relay, because the incoming addresses appear
25529 to be local. If the bang path addresses are received via SMTP, it is safer to
25530 use the &"S"& flag to rewrite them as they are received, so that relay checking
25531 can be done on the rewritten addresses.
25538 . ////////////////////////////////////////////////////////////////////////////
25539 . ////////////////////////////////////////////////////////////////////////////
25541 .chapter "Retry configuration" "CHAPretry"
25542 .scindex IIDretconf1 "retry" "configuration, description of"
25543 .scindex IIDregconf2 "configuration file" "retry section"
25544 The &"retry"& section of the runtime configuration file contains a list of
25545 retry rules that control how often Exim tries to deliver messages that cannot
25546 be delivered at the first attempt. If there are no retry rules (the section is
25547 empty or not present), there are no retries. In this situation, temporary
25548 errors are treated as permanent. The default configuration contains a single,
25549 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
25550 line option can be used to test which retry rule will be used for a given
25551 address, domain and error.
25553 The most common cause of retries is temporary failure to deliver to a remote
25554 host because the host is down, or inaccessible because of a network problem.
25555 Exim's retry processing in this case is applied on a per-host (strictly, per IP
25556 address) basis, not on a per-message basis. Thus, if one message has recently
25557 been delayed, delivery of a new message to the same host is not immediately
25558 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
25559 log selector is set, the message
25560 .cindex "retry" "time not reached"
25561 &"retry time not reached"& is written to the main log whenever a delivery is
25562 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
25563 the handling of errors during remote deliveries.
25565 Retry processing applies to routing as well as to delivering, except as covered
25566 in the next paragraph. The retry rules do not distinguish between these
25567 actions. It is not possible, for example, to specify different behaviour for
25568 failures to route the domain &'snark.fict.example'& and failures to deliver to
25569 the host &'snark.fict.example'&. I didn't think anyone would ever need this
25570 added complication, so did not implement it. However, although they share the
25571 same retry rule, the actual retry times for routing and transporting a given
25572 domain are maintained independently.
25574 When a delivery is not part of a queue run (typically an immediate delivery on
25575 receipt of a message), the routers are always run, and local deliveries are
25576 always attempted, even if retry times are set for them. This makes for better
25577 behaviour if one particular message is causing problems (for example, causing
25578 quota overflow, or provoking an error in a filter file). If such a delivery
25579 suffers a temporary failure, the retry data is updated as normal, and
25580 subsequent delivery attempts from queue runs occur only when the retry time for
25581 the local address is reached.
25583 .section "Changing retry rules" "SECID157"
25584 If you change the retry rules in your configuration, you should consider
25585 whether or not to delete the retry data that is stored in Exim's spool area in
25586 files with names like &_db/retry_&. Deleting any of Exim's hints files is
25587 always safe; that is why they are called &"hints"&.
25589 The hints retry data contains suggested retry times based on the previous
25590 rules. In the case of a long-running problem with a remote host, it might
25591 record the fact that the host has timed out. If your new rules increase the
25592 timeout time for such a host, you should definitely remove the old retry data
25593 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
25594 messages that it should now be retaining.
25598 .section "Format of retry rules" "SECID158"
25599 .cindex "retry" "rules"
25600 Each retry rule occupies one line and consists of three or four parts,
25601 separated by white space: a pattern, an error name, an optional list of sender
25602 addresses, and a list of retry parameters. The pattern and sender lists must be
25603 enclosed in double quotes if they contain white space. The rules are searched
25604 in order until one is found where the pattern, error name, and sender list (if
25605 present) match the failing host or address, the error that occurred, and the
25606 message's sender, respectively.
25609 The pattern is any single item that may appear in an address list (see section
25610 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
25611 which means that it is expanded before being tested against the address that
25612 has been delayed. A negated address list item is permitted. Address
25613 list processing treats a plain domain name as if it were preceded by &"*@"&,
25614 which makes it possible for many retry rules to start with just a domain. For
25617 lookingglass.fict.example * F,24h,30m;
25619 provides a rule for any address in the &'lookingglass.fict.example'& domain,
25622 alice@lookingglass.fict.example * F,24h,30m;
25624 applies only to temporary failures involving the local part &%alice%&.
25625 In practice, almost all rules start with a domain name pattern without a local
25628 .cindex "regular expressions" "in retry rules"
25629 &*Warning*&: If you use a regular expression in a retry rule pattern, it
25630 must match a complete address, not just a domain, because that is how regular
25631 expressions work in address lists.
25633 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
25634 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
25638 .section "Choosing which retry rule to use for address errors" "SECID159"
25639 When Exim is looking for a retry rule after a routing attempt has failed (for
25640 example, after a DNS timeout), each line in the retry configuration is tested
25641 against the complete address only if &%retry_use_local_part%& is set for the
25642 router. Otherwise, only the domain is used, except when matching against a
25643 regular expression, when the local part of the address is replaced with &"*"&.
25644 A domain on its own can match a domain pattern, or a pattern that starts with
25645 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
25646 &%check_local_user%& is true, and false for other routers.
25648 Similarly, when Exim is looking for a retry rule after a local delivery has
25649 failed (for example, after a mailbox full error), each line in the retry
25650 configuration is tested against the complete address only if
25651 &%retry_use_local_part%& is set for the transport (it defaults true for all
25654 .cindex "4&'xx'& responses" "retry rules for"
25655 However, when Exim is looking for a retry rule after a remote delivery attempt
25656 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
25657 whole address is always used as the key when searching the retry rules. The
25658 rule that is found is used to create a retry time for the combination of the
25659 failing address and the message's sender. It is the combination of sender and
25660 recipient that is delayed in subsequent queue runs until its retry time is
25661 reached. You can delay the recipient without regard to the sender by setting
25662 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
25663 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
25668 .section "Choosing which retry rule to use for host and message errors" &&&
25670 For a temporary error that is not related to an individual address (for
25671 example, a connection timeout), each line in the retry configuration is checked
25672 twice. First, the name of the remote host is used as a domain name (preceded by
25673 &"*@"& when matching a regular expression). If this does not match the line,
25674 the domain from the email address is tried in a similar fashion. For example,
25675 suppose the MX records for &'a.b.c.example'& are
25677 a.b.c.example MX 5 x.y.z.example
25681 and the retry rules are
25683 p.q.r.example * F,24h,30m;
25684 a.b.c.example * F,4d,45m;
25686 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
25687 first rule matches neither the host nor the domain, so Exim looks at the second
25688 rule. This does not match the host, but it does match the domain, so it is used
25689 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
25690 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
25691 first retry rule is used, because it matches the host.
25693 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
25694 first rule to determine retry times, but for all the other hosts for the domain
25695 &'a.b.c.example'&, the second rule is used. The second rule is also used if
25696 routing to &'a.b.c.example'& suffers a temporary failure.
25698 &*Note*&: The host name is used when matching the patterns, not its IP address.
25699 However, if a message is routed directly to an IP address without the use of a
25700 host name, for example, if a &(manualroute)& router contains a setting such as:
25702 route_list = *.a.example 192.168.34.23
25704 then the &"host name"& that is used when searching for a retry rule is the
25705 textual form of the IP address.
25707 .section "Retry rules for specific errors" "SECID161"
25708 .cindex "retry" "specific errors; specifying"
25709 The second field in a retry rule is the name of a particular error, or an
25710 asterisk, which matches any error. The errors that can be tested for are:
25713 .vitem &%auth_failed%&
25714 Authentication failed when trying to send to a host in the
25715 &%hosts_require_auth%& list in an &(smtp)& transport.
25717 .vitem &%data_4xx%&
25718 A 4&'xx'& error was received for an outgoing DATA command, either immediately
25719 after the command, or after sending the message's data.
25721 .vitem &%mail_4xx%&
25722 A 4&'xx'& error was received for an outgoing MAIL command.
25724 .vitem &%rcpt_4xx%&
25725 A 4&'xx'& error was received for an outgoing RCPT command.
25728 For the three 4&'xx'& errors, either the first or both of the x's can be given
25729 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
25730 recognize 452 errors given to RCPT commands for addresses in a certain domain,
25731 and have retries every ten minutes with a one-hour timeout, you could set up a
25732 retry rule of this form:
25734 the.domain.name rcpt_452 F,1h,10m
25736 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
25737 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
25740 .vitem &%lost_connection%&
25741 A server unexpectedly closed the SMTP connection. There may, of course,
25742 legitimate reasons for this (host died, network died), but if it repeats a lot
25743 for the same host, it indicates something odd.
25746 A DNS lookup for a host failed.
25747 Note that a &%dnslookup%& router will need to have matched
25748 its &%fail_defer_domains%& option for this retry type to be usable.
25749 Also note that a &%manualroute%& router will probably need
25750 its &%host_find_failed%& option set to &%defer%&.
25752 .vitem &%refused_MX%&
25753 A connection to a host obtained from an MX record was refused.
25755 .vitem &%refused_A%&
25756 A connection to a host not obtained from an MX record was refused.
25759 A connection was refused.
25761 .vitem &%timeout_connect_MX%&
25762 A connection attempt to a host obtained from an MX record timed out.
25764 .vitem &%timeout_connect_A%&
25765 A connection attempt to a host not obtained from an MX record timed out.
25767 .vitem &%timeout_connect%&
25768 A connection attempt timed out.
25770 .vitem &%timeout_MX%&
25771 There was a timeout while connecting or during an SMTP session with a host
25772 obtained from an MX record.
25774 .vitem &%timeout_A%&
25775 There was a timeout while connecting or during an SMTP session with a host not
25776 obtained from an MX record.
25779 There was a timeout while connecting or during an SMTP session.
25781 .vitem &%tls_required%&
25782 The server was required to use TLS (it matched &%hosts_require_tls%& in the
25783 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
25784 to STARTTLS, or there was a problem setting up the TLS connection.
25787 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
25790 .vitem &%quota_%&<&'time'&>
25791 .cindex "quota" "error testing in retry rule"
25792 .cindex "retry" "quota error testing"
25793 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
25794 transport, and the mailbox has not been accessed for <&'time'&>. For example,
25795 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
25799 .cindex "mailbox" "time of last read"
25800 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
25801 timeouts when the mailbox is full and is not being read by its owner. Ideally,
25802 it should be based on the last time that the user accessed the mailbox.
25803 However, it is not always possible to determine this. Exim uses the following
25807 If the mailbox is a single file, the time of last access (the &"atime"&) is
25808 used. As no new messages are being delivered (because the mailbox is over
25809 quota), Exim does not access the file, so this is the time of last user access.
25811 .cindex "maildir format" "time of last read"
25812 For a maildir delivery, the time of last modification of the &_new_&
25813 subdirectory is used. As the mailbox is over quota, no new files are created in
25814 the &_new_& subdirectory, because no new messages are being delivered. Any
25815 change to the &_new_& subdirectory is therefore assumed to be the result of an
25816 MUA moving a new message to the &_cur_& directory when it is first read. The
25817 time that is used is therefore the last time that the user read a new message.
25819 For other kinds of multi-file mailbox, the time of last access cannot be
25820 obtained, so a retry rule that uses this type of error field is never matched.
25823 The quota errors apply both to system-enforced quotas and to Exim's own quota
25824 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
25825 when a local delivery is deferred because a partition is full (the ENOSPC
25830 .section "Retry rules for specified senders" "SECID162"
25831 .cindex "retry" "rules; sender-specific"
25832 You can specify retry rules that apply only when the failing message has a
25833 specific sender. In particular, this can be used to define retry rules that
25834 apply only to bounce messages. The third item in a retry rule can be of this
25837 &`senders=`&<&'address list'&>
25839 The retry timings themselves are then the fourth item. For example:
25841 * rcpt_4xx senders=: F,1h,30m
25843 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
25844 host. If the address list contains white space, it must be enclosed in quotes.
25847 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
25849 &*Warning*&: This facility can be unhelpful if it is used for host errors
25850 (which do not depend on the recipient). The reason is that the sender is used
25851 only to match the retry rule. Once the rule has been found for a host error,
25852 its contents are used to set a retry time for the host, and this will apply to
25853 all messages, not just those with specific senders.
25855 When testing retry rules using &%-brt%&, you can supply a sender using the
25856 &%-f%& command line option, like this:
25858 exim -f "" -brt user@dom.ain
25860 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
25861 list is never matched.
25867 .section "Retry parameters" "SECID163"
25868 .cindex "retry" "parameters in rules"
25869 The third (or fourth, if a senders list is present) field in a retry rule is a
25870 sequence of retry parameter sets, separated by semicolons. Each set consists of
25872 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
25874 The letter identifies the algorithm for computing a new retry time; the cutoff
25875 time is the time beyond which this algorithm no longer applies, and the
25876 arguments vary the algorithm's action. The cutoff time is measured from the
25877 time that the first failure for the domain (combined with the local part if
25878 relevant) was detected, not from the time the message was received.
25880 .cindex "retry" "algorithms"
25881 .cindex "retry" "fixed intervals"
25882 .cindex "retry" "increasing intervals"
25883 .cindex "retry" "random intervals"
25884 The available algorithms are:
25887 &'F'&: retry at fixed intervals. There is a single time parameter specifying
25890 &'G'&: retry at geometrically increasing intervals. The first argument
25891 specifies a starting value for the interval, and the second a multiplier, which
25892 is used to increase the size of the interval at each retry.
25894 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
25895 retry, the previous interval is multiplied by the factor in order to get a
25896 maximum for the next interval. The minimum interval is the first argument of
25897 the parameter, and an actual interval is chosen randomly between them. Such a
25898 rule has been found to be helpful in cluster configurations when all the
25899 members of the cluster restart at once, and may therefore synchronize their
25900 queue processing times.
25903 When computing the next retry time, the algorithm definitions are scanned in
25904 order until one whose cutoff time has not yet passed is reached. This is then
25905 used to compute a new retry time that is later than the current time. In the
25906 case of fixed interval retries, this simply means adding the interval to the
25907 current time. For geometrically increasing intervals, retry intervals are
25908 computed from the rule's parameters until one that is greater than the previous
25909 interval is found. The main configuration variable
25910 .cindex "limit" "retry interval"
25911 .cindex "retry" "interval, maximum"
25912 .oindex "&%retry_interval_max%&"
25913 &%retry_interval_max%& limits the maximum interval between retries. It
25914 cannot be set greater than &`24h`&, which is its default value.
25916 A single remote domain may have a number of hosts associated with it, and each
25917 host may have more than one IP address. Retry algorithms are selected on the
25918 basis of the domain name, but are applied to each IP address independently. If,
25919 for example, a host has two IP addresses and one is unusable, Exim will
25920 generate retry times for it and will not try to use it until its next retry
25921 time comes. Thus the good IP address is likely to be tried first most of the
25924 .cindex "hints database" "use for retrying"
25925 Retry times are hints rather than promises. Exim does not make any attempt to
25926 run deliveries exactly at the computed times. Instead, a queue runner process
25927 starts delivery processes for delayed messages periodically, and these attempt
25928 new deliveries only for those addresses that have passed their next retry time.
25929 If a new message arrives for a deferred address, an immediate delivery attempt
25930 occurs only if the address has passed its retry time. In the absence of new
25931 messages, the minimum time between retries is the interval between queue runner
25932 processes. There is not much point in setting retry times of five minutes if
25933 your queue runners happen only once an hour, unless there are a significant
25934 number of incoming messages (which might be the case on a system that is
25935 sending everything to a smart host, for example).
25937 The data in the retry hints database can be inspected by using the
25938 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
25939 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
25940 &'exinext'& utility script can be used to find out what the next retry times
25941 are for the hosts associated with a particular mail domain, and also for local
25942 deliveries that have been deferred.
25945 .section "Retry rule examples" "SECID164"
25946 Here are some example retry rules:
25948 alice@wonderland.fict.example quota_5d F,7d,3h
25949 wonderland.fict.example quota_5d
25950 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
25951 lookingglass.fict.example * F,24h,30m;
25952 * refused_A F,2h,20m;
25953 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
25955 The first rule sets up special handling for mail to
25956 &'alice@wonderland.fict.example'& when there is an over-quota error and the
25957 mailbox has not been read for at least 5 days. Retries continue every three
25958 hours for 7 days. The second rule handles over-quota errors for all other local
25959 parts at &'wonderland.fict.example'&; the absence of a local part has the same
25960 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
25961 fail are bounced immediately if the mailbox has not been read for at least 5
25964 The third rule handles all other errors at &'wonderland.fict.example'&; retries
25965 happen every 15 minutes for an hour, then with geometrically increasing
25966 intervals until two days have passed since a delivery first failed. After the
25967 first hour there is a delay of one hour, then two hours, then four hours, and
25968 so on (this is a rather extreme example).
25970 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
25971 They happen every 30 minutes for 24 hours only. The remaining two rules handle
25972 all other domains, with special action for connection refusal from hosts that
25973 were not obtained from an MX record.
25975 The final rule in a retry configuration should always have asterisks in the
25976 first two fields so as to provide a general catch-all for any addresses that do
25977 not have their own special handling. This example tries every 15 minutes for 2
25978 hours, then with intervals starting at one hour and increasing by a factor of
25979 1.5 up to 16 hours, then every 8 hours up to 5 days.
25983 .section "Timeout of retry data" "SECID165"
25984 .cindex "timeout" "of retry data"
25985 .oindex "&%retry_data_expire%&"
25986 .cindex "hints database" "data expiry"
25987 .cindex "retry" "timeout of data"
25988 Exim timestamps the data that it writes to its retry hints database. When it
25989 consults the data during a delivery it ignores any that is older than the value
25990 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
25991 been tried for 7 days, Exim will try to deliver to it immediately a message
25992 arrives, and if that fails, it will calculate a retry time as if it were
25993 failing for the first time.
25995 This improves the behaviour for messages routed to rarely-used hosts such as MX
25996 backups. If such a host was down at one time, and happens to be down again when
25997 Exim tries a month later, using the old retry data would imply that it had been
25998 down all the time, which is not a justified assumption.
26000 If a host really is permanently dead, this behaviour causes a burst of retries
26001 every now and again, but only if messages routed to it are rare. If there is a
26002 message at least once every 7 days the retry data never expires.
26007 .section "Long-term failures" "SECID166"
26008 .cindex "delivery failure, long-term"
26009 .cindex "retry" "after long-term failure"
26010 Special processing happens when an email address has been failing for so long
26011 that the cutoff time for the last algorithm is reached. For example, using the
26012 default retry rule:
26014 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
26016 the cutoff time is four days. Reaching the retry cutoff is independent of how
26017 long any specific message has been failing; it is the length of continuous
26018 failure for the recipient address that counts.
26020 When the cutoff time is reached for a local delivery, or for all the IP
26021 addresses associated with a remote delivery, a subsequent delivery failure
26022 causes Exim to give up on the address, and a bounce message is generated.
26023 In order to cater for new messages that use the failing address, a next retry
26024 time is still computed from the final algorithm, and is used as follows:
26026 For local deliveries, one delivery attempt is always made for any subsequent
26027 messages. If this delivery fails, the address fails immediately. The
26028 post-cutoff retry time is not used.
26030 .cindex "final cutoff" "retries, controlling"
26031 .cindex retry "final cutoff"
26032 If the delivery is remote, there are two possibilities, controlled by the
26033 .oindex "&%delay_after_cutoff%&"
26034 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
26035 default. Until the post-cutoff retry time for one of the IP addresses,
26036 as set by the &%retry_data_expire%& option, is
26037 reached, the failing email address is bounced immediately, without a delivery
26038 attempt taking place. After that time, one new delivery attempt is made to
26039 those IP addresses that are past their retry times, and if that still fails,
26040 the address is bounced and new retry times are computed.
26042 In other words, when all the hosts for a given email address have been failing
26043 for a long time, Exim bounces rather then defers until one of the hosts' retry
26044 times is reached. Then it tries once, and bounces if that attempt fails. This
26045 behaviour ensures that few resources are wasted in repeatedly trying to deliver
26046 to a broken destination, but if the host does recover, Exim will eventually
26049 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
26050 addresses are past their final cutoff time, Exim tries to deliver to those IP
26051 addresses that have not been tried since the message arrived. If there are
26052 no suitable IP addresses, or if they all fail, the address is bounced. In other
26053 words, it does not delay when a new message arrives, but tries the expired
26054 addresses immediately, unless they have been tried since the message arrived.
26055 If there is a continuous stream of messages for the failing domains, setting
26056 &%delay_after_cutoff%& false means that there will be many more attempts to
26057 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
26060 .section "Deliveries that work intermittently" "SECID167"
26061 .cindex "retry" "intermittently working deliveries"
26062 Some additional logic is needed to cope with cases where a host is
26063 intermittently available, or when a message has some attribute that prevents
26064 its delivery when others to the same address get through. In this situation,
26065 because some messages are successfully delivered, the &"retry clock"& for the
26066 host or address keeps getting reset by the successful deliveries, and so
26067 failing messages remain in the queue for ever because the cutoff time is never
26070 Two exceptional actions are applied to prevent this happening. The first
26071 applies to errors that are related to a message rather than a remote host.
26072 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
26073 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
26074 commands, and quota failures. For this type of error, if a message's arrival
26075 time is earlier than the &"first failed"& time for the error, the earlier time
26076 is used when scanning the retry rules to decide when to try next and when to
26077 time out the address.
26079 The exceptional second action applies in all cases. If a message has been on
26080 the queue for longer than the cutoff time of any applicable retry rule for a
26081 given address, a delivery is attempted for that address, even if it is not yet
26082 time, and if this delivery fails, the address is timed out. A new retry time is
26083 not computed in this case, so that other messages for the same address are
26084 considered immediately.
26085 .ecindex IIDretconf1
26086 .ecindex IIDregconf2
26093 . ////////////////////////////////////////////////////////////////////////////
26094 . ////////////////////////////////////////////////////////////////////////////
26096 .chapter "SMTP authentication" "CHAPSMTPAUTH"
26097 .scindex IIDauthconf1 "SMTP" "authentication configuration"
26098 .scindex IIDauthconf2 "authentication"
26099 The &"authenticators"& section of Exim's runtime configuration is concerned
26100 with SMTP authentication. This facility is an extension to the SMTP protocol,
26101 described in RFC 2554, which allows a client SMTP host to authenticate itself
26102 to a server. This is a common way for a server to recognize clients that are
26103 permitted to use it as a relay. SMTP authentication is not of relevance to the
26104 transfer of mail between servers that have no managerial connection with each
26107 .cindex "AUTH" "description of"
26108 Very briefly, the way SMTP authentication works is as follows:
26111 The server advertises a number of authentication &'mechanisms'& in response to
26112 the client's EHLO command.
26114 The client issues an AUTH command, naming a specific mechanism. The command
26115 may, optionally, contain some authentication data.
26117 The server may issue one or more &'challenges'&, to which the client must send
26118 appropriate responses. In simple authentication mechanisms, the challenges are
26119 just prompts for user names and passwords. The server does not have to issue
26120 any challenges &-- in some mechanisms the relevant data may all be transmitted
26121 with the AUTH command.
26123 The server either accepts or denies authentication.
26125 If authentication succeeds, the client may optionally make use of the AUTH
26126 option on the MAIL command to pass an authenticated sender in subsequent
26127 mail transactions. Authentication lasts for the remainder of the SMTP
26130 If authentication fails, the client may give up, or it may try a different
26131 authentication mechanism, or it may try transferring mail over the
26132 unauthenticated connection.
26135 If you are setting up a client, and want to know which authentication
26136 mechanisms the server supports, you can use Telnet to connect to port 25 (the
26137 SMTP port) on the server, and issue an EHLO command. The response to this
26138 includes the list of supported mechanisms. For example:
26140 &`$ `&&*&`telnet server.example 25`&*&
26141 &`Trying 192.168.34.25...`&
26142 &`Connected to server.example.`&
26143 &`Escape character is '^]'.`&
26144 &`220 server.example ESMTP Exim 4.20 ...`&
26145 &*&`ehlo client.example`&*&
26146 &`250-server.example Hello client.example [10.8.4.5]`&
26147 &`250-SIZE 52428800`&
26152 The second-last line of this example output shows that the server supports
26153 authentication using the PLAIN mechanism. In Exim, the different authentication
26154 mechanisms are configured by specifying &'authenticator'& drivers. Like the
26155 routers and transports, which authenticators are included in the binary is
26156 controlled by build-time definitions. The following are currently available,
26157 included by setting
26160 AUTH_CYRUS_SASL=yes
26163 AUTH_HEIMDAL_GSSAPI=yes
26168 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
26169 authentication mechanism (RFC 2195), and the second provides an interface to
26170 the Cyrus SASL authentication library.
26171 The third is an interface to Dovecot's authentication system, delegating the
26172 work via a socket interface.
26173 The fourth provides an interface to the GNU SASL authentication library, which
26174 provides mechanisms but typically not data sources.
26175 The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
26176 supporting setting a server keytab.
26177 The sixth can be configured to support
26178 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
26179 not formally documented, but used by several MUAs. The seventh authenticator
26180 supports Microsoft's &'Secure Password Authentication'& mechanism.
26181 The eighth is an Exim authenticator but not an SMTP one;
26182 instead it can use information from a TLS negotiation.
26184 The authenticators are configured using the same syntax as other drivers (see
26185 section &<<SECTfordricon>>&). If no authenticators are required, no
26186 authentication section need be present in the configuration file. Each
26187 authenticator can in principle have both server and client functions. When Exim
26188 is receiving SMTP mail, it is acting as a server; when it is sending out
26189 messages over SMTP, it is acting as a client. Authenticator configuration
26190 options are provided for use in both these circumstances.
26192 To make it clear which options apply to which situation, the prefixes
26193 &%server_%& and &%client_%& are used on option names that are specific to
26194 either the server or the client function, respectively. Server and client
26195 functions are disabled if none of their options are set. If an authenticator is
26196 to be used for both server and client functions, a single definition, using
26197 both sets of options, is required. For example:
26201 public_name = CRAM-MD5
26202 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
26204 client_secret = secret2
26206 The &%server_%& option is used when Exim is acting as a server, and the
26207 &%client_%& options when it is acting as a client.
26209 Descriptions of the individual authenticators are given in subsequent chapters.
26210 The remainder of this chapter covers the generic options for the
26211 authenticators, followed by general discussion of the way authentication works
26214 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
26215 per-mechanism basis. Please read carefully to determine which variables hold
26216 account labels such as usercodes and which hold passwords or other
26217 authenticating data.
26219 Note that some mechanisms support two different identifiers for accounts: the
26220 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
26221 and &'authz'& are commonly encountered. The American spelling is standard here.
26222 Conceptually, authentication data such as passwords are tied to the identifier
26223 used to authenticate; servers may have rules to permit one user to act as a
26224 second user, so that after login the session is treated as though that second
26225 user had logged in. That second user is the &'authorization id'&. A robust
26226 configuration might confirm that the &'authz'& field is empty or matches the
26227 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
26228 as verified data, the &'authz'& as an unverified request which the server might
26231 A &'realm'& is a text string, typically a domain name, presented by a server
26232 to a client to help it select an account and credentials to use. In some
26233 mechanisms, the client and server provably agree on the realm, but clients
26234 typically can not treat the realm as secure data to be blindly trusted.
26238 .section "Generic options for authenticators" "SECID168"
26239 .cindex "authentication" "generic options"
26240 .cindex "options" "generic; for authenticators"
26242 .option client_condition authenticators string&!! unset
26243 When Exim is authenticating as a client, it skips any authenticator whose
26244 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
26245 used, for example, to skip plain text authenticators when the connection is not
26246 encrypted by a setting such as:
26248 client_condition = ${if !eq{$tls_out_cipher}{}}
26252 .option client_set_id authenticators string&!! unset
26253 When client authentication succeeds, this condition is expanded; the
26254 result is used in the log lines for outbound messages.
26255 Typically it will be the user name used for authentication.
26258 .option driver authenticators string unset
26259 This option must always be set. It specifies which of the available
26260 authenticators is to be used.
26263 .option public_name authenticators string unset
26264 This option specifies the name of the authentication mechanism that the driver
26265 implements, and by which it is known to the outside world. These names should
26266 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
26267 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
26268 defaults to the driver's instance name.
26271 .option server_advertise_condition authenticators string&!! unset
26272 When a server is about to advertise an authentication mechanism, the condition
26273 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
26274 mechanism is not advertised.
26275 If the expansion fails, the mechanism is not advertised. If the failure was not
26276 forced, and was not caused by a lookup defer, the incident is logged.
26277 See section &<<SECTauthexiser>>& below for further discussion.
26280 .option server_condition authenticators string&!! unset
26281 This option must be set for a &%plaintext%& server authenticator, where it
26282 is used directly to control authentication. See section &<<SECTplainserver>>&
26285 For the &(gsasl)& authenticator, this option is required for various
26286 mechanisms; see chapter &<<CHAPgsasl>>& for details.
26288 For the other authenticators, &%server_condition%& can be used as an additional
26289 authentication or authorization mechanism that is applied after the other
26290 authenticator conditions succeed. If it is set, it is expanded when the
26291 authenticator would otherwise return a success code. If the expansion is forced
26292 to fail, authentication fails. Any other expansion failure causes a temporary
26293 error code to be returned. If the result of a successful expansion is an empty
26294 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
26295 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
26296 other result, a temporary error code is returned, with the expanded string as
26300 .option server_debug_print authenticators string&!! unset
26301 If this option is set and authentication debugging is enabled (see the &%-d%&
26302 command line option), the string is expanded and included in the debugging
26303 output when the authenticator is run as a server. This can help with checking
26304 out the values of variables.
26305 If expansion of the string fails, the error message is written to the debugging
26306 output, and Exim carries on processing.
26309 .option server_set_id authenticators string&!! unset
26310 .vindex "&$authenticated_id$&"
26311 .vindex "&$authenticated_fail_id$&"
26312 When an Exim server successfully authenticates a client, this string is
26313 expanded using data from the authentication, and preserved for any incoming
26314 messages in the variable &$authenticated_id$&. It is also included in the log
26315 lines for incoming messages. For example, a user/password authenticator
26316 configuration might preserve the user name that was used to authenticate, and
26317 refer to it subsequently during delivery of the message.
26318 On a failing authentication the expansion result is instead saved in
26319 the &$authenticated_fail_id$& variable.
26320 If expansion fails, the option is ignored.
26323 .option server_mail_auth_condition authenticators string&!! unset
26324 This option allows a server to discard authenticated sender addresses supplied
26325 as part of MAIL commands in SMTP connections that are authenticated by the
26326 driver on which &%server_mail_auth_condition%& is set. The option is not used
26327 as part of the authentication process; instead its (unexpanded) value is
26328 remembered for later use.
26329 How it is used is described in the following section.
26335 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
26336 .cindex "authentication" "sender; authenticated"
26337 .cindex "AUTH" "on MAIL command"
26338 When a client supplied an AUTH= item on a MAIL command, Exim applies
26339 the following checks before accepting it as the authenticated sender of the
26343 If the connection is not using extended SMTP (that is, HELO was used rather
26344 than EHLO), the use of AUTH= is a syntax error.
26346 If the value of the AUTH= parameter is &"<>"&, it is ignored.
26348 .vindex "&$authenticated_sender$&"
26349 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
26350 running, the value of &$authenticated_sender$& is set to the value obtained
26351 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
26352 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
26353 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
26354 given for the MAIL command.
26356 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
26357 is accepted and placed in &$authenticated_sender$& only if the client has
26360 If the AUTH= value was accepted by either of the two previous rules, and
26361 the client has authenticated, and the authenticator has a setting for the
26362 &%server_mail_auth_condition%&, the condition is checked at this point. The
26363 valued that was saved from the authenticator is expanded. If the expansion
26364 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
26365 &$authenticated_sender$& is deleted. If the expansion yields any other value,
26366 the value of &$authenticated_sender$& is retained and passed on with the
26371 When &$authenticated_sender$& is set for a message, it is passed on to other
26372 hosts to which Exim authenticates as a client. Do not confuse this value with
26373 &$authenticated_id$&, which is a string obtained from the authentication
26374 process, and which is not usually a complete email address.
26376 .vindex "&$sender_address$&"
26377 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
26378 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
26379 therefore make use of &$authenticated_sender$&. The converse is not true: the
26380 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
26385 .section "Authentication on an Exim server" "SECTauthexiser"
26386 .cindex "authentication" "on an Exim server"
26387 When Exim receives an EHLO command, it advertises the public names of those
26388 authenticators that are configured as servers, subject to the following
26392 The client host must match &%auth_advertise_hosts%& (default *).
26394 It the &%server_advertise_condition%& option is set, its expansion must not
26395 yield the empty string, &"0"&, &"no"&, or &"false"&.
26398 The order in which the authenticators are defined controls the order in which
26399 the mechanisms are advertised.
26401 Some mail clients (for example, some versions of Netscape) require the user to
26402 provide a name and password for authentication whenever AUTH is advertised,
26403 even though authentication may not in fact be needed (for example, Exim may be
26404 set up to allow unconditional relaying from the client by an IP address check).
26405 You can make such clients more friendly by not advertising AUTH to them.
26406 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
26407 that runs for RCPT) to relay without authentication, you should set
26409 auth_advertise_hosts = ! 10.9.8.0/24
26411 so that no authentication mechanisms are advertised to them.
26413 The &%server_advertise_condition%& controls the advertisement of individual
26414 authentication mechanisms. For example, it can be used to restrict the
26415 advertisement of a particular mechanism to encrypted connections, by a setting
26418 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
26420 .vindex "&$tls_in_cipher$&"
26421 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
26422 yields &"yes"&, which allows the advertisement to happen.
26424 When an Exim server receives an AUTH command from a client, it rejects it
26425 immediately if AUTH was not advertised in response to an earlier EHLO
26426 command. This is the case if
26429 The client host does not match &%auth_advertise_hosts%&; or
26431 No authenticators are configured with server options; or
26433 Expansion of &%server_advertise_condition%& blocked the advertising of all the
26434 server authenticators.
26438 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
26439 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
26440 AUTH is accepted from any client host.
26442 If AUTH is not rejected by the ACL, Exim searches its configuration for a
26443 server authentication mechanism that was advertised in response to EHLO and
26444 that matches the one named in the AUTH command. If it finds one, it runs
26445 the appropriate authentication protocol, and authentication either succeeds or
26446 fails. If there is no matching advertised mechanism, the AUTH command is
26447 rejected with a 504 error.
26449 .vindex "&$received_protocol$&"
26450 .vindex "&$sender_host_authenticated$&"
26451 When a message is received from an authenticated host, the value of
26452 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
26453 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
26454 public name) of the authenticator driver that successfully authenticated the
26455 client from which the message was received. This variable is empty if there was
26456 no successful authentication.
26458 .cindex authentication "expansion item"
26459 Successful authentication sets up information used by the
26460 &$authresults$& expansion item.
26465 .section "Testing server authentication" "SECID169"
26466 .cindex "authentication" "testing a server"
26467 .cindex "AUTH" "testing a server"
26468 .cindex "base64 encoding" "creating authentication test data"
26469 Exim's &%-bh%& option can be useful for testing server authentication
26470 configurations. The data for the AUTH command has to be sent using base64
26471 encoding. A quick way to produce such data for testing is the following Perl
26475 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
26477 .cindex "binary zero" "in authentication data"
26478 This interprets its argument as a Perl string, and then encodes it. The
26479 interpretation as a Perl string allows binary zeros, which are required for
26480 some kinds of authentication, to be included in the data. For example, a
26481 command line to run this script on such data might be
26483 encode '\0user\0password'
26485 Note the use of single quotes to prevent the shell interpreting the
26486 backslashes, so that they can be interpreted by Perl to specify characters
26487 whose code value is zero.
26489 &*Warning 1*&: If either of the user or password strings starts with an octal
26490 digit, you must use three zeros instead of one after the leading backslash. If
26491 you do not, the octal digit that starts your string will be incorrectly
26492 interpreted as part of the code for the first character.
26494 &*Warning 2*&: If there are characters in the strings that Perl interprets
26495 specially, you must use a Perl escape to prevent them being misinterpreted. For
26496 example, a command such as
26498 encode '\0user@domain.com\0pas$$word'
26500 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
26502 If you have the &%mimencode%& command installed, another way to do produce
26503 base64-encoded strings is to run the command
26505 echo -e -n `\0user\0password' | mimencode
26507 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
26508 in the argument, and the &%-n%& option specifies no newline at the end of its
26509 output. However, not all versions of &%echo%& recognize these options, so you
26510 should check your version before relying on this suggestion.
26514 .section "Authentication by an Exim client" "SECID170"
26515 .cindex "authentication" "on an Exim client"
26516 The &(smtp)& transport has two options called &%hosts_require_auth%& and
26517 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
26518 announces support for authentication, and the host matches an entry in either
26519 of these options, Exim (as a client) tries to authenticate as follows:
26522 For each authenticator that is configured as a client, in the order in which
26523 they are defined in the configuration, it searches the authentication
26524 mechanisms announced by the server for one whose name matches the public name
26525 of the authenticator.
26528 .vindex "&$host_address$&"
26529 When it finds one that matches, it runs the authenticator's client code. The
26530 variables &$host$& and &$host_address$& are available for any string expansions
26531 that the client might do. They are set to the server's name and IP address. If
26532 any expansion is forced to fail, the authentication attempt is abandoned, and
26533 Exim moves on to the next authenticator. Otherwise an expansion failure causes
26534 delivery to be deferred.
26536 If the result of the authentication attempt is a temporary error or a timeout,
26537 Exim abandons trying to send the message to the host for the moment. It will
26538 try again later. If there are any backup hosts available, they are tried in the
26541 If the response to authentication is a permanent error (5&'xx'& code), Exim
26542 carries on searching the list of authenticators and tries another one if
26543 possible. If all authentication attempts give permanent errors, or if there are
26544 no attempts because no mechanisms match (or option expansions force failure),
26545 what happens depends on whether the host matches &%hosts_require_auth%& or
26546 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
26547 delivery is deferred. The error can be detected in the retry rules, and thereby
26548 turned into a permanent error if you wish. In the second case, Exim tries to
26549 deliver the message unauthenticated.
26552 Note that the hostlist test for whether to do authentication can be
26553 confused if name-IP lookups change between the time the peer is decided
26554 upon and the time that the transport runs. For example, with a manualroute
26555 router given a host name, and with DNS "round-robin" used by that name: if
26556 the local resolver cache times out between the router and the transport
26557 running, the transport may get an IP for the name for its authentication
26558 check which does not match the connection peer IP.
26559 No authentication will then be done, despite the names being identical.
26561 For such cases use a separate transport which always authenticates.
26563 .cindex "AUTH" "on MAIL command"
26564 When Exim has authenticated itself to a remote server, it adds the AUTH
26565 parameter to the MAIL commands it sends, if it has an authenticated sender for
26566 the message. If the message came from a remote host, the authenticated sender
26567 is the one that was receiving on an incoming MAIL command, provided that the
26568 incoming connection was authenticated and the &%server_mail_auth%& condition
26569 allowed the authenticated sender to be retained. If a local process calls Exim
26570 to send a message, the sender address that is built from the login name and
26571 &%qualify_domain%& is treated as authenticated. However, if the
26572 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
26573 the authenticated sender that was received with the message.
26574 .ecindex IIDauthconf1
26575 .ecindex IIDauthconf2
26582 . ////////////////////////////////////////////////////////////////////////////
26583 . ////////////////////////////////////////////////////////////////////////////
26585 .chapter "The plaintext authenticator" "CHAPplaintext"
26586 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
26587 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
26588 The &(plaintext)& authenticator can be configured to support the PLAIN and
26589 LOGIN authentication mechanisms, both of which transfer authentication data as
26590 plain (unencrypted) text (though base64 encoded). The use of plain text is a
26591 security risk; you are strongly advised to insist on the use of SMTP encryption
26592 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
26593 use unencrypted plain text, you should not use the same passwords for SMTP
26594 connections as you do for login accounts.
26596 .section "Plaintext options" "SECID171"
26597 .cindex "options" "&(plaintext)& authenticator (server)"
26598 When configured as a server, &(plaintext)& uses the following options:
26600 .option server_condition authenticators string&!! unset
26601 This is actually a global authentication option, but it must be set in order to
26602 configure the &(plaintext)& driver as a server. Its use is described below.
26604 .option server_prompts plaintext string&!! unset
26605 The contents of this option, after expansion, must be a colon-separated list of
26606 prompt strings. If expansion fails, a temporary authentication rejection is
26609 .section "Using plaintext in a server" "SECTplainserver"
26610 .cindex "AUTH" "in &(plaintext)& authenticator"
26611 .cindex "binary zero" "in &(plaintext)& authenticator"
26612 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
26613 "in &(plaintext)& authenticator"
26614 .vindex "&$auth1$&, &$auth2$&, etc"
26615 .cindex "base64 encoding" "in &(plaintext)& authenticator"
26617 When running as a server, &(plaintext)& performs the authentication test by
26618 expanding a string. The data sent by the client with the AUTH command, or in
26619 response to subsequent prompts, is base64 encoded, and so may contain any byte
26620 values when decoded. If any data is supplied with the command, it is treated as
26621 a list of strings, separated by NULs (binary zeros), the first three of which
26622 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
26623 (neither LOGIN nor PLAIN uses more than three strings).
26625 For compatibility with previous releases of Exim, the values are also placed in
26626 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
26627 variables for this purpose is now deprecated, as it can lead to confusion in
26628 string expansions that also use them for other things.
26630 If there are more strings in &%server_prompts%& than the number of strings
26631 supplied with the AUTH command, the remaining prompts are used to obtain more
26632 data. Each response from the client may be a list of NUL-separated strings.
26634 .vindex "&$authenticated_id$&"
26635 Once a sufficient number of data strings have been received,
26636 &%server_condition%& is expanded. If the expansion is forced to fail,
26637 authentication fails. Any other expansion failure causes a temporary error code
26638 to be returned. If the result of a successful expansion is an empty string,
26639 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
26640 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
26641 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
26642 For any other result, a temporary error code is returned, with the expanded
26643 string as the error text.
26645 &*Warning*&: If you use a lookup in the expansion to find the user's
26646 password, be sure to make the authentication fail if the user is unknown.
26647 There are good and bad examples at the end of the next section.
26651 .section "The PLAIN authentication mechanism" "SECID172"
26652 .cindex "PLAIN authentication mechanism"
26653 .cindex "authentication" "PLAIN mechanism"
26654 .cindex "binary zero" "in &(plaintext)& authenticator"
26655 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
26656 sent as one item of data (that is, one combined string containing two NUL
26657 separators). The data is sent either as part of the AUTH command, or
26658 subsequently in response to an empty prompt from the server.
26660 The second and third strings are a user name and a corresponding password.
26661 Using a single fixed user name and password as an example, this could be
26662 configured as follows:
26666 public_name = PLAIN
26668 server_condition = \
26669 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
26670 server_set_id = $auth2
26672 Note that the default result strings from &%if%& (&"true"& or an empty string)
26673 are exactly what we want here, so they need not be specified. Obviously, if the
26674 password contains expansion-significant characters such as dollar, backslash,
26675 or closing brace, they have to be escaped.
26677 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
26678 the end of a string list are ignored). If all the data comes as part of the
26679 AUTH command, as is commonly the case, the prompt is not used. This
26680 authenticator is advertised in the response to EHLO as
26684 and a client host can authenticate itself by sending the command
26686 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
26688 As this contains three strings (more than the number of prompts), no further
26689 data is required from the client. Alternatively, the client may just send
26693 to initiate authentication, in which case the server replies with an empty
26694 prompt. The client must respond with the combined data string.
26696 The data string is base64 encoded, as required by the RFC. This example,
26697 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
26698 represents a zero byte. This is split up into three strings, the first of which
26699 is empty. The &%server_condition%& option in the authenticator checks that the
26700 second two are &`username`& and &`mysecret`& respectively.
26702 Having just one fixed user name and password, as in this example, is not very
26703 realistic, though for a small organization with only a handful of
26704 authenticating clients it could make sense.
26706 A more sophisticated instance of this authenticator could use the user name in
26707 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
26708 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
26709 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
26710 This is an incorrect example:
26712 server_condition = \
26713 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
26715 The expansion uses the user name (&$auth2$&) as the key to look up a password,
26716 which it then compares to the supplied password (&$auth3$&). Why is this example
26717 incorrect? It works fine for existing users, but consider what happens if a
26718 non-existent user name is given. The lookup fails, but as no success/failure
26719 strings are given for the lookup, it yields an empty string. Thus, to defeat
26720 the authentication, all a client has to do is to supply a non-existent user
26721 name and an empty password. The correct way of writing this test is:
26723 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
26724 {${if eq{$value}{$auth3}}} {false}}
26726 In this case, if the lookup succeeds, the result is checked; if the lookup
26727 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
26728 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
26729 always fails if its second argument is empty. However, the second way of
26730 writing the test makes the logic clearer.
26733 .section "The LOGIN authentication mechanism" "SECID173"
26734 .cindex "LOGIN authentication mechanism"
26735 .cindex "authentication" "LOGIN mechanism"
26736 The LOGIN authentication mechanism is not documented in any RFC, but is in use
26737 in a number of programs. No data is sent with the AUTH command. Instead, a
26738 user name and password are supplied separately, in response to prompts. The
26739 plaintext authenticator can be configured to support this as in this example:
26743 public_name = LOGIN
26744 server_prompts = User Name : Password
26745 server_condition = \
26746 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
26747 server_set_id = $auth1
26749 Because of the way plaintext operates, this authenticator accepts data supplied
26750 with the AUTH command (in contravention of the specification of LOGIN), but
26751 if the client does not supply it (as is the case for LOGIN clients), the prompt
26752 strings are used to obtain two data items.
26754 Some clients are very particular about the precise text of the prompts. For
26755 example, Outlook Express is reported to recognize only &"Username:"& and
26756 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
26757 strings. It uses the &%ldapauth%& expansion condition to check the user
26758 name and password by binding to an LDAP server:
26762 public_name = LOGIN
26763 server_prompts = Username:: : Password::
26764 server_condition = ${if and{{ \
26767 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
26768 pass=${quote:$auth2} \
26769 ldap://ldap.example.org/} }} }
26770 server_set_id = uid=$auth1,ou=people,o=example.org
26772 We have to check that the username is not empty before using it, because LDAP
26773 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
26774 operator to correctly quote the DN for authentication. However, the basic
26775 &%quote%& operator, rather than any of the LDAP quoting operators, is the
26776 correct one to use for the password, because quoting is needed only to make
26777 the password conform to the Exim syntax. At the LDAP level, the password is an
26778 uninterpreted string.
26781 .section "Support for different kinds of authentication" "SECID174"
26782 A number of string expansion features are provided for the purpose of
26783 interfacing to different ways of user authentication. These include checking
26784 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
26785 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
26791 .section "Using plaintext in a client" "SECID175"
26792 .cindex "options" "&(plaintext)& authenticator (client)"
26793 The &(plaintext)& authenticator has two client options:
26795 .option client_ignore_invalid_base64 plaintext boolean false
26796 If the client receives a server prompt that is not a valid base64 string,
26797 authentication is abandoned by default. However, if this option is set true,
26798 the error in the challenge is ignored and the client sends the response as
26801 .option client_send plaintext string&!! unset
26802 The string is a colon-separated list of authentication data strings. Each
26803 string is independently expanded before being sent to the server. The first
26804 string is sent with the AUTH command; any more strings are sent in response
26805 to prompts from the server. Before each string is expanded, the value of the
26806 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
26807 with &$auth1$& for the first prompt. Up to three prompts are stored in this
26808 way. Thus, the prompt that is received in response to sending the first string
26809 (with the AUTH command) can be used in the expansion of the second string, and
26810 so on. If an invalid base64 string is received when
26811 &%client_ignore_invalid_base64%& is set, an empty string is put in the
26812 &$auth$&<&'n'&> variable.
26814 &*Note*&: You cannot use expansion to create multiple strings, because
26815 splitting takes priority and happens first.
26817 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
26818 the data, further processing is applied to each string before it is sent. If
26819 there are any single circumflex characters in the string, they are converted to
26820 NULs. Should an actual circumflex be required as data, it must be doubled in
26823 This is an example of a client configuration that implements the PLAIN
26824 authentication mechanism with a fixed user name and password:
26828 public_name = PLAIN
26829 client_send = ^username^mysecret
26831 The lack of colons means that the entire text is sent with the AUTH
26832 command, with the circumflex characters converted to NULs. A similar example
26833 that uses the LOGIN mechanism is:
26837 public_name = LOGIN
26838 client_send = : username : mysecret
26840 The initial colon means that the first string is empty, so no data is sent with
26841 the AUTH command itself. The remaining strings are sent in response to
26843 .ecindex IIDplaiauth1
26844 .ecindex IIDplaiauth2
26849 . ////////////////////////////////////////////////////////////////////////////
26850 . ////////////////////////////////////////////////////////////////////////////
26852 .chapter "The cram_md5 authenticator" "CHID9"
26853 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
26854 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
26855 .cindex "CRAM-MD5 authentication mechanism"
26856 .cindex "authentication" "CRAM-MD5 mechanism"
26857 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
26858 sends a challenge string to the client, and the response consists of a user
26859 name and the CRAM-MD5 digest of the challenge string combined with a secret
26860 string (password) which is known to both server and client. Thus, the secret
26861 is not sent over the network as plain text, which makes this authenticator more
26862 secure than &(plaintext)&. However, the downside is that the secret has to be
26863 available in plain text at either end.
26866 .section "Using cram_md5 as a server" "SECID176"
26867 .cindex "options" "&(cram_md5)& authenticator (server)"
26868 This authenticator has one server option, which must be set to configure the
26869 authenticator as a server:
26871 .option server_secret cram_md5 string&!! unset
26872 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
26873 When the server receives the client's response, the user name is placed in
26874 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
26875 obtain the password for that user. The server then computes the CRAM-MD5 digest
26876 that the client should have sent, and checks that it received the correct
26877 string. If the expansion of &%server_secret%& is forced to fail, authentication
26878 fails. If the expansion fails for some other reason, a temporary error code is
26879 returned to the client.
26881 For compatibility with previous releases of Exim, the user name is also placed
26882 in &$1$&. However, the use of this variables for this purpose is now
26883 deprecated, as it can lead to confusion in string expansions that also use
26884 numeric variables for other things.
26886 For example, the following authenticator checks that the user name given by the
26887 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
26888 user name, authentication fails.
26892 public_name = CRAM-MD5
26893 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
26894 server_set_id = $auth1
26896 .vindex "&$authenticated_id$&"
26897 If authentication succeeds, the setting of &%server_set_id%& preserves the user
26898 name in &$authenticated_id$&. A more typical configuration might look up the
26899 secret string in a file, using the user name as the key. For example:
26903 public_name = CRAM-MD5
26904 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
26906 server_set_id = $auth1
26908 Note that this expansion explicitly forces failure if the lookup fails
26909 because &$auth1$& contains an unknown user name.
26911 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
26912 using the relevant libraries, you need to know the realm to specify in the
26913 lookup and then ask for the &"userPassword"& attribute for that user in that
26918 public_name = CRAM-MD5
26919 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
26920 dbmjz{/etc/sasldb2}{$value}fail}
26921 server_set_id = $auth1
26924 .section "Using cram_md5 as a client" "SECID177"
26925 .cindex "options" "&(cram_md5)& authenticator (client)"
26926 When used as a client, the &(cram_md5)& authenticator has two options:
26930 .option client_name cram_md5 string&!! "the primary host name"
26931 This string is expanded, and the result used as the user name data when
26932 computing the response to the server's challenge.
26935 .option client_secret cram_md5 string&!! unset
26936 This option must be set for the authenticator to work as a client. Its value is
26937 expanded and the result used as the secret string when computing the response.
26941 .vindex "&$host_address$&"
26942 Different user names and secrets can be used for different servers by referring
26943 to &$host$& or &$host_address$& in the options. Forced failure of either
26944 expansion string is treated as an indication that this authenticator is not
26945 prepared to handle this case. Exim moves on to the next configured client
26946 authenticator. Any other expansion failure causes Exim to give up trying to
26947 send the message to the current server.
26949 A simple example configuration of a &(cram_md5)& authenticator, using fixed
26954 public_name = CRAM-MD5
26956 client_secret = secret
26958 .ecindex IIDcramauth1
26959 .ecindex IIDcramauth2
26963 . ////////////////////////////////////////////////////////////////////////////
26964 . ////////////////////////////////////////////////////////////////////////////
26966 .chapter "The cyrus_sasl authenticator" "CHID10"
26967 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
26968 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
26969 .cindex "Cyrus" "SASL library"
26971 The code for this authenticator was provided by Matthew Byng-Maddick while
26972 at A L Digital Ltd.
26974 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
26975 library implementation of the RFC 2222 (&"Simple Authentication and Security
26976 Layer"&). This library supports a number of authentication mechanisms,
26977 including PLAIN and LOGIN, but also several others that Exim does not support
26978 directly. In particular, there is support for Kerberos authentication.
26980 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
26981 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
26982 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
26983 name of the driver to determine which mechanism to support.
26985 Where access to some kind of secret file is required, for example, in GSSAPI
26986 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
26987 user, and that the Cyrus SASL library has no way of escalating privileges
26988 by default. You may also find you need to set environment variables,
26989 depending on the driver you are using.
26991 The application name provided by Exim is &"exim"&, so various SASL options may
26992 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
26993 Kerberos, note that because of limitations in the GSSAPI interface,
26994 changing the server keytab might need to be communicated down to the Kerberos
26995 layer independently. The mechanism for doing so is dependent upon the Kerberos
26998 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
26999 may be set to point to an alternative keytab file. Exim will pass this
27000 variable through from its own inherited environment when started as root or the
27001 Exim user. The keytab file needs to be readable by the Exim user.
27002 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
27003 environment variable. In practice, for those releases, the Cyrus authenticator
27004 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
27005 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
27008 .section "Using cyrus_sasl as a server" "SECID178"
27009 The &(cyrus_sasl)& authenticator has four private options. It puts the username
27010 (on a successful authentication) into &$auth1$&. For compatibility with
27011 previous releases of Exim, the username is also placed in &$1$&. However, the
27012 use of this variable for this purpose is now deprecated, as it can lead to
27013 confusion in string expansions that also use numeric variables for other
27017 .option server_hostname cyrus_sasl string&!! "see below"
27018 This option selects the hostname that is used when communicating with the
27019 library. The default value is &`$primary_hostname`&. It is up to the underlying
27020 SASL plug-in what it does with this data.
27023 .option server_mech cyrus_sasl string "see below"
27024 This option selects the authentication mechanism this driver should use. The
27025 default is the value of the generic &%public_name%& option. This option allows
27026 you to use a different underlying mechanism from the advertised name. For
27030 driver = cyrus_sasl
27031 public_name = X-ANYTHING
27032 server_mech = CRAM-MD5
27033 server_set_id = $auth1
27036 .option server_realm cyrus_sasl string&!! unset
27037 This specifies the SASL realm that the server claims to be in.
27040 .option server_service cyrus_sasl string &`smtp`&
27041 This is the SASL service that the server claims to implement.
27044 For straightforward cases, you do not need to set any of the authenticator's
27045 private options. All you need to do is to specify an appropriate mechanism as
27046 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
27047 PLAIN, you could have two authenticators as follows:
27050 driver = cyrus_sasl
27051 public_name = CRAM-MD5
27052 server_set_id = $auth1
27055 driver = cyrus_sasl
27056 public_name = PLAIN
27057 server_set_id = $auth2
27059 Cyrus SASL does implement the LOGIN authentication method, even though it is
27060 not a standard method. It is disabled by default in the source distribution,
27061 but it is present in many binary distributions.
27062 .ecindex IIDcyrauth1
27063 .ecindex IIDcyrauth2
27068 . ////////////////////////////////////////////////////////////////////////////
27069 . ////////////////////////////////////////////////////////////////////////////
27070 .chapter "The dovecot authenticator" "CHAPdovecot"
27071 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
27072 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
27073 This authenticator is an interface to the authentication facility of the
27074 Dovecot POP/IMAP server, which can support a number of authentication methods.
27075 Note that Dovecot must be configured to use auth-client not auth-userdb.
27076 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
27077 to use the same mechanisms for SMTP authentication. This is a server
27078 authenticator only. There is only one option:
27080 .option server_socket dovecot string unset
27082 This option must specify the UNIX socket that is the interface to Dovecot
27083 authentication. The &%public_name%& option must specify an authentication
27084 mechanism that Dovecot is configured to support. You can have several
27085 authenticators for different mechanisms. For example:
27089 public_name = PLAIN
27090 server_socket = /var/run/dovecot/auth-client
27091 server_set_id = $auth1
27096 server_socket = /var/run/dovecot/auth-client
27097 server_set_id = $auth1
27099 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
27100 &$received_ip_address$& (that is, the connection is local), the &"secured"&
27101 option is passed in the Dovecot authentication command. If, for a TLS
27102 connection, a client certificate has been verified, the &"valid-client-cert"&
27103 option is passed. When authentication succeeds, the identity of the user
27104 who authenticated is placed in &$auth1$&.
27105 .ecindex IIDdcotauth1
27106 .ecindex IIDdcotauth2
27109 . ////////////////////////////////////////////////////////////////////////////
27110 . ////////////////////////////////////////////////////////////////////////////
27111 .chapter "The gsasl authenticator" "CHAPgsasl"
27112 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
27113 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
27114 .cindex "authentication" "GNU SASL"
27115 .cindex "authentication" "SASL"
27116 .cindex "authentication" "EXTERNAL"
27117 .cindex "authentication" "ANONYMOUS"
27118 .cindex "authentication" "PLAIN"
27119 .cindex "authentication" "LOGIN"
27120 .cindex "authentication" "DIGEST-MD5"
27121 .cindex "authentication" "CRAM-MD5"
27122 .cindex "authentication" "SCRAM-SHA-1"
27123 The &(gsasl)& authenticator provides server integration for the GNU SASL
27124 library and the mechanisms it provides. This is new as of the 4.80 release
27125 and there are a few areas where the library does not let Exim smoothly
27126 scale to handle future authentication mechanisms, so no guarantee can be
27127 made that any particular new authentication mechanism will be supported
27128 without code changes in Exim.
27130 Exim's &(gsasl)& authenticator does not have client-side support at this
27131 time; only the server-side support is implemented. Patches welcome.
27134 .option server_channelbinding gsasl boolean false
27135 Do not set this true without consulting a cryptographic engineer.
27137 Some authentication mechanisms are able to use external context at both ends
27138 of the session to bind the authentication to that context, and fail the
27139 authentication process if that context differs. Specifically, some TLS
27140 ciphersuites can provide identifying information about the cryptographic
27143 This should have meant that certificate identity and verification becomes a
27144 non-issue, as a man-in-the-middle attack will cause the correct client and
27145 server to see different identifiers and authentication will fail.
27147 This is currently only supported when using the GnuTLS library. This is
27148 only usable by mechanisms which support "channel binding"; at time of
27149 writing, that's the SCRAM family.
27151 This defaults off to ensure smooth upgrade across Exim releases, in case
27152 this option causes some clients to start failing. Some future release
27153 of Exim might have switched the default to be true.
27155 However, Channel Binding in TLS has proven to be broken in current versions.
27156 Do not plan to rely upon this feature for security, ever, without consulting
27157 with a subject matter expert (a cryptographic engineer).
27160 .option server_hostname gsasl string&!! "see below"
27161 This option selects the hostname that is used when communicating with the
27162 library. The default value is &`$primary_hostname`&.
27163 Some mechanisms will use this data.
27166 .option server_mech gsasl string "see below"
27167 This option selects the authentication mechanism this driver should use. The
27168 default is the value of the generic &%public_name%& option. This option allows
27169 you to use a different underlying mechanism from the advertised name. For
27174 public_name = X-ANYTHING
27175 server_mech = CRAM-MD5
27176 server_set_id = $auth1
27180 .option server_password gsasl string&!! unset
27181 Various mechanisms need access to the cleartext password on the server, so
27182 that proof-of-possession can be demonstrated on the wire, without sending
27183 the password itself.
27185 The data available for lookup varies per mechanism.
27186 In all cases, &$auth1$& is set to the &'authentication id'&.
27187 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
27188 if available, else the empty string.
27189 The &$auth3$& variable will always be the &'realm'& if available,
27190 else the empty string.
27192 A forced failure will cause authentication to defer.
27194 If using this option, it may make sense to set the &%server_condition%&
27195 option to be simply "true".
27198 .option server_realm gsasl string&!! unset
27199 This specifies the SASL realm that the server claims to be in.
27200 Some mechanisms will use this data.
27203 .option server_scram_iter gsasl string&!! unset
27204 This option provides data for the SCRAM family of mechanisms.
27205 &$auth1$& is not available at evaluation time.
27206 (This may change, as we receive feedback on use)
27209 .option server_scram_salt gsasl string&!! unset
27210 This option provides data for the SCRAM family of mechanisms.
27211 &$auth1$& is not available at evaluation time.
27212 (This may change, as we receive feedback on use)
27215 .option server_service gsasl string &`smtp`&
27216 This is the SASL service that the server claims to implement.
27217 Some mechanisms will use this data.
27220 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
27221 .vindex "&$auth1$&, &$auth2$&, etc"
27222 These may be set when evaluating specific options, as detailed above.
27223 They will also be set when evaluating &%server_condition%&.
27225 Unless otherwise stated below, the &(gsasl)& integration will use the following
27226 meanings for these variables:
27229 .vindex "&$auth1$&"
27230 &$auth1$&: the &'authentication id'&
27232 .vindex "&$auth2$&"
27233 &$auth2$&: the &'authorization id'&
27235 .vindex "&$auth3$&"
27236 &$auth3$&: the &'realm'&
27239 On a per-mechanism basis:
27242 .cindex "authentication" "EXTERNAL"
27243 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
27244 the &%server_condition%& option must be present.
27246 .cindex "authentication" "ANONYMOUS"
27247 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
27248 the &%server_condition%& option must be present.
27250 .cindex "authentication" "GSSAPI"
27251 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
27252 &$auth2$& will be set to the &'authorization id'&,
27253 the &%server_condition%& option must be present.
27256 An &'anonymous token'& is something passed along as an unauthenticated
27257 identifier; this is analogous to FTP anonymous authentication passing an
27258 email address, or software-identifier@, as the "password".
27261 An example showing the password having the realm specified in the callback
27262 and demonstrating a Cyrus SASL to GSASL migration approach is:
27264 gsasl_cyrusless_crammd5:
27266 public_name = CRAM-MD5
27267 server_realm = imap.example.org
27268 server_password = ${lookup{$auth1:$auth3:userPassword}\
27269 dbmjz{/etc/sasldb2}{$value}fail}
27270 server_set_id = ${quote:$auth1}
27271 server_condition = yes
27275 . ////////////////////////////////////////////////////////////////////////////
27276 . ////////////////////////////////////////////////////////////////////////////
27278 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
27279 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
27280 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
27281 .cindex "authentication" "GSSAPI"
27282 .cindex "authentication" "Kerberos"
27283 The &(heimdal_gssapi)& authenticator provides server integration for the
27284 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
27287 .option server_hostname heimdal_gssapi string&!! "see below"
27288 This option selects the hostname that is used, with &%server_service%&,
27289 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
27290 identifier. The default value is &`$primary_hostname`&.
27292 .option server_keytab heimdal_gssapi string&!! unset
27293 If set, then Heimdal will not use the system default keytab (typically
27294 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
27295 The value should be a pathname, with no &"file:"& prefix.
27297 .option server_service heimdal_gssapi string&!! "smtp"
27298 This option specifies the service identifier used, in conjunction with
27299 &%server_hostname%&, for building the identifier for finding credentials
27303 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
27304 Beware that these variables will typically include a realm, thus will appear
27305 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
27306 not verified, so a malicious client can set it to anything.
27308 The &$auth1$& field should be safely trustable as a value from the Key
27309 Distribution Center. Note that these are not quite email addresses.
27310 Each identifier is for a role, and so the left-hand-side may include a
27311 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
27313 .vindex "&$auth1$&, &$auth2$&, etc"
27315 .vindex "&$auth1$&"
27316 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
27318 .vindex "&$auth2$&"
27319 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
27320 authentication. If that was empty, this will also be set to the
27325 . ////////////////////////////////////////////////////////////////////////////
27326 . ////////////////////////////////////////////////////////////////////////////
27328 .chapter "The spa authenticator" "CHAPspa"
27329 .scindex IIDspaauth1 "&(spa)& authenticator"
27330 .scindex IIDspaauth2 "authenticators" "&(spa)&"
27331 .cindex "authentication" "Microsoft Secure Password"
27332 .cindex "authentication" "NTLM"
27333 .cindex "Microsoft Secure Password Authentication"
27334 .cindex "NTLM authentication"
27335 The &(spa)& authenticator provides client support for Microsoft's &'Secure
27336 Password Authentication'& mechanism,
27337 which is also sometimes known as NTLM (NT LanMan). The code for client side of
27338 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
27339 taken from the Samba project (&url(https://www.samba.org/)). The code for the
27340 server side was subsequently contributed by Tom Kistner. The mechanism works as
27344 After the AUTH command has been accepted, the client sends an SPA
27345 authentication request based on the user name and optional domain.
27347 The server sends back a challenge.
27349 The client builds a challenge response which makes use of the user's password
27350 and sends it to the server, which then accepts or rejects it.
27353 Encryption is used to protect the password in transit.
27357 .section "Using spa as a server" "SECID179"
27358 .cindex "options" "&(spa)& authenticator (server)"
27359 The &(spa)& authenticator has just one server option:
27361 .option server_password spa string&!! unset
27362 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
27363 This option is expanded, and the result must be the cleartext password for the
27364 authenticating user, whose name is at this point in &$auth1$&. For
27365 compatibility with previous releases of Exim, the user name is also placed in
27366 &$1$&. However, the use of this variable for this purpose is now deprecated, as
27367 it can lead to confusion in string expansions that also use numeric variables
27368 for other things. For example:
27373 server_password = \
27374 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
27376 If the expansion is forced to fail, authentication fails. Any other expansion
27377 failure causes a temporary error code to be returned.
27383 .section "Using spa as a client" "SECID180"
27384 .cindex "options" "&(spa)& authenticator (client)"
27385 The &(spa)& authenticator has the following client options:
27389 .option client_domain spa string&!! unset
27390 This option specifies an optional domain for the authentication.
27393 .option client_password spa string&!! unset
27394 This option specifies the user's password, and must be set.
27397 .option client_username spa string&!! unset
27398 This option specifies the user name, and must be set. Here is an example of a
27399 configuration of this authenticator for use with the mail servers at
27405 client_username = msn/msn_username
27406 client_password = msn_plaintext_password
27407 client_domain = DOMAIN_OR_UNSET
27409 .ecindex IIDspaauth1
27410 .ecindex IIDspaauth2
27416 . ////////////////////////////////////////////////////////////////////////////
27417 . ////////////////////////////////////////////////////////////////////////////
27419 .chapter "The tls authenticator" "CHAPtlsauth"
27420 .scindex IIDtlsauth1 "&(tls)& authenticator"
27421 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
27422 .cindex "authentication" "Client Certificate"
27423 .cindex "authentication" "X509"
27424 .cindex "Certificate-based authentication"
27425 The &(tls)& authenticator provides server support for
27426 authentication based on client certificates.
27428 It is not an SMTP authentication mechanism and is not
27429 advertised by the server as part of the SMTP EHLO response.
27430 It is an Exim authenticator in the sense that it affects
27431 the protocol element of the log line, can be tested for
27432 by the &%authenticated%& ACL condition, and can set
27433 the &$authenticated_id$& variable.
27435 The client must present a verifiable certificate,
27436 for which it must have been requested via the
27437 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
27438 (see &<<CHAPTLS>>&).
27440 If an authenticator of this type is configured it is
27441 run before any SMTP-level communication is done,
27442 and can authenticate the connection.
27443 If it does, SMTP authentication is not offered.
27445 A maximum of one authenticator of this type may be present.
27448 .cindex "options" "&(tls)& authenticator (server)"
27449 The &(tls)& authenticator has three server options:
27451 .option server_param1 tls string&!! unset
27452 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
27453 This option is expanded after the TLS negotiation and
27454 the result is placed in &$auth1$&.
27455 If the expansion is forced to fail, authentication fails. Any other expansion
27456 failure causes a temporary error code to be returned.
27458 .option server_param2 tls string&!! unset
27459 .option server_param3 tls string&!! unset
27460 As above, for &$auth2$& and &$auth3$&.
27462 &%server_param1%& may also be spelled &%server_param%&.
27469 server_param1 = ${certextract {subj_altname,mail,>:} \
27470 {$tls_in_peercert}}
27471 server_condition = ${if and { {eq{$tls_in_certificate_verified}{1}} \
27474 {${lookup ldap{ldap:///\
27475 mailname=${quote_ldap_dn:${lc:$item}},\
27476 ou=users,LDAP_DC?mailid} {$value}{0} \
27478 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
27480 This accepts a client certificate that is verifiable against any
27481 of your configured trust-anchors
27482 (which usually means the full set of public CAs)
27483 and which has a SAN with a good account name.
27485 Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
27486 The account name is therefore guessable by an opponent.
27487 TLS 1.3 protects both server and client certificates, and is not vulnerable
27489 Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
27491 . An alternative might use
27493 . server_param1 = ${sha256:$tls_in_peercert}
27495 . to require one of a set of specific certs that define a given account
27496 . (the verification is still required, but mostly irrelevant).
27497 . This would help for per-device use.
27499 . However, for the future we really need support for checking a
27500 . user cert in LDAP - which probably wants a base-64 DER.
27502 .ecindex IIDtlsauth1
27503 .ecindex IIDtlsauth2
27506 Note that because authentication is traditionally an SMTP operation,
27507 the &%authenticated%& ACL condition cannot be used in
27508 a connect- or helo-ACL.
27512 . ////////////////////////////////////////////////////////////////////////////
27513 . ////////////////////////////////////////////////////////////////////////////
27515 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
27516 "Encrypted SMTP connections"
27517 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
27518 .scindex IIDencsmtp2 "SMTP" "encryption"
27519 .cindex "TLS" "on SMTP connection"
27522 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
27523 Sockets Layer), is implemented by making use of the OpenSSL library or the
27524 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
27525 cryptographic code in the Exim distribution itself for implementing TLS. In
27526 order to use this feature you must install OpenSSL or GnuTLS, and then build a
27527 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
27528 You also need to understand the basic concepts of encryption at a managerial
27529 level, and in particular, the way that public keys, private keys, and
27530 certificates are used.
27532 RFC 3207 defines how SMTP connections can make use of encryption. Once a
27533 connection is established, the client issues a STARTTLS command. If the
27534 server accepts this, the client and the server negotiate an encryption
27535 mechanism. If the negotiation succeeds, the data that subsequently passes
27536 between them is encrypted.
27538 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
27539 and if so, what cipher suite is in use, whether the client supplied a
27540 certificate, and whether or not that certificate was verified. This makes it
27541 possible for an Exim server to deny or accept certain commands based on the
27544 &*Warning*&: Certain types of firewall and certain anti-virus products can
27545 disrupt TLS connections. You need to turn off SMTP scanning for these products
27546 in order to get TLS to work.
27550 .section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
27552 .cindex "submissions protocol"
27553 .cindex "ssmtp protocol"
27554 .cindex "smtps protocol"
27555 .cindex "SMTP" "submissions protocol"
27556 .cindex "SMTP" "ssmtp protocol"
27557 .cindex "SMTP" "smtps protocol"
27558 The history of port numbers for TLS in SMTP is a little messy and has been
27559 contentious. As of RFC 8314, the common practice of using the historically
27560 allocated port 465 for "email submission but with TLS immediately upon connect
27561 instead of using STARTTLS" is officially blessed by the IETF, and recommended
27562 by them in preference to STARTTLS.
27564 The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
27565 clarity emerged over the dual roles of SMTP, for MX delivery and Email
27566 Submission, nomenclature has shifted. The modern name is now &"submissions"&.
27568 This approach was, for a while, officially abandoned when encrypted SMTP was
27569 standardized, but many clients kept using it, even as the TCP port number was
27570 reassigned for other use.
27571 Thus you may encounter guidance claiming that you shouldn't enable use of
27573 In practice, a number of mail-clients have only ever supported submissions,
27574 not submission with STARTTLS upgrade.
27575 Ideally, offer both submission (587) and submissions (465) service.
27577 Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
27578 global option. Its value must be a list of port numbers;
27579 the most common use is expected to be:
27581 tls_on_connect_ports = 465
27583 The port numbers specified by this option apply to all SMTP connections, both
27584 via the daemon and via &'inetd'&. You still need to specify all the ports that
27585 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
27586 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
27587 an extra port &-- rather, it specifies different behaviour on a port that is
27590 There is also a &%-tls-on-connect%& command line option. This overrides
27591 &%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
27598 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
27599 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
27600 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
27601 followed later, when the first versions of GnuTLS were released. To build Exim
27602 to use GnuTLS, you need to set
27606 in Local/Makefile, in addition to
27610 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
27611 include files and libraries for GnuTLS can be found.
27613 There are some differences in usage when using GnuTLS instead of OpenSSL:
27616 The &%tls_verify_certificates%& option
27617 cannot be the path of a directory
27618 for GnuTLS versions before 3.3.6
27619 (for later versions, or OpenSSL, it can be either).
27621 The default value for &%tls_dhparam%& differs for historical reasons.
27623 .vindex "&$tls_in_peerdn$&"
27624 .vindex "&$tls_out_peerdn$&"
27625 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
27626 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
27627 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
27629 OpenSSL identifies cipher suites using hyphens as separators, for example:
27630 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
27631 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
27632 in a cipher list. To make life simpler, Exim changes underscores to hyphens
27633 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
27634 to handle its own older variants) when processing lists of cipher suites in the
27635 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
27638 The &%tls_require_ciphers%& options operate differently, as described in the
27639 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
27641 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
27642 When using OpenSSL, this option is ignored.
27643 (If an API is found to let OpenSSL be configured in this way,
27644 let the Exim Maintainers know and we'll likely use it).
27646 With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
27647 main option, it must be ordered to match the &%tls_certificate%& list.
27649 Some other recently added features may only be available in one or the other.
27650 This should be documented with the feature. If the documentation does not
27651 explicitly state that the feature is infeasible in the other TLS
27652 implementation, then patches are welcome.
27656 .section "GnuTLS parameter computation" "SECTgnutlsparam"
27657 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
27658 an explicit path; if the latter, then the text about generation still applies,
27659 but not the chosen filename.
27660 By default, as of Exim 4.80 a hard-coded D-H prime is used.
27661 See the documentation of &%tls_dhparam%& for more information.
27663 GnuTLS uses D-H parameters that may take a substantial amount of time
27664 to compute. It is unreasonable to re-compute them for every TLS session.
27665 Therefore, Exim keeps this data in a file in its spool directory, called
27666 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
27668 The file is owned by the Exim user and is readable only by
27669 its owner. Every Exim process that start up GnuTLS reads the D-H
27670 parameters from this file. If the file does not exist, the first Exim process
27671 that needs it computes the data and writes it to a temporary file which is
27672 renamed once it is complete. It does not matter if several Exim processes do
27673 this simultaneously (apart from wasting a few resources). Once a file is in
27674 place, new Exim processes immediately start using it.
27676 For maximum security, the parameters that are stored in this file should be
27677 recalculated periodically, the frequency depending on your paranoia level.
27678 If you are avoiding using the fixed D-H primes published in RFCs, then you
27679 are concerned about some advanced attacks and will wish to do this; if you do
27680 not regenerate then you might as well stick to the standard primes.
27682 Arranging this is easy in principle; just delete the file when you want new
27683 values to be computed. However, there may be a problem. The calculation of new
27684 parameters needs random numbers, and these are obtained from &_/dev/random_&.
27685 If the system is not very active, &_/dev/random_& may delay returning data
27686 until enough randomness (entropy) is available. This may cause Exim to hang for
27687 a substantial amount of time, causing timeouts on incoming connections.
27689 The solution is to generate the parameters externally to Exim. They are stored
27690 in &_gnutls-params-N_& in PEM format, which means that they can be
27691 generated externally using the &(certtool)& command that is part of GnuTLS.
27693 To replace the parameters with new ones, instead of deleting the file
27694 and letting Exim re-create it, you can generate new parameters using
27695 &(certtool)& and, when this has been done, replace Exim's cache file by
27696 renaming. The relevant commands are something like this:
27699 [ look for file; assume gnutls-params-2236 is the most recent ]
27702 # chown exim:exim new-params
27703 # chmod 0600 new-params
27704 # certtool --generate-dh-params --bits 2236 >>new-params
27705 # openssl dhparam -noout -text -in new-params | head
27706 [ check the first line, make sure it's not more than 2236;
27707 if it is, then go back to the start ("rm") and repeat
27708 until the size generated is at most the size requested ]
27709 # chmod 0400 new-params
27710 # mv new-params gnutls-params-2236
27712 If Exim never has to generate the parameters itself, the possibility of
27713 stalling is removed.
27715 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
27716 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
27717 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
27718 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
27719 and Exim does so. This attempt to remove Exim from TLS policy decisions
27720 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
27721 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
27722 which applies to all D-H usage, client or server. If the value returned by
27723 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
27724 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
27725 limit, which is still much higher than Exim historically used.
27727 The filename and bits used will change as the GnuTLS maintainers change the
27728 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
27729 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
27730 2432 bits, while NSS is limited to 2236 bits.
27732 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
27733 increase the chance of the generated prime actually being within acceptable
27734 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
27735 procedure above. There is no sane procedure available to Exim to double-check
27736 the size of the generated prime, so it might still be too large.
27739 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
27740 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
27741 .oindex "&%tls_require_ciphers%&" "OpenSSL"
27742 There is a function in the OpenSSL library that can be passed a list of cipher
27743 suites before the cipher negotiation takes place. This specifies which ciphers
27745 are acceptable for TLS versions prior to 1.3.
27747 The list is colon separated and may contain names like
27748 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
27749 directly to this function call.
27750 Many systems will install the OpenSSL manual-pages, so you may have
27751 &'ciphers(1)'& available to you.
27752 The following quotation from the OpenSSL
27753 documentation specifies what forms of item are allowed in the cipher string:
27756 It can consist of a single cipher suite such as RC4-SHA.
27758 It can represent a list of cipher suites containing a certain algorithm,
27759 or cipher suites of a certain type. For example SHA1 represents all
27760 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
27763 Lists of cipher suites can be combined in a single cipher string using
27764 the + character. This is used as a logical and operation. For example
27765 SHA1+DES represents all cipher suites containing the SHA1 and the DES
27769 Each cipher string can be optionally preceded by one of the characters &`!`&,
27772 If &`!`& is used, the ciphers are permanently deleted from the list. The
27773 ciphers deleted can never reappear in the list even if they are explicitly
27776 If &`-`& is used, the ciphers are deleted from the list, but some or all
27777 of the ciphers can be added again by later options.
27779 If &`+`& is used, the ciphers are moved to the end of the list. This
27780 option does not add any new ciphers; it just moves matching existing ones.
27783 If none of these characters is present, the string is interpreted as
27784 a list of ciphers to be appended to the current preference list. If the list
27785 includes any ciphers already present they will be ignored: that is, they will
27786 not be moved to the end of the list.
27789 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
27792 # note single-quotes to get ! past any shell history expansion
27793 $ openssl ciphers 'HIGH:!MD5:!SHA1'
27796 This example will let the library defaults be permitted on the MX port, where
27797 there's probably no identity verification anyway, but ups the ante on the
27798 submission ports where the administrator might have some influence on the
27799 choice of clients used:
27801 # OpenSSL variant; see man ciphers(1)
27802 tls_require_ciphers = ${if =={$received_port}{25}\
27807 This example will prefer ECDSA-authenticated ciphers over RSA ones:
27809 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
27813 For TLS version 1.3 the control available is less fine-grained
27814 and Exim does not provide access to it at present.
27815 The value of the &%tls_require_ciphers%& option is ignored when
27816 TLS version 1.3 is negotiated.
27818 As of writing the library default cipher suite list for TLSv1.3 is
27820 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
27825 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
27827 .cindex "GnuTLS" "specifying parameters for"
27828 .cindex "TLS" "specifying ciphers (GnuTLS)"
27829 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
27830 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
27831 .cindex "TLS" "specifying protocols (GnuTLS)"
27832 .cindex "TLS" "specifying priority string (GnuTLS)"
27833 .oindex "&%tls_require_ciphers%&" "GnuTLS"
27834 The GnuTLS library allows the caller to provide a "priority string", documented
27835 as part of the &[gnutls_priority_init]& function. This is very similar to the
27836 ciphersuite specification in OpenSSL.
27838 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
27839 and controls both protocols and ciphers.
27841 The &%tls_require_ciphers%& option is available both as an global option,
27842 controlling how Exim behaves as a server, and also as an option of the
27843 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
27844 the value is string expanded. The resulting string is not an Exim list and
27845 the string is given to the GnuTLS library, so that Exim does not need to be
27846 aware of future feature enhancements of GnuTLS.
27848 Documentation of the strings accepted may be found in the GnuTLS manual, under
27849 "Priority strings". This is online as
27850 &url(https://www.gnutls.org/manual/html_node/Priority-Strings.html),
27851 but beware that this relates to GnuTLS 3, which may be newer than the version
27852 installed on your system. If you are using GnuTLS 3,
27853 then the example code
27854 &url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
27855 on that site can be used to test a given string.
27859 # Disable older versions of protocols
27860 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
27863 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
27864 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
27865 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
27867 This example will let the library defaults be permitted on the MX port, where
27868 there's probably no identity verification anyway, and lowers security further
27869 by increasing compatibility; but this ups the ante on the submission ports
27870 where the administrator might have some influence on the choice of clients
27874 tls_require_ciphers = ${if =={$received_port}{25}\
27880 .section "Configuring an Exim server to use TLS" "SECID182"
27881 .cindex "TLS" "configuring an Exim server"
27882 When Exim has been built with TLS support, it advertises the availability of
27883 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
27884 but not to any others. The default value of this option is *, which means
27885 that STARTTLS is always advertised. Set it to blank to never advertise;
27886 this is reasonable for systems that want to use TLS only as a client.
27888 If STARTTLS is to be used you
27889 need to set some other options in order to make TLS available.
27891 If a client issues a STARTTLS command and there is some configuration
27892 problem in the server, the command is rejected with a 454 error. If the client
27893 persists in trying to issue SMTP commands, all except QUIT are rejected
27896 554 Security failure
27898 If a STARTTLS command is issued within an existing TLS session, it is
27899 rejected with a 554 error code.
27901 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
27902 must be set to match some hosts. The default is * which matches all hosts.
27904 If this is all you do, TLS encryption will be enabled but not authentication -
27905 meaning that the peer has no assurance it is actually you he is talking to.
27906 You gain protection from a passive sniffer listening on the wire but not
27907 from someone able to intercept the communication.
27909 Further protection requires some further configuration at the server end.
27911 To make TLS work you need to set, in the server,
27913 tls_certificate = /some/file/name
27914 tls_privatekey = /some/file/name
27916 These options are, in fact, expanded strings, so you can make them depend on
27917 the identity of the client that is connected if you wish. The first file
27918 contains the server's X509 certificate, and the second contains the private key
27919 that goes with it. These files need to be
27920 PEM format and readable by the Exim user, and must
27921 always be given as full path names.
27922 The key must not be password-protected.
27923 They can be the same file if both the
27924 certificate and the key are contained within it. If &%tls_privatekey%& is not
27925 set, or if its expansion is forced to fail or results in an empty string, this
27926 is assumed to be the case. The certificate file may also contain intermediate
27927 certificates that need to be sent to the client to enable it to authenticate
27928 the server's certificate.
27930 For dual-stack (eg. RSA and ECDSA) configurations, these options can be
27931 colon-separated lists of file paths. Ciphers using given authentication
27932 algorithms require the presence of a suitable certificate to supply the
27933 public-key. The server selects among the certificates to present to the
27934 client depending on the selected cipher, hence the priority ordering for
27935 ciphers will affect which certificate is used.
27937 If you do not understand about certificates and keys, please try to find a
27938 source of this background information, which is not Exim-specific. (There are a
27939 few comments below in section &<<SECTcerandall>>&.)
27941 &*Note*&: These options do not apply when Exim is operating as a client &--
27942 they apply only in the case of a server. If you need to use a certificate in an
27943 Exim client, you must set the options of the same names in an &(smtp)&
27946 With just these options, an Exim server will be able to use TLS. It does not
27947 require the client to have a certificate (but see below for how to insist on
27948 this). There is one other option that may be needed in other situations. If
27950 tls_dhparam = /some/file/name
27952 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
27953 with the parameters contained in the file.
27954 Set this to &`none`& to disable use of DH entirely, by making no prime
27959 This may also be set to a string identifying a standard prime to be used for
27960 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
27961 used is &`ike23`&. There are a few standard primes available, see the
27962 documentation for &%tls_dhparam%& for the complete list.
27968 for a way of generating file data.
27970 The strings supplied for these three options are expanded every time a client
27971 host connects. It is therefore possible to use different certificates and keys
27972 for different hosts, if you so wish, by making use of the client's IP address
27973 in &$sender_host_address$& to control the expansion. If a string expansion is
27974 forced to fail, Exim behaves as if the option is not set.
27976 .cindex "cipher" "logging"
27977 .cindex "log" "TLS cipher"
27978 .vindex "&$tls_in_cipher$&"
27979 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
27980 an incoming TLS connection. It is included in the &'Received:'& header of an
27981 incoming message (by default &-- you can, of course, change this), and it is
27982 also included in the log line that records a message's arrival, keyed by
27983 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
27984 condition can be used to test for specific cipher suites in ACLs.
27986 Once TLS has been established, the ACLs that run for subsequent SMTP commands
27987 can check the name of the cipher suite and vary their actions accordingly. The
27988 cipher suite names vary, depending on which TLS library is being used. For
27989 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
27990 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
27991 documentation for more details.
27993 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
27994 (again depending on the &%tls_cipher%& log selector).
27997 .section "Requesting and verifying client certificates" "SECID183"
27998 .cindex "certificate" "verification of client"
27999 .cindex "TLS" "client certificate verification"
28000 If you want an Exim server to request a certificate when negotiating a TLS
28001 session with a client, you must set either &%tls_verify_hosts%& or
28002 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
28003 apply to all TLS connections. For any host that matches one of these options,
28004 Exim requests a certificate as part of the setup of the TLS session. The
28005 contents of the certificate are verified by comparing it with a list of
28006 expected trust-anchors or certificates.
28007 These may be the system default set (depending on library version),
28008 an explicit file or,
28009 depending on library version, a directory, identified by
28010 &%tls_verify_certificates%&.
28012 A file can contain multiple certificates, concatenated end to end. If a
28015 each certificate must be in a separate file, with a name (or a symbolic link)
28016 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
28017 certificate. You can compute the relevant hash by running the command
28019 openssl x509 -hash -noout -in /cert/file
28021 where &_/cert/file_& contains a single certificate.
28023 There is no checking of names of the client against the certificate
28024 Subject Name or Subject Alternate Names.
28026 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
28027 what happens if the client does not supply a certificate, or if the certificate
28028 does not match any of the certificates in the collection named by
28029 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
28030 attempt to set up a TLS session is aborted, and the incoming connection is
28031 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
28032 session continues. ACLs that run for subsequent SMTP commands can detect the
28033 fact that no certificate was verified, and vary their actions accordingly. For
28034 example, you can insist on a certificate before accepting a message for
28035 relaying, but not when the message is destined for local delivery.
28037 .vindex "&$tls_in_peerdn$&"
28038 When a client supplies a certificate (whether it verifies or not), the value of
28039 the Distinguished Name of the certificate is made available in the variable
28040 &$tls_in_peerdn$& during subsequent processing of the message.
28042 .cindex "log" "distinguished name"
28043 Because it is often a long text string, it is not included in the log line or
28044 &'Received:'& header by default. You can arrange for it to be logged, keyed by
28045 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
28046 &%received_header_text%& to change the &'Received:'& header. When no
28047 certificate is supplied, &$tls_in_peerdn$& is empty.
28050 .section "Revoked certificates" "SECID184"
28051 .cindex "TLS" "revoked certificates"
28052 .cindex "revocation list"
28053 .cindex "certificate" "revocation list"
28054 .cindex "OCSP" "stapling"
28055 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
28056 certificates are revoked. If you have such a list, you can pass it to an Exim
28057 server using the global option called &%tls_crl%& and to an Exim client using
28058 an identically named option for the &(smtp)& transport. In each case, the value
28059 of the option is expanded and must then be the name of a file that contains a
28061 The downside is that clients have to periodically re-download a potentially huge
28062 file from every certificate authority they know of.
28064 The way with most moving parts at query time is Online Certificate
28065 Status Protocol (OCSP), where the client verifies the certificate
28066 against an OCSP server run by the CA. This lets the CA track all
28067 usage of the certs. It requires running software with access to the
28068 private key of the CA, to sign the responses to the OCSP queries. OCSP
28069 is based on HTTP and can be proxied accordingly.
28071 The only widespread OCSP server implementation (known to this writer)
28072 comes as part of OpenSSL and aborts on an invalid request, such as
28073 connecting to the port and then disconnecting. This requires
28074 re-entering the passphrase each time some random client does this.
28076 The third way is OCSP Stapling; in this, the server using a certificate
28077 issued by the CA periodically requests an OCSP proof of validity from
28078 the OCSP server, then serves it up inline as part of the TLS
28079 negotiation. This approach adds no extra round trips, does not let the
28080 CA track users, scales well with number of certs issued by the CA and is
28081 resilient to temporary OCSP server failures, as long as the server
28082 starts retrying to fetch an OCSP proof some time before its current
28083 proof expires. The downside is that it requires server support.
28085 Unless Exim is built with the support disabled,
28086 or with GnuTLS earlier than version 3.3.16 / 3.4.8
28087 support for OCSP stapling is included.
28089 There is a global option called &%tls_ocsp_file%&.
28090 The file specified therein is expected to be in DER format, and contain
28091 an OCSP proof. Exim will serve it as part of the TLS handshake. This
28092 option will be re-expanded for SNI, if the &%tls_certificate%& option
28093 contains &`tls_in_sni`&, as per other TLS options.
28095 Exim does not at this time implement any support for fetching a new OCSP
28096 proof. The burden is on the administrator to handle this, outside of
28097 Exim. The file specified should be replaced atomically, so that the
28098 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
28099 on each connection, so a new file will be handled transparently on the
28102 When built with OpenSSL Exim will check for a valid next update timestamp
28103 in the OCSP proof; if not present, or if the proof has expired, it will be
28106 For the client to be able to verify the stapled OCSP the server must
28107 also supply, in its stapled information, any intermediate
28108 certificates for the chain leading to the OCSP proof from the signer
28109 of the server certificate. There may be zero or one such. These
28110 intermediate certificates should be added to the server OCSP stapling
28111 file named by &%tls_ocsp_file%&.
28113 Note that the proof only covers the terminal server certificate,
28114 not any of the chain from CA to it.
28116 There is no current way to staple a proof for a client certificate.
28119 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
28120 OCSP server is supplied. The server URL may be included in the
28121 server certificate, if the CA is helpful.
28123 One failure mode seen was the OCSP Signer cert expiring before the end
28124 of validity of the OCSP proof. The checking done by Exim/OpenSSL
28125 noted this as invalid overall, but the re-fetch script did not.
28131 .section "Configuring an Exim client to use TLS" "SECID185"
28132 .cindex "cipher" "logging"
28133 .cindex "log" "TLS cipher"
28134 .cindex "log" "distinguished name"
28135 .cindex "TLS" "configuring an Exim client"
28136 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
28137 deliveries as well as to incoming, the latter one causing logging of the
28138 server certificate's DN. The remaining client configuration for TLS is all
28139 within the &(smtp)& transport.
28141 It is not necessary to set any options to have TLS work in the &(smtp)&
28142 transport. If Exim is built with TLS support, and TLS is advertised by a
28143 server, the &(smtp)& transport always tries to start a TLS session. However,
28144 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
28145 transport) to a list of server hosts for which TLS should not be used.
28147 If you do not want Exim to attempt to send messages unencrypted when an attempt
28148 to set up an encrypted connection fails in any way, you can set
28149 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
28150 those hosts, delivery is always deferred if an encrypted connection cannot be
28151 set up. If there are any other hosts for the address, they are tried in the
28154 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
28155 the message unencrypted. It always does this if the response to STARTTLS is
28156 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
28157 session after a success response code, what happens is controlled by the
28158 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
28159 delivery to this host is deferred, and other hosts (if available) are tried. If
28160 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
28161 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
28162 negotiation fails, Exim closes the current connection (because it is in an
28163 unknown state), opens a new one to the same host, and then tries the delivery
28166 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
28167 transport provide the client with a certificate, which is passed to the server
28168 if it requests it. If the server is Exim, it will request a certificate only if
28169 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
28171 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
28172 specifies a collection of expected server certificates.
28174 the system default set (depending on library version),
28176 or (depending on library version) a directory.
28177 The client verifies the server's certificate
28178 against this collection, taking into account any revoked certificates that are
28179 in the list defined by &%tls_crl%&.
28180 Failure to verify fails the TLS connection unless either of the
28181 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
28183 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
28184 certificate verification to the listed servers. Verification either must
28185 or need not succeed respectively.
28187 The &%tls_verify_cert_hostnames%& option lists hosts for which additional
28188 checks are made: that the host name (the one in the DNS A record)
28189 is valid for the certificate.
28190 The option defaults to always checking.
28192 The &(smtp)& transport has two OCSP-related options:
28193 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
28194 is requested and required for the connection to proceed. The default
28196 &%hosts_request_ocsp%&; a host-list for which (additionally)
28197 a Certificate Status is requested (but not necessarily verified). The default
28198 value is "*" meaning that requests are made unless configured
28201 The host(s) should also be in &%hosts_require_tls%&, and
28202 &%tls_verify_certificates%& configured for the transport,
28203 for OCSP to be relevant.
28206 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
28207 list of permitted cipher suites. If either of these checks fails, delivery to
28208 the current host is abandoned, and the &(smtp)& transport tries to deliver to
28209 alternative hosts, if any.
28212 These options must be set in the &(smtp)& transport for Exim to use TLS when it
28213 is operating as a client. Exim does not assume that a server certificate (set
28214 by the global options of the same name) should also be used when operating as a
28218 .vindex "&$host_address$&"
28219 All the TLS options in the &(smtp)& transport are expanded before use, with
28220 &$host$& and &$host_address$& containing the name and address of the server to
28221 which the client is connected. Forced failure of an expansion causes Exim to
28222 behave as if the relevant option were unset.
28224 .vindex &$tls_out_bits$&
28225 .vindex &$tls_out_cipher$&
28226 .vindex &$tls_out_peerdn$&
28227 .vindex &$tls_out_sni$&
28228 Before an SMTP connection is established, the
28229 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
28230 variables are emptied. (Until the first connection, they contain the values
28231 that were set when the message was received.) If STARTTLS is subsequently
28232 successfully obeyed, these variables are set to the relevant values for the
28233 outgoing connection.
28237 .section "Use of TLS Server Name Indication" "SECTtlssni"
28238 .cindex "TLS" "Server Name Indication"
28239 .vindex "&$tls_in_sni$&"
28240 .oindex "&%tls_in_sni%&"
28241 With TLS1.0 or above, there is an extension mechanism by which extra
28242 information can be included at various points in the protocol. One of these
28243 extensions, documented in RFC 6066 (and before that RFC 4366) is
28244 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
28245 client in the initial handshake, so that the server can examine the servername
28246 within and possibly choose to use different certificates and keys (and more)
28249 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
28250 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
28253 With SMTP to MX, there are the same problems here as in choosing the identity
28254 against which to validate a certificate: you can't rely on insecure DNS to
28255 provide the identity which you then cryptographically verify. So this will
28256 be of limited use in that environment.
28258 With SMTP to Submission, there is a well-defined hostname which clients are
28259 connecting to and can validate certificates against. Thus clients &*can*&
28260 choose to include this information in the TLS negotiation. If this becomes
28261 wide-spread, then hosters can choose to present different certificates to
28262 different clients. Or even negotiate different cipher suites.
28264 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
28265 if not empty, will be sent on a TLS session as part of the handshake. There's
28266 nothing more to it. Choosing a sensible value not derived insecurely is the
28267 only point of caution. The &$tls_out_sni$& variable will be set to this string
28268 for the lifetime of the client connection (including during authentication).
28270 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
28271 received from a client.
28272 It can be logged with the &%log_selector%& item &`+tls_sni`&.
28274 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
28275 option (prior to expansion) then the following options will be re-expanded
28276 during TLS session handshake, to permit alternative values to be chosen:
28279 &%tls_certificate%&
28285 &%tls_verify_certificates%&
28290 Great care should be taken to deal with matters of case, various injection
28291 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
28292 can always be referenced; it is important to remember that &$tls_in_sni$& is
28293 arbitrary unverified data provided prior to authentication.
28294 Further, the initial certificate is loaded before SNI is arrived, so
28295 an expansion for &%tls_certificate%& must have a default which is used
28296 when &$tls_in_sni$& is empty.
28298 The Exim developers are proceeding cautiously and so far no other TLS options
28301 When Exim is built against OpenSSL, OpenSSL must have been built with support
28302 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
28303 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
28304 see &`-servername`& in the output, then OpenSSL has support.
28306 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
28307 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
28308 built, then you have SNI support).
28312 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
28314 .cindex "multiple SMTP deliveries with TLS"
28315 .cindex "TLS" "multiple message deliveries"
28316 Exim sends multiple messages down the same TCP/IP connection by starting up
28317 an entirely new delivery process for each message, passing the socket from
28318 one process to the next. This implementation does not fit well with the use
28319 of TLS, because there is quite a lot of state information associated with a TLS
28320 connection, not just a socket identification. Passing all the state information
28321 to a new process is not feasible. Consequently, for sending using TLS Exim
28322 starts an additional proxy process for handling the encryption, piping the
28323 unencrypted data stream from and to the delivery processes.
28325 An older mode of operation can be enabled on a per-host basis by the
28326 &%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
28327 this list the proxy process described above is not used; instead Exim
28328 shuts down an existing TLS session being run by the delivery process
28329 before passing the socket to a new process. The new process may then
28330 try to start a new TLS session, and if successful, may try to re-authenticate
28331 if AUTH is in use, before sending the next message.
28333 The RFC is not clear as to whether or not an SMTP session continues in clear
28334 after TLS has been shut down, or whether TLS may be restarted again later, as
28335 just described. However, if the server is Exim, this shutdown and
28336 reinitialization works. It is not known which (if any) other servers operate
28337 successfully if the client closes a TLS session and continues with unencrypted
28338 SMTP, but there are certainly some that do not work. For such servers, Exim
28339 should not pass the socket to another process, because the failure of the
28340 subsequent attempt to use it would cause Exim to record a temporary host error,
28341 and delay other deliveries to that host.
28343 To test for this case, Exim sends an EHLO command to the server after
28344 closing down the TLS session. If this fails in any way, the connection is
28345 closed instead of being passed to a new delivery process, but no retry
28346 information is recorded.
28348 There is also a manual override; you can set &%hosts_nopass_tls%& on the
28349 &(smtp)& transport to match those hosts for which Exim should not pass
28350 connections to new processes if TLS has been used.
28355 .section "Certificates and all that" "SECTcerandall"
28356 .cindex "certificate" "references to discussion"
28357 In order to understand fully how TLS works, you need to know about
28358 certificates, certificate signing, and certificate authorities.
28359 This is a large topic and an introductory guide is unsuitable for the Exim
28360 reference manual, so instead we provide pointers to existing documentation.
28362 The Apache web-server was for a long time the canonical guide, so their
28363 documentation is a good place to start; their SSL module's Introduction
28364 document is currently at
28366 &url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html)
28368 and their FAQ is at
28370 &url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html)
28373 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
28374 0-201-61598-3) in 2001, contains both introductory and more in-depth
28376 More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&,
28377 published by Feisty Duck (ISBN 978-1907117046) in 2013 is good.
28378 Ivan is the author of the popular TLS testing tools at
28379 &url(https://www.ssllabs.com/).
28382 .section "Certificate chains" "SECID186"
28383 The file named by &%tls_certificate%& may contain more than one
28384 certificate. This is useful in the case where the certificate that is being
28385 sent is validated by an intermediate certificate which the other end does
28386 not have. Multiple certificates must be in the correct order in the file.
28387 First the host's certificate itself, then the first intermediate
28388 certificate to validate the issuer of the host certificate, then the next
28389 intermediate certificate to validate the issuer of the first intermediate
28390 certificate, and so on, until finally (optionally) the root certificate.
28391 The root certificate must already be trusted by the recipient for
28392 validation to succeed, of course, but if it's not preinstalled, sending the
28393 root certificate along with the rest makes it available for the user to
28394 install if the receiving end is a client MUA that can interact with a user.
28396 Note that certificates using MD5 are unlikely to work on today's Internet;
28397 even if your libraries allow loading them for use in Exim when acting as a
28398 server, increasingly clients will not accept such certificates. The error
28399 diagnostics in such a case can be frustratingly vague.
28403 .section "Self-signed certificates" "SECID187"
28404 .cindex "certificate" "self-signed"
28405 You can create a self-signed certificate using the &'req'& command provided
28406 with OpenSSL, like this:
28407 . ==== Do not shorten the duration here without reading and considering
28408 . ==== the text below. Please leave it at 9999 days.
28410 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
28413 &_file1_& and &_file2_& can be the same file; the key and the certificate are
28414 delimited and so can be identified independently. The &%-days%& option
28415 specifies a period for which the certificate is valid. The &%-nodes%& option is
28416 important: if you do not set it, the key is encrypted with a passphrase
28417 that you are prompted for, and any use that is made of the key causes more
28418 prompting for the passphrase. This is not helpful if you are going to use
28419 this certificate and key in an MTA, where prompting is not possible.
28421 . ==== I expect to still be working 26 years from now. The less technical
28422 . ==== debt I create, in terms of storing up trouble for my later years, the
28423 . ==== happier I will be then. We really have reached the point where we
28424 . ==== should start, at the very least, provoking thought and making folks
28425 . ==== pause before proceeding, instead of leaving all the fixes until two
28426 . ==== years before 2^31 seconds after the 1970 Unix epoch.
28428 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
28429 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
28430 the above command might produce a date in the past. Think carefully about
28431 the lifetime of the systems you're deploying, and either reduce the duration
28432 of the certificate or reconsider your platform deployment. (At time of
28433 writing, reducing the duration is the most likely choice, but the inexorable
28434 progression of time takes us steadily towards an era where this will not
28435 be a sensible resolution).
28437 A self-signed certificate made in this way is sufficient for testing, and
28438 may be adequate for all your requirements if you are mainly interested in
28439 encrypting transfers, and not in secure identification.
28441 However, many clients require that the certificate presented by the server be a
28442 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
28443 certificate. In this situation, the self-signed certificate described above
28444 must be installed on the client host as a trusted root &'certification
28445 authority'& (CA), and the certificate used by Exim must be a user certificate
28446 signed with that self-signed certificate.
28448 For information on creating self-signed CA certificates and using them to sign
28449 user certificates, see the &'General implementation overview'& chapter of the
28450 Open-source PKI book, available online at
28451 &url(https://sourceforge.net/projects/ospkibook/).
28452 .ecindex IIDencsmtp1
28453 .ecindex IIDencsmtp2
28457 .section DANE "SECDANE"
28459 DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
28460 it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
28461 operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
28462 you and the server still think you have an encrypted connection) and, if one of the "well known" set of
28463 Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
28464 certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
28466 What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
28467 that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
28468 by (a) is thought to be smaller than that of the set of root CAs.
28470 It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
28471 fail to pass on a server's STARTTLS.
28473 DANE scales better than having to maintain (and side-channel communicate) copies of server certificates
28474 for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
28475 client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
28477 DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
28478 that DNS lookups they do for the server have not been tampered with. The domain MX record applying
28479 to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
28481 2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
28482 3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
28484 There are no changes to Exim specific to server-side operation of DANE.
28485 Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
28486 in &_Local/Makefile_&.
28487 If it has been included, the macro "_HAVE_DANE" will be defined.
28489 The TLSA record for the server may have "certificate usage" of DANE-TA(2) or DANE-EE(3).
28490 These are the "Trust Anchor" and "End Entity" variants.
28491 The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
28492 (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
28493 this is appropriate for a single system, using a self-signed certificate.
28494 DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
28496 A private CA at simplest is just a self-signed certificate (with certain
28497 attributes) which is used to sign server certificates, but running one securely
28498 does require careful arrangement.
28499 With DANE-TA, as implemented in Exim and commonly in other MTAs,
28500 the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
28501 DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
28502 all of which point to a single TLSA record.
28503 DANE-TA and DANE-EE can both be used together.
28506 Our recommendation is to use DANE with a certificate from a public CA,
28507 because this enables a variety of strategies for remote clients to verify
28509 You can then publish information both via DANE and another technology,
28510 "MTA-STS", described below.
28512 When you use DANE-TA to publish trust anchor information, you ask entities
28513 outside your administrative control to trust the Certificate Authority for
28514 connections to you.
28515 If using a private CA then you should expect others to still apply the
28516 technical criteria they'd use for a public CA to your certificates.
28517 In particular, you should probably try to follow current best practices for CA
28518 operation around hash algorithms and key sizes.
28519 Do not expect other organizations to lower their security expectations just
28520 because a particular profile might be reasonable for your own internal use.
28522 When this text was last updated, this in practice means to avoid use of SHA-1
28523 and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
28524 than 4096, for interoperability); to use keyUsage fields correctly; to use
28525 random serial numbers.
28526 The list of requirements is subject to change as best practices evolve.
28527 If you're not already using a private CA, or it doesn't meet these
28528 requirements, then we encourage you to avoid all these issues and use a public
28529 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
28532 The TLSA record should have a Selector field of SPKI(1) and a Matching Type field of SHA2-512(2).
28534 At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
28535 is useful for quickly generating TLSA records; and commands like
28538 openssl x509 -in -pubkey -noout <certificate.pem \
28539 | openssl rsa -outform der -pubin 2>/dev/null \
28544 are workable for 4th-field hashes.
28546 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
28549 The Certificate issued by the CA published in the DANE-TA model should be
28550 issued using a strong hash algorithm.
28551 Exim, and importantly various other MTAs sending to you, will not
28552 re-enable hash algorithms which have been disabled by default in TLS
28554 This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
28555 interoperability (and probably the maximum too, in 2018).
28558 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
28559 be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
28560 default of requesting OCSP for all hosts is modified iff DANE is in use, to:
28563 hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
28564 {= {4}{$tls_out_tlsa_usage}} } \
28568 The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
28569 The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
28570 found. If the definition of &%hosts_request_ocsp%& includes the
28571 string "tls_out_tlsa_usage", they are re-expanded in time to
28572 control the OCSP request.
28574 This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
28575 those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
28578 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
28579 and &%dane_require_tls_ciphers%&.
28580 The require variant will result in failure if the target host is not DNSSEC-secured.
28582 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
28584 A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using dnssec.
28585 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
28586 will be required for the host. If it does not, the host will not
28587 be used; there is no fallback to non-DANE or non-TLS.
28589 If DANE is requested and usable, then the TLS cipher list configuration
28590 prefers to use the option &%dane_require_tls_ciphers%& and falls
28591 back to &%tls_require_ciphers%& only if that is unset.
28592 This lets you configure "decent crypto" for DANE and "better than nothing
28593 crypto" as the default. Note though that while GnuTLS lets the string control
28594 which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
28595 limited to ciphersuite constraints.
28597 If DANE is requested and useable (see above) the following transport options are ignored:
28601 tls_try_verify_hosts
28602 tls_verify_certificates
28604 tls_verify_cert_hostnames
28607 If DANE is not usable, whether requested or not, and CA-anchored
28608 verification evaluation is wanted, the above variables should be set appropriately.
28610 Currently the &%dnssec_request_domains%& must be active and &%dnssec_require_domains%& is ignored.
28612 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
28614 There is a new variable &$tls_out_dane$& which will have "yes" if
28615 verification succeeded using DANE and "no" otherwise (only useful
28616 in combination with events; see &<<CHAPevents>>&),
28617 and a new variable &$tls_out_tlsa_usage$& (detailed above).
28619 .cindex DANE reporting
28620 An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
28621 to achieve DANE-verified connection, if one was either requested and offered, or
28622 required. This is intended to support TLS-reporting as defined in
28623 &url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
28624 The &$event_data$& will be one of the Result Types defined in
28625 Section 4.3 of that document.
28627 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
28629 DANE is specified in published RFCs and decouples certificate authority trust
28630 selection from a "race to the bottom" of "you must trust everything for mail
28631 to get through". There is an alternative technology called MTA-STS, which
28632 instead publishes MX trust anchor information on an HTTPS website. At the
28633 time this text was last updated, MTA-STS was still a draft, not yet an RFC.
28634 Exim has no support for MTA-STS as a client, but Exim mail server operators
28635 can choose to publish information describing their TLS configuration using
28636 MTA-STS to let those clients who do use that protocol derive trust
28639 The MTA-STS design requires a certificate from a public Certificate Authority
28640 which is recognized by clients sending to you.
28641 That selection of which CAs are trusted by others is outside your control.
28643 The most interoperable course of action is probably to use
28644 &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
28645 renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
28646 records for DANE clients (such as Exim and Postfix) and to publish anchor
28647 information for MTA-STS as well. This is what is done for the &'exim.org'&
28648 domain itself (with caveats around occasionally broken MTA-STS because of
28649 incompatible specification changes prior to reaching RFC status).
28653 . ////////////////////////////////////////////////////////////////////////////
28654 . ////////////////////////////////////////////////////////////////////////////
28656 .chapter "Access control lists" "CHAPACL"
28657 .scindex IIDacl "&ACL;" "description"
28658 .cindex "control of incoming mail"
28659 .cindex "message" "controlling incoming"
28660 .cindex "policy control" "access control lists"
28661 Access Control Lists (ACLs) are defined in a separate section of the runtime
28662 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
28663 name, terminated by a colon. Here is a complete ACL section that contains just
28664 one very small ACL:
28668 accept hosts = one.host.only
28670 You can have as many lists as you like in the ACL section, and the order in
28671 which they appear does not matter. The lists are self-terminating.
28673 The majority of ACLs are used to control Exim's behaviour when it receives
28674 certain SMTP commands. This applies both to incoming TCP/IP connections, and
28675 when a local process submits a message using SMTP by specifying the &%-bs%&
28676 option. The most common use is for controlling which recipients are accepted
28677 in incoming messages. In addition, you can define an ACL that is used to check
28678 local non-SMTP messages. The default configuration file contains an example of
28679 a realistic ACL for checking RCPT commands. This is discussed in chapter
28680 &<<CHAPdefconfil>>&.
28683 .section "Testing ACLs" "SECID188"
28684 The &%-bh%& command line option provides a way of testing your ACL
28685 configuration locally by running a fake SMTP session with which you interact.
28688 .section "Specifying when ACLs are used" "SECID189"
28689 .cindex "&ACL;" "options for specifying"
28690 In order to cause an ACL to be used, you have to name it in one of the relevant
28691 options in the main part of the configuration. These options are:
28692 .cindex "AUTH" "ACL for"
28693 .cindex "DATA" "ACLs for"
28694 .cindex "ETRN" "ACL for"
28695 .cindex "EXPN" "ACL for"
28696 .cindex "HELO" "ACL for"
28697 .cindex "EHLO" "ACL for"
28698 .cindex "DKIM" "ACL for"
28699 .cindex "MAIL" "ACL for"
28700 .cindex "QUIT, ACL for"
28701 .cindex "RCPT" "ACL for"
28702 .cindex "STARTTLS, ACL for"
28703 .cindex "VRFY" "ACL for"
28704 .cindex "SMTP" "connection, ACL for"
28705 .cindex "non-SMTP messages" "ACLs for"
28706 .cindex "MIME content scanning" "ACL for"
28707 .cindex "PRDR" "ACL for"
28710 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
28711 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
28712 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
28713 .irow &%acl_smtp_auth%& "ACL for AUTH"
28714 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
28715 .irow &%acl_smtp_data%& "ACL after DATA is complete"
28716 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
28717 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
28718 .irow &%acl_smtp_etrn%& "ACL for ETRN"
28719 .irow &%acl_smtp_expn%& "ACL for EXPN"
28720 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
28721 .irow &%acl_smtp_mail%& "ACL for MAIL"
28722 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
28723 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
28724 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
28725 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
28726 .irow &%acl_smtp_quit%& "ACL for QUIT"
28727 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
28728 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
28729 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
28732 For example, if you set
28734 acl_smtp_rcpt = small_acl
28736 the little ACL defined above is used whenever Exim receives a RCPT command
28737 in an SMTP dialogue. The majority of policy tests on incoming messages can be
28738 done when RCPT commands arrive. A rejection of RCPT should cause the
28739 sending MTA to give up on the recipient address contained in the RCPT
28740 command, whereas rejection at other times may cause the client MTA to keep on
28741 trying to deliver the message. It is therefore recommended that you do as much
28742 testing as possible at RCPT time.
28745 .section "The non-SMTP ACLs" "SECID190"
28746 .cindex "non-SMTP messages" "ACLs for"
28747 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
28748 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
28749 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
28750 the state of the SMTP connection such as encryption and authentication) are not
28751 relevant and are forbidden in these ACLs. However, the sender and recipients
28752 are known, so the &%senders%& and &%sender_domains%& conditions and the
28753 &$sender_address$& and &$recipients$& variables can be used. Variables such as
28754 &$authenticated_sender$& are also available. You can specify added header lines
28755 in any of these ACLs.
28757 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
28758 non-SMTP message, before any of the message has been read. (This is the
28759 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
28760 batched SMTP input, it runs after the DATA command has been reached. The
28761 result of this ACL is ignored; it cannot be used to reject a message. If you
28762 really need to, you could set a value in an ACL variable here and reject based
28763 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
28764 controls, and in particular, it can be used to set
28766 control = suppress_local_fixups
28768 This cannot be used in the other non-SMTP ACLs because by the time they are
28769 run, it is too late.
28771 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
28772 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
28774 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
28775 kind of rejection is treated as permanent, because there is no way of sending a
28776 temporary error for these kinds of message.
28779 .section "The SMTP connect ACL" "SECID191"
28780 .cindex "SMTP" "connection, ACL for"
28781 .oindex &%smtp_banner%&
28782 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
28783 session, after the test specified by &%host_reject_connection%& (which is now
28784 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
28785 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
28786 the message override the banner message that is otherwise specified by the
28787 &%smtp_banner%& option.
28790 .section "The EHLO/HELO ACL" "SECID192"
28791 .cindex "EHLO" "ACL for"
28792 .cindex "HELO" "ACL for"
28793 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
28794 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
28795 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
28796 Note that a client may issue more than one EHLO or HELO command in an SMTP
28797 session, and indeed is required to issue a new EHLO or HELO after successfully
28798 setting up encryption following a STARTTLS command.
28800 Note also that a deny neither forces the client to go away nor means that
28801 mail will be refused on the connection. Consider checking for
28802 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
28804 If the command is accepted by an &%accept%& verb that has a &%message%&
28805 modifier, the message may not contain more than one line (it will be truncated
28806 at the first newline and a panic logged if it does). Such a message cannot
28807 affect the EHLO options that are listed on the second and subsequent lines of
28811 .section "The DATA ACLs" "SECID193"
28812 .cindex "DATA" "ACLs for"
28813 Two ACLs are associated with the DATA command, because it is two-stage
28814 command, with two responses being sent to the client.
28815 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
28816 is obeyed. This gives you control after all the RCPT commands, but before
28817 the message itself is received. It offers the opportunity to give a negative
28818 response to the DATA command before the data is transmitted. Header lines
28819 added by MAIL or RCPT ACLs are not visible at this time, but any that
28820 are defined here are visible when the &%acl_smtp_data%& ACL is run.
28822 You cannot test the contents of the message, for example, to verify addresses
28823 in the headers, at RCPT time or when the DATA command is received. Such
28824 tests have to appear in the ACL that is run after the message itself has been
28825 received, before the final response to the DATA command is sent. This is
28826 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
28827 associated with the DATA command.
28829 .cindex CHUNKING "BDAT command"
28830 .cindex BDAT "SMTP command"
28831 .cindex "RFC 3030" CHUNKING
28832 If CHUNKING was advertised and a BDAT command sequence is received,
28833 the &%acl_smtp_predata%& ACL is not run.
28834 . XXX why not? It should be possible, for the first BDAT.
28835 The &%acl_smtp_data%& is run after the last BDAT command and all of
28836 the data specified is received.
28838 For both of these ACLs, it is not possible to reject individual recipients. An
28839 error response rejects the entire message. Unfortunately, it is known that some
28840 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
28841 before or after the data) correctly &-- they keep the message on their queues
28842 and try again later, but that is their problem, though it does waste some of
28845 The &%acl_smtp_data%& ACL is run after
28846 the &%acl_smtp_data_prdr%&,
28847 the &%acl_smtp_dkim%&
28848 and the &%acl_smtp_mime%& ACLs.
28850 .section "The SMTP DKIM ACL" "SECTDKIMACL"
28851 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
28852 enabled (which is the default).
28854 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
28855 received, and is executed for each DKIM signature found in a message. If not
28856 otherwise specified, the default action is to accept.
28858 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
28860 For details on the operation of DKIM, see section &<<SECDKIM>>&.
28863 .section "The SMTP MIME ACL" "SECID194"
28864 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
28865 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
28867 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
28870 .section "The SMTP PRDR ACL" "SECTPRDRACL"
28871 .cindex "PRDR" "ACL for"
28872 .oindex "&%prdr_enable%&"
28873 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
28874 with PRDR support enabled (which is the default).
28875 It becomes active only when the PRDR feature is negotiated between
28876 client and server for a message, and more than one recipient
28879 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
28880 has been received, and is executed once for each recipient of the message
28881 with &$local_part$& and &$domain$& valid.
28882 The test may accept, defer or deny for individual recipients.
28883 The &%acl_smtp_data%& will still be called after this ACL and
28884 can reject the message overall, even if this ACL has accepted it
28885 for some or all recipients.
28887 PRDR may be used to support per-user content filtering. Without it
28888 one must defer any recipient after the first that has a different
28889 content-filter configuration. With PRDR, the RCPT-time check
28890 .cindex "PRDR" "variable for"
28891 for this can be disabled when the variable &$prdr_requested$&
28893 Any required difference in behaviour of the main DATA-time
28894 ACL should however depend on the PRDR-time ACL having run, as Exim
28895 will avoid doing so in some situations (e.g. single-recipient mails).
28897 See also the &%prdr_enable%& global option
28898 and the &%hosts_try_prdr%& smtp transport option.
28900 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
28901 If the ACL is not defined, processing completes as if
28902 the feature was not requested by the client.
28904 .section "The QUIT ACL" "SECTQUITACL"
28905 .cindex "QUIT, ACL for"
28906 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
28907 does not affect the response code to QUIT, which is always 221. Thus, the ACL
28908 does not in fact control any access.
28909 For this reason, it may only accept
28910 or warn as its final result.
28912 This ACL can be used for tasks such as custom logging at the end of an SMTP
28913 session. For example, you can use ACL variables in other ACLs to count
28914 messages, recipients, etc., and log the totals at QUIT time using one or
28915 more &%logwrite%& modifiers on a &%warn%& verb.
28917 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
28918 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
28920 You do not need to have a final &%accept%&, but if you do, you can use a
28921 &%message%& modifier to specify custom text that is sent as part of the 221
28924 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
28925 failure (for example, failure to open a log file, or when Exim is bombing out
28926 because it has detected an unrecoverable error), all SMTP commands from the
28927 client are given temporary error responses until QUIT is received or the
28928 connection is closed. In these special cases, the QUIT ACL does not run.
28931 .section "The not-QUIT ACL" "SECTNOTQUITACL"
28932 .vindex &$acl_smtp_notquit$&
28933 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
28934 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
28935 trouble, such as being unable to write to its log files, this ACL is not run,
28936 because it might try to do things (such as write to log files) that make the
28937 situation even worse.
28939 Like the QUIT ACL, this ACL is provided to make it possible to do customized
28940 logging or to gather statistics, and its outcome is ignored. The &%delay%&
28941 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
28944 .vindex &$smtp_notquit_reason$&
28945 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
28946 to a string that indicates the reason for the termination of the SMTP
28947 connection. The possible values are:
28949 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
28950 .irow &`bad-commands`& "Too many unknown or non-mail commands"
28951 .irow &`command-timeout`& "Timeout while reading SMTP commands"
28952 .irow &`connection-lost`& "The SMTP connection has been lost"
28953 .irow &`data-timeout`& "Timeout while reading message data"
28954 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
28955 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
28956 .irow &`signal-exit`& "SIGTERM or SIGINT"
28957 .irow &`synchronization-error`& "SMTP synchronization error"
28958 .irow &`tls-failed`& "TLS failed to start"
28960 In most cases when an SMTP connection is closed without having received QUIT,
28961 Exim sends an SMTP response message before actually closing the connection.
28962 With the exception of the &`acl-drop`& case, the default message can be
28963 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
28964 &%drop%& verb in another ACL, it is the message from the other ACL that is
28968 .section "Finding an ACL to use" "SECID195"
28969 .cindex "&ACL;" "finding which to use"
28970 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
28971 you can use different ACLs in different circumstances. For example,
28973 acl_smtp_rcpt = ${if ={25}{$interface_port} \
28974 {acl_check_rcpt} {acl_check_rcpt_submit} }
28976 In the default configuration file there are some example settings for
28977 providing an RFC 4409 message &"submission"& service on port 587 and
28978 an RFC 8314 &"submissions"& service on port 465. You can use a string
28979 expansion like this to choose an ACL for MUAs on these ports which is
28980 more appropriate for this purpose than the default ACL on port 25.
28982 The expanded string does not have to be the name of an ACL in the
28983 configuration file; there are other possibilities. Having expanded the
28984 string, Exim searches for an ACL as follows:
28987 If the string begins with a slash, Exim uses it as a filename, and reads its
28988 contents as an ACL. The lines are processed in the same way as lines in the
28989 Exim configuration file. In particular, continuation lines are supported, blank
28990 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
28991 If the file does not exist or cannot be read, an error occurs (typically
28992 causing a temporary failure of whatever caused the ACL to be run). For example:
28994 acl_smtp_data = /etc/acls/\
28995 ${lookup{$sender_host_address}lsearch\
28996 {/etc/acllist}{$value}{default}}
28998 This looks up an ACL file to use on the basis of the host's IP address, falling
28999 back to a default if the lookup fails. If an ACL is successfully read from a
29000 file, it is retained in memory for the duration of the Exim process, so that it
29001 can be re-used without having to re-read the file.
29003 If the string does not start with a slash, and does not contain any spaces,
29004 Exim searches the ACL section of the configuration for an ACL whose name
29005 matches the string.
29007 If no named ACL is found, or if the string contains spaces, Exim parses
29008 the string as an inline ACL. This can save typing in cases where you just
29009 want to have something like
29011 acl_smtp_vrfy = accept
29013 in order to allow free use of the VRFY command. Such a string may contain
29014 newlines; it is processed in the same way as an ACL that is read from a file.
29020 .section "ACL return codes" "SECID196"
29021 .cindex "&ACL;" "return codes"
29022 Except for the QUIT ACL, which does not affect the SMTP return code (see
29023 section &<<SECTQUITACL>>& above), the result of running an ACL is either
29024 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
29025 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
29026 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
29027 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
29028 This also causes a 4&'xx'& return code.
29030 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
29031 &"deny"&, because there is no mechanism for passing temporary errors to the
29032 submitters of non-SMTP messages.
29035 ACLs that are relevant to message reception may also return &"discard"&. This
29036 has the effect of &"accept"&, but causes either the entire message or an
29037 individual recipient address to be discarded. In other words, it is a
29038 blackholing facility. Use it with care.
29040 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
29041 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
29042 RCPT ACL is to discard just the one recipient address. If there are no
29043 recipients left when the message's data is received, the DATA ACL is not
29044 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
29045 remaining recipients. The &"discard"& return is not permitted for the
29046 &%acl_smtp_predata%& ACL.
29048 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
29049 is done on the address and the result determines the SMTP response.
29052 .cindex "&[local_scan()]& function" "when all recipients discarded"
29053 The &[local_scan()]& function is always run, even if there are no remaining
29054 recipients; it may create new recipients.
29058 .section "Unset ACL options" "SECID197"
29059 .cindex "&ACL;" "unset options"
29060 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
29061 all the same. &*Note*&: These defaults apply only when the relevant ACL is
29062 not defined at all. For any defined ACL, the default action when control
29063 reaches the end of the ACL statements is &"deny"&.
29065 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
29066 these two are ACLs that are used only for their side effects. They cannot be
29067 used to accept or reject anything.
29069 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
29070 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
29071 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
29072 when the ACL is not defined is &"accept"&.
29074 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
29075 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
29076 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
29077 messages over an SMTP connection. For an example, see the ACL in the default
29078 configuration file.
29083 .section "Data for message ACLs" "SECID198"
29084 .cindex "&ACL;" "data for message ACL"
29086 .vindex &$local_part$&
29087 .vindex &$sender_address$&
29088 .vindex &$sender_host_address$&
29089 .vindex &$smtp_command$&
29090 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
29091 that contain information about the host and the message's sender (for example,
29092 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
29093 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
29094 &$local_part$& are set from the argument address. The entire SMTP command
29095 is available in &$smtp_command$&.
29097 When an ACL for the AUTH parameter of MAIL is running, the variables that
29098 contain information about the host are set, but &$sender_address$& is not yet
29099 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
29102 .vindex "&$message_size$&"
29103 The &$message_size$& variable is set to the value of the SIZE parameter on
29104 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
29105 that parameter is not given. The value is updated to the true message size by
29106 the time the final DATA ACL is run (after the message data has been
29109 .vindex "&$rcpt_count$&"
29110 .vindex "&$recipients_count$&"
29111 The &$rcpt_count$& variable increases by one for each RCPT command received.
29112 The &$recipients_count$& variable increases by one each time a RCPT command is
29113 accepted, so while an ACL for RCPT is being processed, it contains the number
29114 of previously accepted recipients. At DATA time (for both the DATA ACLs),
29115 &$rcpt_count$& contains the total number of RCPT commands, and
29116 &$recipients_count$& contains the total number of accepted recipients.
29122 .section "Data for non-message ACLs" "SECTdatfornon"
29123 .cindex "&ACL;" "data for non-message ACL"
29124 .vindex &$smtp_command_argument$&
29125 .vindex &$smtp_command$&
29126 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
29127 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
29128 and the entire SMTP command is available in &$smtp_command$&.
29129 These variables can be tested using a &%condition%& condition. For example,
29130 here is an ACL for use with AUTH, which insists that either the session is
29131 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
29132 does not permit authentication methods that use cleartext passwords on
29133 unencrypted connections.
29136 accept encrypted = *
29137 accept condition = ${if eq{${uc:$smtp_command_argument}}\
29139 deny message = TLS encryption or CRAM-MD5 required
29141 (Another way of applying this restriction is to arrange for the authenticators
29142 that use cleartext passwords not to be advertised when the connection is not
29143 encrypted. You can use the generic &%server_advertise_condition%& authenticator
29144 option to do this.)
29148 .section "Format of an ACL" "SECID199"
29149 .cindex "&ACL;" "format of"
29150 .cindex "&ACL;" "verbs, definition of"
29151 An individual ACL consists of a number of statements. Each statement starts
29152 with a verb, optionally followed by a number of conditions and &"modifiers"&.
29153 Modifiers can change the way the verb operates, define error and log messages,
29154 set variables, insert delays, and vary the processing of accepted messages.
29156 If all the conditions are met, the verb is obeyed. The same condition may be
29157 used (with different arguments) more than once in the same statement. This
29158 provides a means of specifying an &"and"& conjunction between conditions. For
29161 deny dnslists = list1.example
29162 dnslists = list2.example
29164 If there are no conditions, the verb is always obeyed. Exim stops evaluating
29165 the conditions and modifiers when it reaches a condition that fails. What
29166 happens then depends on the verb (and in one case, on a special modifier). Not
29167 all the conditions make sense at every testing point. For example, you cannot
29168 test a sender address in the ACL that is run for a VRFY command.
29171 .section "ACL verbs" "SECID200"
29172 The ACL verbs are as follows:
29175 .cindex "&%accept%& ACL verb"
29176 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
29177 of the conditions are not met, what happens depends on whether &%endpass%&
29178 appears among the conditions (for syntax see below). If the failing condition
29179 is before &%endpass%&, control is passed to the next ACL statement; if it is
29180 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
29181 check a RCPT command:
29183 accept domains = +local_domains
29187 If the recipient domain does not match the &%domains%& condition, control
29188 passes to the next statement. If it does match, the recipient is verified, and
29189 the command is accepted if verification succeeds. However, if verification
29190 fails, the ACL yields &"deny"&, because the failing condition is after
29193 The &%endpass%& feature has turned out to be confusing to many people, so its
29194 use is not recommended nowadays. It is always possible to rewrite an ACL so
29195 that &%endpass%& is not needed, and it is no longer used in the default
29198 .cindex "&%message%& ACL modifier" "with &%accept%&"
29199 If a &%message%& modifier appears on an &%accept%& statement, its action
29200 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
29201 (when an &%accept%& verb either accepts or passes control to the next
29202 statement), &%message%& can be used to vary the message that is sent when an
29203 SMTP command is accepted. For example, in a RCPT ACL you could have:
29205 &`accept `&<&'some conditions'&>
29206 &` message = OK, I will allow you through today`&
29208 You can specify an SMTP response code, optionally followed by an &"extended
29209 response code"& at the start of the message, but the first digit must be the
29210 same as would be sent by default, which is 2 for an &%accept%& verb.
29212 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
29213 an error message that is used when access is denied. This behaviour is retained
29214 for backward compatibility, but current &"best practice"& is to avoid the use
29219 .cindex "&%defer%& ACL verb"
29220 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
29221 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
29222 &%defer%& is the same as &%deny%&, because there is no way of sending a
29223 temporary error. For a RCPT command, &%defer%& is much the same as using a
29224 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
29225 be used in any ACL, and even for a recipient it might be a simpler approach.
29229 .cindex "&%deny%& ACL verb"
29230 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
29231 the conditions are not met, control is passed to the next ACL statement. For
29234 deny dnslists = blackholes.mail-abuse.org
29236 rejects commands from hosts that are on a DNS black list.
29240 .cindex "&%discard%& ACL verb"
29241 &%discard%&: This verb behaves like &%accept%&, except that it returns
29242 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
29243 that are concerned with receiving messages. When all the conditions are true,
29244 the sending entity receives a &"success"& response. However, &%discard%& causes
29245 recipients to be discarded. If it is used in an ACL for RCPT, just the one
29246 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
29247 message's recipients are discarded. Recipients that are discarded before DATA
29248 do not appear in the log line when the &%received_recipients%& log selector is set.
29250 If the &%log_message%& modifier is set when &%discard%& operates,
29251 its contents are added to the line that is automatically written to the log.
29252 The &%message%& modifier operates exactly as it does for &%accept%&.
29256 .cindex "&%drop%& ACL verb"
29257 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
29258 forcibly closed after the 5&'xx'& error message has been sent. For example:
29260 drop message = I don't take more than 20 RCPTs
29261 condition = ${if > {$rcpt_count}{20}}
29263 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
29264 The connection is always dropped after sending a 550 response.
29267 .cindex "&%require%& ACL verb"
29268 &%require%&: If all the conditions are met, control is passed to the next ACL
29269 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
29270 example, when checking a RCPT command,
29272 require message = Sender did not verify
29275 passes control to subsequent statements only if the message's sender can be
29276 verified. Otherwise, it rejects the command. Note the positioning of the
29277 &%message%& modifier, before the &%verify%& condition. The reason for this is
29278 discussed in section &<<SECTcondmodproc>>&.
29281 .cindex "&%warn%& ACL verb"
29282 &%warn%&: If all the conditions are true, a line specified by the
29283 &%log_message%& modifier is written to Exim's main log. Control always passes
29284 to the next ACL statement. If any condition is false, the log line is not
29285 written. If an identical log line is requested several times in the same
29286 message, only one copy is actually written to the log. If you want to force
29287 duplicates to be written, use the &%logwrite%& modifier instead.
29289 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
29290 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
29291 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
29292 first failing condition. There is more about adding header lines in section
29293 &<<SECTaddheadacl>>&.
29295 If any condition on a &%warn%& statement cannot be completed (that is, there is
29296 some sort of defer), the log line specified by &%log_message%& is not written.
29297 This does not include the case of a forced failure from a lookup, which
29298 is considered to be a successful completion. After a defer, no further
29299 conditions or modifiers in the &%warn%& statement are processed. The incident
29300 is logged, and the ACL continues to be processed, from the next statement
29304 .vindex "&$acl_verify_message$&"
29305 When one of the &%warn%& conditions is an address verification that fails, the
29306 text of the verification failure message is in &$acl_verify_message$&. If you
29307 want this logged, you must set it up explicitly. For example:
29309 warn !verify = sender
29310 log_message = sender verify failed: $acl_verify_message
29314 At the end of each ACL there is an implicit unconditional &%deny%&.
29316 As you can see from the examples above, the conditions and modifiers are
29317 written one to a line, with the first one on the same line as the verb, and
29318 subsequent ones on following lines. If you have a very long condition, you can
29319 continue it onto several physical lines by the usual backslash continuation
29320 mechanism. It is conventional to align the conditions vertically.
29324 .section "ACL variables" "SECTaclvariables"
29325 .cindex "&ACL;" "variables"
29326 There are some special variables that can be set during ACL processing. They
29327 can be used to pass information between different ACLs, different invocations
29328 of the same ACL in the same SMTP connection, and between ACLs and the routers,
29329 transports, and filters that are used to deliver a message. The names of these
29330 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
29331 an underscore, but the remainder of the name can be any sequence of
29332 alphanumeric characters and underscores that you choose. There is no limit on
29333 the number of ACL variables. The two sets act as follows:
29335 The values of those variables whose names begin with &$acl_c$& persist
29336 throughout an SMTP connection. They are never reset. Thus, a value that is set
29337 while receiving one message is still available when receiving the next message
29338 on the same SMTP connection.
29340 The values of those variables whose names begin with &$acl_m$& persist only
29341 while a message is being received. They are reset afterwards. They are also
29342 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
29345 When a message is accepted, the current values of all the ACL variables are
29346 preserved with the message and are subsequently made available at delivery
29347 time. The ACL variables are set by a modifier called &%set%&. For example:
29349 accept hosts = whatever
29350 set acl_m4 = some value
29351 accept authenticated = *
29352 set acl_c_auth = yes
29354 &*Note*&: A leading dollar sign is not used when naming a variable that is to
29355 be set. If you want to set a variable without taking any action, you can use a
29356 &%warn%& verb without any other modifiers or conditions.
29358 .oindex &%strict_acl_vars%&
29359 What happens if a syntactically valid but undefined ACL variable is
29360 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
29361 false (the default), an empty string is substituted; if it is true, an
29362 error is generated.
29364 Versions of Exim before 4.64 have a limited set of numbered variables, but
29365 their names are compatible, so there is no problem with upgrading.
29368 .section "Condition and modifier processing" "SECTcondmodproc"
29369 .cindex "&ACL;" "conditions; processing"
29370 .cindex "&ACL;" "modifiers; processing"
29371 An exclamation mark preceding a condition negates its result. For example:
29373 deny domains = *.dom.example
29374 !verify = recipient
29376 causes the ACL to return &"deny"& if the recipient domain ends in
29377 &'dom.example'& and the recipient address cannot be verified. Sometimes
29378 negation can be used on the right-hand side of a condition. For example, these
29379 two statements are equivalent:
29381 deny hosts = !192.168.3.4
29382 deny !hosts = 192.168.3.4
29384 However, for many conditions (&%verify%& being a good example), only left-hand
29385 side negation of the whole condition is possible.
29387 The arguments of conditions and modifiers are expanded. A forced failure
29388 of an expansion causes a condition to be ignored, that is, it behaves as if the
29389 condition is true. Consider these two statements:
29391 accept senders = ${lookup{$host_name}lsearch\
29392 {/some/file}{$value}fail}
29393 accept senders = ${lookup{$host_name}lsearch\
29394 {/some/file}{$value}{}}
29396 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
29397 the returned list is searched, but if the lookup fails the behaviour is
29398 different in the two cases. The &%fail%& in the first statement causes the
29399 condition to be ignored, leaving no further conditions. The &%accept%& verb
29400 therefore succeeds. The second statement, however, generates an empty list when
29401 the lookup fails. No sender can match an empty list, so the condition fails,
29402 and therefore the &%accept%& also fails.
29404 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
29405 specify actions that are taken as the conditions for a statement are checked;
29406 others specify text for messages that are used when access is denied or a
29407 warning is generated. The &%control%& modifier affects the way an incoming
29408 message is handled.
29410 The positioning of the modifiers in an ACL statement is important, because the
29411 processing of a verb ceases as soon as its outcome is known. Only those
29412 modifiers that have already been encountered will take effect. For example,
29413 consider this use of the &%message%& modifier:
29415 require message = Can't verify sender
29417 message = Can't verify recipient
29419 message = This message cannot be used
29421 If sender verification fails, Exim knows that the result of the statement is
29422 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
29423 so its text is used as the error message. If sender verification succeeds, but
29424 recipient verification fails, the second message is used. If recipient
29425 verification succeeds, the third message becomes &"current"&, but is never used
29426 because there are no more conditions to cause failure.
29428 For the &%deny%& verb, on the other hand, it is always the last &%message%&
29429 modifier that is used, because all the conditions must be true for rejection to
29430 happen. Specifying more than one &%message%& modifier does not make sense, and
29431 the message can even be specified after all the conditions. For example:
29434 !senders = *@my.domain.example
29435 message = Invalid sender from client host
29437 The &"deny"& result does not happen until the end of the statement is reached,
29438 by which time Exim has set up the message.
29442 .section "ACL modifiers" "SECTACLmodi"
29443 .cindex "&ACL;" "modifiers; list of"
29444 The ACL modifiers are as follows:
29447 .vitem &*add_header*&&~=&~<&'text'&>
29448 This modifier specifies one or more header lines that are to be added to an
29449 incoming message, assuming, of course, that the message is ultimately
29450 accepted. For details, see section &<<SECTaddheadacl>>&.
29452 .vitem &*continue*&&~=&~<&'text'&>
29453 .cindex "&%continue%& ACL modifier"
29454 .cindex "database" "updating in ACL"
29455 This modifier does nothing of itself, and processing of the ACL always
29456 continues with the next condition or modifier. The value of &%continue%& is in
29457 the side effects of expanding its argument. Typically this could be used to
29458 update a database. It is really just a syntactic tidiness, to avoid having to
29459 write rather ugly lines like this:
29461 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
29463 Instead, all you need is
29465 &`continue = `&<&'some expansion'&>
29468 .vitem &*control*&&~=&~<&'text'&>
29469 .cindex "&%control%& ACL modifier"
29470 This modifier affects the subsequent processing of the SMTP connection or of an
29471 incoming message that is accepted. The effect of the first type of control
29472 lasts for the duration of the connection, whereas the effect of the second type
29473 lasts only until the current message has been received. The message-specific
29474 controls always apply to the whole message, not to individual recipients,
29475 even if the &%control%& modifier appears in a RCPT ACL.
29477 As there are now quite a few controls that can be applied, they are described
29478 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
29479 in several different ways. For example:
29481 . ==== As this is a nested list, any displays it contains must be indented
29482 . ==== as otherwise they are too far to the left. That comment applies only
29483 . ==== when xmlto and fop are used; formatting with sdop gets it right either
29487 It can be at the end of an &%accept%& statement:
29489 accept ...some conditions
29490 control = queue_only
29492 In this case, the control is applied when this statement yields &"accept"&, in
29493 other words, when the conditions are all true.
29496 It can be in the middle of an &%accept%& statement:
29498 accept ...some conditions...
29499 control = queue_only
29500 ...some more conditions...
29502 If the first set of conditions are true, the control is applied, even if the
29503 statement does not accept because one of the second set of conditions is false.
29504 In this case, some subsequent statement must yield &"accept"& for the control
29508 It can be used with &%warn%& to apply the control, leaving the
29509 decision about accepting or denying to a subsequent verb. For
29512 warn ...some conditions...
29516 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
29517 &%logwrite%&, so it does not add anything to the message and does not write a
29521 If you want to apply a control unconditionally, you can use it with a
29522 &%require%& verb. For example:
29524 require control = no_multiline_responses
29528 .vitem &*delay*&&~=&~<&'time'&>
29529 .cindex "&%delay%& ACL modifier"
29531 This modifier may appear in any ACL except notquit. It causes Exim to wait for
29532 the time interval before proceeding. However, when testing Exim using the
29533 &%-bh%& option, the delay is not actually imposed (an appropriate message is
29534 output instead). The time is given in the usual Exim notation, and the delay
29535 happens as soon as the modifier is processed. In an SMTP session, pending
29536 output is flushed before the delay is imposed.
29538 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
29541 deny ...some conditions...
29544 The delay happens if all the conditions are true, before the statement returns
29545 &"deny"&. Compare this with:
29548 ...some conditions...
29550 which waits for 30s before processing the conditions. The &%delay%& modifier
29551 can also be used with &%warn%& and together with &%control%&:
29553 warn ...some conditions...
29559 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
29560 responses to several commands are no longer buffered and sent in one packet (as
29561 they would normally be) because all output is flushed before imposing the
29562 delay. This optimization is disabled so that a number of small delays do not
29563 appear to the client as one large aggregated delay that might provoke an
29564 unwanted timeout. You can, however, disable output flushing for &%delay%& by
29565 using a &%control%& modifier to set &%no_delay_flush%&.
29569 .cindex "&%endpass%& ACL modifier"
29570 This modifier, which has no argument, is recognized only in &%accept%& and
29571 &%discard%& statements. It marks the boundary between the conditions whose
29572 failure causes control to pass to the next statement, and the conditions whose
29573 failure causes the ACL to return &"deny"&. This concept has proved to be
29574 confusing to some people, so the use of &%endpass%& is no longer recommended as
29575 &"best practice"&. See the description of &%accept%& above for more details.
29578 .vitem &*log_message*&&~=&~<&'text'&>
29579 .cindex "&%log_message%& ACL modifier"
29580 This modifier sets up a message that is used as part of the log message if the
29581 ACL denies access or a &%warn%& statement's conditions are true. For example:
29583 require log_message = wrong cipher suite $tls_in_cipher
29584 encrypted = DES-CBC3-SHA
29586 &%log_message%& is also used when recipients are discarded by &%discard%&. For
29589 &`discard `&<&'some conditions'&>
29590 &` log_message = Discarded $local_part@$domain because...`&
29592 When access is denied, &%log_message%& adds to any underlying error message
29593 that may exist because of a condition failure. For example, while verifying a
29594 recipient address, a &':fail:'& redirection might have already set up a
29597 The message may be defined before the conditions to which it applies, because
29598 the string expansion does not happen until Exim decides that access is to be
29599 denied. This means that any variables that are set by the condition are
29600 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
29601 variables are set after a DNS black list lookup succeeds. If the expansion of
29602 &%log_message%& fails, or if the result is an empty string, the modifier is
29605 .vindex "&$acl_verify_message$&"
29606 If you want to use a &%warn%& statement to log the result of an address
29607 verification, you can use &$acl_verify_message$& to include the verification
29610 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
29611 the start of the logged message. If the same warning log message is requested
29612 more than once while receiving a single email message, only one copy is
29613 actually logged. If you want to log multiple copies, use &%logwrite%& instead
29614 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
29615 is logged for a successful &%warn%& statement.
29617 If &%log_message%& is not present and there is no underlying error message (for
29618 example, from the failure of address verification), but &%message%& is present,
29619 the &%message%& text is used for logging rejections. However, if any text for
29620 logging contains newlines, only the first line is logged. In the absence of
29621 both &%log_message%& and &%message%&, a default built-in message is used for
29622 logging rejections.
29625 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
29626 .cindex "&%log_reject_target%& ACL modifier"
29627 .cindex "logging in ACL" "specifying which log"
29628 This modifier makes it possible to specify which logs are used for messages
29629 about ACL rejections. Its argument is a colon-separated list of words that can
29630 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
29631 may be empty, in which case a rejection is not logged at all. For example, this
29632 ACL fragment writes no logging information when access is denied:
29634 &`deny `&<&'some conditions'&>
29635 &` log_reject_target =`&
29637 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
29638 permanent and temporary rejections. Its effect lasts for the rest of the
29642 .vitem &*logwrite*&&~=&~<&'text'&>
29643 .cindex "&%logwrite%& ACL modifier"
29644 .cindex "logging in ACL" "immediate"
29645 This modifier writes a message to a log file as soon as it is encountered when
29646 processing an ACL. (Compare &%log_message%&, which, except in the case of
29647 &%warn%& and &%discard%&, is used only if the ACL statement denies
29648 access.) The &%logwrite%& modifier can be used to log special incidents in
29651 &`accept `&<&'some special conditions'&>
29652 &` control = freeze`&
29653 &` logwrite = froze message because ...`&
29655 By default, the message is written to the main log. However, it may begin
29656 with a colon, followed by a comma-separated list of log names, and then
29657 another colon, to specify exactly which logs are to be written. For
29660 logwrite = :main,reject: text for main and reject logs
29661 logwrite = :panic: text for panic log only
29665 .vitem &*message*&&~=&~<&'text'&>
29666 .cindex "&%message%& ACL modifier"
29667 This modifier sets up a text string that is expanded and used as a response
29668 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
29669 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
29670 there is some complication if &%endpass%& is involved; see the description of
29671 &%accept%& for details.)
29673 The expansion of the message happens at the time Exim decides that the ACL is
29674 to end, not at the time it processes &%message%&. If the expansion fails, or
29675 generates an empty string, the modifier is ignored. Here is an example where
29676 &%message%& must be specified first, because the ACL ends with a rejection if
29677 the &%hosts%& condition fails:
29679 require message = Host not recognized
29682 (Once a condition has failed, no further conditions or modifiers are
29685 .cindex "SMTP" "error codes"
29686 .oindex "&%smtp_banner%&
29687 For ACLs that are triggered by SMTP commands, the message is returned as part
29688 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
29689 is meaningful only for SMTP, as no message is returned when a non-SMTP message
29690 is accepted. In the case of the connect ACL, accepting with a message modifier
29691 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
29692 accept message may not contain more than one line (otherwise it will be
29693 truncated at the first newline and a panic logged), and it cannot affect the
29696 When SMTP is involved, the message may begin with an overriding response code,
29697 consisting of three digits optionally followed by an &"extended response code"&
29698 of the form &'n.n.n'&, each code being followed by a space. For example:
29700 deny message = 599 1.2.3 Host not welcome
29701 hosts = 192.168.34.0/24
29703 The first digit of the supplied response code must be the same as would be sent
29704 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
29705 access, but for the predata ACL, note that the default success code is 354, not
29708 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
29709 the message modifier cannot override the 221 response code.
29711 The text in a &%message%& modifier is literal; any quotes are taken as
29712 literals, but because the string is expanded, backslash escapes are processed
29713 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
29716 .vindex "&$acl_verify_message$&"
29717 For ACLs that are called by an &%acl =%& ACL condition, the message is
29718 stored in &$acl_verify_message$&, from which the calling ACL may use it.
29720 If &%message%& is used on a statement that verifies an address, the message
29721 specified overrides any message that is generated by the verification process.
29722 However, the original message is available in the variable
29723 &$acl_verify_message$&, so you can incorporate it into your message if you
29724 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
29725 routers to be passed back as part of the SMTP response, you should either not
29726 use a &%message%& modifier, or make use of &$acl_verify_message$&.
29728 For compatibility with previous releases of Exim, a &%message%& modifier that
29729 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
29730 modifier, but this usage is now deprecated. However, &%message%& acts only when
29731 all the conditions are true, wherever it appears in an ACL command, whereas
29732 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
29733 &%warn%& in an ACL that is not concerned with receiving a message, it has no
29737 .vitem &*queue*&&~=&~<&'text'&>
29738 .cindex "&%queue%& ACL modifier"
29739 .cindex "named queues" "selecting in ACL"
29740 This modifier specifies the use of a named queue for spool files
29742 It can only be used before the message is received (i.e. not in
29744 This could be used, for example, for known high-volume burst sources
29745 of traffic, or for quarantine of messages.
29746 Separate queue-runner processes will be needed for named queues.
29747 If the text after expansion is empty, the default queue is used.
29750 .vitem &*remove_header*&&~=&~<&'text'&>
29751 This modifier specifies one or more header names in a colon-separated list
29752 that are to be removed from an incoming message, assuming, of course, that
29753 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
29756 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
29757 .cindex "&%set%& ACL modifier"
29758 This modifier puts a value into one of the ACL variables (see section
29759 &<<SECTaclvariables>>&).
29762 .vitem &*udpsend*&&~=&~<&'parameters'&>
29763 .cindex "UDP communications"
29764 This modifier sends a UDP packet, for purposes such as statistics
29765 collection or behaviour monitoring. The parameters are expanded, and
29766 the result of the expansion must be a colon-separated list consisting
29767 of a destination server, port number, and the packet contents. The
29768 server can be specified as a host name or IPv4 or IPv6 address. The
29769 separator can be changed with the usual angle bracket syntax. For
29770 example, you might want to collect information on which hosts connect
29773 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
29774 $tod_zulu $sender_host_address
29781 .section "Use of the control modifier" "SECTcontrols"
29782 .cindex "&%control%& ACL modifier"
29783 The &%control%& modifier supports the following settings:
29786 .vitem &*control&~=&~allow_auth_unadvertised*&
29787 This modifier allows a client host to use the SMTP AUTH command even when it
29788 has not been advertised in response to EHLO. Furthermore, because there are
29789 apparently some really broken clients that do this, Exim will accept AUTH after
29790 HELO (rather than EHLO) when this control is set. It should be used only if you
29791 really need it, and you should limit its use to those broken clients that do
29792 not work without it. For example:
29794 warn hosts = 192.168.34.25
29795 control = allow_auth_unadvertised
29797 Normally, when an Exim server receives an AUTH command, it checks the name of
29798 the authentication mechanism that is given in the command to ensure that it
29799 matches an advertised mechanism. When this control is set, the check that a
29800 mechanism has been advertised is bypassed. Any configured mechanism can be used
29801 by the client. This control is permitted only in the connection and HELO ACLs.
29804 .vitem &*control&~=&~caseful_local_part*& &&&
29805 &*control&~=&~caselower_local_part*&
29806 .cindex "&ACL;" "case of local part in"
29807 .cindex "case of local parts"
29808 .vindex "&$local_part$&"
29809 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
29810 (that is, during RCPT processing). By default, the contents of &$local_part$&
29811 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
29812 any uppercase letters in the original local part are restored in &$local_part$&
29813 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
29816 These controls affect only the current recipient. Moreover, they apply only to
29817 local part handling that takes place directly in the ACL (for example, as a key
29818 in lookups). If a test to verify the recipient is obeyed, the case-related
29819 handling of the local part during the verification is controlled by the router
29820 configuration (see the &%caseful_local_part%& generic router option).
29822 This facility could be used, for example, to add a spam score to local parts
29823 containing upper case letters. For example, using &$acl_m4$& to accumulate the
29826 warn control = caseful_local_part
29827 set acl_m4 = ${eval:\
29829 ${if match{$local_part}{[A-Z]}{1}{0}}\
29831 control = caselower_local_part
29833 Notice that we put back the lower cased version afterwards, assuming that
29834 is what is wanted for subsequent tests.
29837 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
29838 .cindex "&ACL;" "cutthrough routing"
29839 .cindex "cutthrough" "requesting"
29840 This option requests delivery be attempted while the item is being received.
29842 The option is usable in the RCPT ACL.
29843 If enabled for a message received via smtp and routed to an smtp transport,
29844 and only one transport, interface, destination host and port combination
29845 is used for all recipients of the message,
29846 then the delivery connection is made while the receiving connection is open
29847 and data is copied from one to the other.
29849 An attempt to set this option for any recipient but the first
29850 for a mail will be quietly ignored.
29851 If a recipient-verify callout
29853 connection is subsequently
29854 requested in the same ACL it is held open and used for
29855 any subsequent recipients and the data,
29856 otherwise one is made after the initial RCPT ACL completes.
29858 Note that routers are used in verify mode,
29859 and cannot depend on content of received headers.
29860 Note also that headers cannot be
29861 modified by any of the post-data ACLs (DATA, MIME and DKIM).
29862 Headers may be modified by routers (subject to the above) and transports.
29863 The &'Received-By:'& header is generated as soon as the body reception starts,
29864 rather than the traditional time after the full message is received;
29865 this will affect the timestamp.
29867 All the usual ACLs are called; if one results in the message being
29868 rejected, all effort spent in delivery (including the costs on
29869 the ultimate destination) will be wasted.
29870 Note that in the case of data-time ACLs this includes the entire
29873 Cutthrough delivery is not supported via transport-filters or when DKIM signing
29874 of outgoing messages is done, because it sends data to the ultimate destination
29875 before the entire message has been received from the source.
29876 It is not supported for messages received with the SMTP PRDR
29880 Should the ultimate destination system positively accept or reject the mail,
29881 a corresponding indication is given to the source system and nothing is queued.
29882 If the item is successfully delivered in cutthrough mode
29883 the delivery log lines are tagged with ">>" rather than "=>" and appear
29884 before the acceptance "<=" line.
29886 If there is a temporary error the item is queued for later delivery in the
29888 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
29889 to the control; the default value is &"spool"& and the alternate value
29890 &"pass"& copies an SMTP defer response from the target back to the initiator
29891 and does not queue the message.
29892 Note that this is independent of any recipient verify conditions in the ACL.
29894 Delivery in this mode avoids the generation of a bounce mail to a
29896 sender when the destination system is doing content-scan based rejection.
29899 .vitem &*control&~=&~debug/*&<&'options'&>
29900 .cindex "&ACL;" "enabling debug logging"
29901 .cindex "debugging" "enabling from an ACL"
29902 This control turns on debug logging, almost as though Exim had been invoked
29903 with &`-d`&, with the output going to a new logfile in the usual logs directory,
29904 by default called &'debuglog'&.
29905 The filename can be adjusted with the &'tag'& option, which
29906 may access any variables already defined. The logging may be adjusted with
29907 the &'opts'& option, which takes the same values as the &`-d`& command-line
29909 Logging started this way may be stopped, and the file removed,
29910 with the &'kill'& option.
29911 Some examples (which depend on variables that don't exist in all
29915 control = debug/tag=.$sender_host_address
29916 control = debug/opts=+expand+acl
29917 control = debug/tag=.$message_exim_id/opts=+expand
29918 control = debug/kill
29922 .vitem &*control&~=&~dkim_disable_verify*&
29923 .cindex "disable DKIM verify"
29924 .cindex "DKIM" "disable verify"
29925 This control turns off DKIM verification processing entirely. For details on
29926 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
29929 .vitem &*control&~=&~dscp/*&<&'value'&>
29930 .cindex "&ACL;" "setting DSCP value"
29931 .cindex "DSCP" "inbound"
29932 This option causes the DSCP value associated with the socket for the inbound
29933 connection to be adjusted to a given value, given as one of a number of fixed
29934 strings or to numeric value.
29935 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
29936 Common values include &`throughput`&, &`mincost`&, and on newer systems
29937 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
29939 The outbound packets from Exim will be marked with this value in the header
29940 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
29941 that these values will have any effect, not be stripped by networking
29942 equipment, or do much of anything without cooperation with your Network
29943 Engineer and those of all network operators between the source and destination.
29946 .vitem &*control&~=&~enforce_sync*& &&&
29947 &*control&~=&~no_enforce_sync*&
29948 .cindex "SMTP" "synchronization checking"
29949 .cindex "synchronization checking in SMTP"
29950 These controls make it possible to be selective about when SMTP synchronization
29951 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
29952 state of the switch (it is true by default). See the description of this option
29953 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
29955 The effect of these two controls lasts for the remainder of the SMTP
29956 connection. They can appear in any ACL except the one for the non-SMTP
29957 messages. The most straightforward place to put them is in the ACL defined by
29958 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
29959 before the first synchronization check. The expected use is to turn off the
29960 synchronization checks for badly-behaved hosts that you nevertheless need to
29964 .vitem &*control&~=&~fakedefer/*&<&'message'&>
29965 .cindex "fake defer"
29966 .cindex "defer, fake"
29967 This control works in exactly the same way as &%fakereject%& (described below)
29968 except that it causes an SMTP 450 response after the message data instead of a
29969 550 response. You must take care when using &%fakedefer%& because it causes the
29970 messages to be duplicated when the sender retries. Therefore, you should not
29971 use &%fakedefer%& if the message is to be delivered normally.
29973 .vitem &*control&~=&~fakereject/*&<&'message'&>
29974 .cindex "fake rejection"
29975 .cindex "rejection, fake"
29976 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
29977 words, only when an SMTP message is being received. If Exim accepts the
29978 message, instead the final 250 response, a 550 rejection message is sent.
29979 However, Exim proceeds to deliver the message as normal. The control applies
29980 only to the current message, not to any subsequent ones that may be received in
29981 the same SMTP connection.
29983 The text for the 550 response is taken from the &%control%& modifier. If no
29984 message is supplied, the following is used:
29986 550-Your message has been rejected but is being
29987 550-kept for evaluation.
29988 550-If it was a legitimate message, it may still be
29989 550 delivered to the target recipient(s).
29991 This facility should be used with extreme caution.
29993 .vitem &*control&~=&~freeze*&
29994 .cindex "frozen messages" "forcing in ACL"
29995 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
29996 other words, only when a message is being received. If the message is accepted,
29997 it is placed on Exim's queue and frozen. The control applies only to the
29998 current message, not to any subsequent ones that may be received in the same
30001 This modifier can optionally be followed by &`/no_tell`&. If the global option
30002 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
30003 is told about the freezing), provided all the &*control=freeze*& modifiers that
30004 are obeyed for the current message have the &`/no_tell`& option.
30006 .vitem &*control&~=&~no_delay_flush*&
30007 .cindex "SMTP" "output flushing, disabling for delay"
30008 Exim normally flushes SMTP output before implementing a delay in an ACL, to
30009 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
30010 use. This control, as long as it is encountered before the &%delay%& modifier,
30011 disables such output flushing.
30013 .vitem &*control&~=&~no_callout_flush*&
30014 .cindex "SMTP" "output flushing, disabling for callout"
30015 Exim normally flushes SMTP output before performing a callout in an ACL, to
30016 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
30017 use. This control, as long as it is encountered before the &%verify%& condition
30018 that causes the callout, disables such output flushing.
30020 .vitem &*control&~=&~no_mbox_unspool*&
30021 This control is available when Exim is compiled with the content scanning
30022 extension. Content scanning may require a copy of the current message, or parts
30023 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
30024 or spam scanner. Normally, such copies are deleted when they are no longer
30025 needed. If this control is set, the copies are not deleted. The control applies
30026 only to the current message, not to any subsequent ones that may be received in
30027 the same SMTP connection. It is provided for debugging purposes and is unlikely
30028 to be useful in production.
30030 .vitem &*control&~=&~no_multiline_responses*&
30031 .cindex "multiline responses, suppressing"
30032 This control is permitted for any ACL except the one for non-SMTP messages.
30033 It seems that there are broken clients in use that cannot handle multiline
30034 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
30036 If this control is set, multiline SMTP responses from ACL rejections are
30037 suppressed. One way of doing this would have been to put out these responses as
30038 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
30039 (&"use multiline responses for more"& it says &-- ha!), and some of the
30040 responses might get close to that. So this facility, which is after all only a
30041 sop to broken clients, is implemented by doing two very easy things:
30044 Extra information that is normally output as part of a rejection caused by
30045 sender verification failure is omitted. Only the final line (typically &"sender
30046 verification failed"&) is sent.
30048 If a &%message%& modifier supplies a multiline response, only the first
30052 The setting of the switch can, of course, be made conditional on the
30053 calling host. Its effect lasts until the end of the SMTP connection.
30055 .vitem &*control&~=&~no_pipelining*&
30056 .cindex "PIPELINING" "suppressing advertising"
30057 This control turns off the advertising of the PIPELINING extension to SMTP in
30058 the current session. To be useful, it must be obeyed before Exim sends its
30059 response to an EHLO command. Therefore, it should normally appear in an ACL
30060 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
30061 &%pipelining_advertise_hosts%&.
30063 .vitem &*control&~=&~queue_only*&
30064 .oindex "&%queue_only%&"
30065 .cindex "queueing incoming messages"
30066 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
30067 other words, only when a message is being received. If the message is accepted,
30068 it is placed on Exim's queue and left there for delivery by a subsequent queue
30069 runner. No immediate delivery process is started. In other words, it has the
30070 effect as the &%queue_only%& global option. However, the control applies only
30071 to the current message, not to any subsequent ones that may be received in the
30072 same SMTP connection.
30074 .vitem &*control&~=&~submission/*&<&'options'&>
30075 .cindex "message" "submission"
30076 .cindex "submission mode"
30077 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
30078 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
30079 the current message is a submission from a local MUA. In this case, Exim
30080 operates in &"submission mode"&, and applies certain fixups to the message if
30081 necessary. For example, it adds a &'Date:'& header line if one is not present.
30082 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
30083 late (the message has already been created).
30085 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
30086 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
30087 submission mode; the available options for this control are described there.
30088 The control applies only to the current message, not to any subsequent ones
30089 that may be received in the same SMTP connection.
30091 .vitem &*control&~=&~suppress_local_fixups*&
30092 .cindex "submission fixups, suppressing"
30093 This control applies to locally submitted (non TCP/IP) messages, and is the
30094 complement of &`control = submission`&. It disables the fixups that are
30095 normally applied to locally-submitted messages. Specifically:
30098 Any &'Sender:'& header line is left alone (in this respect, it is a
30099 dynamic version of &%local_sender_retain%&).
30101 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
30103 There is no check that &'From:'& corresponds to the actual sender.
30106 This control may be useful when a remotely-originated message is accepted,
30107 passed to some scanning program, and then re-submitted for delivery. It can be
30108 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
30109 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
30112 &*Note:*& This control applies only to the current message, not to any others
30113 that are being submitted at the same time using &%-bs%& or &%-bS%&.
30115 .vitem &*control&~=&~utf8_downconvert*&
30116 This control enables conversion of UTF-8 in message addresses
30118 For details see section &<<SECTi18nMTA>>&.
30122 .section "Summary of message fixup control" "SECTsummesfix"
30123 All four possibilities for message fixups can be specified:
30126 Locally submitted, fixups applied: the default.
30128 Locally submitted, no fixups applied: use
30129 &`control = suppress_local_fixups`&.
30131 Remotely submitted, no fixups applied: the default.
30133 Remotely submitted, fixups applied: use &`control = submission`&.
30138 .section "Adding header lines in ACLs" "SECTaddheadacl"
30139 .cindex "header lines" "adding in an ACL"
30140 .cindex "header lines" "position of added lines"
30141 .cindex "&%add_header%& ACL modifier"
30142 The &%add_header%& modifier can be used to add one or more extra header lines
30143 to an incoming message, as in this example:
30145 warn dnslists = sbl.spamhaus.org : \
30146 dialup.mail-abuse.org
30147 add_header = X-blacklisted-at: $dnslist_domain
30149 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
30150 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
30151 receiving a message). The message must ultimately be accepted for
30152 &%add_header%& to have any significant effect. You can use &%add_header%& with
30153 any ACL verb, including &%deny%& (though this is potentially useful only in a
30156 Headers will not be added to the message if the modifier is used in
30157 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
30159 Leading and trailing newlines are removed from
30160 the data for the &%add_header%& modifier; if it then
30161 contains one or more newlines that
30162 are not followed by a space or a tab, it is assumed to contain multiple header
30163 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
30164 front of any line that is not a valid header line.
30166 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
30167 They are added to the message before processing the DATA and MIME ACLs.
30168 However, if an identical header line is requested more than once, only one copy
30169 is actually added to the message. Further header lines may be accumulated
30170 during the DATA and MIME ACLs, after which they are added to the message, again
30171 with duplicates suppressed. Thus, it is possible to add two identical header
30172 lines to an SMTP message, but only if one is added before DATA and one after.
30173 In the case of non-SMTP messages, new headers are accumulated during the
30174 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
30175 message is rejected after DATA or by the non-SMTP ACL, all added header lines
30176 are included in the entry that is written to the reject log.
30178 .cindex "header lines" "added; visibility of"
30179 Header lines are not visible in string expansions
30181 until they are added to the
30182 message. It follows that header lines defined in the MAIL, RCPT, and predata
30183 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
30184 header lines that are added by the DATA or MIME ACLs are not visible in those
30185 ACLs. Because of this restriction, you cannot use header lines as a way of
30186 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
30187 this, you can use ACL variables, as described in section
30188 &<<SECTaclvariables>>&.
30190 The list of headers yet to be added is given by the &%$headers_added%& variable.
30192 The &%add_header%& modifier acts immediately as it is encountered during the
30193 processing of an ACL. Notice the difference between these two cases:
30195 &`accept add_header = ADDED: some text`&
30196 &` `&<&'some condition'&>
30198 &`accept `&<&'some condition'&>
30199 &` add_header = ADDED: some text`&
30201 In the first case, the header line is always added, whether or not the
30202 condition is true. In the second case, the header line is added only if the
30203 condition is true. Multiple occurrences of &%add_header%& may occur in the same
30204 ACL statement. All those that are encountered before a condition fails are
30207 .cindex "&%warn%& ACL verb"
30208 For compatibility with previous versions of Exim, a &%message%& modifier for a
30209 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
30210 effect only if all the conditions are true, even if it appears before some of
30211 them. Furthermore, only the last occurrence of &%message%& is honoured. This
30212 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
30213 are present on a &%warn%& verb, both are processed according to their
30216 By default, new header lines are added to a message at the end of the existing
30217 header lines. However, you can specify that any particular header line should
30218 be added right at the start (before all the &'Received:'& lines), immediately
30219 after the first block of &'Received:'& lines, or immediately before any line
30220 that is not a &'Received:'& or &'Resent-something:'& header.
30222 This is done by specifying &":at_start:"&, &":after_received:"&, or
30223 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
30224 header line, respectively. (Header text cannot start with a colon, as there has
30225 to be a header name first.) For example:
30227 warn add_header = \
30228 :after_received:X-My-Header: something or other...
30230 If more than one header line is supplied in a single &%add_header%& modifier,
30231 each one is treated independently and can therefore be placed differently. If
30232 you add more than one line at the start, or after the Received: block, they end
30233 up in reverse order.
30235 &*Warning*&: This facility currently applies only to header lines that are
30236 added in an ACL. It does NOT work for header lines that are added in a
30237 system filter or in a router or transport.
30241 .section "Removing header lines in ACLs" "SECTremoveheadacl"
30242 .cindex "header lines" "removing in an ACL"
30243 .cindex "header lines" "position of removed lines"
30244 .cindex "&%remove_header%& ACL modifier"
30245 The &%remove_header%& modifier can be used to remove one or more header lines
30246 from an incoming message, as in this example:
30248 warn message = Remove internal headers
30249 remove_header = x-route-mail1 : x-route-mail2
30251 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
30252 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
30253 receiving a message). The message must ultimately be accepted for
30254 &%remove_header%& to have any significant effect. You can use &%remove_header%&
30255 with any ACL verb, including &%deny%&, though this is really not useful for
30256 any verb that doesn't result in a delivered message.
30258 Headers will not be removed from the message if the modifier is used in
30259 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
30261 More than one header can be removed at the same time by using a colon separated
30262 list of header names. The header matching is case insensitive. Wildcards are
30263 not permitted, nor is list expansion performed, so you cannot use hostlists to
30264 create a list of headers, however both connection and message variable expansion
30265 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
30267 warn hosts = +internal_hosts
30268 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
30269 warn message = Remove internal headers
30270 remove_header = $acl_c_ihdrs
30272 Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
30273 Matching header lines are removed from the message before processing the DATA and MIME ACLs.
30274 If multiple header lines match, all are removed.
30275 There is no harm in attempting to remove the same header twice nor in removing
30276 a non-existent header. Further header lines to be removed may be accumulated
30277 during the DATA and MIME ACLs, after which they are removed from the message,
30278 if present. In the case of non-SMTP messages, headers to be removed are
30279 accumulated during the non-SMTP ACLs, and are removed from the message after
30280 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
30281 ACL, there really is no effect because there is no logging of what headers
30282 would have been removed.
30284 .cindex "header lines" "removed; visibility of"
30285 Header lines are not visible in string expansions until the DATA phase when it
30286 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
30287 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
30288 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
30289 this restriction, you cannot use header lines as a way of controlling data
30290 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
30291 you should instead use ACL variables, as described in section
30292 &<<SECTaclvariables>>&.
30294 The &%remove_header%& modifier acts immediately as it is encountered during the
30295 processing of an ACL. Notice the difference between these two cases:
30297 &`accept remove_header = X-Internal`&
30298 &` `&<&'some condition'&>
30300 &`accept `&<&'some condition'&>
30301 &` remove_header = X-Internal`&
30303 In the first case, the header line is always removed, whether or not the
30304 condition is true. In the second case, the header line is removed only if the
30305 condition is true. Multiple occurrences of &%remove_header%& may occur in the
30306 same ACL statement. All those that are encountered before a condition fails
30309 &*Warning*&: This facility currently applies only to header lines that are
30310 present during ACL processing. It does NOT remove header lines that are added
30311 in a system filter or in a router or transport.
30316 .section "ACL conditions" "SECTaclconditions"
30317 .cindex "&ACL;" "conditions; list of"
30318 Some of the conditions listed in this section are available only when Exim is
30319 compiled with the content-scanning extension. They are included here briefly
30320 for completeness. More detailed descriptions can be found in the discussion on
30321 content scanning in chapter &<<CHAPexiscan>>&.
30323 Not all conditions are relevant in all circumstances. For example, testing
30324 senders and recipients does not make sense in an ACL that is being run as the
30325 result of the arrival of an ETRN command, and checks on message headers can be
30326 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
30327 can use the same condition (with different parameters) more than once in the
30328 same ACL statement. This provides a way of specifying an &"and"& conjunction.
30329 The conditions are as follows:
30333 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
30334 .cindex "&ACL;" "nested"
30335 .cindex "&ACL;" "indirect"
30336 .cindex "&ACL;" "arguments"
30337 .cindex "&%acl%& ACL condition"
30338 The possible values of the argument are the same as for the
30339 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
30340 &"accept"& the condition is true; if it returns &"deny"& the condition is
30341 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
30342 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
30343 condition false. This means that further processing of the &%warn%& verb
30344 ceases, but processing of the ACL continues.
30346 If the argument is a named ACL, up to nine space-separated optional values
30347 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
30348 and $acl_narg is set to the count of values.
30349 Previous values of these variables are restored after the call returns.
30350 The name and values are expanded separately.
30351 Note that spaces in complex expansions which are used as arguments
30352 will act as argument separators.
30354 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
30355 the connection is dropped. If it returns &"discard"&, the verb must be
30356 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
30357 conditions are tested.
30359 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
30360 loops. This condition allows you to use different ACLs in different
30361 circumstances. For example, different ACLs can be used to handle RCPT commands
30362 for different local users or different local domains.
30364 .vitem &*authenticated&~=&~*&<&'string&~list'&>
30365 .cindex "&%authenticated%& ACL condition"
30366 .cindex "authentication" "ACL checking"
30367 .cindex "&ACL;" "testing for authentication"
30368 If the SMTP connection is not authenticated, the condition is false. Otherwise,
30369 the name of the authenticator is tested against the list. To test for
30370 authentication by any authenticator, you can set
30375 .vitem &*condition&~=&~*&<&'string'&>
30376 .cindex "&%condition%& ACL condition"
30377 .cindex "customizing" "ACL condition"
30378 .cindex "&ACL;" "customized test"
30379 .cindex "&ACL;" "testing, customized"
30380 This feature allows you to make up custom conditions. If the result of
30381 expanding the string is an empty string, the number zero, or one of the strings
30382 &"no"& or &"false"&, the condition is false. If the result is any non-zero
30383 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
30384 any other value, some error is assumed to have occurred, and the ACL returns
30385 &"defer"&. However, if the expansion is forced to fail, the condition is
30386 ignored. The effect is to treat it as true, whether it is positive or
30389 .vitem &*decode&~=&~*&<&'location'&>
30390 .cindex "&%decode%& ACL condition"
30391 This condition is available only when Exim is compiled with the
30392 content-scanning extension, and it is allowed only in the ACL defined by
30393 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
30394 If all goes well, the condition is true. It is false only if there are
30395 problems such as a syntax error or a memory shortage. For more details, see
30396 chapter &<<CHAPexiscan>>&.
30398 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
30399 .cindex "&%dnslists%& ACL condition"
30400 .cindex "DNS list" "in ACL"
30401 .cindex "black list (DNS)"
30402 .cindex "&ACL;" "testing a DNS list"
30403 This condition checks for entries in DNS black lists. These are also known as
30404 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
30405 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
30406 different variants of this condition to describe briefly here. See sections
30407 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
30409 .vitem &*domains&~=&~*&<&'domain&~list'&>
30410 .cindex "&%domains%& ACL condition"
30411 .cindex "domain" "ACL checking"
30412 .cindex "&ACL;" "testing a recipient domain"
30413 .vindex "&$domain_data$&"
30414 This condition is relevant only after a RCPT command. It checks that the domain
30415 of the recipient address is in the domain list. If percent-hack processing is
30416 enabled, it is done before this test is done. If the check succeeds with a
30417 lookup, the result of the lookup is placed in &$domain_data$& until the next
30420 &*Note carefully*& (because many people seem to fall foul of this): you cannot
30421 use &%domains%& in a DATA ACL.
30424 .vitem &*encrypted&~=&~*&<&'string&~list'&>
30425 .cindex "&%encrypted%& ACL condition"
30426 .cindex "encryption" "checking in an ACL"
30427 .cindex "&ACL;" "testing for encryption"
30428 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
30429 name of the cipher suite in use is tested against the list. To test for
30430 encryption without testing for any specific cipher suite(s), set
30436 .vitem &*hosts&~=&~*&<&'host&~list'&>
30437 .cindex "&%hosts%& ACL condition"
30438 .cindex "host" "ACL checking"
30439 .cindex "&ACL;" "testing the client host"
30440 This condition tests that the calling host matches the host list. If you have
30441 name lookups or wildcarded host names and IP addresses in the same host list,
30442 you should normally put the IP addresses first. For example, you could have:
30444 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
30446 The lookup in this example uses the host name for its key. This is implied by
30447 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
30448 and it wouldn't matter which way round you had these two items.)
30450 The reason for the problem with host names lies in the left-to-right way that
30451 Exim processes lists. It can test IP addresses without doing any DNS lookups,
30452 but when it reaches an item that requires a host name, it fails if it cannot
30453 find a host name to compare with the pattern. If the above list is given in the
30454 opposite order, the &%accept%& statement fails for a host whose name cannot be
30455 found, even if its IP address is 10.9.8.7.
30457 If you really do want to do the name check first, and still recognize the IP
30458 address even if the name lookup fails, you can rewrite the ACL like this:
30460 accept hosts = dbm;/etc/friendly/hosts
30461 accept hosts = 10.9.8.7
30463 The default action on failing to find the host name is to assume that the host
30464 is not in the list, so the first &%accept%& statement fails. The second
30465 statement can then check the IP address.
30467 .vindex "&$host_data$&"
30468 If a &%hosts%& condition is satisfied by means of a lookup, the result
30469 of the lookup is made available in the &$host_data$& variable. This
30470 allows you, for example, to set up a statement like this:
30472 deny hosts = net-lsearch;/some/file
30473 message = $host_data
30475 which gives a custom error message for each denied host.
30477 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
30478 .cindex "&%local_parts%& ACL condition"
30479 .cindex "local part" "ACL checking"
30480 .cindex "&ACL;" "testing a local part"
30481 .vindex "&$local_part_data$&"
30482 This condition is relevant only after a RCPT command. It checks that the local
30483 part of the recipient address is in the list. If percent-hack processing is
30484 enabled, it is done before this test. If the check succeeds with a lookup, the
30485 result of the lookup is placed in &$local_part_data$&, which remains set until
30486 the next &%local_parts%& test.
30488 .vitem &*malware&~=&~*&<&'option'&>
30489 .cindex "&%malware%& ACL condition"
30490 .cindex "&ACL;" "virus scanning"
30491 .cindex "&ACL;" "scanning for viruses"
30492 This condition is available only when Exim is compiled with the
30493 content-scanning extension. It causes the incoming message to be scanned for
30494 viruses. For details, see chapter &<<CHAPexiscan>>&.
30496 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
30497 .cindex "&%mime_regex%& ACL condition"
30498 .cindex "&ACL;" "testing by regex matching"
30499 This condition is available only when Exim is compiled with the
30500 content-scanning extension, and it is allowed only in the ACL defined by
30501 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
30502 with any of the regular expressions. For details, see chapter
30505 .vitem &*ratelimit&~=&~*&<&'parameters'&>
30506 .cindex "rate limiting"
30507 This condition can be used to limit the rate at which a user or host submits
30508 messages. Details are given in section &<<SECTratelimiting>>&.
30510 .vitem &*recipients&~=&~*&<&'address&~list'&>
30511 .cindex "&%recipients%& ACL condition"
30512 .cindex "recipient" "ACL checking"
30513 .cindex "&ACL;" "testing a recipient"
30514 This condition is relevant only after a RCPT command. It checks the entire
30515 recipient address against a list of recipients.
30517 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
30518 .cindex "&%regex%& ACL condition"
30519 .cindex "&ACL;" "testing by regex matching"
30520 This condition is available only when Exim is compiled with the
30521 content-scanning extension, and is available only in the DATA, MIME, and
30522 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
30523 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
30525 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
30526 .cindex "&%sender_domains%& ACL condition"
30527 .cindex "sender" "ACL checking"
30528 .cindex "&ACL;" "testing a sender domain"
30529 .vindex "&$domain$&"
30530 .vindex "&$sender_address_domain$&"
30531 This condition tests the domain of the sender of the message against the given
30532 domain list. &*Note*&: The domain of the sender address is in
30533 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
30534 of this condition. This is an exception to the general rule for testing domain
30535 lists. It is done this way so that, if this condition is used in an ACL for a
30536 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
30537 influence the sender checking.
30539 &*Warning*&: It is a bad idea to use this condition on its own as a control on
30540 relaying, because sender addresses are easily, and commonly, forged.
30542 .vitem &*senders&~=&~*&<&'address&~list'&>
30543 .cindex "&%senders%& ACL condition"
30544 .cindex "sender" "ACL checking"
30545 .cindex "&ACL;" "testing a sender"
30546 This condition tests the sender of the message against the given list. To test
30547 for a bounce message, which has an empty sender, set
30551 &*Warning*&: It is a bad idea to use this condition on its own as a control on
30552 relaying, because sender addresses are easily, and commonly, forged.
30554 .vitem &*spam&~=&~*&<&'username'&>
30555 .cindex "&%spam%& ACL condition"
30556 .cindex "&ACL;" "scanning for spam"
30557 This condition is available only when Exim is compiled with the
30558 content-scanning extension. It causes the incoming message to be scanned by
30559 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
30561 .vitem &*verify&~=&~certificate*&
30562 .cindex "&%verify%& ACL condition"
30563 .cindex "TLS" "client certificate verification"
30564 .cindex "certificate" "verification of client"
30565 .cindex "&ACL;" "certificate verification"
30566 .cindex "&ACL;" "testing a TLS certificate"
30567 This condition is true in an SMTP session if the session is encrypted, and a
30568 certificate was received from the client, and the certificate was verified. The
30569 server requests a certificate only if the client matches &%tls_verify_hosts%&
30570 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
30572 .vitem &*verify&~=&~csa*&
30573 .cindex "CSA verification"
30574 This condition checks whether the sending host (the client) is authorized to
30575 send email. Details of how this works are given in section
30576 &<<SECTverifyCSA>>&.
30578 .vitem &*verify&~=&~header_names_ascii*&
30579 .cindex "&%verify%& ACL condition"
30580 .cindex "&ACL;" "verifying header names only ASCII"
30581 .cindex "header lines" "verifying header names only ASCII"
30582 .cindex "verifying" "header names only ASCII"
30583 This condition is relevant only in an ACL that is run after a message has been
30584 received, that is, in an ACL specified by &%acl_smtp_data%& or
30585 &%acl_not_smtp%&. It checks all header names (not the content) to make sure
30586 there are no non-ASCII characters, also excluding control characters. The
30587 allowable characters are decimal ASCII values 33 through 126.
30589 Exim itself will handle headers with non-ASCII characters, but it can cause
30590 problems for downstream applications, so this option will allow their
30591 detection and rejection in the DATA ACL's.
30593 .vitem &*verify&~=&~header_sender/*&<&'options'&>
30594 .cindex "&%verify%& ACL condition"
30595 .cindex "&ACL;" "verifying sender in the header"
30596 .cindex "header lines" "verifying the sender in"
30597 .cindex "sender" "verifying in header"
30598 .cindex "verifying" "sender in header"
30599 This condition is relevant only in an ACL that is run after a message has been
30600 received, that is, in an ACL specified by &%acl_smtp_data%& or
30601 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
30602 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
30603 is loosely thought of as a &"sender"& address (hence the name of the test).
30604 However, an address that appears in one of these headers need not be an address
30605 that accepts bounce messages; only sender addresses in envelopes are required
30606 to accept bounces. Therefore, if you use the callout option on this check, you
30607 might want to arrange for a non-empty address in the MAIL command.
30609 Details of address verification and the options are given later, starting at
30610 section &<<SECTaddressverification>>& (callouts are described in section
30611 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
30612 condition to restrict it to bounce messages only:
30615 message = A valid sender header is required for bounces
30616 !verify = header_sender
30619 .vitem &*verify&~=&~header_syntax*&
30620 .cindex "&%verify%& ACL condition"
30621 .cindex "&ACL;" "verifying header syntax"
30622 .cindex "header lines" "verifying syntax"
30623 .cindex "verifying" "header syntax"
30624 This condition is relevant only in an ACL that is run after a message has been
30625 received, that is, in an ACL specified by &%acl_smtp_data%& or
30626 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
30627 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
30628 and &'Bcc:'&), returning true if there are no problems.
30629 Unqualified addresses (local parts without domains) are
30630 permitted only in locally generated messages and from hosts that match
30631 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
30634 Note that this condition is a syntax check only. However, a common spamming
30635 ploy used to be to send syntactically invalid headers such as
30639 and this condition can be used to reject such messages, though they are not as
30640 common as they used to be.
30642 .vitem &*verify&~=&~helo*&
30643 .cindex "&%verify%& ACL condition"
30644 .cindex "&ACL;" "verifying HELO/EHLO"
30645 .cindex "HELO" "verifying"
30646 .cindex "EHLO" "verifying"
30647 .cindex "verifying" "EHLO"
30648 .cindex "verifying" "HELO"
30649 This condition is true if a HELO or EHLO command has been received from the
30650 client host, and its contents have been verified. If there has been no previous
30651 attempt to verify the HELO/EHLO contents, it is carried out when this
30652 condition is encountered. See the description of the &%helo_verify_hosts%& and
30653 &%helo_try_verify_hosts%& options for details of how to request verification
30654 independently of this condition.
30656 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
30657 option), this condition is always true.
30660 .vitem &*verify&~=&~not_blind*&
30661 .cindex "verifying" "not blind"
30662 .cindex "bcc recipients, verifying none"
30663 This condition checks that there are no blind (bcc) recipients in the message.
30664 Every envelope recipient must appear either in a &'To:'& header line or in a
30665 &'Cc:'& header line for this condition to be true. Local parts are checked
30666 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
30667 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
30668 used only in a DATA or non-SMTP ACL.
30670 There are, of course, many legitimate messages that make use of blind (bcc)
30671 recipients. This check should not be used on its own for blocking messages.
30674 .vitem &*verify&~=&~recipient/*&<&'options'&>
30675 .cindex "&%verify%& ACL condition"
30676 .cindex "&ACL;" "verifying recipient"
30677 .cindex "recipient" "verifying"
30678 .cindex "verifying" "recipient"
30679 .vindex "&$address_data$&"
30680 This condition is relevant only after a RCPT command. It verifies the current
30681 recipient. Details of address verification are given later, starting at section
30682 &<<SECTaddressverification>>&. After a recipient has been verified, the value
30683 of &$address_data$& is the last value that was set while routing the address.
30684 This applies even if the verification fails. When an address that is being
30685 verified is redirected to a single address, verification continues with the new
30686 address, and in that case, the subsequent value of &$address_data$& is the
30687 value for the child address.
30689 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
30690 .cindex "&%verify%& ACL condition"
30691 .cindex "&ACL;" "verifying host reverse lookup"
30692 .cindex "host" "verifying reverse lookup"
30693 This condition ensures that a verified host name has been looked up from the IP
30694 address of the client host. (This may have happened already if the host name
30695 was needed for checking a host list, or if the host matched &%host_lookup%&.)
30696 Verification ensures that the host name obtained from a reverse DNS lookup, or
30697 one of its aliases, does, when it is itself looked up in the DNS, yield the
30698 original IP address.
30700 There is one possible option, &`defer_ok`&. If this is present and a
30701 DNS operation returns a temporary error, the verify condition succeeds.
30703 If this condition is used for a locally generated message (that is, when there
30704 is no client host involved), it always succeeds.
30706 .vitem &*verify&~=&~sender/*&<&'options'&>
30707 .cindex "&%verify%& ACL condition"
30708 .cindex "&ACL;" "verifying sender"
30709 .cindex "sender" "verifying"
30710 .cindex "verifying" "sender"
30711 This condition is relevant only after a MAIL or RCPT command, or after a
30712 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
30713 the message's sender is empty (that is, this is a bounce message), the
30714 condition is true. Otherwise, the sender address is verified.
30716 .vindex "&$address_data$&"
30717 .vindex "&$sender_address_data$&"
30718 If there is data in the &$address_data$& variable at the end of routing, its
30719 value is placed in &$sender_address_data$& at the end of verification. This
30720 value can be used in subsequent conditions and modifiers in the same ACL
30721 statement. It does not persist after the end of the current statement. If you
30722 want to preserve the value for longer, you can save it in an ACL variable.
30724 Details of verification are given later, starting at section
30725 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
30726 to avoid doing it more than once per message.
30728 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
30729 .cindex "&%verify%& ACL condition"
30730 This is a variation of the previous option, in which a modified address is
30731 verified as a sender.
30733 Note that '/' is legal in local-parts; if the address may have such
30734 (eg. is generated from the received message)
30735 they must be protected from the options parsing by doubling:
30737 verify = sender=${sg{${address:$h_sender:}}{/}{//}}
30743 .section "Using DNS lists" "SECTmorednslists"
30744 .cindex "DNS list" "in ACL"
30745 .cindex "black list (DNS)"
30746 .cindex "&ACL;" "testing a DNS list"
30747 In its simplest form, the &%dnslists%& condition tests whether the calling host
30748 is on at least one of a number of DNS lists by looking up the inverted IP
30749 address in one or more DNS domains. (Note that DNS list domains are not mail
30750 domains, so the &`+`& syntax for named lists doesn't work - it is used for
30751 special options instead.) For example, if the calling host's IP
30752 address is 192.168.62.43, and the ACL statement is
30754 deny dnslists = blackholes.mail-abuse.org : \
30755 dialups.mail-abuse.org
30757 the following records are looked up:
30759 43.62.168.192.blackholes.mail-abuse.org
30760 43.62.168.192.dialups.mail-abuse.org
30762 As soon as Exim finds an existing DNS record, processing of the list stops.
30763 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
30764 to test that a host is on more than one list (an &"and"& conjunction), you can
30765 use two separate conditions:
30767 deny dnslists = blackholes.mail-abuse.org
30768 dnslists = dialups.mail-abuse.org
30770 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
30771 behaves as if the host does not match the list item, that is, as if the DNS
30772 record does not exist. If there are further items in the DNS list, they are
30775 This is usually the required action when &%dnslists%& is used with &%deny%&
30776 (which is the most common usage), because it prevents a DNS failure from
30777 blocking mail. However, you can change this behaviour by putting one of the
30778 following special items in the list:
30780 &`+include_unknown `& behave as if the item is on the list
30781 &`+exclude_unknown `& behave as if the item is not on the list (default)
30782 &`+defer_unknown `& give a temporary error
30784 .cindex "&`+include_unknown`&"
30785 .cindex "&`+exclude_unknown`&"
30786 .cindex "&`+defer_unknown`&"
30787 Each of these applies to any subsequent items on the list. For example:
30789 deny dnslists = +defer_unknown : foo.bar.example
30791 Testing the list of domains stops as soon as a match is found. If you want to
30792 warn for one list and block for another, you can use two different statements:
30794 deny dnslists = blackholes.mail-abuse.org
30795 warn message = X-Warn: sending host is on dialups list
30796 dnslists = dialups.mail-abuse.org
30798 .cindex caching "of dns lookup"
30800 DNS list lookups are cached by Exim for the duration of the SMTP session
30801 (but limited by the DNS return TTL value),
30802 so a lookup based on the IP address is done at most once for any incoming
30803 connection (assuming long-enough TTL).
30804 Exim does not share information between multiple incoming
30805 connections (but your local name server cache should be active).
30807 There are a number of DNS lists to choose from, some commercial, some free,
30808 or free for small deployments. An overview can be found at
30809 &url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists).
30813 .section "Specifying the IP address for a DNS list lookup" "SECID201"
30814 .cindex "DNS list" "keyed by explicit IP address"
30815 By default, the IP address that is used in a DNS list lookup is the IP address
30816 of the calling host. However, you can specify another IP address by listing it
30817 after the domain name, introduced by a slash. For example:
30819 deny dnslists = black.list.tld/192.168.1.2
30821 This feature is not very helpful with explicit IP addresses; it is intended for
30822 use with IP addresses that are looked up, for example, the IP addresses of the
30823 MX hosts or nameservers of an email sender address. For an example, see section
30824 &<<SECTmulkeyfor>>& below.
30829 .section "DNS lists keyed on domain names" "SECID202"
30830 .cindex "DNS list" "keyed by domain name"
30831 There are some lists that are keyed on domain names rather than inverted IP
30832 addresses (see, e.g., the &'domain based zones'& link at
30833 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
30834 with these lists. You can change the name that is looked up in a DNS list by
30835 listing it after the domain name, introduced by a slash. For example,
30837 deny message = Sender's domain is listed at $dnslist_domain
30838 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
30840 This particular example is useful only in ACLs that are obeyed after the
30841 RCPT or DATA commands, when a sender address is available. If (for
30842 example) the message's sender is &'user@tld.example'& the name that is looked
30843 up by this example is
30845 tld.example.dsn.rfc-ignorant.org
30847 A single &%dnslists%& condition can contain entries for both names and IP
30848 addresses. For example:
30850 deny dnslists = sbl.spamhaus.org : \
30851 dsn.rfc-ignorant.org/$sender_address_domain
30853 The first item checks the sending host's IP address; the second checks a domain
30854 name. The whole condition is true if either of the DNS lookups succeeds.
30859 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
30860 .cindex "DNS list" "multiple keys for"
30861 The syntax described above for looking up explicitly-defined values (either
30862 names or IP addresses) in a DNS blacklist is a simplification. After the domain
30863 name for the DNS list, what follows the slash can in fact be a list of items.
30864 As with all lists in Exim, the default separator is a colon. However, because
30865 this is a sublist within the list of DNS blacklist domains, it is necessary
30866 either to double the separators like this:
30868 dnslists = black.list.tld/name.1::name.2
30870 or to change the separator character, like this:
30872 dnslists = black.list.tld/<;name.1;name.2
30874 If an item in the list is an IP address, it is inverted before the DNS
30875 blacklist domain is appended. If it is not an IP address, no inversion
30876 occurs. Consider this condition:
30878 dnslists = black.list.tld/<;192.168.1.2;a.domain
30880 The DNS lookups that occur are:
30882 2.1.168.192.black.list.tld
30883 a.domain.black.list.tld
30885 Once a DNS record has been found (that matches a specific IP return
30886 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
30887 are done. If there is a temporary DNS error, the rest of the sublist of domains
30888 or IP addresses is tried. A temporary error for the whole dnslists item occurs
30889 only if no other DNS lookup in this sublist succeeds. In other words, a
30890 successful lookup for any of the items in the sublist overrides a temporary
30891 error for a previous item.
30893 The ability to supply a list of items after the slash is in some sense just a
30894 syntactic convenience. These two examples have the same effect:
30896 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
30897 dnslists = black.list.tld/a.domain::b.domain
30899 However, when the data for the list is obtained from a lookup, the second form
30900 is usually much more convenient. Consider this example:
30902 deny message = The mail servers for the domain \
30903 $sender_address_domain \
30904 are listed at $dnslist_domain ($dnslist_value); \
30906 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
30907 ${lookup dnsdb {>|mxh=\
30908 $sender_address_domain} }} }
30910 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
30911 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
30912 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
30913 of expanding the condition might be something like this:
30915 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
30917 Thus, this example checks whether or not the IP addresses of the sender
30918 domain's mail servers are on the Spamhaus black list.
30920 The key that was used for a successful DNS list lookup is put into the variable
30921 &$dnslist_matched$& (see section &<<SECID204>>&).
30926 .section "Data returned by DNS lists" "SECID203"
30927 .cindex "DNS list" "data returned from"
30928 DNS lists are constructed using address records in the DNS. The original RBL
30929 just used the address 127.0.0.1 on the right hand side of each record, but the
30930 RBL+ list and some other lists use a number of values with different meanings.
30931 The values used on the RBL+ list are:
30935 127.1.0.3 DUL and RBL
30937 127.1.0.5 RSS and RBL
30938 127.1.0.6 RSS and DUL
30939 127.1.0.7 RSS and DUL and RBL
30941 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
30942 different values. Some DNS lists may return more than one address record;
30943 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
30946 .section "Variables set from DNS lists" "SECID204"
30947 .cindex "expansion" "variables, set from DNS list"
30948 .cindex "DNS list" "variables set from"
30949 .vindex "&$dnslist_domain$&"
30950 .vindex "&$dnslist_matched$&"
30951 .vindex "&$dnslist_text$&"
30952 .vindex "&$dnslist_value$&"
30953 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
30954 the name of the overall domain that matched (for example,
30955 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
30956 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
30957 the DNS record. When the key is an IP address, it is not reversed in
30958 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
30959 cases, for example:
30961 deny dnslists = spamhaus.example
30963 the key is also available in another variable (in this case,
30964 &$sender_host_address$&). In more complicated cases, however, this is not true.
30965 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
30966 might generate a dnslists lookup like this:
30968 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
30970 If this condition succeeds, the value in &$dnslist_matched$& might be
30971 &`192.168.6.7`& (for example).
30973 If more than one address record is returned by the DNS lookup, all the IP
30974 addresses are included in &$dnslist_value$&, separated by commas and spaces.
30975 The variable &$dnslist_text$& contains the contents of any associated TXT
30976 record. For lists such as RBL+ the TXT record for a merged entry is often not
30977 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
30980 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
30981 &-- although these appear before the condition in the ACL, they are not
30982 expanded until after it has failed. For example:
30984 deny hosts = !+local_networks
30985 message = $sender_host_address is listed \
30987 dnslists = rbl-plus.mail-abuse.example
30992 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
30993 .cindex "DNS list" "matching specific returned data"
30994 You can add an equals sign and an IP address after a &%dnslists%& domain name
30995 in order to restrict its action to DNS records with a matching right hand side.
30998 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
31000 rejects only those hosts that yield 127.0.0.2. Without this additional data,
31001 any address record is considered to be a match. For the moment, we assume
31002 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
31003 describes how multiple records are handled.
31005 More than one IP address may be given for checking, using a comma as a
31006 separator. These are alternatives &-- if any one of them matches, the
31007 &%dnslists%& condition is true. For example:
31009 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
31011 If you want to specify a constraining address list and also specify names or IP
31012 addresses to be looked up, the constraining address list must be specified
31013 first. For example:
31015 deny dnslists = dsn.rfc-ignorant.org\
31016 =127.0.0.2/$sender_address_domain
31019 If the character &`&&`& is used instead of &`=`&, the comparison for each
31020 listed IP address is done by a bitwise &"and"& instead of by an equality test.
31021 In other words, the listed addresses are used as bit masks. The comparison is
31022 true if all the bits in the mask are present in the address that is being
31023 tested. For example:
31025 dnslists = a.b.c&0.0.0.3
31027 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
31028 want to test whether one bit or another bit is present (as opposed to both
31029 being present), you must use multiple values. For example:
31031 dnslists = a.b.c&0.0.0.1,0.0.0.2
31033 matches if the final component of the address is an odd number or two times
31038 .section "Negated DNS matching conditions" "SECID205"
31039 You can supply a negative list of IP addresses as part of a &%dnslists%&
31042 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
31044 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
31045 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
31047 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
31049 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
31050 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
31051 words, the result of the test is inverted if an exclamation mark appears before
31052 the &`=`& (or the &`&&`&) sign.
31054 &*Note*&: This kind of negation is not the same as negation in a domain,
31055 host, or address list (which is why the syntax is different).
31057 If you are using just one list, the negation syntax does not gain you much. The
31058 previous example is precisely equivalent to
31060 deny dnslists = a.b.c
31061 !dnslists = a.b.c=127.0.0.2,127.0.0.3
31063 However, if you are using multiple lists, the negation syntax is clearer.
31064 Consider this example:
31066 deny dnslists = sbl.spamhaus.org : \
31068 dnsbl.njabl.org!=127.0.0.3 : \
31071 Using only positive lists, this would have to be:
31073 deny dnslists = sbl.spamhaus.org : \
31075 deny dnslists = dnsbl.njabl.org
31076 !dnslists = dnsbl.njabl.org=127.0.0.3
31077 deny dnslists = relays.ordb.org
31079 which is less clear, and harder to maintain.
31084 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
31085 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
31086 thereby providing more than one IP address. When an item in a &%dnslists%& list
31087 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
31088 the match to specific results from the DNS lookup, there are two ways in which
31089 the checking can be handled. For example, consider the condition:
31091 dnslists = a.b.c=127.0.0.1
31093 What happens if the DNS lookup for the incoming IP address yields both
31094 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
31095 condition true because at least one given value was found, or is it false
31096 because at least one of the found values was not listed? And how does this
31097 affect negated conditions? Both possibilities are provided for with the help of
31098 additional separators &`==`& and &`=&&`&.
31101 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
31102 IP addresses matches one of the listed addresses. For the example above, the
31103 condition is true because 127.0.0.1 matches.
31105 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
31106 looked up IP addresses matches one of the listed addresses. If the condition is
31109 dnslists = a.b.c==127.0.0.1
31111 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
31112 false because 127.0.0.2 is not listed. You would need to have:
31114 dnslists = a.b.c==127.0.0.1,127.0.0.2
31116 for the condition to be true.
31119 When &`!`& is used to negate IP address matching, it inverts the result, giving
31120 the precise opposite of the behaviour above. Thus:
31122 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
31123 addresses matches one of the listed addresses. Consider:
31125 dnslists = a.b.c!&0.0.0.1
31127 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
31128 false because 127.0.0.1 matches.
31130 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
31131 looked up IP address that does not match. Consider:
31133 dnslists = a.b.c!=&0.0.0.1
31135 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
31136 true, because 127.0.0.2 does not match. You would need to have:
31138 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
31140 for the condition to be false.
31142 When the DNS lookup yields only a single IP address, there is no difference
31143 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
31148 .section "Detailed information from merged DNS lists" "SECTmordetinf"
31149 .cindex "DNS list" "information from merged"
31150 When the facility for restricting the matching IP values in a DNS list is used,
31151 the text from the TXT record that is set in &$dnslist_text$& may not reflect
31152 the true reason for rejection. This happens when lists are merged and the IP
31153 address in the A record is used to distinguish them; unfortunately there is
31154 only one TXT record. One way round this is not to use merged lists, but that
31155 can be inefficient because it requires multiple DNS lookups where one would do
31156 in the vast majority of cases when the host of interest is not on any of the
31159 A less inefficient way of solving this problem is available. If
31160 two domain names, comma-separated, are given, the second is used first to
31161 do an initial check, making use of any IP value restrictions that are set.
31162 If there is a match, the first domain is used, without any IP value
31163 restrictions, to get the TXT record. As a byproduct of this, there is also
31164 a check that the IP being tested is indeed on the first list. The first
31165 domain is the one that is put in &$dnslist_domain$&. For example:
31168 rejected because $sender_host_address is blacklisted \
31169 at $dnslist_domain\n$dnslist_text
31171 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
31172 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
31174 For the first blacklist item, this starts by doing a lookup in
31175 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
31176 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
31177 value, and as long as something is found, it looks for the corresponding TXT
31178 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
31179 The second blacklist item is processed similarly.
31181 If you are interested in more than one merged list, the same list must be
31182 given several times, but because the results of the DNS lookups are cached,
31183 the DNS calls themselves are not repeated. For example:
31186 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
31187 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
31188 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
31189 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
31191 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
31192 values matches (or if no record is found), this is the only lookup that is
31193 done. Only if there is a match is one of the more specific lists consulted.
31197 .section "DNS lists and IPv6" "SECTmorednslistslast"
31198 .cindex "IPv6" "DNS black lists"
31199 .cindex "DNS list" "IPv6 usage"
31200 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
31201 nibble by nibble. For example, if the calling host's IP address is
31202 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
31204 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
31205 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
31207 (split over two lines here to fit on the page). Unfortunately, some of the DNS
31208 lists contain wildcard records, intended for IPv4, that interact badly with
31209 IPv6. For example, the DNS entry
31211 *.3.some.list.example. A 127.0.0.1
31213 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
31214 Unfortunately, it also matches the entire 3::/4 IPv6 network.
31216 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
31217 &%condition%& condition, as in this example:
31219 deny condition = ${if isip4{$sender_host_address}}
31220 dnslists = some.list.example
31223 If an explicit key is being used for a DNS lookup and it may be an IPv6
31224 address you should specify alternate list separators for both the outer
31225 (DNS list name) list and inner (lookup keys) list:
31227 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
31230 .section "Rate limiting incoming messages" "SECTratelimiting"
31231 .cindex "rate limiting" "client sending"
31232 .cindex "limiting client sending rates"
31233 .oindex "&%smtp_ratelimit_*%&"
31234 The &%ratelimit%& ACL condition can be used to measure and control the rate at
31235 which clients can send email. This is more powerful than the
31236 &%smtp_ratelimit_*%& options, because those options control the rate of
31237 commands in a single SMTP session only, whereas the &%ratelimit%& condition
31238 works across all connections (concurrent and sequential) from the same client
31239 host. The syntax of the &%ratelimit%& condition is:
31241 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
31243 If the average client sending rate is less than &'m'& messages per time
31244 period &'p'& then the condition is false; otherwise it is true.
31246 As a side-effect, the &%ratelimit%& condition sets the expansion variable
31247 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
31248 configured value of &'m'&, and &$sender_rate_period$& to the configured value
31251 The parameter &'p'& is the smoothing time constant, in the form of an Exim
31252 time interval, for example, &`8h`& for eight hours. A larger time constant
31253 means that it takes Exim longer to forget a client's past behaviour. The
31254 parameter &'m'& is the maximum number of messages that a client is permitted to
31255 send in each time interval. It also specifies the number of messages permitted
31256 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
31257 constant, you can allow a client to send more messages in a burst without
31258 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
31259 both small, messages must be sent at an even rate.
31261 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
31262 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
31263 when deploying the &%ratelimit%& ACL condition. The script prints usage
31264 instructions when it is run with no arguments.
31266 The key is used to look up the data for calculating the client's average
31267 sending rate. This data is stored in Exim's spool directory, alongside the
31268 retry and other hints databases. The default key is &$sender_host_address$&,
31269 which means Exim computes the sending rate of each client host IP address.
31270 By changing the key you can change how Exim identifies clients for the purpose
31271 of ratelimiting. For example, to limit the sending rate of each authenticated
31272 user, independent of the computer they are sending from, set the key to
31273 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
31274 example, &$authenticated_id$& is only meaningful if the client has
31275 authenticated (which you can check with the &%authenticated%& ACL condition).
31277 The lookup key does not have to identify clients: If you want to limit the
31278 rate at which a recipient receives messages, you can use the key
31279 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
31282 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
31283 specifies what Exim measures the rate of, for example, messages or recipients
31284 or bytes. You can adjust the measurement using the &%unique=%& and/or
31285 &%count=%& options. You can also control when Exim updates the recorded rate
31286 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
31287 separated by a slash, like the other parameters. They may appear in any order.
31289 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
31290 any options that alter the meaning of the stored data. The limit &'m'& is not
31291 stored, so you can alter the configured maximum rate and Exim will still
31292 remember clients' past behaviour. If you change the &%per_*%& mode or add or
31293 remove the &%unique=%& option, the lookup key changes so Exim will forget past
31294 behaviour. The lookup key is not affected by changes to the update mode and
31295 the &%count=%& option.
31298 .section "Ratelimit options for what is being measured" "ratoptmea"
31299 .cindex "rate limiting" "per_* options"
31300 The &%per_conn%& option limits the client's connection rate. It is not
31301 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
31302 &%acl_not_smtp_start%& ACLs.
31304 The &%per_mail%& option limits the client's rate of sending messages. This is
31305 the default if none of the &%per_*%& options is specified. It can be used in
31306 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
31307 &%acl_smtp_data%&, or &%acl_not_smtp%&.
31309 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
31310 the same ACLs as the &%per_mail%& option, though it is best to use this option
31311 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
31312 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
31313 in its MAIL command, which may be inaccurate or completely missing. You can
31314 follow the limit &'m'& in the configuration with K, M, or G to specify limits
31315 in kilobytes, megabytes, or gigabytes, respectively.
31317 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
31318 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
31319 &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
31320 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
31321 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
31322 in either case the rate limiting engine will see a message with many
31323 recipients as a large high-speed burst.
31325 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
31326 number of different recipients that the client has sent messages to in the
31327 last time period. That is, if the client repeatedly sends messages to the same
31328 recipient, its measured rate is not increased. This option can only be used in
31331 The &%per_cmd%& option causes Exim to recompute the rate every time the
31332 condition is processed. This can be used to limit the rate of any SMTP
31333 command. If it is used in multiple ACLs it can limit the aggregate rate of
31334 multiple different commands.
31336 The &%count=%& option can be used to alter how much Exim adds to the client's
31337 measured rate. For example, the &%per_byte%& option is equivalent to
31338 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
31339 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
31340 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
31342 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
31345 .section "Ratelimit update modes" "ratoptupd"
31346 .cindex "rate limiting" "reading data without updating"
31347 You can specify one of three options with the &%ratelimit%& condition to
31348 control when its database is updated. This section describes the &%readonly%&
31349 mode, and the next section describes the &%strict%& and &%leaky%& modes.
31351 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
31352 previously-computed rate to check against the limit.
31354 For example, you can test the client's sending rate and deny it access (when
31355 it is too fast) in the connect ACL. If the client passes this check then it
31356 can go on to send a message, in which case its recorded rate will be updated
31357 in the MAIL ACL. Subsequent connections from the same client will check this
31361 deny ratelimit = 100 / 5m / readonly
31362 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
31363 (max $sender_rate_limit)
31366 warn ratelimit = 100 / 5m / strict
31367 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
31368 (max $sender_rate_limit)
31371 If Exim encounters multiple &%ratelimit%& conditions with the same key when
31372 processing a message then it may increase the client's measured rate more than
31373 it should. For example, this will happen if you check the &%per_rcpt%& option
31374 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
31375 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
31376 multiple update problems by using the &%readonly%& option on later ratelimit
31379 The &%per_*%& options described above do not make sense in some ACLs. If you
31380 use a &%per_*%& option in an ACL where it is not normally permitted then the
31381 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
31382 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
31383 next section) so you must specify the &%readonly%& option explicitly.
31386 .section "Ratelimit options for handling fast clients" "ratoptfast"
31387 .cindex "rate limiting" "strict and leaky modes"
31388 If a client's average rate is greater than the maximum, the rate limiting
31389 engine can react in two possible ways, depending on the presence of the
31390 &%strict%& or &%leaky%& update modes. This is independent of the other
31391 counter-measures (such as rejecting the message) that may be specified by the
31394 The &%leaky%& (default) option means that the client's recorded rate is not
31395 updated if it is above the limit. The effect of this is that Exim measures the
31396 client's average rate of successfully sent email,
31398 up to the given limit.
31399 This is appropriate if the countermeasure when the condition is true
31400 consists of refusing the message, and
31401 is generally the better choice if you have clients that retry automatically.
31402 If the action when true is anything more complex then this option is
31403 likely not what is wanted.
31406 The &%strict%& option means that the client's recorded rate is always
31407 updated. The effect of this is that Exim measures the client's average rate
31408 of attempts to send email, which can be much higher than the maximum it is
31409 actually allowed. If the client is over the limit it may be subjected to
31410 counter-measures by the ACL. It must slow down and allow sufficient time to
31411 pass that its computed rate falls below the maximum before it can send email
31412 again. The time (the number of smoothing periods) it must wait and not
31413 attempt to send mail can be calculated with this formula:
31415 ln(peakrate/maxrate)
31419 .section "Limiting the rate of different events" "ratoptuniq"
31420 .cindex "rate limiting" "counting unique events"
31421 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
31422 rate of different events. For example, the &%per_addr%& option uses this
31423 mechanism to count the number of different recipients that the client has
31424 sent messages to in the last time period; it is equivalent to
31425 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
31426 measure the rate that a client uses different sender addresses with the
31427 options &`per_mail/unique=$sender_address`&.
31429 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
31430 has seen for that key. The whole set is thrown away when it is older than the
31431 rate smoothing period &'p'&, so each different event is counted at most once
31432 per period. In the &%leaky%& update mode, an event that causes the client to
31433 go over the limit is not added to the set, in the same way that the client's
31434 recorded rate is not updated in the same situation.
31436 When you combine the &%unique=%& and &%readonly%& options, the specific
31437 &%unique=%& value is ignored, and Exim just retrieves the client's stored
31440 The &%unique=%& mechanism needs more space in the ratelimit database than the
31441 other &%ratelimit%& options in order to store the event set. The number of
31442 unique values is potentially as large as the rate limit, so the extra space
31443 required increases with larger limits.
31445 The uniqueification is not perfect: there is a small probability that Exim
31446 will think a new event has happened before. If the sender's rate is less than
31447 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
31448 the measured rate can go above the limit, in which case Exim may under-count
31449 events by a significant margin. Fortunately, if the rate is high enough (2.7
31450 times the limit) that the false positive rate goes above 9%, then Exim will
31451 throw away the over-full event set before the measured rate falls below the
31452 limit. Therefore the only harm should be that exceptionally high sending rates
31453 are logged incorrectly; any countermeasures you configure will be as effective
31457 .section "Using rate limiting" "useratlim"
31458 Exim's other ACL facilities are used to define what counter-measures are taken
31459 when the rate limit is exceeded. This might be anything from logging a warning
31460 (for example, while measuring existing sending rates in order to define
31461 policy), through time delays to slow down fast senders, up to rejecting the
31462 message. For example:
31464 # Log all senders' rates
31465 warn ratelimit = 0 / 1h / strict
31466 log_message = Sender rate $sender_rate / $sender_rate_period
31468 # Slow down fast senders; note the need to truncate $sender_rate
31469 # at the decimal point.
31470 warn ratelimit = 100 / 1h / per_rcpt / strict
31471 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
31472 $sender_rate_limit }s
31474 # Keep authenticated users under control
31475 deny authenticated = *
31476 ratelimit = 100 / 1d / strict / $authenticated_id
31478 # System-wide rate limit
31479 defer message = Sorry, too busy. Try again later.
31480 ratelimit = 10 / 1s / $primary_hostname
31482 # Restrict incoming rate from each host, with a default
31483 # set using a macro and special cases looked up in a table.
31484 defer message = Sender rate exceeds $sender_rate_limit \
31485 messages per $sender_rate_period
31486 ratelimit = ${lookup {$sender_host_address} \
31487 cdb {DB/ratelimits.cdb} \
31488 {$value} {RATELIMIT} }
31490 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
31491 especially with the &%per_rcpt%& option, you may suffer from a performance
31492 bottleneck caused by locking on the ratelimit hints database. Apart from
31493 making your ACLs less complicated, you can reduce the problem by using a
31494 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
31495 this means that Exim will lose its hints data after a reboot (including retry
31496 hints, the callout cache, and ratelimit data).
31500 .section "Address verification" "SECTaddressverification"
31501 .cindex "verifying address" "options for"
31502 .cindex "policy control" "address verification"
31503 Several of the &%verify%& conditions described in section
31504 &<<SECTaclconditions>>& cause addresses to be verified. Section
31505 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
31506 The verification conditions can be followed by options that modify the
31507 verification process. The options are separated from the keyword and from each
31508 other by slashes, and some of them contain parameters. For example:
31510 verify = sender/callout
31511 verify = recipient/defer_ok/callout=10s,defer_ok
31513 The first stage of address verification, which always happens, is to run the
31514 address through the routers, in &"verify mode"&. Routers can detect the
31515 difference between verification and routing for delivery, and their actions can
31516 be varied by a number of generic options such as &%verify%& and &%verify_only%&
31517 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
31518 The available options are as follows:
31521 If the &%callout%& option is specified, successful routing to one or more
31522 remote hosts is followed by a &"callout"& to those hosts as an additional
31523 check. Callouts and their sub-options are discussed in the next section.
31525 If there is a defer error while doing verification routing, the ACL
31526 normally returns &"defer"&. However, if you include &%defer_ok%& in the
31527 options, the condition is forced to be true instead. Note that this is a main
31528 verification option as well as a suboption for callouts.
31530 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
31531 discusses the reporting of sender address verification failures.
31533 The &%success_on_redirect%& option causes verification always to succeed
31534 immediately after a successful redirection. By default, if a redirection
31535 generates just one address, that address is also verified. See further
31536 discussion in section &<<SECTredirwhilveri>>&.
31539 .cindex "verifying address" "differentiating failures"
31540 .vindex "&$recipient_verify_failure$&"
31541 .vindex "&$sender_verify_failure$&"
31542 .vindex "&$acl_verify_message$&"
31543 After an address verification failure, &$acl_verify_message$& contains the
31544 error message that is associated with the failure. It can be preserved by
31547 warn !verify = sender
31548 set acl_m0 = $acl_verify_message
31550 If you are writing your own custom rejection message or log message when
31551 denying access, you can use this variable to include information about the
31552 verification failure.
31554 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
31555 appropriate) contains one of the following words:
31558 &%qualify%&: The address was unqualified (no domain), and the message
31559 was neither local nor came from an exempted host.
31561 &%route%&: Routing failed.
31563 &%mail%&: Routing succeeded, and a callout was attempted; rejection
31564 occurred at or before the MAIL command (that is, on initial
31565 connection, HELO, or MAIL).
31567 &%recipient%&: The RCPT command in a callout was rejected.
31569 &%postmaster%&: The postmaster check in a callout was rejected.
31572 The main use of these variables is expected to be to distinguish between
31573 rejections of MAIL and rejections of RCPT in callouts.
31576 The above variables may also be set after a &*successful*&
31577 address verification to:
31580 &%random%&: A random local-part callout succeeded
31587 .section "Callout verification" "SECTcallver"
31588 .cindex "verifying address" "by callout"
31589 .cindex "callout" "verification"
31590 .cindex "SMTP" "callout verification"
31591 For non-local addresses, routing verifies the domain, but is unable to do any
31592 checking of the local part. There are situations where some means of verifying
31593 the local part is desirable. One way this can be done is to make an SMTP
31594 &'callback'& to a delivery host for the sender address or a &'callforward'& to
31595 a subsequent host for a recipient address, to see if the host accepts the
31596 address. We use the term &'callout'& to cover both cases. Note that for a
31597 sender address, the callback is not to the client host that is trying to
31598 deliver the message, but to one of the hosts that accepts incoming mail for the
31601 Exim does not do callouts by default. If you want them to happen, you must
31602 request them by setting appropriate options on the &%verify%& condition, as
31603 described below. This facility should be used with care, because it can add a
31604 lot of resource usage to the cost of verifying an address. However, Exim does
31605 cache the results of callouts, which helps to reduce the cost. Details of
31606 caching are in section &<<SECTcallvercache>>&.
31608 Recipient callouts are usually used only between hosts that are controlled by
31609 the same administration. For example, a corporate gateway host could use
31610 callouts to check for valid recipients on an internal mailserver. A successful
31611 callout does not guarantee that a real delivery to the address would succeed;
31612 on the other hand, a failing callout does guarantee that a delivery would fail.
31614 If the &%callout%& option is present on a condition that verifies an address, a
31615 second stage of verification occurs if the address is successfully routed to
31616 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
31617 &(manualroute)& router, where the router specifies the hosts. However, if a
31618 router that does not set up hosts routes to an &(smtp)& transport with a
31619 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
31620 &%hosts_override%& set, its hosts are always used, whether or not the router
31621 supplies a host list.
31622 Callouts are only supported on &(smtp)& transports.
31624 The port that is used is taken from the transport, if it is specified and is a
31625 remote transport. (For routers that do verification only, no transport need be
31626 specified.) Otherwise, the default SMTP port is used. If a remote transport
31627 specifies an outgoing interface, this is used; otherwise the interface is not
31628 specified. Likewise, the text that is used for the HELO command is taken from
31629 the transport's &%helo_data%& option; if there is no transport, the value of
31630 &$smtp_active_hostname$& is used.
31632 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
31633 test whether a bounce message could be delivered to the sender address. The
31634 following SMTP commands are sent:
31636 &`HELO `&<&'local host name'&>
31638 &`RCPT TO:`&<&'the address to be tested'&>
31641 LHLO is used instead of HELO if the transport's &%protocol%& option is
31644 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
31647 A recipient callout check is similar. By default, it also uses an empty address
31648 for the sender. This default is chosen because most hosts do not make use of
31649 the sender address when verifying a recipient. Using the same address means
31650 that a single cache entry can be used for each recipient. Some sites, however,
31651 do make use of the sender address when verifying. These are catered for by the
31652 &%use_sender%& and &%use_postmaster%& options, described in the next section.
31654 If the response to the RCPT command is a 2&'xx'& code, the verification
31655 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
31656 Exim tries the next host, if any. If there is a problem with all the remote
31657 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
31658 &%callout%& option is given, in which case the condition is forced to succeed.
31660 .cindex "SMTP" "output flushing, disabling for callout"
31661 A callout may take a little time. For this reason, Exim normally flushes SMTP
31662 output before performing a callout in an ACL, to avoid unexpected timeouts in
31663 clients when the SMTP PIPELINING extension is in use. The flushing can be
31664 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
31669 .section "Additional parameters for callouts" "CALLaddparcall"
31670 .cindex "callout" "additional parameters for"
31671 The &%callout%& option can be followed by an equals sign and a number of
31672 optional parameters, separated by commas. For example:
31674 verify = recipient/callout=10s,defer_ok
31676 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
31677 separate verify options, is retained for backwards compatibility, but is now
31678 deprecated. The additional parameters for &%callout%& are as follows:
31682 .vitem <&'a&~time&~interval'&>
31683 .cindex "callout" "timeout, specifying"
31684 This specifies the timeout that applies for the callout attempt to each host.
31687 verify = sender/callout=5s
31689 The default is 30 seconds. The timeout is used for each response from the
31690 remote host. It is also used for the initial connection, unless overridden by
31691 the &%connect%& parameter.
31694 .vitem &*connect&~=&~*&<&'time&~interval'&>
31695 .cindex "callout" "connection timeout, specifying"
31696 This parameter makes it possible to set a different (usually smaller) timeout
31697 for making the SMTP connection. For example:
31699 verify = sender/callout=5s,connect=1s
31701 If not specified, this timeout defaults to the general timeout value.
31703 .vitem &*defer_ok*&
31704 .cindex "callout" "defer, action on"
31705 When this parameter is present, failure to contact any host, or any other kind
31706 of temporary error, is treated as success by the ACL. However, the cache is not
31707 updated in this circumstance.
31709 .vitem &*fullpostmaster*&
31710 .cindex "callout" "full postmaster check"
31711 This operates like the &%postmaster%& option (see below), but if the check for
31712 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
31713 accordance with the specification in RFC 2821. The RFC states that the
31714 unqualified address &'postmaster'& should be accepted.
31717 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
31718 .cindex "callout" "sender when verifying header"
31719 When verifying addresses in header lines using the &%header_sender%&
31720 verification option, Exim behaves by default as if the addresses are envelope
31721 sender addresses from a message. Callout verification therefore tests to see
31722 whether a bounce message could be delivered, by using an empty address in the
31723 MAIL command. However, it is arguable that these addresses might never be used
31724 as envelope senders, and could therefore justifiably reject bounce messages
31725 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
31726 address to use in the MAIL command. For example:
31728 require verify = header_sender/callout=mailfrom=abcd@x.y.z
31730 This parameter is available only for the &%header_sender%& verification option.
31733 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
31734 .cindex "callout" "overall timeout, specifying"
31735 This parameter sets an overall timeout for performing a callout verification.
31738 verify = sender/callout=5s,maxwait=30s
31740 This timeout defaults to four times the callout timeout for individual SMTP
31741 commands. The overall timeout applies when there is more than one host that can
31742 be tried. The timeout is checked before trying the next host. This prevents
31743 very long delays if there are a large number of hosts and all are timing out
31744 (for example, when network connections are timing out).
31747 .vitem &*no_cache*&
31748 .cindex "callout" "cache, suppressing"
31749 .cindex "caching callout, suppressing"
31750 When this parameter is given, the callout cache is neither read nor updated.
31752 .vitem &*postmaster*&
31753 .cindex "callout" "postmaster; checking"
31754 When this parameter is set, a successful callout check is followed by a similar
31755 check for the local part &'postmaster'& at the same domain. If this address is
31756 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
31757 the postmaster check is recorded in a cache record; if it is a failure, this is
31758 used to fail subsequent callouts for the domain without a connection being
31759 made, until the cache record expires.
31761 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
31762 The postmaster check uses an empty sender in the MAIL command by default.
31763 You can use this parameter to do a postmaster check using a different address.
31766 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
31768 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
31769 one overrides. The &%postmaster%& parameter is equivalent to this example:
31771 require verify = sender/callout=postmaster_mailfrom=
31773 &*Warning*&: The caching arrangements for postmaster checking do not take
31774 account of the sender address. It is assumed that either the empty address or
31775 a fixed non-empty address will be used. All that Exim remembers is that the
31776 postmaster check for the domain succeeded or failed.
31780 .cindex "callout" "&""random""& check"
31781 When this parameter is set, before doing the normal callout check, Exim does a
31782 check for a &"random"& local part at the same domain. The local part is not
31783 really random &-- it is defined by the expansion of the option
31784 &%callout_random_local_part%&, which defaults to
31786 $primary_hostname-$tod_epoch-testing
31788 The idea here is to try to determine whether the remote host accepts all local
31789 parts without checking. If it does, there is no point in doing callouts for
31790 specific local parts. If the &"random"& check succeeds, the result is saved in
31791 a cache record, and used to force the current and subsequent callout checks to
31792 succeed without a connection being made, until the cache record expires.
31794 .vitem &*use_postmaster*&
31795 .cindex "callout" "sender for recipient check"
31796 This parameter applies to recipient callouts only. For example:
31798 deny !verify = recipient/callout=use_postmaster
31800 .vindex "&$qualify_domain$&"
31801 It causes a non-empty postmaster address to be used in the MAIL command when
31802 performing the callout for the recipient, and also for a &"random"& check if
31803 that is configured. The local part of the address is &`postmaster`& and the
31804 domain is the contents of &$qualify_domain$&.
31806 .vitem &*use_sender*&
31807 This option applies to recipient callouts only. For example:
31809 require verify = recipient/callout=use_sender
31811 It causes the message's actual sender address to be used in the MAIL
31812 command when performing the callout, instead of an empty address. There is no
31813 need to use this option unless you know that the called hosts make use of the
31814 sender when checking recipients. If used indiscriminately, it reduces the
31815 usefulness of callout caching.
31818 This option applies to recipient callouts only. For example:
31820 require verify = recipient/callout=use_sender,hold
31822 It causes the connection to be held open and used for any further recipients
31823 and for eventual delivery (should that be done quickly).
31824 Doing this saves on TCP and SMTP startup costs, and TLS costs also
31825 when that is used for the connections.
31826 The advantage is only gained if there are no callout cache hits
31827 (which could be enforced by the no_cache option),
31828 if the use_sender option is used,
31829 if neither the random nor the use_postmaster option is used,
31830 and if no other callouts intervene.
31833 If you use any of the parameters that set a non-empty sender for the MAIL
31834 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
31835 &%use_sender%&), you should think about possible loops. Recipient checking is
31836 usually done between two hosts that are under the same management, and the host
31837 that receives the callouts is not normally configured to do callouts itself.
31838 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
31839 these circumstances.
31841 However, if you use a non-empty sender address for a callout to an arbitrary
31842 host, there is the likelihood that the remote host will itself initiate a
31843 callout check back to your host. As it is checking what appears to be a message
31844 sender, it is likely to use an empty address in MAIL, thus avoiding a
31845 callout loop. However, to be on the safe side it would be best to set up your
31846 own ACLs so that they do not do sender verification checks when the recipient
31847 is the address you use for header sender or postmaster callout checking.
31849 Another issue to think about when using non-empty senders for callouts is
31850 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
31851 by the sender/recipient combination; thus, for any given recipient, many more
31852 actual callouts are performed than when an empty sender or postmaster is used.
31857 .section "Callout caching" "SECTcallvercache"
31858 .cindex "hints database" "callout cache"
31859 .cindex "callout" "cache, description of"
31860 .cindex "caching" "callout"
31861 Exim caches the results of callouts in order to reduce the amount of resources
31862 used, unless you specify the &%no_cache%& parameter with the &%callout%&
31863 option. A hints database called &"callout"& is used for the cache. Two
31864 different record types are used: one records the result of a callout check for
31865 a specific address, and the other records information that applies to the
31866 entire domain (for example, that it accepts the local part &'postmaster'&).
31868 When an original callout fails, a detailed SMTP error message is given about
31869 the failure. However, for subsequent failures use the cache data, this message
31872 The expiry times for negative and positive address cache records are
31873 independent, and can be set by the global options &%callout_negative_expire%&
31874 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
31876 If a host gives a negative response to an SMTP connection, or rejects any
31877 commands up to and including
31881 (but not including the MAIL command with a non-empty address),
31882 any callout attempt is bound to fail. Exim remembers such failures in a
31883 domain cache record, which it uses to fail callouts for the domain without
31884 making new connections, until the domain record times out. There are two
31885 separate expiry times for domain cache records:
31886 &%callout_domain_negative_expire%& (default 3h) and
31887 &%callout_domain_positive_expire%& (default 7d).
31889 Domain records expire when the negative expiry time is reached if callouts
31890 cannot be made for the domain, or if the postmaster check failed.
31891 Otherwise, they expire when the positive expiry time is reached. This
31892 ensures that, for example, a host that stops accepting &"random"& local parts
31893 will eventually be noticed.
31895 The callout caching mechanism is based on the domain of the address that is
31896 being tested. If the domain routes to several hosts, it is assumed that their
31897 behaviour will be the same.
31901 .section "Sender address verification reporting" "SECTsenaddver"
31902 .cindex "verifying" "suppressing error details"
31903 See section &<<SECTaddressverification>>& for a general discussion of
31904 verification. When sender verification fails in an ACL, the details of the
31905 failure are given as additional output lines before the 550 response to the
31906 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
31909 MAIL FROM:<xyz@abc.example>
31911 RCPT TO:<pqr@def.example>
31912 550-Verification failed for <xyz@abc.example>
31913 550-Called: 192.168.34.43
31914 550-Sent: RCPT TO:<xyz@abc.example>
31915 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
31916 550 Sender verification failed
31918 If more than one RCPT command fails in the same way, the details are given
31919 only for the first of them. However, some administrators do not want to send
31920 out this much information. You can suppress the details by adding
31921 &`/no_details`& to the ACL statement that requests sender verification. For
31924 verify = sender/no_details
31927 .section "Redirection while verifying" "SECTredirwhilveri"
31928 .cindex "verifying" "redirection while"
31929 .cindex "address redirection" "while verifying"
31930 A dilemma arises when a local address is redirected by aliasing or forwarding
31931 during verification: should the generated addresses themselves be verified,
31932 or should the successful expansion of the original address be enough to verify
31933 it? By default, Exim takes the following pragmatic approach:
31936 When an incoming address is redirected to just one child address, verification
31937 continues with the child address, and if that fails to verify, the original
31938 verification also fails.
31940 When an incoming address is redirected to more than one child address,
31941 verification does not continue. A success result is returned.
31944 This seems the most reasonable behaviour for the common use of aliasing as a
31945 way of redirecting different local parts to the same mailbox. It means, for
31946 example, that a pair of alias entries of the form
31949 aw123: :fail: Gone away, no forwarding address
31951 work as expected, with both local parts causing verification failure. When a
31952 redirection generates more than one address, the behaviour is more like a
31953 mailing list, where the existence of the alias itself is sufficient for
31954 verification to succeed.
31956 It is possible, however, to change the default behaviour so that all successful
31957 redirections count as successful verifications, however many new addresses are
31958 generated. This is specified by the &%success_on_redirect%& verification
31959 option. For example:
31961 require verify = recipient/success_on_redirect/callout=10s
31963 In this example, verification succeeds if a router generates a new address, and
31964 the callout does not occur, because no address was routed to a remote host.
31966 When verification is being tested via the &%-bv%& option, the treatment of
31967 redirections is as just described, unless the &%-v%& or any debugging option is
31968 also specified. In that case, full verification is done for every generated
31969 address and a report is output for each of them.
31973 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
31974 .cindex "CSA" "verifying"
31975 Client SMTP Authorization is a system that allows a site to advertise
31976 which machines are and are not permitted to send email. This is done by placing
31977 special SRV records in the DNS; these are looked up using the client's HELO
31978 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
31979 Authorization checks in Exim are performed by the ACL condition:
31983 This fails if the client is not authorized. If there is a DNS problem, or if no
31984 valid CSA SRV record is found, or if the client is authorized, the condition
31985 succeeds. These three cases can be distinguished using the expansion variable
31986 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
31987 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
31988 be likely to cause problems for legitimate email.
31990 The error messages produced by the CSA code include slightly more
31991 detail. If &$csa_status$& is &"defer"&, this may be because of problems
31992 looking up the CSA SRV record, or problems looking up the CSA target
31993 address record. There are four reasons for &$csa_status$& being &"fail"&:
31996 The client's host name is explicitly not authorized.
31998 The client's IP address does not match any of the CSA target IP addresses.
32000 The client's host name is authorized but it has no valid target IP addresses
32001 (for example, the target's addresses are IPv6 and the client is using IPv4).
32003 The client's host name has no CSA SRV record but a parent domain has asserted
32004 that all subdomains must be explicitly authorized.
32007 The &%csa%& verification condition can take an argument which is the domain to
32008 use for the DNS query. The default is:
32010 verify = csa/$sender_helo_name
32012 This implementation includes an extension to CSA. If the query domain
32013 is an address literal such as [192.0.2.95], or if it is a bare IP
32014 address, Exim searches for CSA SRV records in the reverse DNS as if
32015 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
32018 verify = csa/$sender_host_address
32020 In fact, this is the check that Exim performs if the client does not say HELO.
32021 This extension can be turned off by setting the main configuration option
32022 &%dns_csa_use_reverse%& to be false.
32024 If a CSA SRV record is not found for the domain itself, a search
32025 is performed through its parent domains for a record which might be
32026 making assertions about subdomains. The maximum depth of this search is limited
32027 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
32028 default. Exim does not look for CSA SRV records in a top level domain, so the
32029 default settings handle HELO domains as long as seven
32030 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
32031 of legitimate HELO domains.
32033 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
32034 direct SRV lookups, this is not sufficient because of the extra parent domain
32035 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
32036 addresses into lookups in the reverse DNS space. The result of a successful
32039 ${lookup dnsdb {csa=$sender_helo_name}}
32041 has two space-separated fields: an authorization code and a target host name.
32042 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
32043 authorization required but absent, or &"?"& for unknown.
32048 .section "Bounce address tag validation" "SECTverifyPRVS"
32049 .cindex "BATV, verifying"
32050 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
32051 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
32052 Genuine incoming bounce messages should therefore always be addressed to
32053 recipients that have a valid tag. This scheme is a way of detecting unwanted
32054 bounce messages caused by sender address forgeries (often called &"collateral
32055 spam"&), because the recipients of such messages do not include valid tags.
32057 There are two expansion items to help with the implementation of the BATV
32058 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
32059 the original envelope sender address by using a simple key to add a hash of the
32060 address and some time-based randomizing information. The &%prvs%& expansion
32061 item creates a signed address, and the &%prvscheck%& expansion item checks one.
32062 The syntax of these expansion items is described in section
32063 &<<SECTexpansionitems>>&.
32064 The validity period on signed addresses is seven days.
32066 As an example, suppose the secret per-address keys are stored in an MySQL
32067 database. A query to look up the key for an address could be defined as a macro
32070 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
32071 WHERE sender='${quote_mysql:$prvscheck_address}'\
32074 Suppose also that the senders who make use of BATV are defined by an address
32075 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
32078 # Bounces: drop unsigned addresses for BATV senders
32079 deny message = This address does not send an unsigned reverse path
32081 recipients = +batv_senders
32083 # Bounces: In case of prvs-signed address, check signature.
32084 deny message = Invalid reverse path signature.
32086 condition = ${prvscheck {$local_part@$domain}\
32087 {PRVSCHECK_SQL}{1}}
32088 !condition = $prvscheck_result
32090 The first statement rejects recipients for bounce messages that are addressed
32091 to plain BATV sender addresses, because it is known that BATV senders do not
32092 send out messages with plain sender addresses. The second statement rejects
32093 recipients that are prvs-signed, but with invalid signatures (either because
32094 the key is wrong, or the signature has timed out).
32096 A non-prvs-signed address is not rejected by the second statement, because the
32097 &%prvscheck%& expansion yields an empty string if its first argument is not a
32098 prvs-signed address, thus causing the &%condition%& condition to be false. If
32099 the first argument is a syntactically valid prvs-signed address, the yield is
32100 the third string (in this case &"1"&), whether or not the cryptographic and
32101 timeout checks succeed. The &$prvscheck_result$& variable contains the result
32102 of the checks (empty for failure, &"1"& for success).
32104 There is one more issue you must consider when implementing prvs-signing:
32105 you have to ensure that the routers accept prvs-signed addresses and
32106 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
32107 router to remove the signature with a configuration along these lines:
32111 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
32113 This works because, if the third argument of &%prvscheck%& is empty, the result
32114 of the expansion of a prvs-signed address is the decoded value of the original
32115 address. This router should probably be the first of your routers that handles
32118 To create BATV-signed addresses in the first place, a transport of this form
32121 external_smtp_batv:
32123 return_path = ${prvs {$return_path} \
32124 {${lookup mysql{SELECT \
32125 secret FROM batv_prvs WHERE \
32126 sender='${quote_mysql:$sender_address}'} \
32129 If no key can be found for the existing return path, no signing takes place.
32133 .section "Using an ACL to control relaying" "SECTrelaycontrol"
32134 .cindex "&ACL;" "relay control"
32135 .cindex "relaying" "control by ACL"
32136 .cindex "policy control" "relay control"
32137 An MTA is said to &'relay'& a message if it receives it from some host and
32138 delivers it directly to another host as a result of a remote address contained
32139 within it. Redirecting a local address via an alias or forward file and then
32140 passing the message on to another host is not relaying,
32141 .cindex "&""percent hack""&"
32142 but a redirection as a result of the &"percent hack"& is.
32144 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
32145 A host which is acting as a gateway or an MX backup is concerned with incoming
32146 relaying from arbitrary hosts to a specific set of domains. On the other hand,
32147 a host which is acting as a smart host for a number of clients is concerned
32148 with outgoing relaying from those clients to the Internet at large. Often the
32149 same host is fulfilling both functions,
32151 . as illustrated in the diagram below,
32153 but in principle these two kinds of relaying are entirely independent. What is
32154 not wanted is the transmission of mail from arbitrary remote hosts through your
32155 system to arbitrary domains.
32158 You can implement relay control by means of suitable statements in the ACL that
32159 runs for each RCPT command. For convenience, it is often easiest to use
32160 Exim's named list facility to define the domains and hosts involved. For
32161 example, suppose you want to do the following:
32164 Deliver a number of domains to mailboxes on the local host (or process them
32165 locally in some other way). Let's say these are &'my.dom1.example'& and
32166 &'my.dom2.example'&.
32168 Relay mail for a number of other domains for which you are the secondary MX.
32169 These might be &'friend1.example'& and &'friend2.example'&.
32171 Relay mail from the hosts on your local LAN, to whatever domains are involved.
32172 Suppose your LAN is 192.168.45.0/24.
32176 In the main part of the configuration, you put the following definitions:
32178 domainlist local_domains = my.dom1.example : my.dom2.example
32179 domainlist relay_to_domains = friend1.example : friend2.example
32180 hostlist relay_from_hosts = 192.168.45.0/24
32182 Now you can use these definitions in the ACL that is run for every RCPT
32186 accept domains = +local_domains : +relay_to_domains
32187 accept hosts = +relay_from_hosts
32189 The first statement accepts any RCPT command that contains an address in
32190 the local or relay domains. For any other domain, control passes to the second
32191 statement, which accepts the command only if it comes from one of the relay
32192 hosts. In practice, you will probably want to make your ACL more sophisticated
32193 than this, for example, by including sender and recipient verification. The
32194 default configuration includes a more comprehensive example, which is described
32195 in chapter &<<CHAPdefconfil>>&.
32199 .section "Checking a relay configuration" "SECTcheralcon"
32200 .cindex "relaying" "checking control of"
32201 You can check the relay characteristics of your configuration in the same way
32202 that you can test any ACL behaviour for an incoming SMTP connection, by using
32203 the &%-bh%& option to run a fake SMTP session with which you interact.
32208 . ////////////////////////////////////////////////////////////////////////////
32209 . ////////////////////////////////////////////////////////////////////////////
32211 .chapter "Content scanning at ACL time" "CHAPexiscan"
32212 .scindex IIDcosca "content scanning" "at ACL time"
32213 The extension of Exim to include content scanning at ACL time, formerly known
32214 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
32215 was integrated into the main source for Exim release 4.50, and Tom continues to
32216 maintain it. Most of the wording of this chapter is taken from Tom's
32219 It is also possible to scan the content of messages at other times. The
32220 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
32221 scanning after all the ACLs have run. A transport filter can be used to scan
32222 messages at delivery time (see the &%transport_filter%& option, described in
32223 chapter &<<CHAPtransportgeneric>>&).
32225 If you want to include the ACL-time content-scanning features when you compile
32226 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
32227 &_Local/Makefile_&. When you do that, the Exim binary is built with:
32230 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
32231 for all MIME parts for SMTP and non-SMTP messages, respectively.
32233 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
32234 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
32235 run at the end of message reception (the &%acl_smtp_data%& ACL).
32237 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
32238 of messages, or parts of messages, for debugging purposes.
32240 Additional expansion variables that are set in the new ACL and by the new
32243 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
32246 Content-scanning is continually evolving, and new features are still being
32247 added. While such features are still unstable and liable to incompatible
32248 changes, they are made available in Exim by setting options whose names begin
32249 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
32250 this manual. You can find out about them by reading the file called
32251 &_doc/experimental.txt_&.
32253 All the content-scanning facilities work on a MBOX copy of the message that is
32254 temporarily created in a file called:
32256 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
32258 The &_.eml_& extension is a friendly hint to virus scanners that they can
32259 expect an MBOX-like structure inside that file. The file is created when the
32260 first content scanning facility is called. Subsequent calls to content
32261 scanning conditions open the same file again. The directory is recursively
32262 removed when the &%acl_smtp_data%& ACL has finished running, unless
32264 control = no_mbox_unspool
32266 has been encountered. When the MIME ACL decodes files, they are put into the
32267 same directory by default.
32271 .section "Scanning for viruses" "SECTscanvirus"
32272 .cindex "virus scanning"
32273 .cindex "content scanning" "for viruses"
32274 .cindex "content scanning" "the &%malware%& condition"
32275 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
32276 It supports a &"generic"& interface to scanners called via the shell, and
32277 specialized interfaces for &"daemon"& type virus scanners, which are resident
32278 in memory and thus are much faster.
32280 A timeout of 2 minutes is applied to a scanner call (by default);
32281 if it expires then a defer action is taken.
32283 .oindex "&%av_scanner%&"
32284 You can set the &%av_scanner%& option in the main part of the configuration
32285 to specify which scanner to use, together with any additional options that
32286 are needed. The basic syntax is as follows:
32288 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
32290 If you do not set &%av_scanner%&, it defaults to
32292 av_scanner = sophie:/var/run/sophie
32294 If the value of &%av_scanner%& starts with a dollar character, it is expanded
32296 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
32297 The following scanner types are supported in this release,
32298 though individual ones can be included or not at build time:
32302 .cindex "virus scanners" "avast"
32303 This is the scanner daemon of Avast. It has been tested with Avast Core
32304 Security (currently at version 2.2.0).
32305 You can get a trial version at &url(https://www.avast.com) or for Linux
32306 at &url(https://www.avast.com/linux-server-antivirus).
32307 This scanner type takes one option,
32308 which can be either a full path to a UNIX socket,
32309 or host and port specifiers separated by white space.
32310 The host may be a name or an IP address; the port is either a
32311 single number or a pair of numbers with a dash between.
32312 A list of options may follow. These options are interpreted on the
32313 Exim's side of the malware scanner, or are given on separate lines to
32314 the daemon as options before the main scan command.
32316 .cindex &`pass_unscanned`& "avast"
32317 If &`pass_unscanned`&
32318 is set, any files the Avast scanner can't scan (e.g.
32319 decompression bombs, or invalid archives) are considered clean. Use with
32324 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
32325 av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
32326 av_scanner = avast:192.168.2.22 5036
32328 If you omit the argument, the default path
32329 &_/var/run/avast/scan.sock_&
32331 If you use a remote host,
32332 you need to make Exim's spool directory available to it,
32333 as the scanner is passed a file path, not file contents.
32334 For information about available commands and their options you may use
32336 $ socat UNIX:/var/run/avast/scan.sock STDIO:
32342 If the scanner returns a temporary failure (e.g. license issues, or
32343 permission problems), the message is deferred and a paniclog entry is
32344 written. The usual &`defer_ok`& option is available.
32346 .vitem &%aveserver%&
32347 .cindex "virus scanners" "Kaspersky"
32348 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
32349 at &url(https://www.kaspersky.com/). This scanner type takes one option,
32350 which is the path to the daemon's UNIX socket. The default is shown in this
32353 av_scanner = aveserver:/var/run/aveserver
32358 .cindex "virus scanners" "clamd"
32359 This daemon-type scanner is GPL and free. You can get it at
32360 &url(https://www.clamav.net/). Some older versions of clamd do not seem to
32361 unpack MIME containers, so it used to be recommended to unpack MIME attachments
32362 in the MIME ACL. This is no longer believed to be necessary.
32364 The options are a list of server specifiers, which may be
32365 a UNIX socket specification,
32366 a TCP socket specification,
32367 or a (global) option.
32369 A socket specification consists of a space-separated list.
32370 For a Unix socket the first element is a full path for the socket,
32371 for a TCP socket the first element is the IP address
32372 and the second a port number,
32373 Any further elements are per-server (non-global) options.
32374 These per-server options are supported:
32376 retry=<timespec> Retry on connect fail
32379 The &`retry`& option specifies a time after which a single retry for
32380 a failed connect is made. The default is to not retry.
32382 If a Unix socket file is specified, only one server is supported.
32386 av_scanner = clamd:/opt/clamd/socket
32387 av_scanner = clamd:192.0.2.3 1234
32388 av_scanner = clamd:192.0.2.3 1234:local
32389 av_scanner = clamd:192.0.2.3 1234 retry=10s
32390 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
32392 If the value of av_scanner points to a UNIX socket file or contains the
32394 option, then the ClamAV interface will pass a filename containing the data
32395 to be scanned, which should normally result in less I/O happening and be
32396 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
32397 Exim does not assume that there is a common filesystem with the remote host.
32399 The final example shows that multiple TCP targets can be specified. Exim will
32400 randomly use one for each incoming email (i.e. it load balances them). Note
32401 that only TCP targets may be used if specifying a list of scanners; a UNIX
32402 socket cannot be mixed in with TCP targets. If one of the servers becomes
32403 unavailable, Exim will try the remaining one(s) until it finds one that works.
32404 When a clamd server becomes unreachable, Exim will log a message. Exim does
32405 not keep track of scanner state between multiple messages, and the scanner
32406 selection is random, so the message will get logged in the mainlog for each
32407 email that the down scanner gets chosen first (message wrapped to be readable):
32409 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
32410 clamd: connection to localhost, port 3310 failed
32411 (Connection refused)
32414 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
32415 contributing the code for this scanner.
32418 .cindex "virus scanners" "command line interface"
32419 This is the keyword for the generic command line scanner interface. It can be
32420 used to attach virus scanners that are invoked from the shell. This scanner
32421 type takes 3 mandatory options:
32424 The full path and name of the scanner binary, with all command line options,
32425 and a placeholder (&`%s`&) for the directory to scan.
32428 A regular expression to match against the STDOUT and STDERR output of the
32429 virus scanner. If the expression matches, a virus was found. You must make
32430 absolutely sure that this expression matches on &"virus found"&. This is called
32431 the &"trigger"& expression.
32434 Another regular expression, containing exactly one pair of parentheses, to
32435 match the name of the virus found in the scanners output. This is called the
32436 &"name"& expression.
32439 For example, Sophos Sweep reports a virus on a line like this:
32441 Virus 'W32/Magistr-B' found in file ./those.bat
32443 For the trigger expression, we can match the phrase &"found in file"&. For the
32444 name expression, we want to extract the W32/Magistr-B string, so we can match
32445 for the single quotes left and right of it. Altogether, this makes the
32446 configuration setting:
32448 av_scanner = cmdline:\
32449 /path/to/sweep -ss -all -rec -archive %s:\
32450 found in file:'(.+)'
32453 .cindex "virus scanners" "DrWeb"
32454 The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface
32456 either a full path to a UNIX socket,
32457 or host and port specifiers separated by white space.
32458 The host may be a name or an IP address; the port is either a
32459 single number or a pair of numbers with a dash between.
32462 av_scanner = drweb:/var/run/drwebd.sock
32463 av_scanner = drweb:192.168.2.20 31337
32465 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
32466 is used. Thanks to Alex Miller for contributing the code for this scanner.
32469 .cindex "virus scanners" "f-protd"
32470 The f-protd scanner is accessed via HTTP over TCP.
32471 One argument is taken, being a space-separated hostname and port number
32475 av_scanner = f-protd:localhost 10200-10204
32477 If you omit the argument, the default values shown above are used.
32479 .vitem &%f-prot6d%&
32480 .cindex "virus scanners" "f-prot6d"
32481 The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
32482 One argument is taken, being a space-separated hostname and port number.
32485 av_scanner = f-prot6d:localhost 10200
32487 If you omit the argument, the default values show above are used.
32490 .cindex "virus scanners" "F-Secure"
32491 The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one
32492 argument which is the path to a UNIX socket. For example:
32494 av_scanner = fsecure:/path/to/.fsav
32496 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
32497 Thelmen for contributing the code for this scanner.
32499 .vitem &%kavdaemon%&
32500 .cindex "virus scanners" "Kaspersky"
32501 This is the scanner daemon of Kaspersky Version 4. This version of the
32502 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
32503 scanner type takes one option, which is the path to the daemon's UNIX socket.
32506 av_scanner = kavdaemon:/opt/AVP/AvpCtl
32508 The default path is &_/var/run/AvpCtl_&.
32511 .cindex "virus scanners" "mksd"
32512 This was a daemon type scanner that is aimed mainly at Polish users,
32513 though some documentation was available in English.
32514 The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir)
32515 and this appears to be a candidate for removal from Exim, unless
32516 we are informed of other virus scanners which use the same protocol
32518 The only option for this scanner type is
32519 the maximum number of processes used simultaneously to scan the attachments,
32520 provided that mksd has
32521 been run with at least the same number of child processes. For example:
32523 av_scanner = mksd:2
32525 You can safely omit this option (the default value is 1).
32528 .cindex "virus scanners" "simple socket-connected"
32529 This is a general-purpose way of talking to simple scanner daemons
32530 running on the local machine.
32531 There are four options:
32532 an address (which may be an IP address and port, or the path of a Unix socket),
32533 a commandline to send (may include a single %s which will be replaced with
32534 the path to the mail file to be scanned),
32535 an RE to trigger on from the returned data,
32536 and an RE to extract malware_name from the returned data.
32539 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
32541 Note that surrounding whitespace is stripped from each option, meaning
32542 there is no way to specify a trailing newline.
32543 The socket specifier and both regular-expressions are required.
32544 Default for the commandline is &_%s\n_& (note this does have a trailing newline);
32545 specify an empty element to get this.
32548 .cindex "virus scanners" "Sophos and Sophie"
32549 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
32550 You can get Sophie at &url(http://sophie.sourceforge.net/). The only option
32551 for this scanner type is the path to the UNIX socket that Sophie uses for
32552 client communication. For example:
32554 av_scanner = sophie:/tmp/sophie
32556 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
32560 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
32561 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
32564 The &%av_scanner%& option is expanded each time &%malware%& is called. This
32565 makes it possible to use different scanners. See further below for an example.
32566 The &%malware%& condition caches its results, so when you use it multiple times
32567 for the same message, the actual scanning process is only carried out once.
32568 However, using expandable items in &%av_scanner%& disables this caching, in
32569 which case each use of the &%malware%& condition causes a new scan of the
32572 The &%malware%& condition takes a right-hand argument that is expanded before
32573 use and taken as a list, slash-separated by default.
32574 The first element can then be one of
32577 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
32578 The condition succeeds if a virus was found, and fail otherwise. This is the
32581 &"false"& or &"0"& or an empty string, in which case no scanning is done and
32582 the condition fails immediately.
32584 A regular expression, in which case the message is scanned for viruses. The
32585 condition succeeds if a virus is found and its name matches the regular
32586 expression. This allows you to take special actions on certain types of virus.
32587 Note that &"/"& characters in the RE must be doubled due to the list-processing,
32588 unless the separator is changed (in the usual way &<<SECTlistsepchange>>&).
32591 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
32592 messages even if there is a problem with the virus scanner.
32593 Otherwise, such a problem causes the ACL to defer.
32595 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
32596 specify a non-default timeout. The default is two minutes.
32599 malware = * / defer_ok / tmo=10s
32601 A timeout causes the ACL to defer.
32603 .vindex "&$callout_address$&"
32604 When a connection is made to the scanner the expansion variable &$callout_address$&
32605 is set to record the actual address used.
32607 .vindex "&$malware_name$&"
32608 When a virus is found, the condition sets up an expansion variable called
32609 &$malware_name$& that contains the name of the virus. You can use it in a
32610 &%message%& modifier that specifies the error returned to the sender, and/or in
32613 Beware the interaction of Exim's &%message_size_limit%& with any size limits
32614 imposed by your anti-virus scanner.
32616 Here is a very simple scanning example:
32618 deny message = This message contains malware ($malware_name)
32621 The next example accepts messages when there is a problem with the scanner:
32623 deny message = This message contains malware ($malware_name)
32624 malware = */defer_ok
32626 The next example shows how to use an ACL variable to scan with both sophie and
32627 aveserver. It assumes you have set:
32629 av_scanner = $acl_m0
32631 in the main Exim configuration.
32633 deny message = This message contains malware ($malware_name)
32634 set acl_m0 = sophie
32637 deny message = This message contains malware ($malware_name)
32638 set acl_m0 = aveserver
32643 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
32644 .cindex "content scanning" "for spam"
32645 .cindex "spam scanning"
32646 .cindex "SpamAssassin"
32648 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
32649 score and a report for the message.
32650 Support is also provided for Rspamd.
32652 For more information about installation and configuration of SpamAssassin or
32653 Rspamd refer to their respective websites at
32654 &url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/)
32656 SpamAssassin can be installed with CPAN by running:
32658 perl -MCPAN -e 'install Mail::SpamAssassin'
32660 SpamAssassin has its own set of configuration files. Please review its
32661 documentation to see how you can tweak it. The default installation should work
32664 .oindex "&%spamd_address%&"
32665 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
32666 intend to use an instance running on the local host you do not need to set
32667 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
32668 you must set the &%spamd_address%& option in the global part of the Exim
32669 configuration as follows (example):
32671 spamd_address = 192.168.99.45 783
32673 The SpamAssassin protocol relies on a TCP half-close from the client.
32674 If your SpamAssassin client side is running a Linux system with an
32675 iptables firewall, consider setting
32676 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
32677 timeout, Exim uses when waiting for a response from the SpamAssassin
32678 server (currently defaulting to 120s). With a lower value the Linux
32679 connection tracking may consider your half-closed connection as dead too
32683 To use Rspamd (which by default listens on all local addresses
32685 you should add &%variant=rspamd%& after the address/port pair, for example:
32687 spamd_address = 127.0.0.1 11333 variant=rspamd
32690 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
32691 sockets. If you want to us these, supply &%spamd_address%& with an absolute
32692 filename instead of an address/port pair:
32694 spamd_address = /var/run/spamd_socket
32696 You can have multiple &%spamd%& servers to improve scalability. These can
32697 reside on other hardware reachable over the network. To specify multiple
32698 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
32699 option, separated with colons (the separator can be changed in the usual way &<<SECTlistsepchange>>&):
32701 spamd_address = 192.168.2.10 783 : \
32702 192.168.2.11 783 : \
32705 Up to 32 &%spamd%& servers are supported.
32706 When a server fails to respond to the connection attempt, all other
32707 servers are tried until one succeeds. If no server responds, the &%spam%&
32710 Unix and TCP socket specifications may be mixed in any order.
32711 Each element of the list is a list itself, space-separated by default
32712 and changeable in the usual way (&<<SECTlistsepchange>>&);
32713 take care to not double the separator.
32715 For TCP socket specifications a host name or IP (v4 or v6, but
32716 subject to list-separator quoting rules) address can be used,
32717 and the port can be one or a dash-separated pair.
32718 In the latter case, the range is tried in strict order.
32720 Elements after the first for Unix sockets, or second for TCP socket,
32722 The supported options are:
32724 pri=<priority> Selection priority
32725 weight=<value> Selection bias
32726 time=<start>-<end> Use only between these times of day
32727 retry=<timespec> Retry on connect fail
32728 tmo=<timespec> Connection time limit
32729 variant=rspamd Use Rspamd rather than SpamAssassin protocol
32732 The &`pri`& option specifies a priority for the server within the list,
32733 higher values being tried first.
32734 The default priority is 1.
32736 The &`weight`& option specifies a selection bias.
32737 Within a priority set
32738 servers are queried in a random fashion, weighted by this value.
32739 The default value for selection bias is 1.
32741 Time specifications for the &`time`& option are <hour>.<minute>.<second>
32742 in the local time zone; each element being one or more digits.
32743 Either the seconds or both minutes and seconds, plus the leading &`.`&
32744 characters, may be omitted and will be taken as zero.
32746 Timeout specifications for the &`retry`& and &`tmo`& options
32747 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
32749 The &`tmo`& option specifies an overall timeout for communication.
32750 The default value is two minutes.
32752 The &`retry`& option specifies a time after which a single retry for
32753 a failed connect is made.
32754 The default is to not retry.
32756 The &%spamd_address%& variable is expanded before use if it starts with
32757 a dollar sign. In this case, the expansion may return a string that is
32758 used as the list so that multiple spamd servers can be the result of an
32761 .vindex "&$callout_address$&"
32762 When a connection is made to the server the expansion variable &$callout_address$&
32763 is set to record the actual address used.
32765 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
32766 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
32768 deny message = This message was classified as SPAM
32771 The right-hand side of the &%spam%& condition specifies a name. This is
32772 relevant if you have set up multiple SpamAssassin profiles. If you do not want
32773 to scan using a specific profile, but rather use the SpamAssassin system-wide
32774 default profile, you can scan for an unknown name, or simply use &"nobody"&.
32775 Rspamd does not use this setting. However, you must put something on the
32778 The name allows you to use per-domain or per-user antispam profiles in
32779 principle, but this is not straightforward in practice, because a message may
32780 have multiple recipients, not necessarily all in the same domain. Because the
32781 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
32782 read the contents of the message, the variables &$local_part$& and &$domain$&
32784 Careful enforcement of single-recipient messages
32785 (e.g. by responding with defer in the recipient ACL for all recipients
32787 or the use of PRDR,
32788 .cindex "PRDR" "use for per-user SpamAssassin profiles"
32789 are needed to use this feature.
32791 The right-hand side of the &%spam%& condition is expanded before being used, so
32792 you can put lookups or conditions there. When the right-hand side evaluates to
32793 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
32796 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
32797 large ones may cause significant performance degradation. As most spam messages
32798 are quite small, it is recommended that you do not scan the big ones. For
32801 deny message = This message was classified as SPAM
32802 condition = ${if < {$message_size}{10K}}
32806 The &%spam%& condition returns true if the threshold specified in the user's
32807 SpamAssassin profile has been matched or exceeded. If you want to use the
32808 &%spam%& condition for its side effects (see the variables below), you can make
32809 it always return &"true"& by appending &`:true`& to the username.
32811 .cindex "spam scanning" "returned variables"
32812 When the &%spam%& condition is run, it sets up a number of expansion
32814 Except for &$spam_report$&,
32815 these variables are saved with the received message so are
32816 available for use at delivery time.
32819 .vitem &$spam_score$&
32820 The spam score of the message, for example, &"3.4"& or &"30.5"&. This is useful
32821 for inclusion in log or reject messages.
32823 .vitem &$spam_score_int$&
32824 The spam score of the message, multiplied by ten, as an integer value. For
32825 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
32826 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
32827 The integer value is useful for numeric comparisons in conditions.
32829 .vitem &$spam_bar$&
32830 A string consisting of a number of &"+"& or &"-"& characters, representing the
32831 integer part of the spam score value. A spam score of 4.4 would have a
32832 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
32833 headers, since MUAs can match on such strings. The maximum length of the
32834 spam bar is 50 characters.
32836 .vitem &$spam_report$&
32837 A multiline text table, containing the full SpamAssassin report for the
32838 message. Useful for inclusion in headers or reject messages.
32839 This variable is only usable in a DATA-time ACL.
32840 Beware that SpamAssassin may return non-ASCII characters, especially
32841 when running in country-specific locales, which are not legal
32842 unencoded in headers.
32844 .vitem &$spam_action$&
32845 For SpamAssassin either 'reject' or 'no action' depending on the
32846 spam score versus threshold.
32847 For Rspamd, the recommended action.
32851 The &%spam%& condition caches its results unless expansion in
32852 spamd_address was used. If you call it again with the same user name, it
32853 does not scan again, but rather returns the same values as before.
32855 The &%spam%& condition returns DEFER if there is any error while running
32856 the message through SpamAssassin or if the expansion of spamd_address
32857 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
32858 statement block), append &`/defer_ok`& to the right-hand side of the
32859 spam condition, like this:
32861 deny message = This message was classified as SPAM
32862 spam = joe/defer_ok
32864 This causes messages to be accepted even if there is a problem with &%spamd%&.
32866 Here is a longer, commented example of the use of the &%spam%&
32869 # put headers in all messages (no matter if spam or not)
32870 warn spam = nobody:true
32871 add_header = X-Spam-Score: $spam_score ($spam_bar)
32872 add_header = X-Spam-Report: $spam_report
32874 # add second subject line with *SPAM* marker when message
32875 # is over threshold
32877 add_header = Subject: *SPAM* $h_Subject:
32879 # reject spam at high scores (> 12)
32880 deny message = This message scored $spam_score spam points.
32882 condition = ${if >{$spam_score_int}{120}{1}{0}}
32887 .section "Scanning MIME parts" "SECTscanmimepart"
32888 .cindex "content scanning" "MIME parts"
32889 .cindex "MIME content scanning"
32890 .oindex "&%acl_smtp_mime%&"
32891 .oindex "&%acl_not_smtp_mime%&"
32892 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
32893 each MIME part of an SMTP message, including multipart types, in the sequence
32894 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
32895 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
32896 options may both refer to the same ACL if you want the same processing in both
32899 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
32900 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
32901 the case of a non-SMTP message. However, a MIME ACL is called only if the
32902 message contains a &'Content-Type:'& header line. When a call to a MIME
32903 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
32904 result code is sent to the client. In the case of an SMTP message, the
32905 &%acl_smtp_data%& ACL is not called when this happens.
32907 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
32908 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
32909 condition to match against the raw MIME part. You can also use the
32910 &%mime_regex%& condition to match against the decoded MIME part (see section
32911 &<<SECTscanregex>>&).
32913 At the start of a MIME ACL, a number of variables are set from the header
32914 information for the relevant MIME part. These are described below. The contents
32915 of the MIME part are not by default decoded into a disk file except for MIME
32916 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
32917 part into a disk file, you can use the &%decode%& condition. The general
32920 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
32922 The right hand side is expanded before use. After expansion,
32926 &"0"& or &"false"&, in which case no decoding is done.
32928 The string &"default"&. In that case, the file is put in the temporary
32929 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
32930 a sequential filename consisting of the message id and a sequence number. The
32931 full path and name is available in &$mime_decoded_filename$& after decoding.
32933 A full path name starting with a slash. If the full name is an existing
32934 directory, it is used as a replacement for the default directory. The filename
32935 is then sequentially assigned. If the path does not exist, it is used as
32936 the full path and filename.
32938 If the string does not start with a slash, it is used as the
32939 filename, and the default path is then used.
32941 The &%decode%& condition normally succeeds. It is only false for syntax
32942 errors or unusual circumstances such as memory shortages. You can easily decode
32943 a file with its original, proposed filename using
32945 decode = $mime_filename
32947 However, you should keep in mind that &$mime_filename$& might contain
32948 anything. If you place files outside of the default path, they are not
32949 automatically unlinked.
32951 For RFC822 attachments (these are messages attached to messages, with a
32952 content-type of &"message/rfc822"&), the ACL is called again in the same manner
32953 as for the primary message, only that the &$mime_is_rfc822$& expansion
32954 variable is set (see below). Attached messages are always decoded to disk
32955 before being checked, and the files are unlinked once the check is done.
32957 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
32958 used to match regular expressions against raw and decoded MIME parts,
32959 respectively. They are described in section &<<SECTscanregex>>&.
32961 .cindex "MIME content scanning" "returned variables"
32962 The following list describes all expansion variables that are
32963 available in the MIME ACL:
32966 .vitem &$mime_boundary$&
32967 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
32968 have a boundary string, which is stored in this variable. If the current part
32969 has no boundary parameter in the &'Content-Type:'& header, this variable
32970 contains the empty string.
32972 .vitem &$mime_charset$&
32973 This variable contains the character set identifier, if one was found in the
32974 &'Content-Type:'& header. Examples for charset identifiers are:
32980 Please note that this value is not normalized, so you should do matches
32981 case-insensitively.
32983 .vitem &$mime_content_description$&
32984 This variable contains the normalized content of the &'Content-Description:'&
32985 header. It can contain a human-readable description of the parts content. Some
32986 implementations repeat the filename for attachments here, but they are usually
32987 only used for display purposes.
32989 .vitem &$mime_content_disposition$&
32990 This variable contains the normalized content of the &'Content-Disposition:'&
32991 header. You can expect strings like &"attachment"& or &"inline"& here.
32993 .vitem &$mime_content_id$&
32994 This variable contains the normalized content of the &'Content-ID:'& header.
32995 This is a unique ID that can be used to reference a part from another part.
32997 .vitem &$mime_content_size$&
32998 This variable is set only after the &%decode%& modifier (see above) has been
32999 successfully run. It contains the size of the decoded part in kilobytes. The
33000 size is always rounded up to full kilobytes, so only a completely empty part
33001 has a &$mime_content_size$& of zero.
33003 .vitem &$mime_content_transfer_encoding$&
33004 This variable contains the normalized content of the
33005 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
33006 type. Typical values are &"base64"& and &"quoted-printable"&.
33008 .vitem &$mime_content_type$&
33009 If the MIME part has a &'Content-Type:'& header, this variable contains its
33010 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
33011 are some examples of popular MIME types, as they may appear in this variable:
33015 application/octet-stream
33019 If the MIME part has no &'Content-Type:'& header, this variable contains the
33022 .vitem &$mime_decoded_filename$&
33023 This variable is set only after the &%decode%& modifier (see above) has been
33024 successfully run. It contains the full path and filename of the file
33025 containing the decoded data.
33030 .vitem &$mime_filename$&
33031 This is perhaps the most important of the MIME variables. It contains a
33032 proposed filename for an attachment, if one was found in either the
33033 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
33036 decoded, but no additional sanity checks are done.
33038 found, this variable contains the empty string.
33040 .vitem &$mime_is_coverletter$&
33041 This variable attempts to differentiate the &"cover letter"& of an e-mail from
33042 attached data. It can be used to clamp down on flashy or unnecessarily encoded
33043 content in the cover letter, while not restricting attachments at all.
33045 The variable contains 1 (true) for a MIME part believed to be part of the
33046 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
33050 The outermost MIME part of a message is always a cover letter.
33053 If a multipart/alternative or multipart/related MIME part is a cover letter,
33054 so are all MIME subparts within that multipart.
33057 If any other multipart is a cover letter, the first subpart is a cover letter,
33058 and the rest are attachments.
33061 All parts contained within an attachment multipart are attachments.
33064 As an example, the following will ban &"HTML mail"& (including that sent with
33065 alternative plain text), while allowing HTML files to be attached. HTML
33066 coverletter mail attached to non-HTML coverletter mail will also be allowed:
33068 deny message = HTML mail is not accepted here
33069 !condition = $mime_is_rfc822
33070 condition = $mime_is_coverletter
33071 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
33073 .vitem &$mime_is_multipart$&
33074 This variable has the value 1 (true) when the current part has the main type
33075 &"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
33076 Since multipart entities only serve as containers for other parts, you may not
33077 want to carry out specific actions on them.
33079 .vitem &$mime_is_rfc822$&
33080 This variable has the value 1 (true) if the current part is not a part of the
33081 checked message itself, but part of an attached message. Attached message
33082 decoding is fully recursive.
33084 .vitem &$mime_part_count$&
33085 This variable is a counter that is raised for each processed MIME part. It
33086 starts at zero for the very first part (which is usually a multipart). The
33087 counter is per-message, so it is reset when processing RFC822 attachments (see
33088 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
33089 complete, so you can use it in the DATA ACL to determine the number of MIME
33090 parts of a message. For non-MIME messages, this variable contains the value -1.
33095 .section "Scanning with regular expressions" "SECTscanregex"
33096 .cindex "content scanning" "with regular expressions"
33097 .cindex "regular expressions" "content scanning with"
33098 You can specify your own custom regular expression matches on the full body of
33099 the message, or on individual MIME parts.
33101 The &%regex%& condition takes one or more regular expressions as arguments and
33102 matches them against the full message (when called in the DATA ACL) or a raw
33103 MIME part (when called in the MIME ACL). The &%regex%& condition matches
33104 linewise, with a maximum line length of 32K characters. That means you cannot
33105 have multiline matches with the &%regex%& condition.
33107 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
33108 to 32K of decoded content (the whole content at once, not linewise). If the
33109 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
33110 is decoded automatically when &%mime_regex%& is executed (using default path
33111 and filename values). If the decoded data is larger than 32K, only the first
33112 32K characters are checked.
33114 The regular expressions are passed as a colon-separated list. To include a
33115 literal colon, you must double it. Since the whole right-hand side string is
33116 expanded before being used, you must also escape dollar signs and backslashes
33117 with more backslashes, or use the &`\N`& facility to disable expansion.
33118 Here is a simple example that contains two regular expressions:
33120 deny message = contains blacklisted regex ($regex_match_string)
33121 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
33123 The conditions returns true if any one of the regular expressions matches. The
33124 &$regex_match_string$& expansion variable is then set up and contains the
33125 matching regular expression.
33126 The expansion variables &$regex1$& &$regex2$& etc
33127 are set to any substrings captured by the regular expression.
33129 &*Warning*&: With large messages, these conditions can be fairly
33137 . ////////////////////////////////////////////////////////////////////////////
33138 . ////////////////////////////////////////////////////////////////////////////
33140 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
33141 "Local scan function"
33142 .scindex IIDlosca "&[local_scan()]& function" "description of"
33143 .cindex "customizing" "input scan using C function"
33144 .cindex "policy control" "by local scan function"
33145 In these days of email worms, viruses, and ever-increasing spam, some sites
33146 want to apply a lot of checking to messages before accepting them.
33148 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
33149 passing messages to external virus and spam scanning software. You can also do
33150 a certain amount in Exim itself through string expansions and the &%condition%&
33151 condition in the ACL that runs after the SMTP DATA command or the ACL for
33152 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
33154 To allow for further customization to a site's own requirements, there is the
33155 possibility of linking Exim with a private message scanning function, written
33156 in C. If you want to run code that is written in something other than C, you
33157 can of course use a little C stub to call it.
33159 The local scan function is run once for every incoming message, at the point
33160 when Exim is just about to accept the message.
33161 It can therefore be used to control non-SMTP messages from local processes as
33162 well as messages arriving via SMTP.
33164 Exim applies a timeout to calls of the local scan function, and there is an
33165 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
33166 Zero means &"no timeout"&.
33167 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
33168 before calling the local scan function, so that the most common types of crash
33169 are caught. If the timeout is exceeded or one of those signals is caught, the
33170 incoming message is rejected with a temporary error if it is an SMTP message.
33171 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
33172 code. The incident is logged on the main and reject logs.
33176 .section "Building Exim to use a local scan function" "SECID207"
33177 .cindex "&[local_scan()]& function" "building Exim to use"
33178 To make use of the local scan function feature, you must tell Exim where your
33179 function is before building Exim, by setting
33181 both HAVE_LOCAL_SCAN and
33183 LOCAL_SCAN_SOURCE in your
33184 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
33185 directory, so you might set
33187 HAVE_LOCAL_SCAN=yes
33188 LOCAL_SCAN_SOURCE=Local/local_scan.c
33190 for example. The function must be called &[local_scan()]&. It is called by
33191 Exim after it has received a message, when the success return code is about to
33192 be sent. This is after all the ACLs have been run. The return code from your
33193 function controls whether the message is actually accepted or not. There is a
33194 commented template function (that just accepts the message) in the file
33195 _src/local_scan.c_.
33197 If you want to make use of Exim's runtime configuration file to set options
33198 for your &[local_scan()]& function, you must also set
33200 LOCAL_SCAN_HAS_OPTIONS=yes
33202 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
33207 .section "API for local_scan()" "SECTapiforloc"
33208 .cindex "&[local_scan()]& function" "API description"
33209 .cindex &%dlfunc%& "API description"
33210 You must include this line near the start of your code:
33212 #include "local_scan.h"
33214 This header file defines a number of variables and other values, and the
33215 prototype for the function itself. Exim is coded to use unsigned char values
33216 almost exclusively, and one of the things this header defines is a shorthand
33217 for &`unsigned char`& called &`uschar`&.
33218 It also contains the following macro definitions, to simplify casting character
33219 strings and pointers to character strings:
33221 #define CS (char *)
33222 #define CCS (const char *)
33223 #define CSS (char **)
33224 #define US (unsigned char *)
33225 #define CUS (const unsigned char *)
33226 #define USS (unsigned char **)
33228 The function prototype for &[local_scan()]& is:
33230 extern int local_scan(int fd, uschar **return_text);
33232 The arguments are as follows:
33235 &%fd%& is a file descriptor for the file that contains the body of the message
33236 (the -D file). The file is open for reading and writing, but updating it is not
33237 recommended. &*Warning*&: You must &'not'& close this file descriptor.
33239 The descriptor is positioned at character 19 of the file, which is the first
33240 character of the body itself, because the first 19 characters are the message
33241 id followed by &`-D`& and a newline. If you rewind the file, you should use the
33242 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
33243 case this changes in some future version.
33245 &%return_text%& is an address which you can use to return a pointer to a text
33246 string at the end of the function. The value it points to on entry is NULL.
33249 The function must return an &%int%& value which is one of the following macros:
33252 .vitem &`LOCAL_SCAN_ACCEPT`&
33253 .vindex "&$local_scan_data$&"
33254 The message is accepted. If you pass back a string of text, it is saved with
33255 the message, and made available in the variable &$local_scan_data$&. No
33256 newlines are permitted (if there are any, they are turned into spaces) and the
33257 maximum length of text is 1000 characters.
33259 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
33260 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
33261 queued without immediate delivery, and is frozen.
33263 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
33264 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
33265 queued without immediate delivery.
33267 .vitem &`LOCAL_SCAN_REJECT`&
33268 The message is rejected; the returned text is used as an error message which is
33269 passed back to the sender and which is also logged. Newlines are permitted &--
33270 they cause a multiline response for SMTP rejections, but are converted to
33271 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
33274 .vitem &`LOCAL_SCAN_TEMPREJECT`&
33275 The message is temporarily rejected; the returned text is used as an error
33276 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
33279 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
33280 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
33281 message is not written to the reject log. It has the effect of unsetting the
33282 &%rejected_header%& log selector for just this rejection. If
33283 &%rejected_header%& is already unset (see the discussion of the
33284 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
33285 same as LOCAL_SCAN_REJECT.
33287 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
33288 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
33289 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
33292 If the message is not being received by interactive SMTP, rejections are
33293 reported by writing to &%stderr%& or by sending an email, as configured by the
33294 &%-oe%& command line options.
33298 .section "Configuration options for local_scan()" "SECTconoptloc"
33299 .cindex "&[local_scan()]& function" "configuration options"
33300 It is possible to have option settings in the main configuration file
33301 that set values in static variables in the &[local_scan()]& module. If you
33302 want to do this, you must have the line
33304 LOCAL_SCAN_HAS_OPTIONS=yes
33306 in your &_Local/Makefile_& when you build Exim. (This line is in
33307 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
33308 file, you must define static variables to hold the option values, and a table
33311 The table must be a vector called &%local_scan_options%&, of type
33312 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
33313 and a pointer to the variable that holds the value. The entries must appear in
33314 alphabetical order. Following &%local_scan_options%& you must also define a
33315 variable called &%local_scan_options_count%& that contains the number of
33316 entries in the table. Here is a short example, showing two kinds of option:
33318 static int my_integer_option = 42;
33319 static uschar *my_string_option = US"a default string";
33321 optionlist local_scan_options[] = {
33322 { "my_integer", opt_int, &my_integer_option },
33323 { "my_string", opt_stringptr, &my_string_option }
33326 int local_scan_options_count =
33327 sizeof(local_scan_options)/sizeof(optionlist);
33329 The values of the variables can now be changed from Exim's runtime
33330 configuration file by including a local scan section as in this example:
33334 my_string = some string of text...
33336 The available types of option data are as follows:
33339 .vitem &*opt_bool*&
33340 This specifies a boolean (true/false) option. The address should point to a
33341 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
33342 that are defined as &"1"& and &"0"&, respectively. If you want to detect
33343 whether such a variable has been set at all, you can initialize it to
33344 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
33347 .vitem &*opt_fixed*&
33348 This specifies a fixed point number, such as is used for load averages.
33349 The address should point to a variable of type &`int`&. The value is stored
33350 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
33353 This specifies an integer; the address should point to a variable of type
33354 &`int`&. The value may be specified in any of the integer formats accepted by
33357 .vitem &*opt_mkint*&
33358 This is the same as &%opt_int%&, except that when such a value is output in a
33359 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
33360 printed with the suffix K or M.
33362 .vitem &*opt_octint*&
33363 This also specifies an integer, but the value is always interpreted as an
33364 octal integer, whether or not it starts with the digit zero, and it is
33365 always output in octal.
33367 .vitem &*opt_stringptr*&
33368 This specifies a string value; the address must be a pointer to a
33369 variable that points to a string (for example, of type &`uschar *`&).
33371 .vitem &*opt_time*&
33372 This specifies a time interval value. The address must point to a variable of
33373 type &`int`&. The value that is placed there is a number of seconds.
33376 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
33377 out the values of all the &[local_scan()]& options.
33381 .section "Available Exim variables" "SECID208"
33382 .cindex "&[local_scan()]& function" "available Exim variables"
33383 The header &_local_scan.h_& gives you access to a number of C variables. These
33384 are the only ones that are guaranteed to be maintained from release to release.
33385 Note, however, that you can obtain the value of any Exim expansion variable,
33386 including &$recipients$&, by calling &'expand_string()'&. The exported
33387 C variables are as follows:
33390 .vitem &*int&~body_linecount*&
33391 This variable contains the number of lines in the message's body.
33392 It is not valid if the &%spool_files_wireformat%& option is used.
33394 .vitem &*int&~body_zerocount*&
33395 This variable contains the number of binary zero bytes in the message's body.
33396 It is not valid if the &%spool_files_wireformat%& option is used.
33398 .vitem &*unsigned&~int&~debug_selector*&
33399 This variable is set to zero when no debugging is taking place. Otherwise, it
33400 is a bitmap of debugging selectors. Two bits are identified for use in
33401 &[local_scan()]&; they are defined as macros:
33404 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
33405 testing option that is not privileged &-- any caller may set it. All the
33406 other selector bits can be set only by admin users.
33409 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
33410 by the &`+local_scan`& debug selector. It is not included in the default set
33414 Thus, to write to the debugging output only when &`+local_scan`& has been
33415 selected, you should use code like this:
33417 if ((debug_selector & D_local_scan) != 0)
33418 debug_printf("xxx", ...);
33420 .vitem &*uschar&~*expand_string_message*&
33421 After a failing call to &'expand_string()'& (returned value NULL), the
33422 variable &%expand_string_message%& contains the error message, zero-terminated.
33424 .vitem &*header_line&~*header_list*&
33425 A pointer to a chain of header lines. The &%header_line%& structure is
33428 .vitem &*header_line&~*header_last*&
33429 A pointer to the last of the header lines.
33431 .vitem &*uschar&~*headers_charset*&
33432 The value of the &%headers_charset%& configuration option.
33434 .vitem &*BOOL&~host_checking*&
33435 This variable is TRUE during a host checking session that is initiated by the
33436 &%-bh%& command line option.
33438 .vitem &*uschar&~*interface_address*&
33439 The IP address of the interface that received the message, as a string. This
33440 is NULL for locally submitted messages.
33442 .vitem &*int&~interface_port*&
33443 The port on which this message was received. When testing with the &%-bh%&
33444 command line option, the value of this variable is -1 unless a port has been
33445 specified via the &%-oMi%& option.
33447 .vitem &*uschar&~*message_id*&
33448 This variable contains Exim's message id for the incoming message (the value of
33449 &$message_exim_id$&) as a zero-terminated string.
33451 .vitem &*uschar&~*received_protocol*&
33452 The name of the protocol by which the message was received.
33454 .vitem &*int&~recipients_count*&
33455 The number of accepted recipients.
33457 .vitem &*recipient_item&~*recipients_list*&
33458 .cindex "recipient" "adding in local scan"
33459 .cindex "recipient" "removing in local scan"
33460 The list of accepted recipients, held in a vector of length
33461 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
33462 can add additional recipients by calling &'receive_add_recipient()'& (see
33463 below). You can delete recipients by removing them from the vector and
33464 adjusting the value in &%recipients_count%&. In particular, by setting
33465 &%recipients_count%& to zero you remove all recipients. If you then return the
33466 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
33467 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
33468 and then call &'receive_add_recipient()'& as often as needed.
33470 .vitem &*uschar&~*sender_address*&
33471 The envelope sender address. For bounce messages this is the empty string.
33473 .vitem &*uschar&~*sender_host_address*&
33474 The IP address of the sending host, as a string. This is NULL for
33475 locally-submitted messages.
33477 .vitem &*uschar&~*sender_host_authenticated*&
33478 The name of the authentication mechanism that was used, or NULL if the message
33479 was not received over an authenticated SMTP connection.
33481 .vitem &*uschar&~*sender_host_name*&
33482 The name of the sending host, if known.
33484 .vitem &*int&~sender_host_port*&
33485 The port on the sending host.
33487 .vitem &*BOOL&~smtp_input*&
33488 This variable is TRUE for all SMTP input, including BSMTP.
33490 .vitem &*BOOL&~smtp_batched_input*&
33491 This variable is TRUE for BSMTP input.
33493 .vitem &*int&~store_pool*&
33494 The contents of this variable control which pool of memory is used for new
33495 requests. See section &<<SECTmemhanloc>>& for details.
33499 .section "Structure of header lines" "SECID209"
33500 The &%header_line%& structure contains the members listed below.
33501 You can add additional header lines by calling the &'header_add()'& function
33502 (see below). You can cause header lines to be ignored (deleted) by setting
33507 .vitem &*struct&~header_line&~*next*&
33508 A pointer to the next header line, or NULL for the last line.
33510 .vitem &*int&~type*&
33511 A code identifying certain headers that Exim recognizes. The codes are printing
33512 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
33513 Notice in particular that any header line whose type is * is not transmitted
33514 with the message. This flagging is used for header lines that have been
33515 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
33516 lines.) Effectively, * means &"deleted"&.
33518 .vitem &*int&~slen*&
33519 The number of characters in the header line, including the terminating and any
33522 .vitem &*uschar&~*text*&
33523 A pointer to the text of the header. It always ends with a newline, followed by
33524 a zero byte. Internal newlines are preserved.
33529 .section "Structure of recipient items" "SECID210"
33530 The &%recipient_item%& structure contains these members:
33533 .vitem &*uschar&~*address*&
33534 This is a pointer to the recipient address as it was received.
33536 .vitem &*int&~pno*&
33537 This is used in later Exim processing when top level addresses are created by
33538 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
33539 and must always contain -1 at this stage.
33541 .vitem &*uschar&~*errors_to*&
33542 If this value is not NULL, bounce messages caused by failing to deliver to the
33543 recipient are sent to the address it contains. In other words, it overrides the
33544 envelope sender for this one recipient. (Compare the &%errors_to%& generic
33545 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
33546 an unqualified address, Exim qualifies it using the domain from
33547 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
33548 is NULL for all recipients.
33553 .section "Available Exim functions" "SECID211"
33554 .cindex "&[local_scan()]& function" "available Exim functions"
33555 The header &_local_scan.h_& gives you access to a number of Exim functions.
33556 These are the only ones that are guaranteed to be maintained from release to
33560 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
33561 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
33563 This function creates a child process that runs the command specified by
33564 &%argv%&. The environment for the process is specified by &%envp%&, which can
33565 be NULL if no environment variables are to be passed. A new umask is supplied
33566 for the process in &%newumask%&.
33568 Pipes to the standard input and output of the new process are set up
33569 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
33570 standard error is cloned to the standard output. If there are any file
33571 descriptors &"in the way"& in the new process, they are closed. If the final
33572 argument is TRUE, the new process is made into a process group leader.
33574 The function returns the pid of the new process, or -1 if things go wrong.
33576 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
33577 This function waits for a child process to terminate, or for a timeout (in
33578 seconds) to expire. A timeout value of zero means wait as long as it takes. The
33579 return value is as follows:
33584 The process terminated by a normal exit and the value is the process
33590 The process was terminated by a signal and the value is the negation of the
33596 The process timed out.
33600 The was some other error in wait(); &%errno%& is still set.
33603 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
33604 This function provide you with a means of submitting a new message to
33605 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
33606 want, but this packages it all up for you.) The function creates a pipe,
33607 forks a subprocess that is running
33609 exim -t -oem -oi -f <>
33611 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
33612 that is connected to the standard input. The yield of the function is the PID
33613 of the subprocess. You can then write a message to the file descriptor, with
33614 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
33616 When you have finished, call &'child_close()'& to wait for the process to
33617 finish and to collect its ending status. A timeout value of zero is usually
33618 fine in this circumstance. Unless you have made a mistake with the recipient
33619 addresses, you should get a return code of zero.
33622 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
33623 *sender_authentication)*&
33624 This function is a more sophisticated version of &'child_open()'&. The command
33627 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
33629 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
33632 .vitem &*void&~debug_printf(char&~*,&~...)*&
33633 This is Exim's debugging function, with arguments as for &'(printf()'&. The
33634 output is written to the standard error stream. If no debugging is selected,
33635 calls to &'debug_printf()'& have no effect. Normally, you should make calls
33636 conditional on the &`local_scan`& debug selector by coding like this:
33638 if ((debug_selector & D_local_scan) != 0)
33639 debug_printf("xxx", ...);
33642 .vitem &*uschar&~*expand_string(uschar&~*string)*&
33643 This is an interface to Exim's string expansion code. The return value is the
33644 expanded string, or NULL if there was an expansion failure.
33645 The C variable &%expand_string_message%& contains an error message after an
33646 expansion failure. If expansion does not change the string, the return value is
33647 the pointer to the input string. Otherwise, the return value points to a new
33648 block of memory that was obtained by a call to &'store_get()'&. See section
33649 &<<SECTmemhanloc>>& below for a discussion of memory handling.
33651 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
33652 This function allows you to an add additional header line at the end of the
33653 existing ones. The first argument is the type, and should normally be a space
33654 character. The second argument is a format string and any number of
33655 substitution arguments as for &[sprintf()]&. You may include internal newlines
33656 if you want, and you must ensure that the string ends with a newline.
33658 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
33659 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
33660 This function adds a new header line at a specified point in the header
33661 chain. The header itself is specified as for &'header_add()'&.
33663 If &%name%& is NULL, the new header is added at the end of the chain if
33664 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
33665 NULL, the header lines are searched for the first non-deleted header that
33666 matches the name. If one is found, the new header is added before it if
33667 &%after%& is false. If &%after%& is true, the new header is added after the
33668 found header and any adjacent subsequent ones with the same name (even if
33669 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
33670 option controls where the header is added. If it is true, addition is at the
33671 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
33672 headers, or at the top if there are no &'Received:'& headers, you could use
33674 header_add_at_position(TRUE, US"Received", TRUE,
33675 ' ', "X-xxx: ...");
33677 Normally, there is always at least one non-deleted &'Received:'& header, but
33678 there may not be if &%received_header_text%& expands to an empty string.
33681 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
33682 This function removes header lines. If &%occurrence%& is zero or negative, all
33683 occurrences of the header are removed. If occurrence is greater than zero, that
33684 particular instance of the header is removed. If no header(s) can be found that
33685 match the specification, the function does nothing.
33688 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
33689 int&~length,&~BOOL&~notdel)*&"
33690 This function tests whether the given header has the given name. It is not just
33691 a string comparison, because white space is permitted between the name and the
33692 colon. If the &%notdel%& argument is true, a false return is forced for all
33693 &"deleted"& headers; otherwise they are not treated specially. For example:
33695 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
33697 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
33698 .cindex "base64 encoding" "functions for &[local_scan()]& use"
33699 This function base64-encodes a string, which is passed by address and length.
33700 The text may contain bytes of any value, including zero. The result is passed
33701 back in dynamic memory that is obtained by calling &'store_get()'&. It is
33704 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
33705 This function decodes a base64-encoded string. Its arguments are a
33706 zero-terminated base64-encoded string and the address of a variable that is set
33707 to point to the result, which is in dynamic memory. The length of the decoded
33708 string is the yield of the function. If the input is invalid base64 data, the
33709 yield is -1. A zero byte is added to the end of the output string to make it
33710 easy to interpret as a C string (assuming it contains no zeros of its own). The
33711 added zero byte is not included in the returned count.
33713 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
33714 This function checks for a match in a domain list. Domains are always
33715 matched caselessly. The return value is one of the following:
33717 &`OK `& match succeeded
33718 &`FAIL `& match failed
33719 &`DEFER `& match deferred
33721 DEFER is usually caused by some kind of lookup defer, such as the
33722 inability to contact a database.
33724 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
33726 This function checks for a match in a local part list. The third argument
33727 controls case-sensitivity. The return values are as for
33728 &'lss_match_domain()'&.
33730 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
33732 This function checks for a match in an address list. The third argument
33733 controls the case-sensitivity of the local part match. The domain is always
33734 matched caselessly. The return values are as for &'lss_match_domain()'&.
33736 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
33738 This function checks for a match in a host list. The most common usage is
33741 lss_match_host(sender_host_name, sender_host_address, ...)
33743 .vindex "&$sender_host_address$&"
33744 An empty address field matches an empty item in the host list. If the host name
33745 is NULL, the name corresponding to &$sender_host_address$& is automatically
33746 looked up if a host name is required to match an item in the list. The return
33747 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
33748 returns ERROR in the case when it had to look up a host name, but the lookup
33751 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
33753 This function writes to Exim's log files. The first argument should be zero (it
33754 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
33755 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
33756 them. It specifies to which log or logs the message is written. The remaining
33757 arguments are a format and relevant insertion arguments. The string should not
33758 contain any newlines, not even at the end.
33761 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
33762 This function adds an additional recipient to the message. The first argument
33763 is the recipient address. If it is unqualified (has no domain), it is qualified
33764 with the &%qualify_recipient%& domain. The second argument must always be -1.
33766 This function does not allow you to specify a private &%errors_to%& address (as
33767 described with the structure of &%recipient_item%& above), because it pre-dates
33768 the addition of that field to the structure. However, it is easy to add such a
33769 value afterwards. For example:
33771 receive_add_recipient(US"monitor@mydom.example", -1);
33772 recipients_list[recipients_count-1].errors_to =
33773 US"postmaster@mydom.example";
33776 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
33777 This is a convenience function to remove a named recipient from the list of
33778 recipients. It returns true if a recipient was removed, and false if no
33779 matching recipient could be found. The argument must be a complete email
33786 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
33787 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
33788 This function decodes strings that are encoded according to RFC 2047. Typically
33789 these are the contents of header lines. First, each &"encoded word"& is decoded
33790 from the Q or B encoding into a byte-string. Then, if provided with the name of
33791 a charset encoding, and if the &[iconv()]& function is available, an attempt is
33792 made to translate the result to the named character set. If this fails, the
33793 binary string is returned with an error message.
33795 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
33796 maximum MIME word length is enforced. The third argument is the target
33797 encoding, or NULL if no translation is wanted.
33799 .cindex "binary zero" "in RFC 2047 decoding"
33800 .cindex "RFC 2047" "binary zero in"
33801 If a binary zero is encountered in the decoded string, it is replaced by the
33802 contents of the &%zeroval%& argument. For use with Exim headers, the value must
33803 not be 0 because header lines are handled as zero-terminated strings.
33805 The function returns the result of processing the string, zero-terminated; if
33806 &%lenptr%& is not NULL, the length of the result is set in the variable to
33807 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
33809 If an error is encountered, the function returns NULL and uses the &%error%&
33810 argument to return an error message. The variable pointed to by &%error%& is
33811 set to NULL if there is no error; it may be set non-NULL even when the function
33812 returns a non-NULL value if decoding was successful, but there was a problem
33816 .vitem &*int&~smtp_fflush(void)*&
33817 This function is used in conjunction with &'smtp_printf()'&, as described
33820 .vitem &*void&~smtp_printf(char&~*,&~...)*&
33821 The arguments of this function are like &[printf()]&; it writes to the SMTP
33822 output stream. You should use this function only when there is an SMTP output
33823 stream, that is, when the incoming message is being received via interactive
33824 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
33825 is FALSE. If you want to test for an incoming message from another host (as
33826 opposed to a local process that used the &%-bs%& command line option), you can
33827 test the value of &%sender_host_address%&, which is non-NULL when a remote host
33830 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
33831 output function, so it can be used for all forms of SMTP connection.
33833 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
33834 must start with an appropriate response code: 550 if you are going to return
33835 LOCAL_SCAN_REJECT, 451 if you are going to return
33836 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
33837 initial lines of a multi-line response, the code must be followed by a hyphen
33838 to indicate that the line is not the final response line. You must also ensure
33839 that the lines you write terminate with CRLF. For example:
33841 smtp_printf("550-this is some extra info\r\n");
33842 return LOCAL_SCAN_REJECT;
33844 Note that you can also create multi-line responses by including newlines in
33845 the data returned via the &%return_text%& argument. The added value of using
33846 &'smtp_printf()'& is that, for instance, you could introduce delays between
33847 multiple output lines.
33849 The &'smtp_printf()'& function does not return any error indication, because it
33850 does not automatically flush pending output, and therefore does not test
33851 the state of the stream. (In the main code of Exim, flushing and error
33852 detection is done when Exim is ready for the next SMTP input command.) If
33853 you want to flush the output and check for an error (for example, the
33854 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
33855 arguments. It flushes the output stream, and returns a non-zero value if there
33858 .vitem &*void&~*store_get(int)*&
33859 This function accesses Exim's internal store (memory) manager. It gets a new
33860 chunk of memory whose size is given by the argument. Exim bombs out if it ever
33861 runs out of memory. See the next section for a discussion of memory handling.
33863 .vitem &*void&~*store_get_perm(int)*&
33864 This function is like &'store_get()'&, but it always gets memory from the
33865 permanent pool. See the next section for a discussion of memory handling.
33867 .vitem &*uschar&~*string_copy(uschar&~*string)*&
33870 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
33873 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
33874 These three functions create strings using Exim's dynamic memory facilities.
33875 The first makes a copy of an entire string. The second copies up to a maximum
33876 number of characters, indicated by the second argument. The third uses a format
33877 and insertion arguments to create a new string. In each case, the result is a
33878 pointer to a new string in the current memory pool. See the next section for
33884 .section "More about Exim's memory handling" "SECTmemhanloc"
33885 .cindex "&[local_scan()]& function" "memory handling"
33886 No function is provided for freeing memory, because that is never needed.
33887 The dynamic memory that Exim uses when receiving a message is automatically
33888 recycled if another message is received by the same process (this applies only
33889 to incoming SMTP connections &-- other input methods can supply only one
33890 message at a time). After receiving the last message, a reception process
33893 Because it is recycled, the normal dynamic memory cannot be used for holding
33894 data that must be preserved over a number of incoming messages on the same SMTP
33895 connection. However, Exim in fact uses two pools of dynamic memory; the second
33896 one is not recycled, and can be used for this purpose.
33898 If you want to allocate memory that remains available for subsequent messages
33899 in the same SMTP connection, you should set
33901 store_pool = POOL_PERM
33903 before calling the function that does the allocation. There is no need to
33904 restore the value if you do not need to; however, if you do want to revert to
33905 the normal pool, you can either restore the previous value of &%store_pool%& or
33906 set it explicitly to POOL_MAIN.
33908 The pool setting applies to all functions that get dynamic memory, including
33909 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
33910 There is also a convenience function called &'store_get_perm()'& that gets a
33911 block of memory from the permanent pool while preserving the value of
33918 . ////////////////////////////////////////////////////////////////////////////
33919 . ////////////////////////////////////////////////////////////////////////////
33921 .chapter "System-wide message filtering" "CHAPsystemfilter"
33922 .scindex IIDsysfil1 "filter" "system filter"
33923 .scindex IIDsysfil2 "filtering all mail"
33924 .scindex IIDsysfil3 "system filter"
33925 The previous chapters (on ACLs and the local scan function) describe checks
33926 that can be applied to messages before they are accepted by a host. There is
33927 also a mechanism for checking messages once they have been received, but before
33928 they are delivered. This is called the &'system filter'&.
33930 The system filter operates in a similar manner to users' filter files, but it
33931 is run just once per message (however many recipients the message has).
33932 It should not normally be used as a substitute for routing, because &%deliver%&
33933 commands in a system router provide new envelope recipient addresses.
33934 The system filter must be an Exim filter. It cannot be a Sieve filter.
33936 The system filter is run at the start of a delivery attempt, before any routing
33937 is done. If a message fails to be completely delivered at the first attempt,
33938 the system filter is run again at the start of every retry.
33939 If you want your filter to do something only once per message, you can make use
33940 of the &%first_delivery%& condition in an &%if%& command in the filter to
33941 prevent it happening on retries.
33943 .vindex "&$domain$&"
33944 .vindex "&$local_part$&"
33945 &*Warning*&: Because the system filter runs just once, variables that are
33946 specific to individual recipient addresses, such as &$local_part$& and
33947 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
33948 you want to run a centrally-specified filter for each recipient address
33949 independently, you can do so by setting up a suitable &(redirect)& router, as
33950 described in section &<<SECTperaddfil>>& below.
33953 .section "Specifying a system filter" "SECID212"
33954 .cindex "uid (user id)" "system filter"
33955 .cindex "gid (group id)" "system filter"
33956 The name of the file that contains the system filter must be specified by
33957 setting &%system_filter%&. If you want the filter to run under a uid and gid
33958 other than root, you must also set &%system_filter_user%& and
33959 &%system_filter_group%& as appropriate. For example:
33961 system_filter = /etc/mail/exim.filter
33962 system_filter_user = exim
33964 If a system filter generates any deliveries directly to files or pipes (via the
33965 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
33966 specified by setting &%system_filter_file_transport%& and
33967 &%system_filter_pipe_transport%&, respectively. Similarly,
33968 &%system_filter_reply_transport%& must be set to handle any messages generated
33969 by the &%reply%& command.
33972 .section "Testing a system filter" "SECID213"
33973 You can run simple tests of a system filter in the same way as for a user
33974 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
33975 are permitted only in system filters are recognized.
33977 If you want to test the combined effect of a system filter and a user filter,
33978 you can use both &%-bF%& and &%-bf%& on the same command line.
33982 .section "Contents of a system filter" "SECID214"
33983 The language used to specify system filters is the same as for users' filter
33984 files. It is described in the separate end-user document &'Exim's interface to
33985 mail filtering'&. However, there are some additional features that are
33986 available only in system filters; these are described in subsequent sections.
33987 If they are encountered in a user's filter file or when testing with &%-bf%&,
33990 .cindex "frozen messages" "manual thaw; testing in filter"
33991 There are two special conditions which, though available in users' filter
33992 files, are designed for use in system filters. The condition &%first_delivery%&
33993 is true only for the first attempt at delivering a message, and
33994 &%manually_thawed%& is true only if the message has been frozen, and
33995 subsequently thawed by an admin user. An explicit forced delivery counts as a
33996 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
33998 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
33999 specify an &"unseen"& (non-significant) delivery, and that delivery does not
34000 succeed, it will not be tried again.
34001 If you want Exim to retry an unseen delivery until it succeeds, you should
34002 arrange to set it up every time the filter runs.
34004 When a system filter finishes running, the values of the variables &$n0$& &--
34005 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
34006 users' filter files. Thus a system filter can, for example, set up &"scores"&
34007 to which users' filter files can refer.
34011 .section "Additional variable for system filters" "SECID215"
34012 .vindex "&$recipients$&"
34013 The expansion variable &$recipients$&, containing a list of all the recipients
34014 of the message (separated by commas and white space), is available in system
34015 filters. It is not available in users' filters for privacy reasons.
34019 .section "Defer, freeze, and fail commands for system filters" "SECID216"
34020 .cindex "freezing messages"
34021 .cindex "message" "freezing"
34022 .cindex "message" "forced failure"
34023 .cindex "&%fail%&" "in system filter"
34024 .cindex "&%freeze%& in system filter"
34025 .cindex "&%defer%& in system filter"
34026 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
34027 always available in system filters, but are not normally enabled in users'
34028 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
34029 for the &(redirect)& router.) These commands can optionally be followed by the
34030 word &%text%& and a string containing an error message, for example:
34032 fail text "this message looks like spam to me"
34034 The keyword &%text%& is optional if the next character is a double quote.
34036 The &%defer%& command defers delivery of the original recipients of the
34037 message. The &%fail%& command causes all the original recipients to be failed,
34038 and a bounce message to be created. The &%freeze%& command suspends all
34039 delivery attempts for the original recipients. In all cases, any new deliveries
34040 that are specified by the filter are attempted as normal after the filter has
34043 The &%freeze%& command is ignored if the message has been manually unfrozen and
34044 not manually frozen since. This means that automatic freezing by a system
34045 filter can be used as a way of checking out suspicious messages. If a message
34046 is found to be all right, manually unfreezing it allows it to be delivered.
34048 .cindex "log" "&%fail%& command log line"
34049 .cindex "&%fail%&" "log line; reducing"
34050 The text given with a fail command is used as part of the bounce message as
34051 well as being written to the log. If the message is quite long, this can fill
34052 up a lot of log space when such failures are common. To reduce the size of the
34053 log message, Exim interprets the text in a special way if it starts with the
34054 two characters &`<<`& and contains &`>>`& later. The text between these two
34055 strings is written to the log, and the rest of the text is used in the bounce
34056 message. For example:
34058 fail "<<filter test 1>>Your message is rejected \
34059 because it contains attachments that we are \
34060 not prepared to receive."
34063 .cindex "loop" "caused by &%fail%&"
34064 Take great care with the &%fail%& command when basing the decision to fail on
34065 the contents of the message, because the bounce message will of course include
34066 the contents of the original message and will therefore trigger the &%fail%&
34067 command again (causing a mail loop) unless steps are taken to prevent this.
34068 Testing the &%error_message%& condition is one way to prevent this. You could
34071 if $message_body contains "this is spam" and not error_message
34072 then fail text "spam is not wanted here" endif
34074 though of course that might let through unwanted bounce messages. The
34075 alternative is clever checking of the body and/or headers to detect bounces
34076 generated by the filter.
34078 The interpretation of a system filter file ceases after a
34080 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
34081 set up earlier in the filter file are honoured, so you can use a sequence such
34087 to send a specified message when the system filter is freezing (or deferring or
34088 failing) a message. The normal deliveries for the message do not, of course,
34093 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
34094 .cindex "header lines" "adding; in system filter"
34095 .cindex "header lines" "removing; in system filter"
34096 .cindex "filter" "header lines; adding/removing"
34097 Two filter commands that are available only in system filters are:
34099 headers add <string>
34100 headers remove <string>
34102 The argument for the &%headers add%& is a string that is expanded and then
34103 added to the end of the message's headers. It is the responsibility of the
34104 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
34105 space is ignored, and if the string is otherwise empty, or if the expansion is
34106 forced to fail, the command has no effect.
34108 You can use &"\n"& within the string, followed by white space, to specify
34109 continued header lines. More than one header may be added in one command by
34110 including &"\n"& within the string without any following white space. For
34113 headers add "X-header-1: ....\n \
34114 continuation of X-header-1 ...\n\
34117 Note that the header line continuation white space after the first newline must
34118 be placed before the backslash that continues the input string, because white
34119 space after input continuations is ignored.
34121 The argument for &%headers remove%& is a colon-separated list of header names.
34122 This command applies only to those headers that are stored with the message;
34123 those that are added at delivery time (such as &'Envelope-To:'& and
34124 &'Return-Path:'&) cannot be removed by this means. If there is more than one
34125 header with the same name, they are all removed.
34127 The &%headers%& command in a system filter makes an immediate change to the set
34128 of header lines that was received with the message (with possible additions
34129 from ACL processing). Subsequent commands in the system filter operate on the
34130 modified set, which also forms the basis for subsequent message delivery.
34131 Unless further modified during routing or transporting, this set of headers is
34132 used for all recipients of the message.
34134 During routing and transporting, the variables that refer to the contents of
34135 header lines refer only to those lines that are in this set. Thus, header lines
34136 that are added by a system filter are visible to users' filter files and to all
34137 routers and transports. This contrasts with the manipulation of header lines by
34138 routers and transports, which is not immediate, but which instead is saved up
34139 until the message is actually being written (see section
34140 &<<SECTheadersaddrem>>&).
34142 If the message is not delivered at the first attempt, header lines that were
34143 added by the system filter are stored with the message, and so are still
34144 present at the next delivery attempt. Header lines that were removed are still
34145 present, but marked &"deleted"& so that they are not transported with the
34146 message. For this reason, it is usual to make the &%headers%& command
34147 conditional on &%first_delivery%& so that the set of header lines is not
34148 modified more than once.
34150 Because header modification in a system filter acts immediately, you have to
34151 use an indirect approach if you want to modify the contents of a header line.
34154 headers add "Old-Subject: $h_subject:"
34155 headers remove "Subject"
34156 headers add "Subject: new subject (was: $h_old-subject:)"
34157 headers remove "Old-Subject"
34162 .section "Setting an errors address in a system filter" "SECID217"
34163 .cindex "envelope sender"
34164 In a system filter, if a &%deliver%& command is followed by
34166 errors_to <some address>
34168 in order to change the envelope sender (and hence the error reporting) for that
34169 delivery, any address may be specified. (In a user filter, only the current
34170 user's address can be set.) For example, if some mail is being monitored, you
34173 unseen deliver monitor@spying.example errors_to root@local.example
34175 to take a copy which would not be sent back to the normal error reporting
34176 address if its delivery failed.
34180 .section "Per-address filtering" "SECTperaddfil"
34181 .vindex "&$domain$&"
34182 .vindex "&$local_part$&"
34183 In contrast to the system filter, which is run just once per message for each
34184 delivery attempt, it is also possible to set up a system-wide filtering
34185 operation that runs once for each recipient address. In this case, variables
34186 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
34187 filter file could be made dependent on them. This is an example of a router
34188 which implements such a filter:
34193 domains = +local_domains
34194 file = /central/filters/$local_part
34199 The filter is run in a separate process under its own uid. Therefore, either
34200 &%check_local_user%& must be set (as above), in which case the filter is run as
34201 the local user, or the &%user%& option must be used to specify which user to
34202 use. If both are set, &%user%& overrides.
34204 Care should be taken to ensure that none of the commands in the filter file
34205 specify a significant delivery if the message is to go on to be delivered to
34206 its intended recipient. The router will not then claim to have dealt with the
34207 address, so it will be passed on to subsequent routers to be delivered in the
34209 .ecindex IIDsysfil1
34210 .ecindex IIDsysfil2
34211 .ecindex IIDsysfil3
34218 . ////////////////////////////////////////////////////////////////////////////
34219 . ////////////////////////////////////////////////////////////////////////////
34221 .chapter "Message processing" "CHAPmsgproc"
34222 .scindex IIDmesproc "message" "general processing"
34223 Exim performs various transformations on the sender and recipient addresses of
34224 all messages that it handles, and also on the messages' header lines. Some of
34225 these are optional and configurable, while others always take place. All of
34226 this processing, except rewriting as a result of routing, and the addition or
34227 removal of header lines while delivering, happens when a message is received,
34228 before it is placed on Exim's queue.
34230 Some of the automatic processing takes place by default only for
34231 &"locally-originated"& messages. This adjective is used to describe messages
34232 that are not received over TCP/IP, but instead are passed to an Exim process on
34233 its standard input. This includes the interactive &"local SMTP"& case that is
34234 set up by the &%-bs%& command line option.
34236 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
34237 or ::1) are not considered to be locally-originated. Exim does not treat the
34238 loopback interface specially in any way.
34240 If you want the loopback interface to be treated specially, you must ensure
34241 that there are appropriate entries in your ACLs.
34246 .section "Submission mode for non-local messages" "SECTsubmodnon"
34247 .cindex "message" "submission"
34248 .cindex "submission mode"
34249 Processing that happens automatically for locally-originated messages (unless
34250 &%suppress_local_fixups%& is set) can also be requested for messages that are
34251 received over TCP/IP. The term &"submission mode"& is used to describe this
34252 state. Submission mode is set by the modifier
34254 control = submission
34256 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
34257 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
34258 a local submission, and is normally used when the source of the message is
34259 known to be an MUA running on a client host (as opposed to an MTA). For
34260 example, to set submission mode for messages originating on the IPv4 loopback
34261 interface, you could include the following in the MAIL ACL:
34263 warn hosts = 127.0.0.1
34264 control = submission
34266 .cindex "&%sender_retain%& submission option"
34267 There are some options that can be used when setting submission mode. A slash
34268 is used to separate options. For example:
34270 control = submission/sender_retain
34272 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
34273 true and &%local_from_check%& false for the current incoming message. The first
34274 of these allows an existing &'Sender:'& header in the message to remain, and
34275 the second suppresses the check to ensure that &'From:'& matches the
34276 authenticated sender. With this setting, Exim still fixes up messages by adding
34277 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
34278 attempt to check sender authenticity in header lines.
34280 When &%sender_retain%& is not set, a submission mode setting may specify a
34281 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
34284 control = submission/domain=some.domain
34286 The domain may be empty. How this value is used is described in sections
34287 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
34288 that allows you to specify the user's full name for inclusion in a created
34289 &'Sender:'& or &'From:'& header line. For example:
34291 accept authenticated = *
34292 control = submission/domain=wonderland.example/\
34293 name=${lookup {$authenticated_id} \
34294 lsearch {/etc/exim/namelist}}
34296 Because the name may contain any characters, including slashes, the &%name%&
34297 option must be given last. The remainder of the string is used as the name. For
34298 the example above, if &_/etc/exim/namelist_& contains:
34300 bigegg: Humpty Dumpty
34302 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
34305 Sender: Humpty Dumpty <bigegg@wonderland.example>
34307 .cindex "return path" "in submission mode"
34308 By default, submission mode forces the return path to the same address as is
34309 used to create the &'Sender:'& header. However, if &%sender_retain%& is
34310 specified, the return path is also left unchanged.
34312 &*Note*&: The changes caused by submission mode take effect after the predata
34313 ACL. This means that any sender checks performed before the fix-ups use the
34314 untrusted sender address specified by the user, not the trusted sender address
34315 specified by submission mode. Although this might be slightly unexpected, it
34316 does mean that you can configure ACL checks to spot that a user is trying to
34317 spoof another's address.
34319 .section "Line endings" "SECTlineendings"
34320 .cindex "line endings"
34321 .cindex "carriage return"
34323 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
34324 linefeed) is the line ending for messages transmitted over the Internet using
34325 SMTP over TCP/IP. However, within individual operating systems, different
34326 conventions are used. For example, Unix-like systems use just LF, but others
34327 use CRLF or just CR.
34329 Exim was designed for Unix-like systems, and internally, it stores messages
34330 using the system's convention of a single LF as a line terminator. When
34331 receiving a message, all line endings are translated to this standard format.
34332 Originally, it was thought that programs that passed messages directly to an
34333 MTA within an operating system would use that system's convention. Experience
34334 has shown that this is not the case; for example, there are Unix applications
34335 that use CRLF in this circumstance. For this reason, and for compatibility with
34336 other MTAs, the way Exim handles line endings for all messages is now as
34340 LF not preceded by CR is treated as a line ending.
34342 CR is treated as a line ending; if it is immediately followed by LF, the LF
34345 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
34346 nor a local message in the state where a line containing only a dot is a
34349 If a bare CR is encountered within a header line, an extra space is added after
34350 the line terminator so as not to end the header line. The reasoning behind this
34351 is that bare CRs in header lines are most likely either to be mistakes, or
34352 people trying to play silly games.
34354 If the first header line received in a message ends with CRLF, a subsequent
34355 bare LF in a header line is treated in the same way as a bare CR in a header
34363 .section "Unqualified addresses" "SECID218"
34364 .cindex "unqualified addresses"
34365 .cindex "address" "qualification"
34366 By default, Exim expects every envelope address it receives from an external
34367 host to be fully qualified. Unqualified addresses cause negative responses to
34368 SMTP commands. However, because SMTP is used as a means of transporting
34369 messages from MUAs running on personal workstations, there is sometimes a
34370 requirement to accept unqualified addresses from specific hosts or IP networks.
34372 Exim has two options that separately control which hosts may send unqualified
34373 sender or recipient addresses in SMTP commands, namely
34374 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
34375 cases, if an unqualified address is accepted, it is qualified by adding the
34376 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
34378 .oindex "&%qualify_domain%&"
34379 .oindex "&%qualify_recipient%&"
34380 Unqualified addresses in header lines are automatically qualified for messages
34381 that are locally originated, unless the &%-bnq%& option is given on the command
34382 line. For messages received over SMTP, unqualified addresses in header lines
34383 are qualified only if unqualified addresses are permitted in SMTP commands. In
34384 other words, such qualification is also controlled by
34385 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
34390 .section "The UUCP From line" "SECID219"
34391 .cindex "&""From""& line"
34392 .cindex "UUCP" "&""From""& line"
34393 .cindex "sender" "address"
34394 .oindex "&%uucp_from_pattern%&"
34395 .oindex "&%uucp_from_sender%&"
34396 .cindex "envelope sender"
34397 .cindex "Sendmail compatibility" "&""From""& line"
34398 Messages that have come from UUCP (and some other applications) often begin
34399 with a line containing the envelope sender and a timestamp, following the word
34400 &"From"&. Examples of two common formats are:
34402 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
34403 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
34405 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
34406 Exim recognizes such lines at the start of messages that are submitted to it
34407 via the command line (that is, on the standard input). It does not recognize
34408 such lines in incoming SMTP messages, unless the sending host matches
34409 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
34410 and &%ignore_fromline_local%& is set. The recognition is controlled by a
34411 regular expression that is defined by the &%uucp_from_pattern%& option, whose
34412 default value matches the two common cases shown above and puts the address
34413 that follows &"From"& into &$1$&.
34415 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
34416 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
34417 a trusted user, the message's sender address is constructed by expanding the
34418 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
34419 then parsed as an RFC 2822 address. If there is no domain, the local part is
34420 qualified with &%qualify_domain%& unless it is the empty string. However, if
34421 the command line &%-f%& option is used, it overrides the &"From"& line.
34423 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
34424 sender address is not changed. This is also the case for incoming SMTP messages
34425 that are permitted to contain &"From"& lines.
34427 Only one &"From"& line is recognized. If there is more than one, the second is
34428 treated as a data line that starts the body of the message, as it is not valid
34429 as a header line. This also happens if a &"From"& line is present in an
34430 incoming SMTP message from a source that is not permitted to send them.
34434 .section "Resent- header lines" "SECID220"
34435 .cindex "&%Resent-%& header lines"
34436 .cindex "header lines" "Resent-"
34437 RFC 2822 makes provision for sets of header lines starting with the string
34438 &`Resent-`& to be added to a message when it is resent by the original
34439 recipient to somebody else. These headers are &'Resent-Date:'&,
34440 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
34441 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
34444 &'Resent fields are strictly informational. They MUST NOT be used in the normal
34445 processing of replies or other such automatic actions on messages.'&
34448 This leaves things a bit vague as far as other processing actions such as
34449 address rewriting are concerned. Exim treats &%Resent-%& header lines as
34453 A &'Resent-From:'& line that just contains the login id of the submitting user
34454 is automatically rewritten in the same way as &'From:'& (see below).
34456 If there's a rewriting rule for a particular header line, it is also applied to
34457 &%Resent-%& header lines of the same type. For example, a rule that rewrites
34458 &'From:'& also rewrites &'Resent-From:'&.
34460 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
34463 For a locally-submitted message,
34464 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
34465 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
34466 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
34467 included in log lines in this case.
34469 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
34470 &%Resent-%& header lines are present.
34476 .section "The Auto-Submitted: header line" "SECID221"
34477 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
34478 includes the header line:
34480 Auto-Submitted: auto-replied
34483 .section "The Bcc: header line" "SECID222"
34484 .cindex "&'Bcc:'& header line"
34485 If Exim is called with the &%-t%& option, to take recipient addresses from a
34486 message's header, it removes any &'Bcc:'& header line that may exist (after
34487 extracting its addresses). If &%-t%& is not present on the command line, any
34488 existing &'Bcc:'& is not removed.
34491 .section "The Date: header line" "SECID223"
34492 .cindex "&'Date:'& header line"
34493 .cindex "header lines" "Date:"
34494 If a locally-generated or submission-mode message has no &'Date:'& header line,
34495 Exim adds one, using the current date and time, unless the
34496 &%suppress_local_fixups%& control has been specified.
34498 .section "The Delivery-date: header line" "SECID224"
34499 .cindex "&'Delivery-date:'& header line"
34500 .oindex "&%delivery_date_remove%&"
34501 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
34502 set. Exim can be configured to add them to the final delivery of messages. (See
34503 the generic &%delivery_date_add%& transport option.) They should not be present
34504 in messages in transit. If the &%delivery_date_remove%& configuration option is
34505 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
34509 .section "The Envelope-to: header line" "SECID225"
34510 .cindex "&'Envelope-to:'& header line"
34511 .cindex "header lines" "Envelope-to:"
34512 .oindex "&%envelope_to_remove%&"
34513 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
34514 Exim can be configured to add them to the final delivery of messages. (See the
34515 generic &%envelope_to_add%& transport option.) They should not be present in
34516 messages in transit. If the &%envelope_to_remove%& configuration option is set
34517 (the default), Exim removes &'Envelope-to:'& header lines from incoming
34521 .section "The From: header line" "SECTthefrohea"
34522 .cindex "&'From:'& header line"
34523 .cindex "header lines" "From:"
34524 .cindex "Sendmail compatibility" "&""From""& line"
34525 .cindex "message" "submission"
34526 .cindex "submission mode"
34527 If a submission-mode message does not contain a &'From:'& header line, Exim
34528 adds one if either of the following conditions is true:
34531 The envelope sender address is not empty (that is, this is not a bounce
34532 message). The added header line copies the envelope sender address.
34534 .vindex "&$authenticated_id$&"
34535 The SMTP session is authenticated and &$authenticated_id$& is not empty.
34537 .vindex "&$qualify_domain$&"
34538 If no domain is specified by the submission control, the local part is
34539 &$authenticated_id$& and the domain is &$qualify_domain$&.
34541 If a non-empty domain is specified by the submission control, the local
34542 part is &$authenticated_id$&, and the domain is the specified domain.
34544 If an empty domain is specified by the submission control,
34545 &$authenticated_id$& is assumed to be the complete address.
34549 A non-empty envelope sender takes precedence.
34551 If a locally-generated incoming message does not contain a &'From:'& header
34552 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
34553 containing the sender's address. The calling user's login name and full name
34554 are used to construct the address, as described in section &<<SECTconstr>>&.
34555 They are obtained from the password data by calling &[getpwuid()]& (but see the
34556 &%unknown_login%& configuration option). The address is qualified with
34557 &%qualify_domain%&.
34559 For compatibility with Sendmail, if an incoming, non-SMTP message has a
34560 &'From:'& header line containing just the unqualified login name of the calling
34561 user, this is replaced by an address containing the user's login name and full
34562 name as described in section &<<SECTconstr>>&.
34565 .section "The Message-ID: header line" "SECID226"
34566 .cindex "&'Message-ID:'& header line"
34567 .cindex "header lines" "Message-ID:"
34568 .cindex "message" "submission"
34569 .oindex "&%message_id_header_text%&"
34570 If a locally-generated or submission-mode incoming message does not contain a
34571 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
34572 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
34573 to the message. If there are any &'Resent-:'& headers in the message, it
34574 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
34575 message id, preceded by the letter E to ensure it starts with a letter, and
34576 followed by @ and the primary host name. Additional information can be included
34577 in this header line by setting the &%message_id_header_text%& and/or
34578 &%message_id_header_domain%& options.
34581 .section "The Received: header line" "SECID227"
34582 .cindex "&'Received:'& header line"
34583 .cindex "header lines" "Received:"
34584 A &'Received:'& header line is added at the start of every message. The
34585 contents are defined by the &%received_header_text%& configuration option, and
34586 Exim automatically adds a semicolon and a timestamp to the configured string.
34588 The &'Received:'& header is generated as soon as the message's header lines
34589 have been received. At this stage, the timestamp in the &'Received:'& header
34590 line is the time that the message started to be received. This is the value
34591 that is seen by the DATA ACL and by the &[local_scan()]& function.
34593 Once a message is accepted, the timestamp in the &'Received:'& header line is
34594 changed to the time of acceptance, which is (apart from a small delay while the
34595 -H spool file is written) the earliest time at which delivery could start.
34598 .section "The References: header line" "SECID228"
34599 .cindex "&'References:'& header line"
34600 .cindex "header lines" "References:"
34601 Messages created by the &(autoreply)& transport include a &'References:'&
34602 header line. This is constructed according to the rules that are described in
34603 section 3.64 of RFC 2822 (which states that replies should contain such a
34604 header line), and section 3.14 of RFC 3834 (which states that automatic
34605 responses are not different in this respect). However, because some mail
34606 processing software does not cope well with very long header lines, no more
34607 than 12 message IDs are copied from the &'References:'& header line in the
34608 incoming message. If there are more than 12, the first one and then the final
34609 11 are copied, before adding the message ID of the incoming message.
34613 .section "The Return-path: header line" "SECID229"
34614 .cindex "&'Return-path:'& header line"
34615 .cindex "header lines" "Return-path:"
34616 .oindex "&%return_path_remove%&"
34617 &'Return-path:'& header lines are defined as something an MTA may insert when
34618 it does the final delivery of messages. (See the generic &%return_path_add%&
34619 transport option.) Therefore, they should not be present in messages in
34620 transit. If the &%return_path_remove%& configuration option is set (the
34621 default), Exim removes &'Return-path:'& header lines from incoming messages.
34625 .section "The Sender: header line" "SECTthesenhea"
34626 .cindex "&'Sender:'& header line"
34627 .cindex "message" "submission"
34628 .cindex "header lines" "Sender:"
34629 For a locally-originated message from an untrusted user, Exim may remove an
34630 existing &'Sender:'& header line, and it may add a new one. You can modify
34631 these actions by setting the &%local_sender_retain%& option true, the
34632 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
34635 When a local message is received from an untrusted user and
34636 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
34637 control has not been set, a check is made to see if the address given in the
34638 &'From:'& header line is the correct (local) sender of the message. The address
34639 that is expected has the login name as the local part and the value of
34640 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
34641 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
34642 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
34643 line is added to the message.
34645 If you set &%local_from_check%& false, this checking does not occur. However,
34646 the removal of an existing &'Sender:'& line still happens, unless you also set
34647 &%local_sender_retain%& to be true. It is not possible to set both of these
34648 options true at the same time.
34650 .cindex "submission mode"
34651 By default, no processing of &'Sender:'& header lines is done for messages
34652 received over TCP/IP or for messages submitted by trusted users. However, when
34653 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
34654 not specified on the submission control, the following processing takes place:
34656 .vindex "&$authenticated_id$&"
34657 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
34658 authenticated, and &$authenticated_id$& is not empty, a sender address is
34659 created as follows:
34662 .vindex "&$qualify_domain$&"
34663 If no domain is specified by the submission control, the local part is
34664 &$authenticated_id$& and the domain is &$qualify_domain$&.
34666 If a non-empty domain is specified by the submission control, the local part
34667 is &$authenticated_id$&, and the domain is the specified domain.
34669 If an empty domain is specified by the submission control,
34670 &$authenticated_id$& is assumed to be the complete address.
34673 This address is compared with the address in the &'From:'& header line. If they
34674 are different, a &'Sender:'& header line containing the created address is
34675 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
34676 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
34678 .cindex "return path" "created from &'Sender:'&"
34679 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
34680 the message (the envelope sender address) is changed to be the same address,
34681 except in the case of submission mode when &%sender_retain%& is specified.
34685 .section "Adding and removing header lines in routers and transports" &&&
34686 "SECTheadersaddrem"
34687 .cindex "header lines" "adding; in router or transport"
34688 .cindex "header lines" "removing; in router or transport"
34689 When a message is delivered, the addition and removal of header lines can be
34690 specified in a system filter, or on any of the routers and transports that
34691 process the message. Section &<<SECTaddremheasys>>& contains details about
34692 modifying headers in a system filter. Header lines can also be added in an ACL
34693 as a message is received (see section &<<SECTaddheadacl>>&).
34695 In contrast to what happens in a system filter, header modifications that are
34696 specified on routers and transports apply only to the particular recipient
34697 addresses that are being processed by those routers and transports. These
34698 changes do not actually take place until a copy of the message is being
34699 transported. Therefore, they do not affect the basic set of header lines, and
34700 they do not affect the values of the variables that refer to header lines.
34702 &*Note*&: In particular, this means that any expansions in the configuration of
34703 the transport cannot refer to the modified header lines, because such
34704 expansions all occur before the message is actually transported.
34706 For both routers and transports, the argument of a &%headers_add%&
34707 option must be in the form of one or more RFC 2822 header lines, separated by
34708 newlines (coded as &"\n"&). For example:
34710 headers_add = X-added-header: added by $primary_hostname\n\
34711 X-added-second: another added header line
34713 Exim does not check the syntax of these added header lines.
34715 Multiple &%headers_add%& options for a single router or transport can be
34716 specified; the values will append to a single list of header lines.
34717 Each header-line is separately expanded.
34719 The argument of a &%headers_remove%& option must consist of a colon-separated
34720 list of header names. This is confusing, because header names themselves are
34721 often terminated by colons. In this case, the colons are the list separators,
34722 not part of the names. For example:
34724 headers_remove = return-receipt-to:acknowledge-to
34727 Multiple &%headers_remove%& options for a single router or transport can be
34728 specified; the arguments will append to a single header-names list.
34729 Each item is separately expanded.
34730 Note that colons in complex expansions which are used to
34731 form all or part of a &%headers_remove%& list
34732 will act as list separators.
34734 When &%headers_add%& or &%headers_remove%& is specified on a router,
34735 items are expanded at routing time,
34736 and then associated with all addresses that are
34737 accepted by that router, and also with any new addresses that it generates. If
34738 an address passes through several routers as a result of aliasing or
34739 forwarding, the changes are cumulative.
34741 .oindex "&%unseen%&"
34742 However, this does not apply to multiple routers that result from the use of
34743 the &%unseen%& option. Any header modifications that were specified by the
34744 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
34746 Addresses that end up with different &%headers_add%& or &%headers_remove%&
34747 settings cannot be delivered together in a batch, so a transport is always
34748 dealing with a set of addresses that have the same header-processing
34751 The transport starts by writing the original set of header lines that arrived
34752 with the message, possibly modified by the system filter. As it writes out
34753 these lines, it consults the list of header names that were attached to the
34754 recipient address(es) by &%headers_remove%& options in routers, and it also
34755 consults the transport's own &%headers_remove%& option. Header lines whose
34756 names are on either of these lists are not written out. If there are multiple
34757 instances of any listed header, they are all skipped.
34759 After the remaining original header lines have been written, new header
34760 lines that were specified by routers' &%headers_add%& options are written, in
34761 the order in which they were attached to the address. These are followed by any
34762 header lines specified by the transport's &%headers_add%& option.
34764 This way of handling header line modifications in routers and transports has
34765 the following consequences:
34768 The original set of header lines, possibly modified by the system filter,
34769 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
34770 to it, at all times.
34772 Header lines that are added by a router's
34773 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
34774 expansion syntax in subsequent routers or the transport.
34776 Conversely, header lines that are specified for removal by &%headers_remove%&
34777 in a router remain visible to subsequent routers and the transport.
34779 Headers added to an address by &%headers_add%& in a router cannot be removed by
34780 a later router or by a transport.
34782 An added header can refer to the contents of an original header that is to be
34783 removed, even it has the same name as the added header. For example:
34785 headers_remove = subject
34786 headers_add = Subject: new subject (was: $h_subject:)
34790 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
34791 for a &(redirect)& router that has the &%one_time%& option set.
34797 .section "Constructed addresses" "SECTconstr"
34798 .cindex "address" "constructed"
34799 .cindex "constructed address"
34800 When Exim constructs a sender address for a locally-generated message, it uses
34803 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
34807 Zaphod Beeblebrox <zaphod@end.univ.example>
34809 The user name is obtained from the &%-F%& command line option if set, or
34810 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
34811 &"gecos"& field from the password entry. If the &"gecos"& field contains an
34812 ampersand character, this is replaced by the login name with the first letter
34813 upper cased, as is conventional in a number of operating systems. See the
34814 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
34815 The &%unknown_username%& option can be used to specify user names in cases when
34816 there is no password file entry.
34819 In all cases, the user name is made to conform to RFC 2822 by quoting all or
34820 parts of it if necessary. In addition, if it contains any non-printing
34821 characters, it is encoded as described in RFC 2047, which defines a way of
34822 including non-ASCII characters in header lines. The value of the
34823 &%headers_charset%& option specifies the name of the encoding that is used (the
34824 characters are assumed to be in this encoding). The setting of
34825 &%print_topbitchars%& controls whether characters with the top bit set (that
34826 is, with codes greater than 127) count as printing characters or not.
34830 .section "Case of local parts" "SECID230"
34831 .cindex "case of local parts"
34832 .cindex "local part" "case of"
34833 RFC 2822 states that the case of letters in the local parts of addresses cannot
34834 be assumed to be non-significant. Exim preserves the case of local parts of
34835 addresses, but by default it uses a lower-cased form when it is routing,
34836 because on most Unix systems, usernames are in lower case and case-insensitive
34837 routing is required. However, any particular router can be made to use the
34838 original case for local parts by setting the &%caseful_local_part%& generic
34841 .cindex "mixed-case login names"
34842 If you must have mixed-case user names on your system, the best way to proceed,
34843 assuming you want case-independent handling of incoming email, is to set up
34844 your first router to convert incoming local parts in your domains to the
34845 correct case by means of a file lookup. For example:
34849 domains = +local_domains
34850 data = ${lookup{$local_part}cdb\
34851 {/etc/usercased.cdb}{$value}fail}\
34854 For this router, the local part is forced to lower case by the default action
34855 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
34856 up a new local part in the correct case. If you then set &%caseful_local_part%&
34857 on any subsequent routers which process your domains, they will operate on
34858 local parts with the correct case in a case-sensitive manner.
34862 .section "Dots in local parts" "SECID231"
34863 .cindex "dot" "in local part"
34864 .cindex "local part" "dots in"
34865 RFC 2822 forbids empty components in local parts. That is, an unquoted local
34866 part may not begin or end with a dot, nor have two consecutive dots in the
34867 middle. However, it seems that many MTAs do not enforce this, so Exim permits
34868 empty components for compatibility.
34872 .section "Rewriting addresses" "SECID232"
34873 .cindex "rewriting" "addresses"
34874 Rewriting of sender and recipient addresses, and addresses in headers, can
34875 happen automatically, or as the result of configuration options, as described
34876 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
34877 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
34879 Automatic rewriting includes qualification, as mentioned above. The other case
34880 in which it can happen is when an incomplete non-local domain is given. The
34881 routing process may cause this to be expanded into the full domain name. For
34882 example, a header such as
34886 might get rewritten as
34888 To: hare@teaparty.wonderland.fict.example
34890 Rewriting as a result of routing is the one kind of message processing that
34891 does not happen at input time, as it cannot be done until the address has
34894 Strictly, one should not do &'any'& deliveries of a message until all its
34895 addresses have been routed, in case any of the headers get changed as a
34896 result of routing. However, doing this in practice would hold up many
34897 deliveries for unreasonable amounts of time, just because one address could not
34898 immediately be routed. Exim therefore does not delay other deliveries when
34899 routing of one or more addresses is deferred.
34900 .ecindex IIDmesproc
34904 . ////////////////////////////////////////////////////////////////////////////
34905 . ////////////////////////////////////////////////////////////////////////////
34907 .chapter "SMTP processing" "CHAPSMTP"
34908 .scindex IIDsmtpproc1 "SMTP" "processing details"
34909 .scindex IIDsmtpproc2 "LMTP" "processing details"
34910 Exim supports a number of different ways of using the SMTP protocol, and its
34911 LMTP variant, which is an interactive protocol for transferring messages into a
34912 closed mail store application. This chapter contains details of how SMTP is
34913 processed. For incoming mail, the following are available:
34916 SMTP over TCP/IP (Exim daemon or &'inetd'&);
34918 SMTP over the standard input and output (the &%-bs%& option);
34920 Batched SMTP on the standard input (the &%-bS%& option).
34923 For mail delivery, the following are available:
34926 SMTP over TCP/IP (the &(smtp)& transport);
34928 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
34931 LMTP over a pipe to a process running in the local host (the &(lmtp)&
34934 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
34935 the &%use_bsmtp%& option set).
34938 &'Batched SMTP'& is the name for a process in which batches of messages are
34939 stored in or read from files (or pipes), in a format in which SMTP commands are
34940 used to contain the envelope information.
34944 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
34945 .cindex "SMTP" "outgoing over TCP/IP"
34946 .cindex "outgoing SMTP over TCP/IP"
34947 .cindex "LMTP" "over TCP/IP"
34948 .cindex "outgoing LMTP over TCP/IP"
34951 .cindex "SIZE option on MAIL command"
34952 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
34953 The &%protocol%& option selects which protocol is to be used, but the actual
34954 processing is the same in both cases.
34956 If, in response to its EHLO command, Exim is told that the SIZE
34957 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
34958 command. The value of <&'n'&> is the message size plus the value of the
34959 &%size_addition%& option (default 1024) to allow for additions to the message
34960 such as per-transport header lines, or changes made in a
34961 .cindex "transport" "filter"
34962 .cindex "filter" "transport filter"
34963 transport filter. If &%size_addition%& is set negative, the use of SIZE is
34966 If the remote server advertises support for PIPELINING, Exim uses the
34967 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
34968 required for the transaction.
34970 If the remote server advertises support for the STARTTLS command, and Exim
34971 was built to support TLS encryption, it tries to start a TLS session unless the
34972 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
34973 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
34974 is called for verification.
34976 If the remote server advertises support for the AUTH command, Exim scans
34977 the authenticators configuration for any suitable client settings, as described
34978 in chapter &<<CHAPSMTPAUTH>>&.
34980 .cindex "carriage return"
34982 Responses from the remote host are supposed to be terminated by CR followed by
34983 LF. However, there are known to be hosts that do not send CR characters, so in
34984 order to be able to interwork with such hosts, Exim treats LF on its own as a
34987 If a message contains a number of different addresses, all those with the same
34988 characteristics (for example, the same envelope sender) that resolve to the
34989 same set of hosts, in the same order, are sent in a single SMTP transaction,
34990 even if they are for different domains, unless there are more than the setting
34991 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
34992 they are split into groups containing no more than &%max_rcpt%&s addresses
34993 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
34994 in parallel sessions. The order of hosts with identical MX values is not
34995 significant when checking whether addresses can be batched in this way.
34997 When the &(smtp)& transport suffers a temporary failure that is not
34998 message-related, Exim updates its transport-specific database, which contains
34999 records indexed by host name that remember which messages are waiting for each
35000 particular host. It also updates the retry database with new retry times.
35002 .cindex "hints database" "retry keys"
35003 Exim's retry hints are based on host name plus IP address, so if one address of
35004 a multi-homed host is broken, it will soon be skipped most of the time.
35005 See the next section for more detail about error handling.
35007 .cindex "SMTP" "passed connection"
35008 .cindex "SMTP" "batching over TCP/IP"
35009 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
35010 looks in the hints database for the transport to see if there are any queued
35011 messages waiting for the host to which it is connected. If it finds one, it
35012 creates a new Exim process using the &%-MC%& option (which can only be used by
35013 a process running as root or the Exim user) and passes the TCP/IP socket to it
35014 so that it can deliver another message using the same socket. The new process
35015 does only those deliveries that are routed to the connected host, and may in
35016 turn pass the socket on to a third process, and so on.
35018 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
35019 limit the number of messages sent down a single TCP/IP connection.
35021 .cindex "asterisk" "after IP address"
35022 The second and subsequent messages delivered down an existing connection are
35023 identified in the main log by the addition of an asterisk after the closing
35024 square bracket of the IP address.
35029 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
35030 .cindex "error" "in outgoing SMTP"
35031 .cindex "SMTP" "errors in outgoing"
35032 .cindex "host" "error"
35033 Three different kinds of error are recognized for outgoing SMTP: host errors,
35034 message errors, and recipient errors.
35037 .vitem "&*Host errors*&"
35038 A host error is not associated with a particular message or with a
35039 particular recipient of a message. The host errors are:
35042 Connection refused or timed out,
35044 Any error response code on connection,
35046 Any error response code to EHLO or HELO,
35048 Loss of connection at any time, except after &"."&,
35050 I/O errors at any time,
35052 Timeouts during the session, other than in response to MAIL, RCPT or
35053 the &"."& at the end of the data.
35056 For a host error, a permanent error response on connection, or in response to
35057 EHLO, causes all addresses routed to the host to be failed. Any other host
35058 error causes all addresses to be deferred, and retry data to be created for the
35059 host. It is not tried again, for any message, until its retry time arrives. If
35060 the current set of addresses are not all delivered in this run (to some
35061 alternative host), the message is added to the list of those waiting for this
35062 host, so if it is still undelivered when a subsequent successful delivery is
35063 made to the host, it will be sent down the same SMTP connection.
35065 .vitem "&*Message errors*&"
35066 .cindex "message" "error"
35067 A message error is associated with a particular message when sent to a
35068 particular host, but not with a particular recipient of the message. The
35069 message errors are:
35072 Any error response code to MAIL, DATA, or the &"."& that terminates
35075 Timeout after MAIL,
35077 Timeout or loss of connection after the &"."& that terminates the data. A
35078 timeout after the DATA command itself is treated as a host error, as is loss of
35079 connection at any other time.
35082 For a message error, a permanent error response (5&'xx'&) causes all addresses
35083 to be failed, and a delivery error report to be returned to the sender. A
35084 temporary error response (4&'xx'&), or one of the timeouts, causes all
35085 addresses to be deferred. Retry data is not created for the host, but instead,
35086 a retry record for the combination of host plus message id is created. The
35087 message is not added to the list of those waiting for this host. This ensures
35088 that the failing message will not be sent to this host again until the retry
35089 time arrives. However, other messages that are routed to the host are not
35090 affected, so if it is some property of the message that is causing the error,
35091 it will not stop the delivery of other mail.
35093 If the remote host specified support for the SIZE parameter in its response
35094 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
35095 over-large message will cause a message error because the error arrives as a
35098 .vitem "&*Recipient errors*&"
35099 .cindex "recipient" "error"
35100 A recipient error is associated with a particular recipient of a message. The
35101 recipient errors are:
35104 Any error response to RCPT,
35106 Timeout after RCPT.
35109 For a recipient error, a permanent error response (5&'xx'&) causes the
35110 recipient address to be failed, and a bounce message to be returned to the
35111 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
35112 address to be deferred, and routing retry data to be created for it. This is
35113 used to delay processing of the address in subsequent queue runs, until its
35114 routing retry time arrives. This applies to all messages, but because it
35115 operates only in queue runs, one attempt will be made to deliver a new message
35116 to the failing address before the delay starts to operate. This ensures that,
35117 if the failure is really related to the message rather than the recipient
35118 (&"message too big for this recipient"& is a possible example), other messages
35119 have a chance of getting delivered. If a delivery to the address does succeed,
35120 the retry information gets cleared, so all stuck messages get tried again, and
35121 the retry clock is reset.
35123 The message is not added to the list of those waiting for this host. Use of the
35124 host for other messages is unaffected, and except in the case of a timeout,
35125 other recipients are processed independently, and may be successfully delivered
35126 in the current SMTP session. After a timeout it is of course impossible to
35127 proceed with the session, so all addresses get deferred. However, those other
35128 than the one that failed do not suffer any subsequent retry delays. Therefore,
35129 if one recipient is causing trouble, the others have a chance of getting
35130 through when a subsequent delivery attempt occurs before the failing
35131 recipient's retry time.
35134 In all cases, if there are other hosts (or IP addresses) available for the
35135 current set of addresses (for example, from multiple MX records), they are
35136 tried in this run for any undelivered addresses, subject of course to their
35137 own retry data. In other words, recipient error retry data does not take effect
35138 until the next delivery attempt.
35140 Some hosts have been observed to give temporary error responses to every
35141 MAIL command at certain times (&"insufficient space"& has been seen). It
35142 would be nice if such circumstances could be recognized, and defer data for the
35143 host itself created, but this is not possible within the current Exim design.
35144 What actually happens is that retry data for every (host, message) combination
35147 The reason that timeouts after MAIL and RCPT are treated specially is that
35148 these can sometimes arise as a result of the remote host's verification
35149 procedures. Exim makes this assumption, and treats them as if a temporary error
35150 response had been received. A timeout after &"."& is treated specially because
35151 it is known that some broken implementations fail to recognize the end of the
35152 message if the last character of the last line is a binary zero. Thus, it is
35153 helpful to treat this case as a message error.
35155 Timeouts at other times are treated as host errors, assuming a problem with the
35156 host, or the connection to it. If a timeout after MAIL, RCPT,
35157 or &"."& is really a connection problem, the assumption is that at the next try
35158 the timeout is likely to occur at some other point in the dialogue, causing it
35159 then to be treated as a host error.
35161 There is experimental evidence that some MTAs drop the connection after the
35162 terminating &"."& if they do not like the contents of the message for some
35163 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
35164 should be given. That is why Exim treats this case as a message rather than a
35165 host error, in order not to delay other messages to the same host.
35170 .section "Incoming SMTP messages over TCP/IP" "SECID233"
35171 .cindex "SMTP" "incoming over TCP/IP"
35172 .cindex "incoming SMTP over TCP/IP"
35175 Incoming SMTP messages can be accepted in one of two ways: by running a
35176 listening daemon, or by using &'inetd'&. In the latter case, the entry in
35177 &_/etc/inetd.conf_& should be like this:
35179 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
35181 Exim distinguishes between this case and the case of a locally running user
35182 agent using the &%-bs%& option by checking whether or not the standard input is
35183 a socket. When it is, either the port must be privileged (less than 1024), or
35184 the caller must be root or the Exim user. If any other user passes a socket
35185 with an unprivileged port number, Exim prints a message on the standard error
35186 stream and exits with an error code.
35188 By default, Exim does not make a log entry when a remote host connects or
35189 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
35190 unexpected. It can be made to write such log entries by setting the
35191 &%smtp_connection%& log selector.
35193 .cindex "carriage return"
35195 Commands from the remote host are supposed to be terminated by CR followed by
35196 LF. However, there are known to be hosts that do not send CR characters. In
35197 order to be able to interwork with such hosts, Exim treats LF on its own as a
35199 Furthermore, because common code is used for receiving messages from all
35200 sources, a CR on its own is also interpreted as a line terminator. However, the
35201 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
35203 .cindex "EHLO" "invalid data"
35204 .cindex "HELO" "invalid data"
35205 One area that sometimes gives rise to problems concerns the EHLO or
35206 HELO commands. Some clients send syntactically invalid versions of these
35207 commands, which Exim rejects by default. (This is nothing to do with verifying
35208 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
35209 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
35210 match the broken hosts that send invalid commands.
35212 .cindex "SIZE option on MAIL command"
35213 .cindex "MAIL" "SIZE option"
35214 The amount of disk space available is checked whenever SIZE is received on
35215 a MAIL command, independently of whether &%message_size_limit%& or
35216 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
35217 false. A temporary error is given if there is not enough space. If
35218 &%check_spool_space%& is set, the check is for that amount of space plus the
35219 value given with SIZE, that is, it checks that the addition of the incoming
35220 message will not reduce the space below the threshold.
35222 When a message is successfully received, Exim includes the local message id in
35223 its response to the final &"."& that terminates the data. If the remote host
35224 logs this text it can help with tracing what has happened to a message.
35226 The Exim daemon can limit the number of simultaneous incoming connections it is
35227 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
35228 number of simultaneous incoming connections from a single remote host (see the
35229 &%smtp_accept_max_per_host%& option). Additional connection attempts are
35230 rejected using the SMTP temporary error code 421.
35232 The Exim daemon does not rely on the SIGCHLD signal to detect when a
35233 subprocess has finished, as this can get lost at busy times. Instead, it looks
35234 for completed subprocesses every time it wakes up. Provided there are other
35235 things happening (new incoming calls, starts of queue runs), completed
35236 processes will be noticed and tidied away. On very quiet systems you may
35237 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
35238 it will be noticed when the daemon next wakes up.
35240 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
35241 and can also be set up to reject SMTP calls from non-reserved hosts at times of
35242 high system load &-- for details see the &%smtp_accept_reserve%&,
35243 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
35244 applies in both the daemon and &'inetd'& cases.
35246 Exim normally starts a delivery process for each message received, though this
35247 can be varied by means of the &%-odq%& command line option and the
35248 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
35249 number of simultaneously running delivery processes started in this way from
35250 SMTP input can be limited by the &%smtp_accept_queue%& and
35251 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
35252 subsequently received messages are just put on the input queue without starting
35253 a delivery process.
35255 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
35256 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
35257 started up from the &'inetd'& daemon, because in that case each connection is
35258 handled by an entirely independent Exim process. Control by load average is,
35259 however, available with &'inetd'&.
35261 Exim can be configured to verify addresses in incoming SMTP commands as they
35262 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
35263 to rewrite addresses at this time &-- before any syntax checking is done. See
35264 section &<<SECTrewriteS>>&.
35266 Exim can also be configured to limit the rate at which a client host submits
35267 MAIL and RCPT commands in a single SMTP session. See the
35268 &%smtp_ratelimit_hosts%& option.
35272 .section "Unrecognized SMTP commands" "SECID234"
35273 .cindex "SMTP" "unrecognized commands"
35274 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
35275 commands during a single SMTP connection, it drops the connection after sending
35276 the error response to the last command. The default value for
35277 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
35278 abuse that subvert web servers into making connections to SMTP ports; in these
35279 circumstances, a number of non-SMTP lines are sent first.
35282 .section "Syntax and protocol errors in SMTP commands" "SECID235"
35283 .cindex "SMTP" "syntax errors"
35284 .cindex "SMTP" "protocol errors"
35285 A syntax error is detected if an SMTP command is recognized, but there is
35286 something syntactically wrong with its data, for example, a malformed email
35287 address in a RCPT command. Protocol errors include invalid command
35288 sequencing such as RCPT before MAIL. If Exim receives more than
35289 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
35290 drops the connection after sending the error response to the last command. The
35291 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
35292 broken clients that loop sending bad commands (yes, it has been seen).
35296 .section "Use of non-mail SMTP commands" "SECID236"
35297 .cindex "SMTP" "non-mail commands"
35298 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
35299 DATA. Exim counts such commands, and drops the connection if there are too
35300 many of them in a single SMTP session. This action catches some
35301 denial-of-service attempts and things like repeated failing AUTHs, or a mad
35302 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
35303 defines what &"too many"& means. Its default value is 10.
35305 When a new message is expected, one occurrence of RSET is not counted. This
35306 allows a client to send one RSET between messages (this is not necessary,
35307 but some clients do it). Exim also allows one uncounted occurrence of HELO
35308 or EHLO, and one occurrence of STARTTLS between messages. After
35309 starting up a TLS session, another EHLO is expected, and so it too is not
35312 The first occurrence of AUTH in a connection, or immediately following
35313 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
35314 RCPT, DATA, and QUIT are counted.
35316 You can control which hosts are subject to the limit set by
35317 &%smtp_accept_max_nonmail%& by setting
35318 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
35319 the limit apply to all hosts. This option means that you can exclude any
35320 specific badly-behaved hosts that you have to live with.
35325 .section "The VRFY and EXPN commands" "SECID237"
35326 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
35327 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
35328 appropriate) in order to decide whether the command should be accepted or not.
35330 .cindex "VRFY" "processing"
35331 When no ACL is defined for VRFY, or if it rejects without
35332 setting an explicit response code, the command is accepted
35333 (with a 252 SMTP response code)
35334 in order to support awkward clients that do a VRFY before every RCPT.
35335 When VRFY is accepted, it runs exactly the same code as when Exim is
35336 called with the &%-bv%& option, and returns 250/451/550
35337 SMTP response codes.
35339 .cindex "EXPN" "processing"
35340 If no ACL for EXPN is defined, the command is rejected.
35341 When EXPN is accepted, a single-level expansion of the address is done.
35342 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
35343 than a verification (the &%-bv%& option). If an unqualified local part is given
35344 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
35345 of VRFY and EXPN commands are logged on the main and reject logs, and
35346 VRFY verification failures are logged on the main log for consistency with
35351 .section "The ETRN command" "SECTETRN"
35352 .cindex "ETRN" "processing"
35353 RFC 1985 describes an SMTP command called ETRN that is designed to
35354 overcome the security problems of the TURN command (which has fallen into
35355 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
35356 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
35357 should be accepted or not. If no ACL is defined, the command is rejected.
35359 The ETRN command is concerned with &"releasing"& messages that are awaiting
35360 delivery to certain hosts. As Exim does not organize its message queue by host,
35361 the only form of ETRN that is supported by default is the one where the
35362 text starts with the &"#"& prefix, in which case the remainder of the text is
35363 specific to the SMTP server. A valid ETRN command causes a run of Exim with
35364 the &%-R%& option to happen, with the remainder of the ETRN text as its
35365 argument. For example,
35373 which causes a delivery attempt on all messages with undelivered addresses
35374 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
35375 default), Exim prevents the simultaneous execution of more than one queue run
35376 for the same argument string as a result of an ETRN command. This stops
35377 a misbehaving client from starting more than one queue runner at once.
35379 .cindex "hints database" "ETRN serialization"
35380 Exim implements the serialization by means of a hints database in which a
35381 record is written whenever a process is started by ETRN, and deleted when
35382 the process completes. However, Exim does not keep the SMTP session waiting for
35383 the ETRN process to complete. Once ETRN is accepted, the client is sent
35384 a &"success"& return code. Obviously there is scope for hints records to get
35385 left lying around if there is a system or program crash. To guard against this,
35386 Exim ignores any records that are more than six hours old.
35388 .oindex "&%smtp_etrn_command%&"
35389 For more control over what ETRN does, the &%smtp_etrn_command%& option can
35390 used. This specifies a command that is run whenever ETRN is received,
35391 whatever the form of its argument. For
35394 smtp_etrn_command = /etc/etrn_command $domain \
35395 $sender_host_address
35397 .vindex "&$domain$&"
35398 The string is split up into arguments which are independently expanded. The
35399 expansion variable &$domain$& is set to the argument of the ETRN command,
35400 and no syntax checking is done on the contents of this argument. Exim does not
35401 wait for the command to complete, so its status code is not checked. Exim runs
35402 under its own uid and gid when receiving incoming SMTP, so it is not possible
35403 for it to change them before running the command.
35407 .section "Incoming local SMTP" "SECID238"
35408 .cindex "SMTP" "local incoming"
35409 Some user agents use SMTP to pass messages to their local MTA using the
35410 standard input and output, as opposed to passing the envelope on the command
35411 line and writing the message to the standard input. This is supported by the
35412 &%-bs%& option. This form of SMTP is handled in the same way as incoming
35413 messages over TCP/IP (including the use of ACLs), except that the envelope
35414 sender given in a MAIL command is ignored unless the caller is trusted. In
35415 an ACL you can detect this form of SMTP input by testing for an empty host
35416 identification. It is common to have this as the first line in the ACL that
35417 runs for RCPT commands:
35421 This accepts SMTP messages from local processes without doing any other tests.
35425 .section "Outgoing batched SMTP" "SECTbatchSMTP"
35426 .cindex "SMTP" "batched outgoing"
35427 .cindex "batched SMTP output"
35428 Both the &(appendfile)& and &(pipe)& transports can be used for handling
35429 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
35430 be output in BSMTP format. No SMTP responses are possible for this form of
35431 delivery. All it is doing is using SMTP commands as a way of transmitting the
35432 envelope along with the message.
35434 The message is written to the file or pipe preceded by the SMTP commands
35435 MAIL and RCPT, and followed by a line containing a single dot. Lines in
35436 the message that start with a dot have an extra dot added. The SMTP command
35437 HELO is not normally used. If it is required, the &%message_prefix%& option
35438 can be used to specify it.
35440 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
35441 one recipient address at a time by default. However, you can arrange for them
35442 to handle several addresses at once by setting the &%batch_max%& option. When
35443 this is done for BSMTP, messages may contain multiple RCPT commands. See
35444 chapter &<<CHAPbatching>>& for more details.
35447 When one or more addresses are routed to a BSMTP transport by a router that
35448 sets up a host list, the name of the first host on the list is available to the
35449 transport in the variable &$host$&. Here is an example of such a transport and
35454 driver = manualroute
35455 transport = smtp_appendfile
35456 route_list = domain.example batch.host.example
35460 driver = appendfile
35461 directory = /var/bsmtp/$host
35466 This causes messages addressed to &'domain.example'& to be written in BSMTP
35467 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
35468 message (unless there are more than 1000 recipients).
35472 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
35473 .cindex "SMTP" "batched incoming"
35474 .cindex "batched SMTP input"
35475 The &%-bS%& command line option causes Exim to accept one or more messages by
35476 reading SMTP on the standard input, but to generate no responses. If the caller
35477 is trusted, the senders in the MAIL commands are believed; otherwise the
35478 sender is always the caller of Exim. Unqualified senders and receivers are not
35479 rejected (there seems little point) but instead just get qualified. HELO
35480 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
35481 as NOOP; QUIT quits.
35483 Minimal policy checking is done for BSMTP input. Only the non-SMTP
35484 ACL is run in the same way as for non-SMTP local input.
35486 If an error is detected while reading a message, including a missing &"."& at
35487 the end, Exim gives up immediately. It writes details of the error to the
35488 standard output in a stylized way that the calling program should be able to
35489 make some use of automatically, for example:
35491 554 Unexpected end of file
35492 Transaction started in line 10
35493 Error detected in line 14
35495 It writes a more verbose version, for human consumption, to the standard error
35498 An error was detected while processing a file of BSMTP input.
35499 The error message was:
35501 501 '>' missing at end of address
35503 The SMTP transaction started in line 10.
35504 The error was detected in line 12.
35505 The SMTP command at fault was:
35507 rcpt to:<malformed@in.com.plete
35509 1 previous message was successfully processed.
35510 The rest of the batch was abandoned.
35512 The return code from Exim is zero only if there were no errors. It is 1 if some
35513 messages were accepted before an error was detected, and 2 if no messages were
35515 .ecindex IIDsmtpproc1
35516 .ecindex IIDsmtpproc2
35520 . ////////////////////////////////////////////////////////////////////////////
35521 . ////////////////////////////////////////////////////////////////////////////
35523 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
35524 "Customizing messages"
35525 When a message fails to be delivered, or remains in the queue for more than a
35526 configured amount of time, Exim sends a message to the original sender, or
35527 to an alternative configured address. The text of these messages is built into
35528 the code of Exim, but it is possible to change it, either by adding a single
35529 string, or by replacing each of the paragraphs by text supplied in a file.
35531 The &'From:'& and &'To:'& header lines are automatically generated; you can
35532 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
35533 option. Exim also adds the line
35535 Auto-Submitted: auto-generated
35537 to all warning and bounce messages,
35540 .section "Customizing bounce messages" "SECID239"
35541 .cindex "customizing" "bounce message"
35542 .cindex "bounce message" "customizing"
35543 If &%bounce_message_text%& is set, its contents are included in the default
35544 message immediately after &"This message was created automatically by mail
35545 delivery software."& The string is not expanded. It is not used if
35546 &%bounce_message_file%& is set.
35548 When &%bounce_message_file%& is set, it must point to a template file for
35549 constructing error messages. The file consists of a series of text items,
35550 separated by lines consisting of exactly four asterisks. If the file cannot be
35551 opened, default text is used and a message is written to the main and panic
35552 logs. If any text item in the file is empty, default text is used for that
35555 .vindex "&$bounce_recipient$&"
35556 .vindex "&$bounce_return_size_limit$&"
35557 Each item of text that is read from the file is expanded, and there are two
35558 expansion variables which can be of use here: &$bounce_recipient$& is set to
35559 the recipient of an error message while it is being created, and
35560 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
35561 option, rounded to a whole number.
35563 The items must appear in the file in the following order:
35566 The first item is included in the headers, and should include at least a
35567 &'Subject:'& header. Exim does not check the syntax of these headers.
35569 The second item forms the start of the error message. After it, Exim lists the
35570 failing addresses with their error messages.
35572 The third item is used to introduce any text from pipe transports that is to be
35573 returned to the sender. It is omitted if there is no such text.
35575 The fourth, fifth and sixth items will be ignored and may be empty.
35576 The fields exist for back-compatibility
35579 The default state (&%bounce_message_file%& unset) is equivalent to the
35580 following file, in which the sixth item is empty. The &'Subject:'& and some
35581 other lines have been split in order to fit them on the page:
35583 Subject: Mail delivery failed
35584 ${if eq{$sender_address}{$bounce_recipient}
35585 {: returning message to sender}}
35587 This message was created automatically by mail delivery software.
35589 A message ${if eq{$sender_address}{$bounce_recipient}
35590 {that you sent }{sent by
35594 }}could not be delivered to all of its recipients.
35595 This is a permanent error. The following address(es) failed:
35597 The following text was generated during the delivery attempt(s):
35599 ------ This is a copy of the message, including all the headers.
35602 ------ The body of the message is $message_size characters long;
35604 ------ $bounce_return_size_limit or so are included here.
35607 .section "Customizing warning messages" "SECTcustwarn"
35608 .cindex "customizing" "warning message"
35609 .cindex "warning of delay" "customizing the message"
35610 The option &%warn_message_file%& can be pointed at a template file for use when
35611 warnings about message delays are created. In this case there are only three
35615 The first item is included in the headers, and should include at least a
35616 &'Subject:'& header. Exim does not check the syntax of these headers.
35618 The second item forms the start of the warning message. After it, Exim lists
35619 the delayed addresses.
35621 The third item then ends the message.
35624 The default state is equivalent to the following file, except that some lines
35625 have been split here, in order to fit them on the page:
35627 Subject: Warning: message $message_exim_id delayed
35628 $warn_message_delay
35630 This message was created automatically by mail delivery software.
35632 A message ${if eq{$sender_address}{$warn_message_recipients}
35633 {that you sent }{sent by
35637 }}has not been delivered to all of its recipients after
35638 more than $warn_message_delay in the queue on $primary_hostname.
35640 The message identifier is: $message_exim_id
35641 The subject of the message is: $h_subject
35642 The date of the message is: $h_date
35644 The following address(es) have not yet been delivered:
35646 No action is required on your part. Delivery attempts will
35647 continue for some time, and this warning may be repeated at
35648 intervals if the message remains undelivered. Eventually the
35649 mail delivery software will give up, and when that happens,
35650 the message will be returned to you.
35652 .vindex "&$warn_message_delay$&"
35653 .vindex "&$warn_message_recipients$&"
35654 However, in the default state the subject and date lines are omitted if no
35655 appropriate headers exist. During the expansion of this file,
35656 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
35657 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
35658 of recipients for the warning message. There may be more than one if there are
35659 multiple addresses with different &%errors_to%& settings on the routers that
35665 . ////////////////////////////////////////////////////////////////////////////
35666 . ////////////////////////////////////////////////////////////////////////////
35668 .chapter "Some common configuration settings" "CHAPcomconreq"
35669 This chapter discusses some configuration settings that seem to be fairly
35670 common. More examples and discussion can be found in the Exim book.
35674 .section "Sending mail to a smart host" "SECID240"
35675 .cindex "smart host" "example router"
35676 If you want to send all mail for non-local domains to a &"smart host"&, you
35677 should replace the default &(dnslookup)& router with a router which does the
35678 routing explicitly:
35680 send_to_smart_host:
35681 driver = manualroute
35682 route_list = !+local_domains smart.host.name
35683 transport = remote_smtp
35685 You can use the smart host's IP address instead of the name if you wish.
35686 If you are using Exim only to submit messages to a smart host, and not for
35687 receiving incoming messages, you can arrange for it to do the submission
35688 synchronously by setting the &%mua_wrapper%& option (see chapter
35689 &<<CHAPnonqueueing>>&).
35694 .section "Using Exim to handle mailing lists" "SECTmailinglists"
35695 .cindex "mailing lists"
35696 Exim can be used to run simple mailing lists, but for large and/or complicated
35697 requirements, the use of additional specialized mailing list software such as
35698 Majordomo or Mailman is recommended.
35700 The &(redirect)& router can be used to handle mailing lists where each list
35701 is maintained in a separate file, which can therefore be managed by an
35702 independent manager. The &%domains%& router option can be used to run these
35703 lists in a separate domain from normal mail. For example:
35707 domains = lists.example
35708 file = /usr/lists/$local_part
35711 errors_to = $local_part-request@lists.example
35714 This router is skipped for domains other than &'lists.example'&. For addresses
35715 in that domain, it looks for a file that matches the local part. If there is no
35716 such file, the router declines, but because &%no_more%& is set, no subsequent
35717 routers are tried, and so the whole delivery fails.
35719 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
35720 expanded into a filename or a pipe delivery, which is usually inappropriate in
35723 .oindex "&%errors_to%&"
35724 The &%errors_to%& option specifies that any delivery errors caused by addresses
35725 taken from a mailing list are to be sent to the given address rather than the
35726 original sender of the message. However, before acting on this, Exim verifies
35727 the error address, and ignores it if verification fails.
35729 For example, using the configuration above, mail sent to
35730 &'dicts@lists.example'& is passed on to those addresses contained in
35731 &_/usr/lists/dicts_&, with error reports directed to
35732 &'dicts-request@lists.example'&, provided that this address can be verified.
35733 There could be a file called &_/usr/lists/dicts-request_& containing
35734 the address(es) of this particular list's manager(s), but other approaches,
35735 such as setting up an earlier router (possibly using the &%local_part_prefix%&
35736 or &%local_part_suffix%& options) to handle addresses of the form
35737 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
35741 .section "Syntax errors in mailing lists" "SECID241"
35742 .cindex "mailing lists" "syntax errors in"
35743 If an entry in redirection data contains a syntax error, Exim normally defers
35744 delivery of the original address. That means that a syntax error in a mailing
35745 list holds up all deliveries to the list. This may not be appropriate when a
35746 list is being maintained automatically from data supplied by users, and the
35747 addresses are not rigorously checked.
35749 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
35750 entries that fail to parse, noting the incident in the log. If in addition
35751 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
35752 whenever a broken address is skipped. It is usually appropriate to set
35753 &%syntax_errors_to%& to the same address as &%errors_to%&.
35757 .section "Re-expansion of mailing lists" "SECID242"
35758 .cindex "mailing lists" "re-expansion of"
35759 Exim remembers every individual address to which a message has been delivered,
35760 in order to avoid duplication, but it normally stores only the original
35761 recipient addresses with a message. If all the deliveries to a mailing list
35762 cannot be done at the first attempt, the mailing list is re-expanded when the
35763 delivery is next tried. This means that alterations to the list are taken into
35764 account at each delivery attempt, so addresses that have been added to
35765 the list since the message arrived will therefore receive a copy of the
35766 message, even though it pre-dates their subscription.
35768 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
35769 on the &(redirect)& router. If this is done, any addresses generated by the
35770 router that fail to deliver at the first attempt are added to the message as
35771 &"top level"& addresses, and the parent address that generated them is marked
35772 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
35773 subsequent delivery attempts. The disadvantage of this is that if any of the
35774 failing addresses are incorrect, correcting them in the file has no effect on
35775 pre-existing messages.
35777 The original top-level address is remembered with each of the generated
35778 addresses, and is output in any log messages. However, any intermediate parent
35779 addresses are not recorded. This makes a difference to the log only if the
35780 &%all_parents%& selector is set, but for mailing lists there is normally only
35781 one level of expansion anyway.
35785 .section "Closed mailing lists" "SECID243"
35786 .cindex "mailing lists" "closed"
35787 The examples so far have assumed open mailing lists, to which anybody may
35788 send mail. It is also possible to set up closed lists, where mail is accepted
35789 from specified senders only. This is done by making use of the generic
35790 &%senders%& option to restrict the router that handles the list.
35792 The following example uses the same file as a list of recipients and as a list
35793 of permitted senders. It requires three routers:
35797 domains = lists.example
35798 local_part_suffix = -request
35799 file = /usr/lists/$local_part$local_part_suffix
35804 domains = lists.example
35805 senders = ${if exists {/usr/lists/$local_part}\
35806 {lsearch;/usr/lists/$local_part}{*}}
35807 file = /usr/lists/$local_part
35810 errors_to = $local_part-request@lists.example
35815 domains = lists.example
35817 data = :fail: $local_part@lists.example is a closed mailing list
35819 All three routers have the same &%domains%& setting, so for any other domains,
35820 they are all skipped. The first router runs only if the local part ends in
35821 &%-request%&. It handles messages to the list manager(s) by means of an open
35824 The second router runs only if the &%senders%& precondition is satisfied. It
35825 checks for the existence of a list that corresponds to the local part, and then
35826 checks that the sender is on the list by means of a linear search. It is
35827 necessary to check for the existence of the file before trying to search it,
35828 because otherwise Exim thinks there is a configuration error. If the file does
35829 not exist, the expansion of &%senders%& is *, which matches all senders. This
35830 means that the router runs, but because there is no list, declines, and
35831 &%no_more%& ensures that no further routers are run. The address fails with an
35832 &"unrouteable address"& error.
35834 The third router runs only if the second router is skipped, which happens when
35835 a mailing list exists, but the sender is not on it. This router forcibly fails
35836 the address, giving a suitable error message.
35841 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
35843 .cindex "Variable Envelope Return Paths"
35844 .cindex "envelope sender"
35845 Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
35846 are a way of helping mailing list administrators discover which subscription
35847 address is the cause of a particular delivery failure. The idea is to encode
35848 the original recipient address in the outgoing envelope sender address, so that
35849 if the message is forwarded by another host and then subsequently bounces, the
35850 original recipient can be extracted from the recipient address of the bounce.
35852 .oindex &%errors_to%&
35853 .oindex &%return_path%&
35854 Envelope sender addresses can be modified by Exim using two different
35855 facilities: the &%errors_to%& option on a router (as shown in previous mailing
35856 list examples), or the &%return_path%& option on a transport. The second of
35857 these is effective only if the message is successfully delivered to another
35858 host; it is not used for errors detected on the local host (see the description
35859 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
35860 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
35866 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
35867 {$1-request+$local_part=$domain@your.dom.example}fail}
35869 This has the effect of rewriting the return path (envelope sender) on outgoing
35870 SMTP messages, if the local part of the original return path ends in
35871 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
35872 local part and domain of the recipient into the return path. Suppose, for
35873 example, that a message whose return path has been set to
35874 &'somelist-request@your.dom.example'& is sent to
35875 &'subscriber@other.dom.example'&. In the transport, the return path is
35878 somelist-request+subscriber=other.dom.example@your.dom.example
35880 .vindex "&$local_part$&"
35881 For this to work, you must tell Exim to send multiple copies of messages that
35882 have more than one recipient, so that each copy has just one recipient. This is
35883 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
35884 might be sent to several different recipients in the same domain, in which case
35885 &$local_part$& is not available in the transport, because it is not unique.
35887 Unless your host is doing nothing but mailing list deliveries, you should
35888 probably use a separate transport for the VERP deliveries, so as not to use
35889 extra resources in making one-per-recipient copies for other deliveries. This
35890 can easily be done by expanding the &%transport%& option in the router:
35894 domains = ! +local_domains
35896 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
35897 {verp_smtp}{remote_smtp}}
35900 If you want to change the return path using &%errors_to%& in a router instead
35901 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
35902 routers that handle mailing list addresses. This will ensure that all delivery
35903 errors, including those detected on the local host, are sent to the VERP
35906 On a host that does no local deliveries and has no manual routing, only the
35907 &(dnslookup)& router needs to be changed. A special transport is not needed for
35908 SMTP deliveries. Every mailing list recipient has its own return path value,
35909 and so Exim must hand them to the transport one at a time. Here is an example
35910 of a &(dnslookup)& router that implements VERP:
35914 domains = ! +local_domains
35915 transport = remote_smtp
35917 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
35918 {$1-request+$local_part=$domain@your.dom.example}fail}
35921 Before you start sending out messages with VERPed return paths, you must also
35922 configure Exim to accept the bounce messages that come back to those paths.
35923 Typically this is done by setting a &%local_part_suffix%& option for a
35924 router, and using this to route the messages to wherever you want to handle
35927 The overhead incurred in using VERP depends very much on the size of the
35928 message, the number of recipient addresses that resolve to the same remote
35929 host, and the speed of the connection over which the message is being sent. If
35930 a lot of addresses resolve to the same host and the connection is slow, sending
35931 a separate copy of the message for each address may take substantially longer
35932 than sending a single copy with many recipients (for which VERP cannot be
35940 .section "Virtual domains" "SECTvirtualdomains"
35941 .cindex "virtual domains"
35942 .cindex "domain" "virtual"
35943 The phrase &'virtual domain'& is unfortunately used with two rather different
35947 A domain for which there are no real mailboxes; all valid local parts are
35948 aliases for other email addresses. Common examples are organizational
35949 top-level domains and &"vanity"& domains.
35951 One of a number of independent domains that are all handled by the same host,
35952 with mailboxes on that host, but where the mailbox owners do not necessarily
35953 have login accounts on that host.
35956 The first usage is probably more common, and does seem more &"virtual"& than
35957 the second. This kind of domain can be handled in Exim with a straightforward
35958 aliasing router. One approach is to create a separate alias file for each
35959 virtual domain. Exim can test for the existence of the alias file to determine
35960 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
35961 to a router of this form:
35965 domains = dsearch;/etc/mail/virtual
35966 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
35969 The &%domains%& option specifies that the router is to be skipped, unless there
35970 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
35971 domain that is being processed. When the router runs, it looks up the local
35972 part in the file to find a new address (or list of addresses). The &%no_more%&
35973 setting ensures that if the lookup fails (leading to &%data%& being an empty
35974 string), Exim gives up on the address without trying any subsequent routers.
35976 This one router can handle all the virtual domains because the alias filenames
35977 follow a fixed pattern. Permissions can be arranged so that appropriate people
35978 can edit the different alias files. A successful aliasing operation results in
35979 a new envelope recipient address, which is then routed from scratch.
35981 The other kind of &"virtual"& domain can also be handled in a straightforward
35982 way. One approach is to create a file for each domain containing a list of
35983 valid local parts, and use it in a router like this:
35987 domains = dsearch;/etc/mail/domains
35988 local_parts = lsearch;/etc/mail/domains/$domain
35989 transport = my_mailboxes
35991 The address is accepted if there is a file for the domain, and the local part
35992 can be found in the file. The &%domains%& option is used to check for the
35993 file's existence because &%domains%& is tested before the &%local_parts%&
35994 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
35995 because that option is tested after &%local_parts%&. The transport is as
35999 driver = appendfile
36000 file = /var/mail/$domain/$local_part
36003 This uses a directory of mailboxes for each domain. The &%user%& setting is
36004 required, to specify which uid is to be used for writing to the mailboxes.
36006 The configuration shown here is just one example of how you might support this
36007 requirement. There are many other ways this kind of configuration can be set
36008 up, for example, by using a database instead of separate files to hold all the
36009 information about the domains.
36013 .section "Multiple user mailboxes" "SECTmulbox"
36014 .cindex "multiple mailboxes"
36015 .cindex "mailbox" "multiple"
36016 .cindex "local part" "prefix"
36017 .cindex "local part" "suffix"
36018 Heavy email users often want to operate with multiple mailboxes, into which
36019 incoming mail is automatically sorted. A popular way of handling this is to
36020 allow users to use multiple sender addresses, so that replies can easily be
36021 identified. Users are permitted to add prefixes or suffixes to their local
36022 parts for this purpose. The wildcard facility of the generic router options
36023 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
36024 example, consider this router:
36029 file = $home/.forward
36030 local_part_suffix = -*
36031 local_part_suffix_optional
36034 .vindex "&$local_part_suffix$&"
36035 It runs a user's &_.forward_& file for all local parts of the form
36036 &'username-*'&. Within the filter file the user can distinguish different
36037 cases by testing the variable &$local_part_suffix$&. For example:
36039 if $local_part_suffix contains -special then
36040 save /home/$local_part/Mail/special
36043 If the filter file does not exist, or does not deal with such addresses, they
36044 fall through to subsequent routers, and, assuming no subsequent use of the
36045 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
36046 control over which suffixes are valid.
36048 Alternatively, a suffix can be used to trigger the use of a different
36049 &_.forward_& file &-- which is the way a similar facility is implemented in
36055 file = $home/.forward$local_part_suffix
36056 local_part_suffix = -*
36057 local_part_suffix_optional
36060 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
36061 example, &_.forward-special_& is used. Once again, if the appropriate file
36062 does not exist, or does not deal with the address, it is passed on to
36063 subsequent routers, which could, if required, look for an unqualified
36064 &_.forward_& file to use as a default.
36068 .section "Simplified vacation processing" "SECID244"
36069 .cindex "vacation processing"
36070 The traditional way of running the &'vacation'& program is for a user to set up
36071 a pipe command in a &_.forward_& file
36072 (see section &<<SECTspecitredli>>& for syntax details).
36073 This is prone to error by inexperienced users. There are two features of Exim
36074 that can be used to make this process simpler for users:
36077 A local part prefix such as &"vacation-"& can be specified on a router which
36078 can cause the message to be delivered directly to the &'vacation'& program, or
36079 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
36080 &_.forward_& file are then much simpler. For example:
36082 spqr, vacation-spqr
36085 The &%require_files%& generic router option can be used to trigger a
36086 vacation delivery by checking for the existence of a certain file in the
36087 user's home directory. The &%unseen%& generic option should also be used, to
36088 ensure that the original delivery also proceeds. In this case, all the user has
36089 to do is to create a file called, say, &_.vacation_&, containing a vacation
36093 Another advantage of both these methods is that they both work even when the
36094 use of arbitrary pipes by users is locked out.
36098 .section "Taking copies of mail" "SECID245"
36099 .cindex "message" "copying every"
36100 Some installations have policies that require archive copies of all messages to
36101 be made. A single copy of each message can easily be taken by an appropriate
36102 command in a system filter, which could, for example, use a different file for
36103 each day's messages.
36105 There is also a shadow transport mechanism that can be used to take copies of
36106 messages that are successfully delivered by local transports, one copy per
36107 delivery. This could be used, &'inter alia'&, to implement automatic
36108 notification of delivery by sites that insist on doing such things.
36112 .section "Intermittently connected hosts" "SECID246"
36113 .cindex "intermittently connected hosts"
36114 It has become quite common (because it is cheaper) for hosts to connect to the
36115 Internet periodically rather than remain connected all the time. The normal
36116 arrangement is that mail for such hosts accumulates on a system that is
36117 permanently connected.
36119 Exim was designed for use on permanently connected hosts, and so it is not
36120 particularly well-suited to use in an intermittently connected environment.
36121 Nevertheless there are some features that can be used.
36124 .section "Exim on the upstream server host" "SECID247"
36125 It is tempting to arrange for incoming mail for the intermittently connected
36126 host to remain in Exim's queue until the client connects. However, this
36127 approach does not scale very well. Two different kinds of waiting message are
36128 being mixed up in the same queue &-- those that cannot be delivered because of
36129 some temporary problem, and those that are waiting for their destination host
36130 to connect. This makes it hard to manage the queue, as well as wasting
36131 resources, because each queue runner scans the entire queue.
36133 A better approach is to separate off those messages that are waiting for an
36134 intermittently connected host. This can be done by delivering these messages
36135 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
36136 format, from where they are transmitted by other software when their
36137 destination connects. This makes it easy to collect all the mail for one host
36138 in a single directory, and to apply local timeout rules on a per-message basis
36141 On a very small scale, leaving the mail on Exim's queue can be made to work. If
36142 you are doing this, you should configure Exim with a long retry period for the
36143 intermittent host. For example:
36145 cheshire.wonderland.fict.example * F,5d,24h
36147 This stops a lot of failed delivery attempts from occurring, but Exim remembers
36148 which messages it has queued up for that host. Once the intermittent host comes
36149 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
36150 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
36151 causes all the queued up messages to be delivered, often down a single SMTP
36152 connection. While the host remains connected, any new messages get delivered
36155 If the connecting hosts do not have fixed IP addresses, that is, if a host is
36156 issued with a different IP address each time it connects, Exim's retry
36157 mechanisms on the holding host get confused, because the IP address is normally
36158 used as part of the key string for holding retry information. This can be
36159 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
36160 Since this has disadvantages for permanently connected hosts, it is best to
36161 arrange a separate transport for the intermittently connected ones.
36165 .section "Exim on the intermittently connected client host" "SECID248"
36166 The value of &%smtp_accept_queue_per_connection%& should probably be
36167 increased, or even set to zero (that is, disabled) on the intermittently
36168 connected host, so that all incoming messages down a single connection get
36169 delivered immediately.
36171 .cindex "SMTP" "passed connection"
36172 .cindex "SMTP" "multiple deliveries"
36173 .cindex "multiple SMTP deliveries"
36174 Mail waiting to be sent from an intermittently connected host will probably
36175 not have been routed, because without a connection DNS lookups are not
36176 possible. This means that if a normal queue run is done at connection time,
36177 each message is likely to be sent in a separate SMTP session. This can be
36178 avoided by starting the queue run with a command line option beginning with
36179 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
36180 first pass, routing is done but no deliveries take place. The second pass is a
36181 normal queue run; since all the messages have been previously routed, those
36182 destined for the same host are likely to get sent as multiple deliveries in a
36183 single SMTP connection.
36187 . ////////////////////////////////////////////////////////////////////////////
36188 . ////////////////////////////////////////////////////////////////////////////
36190 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
36191 "Exim as a non-queueing client"
36192 .cindex "client, non-queueing"
36193 .cindex "smart host" "suppressing queueing"
36194 On a personal computer, it is a common requirement for all
36195 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
36196 configured to operate that way, for all the popular operating systems.
36197 However, there are some MUAs for Unix-like systems that cannot be so
36198 configured: they submit messages using the command line interface of
36199 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
36202 If the personal computer runs continuously, there is no problem, because it can
36203 run a conventional MTA that handles delivery to the smart host, and deal with
36204 any delays via its queueing mechanism. However, if the computer does not run
36205 continuously or runs different operating systems at different times, queueing
36206 email is not desirable.
36208 There is therefore a requirement for something that can provide the
36209 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
36210 any queueing or retrying facilities. Furthermore, the delivery to the smart
36211 host should be synchronous, so that if it fails, the sending MUA is immediately
36212 informed. In other words, we want something that extends an MUA that submits
36213 to a local MTA via the command line so that it behaves like one that submits
36214 to a remote smart host using TCP/SMTP.
36216 There are a number of applications (for example, there is one called &'ssmtp'&)
36217 that do this job. However, people have found them to be lacking in various
36218 ways. For instance, you might want to allow aliasing and forwarding to be done
36219 before sending a message to the smart host.
36221 Exim already had the necessary infrastructure for doing this job. Just a few
36222 tweaks were needed to make it behave as required, though it is somewhat of an
36223 overkill to use a fully-featured MTA for this purpose.
36225 .oindex "&%mua_wrapper%&"
36226 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
36227 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
36228 assumes that it is being used to &"wrap"& a command-line MUA in the manner
36229 just described. As well as setting &%mua_wrapper%&, you also need to provide a
36230 compatible router and transport configuration. Typically there will be just one
36231 router and one transport, sending everything to a smart host.
36233 When run in MUA wrapping mode, the behaviour of Exim changes in the
36237 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
36238 In other words, the only way to submit messages is via the command line.
36240 Each message is synchronously delivered as soon as it is received (&%-odi%& is
36241 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
36242 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
36243 does not finish until the delivery attempt is complete. If the delivery is
36244 successful, a zero return code is given.
36246 Address redirection is permitted, but the final routing for all addresses must
36247 be to the same remote transport, and to the same list of hosts. Furthermore,
36248 the return address (envelope sender) must be the same for all recipients, as
36249 must any added or deleted header lines. In other words, it must be possible to
36250 deliver the message in a single SMTP transaction, however many recipients there
36253 If these conditions are not met, or if routing any address results in a
36254 failure or defer status, or if Exim is unable to deliver all the recipients
36255 successfully to one of the smart hosts, delivery of the entire message fails.
36257 Because no queueing is allowed, all failures are treated as permanent; there
36258 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
36259 smart host. Furthermore, because only a single yes/no response can be given to
36260 the caller, it is not possible to deliver to some recipients and not others. If
36261 there is an error (temporary or permanent) for any recipient, all are failed.
36263 If more than one smart host is listed, Exim will try another host after a
36264 connection failure or a timeout, in the normal way. However, if this kind of
36265 failure happens for all the hosts, the delivery fails.
36267 When delivery fails, an error message is written to the standard error stream
36268 (as well as to Exim's log), and Exim exits to the caller with a return code
36269 value 1. The message is expunged from Exim's spool files. No bounce messages
36270 are ever generated.
36272 No retry data is maintained, and any retry rules are ignored.
36274 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
36275 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
36276 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
36279 The overall effect is that Exim makes a single synchronous attempt to deliver
36280 the message, failing if there is any kind of problem. Because no local
36281 deliveries are done and no daemon can be run, Exim does not need root
36282 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
36283 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
36284 the advantages and disadvantages of running without root privilege.
36289 . ////////////////////////////////////////////////////////////////////////////
36290 . ////////////////////////////////////////////////////////////////////////////
36292 .chapter "Log files" "CHAPlog"
36293 .scindex IIDloggen "log" "general description"
36294 .cindex "log" "types of"
36295 Exim writes three different logs, referred to as the main log, the reject log,
36300 The main log records the arrival of each message and each delivery in a single
36301 line in each case. The format is as compact as possible, in an attempt to keep
36302 down the size of log files. Two-character flag sequences make it easy to pick
36303 out these lines. A number of other events are recorded in the main log. Some of
36304 them are optional, in which case the &%log_selector%& option controls whether
36305 they are included or not. A Perl script called &'eximstats'&, which does simple
36306 analysis of main log files, is provided in the Exim distribution (see section
36307 &<<SECTmailstat>>&).
36309 .cindex "reject log"
36310 The reject log records information from messages that are rejected as a result
36311 of a configuration option (that is, for policy reasons).
36312 The first line of each rejection is a copy of the line that is also written to
36313 the main log. Then, if the message's header has been read at the time the log
36314 is written, its contents are written to this log. Only the original header
36315 lines are available; header lines added by ACLs are not logged. You can use the
36316 reject log to check that your policy controls are working correctly; on a busy
36317 host this may be easier than scanning the main log for rejection messages. You
36318 can suppress the writing of the reject log by setting &%write_rejectlog%&
36321 .cindex "panic log"
36322 .cindex "system log"
36323 When certain serious errors occur, Exim writes entries to its panic log. If the
36324 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
36325 are usually written to the main log as well, but can get lost amid the mass of
36326 other entries. The panic log should be empty under normal circumstances. It is
36327 therefore a good idea to check it (or to have a &'cron'& script check it)
36328 regularly, in order to become aware of any problems. When Exim cannot open its
36329 panic log, it tries as a last resort to write to the system log (syslog). This
36330 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
36331 message itself is written at priority LOG_CRIT.
36334 Every log line starts with a timestamp, in the format shown in the following
36335 example. Note that many of the examples shown in this chapter are line-wrapped.
36336 In the log file, this would be all on one line:
36338 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
36341 By default, the timestamps are in the local timezone. There are two
36342 ways of changing this:
36345 You can set the &%timezone%& option to a different time zone; in particular, if
36350 the timestamps will be in UTC (aka GMT).
36352 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
36355 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
36359 .cindex "log" "process ids in"
36360 .cindex "pid (process id)" "in log lines"
36361 Exim does not include its process id in log lines by default, but you can
36362 request that it does so by specifying the &`pid`& log selector (see section
36363 &<<SECTlogselector>>&). When this is set, the process id is output, in square
36364 brackets, immediately after the time and date.
36369 .section "Where the logs are written" "SECTwhelogwri"
36370 .cindex "log" "destination"
36371 .cindex "log" "to file"
36372 .cindex "log" "to syslog"
36374 The logs may be written to local files, or to syslog, or both. However, it
36375 should be noted that many syslog implementations use UDP as a transport, and
36376 are therefore unreliable in the sense that messages are not guaranteed to
36377 arrive at the loghost, nor is the ordering of messages necessarily maintained.
36378 It has also been reported that on large log files (tens of megabytes) you may
36379 need to tweak syslog to prevent it syncing the file with each write &-- on
36380 Linux this has been seen to make syslog take 90% plus of CPU time.
36382 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
36383 &_Local/Makefile_& or by setting &%log_file_path%& in the runtime
36384 configuration. This latter string is expanded, so it can contain, for example,
36385 references to the host name:
36387 log_file_path = /var/log/$primary_hostname/exim_%slog
36389 It is generally advisable, however, to set the string in &_Local/Makefile_&
36390 rather than at runtime, because then the setting is available right from the
36391 start of Exim's execution. Otherwise, if there's something it wants to log
36392 before it has read the configuration file (for example, an error in the
36393 configuration file) it will not use the path you want, and may not be able to
36396 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
36397 list, currently limited to at most two items. This is one option where the
36398 facility for changing a list separator may not be used. The list must always be
36399 colon-separated. If an item in the list is &"syslog"& then syslog is used;
36400 otherwise the item must either be an absolute path, containing &`%s`& at the
36401 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
36402 implying the use of a default path.
36404 When Exim encounters an empty item in the list, it searches the list defined by
36405 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
36406 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
36407 mean &"use the path specified at build time"&. It no such item exists, log
36408 files are written in the &_log_& subdirectory of the spool directory. This is
36409 equivalent to the setting:
36411 log_file_path = $spool_directory/log/%slog
36413 If you do not specify anything at build time or runtime,
36414 or if you unset the option at runtime (i.e. &`log_file_path = `&),
36415 that is where the logs are written.
36417 A log file path may also contain &`%D`& or &`%M`& if datestamped log filenames
36418 are in use &-- see section &<<SECTdatlogfil>>& below.
36420 Here are some examples of possible settings:
36422 &`LOG_FILE_PATH=syslog `& syslog only
36423 &`LOG_FILE_PATH=:syslog `& syslog and default path
36424 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
36425 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
36427 If there are more than two paths in the list, the first is used and a panic
36432 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
36433 .cindex "log" "cycling local files"
36434 .cindex "cycling logs"
36435 .cindex "&'exicyclog'&"
36436 .cindex "log" "local files; writing to"
36437 Some operating systems provide centralized and standardized methods for cycling
36438 log files. For those that do not, a utility script called &'exicyclog'& is
36439 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
36440 main and reject logs each time it is called. The maximum number of old logs to
36441 keep can be set. It is suggested this script is run as a daily &'cron'& job.
36443 An Exim delivery process opens the main log when it first needs to write to it,
36444 and it keeps the file open in case subsequent entries are required &-- for
36445 example, if a number of different deliveries are being done for the same
36446 message. However, remote SMTP deliveries can take a long time, and this means
36447 that the file may be kept open long after it is renamed if &'exicyclog'& or
36448 something similar is being used to rename log files on a regular basis. To
36449 ensure that a switch of log files is noticed as soon as possible, Exim calls
36450 &[stat()]& on the main log's name before reusing an open file, and if the file
36451 does not exist, or its inode has changed, the old file is closed and Exim
36452 tries to open the main log from scratch. Thus, an old log file may remain open
36453 for quite some time, but no Exim processes should write to it once it has been
36458 .section "Datestamped log files" "SECTdatlogfil"
36459 .cindex "log" "datestamped files"
36460 Instead of cycling the main and reject log files by renaming them
36461 periodically, some sites like to use files whose names contain a datestamp,
36462 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
36463 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
36464 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
36465 point where the datestamp is required. For example:
36467 log_file_path = /var/spool/exim/log/%slog-%D
36468 log_file_path = /var/log/exim-%s-%D.log
36469 log_file_path = /var/spool/exim/log/%D-%slog
36470 log_file_path = /var/log/exim/%s.%M
36472 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
36473 examples of names generated by the above examples:
36475 /var/spool/exim/log/mainlog-20021225
36476 /var/log/exim-reject-20021225.log
36477 /var/spool/exim/log/20021225-mainlog
36478 /var/log/exim/main.200212
36480 When this form of log file is specified, Exim automatically switches to new
36481 files at midnight. It does not make any attempt to compress old logs; you
36482 will need to write your own script if you require this. You should not
36483 run &'exicyclog'& with this form of logging.
36485 The location of the panic log is also determined by &%log_file_path%&, but it
36486 is not datestamped, because rotation of the panic log does not make sense.
36487 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
36488 the string. In addition, if it immediately follows a slash, a following
36489 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
36490 character is removed. Thus, the four examples above would give these panic
36493 /var/spool/exim/log/paniclog
36494 /var/log/exim-panic.log
36495 /var/spool/exim/log/paniclog
36496 /var/log/exim/panic
36500 .section "Logging to syslog" "SECID249"
36501 .cindex "log" "syslog; writing to"
36502 The use of syslog does not change what Exim logs or the format of its messages,
36503 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
36504 Exim's log lines are omitted when these lines are sent to syslog. Apart from
36505 that, the same strings are written to syslog as to log files. The syslog
36506 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
36507 by default, but you can change these by setting the &%syslog_facility%& and
36508 &%syslog_processname%& options, respectively. If Exim was compiled with
36509 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
36510 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
36511 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
36512 the time and host name to each line.
36513 The three log streams are mapped onto syslog priorities as follows:
36516 &'mainlog'& is mapped to LOG_INFO
36518 &'rejectlog'& is mapped to LOG_NOTICE
36520 &'paniclog'& is mapped to LOG_ALERT
36523 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
36524 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
36525 these are routed by syslog to the same place. You can suppress this duplication
36526 by setting &%syslog_duplication%& false.
36528 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
36529 entries contain multiple lines when headers are included. To cope with both
36530 these cases, entries written to syslog are split into separate &[syslog()]&
36531 calls at each internal newline, and also after a maximum of
36532 870 data characters. (This allows for a total syslog line length of 1024, when
36533 additions such as timestamps are added.) If you are running a syslog
36534 replacement that can handle lines longer than the 1024 characters allowed by
36535 RFC 3164, you should set
36537 SYSLOG_LONG_LINES=yes
36539 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
36540 lines, but it still splits at internal newlines in &'reject'& log entries.
36542 To make it easy to re-assemble split lines later, each component of a split
36543 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
36544 where <&'n'&> is the component number and <&'m'&> is the total number of
36545 components in the entry. The / delimiter is used when the line was split
36546 because it was too long; if it was split because of an internal newline, the \
36547 delimiter is used. For example, supposing the length limit to be 50 instead of
36548 870, the following would be the result of a typical rejection message to
36549 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
36550 name, and pid as added by syslog:
36552 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
36553 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
36554 [3/5] when scanning for sender: missing or malformed lo
36555 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
36558 The same error might cause the following lines to be written to &"rejectlog"&
36561 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
36562 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
36563 [3/18] er when scanning for sender: missing or malformed
36564 [4/18] local part in "<>" (envelope sender is <ph10@cam
36566 [6\18] Recipients: ph10@some.domain.cam.example
36567 [7\18] P Received: from [127.0.0.1] (ident=ph10)
36568 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
36569 [9\18] id 16RdAL-0006pc-00
36570 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
36571 [11\18] 09:43 +0100
36573 [13\18] Subject: this is a test header
36574 [18\18] X-something: this is another header
36575 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
36578 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
36580 Log lines that are neither too long nor contain newlines are written to syslog
36581 without modification.
36583 If only syslog is being used, the Exim monitor is unable to provide a log tail
36584 display, unless syslog is routing &'mainlog'& to a file on the local host and
36585 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
36590 .section "Log line flags" "SECID250"
36591 One line is written to the main log for each message received, and for each
36592 successful, unsuccessful, and delayed delivery. These lines can readily be
36593 picked out by the distinctive two-character flags that immediately follow the
36594 timestamp. The flags are:
36596 &`<=`& message arrival
36597 &`(=`& message fakereject
36598 &`=>`& normal message delivery
36599 &`->`& additional address in same delivery
36600 &`>>`& cutthrough message delivery
36601 &`*>`& delivery suppressed by &%-N%&
36602 &`**`& delivery failed; address bounced
36603 &`==`& delivery deferred; temporary problem
36607 .section "Logging message reception" "SECID251"
36608 .cindex "log" "reception line"
36609 The format of the single-line entry in the main log that is written for every
36610 message received is shown in the basic example below, which is split over
36611 several lines in order to fit it on the page:
36613 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
36614 H=mailer.fict.example [192.168.123.123] U=exim
36615 P=smtp S=5678 id=<incoming message id>
36617 The address immediately following &"<="& is the envelope sender address. A
36618 bounce message is shown with the sender address &"<>"&, and if it is locally
36619 generated, this is followed by an item of the form
36623 which is a reference to the message that caused the bounce to be sent.
36627 For messages from other hosts, the H and U fields identify the remote host and
36628 record the RFC 1413 identity of the user that sent the message, if one was
36629 received. The number given in square brackets is the IP address of the sending
36630 host. If there is a single, unparenthesized host name in the H field, as
36631 above, it has been verified to correspond to the IP address (see the
36632 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
36633 by the remote host in the SMTP HELO or EHLO command, and has not been
36634 verified. If verification yields a different name to that given for HELO or
36635 EHLO, the verified name appears first, followed by the HELO or EHLO
36636 name in parentheses.
36638 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
36639 without brackets, in the HELO or EHLO command, leading to entries in
36640 the log containing text like these examples:
36642 H=(10.21.32.43) [192.168.8.34]
36643 H=([10.21.32.43]) [192.168.8.34]
36645 This can be confusing. Only the final address in square brackets can be relied
36648 For locally generated messages (that is, messages not received over TCP/IP),
36649 the H field is omitted, and the U field contains the login name of the caller
36652 .cindex "authentication" "logging"
36653 .cindex "AUTH" "logging"
36654 For all messages, the P field specifies the protocol used to receive the
36655 message. This is the value that is stored in &$received_protocol$&. In the case
36656 of incoming SMTP messages, the value indicates whether or not any SMTP
36657 extensions (ESMTP), encryption, or authentication were used. If the SMTP
36658 session was encrypted, there is an additional X field that records the cipher
36659 suite that was used.
36661 .cindex log protocol
36662 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
36663 hosts that have authenticated themselves using the SMTP AUTH command. The first
36664 value is used when the SMTP connection was encrypted (&"secure"&). In this case
36665 there is an additional item A= followed by the name of the authenticator that
36666 was used. If an authenticated identification was set up by the authenticator's
36667 &%server_set_id%& option, this is logged too, separated by a colon from the
36668 authenticator name.
36670 .cindex "size" "of message"
36671 The id field records the existing message id, if present. The size of the
36672 received message is given by the S field. When the message is delivered,
36673 headers may be removed or added, so that the size of delivered copies of the
36674 message may not correspond with this value (and indeed may be different to each
36677 The &%log_selector%& option can be used to request the logging of additional
36678 data when a message is received. See section &<<SECTlogselector>>& below.
36682 .section "Logging deliveries" "SECID252"
36683 .cindex "log" "delivery line"
36684 The format of the single-line entry in the main log that is written for every
36685 delivery is shown in one of the examples below, for local and remote
36686 deliveries, respectively. Each example has been split into multiple lines in order
36687 to fit it on the page:
36689 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
36690 <marv@hitch.fict.example> R=localuser T=local_delivery
36691 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
36692 monk@holistic.fict.example R=dnslookup T=remote_smtp
36693 H=holistic.fict.example [192.168.234.234]
36695 For ordinary local deliveries, the original address is given in angle brackets
36696 after the final delivery address, which might be a pipe or a file. If
36697 intermediate address(es) exist between the original and the final address, the
36698 last of these is given in parentheses after the final address. The R and T
36699 fields record the router and transport that were used to process the address.
36701 If SMTP AUTH was used for the delivery there is an additional item A=
36702 followed by the name of the authenticator that was used.
36703 If an authenticated identification was set up by the authenticator's &%client_set_id%&
36704 option, this is logged too, separated by a colon from the authenticator name.
36706 If a shadow transport was run after a successful local delivery, the log line
36707 for the successful delivery has an item added on the end, of the form
36709 &`ST=<`&&'shadow transport name'&&`>`&
36711 If the shadow transport did not succeed, the error message is put in
36712 parentheses afterwards.
36714 .cindex "asterisk" "after IP address"
36715 When more than one address is included in a single delivery (for example, two
36716 SMTP RCPT commands in one transaction) the second and subsequent addresses are
36717 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
36718 down a single SMTP connection, an asterisk follows the IP address in the log
36719 lines for the second and subsequent messages.
36720 When two or more messages are delivered down a single TLS connection, the
36721 DNS and some TLS-related information logged for the first message delivered
36722 will not be present in the log lines for the second and subsequent messages.
36723 TLS cipher information is still available.
36725 .cindex "delivery" "cutthrough; logging"
36726 .cindex "cutthrough" "logging"
36727 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
36728 line precedes the reception line, since cutthrough waits for a possible
36729 rejection from the destination in case it can reject the sourced item.
36731 The generation of a reply message by a filter file gets logged as a
36732 &"delivery"& to the addressee, preceded by &">"&.
36734 The &%log_selector%& option can be used to request the logging of additional
36735 data when a message is delivered. See section &<<SECTlogselector>>& below.
36738 .section "Discarded deliveries" "SECID253"
36739 .cindex "discarded messages"
36740 .cindex "message" "discarded"
36741 .cindex "delivery" "discarded; logging"
36742 When a message is discarded as a result of the command &"seen finish"& being
36743 obeyed in a filter file which generates no deliveries, a log entry of the form
36745 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
36746 <low.club@bridge.example> R=userforward
36748 is written, to record why no deliveries are logged. When a message is discarded
36749 because it is aliased to &":blackhole:"& the log line is like this:
36751 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
36752 <hole@nowhere.example> R=blackhole_router
36756 .section "Deferred deliveries" "SECID254"
36757 When a delivery is deferred, a line of the following form is logged:
36759 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
36760 R=dnslookup T=smtp defer (146): Connection refused
36762 In the case of remote deliveries, the error is the one that was given for the
36763 last IP address that was tried. Details of individual SMTP failures are also
36764 written to the log, so the above line would be preceded by something like
36766 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
36767 mail1.endrest.example [192.168.239.239]: Connection refused
36769 When a deferred address is skipped because its retry time has not been reached,
36770 a message is written to the log, but this can be suppressed by setting an
36771 appropriate value in &%log_selector%&.
36775 .section "Delivery failures" "SECID255"
36776 .cindex "delivery" "failure; logging"
36777 If a delivery fails because an address cannot be routed, a line of the
36778 following form is logged:
36780 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
36781 <jim@trek99.example>: unknown mail domain
36783 If a delivery fails at transport time, the router and transport are shown, and
36784 the response from the remote host is included, as in this example:
36786 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
36787 R=dnslookup T=remote_smtp: SMTP error from remote mailer
36788 after pipelined RCPT TO:<ace400@pb.example>: host
36789 pbmail3.py.example [192.168.63.111]: 553 5.3.0
36790 <ace400@pb.example>...Addressee unknown
36792 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
36793 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
36794 disabling PIPELINING. The log lines for all forms of delivery failure are
36795 flagged with &`**`&.
36799 .section "Fake deliveries" "SECID256"
36800 .cindex "delivery" "fake; logging"
36801 If a delivery does not actually take place because the &%-N%& option has been
36802 used to suppress it, a normal delivery line is written to the log, except that
36803 &"=>"& is replaced by &"*>"&.
36807 .section "Completion" "SECID257"
36810 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
36812 is written to the main log when a message is about to be removed from the spool
36813 at the end of its processing.
36818 .section "Summary of Fields in Log Lines" "SECID258"
36819 .cindex "log" "summary of fields"
36820 A summary of the field identifiers that are used in log lines is shown in
36821 the following table:
36823 &`A `& authenticator name (and optional id and sender)
36824 &`C `& SMTP confirmation on delivery
36825 &` `& command list for &"no mail in SMTP session"&
36826 &`CV `& certificate verification status
36827 &`D `& duration of &"no mail in SMTP session"&
36828 &`DKIM`& domain verified in incoming message
36829 &`DN `& distinguished name from peer certificate
36830 &`DS `& DNSSEC secured lookups
36831 &`DT `& on &`=>`& lines: time taken for a delivery
36832 &`F `& sender address (on delivery lines)
36833 &`H `& host name and IP address
36834 &`I `& local interface used
36835 &`id `& message id for incoming message
36836 &`K `& CHUNKING extension used
36837 &`L `& on &`<=`& and &`=>`& lines: PIPELINING extension used
36838 &`M8S `& 8BITMIME status for incoming message
36839 &`P `& on &`<=`& lines: protocol used
36840 &` `& on &`=>`& and &`**`& lines: return path
36841 &`PRDR`& PRDR extension used
36842 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
36843 &`Q `& alternate queue name
36844 &`QT `& on &`=>`& lines: time spent on queue so far
36845 &` `& on &"Completed"& lines: time spent on queue
36846 &`R `& on &`<=`& lines: reference for local bounce
36847 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
36848 &`RT `& on &`<=`& lines: time taken for reception
36849 &`S `& size of message in bytes
36850 &`SNI `& server name indication from TLS client hello
36851 &`ST `& shadow transport name
36852 &`T `& on &`<=`& lines: message subject (topic)
36853 &`TFO `& connection took advantage of TCP Fast Open
36854 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
36855 &`U `& local user or RFC 1413 identity
36856 &`X `& TLS cipher suite
36860 .section "Other log entries" "SECID259"
36861 Various other types of log entry are written from time to time. Most should be
36862 self-explanatory. Among the more common are:
36865 .cindex "retry" "time not reached"
36866 &'retry time not reached'&&~&~An address previously suffered a temporary error
36867 during routing or local delivery, and the time to retry has not yet arrived.
36868 This message is not written to an individual message log file unless it happens
36869 during the first delivery attempt.
36871 &'retry time not reached for any host'&&~&~An address previously suffered
36872 temporary errors during remote delivery, and the retry time has not yet arrived
36873 for any of the hosts to which it is routed.
36875 .cindex "spool directory" "file locked"
36876 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
36877 some other Exim process is already working on the message. This can be quite
36878 common if queue running processes are started at frequent intervals. The
36879 &'exiwhat'& utility script can be used to find out what Exim processes are
36882 .cindex "error" "ignored"
36883 &'error ignored'&&~&~There are several circumstances that give rise to this
36886 Exim failed to deliver a bounce message whose age was greater than
36887 &%ignore_bounce_errors_after%&. The bounce was discarded.
36889 A filter file set up a delivery using the &"noerror"& option, and the delivery
36890 failed. The delivery was discarded.
36892 A delivery set up by a router configured with
36893 . ==== As this is a nested list, any displays it contains must be indented
36894 . ==== as otherwise they are too far to the left.
36898 failed. The delivery was discarded.
36901 .cindex DKIM "log line"
36902 &'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
36903 logging and the message has a DKIM signature header.
36910 .section "Reducing or increasing what is logged" "SECTlogselector"
36911 .cindex "log" "selectors"
36912 By setting the &%log_selector%& global option, you can disable some of Exim's
36913 default logging, or you can request additional logging. The value of
36914 &%log_selector%& is made up of names preceded by plus or minus characters. For
36917 log_selector = +arguments -retry_defer
36919 The list of optional log items is in the following table, with the default
36920 selection marked by asterisks:
36922 &` 8bitmime `& received 8BITMIME status
36923 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
36924 &` address_rewrite `& address rewriting
36925 &` all_parents `& all parents in => lines
36926 &` arguments `& command line arguments
36927 &`*connection_reject `& connection rejections
36928 &`*delay_delivery `& immediate delivery delayed
36929 &` deliver_time `& time taken to perform delivery
36930 &` delivery_size `& add &`S=`&&'nnn'& to => lines
36931 &`*dkim `& DKIM verified domain on <= lines
36932 &` dkim_verbose `& separate full DKIM verification result line, per signature
36933 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
36934 &` dnssec `& DNSSEC secured lookups
36935 &`*etrn `& ETRN commands
36936 &`*host_lookup_failed `& as it says
36937 &` ident_timeout `& timeout for ident connection
36938 &` incoming_interface `& local interface on <= and => lines
36939 &` incoming_port `& remote port on <= lines
36940 &`*lost_incoming_connection `& as it says (includes timeouts)
36941 &` millisec `& millisecond timestamps and RT,QT,DT,D times
36942 &` outgoing_interface `& local interface on => lines
36943 &` outgoing_port `& add remote port to => lines
36944 &`*queue_run `& start and end queue runs
36945 &` queue_time `& time on queue for one recipient
36946 &` queue_time_overall `& time on queue for whole message
36947 &` pid `& Exim process id
36948 &` pipelining `& PIPELINING use, on <= and => lines
36949 &` proxy `& proxy address on <= and => lines
36950 &` receive_time `& time taken to receive message
36951 &` received_recipients `& recipients on <= lines
36952 &` received_sender `& sender on <= lines
36953 &`*rejected_header `& header contents on reject log
36954 &`*retry_defer `& &"retry time not reached"&
36955 &` return_path_on_delivery `& put return path on => and ** lines
36956 &` sender_on_delivery `& add sender to => lines
36957 &`*sender_verify_fail `& sender verification failures
36958 &`*size_reject `& rejection because too big
36959 &`*skip_delivery `& delivery skipped in a queue run
36960 &`*smtp_confirmation `& SMTP confirmation on => lines
36961 &` smtp_connection `& incoming SMTP connections
36962 &` smtp_incomplete_transaction`& incomplete SMTP transactions
36963 &` smtp_mailauth `& AUTH argument to MAIL commands
36964 &` smtp_no_mail `& session with no MAIL commands
36965 &` smtp_protocol_error `& SMTP protocol errors
36966 &` smtp_syntax_error `& SMTP syntax errors
36967 &` subject `& contents of &'Subject:'& on <= lines
36968 &`*tls_certificate_verified `& certificate verification status
36969 &`*tls_cipher `& TLS cipher suite on <= and => lines
36970 &` tls_peerdn `& TLS peer DN on <= and => lines
36971 &` tls_sni `& TLS SNI on <= lines
36972 &` unknown_in_list `& DNS lookup failed in list match
36974 &` all `& all of the above
36976 See also the &%slow_lookup_log%& main configuration option,
36977 section &<<SECID99>>&
36979 More details on each of these items follows:
36983 .cindex "log" "8BITMIME"
36984 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
36985 which may help in tracking down interoperability issues with ancient MTAs
36986 that are not 8bit clean. This is added to the &"<="& line, tagged with
36987 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
36988 &`7BIT`& and &`8BITMIME`& respectively.
36990 .cindex "&%warn%& ACL verb" "log when skipping"
36991 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
36992 its conditions cannot be evaluated, a log line to this effect is written if
36993 this log selector is set.
36995 .cindex "log" "rewriting"
36996 .cindex "rewriting" "logging"
36997 &%address_rewrite%&: This applies both to global rewrites and per-transport
36998 rewrites, but not to rewrites in filters run as an unprivileged user (because
36999 such users cannot access the log).
37001 .cindex "log" "full parentage"
37002 &%all_parents%&: Normally only the original and final addresses are logged on
37003 delivery lines; with this selector, intermediate parents are given in
37004 parentheses between them.
37006 .cindex "log" "Exim arguments"
37007 .cindex "Exim arguments, logging"
37008 &%arguments%&: This causes Exim to write the arguments with which it was called
37009 to the main log, preceded by the current working directory. This is a debugging
37010 feature, added to make it easier to find out how certain MUAs call
37011 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
37012 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
37013 that are empty or that contain white space are quoted. Non-printing characters
37014 are shown as escape sequences. This facility cannot log unrecognized arguments,
37015 because the arguments are checked before the configuration file is read. The
37016 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
37017 between the caller and Exim.
37019 .cindex "log" "connection rejections"
37020 &%connection_reject%&: A log entry is written whenever an incoming SMTP
37021 connection is rejected, for whatever reason.
37023 .cindex "log" "delayed delivery"
37024 .cindex "delayed delivery, logging"
37025 &%delay_delivery%&: A log entry is written whenever a delivery process is not
37026 started for an incoming message because the load is too high or too many
37027 messages were received on one connection. Logging does not occur if no delivery
37028 process is started because &%queue_only%& is set or &%-odq%& was used.
37030 .cindex "log" "delivery duration"
37031 &%deliver_time%&: For each delivery, the amount of real time it has taken to
37032 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
37033 If millisecond logging is enabled, short times will be shown with greater
37034 precision, eg. &`DT=0.304s`&.
37036 .cindex "log" "message size on delivery"
37037 .cindex "size" "of message"
37038 &%delivery_size%&: For each delivery, the size of message delivered is added to
37039 the &"=>"& line, tagged with S=.
37041 .cindex log "DKIM verification"
37042 .cindex DKIM "verification logging"
37043 &%dkim%&: For message acceptance log lines, when an DKIM signature in the header
37044 verifies successfully a tag of DKIM is added, with one of the verified domains.
37046 .cindex log "DKIM verification"
37047 .cindex DKIM "verification logging"
37048 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
37050 .cindex "log" "dnslist defer"
37051 .cindex "DNS list" "logging defer"
37052 .cindex "black list (DNS)"
37053 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
37054 DNS black list suffers a temporary error.
37057 .cindex dnssec logging
37058 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
37059 dns lookups gave secure results a tag of DS is added.
37060 For acceptance this covers the reverse and forward lookups for host name verification.
37061 It does not cover helo-name verification.
37062 For delivery this covers the SRV, MX, A and/or AAAA lookups.
37064 .cindex "log" "ETRN commands"
37065 .cindex "ETRN" "logging"
37066 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
37067 is run to determine whether or not it is actually accepted. An invalid ETRN
37068 command, or one received within a message transaction is not logged by this
37069 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
37071 .cindex "log" "host lookup failure"
37072 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
37073 any addresses, or when a lookup of an IP address fails to find a host name, a
37074 log line is written. This logging does not apply to direct DNS lookups when
37075 routing email addresses, but it does apply to &"byname"& lookups.
37077 .cindex "log" "ident timeout"
37078 .cindex "RFC 1413" "logging timeout"
37079 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
37080 client's ident port times out.
37082 .cindex "log" "incoming interface"
37083 .cindex "log" "local interface"
37084 .cindex "log" "local address and port"
37085 .cindex "TCP/IP" "logging local address and port"
37086 .cindex "interface" "logging"
37087 &%incoming_interface%&: The interface on which a message was received is added
37088 to the &"<="& line as an IP address in square brackets, tagged by I= and
37089 followed by a colon and the port number. The local interface and port are also
37090 added to other SMTP log lines, for example, &"SMTP connection from"&, to
37091 rejection lines, and (despite the name) to outgoing &"=>"& and &"->"& lines.
37092 The latter can be disabled by turning off the &%outgoing_interface%& option.
37094 .cindex log "incoming proxy address"
37095 .cindex proxy "logging proxy address"
37096 .cindex "TCP/IP" "logging proxy address"
37097 &%proxy%&: The internal (closest to the system running Exim) IP address
37098 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
37099 on a proxied connection
37100 or the &"=>"& line for a message delivered on a proxied connection.
37101 See &<<SECTproxyInbound>>& for more information.
37103 .cindex "log" "incoming remote port"
37104 .cindex "port" "logging remote"
37105 .cindex "TCP/IP" "logging incoming remote port"
37106 .vindex "&$sender_fullhost$&"
37107 .vindex "&$sender_rcvhost$&"
37108 &%incoming_port%&: The remote port number from which a message was received is
37109 added to log entries and &'Received:'& header lines, following the IP address
37110 in square brackets, and separated from it by a colon. This is implemented by
37111 changing the value that is put in the &$sender_fullhost$& and
37112 &$sender_rcvhost$& variables. Recording the remote port number has become more
37113 important with the widening use of NAT (see RFC 2505).
37115 .cindex "log" "dropped connection"
37116 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
37117 connection is unexpectedly dropped.
37119 .cindex "log" "millisecond timestamps"
37120 .cindex millisecond logging
37121 .cindex timestamps "millisecond, in logs"
37122 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
37123 appended to the seconds value.
37125 .cindex "log" "outgoing interface"
37126 .cindex "log" "local interface"
37127 .cindex "log" "local address and port"
37128 .cindex "TCP/IP" "logging local address and port"
37129 .cindex "interface" "logging"
37130 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
37131 interface on which a message was sent is added to delivery lines as an I= tag
37132 followed by IP address in square brackets. You can disable this by turning
37133 off the &%outgoing_interface%& option.
37135 .cindex "log" "outgoing remote port"
37136 .cindex "port" "logging outgoing remote"
37137 .cindex "TCP/IP" "logging outgoing remote port"
37138 &%outgoing_port%&: The remote port number is added to delivery log lines (those
37139 containing => tags) following the IP address.
37140 The local port is also added if &%incoming_interface%& and
37141 &%outgoing_interface%& are both enabled.
37142 This option is not included in the default setting, because for most ordinary
37143 configurations, the remote port number is always 25 (the SMTP port), and the
37144 local port is a random ephemeral port.
37146 .cindex "log" "process ids in"
37147 .cindex "pid (process id)" "in log lines"
37148 &%pid%&: The current process id is added to every log line, in square brackets,
37149 immediately after the time and date.
37152 .cindex log pipelining
37153 .cindex pipelining "logging outgoing"
37154 &%pipelining%&: A field is added to delivery and accept
37155 log lines when the ESMTP PIPELINING extension was used.
37156 The field is a single "L".
37158 On accept lines, where PIPELINING was offered but not used by the client,
37159 the field has a minus appended.
37161 .cindex "log" "queue run"
37162 .cindex "queue runner" "logging"
37163 &%queue_run%&: The start and end of every queue run are logged.
37165 .cindex "log" "queue time"
37166 &%queue_time%&: The amount of time the message has been in the queue on the
37167 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
37168 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
37169 includes reception time as well as the delivery time for the current address.
37170 This means that it may be longer than the difference between the arrival and
37171 delivery log line times, because the arrival log line is not written until the
37172 message has been successfully received.
37173 If millisecond logging is enabled, short times will be shown with greater
37174 precision, eg. &`QT=1.578s`&.
37176 &%queue_time_overall%&: The amount of time the message has been in the queue on
37177 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
37178 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
37179 message, so it includes reception time as well as the total delivery time.
37181 .cindex "log" "receive duration"
37182 &%receive_time%&: For each message, the amount of real time it has taken to
37183 perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
37184 If millisecond logging is enabled, short times will be shown with greater
37185 precision, eg. &`RT=0.204s`&.
37187 .cindex "log" "recipients"
37188 &%received_recipients%&: The recipients of a message are listed in the main log
37189 as soon as the message is received. The list appears at the end of the log line
37190 that is written when a message is received, preceded by the word &"for"&. The
37191 addresses are listed after they have been qualified, but before any rewriting
37193 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
37196 .cindex "log" "sender reception"
37197 &%received_sender%&: The unrewritten original sender of a message is added to
37198 the end of the log line that records the message's arrival, after the word
37199 &"from"& (before the recipients if &%received_recipients%& is also set).
37201 .cindex "log" "header lines for rejection"
37202 &%rejected_header%&: If a message's header has been received at the time a
37203 rejection is written to the reject log, the complete header is added to the
37204 log. Header logging can be turned off individually for messages that are
37205 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
37207 .cindex "log" "retry defer"
37208 &%retry_defer%&: A log line is written if a delivery is deferred because a
37209 retry time has not yet been reached. However, this &"retry time not reached"&
37210 message is always omitted from individual message logs after the first delivery
37213 .cindex "log" "return path"
37214 &%return_path_on_delivery%&: The return path that is being transmitted with
37215 the message is included in delivery and bounce lines, using the tag P=.
37216 This is omitted if no delivery actually happens, for example, if routing fails,
37217 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
37219 .cindex "log" "sender on delivery"
37220 &%sender_on_delivery%&: The message's sender address is added to every delivery
37221 and bounce line, tagged by F= (for &"from"&).
37222 This is the original sender that was received with the message; it is not
37223 necessarily the same as the outgoing return path.
37225 .cindex "log" "sender verify failure"
37226 &%sender_verify_fail%&: If this selector is unset, the separate log line that
37227 gives details of a sender verification failure is not written. Log lines for
37228 the rejection of SMTP commands contain just &"sender verify failed"&, so some
37231 .cindex "log" "size rejection"
37232 &%size_reject%&: A log line is written whenever a message is rejected because
37235 .cindex "log" "frozen messages; skipped"
37236 .cindex "frozen messages" "logging skipping"
37237 &%skip_delivery%&: A log line is written whenever a message is skipped during a
37238 queue run because it is frozen or because another process is already delivering
37240 .cindex "&""spool file is locked""&"
37241 The message that is written is &"spool file is locked"&.
37243 .cindex "log" "smtp confirmation"
37244 .cindex "SMTP" "logging confirmation"
37245 .cindex "LMTP" "logging confirmation"
37246 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
37247 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
37248 A number of MTAs (including Exim) return an identifying string in this
37251 .cindex "log" "SMTP connections"
37252 .cindex "SMTP" "logging connections"
37253 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
37254 established or closed, unless the connection is from a host that matches
37255 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
37256 only when the closure is unexpected.) This applies to connections from local
37257 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
37258 dropped in the middle of a message, a log line is always written, whether or
37259 not this selector is set, but otherwise nothing is written at the start and end
37260 of connections unless this selector is enabled.
37262 For TCP/IP connections to an Exim daemon, the current number of connections is
37263 included in the log message for each new connection, but note that the count is
37264 reset if the daemon is restarted.
37265 Also, because connections are closed (and the closure is logged) in
37266 subprocesses, the count may not include connections that have been closed but
37267 whose termination the daemon has not yet noticed. Thus, while it is possible to
37268 match up the opening and closing of connections in the log, the value of the
37269 logged counts may not be entirely accurate.
37271 .cindex "log" "SMTP transaction; incomplete"
37272 .cindex "SMTP" "logging incomplete transactions"
37273 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
37274 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
37275 and the message sender plus any accepted recipients are included in the log
37276 line. This can provide evidence of dictionary attacks.
37278 .cindex "log" "non-MAIL SMTP sessions"
37279 .cindex "MAIL" "logging session without"
37280 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
37281 connection terminates without having issued a MAIL command. This includes both
37282 the case when the connection is dropped, and the case when QUIT is used. It
37283 does not include cases where the connection is rejected right at the start (by
37284 an ACL, or because there are too many connections, or whatever). These cases
37285 already have their own log lines.
37287 The log line that is written contains the identity of the client in the usual
37288 way, followed by D= and a time, which records the duration of the connection.
37289 If the connection was authenticated, this fact is logged exactly as it is for
37290 an incoming message, with an A= item. If the connection was encrypted, CV=,
37291 DN=, and X= items may appear as they do for an incoming message, controlled by
37292 the same logging options.
37294 Finally, if any SMTP commands were issued during the connection, a C= item
37295 is added to the line, listing the commands that were used. For example,
37299 shows that the client issued QUIT straight after EHLO. If there were fewer
37300 than 20 commands, they are all listed. If there were more than 20 commands,
37301 the last 20 are listed, preceded by &"..."&. However, with the default
37302 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
37303 have been aborted before 20 non-mail commands are processed.
37305 &%smtp_mailauth%&: A third subfield with the authenticated sender,
37306 colon-separated, is appended to the A= item for a message arrival or delivery
37307 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
37308 was accepted or used.
37310 .cindex "log" "SMTP protocol error"
37311 .cindex "SMTP" "logging protocol error"
37312 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
37313 encountered. Exim does not have perfect detection of all protocol errors
37314 because of transmission delays and the use of pipelining. If PIPELINING has
37315 been advertised to a client, an Exim server assumes that the client will use
37316 it, and therefore it does not count &"expected"& errors (for example, RCPT
37317 received after rejecting MAIL) as protocol errors.
37319 .cindex "SMTP" "logging syntax errors"
37320 .cindex "SMTP" "syntax errors; logging"
37321 .cindex "SMTP" "unknown command; logging"
37322 .cindex "log" "unknown SMTP command"
37323 .cindex "log" "SMTP syntax error"
37324 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
37325 encountered. An unrecognized command is treated as a syntax error. For an
37326 external connection, the host identity is given; for an internal connection
37327 using &%-bs%& the sender identification (normally the calling user) is given.
37329 .cindex "log" "subject"
37330 .cindex "subject, logging"
37331 &%subject%&: The subject of the message is added to the arrival log line,
37332 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
37333 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
37334 specifies whether characters with values greater than 127 should be logged
37335 unchanged, or whether they should be rendered as escape sequences.
37337 .cindex "log" "certificate verification"
37339 .cindex DANE logging
37340 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
37341 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
37343 using a CA trust anchor,
37344 &`CA=dane`& if using a DNS trust anchor,
37345 and &`CV=no`& if not.
37347 .cindex "log" "TLS cipher"
37348 .cindex "TLS" "logging cipher"
37349 &%tls_cipher%&: When a message is sent or received over an encrypted
37350 connection, the cipher suite used is added to the log line, preceded by X=.
37352 .cindex "log" "TLS peer DN"
37353 .cindex "TLS" "logging peer DN"
37354 &%tls_peerdn%&: When a message is sent or received over an encrypted
37355 connection, and a certificate is supplied by the remote host, the peer DN is
37356 added to the log line, preceded by DN=.
37358 .cindex "log" "TLS SNI"
37359 .cindex "TLS" "logging SNI"
37360 &%tls_sni%&: When a message is received over an encrypted connection, and
37361 the remote host provided the Server Name Indication extension, the SNI is
37362 added to the log line, preceded by SNI=.
37364 .cindex "log" "DNS failure in list"
37365 &%unknown_in_list%&: This setting causes a log entry to be written when the
37366 result of a list match is failure because a DNS lookup failed.
37370 .section "Message log" "SECID260"
37371 .cindex "message" "log file for"
37372 .cindex "log" "message log; description of"
37373 .cindex "&_msglog_& directory"
37374 .oindex "&%preserve_message_logs%&"
37375 In addition to the general log files, Exim writes a log file for each message
37376 that it handles. The names of these per-message logs are the message ids, and
37377 they are kept in the &_msglog_& sub-directory of the spool directory. Each
37378 message log contains copies of the log lines that apply to the message. This
37379 makes it easier to inspect the status of an individual message without having
37380 to search the main log. A message log is deleted when processing of the message
37381 is complete, unless &%preserve_message_logs%& is set, but this should be used
37382 only with great care because they can fill up your disk very quickly.
37384 On a heavily loaded system, it may be desirable to disable the use of
37385 per-message logs, in order to reduce disk I/O. This can be done by setting the
37386 &%message_logs%& option false.
37392 . ////////////////////////////////////////////////////////////////////////////
37393 . ////////////////////////////////////////////////////////////////////////////
37395 .chapter "Exim utilities" "CHAPutils"
37396 .scindex IIDutils "utilities"
37397 A number of utility scripts and programs are supplied with Exim and are
37398 described in this chapter. There is also the Exim Monitor, which is covered in
37399 the next chapter. The utilities described here are:
37401 .itable none 0 0 3 7* left 15* left 40* left
37402 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
37403 "list what Exim processes are doing"
37404 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
37405 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
37406 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
37407 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
37409 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
37410 .irow &<<SECTmailstat>>& &'eximstats'& &&&
37411 "extract statistics from the log"
37412 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
37413 "check address acceptance from given IP"
37414 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
37415 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
37416 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
37417 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
37418 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
37419 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
37422 Another utility that might be of use to sites with many MTAs is Tom Kistner's
37423 &'exilog'&. It provides log visualizations across multiple Exim servers. See
37424 &url(https://duncanthrax.net/exilog/) for details.
37429 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
37430 .cindex "&'exiwhat'&"
37431 .cindex "process, querying"
37433 On operating systems that can restart a system call after receiving a signal
37434 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
37435 a line describing what it is doing to the file &_exim-process.info_& in the
37436 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
37437 processes it can find, having first emptied the file. It then waits for one
37438 second to allow the Exim processes to react before displaying the results. In
37439 order to run &'exiwhat'& successfully you have to have sufficient privilege to
37440 send the signal to the Exim processes, so it is normally run as root.
37442 &*Warning*&: This is not an efficient process. It is intended for occasional
37443 use by system administrators. It is not sensible, for example, to set up a
37444 script that sends SIGUSR1 signals to Exim processes at short intervals.
37447 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
37448 varies in different operating systems. Not only are different options used,
37449 but the format of the output is different. For this reason, there are some
37450 system configuration options that configure exactly how &'exiwhat'& works. If
37451 it doesn't seem to be working for you, check the following compile-time
37454 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
37455 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
37456 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
37457 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
37459 An example of typical output from &'exiwhat'& is
37461 164 daemon: -q1h, listening on port 25
37462 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
37463 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
37464 [10.19.42.42] (editor@ref.example)
37465 10592 handling incoming call from [192.168.243.242]
37466 10628 accepting a local non-SMTP message
37468 The first number in the output line is the process number. The third line has
37469 been split here, in order to fit it on the page.
37473 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
37474 .cindex "&'exiqgrep'&"
37475 .cindex "queue" "grepping"
37476 This utility is a Perl script contributed by Matt Hubbard. It runs
37480 or (in case &*-a*& switch is specified)
37484 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
37485 contain alternate exim configuration the queue management might be using.
37487 to obtain a queue listing, and then greps the output to select messages
37488 that match given criteria. The following selection options are available:
37491 .vitem &*-f*&&~<&'regex'&>
37492 Match the sender address using a case-insensitive search. The field that is
37493 tested is enclosed in angle brackets, so you can test for bounce messages with
37497 .vitem &*-r*&&~<&'regex'&>
37498 Match a recipient address using a case-insensitive search. The field that is
37499 tested is not enclosed in angle brackets.
37501 .vitem &*-s*&&~<&'regex'&>
37502 Match against the size field.
37504 .vitem &*-y*&&~<&'seconds'&>
37505 Match messages that are younger than the given time.
37507 .vitem &*-o*&&~<&'seconds'&>
37508 Match messages that are older than the given time.
37511 Match only frozen messages.
37514 Match only non-frozen messages.
37517 The following options control the format of the output:
37521 Display only the count of matching messages.
37524 Long format &-- display the full message information as output by Exim. This is
37528 Display message ids only.
37531 Brief format &-- one line per message.
37534 Display messages in reverse order.
37537 Include delivered recipients in queue listing.
37540 There is one more option, &%-h%&, which outputs a list of options.
37544 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
37545 .cindex "&'exiqsumm'&"
37546 .cindex "queue" "summary"
37547 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
37548 -bp`& and produces a summary of the messages in the queue. Thus, you use it by
37549 running a command such as
37551 exim -bp | exiqsumm
37553 The output consists of one line for each domain that has messages waiting for
37554 it, as in the following example:
37556 3 2322 74m 66m msn.com.example
37558 Each line lists the number of pending deliveries for a domain, their total
37559 volume, and the length of time that the oldest and the newest messages have
37560 been waiting. Note that the number of pending deliveries is greater than the
37561 number of messages when messages have more than one recipient.
37563 A summary line is output at the end. By default the output is sorted on the
37564 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
37565 the output to be sorted by oldest message and by count of messages,
37566 respectively. There are also three options that split the messages for each
37567 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
37568 separates frozen messages, and &%-s%& separates messages according to their
37571 The output of &'exim -bp'& contains the original addresses in the message, so
37572 this also applies to the output from &'exiqsumm'&. No domains from addresses
37573 generated by aliasing or forwarding are included (unless the &%one_time%&
37574 option of the &(redirect)& router has been used to convert them into &"top
37575 level"& addresses).
37580 .section "Extracting specific information from the log (exigrep)" &&&
37582 .cindex "&'exigrep'&"
37583 .cindex "log" "extracts; grepping for"
37584 The &'exigrep'& utility is a Perl script that searches one or more main log
37585 files for entries that match a given pattern. When it finds a match, it
37586 extracts all the log entries for the relevant message, not just those that
37587 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
37588 given message, or all mail for a given user, or for a given host, for example.
37589 The input files can be in Exim log format or syslog format.
37590 If a matching log line is not associated with a specific message, it is
37591 included in &'exigrep'&'s output without any additional lines. The usage is:
37593 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
37595 If no log filenames are given on the command line, the standard input is read.
37597 The &%-t%& argument specifies a number of seconds. It adds an additional
37598 condition for message selection. Messages that are complete are shown only if
37599 they spent more than <&'n'&> seconds in the queue.
37601 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
37602 makes it case-sensitive. This may give a performance improvement when searching
37603 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
37604 option; with &%-I%& they do not. In both cases it is possible to change the
37605 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
37607 The &%-l%& option means &"literal"&, that is, treat all characters in the
37608 pattern as standing for themselves. Otherwise the pattern must be a Perl
37609 regular expression.
37611 The &%-v%& option inverts the matching condition. That is, a line is selected
37612 if it does &'not'& match the pattern.
37614 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
37615 that are generated as a result/response to a message that &'exigrep'& matched
37619 user_a sends a message to user_b, which generates a bounce back to user_b. If
37620 &'exigrep'& is used to search for &"user_a"&, only the first message will be
37621 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
37622 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
37623 when searching for &"user_a"& will show both messages since the bounce is
37624 &"related"& to or a &"result"& of the first message that was found by the
37627 If the location of a &'zcat'& command is known from the definition of
37628 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
37629 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
37630 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
37631 autodetection of some well known compression extensions.
37634 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
37635 .cindex "&'exipick'&"
37636 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
37637 lists messages from the queue according to a variety of criteria. For details
37638 of &'exipick'&'s facilities, run &'exipick'& with
37639 the &%--help%& option.
37642 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
37643 .cindex "log" "cycling local files"
37644 .cindex "cycling logs"
37645 .cindex "&'exicyclog'&"
37646 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
37647 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
37648 you are using log files with datestamps in their names (see section
37649 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
37650 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
37651 There are two command line options for &'exicyclog'&:
37653 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
37654 default that is set when Exim is built. The default default is 10.
37656 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
37657 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
37658 overriding the script's default, which is to find the setting from Exim's
37662 Each time &'exicyclog'& is run the filenames get &"shuffled down"& by one. If
37663 the main log filename is &_mainlog_& (the default) then when &'exicyclog'& is
37664 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
37665 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
37666 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
37667 logs are handled similarly.
37669 If the limit is greater than 99, the script uses 3-digit numbers such as
37670 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
37671 to one that is greater, or &'vice versa'&, you will have to fix the names of
37672 any existing log files.
37674 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
37675 the end are deleted. All files with numbers greater than 01 are compressed,
37676 using a compression command which is configured by the COMPRESS_COMMAND
37677 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
37678 root &%crontab%& entry of the form
37680 1 0 * * * su exim -c /usr/exim/bin/exicyclog
37682 assuming you have used the name &"exim"& for the Exim user. You can run
37683 &'exicyclog'& as root if you wish, but there is no need.
37687 .section "Mail statistics (eximstats)" "SECTmailstat"
37688 .cindex "statistics"
37689 .cindex "&'eximstats'&"
37690 A Perl script called &'eximstats'& is provided for extracting statistical
37691 information from log files. The output is either plain text, or HTML.
37692 . --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan
37693 . --- 404 error and everything else points to that.
37695 The &'eximstats'& script has been hacked about quite a bit over time. The
37696 latest version is the result of some extensive revision by Steve Campbell. A
37697 lot of information is given by default, but there are options for suppressing
37698 various parts of it. Following any options, the arguments to the script are a
37699 list of files, which should be main log files. For example:
37701 eximstats -nr /var/spool/exim/log/mainlog.01
37703 By default, &'eximstats'& extracts information about the number and volume of
37704 messages received from or delivered to various hosts. The information is sorted
37705 both by message count and by volume, and the top fifty hosts in each category
37706 are listed on the standard output. Similar information, based on email
37707 addresses or domains instead of hosts can be requested by means of various
37708 options. For messages delivered and received locally, similar statistics are
37709 also produced per user.
37711 The output also includes total counts and statistics about delivery errors, and
37712 histograms showing the number of messages received and deliveries made in each
37713 hour of the day. A delivery with more than one address in its envelope (for
37714 example, an SMTP transaction with more than one RCPT command) is counted
37715 as a single delivery by &'eximstats'&.
37717 Though normally more deliveries than receipts are reported (as messages may
37718 have multiple recipients), it is possible for &'eximstats'& to report more
37719 messages received than delivered, even though the queue is empty at the start
37720 and end of the period in question. If an incoming message contains no valid
37721 recipients, no deliveries are recorded for it. A bounce message is handled as
37722 an entirely separate message.
37724 &'eximstats'& always outputs a grand total summary giving the volume and number
37725 of messages received and deliveries made, and the number of hosts involved in
37726 each case. It also outputs the number of messages that were delayed (that is,
37727 not completely delivered at the first attempt), and the number that had at
37728 least one address that failed.
37730 The remainder of the output is in sections that can be independently disabled
37731 or modified by various options. It consists of a summary of deliveries by
37732 transport, histograms of messages received and delivered per time interval
37733 (default per hour), information about the time messages spent in the queue,
37734 a list of relayed messages, lists of the top fifty sending hosts, local
37735 senders, destination hosts, and destination local users by count and by volume,
37736 and a list of delivery errors that occurred.
37738 The relay information lists messages that were actually relayed, that is, they
37739 came from a remote host and were directly delivered to some other remote host,
37740 without being processed (for example, for aliasing or forwarding) locally.
37742 There are quite a few options for &'eximstats'& to control exactly what it
37743 outputs. These are documented in the Perl script itself, and can be extracted
37744 by running the command &(perldoc)& on the script. For example:
37746 perldoc /usr/exim/bin/eximstats
37749 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
37750 .cindex "&'exim_checkaccess'&"
37751 .cindex "policy control" "checking access"
37752 .cindex "checking access"
37753 The &%-bh%& command line argument allows you to run a fake SMTP session with
37754 debugging output, in order to check what Exim is doing when it is applying
37755 policy controls to incoming SMTP mail. However, not everybody is sufficiently
37756 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
37757 sometimes you just want to answer the question &"Does this address have
37758 access?"& without bothering with any further details.
37760 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
37761 two arguments, an IP address and an email address:
37763 exim_checkaccess 10.9.8.7 A.User@a.domain.example
37765 The utility runs a call to Exim with the &%-bh%& option, to test whether the
37766 given email address would be accepted in a RCPT command in a TCP/IP
37767 connection from the host with the given IP address. The output of the utility
37768 is either the word &"accepted"&, or the SMTP error response, for example:
37771 550 Relay not permitted
37773 When running this test, the utility uses &`<>`& as the envelope sender address
37774 for the MAIL command, but you can change this by providing additional
37775 options. These are passed directly to the Exim command. For example, to specify
37776 that the test is to be run with the sender address &'himself@there.example'&
37779 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
37780 -f himself@there.example
37782 Note that these additional Exim command line items must be given after the two
37783 mandatory arguments.
37785 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
37786 while running its checks. You can run checks that include callouts by using
37787 &%-bhc%&, but this is not yet available in a &"packaged"& form.
37791 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
37792 .cindex "DBM" "building dbm files"
37793 .cindex "building DBM files"
37794 .cindex "&'exim_dbmbuild'&"
37795 .cindex "lower casing"
37796 .cindex "binary zero" "in lookup key"
37797 The &'exim_dbmbuild'& program reads an input file containing keys and data in
37798 the format used by the &(lsearch)& lookup (see section
37799 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
37800 names as keys and the remainder of the information as data. The lower-casing
37801 can be prevented by calling the program with the &%-nolc%& option.
37803 A terminating zero is included as part of the key string. This is expected by
37804 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
37805 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
37806 strings or the data strings. The &(dbmnz)& lookup type can be used with such
37809 The program requires two arguments: the name of the input file (which can be a
37810 single hyphen to indicate the standard input), and the name of the output file.
37811 It creates the output under a temporary name, and then renames it if all went
37815 If the native DB interface is in use (USE_DB is set in a compile-time
37816 configuration file &-- this is common in free versions of Unix) the two
37817 filenames must be different, because in this mode the Berkeley DB functions
37818 create a single output file using exactly the name given. For example,
37820 exim_dbmbuild /etc/aliases /etc/aliases.db
37822 reads the system alias file and creates a DBM version of it in
37823 &_/etc/aliases.db_&.
37825 In systems that use the &'ndbm'& routines (mostly proprietary versions of
37826 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
37827 environment, the suffixes are added to the second argument of
37828 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
37829 when the Berkeley functions are used in compatibility mode (though this is not
37830 recommended), because in that case it adds a &_.db_& suffix to the filename.
37832 If a duplicate key is encountered, the program outputs a warning, and when it
37833 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
37834 option is used. By default, only the first of a set of duplicates is used &--
37835 this makes it compatible with &(lsearch)& lookups. There is an option
37836 &%-lastdup%& which causes it to use the data for the last duplicate instead.
37837 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
37838 &%stderr%&. For other errors, where it doesn't actually make a new file, the
37844 .section "Finding individual retry times (exinext)" "SECTfinindret"
37845 .cindex "retry" "times"
37846 .cindex "&'exinext'&"
37847 A utility called &'exinext'& (mostly a Perl script) provides the ability to
37848 fish specific information out of the retry database. Given a mail domain (or a
37849 complete address), it looks up the hosts for that domain, and outputs any retry
37850 information for the hosts or for the domain. At present, the retry information
37851 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
37852 output. For example:
37854 $ exinext piglet@milne.fict.example
37855 kanga.milne.example:192.168.8.1 error 146: Connection refused
37856 first failed: 21-Feb-1996 14:57:34
37857 last tried: 21-Feb-1996 14:57:34
37858 next try at: 21-Feb-1996 15:02:34
37859 roo.milne.example:192.168.8.3 error 146: Connection refused
37860 first failed: 20-Jan-1996 13:12:08
37861 last tried: 21-Feb-1996 11:42:03
37862 next try at: 21-Feb-1996 19:42:03
37863 past final cutoff time
37865 You can also give &'exinext'& a local part, without a domain, and it
37866 will give any retry information for that local part in your default domain.
37867 A message id can be used to obtain retry information pertaining to a specific
37868 message. This exists only when an attempt to deliver a message to a remote host
37869 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
37870 &'exinext'& is not particularly efficient, but then it is not expected to be
37873 The &'exinext'& utility calls Exim to find out information such as the location
37874 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
37875 passed on to the &'exim'& commands. The first specifies an alternate Exim
37876 configuration file, and the second sets macros for use within the configuration
37877 file. These features are mainly to help in testing, but might also be useful in
37878 environments where more than one configuration file is in use.
37882 .section "Hints database maintenance" "SECThindatmai"
37883 .cindex "hints database" "maintenance"
37884 .cindex "maintaining Exim's hints database"
37885 Three utility programs are provided for maintaining the DBM files that Exim
37886 uses to contain its delivery hint information. Each program requires two
37887 arguments. The first specifies the name of Exim's spool directory, and the
37888 second is the name of the database it is to operate on. These are as follows:
37891 &'retry'&: the database of retry information
37893 &'wait-'&<&'transport name'&>: databases of information about messages waiting
37896 &'callout'&: the callout cache
37898 &'ratelimit'&: the data for implementing the ratelimit ACL condition
37900 &'misc'&: other hints data
37903 The &'misc'& database is used for
37906 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
37908 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
37909 &(smtp)& transport)
37911 Limiting the concurrency of specific transports (when &%max_parallel%& is set
37917 .section "exim_dumpdb" "SECID261"
37918 .cindex "&'exim_dumpdb'&"
37919 The entire contents of a database are written to the standard output by the
37920 &'exim_dumpdb'& program, which has no options or arguments other than the
37921 spool and database names. For example, to dump the retry database:
37923 exim_dumpdb /var/spool/exim retry
37925 Two lines of output are produced for each entry:
37927 T:mail.ref.example:192.168.242.242 146 77 Connection refused
37928 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
37930 The first item on the first line is the key of the record. It starts with one
37931 of the letters R, or T, depending on whether it refers to a routing or
37932 transport retry. For a local delivery, the next part is the local address; for
37933 a remote delivery it is the name of the remote host, followed by its failing IP
37934 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
37935 transport). If the remote port is not the standard one (port 25), it is added
37936 to the IP address. Then there follows an error code, an additional error code,
37937 and a textual description of the error.
37939 The three times on the second line are the time of first failure, the time of
37940 the last delivery attempt, and the computed time for the next attempt. The line
37941 ends with an asterisk if the cutoff time for the last retry rule has been
37944 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
37945 consists of a host name followed by a list of ids for messages that are or were
37946 waiting to be delivered to that host. If there are a very large number for any
37947 one host, continuation records, with a sequence number added to the host name,
37948 may be seen. The data in these records is often out of date, because a message
37949 may be routed to several alternative hosts, and Exim makes no effort to keep
37954 .section "exim_tidydb" "SECID262"
37955 .cindex "&'exim_tidydb'&"
37956 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
37957 database. If run with no options, it removes all records that are more than 30
37958 days old. The age is calculated from the date and time that the record was last
37959 updated. Note that, in the case of the retry database, it is &'not'& the time
37960 since the first delivery failure. Information about a host that has been down
37961 for more than 30 days will remain in the database, provided that the record is
37962 updated sufficiently often.
37964 The cutoff date can be altered by means of the &%-t%& option, which must be
37965 followed by a time. For example, to remove all records older than a week from
37966 the retry database:
37968 exim_tidydb -t 7d /var/spool/exim retry
37970 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
37971 message ids. In the former these appear as data in records keyed by host &--
37972 they were messages that were waiting for that host &-- and in the latter they
37973 are the keys for retry information for messages that have suffered certain
37974 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
37975 message ids in database records are those of messages that are still on the
37976 queue. Message ids for messages that no longer exist are removed from
37977 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
37978 For the &'retry'& database, records whose keys are non-existent message ids are
37979 removed. The &'exim_tidydb'& utility outputs comments on the standard output
37980 whenever it removes information from the database.
37982 Certain records are automatically removed by Exim when they are no longer
37983 needed, but others are not. For example, if all the MX hosts for a domain are
37984 down, a retry record is created for each one. If the primary MX host comes back
37985 first, its record is removed when Exim successfully delivers to it, but the
37986 records for the others remain because Exim has not tried to use those hosts.
37988 It is important, therefore, to run &'exim_tidydb'& periodically on all the
37989 hints databases. You should do this at a quiet time of day, because it requires
37990 a database to be locked (and therefore inaccessible to Exim) while it does its
37991 work. Removing records from a DBM file does not normally make the file smaller,
37992 but all the common DBM libraries are able to re-use the space that is released.
37993 After an initial phase of increasing in size, the databases normally reach a
37994 point at which they no longer get any bigger, as long as they are regularly
37997 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
37998 databases is likely to keep on increasing.
38003 .section "exim_fixdb" "SECID263"
38004 .cindex "&'exim_fixdb'&"
38005 The &'exim_fixdb'& program is a utility for interactively modifying databases.
38006 Its main use is for testing Exim, but it might also be occasionally useful for
38007 getting round problems in a live system. It has no options, and its interface
38008 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
38009 key of a database record can then be entered, and the data for that record is
38012 If &"d"& is typed at the next prompt, the entire record is deleted. For all
38013 except the &'retry'& database, that is the only operation that can be carried
38014 out. For the &'retry'& database, each field is output preceded by a number, and
38015 data for individual fields can be changed by typing the field number followed
38016 by new data, for example:
38020 resets the time of the next delivery attempt. Time values are given as a
38021 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
38022 used as optional separators.
38027 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
38028 .cindex "mailbox" "maintenance"
38029 .cindex "&'exim_lock'&"
38030 .cindex "locking mailboxes"
38031 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
38032 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
38033 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
38034 a user agent while investigating a problem. The utility requires the name of
38035 the file as its first argument. If the locking is successful, the second
38036 argument is run as a command (using C's &[system()]& function); if there is no
38037 second argument, the value of the SHELL environment variable is used; if this
38038 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
38039 is unlocked and the utility ends. The following options are available:
38043 Use &[fcntl()]& locking on the open mailbox.
38046 Use &[flock()]& locking on the open mailbox, provided the operating system
38049 .vitem &%-interval%&
38050 This must be followed by a number, which is a number of seconds; it sets the
38051 interval to sleep between retries (default 3).
38053 .vitem &%-lockfile%&
38054 Create a lock file before opening the mailbox.
38057 Lock the mailbox using MBX rules.
38060 Suppress verification output.
38062 .vitem &%-retries%&
38063 This must be followed by a number; it sets the number of times to try to get
38064 the lock (default 10).
38066 .vitem &%-restore_time%&
38067 This option causes &%exim_lock%& to restore the modified and read times to the
38068 locked file before exiting. This allows you to access a locked mailbox (for
38069 example, to take a backup copy) without disturbing the times that the user
38072 .vitem &%-timeout%&
38073 This must be followed by a number, which is a number of seconds; it sets a
38074 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
38075 default), a non-blocking call is used.
38078 Generate verbose output.
38081 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
38082 default is to create a lock file and also to use &[fcntl()]& locking on the
38083 mailbox, which is the same as Exim's default. The use of &%-flock%& or
38084 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
38085 requires that the directory containing the file be writeable. Locking by lock
38086 file does not last forever; Exim assumes that a lock file is expired if it is
38087 more than 30 minutes old.
38089 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
38090 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
38091 to be taken out on the open mailbox, and an exclusive lock on the file
38092 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
38093 number of the mailbox file. When the locking is released, if an exclusive lock
38094 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
38096 The default output contains verification of the locking that takes place. The
38097 &%-v%& option causes some additional information to be given. The &%-q%& option
38098 suppresses all output except error messages.
38102 exim_lock /var/spool/mail/spqr
38104 runs an interactive shell while the file is locked, whereas
38106 &`exim_lock -q /var/spool/mail/spqr <<End`&
38107 <&'some commands'&>
38110 runs a specific non-interactive sequence of commands while the file is locked,
38111 suppressing all verification output. A single command can be run by a command
38114 exim_lock -q /var/spool/mail/spqr \
38115 "cp /var/spool/mail/spqr /some/where"
38117 Note that if a command is supplied, it must be entirely contained within the
38118 second argument &-- hence the quotes.
38122 . ////////////////////////////////////////////////////////////////////////////
38123 . ////////////////////////////////////////////////////////////////////////////
38125 .chapter "The Exim monitor" "CHAPeximon"
38126 .scindex IIDeximon "Exim monitor" "description"
38127 .cindex "X-windows"
38128 .cindex "&'eximon'&"
38129 .cindex "Local/eximon.conf"
38130 .cindex "&_exim_monitor/EDITME_&"
38131 The Exim monitor is an application which displays in an X window information
38132 about the state of Exim's queue and what Exim is doing. An admin user can
38133 perform certain operations on messages from this GUI interface; however all
38134 such facilities are also available from the command line, and indeed, the
38135 monitor itself makes use of the command line to perform any actions requested.
38139 .section "Running the monitor" "SECID264"
38140 The monitor is started by running the script called &'eximon'&. This is a shell
38141 script that sets up a number of environment variables, and then runs the
38142 binary called &_eximon.bin_&. The default appearance of the monitor window can
38143 be changed by editing the &_Local/eximon.conf_& file created by editing
38144 &_exim_monitor/EDITME_&. Comments in that file describe what the various
38145 parameters are for.
38147 The parameters that get built into the &'eximon'& script can be overridden for
38148 a particular invocation by setting up environment variables of the same names,
38149 preceded by &`EXIMON_`&. For example, a shell command such as
38151 EXIMON_LOG_DEPTH=400 eximon
38153 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
38154 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
38155 overrides the Exim log file configuration. This makes it possible to have
38156 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
38157 syslog messages are routed to a file on the local host.
38159 X resources can be used to change the appearance of the window in the normal
38160 way. For example, a resource setting of the form
38162 Eximon*background: gray94
38164 changes the colour of the background to light grey rather than white. The
38165 stripcharts are drawn with both the data lines and the reference lines in
38166 black. This means that the reference lines are not visible when on top of the
38167 data. However, their colour can be changed by setting a resource called
38168 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
38169 For example, if your X server is running Unix, you could set up lighter
38170 reference lines in the stripcharts by obeying
38173 Eximon*highlight: gray
38176 .cindex "admin user"
38177 In order to see the contents of messages in the queue, and to operate on them,
38178 &'eximon'& must either be run as root or by an admin user.
38180 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
38181 contain X11 resource parameters interpreted by the X11 library. In addition,
38182 if the first parameter starts with the string "gdb" then it is removed and the
38183 binary is invoked under gdb (the parameter is used as the gdb command-name, so
38184 versioned variants of gdb can be invoked).
38186 The monitor's window is divided into three parts. The first contains one or
38187 more stripcharts and two action buttons, the second contains a &"tail"& of the
38188 main log file, and the third is a display of the queue of messages awaiting
38189 delivery, with two more action buttons. The following sections describe these
38190 different parts of the display.
38195 .section "The stripcharts" "SECID265"
38196 .cindex "stripchart"
38197 The first stripchart is always a count of messages in the queue. Its name can
38198 be configured by setting QUEUE_STRIPCHART_NAME in the
38199 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
38200 configuration script by regular expression matches on log file entries, making
38201 it possible to display, for example, counts of messages delivered to certain
38202 hosts or using certain transports. The supplied defaults display counts of
38203 received and delivered messages, and of local and SMTP deliveries. The default
38204 period between stripchart updates is one minute; this can be adjusted by a
38205 parameter in the &_Local/eximon.conf_& file.
38207 The stripchart displays rescale themselves automatically as the value they are
38208 displaying changes. There are always 10 horizontal lines in each chart; the
38209 title string indicates the value of each division when it is greater than one.
38210 For example, &"x2"& means that each division represents a value of 2.
38212 It is also possible to have a stripchart which shows the percentage fullness of
38213 a particular disk partition, which is useful when local deliveries are confined
38214 to a single partition.
38216 .cindex "&%statvfs%& function"
38217 This relies on the availability of the &[statvfs()]& function or equivalent in
38218 the operating system. Most, but not all versions of Unix that support Exim have
38219 this. For this particular stripchart, the top of the chart always represents
38220 100%, and the scale is given as &"x10%"&. This chart is configured by setting
38221 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
38222 &_Local/eximon.conf_& file.
38227 .section "Main action buttons" "SECID266"
38228 .cindex "size" "of monitor window"
38229 .cindex "Exim monitor" "window size"
38230 .cindex "window size"
38231 Below the stripcharts there is an action button for quitting the monitor. Next
38232 to this is another button marked &"Size"&. They are placed here so that
38233 shrinking the window to its default minimum size leaves just the queue count
38234 stripchart and these two buttons visible. Pressing the &"Size"& button causes
38235 the window to expand to its maximum size, unless it is already at the maximum,
38236 in which case it is reduced to its minimum.
38238 When expanding to the maximum, if the window cannot be fully seen where it
38239 currently is, it is moved back to where it was the last time it was at full
38240 size. When it is expanding from its minimum size, the old position is
38241 remembered, and next time it is reduced to the minimum it is moved back there.
38243 The idea is that you can keep a reduced window just showing one or two
38244 stripcharts at a convenient place on your screen, easily expand it to show
38245 the full window when required, and just as easily put it back to what it was.
38246 The idea is copied from what the &'twm'& window manager does for its
38247 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
38248 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
38250 Normally, the monitor starts up with the window at its full size, but it can be
38251 built so that it starts up with the window at its smallest size, by setting
38252 START_SMALL=yes in &_Local/eximon.conf_&.
38256 .section "The log display" "SECID267"
38257 .cindex "log" "tail of; in monitor"
38258 The second section of the window is an area in which a display of the tail of
38259 the main log is maintained.
38260 To save space on the screen, the timestamp on each log line is shortened by
38261 removing the date and, if &%log_timezone%& is set, the timezone.
38262 The log tail is not available when the only destination for logging data is
38263 syslog, unless the syslog lines are routed to a local file whose name is passed
38264 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
38266 The log sub-window has a scroll bar at its lefthand side which can be used to
38267 move back to look at earlier text, and the up and down arrow keys also have a
38268 scrolling effect. The amount of log that is kept depends on the setting of
38269 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
38270 to use. When this is full, the earlier 50% of data is discarded &-- this is
38271 much more efficient than throwing it away line by line. The sub-window also has
38272 a horizontal scroll bar for accessing the ends of long log lines. This is the
38273 only means of horizontal scrolling; the right and left arrow keys are not
38274 available. Text can be cut from this part of the window using the mouse in the
38275 normal way. The size of this subwindow is controlled by parameters in the
38276 configuration file &_Local/eximon.conf_&.
38278 Searches of the text in the log window can be carried out by means of the ^R
38279 and ^S keystrokes, which default to a reverse and a forward search,
38280 respectively. The search covers only the text that is displayed in the window.
38281 It cannot go further back up the log.
38283 The point from which the search starts is indicated by a caret marker. This is
38284 normally at the end of the text in the window, but can be positioned explicitly
38285 by pointing and clicking with the left mouse button, and is moved automatically
38286 by a successful search. If new text arrives in the window when it is scrolled
38287 back, the caret remains where it is, but if the window is not scrolled back,
38288 the caret is moved to the end of the new text.
38290 Pressing ^R or ^S pops up a window into which the search text can be typed.
38291 There are buttons for selecting forward or reverse searching, for carrying out
38292 the search, and for cancelling. If the &"Search"& button is pressed, the search
38293 happens and the window remains so that further searches can be done. If the
38294 &"Return"& key is pressed, a single search is done and the window is closed. If
38295 ^C is typed the search is cancelled.
38297 The searching facility is implemented using the facilities of the Athena text
38298 widget. By default this pops up a window containing both &"search"& and
38299 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
38300 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
38301 However, the linkers in BSDI and HP-UX seem unable to handle an externally
38302 provided version of &%TextPop%& when the remaining parts of the text widget
38303 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
38304 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
38305 on these systems, at the expense of having unwanted items in the search popup
38310 .section "The queue display" "SECID268"
38311 .cindex "queue" "display in monitor"
38312 The bottom section of the monitor window contains a list of all messages that
38313 are in the queue, which includes those currently being received or delivered,
38314 as well as those awaiting delivery. The size of this subwindow is controlled by
38315 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
38316 at which it is updated is controlled by another parameter in the same file &--
38317 the default is 5 minutes, since queue scans can be quite expensive. However,
38318 there is an &"Update"& action button just above the display which can be used
38319 to force an update of the queue display at any time.
38321 When a host is down for some time, a lot of pending mail can build up for it,
38322 and this can make it hard to deal with other messages in the queue. To help
38323 with this situation there is a button next to &"Update"& called &"Hide"&. If
38324 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
38325 type anything in here and press &"Return"&, the text is added to a chain of
38326 such texts, and if every undelivered address in a message matches at least one
38327 of the texts, the message is not displayed.
38329 If there is an address that does not match any of the texts, all the addresses
38330 are displayed as normal. The matching happens on the ends of addresses so, for
38331 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
38332 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
38333 has been set up, a button called &"Unhide"& is displayed. If pressed, it
38334 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
38335 a hide request is automatically cancelled after one hour.
38337 While the dialogue box is displayed, you can't press any buttons or do anything
38338 else to the monitor window. For this reason, if you want to cut text from the
38339 queue display to use in the dialogue box, you have to do the cutting before
38340 pressing the &"Hide"& button.
38342 The queue display contains, for each unhidden queued message, the length of
38343 time it has been in the queue, the size of the message, the message id, the
38344 message sender, and the first undelivered recipient, all on one line. If it is
38345 a bounce message, the sender is shown as &"<>"&. If there is more than one
38346 recipient to which the message has not yet been delivered, subsequent ones are
38347 listed on additional lines, up to a maximum configured number, following which
38348 an ellipsis is displayed. Recipients that have already received the message are
38351 .cindex "frozen messages" "display"
38352 If a message is frozen, an asterisk is displayed at the left-hand side.
38354 The queue display has a vertical scroll bar, and can also be scrolled by means
38355 of the arrow keys. Text can be cut from it using the mouse in the normal way.
38356 The text searching facilities, as described above for the log window, are also
38357 available, but the caret is always moved to the end of the text when the queue
38358 display is updated.
38362 .section "The queue menu" "SECID269"
38363 .cindex "queue" "menu in monitor"
38364 If the &%shift%& key is held down and the left button is clicked when the mouse
38365 pointer is over the text for any message, an action menu pops up, and the first
38366 line of the queue display for the message is highlighted. This does not affect
38369 If you want to use some other event for popping up the menu, you can set the
38370 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
38371 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
38372 value set in this parameter is a standard X event description. For example, to
38373 run eximon using &%ctrl%& rather than &%shift%& you could use
38375 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
38377 The title of the menu is the message id, and it contains entries which act as
38381 &'message log'&: The contents of the message log for the message are displayed
38382 in a new text window.
38384 &'headers'&: Information from the spool file that contains the envelope
38385 information and headers is displayed in a new text window. See chapter
38386 &<<CHAPspool>>& for a description of the format of spool files.
38388 &'body'&: The contents of the spool file containing the body of the message are
38389 displayed in a new text window. There is a default limit of 20,000 bytes to the
38390 amount of data displayed. This can be changed by setting the BODY_MAX
38391 option at compile time, or the EXIMON_BODY_MAX option at runtime.
38393 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
38394 delivery of the message. This causes an automatic thaw if the message is
38395 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
38396 a new text window. The delivery is run in a separate process, to avoid holding
38397 up the monitor while the delivery proceeds.
38399 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
38400 that the message be frozen.
38402 .cindex "thawing messages"
38403 .cindex "unfreezing messages"
38404 .cindex "frozen messages" "thawing"
38405 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
38406 that the message be thawed.
38408 .cindex "delivery" "forcing failure"
38409 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
38410 that Exim gives up trying to deliver the message. A bounce message is generated
38411 for any remaining undelivered addresses.
38413 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
38414 that the message be deleted from the system without generating a bounce
38417 &'add recipient'&: A dialog box is displayed into which a recipient address can
38418 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
38419 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
38420 Otherwise it must be entered as a fully qualified address. Pressing RETURN
38421 causes a call to Exim to be made using the &%-Mar%& option to request that an
38422 additional recipient be added to the message, unless the entry box is empty, in
38423 which case no action is taken.
38425 &'mark delivered'&: A dialog box is displayed into which a recipient address
38426 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
38427 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
38428 Otherwise it must be entered as a fully qualified address. Pressing RETURN
38429 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
38430 recipient address as already delivered, unless the entry box is empty, in which
38431 case no action is taken.
38433 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
38434 mark all recipient addresses as already delivered.
38436 &'edit sender'&: A dialog box is displayed initialized with the current
38437 sender's address. Pressing RETURN causes a call to Exim to be made using the
38438 &%-Mes%& option to replace the sender address, unless the entry box is empty,
38439 in which case no action is taken. If you want to set an empty sender (as in
38440 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
38441 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
38442 the address is qualified with that domain.
38445 When a delivery is forced, a window showing the &%-v%& output is displayed. In
38446 other cases when a call to Exim is made, if there is any output from Exim (in
38447 particular, if the command fails) a window containing the command and the
38448 output is displayed. Otherwise, the results of the action are normally apparent
38449 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
38450 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
38451 if no output is generated.
38453 The queue display is automatically updated for actions such as freezing and
38454 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
38455 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
38456 force an update of the display after one of these actions.
38458 In any text window that is displayed as result of a menu action, the normal
38459 cut-and-paste facility is available, and searching can be carried out using ^R
38460 and ^S, as described above for the log tail window.
38467 . ////////////////////////////////////////////////////////////////////////////
38468 . ////////////////////////////////////////////////////////////////////////////
38470 .chapter "Security considerations" "CHAPsecurity"
38471 .scindex IIDsecurcon "security" "discussion of"
38472 This chapter discusses a number of issues concerned with security, some of
38473 which are also covered in other parts of this manual.
38475 For reasons that this author does not understand, some people have promoted
38476 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
38477 existence of this chapter in the documentation. However, the intent of the
38478 chapter is simply to describe the way Exim works in relation to certain
38479 security concerns, not to make any specific claims about the effectiveness of
38480 its security as compared with other MTAs.
38482 What follows is a description of the way Exim is supposed to be. Best efforts
38483 have been made to try to ensure that the code agrees with the theory, but an
38484 absence of bugs can never be guaranteed. Any that are reported will get fixed
38485 as soon as possible.
38488 .section "Building a more &""hardened""& Exim" "SECID286"
38489 .cindex "security" "build-time features"
38490 There are a number of build-time options that can be set in &_Local/Makefile_&
38491 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
38492 Exim administrator who does not have the root password, or by someone who has
38493 penetrated the Exim (but not the root) account. These options are as follows:
38496 ALT_CONFIG_PREFIX can be set to a string that is required to match the
38497 start of any filenames used with the &%-C%& option. When it is set, these
38498 filenames are also not allowed to contain the sequence &"/../"&. (However, if
38499 the value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
38500 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
38501 default setting for &%ALT_CONFIG_PREFIX%&.
38503 If the permitted configuration files are confined to a directory to
38504 which only root has access, this guards against someone who has broken
38505 into the Exim account from running a privileged Exim with an arbitrary
38506 configuration file, and using it to break into other accounts.
38509 If a non-trusted configuration file (i.e. not the default configuration file
38510 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
38511 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
38512 the next item), then root privilege is retained only if the caller of Exim is
38513 root. This locks out the possibility of testing a configuration using &%-C%&
38514 right through message reception and delivery, even if the caller is root. The
38515 reception works, but by that time, Exim is running as the Exim user, so when
38516 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
38517 privilege to be lost. However, root can test reception and delivery using two
38521 The WHITELIST_D_MACROS build option declares some macros to be safe to override
38522 with &%-D%& if the real uid is one of root, the Exim run-time user or the
38523 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
38524 requiring the run-time value supplied to &%-D%& to match a regex that errs on
38525 the restrictive side. Requiring build-time selection of safe macros is onerous
38526 but this option is intended solely as a transition mechanism to permit
38527 previously-working configurations to continue to work after release 4.73.
38529 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
38532 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
38533 never to be used for any deliveries. This is like the &%never_users%& runtime
38534 option, but it cannot be overridden; the runtime option adds additional users
38535 to the list. The default setting is &"root"&; this prevents a non-root user who
38536 is permitted to modify the runtime file from using Exim as a way to get root.
38541 .section "Root privilege" "SECID270"
38543 .cindex "root privilege"
38544 The Exim binary is normally setuid to root, which means that it gains root
38545 privilege (runs as root) when it starts execution. In some special cases (for
38546 example, when the daemon is not in use and there are no local deliveries), it
38547 may be possible to run Exim setuid to some user other than root. This is
38548 discussed in the next section. However, in most installations, root privilege
38549 is required for two things:
38552 To set up a socket connected to the standard SMTP port (25) when initialising
38553 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
38556 To be able to change uid and gid in order to read users' &_.forward_& files and
38557 perform local deliveries as the receiving user or as specified in the
38561 It is not necessary to be root to do any of the other things Exim does, such as
38562 receiving messages and delivering them externally over SMTP, and it is
38563 obviously more secure if Exim does not run as root except when necessary.
38564 For this reason, a user and group for Exim to use must be defined in
38565 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
38566 group"&. Their values can be changed by the runtime configuration, though this
38567 is not recommended. Often a user called &'exim'& is used, but some sites use
38568 &'mail'& or another user name altogether.
38570 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
38571 abdication; the process cannot regain root afterwards. Prior to release 4.00,
38572 &[seteuid()]& was used in some circumstances, but this is no longer the case.
38574 After a new Exim process has interpreted its command line options, it changes
38575 uid and gid in the following cases:
38580 If the &%-C%& option is used to specify an alternate configuration file, or if
38581 the &%-D%& option is used to define macro values for the configuration, and the
38582 calling process is not running as root, the uid and gid are changed to those of
38583 the calling process.
38584 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
38585 option may not be used at all.
38586 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
38587 can be supplied if the calling process is running as root, the Exim run-time
38588 user or CONFIGURE_OWNER, if defined.
38593 If the expansion test option (&%-be%&) or one of the filter testing options
38594 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
38597 If the process is not a daemon process or a queue runner process or a delivery
38598 process or a process for testing address routing (started with &%-bt%&), the
38599 uid and gid are changed to the Exim user and group. This means that Exim always
38600 runs under its own uid and gid when receiving messages. This also applies when
38601 testing address verification
38604 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
38607 For a daemon, queue runner, delivery, or address testing process, the uid
38608 remains as root at this stage, but the gid is changed to the Exim group.
38611 The processes that initially retain root privilege behave as follows:
38614 A daemon process changes the gid to the Exim group and the uid to the Exim
38615 user after setting up one or more listening sockets. The &[initgroups()]&
38616 function is called, so that if the Exim user is in any additional groups, they
38617 will be used during message reception.
38619 A queue runner process retains root privilege throughout its execution. Its
38620 job is to fork a controlled sequence of delivery processes.
38622 A delivery process retains root privilege throughout most of its execution,
38623 but any actual deliveries (that is, the transports themselves) are run in
38624 subprocesses which always change to a non-root uid and gid. For local
38625 deliveries this is typically the uid and gid of the owner of the mailbox; for
38626 remote deliveries, the Exim uid and gid are used. Once all the delivery
38627 subprocesses have been run, a delivery process changes to the Exim uid and gid
38628 while doing post-delivery tidying up such as updating the retry database and
38629 generating bounce and warning messages.
38631 While the recipient addresses in a message are being routed, the delivery
38632 process runs as root. However, if a user's filter file has to be processed,
38633 this is done in a subprocess that runs under the individual user's uid and
38634 gid. A system filter is run as root unless &%system_filter_user%& is set.
38636 A process that is testing addresses (the &%-bt%& option) runs as root so that
38637 the routing is done in the same environment as a message delivery.
38643 .section "Running Exim without privilege" "SECTrunexiwitpri"
38644 .cindex "privilege, running without"
38645 .cindex "unprivileged running"
38646 .cindex "root privilege" "running without"
38647 Some installations like to run Exim in an unprivileged state for more of its
38648 operation, for added security. Support for this mode of operation is provided
38649 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
38650 gid are changed to the Exim user and group at the start of a delivery process
38651 (and also queue runner and address testing processes). This means that address
38652 routing is no longer run as root, and the deliveries themselves cannot change
38656 .cindex "daemon" "restarting"
38657 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
38658 that the daemon can still be started in the usual way, and it can respond
38659 correctly to SIGHUP because the re-invocation regains root privilege.
38661 An alternative approach is to make Exim setuid to the Exim user and also setgid
38662 to the Exim group. If you do this, the daemon must be started from a root
38663 process. (Calling Exim from a root process makes it behave in the way it does
38664 when it is setuid root.) However, the daemon cannot restart itself after a
38665 SIGHUP signal because it cannot regain privilege.
38667 It is still useful to set &%deliver_drop_privilege%& in this case, because it
38668 stops Exim from trying to re-invoke itself to do a delivery after a message has
38669 been received. Such a re-invocation is a waste of resources because it has no
38672 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
38673 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
38674 to the Exim user seems a clean approach, but there is one complication:
38676 In this style of operation, Exim is running with the real uid and gid set to
38677 those of the calling process, and the effective uid/gid set to Exim's values.
38678 Ideally, any association with the calling process' uid/gid should be dropped,
38679 that is, the real uid/gid should be reset to the effective values so as to
38680 discard any privileges that the caller may have. While some operating systems
38681 have a function that permits this action for a non-root effective uid, quite a
38682 number of them do not. Because of this lack of standardization, Exim does not
38683 address this problem at this time.
38685 For this reason, the recommended approach for &"mostly unprivileged"& running
38686 is to keep the Exim binary setuid to root, and to set
38687 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
38688 be used in the most straightforward way.
38690 If you configure Exim not to run delivery processes as root, there are a
38691 number of restrictions on what you can do:
38694 You can deliver only as the Exim user/group. You should explicitly use the
38695 &%user%& and &%group%& options to override routers or local transports that
38696 normally deliver as the recipient. This makes sure that configurations that
38697 work in this mode function the same way in normal mode. Any implicit or
38698 explicit specification of another user causes an error.
38700 Use of &_.forward_& files is severely restricted, such that it is usually
38701 not worthwhile to include them in the configuration.
38703 Users who wish to use &_.forward_& would have to make their home directory and
38704 the file itself accessible to the Exim user. Pipe and append-to-file entries,
38705 and their equivalents in Exim filters, cannot be used. While they could be
38706 enabled in the Exim user's name, that would be insecure and not very useful.
38708 Unless the local user mailboxes are all owned by the Exim user (possible in
38709 some POP3 or IMAP-only environments):
38712 They must be owned by the Exim group and be writeable by that group. This
38713 implies you must set &%mode%& in the appendfile configuration, as well as the
38714 mode of the mailbox files themselves.
38716 You must set &%no_check_owner%&, since most or all of the files will not be
38717 owned by the Exim user.
38719 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
38720 on a newly created mailbox when unprivileged. This also implies that new
38721 mailboxes need to be created manually.
38726 These restrictions severely restrict what can be done in local deliveries.
38727 However, there are no restrictions on remote deliveries. If you are running a
38728 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
38729 gives more security at essentially no cost.
38731 If you are using the &%mua_wrapper%& facility (see chapter
38732 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
38737 .section "Delivering to local files" "SECID271"
38738 Full details of the checks applied by &(appendfile)& before it writes to a file
38739 are given in chapter &<<CHAPappendfile>>&.
38743 .section "Running local commands" "SECTsecconslocalcmds"
38744 .cindex "security" "local commands"
38745 .cindex "security" "command injection attacks"
38746 There are a number of ways in which an administrator can configure Exim to run
38747 commands based upon received, untrustworthy, data. Further, in some
38748 configurations a user who can control a &_.forward_& file can also arrange to
38749 run commands. Configuration to check includes, but is not limited to:
38752 Use of &%use_shell%& in the pipe transport: various forms of shell command
38753 injection may be possible with this option present. It is dangerous and should
38754 be used only with considerable caution. Consider constraints which whitelist
38755 allowed characters in a variable which is to be used in a pipe transport that
38756 has &%use_shell%& enabled.
38758 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
38759 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
38760 &_.forward_& files in a redirect router. If Exim is running on a central mail
38761 hub to which ordinary users do not have shell access, but home directories are
38762 NFS mounted (for instance) then administrators should review the list of these
38763 forbid options available, and should bear in mind that the options that may
38764 need forbidding can change as new features are added between releases.
38766 The &%${run...}%& expansion item does not use a shell by default, but
38767 administrators can configure use of &_/bin/sh_& as part of the command.
38768 Such invocations should be viewed with prejudicial suspicion.
38770 Administrators who use embedded Perl are advised to explore how Perl's
38771 taint checking might apply to their usage.
38773 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
38774 administrators are well advised to view its use with suspicion, in case (for
38775 instance) it allows a local-part to contain embedded Exim directives.
38777 Use of &%${match_local_part...}%& and friends becomes more dangerous if
38778 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
38779 each can reference arbitrary lists and files, rather than just being a list
38781 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
38782 real-world security vulnerabilities caused by its use with untrustworthy data
38783 injected in, for SQL injection attacks.
38784 Consider the use of the &%inlisti%& expansion condition instead.
38790 .section "Trust in configuration data" "SECTsecconfdata"
38791 .cindex "security" "data sources"
38792 .cindex "security" "regular expressions"
38793 .cindex "regular expressions" "security"
38794 .cindex "PCRE" "security"
38795 If configuration data for Exim can come from untrustworthy sources, there
38796 are some issues to be aware of:
38799 Use of &%${expand...}%& may provide a path for shell injection attacks.
38801 Letting untrusted data provide a regular expression is unwise.
38803 Using &%${match...}%& to apply a fixed regular expression against untrusted
38804 data may result in pathological behaviour within PCRE. Be aware of what
38805 "backtracking" means and consider options for being more strict with a regular
38806 expression. Avenues to explore include limiting what can match (avoiding &`.`&
38807 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
38808 possessive quantifiers or just not using regular expressions against untrusted
38811 It can be important to correctly use &%${quote:...}%&,
38812 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
38813 items to ensure that data is correctly constructed.
38815 Some lookups might return multiple results, even though normal usage is only
38816 expected to yield one result.
38822 .section "IPv4 source routing" "SECID272"
38823 .cindex "source routing" "in IP packets"
38824 .cindex "IP source routing"
38825 Many operating systems suppress IP source-routed packets in the kernel, but
38826 some cannot be made to do this, so Exim does its own check. It logs incoming
38827 IPv4 source-routed TCP calls, and then drops them. Things are all different in
38828 IPv6. No special checking is currently done.
38832 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
38833 Support for these SMTP commands is disabled by default. If required, they can
38834 be enabled by defining suitable ACLs.
38839 .section "Privileged users" "SECID274"
38840 .cindex "trusted users"
38841 .cindex "admin user"
38842 .cindex "privileged user"
38843 .cindex "user" "trusted"
38844 .cindex "user" "admin"
38845 Exim recognizes two sets of users with special privileges. Trusted users are
38846 able to submit new messages to Exim locally, but supply their own sender
38847 addresses and information about a sending host. For other users submitting
38848 local messages, Exim sets up the sender address from the uid, and doesn't
38849 permit a remote host to be specified.
38852 However, an untrusted user is permitted to use the &%-f%& command line option
38853 in the special form &%-f <>%& to indicate that a delivery failure for the
38854 message should not cause an error report. This affects the message's envelope,
38855 but it does not affect the &'Sender:'& header. Untrusted users may also be
38856 permitted to use specific forms of address with the &%-f%& option by setting
38857 the &%untrusted_set_sender%& option.
38859 Trusted users are used to run processes that receive mail messages from some
38860 other mail domain and pass them on to Exim for delivery either locally, or over
38861 the Internet. Exim trusts a caller that is running as root, as the Exim user,
38862 as any user listed in the &%trusted_users%& configuration option, or under any
38863 group listed in the &%trusted_groups%& option.
38865 Admin users are permitted to do things to the messages on Exim's queue. They
38866 can freeze or thaw messages, cause them to be returned to their senders, remove
38867 them entirely, or modify them in various ways. In addition, admin users can run
38868 the Exim monitor and see all the information it is capable of providing, which
38869 includes the contents of files on the spool.
38873 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
38874 delivery of messages on its queue is restricted to admin users. This
38875 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
38876 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
38877 queue is also restricted to admin users. This restriction can be relaxed by
38878 setting &%no_queue_list_requires_admin%&.
38880 Exim recognizes an admin user if the calling process is running as root or as
38881 the Exim user or if any of the groups associated with the calling process is
38882 the Exim group. It is not necessary actually to be running under the Exim
38883 group. However, if admin users who are not root or the Exim user are to access
38884 the contents of files on the spool via the Exim monitor (which runs
38885 unprivileged), Exim must be built to allow group read access to its spool
38888 By default, regular users are trusted to perform basic testing and
38889 introspection commands, as themselves. This setting can be tightened by
38890 setting the &%commandline_checks_require_admin%& option.
38891 This affects most of the checking options,
38892 such as &%-be%& and anything else &%-b*%&.
38895 .section "Spool files" "SECID275"
38896 .cindex "spool directory" "files"
38897 Exim's spool directory and everything it contains is owned by the Exim user and
38898 set to the Exim group. The mode for spool files is defined in the
38899 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
38900 any user who is a member of the Exim group can access these files.
38904 .section "Use of argv[0]" "SECID276"
38905 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
38906 of specific strings, Exim assumes certain options. For example, calling Exim
38907 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
38908 to calling it with the option &%-bS%&. There are no security implications in
38913 .section "Use of %f formatting" "SECID277"
38914 The only use made of &"%f"& by Exim is in formatting load average values. These
38915 are actually stored in integer variables as 1000 times the load average.
38916 Consequently, their range is limited and so therefore is the length of the
38921 .section "Embedded Exim path" "SECID278"
38922 Exim uses its own path name, which is embedded in the code, only when it needs
38923 to re-exec in order to regain root privilege. Therefore, it is not root when it
38924 does so. If some bug allowed the path to get overwritten, it would lead to an
38925 arbitrary program's being run as exim, not as root.
38929 .section "Dynamic module directory" "SECTdynmoddir"
38930 Any dynamically loadable modules must be installed into the directory
38931 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
38935 .section "Use of sprintf()" "SECID279"
38936 .cindex "&[sprintf()]&"
38937 A large number of occurrences of &"sprintf"& in the code are actually calls to
38938 &'string_sprintf()'&, a function that returns the result in malloc'd store.
38939 The intermediate formatting is done into a large fixed buffer by a function
38940 that runs through the format string itself, and checks the length of each
38941 conversion before performing it, thus preventing buffer overruns.
38943 The remaining uses of &[sprintf()]& happen in controlled circumstances where
38944 the output buffer is known to be sufficiently long to contain the converted
38949 .section "Use of debug_printf() and log_write()" "SECID280"
38950 Arbitrary strings are passed to both these functions, but they do their
38951 formatting by calling the function &'string_vformat()'&, which runs through
38952 the format string itself, and checks the length of each conversion.
38956 .section "Use of strcat() and strcpy()" "SECID281"
38957 These are used only in cases where the output buffer is known to be large
38958 enough to hold the result.
38959 .ecindex IIDsecurcon
38964 . ////////////////////////////////////////////////////////////////////////////
38965 . ////////////////////////////////////////////////////////////////////////////
38967 .chapter "Format of spool files" "CHAPspool"
38968 .scindex IIDforspo1 "format" "spool files"
38969 .scindex IIDforspo2 "spool directory" "format of files"
38970 .scindex IIDforspo3 "spool files" "format of"
38971 .cindex "spool files" "editing"
38972 A message on Exim's queue consists of two files, whose names are the message id
38973 followed by -D and -H, respectively. The data portion of the message is kept in
38974 the -D file on its own. The message's envelope, status, and headers are all
38975 kept in the -H file, whose format is described in this chapter. Each of these
38976 two files contains the final component of its own name as its first line. This
38977 is insurance against disk crashes where the directory is lost but the files
38978 themselves are recoverable.
38981 The file formats may be changed, or new formats added, at any release.
38982 Spool files are not intended as an interface to other programs
38983 and should not be used as such.
38986 Some people are tempted into editing -D files in order to modify messages. You
38987 need to be extremely careful if you do this; it is not recommended and you are
38988 on your own if you do it. Here are some of the pitfalls:
38991 You must ensure that Exim does not try to deliver the message while you are
38992 fiddling with it. The safest way is to take out a write lock on the -D file,
38993 which is what Exim itself does, using &[fcntl()]&. If you update the file in
38994 place, the lock will be retained. If you write a new file and rename it, the
38995 lock will be lost at the instant of rename.
38997 .vindex "&$body_linecount$&"
38998 If you change the number of lines in the file, the value of
38999 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
39000 cause incomplete transmission of messages or undeliverable messages.
39002 If the message is in MIME format, you must take care not to break it.
39004 If the message is cryptographically signed, any change will invalidate the
39007 All in all, modifying -D files is fraught with danger.
39009 Files whose names end with -J may also be seen in the &_input_& directory (or
39010 its subdirectories when &%split_spool_directory%& is set). These are journal
39011 files, used to record addresses to which the message has been delivered during
39012 the course of a delivery attempt. If there are still undelivered recipients at
39013 the end, the -H file is updated, and the -J file is deleted. If, however, there
39014 is some kind of crash (for example, a power outage) before this happens, the -J
39015 file remains in existence. When Exim next processes the message, it notices the
39016 -J file and uses it to update the -H file before starting the next delivery
39019 Files whose names end with -K or .eml may also be seen in the spool.
39020 These are temporaries used for DKIM or malware processing, when that is used.
39021 They should be tidied up by normal operations; any old ones are probably
39022 relics of crashes and can be removed.
39024 .section "Format of the -H file" "SECID282"
39025 .cindex "uid (user id)" "in spool file"
39026 .cindex "gid (group id)" "in spool file"
39027 The second line of the -H file contains the login name for the uid of the
39028 process that called Exim to read the message, followed by the numerical uid and
39029 gid. For a locally generated message, this is normally the user who sent the
39030 message. For a message received over TCP/IP via the daemon, it is
39031 normally the Exim user.
39033 The third line of the file contains the address of the message's sender as
39034 transmitted in the envelope, contained in angle brackets. The sender address is
39035 empty for bounce messages. For incoming SMTP mail, the sender address is given
39036 in the MAIL command. For locally generated mail, the sender address is
39037 created by Exim from the login name of the current user and the configured
39038 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
39039 leading &"From&~"& line if the caller is trusted, or if the supplied address is
39040 &"<>"& or an address that matches &%untrusted_set_senders%&.
39042 The fourth line contains two numbers. The first is the time that the message
39043 was received, in the conventional Unix form &-- the number of seconds since the
39044 start of the epoch. The second number is a count of the number of messages
39045 warning of delayed delivery that have been sent to the sender.
39047 There follow a number of lines starting with a hyphen. These can appear in any
39048 order, and are omitted when not relevant:
39051 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
39052 This item is obsolete, and is not generated from Exim release 4.61 onwards;
39053 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
39054 recognized, to provide backward compatibility. In the old format, a line of
39055 this form is present for every ACL variable that is not empty. The number
39056 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
39057 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
39058 the data string for the variable. The string itself starts at the beginning of
39059 the next line, and is followed by a newline character. It may contain internal
39062 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
39063 A line of this form is present for every ACL connection variable that is
39064 defined. Note that there is a space between &%-aclc%& and the rest of the name.
39065 The length is the length of the data string for the variable. The string itself
39066 starts at the beginning of the next line, and is followed by a newline
39067 character. It may contain internal newlines.
39069 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
39070 A line of this form is present for every ACL message variable that is defined.
39071 Note that there is a space between &%-aclm%& and the rest of the name. The
39072 length is the length of the data string for the variable. The string itself
39073 starts at the beginning of the next line, and is followed by a newline
39074 character. It may contain internal newlines.
39076 .vitem "&%-active_hostname%&&~<&'hostname'&>"
39077 This is present if, when the message was received over SMTP, the value of
39078 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
39080 .vitem &%-allow_unqualified_recipient%&
39081 This is present if unqualified recipient addresses are permitted in header
39082 lines (to stop such addresses from being qualified if rewriting occurs at
39083 transport time). Local messages that were input using &%-bnq%& and remote
39084 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
39086 .vitem &%-allow_unqualified_sender%&
39087 This is present if unqualified sender addresses are permitted in header lines
39088 (to stop such addresses from being qualified if rewriting occurs at transport
39089 time). Local messages that were input using &%-bnq%& and remote messages from
39090 hosts that match &%sender_unqualified_hosts%& set this flag.
39092 .vitem "&%-auth_id%&&~<&'text'&>"
39093 The id information for a message received on an authenticated SMTP connection
39094 &-- the value of the &$authenticated_id$& variable.
39096 .vitem "&%-auth_sender%&&~<&'address'&>"
39097 The address of an authenticated sender &-- the value of the
39098 &$authenticated_sender$& variable.
39100 .vitem "&%-body_linecount%&&~<&'number'&>"
39101 This records the number of lines in the body of the message, and is
39102 present unless &%-spool_file_wireformat%& is.
39104 .vitem "&%-body_zerocount%&&~<&'number'&>"
39105 This records the number of binary zero bytes in the body of the message, and is
39106 present if the number is greater than zero.
39108 .vitem &%-deliver_firsttime%&
39109 This is written when a new message is first added to the spool. When the spool
39110 file is updated after a deferral, it is omitted.
39112 .vitem "&%-frozen%&&~<&'time'&>"
39113 .cindex "frozen messages" "spool data"
39114 The message is frozen, and the freezing happened at <&'time'&>.
39116 .vitem "&%-helo_name%&&~<&'text'&>"
39117 This records the host name as specified by a remote host in a HELO or EHLO
39120 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
39121 This records the IP address of the host from which the message was received and
39122 the remote port number that was used. It is omitted for locally generated
39125 .vitem "&%-host_auth%&&~<&'text'&>"
39126 If the message was received on an authenticated SMTP connection, this records
39127 the name of the authenticator &-- the value of the
39128 &$sender_host_authenticated$& variable.
39130 .vitem &%-host_lookup_failed%&
39131 This is present if an attempt to look up the sending host's name from its IP
39132 address failed. It corresponds to the &$host_lookup_failed$& variable.
39134 .vitem "&%-host_name%&&~<&'text'&>"
39135 .cindex "reverse DNS lookup"
39136 .cindex "DNS" "reverse lookup"
39137 This records the name of the remote host from which the message was received,
39138 if the host name was looked up from the IP address when the message was being
39139 received. It is not present if no reverse lookup was done.
39141 .vitem "&%-ident%&&~<&'text'&>"
39142 For locally submitted messages, this records the login of the originating user,
39143 unless it was a trusted user and the &%-oMt%& option was used to specify an
39144 ident value. For messages received over TCP/IP, this records the ident string
39145 supplied by the remote host, if any.
39147 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
39148 This records the IP address of the local interface and the port number through
39149 which a message was received from a remote host. It is omitted for locally
39150 generated messages.
39153 The message is from a local sender.
39155 .vitem &%-localerror%&
39156 The message is a locally-generated bounce message.
39158 .vitem "&%-local_scan%&&~<&'string'&>"
39159 This records the data string that was returned by the &[local_scan()]& function
39160 when the message was received &-- the value of the &$local_scan_data$&
39161 variable. It is omitted if no data was returned.
39163 .vitem &%-manual_thaw%&
39164 The message was frozen but has been thawed manually, that is, by an explicit
39165 Exim command rather than via the auto-thaw process.
39168 A testing delivery process was started using the &%-N%& option to suppress any
39169 actual deliveries, but delivery was deferred. At any further delivery attempts,
39172 .vitem &%-received_protocol%&
39173 This records the value of the &$received_protocol$& variable, which contains
39174 the name of the protocol by which the message was received.
39176 .vitem &%-sender_set_untrusted%&
39177 The envelope sender of this message was set by an untrusted local caller (used
39178 to ensure that the caller is displayed in queue listings).
39180 .vitem "&%-spam_score_int%&&~<&'number'&>"
39181 If a message was scanned by SpamAssassin, this is present. It records the value
39182 of &$spam_score_int$&.
39184 .vitem &%-spool_file_wireformat%&
39185 The -D file for this message is in wire-format (for ESMTP CHUNKING)
39186 rather than Unix-format.
39187 The line-ending is CRLF rather than newline.
39188 There is still, however, no leading-dot-stuffing.
39190 .vitem &%-tls_certificate_verified%&
39191 A TLS certificate was received from the client that sent this message, and the
39192 certificate was verified by the server.
39194 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
39195 When the message was received over an encrypted connection, this records the
39196 name of the cipher suite that was used.
39198 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
39199 When the message was received over an encrypted connection, and a certificate
39200 was received from the client, this records the Distinguished Name from that
39204 Following the options there is a list of those addresses to which the message
39205 is not to be delivered. This set of addresses is initialized from the command
39206 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
39207 is set; otherwise it starts out empty. Whenever a successful delivery is made,
39208 the address is added to this set. The addresses are kept internally as a
39209 balanced binary tree, and it is a representation of that tree which is written
39210 to the spool file. If an address is expanded via an alias or forward file, the
39211 original address is added to the tree when deliveries to all its child
39212 addresses are complete.
39214 If the tree is empty, there is a single line in the spool file containing just
39215 the text &"XX"&. Otherwise, each line consists of two letters, which are either
39216 Y or N, followed by an address. The address is the value for the node of the
39217 tree, and the letters indicate whether the node has a left branch and/or a
39218 right branch attached to it, respectively. If branches exist, they immediately
39219 follow. Here is an example of a three-node tree:
39221 YY darcy@austen.fict.example
39222 NN alice@wonderland.fict.example
39223 NN editor@thesaurus.ref.example
39225 After the non-recipients tree, there is a list of the message's recipients.
39226 This is a simple list, preceded by a count. It includes all the original
39227 recipients of the message, including those to whom the message has already been
39228 delivered. In the simplest case, the list contains one address per line. For
39232 editor@thesaurus.ref.example
39233 darcy@austen.fict.example
39235 alice@wonderland.fict.example
39237 However, when a child address has been added to the top-level addresses as a
39238 result of the use of the &%one_time%& option on a &(redirect)& router, each
39239 line is of the following form:
39241 <&'top-level address'&> <&'errors_to address'&> &&&
39242 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
39244 The 01 flag bit indicates the presence of the three other fields that follow
39245 the top-level address. Other bits may be used in future to support additional
39246 fields. The <&'parent number'&> is the offset in the recipients list of the
39247 original parent of the &"one time"& address. The first two fields are the
39248 envelope sender that is associated with this address and its length. If the
39249 length is zero, there is no special envelope sender (there are then two space
39250 characters in the line). A non-empty field can arise from a &(redirect)& router
39251 that has an &%errors_to%& setting.
39254 A blank line separates the envelope and status information from the headers
39255 which follow. A header may occupy several lines of the file, and to save effort
39256 when reading it in, each header is preceded by a number and an identifying
39257 character. The number is the number of characters in the header, including any
39258 embedded newlines and the terminating newline. The character is one of the
39262 .row <&'blank'&> "header in which Exim has no special interest"
39263 .row &`B`& "&'Bcc:'& header"
39264 .row &`C`& "&'Cc:'& header"
39265 .row &`F`& "&'From:'& header"
39266 .row &`I`& "&'Message-id:'& header"
39267 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
39268 .row &`R`& "&'Reply-To:'& header"
39269 .row &`S`& "&'Sender:'& header"
39270 .row &`T`& "&'To:'& header"
39271 .row &`*`& "replaced or deleted header"
39274 Deleted or replaced (rewritten) headers remain in the spool file for debugging
39275 purposes. They are not transmitted when the message is delivered. Here is a
39276 typical set of headers:
39278 111P Received: by hobbit.fict.example with local (Exim 4.00)
39279 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
39280 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
39281 038* X-rewrote-sender: bb@hobbit.fict.example
39282 042* From: Bilbo Baggins <bb@hobbit.fict.example>
39283 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
39284 099* To: alice@wonderland.fict.example, rdo@foundation,
39285 darcy@austen.fict.example, editor@thesaurus.ref.example
39286 104T To: alice@wonderland.fict.example, rdo@foundation.example,
39287 darcy@austen.fict.example, editor@thesaurus.ref.example
39288 038 Date: Fri, 11 May 2001 10:28:59 +0100
39290 The asterisked headers indicate that the envelope sender, &'From:'& header, and
39291 &'To:'& header have been rewritten, the last one because routing expanded the
39292 unqualified domain &'foundation'&.
39293 .ecindex IIDforspo1
39294 .ecindex IIDforspo2
39295 .ecindex IIDforspo3
39297 .section "Format of the -D file" "SECID282a"
39298 The data file is traditionally in Unix-standard format: lines are ended with
39299 an ASCII newline character.
39300 However, when the &%spool_wireformat%& main option is used some -D files
39301 can have an alternate format.
39302 This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
39303 The -D file lines (not including the first name-component line) are
39304 suitable for direct copying to the wire when transmitting using the
39305 ESMTP CHUNKING option, meaning lower processing overhead.
39306 Lines are terminated with an ASCII CRLF pair.
39307 There is no dot-stuffing (and no dot-termination).
39309 . ////////////////////////////////////////////////////////////////////////////
39310 . ////////////////////////////////////////////////////////////////////////////
39312 .chapter "DKIM and SPF" "CHAPdkim" &&&
39313 "DKIM and SPF Support"
39316 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
39318 DKIM is a mechanism by which messages sent by some entity can be provably
39319 linked to a domain which that entity controls. It permits reputation to
39320 be tracked on a per-domain basis, rather than merely upon source IP address.
39321 DKIM is documented in RFC 6376.
39323 As DKIM relies on the message being unchanged in transit, messages handled
39324 by a mailing-list (which traditionally adds to the message) will not match
39325 any original DKIM signature.
39327 DKIM support is compiled into Exim by default if TLS support is present.
39328 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
39330 Exim's DKIM implementation allows for
39332 Signing outgoing messages: This function is implemented in the SMTP transport.
39333 It can co-exist with all other Exim features
39334 (including transport filters)
39335 except cutthrough delivery.
39337 Verifying signatures in incoming messages: This is implemented by an additional
39338 ACL (acl_smtp_dkim), which can be called several times per message, with
39339 different signature contexts.
39342 In typical Exim style, the verification implementation does not include any
39343 default "policy". Instead it enables you to build your own policy using
39344 Exim's standard controls.
39346 Please note that verification of DKIM signatures in incoming mail is turned
39347 on by default for logging (in the <= line) purposes.
39349 Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
39350 When set, for each signature in incoming email,
39351 exim will log a line displaying the most important signature details, and the
39352 signature status. Here is an example (with line-breaks added for clarity):
39354 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
39355 d=facebookmail.com s=q1-2009b
39356 c=relaxed/relaxed a=rsa-sha1
39357 i=@facebookmail.com t=1252484542 [verification succeeded]
39360 You might want to turn off DKIM verification processing entirely for internal
39361 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
39362 control modifier. This should typically be done in the RCPT ACL, at points
39363 where you accept mail from relay sources (internal hosts or authenticated
39367 .section "Signing outgoing messages" "SECDKIMSIGN"
39368 .cindex "DKIM" "signing"
39370 For signing to be usable you must have published a DKIM record in DNS.
39371 Note that RFC 8301 says:
39373 rsa-sha1 MUST NOT be used for signing or verifying.
39375 Signers MUST use RSA keys of at least 1024 bits for all keys.
39376 Signers SHOULD use RSA keys of at least 2048 bits.
39379 Note also that the key content (the 'p=' field)
39380 in the DNS record is different between RSA and EC keys;
39381 for the former it is the base64 of the ASN.1 for the RSA public key
39382 (equivalent to the private-key .pem with the header/trailer stripped)
39383 but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
39385 Signing is enabled by setting private options on the SMTP transport.
39386 These options take (expandable) strings as arguments.
39388 .option dkim_domain smtp string list&!! unset
39389 The domain(s) you want to sign with.
39390 After expansion, this can be a list.
39391 Each element in turn is put into the &%$dkim_domain%& expansion variable
39392 while expanding the remaining signing options.
39393 If it is empty after expansion, DKIM signing is not done,
39394 and no error will result even if &%dkim_strict%& is set.
39396 .option dkim_selector smtp string list&!! unset
39397 This sets the key selector string.
39398 After expansion, which can use &$dkim_domain$&, this can be a list.
39399 Each element in turn is put in the expansion
39400 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
39401 option along with &%$dkim_domain%&.
39402 If the option is empty after expansion, DKIM signing is not done for this domain,
39403 and no error will result even if &%dkim_strict%& is set.
39405 .option dkim_private_key smtp string&!! unset
39406 This sets the private key to use.
39407 You can use the &%$dkim_domain%& and
39408 &%$dkim_selector%& expansion variables to determine the private key to use.
39409 The result can either
39411 be a valid RSA private key in ASCII armor (.pem file), including line breaks
39413 with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
39414 be a valid Ed25519 private key (same format as above)
39416 start with a slash, in which case it is treated as a file that contains
39419 be "0", "false" or the empty string, in which case the message will not
39420 be signed. This case will not result in an error, even if &%dkim_strict%&
39424 To generate keys under OpenSSL:
39426 openssl genrsa -out dkim_rsa.private 2048
39427 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
39429 Take the base-64 lines from the output of the second command, concatenated,
39430 for the DNS TXT record.
39431 See section 3.6 of RFC6376 for the record specification.
39435 certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
39436 certtool --load-privkey=dkim_rsa.private --pubkey-info
39439 Note that RFC 8301 says:
39441 Signers MUST use RSA keys of at least 1024 bits for all keys.
39442 Signers SHOULD use RSA keys of at least 2048 bits.
39445 Support for EC keys is being developed under
39446 &url(https://datatracker.ietf.org/doc/draft-ietf-dcrup-dkim-crypto/).
39447 They are considerably smaller than RSA keys for equivalent protection.
39448 As they are a recent development, users should consider dual-signing
39449 (by setting a list of selectors, and an expansion for this option)
39450 for some transition period.
39451 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
39454 OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
39456 openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
39457 certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
39460 To produce the required public key value for a DNS record:
39462 openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
39463 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
39466 Note that the format
39467 of Ed25519 keys in DNS has not yet been decided; this release supports
39468 both of the leading candidates at this time, a future release will
39469 probably drop support for whichever proposal loses.
39471 .option dkim_hash smtp string&!! sha256
39472 Can be set to any one of the supported hash methods, which are:
39474 &`sha1`& &-- should not be used, is old and insecure
39476 &`sha256`& &-- the default
39478 &`sha512`& &-- possibly more secure but less well supported
39481 Note that RFC 8301 says:
39483 rsa-sha1 MUST NOT be used for signing or verifying.
39486 .option dkim_identity smtp string&!! unset
39487 If set after expansion, the value is used to set an "i=" tag in
39488 the signing header. The DKIM standards restrict the permissible
39489 syntax of this optional tag to a mail address, with possibly-empty
39490 local part, an @, and a domain identical to or subdomain of the "d="
39491 tag value. Note that Exim does not check the value.
39493 .option dkim_canon smtp string&!! unset
39494 This option sets the canonicalization method used when signing a message.
39495 The DKIM RFC currently supports two methods: "simple" and "relaxed".
39496 The option defaults to "relaxed" when unset. Note: the current implementation
39497 only supports signing with the same canonicalization method for both headers and body.
39499 .option dkim_strict smtp string&!! unset
39500 This option defines how Exim behaves when signing a message that
39501 should be signed fails for some reason. When the expansion evaluates to
39502 either "1" or "true", Exim will defer. Otherwise Exim will send the message
39503 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
39506 .option dkim_sign_headers smtp string&!! "see below"
39507 If set, this option must expand to a colon-separated
39508 list of header names.
39509 Headers with these names, or the absence or such a header, will be included
39510 in the message signature.
39511 When unspecified, the header names listed in RFC4871 will be used,
39512 whether or not each header is present in the message.
39513 The default list is available for the expansion in the macro
39514 "_DKIM_SIGN_HEADERS".
39516 If a name is repeated, multiple headers by that name (or the absence thereof)
39517 will be signed. The textually later headers in the headers part of the
39518 message are signed first, if there are multiples.
39520 A name can be prefixed with either an '=' or a '+' character.
39521 If an '=' prefix is used, all headers that are present with this name
39523 If a '+' prefix if used, all headers that are present with this name
39524 will be signed, and one signature added for a missing header with the
39525 name will be appended.
39528 .option dkim_timestamps smtp integer&!! unset
39529 This option controls the inclusion of timestamp information in the signature.
39530 If not set, no such information will be included.
39531 Otherwise, must be an unsigned number giving an offset in seconds from the current time
39533 (eg. 1209600 for two weeks);
39534 both creation (t=) and expiry (x=) tags will be included.
39536 RFC 6376 lists these tags as RECOMMENDED.
39540 .section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
39541 .cindex "DKIM" "verification"
39544 Verification of DKIM signatures in SMTP incoming email is done for all
39545 messages for which an ACL control &%dkim_disable_verify%& has not been set.
39546 .cindex authentication "expansion item"
39547 Performing verification sets up information used by the
39548 &$authresults$& expansion item.
39551 .new The results of that verification are then made available to the
39552 &%acl_smtp_dkim%& ACL, &new(which can examine and modify them).
39553 By default, this ACL is called once for each
39554 syntactically(!) correct signature in the incoming message.
39555 A missing ACL definition defaults to accept.
39556 If any ACL call does not accept, the message is not accepted.
39557 If a cutthrough delivery was in progress for the message, that is
39558 summarily dropped (having wasted the transmission effort).
39560 To evaluate the &new(verification result) in the ACL
39561 a large number of expansion variables
39562 containing the signature status and its details are set up during the
39563 runtime of the ACL.
39565 Calling the ACL only for existing signatures is not sufficient to build
39566 more advanced policies. For that reason, the global option
39567 &%dkim_verify_signers%&, and a global expansion variable
39568 &%$dkim_signers%& exist.
39570 The global option &%dkim_verify_signers%& can be set to a colon-separated
39571 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
39572 called. It is expanded when the message has been received. At this point,
39573 the expansion variable &%$dkim_signers%& already contains a colon-separated
39574 list of signer domains and identities for the message. When
39575 &%dkim_verify_signers%& is not specified in the main configuration,
39578 dkim_verify_signers = $dkim_signers
39580 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
39581 DKIM signature in the message. Current DKIM verifiers may want to explicitly
39582 call the ACL for known domains or identities. This would be achieved as follows:
39584 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
39586 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
39587 and "ebay.com", plus all domains and identities that have signatures in the message.
39588 You can also be more creative in constructing your policy. For example:
39590 dkim_verify_signers = $sender_address_domain:$dkim_signers
39593 If a domain or identity is listed several times in the (expanded) value of
39594 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
39596 If multiple signatures match a domain (or identity), the ACL is called once
39597 for each matching signature.
39600 Inside the &%acl_smtp_dkim%&, the following expansion variables are
39601 available (from most to least important):
39605 .vitem &%$dkim_cur_signer%&
39606 The signer that is being evaluated in this ACL run. This can be a domain or
39607 an identity. This is one of the list items from the expanded main option
39608 &%dkim_verify_signers%& (see above).
39610 .vitem &%$dkim_verify_status%&
39611 Within the DKIM ACL,
39612 a string describing the general status of the signature. One of
39614 &%none%&: There is no signature in the message for the current domain or
39615 identity (as reflected by &%$dkim_cur_signer%&).
39617 &%invalid%&: The signature could not be verified due to a processing error.
39618 More detail is available in &%$dkim_verify_reason%&.
39620 &%fail%&: Verification of the signature failed. More detail is
39621 available in &%$dkim_verify_reason%&.
39623 &%pass%&: The signature passed verification. It is valid.
39626 This variable can be overwritten using an ACL 'set' modifier.
39627 This might, for instance, be done to enforce a policy restriction on
39628 hash-method or key-size:
39630 warn condition = ${if eq {$dkim_verify_status}{pass}}
39631 condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
39632 condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
39633 {< {$dkim_key_length}{1024}}}}
39634 logwrite = NOTE: forcing DKIM verify fail (was pass)
39635 set dkim_verify_status = fail
39636 set dkim_verify_reason = hash too weak or key too short
39639 So long as a DKIM ACL is defined (it need do no more than accept),
39640 after all the DKIM ACL runs have completed, the value becomes a
39641 colon-separated list of the values after each run.
39642 This is maintained for the mime, prdr and data ACLs.
39644 .vitem &%$dkim_verify_reason%&
39645 A string giving a little bit more detail when &%$dkim_verify_status%& is either
39646 "fail" or "invalid". One of
39648 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
39649 key for the domain could not be retrieved. This may be a temporary problem.
39651 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
39652 record for the domain is syntactically invalid.
39654 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
39655 body hash does not match the one specified in the signature header. This
39656 means that the message body was modified in transit.
39658 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
39659 could not be verified. This may mean that headers were modified,
39660 re-written or otherwise changed in a way which is incompatible with
39661 DKIM verification. It may of course also mean that the signature is forged.
39664 This variable can be overwritten, with any value, using an ACL 'set' modifier.
39666 .vitem &%$dkim_domain%&
39667 The signing domain. IMPORTANT: This variable is only populated if there is
39668 an actual signature in the message for the current domain or identity (as
39669 reflected by &%$dkim_cur_signer%&).
39671 .vitem &%$dkim_identity%&
39672 The signing identity, if present. IMPORTANT: This variable is only populated
39673 if there is an actual signature in the message for the current domain or
39674 identity (as reflected by &%$dkim_cur_signer%&).
39676 .vitem &%$dkim_selector%&
39677 The key record selector string.
39679 .vitem &%$dkim_algo%&
39680 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
39681 If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
39682 may also be 'ed25519-sha256'.
39683 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
39686 Note that RFC 8301 says:
39688 rsa-sha1 MUST NOT be used for signing or verifying.
39690 DKIM signatures identified as having been signed with historic
39691 algorithms (currently, rsa-sha1) have permanently failed evaluation
39694 To enforce this you must have a DKIM ACL which checks this variable
39695 and overwrites the &$dkim_verify_status$& variable as discussed above.
39697 .vitem &%$dkim_canon_body%&
39698 The body canonicalization method. One of 'relaxed' or 'simple'.
39700 .vitem &%$dkim_canon_headers%&
39701 The header canonicalization method. One of 'relaxed' or 'simple'.
39703 .vitem &%$dkim_copiedheaders%&
39704 A transcript of headers and their values which are included in the signature
39705 (copied from the 'z=' tag of the signature).
39706 Note that RFC6376 requires that verification fail if the From: header is
39707 not included in the signature. Exim does not enforce this; sites wishing
39708 strict enforcement should code the check explicitly.
39710 .vitem &%$dkim_bodylength%&
39711 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
39712 limit was set by the signer, "9999999999999" is returned. This makes sure
39713 that this variable always expands to an integer value.
39715 &*Note:*& The presence of the signature tag specifying a signing body length
39716 is one possible route to spoofing of valid DKIM signatures.
39717 A paranoid implementation might wish to regard signature where this variable
39718 shows less than the "no limit" return as being invalid.
39721 .vitem &%$dkim_created%&
39722 UNIX timestamp reflecting the date and time when the signature was created.
39723 When this was not specified by the signer, "0" is returned.
39725 .vitem &%$dkim_expires%&
39726 UNIX timestamp reflecting the date and time when the signer wants the
39727 signature to be treated as "expired". When this was not specified by the
39728 signer, "9999999999999" is returned. This makes it possible to do useful
39729 integer size comparisons against this value.
39730 Note that Exim does not check this value.
39732 .vitem &%$dkim_headernames%&
39733 A colon-separated list of names of headers included in the signature.
39735 .vitem &%$dkim_key_testing%&
39736 "1" if the key record has the "testing" flag set, "0" if not.
39738 .vitem &%$dkim_key_nosubdomains%&
39739 "1" if the key record forbids subdomaining, "0" otherwise.
39741 .vitem &%$dkim_key_srvtype%&
39742 Service type (tag s=) from the key record. Defaults to "*" if not specified
39745 .vitem &%$dkim_key_granularity%&
39746 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
39749 .vitem &%$dkim_key_notes%&
39750 Notes from the key record (tag n=).
39752 .vitem &%$dkim_key_length%&
39753 Number of bits in the key.
39755 Note that RFC 8301 says:
39757 Verifiers MUST NOT consider signatures using RSA keys of
39758 less than 1024 bits as valid signatures.
39761 To enforce this you must have a DKIM ACL which checks this variable
39762 and overwrites the &$dkim_verify_status$& variable as discussed above.
39763 As EC keys are much smaller, the check should only do this for RSA keys.
39767 In addition, two ACL conditions are provided:
39770 .vitem &%dkim_signers%&
39771 ACL condition that checks a colon-separated list of domains or identities
39772 for a match against the domain or identity that the ACL is currently verifying
39773 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
39774 verb to a group of domains or identities. For example:
39777 # Warn when Mail purportedly from GMail has no gmail signature
39778 warn log_message = GMail sender without gmail.com DKIM signature
39779 sender_domains = gmail.com
39780 dkim_signers = gmail.com
39784 Note that the above does not check for a total lack of DKIM signing;
39785 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
39787 .vitem &%dkim_status%&
39788 ACL condition that checks a colon-separated list of possible DKIM verification
39789 results against the actual result of verification. This is typically used
39790 to restrict an ACL verb to a list of verification outcomes, for example:
39793 deny message = Mail from Paypal with invalid/missing signature
39794 sender_domains = paypal.com:paypal.de
39795 dkim_signers = paypal.com:paypal.de
39796 dkim_status = none:invalid:fail
39799 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
39800 see the documentation of the &%$dkim_verify_status%& expansion variable above
39801 for more information of what they mean.
39807 .section "SPF (Sender Policy Framework)" SECSPF
39808 .cindex SPF verification
39810 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
39811 messages with its domain in the envelope from, documented by RFC 7208.
39812 For more information on SPF see &url(http://www.openspf.org).
39813 . --- 2018-09-07: still not https
39815 Messages sent by a system not authorised will fail checking of such assertions.
39816 This includes retransmissions done by traditional forwarders.
39818 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
39819 &_Local/Makefile_&. The support uses the &_libspf2_& library
39820 &url(https://www.libspf2.org/).
39821 There is no Exim involvement in the transmission of messages;
39822 publishing certain DNS records is all that is required.
39824 For verification, an ACL condition and an expansion lookup are provided.
39825 .cindex authentication "expansion item"
39826 Performing verification sets up information used by the
39827 &$authresults$& expansion item.
39830 .cindex SPF "ACL condition"
39831 .cindex ACL "spf condition"
39832 The ACL condition "spf" can be used at or after the MAIL ACL.
39833 It takes as an argument a list of strings giving the outcome of the SPF check,
39834 and will succeed for any matching outcome.
39838 The SPF check passed, the sending host is positively verified by SPF.
39841 The SPF check failed, the sending host is NOT allowed to send mail for the
39842 domain in the envelope-from address.
39844 .vitem &%softfail%&
39845 The SPF check failed, but the queried domain can't absolutely confirm that this
39849 The queried domain does not publish SPF records.
39852 The SPF check returned a "neutral" state. This means the queried domain has
39853 published a SPF record, but wants to allow outside servers to send mail under
39854 its domain as well. This should be treated like "none".
39856 .vitem &%permerror%&
39857 This indicates a syntax error in the SPF record of the queried domain.
39858 You may deny messages when this occurs.
39860 .vitem &%temperror%&
39861 This indicates a temporary error during all processing, including Exim's
39862 SPF processing. You may defer messages when this occurs.
39865 You can prefix each string with an exclamation mark to invert
39866 its meaning, for example "!fail" will match all results but
39867 "fail". The string list is evaluated left-to-right, in a
39868 short-circuit fashion.
39873 message = $sender_host_address is not allowed to send mail from \
39874 ${if def:sender_address_domain \
39875 {$sender_address_domain}{$sender_helo_name}}. \
39876 Please see http://www.openspf.org/Why?scope=\
39877 ${if def:sender_address_domain {mfrom}{helo}};\
39878 identity=${if def:sender_address_domain \
39879 {$sender_address}{$sender_helo_name}};\
39880 ip=$sender_host_address
39883 When the spf condition has run, it sets up several expansion
39886 .cindex SPF "verification variables"
39888 .vitem &$spf_header_comment$&
39889 .vindex &$spf_header_comment$&
39890 This contains a human-readable string describing the outcome
39891 of the SPF check. You can add it to a custom header or use
39892 it for logging purposes.
39894 .vitem &$spf_received$&
39895 .vindex &$spf_received$&
39896 This contains a complete Received-SPF: header that can be
39897 added to the message. Please note that according to the SPF
39898 draft, this header must be added at the top of the header
39899 list. Please see section 10 on how you can do this.
39901 Note: in case of "Best-guess" (see below), the convention is
39902 to put this string in a header called X-SPF-Guess: instead.
39904 .vitem &$spf_result$&
39905 .vindex &$spf_result$&
39906 This contains the outcome of the SPF check in string form,
39907 one of pass, fail, softfail, none, neutral, permerror or
39910 .vitem &$spf_result_guessed$&
39911 .vindex &$spf_result_guessed$&
39912 This boolean is true only if a best-guess operation was used
39913 and required in order to obtain a result.
39915 .vitem &$spf_smtp_comment$&
39916 .vindex &$spf_smtp_comment$&
39917 This contains a string that can be used in a SMTP response
39918 to the calling party. Useful for "fail".
39922 .cindex SPF "ACL condition"
39923 .cindex ACL "spf_guess condition"
39924 .cindex SPF "best guess"
39925 In addition to SPF, you can also perform checks for so-called
39926 "Best-guess". Strictly speaking, "Best-guess" is not standard
39927 SPF, but it is supported by the same framework that enables SPF
39929 Refer to &url(http://www.openspf.org/FAQ/Best_guess_record)
39930 for a description of what it means.
39931 . --- 2018-09-07: still not https:
39933 To access this feature, simply use the spf_guess condition in place
39934 of the spf one. For example:
39937 deny spf_guess = fail
39938 message = $sender_host_address doesn't look trustworthy to me
39941 In case you decide to reject messages based on this check, you
39942 should note that although it uses the same framework, "Best-guess"
39943 is not SPF, and therefore you should not mention SPF at all in your
39946 When the spf_guess condition has run, it sets up the same expansion
39947 variables as when spf condition is run, described above.
39949 Additionally, since Best-guess is not standardized, you may redefine
39950 what "Best-guess" means to you by redefining the main configuration
39951 &%spf_guess%& option.
39952 For example, the following:
39955 spf_guess = v=spf1 a/16 mx/16 ptr ?all
39958 would relax host matching rules to a broader network range.
39961 .cindex SPF "lookup expansion"
39963 A lookup expansion is also available. It takes an email
39964 address as the key and an IP address as the database:
39967 ${lookup {username@domain} spf {ip.ip.ip.ip}}
39970 The lookup will return the same result strings as can appear in
39971 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
39972 Currently, only IPv4 addresses are supported.
39977 . ////////////////////////////////////////////////////////////////////////////
39978 . ////////////////////////////////////////////////////////////////////////////
39980 .chapter "Proxies" "CHAPproxies" &&&
39982 .cindex "proxy support"
39983 .cindex "proxy" "access via"
39985 A proxy is an intermediate system through which communication is passed.
39986 Proxies may provide a security, availability or load-distribution function.
39989 .section "Inbound proxies" SECTproxyInbound
39990 .cindex proxy inbound
39991 .cindex proxy "server side"
39992 .cindex proxy "Proxy protocol"
39993 .cindex "Proxy protocol" proxy
39995 Exim has support for receiving inbound SMTP connections via a proxy
39996 that uses &"Proxy Protocol"& to speak to it.
39997 To include this support, include &"SUPPORT_PROXY=yes"&
40000 It was built on the HAProxy specification, found at
40001 &url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt).
40003 The purpose of this facility is so that an application load balancer,
40004 such as HAProxy, can sit in front of several Exim servers
40005 to distribute load.
40006 Exim uses the local protocol communication with the proxy to obtain
40007 the remote SMTP system IP address and port information.
40008 There is no logging if a host passes or
40009 fails Proxy Protocol negotiation, but it can easily be determined and
40010 recorded in an ACL (example is below).
40012 Use of a proxy is enabled by setting the &%hosts_proxy%&
40013 main configuration option to a hostlist; connections from these
40014 hosts will use Proxy Protocol.
40015 Exim supports both version 1 and version 2 of the Proxy Protocol and
40016 automatically determines which version is in use.
40018 The Proxy Protocol header is the first data received on a TCP connection
40019 and is inserted before any TLS-on-connect handshake from the client; Exim
40020 negotiates TLS between Exim-as-server and the remote client, not between
40021 Exim and the proxy server.
40023 The following expansion variables are usable
40024 (&"internal"& and &"external"& here refer to the interfaces
40027 &'proxy_external_address '& IP of host being proxied or IP of remote interface of proxy
40028 &'proxy_external_port '& Port of host being proxied or Port on remote interface of proxy
40029 &'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
40030 &'proxy_local_port '& Port of proxy server inbound or Port on local interface of proxy
40031 &'proxy_session '& boolean: SMTP connection via proxy
40033 If &$proxy_session$& is set but &$proxy_external_address$& is empty
40034 there was a protocol error.
40036 Since the real connections are all coming from the proxy, and the
40037 per host connection tracking is done before Proxy Protocol is
40038 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
40039 handle all of the parallel volume you expect per inbound proxy.
40040 With the option set so high, you lose the ability
40041 to protect your server from many connections from one IP.
40042 In order to prevent your server from overload, you
40043 need to add a per connection ratelimit to your connect ACL.
40044 A possible solution is:
40046 # Set max number of connections per host
40048 # Or do some kind of IP lookup in a flat file or database
40049 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
40051 defer message = Too many connections from this IP right now
40052 ratelimit = LIMIT / 5s / per_conn / strict
40057 .section "Outbound proxies" SECTproxySOCKS
40058 .cindex proxy outbound
40059 .cindex proxy "client side"
40060 .cindex proxy SOCKS
40061 .cindex SOCKS proxy
40062 Exim has support for sending outbound SMTP via a proxy
40063 using a protocol called SOCKS5 (defined by RFC1928).
40064 The support can be optionally included by defining SUPPORT_SOCKS=yes in
40067 Use of a proxy is enabled by setting the &%socks_proxy%& option
40068 on an smtp transport.
40069 The option value is expanded and should then be a list
40070 (colon-separated by default) of proxy specifiers.
40071 Each proxy specifier is a list
40072 (space-separated by default) where the initial element
40073 is an IP address and any subsequent elements are options.
40075 Options are a string <name>=<value>.
40076 The list of options is in the following table:
40078 &'auth '& authentication method
40079 &'name '& authentication username
40080 &'pass '& authentication password
40082 &'tmo '& connection timeout
40084 &'weight '& selection bias
40087 More details on each of these options follows:
40090 .cindex authentication "to proxy"
40091 .cindex proxy authentication
40092 &%auth%&: Either &"none"& (default) or &"name"&.
40093 Using &"name"& selects username/password authentication per RFC 1929
40094 for access to the proxy.
40095 Default is &"none"&.
40097 &%name%&: sets the username for the &"name"& authentication method.
40100 &%pass%&: sets the password for the &"name"& authentication method.
40103 &%port%&: the TCP port number to use for the connection to the proxy.
40106 &%tmo%&: sets a connection timeout in seconds for this proxy.
40109 &%pri%&: specifies a priority for the proxy within the list,
40110 higher values being tried first.
40111 The default priority is 1.
40113 &%weight%&: specifies a selection bias.
40114 Within a priority set servers are queried in a random fashion,
40115 weighted by this value.
40116 The default value for selection bias is 1.
40119 Proxies from the list are tried according to their priority
40120 and weight settings until one responds. The timeout for the
40121 overall connection applies to the set of proxied attempts.
40123 .section Logging SECTproxyLog
40124 To log the (local) IP of a proxy in the incoming or delivery logline,
40125 add &"+proxy"& to the &%log_selector%& option.
40126 This will add a component tagged with &"PRX="& to the line.
40128 . ////////////////////////////////////////////////////////////////////////////
40129 . ////////////////////////////////////////////////////////////////////////////
40131 .chapter "Internationalisation" "CHAPi18n" &&&
40132 "Internationalisation""
40133 .cindex internationalisation "email address"
40136 .cindex utf8 "mail name handling"
40138 Exim has support for Internationalised mail names.
40139 To include this it must be built with SUPPORT_I18N and the libidn library.
40140 Standards supported are RFCs 2060, 5890, 6530 and 6533.
40142 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
40143 instead of it) then IDNA2008 is supported; this adds an extra library
40144 requirement, upon libidn2.
40146 .section "MTA operations" SECTi18nMTA
40147 .cindex SMTPUTF8 "ESMTP option"
40148 The main configuration option &%smtputf8_advertise_hosts%& specifies
40149 a host list. If this matches the sending host and
40150 accept_8bitmime is true (the default) then the ESMTP option
40151 SMTPUTF8 will be advertised.
40153 If the sender specifies the SMTPUTF8 option on a MAIL command
40154 international handling for the message is enabled and
40155 the expansion variable &$message_smtputf8$& will have value TRUE.
40157 The option &%allow_utf8_domains%& is set to true for this
40158 message. All DNS lookups are converted to a-label form
40159 whatever the setting of &%allow_utf8_domains%&
40160 when Exim is built with SUPPORT_I18N.
40162 Both localparts and domain are maintained as the original
40163 UTF-8 form internally; any comparison or regular-expression use will
40164 require appropriate care. Filenames created, eg. by
40165 the appendfile transport, will have UTF-8 names.
40167 HELO names sent by the smtp transport will have any UTF-8
40168 components expanded to a-label form,
40169 and any certificate name checks will be done using the a-label
40172 .cindex log protocol
40173 .cindex SMTPUTF8 logging
40174 .cindex i18n logging
40175 Log lines and Received-by: header lines will acquire a "utf8"
40176 prefix on the protocol element, eg. utf8esmtp.
40178 The following expansion operators can be used:
40180 ${utf8_domain_to_alabel:str}
40181 ${utf8_domain_from_alabel:str}
40182 ${utf8_localpart_to_alabel:str}
40183 ${utf8_localpart_from_alabel:str}
40186 .cindex utf8 "address downconversion"
40187 .cindex i18n "utf8 address downconversion"
40189 may use the following modifier:
40191 control = utf8_downconvert
40192 control = utf8_downconvert/<value>
40194 This sets a flag requiring that addresses are converted to
40195 a-label form before smtp delivery, for use in a
40196 Message Submission Agent context.
40197 If a value is appended it may be:
40199 &`1 `& (default) mandatory downconversion
40200 &`0 `& no downconversion
40201 &`-1 `& if SMTPUTF8 not supported by destination host
40204 If mua_wrapper is set, the utf8_downconvert control
40205 is initially set to -1.
40208 The smtp transport has an option &%utf8_downconvert%&.
40209 If set it must expand to one of the three values described above,
40210 and it overrides any previously set value.
40214 There is no explicit support for VRFY and EXPN.
40215 Configurations supporting these should inspect
40216 &$smtp_command_argument$& for an SMTPUTF8 argument.
40218 There is no support for LMTP on Unix sockets.
40219 Using the "lmtp" protocol option on an smtp transport,
40220 for LMTP over TCP, should work as expected.
40222 There is no support for DSN unitext handling,
40223 and no provision for converting logging from or to UTF-8.
40227 .section "MDA operations" SECTi18nMDA
40228 To aid in constructing names suitable for IMAP folders
40229 the following expansion operator can be used:
40231 ${imapfolder {<string>} {<sep>} {<specials>}}
40234 The string is converted from the charset specified by
40235 the "headers charset" command (in a filter file)
40236 or &%headers_charset%& main configuration option (otherwise),
40238 modified UTF-7 encoding specified by RFC 2060,
40239 with the following exception: All occurrences of <sep>
40240 (which has to be a single character)
40241 are replaced with periods ("."), and all periods and slashes that are not
40242 <sep> and are not in the <specials> string are BASE64 encoded.
40244 The third argument can be omitted, defaulting to an empty string.
40245 The second argument can be omitted, defaulting to "/".
40247 This is the encoding used by Courier for Maildir names on disk, and followed
40248 by many other IMAP servers.
40252 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
40253 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
40254 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
40257 Note that the source charset setting is vital, and also that characters
40258 must be representable in UTF-16.
40261 . ////////////////////////////////////////////////////////////////////////////
40262 . ////////////////////////////////////////////////////////////////////////////
40264 .chapter "Events" "CHAPevents" &&&
40268 The events mechanism in Exim can be used to intercept processing at a number
40269 of points. It was originally invented to give a way to do customised logging
40270 actions (for example, to a database) but can also be used to modify some
40271 processing actions.
40273 Most installations will never need to use Events.
40274 The support can be left out of a build by defining DISABLE_EVENT=yes
40275 in &_Local/Makefile_&.
40277 There are two major classes of events: main and transport.
40278 The main configuration option &%event_action%& controls reception events;
40279 a transport option &%event_action%& controls delivery events.
40281 Both options are a string which is expanded when the event fires.
40282 An example might look like:
40283 .cindex logging custom
40285 event_action = ${if eq {msg:delivery}{$event_name} \
40286 {${lookup pgsql {SELECT * FROM record_Delivery( \
40287 '${quote_pgsql:$sender_address_domain}',\
40288 '${quote_pgsql:${lc:$sender_address_local_part}}', \
40289 '${quote_pgsql:$domain}', \
40290 '${quote_pgsql:${lc:$local_part}}', \
40291 '${quote_pgsql:$host_address}', \
40292 '${quote_pgsql:${lc:$host}}', \
40293 '${quote_pgsql:$message_exim_id}')}} \
40297 Events have names which correspond to the point in process at which they fire.
40298 The name is placed in the variable &$event_name$& and the event action
40299 expansion must check this, as it will be called for every possible event type.
40301 The current list of events is:
40303 &`dane:fail after transport `& per connection
40304 &`msg:complete after main `& per message
40305 &`msg:delivery after transport `& per recipient
40306 &`msg:rcpt:host:defer after transport `& per recipient per host
40307 &`msg:rcpt:defer after transport `& per recipient
40308 &`msg:host:defer after transport `& per attempt
40309 &`msg:fail:delivery after transport `& per recipient
40310 &`msg:fail:internal after main `& per recipient
40311 &`tcp:connect before transport `& per connection
40312 &`tcp:close after transport `& per connection
40313 &`tls:cert before both `& per certificate in verification chain
40314 &`smtp:connect after transport `& per connection
40316 New event types may be added in future.
40318 The event name is a colon-separated list, defining the type of
40319 event in a tree of possibilities. It may be used as a list
40320 or just matched on as a whole. There will be no spaces in the name.
40322 The second column in the table above describes whether the event fires
40323 before or after the action is associates with. Those which fire before
40324 can be used to affect that action (more on this below).
40326 The third column in the table above says what section of the configuration
40327 should define the event action.
40329 An additional variable, &$event_data$&, is filled with information varying
40330 with the event type:
40332 &`dane:fail `& failure reason
40333 &`msg:delivery `& smtp confirmation message
40334 &`msg:fail:internal `& failure reason
40335 &`msg:fail:delivery `& smtp error message
40336 &`msg:rcpt:host:defer `& error string
40337 &`msg:rcpt:defer `& error string
40338 &`msg:host:defer `& error string
40339 &`tls:cert `& verification chain depth
40340 &`smtp:connect `& smtp banner
40343 The :defer events populate one extra variable: &$event_defer_errno$&.
40345 For complex operations an ACL expansion can be used in &%event_action%&
40346 however due to the multiple contexts that Exim operates in during
40347 the course of its processing:
40349 variables set in transport events will not be visible outside that
40352 acl_m variables in a server context are lost on a new connection,
40353 and after smtp helo/ehlo/mail/starttls/rset commands
40355 Using an ACL expansion with the logwrite modifier can be
40356 a useful way of writing to the main log.
40358 The expansion of the event_action option should normally
40359 return an empty string. Should it return anything else the
40360 following will be forced:
40362 &`tcp:connect `& do not connect
40363 &`tls:cert `& refuse verification
40364 &`smtp:connect `& close connection
40366 All other message types ignore the result string, and
40367 no other use is made of it.
40369 For a tcp:connect event, if the connection is being made to a proxy
40370 then the address and port variables will be that of the proxy and not
40373 For tls:cert events, if GnuTLS is in use this will trigger only per
40374 chain element received on the connection.
40375 For OpenSSL it will trigger for every chain element including those
40378 . ////////////////////////////////////////////////////////////////////////////
40379 . ////////////////////////////////////////////////////////////////////////////
40381 .chapter "Adding new drivers or lookup types" "CHID13" &&&
40382 "Adding drivers or lookups"
40383 .cindex "adding drivers"
40384 .cindex "new drivers, adding"
40385 .cindex "drivers" "adding new"
40386 The following actions have to be taken in order to add a new router, transport,
40387 authenticator, or lookup type to Exim:
40390 Choose a name for the driver or lookup type that does not conflict with any
40391 existing name; I will use &"newdriver"& in what follows.
40393 Add to &_src/EDITME_& the line:
40395 <&'type'&>&`_NEWDRIVER=yes`&
40397 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
40398 code is not to be included in the binary by default, comment this line out. You
40399 should also add any relevant comments about the driver or lookup type.
40401 Add to &_src/config.h.defaults_& the line:
40403 #define <type>_NEWDRIVER
40406 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
40407 and create a table entry as is done for all the other drivers and lookup types.
40409 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
40410 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
40411 Add your &`NEWDRIVER`& to that list.
40412 As long as the dynamic module would be named &_newdriver.so_&, you can use the
40413 simple form that most lookups have.
40415 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
40416 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
40417 driver or lookup type and add it to the definition of OBJ.
40419 Edit &_OS/Makefile-Base_& adding a &_.o_& file for the predefined-macros, to the
40420 definition of OBJ_MACRO. Add a set of line to do the compile also.
40422 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
40425 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
40426 as for other drivers and lookups.
40429 Then all you need to do is write the code! A good way to start is to make a
40430 proforma by copying an existing module of the same type, globally changing all
40431 occurrences of the name, and cutting out most of the code. Note that any
40432 options you create must be listed in alphabetical order, because the tables are
40433 searched using a binary chop procedure.
40435 There is a &_README_& file in each of the sub-directories of &_src_& describing
40436 the interface that is expected.
40441 . ////////////////////////////////////////////////////////////////////////////
40442 . ////////////////////////////////////////////////////////////////////////////
40444 . /////////////////////////////////////////////////////////////////////////////
40445 . These lines are processing instructions for the Simple DocBook Processor that
40446 . Philip Hazel has developed as a less cumbersome way of making PostScript and
40447 . PDFs than using xmlto and fop. They will be ignored by all other XML
40449 . /////////////////////////////////////////////////////////////////////////////
40454 foot_right_recto="&chaptertitle;"
40455 foot_right_verso="&chaptertitle;"
40459 .makeindex "Options index" "option"
40460 .makeindex "Variables index" "variable"
40461 .makeindex "Concept index" "concept"
40464 . /////////////////////////////////////////////////////////////////////////////
40465 . /////////////////////////////////////////////////////////////////////////////