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 "4.92"
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!
374 .cindex "documentation"
375 This edition of the Exim specification applies to version &version() of Exim.
376 Substantive changes from the &previousversion; edition are marked in some
377 renditions of this document; this paragraph is so marked if the rendition is
378 capable of showing a change indicator.
380 This document is very much a reference manual; it is not a tutorial. The reader
381 is expected to have some familiarity with the SMTP mail transfer protocol and
382 with general Unix system administration. Although there are some discussions
383 and examples in places, the information is mostly organized in a way that makes
384 it easy to look up, rather than in a natural order for sequential reading.
385 Furthermore, this manual aims to cover every aspect of Exim in detail, including
386 a number of rarely-used, special-purpose features that are unlikely to be of
389 .cindex "books about Exim"
390 An &"easier"& discussion of Exim which provides more in-depth explanatory,
391 introductory, and tutorial material can be found in a book entitled &'The Exim
392 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
393 (&url(https://www.uit.co.uk/exim-book/)).
395 The book also contains a chapter that gives a general introduction to SMTP and
396 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
397 with the latest release of Exim. (Note that the earlier book about Exim,
398 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
400 .cindex "Debian" "information sources"
401 If you are using a Debian distribution of Exim, you will find information about
402 Debian-specific features in the file
403 &_/usr/share/doc/exim4-base/README.Debian_&.
404 The command &(man update-exim.conf)& is another source of Debian-specific
407 .cindex "&_doc/NewStuff_&"
408 .cindex "&_doc/ChangeLog_&"
410 As Exim develops, there may be features in newer versions that have not
411 yet made it into this document, which is updated only when the most significant
412 digit of the fractional part of the version number changes. Specifications of
413 new features that are not yet in this manual are placed in the file
414 &_doc/NewStuff_& in the Exim distribution.
416 Some features may be classified as &"experimental"&. These may change
417 incompatibly while they are developing, or even be withdrawn. For this reason,
418 they are not documented in this manual. Information about experimental features
419 can be found in the file &_doc/experimental.txt_&.
421 All changes to Exim (whether new features, bug fixes, or other kinds of
422 change) are noted briefly in the file called &_doc/ChangeLog_&.
424 .cindex "&_doc/spec.txt_&"
425 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
426 that it can easily be searched with a text editor. Other files in the &_doc_&
430 .row &_OptionLists.txt_& "list of all options in alphabetical order"
431 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
432 .row &_exim.8_& "a man page of Exim's command line options"
433 .row &_experimental.txt_& "documentation of experimental features"
434 .row &_filter.txt_& "specification of the filter language"
435 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
436 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
437 .row &_openssl.txt_& "installing a current OpenSSL release"
440 The main specification and the specification of the filtering language are also
441 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
442 &<<SECTavail>>& below tells you how to get hold of these.
446 .section "FTP site and websites" "SECID2"
449 The primary site for Exim source distributions is the &%exim.org%& FTP site,
450 available over HTTPS, HTTP and FTP. These services, and the &%exim.org%&
451 website, are hosted at the University of Cambridge.
455 As well as Exim distribution tar files, the Exim website contains a number of
456 differently formatted versions of the documentation. A recent addition to the
457 online information is the Exim wiki (&url(https://wiki.exim.org)),
458 which contains what used to be a separate FAQ, as well as various other
459 examples, tips, and know-how that have been contributed by Exim users.
460 The wiki site should always redirect to the correct place, which is currently
461 provided by GitHub, and is open to editing by anyone with a GitHub account.
464 An Exim Bugzilla exists at &url(https://bugs.exim.org). You can use
465 this to report bugs, and also to add items to the wish list. Please search
466 first to check that you are not duplicating a previous entry.
467 Please do not ask for configuration help in the bug-tracker.
470 .section "Mailing lists" "SECID3"
471 .cindex "mailing lists" "for Exim users"
472 The following Exim mailing lists exist:
475 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
476 .row &'exim-users@exim.org'& "General discussion list"
477 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
478 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
481 You can subscribe to these lists, change your existing subscriptions, and view
482 or search the archives via the mailing lists link on the Exim home page.
483 .cindex "Debian" "mailing list for"
484 If you are using a Debian distribution of Exim, you may wish to subscribe to
485 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
488 &url(https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-exim4-users)
490 Please ask Debian-specific questions on that list and not on the general Exim
493 .section "Bug reports" "SECID5"
494 .cindex "bug reports"
495 .cindex "reporting bugs"
496 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
497 via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
498 whether some behaviour is a bug or not, the best thing to do is to post a
499 message to the &'exim-dev'& mailing list and have it discussed.
503 .section "Where to find the Exim distribution" "SECTavail"
505 .cindex "HTTPS download site"
506 .cindex "distribution" "FTP site"
507 .cindex "distribution" "https site"
508 The master distribution site for the Exim distribution is
510 &url(https://downloads.exim.org/)
512 The service is available over HTTPS, HTTP and FTP.
513 We encourage people to migrate to HTTPS.
515 The content served at &url(https://downloads.exim.org/) is identical to the
516 content served at &url(https://ftp.exim.org/pub/exim) and
517 &url(ftp://ftp.exim.org/pub/exim).
519 If accessing via a hostname containing &'ftp'&, then the file references that
520 follow are relative to the &_exim_& directories at these sites.
521 If accessing via the hostname &'downloads'& then the subdirectories described
522 here are top-level directories.
524 There are now quite a number of independent mirror sites around
525 the world. Those that I know about are listed in the file called &_Mirrors_&.
527 Within the top exim directory there are subdirectories called &_exim3_& (for
528 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
529 distributions), and &_Testing_& for testing versions. In the &_exim4_&
530 subdirectory, the current release can always be found in files called
534 &_exim-n.nn.tar.bz2_&
536 where &'n.nn'& is the highest such version number in the directory. The three
537 files contain identical data; the only difference is the type of compression.
538 The &_.xz_& file is usually the smallest, while the &_.gz_& file is the
539 most portable to old systems.
541 .cindex "distribution" "signing details"
542 .cindex "distribution" "public key"
543 .cindex "public key for signed distribution"
544 The distributions will be PGP signed by an individual key of the Release
545 Coordinator. This key will have a uid containing an email address in the
546 &'exim.org'& domain and will have signatures from other people, including
547 other Exim maintainers. We expect that the key will be in the "strong set" of
548 PGP keys. There should be a trust path to that key from the Exim Maintainer's
549 PGP keys, a version of which can be found in the release directory in the file
550 &_Exim-Maintainers-Keyring.asc_&. All keys used will be available in public keyserver pools,
551 such as &'pool.sks-keyservers.net'&.
553 At the time of the last update, releases were being made by Jeremy Harris and signed
554 with key &'0xBCE58C8CE41F32DF'&. Other recent keys used for signing are those
555 of Heiko Schlittermann, &'0x26101B62F69376CE'&,
556 and of Phil Pennock, &'0x4D1E900E14C1CC04'&.
558 The signatures for the tar bundles are in:
560 &_exim-n.nn.tar.xz.asc_&
561 &_exim-n.nn.tar.gz.asc_&
562 &_exim-n.nn.tar.bz2.asc_&
564 For each released version, the log of changes is made available in a
565 separate file in the directory &_ChangeLogs_& so that it is possible to
566 find out what has changed without having to download the entire distribution.
568 .cindex "documentation" "available formats"
569 The main distribution contains ASCII versions of this specification and other
570 documentation; other formats of the documents are available in separate files
571 inside the &_exim4_& directory of the FTP site:
573 &_exim-html-n.nn.tar.gz_&
574 &_exim-pdf-n.nn.tar.gz_&
575 &_exim-postscript-n.nn.tar.gz_&
576 &_exim-texinfo-n.nn.tar.gz_&
578 These tar files contain only the &_doc_& directory, not the complete
579 distribution, and are also available in &_.bz2_& and &_.xz_& forms.
582 .section "Limitations" "SECID6"
584 .cindex "limitations of Exim"
585 .cindex "bang paths" "not handled by Exim"
586 Exim is designed for use as an Internet MTA, and therefore handles addresses in
587 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
588 simple two-component bang paths can be converted by a straightforward rewriting
589 configuration. This restriction does not prevent Exim from being interfaced to
590 UUCP as a transport mechanism, provided that domain addresses are used.
592 .cindex "domainless addresses"
593 .cindex "address" "without domain"
594 Exim insists that every address it handles has a domain attached. For incoming
595 local messages, domainless addresses are automatically qualified with a
596 configured domain value. Configuration options specify from which remote
597 systems unqualified addresses are acceptable. These are then qualified on
600 .cindex "transport" "external"
601 .cindex "external transports"
602 The only external transport mechanisms that are currently implemented are SMTP
603 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
604 transport is available, and there are facilities for writing messages to files
605 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
606 to send messages to other transport mechanisms such as UUCP, provided they can
607 handle domain-style addresses. Batched SMTP input is also catered for.
609 Exim is not designed for storing mail for dial-in hosts. When the volumes of
610 such mail are large, it is better to get the messages &"delivered"& into files
611 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
614 Although Exim does have basic facilities for scanning incoming messages, these
615 are not comprehensive enough to do full virus or spam scanning. Such operations
616 are best carried out using additional specialized software packages. If you
617 compile Exim with the content-scanning extension, straightforward interfaces to
618 a number of common scanners are provided.
622 .section "Runtime configuration" "SECID7"
623 Exim's runtime configuration is held in a single text file that is divided
624 into a number of sections. The entries in this file consist of keywords and
625 values, in the style of Smail 3 configuration files. A default configuration
626 file which is suitable for simple online installations is provided in the
627 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
630 .section "Calling interface" "SECID8"
631 .cindex "Sendmail compatibility" "command line interface"
632 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
633 can be a straight replacement for &_/usr/lib/sendmail_& or
634 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
635 about Sendmail in order to run Exim. For actions other than sending messages,
636 Sendmail-compatible options also exist, but those that produce output (for
637 example, &%-bp%&, which lists the messages in the queue) do so in Exim's own
638 format. There are also some additional options that are compatible with Smail
639 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
640 documents all Exim's command line options. This information is automatically
641 made into the man page that forms part of the Exim distribution.
643 Control of messages in the queue can be done via certain privileged command
644 line options. There is also an optional monitor program called &'eximon'&,
645 which displays current information in an X window, and which contains a menu
646 interface to Exim's command line administration options.
650 .section "Terminology" "SECID9"
651 .cindex "terminology definitions"
652 .cindex "body of message" "definition of"
653 The &'body'& of a message is the actual data that the sender wants to transmit.
654 It is the last part of a message and is separated from the &'header'& (see
655 below) by a blank line.
657 .cindex "bounce message" "definition of"
658 When a message cannot be delivered, it is normally returned to the sender in a
659 delivery failure message or a &"non-delivery report"& (NDR). The term
660 &'bounce'& is commonly used for this action, and the error reports are often
661 called &'bounce messages'&. This is a convenient shorthand for &"delivery
662 failure error report"&. Such messages have an empty sender address in the
663 message's &'envelope'& (see below) to ensure that they cannot themselves give
664 rise to further bounce messages.
666 The term &'default'& appears frequently in this manual. It is used to qualify a
667 value which is used in the absence of any setting in the configuration. It may
668 also qualify an action which is taken unless a configuration setting specifies
671 The term &'defer'& is used when the delivery of a message to a specific
672 destination cannot immediately take place for some reason (a remote host may be
673 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
676 The word &'domain'& is sometimes used to mean all but the first component of a
677 host's name. It is &'not'& used in that sense here, where it normally refers to
678 the part of an email address following the @ sign.
680 .cindex "envelope, definition of"
681 .cindex "sender" "definition of"
682 A message in transit has an associated &'envelope'&, as well as a header and a
683 body. The envelope contains a sender address (to which bounce messages should
684 be delivered), and any number of recipient addresses. References to the
685 sender or the recipients of a message usually mean the addresses in the
686 envelope. An MTA uses these addresses for delivery, and for returning bounce
687 messages, not the addresses that appear in the header lines.
689 .cindex "message" "header, definition of"
690 .cindex "header section" "definition of"
691 The &'header'& of a message is the first part of a message's text, consisting
692 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
693 &'Subject:'&, etc. Long header lines can be split over several text lines by
694 indenting the continuations. The header is separated from the body by a blank
697 .cindex "local part" "definition of"
698 .cindex "domain" "definition of"
699 The term &'local part'&, which is taken from RFC 2822, is used to refer to the
700 part of an email address that precedes the @ sign. The part that follows the
701 @ sign is called the &'domain'& or &'mail domain'&.
703 .cindex "local delivery" "definition of"
704 .cindex "remote delivery, definition of"
705 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
706 delivery to a file or a pipe on the local host from delivery by SMTP over
707 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
708 host it is running on are &'remote'&.
710 .cindex "return path" "definition of"
711 &'Return path'& is another name that is used for the sender address in a
714 .cindex "queue" "definition of"
715 The term &'queue'& is used to refer to the set of messages awaiting delivery
716 because this term is in widespread use in the context of MTAs. However, in
717 Exim's case, the reality is more like a pool than a queue, because there is
718 normally no ordering of waiting messages.
720 .cindex "queue runner" "definition of"
721 The term &'queue runner'& is used to describe a process that scans the queue
722 and attempts to deliver those messages whose retry times have come. This term
723 is used by other MTAs and also relates to the command &%runq%&, but in Exim
724 the waiting messages are normally processed in an unpredictable order.
726 .cindex "spool directory" "definition of"
727 The term &'spool directory'& is used for a directory in which Exim keeps the
728 messages in its queue &-- that is, those that it is in the process of
729 delivering. This should not be confused with the directory in which local
730 mailboxes are stored, which is called a &"spool directory"& by some people. In
731 the Exim documentation, &"spool"& is always used in the first sense.
738 . ////////////////////////////////////////////////////////////////////////////
739 . ////////////////////////////////////////////////////////////////////////////
741 .chapter "Incorporated code" "CHID2"
742 .cindex "incorporated code"
743 .cindex "regular expressions" "library"
746 A number of pieces of external code are included in the Exim distribution.
749 Regular expressions are supported in the main Exim program and in the
750 Exim monitor using the freely-distributable PCRE library, copyright
751 © University of Cambridge. The source to PCRE is no longer shipped with
752 Exim, so you will need to use the version of PCRE shipped with your system,
753 or obtain and install the full version of the library from
754 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
756 .cindex "cdb" "acknowledgment"
757 Support for the cdb (Constant DataBase) lookup method is provided by code
758 contributed by Nigel Metheringham of (at the time he contributed it) Planet
759 Online Ltd. The implementation is completely contained within the code of Exim.
760 It does not link against an external cdb library. The code contains the
761 following statements:
764 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
766 This program is free software; you can redistribute it and/or modify it under
767 the terms of the GNU General Public License as published by the Free Software
768 Foundation; either version 2 of the License, or (at your option) any later
770 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
771 the spec and sample code for cdb can be obtained from
772 &url(https://cr.yp.to/cdb.html). This implementation borrows
773 some code from Dan Bernstein's implementation (which has no license
774 restrictions applied to it).
777 .cindex "SPA authentication"
778 .cindex "Samba project"
779 .cindex "Microsoft Secure Password Authentication"
780 Client support for Microsoft's &'Secure Password Authentication'& is provided
781 by code contributed by Marc Prud'hommeaux. Server support was contributed by
782 Tom Kistner. This includes code taken from the Samba project, which is released
786 .cindex "&'pwcheck'& daemon"
787 .cindex "&'pwauthd'& daemon"
788 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
789 by code taken from the Cyrus-SASL library and adapted by Alexander S.
790 Sabourenkov. The permission notice appears below, in accordance with the
791 conditions expressed therein.
794 Copyright © 2001 Carnegie Mellon University. All rights reserved.
796 Redistribution and use in source and binary forms, with or without
797 modification, are permitted provided that the following conditions
801 Redistributions of source code must retain the above copyright
802 notice, this list of conditions and the following disclaimer.
804 Redistributions in binary form must reproduce the above copyright
805 notice, this list of conditions and the following disclaimer in
806 the documentation and/or other materials provided with the
809 The name &"Carnegie Mellon University"& must not be used to
810 endorse or promote products derived from this software without
811 prior written permission. For permission or any other legal
812 details, please contact
814 Office of Technology Transfer
815 Carnegie Mellon University
817 Pittsburgh, PA 15213-3890
818 (412) 268-4387, fax: (412) 268-7395
819 tech-transfer@andrew.cmu.edu
822 Redistributions of any form whatsoever must retain the following
825 &"This product includes software developed by Computing Services
826 at Carnegie Mellon University (&url(https://www.cmu.edu/computing/)."&
828 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
829 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
830 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
831 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
832 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
833 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
834 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
839 .cindex "Exim monitor" "acknowledgment"
842 The Exim Monitor program, which is an X-Window application, includes
843 modified versions of the Athena StripChart and TextPop widgets.
844 This code is copyright by DEC and MIT, and their permission notice appears
845 below, in accordance with the conditions expressed therein.
848 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
849 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
853 Permission to use, copy, modify, and distribute this software and its
854 documentation for any purpose and without fee is hereby granted,
855 provided that the above copyright notice appear in all copies and that
856 both that copyright notice and this permission notice appear in
857 supporting documentation, and that the names of Digital or MIT not be
858 used in advertising or publicity pertaining to distribution of the
859 software without specific, written prior permission.
861 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
862 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
863 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
864 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
865 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
866 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
871 .cindex "opendmarc" "acknowledgment"
872 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
873 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
874 derived code are indicated in the respective source files. The full OpenDMARC
875 license is provided in the LICENSE.opendmarc file contained in the distributed
879 Many people have contributed code fragments, some large, some small, that were
880 not covered by any specific license requirements. It is assumed that the
881 contributors are happy to see their code incorporated into Exim under the GPL.
888 . ////////////////////////////////////////////////////////////////////////////
889 . ////////////////////////////////////////////////////////////////////////////
891 .chapter "How Exim receives and delivers mail" "CHID11" &&&
892 "Receiving and delivering mail"
895 .section "Overall philosophy" "SECID10"
896 .cindex "design philosophy"
897 Exim is designed to work efficiently on systems that are permanently connected
898 to the Internet and are handling a general mix of mail. In such circumstances,
899 most messages can be delivered immediately. Consequently, Exim does not
900 maintain independent queues of messages for specific domains or hosts, though
901 it does try to send several messages in a single SMTP connection after a host
902 has been down, and it also maintains per-host retry information.
905 .section "Policy control" "SECID11"
906 .cindex "policy control" "overview"
907 Policy controls are now an important feature of MTAs that are connected to the
908 Internet. Perhaps their most important job is to stop MTAs from being abused as
909 &"open relays"& by misguided individuals who send out vast amounts of
910 unsolicited junk and want to disguise its source. Exim provides flexible
911 facilities for specifying policy controls on incoming mail:
914 .cindex "&ACL;" "introduction"
915 Exim 4 (unlike previous versions of Exim) implements policy controls on
916 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
917 series of statements that may either grant or deny access. ACLs can be used at
918 several places in the SMTP dialogue while receiving a message from a remote
919 host. However, the most common places are after each RCPT command, and at the
920 very end of the message. The sysadmin can specify conditions for accepting or
921 rejecting individual recipients or the entire message, respectively, at these
922 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
925 An ACL is also available for locally generated, non-SMTP messages. In this
926 case, the only available actions are to accept or deny the entire message.
928 When Exim is compiled with the content-scanning extension, facilities are
929 provided in the ACL mechanism for passing the message to external virus and/or
930 spam scanning software. The result of such a scan is passed back to the ACL,
931 which can then use it to decide what to do with the message.
933 When a message has been received, either from a remote host or from the local
934 host, but before the final acknowledgment has been sent, a locally supplied C
935 function called &[local_scan()]& can be run to inspect the message and decide
936 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
937 is accepted, the list of recipients can be modified by the function.
939 Using the &[local_scan()]& mechanism is another way of calling external scanner
940 software. The &%SA-Exim%& add-on package works this way. It does not require
941 Exim to be compiled with the content-scanning extension.
943 After a message has been accepted, a further checking mechanism is available in
944 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
945 runs at the start of every delivery process.
950 .section "User filters" "SECID12"
951 .cindex "filter" "introduction"
952 .cindex "Sieve filter"
953 In a conventional Exim configuration, users are able to run private filters by
954 setting up appropriate &_.forward_& files in their home directories. See
955 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
956 configuration needed to support this, and the separate document entitled
957 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
958 of filtering are available:
961 Sieve filters are written in the standard filtering language that is defined
964 Exim filters are written in a syntax that is unique to Exim, but which is more
965 powerful than Sieve, which it pre-dates.
968 User filters are run as part of the routing process, described below.
972 .section "Message identification" "SECTmessiden"
973 .cindex "message ids" "details of format"
974 .cindex "format" "of message id"
975 .cindex "id of message"
980 Every message handled by Exim is given a &'message id'& which is sixteen
981 characters long. It is divided into three parts, separated by hyphens, for
982 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
983 normally encoding numbers in base 62. However, in the Darwin operating
984 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
985 (avoiding the use of lower case letters) is used instead, because the message
986 id is used to construct filenames, and the names of files in those systems are
987 not always case-sensitive.
989 .cindex "pid (process id)" "re-use of"
990 The detail of the contents of the message id have changed as Exim has evolved.
991 Earlier versions relied on the operating system not re-using a process id (pid)
992 within one second. On modern operating systems, this assumption can no longer
993 be made, so the algorithm had to be changed. To retain backward compatibility,
994 the format of the message id was retained, which is why the following rules are
998 The first six characters of the message id are the time at which the message
999 started to be received, to a granularity of one second. That is, this field
1000 contains the number of seconds since the start of the epoch (the normal Unix
1001 way of representing the date and time of day).
1003 After the first hyphen, the next six characters are the id of the process that
1004 received the message.
1006 There are two different possibilities for the final two characters:
1008 .oindex "&%localhost_number%&"
1009 If &%localhost_number%& is not set, this value is the fractional part of the
1010 time of reception, normally in units of 1/2000 of a second, but for systems
1011 that must use base 36 instead of base 62 (because of case-insensitive file
1012 systems), the units are 1/1000 of a second.
1014 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1015 the fractional part of the time, which in this case is in units of 1/200
1016 (1/100) of a second.
1020 After a message has been received, Exim waits for the clock to tick at the
1021 appropriate resolution before proceeding, so that if another message is
1022 received by the same process, or by another process with the same (re-used)
1023 pid, it is guaranteed that the time will be different. In most cases, the clock
1024 will already have ticked while the message was being received.
1027 .section "Receiving mail" "SECID13"
1028 .cindex "receiving mail"
1029 .cindex "message" "reception"
1030 The only way Exim can receive mail from another host is using SMTP over
1031 TCP/IP, in which case the sender and recipient addresses are transferred using
1032 SMTP commands. However, from a locally running process (such as a user's MUA),
1033 there are several possibilities:
1036 If the process runs Exim with the &%-bm%& option, the message is read
1037 non-interactively (usually via a pipe), with the recipients taken from the
1038 command line, or from the body of the message if &%-t%& is also used.
1040 If the process runs Exim with the &%-bS%& option, the message is also read
1041 non-interactively, but in this case the recipients are listed at the start of
1042 the message in a series of SMTP RCPT commands, terminated by a DATA
1043 command. This is called &"batch SMTP"& format,
1044 but it isn't really SMTP. The SMTP commands are just another way of passing
1045 envelope addresses in a non-interactive submission.
1047 If the process runs Exim with the &%-bs%& option, the message is read
1048 interactively, using the SMTP protocol. A two-way pipe is normally used for
1049 passing data between the local process and the Exim process.
1050 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1051 example, the ACLs for SMTP commands are used for this form of submission.
1053 A local process may also make a TCP/IP call to the host's loopback address
1054 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1055 does not treat the loopback address specially. It treats all such connections
1056 in the same way as connections from other hosts.
1060 .cindex "message sender, constructed by Exim"
1061 .cindex "sender" "constructed by Exim"
1062 In the three cases that do not involve TCP/IP, the sender address is
1063 constructed from the login name of the user that called Exim and a default
1064 qualification domain (which can be set by the &%qualify_domain%& configuration
1065 option). For local or batch SMTP, a sender address that is passed using the
1066 SMTP MAIL command is ignored. However, the system administrator may allow
1067 certain users (&"trusted users"&) to specify a different sender addresses
1068 unconditionally, or all users to specify certain forms of different sender
1069 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1070 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1071 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1072 users to change sender addresses.
1074 Messages received by either of the non-interactive mechanisms are subject to
1075 checking by the non-SMTP ACL if one is defined. Messages received using SMTP
1076 (either over TCP/IP or interacting with a local process) can be checked by a
1077 number of ACLs that operate at different times during the SMTP session. Either
1078 individual recipients or the entire message can be rejected if local policy
1079 requirements are not met. The &[local_scan()]& function (see chapter
1080 &<<CHAPlocalscan>>&) is run for all incoming messages.
1082 Exim can be configured not to start a delivery process when a message is
1083 received; this can be unconditional, or depend on the number of incoming SMTP
1084 connections or the system load. In these situations, new messages wait on the
1085 queue until a queue runner process picks them up. However, in standard
1086 configurations under normal conditions, delivery is started as soon as a
1087 message is received.
1093 .section "Handling an incoming message" "SECID14"
1094 .cindex "spool directory" "files that hold a message"
1095 .cindex "file" "how a message is held"
1096 When Exim accepts a message, it writes two files in its spool directory. The
1097 first contains the envelope information, the current status of the message, and
1098 the header lines, and the second contains the body of the message. The names of
1099 the two spool files consist of the message id, followed by &`-H`& for the
1100 file containing the envelope and header, and &`-D`& for the data file.
1102 .cindex "spool directory" "&_input_& sub-directory"
1103 By default, all these message files are held in a single directory called
1104 &_input_& inside the general Exim spool directory. Some operating systems do
1105 not perform very well if the number of files in a directory gets large; to
1106 improve performance in such cases, the &%split_spool_directory%& option can be
1107 used. This causes Exim to split up the input files into 62 sub-directories
1108 whose names are single letters or digits. When this is done, the queue is
1109 processed one sub-directory at a time instead of all at once, which can improve
1110 overall performance even when there are not enough files in each directory to
1111 affect file system performance.
1113 The envelope information consists of the address of the message's sender and
1114 the addresses of the recipients. This information is entirely separate from
1115 any addresses contained in the header lines. The status of the message includes
1116 a list of recipients who have already received the message. The format of the
1117 first spool file is described in chapter &<<CHAPspool>>&.
1119 .cindex "rewriting" "addresses"
1120 Address rewriting that is specified in the rewrite section of the configuration
1121 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1122 both in the header lines and the envelope, at the time the message is accepted.
1123 If during the course of delivery additional addresses are generated (for
1124 example, via aliasing), these new addresses are rewritten as soon as they are
1125 generated. At the time a message is actually delivered (transported) further
1126 rewriting can take place; because this is a transport option, it can be
1127 different for different forms of delivery. It is also possible to specify the
1128 addition or removal of certain header lines at the time the message is
1129 delivered (see chapters &<<CHAProutergeneric>>& and
1130 &<<CHAPtransportgeneric>>&).
1134 .section "Life of a message" "SECID15"
1135 .cindex "message" "life of"
1136 .cindex "message" "frozen"
1137 A message remains in the spool directory until it is completely delivered to
1138 its recipients or to an error address, or until it is deleted by an
1139 administrator or by the user who originally created it. In cases when delivery
1140 cannot proceed &-- for example when a message can neither be delivered to its
1141 recipients nor returned to its sender, the message is marked &"frozen"& on the
1142 spool, and no more deliveries are attempted.
1144 .cindex "frozen messages" "thawing"
1145 .cindex "message" "thawing frozen"
1146 An administrator can &"thaw"& such messages when the problem has been
1147 corrected, and can also freeze individual messages by hand if necessary. In
1148 addition, an administrator can force a delivery error, causing a bounce message
1151 .oindex "&%timeout_frozen_after%&"
1152 .oindex "&%ignore_bounce_errors_after%&"
1153 There are options called &%ignore_bounce_errors_after%& and
1154 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1155 The first applies only to frozen bounces, the second to all frozen messages.
1157 .cindex "message" "log file for"
1158 .cindex "log" "file for each message"
1159 While Exim is working on a message, it writes information about each delivery
1160 attempt to its main log file. This includes successful, unsuccessful, and
1161 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1162 lines are also written to a separate &'message log'& file for each message.
1163 These logs are solely for the benefit of the administrator and are normally
1164 deleted along with the spool files when processing of a message is complete.
1165 The use of individual message logs can be disabled by setting
1166 &%no_message_logs%&; this might give an improvement in performance on very busy
1169 .cindex "journal file"
1170 .cindex "file" "journal"
1171 All the information Exim itself needs to set up a delivery is kept in the first
1172 spool file, along with the header lines. When a successful delivery occurs, the
1173 address is immediately written at the end of a journal file, whose name is the
1174 message id followed by &`-J`&. At the end of a delivery run, if there are some
1175 addresses left to be tried again later, the first spool file (the &`-H`& file)
1176 is updated to indicate which these are, and the journal file is then deleted.
1177 Updating the spool file is done by writing a new file and renaming it, to
1178 minimize the possibility of data loss.
1180 Should the system or Exim crash after a successful delivery but before
1181 the spool file has been updated, the journal is left lying around. The next
1182 time Exim attempts to deliver the message, it reads the journal file and
1183 updates the spool file before proceeding. This minimizes the chances of double
1184 deliveries caused by crashes.
1188 .section "Processing an address for delivery" "SECTprocaddress"
1189 .cindex "drivers" "definition of"
1190 .cindex "router" "definition of"
1191 .cindex "transport" "definition of"
1192 The main delivery processing elements of Exim are called &'routers'& and
1193 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1194 number of them is provided in the source distribution, and compile-time options
1195 specify which ones are included in the binary. Runtime options specify which
1196 ones are actually used for delivering messages.
1198 .cindex "drivers" "instance definition"
1199 Each driver that is specified in the runtime configuration is an &'instance'&
1200 of that particular driver type. Multiple instances are allowed; for example,
1201 you can set up several different &(smtp)& transports, each with different
1202 option values that might specify different ports or different timeouts. Each
1203 instance has its own identifying name. In what follows we will normally use the
1204 instance name when discussing one particular instance (that is, one specific
1205 configuration of the driver), and the generic driver name when discussing
1206 the driver's features in general.
1208 A &'router'& is a driver that operates on an address, either determining how
1209 its delivery should happen, by assigning it to a specific transport, or
1210 converting the address into one or more new addresses (for example, via an
1211 alias file). A router may also explicitly choose to fail an address, causing it
1214 A &'transport'& is a driver that transmits a copy of the message from Exim's
1215 spool to some destination. There are two kinds of transport: for a &'local'&
1216 transport, the destination is a file or a pipe on the local host, whereas for a
1217 &'remote'& transport the destination is some other host. A message is passed
1218 to a specific transport as a result of successful routing. If a message has
1219 several recipients, it may be passed to a number of different transports.
1221 .cindex "preconditions" "definition of"
1222 An address is processed by passing it to each configured router instance in
1223 turn, subject to certain preconditions, until a router accepts the address or
1224 specifies that it should be bounced. We will describe this process in more
1225 detail shortly. First, as a simple example, we consider how each recipient
1226 address in a message is processed in a small configuration of three routers.
1228 To make this a more concrete example, it is described in terms of some actual
1229 routers, but remember, this is only an example. You can configure Exim's
1230 routers in many different ways, and there may be any number of routers in a
1233 The first router that is specified in a configuration is often one that handles
1234 addresses in domains that are not recognized specifically by the local host.
1235 Typically these are addresses for arbitrary domains on the Internet. A precondition
1236 is set up which looks for the special domains known to the host (for example,
1237 its own domain name), and the router is run for addresses that do &'not'&
1238 match. Typically, this is a router that looks up domains in the DNS in order to
1239 find the hosts to which this address routes. If it succeeds, the address is
1240 assigned to a suitable SMTP transport; if it does not succeed, the router is
1241 configured to fail the address.
1243 The second router is reached only when the domain is recognized as one that
1244 &"belongs"& to the local host. This router does redirection &-- also known as
1245 aliasing and forwarding. When it generates one or more new addresses from the
1246 original, each of them is routed independently from the start. Otherwise, the
1247 router may cause an address to fail, or it may simply decline to handle the
1248 address, in which case the address is passed to the next router.
1250 The final router in many configurations is one that checks to see if the
1251 address belongs to a local mailbox. The precondition may involve a check to
1252 see if the local part is the name of a login account, or it may look up the
1253 local part in a file or a database. If its preconditions are not met, or if
1254 the router declines, we have reached the end of the routers. When this happens,
1255 the address is bounced.
1259 .section "Processing an address for verification" "SECID16"
1260 .cindex "router" "for verification"
1261 .cindex "verifying address" "overview"
1262 As well as being used to decide how to deliver to an address, Exim's routers
1263 are also used for &'address verification'&. Verification can be requested as
1264 one of the checks to be performed in an ACL for incoming messages, on both
1265 sender and recipient addresses, and it can be tested using the &%-bv%& and
1266 &%-bvs%& command line options.
1268 When an address is being verified, the routers are run in &"verify mode"&. This
1269 does not affect the way the routers work, but it is a state that can be
1270 detected. By this means, a router can be skipped or made to behave differently
1271 when verifying. A common example is a configuration in which the first router
1272 sends all messages to a message-scanning program unless they have been
1273 previously scanned. Thus, the first router accepts all addresses without any
1274 checking, making it useless for verifying. Normally, the &%no_verify%& option
1275 would be set for such a router, causing it to be skipped in verify mode.
1280 .section "Running an individual router" "SECTrunindrou"
1281 .cindex "router" "running details"
1282 .cindex "preconditions" "checking"
1283 .cindex "router" "result of running"
1284 As explained in the example above, a number of preconditions are checked before
1285 running a router. If any are not met, the router is skipped, and the address is
1286 passed to the next router. When all the preconditions on a router &'are'& met,
1287 the router is run. What happens next depends on the outcome, which is one of
1291 &'accept'&: The router accepts the address, and either assigns it to a
1292 transport or generates one or more &"child"& addresses. Processing the
1293 original address ceases
1294 .oindex "&%unseen%&"
1295 unless the &%unseen%& option is set on the router. This option
1296 can be used to set up multiple deliveries with different routing (for example,
1297 for keeping archive copies of messages). When &%unseen%& is set, the address is
1298 passed to the next router. Normally, however, an &'accept'& return marks the
1301 Any child addresses generated by the router are processed independently,
1302 starting with the first router by default. It is possible to change this by
1303 setting the &%redirect_router%& option to specify which router to start at for
1304 child addresses. Unlike &%pass_router%& (see below) the router specified by
1305 &%redirect_router%& may be anywhere in the router configuration.
1307 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1308 requests that the address be passed to another router. By default, the address
1309 is passed to the next router, but this can be changed by setting the
1310 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1311 must be below the current router (to avoid loops).
1313 &'decline'&: The router declines to accept the address because it does not
1314 recognize it at all. By default, the address is passed to the next router, but
1315 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1316 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1317 &'decline'& into &'fail'&.
1319 &'fail'&: The router determines that the address should fail, and queues it for
1320 the generation of a bounce message. There is no further processing of the
1321 original address unless &%unseen%& is set on the router.
1323 &'defer'&: The router cannot handle the address at the present time. (A
1324 database may be offline, or a DNS lookup may have timed out.) No further
1325 processing of the address happens in this delivery attempt. It is tried again
1326 next time the message is considered for delivery.
1328 &'error'&: There is some error in the router (for example, a syntax error in
1329 its configuration). The action is as for defer.
1332 If an address reaches the end of the routers without having been accepted by
1333 any of them, it is bounced as unrouteable. The default error message in this
1334 situation is &"unrouteable address"&, but you can set your own message by
1335 making use of the &%cannot_route_message%& option. This can be set for any
1336 router; the value from the last router that &"saw"& the address is used.
1338 Sometimes while routing you want to fail a delivery when some conditions are
1339 met but others are not, instead of passing the address on for further routing.
1340 You can do this by having a second router that explicitly fails the delivery
1341 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1342 facility for this purpose.
1345 .section "Duplicate addresses" "SECID17"
1346 .cindex "case of local parts"
1347 .cindex "address duplicate, discarding"
1348 .cindex "duplicate addresses"
1349 Once routing is complete, Exim scans the addresses that are assigned to local
1350 and remote transports and discards any duplicates that it finds. During this
1351 check, local parts are treated case-sensitively. This happens only when
1352 actually delivering a message; when testing routers with &%-bt%&, all the
1353 routed addresses are shown.
1357 .section "Router preconditions" "SECTrouprecon"
1358 .cindex "router" "preconditions, order of processing"
1359 .cindex "preconditions" "order of processing"
1360 The preconditions that are tested for each router are listed below, in the
1361 order in which they are tested. The individual configuration options are
1362 described in more detail in chapter &<<CHAProutergeneric>>&.
1365 .cindex affix "router precondition"
1366 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1367 the local parts handled by the router may or must have certain prefixes and/or
1368 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1369 skipped. These conditions are tested first. When an affix is present, it is
1370 removed from the local part before further processing, including the evaluation
1371 of any other conditions.
1373 Routers can be designated for use only when not verifying an address, that is,
1374 only when routing it for delivery (or testing its delivery routing). If the
1375 &%verify%& option is set false, the router is skipped when Exim is verifying an
1377 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1378 &%verify_recipient%&, which independently control the use of the router for
1379 sender and recipient verification. You can set these options directly if
1380 you want a router to be used for only one type of verification.
1381 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1383 If the &%address_test%& option is set false, the router is skipped when Exim is
1384 run with the &%-bt%& option to test an address routing. This can be helpful
1385 when the first router sends all new messages to a scanner of some sort; it
1386 makes it possible to use &%-bt%& to test subsequent delivery routing without
1387 having to simulate the effect of the scanner.
1389 Routers can be designated for use only when verifying an address, as
1390 opposed to routing it for delivery. The &%verify_only%& option controls this.
1391 Again, cutthrough delivery counts as a verification.
1393 Individual routers can be explicitly skipped when running the routers to
1394 check an address given in the SMTP EXPN command (see the &%expn%& option).
1396 If the &%domains%& option is set, the domain of the address must be in the set
1397 of domains that it defines.
1399 .vindex "&$local_part_prefix$&"
1400 .vindex "&$local_part$&"
1401 .vindex "&$local_part_suffix$&"
1402 .cindex affix "router precondition"
1403 If the &%local_parts%& option is set, the local part of the address must be in
1404 the set of local parts that it defines. If &%local_part_prefix%& or
1405 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1406 part before this check. If you want to do precondition tests on local parts
1407 that include affixes, you can do so by using a &%condition%& option (see below)
1408 that uses the variables &$local_part$&, &$local_part_prefix$&, and
1409 &$local_part_suffix$& as necessary.
1411 .vindex "&$local_user_uid$&"
1412 .vindex "&$local_user_gid$&"
1414 If the &%check_local_user%& option is set, the local part must be the name of
1415 an account on the local host. If this check succeeds, the uid and gid of the
1416 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1417 user's home directory is placed in &$home$&; these values can be used in the
1418 remaining preconditions.
1420 If the &%router_home_directory%& option is set, it is expanded at this point,
1421 because it overrides the value of &$home$&. If this expansion were left till
1422 later, the value of &$home$& as set by &%check_local_user%& would be used in
1423 subsequent tests. Having two different values of &$home$& in the same router
1424 could lead to confusion.
1426 If the &%senders%& option is set, the envelope sender address must be in the
1427 set of addresses that it defines.
1429 If the &%require_files%& option is set, the existence or non-existence of
1430 specified files is tested.
1432 .cindex "customizing" "precondition"
1433 If the &%condition%& option is set, it is evaluated and tested. This option
1434 uses an expanded string to allow you to set up your own custom preconditions.
1435 Expanded strings are described in chapter &<<CHAPexpand>>&.
1439 Note that &%require_files%& comes near the end of the list, so you cannot use
1440 it to check for the existence of a file in which to lookup up a domain, local
1441 part, or sender. However, as these options are all expanded, you can use the
1442 &%exists%& expansion condition to make such tests within each condition. The
1443 &%require_files%& option is intended for checking files that the router may be
1444 going to use internally, or which are needed by a specific transport (for
1445 example, &_.procmailrc_&).
1449 .section "Delivery in detail" "SECID18"
1450 .cindex "delivery" "in detail"
1451 When a message is to be delivered, the sequence of events is as follows:
1454 If a system-wide filter file is specified, the message is passed to it. The
1455 filter may add recipients to the message, replace the recipients, discard the
1456 message, cause a new message to be generated, or cause the message delivery to
1457 fail. The format of the system filter file is the same as for Exim user filter
1458 files, described in the separate document entitled &'Exim's interfaces to mail
1460 .cindex "Sieve filter" "not available for system filter"
1461 (&*Note*&: Sieve cannot be used for system filter files.)
1463 Some additional features are available in system filters &-- see chapter
1464 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1465 filter only once per delivery attempt, however many recipients it has. However,
1466 if there are several delivery attempts because one or more addresses could not
1467 be immediately delivered, the system filter is run each time. The filter
1468 condition &%first_delivery%& can be used to detect the first run of the system
1471 Each recipient address is offered to each configured router, in turn, subject to
1472 its preconditions, until one is able to handle it. If no router can handle the
1473 address, that is, if they all decline, the address is failed. Because routers
1474 can be targeted at particular domains, several locally handled domains can be
1475 processed entirely independently of each other.
1477 .cindex "routing" "loops in"
1478 .cindex "loop" "while routing"
1479 A router that accepts an address may assign it to a local or a remote
1480 transport. However, the transport is not run at this time. Instead, the address
1481 is placed on a list for the particular transport, which will be run later.
1482 Alternatively, the router may generate one or more new addresses (typically
1483 from alias, forward, or filter files). New addresses are fed back into this
1484 process from the top, but in order to avoid loops, a router ignores any address
1485 which has an identically-named ancestor that was processed by itself.
1487 When all the routing has been done, addresses that have been successfully
1488 handled are passed to their assigned transports. When local transports are
1489 doing real local deliveries, they handle only one address at a time, but if a
1490 local transport is being used as a pseudo-remote transport (for example, to
1491 collect batched SMTP messages for transmission by some other means) multiple
1492 addresses can be handled. Remote transports can always handle more than one
1493 address at a time, but can be configured not to do so, or to restrict multiple
1494 addresses to the same domain.
1496 Each local delivery to a file or a pipe runs in a separate process under a
1497 non-privileged uid, and these deliveries are run one at a time. Remote
1498 deliveries also run in separate processes, normally under a uid that is private
1499 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1500 run in parallel. The maximum number of simultaneous remote deliveries for any
1501 one message is set by the &%remote_max_parallel%& option.
1502 The order in which deliveries are done is not defined, except that all local
1503 deliveries happen before any remote deliveries.
1505 .cindex "queue runner"
1506 When it encounters a local delivery during a queue run, Exim checks its retry
1507 database to see if there has been a previous temporary delivery failure for the
1508 address before running the local transport. If there was a previous failure,
1509 Exim does not attempt a new delivery until the retry time for the address is
1510 reached. However, this happens only for delivery attempts that are part of a
1511 queue run. Local deliveries are always attempted when delivery immediately
1512 follows message reception, even if retry times are set for them. This makes for
1513 better behaviour if one particular message is causing problems (for example,
1514 causing quota overflow, or provoking an error in a filter file).
1516 .cindex "delivery" "retry in remote transports"
1517 Remote transports do their own retry handling, since an address may be
1518 deliverable to one of a number of hosts, each of which may have a different
1519 retry time. If there have been previous temporary failures and no host has
1520 reached its retry time, no delivery is attempted, whether in a queue run or
1521 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1523 If there were any permanent errors, a bounce message is returned to an
1524 appropriate address (the sender in the common case), with details of the error
1525 for each failing address. Exim can be configured to send copies of bounce
1526 messages to other addresses.
1528 .cindex "delivery" "deferral"
1529 If one or more addresses suffered a temporary failure, the message is left on
1530 the queue, to be tried again later. Delivery of these addresses is said to be
1533 When all the recipient addresses have either been delivered or bounced,
1534 handling of the message is complete. The spool files and message log are
1535 deleted, though the message log can optionally be preserved if required.
1541 .section "Retry mechanism" "SECID19"
1542 .cindex "delivery" "retry mechanism"
1543 .cindex "retry" "description of mechanism"
1544 .cindex "queue runner"
1545 Exim's mechanism for retrying messages that fail to get delivered at the first
1546 attempt is the queue runner process. You must either run an Exim daemon that
1547 uses the &%-q%& option with a time interval to start queue runners at regular
1548 intervals or use some other means (such as &'cron'&) to start them. If you do
1549 not arrange for queue runners to be run, messages that fail temporarily at the
1550 first attempt will remain in your queue forever. A queue runner process works
1551 its way through the queue, one message at a time, trying each delivery that has
1552 passed its retry time.
1553 You can run several queue runners at once.
1555 Exim uses a set of configured rules to determine when next to retry the failing
1556 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1557 should give up trying to deliver to the address, at which point it generates a
1558 bounce message. If no retry rules are set for a particular host, address, and
1559 error combination, no retries are attempted, and temporary errors are treated
1564 .section "Temporary delivery failure" "SECID20"
1565 .cindex "delivery" "temporary failure"
1566 There are many reasons why a message may not be immediately deliverable to a
1567 particular address. Failure to connect to a remote machine (because it, or the
1568 connection to it, is down) is one of the most common. Temporary failures may be
1569 detected during routing as well as during the transport stage of delivery.
1570 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1571 is on a file system where the user is over quota. Exim can be configured to
1572 impose its own quotas on local mailboxes; where system quotas are set they will
1575 If a host is unreachable for a period of time, a number of messages may be
1576 waiting for it by the time it recovers, and sending them in a single SMTP
1577 connection is clearly beneficial. Whenever a delivery to a remote host is
1579 .cindex "hints database" "deferred deliveries"
1580 Exim makes a note in its hints database, and whenever a successful
1581 SMTP delivery has happened, it looks to see if any other messages are waiting
1582 for the same host. If any are found, they are sent over the same SMTP
1583 connection, subject to a configuration limit as to the maximum number in any
1588 .section "Permanent delivery failure" "SECID21"
1589 .cindex "delivery" "permanent failure"
1590 .cindex "bounce message" "when generated"
1591 When a message cannot be delivered to some or all of its intended recipients, a
1592 bounce message is generated. Temporary delivery failures turn into permanent
1593 errors when their timeout expires. All the addresses that fail in a given
1594 delivery attempt are listed in a single message. If the original message has
1595 many recipients, it is possible for some addresses to fail in one delivery
1596 attempt and others to fail subsequently, giving rise to more than one bounce
1597 message. The wording of bounce messages can be customized by the administrator.
1598 See chapter &<<CHAPemsgcust>>& for details.
1600 .cindex "&'X-Failed-Recipients:'& header line"
1601 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1602 failed addresses, for the benefit of programs that try to analyse such messages
1605 .cindex "bounce message" "recipient of"
1606 A bounce message is normally sent to the sender of the original message, as
1607 obtained from the message's envelope. For incoming SMTP messages, this is the
1608 address given in the MAIL command. However, when an address is expanded via a
1609 forward or alias file, an alternative address can be specified for delivery
1610 failures of the generated addresses. For a mailing list expansion (see section
1611 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1616 .section "Failures to deliver bounce messages" "SECID22"
1617 .cindex "bounce message" "failure to deliver"
1618 If a bounce message (either locally generated or received from a remote host)
1619 itself suffers a permanent delivery failure, the message is left in the queue,
1620 but it is frozen, awaiting the attention of an administrator. There are options
1621 that can be used to make Exim discard such failed messages, or to keep them
1622 for only a short time (see &%timeout_frozen_after%& and
1623 &%ignore_bounce_errors_after%&).
1629 . ////////////////////////////////////////////////////////////////////////////
1630 . ////////////////////////////////////////////////////////////////////////////
1632 .chapter "Building and installing Exim" "CHID3"
1633 .scindex IIDbuex "building Exim"
1635 .section "Unpacking" "SECID23"
1636 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1637 creates a directory with the name of the current release (for example,
1638 &_exim-&version()_&) into which the following files are placed:
1641 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1642 .irow &_CHANGES_& "contains a reference to where changes are &&&
1644 .irow &_LICENCE_& "the GNU General Public Licence"
1645 .irow &_Makefile_& "top-level make file"
1646 .irow &_NOTICE_& "conditions for the use of Exim"
1647 .irow &_README_& "list of files, directories and simple build &&&
1651 Other files whose names begin with &_README_& may also be present. The
1652 following subdirectories are created:
1655 .irow &_Local_& "an empty directory for local configuration files"
1656 .irow &_OS_& "OS-specific files"
1657 .irow &_doc_& "documentation files"
1658 .irow &_exim_monitor_& "source files for the Exim monitor"
1659 .irow &_scripts_& "scripts used in the build process"
1660 .irow &_src_& "remaining source files"
1661 .irow &_util_& "independent utilities"
1664 The main utility programs are contained in the &_src_& directory and are built
1665 with the Exim binary. The &_util_& directory contains a few optional scripts
1666 that may be useful to some sites.
1669 .section "Multiple machine architectures and operating systems" "SECID24"
1670 .cindex "building Exim" "multiple OS/architectures"
1671 The building process for Exim is arranged to make it easy to build binaries for
1672 a number of different architectures and operating systems from the same set of
1673 source files. Compilation does not take place in the &_src_& directory.
1674 Instead, a &'build directory'& is created for each architecture and operating
1676 .cindex "symbolic link" "to build directory"
1677 Symbolic links to the sources are installed in this directory, which is where
1678 the actual building takes place. In most cases, Exim can discover the machine
1679 architecture and operating system for itself, but the defaults can be
1680 overridden if necessary.
1681 .cindex compiler requirements
1682 .cindex compiler version
1683 A C99-capable compiler will be required for the build.
1686 .section "PCRE library" "SECTpcre"
1687 .cindex "PCRE library"
1688 Exim no longer has an embedded PCRE library as the vast majority of
1689 modern systems include PCRE as a system library, although you may need to
1690 install the PCRE package or the PCRE development package for your operating
1691 system. If your system has a normal PCRE installation the Exim build
1692 process will need no further configuration. If the library or the
1693 headers are in an unusual location you will need to either set the PCRE_LIBS
1694 and INCLUDE directives appropriately,
1695 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1696 If your operating system has no
1697 PCRE support then you will need to obtain and build the current PCRE
1698 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1699 More information on PCRE is available at &url(https://www.pcre.org/).
1701 .section "DBM libraries" "SECTdb"
1702 .cindex "DBM libraries" "discussion of"
1703 .cindex "hints database" "DBM files used for"
1704 Even if you do not use any DBM files in your configuration, Exim still needs a
1705 DBM library in order to operate, because it uses indexed files for its hints
1706 databases. Unfortunately, there are a number of DBM libraries in existence, and
1707 different operating systems often have different ones installed.
1709 .cindex "Solaris" "DBM library for"
1710 .cindex "IRIX, DBM library for"
1711 .cindex "BSD, DBM library for"
1712 .cindex "Linux, DBM library for"
1713 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1714 Linux distribution, the DBM configuration should happen automatically, and you
1715 may be able to ignore this section. Otherwise, you may have to learn more than
1716 you would like about DBM libraries from what follows.
1718 .cindex "&'ndbm'& DBM library"
1719 Licensed versions of Unix normally contain a library of DBM functions operating
1720 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1721 versions of Unix seem to vary in what they contain as standard. In particular,
1722 some early versions of Linux have no default DBM library, and different
1723 distributors have chosen to bundle different libraries with their packaged
1724 versions. However, the more recent releases seem to have standardized on the
1725 Berkeley DB library.
1727 Different DBM libraries have different conventions for naming the files they
1728 use. When a program opens a file called &_dbmfile_&, there are several
1732 A traditional &'ndbm'& implementation, such as that supplied as part of
1733 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1735 .cindex "&'gdbm'& DBM library"
1736 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1737 compatibility interface it makes two different hard links to it with names
1738 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1739 filename is used unmodified.
1741 .cindex "Berkeley DB library"
1742 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1743 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1744 programmer exactly the same as the traditional &'ndbm'& implementation.
1746 If the Berkeley package is used in its native mode, it operates on a single
1747 file called &_dbmfile_&; the programmer's interface is somewhat different to
1748 the traditional &'ndbm'& interface.
1750 To complicate things further, there are several very different versions of the
1751 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1752 2.&'x'& and 3.&'x'& were current for a while, but the latest versions when Exim last revamped support were numbered 4.&'x'&.
1753 Maintenance of some of the earlier releases has ceased. All versions of
1754 Berkeley DB could be obtained from
1755 &url(http://www.sleepycat.com/), which is now a redirect to their new owner's
1756 page with far newer versions listed.
1757 It is probably wise to plan to move your storage configurations away from
1758 Berkeley DB format, as today there are smaller and simpler alternatives more
1759 suited to Exim's usage model.
1761 .cindex "&'tdb'& DBM library"
1762 Yet another DBM library, called &'tdb'&, is available from
1763 &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
1764 operates on a single file.
1768 .cindex "DBM libraries" "configuration for building"
1769 Exim and its utilities can be compiled to use any of these interfaces. In order
1770 to use any version of the Berkeley DB package in native mode, you must set
1771 USE_DB in an appropriate configuration file (typically
1772 &_Local/Makefile_&). For example:
1776 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1777 error is diagnosed if you set more than one of these.
1779 At the lowest level, the build-time configuration sets none of these options,
1780 thereby assuming an interface of type (1). However, some operating system
1781 configuration files (for example, those for the BSD operating systems and
1782 Linux) assume type (4) by setting USE_DB as their default, and the
1783 configuration files for Cygwin set USE_GDBM. Anything you set in
1784 &_Local/Makefile_&, however, overrides these system defaults.
1786 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1787 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1788 in one of these lines:
1793 Settings like that will work if the DBM library is installed in the standard
1794 place. Sometimes it is not, and the library's header file may also not be in
1795 the default path. You may need to set INCLUDE to specify where the header
1796 file is, and to specify the path to the library more fully in DBMLIB, as in
1799 INCLUDE=-I/usr/local/include/db-4.1
1800 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1802 There is further detailed discussion about the various DBM libraries in the
1803 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1807 .section "Pre-building configuration" "SECID25"
1808 .cindex "building Exim" "pre-building configuration"
1809 .cindex "configuration for building Exim"
1810 .cindex "&_Local/Makefile_&"
1811 .cindex "&_src/EDITME_&"
1812 Before building Exim, a local configuration file that specifies options
1813 independent of any operating system has to be created with the name
1814 &_Local/Makefile_&. A template for this file is supplied as the file
1815 &_src/EDITME_&, and it contains full descriptions of all the option settings
1816 therein. These descriptions are therefore not repeated here. If you are
1817 building Exim for the first time, the simplest thing to do is to copy
1818 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1820 There are three settings that you must supply, because Exim will not build
1821 without them. They are the location of the runtime configuration file
1822 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1823 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1824 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1825 a colon-separated list of filenames; Exim uses the first of them that exists.
1827 There are a few other parameters that can be specified either at build time or
1828 at runtime, to enable the same binary to be used on a number of different
1829 machines. However, if the locations of Exim's spool directory and log file
1830 directory (if not within the spool directory) are fixed, it is recommended that
1831 you specify them in &_Local/Makefile_& instead of at runtime, so that errors
1832 detected early in Exim's execution (such as a malformed configuration file) can
1835 .cindex "content scanning" "specifying at build time"
1836 Exim's interfaces for calling virus and spam scanning software directly from
1837 access control lists are not compiled by default. If you want to include these
1838 facilities, you need to set
1840 WITH_CONTENT_SCAN=yes
1842 in your &_Local/Makefile_&. For details of the facilities themselves, see
1843 chapter &<<CHAPexiscan>>&.
1846 .cindex "&_Local/eximon.conf_&"
1847 .cindex "&_exim_monitor/EDITME_&"
1848 If you are going to build the Exim monitor, a similar configuration process is
1849 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1850 your installation and saved under the name &_Local/eximon.conf_&. If you are
1851 happy with the default settings described in &_exim_monitor/EDITME_&,
1852 &_Local/eximon.conf_& can be empty, but it must exist.
1854 This is all the configuration that is needed in straightforward cases for known
1855 operating systems. However, the building process is set up so that it is easy
1856 to override options that are set by default or by operating-system-specific
1857 configuration files, for example, to change the C compiler, which
1858 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1863 .section "Support for iconv()" "SECID26"
1864 .cindex "&[iconv()]& support"
1866 The contents of header lines in messages may be encoded according to the rules
1867 described RFC 2047. This makes it possible to transmit characters that are not
1868 in the ASCII character set, and to label them as being in a particular
1869 character set. When Exim is inspecting header lines by means of the &%$h_%&
1870 mechanism, it decodes them, and translates them into a specified character set
1871 (default is set at build time). The translation is possible only if the operating system
1872 supports the &[iconv()]& function.
1874 However, some of the operating systems that supply &[iconv()]& do not support
1875 very many conversions. The GNU &%libiconv%& library (available from
1876 &url(https://www.gnu.org/software/libiconv/)) can be installed on such
1877 systems to remedy this deficiency, as well as on systems that do not supply
1878 &[iconv()]& at all. After installing &%libiconv%&, you should add
1882 to your &_Local/Makefile_& and rebuild Exim.
1886 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1887 .cindex "TLS" "including support for TLS"
1888 .cindex "encryption" "including support for"
1889 .cindex "SUPPORT_TLS"
1890 .cindex "OpenSSL" "building Exim with"
1891 .cindex "GnuTLS" "building Exim with"
1892 Exim can be built to support encrypted SMTP connections, using the STARTTLS
1893 command as per RFC 2487. It can also support legacy clients that expect to
1894 start a TLS session immediately on connection to a non-standard port (see the
1895 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1898 If you want to build Exim with TLS support, you must first install either the
1899 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1902 If OpenSSL is installed, you should set
1905 TLS_LIBS=-lssl -lcrypto
1907 in &_Local/Makefile_&. You may also need to specify the locations of the
1908 OpenSSL library and include files. For example:
1911 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1912 TLS_INCLUDE=-I/usr/local/openssl/include/
1914 .cindex "pkg-config" "OpenSSL"
1915 If you have &'pkg-config'& available, then instead you can just use:
1918 USE_OPENSSL_PC=openssl
1920 .cindex "USE_GNUTLS"
1921 If GnuTLS is installed, you should set
1925 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1927 in &_Local/Makefile_&, and again you may need to specify the locations of the
1928 library and include files. For example:
1932 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1933 TLS_INCLUDE=-I/usr/gnu/include
1935 .cindex "pkg-config" "GnuTLS"
1936 If you have &'pkg-config'& available, then instead you can just use:
1940 USE_GNUTLS_PC=gnutls
1943 You do not need to set TLS_INCLUDE if the relevant directory is already
1944 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1945 given in chapter &<<CHAPTLS>>&.
1950 .section "Use of tcpwrappers" "SECID27"
1952 .cindex "tcpwrappers, building Exim to support"
1953 .cindex "USE_TCP_WRAPPERS"
1954 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1955 .cindex "tcp_wrappers_daemon_name"
1956 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1957 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1958 alternative to Exim's own checking facilities for installations that are
1959 already making use of &'tcpwrappers'& for other purposes. To do this, you
1960 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1961 &_tcpd.h_& to be available at compile time, and also ensure that the library
1962 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1963 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1966 USE_TCP_WRAPPERS=yes
1967 CFLAGS=-O -I/usr/local/include
1968 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1970 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1971 files is &"exim"&. For example, the line
1973 exim : LOCAL 192.168.1. .friendly.domain.example
1975 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1976 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1977 All other connections are denied. The daemon name used by &'tcpwrappers'&
1978 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1979 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1980 configure file. Consult the &'tcpwrappers'& documentation for
1984 .section "Including support for IPv6" "SECID28"
1985 .cindex "IPv6" "including support for"
1986 Exim contains code for use on systems that have IPv6 support. Setting
1987 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1988 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1989 where the IPv6 support is not fully integrated into the normal include and
1992 Two different types of DNS record for handling IPv6 addresses have been
1993 defined. AAAA records (analogous to A records for IPv4) are in use, and are
1994 currently seen as the mainstream. Another record type called A6 was proposed
1995 as better than AAAA because it had more flexibility. However, it was felt to be
1996 over-complex, and its status was reduced to &"experimental"&.
1998 have a compile option for including A6 record support but this has now been
2003 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
2004 .cindex "lookup modules"
2005 .cindex "dynamic modules"
2006 .cindex ".so building"
2007 On some platforms, Exim supports not compiling all lookup types directly into
2008 the main binary, instead putting some into external modules which can be loaded
2010 This permits packagers to build Exim with support for lookups with extensive
2011 library dependencies without requiring all users to install all of those
2013 Most, but not all, lookup types can be built this way.
2015 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2016 installed; Exim will only load modules from that directory, as a security
2017 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2018 for your OS; see &_OS/Makefile-Linux_& for an example.
2019 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2020 see &_src/EDITME_& for details.
2022 Then, for each module to be loaded dynamically, define the relevant
2023 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2024 For example, this will build in lsearch but load sqlite and mysql support
2033 .section "The building process" "SECID29"
2034 .cindex "build directory"
2035 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2036 created, run &'make'& at the top level. It determines the architecture and
2037 operating system types, and creates a build directory if one does not exist.
2038 For example, on a Sun system running Solaris 8, the directory
2039 &_build-SunOS5-5.8-sparc_& is created.
2040 .cindex "symbolic link" "to source files"
2041 Symbolic links to relevant source files are installed in the build directory.
2043 If this is the first time &'make'& has been run, it calls a script that builds
2044 a make file inside the build directory, using the configuration files from the
2045 &_Local_& directory. The new make file is then passed to another instance of
2046 &'make'&. This does the real work, building a number of utility scripts, and
2047 then compiling and linking the binaries for the Exim monitor (if configured), a
2048 number of utility programs, and finally Exim itself. The command &`make
2049 makefile`& can be used to force a rebuild of the make file in the build
2050 directory, should this ever be necessary.
2052 If you have problems building Exim, check for any comments there may be in the
2053 &_README_& file concerning your operating system, and also take a look at the
2054 FAQ, where some common problems are covered.
2058 .section 'Output from &"make"&' "SECID283"
2059 The output produced by the &'make'& process for compile lines is often very
2060 unreadable, because these lines can be very long. For this reason, the normal
2061 output is suppressed by default, and instead output similar to that which
2062 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2063 each module that is being compiled or linked. However, it is still possible to
2064 get the full output, by calling &'make'& like this:
2068 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2069 command reflection in &'make'&. When you ask for the full output, it is
2070 given in addition to the short output.
2074 .section "Overriding build-time options for Exim" "SECToverride"
2075 .cindex "build-time options, overriding"
2076 The main make file that is created at the beginning of the building process
2077 consists of the concatenation of a number of files which set configuration
2078 values, followed by a fixed set of &'make'& instructions. If a value is set
2079 more than once, the last setting overrides any previous ones. This provides a
2080 convenient way of overriding defaults. The files that are concatenated are, in
2083 &_OS/Makefile-Default_&
2084 &_OS/Makefile-_&<&'ostype'&>
2086 &_Local/Makefile-_&<&'ostype'&>
2087 &_Local/Makefile-_&<&'archtype'&>
2088 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2089 &_OS/Makefile-Base_&
2091 .cindex "&_Local/Makefile_&"
2092 .cindex "building Exim" "operating system type"
2093 .cindex "building Exim" "architecture type"
2094 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2095 architecture type. &_Local/Makefile_& is required to exist, and the building
2096 process fails if it is absent. The other three &_Local_& files are optional,
2097 and are often not needed.
2099 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2100 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2101 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2102 values are used, thereby providing a means of forcing particular settings.
2103 Otherwise, the scripts try to get values from the &%uname%& command. If this
2104 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2105 of &'ad hoc'& transformations are then applied, to produce the standard names
2106 that Exim expects. You can run these scripts directly from the shell in order
2107 to find out what values are being used on your system.
2110 &_OS/Makefile-Default_& contains comments about the variables that are set
2111 therein. Some (but not all) are mentioned below. If there is something that
2112 needs changing, review the contents of this file and the contents of the make
2113 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2117 .cindex "building Exim" "overriding default settings"
2118 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2119 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2120 need to change the original files. Instead, you should make the changes by
2121 putting the new values in an appropriate &_Local_& file. For example,
2122 .cindex "Tru64-Unix build-time settings"
2123 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2124 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2125 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2126 called with the option &%-std1%&, to make it recognize some of the features of
2127 Standard C that Exim uses. (Most other compilers recognize Standard C by
2128 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2129 containing the lines
2134 If you are compiling for just one operating system, it may be easier to put
2135 these lines directly into &_Local/Makefile_&.
2137 Keeping all your local configuration settings separate from the distributed
2138 files makes it easy to transfer them to new versions of Exim simply by copying
2139 the contents of the &_Local_& directory.
2142 .cindex "NIS lookup type" "including support for"
2143 .cindex "NIS+ lookup type" "including support for"
2144 .cindex "LDAP" "including support for"
2145 .cindex "lookup" "inclusion in binary"
2146 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2147 lookup, but not all systems have these components installed, so the default is
2148 not to include the relevant code in the binary. All the different kinds of file
2149 and database lookup that Exim supports are implemented as separate code modules
2150 which are included only if the relevant compile-time options are set. In the
2151 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2157 and similar settings apply to the other lookup types. They are all listed in
2158 &_src/EDITME_&. In many cases the relevant include files and interface
2159 libraries need to be installed before compiling Exim.
2160 .cindex "cdb" "including support for"
2161 However, there are some optional lookup types (such as cdb) for which
2162 the code is entirely contained within Exim, and no external include
2163 files or libraries are required. When a lookup type is not included in the
2164 binary, attempts to configure Exim to use it cause runtime configuration
2167 .cindex "pkg-config" "lookups"
2168 .cindex "pkg-config" "authenticators"
2169 Many systems now use a tool called &'pkg-config'& to encapsulate information
2170 about how to compile against a library; Exim has some initial support for
2171 being able to use pkg-config for lookups and authenticators. For any given
2172 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2173 variable with the &`_PC`& suffix in the name and assign as the value the
2174 name of the package to be queried. The results of querying via the
2175 &'pkg-config'& command will be added to the appropriate Makefile variables
2176 with &`+=`& directives, so your version of &'make'& will need to support that
2177 syntax. For instance:
2180 LOOKUP_SQLITE_PC=sqlite3
2182 AUTH_GSASL_PC=libgsasl
2183 AUTH_HEIMDAL_GSSAPI=yes
2184 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2187 .cindex "Perl" "including support for"
2188 Exim can be linked with an embedded Perl interpreter, allowing Perl
2189 subroutines to be called during string expansion. To enable this facility,
2193 must be defined in &_Local/Makefile_&. Details of this facility are given in
2194 chapter &<<CHAPperl>>&.
2196 .cindex "X11 libraries, location of"
2197 The location of the X11 libraries is something that varies a lot between
2198 operating systems, and there may be different versions of X11 to cope
2199 with. Exim itself makes no use of X11, but if you are compiling the Exim
2200 monitor, the X11 libraries must be available.
2201 The following three variables are set in &_OS/Makefile-Default_&:
2204 XINCLUDE=-I$(X11)/include
2205 XLFLAGS=-L$(X11)/lib
2207 These are overridden in some of the operating-system configuration files. For
2208 example, in &_OS/Makefile-SunOS5_& there is
2211 XINCLUDE=-I$(X11)/include
2212 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2214 If you need to override the default setting for your operating system, place a
2215 definition of all three of these variables into your
2216 &_Local/Makefile-<ostype>_& file.
2219 If you need to add any extra libraries to the link steps, these can be put in a
2220 variable called EXTRALIBS, which appears in all the link commands, but by
2221 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2222 command for linking the main Exim binary, and not for any associated utilities.
2224 .cindex "DBM libraries" "configuration for building"
2225 There is also DBMLIB, which appears in the link commands for binaries that
2226 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2227 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2228 binary, and which can be used, for example, to include additional X11
2231 .cindex "configuration file" "editing"
2232 The make file copes with rebuilding Exim correctly if any of the configuration
2233 files are edited. However, if an optional configuration file is deleted, it is
2234 necessary to touch the associated non-optional file (that is,
2235 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2238 .section "OS-specific header files" "SECID30"
2240 .cindex "building Exim" "OS-specific C header files"
2241 The &_OS_& directory contains a number of files with names of the form
2242 &_os.h-<ostype>_&. These are system-specific C header files that should not
2243 normally need to be changed. There is a list of macro settings that are
2244 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2245 are porting Exim to a new operating system.
2249 .section "Overriding build-time options for the monitor" "SECID31"
2250 .cindex "building Eximon"
2251 A similar process is used for overriding things when building the Exim monitor,
2252 where the files that are involved are
2254 &_OS/eximon.conf-Default_&
2255 &_OS/eximon.conf-_&<&'ostype'&>
2256 &_Local/eximon.conf_&
2257 &_Local/eximon.conf-_&<&'ostype'&>
2258 &_Local/eximon.conf-_&<&'archtype'&>
2259 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2261 .cindex "&_Local/eximon.conf_&"
2262 As with Exim itself, the final three files need not exist, and in this case the
2263 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2264 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2265 variables of the same name, preceded by EXIMON_. For example, setting
2266 EXIMON_LOG_DEPTH in the environment overrides the value of
2267 LOG_DEPTH at runtime.
2271 .section "Installing Exim binaries and scripts" "SECID32"
2272 .cindex "installing Exim"
2273 .cindex "BIN_DIRECTORY"
2274 The command &`make install`& runs the &(exim_install)& script with no
2275 arguments. The script copies binaries and utility scripts into the directory
2276 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2277 .cindex "setuid" "installing Exim with"
2278 The install script copies files only if they are newer than the files they are
2279 going to replace. The Exim binary is required to be owned by root and have the
2280 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2281 install`& as root so that it can set up the Exim binary in this way. However, in
2282 some special situations (for example, if a host is doing no local deliveries)
2283 it may be possible to run Exim without making the binary setuid root (see
2284 chapter &<<CHAPsecurity>>& for details).
2286 .cindex "CONFIGURE_FILE"
2287 Exim's runtime configuration file is named by the CONFIGURE_FILE setting
2288 in &_Local/Makefile_&. If this names a single file, and the file does not
2289 exist, the default configuration file &_src/configure.default_& is copied there
2290 by the installation script. If a runtime configuration file already exists, it
2291 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2292 alternative files, no default is installed.
2294 .cindex "system aliases file"
2295 .cindex "&_/etc/aliases_&"
2296 One change is made to the default configuration file when it is installed: the
2297 default configuration contains a router that references a system aliases file.
2298 The path to this file is set to the value specified by
2299 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2300 If the system aliases file does not exist, the installation script creates it,
2301 and outputs a comment to the user.
2303 The created file contains no aliases, but it does contain comments about the
2304 aliases a site should normally have. Mail aliases have traditionally been
2305 kept in &_/etc/aliases_&. However, some operating systems are now using
2306 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2307 Exim's configuration if necessary.
2309 The default configuration uses the local host's name as the only local domain,
2310 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2311 running as the local user. System aliases and &_.forward_& files in users' home
2312 directories are supported, but no NIS or NIS+ support is configured. Domains
2313 other than the name of the local host are routed using the DNS, with delivery
2316 It is possible to install Exim for special purposes (such as building a binary
2317 distribution) in a private part of the file system. You can do this by a
2320 make DESTDIR=/some/directory/ install
2322 This has the effect of pre-pending the specified directory to all the file
2323 paths, except the name of the system aliases file that appears in the default
2324 configuration. (If a default alias file is created, its name &'is'& modified.)
2325 For backwards compatibility, ROOT is used if DESTDIR is not set,
2326 but this usage is deprecated.
2328 .cindex "installing Exim" "what is not installed"
2329 Running &'make install'& does not copy the Exim 4 conversion script
2330 &'convert4r4'&. You will probably run this only once if you are
2331 upgrading from Exim 3. None of the documentation files in the &_doc_&
2332 directory are copied, except for the info files when you have set
2333 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2335 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2336 to their names. The Exim binary itself, however, is handled differently. It is
2337 installed under a name that includes the version number and the compile number,
2338 for example, &_exim-&version()-1_&. The script then arranges for a symbolic link
2339 called &_exim_& to point to the binary. If you are updating a previous version
2340 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2341 from the directory (as seen by other processes).
2343 .cindex "installing Exim" "testing the script"
2344 If you want to see what the &'make install'& will do before running it for
2345 real, you can pass the &%-n%& option to the installation script by this
2348 make INSTALL_ARG=-n install
2350 The contents of the variable INSTALL_ARG are passed to the installation
2351 script. You do not need to be root to run this test. Alternatively, you can run
2352 the installation script directly, but this must be from within the build
2353 directory. For example, from the top-level Exim directory you could use this
2356 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2358 .cindex "installing Exim" "install script options"
2359 There are two other options that can be supplied to the installation script.
2362 &%-no_chown%& bypasses the call to change the owner of the installed binary
2363 to root, and the call to make it a setuid binary.
2365 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2369 INSTALL_ARG can be used to pass these options to the script. For example:
2371 make INSTALL_ARG=-no_symlink install
2373 The installation script can also be given arguments specifying which files are
2374 to be copied. For example, to install just the Exim binary, and nothing else,
2375 without creating the symbolic link, you could use:
2377 make INSTALL_ARG='-no_symlink exim' install
2382 .section "Installing info documentation" "SECTinsinfdoc"
2383 .cindex "installing Exim" "&'info'& documentation"
2384 Not all systems use the GNU &'info'& system for documentation, and for this
2385 reason, the Texinfo source of Exim's documentation is not included in the main
2386 distribution. Instead it is available separately from the FTP site (see section
2389 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2390 source of the documentation is found in the source tree, running &`make
2391 install`& automatically builds the info files and installs them.
2395 .section "Setting up the spool directory" "SECID33"
2396 .cindex "spool directory" "creating"
2397 When it starts up, Exim tries to create its spool directory if it does not
2398 exist. The Exim uid and gid are used for the owner and group of the spool
2399 directory. Sub-directories are automatically created in the spool directory as
2405 .section "Testing" "SECID34"
2406 .cindex "testing" "installation"
2407 Having installed Exim, you can check that the runtime configuration file is
2408 syntactically valid by running the following command, which assumes that the
2409 Exim binary directory is within your PATH environment variable:
2413 If there are any errors in the configuration file, Exim outputs error messages.
2414 Otherwise it outputs the version number and build date,
2415 the DBM library that is being used, and information about which drivers and
2416 other optional code modules are included in the binary.
2417 Some simple routing tests can be done by using the address testing option. For
2420 &`exim -bt`& <&'local username'&>
2422 should verify that it recognizes a local mailbox, and
2424 &`exim -bt`& <&'remote address'&>
2426 a remote one. Then try getting it to deliver mail, both locally and remotely.
2427 This can be done by passing messages directly to Exim, without going through a
2428 user agent. For example:
2430 exim -v postmaster@your.domain.example
2431 From: user@your.domain.example
2432 To: postmaster@your.domain.example
2433 Subject: Testing Exim
2435 This is a test message.
2438 The &%-v%& option causes Exim to output some verification of what it is doing.
2439 In this case you should see copies of three log lines, one for the message's
2440 arrival, one for its delivery, and one containing &"Completed"&.
2442 .cindex "delivery" "problems with"
2443 If you encounter problems, look at Exim's log files (&'mainlog'& and
2444 &'paniclog'&) to see if there is any relevant information there. Another source
2445 of information is running Exim with debugging turned on, by specifying the
2446 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2447 with debugging turned on by a command of the form
2449 &`exim -d -M`& <&'exim-message-id'&>
2451 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2452 produces rather a lot of output, but you can cut this down to specific areas.
2453 For example, if you use &%-d-all+route%& only the debugging information
2454 relevant to routing is included. (See the &%-d%& option in chapter
2455 &<<CHAPcommandline>>& for more details.)
2457 .cindex '&"sticky"& bit'
2458 .cindex "lock files"
2459 One specific problem that has shown up on some sites is the inability to do
2460 local deliveries into a shared mailbox directory, because it does not have the
2461 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2462 writing to a mailbox file, and if it cannot create the lock file, the delivery
2463 is deferred. You can get round this either by setting the &"sticky bit"& on the
2464 directory, or by setting a specific group for local deliveries and allowing
2465 that group to create files in the directory (see the comments above the
2466 &(local_delivery)& transport in the default configuration file). Another
2467 approach is to configure Exim not to use lock files, but just to rely on
2468 &[fcntl()]& locking instead. However, you should do this only if all user
2469 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2470 see chapter &<<CHAPappendfile>>&.
2472 One thing that cannot be tested on a system that is already running an MTA is
2473 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2474 &%-oX%& option can be used to run an Exim daemon that listens on some other
2475 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2476 &'exim_checkaccess'& utility can be used to check out policy controls on
2479 Testing a new version on a system that is already running Exim can most easily
2480 be done by building a binary with a different CONFIGURE_FILE setting. From
2481 within the runtime configuration, all other file and directory names
2482 that Exim uses can be altered, in order to keep it entirely clear of the
2486 .section "Replacing another MTA with Exim" "SECID35"
2487 .cindex "replacing another MTA"
2488 Building and installing Exim for the first time does not of itself put it in
2489 general use. The name by which the system's MTA is called by mail user agents
2490 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2491 operating system), and it is necessary to make this name point to the &'exim'&
2492 binary in order to get the user agents to pass messages to Exim. This is
2493 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2494 or &_/usr/lib/sendmail_&
2495 .cindex "symbolic link" "to &'exim'& binary"
2496 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2497 privilege and executable status from the old MTA. It is then necessary to stop
2498 and restart the mailer daemon, if one is running.
2500 .cindex "FreeBSD, MTA indirection"
2501 .cindex "&_/etc/mail/mailer.conf_&"
2502 Some operating systems have introduced alternative ways of switching MTAs. For
2503 example, if you are running FreeBSD, you need to edit the file
2504 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2505 described. A typical example of the contents of this file for running Exim is
2508 sendmail /usr/exim/bin/exim
2509 send-mail /usr/exim/bin/exim
2510 mailq /usr/exim/bin/exim -bp
2511 newaliases /usr/bin/true
2513 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2514 your Exim installation is &"live"&. Check it by sending a message from your
2515 favourite user agent.
2517 You should consider what to tell your users about the change of MTA. Exim may
2518 have different capabilities to what was previously running, and there are
2519 various operational differences such as the text of messages produced by
2520 command line options and in bounce messages. If you allow your users to make
2521 use of Exim's filtering capabilities, you should make the document entitled
2522 &'Exim's interface to mail filtering'& available to them.
2526 .section "Upgrading Exim" "SECID36"
2527 .cindex "upgrading Exim"
2528 If you are already running Exim on your host, building and installing a new
2529 version automatically makes it available to MUAs, or any other programs that
2530 call the MTA directly. However, if you are running an Exim daemon, you do need
2531 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2532 new binary. You do not need to stop processing mail in order to install a new
2533 version of Exim. The install script does not modify an existing runtime
2539 .section "Stopping the Exim daemon on Solaris" "SECID37"
2540 .cindex "Solaris" "stopping Exim on"
2541 The standard command for stopping the mailer daemon on Solaris is
2543 /etc/init.d/sendmail stop
2545 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2546 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2547 for the text &"sendmail"&; this is not present because the actual program name
2548 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2549 solution is to replace the line that finds the process id with something like
2551 pid=`cat /var/spool/exim/exim-daemon.pid`
2553 to obtain the daemon's pid directly from the file that Exim saves it in.
2555 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2556 still be received from local processes, and if automatic delivery is configured
2557 (the normal case), deliveries will still occur.
2562 . ////////////////////////////////////////////////////////////////////////////
2563 . ////////////////////////////////////////////////////////////////////////////
2565 .chapter "The Exim command line" "CHAPcommandline"
2566 .scindex IIDclo1 "command line" "options"
2567 .scindex IIDclo2 "options" "command line"
2568 Exim's command line takes the standard Unix form of a sequence of options,
2569 each starting with a hyphen character, followed by a number of arguments. The
2570 options are compatible with the main options of Sendmail, and there are also
2571 some additional options, some of which are compatible with Smail 3. Certain
2572 combinations of options do not make sense, and provoke an error if used.
2573 The form of the arguments depends on which options are set.
2576 .section "Setting options by program name" "SECID38"
2578 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2579 were present before any other options.
2580 The &%-bp%& option requests a listing of the contents of the mail queue on the
2582 This feature is for compatibility with some systems that contain a command of
2583 that name in one of the standard libraries, symbolically linked to
2584 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2587 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2588 were present before any other options, for compatibility with Smail. The
2589 &%-bS%& option is used for reading in a number of messages in batched SMTP
2593 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2594 &%-oee%& options were present before any other options, for compatibility with
2595 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2598 .cindex "queue runner"
2599 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2600 were present before any other options, for compatibility with Smail. The &%-q%&
2601 option causes a single queue runner process to be started.
2603 .cindex "&'newaliases'&"
2604 .cindex "alias file" "building"
2605 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2606 If Exim is called under the name &'newaliases'& it behaves as if the option
2607 &%-bi%& were present before any other options, for compatibility with Sendmail.
2608 This option is used for rebuilding Sendmail's alias file. Exim does not have
2609 the concept of a single alias file, but can be configured to run a given
2610 command if called with the &%-bi%& option.
2613 .section "Trusted and admin users" "SECTtrustedadmin"
2614 Some Exim options are available only to &'trusted users'& and others are
2615 available only to &'admin users'&. In the description below, the phrases &"Exim
2616 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2617 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2618 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2621 .cindex "trusted users" "definition of"
2622 .cindex "user" "trusted definition of"
2623 The trusted users are root, the Exim user, any user listed in the
2624 &%trusted_users%& configuration option, and any user whose current group or any
2625 supplementary group is one of those listed in the &%trusted_groups%&
2626 configuration option. Note that the Exim group is not automatically trusted.
2628 .cindex '&"From"& line'
2629 .cindex "envelope sender"
2630 Trusted users are always permitted to use the &%-f%& option or a leading
2631 &"From&~"& line to specify the envelope sender of a message that is passed to
2632 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2633 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2634 users to set envelope senders.
2636 .cindex "&'From:'& header line"
2637 .cindex "&'Sender:'& header line"
2638 .cindex "header lines" "From:"
2639 .cindex "header lines" "Sender:"
2640 For a trusted user, there is never any check on the contents of the &'From:'&
2641 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2642 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2644 Trusted users may also specify a host name, host address, interface address,
2645 protocol name, ident value, and authentication data when submitting a message
2646 locally. Thus, they are able to insert messages into Exim's queue locally that
2647 have the characteristics of messages received from a remote host. Untrusted
2648 users may in some circumstances use &%-f%&, but can never set the other values
2649 that are available to trusted users.
2651 .cindex "user" "admin definition of"
2652 .cindex "admin user" "definition of"
2653 The admin users are root, the Exim user, and any user that is a member of the
2654 Exim group or of any group listed in the &%admin_groups%& configuration option.
2655 The current group does not have to be one of these groups.
2657 Admin users are permitted to list the queue, and to carry out certain
2658 operations on messages, for example, to force delivery failures. It is also
2659 necessary to be an admin user in order to see the full information provided by
2660 the Exim monitor, and full debugging output.
2662 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2663 Exim to attempt delivery of messages on its queue is restricted to admin users.
2664 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2665 option false (that is, specifying &%no_prod_requires_admin%&).
2667 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2668 is restricted to admin users unless &%queue_list_requires_admin%& is set
2673 &*Warning*&: If you configure your system so that admin users are able to
2674 edit Exim's configuration file, you are giving those users an easy way of
2675 getting root. There is further discussion of this issue at the start of chapter
2681 .section "Command line options" "SECID39"
2682 Exim's command line options are described in alphabetical order below. If none
2683 of the options that specifies a specific action (such as starting the daemon or
2684 a queue runner, or testing an address, or receiving a message in a specific
2685 format, or listing the queue) are present, and there is at least one argument
2686 on the command line, &%-bm%& (accept a local message on the standard input,
2687 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2688 outputs a brief message about itself and exits.
2690 . ////////////////////////////////////////////////////////////////////////////
2691 . Insert a stylized XML comment here, to identify the start of the command line
2692 . options. This is for the benefit of the Perl script that automatically
2693 . creates a man page for the options.
2694 . ////////////////////////////////////////////////////////////////////////////
2697 <!-- === Start of command line options === -->
2704 .cindex "options" "command line; terminating"
2705 This is a pseudo-option whose only purpose is to terminate the options and
2706 therefore to cause subsequent command line items to be treated as arguments
2707 rather than options, even if they begin with hyphens.
2710 .oindex "&%--help%&"
2711 This option causes Exim to output a few sentences stating what it is.
2712 The same output is generated if the Exim binary is called with no options and
2715 .vitem &%--version%&
2716 .oindex "&%--version%&"
2717 This option is an alias for &%-bV%& and causes version information to be
2724 These options are used by Sendmail for selecting configuration files and are
2727 .vitem &%-B%&<&'type'&>
2729 .cindex "8-bit characters"
2730 .cindex "Sendmail compatibility" "8-bit characters"
2731 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2732 clean; it ignores this option.
2737 .cindex "SMTP" "listener"
2738 .cindex "queue runner"
2739 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2740 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2741 that the daemon should also initiate periodic queue runs.
2743 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2744 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2745 disconnect from the controlling terminal. When running this way, it can be
2746 stopped by pressing ctrl-C.
2748 By default, Exim listens for incoming connections to the standard SMTP port on
2749 all the host's running interfaces. However, it is possible to listen on other
2750 ports, on multiple ports, and only on specific interfaces. Chapter
2751 &<<CHAPinterfaces>>& contains a description of the options that control this.
2753 When a listening daemon
2754 .cindex "daemon" "process id (pid)"
2755 .cindex "pid (process id)" "of daemon"
2756 is started without the use of &%-oX%& (that is, without overriding the normal
2757 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2758 in Exim's spool directory. This location can be overridden by setting
2759 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2762 When &%-oX%& is used on the command line to start a listening daemon, the
2763 process id is not written to the normal pid file path. However, &%-oP%& can be
2764 used to specify a path on the command line if a pid file is required.
2768 .cindex "daemon" "restarting"
2769 can be used to cause the daemon to re-execute itself. This should be done
2770 whenever Exim's configuration file, or any file that is incorporated into it by
2771 means of the &%.include%& facility, is changed, and also whenever a new version
2772 of Exim is installed. It is not necessary to do this when other files that are
2773 referenced from the configuration (for example, alias files) are changed,
2774 because these are reread each time they are used.
2778 This option has the same effect as &%-bd%& except that it never disconnects
2779 from the controlling terminal, even when no debugging is specified.
2783 .cindex "testing" "string expansion"
2784 .cindex "expansion" "testing"
2785 Run Exim in expansion testing mode. Exim discards its root privilege, to
2786 prevent ordinary users from using this mode to read otherwise inaccessible
2787 files. If no arguments are given, Exim runs interactively, prompting for lines
2788 of data. Otherwise, it processes each argument in turn.
2790 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2791 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2792 used without command line arguments. If successful, it uses the &[readline()]&
2793 function, which provides extensive line-editing facilities, for reading the
2794 test data. A line history is supported.
2796 Long expansion expressions can be split over several lines by using backslash
2797 continuations. As in Exim's runtime configuration, white space at the start of
2798 continuation lines is ignored. Each argument or data line is passed through the
2799 string expansion mechanism, and the result is output. Variable values from the
2800 configuration file (for example, &$qualify_domain$&) are available, but no
2801 message-specific values (such as &$message_exim_id$&) are set, because no message
2802 is being processed (but see &%-bem%& and &%-Mset%&).
2804 &*Note*&: If you use this mechanism to test lookups, and you change the data
2805 files or databases you are using, you must exit and restart Exim before trying
2806 the same lookup again. Otherwise, because each Exim process caches the results
2807 of lookups, you will just get the same result as before.
2809 Macro processing is done on lines before string-expansion: new macros can be
2810 defined and macros will be expanded.
2811 Because macros in the config file are often used for secrets, those are only
2812 available to admin users.
2814 .vitem &%-bem%&&~<&'filename'&>
2816 .cindex "testing" "string expansion"
2817 .cindex "expansion" "testing"
2818 This option operates like &%-be%& except that it must be followed by the name
2819 of a file. For example:
2821 exim -bem /tmp/testmessage
2823 The file is read as a message (as if receiving a locally-submitted non-SMTP
2824 message) before any of the test expansions are done. Thus, message-specific
2825 variables such as &$message_size$& and &$header_from:$& are available. However,
2826 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2827 recipients are read from the headers in the normal way, and are shown in the
2828 &$recipients$& variable. Note that recipients cannot be given on the command
2829 line, because further arguments are taken as strings to expand (just like
2832 .vitem &%-bF%&&~<&'filename'&>
2834 .cindex "system filter" "testing"
2835 .cindex "testing" "system filter"
2836 This option is the same as &%-bf%& except that it assumes that the filter being
2837 tested is a system filter. The additional commands that are available only in
2838 system filters are recognized.
2840 .vitem &%-bf%&&~<&'filename'&>
2842 .cindex "filter" "testing"
2843 .cindex "testing" "filter file"
2844 .cindex "forward file" "testing"
2845 .cindex "testing" "forward file"
2846 .cindex "Sieve filter" "testing"
2847 This option runs Exim in user filter testing mode; the file is the filter file
2848 to be tested, and a test message must be supplied on the standard input. If
2849 there are no message-dependent tests in the filter, an empty file can be
2852 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2853 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2854 filter and a user filter in the same run. For example:
2856 exim -bF /system/filter -bf /user/filter </test/message
2858 This is helpful when the system filter adds header lines or sets filter
2859 variables that are used by the user filter.
2861 If the test filter file does not begin with one of the special lines
2866 it is taken to be a normal &_.forward_& file, and is tested for validity under
2867 that interpretation. See sections &<<SECTitenonfilred>>& to
2868 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2871 The result of an Exim command that uses &%-bf%&, provided no errors are
2872 detected, is a list of the actions that Exim would try to take if presented
2873 with the message for real. More details of filter testing are given in the
2874 separate document entitled &'Exim's interfaces to mail filtering'&.
2876 When testing a filter file,
2877 .cindex "&""From""& line"
2878 .cindex "envelope sender"
2879 .oindex "&%-f%&" "for filter testing"
2880 the envelope sender can be set by the &%-f%& option,
2881 or by a &"From&~"& line at the start of the test message. Various parameters
2882 that would normally be taken from the envelope recipient address of the message
2883 can be set by means of additional command line options (see the next four
2886 .vitem &%-bfd%&&~<&'domain'&>
2888 .vindex "&$qualify_domain$&"
2889 This sets the domain of the recipient address when a filter file is being
2890 tested by means of the &%-bf%& option. The default is the value of
2893 .vitem &%-bfl%&&~<&'local&~part'&>
2895 This sets the local part of the recipient address when a filter file is being
2896 tested by means of the &%-bf%& option. The default is the username of the
2897 process that calls Exim. A local part should be specified with any prefix or
2898 suffix stripped, because that is how it appears to the filter when a message is
2899 actually being delivered.
2901 .vitem &%-bfp%&&~<&'prefix'&>
2903 .cindex affix "filter testing"
2904 This sets the prefix of the local part of the recipient address when a filter
2905 file is being tested by means of the &%-bf%& option. The default is an empty
2908 .vitem &%-bfs%&&~<&'suffix'&>
2910 .cindex affix "filter testing"
2911 This sets the suffix of the local part of the recipient address when a filter
2912 file is being tested by means of the &%-bf%& option. The default is an empty
2915 .vitem &%-bh%&&~<&'IP&~address'&>
2917 .cindex "testing" "incoming SMTP"
2918 .cindex "SMTP" "testing incoming"
2919 .cindex "testing" "relay control"
2920 .cindex "relaying" "testing configuration"
2921 .cindex "policy control" "testing"
2922 .cindex "debugging" "&%-bh%& option"
2923 This option runs a fake SMTP session as if from the given IP address, using the
2924 standard input and output. The IP address may include a port number at the end,
2925 after a full stop. For example:
2927 exim -bh 10.9.8.7.1234
2928 exim -bh fe80::a00:20ff:fe86:a061.5678
2930 When an IPv6 address is given, it is converted into canonical form. In the case
2931 of the second example above, the value of &$sender_host_address$& after
2932 conversion to the canonical form is
2933 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2935 Comments as to what is going on are written to the standard error file. These
2936 include lines beginning with &"LOG"& for anything that would have been logged.
2937 This facility is provided for testing configuration options for incoming
2938 messages, to make sure they implement the required policy. For example, you can
2939 test your relay controls using &%-bh%&.
2943 You can test features of the configuration that rely on ident (RFC 1413)
2944 information by using the &%-oMt%& option. However, Exim cannot actually perform
2945 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2948 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2949 are also skipped when testing using &%-bh%&. If you want these callouts to
2950 occur, use &%-bhc%& instead.
2952 Messages supplied during the testing session are discarded, and nothing is
2953 written to any of the real log files. There may be pauses when DNS (and other)
2954 lookups are taking place, and of course these may time out. The &%-oMi%& option
2955 can be used to specify a specific IP interface and port if this is important,
2956 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2957 session were authenticated.
2959 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2960 output just states whether a given recipient address from a given host is
2961 acceptable or not. See section &<<SECTcheckaccess>>&.
2963 Features such as authentication and encryption, where the client input is not
2964 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2965 specialized SMTP test program such as
2966 &url(https://www.jetmore.org/john/code/swaks/,swaks).
2968 .vitem &%-bhc%&&~<&'IP&~address'&>
2970 This option operates in the same way as &%-bh%&, except that address
2971 verification callouts are performed if required. This includes consulting and
2972 updating the callout cache database.
2976 .cindex "alias file" "building"
2977 .cindex "building alias file"
2978 .cindex "Sendmail compatibility" "&%-bi%& option"
2979 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2980 Exim does not have the concept of a single alias file, and so it cannot mimic
2981 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2982 tend to appear in various scripts such as NIS make files, so the option must be
2985 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2986 configuration option is run, under the uid and gid of the caller of Exim. If
2987 the &%-oA%& option is used, its value is passed to the command as an argument.
2988 The command set by &%bi_command%& may not contain arguments. The command can
2989 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2990 if this is required. If the &%bi_command%& option is not set, calling Exim with
2993 . // Keep :help first, then the rest in alphabetical order
2995 .oindex "&%-bI:help%&"
2996 .cindex "querying exim information"
2997 We shall provide various options starting &`-bI:`& for querying Exim for
2998 information. The output of many of these will be intended for machine
2999 consumption. This one is not. The &%-bI:help%& option asks Exim for a
3000 synopsis of supported options beginning &`-bI:`&. Use of any of these
3001 options shall cause Exim to exit after producing the requested output.
3004 .oindex "&%-bI:dscp%&"
3005 .cindex "DSCP" "values"
3006 This option causes Exim to emit an alphabetically sorted list of all
3007 recognised DSCP names.
3009 .vitem &%-bI:sieve%&
3010 .oindex "&%-bI:sieve%&"
3011 .cindex "Sieve filter" "capabilities"
3012 This option causes Exim to emit an alphabetically sorted list of all supported
3013 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3014 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3015 &`SIEVE`& capability response line. As the precise list may depend upon
3016 compile-time build options, which this option will adapt to, this is the only
3017 way to guarantee a correct response.
3021 .cindex "local message reception"
3022 This option runs an Exim receiving process that accepts an incoming,
3023 locally-generated message on the standard input. The recipients are given as the
3024 command arguments (except when &%-t%& is also present &-- see below). Each
3025 argument can be a comma-separated list of RFC 2822 addresses. This is the
3026 default option for selecting the overall action of an Exim call; it is assumed
3027 if no other conflicting option is present.
3029 If any addresses in the message are unqualified (have no domain), they are
3030 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3031 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3032 suppressing this for special cases.
3034 Policy checks on the contents of local messages can be enforced by means of
3035 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3037 .cindex "return code" "for &%-bm%&"
3038 The return code is zero if the message is successfully accepted. Otherwise, the
3039 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3042 .cindex "message" "format"
3043 .cindex "format" "message"
3044 .cindex "&""From""& line"
3045 .cindex "UUCP" "&""From""& line"
3046 .cindex "Sendmail compatibility" "&""From""& line"
3047 of the message must be as defined in RFC 2822, except that, for
3048 compatibility with Sendmail and Smail, a line in one of the forms
3050 From sender Fri Jan 5 12:55 GMT 1997
3051 From sender Fri, 5 Jan 97 12:55:01
3053 (with the weekday optional, and possibly with additional text after the date)
3054 is permitted to appear at the start of the message. There appears to be no
3055 authoritative specification of the format of this line. Exim recognizes it by
3056 matching against the regular expression defined by the &%uucp_from_pattern%&
3057 option, which can be changed if necessary.
3059 .oindex "&%-f%&" "overriding &""From""& line"
3060 The specified sender is treated as if it were given as the argument to the
3061 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3062 preference to the address taken from the message. The caller of Exim must be a
3063 trusted user for the sender of a message to be set in this way.
3065 .vitem &%-bmalware%&&~<&'filename'&>
3066 .oindex "&%-bmalware%&"
3067 .cindex "testing", "malware"
3068 .cindex "malware scan test"
3069 This debugging option causes Exim to scan the given file or directory
3070 (depending on the used scanner interface),
3071 using the malware scanning framework. The option of &%av_scanner%& influences
3072 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3073 the expansion should have defaults which apply to this invocation. ACLs are
3074 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3075 will never be populated and &%-bmalware%& will fail.
3077 Exim will have changed working directory before resolving the filename, so
3078 using fully qualified pathnames is advisable. Exim will be running as the Exim
3079 user when it tries to open the file, rather than as the invoking user.
3080 This option requires admin privileges.
3082 The &%-bmalware%& option will not be extended to be more generally useful,
3083 there are better tools for file-scanning. This option exists to help
3084 administrators verify their Exim and AV scanner configuration.
3088 .cindex "address qualification, suppressing"
3089 By default, Exim automatically qualifies unqualified addresses (those
3090 without domains) that appear in messages that are submitted locally (that
3091 is, not over TCP/IP). This qualification applies both to addresses in
3092 envelopes, and addresses in header lines. Sender addresses are qualified using
3093 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3094 defaults to the value of &%qualify_domain%&).
3096 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3097 being used to re-submit messages that originally came from remote hosts after
3098 content scanning, you probably do not want to qualify unqualified addresses in
3099 header lines. (Such lines will be present only if you have not enabled a header
3100 syntax check in the appropriate ACL.)
3102 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3103 messages that originate on the local host. When this is used, unqualified
3104 addresses in the envelope provoke errors (causing message rejection) and
3105 unqualified addresses in header lines are left alone.
3110 .cindex "configuration options" "extracting"
3111 .cindex "options" "configuration &-- extracting"
3112 If this option is given with no arguments, it causes the values of all Exim's
3113 main configuration options to be written to the standard output. The values
3114 of one or more specific options can be requested by giving their names as
3115 arguments, for example:
3117 exim -bP qualify_domain hold_domains
3119 .cindex "hiding configuration option values"
3120 .cindex "configuration options" "hiding value of"
3121 .cindex "options" "hiding value of"
3122 However, any option setting that is preceded by the word &"hide"& in the
3123 configuration file is not shown in full, except to an admin user. For other
3124 users, the output is as in this example:
3126 mysql_servers = <value not displayable>
3128 If &%config%& is given as an argument, the config is
3129 output, as it was parsed, any include file resolved, any comment removed.
3131 If &%config_file%& is given as an argument, the name of the runtime
3132 configuration file is output. (&%configure_file%& works too, for
3133 backward compatibility.)
3134 If a list of configuration files was supplied, the value that is output here
3135 is the name of the file that was actually used.
3137 .cindex "options" "hiding name of"
3138 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3139 name will not be output.
3141 .cindex "daemon" "process id (pid)"
3142 .cindex "pid (process id)" "of daemon"
3143 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3144 directories where log files and daemon pid files are written are output,
3145 respectively. If these values are unset, log files are written in a
3146 sub-directory of the spool directory called &%log%&, and the pid file is
3147 written directly into the spool directory.
3149 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3151 exim -bP +local_domains
3153 it searches for a matching named list of any type (domain, host, address, or
3154 local part) and outputs what it finds.
3156 .cindex "options" "router &-- extracting"
3157 .cindex "options" "transport &-- extracting"
3158 .cindex "options" "authenticator &-- extracting"
3159 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3160 followed by the name of an appropriate driver instance, the option settings for
3161 that driver are output. For example:
3163 exim -bP transport local_delivery
3165 The generic driver options are output first, followed by the driver's private
3166 options. A list of the names of drivers of a particular type can be obtained by
3167 using one of the words &%router_list%&, &%transport_list%&, or
3168 &%authenticator_list%&, and a complete list of all drivers with their option
3169 settings can be obtained by using &%routers%&, &%transports%&, or
3172 .cindex "environment"
3173 If &%environment%& is given as an argument, the set of environment
3174 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3177 .cindex "options" "macro &-- extracting"
3178 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3179 are available, similarly to the drivers. Because macros are sometimes used
3180 for storing passwords, this option is restricted.
3181 The output format is one item per line.
3182 For the "-bP macro <name>" form, if no such macro is found
3183 the exit status will be nonzero.
3187 .cindex "queue" "listing messages in"
3188 .cindex "listing" "messages in the queue"
3189 This option requests a listing of the contents of the mail queue on the
3190 standard output. If the &%-bp%& option is followed by a list of message ids,
3191 just those messages are listed. By default, this option can be used only by an
3192 admin user. However, the &%queue_list_requires_admin%& option can be set false
3193 to allow any user to see the queue.
3195 Each message in the queue is displayed as in the following example:
3197 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3198 red.king@looking-glass.fict.example
3201 .cindex "message" "size in queue listing"
3202 .cindex "size" "of message"
3203 The first line contains the length of time the message has been in the queue
3204 (in this case 25 minutes), the size of the message (2.9K), the unique local
3205 identifier for the message, and the message sender, as contained in the
3206 envelope. For bounce messages, the sender address is empty, and appears as
3207 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3208 the default sender address, the user's login name is shown in parentheses
3209 before the sender address.
3211 .cindex "frozen messages" "in queue listing"
3212 If the message is frozen (attempts to deliver it are suspended) then the text
3213 &"*** frozen ***"& is displayed at the end of this line.
3215 The recipients of the message (taken from the envelope, not the headers) are
3216 displayed on subsequent lines. Those addresses to which the message has already
3217 been delivered are marked with the letter D. If an original address gets
3218 expanded into several addresses via an alias or forward file, the original is
3219 displayed with a D only when deliveries for all of its child addresses are
3225 This option operates like &%-bp%&, but in addition it shows delivered addresses
3226 that were generated from the original top level address(es) in each message by
3227 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3233 .cindex "queue" "count of messages on"
3234 This option counts the number of messages in the queue, and writes the total
3235 to the standard output. It is restricted to admin users, unless
3236 &%queue_list_requires_admin%& is set false.
3241 This option operates like &%-bp%&, but the output is not sorted into
3242 chronological order of message arrival. This can speed it up when there are
3243 lots of messages in the queue, and is particularly useful if the output is
3244 going to be post-processed in a way that doesn't need the sorting.
3248 This option is a combination of &%-bpr%& and &%-bpa%&.
3252 This option is a combination of &%-bpr%& and &%-bpu%&.
3257 This option operates like &%-bp%& but shows only undelivered top-level
3258 addresses for each message displayed. Addresses generated by aliasing or
3259 forwarding are not shown, unless the message was deferred after processing by a
3260 router with the &%one_time%& option set.
3265 .cindex "testing" "retry configuration"
3266 .cindex "retry" "configuration testing"
3267 This option is for testing retry rules, and it must be followed by up to three
3268 arguments. It causes Exim to look for a retry rule that matches the values
3269 and to write it to the standard output. For example:
3271 exim -brt bach.comp.mus.example
3272 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3274 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3275 argument, which is required, can be a complete address in the form
3276 &'local_part@domain'&, or it can be just a domain name. If the second argument
3277 contains a dot, it is interpreted as an optional second domain name; if no
3278 retry rule is found for the first argument, the second is tried. This ties in
3279 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3280 rule is found that matches the host, one that matches the mail domain is
3281 sought. Finally, an argument that is the name of a specific delivery error, as
3282 used in setting up retry rules, can be given. For example:
3284 exim -brt haydn.comp.mus.example quota_3d
3285 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3290 .cindex "testing" "rewriting"
3291 .cindex "rewriting" "testing"
3292 This option is for testing address rewriting rules, and it must be followed by
3293 a single argument, consisting of either a local part without a domain, or a
3294 complete address with a fully qualified domain. Exim outputs how this address
3295 would be rewritten for each possible place it might appear. See chapter
3296 &<<CHAPrewrite>>& for further details.
3300 .cindex "SMTP" "batched incoming"
3301 .cindex "batched SMTP input"
3302 This option is used for batched SMTP input, which is an alternative interface
3303 for non-interactive local message submission. A number of messages can be
3304 submitted in a single run. However, despite its name, this is not really SMTP
3305 input. Exim reads each message's envelope from SMTP commands on the standard
3306 input, but generates no responses. If the caller is trusted, or
3307 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3308 believed; otherwise the sender is always the caller of Exim.
3310 The message itself is read from the standard input, in SMTP format (leading
3311 dots doubled), terminated by a line containing just a single dot. An error is
3312 provoked if the terminating dot is missing. A further message may then follow.
3314 As for other local message submissions, the contents of incoming batch SMTP
3315 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3316 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3317 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3319 Some other SMTP commands are recognized in the input. HELO and EHLO act
3320 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3321 QUIT quits, ignoring the rest of the standard input.
3323 .cindex "return code" "for &%-bS%&"
3324 If any error is encountered, reports are written to the standard output and
3325 error streams, and Exim gives up immediately. The return code is 0 if no error
3326 was detected; it is 1 if one or more messages were accepted before the error
3327 was detected; otherwise it is 2.
3329 More details of input using batched SMTP are given in section
3330 &<<SECTincomingbatchedSMTP>>&.
3334 .cindex "SMTP" "local input"
3335 .cindex "local SMTP input"
3336 This option causes Exim to accept one or more messages by reading SMTP commands
3337 on the standard input, and producing SMTP replies on the standard output. SMTP
3338 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3339 Some user agents use this interface as a way of passing locally-generated
3340 messages to the MTA.
3343 .cindex "sender" "source of"
3344 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3345 set, the senders of messages are taken from the SMTP MAIL commands.
3346 Otherwise the content of these commands is ignored and the sender is set up as
3347 the calling user. Unqualified addresses are automatically qualified using
3348 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3349 &%-bnq%& option is used.
3353 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3354 using a listening daemon. Exim can distinguish the two cases by checking
3355 whether the standard input is a TCP/IP socket. When Exim is called from
3356 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3357 above concerning senders and qualification do not apply. In this situation,
3358 Exim behaves in exactly the same way as it does when receiving a message via
3359 the listening daemon.
3363 .cindex "testing" "addresses"
3364 .cindex "address" "testing"
3365 This option runs Exim in address testing mode, in which each argument is taken
3366 as a recipient address to be tested for deliverability. The results are
3367 written to the standard output. If a test fails, and the caller is not an admin
3368 user, no details of the failure are output, because these might contain
3369 sensitive information such as usernames and passwords for database lookups.
3371 If no arguments are given, Exim runs in an interactive manner, prompting with a
3372 right angle bracket for addresses to be tested.
3374 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3375 &[readline()]& function, because it is running as &'root'& and there are
3378 Each address is handled as if it were the recipient address of a message
3379 (compare the &%-bv%& option). It is passed to the routers and the result is
3380 written to the standard output. However, any router that has
3381 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3382 genuine routing tests if your first router passes everything to a scanner
3385 .cindex "return code" "for &%-bt%&"
3386 The return code is 2 if any address failed outright; it is 1 if no address
3387 failed outright but at least one could not be resolved for some reason. Return
3388 code 0 is given only when all addresses succeed.
3390 .cindex "duplicate addresses"
3391 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3392 addresses after routing is complete, so that only one delivery takes place.
3393 This does not happen when testing with &%-bt%&; the full results of routing are
3396 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3397 routers in the configuration makes any tests on the sender address of a
3399 .oindex "&%-f%&" "for address testing"
3400 you can use the &%-f%& option to set an appropriate sender when running
3401 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3402 default qualifying domain. However, if you have set up (for example) routers
3403 whose behaviour depends on the contents of an incoming message, you cannot test
3404 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3409 .cindex "version number of Exim"
3410 This option causes Exim to write the current version number, compilation
3411 number, and compilation date of the &'exim'& binary to the standard output.
3412 It also lists the DBM library that is being used, the optional modules (such as
3413 specific lookup types), the drivers that are included in the binary, and the
3414 name of the runtime configuration file that is in use.
3416 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3417 configuration file. However, this is a static check only. It cannot check
3418 values that are to be expanded. For example, although a misspelt ACL verb is
3419 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3420 alone to discover (for example) all the typos in the configuration; some
3421 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3422 dynamic testing facilities.
3426 .cindex "verifying address" "using &%-bv%&"
3427 .cindex "address" "verification"
3428 This option runs Exim in address verification mode, in which each argument is
3429 taken as a recipient address to be verified by the routers. (This does
3430 not involve any verification callouts). During normal operation, verification
3431 happens mostly as a consequence processing a &%verify%& condition in an ACL
3432 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3433 including callouts, see the &%-bh%& and &%-bhc%& options.
3435 If verification fails, and the caller is not an admin user, no details of the
3436 failure are output, because these might contain sensitive information such as
3437 usernames and passwords for database lookups.
3439 If no arguments are given, Exim runs in an interactive manner, prompting with a
3440 right angle bracket for addresses to be verified.
3442 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3443 &[readline()]& function, because it is running as &'exim'& and there are
3446 Verification differs from address testing (the &%-bt%& option) in that routers
3447 that have &%no_verify%& set are skipped, and if the address is accepted by a
3448 router that has &%fail_verify%& set, verification fails. The address is
3449 verified as a recipient if &%-bv%& is used; to test verification for a sender
3450 address, &%-bvs%& should be used.
3452 If the &%-v%& option is not set, the output consists of a single line for each
3453 address, stating whether it was verified or not, and giving a reason in the
3454 latter case. Without &%-v%&, generating more than one address by redirection
3455 causes verification to end successfully, without considering the generated
3456 addresses. However, if just one address is generated, processing continues,
3457 and the generated address must verify successfully for the overall verification
3460 When &%-v%& is set, more details are given of how the address has been handled,
3461 and in the case of address redirection, all the generated addresses are also
3462 considered. Verification may succeed for some and fail for others.
3465 .cindex "return code" "for &%-bv%&"
3466 return code is 2 if any address failed outright; it is 1 if no address
3467 failed outright but at least one could not be resolved for some reason. Return
3468 code 0 is given only when all addresses succeed.
3470 If any of the routers in the configuration makes any tests on the sender
3471 address of a message, you should use the &%-f%& option to set an appropriate
3472 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3473 calling user at the default qualifying domain.
3477 This option acts like &%-bv%&, but verifies the address as a sender rather
3478 than a recipient address. This affects any rewriting and qualification that
3485 .cindex "inetd" "wait mode"
3486 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3487 similarly to the &%-bd%& option. All port specifications on the command-line
3488 and in the configuration file are ignored. Queue-running may not be specified.
3490 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3491 listening for connections. This permits the system to start up and have
3492 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3493 each port only when the first connection is received.
3495 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3496 which the daemon will exit, which should cause inetd to listen once more.
3498 .vitem &%-C%&&~<&'filelist'&>
3500 .cindex "configuration file" "alternate"
3501 .cindex "CONFIGURE_FILE"
3502 .cindex "alternate configuration file"
3503 This option causes Exim to find the runtime configuration file from the given
3504 list instead of from the list specified by the CONFIGURE_FILE
3505 compile-time setting. Usually, the list will consist of just a single filename,
3506 but it can be a colon-separated list of names. In this case, the first
3507 file that exists is used. Failure to open an existing file stops Exim from
3508 proceeding any further along the list, and an error is generated.
3510 When this option is used by a caller other than root, and the list is different
3511 from the compiled-in list, Exim gives up its root privilege immediately, and
3512 runs with the real and effective uid and gid set to those of the caller.
3513 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3514 file contains a list of full pathnames, one per line, for configuration files
3515 which are trusted. Root privilege is retained for any configuration file so
3516 listed, as long as the caller is the Exim user (or the user specified in the
3517 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3518 not writeable by inappropriate users or groups.
3520 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3521 configuration using &%-C%& right through message reception and delivery,
3522 even if the caller is root. The reception works, but by that time, Exim is
3523 running as the Exim user, so when it re-executes to regain privilege for the
3524 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3525 test reception and delivery using two separate commands (one to put a message
3526 in the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3528 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3529 prefix string with which any file named in a &%-C%& command line option
3530 must start. In addition, the filename must not contain the sequence &`/../`&.
3531 However, if the value of the &%-C%& option is identical to the value of
3532 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3533 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3534 unset, any filename can be used with &%-C%&.
3536 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3537 to a directory to which only root has access. This prevents someone who has
3538 broken into the Exim account from running a privileged Exim with an arbitrary
3541 The &%-C%& facility is useful for ensuring that configuration files are
3542 syntactically correct, but cannot be used for test deliveries, unless the
3543 caller is privileged, or unless it is an exotic configuration that does not
3544 require privilege. No check is made on the owner or group of the files
3545 specified by this option.
3548 .vitem &%-D%&<&'macro'&>=<&'value'&>
3550 .cindex "macro" "setting on command line"
3551 This option can be used to override macro definitions in the configuration file
3552 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3553 unprivileged caller, it causes Exim to give up its root privilege.
3554 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3555 completely disabled, and its use causes an immediate error exit.
3557 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3558 colon-separated list of macros which are considered safe and, if &%-D%& only
3559 supplies macros from this list, and the values are acceptable, then Exim will
3560 not give up root privilege if the caller is root, the Exim run-time user, or
3561 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3562 to be removed in the future. Acceptable values for the macros satisfy the
3563 regexp: &`^[A-Za-z0-9_/.-]*$`&
3565 The entire option (including equals sign if present) must all be within one
3566 command line item. &%-D%& can be used to set the value of a macro to the empty
3567 string, in which case the equals sign is optional. These two commands are
3573 To include spaces in a macro definition item, quotes must be used. If you use
3574 quotes, spaces are permitted around the macro name and the equals sign. For
3577 exim '-D ABC = something' ...
3579 &%-D%& may be repeated up to 10 times on a command line.
3580 Only macro names up to 22 letters long can be set.
3583 .vitem &%-d%&<&'debug&~options'&>
3585 .cindex "debugging" "list of selectors"
3586 .cindex "debugging" "&%-d%& option"
3587 This option causes debugging information to be written to the standard
3588 error stream. It is restricted to admin users because debugging output may show
3589 database queries that contain password information. Also, the details of users'
3590 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3591 writes an error message to the standard error stream and exits with a non-zero
3594 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3595 standard debugging data is output. This can be reduced, or increased to include
3596 some more rarely needed information, by directly following &%-d%& with a string
3597 made up of names preceded by plus or minus characters. These add or remove sets
3598 of debugging data, respectively. For example, &%-d+filter%& adds filter
3599 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3600 no spaces are allowed in the debug setting. The available debugging categories
3603 &`acl `& ACL interpretation
3604 &`auth `& authenticators
3605 &`deliver `& general delivery logic
3606 &`dns `& DNS lookups (see also resolver)
3607 &`dnsbl `& DNS black list (aka RBL) code
3608 &`exec `& arguments for &[execv()]& calls
3609 &`expand `& detailed debugging for string expansions
3610 &`filter `& filter handling
3611 &`hints_lookup `& hints data lookups
3612 &`host_lookup `& all types of name-to-IP address handling
3613 &`ident `& ident lookup
3614 &`interface `& lists of local interfaces
3615 &`lists `& matching things in lists
3616 &`load `& system load checks
3617 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3618 &<<CHAPlocalscan>>&)
3619 &`lookup `& general lookup code and all lookups
3620 &`memory `& memory handling
3621 &`noutf8 `& modifier: avoid UTF-8 line-drawing
3622 &`pid `& modifier: add pid to debug output lines
3623 &`process_info `& setting info for the process log
3624 &`queue_run `& queue runs
3625 &`receive `& general message reception logic
3626 &`resolver `& turn on the DNS resolver's debugging output
3627 &`retry `& retry handling
3628 &`rewrite `& address rewriting
3629 &`route `& address routing
3630 &`timestamp `& modifier: add timestamp to debug output lines
3632 &`transport `& transports
3633 &`uid `& changes of uid/gid and looking up uid/gid
3634 &`verify `& address verification logic
3635 &`all `& almost all of the above (see below), and also &%-v%&
3637 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3638 for &`-all`&. The reason for this is that &`+all`& is something that people
3639 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3640 is included, an awful lot of output that is very rarely of interest is
3641 generated, so it now has to be explicitly requested. However, &`-all`& does
3642 turn everything off.
3644 .cindex "resolver, debugging output"
3645 .cindex "DNS resolver, debugging output"
3646 The &`resolver`& option produces output only if the DNS resolver was compiled
3647 with DEBUG enabled. This is not the case in some operating systems. Also,
3648 unfortunately, debugging output from the DNS resolver is written to stdout
3651 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3652 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3653 However, the &`pid`& selector is forced when debugging is turned on for a
3654 daemon, which then passes it on to any re-executed Exims. Exim also
3655 automatically adds the pid to debug lines when several remote deliveries are
3658 The &`timestamp`& selector causes the current time to be inserted at the start
3659 of all debug output lines. This can be useful when trying to track down delays
3662 .cindex debugging "UTF-8 in"
3663 .cindex UTF-8 "in debug output"
3664 The &`noutf8`& selector disables the use of
3665 UTF-8 line-drawing characters to group related information.
3666 When disabled. ascii-art is used instead.
3667 Using the &`+all`& option does not set this modifier,
3669 If the &%debug_print%& option is set in any driver, it produces output whenever
3670 any debugging is selected, or if &%-v%& is used.
3672 .vitem &%-dd%&<&'debug&~options'&>
3674 This option behaves exactly like &%-d%& except when used on a command that
3675 starts a daemon process. In that case, debugging is turned off for the
3676 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3677 behaviour of the daemon without creating as much output as full debugging does.
3680 .oindex "&%-dropcr%&"
3681 This is an obsolete option that is now a no-op. It used to affect the way Exim
3682 handled CR and LF characters in incoming messages. What happens now is
3683 described in section &<<SECTlineendings>>&.
3687 .cindex "bounce message" "generating"
3688 This option specifies that an incoming message is a locally-generated delivery
3689 failure report. It is used internally by Exim when handling delivery failures
3690 and is not intended for external use. Its only effect is to stop Exim
3691 generating certain messages to the postmaster, as otherwise message cascades
3692 could occur in some situations. As part of the same option, a message id may
3693 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3694 new message contains the id, following &"R="&, as a cross-reference.
3697 .oindex "&%-e%&&'x'&"
3698 There are a number of Sendmail options starting with &%-oe%& which seem to be
3699 called by various programs without the leading &%o%& in the option. For
3700 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3701 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3703 .vitem &%-F%&&~<&'string'&>
3705 .cindex "sender" "name"
3706 .cindex "name" "of sender"
3707 This option sets the sender's full name for use when a locally-generated
3708 message is being accepted. In the absence of this option, the user's &'gecos'&
3709 entry from the password data is used. As users are generally permitted to alter
3710 their &'gecos'& entries, no security considerations are involved. White space
3711 between &%-F%& and the <&'string'&> is optional.
3713 .vitem &%-f%&&~<&'address'&>
3715 .cindex "sender" "address"
3716 .cindex "address" "sender"
3717 .cindex "trusted users"
3718 .cindex "envelope sender"
3719 .cindex "user" "trusted"
3720 This option sets the address of the envelope sender of a locally-generated
3721 message (also known as the return path). The option can normally be used only
3722 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3725 Processes running as root or the Exim user are always trusted. Other
3726 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3727 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3728 of a local message is set to the caller's login name at the default qualify
3731 There is one exception to the restriction on the use of &%-f%&: an empty sender
3732 can be specified by any user, trusted or not, to create a message that can
3733 never provoke a bounce. An empty sender can be specified either as an empty
3734 string, or as a pair of angle brackets with nothing between them, as in these
3735 examples of shell commands:
3737 exim -f '<>' user@domain
3738 exim -f "" user@domain
3740 In addition, the use of &%-f%& is not restricted when testing a filter file
3741 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3744 Allowing untrusted users to change the sender address does not of itself make
3745 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3746 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3747 though this can be overridden by setting &%no_local_from_check%&.
3750 .cindex "&""From""& line"
3751 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3752 given as two arguments or one combined argument). The sender of a
3753 locally-generated message can also be set (when permitted) by an initial
3754 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3755 if &%-f%& is also present, it overrides &"From&~"&.
3759 .cindex "submission fixups, suppressing (command-line)"
3760 This option is equivalent to an ACL applying:
3762 control = suppress_local_fixups
3764 for every message received. Note that Sendmail will complain about such
3765 bad formatting, where Exim silently just does not fix it up. This may change
3768 As this affects audit information, the caller must be a trusted user to use
3771 .vitem &%-h%&&~<&'number'&>
3773 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3774 This option is accepted for compatibility with Sendmail, but has no effect. (In
3775 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3780 .cindex "Solaris" "&'mail'& command"
3781 .cindex "dot" "in incoming non-SMTP message"
3782 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3783 line by itself should not terminate an incoming, non-SMTP message. I can find
3784 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3785 command in Solaris 2.4 uses it. See also &%-ti%&.
3787 .vitem &%-L%&&~<&'tag'&>
3789 .cindex "syslog" "process name; set with flag"
3790 This option is equivalent to setting &%syslog_processname%& in the config
3791 file and setting &%log_file_path%& to &`syslog`&.
3792 Its use is restricted to administrators. The configuration file has to be
3793 read and parsed, to determine access rights, before this is set and takes
3794 effect, so early configuration file errors will not honour this flag.
3796 The tag should not be longer than 32 characters.
3798 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3800 .cindex "forcing delivery"
3801 .cindex "delivery" "forcing attempt"
3802 .cindex "frozen messages" "forcing delivery"
3803 This option requests Exim to run a delivery attempt on each message in turn. If
3804 any of the messages are frozen, they are automatically thawed before the
3805 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3806 and &%hold_domains%& are ignored.
3809 .cindex "hints database" "overriding retry hints"
3810 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3811 the normal retry time has not yet been reached. This option requires the caller
3812 to be an admin user. However, there is an option called &%prod_requires_admin%&
3813 which can be set false to relax this restriction (and also the same requirement
3814 for the &%-q%&, &%-R%&, and &%-S%& options).
3816 The deliveries happen synchronously, that is, the original Exim process does
3817 not terminate until all the delivery attempts have finished. No output is
3818 produced unless there is a serious error. If you want to see what is happening,
3819 use the &%-v%& option as well, or inspect Exim's main log.
3821 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3823 .cindex "message" "adding recipients"
3824 .cindex "recipient" "adding"
3825 This option requests Exim to add the addresses to the list of recipients of the
3826 message (&"ar"& for &"add recipients"&). The first argument must be a message
3827 id, and the remaining ones must be email addresses. However, if the message is
3828 active (in the middle of a delivery attempt), it is not altered. This option
3829 can be used only by an admin user.
3831 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3832 &~<&'message&~id'&>"
3834 .cindex "SMTP" "passed connection"
3835 .cindex "SMTP" "multiple deliveries"
3836 .cindex "multiple SMTP deliveries"
3837 This option is not intended for use by external callers. It is used internally
3838 by Exim to invoke another instance of itself to deliver a waiting message using
3839 an existing SMTP connection, which is passed as the standard input. Details are
3840 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3841 must be root or the Exim user in order to use it.
3845 This option is not intended for use by external callers. It is used internally
3846 by Exim in conjunction with the &%-MC%& option. It signifies that the
3847 connection to the remote host has been authenticated.
3851 This option is not intended for use by external callers. It is used internally
3852 by Exim in conjunction with the &%-MC%& option. It signifies that the
3853 remote host supports the ESMTP &_DSN_& extension.
3855 .vitem &%-MCG%&&~<&'queue&~name'&>
3857 This option is not intended for use by external callers. It is used internally
3858 by Exim in conjunction with the &%-MC%& option. It signifies that an
3859 alternate queue is used, named by the following argument.
3863 This option is not intended for use by external callers. It is used internally
3864 by Exim in conjunction with the &%-MC%& option. It signifies that a
3865 remote host supports the ESMTP &_CHUNKING_& extension.
3869 This option is not intended for use by external callers. It is used internally
3870 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3871 which Exim is connected supports pipelining.
3873 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3875 This option is not intended for use by external callers. It is used internally
3876 by Exim in conjunction with the &%-MC%& option when the original delivery was
3877 started by a queue runner. It passes on the process id of the queue runner,
3878 together with the file descriptor number of an open pipe. Closure of the pipe
3879 signals the final completion of the sequence of processes that are passing
3880 messages through the same SMTP connection.
3884 This option is not intended for use by external callers. It is used internally
3885 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3886 SMTP SIZE option should be used on messages delivered down the existing
3891 This option is not intended for use by external callers. It is used internally
3892 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3893 host to which Exim is connected supports TLS encryption.
3895 .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
3897 This option is not intended for use by external callers. It is used internally
3898 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3899 connection is being proxied by a parent process for handling TLS encryption.
3900 The arguments give the local address and port being proxied, and the TLS cipher.
3902 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3904 .cindex "hints database" "not overridden by &%-Mc%&"
3905 .cindex "delivery" "manually started &-- not forced"
3906 This option requests Exim to run a delivery attempt on each message, in turn,
3907 but unlike the &%-M%& option, it does check for retry hints, and respects any
3908 that are found. This option is not very useful to external callers. It is
3909 provided mainly for internal use by Exim when it needs to re-invoke itself in
3910 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3911 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3912 respects retry times and other options such as &%hold_domains%& that are
3913 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3914 If you want to run a specific delivery as if in a queue run, you should use
3915 &%-q%& with a message id argument. A distinction between queue run deliveries
3916 and other deliveries is made in one or two places.
3918 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3920 .cindex "message" "changing sender"
3921 .cindex "sender" "changing"
3922 This option requests Exim to change the sender address in the message to the
3923 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3924 &"edit sender"&). There must be exactly two arguments. The first argument must
3925 be a message id, and the second one an email address. However, if the message
3926 is active (in the middle of a delivery attempt), its status is not altered.
3927 This option can be used only by an admin user.
3929 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3931 .cindex "freezing messages"
3932 .cindex "message" "manually freezing"
3933 This option requests Exim to mark each listed message as &"frozen"&. This
3934 prevents any delivery attempts taking place until the message is &"thawed"&,
3935 either manually or as a result of the &%auto_thaw%& configuration option.
3936 However, if any of the messages are active (in the middle of a delivery
3937 attempt), their status is not altered. This option can be used only by an admin
3940 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3942 .cindex "giving up on messages"
3943 .cindex "message" "abandoning delivery attempts"
3944 .cindex "delivery" "abandoning further attempts"
3945 This option requests Exim to give up trying to deliver the listed messages,
3946 including any that are frozen. However, if any of the messages are active,
3947 their status is not altered. For non-bounce messages, a delivery error message
3948 is sent to the sender, containing the text &"cancelled by administrator"&.
3949 Bounce messages are just discarded. This option can be used only by an admin
3952 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3954 .cindex "delivery" "cancelling all"
3955 This option requests Exim to mark all the recipient addresses in the messages
3956 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3957 message is active (in the middle of a delivery attempt), its status is not
3958 altered. This option can be used only by an admin user.
3960 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3962 .cindex "delivery" "cancelling by address"
3963 .cindex "recipient" "removing"
3964 .cindex "removing recipients"
3965 This option requests Exim to mark the given addresses as already delivered
3966 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3967 the remaining ones must be email addresses. These are matched to recipient
3968 addresses in the message in a case-sensitive manner. If the message is active
3969 (in the middle of a delivery attempt), its status is not altered. This option
3970 can be used only by an admin user.
3972 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3974 .cindex "removing messages"
3975 .cindex "abandoning mail"
3976 .cindex "message" "manually discarding"
3977 This option requests Exim to remove the given messages from the queue. No
3978 bounce messages are sent; each message is simply forgotten. However, if any of
3979 the messages are active, their status is not altered. This option can be used
3980 only by an admin user or by the user who originally caused the message to be
3981 placed in the queue.
3986 . .cindex REQUIRETLS
3987 . This option is used to request REQUIRETLS processing on the message.
3988 . It is used internally by Exim in conjunction with -E when generating
3992 .vitem &%-Mset%&&~<&'message&~id'&>
3994 .cindex "testing" "string expansion"
3995 .cindex "expansion" "testing"
3996 This option is useful only in conjunction with &%-be%& (that is, when testing
3997 string expansions). Exim loads the given message from its spool before doing
3998 the test expansions, thus setting message-specific variables such as
3999 &$message_size$& and the header variables. The &$recipients$& variable is made
4000 available. This feature is provided to make it easier to test expansions that
4001 make use of these variables. However, this option can be used only by an admin
4002 user. See also &%-bem%&.
4004 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4006 .cindex "thawing messages"
4007 .cindex "unfreezing messages"
4008 .cindex "frozen messages" "thawing"
4009 .cindex "message" "thawing frozen"
4010 This option requests Exim to &"thaw"& any of the listed messages that are
4011 &"frozen"&, so that delivery attempts can resume. However, if any of the
4012 messages are active, their status is not altered. This option can be used only
4015 .vitem &%-Mvb%&&~<&'message&~id'&>
4017 .cindex "listing" "message body"
4018 .cindex "message" "listing body of"
4019 This option causes the contents of the message body (-D) spool file to be
4020 written to the standard output. This option can be used only by an admin user.
4022 .vitem &%-Mvc%&&~<&'message&~id'&>
4024 .cindex "message" "listing in RFC 2822 format"
4025 .cindex "listing" "message in RFC 2822 format"
4026 This option causes a copy of the complete message (header lines plus body) to
4027 be written to the standard output in RFC 2822 format. This option can be used
4028 only by an admin user.
4030 .vitem &%-Mvh%&&~<&'message&~id'&>
4032 .cindex "listing" "message headers"
4033 .cindex "header lines" "listing"
4034 .cindex "message" "listing header lines"
4035 This option causes the contents of the message headers (-H) spool file to be
4036 written to the standard output. This option can be used only by an admin user.
4038 .vitem &%-Mvl%&&~<&'message&~id'&>
4040 .cindex "listing" "message log"
4041 .cindex "message" "listing message log"
4042 This option causes the contents of the message log spool file to be written to
4043 the standard output. This option can be used only by an admin user.
4047 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
4048 treats it that way too.
4052 .cindex "debugging" "&%-N%& option"
4053 .cindex "debugging" "suppressing delivery"
4054 This is a debugging option that inhibits delivery of a message at the transport
4055 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4056 it just doesn't actually transport the message, but instead behaves as if it
4057 had successfully done so. However, it does not make any updates to the retry
4058 database, and the log entries for deliveries are flagged with &"*>"& rather
4061 Because &%-N%& discards any message to which it applies, only root or the Exim
4062 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4063 words, an ordinary user can use it only when supplying an incoming message to
4064 which it will apply. Although transportation never fails when &%-N%& is set, an
4065 address may be deferred because of a configuration problem on a transport, or a
4066 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4067 the message, and applies to any subsequent delivery attempts that may happen
4072 This option is interpreted by Sendmail to mean &"no aliasing"&.
4073 For normal modes of operation, it is ignored by Exim.
4074 When combined with &%-bP%& it makes the output more terse (suppresses
4075 option names, environment values and config pretty printing).
4077 .vitem &%-O%&&~<&'data'&>
4079 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4082 .vitem &%-oA%&&~<&'file&~name'&>
4084 .cindex "Sendmail compatibility" "&%-oA%& option"
4085 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4086 alternative alias filename. Exim handles &%-bi%& differently; see the
4089 .vitem &%-oB%&&~<&'n'&>
4091 .cindex "SMTP" "passed connection"
4092 .cindex "SMTP" "multiple deliveries"
4093 .cindex "multiple SMTP deliveries"
4094 This is a debugging option which limits the maximum number of messages that can
4095 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4096 transport. If <&'n'&> is omitted, the limit is set to 1.
4100 .cindex "background delivery"
4101 .cindex "delivery" "in the background"
4102 This option applies to all modes in which Exim accepts incoming messages,
4103 including the listening daemon. It requests &"background"& delivery of such
4104 messages, which means that the accepting process automatically starts a
4105 delivery process for each message received, but does not wait for the delivery
4106 processes to finish.
4108 When all the messages have been received, the reception process exits,
4109 leaving the delivery processes to finish in their own time. The standard output
4110 and error streams are closed at the start of each delivery process.
4111 This is the default action if none of the &%-od%& options are present.
4113 If one of the queueing options in the configuration file
4114 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4115 overrides it if &%queue_only_override%& is set true, which is the default
4116 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4120 .cindex "foreground delivery"
4121 .cindex "delivery" "in the foreground"
4122 This option requests &"foreground"& (synchronous) delivery when Exim has
4123 accepted a locally-generated message. (For the daemon it is exactly the same as
4124 &%-odb%&.) A delivery process is automatically started to deliver the message,
4125 and Exim waits for it to complete before proceeding.
4127 The original Exim reception process does not finish until the delivery
4128 process for the final message has ended. The standard error stream is left open
4131 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4132 false and one of the queueing options in the configuration file is in effect.
4134 If there is a temporary delivery error during foreground delivery, the
4135 message is left in the queue for later delivery, and the original reception
4136 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4137 restricted configuration that never queues messages.
4142 This option is synonymous with &%-odf%&. It is provided for compatibility with
4147 .cindex "non-immediate delivery"
4148 .cindex "delivery" "suppressing immediate"
4149 .cindex "queueing incoming messages"
4150 This option applies to all modes in which Exim accepts incoming messages,
4151 including the listening daemon. It specifies that the accepting process should
4152 not automatically start a delivery process for each message received. Messages
4153 are placed in the queue, and remain there until a subsequent queue runner
4154 process encounters them. There are several configuration options (such as
4155 &%queue_only%&) that can be used to queue incoming messages under certain
4156 conditions. This option overrides all of them and also &%-odqs%&. It always
4161 .cindex "SMTP" "delaying delivery"
4162 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4163 However, like &%-odb%& and &%-odi%&, this option has no effect if
4164 &%queue_only_override%& is false and one of the queueing options in the
4165 configuration file is in effect.
4167 When &%-odqs%& does operate, a delivery process is started for each incoming
4168 message, in the background by default, but in the foreground if &%-odi%& is
4169 also present. The recipient addresses are routed, and local deliveries are done
4170 in the normal way. However, if any SMTP deliveries are required, they are not
4171 done at this time, so the message remains in the queue until a subsequent queue
4172 runner process encounters it. Because routing was done, Exim knows which
4173 messages are waiting for which hosts, and so a number of messages for the same
4174 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4175 configuration option has the same effect for specific domains. See also the
4180 .cindex "error" "reporting"
4181 If an error is detected while a non-SMTP message is being received (for
4182 example, a malformed address), the error is reported to the sender in a mail
4185 .cindex "return code" "for &%-oee%&"
4187 this error message is successfully sent, the Exim receiving process
4188 exits with a return code of zero. If not, the return code is 2 if the problem
4189 is that the original message has no recipients, or 1 for any other error.
4190 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4194 .cindex "error" "reporting"
4195 .cindex "return code" "for &%-oem%&"
4196 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4197 return code, whether or not the error message was successfully sent.
4198 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4202 .cindex "error" "reporting"
4203 If an error is detected while a non-SMTP message is being received, the
4204 error is reported by writing a message to the standard error file (stderr).
4205 .cindex "return code" "for &%-oep%&"
4206 The return code is 1 for all errors.
4210 .cindex "error" "reporting"
4211 This option is supported for compatibility with Sendmail, but has the same
4216 .cindex "error" "reporting"
4217 This option is supported for compatibility with Sendmail, but has the same
4222 .cindex "dot" "in incoming non-SMTP message"
4223 This option, which has the same effect as &%-i%&, specifies that a dot on a
4224 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4225 single dot does terminate, though Exim does no special processing for other
4226 lines that start with a dot. This option is set by default if Exim is called as
4227 &'rmail'&. See also &%-ti%&.
4230 .oindex "&%-oitrue%&"
4231 This option is treated as synonymous with &%-oi%&.
4233 .vitem &%-oMa%&&~<&'host&~address'&>
4235 .cindex "sender" "host address, specifying for local message"
4236 A number of options starting with &%-oM%& can be used to set values associated
4237 with remote hosts on locally-submitted messages (that is, messages not received
4238 over TCP/IP). These options can be used by any caller in conjunction with the
4239 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4240 other circumstances, they are ignored unless the caller is trusted.
4242 The &%-oMa%& option sets the sender host address. This may include a port
4243 number at the end, after a full stop (period). For example:
4245 exim -bs -oMa 10.9.8.7.1234
4247 An alternative syntax is to enclose the IP address in square brackets,
4248 followed by a colon and the port number:
4250 exim -bs -oMa [10.9.8.7]:1234
4252 The IP address is placed in the &$sender_host_address$& variable, and the
4253 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4254 are present on the command line, the sender host IP address is taken from
4255 whichever one is last.
4257 .vitem &%-oMaa%&&~<&'name'&>
4259 .cindex "authentication" "name, specifying for local message"
4260 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4261 option sets the value of &$sender_host_authenticated$& (the authenticator
4262 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4263 This option can be used with &%-bh%& and &%-bs%& to set up an
4264 authenticated SMTP session without actually using the SMTP AUTH command.
4266 .vitem &%-oMai%&&~<&'string'&>
4268 .cindex "authentication" "id, specifying for local message"
4269 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4270 option sets the value of &$authenticated_id$& (the id that was authenticated).
4271 This overrides the default value (the caller's login id, except with &%-bh%&,
4272 where there is no default) for messages from local sources. See chapter
4273 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4275 .vitem &%-oMas%&&~<&'address'&>
4277 .cindex "authentication" "sender, specifying for local message"
4278 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4279 option sets the authenticated sender value in &$authenticated_sender$&. It
4280 overrides the sender address that is created from the caller's login id for
4281 messages from local sources, except when &%-bh%& is used, when there is no
4282 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4283 specified on a MAIL command overrides this value. See chapter
4284 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4286 .vitem &%-oMi%&&~<&'interface&~address'&>
4288 .cindex "interface" "address, specifying for local message"
4289 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4290 option sets the IP interface address value. A port number may be included,
4291 using the same syntax as for &%-oMa%&. The interface address is placed in
4292 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4294 .vitem &%-oMm%&&~<&'message&~reference'&>
4296 .cindex "message reference" "message reference, specifying for local message"
4297 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4298 option sets the message reference, e.g. message-id, and is logged during
4299 delivery. This is useful when some kind of audit trail is required to tie
4300 messages together. The format of the message reference is checked and will
4301 abort if the format is invalid. The option will only be accepted if exim is
4302 running in trusted mode, not as any regular user.
4304 The best example of a message reference is when Exim sends a bounce message.
4305 The message reference is the message-id of the original message for which Exim
4306 is sending the bounce.
4308 .vitem &%-oMr%&&~<&'protocol&~name'&>
4310 .cindex "protocol, specifying for local message"
4311 .vindex "&$received_protocol$&"
4312 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4313 option sets the received protocol value that is stored in
4314 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4315 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4316 SMTP protocol names (see the description of &$received_protocol$& in section
4317 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4318 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4319 be set by &%-oMr%&. Repeated use of this option is not supported.
4321 .vitem &%-oMs%&&~<&'host&~name'&>
4323 .cindex "sender" "host name, specifying for local message"
4324 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4325 option sets the sender host name in &$sender_host_name$&. When this option is
4326 present, Exim does not attempt to look up a host name from an IP address; it
4327 uses the name it is given.
4329 .vitem &%-oMt%&&~<&'ident&~string'&>
4331 .cindex "sender" "ident string, specifying for local message"
4332 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4333 option sets the sender ident value in &$sender_ident$&. The default setting for
4334 local callers is the login id of the calling process, except when &%-bh%& is
4335 used, when there is no default.
4339 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4340 In Sendmail, this option means &"me too"&, indicating that the sender of a
4341 message should receive a copy of the message if the sender appears in an alias
4342 expansion. Exim always does this, so the option does nothing.
4346 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4347 This option is ignored. In Sendmail it specifies &"old style headers"&,
4348 whatever that means.
4350 .vitem &%-oP%&&~<&'path'&>
4352 .cindex "pid (process id)" "of daemon"
4353 .cindex "daemon" "process id (pid)"
4354 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4355 value. The option specifies the file to which the process id of the daemon is
4356 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4357 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4358 because in those cases, the normal pid file is not used.
4360 .vitem &%-or%&&~<&'time'&>
4362 .cindex "timeout" "for non-SMTP input"
4363 This option sets a timeout value for incoming non-SMTP messages. If it is not
4364 set, Exim will wait forever for the standard input. The value can also be set
4365 by the &%receive_timeout%& option. The format used for specifying times is
4366 described in section &<<SECTtimeformat>>&.
4368 .vitem &%-os%&&~<&'time'&>
4370 .cindex "timeout" "for SMTP input"
4371 .cindex "SMTP" "input timeout"
4372 This option sets a timeout value for incoming SMTP messages. The timeout
4373 applies to each SMTP command and block of data. The value can also be set by
4374 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4375 for specifying times is described in section &<<SECTtimeformat>>&.
4379 This option has exactly the same effect as &%-v%&.
4381 .vitem &%-oX%&&~<&'number&~or&~string'&>
4383 .cindex "TCP/IP" "setting listening ports"
4384 .cindex "TCP/IP" "setting listening interfaces"
4385 .cindex "port" "receiving TCP/IP"
4386 This option is relevant only when the &%-bd%& (start listening daemon) option
4387 is also given. It controls which ports and interfaces the daemon uses. Details
4388 of the syntax, and how it interacts with configuration file options, are given
4389 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4390 file is written unless &%-oP%& is also present to specify a pid filename.
4394 .cindex "Perl" "starting the interpreter"
4395 This option applies when an embedded Perl interpreter is linked with Exim (see
4396 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4397 option, forcing the starting of the interpreter to be delayed until it is
4402 .cindex "Perl" "starting the interpreter"
4403 This option applies when an embedded Perl interpreter is linked with Exim (see
4404 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4405 option, forcing the starting of the interpreter to occur as soon as Exim is
4408 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4410 For compatibility with Sendmail, this option is equivalent to
4412 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4414 It sets the incoming protocol and host name (for trusted callers). The
4415 host name and its colon can be omitted when only the protocol is to be set.
4416 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4417 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4418 or &`s`& using this option (but that does not seem a real limitation).
4419 Repeated use of this option is not supported.
4423 .cindex "queue runner" "starting manually"
4424 This option is normally restricted to admin users. However, there is a
4425 configuration option called &%prod_requires_admin%& which can be set false to
4426 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4427 and &%-S%& options).
4429 .cindex "queue runner" "description of operation"
4430 If other commandline options do not specify an action,
4431 the &%-q%& option starts one queue runner process. This scans the queue of
4432 waiting messages, and runs a delivery process for each one in turn. It waits
4433 for each delivery process to finish before starting the next one. A delivery
4434 process may not actually do any deliveries if the retry times for the addresses
4435 have not been reached. Use &%-qf%& (see below) if you want to override this.
4438 .cindex "SMTP" "passed connection"
4439 .cindex "SMTP" "multiple deliveries"
4440 .cindex "multiple SMTP deliveries"
4441 the delivery process spawns other processes to deliver other messages down
4442 passed SMTP connections, the queue runner waits for these to finish before
4445 When all the queued messages have been considered, the original queue runner
4446 process terminates. In other words, a single pass is made over the waiting
4447 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4448 this to be repeated periodically.
4450 Exim processes the waiting messages in an unpredictable order. It isn't very
4451 random, but it is likely to be different each time, which is all that matters.
4452 If one particular message screws up a remote MTA, other messages to the same
4453 MTA have a chance of getting through if they get tried first.
4455 It is possible to cause the messages to be processed in lexical message id
4456 order, which is essentially the order in which they arrived, by setting the
4457 &%queue_run_in_order%& option, but this is not recommended for normal use.
4459 .vitem &%-q%&<&'qflags'&>
4460 The &%-q%& option may be followed by one or more flag letters that change its
4461 behaviour. They are all optional, but if more than one is present, they must
4462 appear in the correct order. Each flag is described in a separate item below.
4466 .cindex "queue" "double scanning"
4467 .cindex "queue" "routing"
4468 .cindex "routing" "whole queue before delivery"
4469 An option starting with &%-qq%& requests a two-stage queue run. In the first
4470 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4471 every domain. Addresses are routed, local deliveries happen, but no remote
4474 .cindex "hints database" "remembering routing"
4475 The hints database that remembers which messages are waiting for specific hosts
4476 is updated, as if delivery to those hosts had been deferred. After this is
4477 complete, a second, normal queue scan happens, with routing and delivery taking
4478 place as normal. Messages that are routed to the same host should mostly be
4479 delivered down a single SMTP
4480 .cindex "SMTP" "passed connection"
4481 .cindex "SMTP" "multiple deliveries"
4482 .cindex "multiple SMTP deliveries"
4483 connection because of the hints that were set up during the first queue scan.
4484 This option may be useful for hosts that are connected to the Internet
4487 .vitem &%-q[q]i...%&
4489 .cindex "queue" "initial delivery"
4490 If the &'i'& flag is present, the queue runner runs delivery processes only for
4491 those messages that haven't previously been tried. (&'i'& stands for &"initial
4492 delivery"&.) This can be helpful if you are putting messages in the queue using
4493 &%-odq%& and want a queue runner just to process the new messages.
4495 .vitem &%-q[q][i]f...%&
4497 .cindex "queue" "forcing delivery"
4498 .cindex "delivery" "forcing in queue run"
4499 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4500 message, whereas without &'f'& only those non-frozen addresses that have passed
4501 their retry times are tried.
4503 .vitem &%-q[q][i]ff...%&
4505 .cindex "frozen messages" "forcing delivery"
4506 If &'ff'& is present, a delivery attempt is forced for every message, whether
4509 .vitem &%-q[q][i][f[f]]l%&
4511 .cindex "queue" "local deliveries only"
4512 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4513 be done. If a message requires any remote deliveries, it remains in the queue
4516 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4519 .cindex "named queues"
4520 .cindex "queue" "delivering specific messages"
4521 If the &'G'& flag and a name is present, the queue runner operates on the
4522 queue with the given name rather than the default queue.
4523 The name should not contain a &'/'& character.
4524 For a periodic queue run (see below)
4525 append to the name a slash and a time value.
4527 If other commandline options specify an action, a &'-qG<name>'& option
4528 will specify a queue to operate on.
4531 exim -bp -qGquarantine
4533 exim -qGoffpeak -Rf @special.domain.example
4536 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4537 When scanning the queue, Exim can be made to skip over messages whose ids are
4538 lexically less than a given value by following the &%-q%& option with a
4539 starting message id. For example:
4541 exim -q 0t5C6f-0000c8-00
4543 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4544 second message id is given, messages whose ids are lexically greater than it
4545 are also skipped. If the same id is given twice, for example,
4547 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4549 just one delivery process is started, for that message. This differs from
4550 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4551 that it counts as a delivery from a queue run. Note that the selection
4552 mechanism does not affect the order in which the messages are scanned. There
4553 are also other ways of selecting specific sets of messages for delivery in a
4554 queue run &-- see &%-R%& and &%-S%&.
4556 .vitem &%-q%&<&'qflags'&><&'time'&>
4557 .cindex "queue runner" "starting periodically"
4558 .cindex "periodic queue running"
4559 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4560 starting a queue runner process at intervals specified by the given time value
4561 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4562 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4563 single daemon process handles both functions. A common way of starting up a
4564 combined daemon at system boot time is to use a command such as
4566 /usr/exim/bin/exim -bd -q30m
4568 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4569 process every 30 minutes.
4571 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4572 pid file is written unless one is explicitly requested by the &%-oP%& option.
4574 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4576 This option is synonymous with &%-R%&. It is provided for Sendmail
4579 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4581 This option is synonymous with &%-S%&.
4583 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4585 .cindex "queue runner" "for specific recipients"
4586 .cindex "delivery" "to given domain"
4587 .cindex "domain" "delivery to"
4588 The <&'rsflags'&> may be empty, in which case the white space before the string
4589 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4590 which are the possible values for <&'rsflags'&>. White space is required if
4591 <&'rsflags'&> is not empty.
4593 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4594 perform a single queue run, except that, when scanning the messages on the
4595 queue, Exim processes only those that have at least one undelivered recipient
4596 address containing the given string, which is checked in a case-independent
4597 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4598 regular expression; otherwise it is a literal string.
4600 If you want to do periodic queue runs for messages with specific recipients,
4601 you can combine &%-R%& with &%-q%& and a time value. For example:
4603 exim -q25m -R @special.domain.example
4605 This example does a queue run for messages with recipients in the given domain
4606 every 25 minutes. Any additional flags that are specified with &%-q%& are
4607 applied to each queue run.
4609 Once a message is selected for delivery by this mechanism, all its addresses
4610 are processed. For the first selected message, Exim overrides any retry
4611 information and forces a delivery attempt for each undelivered address. This
4612 means that if delivery of any address in the first message is successful, any
4613 existing retry information is deleted, and so delivery attempts for that
4614 address in subsequently selected messages (which are processed without forcing)
4615 will run. However, if delivery of any address does not succeed, the retry
4616 information is updated, and in subsequently selected messages, the failing
4617 address will be skipped.
4619 .cindex "frozen messages" "forcing delivery"
4620 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4621 all selected messages, not just the first; frozen messages are included when
4624 The &%-R%& option makes it straightforward to initiate delivery of all messages
4625 to a given domain after a host has been down for some time. When the SMTP
4626 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4627 effect is to run Exim with the &%-R%& option, but it can be configured to run
4628 an arbitrary command instead.
4632 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4634 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4636 .cindex "delivery" "from given sender"
4637 .cindex "queue runner" "for specific senders"
4638 This option acts like &%-R%& except that it checks the string against each
4639 message's sender instead of against the recipients. If &%-R%& is also set, both
4640 conditions must be met for a message to be selected. If either of the options
4641 has &'f'& or &'ff'& in its flags, the associated action is taken.
4643 .vitem &%-Tqt%&&~<&'times'&>
4645 This is an option that is exclusively for use by the Exim testing suite. It is not
4646 recognized when Exim is run normally. It allows for the setting up of explicit
4647 &"queue times"& so that various warning/retry features can be tested.
4651 .cindex "recipient" "extracting from header lines"
4652 .cindex "&'Bcc:'& header line"
4653 .cindex "&'Cc:'& header line"
4654 .cindex "&'To:'& header line"
4655 When Exim is receiving a locally-generated, non-SMTP message on its standard
4656 input, the &%-t%& option causes the recipients of the message to be obtained
4657 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4658 from the command arguments. The addresses are extracted before any rewriting
4659 takes place and the &'Bcc:'& header line, if present, is then removed.
4661 .cindex "Sendmail compatibility" "&%-t%& option"
4662 If the command has any arguments, they specify addresses to which the message
4663 is &'not'& to be delivered. That is, the argument addresses are removed from
4664 the recipients list obtained from the headers. This is compatible with Smail 3
4665 and in accordance with the documented behaviour of several versions of
4666 Sendmail, as described in man pages on a number of operating systems (e.g.
4667 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4668 argument addresses to those obtained from the headers, and the O'Reilly
4669 Sendmail book documents it that way. Exim can be made to add argument addresses
4670 instead of subtracting them by setting the option
4671 &%extract_addresses_remove_arguments%& false.
4673 .cindex "&%Resent-%& header lines" "with &%-t%&"
4674 If there are any &%Resent-%& header lines in the message, Exim extracts
4675 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4676 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4677 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4678 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4680 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4681 message is resent several times). The RFC also specifies that they should be
4682 added at the front of the message, and separated by &'Received:'& lines. It is
4683 not at all clear how &%-t%& should operate in the present of multiple sets,
4684 nor indeed exactly what constitutes a &"set"&.
4685 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4686 are often added at the end of the header, and if a message is resent more than
4687 once, it is common for the original set of &%Resent-%& headers to be renamed as
4688 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4692 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4693 compatibility with Sendmail.
4695 .vitem &%-tls-on-connect%&
4696 .oindex "&%-tls-on-connect%&"
4697 .cindex "TLS" "use without STARTTLS"
4698 .cindex "TLS" "automatic start"
4699 This option is available when Exim is compiled with TLS support. It forces all
4700 incoming SMTP connections to behave as if the incoming port is listed in the
4701 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4702 &<<CHAPTLS>>& for further details.
4707 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4708 Sendmail uses this option for &"initial message submission"&, and its
4709 documentation states that in future releases, it may complain about
4710 syntactically invalid messages rather than fixing them when this flag is not
4711 set. Exim ignores this option.
4715 This option causes Exim to write information to the standard error stream,
4716 describing what it is doing. In particular, it shows the log lines for
4717 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4718 dialogue is shown. Some of the log lines shown may not actually be written to
4719 the log if the setting of &%log_selector%& discards them. Any relevant
4720 selectors are shown with each log line. If none are shown, the logging is
4725 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4726 National Language Support extended characters in the body of the mail item"&).
4727 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4730 .vitem &%-X%&&~<&'logfile'&>
4732 This option is interpreted by Sendmail to cause debug information to be sent
4733 to the named file. It is ignored by Exim.
4735 .vitem &%-z%&&~<&'log-line'&>
4737 This option writes its argument to Exim's logfile.
4738 Use is restricted to administrators; the intent is for operational notes.
4739 Quotes should be used to maintain a multi-word item as a single argument,
4747 . ////////////////////////////////////////////////////////////////////////////
4748 . Insert a stylized DocBook comment here, to identify the end of the command
4749 . line options. This is for the benefit of the Perl script that automatically
4750 . creates a man page for the options.
4751 . ////////////////////////////////////////////////////////////////////////////
4754 <!-- === End of command line options === -->
4761 . ////////////////////////////////////////////////////////////////////////////
4762 . ////////////////////////////////////////////////////////////////////////////
4765 .chapter "The Exim runtime configuration file" "CHAPconf" &&&
4766 "The runtime configuration file"
4768 .cindex "runtime configuration"
4769 .cindex "configuration file" "general description"
4770 .cindex "CONFIGURE_FILE"
4771 .cindex "configuration file" "errors in"
4772 .cindex "error" "in configuration file"
4773 .cindex "return code" "for bad configuration"
4774 Exim uses a single runtime configuration file that is read whenever an Exim
4775 binary is executed. Note that in normal operation, this happens frequently,
4776 because Exim is designed to operate in a distributed manner, without central
4779 If a syntax error is detected while reading the configuration file, Exim
4780 writes a message on the standard error, and exits with a non-zero return code.
4781 The message is also written to the panic log. &*Note*&: Only simple syntax
4782 errors can be detected at this time. The values of any expanded options are
4783 not checked until the expansion happens, even when the expansion does not
4784 actually alter the string.
4786 The name of the configuration file is compiled into the binary for security
4787 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4788 most configurations, this specifies a single file. However, it is permitted to
4789 give a colon-separated list of filenames, in which case Exim uses the first
4790 existing file in the list.
4793 .cindex "EXIM_GROUP"
4794 .cindex "CONFIGURE_OWNER"
4795 .cindex "CONFIGURE_GROUP"
4796 .cindex "configuration file" "ownership"
4797 .cindex "ownership" "configuration file"
4798 The runtime configuration file must be owned by root or by the user that is
4799 specified at compile time by the CONFIGURE_OWNER option (if set). The
4800 configuration file must not be world-writeable, or group-writeable unless its
4801 group is the root group or the one specified at compile time by the
4802 CONFIGURE_GROUP option.
4804 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4805 to root, anybody who is able to edit the runtime configuration file has an
4806 easy way to run commands as root. If you specify a user or group in the
4807 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4808 who are members of that group will trivially be able to obtain root privileges.
4810 Up to Exim version 4.72, the runtime configuration file was also permitted to
4811 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4812 since it offered a simple privilege escalation for any attacker who managed to
4813 compromise the Exim user account.
4815 A default configuration file, which will work correctly in simple situations,
4816 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4817 defines just one filename, the installation process copies the default
4818 configuration to a new file of that name if it did not previously exist. If
4819 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4820 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4825 .section "Using a different configuration file" "SECID40"
4826 .cindex "configuration file" "alternate"
4827 A one-off alternate configuration can be specified by the &%-C%& command line
4828 option, which may specify a single file or a list of files. However, when
4829 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4830 unless the argument for &%-C%& is identical to the built-in value from
4831 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4832 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4833 is useful mainly for checking the syntax of configuration files before
4834 installing them. No owner or group checks are done on a configuration file
4835 specified by &%-C%&, if root privilege has been dropped.
4837 Even the Exim user is not trusted to specify an arbitrary configuration file
4838 with the &%-C%& option to be used with root privileges, unless that file is
4839 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4840 testing a configuration using &%-C%& right through message reception and
4841 delivery, even if the caller is root. The reception works, but by that time,
4842 Exim is running as the Exim user, so when it re-execs to regain privilege for
4843 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4844 can test reception and delivery using two separate commands (one to put a
4845 message in the queue, using &%-odq%&, and another to do the delivery, using
4848 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4849 prefix string with which any file named in a &%-C%& command line option must
4850 start. In addition, the filename must not contain the sequence &"&`/../`&"&.
4851 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any
4852 filename can be used with &%-C%&.
4854 One-off changes to a configuration can be specified by the &%-D%& command line
4855 option, which defines and overrides values for macros used inside the
4856 configuration file. However, like &%-C%&, the use of this option by a
4857 non-privileged user causes Exim to discard its root privilege.
4858 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4859 completely disabled, and its use causes an immediate error exit.
4861 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4862 to declare certain macro names trusted, such that root privilege will not
4863 necessarily be discarded.
4864 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4865 considered safe and, if &%-D%& only supplies macros from this list, and the
4866 values are acceptable, then Exim will not give up root privilege if the caller
4867 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4868 transition mechanism and is expected to be removed in the future. Acceptable
4869 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4871 Some sites may wish to use the same Exim binary on different machines that
4872 share a file system, but to use different configuration files on each machine.
4873 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4874 looks for a file whose name is the configuration filename followed by a dot
4875 and the machine's node name, as obtained from the &[uname()]& function. If this
4876 file does not exist, the standard name is tried. This processing occurs for
4877 each filename in the list given by CONFIGURE_FILE or &%-C%&.
4879 In some esoteric situations different versions of Exim may be run under
4880 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4881 help with this. See the comments in &_src/EDITME_& for details.
4885 .section "Configuration file format" "SECTconffilfor"
4886 .cindex "configuration file" "format of"
4887 .cindex "format" "configuration file"
4888 Exim's configuration file is divided into a number of different parts. General
4889 option settings must always appear at the start of the file. The other parts
4890 are all optional, and may appear in any order. Each part other than the first
4891 is introduced by the word &"begin"& followed by at least one literal
4892 space, and the name of the part. The optional parts are:
4895 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4898 .cindex "AUTH" "configuration"
4899 &'authenticators'&: Configuration settings for the authenticator drivers. These
4900 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4902 &'routers'&: Configuration settings for the router drivers. Routers process
4903 addresses and determine how the message is to be delivered (see chapters
4904 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4906 &'transports'&: Configuration settings for the transport drivers. Transports
4907 define mechanisms for copying messages to destinations (see chapters
4908 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4910 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4911 If there is no retry section, or if it is empty (that is, no retry rules are
4912 defined), Exim will not retry deliveries. In this situation, temporary errors
4913 are treated the same as permanent errors. Retry rules are discussed in chapter
4916 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4917 when new addresses are generated during delivery. Rewriting is discussed in
4918 chapter &<<CHAPrewrite>>&.
4920 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4921 want to use this feature, you must set
4923 LOCAL_SCAN_HAS_OPTIONS=yes
4925 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4926 facility are given in chapter &<<CHAPlocalscan>>&.
4929 .cindex "configuration file" "leading white space in"
4930 .cindex "configuration file" "trailing white space in"
4931 .cindex "white space" "in configuration file"
4932 Leading and trailing white space in configuration lines is always ignored.
4934 Blank lines in the file, and lines starting with a # character (ignoring
4935 leading white space) are treated as comments and are ignored. &*Note*&: A
4936 # character other than at the beginning of a line is not treated specially,
4937 and does not introduce a comment.
4939 Any non-comment line can be continued by ending it with a backslash. Note that
4940 the general rule for white space means that trailing white space after the
4941 backslash and leading white space at the start of continuation
4942 lines is ignored. Comment lines beginning with # (but not empty lines) may
4943 appear in the middle of a sequence of continuation lines.
4945 A convenient way to create a configuration file is to start from the
4946 default, which is supplied in &_src/configure.default_&, and add, delete, or
4947 change settings as required.
4949 The ACLs, retry rules, and rewriting rules have their own syntax which is
4950 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4951 respectively. The other parts of the configuration file have some syntactic
4952 items in common, and these are described below, from section &<<SECTcos>>&
4953 onwards. Before that, the inclusion, macro, and conditional facilities are
4958 .section "File inclusions in the configuration file" "SECID41"
4959 .cindex "inclusions in configuration file"
4960 .cindex "configuration file" "including other files"
4961 .cindex "&`.include`& in configuration file"
4962 .cindex "&`.include_if_exists`& in configuration file"
4963 You can include other files inside Exim's runtime configuration file by
4966 &`.include`& <&'filename'&>
4967 &`.include_if_exists`& <&'filename'&>
4969 on a line by itself. Double quotes round the filename are optional. If you use
4970 the first form, a configuration error occurs if the file does not exist; the
4971 second form does nothing for non-existent files.
4972 The first form allows a relative name. It is resolved relative to
4973 the directory of the including file. For the second form an absolute filename
4976 Includes may be nested to any depth, but remember that Exim reads its
4977 configuration file often, so it is a good idea to keep them to a minimum.
4978 If you change the contents of an included file, you must HUP the daemon,
4979 because an included file is read only when the configuration itself is read.
4981 The processing of inclusions happens early, at a physical line level, so, like
4982 comment lines, an inclusion can be used in the middle of an option setting,
4985 hosts_lookup = a.b.c \
4988 Include processing happens after macro processing (see below). Its effect is to
4989 process the lines of the included file as if they occurred inline where the
4994 .section "Macros in the configuration file" "SECTmacrodefs"
4995 .cindex "macro" "description of"
4996 .cindex "configuration file" "macros"
4997 If a line in the main part of the configuration (that is, before the first
4998 &"begin"& line) begins with an upper case letter, it is taken as a macro
4999 definition, and must be of the form
5001 <&'name'&> = <&'rest of line'&>
5003 The name must consist of letters, digits, and underscores, and need not all be
5004 in upper case, though that is recommended. The rest of the line, including any
5005 continuations, is the replacement text, and has leading and trailing white
5006 space removed. Quotes are not removed. The replacement text can never end with
5007 a backslash character, but this doesn't seem to be a serious limitation.
5009 Macros may also be defined between router, transport, authenticator, or ACL
5010 definitions. They may not, however, be defined within an individual driver or
5011 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
5013 .section "Macro substitution" "SECID42"
5014 Once a macro is defined, all subsequent lines in the file (and any included
5015 files) are scanned for the macro name; if there are several macros, the line is
5016 scanned for each, in turn, in the order in which the macros are defined. The
5017 replacement text is not re-scanned for the current macro, though it is scanned
5018 for subsequently defined macros. For this reason, a macro name may not contain
5019 the name of a previously defined macro as a substring. You could, for example,
5022 &`ABCD_XYZ = `&<&'something'&>
5023 &`ABCD = `&<&'something else'&>
5025 but putting the definitions in the opposite order would provoke a configuration
5026 error. Macro expansion is applied to individual physical lines from the file,
5027 before checking for line continuation or file inclusion (see above). If a line
5028 consists solely of a macro name, and the expansion of the macro is empty, the
5029 line is ignored. A macro at the start of a line may turn the line into a
5030 comment line or a &`.include`& line.
5033 .section "Redefining macros" "SECID43"
5034 Once defined, the value of a macro can be redefined later in the configuration
5035 (or in an included file). Redefinition is specified by using &'=='& instead of
5040 MAC == updated value
5042 Redefinition does not alter the order in which the macros are applied to the
5043 subsequent lines of the configuration file. It is still the same order in which
5044 the macros were originally defined. All that changes is the macro's value.
5045 Redefinition makes it possible to accumulate values. For example:
5049 MAC == MAC and something added
5051 This can be helpful in situations where the configuration file is built
5052 from a number of other files.
5054 .section "Overriding macro values" "SECID44"
5055 The values set for macros in the configuration file can be overridden by the
5056 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5057 used, unless called by root or the Exim user. A definition on the command line
5058 using the &%-D%& option causes all definitions and redefinitions within the
5063 .section "Example of macro usage" "SECID45"
5064 As an example of macro usage, consider a configuration where aliases are looked
5065 up in a MySQL database. It helps to keep the file less cluttered if long
5066 strings such as SQL statements are defined separately as macros, for example:
5068 ALIAS_QUERY = select mailbox from user where \
5069 login='${quote_mysql:$local_part}';
5071 This can then be used in a &(redirect)& router setting like this:
5073 data = ${lookup mysql{ALIAS_QUERY}}
5075 In earlier versions of Exim macros were sometimes used for domain, host, or
5076 address lists. In Exim 4 these are handled better by named lists &-- see
5077 section &<<SECTnamedlists>>&.
5080 .section "Builtin macros" "SECTbuiltinmacros"
5081 Exim defines some macros depending on facilities available, which may
5082 differ due to build-time definitions and from one release to another.
5083 All of these macros start with an underscore.
5084 They can be used to conditionally include parts of a configuration
5087 The following classes of macros are defined:
5089 &` _HAVE_* `& build-time defines
5090 &` _DRIVER_ROUTER_* `& router drivers
5091 &` _DRIVER_TRANSPORT_* `& transport drivers
5092 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5093 &` _LOG_* `& log_selector values
5094 &` _OPT_MAIN_* `& main config options
5095 &` _OPT_ROUTERS_* `& generic router options
5096 &` _OPT_TRANSPORTS_* `& generic transport options
5097 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5098 &` _OPT_ROUTER_*_* `& private router options
5099 &` _OPT_TRANSPORT_*_* `& private transport options
5100 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5103 Use an &"exim -bP macros"& command to get the list of macros.
5106 .section "Conditional skips in the configuration file" "SECID46"
5107 .cindex "configuration file" "conditional skips"
5108 .cindex "&`.ifdef`&"
5109 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5110 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5111 portions of the configuration file. The processing happens whenever the file is
5112 read (that is, when an Exim binary starts to run).
5114 The implementation is very simple. Instances of the first four directives must
5115 be followed by text that includes the names of one or macros. The condition
5116 that is tested is whether or not any macro substitution has taken place in the
5120 message_size_limit = 50M
5122 message_size_limit = 100M
5125 sets a message size limit of 50M if the macro &`AAA`& is defined
5126 (or &`A`& or &`AA`&), and 100M
5127 otherwise. If there is more than one macro named on the line, the condition
5128 is true if any of them are defined. That is, it is an &"or"& condition. To
5129 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5131 Although you can use a macro expansion to generate one of these directives,
5132 it is not very useful, because the condition &"there was a macro substitution
5133 in this line"& will always be true.
5135 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5136 to clarify complicated nestings.
5140 .section "Common option syntax" "SECTcos"
5141 .cindex "common option syntax"
5142 .cindex "syntax of common options"
5143 .cindex "configuration file" "common option syntax"
5144 For the main set of options, driver options, and &[local_scan()]& options,
5145 each setting is on a line by itself, and starts with a name consisting of
5146 lower-case letters and underscores. Many options require a data value, and in
5147 these cases the name must be followed by an equals sign (with optional white
5148 space) and then the value. For example:
5150 qualify_domain = mydomain.example.com
5152 .cindex "hiding configuration option values"
5153 .cindex "configuration options" "hiding value of"
5154 .cindex "options" "hiding value of"
5155 Some option settings may contain sensitive data, for example, passwords for
5156 accessing databases. To stop non-admin users from using the &%-bP%& command
5157 line option to read these values, you can precede the option settings with the
5158 word &"hide"&. For example:
5160 hide mysql_servers = localhost/users/admin/secret-password
5162 For non-admin users, such options are displayed like this:
5164 mysql_servers = <value not displayable>
5166 If &"hide"& is used on a driver option, it hides the value of that option on
5167 all instances of the same driver.
5169 The following sections describe the syntax used for the different data types
5170 that are found in option settings.
5173 .section "Boolean options" "SECID47"
5174 .cindex "format" "boolean"
5175 .cindex "boolean configuration values"
5176 .oindex "&%no_%&&'xxx'&"
5177 .oindex "&%not_%&&'xxx'&"
5178 Options whose type is given as boolean are on/off switches. There are two
5179 different ways of specifying such options: with and without a data value. If
5180 the option name is specified on its own without data, the switch is turned on;
5181 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5182 boolean options may be followed by an equals sign and one of the words
5183 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5184 the following two settings have exactly the same effect:
5189 The following two lines also have the same (opposite) effect:
5194 You can use whichever syntax you prefer.
5199 .section "Integer values" "SECID48"
5200 .cindex "integer configuration values"
5201 .cindex "format" "integer"
5202 If an option's type is given as &"integer"&, the value can be given in decimal,
5203 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5204 number is assumed. Otherwise, it is treated as an octal number unless it starts
5205 with the characters &"0x"&, in which case the remainder is interpreted as a
5208 If an integer value is followed by the letter K, it is multiplied by 1024; if
5209 it is followed by the letter M, it is multiplied by 1024x1024;
5210 if by the letter G, 1024x1024x1024.
5212 of integer option settings are output, values which are an exact multiple of
5213 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5214 and M. The printing style is independent of the actual input format that was
5218 .section "Octal integer values" "SECID49"
5219 .cindex "integer format"
5220 .cindex "format" "octal integer"
5221 If an option's type is given as &"octal integer"&, its value is always
5222 interpreted as an octal number, whether or not it starts with the digit zero.
5223 Such options are always output in octal.
5226 .section "Fixed point numbers" "SECID50"
5227 .cindex "fixed point configuration values"
5228 .cindex "format" "fixed point"
5229 If an option's type is given as &"fixed-point"&, its value must be a decimal
5230 integer, optionally followed by a decimal point and up to three further digits.
5234 .section "Time intervals" "SECTtimeformat"
5235 .cindex "time interval" "specifying in configuration"
5236 .cindex "format" "time interval"
5237 A time interval is specified as a sequence of numbers, each followed by one of
5238 the following letters, with no intervening white space:
5248 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5249 intervals are output in the same format. Exim does not restrict the values; it
5250 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5254 .section "String values" "SECTstrings"
5255 .cindex "string" "format of configuration values"
5256 .cindex "format" "string"
5257 If an option's type is specified as &"string"&, the value can be specified with
5258 or without double-quotes. If it does not start with a double-quote, the value
5259 consists of the remainder of the line plus any continuation lines, starting at
5260 the first character after any leading white space, with trailing white space
5261 removed, and with no interpretation of the characters in the string. Because
5262 Exim removes comment lines (those beginning with #) at an early stage, they can
5263 appear in the middle of a multi-line string. The following two settings are
5264 therefore equivalent:
5266 trusted_users = uucp:mail
5267 trusted_users = uucp:\
5268 # This comment line is ignored
5271 .cindex "string" "quoted"
5272 .cindex "escape characters in quoted strings"
5273 If a string does start with a double-quote, it must end with a closing
5274 double-quote, and any backslash characters other than those used for line
5275 continuation are interpreted as escape characters, as follows:
5278 .irow &`\\`& "single backslash"
5279 .irow &`\n`& "newline"
5280 .irow &`\r`& "carriage return"
5282 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5283 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5287 If a backslash is followed by some other character, including a double-quote
5288 character, that character replaces the pair.
5290 Quoting is necessary only if you want to make use of the backslash escapes to
5291 insert special characters, or if you need to specify a value with leading or
5292 trailing spaces. These cases are rare, so quoting is almost never needed in
5293 current versions of Exim. In versions of Exim before 3.14, quoting was required
5294 in order to continue lines, so you may come across older configuration files
5295 and examples that apparently quote unnecessarily.
5298 .section "Expanded strings" "SECID51"
5299 .cindex "expansion" "definition of"
5300 Some strings in the configuration file are subjected to &'string expansion'&,
5301 by which means various parts of the string may be changed according to the
5302 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5303 is as just described; in particular, the handling of backslashes in quoted
5304 strings is done as part of the input process, before expansion takes place.
5305 However, backslash is also an escape character for the expander, so any
5306 backslashes that are required for that reason must be doubled if they are
5307 within a quoted configuration string.
5310 .section "User and group names" "SECID52"
5311 .cindex "user name" "format of"
5312 .cindex "format" "user name"
5313 .cindex "groups" "name format"
5314 .cindex "format" "group name"
5315 User and group names are specified as strings, using the syntax described
5316 above, but the strings are interpreted specially. A user or group name must
5317 either consist entirely of digits, or be a name that can be looked up using the
5318 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5321 .section "List construction" "SECTlistconstruct"
5322 .cindex "list" "syntax of in configuration"
5323 .cindex "format" "list item in configuration"
5324 .cindex "string" "list, definition of"
5325 The data for some configuration options is a list of items, with colon as the
5326 default separator. Many of these options are shown with type &"string list"& in
5327 the descriptions later in this document. Others are listed as &"domain list"&,
5328 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5329 are all the same; however, those other than &"string list"& are subject to
5330 particular kinds of interpretation, as described in chapter
5331 &<<CHAPdomhosaddlists>>&.
5333 In all these cases, the entire list is treated as a single string as far as the
5334 input syntax is concerned. The &%trusted_users%& setting in section
5335 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5336 in a list, it must be entered as two colons. Leading and trailing white space
5337 on each item in a list is ignored. This makes it possible to include items that
5338 start with a colon, and in particular, certain forms of IPv6 address. For
5341 local_interfaces = 127.0.0.1 : ::::1
5343 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5345 &*Note*&: Although leading and trailing white space is ignored in individual
5346 list items, it is not ignored when parsing the list. The space after the first
5347 colon in the example above is necessary. If it were not there, the list would
5348 be interpreted as the two items 127.0.0.1:: and 1.
5350 .section "Changing list separators" "SECTlistsepchange"
5351 .cindex "list separator" "changing"
5352 .cindex "IPv6" "addresses in lists"
5353 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5354 introduced to allow the separator character to be changed. If a list begins
5355 with a left angle bracket, followed by any punctuation character, that
5356 character is used instead of colon as the list separator. For example, the list
5357 above can be rewritten to use a semicolon separator like this:
5359 local_interfaces = <; 127.0.0.1 ; ::1
5361 This facility applies to all lists, with the exception of the list in
5362 &%log_file_path%&. It is recommended that the use of non-colon separators be
5363 confined to circumstances where they really are needed.
5365 .cindex "list separator" "newline as"
5366 .cindex "newline" "as list separator"
5367 It is also possible to use newline and other control characters (those with
5368 code values less than 32, plus DEL) as separators in lists. Such separators
5369 must be provided literally at the time the list is processed. For options that
5370 are string-expanded, you can write the separator using a normal escape
5371 sequence. This will be processed by the expander before the string is
5372 interpreted as a list. For example, if a newline-separated list of domains is
5373 generated by a lookup, you can process it directly by a line such as this:
5375 domains = <\n ${lookup mysql{.....}}
5377 This avoids having to change the list separator in such data. You are unlikely
5378 to want to use a control character as a separator in an option that is not
5379 expanded, because the value is literal text. However, it can be done by giving
5380 the value in quotes. For example:
5382 local_interfaces = "<\n 127.0.0.1 \n ::1"
5384 Unlike printing character separators, which can be included in list items by
5385 doubling, it is not possible to include a control character as data when it is
5386 set as the separator. Two such characters in succession are interpreted as
5387 enclosing an empty list item.
5391 .section "Empty items in lists" "SECTempitelis"
5392 .cindex "list" "empty item in"
5393 An empty item at the end of a list is always ignored. In other words, trailing
5394 separator characters are ignored. Thus, the list in
5396 senders = user@domain :
5398 contains only a single item. If you want to include an empty string as one item
5399 in a list, it must not be the last item. For example, this list contains three
5400 items, the second of which is empty:
5402 senders = user1@domain : : user2@domain
5404 &*Note*&: There must be white space between the two colons, as otherwise they
5405 are interpreted as representing a single colon data character (and the list
5406 would then contain just one item). If you want to specify a list that contains
5407 just one, empty item, you can do it as in this example:
5411 In this case, the first item is empty, and the second is discarded because it
5412 is at the end of the list.
5417 .section "Format of driver configurations" "SECTfordricon"
5418 .cindex "drivers" "configuration format"
5419 There are separate parts in the configuration for defining routers, transports,
5420 and authenticators. In each part, you are defining a number of driver
5421 instances, each with its own set of options. Each driver instance is defined by
5422 a sequence of lines like this:
5424 <&'instance name'&>:
5429 In the following example, the instance name is &(localuser)&, and it is
5430 followed by three options settings:
5435 transport = local_delivery
5437 For each driver instance, you specify which Exim code module it uses &-- by the
5438 setting of the &%driver%& option &-- and (optionally) some configuration
5439 settings. For example, in the case of transports, if you want a transport to
5440 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5441 a local file you would use the &(appendfile)& driver. Each of the drivers is
5442 described in detail in its own separate chapter later in this manual.
5444 You can have several routers, transports, or authenticators that are based on
5445 the same underlying driver (each must have a different instance name).
5447 The order in which routers are defined is important, because addresses are
5448 passed to individual routers one by one, in order. The order in which
5449 transports are defined does not matter at all. The order in which
5450 authenticators are defined is used only when Exim, as a client, is searching
5451 them to find one that matches an authentication mechanism offered by the
5454 .cindex "generic options"
5455 .cindex "options" "generic &-- definition of"
5456 Within a driver instance definition, there are two kinds of option: &'generic'&
5457 and &'private'&. The generic options are those that apply to all drivers of the
5458 same type (that is, all routers, all transports or all authenticators). The
5459 &%driver%& option is a generic option that must appear in every definition.
5460 .cindex "private options"
5461 The private options are special for each driver, and none need appear, because
5462 they all have default values.
5464 The options may appear in any order, except that the &%driver%& option must
5465 precede any private options, since these depend on the particular driver. For
5466 this reason, it is recommended that &%driver%& always be the first option.
5468 Driver instance names, which are used for reference in log entries and
5469 elsewhere, can be any sequence of letters, digits, and underscores (starting
5470 with a letter) and must be unique among drivers of the same type. A router and
5471 a transport (for example) can each have the same name, but no two router
5472 instances can have the same name. The name of a driver instance should not be
5473 confused with the name of the underlying driver module. For example, the
5474 configuration lines:
5479 create an instance of the &(smtp)& transport driver whose name is
5480 &(remote_smtp)&. The same driver code can be used more than once, with
5481 different instance names and different option settings each time. A second
5482 instance of the &(smtp)& transport, with different options, might be defined
5488 command_timeout = 10s
5490 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5491 these transport instances from routers, and these names would appear in log
5494 Comment lines may be present in the middle of driver specifications. The full
5495 list of option settings for any particular driver instance, including all the
5496 defaulted values, can be extracted by making use of the &%-bP%& command line
5504 . ////////////////////////////////////////////////////////////////////////////
5505 . ////////////////////////////////////////////////////////////////////////////
5507 .chapter "The default configuration file" "CHAPdefconfil"
5508 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5509 .cindex "default" "configuration file &""walk through""&"
5510 The default configuration file supplied with Exim as &_src/configure.default_&
5511 is sufficient for a host with simple mail requirements. As an introduction to
5512 the way Exim is configured, this chapter &"walks through"& the default
5513 configuration, giving brief explanations of the settings. Detailed descriptions
5514 of the options are given in subsequent chapters. The default configuration file
5515 itself contains extensive comments about ways you might want to modify the
5516 initial settings. However, note that there are many options that are not
5517 mentioned at all in the default configuration.
5521 .section "Macros" "SECTdefconfmacros"
5522 All macros should be defined before any options.
5524 One macro is specified, but commented out, in the default configuration:
5526 # ROUTER_SMARTHOST=MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
5528 If all off-site mail is expected to be delivered to a "smarthost", then set the
5529 hostname here and uncomment the macro. This will affect which router is used
5530 later on. If this is left commented out, then Exim will perform direct-to-MX
5531 deliveries using a &(dnslookup)& router.
5533 In addition to macros defined here, Exim includes a number of built-in macros
5534 to enable configuration to be guarded by a binary built with support for a
5535 given feature. See section &<<SECTbuiltinmacros>>& for more details.
5538 .section "Main configuration settings" "SECTdefconfmain"
5539 The main (global) configuration option settings section must always come first
5540 in the file, after the macros.
5541 The first thing you'll see in the file, after some initial comments, is the line
5543 # primary_hostname =
5545 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5546 to know the official, fully qualified name of your host, and this is where you
5547 can specify it. However, in most cases you do not need to set this option. When
5548 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5550 The first three non-comment configuration lines are as follows:
5552 domainlist local_domains = @
5553 domainlist relay_to_domains =
5554 hostlist relay_from_hosts = 127.0.0.1
5556 These are not, in fact, option settings. They are definitions of two named
5557 domain lists and one named host list. Exim allows you to give names to lists of
5558 domains, hosts, and email addresses, in order to make it easier to manage the
5559 configuration file (see section &<<SECTnamedlists>>&).
5561 The first line defines a domain list called &'local_domains'&; this is used
5562 later in the configuration to identify domains that are to be delivered
5565 .cindex "@ in a domain list"
5566 There is just one item in this list, the string &"@"&. This is a special form
5567 of entry which means &"the name of the local host"&. Thus, if the local host is
5568 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5569 be delivered locally. Because the local host's name is referenced indirectly,
5570 the same configuration file can be used on different hosts.
5572 The second line defines a domain list called &'relay_to_domains'&, but the
5573 list itself is empty. Later in the configuration we will come to the part that
5574 controls mail relaying through the local host; it allows relaying to any
5575 domains in this list. By default, therefore, no relaying on the basis of a mail
5576 domain is permitted.
5578 The third line defines a host list called &'relay_from_hosts'&. This list is
5579 used later in the configuration to permit relaying from any host or IP address
5580 that matches the list. The default contains just the IP address of the IPv4
5581 loopback interface, which means that processes on the local host are able to
5582 submit mail for relaying by sending it over TCP/IP to that interface. No other
5583 hosts are permitted to submit messages for relaying.
5585 Just to be sure there's no misunderstanding: at this point in the configuration
5586 we aren't actually setting up any controls. We are just defining some domains
5587 and hosts that will be used in the controls that are specified later.
5589 The next two configuration lines are genuine option settings:
5591 acl_smtp_rcpt = acl_check_rcpt
5592 acl_smtp_data = acl_check_data
5594 These options specify &'Access Control Lists'& (ACLs) that are to be used
5595 during an incoming SMTP session for every recipient of a message (every RCPT
5596 command), and after the contents of the message have been received,
5597 respectively. The names of the lists are &'acl_check_rcpt'& and
5598 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5599 section of the configuration. The RCPT ACL controls which recipients are
5600 accepted for an incoming message &-- if a configuration does not provide an ACL
5601 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5602 contents of a message to be checked.
5604 Two commented-out option settings are next:
5606 # av_scanner = clamd:/tmp/clamd
5607 # spamd_address = 127.0.0.1 783
5609 These are example settings that can be used when Exim is compiled with the
5610 content-scanning extension. The first specifies the interface to the virus
5611 scanner, and the second specifies the interface to SpamAssassin. Further
5612 details are given in chapter &<<CHAPexiscan>>&.
5614 Three more commented-out option settings follow:
5616 # tls_advertise_hosts = *
5617 # tls_certificate = /etc/ssl/exim.crt
5618 # tls_privatekey = /etc/ssl/exim.pem
5620 These are example settings that can be used when Exim is compiled with
5621 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5622 first one specifies the list of clients that are allowed to use TLS when
5623 connecting to this server; in this case, the wildcard means all clients. The
5624 other options specify where Exim should find its TLS certificate and private
5625 key, which together prove the server's identity to any clients that connect.
5626 More details are given in chapter &<<CHAPTLS>>&.
5628 Another two commented-out option settings follow:
5630 # daemon_smtp_ports = 25 : 465 : 587
5631 # tls_on_connect_ports = 465
5633 .cindex "port" "465 and 587"
5634 .cindex "port" "for message submission"
5635 .cindex "message" "submission, ports for"
5636 .cindex "submissions protocol"
5637 .cindex "smtps protocol"
5638 .cindex "ssmtp protocol"
5639 .cindex "SMTP" "submissions protocol"
5640 .cindex "SMTP" "ssmtp protocol"
5641 .cindex "SMTP" "smtps protocol"
5642 These options provide better support for roaming users who wish to use this
5643 server for message submission. They are not much use unless you have turned on
5644 TLS (as described in the previous paragraph) and authentication (about which
5645 more in section &<<SECTdefconfauth>>&).
5646 Mail submission from mail clients (MUAs) should be separate from inbound mail
5647 to your domain (MX delivery) for various good reasons (eg, ability to impose
5648 much saner TLS protocol and ciphersuite requirements without unintended
5650 RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
5651 which uses STARTTLS, so this is the &"submission"& port.
5652 RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
5653 which should be used in preference to 587.
5654 You should also consider deploying SRV records to help clients find
5656 Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
5658 Two more commented-out options settings follow:
5661 # qualify_recipient =
5663 The first of these specifies a domain that Exim uses when it constructs a
5664 complete email address from a local login name. This is often needed when Exim
5665 receives a message from a local process. If you do not set &%qualify_domain%&,
5666 the value of &%primary_hostname%& is used. If you set both of these options,
5667 you can have different qualification domains for sender and recipient
5668 addresses. If you set only the first one, its value is used in both cases.
5670 .cindex "domain literal" "recognizing format"
5671 The following line must be uncommented if you want Exim to recognize
5672 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5673 (an IP address within square brackets) instead of a named domain.
5675 # allow_domain_literals
5677 The RFCs still require this form, but many people think that in the modern
5678 Internet it makes little sense to permit mail to be sent to specific hosts by
5679 quoting their IP addresses. This ancient format has been used by people who
5680 try to abuse hosts by using them for unwanted relaying. However, some
5681 people believe there are circumstances (for example, messages addressed to
5682 &'postmaster'&) where domain literals are still useful.
5684 The next configuration line is a kind of trigger guard:
5688 It specifies that no delivery must ever be run as the root user. The normal
5689 convention is to set up &'root'& as an alias for the system administrator. This
5690 setting is a guard against slips in the configuration.
5691 The list of users specified by &%never_users%& is not, however, the complete
5692 list; the build-time configuration in &_Local/Makefile_& has an option called
5693 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5694 contents of &%never_users%& are added to this list. By default
5695 FIXED_NEVER_USERS also specifies root.
5697 When a remote host connects to Exim in order to send mail, the only information
5698 Exim has about the host's identity is its IP address. The next configuration
5703 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5704 in order to get a host name. This improves the quality of the logging
5705 information, but if you feel it is too expensive, you can remove it entirely,
5706 or restrict the lookup to hosts on &"nearby"& networks.
5707 Note that it is not always possible to find a host name from an IP address,
5708 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5711 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5712 1413 (hence their names):
5715 rfc1413_query_timeout = 0s
5717 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5718 Few hosts offer RFC1413 service these days; calls have to be
5719 terminated by a timeout and this needlessly delays the startup
5720 of an incoming SMTP connection.
5721 If you have hosts for which you trust RFC1413 and need this
5722 information, you can change this.
5724 This line enables an efficiency SMTP option. It is negotiated by clients
5725 and not expected to cause problems but can be disabled if needed.
5730 When Exim receives messages over SMTP connections, it expects all addresses to
5731 be fully qualified with a domain, as required by the SMTP definition. However,
5732 if you are running a server to which simple clients submit messages, you may
5733 find that they send unqualified addresses. The two commented-out options:
5735 # sender_unqualified_hosts =
5736 # recipient_unqualified_hosts =
5738 show how you can specify hosts that are permitted to send unqualified sender
5739 and recipient addresses, respectively.
5741 The &%log_selector%& option is used to increase the detail of logging
5744 log_selector = +smtp_protocol_error +smtp_syntax_error \
5745 +tls_certificate_verified
5748 The &%percent_hack_domains%& option is also commented out:
5750 # percent_hack_domains =
5752 It provides a list of domains for which the &"percent hack"& is to operate.
5753 This is an almost obsolete form of explicit email routing. If you do not know
5754 anything about it, you can safely ignore this topic.
5756 The next two settings in the main part of the default configuration are
5757 concerned with messages that have been &"frozen"& on Exim's queue. When a
5758 message is frozen, Exim no longer continues to try to deliver it. Freezing
5759 occurs when a bounce message encounters a permanent failure because the sender
5760 address of the original message that caused the bounce is invalid, so the
5761 bounce cannot be delivered. This is probably the most common case, but there
5762 are also other conditions that cause freezing, and frozen messages are not
5763 always bounce messages.
5765 ignore_bounce_errors_after = 2d
5766 timeout_frozen_after = 7d
5768 The first of these options specifies that failing bounce messages are to be
5769 discarded after 2 days in the queue. The second specifies that any frozen
5770 message (whether a bounce message or not) is to be timed out (and discarded)
5771 after a week. In this configuration, the first setting ensures that no failing
5772 bounce message ever lasts a week.
5774 Exim queues it's messages in a spool directory. If you expect to have
5775 large queues, you may consider using this option. It splits the spool
5776 directory into subdirectories to avoid file system degradation from
5777 many files in a single directory, resulting in better performance.
5778 Manual manipulation of queued messages becomes more complex (though fortunately
5781 # split_spool_directory = true
5784 In an ideal world everybody follows the standards. For non-ASCII
5785 messages RFC 2047 is a standard, allowing a maximum line length of 76
5786 characters. Exim adheres that standard and won't process messages which
5787 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5788 In particular, the Exim maintainers have had multiple reports of
5789 problems from Russian administrators of issues until they disable this
5790 check, because of some popular, yet buggy, mail composition software.
5792 # check_rfc2047_length = false
5795 If you need to be strictly RFC compliant you may wish to disable the
5796 8BITMIME advertisement. Use this, if you exchange mails with systems
5797 that are not 8-bit clean.
5799 # accept_8bitmime = false
5802 Libraries you use may depend on specific environment settings. This
5803 imposes a security risk (e.g. PATH). There are two lists:
5804 &%keep_environment%& for the variables to import as they are, and
5805 &%add_environment%& for variables we want to set to a fixed value.
5806 Note that TZ is handled separately, by the $%timezone%$ runtime
5807 option and by the TIMEZONE_DEFAULT buildtime option.
5809 # keep_environment = ^LDAP
5810 # add_environment = PATH=/usr/bin::/bin
5814 .section "ACL configuration" "SECID54"
5815 .cindex "default" "ACLs"
5816 .cindex "&ACL;" "default configuration"
5817 In the default configuration, the ACL section follows the main configuration.
5818 It starts with the line
5822 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5823 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5824 and &%acl_smtp_data%& above.
5826 .cindex "RCPT" "ACL for"
5827 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5828 RCPT command specifies one of the message's recipients. The ACL statements
5829 are considered in order, until the recipient address is either accepted or
5830 rejected. The RCPT command is then accepted or rejected, according to the
5831 result of the ACL processing.
5835 This line, consisting of a name terminated by a colon, marks the start of the
5840 This ACL statement accepts the recipient if the sending host matches the list.
5841 But what does that strange list mean? It doesn't actually contain any host
5842 names or IP addresses. The presence of the colon puts an empty item in the
5843 list; Exim matches this only if the incoming message did not come from a remote
5844 host, because in that case, the remote hostname is empty. The colon is
5845 important. Without it, the list itself is empty, and can never match anything.
5847 What this statement is doing is to accept unconditionally all recipients in
5848 messages that are submitted by SMTP from local processes using the standard
5849 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5852 deny message = Restricted characters in address
5853 domains = +local_domains
5854 local_parts = ^[.] : ^.*[@%!/|]
5856 deny message = Restricted characters in address
5857 domains = !+local_domains
5858 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5860 These statements are concerned with local parts that contain any of the
5861 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5862 Although these characters are entirely legal in local parts (in the case of
5863 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5864 in Internet mail addresses.
5866 The first three have in the past been associated with explicitly routed
5867 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5868 option). Addresses containing these characters are regularly tried by spammers
5869 in an attempt to bypass relaying restrictions, and also by open relay testing
5870 programs. Unless you really need them it is safest to reject these characters
5871 at this early stage. This configuration is heavy-handed in rejecting these
5872 characters for all messages it accepts from remote hosts. This is a deliberate
5873 policy of being as safe as possible.
5875 The first rule above is stricter, and is applied to messages that are addressed
5876 to one of the local domains handled by this host. This is implemented by the
5877 first condition, which restricts it to domains that are listed in the
5878 &'local_domains'& domain list. The &"+"& character is used to indicate a
5879 reference to a named list. In this configuration, there is just one domain in
5880 &'local_domains'&, but in general there may be many.
5882 The second condition on the first statement uses two regular expressions to
5883 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5884 or &"|"&. If you have local accounts that include these characters, you will
5885 have to modify this rule.
5887 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5888 allows them because they have been encountered in practice. (Consider the
5889 common convention of local parts constructed as
5890 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5891 the author of Exim, who has no second initial.) However, a local part starting
5892 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5893 filename (for example, for a mailing list). This is also true for local parts
5894 that contain slashes. A pipe symbol can also be troublesome if the local part
5895 is incorporated unthinkingly into a shell command line.
5897 The second rule above applies to all other domains, and is less strict. This
5898 allows your own users to send outgoing messages to sites that use slashes
5899 and vertical bars in their local parts. It blocks local parts that begin
5900 with a dot, slash, or vertical bar, but allows these characters within the
5901 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5902 and &"!"& is blocked, as before. The motivation here is to prevent your users
5903 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5905 accept local_parts = postmaster
5906 domains = +local_domains
5908 This statement, which has two conditions, accepts an incoming address if the
5909 local part is &'postmaster'& and the domain is one of those listed in the
5910 &'local_domains'& domain list. The &"+"& character is used to indicate a
5911 reference to a named list. In this configuration, there is just one domain in
5912 &'local_domains'&, but in general there may be many.
5914 The presence of this statement means that mail to postmaster is never blocked
5915 by any of the subsequent tests. This can be helpful while sorting out problems
5916 in cases where the subsequent tests are incorrectly denying access.
5918 require verify = sender
5920 This statement requires the sender address to be verified before any subsequent
5921 ACL statement can be used. If verification fails, the incoming recipient
5922 address is refused. Verification consists of trying to route the address, to
5923 see if a bounce message could be delivered to it. In the case of remote
5924 addresses, basic verification checks only the domain, but &'callouts'& can be
5925 used for more verification if required. Section &<<SECTaddressverification>>&
5926 discusses the details of address verification.
5928 accept hosts = +relay_from_hosts
5929 control = submission
5931 This statement accepts the address if the message is coming from one of the
5932 hosts that are defined as being allowed to relay through this host. Recipient
5933 verification is omitted here, because in many cases the clients are dumb MUAs
5934 that do not cope well with SMTP error responses. For the same reason, the
5935 second line specifies &"submission mode"& for messages that are accepted. This
5936 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5937 messages that are deficient in some way, for example, because they lack a
5938 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5939 probably add recipient verification here, and disable submission mode.
5941 accept authenticated = *
5942 control = submission
5944 This statement accepts the address if the client host has authenticated itself.
5945 Submission mode is again specified, on the grounds that such messages are most
5946 likely to come from MUAs. The default configuration does not define any
5947 authenticators, though it does include some nearly complete commented-out
5948 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5949 fact authenticate until you complete the authenticator definitions.
5951 require message = relay not permitted
5952 domains = +local_domains : +relay_to_domains
5954 This statement rejects the address if its domain is neither a local domain nor
5955 one of the domains for which this host is a relay.
5957 require verify = recipient
5959 This statement requires the recipient address to be verified; if verification
5960 fails, the address is rejected.
5962 # deny message = rejected because $sender_host_address \
5963 # is in a black list at $dnslist_domain\n\
5965 # dnslists = black.list.example
5967 # warn dnslists = black.list.example
5968 # add_header = X-Warning: $sender_host_address is in \
5969 # a black list at $dnslist_domain
5970 # log_message = found in $dnslist_domain
5972 These commented-out lines are examples of how you could configure Exim to check
5973 sending hosts against a DNS black list. The first statement rejects messages
5974 from blacklisted hosts, whereas the second just inserts a warning header
5977 # require verify = csa
5979 This commented-out line is an example of how you could turn on client SMTP
5980 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5985 The final statement in the first ACL unconditionally accepts any recipient
5986 address that has successfully passed all the previous tests.
5990 This line marks the start of the second ACL, and names it. Most of the contents
5991 of this ACL are commented out:
5994 # message = This message contains a virus \
5997 These lines are examples of how to arrange for messages to be scanned for
5998 viruses when Exim has been compiled with the content-scanning extension, and a
5999 suitable virus scanner is installed. If the message is found to contain a
6000 virus, it is rejected with the given custom error message.
6002 # warn spam = nobody
6003 # message = X-Spam_score: $spam_score\n\
6004 # X-Spam_score_int: $spam_score_int\n\
6005 # X-Spam_bar: $spam_bar\n\
6006 # X-Spam_report: $spam_report
6008 These lines are an example of how to arrange for messages to be scanned by
6009 SpamAssassin when Exim has been compiled with the content-scanning extension,
6010 and SpamAssassin has been installed. The SpamAssassin check is run with
6011 &`nobody`& as its user parameter, and the results are added to the message as a
6012 series of extra header line. In this case, the message is not rejected,
6013 whatever the spam score.
6017 This final line in the DATA ACL accepts the message unconditionally.
6020 .section "Router configuration" "SECID55"
6021 .cindex "default" "routers"
6022 .cindex "routers" "default"
6023 The router configuration comes next in the default configuration, introduced
6028 Routers are the modules in Exim that make decisions about where to send
6029 messages. An address is passed to each router, in turn, until it is either
6030 accepted, or failed. This means that the order in which you define the routers
6031 matters. Each router is fully described in its own chapter later in this
6032 manual. Here we give only brief overviews.
6035 # driver = ipliteral
6036 # domains = !+local_domains
6037 # transport = remote_smtp
6039 .cindex "domain literal" "default router"
6040 This router is commented out because the majority of sites do not want to
6041 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
6042 you uncomment this router, you also need to uncomment the setting of
6043 &%allow_domain_literals%& in the main part of the configuration.
6045 Which router is used next depends upon whether or not the ROUTER_SMARTHOST
6046 macro has been defined, per
6048 .ifdef ROUTER_SMARTHOST
6057 If ROUTER_SMARTHOST has been defined, either at the top of the file or on the
6058 command-line, then we route all non-local mail to that smarthost; otherwise, we'll
6059 perform DNS lookups for direct-to-MX lookup. Any mail which is to a local domain will
6060 skip these routers because of the &%domains%& option.
6064 driver = manualroute
6065 domains = ! +local_domains
6066 transport = smarthost_smtp
6067 route_data = ROUTER_SMARTHOST
6068 ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
6071 This router only handles mail which is not to any local domains; this is
6072 specified by the line
6074 domains = ! +local_domains
6076 The &%domains%& option lists the domains to which this router applies, but the
6077 exclamation mark is a negation sign, so the router is used only for domains
6078 that are not in the domain list called &'local_domains'& (which was defined at
6079 the start of the configuration). The plus sign before &'local_domains'&
6080 indicates that it is referring to a named list. Addresses in other domains are
6081 passed on to the following routers.
6083 The name of the router driver is &(manualroute)& because we are manually
6084 specifying how mail should be routed onwards, instead of using DNS MX.
6085 While the name of this router instance is arbitrary, the &%driver%& option must
6086 be one of the driver modules that is in the Exim binary.
6088 With no pre-conditions other than &%domains%&, all mail for non-local domains
6089 will be handled by this router, and the &%no_more%& setting will ensure that no
6090 other routers will be used for messages matching the pre-conditions. See
6091 &<<SECTrouprecon>>& for more on how the pre-conditions apply. For messages which
6092 are handled by this router, we provide a hostname to deliver to in &%route_data%&
6093 and the macro supplies the value; the address is then queued for the
6094 &(smarthost_smtp)& transport.
6099 domains = ! +local_domains
6100 transport = remote_smtp
6101 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
6104 The &%domains%& option behaves as per smarthost, above.
6106 The name of the router driver is &(dnslookup)&,
6107 and is specified by the &%driver%& option. Do not be confused by the fact that
6108 the name of this router instance is the same as the name of the driver. The
6109 instance name is arbitrary, but the name set in the &%driver%& option must be
6110 one of the driver modules that is in the Exim binary.
6112 The &(dnslookup)& router routes addresses by looking up their domains in the
6113 DNS in order to obtain a list of hosts to which the address is routed. If the
6114 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6115 specified by the &%transport%& option. If the router does not find the domain
6116 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6117 the address fails and is bounced.
6119 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6120 be entirely ignored. This option is present because a number of cases have been
6121 encountered where MX records in the DNS point to host names
6122 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6123 Completely ignoring these IP addresses causes Exim to fail to route the
6124 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6125 continue to try to deliver the message periodically until the address timed
6132 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6134 file_transport = address_file
6135 pipe_transport = address_pipe
6137 Control reaches this and subsequent routers only for addresses in the local
6138 domains. This router checks to see whether the local part is defined as an
6139 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6140 data that it looks up from that file. If no data is found for the local part,
6141 the value of the &%data%& option is empty, causing the address to be passed to
6144 &_/etc/aliases_& is a conventional name for the system aliases file that is
6145 often used. That is why it is referenced by from the default configuration
6146 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6147 &_Local/Makefile_& before building Exim.
6152 # local_part_suffix = +* : -*
6153 # local_part_suffix_optional
6154 file = $home/.forward
6159 file_transport = address_file
6160 pipe_transport = address_pipe
6161 reply_transport = address_reply
6163 This is the most complicated router in the default configuration. It is another
6164 redirection router, but this time it is looking for forwarding data set up by
6165 individual users. The &%check_local_user%& setting specifies a check that the
6166 local part of the address is the login name of a local user. If it is not, the
6167 router is skipped. The two commented options that follow &%check_local_user%&,
6170 # local_part_suffix = +* : -*
6171 # local_part_suffix_optional
6173 .vindex "&$local_part_suffix$&"
6174 show how you can specify the recognition of local part suffixes. If the first
6175 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6176 by any sequence of characters, is removed from the local part and placed in the
6177 variable &$local_part_suffix$&. The second suffix option specifies that the
6178 presence of a suffix in the local part is optional. When a suffix is present,
6179 the check for a local login uses the local part with the suffix removed.
6181 When a local user account is found, the file called &_.forward_& in the user's
6182 home directory is consulted. If it does not exist, or is empty, the router
6183 declines. Otherwise, the contents of &_.forward_& are interpreted as
6184 redirection data (see chapter &<<CHAPredirect>>& for more details).
6186 .cindex "Sieve filter" "enabling in default router"
6187 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6188 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6189 is commented out by default), the contents of the file are interpreted as a set
6190 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6191 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6192 separate document entitled &'Exim's interfaces to mail filtering'&.
6194 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6195 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6196 There are two reasons for doing this:
6199 Whether or not a local user has a &_.forward_& file is not really relevant when
6200 checking an address for validity; it makes sense not to waste resources doing
6203 More importantly, when Exim is verifying addresses or handling an EXPN
6204 command during an SMTP session, it is running as the Exim user, not as root.
6205 The group is the Exim group, and no additional groups are set up.
6206 It may therefore not be possible for Exim to read users' &_.forward_& files at
6210 The setting of &%check_ancestor%& prevents the router from generating a new
6211 address that is the same as any previous address that was redirected. (This
6212 works round a problem concerning a bad interaction between aliasing and
6213 forwarding &-- see section &<<SECTredlocmai>>&).
6215 The final three option settings specify the transports that are to be used when
6216 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6217 auto-reply, respectively. For example, if a &_.forward_& file contains
6219 a.nother@elsewhere.example, /home/spqr/archive
6221 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6227 # local_part_suffix = +* : -*
6228 # local_part_suffix_optional
6229 transport = local_delivery
6231 The final router sets up delivery into local mailboxes, provided that the local
6232 part is the name of a local login, by accepting the address and assigning it to
6233 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6234 routers, so the address is bounced. The commented suffix settings fulfil the
6235 same purpose as they do for the &(userforward)& router.
6238 .section "Transport configuration" "SECID56"
6239 .cindex "default" "transports"
6240 .cindex "transports" "default"
6241 Transports define mechanisms for actually delivering messages. They operate
6242 only when referenced from routers, so the order in which they are defined does
6243 not matter. The transports section of the configuration starts with
6247 Two remote transports and four local transports are defined.
6251 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6253 dnssec_request_domains = *
6260 This transport is used for delivering messages over SMTP connections.
6261 The list of remote hosts comes from the router.
6262 The &%message_size_limit%& usage is a hack to avoid sending on messages
6263 with over-long lines. The built-in macro _HAVE_DANE guards configuration
6264 to try to use DNSSEC for all queries and to use DANE for delivery;
6265 see section &<<SECDANE>>& for more details.
6267 The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
6268 negotiated between client and server and not expected to cause problems
6269 but can be disabled if needed. The built-in macro _HAVE_PRDR guards the
6270 use of the &%hosts_try_prdr%& configuration option.
6272 The other remote transport is used when delivering to a specific smarthost
6273 with whom there must be some kind of existing relationship, instead of the
6274 usual federated system.
6279 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6283 # Comment out any of these which you have to, then file a Support
6284 # request with your smarthost provider to get things fixed:
6285 hosts_require_tls = *
6286 tls_verify_hosts = *
6287 # As long as tls_verify_hosts is enabled, this won't matter, but if you
6288 # have to comment it out then this will at least log whether you succeed
6290 tls_try_verify_hosts = *
6292 # The SNI name should match the name which we'll expect to verify;
6293 # many mail systems don't use SNI and this doesn't matter, but if it does,
6294 # we need to send a name which the remote site will recognize.
6295 # This _should_ be the name which the smarthost operators specified as
6296 # the hostname for sending your mail to.
6297 tls_sni = ROUTER_SMARTHOST
6299 .ifdef _HAVE_OPENSSL
6300 tls_require_ciphers = HIGH:!aNULL:@STRENGTH
6303 tls_require_ciphers = SECURE192:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1
6310 After the same &%message_size_limit%& hack, we then specify that this Transport
6311 can handle messages to multiple domains in one run. The assumption here is
6312 that you're routing all non-local mail to the same place and that place is
6313 happy to take all messages from you as quickly as possible.
6314 All other options depend upon built-in macros; if Exim was built without TLS support
6315 then no other options are defined.
6316 If TLS is available, then we configure "stronger than default" TLS ciphersuites
6317 and versions using the &%tls_require_ciphers%& option, where the value to be
6318 used depends upon the library providing TLS.
6319 Beyond that, the options adopt the stance that you should have TLS support available
6320 from your smarthost on today's Internet, so we turn on requiring TLS for the
6321 mail to be delivered, and requiring that the certificate be valid, and match
6322 the expected hostname. The &%tls_sni%& option can be used by service providers
6323 to select an appropriate certificate to present to you and here we re-use the
6324 ROUTER_SMARTHOST macro, because that is unaffected by CNAMEs present in DNS.
6325 You want to specify the hostname which you'll expect to validate for, and that
6326 should not be subject to insecure tampering via DNS results.
6328 For the &%hosts_try_prdr%& option see the previous transport.
6330 All other options are defaulted.
6334 file = /var/mail/$local_part
6341 This &(appendfile)& transport is used for local delivery to user mailboxes in
6342 traditional BSD mailbox format. By default it runs under the uid and gid of the
6343 local user, which requires the sticky bit to be set on the &_/var/mail_&
6344 directory. Some systems use the alternative approach of running mail deliveries
6345 under a particular group instead of using the sticky bit. The commented options
6346 show how this can be done.
6348 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6349 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6350 similarly-named options above.
6356 This transport is used for handling deliveries to pipes that are generated by
6357 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6358 option specifies that any output on stdout or stderr generated by the pipe is to
6359 be returned to the sender.
6367 This transport is used for handling deliveries to files that are generated by
6368 redirection. The name of the file is not specified in this instance of
6369 &(appendfile)&, because it comes from the &(redirect)& router.
6374 This transport is used for handling automatic replies generated by users'
6379 .section "Default retry rule" "SECID57"
6380 .cindex "retry" "default rule"
6381 .cindex "default" "retry rule"
6382 The retry section of the configuration file contains rules which affect the way
6383 Exim retries deliveries that cannot be completed at the first attempt. It is
6384 introduced by the line
6388 In the default configuration, there is just one rule, which applies to all
6391 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6393 This causes any temporarily failing address to be retried every 15 minutes for
6394 2 hours, then at intervals starting at one hour and increasing by a factor of
6395 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6396 is not delivered after 4 days of temporary failure, it is bounced. The time is
6397 measured from first failure, not from the time the message was received.
6399 If the retry section is removed from the configuration, or is empty (that is,
6400 if no retry rules are defined), Exim will not retry deliveries. This turns
6401 temporary errors into permanent errors.
6404 .section "Rewriting configuration" "SECID58"
6405 The rewriting section of the configuration, introduced by
6409 contains rules for rewriting addresses in messages as they arrive. There are no
6410 rewriting rules in the default configuration file.
6414 .section "Authenticators configuration" "SECTdefconfauth"
6415 .cindex "AUTH" "configuration"
6416 The authenticators section of the configuration, introduced by
6418 begin authenticators
6420 defines mechanisms for the use of the SMTP AUTH command. The default
6421 configuration file contains two commented-out example authenticators
6422 which support plaintext username/password authentication using the
6423 standard PLAIN mechanism and the traditional but non-standard LOGIN
6424 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6425 to support most MUA software.
6427 The example PLAIN authenticator looks like this:
6430 # driver = plaintext
6431 # server_set_id = $auth2
6432 # server_prompts = :
6433 # server_condition = Authentication is not yet configured
6434 # server_advertise_condition = ${if def:tls_in_cipher }
6436 And the example LOGIN authenticator looks like this:
6439 # driver = plaintext
6440 # server_set_id = $auth1
6441 # server_prompts = <| Username: | Password:
6442 # server_condition = Authentication is not yet configured
6443 # server_advertise_condition = ${if def:tls_in_cipher }
6446 The &%server_set_id%& option makes Exim remember the authenticated username
6447 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6448 &%server_prompts%& option configures the &(plaintext)& authenticator so
6449 that it implements the details of the specific authentication mechanism,
6450 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6451 when Exim offers authentication to clients; in the examples, this is only
6452 when TLS or SSL has been started, so to enable the authenticators you also
6453 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6455 The &%server_condition%& setting defines how to verify that the username and
6456 password are correct. In the examples it just produces an error message.
6457 To make the authenticators work, you can use a string expansion
6458 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6460 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6461 usercode and password are in different positions.
6462 Chapter &<<CHAPplaintext>>& covers both.
6464 .ecindex IIDconfiwal
6468 . ////////////////////////////////////////////////////////////////////////////
6469 . ////////////////////////////////////////////////////////////////////////////
6471 .chapter "Regular expressions" "CHAPregexp"
6473 .cindex "regular expressions" "library"
6475 Exim supports the use of regular expressions in many of its options. It
6476 uses the PCRE regular expression library; this provides regular expression
6477 matching that is compatible with Perl 5. The syntax and semantics of
6478 regular expressions is discussed in
6479 online Perl manpages, in
6480 many Perl reference books, and also in
6481 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6482 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6483 . --- the http: URL here redirects to another page with the ISBN in the URL
6484 . --- where trying to use https: just redirects back to http:, so sticking
6485 . --- to the old URL for now. 2018-09-07.
6487 The documentation for the syntax and semantics of the regular expressions that
6488 are supported by PCRE is included in the PCRE distribution, and no further
6489 description is included here. The PCRE functions are called from Exim using
6490 the default option settings (that is, with no PCRE options set), except that
6491 the PCRE_CASELESS option is set when the matching is required to be
6494 In most cases, when a regular expression is required in an Exim configuration,
6495 it has to start with a circumflex, in order to distinguish it from plain text
6496 or an &"ends with"& wildcard. In this example of a configuration setting, the
6497 second item in the colon-separated list is a regular expression.
6499 domains = a.b.c : ^\\d{3} : *.y.z : ...
6501 The doubling of the backslash is required because of string expansion that
6502 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6503 of this issue, and a way of avoiding the need for doubling backslashes. The
6504 regular expression that is eventually used in this example contains just one
6505 backslash. The circumflex is included in the regular expression, and has the
6506 normal effect of &"anchoring"& it to the start of the string that is being
6509 There are, however, two cases where a circumflex is not required for the
6510 recognition of a regular expression: these are the &%match%& condition in a
6511 string expansion, and the &%matches%& condition in an Exim filter file. In
6512 these cases, the relevant string is always treated as a regular expression; if
6513 it does not start with a circumflex, the expression is not anchored, and can
6514 match anywhere in the subject string.
6516 In all cases, if you want a regular expression to match at the end of a string,
6517 you must code the $ metacharacter to indicate this. For example:
6519 domains = ^\\d{3}\\.example
6521 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6524 domains = ^\\d{3}\\.example\$
6526 if you want &'example'& to be the top-level domain. The backslash before the
6527 $ is needed because string expansion also interprets dollar characters.
6531 . ////////////////////////////////////////////////////////////////////////////
6532 . ////////////////////////////////////////////////////////////////////////////
6534 .chapter "File and database lookups" "CHAPfdlookup"
6535 .scindex IIDfidalo1 "file" "lookups"
6536 .scindex IIDfidalo2 "database" "lookups"
6537 .cindex "lookup" "description of"
6538 Exim can be configured to look up data in files or databases as it processes
6539 messages. Two different kinds of syntax are used:
6542 A string that is to be expanded may contain explicit lookup requests. These
6543 cause parts of the string to be replaced by data that is obtained from the
6544 lookup. Lookups of this type are conditional expansion items. Different results
6545 can be defined for the cases of lookup success and failure. See chapter
6546 &<<CHAPexpand>>&, where string expansions are described in detail.
6547 The key for the lookup is specified as part of the string expansion.
6549 Lists of domains, hosts, and email addresses can contain lookup requests as a
6550 way of avoiding excessively long linear lists. In this case, the data that is
6551 returned by the lookup is often (but not always) discarded; whether the lookup
6552 succeeds or fails is what really counts. These kinds of list are described in
6553 chapter &<<CHAPdomhosaddlists>>&.
6554 The key for the lookup is given by the context in which the list is expanded.
6557 String expansions, lists, and lookups interact with each other in such a way
6558 that there is no order in which to describe any one of them that does not
6559 involve references to the others. Each of these three chapters makes more sense
6560 if you have read the other two first. If you are reading this for the first
6561 time, be aware that some of it will make a lot more sense after you have read
6562 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6564 .section "Examples of different lookup syntax" "SECID60"
6565 It is easy to confuse the two different kinds of lookup, especially as the
6566 lists that may contain the second kind are always expanded before being
6567 processed as lists. Therefore, they may also contain lookups of the first kind.
6568 Be careful to distinguish between the following two examples:
6570 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6571 domains = lsearch;/some/file
6573 The first uses a string expansion, the result of which must be a domain list.
6574 No strings have been specified for a successful or a failing lookup; the
6575 defaults in this case are the looked-up data and an empty string, respectively.
6576 The expansion takes place before the string is processed as a list, and the
6577 file that is searched could contain lines like this:
6579 192.168.3.4: domain1:domain2:...
6580 192.168.1.9: domain3:domain4:...
6582 When the lookup succeeds, the result of the expansion is a list of domains (and
6583 possibly other types of item that are allowed in domain lists).
6585 In the second example, the lookup is a single item in a domain list. It causes
6586 Exim to use a lookup to see if the domain that is being processed can be found
6587 in the file. The file could contains lines like this:
6592 Any data that follows the keys is not relevant when checking that the domain
6593 matches the list item.
6595 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6596 Consider a file containing lines like this:
6598 192.168.5.6: lsearch;/another/file
6600 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6601 first &%domains%& setting above generates the second setting, which therefore
6602 causes a second lookup to occur.
6604 The rest of this chapter describes the different lookup types that are
6605 available. Any of them can be used in any part of the configuration where a
6606 lookup is permitted.
6609 .section "Lookup types" "SECID61"
6610 .cindex "lookup" "types of"
6611 .cindex "single-key lookup" "definition of"
6612 Two different types of data lookup are implemented:
6615 The &'single-key'& type requires the specification of a file in which to look,
6616 and a single key to search for. The key must be a non-empty string for the
6617 lookup to succeed. The lookup type determines how the file is searched.
6619 .cindex "query-style lookup" "definition of"
6620 The &'query-style'& type accepts a generalized database query. No particular
6621 key value is assumed by Exim for query-style lookups. You can use whichever
6622 Exim variables you need to construct the database query.
6625 The code for each lookup type is in a separate source file that is included in
6626 the binary of Exim only if the corresponding compile-time option is set. The
6627 default settings in &_src/EDITME_& are:
6632 which means that only linear searching and DBM lookups are included by default.
6633 For some types of lookup (e.g. SQL databases), you need to install appropriate
6634 libraries and header files before building Exim.
6639 .section "Single-key lookup types" "SECTsinglekeylookups"
6640 .cindex "lookup" "single-key types"
6641 .cindex "single-key lookup" "list of types"
6642 The following single-key lookup types are implemented:
6645 .cindex "cdb" "description of"
6646 .cindex "lookup" "cdb"
6647 .cindex "binary zero" "in lookup key"
6648 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6649 string without a terminating binary zero. The cdb format is designed for
6650 indexed files that are read frequently and never updated, except by total
6651 re-creation. As such, it is particularly suitable for large files containing
6652 aliases or other indexed data referenced by an MTA. Information about cdb and
6653 tools for building the files can be found in several places:
6655 &url(https://cr.yp.to/cdb.html)
6656 &url(http://www.corpit.ru/mjt/tinycdb.html)
6657 &url(https://packages.debian.org/stable/utils/freecdb)
6658 &url(https://github.com/philpennock/cdbtools) (in Go)
6660 . --- 2018-09-07: corpit.ru http:-only
6661 A cdb distribution is not needed in order to build Exim with cdb support,
6662 because the code for reading cdb files is included directly in Exim itself.
6663 However, no means of building or testing cdb files is provided with Exim, so
6664 you need to obtain a cdb distribution in order to do this.
6666 .cindex "DBM" "lookup type"
6667 .cindex "lookup" "dbm"
6668 .cindex "binary zero" "in lookup key"
6669 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6670 DBM file by looking up the record with the given key. A terminating binary
6671 zero is included in the key that is passed to the DBM library. See section
6672 &<<SECTdb>>& for a discussion of DBM libraries.
6674 .cindex "Berkeley DB library" "file format"
6675 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6676 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6677 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6678 the DB_UNKNOWN option. This enables it to handle any of the types of database
6679 that the library supports, and can be useful for accessing DBM files created by
6680 other applications. (For earlier DB versions, DB_HASH is always used.)
6682 .cindex "lookup" "dbmjz"
6683 .cindex "lookup" "dbm &-- embedded NULs"
6685 .cindex "dbmjz lookup type"
6686 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6687 interpreted as an Exim list; the elements of the list are joined together with
6688 ASCII NUL characters to form the lookup key. An example usage would be to
6689 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6690 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6691 &(cram_md5)& authenticator.
6693 .cindex "lookup" "dbmnz"
6694 .cindex "lookup" "dbm &-- terminating zero"
6695 .cindex "binary zero" "in lookup key"
6697 .cindex "&_/etc/userdbshadow.dat_&"
6698 .cindex "dbmnz lookup type"
6699 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6700 is not included in the key that is passed to the DBM library. You may need this
6701 if you want to look up data in files that are created by or shared with some
6702 other application that does not use terminating zeros. For example, you need to
6703 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6704 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6705 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6706 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6708 .cindex "lookup" "dsearch"
6709 .cindex "dsearch lookup type"
6710 &(dsearch)&: The given file must be a directory; this is searched for an entry
6711 whose name is the key by calling the &[lstat()]& function. The key may not
6712 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6713 the lookup is the name of the entry, which may be a file, directory,
6714 symbolic link, or any other kind of directory entry. An example of how this
6715 lookup can be used to support virtual domains is given in section
6716 &<<SECTvirtualdomains>>&.
6718 .cindex "lookup" "iplsearch"
6719 .cindex "iplsearch lookup type"
6720 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6721 terminated by a colon or white space or the end of the line. The keys in the
6722 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6723 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6724 being interpreted as a key terminator. For example:
6726 1.2.3.4: data for 1.2.3.4
6727 192.168.0.0/16: data for 192.168.0.0/16
6728 "abcd::cdab": data for abcd::cdab
6729 "abcd:abcd::/32" data for abcd:abcd::/32
6731 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6732 file is searched linearly, using the CIDR masks where present, until a matching
6733 key is found. The first key that matches is used; there is no attempt to find a
6734 &"best"& match. Apart from the way the keys are matched, the processing for
6735 &(iplsearch)& is the same as for &(lsearch)&.
6737 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6738 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6739 lookup types support only literal keys.
6741 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6742 the implicit key is the host's IP address rather than its name (see section
6743 &<<SECThoslispatsikey>>&).
6745 .cindex "linear search"
6746 .cindex "lookup" "lsearch"
6747 .cindex "lsearch lookup type"
6748 .cindex "case sensitivity" "in lsearch lookup"
6749 &(lsearch)&: The given file is a text file that is searched linearly for a
6750 line beginning with the search key, terminated by a colon or white space or the
6751 end of the line. The search is case-insensitive; that is, upper and lower case
6752 letters are treated as the same. The first occurrence of the key that is found
6753 in the file is used.
6755 White space between the key and the colon is permitted. The remainder of the
6756 line, with leading and trailing white space removed, is the data. This can be
6757 continued onto subsequent lines by starting them with any amount of white
6758 space, but only a single space character is included in the data at such a
6759 junction. If the data begins with a colon, the key must be terminated by a
6764 Empty lines and lines beginning with # are ignored, even if they occur in the
6765 middle of an item. This is the traditional textual format of alias files. Note
6766 that the keys in an &(lsearch)& file are literal strings. There is no
6767 wildcarding of any kind.
6769 .cindex "lookup" "lsearch &-- colons in keys"
6770 .cindex "white space" "in lsearch key"
6771 In most &(lsearch)& files, keys are not required to contain colons or #
6772 characters, or white space. However, if you need this feature, it is available.
6773 If a key begins with a doublequote character, it is terminated only by a
6774 matching quote (or end of line), and the normal escaping rules apply to its
6775 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6776 quoted keys (exactly as for unquoted keys). There is no special handling of
6777 quotes for the data part of an &(lsearch)& line.
6780 .cindex "NIS lookup type"
6781 .cindex "lookup" "NIS"
6782 .cindex "binary zero" "in lookup key"
6783 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6784 the given key, without a terminating binary zero. There is a variant called
6785 &(nis0)& which does include the terminating binary zero in the key. This is
6786 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6787 aliases; the full map names must be used.
6790 .cindex "wildlsearch lookup type"
6791 .cindex "lookup" "wildlsearch"
6792 .cindex "nwildlsearch lookup type"
6793 .cindex "lookup" "nwildlsearch"
6794 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6795 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6796 the file may be wildcarded. The difference between these two lookup types is
6797 that for &(wildlsearch)&, each key in the file is string-expanded before being
6798 used, whereas for &(nwildlsearch)&, no expansion takes place.
6800 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6801 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6802 file that are regular expressions can be made case-sensitive by the use of
6803 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6805 . ==== As this is a nested list, any displays it contains must be indented
6806 . ==== as otherwise they are too far to the left.
6809 The string may begin with an asterisk to mean &"ends with"&. For example:
6811 *.a.b.c data for anything.a.b.c
6812 *fish data for anythingfish
6815 The string may begin with a circumflex to indicate a regular expression. For
6816 example, for &(wildlsearch)&:
6818 ^\N\d+\.a\.b\N data for <digits>.a.b
6820 Note the use of &`\N`& to disable expansion of the contents of the regular
6821 expression. If you are using &(nwildlsearch)&, where the keys are not
6822 string-expanded, the equivalent entry is:
6824 ^\d+\.a\.b data for <digits>.a.b
6826 The case-insensitive flag is set at the start of compiling the regular
6827 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6828 For example, to make the entire pattern case-sensitive:
6830 ^(?-i)\d+\.a\.b data for <digits>.a.b
6833 If the regular expression contains white space or colon characters, you must
6834 either quote it (see &(lsearch)& above), or represent these characters in other
6835 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6836 colon. This may be easier than quoting, because if you quote, you have to
6837 escape all the backslashes inside the quotes.
6839 &*Note*&: It is not possible to capture substrings in a regular expression
6840 match for later use, because the results of all lookups are cached. If a lookup
6841 is repeated, the result is taken from the cache, and no actual pattern matching
6842 takes place. The values of all the numeric variables are unset after a
6843 &((n)wildlsearch)& match.
6846 Although I cannot see it being of much use, the general matching function that
6847 is used to implement &((n)wildlsearch)& means that the string may begin with a
6848 lookup name terminated by a semicolon, and followed by lookup data. For
6851 cdb;/some/file data for keys that match the file
6853 The data that is obtained from the nested lookup is discarded.
6856 Keys that do not match any of these patterns are interpreted literally. The
6857 continuation rules for the data are the same as for &(lsearch)&, and keys may
6858 be followed by optional colons.
6860 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6861 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6862 lookup types support only literal keys.
6865 .cindex "lookup" "spf"
6866 If Exim is built with SPF support, manual lookups can be done
6867 (as opposed to the standard ACL condition method.
6868 For details see section &<<SECSPF>>&.
6872 .section "Query-style lookup types" "SECTquerystylelookups"
6873 .cindex "lookup" "query-style types"
6874 .cindex "query-style lookup" "list of types"
6875 The supported query-style lookup types are listed below. Further details about
6876 many of them are given in later sections.
6879 .cindex "DNS" "as a lookup type"
6880 .cindex "lookup" "DNS"
6881 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6882 are given in the supplied query. The resulting data is the contents of the
6883 records. See section &<<SECTdnsdb>>&.
6885 .cindex "InterBase lookup type"
6886 .cindex "lookup" "InterBase"
6887 &(ibase)&: This does a lookup in an InterBase database.
6889 .cindex "LDAP" "lookup type"
6890 .cindex "lookup" "LDAP"
6891 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6892 returns attributes from a single entry. There is a variant called &(ldapm)&
6893 that permits values from multiple entries to be returned. A third variant
6894 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6895 any attribute values. See section &<<SECTldap>>&.
6897 .cindex "MySQL" "lookup type"
6898 .cindex "lookup" "MySQL"
6899 &(mysql)&: The format of the query is an SQL statement that is passed to a
6900 MySQL database. See section &<<SECTsql>>&.
6902 .cindex "NIS+ lookup type"
6903 .cindex "lookup" "NIS+"
6904 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6905 the field to be returned. See section &<<SECTnisplus>>&.
6907 .cindex "Oracle" "lookup type"
6908 .cindex "lookup" "Oracle"
6909 &(oracle)&: The format of the query is an SQL statement that is passed to an
6910 Oracle database. See section &<<SECTsql>>&.
6912 .cindex "lookup" "passwd"
6913 .cindex "passwd lookup type"
6914 .cindex "&_/etc/passwd_&"
6915 &(passwd)& is a query-style lookup with queries that are just user names. The
6916 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6917 success, the result string is the same as you would get from an &(lsearch)&
6918 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6919 password value. For example:
6921 *:42:42:King Rat:/home/kr:/bin/bash
6924 .cindex "PostgreSQL lookup type"
6925 .cindex "lookup" "PostgreSQL"
6926 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6927 PostgreSQL database. See section &<<SECTsql>>&.
6930 .cindex "Redis lookup type"
6931 .cindex lookup Redis
6932 &(redis)&: The format of the query is either a simple get or simple set,
6933 passed to a Redis database. See section &<<SECTsql>>&.
6936 .cindex "sqlite lookup type"
6937 .cindex "lookup" "sqlite"
6938 &(sqlite)&: The format of the query is a filename followed by an SQL statement
6939 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6942 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6943 not likely to be useful in normal operation.
6945 .cindex "whoson lookup type"
6946 .cindex "lookup" "whoson"
6947 . --- still http:-only, 2018-09-07
6948 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6949 allows a server to check whether a particular (dynamically allocated) IP
6950 address is currently allocated to a known (trusted) user and, optionally, to
6951 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6952 at one time for &"POP before SMTP"& authentication, but that approach has been
6953 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6954 &"POP before SMTP"& checking using ACL statements such as
6956 require condition = \
6957 ${lookup whoson {$sender_host_address}{yes}{no}}
6959 The query consists of a single IP address. The value returned is the name of
6960 the authenticated user, which is stored in the variable &$value$&. However, in
6961 this example, the data in &$value$& is not used; the result of the lookup is
6962 one of the fixed strings &"yes"& or &"no"&.
6967 .section "Temporary errors in lookups" "SECID63"
6968 .cindex "lookup" "temporary error in"
6969 Lookup functions can return temporary error codes if the lookup cannot be
6970 completed. For example, an SQL or LDAP database might be unavailable. For this
6971 reason, it is not advisable to use a lookup that might do this for critical
6972 options such as a list of local domains.
6974 When a lookup cannot be completed in a router or transport, delivery
6975 of the message (to the relevant address) is deferred, as for any other
6976 temporary error. In other circumstances Exim may assume the lookup has failed,
6977 or may give up altogether.
6981 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6982 .cindex "wildcard lookups"
6983 .cindex "lookup" "default values"
6984 .cindex "lookup" "wildcard"
6985 .cindex "lookup" "* added to type"
6986 .cindex "default" "in single-key lookups"
6987 In this context, a &"default value"& is a value specified by the administrator
6988 that is to be used if a lookup fails.
6990 &*Note:*& This section applies only to single-key lookups. For query-style
6991 lookups, the facilities of the query language must be used. An attempt to
6992 specify a default for a query-style lookup provokes an error.
6994 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6995 and the initial lookup fails, the key &"*"& is looked up in the file to
6996 provide a default value. See also the section on partial matching below.
6998 .cindex "*@ with single-key lookup"
6999 .cindex "lookup" "*@ added to type"
7000 .cindex "alias file" "per-domain default"
7001 Alternatively, if &"*@"& is added to a single-key lookup type (for example
7002 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
7003 character, a second lookup is done with everything before the last @ replaced
7004 by *. This makes it possible to provide per-domain defaults in alias files
7005 that include the domains in the keys. If the second lookup fails (or doesn't
7006 take place because there is no @ in the key), &"*"& is looked up.
7007 For example, a &(redirect)& router might contain:
7009 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
7011 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
7012 looks up these keys, in this order:
7018 The data is taken from whichever key it finds first. &*Note*&: In an
7019 &(lsearch)& file, this does not mean the first of these keys in the file. A
7020 complete scan is done for each key, and only if it is not found at all does
7021 Exim move on to try the next key.
7025 .section "Partial matching in single-key lookups" "SECTpartiallookup"
7026 .cindex "partial matching"
7027 .cindex "wildcard lookups"
7028 .cindex "lookup" "partial matching"
7029 .cindex "lookup" "wildcard"
7030 .cindex "asterisk" "in search type"
7031 The normal operation of a single-key lookup is to search the file for an exact
7032 match with the given key. However, in a number of situations where domains are
7033 being looked up, it is useful to be able to do partial matching. In this case,
7034 information in the file that has a key starting with &"*."& is matched by any
7035 domain that ends with the components that follow the full stop. For example, if
7036 a key in a DBM file is
7038 *.dates.fict.example
7040 then when partial matching is enabled this is matched by (amongst others)
7041 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
7042 by &'dates.fict.example'&, if that does not appear as a separate key in the
7045 &*Note*&: Partial matching is not available for query-style lookups. It is
7046 also not available for any lookup items in address lists (see section
7047 &<<SECTaddresslist>>&).
7049 Partial matching is implemented by doing a series of separate lookups using
7050 keys constructed by modifying the original subject key. This means that it can
7051 be used with any of the single-key lookup types, provided that
7052 partial matching keys
7053 beginning with a special prefix (default &"*."&) are included in the data file.
7054 Keys in the file that do not begin with the prefix are matched only by
7055 unmodified subject keys when partial matching is in use.
7057 Partial matching is requested by adding the string &"partial-"& to the front of
7058 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
7059 is done, the subject key is first looked up unmodified; if that fails, &"*."&
7060 is added at the start of the subject key, and it is looked up again. If that
7061 fails, further lookups are tried with dot-separated components removed from the
7062 start of the subject key, one-by-one, and &"*."& added on the front of what
7065 A minimum number of two non-* components are required. This can be adjusted
7066 by including a number before the hyphen in the search type. For example,
7067 &%partial3-lsearch%& specifies a minimum of three non-* components in the
7068 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
7069 subject key is &'2250.dates.fict.example'& then the following keys are looked
7070 up when the minimum number of non-* components is two:
7072 2250.dates.fict.example
7073 *.2250.dates.fict.example
7074 *.dates.fict.example
7077 As soon as one key in the sequence is successfully looked up, the lookup
7080 .cindex "lookup" "partial matching &-- changing prefix"
7081 .cindex "prefix" "for partial matching"
7082 The use of &"*."& as the partial matching prefix is a default that can be
7083 changed. The motivation for this feature is to allow Exim to operate with file
7084 formats that are used by other MTAs. A different prefix can be supplied in
7085 parentheses instead of the hyphen after &"partial"&. For example:
7087 domains = partial(.)lsearch;/some/file
7089 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
7090 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
7091 components is unchanged). The prefix may consist of any punctuation characters
7092 other than a closing parenthesis. It may be empty, for example:
7094 domains = partial1()cdb;/some/file
7096 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
7097 &`a.b.c`&, &`b.c`&, and &`c`&.
7099 If &"partial0"& is specified, what happens at the end (when the lookup with
7100 just one non-wild component has failed, and the original key is shortened right
7101 down to the null string) depends on the prefix:
7104 If the prefix has zero length, the whole lookup fails.
7106 If the prefix has length 1, a lookup for just the prefix is done. For
7107 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
7109 Otherwise, if the prefix ends in a dot, the dot is removed, and the
7110 remainder is looked up. With the default prefix, therefore, the final lookup is
7111 for &"*"& on its own.
7113 Otherwise, the whole prefix is looked up.
7117 If the search type ends in &"*"& or &"*@"& (see section
7118 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
7119 this implies happens after all partial lookups have failed. If &"partial0"& is
7120 specified, adding &"*"& to the search type has no effect with the default
7121 prefix, because the &"*"& key is already included in the sequence of partial
7122 lookups. However, there might be a use for lookup types such as
7123 &"partial0(.)lsearch*"&.
7125 The use of &"*"& in lookup partial matching differs from its use as a wildcard
7126 in domain lists and the like. Partial matching works only in terms of
7127 dot-separated components; a key such as &`*fict.example`&
7128 in a database file is useless, because the asterisk in a partial matching
7129 subject key is always followed by a dot.
7134 .section "Lookup caching" "SECID64"
7135 .cindex "lookup" "caching"
7136 .cindex "caching" "lookup data"
7137 Exim caches all lookup results in order to avoid needless repetition of
7138 lookups. However, because (apart from the daemon) Exim operates as a collection
7139 of independent, short-lived processes, this caching applies only within a
7140 single Exim process. There is no inter-process lookup caching facility.
7142 For single-key lookups, Exim keeps the relevant files open in case there is
7143 another lookup that needs them. In some types of configuration this can lead to
7144 many files being kept open for messages with many recipients. To avoid hitting
7145 the operating system limit on the number of simultaneously open files, Exim
7146 closes the least recently used file when it needs to open more files than its
7147 own internal limit, which can be changed via the &%lookup_open_max%& option.
7149 The single-key lookup files are closed and the lookup caches are flushed at
7150 strategic points during delivery &-- for example, after all routing is
7156 .section "Quoting lookup data" "SECID65"
7157 .cindex "lookup" "quoting"
7158 .cindex "quoting" "in lookups"
7159 When data from an incoming message is included in a query-style lookup, there
7160 is the possibility of special characters in the data messing up the syntax of
7161 the query. For example, a NIS+ query that contains
7165 will be broken if the local part happens to contain a closing square bracket.
7166 For NIS+, data can be enclosed in double quotes like this:
7168 [name="$local_part"]
7170 but this still leaves the problem of a double quote in the data. The rule for
7171 NIS+ is that double quotes must be doubled. Other lookup types have different
7172 rules, and to cope with the differing requirements, an expansion operator
7173 of the following form is provided:
7175 ${quote_<lookup-type>:<string>}
7177 For example, the safest way to write the NIS+ query is
7179 [name="${quote_nisplus:$local_part}"]
7181 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
7182 operator can be used for all lookup types, but has no effect for single-key
7183 lookups, since no quoting is ever needed in their key strings.
7188 .section "More about dnsdb" "SECTdnsdb"
7189 .cindex "dnsdb lookup"
7190 .cindex "lookup" "dnsdb"
7191 .cindex "DNS" "as a lookup type"
7192 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7193 of a record type and a domain name, separated by an equals sign. For example,
7194 an expansion string could contain:
7196 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7198 If the lookup succeeds, the result is placed in &$value$&, which in this case
7199 is used on its own as the result. If the lookup does not succeed, the
7200 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7201 &<<SECTforexpfai>>& for an explanation of what this means.
7203 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7204 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7205 If no type is given, TXT is assumed.
7207 For any record type, if multiple records are found, the data is returned as a
7208 concatenation, with newline as the default separator. The order, of course,
7209 depends on the DNS resolver. You can specify a different separator character
7210 between multiple records by putting a right angle-bracket followed immediately
7211 by the new separator at the start of the query. For example:
7213 ${lookup dnsdb{>: a=host1.example}}
7215 It is permitted to specify a space as the separator character. Further
7216 white space is ignored.
7217 For lookup types that return multiple fields per record,
7218 an alternate field separator can be specified using a comma after the main
7219 separator character, followed immediately by the field separator.
7221 .cindex "PTR record" "in &(dnsdb)& lookup"
7222 When the type is PTR,
7223 the data can be an IP address, written as normal; inversion and the addition of
7224 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7226 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7228 If the data for a PTR record is not a syntactically valid IP address, it is not
7229 altered and nothing is added.
7231 .cindex "MX record" "in &(dnsdb)& lookup"
7232 .cindex "SRV record" "in &(dnsdb)& lookup"
7233 For an MX lookup, both the preference value and the host name are returned for
7234 each record, separated by a space. For an SRV lookup, the priority, weight,
7235 port, and host name are returned for each record, separated by spaces.
7236 The field separator can be modified as above.
7238 .cindex "TXT record" "in &(dnsdb)& lookup"
7239 .cindex "SPF record" "in &(dnsdb)& lookup"
7240 For TXT records with multiple items of data, only the first item is returned,
7241 unless a field separator is specified.
7242 To concatenate items without a separator, use a semicolon instead.
7244 default behaviour is to concatenate multiple items without using a separator.
7246 ${lookup dnsdb{>\n,: txt=a.b.example}}
7247 ${lookup dnsdb{>\n; txt=a.b.example}}
7248 ${lookup dnsdb{spf=example.org}}
7250 It is permitted to specify a space as the separator character. Further
7251 white space is ignored.
7253 .cindex "SOA record" "in &(dnsdb)& lookup"
7254 For an SOA lookup, while no result is obtained the lookup is redone with
7255 successively more leading components dropped from the given domain.
7256 Only the primary-nameserver field is returned unless a field separator is
7259 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7262 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7263 .cindex "dnsdb modifiers"
7264 .cindex "modifiers" "dnsdb"
7265 .cindex "options" "dnsdb"
7266 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7267 each followed by a comma,
7268 that may appear before the record type.
7270 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7271 temporary DNS error for any of them, the behaviour is controlled by
7272 a defer-option modifier.
7273 The possible keywords are
7274 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7275 With &"strict"& behaviour, any temporary DNS error causes the
7276 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7277 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7278 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7279 error causes the whole lookup to defer only if none of the other lookups
7280 succeed. The default is &"lax"&, so the following lookups are equivalent:
7282 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7283 ${lookup dnsdb{a=one.host.com:two.host.com}}
7285 Thus, in the default case, as long as at least one of the DNS lookups
7286 yields some data, the lookup succeeds.
7288 .cindex "DNSSEC" "dns lookup"
7289 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7290 The possible keywords are
7291 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7292 With &"strict"& or &"lax"& DNSSEC information is requested
7294 With &"strict"& a response from the DNS resolver that
7295 is not labelled as authenticated data
7296 is treated as equivalent to a temporary DNS error.
7297 The default is &"never"&.
7299 See also the &$lookup_dnssec_authenticated$& variable.
7301 .cindex timeout "dns lookup"
7302 .cindex "DNS" timeout
7303 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7304 The form is &"retrans_VAL"& where VAL is an Exim time specification
7306 The default value is set by the main configuration option &%dns_retrans%&.
7308 Retries for the dnsdb lookup can be controlled by a retry modifier.
7309 The form if &"retry_VAL"& where VAL is an integer.
7310 The default count is set by the main configuration option &%dns_retry%&.
7312 .cindex caching "of dns lookup"
7313 .cindex TTL "of dns lookup"
7315 Dnsdb lookup results are cached within a single process (and its children).
7316 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7317 value of the set of returned DNS records.
7320 .section "Pseudo dnsdb record types" "SECID66"
7321 .cindex "MX record" "in &(dnsdb)& lookup"
7322 By default, both the preference value and the host name are returned for
7323 each MX record, separated by a space. If you want only host names, you can use
7324 the pseudo-type MXH:
7326 ${lookup dnsdb{mxh=a.b.example}}
7328 In this case, the preference values are omitted, and just the host names are
7331 .cindex "name server for enclosing domain"
7332 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7333 records on the given domain, but if none are found, it removes the first
7334 component of the domain name, and tries again. This process continues until NS
7335 records are found or there are no more components left (or there is a DNS
7336 error). In other words, it may return the name servers for a top-level domain,
7337 but it never returns the root name servers. If there are no NS records for the
7338 top-level domain, the lookup fails. Consider these examples:
7340 ${lookup dnsdb{zns=xxx.quercite.com}}
7341 ${lookup dnsdb{zns=xxx.edu}}
7343 Assuming that in each case there are no NS records for the full domain name,
7344 the first returns the name servers for &%quercite.com%&, and the second returns
7345 the name servers for &%edu%&.
7347 You should be careful about how you use this lookup because, unless the
7348 top-level domain does not exist, the lookup always returns some host names. The
7349 sort of use to which this might be put is for seeing if the name servers for a
7350 given domain are on a blacklist. You can probably assume that the name servers
7351 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7354 .cindex "CSA" "in &(dnsdb)& lookup"
7355 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7356 records according to the CSA rules, which are described in section
7357 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7358 not sufficient because of the extra parent domain search behaviour of CSA. The
7359 result of a successful lookup such as:
7361 ${lookup dnsdb {csa=$sender_helo_name}}
7363 has two space-separated fields: an authorization code and a target host name.
7364 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7365 authorization required but absent, or &"?"& for unknown.
7367 .cindex "A+" "in &(dnsdb)& lookup"
7368 The pseudo-type A+ performs an AAAA
7369 and then an A lookup. All results are returned; defer processing
7370 (see below) is handled separately for each lookup. Example:
7372 ${lookup dnsdb {>; a+=$sender_helo_name}}
7376 .section "Multiple dnsdb lookups" "SECID67"
7377 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7378 However, you can specify a list of domains or IP addresses in a single
7379 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7380 the default separator, but with the ability to change this. For example:
7382 ${lookup dnsdb{one.domain.com:two.domain.com}}
7383 ${lookup dnsdb{a=one.host.com:two.host.com}}
7384 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7386 In order to retain backwards compatibility, there is one special case: if
7387 the lookup type is PTR and no change of separator is specified, Exim looks
7388 to see if the rest of the string is precisely one IPv6 address. In this
7389 case, it does not treat it as a list.
7391 The data from each lookup is concatenated, with newline separators by default,
7392 in the same way that multiple DNS records for a single item are handled. A
7393 different separator can be specified, as described above.
7398 .section "More about LDAP" "SECTldap"
7399 .cindex "LDAP" "lookup, more about"
7400 .cindex "lookup" "LDAP"
7401 .cindex "Solaris" "LDAP"
7402 The original LDAP implementation came from the University of Michigan; this has
7403 become &"Open LDAP"&, and there are now two different releases. Another
7404 implementation comes from Netscape, and Solaris 7 and subsequent releases
7405 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7406 the lookup function level, their error handling is different. For this reason
7407 it is necessary to set a compile-time variable when building Exim with LDAP, to
7408 indicate which LDAP library is in use. One of the following should appear in
7409 your &_Local/Makefile_&:
7411 LDAP_LIB_TYPE=UMICHIGAN
7412 LDAP_LIB_TYPE=OPENLDAP1
7413 LDAP_LIB_TYPE=OPENLDAP2
7414 LDAP_LIB_TYPE=NETSCAPE
7415 LDAP_LIB_TYPE=SOLARIS
7417 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7418 same interface as the University of Michigan version.
7420 There are three LDAP lookup types in Exim. These behave slightly differently in
7421 the way they handle the results of a query:
7424 &(ldap)& requires the result to contain just one entry; if there are more, it
7427 &(ldapdn)& also requires the result to contain just one entry, but it is the
7428 Distinguished Name that is returned rather than any attribute values.
7430 &(ldapm)& permits the result to contain more than one entry; the attributes
7431 from all of them are returned.
7435 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7436 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7437 the data returned by a successful lookup is described in the next section.
7438 First we explain how LDAP queries are coded.
7441 .section "Format of LDAP queries" "SECTforldaque"
7442 .cindex "LDAP" "query format"
7443 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7444 the configuration of a &(redirect)& router one might have this setting:
7446 data = ${lookup ldap \
7447 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7448 c=UK?mailbox?base?}}
7450 .cindex "LDAP" "with TLS"
7451 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7452 secure (encrypted) LDAP connections. The second of these ensures that an
7453 encrypted TLS connection is used.
7455 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7456 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7457 See the &%ldap_start_tls%& option.
7459 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7460 controlled. Every part of the TLS configuration can be configured by settings in
7461 &_exim.conf_&. Depending on the version of the client libraries installed on
7462 your system, some of the initialization may have required setting options in
7463 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7464 certificates. This revealed a nuance where the current UID that exim was
7465 running as could affect which config files it read. With Exim 4.83, these
7466 methods become optional, only taking effect if not specifically set in
7470 .section "LDAP quoting" "SECID68"
7471 .cindex "LDAP" "quoting"
7472 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7473 and the second because the LDAP query is represented as a URL. Furthermore,
7474 within an LDAP query, two different kinds of quoting are required. For this
7475 reason, there are two different LDAP-specific quoting operators.
7477 The &%quote_ldap%& operator is designed for use on strings that are part of
7478 filter specifications. Conceptually, it first does the following conversions on
7486 in accordance with RFC 2254. The resulting string is then quoted according
7487 to the rules for URLs, that is, all non-alphanumeric characters except
7491 are converted to their hex values, preceded by a percent sign. For example:
7493 ${quote_ldap: a(bc)*, a<yz>; }
7497 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7499 Removing the URL quoting, this is (with a leading and a trailing space):
7501 a\28bc\29\2A, a<yz>;
7503 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7504 base DN specifications in queries. Conceptually, it first converts the string
7505 by inserting a backslash in front of any of the following characters:
7509 It also inserts a backslash before any leading spaces or # characters, and
7510 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7511 is then quoted according to the rules for URLs. For example:
7513 ${quote_ldap_dn: a(bc)*, a<yz>; }
7517 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7519 Removing the URL quoting, this is (with a trailing space):
7521 \ a(bc)*\, a\<yz\>\;\
7523 There are some further comments about quoting in the section on LDAP
7524 authentication below.
7527 .section "LDAP connections" "SECID69"
7528 .cindex "LDAP" "connections"
7529 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7530 is in use, via a Unix domain socket. The example given above does not specify
7531 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7534 ldap://<hostname>:<port>/...
7536 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7537 used. When no server is specified in a query, a list of default servers is
7538 taken from the &%ldap_default_servers%& configuration option. This supplies a
7539 colon-separated list of servers which are tried in turn until one successfully
7540 handles a query, or there is a serious error. Successful handling either
7541 returns the requested data, or indicates that it does not exist. Serious errors
7542 are syntactical, or multiple values when only a single value is expected.
7543 Errors which cause the next server to be tried are connection failures, bind
7544 failures, and timeouts.
7546 For each server name in the list, a port number can be given. The standard way
7547 of specifying a host and port is to use a colon separator (RFC 1738). Because
7548 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7549 doubled. For example
7551 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7553 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7554 to the LDAP library with no server name, and the library's default (normally
7555 the local host) is used.
7557 If you are using the OpenLDAP library, you can connect to an LDAP server using
7558 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7559 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7560 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7563 For this type of connection, instead of a host name for the server, a pathname
7564 for the socket is required, and the port number is not relevant. The pathname
7565 can be specified either as an item in &%ldap_default_servers%&, or inline in
7566 the query. In the former case, you can have settings such as
7568 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7570 When the pathname is given in the query, you have to escape the slashes as
7571 &`%2F`& to fit in with the LDAP URL syntax. For example:
7573 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7575 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7576 a pathname, it uses the Unix domain socket code, even if the query actually
7577 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7578 socket connection. This behaviour means that you can use a setting of
7579 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7580 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7581 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7584 If an explicit &`ldapi`& type is given in a query when a host name is
7585 specified, an error is diagnosed. However, if there are more items in
7586 &%ldap_default_servers%&, they are tried. In other words:
7589 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7592 Using &`ldapi`& with a host name causes an error.
7596 Using &`ldapi`& with no host or path in the query, and no setting of
7597 &%ldap_default_servers%&, does whatever the library does by default.
7601 .section "LDAP authentication and control information" "SECID70"
7602 .cindex "LDAP" "authentication"
7603 The LDAP URL syntax provides no way of passing authentication and other control
7604 information to the server. To make this possible, the URL in an LDAP query may
7605 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7606 spaces. If a value contains spaces it must be enclosed in double quotes, and
7607 when double quotes are used, backslash is interpreted in the usual way inside
7608 them. The following names are recognized:
7610 &`DEREFERENCE`& set the dereferencing parameter
7611 &`NETTIME `& set a timeout for a network operation
7612 &`USER `& set the DN, for authenticating the LDAP bind
7613 &`PASS `& set the password, likewise
7614 &`REFERRALS `& set the referrals parameter
7615 &`SERVERS `& set alternate server list for this query only
7616 &`SIZE `& set the limit for the number of entries returned
7617 &`TIME `& set the maximum waiting time for a query
7619 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7620 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7621 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7622 library from trying to follow referrals issued by the LDAP server.
7624 .cindex LDAP timeout
7625 .cindex timeout "LDAP lookup"
7626 The name CONNECT is an obsolete name for NETTIME, retained for
7627 backwards compatibility. This timeout (specified as a number of seconds) is
7628 enforced from the client end for operations that can be carried out over a
7629 network. Specifically, it applies to network connections and calls to the
7630 &'ldap_result()'& function. If the value is greater than zero, it is used if
7631 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7632 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7633 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7634 Netscape SDK; for OpenLDAP no action is taken.
7636 The TIME parameter (also a number of seconds) is passed to the server to
7637 set a server-side limit on the time taken to complete a search.
7639 The SERVERS parameter allows you to specify an alternate list of ldap servers
7640 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7641 default list of ldap servers, and a single lookup can specify a single ldap
7642 server to use. But when you need to do a lookup with a list of servers that is
7643 different than the default list (maybe different order, maybe a completely
7644 different set of servers), the SERVERS parameter allows you to specify this
7645 alternate list (colon-separated).
7647 Here is an example of an LDAP query in an Exim lookup that uses some of these
7648 values. This is a single line, folded to fit on the page:
7651 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7652 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7655 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7656 any of the auxiliary data. Exim configuration settings that include lookups
7657 which contain password information should be preceded by &"hide"& to prevent
7658 non-admin users from using the &%-bP%& option to see their values.
7660 The auxiliary data items may be given in any order. The default is no
7661 connection timeout (the system timeout is used), no user or password, no limit
7662 on the number of entries returned, and no time limit on queries.
7664 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7665 removes any URL quoting that it may contain before passing it LDAP. Apparently
7666 some libraries do this for themselves, but some do not. Removing the URL
7667 quoting has two advantages:
7670 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7671 DNs as with DNs inside actual queries.
7673 It permits spaces inside USER= DNs.
7676 For example, a setting such as
7678 USER=cn=${quote_ldap_dn:$1}
7680 should work even if &$1$& contains spaces.
7682 Expanded data for the PASS= value should be quoted using the &%quote%&
7683 expansion operator, rather than the LDAP quote operators. The only reason this
7684 field needs quoting is to ensure that it conforms to the Exim syntax, which
7685 does not allow unquoted spaces. For example:
7689 The LDAP authentication mechanism can be used to check passwords as part of
7690 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7695 .section "Format of data returned by LDAP" "SECID71"
7696 .cindex "LDAP" "returned data formats"
7697 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7698 as a sequence of values, for example
7700 cn=manager,o=University of Cambridge,c=UK
7702 The &(ldap)& lookup type generates an error if more than one entry matches the
7703 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7704 the result between the data from different entries. It is possible for multiple
7705 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7706 you know that whatever values are returned all came from a single entry in the
7709 In the common case where you specify a single attribute in your LDAP query, the
7710 result is not quoted, and does not contain the attribute name. If the attribute
7711 has multiple values, they are separated by commas. Any comma that is
7712 part of an attribute's value is doubled.
7714 If you specify multiple attributes, the result contains space-separated, quoted
7715 strings, each preceded by the attribute name and an equals sign. Within the
7716 quotes, the quote character, backslash, and newline are escaped with
7717 backslashes, and commas are used to separate multiple values for the attribute.
7718 Any commas in attribute values are doubled
7719 (permitting treatment of the values as a comma-separated list).
7720 Apart from the escaping, the string within quotes takes the same form as the
7721 output when a single attribute is requested. Specifying no attributes is the
7722 same as specifying all of an entry's attributes.
7724 Here are some examples of the output format. The first line of each pair is an
7725 LDAP query, and the second is the data that is returned. The attribute called
7726 &%attr1%& has two values, one of them with an embedded comma, whereas
7727 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7728 (they have SUP &%attr%& in their schema definitions).
7731 ldap:///o=base?attr1?sub?(uid=fred)
7734 ldap:///o=base?attr2?sub?(uid=fred)
7737 ldap:///o=base?attr?sub?(uid=fred)
7738 value1.1,value1,,2,value two
7740 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7741 attr1="value1.1,value1,,2" attr2="value two"
7743 ldap:///o=base??sub?(uid=fred)
7744 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7747 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7748 results of LDAP lookups.
7749 The &%extract%& operator in string expansions can be used to pick out
7750 individual fields from data that consists of &'key'&=&'value'& pairs.
7751 The &%listextract%& operator should be used to pick out individual values
7752 of attributes, even when only a single value is expected.
7753 The doubling of embedded commas allows you to use the returned data as a
7754 comma separated list (using the "<," syntax for changing the input list separator).
7759 .section "More about NIS+" "SECTnisplus"
7760 .cindex "NIS+ lookup type"
7761 .cindex "lookup" "NIS+"
7762 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7763 and field name. If this is given, the result of a successful query is the
7764 contents of the named field; otherwise the result consists of a concatenation
7765 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7766 values containing spaces are quoted. For example, the query
7768 [name=mg1456],passwd.org_dir
7770 might return the string
7772 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7773 home=/home/mg1456 shell=/bin/bash shadow=""
7775 (split over two lines here to fit on the page), whereas
7777 [name=mg1456],passwd.org_dir:gcos
7783 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7784 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7785 operator is to double any quote characters within the text.
7789 .section "SQL lookups" "SECTsql"
7790 .cindex "SQL lookup types"
7791 .cindex "MySQL" "lookup type"
7792 .cindex "PostgreSQL lookup type"
7793 .cindex "lookup" "MySQL"
7794 .cindex "lookup" "PostgreSQL"
7795 .cindex "Oracle" "lookup type"
7796 .cindex "lookup" "Oracle"
7797 .cindex "InterBase lookup type"
7798 .cindex "lookup" "InterBase"
7799 .cindex "Redis lookup type"
7800 .cindex lookup Redis
7801 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
7803 databases. Queries for these databases contain SQL statements, so an example
7806 ${lookup mysql{select mailbox from users where id='userx'}\
7809 If the result of the query contains more than one field, the data for each
7810 field in the row is returned, preceded by its name, so the result of
7812 ${lookup pgsql{select home,name from users where id='userx'}\
7817 home=/home/userx name="Mister X"
7819 Empty values and values containing spaces are double quoted, with embedded
7820 quotes escaped by a backslash. If the result of the query contains just one
7821 field, the value is passed back verbatim, without a field name, for example:
7825 If the result of the query yields more than one row, it is all concatenated,
7826 with a newline between the data for each row.
7829 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
7830 .cindex "MySQL" "lookup type"
7831 .cindex "PostgreSQL lookup type"
7832 .cindex "lookup" "MySQL"
7833 .cindex "lookup" "PostgreSQL"
7834 .cindex "Oracle" "lookup type"
7835 .cindex "lookup" "Oracle"
7836 .cindex "InterBase lookup type"
7837 .cindex "lookup" "InterBase"
7838 .cindex "Redis lookup type"
7839 .cindex lookup Redis
7840 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
7841 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
7842 or &%redis_servers%&
7843 option (as appropriate) must be set to a colon-separated list of server
7845 (For MySQL and PostgreSQL, the global option need not be set if all
7846 queries contain their own server information &-- see section
7847 &<<SECTspeserque>>&.)
7849 each item in the list is a slash-separated list of four
7850 items: host name, database name, user name, and password. In the case of
7851 Oracle, the host name field is used for the &"service name"&, and the database
7852 name field is not used and should be empty. For example:
7854 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7856 Because password data is sensitive, you should always precede the setting with
7857 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7858 option. Here is an example where two MySQL servers are listed:
7860 hide mysql_servers = localhost/users/root/secret:\
7861 otherhost/users/root/othersecret
7863 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7864 because this is a colon-separated list, the colon has to be doubled. For each
7865 query, these parameter groups are tried in order until a connection is made and
7866 a query is successfully processed. The result of a query may be that no data is
7867 found, but that is still a successful query. In other words, the list of
7868 servers provides a backup facility, not a list of different places to look.
7870 For Redis the global option need not be specified if all queries contain their
7871 own server information &-- see section &<<SECTspeserque>>&.
7872 If specified, the option must be set to a colon-separated list of server
7874 Each item in the list is a slash-separated list of three items:
7875 host, database number, and password.
7877 The host is required and may be either an IPv4 address and optional
7878 port number (separated by a colon, which needs doubling due to the
7879 higher-level list), or a Unix socket pathname enclosed in parentheses
7881 The database number is optional; if present that number is selected in the backend
7883 The password is optional; if present it is used to authenticate to the backend
7886 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7887 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7888 respectively, and the characters single-quote, double-quote, and backslash
7889 itself are escaped with backslashes.
7891 The &%quote_redis%& expansion operator
7892 escapes whitespace and backslash characters with a backslash.
7894 .section "Specifying the server in the query" "SECTspeserque"
7895 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
7896 it is possible to specify a list of servers with an individual query. This is
7897 done by starting the query with
7899 &`servers=`&&'server1:server2:server3:...'&&`;`&
7901 Each item in the list may take one of two forms:
7903 If it contains no slashes it is assumed to be just a host name. The appropriate
7904 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7905 of the same name, and the remaining parameters (database, user, password) are
7908 If it contains any slashes, it is taken as a complete parameter set.
7910 The list of servers is used in exactly the same way as the global list.
7911 Once a connection to a server has happened and a query has been
7912 successfully executed, processing of the lookup ceases.
7914 This feature is intended for use in master/slave situations where updates
7915 are occurring and you want to update the master rather than a slave. If the
7916 master is in the list as a backup for reading, you might have a global setting
7919 mysql_servers = slave1/db/name/pw:\
7923 In an updating lookup, you could then write:
7925 ${lookup mysql{servers=master; UPDATE ...} }
7927 That query would then be sent only to the master server. If, on the other hand,
7928 the master is not to be used for reading, and so is not present in the global
7929 option, you can still update it by a query of this form:
7931 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7935 .section "Special MySQL features" "SECID73"
7936 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7937 causes a connection to the server on the local host by means of a Unix domain
7938 socket. An alternate socket can be specified in parentheses.
7939 An option group name for MySQL option files can be specified in square brackets;
7940 the default value is &"exim"&.
7941 The full syntax of each item in &%mysql_servers%& is:
7943 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
7944 <&'database'&>/<&'user'&>/<&'password'&>
7946 Any of the four sub-parts of the first field can be omitted. For normal use on
7947 the local host it can be left blank or set to just &"localhost"&.
7949 No database need be supplied &-- but if it is absent here, it must be given in
7952 If a MySQL query is issued that does not request any data (an insert, update,
7953 or delete command), the result of the lookup is the number of rows affected.
7955 &*Warning*&: This can be misleading. If an update does not actually change
7956 anything (for example, setting a field to the value it already has), the result
7957 is zero because no rows are affected.
7960 .section "Special PostgreSQL features" "SECID74"
7961 PostgreSQL lookups can also use Unix domain socket connections to the database.
7962 This is usually faster and costs less CPU time than a TCP/IP connection.
7963 However it can be used only if the mail server runs on the same machine as the
7964 database server. A configuration line for PostgreSQL via Unix domain sockets
7967 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7969 In other words, instead of supplying a host name, a path to the socket is
7970 given. The path name is enclosed in parentheses so that its slashes aren't
7971 visually confused with the delimiters for the other server parameters.
7973 If a PostgreSQL query is issued that does not request any data (an insert,
7974 update, or delete command), the result of the lookup is the number of rows
7977 .section "More about SQLite" "SECTsqlite"
7978 .cindex "lookup" "SQLite"
7979 .cindex "sqlite lookup type"
7980 SQLite is different to the other SQL lookups because a filename is required in
7981 addition to the SQL query. An SQLite database is a single file, and there is no
7982 daemon as in the other SQL databases. The interface to Exim requires the name
7983 of the file, as an absolute path, to be given at the start of the query. It is
7984 separated from the query by white space. This means that the path name cannot
7985 contain white space. Here is a lookup expansion example:
7987 ${lookup sqlite {/some/thing/sqlitedb \
7988 select name from aliases where id='userx';}}
7990 In a list, the syntax is similar. For example:
7992 domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \
7993 select * from relays where ip='$sender_host_address';
7995 The only character affected by the &%quote_sqlite%& operator is a single
7996 quote, which it doubles.
7998 .cindex timeout SQLite
7999 .cindex sqlite "lookup timeout"
8000 The SQLite library handles multiple simultaneous accesses to the database
8001 internally. Multiple readers are permitted, but only one process can
8002 update at once. Attempts to access the database while it is being updated
8003 are rejected after a timeout period, during which the SQLite library
8004 waits for the lock to be released. In Exim, the default timeout is set
8005 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
8008 .section "More about Redis" "SECTredis"
8009 .cindex "lookup" "Redis"
8010 .cindex "redis lookup type"
8011 Redis is a non-SQL database. Commands are simple get and set.
8014 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
8015 ${lookup redis{get keyname}}
8018 As of release 4.91, "lightweight" support for Redis Cluster is available.
8019 Requires &%redis_servers%& list to contain all the servers in the cluster, all
8020 of which must be reachable from the running exim instance. If the cluster has
8021 master/slave replication, the list must contain all the master and slave
8024 When the Redis Cluster returns a "MOVED" response to a query, Exim does not
8025 immediately follow the redirection but treats the response as a DEFER, moving on
8026 to the next server in the &%redis_servers%& list until the correct server is
8033 . ////////////////////////////////////////////////////////////////////////////
8034 . ////////////////////////////////////////////////////////////////////////////
8036 .chapter "Domain, host, address, and local part lists" &&&
8037 "CHAPdomhosaddlists" &&&
8038 "Domain, host, and address lists"
8039 .scindex IIDdohoadli "lists of domains; hosts; etc."
8040 A number of Exim configuration options contain lists of domains, hosts,
8041 email addresses, or local parts. For example, the &%hold_domains%& option
8042 contains a list of domains whose delivery is currently suspended. These lists
8043 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
8044 arguments to expansion conditions such as &%match_domain%&.
8046 Each item in one of these lists is a pattern to be matched against a domain,
8047 host, email address, or local part, respectively. In the sections below, the
8048 different types of pattern for each case are described, but first we cover some
8049 general facilities that apply to all four kinds of list.
8051 Note that other parts of Exim use a &'string list'& which does not
8052 support all the complexity available in
8053 domain, host, address and local part lists.
8057 .section "Expansion of lists" "SECTlistexpand"
8058 .cindex "expansion" "of lists"
8059 Each list is expanded as a single string before it is used.
8061 &'Exception: the router headers_remove option, where list-item
8062 splitting is done before string-expansion.'&
8065 expansion must be a list, possibly containing empty items, which is split up
8066 into separate items for matching. By default, colon is the separator character,
8067 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
8068 &<<SECTempitelis>>& for details of the list syntax; the second of these
8069 discusses the way to specify empty list items.
8072 If the string expansion is forced to fail, Exim behaves as if the item it is
8073 testing (domain, host, address, or local part) is not in the list. Other
8074 expansion failures cause temporary errors.
8076 If an item in a list is a regular expression, backslashes, dollars and possibly
8077 other special characters in the expression must be protected against
8078 misinterpretation by the string expander. The easiest way to do this is to use
8079 the &`\N`& expansion feature to indicate that the contents of the regular
8080 expression should not be expanded. For example, in an ACL you might have:
8082 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
8083 ${lookup{$domain}lsearch{/badsenders/bydomain}}
8085 The first item is a regular expression that is protected from expansion by
8086 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
8087 senders based on the receiving domain.
8092 .section "Negated items in lists" "SECID76"
8093 .cindex "list" "negation"
8094 .cindex "negation" "in lists"
8095 Items in a list may be positive or negative. Negative items are indicated by a
8096 leading exclamation mark, which may be followed by optional white space. A list
8097 defines a set of items (domains, etc). When Exim processes one of these lists,
8098 it is trying to find out whether a domain, host, address, or local part
8099 (respectively) is in the set that is defined by the list. It works like this:
8101 The list is scanned from left to right. If a positive item is matched, the
8102 subject that is being checked is in the set; if a negative item is matched, the
8103 subject is not in the set. If the end of the list is reached without the
8104 subject having matched any of the patterns, it is in the set if the last item
8105 was a negative one, but not if it was a positive one. For example, the list in
8107 domainlist relay_to_domains = !a.b.c : *.b.c
8109 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
8110 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
8111 list is positive. However, if the setting were
8113 domainlist relay_to_domains = !a.b.c
8115 then all domains other than &'a.b.c'& would match because the last item in the
8116 list is negative. In other words, a list that ends with a negative item behaves
8117 as if it had an extra item &`:*`& on the end.
8119 Another way of thinking about positive and negative items in lists is to read
8120 the connector as &"or"& after a positive item and as &"and"& after a negative
8125 .section "File names in lists" "SECTfilnamlis"
8126 .cindex "list" "filename in"
8127 If an item in a domain, host, address, or local part list is an absolute
8128 filename (beginning with a slash character), each line of the file is read and
8129 processed as if it were an independent item in the list, except that further
8130 filenames are not allowed,
8131 and no expansion of the data from the file takes place.
8132 Empty lines in the file are ignored, and the file may also contain comment
8136 For domain and host lists, if a # character appears anywhere in a line of the
8137 file, it and all following characters are ignored.
8139 Because local parts may legitimately contain # characters, a comment in an
8140 address list or local part list file is recognized only if # is preceded by
8141 white space or the start of the line. For example:
8143 not#comment@x.y.z # but this is a comment
8147 Putting a filename in a list has the same effect as inserting each line of the
8148 file as an item in the list (blank lines and comments excepted). However, there
8149 is one important difference: the file is read each time the list is processed,
8150 so if its contents vary over time, Exim's behaviour changes.
8152 If a filename is preceded by an exclamation mark, the sense of any match
8153 within the file is inverted. For example, if
8155 hold_domains = !/etc/nohold-domains
8157 and the file contains the lines
8162 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
8163 any domain matching &`*.b.c`& is not.
8167 .section "An lsearch file is not an out-of-line list" "SECID77"
8168 As will be described in the sections that follow, lookups can be used in lists
8169 to provide indexed methods of checking list membership. There has been some
8170 confusion about the way &(lsearch)& lookups work in lists. Because
8171 an &(lsearch)& file contains plain text and is scanned sequentially, it is
8172 sometimes thought that it is allowed to contain wild cards and other kinds of
8173 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
8174 always fixed strings, just as for any other single-key lookup type.
8176 If you want to use a file to contain wild-card patterns that form part of a
8177 list, just give the filename on its own, without a search type, as described
8178 in the previous section. You could also use the &(wildlsearch)& or
8179 &(nwildlsearch)&, but there is no advantage in doing this.
8184 .section "Named lists" "SECTnamedlists"
8185 .cindex "named lists"
8186 .cindex "list" "named"
8187 A list of domains, hosts, email addresses, or local parts can be given a name
8188 which is then used to refer to the list elsewhere in the configuration. This is
8189 particularly convenient if the same list is required in several different
8190 places. It also allows lists to be given meaningful names, which can improve
8191 the readability of the configuration. For example, it is conventional to define
8192 a domain list called &'local_domains'& for all the domains that are handled
8193 locally on a host, using a configuration line such as
8195 domainlist local_domains = localhost:my.dom.example
8197 Named lists are referenced by giving their name preceded by a plus sign, so,
8198 for example, a router that is intended to handle local domains would be
8199 configured with the line
8201 domains = +local_domains
8203 The first router in a configuration is often one that handles all domains
8204 except the local ones, using a configuration with a negated item like this:
8208 domains = ! +local_domains
8209 transport = remote_smtp
8212 The four kinds of named list are created by configuration lines starting with
8213 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8214 respectively. Then there follows the name that you are defining, followed by an
8215 equals sign and the list itself. For example:
8217 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8218 addresslist bad_senders = cdb;/etc/badsenders
8220 A named list may refer to other named lists:
8222 domainlist dom1 = first.example : second.example
8223 domainlist dom2 = +dom1 : third.example
8224 domainlist dom3 = fourth.example : +dom2 : fifth.example
8226 &*Warning*&: If the last item in a referenced list is a negative one, the
8227 effect may not be what you intended, because the negation does not propagate
8228 out to the higher level. For example, consider:
8230 domainlist dom1 = !a.b
8231 domainlist dom2 = +dom1 : *.b
8233 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8234 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8235 means it matches the second list as well. The effect is not the same as
8237 domainlist dom2 = !a.b : *.b
8239 where &'x.y'& does not match. It's best to avoid negation altogether in
8240 referenced lists if you can.
8242 Named lists may have a performance advantage. When Exim is routing an
8243 address or checking an incoming message, it caches the result of tests on named
8244 lists. So, if you have a setting such as
8246 domains = +local_domains
8248 on several of your routers
8249 or in several ACL statements,
8250 the actual test is done only for the first one. However, the caching works only
8251 if there are no expansions within the list itself or any sublists that it
8252 references. In other words, caching happens only for lists that are known to be
8253 the same each time they are referenced.
8255 By default, there may be up to 16 named lists of each type. This limit can be
8256 extended by changing a compile-time variable. The use of domain and host lists
8257 is recommended for concepts such as local domains, relay domains, and relay
8258 hosts. The default configuration is set up like this.
8262 .section "Named lists compared with macros" "SECID78"
8263 .cindex "list" "named compared with macro"
8264 .cindex "macro" "compared with named list"
8265 At first sight, named lists might seem to be no different from macros in the
8266 configuration file. However, macros are just textual substitutions. If you
8269 ALIST = host1 : host2
8270 auth_advertise_hosts = !ALIST
8272 it probably won't do what you want, because that is exactly the same as
8274 auth_advertise_hosts = !host1 : host2
8276 Notice that the second host name is not negated. However, if you use a host
8279 hostlist alist = host1 : host2
8280 auth_advertise_hosts = ! +alist
8282 the negation applies to the whole list, and so that is equivalent to
8284 auth_advertise_hosts = !host1 : !host2
8288 .section "Named list caching" "SECID79"
8289 .cindex "list" "caching of named"
8290 .cindex "caching" "named lists"
8291 While processing a message, Exim caches the result of checking a named list if
8292 it is sure that the list is the same each time. In practice, this means that
8293 the cache operates only if the list contains no $ characters, which guarantees
8294 that it will not change when it is expanded. Sometimes, however, you may have
8295 an expanded list that you know will be the same each time within a given
8296 message. For example:
8298 domainlist special_domains = \
8299 ${lookup{$sender_host_address}cdb{/some/file}}
8301 This provides a list of domains that depends only on the sending host's IP
8302 address. If this domain list is referenced a number of times (for example,
8303 in several ACL lines, or in several routers) the result of the check is not
8304 cached by default, because Exim does not know that it is going to be the
8305 same list each time.
8307 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8308 cache the result anyway. For example:
8310 domainlist_cache special_domains = ${lookup{...
8312 If you do this, you should be absolutely sure that caching is going to do
8313 the right thing in all cases. When in doubt, leave it out.
8317 .section "Domain lists" "SECTdomainlist"
8318 .cindex "domain list" "patterns for"
8319 .cindex "list" "domain list"
8320 Domain lists contain patterns that are to be matched against a mail domain.
8321 The following types of item may appear in domain lists:
8324 .cindex "primary host name"
8325 .cindex "host name" "matched in domain list"
8326 .oindex "&%primary_hostname%&"
8327 .cindex "domain list" "matching primary host name"
8328 .cindex "@ in a domain list"
8329 If a pattern consists of a single @ character, it matches the local host name,
8330 as set by the &%primary_hostname%& option (or defaulted). This makes it
8331 possible to use the same configuration file on several different hosts that
8332 differ only in their names.
8334 .cindex "@[] in a domain list"
8335 .cindex "domain list" "matching local IP interfaces"
8336 .cindex "domain literal"
8337 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8338 in square brackets (as in an email address that contains a domain literal), but
8339 only if that IP address is recognized as local for email routing purposes. The
8340 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8341 control which of a host's several IP addresses are treated as local.
8342 In today's Internet, the use of domain literals is controversial.
8345 .cindex "@mx_primary"
8346 .cindex "@mx_secondary"
8347 .cindex "domain list" "matching MX pointers to local host"
8348 If a pattern consists of the string &`@mx_any`& it matches any domain that
8349 has an MX record pointing to the local host or to any host that is listed in
8350 .oindex "&%hosts_treat_as_local%&"
8351 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8352 are similar, except that the first matches only when a primary MX target is the
8353 local host, and the second only when no primary MX target is the local host,
8354 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8355 preference value &-- there may of course be more than one of them.
8357 The MX lookup that takes place when matching a pattern of this type is
8358 performed with the resolver options for widening names turned off. Thus, for
8359 example, a single-component domain will &'not'& be expanded by adding the
8360 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8361 options of the &(dnslookup)& router for a discussion of domain widening.
8363 Sometimes you may want to ignore certain IP addresses when using one of these
8364 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8365 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8366 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8367 on a router). For example:
8369 domains = @mx_any/ignore=127.0.0.1
8371 This example matches any domain that has an MX record pointing to one of
8372 the local host's IP addresses other than 127.0.0.1.
8374 The list of IP addresses is in fact processed by the same code that processes
8375 host lists, so it may contain CIDR-coded network specifications and it may also
8376 contain negative items.
8378 Because the list of IP addresses is a sublist within a domain list, you have to
8379 be careful about delimiters if there is more than one address. Like any other
8380 list, the default delimiter can be changed. Thus, you might have:
8382 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8383 an.other.domain : ...
8385 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8386 involved, it is easiest to change the delimiter for the main list as well:
8388 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8389 an.other.domain ? ...
8392 .cindex "asterisk" "in domain list"
8393 .cindex "domain list" "asterisk in"
8394 .cindex "domain list" "matching &""ends with""&"
8395 If a pattern starts with an asterisk, the remaining characters of the pattern
8396 are compared with the terminating characters of the domain. The use of &"*"& in
8397 domain lists differs from its use in partial matching lookups. In a domain
8398 list, the character following the asterisk need not be a dot, whereas partial
8399 matching works only in terms of dot-separated components. For example, a domain
8400 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8404 .cindex "regular expressions" "in domain list"
8405 .cindex "domain list" "matching regular expression"
8406 If a pattern starts with a circumflex character, it is treated as a regular
8407 expression, and matched against the domain using a regular expression matching
8408 function. The circumflex is treated as part of the regular expression.
8409 Email domains are case-independent, so this regular expression match is by
8410 default case-independent, but you can make it case-dependent by starting it
8411 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8412 are given in chapter &<<CHAPregexp>>&.
8414 &*Warning*&: Because domain lists are expanded before being processed, you
8415 must escape any backslash and dollar characters in the regular expression, or
8416 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8417 it is not to be expanded (unless you really do want to build a regular
8418 expression by expansion, of course).
8420 .cindex "lookup" "in domain list"
8421 .cindex "domain list" "matching by lookup"
8422 If a pattern starts with the name of a single-key lookup type followed by a
8423 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8424 must be a filename in a suitable format for the lookup type. For example, for
8425 &"cdb;"& it must be an absolute path:
8427 domains = cdb;/etc/mail/local_domains.cdb
8429 The appropriate type of lookup is done on the file using the domain name as the
8430 key. In most cases, the data that is looked up is not used; Exim is interested
8431 only in whether or not the key is present in the file. However, when a lookup
8432 is used for the &%domains%& option on a router
8433 or a &%domains%& condition in an ACL statement, the data is preserved in the
8434 &$domain_data$& variable and can be referred to in other router options or
8435 other statements in the same ACL.
8438 Any of the single-key lookup type names may be preceded by
8439 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8441 domains = partial-dbm;/partial/domains
8443 This causes partial matching logic to be invoked; a description of how this
8444 works is given in section &<<SECTpartiallookup>>&.
8447 .cindex "asterisk" "in lookup type"
8448 Any of the single-key lookup types may be followed by an asterisk. This causes
8449 a default lookup for a key consisting of a single asterisk to be done if the
8450 original lookup fails. This is not a useful feature when using a domain list to
8451 select particular domains (because any domain would match), but it might have
8452 value if the result of the lookup is being used via the &$domain_data$&
8455 If the pattern starts with the name of a query-style lookup type followed by a
8456 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8457 pattern must be an appropriate query for the lookup type, as described in
8458 chapter &<<CHAPfdlookup>>&. For example:
8460 hold_domains = mysql;select domain from holdlist \
8461 where domain = '${quote_mysql:$domain}';
8463 In most cases, the data that is looked up is not used (so for an SQL query, for
8464 example, it doesn't matter what field you select). Exim is interested only in
8465 whether or not the query succeeds. However, when a lookup is used for the
8466 &%domains%& option on a router, the data is preserved in the &$domain_data$&
8467 variable and can be referred to in other options.
8469 .cindex "domain list" "matching literal domain name"
8470 If none of the above cases apply, a caseless textual comparison is made
8471 between the pattern and the domain.
8474 Here is an example that uses several different kinds of pattern:
8476 domainlist funny_domains = \
8479 *.foundation.fict.example : \
8480 \N^[1-2]\d{3}\.fict\.example$\N : \
8481 partial-dbm;/opt/data/penguin/book : \
8482 nis;domains.byname : \
8483 nisplus;[name=$domain,status=local],domains.org_dir
8485 There are obvious processing trade-offs among the various matching modes. Using
8486 an asterisk is faster than a regular expression, and listing a few names
8487 explicitly probably is too. The use of a file or database lookup is expensive,
8488 but may be the only option if hundreds of names are required. Because the
8489 patterns are tested in order, it makes sense to put the most commonly matched
8494 .section "Host lists" "SECThostlist"
8495 .cindex "host list" "patterns in"
8496 .cindex "list" "host list"
8497 Host lists are used to control what remote hosts are allowed to do. For
8498 example, some hosts may be allowed to use the local host as a relay, and some
8499 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8500 two different ways, by name or by IP address. In a host list, some types of
8501 pattern are matched to a host name, and some are matched to an IP address.
8502 You need to be particularly careful with this when single-key lookups are
8503 involved, to ensure that the right value is being used as the key.
8506 .section "Special host list patterns" "SECID80"
8507 .cindex "empty item in hosts list"
8508 .cindex "host list" "empty string in"
8509 If a host list item is the empty string, it matches only when no remote host is
8510 involved. This is the case when a message is being received from a local
8511 process using SMTP on the standard input, that is, when a TCP/IP connection is
8514 .cindex "asterisk" "in host list"
8515 The special pattern &"*"& in a host list matches any host or no host. Neither
8516 the IP address nor the name is actually inspected.
8520 .section "Host list patterns that match by IP address" "SECThoslispatip"
8521 .cindex "host list" "matching IP addresses"
8522 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8523 the incoming address actually appears in the IPv6 host as
8524 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8525 list, it is converted into a traditional IPv4 address first. (Not all operating
8526 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8529 The following types of pattern in a host list check the remote host by
8530 inspecting its IP address:
8533 If the pattern is a plain domain name (not a regular expression, not starting
8534 with *, not a lookup of any kind), Exim calls the operating system function
8535 to find the associated IP address(es). Exim uses the newer
8536 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8537 This typically causes a forward DNS lookup of the name. The result is compared
8538 with the IP address of the subject host.
8540 If there is a temporary problem (such as a DNS timeout) with the host name
8541 lookup, a temporary error occurs. For example, if the list is being used in an
8542 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8543 temporary SMTP error code. If no IP address can be found for the host name,
8544 what happens is described in section &<<SECTbehipnot>>& below.
8547 .cindex "@ in a host list"
8548 If the pattern is &"@"&, the primary host name is substituted and used as a
8549 domain name, as just described.
8552 If the pattern is an IP address, it is matched against the IP address of the
8553 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8554 IPv6 addresses can be given in colon-separated format, but the colons have to
8555 be doubled so as not to be taken as item separators when the default list
8556 separator is used. IPv6 addresses are recognized even when Exim is compiled
8557 without IPv6 support. This means that if they appear in a host list on an
8558 IPv4-only host, Exim will not treat them as host names. They are just addresses
8559 that can never match a client host.
8562 .cindex "@[] in a host list"
8563 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8564 the local host. For example, if the local host is an IPv4 host with one
8565 interface address 10.45.23.56, these two ACL statements have the same effect:
8567 accept hosts = 127.0.0.1 : 10.45.23.56
8571 .cindex "CIDR notation"
8572 If the pattern is an IP address followed by a slash and a mask length (for
8573 example 10.11.42.0/24), it is matched against the IP address of the subject
8574 host under the given mask. This allows, an entire network of hosts to be
8575 included (or excluded) by a single item. The mask uses CIDR notation; it
8576 specifies the number of address bits that must match, starting from the most
8577 significant end of the address.
8579 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8580 of a range of addresses. It is the number of bits in the network portion of the
8581 address. The above example specifies a 24-bit netmask, so it matches all 256
8582 addresses in the 10.11.42.0 network. An item such as
8586 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8587 32 for an IPv4 address is the same as no mask at all; just a single address
8590 Here is another example which shows an IPv4 and an IPv6 network:
8592 recipient_unqualified_hosts = 192.168.0.0/16: \
8593 3ffe::ffff::836f::::/48
8595 The doubling of list separator characters applies only when these items
8596 appear inline in a host list. It is not required when indirecting via a file.
8599 recipient_unqualified_hosts = /opt/exim/unqualnets
8601 could make use of a file containing
8606 to have exactly the same effect as the previous example. When listing IPv6
8607 addresses inline, it is usually more convenient to use the facility for
8608 changing separator characters. This list contains the same two networks:
8610 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8613 The separator is changed to semicolon by the leading &"<;"& at the start of the
8619 .section "Host list patterns for single-key lookups by host address" &&&
8620 "SECThoslispatsikey"
8621 .cindex "host list" "lookup of IP address"
8622 When a host is to be identified by a single-key lookup of its complete IP
8623 address, the pattern takes this form:
8625 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8629 hosts_lookup = net-cdb;/hosts-by-ip.db
8631 The text form of the IP address of the subject host is used as the lookup key.
8632 IPv6 addresses are converted to an unabbreviated form, using lower case
8633 letters, with dots as separators because colon is the key terminator in
8634 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8635 quoting the keys, but this is a facility that was added later.] The data
8636 returned by the lookup is not used.
8638 .cindex "IP address" "masking"
8639 .cindex "host list" "masked IP address"
8640 Single-key lookups can also be performed using masked IP addresses, using
8641 patterns of this form:
8643 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8647 net24-dbm;/networks.db
8649 The IP address of the subject host is masked using <&'number'&> as the mask
8650 length. A textual string is constructed from the masked value, followed by the
8651 mask, and this is used as the lookup key. For example, if the host's IP address
8652 is 192.168.34.6, the key that is looked up for the above example is
8653 &"192.168.34.0/24"&.
8655 When an IPv6 address is converted to a string, dots are normally used instead
8656 of colons, so that keys in &(lsearch)& files need not contain colons (which
8657 terminate &(lsearch)& keys). This was implemented some time before the ability
8658 to quote keys was made available in &(lsearch)& files. However, the more
8659 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8660 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8661 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8662 converted using colons and not dots. In all cases, full, unabbreviated IPv6
8663 addresses are always used.
8665 Ideally, it would be nice to tidy up this anomalous situation by changing to
8666 colons in all cases, given that quoting is now available for &(lsearch)&.
8667 However, this would be an incompatible change that might break some existing
8670 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8671 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8672 the former case the key strings include the mask value, whereas in the latter
8673 case the IP address is used on its own.
8677 .section "Host list patterns that match by host name" "SECThoslispatnam"
8678 .cindex "host" "lookup failures"
8679 .cindex "unknown host name"
8680 .cindex "host list" "matching host name"
8681 There are several types of pattern that require Exim to know the name of the
8682 remote host. These are either wildcard patterns or lookups by name. (If a
8683 complete hostname is given without any wildcarding, it is used to find an IP
8684 address to match against, as described in section &<<SECThoslispatip>>&
8687 If the remote host name is not already known when Exim encounters one of these
8688 patterns, it has to be found from the IP address.
8689 Although many sites on the Internet are conscientious about maintaining reverse
8690 DNS data for their hosts, there are also many that do not do this.
8691 Consequently, a name cannot always be found, and this may lead to unwanted
8692 effects. Take care when configuring host lists with wildcarded name patterns.
8693 Consider what will happen if a name cannot be found.
8695 Because of the problems of determining host names from IP addresses, matching
8696 against host names is not as common as matching against IP addresses.
8698 By default, in order to find a host name, Exim first does a reverse DNS lookup;
8699 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
8700 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
8701 are done can be changed by setting the &%host_lookup_order%& option. For
8702 security, once Exim has found one or more names, it looks up the IP addresses
8703 for these names and compares them with the IP address that it started with.
8704 Only those names whose IP addresses match are accepted. Any other names are
8705 discarded. If no names are left, Exim behaves as if the host name cannot be
8706 found. In the most common case there is only one name and one IP address.
8708 There are some options that control what happens if a host name cannot be
8709 found. These are described in section &<<SECTbehipnot>>& below.
8711 .cindex "host" "alias for"
8712 .cindex "alias for host"
8713 As a result of aliasing, hosts may have more than one name. When processing any
8714 of the following types of pattern, all the host's names are checked:
8717 .cindex "asterisk" "in host list"
8718 If a pattern starts with &"*"& the remainder of the item must match the end of
8719 the host name. For example, &`*.b.c`& matches all hosts whose names end in
8720 &'.b.c'&. This special simple form is provided because this is a very common
8721 requirement. Other kinds of wildcarding require the use of a regular
8724 .cindex "regular expressions" "in host list"
8725 .cindex "host list" "regular expression in"
8726 If the item starts with &"^"& it is taken to be a regular expression which is
8727 matched against the host name. Host names are case-independent, so this regular
8728 expression match is by default case-independent, but you can make it
8729 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
8730 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
8735 is a regular expression that matches either of the two hosts &'a.c.d'& or
8736 &'b.c.d'&. When a regular expression is used in a host list, you must take care
8737 that backslash and dollar characters are not misinterpreted as part of the
8738 string expansion. The simplest way to do this is to use &`\N`& to mark that
8739 part of the string as non-expandable. For example:
8741 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
8743 &*Warning*&: If you want to match a complete host name, you must include the
8744 &`$`& terminating metacharacter in the regular expression, as in the above
8745 example. Without it, a match at the start of the host name is all that is
8752 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
8753 .cindex "host" "lookup failures, permanent"
8754 While processing a host list, Exim may need to look up an IP address from a
8755 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
8756 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
8757 behaviour when it fails to find the information it is seeking is the same.
8759 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
8760 apply to temporary DNS errors, whose handling is described in the next section.
8762 .cindex "&`+include_unknown`&"
8763 .cindex "&`+ignore_unknown`&"
8764 Exim parses a host list from left to right. If it encounters a permanent
8765 lookup failure in any item in the host list before it has found a match,
8766 Exim treats it as a failure and the default behavior is as if the host
8767 does not match the list. This may not always be what you want to happen.
8768 To change Exim's behaviour, the special items &`+include_unknown`& or
8769 &`+ignore_unknown`& may appear in the list (at top level &-- they are
8770 not recognized in an indirected file).
8773 If any item that follows &`+include_unknown`& requires information that
8774 cannot found, Exim behaves as if the host does match the list. For example,
8776 host_reject_connection = +include_unknown:*.enemy.ex
8778 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
8779 any hosts whose name it cannot find.
8782 If any item that follows &`+ignore_unknown`& requires information that cannot
8783 be found, Exim ignores that item and proceeds to the rest of the list. For
8786 accept hosts = +ignore_unknown : friend.example : \
8789 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8790 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8791 name can be found for 192.168.4.5, it is rejected.
8794 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8795 list. The effect of each one lasts until the next, or until the end of the
8798 .section "Mixing wildcarded host names and addresses in host lists" &&&
8800 .cindex "host list" "mixing names and addresses in"
8802 This section explains the host/ip processing logic with the same concepts
8803 as the previous section, but specifically addresses what happens when a
8804 wildcarded hostname is one of the items in the hostlist.
8807 If you have name lookups or wildcarded host names and
8808 IP addresses in the same host list, you should normally put the IP
8809 addresses first. For example, in an ACL you could have:
8811 accept hosts = 10.9.8.7 : *.friend.example
8813 The reason you normally would order it this way lies in the
8814 left-to-right way that Exim processes lists. It can test IP addresses
8815 without doing any DNS lookups, but when it reaches an item that requires
8816 a host name, it fails if it cannot find a host name to compare with the
8817 pattern. If the above list is given in the opposite order, the
8818 &%accept%& statement fails for a host whose name cannot be found, even
8819 if its IP address is 10.9.8.7.
8822 If you really do want to do the name check first, and still recognize the IP
8823 address, you can rewrite the ACL like this:
8825 accept hosts = *.friend.example
8826 accept hosts = 10.9.8.7
8828 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8829 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
8830 &`+ignore_unknown`&, which was discussed in depth in the first example in
8835 .section "Temporary DNS errors when looking up host information" &&&
8837 .cindex "host" "lookup failures, temporary"
8838 .cindex "&`+include_defer`&"
8839 .cindex "&`+ignore_defer`&"
8840 A temporary DNS lookup failure normally causes a defer action (except when
8841 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8842 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
8843 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8844 section. These options should be used with care, probably only in non-critical
8845 host lists such as whitelists.
8849 .section "Host list patterns for single-key lookups by host name" &&&
8850 "SECThoslispatnamsk"
8851 .cindex "unknown host name"
8852 .cindex "host list" "matching host name"
8853 If a pattern is of the form
8855 <&'single-key-search-type'&>;<&'search-data'&>
8859 dbm;/host/accept/list
8861 a single-key lookup is performed, using the host name as its key. If the
8862 lookup succeeds, the host matches the item. The actual data that is looked up
8865 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8866 keys in the file, not IP addresses. If you want to do lookups based on IP
8867 addresses, you must precede the search type with &"net-"& (see section
8868 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8869 two items in the same list, one doing an address lookup and one doing a name
8870 lookup, both using the same file.
8874 .section "Host list patterns for query-style lookups" "SECID81"
8875 If a pattern is of the form
8877 <&'query-style-search-type'&>;<&'query'&>
8879 the query is obeyed, and if it succeeds, the host matches the item. The actual
8880 data that is looked up is not used. The variables &$sender_host_address$& and
8881 &$sender_host_name$& can be used in the query. For example:
8883 hosts_lookup = pgsql;\
8884 select ip from hostlist where ip='$sender_host_address'
8886 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8887 can use the &%sg%& expansion item to change this if you need to. If you want to
8888 use masked IP addresses in database queries, you can use the &%mask%& expansion
8891 If the query contains a reference to &$sender_host_name$&, Exim automatically
8892 looks up the host name if it has not already done so. (See section
8893 &<<SECThoslispatnam>>& for comments on finding host names.)
8895 Historical note: prior to release 4.30, Exim would always attempt to find a
8896 host name before running the query, unless the search type was preceded by
8897 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8898 still recognized for query-style lookups, but its presence or absence has no
8899 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8900 See section &<<SECThoslispatsikey>>&.)
8906 .section "Address lists" "SECTaddresslist"
8907 .cindex "list" "address list"
8908 .cindex "address list" "empty item"
8909 .cindex "address list" "patterns"
8910 Address lists contain patterns that are matched against mail addresses. There
8911 is one special case to be considered: the sender address of a bounce message is
8912 always empty. You can test for this by providing an empty item in an address
8913 list. For example, you can set up a router to process bounce messages by
8914 using this option setting:
8918 The presence of the colon creates an empty item. If you do not provide any
8919 data, the list is empty and matches nothing. The empty sender can also be
8920 detected by a regular expression that matches an empty string,
8921 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8923 Non-empty items in an address list can be straightforward email addresses. For
8926 senders = jbc@askone.example : hs@anacreon.example
8928 A certain amount of wildcarding is permitted. If a pattern contains an @
8929 character, but is not a regular expression and does not begin with a
8930 semicolon-terminated lookup type (described below), the local part of the
8931 subject address is compared with the local part of the pattern, which may start
8932 with an asterisk. If the local parts match, the domain is checked in exactly
8933 the same way as for a pattern in a domain list. For example, the domain can be
8934 wildcarded, refer to a named list, or be a lookup:
8936 deny senders = *@*.spamming.site:\
8937 *@+hostile_domains:\
8938 bozo@partial-lsearch;/list/of/dodgy/sites:\
8939 *@dbm;/bad/domains.db
8941 .cindex "local part" "starting with !"
8942 .cindex "address list" "local part starting with !"
8943 If a local part that begins with an exclamation mark is required, it has to be
8944 specified using a regular expression, because otherwise the exclamation mark is
8945 treated as a sign of negation, as is standard in lists.
8947 If a non-empty pattern that is not a regular expression or a lookup does not
8948 contain an @ character, it is matched against the domain part of the subject
8949 address. The only two formats that are recognized this way are a literal
8950 domain, or a domain pattern that starts with *. In both these cases, the effect
8951 is the same as if &`*@`& preceded the pattern. For example:
8953 deny senders = enemy.domain : *.enemy.domain
8956 The following kinds of more complicated address list pattern can match any
8957 address, including the empty address that is characteristic of bounce message
8961 .cindex "regular expressions" "in address list"
8962 .cindex "address list" "regular expression in"
8963 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8964 done against the complete address, with the pattern as the regular expression.
8965 You must take care that backslash and dollar characters are not misinterpreted
8966 as part of the string expansion. The simplest way to do this is to use &`\N`&
8967 to mark that part of the string as non-expandable. For example:
8969 deny senders = \N^.*this.*@example\.com$\N : \
8970 \N^\d{8}.+@spamhaus.example$\N : ...
8972 The &`\N`& sequences are removed by the expansion, so these items do indeed
8973 start with &"^"& by the time they are being interpreted as address patterns.
8976 .cindex "address list" "lookup for complete address"
8977 Complete addresses can be looked up by using a pattern that starts with a
8978 lookup type terminated by a semicolon, followed by the data for the lookup. For
8981 deny senders = cdb;/etc/blocked.senders : \
8982 mysql;select address from blocked where \
8983 address='${quote_mysql:$sender_address}'
8985 Both query-style and single-key lookup types can be used. For a single-key
8986 lookup type, Exim uses the complete address as the key. However, empty keys are
8987 not supported for single-key lookups, so a match against the empty address
8988 always fails. This restriction does not apply to query-style lookups.
8990 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8991 cannot be used, and is ignored if specified, with an entry being written to the
8993 .cindex "*@ with single-key lookup"
8994 However, you can configure lookup defaults, as described in section
8995 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8996 default. For example, with this lookup:
8998 accept senders = lsearch*@;/some/file
9000 the file could contains lines like this:
9002 user1@domain1.example
9005 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
9008 nimrod@jaeger.example
9012 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
9013 would mean that every address matches, thus rendering the test useless.
9015 &*Warning 2*&: Do not confuse these two kinds of item:
9017 deny recipients = dbm*@;/some/file
9018 deny recipients = *@dbm;/some/file
9020 The first does a whole address lookup, with defaulting, as just described,
9021 because it starts with a lookup type. The second matches the local part and
9022 domain independently, as described in a bullet point below.
9026 The following kinds of address list pattern can match only non-empty addresses.
9027 If the subject address is empty, a match against any of these pattern types
9032 .cindex "@@ with single-key lookup"
9033 .cindex "address list" "@@ lookup type"
9034 .cindex "address list" "split local part and domain"
9035 If a pattern starts with &"@@"& followed by a single-key lookup item
9036 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
9037 split into a local part and a domain. The domain is looked up in the file. If
9038 it is not found, there is no match. If it is found, the data that is looked up
9039 from the file is treated as a colon-separated list of local part patterns, each
9040 of which is matched against the subject local part in turn.
9042 .cindex "asterisk" "in address list"
9043 The lookup may be a partial one, and/or one involving a search for a default
9044 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
9045 patterns that are looked up can be regular expressions or begin with &"*"&, or
9046 even be further lookups. They may also be independently negated. For example,
9049 deny senders = @@dbm;/etc/reject-by-domain
9051 the data from which the DBM file is built could contain lines like
9053 baddomain.com: !postmaster : *
9055 to reject all senders except &%postmaster%& from that domain.
9057 .cindex "local part" "starting with !"
9058 If a local part that actually begins with an exclamation mark is required, it
9059 has to be specified using a regular expression. In &(lsearch)& files, an entry
9060 may be split over several lines by indenting the second and subsequent lines,
9061 but the separating colon must still be included at line breaks. White space
9062 surrounding the colons is ignored. For example:
9064 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
9067 As in all colon-separated lists in Exim, a colon can be included in an item by
9070 If the last item in the list starts with a right angle-bracket, the remainder
9071 of the item is taken as a new key to look up in order to obtain a continuation
9072 list of local parts. The new key can be any sequence of characters. Thus one
9073 might have entries like
9075 aol.com: spammer1 : spammer 2 : >*
9076 xyz.com: spammer3 : >*
9079 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
9080 local parts for all domains, in addition to the specific local parts listed for
9081 each domain. Of course, using this feature costs another lookup each time a
9082 chain is followed, but the effort needed to maintain the data is reduced.
9084 .cindex "loop" "in lookups"
9085 It is possible to construct loops using this facility, and in order to catch
9086 them, the chains may be no more than fifty items long.
9089 The @@<&'lookup'&> style of item can also be used with a query-style
9090 lookup, but in this case, the chaining facility is not available. The lookup
9091 can only return a single list of local parts.
9094 &*Warning*&: There is an important difference between the address list items
9095 in these two examples:
9098 senders = *@+my_list
9100 In the first one, &`my_list`& is a named address list, whereas in the second
9101 example it is a named domain list.
9106 .section "Case of letters in address lists" "SECTcasletadd"
9107 .cindex "case of local parts"
9108 .cindex "address list" "case forcing"
9109 .cindex "case forcing in address lists"
9110 Domains in email addresses are always handled caselessly, but for local parts
9111 case may be significant on some systems (see &%caseful_local_part%& for how
9112 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
9113 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
9114 blocking lists should be done in a case-independent manner. Since most address
9115 lists in Exim are used for this kind of control, Exim attempts to do this by
9118 The domain portion of an address is always lowercased before matching it to an
9119 address list. The local part is lowercased by default, and any string
9120 comparisons that take place are done caselessly. This means that the data in
9121 the address list itself, in files included as plain filenames, and in any file
9122 that is looked up using the &"@@"& mechanism, can be in any case. However, the
9123 keys in files that are looked up by a search type other than &(lsearch)& (which
9124 works caselessly) must be in lower case, because these lookups are not
9127 .cindex "&`+caseful`&"
9128 To allow for the possibility of caseful address list matching, if an item in
9129 an address list is the string &"+caseful"&, the original case of the local
9130 part is restored for any comparisons that follow, and string comparisons are no
9131 longer case-independent. This does not affect the domain, which remains in
9132 lower case. However, although independent matches on the domain alone are still
9133 performed caselessly, regular expressions that match against an entire address
9134 become case-sensitive after &"+caseful"& has been seen.
9138 .section "Local part lists" "SECTlocparlis"
9139 .cindex "list" "local part list"
9140 .cindex "local part" "list"
9141 Case-sensitivity in local part lists is handled in the same way as for address
9142 lists, as just described. The &"+caseful"& item can be used if required. In a
9143 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
9144 set false, the subject is lowercased and the matching is initially
9145 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
9146 matching in the local part list, but not elsewhere in the router. If
9147 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
9148 option is case-sensitive from the start.
9150 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
9151 comments are handled in the same way as address lists &-- they are recognized
9152 only if the # is preceded by white space or the start of the line.
9153 Otherwise, local part lists are matched in the same way as domain lists, except
9154 that the special items that refer to the local host (&`@`&, &`@[]`&,
9155 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
9156 Refer to section &<<SECTdomainlist>>& for details of the other available item
9158 .ecindex IIDdohoadli
9163 . ////////////////////////////////////////////////////////////////////////////
9164 . ////////////////////////////////////////////////////////////////////////////
9166 .chapter "String expansions" "CHAPexpand"
9167 .scindex IIDstrexp "expansion" "of strings"
9168 Many strings in Exim's runtime configuration are expanded before use. Some of
9169 them are expanded every time they are used; others are expanded only once.
9171 When a string is being expanded it is copied verbatim from left to right except
9172 when a dollar or backslash character is encountered. A dollar specifies the
9173 start of a portion of the string that is interpreted and replaced as described
9174 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
9175 escape character, as described in the following section.
9177 Whether a string is expanded depends upon the context. Usually this is solely
9178 dependent upon the option for which a value is sought; in this documentation,
9179 options for which string expansion is performed are marked with † after
9180 the data type. ACL rules always expand strings. A couple of expansion
9181 conditions do not expand some of the brace-delimited branches, for security
9186 .section "Literal text in expanded strings" "SECTlittext"
9187 .cindex "expansion" "including literal text"
9188 An uninterpreted dollar can be included in an expanded string by putting a
9189 backslash in front of it. A backslash can be used to prevent any special
9190 character being treated specially in an expansion, including backslash itself.
9191 If the string appears in quotes in the configuration file, two backslashes are
9192 required because the quotes themselves cause interpretation of backslashes when
9193 the string is read in (see section &<<SECTstrings>>&).
9195 .cindex "expansion" "non-expandable substrings"
9196 A portion of the string can specified as non-expandable by placing it between
9197 two occurrences of &`\N`&. This is particularly useful for protecting regular
9198 expressions, which often contain backslashes and dollar signs. For example:
9200 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
9202 On encountering the first &`\N`&, the expander copies subsequent characters
9203 without interpretation until it reaches the next &`\N`& or the end of the
9208 .section "Character escape sequences in expanded strings" "SECID82"
9209 .cindex "expansion" "escape sequences"
9210 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9211 expanded string is recognized as an escape sequence for the character newline,
9212 carriage return, or tab, respectively. A backslash followed by up to three
9213 octal digits is recognized as an octal encoding for a single character, and a
9214 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9217 These escape sequences are also recognized in quoted strings when they are read
9218 in. Their interpretation in expansions as well is useful for unquoted strings,
9219 and for other cases such as looked-up strings that are then expanded.
9222 .section "Testing string expansions" "SECID83"
9223 .cindex "expansion" "testing"
9224 .cindex "testing" "string expansion"
9226 Many expansions can be tested by calling Exim with the &%-be%& option. This
9227 takes the command arguments, or lines from the standard input if there are no
9228 arguments, runs them through the string expansion code, and writes the results
9229 to the standard output. Variables based on configuration values are set up, but
9230 since no message is being processed, variables such as &$local_part$& have no
9231 value. Nevertheless the &%-be%& option can be useful for checking out file and
9232 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9235 Exim gives up its root privilege when it is called with the &%-be%& option, and
9236 instead runs under the uid and gid it was called with, to prevent users from
9237 using &%-be%& for reading files to which they do not have access.
9240 If you want to test expansions that include variables whose values are taken
9241 from a message, there are two other options that can be used. The &%-bem%&
9242 option is like &%-be%& except that it is followed by a filename. The file is
9243 read as a message before doing the test expansions. For example:
9245 exim -bem /tmp/test.message '$h_subject:'
9247 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9248 Exim message identifier. For example:
9250 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9252 This loads the message from Exim's spool before doing the test expansions, and
9253 is therefore restricted to admin users.
9256 .section "Forced expansion failure" "SECTforexpfai"
9257 .cindex "expansion" "forced failure"
9258 A number of expansions that are described in the following section have
9259 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9260 (which are sometimes called &"curly brackets"&). Which of the two strings is
9261 used depends on some condition that is evaluated as part of the expansion. If,
9262 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9263 the entire string expansion fails in a way that can be detected by the code
9264 that requested the expansion. This is called &"forced expansion failure"&, and
9265 its consequences depend on the circumstances. In some cases it is no different
9266 from any other expansion failure, but in others a different action may be
9267 taken. Such variations are mentioned in the documentation of the option that is
9273 .section "Expansion items" "SECTexpansionitems"
9274 The following items are recognized in expanded strings. White space may be used
9275 between sub-items that are keywords or substrings enclosed in braces inside an
9276 outer set of braces, to improve readability. &*Warning*&: Within braces,
9277 white space is significant.
9280 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9281 .cindex "expansion" "variables"
9282 Substitute the contents of the named variable, for example:
9287 The second form can be used to separate the name from subsequent alphanumeric
9288 characters. This form (using braces) is available only for variables; it does
9289 &'not'& apply to message headers. The names of the variables are given in
9290 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9291 given, the expansion fails.
9293 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9294 .cindex "expansion" "operators"
9295 The string is first itself expanded, and then the operation specified by
9296 <&'op'&> is applied to it. For example:
9300 The string starts with the first character after the colon, which may be
9301 leading white space. A list of operators is given in section &<<SECTexpop>>&
9302 below. The operator notation is used for simple expansion items that have just
9303 one argument, because it reduces the number of braces and therefore makes the
9304 string easier to understand.
9306 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9307 This item inserts &"basic"& header lines. It is described with the &%header%&
9308 expansion item below.
9311 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9312 .cindex "expansion" "calling an acl"
9313 .cindex "&%acl%&" "call from expansion"
9314 The name and zero to nine argument strings are first expanded separately. The expanded
9315 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9316 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9317 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9318 and may use the variables; if another acl expansion is used the values
9319 are restored after it returns. If the ACL sets
9320 a value using a "message =" modifier and returns accept or deny, the value becomes
9321 the result of the expansion.
9322 If no message is set and the ACL returns accept or deny
9323 the expansion result is an empty string.
9324 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9327 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
9328 .cindex authentication "results header"
9329 .cindex headers "authentication-results:"
9330 .cindex authentication "expansion item"
9331 This item returns a string suitable for insertion as an
9332 &'Authentication-Results"'&
9334 The given <&'authserv-id'&> is included in the result; typically this
9335 will be a domain name identifying the system performing the authentications.
9336 Methods that might be present in the result include:
9345 Example use (as an ACL modifier):
9347 add_header = :at_start:${authresults {$primary_hostname}}
9349 This is safe even if no authentication results are available.
9352 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9353 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9354 .cindex "expansion" "extracting certificate fields"
9355 .cindex "&%certextract%&" "certificate fields"
9356 .cindex "certificate" "extracting fields"
9357 The <&'certificate'&> must be a variable of type certificate.
9358 The field name is expanded and used to retrieve the relevant field from
9359 the certificate. Supported fields are:
9363 &`subject `& RFC4514 DN
9364 &`issuer `& RFC4514 DN
9369 &`subj_altname `& tagged list
9373 If the field is found,
9374 <&'string2'&> is expanded, and replaces the whole item;
9375 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9376 variable &$value$& contains the value that has been extracted. Afterwards, it
9377 is restored to any previous value it might have had.
9379 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9380 key is not found. If {<&'string2'&>} is also omitted, the value that was
9383 Some field names take optional modifiers, appended and separated by commas.
9385 The field selectors marked as "RFC4514" above
9386 output a Distinguished Name string which is
9388 parseable by Exim as a comma-separated tagged list
9389 (the exceptions being elements containing commas).
9390 RDN elements of a single type may be selected by
9391 a modifier of the type label; if so the expansion
9392 result is a list (newline-separated by default).
9393 The separator may be changed by another modifier of
9394 a right angle-bracket followed immediately by the new separator.
9395 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9397 The field selectors marked as "time" above
9398 take an optional modifier of "int"
9399 for which the result is the number of seconds since epoch.
9400 Otherwise the result is a human-readable string
9401 in the timezone selected by the main "timezone" option.
9403 The field selectors marked as "list" above return a list,
9404 newline-separated by default,
9405 (embedded separator characters in elements are doubled).
9406 The separator may be changed by a modifier of
9407 a right angle-bracket followed immediately by the new separator.
9409 The field selectors marked as "tagged" above
9410 prefix each list element with a type string and an equals sign.
9411 Elements of only one type may be selected by a modifier
9412 which is one of "dns", "uri" or "mail";
9413 if so the element tags are omitted.
9415 If not otherwise noted field values are presented in human-readable form.
9417 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9418 {*&<&'arg'&>&*}...}*&"
9420 This expansion dynamically loads and then calls a locally-written C function.
9421 This functionality is available only if Exim is compiled with
9425 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9426 object so that it doesn't reload the same object file in the same Exim process
9427 (but of course Exim does start new processes frequently).
9429 There may be from zero to eight arguments to the function. When compiling
9430 a local function that is to be called in this way, &_local_scan.h_& should be
9431 included. The Exim variables and functions that are defined by that API
9432 are also available for dynamically loaded functions. The function itself
9433 must have the following type:
9435 int dlfunction(uschar **yield, int argc, uschar *argv[])
9437 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9438 function should return one of the following values:
9440 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9441 into the expanded string that is being built.
9443 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9444 from &'yield'&, if it is set.
9446 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9447 taken from &'yield'& if it is set.
9449 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9451 When compiling a function that is to be used in this way with gcc,
9452 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9453 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9456 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9457 .cindex "expansion" "extracting value from environment"
9458 .cindex "environment" "values from"
9459 The key is first expanded separately, and leading and trailing white space
9461 This is then searched for as a name in the environment.
9462 If a variable is found then its value is placed in &$value$&
9463 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9465 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9466 appear, for example:
9468 ${env{USER}{$value} fail }
9470 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9471 {<&'string1'&>} must be present for &"fail"& to be recognized.
9473 If {<&'string2'&>} is omitted an empty string is substituted on
9475 If {<&'string1'&>} is omitted the search result is substituted on
9478 The environment is adjusted by the &%keep_environment%& and
9479 &%add_environment%& main section options.
9482 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9483 {*&<&'string3'&>&*}}*&"
9484 .cindex "expansion" "extracting substrings by key"
9485 .cindex "&%extract%&" "substrings by key"
9486 The key and <&'string1'&> are first expanded separately. Leading and trailing
9487 white space is removed from the key (but not from any of the strings). The key
9488 must not be empty and must not consist entirely of digits.
9489 The expanded <&'string1'&> must be of the form:
9491 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9494 where the equals signs and spaces (but not both) are optional. If any of the
9495 values contain white space, they must be enclosed in double quotes, and any
9496 values that are enclosed in double quotes are subject to escape processing as
9497 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9498 for the value that corresponds to the key. The search is case-insensitive. If
9499 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9500 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9501 variable &$value$& contains the value that has been extracted. Afterwards, it
9502 is restored to any previous value it might have had.
9504 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9505 key is not found. If {<&'string2'&>} is also omitted, the value that was
9506 extracted is used. Thus, for example, these two expansions are identical, and
9509 ${extract{gid}{uid=1984 gid=2001}}
9510 ${extract{gid}{uid=1984 gid=2001}{$value}}
9512 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9513 appear, for example:
9515 ${extract{Z}{A=... B=...}{$value} fail }
9517 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9518 {<&'string2'&>} must be present for &"fail"& to be recognized.
9520 .vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9521 {*&<&'string3'&>&*}}*&"
9522 .cindex "expansion" "extracting from JSON object"
9523 .cindex JSON expansions
9524 The key and <&'string1'&> are first expanded separately. Leading and trailing
9525 white space is removed from the key (but not from any of the strings). The key
9526 must not be empty and must not consist entirely of digits.
9527 The expanded <&'string1'&> must be of the form:
9529 { <&'"key1"'&> : <&'value1'&> , <&'"key2"'&> , <&'value2'&> ... }
9532 The braces, commas and colons, and the quoting of the member name are required;
9533 the spaces are optional.
9534 Matching of the key against the member names is done case-sensitively.
9535 . XXX should be a UTF-8 compare
9537 The results of matching are handled as above.
9540 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9541 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9542 .cindex "expansion" "extracting substrings by number"
9543 .cindex "&%extract%&" "substrings by number"
9544 The <&'number'&> argument must consist entirely of decimal digits,
9545 apart from leading and trailing white space, which is ignored.
9546 This is what distinguishes this form of &%extract%& from the previous kind. It
9547 behaves in the same way, except that, instead of extracting a named field, it
9548 extracts from <&'string1'&> the field whose number is given as the first
9549 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9550 <&'string3'&> as before.
9552 The fields in the string are separated by any one of the characters in the
9553 separator string. These may include space or tab characters.
9554 The first field is numbered one. If the number is negative, the fields are
9555 counted from the end of the string, with the rightmost one numbered -1. If the
9556 number given is zero, the entire string is returned. If the modulus of the
9557 number is greater than the number of fields in the string, the result is the
9558 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9559 provided. For example:
9561 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9565 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9567 yields &"99"&. Two successive separators mean that the field between them is
9568 empty (for example, the fifth field above).
9571 .vitem "&*${extract json{*&<&'number'&>&*}}&&&
9572 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9573 .cindex "expansion" "extracting from JSON array"
9574 .cindex JSON expansions
9575 The <&'number'&> argument must consist entirely of decimal digits,
9576 apart from leading and trailing white space, which is ignored.
9578 Field selection and result handling is as above;
9579 there is no choice of field separator.
9582 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9583 .cindex "list" "selecting by condition"
9584 .cindex "expansion" "selecting from list by condition"
9586 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9587 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
9589 in this list, its value is place in &$item$&, and then the condition is
9590 evaluated. If the condition is true, &$item$& is added to the output as an
9591 item in a new list; if the condition is false, the item is discarded. The
9592 separator used for the output list is the same as the one used for the
9593 input, but a separator setting is not included in the output. For example:
9595 ${filter{a:b:c}{!eq{$item}{b}}}
9597 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9598 to what it was before. See also the &*map*& and &*reduce*& expansion items.
9601 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9602 .cindex "hash function" "textual"
9603 .cindex "expansion" "textual hash"
9604 This is a textual hashing function, and was the first to be implemented in
9605 early versions of Exim. In current releases, there are other hashing functions
9606 (numeric, MD5, and SHA-1), which are described below.
9608 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9609 <&'n'&>. If you are using fixed values for these numbers, that is, if
9610 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9611 use the simpler operator notation that avoids some of the braces:
9613 ${hash_<n>_<m>:<string>}
9615 The second number is optional (in both notations). If <&'n'&> is greater than
9616 or equal to the length of the string, the expansion item returns the string.
9617 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9618 function to the string. The new string consists of characters taken from the
9619 first <&'m'&> characters of the string
9621 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9623 If <&'m'&> is not present the value 26 is used, so that only lower case
9624 letters appear. For example:
9626 &`$hash{3}{monty}} `& yields &`jmg`&
9627 &`$hash{5}{monty}} `& yields &`monty`&
9628 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9631 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9632 &*$h_*&<&'header&~name'&>&*:*&" &&&
9633 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9634 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9635 "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9636 &*$lh_*&<&'header&~name'&>&*:*&"
9637 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9638 &*$rh_*&<&'header&~name'&>&*:*&"
9639 .cindex "expansion" "header insertion"
9640 .vindex "&$header_$&"
9641 .vindex "&$bheader_$&"
9642 .vindex "&$lheader_$&"
9643 .vindex "&$rheader_$&"
9644 .cindex "header lines" "in expansion strings"
9645 .cindex "header lines" "character sets"
9646 .cindex "header lines" "decoding"
9647 Substitute the contents of the named message header line, for example
9651 The newline that terminates a header line is not included in the expansion, but
9652 internal newlines (caused by splitting the header line over several physical
9653 lines) may be present.
9655 The difference between the four pairs of expansions is in the way
9656 the data in the header line is interpreted.
9659 .cindex "white space" "in header lines"
9660 &%rheader%& gives the original &"raw"& content of the header line, with no
9661 processing at all, and without the removal of leading and trailing white space.
9664 .cindex "list" "of header lines"
9665 &%lheader%& gives a colon-separated list, one element per header when there
9666 are multiple headers with a given name.
9667 Any embedded colon characters within an element are doubled, so normal Exim
9668 list-processing facilities can be used.
9669 The terminating newline of each element is removed; in other respects
9670 the content is &"raw"&.
9673 .cindex "base64 encoding" "in header lines"
9674 &%bheader%& removes leading and trailing white space, and then decodes base64
9675 or quoted-printable MIME &"words"& within the header text, but does no
9676 character set translation. If decoding of what looks superficially like a MIME
9677 &"word"& fails, the raw string is returned. If decoding
9678 .cindex "binary zero" "in header line"
9679 produces a binary zero character, it is replaced by a question mark &-- this is
9680 what Exim does for binary zeros that are actually received in header lines.
9683 &%header%& tries to translate the string as decoded by &%bheader%& to a
9684 standard character set. This is an attempt to produce the same string as would
9685 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
9686 returned. Translation is attempted only on operating systems that support the
9687 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
9688 a system Makefile or in &_Local/Makefile_&.
9691 In a filter file, the target character set for &%header%& can be specified by a
9692 command of the following form:
9694 headers charset "UTF-8"
9696 This command affects all references to &$h_$& (or &$header_$&) expansions in
9697 subsequently obeyed filter commands. In the absence of this command, the target
9698 character set in a filter is taken from the setting of the &%headers_charset%&
9699 option in the runtime configuration. The value of this option defaults to the
9700 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
9703 Header names follow the syntax of RFC 2822, which states that they may contain
9704 any printing characters except space and colon. Consequently, curly brackets
9705 &'do not'& terminate header names, and should not be used to enclose them as
9706 if they were variables. Attempting to do so causes a syntax error.
9708 Only header lines that are common to all copies of a message are visible to
9709 this mechanism. These are the original header lines that are received with the
9710 message, and any that are added by an ACL statement or by a system
9711 filter. Header lines that are added to a particular copy of a message by a
9712 router or transport are not accessible.
9714 For incoming SMTP messages, no header lines are visible in
9715 ACLs that are obeyed before the data phase completes,
9716 because the header structure is not set up until the message is received.
9717 They are visible in DKIM, PRDR and DATA ACLs.
9718 Header lines that are added in a RCPT ACL (for example)
9719 are saved until the message's incoming header lines are available, at which
9720 point they are added.
9721 When any of the above ACLs ar
9722 running, however, header lines added by earlier ACLs are visible.
9724 Upper case and lower case letters are synonymous in header names. If the
9725 following character is white space, the terminating colon may be omitted, but
9726 this is not recommended, because you may then forget it when it is needed. When
9727 white space terminates the header name, this white space is included in the
9728 expanded string. If the message does not contain the given header, the
9729 expansion item is replaced by an empty string. (See the &%def%& condition in
9730 section &<<SECTexpcond>>& for a means of testing for the existence of a
9733 If there is more than one header with the same name, they are all concatenated
9734 to form the substitution string, up to a maximum length of 64K. Unless
9735 &%rheader%& is being used, leading and trailing white space is removed from
9736 each header before concatenation, and a completely empty header is ignored. A
9737 newline character is then inserted between non-empty headers, but there is no
9738 newline at the very end. For the &%header%& and &%bheader%& expansion, for
9739 those headers that contain lists of addresses, a comma is also inserted at the
9740 junctions between headers. This does not happen for the &%rheader%& expansion.
9743 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
9744 .cindex "expansion" "hmac hashing"
9746 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
9747 shared secret and some text into a message authentication code, as specified in
9748 RFC 2104. This differs from &`${md5:secret_text...}`& or
9749 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
9750 cryptographic hash, allowing for authentication that is not possible with MD5
9751 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
9752 present. For example:
9754 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
9756 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
9759 dd97e3ba5d1a61b5006108f8c8252953
9761 As an example of how this might be used, you might put in the main part of
9762 an Exim configuration:
9764 SPAMSCAN_SECRET=cohgheeLei2thahw
9766 In a router or a transport you could then have:
9769 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
9770 ${hmac{md5}{SPAMSCAN_SECRET}\
9771 {${primary_hostname},${message_exim_id},$h_message-id:}}
9773 Then given a message, you can check where it was scanned by looking at the
9774 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
9775 this header line is authentic by recomputing the authentication code from the
9776 host name, message ID and the &'Message-id:'& header line. This can be done
9777 using Exim's &%-be%& option, or by other means, for example, by using the
9778 &'hmac_md5_hex()'& function in Perl.
9781 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9782 .cindex "expansion" "conditional"
9783 .cindex "&%if%&, expansion item"
9784 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
9785 item; otherwise <&'string2'&> is used. The available conditions are described
9786 in section &<<SECTexpcond>>& below. For example:
9788 ${if eq {$local_part}{postmaster} {yes}{no} }
9790 The second string need not be present; if it is not and the condition is not
9791 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
9792 be present instead of the second string (without any curly brackets). In this
9793 case, the expansion is forced to fail if the condition is not true (see section
9794 &<<SECTforexpfai>>&).
9796 If both strings are omitted, the result is the string &`true`& if the condition
9797 is true, and the empty string if the condition is false. This makes it less
9798 cumbersome to write custom ACL and router conditions. For example, instead of
9800 condition = ${if >{$acl_m4}{3}{true}{false}}
9804 condition = ${if >{$acl_m4}{3}}
9809 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
9810 .cindex expansion "imap folder"
9811 .cindex "&%imapfolder%& expansion item"
9812 This item converts a (possibly multilevel, or with non-ASCII characters)
9813 folder specification to a Maildir name for filesystem use.
9814 For information on internationalisation support see &<<SECTi18nMDA>>&.
9818 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9819 .cindex "expansion" "string truncation"
9820 .cindex "&%length%& expansion item"
9821 The &%length%& item is used to extract the initial portion of a string. Both
9822 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
9823 you are using a fixed value for the number, that is, if <&'string1'&> does not
9824 change when expanded, you can use the simpler operator notation that avoids
9827 ${length_<n>:<string>}
9829 The result of this item is either the first <&'n'&> bytes or the whole
9830 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
9831 &%strlen%&, which gives the length of a string.
9832 All measurement is done in bytes and is not UTF-8 aware.
9835 .vitem "&*${listextract{*&<&'number'&>&*}&&&
9836 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9837 .cindex "expansion" "extracting list elements by number"
9838 .cindex "&%listextract%&" "extract list elements by number"
9839 .cindex "list" "extracting elements by number"
9840 The <&'number'&> argument must consist entirely of decimal digits,
9841 apart from an optional leading minus,
9842 and leading and trailing white space (which is ignored).
9844 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9845 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
9847 The first field of the list is numbered one.
9848 If the number is negative, the fields are
9849 counted from the end of the list, with the rightmost one numbered -1.
9850 The numbered element of the list is extracted and placed in &$value$&,
9851 then <&'string2'&> is expanded as the result.
9853 If the modulus of the
9854 number is zero or greater than the number of fields in the string,
9855 the result is the expansion of <&'string3'&>.
9859 ${listextract{2}{x:42:99}}
9863 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
9865 yields &"result: 42"&.
9867 If {<&'string3'&>} is omitted, an empty string is used for string3.
9868 If {<&'string2'&>} is also omitted, the value that was
9870 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
9873 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
9874 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9875 This is the first of one of two different types of lookup item, which are both
9876 described in the next item.
9878 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
9879 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9880 .cindex "expansion" "lookup in"
9881 .cindex "file" "lookups"
9882 .cindex "lookup" "in expanded string"
9883 The two forms of lookup item specify data lookups in files and databases, as
9884 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
9885 lookups, and the second is used for query-style lookups. The <&'key'&>,
9886 <&'file'&>, and <&'query'&> strings are expanded before use.
9888 If there is any white space in a lookup item which is part of a filter command,
9889 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
9890 other place where white space is significant, the lookup item must be enclosed
9891 in double quotes. The use of data lookups in users' filter files may be locked
9892 out by the system administrator.
9895 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
9896 During its expansion, the variable &$value$& contains the data returned by the
9897 lookup. Afterwards it reverts to the value it had previously (at the outer
9898 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
9899 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
9900 string on failure. If <&'string2'&> is provided, it can itself be a nested
9901 lookup, thus providing a mechanism for looking up a default value when the
9902 original lookup fails.
9904 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
9905 data for the outer lookup while the parameters of the second lookup are
9906 expanded, and also while <&'string2'&> of the second lookup is expanded, should
9907 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
9908 appear, and in this case, if the lookup fails, the entire expansion is forced
9909 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
9910 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
9911 successful lookup, and nothing in the case of failure.
9913 For single-key lookups, the string &"partial"& is permitted to precede the
9914 search type in order to do partial matching, and * or *@ may follow a search
9915 type to request default lookups if the key does not match (see sections
9916 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
9918 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
9919 If a partial search is used, the variables &$1$& and &$2$& contain the wild
9920 and non-wild parts of the key during the expansion of the replacement text.
9921 They return to their previous values at the end of the lookup item.
9923 This example looks up the postmaster alias in the conventional alias file:
9925 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
9927 This example uses NIS+ to look up the full name of the user corresponding to
9928 the local part of an address, forcing the expansion to fail if it is not found:
9930 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
9935 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9936 .cindex "expansion" "list creation"
9938 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9939 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
9941 in this list, its value is place in &$item$&, and then <&'string2'&> is
9942 expanded and added to the output as an item in a new list. The separator used
9943 for the output list is the same as the one used for the input, but a separator
9944 setting is not included in the output. For example:
9946 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
9948 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
9949 value of &$item$& is restored to what it was before. See also the &*filter*&
9950 and &*reduce*& expansion items.
9952 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9953 .cindex "expansion" "numeric hash"
9954 .cindex "hash function" "numeric"
9955 The three strings are expanded; the first two must yield numbers. Call them
9956 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9957 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9958 can use the simpler operator notation that avoids some of the braces:
9960 ${nhash_<n>_<m>:<string>}
9962 The second number is optional (in both notations). If there is only one number,
9963 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
9964 processed by a div/mod hash function that returns two numbers, separated by a
9965 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
9968 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
9970 returns the string &"6/33"&.
9974 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
9975 .cindex "Perl" "use in expanded string"
9976 .cindex "expansion" "calling Perl from"
9977 This item is available only if Exim has been built to include an embedded Perl
9978 interpreter. The subroutine name and the arguments are first separately
9979 expanded, and then the Perl subroutine is called with those arguments. No
9980 additional arguments need be given; the maximum number permitted, including the
9981 name of the subroutine, is nine.
9983 The return value of the subroutine is inserted into the expanded string, unless
9984 the return value is &%undef%&. In that case, the expansion fails in the same
9985 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
9986 Whatever you return is evaluated in a scalar context. For example, if you
9987 return the name of a Perl vector, the return value is the size of the vector,
9990 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
9991 with the error message that was passed to &%die%&. More details of the embedded
9992 Perl facility are given in chapter &<<CHAPperl>>&.
9994 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
9995 out the use of this expansion item in filter files.
9998 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
9999 .cindex "&%prvs%& expansion item"
10000 The first argument is a complete email address and the second is secret
10001 keystring. The third argument, specifying a key number, is optional. If absent,
10002 it defaults to 0. The result of the expansion is a prvs-signed email address,
10003 to be typically used with the &%return_path%& option on an &(smtp)& transport
10004 as part of a bounce address tag validation (BATV) scheme. For more discussion
10005 and an example, see section &<<SECTverifyPRVS>>&.
10007 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
10008 {*&<&'string'&>&*}}*&"
10009 .cindex "&%prvscheck%& expansion item"
10010 This expansion item is the complement of the &%prvs%& item. It is used for
10011 checking prvs-signed addresses. If the expansion of the first argument does not
10012 yield a syntactically valid prvs-signed address, the whole item expands to the
10013 empty string. When the first argument does expand to a syntactically valid
10014 prvs-signed address, the second argument is expanded, with the prvs-decoded
10015 version of the address and the key number extracted from the address in the
10016 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
10018 These two variables can be used in the expansion of the second argument to
10019 retrieve the secret. The validity of the prvs-signed address is then checked
10020 against the secret. The result is stored in the variable &$prvscheck_result$&,
10021 which is empty for failure or &"1"& for success.
10023 The third argument is optional; if it is missing, it defaults to an empty
10024 string. This argument is now expanded. If the result is an empty string, the
10025 result of the expansion is the decoded version of the address. This is the case
10026 whether or not the signature was valid. Otherwise, the result of the expansion
10027 is the expansion of the third argument.
10029 All three variables can be used in the expansion of the third argument.
10030 However, once the expansion is complete, only &$prvscheck_result$& remains set.
10031 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
10033 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
10034 .cindex "expansion" "inserting an entire file"
10035 .cindex "file" "inserting into expansion"
10036 .cindex "&%readfile%& expansion item"
10037 The filename and end-of-line string are first expanded separately. The file is
10038 then read, and its contents replace the entire item. All newline characters in
10039 the file are replaced by the end-of-line string if it is present. Otherwise,
10040 newlines are left in the string.
10041 String expansion is not applied to the contents of the file. If you want this,
10042 you must wrap the item in an &%expand%& operator. If the file cannot be read,
10043 the string expansion fails.
10045 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
10046 locks out the use of this expansion item in filter files.
10050 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
10051 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
10052 .cindex "expansion" "inserting from a socket"
10053 .cindex "socket, use of in expansion"
10054 .cindex "&%readsocket%& expansion item"
10055 This item inserts data from a Unix domain or TCP socket into the expanded
10056 string. The minimal way of using it uses just two arguments, as in these
10059 ${readsocket{/socket/name}{request string}}
10060 ${readsocket{inet:some.host:1234}{request string}}
10062 For a Unix domain socket, the first substring must be the path to the socket.
10063 For an Internet socket, the first substring must contain &`inet:`& followed by
10064 a host name or IP address, followed by a colon and a port, which can be a
10065 number or the name of a TCP port in &_/etc/services_&. An IP address may
10066 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
10069 ${readsocket{inet:[::1]:1234}{request string}}
10071 Only a single host name may be given, but if looking it up yields more than
10072 one IP address, they are each tried in turn until a connection is made. For
10073 both kinds of socket, Exim makes a connection, writes the request string
10074 unless it is an empty string; and no terminating NUL is ever sent)
10075 and reads from the socket until an end-of-file
10076 is read. A timeout of 5 seconds is applied. Additional, optional arguments
10077 extend what can be done. Firstly, you can vary the timeout. For example:
10079 ${readsocket{/socket/name}{request string}{3s}}
10082 The third argument is a list of options, of which the first element is the timeout
10083 and must be present if the argument is given.
10084 Further elements are options of form &'name=value'&.
10085 Two option types is currently recognised: shutdown and tls.
10086 The first defines whether (the default)
10087 or not a shutdown is done on the connection after sending the request.
10088 Example, to not do so (preferred, eg. by some webservers):
10090 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
10092 The second, tls, controls the use of TLS on the connection. Example:
10094 ${readsocket{/socket/name}{request string}{3s:tls=yes}}
10096 The default is to not use TLS.
10097 If it is enabled, a shutdown as descripbed above is never done.
10099 A fourth argument allows you to change any newlines that are in the data
10100 that is read, in the same way as for &%readfile%& (see above). This example
10101 turns them into spaces:
10103 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
10105 As with all expansions, the substrings are expanded before the processing
10106 happens. Errors in these sub-expansions cause the expansion to fail. In
10107 addition, the following errors can occur:
10110 Failure to create a socket file descriptor;
10112 Failure to connect the socket;
10114 Failure to write the request string;
10116 Timeout on reading from the socket.
10119 By default, any of these errors causes the expansion to fail. However, if
10120 you supply a fifth substring, it is expanded and used when any of the above
10121 errors occurs. For example:
10123 ${readsocket{/socket/name}{request string}{3s}{\n}\
10126 You can test for the existence of a Unix domain socket by wrapping this
10127 expansion in &`${if exists`&, but there is a race condition between that test
10128 and the actual opening of the socket, so it is safer to use the fifth argument
10129 if you want to be absolutely sure of avoiding an expansion error for a
10130 non-existent Unix domain socket, or a failure to connect to an Internet socket.
10132 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
10133 locks out the use of this expansion item in filter files.
10136 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10137 .cindex "expansion" "reducing a list to a scalar"
10138 .cindex "list" "reducing to a scalar"
10139 .vindex "&$value$&"
10141 This operation reduces a list to a single, scalar string. After expansion,
10142 <&'string1'&> is interpreted as a list, colon-separated by default, but the
10143 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10144 Then <&'string2'&> is expanded and
10145 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
10146 list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
10147 them. The result of that expansion is assigned to &$value$& before the next
10148 iteration. When the end of the list is reached, the final value of &$value$& is
10149 added to the expansion output. The &*reduce*& expansion item can be used in a
10150 number of ways. For example, to add up a list of numbers:
10152 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
10154 The result of that expansion would be &`6`&. The maximum of a list of numbers
10157 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
10159 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
10160 restored to what they were before. See also the &*filter*& and &*map*&
10163 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
10164 This item inserts &"raw"& header lines. It is described with the &%header%&
10165 expansion item in section &<<SECTexpansionitems>>& above.
10167 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
10168 {*&<&'string2'&>&*}}*&"
10169 .cindex "expansion" "running a command"
10170 .cindex "&%run%& expansion item"
10171 The command and its arguments are first expanded as one string. The string is
10172 split apart into individual arguments by spaces, and then the command is run
10173 in a separate process, but under the same uid and gid. As in other command
10174 executions from Exim, a shell is not used by default. If the command requires
10175 a shell, you must explicitly code it.
10177 Since the arguments are split by spaces, when there is a variable expansion
10178 which has an empty result, it will cause the situation that the argument will
10179 simply be omitted when the program is actually executed by Exim. If the
10180 script/program requires a specific number of arguments and the expanded
10181 variable could possibly result in this empty expansion, the variable must be
10182 quoted. This is more difficult if the expanded variable itself could result
10183 in a string containing quotes, because it would interfere with the quotes
10184 around the command arguments. A possible guard against this is to wrap the
10185 variable in the &%sg%& operator to change any quote marks to some other
10188 The standard input for the command exists, but is empty. The standard output
10189 and standard error are set to the same file descriptor.
10190 .cindex "return code" "from &%run%& expansion"
10191 .vindex "&$value$&"
10192 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
10193 and replaces the entire item; during this expansion, the standard output/error
10194 from the command is in the variable &$value$&. If the command fails,
10195 <&'string2'&>, if present, is expanded and used. Once again, during the
10196 expansion, the standard output/error from the command is in the variable
10199 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
10200 can be the word &"fail"& (not in braces) to force expansion failure if the
10201 command does not succeed. If both strings are omitted, the result is contents
10202 of the standard output/error on success, and nothing on failure.
10204 .vindex "&$run_in_acl$&"
10205 The standard output/error of the command is put in the variable &$value$&.
10206 In this ACL example, the output of a command is logged for the admin to
10209 warn condition = ${run{/usr/bin/id}{yes}{no}}
10210 log_message = Output of id: $value
10212 If the command requires shell idioms, such as the > redirect operator, the
10213 shell must be invoked directly, such as with:
10215 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
10218 .vindex "&$runrc$&"
10219 The return code from the command is put in the variable &$runrc$&, and this
10220 remains set afterwards, so in a filter file you can do things like this:
10222 if "${run{x y z}{}}$runrc" is 1 then ...
10223 elif $runrc is 2 then ...
10227 If execution of the command fails (for example, the command does not exist),
10228 the return code is 127 &-- the same code that shells use for non-existent
10231 &*Warning*&: In a router or transport, you cannot assume the order in which
10232 option values are expanded, except for those preconditions whose order of
10233 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
10234 by the expansion of one option, and use it in another.
10236 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
10237 out the use of this expansion item in filter files.
10240 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
10241 .cindex "expansion" "string substitution"
10242 .cindex "&%sg%& expansion item"
10243 This item works like Perl's substitution operator (s) with the global (/g)
10244 option; hence its name. However, unlike the Perl equivalent, Exim does not
10245 modify the subject string; instead it returns the modified string for insertion
10246 into the overall expansion. The item takes three arguments: the subject string,
10247 a regular expression, and a substitution string. For example:
10249 ${sg{abcdefabcdef}{abc}{xyz}}
10251 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
10252 if any $, } or \ characters are required in the regular expression or in the
10253 substitution string, they have to be escaped. For example:
10255 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
10257 yields &"defabc"&, and
10259 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
10261 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
10262 the regular expression from string expansion.
10264 The regular expression is compiled in 8-bit mode, working against bytes
10265 rather than any Unicode-aware character handling.
10268 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
10269 .cindex sorting "a list"
10270 .cindex list sorting
10271 .cindex expansion "list sorting"
10272 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10273 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10274 The <&'comparator'&> argument is interpreted as the operator
10275 of a two-argument expansion condition.
10276 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
10277 The comparison should return true when applied to two values
10278 if the first value should sort before the second value.
10279 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
10280 the element being placed in &$item$&,
10281 to give values for comparison.
10283 The item result is a sorted list,
10284 with the original list separator,
10285 of the list elements (in full) of the original.
10289 ${sort{3:2:1:4}{<}{$item}}
10291 sorts a list of numbers, and
10293 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10295 will sort an MX lookup into priority order.
10298 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10299 .cindex "&%substr%& expansion item"
10300 .cindex "substring extraction"
10301 .cindex "expansion" "substring extraction"
10302 The three strings are expanded; the first two must yield numbers. Call them
10303 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10304 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10305 can use the simpler operator notation that avoids some of the braces:
10307 ${substr_<n>_<m>:<string>}
10309 The second number is optional (in both notations).
10310 If it is absent in the simpler format, the preceding underscore must also be
10313 The &%substr%& item can be used to extract more general substrings than
10314 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10315 length required. For example
10317 ${substr{3}{2}{$local_part}}
10319 If the starting offset is greater than the string length the result is the
10320 null string; if the length plus starting offset is greater than the string
10321 length, the result is the right-hand part of the string, starting from the
10322 given offset. The first byte (character) in the string has offset zero.
10324 The &%substr%& expansion item can take negative offset values to count
10325 from the right-hand end of its operand. The last byte (character) is offset -1,
10326 the second-last is offset -2, and so on. Thus, for example,
10328 ${substr{-5}{2}{1234567}}
10330 yields &"34"&. If the absolute value of a negative offset is greater than the
10331 length of the string, the substring starts at the beginning of the string, and
10332 the length is reduced by the amount of overshoot. Thus, for example,
10334 ${substr{-5}{2}{12}}
10336 yields an empty string, but
10338 ${substr{-3}{2}{12}}
10342 When the second number is omitted from &%substr%&, the remainder of the string
10343 is taken if the offset is positive. If it is negative, all bytes (characters) in the
10344 string preceding the offset point are taken. For example, an offset of -1 and
10345 no length, as in these semantically identical examples:
10348 ${substr{-1}{abcde}}
10350 yields all but the last character of the string, that is, &"abcd"&.
10352 All measurement is done in bytes and is not UTF-8 aware.
10356 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10357 {*&<&'replacements'&>&*}}*&"
10358 .cindex "expansion" "character translation"
10359 .cindex "&%tr%& expansion item"
10360 This item does single-character (in bytes) translation on its subject string. The second
10361 argument is a list of characters to be translated in the subject string. Each
10362 matching character is replaced by the corresponding character from the
10363 replacement list. For example
10365 ${tr{abcdea}{ac}{13}}
10367 yields &`1b3de1`&. If there are duplicates in the second character string, the
10368 last occurrence is used. If the third string is shorter than the second, its
10369 last character is replicated. However, if it is empty, no translation takes
10372 All character handling is done in bytes and is not UTF-8 aware.
10378 .section "Expansion operators" "SECTexpop"
10379 .cindex "expansion" "operators"
10380 For expansion items that perform transformations on a single argument string,
10381 the &"operator"& notation is used because it is simpler and uses fewer braces.
10382 The substring is first expanded before the operation is applied to it. The
10383 following operations can be performed:
10386 .vitem &*${address:*&<&'string'&>&*}*&
10387 .cindex "expansion" "RFC 2822 address handling"
10388 .cindex "&%address%& expansion item"
10389 The string is interpreted as an RFC 2822 address, as it might appear in a
10390 header line, and the effective address is extracted from it. If the string does
10391 not parse successfully, the result is empty.
10393 The parsing correctly handles SMTPUTF8 Unicode in the string.
10396 .vitem &*${addresses:*&<&'string'&>&*}*&
10397 .cindex "expansion" "RFC 2822 address handling"
10398 .cindex "&%addresses%& expansion item"
10399 The string (after expansion) is interpreted as a list of addresses in RFC
10400 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10401 operative address (&'local-part@domain'&) is extracted from each item, and the
10402 result of the expansion is a colon-separated list, with appropriate
10403 doubling of colons should any happen to be present in the email addresses.
10404 Syntactically invalid RFC2822 address items are omitted from the output.
10406 It is possible to specify a character other than colon for the output
10407 separator by starting the string with > followed by the new separator
10408 character. For example:
10410 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10412 expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
10413 first, so if the expanded string starts with >, it may change the output
10414 separator unintentionally. This can be avoided by setting the output
10415 separator explicitly:
10417 ${addresses:>:$h_from:}
10420 Compare the &*address*& (singular)
10421 expansion item, which extracts the working address from a single RFC2822
10422 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
10425 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10426 a strict interpretation of header line formatting. Exim parses the bare,
10427 unquoted portion of an email address and if it finds a comma, treats it as an
10428 email address separator. For the example header line:
10430 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10432 The first example below demonstrates that Q-encoded email addresses are parsed
10433 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10434 It does not see the comma because it's still encoded as "=2C". The second
10435 example below is passed the contents of &`$header_from:`&, meaning it gets
10436 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10437 The third example shows that the presence of a comma is skipped when it is
10438 quoted. The fourth example shows SMTPUTF8 handling.
10440 # exim -be '${addresses:From: \
10441 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10443 # exim -be '${addresses:From: Last, First <user@example.com>}'
10444 Last:user@example.com
10445 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10447 # exim -be '${addresses:フィル <フィリップ@example.jp>}'
10451 .vitem &*${base32:*&<&'digits'&>&*}*&
10452 .cindex "&%base32%& expansion item"
10453 .cindex "expansion" "conversion to base 32"
10454 The string must consist entirely of decimal digits. The number is converted to
10455 base 32 and output as a (empty, for zero) string of characters.
10456 Only lowercase letters are used.
10458 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10459 .cindex "&%base32d%& expansion item"
10460 .cindex "expansion" "conversion to base 32"
10461 The string must consist entirely of base-32 digits.
10462 The number is converted to decimal and output as a string.
10464 .vitem &*${base62:*&<&'digits'&>&*}*&
10465 .cindex "&%base62%& expansion item"
10466 .cindex "expansion" "conversion to base 62"
10467 The string must consist entirely of decimal digits. The number is converted to
10468 base 62 and output as a string of six characters, including leading zeros. In
10469 the few operating environments where Exim uses base 36 instead of base 62 for
10470 its message identifiers (because those systems do not have case-sensitive
10471 filenames), base 36 is used by this operator, despite its name. &*Note*&: Just
10472 to be absolutely clear: this is &'not'& base64 encoding.
10474 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10475 .cindex "&%base62d%& expansion item"
10476 .cindex "expansion" "conversion to base 62"
10477 The string must consist entirely of base-62 digits, or, in operating
10478 environments where Exim uses base 36 instead of base 62 for its message
10479 identifiers, base-36 digits. The number is converted to decimal and output as a
10482 .vitem &*${base64:*&<&'string'&>&*}*&
10483 .cindex "expansion" "base64 encoding"
10484 .cindex "base64 encoding" "in string expansion"
10485 .cindex "&%base64%& expansion item"
10486 .cindex certificate "base64 of DER"
10487 This operator converts a string into one that is base64 encoded.
10489 If the string is a single variable of type certificate,
10490 returns the base64 encoding of the DER form of the certificate.
10493 .vitem &*${base64d:*&<&'string'&>&*}*&
10494 .cindex "expansion" "base64 decoding"
10495 .cindex "base64 decoding" "in string expansion"
10496 .cindex "&%base64d%& expansion item"
10497 This operator converts a base64-encoded string into the un-coded form.
10500 .vitem &*${domain:*&<&'string'&>&*}*&
10501 .cindex "domain" "extraction"
10502 .cindex "expansion" "domain extraction"
10503 The string is interpreted as an RFC 2822 address and the domain is extracted
10504 from it. If the string does not parse successfully, the result is empty.
10507 .vitem &*${escape:*&<&'string'&>&*}*&
10508 .cindex "expansion" "escaping non-printing characters"
10509 .cindex "&%escape%& expansion item"
10510 If the string contains any non-printing characters, they are converted to
10511 escape sequences starting with a backslash. Whether characters with the most
10512 significant bit set (so-called &"8-bit characters"&) count as printing or not
10513 is controlled by the &%print_topbitchars%& option.
10515 .vitem &*${escape8bit:*&<&'string'&>&*}*&
10516 .cindex "expansion" "escaping 8-bit characters"
10517 .cindex "&%escape8bit%& expansion item"
10518 If the string contains and characters with the most significant bit set,
10519 they are converted to escape sequences starting with a backslash.
10520 Backslashes and DEL characters are also converted.
10523 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
10524 .cindex "expansion" "expression evaluation"
10525 .cindex "expansion" "arithmetic expression"
10526 .cindex "&%eval%& expansion item"
10527 These items supports simple arithmetic and bitwise logical operations in
10528 expansion strings. The string (after expansion) must be a conventional
10529 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
10530 logical operators, and parentheses. All operations are carried out using
10531 integer arithmetic. The operator priorities are as follows (the same as in the
10532 C programming language):
10534 .irow &'highest:'& "not (~), negate (-)"
10535 .irow "" "multiply (*), divide (/), remainder (%)"
10536 .irow "" "plus (+), minus (-)"
10537 .irow "" "shift-left (<<), shift-right (>>)"
10538 .irow "" "and (&&)"
10540 .irow &'lowest:'& "or (|)"
10542 Binary operators with the same priority are evaluated from left to right. White
10543 space is permitted before or after operators.
10545 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
10546 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
10547 decimal, even if they start with a leading zero; hexadecimal numbers are not
10548 permitted. This can be useful when processing numbers extracted from dates or
10549 times, which often do have leading zeros.
10551 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
10553 respectively. Negative numbers are supported. The result of the computation is
10554 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
10557 &`${eval:1+1} `& yields 2
10558 &`${eval:1+2*3} `& yields 7
10559 &`${eval:(1+2)*3} `& yields 9
10560 &`${eval:2+42%5} `& yields 4
10561 &`${eval:0xc&5} `& yields 4
10562 &`${eval:0xc|5} `& yields 13
10563 &`${eval:0xc^5} `& yields 9
10564 &`${eval:0xc>>1} `& yields 6
10565 &`${eval:0xc<<1} `& yields 24
10566 &`${eval:~255&0x1234} `& yields 4608
10567 &`${eval:-(~255&0x1234)} `& yields -4608
10570 As a more realistic example, in an ACL you might have
10572 deny message = Too many bad recipients
10575 {>{$rcpt_count}{10}} \
10578 {$recipients_count} \
10579 {${eval:$rcpt_count/2}} \
10583 The condition is true if there have been more than 10 RCPT commands and
10584 fewer than half of them have resulted in a valid recipient.
10587 .vitem &*${expand:*&<&'string'&>&*}*&
10588 .cindex "expansion" "re-expansion of substring"
10589 The &%expand%& operator causes a string to be expanded for a second time. For
10592 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
10594 first looks up a string in a file while expanding the operand for &%expand%&,
10595 and then re-expands what it has found.
10598 .vitem &*${from_utf8:*&<&'string'&>&*}*&
10600 .cindex "UTF-8" "conversion from"
10601 .cindex "expansion" "UTF-8 conversion"
10602 .cindex "&%from_utf8%& expansion item"
10603 The world is slowly moving towards Unicode, although there are no standards for
10604 email yet. However, other applications (including some databases) are starting
10605 to store data in Unicode, using UTF-8 encoding. This operator converts from a
10606 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
10607 converted to underscores. The input must be a valid UTF-8 string. If it is not,
10608 the result is an undefined sequence of bytes.
10610 Unicode code points with values less than 256 are compatible with ASCII and
10611 ISO-8859-1 (also known as Latin-1).
10612 For example, character 169 is the copyright symbol in both cases, though the
10613 way it is encoded is different. In UTF-8, more than one byte is needed for
10614 characters with code values greater than 127, whereas ISO-8859-1 is a
10615 single-byte encoding (but thereby limited to 256 characters). This makes
10616 translation from UTF-8 to ISO-8859-1 straightforward.
10619 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10620 .cindex "hash function" "textual"
10621 .cindex "expansion" "textual hash"
10622 The &%hash%& operator is a simpler interface to the hashing function that can
10623 be used when the two parameters are fixed numbers (as opposed to strings that
10624 change when expanded). The effect is the same as
10626 ${hash{<n>}{<m>}{<string>}}
10628 See the description of the general &%hash%& item above for details. The
10629 abbreviation &%h%& can be used when &%hash%& is used as an operator.
10633 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
10634 .cindex "base64 encoding" "conversion from hex"
10635 .cindex "expansion" "hex to base64"
10636 .cindex "&%hex2b64%& expansion item"
10637 This operator converts a hex string into one that is base64 encoded. This can
10638 be useful for processing the output of the various hashing functions.
10642 .vitem &*${hexquote:*&<&'string'&>&*}*&
10643 .cindex "quoting" "hex-encoded unprintable characters"
10644 .cindex "&%hexquote%& expansion item"
10645 This operator converts non-printable characters in a string into a hex
10646 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
10647 as is, and other byte values are converted to &`\xNN`&, for example, a
10648 byte value 127 is converted to &`\x7f`&.
10651 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
10652 .cindex "&%ipv6denorm%& expansion item"
10653 .cindex "IP address" normalisation
10654 This expands an IPv6 address to a full eight-element colon-separated set
10655 of hex digits including leading zeroes.
10656 A trailing ipv4-style dotted-decimal set is converted to hex.
10657 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10659 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
10660 .cindex "&%ipv6norm%& expansion item"
10661 .cindex "IP address" normalisation
10662 .cindex "IP address" "canonical form"
10663 This converts an IPv6 address to canonical form.
10664 Leading zeroes of groups are omitted, and the longest
10665 set of zero-valued groups is replaced with a double colon.
10666 A trailing ipv4-style dotted-decimal set is converted to hex.
10667 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10670 .vitem &*${lc:*&<&'string'&>&*}*&
10671 .cindex "case forcing in strings"
10672 .cindex "string" "case forcing"
10673 .cindex "lower casing"
10674 .cindex "expansion" "case forcing"
10675 .cindex "&%lc%& expansion item"
10676 This forces the letters in the string into lower-case, for example:
10680 Case is defined per the system C locale.
10682 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
10683 .cindex "expansion" "string truncation"
10684 .cindex "&%length%& expansion item"
10685 The &%length%& operator is a simpler interface to the &%length%& function that
10686 can be used when the parameter is a fixed number (as opposed to a string that
10687 changes when expanded). The effect is the same as
10689 ${length{<number>}{<string>}}
10691 See the description of the general &%length%& item above for details. Note that
10692 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
10693 when &%length%& is used as an operator.
10694 All measurement is done in bytes and is not UTF-8 aware.
10697 .vitem &*${listcount:*&<&'string'&>&*}*&
10698 .cindex "expansion" "list item count"
10699 .cindex "list" "item count"
10700 .cindex "list" "count of items"
10701 .cindex "&%listcount%& expansion item"
10702 The string is interpreted as a list and the number of items is returned.
10705 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
10706 .cindex "expansion" "named list"
10707 .cindex "&%listnamed%& expansion item"
10708 The name is interpreted as a named list and the content of the list is returned,
10709 expanding any referenced lists, re-quoting as needed for colon-separation.
10710 If the optional type is given it must be one of "a", "d", "h" or "l"
10711 and selects address-, domain-, host- or localpart- lists to search among respectively.
10712 Otherwise all types are searched in an undefined order and the first
10713 matching list is returned.
10716 .vitem &*${local_part:*&<&'string'&>&*}*&
10717 .cindex "expansion" "local part extraction"
10718 .cindex "&%local_part%& expansion item"
10719 The string is interpreted as an RFC 2822 address and the local part is
10720 extracted from it. If the string does not parse successfully, the result is
10722 The parsing correctly handles SMTPUTF8 Unicode in the string.
10725 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
10726 .cindex "masked IP address"
10727 .cindex "IP address" "masking"
10728 .cindex "CIDR notation"
10729 .cindex "expansion" "IP address masking"
10730 .cindex "&%mask%& expansion item"
10731 If the form of the string to be operated on is not an IP address followed by a
10732 slash and an integer (that is, a network address in CIDR notation), the
10733 expansion fails. Otherwise, this operator converts the IP address to binary,
10734 masks off the least significant bits according to the bit count, and converts
10735 the result back to text, with mask appended. For example,
10737 ${mask:10.111.131.206/28}
10739 returns the string &"10.111.131.192/28"&. Since this operation is expected to
10740 be mostly used for looking up masked addresses in files, the result for an IPv6
10741 address uses dots to separate components instead of colons, because colon
10742 terminates a key string in lsearch files. So, for example,
10744 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
10748 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
10750 Letters in IPv6 addresses are always output in lower case.
10753 .vitem &*${md5:*&<&'string'&>&*}*&
10755 .cindex "expansion" "MD5 hash"
10756 .cindex certificate fingerprint
10757 .cindex "&%md5%& expansion item"
10758 The &%md5%& operator computes the MD5 hash value of the string, and returns it
10759 as a 32-digit hexadecimal number, in which any letters are in lower case.
10761 If the string is a single variable of type certificate,
10762 returns the MD5 hash fingerprint of the certificate.
10765 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10766 .cindex "expansion" "numeric hash"
10767 .cindex "hash function" "numeric"
10768 The &%nhash%& operator is a simpler interface to the numeric hashing function
10769 that can be used when the two parameters are fixed numbers (as opposed to
10770 strings that change when expanded). The effect is the same as
10772 ${nhash{<n>}{<m>}{<string>}}
10774 See the description of the general &%nhash%& item above for details.
10777 .vitem &*${quote:*&<&'string'&>&*}*&
10778 .cindex "quoting" "in string expansions"
10779 .cindex "expansion" "quoting"
10780 .cindex "&%quote%& expansion item"
10781 The &%quote%& operator puts its argument into double quotes if it
10782 is an empty string or
10783 contains anything other than letters, digits, underscores, dots, and hyphens.
10784 Any occurrences of double quotes and backslashes are escaped with a backslash.
10785 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
10786 respectively For example,
10794 The place where this is useful is when the argument is a substitution from a
10795 variable or a message header.
10797 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
10798 .cindex "&%quote_local_part%& expansion item"
10799 This operator is like &%quote%&, except that it quotes the string only if
10800 required to do so by the rules of RFC 2822 for quoting local parts. For
10801 example, a plus sign would not cause quoting (but it would for &%quote%&).
10802 If you are creating a new email address from the contents of &$local_part$&
10803 (or any other unknown data), you should always use this operator.
10805 This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
10806 will likely use the quoting form.
10807 Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
10810 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
10811 .cindex "quoting" "lookup-specific"
10812 This operator applies lookup-specific quoting rules to the string. Each
10813 query-style lookup type has its own quoting rules which are described with
10814 the lookups in chapter &<<CHAPfdlookup>>&. For example,
10816 ${quote_ldap:two * two}
10822 For single-key lookup types, no quoting is ever necessary and this operator
10823 yields an unchanged string.
10826 .vitem &*${randint:*&<&'n'&>&*}*&
10827 .cindex "random number"
10828 This operator returns a somewhat random number which is less than the
10829 supplied number and is at least 0. The quality of this randomness depends
10830 on how Exim was built; the values are not suitable for keying material.
10831 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
10832 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
10833 for versions of GnuTLS with that function.
10834 Otherwise, the implementation may be arc4random(), random() seeded by
10835 srandomdev() or srandom(), or a custom implementation even weaker than
10839 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
10840 .cindex "expansion" "IP address"
10841 This operator reverses an IP address; for IPv4 addresses, the result is in
10842 dotted-quad decimal form, while for IPv6 addresses the result is in
10843 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
10844 for DNS. For example,
10846 ${reverse_ip:192.0.2.4}
10847 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
10852 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
10856 .vitem &*${rfc2047:*&<&'string'&>&*}*&
10857 .cindex "expansion" "RFC 2047"
10858 .cindex "RFC 2047" "expansion operator"
10859 .cindex "&%rfc2047%& expansion item"
10860 This operator encodes text according to the rules of RFC 2047. This is an
10861 encoding that is used in header lines to encode non-ASCII characters. It is
10862 assumed that the input string is in the encoding specified by the
10863 &%headers_charset%& option, which gets its default at build time. If the string
10864 contains only characters in the range 33&--126, and no instances of the
10867 ? = ( ) < > @ , ; : \ " . [ ] _
10869 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
10870 string, using as many &"encoded words"& as necessary to encode all the
10874 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
10875 .cindex "expansion" "RFC 2047"
10876 .cindex "RFC 2047" "decoding"
10877 .cindex "&%rfc2047d%& expansion item"
10878 This operator decodes strings that are encoded as per RFC 2047. Binary zero
10879 bytes are replaced by question marks. Characters are converted into the
10880 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
10881 not recognized unless &%check_rfc2047_length%& is set false.
10883 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
10884 access a header line, RFC 2047 decoding is done automatically. You do not need
10885 to use this operator as well.
10889 .vitem &*${rxquote:*&<&'string'&>&*}*&
10890 .cindex "quoting" "in regular expressions"
10891 .cindex "regular expressions" "quoting"
10892 .cindex "&%rxquote%& expansion item"
10893 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
10894 characters in its argument. This is useful when substituting the values of
10895 variables or headers inside regular expressions.
10898 .vitem &*${sha1:*&<&'string'&>&*}*&
10899 .cindex "SHA-1 hash"
10900 .cindex "expansion" "SHA-1 hashing"
10901 .cindex certificate fingerprint
10902 .cindex "&%sha1%& expansion item"
10903 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
10904 it as a 40-digit hexadecimal number, in which any letters are in upper case.
10906 If the string is a single variable of type certificate,
10907 returns the SHA-1 hash fingerprint of the certificate.
10910 .vitem &*${sha256:*&<&'string'&>&*}*&
10911 .cindex "SHA-256 hash"
10912 .cindex certificate fingerprint
10913 .cindex "expansion" "SHA-256 hashing"
10914 .cindex "&%sha256%& expansion item"
10915 The &%sha256%& operator computes the SHA-256 hash value of the string
10917 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10919 If the string is a single variable of type certificate,
10920 returns the SHA-256 hash fingerprint of the certificate.
10923 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
10924 &*${sha3_<n>:*&<&'string'&>&*}*&
10925 .cindex "SHA3 hash"
10926 .cindex "expansion" "SHA3 hashing"
10927 .cindex "&%sha3%& expansion item"
10928 The &%sha3%& operator computes the SHA3-256 hash value of the string
10930 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10932 If a number is appended, separated by an underbar, it specifies
10933 the output length. Values of 224, 256, 384 and 512 are accepted;
10934 with 256 being the default.
10936 The &%sha3%& expansion item is only supported if Exim has been
10937 compiled with GnuTLS 3.5.0 or later,
10938 or OpenSSL 1.1.1 or later.
10939 The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
10942 .vitem &*${stat:*&<&'string'&>&*}*&
10943 .cindex "expansion" "statting a file"
10944 .cindex "file" "extracting characteristics"
10945 .cindex "&%stat%& expansion item"
10946 The string, after expansion, must be a file path. A call to the &[stat()]&
10947 function is made for this path. If &[stat()]& fails, an error occurs and the
10948 expansion fails. If it succeeds, the data from the stat replaces the item, as a
10949 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
10950 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
10951 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
10952 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
10953 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
10954 can extract individual fields using the &%extract%& expansion item.
10956 The use of the &%stat%& expansion in users' filter files can be locked out by
10957 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
10958 systems for files larger than 2GB.
10960 .vitem &*${str2b64:*&<&'string'&>&*}*&
10961 .cindex "&%str2b64%& expansion item"
10962 Now deprecated, a synonym for the &%base64%& expansion operator.
10966 .vitem &*${strlen:*&<&'string'&>&*}*&
10967 .cindex "expansion" "string length"
10968 .cindex "string" "length in expansion"
10969 .cindex "&%strlen%& expansion item"
10970 The item is replace by the length of the expanded string, expressed as a
10971 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
10972 All measurement is done in bytes and is not UTF-8 aware.
10975 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
10976 .cindex "&%substr%& expansion item"
10977 .cindex "substring extraction"
10978 .cindex "expansion" "substring expansion"
10979 The &%substr%& operator is a simpler interface to the &%substr%& function that
10980 can be used when the two parameters are fixed numbers (as opposed to strings
10981 that change when expanded). The effect is the same as
10983 ${substr{<start>}{<length>}{<string>}}
10985 See the description of the general &%substr%& item above for details. The
10986 abbreviation &%s%& can be used when &%substr%& is used as an operator.
10987 All measurement is done in bytes and is not UTF-8 aware.
10989 .vitem &*${time_eval:*&<&'string'&>&*}*&
10990 .cindex "&%time_eval%& expansion item"
10991 .cindex "time interval" "decoding"
10992 This item converts an Exim time interval such as &`2d4h5m`& into a number of
10995 .vitem &*${time_interval:*&<&'string'&>&*}*&
10996 .cindex "&%time_interval%& expansion item"
10997 .cindex "time interval" "formatting"
10998 The argument (after sub-expansion) must be a sequence of decimal digits that
10999 represents an interval of time as a number of seconds. It is converted into a
11000 number of larger units and output in Exim's normal time format, for example,
11003 .vitem &*${uc:*&<&'string'&>&*}*&
11004 .cindex "case forcing in strings"
11005 .cindex "string" "case forcing"
11006 .cindex "upper casing"
11007 .cindex "expansion" "case forcing"
11008 .cindex "&%uc%& expansion item"
11009 This forces the letters in the string into upper-case.
11010 Case is defined per the system C locale.
11012 .vitem &*${utf8clean:*&<&'string'&>&*}*&
11013 .cindex "correction of invalid utf-8 sequences in strings"
11014 .cindex "utf-8" "utf-8 sequences"
11015 .cindex "incorrect utf-8"
11016 .cindex "expansion" "utf-8 forcing"
11017 .cindex "&%utf8clean%& expansion item"
11018 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
11019 In versions of Exim before 4.92, this did not correctly do so for a truncated
11020 final codepoint's encoding, and the character would be silently dropped.
11021 If you must handle detection of this scenario across both sets of Exim behavior,
11022 the complexity will depend upon the task.
11023 For instance, to detect if the first character is multibyte and a 1-byte
11024 extraction can be successfully used as a path component (as is common for
11025 dividing up delivery folders), you might use:
11027 condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
11029 (which will false-positive if the first character of the local part is a
11030 literal question mark).
11032 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
11033 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
11034 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
11035 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
11036 .cindex expansion UTF-8
11037 .cindex UTF-8 expansion
11039 .cindex internationalisation
11040 .cindex "&%utf8_domain_to_alabel%& expansion item"
11041 .cindex "&%utf8_domain_from_alabel%& expansion item"
11042 .cindex "&%utf8_localpart_to_alabel%& expansion item"
11043 .cindex "&%utf8_localpart_from_alabel%& expansion item"
11044 These convert EAI mail name components between UTF-8 and a-label forms.
11045 For information on internationalisation support see &<<SECTi18nMTA>>&.
11053 .section "Expansion conditions" "SECTexpcond"
11054 .scindex IIDexpcond "expansion" "conditions"
11055 The following conditions are available for testing by the &%${if%& construct
11056 while expanding strings:
11059 .vitem &*!*&<&'condition'&>
11060 .cindex "expansion" "negating a condition"
11061 .cindex "negation" "in expansion condition"
11062 Preceding any condition with an exclamation mark negates the result of the
11065 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11066 .cindex "numeric comparison"
11067 .cindex "expansion" "numeric comparison"
11068 There are a number of symbolic operators for doing numeric comparisons. They
11074 &`>= `& greater or equal
11076 &`<= `& less or equal
11080 ${if >{$message_size}{10M} ...
11082 Note that the general negation operator provides for inequality testing. The
11083 two strings must take the form of optionally signed decimal integers,
11084 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
11085 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
11086 As a special case, the numerical value of an empty string is taken as
11089 In all cases, a relative comparator OP is testing if <&'string1'&> OP
11090 <&'string2'&>; the above example is checking if &$message_size$& is larger than
11091 10M, not if 10M is larger than &$message_size$&.
11094 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
11095 {*&<&'arg2'&>&*}...}*&
11096 .cindex "expansion" "calling an acl"
11097 .cindex "&%acl%&" "expansion condition"
11098 The name and zero to nine argument strings are first expanded separately. The expanded
11099 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
11100 Any unused are made empty. The variable &$acl_narg$& is set to the number of
11101 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
11102 and may use the variables; if another acl expansion is used the values
11103 are restored after it returns. If the ACL sets
11104 a value using a "message =" modifier the variable $value becomes
11105 the result of the expansion, otherwise it is empty.
11106 If the ACL returns accept the condition is true; if deny, false.
11107 If the ACL returns defer the result is a forced-fail.
11109 .vitem &*bool&~{*&<&'string'&>&*}*&
11110 .cindex "expansion" "boolean parsing"
11111 .cindex "&%bool%& expansion condition"
11112 This condition turns a string holding a true or false representation into
11113 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
11114 (case-insensitively); also integer numbers map to true if non-zero,
11116 An empty string is treated as false.
11117 Leading and trailing whitespace is ignored;
11118 thus a string consisting only of whitespace is false.
11119 All other string values will result in expansion failure.
11121 When combined with ACL variables, this expansion condition will let you
11122 make decisions in one place and act on those decisions in another place.
11125 ${if bool{$acl_m_privileged_sender} ...
11129 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
11130 .cindex "expansion" "boolean parsing"
11131 .cindex "&%bool_lax%& expansion condition"
11132 Like &%bool%&, this condition turns a string into a boolean state. But
11133 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
11134 loose definition that the Router &%condition%& option uses. The empty string
11135 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
11136 true. Leading and trailing whitespace is ignored.
11138 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
11140 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11141 .cindex "expansion" "encrypted comparison"
11142 .cindex "encrypted strings, comparing"
11143 .cindex "&%crypteq%& expansion condition"
11144 This condition is included in the Exim binary if it is built to support any
11145 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
11146 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
11147 included in the binary.
11149 The &%crypteq%& condition has two arguments. The first is encrypted and
11150 compared against the second, which is already encrypted. The second string may
11151 be in the LDAP form for storing encrypted strings, which starts with the
11152 encryption type in curly brackets, followed by the data. If the second string
11153 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
11154 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
11155 Typically this will be a field from a password file. An example of an encrypted
11156 string in LDAP form is:
11158 {md5}CY9rzUYh03PK3k6DJie09g==
11160 If such a string appears directly in an expansion, the curly brackets have to
11161 be quoted, because they are part of the expansion syntax. For example:
11163 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
11165 The following encryption types (whose names are matched case-independently) are
11170 .cindex "base64 encoding" "in encrypted password"
11171 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
11172 printable characters to compare with the remainder of the second string. If the
11173 length of the comparison string is 24, Exim assumes that it is base64 encoded
11174 (as in the above example). If the length is 32, Exim assumes that it is a
11175 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
11179 .cindex "SHA-1 hash"
11180 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
11181 printable characters to compare with the remainder of the second string. If the
11182 length of the comparison string is 28, Exim assumes that it is base64 encoded.
11183 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
11184 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
11187 .cindex "&[crypt()]&"
11188 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
11189 only the first eight characters of the password. However, in modern operating
11190 systems this is no longer true, and in many cases the entire password is used,
11191 whatever its length.
11194 .cindex "&[crypt16()]&"
11195 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
11196 use up to 16 characters of the password in some operating systems. Again, in
11197 modern operating systems, more characters may be used.
11199 Exim has its own version of &[crypt16()]&, which is just a double call to
11200 &[crypt()]&. For operating systems that have their own version, setting
11201 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
11202 operating system version instead of its own. This option is set by default in
11203 the OS-dependent &_Makefile_& for those operating systems that are known to
11204 support &[crypt16()]&.
11206 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
11207 it was not using the same algorithm as some operating systems' versions. It
11208 turns out that as well as &[crypt16()]& there is a function called
11209 &[bigcrypt()]& in some operating systems. This may or may not use the same
11210 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
11212 However, since there is now a move away from the traditional &[crypt()]&
11213 functions towards using SHA1 and other algorithms, tidying up this area of
11214 Exim is seen as very low priority.
11216 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
11217 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
11218 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
11219 default is &`{crypt}`&. Whatever the default, you can always use either
11220 function by specifying it explicitly in curly brackets.
11222 .vitem &*def:*&<&'variable&~name'&>
11223 .cindex "expansion" "checking for empty variable"
11224 .cindex "&%def%& expansion condition"
11225 The &%def%& condition must be followed by the name of one of the expansion
11226 variables defined in section &<<SECTexpvar>>&. The condition is true if the
11227 variable does not contain the empty string. For example:
11229 ${if def:sender_ident {from $sender_ident}}
11231 Note that the variable name is given without a leading &%$%& character. If the
11232 variable does not exist, the expansion fails.
11234 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
11235 &~&*def:h_*&<&'header&~name'&>&*:*&"
11236 .cindex "expansion" "checking header line existence"
11237 This condition is true if a message is being processed and the named header
11238 exists in the message. For example,
11240 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
11242 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
11243 the header name must be terminated by a colon if white space does not follow.
11245 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11246 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11247 .cindex "string" "comparison"
11248 .cindex "expansion" "string comparison"
11249 .cindex "&%eq%& expansion condition"
11250 .cindex "&%eqi%& expansion condition"
11251 The two substrings are first expanded. The condition is true if the two
11252 resulting strings are identical. For &%eq%& the comparison includes the case of
11253 letters, whereas for &%eqi%& the comparison is case-independent, where
11254 case is defined per the system C locale.
11256 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
11257 .cindex "expansion" "file existence test"
11258 .cindex "file" "existence test"
11259 .cindex "&%exists%&, expansion condition"
11260 The substring is first expanded and then interpreted as an absolute path. The
11261 condition is true if the named file (or directory) exists. The existence test
11262 is done by calling the &[stat()]& function. The use of the &%exists%& test in
11263 users' filter files may be locked out by the system administrator.
11265 .vitem &*first_delivery*&
11266 .cindex "delivery" "first"
11267 .cindex "first delivery"
11268 .cindex "expansion" "first delivery test"
11269 .cindex "&%first_delivery%& expansion condition"
11270 This condition, which has no data, is true during a message's first delivery
11271 attempt. It is false during any subsequent delivery attempts.
11274 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
11275 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
11276 .cindex "list" "iterative conditions"
11277 .cindex "expansion" "&*forall*& condition"
11278 .cindex "expansion" "&*forany*& condition"
11280 These conditions iterate over a list. The first argument is expanded to form
11281 the list. By default, the list separator is a colon, but it can be changed by
11282 the normal method (&<<SECTlistsepchange>>&).
11283 The second argument is interpreted as a condition that is to
11284 be applied to each item in the list in turn. During the interpretation of the
11285 condition, the current list item is placed in a variable called &$item$&.
11287 For &*forany*&, interpretation stops if the condition is true for any item, and
11288 the result of the whole condition is true. If the condition is false for all
11289 items in the list, the overall condition is false.
11291 For &*forall*&, interpretation stops if the condition is false for any item,
11292 and the result of the whole condition is false. If the condition is true for
11293 all items in the list, the overall condition is true.
11295 Note that negation of &*forany*& means that the condition must be false for all
11296 items for the overall condition to succeed, and negation of &*forall*& means
11297 that the condition must be false for at least one item. In this example, the
11298 list separator is changed to a comma:
11300 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
11302 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
11303 being processed, to enable these expansion items to be nested.
11305 To scan a named list, expand it with the &*listnamed*& operator.
11308 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11309 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11310 .cindex "string" "comparison"
11311 .cindex "expansion" "string comparison"
11312 .cindex "&%ge%& expansion condition"
11313 .cindex "&%gei%& expansion condition"
11314 The two substrings are first expanded. The condition is true if the first
11315 string is lexically greater than or equal to the second string. For &%ge%& the
11316 comparison includes the case of letters, whereas for &%gei%& the comparison is
11318 Case and collation order are defined per the system C locale.
11320 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11321 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11322 .cindex "string" "comparison"
11323 .cindex "expansion" "string comparison"
11324 .cindex "&%gt%& expansion condition"
11325 .cindex "&%gti%& expansion condition"
11326 The two substrings are first expanded. The condition is true if the first
11327 string is lexically greater than the second string. For &%gt%& the comparison
11328 includes the case of letters, whereas for &%gti%& the comparison is
11330 Case and collation order are defined per the system C locale.
11332 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11333 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11334 .cindex "string" "comparison"
11335 .cindex "list" "iterative conditions"
11336 Both strings are expanded; the second string is treated as a list of simple
11337 strings; if the first string is a member of the second, then the condition
11339 For the case-independent &%inlisti%& condition, case is defined per the system C locale.
11341 These are simpler to use versions of the more powerful &*forany*& condition.
11342 Examples, and the &*forany*& equivalents:
11344 ${if inlist{needle}{foo:needle:bar}}
11345 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11346 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11347 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11350 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11351 &*isip4&~{*&<&'string'&>&*}*& &&&
11352 &*isip6&~{*&<&'string'&>&*}*&
11353 .cindex "IP address" "testing string format"
11354 .cindex "string" "testing for IP address"
11355 .cindex "&%isip%& expansion condition"
11356 .cindex "&%isip4%& expansion condition"
11357 .cindex "&%isip6%& expansion condition"
11358 The substring is first expanded, and then tested to see if it has the form of
11359 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11360 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11362 For an IPv4 address, the test is for four dot-separated components, each of
11363 which consists of from one to three digits. For an IPv6 address, up to eight
11364 colon-separated components are permitted, each containing from one to four
11365 hexadecimal digits. There may be fewer than eight components if an empty
11366 component (adjacent colons) is present. Only one empty component is permitted.
11368 &*Note*&: The checks used to be just on the form of the address; actual numerical
11369 values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
11371 This is no longer the case.
11373 The main use of these tests is to distinguish between IP addresses and
11374 host names, or between IPv4 and IPv6 addresses. For example, you could use
11376 ${if isip4{$sender_host_address}...
11378 to test which IP version an incoming SMTP connection is using.
11380 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11381 .cindex "LDAP" "use for authentication"
11382 .cindex "expansion" "LDAP authentication test"
11383 .cindex "&%ldapauth%& expansion condition"
11384 This condition supports user authentication using LDAP. See section
11385 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11386 queries. For this use, the query must contain a user name and password. The
11387 query itself is not used, and can be empty. The condition is true if the
11388 password is not empty, and the user name and password are accepted by the LDAP
11389 server. An empty password is rejected without calling LDAP because LDAP binds
11390 with an empty password are considered anonymous regardless of the username, and
11391 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11392 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11396 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11397 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11398 .cindex "string" "comparison"
11399 .cindex "expansion" "string comparison"
11400 .cindex "&%le%& expansion condition"
11401 .cindex "&%lei%& expansion condition"
11402 The two substrings are first expanded. The condition is true if the first
11403 string is lexically less than or equal to the second string. For &%le%& the
11404 comparison includes the case of letters, whereas for &%lei%& the comparison is
11406 Case and collation order are defined per the system C locale.
11408 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11409 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11410 .cindex "string" "comparison"
11411 .cindex "expansion" "string comparison"
11412 .cindex "&%lt%& expansion condition"
11413 .cindex "&%lti%& expansion condition"
11414 The two substrings are first expanded. The condition is true if the first
11415 string is lexically less than the second string. For &%lt%& the comparison
11416 includes the case of letters, whereas for &%lti%& the comparison is
11418 Case and collation order are defined per the system C locale.
11421 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11422 .cindex "expansion" "regular expression comparison"
11423 .cindex "regular expressions" "match in expanded string"
11424 .cindex "&%match%& expansion condition"
11425 The two substrings are first expanded. The second is then treated as a regular
11426 expression and applied to the first. Because of the pre-expansion, if the
11427 regular expression contains dollar, or backslash characters, they must be
11428 escaped. Care must also be taken if the regular expression contains braces
11429 (curly brackets). A closing brace must be escaped so that it is not taken as a
11430 premature termination of <&'string2'&>. The easiest approach is to use the
11431 &`\N`& feature to disable expansion of the regular expression.
11434 ${if match {$local_part}{\N^\d{3}\N} ...
11436 If the whole expansion string is in double quotes, further escaping of
11437 backslashes is also required.
11439 The condition is true if the regular expression match succeeds.
11440 The regular expression is not required to begin with a circumflex
11441 metacharacter, but if there is no circumflex, the expression is not anchored,
11442 and it may match anywhere in the subject, not just at the start. If you want
11443 the pattern to match at the end of the subject, you must include the &`$`&
11444 metacharacter at an appropriate point.
11445 All character handling is done in bytes and is not UTF-8 aware,
11446 but we might change this in a future Exim release.
11448 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11449 At the start of an &%if%& expansion the values of the numeric variable
11450 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11451 succeeds causes them to be reset to the substrings of that condition and they
11452 will have these values during the expansion of the success string. At the end
11453 of the &%if%& expansion, the previous values are restored. After testing a
11454 combination of conditions using &%or%&, the subsequent values of the numeric
11455 variables are those of the condition that succeeded.
11457 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11458 .cindex "&%match_address%& expansion condition"
11459 See &*match_local_part*&.
11461 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11462 .cindex "&%match_domain%& expansion condition"
11463 See &*match_local_part*&.
11465 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11466 .cindex "&%match_ip%& expansion condition"
11467 This condition matches an IP address to a list of IP address patterns. It must
11468 be followed by two argument strings. The first (after expansion) must be an IP
11469 address or an empty string. The second (not expanded) is a restricted host
11470 list that can match only an IP address, not a host name. For example:
11472 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
11474 The specific types of host list item that are permitted in the list are:
11477 An IP address, optionally with a CIDR mask.
11479 A single asterisk, which matches any IP address.
11481 An empty item, which matches only if the IP address is empty. This could be
11482 useful for testing for a locally submitted message or one from specific hosts
11483 in a single test such as
11484 . ==== As this is a nested list, any displays it contains must be indented
11485 . ==== as otherwise they are too far to the left. This comment applies to
11486 . ==== the use of xmlto plus fop. There's no problem when formatting with
11487 . ==== sdop, with or without the extra indent.
11489 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
11491 where the first item in the list is the empty string.
11493 The item @[] matches any of the local host's interface addresses.
11495 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
11496 even if &`net-`& is not specified. There is never any attempt to turn the IP
11497 address into a host name. The most common type of linear search for
11498 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
11499 masks. For example:
11501 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
11503 It is of course possible to use other kinds of lookup, and in such a case, you
11504 do need to specify the &`net-`& prefix if you want to specify a specific
11505 address mask, for example:
11507 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
11509 However, unless you are combining a &%match_ip%& condition with others, it is
11510 just as easy to use the fact that a lookup is itself a condition, and write:
11512 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
11516 Note that <&'string2'&> is not itself subject to string expansion, unless
11517 Exim was built with the EXPAND_LISTMATCH_RHS option.
11519 Consult section &<<SECThoslispatip>>& for further details of these patterns.
11521 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11522 .cindex "domain list" "in expansion condition"
11523 .cindex "address list" "in expansion condition"
11524 .cindex "local part" "list, in expansion condition"
11525 .cindex "&%match_local_part%& expansion condition"
11526 This condition, together with &%match_address%& and &%match_domain%&, make it
11527 possible to test domain, address, and local part lists within expansions. Each
11528 condition requires two arguments: an item and a list to match. A trivial
11531 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
11533 In each case, the second argument may contain any of the allowable items for a
11534 list of the appropriate type. Also, because the second argument
11535 is a standard form of list, it is possible to refer to a named list.
11536 Thus, you can use conditions like this:
11538 ${if match_domain{$domain}{+local_domains}{...
11540 .cindex "&`+caseful`&"
11541 For address lists, the matching starts off caselessly, but the &`+caseful`&
11542 item can be used, as in all address lists, to cause subsequent items to
11543 have their local parts matched casefully. Domains are always matched
11546 Note that <&'string2'&> is not itself subject to string expansion, unless
11547 Exim was built with the EXPAND_LISTMATCH_RHS option.
11549 &*Note*&: Host lists are &'not'& supported in this way. This is because
11550 hosts have two identities: a name and an IP address, and it is not clear
11551 how to specify cleanly how such a test would work. However, IP addresses can be
11552 matched using &%match_ip%&.
11554 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
11555 .cindex "PAM authentication"
11556 .cindex "AUTH" "with PAM"
11557 .cindex "Solaris" "PAM support"
11558 .cindex "expansion" "PAM authentication test"
11559 .cindex "&%pam%& expansion condition"
11560 &'Pluggable Authentication Modules'&
11561 (&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
11562 available in the latest releases of Solaris and in some GNU/Linux
11563 distributions. The Exim support, which is intended for use in conjunction with
11564 the SMTP AUTH command, is available only if Exim is compiled with
11568 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
11569 in some releases of GNU/Linux &%-ldl%& is also needed.
11571 The argument string is first expanded, and the result must be a
11572 colon-separated list of strings. Leading and trailing white space is ignored.
11573 The PAM module is initialized with the service name &"exim"& and the user name
11574 taken from the first item in the colon-separated data string (<&'string1'&>).
11575 The remaining items in the data string are passed over in response to requests
11576 from the authentication function. In the simple case there will only be one
11577 request, for a password, so the data consists of just two strings.
11579 There can be problems if any of the strings are permitted to contain colon
11580 characters. In the usual way, these have to be doubled to avoid being taken as
11581 separators. If the data is being inserted from a variable, the &%sg%& expansion
11582 item can be used to double any existing colons. For example, the configuration
11583 of a LOGIN authenticator might contain this setting:
11585 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
11587 For a PLAIN authenticator you could use:
11589 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
11591 In some operating systems, PAM authentication can be done only from a process
11592 running as root. Since Exim is running as the Exim user when receiving
11593 messages, this means that PAM cannot be used directly in those systems.
11594 . --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that
11597 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
11598 .cindex "&'pwcheck'& daemon"
11600 .cindex "expansion" "&'pwcheck'& authentication test"
11601 .cindex "&%pwcheck%& expansion condition"
11602 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
11603 This is one way of making it possible for passwords to be checked by a process
11604 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
11605 deprecated. Its replacement is &'saslauthd'& (see below).
11607 The pwcheck support is not included in Exim by default. You need to specify
11608 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
11609 building Exim. For example:
11611 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
11613 You do not need to install the full Cyrus software suite in order to use
11614 the pwcheck daemon. You can compile and install just the daemon alone
11615 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
11616 access to the &_/var/pwcheck_& directory.
11618 The &%pwcheck%& condition takes one argument, which must be the user name and
11619 password, separated by a colon. For example, in a LOGIN authenticator
11620 configuration, you might have this:
11622 server_condition = ${if pwcheck{$auth1:$auth2}}
11624 Again, for a PLAIN authenticator configuration, this would be:
11626 server_condition = ${if pwcheck{$auth2:$auth3}}
11628 .vitem &*queue_running*&
11629 .cindex "queue runner" "detecting when delivering from"
11630 .cindex "expansion" "queue runner test"
11631 .cindex "&%queue_running%& expansion condition"
11632 This condition, which has no data, is true during delivery attempts that are
11633 initiated by queue runner processes, and false otherwise.
11636 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
11638 .cindex "expansion" "Radius authentication"
11639 .cindex "&%radius%& expansion condition"
11640 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
11641 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
11642 the Radius client configuration file in order to build Exim with Radius
11645 With just that one setting, Exim expects to be linked with the &%radiusclient%&
11646 library, using the original API. If you are using release 0.4.0 or later of
11647 this library, you need to set
11649 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
11651 in &_Local/Makefile_& when building Exim. You can also link Exim with the
11652 &%libradius%& library that comes with FreeBSD. To do this, set
11654 RADIUS_LIB_TYPE=RADLIB
11656 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
11657 You may also have to supply a suitable setting in EXTRALIBS so that the
11658 Radius library can be found when Exim is linked.
11660 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
11661 Radius client library, which calls the Radius server. The condition is true if
11662 the authentication is successful. For example:
11664 server_condition = ${if radius{<arguments>}}
11668 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
11669 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
11670 .cindex "&'saslauthd'& daemon"
11672 .cindex "expansion" "&'saslauthd'& authentication test"
11673 .cindex "&%saslauthd%& expansion condition"
11674 This condition supports user authentication using the Cyrus &'saslauthd'&
11675 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
11676 Using this daemon is one way of making it possible for passwords to be checked
11677 by a process that is not running as root.
11679 The saslauthd support is not included in Exim by default. You need to specify
11680 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
11681 building Exim. For example:
11683 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
11685 You do not need to install the full Cyrus software suite in order to use
11686 the saslauthd daemon. You can compile and install just the daemon alone
11687 from the Cyrus SASL library.
11689 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
11690 two are mandatory. For example:
11692 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
11694 The service and the realm are optional (which is why the arguments are enclosed
11695 in their own set of braces). For details of the meaning of the service and
11696 realm, and how to run the daemon, consult the Cyrus documentation.
11701 .section "Combining expansion conditions" "SECID84"
11702 .cindex "expansion" "combining conditions"
11703 Several conditions can be tested at once by combining them using the &%and%&
11704 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
11705 conditions on their own, and precede their lists of sub-conditions. Each
11706 sub-condition must be enclosed in braces within the overall braces that contain
11707 the list. No repetition of &%if%& is used.
11711 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11712 .cindex "&""or""& expansion condition"
11713 .cindex "expansion" "&""or""& of conditions"
11714 The sub-conditions are evaluated from left to right. The condition is true if
11715 any one of the sub-conditions is true.
11718 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
11720 When a true sub-condition is found, the following ones are parsed but not
11721 evaluated. If there are several &"match"& sub-conditions the values of the
11722 numeric variables afterwards are taken from the first one that succeeds.
11724 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11725 .cindex "&""and""& expansion condition"
11726 .cindex "expansion" "&""and""& of conditions"
11727 The sub-conditions are evaluated from left to right. The condition is true if
11728 all of the sub-conditions are true. If there are several &"match"&
11729 sub-conditions, the values of the numeric variables afterwards are taken from
11730 the last one. When a false sub-condition is found, the following ones are
11731 parsed but not evaluated.
11733 .ecindex IIDexpcond
11738 .section "Expansion variables" "SECTexpvar"
11739 .cindex "expansion" "variables, list of"
11740 This section contains an alphabetical list of all the expansion variables. Some
11741 of them are available only when Exim is compiled with specific options such as
11742 support for TLS or the content scanning extension.
11745 .vitem "&$0$&, &$1$&, etc"
11746 .cindex "numerical variables (&$1$& &$2$& etc)"
11747 When a &%match%& expansion condition succeeds, these variables contain the
11748 captured substrings identified by the regular expression during subsequent
11749 processing of the success string of the containing &%if%& expansion item.
11750 In the expansion condition case
11751 they do not retain their values afterwards; in fact, their previous
11752 values are restored at the end of processing an &%if%& item. The numerical
11753 variables may also be set externally by some other matching process which
11754 precedes the expansion of the string. For example, the commands available in
11755 Exim filter files include an &%if%& command with its own regular expression
11756 matching condition.
11758 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
11759 Within an acl condition, expansion condition or expansion item
11760 any arguments are copied to these variables,
11761 any unused variables being made empty.
11763 .vitem "&$acl_c...$&"
11764 Values can be placed in these variables by the &%set%& modifier in an ACL. They
11765 can be given any name that starts with &$acl_c$& and is at least six characters
11766 long, but the sixth character must be either a digit or an underscore. For
11767 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
11768 variables persist throughout the lifetime of an SMTP connection. They can be
11769 used to pass information between ACLs and between different invocations of the
11770 same ACL. When a message is received, the values of these variables are saved
11771 with the message, and can be accessed by filters, routers, and transports
11772 during subsequent delivery.
11774 .vitem "&$acl_m...$&"
11775 These variables are like the &$acl_c...$& variables, except that their values
11776 are reset after a message has been received. Thus, if several messages are
11777 received in one SMTP connection, &$acl_m...$& values are not passed on from one
11778 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
11779 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
11780 message is received, the values of these variables are saved with the message,
11781 and can be accessed by filters, routers, and transports during subsequent
11784 .vitem &$acl_narg$&
11785 Within an acl condition, expansion condition or expansion item
11786 this variable has the number of arguments.
11788 .vitem &$acl_verify_message$&
11789 .vindex "&$acl_verify_message$&"
11790 After an address verification has failed, this variable contains the failure
11791 message. It retains its value for use in subsequent modifiers. The message can
11792 be preserved by coding like this:
11794 warn !verify = sender
11795 set acl_m0 = $acl_verify_message
11797 You can use &$acl_verify_message$& during the expansion of the &%message%& or
11798 &%log_message%& modifiers, to include information about the verification
11801 .vitem &$address_data$&
11802 .vindex "&$address_data$&"
11803 This variable is set by means of the &%address_data%& option in routers. The
11804 value then remains with the address while it is processed by subsequent routers
11805 and eventually a transport. If the transport is handling multiple addresses,
11806 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
11807 for more details. &*Note*&: The contents of &$address_data$& are visible in
11810 If &$address_data$& is set when the routers are called from an ACL to verify
11811 a recipient address, the final value is still in the variable for subsequent
11812 conditions and modifiers of the ACL statement. If routing the address caused it
11813 to be redirected to just one address, the child address is also routed as part
11814 of the verification, and in this case the final value of &$address_data$& is
11815 from the child's routing.
11817 If &$address_data$& is set when the routers are called from an ACL to verify a
11818 sender address, the final value is also preserved, but this time in
11819 &$sender_address_data$&, to distinguish it from data from a recipient
11822 In both cases (recipient and sender verification), the value does not persist
11823 after the end of the current ACL statement. If you want to preserve
11824 these values for longer, you can save them in ACL variables.
11826 .vitem &$address_file$&
11827 .vindex "&$address_file$&"
11828 When, as a result of aliasing, forwarding, or filtering, a message is directed
11829 to a specific file, this variable holds the name of the file when the transport
11830 is running. At other times, the variable is empty. For example, using the
11831 default configuration, if user &%r2d2%& has a &_.forward_& file containing
11833 /home/r2d2/savemail
11835 then when the &(address_file)& transport is running, &$address_file$&
11836 contains the text string &`/home/r2d2/savemail`&.
11837 .cindex "Sieve filter" "value of &$address_file$&"
11838 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
11839 then up to the transport configuration to generate an appropriate absolute path
11840 to the relevant file.
11842 .vitem &$address_pipe$&
11843 .vindex "&$address_pipe$&"
11844 When, as a result of aliasing or forwarding, a message is directed to a pipe,
11845 this variable holds the pipe command when the transport is running.
11847 .vitem "&$auth1$& &-- &$auth3$&"
11848 .vindex "&$auth1$&, &$auth2$&, etc"
11849 These variables are used in SMTP authenticators (see chapters
11850 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
11852 .vitem &$authenticated_id$&
11853 .cindex "authentication" "id"
11854 .vindex "&$authenticated_id$&"
11855 When a server successfully authenticates a client it may be configured to
11856 preserve some of the authentication information in the variable
11857 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
11858 user/password authenticator configuration might preserve the user name for use
11859 in the routers. Note that this is not the same information that is saved in
11860 &$sender_host_authenticated$&.
11862 When a message is submitted locally (that is, not over a TCP connection)
11863 the value of &$authenticated_id$& is normally the login name of the calling
11864 process. However, a trusted user can override this by means of the &%-oMai%&
11865 command line option.
11866 This second case also sets up information used by the
11867 &$authresults$& expansion item.
11869 .vitem &$authenticated_fail_id$&
11870 .cindex "authentication" "fail" "id"
11871 .vindex "&$authenticated_fail_id$&"
11872 When an authentication attempt fails, the variable &$authenticated_fail_id$&
11873 will contain the failed authentication id. If more than one authentication
11874 id is attempted, it will contain only the last one. The variable is
11875 available for processing in the ACL's, generally the quit or notquit ACL.
11876 A message to a local recipient could still be accepted without requiring
11877 authentication, which means this variable could also be visible in all of
11881 .vitem &$authenticated_sender$&
11882 .cindex "sender" "authenticated"
11883 .cindex "authentication" "sender"
11884 .cindex "AUTH" "on MAIL command"
11885 .vindex "&$authenticated_sender$&"
11886 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
11887 SMTP MAIL command if it believes the sender is sufficiently trusted, as
11888 described in section &<<SECTauthparamail>>&. Unless the data is the string
11889 &"<>"&, it is set as the authenticated sender of the message, and the value is
11890 available during delivery in the &$authenticated_sender$& variable. If the
11891 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
11893 .vindex "&$qualify_domain$&"
11894 When a message is submitted locally (that is, not over a TCP connection), the
11895 value of &$authenticated_sender$& is an address constructed from the login
11896 name of the calling process and &$qualify_domain$&, except that a trusted user
11897 can override this by means of the &%-oMas%& command line option.
11900 .vitem &$authentication_failed$&
11901 .cindex "authentication" "failure"
11902 .vindex "&$authentication_failed$&"
11903 This variable is set to &"1"& in an Exim server if a client issues an AUTH
11904 command that does not succeed. Otherwise it is set to &"0"&. This makes it
11905 possible to distinguish between &"did not try to authenticate"&
11906 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
11907 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
11908 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
11909 negative response to an AUTH command, including (for example) an attempt to use
11910 an undefined mechanism.
11912 .vitem &$av_failed$&
11913 .cindex "content scanning" "AV scanner failure"
11914 This variable is available when Exim is compiled with the content-scanning
11915 extension. It is set to &"0"& by default, but will be set to &"1"& if any
11916 problem occurs with the virus scanner (specified by &%av_scanner%&) during
11917 the ACL malware condition.
11919 .vitem &$body_linecount$&
11920 .cindex "message body" "line count"
11921 .cindex "body of message" "line count"
11922 .vindex "&$body_linecount$&"
11923 When a message is being received or delivered, this variable contains the
11924 number of lines in the message's body. See also &$message_linecount$&.
11926 .vitem &$body_zerocount$&
11927 .cindex "message body" "binary zero count"
11928 .cindex "body of message" "binary zero count"
11929 .cindex "binary zero" "in message body"
11930 .vindex "&$body_zerocount$&"
11931 When a message is being received or delivered, this variable contains the
11932 number of binary zero bytes (ASCII NULs) in the message's body.
11934 .vitem &$bounce_recipient$&
11935 .vindex "&$bounce_recipient$&"
11936 This is set to the recipient address of a bounce message while Exim is creating
11937 it. It is useful if a customized bounce message text file is in use (see
11938 chapter &<<CHAPemsgcust>>&).
11940 .vitem &$bounce_return_size_limit$&
11941 .vindex "&$bounce_return_size_limit$&"
11942 This contains the value set in the &%bounce_return_size_limit%& option, rounded
11943 up to a multiple of 1000. It is useful when a customized error message text
11944 file is in use (see chapter &<<CHAPemsgcust>>&).
11946 .vitem &$caller_gid$&
11947 .cindex "gid (group id)" "caller"
11948 .vindex "&$caller_gid$&"
11949 The real group id under which the process that called Exim was running. This is
11950 not the same as the group id of the originator of a message (see
11951 &$originator_gid$&). If Exim re-execs itself, this variable in the new
11952 incarnation normally contains the Exim gid.
11954 .vitem &$caller_uid$&
11955 .cindex "uid (user id)" "caller"
11956 .vindex "&$caller_uid$&"
11957 The real user id under which the process that called Exim was running. This is
11958 not the same as the user id of the originator of a message (see
11959 &$originator_uid$&). If Exim re-execs itself, this variable in the new
11960 incarnation normally contains the Exim uid.
11962 .vitem &$callout_address$&
11963 .vindex "&$callout_address$&"
11964 After a callout for verification, spamd or malware daemon service, the
11965 address that was connected to.
11967 .vitem &$compile_number$&
11968 .vindex "&$compile_number$&"
11969 The building process for Exim keeps a count of the number
11970 of times it has been compiled. This serves to distinguish different
11971 compilations of the same version of Exim.
11973 .vitem &$config_dir$&
11974 .vindex "&$config_dir$&"
11975 The directory name of the main configuration file. That is, the content of
11976 &$config_file$& with the last component stripped. The value does not
11977 contain the trailing slash. If &$config_file$& does not contain a slash,
11978 &$config_dir$& is ".".
11980 .vitem &$config_file$&
11981 .vindex "&$config_file$&"
11982 The name of the main configuration file Exim is using.
11984 .vitem &$dkim_verify_status$&
11985 Results of DKIM verification.
11986 For details see section &<<SECDKIMVFY>>&.
11988 .vitem &$dkim_cur_signer$& &&&
11989 &$dkim_verify_reason$& &&&
11990 &$dkim_domain$& &&&
11991 &$dkim_identity$& &&&
11992 &$dkim_selector$& &&&
11994 &$dkim_canon_body$& &&&
11995 &$dkim_canon_headers$& &&&
11996 &$dkim_copiedheaders$& &&&
11997 &$dkim_bodylength$& &&&
11998 &$dkim_created$& &&&
11999 &$dkim_expires$& &&&
12000 &$dkim_headernames$& &&&
12001 &$dkim_key_testing$& &&&
12002 &$dkim_key_nosubdomains$& &&&
12003 &$dkim_key_srvtype$& &&&
12004 &$dkim_key_granularity$& &&&
12005 &$dkim_key_notes$& &&&
12006 &$dkim_key_length$&
12007 These variables are only available within the DKIM ACL.
12008 For details see section &<<SECDKIMVFY>>&.
12010 .vitem &$dkim_signers$&
12011 .vindex &$dkim_signers$&
12012 When a message has been received this variable contains
12013 a colon-separated list of signer domains and identities for the message.
12014 For details see section &<<SECDKIMVFY>>&.
12016 .vitem &$dnslist_domain$& &&&
12017 &$dnslist_matched$& &&&
12018 &$dnslist_text$& &&&
12020 .vindex "&$dnslist_domain$&"
12021 .vindex "&$dnslist_matched$&"
12022 .vindex "&$dnslist_text$&"
12023 .vindex "&$dnslist_value$&"
12024 .cindex "black list (DNS)"
12025 When a DNS (black) list lookup succeeds, these variables are set to contain
12026 the following data from the lookup: the list's domain name, the key that was
12027 looked up, the contents of any associated TXT record, and the value from the
12028 main A record. See section &<<SECID204>>& for more details.
12031 .vindex "&$domain$&"
12032 When an address is being routed, or delivered on its own, this variable
12033 contains the domain. Uppercase letters in the domain are converted into lower
12034 case for &$domain$&.
12036 Global address rewriting happens when a message is received, so the value of
12037 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
12038 is set during user filtering, but not during system filtering, because a
12039 message may have many recipients and the system filter is called just once.
12041 When more than one address is being delivered at once (for example, several
12042 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
12043 have the same domain. Transports can be restricted to handling only one domain
12044 at a time if the value of &$domain$& is required at transport time &-- this is
12045 the default for local transports. For further details of the environment in
12046 which local transports are run, see chapter &<<CHAPenvironment>>&.
12048 .oindex "&%delay_warning_condition%&"
12049 At the end of a delivery, if all deferred addresses have the same domain, it is
12050 set in &$domain$& during the expansion of &%delay_warning_condition%&.
12052 The &$domain$& variable is also used in some other circumstances:
12055 When an ACL is running for a RCPT command, &$domain$& contains the domain of
12056 the recipient address. The domain of the &'sender'& address is in
12057 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
12058 normally set during the running of the MAIL ACL. However, if the sender address
12059 is verified with a callout during the MAIL ACL, the sender domain is placed in
12060 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
12061 the &(smtp)& transport.
12064 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12065 &$domain$& contains the domain portion of the address that is being rewritten;
12066 it can be used in the expansion of the replacement address, for example, to
12067 rewrite domains by file lookup.
12070 With one important exception, whenever a domain list is being scanned,
12071 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
12072 a &%sender_domains%& condition in an ACL is being processed, the subject domain
12073 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
12074 that, in a RCPT ACL, the sender domain list can be dependent on the
12075 recipient domain (which is what is in &$domain$& at this time).
12078 .cindex "ETRN" "value of &$domain$&"
12079 .oindex "&%smtp_etrn_command%&"
12080 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
12081 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
12085 .vitem &$domain_data$&
12086 .vindex "&$domain_data$&"
12087 When the &%domains%& option on a router matches a domain by
12088 means of a lookup, the data read by the lookup is available during the running
12089 of the router as &$domain_data$&. In addition, if the driver routes the
12090 address to a transport, the value is available in that transport. If the
12091 transport is handling multiple addresses, the value from the first address is
12094 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
12095 domain by means of a lookup. The data read by the lookup is available during
12096 the rest of the ACL statement. In all other situations, this variable expands
12099 .vitem &$exim_gid$&
12100 .vindex "&$exim_gid$&"
12101 This variable contains the numerical value of the Exim group id.
12103 .vitem &$exim_path$&
12104 .vindex "&$exim_path$&"
12105 This variable contains the path to the Exim binary.
12107 .vitem &$exim_uid$&
12108 .vindex "&$exim_uid$&"
12109 This variable contains the numerical value of the Exim user id.
12111 .vitem &$exim_version$&
12112 .vindex "&$exim_version$&"
12113 This variable contains the version string of the Exim build.
12114 The first character is a major version number, currently 4.
12115 Then after a dot, the next group of digits is a minor version number.
12116 There may be other characters following the minor version.
12118 .vitem &$header_$&<&'name'&>
12119 This is not strictly an expansion variable. It is expansion syntax for
12120 inserting the message header line with the given name. Note that the name must
12121 be terminated by colon or white space, because it may contain a wide variety of
12122 characters. Note also that braces must &'not'& be used.
12123 See the full description in section &<<SECTexpansionitems>>& above.
12125 .vitem &$headers_added$&
12126 .vindex "&$headers_added$&"
12127 Within an ACL this variable contains the headers added so far by
12128 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
12129 The headers are a newline-separated list.
12133 When the &%check_local_user%& option is set for a router, the user's home
12134 directory is placed in &$home$& when the check succeeds. In particular, this
12135 means it is set during the running of users' filter files. A router may also
12136 explicitly set a home directory for use by a transport; this can be overridden
12137 by a setting on the transport itself.
12139 When running a filter test via the &%-bf%& option, &$home$& is set to the value
12140 of the environment variable HOME, which is subject to the
12141 &%keep_environment%& and &%add_environment%& main config options.
12145 If a router assigns an address to a transport (any transport), and passes a
12146 list of hosts with the address, the value of &$host$& when the transport starts
12147 to run is the name of the first host on the list. Note that this applies both
12148 to local and remote transports.
12150 .cindex "transport" "filter"
12151 .cindex "filter" "transport filter"
12152 For the &(smtp)& transport, if there is more than one host, the value of
12153 &$host$& changes as the transport works its way through the list. In
12154 particular, when the &(smtp)& transport is expanding its options for encryption
12155 using TLS, or for specifying a transport filter (see chapter
12156 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
12159 When used in the client part of an authenticator configuration (see chapter
12160 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
12161 client is connected.
12164 .vitem &$host_address$&
12165 .vindex "&$host_address$&"
12166 This variable is set to the remote host's IP address whenever &$host$& is set
12167 for a remote connection. It is also set to the IP address that is being checked
12168 when the &%ignore_target_hosts%& option is being processed.
12170 .vitem &$host_data$&
12171 .vindex "&$host_data$&"
12172 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
12173 result of the lookup is made available in the &$host_data$& variable. This
12174 allows you, for example, to do things like this:
12176 deny hosts = net-lsearch;/some/file
12177 message = $host_data
12179 .vitem &$host_lookup_deferred$&
12180 .cindex "host name" "lookup, failure of"
12181 .vindex "&$host_lookup_deferred$&"
12182 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
12183 message comes from a remote host and there is an attempt to look up the host's
12184 name from its IP address, and the attempt is not successful, one of these
12185 variables is set to &"1"&.
12188 If the lookup receives a definite negative response (for example, a DNS lookup
12189 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
12192 If there is any kind of problem during the lookup, such that Exim cannot
12193 tell whether or not the host name is defined (for example, a timeout for a DNS
12194 lookup), &$host_lookup_deferred$& is set to &"1"&.
12197 Looking up a host's name from its IP address consists of more than just a
12198 single reverse lookup. Exim checks that a forward lookup of at least one of the
12199 names it receives from a reverse lookup yields the original IP address. If this
12200 is not the case, Exim does not accept the looked up name(s), and
12201 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
12202 IP address (for example, the existence of a PTR record in the DNS) is not
12203 sufficient on its own for the success of a host name lookup. If the reverse
12204 lookup succeeds, but there is a lookup problem such as a timeout when checking
12205 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
12206 &"1"&. See also &$sender_host_name$&.
12208 .cindex authentication "expansion item"
12209 Performing these checks sets up information used by the
12210 &$authresults$& expansion item.
12213 .vitem &$host_lookup_failed$&
12214 .vindex "&$host_lookup_failed$&"
12215 See &$host_lookup_deferred$&.
12217 .vitem &$host_port$&
12218 .vindex "&$host_port$&"
12219 This variable is set to the remote host's TCP port whenever &$host$& is set
12220 for an outbound connection.
12222 .vitem &$initial_cwd$&
12223 .vindex "&$initial_cwd$&
12224 This variable contains the full path name of the initial working
12225 directory of the current Exim process. This may differ from the current
12226 working directory, as Exim changes this to "/" during early startup, and
12227 to &$spool_directory$& later.
12230 .vindex "&$inode$&"
12231 The only time this variable is set is while expanding the &%directory_file%&
12232 option in the &(appendfile)& transport. The variable contains the inode number
12233 of the temporary file which is about to be renamed. It can be used to construct
12234 a unique name for the file.
12236 .vitem &$interface_address$&
12237 .vindex "&$interface_address$&"
12238 This is an obsolete name for &$received_ip_address$&.
12240 .vitem &$interface_port$&
12241 .vindex "&$interface_port$&"
12242 This is an obsolete name for &$received_port$&.
12246 This variable is used during the expansion of &*forall*& and &*forany*&
12247 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
12248 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
12252 .vindex "&$ldap_dn$&"
12253 This variable, which is available only when Exim is compiled with LDAP support,
12254 contains the DN from the last entry in the most recently successful LDAP
12257 .vitem &$load_average$&
12258 .vindex "&$load_average$&"
12259 This variable contains the system load average, multiplied by 1000 so that it
12260 is an integer. For example, if the load average is 0.21, the value of the
12261 variable is 210. The value is recomputed every time the variable is referenced.
12263 .vitem &$local_part$&
12264 .vindex "&$local_part$&"
12265 When an address is being routed, or delivered on its own, this
12266 variable contains the local part. When a number of addresses are being
12267 delivered together (for example, multiple RCPT commands in an SMTP
12268 session), &$local_part$& is not set.
12270 Global address rewriting happens when a message is received, so the value of
12271 &$local_part$& during routing and delivery is the value after rewriting.
12272 &$local_part$& is set during user filtering, but not during system filtering,
12273 because a message may have many recipients and the system filter is called just
12276 .vindex "&$local_part_prefix$&"
12277 .vindex "&$local_part_suffix$&"
12278 .cindex affix variables
12279 If a local part prefix or suffix has been recognized, it is not included in the
12280 value of &$local_part$& during routing and subsequent delivery. The values of
12281 any prefix or suffix are in &$local_part_prefix$& and
12282 &$local_part_suffix$&, respectively.
12284 When a message is being delivered to a file, pipe, or autoreply transport as a
12285 result of aliasing or forwarding, &$local_part$& is set to the local part of
12286 the parent address, not to the filename or command (see &$address_file$& and
12289 When an ACL is running for a RCPT command, &$local_part$& contains the
12290 local part of the recipient address.
12292 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12293 &$local_part$& contains the local part of the address that is being rewritten;
12294 it can be used in the expansion of the replacement address, for example.
12296 In all cases, all quoting is removed from the local part. For example, for both
12299 "abc:xyz"@test.example
12300 abc\:xyz@test.example
12302 the value of &$local_part$& is
12306 If you use &$local_part$& to create another address, you should always wrap it
12307 inside a quoting operator. For example, in a &(redirect)& router you could
12310 data = ${quote_local_part:$local_part}@new.domain.example
12312 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
12313 to process local parts in a case-dependent manner in a router, you can set the
12314 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
12316 .vitem &$local_part_data$&
12317 .vindex "&$local_part_data$&"
12318 When the &%local_parts%& option on a router matches a local part by means of a
12319 lookup, the data read by the lookup is available during the running of the
12320 router as &$local_part_data$&. In addition, if the driver routes the address
12321 to a transport, the value is available in that transport. If the transport is
12322 handling multiple addresses, the value from the first address is used.
12324 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
12325 matches a local part by means of a lookup. The data read by the lookup is
12326 available during the rest of the ACL statement. In all other situations, this
12327 variable expands to nothing.
12329 .vitem &$local_part_prefix$&
12330 .vindex "&$local_part_prefix$&"
12331 .cindex affix variables
12332 When an address is being routed or delivered, and a
12333 specific prefix for the local part was recognized, it is available in this
12334 variable, having been removed from &$local_part$&.
12336 .vitem &$local_part_suffix$&
12337 .vindex "&$local_part_suffix$&"
12338 When an address is being routed or delivered, and a
12339 specific suffix for the local part was recognized, it is available in this
12340 variable, having been removed from &$local_part$&.
12342 .vitem &$local_scan_data$&
12343 .vindex "&$local_scan_data$&"
12344 This variable contains the text returned by the &[local_scan()]& function when
12345 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
12347 .vitem &$local_user_gid$&
12348 .vindex "&$local_user_gid$&"
12349 See &$local_user_uid$&.
12351 .vitem &$local_user_uid$&
12352 .vindex "&$local_user_uid$&"
12353 This variable and &$local_user_gid$& are set to the uid and gid after the
12354 &%check_local_user%& router precondition succeeds. This means that their values
12355 are available for the remaining preconditions (&%senders%&, &%require_files%&,
12356 and &%condition%&), for the &%address_data%& expansion, and for any
12357 router-specific expansions. At all other times, the values in these variables
12358 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
12360 .vitem &$localhost_number$&
12361 .vindex "&$localhost_number$&"
12362 This contains the expanded value of the
12363 &%localhost_number%& option. The expansion happens after the main options have
12366 .vitem &$log_inodes$&
12367 .vindex "&$log_inodes$&"
12368 The number of free inodes in the disk partition where Exim's
12369 log files are being written. The value is recalculated whenever the variable is
12370 referenced. If the relevant file system does not have the concept of inodes,
12371 the value of is -1. See also the &%check_log_inodes%& option.
12373 .vitem &$log_space$&
12374 .vindex "&$log_space$&"
12375 The amount of free space (as a number of kilobytes) in the disk
12376 partition where Exim's log files are being written. The value is recalculated
12377 whenever the variable is referenced. If the operating system does not have the
12378 ability to find the amount of free space (only true for experimental systems),
12379 the space value is -1. See also the &%check_log_space%& option.
12382 .vitem &$lookup_dnssec_authenticated$&
12383 .vindex "&$lookup_dnssec_authenticated$&"
12384 This variable is set after a DNS lookup done by
12385 a dnsdb lookup expansion, dnslookup router or smtp transport.
12386 .cindex "DNS" "DNSSEC"
12387 It will be empty if &(DNSSEC)& was not requested,
12388 &"no"& if the result was not labelled as authenticated data
12389 and &"yes"& if it was.
12390 Results that are labelled as authoritative answer that match
12391 the &%dns_trust_aa%& configuration variable count also
12392 as authenticated data.
12394 .vitem &$mailstore_basename$&
12395 .vindex "&$mailstore_basename$&"
12396 This variable is set only when doing deliveries in &"mailstore"& format in the
12397 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
12398 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
12399 contains the basename of the files that are being written, that is, the name
12400 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
12403 .vitem &$malware_name$&
12404 .vindex "&$malware_name$&"
12405 This variable is available when Exim is compiled with the
12406 content-scanning extension. It is set to the name of the virus that was found
12407 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12409 .vitem &$max_received_linelength$&
12410 .vindex "&$max_received_linelength$&"
12411 .cindex "maximum" "line length"
12412 .cindex "line length" "maximum"
12413 This variable contains the number of bytes in the longest line that was
12414 received as part of the message, not counting the line termination
12416 It is not valid if the &%spool_files_wireformat%& option is used.
12418 .vitem &$message_age$&
12419 .cindex "message" "age of"
12420 .vindex "&$message_age$&"
12421 This variable is set at the start of a delivery attempt to contain the number
12422 of seconds since the message was received. It does not change during a single
12425 .vitem &$message_body$&
12426 .cindex "body of message" "expansion variable"
12427 .cindex "message body" "in expansion"
12428 .cindex "binary zero" "in message body"
12429 .vindex "&$message_body$&"
12430 .oindex "&%message_body_visible%&"
12431 This variable contains the initial portion of a message's body while it is
12432 being delivered, and is intended mainly for use in filter files. The maximum
12433 number of characters of the body that are put into the variable is set by the
12434 &%message_body_visible%& configuration option; the default is 500.
12436 .oindex "&%message_body_newlines%&"
12437 By default, newlines are converted into spaces in &$message_body$&, to make it
12438 easier to search for phrases that might be split over a line break. However,
12439 this can be disabled by setting &%message_body_newlines%& to be true. Binary
12440 zeros are always converted into spaces.
12442 .vitem &$message_body_end$&
12443 .cindex "body of message" "expansion variable"
12444 .cindex "message body" "in expansion"
12445 .vindex "&$message_body_end$&"
12446 This variable contains the final portion of a message's
12447 body while it is being delivered. The format and maximum size are as for
12450 .vitem &$message_body_size$&
12451 .cindex "body of message" "size"
12452 .cindex "message body" "size"
12453 .vindex "&$message_body_size$&"
12454 When a message is being delivered, this variable contains the size of the body
12455 in bytes. The count starts from the character after the blank line that
12456 separates the body from the header. Newlines are included in the count. See
12457 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
12459 If the spool file is wireformat
12460 (see the &%spool_files_wireformat%& main option)
12461 the CRLF line-terminators are included in the count.
12463 .vitem &$message_exim_id$&
12464 .vindex "&$message_exim_id$&"
12465 When a message is being received or delivered, this variable contains the
12466 unique message id that is generated and used by Exim to identify the message.
12467 An id is not created for a message until after its header has been successfully
12468 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
12469 line; it is the local id that Exim assigns to the message, for example:
12470 &`1BXTIK-0001yO-VA`&.
12472 .vitem &$message_headers$&
12473 .vindex &$message_headers$&
12474 This variable contains a concatenation of all the header lines when a message
12475 is being processed, except for lines added by routers or transports. The header
12476 lines are separated by newline characters. Their contents are decoded in the
12477 same way as a header line that is inserted by &%bheader%&.
12479 .vitem &$message_headers_raw$&
12480 .vindex &$message_headers_raw$&
12481 This variable is like &$message_headers$& except that no processing of the
12482 contents of header lines is done.
12484 .vitem &$message_id$&
12485 This is an old name for &$message_exim_id$&. It is now deprecated.
12487 .vitem &$message_linecount$&
12488 .vindex "&$message_linecount$&"
12489 This variable contains the total number of lines in the header and body of the
12490 message. Compare &$body_linecount$&, which is the count for the body only.
12491 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
12492 number of lines received. Before delivery happens (that is, before filters,
12493 routers, and transports run) the count is increased to include the
12494 &'Received:'& header line that Exim standardly adds, and also any other header
12495 lines that are added by ACLs. The blank line that separates the message header
12496 from the body is not counted.
12498 As with the special case of &$message_size$&, during the expansion of the
12499 appendfile transport's maildir_tag option in maildir format, the value of
12500 &$message_linecount$& is the precise size of the number of newlines in the
12501 file that has been written (minus one for the blank line between the
12502 header and the body).
12504 Here is an example of the use of this variable in a DATA ACL:
12506 deny message = Too many lines in message header
12508 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
12510 In the MAIL and RCPT ACLs, the value is zero because at that stage the
12511 message has not yet been received.
12513 This variable is not valid if the &%spool_files_wireformat%& option is used.
12515 .vitem &$message_size$&
12516 .cindex "size" "of message"
12517 .cindex "message" "size"
12518 .vindex "&$message_size$&"
12519 When a message is being processed, this variable contains its size in bytes. In
12520 most cases, the size includes those headers that were received with the
12521 message, but not those (such as &'Envelope-to:'&) that are added to individual
12522 deliveries as they are written. However, there is one special case: during the
12523 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
12524 doing a delivery in maildir format, the value of &$message_size$& is the
12525 precise size of the file that has been written. See also
12526 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
12528 .cindex "RCPT" "value of &$message_size$&"
12529 While running a per message ACL (mail/rcpt/predata), &$message_size$&
12530 contains the size supplied on the MAIL command, or -1 if no size was given. The
12531 value may not, of course, be truthful.
12533 .vitem &$mime_$&&'xxx'&
12534 A number of variables whose names start with &$mime$& are
12535 available when Exim is compiled with the content-scanning extension. For
12536 details, see section &<<SECTscanmimepart>>&.
12538 .vitem "&$n0$& &-- &$n9$&"
12539 These variables are counters that can be incremented by means
12540 of the &%add%& command in filter files.
12542 .vitem &$original_domain$&
12543 .vindex "&$domain$&"
12544 .vindex "&$original_domain$&"
12545 When a top-level address is being processed for delivery, this contains the
12546 same value as &$domain$&. However, if a &"child"& address (for example,
12547 generated by an alias, forward, or filter file) is being processed, this
12548 variable contains the domain of the original address (lower cased). This
12549 differs from &$parent_domain$& only when there is more than one level of
12550 aliasing or forwarding. When more than one address is being delivered in a
12551 single transport run, &$original_domain$& is not set.
12553 If a new address is created by means of a &%deliver%& command in a system
12554 filter, it is set up with an artificial &"parent"& address. This has the local
12555 part &'system-filter'& and the default qualify domain.
12557 .vitem &$original_local_part$&
12558 .vindex "&$local_part$&"
12559 .vindex "&$original_local_part$&"
12560 When a top-level address is being processed for delivery, this contains the
12561 same value as &$local_part$&, unless a prefix or suffix was removed from the
12562 local part, because &$original_local_part$& always contains the full local
12563 part. When a &"child"& address (for example, generated by an alias, forward, or
12564 filter file) is being processed, this variable contains the full local part of
12565 the original address.
12567 If the router that did the redirection processed the local part
12568 case-insensitively, the value in &$original_local_part$& is in lower case.
12569 This variable differs from &$parent_local_part$& only when there is more than
12570 one level of aliasing or forwarding. When more than one address is being
12571 delivered in a single transport run, &$original_local_part$& is not set.
12573 If a new address is created by means of a &%deliver%& command in a system
12574 filter, it is set up with an artificial &"parent"& address. This has the local
12575 part &'system-filter'& and the default qualify domain.
12577 .vitem &$originator_gid$&
12578 .cindex "gid (group id)" "of originating user"
12579 .cindex "sender" "gid"
12580 .vindex "&$caller_gid$&"
12581 .vindex "&$originator_gid$&"
12582 This variable contains the value of &$caller_gid$& that was set when the
12583 message was received. For messages received via the command line, this is the
12584 gid of the sending user. For messages received by SMTP over TCP/IP, this is
12585 normally the gid of the Exim user.
12587 .vitem &$originator_uid$&
12588 .cindex "uid (user id)" "of originating user"
12589 .cindex "sender" "uid"
12590 .vindex "&$caller_uid$&"
12591 .vindex "&$originator_uid$&"
12592 The value of &$caller_uid$& that was set when the message was received. For
12593 messages received via the command line, this is the uid of the sending user.
12594 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
12597 .vitem &$parent_domain$&
12598 .vindex "&$parent_domain$&"
12599 This variable is similar to &$original_domain$& (see
12600 above), except that it refers to the immediately preceding parent address.
12602 .vitem &$parent_local_part$&
12603 .vindex "&$parent_local_part$&"
12604 This variable is similar to &$original_local_part$&
12605 (see above), except that it refers to the immediately preceding parent address.
12608 .cindex "pid (process id)" "of current process"
12610 This variable contains the current process id.
12612 .vitem &$pipe_addresses$&
12613 .cindex "filter" "transport filter"
12614 .cindex "transport" "filter"
12615 .vindex "&$pipe_addresses$&"
12616 This is not an expansion variable, but is mentioned here because the string
12617 &`$pipe_addresses`& is handled specially in the command specification for the
12618 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
12619 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
12620 It cannot be used in general expansion strings, and provokes an &"unknown
12621 variable"& error if encountered.
12623 .vitem &$primary_hostname$&
12624 .vindex "&$primary_hostname$&"
12625 This variable contains the value set by &%primary_hostname%& in the
12626 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
12627 a single-component name, Exim calls &[gethostbyname()]& (or
12628 &[getipnodebyname()]& where available) in an attempt to acquire a fully
12629 qualified host name. See also &$smtp_active_hostname$&.
12632 .vitem &$proxy_external_address$& &&&
12633 &$proxy_external_port$& &&&
12634 &$proxy_local_address$& &&&
12635 &$proxy_local_port$& &&&
12637 These variables are only available when built with Proxy Protocol
12639 For details see chapter &<<SECTproxyInbound>>&.
12641 .vitem &$prdr_requested$&
12642 .cindex "PRDR" "variable for"
12643 This variable is set to &"yes"& if PRDR was requested by the client for the
12644 current message, otherwise &"no"&.
12646 .vitem &$prvscheck_address$&
12647 This variable is used in conjunction with the &%prvscheck%& expansion item,
12648 which is described in sections &<<SECTexpansionitems>>& and
12649 &<<SECTverifyPRVS>>&.
12651 .vitem &$prvscheck_keynum$&
12652 This variable is used in conjunction with the &%prvscheck%& expansion item,
12653 which is described in sections &<<SECTexpansionitems>>& and
12654 &<<SECTverifyPRVS>>&.
12656 .vitem &$prvscheck_result$&
12657 This variable is used in conjunction with the &%prvscheck%& expansion item,
12658 which is described in sections &<<SECTexpansionitems>>& and
12659 &<<SECTverifyPRVS>>&.
12661 .vitem &$qualify_domain$&
12662 .vindex "&$qualify_domain$&"
12663 The value set for the &%qualify_domain%& option in the configuration file.
12665 .vitem &$qualify_recipient$&
12666 .vindex "&$qualify_recipient$&"
12667 The value set for the &%qualify_recipient%& option in the configuration file,
12668 or if not set, the value of &$qualify_domain$&.
12670 .vitem &$queue_name$&
12671 .vindex &$queue_name$&
12672 .cindex "named queues"
12673 .cindex queues named
12674 The name of the spool queue in use; empty for the default queue.
12676 .vitem &$rcpt_count$&
12677 .vindex "&$rcpt_count$&"
12678 When a message is being received by SMTP, this variable contains the number of
12679 RCPT commands received for the current message. If this variable is used in a
12680 RCPT ACL, its value includes the current command.
12682 .vitem &$rcpt_defer_count$&
12683 .vindex "&$rcpt_defer_count$&"
12684 .cindex "4&'xx'& responses" "count of"
12685 When a message is being received by SMTP, this variable contains the number of
12686 RCPT commands in the current message that have previously been rejected with a
12687 temporary (4&'xx'&) response.
12689 .vitem &$rcpt_fail_count$&
12690 .vindex "&$rcpt_fail_count$&"
12691 When a message is being received by SMTP, this variable contains the number of
12692 RCPT commands in the current message that have previously been rejected with a
12693 permanent (5&'xx'&) response.
12695 .vitem &$received_count$&
12696 .vindex "&$received_count$&"
12697 This variable contains the number of &'Received:'& header lines in the message,
12698 including the one added by Exim (so its value is always greater than zero). It
12699 is available in the DATA ACL, the non-SMTP ACL, and while routing and
12702 .vitem &$received_for$&
12703 .vindex "&$received_for$&"
12704 If there is only a single recipient address in an incoming message, this
12705 variable contains that address when the &'Received:'& header line is being
12706 built. The value is copied after recipient rewriting has happened, but before
12707 the &[local_scan()]& function is run.
12709 .vitem &$received_ip_address$&
12710 .vindex "&$received_ip_address$&"
12711 As soon as an Exim server starts processing an incoming TCP/IP connection, this
12712 variable is set to the address of the local IP interface, and &$received_port$&
12713 is set to the local port number. (The remote IP address and port are in
12714 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
12715 the port value is -1 unless it has been set using the &%-oMi%& command line
12718 As well as being useful in ACLs (including the &"connect"& ACL), these variable
12719 could be used, for example, to make the filename for a TLS certificate depend
12720 on which interface and/or port is being used for the incoming connection. The
12721 values of &$received_ip_address$& and &$received_port$& are saved with any
12722 messages that are received, thus making these variables available at delivery
12724 For outbound connections see &$sending_ip_address$&.
12726 .vitem &$received_port$&
12727 .vindex "&$received_port$&"
12728 See &$received_ip_address$&.
12730 .vitem &$received_protocol$&
12731 .vindex "&$received_protocol$&"
12732 When a message is being processed, this variable contains the name of the
12733 protocol by which it was received. Most of the names used by Exim are defined
12734 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
12735 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
12736 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
12737 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
12738 connection and the client was successfully authenticated.
12740 Exim uses the protocol name &"smtps"& for the case when encryption is
12741 automatically set up on connection without the use of STARTTLS (see
12742 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
12743 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
12744 where the client initially uses EHLO, sets up an encrypted connection using
12745 STARTTLS, and then uses HELO afterwards.
12747 The &%-oMr%& option provides a way of specifying a custom protocol name for
12748 messages that are injected locally by trusted callers. This is commonly used to
12749 identify messages that are being re-injected after some kind of scanning.
12751 .vitem &$received_time$&
12752 .vindex "&$received_time$&"
12753 This variable contains the date and time when the current message was received,
12754 as a number of seconds since the start of the Unix epoch.
12756 .vitem &$recipient_data$&
12757 .vindex "&$recipient_data$&"
12758 This variable is set after an indexing lookup success in an ACL &%recipients%&
12759 condition. It contains the data from the lookup, and the value remains set
12760 until the next &%recipients%& test. Thus, you can do things like this:
12762 &`require recipients = cdb*@;/some/file`&
12763 &`deny `&&'some further test involving'& &`$recipient_data`&
12765 &*Warning*&: This variable is set only when a lookup is used as an indexing
12766 method in the address list, using the semicolon syntax as in the example above.
12767 The variable is not set for a lookup that is used as part of the string
12768 expansion that all such lists undergo before being interpreted.
12770 .vitem &$recipient_verify_failure$&
12771 .vindex "&$recipient_verify_failure$&"
12772 In an ACL, when a recipient verification fails, this variable contains
12773 information about the failure. It is set to one of the following words:
12776 &"qualify"&: The address was unqualified (no domain), and the message
12777 was neither local nor came from an exempted host.
12780 &"route"&: Routing failed.
12783 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
12784 or before the MAIL command (that is, on initial connection, HELO, or
12788 &"recipient"&: The RCPT command in a callout was rejected.
12791 &"postmaster"&: The postmaster check in a callout was rejected.
12794 The main use of this variable is expected to be to distinguish between
12795 rejections of MAIL and rejections of RCPT.
12797 .vitem &$recipients$&
12798 .vindex "&$recipients$&"
12799 This variable contains a list of envelope recipients for a message. A comma and
12800 a space separate the addresses in the replacement text. However, the variable
12801 is not generally available, to prevent exposure of Bcc recipients in
12802 unprivileged users' filter files. You can use &$recipients$& only in these
12806 In a system filter file.
12808 In the ACLs associated with the DATA command and with non-SMTP messages, that
12809 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
12810 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
12811 &%acl_not_smtp_mime%&.
12813 From within a &[local_scan()]& function.
12817 .vitem &$recipients_count$&
12818 .vindex "&$recipients_count$&"
12819 When a message is being processed, this variable contains the number of
12820 envelope recipients that came with the message. Duplicates are not excluded
12821 from the count. While a message is being received over SMTP, the number
12822 increases for each accepted recipient. It can be referenced in an ACL.
12825 .vitem &$regex_match_string$&
12826 .vindex "&$regex_match_string$&"
12827 This variable is set to contain the matching regular expression after a
12828 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
12830 .vitem "&$regex1$&, &$regex2$&, etc"
12831 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
12832 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
12833 these variables contain the
12834 captured substrings identified by the regular expression.
12837 .vitem &$reply_address$&
12838 .vindex "&$reply_address$&"
12839 When a message is being processed, this variable contains the contents of the
12840 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
12841 contents of the &'From:'& header line. Apart from the removal of leading
12842 white space, the value is not processed in any way. In particular, no RFC 2047
12843 decoding or character code translation takes place.
12845 .vitem &$return_path$&
12846 .vindex "&$return_path$&"
12847 When a message is being delivered, this variable contains the return path &--
12848 the sender field that will be sent as part of the envelope. It is not enclosed
12849 in <> characters. At the start of routing an address, &$return_path$& has the
12850 same value as &$sender_address$&, but if, for example, an incoming message to a
12851 mailing list has been expanded by a router which specifies a different address
12852 for bounce messages, &$return_path$& subsequently contains the new bounce
12853 address, whereas &$sender_address$& always contains the original sender address
12854 that was received with the message. In other words, &$sender_address$& contains
12855 the incoming envelope sender, and &$return_path$& contains the outgoing
12858 .vitem &$return_size_limit$&
12859 .vindex "&$return_size_limit$&"
12860 This is an obsolete name for &$bounce_return_size_limit$&.
12862 .vitem &$router_name$&
12863 .cindex "router" "name"
12864 .cindex "name" "of router"
12865 .vindex "&$router_name$&"
12866 During the running of a router this variable contains its name.
12869 .cindex "return code" "from &%run%& expansion"
12870 .vindex "&$runrc$&"
12871 This variable contains the return code from a command that is run by the
12872 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
12873 assume the order in which option values are expanded, except for those
12874 preconditions whose order of testing is documented. Therefore, you cannot
12875 reliably expect to set &$runrc$& by the expansion of one option, and use it in
12878 .vitem &$self_hostname$&
12879 .oindex "&%self%&" "value of host name"
12880 .vindex "&$self_hostname$&"
12881 When an address is routed to a supposedly remote host that turns out to be the
12882 local host, what happens is controlled by the &%self%& generic router option.
12883 One of its values causes the address to be passed to another router. When this
12884 happens, &$self_hostname$& is set to the name of the local host that the
12885 original router encountered. In other circumstances its contents are null.
12887 .vitem &$sender_address$&
12888 .vindex "&$sender_address$&"
12889 When a message is being processed, this variable contains the sender's address
12890 that was received in the message's envelope. The case of letters in the address
12891 is retained, in both the local part and the domain. For bounce messages, the
12892 value of this variable is the empty string. See also &$return_path$&.
12894 .vitem &$sender_address_data$&
12895 .vindex "&$address_data$&"
12896 .vindex "&$sender_address_data$&"
12897 If &$address_data$& is set when the routers are called from an ACL to verify a
12898 sender address, the final value is preserved in &$sender_address_data$&, to
12899 distinguish it from data from a recipient address. The value does not persist
12900 after the end of the current ACL statement. If you want to preserve it for
12901 longer, you can save it in an ACL variable.
12903 .vitem &$sender_address_domain$&
12904 .vindex "&$sender_address_domain$&"
12905 The domain portion of &$sender_address$&.
12907 .vitem &$sender_address_local_part$&
12908 .vindex "&$sender_address_local_part$&"
12909 The local part portion of &$sender_address$&.
12911 .vitem &$sender_data$&
12912 .vindex "&$sender_data$&"
12913 This variable is set after a lookup success in an ACL &%senders%& condition or
12914 in a router &%senders%& option. It contains the data from the lookup, and the
12915 value remains set until the next &%senders%& test. Thus, you can do things like
12918 &`require senders = cdb*@;/some/file`&
12919 &`deny `&&'some further test involving'& &`$sender_data`&
12921 &*Warning*&: This variable is set only when a lookup is used as an indexing
12922 method in the address list, using the semicolon syntax as in the example above.
12923 The variable is not set for a lookup that is used as part of the string
12924 expansion that all such lists undergo before being interpreted.
12926 .vitem &$sender_fullhost$&
12927 .vindex "&$sender_fullhost$&"
12928 When a message is received from a remote host, this variable contains the host
12929 name and IP address in a single string. It ends with the IP address in square
12930 brackets, followed by a colon and a port number if the logging of ports is
12931 enabled. The format of the rest of the string depends on whether the host
12932 issued a HELO or EHLO SMTP command, and whether the host name was verified by
12933 looking up its IP address. (Looking up the IP address can be forced by the
12934 &%host_lookup%& option, independent of verification.) A plain host name at the
12935 start of the string is a verified host name; if this is not present,
12936 verification either failed or was not requested. A host name in parentheses is
12937 the argument of a HELO or EHLO command. This is omitted if it is identical to
12938 the verified host name or to the host's IP address in square brackets.
12940 .vitem &$sender_helo_dnssec$&
12941 .vindex "&$sender_helo_dnssec$&"
12942 This boolean variable is true if a successful HELO verification was
12943 .cindex "DNS" "DNSSEC"
12944 done using DNS information the resolver library stated was authenticated data.
12946 .vitem &$sender_helo_name$&
12947 .vindex "&$sender_helo_name$&"
12948 When a message is received from a remote host that has issued a HELO or EHLO
12949 command, the argument of that command is placed in this variable. It is also
12950 set if HELO or EHLO is used when a message is received using SMTP locally via
12951 the &%-bs%& or &%-bS%& options.
12953 .vitem &$sender_host_address$&
12954 .vindex "&$sender_host_address$&"
12955 When a message is received from a remote host using SMTP,
12956 this variable contains that
12957 host's IP address. For locally non-SMTP submitted messages, it is empty.
12959 .vitem &$sender_host_authenticated$&
12960 .vindex "&$sender_host_authenticated$&"
12961 This variable contains the name (not the public name) of the authenticator
12962 driver that successfully authenticated the client from which the message was
12963 received. It is empty if there was no successful authentication. See also
12964 &$authenticated_id$&.
12966 .vitem &$sender_host_dnssec$&
12967 .vindex "&$sender_host_dnssec$&"
12968 If an attempt to populate &$sender_host_name$& has been made
12969 (by reference, &%hosts_lookup%& or
12970 otherwise) then this boolean will have been set true if, and only if, the
12971 resolver library states that both
12972 the reverse and forward DNS were authenticated data. At all
12973 other times, this variable is false.
12975 .cindex "DNS" "DNSSEC"
12976 It is likely that you will need to coerce DNSSEC support on in the resolver
12977 library, by setting:
12982 Exim does not perform DNSSEC validation itself, instead leaving that to a
12983 validating resolver (e.g. unbound, or bind with suitable configuration).
12985 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
12986 mechanism in the list, then this variable will be false.
12988 This requires that your system resolver library support EDNS0 (and that
12989 DNSSEC flags exist in the system headers). If the resolver silently drops
12990 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
12991 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
12994 .vitem &$sender_host_name$&
12995 .vindex "&$sender_host_name$&"
12996 When a message is received from a remote host, this variable contains the
12997 host's name as obtained by looking up its IP address. For messages received by
12998 other means, this variable is empty.
13000 .vindex "&$host_lookup_failed$&"
13001 If the host name has not previously been looked up, a reference to
13002 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
13003 A looked up name is accepted only if it leads back to the original IP address
13004 via a forward lookup. If either the reverse or the forward lookup fails to find
13005 any data, or if the forward lookup does not yield the original IP address,
13006 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
13008 .vindex "&$host_lookup_deferred$&"
13009 However, if either of the lookups cannot be completed (for example, there is a
13010 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
13011 &$host_lookup_failed$& remains set to &"0"&.
13013 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
13014 host name again if there is a subsequent reference to &$sender_host_name$&
13015 in the same Exim process, but it does try again if &$host_lookup_deferred$&
13018 Exim does not automatically look up every calling host's name. If you want
13019 maximum efficiency, you should arrange your configuration so that it avoids
13020 these lookups altogether. The lookup happens only if one or more of the
13021 following are true:
13024 A string containing &$sender_host_name$& is expanded.
13026 The calling host matches the list in &%host_lookup%&. In the default
13027 configuration, this option is set to *, so it must be changed if lookups are
13028 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
13030 Exim needs the host name in order to test an item in a host list. The items
13031 that require this are described in sections &<<SECThoslispatnam>>& and
13032 &<<SECThoslispatnamsk>>&.
13034 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
13035 In this case, the host name is required to compare with the name quoted in any
13036 EHLO or HELO commands that the client issues.
13038 The remote host issues a EHLO or HELO command that quotes one of the
13039 domains in &%helo_lookup_domains%&. The default value of this option is
13040 . ==== As this is a nested list, any displays it contains must be indented
13041 . ==== as otherwise they are too far to the left.
13043 helo_lookup_domains = @ : @[]
13045 which causes a lookup if a remote host (incorrectly) gives the server's name or
13046 IP address in an EHLO or HELO command.
13050 .vitem &$sender_host_port$&
13051 .vindex "&$sender_host_port$&"
13052 When a message is received from a remote host, this variable contains the port
13053 number that was used on the remote host.
13055 .vitem &$sender_ident$&
13056 .vindex "&$sender_ident$&"
13057 When a message is received from a remote host, this variable contains the
13058 identification received in response to an RFC 1413 request. When a message has
13059 been received locally, this variable contains the login name of the user that
13062 .vitem &$sender_rate_$&&'xxx'&
13063 A number of variables whose names begin &$sender_rate_$& are set as part of the
13064 &%ratelimit%& ACL condition. Details are given in section
13065 &<<SECTratelimiting>>&.
13067 .vitem &$sender_rcvhost$&
13068 .cindex "DNS" "reverse lookup"
13069 .cindex "reverse DNS lookup"
13070 .vindex "&$sender_rcvhost$&"
13071 This is provided specifically for use in &'Received:'& headers. It starts with
13072 either the verified host name (as obtained from a reverse DNS lookup) or, if
13073 there is no verified host name, the IP address in square brackets. After that
13074 there may be text in parentheses. When the first item is a verified host name,
13075 the first thing in the parentheses is the IP address in square brackets,
13076 followed by a colon and a port number if port logging is enabled. When the
13077 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
13080 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
13081 was used and its argument was not identical to the real host name or IP
13082 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
13083 all three items are present in the parentheses, a newline and tab are inserted
13084 into the string, to improve the formatting of the &'Received:'& header.
13086 .vitem &$sender_verify_failure$&
13087 .vindex "&$sender_verify_failure$&"
13088 In an ACL, when a sender verification fails, this variable contains information
13089 about the failure. The details are the same as for
13090 &$recipient_verify_failure$&.
13092 .vitem &$sending_ip_address$&
13093 .vindex "&$sending_ip_address$&"
13094 This variable is set whenever an outgoing SMTP connection to another host has
13095 been set up. It contains the IP address of the local interface that is being
13096 used. This is useful if a host that has more than one IP address wants to take
13097 on different personalities depending on which one is being used. For incoming
13098 connections, see &$received_ip_address$&.
13100 .vitem &$sending_port$&
13101 .vindex "&$sending_port$&"
13102 This variable is set whenever an outgoing SMTP connection to another host has
13103 been set up. It contains the local port that is being used. For incoming
13104 connections, see &$received_port$&.
13106 .vitem &$smtp_active_hostname$&
13107 .vindex "&$smtp_active_hostname$&"
13108 During an incoming SMTP session, this variable contains the value of the active
13109 host name, as specified by the &%smtp_active_hostname%& option. The value of
13110 &$smtp_active_hostname$& is saved with any message that is received, so its
13111 value can be consulted during routing and delivery.
13113 .vitem &$smtp_command$&
13114 .vindex "&$smtp_command$&"
13115 During the processing of an incoming SMTP command, this variable contains the
13116 entire command. This makes it possible to distinguish between HELO and EHLO in
13117 the HELO ACL, and also to distinguish between commands such as these:
13122 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
13123 command, the address in &$smtp_command$& is the original address before any
13124 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
13125 the address after SMTP-time rewriting.
13127 .vitem &$smtp_command_argument$&
13128 .cindex "SMTP" "command, argument for"
13129 .vindex "&$smtp_command_argument$&"
13130 While an ACL is running to check an SMTP command, this variable contains the
13131 argument, that is, the text that follows the command name, with leading white
13132 space removed. Following the introduction of &$smtp_command$&, this variable is
13133 somewhat redundant, but is retained for backwards compatibility.
13135 .vitem &$smtp_command_history$&
13136 .cindex SMTP "command history"
13137 .vindex "&$smtp_command_history$&"
13138 A comma-separated list (with no whitespace) of the most-recent SMTP commands
13139 received, in time-order left to right. Only a limited number of commands
13142 .vitem &$smtp_count_at_connection_start$&
13143 .vindex "&$smtp_count_at_connection_start$&"
13144 This variable is set greater than zero only in processes spawned by the Exim
13145 daemon for handling incoming SMTP connections. The name is deliberately long,
13146 in order to emphasize what the contents are. When the daemon accepts a new
13147 connection, it increments this variable. A copy of the variable is passed to
13148 the child process that handles the connection, but its value is fixed, and
13149 never changes. It is only an approximation of how many incoming connections
13150 there actually are, because many other connections may come and go while a
13151 single connection is being processed. When a child process terminates, the
13152 daemon decrements its copy of the variable.
13154 .vitem "&$sn0$& &-- &$sn9$&"
13155 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
13156 that were current at the end of the system filter file. This allows a system
13157 filter file to set values that can be tested in users' filter files. For
13158 example, a system filter could set a value indicating how likely it is that a
13159 message is junk mail.
13161 .vitem &$spam_$&&'xxx'&
13162 A number of variables whose names start with &$spam$& are available when Exim
13163 is compiled with the content-scanning extension. For details, see section
13164 &<<SECTscanspamass>>&.
13166 .vitem &$spf_header_comment$& &&&
13167 &$spf_received$& &&&
13169 &$spf_result_guessed$& &&&
13170 &$spf_smtp_comment$&
13171 These variables are only available if Exim is built with SPF support.
13172 For details see section &<<SECSPF>>&.
13174 .vitem &$spool_directory$&
13175 .vindex "&$spool_directory$&"
13176 The name of Exim's spool directory.
13178 .vitem &$spool_inodes$&
13179 .vindex "&$spool_inodes$&"
13180 The number of free inodes in the disk partition where Exim's spool files are
13181 being written. The value is recalculated whenever the variable is referenced.
13182 If the relevant file system does not have the concept of inodes, the value of
13183 is -1. See also the &%check_spool_inodes%& option.
13185 .vitem &$spool_space$&
13186 .vindex "&$spool_space$&"
13187 The amount of free space (as a number of kilobytes) in the disk partition where
13188 Exim's spool files are being written. The value is recalculated whenever the
13189 variable is referenced. If the operating system does not have the ability to
13190 find the amount of free space (only true for experimental systems), the space
13191 value is -1. For example, to check in an ACL that there is at least 50
13192 megabytes free on the spool, you could write:
13194 condition = ${if > {$spool_space}{50000}}
13196 See also the &%check_spool_space%& option.
13199 .vitem &$thisaddress$&
13200 .vindex "&$thisaddress$&"
13201 This variable is set only during the processing of the &%foranyaddress%&
13202 command in a filter file. Its use is explained in the description of that
13203 command, which can be found in the separate document entitled &'Exim's
13204 interfaces to mail filtering'&.
13206 .vitem &$tls_in_bits$&
13207 .vindex "&$tls_in_bits$&"
13208 Contains an approximation of the TLS cipher's bit-strength
13209 on the inbound connection; the meaning of
13210 this depends upon the TLS implementation used.
13211 If TLS has not been negotiated, the value will be 0.
13212 The value of this is automatically fed into the Cyrus SASL authenticator
13213 when acting as a server, to specify the "external SSF" (a SASL term).
13215 The deprecated &$tls_bits$& variable refers to the inbound side
13216 except when used in the context of an outbound SMTP delivery, when it refers to
13219 .vitem &$tls_out_bits$&
13220 .vindex "&$tls_out_bits$&"
13221 Contains an approximation of the TLS cipher's bit-strength
13222 on an outbound SMTP connection; the meaning of
13223 this depends upon the TLS implementation used.
13224 If TLS has not been negotiated, the value will be 0.
13226 .vitem &$tls_in_ourcert$&
13227 .vindex "&$tls_in_ourcert$&"
13228 .cindex certificate variables
13229 This variable refers to the certificate presented to the peer of an
13230 inbound connection when the message was received.
13231 It is only useful as the argument of a
13232 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13233 or a &%def%& condition.
13235 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
13236 when a list of more than one
13237 file is used for &%tls_certificate%&, this variable is not reliable.
13239 .vitem &$tls_in_peercert$&
13240 .vindex "&$tls_in_peercert$&"
13241 This variable refers to the certificate presented by 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.
13246 If certificate verification fails it may refer to a failing chain element
13247 which is not the leaf.
13249 .vitem &$tls_out_ourcert$&
13250 .vindex "&$tls_out_ourcert$&"
13251 This variable refers to the certificate presented to the peer of an
13252 outbound connection. It is only useful as the argument of a
13253 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13254 or a &%def%& condition.
13256 .vitem &$tls_out_peercert$&
13257 .vindex "&$tls_out_peercert$&"
13258 This variable refers to the certificate presented by the peer of an
13259 outbound connection. It is only useful as the argument of a
13260 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13261 or a &%def%& condition.
13262 If certificate verification fails it may refer to a failing chain element
13263 which is not the leaf.
13265 .vitem &$tls_in_certificate_verified$&
13266 .vindex "&$tls_in_certificate_verified$&"
13267 This variable is set to &"1"& if a TLS certificate was verified when the
13268 message was received, and &"0"& otherwise.
13270 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
13271 except when used in the context of an outbound SMTP delivery, when it refers to
13274 .vitem &$tls_out_certificate_verified$&
13275 .vindex "&$tls_out_certificate_verified$&"
13276 This variable is set to &"1"& if a TLS certificate was verified when an
13277 outbound SMTP connection was made,
13278 and &"0"& otherwise.
13280 .vitem &$tls_in_cipher$&
13281 .vindex "&$tls_in_cipher$&"
13282 .vindex "&$tls_cipher$&"
13283 When a message is received from a remote host over an encrypted SMTP
13284 connection, this variable is set to the cipher suite that was negotiated, for
13285 example DES-CBC3-SHA. In other circumstances, in particular, for message
13286 received over unencrypted connections, the variable is empty. Testing
13287 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
13288 non-encrypted connections during ACL processing.
13290 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
13291 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
13292 becomes the same as &$tls_out_cipher$&.
13294 .vitem &$tls_out_cipher$&
13295 .vindex "&$tls_out_cipher$&"
13297 cleared before any outgoing SMTP connection is made,
13298 and then set to the outgoing cipher suite if one is negotiated. See chapter
13299 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
13300 details of the &(smtp)& transport.
13302 .vitem &$tls_out_dane$&
13303 .vindex &$tls_out_dane$&
13304 DANE active status. See section &<<SECDANE>>&.
13306 .vitem &$tls_in_ocsp$&
13307 .vindex "&$tls_in_ocsp$&"
13308 When a message is received from a remote client connection
13309 the result of any OCSP request from the client is encoded in this variable:
13311 0 OCSP proof was not requested (default value)
13312 1 No response to request
13313 2 Response not verified
13314 3 Verification failed
13315 4 Verification succeeded
13318 .vitem &$tls_out_ocsp$&
13319 .vindex "&$tls_out_ocsp$&"
13320 When a message is sent to a remote host connection
13321 the result of any OCSP request made is encoded in this variable.
13322 See &$tls_in_ocsp$& for values.
13324 .vitem &$tls_in_peerdn$&
13325 .vindex "&$tls_in_peerdn$&"
13326 .vindex "&$tls_peerdn$&"
13327 .cindex certificate "extracting fields"
13328 When a message is received from a remote host over an encrypted SMTP
13329 connection, and Exim is configured to request a certificate from the client,
13330 the value of the Distinguished Name of the certificate is made available in the
13331 &$tls_in_peerdn$& during subsequent processing.
13332 If certificate verification fails it may refer to a failing chain element
13333 which is not the leaf.
13335 The deprecated &$tls_peerdn$& variable refers to the inbound side
13336 except when used in the context of an outbound SMTP delivery, when it refers to
13339 .vitem &$tls_out_peerdn$&
13340 .vindex "&$tls_out_peerdn$&"
13341 When a message is being delivered to a remote host over an encrypted SMTP
13342 connection, and Exim is configured to request a certificate from the server,
13343 the value of the Distinguished Name of the certificate is made available in the
13344 &$tls_out_peerdn$& during subsequent processing.
13345 If certificate verification fails it may refer to a failing chain element
13346 which is not the leaf.
13348 .vitem &$tls_in_sni$&
13349 .vindex "&$tls_in_sni$&"
13350 .vindex "&$tls_sni$&"
13351 .cindex "TLS" "Server Name Indication"
13352 When a TLS session is being established, if the client sends the Server
13353 Name Indication extension, the value will be placed in this variable.
13354 If the variable appears in &%tls_certificate%& then this option and
13355 some others, described in &<<SECTtlssni>>&,
13356 will be re-expanded early in the TLS session, to permit
13357 a different certificate to be presented (and optionally a different key to be
13358 used) to the client, based upon the value of the SNI extension.
13360 The deprecated &$tls_sni$& variable refers to the inbound side
13361 except when used in the context of an outbound SMTP delivery, when it refers to
13364 .vitem &$tls_out_sni$&
13365 .vindex "&$tls_out_sni$&"
13366 .cindex "TLS" "Server Name Indication"
13368 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
13371 .vitem &$tls_out_tlsa_usage$&
13372 .vindex &$tls_out_tlsa_usage$&
13373 Bitfield of TLSA record types found. See section &<<SECDANE>>&.
13375 .vitem &$tod_bsdinbox$&
13376 .vindex "&$tod_bsdinbox$&"
13377 The time of day and the date, in the format required for BSD-style mailbox
13378 files, for example: Thu Oct 17 17:14:09 1995.
13380 .vitem &$tod_epoch$&
13381 .vindex "&$tod_epoch$&"
13382 The time and date as a number of seconds since the start of the Unix epoch.
13384 .vitem &$tod_epoch_l$&
13385 .vindex "&$tod_epoch_l$&"
13386 The time and date as a number of microseconds since the start of the Unix epoch.
13388 .vitem &$tod_full$&
13389 .vindex "&$tod_full$&"
13390 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
13391 +0100. The timezone is always given as a numerical offset from UTC, with
13392 positive values used for timezones that are ahead (east) of UTC, and negative
13393 values for those that are behind (west).
13396 .vindex "&$tod_log$&"
13397 The time and date in the format used for writing Exim's log files, for example:
13398 1995-10-12 15:32:29, but without a timezone.
13400 .vitem &$tod_logfile$&
13401 .vindex "&$tod_logfile$&"
13402 This variable contains the date in the format yyyymmdd. This is the format that
13403 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
13406 .vitem &$tod_zone$&
13407 .vindex "&$tod_zone$&"
13408 This variable contains the numerical value of the local timezone, for example:
13411 .vitem &$tod_zulu$&
13412 .vindex "&$tod_zulu$&"
13413 This variable contains the UTC date and time in &"Zulu"& format, as specified
13414 by ISO 8601, for example: 20030221154023Z.
13416 .vitem &$transport_name$&
13417 .cindex "transport" "name"
13418 .cindex "name" "of transport"
13419 .vindex "&$transport_name$&"
13420 During the running of a transport, this variable contains its name.
13423 .vindex "&$value$&"
13424 This variable contains the result of an expansion lookup, extraction operation,
13425 or external command, as described above. It is also used during a
13426 &*reduce*& expansion.
13428 .vitem &$verify_mode$&
13429 .vindex "&$verify_mode$&"
13430 While a router or transport is being run in verify mode or for cutthrough delivery,
13431 contains "S" for sender-verification or "R" for recipient-verification.
13434 .vitem &$version_number$&
13435 .vindex "&$version_number$&"
13436 The version number of Exim.
13438 .vitem &$warn_message_delay$&
13439 .vindex "&$warn_message_delay$&"
13440 This variable is set only during the creation of a message warning about a
13441 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13443 .vitem &$warn_message_recipients$&
13444 .vindex "&$warn_message_recipients$&"
13445 This variable is set only during the creation of a message warning about a
13446 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13452 . ////////////////////////////////////////////////////////////////////////////
13453 . ////////////////////////////////////////////////////////////////////////////
13455 .chapter "Embedded Perl" "CHAPperl"
13456 .scindex IIDperl "Perl" "calling from Exim"
13457 Exim can be built to include an embedded Perl interpreter. When this is done,
13458 Perl subroutines can be called as part of the string expansion process. To make
13459 use of the Perl support, you need version 5.004 or later of Perl installed on
13460 your system. To include the embedded interpreter in the Exim binary, include
13465 in your &_Local/Makefile_& and then build Exim in the normal way.
13468 .section "Setting up so Perl can be used" "SECID85"
13469 .oindex "&%perl_startup%&"
13470 Access to Perl subroutines is via a global configuration option called
13471 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
13472 no &%perl_startup%& option in the Exim configuration file then no Perl
13473 interpreter is started and there is almost no overhead for Exim (since none of
13474 the Perl library will be paged in unless used). If there is a &%perl_startup%&
13475 option then the associated value is taken to be Perl code which is executed in
13476 a newly created Perl interpreter.
13478 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
13479 need backslashes before any characters to escape special meanings. The option
13480 should usually be something like
13482 perl_startup = do '/etc/exim.pl'
13484 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
13485 use from Exim. Exim can be configured either to start up a Perl interpreter as
13486 soon as it is entered, or to wait until the first time it is needed. Starting
13487 the interpreter at the beginning ensures that it is done while Exim still has
13488 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
13489 fact used in a particular run. Also, note that this does not mean that Exim is
13490 necessarily running as root when Perl is called at a later time. By default,
13491 the interpreter is started only when it is needed, but this can be changed in
13495 .oindex "&%perl_at_start%&"
13496 Setting &%perl_at_start%& (a boolean option) in the configuration requests
13497 a startup when Exim is entered.
13499 The command line option &%-ps%& also requests a startup when Exim is entered,
13500 overriding the setting of &%perl_at_start%&.
13503 There is also a command line option &%-pd%& (for delay) which suppresses the
13504 initial startup, even if &%perl_at_start%& is set.
13507 .oindex "&%perl_taintmode%&"
13508 .cindex "Perl" "taintmode"
13509 To provide more security executing Perl code via the embedded Perl
13510 interpreter, the &%perl_taintmode%& option can be set. This enables the
13511 taint mode of the Perl interpreter. You are encouraged to set this
13512 option to a true value. To avoid breaking existing installations, it
13516 .section "Calling Perl subroutines" "SECID86"
13517 When the configuration file includes a &%perl_startup%& option you can make use
13518 of the string expansion item to call the Perl subroutines that are defined
13519 by the &%perl_startup%& code. The operator is used in any of the following
13523 ${perl{foo}{argument}}
13524 ${perl{foo}{argument1}{argument2} ... }
13526 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
13527 arguments may be passed. Passing more than this results in an expansion failure
13528 with an error message of the form
13530 Too many arguments passed to Perl subroutine "foo" (max is 8)
13532 The return value of the Perl subroutine is evaluated in a scalar context before
13533 it is passed back to Exim to be inserted into the expanded string. If the
13534 return value is &'undef'&, the expansion is forced to fail in the same way as
13535 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
13536 by obeying Perl's &%die%& function, the expansion fails with the error message
13537 that was passed to &%die%&.
13540 .section "Calling Exim functions from Perl" "SECID87"
13541 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
13542 is available to call back into Exim's string expansion function. For example,
13545 my $lp = Exim::expand_string('$local_part');
13547 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
13548 Note those are single quotes and not double quotes to protect against
13549 &$local_part$& being interpolated as a Perl variable.
13551 If the string expansion is forced to fail by a &"fail"& item, the result of
13552 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
13553 expansion string, the Perl call from the original expansion string fails with
13554 an appropriate error message, in the same way as if &%die%& were used.
13556 .cindex "debugging" "from embedded Perl"
13557 .cindex "log" "writing from embedded Perl"
13558 Two other Exim functions are available for use from within Perl code.
13559 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
13560 debugging is enabled. If you want a newline at the end, you must supply it.
13561 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
13562 timestamp. In this case, you should not supply a terminating newline.
13565 .section "Use of standard output and error by Perl" "SECID88"
13566 .cindex "Perl" "standard output and error"
13567 You should not write to the standard error or output streams from within your
13568 Perl code, as it is not defined how these are set up. In versions of Exim
13569 before 4.50, it is possible for the standard output or error to refer to the
13570 SMTP connection during message reception via the daemon. Writing to this stream
13571 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
13572 error streams are connected to &_/dev/null_& in the daemon. The chaos is
13573 avoided, but the output is lost.
13575 .cindex "Perl" "use of &%warn%&"
13576 The Perl &%warn%& statement writes to the standard error stream by default.
13577 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
13578 you have no control. When Exim starts up the Perl interpreter, it arranges for
13579 output from the &%warn%& statement to be written to the Exim main log. You can
13580 change this by including appropriate Perl magic somewhere in your Perl code.
13581 For example, to discard &%warn%& output completely, you need this:
13583 $SIG{__WARN__} = sub { };
13585 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
13586 example, the code for the subroutine is empty, so it does nothing, but you can
13587 include any Perl code that you like. The text of the &%warn%& message is passed
13588 as the first subroutine argument.
13592 . ////////////////////////////////////////////////////////////////////////////
13593 . ////////////////////////////////////////////////////////////////////////////
13595 .chapter "Starting the daemon and the use of network interfaces" &&&
13596 "CHAPinterfaces" &&&
13597 "Starting the daemon"
13598 .cindex "daemon" "starting"
13599 .cindex "interface" "listening"
13600 .cindex "network interface"
13601 .cindex "interface" "network"
13602 .cindex "IP address" "for listening"
13603 .cindex "daemon" "listening IP addresses"
13604 .cindex "TCP/IP" "setting listening interfaces"
13605 .cindex "TCP/IP" "setting listening ports"
13606 A host that is connected to a TCP/IP network may have one or more physical
13607 hardware network interfaces. Each of these interfaces may be configured as one
13608 or more &"logical"& interfaces, which are the entities that a program actually
13609 works with. Each of these logical interfaces is associated with an IP address.
13610 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
13611 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
13612 knowledge about the host's interfaces for use in three different circumstances:
13615 When a listening daemon is started, Exim needs to know which interfaces
13616 and ports to listen on.
13618 When Exim is routing an address, it needs to know which IP addresses
13619 are associated with local interfaces. This is required for the correct
13620 processing of MX lists by removing the local host and others with the
13621 same or higher priority values. Also, Exim needs to detect cases
13622 when an address is routed to an IP address that in fact belongs to the
13623 local host. Unless the &%self%& router option or the &%allow_localhost%&
13624 option of the smtp transport is set (as appropriate), this is treated
13625 as an error situation.
13627 When Exim connects to a remote host, it may need to know which interface to use
13628 for the outgoing connection.
13632 Exim's default behaviour is likely to be appropriate in the vast majority
13633 of cases. If your host has only one interface, and you want all its IP
13634 addresses to be treated in the same way, and you are using only the
13635 standard SMTP port, you should not need to take any special action. The
13636 rest of this chapter does not apply to you.
13638 In a more complicated situation you may want to listen only on certain
13639 interfaces, or on different ports, and for this reason there are a number of
13640 options that can be used to influence Exim's behaviour. The rest of this
13641 chapter describes how they operate.
13643 When a message is received over TCP/IP, the interface and port that were
13644 actually used are set in &$received_ip_address$& and &$received_port$&.
13648 .section "Starting a listening daemon" "SECID89"
13649 When a listening daemon is started (by means of the &%-bd%& command line
13650 option), the interfaces and ports on which it listens are controlled by the
13654 &%daemon_smtp_ports%& contains a list of default ports
13656 (For backward compatibility, this option can also be specified in the singular.)
13658 &%local_interfaces%& contains list of interface IP addresses on which to
13659 listen. Each item may optionally also specify a port.
13662 The default list separator in both cases is a colon, but this can be changed as
13663 described in section &<<SECTlistsepchange>>&. When IPv6 addresses are involved,
13664 it is usually best to change the separator to avoid having to double all the
13665 colons. For example:
13667 local_interfaces = <; 127.0.0.1 ; \
13670 3ffe:ffff:836f::fe86:a061
13672 There are two different formats for specifying a port along with an IP address
13673 in &%local_interfaces%&:
13676 The port is added onto the address with a dot separator. For example, to listen
13677 on port 1234 on two different IP addresses:
13679 local_interfaces = <; 192.168.23.65.1234 ; \
13680 3ffe:ffff:836f::fe86:a061.1234
13683 The IP address is enclosed in square brackets, and the port is added
13684 with a colon separator, for example:
13686 local_interfaces = <; [192.168.23.65]:1234 ; \
13687 [3ffe:ffff:836f::fe86:a061]:1234
13691 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
13692 default setting contains just one port:
13694 daemon_smtp_ports = smtp
13696 If more than one port is listed, each interface that does not have its own port
13697 specified listens on all of them. Ports that are listed in
13698 &%daemon_smtp_ports%& can be identified either by name (defined in
13699 &_/etc/services_&) or by number. However, when ports are given with individual
13700 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
13704 .section "Special IP listening addresses" "SECID90"
13705 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
13706 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
13707 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
13708 instead of setting up separate listening sockets for each interface. The
13709 default value of &%local_interfaces%& is
13711 local_interfaces = 0.0.0.0
13713 when Exim is built without IPv6 support; otherwise it is:
13715 local_interfaces = <; ::0 ; 0.0.0.0
13717 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
13721 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
13722 The &%-oX%& command line option can be used to override the values of
13723 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
13724 instance. Another way of doing this would be to use macros and the &%-D%&
13725 option. However, &%-oX%& can be used by any admin user, whereas modification of
13726 the runtime configuration by &%-D%& is allowed only when the caller is root or
13729 The value of &%-oX%& is a list of items. The default colon separator can be
13730 changed in the usual way (&<<SECTlistsepchange>>&) if required.
13731 If there are any items that do not
13732 contain dots or colons (that is, are not IP addresses), the value of
13733 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
13734 items that do contain dots or colons, the value of &%local_interfaces%& is
13735 replaced by those items. Thus, for example,
13739 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
13742 -oX 192.168.34.5.1125
13744 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
13745 (However, since &%local_interfaces%& now contains no items without ports, the
13746 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
13750 .section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
13751 .cindex "submissions protocol"
13752 .cindex "ssmtp protocol"
13753 .cindex "smtps protocol"
13754 .cindex "SMTP" "ssmtp protocol"
13755 .cindex "SMTP" "smtps protocol"
13756 Exim supports the use of TLS-on-connect, used by mail clients in the
13757 &"submissions"& protocol, historically also known as SMTPS or SSMTP.
13758 For some years, IETF Standards Track documents only blessed the
13759 STARTTLS-based Submission service (port 587) while common practice was to support
13760 the same feature set on port 465, but using TLS-on-connect.
13761 If your installation needs to provide service to mail clients
13762 (Mail User Agents, MUAs) then you should provide service on both the 587 and
13765 If the &%tls_on_connect_ports%& option is set to a list of port numbers or
13766 service names, connections to those ports must first establish TLS, before
13767 proceeding to the application layer use of the SMTP protocol.
13769 The common use of this option is expected to be
13771 tls_on_connect_ports = 465
13774 There is also a command line option &%-tls-on-connect%&, which forces all ports
13775 to behave in this way when a daemon is started.
13777 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
13778 daemon to listen on those ports. You must still specify them in
13779 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
13780 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
13781 connections via the daemon.)
13786 .section "IPv6 address scopes" "SECID92"
13787 .cindex "IPv6" "address scopes"
13788 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
13789 can, in principle, have the same link-local IPv6 address on different
13790 interfaces. Thus, additional information is needed, over and above the IP
13791 address, to distinguish individual interfaces. A convention of using a
13792 percent sign followed by something (often the interface name) has been
13793 adopted in some cases, leading to addresses like this:
13795 fe80::202:b3ff:fe03:45c1%eth0
13797 To accommodate this usage, a percent sign followed by an arbitrary string is
13798 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
13799 to convert a textual IPv6 address for actual use. This function recognizes the
13800 percent convention in operating systems that support it, and it processes the
13801 address appropriately. Unfortunately, some older libraries have problems with
13802 &[getaddrinfo()]&. If
13804 IPV6_USE_INET_PTON=yes
13806 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
13807 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
13808 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
13809 function.) Of course, this means that the additional functionality of
13810 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
13812 .section "Disabling IPv6" "SECID93"
13813 .cindex "IPv6" "disabling"
13814 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
13815 run on a host whose kernel does not support IPv6. The binary will fall back to
13816 using IPv4, but it may waste resources looking up AAAA records, and trying to
13817 connect to IPv6 addresses, causing delays to mail delivery. If you set the
13818 .oindex "&%disable_ipv6%&"
13819 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
13820 activities take place. AAAA records are never looked up, and any IPv6 addresses
13821 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
13822 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13823 to handle IPv6 literal addresses.
13825 On the other hand, when IPv6 is in use, there may be times when you want to
13826 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
13827 option to globally suppress the lookup of AAAA records for specified domains,
13828 and you can use the &%ignore_target_hosts%& generic router option to ignore
13829 IPv6 addresses in an individual router.
13833 .section "Examples of starting a listening daemon" "SECID94"
13834 The default case in an IPv6 environment is
13836 daemon_smtp_ports = smtp
13837 local_interfaces = <; ::0 ; 0.0.0.0
13839 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
13840 Either one or two sockets may be used, depending on the characteristics of
13841 the TCP/IP stack. (This is complicated and messy; for more information,
13842 read the comments in the &_daemon.c_& source file.)
13844 To specify listening on ports 25 and 26 on all interfaces:
13846 daemon_smtp_ports = 25 : 26
13848 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
13850 local_interfaces = <; ::0.25 ; ::0.26 \
13851 0.0.0.0.25 ; 0.0.0.0.26
13853 To listen on the default port on all IPv4 interfaces, and on port 26 on the
13854 IPv4 loopback address only:
13856 local_interfaces = 0.0.0.0 : 127.0.0.1.26
13858 To specify listening on the default port on specific interfaces only:
13860 local_interfaces = 10.0.0.67 : 192.168.34.67
13862 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
13866 .section "Recognizing the local host" "SECTreclocipadd"
13867 The &%local_interfaces%& option is also used when Exim needs to determine
13868 whether or not an IP address refers to the local host. That is, the IP
13869 addresses of all the interfaces on which a daemon is listening are always
13872 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
13873 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
13874 available interfaces from the operating system, and extracts the relevant
13875 (that is, IPv4 or IPv6) addresses to use for checking.
13877 Some systems set up large numbers of virtual interfaces in order to provide
13878 many virtual web servers. In this situation, you may want to listen for
13879 email on only a few of the available interfaces, but nevertheless treat all
13880 interfaces as local when routing. You can do this by setting
13881 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
13882 &"all"& wildcard values. These addresses are recognized as local, but are not
13883 used for listening. Consider this example:
13885 local_interfaces = <; 127.0.0.1 ; ::1 ; \
13887 3ffe:2101:12:1:a00:20ff:fe86:a061
13889 extra_local_interfaces = <; ::0 ; 0.0.0.0
13891 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
13892 address, but all available interface addresses are treated as local when
13895 In some environments the local host name may be in an MX list, but with an IP
13896 address that is not assigned to any local interface. In other cases it may be
13897 desirable to treat other host names as if they referred to the local host. Both
13898 these cases can be handled by setting the &%hosts_treat_as_local%& option.
13899 This contains host names rather than IP addresses. When a host is referenced
13900 during routing, either via an MX record or directly, it is treated as the local
13901 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
13902 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
13906 .section "Delivering to a remote host" "SECID95"
13907 Delivery to a remote host is handled by the smtp transport. By default, it
13908 allows the system's TCP/IP functions to choose which interface to use (if
13909 there is more than one) when connecting to a remote host. However, the
13910 &%interface%& option can be set to specify which interface is used. See the
13911 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
13917 . ////////////////////////////////////////////////////////////////////////////
13918 . ////////////////////////////////////////////////////////////////////////////
13920 .chapter "Main configuration" "CHAPmainconfig"
13921 .scindex IIDconfima "configuration file" "main section"
13922 .scindex IIDmaiconf "main configuration"
13923 The first part of the runtime configuration file contains three types of item:
13926 Macro definitions: These lines start with an upper case letter. See section
13927 &<<SECTmacrodefs>>& for details of macro processing.
13929 Named list definitions: These lines start with one of the words &"domainlist"&,
13930 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
13931 section &<<SECTnamedlists>>&.
13933 Main configuration settings: Each setting occupies one line of the file
13934 (with possible continuations). If any setting is preceded by the word
13935 &"hide"&, the &%-bP%& command line option displays its value to admin users
13936 only. See section &<<SECTcos>>& for a description of the syntax of these option
13940 This chapter specifies all the main configuration options, along with their
13941 types and default values. For ease of finding a particular option, they appear
13942 in alphabetical order in section &<<SECTalomo>>& below. However, because there
13943 are now so many options, they are first listed briefly in functional groups, as
13944 an aid to finding the name of the option you are looking for. Some options are
13945 listed in more than one group.
13947 .section "Miscellaneous" "SECID96"
13949 .row &%bi_command%& "to run for &%-bi%& command line option"
13950 .row &%debug_store%& "do extra internal checks"
13951 .row &%disable_ipv6%& "do no IPv6 processing"
13952 .row &%keep_malformed%& "for broken files &-- should not happen"
13953 .row &%localhost_number%& "for unique message ids in clusters"
13954 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
13955 .row &%message_body_visible%& "how much to show in &$message_body$&"
13956 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
13957 .row &%print_topbitchars%& "top-bit characters are printing"
13958 .row &%spool_wireformat%& "use wire-format spool data files when possible"
13959 .row &%timezone%& "force time zone"
13963 .section "Exim parameters" "SECID97"
13965 .row &%exim_group%& "override compiled-in value"
13966 .row &%exim_path%& "override compiled-in value"
13967 .row &%exim_user%& "override compiled-in value"
13968 .row &%primary_hostname%& "default from &[uname()]&"
13969 .row &%split_spool_directory%& "use multiple directories"
13970 .row &%spool_directory%& "override compiled-in value"
13975 .section "Privilege controls" "SECID98"
13977 .row &%admin_groups%& "groups that are Exim admin users"
13978 .row &%commandline_checks_require_admin%& "require admin for various checks"
13979 .row &%deliver_drop_privilege%& "drop root for delivery processes"
13980 .row &%local_from_check%& "insert &'Sender:'& if necessary"
13981 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
13982 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
13983 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
13984 .row &%never_users%& "do not run deliveries as these"
13985 .row &%prod_requires_admin%& "forced delivery requires admin user"
13986 .row &%queue_list_requires_admin%& "queue listing requires admin user"
13987 .row &%trusted_groups%& "groups that are trusted"
13988 .row &%trusted_users%& "users that are trusted"
13993 .section "Logging" "SECID99"
13995 .row &%event_action%& "custom logging"
13996 .row &%hosts_connection_nolog%& "exemption from connect logging"
13997 .row &%log_file_path%& "override compiled-in value"
13998 .row &%log_selector%& "set/unset optional logging"
13999 .row &%log_timezone%& "add timezone to log lines"
14000 .row &%message_logs%& "create per-message logs"
14001 .row &%preserve_message_logs%& "after message completion"
14002 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
14003 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
14004 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
14005 .row &%syslog_facility%& "set syslog &""facility""& field"
14006 .row &%syslog_pid%& "pid in syslog lines"
14007 .row &%syslog_processname%& "set syslog &""ident""& field"
14008 .row &%syslog_timestamp%& "timestamp syslog lines"
14009 .row &%write_rejectlog%& "control use of message log"
14014 .section "Frozen messages" "SECID100"
14016 .row &%auto_thaw%& "sets time for retrying frozen messages"
14017 .row &%freeze_tell%& "send message when freezing"
14018 .row &%move_frozen_messages%& "to another directory"
14019 .row &%timeout_frozen_after%& "keep frozen messages only so long"
14024 .section "Data lookups" "SECID101"
14026 .row &%ibase_servers%& "InterBase servers"
14027 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
14028 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
14029 .row &%ldap_cert_file%& "client cert file for LDAP"
14030 .row &%ldap_cert_key%& "client key file for LDAP"
14031 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
14032 .row &%ldap_default_servers%& "used if no server in query"
14033 .row &%ldap_require_cert%& "action to take without LDAP server cert"
14034 .row &%ldap_start_tls%& "require TLS within LDAP"
14035 .row &%ldap_version%& "set protocol version"
14036 .row &%lookup_open_max%& "lookup files held open"
14037 .row &%mysql_servers%& "default MySQL servers"
14038 .row &%oracle_servers%& "Oracle servers"
14039 .row &%pgsql_servers%& "default PostgreSQL servers"
14040 .row &%sqlite_lock_timeout%& "as it says"
14045 .section "Message ids" "SECID102"
14047 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
14048 .row &%message_id_header_text%& "ditto"
14053 .section "Embedded Perl Startup" "SECID103"
14055 .row &%perl_at_start%& "always start the interpreter"
14056 .row &%perl_startup%& "code to obey when starting Perl"
14057 .row &%perl_taintmode%& "enable taint mode in Perl"
14062 .section "Daemon" "SECID104"
14064 .row &%daemon_smtp_ports%& "default ports"
14065 .row &%daemon_startup_retries%& "number of times to retry"
14066 .row &%daemon_startup_sleep%& "time to sleep between tries"
14067 .row &%extra_local_interfaces%& "not necessarily listened on"
14068 .row &%local_interfaces%& "on which to listen, with optional ports"
14069 .row &%pid_file_path%& "override compiled-in value"
14070 .row &%queue_run_max%& "maximum simultaneous queue runners"
14075 .section "Resource control" "SECID105"
14077 .row &%check_log_inodes%& "before accepting a message"
14078 .row &%check_log_space%& "before accepting a message"
14079 .row &%check_spool_inodes%& "before accepting a message"
14080 .row &%check_spool_space%& "before accepting a message"
14081 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
14082 .row &%queue_only_load%& "queue incoming if load high"
14083 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14084 .row &%queue_run_max%& "maximum simultaneous queue runners"
14085 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14086 .row &%smtp_accept_max%& "simultaneous incoming connections"
14087 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14088 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14089 .row &%smtp_accept_max_per_connection%& "messages per connection"
14090 .row &%smtp_accept_max_per_host%& "connections from one host"
14091 .row &%smtp_accept_queue%& "queue mail if more connections"
14092 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14094 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14095 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14096 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14097 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
14098 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14103 .section "Policy controls" "SECID106"
14105 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
14106 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
14107 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
14108 .row &%acl_smtp_auth%& "ACL for AUTH"
14109 .row &%acl_smtp_connect%& "ACL for connection"
14110 .row &%acl_smtp_data%& "ACL for DATA"
14111 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
14112 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
14113 .row &%acl_smtp_etrn%& "ACL for ETRN"
14114 .row &%acl_smtp_expn%& "ACL for EXPN"
14115 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
14116 .row &%acl_smtp_mail%& "ACL for MAIL"
14117 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
14118 .row &%acl_smtp_mime%& "ACL for MIME parts"
14119 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
14120 .row &%acl_smtp_predata%& "ACL for start of data"
14121 .row &%acl_smtp_quit%& "ACL for QUIT"
14122 .row &%acl_smtp_rcpt%& "ACL for RCPT"
14123 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
14124 .row &%acl_smtp_vrfy%& "ACL for VRFY"
14125 .row &%av_scanner%& "specify virus scanner"
14126 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14128 .row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
14129 .row &%dns_csa_search_limit%& "control CSA parent search depth"
14130 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
14131 .row &%header_maxsize%& "total size of message header"
14132 .row &%header_line_maxsize%& "individual header line limit"
14133 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
14134 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
14135 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
14136 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
14137 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
14138 .row &%host_lookup%& "host name looked up for these hosts"
14139 .row &%host_lookup_order%& "order of DNS and local name lookups"
14140 .row &%hosts_proxy%& "use proxy protocol for these hosts"
14141 .row &%host_reject_connection%& "reject connection from these hosts"
14142 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
14143 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
14144 .row &%message_size_limit%& "for all messages"
14145 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14146 .row &%spamd_address%& "set interface to SpamAssassin"
14147 .row &%strict_acl_vars%& "object to unset ACL variables"
14152 .section "Callout cache" "SECID107"
14154 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
14156 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
14158 .row &%callout_negative_expire%& "timeout for negative address cache item"
14159 .row &%callout_positive_expire%& "timeout for positive address cache item"
14160 .row &%callout_random_local_part%& "string to use for &""random""& testing"
14165 .section "TLS" "SECID108"
14167 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
14168 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
14169 .row &%openssl_options%& "adjust OpenSSL compatibility options"
14170 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14171 .row &%tls_certificate%& "location of server certificate"
14172 .row &%tls_crl%& "certificate revocation list"
14173 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
14174 .row &%tls_dhparam%& "DH parameters for server"
14175 .row &%tls_eccurve%& "EC curve selection for server"
14176 .row &%tls_ocsp_file%& "location of server certificate status proof"
14177 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
14178 .row &%tls_privatekey%& "location of server private key"
14179 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
14180 .row &%tls_require_ciphers%& "specify acceptable ciphers"
14181 .row &%tls_try_verify_hosts%& "try to verify client certificate"
14182 .row &%tls_verify_certificates%& "expected client certificates"
14183 .row &%tls_verify_hosts%& "insist on client certificate verify"
14188 .section "Local user handling" "SECID109"
14190 .row &%finduser_retries%& "useful in NIS environments"
14191 .row &%gecos_name%& "used when creating &'Sender:'&"
14192 .row &%gecos_pattern%& "ditto"
14193 .row &%max_username_length%& "for systems that truncate"
14194 .row &%unknown_login%& "used when no login name found"
14195 .row &%unknown_username%& "ditto"
14196 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
14197 .row &%uucp_from_sender%& "ditto"
14202 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
14204 .row &%header_maxsize%& "total size of message header"
14205 .row &%header_line_maxsize%& "individual header line limit"
14206 .row &%message_size_limit%& "applies to all messages"
14207 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14208 .row &%received_header_text%& "expanded to make &'Received:'&"
14209 .row &%received_headers_max%& "for mail loop detection"
14210 .row &%recipients_max%& "limit per message"
14211 .row &%recipients_max_reject%& "permanently reject excess recipients"
14217 .section "Non-SMTP incoming messages" "SECID111"
14219 .row &%receive_timeout%& "for non-SMTP messages"
14226 .section "Incoming SMTP messages" "SECID112"
14227 See also the &'Policy controls'& section above.
14230 .row &%dkim_verify_signers%& "DKIM domain for which DKIM ACL is run"
14231 .row &%host_lookup%& "host name looked up for these hosts"
14232 .row &%host_lookup_order%& "order of DNS and local name lookups"
14233 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
14234 .row &%rfc1413_hosts%& "make ident calls to these hosts"
14235 .row &%rfc1413_query_timeout%& "zero disables ident calls"
14236 .row &%sender_unqualified_hosts%& "may send unqualified senders"
14237 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
14238 .row &%smtp_accept_max%& "simultaneous incoming connections"
14239 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14240 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14241 .row &%smtp_accept_max_per_connection%& "messages per connection"
14242 .row &%smtp_accept_max_per_host%& "connections from one host"
14243 .row &%smtp_accept_queue%& "queue mail if more connections"
14244 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14246 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14247 .row &%smtp_active_hostname%& "host name to use in messages"
14248 .row &%smtp_banner%& "text for welcome banner"
14249 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14250 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14251 .row &%smtp_enforce_sync%& "of SMTP command/responses"
14252 .row &%smtp_etrn_command%& "what to run for ETRN"
14253 .row &%smtp_etrn_serialize%& "only one at once"
14254 .row &%smtp_load_reserve%& "only reserve hosts if this load"
14255 .row &%smtp_max_unknown_commands%& "before dropping connection"
14256 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
14257 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
14258 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
14259 .row &%smtp_receive_timeout%& "per command or data line"
14260 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14261 .row &%smtp_return_error_details%& "give detail on rejections"
14266 .section "SMTP extensions" "SECID113"
14268 .row &%accept_8bitmime%& "advertise 8BITMIME"
14269 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
14270 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
14271 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
14272 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
14273 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
14274 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
14275 .row &%prdr_enable%& "advertise PRDR to all hosts"
14276 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
14277 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14282 .section "Processing messages" "SECID114"
14284 .row &%allow_domain_literals%& "recognize domain literal syntax"
14285 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
14286 .row &%allow_utf8_domains%& "in addresses"
14287 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14289 .row &%delivery_date_remove%& "from incoming messages"
14290 .row &%envelope_to_remove%& "from incoming messages"
14291 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
14292 .row &%headers_charset%& "default for translations"
14293 .row &%qualify_domain%& "default for senders"
14294 .row &%qualify_recipient%& "default for recipients"
14295 .row &%return_path_remove%& "from incoming messages"
14296 .row &%strip_excess_angle_brackets%& "in addresses"
14297 .row &%strip_trailing_dot%& "at end of addresses"
14298 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
14303 .section "System filter" "SECID115"
14305 .row &%system_filter%& "locate system filter"
14306 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
14308 .row &%system_filter_file_transport%& "transport for delivery to a file"
14309 .row &%system_filter_group%& "group for filter running"
14310 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
14311 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
14312 .row &%system_filter_user%& "user for filter running"
14317 .section "Routing and delivery" "SECID116"
14319 .row &%disable_ipv6%& "do no IPv6 processing"
14320 .row &%dns_again_means_nonexist%& "for broken domains"
14321 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
14322 .row &%dns_dnssec_ok%& "parameter for resolver"
14323 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
14324 .row &%dns_retrans%& "parameter for resolver"
14325 .row &%dns_retry%& "parameter for resolver"
14326 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
14327 .row &%dns_use_edns0%& "parameter for resolver"
14328 .row &%hold_domains%& "hold delivery for these domains"
14329 .row &%local_interfaces%& "for routing checks"
14330 .row &%queue_domains%& "no immediate delivery for these"
14331 .row &%queue_only%& "no immediate delivery at all"
14332 .row &%queue_only_file%& "no immediate delivery if file exists"
14333 .row &%queue_only_load%& "no immediate delivery if load is high"
14334 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14335 .row &%queue_only_override%& "allow command line to override"
14336 .row &%queue_run_in_order%& "order of arrival"
14337 .row &%queue_run_max%& "of simultaneous queue runners"
14338 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
14339 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14340 .row &%remote_sort_domains%& "order of remote deliveries"
14341 .row &%retry_data_expire%& "timeout for retry data"
14342 .row &%retry_interval_max%& "safety net for retry rules"
14347 .section "Bounce and warning messages" "SECID117"
14349 .row &%bounce_message_file%& "content of bounce"
14350 .row &%bounce_message_text%& "content of bounce"
14351 .row &%bounce_return_body%& "include body if returning message"
14352 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
14353 .row &%bounce_return_message%& "include original message in bounce"
14354 .row &%bounce_return_size_limit%& "limit on returned message"
14355 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
14356 .row &%dsn_from%& "set &'From:'& contents in bounces"
14357 .row &%errors_copy%& "copy bounce messages"
14358 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
14359 .row &%delay_warning%& "time schedule"
14360 .row &%delay_warning_condition%& "condition for warning messages"
14361 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
14362 .row &%smtp_return_error_details%& "give detail on rejections"
14363 .row &%warn_message_file%& "content of warning message"
14368 .section "Alphabetical list of main options" "SECTalomo"
14369 Those options that undergo string expansion before use are marked with
14372 .option accept_8bitmime main boolean true
14374 .cindex "8-bit characters"
14375 .cindex "log" "selectors"
14376 .cindex "log" "8BITMIME"
14377 This option causes Exim to send 8BITMIME in its response to an SMTP
14378 EHLO command, and to accept the BODY= parameter on MAIL commands.
14379 However, though Exim is 8-bit clean, it is not a protocol converter, and it
14380 takes no steps to do anything special with messages received by this route.
14382 Historically Exim kept this option off by default, but the maintainers
14383 feel that in today's Internet, this causes more problems than it solves.
14384 It now defaults to true.
14385 A more detailed analysis of the issues is provided by Dan Bernstein:
14387 &url(https://cr.yp.to/smtp/8bitmime.html)
14390 To log received 8BITMIME status use
14392 log_selector = +8bitmime
14395 .option acl_not_smtp main string&!! unset
14396 .cindex "&ACL;" "for non-SMTP messages"
14397 .cindex "non-SMTP messages" "ACLs for"
14398 This option defines the ACL that is run when a non-SMTP message has been
14399 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
14402 .option acl_not_smtp_mime main string&!! unset
14403 This option defines the ACL that is run for individual MIME parts of non-SMTP
14404 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
14407 .option acl_not_smtp_start main string&!! unset
14408 .cindex "&ACL;" "at start of non-SMTP message"
14409 .cindex "non-SMTP messages" "ACLs for"
14410 This option defines the ACL that is run before Exim starts reading a
14411 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
14413 .option acl_smtp_auth main string&!! unset
14414 .cindex "&ACL;" "setting up for SMTP commands"
14415 .cindex "AUTH" "ACL for"
14416 This option defines the ACL that is run when an SMTP AUTH command is
14417 received. See chapter &<<CHAPACL>>& for further details.
14419 .option acl_smtp_connect main string&!! unset
14420 .cindex "&ACL;" "on SMTP connection"
14421 This option defines the ACL that is run when an SMTP connection is received.
14422 See chapter &<<CHAPACL>>& for further details.
14424 .option acl_smtp_data main string&!! unset
14425 .cindex "DATA" "ACL for"
14426 This option defines the ACL that is run after an SMTP DATA command has been
14427 processed and the message itself has been received, but before the final
14428 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
14430 .option acl_smtp_data_prdr main string&!! accept
14431 .cindex "PRDR" "ACL for"
14432 .cindex "DATA" "PRDR ACL for"
14433 .cindex "&ACL;" "PRDR-related"
14434 .cindex "&ACL;" "per-user data processing"
14435 This option defines the ACL that,
14436 if the PRDR feature has been negotiated,
14437 is run for each recipient after an SMTP DATA command has been
14438 processed and the message itself has been received, but before the
14439 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
14441 .option acl_smtp_dkim main string&!! unset
14442 .cindex DKIM "ACL for"
14443 This option defines the ACL that is run for each DKIM signature
14444 (by default, or as specified in the dkim_verify_signers option)
14445 of a received message.
14446 See section &<<SECDKIMVFY>>& for further details.
14448 .option acl_smtp_etrn main string&!! unset
14449 .cindex "ETRN" "ACL for"
14450 This option defines the ACL that is run when an SMTP ETRN command is
14451 received. See chapter &<<CHAPACL>>& for further details.
14453 .option acl_smtp_expn main string&!! unset
14454 .cindex "EXPN" "ACL for"
14455 This option defines the ACL that is run when an SMTP EXPN command is
14456 received. See chapter &<<CHAPACL>>& for further details.
14458 .option acl_smtp_helo main string&!! unset
14459 .cindex "EHLO" "ACL for"
14460 .cindex "HELO" "ACL for"
14461 This option defines the ACL that is run when an SMTP EHLO or HELO
14462 command is received. See chapter &<<CHAPACL>>& for further details.
14465 .option acl_smtp_mail main string&!! unset
14466 .cindex "MAIL" "ACL for"
14467 This option defines the ACL that is run when an SMTP MAIL command is
14468 received. See chapter &<<CHAPACL>>& for further details.
14470 .option acl_smtp_mailauth main string&!! unset
14471 .cindex "AUTH" "on MAIL command"
14472 This option defines the ACL that is run when there is an AUTH parameter on
14473 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
14474 &<<CHAPSMTPAUTH>>& for details of authentication.
14476 .option acl_smtp_mime main string&!! unset
14477 .cindex "MIME content scanning" "ACL for"
14478 This option is available when Exim is built with the content-scanning
14479 extension. It defines the ACL that is run for each MIME part in a message. See
14480 section &<<SECTscanmimepart>>& for details.
14482 .option acl_smtp_notquit main string&!! unset
14483 .cindex "not-QUIT, ACL for"
14484 This option defines the ACL that is run when an SMTP session
14485 ends without a QUIT command being received.
14486 See chapter &<<CHAPACL>>& for further details.
14488 .option acl_smtp_predata main string&!! unset
14489 This option defines the ACL that is run when an SMTP DATA command is
14490 received, before the message itself is received. See chapter &<<CHAPACL>>& for
14493 .option acl_smtp_quit main string&!! unset
14494 .cindex "QUIT, ACL for"
14495 This option defines the ACL that is run when an SMTP QUIT command is
14496 received. See chapter &<<CHAPACL>>& for further details.
14498 .option acl_smtp_rcpt main string&!! unset
14499 .cindex "RCPT" "ACL for"
14500 This option defines the ACL that is run when an SMTP RCPT command is
14501 received. See chapter &<<CHAPACL>>& for further details.
14503 .option acl_smtp_starttls main string&!! unset
14504 .cindex "STARTTLS, ACL for"
14505 This option defines the ACL that is run when an SMTP STARTTLS command is
14506 received. See chapter &<<CHAPACL>>& for further details.
14508 .option acl_smtp_vrfy main string&!! unset
14509 .cindex "VRFY" "ACL for"
14510 This option defines the ACL that is run when an SMTP VRFY command is
14511 received. See chapter &<<CHAPACL>>& for further details.
14513 .option add_environment main "string list" empty
14514 .cindex "environment" "set values"
14515 This option allows to set individual environment variables that the
14516 currently linked libraries and programs in child processes use.
14517 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
14519 .option admin_groups main "string list&!!" unset
14520 .cindex "admin user"
14521 This option is expanded just once, at the start of Exim's processing. If the
14522 current group or any of the supplementary groups of an Exim caller is in this
14523 colon-separated list, the caller has admin privileges. If all your system
14524 programmers are in a specific group, for example, you can give them all Exim
14525 admin privileges by putting that group in &%admin_groups%&. However, this does
14526 not permit them to read Exim's spool files (whose group owner is the Exim gid).
14527 To permit this, you have to add individuals to the Exim group.
14529 .option allow_domain_literals main boolean false
14530 .cindex "domain literal"
14531 If this option is set, the RFC 2822 domain literal format is permitted in
14532 email addresses. The option is not set by default, because the domain literal
14533 format is not normally required these days, and few people know about it. It
14534 has, however, been exploited by mail abusers.
14536 Unfortunately, it seems that some DNS black list maintainers are using this
14537 format to report black listing to postmasters. If you want to accept messages
14538 addressed to your hosts by IP address, you need to set
14539 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
14540 domains (defined in the named domain list &%local_domains%& in the default
14541 configuration). This &"magic string"& matches the domain literal form of all
14542 the local host's IP addresses.
14545 .option allow_mx_to_ip main boolean false
14546 .cindex "MX record" "pointing to IP address"
14547 It appears that more and more DNS zone administrators are breaking the rules
14548 and putting domain names that look like IP addresses on the right hand side of
14549 MX records. Exim follows the rules and rejects this, giving an error message
14550 that explains the misconfiguration. However, some other MTAs support this
14551 practice, so to avoid &"Why can't Exim do this?"& complaints,
14552 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
14553 recommended, except when you have no other choice.
14555 .option allow_utf8_domains main boolean false
14556 .cindex "domain" "UTF-8 characters in"
14557 .cindex "UTF-8" "in domain name"
14558 Lots of discussion is going on about internationalized domain names. One
14559 camp is strongly in favour of just using UTF-8 characters, and it seems
14560 that at least two other MTAs permit this. This option allows Exim users to
14561 experiment if they wish.
14563 If it is set true, Exim's domain parsing function allows valid
14564 UTF-8 multicharacters to appear in domain name components, in addition to
14565 letters, digits, and hyphens. However, just setting this option is not
14566 enough; if you want to look up these domain names in the DNS, you must also
14567 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
14568 suitable setting is:
14570 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
14571 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
14573 Alternatively, you can just disable this feature by setting
14575 dns_check_names_pattern =
14577 That is, set the option to an empty string so that no check is done.
14580 .option auth_advertise_hosts main "host list&!!" *
14581 .cindex "authentication" "advertising"
14582 .cindex "AUTH" "advertising"
14583 If any server authentication mechanisms are configured, Exim advertises them in
14584 response to an EHLO command only if the calling host matches this list.
14585 Otherwise, Exim does not advertise AUTH.
14586 Exim does not accept AUTH commands from clients to which it has not
14587 advertised the availability of AUTH. The advertising of individual
14588 authentication mechanisms can be controlled by the use of the
14589 &%server_advertise_condition%& generic authenticator option on the individual
14590 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
14592 Certain mail clients (for example, Netscape) require the user to provide a name
14593 and password for authentication if AUTH is advertised, even though it may
14594 not be needed (the host may accept messages from hosts on its local LAN without
14595 authentication, for example). The &%auth_advertise_hosts%& option can be used
14596 to make these clients more friendly by excluding them from the set of hosts to
14597 which Exim advertises AUTH.
14599 .cindex "AUTH" "advertising when encrypted"
14600 If you want to advertise the availability of AUTH only when the connection
14601 is encrypted using TLS, you can make use of the fact that the value of this
14602 option is expanded, with a setting like this:
14604 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
14606 .vindex "&$tls_in_cipher$&"
14607 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
14608 the expansion is empty, thus matching no hosts. Otherwise, the result of the
14609 expansion is *, which matches all hosts.
14612 .option auto_thaw main time 0s
14613 .cindex "thawing messages"
14614 .cindex "unfreezing messages"
14615 If this option is set to a time greater than zero, a queue runner will try a
14616 new delivery attempt on any frozen message, other than a bounce message, if
14617 this much time has passed since it was frozen. This may result in the message
14618 being re-frozen if nothing has changed since the last attempt. It is a way of
14619 saying &"keep on trying, even though there are big problems"&.
14621 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
14622 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
14623 thought to be very useful any more, and its use should probably be avoided.
14626 .option av_scanner main string "see below"
14627 This option is available if Exim is built with the content-scanning extension.
14628 It specifies which anti-virus scanner to use. The default value is:
14630 sophie:/var/run/sophie
14632 If the value of &%av_scanner%& starts with a dollar character, it is expanded
14633 before use. See section &<<SECTscanvirus>>& for further details.
14636 .option bi_command main string unset
14638 This option supplies the name of a command that is run when Exim is called with
14639 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
14640 just the command name, it is not a complete command line. If an argument is
14641 required, it must come from the &%-oA%& command line option.
14644 .option bounce_message_file main string unset
14645 .cindex "bounce message" "customizing"
14646 .cindex "customizing" "bounce message"
14647 This option defines a template file containing paragraphs of text to be used
14648 for constructing bounce messages. Details of the file's contents are given in
14649 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
14652 .option bounce_message_text main string unset
14653 When this option is set, its contents are included in the default bounce
14654 message immediately after &"This message was created automatically by mail
14655 delivery software."& It is not used if &%bounce_message_file%& is set.
14657 .option bounce_return_body main boolean true
14658 .cindex "bounce message" "including body"
14659 This option controls whether the body of an incoming message is included in a
14660 bounce message when &%bounce_return_message%& is true. The default setting
14661 causes the entire message, both header and body, to be returned (subject to the
14662 value of &%bounce_return_size_limit%&). If this option is false, only the
14663 message header is included. In the case of a non-SMTP message containing an
14664 error that is detected during reception, only those header lines preceding the
14665 point at which the error was detected are returned.
14666 .cindex "bounce message" "including original"
14668 .option bounce_return_linesize_limit main integer 998
14669 .cindex "size" "of bounce lines, limit"
14670 .cindex "bounce message" "line length limit"
14671 .cindex "limit" "bounce message line length"
14672 This option sets a limit in bytes on the line length of messages
14673 that are returned to senders due to delivery problems,
14674 when &%bounce_return_message%& is true.
14675 The default value corresponds to RFC limits.
14676 If the message being returned has lines longer than this value it is
14677 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
14679 The option also applies to bounces returned when an error is detected
14680 during reception of a message.
14681 In this case lines from the original are truncated.
14683 The option does not apply to messages generated by an &(autoreply)& transport.
14686 .option bounce_return_message main boolean true
14687 If this option is set false, none of the original message is included in
14688 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
14689 &%bounce_return_body%&.
14692 .option bounce_return_size_limit main integer 100K
14693 .cindex "size" "of bounce, limit"
14694 .cindex "bounce message" "size limit"
14695 .cindex "limit" "bounce message size"
14696 This option sets a limit in bytes on the size of messages that are returned to
14697 senders as part of bounce messages when &%bounce_return_message%& is true. The
14698 limit should be less than the value of the global &%message_size_limit%& and of
14699 any &%message_size_limit%& settings on transports, to allow for the bounce text
14700 that Exim generates. If this option is set to zero there is no limit.
14702 When the body of any message that is to be included in a bounce message is
14703 greater than the limit, it is truncated, and a comment pointing this out is
14704 added at the top. The actual cutoff may be greater than the value given, owing
14705 to the use of buffering for transferring the message in chunks (typically 8K in
14706 size). The idea is to save bandwidth on those undeliverable 15-megabyte
14709 .option bounce_sender_authentication main string unset
14710 .cindex "bounce message" "sender authentication"
14711 .cindex "authentication" "bounce message"
14712 .cindex "AUTH" "on bounce message"
14713 This option provides an authenticated sender address that is sent with any
14714 bounce messages generated by Exim that are sent over an authenticated SMTP
14715 connection. A typical setting might be:
14717 bounce_sender_authentication = mailer-daemon@my.domain.example
14719 which would cause bounce messages to be sent using the SMTP command:
14721 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
14723 The value of &%bounce_sender_authentication%& must always be a complete email
14726 .option callout_domain_negative_expire main time 3h
14727 .cindex "caching" "callout timeouts"
14728 .cindex "callout" "caching timeouts"
14729 This option specifies the expiry time for negative callout cache data for a
14730 domain. See section &<<SECTcallver>>& for details of callout verification, and
14731 section &<<SECTcallvercache>>& for details of the caching.
14734 .option callout_domain_positive_expire main time 7d
14735 This option specifies the expiry time for positive callout cache data for a
14736 domain. See section &<<SECTcallver>>& for details of callout verification, and
14737 section &<<SECTcallvercache>>& for details of the caching.
14740 .option callout_negative_expire main time 2h
14741 This option specifies the expiry time for negative callout cache data for an
14742 address. See section &<<SECTcallver>>& for details of callout verification, and
14743 section &<<SECTcallvercache>>& for details of the caching.
14746 .option callout_positive_expire main time 24h
14747 This option specifies the expiry time for positive callout cache data for an
14748 address. See section &<<SECTcallver>>& for details of callout verification, and
14749 section &<<SECTcallvercache>>& for details of the caching.
14752 .option callout_random_local_part main string&!! "see below"
14753 This option defines the &"random"& local part that can be used as part of
14754 callout verification. The default value is
14756 $primary_hostname-$tod_epoch-testing
14758 See section &<<CALLaddparcall>>& for details of how this value is used.
14761 .option check_log_inodes main integer 100
14762 See &%check_spool_space%& below.
14765 .option check_log_space main integer 10M
14766 See &%check_spool_space%& below.
14768 .oindex "&%check_rfc2047_length%&"
14769 .cindex "RFC 2047" "disabling length check"
14770 .option check_rfc2047_length main boolean true
14771 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
14772 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
14773 word; strings to be encoded that exceed this length are supposed to use
14774 multiple encoded words. By default, Exim does not recognize encoded words that
14775 exceed the maximum length. However, it seems that some software, in violation
14776 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
14777 set false, Exim recognizes encoded words of any length.
14780 .option check_spool_inodes main integer 100
14781 See &%check_spool_space%& below.
14784 .option check_spool_space main integer 10M
14785 .cindex "checking disk space"
14786 .cindex "disk space, checking"
14787 .cindex "spool directory" "checking space"
14788 The four &%check_...%& options allow for checking of disk resources before a
14789 message is accepted.
14791 .vindex "&$log_inodes$&"
14792 .vindex "&$log_space$&"
14793 .vindex "&$spool_inodes$&"
14794 .vindex "&$spool_space$&"
14795 When any of these options are nonzero, they apply to all incoming messages. If you
14796 want to apply different checks to different kinds of message, you can do so by
14797 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
14798 &$spool_space$& in an ACL with appropriate additional conditions.
14801 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
14802 either value is greater than zero, for example:
14804 check_spool_space = 100M
14805 check_spool_inodes = 100
14807 The spool partition is the one that contains the directory defined by
14808 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
14811 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
14812 files are written if either is greater than zero. These should be set only if
14813 &%log_file_path%& and &%spool_directory%& refer to different partitions.
14815 If there is less space or fewer inodes than requested, Exim refuses to accept
14816 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
14817 error response to the MAIL command. If ESMTP is in use and there was a
14818 SIZE parameter on the MAIL command, its value is added to the
14819 &%check_spool_space%& value, and the check is performed even if
14820 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
14822 The values for &%check_spool_space%& and &%check_log_space%& are held as a
14823 number of kilobytes (though specified in bytes).
14824 If a non-multiple of 1024 is specified, it is rounded up.
14826 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
14827 failure a message is written to stderr and Exim exits with a non-zero code, as
14828 it obviously cannot send an error message of any kind.
14830 There is a slight performance penalty for these checks.
14831 Versions of Exim preceding 4.88 had these disabled by default;
14832 high-rate installations confident they will never run out of resources
14833 may wish to deliberately disable them.
14835 .option chunking_advertise_hosts main "host list&!!" *
14836 .cindex CHUNKING advertisement
14837 .cindex "RFC 3030" "CHUNKING"
14838 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
14840 Hosts may use the BDAT command as an alternate to DATA.
14842 .option commandline_checks_require_admin main boolean &`false`&
14843 .cindex "restricting access to features"
14844 This option restricts various basic checking features to require an
14845 administrative user.
14846 This affects most of the &%-b*%& options, such as &%-be%&.
14848 .option debug_store main boolean &`false`&
14849 .cindex debugging "memory corruption"
14850 .cindex memory debugging
14851 This option, when true, enables extra checking in Exim's internal memory
14852 management. For use when a memory corruption issue is being investigated,
14853 it should normally be left as default.
14855 .option daemon_smtp_ports main string &`smtp`&
14856 .cindex "port" "for daemon"
14857 .cindex "TCP/IP" "setting listening ports"
14858 This option specifies one or more default SMTP ports on which the Exim daemon
14859 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
14860 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
14862 .option daemon_startup_retries main integer 9
14863 .cindex "daemon startup, retrying"
14864 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
14865 the daemon at startup when it cannot immediately bind a listening socket
14866 (typically because the socket is already in use): &%daemon_startup_retries%&
14867 defines the number of retries after the first failure, and
14868 &%daemon_startup_sleep%& defines the length of time to wait between retries.
14870 .option daemon_startup_sleep main time 30s
14871 See &%daemon_startup_retries%&.
14873 .option delay_warning main "time list" 24h
14874 .cindex "warning of delay"
14875 .cindex "delay warning, specifying"
14876 .cindex "queue" "delay warning"
14877 When a message is delayed, Exim sends a warning message to the sender at
14878 intervals specified by this option. The data is a colon-separated list of times
14879 after which to send warning messages. If the value of the option is an empty
14880 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
14881 message has been in the queue for longer than the last time, the last interval
14882 between the times is used to compute subsequent warning times. For example,
14885 delay_warning = 4h:8h:24h
14887 the first message is sent after 4 hours, the second after 8 hours, and
14888 the third one after 24 hours. After that, messages are sent every 16 hours,
14889 because that is the interval between the last two times on the list. If you set
14890 just one time, it specifies the repeat interval. For example, with:
14894 messages are repeated every six hours. To stop warnings after a given time, set
14895 a very large time at the end of the list. For example:
14897 delay_warning = 2h:12h:99d
14899 Note that the option is only evaluated at the time a delivery attempt fails,
14900 which depends on retry and queue-runner configuration.
14901 Typically retries will be configured more frequently than warning messages.
14903 .option delay_warning_condition main string&!! "see below"
14904 .vindex "&$domain$&"
14905 The string is expanded at the time a warning message might be sent. If all the
14906 deferred addresses have the same domain, it is set in &$domain$& during the
14907 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
14908 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
14909 &"false"& (the comparison being done caselessly) then the warning message is
14910 not sent. The default is:
14912 delay_warning_condition = ${if or {\
14913 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
14914 { match{$h_precedence:}{(?i)bulk|list|junk} }\
14915 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
14918 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
14919 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
14920 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
14921 &"auto-replied"& in an &'Auto-Submitted:'& header.
14923 .option deliver_drop_privilege main boolean false
14924 .cindex "unprivileged delivery"
14925 .cindex "delivery" "unprivileged"
14926 If this option is set true, Exim drops its root privilege at the start of a
14927 delivery process, and runs as the Exim user throughout. This severely restricts
14928 the kinds of local delivery that are possible, but is viable in certain types
14929 of configuration. There is a discussion about the use of root privilege in
14930 chapter &<<CHAPsecurity>>&.
14932 .option deliver_queue_load_max main fixed-point unset
14933 .cindex "load average"
14934 .cindex "queue runner" "abandoning"
14935 When this option is set, a queue run is abandoned if the system load average
14936 becomes greater than the value of the option. The option has no effect on
14937 ancient operating systems on which Exim cannot determine the load average.
14938 See also &%queue_only_load%& and &%smtp_load_reserve%&.
14941 .option delivery_date_remove main boolean true
14942 .cindex "&'Delivery-date:'& header line"
14943 Exim's transports have an option for adding a &'Delivery-date:'& header to a
14944 message when it is delivered, in exactly the same way as &'Return-path:'& is
14945 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
14946 should not be present in incoming messages, and this option causes them to be
14947 removed at the time the message is received, to avoid any problems that might
14948 occur when a delivered message is subsequently sent on to some other recipient.
14950 .option disable_fsync main boolean false
14951 .cindex "&[fsync()]&, disabling"
14952 This option is available only if Exim was built with the compile-time option
14953 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
14954 a runtime configuration generates an &"unknown option"& error. You should not
14955 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
14956 really, really, really understand what you are doing. &'No pre-compiled
14957 distributions of Exim should ever make this option available.'&
14959 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
14960 updated files' data to be written to disc before continuing. Unexpected events
14961 such as crashes and power outages may cause data to be lost or scrambled.
14962 Here be Dragons. &*Beware.*&
14965 .option disable_ipv6 main boolean false
14966 .cindex "IPv6" "disabling"
14967 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
14968 activities take place. AAAA records are never looked up, and any IPv6 addresses
14969 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
14970 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14971 to handle IPv6 literal addresses.
14974 .option dkim_verify_signers main "domain list&!!" $dkim_signers
14975 .cindex DKIM "controlling calls to the ACL"
14976 This option gives a list of DKIM domains for which the DKIM ACL is run.
14977 It is expanded after the message is received; by default it runs
14978 the ACL once for each signature in the message.
14979 See section &<<SECDKIMVFY>>&.
14982 .option dns_again_means_nonexist main "domain list&!!" unset
14983 .cindex "DNS" "&""try again""& response; overriding"
14984 DNS lookups give a &"try again"& response for the DNS errors
14985 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
14986 keep trying to deliver a message, or to give repeated temporary errors to
14987 incoming mail. Sometimes the effect is caused by a badly set up name server and
14988 may persist for a long time. If a domain which exhibits this problem matches
14989 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
14990 This option should be used with care. You can make it apply to reverse lookups
14991 by a setting such as this:
14993 dns_again_means_nonexist = *.in-addr.arpa
14995 This option applies to all DNS lookups that Exim does. It also applies when the
14996 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
14997 since these are most likely to be caused by DNS lookup problems. The
14998 &(dnslookup)& router has some options of its own for controlling what happens
14999 when lookups for MX or SRV records give temporary errors. These more specific
15000 options are applied after this global option.
15002 .option dns_check_names_pattern main string "see below"
15003 .cindex "DNS" "pre-check of name syntax"
15004 When this option is set to a non-empty string, it causes Exim to check domain
15005 names for characters that are not allowed in host names before handing them to
15006 the DNS resolver, because some resolvers give temporary errors for names that
15007 contain unusual characters. If a domain name contains any unwanted characters,
15008 a &"not found"& result is forced, and the resolver is not called. The check is
15009 done by matching the domain name against a regular expression, which is the
15010 value of this option. The default pattern is
15012 dns_check_names_pattern = \
15013 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
15015 which permits only letters, digits, slashes, and hyphens in components, but
15016 they must start and end with a letter or digit. Slashes are not, in fact,
15017 permitted in host names, but they are found in certain NS records (which can be
15018 accessed in Exim by using a &%dnsdb%& lookup). If you set
15019 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
15022 .option dns_csa_search_limit main integer 5
15023 This option controls the depth of parental searching for CSA SRV records in the
15024 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
15026 .option dns_csa_use_reverse main boolean true
15027 This option controls whether or not an IP address, given as a CSA domain, is
15028 reversed and looked up in the reverse DNS, as described in more detail in
15029 section &<<SECTverifyCSA>>&.
15031 .option dns_cname_loops main integer 1
15032 .cindex DNS "CNAME following"
15033 This option controls the following of CNAME chains, needed if the resolver does
15034 not do it internally.
15035 As of 2018 most should, and the default can be left.
15036 If you have an ancient one, a value of 10 is likely needed.
15038 The default value of one CNAME-follow is needed
15039 thanks to the observed return for an MX request,
15040 given no MX presence but a CNAME to an A, of the CNAME.
15043 .option dns_dnssec_ok main integer -1
15044 .cindex "DNS" "resolver options"
15045 .cindex "DNS" "DNSSEC"
15046 If this option is set to a non-negative number then Exim will initialise the
15047 DNS resolver library to either use or not use DNSSEC, overriding the system
15048 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
15050 If the resolver library does not support DNSSEC then this option has no effect.
15053 .option dns_ipv4_lookup main "domain list&!!" unset
15054 .cindex "IPv6" "DNS lookup for AAAA records"
15055 .cindex "DNS" "IPv6 lookup for AAAA records"
15056 .cindex DNS "IPv6 disabling"
15057 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
15058 looks for IPv6 address records (AAAA records) as well as IPv4 address records
15059 (A records) when trying to find IP addresses for hosts, unless the host's
15060 domain matches this list.
15062 This is a fudge to help with name servers that give big delays or otherwise do
15063 not work for the AAAA record type. In due course, when the world's name
15064 servers have all been upgraded, there should be no need for this option.
15067 .option dns_retrans main time 0s
15068 .cindex "DNS" "resolver options"
15069 .cindex timeout "dns lookup"
15070 .cindex "DNS" timeout
15071 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
15072 retransmission and retry parameters for DNS lookups. Values of zero (the
15073 defaults) leave the system default settings unchanged. The first value is the
15074 time between retries, and the second is the number of retries. It isn't
15075 totally clear exactly how these settings affect the total time a DNS lookup may
15076 take. I haven't found any documentation about timeouts on DNS lookups; these
15077 parameter values are available in the external resolver interface structure,
15078 but nowhere does it seem to describe how they are used or what you might want
15080 See also the &%slow_lookup_log%& option.
15083 .option dns_retry main integer 0
15084 See &%dns_retrans%& above.
15087 .option dns_trust_aa main "domain list&!!" unset
15088 .cindex "DNS" "resolver options"
15089 .cindex "DNS" "DNSSEC"
15090 If this option is set then lookup results marked with the AA bit
15091 (Authoritative Answer) are trusted the same way as if they were
15092 DNSSEC-verified. The authority section's name of the answer must
15093 match with this expanded domain list.
15095 Use this option only if you talk directly to a resolver that is
15096 authoritative for some zones and does not set the AD (Authentic Data)
15097 bit in the answer. Some DNS servers may have an configuration option to
15098 mark the answers from their own zones as verified (they set the AD bit).
15099 Others do not have this option. It is considered as poor practice using
15100 a resolver that is an authoritative server for some zones.
15102 Use this option only if you really have to (e.g. if you want
15103 to use DANE for remote delivery to a server that is listed in the DNS
15104 zones that your resolver is authoritative for).
15106 If the DNS answer packet has the AA bit set and contains resource record
15107 in the answer section, the name of the first NS record appearing in the
15108 authority section is compared against the list. If the answer packet is
15109 authoritative but the answer section is empty, the name of the first SOA
15110 record in the authoritative section is used instead.
15112 .cindex "DNS" "resolver options"
15113 .option dns_use_edns0 main integer -1
15114 .cindex "DNS" "resolver options"
15115 .cindex "DNS" "EDNS0"
15116 .cindex "DNS" "OpenBSD
15117 If this option is set to a non-negative number then Exim will initialise the
15118 DNS resolver library to either use or not use EDNS0 extensions, overriding
15119 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
15122 If the resolver library does not support EDNS0 then this option has no effect.
15124 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
15125 means that DNSSEC will not work with Exim on that platform either, unless Exim
15126 is linked against an alternative DNS client library.
15129 .option drop_cr main boolean false
15130 This is an obsolete option that is now a no-op. It used to affect the way Exim
15131 handled CR and LF characters in incoming messages. What happens now is
15132 described in section &<<SECTlineendings>>&.
15134 .option dsn_advertise_hosts main "host list&!!" unset
15135 .cindex "bounce messages" "success"
15136 .cindex "DSN" "success"
15137 .cindex "Delivery Status Notification" "success"
15138 DSN extensions (RFC3461) will be advertised in the EHLO message to,
15139 and accepted from, these hosts.
15140 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
15141 and RET and ORCPT options on MAIL FROM commands.
15142 A NOTIFY=SUCCESS option requests success-DSN messages.
15143 A NOTIFY= option with no argument requests that no delay or failure DSNs
15146 .option dsn_from main "string&!!" "see below"
15147 .cindex "&'From:'& header line" "in bounces"
15148 .cindex "bounce messages" "&'From:'& line, specifying"
15149 This option can be used to vary the contents of &'From:'& header lines in
15150 bounces and other automatically generated messages (&"Delivery Status
15151 Notifications"& &-- hence the name of the option). The default setting is:
15153 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
15155 The value is expanded every time it is needed. If the expansion fails, a
15156 panic is logged, and the default value is used.
15158 .option envelope_to_remove main boolean true
15159 .cindex "&'Envelope-to:'& header line"
15160 Exim's transports have an option for adding an &'Envelope-to:'& header to a
15161 message when it is delivered, in exactly the same way as &'Return-path:'& is
15162 handled. &'Envelope-to:'& records the original recipient address from the
15163 message's envelope that caused the delivery to happen. Such headers should not
15164 be present in incoming messages, and this option causes them to be removed at
15165 the time the message is received, to avoid any problems that might occur when a
15166 delivered message is subsequently sent on to some other recipient.
15169 .option errors_copy main "string list&!!" unset
15170 .cindex "bounce message" "copy to other address"
15171 .cindex "copy of bounce message"
15172 Setting this option causes Exim to send bcc copies of bounce messages that it
15173 generates to other addresses. &*Note*&: This does not apply to bounce messages
15174 coming from elsewhere. The value of the option is a colon-separated list of
15175 items. Each item consists of a pattern, terminated by white space, followed by
15176 a comma-separated list of email addresses. If a pattern contains spaces, it
15177 must be enclosed in double quotes.
15179 Each pattern is processed in the same way as a single item in an address list
15180 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
15181 the bounce message, the message is copied to the addresses on the list. The
15182 items are scanned in order, and once a matching one is found, no further items
15183 are examined. For example:
15185 errors_copy = spqr@mydomain postmaster@mydomain.example :\
15186 rqps@mydomain hostmaster@mydomain.example,\
15187 postmaster@mydomain.example
15189 .vindex "&$domain$&"
15190 .vindex "&$local_part$&"
15191 The address list is expanded before use. The expansion variables &$local_part$&
15192 and &$domain$& are set from the original recipient of the error message, and if
15193 there was any wildcard matching in the pattern, the expansion
15194 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
15195 variables &$0$&, &$1$&, etc. are set in the normal way.
15198 .option errors_reply_to main string unset
15199 .cindex "bounce message" "&'Reply-to:'& in"
15200 By default, Exim's bounce and delivery warning messages contain the header line
15202 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
15204 .oindex &%quota_warn_message%&
15205 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
15206 A warning message that is generated by the &%quota_warn_message%& option in an
15207 &(appendfile)& transport may contain its own &'From:'& header line that
15208 overrides the default.
15210 Experience shows that people reply to bounce messages. If the
15211 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
15212 and warning messages. For example:
15214 errors_reply_to = postmaster@my.domain.example
15216 The value of the option is not expanded. It must specify a valid RFC 2822
15217 address. However, if a warning message that is generated by the
15218 &%quota_warn_message%& option in an &(appendfile)& transport contain its
15219 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
15223 .option event_action main string&!! unset
15225 This option declares a string to be expanded for Exim's events mechanism.
15226 For details see chapter &<<CHAPevents>>&.
15229 .option exim_group main string "compile-time configured"
15230 .cindex "gid (group id)" "Exim's own"
15231 .cindex "Exim group"
15232 This option changes the gid under which Exim runs when it gives up root
15233 privilege. The default value is compiled into the binary. The value of this
15234 option is used only when &%exim_user%& is also set. Unless it consists entirely
15235 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
15236 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
15240 .option exim_path main string "see below"
15241 .cindex "Exim binary, path name"
15242 This option specifies the path name of the Exim binary, which is used when Exim
15243 needs to re-exec itself. The default is set up to point to the file &'exim'& in
15244 the directory configured at compile time by the BIN_DIRECTORY setting. It
15245 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
15247 &*Warning*&: Do not use a macro to define the value of this option, because
15248 you will break those Exim utilities that scan the configuration file to find
15249 where the binary is. (They then use the &%-bP%& option to extract option
15250 settings such as the value of &%spool_directory%&.)
15253 .option exim_user main string "compile-time configured"
15254 .cindex "uid (user id)" "Exim's own"
15255 .cindex "Exim user"
15256 This option changes the uid under which Exim runs when it gives up root
15257 privilege. The default value is compiled into the binary. Ownership of the run
15258 time configuration file and the use of the &%-C%& and &%-D%& command line
15259 options is checked against the values in the binary, not what is set here.
15261 Unless it consists entirely of digits, the string is looked up using
15262 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
15263 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
15264 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
15267 .option extra_local_interfaces main "string list" unset
15268 This option defines network interfaces that are to be considered local when
15269 routing, but which are not used for listening by the daemon. See section
15270 &<<SECTreclocipadd>>& for details.
15273 . Allow this long option name to split; give it unsplit as a fifth argument
15274 . for the automatic .oindex that is generated by .option.
15276 .option "extract_addresses_remove_arguments" main boolean true &&&
15277 extract_addresses_remove_arguments
15279 .cindex "command line" "addresses with &%-t%&"
15280 .cindex "Sendmail compatibility" "&%-t%& option"
15281 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
15282 are present on the command line when the &%-t%& option is used to build an
15283 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
15284 line addresses are removed from the recipients list. This is also how Smail
15285 behaves. However, other Sendmail documentation (the O'Reilly book) states that
15286 command line addresses are added to those obtained from the header lines. When
15287 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
15288 argument headers. If it is set false, Exim adds rather than removes argument
15292 .option finduser_retries main integer 0
15293 .cindex "NIS, retrying user lookups"
15294 On systems running NIS or other schemes in which user and group information is
15295 distributed from a remote system, there can be times when &[getpwnam()]& and
15296 related functions fail, even when given valid data, because things time out.
15297 Unfortunately these failures cannot be distinguished from genuine &"not found"&
15298 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
15299 many extra times to find a user or a group, waiting for one second between
15302 .cindex "&_/etc/passwd_&" "multiple reading of"
15303 You should not set this option greater than zero if your user information is in
15304 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
15305 search the file multiple times for non-existent users, and also cause delay.
15309 .option freeze_tell main "string list, comma separated" unset
15310 .cindex "freezing messages" "sending a message when freezing"
15311 On encountering certain errors, or when configured to do so in a system filter,
15312 ACL, or special router, Exim freezes a message. This means that no further
15313 delivery attempts take place until an administrator thaws the message, or the
15314 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
15315 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
15316 warning message whenever it freezes something, unless the message it is
15317 freezing is a locally-generated bounce message. (Without this exception there
15318 is the possibility of looping.) The warning message is sent to the addresses
15319 supplied as the comma-separated value of this option. If several of the
15320 message's addresses cause freezing, only a single message is sent. If the
15321 freezing was automatic, the reason(s) for freezing can be found in the message
15322 log. If you configure freezing in a filter or ACL, you must arrange for any
15323 logging that you require.
15326 .option gecos_name main string&!! unset
15328 .cindex "&""gecos""& field, parsing"
15329 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
15330 password file to hold other information in addition to users' real names. Exim
15331 looks up this field for use when it is creating &'Sender:'& or &'From:'&
15332 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
15333 of the field are used unchanged, except that, if an ampersand is encountered,
15334 it is replaced by the user's login name with the first character forced to
15335 upper case, since this is a convention that is observed on many systems.
15337 When these options are set, &%gecos_pattern%& is treated as a regular
15338 expression that is to be applied to the field (again with && replaced by the
15339 login name), and if it matches, &%gecos_name%& is expanded and used as the
15342 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
15343 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
15344 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
15345 name terminates at the first comma, the following can be used:
15347 gecos_pattern = ([^,]*)
15351 .option gecos_pattern main string unset
15352 See &%gecos_name%& above.
15355 .option gnutls_compat_mode main boolean unset
15356 This option controls whether GnuTLS is used in compatibility mode in an Exim
15357 server. This reduces security slightly, but improves interworking with older
15358 implementations of TLS.
15361 .option gnutls_allow_auto_pkcs11 main boolean unset
15362 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
15363 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
15366 &url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
15371 .option headers_charset main string "see below"
15372 This option sets a default character set for translating from encoded MIME
15373 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
15374 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
15375 ultimate default is ISO-8859-1. For more details see the description of header
15376 insertions in section &<<SECTexpansionitems>>&.
15380 .option header_maxsize main integer "see below"
15381 .cindex "header section" "maximum size of"
15382 .cindex "limit" "size of message header section"
15383 This option controls the overall maximum size of a message's header
15384 section. The default is the value of HEADER_MAXSIZE in
15385 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
15386 sections are rejected.
15389 .option header_line_maxsize main integer 0
15390 .cindex "header lines" "maximum size of"
15391 .cindex "limit" "size of one header line"
15392 This option limits the length of any individual header line in a message, after
15393 all the continuations have been joined together. Messages with individual
15394 header lines that are longer than the limit are rejected. The default value of
15395 zero means &"no limit"&.
15400 .option helo_accept_junk_hosts main "host list&!!" unset
15401 .cindex "HELO" "accepting junk data"
15402 .cindex "EHLO" "accepting junk data"
15403 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
15404 mail, and gives an error response for invalid data. Unfortunately, there are
15405 some SMTP clients that send syntactic junk. They can be accommodated by setting
15406 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
15407 if you want to do semantic checking.
15408 See also &%helo_allow_chars%& for a way of extending the permitted character
15412 .option helo_allow_chars main string unset
15413 .cindex "HELO" "underscores in"
15414 .cindex "EHLO" "underscores in"
15415 .cindex "underscore in EHLO/HELO"
15416 This option can be set to a string of rogue characters that are permitted in
15417 all EHLO and HELO names in addition to the standard letters, digits,
15418 hyphens, and dots. If you really must allow underscores, you can set
15420 helo_allow_chars = _
15422 Note that the value is one string, not a list.
15425 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
15426 .cindex "HELO" "forcing reverse lookup"
15427 .cindex "EHLO" "forcing reverse lookup"
15428 If the domain given by a client in a HELO or EHLO command matches this
15429 list, a reverse lookup is done in order to establish the host's true name. The
15430 default forces a lookup if the client host gives the server's name or any of
15431 its IP addresses (in brackets), something that broken clients have been seen to
15435 .option helo_try_verify_hosts main "host list&!!" unset
15436 .cindex "HELO verifying" "optional"
15437 .cindex "EHLO" "verifying, optional"
15438 By default, Exim just checks the syntax of HELO and EHLO commands (see
15439 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
15440 to do more extensive checking of the data supplied by these commands. The ACL
15441 condition &`verify = helo`& is provided to make this possible.
15442 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
15443 to force the check to occur. From release 4.53 onwards, this is no longer
15444 necessary. If the check has not been done before &`verify = helo`& is
15445 encountered, it is done at that time. Consequently, this option is obsolete.
15446 Its specification is retained here for backwards compatibility.
15448 When an EHLO or HELO command is received, if the calling host matches
15449 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
15450 EHLO command either:
15453 is an IP literal matching the calling address of the host, or
15455 .cindex "DNS" "reverse lookup"
15456 .cindex "reverse DNS lookup"
15457 matches the host name that Exim obtains by doing a reverse lookup of the
15458 calling host address, or
15460 when looked up in DNS yields the calling host address.
15463 However, the EHLO or HELO command is not rejected if any of the checks
15464 fail. Processing continues, but the result of the check is remembered, and can
15465 be detected later in an ACL by the &`verify = helo`& condition.
15467 If DNS was used for successful verification, the variable
15468 .cindex "DNS" "DNSSEC"
15469 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
15471 .option helo_verify_hosts main "host list&!!" unset
15472 .cindex "HELO verifying" "mandatory"
15473 .cindex "EHLO" "verifying, mandatory"
15474 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
15475 backwards compatibility. For hosts that match this option, Exim checks the host
15476 name given in the HELO or EHLO in the same way as for
15477 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
15478 rejected with a 550 error, and entries are written to the main and reject logs.
15479 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
15482 .option hold_domains main "domain list&!!" unset
15483 .cindex "domain" "delaying delivery"
15484 .cindex "delivery" "delaying certain domains"
15485 This option allows mail for particular domains to be held in the queue
15486 manually. The option is overridden if a message delivery is forced with the
15487 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
15488 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
15489 item in &%hold_domains%&, no routing or delivery for that address is done, and
15490 it is deferred every time the message is looked at.
15492 This option is intended as a temporary operational measure for delaying the
15493 delivery of mail while some problem is being sorted out, or some new
15494 configuration tested. If you just want to delay the processing of some
15495 domains until a queue run occurs, you should use &%queue_domains%& or
15496 &%queue_smtp_domains%&, not &%hold_domains%&.
15498 A setting of &%hold_domains%& does not override Exim's code for removing
15499 messages from the queue if they have been there longer than the longest retry
15500 time in any retry rule. If you want to hold messages for longer than the normal
15501 retry times, insert a dummy retry rule with a long retry time.
15504 .option host_lookup main "host list&!!" unset
15505 .cindex "host name" "lookup, forcing"
15506 Exim does not look up the name of a calling host from its IP address unless it
15507 is required to compare against some host list, or the host matches
15508 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
15509 option (which normally contains IP addresses rather than host names). The
15510 default configuration file contains
15514 which causes a lookup to happen for all hosts. If the expense of these lookups
15515 is felt to be too great, the setting can be changed or removed.
15517 After a successful reverse lookup, Exim does a forward lookup on the name it
15518 has obtained, to verify that it yields the IP address that it started with. If
15519 this check fails, Exim behaves as if the name lookup failed.
15521 .vindex "&$host_lookup_failed$&"
15522 .vindex "&$sender_host_name$&"
15523 After any kind of failure, the host name (in &$sender_host_name$&) remains
15524 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
15525 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
15526 &`verify = reverse_host_lookup`& in ACLs.
15529 .option host_lookup_order main "string list" &`bydns:byaddr`&
15530 This option specifies the order of different lookup methods when Exim is trying
15531 to find a host name from an IP address. The default is to do a DNS lookup
15532 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
15533 if that fails. You can change the order of these lookups, or omit one entirely,
15536 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
15537 multiple PTR records in the DNS and the IP address is not listed in
15538 &_/etc/hosts_&. Different operating systems give different results in this
15539 case. That is why the default tries a DNS lookup first.
15543 .option host_reject_connection main "host list&!!" unset
15544 .cindex "host" "rejecting connections from"
15545 If this option is set, incoming SMTP calls from the hosts listed are rejected
15546 as soon as the connection is made.
15547 This option is obsolete, and retained only for backward compatibility, because
15548 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
15549 connections immediately.
15551 The ability to give an immediate rejection (either by this option or using an
15552 ACL) is provided for use in unusual cases. Many hosts will just try again,
15553 sometimes without much delay. Normally, it is better to use an ACL to reject
15554 incoming messages at a later stage, such as after RCPT commands. See
15555 chapter &<<CHAPACL>>&.
15558 .option hosts_connection_nolog main "host list&!!" unset
15559 .cindex "host" "not logging connections from"
15560 This option defines a list of hosts for which connection logging does not
15561 happen, even though the &%smtp_connection%& log selector is set. For example,
15562 you might want not to log SMTP connections from local processes, or from
15563 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
15564 the daemon; you should therefore strive to restrict its value to a short inline
15565 list of IP addresses and networks. To disable logging SMTP connections from
15566 local processes, you must create a host list with an empty item. For example:
15568 hosts_connection_nolog = :
15570 If the &%smtp_connection%& log selector is not set, this option has no effect.
15574 .option hosts_proxy main "host list&!!" unset
15575 .cindex proxy "proxy protocol"
15576 This option enables use of Proxy Protocol proxies for incoming
15577 connections. For details see section &<<SECTproxyInbound>>&.
15580 .option hosts_treat_as_local main "domain list&!!" unset
15581 .cindex "local host" "domains treated as"
15582 .cindex "host" "treated as local"
15583 If this option is set, any host names that match the domain list are treated as
15584 if they were the local host when Exim is scanning host lists obtained from MX
15586 or other sources. Note that the value of this option is a domain list, not a
15587 host list, because it is always used to check host names, not IP addresses.
15589 This option also applies when Exim is matching the special items
15590 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
15591 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
15592 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
15593 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
15594 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
15595 interfaces and recognizing the local host.
15598 .option ibase_servers main "string list" unset
15599 .cindex "InterBase" "server list"
15600 This option provides a list of InterBase servers and associated connection data,
15601 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
15602 The option is available only if Exim has been built with InterBase support.
15606 .option ignore_bounce_errors_after main time 10w
15607 .cindex "bounce message" "discarding"
15608 .cindex "discarding bounce message"
15609 This option affects the processing of bounce messages that cannot be delivered,
15610 that is, those that suffer a permanent delivery failure. (Bounce messages that
15611 suffer temporary delivery failures are of course retried in the usual way.)
15613 After a permanent delivery failure, bounce messages are frozen,
15614 because there is no sender to whom they can be returned. When a frozen bounce
15615 message has been in the queue for more than the given time, it is unfrozen at
15616 the next queue run, and a further delivery is attempted. If delivery fails
15617 again, the bounce message is discarded. This makes it possible to keep failed
15618 bounce messages around for a shorter time than the normal maximum retry time
15619 for frozen messages. For example,
15621 ignore_bounce_errors_after = 12h
15623 retries failed bounce message deliveries after 12 hours, discarding any further
15624 failures. If the value of this option is set to a zero time period, bounce
15625 failures are discarded immediately. Setting a very long time (as in the default
15626 value) has the effect of disabling this option. For ways of automatically
15627 dealing with other kinds of frozen message, see &%auto_thaw%& and
15628 &%timeout_frozen_after%&.
15631 .option ignore_fromline_hosts main "host list&!!" unset
15632 .cindex "&""From""& line"
15633 .cindex "UUCP" "&""From""& line"
15634 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
15635 the headers of a message. By default this is treated as the start of the
15636 message's body, which means that any following headers are not recognized as
15637 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
15638 match those hosts that insist on sending it. If the sender is actually a local
15639 process rather than a remote host, and is using &%-bs%& to inject the messages,
15640 &%ignore_fromline_local%& must be set to achieve this effect.
15643 .option ignore_fromline_local main boolean false
15644 See &%ignore_fromline_hosts%& above.
15646 .option keep_environment main "string list" unset
15647 .cindex "environment" "values from"
15648 This option contains a string list of environment variables to keep.
15649 You have to trust these variables or you have to be sure that
15650 these variables do not impose any security risk. Keep in mind that
15651 during the startup phase Exim is running with an effective UID 0 in most
15652 installations. As the default value is an empty list, the default
15653 environment for using libraries, running embedded Perl code, or running
15654 external binaries is empty, and does not not even contain PATH or HOME.
15656 Actually the list is interpreted as a list of patterns
15657 (&<<SECTlistexpand>>&), except that it is not expanded first.
15659 WARNING: Macro substitution is still done first, so having a macro
15660 FOO and having FOO_HOME in your &%keep_environment%& option may have
15661 unexpected results. You may work around this using a regular expression
15662 that does not match the macro name: ^[F]OO_HOME$.
15664 Current versions of Exim issue a warning during startup if you do not mention
15665 &%keep_environment%& in your runtime configuration file and if your
15666 current environment is not empty. Future versions may not issue that warning
15669 See the &%add_environment%& main config option for a way to set
15670 environment variables to a fixed value. The environment for &(pipe)&
15671 transports is handled separately, see section &<<SECTpipeenv>>& for
15675 .option keep_malformed main time 4d
15676 This option specifies the length of time to keep messages whose spool files
15677 have been corrupted in some way. This should, of course, never happen. At the
15678 next attempt to deliver such a message, it gets removed. The incident is
15682 .option ldap_ca_cert_dir main string unset
15683 .cindex "LDAP", "TLS CA certificate directory"
15684 .cindex certificate "directory for LDAP"
15685 This option indicates which directory contains CA certificates for verifying
15686 a TLS certificate presented by an LDAP server.
15687 While Exim does not provide a default value, your SSL library may.
15688 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
15689 and constrained to be a directory.
15692 .option ldap_ca_cert_file main string unset
15693 .cindex "LDAP", "TLS CA certificate file"
15694 .cindex certificate "file for LDAP"
15695 This option indicates which file contains CA certificates for verifying
15696 a TLS certificate presented by an LDAP server.
15697 While Exim does not provide a default value, your SSL library may.
15698 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
15699 and constrained to be a file.
15702 .option ldap_cert_file main string unset
15703 .cindex "LDAP" "TLS client certificate file"
15704 .cindex certificate "file for LDAP"
15705 This option indicates which file contains an TLS client certificate which
15706 Exim should present to the LDAP server during TLS negotiation.
15707 Should be used together with &%ldap_cert_key%&.
15710 .option ldap_cert_key main string unset
15711 .cindex "LDAP" "TLS client key file"
15712 .cindex certificate "key for LDAP"
15713 This option indicates which file contains the secret/private key to use
15714 to prove identity to the LDAP server during TLS negotiation.
15715 Should be used together with &%ldap_cert_file%&, which contains the
15716 identity to be proven.
15719 .option ldap_cipher_suite main string unset
15720 .cindex "LDAP" "TLS cipher suite"
15721 This controls the TLS cipher-suite negotiation during TLS negotiation with
15722 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
15723 cipher-suite options with OpenSSL (as used by LDAP client libraries).
15726 .option ldap_default_servers main "string list" unset
15727 .cindex "LDAP" "default servers"
15728 This option provides a list of LDAP servers which are tried in turn when an
15729 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
15730 details of LDAP queries. This option is available only when Exim has been built
15734 .option ldap_require_cert main string unset.
15735 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
15736 This should be one of the values "hard", "demand", "allow", "try" or "never".
15737 A value other than one of these is interpreted as "never".
15738 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
15739 Although Exim does not set a default, the LDAP library probably defaults
15743 .option ldap_start_tls main boolean false
15744 .cindex "LDAP" "whether or not to negotiate TLS"
15745 If set, Exim will attempt to negotiate TLS with the LDAP server when
15746 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
15747 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
15749 In the event of failure to negotiate TLS, the action taken is controlled
15750 by &%ldap_require_cert%&.
15751 This option is ignored for &`ldapi`& connections.
15754 .option ldap_version main integer unset
15755 .cindex "LDAP" "protocol version, forcing"
15756 This option can be used to force Exim to set a specific protocol version for
15757 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
15758 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
15759 the LDAP headers; otherwise it is 2. This option is available only when Exim
15760 has been built with LDAP support.
15764 .option local_from_check main boolean true
15765 .cindex "&'Sender:'& header line" "disabling addition of"
15766 .cindex "&'From:'& header line" "disabling checking of"
15767 When a message is submitted locally (that is, not over a TCP/IP connection) by
15768 an untrusted user, Exim removes any existing &'Sender:'& header line, and
15769 checks that the &'From:'& header line matches the login of the calling user and
15770 the domain specified by &%qualify_domain%&.
15772 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
15773 locally submitted message is automatically qualified by Exim, unless the
15774 &%-bnq%& command line option is used.
15776 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
15777 on the local part. If the &'From:'& header line does not match, Exim adds a
15778 &'Sender:'& header with an address constructed from the calling user's login
15779 and the default qualify domain.
15781 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
15782 and no &'Sender:'& header is ever added. If, in addition, you want to retain
15783 &'Sender:'& header lines supplied by untrusted users, you must also set
15784 &%local_sender_retain%& to be true.
15786 .cindex "envelope sender"
15787 These options affect only the header lines in the message. The envelope sender
15788 is still forced to be the login id at the qualify domain unless
15789 &%untrusted_set_sender%& permits the user to supply an envelope sender.
15791 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
15792 request similar header line checking. See section &<<SECTthesenhea>>&, which
15793 has more details about &'Sender:'& processing.
15798 .option local_from_prefix main string unset
15799 When Exim checks the &'From:'& header line of locally submitted messages for
15800 matching the login id (see &%local_from_check%& above), it can be configured to
15801 ignore certain prefixes and suffixes in the local part of the address. This is
15802 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
15803 appropriate lists, in the same form as the &%local_part_prefix%& and
15804 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
15807 local_from_prefix = *-
15809 is set, a &'From:'& line containing
15811 From: anything-user@your.domain.example
15813 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
15814 matches the actual sender address that is constructed from the login name and
15818 .option local_from_suffix main string unset
15819 See &%local_from_prefix%& above.
15822 .option local_interfaces main "string list" "see below"
15823 This option controls which network interfaces are used by the daemon for
15824 listening; they are also used to identify the local host when routing. Chapter
15825 &<<CHAPinterfaces>>& contains a full description of this option and the related
15826 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
15827 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
15828 &%local_interfaces%& is
15830 local_interfaces = 0.0.0.0
15832 when Exim is built without IPv6 support; otherwise it is
15834 local_interfaces = <; ::0 ; 0.0.0.0
15837 .option local_scan_timeout main time 5m
15838 .cindex "timeout" "for &[local_scan()]& function"
15839 .cindex "&[local_scan()]& function" "timeout"
15840 This timeout applies to the &[local_scan()]& function (see chapter
15841 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
15842 the incoming message is rejected with a temporary error if it is an SMTP
15843 message. For a non-SMTP message, the message is dropped and Exim ends with a
15844 non-zero code. The incident is logged on the main and reject logs.
15848 .option local_sender_retain main boolean false
15849 .cindex "&'Sender:'& header line" "retaining from local submission"
15850 When a message is submitted locally (that is, not over a TCP/IP connection) by
15851 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
15852 do not want this to happen, you must set &%local_sender_retain%&, and you must
15853 also set &%local_from_check%& to be false (Exim will complain if you do not).
15854 See also the ACL modifier &`control = suppress_local_fixups`&. Section
15855 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
15860 .option localhost_number main string&!! unset
15861 .cindex "host" "locally unique number for"
15862 .cindex "message ids" "with multiple hosts"
15863 .vindex "&$localhost_number$&"
15864 Exim's message ids are normally unique only within the local host. If
15865 uniqueness among a set of hosts is required, each host must set a different
15866 value for the &%localhost_number%& option. The string is expanded immediately
15867 after reading the configuration file (so that a number can be computed from the
15868 host name, for example) and the result of the expansion must be a number in the
15869 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
15870 systems). This is available in subsequent string expansions via the variable
15871 &$localhost_number$&. When &%localhost_number is set%&, the final two
15872 characters of the message id, instead of just being a fractional part of the
15873 time, are computed from the time and the local host number as described in
15874 section &<<SECTmessiden>>&.
15878 .option log_file_path main "string list&!!" "set at compile time"
15879 .cindex "log" "file path for"
15880 This option sets the path which is used to determine the names of Exim's log
15881 files, or indicates that logging is to be to syslog, or both. It is expanded
15882 when Exim is entered, so it can, for example, contain a reference to the host
15883 name. If no specific path is set for the log files at compile or runtime,
15884 or if the option is unset at runtime (i.e. &`log_file_path = `&)
15885 they are written in a sub-directory called &_log_& in Exim's spool directory.
15886 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
15887 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
15888 used. If this string is fixed at your installation (contains no expansion
15889 variables) it is recommended that you do not set this option in the
15890 configuration file, but instead supply the path using LOG_FILE_PATH in
15891 &_Local/Makefile_& so that it is available to Exim for logging errors detected
15892 early on &-- in particular, failure to read the configuration file.
15895 .option log_selector main string unset
15896 .cindex "log" "selectors"
15897 This option can be used to reduce or increase the number of things that Exim
15898 writes to its log files. Its argument is made up of names preceded by plus or
15899 minus characters. For example:
15901 log_selector = +arguments -retry_defer
15903 A list of possible names and what they control is given in the chapter on
15904 logging, in section &<<SECTlogselector>>&.
15907 .option log_timezone main boolean false
15908 .cindex "log" "timezone for entries"
15909 .vindex "&$tod_log$&"
15910 .vindex "&$tod_zone$&"
15911 By default, the timestamps on log lines are in local time without the
15912 timezone. This means that if your timezone changes twice a year, the timestamps
15913 in log lines are ambiguous for an hour when the clocks go back. One way of
15914 avoiding this problem is to set the timezone to UTC. An alternative is to set
15915 &%log_timezone%& true. This turns on the addition of the timezone offset to
15916 timestamps in log lines. Turning on this option can add quite a lot to the size
15917 of log files because each line is extended by 6 characters. Note that the
15918 &$tod_log$& variable contains the log timestamp without the zone, but there is
15919 another variable called &$tod_zone$& that contains just the timezone offset.
15922 .option lookup_open_max main integer 25
15923 .cindex "too many open files"
15924 .cindex "open files, too many"
15925 .cindex "file" "too many open"
15926 .cindex "lookup" "maximum open files"
15927 .cindex "limit" "open files for lookups"
15928 This option limits the number of simultaneously open files for single-key
15929 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
15930 Exim normally keeps these files open during routing, because often the same
15931 file is required several times. If the limit is reached, Exim closes the least
15932 recently used file. Note that if you are using the &'ndbm'& library, it
15933 actually opens two files for each logical DBM database, though it still counts
15934 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
15935 open files"& errors with NDBM, you need to reduce the value of
15936 &%lookup_open_max%&.
15939 .option max_username_length main integer 0
15940 .cindex "length of login name"
15941 .cindex "user name" "maximum length"
15942 .cindex "limit" "user name length"
15943 Some operating systems are broken in that they truncate long arguments to
15944 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
15945 this option is set greater than zero, any attempt to call &[getpwnam()]& with
15946 an argument that is longer behaves as if &[getpwnam()]& failed.
15949 .option message_body_newlines main bool false
15950 .cindex "message body" "newlines in variables"
15951 .cindex "newline" "in message body variables"
15952 .vindex "&$message_body$&"
15953 .vindex "&$message_body_end$&"
15954 By default, newlines in the message body are replaced by spaces when setting
15955 the &$message_body$& and &$message_body_end$& expansion variables. If this
15956 option is set true, this no longer happens.
15959 .option message_body_visible main integer 500
15960 .cindex "body of message" "visible size"
15961 .cindex "message body" "visible size"
15962 .vindex "&$message_body$&"
15963 .vindex "&$message_body_end$&"
15964 This option specifies how much of a message's body is to be included in the
15965 &$message_body$& and &$message_body_end$& expansion variables.
15968 .option message_id_header_domain main string&!! unset
15969 .cindex "&'Message-ID:'& header line"
15970 If this option is set, the string is expanded and used as the right hand side
15971 (domain) of the &'Message-ID:'& header that Exim creates if a
15972 locally-originated incoming message does not have one. &"Locally-originated"&
15973 means &"not received over TCP/IP."&
15974 Otherwise, the primary host name is used.
15975 Only letters, digits, dot and hyphen are accepted; any other characters are
15976 replaced by hyphens. If the expansion is forced to fail, or if the result is an
15977 empty string, the option is ignored.
15980 .option message_id_header_text main string&!! unset
15981 If this variable is set, the string is expanded and used to augment the text of
15982 the &'Message-id:'& header that Exim creates if a locally-originated incoming
15983 message does not have one. The text of this header is required by RFC 2822 to
15984 take the form of an address. By default, Exim uses its internal message id as
15985 the local part, and the primary host name as the domain. If this option is set,
15986 it is expanded, and provided the expansion is not forced to fail, and does not
15987 yield an empty string, the result is inserted into the header immediately
15988 before the @, separated from the internal message id by a dot. Any characters
15989 that are illegal in an address are automatically converted into hyphens. This
15990 means that variables such as &$tod_log$& can be used, because the spaces and
15991 colons will become hyphens.
15994 .option message_logs main boolean true
15995 .cindex "message logs" "disabling"
15996 .cindex "log" "message log; disabling"
15997 If this option is turned off, per-message log files are not created in the
15998 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
15999 Exim, by reducing the number of files involved in handling a message from a
16000 minimum of four (header spool file, body spool file, delivery journal, and
16001 per-message log) to three. The other major I/O activity is Exim's main log,
16002 which is not affected by this option.
16005 .option message_size_limit main string&!! 50M
16006 .cindex "message" "size limit"
16007 .cindex "limit" "message size"
16008 .cindex "size" "of message, limit"
16009 This option limits the maximum size of message that Exim will process. The
16010 value is expanded for each incoming connection so, for example, it can be made
16011 to depend on the IP address of the remote host for messages arriving via
16012 TCP/IP. After expansion, the value must be a sequence of decimal digits,
16013 optionally followed by K or M.
16015 &*Note*&: This limit cannot be made to depend on a message's sender or any
16016 other properties of an individual message, because it has to be advertised in
16017 the server's response to EHLO. String expansion failure causes a temporary
16018 error. A value of zero means no limit, but its use is not recommended. See also
16019 &%bounce_return_size_limit%&.
16021 Incoming SMTP messages are failed with a 552 error if the limit is
16022 exceeded; locally-generated messages either get a stderr message or a delivery
16023 failure message to the sender, depending on the &%-oe%& setting. Rejection of
16024 an oversized message is logged in both the main and the reject logs. See also
16025 the generic transport option &%message_size_limit%&, which limits the size of
16026 message that an individual transport can process.
16028 If you use a virus-scanner and set this option to to a value larger than the
16029 maximum size that your virus-scanner is configured to support, you may get
16030 failures triggered by large mails. The right size to configure for the
16031 virus-scanner depends upon what data is passed and the options in use but it's
16032 probably safest to just set it to a little larger than this value. E.g., with a
16033 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
16034 some problems may result.
16036 A value of 0 will disable size limit checking; Exim will still advertise the
16037 SIZE extension in an EHLO response, but without a limit, so as to permit
16038 SMTP clients to still indicate the message size along with the MAIL verb.
16041 .option move_frozen_messages main boolean false
16042 .cindex "frozen messages" "moving"
16043 This option, which is available only if Exim has been built with the setting
16045 SUPPORT_MOVE_FROZEN_MESSAGES=yes
16047 in &_Local/Makefile_&, causes frozen messages and their message logs to be
16048 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
16049 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
16050 standard utilities for handling such moved messages, and they do not show up in
16051 lists generated by &%-bp%& or by the Exim monitor.
16054 .option mua_wrapper main boolean false
16055 Setting this option true causes Exim to run in a very restrictive mode in which
16056 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
16057 contains a full description of this facility.
16061 .option mysql_servers main "string list" unset
16062 .cindex "MySQL" "server list"
16063 This option provides a list of MySQL servers and associated connection data, to
16064 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
16065 option is available only if Exim has been built with MySQL support.
16068 .option never_users main "string list&!!" unset
16069 This option is expanded just once, at the start of Exim's processing. Local
16070 message deliveries are normally run in processes that are setuid to the
16071 recipient, and remote deliveries are normally run under Exim's own uid and gid.
16072 It is usually desirable to prevent any deliveries from running as root, as a
16075 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
16076 list of users that must not be used for local deliveries. This list is fixed in
16077 the binary and cannot be overridden by the configuration file. By default, it
16078 contains just the single user name &"root"&. The &%never_users%& runtime option
16079 can be used to add more users to the fixed list.
16081 If a message is to be delivered as one of the users on the fixed list or the
16082 &%never_users%& list, an error occurs, and delivery is deferred. A common
16085 never_users = root:daemon:bin
16087 Including root is redundant if it is also on the fixed list, but it does no
16088 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
16092 .option openssl_options main "string list" "+no_sslv2 +single_dh_use +no_ticket"
16093 .cindex "OpenSSL "compatibility options"
16094 This option allows an administrator to adjust the SSL options applied
16095 by OpenSSL to connections. It is given as a space-separated list of items,
16096 each one to be +added or -subtracted from the current value.
16098 This option is only available if Exim is built against OpenSSL. The values
16099 available for this option vary according to the age of your OpenSSL install.
16100 The &"all"& value controls a subset of flags which are available, typically
16101 the bug workaround options. The &'SSL_CTX_set_options'& man page will
16102 list the values known on your system and Exim should support all the
16103 &"bug workaround"& options and many of the &"modifying"& options. The Exim
16104 names lose the leading &"SSL_OP_"& and are lower-cased.
16106 Note that adjusting the options can have severe impact upon the security of
16107 SSL as used by Exim. It is possible to disable safety checks and shoot
16108 yourself in the foot in various unpleasant ways. This option should not be
16109 adjusted lightly. An unrecognised item will be detected at startup, by
16110 invoking Exim with the &%-bV%& flag.
16112 The option affects Exim operating both as a server and as a client.
16114 Historical note: prior to release 4.80, Exim defaulted this value to
16115 "+dont_insert_empty_fragments", which may still be needed for compatibility
16116 with some clients, but which lowers security by increasing exposure to
16117 some now infamous attacks.
16121 # Make both old MS and old Eudora happy:
16122 openssl_options = -all +microsoft_big_sslv3_buffer \
16123 +dont_insert_empty_fragments
16125 # Disable older protocol versions:
16126 openssl_options = +no_sslv2 +no_sslv3
16129 Possible options may include:
16133 &`allow_unsafe_legacy_renegotiation`&
16135 &`cipher_server_preference`&
16137 &`dont_insert_empty_fragments`&
16141 &`legacy_server_connect`&
16143 &`microsoft_big_sslv3_buffer`&
16145 &`microsoft_sess_id_bug`&
16147 &`msie_sslv2_rsa_padding`&
16149 &`netscape_challenge_bug`&
16151 &`netscape_reuse_cipher_change_bug`&
16155 &`no_session_resumption_on_renegotiation`&
16169 &`safari_ecdhe_ecdsa_bug`&
16173 &`single_ecdh_use`&
16175 &`ssleay_080_client_dh_bug`&
16177 &`sslref2_reuse_cert_type_bug`&
16179 &`tls_block_padding_bug`&
16183 &`tls_rollback_bug`&
16186 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
16187 all clients connecting using the MacOS SecureTransport TLS facility prior
16188 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
16189 to negotiate TLS then this option value might help, provided that your OpenSSL
16190 release is new enough to contain this work-around. This may be a situation
16191 where you have to upgrade OpenSSL to get buggy clients working.
16194 .option oracle_servers main "string list" unset
16195 .cindex "Oracle" "server list"
16196 This option provides a list of Oracle servers and associated connection data,
16197 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
16198 The option is available only if Exim has been built with Oracle support.
16201 .option percent_hack_domains main "domain list&!!" unset
16202 .cindex "&""percent hack""&"
16203 .cindex "source routing" "in email address"
16204 .cindex "address" "source-routed"
16205 The &"percent hack"& is the convention whereby a local part containing a
16206 percent sign is re-interpreted as a new email address, with the percent
16207 replaced by @. This is sometimes called &"source routing"&, though that term is
16208 also applied to RFC 2822 addresses that begin with an @ character. If this
16209 option is set, Exim implements the percent facility for those domains listed,
16210 but no others. This happens before an incoming SMTP address is tested against
16213 &*Warning*&: The &"percent hack"& has often been abused by people who are
16214 trying to get round relaying restrictions. For this reason, it is best avoided
16215 if at all possible. Unfortunately, a number of less security-conscious MTAs
16216 implement it unconditionally. If you are running Exim on a gateway host, and
16217 routing mail through to internal MTAs without processing the local parts, it is
16218 a good idea to reject recipient addresses with percent characters in their
16219 local parts. Exim's default configuration does this.
16222 .option perl_at_start main boolean false
16224 This option is available only when Exim is built with an embedded Perl
16225 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16228 .option perl_startup main string unset
16230 This option is available only when Exim is built with an embedded Perl
16231 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16233 .option perl_startup main boolean false
16235 This Option enables the taint mode of the embedded Perl interpreter.
16238 .option pgsql_servers main "string list" unset
16239 .cindex "PostgreSQL lookup type" "server list"
16240 This option provides a list of PostgreSQL servers and associated connection
16241 data, to be used in conjunction with &(pgsql)& lookups (see section
16242 &<<SECID72>>&). The option is available only if Exim has been built with
16243 PostgreSQL support.
16246 .option pid_file_path main string&!! "set at compile time"
16247 .cindex "daemon" "pid file path"
16248 .cindex "pid file, path for"
16249 This option sets the name of the file to which the Exim daemon writes its
16250 process id. The string is expanded, so it can contain, for example, references
16253 pid_file_path = /var/log/$primary_hostname/exim.pid
16255 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
16257 The value set by the option can be overridden by the &%-oP%& command line
16258 option. A pid file is not written if a &"non-standard"& daemon is run by means
16259 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
16262 .option pipelining_advertise_hosts main "host list&!!" *
16263 .cindex "PIPELINING" "suppressing advertising"
16264 This option can be used to suppress the advertisement of the SMTP
16265 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
16266 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
16267 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
16268 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
16269 that clients will use it; &"out of order"& commands that are &"expected"& do
16270 not count as protocol errors (see &%smtp_max_synprot_errors%&).
16273 .option prdr_enable main boolean false
16274 .cindex "PRDR" "enabling on server"
16275 This option can be used to enable the Per-Recipient Data Response extension
16276 to SMTP, defined by Eric Hall.
16277 If the option is set, PRDR is advertised by Exim when operating as a server.
16278 If the client requests PRDR, and more than one recipient, for a message
16279 an additional ACL is called for each recipient after the message content
16280 is received. See section &<<SECTPRDRACL>>&.
16282 .option preserve_message_logs main boolean false
16283 .cindex "message logs" "preserving"
16284 If this option is set, message log files are not deleted when messages are
16285 completed. Instead, they are moved to a sub-directory of the spool directory
16286 called &_msglog.OLD_&, where they remain available for statistical or debugging
16287 purposes. This is a dangerous option to set on systems with any appreciable
16288 volume of mail. Use with care!
16291 .option primary_hostname main string "see below"
16292 .cindex "name" "of local host"
16293 .cindex "host" "name of local"
16294 .cindex "local host" "name of"
16295 .vindex "&$primary_hostname$&"
16296 This specifies the name of the current host. It is used in the default EHLO or
16297 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
16298 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
16299 The value is also used by default in some SMTP response messages from an Exim
16300 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
16302 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
16303 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
16304 contains only one component, Exim passes it to &[gethostbyname()]& (or
16305 &[getipnodebyname()]& when available) in order to obtain the fully qualified
16306 version. The variable &$primary_hostname$& contains the host name, whether set
16307 explicitly by this option, or defaulted.
16310 .option print_topbitchars main boolean false
16311 .cindex "printing characters"
16312 .cindex "8-bit characters"
16313 By default, Exim considers only those characters whose codes lie in the range
16314 32&--126 to be printing characters. In a number of circumstances (for example,
16315 when writing log entries) non-printing characters are converted into escape
16316 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
16317 is set, code values of 128 and above are also considered to be printing
16320 This option also affects the header syntax checks performed by the
16321 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
16322 the user's full name when constructing From: and Sender: addresses (as
16323 described in section &<<SECTconstr>>&). Setting this option can cause
16324 Exim to generate eight bit message headers that do not conform to the
16328 .option process_log_path main string unset
16329 .cindex "process log path"
16330 .cindex "log" "process log"
16331 .cindex "&'exiwhat'&"
16332 This option sets the name of the file to which an Exim process writes its
16333 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
16334 utility script. If this option is unset, the file called &_exim-process.info_&
16335 in Exim's spool directory is used. The ability to specify the name explicitly
16336 can be useful in environments where two different Exims are running, using
16337 different spool directories.
16340 .option prod_requires_admin main boolean true
16341 .cindex "restricting access to features"
16345 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
16346 admin user unless &%prod_requires_admin%& is set false. See also
16347 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
16350 .option qualify_domain main string "see below"
16351 .cindex "domain" "for qualifying addresses"
16352 .cindex "address" "qualification"
16353 This option specifies the domain name that is added to any envelope sender
16354 addresses that do not have a domain qualification. It also applies to
16355 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
16356 are accepted by default only for locally-generated messages. Qualification is
16357 also applied to addresses in header lines such as &'From:'& and &'To:'& for
16358 locally-generated messages, unless the &%-bnq%& command line option is used.
16360 Messages from external sources must always contain fully qualified addresses,
16361 unless the sending host matches &%sender_unqualified_hosts%& or
16362 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
16363 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
16364 necessary. Internally, Exim always works with fully qualified envelope
16365 addresses. If &%qualify_domain%& is not set, it defaults to the
16366 &%primary_hostname%& value.
16369 .option qualify_recipient main string "see below"
16370 This option allows you to specify a different domain for qualifying recipient
16371 addresses to the one that is used for senders. See &%qualify_domain%& above.
16375 .option queue_domains main "domain list&!!" unset
16376 .cindex "domain" "specifying non-immediate delivery"
16377 .cindex "queueing incoming messages"
16378 .cindex "message" "queueing certain domains"
16379 This option lists domains for which immediate delivery is not required.
16380 A delivery process is started whenever a message is received, but only those
16381 domains that do not match are processed. All other deliveries wait until the
16382 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
16385 .option queue_list_requires_admin main boolean true
16386 .cindex "restricting access to features"
16388 The &%-bp%& command-line option, which lists the messages that are on the
16389 queue, requires the caller to be an admin user unless
16390 &%queue_list_requires_admin%& is set false.
16391 See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
16394 .option queue_only main boolean false
16395 .cindex "queueing incoming messages"
16396 .cindex "message" "queueing unconditionally"
16397 If &%queue_only%& is set, a delivery process is not automatically started
16398 whenever a message is received. Instead, the message waits in the queue for the
16399 next queue run. Even if &%queue_only%& is false, incoming messages may not get
16400 delivered immediately when certain conditions (such as heavy load) occur.
16402 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
16403 and &%-odi%& command line options override &%queue_only%& unless
16404 &%queue_only_override%& is set false. See also &%queue_only_file%&,
16405 &%queue_only_load%&, and &%smtp_accept_queue%&.
16408 .option queue_only_file main string unset
16409 .cindex "queueing incoming messages"
16410 .cindex "message" "queueing by file existence"
16411 This option can be set to a colon-separated list of absolute path names, each
16412 one optionally preceded by &"smtp"&. When Exim is receiving a message,
16413 it tests for the existence of each listed path using a call to &[stat()]&. For
16414 each path that exists, the corresponding queueing option is set.
16415 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
16416 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
16418 queue_only_file = smtp/some/file
16420 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
16421 &_/some/file_& exists.
16424 .option queue_only_load main fixed-point unset
16425 .cindex "load average"
16426 .cindex "queueing incoming messages"
16427 .cindex "message" "queueing by load"
16428 If the system load average is higher than this value, incoming messages from
16429 all sources are queued, and no automatic deliveries are started. If this
16430 happens during local or remote SMTP input, all subsequent messages received on
16431 the same SMTP connection are queued by default, whatever happens to the load in
16432 the meantime, but this can be changed by setting &%queue_only_load_latch%&
16435 Deliveries will subsequently be performed by queue runner processes. This
16436 option has no effect on ancient operating systems on which Exim cannot
16437 determine the load average. See also &%deliver_queue_load_max%& and
16438 &%smtp_load_reserve%&.
16441 .option queue_only_load_latch main boolean true
16442 .cindex "load average" "re-evaluating per message"
16443 When this option is true (the default), once one message has been queued
16444 because the load average is higher than the value set by &%queue_only_load%&,
16445 all subsequent messages received on the same SMTP connection are also queued.
16446 This is a deliberate choice; even though the load average may fall below the
16447 threshold, it doesn't seem right to deliver later messages on the same
16448 connection when not delivering earlier ones. However, there are special
16449 circumstances such as very long-lived connections from scanning appliances
16450 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
16451 should be set false. This causes the value of the load average to be
16452 re-evaluated for each message.
16455 .option queue_only_override main boolean true
16456 .cindex "queueing incoming messages"
16457 When this option is true, the &%-od%&&'x'& command line options override the
16458 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
16459 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
16460 to override; they are accepted, but ignored.
16463 .option queue_run_in_order main boolean false
16464 .cindex "queue runner" "processing messages in order"
16465 If this option is set, queue runs happen in order of message arrival instead of
16466 in an arbitrary order. For this to happen, a complete list of the entire queue
16467 must be set up before the deliveries start. When the queue is all held in a
16468 single directory (the default), a single list is created for both the ordered
16469 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
16470 single list is not created when &%queue_run_in_order%& is false. In this case,
16471 the sub-directories are processed one at a time (in a random order), and this
16472 avoids setting up one huge list for the whole queue. Thus, setting
16473 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
16474 when the queue is large, because of the extra work in setting up the single,
16475 large list. In most situations, &%queue_run_in_order%& should not be set.
16479 .option queue_run_max main integer&!! 5
16480 .cindex "queue runner" "maximum number of"
16481 This controls the maximum number of queue runner processes that an Exim daemon
16482 can run simultaneously. This does not mean that it starts them all at once,
16483 but rather that if the maximum number are still running when the time comes to
16484 start another one, it refrains from starting another one. This can happen with
16485 very large queues and/or very sluggish deliveries. This option does not,
16486 however, interlock with other processes, so additional queue runners can be
16487 started by other means, or by killing and restarting the daemon.
16489 Setting this option to zero does not suppress queue runs; rather, it disables
16490 the limit, allowing any number of simultaneous queue runner processes to be
16491 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
16492 the daemon's command line.
16494 .cindex queues named
16495 .cindex "named queues"
16496 To set limits for different named queues use
16497 an expansion depending on the &$queue_name$& variable.
16499 .option queue_smtp_domains main "domain list&!!" unset
16500 .cindex "queueing incoming messages"
16501 .cindex "message" "queueing remote deliveries"
16502 When this option is set, a delivery process is started whenever a message is
16503 received, routing is performed, and local deliveries take place.
16504 However, if any SMTP deliveries are required for domains that match
16505 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
16506 message waits in the queue for the next queue run. Since routing of the message
16507 has taken place, Exim knows to which remote hosts it must be delivered, and so
16508 when the queue run happens, multiple messages for the same host are delivered
16509 over a single SMTP connection. The &%-odqs%& command line option causes all
16510 SMTP deliveries to be queued in this way, and is equivalent to setting
16511 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
16515 .option receive_timeout main time 0s
16516 .cindex "timeout" "for non-SMTP input"
16517 This option sets the timeout for accepting a non-SMTP message, that is, the
16518 maximum time that Exim waits when reading a message on the standard input. If
16519 the value is zero, it will wait forever. This setting is overridden by the
16520 &%-or%& command line option. The timeout for incoming SMTP messages is
16521 controlled by &%smtp_receive_timeout%&.
16523 .option received_header_text main string&!! "see below"
16524 .cindex "customizing" "&'Received:'& header"
16525 .cindex "&'Received:'& header line" "customizing"
16526 This string defines the contents of the &'Received:'& message header that is
16527 added to each message, except for the timestamp, which is automatically added
16528 on at the end (preceded by a semicolon). The string is expanded each time it is
16529 used. If the expansion yields an empty string, no &'Received:'& header line is
16530 added to the message. Otherwise, the string should start with the text
16531 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
16532 header lines. The default setting is:
16535 received_header_text = Received: \
16536 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
16537 {${if def:sender_ident \
16538 {from ${quote_local_part:$sender_ident} }}\
16539 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
16540 by $primary_hostname \
16541 ${if def:received_protocol {with $received_protocol}} \
16542 ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\
16543 (Exim $version_number)\n\t\
16544 ${if def:sender_address \
16545 {(envelope-from <$sender_address>)\n\t}}\
16546 id $message_exim_id\
16547 ${if def:received_for {\n\tfor $received_for}}
16550 The reference to the TLS cipher is omitted when Exim is built without TLS
16551 support. The use of conditional expansions ensures that this works for both
16552 locally generated messages and messages received from remote hosts, giving
16553 header lines such as the following:
16555 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
16556 by marley.carol.example with esmtp (Exim 4.00)
16557 (envelope-from <bob@carol.example>)
16558 id 16IOWa-00019l-00
16559 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
16560 Received: by scrooge.carol.example with local (Exim 4.00)
16561 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
16563 Until the body of the message has been received, the timestamp is the time when
16564 the message started to be received. Once the body has arrived, and all policy
16565 checks have taken place, the timestamp is updated to the time at which the
16566 message was accepted.
16569 .option received_headers_max main integer 30
16570 .cindex "loop" "prevention"
16571 .cindex "mail loop prevention"
16572 .cindex "&'Received:'& header line" "counting"
16573 When a message is to be delivered, the number of &'Received:'& headers is
16574 counted, and if it is greater than this parameter, a mail loop is assumed to
16575 have occurred, the delivery is abandoned, and an error message is generated.
16576 This applies to both local and remote deliveries.
16579 .option recipient_unqualified_hosts main "host list&!!" unset
16580 .cindex "unqualified addresses"
16581 .cindex "host" "unqualified addresses from"
16582 This option lists those hosts from which Exim is prepared to accept unqualified
16583 recipient addresses in message envelopes. The addresses are made fully
16584 qualified by the addition of the &%qualify_recipient%& value. This option also
16585 affects message header lines. Exim does not reject unqualified recipient
16586 addresses in headers, but it qualifies them only if the message came from a
16587 host that matches &%recipient_unqualified_hosts%&,
16588 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
16589 option was not set.
16592 .option recipients_max main integer 0
16593 .cindex "limit" "number of recipients"
16594 .cindex "recipient" "maximum number"
16595 If this option is set greater than zero, it specifies the maximum number of
16596 original recipients for any message. Additional recipients that are generated
16597 by aliasing or forwarding do not count. SMTP messages get a 452 response for
16598 all recipients over the limit; earlier recipients are delivered as normal.
16599 Non-SMTP messages with too many recipients are failed, and no deliveries are
16602 .cindex "RCPT" "maximum number of incoming"
16603 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
16604 RCPT commands in a single message.
16607 .option recipients_max_reject main boolean false
16608 If this option is set true, Exim rejects SMTP messages containing too many
16609 recipients by giving 552 errors to the surplus RCPT commands, and a 554
16610 error to the eventual DATA command. Otherwise (the default) it gives a 452
16611 error to the surplus RCPT commands and accepts the message on behalf of the
16612 initial set of recipients. The remote server should then re-send the message
16613 for the remaining recipients at a later time.
16616 .option remote_max_parallel main integer 2
16617 .cindex "delivery" "parallelism for remote"
16618 This option controls parallel delivery of one message to a number of remote
16619 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
16620 does all the remote deliveries for a message one by one. Otherwise, if a single
16621 message has to be delivered to more than one remote host, or if several copies
16622 have to be sent to the same remote host, up to &%remote_max_parallel%&
16623 deliveries are done simultaneously. If more than &%remote_max_parallel%&
16624 deliveries are required, the maximum number of processes are started, and as
16625 each one finishes, another is begun. The order of starting processes is the
16626 same as if sequential delivery were being done, and can be controlled by the
16627 &%remote_sort_domains%& option. If parallel delivery takes place while running
16628 with debugging turned on, the debugging output from each delivery process is
16629 tagged with its process id.
16631 This option controls only the maximum number of parallel deliveries for one
16632 message in one Exim delivery process. Because Exim has no central queue
16633 manager, there is no way of controlling the total number of simultaneous
16634 deliveries if the configuration allows a delivery attempt as soon as a message
16637 .cindex "number of deliveries"
16638 .cindex "delivery" "maximum number of"
16639 If you want to control the total number of deliveries on the system, you
16640 need to set the &%queue_only%& option. This ensures that all incoming messages
16641 are added to the queue without starting a delivery process. Then set up an Exim
16642 daemon to start queue runner processes at appropriate intervals (probably
16643 fairly often, for example, every minute), and limit the total number of queue
16644 runners by setting the &%queue_run_max%& parameter. Because each queue runner
16645 delivers only one message at a time, the maximum number of deliveries that can
16646 then take place at once is &%queue_run_max%& multiplied by
16647 &%remote_max_parallel%&.
16649 If it is purely remote deliveries you want to control, use
16650 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
16651 doing the SMTP routing before queueing, so that several messages for the same
16652 host will eventually get delivered down the same connection.
16655 .option remote_sort_domains main "domain list&!!" unset
16656 .cindex "sorting remote deliveries"
16657 .cindex "delivery" "sorting remote"
16658 When there are a number of remote deliveries for a message, they are sorted by
16659 domain into the order given by this list. For example,
16661 remote_sort_domains = *.cam.ac.uk:*.uk
16663 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
16664 then to those in the &%uk%& domain, then to any others.
16667 .option retry_data_expire main time 7d
16668 .cindex "hints database" "data expiry"
16669 This option sets a &"use before"& time on retry information in Exim's hints
16670 database. Any older retry data is ignored. This means that, for example, once a
16671 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
16675 .option retry_interval_max main time 24h
16676 .cindex "retry" "limit on interval"
16677 .cindex "limit" "on retry interval"
16678 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
16679 intervals between delivery attempts for messages that cannot be delivered
16680 straight away. This option sets an overall limit to the length of time between
16681 retries. It cannot be set greater than 24 hours; any attempt to do so forces
16685 .option return_path_remove main boolean true
16686 .cindex "&'Return-path:'& header line" "removing"
16687 RFC 2821, section 4.4, states that an SMTP server must insert a
16688 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
16689 The &'Return-path:'& header preserves the sender address as received in the
16690 MAIL command. This description implies that this header should not be present
16691 in an incoming message. If &%return_path_remove%& is true, any existing
16692 &'Return-path:'& headers are removed from messages at the time they are
16693 received. Exim's transports have options for adding &'Return-path:'& headers at
16694 the time of delivery. They are normally used only for final local deliveries.
16697 .option return_size_limit main integer 100K
16698 This option is an obsolete synonym for &%bounce_return_size_limit%&.
16701 .option rfc1413_hosts main "host list&!!" @[]
16703 .cindex "host" "for RFC 1413 calls"
16704 RFC 1413 identification calls are made to any client host which matches
16705 an item in the list.
16706 The default value specifies just this host, being any local interface
16709 .option rfc1413_query_timeout main time 0s
16710 .cindex "RFC 1413" "query timeout"
16711 .cindex "timeout" "for RFC 1413 call"
16712 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
16713 no RFC 1413 calls are ever made.
16716 .option sender_unqualified_hosts main "host list&!!" unset
16717 .cindex "unqualified addresses"
16718 .cindex "host" "unqualified addresses from"
16719 This option lists those hosts from which Exim is prepared to accept unqualified
16720 sender addresses. The addresses are made fully qualified by the addition of
16721 &%qualify_domain%&. This option also affects message header lines. Exim does
16722 not reject unqualified addresses in headers that contain sender addresses, but
16723 it qualifies them only if the message came from a host that matches
16724 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
16725 using TCP/IP), and the &%-bnq%& option was not set.
16727 .option set_environment main "string list" empty
16728 .cindex "environment"
16729 This option allows to set individual environment variables that the
16730 currently linked libraries and programs in child processes use. The
16731 default list is empty,
16734 .option slow_lookup_log main integer 0
16735 .cindex "logging" "slow lookups"
16736 .cindex "dns" "logging slow lookups"
16737 This option controls logging of slow lookups.
16738 If the value is nonzero it is taken as a number of milliseconds
16739 and lookups taking longer than this are logged.
16740 Currently this applies only to DNS lookups.
16744 .option smtp_accept_keepalive main boolean true
16745 .cindex "keepalive" "on incoming connection"
16746 This option controls the setting of the SO_KEEPALIVE option on incoming
16747 TCP/IP socket connections. When set, it causes the kernel to probe idle
16748 connections periodically, by sending packets with &"old"& sequence numbers. The
16749 other end of the connection should send an acknowledgment if the connection is
16750 still okay or a reset if the connection has been aborted. The reason for doing
16751 this is that it has the beneficial effect of freeing up certain types of
16752 connection that can get stuck when the remote host is disconnected without
16753 tidying up the TCP/IP call properly. The keepalive mechanism takes several
16754 hours to detect unreachable hosts.
16758 .option smtp_accept_max main integer 20
16759 .cindex "limit" "incoming SMTP connections"
16760 .cindex "SMTP" "incoming connection count"
16762 This option specifies the maximum number of simultaneous incoming SMTP calls
16763 that Exim will accept. It applies only to the listening daemon; there is no
16764 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
16765 value is set to zero, no limit is applied. However, it is required to be
16766 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
16767 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
16769 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
16770 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
16771 that limit has not been reached for the client host, &%smtp_accept_reserve%&
16772 and &%smtp_load_reserve%& are then checked before accepting the connection.
16775 .option smtp_accept_max_nonmail main integer 10
16776 .cindex "limit" "non-mail SMTP commands"
16777 .cindex "SMTP" "limiting non-mail commands"
16778 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
16779 the connection if there are too many. This option defines &"too many"&. The
16780 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
16781 client looping sending EHLO, for example. The check is applied only if the
16782 client host matches &%smtp_accept_max_nonmail_hosts%&.
16784 When a new message is expected, one occurrence of RSET is not counted. This
16785 allows a client to send one RSET between messages (this is not necessary,
16786 but some clients do it). Exim also allows one uncounted occurrence of HELO
16787 or EHLO, and one occurrence of STARTTLS between messages. After
16788 starting up a TLS session, another EHLO is expected, and so it too is not
16789 counted. The first occurrence of AUTH in a connection, or immediately
16790 following STARTTLS is not counted. Otherwise, all commands other than
16791 MAIL, RCPT, DATA, and QUIT are counted.
16794 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
16795 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
16796 check by setting this option. The default value makes it apply to all hosts. By
16797 changing the value, you can exclude any badly-behaved hosts that you have to
16801 . Allow this long option name to split; give it unsplit as a fifth argument
16802 . for the automatic .oindex that is generated by .option.
16803 . We insert " &~&~" which is both pretty nasty visually and results in
16804 . non-searchable text. HowItWorks.txt mentions an option for inserting
16805 . zero-width-space, which would be nicer visually and results in (at least)
16806 . html that Firefox will split on when it's forced to reflow (rather than
16807 . inserting a horizontal scrollbar). However, the text is still not
16808 . searchable. NM changed this occurrence for bug 1197 to no longer allow
16809 . the option name to split.
16811 .option "smtp_accept_max_per_connection" main integer 1000 &&&
16812 smtp_accept_max_per_connection
16813 .cindex "SMTP" "limiting incoming message count"
16814 .cindex "limit" "messages per SMTP connection"
16815 The value of this option limits the number of MAIL commands that Exim is
16816 prepared to accept over a single SMTP connection, whether or not each command
16817 results in the transfer of a message. After the limit is reached, a 421
16818 response is given to subsequent MAIL commands. This limit is a safety
16819 precaution against a client that goes mad (incidents of this type have been
16823 .option smtp_accept_max_per_host main string&!! unset
16824 .cindex "limit" "SMTP connections from one host"
16825 .cindex "host" "limiting SMTP connections from"
16826 This option restricts the number of simultaneous IP connections from a single
16827 host (strictly, from a single IP address) to the Exim daemon. The option is
16828 expanded, to enable different limits to be applied to different hosts by
16829 reference to &$sender_host_address$&. Once the limit is reached, additional
16830 connection attempts from the same host are rejected with error code 421. This
16831 is entirely independent of &%smtp_accept_reserve%&. The option's default value
16832 of zero imposes no limit. If this option is set greater than zero, it is
16833 required that &%smtp_accept_max%& be non-zero.
16835 &*Warning*&: When setting this option you should not use any expansion
16836 constructions that take an appreciable amount of time. The expansion and test
16837 happen in the main daemon loop, in order to reject additional connections
16838 without forking additional processes (otherwise a denial-of-service attack
16839 could cause a vast number or processes to be created). While the daemon is
16840 doing this processing, it cannot accept any other incoming connections.
16844 .option smtp_accept_queue main integer 0
16845 .cindex "SMTP" "incoming connection count"
16846 .cindex "queueing incoming messages"
16847 .cindex "message" "queueing by SMTP connection count"
16848 If the number of simultaneous incoming SMTP connections being handled via the
16849 listening daemon exceeds this value, messages received by SMTP are just placed
16850 in the queue; no delivery processes are started automatically. The count is
16851 fixed at the start of an SMTP connection. It cannot be updated in the
16852 subprocess that receives messages, and so the queueing or not queueing applies
16853 to all messages received in the same connection.
16855 A value of zero implies no limit, and clearly any non-zero value is useful only
16856 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
16857 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
16858 various &%-od%&&'x'& command line options.
16861 . See the comment on smtp_accept_max_per_connection
16863 .option "smtp_accept_queue_per_connection" main integer 10 &&&
16864 smtp_accept_queue_per_connection
16865 .cindex "queueing incoming messages"
16866 .cindex "message" "queueing by message count"
16867 This option limits the number of delivery processes that Exim starts
16868 automatically when receiving messages via SMTP, whether via the daemon or by
16869 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
16870 and the number of messages received in a single SMTP session exceeds this
16871 number, subsequent messages are placed in the queue, but no delivery processes
16872 are started. This helps to limit the number of Exim processes when a server
16873 restarts after downtime and there is a lot of mail waiting for it on other
16874 systems. On large systems, the default should probably be increased, and on
16875 dial-in client systems it should probably be set to zero (that is, disabled).
16878 .option smtp_accept_reserve main integer 0
16879 .cindex "SMTP" "incoming call count"
16880 .cindex "host" "reserved"
16881 When &%smtp_accept_max%& is set greater than zero, this option specifies a
16882 number of SMTP connections that are reserved for connections from the hosts
16883 that are specified in &%smtp_reserve_hosts%&. The value set in
16884 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
16885 restricted to this number of connections; the option specifies a minimum number
16886 of connection slots for them, not a maximum. It is a guarantee that this group
16887 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
16888 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
16891 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
16892 set to 5, once there are 45 active connections (from any hosts), new
16893 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
16894 provided the other criteria for acceptance are met.
16897 .option smtp_active_hostname main string&!! unset
16898 .cindex "host" "name in SMTP responses"
16899 .cindex "SMTP" "host name in responses"
16900 .vindex "&$primary_hostname$&"
16901 This option is provided for multi-homed servers that want to masquerade as
16902 several different hosts. At the start of an incoming SMTP connection, its value
16903 is expanded and used instead of the value of &$primary_hostname$& in SMTP
16904 responses. For example, it is used as domain name in the response to an
16905 incoming HELO or EHLO command.
16907 .vindex "&$smtp_active_hostname$&"
16908 The active hostname is placed in the &$smtp_active_hostname$& variable, which
16909 is saved with any messages that are received. It is therefore available for use
16910 in routers and transports when the message is later delivered.
16912 If this option is unset, or if its expansion is forced to fail, or if the
16913 expansion results in an empty string, the value of &$primary_hostname$& is
16914 used. Other expansion failures cause a message to be written to the main and
16915 panic logs, and the SMTP command receives a temporary error. Typically, the
16916 value of &%smtp_active_hostname%& depends on the incoming interface address.
16919 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
16920 {cox.mydomain}{box.mydomain}}
16923 Although &$smtp_active_hostname$& is primarily concerned with incoming
16924 messages, it is also used as the default for HELO commands in callout
16925 verification if there is no remote transport from which to obtain a
16926 &%helo_data%& value.
16928 .option smtp_banner main string&!! "see below"
16929 .cindex "SMTP" "welcome banner"
16930 .cindex "banner for SMTP"
16931 .cindex "welcome banner for SMTP"
16932 .cindex "customizing" "SMTP banner"
16933 This string, which is expanded every time it is used, is output as the initial
16934 positive response to an SMTP connection. The default setting is:
16936 smtp_banner = $smtp_active_hostname ESMTP Exim \
16937 $version_number $tod_full
16939 Failure to expand the string causes a panic error. If you want to create a
16940 multiline response to the initial SMTP connection, use &"\n"& in the string at
16941 appropriate points, but not at the end. Note that the 220 code is not included
16942 in this string. Exim adds it automatically (several times in the case of a
16943 multiline response).
16946 .option smtp_check_spool_space main boolean true
16947 .cindex "checking disk space"
16948 .cindex "disk space, checking"
16949 .cindex "spool directory" "checking space"
16950 When this option is set, if an incoming SMTP session encounters the SIZE
16951 option on a MAIL command, it checks that there is enough space in the
16952 spool directory's partition to accept a message of that size, while still
16953 leaving free the amount specified by &%check_spool_space%& (even if that value
16954 is zero). If there isn't enough space, a temporary error code is returned.
16957 .option smtp_connect_backlog main integer 20
16958 .cindex "connection backlog"
16959 .cindex "SMTP" "connection backlog"
16960 .cindex "backlog of connections"
16961 This option specifies a maximum number of waiting SMTP connections. Exim passes
16962 this value to the TCP/IP system when it sets up its listener. Once this number
16963 of connections are waiting for the daemon's attention, subsequent connection
16964 attempts are refused at the TCP/IP level. At least, that is what the manuals
16965 say; in some circumstances such connection attempts have been observed to time
16966 out instead. For large systems it is probably a good idea to increase the
16967 value (to 50, say). It also gives some protection against denial-of-service
16968 attacks by SYN flooding.
16971 .option smtp_enforce_sync main boolean true
16972 .cindex "SMTP" "synchronization checking"
16973 .cindex "synchronization checking in SMTP"
16974 The SMTP protocol specification requires the client to wait for a response from
16975 the server at certain points in the dialogue. Without PIPELINING these
16976 synchronization points are after every command; with PIPELINING they are
16977 fewer, but they still exist.
16979 Some spamming sites send out a complete set of SMTP commands without waiting
16980 for any response. Exim protects against this by rejecting a message if the
16981 client has sent further input when it should not have. The error response &"554
16982 SMTP synchronization error"& is sent, and the connection is dropped. Testing
16983 for this error cannot be perfect because of transmission delays (unexpected
16984 input may be on its way but not yet received when Exim checks). However, it
16985 does detect many instances.
16987 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
16988 If you want to disable the check selectively (for example, only for certain
16989 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
16990 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
16994 .option smtp_etrn_command main string&!! unset
16995 .cindex "ETRN" "command to be run"
16996 .vindex "&$domain$&"
16997 If this option is set, the given command is run whenever an SMTP ETRN
16998 command is received from a host that is permitted to issue such commands (see
16999 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
17000 are independently expanded. The expansion variable &$domain$& is set to the
17001 argument of the ETRN command, and no syntax checking is done on it. For
17004 smtp_etrn_command = /etc/etrn_command $domain \
17005 $sender_host_address
17007 A new process is created to run the command, but Exim does not wait for it to
17008 complete. Consequently, its status cannot be checked. If the command cannot be
17009 run, a line is written to the panic log, but the ETRN caller still receives
17010 a 250 success response. Exim is normally running under its own uid when
17011 receiving SMTP, so it is not possible for it to change the uid before running
17015 .option smtp_etrn_serialize main boolean true
17016 .cindex "ETRN" "serializing"
17017 When this option is set, it prevents the simultaneous execution of more than
17018 one identical command as a result of ETRN in an SMTP connection. See
17019 section &<<SECTETRN>>& for details.
17022 .option smtp_load_reserve main fixed-point unset
17023 .cindex "load average"
17024 If the system load average ever gets higher than this, incoming SMTP calls are
17025 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
17026 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
17027 the load is over the limit. The option has no effect on ancient operating
17028 systems on which Exim cannot determine the load average. See also
17029 &%deliver_queue_load_max%& and &%queue_only_load%&.
17033 .option smtp_max_synprot_errors main integer 3
17034 .cindex "SMTP" "limiting syntax and protocol errors"
17035 .cindex "limit" "SMTP syntax and protocol errors"
17036 Exim rejects SMTP commands that contain syntax or protocol errors. In
17037 particular, a syntactically invalid email address, as in this command:
17039 RCPT TO:<abc xyz@a.b.c>
17041 causes immediate rejection of the command, before any other tests are done.
17042 (The ACL cannot be run if there is no valid address to set up for it.) An
17043 example of a protocol error is receiving RCPT before MAIL. If there are
17044 too many syntax or protocol errors in one SMTP session, the connection is
17045 dropped. The limit is set by this option.
17047 .cindex "PIPELINING" "expected errors"
17048 When the PIPELINING extension to SMTP is in use, some protocol errors are
17049 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
17050 Exim assumes that PIPELINING will be used if it advertises it (see
17051 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
17052 not count towards the limit.
17056 .option smtp_max_unknown_commands main integer 3
17057 .cindex "SMTP" "limiting unknown commands"
17058 .cindex "limit" "unknown SMTP commands"
17059 If there are too many unrecognized commands in an incoming SMTP session, an
17060 Exim server drops the connection. This is a defence against some kinds of abuse
17063 into making connections to SMTP ports; in these circumstances, a number of
17064 non-SMTP command lines are sent first.
17068 .option smtp_ratelimit_hosts main "host list&!!" unset
17069 .cindex "SMTP" "rate limiting"
17070 .cindex "limit" "rate of message arrival"
17071 .cindex "RCPT" "rate limiting"
17072 Some sites find it helpful to be able to limit the rate at which certain hosts
17073 can send them messages, and the rate at which an individual message can specify
17076 Exim has two rate-limiting facilities. This section describes the older
17077 facility, which can limit rates within a single connection. The newer
17078 &%ratelimit%& ACL condition can limit rates across all connections. See section
17079 &<<SECTratelimiting>>& for details of the newer facility.
17081 When a host matches &%smtp_ratelimit_hosts%&, the values of
17082 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
17083 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
17084 respectively. Each option, if set, must contain a set of four comma-separated
17088 A threshold, before which there is no rate limiting.
17090 An initial time delay. Unlike other times in Exim, numbers with decimal
17091 fractional parts are allowed here.
17093 A factor by which to increase the delay each time.
17095 A maximum value for the delay. This should normally be less than 5 minutes,
17096 because after that time, the client is liable to timeout the SMTP command.
17099 For example, these settings have been used successfully at the site which
17100 first suggested this feature, for controlling mail from their customers:
17102 smtp_ratelimit_mail = 2,0.5s,1.05,4m
17103 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
17105 The first setting specifies delays that are applied to MAIL commands after
17106 two have been received over a single connection. The initial delay is 0.5
17107 seconds, increasing by a factor of 1.05 each time. The second setting applies
17108 delays to RCPT commands when more than four occur in a single message.
17111 .option smtp_ratelimit_mail main string unset
17112 See &%smtp_ratelimit_hosts%& above.
17115 .option smtp_ratelimit_rcpt main string unset
17116 See &%smtp_ratelimit_hosts%& above.
17119 .option smtp_receive_timeout main time&!! 5m
17120 .cindex "timeout" "for SMTP input"
17121 .cindex "SMTP" "input timeout"
17122 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
17123 input, including batch SMTP. If a line of input (either an SMTP command or a
17124 data line) is not received within this time, the SMTP connection is dropped and
17125 the message is abandoned.
17126 A line is written to the log containing one of the following messages:
17128 SMTP command timeout on connection from...
17129 SMTP data timeout on connection from...
17131 The former means that Exim was expecting to read an SMTP command; the latter
17132 means that it was in the DATA phase, reading the contents of a message.
17134 If the first character of the option is a &"$"& the option is
17135 expanded before use and may depend on
17136 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
17140 The value set by this option can be overridden by the
17141 &%-os%& command-line option. A setting of zero time disables the timeout, but
17142 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
17143 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
17144 timeout is controlled by &%receive_timeout%& and &%-or%&.
17147 .option smtp_reserve_hosts main "host list&!!" unset
17148 This option defines hosts for which SMTP connections are reserved; see
17149 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
17152 .option smtp_return_error_details main boolean false
17153 .cindex "SMTP" "details policy failures"
17154 .cindex "policy control" "rejection, returning details"
17155 In the default state, Exim uses bland messages such as
17156 &"Administrative prohibition"& when it rejects SMTP commands for policy
17157 reasons. Many sysadmins like this because it gives away little information
17158 to spammers. However, some other sysadmins who are applying strict checking
17159 policies want to give out much fuller information about failures. Setting
17160 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
17161 example, instead of &"Administrative prohibition"&, it might give:
17163 550-Rejected after DATA: '>' missing at end of address:
17164 550 failing address in "From" header is: <user@dom.ain
17168 .option smtputf8_advertise_hosts main "host list&!!" *
17169 .cindex "SMTPUTF8" "advertising"
17170 When Exim is built with support for internationalised mail names,
17171 the availability thereof is advertised in
17172 response to EHLO only to those client hosts that match this option. See
17173 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
17176 .option spamd_address main string "127.0.0.1 783"
17177 This option is available when Exim is compiled with the content-scanning
17178 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
17179 See section &<<SECTscanspamass>>& for more details.
17183 .option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
17184 This option is available when Exim is compiled with SPF support.
17185 See section &<<SECSPF>>& for more details.
17189 .option split_spool_directory main boolean false
17190 .cindex "multiple spool directories"
17191 .cindex "spool directory" "split"
17192 .cindex "directories, multiple"
17193 If this option is set, it causes Exim to split its input directory into 62
17194 subdirectories, each with a single alphanumeric character as its name. The
17195 sixth character of the message id is used to allocate messages to
17196 subdirectories; this is the least significant base-62 digit of the time of
17197 arrival of the message.
17199 Splitting up the spool in this way may provide better performance on systems
17200 where there are long mail queues, by reducing the number of files in any one
17201 directory. The msglog directory is also split up in a similar way to the input
17202 directory; however, if &%preserve_message_logs%& is set, all old msglog files
17203 are still placed in the single directory &_msglog.OLD_&.
17205 It is not necessary to take any special action for existing messages when
17206 changing &%split_spool_directory%&. Exim notices messages that are in the
17207 &"wrong"& place, and continues to process them. If the option is turned off
17208 after a period of being on, the subdirectories will eventually empty and be
17209 automatically deleted.
17211 When &%split_spool_directory%& is set, the behaviour of queue runner processes
17212 changes. Instead of creating a list of all messages in the queue, and then
17213 trying to deliver each one, in turn, it constructs a list of those in one
17214 sub-directory and tries to deliver them, before moving on to the next
17215 sub-directory. The sub-directories are processed in a random order. This
17216 spreads out the scanning of the input directories, and uses less memory. It is
17217 particularly beneficial when there are lots of messages in the queue. However,
17218 if &%queue_run_in_order%& is set, none of this new processing happens. The
17219 entire queue has to be scanned and sorted before any deliveries can start.
17222 .option spool_directory main string&!! "set at compile time"
17223 .cindex "spool directory" "path to"
17224 This defines the directory in which Exim keeps its spool, that is, the messages
17225 it is waiting to deliver. The default value is taken from the compile-time
17226 configuration setting, if there is one. If not, this option must be set. The
17227 string is expanded, so it can contain, for example, a reference to
17228 &$primary_hostname$&.
17230 If the spool directory name is fixed on your installation, it is recommended
17231 that you set it at build time rather than from this option, particularly if the
17232 log files are being written to the spool directory (see &%log_file_path%&).
17233 Otherwise log files cannot be used for errors that are detected early on, such
17234 as failures in the configuration file.
17236 By using this option to override the compiled-in path, it is possible to run
17237 tests of Exim without using the standard spool.
17239 .option spool_wireformat main boolean false
17240 .cindex "spool directory" "file formats"
17241 If this option is set, Exim may for some messages use an alternative format
17242 for data-files in the spool which matches the wire format.
17243 Doing this permits more efficient message reception and transmission.
17244 Currently it is only done for messages received using the ESMTP CHUNKING
17247 The following variables will not have useful values:
17249 $max_received_linelength
17254 Users of the local_scan() API (see &<<CHAPlocalscan>>&),
17255 and any external programs which are passed a reference to a message data file
17256 (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
17257 will need to be aware of the different formats potentially available.
17259 Using any of the ACL conditions noted will negate the reception benefit
17260 (as a Unix-mbox-format file is constructed for them).
17261 The transmission benefit is maintained.
17263 .option sqlite_lock_timeout main time 5s
17264 .cindex "sqlite lookup type" "lock timeout"
17265 This option controls the timeout that the &(sqlite)& lookup uses when trying to
17266 access an SQLite database. See section &<<SECTsqlite>>& for more details.
17268 .option strict_acl_vars main boolean false
17269 .cindex "&ACL;" "variables, handling unset"
17270 This option controls what happens if a syntactically valid but undefined ACL
17271 variable is referenced. If it is false (the default), an empty string
17272 is substituted; if it is true, an error is generated. See section
17273 &<<SECTaclvariables>>& for details of ACL variables.
17275 .option strip_excess_angle_brackets main boolean false
17276 .cindex "angle brackets, excess"
17277 If this option is set, redundant pairs of angle brackets round &"route-addr"&
17278 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
17279 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
17280 passed on to another MTA, the excess angle brackets are not passed on. If this
17281 option is not set, multiple pairs of angle brackets cause a syntax error.
17284 .option strip_trailing_dot main boolean false
17285 .cindex "trailing dot on domain"
17286 .cindex "dot" "trailing on domain"
17287 If this option is set, a trailing dot at the end of a domain in an address is
17288 ignored. If this is in the envelope and the message is passed on to another
17289 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
17290 domain causes a syntax error.
17291 However, addresses in header lines are checked only when an ACL requests header
17295 .option syslog_duplication main boolean true
17296 .cindex "syslog" "duplicate log lines; suppressing"
17297 When Exim is logging to syslog, it writes the log lines for its three
17298 separate logs at different syslog priorities so that they can in principle
17299 be separated on the logging hosts. Some installations do not require this
17300 separation, and in those cases, the duplication of certain log lines is a
17301 nuisance. If &%syslog_duplication%& is set false, only one copy of any
17302 particular log line is written to syslog. For lines that normally go to
17303 both the main log and the reject log, the reject log version (possibly
17304 containing message header lines) is written, at LOG_NOTICE priority.
17305 Lines that normally go to both the main and the panic log are written at
17306 the LOG_ALERT priority.
17309 .option syslog_facility main string unset
17310 .cindex "syslog" "facility; setting"
17311 This option sets the syslog &"facility"& name, used when Exim is logging to
17312 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
17313 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
17314 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
17315 details of Exim's logging.
17318 .option syslog_pid main boolean true
17319 .cindex "syslog" "pid"
17320 If &%syslog_pid%& is set false, the PID on Exim's log lines are
17321 omitted when these lines are sent to syslog. (Syslog normally prefixes
17322 the log lines with the PID of the logging process automatically.) You need
17323 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
17324 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
17328 .option syslog_processname main string &`exim`&
17329 .cindex "syslog" "process name; setting"
17330 This option sets the syslog &"ident"& name, used when Exim is logging to
17331 syslog. The value must be no longer than 32 characters. See chapter
17332 &<<CHAPlog>>& for details of Exim's logging.
17336 .option syslog_timestamp main boolean true
17337 .cindex "syslog" "timestamps"
17338 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
17339 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
17340 details of Exim's logging.
17343 .option system_filter main string&!! unset
17344 .cindex "filter" "system filter"
17345 .cindex "system filter" "specifying"
17346 .cindex "Sieve filter" "not available for system filter"
17347 This option specifies an Exim filter file that is applied to all messages at
17348 the start of each delivery attempt, before any routing is done. System filters
17349 must be Exim filters; they cannot be Sieve filters. If the system filter
17350 generates any deliveries to files or pipes, or any new mail messages, the
17351 appropriate &%system_filter_..._transport%& option(s) must be set, to define
17352 which transports are to be used. Details of this facility are given in chapter
17353 &<<CHAPsystemfilter>>&.
17354 A forced expansion failure results in no filter operation.
17357 .option system_filter_directory_transport main string&!! unset
17358 .vindex "&$address_file$&"
17359 This sets the name of the transport driver that is to be used when the
17360 &%save%& command in a system message filter specifies a path ending in &"/"&,
17361 implying delivery of each message into a separate file in some directory.
17362 During the delivery, the variable &$address_file$& contains the path name.
17365 .option system_filter_file_transport main string&!! unset
17366 .cindex "file" "transport for system filter"
17367 This sets the name of the transport driver that is to be used when the &%save%&
17368 command in a system message filter specifies a path not ending in &"/"&. During
17369 the delivery, the variable &$address_file$& contains the path name.
17371 .option system_filter_group main string unset
17372 .cindex "gid (group id)" "system filter"
17373 This option is used only when &%system_filter_user%& is also set. It sets the
17374 gid under which the system filter is run, overriding any gid that is associated
17375 with the user. The value may be numerical or symbolic.
17377 .option system_filter_pipe_transport main string&!! unset
17378 .cindex "&(pipe)& transport" "for system filter"
17379 .vindex "&$address_pipe$&"
17380 This specifies the transport driver that is to be used when a &%pipe%& command
17381 is used in a system filter. During the delivery, the variable &$address_pipe$&
17382 contains the pipe command.
17385 .option system_filter_reply_transport main string&!! unset
17386 .cindex "&(autoreply)& transport" "for system filter"
17387 This specifies the transport driver that is to be used when a &%mail%& command
17388 is used in a system filter.
17391 .option system_filter_user main string unset
17392 .cindex "uid (user id)" "system filter"
17393 If this option is set to root, the system filter is run in the main Exim
17394 delivery process, as root. Otherwise, the system filter runs in a separate
17395 process, as the given user, defaulting to the Exim run-time user.
17396 Unless the string consists entirely of digits, it
17397 is looked up in the password data. Failure to find the named user causes a
17398 configuration error. The gid is either taken from the password data, or
17399 specified by &%system_filter_group%&. When the uid is specified numerically,
17400 &%system_filter_group%& is required to be set.
17402 If the system filter generates any pipe, file, or reply deliveries, the uid
17403 under which the filter is run is used when transporting them, unless a
17404 transport option overrides.
17407 .option tcp_nodelay main boolean true
17408 .cindex "daemon" "TCP_NODELAY on sockets"
17409 .cindex "Nagle algorithm"
17410 .cindex "TCP_NODELAY on listening sockets"
17411 If this option is set false, it stops the Exim daemon setting the
17412 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
17413 turns off the &"Nagle algorithm"&, which is a way of improving network
17414 performance in interactive (character-by-character) situations. Turning it off
17415 should improve Exim's performance a bit, so that is what happens by default.
17416 However, it appears that some broken clients cannot cope, and time out. Hence
17417 this option. It affects only those sockets that are set up for listening by the
17418 daemon. Sockets created by the smtp transport for delivering mail always set
17422 .option timeout_frozen_after main time 0s
17423 .cindex "frozen messages" "timing out"
17424 .cindex "timeout" "frozen messages"
17425 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
17426 message of any kind that has been in the queue for longer than the given time
17427 is automatically cancelled at the next queue run. If the frozen message is a
17428 bounce message, it is just discarded; otherwise, a bounce is sent to the
17429 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
17430 If you want to timeout frozen bounce messages earlier than other kinds of
17431 frozen message, see &%ignore_bounce_errors_after%&.
17433 &*Note:*& the default value of zero means no timeouts; with this setting,
17434 frozen messages remain in the queue forever (except for any frozen bounce
17435 messages that are released by &%ignore_bounce_errors_after%&).
17438 .option timezone main string unset
17439 .cindex "timezone, setting"
17440 .cindex "environment" "values from"
17441 The value of &%timezone%& is used to set the environment variable TZ while
17442 running Exim (if it is different on entry). This ensures that all timestamps
17443 created by Exim are in the required timezone. If you want all your timestamps
17444 to be in UTC (aka GMT) you should set
17448 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
17449 or, if that is not set, from the value of the TZ environment variable when Exim
17450 is built. If &%timezone%& is set to the empty string, either at build or run
17451 time, any existing TZ variable is removed from the environment when Exim
17452 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
17453 unfortunately not all, operating systems.
17456 .option tls_advertise_hosts main "host list&!!" *
17457 .cindex "TLS" "advertising"
17458 .cindex "encryption" "on SMTP connection"
17459 .cindex "SMTP" "encrypted connection"
17460 When Exim is built with support for TLS encrypted connections, the availability
17461 of the STARTTLS command to set up an encrypted session is advertised in
17462 response to EHLO only to those client hosts that match this option. See
17463 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
17464 Note that the default value requires that a certificate be supplied
17465 using the &%tls_certificate%& option. If TLS support for incoming connections
17466 is not required the &%tls_advertise_hosts%& option should be set empty.
17469 .option tls_certificate main string list&!! unset
17470 .cindex "TLS" "server certificate; location of"
17471 .cindex "certificate" "server, location of"
17472 The value of this option is expanded, and must then be a list of absolute paths to
17473 files which contains the server's certificates. Commonly only one file is
17475 The server's private key is also
17476 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
17477 &<<CHAPTLS>>& for further details.
17479 &*Note*&: The certificates defined by this option are used only when Exim is
17480 receiving incoming messages as a server. If you want to supply certificates for
17481 use when sending messages as a client, you must set the &%tls_certificate%&
17482 option in the relevant &(smtp)& transport.
17484 &*Note*&: If you use filenames based on IP addresses, change the list
17485 separator in the usual way (&<<SECTlistsepchange>>&) >to avoid confusion under IPv6.
17487 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
17488 when a list of more than one
17489 file is used, the &$tls_in_ourcert$& variable is unreliable.
17491 &*Note*&: OCSP stapling is not usable under OpenSSL
17492 when a list of more than one file is used.
17494 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
17495 if the OpenSSL build supports TLS extensions and the TLS client sends the
17496 Server Name Indication extension, then this option and others documented in
17497 &<<SECTtlssni>>& will be re-expanded.
17499 If this option is unset or empty a fresh self-signed certificate will be
17500 generated for every connection.
17502 .option tls_crl main string&!! unset
17503 .cindex "TLS" "server certificate revocation list"
17504 .cindex "certificate" "revocation list for server"
17505 This option specifies a certificate revocation list. The expanded value must
17506 be the name of a file that contains CRLs in PEM format.
17508 Under OpenSSL the option can specify a directory with CRL files.
17510 &*Note:*& Under OpenSSL the option must, if given, supply a CRL
17511 for each signing element of the certificate chain (i.e. all but the leaf).
17512 For the file variant this can be multiple PEM blocks in the one file.
17514 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17517 .option tls_dh_max_bits main integer 2236
17518 .cindex "TLS" "D-H bit count"
17519 The number of bits used for Diffie-Hellman key-exchange may be suggested by
17520 the chosen TLS library. That value might prove to be too high for
17521 interoperability. This option provides a maximum clamp on the value
17522 suggested, trading off security for interoperability.
17524 The value must be at least 1024.
17526 The value 2236 was chosen because, at time of adding the option, it was the
17527 hard-coded maximum value supported by the NSS cryptographic library, as used
17528 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
17530 If you prefer more security and are willing to break some clients, raise this
17533 Note that the value passed to GnuTLS for *generating* a new prime may be a
17534 little less than this figure, because GnuTLS is inexact and may produce a
17535 larger prime than requested.
17538 .option tls_dhparam main string&!! unset
17539 .cindex "TLS" "D-H parameters for server"
17540 The value of this option is expanded and indicates the source of DH parameters
17541 to be used by Exim.
17543 &*Note: The Exim Maintainers strongly recommend using a filename with site-generated
17544 local DH parameters*&, which has been supported across all versions of Exim. The
17545 other specific constants available are a fallback so that even when
17546 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
17548 If &%tls_dhparam%& is a filename starting with a &`/`&,
17549 then it names a file from which DH
17550 parameters should be loaded. If the file exists, it should hold a PEM-encoded
17551 PKCS#3 representation of the DH prime. If the file does not exist, for
17552 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
17553 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
17554 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
17555 and treated as though the &%tls_dhparam%& were set to "none".
17557 If this option expands to the string "none", then no DH parameters will be
17560 If this option expands to the string "historic" and Exim is using GnuTLS, then
17561 Exim will attempt to load a file from inside the spool directory. If the file
17562 does not exist, Exim will attempt to create it.
17563 See section &<<SECTgnutlsparam>>& for further details.
17565 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
17566 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
17568 In older versions of Exim the default was the 2048 bit prime described in section
17569 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
17570 in IKE is assigned number 23.
17572 Otherwise, the option must expand to the name used by Exim for any of a number
17573 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
17574 sources. As names, Exim uses a standard specified name, else "ike" followed by
17575 the number used by IKE, or "default" which corresponds to
17576 &`exim.dev.20160529.3`&.
17578 The available standard primes are:
17579 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
17580 &`ike1`&, &`ike2`&, &`ike5`&,
17581 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
17582 &`ike22`&, &`ike23`& and &`ike24`&.
17584 The available additional primes are:
17585 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
17587 Some of these will be too small to be accepted by clients.
17588 Some may be too large to be accepted by clients.
17589 The open cryptographic community has suspicions about the integrity of some
17590 of the later IKE values, which led into RFC7919 providing new fixed constants
17591 (the "ffdhe" identifiers).
17593 At this point, all of the "ike" values should be considered obsolete;
17594 they're still in Exim to avoid breaking unusual configurations, but are
17595 candidates for removal the next time we have backwards-incompatible changes.
17597 The TLS protocol does not negotiate an acceptable size for this; clients tend
17598 to hard-drop connections if what is offered by the server is unacceptable,
17599 whether too large or too small, and there's no provision for the client to
17600 tell the server what these constraints are. Thus, as a server operator, you
17601 need to make an educated guess as to what is most likely to work for your
17604 Some known size constraints suggest that a bit-size in the range 2048 to 2236
17605 is most likely to maximise interoperability. The upper bound comes from
17606 applications using the Mozilla Network Security Services (NSS) library, which
17607 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
17608 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
17609 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
17610 acceptable bound from 1024 to 2048.
17613 .option tls_eccurve main string&!! &`auto`&
17614 .cindex TLS "EC cryptography"
17615 This option selects a EC curve for use by Exim when used with OpenSSL.
17616 It has no effect when Exim is used with GnuTLS.
17618 After expansion it must contain a valid EC curve parameter, such as
17619 &`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
17620 for valid selections.
17622 For OpenSSL versions before (and not including) 1.0.2, the string
17623 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
17624 &`auto`& tells the library to choose.
17626 If the option expands to an empty string, no EC curves will be enabled.
17629 .option tls_ocsp_file main string&!! unset
17630 .cindex TLS "certificate status"
17631 .cindex TLS "OCSP proof file"
17633 must if set expand to the absolute path to a file which contains a current
17634 status proof for the server's certificate, as obtained from the
17635 Certificate Authority.
17637 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
17639 For GnuTLS 3.5.6 or later the expanded value of this option can be a list
17640 of files, to match a list given for the &%tls_certificate%& option.
17641 The ordering of the two lists must match.
17644 .option tls_on_connect_ports main "string list" unset
17647 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
17648 operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
17649 set up without waiting for the client to issue a STARTTLS command. For
17650 further details, see section &<<SECTsupobssmt>>&.
17654 .option tls_privatekey main string list&!! unset
17655 .cindex "TLS" "server private key; location of"
17656 The value of this option is expanded, and must then be a list of absolute paths to
17657 files which contains the server's private keys.
17658 If this option is unset, or if
17659 the expansion is forced to fail, or the result is an empty string, the private
17660 key is assumed to be in the same file as the server's certificates. See chapter
17661 &<<CHAPTLS>>& for further details.
17663 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17666 .option tls_remember_esmtp main boolean false
17667 .cindex "TLS" "esmtp state; remembering"
17668 .cindex "TLS" "broken clients"
17669 If this option is set true, Exim violates the RFCs by remembering that it is in
17670 &"esmtp"& state after successfully negotiating a TLS session. This provides
17671 support for broken clients that fail to send a new EHLO after starting a
17675 .option tls_require_ciphers main string&!! unset
17676 .cindex "TLS" "requiring specific ciphers"
17677 .cindex "cipher" "requiring specific"
17678 This option controls which ciphers can be used for incoming TLS connections.
17679 The &(smtp)& transport has an option of the same name for controlling outgoing
17680 connections. This option is expanded for each connection, so can be varied for
17681 different clients if required. The value of this option must be a list of
17682 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
17683 in somewhat different ways. If GnuTLS is being used, the client controls the
17684 preference order of the available ciphers. Details are given in sections
17685 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
17688 .option tls_try_verify_hosts main "host list&!!" unset
17689 .cindex "TLS" "client certificate verification"
17690 .cindex "certificate" "verification of client"
17691 See &%tls_verify_hosts%& below.
17694 .option tls_verify_certificates main string&!! system
17695 .cindex "TLS" "client certificate verification"
17696 .cindex "certificate" "verification of client"
17697 The value of this option is expanded, and must then be either the
17699 or the absolute path to
17700 a file or directory containing permitted certificates for clients that
17701 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
17703 The "system" value for the option will use a
17704 system default location compiled into the SSL library.
17705 This is not available for GnuTLS versions preceding 3.0.20,
17706 and will be taken as empty; an explicit location
17709 The use of a directory for the option value is not available for GnuTLS versions
17710 preceding 3.3.6 and a single file must be used.
17712 With OpenSSL the certificates specified
17714 either by file or directory
17715 are added to those given by the system default location.
17717 These certificates should be for the certificate authorities trusted, rather
17718 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
17719 the value is a file then the certificates are sent by Exim as a server to
17720 connecting clients, defining the list of accepted certificate authorities.
17721 Thus the values defined should be considered public data. To avoid this,
17722 use the explicit directory version.
17724 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17726 A forced expansion failure or setting to an empty string is equivalent to
17730 .option tls_verify_hosts main "host list&!!" unset
17731 .cindex "TLS" "client certificate verification"
17732 .cindex "certificate" "verification of client"
17733 This option, along with &%tls_try_verify_hosts%&, controls the checking of
17734 certificates from clients. The expected certificates are defined by
17735 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
17736 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
17737 &%tls_verify_certificates%& is not set.
17739 Any client that matches &%tls_verify_hosts%& is constrained by
17740 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
17741 present one of the listed certificates. If it does not, the connection is
17742 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
17743 the host to use TLS. It can still send SMTP commands through unencrypted
17744 connections. Forcing a client to use TLS has to be done separately using an
17745 ACL to reject inappropriate commands when the connection is not encrypted.
17747 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
17748 matches this option (but not &%tls_verify_hosts%&), Exim requests a
17749 certificate and checks it against &%tls_verify_certificates%&, but does not
17750 abort the connection if there is no certificate or if it does not match. This
17751 state can be detected in an ACL, which makes it possible to implement policies
17752 such as &"accept for relay only if a verified certificate has been received,
17753 but accept for local delivery if encrypted, even without a verified
17756 Client hosts that match neither of these lists are not asked to present
17760 .option trusted_groups main "string list&!!" unset
17761 .cindex "trusted groups"
17762 .cindex "groups" "trusted"
17763 This option is expanded just once, at the start of Exim's processing. If this
17764 option is set, any process that is running in one of the listed groups, or
17765 which has one of them as a supplementary group, is trusted. The groups can be
17766 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
17767 details of what trusted callers are permitted to do. If neither
17768 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
17771 .option trusted_users main "string list&!!" unset
17772 .cindex "trusted users"
17773 .cindex "user" "trusted"
17774 This option is expanded just once, at the start of Exim's processing. If this
17775 option is set, any process that is running as one of the listed users is
17776 trusted. The users can be specified numerically or by name. See section
17777 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
17778 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
17779 Exim user are trusted.
17781 .option unknown_login main string&!! unset
17782 .cindex "uid (user id)" "unknown caller"
17783 .vindex "&$caller_uid$&"
17784 This is a specialized feature for use in unusual configurations. By default, if
17785 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
17786 gives up. The &%unknown_login%& option can be used to set a login name to be
17787 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
17788 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
17789 is used for the user's real name (gecos field), unless this has been set by the
17792 .option unknown_username main string unset
17793 See &%unknown_login%&.
17795 .option untrusted_set_sender main "address list&!!" unset
17796 .cindex "trusted users"
17797 .cindex "sender" "setting by untrusted user"
17798 .cindex "untrusted user setting sender"
17799 .cindex "user" "untrusted setting sender"
17800 .cindex "envelope sender"
17801 When an untrusted user submits a message to Exim using the standard input, Exim
17802 normally creates an envelope sender address from the user's login and the
17803 default qualification domain. Data from the &%-f%& option (for setting envelope
17804 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
17805 is used) is ignored.
17807 However, untrusted users are permitted to set an empty envelope sender address,
17808 to declare that a message should never generate any bounces. For example:
17810 exim -f '<>' user@domain.example
17812 .vindex "&$sender_ident$&"
17813 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
17814 other envelope sender addresses in a controlled way. When it is set, untrusted
17815 users are allowed to set envelope sender addresses that match any of the
17816 patterns in the list. Like all address lists, the string is expanded. The
17817 identity of the user is in &$sender_ident$&, so you can, for example, restrict
17818 users to setting senders that start with their login ids
17819 followed by a hyphen
17820 by a setting like this:
17822 untrusted_set_sender = ^$sender_ident-
17824 If you want to allow untrusted users to set envelope sender addresses without
17825 restriction, you can use
17827 untrusted_set_sender = *
17829 The &%untrusted_set_sender%& option applies to all forms of local input, but
17830 only to the setting of the envelope sender. It does not permit untrusted users
17831 to use the other options which trusted user can use to override message
17832 parameters. Furthermore, it does not stop Exim from removing an existing
17833 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
17834 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
17835 overriding these actions. The handling of the &'Sender:'& header is also
17836 described in section &<<SECTthesenhea>>&.
17838 The log line for a message's arrival shows the envelope sender following
17839 &"<="&. For local messages, the user's login always follows, after &"U="&. In
17840 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
17841 envelope sender address, the user's login is shown in parentheses after the
17845 .option uucp_from_pattern main string "see below"
17846 .cindex "&""From""& line"
17847 .cindex "UUCP" "&""From""& line"
17848 Some applications that pass messages to an MTA via a command line interface use
17849 an initial line starting with &"From&~"& to pass the envelope sender. In
17850 particular, this is used by UUCP software. Exim recognizes such a line by means
17851 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
17852 matches, the sender address is constructed by expanding the contents of
17853 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
17854 default pattern recognizes lines in the following two forms:
17856 From ph10 Fri Jan 5 12:35 GMT 1996
17857 From ph10 Fri, 7 Jan 97 14:00:00 GMT
17859 The pattern can be seen by running
17861 exim -bP uucp_from_pattern
17863 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
17864 year in the second case. The first word after &"From&~"& is matched in the
17865 regular expression by a parenthesized subpattern. The default value for
17866 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
17867 (&"ph10"& in the example above) as the message's sender. See also
17868 &%ignore_fromline_hosts%&.
17871 .option uucp_from_sender main string&!! &`$1`&
17872 See &%uucp_from_pattern%& above.
17875 .option warn_message_file main string unset
17876 .cindex "warning of delay" "customizing the message"
17877 .cindex "customizing" "warning message"
17878 This option defines a template file containing paragraphs of text to be used
17879 for constructing the warning message which is sent by Exim when a message has
17880 been in the queue for a specified amount of time, as specified by
17881 &%delay_warning%&. Details of the file's contents are given in chapter
17882 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
17885 .option write_rejectlog main boolean true
17886 .cindex "reject log" "disabling"
17887 If this option is set false, Exim no longer writes anything to the reject log.
17888 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
17889 .ecindex IIDconfima
17890 .ecindex IIDmaiconf
17895 . ////////////////////////////////////////////////////////////////////////////
17896 . ////////////////////////////////////////////////////////////////////////////
17898 .chapter "Generic options for routers" "CHAProutergeneric"
17899 .scindex IIDgenoprou1 "options" "generic; for routers"
17900 .scindex IIDgenoprou2 "generic options" "router"
17901 This chapter describes the generic options that apply to all routers.
17902 Those that are preconditions are marked with ‡ in the &"use"& field.
17904 For a general description of how a router operates, see sections
17905 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
17906 which the preconditions are tested. The order of expansion of the options that
17907 provide data for a transport is: &%errors_to%&, &%headers_add%&,
17908 &%headers_remove%&, &%transport%&.
17912 .option address_data routers string&!! unset
17913 .cindex "router" "data attached to address"
17914 The string is expanded just before the router is run, that is, after all the
17915 precondition tests have succeeded. If the expansion is forced to fail, the
17916 router declines, the value of &%address_data%& remains unchanged, and the
17917 &%more%& option controls what happens next. Other expansion failures cause
17918 delivery of the address to be deferred.
17920 .vindex "&$address_data$&"
17921 When the expansion succeeds, the value is retained with the address, and can be
17922 accessed using the variable &$address_data$& in the current router, subsequent
17923 routers, and the eventual transport.
17925 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
17926 that runs a user's filter file, the contents of &$address_data$& are accessible
17927 in the filter. This is not normally a problem, because such data is usually
17928 either not confidential or it &"belongs"& to the current user, but if you do
17929 put confidential data into &$address_data$& you need to remember this point.
17931 Even if the router declines or passes, the value of &$address_data$& remains
17932 with the address, though it can be changed by another &%address_data%& setting
17933 on a subsequent router. If a router generates child addresses, the value of
17934 &$address_data$& propagates to them. This also applies to the special kind of
17935 &"child"& that is generated by a router with the &%unseen%& option.
17937 The idea of &%address_data%& is that you can use it to look up a lot of data
17938 for the address once, and then pick out parts of the data later. For example,
17939 you could use a single LDAP lookup to return a string of the form
17941 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
17943 In the transport you could pick out the mailbox by a setting such as
17945 file = ${extract{mailbox}{$address_data}}
17947 This makes the configuration file less messy, and also reduces the number of
17948 lookups (though Exim does cache lookups).
17950 .vindex "&$sender_address_data$&"
17951 .vindex "&$address_data$&"
17952 The &%address_data%& facility is also useful as a means of passing information
17953 from one router to another, and from a router to a transport. In addition, if
17954 &$address_data$& is set by a router when verifying a recipient address from an
17955 ACL, it remains available for use in the rest of the ACL statement. After
17956 verifying a sender, the value is transferred to &$sender_address_data$&.
17960 .option address_test routers&!? boolean true
17962 .cindex "router" "skipping when address testing"
17963 If this option is set false, the router is skipped when routing is being tested
17964 by means of the &%-bt%& command line option. This can be a convenience when
17965 your first router sends messages to an external scanner, because it saves you
17966 having to set the &"already scanned"& indicator when testing real address
17971 .option cannot_route_message routers string&!! unset
17972 .cindex "router" "customizing &""cannot route""& message"
17973 .cindex "customizing" "&""cannot route""& message"
17974 This option specifies a text message that is used when an address cannot be
17975 routed because Exim has run out of routers. The default message is
17976 &"Unrouteable address"&. This option is useful only on routers that have
17977 &%more%& set false, or on the very last router in a configuration, because the
17978 value that is used is taken from the last router that is considered. This
17979 includes a router that is skipped because its preconditions are not met, as
17980 well as a router that declines. For example, using the default configuration,
17983 cannot_route_message = Remote domain not found in DNS
17985 on the first router, which is a &(dnslookup)& router with &%more%& set false,
17988 cannot_route_message = Unknown local user
17990 on the final router that checks for local users. If string expansion fails for
17991 this option, the default message is used. Unless the expansion failure was
17992 explicitly forced, a message about the failure is written to the main and panic
17993 logs, in addition to the normal message about the routing failure.
17996 .option caseful_local_part routers boolean false
17997 .cindex "case of local parts"
17998 .cindex "router" "case of local parts"
17999 By default, routers handle the local parts of addresses in a case-insensitive
18000 manner, though the actual case is preserved for transmission with the message.
18001 If you want the case of letters to be significant in a router, you must set
18002 this option true. For individual router options that contain address or local
18003 part lists (for example, &%local_parts%&), case-sensitive matching can be
18004 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
18007 .vindex "&$local_part$&"
18008 .vindex "&$original_local_part$&"
18009 .vindex "&$parent_local_part$&"
18010 The value of the &$local_part$& variable is forced to lower case while a
18011 router is running unless &%caseful_local_part%& is set. When a router assigns
18012 an address to a transport, the value of &$local_part$& when the transport runs
18013 is the same as it was in the router. Similarly, when a router generates child
18014 addresses by aliasing or forwarding, the values of &$original_local_part$&
18015 and &$parent_local_part$& are those that were used by the redirecting router.
18017 This option applies to the processing of an address by a router. When a
18018 recipient address is being processed in an ACL, there is a separate &%control%&
18019 modifier that can be used to specify case-sensitive processing within the ACL
18020 (see section &<<SECTcontrols>>&).
18024 .option check_local_user routers&!? boolean false
18025 .cindex "local user, checking in router"
18026 .cindex "router" "checking for local user"
18027 .cindex "&_/etc/passwd_&"
18029 When this option is true, Exim checks that the local part of the recipient
18030 address (with affixes removed if relevant) is the name of an account on the
18031 local system. The check is done by calling the &[getpwnam()]& function rather
18032 than trying to read &_/etc/passwd_& directly. This means that other methods of
18033 holding password data (such as NIS) are supported. If the local part is a local
18034 user, &$home$& is set from the password data, and can be tested in other
18035 preconditions that are evaluated after this one (the order of evaluation is
18036 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
18037 overridden by &%router_home_directory%&. If the local part is not a local user,
18038 the router is skipped.
18040 If you want to check that the local part is either the name of a local user
18041 or matches something else, you cannot combine &%check_local_user%& with a
18042 setting of &%local_parts%&, because that specifies the logical &'and'& of the
18043 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
18044 setting to achieve this. For example:
18046 local_parts = passwd;$local_part : lsearch;/etc/other/users
18048 Note, however, that the side effects of &%check_local_user%& (such as setting
18049 up a home directory) do not occur when a &(passwd)& lookup is used in a
18050 &%local_parts%& (or any other) precondition.
18054 .option condition routers&!? string&!! unset
18055 .cindex "router" "customized precondition"
18056 This option specifies a general precondition test that has to succeed for the
18057 router to be called. The &%condition%& option is the last precondition to be
18058 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
18059 result is a forced failure, or an empty string, or one of the strings &"0"& or
18060 &"no"& or &"false"& (checked without regard to the case of the letters), the
18061 router is skipped, and the address is offered to the next one.
18063 If the result is any other value, the router is run (as this is the last
18064 precondition to be evaluated, all the other preconditions must be true).
18066 This option is unusual in that multiple &%condition%& options may be present.
18067 All &%condition%& options must succeed.
18069 The &%condition%& option provides a means of applying custom conditions to the
18070 running of routers. Note that in the case of a simple conditional expansion,
18071 the default expansion values are exactly what is wanted. For example:
18073 condition = ${if >{$message_age}{600}}
18075 Because of the default behaviour of the string expansion, this is equivalent to
18077 condition = ${if >{$message_age}{600}{true}{}}
18080 A multiple condition example, which succeeds:
18082 condition = ${if >{$message_age}{600}}
18083 condition = ${if !eq{${lc:$local_part}}{postmaster}}
18087 If the expansion fails (other than forced failure) delivery is deferred. Some
18088 of the other precondition options are common special cases that could in fact
18089 be specified using &%condition%&.
18091 Historical note: We have &%condition%& on ACLs and on Routers. Routers
18092 are far older, and use one set of semantics. ACLs are newer and when
18093 they were created, the ACL &%condition%& process was given far stricter
18094 parse semantics. The &%bool{}%& expansion condition uses the same rules as
18095 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
18096 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
18097 Router rules processing behavior.
18099 This is best illustrated in an example:
18101 # If used in an ACL condition will fail with a syntax error, but
18102 # in a router condition any extra characters are treated as a string
18104 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
18107 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
18110 In each example above, the &%if%& statement actually ends after
18111 &"{google.com}}"&. Since no true or false braces were defined, the
18112 default &%if%& behavior is to return a boolean true or a null answer
18113 (which evaluates to false). The rest of the line is then treated as a
18114 string. So the first example resulted in the boolean answer &"true"&
18115 with the string &" {yes} {no}}"& appended to it. The second example
18116 resulted in the null output (indicating false) with the string
18117 &" {yes} {no}}"& appended to it.
18119 In fact you can put excess forward braces in too. In the router
18120 &%condition%&, Exim's parser only looks for &"{"& symbols when they
18121 mean something, like after a &"$"& or when required as part of a
18122 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
18125 Thus, in a Router, the above expansion strings will both always evaluate
18126 true, as the result of expansion is a non-empty string which doesn't
18127 match an explicit false value. This can be tricky to debug. By
18128 contrast, in an ACL either of those strings will always result in an
18129 expansion error because the result doesn't look sufficiently boolean.
18132 .option debug_print routers string&!! unset
18133 .cindex "testing" "variables in drivers"
18134 If this option is set and debugging is enabled (see the &%-d%& command line
18135 option) or in address-testing mode (see the &%-bt%& command line option),
18136 the string is expanded and included in the debugging output.
18137 If expansion of the string fails, the error message is written to the debugging
18138 output, and Exim carries on processing.
18139 This option is provided to help with checking out the values of variables and
18140 so on when debugging router configurations. For example, if a &%condition%&
18141 option appears not to be working, &%debug_print%& can be used to output the
18142 variables it references. The output happens after checks for &%domains%&,
18143 &%local_parts%&, and &%check_local_user%& but before any other preconditions
18144 are tested. A newline is added to the text if it does not end with one.
18145 The variable &$router_name$& contains the name of the router.
18149 .option disable_logging routers boolean false
18150 If this option is set true, nothing is logged for any routing errors
18151 or for any deliveries caused by this router. You should not set this option
18152 unless you really, really know what you are doing. See also the generic
18153 transport option of the same name.
18155 .option dnssec_request_domains routers "domain list&!!" unset
18156 .cindex "MX record" "security"
18157 .cindex "DNSSEC" "MX lookup"
18158 .cindex "security" "MX lookup"
18159 .cindex "DNS" "DNSSEC"
18160 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
18161 the dnssec request bit set.
18162 This applies to all of the SRV, MX, AAAA, A lookup sequence.
18164 .option dnssec_require_domains routers "domain list&!!" unset
18165 .cindex "MX record" "security"
18166 .cindex "DNSSEC" "MX lookup"
18167 .cindex "security" "MX lookup"
18168 .cindex "DNS" "DNSSEC"
18169 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
18170 the dnssec request bit set. Any returns not having the Authenticated Data bit
18171 (AD bit) set will be ignored and logged as a host-lookup failure.
18172 This applies to all of the SRV, MX, AAAA, A lookup sequence.
18175 .option domains routers&!? "domain list&!!" unset
18176 .cindex "router" "restricting to specific domains"
18177 .vindex "&$domain_data$&"
18178 If this option is set, the router is skipped unless the current domain matches
18179 the list. If the match is achieved by means of a file lookup, the data that the
18180 lookup returned for the domain is placed in &$domain_data$& for use in string
18181 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
18182 a list of the order in which preconditions are evaluated.
18186 .option driver routers string unset
18187 This option must always be set. It specifies which of the available routers is
18191 .option dsn_lasthop routers boolean false
18192 .cindex "DSN" "success"
18193 .cindex "Delivery Status Notification" "success"
18194 If this option is set true, and extended DSN (RFC3461) processing is in effect,
18195 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
18196 instead send a success DSN as if the next hop does not support DSN.
18197 Not effective on redirect routers.
18201 .option errors_to routers string&!! unset
18202 .cindex "envelope sender"
18203 .cindex "router" "changing address for errors"
18204 If a router successfully handles an address, it may assign the address to a
18205 transport for delivery or it may generate child addresses. In both cases, if
18206 there is a delivery problem during later processing, the resulting bounce
18207 message is sent to the address that results from expanding this string,
18208 provided that the address verifies successfully. The &%errors_to%& option is
18209 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
18211 The &%errors_to%& setting associated with an address can be overridden if it
18212 subsequently passes through other routers that have their own &%errors_to%&
18213 settings, or if the message is delivered by a transport with a &%return_path%&
18216 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
18217 the expansion fails to verify, the errors address associated with the incoming
18218 address is used. At top level, this is the envelope sender. A non-forced
18219 expansion failure causes delivery to be deferred.
18221 If an address for which &%errors_to%& has been set ends up being delivered over
18222 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
18223 any bounces that are generated by other MTAs on the delivery route are also
18224 sent there. You can set &%errors_to%& to the empty string by either of these
18230 An expansion item that yields an empty string has the same effect. If you do
18231 this, a locally detected delivery error for addresses processed by this router
18232 no longer gives rise to a bounce message; the error is discarded. If the
18233 address is delivered to a remote host, the return path is set to &`<>`&, unless
18234 overridden by the &%return_path%& option on the transport.
18236 .vindex "&$address_data$&"
18237 If for some reason you want to discard local errors, but use a non-empty
18238 MAIL command for remote delivery, you can preserve the original return
18239 path in &$address_data$& in the router, and reinstate it in the transport by
18240 setting &%return_path%&.
18242 The most common use of &%errors_to%& is to direct mailing list bounces to the
18243 manager of the list, as described in section &<<SECTmailinglists>>&, or to
18244 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
18248 .option expn routers&!? boolean true
18249 .cindex "address" "testing"
18250 .cindex "testing" "addresses"
18251 .cindex "EXPN" "router skipping"
18252 .cindex "router" "skipping for EXPN"
18253 If this option is turned off, the router is skipped when testing an address
18254 as a result of processing an SMTP EXPN command. You might, for example,
18255 want to turn it off on a router for users' &_.forward_& files, while leaving it
18256 on for the system alias file.
18257 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18260 The use of the SMTP EXPN command is controlled by an ACL (see chapter
18261 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
18262 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
18266 .option fail_verify routers boolean false
18267 .cindex "router" "forcing verification failure"
18268 Setting this option has the effect of setting both &%fail_verify_sender%& and
18269 &%fail_verify_recipient%& to the same value.
18273 .option fail_verify_recipient routers boolean false
18274 If this option is true and an address is accepted by this router when
18275 verifying a recipient, verification fails.
18279 .option fail_verify_sender routers boolean false
18280 If this option is true and an address is accepted by this router when
18281 verifying a sender, verification fails.
18285 .option fallback_hosts routers "string list" unset
18286 .cindex "router" "fallback hosts"
18287 .cindex "fallback" "hosts specified on router"
18288 String expansion is not applied to this option. The argument must be a
18289 colon-separated list of host names or IP addresses. The list separator can be
18290 changed (see section &<<SECTlistsepchange>>&), and a port can be specified with
18291 each name or address. In fact, the format of each item is exactly the same as
18292 defined for the list of hosts in a &(manualroute)& router (see section
18293 &<<SECTformatonehostitem>>&).
18295 If a router queues an address for a remote transport, this host list is
18296 associated with the address, and used instead of the transport's fallback host
18297 list. If &%hosts_randomize%& is set on the transport, the order of the list is
18298 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
18299 transport for further details.
18302 .option group routers string&!! "see below"
18303 .cindex "gid (group id)" "local delivery"
18304 .cindex "local transports" "uid and gid"
18305 .cindex "transport" "local"
18306 .cindex "router" "setting group"
18307 When a router queues an address for a transport, and the transport does not
18308 specify a group, the group given here is used when running the delivery
18310 The group may be specified numerically or by name. If expansion fails, the
18311 error is logged and delivery is deferred.
18312 The default is unset, unless &%check_local_user%& is set, when the default
18313 is taken from the password information. See also &%initgroups%& and &%user%&
18314 and the discussion in chapter &<<CHAPenvironment>>&.
18318 .option headers_add routers list&!! unset
18319 .cindex "header lines" "adding"
18320 .cindex "router" "adding header lines"
18321 This option specifies a list of text headers,
18322 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
18323 that is associated with any addresses that are accepted by the router.
18324 Each item is separately expanded, at routing time. However, this
18325 option has no effect when an address is just being verified. The way in which
18326 the text is used to add header lines at transport time is described in section
18327 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
18328 message is in the process of being transported. This means that references to
18329 header lines in string expansions in the transport's configuration do not
18330 &"see"& the added header lines.
18332 The &%headers_add%& option is expanded after &%errors_to%&, but before
18333 &%headers_remove%& and &%transport%&. If an item is empty, or if
18334 an item expansion is forced to fail, the item has no effect. Other expansion
18335 failures are treated as configuration errors.
18337 Unlike most options, &%headers_add%& can be specified multiple times
18338 for a router; all listed headers are added.
18340 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
18341 router that has the &%one_time%& option set.
18343 .cindex "duplicate addresses"
18344 .oindex "&%unseen%&"
18345 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
18346 additions are deleted when the address is passed on to subsequent routers.
18347 For a &%redirect%& router, if a generated address is the same as the incoming
18348 address, this can lead to duplicate addresses with different header
18349 modifications. Exim does not do duplicate deliveries (except, in certain
18350 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
18351 which of the duplicates is discarded, so this ambiguous situation should be
18352 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
18356 .option headers_remove routers list&!! unset
18357 .cindex "header lines" "removing"
18358 .cindex "router" "removing header lines"
18359 This option specifies a list of text headers,
18360 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
18361 that is associated with any addresses that are accepted by the router.
18362 Each item is separately expanded, at routing time. However, this
18363 option has no effect when an address is just being verified. The way in which
18364 the text is used to remove header lines at transport time is described in
18365 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
18366 the message is in the process of being transported. This means that references
18367 to header lines in string expansions in the transport's configuration still
18368 &"see"& the original header lines.
18370 The &%headers_remove%& option is expanded after &%errors_to%& and
18371 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
18372 the item has no effect. Other expansion failures are treated as configuration
18375 Unlike most options, &%headers_remove%& can be specified multiple times
18376 for a router; all listed headers are removed.
18378 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
18379 router that has the &%one_time%& option set.
18381 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
18382 removal requests are deleted when the address is passed on to subsequent
18383 routers, and this can lead to problems with duplicates -- see the similar
18384 warning for &%headers_add%& above.
18386 &*Warning 3*&: Because of the separate expansion of the list items,
18387 items that contain a list separator must have it doubled.
18388 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
18392 .option ignore_target_hosts routers "host list&!!" unset
18393 .cindex "IP address" "discarding"
18394 .cindex "router" "discarding IP addresses"
18395 Although this option is a host list, it should normally contain IP address
18396 entries rather than names. If any host that is looked up by the router has an
18397 IP address that matches an item in this list, Exim behaves as if that IP
18398 address did not exist. This option allows you to cope with rogue DNS entries
18401 remote.domain.example. A 127.0.0.1
18405 ignore_target_hosts = 127.0.0.1
18407 on the relevant router. If all the hosts found by a &(dnslookup)& router are
18408 discarded in this way, the router declines. In a conventional configuration, an
18409 attempt to mail to such a domain would normally provoke the &"unrouteable
18410 domain"& error, and an attempt to verify an address in the domain would fail.
18411 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
18412 router declines if presented with one of the listed addresses.
18414 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
18415 means of the first or the second of the following settings, respectively:
18417 ignore_target_hosts = 0.0.0.0/0
18418 ignore_target_hosts = <; 0::0/0
18420 The pattern in the first line matches all IPv4 addresses, whereas the pattern
18421 in the second line matches all IPv6 addresses.
18423 This option may also be useful for ignoring link-local and site-local IPv6
18424 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
18425 is expanded before use as a list, it is possible to make it dependent on the
18426 domain that is being routed.
18428 .vindex "&$host_address$&"
18429 During its expansion, &$host_address$& is set to the IP address that is being
18432 .option initgroups routers boolean false
18433 .cindex "additional groups"
18434 .cindex "groups" "additional"
18435 .cindex "local transports" "uid and gid"
18436 .cindex "transport" "local"
18437 If the router queues an address for a transport, and this option is true, and
18438 the uid supplied by the router is not overridden by the transport, the
18439 &[initgroups()]& function is called when running the transport to ensure that
18440 any additional groups associated with the uid are set up. See also &%group%&
18441 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
18445 .option local_part_prefix routers&!? "string list" unset
18446 .cindex affix "router precondition"
18447 .cindex "router" "prefix for local part"
18448 .cindex "prefix" "for local part, used in router"
18449 If this option is set, the router is skipped unless the local part starts with
18450 one of the given strings, or &%local_part_prefix_optional%& is true. See
18451 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
18454 The list is scanned from left to right, and the first prefix that matches is
18455 used. A limited form of wildcard is available; if the prefix begins with an
18456 asterisk, it matches the longest possible sequence of arbitrary characters at
18457 the start of the local part. An asterisk should therefore always be followed by
18458 some character that does not occur in normal local parts.
18459 .cindex "multiple mailboxes"
18460 .cindex "mailbox" "multiple"
18461 Wildcarding can be used to set up multiple user mailboxes, as described in
18462 section &<<SECTmulbox>>&.
18464 .vindex "&$local_part$&"
18465 .vindex "&$local_part_prefix$&"
18466 During the testing of the &%local_parts%& option, and while the router is
18467 running, the prefix is removed from the local part, and is available in the
18468 expansion variable &$local_part_prefix$&. When a message is being delivered, if
18469 the router accepts the address, this remains true during subsequent delivery by
18470 a transport. In particular, the local part that is transmitted in the RCPT
18471 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
18472 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
18473 the relevant transport.
18475 When an address is being verified, &%local_part_prefix%& affects only the
18476 behaviour of the router. If the callout feature of verification is in use, this
18477 means that the full address, including the prefix, will be used during the
18480 The prefix facility is commonly used to handle local parts of the form
18481 &%owner-something%&. Another common use is to support local parts of the form
18482 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
18483 to tell a user their forwarding is broken &-- by placing a router like this one
18484 immediately before the router that handles &_.forward_& files:
18488 local_part_prefix = real-
18490 transport = local_delivery
18492 For security, it would probably be a good idea to restrict the use of this
18493 router to locally-generated messages, using a condition such as this:
18495 condition = ${if match {$sender_host_address}\
18496 {\N^(|127\.0\.0\.1)$\N}}
18499 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
18500 both conditions must be met if not optional. Care must be taken if wildcards
18501 are used in both a prefix and a suffix on the same router. Different
18502 separator characters must be used to avoid ambiguity.
18505 .option local_part_prefix_optional routers boolean false
18506 See &%local_part_prefix%& above.
18510 .option local_part_suffix routers&!? "string list" unset
18511 .cindex "router" "suffix for local part"
18512 .cindex "suffix for local part" "used in router"
18513 This option operates in the same way as &%local_part_prefix%&, except that the
18514 local part must end (rather than start) with the given string, the
18515 &%local_part_suffix_optional%& option determines whether the suffix is
18516 mandatory, and the wildcard * character, if present, must be the last
18517 character of the suffix. This option facility is commonly used to handle local
18518 parts of the form &%something-request%& and multiple user mailboxes of the form
18522 .option local_part_suffix_optional routers boolean false
18523 See &%local_part_suffix%& above.
18527 .option local_parts routers&!? "local part list&!!" unset
18528 .cindex "router" "restricting to specific local parts"
18529 .cindex "local part" "checking in router"
18530 The router is run only if the local part of the address matches the list.
18531 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18533 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
18534 string is expanded, it is possible to make it depend on the domain, for
18537 local_parts = dbm;/usr/local/specials/$domain
18539 .vindex "&$local_part_data$&"
18540 If the match is achieved by a lookup, the data that the lookup returned
18541 for the local part is placed in the variable &$local_part_data$& for use in
18542 expansions of the router's private options. You might use this option, for
18543 example, if you have a large number of local virtual domains, and you want to
18544 send all postmaster mail to the same place without having to set up an alias in
18545 each virtual domain:
18549 local_parts = postmaster
18550 data = postmaster@real.domain.example
18554 .option log_as_local routers boolean "see below"
18555 .cindex "log" "delivery line"
18556 .cindex "delivery" "log line format"
18557 Exim has two logging styles for delivery, the idea being to make local
18558 deliveries stand out more visibly from remote ones. In the &"local"& style, the
18559 recipient address is given just as the local part, without a domain. The use of
18560 this style is controlled by this option. It defaults to true for the &(accept)&
18561 router, and false for all the others. This option applies only when a
18562 router assigns an address to a transport. It has no effect on routers that
18563 redirect addresses.
18567 .option more routers boolean&!! true
18568 The result of string expansion for this option must be a valid boolean value,
18569 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
18570 result causes an error, and delivery is deferred. If the expansion is forced to
18571 fail, the default value for the option (true) is used. Other failures cause
18572 delivery to be deferred.
18574 If this option is set false, and the router declines to handle the address, no
18575 further routers are tried, routing fails, and the address is bounced.
18577 However, if the router explicitly passes an address to the following router by
18578 means of the setting
18582 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
18583 does not affect the behaviour if one of the precondition tests fails. In that
18584 case, the address is always passed to the next router.
18586 Note that &%address_data%& is not considered to be a precondition. If its
18587 expansion is forced to fail, the router declines, and the value of &%more%&
18588 controls what happens next.
18591 .option pass_on_timeout routers boolean false
18592 .cindex "timeout" "of router"
18593 .cindex "router" "timeout"
18594 If a router times out during a host lookup, it normally causes deferral of the
18595 address. If &%pass_on_timeout%& is set, the address is passed on to the next
18596 router, overriding &%no_more%&. This may be helpful for systems that are
18597 intermittently connected to the Internet, or those that want to pass to a smart
18598 host any messages that cannot immediately be delivered.
18600 There are occasional other temporary errors that can occur while doing DNS
18601 lookups. They are treated in the same way as a timeout, and this option
18602 applies to all of them.
18606 .option pass_router routers string unset
18607 .cindex "router" "go to after &""pass""&"
18608 Routers that recognize the generic &%self%& option (&(dnslookup)&,
18609 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
18610 routing to continue, and overriding a false setting of &%more%&. When one of
18611 these routers returns &"pass"&, the address is normally handed on to the next
18612 router in sequence. This can be changed by setting &%pass_router%& to the name
18613 of another router. However (unlike &%redirect_router%&) the named router must
18614 be below the current router, to avoid loops. Note that this option applies only
18615 to the special case of &"pass"&. It does not apply when a router returns
18616 &"decline"& because it cannot handle an address.
18620 .option redirect_router routers string unset
18621 .cindex "router" "start at after redirection"
18622 Sometimes an administrator knows that it is pointless to reprocess addresses
18623 generated from alias or forward files with the same router again. For
18624 example, if an alias file translates real names into login ids there is no
18625 point searching the alias file a second time, especially if it is a large file.
18627 The &%redirect_router%& option can be set to the name of any router instance.
18628 It causes the routing of any generated addresses to start at the named router
18629 instead of at the first router. This option has no effect if the router in
18630 which it is set does not generate new addresses.
18634 .option require_files routers&!? "string list&!!" unset
18635 .cindex "file" "requiring for router"
18636 .cindex "router" "requiring file existence"
18637 This option provides a general mechanism for predicating the running of a
18638 router on the existence or non-existence of certain files or directories.
18639 Before running a router, as one of its precondition tests, Exim works its way
18640 through the &%require_files%& list, expanding each item separately.
18642 Because the list is split before expansion, any colons in expansion items must
18643 be doubled, or the facility for using a different list separator must be used
18644 (&<<SECTlistsepchange>>&).
18645 If any expansion is forced to fail, the item is ignored. Other expansion
18646 failures cause routing of the address to be deferred.
18648 If any expanded string is empty, it is ignored. Otherwise, except as described
18649 below, each string must be a fully qualified file path, optionally preceded by
18650 &"!"&. The paths are passed to the &[stat()]& function to test for the
18651 existence of the files or directories. The router is skipped if any paths not
18652 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
18655 If &[stat()]& cannot determine whether a file exists or not, delivery of
18656 the message is deferred. This can happen when NFS-mounted filesystems are
18659 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
18660 options, so you cannot use it to check for the existence of a file in which to
18661 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
18662 full list of the order in which preconditions are evaluated.) However, as
18663 these options are all expanded, you can use the &%exists%& expansion condition
18664 to make such tests. The &%require_files%& option is intended for checking files
18665 that the router may be going to use internally, or which are needed by a
18666 transport (e.g., &_.procmailrc_&).
18668 During delivery, the &[stat()]& function is run as root, but there is a
18669 facility for some checking of the accessibility of a file by another user.
18670 This is not a proper permissions check, but just a &"rough"& check that
18671 operates as follows:
18673 If an item in a &%require_files%& list does not contain any forward slash
18674 characters, it is taken to be the user (and optional group, separated by a
18675 comma) to be checked for subsequent files in the list. If no group is specified
18676 but the user is specified symbolically, the gid associated with the uid is
18679 require_files = mail:/some/file
18680 require_files = $local_part:$home/.procmailrc
18682 If a user or group name in a &%require_files%& list does not exist, the
18683 &%require_files%& condition fails.
18685 Exim performs the check by scanning along the components of the file path, and
18686 checking the access for the given uid and gid. It checks for &"x"& access on
18687 directories, and &"r"& access on the final file. Note that this means that file
18688 access control lists, if the operating system has them, are ignored.
18690 &*Warning 1*&: When the router is being run to verify addresses for an
18691 incoming SMTP message, Exim is not running as root, but under its own uid. This
18692 may affect the result of a &%require_files%& check. In particular, &[stat()]&
18693 may yield the error EACCES (&"Permission denied"&). This means that the Exim
18694 user is not permitted to read one of the directories on the file's path.
18696 &*Warning 2*&: Even when Exim is running as root while delivering a message,
18697 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
18698 without root access. In this case, if a check for access by a particular user
18699 is requested, Exim creates a subprocess that runs as that user, and tries the
18700 check again in that process.
18702 The default action for handling an unresolved EACCES is to consider it to
18703 be caused by a configuration error, and routing is deferred because the
18704 existence or non-existence of the file cannot be determined. However, in some
18705 circumstances it may be desirable to treat this condition as if the file did
18706 not exist. If the filename (or the exclamation mark that precedes the filename
18707 for non-existence) is preceded by a plus sign, the EACCES error is treated
18708 as if the file did not exist. For example:
18710 require_files = +/some/file
18712 If the router is not an essential part of verification (for example, it
18713 handles users' &_.forward_& files), another solution is to set the &%verify%&
18714 option false so that the router is skipped when verifying.
18718 .option retry_use_local_part routers boolean "see below"
18719 .cindex "hints database" "retry keys"
18720 .cindex "local part" "in retry keys"
18721 When a delivery suffers a temporary routing failure, a retry record is created
18722 in Exim's hints database. For addresses whose routing depends only on the
18723 domain, the key for the retry record should not involve the local part, but for
18724 other addresses, both the domain and the local part should be included.
18725 Usually, remote routing is of the former kind, and local routing is of the
18728 This option controls whether the local part is used to form the key for retry
18729 hints for addresses that suffer temporary errors while being handled by this
18730 router. The default value is true for any router that has &%check_local_user%&
18731 set, and false otherwise. Note that this option does not apply to hints keys
18732 for transport delays; they are controlled by a generic transport option of the
18735 The setting of &%retry_use_local_part%& applies only to the router on which it
18736 appears. If the router generates child addresses, they are routed
18737 independently; this setting does not become attached to them.
18741 .option router_home_directory routers string&!! unset
18742 .cindex "router" "home directory for"
18743 .cindex "home directory" "for router"
18745 This option sets a home directory for use while the router is running. (Compare
18746 &%transport_home_directory%&, which sets a home directory for later
18747 transporting.) In particular, if used on a &(redirect)& router, this option
18748 sets a value for &$home$& while a filter is running. The value is expanded;
18749 forced expansion failure causes the option to be ignored &-- other failures
18750 cause the router to defer.
18752 Expansion of &%router_home_directory%& happens immediately after the
18753 &%check_local_user%& test (if configured), before any further expansions take
18755 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18757 While the router is running, &%router_home_directory%& overrides the value of
18758 &$home$& that came from &%check_local_user%&.
18760 When a router accepts an address and assigns it to a local transport (including
18761 the cases when a &(redirect)& router generates a pipe, file, or autoreply
18762 delivery), the home directory setting for the transport is taken from the first
18763 of these values that is set:
18766 The &%home_directory%& option on the transport;
18768 The &%transport_home_directory%& option on the router;
18770 The password data if &%check_local_user%& is set on the router;
18772 The &%router_home_directory%& option on the router.
18775 In other words, &%router_home_directory%& overrides the password data for the
18776 router, but not for the transport.
18780 .option self routers string freeze
18781 .cindex "MX record" "pointing to local host"
18782 .cindex "local host" "MX pointing to"
18783 This option applies to those routers that use a recipient address to find a
18784 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
18785 and &(manualroute)& routers.
18786 Certain configurations of the &(queryprogram)& router can also specify a list
18788 Usually such routers are configured to send the message to a remote host via an
18789 &(smtp)& transport. The &%self%& option specifies what happens when the first
18790 host on the list turns out to be the local host.
18791 The way in which Exim checks for the local host is described in section
18792 &<<SECTreclocipadd>>&.
18794 Normally this situation indicates either an error in Exim's configuration (for
18795 example, the router should be configured not to process this domain), or an
18796 error in the DNS (for example, the MX should not point to this host). For this
18797 reason, the default action is to log the incident, defer the address, and
18798 freeze the message. The following alternatives are provided for use in special
18803 Delivery of the message is tried again later, but the message is not frozen.
18805 .vitem "&%reroute%&: <&'domain'&>"
18806 The domain is changed to the given domain, and the address is passed back to
18807 be reprocessed by the routers. No rewriting of headers takes place. This
18808 behaviour is essentially a redirection.
18810 .vitem "&%reroute: rewrite:%& <&'domain'&>"
18811 The domain is changed to the given domain, and the address is passed back to be
18812 reprocessed by the routers. Any headers that contain the original domain are
18817 .vindex "&$self_hostname$&"
18818 The router passes the address to the next router, or to the router named in the
18819 &%pass_router%& option if it is set. This overrides &%no_more%&. During
18820 subsequent routing and delivery, the variable &$self_hostname$& contains the
18821 name of the local host that the router encountered. This can be used to
18822 distinguish between different cases for hosts with multiple names. The
18828 ensures that only those addresses that routed to the local host are passed on.
18829 Without &%no_more%&, addresses that were declined for other reasons would also
18830 be passed to the next router.
18833 Delivery fails and an error report is generated.
18836 .cindex "local host" "sending to"
18837 The anomaly is ignored and the address is queued for the transport. This
18838 setting should be used with extreme caution. For an &(smtp)& transport, it
18839 makes sense only in cases where the program that is listening on the SMTP port
18840 is not this version of Exim. That is, it must be some other MTA, or Exim with a
18841 different configuration file that handles the domain in another way.
18846 .option senders routers&!? "address list&!!" unset
18847 .cindex "router" "checking senders"
18848 If this option is set, the router is skipped unless the message's sender
18849 address matches something on the list.
18850 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18853 There are issues concerning verification when the running of routers is
18854 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
18855 setting, it sets the sender to the null string. When using the &%-bt%& option
18856 to check a configuration file, it is necessary also to use the &%-f%& option to
18857 set an appropriate sender. For incoming mail, the sender is unset when
18858 verifying the sender, but is available when verifying any recipients. If the
18859 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
18863 .option translate_ip_address routers string&!! unset
18864 .cindex "IP address" "translating"
18865 .cindex "packet radio"
18866 .cindex "router" "IP address translation"
18867 There exist some rare networking situations (for example, packet radio) where
18868 it is helpful to be able to translate IP addresses generated by normal routing
18869 mechanisms into other IP addresses, thus performing a kind of manual IP
18870 routing. This should be done only if the normal IP routing of the TCP/IP stack
18871 is inadequate or broken. Because this is an extremely uncommon requirement, the
18872 code to support this option is not included in the Exim binary unless
18873 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
18875 .vindex "&$host_address$&"
18876 The &%translate_ip_address%& string is expanded for every IP address generated
18877 by the router, with the generated address set in &$host_address$&. If the
18878 expansion is forced to fail, no action is taken.
18879 For any other expansion error, delivery of the message is deferred.
18880 If the result of the expansion is an IP address, that replaces the original
18881 address; otherwise the result is assumed to be a host name &-- this is looked
18882 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
18883 produce one or more replacement IP addresses. For example, to subvert all IP
18884 addresses in some specific networks, this could be added to a router:
18886 translate_ip_address = \
18887 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
18890 The file would contain lines like
18892 10.2.3.128/26 some.host
18893 10.8.4.34/26 10.44.8.15
18895 You should not make use of this facility unless you really understand what you
18900 .option transport routers string&!! unset
18901 This option specifies the transport to be used when a router accepts an address
18902 and sets it up for delivery. A transport is never needed if a router is used
18903 only for verification. The value of the option is expanded at routing time,
18904 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
18905 and result must be the name of one of the configured transports. If it is not,
18906 delivery is deferred.
18908 The &%transport%& option is not used by the &(redirect)& router, but it does
18909 have some private options that set up transports for pipe and file deliveries
18910 (see chapter &<<CHAPredirect>>&).
18914 .option transport_current_directory routers string&!! unset
18915 .cindex "current directory for local transport"
18916 This option associates a current directory with any address that is routed
18917 to a local transport. This can happen either because a transport is
18918 explicitly configured for the router, or because it generates a delivery to a
18919 file or a pipe. During the delivery process (that is, at transport time), this
18920 option string is expanded and is set as the current directory, unless
18921 overridden by a setting on the transport.
18922 If the expansion fails for any reason, including forced failure, an error is
18923 logged, and delivery is deferred.
18924 See chapter &<<CHAPenvironment>>& for details of the local delivery
18930 .option transport_home_directory routers string&!! "see below"
18931 .cindex "home directory" "for local transport"
18932 This option associates a home directory with any address that is routed to a
18933 local transport. This can happen either because a transport is explicitly
18934 configured for the router, or because it generates a delivery to a file or a
18935 pipe. During the delivery process (that is, at transport time), the option
18936 string is expanded and is set as the home directory, unless overridden by a
18937 setting of &%home_directory%& on the transport.
18938 If the expansion fails for any reason, including forced failure, an error is
18939 logged, and delivery is deferred.
18941 If the transport does not specify a home directory, and
18942 &%transport_home_directory%& is not set for the router, the home directory for
18943 the transport is taken from the password data if &%check_local_user%& is set for
18944 the router. Otherwise it is taken from &%router_home_directory%& if that option
18945 is set; if not, no home directory is set for the transport.
18947 See chapter &<<CHAPenvironment>>& for further details of the local delivery
18953 .option unseen routers boolean&!! false
18954 .cindex "router" "carrying on after success"
18955 The result of string expansion for this option must be a valid boolean value,
18956 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
18957 result causes an error, and delivery is deferred. If the expansion is forced to
18958 fail, the default value for the option (false) is used. Other failures cause
18959 delivery to be deferred.
18961 When this option is set true, routing does not cease if the router accepts the
18962 address. Instead, a copy of the incoming address is passed to the next router,
18963 overriding a false setting of &%more%&. There is little point in setting
18964 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
18965 the value of &%unseen%& contains expansion items (and therefore, presumably, is
18966 sometimes true and sometimes false).
18968 .cindex "copy of message (&%unseen%& option)"
18969 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
18970 qualifier in filter files. It can be used to cause copies of messages to be
18971 delivered to some other destination, while also carrying out a normal delivery.
18972 In effect, the current address is made into a &"parent"& that has two children
18973 &-- one that is delivered as specified by this router, and a clone that goes on
18974 to be routed further. For this reason, &%unseen%& may not be combined with the
18975 &%one_time%& option in a &(redirect)& router.
18977 &*Warning*&: Header lines added to the address (or specified for removal) by
18978 this router or by previous routers affect the &"unseen"& copy of the message
18979 only. The clone that continues to be processed by further routers starts with
18980 no added headers and none specified for removal. For a &%redirect%& router, if
18981 a generated address is the same as the incoming address, this can lead to
18982 duplicate addresses with different header modifications. Exim does not do
18983 duplicate deliveries (except, in certain circumstances, to pipes -- see section
18984 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
18985 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
18986 &%redirect%& router may be of help.
18988 Unlike the handling of header modifications, any data that was set by the
18989 &%address_data%& option in the current or previous routers &'is'& passed on to
18990 subsequent routers.
18993 .option user routers string&!! "see below"
18994 .cindex "uid (user id)" "local delivery"
18995 .cindex "local transports" "uid and gid"
18996 .cindex "transport" "local"
18997 .cindex "router" "user for filter processing"
18998 .cindex "filter" "user for processing"
18999 When a router queues an address for a transport, and the transport does not
19000 specify a user, the user given here is used when running the delivery process.
19001 The user may be specified numerically or by name. If expansion fails, the
19002 error is logged and delivery is deferred.
19003 This user is also used by the &(redirect)& router when running a filter file.
19004 The default is unset, except when &%check_local_user%& is set. In this case,
19005 the default is taken from the password information. If the user is specified as
19006 a name, and &%group%& is not set, the group associated with the user is used.
19007 See also &%initgroups%& and &%group%& and the discussion in chapter
19008 &<<CHAPenvironment>>&.
19012 .option verify routers&!? boolean true
19013 Setting this option has the effect of setting &%verify_sender%& and
19014 &%verify_recipient%& to the same value.
19017 .option verify_only routers&!? boolean false
19018 .cindex "EXPN" "with &%verify_only%&"
19020 .cindex "router" "used only when verifying"
19021 If this option is set, the router is used only when verifying an address,
19022 delivering in cutthrough mode or
19023 testing with the &%-bv%& option, not when actually doing a delivery, testing
19024 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
19025 restricted to verifying only senders or recipients by means of
19026 &%verify_sender%& and &%verify_recipient%&.
19028 &*Warning*&: When the router is being run to verify addresses for an incoming
19029 SMTP message, Exim is not running as root, but under its own uid. If the router
19030 accesses any files, you need to make sure that they are accessible to the Exim
19034 .option verify_recipient routers&!? boolean true
19035 If this option is false, the router is skipped when verifying recipient
19037 delivering in cutthrough mode
19038 or testing recipient verification using &%-bv%&.
19039 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19041 See also the &$verify_mode$& variable.
19044 .option verify_sender routers&!? boolean true
19045 If this option is false, the router is skipped when verifying sender addresses
19046 or testing sender verification using &%-bvs%&.
19047 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19049 See also the &$verify_mode$& variable.
19050 .ecindex IIDgenoprou1
19051 .ecindex IIDgenoprou2
19058 . ////////////////////////////////////////////////////////////////////////////
19059 . ////////////////////////////////////////////////////////////////////////////
19061 .chapter "The accept router" "CHID4"
19062 .cindex "&(accept)& router"
19063 .cindex "routers" "&(accept)&"
19064 The &(accept)& router has no private options of its own. Unless it is being
19065 used purely for verification (see &%verify_only%&) a transport is required to
19066 be defined by the generic &%transport%& option. If the preconditions that are
19067 specified by generic options are met, the router accepts the address and queues
19068 it for the given transport. The most common use of this router is for setting
19069 up deliveries to local mailboxes. For example:
19073 domains = mydomain.example
19075 transport = local_delivery
19077 The &%domains%& condition in this example checks the domain of the address, and
19078 &%check_local_user%& checks that the local part is the login of a local user.
19079 When both preconditions are met, the &(accept)& router runs, and queues the
19080 address for the &(local_delivery)& transport.
19087 . ////////////////////////////////////////////////////////////////////////////
19088 . ////////////////////////////////////////////////////////////////////////////
19090 .chapter "The dnslookup router" "CHAPdnslookup"
19091 .scindex IIDdnsrou1 "&(dnslookup)& router"
19092 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
19093 The &(dnslookup)& router looks up the hosts that handle mail for the
19094 recipient's domain in the DNS. A transport must always be set for this router,
19095 unless &%verify_only%& is set.
19097 If SRV support is configured (see &%check_srv%& below), Exim first searches for
19098 SRV records. If none are found, or if SRV support is not configured,
19099 MX records are looked up. If no MX records exist, address records are sought.
19100 However, &%mx_domains%& can be set to disable the direct use of address
19103 MX records of equal priority are sorted by Exim into a random order. Exim then
19104 looks for address records for the host names obtained from MX or SRV records.
19105 When a host has more than one IP address, they are sorted into a random order,
19106 except that IPv6 addresses are sorted before IPv4 addresses. If all the
19107 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
19108 generic option, the router declines.
19110 Unless they have the highest priority (lowest MX value), MX records that point
19111 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
19112 are discarded, together with any other MX records of equal or lower priority.
19114 .cindex "MX record" "pointing to local host"
19115 .cindex "local host" "MX pointing to"
19116 .oindex "&%self%&" "in &(dnslookup)& router"
19117 If the host pointed to by the highest priority MX record, or looked up as an
19118 address record, is the local host, or matches &%hosts_treat_as_local%&, what
19119 happens is controlled by the generic &%self%& option.
19122 .section "Problems with DNS lookups" "SECTprowitdnsloo"
19123 There have been problems with DNS servers when SRV records are looked up.
19124 Some misbehaving servers return a DNS error or timeout when a non-existent
19125 SRV record is sought. Similar problems have in the past been reported for
19126 MX records. The global &%dns_again_means_nonexist%& option can help with this
19127 problem, but it is heavy-handed because it is a global option.
19129 For this reason, there are two options, &%srv_fail_domains%& and
19130 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
19131 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
19132 an attempt to look up an SRV or MX record causes one of these results, and the
19133 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
19134 such record"&. In the case of an SRV lookup, this means that the router
19135 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
19136 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
19137 case routing fails.
19140 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
19141 .cindex "&(dnslookup)& router" "declines"
19142 There are a few cases where a &(dnslookup)& router will decline to accept
19143 an address; if such a router is expected to handle "all remaining non-local
19144 domains", then it is important to set &%no_more%&.
19146 The router will defer rather than decline if the domain
19147 is found in the &%fail_defer_domains%& router option.
19149 Reasons for a &(dnslookup)& router to decline currently include:
19151 The domain does not exist in DNS
19153 The domain exists but the MX record's host part is just "."; this is a common
19154 convention (borrowed from SRV) used to indicate that there is no such service
19155 for this domain and to not fall back to trying A/AAAA records.
19157 Ditto, but for SRV records, when &%check_srv%& is set on this router.
19159 MX record points to a non-existent host.
19161 MX record points to an IP address and the main section option
19162 &%allow_mx_to_ip%& is not set.
19164 MX records exist and point to valid hosts, but all hosts resolve only to
19165 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
19167 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
19168 &%dns_check_names_pattern%& for handling one variant of this)
19170 &%check_secondary_mx%& is set on this router but the local host can
19171 not be found in the MX records (see below)
19177 .section "Private options for dnslookup" "SECID118"
19178 .cindex "options" "&(dnslookup)& router"
19179 The private options for the &(dnslookup)& router are as follows:
19181 .option check_secondary_mx dnslookup boolean false
19182 .cindex "MX record" "checking for secondary"
19183 If this option is set, the router declines unless the local host is found in
19184 (and removed from) the list of hosts obtained by MX lookup. This can be used to
19185 process domains for which the local host is a secondary mail exchanger
19186 differently to other domains. The way in which Exim decides whether a host is
19187 the local host is described in section &<<SECTreclocipadd>>&.
19190 .option check_srv dnslookup string&!! unset
19191 .cindex "SRV record" "enabling use of"
19192 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
19193 addition to MX and address records. The support is disabled by default. To
19194 enable SRV support, set the &%check_srv%& option to the name of the service
19195 required. For example,
19199 looks for SRV records that refer to the normal smtp service. The option is
19200 expanded, so the service name can vary from message to message or address
19201 to address. This might be helpful if SRV records are being used for a
19202 submission service. If the expansion is forced to fail, the &%check_srv%&
19203 option is ignored, and the router proceeds to look for MX records in the
19206 When the expansion succeeds, the router searches first for SRV records for
19207 the given service (it assumes TCP protocol). A single SRV record with a
19208 host name that consists of just a single dot indicates &"no such service for
19209 this domain"&; if this is encountered, the router declines. If other kinds of
19210 SRV record are found, they are used to construct a host list for delivery
19211 according to the rules of RFC 2782. MX records are not sought in this case.
19213 When no SRV records are found, MX records (and address records) are sought in
19214 the traditional way. In other words, SRV records take precedence over MX
19215 records, just as MX records take precedence over address records. Note that
19216 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
19217 defined it. It is apparently believed that MX records are sufficient for email
19218 and that SRV records should not be used for this purpose. However, SRV records
19219 have an additional &"weight"& feature which some people might find useful when
19220 trying to split an SMTP load between hosts of different power.
19222 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
19223 when there is a DNS lookup error.
19228 .option fail_defer_domains dnslookup "domain list&!!" unset
19229 .cindex "MX record" "not found"
19230 DNS lookups for domains matching &%fail_defer_domains%&
19231 which find no matching record will cause the router to defer
19232 rather than the default behaviour of decline.
19233 This maybe be useful for queueing messages for a newly created
19234 domain while the DNS configuration is not ready.
19235 However, it will result in any message with mistyped domains
19239 .option ipv4_only "string&!!" unset
19240 .cindex IPv6 disabling
19241 .cindex DNS "IPv6 disabling"
19242 The string is expanded, and if the result is anything but a forced failure,
19243 or an empty string, or one of the strings “0” or “no” or “false”
19244 (checked without regard to the case of the letters),
19245 only A records are used.
19247 .option ipv4_prefer "string&!!" unset
19248 .cindex IPv4 preference
19249 .cindex DNS "IPv4 preference"
19250 The string is expanded, and if the result is anything but a forced failure,
19251 or an empty string, or one of the strings “0” or “no” or “false”
19252 (checked without regard to the case of the letters),
19253 A records are sorted before AAAA records (inverting the default).
19255 .option mx_domains dnslookup "domain list&!!" unset
19256 .cindex "MX record" "required to exist"
19257 .cindex "SRV record" "required to exist"
19258 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
19259 record in order to be recognized. (The name of this option could be improved.)
19260 For example, if all the mail hosts in &'fict.example'& are known to have MX
19261 records, except for those in &'discworld.fict.example'&, you could use this
19264 mx_domains = ! *.discworld.fict.example : *.fict.example
19266 This specifies that messages addressed to a domain that matches the list but
19267 has no MX record should be bounced immediately instead of being routed using
19268 the address record.
19271 .option mx_fail_domains dnslookup "domain list&!!" unset
19272 If the DNS lookup for MX records for one of the domains in this list causes a
19273 DNS lookup error, Exim behaves as if no MX records were found. See section
19274 &<<SECTprowitdnsloo>>& for more discussion.
19279 .option qualify_single dnslookup boolean true
19280 .cindex "DNS" "resolver options"
19281 .cindex "DNS" "qualifying single-component names"
19282 When this option is true, the resolver option RES_DEFNAMES is set for DNS
19283 lookups. Typically, but not standardly, this causes the resolver to qualify
19284 single-component names with the default domain. For example, on a machine
19285 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
19286 &'thesaurus.ref.example'& inside the resolver. For details of what your
19287 resolver actually does, consult your man pages for &'resolver'& and
19292 .option rewrite_headers dnslookup boolean true
19293 .cindex "rewriting" "header lines"
19294 .cindex "header lines" "rewriting"
19295 If the domain name in the address that is being processed is not fully
19296 qualified, it may be expanded to its full form by a DNS lookup. For example, if
19297 an address is specified as &'dormouse@teaparty'&, the domain might be
19298 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
19299 occur as a result of setting the &%widen_domains%& option. If
19300 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
19301 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
19302 header lines of the message are rewritten with the full domain name.
19304 This option should be turned off only when it is known that no message is
19305 ever going to be sent outside an environment where the abbreviation makes
19308 When an MX record is looked up in the DNS and matches a wildcard record, name
19309 servers normally return a record containing the name that has been looked up,
19310 making it impossible to detect whether a wildcard was present or not. However,
19311 some name servers have recently been seen to return the wildcard entry. If the
19312 name returned by a DNS lookup begins with an asterisk, it is not used for
19316 .option same_domain_copy_routing dnslookup boolean false
19317 .cindex "address" "copying routing"
19318 Addresses with the same domain are normally routed by the &(dnslookup)& router
19319 to the same list of hosts. However, this cannot be presumed, because the router
19320 options and preconditions may refer to the local part of the address. By
19321 default, therefore, Exim routes each address in a message independently. DNS
19322 servers run caches, so repeated DNS lookups are not normally expensive, and in
19323 any case, personal messages rarely have more than a few recipients.
19325 If you are running mailing lists with large numbers of subscribers at the same
19326 domain, and you are using a &(dnslookup)& router which is independent of the
19327 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
19328 lookups for identical domains in one message. In this case, when &(dnslookup)&
19329 routes an address to a remote transport, any other unrouted addresses in the
19330 message that have the same domain are automatically given the same routing
19331 without processing them independently,
19332 provided the following conditions are met:
19335 No router that processed the address specified &%headers_add%& or
19336 &%headers_remove%&.
19338 The router did not change the address in any way, for example, by &"widening"&
19345 .option search_parents dnslookup boolean false
19346 .cindex "DNS" "resolver options"
19347 When this option is true, the resolver option RES_DNSRCH is set for DNS
19348 lookups. This is different from the &%qualify_single%& option in that it
19349 applies to domains containing dots. Typically, but not standardly, it causes
19350 the resolver to search for the name in the current domain and in parent
19351 domains. For example, on a machine in the &'fict.example'& domain, if looking
19352 up &'teaparty.wonderland'& failed, the resolver would try
19353 &'teaparty.wonderland.fict.example'&. For details of what your resolver
19354 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
19356 Setting this option true can cause problems in domains that have a wildcard MX
19357 record, because any domain that does not have its own MX record matches the
19362 .option srv_fail_domains dnslookup "domain list&!!" unset
19363 If the DNS lookup for SRV records for one of the domains in this list causes a
19364 DNS lookup error, Exim behaves as if no SRV records were found. See section
19365 &<<SECTprowitdnsloo>>& for more discussion.
19370 .option widen_domains dnslookup "string list" unset
19371 .cindex "domain" "partial; widening"
19372 If a DNS lookup fails and this option is set, each of its strings in turn is
19373 added onto the end of the domain, and the lookup is tried again. For example,
19376 widen_domains = fict.example:ref.example
19378 is set and a lookup of &'klingon.dictionary'& fails,
19379 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
19380 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
19381 and &%search_parents%& options can cause some widening to be undertaken inside
19382 the DNS resolver. &%widen_domains%& is not applied to sender addresses
19383 when verifying, unless &%rewrite_headers%& is false (not the default).
19386 .section "Effect of qualify_single and search_parents" "SECID119"
19387 When a domain from an envelope recipient is changed by the resolver as a result
19388 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
19389 corresponding address in the message's header lines unless &%rewrite_headers%&
19390 is set false. Exim then re-routes the address, using the full domain.
19392 These two options affect only the DNS lookup that takes place inside the router
19393 for the domain of the address that is being routed. They do not affect lookups
19394 such as that implied by
19398 that may happen while processing a router precondition before the router is
19399 entered. No widening ever takes place for these lookups.
19400 .ecindex IIDdnsrou1
19401 .ecindex IIDdnsrou2
19411 . ////////////////////////////////////////////////////////////////////////////
19412 . ////////////////////////////////////////////////////////////////////////////
19414 .chapter "The ipliteral router" "CHID5"
19415 .cindex "&(ipliteral)& router"
19416 .cindex "domain literal" "routing"
19417 .cindex "routers" "&(ipliteral)&"
19418 This router has no private options. Unless it is being used purely for
19419 verification (see &%verify_only%&) a transport is required to be defined by the
19420 generic &%transport%& option. The router accepts the address if its domain part
19421 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
19422 router handles the address
19426 by setting up delivery to the host with that IP address. IPv4 domain literals
19427 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
19428 are similar, but the address is preceded by &`ipv6:`&. For example:
19430 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
19432 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
19433 grounds that sooner or later somebody will try it.
19435 .oindex "&%self%&" "in &(ipliteral)& router"
19436 If the IP address matches something in &%ignore_target_hosts%&, the router
19437 declines. If an IP literal turns out to refer to the local host, the generic
19438 &%self%& option determines what happens.
19440 The RFCs require support for domain literals; however, their use is
19441 controversial in today's Internet. If you want to use this router, you must
19442 also set the main configuration option &%allow_domain_literals%&. Otherwise,
19443 Exim will not recognize the domain literal syntax in addresses.
19447 . ////////////////////////////////////////////////////////////////////////////
19448 . ////////////////////////////////////////////////////////////////////////////
19450 .chapter "The iplookup router" "CHID6"
19451 .cindex "&(iplookup)& router"
19452 .cindex "routers" "&(iplookup)&"
19453 The &(iplookup)& router was written to fulfil a specific requirement in
19454 Cambridge University (which in fact no longer exists). For this reason, it is
19455 not included in the binary of Exim by default. If you want to include it, you
19458 ROUTER_IPLOOKUP=yes
19460 in your &_Local/Makefile_& configuration file.
19462 The &(iplookup)& router routes an address by sending it over a TCP or UDP
19463 connection to one or more specific hosts. The host can then return the same or
19464 a different address &-- in effect rewriting the recipient address in the
19465 message's envelope. The new address is then passed on to subsequent routers. If
19466 this process fails, the address can be passed on to other routers, or delivery
19467 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
19468 must not be specified for it.
19470 .cindex "options" "&(iplookup)& router"
19471 .option hosts iplookup string unset
19472 This option must be supplied. Its value is a colon-separated list of host
19473 names. The hosts are looked up using &[gethostbyname()]&
19474 (or &[getipnodebyname()]& when available)
19475 and are tried in order until one responds to the query. If none respond, what
19476 happens is controlled by &%optional%&.
19479 .option optional iplookup boolean false
19480 If &%optional%& is true, if no response is obtained from any host, the address
19481 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
19482 delivery to the address is deferred.
19485 .option port iplookup integer 0
19486 .cindex "port" "&(iplookup)& router"
19487 This option must be supplied. It specifies the port number for the TCP or UDP
19491 .option protocol iplookup string udp
19492 This option can be set to &"udp"& or &"tcp"& to specify which of the two
19493 protocols is to be used.
19496 .option query iplookup string&!! "see below"
19497 This defines the content of the query that is sent to the remote hosts. The
19500 $local_part@$domain $local_part@$domain
19502 The repetition serves as a way of checking that a response is to the correct
19503 query in the default case (see &%response_pattern%& below).
19506 .option reroute iplookup string&!! unset
19507 If this option is not set, the rerouted address is precisely the byte string
19508 returned by the remote host, up to the first white space, if any. If set, the
19509 string is expanded to form the rerouted address. It can include parts matched
19510 in the response by &%response_pattern%& by means of numeric variables such as
19511 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
19512 whether or not a pattern is in use. In all cases, the rerouted address must end
19513 up in the form &'local_part@domain'&.
19516 .option response_pattern iplookup string unset
19517 This option can be set to a regular expression that is applied to the string
19518 returned from the remote host. If the pattern does not match the response, the
19519 router declines. If &%response_pattern%& is not set, no checking of the
19520 response is done, unless the query was defaulted, in which case there is a
19521 check that the text returned after the first white space is the original
19522 address. This checks that the answer that has been received is in response to
19523 the correct question. For example, if the response is just a new domain, the
19524 following could be used:
19526 response_pattern = ^([^@]+)$
19527 reroute = $local_part@$1
19530 .option timeout iplookup time 5s
19531 This specifies the amount of time to wait for a response from the remote
19532 machine. The same timeout is used for the &[connect()]& function for a TCP
19533 call. It does not apply to UDP.
19538 . ////////////////////////////////////////////////////////////////////////////
19539 . ////////////////////////////////////////////////////////////////////////////
19541 .chapter "The manualroute router" "CHID7"
19542 .scindex IIDmanrou1 "&(manualroute)& router"
19543 .scindex IIDmanrou2 "routers" "&(manualroute)&"
19544 .cindex "domain" "manually routing"
19545 The &(manualroute)& router is so-called because it provides a way of manually
19546 routing an address according to its domain. It is mainly used when you want to
19547 route addresses to remote hosts according to your own rules, bypassing the
19548 normal DNS routing that looks up MX records. However, &(manualroute)& can also
19549 route to local transports, a facility that may be useful if you want to save
19550 messages for dial-in hosts in local files.
19552 The &(manualroute)& router compares a list of domain patterns with the domain
19553 it is trying to route. If there is no match, the router declines. Each pattern
19554 has associated with it a list of hosts and some other optional data, which may
19555 include a transport. The combination of a pattern and its data is called a
19556 &"routing rule"&. For patterns that do not have an associated transport, the
19557 generic &%transport%& option must specify a transport, unless the router is
19558 being used purely for verification (see &%verify_only%&).
19561 In the case of verification, matching the domain pattern is sufficient for the
19562 router to accept the address. When actually routing an address for delivery,
19563 an address that matches a domain pattern is queued for the associated
19564 transport. If the transport is not a local one, a host list must be associated
19565 with the pattern; IP addresses are looked up for the hosts, and these are
19566 passed to the transport along with the mail address. For local transports, a
19567 host list is optional. If it is present, it is passed in &$host$& as a single
19570 The list of routing rules can be provided as an inline string in
19571 &%route_list%&, or the data can be obtained by looking up the domain in a file
19572 or database by setting &%route_data%&. Only one of these settings may appear in
19573 any one instance of &(manualroute)&. The format of routing rules is described
19574 below, following the list of private options.
19577 .section "Private options for manualroute" "SECTprioptman"
19579 .cindex "options" "&(manualroute)& router"
19580 The private options for the &(manualroute)& router are as follows:
19582 .option host_all_ignored manualroute string defer
19583 See &%host_find_failed%&.
19585 .option host_find_failed manualroute string freeze
19586 This option controls what happens when &(manualroute)& tries to find an IP
19587 address for a host, and the host does not exist. The option can be set to one
19588 of the following values:
19597 The default (&"freeze"&) assumes that this state is a serious configuration
19598 error. The difference between &"pass"& and &"decline"& is that the former
19599 forces the address to be passed to the next router (or the router defined by
19602 overriding &%no_more%&, whereas the latter passes the address to the next
19603 router only if &%more%& is true.
19605 The value &"ignore"& causes Exim to completely ignore a host whose IP address
19606 cannot be found. If all the hosts in the list are ignored, the behaviour is
19607 controlled by the &%host_all_ignored%& option. This takes the same values
19608 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
19610 The &%host_find_failed%& option applies only to a definite &"does not exist"&
19611 state; if a host lookup gets a temporary error, delivery is deferred unless the
19612 generic &%pass_on_timeout%& option is set.
19615 .option hosts_randomize manualroute boolean false
19616 .cindex "randomized host list"
19617 .cindex "host" "list of; randomized"
19618 If this option is set, the order of the items in a host list in a routing rule
19619 is randomized each time the list is used, unless an option in the routing rule
19620 overrides (see below). Randomizing the order of a host list can be used to do
19621 crude load sharing. However, if more than one mail address is routed by the
19622 same router to the same host list, the host lists are considered to be the same
19623 (even though they may be randomized into different orders) for the purpose of
19624 deciding whether to batch the deliveries into a single SMTP transaction.
19626 When &%hosts_randomize%& is true, a host list may be split
19627 into groups whose order is separately randomized. This makes it possible to
19628 set up MX-like behaviour. The boundaries between groups are indicated by an
19629 item that is just &`+`& in the host list. For example:
19631 route_list = * host1:host2:host3:+:host4:host5
19633 The order of the first three hosts and the order of the last two hosts is
19634 randomized for each use, but the first three always end up before the last two.
19635 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
19636 randomized host list is passed to an &(smtp)& transport that also has
19637 &%hosts_randomize set%&, the list is not re-randomized.
19640 .option route_data manualroute string&!! unset
19641 If this option is set, it must expand to yield the data part of a routing rule.
19642 Typically, the expansion string includes a lookup based on the domain. For
19645 route_data = ${lookup{$domain}dbm{/etc/routes}}
19647 If the expansion is forced to fail, or the result is an empty string, the
19648 router declines. Other kinds of expansion failure cause delivery to be
19652 .option route_list manualroute "string list" unset
19653 This string is a list of routing rules, in the form defined below. Note that,
19654 unlike most string lists, the items are separated by semicolons. This is so
19655 that they may contain colon-separated host lists.
19658 .option same_domain_copy_routing manualroute boolean false
19659 .cindex "address" "copying routing"
19660 Addresses with the same domain are normally routed by the &(manualroute)&
19661 router to the same list of hosts. However, this cannot be presumed, because the
19662 router options and preconditions may refer to the local part of the address. By
19663 default, therefore, Exim routes each address in a message independently. DNS
19664 servers run caches, so repeated DNS lookups are not normally expensive, and in
19665 any case, personal messages rarely have more than a few recipients.
19667 If you are running mailing lists with large numbers of subscribers at the same
19668 domain, and you are using a &(manualroute)& router which is independent of the
19669 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
19670 lookups for identical domains in one message. In this case, when
19671 &(manualroute)& routes an address to a remote transport, any other unrouted
19672 addresses in the message that have the same domain are automatically given the
19673 same routing without processing them independently. However, this is only done
19674 if &%headers_add%& and &%headers_remove%& are unset.
19679 .section "Routing rules in route_list" "SECID120"
19680 The value of &%route_list%& is a string consisting of a sequence of routing
19681 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
19682 entered as two semicolons. Alternatively, the list separator can be changed as
19683 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
19684 Empty rules are ignored. The format of each rule is
19686 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
19688 The following example contains two rules, each with a simple domain pattern and
19692 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
19693 thes.ref.example mail-3.ref.example:mail-4.ref.example
19695 The three parts of a rule are separated by white space. The pattern and the
19696 list of hosts can be enclosed in quotes if necessary, and if they are, the
19697 usual quoting rules apply. Each rule in a &%route_list%& must start with a
19698 single domain pattern, which is the only mandatory item in the rule. The
19699 pattern is in the same format as one item in a domain list (see section
19700 &<<SECTdomainlist>>&),
19701 except that it may not be the name of an interpolated file.
19702 That is, it may be wildcarded, or a regular expression, or a file or database
19703 lookup (with semicolons doubled, because of the use of semicolon as a separator
19704 in a &%route_list%&).
19706 The rules in &%route_list%& are searched in order until one of the patterns
19707 matches the domain that is being routed. The list of hosts and then options are
19708 then used as described below. If there is no match, the router declines. When
19709 &%route_list%& is set, &%route_data%& must not be set.
19713 .section "Routing rules in route_data" "SECID121"
19714 The use of &%route_list%& is convenient when there are only a small number of
19715 routing rules. For larger numbers, it is easier to use a file or database to
19716 hold the routing information, and use the &%route_data%& option instead.
19717 The value of &%route_data%& is a list of hosts, followed by (optional) options.
19718 Most commonly, &%route_data%& is set as a string that contains an
19719 expansion lookup. For example, suppose we place two routing rules in a file
19722 dict.ref.example: mail-1.ref.example:mail-2.ref.example
19723 thes.ref.example: mail-3.ref.example:mail-4.ref.example
19725 This data can be accessed by setting
19727 route_data = ${lookup{$domain}lsearch{/the/file/name}}
19729 Failure of the lookup results in an empty string, causing the router to
19730 decline. However, you do not have to use a lookup in &%route_data%&. The only
19731 requirement is that the result of expanding the string is a list of hosts,
19732 possibly followed by options, separated by white space. The list of hosts must
19733 be enclosed in quotes if it contains white space.
19738 .section "Format of the list of hosts" "SECID122"
19739 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
19740 always separately expanded before use. If the expansion fails, the router
19741 declines. The result of the expansion must be a colon-separated list of names
19742 and/or IP addresses, optionally also including ports.
19743 If the list is written with spaces, it must be protected with quotes.
19744 The format of each item
19745 in the list is described in the next section. The list separator can be changed
19746 as described in section &<<SECTlistsepchange>>&.
19748 If the list of hosts was obtained from a &%route_list%& item, the following
19749 variables are set during its expansion:
19752 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
19753 If the domain was matched against a regular expression, the numeric variables
19754 &$1$&, &$2$&, etc. may be set. For example:
19756 route_list = ^domain(\d+) host-$1.text.example
19759 &$0$& is always set to the entire domain.
19761 &$1$& is also set when partial matching is done in a file lookup.
19764 .vindex "&$value$&"
19765 If the pattern that matched the domain was a lookup item, the data that was
19766 looked up is available in the expansion variable &$value$&. For example:
19768 route_list = lsearch;;/some/file.routes $value
19772 Note the doubling of the semicolon in the pattern that is necessary because
19773 semicolon is the default route list separator.
19777 .section "Format of one host item" "SECTformatonehostitem"
19778 Each item in the list of hosts is either a host name or an IP address,
19779 optionally with an attached port number. When no port is given, an IP address
19780 is not enclosed in brackets. When a port is specified, it overrides the port
19781 specification on the transport. The port is separated from the name or address
19782 by a colon. This leads to some complications:
19785 Because colon is the default separator for the list of hosts, either
19786 the colon that specifies a port must be doubled, or the list separator must
19787 be changed. The following two examples have the same effect:
19789 route_list = * "host1.tld::1225 : host2.tld::1226"
19790 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
19793 When IPv6 addresses are involved, it gets worse, because they contain
19794 colons of their own. To make this case easier, it is permitted to
19795 enclose an IP address (either v4 or v6) in square brackets if a port
19796 number follows. For example:
19798 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
19802 .section "How the list of hosts is used" "SECThostshowused"
19803 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
19804 the hosts is tried, in the order specified, when carrying out the SMTP
19805 delivery. However, the order can be changed by setting the &%hosts_randomize%&
19806 option, either on the router (see section &<<SECTprioptman>>& above), or on the
19809 Hosts may be listed by name or by IP address. An unadorned name in the list of
19810 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
19811 interpreted as an indirection to a sublist of hosts obtained by looking up MX
19812 records in the DNS. For example:
19814 route_list = * x.y.z:p.q.r/MX:e.f.g
19816 If this feature is used with a port specifier, the port must come last. For
19819 route_list = * dom1.tld/mx::1225
19821 If the &%hosts_randomize%& option is set, the order of the items in the list is
19822 randomized before any lookups are done. Exim then scans the list; for any name
19823 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
19824 be an interface on the local host and the item is not the first in the list,
19825 Exim discards it and any subsequent items. If it is the first item, what
19826 happens is controlled by the
19827 .oindex "&%self%&" "in &(manualroute)& router"
19828 &%self%& option of the router.
19830 A name on the list that is followed by &`/MX`& is replaced with the list of
19831 hosts obtained by looking up MX records for the name. This is always a DNS
19832 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
19833 below) are not relevant here. The order of these hosts is determined by the
19834 preference values in the MX records, according to the usual rules. Because
19835 randomizing happens before the MX lookup, it does not affect the order that is
19836 defined by MX preferences.
19838 If the local host is present in the sublist obtained from MX records, but is
19839 not the most preferred host in that list, it and any equally or less
19840 preferred hosts are removed before the sublist is inserted into the main list.
19842 If the local host is the most preferred host in the MX list, what happens
19843 depends on where in the original list of hosts the &`/MX`& item appears. If it
19844 is not the first item (that is, there are previous hosts in the main list),
19845 Exim discards this name and any subsequent items in the main list.
19847 If the MX item is first in the list of hosts, and the local host is the
19848 most preferred host, what happens is controlled by the &%self%& option of the
19851 DNS failures when lookup up the MX records are treated in the same way as DNS
19852 failures when looking up IP addresses: &%pass_on_timeout%& and
19853 &%host_find_failed%& are used when relevant.
19855 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
19856 whether obtained from an MX lookup or not.
19860 .section "How the options are used" "SECThowoptused"
19861 The options are a sequence of words, space-separated.
19862 One of the words can be the name of a transport; this overrides the
19863 &%transport%& option on the router for this particular routing rule only. The
19864 other words (if present) control randomization of the list of hosts on a
19865 per-rule basis, and how the IP addresses of the hosts are to be found when
19866 routing to a remote transport. These options are as follows:
19869 &%randomize%&: randomize the order of the hosts in this list, overriding the
19870 setting of &%hosts_randomize%& for this routing rule only.
19872 &%no_randomize%&: do not randomize the order of the hosts in this list,
19873 overriding the setting of &%hosts_randomize%& for this routing rule only.
19875 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
19876 find IP addresses. This function may ultimately cause a DNS lookup, but it may
19877 also look in &_/etc/hosts_& or other sources of information.
19879 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
19880 no address records are found. If there is a temporary DNS error (such as a
19881 timeout), delivery is deferred.
19883 &%ipv4_only%&: in direct DNS lookups, look up only A records.
19885 &%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
19890 route_list = domain1 host1:host2:host3 randomize bydns;\
19891 domain2 host4:host5
19893 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
19894 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
19895 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
19896 or &[gethostbyname()]&, and the result of the lookup is the result of that
19899 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
19900 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
19901 instead of TRY_AGAIN. That is why the default action is to try a DNS
19902 lookup first. Only if that gives a definite &"no such host"& is the local
19905 &*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
19906 inadvertent constraint that a transport name as an option had to be the last
19911 If no IP address for a host can be found, what happens is controlled by the
19912 &%host_find_failed%& option.
19915 When an address is routed to a local transport, IP addresses are not looked up.
19916 The host list is passed to the transport in the &$host$& variable.
19920 .section "Manualroute examples" "SECID123"
19921 In some of the examples that follow, the presence of the &%remote_smtp%&
19922 transport, as defined in the default configuration file, is assumed:
19925 .cindex "smart host" "example router"
19926 The &(manualroute)& router can be used to forward all external mail to a
19927 &'smart host'&. If you have set up, in the main part of the configuration, a
19928 named domain list that contains your local domains, for example:
19930 domainlist local_domains = my.domain.example
19932 You can arrange for all other domains to be routed to a smart host by making
19933 your first router something like this:
19936 driver = manualroute
19937 domains = !+local_domains
19938 transport = remote_smtp
19939 route_list = * smarthost.ref.example
19941 This causes all non-local addresses to be sent to the single host
19942 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
19943 they are tried in order
19944 (but you can use &%hosts_randomize%& to vary the order each time).
19945 Another way of configuring the same thing is this:
19948 driver = manualroute
19949 transport = remote_smtp
19950 route_list = !+local_domains smarthost.ref.example
19952 There is no difference in behaviour between these two routers as they stand.
19953 However, they behave differently if &%no_more%& is added to them. In the first
19954 example, the router is skipped if the domain does not match the &%domains%&
19955 precondition; the following router is always tried. If the router runs, it
19956 always matches the domain and so can never decline. Therefore, &%no_more%&
19957 would have no effect. In the second case, the router is never skipped; it
19958 always runs. However, if it doesn't match the domain, it declines. In this case
19959 &%no_more%& would prevent subsequent routers from running.
19962 .cindex "mail hub example"
19963 A &'mail hub'& is a host which receives mail for a number of domains via MX
19964 records in the DNS and delivers it via its own private routing mechanism. Often
19965 the final destinations are behind a firewall, with the mail hub being the one
19966 machine that can connect to machines both inside and outside the firewall. The
19967 &(manualroute)& router is usually used on a mail hub to route incoming messages
19968 to the correct hosts. For a small number of domains, the routing can be inline,
19969 using the &%route_list%& option, but for a larger number a file or database
19970 lookup is easier to manage.
19972 If the domain names are in fact the names of the machines to which the mail is
19973 to be sent by the mail hub, the configuration can be quite simple. For
19977 driver = manualroute
19978 transport = remote_smtp
19979 route_list = *.rhodes.tvs.example $domain
19981 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
19982 whose names are the same as the mail domains. A similar approach can be taken
19983 if the host name can be obtained from the domain name by a string manipulation
19984 that the expansion facilities can handle. Otherwise, a lookup based on the
19985 domain can be used to find the host:
19988 driver = manualroute
19989 transport = remote_smtp
19990 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
19992 The result of the lookup must be the name or IP address of the host (or
19993 hosts) to which the address is to be routed. If the lookup fails, the route
19994 data is empty, causing the router to decline. The address then passes to the
19998 .cindex "batched SMTP output example"
19999 .cindex "SMTP" "batched outgoing; example"
20000 You can use &(manualroute)& to deliver messages to pipes or files in batched
20001 SMTP format for onward transportation by some other means. This is one way of
20002 storing mail for a dial-up host when it is not connected. The route list entry
20003 can be as simple as a single domain name in a configuration like this:
20006 driver = manualroute
20007 transport = batchsmtp_appendfile
20008 route_list = saved.domain.example
20010 though often a pattern is used to pick up more than one domain. If there are
20011 several domains or groups of domains with different transport requirements,
20012 different transports can be listed in the routing information:
20015 driver = manualroute
20017 *.saved.domain1.example $domain batch_appendfile; \
20018 *.saved.domain2.example \
20019 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
20022 .vindex "&$domain$&"
20024 The first of these just passes the domain in the &$host$& variable, which
20025 doesn't achieve much (since it is also in &$domain$&), but the second does a
20026 file lookup to find a value to pass, causing the router to decline to handle
20027 the address if the lookup fails.
20030 .cindex "UUCP" "example of router for"
20031 Routing mail directly to UUCP software is a specific case of the use of
20032 &(manualroute)& in a gateway to another mail environment. This is an example of
20033 one way it can be done:
20039 command = /usr/local/bin/uux -r - \
20040 ${substr_-5:$host}!rmail ${local_part}
20041 return_fail_output = true
20046 driver = manualroute
20048 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
20050 The file &_/usr/local/exim/uucphosts_& contains entries like
20052 darksite.ethereal.example: darksite.UUCP
20054 It can be set up more simply without adding and removing &".UUCP"& but this way
20055 makes clear the distinction between the domain name
20056 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
20058 .ecindex IIDmanrou1
20059 .ecindex IIDmanrou2
20068 . ////////////////////////////////////////////////////////////////////////////
20069 . ////////////////////////////////////////////////////////////////////////////
20071 .chapter "The queryprogram router" "CHAPdriverlast"
20072 .scindex IIDquerou1 "&(queryprogram)& router"
20073 .scindex IIDquerou2 "routers" "&(queryprogram)&"
20074 .cindex "routing" "by external program"
20075 The &(queryprogram)& router routes an address by running an external command
20076 and acting on its output. This is an expensive way to route, and is intended
20077 mainly for use in lightly-loaded systems, or for performing experiments.
20078 However, if it is possible to use the precondition options (&%domains%&,
20079 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
20080 be used in special cases, even on a busy host. There are the following private
20082 .cindex "options" "&(queryprogram)& router"
20084 .option command queryprogram string&!! unset
20085 This option must be set. It specifies the command that is to be run. The
20086 command is split up into a command name and arguments, and then each is
20087 expanded separately (exactly as for a &(pipe)& transport, described in chapter
20088 &<<CHAPpipetransport>>&).
20091 .option command_group queryprogram string unset
20092 .cindex "gid (group id)" "in &(queryprogram)& router"
20093 This option specifies a gid to be set when running the command while routing an
20094 address for deliver. It must be set if &%command_user%& specifies a numerical
20095 uid. If it begins with a digit, it is interpreted as the numerical value of the
20096 gid. Otherwise it is looked up using &[getgrnam()]&.
20099 .option command_user queryprogram string unset
20100 .cindex "uid (user id)" "for &(queryprogram)&"
20101 This option must be set. It specifies the uid which is set when running the
20102 command while routing an address for delivery. If the value begins with a digit,
20103 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
20104 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
20105 not set, a value for the gid also.
20107 &*Warning:*& Changing uid and gid is possible only when Exim is running as
20108 root, which it does during a normal delivery in a conventional configuration.
20109 However, when an address is being verified during message reception, Exim is
20110 usually running as the Exim user, not as root. If the &(queryprogram)& router
20111 is called from a non-root process, Exim cannot change uid or gid before running
20112 the command. In this circumstance the command runs under the current uid and
20116 .option current_directory queryprogram string /
20117 This option specifies an absolute path which is made the current directory
20118 before running the command.
20121 .option timeout queryprogram time 1h
20122 If the command does not complete within the timeout period, its process group
20123 is killed and the message is frozen. A value of zero time specifies no
20127 The standard output of the command is connected to a pipe, which is read when
20128 the command terminates. It should consist of a single line of output,
20129 containing up to five fields, separated by white space. The maximum length of
20130 the line is 1023 characters. Longer lines are silently truncated. The first
20131 field is one of the following words (case-insensitive):
20134 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
20137 &'Decline'&: the router declines; pass the address to the next router, unless
20138 &%no_more%& is set.
20140 &'Fail'&: routing failed; do not pass the address to any more routers. Any
20141 subsequent text on the line is an error message. If the router is run as part
20142 of address verification during an incoming SMTP message, the message is
20143 included in the SMTP response.
20145 &'Defer'&: routing could not be completed at this time; try again later. Any
20146 subsequent text on the line is an error message which is logged. It is not
20147 included in any SMTP response.
20149 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
20151 &'Pass'&: pass the address to the next router (or the router specified by
20152 &%pass_router%&), overriding &%no_more%&.
20154 &'Redirect'&: the message is redirected. The remainder of the line is a list of
20155 new addresses, which are routed independently, starting with the first router,
20156 or the router specified by &%redirect_router%&, if set.
20159 When the first word is &'accept'&, the remainder of the line consists of a
20160 number of keyed data values, as follows (split into two lines here, to fit on
20163 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
20164 LOOKUP=byname|bydns DATA=<text>
20166 The data items can be given in any order, and all are optional. If no transport
20167 is included, the transport specified by the generic &%transport%& option is
20168 used. The list of hosts and the lookup type are needed only if the transport is
20169 an &(smtp)& transport that does not itself supply a list of hosts.
20171 The format of the list of hosts is the same as for the &(manualroute)& router.
20172 As well as host names and IP addresses with optional port numbers, as described
20173 in section &<<SECTformatonehostitem>>&, it may contain names followed by
20174 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
20175 (see section &<<SECThostshowused>>&).
20177 If the lookup type is not specified, Exim behaves as follows when trying to
20178 find an IP address for each host: First, a DNS lookup is done. If this yields
20179 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
20180 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
20181 result of the lookup is the result of that call.
20183 .vindex "&$address_data$&"
20184 If the DATA field is set, its value is placed in the &$address_data$&
20185 variable. For example, this return line
20187 accept hosts=x1.y.example:x2.y.example data="rule1"
20189 routes the address to the default transport, passing a list of two hosts. When
20190 the transport runs, the string &"rule1"& is in &$address_data$&.
20191 .ecindex IIDquerou1
20192 .ecindex IIDquerou2
20197 . ////////////////////////////////////////////////////////////////////////////
20198 . ////////////////////////////////////////////////////////////////////////////
20200 .chapter "The redirect router" "CHAPredirect"
20201 .scindex IIDredrou1 "&(redirect)& router"
20202 .scindex IIDredrou2 "routers" "&(redirect)&"
20203 .cindex "alias file" "in a &(redirect)& router"
20204 .cindex "address redirection" "&(redirect)& router"
20205 The &(redirect)& router handles several kinds of address redirection. Its most
20206 common uses are for resolving local part aliases from a central alias file
20207 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
20208 files, but it has many other potential uses. The incoming address can be
20209 redirected in several different ways:
20212 It can be replaced by one or more new addresses which are themselves routed
20215 It can be routed to be delivered to a given file or directory.
20217 It can be routed to be delivered to a specified pipe command.
20219 It can cause an automatic reply to be generated.
20221 It can be forced to fail, optionally with a custom error message.
20223 It can be temporarily deferred, optionally with a custom message.
20225 It can be discarded.
20228 The generic &%transport%& option must not be set for &(redirect)& routers.
20229 However, there are some private options which define transports for delivery to
20230 files and pipes, and for generating autoreplies. See the &%file_transport%&,
20231 &%pipe_transport%& and &%reply_transport%& descriptions below.
20233 If success DSNs have been requested
20234 .cindex "DSN" "success"
20235 .cindex "Delivery Status Notification" "success"
20236 redirection triggers one and the DSN options are not passed any further.
20240 .section "Redirection data" "SECID124"
20241 The router operates by interpreting a text string which it obtains either by
20242 expanding the contents of the &%data%& option, or by reading the entire
20243 contents of a file whose name is given in the &%file%& option. These two
20244 options are mutually exclusive. The first is commonly used for handling system
20245 aliases, in a configuration like this:
20249 data = ${lookup{$local_part}lsearch{/etc/aliases}}
20251 If the lookup fails, the expanded string in this example is empty. When the
20252 expansion of &%data%& results in an empty string, the router declines. A forced
20253 expansion failure also causes the router to decline; other expansion failures
20254 cause delivery to be deferred.
20256 A configuration using &%file%& is commonly used for handling users'
20257 &_.forward_& files, like this:
20262 file = $home/.forward
20265 If the file does not exist, or causes no action to be taken (for example, it is
20266 empty or consists only of comments), the router declines. &*Warning*&: This
20267 is not the case when the file contains syntactically valid items that happen to
20268 yield empty addresses, for example, items containing only RFC 2822 address
20273 .section "Forward files and address verification" "SECID125"
20274 .cindex "address redirection" "while verifying"
20275 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
20276 &_.forward_& files, as in the example above. There are two reasons for this:
20279 When Exim is receiving an incoming SMTP message from a remote host, it is
20280 running under the Exim uid, not as root. Exim is unable to change uid to read
20281 the file as the user, and it may not be able to read it as the Exim user. So in
20282 practice the router may not be able to operate.
20284 However, even when the router can operate, the existence of a &_.forward_& file
20285 is unimportant when verifying an address. What should be checked is whether the
20286 local part is a valid user name or not. Cutting out the redirection processing
20287 saves some resources.
20295 .section "Interpreting redirection data" "SECID126"
20296 .cindex "Sieve filter" "specifying in redirection data"
20297 .cindex "filter" "specifying in redirection data"
20298 The contents of the data string, whether obtained from &%data%& or &%file%&,
20299 can be interpreted in two different ways:
20302 If the &%allow_filter%& option is set true, and the data begins with the text
20303 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
20304 &'filtering'& instructions in the form of an Exim or Sieve filter file,
20305 respectively. Details of the syntax and semantics of filter files are described
20306 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
20307 document is intended for use by end users.
20309 Otherwise, the data must be a comma-separated list of redirection items, as
20310 described in the next section.
20313 When a message is redirected to a file (a &"mail folder"&), the filename given
20314 in a non-filter redirection list must always be an absolute path. A filter may
20315 generate a relative path &-- how this is handled depends on the transport's
20316 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
20317 for the &(appendfile)& transport.
20321 .section "Items in a non-filter redirection list" "SECTitenonfilred"
20322 .cindex "address redirection" "non-filter list items"
20323 When the redirection data is not an Exim or Sieve filter, for example, if it
20324 comes from a conventional alias or forward file, it consists of a list of
20325 addresses, filenames, pipe commands, or certain special items (see section
20326 &<<SECTspecitredli>>& below). The special items can be individually enabled or
20327 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
20328 depending on their default values. The items in the list are separated by
20329 commas or newlines.
20330 If a comma is required in an item, the entire item must be enclosed in double
20333 Lines starting with a # character are comments, and are ignored, and # may
20334 also appear following a comma, in which case everything between the # and the
20335 next newline character is ignored.
20337 If an item is entirely enclosed in double quotes, these are removed. Otherwise
20338 double quotes are retained because some forms of mail address require their use
20339 (but never to enclose the entire address). In the following description,
20340 &"item"& refers to what remains after any surrounding double quotes have been
20343 .vindex "&$local_part$&"
20344 &*Warning*&: If you use an Exim expansion to construct a redirection address,
20345 and the expansion contains a reference to &$local_part$&, you should make use
20346 of the &%quote_local_part%& expansion operator, in case the local part contains
20347 special characters. For example, to redirect all mail for the domain
20348 &'obsolete.example'&, retaining the existing local part, you could use this
20351 data = ${quote_local_part:$local_part}@newdomain.example
20355 .section "Redirecting to a local mailbox" "SECTredlocmai"
20356 .cindex "routing" "loops in"
20357 .cindex "loop" "while routing, avoidance of"
20358 .cindex "address redirection" "to local mailbox"
20359 A redirection item may safely be the same as the address currently under
20360 consideration. This does not cause a routing loop, because a router is
20361 automatically skipped if any ancestor of the address that is being processed
20362 is the same as the current address and was processed by the current router.
20363 Such an address is therefore passed to the following routers, so it is handled
20364 as if there were no redirection. When making this loop-avoidance test, the
20365 complete local part, including any prefix or suffix, is used.
20367 .cindex "address redirection" "local part without domain"
20368 Specifying the same local part without a domain is a common usage in personal
20369 filter files when the user wants to have messages delivered to the local
20370 mailbox and also forwarded elsewhere. For example, the user whose login is
20371 &'cleo'& might have a &_.forward_& file containing this:
20373 cleo, cleopatra@egypt.example
20375 .cindex "backslash in alias file"
20376 .cindex "alias file" "backslash in"
20377 For compatibility with other MTAs, such unqualified local parts may be
20378 preceded by &"\"&, but this is not a requirement for loop prevention. However,
20379 it does make a difference if more than one domain is being handled
20382 If an item begins with &"\"& and the rest of the item parses as a valid RFC
20383 2822 address that does not include a domain, the item is qualified using the
20384 domain of the incoming address. In the absence of a leading &"\"&, unqualified
20385 addresses are qualified using the value in &%qualify_recipient%&, but you can
20386 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
20388 Care must be taken if there are alias names for local users.
20389 Consider an MTA handling a single local domain where the system alias file
20394 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
20395 messages in the local mailbox, and also forward copies elsewhere. He creates
20398 Sam.Reman, spqr@reme.elsewhere.example
20400 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
20401 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
20402 second time round, because it has previously routed it,
20403 and the following routers presumably cannot handle the alias. The forward file
20404 should really contain
20406 spqr, spqr@reme.elsewhere.example
20408 but because this is such a common error, the &%check_ancestor%& option (see
20409 below) exists to provide a way to get round it. This is normally set on a
20410 &(redirect)& router that is handling users' &_.forward_& files.
20414 .section "Special items in redirection lists" "SECTspecitredli"
20415 In addition to addresses, the following types of item may appear in redirection
20416 lists (that is, in non-filter redirection data):
20419 .cindex "pipe" "in redirection list"
20420 .cindex "address redirection" "to pipe"
20421 An item is treated as a pipe command if it begins with &"|"& and does not parse
20422 as a valid RFC 2822 address that includes a domain. A transport for running the
20423 command must be specified by the &%pipe_transport%& option.
20424 Normally, either the router or the transport specifies a user and a group under
20425 which to run the delivery. The default is to use the Exim user and group.
20427 Single or double quotes can be used for enclosing the individual arguments of
20428 the pipe command; no interpretation of escapes is done for single quotes. If
20429 the command contains a comma character, it is necessary to put the whole item
20430 in double quotes, for example:
20432 "|/some/command ready,steady,go"
20434 since items in redirection lists are terminated by commas. Do not, however,
20435 quote just the command. An item such as
20437 |"/some/command ready,steady,go"
20439 is interpreted as a pipe with a rather strange command name, and no arguments.
20441 Note that the above example assumes that the text comes from a lookup source
20442 of some sort, so that the quotes are part of the data. If composing a
20443 redirect router with a &%data%& option directly specifying this command, the
20444 quotes will be used by the configuration parser to define the extent of one
20445 string, but will not be passed down into the redirect router itself. There
20446 are two main approaches to get around this: escape quotes to be part of the
20447 data itself, or avoid using this mechanism and instead create a custom
20448 transport with the &%command%& option set and reference that transport from
20449 an &%accept%& router.
20452 .cindex "file" "in redirection list"
20453 .cindex "address redirection" "to file"
20454 An item is interpreted as a path name if it begins with &"/"& and does not
20455 parse as a valid RFC 2822 address that includes a domain. For example,
20457 /home/world/minbari
20459 is treated as a filename, but
20461 /s=molari/o=babylon/@x400gate.way
20463 is treated as an address. For a filename, a transport must be specified using
20464 the &%file_transport%& option. However, if the generated path name ends with a
20465 forward slash character, it is interpreted as a directory name rather than a
20466 filename, and &%directory_transport%& is used instead.
20468 Normally, either the router or the transport specifies a user and a group under
20469 which to run the delivery. The default is to use the Exim user and group.
20471 .cindex "&_/dev/null_&"
20472 However, if a redirection item is the path &_/dev/null_&, delivery to it is
20473 bypassed at a high level, and the log entry shows &"**bypassed**"&
20474 instead of a transport name. In this case the user and group are not used.
20477 .cindex "included address list"
20478 .cindex "address redirection" "included external list"
20479 If an item is of the form
20481 :include:<path name>
20483 a list of further items is taken from the given file and included at that
20484 point. &*Note*&: Such a file can not be a filter file; it is just an
20485 out-of-line addition to the list. The items in the included list are separated
20486 by commas or newlines and are not subject to expansion. If this is the first
20487 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
20488 the alias name. This example is incorrect:
20490 list1 :include:/opt/lists/list1
20492 It must be given as
20494 list1: :include:/opt/lists/list1
20497 .cindex "address redirection" "to black hole"
20498 .cindex "delivery" "discard"
20499 .cindex "delivery" "blackhole"
20500 .cindex "black hole"
20501 .cindex "abandoning mail"
20502 Sometimes you want to throw away mail to a particular local part. Making the
20503 &%data%& option expand to an empty string does not work, because that causes
20504 the router to decline. Instead, the alias item
20508 can be used. It does what its name implies. No delivery is
20509 done, and no error message is generated. This has the same effect as specifying
20510 &_/dev/null_& as a destination, but it can be independently disabled.
20512 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
20513 delivery is done for the original local part, even if other redirection items
20514 are present. If you are generating a multi-item list (for example, by reading a
20515 database) and need the ability to provide a no-op item, you must use
20519 .cindex "delivery" "forcing failure"
20520 .cindex "delivery" "forcing deferral"
20521 .cindex "failing delivery" "forcing"
20522 .cindex "deferred delivery, forcing"
20523 .cindex "customizing" "failure message"
20524 An attempt to deliver a particular address can be deferred or forced to fail by
20525 redirection items of the form
20530 respectively. When a redirection list contains such an item, it applies
20531 to the entire redirection; any other items in the list are ignored. Any
20532 text following &':fail:'& or &':defer:'& is placed in the error text
20533 associated with the failure. For example, an alias file might contain:
20535 X.Employee: :fail: Gone away, no forwarding address
20537 In the case of an address that is being verified from an ACL or as the subject
20539 .cindex "VRFY" "error text, display of"
20540 VRFY command, the text is included in the SMTP error response by
20542 .cindex "EXPN" "error text, display of"
20543 The text is not included in the response to an EXPN command. In non-SMTP cases
20544 the text is included in the error message that Exim generates.
20546 .cindex "SMTP" "error codes"
20547 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
20548 &':fail:'&. However, if the message starts with three digits followed by a
20549 space, optionally followed by an extended code of the form &'n.n.n'&, also
20550 followed by a space, and the very first digit is the same as the default error
20551 code, the code from the message is used instead. If the very first digit is
20552 incorrect, a panic error is logged, and the default code is used. You can
20553 suppress the use of the supplied code in a redirect router by setting the
20554 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
20557 .vindex "&$acl_verify_message$&"
20558 In an ACL, an explicitly provided message overrides the default, but the
20559 default message is available in the variable &$acl_verify_message$& and can
20560 therefore be included in a custom message if this is desired.
20562 Normally the error text is the rest of the redirection list &-- a comma does
20563 not terminate it &-- but a newline does act as a terminator. Newlines are not
20564 normally present in alias expansions. In &(lsearch)& lookups they are removed
20565 as part of the continuation process, but they may exist in other kinds of
20566 lookup and in &':include:'& files.
20568 During routing for message delivery (as opposed to verification), a redirection
20569 containing &':fail:'& causes an immediate failure of the incoming address,
20570 whereas &':defer:'& causes the message to remain in the queue so that a
20571 subsequent delivery attempt can happen at a later time. If an address is
20572 deferred for too long, it will ultimately fail, because the normal retry
20576 .cindex "alias file" "exception to default"
20577 Sometimes it is useful to use a single-key search type with a default (see
20578 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
20579 for exceptions to the default. These can be handled by aliasing them to
20580 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
20581 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
20582 results in an empty redirection list has the same effect.
20586 .section "Duplicate addresses" "SECTdupaddr"
20587 .cindex "duplicate addresses"
20588 .cindex "address duplicate, discarding"
20589 .cindex "pipe" "duplicated"
20590 Exim removes duplicate addresses from the list to which it is delivering, so as
20591 to deliver just one copy to each address. This does not apply to deliveries
20592 routed to pipes by different immediate parent addresses, but an indirect
20593 aliasing scheme of the type
20595 pipe: |/some/command $local_part
20599 does not work with a message that is addressed to both local parts, because
20600 when the second is aliased to the intermediate local part &"pipe"& it gets
20601 discarded as being the same as a previously handled address. However, a scheme
20604 localpart1: |/some/command $local_part
20605 localpart2: |/some/command $local_part
20607 does result in two different pipe deliveries, because the immediate parents of
20608 the pipes are distinct.
20612 .section "Repeated redirection expansion" "SECID128"
20613 .cindex "repeated redirection expansion"
20614 .cindex "address redirection" "repeated for each delivery attempt"
20615 When a message cannot be delivered to all of its recipients immediately,
20616 leading to two or more delivery attempts, redirection expansion is carried out
20617 afresh each time for those addresses whose children were not all previously
20618 delivered. If redirection is being used as a mailing list, this can lead to new
20619 members of the list receiving copies of old messages. The &%one_time%& option
20620 can be used to avoid this.
20623 .section "Errors in redirection lists" "SECID129"
20624 .cindex "address redirection" "errors"
20625 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
20626 error is skipped, and an entry is written to the main log. This may be useful
20627 for mailing lists that are automatically managed. Otherwise, if an error is
20628 detected while generating the list of new addresses, the original address is
20629 deferred. See also &%syntax_errors_to%&.
20633 .section "Private options for the redirect router" "SECID130"
20635 .cindex "options" "&(redirect)& router"
20636 The private options for the &(redirect)& router are as follows:
20639 .option allow_defer redirect boolean false
20640 Setting this option allows the use of &':defer:'& in non-filter redirection
20641 data, or the &%defer%& command in an Exim filter file.
20644 .option allow_fail redirect boolean false
20645 .cindex "failing delivery" "from filter"
20646 If this option is true, the &':fail:'& item can be used in a redirection list,
20647 and the &%fail%& command may be used in an Exim filter file.
20650 .option allow_filter redirect boolean false
20651 .cindex "filter" "enabling use of"
20652 .cindex "Sieve filter" "enabling use of"
20653 Setting this option allows Exim to interpret redirection data that starts with
20654 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
20655 are some features of Exim filter files that some administrators may wish to
20656 lock out; see the &%forbid_filter_%&&'xxx'& options below.
20658 It is also possible to lock out Exim filters or Sieve filters while allowing
20659 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
20662 The filter is run using the uid and gid set by the generic &%user%& and
20663 &%group%& options. These take their defaults from the password data if
20664 &%check_local_user%& is set, so in the normal case of users' personal filter
20665 files, the filter is run as the relevant user. When &%allow_filter%& is set
20666 true, Exim insists that either &%check_local_user%& or &%user%& is set.
20670 .option allow_freeze redirect boolean false
20671 .cindex "freezing messages" "allowing in filter"
20672 Setting this option allows the use of the &%freeze%& command in an Exim filter.
20673 This command is more normally encountered in system filters, and is disabled by
20674 default for redirection filters because it isn't something you usually want to
20675 let ordinary users do.
20679 .option check_ancestor redirect boolean false
20680 This option is concerned with handling generated addresses that are the same
20681 as some address in the list of redirection ancestors of the current address.
20682 Although it is turned off by default in the code, it is set in the default
20683 configuration file for handling users' &_.forward_& files. It is recommended
20684 for this use of the &(redirect)& router.
20686 When &%check_ancestor%& is set, if a generated address (including the domain)
20687 is the same as any ancestor of the current address, it is replaced by a copy of
20688 the current address. This helps in the case where local part A is aliased to B,
20689 and B has a &_.forward_& file pointing back to A. For example, within a single
20690 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
20691 &_&~jb/.forward_& contains:
20693 \Joe.Bloggs, <other item(s)>
20695 Without the &%check_ancestor%& setting, either local part (&"jb"& or
20696 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
20697 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
20698 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
20699 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
20700 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
20701 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
20702 original address. See also the &%repeat_use%& option below.
20705 .option check_group redirect boolean "see below"
20706 When the &%file%& option is used, the group owner of the file is checked only
20707 when this option is set. The permitted groups are those listed in the
20708 &%owngroups%& option, together with the user's default group if
20709 &%check_local_user%& is set. If the file has the wrong group, routing is
20710 deferred. The default setting for this option is true if &%check_local_user%&
20711 is set and the &%modemask%& option permits the group write bit, or if the
20712 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
20716 .option check_owner redirect boolean "see below"
20717 When the &%file%& option is used, the owner of the file is checked only when
20718 this option is set. If &%check_local_user%& is set, the local user is
20719 permitted; otherwise the owner must be one of those listed in the &%owners%&
20720 option. The default value for this option is true if &%check_local_user%& or
20721 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
20724 .option data redirect string&!! unset
20725 This option is mutually exclusive with &%file%&. One or other of them must be
20726 set, but not both. The contents of &%data%& are expanded, and then used as the
20727 list of forwarding items, or as a set of filtering instructions. If the
20728 expansion is forced to fail, or the result is an empty string or a string that
20729 has no effect (consists entirely of comments), the router declines.
20731 When filtering instructions are used, the string must begin with &"#Exim
20732 filter"&, and all comments in the string, including this initial one, must be
20733 terminated with newline characters. For example:
20735 data = #Exim filter\n\
20736 if $h_to: contains Exim then save $home/mail/exim endif
20738 If you are reading the data from a database where newlines cannot be included,
20739 you can use the &${sg}$& expansion item to turn the escape string of your
20740 choice into a newline.
20743 .option directory_transport redirect string&!! unset
20744 A &(redirect)& router sets up a direct delivery to a directory when a path name
20745 ending with a slash is specified as a new &"address"&. The transport used is
20746 specified by this option, which, after expansion, must be the name of a
20747 configured transport. This should normally be an &(appendfile)& transport.
20750 .option file redirect string&!! unset
20751 This option specifies the name of a file that contains the redirection data. It
20752 is mutually exclusive with the &%data%& option. The string is expanded before
20753 use; if the expansion is forced to fail, the router declines. Other expansion
20754 failures cause delivery to be deferred. The result of a successful expansion
20755 must be an absolute path. The entire file is read and used as the redirection
20756 data. If the data is an empty string or a string that has no effect (consists
20757 entirely of comments), the router declines.
20759 .cindex "NFS" "checking for file existence"
20760 If the attempt to open the file fails with a &"does not exist"& error, Exim
20761 runs a check on the containing directory,
20762 unless &%ignore_enotdir%& is true (see below).
20763 If the directory does not appear to exist, delivery is deferred. This can
20764 happen when users' &_.forward_& files are in NFS-mounted directories, and there
20765 is a mount problem. If the containing directory does exist, but the file does
20766 not, the router declines.
20769 .option file_transport redirect string&!! unset
20770 .vindex "&$address_file$&"
20771 A &(redirect)& router sets up a direct delivery to a file when a path name not
20772 ending in a slash is specified as a new &"address"&. The transport used is
20773 specified by this option, which, after expansion, must be the name of a
20774 configured transport. This should normally be an &(appendfile)& transport. When
20775 it is running, the filename is in &$address_file$&.
20778 .option filter_prepend_home redirect boolean true
20779 When this option is true, if a &(save)& command in an Exim filter specifies a
20780 relative path, and &$home$& is defined, it is automatically prepended to the
20781 relative path. If this option is set false, this action does not happen. The
20782 relative path is then passed to the transport unmodified.
20785 .option forbid_blackhole redirect boolean false
20786 .cindex "restricting access to features"
20787 .cindex "filter" "locking out certain features"
20788 If this option is true, the &':blackhole:'& item may not appear in a
20792 .option forbid_exim_filter redirect boolean false
20793 .cindex "restricting access to features"
20794 .cindex "filter" "locking out certain features"
20795 If this option is set true, only Sieve filters are permitted when
20796 &%allow_filter%& is true.
20801 .option forbid_file redirect boolean false
20802 .cindex "restricting access to features"
20803 .cindex "delivery" "to file; forbidding"
20804 .cindex "filter" "locking out certain features"
20805 .cindex "Sieve filter" "forbidding delivery to a file"
20806 .cindex "Sieve filter" "&""keep""& facility; disabling"
20807 If this option is true, this router may not generate a new address that
20808 specifies delivery to a local file or directory, either from a filter or from a
20809 conventional forward file. This option is forced to be true if &%one_time%& is
20810 set. It applies to Sieve filters as well as to Exim filters, but if true, it
20811 locks out the Sieve's &"keep"& facility.
20814 .option forbid_filter_dlfunc redirect boolean false
20815 .cindex "restricting access to features"
20816 .cindex "filter" "locking out certain features"
20817 If this option is true, string expansions in Exim filters are not allowed to
20818 make use of the &%dlfunc%& expansion facility to run dynamically loaded
20821 .option forbid_filter_existstest redirect boolean false
20822 .cindex "restricting access to features"
20823 .cindex "filter" "locking out certain features"
20824 .cindex "expansion" "statting a file"
20825 If this option is true, string expansions in Exim filters are not allowed to
20826 make use of the &%exists%& condition or the &%stat%& expansion item.
20828 .option forbid_filter_logwrite redirect boolean false
20829 .cindex "restricting access to features"
20830 .cindex "filter" "locking out certain features"
20831 If this option is true, use of the logging facility in Exim filters is not
20832 permitted. Logging is in any case available only if the filter is being run
20833 under some unprivileged uid (which is normally the case for ordinary users'
20834 &_.forward_& files).
20837 .option forbid_filter_lookup redirect boolean false
20838 .cindex "restricting access to features"
20839 .cindex "filter" "locking out certain features"
20840 If this option is true, string expansions in Exim filter files are not allowed
20841 to make use of &%lookup%& items.
20844 .option forbid_filter_perl redirect boolean false
20845 .cindex "restricting access to features"
20846 .cindex "filter" "locking out certain features"
20847 This option has an effect only if Exim is built with embedded Perl support. If
20848 it is true, string expansions in Exim filter files are not allowed to make use
20849 of the embedded Perl support.
20852 .option forbid_filter_readfile redirect boolean false
20853 .cindex "restricting access to features"
20854 .cindex "filter" "locking out certain features"
20855 If this option is true, string expansions in Exim filter files are not allowed
20856 to make use of &%readfile%& items.
20859 .option forbid_filter_readsocket redirect boolean false
20860 .cindex "restricting access to features"
20861 .cindex "filter" "locking out certain features"
20862 If this option is true, string expansions in Exim filter files are not allowed
20863 to make use of &%readsocket%& items.
20866 .option forbid_filter_reply redirect boolean false
20867 .cindex "restricting access to features"
20868 .cindex "filter" "locking out certain features"
20869 If this option is true, this router may not generate an automatic reply
20870 message. Automatic replies can be generated only from Exim or Sieve filter
20871 files, not from traditional forward files. This option is forced to be true if
20872 &%one_time%& is set.
20875 .option forbid_filter_run redirect boolean false
20876 .cindex "restricting access to features"
20877 .cindex "filter" "locking out certain features"
20878 If this option is true, string expansions in Exim filter files are not allowed
20879 to make use of &%run%& items.
20882 .option forbid_include redirect boolean false
20883 .cindex "restricting access to features"
20884 .cindex "filter" "locking out certain features"
20885 If this option is true, items of the form
20887 :include:<path name>
20889 are not permitted in non-filter redirection lists.
20892 .option forbid_pipe redirect boolean false
20893 .cindex "restricting access to features"
20894 .cindex "filter" "locking out certain features"
20895 .cindex "delivery" "to pipe; forbidding"
20896 If this option is true, this router may not generate a new address which
20897 specifies delivery to a pipe, either from an Exim filter or from a conventional
20898 forward file. This option is forced to be true if &%one_time%& is set.
20901 .option forbid_sieve_filter redirect boolean false
20902 .cindex "restricting access to features"
20903 .cindex "filter" "locking out certain features"
20904 If this option is set true, only Exim filters are permitted when
20905 &%allow_filter%& is true.
20908 .cindex "SMTP" "error codes"
20909 .option forbid_smtp_code redirect boolean false
20910 If this option is set true, any SMTP error codes that are present at the start
20911 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
20912 the default codes (451 and 550, respectively) are always used.
20917 .option hide_child_in_errmsg redirect boolean false
20918 .cindex "bounce message" "redirection details; suppressing"
20919 If this option is true, it prevents Exim from quoting a child address if it
20920 generates a bounce or delay message for it. Instead it says &"an address
20921 generated from <&'the top level address'&>"&. Of course, this applies only to
20922 bounces generated locally. If a message is forwarded to another host, &'its'&
20923 bounce may well quote the generated address.
20926 .option ignore_eacces redirect boolean false
20928 If this option is set and an attempt to open a redirection file yields the
20929 EACCES error (permission denied), the &(redirect)& router behaves as if the
20930 file did not exist.
20933 .option ignore_enotdir redirect boolean false
20935 If this option is set and an attempt to open a redirection file yields the
20936 ENOTDIR error (something on the path is not a directory), the &(redirect)&
20937 router behaves as if the file did not exist.
20939 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
20940 router that has the &%file%& option set discovers that the file does not exist
20941 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
20942 against unmounted NFS directories. If the parent can not be statted, delivery
20943 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
20944 is set, because that option tells Exim to ignore &"something on the path is not
20945 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
20946 that some operating systems give ENOENT where others give ENOTDIR.
20950 .option include_directory redirect string unset
20951 If this option is set, the path names of any &':include:'& items in a
20952 redirection list must start with this directory.
20955 .option modemask redirect "octal integer" 022
20956 This specifies mode bits which must not be set for a file specified by the
20957 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
20960 .option one_time redirect boolean false
20961 .cindex "one-time aliasing/forwarding expansion"
20962 .cindex "alias file" "one-time expansion"
20963 .cindex "forward file" "one-time expansion"
20964 .cindex "mailing lists" "one-time expansion"
20965 .cindex "address redirection" "one-time expansion"
20966 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
20967 files each time it tries to deliver a message causes a problem when one or more
20968 of the generated addresses fails be delivered at the first attempt. The problem
20969 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
20970 but of what happens when the redirection list changes during the time that the
20971 message is on Exim's queue. This is particularly true in the case of mailing
20972 lists, where new subscribers might receive copies of messages that were posted
20973 before they subscribed.
20975 If &%one_time%& is set and any addresses generated by the router fail to
20976 deliver at the first attempt, the failing addresses are added to the message as
20977 &"top level"& addresses, and the parent address that generated them is marked
20978 &"delivered"&. Thus, redirection does not happen again at the next delivery
20981 &*Warning 1*&: Any header line addition or removal that is specified by this
20982 router would be lost if delivery did not succeed at the first attempt. For this
20983 reason, the &%headers_add%& and &%headers_remove%& generic options are not
20984 permitted when &%one_time%& is set.
20986 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
20987 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
20988 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
20990 &*Warning 3*&: The &%unseen%& generic router option may not be set with
20993 The original top-level address is remembered with each of the generated
20994 addresses, and is output in any log messages. However, any intermediate parent
20995 addresses are not recorded. This makes a difference to the log only if
20996 &%all_parents%& log selector is set. It is expected that &%one_time%& will
20997 typically be used for mailing lists, where there is normally just one level of
21001 .option owners redirect "string list" unset
21002 .cindex "ownership" "alias file"
21003 .cindex "ownership" "forward file"
21004 .cindex "alias file" "ownership"
21005 .cindex "forward file" "ownership"
21006 This specifies a list of permitted owners for the file specified by &%file%&.
21007 This list is in addition to the local user when &%check_local_user%& is set.
21008 See &%check_owner%& above.
21011 .option owngroups redirect "string list" unset
21012 This specifies a list of permitted groups for the file specified by &%file%&.
21013 The list is in addition to the local user's primary group when
21014 &%check_local_user%& is set. See &%check_group%& above.
21017 .option pipe_transport redirect string&!! unset
21018 .vindex "&$address_pipe$&"
21019 A &(redirect)& router sets up a direct delivery to a pipe when a string
21020 starting with a vertical bar character is specified as a new &"address"&. The
21021 transport used is specified by this option, which, after expansion, must be the
21022 name of a configured transport. This should normally be a &(pipe)& transport.
21023 When the transport is run, the pipe command is in &$address_pipe$&.
21026 .option qualify_domain redirect string&!! unset
21027 .vindex "&$qualify_recipient$&"
21028 If this option is set, and an unqualified address (one without a domain) is
21029 generated, and that address would normally be qualified by the global setting
21030 in &%qualify_recipient%&, it is instead qualified with the domain specified by
21031 expanding this string. If the expansion fails, the router declines. If you want
21032 to revert to the default, you can have the expansion generate
21033 &$qualify_recipient$&.
21035 This option applies to all unqualified addresses generated by Exim filters,
21036 but for traditional &_.forward_& files, it applies only to addresses that are
21037 not preceded by a backslash. Sieve filters cannot generate unqualified
21040 .option qualify_preserve_domain redirect boolean false
21041 .cindex "domain" "in redirection; preserving"
21042 .cindex "preserving domain in redirection"
21043 .cindex "address redirection" "domain; preserving"
21044 If this option is set, the router's local &%qualify_domain%& option must not be
21045 set (a configuration error occurs if it is). If an unqualified address (one
21046 without a domain) is generated, it is qualified with the domain of the parent
21047 address (the immediately preceding ancestor) instead of the global
21048 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
21049 this applies whether or not the address is preceded by a backslash.
21052 .option repeat_use redirect boolean true
21053 If this option is set false, the router is skipped for a child address that has
21054 any ancestor that was routed by this router. This test happens before any of
21055 the other preconditions are tested. Exim's default anti-looping rules skip
21056 only when the ancestor is the same as the current address. See also
21057 &%check_ancestor%& above and the generic &%redirect_router%& option.
21060 .option reply_transport redirect string&!! unset
21061 A &(redirect)& router sets up an automatic reply when a &%mail%& or
21062 &%vacation%& command is used in a filter file. The transport used is specified
21063 by this option, which, after expansion, must be the name of a configured
21064 transport. This should normally be an &(autoreply)& transport. Other transports
21065 are unlikely to do anything sensible or useful.
21068 .option rewrite redirect boolean true
21069 .cindex "address redirection" "disabling rewriting"
21070 If this option is set false, addresses generated by the router are not
21071 subject to address rewriting. Otherwise, they are treated like new addresses
21072 and are rewritten according to the global rewriting rules.
21075 .option sieve_subaddress redirect string&!! unset
21076 The value of this option is passed to a Sieve filter to specify the
21077 :subaddress part of an address.
21079 .option sieve_useraddress redirect string&!! unset
21080 The value of this option is passed to a Sieve filter to specify the :user part
21081 of an address. However, if it is unset, the entire original local part
21082 (including any prefix or suffix) is used for :user.
21085 .option sieve_vacation_directory redirect string&!! unset
21086 .cindex "Sieve filter" "vacation directory"
21087 To enable the &"vacation"& extension for Sieve filters, you must set
21088 &%sieve_vacation_directory%& to the directory where vacation databases are held
21089 (do not put anything else in that directory), and ensure that the
21090 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
21091 needs their own directory; Exim will create it if necessary.
21095 .option skip_syntax_errors redirect boolean false
21096 .cindex "forward file" "broken"
21097 .cindex "address redirection" "broken files"
21098 .cindex "alias file" "broken"
21099 .cindex "broken alias or forward files"
21100 .cindex "ignoring faulty addresses"
21101 .cindex "skipping faulty addresses"
21102 .cindex "error" "skipping bad syntax"
21103 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
21104 non-filter redirection data are skipped, and each failing address is logged. If
21105 &%syntax_errors_to%& is set, a message is sent to the address it defines,
21106 giving details of the failures. If &%syntax_errors_text%& is set, its contents
21107 are expanded and placed at the head of the error message generated by
21108 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
21109 be the same address as the generic &%errors_to%& option. The
21110 &%skip_syntax_errors%& option is often used when handling mailing lists.
21112 If all the addresses in a redirection list are skipped because of syntax
21113 errors, the router declines to handle the original address, and it is passed to
21114 the following routers.
21116 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
21117 error in the filter causes filtering to be abandoned without any action being
21118 taken. The incident is logged, and the router declines to handle the address,
21119 so it is passed to the following routers.
21121 .cindex "Sieve filter" "syntax errors in"
21122 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
21123 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
21124 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
21126 &%skip_syntax_errors%& can be used to specify that errors in users' forward
21127 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
21128 option, used with an address that does not get redirected, can be used to
21129 notify users of these errors, by means of a router like this:
21135 file = $home/.forward
21136 file_transport = address_file
21137 pipe_transport = address_pipe
21138 reply_transport = address_reply
21141 syntax_errors_to = real-$local_part@$domain
21142 syntax_errors_text = \
21143 This is an automatically generated message. An error has\n\
21144 been found in your .forward file. Details of the error are\n\
21145 reported below. While this error persists, you will receive\n\
21146 a copy of this message for every message that is addressed\n\
21147 to you. If your .forward file is a filter file, or if it is\n\
21148 a non-filter file containing no valid forwarding addresses,\n\
21149 a copy of each incoming message will be put in your normal\n\
21150 mailbox. If a non-filter file contains at least one valid\n\
21151 forwarding address, forwarding to the valid addresses will\n\
21152 happen, and those will be the only deliveries that occur.
21154 You also need a router to ensure that local addresses that are prefixed by
21155 &`real-`& are recognized, but not forwarded or filtered. For example, you could
21156 put this immediately before the &(userforward)& router:
21161 local_part_prefix = real-
21162 transport = local_delivery
21164 For security, it would probably be a good idea to restrict the use of this
21165 router to locally-generated messages, using a condition such as this:
21167 condition = ${if match {$sender_host_address}\
21168 {\N^(|127\.0\.0\.1)$\N}}
21172 .option syntax_errors_text redirect string&!! unset
21173 See &%skip_syntax_errors%& above.
21176 .option syntax_errors_to redirect string unset
21177 See &%skip_syntax_errors%& above.
21178 .ecindex IIDredrou1
21179 .ecindex IIDredrou2
21186 . ////////////////////////////////////////////////////////////////////////////
21187 . ////////////////////////////////////////////////////////////////////////////
21189 .chapter "Environment for running local transports" "CHAPenvironment" &&&
21190 "Environment for local transports"
21191 .scindex IIDenvlotra1 "local transports" "environment for"
21192 .scindex IIDenvlotra2 "environment" "local transports"
21193 .scindex IIDenvlotra3 "transport" "local; environment for"
21194 Local transports handle deliveries to files and pipes. (The &(autoreply)&
21195 transport can be thought of as similar to a pipe.) Exim always runs transports
21196 in subprocesses, under specified uids and gids. Typical deliveries to local
21197 mailboxes run under the uid and gid of the local user.
21199 Exim also sets a specific current directory while running the transport; for
21200 some transports a home directory setting is also relevant. The &(pipe)&
21201 transport is the only one that sets up environment variables; see section
21202 &<<SECTpipeenv>>& for details.
21204 The values used for the uid, gid, and the directories may come from several
21205 different places. In many cases, the router that handles the address associates
21206 settings with that address as a result of its &%check_local_user%&, &%group%&,
21207 or &%user%& options. However, values may also be given in the transport's own
21208 configuration, and these override anything that comes from the router.
21212 .section "Concurrent deliveries" "SECID131"
21213 .cindex "concurrent deliveries"
21214 .cindex "simultaneous deliveries"
21215 If two different messages for the same local recipient arrive more or less
21216 simultaneously, the two delivery processes are likely to run concurrently. When
21217 the &(appendfile)& transport is used to write to a file, Exim applies locking
21218 rules to stop concurrent processes from writing to the same file at the same
21221 However, when you use a &(pipe)& transport, it is up to you to arrange any
21222 locking that is needed. Here is a silly example:
21226 command = /bin/sh -c 'cat >>/some/file'
21228 This is supposed to write the message at the end of the file. However, if two
21229 messages arrive at the same time, the file will be scrambled. You can use the
21230 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
21231 file using the same algorithm that Exim itself uses.
21236 .section "Uids and gids" "SECTenvuidgid"
21237 .cindex "local transports" "uid and gid"
21238 .cindex "transport" "local; uid and gid"
21239 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
21240 overrides any group that the router set in the address, even if &%user%& is not
21241 set for the transport. This makes it possible, for example, to run local mail
21242 delivery under the uid of the recipient (set by the router), but in a special
21243 group (set by the transport). For example:
21246 # User/group are set by check_local_user in this router
21250 transport = group_delivery
21253 # This transport overrides the group
21255 driver = appendfile
21256 file = /var/spool/mail/$local_part
21259 If &%user%& is set for a transport, its value overrides what is set in the
21260 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
21261 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
21264 .oindex "&%initgroups%&"
21265 When the uid is taken from the transport's configuration, the &[initgroups()]&
21266 function is called for the groups associated with that uid if the
21267 &%initgroups%& option is set for the transport. When the uid is not specified
21268 by the transport, but is associated with the address by a router, the option
21269 for calling &[initgroups()]& is taken from the router configuration.
21271 .cindex "&(pipe)& transport" "uid for"
21272 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
21273 is set and &%user%& is not set, the uid of the process that called Exim to
21274 receive the message is used, and if &%group%& is not set, the corresponding
21275 original gid is also used.
21277 This is the detailed preference order for obtaining a gid; the first of the
21278 following that is set is used:
21281 A &%group%& setting of the transport;
21283 A &%group%& setting of the router;
21285 A gid associated with a user setting of the router, either as a result of
21286 &%check_local_user%& or an explicit non-numeric &%user%& setting;
21288 The group associated with a non-numeric &%user%& setting of the transport;
21290 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
21291 the uid is the creator's uid;
21293 The Exim gid if the Exim uid is being used as a default.
21296 If, for example, the user is specified numerically on the router and there are
21297 no group settings, no gid is available. In this situation, an error occurs.
21298 This is different for the uid, for which there always is an ultimate default.
21299 The first of the following that is set is used:
21302 A &%user%& setting of the transport;
21304 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
21306 A &%user%& setting of the router;
21308 A &%check_local_user%& setting of the router;
21313 Of course, an error will still occur if the uid that is chosen is on the
21314 &%never_users%& list.
21320 .section "Current and home directories" "SECID132"
21321 .cindex "current directory for local transport"
21322 .cindex "home directory" "for local transport"
21323 .cindex "transport" "local; home directory for"
21324 .cindex "transport" "local; current directory for"
21325 Routers may set current and home directories for local transports by means of
21326 the &%transport_current_directory%& and &%transport_home_directory%& options.
21327 However, if the transport's &%current_directory%& or &%home_directory%& options
21328 are set, they override the router's values. In detail, the home directory
21329 for a local transport is taken from the first of these values that is set:
21332 The &%home_directory%& option on the transport;
21334 The &%transport_home_directory%& option on the router;
21336 The password data if &%check_local_user%& is set on the router;
21338 The &%router_home_directory%& option on the router.
21341 The current directory is taken from the first of these values that is set:
21344 The &%current_directory%& option on the transport;
21346 The &%transport_current_directory%& option on the router.
21350 If neither the router nor the transport sets a current directory, Exim uses the
21351 value of the home directory, if it is set. Otherwise it sets the current
21352 directory to &_/_& before running a local transport.
21356 .section "Expansion variables derived from the address" "SECID133"
21357 .vindex "&$domain$&"
21358 .vindex "&$local_part$&"
21359 .vindex "&$original_domain$&"
21360 Normally a local delivery is handling a single address, and in that case the
21361 variables such as &$domain$& and &$local_part$& are set during local
21362 deliveries. However, in some circumstances more than one address may be handled
21363 at once (for example, while writing batch SMTP for onward transmission by some
21364 other means). In this case, the variables associated with the local part are
21365 never set, &$domain$& is set only if all the addresses have the same domain,
21366 and &$original_domain$& is never set.
21367 .ecindex IIDenvlotra1
21368 .ecindex IIDenvlotra2
21369 .ecindex IIDenvlotra3
21377 . ////////////////////////////////////////////////////////////////////////////
21378 . ////////////////////////////////////////////////////////////////////////////
21380 .chapter "Generic options for transports" "CHAPtransportgeneric"
21381 .scindex IIDgenoptra1 "generic options" "transport"
21382 .scindex IIDgenoptra2 "options" "generic; for transports"
21383 .scindex IIDgenoptra3 "transport" "generic options for"
21384 The following generic options apply to all transports:
21387 .option body_only transports boolean false
21388 .cindex "transport" "body only"
21389 .cindex "message" "transporting body only"
21390 .cindex "body of message" "transporting"
21391 If this option is set, the message's headers are not transported. It is
21392 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
21393 or &(pipe)& transports, the settings of &%message_prefix%& and
21394 &%message_suffix%& should be checked, because this option does not
21395 automatically suppress them.
21398 .option current_directory transports string&!! unset
21399 .cindex "transport" "current directory for"
21400 This specifies the current directory that is to be set while running the
21401 transport, overriding any value that may have been set by the router.
21402 If the expansion fails for any reason, including forced failure, an error is
21403 logged, and delivery is deferred.
21406 .option disable_logging transports boolean false
21407 If this option is set true, nothing is logged for any
21408 deliveries by the transport or for any
21409 transport errors. You should not set this option unless you really, really know
21410 what you are doing.
21413 .option debug_print transports string&!! unset
21414 .cindex "testing" "variables in drivers"
21415 If this option is set and debugging is enabled (see the &%-d%& command line
21416 option), the string is expanded and included in the debugging output when the
21418 If expansion of the string fails, the error message is written to the debugging
21419 output, and Exim carries on processing.
21420 This facility is provided to help with checking out the values of variables and
21421 so on when debugging driver configurations. For example, if a &%headers_add%&
21422 option is not working properly, &%debug_print%& could be used to output the
21423 variables it references. A newline is added to the text if it does not end with
21425 The variables &$transport_name$& and &$router_name$& contain the name of the
21426 transport and the router that called it.
21428 .option delivery_date_add transports boolean false
21429 .cindex "&'Delivery-date:'& header line"
21430 If this option is true, a &'Delivery-date:'& header is added to the message.
21431 This gives the actual time the delivery was made. As this is not a standard
21432 header, Exim has a configuration option (&%delivery_date_remove%&) which
21433 requests its removal from incoming messages, so that delivered messages can
21434 safely be resent to other recipients.
21437 .option driver transports string unset
21438 This specifies which of the available transport drivers is to be used.
21439 There is no default, and this option must be set for every transport.
21442 .option envelope_to_add transports boolean false
21443 .cindex "&'Envelope-to:'& header line"
21444 If this option is true, an &'Envelope-to:'& header is added to the message.
21445 This gives the original address(es) in the incoming envelope that caused this
21446 delivery to happen. More than one address may be present if the transport is
21447 configured to handle several addresses at once, or if more than one original
21448 address was redirected to the same final address. As this is not a standard
21449 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
21450 its removal from incoming messages, so that delivered messages can safely be
21451 resent to other recipients.
21454 .option event_action transports string&!! unset
21456 This option declares a string to be expanded for Exim's events mechanism.
21457 For details see chapter &<<CHAPevents>>&.
21460 .option group transports string&!! "Exim group"
21461 .cindex "transport" "group; specifying"
21462 This option specifies a gid for running the transport process, overriding any
21463 value that the router supplies, and also overriding any value associated with
21464 &%user%& (see below).
21467 .option headers_add transports list&!! unset
21468 .cindex "header lines" "adding in transport"
21469 .cindex "transport" "header lines; adding"
21470 This option specifies a list of text headers,
21471 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
21472 which are (separately) expanded and added to the header
21473 portion of a message as it is transported, as described in section
21474 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
21475 routers. If the result of the expansion is an empty string, or if the expansion
21476 is forced to fail, no action is taken. Other expansion failures are treated as
21477 errors and cause the delivery to be deferred.
21479 Unlike most options, &%headers_add%& can be specified multiple times
21480 for a transport; all listed headers are added.
21483 .option headers_only transports boolean false
21484 .cindex "transport" "header lines only"
21485 .cindex "message" "transporting headers only"
21486 .cindex "header lines" "transporting"
21487 If this option is set, the message's body is not transported. It is mutually
21488 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
21489 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
21490 checked, since this option does not automatically suppress them.
21493 .option headers_remove transports list&!! unset
21494 .cindex "header lines" "removing"
21495 .cindex "transport" "header lines; removing"
21496 This option specifies a list of header names,
21497 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&);
21498 these headers are omitted from the message as it is transported, as described
21499 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
21501 Each list item is separately expanded.
21502 If the result of the expansion is an empty string, or if the expansion
21503 is forced to fail, no action is taken. Other expansion failures are treated as
21504 errors and cause the delivery to be deferred.
21506 Unlike most options, &%headers_remove%& can be specified multiple times
21507 for a transport; all listed headers are removed.
21509 &*Warning*&: Because of the separate expansion of the list items,
21510 items that contain a list separator must have it doubled.
21511 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
21515 .option headers_rewrite transports string unset
21516 .cindex "transport" "header lines; rewriting"
21517 .cindex "rewriting" "at transport time"
21518 This option allows addresses in header lines to be rewritten at transport time,
21519 that is, as the message is being copied to its destination. The contents of the
21520 option are a colon-separated list of rewriting rules. Each rule is in exactly
21521 the same form as one of the general rewriting rules that are applied when a
21522 message is received. These are described in chapter &<<CHAPrewrite>>&. For
21525 headers_rewrite = a@b c@d f : \
21528 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
21529 &'w@z'& in all address-bearing header lines. The rules are applied to the
21530 header lines just before they are written out at transport time, so they affect
21531 only those copies of the message that pass through the transport. However, only
21532 the message's original header lines, and any that were added by a system
21533 filter, are rewritten. If a router or transport adds header lines, they are not
21534 affected by this option. These rewriting rules are &'not'& applied to the
21535 envelope. You can change the return path using &%return_path%&, but you cannot
21536 change envelope recipients at this time.
21539 .option home_directory transports string&!! unset
21540 .cindex "transport" "home directory for"
21542 This option specifies a home directory setting for a local transport,
21543 overriding any value that may be set by the router. The home directory is
21544 placed in &$home$& while expanding the transport's private options. It is also
21545 used as the current directory if no current directory is set by the
21546 &%current_directory%& option on the transport or the
21547 &%transport_current_directory%& option on the router. If the expansion fails
21548 for any reason, including forced failure, an error is logged, and delivery is
21552 .option initgroups transports boolean false
21553 .cindex "additional groups"
21554 .cindex "groups" "additional"
21555 .cindex "transport" "group; additional"
21556 If this option is true and the uid for the delivery process is provided by the
21557 transport, the &[initgroups()]& function is called when running the transport
21558 to ensure that any additional groups associated with the uid are set up.
21561 .option max_parallel transports integer&!! unset
21562 .cindex limit "transport parallelism"
21563 .cindex transport "parallel processes"
21564 .cindex transport "concurrency limit"
21565 .cindex "delivery" "parallelism for transport"
21566 If this option is set and expands to an integer greater than zero
21567 it limits the number of concurrent runs of the transport.
21568 The control does not apply to shadow transports.
21570 .cindex "hints database" "transport concurrency control"
21571 Exim implements this control by means of a hints database in which a record is
21572 incremented whenever a transport process is being created. The record
21573 is decremented and possibly removed when the process terminates.
21574 Obviously there is scope for
21575 records to get left lying around if there is a system or program crash. To
21576 guard against this, Exim ignores any records that are more than six hours old.
21578 If you use this option, you should also arrange to delete the
21579 relevant hints database whenever your system reboots. The names of the files
21580 start with &_misc_& and they are kept in the &_spool/db_& directory. There
21581 may be one or two files, depending on the type of DBM in use. The same files
21582 are used for ETRN and smtp transport serialization.
21585 .option message_size_limit transports string&!! 0
21586 .cindex "limit" "message size per transport"
21587 .cindex "size" "of message, limit"
21588 .cindex "transport" "message size; limiting"
21589 This option controls the size of messages passed through the transport. It is
21590 expanded before use; the result of the expansion must be a sequence of decimal
21591 digits, optionally followed by K or M. If the expansion fails for any reason,
21592 including forced failure, or if the result is not of the required form,
21593 delivery is deferred. If the value is greater than zero and the size of a
21594 message exceeds this limit, the address is failed. If there is any chance that
21595 the resulting bounce message could be routed to the same transport, you should
21596 ensure that &%return_size_limit%& is less than the transport's
21597 &%message_size_limit%&, as otherwise the bounce message will fail to get
21602 .option rcpt_include_affixes transports boolean false
21603 .cindex "prefix" "for local part, including in envelope"
21604 .cindex "suffix for local part" "including in envelope"
21605 .cindex "local part" "prefix"
21606 .cindex "local part" "suffix"
21607 When this option is false (the default), and an address that has had any
21608 affixes (prefixes or suffixes) removed from the local part is delivered by any
21609 form of SMTP or LMTP, the affixes are not included. For example, if a router
21612 local_part_prefix = *-
21614 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
21617 RCPT TO:<xyz@some.domain>
21619 This is also the case when an ACL-time callout is being used to verify a
21620 recipient address. However, if &%rcpt_include_affixes%& is set true, the
21621 whole local part is included in the RCPT command. This option applies to BSMTP
21622 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
21623 &(lmtp)& and &(smtp)& transports.
21626 .option retry_use_local_part transports boolean "see below"
21627 .cindex "hints database" "retry keys"
21628 When a delivery suffers a temporary failure, a retry record is created
21629 in Exim's hints database. For remote deliveries, the key for the retry record
21630 is based on the name and/or IP address of the failing remote host. For local
21631 deliveries, the key is normally the entire address, including both the local
21632 part and the domain. This is suitable for most common cases of local delivery
21633 temporary failure &-- for example, exceeding a mailbox quota should delay only
21634 deliveries to that mailbox, not to the whole domain.
21636 However, in some special cases you may want to treat a temporary local delivery
21637 as a failure associated with the domain, and not with a particular local part.
21638 (For example, if you are storing all mail for some domain in files.) You can do
21639 this by setting &%retry_use_local_part%& false.
21641 For all the local transports, its default value is true. For remote transports,
21642 the default value is false for tidiness, but changing the value has no effect
21643 on a remote transport in the current implementation.
21646 .option return_path transports string&!! unset
21647 .cindex "envelope sender"
21648 .cindex "transport" "return path; changing"
21649 .cindex "return path" "changing in transport"
21650 If this option is set, the string is expanded at transport time and replaces
21651 the existing return path (envelope sender) value in the copy of the message
21652 that is being delivered. An empty return path is permitted. This feature is
21653 designed for remote deliveries, where the value of this option is used in the
21654 SMTP MAIL command. If you set &%return_path%& for a local transport, the
21655 only effect is to change the address that is placed in the &'Return-path:'&
21656 header line, if one is added to the message (see the next option).
21658 &*Note:*& A changed return path is not logged unless you add
21659 &%return_path_on_delivery%& to the log selector.
21661 .vindex "&$return_path$&"
21662 The expansion can refer to the existing value via &$return_path$&. This is
21663 either the message's envelope sender, or an address set by the
21664 &%errors_to%& option on a router. If the expansion is forced to fail, no
21665 replacement occurs; if it fails for another reason, delivery is deferred. This
21666 option can be used to support VERP (Variable Envelope Return Paths) &-- see
21667 section &<<SECTverp>>&.
21669 &*Note*&: If a delivery error is detected locally, including the case when a
21670 remote server rejects a message at SMTP time, the bounce message is not sent to
21671 the value of this option. It is sent to the previously set errors address.
21672 This defaults to the incoming sender address, but can be changed by setting
21673 &%errors_to%& in a router.
21677 .option return_path_add transports boolean false
21678 .cindex "&'Return-path:'& header line"
21679 If this option is true, a &'Return-path:'& header is added to the message.
21680 Although the return path is normally available in the prefix line of BSD
21681 mailboxes, this is commonly not displayed by MUAs, and so the user does not
21682 have easy access to it.
21684 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
21685 the delivery SMTP server makes the final delivery"&. This implies that this
21686 header should not be present in incoming messages. Exim has a configuration
21687 option, &%return_path_remove%&, which requests removal of this header from
21688 incoming messages, so that delivered messages can safely be resent to other
21692 .option shadow_condition transports string&!! unset
21693 See &%shadow_transport%& below.
21696 .option shadow_transport transports string unset
21697 .cindex "shadow transport"
21698 .cindex "transport" "shadow"
21699 A local transport may set the &%shadow_transport%& option to the name of
21700 another local transport. Shadow remote transports are not supported.
21702 Whenever a delivery to the main transport succeeds, and either
21703 &%shadow_condition%& is unset, or its expansion does not result in the empty
21704 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
21705 passed to the shadow transport, with the same delivery address or addresses. If
21706 expansion fails, no action is taken except that non-forced expansion failures
21707 cause a log line to be written.
21709 The result of the shadow transport is discarded and does not affect the
21710 subsequent processing of the message. Only a single level of shadowing is
21711 provided; the &%shadow_transport%& option is ignored on any transport when it
21712 is running as a shadow. Options concerned with output from pipes are also
21713 ignored. The log line for the successful delivery has an item added on the end,
21716 ST=<shadow transport name>
21718 If the shadow transport did not succeed, the error message is put in
21719 parentheses afterwards. Shadow transports can be used for a number of different
21720 purposes, including keeping more detailed log information than Exim normally
21721 provides, and implementing automatic acknowledgment policies based on message
21722 headers that some sites insist on.
21725 .option transport_filter transports string&!! unset
21726 .cindex "transport" "filter"
21727 .cindex "filter" "transport filter"
21728 This option sets up a filtering (in the Unix shell sense) process for messages
21729 at transport time. It should not be confused with mail filtering as set up by
21730 individual users or via a system filter.
21731 If unset, or expanding to an empty string, no filtering is done.
21733 When the message is about to be written out, the command specified by
21734 &%transport_filter%& is started up in a separate, parallel process, and
21735 the entire message, including the header lines, is passed to it on its standard
21736 input (this in fact is done from a third process, to avoid deadlock). The
21737 command must be specified as an absolute path.
21739 The lines of the message that are written to the transport filter are
21740 terminated by newline (&"\n"&). The message is passed to the filter before any
21741 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
21742 lines beginning with a dot, and also before any processing implied by the
21743 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
21744 &(pipe)& transports.
21746 The standard error for the filter process is set to the same destination as its
21747 standard output; this is read and written to the message's ultimate
21748 destination. The process that writes the message to the filter, the
21749 filter itself, and the original process that reads the result and delivers it
21750 are all run in parallel, like a shell pipeline.
21752 The filter can perform any transformations it likes, but of course should take
21753 care not to break RFC 2822 syntax. Exim does not check the result, except to
21754 test for a final newline when SMTP is in use. All messages transmitted over
21755 SMTP must end with a newline, so Exim supplies one if it is missing.
21757 .cindex "content scanning" "per user"
21758 A transport filter can be used to provide content-scanning on a per-user basis
21759 at delivery time if the only required effect of the scan is to modify the
21760 message. For example, a content scan could insert a new header line containing
21761 a spam score. This could be interpreted by a filter in the user's MUA. It is
21762 not possible to discard a message at this stage.
21764 .cindex "SMTP" "SIZE"
21765 A problem might arise if the filter increases the size of a message that is
21766 being sent down an SMTP connection. If the receiving SMTP server has indicated
21767 support for the SIZE parameter, Exim will have sent the size of the message
21768 at the start of the SMTP session. If what is actually sent is substantially
21769 more, the server might reject the message. This can be worked round by setting
21770 the &%size_addition%& option on the &(smtp)& transport, either to allow for
21771 additions to the message, or to disable the use of SIZE altogether.
21773 .vindex "&$pipe_addresses$&"
21774 The value of the &%transport_filter%& option is the command string for starting
21775 the filter, which is run directly from Exim, not under a shell. The string is
21776 parsed by Exim in the same way as a command string for the &(pipe)& transport:
21777 Exim breaks it up into arguments and then expands each argument separately (see
21778 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
21779 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
21780 of arguments, one for each address that applies to this delivery. (This isn't
21781 an ideal name for this feature here, but as it was already implemented for the
21782 &(pipe)& transport, it seemed sensible not to change it.)
21785 .vindex "&$host_address$&"
21786 The expansion variables &$host$& and &$host_address$& are available when the
21787 transport is a remote one. They contain the name and IP address of the host to
21788 which the message is being sent. For example:
21790 transport_filter = /some/directory/transport-filter.pl \
21791 $host $host_address $sender_address $pipe_addresses
21794 Two problems arise if you want to use more complicated expansion items to
21795 generate transport filter commands, both of which due to the fact that the
21796 command is split up &'before'& expansion.
21798 If an expansion item contains white space, you must quote it, so that it is all
21799 part of the same command item. If the entire option setting is one such
21800 expansion item, you have to take care what kind of quoting you use. For
21803 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
21805 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
21806 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
21807 stripped by Exim when it read the option's value. When the value is used, if
21808 the single quotes were missing, the line would be split into two items,
21809 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
21810 Exim tried to expand the first one.
21812 Except for the special case of &$pipe_addresses$& that is mentioned above, an
21813 expansion cannot generate multiple arguments, or a command name followed by
21814 arguments. Consider this example:
21816 transport_filter = ${lookup{$host}lsearch{/a/file}\
21817 {$value}{/bin/cat}}
21819 The result of the lookup is interpreted as the name of the command, even
21820 if it contains white space. The simplest way round this is to use a shell:
21822 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
21823 {$value}{/bin/cat}}
21827 The filter process is run under the same uid and gid as the normal delivery.
21828 For remote deliveries this is the Exim uid/gid by default. The command should
21829 normally yield a zero return code. Transport filters are not supposed to fail.
21830 A non-zero code is taken to mean that the transport filter encountered some
21831 serious problem. Delivery of the message is deferred; the message remains on
21832 the queue and is tried again later. It is not possible to cause a message to be
21833 bounced from a transport filter.
21835 If a transport filter is set on an autoreply transport, the original message is
21836 passed through the filter as it is being copied into the newly generated
21837 message, which happens if the &%return_message%& option is set.
21840 .option transport_filter_timeout transports time 5m
21841 .cindex "transport" "filter, timeout"
21842 When Exim is reading the output of a transport filter, it applies a timeout
21843 that can be set by this option. Exceeding the timeout is normally treated as a
21844 temporary delivery failure. However, if a transport filter is used with a
21845 &(pipe)& transport, a timeout in the transport filter is treated in the same
21846 way as a timeout in the pipe command itself. By default, a timeout is a hard
21847 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
21848 becomes a temporary error.
21851 .option user transports string&!! "Exim user"
21852 .cindex "uid (user id)" "local delivery"
21853 .cindex "transport" "user, specifying"
21854 This option specifies the user under whose uid the delivery process is to be
21855 run, overriding any uid that may have been set by the router. If the user is
21856 given as a name, the uid is looked up from the password data, and the
21857 associated group is taken as the value of the gid to be used if the &%group%&
21860 For deliveries that use local transports, a user and group are normally
21861 specified explicitly or implicitly (for example, as a result of
21862 &%check_local_user%&) by the router or transport.
21864 .cindex "hints database" "access by remote transport"
21865 For remote transports, you should leave this option unset unless you really are
21866 sure you know what you are doing. When a remote transport is running, it needs
21867 to be able to access Exim's hints databases, because each host may have its own
21869 .ecindex IIDgenoptra1
21870 .ecindex IIDgenoptra2
21871 .ecindex IIDgenoptra3
21878 . ////////////////////////////////////////////////////////////////////////////
21879 . ////////////////////////////////////////////////////////////////////////////
21881 .chapter "Address batching in local transports" "CHAPbatching" &&&
21883 .cindex "transport" "local; address batching in"
21884 The only remote transport (&(smtp)&) is normally configured to handle more than
21885 one address at a time, so that when several addresses are routed to the same
21886 remote host, just one copy of the message is sent. Local transports, however,
21887 normally handle one address at a time. That is, a separate instance of the
21888 transport is run for each address that is routed to the transport. A separate
21889 copy of the message is delivered each time.
21891 .cindex "batched local delivery"
21892 .oindex "&%batch_max%&"
21893 .oindex "&%batch_id%&"
21894 In special cases, it may be desirable to handle several addresses at once in a
21895 local transport, for example:
21898 In an &(appendfile)& transport, when storing messages in files for later
21899 delivery by some other means, a single copy of the message with multiple
21900 recipients saves space.
21902 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
21903 a single copy saves time, and is the normal way LMTP is expected to work.
21905 In a &(pipe)& transport, when passing the message
21906 to a scanner program or
21907 to some other delivery mechanism such as UUCP, multiple recipients may be
21911 These three local transports all have the same options for controlling multiple
21912 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
21913 repeating the information for each transport, these options are described here.
21915 The &%batch_max%& option specifies the maximum number of addresses that can be
21916 delivered together in a single run of the transport. Its default value is one
21917 (no batching). When more than one address is routed to a transport that has a
21918 &%batch_max%& value greater than one, the addresses are delivered in a batch
21919 (that is, in a single run of the transport with multiple recipients), subject
21920 to certain conditions:
21923 .vindex "&$local_part$&"
21924 If any of the transport's options contain a reference to &$local_part$&, no
21925 batching is possible.
21927 .vindex "&$domain$&"
21928 If any of the transport's options contain a reference to &$domain$&, only
21929 addresses with the same domain are batched.
21931 .cindex "customizing" "batching condition"
21932 If &%batch_id%& is set, it is expanded for each address, and only those
21933 addresses with the same expanded value are batched. This allows you to specify
21934 customized batching conditions. Failure of the expansion for any reason,
21935 including forced failure, disables batching, but it does not stop the delivery
21938 Batched addresses must also have the same errors address (where to send
21939 delivery errors), the same header additions and removals, the same user and
21940 group for the transport, and if a host list is present, the first host must
21944 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
21945 both when the file or pipe command is specified in the transport, and when it
21946 is specified by a &(redirect)& router, but all the batched addresses must of
21947 course be routed to the same file or pipe command. These two transports have an
21948 option called &%use_bsmtp%&, which causes them to deliver the message in
21949 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
21950 &%check_string%& and &%escape_string%& options are forced to the values
21953 escape_string = ".."
21955 when batched SMTP is in use. A full description of the batch SMTP mechanism is
21956 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
21957 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
21959 .cindex "&'Envelope-to:'& header line"
21960 If the generic &%envelope_to_add%& option is set for a batching transport, the
21961 &'Envelope-to:'& header that is added to the message contains all the addresses
21962 that are being processed together. If you are using a batching &(appendfile)&
21963 transport without &%use_bsmtp%&, the only way to preserve the recipient
21964 addresses is to set the &%envelope_to_add%& option.
21966 .cindex "&(pipe)& transport" "with multiple addresses"
21967 .vindex "&$pipe_addresses$&"
21968 If you are using a &(pipe)& transport without BSMTP, and setting the
21969 transport's &%command%& option, you can include &$pipe_addresses$& as part of
21970 the command. This is not a true variable; it is a bit of magic that causes each
21971 of the recipient addresses to be inserted into the command as a separate
21972 argument. This provides a way of accessing all the addresses that are being
21973 delivered in the batch. &*Note:*& This is not possible for pipe commands that
21974 are specified by a &(redirect)& router.
21979 . ////////////////////////////////////////////////////////////////////////////
21980 . ////////////////////////////////////////////////////////////////////////////
21982 .chapter "The appendfile transport" "CHAPappendfile"
21983 .scindex IIDapptra1 "&(appendfile)& transport"
21984 .scindex IIDapptra2 "transports" "&(appendfile)&"
21985 .cindex "directory creation"
21986 .cindex "creating directories"
21987 The &(appendfile)& transport delivers a message by appending it to an existing
21988 file, or by creating an entirely new file in a specified directory. Single
21989 files to which messages are appended can be in the traditional Unix mailbox
21990 format, or optionally in the MBX format supported by the Pine MUA and
21991 University of Washington IMAP daemon, &'inter alia'&. When each message is
21992 being delivered as a separate file, &"maildir"& format can optionally be used
21993 to give added protection against failures that happen part-way through the
21994 delivery. A third form of separate-file delivery known as &"mailstore"& is also
21995 supported. For all file formats, Exim attempts to create as many levels of
21996 directory as necessary, provided that &%create_directory%& is set.
21998 The code for the optional formats is not included in the Exim binary by
21999 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
22000 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
22003 .cindex "quota" "system"
22004 Exim recognizes system quota errors, and generates an appropriate message. Exim
22005 also supports its own quota control within the transport, for use when the
22006 system facility is unavailable or cannot be used for some reason.
22008 If there is an error while appending to a file (for example, quota exceeded or
22009 partition filled), Exim attempts to reset the file's length and last
22010 modification time back to what they were before. If there is an error while
22011 creating an entirely new file, the new file is removed.
22013 Before appending to a file, a number of security checks are made, and the
22014 file is locked. A detailed description is given below, after the list of
22017 The &(appendfile)& transport is most commonly used for local deliveries to
22018 users' mailboxes. However, it can also be used as a pseudo-remote transport for
22019 putting messages into files for remote delivery by some means other than Exim.
22020 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
22025 .section "The file and directory options" "SECTfildiropt"
22026 The &%file%& option specifies a single file, to which the message is appended;
22027 the &%directory%& option specifies a directory, in which a new file containing
22028 the message is created. Only one of these two options can be set, and for
22029 normal deliveries to mailboxes, one of them &'must'& be set.
22031 .vindex "&$address_file$&"
22032 .vindex "&$local_part$&"
22033 However, &(appendfile)& is also used for delivering messages to files or
22034 directories whose names (or parts of names) are obtained from alias,
22035 forwarding, or filtering operations (for example, a &%save%& command in a
22036 user's Exim filter). When such a transport is running, &$local_part$& contains
22037 the local part that was aliased or forwarded, and &$address_file$& contains the
22038 name (or partial name) of the file or directory generated by the redirection
22039 operation. There are two cases:
22042 If neither &%file%& nor &%directory%& is set, the redirection operation
22043 must specify an absolute path (one that begins with &`/`&). This is the most
22044 common case when users with local accounts use filtering to sort mail into
22045 different folders. See for example, the &(address_file)& transport in the
22046 default configuration. If the path ends with a slash, it is assumed to be the
22047 name of a directory. A delivery to a directory can also be forced by setting
22048 &%maildir_format%& or &%mailstore_format%&.
22050 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
22051 used to determine the file or directory name for the delivery. Normally, the
22052 contents of &$address_file$& are used in some way in the string expansion.
22056 .cindex "Sieve filter" "configuring &(appendfile)&"
22057 .cindex "Sieve filter" "relative mailbox path handling"
22058 As an example of the second case, consider an environment where users do not
22059 have home directories. They may be permitted to use Exim filter commands of the
22064 or Sieve filter commands of the form:
22066 require "fileinto";
22067 fileinto "folder23";
22069 In this situation, the expansion of &%file%& or &%directory%& in the transport
22070 must transform the relative path into an appropriate absolute filename. In the
22071 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
22072 is used as a result of a &"keep"& action in the filter. This example shows one
22073 way of handling this requirement:
22075 file = ${if eq{$address_file}{inbox} \
22076 {/var/mail/$local_part} \
22077 {${if eq{${substr_0_1:$address_file}}{/} \
22079 {$home/mail/$address_file} \
22083 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
22084 location, absolute paths are used without change, and other folders are in the
22085 &_mail_& directory within the home directory.
22087 &*Note 1*&: While processing an Exim filter, a relative path such as
22088 &_folder23_& is turned into an absolute path if a home directory is known to
22089 the router. In particular, this is the case if &%check_local_user%& is set. If
22090 you want to prevent this happening at routing time, you can set
22091 &%router_home_directory%& empty. This forces the router to pass the relative
22092 path to the transport.
22094 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
22095 the &%file%& or &%directory%& option is still used if it is set.
22100 .section "Private options for appendfile" "SECID134"
22101 .cindex "options" "&(appendfile)& transport"
22105 .option allow_fifo appendfile boolean false
22106 .cindex "fifo (named pipe)"
22107 .cindex "named pipe (fifo)"
22108 .cindex "pipe" "named (fifo)"
22109 Setting this option permits delivery to named pipes (FIFOs) as well as to
22110 regular files. If no process is reading the named pipe at delivery time, the
22111 delivery is deferred.
22114 .option allow_symlink appendfile boolean false
22115 .cindex "symbolic link" "to mailbox"
22116 .cindex "mailbox" "symbolic link"
22117 By default, &(appendfile)& will not deliver if the path name for the file is
22118 that of a symbolic link. Setting this option relaxes that constraint, but there
22119 are security issues involved in the use of symbolic links. Be sure you know
22120 what you are doing if you set this. Details of exactly what this option affects
22121 are included in the discussion which follows this list of options.
22124 .option batch_id appendfile string&!! unset
22125 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22126 However, batching is automatically disabled for &(appendfile)& deliveries that
22127 happen as a result of forwarding or aliasing or other redirection directly to a
22131 .option batch_max appendfile integer 1
22132 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22135 .option check_group appendfile boolean false
22136 When this option is set, the group owner of the file defined by the &%file%&
22137 option is checked to see that it is the same as the group under which the
22138 delivery process is running. The default setting is false because the default
22139 file mode is 0600, which means that the group is irrelevant.
22142 .option check_owner appendfile boolean true
22143 When this option is set, the owner of the file defined by the &%file%& option
22144 is checked to ensure that it is the same as the user under which the delivery
22145 process is running.
22148 .option check_string appendfile string "see below"
22149 .cindex "&""From""& line"
22150 As &(appendfile)& writes the message, the start of each line is tested for
22151 matching &%check_string%&, and if it does, the initial matching characters are
22152 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
22153 a literal string, not a regular expression, and the case of any letters it
22154 contains is significant.
22156 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
22157 are forced to &"."& and &".."& respectively, and any settings in the
22158 configuration are ignored. Otherwise, they default to &"From&~"& and
22159 &">From&~"& when the &%file%& option is set, and unset when any of the
22160 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
22162 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
22163 suitable for traditional &"BSD"& mailboxes, where a line beginning with
22164 &"From&~"& indicates the start of a new message. All four options need changing
22165 if another format is used. For example, to deliver to mailboxes in MMDF format:
22166 .cindex "MMDF format mailbox"
22167 .cindex "mailbox" "MMDF format"
22169 check_string = "\1\1\1\1\n"
22170 escape_string = "\1\1\1\1 \n"
22171 message_prefix = "\1\1\1\1\n"
22172 message_suffix = "\1\1\1\1\n"
22174 .option create_directory appendfile boolean true
22175 .cindex "directory creation"
22176 When this option is true, Exim attempts to create any missing superior
22177 directories for the file that it is about to write. A created directory's mode
22178 is given by the &%directory_mode%& option.
22180 The group ownership of a newly created directory is highly dependent on the
22181 operating system (and possibly the file system) that is being used. For
22182 example, in Solaris, if the parent directory has the setgid bit set, its group
22183 is propagated to the child; if not, the currently set group is used. However,
22184 in FreeBSD, the parent's group is always used.
22188 .option create_file appendfile string anywhere
22189 This option constrains the location of files and directories that are created
22190 by this transport. It applies to files defined by the &%file%& option and
22191 directories defined by the &%directory%& option. In the case of maildir
22192 delivery, it applies to the top level directory, not the maildir directories
22195 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
22196 &"belowhome"&. In the second and third cases, a home directory must have been
22197 set for the transport. This option is not useful when an explicit filename is
22198 given for normal mailbox deliveries. It is intended for the case when filenames
22199 are generated from users' &_.forward_& files. These are usually handled
22200 by an &(appendfile)& transport called &%address_file%&. See also
22201 &%file_must_exist%&.
22204 .option directory appendfile string&!! unset
22205 This option is mutually exclusive with the &%file%& option, but one of &%file%&
22206 or &%directory%& must be set, unless the delivery is the direct result of a
22207 redirection (see section &<<SECTfildiropt>>&).
22209 When &%directory%& is set, the string is expanded, and the message is delivered
22210 into a new file or files in or below the given directory, instead of being
22211 appended to a single mailbox file. A number of different formats are provided
22212 (see &%maildir_format%& and &%mailstore_format%&), and see section
22213 &<<SECTopdir>>& for further details of this form of delivery.
22216 .option directory_file appendfile string&!! "see below"
22218 .vindex "&$inode$&"
22219 When &%directory%& is set, but neither &%maildir_format%& nor
22220 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
22221 whose name is obtained by expanding this string. The default value is:
22223 q${base62:$tod_epoch}-$inode
22225 This generates a unique name from the current time, in base 62 form, and the
22226 inode of the file. The variable &$inode$& is available only when expanding this
22230 .option directory_mode appendfile "octal integer" 0700
22231 If &(appendfile)& creates any directories as a result of the
22232 &%create_directory%& option, their mode is specified by this option.
22235 .option escape_string appendfile string "see description"
22236 See &%check_string%& above.
22239 .option file appendfile string&!! unset
22240 This option is mutually exclusive with the &%directory%& option, but one of
22241 &%file%& or &%directory%& must be set, unless the delivery is the direct result
22242 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
22243 specifies a single file, to which the message is appended. One or more of
22244 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
22247 .cindex "NFS" "lock file"
22248 .cindex "locking files"
22249 .cindex "lock files"
22250 If you are using more than one host to deliver over NFS into the same
22251 mailboxes, you should always use lock files.
22253 The string value is expanded for each delivery, and must yield an absolute
22254 path. The most common settings of this option are variations on one of these
22257 file = /var/spool/mail/$local_part
22258 file = /home/$local_part/inbox
22261 .cindex "&""sticky""& bit"
22262 In the first example, all deliveries are done into the same directory. If Exim
22263 is configured to use lock files (see &%use_lockfile%& below) it must be able to
22264 create a file in the directory, so the &"sticky"& bit must be turned on for
22265 deliveries to be possible, or alternatively the &%group%& option can be used to
22266 run the delivery under a group id which has write access to the directory.
22270 .option file_format appendfile string unset
22271 .cindex "file" "mailbox; checking existing format"
22272 This option requests the transport to check the format of an existing file
22273 before adding to it. The check consists of matching a specific string at the
22274 start of the file. The value of the option consists of an even number of
22275 colon-separated strings. The first of each pair is the test string, and the
22276 second is the name of a transport. If the transport associated with a matched
22277 string is not the current transport, control is passed over to the other
22278 transport. For example, suppose the standard &(local_delivery)& transport has
22281 file_format = "From : local_delivery :\
22282 \1\1\1\1\n : local_mmdf_delivery"
22284 Mailboxes that begin with &"From"& are still handled by this transport, but if
22285 a mailbox begins with four binary ones followed by a newline, control is passed
22286 to a transport called &%local_mmdf_delivery%&, which presumably is configured
22287 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
22288 is assumed to match the current transport. If the start of a mailbox doesn't
22289 match any string, or if the transport named for a given string is not defined,
22290 delivery is deferred.
22293 .option file_must_exist appendfile boolean false
22294 If this option is true, the file specified by the &%file%& option must exist.
22295 A temporary error occurs if it does not, causing delivery to be deferred.
22296 If this option is false, the file is created if it does not exist.
22299 .option lock_fcntl_timeout appendfile time 0s
22300 .cindex "timeout" "mailbox locking"
22301 .cindex "mailbox" "locking, blocking and non-blocking"
22302 .cindex "locking files"
22303 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
22304 when locking an open mailbox file. If the call fails, the delivery process
22305 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
22306 Non-blocking calls are used so that the file is not kept open during the wait
22307 for the lock; the reason for this is to make it as safe as possible for
22308 deliveries over NFS in the case when processes might be accessing an NFS
22309 mailbox without using a lock file. This should not be done, but
22310 misunderstandings and hence misconfigurations are not unknown.
22312 On a busy system, however, the performance of a non-blocking lock approach is
22313 not as good as using a blocking lock with a timeout. In this case, the waiting
22314 is done inside the system call, and Exim's delivery process acquires the lock
22315 and can proceed as soon as the previous lock holder releases it.
22317 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
22318 timeout, are used. There may still be some retrying: the maximum number of
22321 (lock_retries * lock_interval) / lock_fcntl_timeout
22323 rounded up to the next whole number. In other words, the total time during
22324 which &(appendfile)& is trying to get a lock is roughly the same, unless
22325 &%lock_fcntl_timeout%& is set very large.
22327 You should consider setting this option if you are getting a lot of delayed
22328 local deliveries because of errors of the form
22330 failed to lock mailbox /some/file (fcntl)
22333 .option lock_flock_timeout appendfile time 0s
22334 This timeout applies to file locking when using &[flock()]& (see
22335 &%use_flock%&); the timeout operates in a similar manner to
22336 &%lock_fcntl_timeout%&.
22339 .option lock_interval appendfile time 3s
22340 This specifies the time to wait between attempts to lock the file. See below
22341 for details of locking.
22344 .option lock_retries appendfile integer 10
22345 This specifies the maximum number of attempts to lock the file. A value of zero
22346 is treated as 1. See below for details of locking.
22349 .option lockfile_mode appendfile "octal integer" 0600
22350 This specifies the mode of the created lock file, when a lock file is being
22351 used (see &%use_lockfile%& and &%use_mbx_lock%&).
22354 .option lockfile_timeout appendfile time 30m
22355 .cindex "timeout" "mailbox locking"
22356 When a lock file is being used (see &%use_lockfile%&), if a lock file already
22357 exists and is older than this value, it is assumed to have been left behind by
22358 accident, and Exim attempts to remove it.
22361 .option mailbox_filecount appendfile string&!! unset
22362 .cindex "mailbox" "specifying size of"
22363 .cindex "size" "of mailbox"
22364 If this option is set, it is expanded, and the result is taken as the current
22365 number of files in the mailbox. It must be a decimal number, optionally
22366 followed by K or M. This provides a way of obtaining this information from an
22367 external source that maintains the data.
22370 .option mailbox_size appendfile string&!! unset
22371 .cindex "mailbox" "specifying size of"
22372 .cindex "size" "of mailbox"
22373 If this option is set, it is expanded, and the result is taken as the current
22374 size the mailbox. It must be a decimal number, optionally followed by K or M.
22375 This provides a way of obtaining this information from an external source that
22376 maintains the data. This is likely to be helpful for maildir deliveries where
22377 it is computationally expensive to compute the size of a mailbox.
22381 .option maildir_format appendfile boolean false
22382 .cindex "maildir format" "specifying"
22383 If this option is set with the &%directory%& option, the delivery is into a new
22384 file, in the &"maildir"& format that is used by other mail software. When the
22385 transport is activated directly from a &(redirect)& router (for example, the
22386 &(address_file)& transport in the default configuration), setting
22387 &%maildir_format%& causes the path received from the router to be treated as a
22388 directory, whether or not it ends with &`/`&. This option is available only if
22389 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
22390 &<<SECTmaildirdelivery>>& below for further details.
22393 .option maildir_quota_directory_regex appendfile string "See below"
22394 .cindex "maildir format" "quota; directories included in"
22395 .cindex "quota" "maildir; directories included in"
22396 This option is relevant only when &%maildir_use_size_file%& is set. It defines
22397 a regular expression for specifying directories, relative to the quota
22398 directory (see &%quota_directory%&), that should be included in the quota
22399 calculation. The default value is:
22401 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
22403 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
22404 (directories whose names begin with a dot). If you want to exclude the
22406 folder from the count (as some sites do), you need to change this setting to
22408 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
22410 This uses a negative lookahead in the regular expression to exclude the
22411 directory whose name is &_.Trash_&. When a directory is excluded from quota
22412 calculations, quota processing is bypassed for any messages that are delivered
22413 directly into that directory.
22416 .option maildir_retries appendfile integer 10
22417 This option specifies the number of times to retry when writing a file in
22418 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
22421 .option maildir_tag appendfile string&!! unset
22422 This option applies only to deliveries in maildir format, and is described in
22423 section &<<SECTmaildirdelivery>>& below.
22426 .option maildir_use_size_file appendfile&!! boolean false
22427 .cindex "maildir format" "&_maildirsize_& file"
22428 The result of string expansion for this option must be a valid boolean value.
22429 If it is true, it enables support for &_maildirsize_& files. Exim
22430 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
22431 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
22432 value is zero. See &%maildir_quota_directory_regex%& above and section
22433 &<<SECTmaildirdelivery>>& below for further details.
22435 .option maildirfolder_create_regex appendfile string unset
22436 .cindex "maildir format" "&_maildirfolder_& file"
22437 .cindex "&_maildirfolder_&, creating"
22438 The value of this option is a regular expression. If it is unset, it has no
22439 effect. Otherwise, before a maildir delivery takes place, the pattern is
22440 matched against the name of the maildir directory, that is, the directory
22441 containing the &_new_& and &_tmp_& subdirectories that will be used for the
22442 delivery. If there is a match, Exim checks for the existence of a file called
22443 &_maildirfolder_& in the directory, and creates it if it does not exist.
22444 See section &<<SECTmaildirdelivery>>& for more details.
22447 .option mailstore_format appendfile boolean false
22448 .cindex "mailstore format" "specifying"
22449 If this option is set with the &%directory%& option, the delivery is into two
22450 new files in &"mailstore"& format. The option is available only if
22451 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
22452 below for further details.
22455 .option mailstore_prefix appendfile string&!! unset
22456 This option applies only to deliveries in mailstore format, and is described in
22457 section &<<SECTopdir>>& below.
22460 .option mailstore_suffix appendfile string&!! unset
22461 This option applies only to deliveries in mailstore format, and is described in
22462 section &<<SECTopdir>>& below.
22465 .option mbx_format appendfile boolean false
22466 .cindex "locking files"
22467 .cindex "file" "locking"
22468 .cindex "file" "MBX format"
22469 .cindex "MBX format, specifying"
22470 This option is available only if Exim has been compiled with SUPPORT_MBX
22471 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
22472 the message is appended to the mailbox file in MBX format instead of
22473 traditional Unix format. This format is supported by Pine4 and its associated
22474 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
22476 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
22477 automatically changed by the use of &%mbx_format%&. They should normally be set
22478 empty when using MBX format, so this option almost always appears in this
22485 If none of the locking options are mentioned in the configuration,
22486 &%use_mbx_lock%& is assumed and the other locking options default to false. It
22487 is possible to specify the other kinds of locking with &%mbx_format%&, but
22488 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
22489 interworks with &'c-client'&, providing for shared access to the mailbox. It
22490 should not be used if any program that does not use this form of locking is
22491 going to access the mailbox, nor should it be used if the mailbox file is NFS
22492 mounted, because it works only when the mailbox is accessed from a single host.
22494 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
22495 the standard version of &'c-client'&, because as long as it has a mailbox open
22496 (this means for the whole of a Pine or IMAP session), Exim will not be able to
22497 append messages to it.
22500 .option message_prefix appendfile string&!! "see below"
22501 .cindex "&""From""& line"
22502 The string specified here is expanded and output at the start of every message.
22503 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
22504 in which case it is:
22506 message_prefix = "From ${if def:return_path{$return_path}\
22507 {MAILER-DAEMON}} $tod_bsdinbox\n"
22509 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22510 &`\n`& to &`\r\n`& in &%message_prefix%&.
22512 .option message_suffix appendfile string&!! "see below"
22513 The string specified here is expanded and output at the end of every message.
22514 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
22515 in which case it is a single newline character. The suffix can be suppressed by
22520 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22521 &`\n`& to &`\r\n`& in &%message_suffix%&.
22523 .option mode appendfile "octal integer" 0600
22524 If the output file is created, it is given this mode. If it already exists and
22525 has wider permissions, they are reduced to this mode. If it has narrower
22526 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
22527 if the delivery is the result of a &%save%& command in a filter file specifying
22528 a particular mode, the mode of the output file is always forced to take that
22529 value, and this option is ignored.
22532 .option mode_fail_narrower appendfile boolean true
22533 This option applies in the case when an existing mailbox file has a narrower
22534 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
22535 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
22536 continues with the delivery attempt, using the existing mode of the file.
22539 .option notify_comsat appendfile boolean false
22540 If this option is true, the &'comsat'& daemon is notified after every
22541 successful delivery to a user mailbox. This is the daemon that notifies logged
22542 on users about incoming mail.
22545 .option quota appendfile string&!! unset
22546 .cindex "quota" "imposed by Exim"
22547 This option imposes a limit on the size of the file to which Exim is appending,
22548 or to the total space used in the directory tree when the &%directory%& option
22549 is set. In the latter case, computation of the space used is expensive, because
22550 all the files in the directory (and any sub-directories) have to be
22551 individually inspected and their sizes summed. (See &%quota_size_regex%& and
22552 &%maildir_use_size_file%& for ways to avoid this in environments where users
22553 have no shell access to their mailboxes).
22555 As there is no interlock against two simultaneous deliveries into a
22556 multi-file mailbox, it is possible for the quota to be overrun in this case.
22557 For single-file mailboxes, of course, an interlock is a necessity.
22559 A file's size is taken as its &'used'& value. Because of blocking effects, this
22560 may be a lot less than the actual amount of disk space allocated to the file.
22561 If the sizes of a number of files are being added up, the rounding effect can
22562 become quite noticeable, especially on systems that have large block sizes.
22563 Nevertheless, it seems best to stick to the &'used'& figure, because this is
22564 the obvious value which users understand most easily.
22566 The value of the option is expanded, and must then be a numerical value
22567 (decimal point allowed), optionally followed by one of the letters K, M, or G,
22568 for kilobytes, megabytes, or gigabytes, optionally followed by a slash
22569 and further option modifiers. If Exim is running on a system with
22570 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
22573 The option modifier &%no_check%& can be used to force delivery even if the over
22574 quota condition is met. The quota gets updated as usual.
22576 &*Note*&: A value of zero is interpreted as &"no quota"&.
22578 The expansion happens while Exim is running as root, before it changes uid for
22579 the delivery. This means that files that are inaccessible to the end user can
22580 be used to hold quota values that are looked up in the expansion. When delivery
22581 fails because this quota is exceeded, the handling of the error is as for
22582 system quota failures.
22584 By default, Exim's quota checking mimics system quotas, and restricts the
22585 mailbox to the specified maximum size, though the value is not accurate to the
22586 last byte, owing to separator lines and additional headers that may get added
22587 during message delivery. When a mailbox is nearly full, large messages may get
22588 refused even though small ones are accepted, because the size of the current
22589 message is added to the quota when the check is made. This behaviour can be
22590 changed by setting &%quota_is_inclusive%& false. When this is done, the check
22591 for exceeding the quota does not include the current message. Thus, deliveries
22592 continue until the quota has been exceeded; thereafter, no further messages are
22593 delivered. See also &%quota_warn_threshold%&.
22596 .option quota_directory appendfile string&!! unset
22597 This option defines the directory to check for quota purposes when delivering
22598 into individual files. The default is the delivery directory, or, if a file
22599 called &_maildirfolder_& exists in a maildir directory, the parent of the
22600 delivery directory.
22603 .option quota_filecount appendfile string&!! 0
22604 This option applies when the &%directory%& option is set. It limits the total
22605 number of files in the directory (compare the inode limit in system quotas). It
22606 can only be used if &%quota%& is also set. The value is expanded; an expansion
22607 failure causes delivery to be deferred. A value of zero is interpreted as
22610 The option modifier &%no_check%& can be used to force delivery even if the over
22611 quota condition is met. The quota gets updated as usual.
22613 .option quota_is_inclusive appendfile boolean true
22614 See &%quota%& above.
22617 .option quota_size_regex appendfile string unset
22618 This option applies when one of the delivery modes that writes a separate file
22619 for each message is being used. When Exim wants to find the size of one of
22620 these files in order to test the quota, it first checks &%quota_size_regex%&.
22621 If this is set to a regular expression that matches the filename, and it
22622 captures one string, that string is interpreted as a representation of the
22623 file's size. The value of &%quota_size_regex%& is not expanded.
22625 This feature is useful only when users have no shell access to their mailboxes
22626 &-- otherwise they could defeat the quota simply by renaming the files. This
22627 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
22628 the file length to the filename. For example:
22630 maildir_tag = ,S=$message_size
22631 quota_size_regex = ,S=(\d+)
22633 An alternative to &$message_size$& is &$message_linecount$&, which contains the
22634 number of lines in the message.
22636 The regular expression should not assume that the length is at the end of the
22637 filename (even though &%maildir_tag%& puts it there) because maildir MUAs
22638 sometimes add other information onto the ends of message filenames.
22640 Section &<<SECID136>>& contains further information.
22643 .option quota_warn_message appendfile string&!! "see below"
22644 See below for the use of this option. If it is not set when
22645 &%quota_warn_threshold%& is set, it defaults to
22647 quota_warn_message = "\
22648 To: $local_part@$domain\n\
22649 Subject: Your mailbox\n\n\
22650 This message is automatically created \
22651 by mail delivery software.\n\n\
22652 The size of your mailbox has exceeded \
22653 a warning threshold that is\n\
22654 set by the system administrator.\n"
22658 .option quota_warn_threshold appendfile string&!! 0
22659 .cindex "quota" "warning threshold"
22660 .cindex "mailbox" "size warning"
22661 .cindex "size" "of mailbox"
22662 This option is expanded in the same way as &%quota%& (see above). If the
22663 resulting value is greater than zero, and delivery of the message causes the
22664 size of the file or total space in the directory tree to cross the given
22665 threshold, a warning message is sent. If &%quota%& is also set, the threshold
22666 may be specified as a percentage of it by following the value with a percent
22670 quota_warn_threshold = 75%
22672 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
22673 percent sign is ignored.
22675 The warning message itself is specified by the &%quota_warn_message%& option,
22676 and it must start with a &'To:'& header line containing the recipient(s) of the
22677 warning message. These do not necessarily have to include the recipient(s) of
22678 the original message. A &'Subject:'& line should also normally be supplied. You
22679 can include any other header lines that you want. If you do not include a
22680 &'From:'& line, the default is:
22682 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
22684 .oindex &%errors_reply_to%&
22685 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
22688 The &%quota%& option does not have to be set in order to use this option; they
22689 are independent of one another except when the threshold is specified as a
22693 .option use_bsmtp appendfile boolean false
22694 .cindex "envelope sender"
22695 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
22696 format, with the envelope sender and recipient(s) included as SMTP commands. If
22697 you want to include a leading HELO command with such messages, you can do
22698 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
22699 for details of batch SMTP.
22702 .option use_crlf appendfile boolean false
22703 .cindex "carriage return"
22705 This option causes lines to be terminated with the two-character CRLF sequence
22706 (carriage return, linefeed) instead of just a linefeed character. In the case
22707 of batched SMTP, the byte sequence written to the file is then an exact image
22708 of what would be sent down a real SMTP connection.
22710 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
22711 (which are used to supply the traditional &"From&~"& and blank line separators
22712 in Berkeley-style mailboxes) are written verbatim, so must contain their own
22713 carriage return characters if these are needed. In cases where these options
22714 have non-empty defaults, the values end with a single linefeed, so they must be
22715 changed to end with &`\r\n`& if &%use_crlf%& is set.
22718 .option use_fcntl_lock appendfile boolean "see below"
22719 This option controls the use of the &[fcntl()]& function to lock a file for
22720 exclusive use when a message is being appended. It is set by default unless
22721 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
22722 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
22723 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
22726 .option use_flock_lock appendfile boolean false
22727 This option is provided to support the use of &[flock()]& for file locking, for
22728 the few situations where it is needed. Most modern operating systems support
22729 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
22730 each other. Exim uses &[fcntl()]& locking by default.
22732 This option is required only if you are using an operating system where
22733 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
22734 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
22735 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
22737 .cindex "Solaris" "&[flock()]& support"
22738 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
22739 have it (and some, I think, provide a not quite right version built on top of
22740 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
22741 the ability to use it, and any attempt to do so will cause a configuration
22744 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
22745 is just being mapped onto &[fcntl()]& by the OS).
22748 .option use_lockfile appendfile boolean "see below"
22749 If this option is turned off, Exim does not attempt to create a lock file when
22750 appending to a mailbox file. In this situation, the only locking is by
22751 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
22752 sure that every MUA that is ever going to look at your users' mailboxes uses
22753 &[fcntl()]& rather than a lock file, and even then only when you are not
22754 delivering over NFS from more than one host.
22756 .cindex "NFS" "lock file"
22757 In order to append to an NFS file safely from more than one host, it is
22758 necessary to take out a lock &'before'& opening the file, and the lock file
22759 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
22762 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
22763 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
22764 except when &%mbx_format%& is set.
22767 .option use_mbx_lock appendfile boolean "see below"
22768 This option is available only if Exim has been compiled with SUPPORT_MBX
22769 set in &_Local/Makefile_&. Setting the option specifies that special MBX
22770 locking rules be used. It is set by default if &%mbx_format%& is set and none
22771 of the locking options are mentioned in the configuration. The locking rules
22772 are the same as are used by the &'c-client'& library that underlies Pine and
22773 the IMAP4 and POP daemons that come with it (see the discussion below). The
22774 rules allow for shared access to the mailbox. However, this kind of locking
22775 does not work when the mailbox is NFS mounted.
22777 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
22778 &%use_flock_lock%& to control what kind of locking is used in implementing the
22779 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
22780 without &%use_fcntl_lock%& or &%use_flock_lock%&.
22785 .section "Operational details for appending" "SECTopappend"
22786 .cindex "appending to a file"
22787 .cindex "file" "appending"
22788 Before appending to a file, the following preparations are made:
22791 If the name of the file is &_/dev/null_&, no action is taken, and a success
22795 .cindex "directory creation"
22796 If any directories on the file's path are missing, Exim creates them if the
22797 &%create_directory%& option is set. A created directory's mode is given by the
22798 &%directory_mode%& option.
22801 If &%file_format%& is set, the format of an existing file is checked. If this
22802 indicates that a different transport should be used, control is passed to that
22806 .cindex "file" "locking"
22807 .cindex "locking files"
22808 .cindex "NFS" "lock file"
22809 If &%use_lockfile%& is set, a lock file is built in a way that will work
22810 reliably over NFS, as follows:
22813 Create a &"hitching post"& file whose name is that of the lock file with the
22814 current time, primary host name, and process id added, by opening for writing
22815 as a new file. If this fails with an access error, delivery is deferred.
22817 Close the hitching post file, and hard link it to the lock filename.
22819 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
22820 Unlink the hitching post name.
22822 Otherwise, use &[stat()]& to get information about the hitching post file, and
22823 then unlink hitching post name. If the number of links is exactly two, creation
22824 of the lock file succeeded but something (for example, an NFS server crash and
22825 restart) caused this fact not to be communicated to the &[link()]& call.
22827 If creation of the lock file failed, wait for &%lock_interval%& and try again,
22828 up to &%lock_retries%& times. However, since any program that writes to a
22829 mailbox should complete its task very quickly, it is reasonable to time out old
22830 lock files that are normally the result of user agent and system crashes. If an
22831 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
22832 it before trying again.
22836 A call is made to &[lstat()]& to discover whether the main file exists, and if
22837 so, what its characteristics are. If &[lstat()]& fails for any reason other
22838 than non-existence, delivery is deferred.
22841 .cindex "symbolic link" "to mailbox"
22842 .cindex "mailbox" "symbolic link"
22843 If the file does exist and is a symbolic link, delivery is deferred, unless the
22844 &%allow_symlink%& option is set, in which case the ownership of the link is
22845 checked, and then &[stat()]& is called to find out about the real file, which
22846 is then subjected to the checks below. The check on the top-level link
22847 ownership prevents one user creating a link for another's mailbox in a sticky
22848 directory, though allowing symbolic links in this case is definitely not a good
22849 idea. If there is a chain of symbolic links, the intermediate ones are not
22853 If the file already exists but is not a regular file, or if the file's owner
22854 and group (if the group is being checked &-- see &%check_group%& above) are
22855 different from the user and group under which the delivery is running,
22856 delivery is deferred.
22859 If the file's permissions are more generous than specified, they are reduced.
22860 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
22861 is set false, in which case the delivery is tried using the existing
22865 The file's inode number is saved, and the file is then opened for appending.
22866 If this fails because the file has vanished, &(appendfile)& behaves as if it
22867 hadn't existed (see below). For any other failures, delivery is deferred.
22870 If the file is opened successfully, check that the inode number hasn't
22871 changed, that it is still a regular file, and that the owner and permissions
22872 have not changed. If anything is wrong, defer delivery and freeze the message.
22875 If the file did not exist originally, defer delivery if the &%file_must_exist%&
22876 option is set. Otherwise, check that the file is being created in a permitted
22877 directory if the &%create_file%& option is set (deferring on failure), and then
22878 open for writing as a new file, with the O_EXCL and O_CREAT options,
22879 except when dealing with a symbolic link (the &%allow_symlink%& option must be
22880 set). In this case, which can happen if the link points to a non-existent file,
22881 the file is opened for writing using O_CREAT but not O_EXCL, because
22882 that prevents link following.
22885 .cindex "loop" "while file testing"
22886 If opening fails because the file exists, obey the tests given above for
22887 existing files. However, to avoid looping in a situation where the file is
22888 being continuously created and destroyed, the exists/not-exists loop is broken
22889 after 10 repetitions, and the message is then frozen.
22892 If opening fails with any other error, defer delivery.
22895 .cindex "file" "locking"
22896 .cindex "locking files"
22897 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
22898 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
22899 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
22900 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
22901 file, and an exclusive lock on the file whose name is
22903 /tmp/.<device-number>.<inode-number>
22905 using the device and inode numbers of the open mailbox file, in accordance with
22906 the MBX locking rules. This file is created with a mode that is specified by
22907 the &%lockfile_mode%& option.
22909 If Exim fails to lock the file, there are two possible courses of action,
22910 depending on the value of the locking timeout. This is obtained from
22911 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
22913 If the timeout value is zero, the file is closed, Exim waits for
22914 &%lock_interval%&, and then goes back and re-opens the file as above and tries
22915 to lock it again. This happens up to &%lock_retries%& times, after which the
22916 delivery is deferred.
22918 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
22919 &[flock()]& are used (with the given timeout), so there has already been some
22920 waiting involved by the time locking fails. Nevertheless, Exim does not give up
22921 immediately. It retries up to
22923 (lock_retries * lock_interval) / <timeout>
22925 times (rounded up).
22928 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
22929 and/or &[flock()]& locks) and then deletes the lock file if one was created.
22932 .section "Operational details for delivery to a new file" "SECTopdir"
22933 .cindex "delivery" "to single file"
22934 .cindex "&""From""& line"
22935 When the &%directory%& option is set instead of &%file%&, each message is
22936 delivered into a newly-created file or set of files. When &(appendfile)& is
22937 activated directly from a &(redirect)& router, neither &%file%& nor
22938 &%directory%& is normally set, because the path for delivery is supplied by the
22939 router. (See for example, the &(address_file)& transport in the default
22940 configuration.) In this case, delivery is to a new file if either the path name
22941 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
22943 No locking is required while writing the message to a new file, so the various
22944 locking options of the transport are ignored. The &"From"& line that by default
22945 separates messages in a single file is not normally needed, nor is the escaping
22946 of message lines that start with &"From"&, and there is no need to ensure a
22947 newline at the end of each message. Consequently, the default values for
22948 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
22949 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
22951 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
22952 the files in the delivery directory by default. However, you can specify a
22953 different directory by setting &%quota_directory%&. Also, for maildir
22954 deliveries (see below) the &_maildirfolder_& convention is honoured.
22957 .cindex "maildir format"
22958 .cindex "mailstore format"
22959 There are three different ways in which delivery to individual files can be
22960 done, controlled by the settings of the &%maildir_format%& and
22961 &%mailstore_format%& options. Note that code to support maildir or mailstore
22962 formats is not included in the binary unless SUPPORT_MAILDIR or
22963 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
22965 .cindex "directory creation"
22966 In all three cases an attempt is made to create the directory and any necessary
22967 sub-directories if they do not exist, provided that the &%create_directory%&
22968 option is set (the default). The location of a created directory can be
22969 constrained by setting &%create_file%&. A created directory's mode is given by
22970 the &%directory_mode%& option. If creation fails, or if the
22971 &%create_directory%& option is not set when creation is required, delivery is
22976 .section "Maildir delivery" "SECTmaildirdelivery"
22977 .cindex "maildir format" "description of"
22978 If the &%maildir_format%& option is true, Exim delivers each message by writing
22979 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
22980 directory that is defined by the &%directory%& option (the &"delivery
22981 directory"&). If the delivery is successful, the file is renamed into the
22982 &_new_& subdirectory.
22984 In the filename, <&'stime'&> is the current time of day in seconds, and
22985 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
22986 Exim checks that the time-of-day clock has moved on by at least one microsecond
22987 before terminating the delivery process. This guarantees uniqueness for the
22988 filename. However, as a precaution, Exim calls &[stat()]& for the file before
22989 opening it. If any response other than ENOENT (does not exist) is given,
22990 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
22992 Before Exim carries out a maildir delivery, it ensures that subdirectories
22993 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
22994 do not exist, Exim tries to create them and any superior directories in their
22995 path, subject to the &%create_directory%& and &%create_file%& options. If the
22996 &%maildirfolder_create_regex%& option is set, and the regular expression it
22997 contains matches the delivery directory, Exim also ensures that a file called
22998 &_maildirfolder_& exists in the delivery directory. If a missing directory or
22999 &_maildirfolder_& file cannot be created, delivery is deferred.
23001 These features make it possible to use Exim to create all the necessary files
23002 and directories in a maildir mailbox, including subdirectories for maildir++
23003 folders. Consider this example:
23005 maildir_format = true
23006 directory = /var/mail/$local_part\
23007 ${if eq{$local_part_suffix}{}{}\
23008 {/.${substr_1:$local_part_suffix}}}
23009 maildirfolder_create_regex = /\.[^/]+$
23011 If &$local_part_suffix$& is empty (there was no suffix for the local part),
23012 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
23013 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
23014 not match this name, so Exim will not look for or create the file
23015 &_/var/mail/pimbo/maildirfolder_&, though it will create
23016 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
23018 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
23019 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
23020 does match &%maildirfolder_create_regex%&. In this case, Exim will create
23021 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
23022 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
23024 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
23025 not inadvertently match the toplevel maildir directory, because a
23026 &_maildirfolder_& file at top level would completely break quota calculations.
23028 .cindex "quota" "in maildir delivery"
23029 .cindex "maildir++"
23030 If Exim is required to check a &%quota%& setting before a maildir delivery, and
23031 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
23032 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
23033 Exim assumes the directory is a maildir++ folder directory, which is one level
23034 down from the user's top level mailbox directory. This causes it to start at
23035 the parent directory instead of the current directory when calculating the
23036 amount of space used.
23038 One problem with delivering into a multi-file mailbox is that it is
23039 computationally expensive to compute the size of the mailbox for quota
23040 checking. Various approaches have been taken to reduce the amount of work
23041 needed. The next two sections describe two of them. A third alternative is to
23042 use some external process for maintaining the size data, and use the expansion
23043 of the &%mailbox_size%& option as a way of importing it into Exim.
23048 .section "Using tags to record message sizes" "SECID135"
23049 If &%maildir_tag%& is set, the string is expanded for each delivery.
23050 When the maildir file is renamed into the &_new_& sub-directory, the
23051 tag is added to its name. However, if adding the tag takes the length of the
23052 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
23053 the tag is dropped and the maildir file is created with no tag.
23056 .vindex "&$message_size$&"
23057 Tags can be used to encode the size of files in their names; see
23058 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
23059 happens after the message has been written. The value of the &$message_size$&
23060 variable is set to the number of bytes actually written. If the expansion is
23061 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
23062 be deferred. The expanded tag may contain any printing characters except &"/"&.
23063 Non-printing characters in the string are ignored; if the resulting string is
23064 empty, it is ignored. If it starts with an alphanumeric character, a leading
23065 colon is inserted; this default has not proven to be the path that popular
23066 maildir implementations have chosen (but changing it in Exim would break
23067 backwards compatibility).
23069 For one common implementation, you might set:
23071 maildir_tag = ,S=${message_size}
23073 but you should check the documentation of the other software to be sure.
23075 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
23076 as this allows Exim to extract the size from your tag, instead of having to
23077 &[stat()]& each message file.
23080 .section "Using a maildirsize file" "SECID136"
23081 .cindex "quota" "in maildir delivery"
23082 .cindex "maildir format" "&_maildirsize_& file"
23083 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
23084 storing quota and message size information in a file called &_maildirsize_&
23085 within the toplevel maildir directory. If this file does not exist, Exim
23086 creates it, setting the quota from the &%quota%& option of the transport. If
23087 the maildir directory itself does not exist, it is created before any attempt
23088 to write a &_maildirsize_& file.
23090 The &_maildirsize_& file is used to hold information about the sizes of
23091 messages in the maildir, thus speeding up quota calculations. The quota value
23092 in the file is just a cache; if the quota is changed in the transport, the new
23093 value overrides the cached value when the next message is delivered. The cache
23094 is maintained for the benefit of other programs that access the maildir and
23095 need to know the quota.
23097 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
23098 file is maintained (with a zero quota setting), but no quota is imposed.
23100 A regular expression is available for controlling which directories in the
23101 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
23102 See the description of the &%maildir_quota_directory_regex%& option above for
23106 .section "Mailstore delivery" "SECID137"
23107 .cindex "mailstore format" "description of"
23108 If the &%mailstore_format%& option is true, each message is written as two
23109 files in the given directory. A unique base name is constructed from the
23110 message id and the current delivery process, and the files that are written use
23111 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
23112 contains the message's envelope, and the &_.msg_& file contains the message
23113 itself. The base name is placed in the variable &$mailstore_basename$&.
23115 During delivery, the envelope is first written to a file with the suffix
23116 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
23117 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
23118 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
23119 file before accessing either of them. An alternative approach is to wait for
23120 the absence of a &_.tmp_& file.
23122 The envelope file starts with any text defined by the &%mailstore_prefix%&
23123 option, expanded and terminated by a newline if there isn't one. Then follows
23124 the sender address on one line, then all the recipient addresses, one per line.
23125 There can be more than one recipient only if the &%batch_max%& option is set
23126 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
23127 appended to the file, followed by a newline if it does not end with one.
23129 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
23130 failure, it is ignored. Other expansion errors are treated as serious
23131 configuration errors, and delivery is deferred. The variable
23132 &$mailstore_basename$& is available for use during these expansions.
23135 .section "Non-special new file delivery" "SECID138"
23136 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
23137 file is created directly in the named directory. For example, when delivering
23138 messages into files in batched SMTP format for later delivery to some host (see
23139 section &<<SECTbatchSMTP>>&), a setting such as
23141 directory = /var/bsmtp/$host
23143 might be used. A message is written to a file with a temporary name, which is
23144 then renamed when the delivery is complete. The final name is obtained by
23145 expanding the contents of the &%directory_file%& option.
23146 .ecindex IIDapptra1
23147 .ecindex IIDapptra2
23154 . ////////////////////////////////////////////////////////////////////////////
23155 . ////////////////////////////////////////////////////////////////////////////
23157 .chapter "The autoreply transport" "CHID8"
23158 .scindex IIDauttra1 "transports" "&(autoreply)&"
23159 .scindex IIDauttra2 "&(autoreply)& transport"
23160 The &(autoreply)& transport is not a true transport in that it does not cause
23161 the message to be transmitted. Instead, it generates a new mail message as an
23162 automatic reply to the incoming message. &'References:'& and
23163 &'Auto-Submitted:'& header lines are included. These are constructed according
23164 to the rules in RFCs 2822 and 3834, respectively.
23166 If the router that passes the message to this transport does not have the
23167 &%unseen%& option set, the original message (for the current recipient) is not
23168 delivered anywhere. However, when the &%unseen%& option is set on the router
23169 that passes the message to this transport, routing of the address continues, so
23170 another router can set up a normal message delivery.
23173 The &(autoreply)& transport is usually run as the result of mail filtering, a
23174 &"vacation"& message being the standard example. However, it can also be run
23175 directly from a router like any other transport. To reduce the possibility of
23176 message cascades, messages created by the &(autoreply)& transport always have
23177 empty envelope sender addresses, like bounce messages.
23179 The parameters of the message to be sent can be specified in the configuration
23180 by options described below. However, these are used only when the address
23181 passed to the transport does not contain its own reply information. When the
23182 transport is run as a consequence of a
23184 or &%vacation%& command in a filter file, the parameters of the message are
23185 supplied by the filter, and passed with the address. The transport's options
23186 that define the message are then ignored (so they are not usually set in this
23187 case). The message is specified entirely by the filter or by the transport; it
23188 is never built from a mixture of options. However, the &%file_optional%&,
23189 &%mode%&, and &%return_message%& options apply in all cases.
23191 &(Autoreply)& is implemented as a local transport. When used as a result of a
23192 command in a user's filter file, &(autoreply)& normally runs under the uid and
23193 gid of the user, and with appropriate current and home directories (see chapter
23194 &<<CHAPenvironment>>&).
23196 There is a subtle difference between routing a message to a &(pipe)& transport
23197 that generates some text to be returned to the sender, and routing it to an
23198 &(autoreply)& transport. This difference is noticeable only if more than one
23199 address from the same message is so handled. In the case of a pipe, the
23200 separate outputs from the different addresses are gathered up and returned to
23201 the sender in a single message, whereas if &(autoreply)& is used, a separate
23202 message is generated for each address that is passed to it.
23204 Non-printing characters are not permitted in the header lines generated for the
23205 message that &(autoreply)& creates, with the exception of newlines that are
23206 immediately followed by white space. If any non-printing characters are found,
23207 the transport defers.
23208 Whether characters with the top bit set count as printing characters or not is
23209 controlled by the &%print_topbitchars%& global option.
23211 If any of the generic options for manipulating headers (for example,
23212 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
23213 of the original message that is included in the generated message when
23214 &%return_message%& is set. They do not apply to the generated message itself.
23216 .vindex "&$sender_address$&"
23217 If the &(autoreply)& transport receives return code 2 from Exim when it submits
23218 the message, indicating that there were no recipients, it does not treat this
23219 as an error. This means that autoreplies sent to &$sender_address$& when this
23220 is empty (because the incoming message is a bounce message) do not cause
23221 problems. They are just discarded.
23225 .section "Private options for autoreply" "SECID139"
23226 .cindex "options" "&(autoreply)& transport"
23228 .option bcc autoreply string&!! unset
23229 This specifies the addresses that are to receive &"blind carbon copies"& of the
23230 message when the message is specified by the transport.
23233 .option cc autoreply string&!! unset
23234 This specifies recipients of the message and the contents of the &'Cc:'& header
23235 when the message is specified by the transport.
23238 .option file autoreply string&!! unset
23239 The contents of the file are sent as the body of the message when the message
23240 is specified by the transport. If both &%file%& and &%text%& are set, the text
23241 string comes first.
23244 .option file_expand autoreply boolean false
23245 If this is set, the contents of the file named by the &%file%& option are
23246 subjected to string expansion as they are added to the message.
23249 .option file_optional autoreply boolean false
23250 If this option is true, no error is generated if the file named by the &%file%&
23251 option or passed with the address does not exist or cannot be read.
23254 .option from autoreply string&!! unset
23255 This specifies the contents of the &'From:'& header when the message is
23256 specified by the transport.
23259 .option headers autoreply string&!! unset
23260 This specifies additional RFC 2822 headers that are to be added to the message
23261 when the message is specified by the transport. Several can be given by using
23262 &"\n"& to separate them. There is no check on the format.
23265 .option log autoreply string&!! unset
23266 This option names a file in which a record of every message sent is logged when
23267 the message is specified by the transport.
23270 .option mode autoreply "octal integer" 0600
23271 If either the log file or the &"once"& file has to be created, this mode is
23275 .option never_mail autoreply "address list&!!" unset
23276 If any run of the transport creates a message with a recipient that matches any
23277 item in the list, that recipient is quietly discarded. If all recipients are
23278 discarded, no message is created. This applies both when the recipients are
23279 generated by a filter and when they are specified in the transport.
23283 .option once autoreply string&!! unset
23284 This option names a file or DBM database in which a record of each &'To:'&
23285 recipient is kept when the message is specified by the transport. &*Note*&:
23286 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
23288 If &%once%& is unset, or is set to an empty string, the message is always sent.
23289 By default, if &%once%& is set to a non-empty filename, the message
23290 is not sent if a potential recipient is already listed in the database.
23291 However, if the &%once_repeat%& option specifies a time greater than zero, the
23292 message is sent if that much time has elapsed since a message was last sent to
23293 this recipient. A setting of zero time for &%once_repeat%& (the default)
23294 prevents a message from being sent a second time &-- in this case, zero means
23297 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
23298 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
23299 greater than zero, it changes the way Exim implements the &%once%& option.
23300 Instead of using a DBM file to record every recipient it sends to, it uses a
23301 regular file, whose size will never get larger than the given value.
23303 In the file, Exim keeps a linear list of recipient addresses and the times at
23304 which they were sent messages. If the file is full when a new address needs to
23305 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
23306 means that a given recipient may receive multiple messages, but at
23307 unpredictable intervals that depend on the rate of turnover of addresses in the
23308 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
23311 .option once_file_size autoreply integer 0
23312 See &%once%& above.
23315 .option once_repeat autoreply time&!! 0s
23316 See &%once%& above.
23317 After expansion, the value of this option must be a valid time value.
23320 .option reply_to autoreply string&!! unset
23321 This specifies the contents of the &'Reply-To:'& header when the message is
23322 specified by the transport.
23325 .option return_message autoreply boolean false
23326 If this is set, a copy of the original message is returned with the new
23327 message, subject to the maximum size set in the &%return_size_limit%& global
23328 configuration option.
23331 .option subject autoreply string&!! unset
23332 This specifies the contents of the &'Subject:'& header when the message is
23333 specified by the transport. It is tempting to quote the original subject in
23334 automatic responses. For example:
23336 subject = Re: $h_subject:
23338 There is a danger in doing this, however. It may allow a third party to
23339 subscribe your users to an opt-in mailing list, provided that the list accepts
23340 bounce messages as subscription confirmations. Well-managed lists require a
23341 non-bounce message to confirm a subscription, so the danger is relatively
23346 .option text autoreply string&!! unset
23347 This specifies a single string to be used as the body of the message when the
23348 message is specified by the transport. If both &%text%& and &%file%& are set,
23349 the text comes first.
23352 .option to autoreply string&!! unset
23353 This specifies recipients of the message and the contents of the &'To:'& header
23354 when the message is specified by the transport.
23355 .ecindex IIDauttra1
23356 .ecindex IIDauttra2
23361 . ////////////////////////////////////////////////////////////////////////////
23362 . ////////////////////////////////////////////////////////////////////////////
23364 .chapter "The lmtp transport" "CHAPLMTP"
23365 .cindex "transports" "&(lmtp)&"
23366 .cindex "&(lmtp)& transport"
23367 .cindex "LMTP" "over a pipe"
23368 .cindex "LMTP" "over a socket"
23369 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
23371 or by interacting with a Unix domain socket.
23372 This transport is something of a cross between the &(pipe)& and &(smtp)&
23373 transports. Exim also has support for using LMTP over TCP/IP; this is
23374 implemented as an option for the &(smtp)& transport. Because LMTP is expected
23375 to be of minority interest, the default build-time configure in &_src/EDITME_&
23376 has it commented out. You need to ensure that
23380 .cindex "options" "&(lmtp)& transport"
23381 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
23382 included in the Exim binary. The private options of the &(lmtp)& transport are
23385 .option batch_id lmtp string&!! unset
23386 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23389 .option batch_max lmtp integer 1
23390 This limits the number of addresses that can be handled in a single delivery.
23391 Most LMTP servers can handle several addresses at once, so it is normally a
23392 good idea to increase this value. See the description of local delivery
23393 batching in chapter &<<CHAPbatching>>&.
23396 .option command lmtp string&!! unset
23397 This option must be set if &%socket%& is not set. The string is a command which
23398 is run in a separate process. It is split up into a command name and list of
23399 arguments, each of which is separately expanded (so expansion cannot change the
23400 number of arguments). The command is run directly, not via a shell. The message
23401 is passed to the new process using the standard input and output to operate the
23404 .option ignore_quota lmtp boolean false
23405 .cindex "LMTP" "ignoring quota errors"
23406 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
23407 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
23408 in its response to the LHLO command.
23410 .option socket lmtp string&!! unset
23411 This option must be set if &%command%& is not set. The result of expansion must
23412 be the name of a Unix domain socket. The transport connects to the socket and
23413 delivers the message to it using the LMTP protocol.
23416 .option timeout lmtp time 5m
23417 The transport is aborted if the created process or Unix domain socket does not
23418 respond to LMTP commands or message input within this timeout. Delivery
23419 is deferred, and will be tried again later. Here is an example of a typical
23424 command = /some/local/lmtp/delivery/program
23428 This delivers up to 20 addresses at a time, in a mixture of domains if
23429 necessary, running as the user &'exim'&.
23433 . ////////////////////////////////////////////////////////////////////////////
23434 . ////////////////////////////////////////////////////////////////////////////
23436 .chapter "The pipe transport" "CHAPpipetransport"
23437 .scindex IIDpiptra1 "transports" "&(pipe)&"
23438 .scindex IIDpiptra2 "&(pipe)& transport"
23439 The &(pipe)& transport is used to deliver messages via a pipe to a command
23440 running in another process. One example is the use of &(pipe)& as a
23441 pseudo-remote transport for passing messages to some other delivery mechanism
23442 (such as UUCP). Another is the use by individual users to automatically process
23443 their incoming messages. The &(pipe)& transport can be used in one of the
23447 .vindex "&$local_part$&"
23448 A router routes one address to a transport in the normal way, and the
23449 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
23450 contains the local part of the address (as usual), and the command that is run
23451 is specified by the &%command%& option on the transport.
23453 .vindex "&$pipe_addresses$&"
23454 If the &%batch_max%& option is set greater than 1 (the default is 1), the
23455 transport can handle more than one address in a single run. In this case, when
23456 more than one address is routed to the transport, &$local_part$& is not set
23457 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
23458 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
23459 that are routed to the transport.
23461 .vindex "&$address_pipe$&"
23462 A router redirects an address directly to a pipe command (for example, from an
23463 alias or forward file). In this case, &$address_pipe$& contains the text of the
23464 pipe command, and the &%command%& option on the transport is ignored unless
23465 &%force_command%& is set. If only one address is being transported
23466 (&%batch_max%& is not greater than one, or only one address was redirected to
23467 this pipe command), &$local_part$& contains the local part that was redirected.
23471 The &(pipe)& transport is a non-interactive delivery method. Exim can also
23472 deliver messages over pipes using the LMTP interactive protocol. This is
23473 implemented by the &(lmtp)& transport.
23475 In the case when &(pipe)& is run as a consequence of an entry in a local user's
23476 &_.forward_& file, the command runs under the uid and gid of that user. In
23477 other cases, the uid and gid have to be specified explicitly, either on the
23478 transport or on the router that handles the address. Current and &"home"&
23479 directories are also controllable. See chapter &<<CHAPenvironment>>& for
23480 details of the local delivery environment and chapter &<<CHAPbatching>>&
23481 for a discussion of local delivery batching.
23484 .section "Concurrent delivery" "SECID140"
23485 If two messages arrive at almost the same time, and both are routed to a pipe
23486 delivery, the two pipe transports may be run concurrently. You must ensure that
23487 any pipe commands you set up are robust against this happening. If the commands
23488 write to a file, the &%exim_lock%& utility might be of use.
23489 Alternatively the &%max_parallel%& option could be used with a value
23490 of "1" to enforce serialization.
23495 .section "Returned status and data" "SECID141"
23496 .cindex "&(pipe)& transport" "returned data"
23497 If the command exits with a non-zero return code, the delivery is deemed to
23498 have failed, unless either the &%ignore_status%& option is set (in which case
23499 the return code is treated as zero), or the return code is one of those listed
23500 in the &%temp_errors%& option, which are interpreted as meaning &"try again
23501 later"&. In this case, delivery is deferred. Details of a permanent failure are
23502 logged, but are not included in the bounce message, which merely contains
23503 &"local delivery failed"&.
23505 If the command exits on a signal and the &%freeze_signal%& option is set then
23506 the message will be frozen in the queue. If that option is not set, a bounce
23507 will be sent as normal.
23509 If the return code is greater than 128 and the command being run is a shell
23510 script, it normally means that the script was terminated by a signal whose
23511 value is the return code minus 128. The &%freeze_signal%& option does not
23512 apply in this case.
23514 If Exim is unable to run the command (that is, if &[execve()]& fails), the
23515 return code is set to 127. This is the value that a shell returns if it is
23516 asked to run a non-existent command. The wording for the log line suggests that
23517 a non-existent command may be the problem.
23519 The &%return_output%& option can affect the result of a pipe delivery. If it is
23520 set and the command produces any output on its standard output or standard
23521 error streams, the command is considered to have failed, even if it gave a zero
23522 return code or if &%ignore_status%& is set. The output from the command is
23523 included as part of the bounce message. The &%return_fail_output%& option is
23524 similar, except that output is returned only when the command exits with a
23525 failure return code, that is, a value other than zero or a code that matches
23530 .section "How the command is run" "SECThowcommandrun"
23531 .cindex "&(pipe)& transport" "path for command"
23532 The command line is (by default) broken down into a command name and arguments
23533 by the &(pipe)& transport itself. The &%allow_commands%& and
23534 &%restrict_to_path%& options can be used to restrict the commands that may be
23537 .cindex "quoting" "in pipe command"
23538 Unquoted arguments are delimited by white space. If an argument appears in
23539 double quotes, backslash is interpreted as an escape character in the usual
23540 way. If an argument appears in single quotes, no escaping is done.
23542 String expansion is applied to the command line except when it comes from a
23543 traditional &_.forward_& file (commands from a filter file are expanded). The
23544 expansion is applied to each argument in turn rather than to the whole line.
23545 For this reason, any string expansion item that contains white space must be
23546 quoted so as to be contained within a single argument. A setting such as
23548 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
23550 will not work, because the expansion item gets split between several
23551 arguments. You have to write
23553 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
23555 to ensure that it is all in one argument. The expansion is done in this way,
23556 argument by argument, so that the number of arguments cannot be changed as a
23557 result of expansion, and quotes or backslashes in inserted variables do not
23558 interact with external quoting. However, this leads to problems if you want to
23559 generate multiple arguments (or the command name plus arguments) from a single
23560 expansion. In this situation, the simplest solution is to use a shell. For
23563 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
23566 .cindex "transport" "filter"
23567 .cindex "filter" "transport filter"
23568 .vindex "&$pipe_addresses$&"
23569 Special handling takes place when an argument consists of precisely the text
23570 &`$pipe_addresses`& (no quotes).
23571 This is not a general expansion variable; the only
23572 place this string is recognized is when it appears as an argument for a pipe or
23573 transport filter command. It causes each address that is being handled to be
23574 inserted in the argument list at that point &'as a separate argument'&. This
23575 avoids any problems with spaces or shell metacharacters, and is of use when a
23576 &(pipe)& transport is handling groups of addresses in a batch.
23578 If &%force_command%& is enabled on the transport, Special handling takes place
23579 for an argument that consists of precisely the text &`$address_pipe`&. It
23580 is handled similarly to &$pipe_addresses$& above. It is expanded and each
23581 argument is inserted in the argument list at that point
23582 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
23583 the only item in the argument; in fact, if it were then &%force_command%&
23584 should behave as a no-op. Rather, it should be used to adjust the command
23585 run while preserving the argument vector separation.
23587 After splitting up into arguments and expansion, the resulting command is run
23588 in a subprocess directly from the transport, &'not'& under a shell. The
23589 message that is being delivered is supplied on the standard input, and the
23590 standard output and standard error are both connected to a single pipe that is
23591 read by Exim. The &%max_output%& option controls how much output the command
23592 may produce, and the &%return_output%& and &%return_fail_output%& options
23593 control what is done with it.
23595 Not running the command under a shell (by default) lessens the security risks
23596 in cases when a command from a user's filter file is built out of data that was
23597 taken from an incoming message. If a shell is required, it can of course be
23598 explicitly specified as the command to be run. However, there are circumstances
23599 where existing commands (for example, in &_.forward_& files) expect to be run
23600 under a shell and cannot easily be modified. To allow for these cases, there is
23601 an option called &%use_shell%&, which changes the way the &(pipe)& transport
23602 works. Instead of breaking up the command line as just described, it expands it
23603 as a single string and passes the result to &_/bin/sh_&. The
23604 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
23605 with &%use_shell%&, and the whole mechanism is inherently less secure.
23609 .section "Environment variables" "SECTpipeenv"
23610 .cindex "&(pipe)& transport" "environment for command"
23611 .cindex "environment" "&(pipe)& transport"
23612 The environment variables listed below are set up when the command is invoked.
23613 This list is a compromise for maximum compatibility with other MTAs. Note that
23614 the &%environment%& option can be used to add additional variables to this
23615 environment. The environment for the &(pipe)& transport is not subject
23616 to the &%add_environment%& and &%keep_environment%& main config options.
23618 &`DOMAIN `& the domain of the address
23619 &`HOME `& the home directory, if set
23620 &`HOST `& the host name when called from a router (see below)
23621 &`LOCAL_PART `& see below
23622 &`LOCAL_PART_PREFIX `& see below
23623 &`LOCAL_PART_SUFFIX `& see below
23624 &`LOGNAME `& see below
23625 &`MESSAGE_ID `& Exim's local ID for the message
23626 &`PATH `& as specified by the &%path%& option below
23627 &`QUALIFY_DOMAIN `& the sender qualification domain
23628 &`RECIPIENT `& the complete recipient address
23629 &`SENDER `& the sender of the message (empty if a bounce)
23630 &`SHELL `& &`/bin/sh`&
23631 &`TZ `& the value of the &%timezone%& option, if set
23632 &`USER `& see below
23634 When a &(pipe)& transport is called directly from (for example) an &(accept)&
23635 router, LOCAL_PART is set to the local part of the address. When it is
23636 called as a result of a forward or alias expansion, LOCAL_PART is set to
23637 the local part of the address that was expanded. In both cases, any affixes are
23638 removed from the local part, and made available in LOCAL_PART_PREFIX and
23639 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
23640 same value as LOCAL_PART for compatibility with other MTAs.
23643 HOST is set only when a &(pipe)& transport is called from a router that
23644 associates hosts with an address, typically when using &(pipe)& as a
23645 pseudo-remote transport. HOST is set to the first host name specified by
23649 If the transport's generic &%home_directory%& option is set, its value is used
23650 for the HOME environment variable. Otherwise, a home directory may be set
23651 by the router's &%transport_home_directory%& option, which defaults to the
23652 user's home directory if &%check_local_user%& is set.
23655 .section "Private options for pipe" "SECID142"
23656 .cindex "options" "&(pipe)& transport"
23660 .option allow_commands pipe "string list&!!" unset
23661 .cindex "&(pipe)& transport" "permitted commands"
23662 The string is expanded, and is then interpreted as a colon-separated list of
23663 permitted commands. If &%restrict_to_path%& is not set, the only commands
23664 permitted are those in the &%allow_commands%& list. They need not be absolute
23665 paths; the &%path%& option is still used for relative paths. If
23666 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
23667 in the &%allow_commands%& list, or a name without any slashes that is found on
23668 the path. In other words, if neither &%allow_commands%& nor
23669 &%restrict_to_path%& is set, there is no restriction on the command, but
23670 otherwise only commands that are permitted by one or the other are allowed. For
23673 allow_commands = /usr/bin/vacation
23675 and &%restrict_to_path%& is not set, the only permitted command is
23676 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
23677 &%use_shell%& is set.
23680 .option batch_id pipe string&!! unset
23681 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23684 .option batch_max pipe integer 1
23685 This limits the number of addresses that can be handled in a single delivery.
23686 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23689 .option check_string pipe string unset
23690 As &(pipe)& writes the message, the start of each line is tested for matching
23691 &%check_string%&, and if it does, the initial matching characters are replaced
23692 by the contents of &%escape_string%&, provided both are set. The value of
23693 &%check_string%& is a literal string, not a regular expression, and the case of
23694 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
23695 of &%check_string%& and &%escape_string%& are forced to values that implement
23696 the SMTP escaping protocol. Any settings made in the configuration file are
23700 .option command pipe string&!! unset
23701 This option need not be set when &(pipe)& is being used to deliver to pipes
23702 obtained directly from address redirections. In other cases, the option must be
23703 set, to provide a command to be run. It need not yield an absolute path (see
23704 the &%path%& option below). The command is split up into separate arguments by
23705 Exim, and each argument is separately expanded, as described in section
23706 &<<SECThowcommandrun>>& above.
23709 .option environment pipe string&!! unset
23710 .cindex "&(pipe)& transport" "environment for command"
23711 .cindex "environment" "&(pipe)& transport"
23712 This option is used to add additional variables to the environment in which the
23713 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
23714 a string which is expanded, and then interpreted as a colon-separated list of
23715 environment settings of the form <&'name'&>=<&'value'&>.
23718 .option escape_string pipe string unset
23719 See &%check_string%& above.
23722 .option freeze_exec_fail pipe boolean false
23723 .cindex "exec failure"
23724 .cindex "failure of exec"
23725 .cindex "&(pipe)& transport" "failure of exec"
23726 Failure to exec the command in a pipe transport is by default treated like
23727 any other failure while running the command. However, if &%freeze_exec_fail%&
23728 is set, failure to exec is treated specially, and causes the message to be
23729 frozen, whatever the setting of &%ignore_status%&.
23732 .option freeze_signal pipe boolean false
23733 .cindex "signal exit"
23734 .cindex "&(pipe)& transport", "signal exit"
23735 Normally if the process run by a command in a pipe transport exits on a signal,
23736 a bounce message is sent. If &%freeze_signal%& is set, the message will be
23737 frozen in Exim's queue instead.
23740 .option force_command pipe boolean false
23741 .cindex "force command"
23742 .cindex "&(pipe)& transport", "force command"
23743 Normally when a router redirects an address directly to a pipe command
23744 the &%command%& option on the transport is ignored. If &%force_command%&
23745 is set, the &%command%& option will used. This is especially
23746 useful for forcing a wrapper or additional argument to be added to the
23747 command. For example:
23749 command = /usr/bin/remote_exec myhost -- $address_pipe
23753 Note that &$address_pipe$& is handled specially in &%command%& when
23754 &%force_command%& is set, expanding out to the original argument vector as
23755 separate items, similarly to a Unix shell &`"$@"`& construct.
23758 .option ignore_status pipe boolean false
23759 If this option is true, the status returned by the subprocess that is set up to
23760 run the command is ignored, and Exim behaves as if zero had been returned.
23761 Otherwise, a non-zero status or termination by signal causes an error return
23762 from the transport unless the status value is one of those listed in
23763 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
23765 &*Note*&: This option does not apply to timeouts, which do not return a status.
23766 See the &%timeout_defer%& option for how timeouts are handled.
23769 .option log_defer_output pipe boolean false
23770 .cindex "&(pipe)& transport" "logging output"
23771 If this option is set, and the status returned by the command is
23772 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
23773 and any output was produced on stdout or stderr, the first line of it is
23774 written to the main log.
23777 .option log_fail_output pipe boolean false
23778 If this option is set, and the command returns any output on stdout or
23779 stderr, and also ends with a return code that is neither zero nor one of
23780 the return codes listed in &%temp_errors%& (that is, the delivery
23781 failed), the first line of output is written to the main log. This
23782 option and &%log_output%& are mutually exclusive. Only one of them may
23786 .option log_output pipe boolean false
23787 If this option is set and the command returns any output on stdout or
23788 stderr, the first line of output is written to the main log, whatever
23789 the return code. This option and &%log_fail_output%& are mutually
23790 exclusive. Only one of them may be set.
23793 .option max_output pipe integer 20K
23794 This specifies the maximum amount of output that the command may produce on its
23795 standard output and standard error file combined. If the limit is exceeded, the
23796 process running the command is killed. This is intended as a safety measure to
23797 catch runaway processes. The limit is applied independently of the settings of
23798 the options that control what is done with such output (for example,
23799 &%return_output%&). Because of buffering effects, the amount of output may
23800 exceed the limit by a small amount before Exim notices.
23803 .option message_prefix pipe string&!! "see below"
23804 The string specified here is expanded and output at the start of every message.
23805 The default is unset if &%use_bsmtp%& is set. Otherwise it is
23808 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
23812 .cindex "&%tmail%&"
23813 .cindex "&""From""& line"
23814 This is required by the commonly used &_/usr/bin/vacation_& program.
23815 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
23816 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
23821 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23822 &`\n`& to &`\r\n`& in &%message_prefix%&.
23825 .option message_suffix pipe string&!! "see below"
23826 The string specified here is expanded and output at the end of every message.
23827 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
23828 The suffix can be suppressed by setting
23832 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23833 &`\n`& to &`\r\n`& in &%message_suffix%&.
23836 .option path pipe string&!! "/bin:/usr/bin"
23837 This option is expanded and
23838 specifies the string that is set up in the PATH environment
23839 variable of the subprocess.
23840 If the &%command%& option does not yield an absolute path name, the command is
23841 sought in the PATH directories, in the usual way. &*Warning*&: This does not
23842 apply to a command specified as a transport filter.
23845 .option permit_coredump pipe boolean false
23846 Normally Exim inhibits core-dumps during delivery. If you have a need to get
23847 a core-dump of a pipe command, enable this command. This enables core-dumps
23848 during delivery and affects both the Exim binary and the pipe command run.
23849 It is recommended that this option remain off unless and until you have a need
23850 for it and that this only be enabled when needed, as the risk of excessive
23851 resource consumption can be quite high. Note also that Exim is typically
23852 installed as a setuid binary and most operating systems will inhibit coredumps
23853 of these by default, so further OS-specific action may be required.
23856 .option pipe_as_creator pipe boolean false
23857 .cindex "uid (user id)" "local delivery"
23858 If the generic &%user%& option is not set and this option is true, the delivery
23859 process is run under the uid that was in force when Exim was originally called
23860 to accept the message. If the group id is not otherwise set (via the generic
23861 &%group%& option), the gid that was in force when Exim was originally called to
23862 accept the message is used.
23865 .option restrict_to_path pipe boolean false
23866 When this option is set, any command name not listed in &%allow_commands%& must
23867 contain no slashes. The command is searched for only in the directories listed
23868 in the &%path%& option. This option is intended for use in the case when a pipe
23869 command has been generated from a user's &_.forward_& file. This is usually
23870 handled by a &(pipe)& transport called &%address_pipe%&.
23873 .option return_fail_output pipe boolean false
23874 If this option is true, and the command produced any output and ended with a
23875 return code other than zero or one of the codes listed in &%temp_errors%& (that
23876 is, the delivery failed), the output is returned in the bounce message.
23877 However, if the message has a null sender (that is, it is itself a bounce
23878 message), output from the command is discarded. This option and
23879 &%return_output%& are mutually exclusive. Only one of them may be set.
23883 .option return_output pipe boolean false
23884 If this option is true, and the command produced any output, the delivery is
23885 deemed to have failed whatever the return code from the command, and the output
23886 is returned in the bounce message. Otherwise, the output is just discarded.
23887 However, if the message has a null sender (that is, it is a bounce message),
23888 output from the command is always discarded, whatever the setting of this
23889 option. This option and &%return_fail_output%& are mutually exclusive. Only one
23890 of them may be set.
23894 .option temp_errors pipe "string list" "see below"
23895 .cindex "&(pipe)& transport" "temporary failure"
23896 This option contains either a colon-separated list of numbers, or a single
23897 asterisk. If &%ignore_status%& is false
23898 and &%return_output%& is not set,
23899 and the command exits with a non-zero return code, the failure is treated as
23900 temporary and the delivery is deferred if the return code matches one of the
23901 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
23902 codes are treated as permanent errors. The default setting contains the codes
23903 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
23904 compiled on a system that does not define these macros, it assumes values of 75
23905 and 73, respectively.
23908 .option timeout pipe time 1h
23909 If the command fails to complete within this time, it is killed. This normally
23910 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
23911 specifies no timeout. In order to ensure that any subprocesses created by the
23912 command are also killed, Exim makes the initial process a process group leader,
23913 and kills the whole process group on a timeout. However, this can be defeated
23914 if one of the processes starts a new process group.
23916 .option timeout_defer pipe boolean false
23917 A timeout in a &(pipe)& transport, either in the command that the transport
23918 runs, or in a transport filter that is associated with it, is by default
23919 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
23920 is set true, both kinds of timeout become temporary errors, causing the
23921 delivery to be deferred.
23923 .option umask pipe "octal integer" 022
23924 This specifies the umask setting for the subprocess that runs the command.
23927 .option use_bsmtp pipe boolean false
23928 .cindex "envelope sender"
23929 If this option is set true, the &(pipe)& transport writes messages in &"batch
23930 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
23931 commands. If you want to include a leading HELO command with such messages,
23932 you can do so by setting the &%message_prefix%& option. See section
23933 &<<SECTbatchSMTP>>& for details of batch SMTP.
23935 .option use_classresources pipe boolean false
23936 .cindex "class resources (BSD)"
23937 This option is available only when Exim is running on FreeBSD, NetBSD, or
23938 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
23939 resource limits when a &(pipe)& transport is run to perform a delivery. The
23940 limits for the uid under which the pipe is to run are obtained from the login
23944 .option use_crlf pipe boolean false
23945 .cindex "carriage return"
23947 This option causes lines to be terminated with the two-character CRLF sequence
23948 (carriage return, linefeed) instead of just a linefeed character. In the case
23949 of batched SMTP, the byte sequence written to the pipe is then an exact image
23950 of what would be sent down a real SMTP connection.
23952 The contents of the &%message_prefix%& and &%message_suffix%& options are
23953 written verbatim, so must contain their own carriage return characters if these
23954 are needed. When &%use_bsmtp%& is not set, the default values for both
23955 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
23956 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
23959 .option use_shell pipe boolean false
23960 .vindex "&$pipe_addresses$&"
23961 If this option is set, it causes the command to be passed to &_/bin/sh_&
23962 instead of being run directly from the transport, as described in section
23963 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
23964 where the command is expected to be run under a shell and cannot easily be
23965 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
23966 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
23967 command is expanded as a single string, and handed to &_/bin/sh_& as data for
23972 .section "Using an external local delivery agent" "SECID143"
23973 .cindex "local delivery" "using an external agent"
23974 .cindex "&'procmail'&"
23975 .cindex "external local delivery"
23976 .cindex "delivery" "&'procmail'&"
23977 .cindex "delivery" "by external agent"
23978 The &(pipe)& transport can be used to pass all messages that require local
23979 delivery to a separate local delivery agent such as &%procmail%&. When doing
23980 this, care must be taken to ensure that the pipe is run under an appropriate
23981 uid and gid. In some configurations one wants this to be a uid that is trusted
23982 by the delivery agent to supply the correct sender of the message. It may be
23983 necessary to recompile or reconfigure the delivery agent so that it trusts an
23984 appropriate user. The following is an example transport and router
23985 configuration for &%procmail%&:
23990 command = /usr/local/bin/procmail -d $local_part
23994 check_string = "From "
23995 escape_string = ">From "
24004 transport = procmail_pipe
24006 In this example, the pipe is run as the local user, but with the group set to
24007 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
24008 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
24009 user to supply a correct sender address. If you do not specify either a
24010 &%group%& or a &%user%& option, the pipe command is run as the local user. The
24011 home directory is the user's home directory by default.
24013 &*Note*&: The command that the pipe transport runs does &'not'& begin with
24017 as shown in some &%procmail%& documentation, because Exim does not by default
24018 use a shell to run pipe commands.
24021 The next example shows a transport and a router for a system where local
24022 deliveries are handled by the Cyrus IMAP server.
24025 local_delivery_cyrus:
24027 command = /usr/cyrus/bin/deliver \
24028 -m ${substr_1:$local_part_suffix} -- $local_part
24040 local_part_suffix = .*
24041 transport = local_delivery_cyrus
24043 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
24044 &%return_output%& to cause any text written by Cyrus to be returned to the
24046 .ecindex IIDpiptra1
24047 .ecindex IIDpiptra2
24050 . ////////////////////////////////////////////////////////////////////////////
24051 . ////////////////////////////////////////////////////////////////////////////
24053 .chapter "The smtp transport" "CHAPsmtptrans"
24054 .scindex IIDsmttra1 "transports" "&(smtp)&"
24055 .scindex IIDsmttra2 "&(smtp)& transport"
24056 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
24057 or LMTP protocol. The list of hosts to try can either be taken from the address
24058 that is being processed (having been set up by the router), or specified
24059 explicitly for the transport. Timeout and retry processing (see chapter
24060 &<<CHAPretry>>&) is applied to each IP address independently.
24063 .section "Multiple messages on a single connection" "SECID144"
24064 The sending of multiple messages over a single TCP/IP connection can arise in
24068 If a message contains more than &%max_rcpt%& (see below) addresses that are
24069 routed to the same host, more than one copy of the message has to be sent to
24070 that host. In this situation, multiple copies may be sent in a single run of
24071 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
24072 does when it has too many addresses to send in one message also depends on the
24073 value of the global &%remote_max_parallel%& option. Details are given in
24074 section &<<SECToutSMTPTCP>>&.)
24076 .cindex "hints database" "remembering routing"
24077 When a message has been successfully delivered over a TCP/IP connection, Exim
24078 looks in its hints database to see if there are any other messages awaiting a
24079 connection to the same host. If there are, a new delivery process is started
24080 for one of them, and the current TCP/IP connection is passed on to it. The new
24081 process may in turn send multiple copies and possibly create yet another
24086 For each copy sent over the same TCP/IP connection, a sequence counter is
24087 incremented, and if it ever gets to the value of &%connection_max_messages%&,
24088 no further messages are sent over that connection.
24092 .section "Use of the $host and $host_address variables" "SECID145"
24094 .vindex "&$host_address$&"
24095 At the start of a run of the &(smtp)& transport, the values of &$host$& and
24096 &$host_address$& are the name and IP address of the first host on the host list
24097 passed by the router. However, when the transport is about to connect to a
24098 specific host, and while it is connected to that host, &$host$& and
24099 &$host_address$& are set to the values for that host. These are the values
24100 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
24101 &%serialize_hosts%&, and the various TLS options are expanded.
24104 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
24105 .vindex &$tls_bits$&
24106 .vindex &$tls_cipher$&
24107 .vindex &$tls_peerdn$&
24108 .vindex &$tls_sni$&
24109 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
24110 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
24111 are the values that were set when the message was received.
24112 These are the values that are used for options that are expanded before any
24113 SMTP connections are made. Just before each connection is made, these four
24114 variables are emptied. If TLS is subsequently started, they are set to the
24115 appropriate values for the outgoing connection, and these are the values that
24116 are in force when any authenticators are run and when the
24117 &%authenticated_sender%& option is expanded.
24119 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
24120 and will be removed in a future release.
24123 .section "Private options for smtp" "SECID146"
24124 .cindex "options" "&(smtp)& transport"
24125 The private options of the &(smtp)& transport are as follows:
24128 .option address_retry_include_sender smtp boolean true
24129 .cindex "4&'xx'& responses" "retrying after"
24130 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
24131 is the combination of sender and recipient that is delayed in subsequent queue
24132 runs until the retry time is reached. You can delay the recipient without
24133 reference to the sender (which is what earlier versions of Exim did), by
24134 setting &%address_retry_include_sender%& false. However, this can lead to
24135 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
24137 .option allow_localhost smtp boolean false
24138 .cindex "local host" "sending to"
24139 .cindex "fallback" "hosts specified on transport"
24140 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
24141 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
24142 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
24143 the delivery anyway. This should be used only in special cases when the
24144 configuration ensures that no looping will result (for example, a differently
24145 configured Exim is listening on the port to which the message is sent).
24148 .option authenticated_sender smtp string&!! unset
24150 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
24151 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
24152 overriding any existing authenticated sender value. If the string expansion is
24153 forced to fail, the option is ignored. Other expansion failures cause delivery
24154 to be deferred. If the result of expansion is an empty string, that is also
24157 The expansion happens after the outgoing connection has been made and TLS
24158 started, if required. This means that the &$host$&, &$host_address$&,
24159 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
24160 particular connection.
24162 If the SMTP session is not authenticated, the expansion of
24163 &%authenticated_sender%& still happens (and can cause the delivery to be
24164 deferred if it fails), but no AUTH= item is added to MAIL commands
24165 unless &%authenticated_sender_force%& is true.
24167 This option allows you to use the &(smtp)& transport in LMTP mode to
24168 deliver mail to Cyrus IMAP and provide the proper local part as the
24169 &"authenticated sender"&, via a setting such as:
24171 authenticated_sender = $local_part
24173 This removes the need for IMAP subfolders to be assigned special ACLs to
24174 allow direct delivery to those subfolders.
24176 Because of expected uses such as that just described for Cyrus (when no
24177 domain is involved), there is no checking on the syntax of the provided
24181 .option authenticated_sender_force smtp boolean false
24182 If this option is set true, the &%authenticated_sender%& option's value
24183 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
24184 authenticated as a client.
24187 .option command_timeout smtp time 5m
24188 This sets a timeout for receiving a response to an SMTP command that has been
24189 sent out. It is also used when waiting for the initial banner line from the
24190 remote host. Its value must not be zero.
24193 .option connect_timeout smtp time 5m
24194 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
24195 to a remote host. A setting of zero allows the system timeout (typically
24196 several minutes) to act. To have any effect, the value of this option must be
24197 less than the system timeout. However, it has been observed that on some
24198 systems there is no system timeout, which is why the default value for this
24199 option is 5 minutes, a value recommended by RFC 1123.
24202 .option connection_max_messages smtp integer 500
24203 .cindex "SMTP" "passed connection"
24204 .cindex "SMTP" "multiple deliveries"
24205 .cindex "multiple SMTP deliveries"
24206 This controls the maximum number of separate message deliveries that are sent
24207 over a single TCP/IP connection. If the value is zero, there is no limit.
24208 For testing purposes, this value can be overridden by the &%-oB%& command line
24212 .option dane_require_tls_ciphers smtp string&!! unset
24213 .cindex "TLS" "requiring specific ciphers for DANE"
24214 .cindex "cipher" "requiring specific"
24215 .cindex DANE "TLS ciphers"
24216 This option may be used to override &%tls_require_ciphers%& for connections
24217 where DANE has been determined to be in effect.
24218 If not set, then &%tls_require_ciphers%& will be used.
24219 Normal SMTP delivery is not able to make strong demands of TLS cipher
24220 configuration, because delivery will fall back to plaintext. Once DANE has
24221 been determined to be in effect, there is no plaintext fallback and making the
24222 TLS cipherlist configuration stronger will increase security, rather than
24223 counter-intuitively decreasing it.
24224 If the option expands to be empty or is forced to fail, then it will
24225 be treated as unset and &%tls_require_ciphers%& will be used instead.
24228 .option data_timeout smtp time 5m
24229 This sets a timeout for the transmission of each block in the data portion of
24230 the message. As a result, the overall timeout for a message depends on the size
24231 of the message. Its value must not be zero. See also &%final_timeout%&.
24234 .option dkim_canon smtp string&!! unset
24235 .option dkim_domain smtp string list&!! unset
24236 .option dkim_hash smtp string&!! sha256
24237 .option dkim_identity smtp string&!! unset
24238 .option dkim_private_key smtp string&!! unset
24239 .option dkim_selector smtp string&!! unset
24240 .option dkim_strict smtp string&!! unset
24241 .option dkim_sign_headers smtp string&!! "per RFC"
24242 .option dkim_timestamps smtp string&!! unset
24243 DKIM signing options. For details see section &<<SECDKIMSIGN>>&.
24246 .option delay_after_cutoff smtp boolean true
24247 .cindex "final cutoff" "retries, controlling"
24248 .cindex retry "final cutoff"
24249 This option controls what happens when all remote IP addresses for a given
24250 domain have been inaccessible for so long that they have passed their retry
24253 In the default state, if the next retry time has not been reached for any of
24254 them, the address is bounced without trying any deliveries. In other words,
24255 Exim delays retrying an IP address after the final cutoff time until a new
24256 retry time is reached, and can therefore bounce an address without ever trying
24257 a delivery, when machines have been down for a long time. Some people are
24258 unhappy at this prospect, so...
24260 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
24261 addresses are past their final cutoff time, Exim tries to deliver to those
24262 IP addresses that have not been tried since the message arrived. If there are
24263 none, of if they all fail, the address is bounced. In other words, it does not
24264 delay when a new message arrives, but immediately tries those expired IP
24265 addresses that haven't been tried since the message arrived. If there is a
24266 continuous stream of messages for the dead hosts, unsetting
24267 &%delay_after_cutoff%& means that there will be many more attempts to deliver
24271 .option dns_qualify_single smtp boolean true
24272 If the &%hosts%& or &%fallback_hosts%& option is being used,
24273 and the &%gethostbyname%& option is false,
24274 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
24275 in chapter &<<CHAPdnslookup>>& for more details.
24278 .option dns_search_parents smtp boolean false
24279 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
24280 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
24281 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
24285 .option dnssec_request_domains smtp "domain list&!!" unset
24286 .cindex "MX record" "security"
24287 .cindex "DNSSEC" "MX lookup"
24288 .cindex "security" "MX lookup"
24289 .cindex "DNS" "DNSSEC"
24290 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
24291 the dnssec request bit set.
24292 This applies to all of the SRV, MX, AAAA, A lookup sequence.
24296 .option dnssec_require_domains smtp "domain list&!!" unset
24297 .cindex "MX record" "security"
24298 .cindex "DNSSEC" "MX lookup"
24299 .cindex "security" "MX lookup"
24300 .cindex "DNS" "DNSSEC"
24301 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
24302 the dnssec request bit set. Any returns not having the Authenticated Data bit
24303 (AD bit) set will be ignored and logged as a host-lookup failure.
24304 This applies to all of the SRV, MX, AAAA, A lookup sequence.
24308 .option dscp smtp string&!! unset
24309 .cindex "DCSP" "outbound"
24310 This option causes the DSCP value associated with a socket to be set to one
24311 of a number of fixed strings or to numeric value.
24312 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
24313 Common values include &`throughput`&, &`mincost`&, and on newer systems
24314 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
24316 The outbound packets from Exim will be marked with this value in the header
24317 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
24318 that these values will have any effect, not be stripped by networking
24319 equipment, or do much of anything without cooperation with your Network
24320 Engineer and those of all network operators between the source and destination.
24323 .option fallback_hosts smtp "string list" unset
24324 .cindex "fallback" "hosts specified on transport"
24325 String expansion is not applied to this option. The argument must be a
24326 colon-separated list of host names or IP addresses, optionally also including
24327 port numbers, though the separator can be changed, as described in section
24328 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
24329 item in a &%route_list%& setting for the &(manualroute)& router, as described
24330 in section &<<SECTformatonehostitem>>&.
24332 Fallback hosts can also be specified on routers, which associate them with the
24333 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
24334 &%fallback_hosts%& specified on the transport is used only if the address does
24335 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
24336 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
24337 However, &%hosts_randomize%& does apply to fallback host lists.
24339 If Exim is unable to deliver to any of the hosts for a particular address, and
24340 the errors are not permanent rejections, the address is put on a separate
24341 transport queue with its host list replaced by the fallback hosts, unless the
24342 address was routed via MX records and the current host was in the original MX
24343 list. In that situation, the fallback host list is not used.
24345 Once normal deliveries are complete, the fallback queue is delivered by
24346 re-running the same transports with the new host lists. If several failing
24347 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
24348 copy of the message is sent.
24350 The resolution of the host names on the fallback list is controlled by the
24351 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
24352 both to cases when the host list comes with the address and when it is taken
24353 from &%hosts%&. This option provides a &"use a smart host only if delivery
24357 .option final_timeout smtp time 10m
24358 This is the timeout that applies while waiting for the response to the final
24359 line containing just &"."& that terminates a message. Its value must not be
24362 .option gethostbyname smtp boolean false
24363 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
24364 being used, names are looked up using &[gethostbyname()]&
24365 (or &[getipnodebyname()]& when available)
24366 instead of using the DNS. Of course, that function may in fact use the DNS, but
24367 it may also consult other sources of information such as &_/etc/hosts_&.
24369 .option gnutls_compat_mode smtp boolean unset
24370 This option controls whether GnuTLS is used in compatibility mode in an Exim
24371 server. This reduces security slightly, but improves interworking with older
24372 implementations of TLS.
24374 .option helo_data smtp string&!! "see below"
24375 .cindex "HELO" "argument, setting"
24376 .cindex "EHLO" "argument, setting"
24377 .cindex "LHLO argument setting"
24378 The value of this option is expanded after a connection to a another host has
24379 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
24380 command that starts the outgoing SMTP or LMTP session. The default value of the
24385 During the expansion, the variables &$host$& and &$host_address$& are set to
24386 the identity of the remote host, and the variables &$sending_ip_address$& and
24387 &$sending_port$& are set to the local IP address and port number that are being
24388 used. These variables can be used to generate different values for different
24389 servers or different local IP addresses. For example, if you want the string
24390 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
24391 interface address, you could use this:
24393 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
24394 {$primary_hostname}}
24396 The use of &%helo_data%& applies both to sending messages and when doing
24399 .option hosts smtp "string list&!!" unset
24400 Hosts are associated with an address by a router such as &(dnslookup)&, which
24401 finds the hosts by looking up the address domain in the DNS, or by
24402 &(manualroute)&, which has lists of hosts in its configuration. However,
24403 email addresses can be passed to the &(smtp)& transport by any router, and not
24404 all of them can provide an associated list of hosts.
24406 The &%hosts%& option specifies a list of hosts to be used if the address being
24407 processed does not have any hosts associated with it. The hosts specified by
24408 &%hosts%& are also used, whether or not the address has its own hosts, if
24409 &%hosts_override%& is set.
24411 The string is first expanded, before being interpreted as a colon-separated
24412 list of host names or IP addresses, possibly including port numbers. The
24413 separator may be changed to something other than colon, as described in section
24414 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
24415 item in a &%route_list%& setting for the &(manualroute)& router, as described
24416 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
24417 of the &(manualroute)& router is not available here.
24419 If the expansion fails, delivery is deferred. Unless the failure was caused by
24420 the inability to complete a lookup, the error is logged to the panic log as
24421 well as the main log. Host names are looked up either by searching directly for
24422 address records in the DNS or by calling &[gethostbyname()]& (or
24423 &[getipnodebyname()]& when available), depending on the setting of the
24424 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
24425 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
24428 During delivery, the hosts are tried in order, subject to their retry status,
24429 unless &%hosts_randomize%& is set.
24432 .option hosts_avoid_esmtp smtp "host list&!!" unset
24433 .cindex "ESMTP, avoiding use of"
24434 .cindex "HELO" "forcing use of"
24435 .cindex "EHLO" "avoiding use of"
24436 .cindex "PIPELINING" "avoiding the use of"
24437 This option is for use with broken hosts that announce ESMTP facilities (for
24438 example, PIPELINING) and then fail to implement them properly. When a host
24439 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
24440 start of the SMTP session. This means that it cannot use any of the ESMTP
24441 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
24444 .option hosts_avoid_pipelining smtp "host list&!!" unset
24445 .cindex "PIPELINING" "avoiding the use of"
24446 Exim will not use the SMTP PIPELINING extension when delivering to any host
24447 that matches this list, even if the server host advertises PIPELINING support.
24450 .option hosts_avoid_tls smtp "host list&!!" unset
24451 .cindex "TLS" "avoiding for certain hosts"
24452 Exim will not try to start a TLS session when delivering to any host that
24453 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
24455 .option hosts_verify_avoid_tls smtp "host list&!!" unset
24456 .cindex "TLS" "avoiding for certain hosts"
24457 Exim will not try to start a TLS session for a verify callout,
24458 or when delivering in cutthrough mode,
24459 to any host that matches this list.
24462 .option hosts_max_try smtp integer 5
24463 .cindex "host" "maximum number to try"
24464 .cindex "limit" "number of hosts tried"
24465 .cindex "limit" "number of MX tried"
24466 .cindex "MX record" "maximum tried"
24467 This option limits the number of IP addresses that are tried for any one
24468 delivery in cases where there are temporary delivery errors. Section
24469 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
24472 .option hosts_max_try_hardlimit smtp integer 50
24473 This is an additional check on the maximum number of IP addresses that Exim
24474 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
24479 .option hosts_nopass_tls smtp "host list&!!" unset
24480 .cindex "TLS" "passing connection"
24481 .cindex "multiple SMTP deliveries"
24482 .cindex "TLS" "multiple message deliveries"
24483 For any host that matches this list, a connection on which a TLS session has
24484 been started will not be passed to a new delivery process for sending another
24485 message on the same connection. See section &<<SECTmulmessam>>& for an
24486 explanation of when this might be needed.
24488 .option hosts_noproxy_tls smtp "host list&!!" *
24489 .cindex "TLS" "passing connection"
24490 .cindex "multiple SMTP deliveries"
24491 .cindex "TLS" "multiple message deliveries"
24492 For any host that matches this list, a TLS session which has
24493 been started will not be passed to a new delivery process for sending another
24494 message on the same session.
24496 The traditional implementation closes down TLS and re-starts it in the new
24497 process, on the same open TCP connection, for each successive message
24498 sent. If permitted by this option a pipe to to the new process is set up
24499 instead, and the original process maintains the TLS connection and proxies
24500 the SMTP connection from and to the new process and any subsequents.
24501 The new process has no access to TLS information, so cannot include it in
24506 .option hosts_override smtp boolean false
24507 If this option is set and the &%hosts%& option is also set, any hosts that are
24508 attached to the address are ignored, and instead the hosts specified by the
24509 &%hosts%& option are always used. This option does not apply to
24510 &%fallback_hosts%&.
24513 .option hosts_randomize smtp boolean false
24514 .cindex "randomized host list"
24515 .cindex "host" "list of; randomized"
24516 .cindex "fallback" "randomized hosts"
24517 If this option is set, and either the list of hosts is taken from the
24518 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
24519 were not obtained from MX records (this includes fallback hosts from the
24520 router), and were not randomized by the router, the order of trying the hosts
24521 is randomized each time the transport runs. Randomizing the order of a host
24522 list can be used to do crude load sharing.
24524 When &%hosts_randomize%& is true, a host list may be split into groups whose
24525 order is separately randomized. This makes it possible to set up MX-like
24526 behaviour. The boundaries between groups are indicated by an item that is just
24527 &`+`& in the host list. For example:
24529 hosts = host1:host2:host3:+:host4:host5
24531 The order of the first three hosts and the order of the last two hosts is
24532 randomized for each use, but the first three always end up before the last two.
24533 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
24535 .option hosts_require_auth smtp "host list&!!" unset
24536 .cindex "authentication" "required by client"
24537 This option provides a list of servers for which authentication must succeed
24538 before Exim will try to transfer a message. If authentication fails for
24539 servers which are not in this list, Exim tries to send unauthenticated. If
24540 authentication fails for one of these servers, delivery is deferred. This
24541 temporary error is detectable in the retry rules, so it can be turned into a
24542 hard failure if required. See also &%hosts_try_auth%&, and chapter
24543 &<<CHAPSMTPAUTH>>& for details of authentication.
24546 .option hosts_request_ocsp smtp "host list&!!" *
24547 .cindex "TLS" "requiring for certain servers"
24548 Exim will request a Certificate Status on a
24549 TLS session for any host that matches this list.
24550 &%tls_verify_certificates%& should also be set for the transport.
24552 .option hosts_require_dane smtp "host list&!!" unset
24553 .cindex DANE "transport options"
24554 .cindex DANE "requiring for certain servers"
24555 If built with DANE support, Exim will require that a DNSSEC-validated
24556 TLSA record is present for any host matching the list,
24557 and that a DANE-verified TLS connection is made.
24558 There will be no fallback to in-clear communication.
24559 See section &<<SECDANE>>&.
24561 .option hosts_require_ocsp smtp "host list&!!" unset
24562 .cindex "TLS" "requiring for certain servers"
24563 Exim will request, and check for a valid Certificate Status being given, on a
24564 TLS session for any host that matches this list.
24565 &%tls_verify_certificates%& should also be set for the transport.
24567 .option hosts_require_tls smtp "host list&!!" unset
24568 .cindex "TLS" "requiring for certain servers"
24569 Exim will insist on using a TLS session when delivering to any host that
24570 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
24571 &*Note*&: This option affects outgoing mail only. To insist on TLS for
24572 incoming messages, use an appropriate ACL.
24574 .option hosts_try_auth smtp "host list&!!" unset
24575 .cindex "authentication" "optional in client"
24576 This option provides a list of servers to which, provided they announce
24577 authentication support, Exim will attempt to authenticate as a client when it
24578 connects. If authentication fails, Exim will try to transfer the message
24579 unauthenticated. See also &%hosts_require_auth%&, and chapter
24580 &<<CHAPSMTPAUTH>>& for details of authentication.
24582 .option hosts_try_chunking smtp "host list&!!" *
24583 .cindex CHUNKING "enabling, in client"
24584 .cindex BDAT "SMTP command"
24585 .cindex "RFC 3030" "CHUNKING"
24586 This option provides a list of servers to which, provided they announce
24587 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
24588 BDAT will not be used in conjunction with a transport filter.
24590 .option hosts_try_dane smtp "host list&!!" unset
24591 .cindex DANE "transport options"
24592 .cindex DANE "attempting for certain servers"
24593 If built with DANE support, Exim will lookup a
24594 TLSA record for any host matching the list.
24595 If found and verified by DNSSEC,
24596 a DANE-verified TLS connection is made to that host;
24597 there will be no fallback to in-clear communication.
24598 See section &<<SECDANE>>&.
24600 .option hosts_try_fastopen smtp "host list&!!" unset
24601 .cindex "fast open, TCP" "enabling, in client"
24602 .cindex "TCP Fast Open" "enabling, in client"
24603 .cindex "RFC 7413" "TCP Fast Open"
24604 This option provides a list of servers to which, provided
24605 the facility is supported by this system, Exim will attempt to
24606 perform a TCP Fast Open.
24607 No data is sent on the SYN segment but, if the remote server also
24608 supports the facility, it can send its SMTP banner immediately after
24609 the SYN,ACK segment. This can save up to one round-trip time.
24611 The facility is only active for previously-contacted servers,
24612 as the initiator must present a cookie in the SYN segment.
24614 On (at least some) current Linux distributions the facility must be enabled
24615 in the kernel by the sysadmin before the support is usable.
24616 There is no option for control of the server side; if the system supports
24617 it it is always enabled. Note that lengthy operations in the connect ACL,
24618 such as DNSBL lookups, will still delay the emission of the SMTP banner.
24620 .option hosts_try_prdr smtp "host list&!!" *
24621 .cindex "PRDR" "enabling, optional in client"
24622 This option provides a list of servers to which, provided they announce
24623 PRDR support, Exim will attempt to negotiate PRDR
24624 for multi-recipient messages.
24625 The option can usually be left as default.
24627 .option interface smtp "string list&!!" unset
24628 .cindex "bind IP address"
24629 .cindex "IP address" "binding"
24631 .vindex "&$host_address$&"
24632 This option specifies which interface to bind to when making an outgoing SMTP
24633 call. The value is an IP address, not an interface name such as
24634 &`eth0`&. Do not confuse this with the interface address that was used when a
24635 message was received, which is in &$received_ip_address$&, formerly known as
24636 &$interface_address$&. The name was changed to minimize confusion with the
24637 outgoing interface address. There is no variable that contains an outgoing
24638 interface address because, unless it is set by this option, its value is
24641 During the expansion of the &%interface%& option the variables &$host$& and
24642 &$host_address$& refer to the host to which a connection is about to be made
24643 during the expansion of the string. Forced expansion failure, or an empty
24644 string result causes the option to be ignored. Otherwise, after expansion, the
24645 string must be a list of IP addresses, colon-separated by default, but the
24646 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
24649 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
24651 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
24652 connection. If none of them are the correct type, the option is ignored. If
24653 &%interface%& is not set, or is ignored, the system's IP functions choose which
24654 interface to use if the host has more than one.
24657 .option keepalive smtp boolean true
24658 .cindex "keepalive" "on outgoing connection"
24659 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
24660 connections. When set, it causes the kernel to probe idle connections
24661 periodically, by sending packets with &"old"& sequence numbers. The other end
24662 of the connection should send a acknowledgment if the connection is still okay
24663 or a reset if the connection has been aborted. The reason for doing this is
24664 that it has the beneficial effect of freeing up certain types of connection
24665 that can get stuck when the remote host is disconnected without tidying up the
24666 TCP/IP call properly. The keepalive mechanism takes several hours to detect
24670 .option lmtp_ignore_quota smtp boolean false
24671 .cindex "LMTP" "ignoring quota errors"
24672 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
24673 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
24674 has advertised support for IGNOREQUOTA in its response to the LHLO command.
24676 .option max_rcpt smtp integer 100
24677 .cindex "RCPT" "maximum number of outgoing"
24678 This option limits the number of RCPT commands that are sent in a single
24679 SMTP message transaction. Each set of addresses is treated independently, and
24680 so can cause parallel connections to the same host if &%remote_max_parallel%&
24684 .option multi_domain smtp boolean&!! true
24685 .vindex "&$domain$&"
24686 When this option is set, the &(smtp)& transport can handle a number of
24687 addresses containing a mixture of different domains provided they all resolve
24688 to the same list of hosts. Turning the option off restricts the transport to
24689 handling only one domain at a time. This is useful if you want to use
24690 &$domain$& in an expansion for the transport, because it is set only when there
24691 is a single domain involved in a remote delivery.
24693 It is expanded per-address and can depend on any of
24694 &$address_data$&, &$domain_data$&, &$local_part_data$&,
24695 &$host$&, &$host_address$& and &$host_port$&.
24697 .option port smtp string&!! "see below"
24698 .cindex "port" "sending TCP/IP"
24699 .cindex "TCP/IP" "setting outgoing port"
24700 This option specifies the TCP/IP port on the server to which Exim connects.
24701 &*Note:*& Do not confuse this with the port that was used when a message was
24702 received, which is in &$received_port$&, formerly known as &$interface_port$&.
24703 The name was changed to minimize confusion with the outgoing port. There is no
24704 variable that contains an outgoing port.
24706 If the value of this option begins with a digit it is taken as a port number;
24707 otherwise it is looked up using &[getservbyname()]&. The default value is
24709 but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"&
24710 and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
24711 If the expansion fails, or if a port number cannot be found, delivery
24714 Note that at least one Linux distribution has been seen failing
24715 to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
24719 .option protocol smtp string smtp
24720 .cindex "LMTP" "over TCP/IP"
24721 .cindex "ssmtp protocol" "outbound"
24722 .cindex "TLS" "SSL-on-connect outbound"
24724 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
24725 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
24726 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
24727 deliveries into closed message stores. Exim also has support for running LMTP
24728 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
24730 If this option is set to &"smtps"&, the default value for the &%port%& option
24731 changes to &"smtps"&, and the transport initiates TLS immediately after
24732 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
24733 The Internet standards bodies used to strongly discourage use of this mode,
24734 but as of RFC 8314 it is perferred over STARTTLS for message submission
24735 (as distinct from MTA-MTA communication).
24738 .option retry_include_ip_address smtp boolean&!! true
24739 Exim normally includes both the host name and the IP address in the key it
24740 constructs for indexing retry data after a temporary delivery failure. This
24741 means that when one of several IP addresses for a host is failing, it gets
24742 tried periodically (controlled by the retry rules), but use of the other IP
24743 addresses is not affected.
24745 However, in some dialup environments hosts are assigned a different IP address
24746 each time they connect. In this situation the use of the IP address as part of
24747 the retry key leads to undesirable behaviour. Setting this option false causes
24748 Exim to use only the host name.
24749 Since it is expanded it can be made to depend on the host or domain.
24752 .option serialize_hosts smtp "host list&!!" unset
24753 .cindex "serializing connections"
24754 .cindex "host" "serializing connections"
24755 Because Exim operates in a distributed manner, if several messages for the same
24756 host arrive at around the same time, more than one simultaneous connection to
24757 the remote host can occur. This is not usually a problem except when there is a
24758 slow link between the hosts. In that situation it may be helpful to restrict
24759 Exim to one connection at a time. This can be done by setting
24760 &%serialize_hosts%& to match the relevant hosts.
24762 .cindex "hints database" "serializing deliveries to a host"
24763 Exim implements serialization by means of a hints database in which a record is
24764 written whenever a process connects to one of the restricted hosts. The record
24765 is deleted when the connection is completed. Obviously there is scope for
24766 records to get left lying around if there is a system or program crash. To
24767 guard against this, Exim ignores any records that are more than six hours old.
24769 If you set up this kind of serialization, you should also arrange to delete the
24770 relevant hints database whenever your system reboots. The names of the files
24771 start with &_misc_& and they are kept in the &_spool/db_& directory. There
24772 may be one or two files, depending on the type of DBM in use. The same files
24773 are used for ETRN serialization.
24775 See also the &%max_parallel%& generic transport option.
24778 .option size_addition smtp integer 1024
24779 .cindex "SMTP" "SIZE"
24780 .cindex "message" "size issue for transport filter"
24781 .cindex "size" "of message"
24782 .cindex "transport" "filter"
24783 .cindex "filter" "transport filter"
24784 If a remote SMTP server indicates that it supports the SIZE option of the
24785 MAIL command, Exim uses this to pass over the message size at the start of
24786 an SMTP transaction. It adds the value of &%size_addition%& to the value it
24787 sends, to allow for headers and other text that may be added during delivery by
24788 configuration options or in a transport filter. It may be necessary to increase
24789 this if a lot of text is added to messages.
24791 Alternatively, if the value of &%size_addition%& is set negative, it disables
24792 the use of the SIZE option altogether.
24795 .option socks_proxy smtp string&!! unset
24796 .cindex proxy SOCKS
24797 This option enables use of SOCKS proxies for connections made by the
24798 transport. For details see section &<<SECTproxySOCKS>>&.
24801 .option tls_certificate smtp string&!! unset
24802 .cindex "TLS" "client certificate, location of"
24803 .cindex "certificate" "client, location of"
24805 .vindex "&$host_address$&"
24806 The value of this option must be the absolute path to a file which contains the
24807 client's certificate, for possible use when sending a message over an encrypted
24808 connection. The values of &$host$& and &$host_address$& are set to the name and
24809 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
24812 &*Note*&: This option must be set if you want Exim to be able to use a TLS
24813 certificate when sending messages as a client. The global option of the same
24814 name specifies the certificate for Exim as a server; it is not automatically
24815 assumed that the same certificate should be used when Exim is operating as a
24819 .option tls_crl smtp string&!! unset
24820 .cindex "TLS" "client certificate revocation list"
24821 .cindex "certificate" "revocation list for client"
24822 This option specifies a certificate revocation list. The expanded value must
24823 be the name of a file that contains a CRL in PEM format.
24826 .option tls_dh_min_bits smtp integer 1024
24827 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
24828 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
24829 key agreement is negotiated, the server will provide a large prime number
24830 for use. This option establishes the minimum acceptable size of that number.
24831 If the parameter offered by the server is too small, then the TLS handshake
24834 Only supported when using GnuTLS.
24837 .option tls_privatekey smtp string&!! unset
24838 .cindex "TLS" "client private key, location of"
24840 .vindex "&$host_address$&"
24841 The value of this option must be the absolute path to a file which contains the
24842 client's private key. This is used when sending a message over an encrypted
24843 connection using a client certificate. The values of &$host$& and
24844 &$host_address$& are set to the name and address of the server during the
24845 expansion. If this option is unset, or the expansion is forced to fail, or the
24846 result is an empty string, the private key is assumed to be in the same file as
24847 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
24850 .option tls_require_ciphers smtp string&!! unset
24851 .cindex "TLS" "requiring specific ciphers"
24852 .cindex "cipher" "requiring specific"
24854 .vindex "&$host_address$&"
24855 The value of this option must be a list of permitted cipher suites, for use
24856 when setting up an outgoing encrypted connection. (There is a global option of
24857 the same name for controlling incoming connections.) The values of &$host$& and
24858 &$host_address$& are set to the name and address of the server during the
24859 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
24860 is used in different ways by OpenSSL and GnuTLS (see sections
24861 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
24862 ciphers is a preference order.
24866 .option tls_sni smtp string&!! unset
24867 .cindex "TLS" "Server Name Indication"
24868 .vindex "&$tls_sni$&"
24869 If this option is set then it sets the $tls_out_sni variable and causes any
24870 TLS session to pass this value as the Server Name Indication extension to
24871 the remote side, which can be used by the remote side to select an appropriate
24872 certificate and private key for the session.
24874 See &<<SECTtlssni>>& for more information.
24876 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
24882 .option tls_tempfail_tryclear smtp boolean true
24883 .cindex "4&'xx'& responses" "to STARTTLS"
24884 When the server host is not in &%hosts_require_tls%&, and there is a problem in
24885 setting up a TLS session, this option determines whether or not Exim should try
24886 to deliver the message unencrypted. If it is set false, delivery to the
24887 current host is deferred; if there are other hosts, they are tried. If this
24888 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
24889 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
24890 TLS negotiation fails, Exim closes the current connection (because it is in an
24891 unknown state), opens a new one to the same host, and then tries the delivery
24895 .option tls_try_verify_hosts smtp "host list&!!" *
24896 .cindex "TLS" "server certificate verification"
24897 .cindex "certificate" "verification of server"
24898 This option gives a list of hosts for which, on encrypted connections,
24899 certificate verification will be tried but need not succeed.
24900 The &%tls_verify_certificates%& option must also be set.
24901 Note that unless the host is in this list
24902 TLS connections will be denied to hosts using self-signed certificates
24903 when &%tls_verify_certificates%& is matched.
24904 The &$tls_out_certificate_verified$& variable is set when
24905 certificate verification succeeds.
24908 .option tls_verify_cert_hostnames smtp "host list&!!" *
24909 .cindex "TLS" "server certificate hostname verification"
24910 .cindex "certificate" "verification of server"
24911 This option give a list of hosts for which,
24912 while verifying the server certificate,
24913 checks will be included on the host name
24914 (note that this will generally be the result of a DNS MX lookup)
24915 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
24916 limited to being the initial component of a 3-or-more component FQDN.
24918 There is no equivalent checking on client certificates.
24921 .option tls_verify_certificates smtp string&!! system
24922 .cindex "TLS" "server certificate verification"
24923 .cindex "certificate" "verification of server"
24925 .vindex "&$host_address$&"
24926 The value of this option must be either the
24928 or the absolute path to
24929 a file or directory containing permitted certificates for servers,
24930 for use when setting up an encrypted connection.
24932 The "system" value for the option will use a location compiled into the SSL library.
24933 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
24934 is taken as empty and an explicit location
24937 The use of a directory for the option value is not available for GnuTLS versions
24938 preceding 3.3.6 and a single file must be used.
24940 With OpenSSL the certificates specified
24942 either by file or directory
24943 are added to those given by the system default location.
24945 The values of &$host$& and
24946 &$host_address$& are set to the name and address of the server during the
24947 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
24949 For back-compatibility,
24950 if neither tls_verify_hosts nor tls_try_verify_hosts are set
24951 (a single-colon empty list counts as being set)
24952 and certificate verification fails the TLS connection is closed.
24955 .option tls_verify_hosts smtp "host list&!!" unset
24956 .cindex "TLS" "server certificate verification"
24957 .cindex "certificate" "verification of server"
24958 This option gives a list of hosts for which, on encrypted connections,
24959 certificate verification must succeed.
24960 The &%tls_verify_certificates%& option must also be set.
24961 If both this option and &%tls_try_verify_hosts%& are unset
24962 operation is as if this option selected all hosts.
24964 .option utf8_downconvert smtp integer!! unset
24965 .cindex utf8 "address downconversion"
24966 .cindex i18n "utf8 address downconversion"
24967 If built with internationalization support,
24968 this option controls conversion of UTF-8 in message addresses
24970 For details see section &<<SECTi18nMTA>>&.
24975 .section "How the limits for the number of hosts to try are used" &&&
24977 .cindex "host" "maximum number to try"
24978 .cindex "limit" "hosts; maximum number tried"
24979 There are two options that are concerned with the number of hosts that are
24980 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
24981 &%hosts_max_try_hardlimit%&.
24984 The &%hosts_max_try%& option limits the number of hosts that are tried
24985 for a single delivery. However, despite the term &"host"& in its name, the
24986 option actually applies to each IP address independently. In other words, a
24987 multihomed host is treated as several independent hosts, just as it is for
24990 Many of the larger ISPs have multiple MX records which often point to
24991 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
24992 created as a result of routing one of these domains.
24994 Trying every single IP address on such a long list does not seem sensible; if
24995 several at the top of the list fail, it is reasonable to assume there is some
24996 problem that is likely to affect all of them. Roughly speaking, the value of
24997 &%hosts_max_try%& is the maximum number that are tried before deferring the
24998 delivery. However, the logic cannot be quite that simple.
25000 Firstly, IP addresses that are skipped because their retry times have not
25001 arrived do not count, and in addition, addresses that are past their retry
25002 limits are also not counted, even when they are tried. This means that when
25003 some IP addresses are past their retry limits, more than the value of
25004 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
25005 that all IP addresses are considered before timing out an email address (but
25006 see below for an exception).
25008 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
25009 list to see if there is a subsequent host with a different (higher valued) MX.
25010 If there is, that host is considered next, and the current IP address is used
25011 but not counted. This behaviour helps in the case of a domain with a retry rule
25012 that hardly ever delays any hosts, as is now explained:
25014 Consider the case of a long list of hosts with one MX value, and a few with a
25015 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
25016 hosts at the top of the list are tried at first. With the default retry rule,
25017 which specifies increasing retry times, the higher MX hosts are eventually
25018 tried when those at the top of the list are skipped because they have not
25019 reached their retry times.
25021 However, it is common practice to put a fixed short retry time on domains for
25022 large ISPs, on the grounds that their servers are rarely down for very long.
25023 Unfortunately, these are exactly the domains that tend to resolve to long lists
25024 of hosts. The short retry time means that the lowest MX hosts are tried every
25025 time. The attempts may be in a different order because of random sorting, but
25026 without the special MX check, the higher MX hosts would never be tried until
25027 all the lower MX hosts had timed out (which might be several days), because
25028 there are always some lower MX hosts that have reached their retry times. With
25029 the special check, Exim considers at least one IP address from each MX value at
25030 every delivery attempt, even if the &%hosts_max_try%& limit has already been
25033 The above logic means that &%hosts_max_try%& is not a hard limit, and in
25034 particular, Exim normally eventually tries all the IP addresses before timing
25035 out an email address. When &%hosts_max_try%& was implemented, this seemed a
25036 reasonable thing to do. Recently, however, some lunatic DNS configurations have
25037 been set up with hundreds of IP addresses for some domains. It can
25038 take a very long time indeed for an address to time out in these cases.
25040 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
25041 Exim never tries more than this number of IP addresses; if it hits this limit
25042 and they are all timed out, the email address is bounced, even though not all
25043 possible IP addresses have been tried.
25044 .ecindex IIDsmttra1
25045 .ecindex IIDsmttra2
25051 . ////////////////////////////////////////////////////////////////////////////
25052 . ////////////////////////////////////////////////////////////////////////////
25054 .chapter "Address rewriting" "CHAPrewrite"
25055 .scindex IIDaddrew "rewriting" "addresses"
25056 There are some circumstances in which Exim automatically rewrites domains in
25057 addresses. The two most common are when an address is given without a domain
25058 (referred to as an &"unqualified address"&) or when an address contains an
25059 abbreviated domain that is expanded by DNS lookup.
25061 Unqualified envelope addresses are accepted only for locally submitted
25062 messages, or for messages that are received from hosts matching
25063 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
25064 appropriate. Unqualified addresses in header lines are qualified if they are in
25065 locally submitted messages, or messages from hosts that are permitted to send
25066 unqualified envelope addresses. Otherwise, unqualified addresses in header
25067 lines are neither qualified nor rewritten.
25069 One situation in which Exim does &'not'& automatically rewrite a domain is
25070 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
25071 such a domain should be rewritten using the &"canonical"& name, and some MTAs
25072 do this. The new RFCs do not contain this suggestion.
25075 .section "Explicitly configured address rewriting" "SECID147"
25076 This chapter describes the rewriting rules that can be used in the
25077 main rewrite section of the configuration file, and also in the generic
25078 &%headers_rewrite%& option that can be set on any transport.
25080 Some people believe that configured address rewriting is a Mortal Sin.
25081 Others believe that life is not possible without it. Exim provides the
25082 facility; you do not have to use it.
25084 The main rewriting rules that appear in the &"rewrite"& section of the
25085 configuration file are applied to addresses in incoming messages, both envelope
25086 addresses and addresses in header lines. Each rule specifies the types of
25087 address to which it applies.
25089 Whether or not addresses in header lines are rewritten depends on the origin of
25090 the headers and the type of rewriting. Global rewriting, that is, rewriting
25091 rules from the rewrite section of the configuration file, is applied only to
25092 those headers that were received with the message. Header lines that are added
25093 by ACLs or by a system filter or by individual routers or transports (which
25094 are specific to individual recipient addresses) are not rewritten by the global
25097 Rewriting at transport time, by means of the &%headers_rewrite%& option,
25098 applies all headers except those added by routers and transports. That is, as
25099 well as the headers that were received with the message, it also applies to
25100 headers that were added by an ACL or a system filter.
25103 In general, rewriting addresses from your own system or domain has some
25104 legitimacy. Rewriting other addresses should be done only with great care and
25105 in special circumstances. The author of Exim believes that rewriting should be
25106 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
25107 Although it can sometimes be used as a routing tool, this is very strongly
25110 There are two commonly encountered circumstances where rewriting is used, as
25111 illustrated by these examples:
25114 The company whose domain is &'hitch.fict.example'& has a number of hosts that
25115 exchange mail with each other behind a firewall, but there is only a single
25116 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
25117 &'hitch.fict.example'& when sending mail off-site.
25119 A host rewrites the local parts of its own users so that, for example,
25120 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
25125 .section "When does rewriting happen?" "SECID148"
25126 .cindex "rewriting" "timing of"
25127 .cindex "&ACL;" "rewriting addresses in"
25128 Configured address rewriting can take place at several different stages of a
25129 message's processing.
25131 .vindex "&$sender_address$&"
25132 At the start of an ACL for MAIL, the sender address may have been rewritten
25133 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
25134 ordinary rewrite rules have yet been applied. If, however, the sender address
25135 is verified in the ACL, it is rewritten before verification, and remains
25136 rewritten thereafter. The subsequent value of &$sender_address$& is the
25137 rewritten address. This also applies if sender verification happens in a
25138 RCPT ACL. Otherwise, when the sender address is not verified, it is
25139 rewritten as soon as a message's header lines have been received.
25141 .vindex "&$domain$&"
25142 .vindex "&$local_part$&"
25143 Similarly, at the start of an ACL for RCPT, the current recipient's address
25144 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
25145 rewrite rules have yet been applied to it. However, the behaviour is different
25146 from the sender address when a recipient is verified. The address is rewritten
25147 for the verification, but the rewriting is not remembered at this stage. The
25148 value of &$local_part$& and &$domain$& after verification are always the same
25149 as they were before (that is, they contain the unrewritten &-- except for
25150 SMTP-time rewriting &-- address).
25152 As soon as a message's header lines have been received, all the envelope
25153 recipient addresses are permanently rewritten, and rewriting is also applied to
25154 the addresses in the header lines (if configured). This happens before adding
25155 any header lines that were specified in MAIL or RCPT ACLs, and
25156 .cindex "&[local_scan()]& function" "address rewriting; timing of"
25157 before the DATA ACL and &[local_scan()]& functions are run.
25159 When an address is being routed, either for delivery or for verification,
25160 rewriting is applied immediately to child addresses that are generated by
25161 redirection, unless &%no_rewrite%& is set on the router.
25163 .cindex "envelope sender" "rewriting at transport time"
25164 .cindex "rewriting" "at transport time"
25165 .cindex "header lines" "rewriting at transport time"
25166 At transport time, additional rewriting of addresses in header lines can be
25167 specified by setting the generic &%headers_rewrite%& option on a transport.
25168 This option contains rules that are identical in form to those in the rewrite
25169 section of the configuration file. They are applied to the original message
25170 header lines and any that were added by ACLs or a system filter. They are not
25171 applied to header lines that are added by routers or the transport.
25173 The outgoing envelope sender can be rewritten by means of the &%return_path%&
25174 transport option. However, it is not possible to rewrite envelope recipients at
25180 .section "Testing the rewriting rules that apply on input" "SECID149"
25181 .cindex "rewriting" "testing"
25182 .cindex "testing" "rewriting"
25183 Exim's input rewriting configuration appears in a part of the runtime
25184 configuration file headed by &"begin rewrite"&. It can be tested by the
25185 &%-brw%& command line option. This takes an address (which can be a full RFC
25186 2822 address) as its argument. The output is a list of how the address would be
25187 transformed by the rewriting rules for each of the different places it might
25188 appear in an incoming message, that is, for each different header and for the
25189 envelope sender and recipient fields. For example,
25191 exim -brw ph10@exim.workshop.example
25193 might produce the output
25195 sender: Philip.Hazel@exim.workshop.example
25196 from: Philip.Hazel@exim.workshop.example
25197 to: ph10@exim.workshop.example
25198 cc: ph10@exim.workshop.example
25199 bcc: ph10@exim.workshop.example
25200 reply-to: Philip.Hazel@exim.workshop.example
25201 env-from: Philip.Hazel@exim.workshop.example
25202 env-to: ph10@exim.workshop.example
25204 which shows that rewriting has been set up for that address when used in any of
25205 the source fields, but not when it appears as a recipient address. At the
25206 present time, there is no equivalent way of testing rewriting rules that are
25207 set for a particular transport.
25210 .section "Rewriting rules" "SECID150"
25211 .cindex "rewriting" "rules"
25212 The rewrite section of the configuration file consists of lines of rewriting
25215 <&'source pattern'&> <&'replacement'&> <&'flags'&>
25217 Rewriting rules that are specified for the &%headers_rewrite%& generic
25218 transport option are given as a colon-separated list. Each item in the list
25219 takes the same form as a line in the main rewriting configuration (except that
25220 any colons must be doubled, of course).
25222 The formats of source patterns and replacement strings are described below.
25223 Each is terminated by white space, unless enclosed in double quotes, in which
25224 case normal quoting conventions apply inside the quotes. The flags are single
25225 characters which may appear in any order. Spaces and tabs between them are
25228 For each address that could potentially be rewritten, the rules are scanned in
25229 order, and replacements for the address from earlier rules can themselves be
25230 replaced by later rules (but see the &"q"& and &"R"& flags).
25232 The order in which addresses are rewritten is undefined, may change between
25233 releases, and must not be relied on, with one exception: when a message is
25234 received, the envelope sender is always rewritten first, before any header
25235 lines are rewritten. For example, the replacement string for a rewrite of an
25236 address in &'To:'& must not assume that the message's address in &'From:'& has
25237 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
25238 that the envelope sender has already been rewritten.
25240 .vindex "&$domain$&"
25241 .vindex "&$local_part$&"
25242 The variables &$local_part$& and &$domain$& can be used in the replacement
25243 string to refer to the address that is being rewritten. Note that lookup-driven
25244 rewriting can be done by a rule of the form
25248 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
25249 refer to the address that is being rewritten.
25252 .section "Rewriting patterns" "SECID151"
25253 .cindex "rewriting" "patterns"
25254 .cindex "address list" "in a rewriting pattern"
25255 The source pattern in a rewriting rule is any item which may appear in an
25256 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
25257 single-item address list, which means that it is expanded before being tested
25258 against the address. As always, if you use a regular expression as a pattern,
25259 you must take care to escape dollar and backslash characters, or use the &`\N`&
25260 facility to suppress string expansion within the regular expression.
25262 Domains in patterns should be given in lower case. Local parts in patterns are
25263 case-sensitive. If you want to do case-insensitive matching of local parts, you
25264 can use a regular expression that starts with &`^(?i)`&.
25266 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
25267 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
25268 depending on the type of match which occurred. These can be used in the
25269 replacement string to insert portions of the incoming address. &$0$& always
25270 refers to the complete incoming address. When a regular expression is used, the
25271 numerical variables are set from its capturing subexpressions. For other types
25272 of pattern they are set as follows:
25275 If a local part or domain starts with an asterisk, the numerical variables
25276 refer to the character strings matched by asterisks, with &$1$& associated with
25277 the first asterisk, and &$2$& with the second, if present. For example, if the
25280 *queen@*.fict.example
25282 is matched against the address &'hearts-queen@wonderland.fict.example'& then
25284 $0 = hearts-queen@wonderland.fict.example
25288 Note that if the local part does not start with an asterisk, but the domain
25289 does, it is &$1$& that contains the wild part of the domain.
25292 If the domain part of the pattern is a partial lookup, the wild and fixed parts
25293 of the domain are placed in the next available numerical variables. Suppose,
25294 for example, that the address &'foo@bar.baz.example'& is processed by a
25295 rewriting rule of the form
25297 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
25299 and the key in the file that matches the domain is &`*.baz.example`&. Then
25305 If the address &'foo@baz.example'& is looked up, this matches the same
25306 wildcard file entry, and in this case &$2$& is set to the empty string, but
25307 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
25308 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
25309 whole domain. For non-partial domain lookups, no numerical variables are set.
25313 .section "Rewriting replacements" "SECID152"
25314 .cindex "rewriting" "replacements"
25315 If the replacement string for a rule is a single asterisk, addresses that
25316 match the pattern and the flags are &'not'& rewritten, and no subsequent
25317 rewriting rules are scanned. For example,
25319 hatta@lookingglass.fict.example * f
25321 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
25324 .vindex "&$domain$&"
25325 .vindex "&$local_part$&"
25326 If the replacement string is not a single asterisk, it is expanded, and must
25327 yield a fully qualified address. Within the expansion, the variables
25328 &$local_part$& and &$domain$& refer to the address that is being rewritten.
25329 Any letters they contain retain their original case &-- they are not lower
25330 cased. The numerical variables are set up according to the type of pattern that
25331 matched the address, as described above. If the expansion is forced to fail by
25332 the presence of &"fail"& in a conditional or lookup item, rewriting by the
25333 current rule is abandoned, but subsequent rules may take effect. Any other
25334 expansion failure causes the entire rewriting operation to be abandoned, and an
25335 entry written to the panic log.
25339 .section "Rewriting flags" "SECID153"
25340 There are three different kinds of flag that may appear on rewriting rules:
25343 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
25346 A flag that specifies rewriting at SMTP time: S.
25348 Flags that control the rewriting process: Q, q, R, w.
25351 For rules that are part of the &%headers_rewrite%& generic transport option,
25352 E, F, T, and S are not permitted.
25356 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
25358 .cindex "rewriting" "flags"
25359 If none of the following flag letters, nor the &"S"& flag (see section
25360 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
25361 and to both the sender and recipient fields of the envelope, whereas a
25362 transport-time rewriting rule just applies to all headers. Otherwise, the
25363 rewriting rule is skipped unless the relevant addresses are being processed.
25365 &`E`& rewrite all envelope fields
25366 &`F`& rewrite the envelope From field
25367 &`T`& rewrite the envelope To field
25368 &`b`& rewrite the &'Bcc:'& header
25369 &`c`& rewrite the &'Cc:'& header
25370 &`f`& rewrite the &'From:'& header
25371 &`h`& rewrite all headers
25372 &`r`& rewrite the &'Reply-To:'& header
25373 &`s`& rewrite the &'Sender:'& header
25374 &`t`& rewrite the &'To:'& header
25376 "All headers" means all of the headers listed above that can be selected
25377 individually, plus their &'Resent-'& versions. It does not include
25378 other headers such as &'Subject:'& etc.
25380 You should be particularly careful about rewriting &'Sender:'& headers, and
25381 restrict this to special known cases in your own domains.
25384 .section "The SMTP-time rewriting flag" "SECTrewriteS"
25385 .cindex "SMTP" "rewriting malformed addresses"
25386 .cindex "RCPT" "rewriting argument of"
25387 .cindex "MAIL" "rewriting argument of"
25388 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
25389 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
25390 before any other processing; even before syntax checking. The pattern is
25391 required to be a regular expression, and it is matched against the whole of the
25392 data for the command, including any surrounding angle brackets.
25394 .vindex "&$domain$&"
25395 .vindex "&$local_part$&"
25396 This form of rewrite rule allows for the handling of addresses that are not
25397 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
25398 input). Because the input is not required to be a syntactically valid address,
25399 the variables &$local_part$& and &$domain$& are not available during the
25400 expansion of the replacement string. The result of rewriting replaces the
25401 original address in the MAIL or RCPT command.
25404 .section "Flags controlling the rewriting process" "SECID155"
25405 There are four flags which control the way the rewriting process works. These
25406 take effect only when a rule is invoked, that is, when the address is of the
25407 correct type (matches the flags) and matches the pattern:
25410 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
25411 unqualified local part. It is qualified with &%qualify_recipient%&. In the
25412 absence of &"Q"& the rewritten address must always include a domain.
25414 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
25415 even if no rewriting actually takes place because of a &"fail"& in the
25416 expansion. The &"q"& flag is not effective if the address is of the wrong type
25417 (does not match the flags) or does not match the pattern.
25419 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
25420 address, up to ten times. It can be combined with the &"q"& flag, to stop
25421 rewriting once it fails to match (after at least one successful rewrite).
25423 .cindex "rewriting" "whole addresses"
25424 When an address in a header is rewritten, the rewriting normally applies only
25425 to the working part of the address, with any comments and RFC 2822 &"phrase"&
25426 left unchanged. For example, rewriting might change
25428 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
25432 From: Ford Prefect <prefectf@hitch.fict.example>
25435 Sometimes there is a need to replace the whole address item, and this can be
25436 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
25437 causes an address in a header line to be rewritten, the entire address is
25438 replaced, not just the working part. The replacement must be a complete RFC
25439 2822 address, including the angle brackets if necessary. If text outside angle
25440 brackets contains a character whose value is greater than 126 or less than 32
25441 (except for tab), the text is encoded according to RFC 2047. The character set
25442 is taken from &%headers_charset%&, which gets its default at build time.
25444 When the &"w"& flag is set on a rule that causes an envelope address to be
25445 rewritten, all but the working part of the replacement address is discarded.
25449 .section "Rewriting examples" "SECID156"
25450 Here is an example of the two common rewriting paradigms:
25452 *@*.hitch.fict.example $1@hitch.fict.example
25453 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
25454 {$value}fail}@hitch.fict.example bctfrF
25456 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
25457 the string expansion to fail if the lookup does not succeed. In this context it
25458 has the effect of leaving the original address unchanged, but Exim goes on to
25459 consider subsequent rewriting rules, if any, because the &"q"& flag is not
25460 present in that rule. An alternative to &"fail"& would be to supply &$1$&
25461 explicitly, which would cause the rewritten address to be the same as before,
25462 at the cost of a small bit of processing. Not supplying either of these is an
25463 error, since the rewritten address would then contain no local part.
25465 The first example above replaces the domain with a superior, more general
25466 domain. This may not be desirable for certain local parts. If the rule
25468 root@*.hitch.fict.example *
25470 were inserted before the first rule, rewriting would be suppressed for the
25471 local part &'root'& at any domain ending in &'hitch.fict.example'&.
25473 Rewriting can be made conditional on a number of tests, by making use of
25474 &${if$& in the expansion item. For example, to apply a rewriting rule only to
25475 messages that originate outside the local host:
25477 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
25478 {$1@hitch.fict.example}fail}"
25480 The replacement string is quoted in this example because it contains white
25483 .cindex "rewriting" "bang paths"
25484 .cindex "bang paths" "rewriting"
25485 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
25486 an address it treats it as an unqualified local part which it qualifies with
25487 the local qualification domain (if the source of the message is local or if the
25488 remote host is permitted to send unqualified addresses). Rewriting can
25489 sometimes be used to handle simple bang paths with a fixed number of
25490 components. For example, the rule
25492 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
25494 rewrites a two-component bang path &'host.name!user'& as the domain address
25495 &'user@host.name'&. However, there is a security implication in using this as
25496 a global rewriting rule for envelope addresses. It can provide a backdoor
25497 method for using your system as a relay, because the incoming addresses appear
25498 to be local. If the bang path addresses are received via SMTP, it is safer to
25499 use the &"S"& flag to rewrite them as they are received, so that relay checking
25500 can be done on the rewritten addresses.
25507 . ////////////////////////////////////////////////////////////////////////////
25508 . ////////////////////////////////////////////////////////////////////////////
25510 .chapter "Retry configuration" "CHAPretry"
25511 .scindex IIDretconf1 "retry" "configuration, description of"
25512 .scindex IIDregconf2 "configuration file" "retry section"
25513 The &"retry"& section of the runtime configuration file contains a list of
25514 retry rules that control how often Exim tries to deliver messages that cannot
25515 be delivered at the first attempt. If there are no retry rules (the section is
25516 empty or not present), there are no retries. In this situation, temporary
25517 errors are treated as permanent. The default configuration contains a single,
25518 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
25519 line option can be used to test which retry rule will be used for a given
25520 address, domain and error.
25522 The most common cause of retries is temporary failure to deliver to a remote
25523 host because the host is down, or inaccessible because of a network problem.
25524 Exim's retry processing in this case is applied on a per-host (strictly, per IP
25525 address) basis, not on a per-message basis. Thus, if one message has recently
25526 been delayed, delivery of a new message to the same host is not immediately
25527 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
25528 log selector is set, the message
25529 .cindex "retry" "time not reached"
25530 &"retry time not reached"& is written to the main log whenever a delivery is
25531 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
25532 the handling of errors during remote deliveries.
25534 Retry processing applies to routing as well as to delivering, except as covered
25535 in the next paragraph. The retry rules do not distinguish between these
25536 actions. It is not possible, for example, to specify different behaviour for
25537 failures to route the domain &'snark.fict.example'& and failures to deliver to
25538 the host &'snark.fict.example'&. I didn't think anyone would ever need this
25539 added complication, so did not implement it. However, although they share the
25540 same retry rule, the actual retry times for routing and transporting a given
25541 domain are maintained independently.
25543 When a delivery is not part of a queue run (typically an immediate delivery on
25544 receipt of a message), the routers are always run, and local deliveries are
25545 always attempted, even if retry times are set for them. This makes for better
25546 behaviour if one particular message is causing problems (for example, causing
25547 quota overflow, or provoking an error in a filter file). If such a delivery
25548 suffers a temporary failure, the retry data is updated as normal, and
25549 subsequent delivery attempts from queue runs occur only when the retry time for
25550 the local address is reached.
25552 .section "Changing retry rules" "SECID157"
25553 If you change the retry rules in your configuration, you should consider
25554 whether or not to delete the retry data that is stored in Exim's spool area in
25555 files with names like &_db/retry_&. Deleting any of Exim's hints files is
25556 always safe; that is why they are called &"hints"&.
25558 The hints retry data contains suggested retry times based on the previous
25559 rules. In the case of a long-running problem with a remote host, it might
25560 record the fact that the host has timed out. If your new rules increase the
25561 timeout time for such a host, you should definitely remove the old retry data
25562 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
25563 messages that it should now be retaining.
25567 .section "Format of retry rules" "SECID158"
25568 .cindex "retry" "rules"
25569 Each retry rule occupies one line and consists of three or four parts,
25570 separated by white space: a pattern, an error name, an optional list of sender
25571 addresses, and a list of retry parameters. The pattern and sender lists must be
25572 enclosed in double quotes if they contain white space. The rules are searched
25573 in order until one is found where the pattern, error name, and sender list (if
25574 present) match the failing host or address, the error that occurred, and the
25575 message's sender, respectively.
25578 The pattern is any single item that may appear in an address list (see section
25579 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
25580 which means that it is expanded before being tested against the address that
25581 has been delayed. A negated address list item is permitted. Address
25582 list processing treats a plain domain name as if it were preceded by &"*@"&,
25583 which makes it possible for many retry rules to start with just a domain. For
25586 lookingglass.fict.example * F,24h,30m;
25588 provides a rule for any address in the &'lookingglass.fict.example'& domain,
25591 alice@lookingglass.fict.example * F,24h,30m;
25593 applies only to temporary failures involving the local part &%alice%&.
25594 In practice, almost all rules start with a domain name pattern without a local
25597 .cindex "regular expressions" "in retry rules"
25598 &*Warning*&: If you use a regular expression in a retry rule pattern, it
25599 must match a complete address, not just a domain, because that is how regular
25600 expressions work in address lists.
25602 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
25603 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
25607 .section "Choosing which retry rule to use for address errors" "SECID159"
25608 When Exim is looking for a retry rule after a routing attempt has failed (for
25609 example, after a DNS timeout), each line in the retry configuration is tested
25610 against the complete address only if &%retry_use_local_part%& is set for the
25611 router. Otherwise, only the domain is used, except when matching against a
25612 regular expression, when the local part of the address is replaced with &"*"&.
25613 A domain on its own can match a domain pattern, or a pattern that starts with
25614 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
25615 &%check_local_user%& is true, and false for other routers.
25617 Similarly, when Exim is looking for a retry rule after a local delivery has
25618 failed (for example, after a mailbox full error), each line in the retry
25619 configuration is tested against the complete address only if
25620 &%retry_use_local_part%& is set for the transport (it defaults true for all
25623 .cindex "4&'xx'& responses" "retry rules for"
25624 However, when Exim is looking for a retry rule after a remote delivery attempt
25625 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
25626 whole address is always used as the key when searching the retry rules. The
25627 rule that is found is used to create a retry time for the combination of the
25628 failing address and the message's sender. It is the combination of sender and
25629 recipient that is delayed in subsequent queue runs until its retry time is
25630 reached. You can delay the recipient without regard to the sender by setting
25631 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
25632 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
25637 .section "Choosing which retry rule to use for host and message errors" &&&
25639 For a temporary error that is not related to an individual address (for
25640 example, a connection timeout), each line in the retry configuration is checked
25641 twice. First, the name of the remote host is used as a domain name (preceded by
25642 &"*@"& when matching a regular expression). If this does not match the line,
25643 the domain from the email address is tried in a similar fashion. For example,
25644 suppose the MX records for &'a.b.c.example'& are
25646 a.b.c.example MX 5 x.y.z.example
25650 and the retry rules are
25652 p.q.r.example * F,24h,30m;
25653 a.b.c.example * F,4d,45m;
25655 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
25656 first rule matches neither the host nor the domain, so Exim looks at the second
25657 rule. This does not match the host, but it does match the domain, so it is used
25658 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
25659 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
25660 first retry rule is used, because it matches the host.
25662 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
25663 first rule to determine retry times, but for all the other hosts for the domain
25664 &'a.b.c.example'&, the second rule is used. The second rule is also used if
25665 routing to &'a.b.c.example'& suffers a temporary failure.
25667 &*Note*&: The host name is used when matching the patterns, not its IP address.
25668 However, if a message is routed directly to an IP address without the use of a
25669 host name, for example, if a &(manualroute)& router contains a setting such as:
25671 route_list = *.a.example 192.168.34.23
25673 then the &"host name"& that is used when searching for a retry rule is the
25674 textual form of the IP address.
25676 .section "Retry rules for specific errors" "SECID161"
25677 .cindex "retry" "specific errors; specifying"
25678 The second field in a retry rule is the name of a particular error, or an
25679 asterisk, which matches any error. The errors that can be tested for are:
25682 .vitem &%auth_failed%&
25683 Authentication failed when trying to send to a host in the
25684 &%hosts_require_auth%& list in an &(smtp)& transport.
25686 .vitem &%data_4xx%&
25687 A 4&'xx'& error was received for an outgoing DATA command, either immediately
25688 after the command, or after sending the message's data.
25690 .vitem &%mail_4xx%&
25691 A 4&'xx'& error was received for an outgoing MAIL command.
25693 .vitem &%rcpt_4xx%&
25694 A 4&'xx'& error was received for an outgoing RCPT command.
25697 For the three 4&'xx'& errors, either the first or both of the x's can be given
25698 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
25699 recognize 452 errors given to RCPT commands for addresses in a certain domain,
25700 and have retries every ten minutes with a one-hour timeout, you could set up a
25701 retry rule of this form:
25703 the.domain.name rcpt_452 F,1h,10m
25705 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
25706 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
25709 .vitem &%lost_connection%&
25710 A server unexpectedly closed the SMTP connection. There may, of course,
25711 legitimate reasons for this (host died, network died), but if it repeats a lot
25712 for the same host, it indicates something odd.
25715 A DNS lookup for a host failed.
25716 Note that a &%dnslookup%& router will need to have matched
25717 its &%fail_defer_domains%& option for this retry type to be usable.
25718 Also note that a &%manualroute%& router will probably need
25719 its &%host_find_failed%& option set to &%defer%&.
25721 .vitem &%refused_MX%&
25722 A connection to a host obtained from an MX record was refused.
25724 .vitem &%refused_A%&
25725 A connection to a host not obtained from an MX record was refused.
25728 A connection was refused.
25730 .vitem &%timeout_connect_MX%&
25731 A connection attempt to a host obtained from an MX record timed out.
25733 .vitem &%timeout_connect_A%&
25734 A connection attempt to a host not obtained from an MX record timed out.
25736 .vitem &%timeout_connect%&
25737 A connection attempt timed out.
25739 .vitem &%timeout_MX%&
25740 There was a timeout while connecting or during an SMTP session with a host
25741 obtained from an MX record.
25743 .vitem &%timeout_A%&
25744 There was a timeout while connecting or during an SMTP session with a host not
25745 obtained from an MX record.
25748 There was a timeout while connecting or during an SMTP session.
25750 .vitem &%tls_required%&
25751 The server was required to use TLS (it matched &%hosts_require_tls%& in the
25752 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
25753 to STARTTLS, or there was a problem setting up the TLS connection.
25756 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
25759 .vitem &%quota_%&<&'time'&>
25760 .cindex "quota" "error testing in retry rule"
25761 .cindex "retry" "quota error testing"
25762 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
25763 transport, and the mailbox has not been accessed for <&'time'&>. For example,
25764 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
25768 .cindex "mailbox" "time of last read"
25769 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
25770 timeouts when the mailbox is full and is not being read by its owner. Ideally,
25771 it should be based on the last time that the user accessed the mailbox.
25772 However, it is not always possible to determine this. Exim uses the following
25776 If the mailbox is a single file, the time of last access (the &"atime"&) is
25777 used. As no new messages are being delivered (because the mailbox is over
25778 quota), Exim does not access the file, so this is the time of last user access.
25780 .cindex "maildir format" "time of last read"
25781 For a maildir delivery, the time of last modification of the &_new_&
25782 subdirectory is used. As the mailbox is over quota, no new files are created in
25783 the &_new_& subdirectory, because no new messages are being delivered. Any
25784 change to the &_new_& subdirectory is therefore assumed to be the result of an
25785 MUA moving a new message to the &_cur_& directory when it is first read. The
25786 time that is used is therefore the last time that the user read a new message.
25788 For other kinds of multi-file mailbox, the time of last access cannot be
25789 obtained, so a retry rule that uses this type of error field is never matched.
25792 The quota errors apply both to system-enforced quotas and to Exim's own quota
25793 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
25794 when a local delivery is deferred because a partition is full (the ENOSPC
25799 .section "Retry rules for specified senders" "SECID162"
25800 .cindex "retry" "rules; sender-specific"
25801 You can specify retry rules that apply only when the failing message has a
25802 specific sender. In particular, this can be used to define retry rules that
25803 apply only to bounce messages. The third item in a retry rule can be of this
25806 &`senders=`&<&'address list'&>
25808 The retry timings themselves are then the fourth item. For example:
25810 * rcpt_4xx senders=: F,1h,30m
25812 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
25813 host. If the address list contains white space, it must be enclosed in quotes.
25816 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
25818 &*Warning*&: This facility can be unhelpful if it is used for host errors
25819 (which do not depend on the recipient). The reason is that the sender is used
25820 only to match the retry rule. Once the rule has been found for a host error,
25821 its contents are used to set a retry time for the host, and this will apply to
25822 all messages, not just those with specific senders.
25824 When testing retry rules using &%-brt%&, you can supply a sender using the
25825 &%-f%& command line option, like this:
25827 exim -f "" -brt user@dom.ain
25829 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
25830 list is never matched.
25836 .section "Retry parameters" "SECID163"
25837 .cindex "retry" "parameters in rules"
25838 The third (or fourth, if a senders list is present) field in a retry rule is a
25839 sequence of retry parameter sets, separated by semicolons. Each set consists of
25841 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
25843 The letter identifies the algorithm for computing a new retry time; the cutoff
25844 time is the time beyond which this algorithm no longer applies, and the
25845 arguments vary the algorithm's action. The cutoff time is measured from the
25846 time that the first failure for the domain (combined with the local part if
25847 relevant) was detected, not from the time the message was received.
25849 .cindex "retry" "algorithms"
25850 .cindex "retry" "fixed intervals"
25851 .cindex "retry" "increasing intervals"
25852 .cindex "retry" "random intervals"
25853 The available algorithms are:
25856 &'F'&: retry at fixed intervals. There is a single time parameter specifying
25859 &'G'&: retry at geometrically increasing intervals. The first argument
25860 specifies a starting value for the interval, and the second a multiplier, which
25861 is used to increase the size of the interval at each retry.
25863 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
25864 retry, the previous interval is multiplied by the factor in order to get a
25865 maximum for the next interval. The minimum interval is the first argument of
25866 the parameter, and an actual interval is chosen randomly between them. Such a
25867 rule has been found to be helpful in cluster configurations when all the
25868 members of the cluster restart at once, and may therefore synchronize their
25869 queue processing times.
25872 When computing the next retry time, the algorithm definitions are scanned in
25873 order until one whose cutoff time has not yet passed is reached. This is then
25874 used to compute a new retry time that is later than the current time. In the
25875 case of fixed interval retries, this simply means adding the interval to the
25876 current time. For geometrically increasing intervals, retry intervals are
25877 computed from the rule's parameters until one that is greater than the previous
25878 interval is found. The main configuration variable
25879 .cindex "limit" "retry interval"
25880 .cindex "retry" "interval, maximum"
25881 .oindex "&%retry_interval_max%&"
25882 &%retry_interval_max%& limits the maximum interval between retries. It
25883 cannot be set greater than &`24h`&, which is its default value.
25885 A single remote domain may have a number of hosts associated with it, and each
25886 host may have more than one IP address. Retry algorithms are selected on the
25887 basis of the domain name, but are applied to each IP address independently. If,
25888 for example, a host has two IP addresses and one is unusable, Exim will
25889 generate retry times for it and will not try to use it until its next retry
25890 time comes. Thus the good IP address is likely to be tried first most of the
25893 .cindex "hints database" "use for retrying"
25894 Retry times are hints rather than promises. Exim does not make any attempt to
25895 run deliveries exactly at the computed times. Instead, a queue runner process
25896 starts delivery processes for delayed messages periodically, and these attempt
25897 new deliveries only for those addresses that have passed their next retry time.
25898 If a new message arrives for a deferred address, an immediate delivery attempt
25899 occurs only if the address has passed its retry time. In the absence of new
25900 messages, the minimum time between retries is the interval between queue runner
25901 processes. There is not much point in setting retry times of five minutes if
25902 your queue runners happen only once an hour, unless there are a significant
25903 number of incoming messages (which might be the case on a system that is
25904 sending everything to a smart host, for example).
25906 The data in the retry hints database can be inspected by using the
25907 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
25908 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
25909 &'exinext'& utility script can be used to find out what the next retry times
25910 are for the hosts associated with a particular mail domain, and also for local
25911 deliveries that have been deferred.
25914 .section "Retry rule examples" "SECID164"
25915 Here are some example retry rules:
25917 alice@wonderland.fict.example quota_5d F,7d,3h
25918 wonderland.fict.example quota_5d
25919 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
25920 lookingglass.fict.example * F,24h,30m;
25921 * refused_A F,2h,20m;
25922 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
25924 The first rule sets up special handling for mail to
25925 &'alice@wonderland.fict.example'& when there is an over-quota error and the
25926 mailbox has not been read for at least 5 days. Retries continue every three
25927 hours for 7 days. The second rule handles over-quota errors for all other local
25928 parts at &'wonderland.fict.example'&; the absence of a local part has the same
25929 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
25930 fail are bounced immediately if the mailbox has not been read for at least 5
25933 The third rule handles all other errors at &'wonderland.fict.example'&; retries
25934 happen every 15 minutes for an hour, then with geometrically increasing
25935 intervals until two days have passed since a delivery first failed. After the
25936 first hour there is a delay of one hour, then two hours, then four hours, and
25937 so on (this is a rather extreme example).
25939 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
25940 They happen every 30 minutes for 24 hours only. The remaining two rules handle
25941 all other domains, with special action for connection refusal from hosts that
25942 were not obtained from an MX record.
25944 The final rule in a retry configuration should always have asterisks in the
25945 first two fields so as to provide a general catch-all for any addresses that do
25946 not have their own special handling. This example tries every 15 minutes for 2
25947 hours, then with intervals starting at one hour and increasing by a factor of
25948 1.5 up to 16 hours, then every 8 hours up to 5 days.
25952 .section "Timeout of retry data" "SECID165"
25953 .cindex "timeout" "of retry data"
25954 .oindex "&%retry_data_expire%&"
25955 .cindex "hints database" "data expiry"
25956 .cindex "retry" "timeout of data"
25957 Exim timestamps the data that it writes to its retry hints database. When it
25958 consults the data during a delivery it ignores any that is older than the value
25959 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
25960 been tried for 7 days, Exim will try to deliver to it immediately a message
25961 arrives, and if that fails, it will calculate a retry time as if it were
25962 failing for the first time.
25964 This improves the behaviour for messages routed to rarely-used hosts such as MX
25965 backups. If such a host was down at one time, and happens to be down again when
25966 Exim tries a month later, using the old retry data would imply that it had been
25967 down all the time, which is not a justified assumption.
25969 If a host really is permanently dead, this behaviour causes a burst of retries
25970 every now and again, but only if messages routed to it are rare. If there is a
25971 message at least once every 7 days the retry data never expires.
25976 .section "Long-term failures" "SECID166"
25977 .cindex "delivery failure, long-term"
25978 .cindex "retry" "after long-term failure"
25979 Special processing happens when an email address has been failing for so long
25980 that the cutoff time for the last algorithm is reached. For example, using the
25981 default retry rule:
25983 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
25985 the cutoff time is four days. Reaching the retry cutoff is independent of how
25986 long any specific message has been failing; it is the length of continuous
25987 failure for the recipient address that counts.
25989 When the cutoff time is reached for a local delivery, or for all the IP
25990 addresses associated with a remote delivery, a subsequent delivery failure
25991 causes Exim to give up on the address, and a bounce message is generated.
25992 In order to cater for new messages that use the failing address, a next retry
25993 time is still computed from the final algorithm, and is used as follows:
25995 For local deliveries, one delivery attempt is always made for any subsequent
25996 messages. If this delivery fails, the address fails immediately. The
25997 post-cutoff retry time is not used.
25999 .cindex "final cutoff" "retries, controlling"
26000 .cindex retry "final cutoff"
26001 If the delivery is remote, there are two possibilities, controlled by the
26002 .oindex "&%delay_after_cutoff%&"
26003 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
26004 default. Until the post-cutoff retry time for one of the IP addresses,
26005 as set by the &%retry_data_expire%& option, is
26006 reached, the failing email address is bounced immediately, without a delivery
26007 attempt taking place. After that time, one new delivery attempt is made to
26008 those IP addresses that are past their retry times, and if that still fails,
26009 the address is bounced and new retry times are computed.
26011 In other words, when all the hosts for a given email address have been failing
26012 for a long time, Exim bounces rather then defers until one of the hosts' retry
26013 times is reached. Then it tries once, and bounces if that attempt fails. This
26014 behaviour ensures that few resources are wasted in repeatedly trying to deliver
26015 to a broken destination, but if the host does recover, Exim will eventually
26018 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
26019 addresses are past their final cutoff time, Exim tries to deliver to those IP
26020 addresses that have not been tried since the message arrived. If there are
26021 no suitable IP addresses, or if they all fail, the address is bounced. In other
26022 words, it does not delay when a new message arrives, but tries the expired
26023 addresses immediately, unless they have been tried since the message arrived.
26024 If there is a continuous stream of messages for the failing domains, setting
26025 &%delay_after_cutoff%& false means that there will be many more attempts to
26026 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
26029 .section "Deliveries that work intermittently" "SECID167"
26030 .cindex "retry" "intermittently working deliveries"
26031 Some additional logic is needed to cope with cases where a host is
26032 intermittently available, or when a message has some attribute that prevents
26033 its delivery when others to the same address get through. In this situation,
26034 because some messages are successfully delivered, the &"retry clock"& for the
26035 host or address keeps getting reset by the successful deliveries, and so
26036 failing messages remain in the queue for ever because the cutoff time is never
26039 Two exceptional actions are applied to prevent this happening. The first
26040 applies to errors that are related to a message rather than a remote host.
26041 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
26042 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
26043 commands, and quota failures. For this type of error, if a message's arrival
26044 time is earlier than the &"first failed"& time for the error, the earlier time
26045 is used when scanning the retry rules to decide when to try next and when to
26046 time out the address.
26048 The exceptional second action applies in all cases. If a message has been on
26049 the queue for longer than the cutoff time of any applicable retry rule for a
26050 given address, a delivery is attempted for that address, even if it is not yet
26051 time, and if this delivery fails, the address is timed out. A new retry time is
26052 not computed in this case, so that other messages for the same address are
26053 considered immediately.
26054 .ecindex IIDretconf1
26055 .ecindex IIDregconf2
26062 . ////////////////////////////////////////////////////////////////////////////
26063 . ////////////////////////////////////////////////////////////////////////////
26065 .chapter "SMTP authentication" "CHAPSMTPAUTH"
26066 .scindex IIDauthconf1 "SMTP" "authentication configuration"
26067 .scindex IIDauthconf2 "authentication"
26068 The &"authenticators"& section of Exim's runtime configuration is concerned
26069 with SMTP authentication. This facility is an extension to the SMTP protocol,
26070 described in RFC 2554, which allows a client SMTP host to authenticate itself
26071 to a server. This is a common way for a server to recognize clients that are
26072 permitted to use it as a relay. SMTP authentication is not of relevance to the
26073 transfer of mail between servers that have no managerial connection with each
26076 .cindex "AUTH" "description of"
26077 Very briefly, the way SMTP authentication works is as follows:
26080 The server advertises a number of authentication &'mechanisms'& in response to
26081 the client's EHLO command.
26083 The client issues an AUTH command, naming a specific mechanism. The command
26084 may, optionally, contain some authentication data.
26086 The server may issue one or more &'challenges'&, to which the client must send
26087 appropriate responses. In simple authentication mechanisms, the challenges are
26088 just prompts for user names and passwords. The server does not have to issue
26089 any challenges &-- in some mechanisms the relevant data may all be transmitted
26090 with the AUTH command.
26092 The server either accepts or denies authentication.
26094 If authentication succeeds, the client may optionally make use of the AUTH
26095 option on the MAIL command to pass an authenticated sender in subsequent
26096 mail transactions. Authentication lasts for the remainder of the SMTP
26099 If authentication fails, the client may give up, or it may try a different
26100 authentication mechanism, or it may try transferring mail over the
26101 unauthenticated connection.
26104 If you are setting up a client, and want to know which authentication
26105 mechanisms the server supports, you can use Telnet to connect to port 25 (the
26106 SMTP port) on the server, and issue an EHLO command. The response to this
26107 includes the list of supported mechanisms. For example:
26109 &`$ `&&*&`telnet server.example 25`&*&
26110 &`Trying 192.168.34.25...`&
26111 &`Connected to server.example.`&
26112 &`Escape character is '^]'.`&
26113 &`220 server.example ESMTP Exim 4.20 ...`&
26114 &*&`ehlo client.example`&*&
26115 &`250-server.example Hello client.example [10.8.4.5]`&
26116 &`250-SIZE 52428800`&
26121 The second-last line of this example output shows that the server supports
26122 authentication using the PLAIN mechanism. In Exim, the different authentication
26123 mechanisms are configured by specifying &'authenticator'& drivers. Like the
26124 routers and transports, which authenticators are included in the binary is
26125 controlled by build-time definitions. The following are currently available,
26126 included by setting
26129 AUTH_CYRUS_SASL=yes
26132 AUTH_HEIMDAL_GSSAPI=yes
26137 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
26138 authentication mechanism (RFC 2195), and the second provides an interface to
26139 the Cyrus SASL authentication library.
26140 The third is an interface to Dovecot's authentication system, delegating the
26141 work via a socket interface.
26142 The fourth provides an interface to the GNU SASL authentication library, which
26143 provides mechanisms but typically not data sources.
26144 The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
26145 supporting setting a server keytab.
26146 The sixth can be configured to support
26147 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
26148 not formally documented, but used by several MUAs. The seventh authenticator
26149 supports Microsoft's &'Secure Password Authentication'& mechanism.
26150 The eighth is an Exim authenticator but not an SMTP one;
26151 instead it can use information from a TLS negotiation.
26153 The authenticators are configured using the same syntax as other drivers (see
26154 section &<<SECTfordricon>>&). If no authenticators are required, no
26155 authentication section need be present in the configuration file. Each
26156 authenticator can in principle have both server and client functions. When Exim
26157 is receiving SMTP mail, it is acting as a server; when it is sending out
26158 messages over SMTP, it is acting as a client. Authenticator configuration
26159 options are provided for use in both these circumstances.
26161 To make it clear which options apply to which situation, the prefixes
26162 &%server_%& and &%client_%& are used on option names that are specific to
26163 either the server or the client function, respectively. Server and client
26164 functions are disabled if none of their options are set. If an authenticator is
26165 to be used for both server and client functions, a single definition, using
26166 both sets of options, is required. For example:
26170 public_name = CRAM-MD5
26171 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
26173 client_secret = secret2
26175 The &%server_%& option is used when Exim is acting as a server, and the
26176 &%client_%& options when it is acting as a client.
26178 Descriptions of the individual authenticators are given in subsequent chapters.
26179 The remainder of this chapter covers the generic options for the
26180 authenticators, followed by general discussion of the way authentication works
26183 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
26184 per-mechanism basis. Please read carefully to determine which variables hold
26185 account labels such as usercodes and which hold passwords or other
26186 authenticating data.
26188 Note that some mechanisms support two different identifiers for accounts: the
26189 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
26190 and &'authz'& are commonly encountered. The American spelling is standard here.
26191 Conceptually, authentication data such as passwords are tied to the identifier
26192 used to authenticate; servers may have rules to permit one user to act as a
26193 second user, so that after login the session is treated as though that second
26194 user had logged in. That second user is the &'authorization id'&. A robust
26195 configuration might confirm that the &'authz'& field is empty or matches the
26196 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
26197 as verified data, the &'authz'& as an unverified request which the server might
26200 A &'realm'& is a text string, typically a domain name, presented by a server
26201 to a client to help it select an account and credentials to use. In some
26202 mechanisms, the client and server provably agree on the realm, but clients
26203 typically can not treat the realm as secure data to be blindly trusted.
26207 .section "Generic options for authenticators" "SECID168"
26208 .cindex "authentication" "generic options"
26209 .cindex "options" "generic; for authenticators"
26211 .option client_condition authenticators string&!! unset
26212 When Exim is authenticating as a client, it skips any authenticator whose
26213 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
26214 used, for example, to skip plain text authenticators when the connection is not
26215 encrypted by a setting such as:
26217 client_condition = ${if !eq{$tls_out_cipher}{}}
26221 .option client_set_id authenticators string&!! unset
26222 When client authentication succeeds, this condition is expanded; the
26223 result is used in the log lines for outbound messages.
26224 Typically it will be the user name used for authentication.
26227 .option driver authenticators string unset
26228 This option must always be set. It specifies which of the available
26229 authenticators is to be used.
26232 .option public_name authenticators string unset
26233 This option specifies the name of the authentication mechanism that the driver
26234 implements, and by which it is known to the outside world. These names should
26235 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
26236 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
26237 defaults to the driver's instance name.
26240 .option server_advertise_condition authenticators string&!! unset
26241 When a server is about to advertise an authentication mechanism, the condition
26242 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
26243 mechanism is not advertised.
26244 If the expansion fails, the mechanism is not advertised. If the failure was not
26245 forced, and was not caused by a lookup defer, the incident is logged.
26246 See section &<<SECTauthexiser>>& below for further discussion.
26249 .option server_condition authenticators string&!! unset
26250 This option must be set for a &%plaintext%& server authenticator, where it
26251 is used directly to control authentication. See section &<<SECTplainserver>>&
26254 For the &(gsasl)& authenticator, this option is required for various
26255 mechanisms; see chapter &<<CHAPgsasl>>& for details.
26257 For the other authenticators, &%server_condition%& can be used as an additional
26258 authentication or authorization mechanism that is applied after the other
26259 authenticator conditions succeed. If it is set, it is expanded when the
26260 authenticator would otherwise return a success code. If the expansion is forced
26261 to fail, authentication fails. Any other expansion failure causes a temporary
26262 error code to be returned. If the result of a successful expansion is an empty
26263 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
26264 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
26265 other result, a temporary error code is returned, with the expanded string as
26269 .option server_debug_print authenticators string&!! unset
26270 If this option is set and authentication debugging is enabled (see the &%-d%&
26271 command line option), the string is expanded and included in the debugging
26272 output when the authenticator is run as a server. This can help with checking
26273 out the values of variables.
26274 If expansion of the string fails, the error message is written to the debugging
26275 output, and Exim carries on processing.
26278 .option server_set_id authenticators string&!! unset
26279 .vindex "&$authenticated_id$&"
26280 .vindex "&$authenticated_fail_id$&"
26281 When an Exim server successfully authenticates a client, this string is
26282 expanded using data from the authentication, and preserved for any incoming
26283 messages in the variable &$authenticated_id$&. It is also included in the log
26284 lines for incoming messages. For example, a user/password authenticator
26285 configuration might preserve the user name that was used to authenticate, and
26286 refer to it subsequently during delivery of the message.
26287 On a failing authentication the expansion result is instead saved in
26288 the &$authenticated_fail_id$& variable.
26289 If expansion fails, the option is ignored.
26292 .option server_mail_auth_condition authenticators string&!! unset
26293 This option allows a server to discard authenticated sender addresses supplied
26294 as part of MAIL commands in SMTP connections that are authenticated by the
26295 driver on which &%server_mail_auth_condition%& is set. The option is not used
26296 as part of the authentication process; instead its (unexpanded) value is
26297 remembered for later use.
26298 How it is used is described in the following section.
26304 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
26305 .cindex "authentication" "sender; authenticated"
26306 .cindex "AUTH" "on MAIL command"
26307 When a client supplied an AUTH= item on a MAIL command, Exim applies
26308 the following checks before accepting it as the authenticated sender of the
26312 If the connection is not using extended SMTP (that is, HELO was used rather
26313 than EHLO), the use of AUTH= is a syntax error.
26315 If the value of the AUTH= parameter is &"<>"&, it is ignored.
26317 .vindex "&$authenticated_sender$&"
26318 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
26319 running, the value of &$authenticated_sender$& is set to the value obtained
26320 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
26321 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
26322 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
26323 given for the MAIL command.
26325 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
26326 is accepted and placed in &$authenticated_sender$& only if the client has
26329 If the AUTH= value was accepted by either of the two previous rules, and
26330 the client has authenticated, and the authenticator has a setting for the
26331 &%server_mail_auth_condition%&, the condition is checked at this point. The
26332 valued that was saved from the authenticator is expanded. If the expansion
26333 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
26334 &$authenticated_sender$& is deleted. If the expansion yields any other value,
26335 the value of &$authenticated_sender$& is retained and passed on with the
26340 When &$authenticated_sender$& is set for a message, it is passed on to other
26341 hosts to which Exim authenticates as a client. Do not confuse this value with
26342 &$authenticated_id$&, which is a string obtained from the authentication
26343 process, and which is not usually a complete email address.
26345 .vindex "&$sender_address$&"
26346 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
26347 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
26348 therefore make use of &$authenticated_sender$&. The converse is not true: the
26349 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
26354 .section "Authentication on an Exim server" "SECTauthexiser"
26355 .cindex "authentication" "on an Exim server"
26356 When Exim receives an EHLO command, it advertises the public names of those
26357 authenticators that are configured as servers, subject to the following
26361 The client host must match &%auth_advertise_hosts%& (default *).
26363 It the &%server_advertise_condition%& option is set, its expansion must not
26364 yield the empty string, &"0"&, &"no"&, or &"false"&.
26367 The order in which the authenticators are defined controls the order in which
26368 the mechanisms are advertised.
26370 Some mail clients (for example, some versions of Netscape) require the user to
26371 provide a name and password for authentication whenever AUTH is advertised,
26372 even though authentication may not in fact be needed (for example, Exim may be
26373 set up to allow unconditional relaying from the client by an IP address check).
26374 You can make such clients more friendly by not advertising AUTH to them.
26375 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
26376 that runs for RCPT) to relay without authentication, you should set
26378 auth_advertise_hosts = ! 10.9.8.0/24
26380 so that no authentication mechanisms are advertised to them.
26382 The &%server_advertise_condition%& controls the advertisement of individual
26383 authentication mechanisms. For example, it can be used to restrict the
26384 advertisement of a particular mechanism to encrypted connections, by a setting
26387 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
26389 .vindex "&$tls_in_cipher$&"
26390 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
26391 yields &"yes"&, which allows the advertisement to happen.
26393 When an Exim server receives an AUTH command from a client, it rejects it
26394 immediately if AUTH was not advertised in response to an earlier EHLO
26395 command. This is the case if
26398 The client host does not match &%auth_advertise_hosts%&; or
26400 No authenticators are configured with server options; or
26402 Expansion of &%server_advertise_condition%& blocked the advertising of all the
26403 server authenticators.
26407 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
26408 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
26409 AUTH is accepted from any client host.
26411 If AUTH is not rejected by the ACL, Exim searches its configuration for a
26412 server authentication mechanism that was advertised in response to EHLO and
26413 that matches the one named in the AUTH command. If it finds one, it runs
26414 the appropriate authentication protocol, and authentication either succeeds or
26415 fails. If there is no matching advertised mechanism, the AUTH command is
26416 rejected with a 504 error.
26418 .vindex "&$received_protocol$&"
26419 .vindex "&$sender_host_authenticated$&"
26420 When a message is received from an authenticated host, the value of
26421 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
26422 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
26423 public name) of the authenticator driver that successfully authenticated the
26424 client from which the message was received. This variable is empty if there was
26425 no successful authentication.
26427 .cindex authentication "expansion item"
26428 Successful authentication sets up information used by the
26429 &$authresults$& expansion item.
26434 .section "Testing server authentication" "SECID169"
26435 .cindex "authentication" "testing a server"
26436 .cindex "AUTH" "testing a server"
26437 .cindex "base64 encoding" "creating authentication test data"
26438 Exim's &%-bh%& option can be useful for testing server authentication
26439 configurations. The data for the AUTH command has to be sent using base64
26440 encoding. A quick way to produce such data for testing is the following Perl
26444 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
26446 .cindex "binary zero" "in authentication data"
26447 This interprets its argument as a Perl string, and then encodes it. The
26448 interpretation as a Perl string allows binary zeros, which are required for
26449 some kinds of authentication, to be included in the data. For example, a
26450 command line to run this script on such data might be
26452 encode '\0user\0password'
26454 Note the use of single quotes to prevent the shell interpreting the
26455 backslashes, so that they can be interpreted by Perl to specify characters
26456 whose code value is zero.
26458 &*Warning 1*&: If either of the user or password strings starts with an octal
26459 digit, you must use three zeros instead of one after the leading backslash. If
26460 you do not, the octal digit that starts your string will be incorrectly
26461 interpreted as part of the code for the first character.
26463 &*Warning 2*&: If there are characters in the strings that Perl interprets
26464 specially, you must use a Perl escape to prevent them being misinterpreted. For
26465 example, a command such as
26467 encode '\0user@domain.com\0pas$$word'
26469 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
26471 If you have the &%mimencode%& command installed, another way to do produce
26472 base64-encoded strings is to run the command
26474 echo -e -n `\0user\0password' | mimencode
26476 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
26477 in the argument, and the &%-n%& option specifies no newline at the end of its
26478 output. However, not all versions of &%echo%& recognize these options, so you
26479 should check your version before relying on this suggestion.
26483 .section "Authentication by an Exim client" "SECID170"
26484 .cindex "authentication" "on an Exim client"
26485 The &(smtp)& transport has two options called &%hosts_require_auth%& and
26486 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
26487 announces support for authentication, and the host matches an entry in either
26488 of these options, Exim (as a client) tries to authenticate as follows:
26491 For each authenticator that is configured as a client, in the order in which
26492 they are defined in the configuration, it searches the authentication
26493 mechanisms announced by the server for one whose name matches the public name
26494 of the authenticator.
26497 .vindex "&$host_address$&"
26498 When it finds one that matches, it runs the authenticator's client code. The
26499 variables &$host$& and &$host_address$& are available for any string expansions
26500 that the client might do. They are set to the server's name and IP address. If
26501 any expansion is forced to fail, the authentication attempt is abandoned, and
26502 Exim moves on to the next authenticator. Otherwise an expansion failure causes
26503 delivery to be deferred.
26505 If the result of the authentication attempt is a temporary error or a timeout,
26506 Exim abandons trying to send the message to the host for the moment. It will
26507 try again later. If there are any backup hosts available, they are tried in the
26510 If the response to authentication is a permanent error (5&'xx'& code), Exim
26511 carries on searching the list of authenticators and tries another one if
26512 possible. If all authentication attempts give permanent errors, or if there are
26513 no attempts because no mechanisms match (or option expansions force failure),
26514 what happens depends on whether the host matches &%hosts_require_auth%& or
26515 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
26516 delivery is deferred. The error can be detected in the retry rules, and thereby
26517 turned into a permanent error if you wish. In the second case, Exim tries to
26518 deliver the message unauthenticated.
26521 Note that the hostlist test for whether to do authentication can be
26522 confused if name-IP lookups change between the time the peer is decided
26523 upon and the time that the transport runs. For example, with a manualroute
26524 router given a host name, and with DNS "round-robin" used by that name: if
26525 the local resolver cache times out between the router and the transport
26526 running, the transport may get an IP for the name for its authentication
26527 check which does not match the connection peer IP.
26528 No authentication will then be done, despite the names being identical.
26530 For such cases use a separate transport which always authenticates.
26532 .cindex "AUTH" "on MAIL command"
26533 When Exim has authenticated itself to a remote server, it adds the AUTH
26534 parameter to the MAIL commands it sends, if it has an authenticated sender for
26535 the message. If the message came from a remote host, the authenticated sender
26536 is the one that was receiving on an incoming MAIL command, provided that the
26537 incoming connection was authenticated and the &%server_mail_auth%& condition
26538 allowed the authenticated sender to be retained. If a local process calls Exim
26539 to send a message, the sender address that is built from the login name and
26540 &%qualify_domain%& is treated as authenticated. However, if the
26541 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
26542 the authenticated sender that was received with the message.
26543 .ecindex IIDauthconf1
26544 .ecindex IIDauthconf2
26551 . ////////////////////////////////////////////////////////////////////////////
26552 . ////////////////////////////////////////////////////////////////////////////
26554 .chapter "The plaintext authenticator" "CHAPplaintext"
26555 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
26556 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
26557 The &(plaintext)& authenticator can be configured to support the PLAIN and
26558 LOGIN authentication mechanisms, both of which transfer authentication data as
26559 plain (unencrypted) text (though base64 encoded). The use of plain text is a
26560 security risk; you are strongly advised to insist on the use of SMTP encryption
26561 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
26562 use unencrypted plain text, you should not use the same passwords for SMTP
26563 connections as you do for login accounts.
26565 .section "Plaintext options" "SECID171"
26566 .cindex "options" "&(plaintext)& authenticator (server)"
26567 When configured as a server, &(plaintext)& uses the following options:
26569 .option server_condition authenticators string&!! unset
26570 This is actually a global authentication option, but it must be set in order to
26571 configure the &(plaintext)& driver as a server. Its use is described below.
26573 .option server_prompts plaintext string&!! unset
26574 The contents of this option, after expansion, must be a colon-separated list of
26575 prompt strings. If expansion fails, a temporary authentication rejection is
26578 .section "Using plaintext in a server" "SECTplainserver"
26579 .cindex "AUTH" "in &(plaintext)& authenticator"
26580 .cindex "binary zero" "in &(plaintext)& authenticator"
26581 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
26582 "in &(plaintext)& authenticator"
26583 .vindex "&$auth1$&, &$auth2$&, etc"
26584 .cindex "base64 encoding" "in &(plaintext)& authenticator"
26586 When running as a server, &(plaintext)& performs the authentication test by
26587 expanding a string. The data sent by the client with the AUTH command, or in
26588 response to subsequent prompts, is base64 encoded, and so may contain any byte
26589 values when decoded. If any data is supplied with the command, it is treated as
26590 a list of strings, separated by NULs (binary zeros), the first three of which
26591 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
26592 (neither LOGIN nor PLAIN uses more than three strings).
26594 For compatibility with previous releases of Exim, the values are also placed in
26595 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
26596 variables for this purpose is now deprecated, as it can lead to confusion in
26597 string expansions that also use them for other things.
26599 If there are more strings in &%server_prompts%& than the number of strings
26600 supplied with the AUTH command, the remaining prompts are used to obtain more
26601 data. Each response from the client may be a list of NUL-separated strings.
26603 .vindex "&$authenticated_id$&"
26604 Once a sufficient number of data strings have been received,
26605 &%server_condition%& is expanded. If the expansion is forced to fail,
26606 authentication fails. Any other expansion failure causes a temporary error code
26607 to be returned. If the result of a successful expansion is an empty string,
26608 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
26609 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
26610 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
26611 For any other result, a temporary error code is returned, with the expanded
26612 string as the error text.
26614 &*Warning*&: If you use a lookup in the expansion to find the user's
26615 password, be sure to make the authentication fail if the user is unknown.
26616 There are good and bad examples at the end of the next section.
26620 .section "The PLAIN authentication mechanism" "SECID172"
26621 .cindex "PLAIN authentication mechanism"
26622 .cindex "authentication" "PLAIN mechanism"
26623 .cindex "binary zero" "in &(plaintext)& authenticator"
26624 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
26625 sent as one item of data (that is, one combined string containing two NUL
26626 separators). The data is sent either as part of the AUTH command, or
26627 subsequently in response to an empty prompt from the server.
26629 The second and third strings are a user name and a corresponding password.
26630 Using a single fixed user name and password as an example, this could be
26631 configured as follows:
26635 public_name = PLAIN
26637 server_condition = \
26638 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
26639 server_set_id = $auth2
26641 Note that the default result strings from &%if%& (&"true"& or an empty string)
26642 are exactly what we want here, so they need not be specified. Obviously, if the
26643 password contains expansion-significant characters such as dollar, backslash,
26644 or closing brace, they have to be escaped.
26646 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
26647 the end of a string list are ignored). If all the data comes as part of the
26648 AUTH command, as is commonly the case, the prompt is not used. This
26649 authenticator is advertised in the response to EHLO as
26653 and a client host can authenticate itself by sending the command
26655 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
26657 As this contains three strings (more than the number of prompts), no further
26658 data is required from the client. Alternatively, the client may just send
26662 to initiate authentication, in which case the server replies with an empty
26663 prompt. The client must respond with the combined data string.
26665 The data string is base64 encoded, as required by the RFC. This example,
26666 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
26667 represents a zero byte. This is split up into three strings, the first of which
26668 is empty. The &%server_condition%& option in the authenticator checks that the
26669 second two are &`username`& and &`mysecret`& respectively.
26671 Having just one fixed user name and password, as in this example, is not very
26672 realistic, though for a small organization with only a handful of
26673 authenticating clients it could make sense.
26675 A more sophisticated instance of this authenticator could use the user name in
26676 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
26677 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
26678 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
26679 This is an incorrect example:
26681 server_condition = \
26682 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
26684 The expansion uses the user name (&$auth2$&) as the key to look up a password,
26685 which it then compares to the supplied password (&$auth3$&). Why is this example
26686 incorrect? It works fine for existing users, but consider what happens if a
26687 non-existent user name is given. The lookup fails, but as no success/failure
26688 strings are given for the lookup, it yields an empty string. Thus, to defeat
26689 the authentication, all a client has to do is to supply a non-existent user
26690 name and an empty password. The correct way of writing this test is:
26692 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
26693 {${if eq{$value}{$auth3}}} {false}}
26695 In this case, if the lookup succeeds, the result is checked; if the lookup
26696 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
26697 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
26698 always fails if its second argument is empty. However, the second way of
26699 writing the test makes the logic clearer.
26702 .section "The LOGIN authentication mechanism" "SECID173"
26703 .cindex "LOGIN authentication mechanism"
26704 .cindex "authentication" "LOGIN mechanism"
26705 The LOGIN authentication mechanism is not documented in any RFC, but is in use
26706 in a number of programs. No data is sent with the AUTH command. Instead, a
26707 user name and password are supplied separately, in response to prompts. The
26708 plaintext authenticator can be configured to support this as in this example:
26712 public_name = LOGIN
26713 server_prompts = User Name : Password
26714 server_condition = \
26715 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
26716 server_set_id = $auth1
26718 Because of the way plaintext operates, this authenticator accepts data supplied
26719 with the AUTH command (in contravention of the specification of LOGIN), but
26720 if the client does not supply it (as is the case for LOGIN clients), the prompt
26721 strings are used to obtain two data items.
26723 Some clients are very particular about the precise text of the prompts. For
26724 example, Outlook Express is reported to recognize only &"Username:"& and
26725 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
26726 strings. It uses the &%ldapauth%& expansion condition to check the user
26727 name and password by binding to an LDAP server:
26731 public_name = LOGIN
26732 server_prompts = Username:: : Password::
26733 server_condition = ${if and{{ \
26736 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
26737 pass=${quote:$auth2} \
26738 ldap://ldap.example.org/} }} }
26739 server_set_id = uid=$auth1,ou=people,o=example.org
26741 We have to check that the username is not empty before using it, because LDAP
26742 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
26743 operator to correctly quote the DN for authentication. However, the basic
26744 &%quote%& operator, rather than any of the LDAP quoting operators, is the
26745 correct one to use for the password, because quoting is needed only to make
26746 the password conform to the Exim syntax. At the LDAP level, the password is an
26747 uninterpreted string.
26750 .section "Support for different kinds of authentication" "SECID174"
26751 A number of string expansion features are provided for the purpose of
26752 interfacing to different ways of user authentication. These include checking
26753 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
26754 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
26760 .section "Using plaintext in a client" "SECID175"
26761 .cindex "options" "&(plaintext)& authenticator (client)"
26762 The &(plaintext)& authenticator has two client options:
26764 .option client_ignore_invalid_base64 plaintext boolean false
26765 If the client receives a server prompt that is not a valid base64 string,
26766 authentication is abandoned by default. However, if this option is set true,
26767 the error in the challenge is ignored and the client sends the response as
26770 .option client_send plaintext string&!! unset
26771 The string is a colon-separated list of authentication data strings. Each
26772 string is independently expanded before being sent to the server. The first
26773 string is sent with the AUTH command; any more strings are sent in response
26774 to prompts from the server. Before each string is expanded, the value of the
26775 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
26776 with &$auth1$& for the first prompt. Up to three prompts are stored in this
26777 way. Thus, the prompt that is received in response to sending the first string
26778 (with the AUTH command) can be used in the expansion of the second string, and
26779 so on. If an invalid base64 string is received when
26780 &%client_ignore_invalid_base64%& is set, an empty string is put in the
26781 &$auth$&<&'n'&> variable.
26783 &*Note*&: You cannot use expansion to create multiple strings, because
26784 splitting takes priority and happens first.
26786 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
26787 the data, further processing is applied to each string before it is sent. If
26788 there are any single circumflex characters in the string, they are converted to
26789 NULs. Should an actual circumflex be required as data, it must be doubled in
26792 This is an example of a client configuration that implements the PLAIN
26793 authentication mechanism with a fixed user name and password:
26797 public_name = PLAIN
26798 client_send = ^username^mysecret
26800 The lack of colons means that the entire text is sent with the AUTH
26801 command, with the circumflex characters converted to NULs. A similar example
26802 that uses the LOGIN mechanism is:
26806 public_name = LOGIN
26807 client_send = : username : mysecret
26809 The initial colon means that the first string is empty, so no data is sent with
26810 the AUTH command itself. The remaining strings are sent in response to
26812 .ecindex IIDplaiauth1
26813 .ecindex IIDplaiauth2
26818 . ////////////////////////////////////////////////////////////////////////////
26819 . ////////////////////////////////////////////////////////////////////////////
26821 .chapter "The cram_md5 authenticator" "CHID9"
26822 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
26823 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
26824 .cindex "CRAM-MD5 authentication mechanism"
26825 .cindex "authentication" "CRAM-MD5 mechanism"
26826 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
26827 sends a challenge string to the client, and the response consists of a user
26828 name and the CRAM-MD5 digest of the challenge string combined with a secret
26829 string (password) which is known to both server and client. Thus, the secret
26830 is not sent over the network as plain text, which makes this authenticator more
26831 secure than &(plaintext)&. However, the downside is that the secret has to be
26832 available in plain text at either end.
26835 .section "Using cram_md5 as a server" "SECID176"
26836 .cindex "options" "&(cram_md5)& authenticator (server)"
26837 This authenticator has one server option, which must be set to configure the
26838 authenticator as a server:
26840 .option server_secret cram_md5 string&!! unset
26841 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
26842 When the server receives the client's response, the user name is placed in
26843 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
26844 obtain the password for that user. The server then computes the CRAM-MD5 digest
26845 that the client should have sent, and checks that it received the correct
26846 string. If the expansion of &%server_secret%& is forced to fail, authentication
26847 fails. If the expansion fails for some other reason, a temporary error code is
26848 returned to the client.
26850 For compatibility with previous releases of Exim, the user name is also placed
26851 in &$1$&. However, the use of this variables for this purpose is now
26852 deprecated, as it can lead to confusion in string expansions that also use
26853 numeric variables for other things.
26855 For example, the following authenticator checks that the user name given by the
26856 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
26857 user name, authentication fails.
26861 public_name = CRAM-MD5
26862 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
26863 server_set_id = $auth1
26865 .vindex "&$authenticated_id$&"
26866 If authentication succeeds, the setting of &%server_set_id%& preserves the user
26867 name in &$authenticated_id$&. A more typical configuration might look up the
26868 secret string in a file, using the user name as the key. For example:
26872 public_name = CRAM-MD5
26873 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
26875 server_set_id = $auth1
26877 Note that this expansion explicitly forces failure if the lookup fails
26878 because &$auth1$& contains an unknown user name.
26880 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
26881 using the relevant libraries, you need to know the realm to specify in the
26882 lookup and then ask for the &"userPassword"& attribute for that user in that
26887 public_name = CRAM-MD5
26888 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
26889 dbmjz{/etc/sasldb2}{$value}fail}
26890 server_set_id = $auth1
26893 .section "Using cram_md5 as a client" "SECID177"
26894 .cindex "options" "&(cram_md5)& authenticator (client)"
26895 When used as a client, the &(cram_md5)& authenticator has two options:
26899 .option client_name cram_md5 string&!! "the primary host name"
26900 This string is expanded, and the result used as the user name data when
26901 computing the response to the server's challenge.
26904 .option client_secret cram_md5 string&!! unset
26905 This option must be set for the authenticator to work as a client. Its value is
26906 expanded and the result used as the secret string when computing the response.
26910 .vindex "&$host_address$&"
26911 Different user names and secrets can be used for different servers by referring
26912 to &$host$& or &$host_address$& in the options. Forced failure of either
26913 expansion string is treated as an indication that this authenticator is not
26914 prepared to handle this case. Exim moves on to the next configured client
26915 authenticator. Any other expansion failure causes Exim to give up trying to
26916 send the message to the current server.
26918 A simple example configuration of a &(cram_md5)& authenticator, using fixed
26923 public_name = CRAM-MD5
26925 client_secret = secret
26927 .ecindex IIDcramauth1
26928 .ecindex IIDcramauth2
26932 . ////////////////////////////////////////////////////////////////////////////
26933 . ////////////////////////////////////////////////////////////////////////////
26935 .chapter "The cyrus_sasl authenticator" "CHID10"
26936 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
26937 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
26938 .cindex "Cyrus" "SASL library"
26940 The code for this authenticator was provided by Matthew Byng-Maddick while
26941 at A L Digital Ltd.
26943 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
26944 library implementation of the RFC 2222 (&"Simple Authentication and Security
26945 Layer"&). This library supports a number of authentication mechanisms,
26946 including PLAIN and LOGIN, but also several others that Exim does not support
26947 directly. In particular, there is support for Kerberos authentication.
26949 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
26950 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
26951 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
26952 name of the driver to determine which mechanism to support.
26954 Where access to some kind of secret file is required, for example, in GSSAPI
26955 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
26956 user, and that the Cyrus SASL library has no way of escalating privileges
26957 by default. You may also find you need to set environment variables,
26958 depending on the driver you are using.
26960 The application name provided by Exim is &"exim"&, so various SASL options may
26961 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
26962 Kerberos, note that because of limitations in the GSSAPI interface,
26963 changing the server keytab might need to be communicated down to the Kerberos
26964 layer independently. The mechanism for doing so is dependent upon the Kerberos
26967 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
26968 may be set to point to an alternative keytab file. Exim will pass this
26969 variable through from its own inherited environment when started as root or the
26970 Exim user. The keytab file needs to be readable by the Exim user.
26971 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
26972 environment variable. In practice, for those releases, the Cyrus authenticator
26973 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
26974 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
26977 .section "Using cyrus_sasl as a server" "SECID178"
26978 The &(cyrus_sasl)& authenticator has four private options. It puts the username
26979 (on a successful authentication) into &$auth1$&. For compatibility with
26980 previous releases of Exim, the username is also placed in &$1$&. However, the
26981 use of this variable for this purpose is now deprecated, as it can lead to
26982 confusion in string expansions that also use numeric variables for other
26986 .option server_hostname cyrus_sasl string&!! "see below"
26987 This option selects the hostname that is used when communicating with the
26988 library. The default value is &`$primary_hostname`&. It is up to the underlying
26989 SASL plug-in what it does with this data.
26992 .option server_mech cyrus_sasl string "see below"
26993 This option selects the authentication mechanism this driver should use. The
26994 default is the value of the generic &%public_name%& option. This option allows
26995 you to use a different underlying mechanism from the advertised name. For
26999 driver = cyrus_sasl
27000 public_name = X-ANYTHING
27001 server_mech = CRAM-MD5
27002 server_set_id = $auth1
27005 .option server_realm cyrus_sasl string&!! unset
27006 This specifies the SASL realm that the server claims to be in.
27009 .option server_service cyrus_sasl string &`smtp`&
27010 This is the SASL service that the server claims to implement.
27013 For straightforward cases, you do not need to set any of the authenticator's
27014 private options. All you need to do is to specify an appropriate mechanism as
27015 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
27016 PLAIN, you could have two authenticators as follows:
27019 driver = cyrus_sasl
27020 public_name = CRAM-MD5
27021 server_set_id = $auth1
27024 driver = cyrus_sasl
27025 public_name = PLAIN
27026 server_set_id = $auth2
27028 Cyrus SASL does implement the LOGIN authentication method, even though it is
27029 not a standard method. It is disabled by default in the source distribution,
27030 but it is present in many binary distributions.
27031 .ecindex IIDcyrauth1
27032 .ecindex IIDcyrauth2
27037 . ////////////////////////////////////////////////////////////////////////////
27038 . ////////////////////////////////////////////////////////////////////////////
27039 .chapter "The dovecot authenticator" "CHAPdovecot"
27040 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
27041 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
27042 This authenticator is an interface to the authentication facility of the
27043 Dovecot POP/IMAP server, which can support a number of authentication methods.
27044 Note that Dovecot must be configured to use auth-client not auth-userdb.
27045 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
27046 to use the same mechanisms for SMTP authentication. This is a server
27047 authenticator only. There is only one option:
27049 .option server_socket dovecot string unset
27051 This option must specify the UNIX socket that is the interface to Dovecot
27052 authentication. The &%public_name%& option must specify an authentication
27053 mechanism that Dovecot is configured to support. You can have several
27054 authenticators for different mechanisms. For example:
27058 public_name = PLAIN
27059 server_socket = /var/run/dovecot/auth-client
27060 server_set_id = $auth1
27065 server_socket = /var/run/dovecot/auth-client
27066 server_set_id = $auth1
27068 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
27069 &$received_ip_address$& (that is, the connection is local), the &"secured"&
27070 option is passed in the Dovecot authentication command. If, for a TLS
27071 connection, a client certificate has been verified, the &"valid-client-cert"&
27072 option is passed. When authentication succeeds, the identity of the user
27073 who authenticated is placed in &$auth1$&.
27074 .ecindex IIDdcotauth1
27075 .ecindex IIDdcotauth2
27078 . ////////////////////////////////////////////////////////////////////////////
27079 . ////////////////////////////////////////////////////////////////////////////
27080 .chapter "The gsasl authenticator" "CHAPgsasl"
27081 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
27082 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
27083 .cindex "authentication" "GNU SASL"
27084 .cindex "authentication" "SASL"
27085 .cindex "authentication" "EXTERNAL"
27086 .cindex "authentication" "ANONYMOUS"
27087 .cindex "authentication" "PLAIN"
27088 .cindex "authentication" "LOGIN"
27089 .cindex "authentication" "DIGEST-MD5"
27090 .cindex "authentication" "CRAM-MD5"
27091 .cindex "authentication" "SCRAM-SHA-1"
27092 The &(gsasl)& authenticator provides server integration for the GNU SASL
27093 library and the mechanisms it provides. This is new as of the 4.80 release
27094 and there are a few areas where the library does not let Exim smoothly
27095 scale to handle future authentication mechanisms, so no guarantee can be
27096 made that any particular new authentication mechanism will be supported
27097 without code changes in Exim.
27099 Exim's &(gsasl)& authenticator does not have client-side support at this
27100 time; only the server-side support is implemented. Patches welcome.
27103 .option server_channelbinding gsasl boolean false
27104 Do not set this true without consulting a cryptographic engineer.
27106 Some authentication mechanisms are able to use external context at both ends
27107 of the session to bind the authentication to that context, and fail the
27108 authentication process if that context differs. Specifically, some TLS
27109 ciphersuites can provide identifying information about the cryptographic
27112 This should have meant that certificate identity and verification becomes a
27113 non-issue, as a man-in-the-middle attack will cause the correct client and
27114 server to see different identifiers and authentication will fail.
27116 This is currently only supported when using the GnuTLS library. This is
27117 only usable by mechanisms which support "channel binding"; at time of
27118 writing, that's the SCRAM family.
27120 This defaults off to ensure smooth upgrade across Exim releases, in case
27121 this option causes some clients to start failing. Some future release
27122 of Exim might have switched the default to be true.
27124 However, Channel Binding in TLS has proven to be broken in current versions.
27125 Do not plan to rely upon this feature for security, ever, without consulting
27126 with a subject matter expert (a cryptographic engineer).
27129 .option server_hostname gsasl string&!! "see below"
27130 This option selects the hostname that is used when communicating with the
27131 library. The default value is &`$primary_hostname`&.
27132 Some mechanisms will use this data.
27135 .option server_mech gsasl string "see below"
27136 This option selects the authentication mechanism this driver should use. The
27137 default is the value of the generic &%public_name%& option. This option allows
27138 you to use a different underlying mechanism from the advertised name. For
27143 public_name = X-ANYTHING
27144 server_mech = CRAM-MD5
27145 server_set_id = $auth1
27149 .option server_password gsasl string&!! unset
27150 Various mechanisms need access to the cleartext password on the server, so
27151 that proof-of-possession can be demonstrated on the wire, without sending
27152 the password itself.
27154 The data available for lookup varies per mechanism.
27155 In all cases, &$auth1$& is set to the &'authentication id'&.
27156 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
27157 if available, else the empty string.
27158 The &$auth3$& variable will always be the &'realm'& if available,
27159 else the empty string.
27161 A forced failure will cause authentication to defer.
27163 If using this option, it may make sense to set the &%server_condition%&
27164 option to be simply "true".
27167 .option server_realm gsasl string&!! unset
27168 This specifies the SASL realm that the server claims to be in.
27169 Some mechanisms will use this data.
27172 .option server_scram_iter gsasl string&!! unset
27173 This option provides data for the SCRAM family of mechanisms.
27174 &$auth1$& is not available at evaluation time.
27175 (This may change, as we receive feedback on use)
27178 .option server_scram_salt gsasl string&!! unset
27179 This option provides data for the SCRAM family of mechanisms.
27180 &$auth1$& is not available at evaluation time.
27181 (This may change, as we receive feedback on use)
27184 .option server_service gsasl string &`smtp`&
27185 This is the SASL service that the server claims to implement.
27186 Some mechanisms will use this data.
27189 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
27190 .vindex "&$auth1$&, &$auth2$&, etc"
27191 These may be set when evaluating specific options, as detailed above.
27192 They will also be set when evaluating &%server_condition%&.
27194 Unless otherwise stated below, the &(gsasl)& integration will use the following
27195 meanings for these variables:
27198 .vindex "&$auth1$&"
27199 &$auth1$&: the &'authentication id'&
27201 .vindex "&$auth2$&"
27202 &$auth2$&: the &'authorization id'&
27204 .vindex "&$auth3$&"
27205 &$auth3$&: the &'realm'&
27208 On a per-mechanism basis:
27211 .cindex "authentication" "EXTERNAL"
27212 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
27213 the &%server_condition%& option must be present.
27215 .cindex "authentication" "ANONYMOUS"
27216 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
27217 the &%server_condition%& option must be present.
27219 .cindex "authentication" "GSSAPI"
27220 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
27221 &$auth2$& will be set to the &'authorization id'&,
27222 the &%server_condition%& option must be present.
27225 An &'anonymous token'& is something passed along as an unauthenticated
27226 identifier; this is analogous to FTP anonymous authentication passing an
27227 email address, or software-identifier@, as the "password".
27230 An example showing the password having the realm specified in the callback
27231 and demonstrating a Cyrus SASL to GSASL migration approach is:
27233 gsasl_cyrusless_crammd5:
27235 public_name = CRAM-MD5
27236 server_realm = imap.example.org
27237 server_password = ${lookup{$auth1:$auth3:userPassword}\
27238 dbmjz{/etc/sasldb2}{$value}fail}
27239 server_set_id = ${quote:$auth1}
27240 server_condition = yes
27244 . ////////////////////////////////////////////////////////////////////////////
27245 . ////////////////////////////////////////////////////////////////////////////
27247 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
27248 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
27249 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
27250 .cindex "authentication" "GSSAPI"
27251 .cindex "authentication" "Kerberos"
27252 The &(heimdal_gssapi)& authenticator provides server integration for the
27253 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
27256 .option server_hostname heimdal_gssapi string&!! "see below"
27257 This option selects the hostname that is used, with &%server_service%&,
27258 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
27259 identifier. The default value is &`$primary_hostname`&.
27261 .option server_keytab heimdal_gssapi string&!! unset
27262 If set, then Heimdal will not use the system default keytab (typically
27263 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
27264 The value should be a pathname, with no &"file:"& prefix.
27266 .option server_service heimdal_gssapi string&!! "smtp"
27267 This option specifies the service identifier used, in conjunction with
27268 &%server_hostname%&, for building the identifier for finding credentials
27272 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
27273 Beware that these variables will typically include a realm, thus will appear
27274 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
27275 not verified, so a malicious client can set it to anything.
27277 The &$auth1$& field should be safely trustable as a value from the Key
27278 Distribution Center. Note that these are not quite email addresses.
27279 Each identifier is for a role, and so the left-hand-side may include a
27280 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
27282 .vindex "&$auth1$&, &$auth2$&, etc"
27284 .vindex "&$auth1$&"
27285 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
27287 .vindex "&$auth2$&"
27288 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
27289 authentication. If that was empty, this will also be set to the
27294 . ////////////////////////////////////////////////////////////////////////////
27295 . ////////////////////////////////////////////////////////////////////////////
27297 .chapter "The spa authenticator" "CHAPspa"
27298 .scindex IIDspaauth1 "&(spa)& authenticator"
27299 .scindex IIDspaauth2 "authenticators" "&(spa)&"
27300 .cindex "authentication" "Microsoft Secure Password"
27301 .cindex "authentication" "NTLM"
27302 .cindex "Microsoft Secure Password Authentication"
27303 .cindex "NTLM authentication"
27304 The &(spa)& authenticator provides client support for Microsoft's &'Secure
27305 Password Authentication'& mechanism,
27306 which is also sometimes known as NTLM (NT LanMan). The code for client side of
27307 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
27308 taken from the Samba project (&url(https://www.samba.org/)). The code for the
27309 server side was subsequently contributed by Tom Kistner. The mechanism works as
27313 After the AUTH command has been accepted, the client sends an SPA
27314 authentication request based on the user name and optional domain.
27316 The server sends back a challenge.
27318 The client builds a challenge response which makes use of the user's password
27319 and sends it to the server, which then accepts or rejects it.
27322 Encryption is used to protect the password in transit.
27326 .section "Using spa as a server" "SECID179"
27327 .cindex "options" "&(spa)& authenticator (server)"
27328 The &(spa)& authenticator has just one server option:
27330 .option server_password spa string&!! unset
27331 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
27332 This option is expanded, and the result must be the cleartext password for the
27333 authenticating user, whose name is at this point in &$auth1$&. For
27334 compatibility with previous releases of Exim, the user name is also placed in
27335 &$1$&. However, the use of this variable for this purpose is now deprecated, as
27336 it can lead to confusion in string expansions that also use numeric variables
27337 for other things. For example:
27342 server_password = \
27343 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
27345 If the expansion is forced to fail, authentication fails. Any other expansion
27346 failure causes a temporary error code to be returned.
27352 .section "Using spa as a client" "SECID180"
27353 .cindex "options" "&(spa)& authenticator (client)"
27354 The &(spa)& authenticator has the following client options:
27358 .option client_domain spa string&!! unset
27359 This option specifies an optional domain for the authentication.
27362 .option client_password spa string&!! unset
27363 This option specifies the user's password, and must be set.
27366 .option client_username spa string&!! unset
27367 This option specifies the user name, and must be set. Here is an example of a
27368 configuration of this authenticator for use with the mail servers at
27374 client_username = msn/msn_username
27375 client_password = msn_plaintext_password
27376 client_domain = DOMAIN_OR_UNSET
27378 .ecindex IIDspaauth1
27379 .ecindex IIDspaauth2
27385 . ////////////////////////////////////////////////////////////////////////////
27386 . ////////////////////////////////////////////////////////////////////////////
27388 .chapter "The tls authenticator" "CHAPtlsauth"
27389 .scindex IIDtlsauth1 "&(tls)& authenticator"
27390 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
27391 .cindex "authentication" "Client Certificate"
27392 .cindex "authentication" "X509"
27393 .cindex "Certificate-based authentication"
27394 The &(tls)& authenticator provides server support for
27395 authentication based on client certificates.
27397 It is not an SMTP authentication mechanism and is not
27398 advertised by the server as part of the SMTP EHLO response.
27399 It is an Exim authenticator in the sense that it affects
27400 the protocol element of the log line, can be tested for
27401 by the &%authenticated%& ACL condition, and can set
27402 the &$authenticated_id$& variable.
27404 The client must present a verifiable certificate,
27405 for which it must have been requested via the
27406 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
27407 (see &<<CHAPTLS>>&).
27409 If an authenticator of this type is configured it is
27410 run before any SMTP-level communication is done,
27411 and can authenticate the connection.
27412 If it does, SMTP authentication is not offered.
27414 A maximum of one authenticator of this type may be present.
27417 .cindex "options" "&(tls)& authenticator (server)"
27418 The &(tls)& authenticator has three server options:
27420 .option server_param1 tls string&!! unset
27421 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
27422 This option is expanded after the TLS negotiation and
27423 the result is placed in &$auth1$&.
27424 If the expansion is forced to fail, authentication fails. Any other expansion
27425 failure causes a temporary error code to be returned.
27427 .option server_param2 tls string&!! unset
27428 .option server_param3 tls string&!! unset
27429 As above, for &$auth2$& and &$auth3$&.
27431 &%server_param1%& may also be spelled &%server_param%&.
27438 server_param1 = ${certextract {subj_altname,mail,>:} \
27439 {$tls_in_peercert}}
27440 server_condition = ${if and { {eq{$tls_in_certificate_verified}{1}} \
27443 {${lookup ldap{ldap:///\
27444 mailname=${quote_ldap_dn:${lc:$item}},\
27445 ou=users,LDAP_DC?mailid} {$value}{0} \
27447 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
27449 This accepts a client certificate that is verifiable against any
27450 of your configured trust-anchors
27451 (which usually means the full set of public CAs)
27452 and which has a SAN with a good account name.
27454 Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
27455 The account name is therefore guessable by an opponent.
27456 TLS 1.3 protects both server and client certificates, and is not vulnerable
27458 Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
27460 . An alternative might use
27462 . server_param1 = ${sha256:$tls_in_peercert}
27464 . to require one of a set of specific certs that define a given account
27465 . (the verification is still required, but mostly irrelevant).
27466 . This would help for per-device use.
27468 . However, for the future we really need support for checking a
27469 . user cert in LDAP - which probably wants a base-64 DER.
27471 .ecindex IIDtlsauth1
27472 .ecindex IIDtlsauth2
27475 Note that because authentication is traditionally an SMTP operation,
27476 the &%authenticated%& ACL condition cannot be used in
27477 a connect- or helo-ACL.
27481 . ////////////////////////////////////////////////////////////////////////////
27482 . ////////////////////////////////////////////////////////////////////////////
27484 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
27485 "Encrypted SMTP connections"
27486 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
27487 .scindex IIDencsmtp2 "SMTP" "encryption"
27488 .cindex "TLS" "on SMTP connection"
27491 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
27492 Sockets Layer), is implemented by making use of the OpenSSL library or the
27493 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
27494 cryptographic code in the Exim distribution itself for implementing TLS. In
27495 order to use this feature you must install OpenSSL or GnuTLS, and then build a
27496 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
27497 You also need to understand the basic concepts of encryption at a managerial
27498 level, and in particular, the way that public keys, private keys, and
27499 certificates are used.
27501 RFC 3207 defines how SMTP connections can make use of encryption. Once a
27502 connection is established, the client issues a STARTTLS command. If the
27503 server accepts this, the client and the server negotiate an encryption
27504 mechanism. If the negotiation succeeds, the data that subsequently passes
27505 between them is encrypted.
27507 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
27508 and if so, what cipher suite is in use, whether the client supplied a
27509 certificate, and whether or not that certificate was verified. This makes it
27510 possible for an Exim server to deny or accept certain commands based on the
27513 &*Warning*&: Certain types of firewall and certain anti-virus products can
27514 disrupt TLS connections. You need to turn off SMTP scanning for these products
27515 in order to get TLS to work.
27519 .section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
27521 .cindex "submissions protocol"
27522 .cindex "ssmtp protocol"
27523 .cindex "smtps protocol"
27524 .cindex "SMTP" "submissions protocol"
27525 .cindex "SMTP" "ssmtp protocol"
27526 .cindex "SMTP" "smtps protocol"
27527 The history of port numbers for TLS in SMTP is a little messy and has been
27528 contentious. As of RFC 8314, the common practice of using the historically
27529 allocated port 465 for "email submission but with TLS immediately upon connect
27530 instead of using STARTTLS" is officially blessed by the IETF, and recommended
27531 by them in preference to STARTTLS.
27533 The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
27534 clarity emerged over the dual roles of SMTP, for MX delivery and Email
27535 Submission, nomenclature has shifted. The modern name is now &"submissions"&.
27537 This approach was, for a while, officially abandoned when encrypted SMTP was
27538 standardized, but many clients kept using it, even as the TCP port number was
27539 reassigned for other use.
27540 Thus you may encounter guidance claiming that you shouldn't enable use of
27542 In practice, a number of mail-clients have only ever supported submissions,
27543 not submission with STARTTLS upgrade.
27544 Ideally, offer both submission (587) and submissions (465) service.
27546 Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
27547 global option. Its value must be a list of port numbers;
27548 the most common use is expected to be:
27550 tls_on_connect_ports = 465
27552 The port numbers specified by this option apply to all SMTP connections, both
27553 via the daemon and via &'inetd'&. You still need to specify all the ports that
27554 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
27555 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
27556 an extra port &-- rather, it specifies different behaviour on a port that is
27559 There is also a &%-tls-on-connect%& command line option. This overrides
27560 &%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
27567 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
27568 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
27569 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
27570 followed later, when the first versions of GnuTLS were released. To build Exim
27571 to use GnuTLS, you need to set
27575 in Local/Makefile, in addition to
27579 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
27580 include files and libraries for GnuTLS can be found.
27582 There are some differences in usage when using GnuTLS instead of OpenSSL:
27585 The &%tls_verify_certificates%& option
27586 cannot be the path of a directory
27587 for GnuTLS versions before 3.3.6
27588 (for later versions, or OpenSSL, it can be either).
27590 The default value for &%tls_dhparam%& differs for historical reasons.
27592 .vindex "&$tls_in_peerdn$&"
27593 .vindex "&$tls_out_peerdn$&"
27594 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
27595 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
27596 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
27598 OpenSSL identifies cipher suites using hyphens as separators, for example:
27599 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
27600 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
27601 in a cipher list. To make life simpler, Exim changes underscores to hyphens
27602 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
27603 to handle its own older variants) when processing lists of cipher suites in the
27604 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
27607 The &%tls_require_ciphers%& options operate differently, as described in the
27608 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
27610 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
27611 When using OpenSSL, this option is ignored.
27612 (If an API is found to let OpenSSL be configured in this way,
27613 let the Exim Maintainers know and we'll likely use it).
27615 With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
27616 main option, it must be ordered to match the &%tls_certificate%& list.
27618 Some other recently added features may only be available in one or the other.
27619 This should be documented with the feature. If the documentation does not
27620 explicitly state that the feature is infeasible in the other TLS
27621 implementation, then patches are welcome.
27625 .section "GnuTLS parameter computation" "SECTgnutlsparam"
27626 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
27627 an explicit path; if the latter, then the text about generation still applies,
27628 but not the chosen filename.
27629 By default, as of Exim 4.80 a hard-coded D-H prime is used.
27630 See the documentation of &%tls_dhparam%& for more information.
27632 GnuTLS uses D-H parameters that may take a substantial amount of time
27633 to compute. It is unreasonable to re-compute them for every TLS session.
27634 Therefore, Exim keeps this data in a file in its spool directory, called
27635 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
27637 The file is owned by the Exim user and is readable only by
27638 its owner. Every Exim process that start up GnuTLS reads the D-H
27639 parameters from this file. If the file does not exist, the first Exim process
27640 that needs it computes the data and writes it to a temporary file which is
27641 renamed once it is complete. It does not matter if several Exim processes do
27642 this simultaneously (apart from wasting a few resources). Once a file is in
27643 place, new Exim processes immediately start using it.
27645 For maximum security, the parameters that are stored in this file should be
27646 recalculated periodically, the frequency depending on your paranoia level.
27647 If you are avoiding using the fixed D-H primes published in RFCs, then you
27648 are concerned about some advanced attacks and will wish to do this; if you do
27649 not regenerate then you might as well stick to the standard primes.
27651 Arranging this is easy in principle; just delete the file when you want new
27652 values to be computed. However, there may be a problem. The calculation of new
27653 parameters needs random numbers, and these are obtained from &_/dev/random_&.
27654 If the system is not very active, &_/dev/random_& may delay returning data
27655 until enough randomness (entropy) is available. This may cause Exim to hang for
27656 a substantial amount of time, causing timeouts on incoming connections.
27658 The solution is to generate the parameters externally to Exim. They are stored
27659 in &_gnutls-params-N_& in PEM format, which means that they can be
27660 generated externally using the &(certtool)& command that is part of GnuTLS.
27662 To replace the parameters with new ones, instead of deleting the file
27663 and letting Exim re-create it, you can generate new parameters using
27664 &(certtool)& and, when this has been done, replace Exim's cache file by
27665 renaming. The relevant commands are something like this:
27668 [ look for file; assume gnutls-params-2236 is the most recent ]
27671 # chown exim:exim new-params
27672 # chmod 0600 new-params
27673 # certtool --generate-dh-params --bits 2236 >>new-params
27674 # openssl dhparam -noout -text -in new-params | head
27675 [ check the first line, make sure it's not more than 2236;
27676 if it is, then go back to the start ("rm") and repeat
27677 until the size generated is at most the size requested ]
27678 # chmod 0400 new-params
27679 # mv new-params gnutls-params-2236
27681 If Exim never has to generate the parameters itself, the possibility of
27682 stalling is removed.
27684 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
27685 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
27686 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
27687 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
27688 and Exim does so. This attempt to remove Exim from TLS policy decisions
27689 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
27690 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
27691 which applies to all D-H usage, client or server. If the value returned by
27692 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
27693 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
27694 limit, which is still much higher than Exim historically used.
27696 The filename and bits used will change as the GnuTLS maintainers change the
27697 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
27698 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
27699 2432 bits, while NSS is limited to 2236 bits.
27701 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
27702 increase the chance of the generated prime actually being within acceptable
27703 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
27704 procedure above. There is no sane procedure available to Exim to double-check
27705 the size of the generated prime, so it might still be too large.
27708 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
27709 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
27710 .oindex "&%tls_require_ciphers%&" "OpenSSL"
27711 There is a function in the OpenSSL library that can be passed a list of cipher
27712 suites before the cipher negotiation takes place. This specifies which ciphers
27713 are acceptable for TLS versions prior to 1.3.
27714 The list is colon separated and may contain names like
27715 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
27716 directly to this function call.
27717 Many systems will install the OpenSSL manual-pages, so you may have
27718 &'ciphers(1)'& available to you.
27719 The following quotation from the OpenSSL
27720 documentation specifies what forms of item are allowed in the cipher string:
27723 It can consist of a single cipher suite such as RC4-SHA.
27725 It can represent a list of cipher suites containing a certain algorithm,
27726 or cipher suites of a certain type. For example SHA1 represents all
27727 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
27730 Lists of cipher suites can be combined in a single cipher string using
27731 the + character. This is used as a logical and operation. For example
27732 SHA1+DES represents all cipher suites containing the SHA1 and the DES
27736 Each cipher string can be optionally preceded by one of the characters &`!`&,
27739 If &`!`& is used, the ciphers are permanently deleted from the list. The
27740 ciphers deleted can never reappear in the list even if they are explicitly
27743 If &`-`& is used, the ciphers are deleted from the list, but some or all
27744 of the ciphers can be added again by later options.
27746 If &`+`& is used, the ciphers are moved to the end of the list. This
27747 option does not add any new ciphers; it just moves matching existing ones.
27750 If none of these characters is present, the string is interpreted as
27751 a list of ciphers to be appended to the current preference list. If the list
27752 includes any ciphers already present they will be ignored: that is, they will
27753 not be moved to the end of the list.
27756 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
27759 # note single-quotes to get ! past any shell history expansion
27760 $ openssl ciphers 'HIGH:!MD5:!SHA1'
27763 This example will let the library defaults be permitted on the MX port, where
27764 there's probably no identity verification anyway, but ups the ante on the
27765 submission ports where the administrator might have some influence on the
27766 choice of clients used:
27768 # OpenSSL variant; see man ciphers(1)
27769 tls_require_ciphers = ${if =={$received_port}{25}\
27774 This example will prefer ECDSA-authenticated ciphers over RSA ones:
27776 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
27779 For TLS version 1.3 the control available is less fine-grained
27780 and Exim does not provide access to it at present.
27781 The value of the &%tls_require_ciphers%& option is ignored when
27782 TLS version 1.3 is negotiated.
27784 As of writing the library default cipher suite list for TLSv1.3 is
27786 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
27790 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
27792 .cindex "GnuTLS" "specifying parameters for"
27793 .cindex "TLS" "specifying ciphers (GnuTLS)"
27794 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
27795 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
27796 .cindex "TLS" "specifying protocols (GnuTLS)"
27797 .cindex "TLS" "specifying priority string (GnuTLS)"
27798 .oindex "&%tls_require_ciphers%&" "GnuTLS"
27799 The GnuTLS library allows the caller to provide a "priority string", documented
27800 as part of the &[gnutls_priority_init]& function. This is very similar to the
27801 ciphersuite specification in OpenSSL.
27803 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
27804 and controls both protocols and ciphers.
27806 The &%tls_require_ciphers%& option is available both as an global option,
27807 controlling how Exim behaves as a server, and also as an option of the
27808 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
27809 the value is string expanded. The resulting string is not an Exim list and
27810 the string is given to the GnuTLS library, so that Exim does not need to be
27811 aware of future feature enhancements of GnuTLS.
27813 Documentation of the strings accepted may be found in the GnuTLS manual, under
27814 "Priority strings". This is online as
27815 &url(https://www.gnutls.org/manual/html_node/Priority-Strings.html),
27816 but beware that this relates to GnuTLS 3, which may be newer than the version
27817 installed on your system. If you are using GnuTLS 3,
27818 then the example code
27819 &url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
27820 on that site can be used to test a given string.
27824 # Disable older versions of protocols
27825 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
27828 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
27829 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
27830 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
27832 This example will let the library defaults be permitted on the MX port, where
27833 there's probably no identity verification anyway, and lowers security further
27834 by increasing compatibility; but this ups the ante on the submission ports
27835 where the administrator might have some influence on the choice of clients
27839 tls_require_ciphers = ${if =={$received_port}{25}\
27845 .section "Configuring an Exim server to use TLS" "SECID182"
27846 .cindex "TLS" "configuring an Exim server"
27847 When Exim has been built with TLS support, it advertises the availability of
27848 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
27849 but not to any others. The default value of this option is *, which means
27850 that STARTTLS is always advertised. Set it to blank to never advertise;
27851 this is reasonable for systems that want to use TLS only as a client.
27853 If STARTTLS is to be used you
27854 need to set some other options in order to make TLS available.
27856 If a client issues a STARTTLS command and there is some configuration
27857 problem in the server, the command is rejected with a 454 error. If the client
27858 persists in trying to issue SMTP commands, all except QUIT are rejected
27861 554 Security failure
27863 If a STARTTLS command is issued within an existing TLS session, it is
27864 rejected with a 554 error code.
27866 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
27867 must be set to match some hosts. The default is * which matches all hosts.
27869 If this is all you do, TLS encryption will be enabled but not authentication -
27870 meaning that the peer has no assurance it is actually you he is talking to.
27871 You gain protection from a passive sniffer listening on the wire but not
27872 from someone able to intercept the communication.
27874 Further protection requires some further configuration at the server end.
27876 To make TLS work you need to set, in the server,
27878 tls_certificate = /some/file/name
27879 tls_privatekey = /some/file/name
27881 These options are, in fact, expanded strings, so you can make them depend on
27882 the identity of the client that is connected if you wish. The first file
27883 contains the server's X509 certificate, and the second contains the private key
27884 that goes with it. These files need to be
27885 PEM format and readable by the Exim user, and must
27886 always be given as full path names.
27887 The key must not be password-protected.
27888 They can be the same file if both the
27889 certificate and the key are contained within it. If &%tls_privatekey%& is not
27890 set, or if its expansion is forced to fail or results in an empty string, this
27891 is assumed to be the case. The certificate file may also contain intermediate
27892 certificates that need to be sent to the client to enable it to authenticate
27893 the server's certificate.
27895 For dual-stack (eg. RSA and ECDSA) configurations, these options can be
27896 colon-separated lists of file paths. Ciphers using given authentication
27897 algorithms require the presence of a suitable certificate to supply the
27898 public-key. The server selects among the certificates to present to the
27899 client depending on the selected cipher, hence the priority ordering for
27900 ciphers will affect which certificate is used.
27902 If you do not understand about certificates and keys, please try to find a
27903 source of this background information, which is not Exim-specific. (There are a
27904 few comments below in section &<<SECTcerandall>>&.)
27906 &*Note*&: These options do not apply when Exim is operating as a client &--
27907 they apply only in the case of a server. If you need to use a certificate in an
27908 Exim client, you must set the options of the same names in an &(smtp)&
27911 With just these options, an Exim server will be able to use TLS. It does not
27912 require the client to have a certificate (but see below for how to insist on
27913 this). There is one other option that may be needed in other situations. If
27915 tls_dhparam = /some/file/name
27917 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
27918 with the parameters contained in the file.
27919 Set this to &`none`& to disable use of DH entirely, by making no prime
27924 This may also be set to a string identifying a standard prime to be used for
27925 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
27926 used is &`ike23`&. There are a few standard primes available, see the
27927 documentation for &%tls_dhparam%& for the complete list.
27933 for a way of generating file data.
27935 The strings supplied for these three options are expanded every time a client
27936 host connects. It is therefore possible to use different certificates and keys
27937 for different hosts, if you so wish, by making use of the client's IP address
27938 in &$sender_host_address$& to control the expansion. If a string expansion is
27939 forced to fail, Exim behaves as if the option is not set.
27941 .cindex "cipher" "logging"
27942 .cindex "log" "TLS cipher"
27943 .vindex "&$tls_in_cipher$&"
27944 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
27945 an incoming TLS connection. It is included in the &'Received:'& header of an
27946 incoming message (by default &-- you can, of course, change this), and it is
27947 also included in the log line that records a message's arrival, keyed by
27948 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
27949 condition can be used to test for specific cipher suites in ACLs.
27951 Once TLS has been established, the ACLs that run for subsequent SMTP commands
27952 can check the name of the cipher suite and vary their actions accordingly. The
27953 cipher suite names vary, depending on which TLS library is being used. For
27954 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
27955 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
27956 documentation for more details.
27958 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
27959 (again depending on the &%tls_cipher%& log selector).
27962 .section "Requesting and verifying client certificates" "SECID183"
27963 .cindex "certificate" "verification of client"
27964 .cindex "TLS" "client certificate verification"
27965 If you want an Exim server to request a certificate when negotiating a TLS
27966 session with a client, you must set either &%tls_verify_hosts%& or
27967 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
27968 apply to all TLS connections. For any host that matches one of these options,
27969 Exim requests a certificate as part of the setup of the TLS session. The
27970 contents of the certificate are verified by comparing it with a list of
27971 expected trust-anchors or certificates.
27972 These may be the system default set (depending on library version),
27973 an explicit file or,
27974 depending on library version, a directory, identified by
27975 &%tls_verify_certificates%&.
27977 A file can contain multiple certificates, concatenated end to end. If a
27980 each certificate must be in a separate file, with a name (or a symbolic link)
27981 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
27982 certificate. You can compute the relevant hash by running the command
27984 openssl x509 -hash -noout -in /cert/file
27986 where &_/cert/file_& contains a single certificate.
27988 There is no checking of names of the client against the certificate
27989 Subject Name or Subject Alternate Names.
27991 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
27992 what happens if the client does not supply a certificate, or if the certificate
27993 does not match any of the certificates in the collection named by
27994 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
27995 attempt to set up a TLS session is aborted, and the incoming connection is
27996 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
27997 session continues. ACLs that run for subsequent SMTP commands can detect the
27998 fact that no certificate was verified, and vary their actions accordingly. For
27999 example, you can insist on a certificate before accepting a message for
28000 relaying, but not when the message is destined for local delivery.
28002 .vindex "&$tls_in_peerdn$&"
28003 When a client supplies a certificate (whether it verifies or not), the value of
28004 the Distinguished Name of the certificate is made available in the variable
28005 &$tls_in_peerdn$& during subsequent processing of the message.
28007 .cindex "log" "distinguished name"
28008 Because it is often a long text string, it is not included in the log line or
28009 &'Received:'& header by default. You can arrange for it to be logged, keyed by
28010 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
28011 &%received_header_text%& to change the &'Received:'& header. When no
28012 certificate is supplied, &$tls_in_peerdn$& is empty.
28015 .section "Revoked certificates" "SECID184"
28016 .cindex "TLS" "revoked certificates"
28017 .cindex "revocation list"
28018 .cindex "certificate" "revocation list"
28019 .cindex "OCSP" "stapling"
28020 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
28021 certificates are revoked. If you have such a list, you can pass it to an Exim
28022 server using the global option called &%tls_crl%& and to an Exim client using
28023 an identically named option for the &(smtp)& transport. In each case, the value
28024 of the option is expanded and must then be the name of a file that contains a
28026 The downside is that clients have to periodically re-download a potentially huge
28027 file from every certificate authority they know of.
28029 The way with most moving parts at query time is Online Certificate
28030 Status Protocol (OCSP), where the client verifies the certificate
28031 against an OCSP server run by the CA. This lets the CA track all
28032 usage of the certs. It requires running software with access to the
28033 private key of the CA, to sign the responses to the OCSP queries. OCSP
28034 is based on HTTP and can be proxied accordingly.
28036 The only widespread OCSP server implementation (known to this writer)
28037 comes as part of OpenSSL and aborts on an invalid request, such as
28038 connecting to the port and then disconnecting. This requires
28039 re-entering the passphrase each time some random client does this.
28041 The third way is OCSP Stapling; in this, the server using a certificate
28042 issued by the CA periodically requests an OCSP proof of validity from
28043 the OCSP server, then serves it up inline as part of the TLS
28044 negotiation. This approach adds no extra round trips, does not let the
28045 CA track users, scales well with number of certs issued by the CA and is
28046 resilient to temporary OCSP server failures, as long as the server
28047 starts retrying to fetch an OCSP proof some time before its current
28048 proof expires. The downside is that it requires server support.
28050 Unless Exim is built with the support disabled,
28051 or with GnuTLS earlier than version 3.3.16 / 3.4.8
28052 support for OCSP stapling is included.
28054 There is a global option called &%tls_ocsp_file%&.
28055 The file specified therein is expected to be in DER format, and contain
28056 an OCSP proof. Exim will serve it as part of the TLS handshake. This
28057 option will be re-expanded for SNI, if the &%tls_certificate%& option
28058 contains &`tls_in_sni`&, as per other TLS options.
28060 Exim does not at this time implement any support for fetching a new OCSP
28061 proof. The burden is on the administrator to handle this, outside of
28062 Exim. The file specified should be replaced atomically, so that the
28063 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
28064 on each connection, so a new file will be handled transparently on the
28067 When built with OpenSSL Exim will check for a valid next update timestamp
28068 in the OCSP proof; if not present, or if the proof has expired, it will be
28071 For the client to be able to verify the stapled OCSP the server must
28072 also supply, in its stapled information, any intermediate
28073 certificates for the chain leading to the OCSP proof from the signer
28074 of the server certificate. There may be zero or one such. These
28075 intermediate certificates should be added to the server OCSP stapling
28076 file named by &%tls_ocsp_file%&.
28078 Note that the proof only covers the terminal server certificate,
28079 not any of the chain from CA to it.
28081 There is no current way to staple a proof for a client certificate.
28084 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
28085 OCSP server is supplied. The server URL may be included in the
28086 server certificate, if the CA is helpful.
28088 One failure mode seen was the OCSP Signer cert expiring before the end
28089 of validity of the OCSP proof. The checking done by Exim/OpenSSL
28090 noted this as invalid overall, but the re-fetch script did not.
28096 .section "Configuring an Exim client to use TLS" "SECID185"
28097 .cindex "cipher" "logging"
28098 .cindex "log" "TLS cipher"
28099 .cindex "log" "distinguished name"
28100 .cindex "TLS" "configuring an Exim client"
28101 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
28102 deliveries as well as to incoming, the latter one causing logging of the
28103 server certificate's DN. The remaining client configuration for TLS is all
28104 within the &(smtp)& transport.
28106 It is not necessary to set any options to have TLS work in the &(smtp)&
28107 transport. If Exim is built with TLS support, and TLS is advertised by a
28108 server, the &(smtp)& transport always tries to start a TLS session. However,
28109 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
28110 transport) to a list of server hosts for which TLS should not be used.
28112 If you do not want Exim to attempt to send messages unencrypted when an attempt
28113 to set up an encrypted connection fails in any way, you can set
28114 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
28115 those hosts, delivery is always deferred if an encrypted connection cannot be
28116 set up. If there are any other hosts for the address, they are tried in the
28119 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
28120 the message unencrypted. It always does this if the response to STARTTLS is
28121 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
28122 session after a success response code, what happens is controlled by the
28123 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
28124 delivery to this host is deferred, and other hosts (if available) are tried. If
28125 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
28126 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
28127 negotiation fails, Exim closes the current connection (because it is in an
28128 unknown state), opens a new one to the same host, and then tries the delivery
28131 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
28132 transport provide the client with a certificate, which is passed to the server
28133 if it requests it. If the server is Exim, it will request a certificate only if
28134 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
28136 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
28137 specifies a collection of expected server certificates.
28139 the system default set (depending on library version),
28141 or (depending on library version) a directory.
28142 The client verifies the server's certificate
28143 against this collection, taking into account any revoked certificates that are
28144 in the list defined by &%tls_crl%&.
28145 Failure to verify fails the TLS connection unless either of the
28146 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
28148 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
28149 certificate verification to the listed servers. Verification either must
28150 or need not succeed respectively.
28152 The &%tls_verify_cert_hostnames%& option lists hosts for which additional
28153 checks are made: that the host name (the one in the DNS A record)
28154 is valid for the certificate.
28155 The option defaults to always checking.
28157 The &(smtp)& transport has two OCSP-related options:
28158 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
28159 is requested and required for the connection to proceed. The default
28161 &%hosts_request_ocsp%&; a host-list for which (additionally)
28162 a Certificate Status is requested (but not necessarily verified). The default
28163 value is "*" meaning that requests are made unless configured
28166 The host(s) should also be in &%hosts_require_tls%&, and
28167 &%tls_verify_certificates%& configured for the transport,
28168 for OCSP to be relevant.
28171 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
28172 list of permitted cipher suites. If either of these checks fails, delivery to
28173 the current host is abandoned, and the &(smtp)& transport tries to deliver to
28174 alternative hosts, if any.
28177 These options must be set in the &(smtp)& transport for Exim to use TLS when it
28178 is operating as a client. Exim does not assume that a server certificate (set
28179 by the global options of the same name) should also be used when operating as a
28183 .vindex "&$host_address$&"
28184 All the TLS options in the &(smtp)& transport are expanded before use, with
28185 &$host$& and &$host_address$& containing the name and address of the server to
28186 which the client is connected. Forced failure of an expansion causes Exim to
28187 behave as if the relevant option were unset.
28189 .vindex &$tls_out_bits$&
28190 .vindex &$tls_out_cipher$&
28191 .vindex &$tls_out_peerdn$&
28192 .vindex &$tls_out_sni$&
28193 Before an SMTP connection is established, the
28194 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
28195 variables are emptied. (Until the first connection, they contain the values
28196 that were set when the message was received.) If STARTTLS is subsequently
28197 successfully obeyed, these variables are set to the relevant values for the
28198 outgoing connection.
28202 .section "Use of TLS Server Name Indication" "SECTtlssni"
28203 .cindex "TLS" "Server Name Indication"
28204 .vindex "&$tls_in_sni$&"
28205 .oindex "&%tls_in_sni%&"
28206 With TLS1.0 or above, there is an extension mechanism by which extra
28207 information can be included at various points in the protocol. One of these
28208 extensions, documented in RFC 6066 (and before that RFC 4366) is
28209 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
28210 client in the initial handshake, so that the server can examine the servername
28211 within and possibly choose to use different certificates and keys (and more)
28214 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
28215 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
28218 With SMTP to MX, there are the same problems here as in choosing the identity
28219 against which to validate a certificate: you can't rely on insecure DNS to
28220 provide the identity which you then cryptographically verify. So this will
28221 be of limited use in that environment.
28223 With SMTP to Submission, there is a well-defined hostname which clients are
28224 connecting to and can validate certificates against. Thus clients &*can*&
28225 choose to include this information in the TLS negotiation. If this becomes
28226 wide-spread, then hosters can choose to present different certificates to
28227 different clients. Or even negotiate different cipher suites.
28229 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
28230 if not empty, will be sent on a TLS session as part of the handshake. There's
28231 nothing more to it. Choosing a sensible value not derived insecurely is the
28232 only point of caution. The &$tls_out_sni$& variable will be set to this string
28233 for the lifetime of the client connection (including during authentication).
28235 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
28236 received from a client.
28237 It can be logged with the &%log_selector%& item &`+tls_sni`&.
28239 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
28240 option (prior to expansion) then the following options will be re-expanded
28241 during TLS session handshake, to permit alternative values to be chosen:
28244 &%tls_certificate%&
28250 &%tls_verify_certificates%&
28255 Great care should be taken to deal with matters of case, various injection
28256 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
28257 can always be referenced; it is important to remember that &$tls_in_sni$& is
28258 arbitrary unverified data provided prior to authentication.
28259 Further, the initial certificate is loaded before SNI is arrived, so
28260 an expansion for &%tls_certificate%& must have a default which is used
28261 when &$tls_in_sni$& is empty.
28263 The Exim developers are proceeding cautiously and so far no other TLS options
28266 When Exim is built against OpenSSL, OpenSSL must have been built with support
28267 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
28268 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
28269 see &`-servername`& in the output, then OpenSSL has support.
28271 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
28272 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
28273 built, then you have SNI support).
28277 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
28279 .cindex "multiple SMTP deliveries with TLS"
28280 .cindex "TLS" "multiple message deliveries"
28281 Exim sends multiple messages down the same TCP/IP connection by starting up
28282 an entirely new delivery process for each message, passing the socket from
28283 one process to the next. This implementation does not fit well with the use
28284 of TLS, because there is quite a lot of state information associated with a TLS
28285 connection, not just a socket identification. Passing all the state information
28286 to a new process is not feasible. Consequently, for sending using TLS Exim
28287 starts an additional proxy process for handling the encryption, piping the
28288 unencrypted data stream from and to the delivery processes.
28290 An older mode of operation can be enabled on a per-host basis by the
28291 &%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
28292 this list the proxy process described above is not used; instead Exim
28293 shuts down an existing TLS session being run by the delivery process
28294 before passing the socket to a new process. The new process may then
28295 try to start a new TLS session, and if successful, may try to re-authenticate
28296 if AUTH is in use, before sending the next message.
28298 The RFC is not clear as to whether or not an SMTP session continues in clear
28299 after TLS has been shut down, or whether TLS may be restarted again later, as
28300 just described. However, if the server is Exim, this shutdown and
28301 reinitialization works. It is not known which (if any) other servers operate
28302 successfully if the client closes a TLS session and continues with unencrypted
28303 SMTP, but there are certainly some that do not work. For such servers, Exim
28304 should not pass the socket to another process, because the failure of the
28305 subsequent attempt to use it would cause Exim to record a temporary host error,
28306 and delay other deliveries to that host.
28308 To test for this case, Exim sends an EHLO command to the server after
28309 closing down the TLS session. If this fails in any way, the connection is
28310 closed instead of being passed to a new delivery process, but no retry
28311 information is recorded.
28313 There is also a manual override; you can set &%hosts_nopass_tls%& on the
28314 &(smtp)& transport to match those hosts for which Exim should not pass
28315 connections to new processes if TLS has been used.
28320 .section "Certificates and all that" "SECTcerandall"
28321 .cindex "certificate" "references to discussion"
28322 In order to understand fully how TLS works, you need to know about
28323 certificates, certificate signing, and certificate authorities.
28324 This is a large topic and an introductory guide is unsuitable for the Exim
28325 reference manual, so instead we provide pointers to existing documentation.
28327 The Apache web-server was for a long time the canonical guide, so their
28328 documentation is a good place to start; their SSL module's Introduction
28329 document is currently at
28331 &url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html)
28333 and their FAQ is at
28335 &url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html)
28338 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
28339 0-201-61598-3) in 2001, contains both introductory and more in-depth
28341 More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&,
28342 published by Feisty Duck (ISBN 978-1907117046) in 2013 is good.
28343 Ivan is the author of the popular TLS testing tools at
28344 &url(https://www.ssllabs.com/).
28347 .section "Certificate chains" "SECID186"
28348 The file named by &%tls_certificate%& may contain more than one
28349 certificate. This is useful in the case where the certificate that is being
28350 sent is validated by an intermediate certificate which the other end does
28351 not have. Multiple certificates must be in the correct order in the file.
28352 First the host's certificate itself, then the first intermediate
28353 certificate to validate the issuer of the host certificate, then the next
28354 intermediate certificate to validate the issuer of the first intermediate
28355 certificate, and so on, until finally (optionally) the root certificate.
28356 The root certificate must already be trusted by the recipient for
28357 validation to succeed, of course, but if it's not preinstalled, sending the
28358 root certificate along with the rest makes it available for the user to
28359 install if the receiving end is a client MUA that can interact with a user.
28361 Note that certificates using MD5 are unlikely to work on today's Internet;
28362 even if your libraries allow loading them for use in Exim when acting as a
28363 server, increasingly clients will not accept such certificates. The error
28364 diagnostics in such a case can be frustratingly vague.
28368 .section "Self-signed certificates" "SECID187"
28369 .cindex "certificate" "self-signed"
28370 You can create a self-signed certificate using the &'req'& command provided
28371 with OpenSSL, like this:
28372 . ==== Do not shorten the duration here without reading and considering
28373 . ==== the text below. Please leave it at 9999 days.
28375 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
28378 &_file1_& and &_file2_& can be the same file; the key and the certificate are
28379 delimited and so can be identified independently. The &%-days%& option
28380 specifies a period for which the certificate is valid. The &%-nodes%& option is
28381 important: if you do not set it, the key is encrypted with a passphrase
28382 that you are prompted for, and any use that is made of the key causes more
28383 prompting for the passphrase. This is not helpful if you are going to use
28384 this certificate and key in an MTA, where prompting is not possible.
28386 . ==== I expect to still be working 26 years from now. The less technical
28387 . ==== debt I create, in terms of storing up trouble for my later years, the
28388 . ==== happier I will be then. We really have reached the point where we
28389 . ==== should start, at the very least, provoking thought and making folks
28390 . ==== pause before proceeding, instead of leaving all the fixes until two
28391 . ==== years before 2^31 seconds after the 1970 Unix epoch.
28393 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
28394 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
28395 the above command might produce a date in the past. Think carefully about
28396 the lifetime of the systems you're deploying, and either reduce the duration
28397 of the certificate or reconsider your platform deployment. (At time of
28398 writing, reducing the duration is the most likely choice, but the inexorable
28399 progression of time takes us steadily towards an era where this will not
28400 be a sensible resolution).
28402 A self-signed certificate made in this way is sufficient for testing, and
28403 may be adequate for all your requirements if you are mainly interested in
28404 encrypting transfers, and not in secure identification.
28406 However, many clients require that the certificate presented by the server be a
28407 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
28408 certificate. In this situation, the self-signed certificate described above
28409 must be installed on the client host as a trusted root &'certification
28410 authority'& (CA), and the certificate used by Exim must be a user certificate
28411 signed with that self-signed certificate.
28413 For information on creating self-signed CA certificates and using them to sign
28414 user certificates, see the &'General implementation overview'& chapter of the
28415 Open-source PKI book, available online at
28416 &url(https://sourceforge.net/projects/ospkibook/).
28417 .ecindex IIDencsmtp1
28418 .ecindex IIDencsmtp2
28422 .section DANE "SECDANE"
28424 DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
28425 it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
28426 operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
28427 you and the server still think you have an encrypted connection) and, if one of the "well known" set of
28428 Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
28429 certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
28431 What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
28432 that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
28433 by (a) is thought to be smaller than that of the set of root CAs.
28435 It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
28436 fail to pass on a server's STARTTLS.
28438 DANE scales better than having to maintain (and side-channel communicate) copies of server certificates
28439 for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
28440 client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
28442 DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
28443 that DNS lookups they do for the server have not been tampered with. The domain MX record applying
28444 to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
28446 2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
28447 3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
28449 There are no changes to Exim specific to server-side operation of DANE.
28450 Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
28451 in &_Local/Makefile_&.
28452 If it has been included, the macro "_HAVE_DANE" will be defined.
28454 The TLSA record for the server may have "certificate usage" of DANE-TA(2) or DANE-EE(3).
28455 These are the "Trust Anchor" and "End Entity" variants.
28456 The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
28457 (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
28458 this is appropriate for a single system, using a self-signed certificate.
28459 DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
28461 A private CA at simplest is just a self-signed certificate (with certain
28462 attributes) which is used to sign server certificates, but running one securely
28463 does require careful arrangement.
28464 With DANE-TA, as implemented in Exim and commonly in other MTAs,
28465 the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
28466 DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
28467 all of which point to a single TLSA record.
28468 DANE-TA and DANE-EE can both be used together.
28470 Our recommendation is to use DANE with a certificate from a public CA,
28471 because this enables a variety of strategies for remote clients to verify
28473 You can then publish information both via DANE and another technology,
28474 "MTA-STS", described below.
28476 When you use DANE-TA to publish trust anchor information, you ask entities
28477 outside your administrative control to trust the Certificate Authority for
28478 connections to you.
28479 If using a private CA then you should expect others to still apply the
28480 technical criteria they'd use for a public CA to your certificates.
28481 In particular, you should probably try to follow current best practices for CA
28482 operation around hash algorithms and key sizes.
28483 Do not expect other organizations to lower their security expectations just
28484 because a particular profile might be reasonable for your own internal use.
28486 When this text was last updated, this in practice means to avoid use of SHA-1
28487 and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
28488 than 4096, for interoperability); to use keyUsage fields correctly; to use
28489 random serial numbers.
28490 The list of requirements is subject to change as best practices evolve.
28491 If you're not already using a private CA, or it doesn't meet these
28492 requirements, then we encourage you to avoid all these issues and use a public
28493 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
28495 The TLSA record should have a Selector field of SPKI(1) and a Matching Type field of SHA2-512(2).
28497 At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
28498 is useful for quickly generating TLSA records; and commands like
28501 openssl x509 -in -pubkey -noout <certificate.pem \
28502 | openssl rsa -outform der -pubin 2>/dev/null \
28507 are workable for 4th-field hashes.
28509 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
28511 The Certificate issued by the CA published in the DANE-TA model should be
28512 issued using a strong hash algorithm.
28513 Exim, and importantly various other MTAs sending to you, will not
28514 re-enable hash algorithms which have been disabled by default in TLS
28516 This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
28517 interoperability (and probably the maximum too, in 2018).
28519 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
28520 be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
28521 default of requesting OCSP for all hosts is modified iff DANE is in use, to:
28524 hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
28525 {= {4}{$tls_out_tlsa_usage}} } \
28529 The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
28530 The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
28531 found. If the definition of &%hosts_request_ocsp%& includes the
28532 string "tls_out_tlsa_usage", they are re-expanded in time to
28533 control the OCSP request.
28535 This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
28536 those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
28539 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
28540 and &%dane_require_tls_ciphers%&.
28541 The require variant will result in failure if the target host is not DNSSEC-secured.
28543 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
28545 A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using dnssec.
28546 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
28547 will be required for the host. If it does not, the host will not
28548 be used; there is no fallback to non-DANE or non-TLS.
28550 If DANE is requested and usable, then the TLS cipher list configuration
28551 prefers to use the option &%dane_require_tls_ciphers%& and falls
28552 back to &%tls_require_ciphers%& only if that is unset.
28553 This lets you configure "decent crypto" for DANE and "better than nothing
28554 crypto" as the default. Note though that while GnuTLS lets the string control
28555 which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
28556 limited to ciphersuite constraints.
28558 If DANE is requested and useable (see above) the following transport options are ignored:
28562 tls_try_verify_hosts
28563 tls_verify_certificates
28565 tls_verify_cert_hostnames
28568 If DANE is not usable, whether requested or not, and CA-anchored
28569 verification evaluation is wanted, the above variables should be set appropriately.
28571 Currently the &%dnssec_request_domains%& must be active and &%dnssec_require_domains%& is ignored.
28573 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
28575 There is a new variable &$tls_out_dane$& which will have "yes" if
28576 verification succeeded using DANE and "no" otherwise (only useful
28577 in combination with events; see &<<CHAPevents>>&),
28578 and a new variable &$tls_out_tlsa_usage$& (detailed above).
28580 .cindex DANE reporting
28581 An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
28582 to achieve DANE-verified connection, if one was either requested and offered, or
28583 required. This is intended to support TLS-reporting as defined in
28584 &url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
28585 The &$event_data$& will be one of the Result Types defined in
28586 Section 4.3 of that document.
28588 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
28590 DANE is specified in published RFCs and decouples certificate authority trust
28591 selection from a "race to the bottom" of "you must trust everything for mail
28592 to get through". There is an alternative technology called MTA-STS, which
28593 instead publishes MX trust anchor information on an HTTPS website. At the
28594 time this text was last updated, MTA-STS was still a draft, not yet an RFC.
28595 Exim has no support for MTA-STS as a client, but Exim mail server operators
28596 can choose to publish information describing their TLS configuration using
28597 MTA-STS to let those clients who do use that protocol derive trust
28600 The MTA-STS design requires a certificate from a public Certificate Authority
28601 which is recognized by clients sending to you.
28602 That selection of which CAs are trusted by others is outside your control.
28604 The most interoperable course of action is probably to use
28605 &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
28606 renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
28607 records for DANE clients (such as Exim and Postfix) and to publish anchor
28608 information for MTA-STS as well. This is what is done for the &'exim.org'&
28609 domain itself (with caveats around occasionally broken MTA-STS because of
28610 incompatible specification changes prior to reaching RFC status).
28614 . ////////////////////////////////////////////////////////////////////////////
28615 . ////////////////////////////////////////////////////////////////////////////
28617 .chapter "Access control lists" "CHAPACL"
28618 .scindex IIDacl "&ACL;" "description"
28619 .cindex "control of incoming mail"
28620 .cindex "message" "controlling incoming"
28621 .cindex "policy control" "access control lists"
28622 Access Control Lists (ACLs) are defined in a separate section of the runtime
28623 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
28624 name, terminated by a colon. Here is a complete ACL section that contains just
28625 one very small ACL:
28629 accept hosts = one.host.only
28631 You can have as many lists as you like in the ACL section, and the order in
28632 which they appear does not matter. The lists are self-terminating.
28634 The majority of ACLs are used to control Exim's behaviour when it receives
28635 certain SMTP commands. This applies both to incoming TCP/IP connections, and
28636 when a local process submits a message using SMTP by specifying the &%-bs%&
28637 option. The most common use is for controlling which recipients are accepted
28638 in incoming messages. In addition, you can define an ACL that is used to check
28639 local non-SMTP messages. The default configuration file contains an example of
28640 a realistic ACL for checking RCPT commands. This is discussed in chapter
28641 &<<CHAPdefconfil>>&.
28644 .section "Testing ACLs" "SECID188"
28645 The &%-bh%& command line option provides a way of testing your ACL
28646 configuration locally by running a fake SMTP session with which you interact.
28649 .section "Specifying when ACLs are used" "SECID189"
28650 .cindex "&ACL;" "options for specifying"
28651 In order to cause an ACL to be used, you have to name it in one of the relevant
28652 options in the main part of the configuration. These options are:
28653 .cindex "AUTH" "ACL for"
28654 .cindex "DATA" "ACLs for"
28655 .cindex "ETRN" "ACL for"
28656 .cindex "EXPN" "ACL for"
28657 .cindex "HELO" "ACL for"
28658 .cindex "EHLO" "ACL for"
28659 .cindex "DKIM" "ACL for"
28660 .cindex "MAIL" "ACL for"
28661 .cindex "QUIT, ACL for"
28662 .cindex "RCPT" "ACL for"
28663 .cindex "STARTTLS, ACL for"
28664 .cindex "VRFY" "ACL for"
28665 .cindex "SMTP" "connection, ACL for"
28666 .cindex "non-SMTP messages" "ACLs for"
28667 .cindex "MIME content scanning" "ACL for"
28668 .cindex "PRDR" "ACL for"
28671 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
28672 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
28673 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
28674 .irow &%acl_smtp_auth%& "ACL for AUTH"
28675 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
28676 .irow &%acl_smtp_data%& "ACL after DATA is complete"
28677 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
28678 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
28679 .irow &%acl_smtp_etrn%& "ACL for ETRN"
28680 .irow &%acl_smtp_expn%& "ACL for EXPN"
28681 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
28682 .irow &%acl_smtp_mail%& "ACL for MAIL"
28683 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
28684 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
28685 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
28686 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
28687 .irow &%acl_smtp_quit%& "ACL for QUIT"
28688 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
28689 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
28690 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
28693 For example, if you set
28695 acl_smtp_rcpt = small_acl
28697 the little ACL defined above is used whenever Exim receives a RCPT command
28698 in an SMTP dialogue. The majority of policy tests on incoming messages can be
28699 done when RCPT commands arrive. A rejection of RCPT should cause the
28700 sending MTA to give up on the recipient address contained in the RCPT
28701 command, whereas rejection at other times may cause the client MTA to keep on
28702 trying to deliver the message. It is therefore recommended that you do as much
28703 testing as possible at RCPT time.
28706 .section "The non-SMTP ACLs" "SECID190"
28707 .cindex "non-SMTP messages" "ACLs for"
28708 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
28709 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
28710 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
28711 the state of the SMTP connection such as encryption and authentication) are not
28712 relevant and are forbidden in these ACLs. However, the sender and recipients
28713 are known, so the &%senders%& and &%sender_domains%& conditions and the
28714 &$sender_address$& and &$recipients$& variables can be used. Variables such as
28715 &$authenticated_sender$& are also available. You can specify added header lines
28716 in any of these ACLs.
28718 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
28719 non-SMTP message, before any of the message has been read. (This is the
28720 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
28721 batched SMTP input, it runs after the DATA command has been reached. The
28722 result of this ACL is ignored; it cannot be used to reject a message. If you
28723 really need to, you could set a value in an ACL variable here and reject based
28724 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
28725 controls, and in particular, it can be used to set
28727 control = suppress_local_fixups
28729 This cannot be used in the other non-SMTP ACLs because by the time they are
28730 run, it is too late.
28732 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
28733 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
28735 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
28736 kind of rejection is treated as permanent, because there is no way of sending a
28737 temporary error for these kinds of message.
28740 .section "The SMTP connect ACL" "SECID191"
28741 .cindex "SMTP" "connection, ACL for"
28742 .oindex &%smtp_banner%&
28743 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
28744 session, after the test specified by &%host_reject_connection%& (which is now
28745 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
28746 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
28747 the message override the banner message that is otherwise specified by the
28748 &%smtp_banner%& option.
28751 .section "The EHLO/HELO ACL" "SECID192"
28752 .cindex "EHLO" "ACL for"
28753 .cindex "HELO" "ACL for"
28754 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
28755 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
28756 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
28757 Note that a client may issue more than one EHLO or HELO command in an SMTP
28758 session, and indeed is required to issue a new EHLO or HELO after successfully
28759 setting up encryption following a STARTTLS command.
28761 Note also that a deny neither forces the client to go away nor means that
28762 mail will be refused on the connection. Consider checking for
28763 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
28765 If the command is accepted by an &%accept%& verb that has a &%message%&
28766 modifier, the message may not contain more than one line (it will be truncated
28767 at the first newline and a panic logged if it does). Such a message cannot
28768 affect the EHLO options that are listed on the second and subsequent lines of
28772 .section "The DATA ACLs" "SECID193"
28773 .cindex "DATA" "ACLs for"
28774 Two ACLs are associated with the DATA command, because it is two-stage
28775 command, with two responses being sent to the client.
28776 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
28777 is obeyed. This gives you control after all the RCPT commands, but before
28778 the message itself is received. It offers the opportunity to give a negative
28779 response to the DATA command before the data is transmitted. Header lines
28780 added by MAIL or RCPT ACLs are not visible at this time, but any that
28781 are defined here are visible when the &%acl_smtp_data%& ACL is run.
28783 You cannot test the contents of the message, for example, to verify addresses
28784 in the headers, at RCPT time or when the DATA command is received. Such
28785 tests have to appear in the ACL that is run after the message itself has been
28786 received, before the final response to the DATA command is sent. This is
28787 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
28788 associated with the DATA command.
28790 .cindex CHUNKING "BDAT command"
28791 .cindex BDAT "SMTP command"
28792 .cindex "RFC 3030" CHUNKING
28793 If CHUNKING was advertised and a BDAT command sequence is received,
28794 the &%acl_smtp_predata%& ACL is not run.
28795 . XXX why not? It should be possible, for the first BDAT.
28796 The &%acl_smtp_data%& is run after the last BDAT command and all of
28797 the data specified is received.
28799 For both of these ACLs, it is not possible to reject individual recipients. An
28800 error response rejects the entire message. Unfortunately, it is known that some
28801 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
28802 before or after the data) correctly &-- they keep the message on their queues
28803 and try again later, but that is their problem, though it does waste some of
28806 The &%acl_smtp_data%& ACL is run after
28807 the &%acl_smtp_data_prdr%&,
28808 the &%acl_smtp_dkim%&
28809 and the &%acl_smtp_mime%& ACLs.
28811 .section "The SMTP DKIM ACL" "SECTDKIMACL"
28812 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
28813 enabled (which is the default).
28815 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
28816 received, and is executed for each DKIM signature found in a message. If not
28817 otherwise specified, the default action is to accept.
28819 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
28821 For details on the operation of DKIM, see section &<<SECDKIM>>&.
28824 .section "The SMTP MIME ACL" "SECID194"
28825 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
28826 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
28828 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
28831 .section "The SMTP PRDR ACL" "SECTPRDRACL"
28832 .cindex "PRDR" "ACL for"
28833 .oindex "&%prdr_enable%&"
28834 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
28835 with PRDR support enabled (which is the default).
28836 It becomes active only when the PRDR feature is negotiated between
28837 client and server for a message, and more than one recipient
28840 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
28841 has been received, and is executed once for each recipient of the message
28842 with &$local_part$& and &$domain$& valid.
28843 The test may accept, defer or deny for individual recipients.
28844 The &%acl_smtp_data%& will still be called after this ACL and
28845 can reject the message overall, even if this ACL has accepted it
28846 for some or all recipients.
28848 PRDR may be used to support per-user content filtering. Without it
28849 one must defer any recipient after the first that has a different
28850 content-filter configuration. With PRDR, the RCPT-time check
28851 .cindex "PRDR" "variable for"
28852 for this can be disabled when the variable &$prdr_requested$&
28854 Any required difference in behaviour of the main DATA-time
28855 ACL should however depend on the PRDR-time ACL having run, as Exim
28856 will avoid doing so in some situations (e.g. single-recipient mails).
28858 See also the &%prdr_enable%& global option
28859 and the &%hosts_try_prdr%& smtp transport option.
28861 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
28862 If the ACL is not defined, processing completes as if
28863 the feature was not requested by the client.
28865 .section "The QUIT ACL" "SECTQUITACL"
28866 .cindex "QUIT, ACL for"
28867 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
28868 does not affect the response code to QUIT, which is always 221. Thus, the ACL
28869 does not in fact control any access.
28870 For this reason, it may only accept
28871 or warn as its final result.
28873 This ACL can be used for tasks such as custom logging at the end of an SMTP
28874 session. For example, you can use ACL variables in other ACLs to count
28875 messages, recipients, etc., and log the totals at QUIT time using one or
28876 more &%logwrite%& modifiers on a &%warn%& verb.
28878 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
28879 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
28881 You do not need to have a final &%accept%&, but if you do, you can use a
28882 &%message%& modifier to specify custom text that is sent as part of the 221
28885 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
28886 failure (for example, failure to open a log file, or when Exim is bombing out
28887 because it has detected an unrecoverable error), all SMTP commands from the
28888 client are given temporary error responses until QUIT is received or the
28889 connection is closed. In these special cases, the QUIT ACL does not run.
28892 .section "The not-QUIT ACL" "SECTNOTQUITACL"
28893 .vindex &$acl_smtp_notquit$&
28894 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
28895 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
28896 trouble, such as being unable to write to its log files, this ACL is not run,
28897 because it might try to do things (such as write to log files) that make the
28898 situation even worse.
28900 Like the QUIT ACL, this ACL is provided to make it possible to do customized
28901 logging or to gather statistics, and its outcome is ignored. The &%delay%&
28902 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
28905 .vindex &$smtp_notquit_reason$&
28906 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
28907 to a string that indicates the reason for the termination of the SMTP
28908 connection. The possible values are:
28910 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
28911 .irow &`bad-commands`& "Too many unknown or non-mail commands"
28912 .irow &`command-timeout`& "Timeout while reading SMTP commands"
28913 .irow &`connection-lost`& "The SMTP connection has been lost"
28914 .irow &`data-timeout`& "Timeout while reading message data"
28915 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
28916 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
28917 .irow &`signal-exit`& "SIGTERM or SIGINT"
28918 .irow &`synchronization-error`& "SMTP synchronization error"
28919 .irow &`tls-failed`& "TLS failed to start"
28921 In most cases when an SMTP connection is closed without having received QUIT,
28922 Exim sends an SMTP response message before actually closing the connection.
28923 With the exception of the &`acl-drop`& case, the default message can be
28924 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
28925 &%drop%& verb in another ACL, it is the message from the other ACL that is
28929 .section "Finding an ACL to use" "SECID195"
28930 .cindex "&ACL;" "finding which to use"
28931 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
28932 you can use different ACLs in different circumstances. For example,
28934 acl_smtp_rcpt = ${if ={25}{$interface_port} \
28935 {acl_check_rcpt} {acl_check_rcpt_submit} }
28937 In the default configuration file there are some example settings for
28938 providing an RFC 4409 message &"submission"& service on port 587 and
28939 an RFC 8314 &"submissions"& service on port 465. You can use a string
28940 expansion like this to choose an ACL for MUAs on these ports which is
28941 more appropriate for this purpose than the default ACL on port 25.
28943 The expanded string does not have to be the name of an ACL in the
28944 configuration file; there are other possibilities. Having expanded the
28945 string, Exim searches for an ACL as follows:
28948 If the string begins with a slash, Exim uses it as a filename, and reads its
28949 contents as an ACL. The lines are processed in the same way as lines in the
28950 Exim configuration file. In particular, continuation lines are supported, blank
28951 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
28952 If the file does not exist or cannot be read, an error occurs (typically
28953 causing a temporary failure of whatever caused the ACL to be run). For example:
28955 acl_smtp_data = /etc/acls/\
28956 ${lookup{$sender_host_address}lsearch\
28957 {/etc/acllist}{$value}{default}}
28959 This looks up an ACL file to use on the basis of the host's IP address, falling
28960 back to a default if the lookup fails. If an ACL is successfully read from a
28961 file, it is retained in memory for the duration of the Exim process, so that it
28962 can be re-used without having to re-read the file.
28964 If the string does not start with a slash, and does not contain any spaces,
28965 Exim searches the ACL section of the configuration for an ACL whose name
28966 matches the string.
28968 If no named ACL is found, or if the string contains spaces, Exim parses
28969 the string as an inline ACL. This can save typing in cases where you just
28970 want to have something like
28972 acl_smtp_vrfy = accept
28974 in order to allow free use of the VRFY command. Such a string may contain
28975 newlines; it is processed in the same way as an ACL that is read from a file.
28981 .section "ACL return codes" "SECID196"
28982 .cindex "&ACL;" "return codes"
28983 Except for the QUIT ACL, which does not affect the SMTP return code (see
28984 section &<<SECTQUITACL>>& above), the result of running an ACL is either
28985 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
28986 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
28987 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
28988 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
28989 This also causes a 4&'xx'& return code.
28991 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
28992 &"deny"&, because there is no mechanism for passing temporary errors to the
28993 submitters of non-SMTP messages.
28996 ACLs that are relevant to message reception may also return &"discard"&. This
28997 has the effect of &"accept"&, but causes either the entire message or an
28998 individual recipient address to be discarded. In other words, it is a
28999 blackholing facility. Use it with care.
29001 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
29002 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
29003 RCPT ACL is to discard just the one recipient address. If there are no
29004 recipients left when the message's data is received, the DATA ACL is not
29005 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
29006 remaining recipients. The &"discard"& return is not permitted for the
29007 &%acl_smtp_predata%& ACL.
29009 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
29010 is done on the address and the result determines the SMTP response.
29013 .cindex "&[local_scan()]& function" "when all recipients discarded"
29014 The &[local_scan()]& function is always run, even if there are no remaining
29015 recipients; it may create new recipients.
29019 .section "Unset ACL options" "SECID197"
29020 .cindex "&ACL;" "unset options"
29021 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
29022 all the same. &*Note*&: These defaults apply only when the relevant ACL is
29023 not defined at all. For any defined ACL, the default action when control
29024 reaches the end of the ACL statements is &"deny"&.
29026 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
29027 these two are ACLs that are used only for their side effects. They cannot be
29028 used to accept or reject anything.
29030 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
29031 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
29032 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
29033 when the ACL is not defined is &"accept"&.
29035 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
29036 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
29037 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
29038 messages over an SMTP connection. For an example, see the ACL in the default
29039 configuration file.
29044 .section "Data for message ACLs" "SECID198"
29045 .cindex "&ACL;" "data for message ACL"
29047 .vindex &$local_part$&
29048 .vindex &$sender_address$&
29049 .vindex &$sender_host_address$&
29050 .vindex &$smtp_command$&
29051 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
29052 that contain information about the host and the message's sender (for example,
29053 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
29054 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
29055 &$local_part$& are set from the argument address. The entire SMTP command
29056 is available in &$smtp_command$&.
29058 When an ACL for the AUTH parameter of MAIL is running, the variables that
29059 contain information about the host are set, but &$sender_address$& is not yet
29060 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
29063 .vindex "&$message_size$&"
29064 The &$message_size$& variable is set to the value of the SIZE parameter on
29065 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
29066 that parameter is not given. The value is updated to the true message size by
29067 the time the final DATA ACL is run (after the message data has been
29070 .vindex "&$rcpt_count$&"
29071 .vindex "&$recipients_count$&"
29072 The &$rcpt_count$& variable increases by one for each RCPT command received.
29073 The &$recipients_count$& variable increases by one each time a RCPT command is
29074 accepted, so while an ACL for RCPT is being processed, it contains the number
29075 of previously accepted recipients. At DATA time (for both the DATA ACLs),
29076 &$rcpt_count$& contains the total number of RCPT commands, and
29077 &$recipients_count$& contains the total number of accepted recipients.
29083 .section "Data for non-message ACLs" "SECTdatfornon"
29084 .cindex "&ACL;" "data for non-message ACL"
29085 .vindex &$smtp_command_argument$&
29086 .vindex &$smtp_command$&
29087 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
29088 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
29089 and the entire SMTP command is available in &$smtp_command$&.
29090 These variables can be tested using a &%condition%& condition. For example,
29091 here is an ACL for use with AUTH, which insists that either the session is
29092 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
29093 does not permit authentication methods that use cleartext passwords on
29094 unencrypted connections.
29097 accept encrypted = *
29098 accept condition = ${if eq{${uc:$smtp_command_argument}}\
29100 deny message = TLS encryption or CRAM-MD5 required
29102 (Another way of applying this restriction is to arrange for the authenticators
29103 that use cleartext passwords not to be advertised when the connection is not
29104 encrypted. You can use the generic &%server_advertise_condition%& authenticator
29105 option to do this.)
29109 .section "Format of an ACL" "SECID199"
29110 .cindex "&ACL;" "format of"
29111 .cindex "&ACL;" "verbs, definition of"
29112 An individual ACL consists of a number of statements. Each statement starts
29113 with a verb, optionally followed by a number of conditions and &"modifiers"&.
29114 Modifiers can change the way the verb operates, define error and log messages,
29115 set variables, insert delays, and vary the processing of accepted messages.
29117 If all the conditions are met, the verb is obeyed. The same condition may be
29118 used (with different arguments) more than once in the same statement. This
29119 provides a means of specifying an &"and"& conjunction between conditions. For
29122 deny dnslists = list1.example
29123 dnslists = list2.example
29125 If there are no conditions, the verb is always obeyed. Exim stops evaluating
29126 the conditions and modifiers when it reaches a condition that fails. What
29127 happens then depends on the verb (and in one case, on a special modifier). Not
29128 all the conditions make sense at every testing point. For example, you cannot
29129 test a sender address in the ACL that is run for a VRFY command.
29132 .section "ACL verbs" "SECID200"
29133 The ACL verbs are as follows:
29136 .cindex "&%accept%& ACL verb"
29137 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
29138 of the conditions are not met, what happens depends on whether &%endpass%&
29139 appears among the conditions (for syntax see below). If the failing condition
29140 is before &%endpass%&, control is passed to the next ACL statement; if it is
29141 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
29142 check a RCPT command:
29144 accept domains = +local_domains
29148 If the recipient domain does not match the &%domains%& condition, control
29149 passes to the next statement. If it does match, the recipient is verified, and
29150 the command is accepted if verification succeeds. However, if verification
29151 fails, the ACL yields &"deny"&, because the failing condition is after
29154 The &%endpass%& feature has turned out to be confusing to many people, so its
29155 use is not recommended nowadays. It is always possible to rewrite an ACL so
29156 that &%endpass%& is not needed, and it is no longer used in the default
29159 .cindex "&%message%& ACL modifier" "with &%accept%&"
29160 If a &%message%& modifier appears on an &%accept%& statement, its action
29161 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
29162 (when an &%accept%& verb either accepts or passes control to the next
29163 statement), &%message%& can be used to vary the message that is sent when an
29164 SMTP command is accepted. For example, in a RCPT ACL you could have:
29166 &`accept `&<&'some conditions'&>
29167 &` message = OK, I will allow you through today`&
29169 You can specify an SMTP response code, optionally followed by an &"extended
29170 response code"& at the start of the message, but the first digit must be the
29171 same as would be sent by default, which is 2 for an &%accept%& verb.
29173 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
29174 an error message that is used when access is denied. This behaviour is retained
29175 for backward compatibility, but current &"best practice"& is to avoid the use
29180 .cindex "&%defer%& ACL verb"
29181 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
29182 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
29183 &%defer%& is the same as &%deny%&, because there is no way of sending a
29184 temporary error. For a RCPT command, &%defer%& is much the same as using a
29185 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
29186 be used in any ACL, and even for a recipient it might be a simpler approach.
29190 .cindex "&%deny%& ACL verb"
29191 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
29192 the conditions are not met, control is passed to the next ACL statement. For
29195 deny dnslists = blackholes.mail-abuse.org
29197 rejects commands from hosts that are on a DNS black list.
29201 .cindex "&%discard%& ACL verb"
29202 &%discard%&: This verb behaves like &%accept%&, except that it returns
29203 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
29204 that are concerned with receiving messages. When all the conditions are true,
29205 the sending entity receives a &"success"& response. However, &%discard%& causes
29206 recipients to be discarded. If it is used in an ACL for RCPT, just the one
29207 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
29208 message's recipients are discarded. Recipients that are discarded before DATA
29209 do not appear in the log line when the &%received_recipients%& log selector is set.
29211 If the &%log_message%& modifier is set when &%discard%& operates,
29212 its contents are added to the line that is automatically written to the log.
29213 The &%message%& modifier operates exactly as it does for &%accept%&.
29217 .cindex "&%drop%& ACL verb"
29218 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
29219 forcibly closed after the 5&'xx'& error message has been sent. For example:
29221 drop message = I don't take more than 20 RCPTs
29222 condition = ${if > {$rcpt_count}{20}}
29224 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
29225 The connection is always dropped after sending a 550 response.
29228 .cindex "&%require%& ACL verb"
29229 &%require%&: If all the conditions are met, control is passed to the next ACL
29230 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
29231 example, when checking a RCPT command,
29233 require message = Sender did not verify
29236 passes control to subsequent statements only if the message's sender can be
29237 verified. Otherwise, it rejects the command. Note the positioning of the
29238 &%message%& modifier, before the &%verify%& condition. The reason for this is
29239 discussed in section &<<SECTcondmodproc>>&.
29242 .cindex "&%warn%& ACL verb"
29243 &%warn%&: If all the conditions are true, a line specified by the
29244 &%log_message%& modifier is written to Exim's main log. Control always passes
29245 to the next ACL statement. If any condition is false, the log line is not
29246 written. If an identical log line is requested several times in the same
29247 message, only one copy is actually written to the log. If you want to force
29248 duplicates to be written, use the &%logwrite%& modifier instead.
29250 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
29251 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
29252 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
29253 first failing condition. There is more about adding header lines in section
29254 &<<SECTaddheadacl>>&.
29256 If any condition on a &%warn%& statement cannot be completed (that is, there is
29257 some sort of defer), the log line specified by &%log_message%& is not written.
29258 This does not include the case of a forced failure from a lookup, which
29259 is considered to be a successful completion. After a defer, no further
29260 conditions or modifiers in the &%warn%& statement are processed. The incident
29261 is logged, and the ACL continues to be processed, from the next statement
29265 .vindex "&$acl_verify_message$&"
29266 When one of the &%warn%& conditions is an address verification that fails, the
29267 text of the verification failure message is in &$acl_verify_message$&. If you
29268 want this logged, you must set it up explicitly. For example:
29270 warn !verify = sender
29271 log_message = sender verify failed: $acl_verify_message
29275 At the end of each ACL there is an implicit unconditional &%deny%&.
29277 As you can see from the examples above, the conditions and modifiers are
29278 written one to a line, with the first one on the same line as the verb, and
29279 subsequent ones on following lines. If you have a very long condition, you can
29280 continue it onto several physical lines by the usual backslash continuation
29281 mechanism. It is conventional to align the conditions vertically.
29285 .section "ACL variables" "SECTaclvariables"
29286 .cindex "&ACL;" "variables"
29287 There are some special variables that can be set during ACL processing. They
29288 can be used to pass information between different ACLs, different invocations
29289 of the same ACL in the same SMTP connection, and between ACLs and the routers,
29290 transports, and filters that are used to deliver a message. The names of these
29291 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
29292 an underscore, but the remainder of the name can be any sequence of
29293 alphanumeric characters and underscores that you choose. There is no limit on
29294 the number of ACL variables. The two sets act as follows:
29296 The values of those variables whose names begin with &$acl_c$& persist
29297 throughout an SMTP connection. They are never reset. Thus, a value that is set
29298 while receiving one message is still available when receiving the next message
29299 on the same SMTP connection.
29301 The values of those variables whose names begin with &$acl_m$& persist only
29302 while a message is being received. They are reset afterwards. They are also
29303 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
29306 When a message is accepted, the current values of all the ACL variables are
29307 preserved with the message and are subsequently made available at delivery
29308 time. The ACL variables are set by a modifier called &%set%&. For example:
29310 accept hosts = whatever
29311 set acl_m4 = some value
29312 accept authenticated = *
29313 set acl_c_auth = yes
29315 &*Note*&: A leading dollar sign is not used when naming a variable that is to
29316 be set. If you want to set a variable without taking any action, you can use a
29317 &%warn%& verb without any other modifiers or conditions.
29319 .oindex &%strict_acl_vars%&
29320 What happens if a syntactically valid but undefined ACL variable is
29321 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
29322 false (the default), an empty string is substituted; if it is true, an
29323 error is generated.
29325 Versions of Exim before 4.64 have a limited set of numbered variables, but
29326 their names are compatible, so there is no problem with upgrading.
29329 .section "Condition and modifier processing" "SECTcondmodproc"
29330 .cindex "&ACL;" "conditions; processing"
29331 .cindex "&ACL;" "modifiers; processing"
29332 An exclamation mark preceding a condition negates its result. For example:
29334 deny domains = *.dom.example
29335 !verify = recipient
29337 causes the ACL to return &"deny"& if the recipient domain ends in
29338 &'dom.example'& and the recipient address cannot be verified. Sometimes
29339 negation can be used on the right-hand side of a condition. For example, these
29340 two statements are equivalent:
29342 deny hosts = !192.168.3.4
29343 deny !hosts = 192.168.3.4
29345 However, for many conditions (&%verify%& being a good example), only left-hand
29346 side negation of the whole condition is possible.
29348 The arguments of conditions and modifiers are expanded. A forced failure
29349 of an expansion causes a condition to be ignored, that is, it behaves as if the
29350 condition is true. Consider these two statements:
29352 accept senders = ${lookup{$host_name}lsearch\
29353 {/some/file}{$value}fail}
29354 accept senders = ${lookup{$host_name}lsearch\
29355 {/some/file}{$value}{}}
29357 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
29358 the returned list is searched, but if the lookup fails the behaviour is
29359 different in the two cases. The &%fail%& in the first statement causes the
29360 condition to be ignored, leaving no further conditions. The &%accept%& verb
29361 therefore succeeds. The second statement, however, generates an empty list when
29362 the lookup fails. No sender can match an empty list, so the condition fails,
29363 and therefore the &%accept%& also fails.
29365 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
29366 specify actions that are taken as the conditions for a statement are checked;
29367 others specify text for messages that are used when access is denied or a
29368 warning is generated. The &%control%& modifier affects the way an incoming
29369 message is handled.
29371 The positioning of the modifiers in an ACL statement is important, because the
29372 processing of a verb ceases as soon as its outcome is known. Only those
29373 modifiers that have already been encountered will take effect. For example,
29374 consider this use of the &%message%& modifier:
29376 require message = Can't verify sender
29378 message = Can't verify recipient
29380 message = This message cannot be used
29382 If sender verification fails, Exim knows that the result of the statement is
29383 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
29384 so its text is used as the error message. If sender verification succeeds, but
29385 recipient verification fails, the second message is used. If recipient
29386 verification succeeds, the third message becomes &"current"&, but is never used
29387 because there are no more conditions to cause failure.
29389 For the &%deny%& verb, on the other hand, it is always the last &%message%&
29390 modifier that is used, because all the conditions must be true for rejection to
29391 happen. Specifying more than one &%message%& modifier does not make sense, and
29392 the message can even be specified after all the conditions. For example:
29395 !senders = *@my.domain.example
29396 message = Invalid sender from client host
29398 The &"deny"& result does not happen until the end of the statement is reached,
29399 by which time Exim has set up the message.
29403 .section "ACL modifiers" "SECTACLmodi"
29404 .cindex "&ACL;" "modifiers; list of"
29405 The ACL modifiers are as follows:
29408 .vitem &*add_header*&&~=&~<&'text'&>
29409 This modifier specifies one or more header lines that are to be added to an
29410 incoming message, assuming, of course, that the message is ultimately
29411 accepted. For details, see section &<<SECTaddheadacl>>&.
29413 .vitem &*continue*&&~=&~<&'text'&>
29414 .cindex "&%continue%& ACL modifier"
29415 .cindex "database" "updating in ACL"
29416 This modifier does nothing of itself, and processing of the ACL always
29417 continues with the next condition or modifier. The value of &%continue%& is in
29418 the side effects of expanding its argument. Typically this could be used to
29419 update a database. It is really just a syntactic tidiness, to avoid having to
29420 write rather ugly lines like this:
29422 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
29424 Instead, all you need is
29426 &`continue = `&<&'some expansion'&>
29429 .vitem &*control*&&~=&~<&'text'&>
29430 .cindex "&%control%& ACL modifier"
29431 This modifier affects the subsequent processing of the SMTP connection or of an
29432 incoming message that is accepted. The effect of the first type of control
29433 lasts for the duration of the connection, whereas the effect of the second type
29434 lasts only until the current message has been received. The message-specific
29435 controls always apply to the whole message, not to individual recipients,
29436 even if the &%control%& modifier appears in a RCPT ACL.
29438 As there are now quite a few controls that can be applied, they are described
29439 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
29440 in several different ways. For example:
29442 . ==== As this is a nested list, any displays it contains must be indented
29443 . ==== as otherwise they are too far to the left. That comment applies only
29444 . ==== when xmlto and fop are used; formatting with sdop gets it right either
29448 It can be at the end of an &%accept%& statement:
29450 accept ...some conditions
29451 control = queue_only
29453 In this case, the control is applied when this statement yields &"accept"&, in
29454 other words, when the conditions are all true.
29457 It can be in the middle of an &%accept%& statement:
29459 accept ...some conditions...
29460 control = queue_only
29461 ...some more conditions...
29463 If the first set of conditions are true, the control is applied, even if the
29464 statement does not accept because one of the second set of conditions is false.
29465 In this case, some subsequent statement must yield &"accept"& for the control
29469 It can be used with &%warn%& to apply the control, leaving the
29470 decision about accepting or denying to a subsequent verb. For
29473 warn ...some conditions...
29477 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
29478 &%logwrite%&, so it does not add anything to the message and does not write a
29482 If you want to apply a control unconditionally, you can use it with a
29483 &%require%& verb. For example:
29485 require control = no_multiline_responses
29489 .vitem &*delay*&&~=&~<&'time'&>
29490 .cindex "&%delay%& ACL modifier"
29492 This modifier may appear in any ACL except notquit. It causes Exim to wait for
29493 the time interval before proceeding. However, when testing Exim using the
29494 &%-bh%& option, the delay is not actually imposed (an appropriate message is
29495 output instead). The time is given in the usual Exim notation, and the delay
29496 happens as soon as the modifier is processed. In an SMTP session, pending
29497 output is flushed before the delay is imposed.
29499 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
29502 deny ...some conditions...
29505 The delay happens if all the conditions are true, before the statement returns
29506 &"deny"&. Compare this with:
29509 ...some conditions...
29511 which waits for 30s before processing the conditions. The &%delay%& modifier
29512 can also be used with &%warn%& and together with &%control%&:
29514 warn ...some conditions...
29520 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
29521 responses to several commands are no longer buffered and sent in one packet (as
29522 they would normally be) because all output is flushed before imposing the
29523 delay. This optimization is disabled so that a number of small delays do not
29524 appear to the client as one large aggregated delay that might provoke an
29525 unwanted timeout. You can, however, disable output flushing for &%delay%& by
29526 using a &%control%& modifier to set &%no_delay_flush%&.
29530 .cindex "&%endpass%& ACL modifier"
29531 This modifier, which has no argument, is recognized only in &%accept%& and
29532 &%discard%& statements. It marks the boundary between the conditions whose
29533 failure causes control to pass to the next statement, and the conditions whose
29534 failure causes the ACL to return &"deny"&. This concept has proved to be
29535 confusing to some people, so the use of &%endpass%& is no longer recommended as
29536 &"best practice"&. See the description of &%accept%& above for more details.
29539 .vitem &*log_message*&&~=&~<&'text'&>
29540 .cindex "&%log_message%& ACL modifier"
29541 This modifier sets up a message that is used as part of the log message if the
29542 ACL denies access or a &%warn%& statement's conditions are true. For example:
29544 require log_message = wrong cipher suite $tls_in_cipher
29545 encrypted = DES-CBC3-SHA
29547 &%log_message%& is also used when recipients are discarded by &%discard%&. For
29550 &`discard `&<&'some conditions'&>
29551 &` log_message = Discarded $local_part@$domain because...`&
29553 When access is denied, &%log_message%& adds to any underlying error message
29554 that may exist because of a condition failure. For example, while verifying a
29555 recipient address, a &':fail:'& redirection might have already set up a
29558 The message may be defined before the conditions to which it applies, because
29559 the string expansion does not happen until Exim decides that access is to be
29560 denied. This means that any variables that are set by the condition are
29561 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
29562 variables are set after a DNS black list lookup succeeds. If the expansion of
29563 &%log_message%& fails, or if the result is an empty string, the modifier is
29566 .vindex "&$acl_verify_message$&"
29567 If you want to use a &%warn%& statement to log the result of an address
29568 verification, you can use &$acl_verify_message$& to include the verification
29571 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
29572 the start of the logged message. If the same warning log message is requested
29573 more than once while receiving a single email message, only one copy is
29574 actually logged. If you want to log multiple copies, use &%logwrite%& instead
29575 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
29576 is logged for a successful &%warn%& statement.
29578 If &%log_message%& is not present and there is no underlying error message (for
29579 example, from the failure of address verification), but &%message%& is present,
29580 the &%message%& text is used for logging rejections. However, if any text for
29581 logging contains newlines, only the first line is logged. In the absence of
29582 both &%log_message%& and &%message%&, a default built-in message is used for
29583 logging rejections.
29586 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
29587 .cindex "&%log_reject_target%& ACL modifier"
29588 .cindex "logging in ACL" "specifying which log"
29589 This modifier makes it possible to specify which logs are used for messages
29590 about ACL rejections. Its argument is a colon-separated list of words that can
29591 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
29592 may be empty, in which case a rejection is not logged at all. For example, this
29593 ACL fragment writes no logging information when access is denied:
29595 &`deny `&<&'some conditions'&>
29596 &` log_reject_target =`&
29598 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
29599 permanent and temporary rejections. Its effect lasts for the rest of the
29603 .vitem &*logwrite*&&~=&~<&'text'&>
29604 .cindex "&%logwrite%& ACL modifier"
29605 .cindex "logging in ACL" "immediate"
29606 This modifier writes a message to a log file as soon as it is encountered when
29607 processing an ACL. (Compare &%log_message%&, which, except in the case of
29608 &%warn%& and &%discard%&, is used only if the ACL statement denies
29609 access.) The &%logwrite%& modifier can be used to log special incidents in
29612 &`accept `&<&'some special conditions'&>
29613 &` control = freeze`&
29614 &` logwrite = froze message because ...`&
29616 By default, the message is written to the main log. However, it may begin
29617 with a colon, followed by a comma-separated list of log names, and then
29618 another colon, to specify exactly which logs are to be written. For
29621 logwrite = :main,reject: text for main and reject logs
29622 logwrite = :panic: text for panic log only
29626 .vitem &*message*&&~=&~<&'text'&>
29627 .cindex "&%message%& ACL modifier"
29628 This modifier sets up a text string that is expanded and used as a response
29629 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
29630 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
29631 there is some complication if &%endpass%& is involved; see the description of
29632 &%accept%& for details.)
29634 The expansion of the message happens at the time Exim decides that the ACL is
29635 to end, not at the time it processes &%message%&. If the expansion fails, or
29636 generates an empty string, the modifier is ignored. Here is an example where
29637 &%message%& must be specified first, because the ACL ends with a rejection if
29638 the &%hosts%& condition fails:
29640 require message = Host not recognized
29643 (Once a condition has failed, no further conditions or modifiers are
29646 .cindex "SMTP" "error codes"
29647 .oindex "&%smtp_banner%&
29648 For ACLs that are triggered by SMTP commands, the message is returned as part
29649 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
29650 is meaningful only for SMTP, as no message is returned when a non-SMTP message
29651 is accepted. In the case of the connect ACL, accepting with a message modifier
29652 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
29653 accept message may not contain more than one line (otherwise it will be
29654 truncated at the first newline and a panic logged), and it cannot affect the
29657 When SMTP is involved, the message may begin with an overriding response code,
29658 consisting of three digits optionally followed by an &"extended response code"&
29659 of the form &'n.n.n'&, each code being followed by a space. For example:
29661 deny message = 599 1.2.3 Host not welcome
29662 hosts = 192.168.34.0/24
29664 The first digit of the supplied response code must be the same as would be sent
29665 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
29666 access, but for the predata ACL, note that the default success code is 354, not
29669 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
29670 the message modifier cannot override the 221 response code.
29672 The text in a &%message%& modifier is literal; any quotes are taken as
29673 literals, but because the string is expanded, backslash escapes are processed
29674 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
29677 .vindex "&$acl_verify_message$&"
29678 For ACLs that are called by an &%acl =%& ACL condition, the message is
29679 stored in &$acl_verify_message$&, from which the calling ACL may use it.
29681 If &%message%& is used on a statement that verifies an address, the message
29682 specified overrides any message that is generated by the verification process.
29683 However, the original message is available in the variable
29684 &$acl_verify_message$&, so you can incorporate it into your message if you
29685 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
29686 routers to be passed back as part of the SMTP response, you should either not
29687 use a &%message%& modifier, or make use of &$acl_verify_message$&.
29689 For compatibility with previous releases of Exim, a &%message%& modifier that
29690 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
29691 modifier, but this usage is now deprecated. However, &%message%& acts only when
29692 all the conditions are true, wherever it appears in an ACL command, whereas
29693 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
29694 &%warn%& in an ACL that is not concerned with receiving a message, it has no
29698 .vitem &*queue*&&~=&~<&'text'&>
29699 .cindex "&%queue%& ACL modifier"
29700 .cindex "named queues" "selecting in ACL"
29701 This modifier specifies the use of a named queue for spool files
29703 It can only be used before the message is received (i.e. not in
29705 This could be used, for example, for known high-volume burst sources
29706 of traffic, or for quarantine of messages.
29707 Separate queue-runner processes will be needed for named queues.
29708 If the text after expansion is empty, the default queue is used.
29711 .vitem &*remove_header*&&~=&~<&'text'&>
29712 This modifier specifies one or more header names in a colon-separated list
29713 that are to be removed from an incoming message, assuming, of course, that
29714 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
29717 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
29718 .cindex "&%set%& ACL modifier"
29719 This modifier puts a value into one of the ACL variables (see section
29720 &<<SECTaclvariables>>&).
29723 .vitem &*udpsend*&&~=&~<&'parameters'&>
29724 .cindex "UDP communications"
29725 This modifier sends a UDP packet, for purposes such as statistics
29726 collection or behaviour monitoring. The parameters are expanded, and
29727 the result of the expansion must be a colon-separated list consisting
29728 of a destination server, port number, and the packet contents. The
29729 server can be specified as a host name or IPv4 or IPv6 address. The
29730 separator can be changed with the usual angle bracket syntax. For
29731 example, you might want to collect information on which hosts connect
29734 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
29735 $tod_zulu $sender_host_address
29742 .section "Use of the control modifier" "SECTcontrols"
29743 .cindex "&%control%& ACL modifier"
29744 The &%control%& modifier supports the following settings:
29747 .vitem &*control&~=&~allow_auth_unadvertised*&
29748 This modifier allows a client host to use the SMTP AUTH command even when it
29749 has not been advertised in response to EHLO. Furthermore, because there are
29750 apparently some really broken clients that do this, Exim will accept AUTH after
29751 HELO (rather than EHLO) when this control is set. It should be used only if you
29752 really need it, and you should limit its use to those broken clients that do
29753 not work without it. For example:
29755 warn hosts = 192.168.34.25
29756 control = allow_auth_unadvertised
29758 Normally, when an Exim server receives an AUTH command, it checks the name of
29759 the authentication mechanism that is given in the command to ensure that it
29760 matches an advertised mechanism. When this control is set, the check that a
29761 mechanism has been advertised is bypassed. Any configured mechanism can be used
29762 by the client. This control is permitted only in the connection and HELO ACLs.
29765 .vitem &*control&~=&~caseful_local_part*& &&&
29766 &*control&~=&~caselower_local_part*&
29767 .cindex "&ACL;" "case of local part in"
29768 .cindex "case of local parts"
29769 .vindex "&$local_part$&"
29770 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
29771 (that is, during RCPT processing). By default, the contents of &$local_part$&
29772 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
29773 any uppercase letters in the original local part are restored in &$local_part$&
29774 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
29777 These controls affect only the current recipient. Moreover, they apply only to
29778 local part handling that takes place directly in the ACL (for example, as a key
29779 in lookups). If a test to verify the recipient is obeyed, the case-related
29780 handling of the local part during the verification is controlled by the router
29781 configuration (see the &%caseful_local_part%& generic router option).
29783 This facility could be used, for example, to add a spam score to local parts
29784 containing upper case letters. For example, using &$acl_m4$& to accumulate the
29787 warn control = caseful_local_part
29788 set acl_m4 = ${eval:\
29790 ${if match{$local_part}{[A-Z]}{1}{0}}\
29792 control = caselower_local_part
29794 Notice that we put back the lower cased version afterwards, assuming that
29795 is what is wanted for subsequent tests.
29798 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
29799 .cindex "&ACL;" "cutthrough routing"
29800 .cindex "cutthrough" "requesting"
29801 This option requests delivery be attempted while the item is being received.
29803 The option is usable in the RCPT ACL.
29804 If enabled for a message received via smtp and routed to an smtp transport,
29805 and only one transport, interface, destination host and port combination
29806 is used for all recipients of the message,
29807 then the delivery connection is made while the receiving connection is open
29808 and data is copied from one to the other.
29810 An attempt to set this option for any recipient but the first
29811 for a mail will be quietly ignored.
29812 If a recipient-verify callout
29814 connection is subsequently
29815 requested in the same ACL it is held open and used for
29816 any subsequent recipients and the data,
29817 otherwise one is made after the initial RCPT ACL completes.
29819 Note that routers are used in verify mode,
29820 and cannot depend on content of received headers.
29821 Note also that headers cannot be
29822 modified by any of the post-data ACLs (DATA, MIME and DKIM).
29823 Headers may be modified by routers (subject to the above) and transports.
29824 The &'Received-By:'& header is generated as soon as the body reception starts,
29825 rather than the traditional time after the full message is received;
29826 this will affect the timestamp.
29828 All the usual ACLs are called; if one results in the message being
29829 rejected, all effort spent in delivery (including the costs on
29830 the ultimate destination) will be wasted.
29831 Note that in the case of data-time ACLs this includes the entire
29834 Cutthrough delivery is not supported via transport-filters or when DKIM signing
29835 of outgoing messages is done, because it sends data to the ultimate destination
29836 before the entire message has been received from the source.
29837 It is not supported for messages received with the SMTP PRDR
29841 Should the ultimate destination system positively accept or reject the mail,
29842 a corresponding indication is given to the source system and nothing is queued.
29843 If the item is successfully delivered in cutthrough mode
29844 the delivery log lines are tagged with ">>" rather than "=>" and appear
29845 before the acceptance "<=" line.
29847 If there is a temporary error the item is queued for later delivery in the
29849 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
29850 to the control; the default value is &"spool"& and the alternate value
29851 &"pass"& copies an SMTP defer response from the target back to the initiator
29852 and does not queue the message.
29853 Note that this is independent of any recipient verify conditions in the ACL.
29855 Delivery in this mode avoids the generation of a bounce mail to a
29857 sender when the destination system is doing content-scan based rejection.
29860 .vitem &*control&~=&~debug/*&<&'options'&>
29861 .cindex "&ACL;" "enabling debug logging"
29862 .cindex "debugging" "enabling from an ACL"
29863 This control turns on debug logging, almost as though Exim had been invoked
29864 with &`-d`&, with the output going to a new logfile in the usual logs directory,
29865 by default called &'debuglog'&.
29866 The filename can be adjusted with the &'tag'& option, which
29867 may access any variables already defined. The logging may be adjusted with
29868 the &'opts'& option, which takes the same values as the &`-d`& command-line
29870 Logging started this way may be stopped, and the file removed,
29871 with the &'kill'& option.
29872 Some examples (which depend on variables that don't exist in all
29876 control = debug/tag=.$sender_host_address
29877 control = debug/opts=+expand+acl
29878 control = debug/tag=.$message_exim_id/opts=+expand
29879 control = debug/kill
29883 .vitem &*control&~=&~dkim_disable_verify*&
29884 .cindex "disable DKIM verify"
29885 .cindex "DKIM" "disable verify"
29886 This control turns off DKIM verification processing entirely. For details on
29887 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
29890 .vitem &*control&~=&~dscp/*&<&'value'&>
29891 .cindex "&ACL;" "setting DSCP value"
29892 .cindex "DSCP" "inbound"
29893 This option causes the DSCP value associated with the socket for the inbound
29894 connection to be adjusted to a given value, given as one of a number of fixed
29895 strings or to numeric value.
29896 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
29897 Common values include &`throughput`&, &`mincost`&, and on newer systems
29898 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
29900 The outbound packets from Exim will be marked with this value in the header
29901 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
29902 that these values will have any effect, not be stripped by networking
29903 equipment, or do much of anything without cooperation with your Network
29904 Engineer and those of all network operators between the source and destination.
29907 .vitem &*control&~=&~enforce_sync*& &&&
29908 &*control&~=&~no_enforce_sync*&
29909 .cindex "SMTP" "synchronization checking"
29910 .cindex "synchronization checking in SMTP"
29911 These controls make it possible to be selective about when SMTP synchronization
29912 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
29913 state of the switch (it is true by default). See the description of this option
29914 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
29916 The effect of these two controls lasts for the remainder of the SMTP
29917 connection. They can appear in any ACL except the one for the non-SMTP
29918 messages. The most straightforward place to put them is in the ACL defined by
29919 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
29920 before the first synchronization check. The expected use is to turn off the
29921 synchronization checks for badly-behaved hosts that you nevertheless need to
29925 .vitem &*control&~=&~fakedefer/*&<&'message'&>
29926 .cindex "fake defer"
29927 .cindex "defer, fake"
29928 This control works in exactly the same way as &%fakereject%& (described below)
29929 except that it causes an SMTP 450 response after the message data instead of a
29930 550 response. You must take care when using &%fakedefer%& because it causes the
29931 messages to be duplicated when the sender retries. Therefore, you should not
29932 use &%fakedefer%& if the message is to be delivered normally.
29934 .vitem &*control&~=&~fakereject/*&<&'message'&>
29935 .cindex "fake rejection"
29936 .cindex "rejection, fake"
29937 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
29938 words, only when an SMTP message is being received. If Exim accepts the
29939 message, instead the final 250 response, a 550 rejection message is sent.
29940 However, Exim proceeds to deliver the message as normal. The control applies
29941 only to the current message, not to any subsequent ones that may be received in
29942 the same SMTP connection.
29944 The text for the 550 response is taken from the &%control%& modifier. If no
29945 message is supplied, the following is used:
29947 550-Your message has been rejected but is being
29948 550-kept for evaluation.
29949 550-If it was a legitimate message, it may still be
29950 550 delivered to the target recipient(s).
29952 This facility should be used with extreme caution.
29954 .vitem &*control&~=&~freeze*&
29955 .cindex "frozen messages" "forcing in ACL"
29956 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
29957 other words, only when a message is being received. If the message is accepted,
29958 it is placed on Exim's queue and frozen. The control applies only to the
29959 current message, not to any subsequent ones that may be received in the same
29962 This modifier can optionally be followed by &`/no_tell`&. If the global option
29963 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
29964 is told about the freezing), provided all the &*control=freeze*& modifiers that
29965 are obeyed for the current message have the &`/no_tell`& option.
29967 .vitem &*control&~=&~no_delay_flush*&
29968 .cindex "SMTP" "output flushing, disabling for delay"
29969 Exim normally flushes SMTP output before implementing a delay in an ACL, to
29970 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
29971 use. This control, as long as it is encountered before the &%delay%& modifier,
29972 disables such output flushing.
29974 .vitem &*control&~=&~no_callout_flush*&
29975 .cindex "SMTP" "output flushing, disabling for callout"
29976 Exim normally flushes SMTP output before performing a callout in an ACL, to
29977 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
29978 use. This control, as long as it is encountered before the &%verify%& condition
29979 that causes the callout, disables such output flushing.
29981 .vitem &*control&~=&~no_mbox_unspool*&
29982 This control is available when Exim is compiled with the content scanning
29983 extension. Content scanning may require a copy of the current message, or parts
29984 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
29985 or spam scanner. Normally, such copies are deleted when they are no longer
29986 needed. If this control is set, the copies are not deleted. The control applies
29987 only to the current message, not to any subsequent ones that may be received in
29988 the same SMTP connection. It is provided for debugging purposes and is unlikely
29989 to be useful in production.
29991 .vitem &*control&~=&~no_multiline_responses*&
29992 .cindex "multiline responses, suppressing"
29993 This control is permitted for any ACL except the one for non-SMTP messages.
29994 It seems that there are broken clients in use that cannot handle multiline
29995 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
29997 If this control is set, multiline SMTP responses from ACL rejections are
29998 suppressed. One way of doing this would have been to put out these responses as
29999 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
30000 (&"use multiline responses for more"& it says &-- ha!), and some of the
30001 responses might get close to that. So this facility, which is after all only a
30002 sop to broken clients, is implemented by doing two very easy things:
30005 Extra information that is normally output as part of a rejection caused by
30006 sender verification failure is omitted. Only the final line (typically &"sender
30007 verification failed"&) is sent.
30009 If a &%message%& modifier supplies a multiline response, only the first
30013 The setting of the switch can, of course, be made conditional on the
30014 calling host. Its effect lasts until the end of the SMTP connection.
30016 .vitem &*control&~=&~no_pipelining*&
30017 .cindex "PIPELINING" "suppressing advertising"
30018 This control turns off the advertising of the PIPELINING extension to SMTP in
30019 the current session. To be useful, it must be obeyed before Exim sends its
30020 response to an EHLO command. Therefore, it should normally appear in an ACL
30021 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
30022 &%pipelining_advertise_hosts%&.
30024 .vitem &*control&~=&~queue_only*&
30025 .oindex "&%queue_only%&"
30026 .cindex "queueing incoming messages"
30027 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
30028 other words, only when a message is being received. If the message is accepted,
30029 it is placed on Exim's queue and left there for delivery by a subsequent queue
30030 runner. No immediate delivery process is started. In other words, it has the
30031 effect as the &%queue_only%& global option. However, the control applies only
30032 to the current message, not to any subsequent ones that may be received in the
30033 same SMTP connection.
30035 .vitem &*control&~=&~submission/*&<&'options'&>
30036 .cindex "message" "submission"
30037 .cindex "submission mode"
30038 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
30039 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
30040 the current message is a submission from a local MUA. In this case, Exim
30041 operates in &"submission mode"&, and applies certain fixups to the message if
30042 necessary. For example, it adds a &'Date:'& header line if one is not present.
30043 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
30044 late (the message has already been created).
30046 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
30047 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
30048 submission mode; the available options for this control are described there.
30049 The control applies only to the current message, not to any subsequent ones
30050 that may be received in the same SMTP connection.
30052 .vitem &*control&~=&~suppress_local_fixups*&
30053 .cindex "submission fixups, suppressing"
30054 This control applies to locally submitted (non TCP/IP) messages, and is the
30055 complement of &`control = submission`&. It disables the fixups that are
30056 normally applied to locally-submitted messages. Specifically:
30059 Any &'Sender:'& header line is left alone (in this respect, it is a
30060 dynamic version of &%local_sender_retain%&).
30062 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
30064 There is no check that &'From:'& corresponds to the actual sender.
30067 This control may be useful when a remotely-originated message is accepted,
30068 passed to some scanning program, and then re-submitted for delivery. It can be
30069 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
30070 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
30073 &*Note:*& This control applies only to the current message, not to any others
30074 that are being submitted at the same time using &%-bs%& or &%-bS%&.
30076 .vitem &*control&~=&~utf8_downconvert*&
30077 This control enables conversion of UTF-8 in message addresses
30079 For details see section &<<SECTi18nMTA>>&.
30083 .section "Summary of message fixup control" "SECTsummesfix"
30084 All four possibilities for message fixups can be specified:
30087 Locally submitted, fixups applied: the default.
30089 Locally submitted, no fixups applied: use
30090 &`control = suppress_local_fixups`&.
30092 Remotely submitted, no fixups applied: the default.
30094 Remotely submitted, fixups applied: use &`control = submission`&.
30099 .section "Adding header lines in ACLs" "SECTaddheadacl"
30100 .cindex "header lines" "adding in an ACL"
30101 .cindex "header lines" "position of added lines"
30102 .cindex "&%add_header%& ACL modifier"
30103 The &%add_header%& modifier can be used to add one or more extra header lines
30104 to an incoming message, as in this example:
30106 warn dnslists = sbl.spamhaus.org : \
30107 dialup.mail-abuse.org
30108 add_header = X-blacklisted-at: $dnslist_domain
30110 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
30111 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
30112 receiving a message). The message must ultimately be accepted for
30113 &%add_header%& to have any significant effect. You can use &%add_header%& with
30114 any ACL verb, including &%deny%& (though this is potentially useful only in a
30117 Headers will not be added to the message if the modifier is used in
30118 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
30120 Leading and trailing newlines are removed from
30121 the data for the &%add_header%& modifier; if it then
30122 contains one or more newlines that
30123 are not followed by a space or a tab, it is assumed to contain multiple header
30124 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
30125 front of any line that is not a valid header line.
30127 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
30128 They are added to the message before processing the DATA and MIME ACLs.
30129 However, if an identical header line is requested more than once, only one copy
30130 is actually added to the message. Further header lines may be accumulated
30131 during the DATA and MIME ACLs, after which they are added to the message, again
30132 with duplicates suppressed. Thus, it is possible to add two identical header
30133 lines to an SMTP message, but only if one is added before DATA and one after.
30134 In the case of non-SMTP messages, new headers are accumulated during the
30135 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
30136 message is rejected after DATA or by the non-SMTP ACL, all added header lines
30137 are included in the entry that is written to the reject log.
30139 .cindex "header lines" "added; visibility of"
30140 Header lines are not visible in string expansions
30142 until they are added to the
30143 message. It follows that header lines defined in the MAIL, RCPT, and predata
30144 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
30145 header lines that are added by the DATA or MIME ACLs are not visible in those
30146 ACLs. Because of this restriction, you cannot use header lines as a way of
30147 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
30148 this, you can use ACL variables, as described in section
30149 &<<SECTaclvariables>>&.
30151 The list of headers yet to be added is given by the &%$headers_added%& variable.
30153 The &%add_header%& modifier acts immediately as it is encountered during the
30154 processing of an ACL. Notice the difference between these two cases:
30156 &`accept add_header = ADDED: some text`&
30157 &` `&<&'some condition'&>
30159 &`accept `&<&'some condition'&>
30160 &` add_header = ADDED: some text`&
30162 In the first case, the header line is always added, whether or not the
30163 condition is true. In the second case, the header line is added only if the
30164 condition is true. Multiple occurrences of &%add_header%& may occur in the same
30165 ACL statement. All those that are encountered before a condition fails are
30168 .cindex "&%warn%& ACL verb"
30169 For compatibility with previous versions of Exim, a &%message%& modifier for a
30170 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
30171 effect only if all the conditions are true, even if it appears before some of
30172 them. Furthermore, only the last occurrence of &%message%& is honoured. This
30173 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
30174 are present on a &%warn%& verb, both are processed according to their
30177 By default, new header lines are added to a message at the end of the existing
30178 header lines. However, you can specify that any particular header line should
30179 be added right at the start (before all the &'Received:'& lines), immediately
30180 after the first block of &'Received:'& lines, or immediately before any line
30181 that is not a &'Received:'& or &'Resent-something:'& header.
30183 This is done by specifying &":at_start:"&, &":after_received:"&, or
30184 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
30185 header line, respectively. (Header text cannot start with a colon, as there has
30186 to be a header name first.) For example:
30188 warn add_header = \
30189 :after_received:X-My-Header: something or other...
30191 If more than one header line is supplied in a single &%add_header%& modifier,
30192 each one is treated independently and can therefore be placed differently. If
30193 you add more than one line at the start, or after the Received: block, they end
30194 up in reverse order.
30196 &*Warning*&: This facility currently applies only to header lines that are
30197 added in an ACL. It does NOT work for header lines that are added in a
30198 system filter or in a router or transport.
30202 .section "Removing header lines in ACLs" "SECTremoveheadacl"
30203 .cindex "header lines" "removing in an ACL"
30204 .cindex "header lines" "position of removed lines"
30205 .cindex "&%remove_header%& ACL modifier"
30206 The &%remove_header%& modifier can be used to remove one or more header lines
30207 from an incoming message, as in this example:
30209 warn message = Remove internal headers
30210 remove_header = x-route-mail1 : x-route-mail2
30212 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
30213 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
30214 receiving a message). The message must ultimately be accepted for
30215 &%remove_header%& to have any significant effect. You can use &%remove_header%&
30216 with any ACL verb, including &%deny%&, though this is really not useful for
30217 any verb that doesn't result in a delivered message.
30219 Headers will not be removed from the message if the modifier is used in
30220 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
30222 More than one header can be removed at the same time by using a colon separated
30223 list of header names. The header matching is case insensitive. Wildcards are
30224 not permitted, nor is list expansion performed, so you cannot use hostlists to
30225 create a list of headers, however both connection and message variable expansion
30226 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
30228 warn hosts = +internal_hosts
30229 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
30230 warn message = Remove internal headers
30231 remove_header = $acl_c_ihdrs
30233 Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
30234 Matching header lines are removed from the message before processing the DATA and MIME ACLs.
30235 If multiple header lines match, all are removed.
30236 There is no harm in attempting to remove the same header twice nor in removing
30237 a non-existent header. Further header lines to be removed may be accumulated
30238 during the DATA and MIME ACLs, after which they are removed from the message,
30239 if present. In the case of non-SMTP messages, headers to be removed are
30240 accumulated during the non-SMTP ACLs, and are removed from the message after
30241 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
30242 ACL, there really is no effect because there is no logging of what headers
30243 would have been removed.
30245 .cindex "header lines" "removed; visibility of"
30246 Header lines are not visible in string expansions until the DATA phase when it
30247 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
30248 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
30249 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
30250 this restriction, you cannot use header lines as a way of controlling data
30251 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
30252 you should instead use ACL variables, as described in section
30253 &<<SECTaclvariables>>&.
30255 The &%remove_header%& modifier acts immediately as it is encountered during the
30256 processing of an ACL. Notice the difference between these two cases:
30258 &`accept remove_header = X-Internal`&
30259 &` `&<&'some condition'&>
30261 &`accept `&<&'some condition'&>
30262 &` remove_header = X-Internal`&
30264 In the first case, the header line is always removed, whether or not the
30265 condition is true. In the second case, the header line is removed only if the
30266 condition is true. Multiple occurrences of &%remove_header%& may occur in the
30267 same ACL statement. All those that are encountered before a condition fails
30270 &*Warning*&: This facility currently applies only to header lines that are
30271 present during ACL processing. It does NOT remove header lines that are added
30272 in a system filter or in a router or transport.
30277 .section "ACL conditions" "SECTaclconditions"
30278 .cindex "&ACL;" "conditions; list of"
30279 Some of the conditions listed in this section are available only when Exim is
30280 compiled with the content-scanning extension. They are included here briefly
30281 for completeness. More detailed descriptions can be found in the discussion on
30282 content scanning in chapter &<<CHAPexiscan>>&.
30284 Not all conditions are relevant in all circumstances. For example, testing
30285 senders and recipients does not make sense in an ACL that is being run as the
30286 result of the arrival of an ETRN command, and checks on message headers can be
30287 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
30288 can use the same condition (with different parameters) more than once in the
30289 same ACL statement. This provides a way of specifying an &"and"& conjunction.
30290 The conditions are as follows:
30294 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
30295 .cindex "&ACL;" "nested"
30296 .cindex "&ACL;" "indirect"
30297 .cindex "&ACL;" "arguments"
30298 .cindex "&%acl%& ACL condition"
30299 The possible values of the argument are the same as for the
30300 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
30301 &"accept"& the condition is true; if it returns &"deny"& the condition is
30302 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
30303 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
30304 condition false. This means that further processing of the &%warn%& verb
30305 ceases, but processing of the ACL continues.
30307 If the argument is a named ACL, up to nine space-separated optional values
30308 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
30309 and $acl_narg is set to the count of values.
30310 Previous values of these variables are restored after the call returns.
30311 The name and values are expanded separately.
30312 Note that spaces in complex expansions which are used as arguments
30313 will act as argument separators.
30315 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
30316 the connection is dropped. If it returns &"discard"&, the verb must be
30317 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
30318 conditions are tested.
30320 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
30321 loops. This condition allows you to use different ACLs in different
30322 circumstances. For example, different ACLs can be used to handle RCPT commands
30323 for different local users or different local domains.
30325 .vitem &*authenticated&~=&~*&<&'string&~list'&>
30326 .cindex "&%authenticated%& ACL condition"
30327 .cindex "authentication" "ACL checking"
30328 .cindex "&ACL;" "testing for authentication"
30329 If the SMTP connection is not authenticated, the condition is false. Otherwise,
30330 the name of the authenticator is tested against the list. To test for
30331 authentication by any authenticator, you can set
30336 .vitem &*condition&~=&~*&<&'string'&>
30337 .cindex "&%condition%& ACL condition"
30338 .cindex "customizing" "ACL condition"
30339 .cindex "&ACL;" "customized test"
30340 .cindex "&ACL;" "testing, customized"
30341 This feature allows you to make up custom conditions. If the result of
30342 expanding the string is an empty string, the number zero, or one of the strings
30343 &"no"& or &"false"&, the condition is false. If the result is any non-zero
30344 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
30345 any other value, some error is assumed to have occurred, and the ACL returns
30346 &"defer"&. However, if the expansion is forced to fail, the condition is
30347 ignored. The effect is to treat it as true, whether it is positive or
30350 .vitem &*decode&~=&~*&<&'location'&>
30351 .cindex "&%decode%& ACL condition"
30352 This condition is available only when Exim is compiled with the
30353 content-scanning extension, and it is allowed only in the ACL defined by
30354 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
30355 If all goes well, the condition is true. It is false only if there are
30356 problems such as a syntax error or a memory shortage. For more details, see
30357 chapter &<<CHAPexiscan>>&.
30359 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
30360 .cindex "&%dnslists%& ACL condition"
30361 .cindex "DNS list" "in ACL"
30362 .cindex "black list (DNS)"
30363 .cindex "&ACL;" "testing a DNS list"
30364 This condition checks for entries in DNS black lists. These are also known as
30365 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
30366 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
30367 different variants of this condition to describe briefly here. See sections
30368 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
30370 .vitem &*domains&~=&~*&<&'domain&~list'&>
30371 .cindex "&%domains%& ACL condition"
30372 .cindex "domain" "ACL checking"
30373 .cindex "&ACL;" "testing a recipient domain"
30374 .vindex "&$domain_data$&"
30375 This condition is relevant only after a RCPT command. It checks that the domain
30376 of the recipient address is in the domain list. If percent-hack processing is
30377 enabled, it is done before this test is done. If the check succeeds with a
30378 lookup, the result of the lookup is placed in &$domain_data$& until the next
30381 &*Note carefully*& (because many people seem to fall foul of this): you cannot
30382 use &%domains%& in a DATA ACL.
30385 .vitem &*encrypted&~=&~*&<&'string&~list'&>
30386 .cindex "&%encrypted%& ACL condition"
30387 .cindex "encryption" "checking in an ACL"
30388 .cindex "&ACL;" "testing for encryption"
30389 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
30390 name of the cipher suite in use is tested against the list. To test for
30391 encryption without testing for any specific cipher suite(s), set
30397 .vitem &*hosts&~=&~*&<&'host&~list'&>
30398 .cindex "&%hosts%& ACL condition"
30399 .cindex "host" "ACL checking"
30400 .cindex "&ACL;" "testing the client host"
30401 This condition tests that the calling host matches the host list. If you have
30402 name lookups or wildcarded host names and IP addresses in the same host list,
30403 you should normally put the IP addresses first. For example, you could have:
30405 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
30407 The lookup in this example uses the host name for its key. This is implied by
30408 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
30409 and it wouldn't matter which way round you had these two items.)
30411 The reason for the problem with host names lies in the left-to-right way that
30412 Exim processes lists. It can test IP addresses without doing any DNS lookups,
30413 but when it reaches an item that requires a host name, it fails if it cannot
30414 find a host name to compare with the pattern. If the above list is given in the
30415 opposite order, the &%accept%& statement fails for a host whose name cannot be
30416 found, even if its IP address is 10.9.8.7.
30418 If you really do want to do the name check first, and still recognize the IP
30419 address even if the name lookup fails, you can rewrite the ACL like this:
30421 accept hosts = dbm;/etc/friendly/hosts
30422 accept hosts = 10.9.8.7
30424 The default action on failing to find the host name is to assume that the host
30425 is not in the list, so the first &%accept%& statement fails. The second
30426 statement can then check the IP address.
30428 .vindex "&$host_data$&"
30429 If a &%hosts%& condition is satisfied by means of a lookup, the result
30430 of the lookup is made available in the &$host_data$& variable. This
30431 allows you, for example, to set up a statement like this:
30433 deny hosts = net-lsearch;/some/file
30434 message = $host_data
30436 which gives a custom error message for each denied host.
30438 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
30439 .cindex "&%local_parts%& ACL condition"
30440 .cindex "local part" "ACL checking"
30441 .cindex "&ACL;" "testing a local part"
30442 .vindex "&$local_part_data$&"
30443 This condition is relevant only after a RCPT command. It checks that the local
30444 part of the recipient address is in the list. If percent-hack processing is
30445 enabled, it is done before this test. If the check succeeds with a lookup, the
30446 result of the lookup is placed in &$local_part_data$&, which remains set until
30447 the next &%local_parts%& test.
30449 .vitem &*malware&~=&~*&<&'option'&>
30450 .cindex "&%malware%& ACL condition"
30451 .cindex "&ACL;" "virus scanning"
30452 .cindex "&ACL;" "scanning for viruses"
30453 This condition is available only when Exim is compiled with the
30454 content-scanning extension. It causes the incoming message to be scanned for
30455 viruses. For details, see chapter &<<CHAPexiscan>>&.
30457 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
30458 .cindex "&%mime_regex%& ACL condition"
30459 .cindex "&ACL;" "testing by regex matching"
30460 This condition is available only when Exim is compiled with the
30461 content-scanning extension, and it is allowed only in the ACL defined by
30462 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
30463 with any of the regular expressions. For details, see chapter
30466 .vitem &*ratelimit&~=&~*&<&'parameters'&>
30467 .cindex "rate limiting"
30468 This condition can be used to limit the rate at which a user or host submits
30469 messages. Details are given in section &<<SECTratelimiting>>&.
30471 .vitem &*recipients&~=&~*&<&'address&~list'&>
30472 .cindex "&%recipients%& ACL condition"
30473 .cindex "recipient" "ACL checking"
30474 .cindex "&ACL;" "testing a recipient"
30475 This condition is relevant only after a RCPT command. It checks the entire
30476 recipient address against a list of recipients.
30478 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
30479 .cindex "&%regex%& ACL condition"
30480 .cindex "&ACL;" "testing by regex matching"
30481 This condition is available only when Exim is compiled with the
30482 content-scanning extension, and is available only in the DATA, MIME, and
30483 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
30484 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
30486 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
30487 .cindex "&%sender_domains%& ACL condition"
30488 .cindex "sender" "ACL checking"
30489 .cindex "&ACL;" "testing a sender domain"
30490 .vindex "&$domain$&"
30491 .vindex "&$sender_address_domain$&"
30492 This condition tests the domain of the sender of the message against the given
30493 domain list. &*Note*&: The domain of the sender address is in
30494 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
30495 of this condition. This is an exception to the general rule for testing domain
30496 lists. It is done this way so that, if this condition is used in an ACL for a
30497 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
30498 influence the sender checking.
30500 &*Warning*&: It is a bad idea to use this condition on its own as a control on
30501 relaying, because sender addresses are easily, and commonly, forged.
30503 .vitem &*senders&~=&~*&<&'address&~list'&>
30504 .cindex "&%senders%& ACL condition"
30505 .cindex "sender" "ACL checking"
30506 .cindex "&ACL;" "testing a sender"
30507 This condition tests the sender of the message against the given list. To test
30508 for a bounce message, which has an empty sender, set
30512 &*Warning*&: It is a bad idea to use this condition on its own as a control on
30513 relaying, because sender addresses are easily, and commonly, forged.
30515 .vitem &*spam&~=&~*&<&'username'&>
30516 .cindex "&%spam%& ACL condition"
30517 .cindex "&ACL;" "scanning for spam"
30518 This condition is available only when Exim is compiled with the
30519 content-scanning extension. It causes the incoming message to be scanned by
30520 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
30522 .vitem &*verify&~=&~certificate*&
30523 .cindex "&%verify%& ACL condition"
30524 .cindex "TLS" "client certificate verification"
30525 .cindex "certificate" "verification of client"
30526 .cindex "&ACL;" "certificate verification"
30527 .cindex "&ACL;" "testing a TLS certificate"
30528 This condition is true in an SMTP session if the session is encrypted, and a
30529 certificate was received from the client, and the certificate was verified. The
30530 server requests a certificate only if the client matches &%tls_verify_hosts%&
30531 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
30533 .vitem &*verify&~=&~csa*&
30534 .cindex "CSA verification"
30535 This condition checks whether the sending host (the client) is authorized to
30536 send email. Details of how this works are given in section
30537 &<<SECTverifyCSA>>&.
30539 .vitem &*verify&~=&~header_names_ascii*&
30540 .cindex "&%verify%& ACL condition"
30541 .cindex "&ACL;" "verifying header names only ASCII"
30542 .cindex "header lines" "verifying header names only ASCII"
30543 .cindex "verifying" "header names only ASCII"
30544 This condition is relevant only in an ACL that is run after a message has been
30545 received, that is, in an ACL specified by &%acl_smtp_data%& or
30546 &%acl_not_smtp%&. It checks all header names (not the content) to make sure
30547 there are no non-ASCII characters, also excluding control characters. The
30548 allowable characters are decimal ASCII values 33 through 126.
30550 Exim itself will handle headers with non-ASCII characters, but it can cause
30551 problems for downstream applications, so this option will allow their
30552 detection and rejection in the DATA ACL's.
30554 .vitem &*verify&~=&~header_sender/*&<&'options'&>
30555 .cindex "&%verify%& ACL condition"
30556 .cindex "&ACL;" "verifying sender in the header"
30557 .cindex "header lines" "verifying the sender in"
30558 .cindex "sender" "verifying in header"
30559 .cindex "verifying" "sender in header"
30560 This condition is relevant only in an ACL that is run after a message has been
30561 received, that is, in an ACL specified by &%acl_smtp_data%& or
30562 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
30563 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
30564 is loosely thought of as a &"sender"& address (hence the name of the test).
30565 However, an address that appears in one of these headers need not be an address
30566 that accepts bounce messages; only sender addresses in envelopes are required
30567 to accept bounces. Therefore, if you use the callout option on this check, you
30568 might want to arrange for a non-empty address in the MAIL command.
30570 Details of address verification and the options are given later, starting at
30571 section &<<SECTaddressverification>>& (callouts are described in section
30572 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
30573 condition to restrict it to bounce messages only:
30576 message = A valid sender header is required for bounces
30577 !verify = header_sender
30580 .vitem &*verify&~=&~header_syntax*&
30581 .cindex "&%verify%& ACL condition"
30582 .cindex "&ACL;" "verifying header syntax"
30583 .cindex "header lines" "verifying syntax"
30584 .cindex "verifying" "header syntax"
30585 This condition is relevant only in an ACL that is run after a message has been
30586 received, that is, in an ACL specified by &%acl_smtp_data%& or
30587 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
30588 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
30589 and &'Bcc:'&), returning true if there are no problems.
30590 Unqualified addresses (local parts without domains) are
30591 permitted only in locally generated messages and from hosts that match
30592 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
30595 Note that this condition is a syntax check only. However, a common spamming
30596 ploy used to be to send syntactically invalid headers such as
30600 and this condition can be used to reject such messages, though they are not as
30601 common as they used to be.
30603 .vitem &*verify&~=&~helo*&
30604 .cindex "&%verify%& ACL condition"
30605 .cindex "&ACL;" "verifying HELO/EHLO"
30606 .cindex "HELO" "verifying"
30607 .cindex "EHLO" "verifying"
30608 .cindex "verifying" "EHLO"
30609 .cindex "verifying" "HELO"
30610 This condition is true if a HELO or EHLO command has been received from the
30611 client host, and its contents have been verified. If there has been no previous
30612 attempt to verify the HELO/EHLO contents, it is carried out when this
30613 condition is encountered. See the description of the &%helo_verify_hosts%& and
30614 &%helo_try_verify_hosts%& options for details of how to request verification
30615 independently of this condition.
30617 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
30618 option), this condition is always true.
30621 .vitem &*verify&~=&~not_blind*&
30622 .cindex "verifying" "not blind"
30623 .cindex "bcc recipients, verifying none"
30624 This condition checks that there are no blind (bcc) recipients in the message.
30625 Every envelope recipient must appear either in a &'To:'& header line or in a
30626 &'Cc:'& header line for this condition to be true. Local parts are checked
30627 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
30628 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
30629 used only in a DATA or non-SMTP ACL.
30631 There are, of course, many legitimate messages that make use of blind (bcc)
30632 recipients. This check should not be used on its own for blocking messages.
30635 .vitem &*verify&~=&~recipient/*&<&'options'&>
30636 .cindex "&%verify%& ACL condition"
30637 .cindex "&ACL;" "verifying recipient"
30638 .cindex "recipient" "verifying"
30639 .cindex "verifying" "recipient"
30640 .vindex "&$address_data$&"
30641 This condition is relevant only after a RCPT command. It verifies the current
30642 recipient. Details of address verification are given later, starting at section
30643 &<<SECTaddressverification>>&. After a recipient has been verified, the value
30644 of &$address_data$& is the last value that was set while routing the address.
30645 This applies even if the verification fails. When an address that is being
30646 verified is redirected to a single address, verification continues with the new
30647 address, and in that case, the subsequent value of &$address_data$& is the
30648 value for the child address.
30650 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
30651 .cindex "&%verify%& ACL condition"
30652 .cindex "&ACL;" "verifying host reverse lookup"
30653 .cindex "host" "verifying reverse lookup"
30654 This condition ensures that a verified host name has been looked up from the IP
30655 address of the client host. (This may have happened already if the host name
30656 was needed for checking a host list, or if the host matched &%host_lookup%&.)
30657 Verification ensures that the host name obtained from a reverse DNS lookup, or
30658 one of its aliases, does, when it is itself looked up in the DNS, yield the
30659 original IP address.
30661 There is one possible option, &`defer_ok`&. If this is present and a
30662 DNS operation returns a temporary error, the verify condition succeeds.
30664 If this condition is used for a locally generated message (that is, when there
30665 is no client host involved), it always succeeds.
30667 .vitem &*verify&~=&~sender/*&<&'options'&>
30668 .cindex "&%verify%& ACL condition"
30669 .cindex "&ACL;" "verifying sender"
30670 .cindex "sender" "verifying"
30671 .cindex "verifying" "sender"
30672 This condition is relevant only after a MAIL or RCPT command, or after a
30673 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
30674 the message's sender is empty (that is, this is a bounce message), the
30675 condition is true. Otherwise, the sender address is verified.
30677 .vindex "&$address_data$&"
30678 .vindex "&$sender_address_data$&"
30679 If there is data in the &$address_data$& variable at the end of routing, its
30680 value is placed in &$sender_address_data$& at the end of verification. This
30681 value can be used in subsequent conditions and modifiers in the same ACL
30682 statement. It does not persist after the end of the current statement. If you
30683 want to preserve the value for longer, you can save it in an ACL variable.
30685 Details of verification are given later, starting at section
30686 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
30687 to avoid doing it more than once per message.
30689 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
30690 .cindex "&%verify%& ACL condition"
30691 This is a variation of the previous option, in which a modified address is
30692 verified as a sender.
30694 Note that '/' is legal in local-parts; if the address may have such
30695 (eg. is generated from the received message)
30696 they must be protected from the options parsing by doubling:
30698 verify = sender=${sg{${address:$h_sender:}}{/}{//}}
30704 .section "Using DNS lists" "SECTmorednslists"
30705 .cindex "DNS list" "in ACL"
30706 .cindex "black list (DNS)"
30707 .cindex "&ACL;" "testing a DNS list"
30708 In its simplest form, the &%dnslists%& condition tests whether the calling host
30709 is on at least one of a number of DNS lists by looking up the inverted IP
30710 address in one or more DNS domains. (Note that DNS list domains are not mail
30711 domains, so the &`+`& syntax for named lists doesn't work - it is used for
30712 special options instead.) For example, if the calling host's IP
30713 address is 192.168.62.43, and the ACL statement is
30715 deny dnslists = blackholes.mail-abuse.org : \
30716 dialups.mail-abuse.org
30718 the following records are looked up:
30720 43.62.168.192.blackholes.mail-abuse.org
30721 43.62.168.192.dialups.mail-abuse.org
30723 As soon as Exim finds an existing DNS record, processing of the list stops.
30724 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
30725 to test that a host is on more than one list (an &"and"& conjunction), you can
30726 use two separate conditions:
30728 deny dnslists = blackholes.mail-abuse.org
30729 dnslists = dialups.mail-abuse.org
30731 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
30732 behaves as if the host does not match the list item, that is, as if the DNS
30733 record does not exist. If there are further items in the DNS list, they are
30736 This is usually the required action when &%dnslists%& is used with &%deny%&
30737 (which is the most common usage), because it prevents a DNS failure from
30738 blocking mail. However, you can change this behaviour by putting one of the
30739 following special items in the list:
30741 &`+include_unknown `& behave as if the item is on the list
30742 &`+exclude_unknown `& behave as if the item is not on the list (default)
30743 &`+defer_unknown `& give a temporary error
30745 .cindex "&`+include_unknown`&"
30746 .cindex "&`+exclude_unknown`&"
30747 .cindex "&`+defer_unknown`&"
30748 Each of these applies to any subsequent items on the list. For example:
30750 deny dnslists = +defer_unknown : foo.bar.example
30752 Testing the list of domains stops as soon as a match is found. If you want to
30753 warn for one list and block for another, you can use two different statements:
30755 deny dnslists = blackholes.mail-abuse.org
30756 warn message = X-Warn: sending host is on dialups list
30757 dnslists = dialups.mail-abuse.org
30759 .cindex caching "of dns lookup"
30761 DNS list lookups are cached by Exim for the duration of the SMTP session
30762 (but limited by the DNS return TTL value),
30763 so a lookup based on the IP address is done at most once for any incoming
30764 connection (assuming long-enough TTL).
30765 Exim does not share information between multiple incoming
30766 connections (but your local name server cache should be active).
30768 There are a number of DNS lists to choose from, some commercial, some free,
30769 or free for small deployments. An overview can be found at
30770 &url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists).
30774 .section "Specifying the IP address for a DNS list lookup" "SECID201"
30775 .cindex "DNS list" "keyed by explicit IP address"
30776 By default, the IP address that is used in a DNS list lookup is the IP address
30777 of the calling host. However, you can specify another IP address by listing it
30778 after the domain name, introduced by a slash. For example:
30780 deny dnslists = black.list.tld/192.168.1.2
30782 This feature is not very helpful with explicit IP addresses; it is intended for
30783 use with IP addresses that are looked up, for example, the IP addresses of the
30784 MX hosts or nameservers of an email sender address. For an example, see section
30785 &<<SECTmulkeyfor>>& below.
30790 .section "DNS lists keyed on domain names" "SECID202"
30791 .cindex "DNS list" "keyed by domain name"
30792 There are some lists that are keyed on domain names rather than inverted IP
30793 addresses (see, e.g., the &'domain based zones'& link at
30794 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
30795 with these lists. You can change the name that is looked up in a DNS list by
30796 listing it after the domain name, introduced by a slash. For example,
30798 deny message = Sender's domain is listed at $dnslist_domain
30799 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
30801 This particular example is useful only in ACLs that are obeyed after the
30802 RCPT or DATA commands, when a sender address is available. If (for
30803 example) the message's sender is &'user@tld.example'& the name that is looked
30804 up by this example is
30806 tld.example.dsn.rfc-ignorant.org
30808 A single &%dnslists%& condition can contain entries for both names and IP
30809 addresses. For example:
30811 deny dnslists = sbl.spamhaus.org : \
30812 dsn.rfc-ignorant.org/$sender_address_domain
30814 The first item checks the sending host's IP address; the second checks a domain
30815 name. The whole condition is true if either of the DNS lookups succeeds.
30820 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
30821 .cindex "DNS list" "multiple keys for"
30822 The syntax described above for looking up explicitly-defined values (either
30823 names or IP addresses) in a DNS blacklist is a simplification. After the domain
30824 name for the DNS list, what follows the slash can in fact be a list of items.
30825 As with all lists in Exim, the default separator is a colon. However, because
30826 this is a sublist within the list of DNS blacklist domains, it is necessary
30827 either to double the separators like this:
30829 dnslists = black.list.tld/name.1::name.2
30831 or to change the separator character, like this:
30833 dnslists = black.list.tld/<;name.1;name.2
30835 If an item in the list is an IP address, it is inverted before the DNS
30836 blacklist domain is appended. If it is not an IP address, no inversion
30837 occurs. Consider this condition:
30839 dnslists = black.list.tld/<;192.168.1.2;a.domain
30841 The DNS lookups that occur are:
30843 2.1.168.192.black.list.tld
30844 a.domain.black.list.tld
30846 Once a DNS record has been found (that matches a specific IP return
30847 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
30848 are done. If there is a temporary DNS error, the rest of the sublist of domains
30849 or IP addresses is tried. A temporary error for the whole dnslists item occurs
30850 only if no other DNS lookup in this sublist succeeds. In other words, a
30851 successful lookup for any of the items in the sublist overrides a temporary
30852 error for a previous item.
30854 The ability to supply a list of items after the slash is in some sense just a
30855 syntactic convenience. These two examples have the same effect:
30857 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
30858 dnslists = black.list.tld/a.domain::b.domain
30860 However, when the data for the list is obtained from a lookup, the second form
30861 is usually much more convenient. Consider this example:
30863 deny message = The mail servers for the domain \
30864 $sender_address_domain \
30865 are listed at $dnslist_domain ($dnslist_value); \
30867 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
30868 ${lookup dnsdb {>|mxh=\
30869 $sender_address_domain} }} }
30871 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
30872 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
30873 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
30874 of expanding the condition might be something like this:
30876 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
30878 Thus, this example checks whether or not the IP addresses of the sender
30879 domain's mail servers are on the Spamhaus black list.
30881 The key that was used for a successful DNS list lookup is put into the variable
30882 &$dnslist_matched$& (see section &<<SECID204>>&).
30887 .section "Data returned by DNS lists" "SECID203"
30888 .cindex "DNS list" "data returned from"
30889 DNS lists are constructed using address records in the DNS. The original RBL
30890 just used the address 127.0.0.1 on the right hand side of each record, but the
30891 RBL+ list and some other lists use a number of values with different meanings.
30892 The values used on the RBL+ list are:
30896 127.1.0.3 DUL and RBL
30898 127.1.0.5 RSS and RBL
30899 127.1.0.6 RSS and DUL
30900 127.1.0.7 RSS and DUL and RBL
30902 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
30903 different values. Some DNS lists may return more than one address record;
30904 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
30907 .section "Variables set from DNS lists" "SECID204"
30908 .cindex "expansion" "variables, set from DNS list"
30909 .cindex "DNS list" "variables set from"
30910 .vindex "&$dnslist_domain$&"
30911 .vindex "&$dnslist_matched$&"
30912 .vindex "&$dnslist_text$&"
30913 .vindex "&$dnslist_value$&"
30914 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
30915 the name of the overall domain that matched (for example,
30916 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
30917 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
30918 the DNS record. When the key is an IP address, it is not reversed in
30919 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
30920 cases, for example:
30922 deny dnslists = spamhaus.example
30924 the key is also available in another variable (in this case,
30925 &$sender_host_address$&). In more complicated cases, however, this is not true.
30926 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
30927 might generate a dnslists lookup like this:
30929 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
30931 If this condition succeeds, the value in &$dnslist_matched$& might be
30932 &`192.168.6.7`& (for example).
30934 If more than one address record is returned by the DNS lookup, all the IP
30935 addresses are included in &$dnslist_value$&, separated by commas and spaces.
30936 The variable &$dnslist_text$& contains the contents of any associated TXT
30937 record. For lists such as RBL+ the TXT record for a merged entry is often not
30938 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
30941 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
30942 &-- although these appear before the condition in the ACL, they are not
30943 expanded until after it has failed. For example:
30945 deny hosts = !+local_networks
30946 message = $sender_host_address is listed \
30948 dnslists = rbl-plus.mail-abuse.example
30953 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
30954 .cindex "DNS list" "matching specific returned data"
30955 You can add an equals sign and an IP address after a &%dnslists%& domain name
30956 in order to restrict its action to DNS records with a matching right hand side.
30959 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
30961 rejects only those hosts that yield 127.0.0.2. Without this additional data,
30962 any address record is considered to be a match. For the moment, we assume
30963 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
30964 describes how multiple records are handled.
30966 More than one IP address may be given for checking, using a comma as a
30967 separator. These are alternatives &-- if any one of them matches, the
30968 &%dnslists%& condition is true. For example:
30970 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
30972 If you want to specify a constraining address list and also specify names or IP
30973 addresses to be looked up, the constraining address list must be specified
30974 first. For example:
30976 deny dnslists = dsn.rfc-ignorant.org\
30977 =127.0.0.2/$sender_address_domain
30980 If the character &`&&`& is used instead of &`=`&, the comparison for each
30981 listed IP address is done by a bitwise &"and"& instead of by an equality test.
30982 In other words, the listed addresses are used as bit masks. The comparison is
30983 true if all the bits in the mask are present in the address that is being
30984 tested. For example:
30986 dnslists = a.b.c&0.0.0.3
30988 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
30989 want to test whether one bit or another bit is present (as opposed to both
30990 being present), you must use multiple values. For example:
30992 dnslists = a.b.c&0.0.0.1,0.0.0.2
30994 matches if the final component of the address is an odd number or two times
30999 .section "Negated DNS matching conditions" "SECID205"
31000 You can supply a negative list of IP addresses as part of a &%dnslists%&
31003 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
31005 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
31006 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
31008 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
31010 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
31011 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
31012 words, the result of the test is inverted if an exclamation mark appears before
31013 the &`=`& (or the &`&&`&) sign.
31015 &*Note*&: This kind of negation is not the same as negation in a domain,
31016 host, or address list (which is why the syntax is different).
31018 If you are using just one list, the negation syntax does not gain you much. The
31019 previous example is precisely equivalent to
31021 deny dnslists = a.b.c
31022 !dnslists = a.b.c=127.0.0.2,127.0.0.3
31024 However, if you are using multiple lists, the negation syntax is clearer.
31025 Consider this example:
31027 deny dnslists = sbl.spamhaus.org : \
31029 dnsbl.njabl.org!=127.0.0.3 : \
31032 Using only positive lists, this would have to be:
31034 deny dnslists = sbl.spamhaus.org : \
31036 deny dnslists = dnsbl.njabl.org
31037 !dnslists = dnsbl.njabl.org=127.0.0.3
31038 deny dnslists = relays.ordb.org
31040 which is less clear, and harder to maintain.
31045 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
31046 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
31047 thereby providing more than one IP address. When an item in a &%dnslists%& list
31048 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
31049 the match to specific results from the DNS lookup, there are two ways in which
31050 the checking can be handled. For example, consider the condition:
31052 dnslists = a.b.c=127.0.0.1
31054 What happens if the DNS lookup for the incoming IP address yields both
31055 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
31056 condition true because at least one given value was found, or is it false
31057 because at least one of the found values was not listed? And how does this
31058 affect negated conditions? Both possibilities are provided for with the help of
31059 additional separators &`==`& and &`=&&`&.
31062 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
31063 IP addresses matches one of the listed addresses. For the example above, the
31064 condition is true because 127.0.0.1 matches.
31066 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
31067 looked up IP addresses matches one of the listed addresses. If the condition is
31070 dnslists = a.b.c==127.0.0.1
31072 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
31073 false because 127.0.0.2 is not listed. You would need to have:
31075 dnslists = a.b.c==127.0.0.1,127.0.0.2
31077 for the condition to be true.
31080 When &`!`& is used to negate IP address matching, it inverts the result, giving
31081 the precise opposite of the behaviour above. Thus:
31083 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
31084 addresses matches one of the listed addresses. Consider:
31086 dnslists = a.b.c!&0.0.0.1
31088 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
31089 false because 127.0.0.1 matches.
31091 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
31092 looked up IP address that does not match. Consider:
31094 dnslists = a.b.c!=&0.0.0.1
31096 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
31097 true, because 127.0.0.2 does not match. You would need to have:
31099 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
31101 for the condition to be false.
31103 When the DNS lookup yields only a single IP address, there is no difference
31104 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
31109 .section "Detailed information from merged DNS lists" "SECTmordetinf"
31110 .cindex "DNS list" "information from merged"
31111 When the facility for restricting the matching IP values in a DNS list is used,
31112 the text from the TXT record that is set in &$dnslist_text$& may not reflect
31113 the true reason for rejection. This happens when lists are merged and the IP
31114 address in the A record is used to distinguish them; unfortunately there is
31115 only one TXT record. One way round this is not to use merged lists, but that
31116 can be inefficient because it requires multiple DNS lookups where one would do
31117 in the vast majority of cases when the host of interest is not on any of the
31120 A less inefficient way of solving this problem is available. If
31121 two domain names, comma-separated, are given, the second is used first to
31122 do an initial check, making use of any IP value restrictions that are set.
31123 If there is a match, the first domain is used, without any IP value
31124 restrictions, to get the TXT record. As a byproduct of this, there is also
31125 a check that the IP being tested is indeed on the first list. The first
31126 domain is the one that is put in &$dnslist_domain$&. For example:
31129 rejected because $sender_host_address is blacklisted \
31130 at $dnslist_domain\n$dnslist_text
31132 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
31133 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
31135 For the first blacklist item, this starts by doing a lookup in
31136 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
31137 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
31138 value, and as long as something is found, it looks for the corresponding TXT
31139 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
31140 The second blacklist item is processed similarly.
31142 If you are interested in more than one merged list, the same list must be
31143 given several times, but because the results of the DNS lookups are cached,
31144 the DNS calls themselves are not repeated. For example:
31147 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
31148 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
31149 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
31150 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
31152 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
31153 values matches (or if no record is found), this is the only lookup that is
31154 done. Only if there is a match is one of the more specific lists consulted.
31158 .section "DNS lists and IPv6" "SECTmorednslistslast"
31159 .cindex "IPv6" "DNS black lists"
31160 .cindex "DNS list" "IPv6 usage"
31161 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
31162 nibble by nibble. For example, if the calling host's IP address is
31163 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
31165 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
31166 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
31168 (split over two lines here to fit on the page). Unfortunately, some of the DNS
31169 lists contain wildcard records, intended for IPv4, that interact badly with
31170 IPv6. For example, the DNS entry
31172 *.3.some.list.example. A 127.0.0.1
31174 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
31175 Unfortunately, it also matches the entire 3::/4 IPv6 network.
31177 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
31178 &%condition%& condition, as in this example:
31180 deny condition = ${if isip4{$sender_host_address}}
31181 dnslists = some.list.example
31184 If an explicit key is being used for a DNS lookup and it may be an IPv6
31185 address you should specify alternate list separators for both the outer
31186 (DNS list name) list and inner (lookup keys) list:
31188 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
31191 .section "Rate limiting incoming messages" "SECTratelimiting"
31192 .cindex "rate limiting" "client sending"
31193 .cindex "limiting client sending rates"
31194 .oindex "&%smtp_ratelimit_*%&"
31195 The &%ratelimit%& ACL condition can be used to measure and control the rate at
31196 which clients can send email. This is more powerful than the
31197 &%smtp_ratelimit_*%& options, because those options control the rate of
31198 commands in a single SMTP session only, whereas the &%ratelimit%& condition
31199 works across all connections (concurrent and sequential) from the same client
31200 host. The syntax of the &%ratelimit%& condition is:
31202 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
31204 If the average client sending rate is less than &'m'& messages per time
31205 period &'p'& then the condition is false; otherwise it is true.
31207 As a side-effect, the &%ratelimit%& condition sets the expansion variable
31208 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
31209 configured value of &'m'&, and &$sender_rate_period$& to the configured value
31212 The parameter &'p'& is the smoothing time constant, in the form of an Exim
31213 time interval, for example, &`8h`& for eight hours. A larger time constant
31214 means that it takes Exim longer to forget a client's past behaviour. The
31215 parameter &'m'& is the maximum number of messages that a client is permitted to
31216 send in each time interval. It also specifies the number of messages permitted
31217 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
31218 constant, you can allow a client to send more messages in a burst without
31219 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
31220 both small, messages must be sent at an even rate.
31222 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
31223 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
31224 when deploying the &%ratelimit%& ACL condition. The script prints usage
31225 instructions when it is run with no arguments.
31227 The key is used to look up the data for calculating the client's average
31228 sending rate. This data is stored in Exim's spool directory, alongside the
31229 retry and other hints databases. The default key is &$sender_host_address$&,
31230 which means Exim computes the sending rate of each client host IP address.
31231 By changing the key you can change how Exim identifies clients for the purpose
31232 of ratelimiting. For example, to limit the sending rate of each authenticated
31233 user, independent of the computer they are sending from, set the key to
31234 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
31235 example, &$authenticated_id$& is only meaningful if the client has
31236 authenticated (which you can check with the &%authenticated%& ACL condition).
31238 The lookup key does not have to identify clients: If you want to limit the
31239 rate at which a recipient receives messages, you can use the key
31240 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
31243 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
31244 specifies what Exim measures the rate of, for example, messages or recipients
31245 or bytes. You can adjust the measurement using the &%unique=%& and/or
31246 &%count=%& options. You can also control when Exim updates the recorded rate
31247 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
31248 separated by a slash, like the other parameters. They may appear in any order.
31250 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
31251 any options that alter the meaning of the stored data. The limit &'m'& is not
31252 stored, so you can alter the configured maximum rate and Exim will still
31253 remember clients' past behaviour. If you change the &%per_*%& mode or add or
31254 remove the &%unique=%& option, the lookup key changes so Exim will forget past
31255 behaviour. The lookup key is not affected by changes to the update mode and
31256 the &%count=%& option.
31259 .section "Ratelimit options for what is being measured" "ratoptmea"
31260 .cindex "rate limiting" "per_* options"
31261 The &%per_conn%& option limits the client's connection rate. It is not
31262 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
31263 &%acl_not_smtp_start%& ACLs.
31265 The &%per_mail%& option limits the client's rate of sending messages. This is
31266 the default if none of the &%per_*%& options is specified. It can be used in
31267 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
31268 &%acl_smtp_data%&, or &%acl_not_smtp%&.
31270 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
31271 the same ACLs as the &%per_mail%& option, though it is best to use this option
31272 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
31273 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
31274 in its MAIL command, which may be inaccurate or completely missing. You can
31275 follow the limit &'m'& in the configuration with K, M, or G to specify limits
31276 in kilobytes, megabytes, or gigabytes, respectively.
31278 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
31279 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
31280 &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
31281 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
31282 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
31283 in either case the rate limiting engine will see a message with many
31284 recipients as a large high-speed burst.
31286 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
31287 number of different recipients that the client has sent messages to in the
31288 last time period. That is, if the client repeatedly sends messages to the same
31289 recipient, its measured rate is not increased. This option can only be used in
31292 The &%per_cmd%& option causes Exim to recompute the rate every time the
31293 condition is processed. This can be used to limit the rate of any SMTP
31294 command. If it is used in multiple ACLs it can limit the aggregate rate of
31295 multiple different commands.
31297 The &%count=%& option can be used to alter how much Exim adds to the client's
31298 measured rate. For example, the &%per_byte%& option is equivalent to
31299 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
31300 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
31301 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
31303 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
31306 .section "Ratelimit update modes" "ratoptupd"
31307 .cindex "rate limiting" "reading data without updating"
31308 You can specify one of three options with the &%ratelimit%& condition to
31309 control when its database is updated. This section describes the &%readonly%&
31310 mode, and the next section describes the &%strict%& and &%leaky%& modes.
31312 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
31313 previously-computed rate to check against the limit.
31315 For example, you can test the client's sending rate and deny it access (when
31316 it is too fast) in the connect ACL. If the client passes this check then it
31317 can go on to send a message, in which case its recorded rate will be updated
31318 in the MAIL ACL. Subsequent connections from the same client will check this
31322 deny ratelimit = 100 / 5m / readonly
31323 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
31324 (max $sender_rate_limit)
31327 warn ratelimit = 100 / 5m / strict
31328 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
31329 (max $sender_rate_limit)
31332 If Exim encounters multiple &%ratelimit%& conditions with the same key when
31333 processing a message then it may increase the client's measured rate more than
31334 it should. For example, this will happen if you check the &%per_rcpt%& option
31335 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
31336 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
31337 multiple update problems by using the &%readonly%& option on later ratelimit
31340 The &%per_*%& options described above do not make sense in some ACLs. If you
31341 use a &%per_*%& option in an ACL where it is not normally permitted then the
31342 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
31343 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
31344 next section) so you must specify the &%readonly%& option explicitly.
31347 .section "Ratelimit options for handling fast clients" "ratoptfast"
31348 .cindex "rate limiting" "strict and leaky modes"
31349 If a client's average rate is greater than the maximum, the rate limiting
31350 engine can react in two possible ways, depending on the presence of the
31351 &%strict%& or &%leaky%& update modes. This is independent of the other
31352 counter-measures (such as rejecting the message) that may be specified by the
31355 The &%leaky%& (default) option means that the client's recorded rate is not
31356 updated if it is above the limit. The effect of this is that Exim measures the
31357 client's average rate of successfully sent email,
31358 up to the given limit.
31359 This is appropriate if the countermeasure when the condition is true
31360 consists of refusing the message, and
31361 is generally the better choice if you have clients that retry automatically.
31362 If the action when true is anything more complex then this option is
31363 likely not what is wanted.
31365 The &%strict%& option means that the client's recorded rate is always
31366 updated. The effect of this is that Exim measures the client's average rate
31367 of attempts to send email, which can be much higher than the maximum it is
31368 actually allowed. If the client is over the limit it may be subjected to
31369 counter-measures by the ACL. It must slow down and allow sufficient time to
31370 pass that its computed rate falls below the maximum before it can send email
31371 again. The time (the number of smoothing periods) it must wait and not
31372 attempt to send mail can be calculated with this formula:
31374 ln(peakrate/maxrate)
31378 .section "Limiting the rate of different events" "ratoptuniq"
31379 .cindex "rate limiting" "counting unique events"
31380 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
31381 rate of different events. For example, the &%per_addr%& option uses this
31382 mechanism to count the number of different recipients that the client has
31383 sent messages to in the last time period; it is equivalent to
31384 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
31385 measure the rate that a client uses different sender addresses with the
31386 options &`per_mail/unique=$sender_address`&.
31388 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
31389 has seen for that key. The whole set is thrown away when it is older than the
31390 rate smoothing period &'p'&, so each different event is counted at most once
31391 per period. In the &%leaky%& update mode, an event that causes the client to
31392 go over the limit is not added to the set, in the same way that the client's
31393 recorded rate is not updated in the same situation.
31395 When you combine the &%unique=%& and &%readonly%& options, the specific
31396 &%unique=%& value is ignored, and Exim just retrieves the client's stored
31399 The &%unique=%& mechanism needs more space in the ratelimit database than the
31400 other &%ratelimit%& options in order to store the event set. The number of
31401 unique values is potentially as large as the rate limit, so the extra space
31402 required increases with larger limits.
31404 The uniqueification is not perfect: there is a small probability that Exim
31405 will think a new event has happened before. If the sender's rate is less than
31406 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
31407 the measured rate can go above the limit, in which case Exim may under-count
31408 events by a significant margin. Fortunately, if the rate is high enough (2.7
31409 times the limit) that the false positive rate goes above 9%, then Exim will
31410 throw away the over-full event set before the measured rate falls below the
31411 limit. Therefore the only harm should be that exceptionally high sending rates
31412 are logged incorrectly; any countermeasures you configure will be as effective
31416 .section "Using rate limiting" "useratlim"
31417 Exim's other ACL facilities are used to define what counter-measures are taken
31418 when the rate limit is exceeded. This might be anything from logging a warning
31419 (for example, while measuring existing sending rates in order to define
31420 policy), through time delays to slow down fast senders, up to rejecting the
31421 message. For example:
31423 # Log all senders' rates
31424 warn ratelimit = 0 / 1h / strict
31425 log_message = Sender rate $sender_rate / $sender_rate_period
31427 # Slow down fast senders; note the need to truncate $sender_rate
31428 # at the decimal point.
31429 warn ratelimit = 100 / 1h / per_rcpt / strict
31430 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
31431 $sender_rate_limit }s
31433 # Keep authenticated users under control
31434 deny authenticated = *
31435 ratelimit = 100 / 1d / strict / $authenticated_id
31437 # System-wide rate limit
31438 defer message = Sorry, too busy. Try again later.
31439 ratelimit = 10 / 1s / $primary_hostname
31441 # Restrict incoming rate from each host, with a default
31442 # set using a macro and special cases looked up in a table.
31443 defer message = Sender rate exceeds $sender_rate_limit \
31444 messages per $sender_rate_period
31445 ratelimit = ${lookup {$sender_host_address} \
31446 cdb {DB/ratelimits.cdb} \
31447 {$value} {RATELIMIT} }
31449 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
31450 especially with the &%per_rcpt%& option, you may suffer from a performance
31451 bottleneck caused by locking on the ratelimit hints database. Apart from
31452 making your ACLs less complicated, you can reduce the problem by using a
31453 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
31454 this means that Exim will lose its hints data after a reboot (including retry
31455 hints, the callout cache, and ratelimit data).
31459 .section "Address verification" "SECTaddressverification"
31460 .cindex "verifying address" "options for"
31461 .cindex "policy control" "address verification"
31462 Several of the &%verify%& conditions described in section
31463 &<<SECTaclconditions>>& cause addresses to be verified. Section
31464 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
31465 The verification conditions can be followed by options that modify the
31466 verification process. The options are separated from the keyword and from each
31467 other by slashes, and some of them contain parameters. For example:
31469 verify = sender/callout
31470 verify = recipient/defer_ok/callout=10s,defer_ok
31472 The first stage of address verification, which always happens, is to run the
31473 address through the routers, in &"verify mode"&. Routers can detect the
31474 difference between verification and routing for delivery, and their actions can
31475 be varied by a number of generic options such as &%verify%& and &%verify_only%&
31476 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
31477 The available options are as follows:
31480 If the &%callout%& option is specified, successful routing to one or more
31481 remote hosts is followed by a &"callout"& to those hosts as an additional
31482 check. Callouts and their sub-options are discussed in the next section.
31484 If there is a defer error while doing verification routing, the ACL
31485 normally returns &"defer"&. However, if you include &%defer_ok%& in the
31486 options, the condition is forced to be true instead. Note that this is a main
31487 verification option as well as a suboption for callouts.
31489 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
31490 discusses the reporting of sender address verification failures.
31492 The &%success_on_redirect%& option causes verification always to succeed
31493 immediately after a successful redirection. By default, if a redirection
31494 generates just one address, that address is also verified. See further
31495 discussion in section &<<SECTredirwhilveri>>&.
31498 .cindex "verifying address" "differentiating failures"
31499 .vindex "&$recipient_verify_failure$&"
31500 .vindex "&$sender_verify_failure$&"
31501 .vindex "&$acl_verify_message$&"
31502 After an address verification failure, &$acl_verify_message$& contains the
31503 error message that is associated with the failure. It can be preserved by
31506 warn !verify = sender
31507 set acl_m0 = $acl_verify_message
31509 If you are writing your own custom rejection message or log message when
31510 denying access, you can use this variable to include information about the
31511 verification failure.
31513 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
31514 appropriate) contains one of the following words:
31517 &%qualify%&: The address was unqualified (no domain), and the message
31518 was neither local nor came from an exempted host.
31520 &%route%&: Routing failed.
31522 &%mail%&: Routing succeeded, and a callout was attempted; rejection
31523 occurred at or before the MAIL command (that is, on initial
31524 connection, HELO, or MAIL).
31526 &%recipient%&: The RCPT command in a callout was rejected.
31528 &%postmaster%&: The postmaster check in a callout was rejected.
31531 The main use of these variables is expected to be to distinguish between
31532 rejections of MAIL and rejections of RCPT in callouts.
31534 The above variables may also be set after a &*successful*&
31535 address verification to:
31538 &%random%&: A random local-part callout succeeded
31544 .section "Callout verification" "SECTcallver"
31545 .cindex "verifying address" "by callout"
31546 .cindex "callout" "verification"
31547 .cindex "SMTP" "callout verification"
31548 For non-local addresses, routing verifies the domain, but is unable to do any
31549 checking of the local part. There are situations where some means of verifying
31550 the local part is desirable. One way this can be done is to make an SMTP
31551 &'callback'& to a delivery host for the sender address or a &'callforward'& to
31552 a subsequent host for a recipient address, to see if the host accepts the
31553 address. We use the term &'callout'& to cover both cases. Note that for a
31554 sender address, the callback is not to the client host that is trying to
31555 deliver the message, but to one of the hosts that accepts incoming mail for the
31558 Exim does not do callouts by default. If you want them to happen, you must
31559 request them by setting appropriate options on the &%verify%& condition, as
31560 described below. This facility should be used with care, because it can add a
31561 lot of resource usage to the cost of verifying an address. However, Exim does
31562 cache the results of callouts, which helps to reduce the cost. Details of
31563 caching are in section &<<SECTcallvercache>>&.
31565 Recipient callouts are usually used only between hosts that are controlled by
31566 the same administration. For example, a corporate gateway host could use
31567 callouts to check for valid recipients on an internal mailserver. A successful
31568 callout does not guarantee that a real delivery to the address would succeed;
31569 on the other hand, a failing callout does guarantee that a delivery would fail.
31571 If the &%callout%& option is present on a condition that verifies an address, a
31572 second stage of verification occurs if the address is successfully routed to
31573 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
31574 &(manualroute)& router, where the router specifies the hosts. However, if a
31575 router that does not set up hosts routes to an &(smtp)& transport with a
31576 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
31577 &%hosts_override%& set, its hosts are always used, whether or not the router
31578 supplies a host list.
31579 Callouts are only supported on &(smtp)& transports.
31581 The port that is used is taken from the transport, if it is specified and is a
31582 remote transport. (For routers that do verification only, no transport need be
31583 specified.) Otherwise, the default SMTP port is used. If a remote transport
31584 specifies an outgoing interface, this is used; otherwise the interface is not
31585 specified. Likewise, the text that is used for the HELO command is taken from
31586 the transport's &%helo_data%& option; if there is no transport, the value of
31587 &$smtp_active_hostname$& is used.
31589 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
31590 test whether a bounce message could be delivered to the sender address. The
31591 following SMTP commands are sent:
31593 &`HELO `&<&'local host name'&>
31595 &`RCPT TO:`&<&'the address to be tested'&>
31598 LHLO is used instead of HELO if the transport's &%protocol%& option is
31601 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
31604 A recipient callout check is similar. By default, it also uses an empty address
31605 for the sender. This default is chosen because most hosts do not make use of
31606 the sender address when verifying a recipient. Using the same address means
31607 that a single cache entry can be used for each recipient. Some sites, however,
31608 do make use of the sender address when verifying. These are catered for by the
31609 &%use_sender%& and &%use_postmaster%& options, described in the next section.
31611 If the response to the RCPT command is a 2&'xx'& code, the verification
31612 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
31613 Exim tries the next host, if any. If there is a problem with all the remote
31614 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
31615 &%callout%& option is given, in which case the condition is forced to succeed.
31617 .cindex "SMTP" "output flushing, disabling for callout"
31618 A callout may take a little time. For this reason, Exim normally flushes SMTP
31619 output before performing a callout in an ACL, to avoid unexpected timeouts in
31620 clients when the SMTP PIPELINING extension is in use. The flushing can be
31621 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
31626 .section "Additional parameters for callouts" "CALLaddparcall"
31627 .cindex "callout" "additional parameters for"
31628 The &%callout%& option can be followed by an equals sign and a number of
31629 optional parameters, separated by commas. For example:
31631 verify = recipient/callout=10s,defer_ok
31633 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
31634 separate verify options, is retained for backwards compatibility, but is now
31635 deprecated. The additional parameters for &%callout%& are as follows:
31639 .vitem <&'a&~time&~interval'&>
31640 .cindex "callout" "timeout, specifying"
31641 This specifies the timeout that applies for the callout attempt to each host.
31644 verify = sender/callout=5s
31646 The default is 30 seconds. The timeout is used for each response from the
31647 remote host. It is also used for the initial connection, unless overridden by
31648 the &%connect%& parameter.
31651 .vitem &*connect&~=&~*&<&'time&~interval'&>
31652 .cindex "callout" "connection timeout, specifying"
31653 This parameter makes it possible to set a different (usually smaller) timeout
31654 for making the SMTP connection. For example:
31656 verify = sender/callout=5s,connect=1s
31658 If not specified, this timeout defaults to the general timeout value.
31660 .vitem &*defer_ok*&
31661 .cindex "callout" "defer, action on"
31662 When this parameter is present, failure to contact any host, or any other kind
31663 of temporary error, is treated as success by the ACL. However, the cache is not
31664 updated in this circumstance.
31666 .vitem &*fullpostmaster*&
31667 .cindex "callout" "full postmaster check"
31668 This operates like the &%postmaster%& option (see below), but if the check for
31669 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
31670 accordance with the specification in RFC 2821. The RFC states that the
31671 unqualified address &'postmaster'& should be accepted.
31674 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
31675 .cindex "callout" "sender when verifying header"
31676 When verifying addresses in header lines using the &%header_sender%&
31677 verification option, Exim behaves by default as if the addresses are envelope
31678 sender addresses from a message. Callout verification therefore tests to see
31679 whether a bounce message could be delivered, by using an empty address in the
31680 MAIL command. However, it is arguable that these addresses might never be used
31681 as envelope senders, and could therefore justifiably reject bounce messages
31682 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
31683 address to use in the MAIL command. For example:
31685 require verify = header_sender/callout=mailfrom=abcd@x.y.z
31687 This parameter is available only for the &%header_sender%& verification option.
31690 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
31691 .cindex "callout" "overall timeout, specifying"
31692 This parameter sets an overall timeout for performing a callout verification.
31695 verify = sender/callout=5s,maxwait=30s
31697 This timeout defaults to four times the callout timeout for individual SMTP
31698 commands. The overall timeout applies when there is more than one host that can
31699 be tried. The timeout is checked before trying the next host. This prevents
31700 very long delays if there are a large number of hosts and all are timing out
31701 (for example, when network connections are timing out).
31704 .vitem &*no_cache*&
31705 .cindex "callout" "cache, suppressing"
31706 .cindex "caching callout, suppressing"
31707 When this parameter is given, the callout cache is neither read nor updated.
31709 .vitem &*postmaster*&
31710 .cindex "callout" "postmaster; checking"
31711 When this parameter is set, a successful callout check is followed by a similar
31712 check for the local part &'postmaster'& at the same domain. If this address is
31713 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
31714 the postmaster check is recorded in a cache record; if it is a failure, this is
31715 used to fail subsequent callouts for the domain without a connection being
31716 made, until the cache record expires.
31718 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
31719 The postmaster check uses an empty sender in the MAIL command by default.
31720 You can use this parameter to do a postmaster check using a different address.
31723 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
31725 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
31726 one overrides. The &%postmaster%& parameter is equivalent to this example:
31728 require verify = sender/callout=postmaster_mailfrom=
31730 &*Warning*&: The caching arrangements for postmaster checking do not take
31731 account of the sender address. It is assumed that either the empty address or
31732 a fixed non-empty address will be used. All that Exim remembers is that the
31733 postmaster check for the domain succeeded or failed.
31737 .cindex "callout" "&""random""& check"
31738 When this parameter is set, before doing the normal callout check, Exim does a
31739 check for a &"random"& local part at the same domain. The local part is not
31740 really random &-- it is defined by the expansion of the option
31741 &%callout_random_local_part%&, which defaults to
31743 $primary_hostname-$tod_epoch-testing
31745 The idea here is to try to determine whether the remote host accepts all local
31746 parts without checking. If it does, there is no point in doing callouts for
31747 specific local parts. If the &"random"& check succeeds, the result is saved in
31748 a cache record, and used to force the current and subsequent callout checks to
31749 succeed without a connection being made, until the cache record expires.
31751 .vitem &*use_postmaster*&
31752 .cindex "callout" "sender for recipient check"
31753 This parameter applies to recipient callouts only. For example:
31755 deny !verify = recipient/callout=use_postmaster
31757 .vindex "&$qualify_domain$&"
31758 It causes a non-empty postmaster address to be used in the MAIL command when
31759 performing the callout for the recipient, and also for a &"random"& check if
31760 that is configured. The local part of the address is &`postmaster`& and the
31761 domain is the contents of &$qualify_domain$&.
31763 .vitem &*use_sender*&
31764 This option applies to recipient callouts only. For example:
31766 require verify = recipient/callout=use_sender
31768 It causes the message's actual sender address to be used in the MAIL
31769 command when performing the callout, instead of an empty address. There is no
31770 need to use this option unless you know that the called hosts make use of the
31771 sender when checking recipients. If used indiscriminately, it reduces the
31772 usefulness of callout caching.
31775 This option applies to recipient callouts only. For example:
31777 require verify = recipient/callout=use_sender,hold
31779 It causes the connection to be held open and used for any further recipients
31780 and for eventual delivery (should that be done quickly).
31781 Doing this saves on TCP and SMTP startup costs, and TLS costs also
31782 when that is used for the connections.
31783 The advantage is only gained if there are no callout cache hits
31784 (which could be enforced by the no_cache option),
31785 if the use_sender option is used,
31786 if neither the random nor the use_postmaster option is used,
31787 and if no other callouts intervene.
31790 If you use any of the parameters that set a non-empty sender for the MAIL
31791 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
31792 &%use_sender%&), you should think about possible loops. Recipient checking is
31793 usually done between two hosts that are under the same management, and the host
31794 that receives the callouts is not normally configured to do callouts itself.
31795 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
31796 these circumstances.
31798 However, if you use a non-empty sender address for a callout to an arbitrary
31799 host, there is the likelihood that the remote host will itself initiate a
31800 callout check back to your host. As it is checking what appears to be a message
31801 sender, it is likely to use an empty address in MAIL, thus avoiding a
31802 callout loop. However, to be on the safe side it would be best to set up your
31803 own ACLs so that they do not do sender verification checks when the recipient
31804 is the address you use for header sender or postmaster callout checking.
31806 Another issue to think about when using non-empty senders for callouts is
31807 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
31808 by the sender/recipient combination; thus, for any given recipient, many more
31809 actual callouts are performed than when an empty sender or postmaster is used.
31814 .section "Callout caching" "SECTcallvercache"
31815 .cindex "hints database" "callout cache"
31816 .cindex "callout" "cache, description of"
31817 .cindex "caching" "callout"
31818 Exim caches the results of callouts in order to reduce the amount of resources
31819 used, unless you specify the &%no_cache%& parameter with the &%callout%&
31820 option. A hints database called &"callout"& is used for the cache. Two
31821 different record types are used: one records the result of a callout check for
31822 a specific address, and the other records information that applies to the
31823 entire domain (for example, that it accepts the local part &'postmaster'&).
31825 When an original callout fails, a detailed SMTP error message is given about
31826 the failure. However, for subsequent failures use the cache data, this message
31829 The expiry times for negative and positive address cache records are
31830 independent, and can be set by the global options &%callout_negative_expire%&
31831 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
31833 If a host gives a negative response to an SMTP connection, or rejects any
31834 commands up to and including
31838 (but not including the MAIL command with a non-empty address),
31839 any callout attempt is bound to fail. Exim remembers such failures in a
31840 domain cache record, which it uses to fail callouts for the domain without
31841 making new connections, until the domain record times out. There are two
31842 separate expiry times for domain cache records:
31843 &%callout_domain_negative_expire%& (default 3h) and
31844 &%callout_domain_positive_expire%& (default 7d).
31846 Domain records expire when the negative expiry time is reached if callouts
31847 cannot be made for the domain, or if the postmaster check failed.
31848 Otherwise, they expire when the positive expiry time is reached. This
31849 ensures that, for example, a host that stops accepting &"random"& local parts
31850 will eventually be noticed.
31852 The callout caching mechanism is based on the domain of the address that is
31853 being tested. If the domain routes to several hosts, it is assumed that their
31854 behaviour will be the same.
31858 .section "Sender address verification reporting" "SECTsenaddver"
31859 .cindex "verifying" "suppressing error details"
31860 See section &<<SECTaddressverification>>& for a general discussion of
31861 verification. When sender verification fails in an ACL, the details of the
31862 failure are given as additional output lines before the 550 response to the
31863 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
31866 MAIL FROM:<xyz@abc.example>
31868 RCPT TO:<pqr@def.example>
31869 550-Verification failed for <xyz@abc.example>
31870 550-Called: 192.168.34.43
31871 550-Sent: RCPT TO:<xyz@abc.example>
31872 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
31873 550 Sender verification failed
31875 If more than one RCPT command fails in the same way, the details are given
31876 only for the first of them. However, some administrators do not want to send
31877 out this much information. You can suppress the details by adding
31878 &`/no_details`& to the ACL statement that requests sender verification. For
31881 verify = sender/no_details
31884 .section "Redirection while verifying" "SECTredirwhilveri"
31885 .cindex "verifying" "redirection while"
31886 .cindex "address redirection" "while verifying"
31887 A dilemma arises when a local address is redirected by aliasing or forwarding
31888 during verification: should the generated addresses themselves be verified,
31889 or should the successful expansion of the original address be enough to verify
31890 it? By default, Exim takes the following pragmatic approach:
31893 When an incoming address is redirected to just one child address, verification
31894 continues with the child address, and if that fails to verify, the original
31895 verification also fails.
31897 When an incoming address is redirected to more than one child address,
31898 verification does not continue. A success result is returned.
31901 This seems the most reasonable behaviour for the common use of aliasing as a
31902 way of redirecting different local parts to the same mailbox. It means, for
31903 example, that a pair of alias entries of the form
31906 aw123: :fail: Gone away, no forwarding address
31908 work as expected, with both local parts causing verification failure. When a
31909 redirection generates more than one address, the behaviour is more like a
31910 mailing list, where the existence of the alias itself is sufficient for
31911 verification to succeed.
31913 It is possible, however, to change the default behaviour so that all successful
31914 redirections count as successful verifications, however many new addresses are
31915 generated. This is specified by the &%success_on_redirect%& verification
31916 option. For example:
31918 require verify = recipient/success_on_redirect/callout=10s
31920 In this example, verification succeeds if a router generates a new address, and
31921 the callout does not occur, because no address was routed to a remote host.
31923 When verification is being tested via the &%-bv%& option, the treatment of
31924 redirections is as just described, unless the &%-v%& or any debugging option is
31925 also specified. In that case, full verification is done for every generated
31926 address and a report is output for each of them.
31930 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
31931 .cindex "CSA" "verifying"
31932 Client SMTP Authorization is a system that allows a site to advertise
31933 which machines are and are not permitted to send email. This is done by placing
31934 special SRV records in the DNS; these are looked up using the client's HELO
31935 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
31936 Authorization checks in Exim are performed by the ACL condition:
31940 This fails if the client is not authorized. If there is a DNS problem, or if no
31941 valid CSA SRV record is found, or if the client is authorized, the condition
31942 succeeds. These three cases can be distinguished using the expansion variable
31943 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
31944 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
31945 be likely to cause problems for legitimate email.
31947 The error messages produced by the CSA code include slightly more
31948 detail. If &$csa_status$& is &"defer"&, this may be because of problems
31949 looking up the CSA SRV record, or problems looking up the CSA target
31950 address record. There are four reasons for &$csa_status$& being &"fail"&:
31953 The client's host name is explicitly not authorized.
31955 The client's IP address does not match any of the CSA target IP addresses.
31957 The client's host name is authorized but it has no valid target IP addresses
31958 (for example, the target's addresses are IPv6 and the client is using IPv4).
31960 The client's host name has no CSA SRV record but a parent domain has asserted
31961 that all subdomains must be explicitly authorized.
31964 The &%csa%& verification condition can take an argument which is the domain to
31965 use for the DNS query. The default is:
31967 verify = csa/$sender_helo_name
31969 This implementation includes an extension to CSA. If the query domain
31970 is an address literal such as [192.0.2.95], or if it is a bare IP
31971 address, Exim searches for CSA SRV records in the reverse DNS as if
31972 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
31975 verify = csa/$sender_host_address
31977 In fact, this is the check that Exim performs if the client does not say HELO.
31978 This extension can be turned off by setting the main configuration option
31979 &%dns_csa_use_reverse%& to be false.
31981 If a CSA SRV record is not found for the domain itself, a search
31982 is performed through its parent domains for a record which might be
31983 making assertions about subdomains. The maximum depth of this search is limited
31984 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
31985 default. Exim does not look for CSA SRV records in a top level domain, so the
31986 default settings handle HELO domains as long as seven
31987 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
31988 of legitimate HELO domains.
31990 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
31991 direct SRV lookups, this is not sufficient because of the extra parent domain
31992 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
31993 addresses into lookups in the reverse DNS space. The result of a successful
31996 ${lookup dnsdb {csa=$sender_helo_name}}
31998 has two space-separated fields: an authorization code and a target host name.
31999 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
32000 authorization required but absent, or &"?"& for unknown.
32005 .section "Bounce address tag validation" "SECTverifyPRVS"
32006 .cindex "BATV, verifying"
32007 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
32008 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
32009 Genuine incoming bounce messages should therefore always be addressed to
32010 recipients that have a valid tag. This scheme is a way of detecting unwanted
32011 bounce messages caused by sender address forgeries (often called &"collateral
32012 spam"&), because the recipients of such messages do not include valid tags.
32014 There are two expansion items to help with the implementation of the BATV
32015 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
32016 the original envelope sender address by using a simple key to add a hash of the
32017 address and some time-based randomizing information. The &%prvs%& expansion
32018 item creates a signed address, and the &%prvscheck%& expansion item checks one.
32019 The syntax of these expansion items is described in section
32020 &<<SECTexpansionitems>>&.
32021 The validity period on signed addresses is seven days.
32023 As an example, suppose the secret per-address keys are stored in an MySQL
32024 database. A query to look up the key for an address could be defined as a macro
32027 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
32028 WHERE sender='${quote_mysql:$prvscheck_address}'\
32031 Suppose also that the senders who make use of BATV are defined by an address
32032 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
32035 # Bounces: drop unsigned addresses for BATV senders
32036 deny message = This address does not send an unsigned reverse path
32038 recipients = +batv_senders
32040 # Bounces: In case of prvs-signed address, check signature.
32041 deny message = Invalid reverse path signature.
32043 condition = ${prvscheck {$local_part@$domain}\
32044 {PRVSCHECK_SQL}{1}}
32045 !condition = $prvscheck_result
32047 The first statement rejects recipients for bounce messages that are addressed
32048 to plain BATV sender addresses, because it is known that BATV senders do not
32049 send out messages with plain sender addresses. The second statement rejects
32050 recipients that are prvs-signed, but with invalid signatures (either because
32051 the key is wrong, or the signature has timed out).
32053 A non-prvs-signed address is not rejected by the second statement, because the
32054 &%prvscheck%& expansion yields an empty string if its first argument is not a
32055 prvs-signed address, thus causing the &%condition%& condition to be false. If
32056 the first argument is a syntactically valid prvs-signed address, the yield is
32057 the third string (in this case &"1"&), whether or not the cryptographic and
32058 timeout checks succeed. The &$prvscheck_result$& variable contains the result
32059 of the checks (empty for failure, &"1"& for success).
32061 There is one more issue you must consider when implementing prvs-signing:
32062 you have to ensure that the routers accept prvs-signed addresses and
32063 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
32064 router to remove the signature with a configuration along these lines:
32068 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
32070 This works because, if the third argument of &%prvscheck%& is empty, the result
32071 of the expansion of a prvs-signed address is the decoded value of the original
32072 address. This router should probably be the first of your routers that handles
32075 To create BATV-signed addresses in the first place, a transport of this form
32078 external_smtp_batv:
32080 return_path = ${prvs {$return_path} \
32081 {${lookup mysql{SELECT \
32082 secret FROM batv_prvs WHERE \
32083 sender='${quote_mysql:$sender_address}'} \
32086 If no key can be found for the existing return path, no signing takes place.
32090 .section "Using an ACL to control relaying" "SECTrelaycontrol"
32091 .cindex "&ACL;" "relay control"
32092 .cindex "relaying" "control by ACL"
32093 .cindex "policy control" "relay control"
32094 An MTA is said to &'relay'& a message if it receives it from some host and
32095 delivers it directly to another host as a result of a remote address contained
32096 within it. Redirecting a local address via an alias or forward file and then
32097 passing the message on to another host is not relaying,
32098 .cindex "&""percent hack""&"
32099 but a redirection as a result of the &"percent hack"& is.
32101 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
32102 A host which is acting as a gateway or an MX backup is concerned with incoming
32103 relaying from arbitrary hosts to a specific set of domains. On the other hand,
32104 a host which is acting as a smart host for a number of clients is concerned
32105 with outgoing relaying from those clients to the Internet at large. Often the
32106 same host is fulfilling both functions,
32108 . as illustrated in the diagram below,
32110 but in principle these two kinds of relaying are entirely independent. What is
32111 not wanted is the transmission of mail from arbitrary remote hosts through your
32112 system to arbitrary domains.
32115 You can implement relay control by means of suitable statements in the ACL that
32116 runs for each RCPT command. For convenience, it is often easiest to use
32117 Exim's named list facility to define the domains and hosts involved. For
32118 example, suppose you want to do the following:
32121 Deliver a number of domains to mailboxes on the local host (or process them
32122 locally in some other way). Let's say these are &'my.dom1.example'& and
32123 &'my.dom2.example'&.
32125 Relay mail for a number of other domains for which you are the secondary MX.
32126 These might be &'friend1.example'& and &'friend2.example'&.
32128 Relay mail from the hosts on your local LAN, to whatever domains are involved.
32129 Suppose your LAN is 192.168.45.0/24.
32133 In the main part of the configuration, you put the following definitions:
32135 domainlist local_domains = my.dom1.example : my.dom2.example
32136 domainlist relay_to_domains = friend1.example : friend2.example
32137 hostlist relay_from_hosts = 192.168.45.0/24
32139 Now you can use these definitions in the ACL that is run for every RCPT
32143 accept domains = +local_domains : +relay_to_domains
32144 accept hosts = +relay_from_hosts
32146 The first statement accepts any RCPT command that contains an address in
32147 the local or relay domains. For any other domain, control passes to the second
32148 statement, which accepts the command only if it comes from one of the relay
32149 hosts. In practice, you will probably want to make your ACL more sophisticated
32150 than this, for example, by including sender and recipient verification. The
32151 default configuration includes a more comprehensive example, which is described
32152 in chapter &<<CHAPdefconfil>>&.
32156 .section "Checking a relay configuration" "SECTcheralcon"
32157 .cindex "relaying" "checking control of"
32158 You can check the relay characteristics of your configuration in the same way
32159 that you can test any ACL behaviour for an incoming SMTP connection, by using
32160 the &%-bh%& option to run a fake SMTP session with which you interact.
32165 . ////////////////////////////////////////////////////////////////////////////
32166 . ////////////////////////////////////////////////////////////////////////////
32168 .chapter "Content scanning at ACL time" "CHAPexiscan"
32169 .scindex IIDcosca "content scanning" "at ACL time"
32170 The extension of Exim to include content scanning at ACL time, formerly known
32171 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
32172 was integrated into the main source for Exim release 4.50, and Tom continues to
32173 maintain it. Most of the wording of this chapter is taken from Tom's
32176 It is also possible to scan the content of messages at other times. The
32177 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
32178 scanning after all the ACLs have run. A transport filter can be used to scan
32179 messages at delivery time (see the &%transport_filter%& option, described in
32180 chapter &<<CHAPtransportgeneric>>&).
32182 If you want to include the ACL-time content-scanning features when you compile
32183 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
32184 &_Local/Makefile_&. When you do that, the Exim binary is built with:
32187 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
32188 for all MIME parts for SMTP and non-SMTP messages, respectively.
32190 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
32191 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
32192 run at the end of message reception (the &%acl_smtp_data%& ACL).
32194 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
32195 of messages, or parts of messages, for debugging purposes.
32197 Additional expansion variables that are set in the new ACL and by the new
32200 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
32203 Content-scanning is continually evolving, and new features are still being
32204 added. While such features are still unstable and liable to incompatible
32205 changes, they are made available in Exim by setting options whose names begin
32206 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
32207 this manual. You can find out about them by reading the file called
32208 &_doc/experimental.txt_&.
32210 All the content-scanning facilities work on a MBOX copy of the message that is
32211 temporarily created in a file called:
32213 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
32215 The &_.eml_& extension is a friendly hint to virus scanners that they can
32216 expect an MBOX-like structure inside that file. The file is created when the
32217 first content scanning facility is called. Subsequent calls to content
32218 scanning conditions open the same file again. The directory is recursively
32219 removed when the &%acl_smtp_data%& ACL has finished running, unless
32221 control = no_mbox_unspool
32223 has been encountered. When the MIME ACL decodes files, they are put into the
32224 same directory by default.
32228 .section "Scanning for viruses" "SECTscanvirus"
32229 .cindex "virus scanning"
32230 .cindex "content scanning" "for viruses"
32231 .cindex "content scanning" "the &%malware%& condition"
32232 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
32233 It supports a &"generic"& interface to scanners called via the shell, and
32234 specialized interfaces for &"daemon"& type virus scanners, which are resident
32235 in memory and thus are much faster.
32237 A timeout of 2 minutes is applied to a scanner call (by default);
32238 if it expires then a defer action is taken.
32240 .oindex "&%av_scanner%&"
32241 You can set the &%av_scanner%& option in the main part of the configuration
32242 to specify which scanner to use, together with any additional options that
32243 are needed. The basic syntax is as follows:
32245 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
32247 If you do not set &%av_scanner%&, it defaults to
32249 av_scanner = sophie:/var/run/sophie
32251 If the value of &%av_scanner%& starts with a dollar character, it is expanded
32253 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
32254 The following scanner types are supported in this release,
32255 though individual ones can be included or not at build time:
32259 .cindex "virus scanners" "avast"
32260 This is the scanner daemon of Avast. It has been tested with Avast Core
32261 Security (currently at version 2.2.0).
32262 You can get a trial version at &url(https://www.avast.com) or for Linux
32263 at &url(https://www.avast.com/linux-server-antivirus).
32264 This scanner type takes one option,
32265 which can be either a full path to a UNIX socket,
32266 or host and port specifiers separated by white space.
32267 The host may be a name or an IP address; the port is either a
32268 single number or a pair of numbers with a dash between.
32269 A list of options may follow. These options are interpreted on the
32270 Exim's side of the malware scanner, or are given on separate lines to
32271 the daemon as options before the main scan command.
32273 .cindex &`pass_unscanned`& "avast"
32274 If &`pass_unscanned`&
32275 is set, any files the Avast scanner can't scan (e.g.
32276 decompression bombs, or invalid archives) are considered clean. Use with
32281 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
32282 av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
32283 av_scanner = avast:192.168.2.22 5036
32285 If you omit the argument, the default path
32286 &_/var/run/avast/scan.sock_&
32288 If you use a remote host,
32289 you need to make Exim's spool directory available to it,
32290 as the scanner is passed a file path, not file contents.
32291 For information about available commands and their options you may use
32293 $ socat UNIX:/var/run/avast/scan.sock STDIO:
32299 If the scanner returns a temporary failure (e.g. license issues, or
32300 permission problems), the message is deferred and a paniclog entry is
32301 written. The usual &`defer_ok`& option is available.
32303 .vitem &%aveserver%&
32304 .cindex "virus scanners" "Kaspersky"
32305 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
32306 at &url(https://www.kaspersky.com/). This scanner type takes one option,
32307 which is the path to the daemon's UNIX socket. The default is shown in this
32310 av_scanner = aveserver:/var/run/aveserver
32315 .cindex "virus scanners" "clamd"
32316 This daemon-type scanner is GPL and free. You can get it at
32317 &url(https://www.clamav.net/). Some older versions of clamd do not seem to
32318 unpack MIME containers, so it used to be recommended to unpack MIME attachments
32319 in the MIME ACL. This is no longer believed to be necessary.
32321 The options are a list of server specifiers, which may be
32322 a UNIX socket specification,
32323 a TCP socket specification,
32324 or a (global) option.
32326 A socket specification consists of a space-separated list.
32327 For a Unix socket the first element is a full path for the socket,
32328 for a TCP socket the first element is the IP address
32329 and the second a port number,
32330 Any further elements are per-server (non-global) options.
32331 These per-server options are supported:
32333 retry=<timespec> Retry on connect fail
32336 The &`retry`& option specifies a time after which a single retry for
32337 a failed connect is made. The default is to not retry.
32339 If a Unix socket file is specified, only one server is supported.
32343 av_scanner = clamd:/opt/clamd/socket
32344 av_scanner = clamd:192.0.2.3 1234
32345 av_scanner = clamd:192.0.2.3 1234:local
32346 av_scanner = clamd:192.0.2.3 1234 retry=10s
32347 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
32349 If the value of av_scanner points to a UNIX socket file or contains the
32351 option, then the ClamAV interface will pass a filename containing the data
32352 to be scanned, which should normally result in less I/O happening and be
32353 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
32354 Exim does not assume that there is a common filesystem with the remote host.
32356 The final example shows that multiple TCP targets can be specified. Exim will
32357 randomly use one for each incoming email (i.e. it load balances them). Note
32358 that only TCP targets may be used if specifying a list of scanners; a UNIX
32359 socket cannot be mixed in with TCP targets. If one of the servers becomes
32360 unavailable, Exim will try the remaining one(s) until it finds one that works.
32361 When a clamd server becomes unreachable, Exim will log a message. Exim does
32362 not keep track of scanner state between multiple messages, and the scanner
32363 selection is random, so the message will get logged in the mainlog for each
32364 email that the down scanner gets chosen first (message wrapped to be readable):
32366 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
32367 clamd: connection to localhost, port 3310 failed
32368 (Connection refused)
32371 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
32372 contributing the code for this scanner.
32375 .cindex "virus scanners" "command line interface"
32376 This is the keyword for the generic command line scanner interface. It can be
32377 used to attach virus scanners that are invoked from the shell. This scanner
32378 type takes 3 mandatory options:
32381 The full path and name of the scanner binary, with all command line options,
32382 and a placeholder (&`%s`&) for the directory to scan.
32385 A regular expression to match against the STDOUT and STDERR output of the
32386 virus scanner. If the expression matches, a virus was found. You must make
32387 absolutely sure that this expression matches on &"virus found"&. This is called
32388 the &"trigger"& expression.
32391 Another regular expression, containing exactly one pair of parentheses, to
32392 match the name of the virus found in the scanners output. This is called the
32393 &"name"& expression.
32396 For example, Sophos Sweep reports a virus on a line like this:
32398 Virus 'W32/Magistr-B' found in file ./those.bat
32400 For the trigger expression, we can match the phrase &"found in file"&. For the
32401 name expression, we want to extract the W32/Magistr-B string, so we can match
32402 for the single quotes left and right of it. Altogether, this makes the
32403 configuration setting:
32405 av_scanner = cmdline:\
32406 /path/to/sweep -ss -all -rec -archive %s:\
32407 found in file:'(.+)'
32410 .cindex "virus scanners" "DrWeb"
32411 The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface
32413 either a full path to a UNIX socket,
32414 or host and port specifiers separated by white space.
32415 The host may be a name or an IP address; the port is either a
32416 single number or a pair of numbers with a dash between.
32419 av_scanner = drweb:/var/run/drwebd.sock
32420 av_scanner = drweb:192.168.2.20 31337
32422 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
32423 is used. Thanks to Alex Miller for contributing the code for this scanner.
32426 .cindex "virus scanners" "f-protd"
32427 The f-protd scanner is accessed via HTTP over TCP.
32428 One argument is taken, being a space-separated hostname and port number
32432 av_scanner = f-protd:localhost 10200-10204
32434 If you omit the argument, the default values shown above are used.
32436 .vitem &%f-prot6d%&
32437 .cindex "virus scanners" "f-prot6d"
32438 The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
32439 One argument is taken, being a space-separated hostname and port number.
32442 av_scanner = f-prot6d:localhost 10200
32444 If you omit the argument, the default values show above are used.
32447 .cindex "virus scanners" "F-Secure"
32448 The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one
32449 argument which is the path to a UNIX socket. For example:
32451 av_scanner = fsecure:/path/to/.fsav
32453 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
32454 Thelmen for contributing the code for this scanner.
32456 .vitem &%kavdaemon%&
32457 .cindex "virus scanners" "Kaspersky"
32458 This is the scanner daemon of Kaspersky Version 4. This version of the
32459 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
32460 scanner type takes one option, which is the path to the daemon's UNIX socket.
32463 av_scanner = kavdaemon:/opt/AVP/AvpCtl
32465 The default path is &_/var/run/AvpCtl_&.
32468 .cindex "virus scanners" "mksd"
32469 This was a daemon type scanner that is aimed mainly at Polish users,
32470 though some documentation was available in English.
32471 The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir)
32472 and this appears to be a candidate for removal from Exim, unless
32473 we are informed of other virus scanners which use the same protocol
32475 The only option for this scanner type is
32476 the maximum number of processes used simultaneously to scan the attachments,
32477 provided that mksd has
32478 been run with at least the same number of child processes. For example:
32480 av_scanner = mksd:2
32482 You can safely omit this option (the default value is 1).
32485 .cindex "virus scanners" "simple socket-connected"
32486 This is a general-purpose way of talking to simple scanner daemons
32487 running on the local machine.
32488 There are four options:
32489 an address (which may be an IP address and port, or the path of a Unix socket),
32490 a commandline to send (may include a single %s which will be replaced with
32491 the path to the mail file to be scanned),
32492 an RE to trigger on from the returned data,
32493 and an RE to extract malware_name from the returned data.
32496 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
32498 Note that surrounding whitespace is stripped from each option, meaning
32499 there is no way to specify a trailing newline.
32500 The socket specifier and both regular-expressions are required.
32501 Default for the commandline is &_%s\n_& (note this does have a trailing newline);
32502 specify an empty element to get this.
32505 .cindex "virus scanners" "Sophos and Sophie"
32506 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
32507 You can get Sophie at &url(http://sophie.sourceforge.net/). The only option
32508 for this scanner type is the path to the UNIX socket that Sophie uses for
32509 client communication. For example:
32511 av_scanner = sophie:/tmp/sophie
32513 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
32517 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
32518 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
32521 The &%av_scanner%& option is expanded each time &%malware%& is called. This
32522 makes it possible to use different scanners. See further below for an example.
32523 The &%malware%& condition caches its results, so when you use it multiple times
32524 for the same message, the actual scanning process is only carried out once.
32525 However, using expandable items in &%av_scanner%& disables this caching, in
32526 which case each use of the &%malware%& condition causes a new scan of the
32529 The &%malware%& condition takes a right-hand argument that is expanded before
32530 use and taken as a list, slash-separated by default.
32531 The first element can then be one of
32534 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
32535 The condition succeeds if a virus was found, and fail otherwise. This is the
32538 &"false"& or &"0"& or an empty string, in which case no scanning is done and
32539 the condition fails immediately.
32541 A regular expression, in which case the message is scanned for viruses. The
32542 condition succeeds if a virus is found and its name matches the regular
32543 expression. This allows you to take special actions on certain types of virus.
32544 Note that &"/"& characters in the RE must be doubled due to the list-processing,
32545 unless the separator is changed (in the usual way &<<SECTlistsepchange>>&).
32548 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
32549 messages even if there is a problem with the virus scanner.
32550 Otherwise, such a problem causes the ACL to defer.
32552 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
32553 specify a non-default timeout. The default is two minutes.
32556 malware = * / defer_ok / tmo=10s
32558 A timeout causes the ACL to defer.
32560 .vindex "&$callout_address$&"
32561 When a connection is made to the scanner the expansion variable &$callout_address$&
32562 is set to record the actual address used.
32564 .vindex "&$malware_name$&"
32565 When a virus is found, the condition sets up an expansion variable called
32566 &$malware_name$& that contains the name of the virus. You can use it in a
32567 &%message%& modifier that specifies the error returned to the sender, and/or in
32570 Beware the interaction of Exim's &%message_size_limit%& with any size limits
32571 imposed by your anti-virus scanner.
32573 Here is a very simple scanning example:
32575 deny message = This message contains malware ($malware_name)
32578 The next example accepts messages when there is a problem with the scanner:
32580 deny message = This message contains malware ($malware_name)
32581 malware = */defer_ok
32583 The next example shows how to use an ACL variable to scan with both sophie and
32584 aveserver. It assumes you have set:
32586 av_scanner = $acl_m0
32588 in the main Exim configuration.
32590 deny message = This message contains malware ($malware_name)
32591 set acl_m0 = sophie
32594 deny message = This message contains malware ($malware_name)
32595 set acl_m0 = aveserver
32600 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
32601 .cindex "content scanning" "for spam"
32602 .cindex "spam scanning"
32603 .cindex "SpamAssassin"
32605 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
32606 score and a report for the message.
32607 Support is also provided for Rspamd.
32609 For more information about installation and configuration of SpamAssassin or
32610 Rspamd refer to their respective websites at
32611 &url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/)
32613 SpamAssassin can be installed with CPAN by running:
32615 perl -MCPAN -e 'install Mail::SpamAssassin'
32617 SpamAssassin has its own set of configuration files. Please review its
32618 documentation to see how you can tweak it. The default installation should work
32621 .oindex "&%spamd_address%&"
32622 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
32623 intend to use an instance running on the local host you do not need to set
32624 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
32625 you must set the &%spamd_address%& option in the global part of the Exim
32626 configuration as follows (example):
32628 spamd_address = 192.168.99.45 783
32630 The SpamAssassin protocol relies on a TCP half-close from the client.
32631 If your SpamAssassin client side is running a Linux system with an
32632 iptables firewall, consider setting
32633 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
32634 timeout, Exim uses when waiting for a response from the SpamAssassin
32635 server (currently defaulting to 120s). With a lower value the Linux
32636 connection tracking may consider your half-closed connection as dead too
32640 To use Rspamd (which by default listens on all local addresses
32642 you should add &%variant=rspamd%& after the address/port pair, for example:
32644 spamd_address = 127.0.0.1 11333 variant=rspamd
32647 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
32648 sockets. If you want to us these, supply &%spamd_address%& with an absolute
32649 filename instead of an address/port pair:
32651 spamd_address = /var/run/spamd_socket
32653 You can have multiple &%spamd%& servers to improve scalability. These can
32654 reside on other hardware reachable over the network. To specify multiple
32655 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
32656 option, separated with colons (the separator can be changed in the usual way &<<SECTlistsepchange>>&):
32658 spamd_address = 192.168.2.10 783 : \
32659 192.168.2.11 783 : \
32662 Up to 32 &%spamd%& servers are supported.
32663 When a server fails to respond to the connection attempt, all other
32664 servers are tried until one succeeds. If no server responds, the &%spam%&
32667 Unix and TCP socket specifications may be mixed in any order.
32668 Each element of the list is a list itself, space-separated by default
32669 and changeable in the usual way (&<<SECTlistsepchange>>&);
32670 take care to not double the separator.
32672 For TCP socket specifications a host name or IP (v4 or v6, but
32673 subject to list-separator quoting rules) address can be used,
32674 and the port can be one or a dash-separated pair.
32675 In the latter case, the range is tried in strict order.
32677 Elements after the first for Unix sockets, or second for TCP socket,
32679 The supported options are:
32681 pri=<priority> Selection priority
32682 weight=<value> Selection bias
32683 time=<start>-<end> Use only between these times of day
32684 retry=<timespec> Retry on connect fail
32685 tmo=<timespec> Connection time limit
32686 variant=rspamd Use Rspamd rather than SpamAssassin protocol
32689 The &`pri`& option specifies a priority for the server within the list,
32690 higher values being tried first.
32691 The default priority is 1.
32693 The &`weight`& option specifies a selection bias.
32694 Within a priority set
32695 servers are queried in a random fashion, weighted by this value.
32696 The default value for selection bias is 1.
32698 Time specifications for the &`time`& option are <hour>.<minute>.<second>
32699 in the local time zone; each element being one or more digits.
32700 Either the seconds or both minutes and seconds, plus the leading &`.`&
32701 characters, may be omitted and will be taken as zero.
32703 Timeout specifications for the &`retry`& and &`tmo`& options
32704 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
32706 The &`tmo`& option specifies an overall timeout for communication.
32707 The default value is two minutes.
32709 The &`retry`& option specifies a time after which a single retry for
32710 a failed connect is made.
32711 The default is to not retry.
32713 The &%spamd_address%& variable is expanded before use if it starts with
32714 a dollar sign. In this case, the expansion may return a string that is
32715 used as the list so that multiple spamd servers can be the result of an
32718 .vindex "&$callout_address$&"
32719 When a connection is made to the server the expansion variable &$callout_address$&
32720 is set to record the actual address used.
32722 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
32723 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
32725 deny message = This message was classified as SPAM
32728 The right-hand side of the &%spam%& condition specifies a name. This is
32729 relevant if you have set up multiple SpamAssassin profiles. If you do not want
32730 to scan using a specific profile, but rather use the SpamAssassin system-wide
32731 default profile, you can scan for an unknown name, or simply use &"nobody"&.
32732 Rspamd does not use this setting. However, you must put something on the
32735 The name allows you to use per-domain or per-user antispam profiles in
32736 principle, but this is not straightforward in practice, because a message may
32737 have multiple recipients, not necessarily all in the same domain. Because the
32738 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
32739 read the contents of the message, the variables &$local_part$& and &$domain$&
32741 Careful enforcement of single-recipient messages
32742 (e.g. by responding with defer in the recipient ACL for all recipients
32744 or the use of PRDR,
32745 .cindex "PRDR" "use for per-user SpamAssassin profiles"
32746 are needed to use this feature.
32748 The right-hand side of the &%spam%& condition is expanded before being used, so
32749 you can put lookups or conditions there. When the right-hand side evaluates to
32750 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
32753 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
32754 large ones may cause significant performance degradation. As most spam messages
32755 are quite small, it is recommended that you do not scan the big ones. For
32758 deny message = This message was classified as SPAM
32759 condition = ${if < {$message_size}{10K}}
32763 The &%spam%& condition returns true if the threshold specified in the user's
32764 SpamAssassin profile has been matched or exceeded. If you want to use the
32765 &%spam%& condition for its side effects (see the variables below), you can make
32766 it always return &"true"& by appending &`:true`& to the username.
32768 .cindex "spam scanning" "returned variables"
32769 When the &%spam%& condition is run, it sets up a number of expansion
32771 Except for &$spam_report$&,
32772 these variables are saved with the received message so are
32773 available for use at delivery time.
32776 .vitem &$spam_score$&
32777 The spam score of the message, for example, &"3.4"& or &"30.5"&. This is useful
32778 for inclusion in log or reject messages.
32780 .vitem &$spam_score_int$&
32781 The spam score of the message, multiplied by ten, as an integer value. For
32782 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
32783 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
32784 The integer value is useful for numeric comparisons in conditions.
32786 .vitem &$spam_bar$&
32787 A string consisting of a number of &"+"& or &"-"& characters, representing the
32788 integer part of the spam score value. A spam score of 4.4 would have a
32789 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
32790 headers, since MUAs can match on such strings. The maximum length of the
32791 spam bar is 50 characters.
32793 .vitem &$spam_report$&
32794 A multiline text table, containing the full SpamAssassin report for the
32795 message. Useful for inclusion in headers or reject messages.
32796 This variable is only usable in a DATA-time ACL.
32797 Beware that SpamAssassin may return non-ASCII characters, especially
32798 when running in country-specific locales, which are not legal
32799 unencoded in headers.
32801 .vitem &$spam_action$&
32802 For SpamAssassin either 'reject' or 'no action' depending on the
32803 spam score versus threshold.
32804 For Rspamd, the recommended action.
32808 The &%spam%& condition caches its results unless expansion in
32809 spamd_address was used. If you call it again with the same user name, it
32810 does not scan again, but rather returns the same values as before.
32812 The &%spam%& condition returns DEFER if there is any error while running
32813 the message through SpamAssassin or if the expansion of spamd_address
32814 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
32815 statement block), append &`/defer_ok`& to the right-hand side of the
32816 spam condition, like this:
32818 deny message = This message was classified as SPAM
32819 spam = joe/defer_ok
32821 This causes messages to be accepted even if there is a problem with &%spamd%&.
32823 Here is a longer, commented example of the use of the &%spam%&
32826 # put headers in all messages (no matter if spam or not)
32827 warn spam = nobody:true
32828 add_header = X-Spam-Score: $spam_score ($spam_bar)
32829 add_header = X-Spam-Report: $spam_report
32831 # add second subject line with *SPAM* marker when message
32832 # is over threshold
32834 add_header = Subject: *SPAM* $h_Subject:
32836 # reject spam at high scores (> 12)
32837 deny message = This message scored $spam_score spam points.
32839 condition = ${if >{$spam_score_int}{120}{1}{0}}
32844 .section "Scanning MIME parts" "SECTscanmimepart"
32845 .cindex "content scanning" "MIME parts"
32846 .cindex "MIME content scanning"
32847 .oindex "&%acl_smtp_mime%&"
32848 .oindex "&%acl_not_smtp_mime%&"
32849 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
32850 each MIME part of an SMTP message, including multipart types, in the sequence
32851 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
32852 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
32853 options may both refer to the same ACL if you want the same processing in both
32856 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
32857 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
32858 the case of a non-SMTP message. However, a MIME ACL is called only if the
32859 message contains a &'Content-Type:'& header line. When a call to a MIME
32860 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
32861 result code is sent to the client. In the case of an SMTP message, the
32862 &%acl_smtp_data%& ACL is not called when this happens.
32864 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
32865 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
32866 condition to match against the raw MIME part. You can also use the
32867 &%mime_regex%& condition to match against the decoded MIME part (see section
32868 &<<SECTscanregex>>&).
32870 At the start of a MIME ACL, a number of variables are set from the header
32871 information for the relevant MIME part. These are described below. The contents
32872 of the MIME part are not by default decoded into a disk file except for MIME
32873 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
32874 part into a disk file, you can use the &%decode%& condition. The general
32877 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
32879 The right hand side is expanded before use. After expansion,
32883 &"0"& or &"false"&, in which case no decoding is done.
32885 The string &"default"&. In that case, the file is put in the temporary
32886 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
32887 a sequential filename consisting of the message id and a sequence number. The
32888 full path and name is available in &$mime_decoded_filename$& after decoding.
32890 A full path name starting with a slash. If the full name is an existing
32891 directory, it is used as a replacement for the default directory. The filename
32892 is then sequentially assigned. If the path does not exist, it is used as
32893 the full path and filename.
32895 If the string does not start with a slash, it is used as the
32896 filename, and the default path is then used.
32898 The &%decode%& condition normally succeeds. It is only false for syntax
32899 errors or unusual circumstances such as memory shortages. You can easily decode
32900 a file with its original, proposed filename using
32902 decode = $mime_filename
32904 However, you should keep in mind that &$mime_filename$& might contain
32905 anything. If you place files outside of the default path, they are not
32906 automatically unlinked.
32908 For RFC822 attachments (these are messages attached to messages, with a
32909 content-type of &"message/rfc822"&), the ACL is called again in the same manner
32910 as for the primary message, only that the &$mime_is_rfc822$& expansion
32911 variable is set (see below). Attached messages are always decoded to disk
32912 before being checked, and the files are unlinked once the check is done.
32914 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
32915 used to match regular expressions against raw and decoded MIME parts,
32916 respectively. They are described in section &<<SECTscanregex>>&.
32918 .cindex "MIME content scanning" "returned variables"
32919 The following list describes all expansion variables that are
32920 available in the MIME ACL:
32923 .vitem &$mime_boundary$&
32924 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
32925 have a boundary string, which is stored in this variable. If the current part
32926 has no boundary parameter in the &'Content-Type:'& header, this variable
32927 contains the empty string.
32929 .vitem &$mime_charset$&
32930 This variable contains the character set identifier, if one was found in the
32931 &'Content-Type:'& header. Examples for charset identifiers are:
32937 Please note that this value is not normalized, so you should do matches
32938 case-insensitively.
32940 .vitem &$mime_content_description$&
32941 This variable contains the normalized content of the &'Content-Description:'&
32942 header. It can contain a human-readable description of the parts content. Some
32943 implementations repeat the filename for attachments here, but they are usually
32944 only used for display purposes.
32946 .vitem &$mime_content_disposition$&
32947 This variable contains the normalized content of the &'Content-Disposition:'&
32948 header. You can expect strings like &"attachment"& or &"inline"& here.
32950 .vitem &$mime_content_id$&
32951 This variable contains the normalized content of the &'Content-ID:'& header.
32952 This is a unique ID that can be used to reference a part from another part.
32954 .vitem &$mime_content_size$&
32955 This variable is set only after the &%decode%& modifier (see above) has been
32956 successfully run. It contains the size of the decoded part in kilobytes. The
32957 size is always rounded up to full kilobytes, so only a completely empty part
32958 has a &$mime_content_size$& of zero.
32960 .vitem &$mime_content_transfer_encoding$&
32961 This variable contains the normalized content of the
32962 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
32963 type. Typical values are &"base64"& and &"quoted-printable"&.
32965 .vitem &$mime_content_type$&
32966 If the MIME part has a &'Content-Type:'& header, this variable contains its
32967 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
32968 are some examples of popular MIME types, as they may appear in this variable:
32972 application/octet-stream
32976 If the MIME part has no &'Content-Type:'& header, this variable contains the
32979 .vitem &$mime_decoded_filename$&
32980 This variable is set only after the &%decode%& modifier (see above) has been
32981 successfully run. It contains the full path and filename of the file
32982 containing the decoded data.
32987 .vitem &$mime_filename$&
32988 This is perhaps the most important of the MIME variables. It contains a
32989 proposed filename for an attachment, if one was found in either the
32990 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
32993 decoded, but no additional sanity checks are done.
32995 found, this variable contains the empty string.
32997 .vitem &$mime_is_coverletter$&
32998 This variable attempts to differentiate the &"cover letter"& of an e-mail from
32999 attached data. It can be used to clamp down on flashy or unnecessarily encoded
33000 content in the cover letter, while not restricting attachments at all.
33002 The variable contains 1 (true) for a MIME part believed to be part of the
33003 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
33007 The outermost MIME part of a message is always a cover letter.
33010 If a multipart/alternative or multipart/related MIME part is a cover letter,
33011 so are all MIME subparts within that multipart.
33014 If any other multipart is a cover letter, the first subpart is a cover letter,
33015 and the rest are attachments.
33018 All parts contained within an attachment multipart are attachments.
33021 As an example, the following will ban &"HTML mail"& (including that sent with
33022 alternative plain text), while allowing HTML files to be attached. HTML
33023 coverletter mail attached to non-HTML coverletter mail will also be allowed:
33025 deny message = HTML mail is not accepted here
33026 !condition = $mime_is_rfc822
33027 condition = $mime_is_coverletter
33028 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
33030 .vitem &$mime_is_multipart$&
33031 This variable has the value 1 (true) when the current part has the main type
33032 &"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
33033 Since multipart entities only serve as containers for other parts, you may not
33034 want to carry out specific actions on them.
33036 .vitem &$mime_is_rfc822$&
33037 This variable has the value 1 (true) if the current part is not a part of the
33038 checked message itself, but part of an attached message. Attached message
33039 decoding is fully recursive.
33041 .vitem &$mime_part_count$&
33042 This variable is a counter that is raised for each processed MIME part. It
33043 starts at zero for the very first part (which is usually a multipart). The
33044 counter is per-message, so it is reset when processing RFC822 attachments (see
33045 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
33046 complete, so you can use it in the DATA ACL to determine the number of MIME
33047 parts of a message. For non-MIME messages, this variable contains the value -1.
33052 .section "Scanning with regular expressions" "SECTscanregex"
33053 .cindex "content scanning" "with regular expressions"
33054 .cindex "regular expressions" "content scanning with"
33055 You can specify your own custom regular expression matches on the full body of
33056 the message, or on individual MIME parts.
33058 The &%regex%& condition takes one or more regular expressions as arguments and
33059 matches them against the full message (when called in the DATA ACL) or a raw
33060 MIME part (when called in the MIME ACL). The &%regex%& condition matches
33061 linewise, with a maximum line length of 32K characters. That means you cannot
33062 have multiline matches with the &%regex%& condition.
33064 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
33065 to 32K of decoded content (the whole content at once, not linewise). If the
33066 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
33067 is decoded automatically when &%mime_regex%& is executed (using default path
33068 and filename values). If the decoded data is larger than 32K, only the first
33069 32K characters are checked.
33071 The regular expressions are passed as a colon-separated list. To include a
33072 literal colon, you must double it. Since the whole right-hand side string is
33073 expanded before being used, you must also escape dollar signs and backslashes
33074 with more backslashes, or use the &`\N`& facility to disable expansion.
33075 Here is a simple example that contains two regular expressions:
33077 deny message = contains blacklisted regex ($regex_match_string)
33078 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
33080 The conditions returns true if any one of the regular expressions matches. The
33081 &$regex_match_string$& expansion variable is then set up and contains the
33082 matching regular expression.
33083 The expansion variables &$regex1$& &$regex2$& etc
33084 are set to any substrings captured by the regular expression.
33086 &*Warning*&: With large messages, these conditions can be fairly
33094 . ////////////////////////////////////////////////////////////////////////////
33095 . ////////////////////////////////////////////////////////////////////////////
33097 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
33098 "Local scan function"
33099 .scindex IIDlosca "&[local_scan()]& function" "description of"
33100 .cindex "customizing" "input scan using C function"
33101 .cindex "policy control" "by local scan function"
33102 In these days of email worms, viruses, and ever-increasing spam, some sites
33103 want to apply a lot of checking to messages before accepting them.
33105 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
33106 passing messages to external virus and spam scanning software. You can also do
33107 a certain amount in Exim itself through string expansions and the &%condition%&
33108 condition in the ACL that runs after the SMTP DATA command or the ACL for
33109 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
33111 To allow for further customization to a site's own requirements, there is the
33112 possibility of linking Exim with a private message scanning function, written
33113 in C. If you want to run code that is written in something other than C, you
33114 can of course use a little C stub to call it.
33116 The local scan function is run once for every incoming message, at the point
33117 when Exim is just about to accept the message.
33118 It can therefore be used to control non-SMTP messages from local processes as
33119 well as messages arriving via SMTP.
33121 Exim applies a timeout to calls of the local scan function, and there is an
33122 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
33123 Zero means &"no timeout"&.
33124 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
33125 before calling the local scan function, so that the most common types of crash
33126 are caught. If the timeout is exceeded or one of those signals is caught, the
33127 incoming message is rejected with a temporary error if it is an SMTP message.
33128 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
33129 code. The incident is logged on the main and reject logs.
33133 .section "Building Exim to use a local scan function" "SECID207"
33134 .cindex "&[local_scan()]& function" "building Exim to use"
33135 To make use of the local scan function feature, you must tell Exim where your
33136 function is before building Exim, by setting
33137 both HAVE_LOCAL_SCAN and
33138 LOCAL_SCAN_SOURCE in your
33139 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
33140 directory, so you might set
33142 HAVE_LOCAL_SCAN=yes
33143 LOCAL_SCAN_SOURCE=Local/local_scan.c
33145 for example. The function must be called &[local_scan()]&. It is called by
33146 Exim after it has received a message, when the success return code is about to
33147 be sent. This is after all the ACLs have been run. The return code from your
33148 function controls whether the message is actually accepted or not. There is a
33149 commented template function (that just accepts the message) in the file
33150 _src/local_scan.c_.
33152 If you want to make use of Exim's runtime configuration file to set options
33153 for your &[local_scan()]& function, you must also set
33155 LOCAL_SCAN_HAS_OPTIONS=yes
33157 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
33162 .section "API for local_scan()" "SECTapiforloc"
33163 .cindex "&[local_scan()]& function" "API description"
33164 .cindex &%dlfunc%& "API description"
33165 You must include this line near the start of your code:
33167 #include "local_scan.h"
33169 This header file defines a number of variables and other values, and the
33170 prototype for the function itself. Exim is coded to use unsigned char values
33171 almost exclusively, and one of the things this header defines is a shorthand
33172 for &`unsigned char`& called &`uschar`&.
33173 It also contains the following macro definitions, to simplify casting character
33174 strings and pointers to character strings:
33176 #define CS (char *)
33177 #define CCS (const char *)
33178 #define CSS (char **)
33179 #define US (unsigned char *)
33180 #define CUS (const unsigned char *)
33181 #define USS (unsigned char **)
33183 The function prototype for &[local_scan()]& is:
33185 extern int local_scan(int fd, uschar **return_text);
33187 The arguments are as follows:
33190 &%fd%& is a file descriptor for the file that contains the body of the message
33191 (the -D file). The file is open for reading and writing, but updating it is not
33192 recommended. &*Warning*&: You must &'not'& close this file descriptor.
33194 The descriptor is positioned at character 19 of the file, which is the first
33195 character of the body itself, because the first 19 characters are the message
33196 id followed by &`-D`& and a newline. If you rewind the file, you should use the
33197 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
33198 case this changes in some future version.
33200 &%return_text%& is an address which you can use to return a pointer to a text
33201 string at the end of the function. The value it points to on entry is NULL.
33204 The function must return an &%int%& value which is one of the following macros:
33207 .vitem &`LOCAL_SCAN_ACCEPT`&
33208 .vindex "&$local_scan_data$&"
33209 The message is accepted. If you pass back a string of text, it is saved with
33210 the message, and made available in the variable &$local_scan_data$&. No
33211 newlines are permitted (if there are any, they are turned into spaces) and the
33212 maximum length of text is 1000 characters.
33214 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
33215 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
33216 queued without immediate delivery, and is frozen.
33218 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
33219 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
33220 queued without immediate delivery.
33222 .vitem &`LOCAL_SCAN_REJECT`&
33223 The message is rejected; the returned text is used as an error message which is
33224 passed back to the sender and which is also logged. Newlines are permitted &--
33225 they cause a multiline response for SMTP rejections, but are converted to
33226 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
33229 .vitem &`LOCAL_SCAN_TEMPREJECT`&
33230 The message is temporarily rejected; the returned text is used as an error
33231 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
33234 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
33235 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
33236 message is not written to the reject log. It has the effect of unsetting the
33237 &%rejected_header%& log selector for just this rejection. If
33238 &%rejected_header%& is already unset (see the discussion of the
33239 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
33240 same as LOCAL_SCAN_REJECT.
33242 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
33243 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
33244 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
33247 If the message is not being received by interactive SMTP, rejections are
33248 reported by writing to &%stderr%& or by sending an email, as configured by the
33249 &%-oe%& command line options.
33253 .section "Configuration options for local_scan()" "SECTconoptloc"
33254 .cindex "&[local_scan()]& function" "configuration options"
33255 It is possible to have option settings in the main configuration file
33256 that set values in static variables in the &[local_scan()]& module. If you
33257 want to do this, you must have the line
33259 LOCAL_SCAN_HAS_OPTIONS=yes
33261 in your &_Local/Makefile_& when you build Exim. (This line is in
33262 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
33263 file, you must define static variables to hold the option values, and a table
33266 The table must be a vector called &%local_scan_options%&, of type
33267 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
33268 and a pointer to the variable that holds the value. The entries must appear in
33269 alphabetical order. Following &%local_scan_options%& you must also define a
33270 variable called &%local_scan_options_count%& that contains the number of
33271 entries in the table. Here is a short example, showing two kinds of option:
33273 static int my_integer_option = 42;
33274 static uschar *my_string_option = US"a default string";
33276 optionlist local_scan_options[] = {
33277 { "my_integer", opt_int, &my_integer_option },
33278 { "my_string", opt_stringptr, &my_string_option }
33281 int local_scan_options_count =
33282 sizeof(local_scan_options)/sizeof(optionlist);
33284 The values of the variables can now be changed from Exim's runtime
33285 configuration file by including a local scan section as in this example:
33289 my_string = some string of text...
33291 The available types of option data are as follows:
33294 .vitem &*opt_bool*&
33295 This specifies a boolean (true/false) option. The address should point to a
33296 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
33297 that are defined as &"1"& and &"0"&, respectively. If you want to detect
33298 whether such a variable has been set at all, you can initialize it to
33299 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
33302 .vitem &*opt_fixed*&
33303 This specifies a fixed point number, such as is used for load averages.
33304 The address should point to a variable of type &`int`&. The value is stored
33305 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
33308 This specifies an integer; the address should point to a variable of type
33309 &`int`&. The value may be specified in any of the integer formats accepted by
33312 .vitem &*opt_mkint*&
33313 This is the same as &%opt_int%&, except that when such a value is output in a
33314 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
33315 printed with the suffix K or M.
33317 .vitem &*opt_octint*&
33318 This also specifies an integer, but the value is always interpreted as an
33319 octal integer, whether or not it starts with the digit zero, and it is
33320 always output in octal.
33322 .vitem &*opt_stringptr*&
33323 This specifies a string value; the address must be a pointer to a
33324 variable that points to a string (for example, of type &`uschar *`&).
33326 .vitem &*opt_time*&
33327 This specifies a time interval value. The address must point to a variable of
33328 type &`int`&. The value that is placed there is a number of seconds.
33331 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
33332 out the values of all the &[local_scan()]& options.
33336 .section "Available Exim variables" "SECID208"
33337 .cindex "&[local_scan()]& function" "available Exim variables"
33338 The header &_local_scan.h_& gives you access to a number of C variables. These
33339 are the only ones that are guaranteed to be maintained from release to release.
33340 Note, however, that you can obtain the value of any Exim expansion variable,
33341 including &$recipients$&, by calling &'expand_string()'&. The exported
33342 C variables are as follows:
33345 .vitem &*int&~body_linecount*&
33346 This variable contains the number of lines in the message's body.
33347 It is not valid if the &%spool_files_wireformat%& option is used.
33349 .vitem &*int&~body_zerocount*&
33350 This variable contains the number of binary zero bytes in the message's body.
33351 It is not valid if the &%spool_files_wireformat%& option is used.
33353 .vitem &*unsigned&~int&~debug_selector*&
33354 This variable is set to zero when no debugging is taking place. Otherwise, it
33355 is a bitmap of debugging selectors. Two bits are identified for use in
33356 &[local_scan()]&; they are defined as macros:
33359 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
33360 testing option that is not privileged &-- any caller may set it. All the
33361 other selector bits can be set only by admin users.
33364 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
33365 by the &`+local_scan`& debug selector. It is not included in the default set
33369 Thus, to write to the debugging output only when &`+local_scan`& has been
33370 selected, you should use code like this:
33372 if ((debug_selector & D_local_scan) != 0)
33373 debug_printf("xxx", ...);
33375 .vitem &*uschar&~*expand_string_message*&
33376 After a failing call to &'expand_string()'& (returned value NULL), the
33377 variable &%expand_string_message%& contains the error message, zero-terminated.
33379 .vitem &*header_line&~*header_list*&
33380 A pointer to a chain of header lines. The &%header_line%& structure is
33383 .vitem &*header_line&~*header_last*&
33384 A pointer to the last of the header lines.
33386 .vitem &*uschar&~*headers_charset*&
33387 The value of the &%headers_charset%& configuration option.
33389 .vitem &*BOOL&~host_checking*&
33390 This variable is TRUE during a host checking session that is initiated by the
33391 &%-bh%& command line option.
33393 .vitem &*uschar&~*interface_address*&
33394 The IP address of the interface that received the message, as a string. This
33395 is NULL for locally submitted messages.
33397 .vitem &*int&~interface_port*&
33398 The port on which this message was received. When testing with the &%-bh%&
33399 command line option, the value of this variable is -1 unless a port has been
33400 specified via the &%-oMi%& option.
33402 .vitem &*uschar&~*message_id*&
33403 This variable contains Exim's message id for the incoming message (the value of
33404 &$message_exim_id$&) as a zero-terminated string.
33406 .vitem &*uschar&~*received_protocol*&
33407 The name of the protocol by which the message was received.
33409 .vitem &*int&~recipients_count*&
33410 The number of accepted recipients.
33412 .vitem &*recipient_item&~*recipients_list*&
33413 .cindex "recipient" "adding in local scan"
33414 .cindex "recipient" "removing in local scan"
33415 The list of accepted recipients, held in a vector of length
33416 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
33417 can add additional recipients by calling &'receive_add_recipient()'& (see
33418 below). You can delete recipients by removing them from the vector and
33419 adjusting the value in &%recipients_count%&. In particular, by setting
33420 &%recipients_count%& to zero you remove all recipients. If you then return the
33421 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
33422 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
33423 and then call &'receive_add_recipient()'& as often as needed.
33425 .vitem &*uschar&~*sender_address*&
33426 The envelope sender address. For bounce messages this is the empty string.
33428 .vitem &*uschar&~*sender_host_address*&
33429 The IP address of the sending host, as a string. This is NULL for
33430 locally-submitted messages.
33432 .vitem &*uschar&~*sender_host_authenticated*&
33433 The name of the authentication mechanism that was used, or NULL if the message
33434 was not received over an authenticated SMTP connection.
33436 .vitem &*uschar&~*sender_host_name*&
33437 The name of the sending host, if known.
33439 .vitem &*int&~sender_host_port*&
33440 The port on the sending host.
33442 .vitem &*BOOL&~smtp_input*&
33443 This variable is TRUE for all SMTP input, including BSMTP.
33445 .vitem &*BOOL&~smtp_batched_input*&
33446 This variable is TRUE for BSMTP input.
33448 .vitem &*int&~store_pool*&
33449 The contents of this variable control which pool of memory is used for new
33450 requests. See section &<<SECTmemhanloc>>& for details.
33454 .section "Structure of header lines" "SECID209"
33455 The &%header_line%& structure contains the members listed below.
33456 You can add additional header lines by calling the &'header_add()'& function
33457 (see below). You can cause header lines to be ignored (deleted) by setting
33462 .vitem &*struct&~header_line&~*next*&
33463 A pointer to the next header line, or NULL for the last line.
33465 .vitem &*int&~type*&
33466 A code identifying certain headers that Exim recognizes. The codes are printing
33467 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
33468 Notice in particular that any header line whose type is * is not transmitted
33469 with the message. This flagging is used for header lines that have been
33470 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
33471 lines.) Effectively, * means &"deleted"&.
33473 .vitem &*int&~slen*&
33474 The number of characters in the header line, including the terminating and any
33477 .vitem &*uschar&~*text*&
33478 A pointer to the text of the header. It always ends with a newline, followed by
33479 a zero byte. Internal newlines are preserved.
33484 .section "Structure of recipient items" "SECID210"
33485 The &%recipient_item%& structure contains these members:
33488 .vitem &*uschar&~*address*&
33489 This is a pointer to the recipient address as it was received.
33491 .vitem &*int&~pno*&
33492 This is used in later Exim processing when top level addresses are created by
33493 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
33494 and must always contain -1 at this stage.
33496 .vitem &*uschar&~*errors_to*&
33497 If this value is not NULL, bounce messages caused by failing to deliver to the
33498 recipient are sent to the address it contains. In other words, it overrides the
33499 envelope sender for this one recipient. (Compare the &%errors_to%& generic
33500 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
33501 an unqualified address, Exim qualifies it using the domain from
33502 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
33503 is NULL for all recipients.
33508 .section "Available Exim functions" "SECID211"
33509 .cindex "&[local_scan()]& function" "available Exim functions"
33510 The header &_local_scan.h_& gives you access to a number of Exim functions.
33511 These are the only ones that are guaranteed to be maintained from release to
33515 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
33516 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
33518 This function creates a child process that runs the command specified by
33519 &%argv%&. The environment for the process is specified by &%envp%&, which can
33520 be NULL if no environment variables are to be passed. A new umask is supplied
33521 for the process in &%newumask%&.
33523 Pipes to the standard input and output of the new process are set up
33524 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
33525 standard error is cloned to the standard output. If there are any file
33526 descriptors &"in the way"& in the new process, they are closed. If the final
33527 argument is TRUE, the new process is made into a process group leader.
33529 The function returns the pid of the new process, or -1 if things go wrong.
33531 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
33532 This function waits for a child process to terminate, or for a timeout (in
33533 seconds) to expire. A timeout value of zero means wait as long as it takes. The
33534 return value is as follows:
33539 The process terminated by a normal exit and the value is the process
33545 The process was terminated by a signal and the value is the negation of the
33551 The process timed out.
33555 The was some other error in wait(); &%errno%& is still set.
33558 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
33559 This function provide you with a means of submitting a new message to
33560 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
33561 want, but this packages it all up for you.) The function creates a pipe,
33562 forks a subprocess that is running
33564 exim -t -oem -oi -f <>
33566 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
33567 that is connected to the standard input. The yield of the function is the PID
33568 of the subprocess. You can then write a message to the file descriptor, with
33569 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
33571 When you have finished, call &'child_close()'& to wait for the process to
33572 finish and to collect its ending status. A timeout value of zero is usually
33573 fine in this circumstance. Unless you have made a mistake with the recipient
33574 addresses, you should get a return code of zero.
33577 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
33578 *sender_authentication)*&
33579 This function is a more sophisticated version of &'child_open()'&. The command
33582 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
33584 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
33587 .vitem &*void&~debug_printf(char&~*,&~...)*&
33588 This is Exim's debugging function, with arguments as for &'(printf()'&. The
33589 output is written to the standard error stream. If no debugging is selected,
33590 calls to &'debug_printf()'& have no effect. Normally, you should make calls
33591 conditional on the &`local_scan`& debug selector by coding like this:
33593 if ((debug_selector & D_local_scan) != 0)
33594 debug_printf("xxx", ...);
33597 .vitem &*uschar&~*expand_string(uschar&~*string)*&
33598 This is an interface to Exim's string expansion code. The return value is the
33599 expanded string, or NULL if there was an expansion failure.
33600 The C variable &%expand_string_message%& contains an error message after an
33601 expansion failure. If expansion does not change the string, the return value is
33602 the pointer to the input string. Otherwise, the return value points to a new
33603 block of memory that was obtained by a call to &'store_get()'&. See section
33604 &<<SECTmemhanloc>>& below for a discussion of memory handling.
33606 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
33607 This function allows you to an add additional header line at the end of the
33608 existing ones. The first argument is the type, and should normally be a space
33609 character. The second argument is a format string and any number of
33610 substitution arguments as for &[sprintf()]&. You may include internal newlines
33611 if you want, and you must ensure that the string ends with a newline.
33613 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
33614 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
33615 This function adds a new header line at a specified point in the header
33616 chain. The header itself is specified as for &'header_add()'&.
33618 If &%name%& is NULL, the new header is added at the end of the chain if
33619 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
33620 NULL, the header lines are searched for the first non-deleted header that
33621 matches the name. If one is found, the new header is added before it if
33622 &%after%& is false. If &%after%& is true, the new header is added after the
33623 found header and any adjacent subsequent ones with the same name (even if
33624 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
33625 option controls where the header is added. If it is true, addition is at the
33626 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
33627 headers, or at the top if there are no &'Received:'& headers, you could use
33629 header_add_at_position(TRUE, US"Received", TRUE,
33630 ' ', "X-xxx: ...");
33632 Normally, there is always at least one non-deleted &'Received:'& header, but
33633 there may not be if &%received_header_text%& expands to an empty string.
33636 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
33637 This function removes header lines. If &%occurrence%& is zero or negative, all
33638 occurrences of the header are removed. If occurrence is greater than zero, that
33639 particular instance of the header is removed. If no header(s) can be found that
33640 match the specification, the function does nothing.
33643 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
33644 int&~length,&~BOOL&~notdel)*&"
33645 This function tests whether the given header has the given name. It is not just
33646 a string comparison, because white space is permitted between the name and the
33647 colon. If the &%notdel%& argument is true, a false return is forced for all
33648 &"deleted"& headers; otherwise they are not treated specially. For example:
33650 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
33652 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
33653 .cindex "base64 encoding" "functions for &[local_scan()]& use"
33654 This function base64-encodes a string, which is passed by address and length.
33655 The text may contain bytes of any value, including zero. The result is passed
33656 back in dynamic memory that is obtained by calling &'store_get()'&. It is
33659 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
33660 This function decodes a base64-encoded string. Its arguments are a
33661 zero-terminated base64-encoded string and the address of a variable that is set
33662 to point to the result, which is in dynamic memory. The length of the decoded
33663 string is the yield of the function. If the input is invalid base64 data, the
33664 yield is -1. A zero byte is added to the end of the output string to make it
33665 easy to interpret as a C string (assuming it contains no zeros of its own). The
33666 added zero byte is not included in the returned count.
33668 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
33669 This function checks for a match in a domain list. Domains are always
33670 matched caselessly. The return value is one of the following:
33672 &`OK `& match succeeded
33673 &`FAIL `& match failed
33674 &`DEFER `& match deferred
33676 DEFER is usually caused by some kind of lookup defer, such as the
33677 inability to contact a database.
33679 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
33681 This function checks for a match in a local part list. The third argument
33682 controls case-sensitivity. The return values are as for
33683 &'lss_match_domain()'&.
33685 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
33687 This function checks for a match in an address list. The third argument
33688 controls the case-sensitivity of the local part match. The domain is always
33689 matched caselessly. The return values are as for &'lss_match_domain()'&.
33691 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
33693 This function checks for a match in a host list. The most common usage is
33696 lss_match_host(sender_host_name, sender_host_address, ...)
33698 .vindex "&$sender_host_address$&"
33699 An empty address field matches an empty item in the host list. If the host name
33700 is NULL, the name corresponding to &$sender_host_address$& is automatically
33701 looked up if a host name is required to match an item in the list. The return
33702 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
33703 returns ERROR in the case when it had to look up a host name, but the lookup
33706 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
33708 This function writes to Exim's log files. The first argument should be zero (it
33709 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
33710 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
33711 them. It specifies to which log or logs the message is written. The remaining
33712 arguments are a format and relevant insertion arguments. The string should not
33713 contain any newlines, not even at the end.
33716 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
33717 This function adds an additional recipient to the message. The first argument
33718 is the recipient address. If it is unqualified (has no domain), it is qualified
33719 with the &%qualify_recipient%& domain. The second argument must always be -1.
33721 This function does not allow you to specify a private &%errors_to%& address (as
33722 described with the structure of &%recipient_item%& above), because it pre-dates
33723 the addition of that field to the structure. However, it is easy to add such a
33724 value afterwards. For example:
33726 receive_add_recipient(US"monitor@mydom.example", -1);
33727 recipients_list[recipients_count-1].errors_to =
33728 US"postmaster@mydom.example";
33731 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
33732 This is a convenience function to remove a named recipient from the list of
33733 recipients. It returns true if a recipient was removed, and false if no
33734 matching recipient could be found. The argument must be a complete email
33741 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
33742 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
33743 This function decodes strings that are encoded according to RFC 2047. Typically
33744 these are the contents of header lines. First, each &"encoded word"& is decoded
33745 from the Q or B encoding into a byte-string. Then, if provided with the name of
33746 a charset encoding, and if the &[iconv()]& function is available, an attempt is
33747 made to translate the result to the named character set. If this fails, the
33748 binary string is returned with an error message.
33750 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
33751 maximum MIME word length is enforced. The third argument is the target
33752 encoding, or NULL if no translation is wanted.
33754 .cindex "binary zero" "in RFC 2047 decoding"
33755 .cindex "RFC 2047" "binary zero in"
33756 If a binary zero is encountered in the decoded string, it is replaced by the
33757 contents of the &%zeroval%& argument. For use with Exim headers, the value must
33758 not be 0 because header lines are handled as zero-terminated strings.
33760 The function returns the result of processing the string, zero-terminated; if
33761 &%lenptr%& is not NULL, the length of the result is set in the variable to
33762 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
33764 If an error is encountered, the function returns NULL and uses the &%error%&
33765 argument to return an error message. The variable pointed to by &%error%& is
33766 set to NULL if there is no error; it may be set non-NULL even when the function
33767 returns a non-NULL value if decoding was successful, but there was a problem
33771 .vitem &*int&~smtp_fflush(void)*&
33772 This function is used in conjunction with &'smtp_printf()'&, as described
33775 .vitem &*void&~smtp_printf(char&~*,&~...)*&
33776 The arguments of this function are like &[printf()]&; it writes to the SMTP
33777 output stream. You should use this function only when there is an SMTP output
33778 stream, that is, when the incoming message is being received via interactive
33779 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
33780 is FALSE. If you want to test for an incoming message from another host (as
33781 opposed to a local process that used the &%-bs%& command line option), you can
33782 test the value of &%sender_host_address%&, which is non-NULL when a remote host
33785 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
33786 output function, so it can be used for all forms of SMTP connection.
33788 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
33789 must start with an appropriate response code: 550 if you are going to return
33790 LOCAL_SCAN_REJECT, 451 if you are going to return
33791 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
33792 initial lines of a multi-line response, the code must be followed by a hyphen
33793 to indicate that the line is not the final response line. You must also ensure
33794 that the lines you write terminate with CRLF. For example:
33796 smtp_printf("550-this is some extra info\r\n");
33797 return LOCAL_SCAN_REJECT;
33799 Note that you can also create multi-line responses by including newlines in
33800 the data returned via the &%return_text%& argument. The added value of using
33801 &'smtp_printf()'& is that, for instance, you could introduce delays between
33802 multiple output lines.
33804 The &'smtp_printf()'& function does not return any error indication, because it
33805 does not automatically flush pending output, and therefore does not test
33806 the state of the stream. (In the main code of Exim, flushing and error
33807 detection is done when Exim is ready for the next SMTP input command.) If
33808 you want to flush the output and check for an error (for example, the
33809 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
33810 arguments. It flushes the output stream, and returns a non-zero value if there
33813 .vitem &*void&~*store_get(int)*&
33814 This function accesses Exim's internal store (memory) manager. It gets a new
33815 chunk of memory whose size is given by the argument. Exim bombs out if it ever
33816 runs out of memory. See the next section for a discussion of memory handling.
33818 .vitem &*void&~*store_get_perm(int)*&
33819 This function is like &'store_get()'&, but it always gets memory from the
33820 permanent pool. See the next section for a discussion of memory handling.
33822 .vitem &*uschar&~*string_copy(uschar&~*string)*&
33825 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
33828 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
33829 These three functions create strings using Exim's dynamic memory facilities.
33830 The first makes a copy of an entire string. The second copies up to a maximum
33831 number of characters, indicated by the second argument. The third uses a format
33832 and insertion arguments to create a new string. In each case, the result is a
33833 pointer to a new string in the current memory pool. See the next section for
33839 .section "More about Exim's memory handling" "SECTmemhanloc"
33840 .cindex "&[local_scan()]& function" "memory handling"
33841 No function is provided for freeing memory, because that is never needed.
33842 The dynamic memory that Exim uses when receiving a message is automatically
33843 recycled if another message is received by the same process (this applies only
33844 to incoming SMTP connections &-- other input methods can supply only one
33845 message at a time). After receiving the last message, a reception process
33848 Because it is recycled, the normal dynamic memory cannot be used for holding
33849 data that must be preserved over a number of incoming messages on the same SMTP
33850 connection. However, Exim in fact uses two pools of dynamic memory; the second
33851 one is not recycled, and can be used for this purpose.
33853 If you want to allocate memory that remains available for subsequent messages
33854 in the same SMTP connection, you should set
33856 store_pool = POOL_PERM
33858 before calling the function that does the allocation. There is no need to
33859 restore the value if you do not need to; however, if you do want to revert to
33860 the normal pool, you can either restore the previous value of &%store_pool%& or
33861 set it explicitly to POOL_MAIN.
33863 The pool setting applies to all functions that get dynamic memory, including
33864 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
33865 There is also a convenience function called &'store_get_perm()'& that gets a
33866 block of memory from the permanent pool while preserving the value of
33873 . ////////////////////////////////////////////////////////////////////////////
33874 . ////////////////////////////////////////////////////////////////////////////
33876 .chapter "System-wide message filtering" "CHAPsystemfilter"
33877 .scindex IIDsysfil1 "filter" "system filter"
33878 .scindex IIDsysfil2 "filtering all mail"
33879 .scindex IIDsysfil3 "system filter"
33880 The previous chapters (on ACLs and the local scan function) describe checks
33881 that can be applied to messages before they are accepted by a host. There is
33882 also a mechanism for checking messages once they have been received, but before
33883 they are delivered. This is called the &'system filter'&.
33885 The system filter operates in a similar manner to users' filter files, but it
33886 is run just once per message (however many recipients the message has).
33887 It should not normally be used as a substitute for routing, because &%deliver%&
33888 commands in a system router provide new envelope recipient addresses.
33889 The system filter must be an Exim filter. It cannot be a Sieve filter.
33891 The system filter is run at the start of a delivery attempt, before any routing
33892 is done. If a message fails to be completely delivered at the first attempt,
33893 the system filter is run again at the start of every retry.
33894 If you want your filter to do something only once per message, you can make use
33895 of the &%first_delivery%& condition in an &%if%& command in the filter to
33896 prevent it happening on retries.
33898 .vindex "&$domain$&"
33899 .vindex "&$local_part$&"
33900 &*Warning*&: Because the system filter runs just once, variables that are
33901 specific to individual recipient addresses, such as &$local_part$& and
33902 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
33903 you want to run a centrally-specified filter for each recipient address
33904 independently, you can do so by setting up a suitable &(redirect)& router, as
33905 described in section &<<SECTperaddfil>>& below.
33908 .section "Specifying a system filter" "SECID212"
33909 .cindex "uid (user id)" "system filter"
33910 .cindex "gid (group id)" "system filter"
33911 The name of the file that contains the system filter must be specified by
33912 setting &%system_filter%&. If you want the filter to run under a uid and gid
33913 other than root, you must also set &%system_filter_user%& and
33914 &%system_filter_group%& as appropriate. For example:
33916 system_filter = /etc/mail/exim.filter
33917 system_filter_user = exim
33919 If a system filter generates any deliveries directly to files or pipes (via the
33920 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
33921 specified by setting &%system_filter_file_transport%& and
33922 &%system_filter_pipe_transport%&, respectively. Similarly,
33923 &%system_filter_reply_transport%& must be set to handle any messages generated
33924 by the &%reply%& command.
33927 .section "Testing a system filter" "SECID213"
33928 You can run simple tests of a system filter in the same way as for a user
33929 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
33930 are permitted only in system filters are recognized.
33932 If you want to test the combined effect of a system filter and a user filter,
33933 you can use both &%-bF%& and &%-bf%& on the same command line.
33937 .section "Contents of a system filter" "SECID214"
33938 The language used to specify system filters is the same as for users' filter
33939 files. It is described in the separate end-user document &'Exim's interface to
33940 mail filtering'&. However, there are some additional features that are
33941 available only in system filters; these are described in subsequent sections.
33942 If they are encountered in a user's filter file or when testing with &%-bf%&,
33945 .cindex "frozen messages" "manual thaw; testing in filter"
33946 There are two special conditions which, though available in users' filter
33947 files, are designed for use in system filters. The condition &%first_delivery%&
33948 is true only for the first attempt at delivering a message, and
33949 &%manually_thawed%& is true only if the message has been frozen, and
33950 subsequently thawed by an admin user. An explicit forced delivery counts as a
33951 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
33953 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
33954 specify an &"unseen"& (non-significant) delivery, and that delivery does not
33955 succeed, it will not be tried again.
33956 If you want Exim to retry an unseen delivery until it succeeds, you should
33957 arrange to set it up every time the filter runs.
33959 When a system filter finishes running, the values of the variables &$n0$& &--
33960 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
33961 users' filter files. Thus a system filter can, for example, set up &"scores"&
33962 to which users' filter files can refer.
33966 .section "Additional variable for system filters" "SECID215"
33967 .vindex "&$recipients$&"
33968 The expansion variable &$recipients$&, containing a list of all the recipients
33969 of the message (separated by commas and white space), is available in system
33970 filters. It is not available in users' filters for privacy reasons.
33974 .section "Defer, freeze, and fail commands for system filters" "SECID216"
33975 .cindex "freezing messages"
33976 .cindex "message" "freezing"
33977 .cindex "message" "forced failure"
33978 .cindex "&%fail%&" "in system filter"
33979 .cindex "&%freeze%& in system filter"
33980 .cindex "&%defer%& in system filter"
33981 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
33982 always available in system filters, but are not normally enabled in users'
33983 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
33984 for the &(redirect)& router.) These commands can optionally be followed by the
33985 word &%text%& and a string containing an error message, for example:
33987 fail text "this message looks like spam to me"
33989 The keyword &%text%& is optional if the next character is a double quote.
33991 The &%defer%& command defers delivery of the original recipients of the
33992 message. The &%fail%& command causes all the original recipients to be failed,
33993 and a bounce message to be created. The &%freeze%& command suspends all
33994 delivery attempts for the original recipients. In all cases, any new deliveries
33995 that are specified by the filter are attempted as normal after the filter has
33998 The &%freeze%& command is ignored if the message has been manually unfrozen and
33999 not manually frozen since. This means that automatic freezing by a system
34000 filter can be used as a way of checking out suspicious messages. If a message
34001 is found to be all right, manually unfreezing it allows it to be delivered.
34003 .cindex "log" "&%fail%& command log line"
34004 .cindex "&%fail%&" "log line; reducing"
34005 The text given with a fail command is used as part of the bounce message as
34006 well as being written to the log. If the message is quite long, this can fill
34007 up a lot of log space when such failures are common. To reduce the size of the
34008 log message, Exim interprets the text in a special way if it starts with the
34009 two characters &`<<`& and contains &`>>`& later. The text between these two
34010 strings is written to the log, and the rest of the text is used in the bounce
34011 message. For example:
34013 fail "<<filter test 1>>Your message is rejected \
34014 because it contains attachments that we are \
34015 not prepared to receive."
34018 .cindex "loop" "caused by &%fail%&"
34019 Take great care with the &%fail%& command when basing the decision to fail on
34020 the contents of the message, because the bounce message will of course include
34021 the contents of the original message and will therefore trigger the &%fail%&
34022 command again (causing a mail loop) unless steps are taken to prevent this.
34023 Testing the &%error_message%& condition is one way to prevent this. You could
34026 if $message_body contains "this is spam" and not error_message
34027 then fail text "spam is not wanted here" endif
34029 though of course that might let through unwanted bounce messages. The
34030 alternative is clever checking of the body and/or headers to detect bounces
34031 generated by the filter.
34033 The interpretation of a system filter file ceases after a
34035 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
34036 set up earlier in the filter file are honoured, so you can use a sequence such
34042 to send a specified message when the system filter is freezing (or deferring or
34043 failing) a message. The normal deliveries for the message do not, of course,
34048 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
34049 .cindex "header lines" "adding; in system filter"
34050 .cindex "header lines" "removing; in system filter"
34051 .cindex "filter" "header lines; adding/removing"
34052 Two filter commands that are available only in system filters are:
34054 headers add <string>
34055 headers remove <string>
34057 The argument for the &%headers add%& is a string that is expanded and then
34058 added to the end of the message's headers. It is the responsibility of the
34059 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
34060 space is ignored, and if the string is otherwise empty, or if the expansion is
34061 forced to fail, the command has no effect.
34063 You can use &"\n"& within the string, followed by white space, to specify
34064 continued header lines. More than one header may be added in one command by
34065 including &"\n"& within the string without any following white space. For
34068 headers add "X-header-1: ....\n \
34069 continuation of X-header-1 ...\n\
34072 Note that the header line continuation white space after the first newline must
34073 be placed before the backslash that continues the input string, because white
34074 space after input continuations is ignored.
34076 The argument for &%headers remove%& is a colon-separated list of header names.
34077 This command applies only to those headers that are stored with the message;
34078 those that are added at delivery time (such as &'Envelope-To:'& and
34079 &'Return-Path:'&) cannot be removed by this means. If there is more than one
34080 header with the same name, they are all removed.
34082 The &%headers%& command in a system filter makes an immediate change to the set
34083 of header lines that was received with the message (with possible additions
34084 from ACL processing). Subsequent commands in the system filter operate on the
34085 modified set, which also forms the basis for subsequent message delivery.
34086 Unless further modified during routing or transporting, this set of headers is
34087 used for all recipients of the message.
34089 During routing and transporting, the variables that refer to the contents of
34090 header lines refer only to those lines that are in this set. Thus, header lines
34091 that are added by a system filter are visible to users' filter files and to all
34092 routers and transports. This contrasts with the manipulation of header lines by
34093 routers and transports, which is not immediate, but which instead is saved up
34094 until the message is actually being written (see section
34095 &<<SECTheadersaddrem>>&).
34097 If the message is not delivered at the first attempt, header lines that were
34098 added by the system filter are stored with the message, and so are still
34099 present at the next delivery attempt. Header lines that were removed are still
34100 present, but marked &"deleted"& so that they are not transported with the
34101 message. For this reason, it is usual to make the &%headers%& command
34102 conditional on &%first_delivery%& so that the set of header lines is not
34103 modified more than once.
34105 Because header modification in a system filter acts immediately, you have to
34106 use an indirect approach if you want to modify the contents of a header line.
34109 headers add "Old-Subject: $h_subject:"
34110 headers remove "Subject"
34111 headers add "Subject: new subject (was: $h_old-subject:)"
34112 headers remove "Old-Subject"
34117 .section "Setting an errors address in a system filter" "SECID217"
34118 .cindex "envelope sender"
34119 In a system filter, if a &%deliver%& command is followed by
34121 errors_to <some address>
34123 in order to change the envelope sender (and hence the error reporting) for that
34124 delivery, any address may be specified. (In a user filter, only the current
34125 user's address can be set.) For example, if some mail is being monitored, you
34128 unseen deliver monitor@spying.example errors_to root@local.example
34130 to take a copy which would not be sent back to the normal error reporting
34131 address if its delivery failed.
34135 .section "Per-address filtering" "SECTperaddfil"
34136 .vindex "&$domain$&"
34137 .vindex "&$local_part$&"
34138 In contrast to the system filter, which is run just once per message for each
34139 delivery attempt, it is also possible to set up a system-wide filtering
34140 operation that runs once for each recipient address. In this case, variables
34141 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
34142 filter file could be made dependent on them. This is an example of a router
34143 which implements such a filter:
34148 domains = +local_domains
34149 file = /central/filters/$local_part
34154 The filter is run in a separate process under its own uid. Therefore, either
34155 &%check_local_user%& must be set (as above), in which case the filter is run as
34156 the local user, or the &%user%& option must be used to specify which user to
34157 use. If both are set, &%user%& overrides.
34159 Care should be taken to ensure that none of the commands in the filter file
34160 specify a significant delivery if the message is to go on to be delivered to
34161 its intended recipient. The router will not then claim to have dealt with the
34162 address, so it will be passed on to subsequent routers to be delivered in the
34164 .ecindex IIDsysfil1
34165 .ecindex IIDsysfil2
34166 .ecindex IIDsysfil3
34173 . ////////////////////////////////////////////////////////////////////////////
34174 . ////////////////////////////////////////////////////////////////////////////
34176 .chapter "Message processing" "CHAPmsgproc"
34177 .scindex IIDmesproc "message" "general processing"
34178 Exim performs various transformations on the sender and recipient addresses of
34179 all messages that it handles, and also on the messages' header lines. Some of
34180 these are optional and configurable, while others always take place. All of
34181 this processing, except rewriting as a result of routing, and the addition or
34182 removal of header lines while delivering, happens when a message is received,
34183 before it is placed on Exim's queue.
34185 Some of the automatic processing takes place by default only for
34186 &"locally-originated"& messages. This adjective is used to describe messages
34187 that are not received over TCP/IP, but instead are passed to an Exim process on
34188 its standard input. This includes the interactive &"local SMTP"& case that is
34189 set up by the &%-bs%& command line option.
34191 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
34192 or ::1) are not considered to be locally-originated. Exim does not treat the
34193 loopback interface specially in any way.
34195 If you want the loopback interface to be treated specially, you must ensure
34196 that there are appropriate entries in your ACLs.
34201 .section "Submission mode for non-local messages" "SECTsubmodnon"
34202 .cindex "message" "submission"
34203 .cindex "submission mode"
34204 Processing that happens automatically for locally-originated messages (unless
34205 &%suppress_local_fixups%& is set) can also be requested for messages that are
34206 received over TCP/IP. The term &"submission mode"& is used to describe this
34207 state. Submission mode is set by the modifier
34209 control = submission
34211 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
34212 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
34213 a local submission, and is normally used when the source of the message is
34214 known to be an MUA running on a client host (as opposed to an MTA). For
34215 example, to set submission mode for messages originating on the IPv4 loopback
34216 interface, you could include the following in the MAIL ACL:
34218 warn hosts = 127.0.0.1
34219 control = submission
34221 .cindex "&%sender_retain%& submission option"
34222 There are some options that can be used when setting submission mode. A slash
34223 is used to separate options. For example:
34225 control = submission/sender_retain
34227 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
34228 true and &%local_from_check%& false for the current incoming message. The first
34229 of these allows an existing &'Sender:'& header in the message to remain, and
34230 the second suppresses the check to ensure that &'From:'& matches the
34231 authenticated sender. With this setting, Exim still fixes up messages by adding
34232 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
34233 attempt to check sender authenticity in header lines.
34235 When &%sender_retain%& is not set, a submission mode setting may specify a
34236 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
34239 control = submission/domain=some.domain
34241 The domain may be empty. How this value is used is described in sections
34242 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
34243 that allows you to specify the user's full name for inclusion in a created
34244 &'Sender:'& or &'From:'& header line. For example:
34246 accept authenticated = *
34247 control = submission/domain=wonderland.example/\
34248 name=${lookup {$authenticated_id} \
34249 lsearch {/etc/exim/namelist}}
34251 Because the name may contain any characters, including slashes, the &%name%&
34252 option must be given last. The remainder of the string is used as the name. For
34253 the example above, if &_/etc/exim/namelist_& contains:
34255 bigegg: Humpty Dumpty
34257 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
34260 Sender: Humpty Dumpty <bigegg@wonderland.example>
34262 .cindex "return path" "in submission mode"
34263 By default, submission mode forces the return path to the same address as is
34264 used to create the &'Sender:'& header. However, if &%sender_retain%& is
34265 specified, the return path is also left unchanged.
34267 &*Note*&: The changes caused by submission mode take effect after the predata
34268 ACL. This means that any sender checks performed before the fix-ups use the
34269 untrusted sender address specified by the user, not the trusted sender address
34270 specified by submission mode. Although this might be slightly unexpected, it
34271 does mean that you can configure ACL checks to spot that a user is trying to
34272 spoof another's address.
34274 .section "Line endings" "SECTlineendings"
34275 .cindex "line endings"
34276 .cindex "carriage return"
34278 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
34279 linefeed) is the line ending for messages transmitted over the Internet using
34280 SMTP over TCP/IP. However, within individual operating systems, different
34281 conventions are used. For example, Unix-like systems use just LF, but others
34282 use CRLF or just CR.
34284 Exim was designed for Unix-like systems, and internally, it stores messages
34285 using the system's convention of a single LF as a line terminator. When
34286 receiving a message, all line endings are translated to this standard format.
34287 Originally, it was thought that programs that passed messages directly to an
34288 MTA within an operating system would use that system's convention. Experience
34289 has shown that this is not the case; for example, there are Unix applications
34290 that use CRLF in this circumstance. For this reason, and for compatibility with
34291 other MTAs, the way Exim handles line endings for all messages is now as
34295 LF not preceded by CR is treated as a line ending.
34297 CR is treated as a line ending; if it is immediately followed by LF, the LF
34300 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
34301 nor a local message in the state where a line containing only a dot is a
34304 If a bare CR is encountered within a header line, an extra space is added after
34305 the line terminator so as not to end the header line. The reasoning behind this
34306 is that bare CRs in header lines are most likely either to be mistakes, or
34307 people trying to play silly games.
34309 If the first header line received in a message ends with CRLF, a subsequent
34310 bare LF in a header line is treated in the same way as a bare CR in a header
34318 .section "Unqualified addresses" "SECID218"
34319 .cindex "unqualified addresses"
34320 .cindex "address" "qualification"
34321 By default, Exim expects every envelope address it receives from an external
34322 host to be fully qualified. Unqualified addresses cause negative responses to
34323 SMTP commands. However, because SMTP is used as a means of transporting
34324 messages from MUAs running on personal workstations, there is sometimes a
34325 requirement to accept unqualified addresses from specific hosts or IP networks.
34327 Exim has two options that separately control which hosts may send unqualified
34328 sender or recipient addresses in SMTP commands, namely
34329 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
34330 cases, if an unqualified address is accepted, it is qualified by adding the
34331 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
34333 .oindex "&%qualify_domain%&"
34334 .oindex "&%qualify_recipient%&"
34335 Unqualified addresses in header lines are automatically qualified for messages
34336 that are locally originated, unless the &%-bnq%& option is given on the command
34337 line. For messages received over SMTP, unqualified addresses in header lines
34338 are qualified only if unqualified addresses are permitted in SMTP commands. In
34339 other words, such qualification is also controlled by
34340 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
34345 .section "The UUCP From line" "SECID219"
34346 .cindex "&""From""& line"
34347 .cindex "UUCP" "&""From""& line"
34348 .cindex "sender" "address"
34349 .oindex "&%uucp_from_pattern%&"
34350 .oindex "&%uucp_from_sender%&"
34351 .cindex "envelope sender"
34352 .cindex "Sendmail compatibility" "&""From""& line"
34353 Messages that have come from UUCP (and some other applications) often begin
34354 with a line containing the envelope sender and a timestamp, following the word
34355 &"From"&. Examples of two common formats are:
34357 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
34358 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
34360 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
34361 Exim recognizes such lines at the start of messages that are submitted to it
34362 via the command line (that is, on the standard input). It does not recognize
34363 such lines in incoming SMTP messages, unless the sending host matches
34364 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
34365 and &%ignore_fromline_local%& is set. The recognition is controlled by a
34366 regular expression that is defined by the &%uucp_from_pattern%& option, whose
34367 default value matches the two common cases shown above and puts the address
34368 that follows &"From"& into &$1$&.
34370 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
34371 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
34372 a trusted user, the message's sender address is constructed by expanding the
34373 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
34374 then parsed as an RFC 2822 address. If there is no domain, the local part is
34375 qualified with &%qualify_domain%& unless it is the empty string. However, if
34376 the command line &%-f%& option is used, it overrides the &"From"& line.
34378 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
34379 sender address is not changed. This is also the case for incoming SMTP messages
34380 that are permitted to contain &"From"& lines.
34382 Only one &"From"& line is recognized. If there is more than one, the second is
34383 treated as a data line that starts the body of the message, as it is not valid
34384 as a header line. This also happens if a &"From"& line is present in an
34385 incoming SMTP message from a source that is not permitted to send them.
34389 .section "Resent- header lines" "SECID220"
34390 .cindex "&%Resent-%& header lines"
34391 .cindex "header lines" "Resent-"
34392 RFC 2822 makes provision for sets of header lines starting with the string
34393 &`Resent-`& to be added to a message when it is resent by the original
34394 recipient to somebody else. These headers are &'Resent-Date:'&,
34395 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
34396 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
34399 &'Resent fields are strictly informational. They MUST NOT be used in the normal
34400 processing of replies or other such automatic actions on messages.'&
34403 This leaves things a bit vague as far as other processing actions such as
34404 address rewriting are concerned. Exim treats &%Resent-%& header lines as
34408 A &'Resent-From:'& line that just contains the login id of the submitting user
34409 is automatically rewritten in the same way as &'From:'& (see below).
34411 If there's a rewriting rule for a particular header line, it is also applied to
34412 &%Resent-%& header lines of the same type. For example, a rule that rewrites
34413 &'From:'& also rewrites &'Resent-From:'&.
34415 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
34418 For a locally-submitted message,
34419 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
34420 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
34421 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
34422 included in log lines in this case.
34424 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
34425 &%Resent-%& header lines are present.
34431 .section "The Auto-Submitted: header line" "SECID221"
34432 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
34433 includes the header line:
34435 Auto-Submitted: auto-replied
34438 .section "The Bcc: header line" "SECID222"
34439 .cindex "&'Bcc:'& header line"
34440 If Exim is called with the &%-t%& option, to take recipient addresses from a
34441 message's header, it removes any &'Bcc:'& header line that may exist (after
34442 extracting its addresses). If &%-t%& is not present on the command line, any
34443 existing &'Bcc:'& is not removed.
34446 .section "The Date: header line" "SECID223"
34447 .cindex "&'Date:'& header line"
34448 .cindex "header lines" "Date:"
34449 If a locally-generated or submission-mode message has no &'Date:'& header line,
34450 Exim adds one, using the current date and time, unless the
34451 &%suppress_local_fixups%& control has been specified.
34453 .section "The Delivery-date: header line" "SECID224"
34454 .cindex "&'Delivery-date:'& header line"
34455 .oindex "&%delivery_date_remove%&"
34456 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
34457 set. Exim can be configured to add them to the final delivery of messages. (See
34458 the generic &%delivery_date_add%& transport option.) They should not be present
34459 in messages in transit. If the &%delivery_date_remove%& configuration option is
34460 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
34464 .section "The Envelope-to: header line" "SECID225"
34465 .cindex "&'Envelope-to:'& header line"
34466 .cindex "header lines" "Envelope-to:"
34467 .oindex "&%envelope_to_remove%&"
34468 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
34469 Exim can be configured to add them to the final delivery of messages. (See the
34470 generic &%envelope_to_add%& transport option.) They should not be present in
34471 messages in transit. If the &%envelope_to_remove%& configuration option is set
34472 (the default), Exim removes &'Envelope-to:'& header lines from incoming
34476 .section "The From: header line" "SECTthefrohea"
34477 .cindex "&'From:'& header line"
34478 .cindex "header lines" "From:"
34479 .cindex "Sendmail compatibility" "&""From""& line"
34480 .cindex "message" "submission"
34481 .cindex "submission mode"
34482 If a submission-mode message does not contain a &'From:'& header line, Exim
34483 adds one if either of the following conditions is true:
34486 The envelope sender address is not empty (that is, this is not a bounce
34487 message). The added header line copies the envelope sender address.
34489 .vindex "&$authenticated_id$&"
34490 The SMTP session is authenticated and &$authenticated_id$& is not empty.
34492 .vindex "&$qualify_domain$&"
34493 If no domain is specified by the submission control, the local part is
34494 &$authenticated_id$& and the domain is &$qualify_domain$&.
34496 If a non-empty domain is specified by the submission control, the local
34497 part is &$authenticated_id$&, and the domain is the specified domain.
34499 If an empty domain is specified by the submission control,
34500 &$authenticated_id$& is assumed to be the complete address.
34504 A non-empty envelope sender takes precedence.
34506 If a locally-generated incoming message does not contain a &'From:'& header
34507 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
34508 containing the sender's address. The calling user's login name and full name
34509 are used to construct the address, as described in section &<<SECTconstr>>&.
34510 They are obtained from the password data by calling &[getpwuid()]& (but see the
34511 &%unknown_login%& configuration option). The address is qualified with
34512 &%qualify_domain%&.
34514 For compatibility with Sendmail, if an incoming, non-SMTP message has a
34515 &'From:'& header line containing just the unqualified login name of the calling
34516 user, this is replaced by an address containing the user's login name and full
34517 name as described in section &<<SECTconstr>>&.
34520 .section "The Message-ID: header line" "SECID226"
34521 .cindex "&'Message-ID:'& header line"
34522 .cindex "header lines" "Message-ID:"
34523 .cindex "message" "submission"
34524 .oindex "&%message_id_header_text%&"
34525 If a locally-generated or submission-mode incoming message does not contain a
34526 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
34527 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
34528 to the message. If there are any &'Resent-:'& headers in the message, it
34529 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
34530 message id, preceded by the letter E to ensure it starts with a letter, and
34531 followed by @ and the primary host name. Additional information can be included
34532 in this header line by setting the &%message_id_header_text%& and/or
34533 &%message_id_header_domain%& options.
34536 .section "The Received: header line" "SECID227"
34537 .cindex "&'Received:'& header line"
34538 .cindex "header lines" "Received:"
34539 A &'Received:'& header line is added at the start of every message. The
34540 contents are defined by the &%received_header_text%& configuration option, and
34541 Exim automatically adds a semicolon and a timestamp to the configured string.
34543 The &'Received:'& header is generated as soon as the message's header lines
34544 have been received. At this stage, the timestamp in the &'Received:'& header
34545 line is the time that the message started to be received. This is the value
34546 that is seen by the DATA ACL and by the &[local_scan()]& function.
34548 Once a message is accepted, the timestamp in the &'Received:'& header line is
34549 changed to the time of acceptance, which is (apart from a small delay while the
34550 -H spool file is written) the earliest time at which delivery could start.
34553 .section "The References: header line" "SECID228"
34554 .cindex "&'References:'& header line"
34555 .cindex "header lines" "References:"
34556 Messages created by the &(autoreply)& transport include a &'References:'&
34557 header line. This is constructed according to the rules that are described in
34558 section 3.64 of RFC 2822 (which states that replies should contain such a
34559 header line), and section 3.14 of RFC 3834 (which states that automatic
34560 responses are not different in this respect). However, because some mail
34561 processing software does not cope well with very long header lines, no more
34562 than 12 message IDs are copied from the &'References:'& header line in the
34563 incoming message. If there are more than 12, the first one and then the final
34564 11 are copied, before adding the message ID of the incoming message.
34568 .section "The Return-path: header line" "SECID229"
34569 .cindex "&'Return-path:'& header line"
34570 .cindex "header lines" "Return-path:"
34571 .oindex "&%return_path_remove%&"
34572 &'Return-path:'& header lines are defined as something an MTA may insert when
34573 it does the final delivery of messages. (See the generic &%return_path_add%&
34574 transport option.) Therefore, they should not be present in messages in
34575 transit. If the &%return_path_remove%& configuration option is set (the
34576 default), Exim removes &'Return-path:'& header lines from incoming messages.
34580 .section "The Sender: header line" "SECTthesenhea"
34581 .cindex "&'Sender:'& header line"
34582 .cindex "message" "submission"
34583 .cindex "header lines" "Sender:"
34584 For a locally-originated message from an untrusted user, Exim may remove an
34585 existing &'Sender:'& header line, and it may add a new one. You can modify
34586 these actions by setting the &%local_sender_retain%& option true, the
34587 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
34590 When a local message is received from an untrusted user and
34591 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
34592 control has not been set, a check is made to see if the address given in the
34593 &'From:'& header line is the correct (local) sender of the message. The address
34594 that is expected has the login name as the local part and the value of
34595 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
34596 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
34597 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
34598 line is added to the message.
34600 If you set &%local_from_check%& false, this checking does not occur. However,
34601 the removal of an existing &'Sender:'& line still happens, unless you also set
34602 &%local_sender_retain%& to be true. It is not possible to set both of these
34603 options true at the same time.
34605 .cindex "submission mode"
34606 By default, no processing of &'Sender:'& header lines is done for messages
34607 received over TCP/IP or for messages submitted by trusted users. However, when
34608 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
34609 not specified on the submission control, the following processing takes place:
34611 .vindex "&$authenticated_id$&"
34612 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
34613 authenticated, and &$authenticated_id$& is not empty, a sender address is
34614 created as follows:
34617 .vindex "&$qualify_domain$&"
34618 If no domain is specified by the submission control, the local part is
34619 &$authenticated_id$& and the domain is &$qualify_domain$&.
34621 If a non-empty domain is specified by the submission control, the local part
34622 is &$authenticated_id$&, and the domain is the specified domain.
34624 If an empty domain is specified by the submission control,
34625 &$authenticated_id$& is assumed to be the complete address.
34628 This address is compared with the address in the &'From:'& header line. If they
34629 are different, a &'Sender:'& header line containing the created address is
34630 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
34631 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
34633 .cindex "return path" "created from &'Sender:'&"
34634 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
34635 the message (the envelope sender address) is changed to be the same address,
34636 except in the case of submission mode when &%sender_retain%& is specified.
34640 .section "Adding and removing header lines in routers and transports" &&&
34641 "SECTheadersaddrem"
34642 .cindex "header lines" "adding; in router or transport"
34643 .cindex "header lines" "removing; in router or transport"
34644 When a message is delivered, the addition and removal of header lines can be
34645 specified in a system filter, or on any of the routers and transports that
34646 process the message. Section &<<SECTaddremheasys>>& contains details about
34647 modifying headers in a system filter. Header lines can also be added in an ACL
34648 as a message is received (see section &<<SECTaddheadacl>>&).
34650 In contrast to what happens in a system filter, header modifications that are
34651 specified on routers and transports apply only to the particular recipient
34652 addresses that are being processed by those routers and transports. These
34653 changes do not actually take place until a copy of the message is being
34654 transported. Therefore, they do not affect the basic set of header lines, and
34655 they do not affect the values of the variables that refer to header lines.
34657 &*Note*&: In particular, this means that any expansions in the configuration of
34658 the transport cannot refer to the modified header lines, because such
34659 expansions all occur before the message is actually transported.
34661 For both routers and transports, the argument of a &%headers_add%&
34662 option must be in the form of one or more RFC 2822 header lines, separated by
34663 newlines (coded as &"\n"&). For example:
34665 headers_add = X-added-header: added by $primary_hostname\n\
34666 X-added-second: another added header line
34668 Exim does not check the syntax of these added header lines.
34670 Multiple &%headers_add%& options for a single router or transport can be
34671 specified; the values will append to a single list of header lines.
34672 Each header-line is separately expanded.
34674 The argument of a &%headers_remove%& option must consist of a colon-separated
34675 list of header names. This is confusing, because header names themselves are
34676 often terminated by colons. In this case, the colons are the list separators,
34677 not part of the names. For example:
34679 headers_remove = return-receipt-to:acknowledge-to
34682 Multiple &%headers_remove%& options for a single router or transport can be
34683 specified; the arguments will append to a single header-names list.
34684 Each item is separately expanded.
34685 Note that colons in complex expansions which are used to
34686 form all or part of a &%headers_remove%& list
34687 will act as list separators.
34689 When &%headers_add%& or &%headers_remove%& is specified on a router,
34690 items are expanded at routing time,
34691 and then associated with all addresses that are
34692 accepted by that router, and also with any new addresses that it generates. If
34693 an address passes through several routers as a result of aliasing or
34694 forwarding, the changes are cumulative.
34696 .oindex "&%unseen%&"
34697 However, this does not apply to multiple routers that result from the use of
34698 the &%unseen%& option. Any header modifications that were specified by the
34699 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
34701 Addresses that end up with different &%headers_add%& or &%headers_remove%&
34702 settings cannot be delivered together in a batch, so a transport is always
34703 dealing with a set of addresses that have the same header-processing
34706 The transport starts by writing the original set of header lines that arrived
34707 with the message, possibly modified by the system filter. As it writes out
34708 these lines, it consults the list of header names that were attached to the
34709 recipient address(es) by &%headers_remove%& options in routers, and it also
34710 consults the transport's own &%headers_remove%& option. Header lines whose
34711 names are on either of these lists are not written out. If there are multiple
34712 instances of any listed header, they are all skipped.
34714 After the remaining original header lines have been written, new header
34715 lines that were specified by routers' &%headers_add%& options are written, in
34716 the order in which they were attached to the address. These are followed by any
34717 header lines specified by the transport's &%headers_add%& option.
34719 This way of handling header line modifications in routers and transports has
34720 the following consequences:
34723 The original set of header lines, possibly modified by the system filter,
34724 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
34725 to it, at all times.
34727 Header lines that are added by a router's
34728 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
34729 expansion syntax in subsequent routers or the transport.
34731 Conversely, header lines that are specified for removal by &%headers_remove%&
34732 in a router remain visible to subsequent routers and the transport.
34734 Headers added to an address by &%headers_add%& in a router cannot be removed by
34735 a later router or by a transport.
34737 An added header can refer to the contents of an original header that is to be
34738 removed, even it has the same name as the added header. For example:
34740 headers_remove = subject
34741 headers_add = Subject: new subject (was: $h_subject:)
34745 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
34746 for a &(redirect)& router that has the &%one_time%& option set.
34752 .section "Constructed addresses" "SECTconstr"
34753 .cindex "address" "constructed"
34754 .cindex "constructed address"
34755 When Exim constructs a sender address for a locally-generated message, it uses
34758 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
34762 Zaphod Beeblebrox <zaphod@end.univ.example>
34764 The user name is obtained from the &%-F%& command line option if set, or
34765 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
34766 &"gecos"& field from the password entry. If the &"gecos"& field contains an
34767 ampersand character, this is replaced by the login name with the first letter
34768 upper cased, as is conventional in a number of operating systems. See the
34769 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
34770 The &%unknown_username%& option can be used to specify user names in cases when
34771 there is no password file entry.
34774 In all cases, the user name is made to conform to RFC 2822 by quoting all or
34775 parts of it if necessary. In addition, if it contains any non-printing
34776 characters, it is encoded as described in RFC 2047, which defines a way of
34777 including non-ASCII characters in header lines. The value of the
34778 &%headers_charset%& option specifies the name of the encoding that is used (the
34779 characters are assumed to be in this encoding). The setting of
34780 &%print_topbitchars%& controls whether characters with the top bit set (that
34781 is, with codes greater than 127) count as printing characters or not.
34785 .section "Case of local parts" "SECID230"
34786 .cindex "case of local parts"
34787 .cindex "local part" "case of"
34788 RFC 2822 states that the case of letters in the local parts of addresses cannot
34789 be assumed to be non-significant. Exim preserves the case of local parts of
34790 addresses, but by default it uses a lower-cased form when it is routing,
34791 because on most Unix systems, usernames are in lower case and case-insensitive
34792 routing is required. However, any particular router can be made to use the
34793 original case for local parts by setting the &%caseful_local_part%& generic
34796 .cindex "mixed-case login names"
34797 If you must have mixed-case user names on your system, the best way to proceed,
34798 assuming you want case-independent handling of incoming email, is to set up
34799 your first router to convert incoming local parts in your domains to the
34800 correct case by means of a file lookup. For example:
34804 domains = +local_domains
34805 data = ${lookup{$local_part}cdb\
34806 {/etc/usercased.cdb}{$value}fail}\
34809 For this router, the local part is forced to lower case by the default action
34810 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
34811 up a new local part in the correct case. If you then set &%caseful_local_part%&
34812 on any subsequent routers which process your domains, they will operate on
34813 local parts with the correct case in a case-sensitive manner.
34817 .section "Dots in local parts" "SECID231"
34818 .cindex "dot" "in local part"
34819 .cindex "local part" "dots in"
34820 RFC 2822 forbids empty components in local parts. That is, an unquoted local
34821 part may not begin or end with a dot, nor have two consecutive dots in the
34822 middle. However, it seems that many MTAs do not enforce this, so Exim permits
34823 empty components for compatibility.
34827 .section "Rewriting addresses" "SECID232"
34828 .cindex "rewriting" "addresses"
34829 Rewriting of sender and recipient addresses, and addresses in headers, can
34830 happen automatically, or as the result of configuration options, as described
34831 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
34832 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
34834 Automatic rewriting includes qualification, as mentioned above. The other case
34835 in which it can happen is when an incomplete non-local domain is given. The
34836 routing process may cause this to be expanded into the full domain name. For
34837 example, a header such as
34841 might get rewritten as
34843 To: hare@teaparty.wonderland.fict.example
34845 Rewriting as a result of routing is the one kind of message processing that
34846 does not happen at input time, as it cannot be done until the address has
34849 Strictly, one should not do &'any'& deliveries of a message until all its
34850 addresses have been routed, in case any of the headers get changed as a
34851 result of routing. However, doing this in practice would hold up many
34852 deliveries for unreasonable amounts of time, just because one address could not
34853 immediately be routed. Exim therefore does not delay other deliveries when
34854 routing of one or more addresses is deferred.
34855 .ecindex IIDmesproc
34859 . ////////////////////////////////////////////////////////////////////////////
34860 . ////////////////////////////////////////////////////////////////////////////
34862 .chapter "SMTP processing" "CHAPSMTP"
34863 .scindex IIDsmtpproc1 "SMTP" "processing details"
34864 .scindex IIDsmtpproc2 "LMTP" "processing details"
34865 Exim supports a number of different ways of using the SMTP protocol, and its
34866 LMTP variant, which is an interactive protocol for transferring messages into a
34867 closed mail store application. This chapter contains details of how SMTP is
34868 processed. For incoming mail, the following are available:
34871 SMTP over TCP/IP (Exim daemon or &'inetd'&);
34873 SMTP over the standard input and output (the &%-bs%& option);
34875 Batched SMTP on the standard input (the &%-bS%& option).
34878 For mail delivery, the following are available:
34881 SMTP over TCP/IP (the &(smtp)& transport);
34883 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
34886 LMTP over a pipe to a process running in the local host (the &(lmtp)&
34889 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
34890 the &%use_bsmtp%& option set).
34893 &'Batched SMTP'& is the name for a process in which batches of messages are
34894 stored in or read from files (or pipes), in a format in which SMTP commands are
34895 used to contain the envelope information.
34899 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
34900 .cindex "SMTP" "outgoing over TCP/IP"
34901 .cindex "outgoing SMTP over TCP/IP"
34902 .cindex "LMTP" "over TCP/IP"
34903 .cindex "outgoing LMTP over TCP/IP"
34906 .cindex "SIZE option on MAIL command"
34907 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
34908 The &%protocol%& option selects which protocol is to be used, but the actual
34909 processing is the same in both cases.
34911 If, in response to its EHLO command, Exim is told that the SIZE
34912 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
34913 command. The value of <&'n'&> is the message size plus the value of the
34914 &%size_addition%& option (default 1024) to allow for additions to the message
34915 such as per-transport header lines, or changes made in a
34916 .cindex "transport" "filter"
34917 .cindex "filter" "transport filter"
34918 transport filter. If &%size_addition%& is set negative, the use of SIZE is
34921 If the remote server advertises support for PIPELINING, Exim uses the
34922 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
34923 required for the transaction.
34925 If the remote server advertises support for the STARTTLS command, and Exim
34926 was built to support TLS encryption, it tries to start a TLS session unless the
34927 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
34928 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
34929 is called for verification.
34931 If the remote server advertises support for the AUTH command, Exim scans
34932 the authenticators configuration for any suitable client settings, as described
34933 in chapter &<<CHAPSMTPAUTH>>&.
34935 .cindex "carriage return"
34937 Responses from the remote host are supposed to be terminated by CR followed by
34938 LF. However, there are known to be hosts that do not send CR characters, so in
34939 order to be able to interwork with such hosts, Exim treats LF on its own as a
34942 If a message contains a number of different addresses, all those with the same
34943 characteristics (for example, the same envelope sender) that resolve to the
34944 same set of hosts, in the same order, are sent in a single SMTP transaction,
34945 even if they are for different domains, unless there are more than the setting
34946 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
34947 they are split into groups containing no more than &%max_rcpt%&s addresses
34948 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
34949 in parallel sessions. The order of hosts with identical MX values is not
34950 significant when checking whether addresses can be batched in this way.
34952 When the &(smtp)& transport suffers a temporary failure that is not
34953 message-related, Exim updates its transport-specific database, which contains
34954 records indexed by host name that remember which messages are waiting for each
34955 particular host. It also updates the retry database with new retry times.
34957 .cindex "hints database" "retry keys"
34958 Exim's retry hints are based on host name plus IP address, so if one address of
34959 a multi-homed host is broken, it will soon be skipped most of the time.
34960 See the next section for more detail about error handling.
34962 .cindex "SMTP" "passed connection"
34963 .cindex "SMTP" "batching over TCP/IP"
34964 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
34965 looks in the hints database for the transport to see if there are any queued
34966 messages waiting for the host to which it is connected. If it finds one, it
34967 creates a new Exim process using the &%-MC%& option (which can only be used by
34968 a process running as root or the Exim user) and passes the TCP/IP socket to it
34969 so that it can deliver another message using the same socket. The new process
34970 does only those deliveries that are routed to the connected host, and may in
34971 turn pass the socket on to a third process, and so on.
34973 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
34974 limit the number of messages sent down a single TCP/IP connection.
34976 .cindex "asterisk" "after IP address"
34977 The second and subsequent messages delivered down an existing connection are
34978 identified in the main log by the addition of an asterisk after the closing
34979 square bracket of the IP address.
34984 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
34985 .cindex "error" "in outgoing SMTP"
34986 .cindex "SMTP" "errors in outgoing"
34987 .cindex "host" "error"
34988 Three different kinds of error are recognized for outgoing SMTP: host errors,
34989 message errors, and recipient errors.
34992 .vitem "&*Host errors*&"
34993 A host error is not associated with a particular message or with a
34994 particular recipient of a message. The host errors are:
34997 Connection refused or timed out,
34999 Any error response code on connection,
35001 Any error response code to EHLO or HELO,
35003 Loss of connection at any time, except after &"."&,
35005 I/O errors at any time,
35007 Timeouts during the session, other than in response to MAIL, RCPT or
35008 the &"."& at the end of the data.
35011 For a host error, a permanent error response on connection, or in response to
35012 EHLO, causes all addresses routed to the host to be failed. Any other host
35013 error causes all addresses to be deferred, and retry data to be created for the
35014 host. It is not tried again, for any message, until its retry time arrives. If
35015 the current set of addresses are not all delivered in this run (to some
35016 alternative host), the message is added to the list of those waiting for this
35017 host, so if it is still undelivered when a subsequent successful delivery is
35018 made to the host, it will be sent down the same SMTP connection.
35020 .vitem "&*Message errors*&"
35021 .cindex "message" "error"
35022 A message error is associated with a particular message when sent to a
35023 particular host, but not with a particular recipient of the message. The
35024 message errors are:
35027 Any error response code to MAIL, DATA, or the &"."& that terminates
35030 Timeout after MAIL,
35032 Timeout or loss of connection after the &"."& that terminates the data. A
35033 timeout after the DATA command itself is treated as a host error, as is loss of
35034 connection at any other time.
35037 For a message error, a permanent error response (5&'xx'&) causes all addresses
35038 to be failed, and a delivery error report to be returned to the sender. A
35039 temporary error response (4&'xx'&), or one of the timeouts, causes all
35040 addresses to be deferred. Retry data is not created for the host, but instead,
35041 a retry record for the combination of host plus message id is created. The
35042 message is not added to the list of those waiting for this host. This ensures
35043 that the failing message will not be sent to this host again until the retry
35044 time arrives. However, other messages that are routed to the host are not
35045 affected, so if it is some property of the message that is causing the error,
35046 it will not stop the delivery of other mail.
35048 If the remote host specified support for the SIZE parameter in its response
35049 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
35050 over-large message will cause a message error because the error arrives as a
35053 .vitem "&*Recipient errors*&"
35054 .cindex "recipient" "error"
35055 A recipient error is associated with a particular recipient of a message. The
35056 recipient errors are:
35059 Any error response to RCPT,
35061 Timeout after RCPT.
35064 For a recipient error, a permanent error response (5&'xx'&) causes the
35065 recipient address to be failed, and a bounce message to be returned to the
35066 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
35067 address to be deferred, and routing retry data to be created for it. This is
35068 used to delay processing of the address in subsequent queue runs, until its
35069 routing retry time arrives. This applies to all messages, but because it
35070 operates only in queue runs, one attempt will be made to deliver a new message
35071 to the failing address before the delay starts to operate. This ensures that,
35072 if the failure is really related to the message rather than the recipient
35073 (&"message too big for this recipient"& is a possible example), other messages
35074 have a chance of getting delivered. If a delivery to the address does succeed,
35075 the retry information gets cleared, so all stuck messages get tried again, and
35076 the retry clock is reset.
35078 The message is not added to the list of those waiting for this host. Use of the
35079 host for other messages is unaffected, and except in the case of a timeout,
35080 other recipients are processed independently, and may be successfully delivered
35081 in the current SMTP session. After a timeout it is of course impossible to
35082 proceed with the session, so all addresses get deferred. However, those other
35083 than the one that failed do not suffer any subsequent retry delays. Therefore,
35084 if one recipient is causing trouble, the others have a chance of getting
35085 through when a subsequent delivery attempt occurs before the failing
35086 recipient's retry time.
35089 In all cases, if there are other hosts (or IP addresses) available for the
35090 current set of addresses (for example, from multiple MX records), they are
35091 tried in this run for any undelivered addresses, subject of course to their
35092 own retry data. In other words, recipient error retry data does not take effect
35093 until the next delivery attempt.
35095 Some hosts have been observed to give temporary error responses to every
35096 MAIL command at certain times (&"insufficient space"& has been seen). It
35097 would be nice if such circumstances could be recognized, and defer data for the
35098 host itself created, but this is not possible within the current Exim design.
35099 What actually happens is that retry data for every (host, message) combination
35102 The reason that timeouts after MAIL and RCPT are treated specially is that
35103 these can sometimes arise as a result of the remote host's verification
35104 procedures. Exim makes this assumption, and treats them as if a temporary error
35105 response had been received. A timeout after &"."& is treated specially because
35106 it is known that some broken implementations fail to recognize the end of the
35107 message if the last character of the last line is a binary zero. Thus, it is
35108 helpful to treat this case as a message error.
35110 Timeouts at other times are treated as host errors, assuming a problem with the
35111 host, or the connection to it. If a timeout after MAIL, RCPT,
35112 or &"."& is really a connection problem, the assumption is that at the next try
35113 the timeout is likely to occur at some other point in the dialogue, causing it
35114 then to be treated as a host error.
35116 There is experimental evidence that some MTAs drop the connection after the
35117 terminating &"."& if they do not like the contents of the message for some
35118 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
35119 should be given. That is why Exim treats this case as a message rather than a
35120 host error, in order not to delay other messages to the same host.
35125 .section "Incoming SMTP messages over TCP/IP" "SECID233"
35126 .cindex "SMTP" "incoming over TCP/IP"
35127 .cindex "incoming SMTP over TCP/IP"
35130 Incoming SMTP messages can be accepted in one of two ways: by running a
35131 listening daemon, or by using &'inetd'&. In the latter case, the entry in
35132 &_/etc/inetd.conf_& should be like this:
35134 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
35136 Exim distinguishes between this case and the case of a locally running user
35137 agent using the &%-bs%& option by checking whether or not the standard input is
35138 a socket. When it is, either the port must be privileged (less than 1024), or
35139 the caller must be root or the Exim user. If any other user passes a socket
35140 with an unprivileged port number, Exim prints a message on the standard error
35141 stream and exits with an error code.
35143 By default, Exim does not make a log entry when a remote host connects or
35144 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
35145 unexpected. It can be made to write such log entries by setting the
35146 &%smtp_connection%& log selector.
35148 .cindex "carriage return"
35150 Commands from the remote host are supposed to be terminated by CR followed by
35151 LF. However, there are known to be hosts that do not send CR characters. In
35152 order to be able to interwork with such hosts, Exim treats LF on its own as a
35154 Furthermore, because common code is used for receiving messages from all
35155 sources, a CR on its own is also interpreted as a line terminator. However, the
35156 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
35158 .cindex "EHLO" "invalid data"
35159 .cindex "HELO" "invalid data"
35160 One area that sometimes gives rise to problems concerns the EHLO or
35161 HELO commands. Some clients send syntactically invalid versions of these
35162 commands, which Exim rejects by default. (This is nothing to do with verifying
35163 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
35164 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
35165 match the broken hosts that send invalid commands.
35167 .cindex "SIZE option on MAIL command"
35168 .cindex "MAIL" "SIZE option"
35169 The amount of disk space available is checked whenever SIZE is received on
35170 a MAIL command, independently of whether &%message_size_limit%& or
35171 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
35172 false. A temporary error is given if there is not enough space. If
35173 &%check_spool_space%& is set, the check is for that amount of space plus the
35174 value given with SIZE, that is, it checks that the addition of the incoming
35175 message will not reduce the space below the threshold.
35177 When a message is successfully received, Exim includes the local message id in
35178 its response to the final &"."& that terminates the data. If the remote host
35179 logs this text it can help with tracing what has happened to a message.
35181 The Exim daemon can limit the number of simultaneous incoming connections it is
35182 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
35183 number of simultaneous incoming connections from a single remote host (see the
35184 &%smtp_accept_max_per_host%& option). Additional connection attempts are
35185 rejected using the SMTP temporary error code 421.
35187 The Exim daemon does not rely on the SIGCHLD signal to detect when a
35188 subprocess has finished, as this can get lost at busy times. Instead, it looks
35189 for completed subprocesses every time it wakes up. Provided there are other
35190 things happening (new incoming calls, starts of queue runs), completed
35191 processes will be noticed and tidied away. On very quiet systems you may
35192 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
35193 it will be noticed when the daemon next wakes up.
35195 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
35196 and can also be set up to reject SMTP calls from non-reserved hosts at times of
35197 high system load &-- for details see the &%smtp_accept_reserve%&,
35198 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
35199 applies in both the daemon and &'inetd'& cases.
35201 Exim normally starts a delivery process for each message received, though this
35202 can be varied by means of the &%-odq%& command line option and the
35203 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
35204 number of simultaneously running delivery processes started in this way from
35205 SMTP input can be limited by the &%smtp_accept_queue%& and
35206 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
35207 subsequently received messages are just put on the input queue without starting
35208 a delivery process.
35210 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
35211 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
35212 started up from the &'inetd'& daemon, because in that case each connection is
35213 handled by an entirely independent Exim process. Control by load average is,
35214 however, available with &'inetd'&.
35216 Exim can be configured to verify addresses in incoming SMTP commands as they
35217 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
35218 to rewrite addresses at this time &-- before any syntax checking is done. See
35219 section &<<SECTrewriteS>>&.
35221 Exim can also be configured to limit the rate at which a client host submits
35222 MAIL and RCPT commands in a single SMTP session. See the
35223 &%smtp_ratelimit_hosts%& option.
35227 .section "Unrecognized SMTP commands" "SECID234"
35228 .cindex "SMTP" "unrecognized commands"
35229 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
35230 commands during a single SMTP connection, it drops the connection after sending
35231 the error response to the last command. The default value for
35232 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
35233 abuse that subvert web servers into making connections to SMTP ports; in these
35234 circumstances, a number of non-SMTP lines are sent first.
35237 .section "Syntax and protocol errors in SMTP commands" "SECID235"
35238 .cindex "SMTP" "syntax errors"
35239 .cindex "SMTP" "protocol errors"
35240 A syntax error is detected if an SMTP command is recognized, but there is
35241 something syntactically wrong with its data, for example, a malformed email
35242 address in a RCPT command. Protocol errors include invalid command
35243 sequencing such as RCPT before MAIL. If Exim receives more than
35244 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
35245 drops the connection after sending the error response to the last command. The
35246 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
35247 broken clients that loop sending bad commands (yes, it has been seen).
35251 .section "Use of non-mail SMTP commands" "SECID236"
35252 .cindex "SMTP" "non-mail commands"
35253 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
35254 DATA. Exim counts such commands, and drops the connection if there are too
35255 many of them in a single SMTP session. This action catches some
35256 denial-of-service attempts and things like repeated failing AUTHs, or a mad
35257 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
35258 defines what &"too many"& means. Its default value is 10.
35260 When a new message is expected, one occurrence of RSET is not counted. This
35261 allows a client to send one RSET between messages (this is not necessary,
35262 but some clients do it). Exim also allows one uncounted occurrence of HELO
35263 or EHLO, and one occurrence of STARTTLS between messages. After
35264 starting up a TLS session, another EHLO is expected, and so it too is not
35267 The first occurrence of AUTH in a connection, or immediately following
35268 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
35269 RCPT, DATA, and QUIT are counted.
35271 You can control which hosts are subject to the limit set by
35272 &%smtp_accept_max_nonmail%& by setting
35273 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
35274 the limit apply to all hosts. This option means that you can exclude any
35275 specific badly-behaved hosts that you have to live with.
35280 .section "The VRFY and EXPN commands" "SECID237"
35281 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
35282 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
35283 appropriate) in order to decide whether the command should be accepted or not.
35285 .cindex "VRFY" "processing"
35286 When no ACL is defined for VRFY, or if it rejects without
35287 setting an explicit response code, the command is accepted
35288 (with a 252 SMTP response code)
35289 in order to support awkward clients that do a VRFY before every RCPT.
35290 When VRFY is accepted, it runs exactly the same code as when Exim is
35291 called with the &%-bv%& option, and returns 250/451/550
35292 SMTP response codes.
35294 .cindex "EXPN" "processing"
35295 If no ACL for EXPN is defined, the command is rejected.
35296 When EXPN is accepted, a single-level expansion of the address is done.
35297 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
35298 than a verification (the &%-bv%& option). If an unqualified local part is given
35299 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
35300 of VRFY and EXPN commands are logged on the main and reject logs, and
35301 VRFY verification failures are logged on the main log for consistency with
35306 .section "The ETRN command" "SECTETRN"
35307 .cindex "ETRN" "processing"
35308 RFC 1985 describes an SMTP command called ETRN that is designed to
35309 overcome the security problems of the TURN command (which has fallen into
35310 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
35311 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
35312 should be accepted or not. If no ACL is defined, the command is rejected.
35314 The ETRN command is concerned with &"releasing"& messages that are awaiting
35315 delivery to certain hosts. As Exim does not organize its message queue by host,
35316 the only form of ETRN that is supported by default is the one where the
35317 text starts with the &"#"& prefix, in which case the remainder of the text is
35318 specific to the SMTP server. A valid ETRN command causes a run of Exim with
35319 the &%-R%& option to happen, with the remainder of the ETRN text as its
35320 argument. For example,
35328 which causes a delivery attempt on all messages with undelivered addresses
35329 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
35330 default), Exim prevents the simultaneous execution of more than one queue run
35331 for the same argument string as a result of an ETRN command. This stops
35332 a misbehaving client from starting more than one queue runner at once.
35334 .cindex "hints database" "ETRN serialization"
35335 Exim implements the serialization by means of a hints database in which a
35336 record is written whenever a process is started by ETRN, and deleted when
35337 the process completes. However, Exim does not keep the SMTP session waiting for
35338 the ETRN process to complete. Once ETRN is accepted, the client is sent
35339 a &"success"& return code. Obviously there is scope for hints records to get
35340 left lying around if there is a system or program crash. To guard against this,
35341 Exim ignores any records that are more than six hours old.
35343 .oindex "&%smtp_etrn_command%&"
35344 For more control over what ETRN does, the &%smtp_etrn_command%& option can
35345 used. This specifies a command that is run whenever ETRN is received,
35346 whatever the form of its argument. For
35349 smtp_etrn_command = /etc/etrn_command $domain \
35350 $sender_host_address
35352 .vindex "&$domain$&"
35353 The string is split up into arguments which are independently expanded. The
35354 expansion variable &$domain$& is set to the argument of the ETRN command,
35355 and no syntax checking is done on the contents of this argument. Exim does not
35356 wait for the command to complete, so its status code is not checked. Exim runs
35357 under its own uid and gid when receiving incoming SMTP, so it is not possible
35358 for it to change them before running the command.
35362 .section "Incoming local SMTP" "SECID238"
35363 .cindex "SMTP" "local incoming"
35364 Some user agents use SMTP to pass messages to their local MTA using the
35365 standard input and output, as opposed to passing the envelope on the command
35366 line and writing the message to the standard input. This is supported by the
35367 &%-bs%& option. This form of SMTP is handled in the same way as incoming
35368 messages over TCP/IP (including the use of ACLs), except that the envelope
35369 sender given in a MAIL command is ignored unless the caller is trusted. In
35370 an ACL you can detect this form of SMTP input by testing for an empty host
35371 identification. It is common to have this as the first line in the ACL that
35372 runs for RCPT commands:
35376 This accepts SMTP messages from local processes without doing any other tests.
35380 .section "Outgoing batched SMTP" "SECTbatchSMTP"
35381 .cindex "SMTP" "batched outgoing"
35382 .cindex "batched SMTP output"
35383 Both the &(appendfile)& and &(pipe)& transports can be used for handling
35384 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
35385 be output in BSMTP format. No SMTP responses are possible for this form of
35386 delivery. All it is doing is using SMTP commands as a way of transmitting the
35387 envelope along with the message.
35389 The message is written to the file or pipe preceded by the SMTP commands
35390 MAIL and RCPT, and followed by a line containing a single dot. Lines in
35391 the message that start with a dot have an extra dot added. The SMTP command
35392 HELO is not normally used. If it is required, the &%message_prefix%& option
35393 can be used to specify it.
35395 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
35396 one recipient address at a time by default. However, you can arrange for them
35397 to handle several addresses at once by setting the &%batch_max%& option. When
35398 this is done for BSMTP, messages may contain multiple RCPT commands. See
35399 chapter &<<CHAPbatching>>& for more details.
35402 When one or more addresses are routed to a BSMTP transport by a router that
35403 sets up a host list, the name of the first host on the list is available to the
35404 transport in the variable &$host$&. Here is an example of such a transport and
35409 driver = manualroute
35410 transport = smtp_appendfile
35411 route_list = domain.example batch.host.example
35415 driver = appendfile
35416 directory = /var/bsmtp/$host
35421 This causes messages addressed to &'domain.example'& to be written in BSMTP
35422 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
35423 message (unless there are more than 1000 recipients).
35427 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
35428 .cindex "SMTP" "batched incoming"
35429 .cindex "batched SMTP input"
35430 The &%-bS%& command line option causes Exim to accept one or more messages by
35431 reading SMTP on the standard input, but to generate no responses. If the caller
35432 is trusted, the senders in the MAIL commands are believed; otherwise the
35433 sender is always the caller of Exim. Unqualified senders and receivers are not
35434 rejected (there seems little point) but instead just get qualified. HELO
35435 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
35436 as NOOP; QUIT quits.
35438 Minimal policy checking is done for BSMTP input. Only the non-SMTP
35439 ACL is run in the same way as for non-SMTP local input.
35441 If an error is detected while reading a message, including a missing &"."& at
35442 the end, Exim gives up immediately. It writes details of the error to the
35443 standard output in a stylized way that the calling program should be able to
35444 make some use of automatically, for example:
35446 554 Unexpected end of file
35447 Transaction started in line 10
35448 Error detected in line 14
35450 It writes a more verbose version, for human consumption, to the standard error
35453 An error was detected while processing a file of BSMTP input.
35454 The error message was:
35456 501 '>' missing at end of address
35458 The SMTP transaction started in line 10.
35459 The error was detected in line 12.
35460 The SMTP command at fault was:
35462 rcpt to:<malformed@in.com.plete
35464 1 previous message was successfully processed.
35465 The rest of the batch was abandoned.
35467 The return code from Exim is zero only if there were no errors. It is 1 if some
35468 messages were accepted before an error was detected, and 2 if no messages were
35470 .ecindex IIDsmtpproc1
35471 .ecindex IIDsmtpproc2
35475 . ////////////////////////////////////////////////////////////////////////////
35476 . ////////////////////////////////////////////////////////////////////////////
35478 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
35479 "Customizing messages"
35480 When a message fails to be delivered, or remains in the queue for more than a
35481 configured amount of time, Exim sends a message to the original sender, or
35482 to an alternative configured address. The text of these messages is built into
35483 the code of Exim, but it is possible to change it, either by adding a single
35484 string, or by replacing each of the paragraphs by text supplied in a file.
35486 The &'From:'& and &'To:'& header lines are automatically generated; you can
35487 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
35488 option. Exim also adds the line
35490 Auto-Submitted: auto-generated
35492 to all warning and bounce messages,
35495 .section "Customizing bounce messages" "SECID239"
35496 .cindex "customizing" "bounce message"
35497 .cindex "bounce message" "customizing"
35498 If &%bounce_message_text%& is set, its contents are included in the default
35499 message immediately after &"This message was created automatically by mail
35500 delivery software."& The string is not expanded. It is not used if
35501 &%bounce_message_file%& is set.
35503 When &%bounce_message_file%& is set, it must point to a template file for
35504 constructing error messages. The file consists of a series of text items,
35505 separated by lines consisting of exactly four asterisks. If the file cannot be
35506 opened, default text is used and a message is written to the main and panic
35507 logs. If any text item in the file is empty, default text is used for that
35510 .vindex "&$bounce_recipient$&"
35511 .vindex "&$bounce_return_size_limit$&"
35512 Each item of text that is read from the file is expanded, and there are two
35513 expansion variables which can be of use here: &$bounce_recipient$& is set to
35514 the recipient of an error message while it is being created, and
35515 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
35516 option, rounded to a whole number.
35518 The items must appear in the file in the following order:
35521 The first item is included in the headers, and should include at least a
35522 &'Subject:'& header. Exim does not check the syntax of these headers.
35524 The second item forms the start of the error message. After it, Exim lists the
35525 failing addresses with their error messages.
35527 The third item is used to introduce any text from pipe transports that is to be
35528 returned to the sender. It is omitted if there is no such text.
35530 The fourth, fifth and sixth items will be ignored and may be empty.
35531 The fields exist for back-compatibility
35534 The default state (&%bounce_message_file%& unset) is equivalent to the
35535 following file, in which the sixth item is empty. The &'Subject:'& and some
35536 other lines have been split in order to fit them on the page:
35538 Subject: Mail delivery failed
35539 ${if eq{$sender_address}{$bounce_recipient}
35540 {: returning message to sender}}
35542 This message was created automatically by mail delivery software.
35544 A message ${if eq{$sender_address}{$bounce_recipient}
35545 {that you sent }{sent by
35549 }}could not be delivered to all of its recipients.
35550 This is a permanent error. The following address(es) failed:
35552 The following text was generated during the delivery attempt(s):
35554 ------ This is a copy of the message, including all the headers.
35557 ------ The body of the message is $message_size characters long;
35559 ------ $bounce_return_size_limit or so are included here.
35562 .section "Customizing warning messages" "SECTcustwarn"
35563 .cindex "customizing" "warning message"
35564 .cindex "warning of delay" "customizing the message"
35565 The option &%warn_message_file%& can be pointed at a template file for use when
35566 warnings about message delays are created. In this case there are only three
35570 The first item is included in the headers, and should include at least a
35571 &'Subject:'& header. Exim does not check the syntax of these headers.
35573 The second item forms the start of the warning message. After it, Exim lists
35574 the delayed addresses.
35576 The third item then ends the message.
35579 The default state is equivalent to the following file, except that some lines
35580 have been split here, in order to fit them on the page:
35582 Subject: Warning: message $message_exim_id delayed
35583 $warn_message_delay
35585 This message was created automatically by mail delivery software.
35587 A message ${if eq{$sender_address}{$warn_message_recipients}
35588 {that you sent }{sent by
35592 }}has not been delivered to all of its recipients after
35593 more than $warn_message_delay in the queue on $primary_hostname.
35595 The message identifier is: $message_exim_id
35596 The subject of the message is: $h_subject
35597 The date of the message is: $h_date
35599 The following address(es) have not yet been delivered:
35601 No action is required on your part. Delivery attempts will
35602 continue for some time, and this warning may be repeated at
35603 intervals if the message remains undelivered. Eventually the
35604 mail delivery software will give up, and when that happens,
35605 the message will be returned to you.
35607 .vindex "&$warn_message_delay$&"
35608 .vindex "&$warn_message_recipients$&"
35609 However, in the default state the subject and date lines are omitted if no
35610 appropriate headers exist. During the expansion of this file,
35611 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
35612 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
35613 of recipients for the warning message. There may be more than one if there are
35614 multiple addresses with different &%errors_to%& settings on the routers that
35620 . ////////////////////////////////////////////////////////////////////////////
35621 . ////////////////////////////////////////////////////////////////////////////
35623 .chapter "Some common configuration settings" "CHAPcomconreq"
35624 This chapter discusses some configuration settings that seem to be fairly
35625 common. More examples and discussion can be found in the Exim book.
35629 .section "Sending mail to a smart host" "SECID240"
35630 .cindex "smart host" "example router"
35631 If you want to send all mail for non-local domains to a &"smart host"&, you
35632 should replace the default &(dnslookup)& router with a router which does the
35633 routing explicitly:
35635 send_to_smart_host:
35636 driver = manualroute
35637 route_list = !+local_domains smart.host.name
35638 transport = remote_smtp
35640 You can use the smart host's IP address instead of the name if you wish.
35641 If you are using Exim only to submit messages to a smart host, and not for
35642 receiving incoming messages, you can arrange for it to do the submission
35643 synchronously by setting the &%mua_wrapper%& option (see chapter
35644 &<<CHAPnonqueueing>>&).
35649 .section "Using Exim to handle mailing lists" "SECTmailinglists"
35650 .cindex "mailing lists"
35651 Exim can be used to run simple mailing lists, but for large and/or complicated
35652 requirements, the use of additional specialized mailing list software such as
35653 Majordomo or Mailman is recommended.
35655 The &(redirect)& router can be used to handle mailing lists where each list
35656 is maintained in a separate file, which can therefore be managed by an
35657 independent manager. The &%domains%& router option can be used to run these
35658 lists in a separate domain from normal mail. For example:
35662 domains = lists.example
35663 file = /usr/lists/$local_part
35666 errors_to = $local_part-request@lists.example
35669 This router is skipped for domains other than &'lists.example'&. For addresses
35670 in that domain, it looks for a file that matches the local part. If there is no
35671 such file, the router declines, but because &%no_more%& is set, no subsequent
35672 routers are tried, and so the whole delivery fails.
35674 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
35675 expanded into a filename or a pipe delivery, which is usually inappropriate in
35678 .oindex "&%errors_to%&"
35679 The &%errors_to%& option specifies that any delivery errors caused by addresses
35680 taken from a mailing list are to be sent to the given address rather than the
35681 original sender of the message. However, before acting on this, Exim verifies
35682 the error address, and ignores it if verification fails.
35684 For example, using the configuration above, mail sent to
35685 &'dicts@lists.example'& is passed on to those addresses contained in
35686 &_/usr/lists/dicts_&, with error reports directed to
35687 &'dicts-request@lists.example'&, provided that this address can be verified.
35688 There could be a file called &_/usr/lists/dicts-request_& containing
35689 the address(es) of this particular list's manager(s), but other approaches,
35690 such as setting up an earlier router (possibly using the &%local_part_prefix%&
35691 or &%local_part_suffix%& options) to handle addresses of the form
35692 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
35696 .section "Syntax errors in mailing lists" "SECID241"
35697 .cindex "mailing lists" "syntax errors in"
35698 If an entry in redirection data contains a syntax error, Exim normally defers
35699 delivery of the original address. That means that a syntax error in a mailing
35700 list holds up all deliveries to the list. This may not be appropriate when a
35701 list is being maintained automatically from data supplied by users, and the
35702 addresses are not rigorously checked.
35704 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
35705 entries that fail to parse, noting the incident in the log. If in addition
35706 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
35707 whenever a broken address is skipped. It is usually appropriate to set
35708 &%syntax_errors_to%& to the same address as &%errors_to%&.
35712 .section "Re-expansion of mailing lists" "SECID242"
35713 .cindex "mailing lists" "re-expansion of"
35714 Exim remembers every individual address to which a message has been delivered,
35715 in order to avoid duplication, but it normally stores only the original
35716 recipient addresses with a message. If all the deliveries to a mailing list
35717 cannot be done at the first attempt, the mailing list is re-expanded when the
35718 delivery is next tried. This means that alterations to the list are taken into
35719 account at each delivery attempt, so addresses that have been added to
35720 the list since the message arrived will therefore receive a copy of the
35721 message, even though it pre-dates their subscription.
35723 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
35724 on the &(redirect)& router. If this is done, any addresses generated by the
35725 router that fail to deliver at the first attempt are added to the message as
35726 &"top level"& addresses, and the parent address that generated them is marked
35727 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
35728 subsequent delivery attempts. The disadvantage of this is that if any of the
35729 failing addresses are incorrect, correcting them in the file has no effect on
35730 pre-existing messages.
35732 The original top-level address is remembered with each of the generated
35733 addresses, and is output in any log messages. However, any intermediate parent
35734 addresses are not recorded. This makes a difference to the log only if the
35735 &%all_parents%& selector is set, but for mailing lists there is normally only
35736 one level of expansion anyway.
35740 .section "Closed mailing lists" "SECID243"
35741 .cindex "mailing lists" "closed"
35742 The examples so far have assumed open mailing lists, to which anybody may
35743 send mail. It is also possible to set up closed lists, where mail is accepted
35744 from specified senders only. This is done by making use of the generic
35745 &%senders%& option to restrict the router that handles the list.
35747 The following example uses the same file as a list of recipients and as a list
35748 of permitted senders. It requires three routers:
35752 domains = lists.example
35753 local_part_suffix = -request
35754 file = /usr/lists/$local_part$local_part_suffix
35759 domains = lists.example
35760 senders = ${if exists {/usr/lists/$local_part}\
35761 {lsearch;/usr/lists/$local_part}{*}}
35762 file = /usr/lists/$local_part
35765 errors_to = $local_part-request@lists.example
35770 domains = lists.example
35772 data = :fail: $local_part@lists.example is a closed mailing list
35774 All three routers have the same &%domains%& setting, so for any other domains,
35775 they are all skipped. The first router runs only if the local part ends in
35776 &%-request%&. It handles messages to the list manager(s) by means of an open
35779 The second router runs only if the &%senders%& precondition is satisfied. It
35780 checks for the existence of a list that corresponds to the local part, and then
35781 checks that the sender is on the list by means of a linear search. It is
35782 necessary to check for the existence of the file before trying to search it,
35783 because otherwise Exim thinks there is a configuration error. If the file does
35784 not exist, the expansion of &%senders%& is *, which matches all senders. This
35785 means that the router runs, but because there is no list, declines, and
35786 &%no_more%& ensures that no further routers are run. The address fails with an
35787 &"unrouteable address"& error.
35789 The third router runs only if the second router is skipped, which happens when
35790 a mailing list exists, but the sender is not on it. This router forcibly fails
35791 the address, giving a suitable error message.
35796 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
35798 .cindex "Variable Envelope Return Paths"
35799 .cindex "envelope sender"
35800 Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
35801 are a way of helping mailing list administrators discover which subscription
35802 address is the cause of a particular delivery failure. The idea is to encode
35803 the original recipient address in the outgoing envelope sender address, so that
35804 if the message is forwarded by another host and then subsequently bounces, the
35805 original recipient can be extracted from the recipient address of the bounce.
35807 .oindex &%errors_to%&
35808 .oindex &%return_path%&
35809 Envelope sender addresses can be modified by Exim using two different
35810 facilities: the &%errors_to%& option on a router (as shown in previous mailing
35811 list examples), or the &%return_path%& option on a transport. The second of
35812 these is effective only if the message is successfully delivered to another
35813 host; it is not used for errors detected on the local host (see the description
35814 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
35815 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
35821 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
35822 {$1-request+$local_part=$domain@your.dom.example}fail}
35824 This has the effect of rewriting the return path (envelope sender) on outgoing
35825 SMTP messages, if the local part of the original return path ends in
35826 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
35827 local part and domain of the recipient into the return path. Suppose, for
35828 example, that a message whose return path has been set to
35829 &'somelist-request@your.dom.example'& is sent to
35830 &'subscriber@other.dom.example'&. In the transport, the return path is
35833 somelist-request+subscriber=other.dom.example@your.dom.example
35835 .vindex "&$local_part$&"
35836 For this to work, you must tell Exim to send multiple copies of messages that
35837 have more than one recipient, so that each copy has just one recipient. This is
35838 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
35839 might be sent to several different recipients in the same domain, in which case
35840 &$local_part$& is not available in the transport, because it is not unique.
35842 Unless your host is doing nothing but mailing list deliveries, you should
35843 probably use a separate transport for the VERP deliveries, so as not to use
35844 extra resources in making one-per-recipient copies for other deliveries. This
35845 can easily be done by expanding the &%transport%& option in the router:
35849 domains = ! +local_domains
35851 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
35852 {verp_smtp}{remote_smtp}}
35855 If you want to change the return path using &%errors_to%& in a router instead
35856 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
35857 routers that handle mailing list addresses. This will ensure that all delivery
35858 errors, including those detected on the local host, are sent to the VERP
35861 On a host that does no local deliveries and has no manual routing, only the
35862 &(dnslookup)& router needs to be changed. A special transport is not needed for
35863 SMTP deliveries. Every mailing list recipient has its own return path value,
35864 and so Exim must hand them to the transport one at a time. Here is an example
35865 of a &(dnslookup)& router that implements VERP:
35869 domains = ! +local_domains
35870 transport = remote_smtp
35872 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
35873 {$1-request+$local_part=$domain@your.dom.example}fail}
35876 Before you start sending out messages with VERPed return paths, you must also
35877 configure Exim to accept the bounce messages that come back to those paths.
35878 Typically this is done by setting a &%local_part_suffix%& option for a
35879 router, and using this to route the messages to wherever you want to handle
35882 The overhead incurred in using VERP depends very much on the size of the
35883 message, the number of recipient addresses that resolve to the same remote
35884 host, and the speed of the connection over which the message is being sent. If
35885 a lot of addresses resolve to the same host and the connection is slow, sending
35886 a separate copy of the message for each address may take substantially longer
35887 than sending a single copy with many recipients (for which VERP cannot be
35895 .section "Virtual domains" "SECTvirtualdomains"
35896 .cindex "virtual domains"
35897 .cindex "domain" "virtual"
35898 The phrase &'virtual domain'& is unfortunately used with two rather different
35902 A domain for which there are no real mailboxes; all valid local parts are
35903 aliases for other email addresses. Common examples are organizational
35904 top-level domains and &"vanity"& domains.
35906 One of a number of independent domains that are all handled by the same host,
35907 with mailboxes on that host, but where the mailbox owners do not necessarily
35908 have login accounts on that host.
35911 The first usage is probably more common, and does seem more &"virtual"& than
35912 the second. This kind of domain can be handled in Exim with a straightforward
35913 aliasing router. One approach is to create a separate alias file for each
35914 virtual domain. Exim can test for the existence of the alias file to determine
35915 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
35916 to a router of this form:
35920 domains = dsearch;/etc/mail/virtual
35921 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
35924 The &%domains%& option specifies that the router is to be skipped, unless there
35925 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
35926 domain that is being processed. When the router runs, it looks up the local
35927 part in the file to find a new address (or list of addresses). The &%no_more%&
35928 setting ensures that if the lookup fails (leading to &%data%& being an empty
35929 string), Exim gives up on the address without trying any subsequent routers.
35931 This one router can handle all the virtual domains because the alias filenames
35932 follow a fixed pattern. Permissions can be arranged so that appropriate people
35933 can edit the different alias files. A successful aliasing operation results in
35934 a new envelope recipient address, which is then routed from scratch.
35936 The other kind of &"virtual"& domain can also be handled in a straightforward
35937 way. One approach is to create a file for each domain containing a list of
35938 valid local parts, and use it in a router like this:
35942 domains = dsearch;/etc/mail/domains
35943 local_parts = lsearch;/etc/mail/domains/$domain
35944 transport = my_mailboxes
35946 The address is accepted if there is a file for the domain, and the local part
35947 can be found in the file. The &%domains%& option is used to check for the
35948 file's existence because &%domains%& is tested before the &%local_parts%&
35949 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
35950 because that option is tested after &%local_parts%&. The transport is as
35954 driver = appendfile
35955 file = /var/mail/$domain/$local_part
35958 This uses a directory of mailboxes for each domain. The &%user%& setting is
35959 required, to specify which uid is to be used for writing to the mailboxes.
35961 The configuration shown here is just one example of how you might support this
35962 requirement. There are many other ways this kind of configuration can be set
35963 up, for example, by using a database instead of separate files to hold all the
35964 information about the domains.
35968 .section "Multiple user mailboxes" "SECTmulbox"
35969 .cindex "multiple mailboxes"
35970 .cindex "mailbox" "multiple"
35971 .cindex "local part" "prefix"
35972 .cindex "local part" "suffix"
35973 Heavy email users often want to operate with multiple mailboxes, into which
35974 incoming mail is automatically sorted. A popular way of handling this is to
35975 allow users to use multiple sender addresses, so that replies can easily be
35976 identified. Users are permitted to add prefixes or suffixes to their local
35977 parts for this purpose. The wildcard facility of the generic router options
35978 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
35979 example, consider this router:
35984 file = $home/.forward
35985 local_part_suffix = -*
35986 local_part_suffix_optional
35989 .vindex "&$local_part_suffix$&"
35990 It runs a user's &_.forward_& file for all local parts of the form
35991 &'username-*'&. Within the filter file the user can distinguish different
35992 cases by testing the variable &$local_part_suffix$&. For example:
35994 if $local_part_suffix contains -special then
35995 save /home/$local_part/Mail/special
35998 If the filter file does not exist, or does not deal with such addresses, they
35999 fall through to subsequent routers, and, assuming no subsequent use of the
36000 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
36001 control over which suffixes are valid.
36003 Alternatively, a suffix can be used to trigger the use of a different
36004 &_.forward_& file &-- which is the way a similar facility is implemented in
36010 file = $home/.forward$local_part_suffix
36011 local_part_suffix = -*
36012 local_part_suffix_optional
36015 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
36016 example, &_.forward-special_& is used. Once again, if the appropriate file
36017 does not exist, or does not deal with the address, it is passed on to
36018 subsequent routers, which could, if required, look for an unqualified
36019 &_.forward_& file to use as a default.
36023 .section "Simplified vacation processing" "SECID244"
36024 .cindex "vacation processing"
36025 The traditional way of running the &'vacation'& program is for a user to set up
36026 a pipe command in a &_.forward_& file
36027 (see section &<<SECTspecitredli>>& for syntax details).
36028 This is prone to error by inexperienced users. There are two features of Exim
36029 that can be used to make this process simpler for users:
36032 A local part prefix such as &"vacation-"& can be specified on a router which
36033 can cause the message to be delivered directly to the &'vacation'& program, or
36034 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
36035 &_.forward_& file are then much simpler. For example:
36037 spqr, vacation-spqr
36040 The &%require_files%& generic router option can be used to trigger a
36041 vacation delivery by checking for the existence of a certain file in the
36042 user's home directory. The &%unseen%& generic option should also be used, to
36043 ensure that the original delivery also proceeds. In this case, all the user has
36044 to do is to create a file called, say, &_.vacation_&, containing a vacation
36048 Another advantage of both these methods is that they both work even when the
36049 use of arbitrary pipes by users is locked out.
36053 .section "Taking copies of mail" "SECID245"
36054 .cindex "message" "copying every"
36055 Some installations have policies that require archive copies of all messages to
36056 be made. A single copy of each message can easily be taken by an appropriate
36057 command in a system filter, which could, for example, use a different file for
36058 each day's messages.
36060 There is also a shadow transport mechanism that can be used to take copies of
36061 messages that are successfully delivered by local transports, one copy per
36062 delivery. This could be used, &'inter alia'&, to implement automatic
36063 notification of delivery by sites that insist on doing such things.
36067 .section "Intermittently connected hosts" "SECID246"
36068 .cindex "intermittently connected hosts"
36069 It has become quite common (because it is cheaper) for hosts to connect to the
36070 Internet periodically rather than remain connected all the time. The normal
36071 arrangement is that mail for such hosts accumulates on a system that is
36072 permanently connected.
36074 Exim was designed for use on permanently connected hosts, and so it is not
36075 particularly well-suited to use in an intermittently connected environment.
36076 Nevertheless there are some features that can be used.
36079 .section "Exim on the upstream server host" "SECID247"
36080 It is tempting to arrange for incoming mail for the intermittently connected
36081 host to remain in Exim's queue until the client connects. However, this
36082 approach does not scale very well. Two different kinds of waiting message are
36083 being mixed up in the same queue &-- those that cannot be delivered because of
36084 some temporary problem, and those that are waiting for their destination host
36085 to connect. This makes it hard to manage the queue, as well as wasting
36086 resources, because each queue runner scans the entire queue.
36088 A better approach is to separate off those messages that are waiting for an
36089 intermittently connected host. This can be done by delivering these messages
36090 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
36091 format, from where they are transmitted by other software when their
36092 destination connects. This makes it easy to collect all the mail for one host
36093 in a single directory, and to apply local timeout rules on a per-message basis
36096 On a very small scale, leaving the mail on Exim's queue can be made to work. If
36097 you are doing this, you should configure Exim with a long retry period for the
36098 intermittent host. For example:
36100 cheshire.wonderland.fict.example * F,5d,24h
36102 This stops a lot of failed delivery attempts from occurring, but Exim remembers
36103 which messages it has queued up for that host. Once the intermittent host comes
36104 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
36105 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
36106 causes all the queued up messages to be delivered, often down a single SMTP
36107 connection. While the host remains connected, any new messages get delivered
36110 If the connecting hosts do not have fixed IP addresses, that is, if a host is
36111 issued with a different IP address each time it connects, Exim's retry
36112 mechanisms on the holding host get confused, because the IP address is normally
36113 used as part of the key string for holding retry information. This can be
36114 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
36115 Since this has disadvantages for permanently connected hosts, it is best to
36116 arrange a separate transport for the intermittently connected ones.
36120 .section "Exim on the intermittently connected client host" "SECID248"
36121 The value of &%smtp_accept_queue_per_connection%& should probably be
36122 increased, or even set to zero (that is, disabled) on the intermittently
36123 connected host, so that all incoming messages down a single connection get
36124 delivered immediately.
36126 .cindex "SMTP" "passed connection"
36127 .cindex "SMTP" "multiple deliveries"
36128 .cindex "multiple SMTP deliveries"
36129 Mail waiting to be sent from an intermittently connected host will probably
36130 not have been routed, because without a connection DNS lookups are not
36131 possible. This means that if a normal queue run is done at connection time,
36132 each message is likely to be sent in a separate SMTP session. This can be
36133 avoided by starting the queue run with a command line option beginning with
36134 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
36135 first pass, routing is done but no deliveries take place. The second pass is a
36136 normal queue run; since all the messages have been previously routed, those
36137 destined for the same host are likely to get sent as multiple deliveries in a
36138 single SMTP connection.
36142 . ////////////////////////////////////////////////////////////////////////////
36143 . ////////////////////////////////////////////////////////////////////////////
36145 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
36146 "Exim as a non-queueing client"
36147 .cindex "client, non-queueing"
36148 .cindex "smart host" "suppressing queueing"
36149 On a personal computer, it is a common requirement for all
36150 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
36151 configured to operate that way, for all the popular operating systems.
36152 However, there are some MUAs for Unix-like systems that cannot be so
36153 configured: they submit messages using the command line interface of
36154 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
36157 If the personal computer runs continuously, there is no problem, because it can
36158 run a conventional MTA that handles delivery to the smart host, and deal with
36159 any delays via its queueing mechanism. However, if the computer does not run
36160 continuously or runs different operating systems at different times, queueing
36161 email is not desirable.
36163 There is therefore a requirement for something that can provide the
36164 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
36165 any queueing or retrying facilities. Furthermore, the delivery to the smart
36166 host should be synchronous, so that if it fails, the sending MUA is immediately
36167 informed. In other words, we want something that extends an MUA that submits
36168 to a local MTA via the command line so that it behaves like one that submits
36169 to a remote smart host using TCP/SMTP.
36171 There are a number of applications (for example, there is one called &'ssmtp'&)
36172 that do this job. However, people have found them to be lacking in various
36173 ways. For instance, you might want to allow aliasing and forwarding to be done
36174 before sending a message to the smart host.
36176 Exim already had the necessary infrastructure for doing this job. Just a few
36177 tweaks were needed to make it behave as required, though it is somewhat of an
36178 overkill to use a fully-featured MTA for this purpose.
36180 .oindex "&%mua_wrapper%&"
36181 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
36182 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
36183 assumes that it is being used to &"wrap"& a command-line MUA in the manner
36184 just described. As well as setting &%mua_wrapper%&, you also need to provide a
36185 compatible router and transport configuration. Typically there will be just one
36186 router and one transport, sending everything to a smart host.
36188 When run in MUA wrapping mode, the behaviour of Exim changes in the
36192 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
36193 In other words, the only way to submit messages is via the command line.
36195 Each message is synchronously delivered as soon as it is received (&%-odi%& is
36196 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
36197 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
36198 does not finish until the delivery attempt is complete. If the delivery is
36199 successful, a zero return code is given.
36201 Address redirection is permitted, but the final routing for all addresses must
36202 be to the same remote transport, and to the same list of hosts. Furthermore,
36203 the return address (envelope sender) must be the same for all recipients, as
36204 must any added or deleted header lines. In other words, it must be possible to
36205 deliver the message in a single SMTP transaction, however many recipients there
36208 If these conditions are not met, or if routing any address results in a
36209 failure or defer status, or if Exim is unable to deliver all the recipients
36210 successfully to one of the smart hosts, delivery of the entire message fails.
36212 Because no queueing is allowed, all failures are treated as permanent; there
36213 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
36214 smart host. Furthermore, because only a single yes/no response can be given to
36215 the caller, it is not possible to deliver to some recipients and not others. If
36216 there is an error (temporary or permanent) for any recipient, all are failed.
36218 If more than one smart host is listed, Exim will try another host after a
36219 connection failure or a timeout, in the normal way. However, if this kind of
36220 failure happens for all the hosts, the delivery fails.
36222 When delivery fails, an error message is written to the standard error stream
36223 (as well as to Exim's log), and Exim exits to the caller with a return code
36224 value 1. The message is expunged from Exim's spool files. No bounce messages
36225 are ever generated.
36227 No retry data is maintained, and any retry rules are ignored.
36229 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
36230 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
36231 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
36234 The overall effect is that Exim makes a single synchronous attempt to deliver
36235 the message, failing if there is any kind of problem. Because no local
36236 deliveries are done and no daemon can be run, Exim does not need root
36237 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
36238 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
36239 the advantages and disadvantages of running without root privilege.
36244 . ////////////////////////////////////////////////////////////////////////////
36245 . ////////////////////////////////////////////////////////////////////////////
36247 .chapter "Log files" "CHAPlog"
36248 .scindex IIDloggen "log" "general description"
36249 .cindex "log" "types of"
36250 Exim writes three different logs, referred to as the main log, the reject log,
36255 The main log records the arrival of each message and each delivery in a single
36256 line in each case. The format is as compact as possible, in an attempt to keep
36257 down the size of log files. Two-character flag sequences make it easy to pick
36258 out these lines. A number of other events are recorded in the main log. Some of
36259 them are optional, in which case the &%log_selector%& option controls whether
36260 they are included or not. A Perl script called &'eximstats'&, which does simple
36261 analysis of main log files, is provided in the Exim distribution (see section
36262 &<<SECTmailstat>>&).
36264 .cindex "reject log"
36265 The reject log records information from messages that are rejected as a result
36266 of a configuration option (that is, for policy reasons).
36267 The first line of each rejection is a copy of the line that is also written to
36268 the main log. Then, if the message's header has been read at the time the log
36269 is written, its contents are written to this log. Only the original header
36270 lines are available; header lines added by ACLs are not logged. You can use the
36271 reject log to check that your policy controls are working correctly; on a busy
36272 host this may be easier than scanning the main log for rejection messages. You
36273 can suppress the writing of the reject log by setting &%write_rejectlog%&
36276 .cindex "panic log"
36277 .cindex "system log"
36278 When certain serious errors occur, Exim writes entries to its panic log. If the
36279 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
36280 are usually written to the main log as well, but can get lost amid the mass of
36281 other entries. The panic log should be empty under normal circumstances. It is
36282 therefore a good idea to check it (or to have a &'cron'& script check it)
36283 regularly, in order to become aware of any problems. When Exim cannot open its
36284 panic log, it tries as a last resort to write to the system log (syslog). This
36285 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
36286 message itself is written at priority LOG_CRIT.
36289 Every log line starts with a timestamp, in the format shown in the following
36290 example. Note that many of the examples shown in this chapter are line-wrapped.
36291 In the log file, this would be all on one line:
36293 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
36296 By default, the timestamps are in the local timezone. There are two
36297 ways of changing this:
36300 You can set the &%timezone%& option to a different time zone; in particular, if
36305 the timestamps will be in UTC (aka GMT).
36307 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
36310 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
36314 .cindex "log" "process ids in"
36315 .cindex "pid (process id)" "in log lines"
36316 Exim does not include its process id in log lines by default, but you can
36317 request that it does so by specifying the &`pid`& log selector (see section
36318 &<<SECTlogselector>>&). When this is set, the process id is output, in square
36319 brackets, immediately after the time and date.
36324 .section "Where the logs are written" "SECTwhelogwri"
36325 .cindex "log" "destination"
36326 .cindex "log" "to file"
36327 .cindex "log" "to syslog"
36329 The logs may be written to local files, or to syslog, or both. However, it
36330 should be noted that many syslog implementations use UDP as a transport, and
36331 are therefore unreliable in the sense that messages are not guaranteed to
36332 arrive at the loghost, nor is the ordering of messages necessarily maintained.
36333 It has also been reported that on large log files (tens of megabytes) you may
36334 need to tweak syslog to prevent it syncing the file with each write &-- on
36335 Linux this has been seen to make syslog take 90% plus of CPU time.
36337 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
36338 &_Local/Makefile_& or by setting &%log_file_path%& in the runtime
36339 configuration. This latter string is expanded, so it can contain, for example,
36340 references to the host name:
36342 log_file_path = /var/log/$primary_hostname/exim_%slog
36344 It is generally advisable, however, to set the string in &_Local/Makefile_&
36345 rather than at runtime, because then the setting is available right from the
36346 start of Exim's execution. Otherwise, if there's something it wants to log
36347 before it has read the configuration file (for example, an error in the
36348 configuration file) it will not use the path you want, and may not be able to
36351 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
36352 list, currently limited to at most two items. This is one option where the
36353 facility for changing a list separator may not be used. The list must always be
36354 colon-separated. If an item in the list is &"syslog"& then syslog is used;
36355 otherwise the item must either be an absolute path, containing &`%s`& at the
36356 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
36357 implying the use of a default path.
36359 When Exim encounters an empty item in the list, it searches the list defined by
36360 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
36361 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
36362 mean &"use the path specified at build time"&. It no such item exists, log
36363 files are written in the &_log_& subdirectory of the spool directory. This is
36364 equivalent to the setting:
36366 log_file_path = $spool_directory/log/%slog
36368 If you do not specify anything at build time or runtime,
36369 or if you unset the option at runtime (i.e. &`log_file_path = `&),
36370 that is where the logs are written.
36372 A log file path may also contain &`%D`& or &`%M`& if datestamped log filenames
36373 are in use &-- see section &<<SECTdatlogfil>>& below.
36375 Here are some examples of possible settings:
36377 &`LOG_FILE_PATH=syslog `& syslog only
36378 &`LOG_FILE_PATH=:syslog `& syslog and default path
36379 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
36380 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
36382 If there are more than two paths in the list, the first is used and a panic
36387 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
36388 .cindex "log" "cycling local files"
36389 .cindex "cycling logs"
36390 .cindex "&'exicyclog'&"
36391 .cindex "log" "local files; writing to"
36392 Some operating systems provide centralized and standardized methods for cycling
36393 log files. For those that do not, a utility script called &'exicyclog'& is
36394 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
36395 main and reject logs each time it is called. The maximum number of old logs to
36396 keep can be set. It is suggested this script is run as a daily &'cron'& job.
36398 An Exim delivery process opens the main log when it first needs to write to it,
36399 and it keeps the file open in case subsequent entries are required &-- for
36400 example, if a number of different deliveries are being done for the same
36401 message. However, remote SMTP deliveries can take a long time, and this means
36402 that the file may be kept open long after it is renamed if &'exicyclog'& or
36403 something similar is being used to rename log files on a regular basis. To
36404 ensure that a switch of log files is noticed as soon as possible, Exim calls
36405 &[stat()]& on the main log's name before reusing an open file, and if the file
36406 does not exist, or its inode has changed, the old file is closed and Exim
36407 tries to open the main log from scratch. Thus, an old log file may remain open
36408 for quite some time, but no Exim processes should write to it once it has been
36413 .section "Datestamped log files" "SECTdatlogfil"
36414 .cindex "log" "datestamped files"
36415 Instead of cycling the main and reject log files by renaming them
36416 periodically, some sites like to use files whose names contain a datestamp,
36417 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
36418 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
36419 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
36420 point where the datestamp is required. For example:
36422 log_file_path = /var/spool/exim/log/%slog-%D
36423 log_file_path = /var/log/exim-%s-%D.log
36424 log_file_path = /var/spool/exim/log/%D-%slog
36425 log_file_path = /var/log/exim/%s.%M
36427 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
36428 examples of names generated by the above examples:
36430 /var/spool/exim/log/mainlog-20021225
36431 /var/log/exim-reject-20021225.log
36432 /var/spool/exim/log/20021225-mainlog
36433 /var/log/exim/main.200212
36435 When this form of log file is specified, Exim automatically switches to new
36436 files at midnight. It does not make any attempt to compress old logs; you
36437 will need to write your own script if you require this. You should not
36438 run &'exicyclog'& with this form of logging.
36440 The location of the panic log is also determined by &%log_file_path%&, but it
36441 is not datestamped, because rotation of the panic log does not make sense.
36442 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
36443 the string. In addition, if it immediately follows a slash, a following
36444 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
36445 character is removed. Thus, the four examples above would give these panic
36448 /var/spool/exim/log/paniclog
36449 /var/log/exim-panic.log
36450 /var/spool/exim/log/paniclog
36451 /var/log/exim/panic
36455 .section "Logging to syslog" "SECID249"
36456 .cindex "log" "syslog; writing to"
36457 The use of syslog does not change what Exim logs or the format of its messages,
36458 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
36459 Exim's log lines are omitted when these lines are sent to syslog. Apart from
36460 that, the same strings are written to syslog as to log files. The syslog
36461 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
36462 by default, but you can change these by setting the &%syslog_facility%& and
36463 &%syslog_processname%& options, respectively. If Exim was compiled with
36464 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
36465 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
36466 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
36467 the time and host name to each line.
36468 The three log streams are mapped onto syslog priorities as follows:
36471 &'mainlog'& is mapped to LOG_INFO
36473 &'rejectlog'& is mapped to LOG_NOTICE
36475 &'paniclog'& is mapped to LOG_ALERT
36478 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
36479 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
36480 these are routed by syslog to the same place. You can suppress this duplication
36481 by setting &%syslog_duplication%& false.
36483 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
36484 entries contain multiple lines when headers are included. To cope with both
36485 these cases, entries written to syslog are split into separate &[syslog()]&
36486 calls at each internal newline, and also after a maximum of
36487 870 data characters. (This allows for a total syslog line length of 1024, when
36488 additions such as timestamps are added.) If you are running a syslog
36489 replacement that can handle lines longer than the 1024 characters allowed by
36490 RFC 3164, you should set
36492 SYSLOG_LONG_LINES=yes
36494 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
36495 lines, but it still splits at internal newlines in &'reject'& log entries.
36497 To make it easy to re-assemble split lines later, each component of a split
36498 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
36499 where <&'n'&> is the component number and <&'m'&> is the total number of
36500 components in the entry. The / delimiter is used when the line was split
36501 because it was too long; if it was split because of an internal newline, the \
36502 delimiter is used. For example, supposing the length limit to be 50 instead of
36503 870, the following would be the result of a typical rejection message to
36504 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
36505 name, and pid as added by syslog:
36507 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
36508 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
36509 [3/5] when scanning for sender: missing or malformed lo
36510 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
36513 The same error might cause the following lines to be written to &"rejectlog"&
36516 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
36517 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
36518 [3/18] er when scanning for sender: missing or malformed
36519 [4/18] local part in "<>" (envelope sender is <ph10@cam
36521 [6\18] Recipients: ph10@some.domain.cam.example
36522 [7\18] P Received: from [127.0.0.1] (ident=ph10)
36523 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
36524 [9\18] id 16RdAL-0006pc-00
36525 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
36526 [11\18] 09:43 +0100
36528 [13\18] Subject: this is a test header
36529 [18\18] X-something: this is another header
36530 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
36533 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
36535 Log lines that are neither too long nor contain newlines are written to syslog
36536 without modification.
36538 If only syslog is being used, the Exim monitor is unable to provide a log tail
36539 display, unless syslog is routing &'mainlog'& to a file on the local host and
36540 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
36545 .section "Log line flags" "SECID250"
36546 One line is written to the main log for each message received, and for each
36547 successful, unsuccessful, and delayed delivery. These lines can readily be
36548 picked out by the distinctive two-character flags that immediately follow the
36549 timestamp. The flags are:
36551 &`<=`& message arrival
36552 &`(=`& message fakereject
36553 &`=>`& normal message delivery
36554 &`->`& additional address in same delivery
36555 &`>>`& cutthrough message delivery
36556 &`*>`& delivery suppressed by &%-N%&
36557 &`**`& delivery failed; address bounced
36558 &`==`& delivery deferred; temporary problem
36562 .section "Logging message reception" "SECID251"
36563 .cindex "log" "reception line"
36564 The format of the single-line entry in the main log that is written for every
36565 message received is shown in the basic example below, which is split over
36566 several lines in order to fit it on the page:
36568 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
36569 H=mailer.fict.example [192.168.123.123] U=exim
36570 P=smtp S=5678 id=<incoming message id>
36572 The address immediately following &"<="& is the envelope sender address. A
36573 bounce message is shown with the sender address &"<>"&, and if it is locally
36574 generated, this is followed by an item of the form
36578 which is a reference to the message that caused the bounce to be sent.
36582 For messages from other hosts, the H and U fields identify the remote host and
36583 record the RFC 1413 identity of the user that sent the message, if one was
36584 received. The number given in square brackets is the IP address of the sending
36585 host. If there is a single, unparenthesized host name in the H field, as
36586 above, it has been verified to correspond to the IP address (see the
36587 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
36588 by the remote host in the SMTP HELO or EHLO command, and has not been
36589 verified. If verification yields a different name to that given for HELO or
36590 EHLO, the verified name appears first, followed by the HELO or EHLO
36591 name in parentheses.
36593 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
36594 without brackets, in the HELO or EHLO command, leading to entries in
36595 the log containing text like these examples:
36597 H=(10.21.32.43) [192.168.8.34]
36598 H=([10.21.32.43]) [192.168.8.34]
36600 This can be confusing. Only the final address in square brackets can be relied
36603 For locally generated messages (that is, messages not received over TCP/IP),
36604 the H field is omitted, and the U field contains the login name of the caller
36607 .cindex "authentication" "logging"
36608 .cindex "AUTH" "logging"
36609 For all messages, the P field specifies the protocol used to receive the
36610 message. This is the value that is stored in &$received_protocol$&. In the case
36611 of incoming SMTP messages, the value indicates whether or not any SMTP
36612 extensions (ESMTP), encryption, or authentication were used. If the SMTP
36613 session was encrypted, there is an additional X field that records the cipher
36614 suite that was used.
36616 .cindex log protocol
36617 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
36618 hosts that have authenticated themselves using the SMTP AUTH command. The first
36619 value is used when the SMTP connection was encrypted (&"secure"&). In this case
36620 there is an additional item A= followed by the name of the authenticator that
36621 was used. If an authenticated identification was set up by the authenticator's
36622 &%server_set_id%& option, this is logged too, separated by a colon from the
36623 authenticator name.
36625 .cindex "size" "of message"
36626 The id field records the existing message id, if present. The size of the
36627 received message is given by the S field. When the message is delivered,
36628 headers may be removed or added, so that the size of delivered copies of the
36629 message may not correspond with this value (and indeed may be different to each
36632 The &%log_selector%& option can be used to request the logging of additional
36633 data when a message is received. See section &<<SECTlogselector>>& below.
36637 .section "Logging deliveries" "SECID252"
36638 .cindex "log" "delivery line"
36639 The format of the single-line entry in the main log that is written for every
36640 delivery is shown in one of the examples below, for local and remote
36641 deliveries, respectively. Each example has been split into multiple lines in order
36642 to fit it on the page:
36644 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
36645 <marv@hitch.fict.example> R=localuser T=local_delivery
36646 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
36647 monk@holistic.fict.example R=dnslookup T=remote_smtp
36648 H=holistic.fict.example [192.168.234.234]
36650 For ordinary local deliveries, the original address is given in angle brackets
36651 after the final delivery address, which might be a pipe or a file. If
36652 intermediate address(es) exist between the original and the final address, the
36653 last of these is given in parentheses after the final address. The R and T
36654 fields record the router and transport that were used to process the address.
36656 If SMTP AUTH was used for the delivery there is an additional item A=
36657 followed by the name of the authenticator that was used.
36658 If an authenticated identification was set up by the authenticator's &%client_set_id%&
36659 option, this is logged too, separated by a colon from the authenticator name.
36661 If a shadow transport was run after a successful local delivery, the log line
36662 for the successful delivery has an item added on the end, of the form
36664 &`ST=<`&&'shadow transport name'&&`>`&
36666 If the shadow transport did not succeed, the error message is put in
36667 parentheses afterwards.
36669 .cindex "asterisk" "after IP address"
36670 When more than one address is included in a single delivery (for example, two
36671 SMTP RCPT commands in one transaction) the second and subsequent addresses are
36672 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
36673 down a single SMTP connection, an asterisk follows the IP address in the log
36674 lines for the second and subsequent messages.
36675 When two or more messages are delivered down a single TLS connection, the
36676 DNS and some TLS-related information logged for the first message delivered
36677 will not be present in the log lines for the second and subsequent messages.
36678 TLS cipher information is still available.
36680 .cindex "delivery" "cutthrough; logging"
36681 .cindex "cutthrough" "logging"
36682 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
36683 line precedes the reception line, since cutthrough waits for a possible
36684 rejection from the destination in case it can reject the sourced item.
36686 The generation of a reply message by a filter file gets logged as a
36687 &"delivery"& to the addressee, preceded by &">"&.
36689 The &%log_selector%& option can be used to request the logging of additional
36690 data when a message is delivered. See section &<<SECTlogselector>>& below.
36693 .section "Discarded deliveries" "SECID253"
36694 .cindex "discarded messages"
36695 .cindex "message" "discarded"
36696 .cindex "delivery" "discarded; logging"
36697 When a message is discarded as a result of the command &"seen finish"& being
36698 obeyed in a filter file which generates no deliveries, a log entry of the form
36700 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
36701 <low.club@bridge.example> R=userforward
36703 is written, to record why no deliveries are logged. When a message is discarded
36704 because it is aliased to &":blackhole:"& the log line is like this:
36706 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
36707 <hole@nowhere.example> R=blackhole_router
36711 .section "Deferred deliveries" "SECID254"
36712 When a delivery is deferred, a line of the following form is logged:
36714 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
36715 R=dnslookup T=smtp defer (146): Connection refused
36717 In the case of remote deliveries, the error is the one that was given for the
36718 last IP address that was tried. Details of individual SMTP failures are also
36719 written to the log, so the above line would be preceded by something like
36721 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
36722 mail1.endrest.example [192.168.239.239]: Connection refused
36724 When a deferred address is skipped because its retry time has not been reached,
36725 a message is written to the log, but this can be suppressed by setting an
36726 appropriate value in &%log_selector%&.
36730 .section "Delivery failures" "SECID255"
36731 .cindex "delivery" "failure; logging"
36732 If a delivery fails because an address cannot be routed, a line of the
36733 following form is logged:
36735 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
36736 <jim@trek99.example>: unknown mail domain
36738 If a delivery fails at transport time, the router and transport are shown, and
36739 the response from the remote host is included, as in this example:
36741 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
36742 R=dnslookup T=remote_smtp: SMTP error from remote mailer
36743 after pipelined RCPT TO:<ace400@pb.example>: host
36744 pbmail3.py.example [192.168.63.111]: 553 5.3.0
36745 <ace400@pb.example>...Addressee unknown
36747 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
36748 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
36749 disabling PIPELINING. The log lines for all forms of delivery failure are
36750 flagged with &`**`&.
36754 .section "Fake deliveries" "SECID256"
36755 .cindex "delivery" "fake; logging"
36756 If a delivery does not actually take place because the &%-N%& option has been
36757 used to suppress it, a normal delivery line is written to the log, except that
36758 &"=>"& is replaced by &"*>"&.
36762 .section "Completion" "SECID257"
36765 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
36767 is written to the main log when a message is about to be removed from the spool
36768 at the end of its processing.
36773 .section "Summary of Fields in Log Lines" "SECID258"
36774 .cindex "log" "summary of fields"
36775 A summary of the field identifiers that are used in log lines is shown in
36776 the following table:
36778 &`A `& authenticator name (and optional id and sender)
36779 &`C `& SMTP confirmation on delivery
36780 &` `& command list for &"no mail in SMTP session"&
36781 &`CV `& certificate verification status
36782 &`D `& duration of &"no mail in SMTP session"&
36783 &`DKIM`& domain verified in incoming message
36784 &`DN `& distinguished name from peer certificate
36785 &`DS `& DNSSEC secured lookups
36786 &`DT `& on &`=>`& lines: time taken for a delivery
36787 &`F `& sender address (on delivery lines)
36788 &`H `& host name and IP address
36789 &`I `& local interface used
36790 &`id `& message id for incoming message
36791 &`K `& CHUNKING extension used
36792 &`L `& on &`<=`& and &`=>`& lines: PIPELINING extension used
36793 &`M8S `& 8BITMIME status for incoming message
36794 &`P `& on &`<=`& lines: protocol used
36795 &` `& on &`=>`& and &`**`& lines: return path
36796 &`PRDR`& PRDR extension used
36797 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
36798 &`Q `& alternate queue name
36799 &`QT `& on &`=>`& lines: time spent on queue so far
36800 &` `& on &"Completed"& lines: time spent on queue
36801 &`R `& on &`<=`& lines: reference for local bounce
36802 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
36803 &`RT `& on &`<=`& lines: time taken for reception
36804 &`S `& size of message in bytes
36805 &`SNI `& server name indication from TLS client hello
36806 &`ST `& shadow transport name
36807 &`T `& on &`<=`& lines: message subject (topic)
36808 &`TFO `& connection took advantage of TCP Fast Open
36809 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
36810 &`U `& local user or RFC 1413 identity
36811 &`X `& TLS cipher suite
36815 .section "Other log entries" "SECID259"
36816 Various other types of log entry are written from time to time. Most should be
36817 self-explanatory. Among the more common are:
36820 .cindex "retry" "time not reached"
36821 &'retry time not reached'&&~&~An address previously suffered a temporary error
36822 during routing or local delivery, and the time to retry has not yet arrived.
36823 This message is not written to an individual message log file unless it happens
36824 during the first delivery attempt.
36826 &'retry time not reached for any host'&&~&~An address previously suffered
36827 temporary errors during remote delivery, and the retry time has not yet arrived
36828 for any of the hosts to which it is routed.
36830 .cindex "spool directory" "file locked"
36831 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
36832 some other Exim process is already working on the message. This can be quite
36833 common if queue running processes are started at frequent intervals. The
36834 &'exiwhat'& utility script can be used to find out what Exim processes are
36837 .cindex "error" "ignored"
36838 &'error ignored'&&~&~There are several circumstances that give rise to this
36841 Exim failed to deliver a bounce message whose age was greater than
36842 &%ignore_bounce_errors_after%&. The bounce was discarded.
36844 A filter file set up a delivery using the &"noerror"& option, and the delivery
36845 failed. The delivery was discarded.
36847 A delivery set up by a router configured with
36848 . ==== As this is a nested list, any displays it contains must be indented
36849 . ==== as otherwise they are too far to the left.
36853 failed. The delivery was discarded.
36856 .cindex DKIM "log line"
36857 &'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
36858 logging and the message has a DKIM signature header.
36865 .section "Reducing or increasing what is logged" "SECTlogselector"
36866 .cindex "log" "selectors"
36867 By setting the &%log_selector%& global option, you can disable some of Exim's
36868 default logging, or you can request additional logging. The value of
36869 &%log_selector%& is made up of names preceded by plus or minus characters. For
36872 log_selector = +arguments -retry_defer
36874 The list of optional log items is in the following table, with the default
36875 selection marked by asterisks:
36877 &` 8bitmime `& received 8BITMIME status
36878 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
36879 &` address_rewrite `& address rewriting
36880 &` all_parents `& all parents in => lines
36881 &` arguments `& command line arguments
36882 &`*connection_reject `& connection rejections
36883 &`*delay_delivery `& immediate delivery delayed
36884 &` deliver_time `& time taken to perform delivery
36885 &` delivery_size `& add &`S=`&&'nnn'& to => lines
36886 &`*dkim `& DKIM verified domain on <= lines
36887 &` dkim_verbose `& separate full DKIM verification result line, per signature
36888 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
36889 &` dnssec `& DNSSEC secured lookups
36890 &`*etrn `& ETRN commands
36891 &`*host_lookup_failed `& as it says
36892 &` ident_timeout `& timeout for ident connection
36893 &` incoming_interface `& local interface on <= and => lines
36894 &` incoming_port `& remote port on <= lines
36895 &`*lost_incoming_connection `& as it says (includes timeouts)
36896 &` millisec `& millisecond timestamps and RT,QT,DT,D times
36897 &` outgoing_interface `& local interface on => lines
36898 &` outgoing_port `& add remote port to => lines
36899 &`*queue_run `& start and end queue runs
36900 &` queue_time `& time on queue for one recipient
36901 &` queue_time_overall `& time on queue for whole message
36902 &` pid `& Exim process id
36903 &` pipelining `& PIPELINING use, on <= and => lines
36904 &` proxy `& proxy address on <= and => lines
36905 &` receive_time `& time taken to receive message
36906 &` received_recipients `& recipients on <= lines
36907 &` received_sender `& sender on <= lines
36908 &`*rejected_header `& header contents on reject log
36909 &`*retry_defer `& &"retry time not reached"&
36910 &` return_path_on_delivery `& put return path on => and ** lines
36911 &` sender_on_delivery `& add sender to => lines
36912 &`*sender_verify_fail `& sender verification failures
36913 &`*size_reject `& rejection because too big
36914 &`*skip_delivery `& delivery skipped in a queue run
36915 &`*smtp_confirmation `& SMTP confirmation on => lines
36916 &` smtp_connection `& incoming SMTP connections
36917 &` smtp_incomplete_transaction`& incomplete SMTP transactions
36918 &` smtp_mailauth `& AUTH argument to MAIL commands
36919 &` smtp_no_mail `& session with no MAIL commands
36920 &` smtp_protocol_error `& SMTP protocol errors
36921 &` smtp_syntax_error `& SMTP syntax errors
36922 &` subject `& contents of &'Subject:'& on <= lines
36923 &`*tls_certificate_verified `& certificate verification status
36924 &`*tls_cipher `& TLS cipher suite on <= and => lines
36925 &` tls_peerdn `& TLS peer DN on <= and => lines
36926 &` tls_sni `& TLS SNI on <= lines
36927 &` unknown_in_list `& DNS lookup failed in list match
36929 &` all `& all of the above
36931 See also the &%slow_lookup_log%& main configuration option,
36932 section &<<SECID99>>&
36934 More details on each of these items follows:
36938 .cindex "log" "8BITMIME"
36939 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
36940 which may help in tracking down interoperability issues with ancient MTAs
36941 that are not 8bit clean. This is added to the &"<="& line, tagged with
36942 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
36943 &`7BIT`& and &`8BITMIME`& respectively.
36945 .cindex "&%warn%& ACL verb" "log when skipping"
36946 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
36947 its conditions cannot be evaluated, a log line to this effect is written if
36948 this log selector is set.
36950 .cindex "log" "rewriting"
36951 .cindex "rewriting" "logging"
36952 &%address_rewrite%&: This applies both to global rewrites and per-transport
36953 rewrites, but not to rewrites in filters run as an unprivileged user (because
36954 such users cannot access the log).
36956 .cindex "log" "full parentage"
36957 &%all_parents%&: Normally only the original and final addresses are logged on
36958 delivery lines; with this selector, intermediate parents are given in
36959 parentheses between them.
36961 .cindex "log" "Exim arguments"
36962 .cindex "Exim arguments, logging"
36963 &%arguments%&: This causes Exim to write the arguments with which it was called
36964 to the main log, preceded by the current working directory. This is a debugging
36965 feature, added to make it easier to find out how certain MUAs call
36966 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
36967 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
36968 that are empty or that contain white space are quoted. Non-printing characters
36969 are shown as escape sequences. This facility cannot log unrecognized arguments,
36970 because the arguments are checked before the configuration file is read. The
36971 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
36972 between the caller and Exim.
36974 .cindex "log" "connection rejections"
36975 &%connection_reject%&: A log entry is written whenever an incoming SMTP
36976 connection is rejected, for whatever reason.
36978 .cindex "log" "delayed delivery"
36979 .cindex "delayed delivery, logging"
36980 &%delay_delivery%&: A log entry is written whenever a delivery process is not
36981 started for an incoming message because the load is too high or too many
36982 messages were received on one connection. Logging does not occur if no delivery
36983 process is started because &%queue_only%& is set or &%-odq%& was used.
36985 .cindex "log" "delivery duration"
36986 &%deliver_time%&: For each delivery, the amount of real time it has taken to
36987 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
36988 If millisecond logging is enabled, short times will be shown with greater
36989 precision, eg. &`DT=0.304s`&.
36991 .cindex "log" "message size on delivery"
36992 .cindex "size" "of message"
36993 &%delivery_size%&: For each delivery, the size of message delivered is added to
36994 the &"=>"& line, tagged with S=.
36996 .cindex log "DKIM verification"
36997 .cindex DKIM "verification logging"
36998 &%dkim%&: For message acceptance log lines, when an DKIM signature in the header
36999 verifies successfully a tag of DKIM is added, with one of the verified domains.
37001 .cindex log "DKIM verification"
37002 .cindex DKIM "verification logging"
37003 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
37005 .cindex "log" "dnslist defer"
37006 .cindex "DNS list" "logging defer"
37007 .cindex "black list (DNS)"
37008 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
37009 DNS black list suffers a temporary error.
37012 .cindex dnssec logging
37013 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
37014 dns lookups gave secure results a tag of DS is added.
37015 For acceptance this covers the reverse and forward lookups for host name verification.
37016 It does not cover helo-name verification.
37017 For delivery this covers the SRV, MX, A and/or AAAA lookups.
37019 .cindex "log" "ETRN commands"
37020 .cindex "ETRN" "logging"
37021 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
37022 is run to determine whether or not it is actually accepted. An invalid ETRN
37023 command, or one received within a message transaction is not logged by this
37024 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
37026 .cindex "log" "host lookup failure"
37027 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
37028 any addresses, or when a lookup of an IP address fails to find a host name, a
37029 log line is written. This logging does not apply to direct DNS lookups when
37030 routing email addresses, but it does apply to &"byname"& lookups.
37032 .cindex "log" "ident timeout"
37033 .cindex "RFC 1413" "logging timeout"
37034 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
37035 client's ident port times out.
37037 .cindex "log" "incoming interface"
37038 .cindex "log" "local interface"
37039 .cindex "log" "local address and port"
37040 .cindex "TCP/IP" "logging local address and port"
37041 .cindex "interface" "logging"
37042 &%incoming_interface%&: The interface on which a message was received is added
37043 to the &"<="& line as an IP address in square brackets, tagged by I= and
37044 followed by a colon and the port number. The local interface and port are also
37045 added to other SMTP log lines, for example, &"SMTP connection from"&, to
37046 rejection lines, and (despite the name) to outgoing &"=>"& and &"->"& lines.
37047 The latter can be disabled by turning off the &%outgoing_interface%& option.
37049 .cindex log "incoming proxy address"
37050 .cindex proxy "logging proxy address"
37051 .cindex "TCP/IP" "logging proxy address"
37052 &%proxy%&: The internal (closest to the system running Exim) IP address
37053 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
37054 on a proxied connection
37055 or the &"=>"& line for a message delivered on a proxied connection.
37056 See &<<SECTproxyInbound>>& for more information.
37058 .cindex "log" "incoming remote port"
37059 .cindex "port" "logging remote"
37060 .cindex "TCP/IP" "logging incoming remote port"
37061 .vindex "&$sender_fullhost$&"
37062 .vindex "&$sender_rcvhost$&"
37063 &%incoming_port%&: The remote port number from which a message was received is
37064 added to log entries and &'Received:'& header lines, following the IP address
37065 in square brackets, and separated from it by a colon. This is implemented by
37066 changing the value that is put in the &$sender_fullhost$& and
37067 &$sender_rcvhost$& variables. Recording the remote port number has become more
37068 important with the widening use of NAT (see RFC 2505).
37070 .cindex "log" "dropped connection"
37071 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
37072 connection is unexpectedly dropped.
37074 .cindex "log" "millisecond timestamps"
37075 .cindex millisecond logging
37076 .cindex timestamps "millisecond, in logs"
37077 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
37078 appended to the seconds value.
37080 .cindex "log" "outgoing interface"
37081 .cindex "log" "local interface"
37082 .cindex "log" "local address and port"
37083 .cindex "TCP/IP" "logging local address and port"
37084 .cindex "interface" "logging"
37085 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
37086 interface on which a message was sent is added to delivery lines as an I= tag
37087 followed by IP address in square brackets. You can disable this by turning
37088 off the &%outgoing_interface%& option.
37090 .cindex "log" "outgoing remote port"
37091 .cindex "port" "logging outgoing remote"
37092 .cindex "TCP/IP" "logging outgoing remote port"
37093 &%outgoing_port%&: The remote port number is added to delivery log lines (those
37094 containing => tags) following the IP address.
37095 The local port is also added if &%incoming_interface%& and
37096 &%outgoing_interface%& are both enabled.
37097 This option is not included in the default setting, because for most ordinary
37098 configurations, the remote port number is always 25 (the SMTP port), and the
37099 local port is a random ephemeral port.
37101 .cindex "log" "process ids in"
37102 .cindex "pid (process id)" "in log lines"
37103 &%pid%&: The current process id is added to every log line, in square brackets,
37104 immediately after the time and date.
37106 .cindex log pipelining
37107 .cindex pipelining "logging outgoing"
37108 &%pipelining%&: A field is added to delivery and accept
37109 log lines when the ESMTP PIPELINING extension was used.
37110 The field is a single "L".
37112 On accept lines, where PIPELINING was offered but not used by the client,
37113 the field has a minus appended.
37115 .cindex "log" "queue run"
37116 .cindex "queue runner" "logging"
37117 &%queue_run%&: The start and end of every queue run are logged.
37119 .cindex "log" "queue time"
37120 &%queue_time%&: The amount of time the message has been in the queue on the
37121 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
37122 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
37123 includes reception time as well as the delivery time for the current address.
37124 This means that it may be longer than the difference between the arrival and
37125 delivery log line times, because the arrival log line is not written until the
37126 message has been successfully received.
37127 If millisecond logging is enabled, short times will be shown with greater
37128 precision, eg. &`QT=1.578s`&.
37130 &%queue_time_overall%&: The amount of time the message has been in the queue on
37131 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
37132 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
37133 message, so it includes reception time as well as the total delivery time.
37135 .cindex "log" "receive duration"
37136 &%receive_time%&: For each message, the amount of real time it has taken to
37137 perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
37138 If millisecond logging is enabled, short times will be shown with greater
37139 precision, eg. &`RT=0.204s`&.
37141 .cindex "log" "recipients"
37142 &%received_recipients%&: The recipients of a message are listed in the main log
37143 as soon as the message is received. The list appears at the end of the log line
37144 that is written when a message is received, preceded by the word &"for"&. The
37145 addresses are listed after they have been qualified, but before any rewriting
37147 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
37150 .cindex "log" "sender reception"
37151 &%received_sender%&: The unrewritten original sender of a message is added to
37152 the end of the log line that records the message's arrival, after the word
37153 &"from"& (before the recipients if &%received_recipients%& is also set).
37155 .cindex "log" "header lines for rejection"
37156 &%rejected_header%&: If a message's header has been received at the time a
37157 rejection is written to the reject log, the complete header is added to the
37158 log. Header logging can be turned off individually for messages that are
37159 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
37161 .cindex "log" "retry defer"
37162 &%retry_defer%&: A log line is written if a delivery is deferred because a
37163 retry time has not yet been reached. However, this &"retry time not reached"&
37164 message is always omitted from individual message logs after the first delivery
37167 .cindex "log" "return path"
37168 &%return_path_on_delivery%&: The return path that is being transmitted with
37169 the message is included in delivery and bounce lines, using the tag P=.
37170 This is omitted if no delivery actually happens, for example, if routing fails,
37171 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
37173 .cindex "log" "sender on delivery"
37174 &%sender_on_delivery%&: The message's sender address is added to every delivery
37175 and bounce line, tagged by F= (for &"from"&).
37176 This is the original sender that was received with the message; it is not
37177 necessarily the same as the outgoing return path.
37179 .cindex "log" "sender verify failure"
37180 &%sender_verify_fail%&: If this selector is unset, the separate log line that
37181 gives details of a sender verification failure is not written. Log lines for
37182 the rejection of SMTP commands contain just &"sender verify failed"&, so some
37185 .cindex "log" "size rejection"
37186 &%size_reject%&: A log line is written whenever a message is rejected because
37189 .cindex "log" "frozen messages; skipped"
37190 .cindex "frozen messages" "logging skipping"
37191 &%skip_delivery%&: A log line is written whenever a message is skipped during a
37192 queue run because it is frozen or because another process is already delivering
37194 .cindex "&""spool file is locked""&"
37195 The message that is written is &"spool file is locked"&.
37197 .cindex "log" "smtp confirmation"
37198 .cindex "SMTP" "logging confirmation"
37199 .cindex "LMTP" "logging confirmation"
37200 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
37201 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
37202 A number of MTAs (including Exim) return an identifying string in this
37205 .cindex "log" "SMTP connections"
37206 .cindex "SMTP" "logging connections"
37207 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
37208 established or closed, unless the connection is from a host that matches
37209 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
37210 only when the closure is unexpected.) This applies to connections from local
37211 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
37212 dropped in the middle of a message, a log line is always written, whether or
37213 not this selector is set, but otherwise nothing is written at the start and end
37214 of connections unless this selector is enabled.
37216 For TCP/IP connections to an Exim daemon, the current number of connections is
37217 included in the log message for each new connection, but note that the count is
37218 reset if the daemon is restarted.
37219 Also, because connections are closed (and the closure is logged) in
37220 subprocesses, the count may not include connections that have been closed but
37221 whose termination the daemon has not yet noticed. Thus, while it is possible to
37222 match up the opening and closing of connections in the log, the value of the
37223 logged counts may not be entirely accurate.
37225 .cindex "log" "SMTP transaction; incomplete"
37226 .cindex "SMTP" "logging incomplete transactions"
37227 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
37228 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
37229 and the message sender plus any accepted recipients are included in the log
37230 line. This can provide evidence of dictionary attacks.
37232 .cindex "log" "non-MAIL SMTP sessions"
37233 .cindex "MAIL" "logging session without"
37234 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
37235 connection terminates without having issued a MAIL command. This includes both
37236 the case when the connection is dropped, and the case when QUIT is used. It
37237 does not include cases where the connection is rejected right at the start (by
37238 an ACL, or because there are too many connections, or whatever). These cases
37239 already have their own log lines.
37241 The log line that is written contains the identity of the client in the usual
37242 way, followed by D= and a time, which records the duration of the connection.
37243 If the connection was authenticated, this fact is logged exactly as it is for
37244 an incoming message, with an A= item. If the connection was encrypted, CV=,
37245 DN=, and X= items may appear as they do for an incoming message, controlled by
37246 the same logging options.
37248 Finally, if any SMTP commands were issued during the connection, a C= item
37249 is added to the line, listing the commands that were used. For example,
37253 shows that the client issued QUIT straight after EHLO. If there were fewer
37254 than 20 commands, they are all listed. If there were more than 20 commands,
37255 the last 20 are listed, preceded by &"..."&. However, with the default
37256 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
37257 have been aborted before 20 non-mail commands are processed.
37259 &%smtp_mailauth%&: A third subfield with the authenticated sender,
37260 colon-separated, is appended to the A= item for a message arrival or delivery
37261 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
37262 was accepted or used.
37264 .cindex "log" "SMTP protocol error"
37265 .cindex "SMTP" "logging protocol error"
37266 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
37267 encountered. Exim does not have perfect detection of all protocol errors
37268 because of transmission delays and the use of pipelining. If PIPELINING has
37269 been advertised to a client, an Exim server assumes that the client will use
37270 it, and therefore it does not count &"expected"& errors (for example, RCPT
37271 received after rejecting MAIL) as protocol errors.
37273 .cindex "SMTP" "logging syntax errors"
37274 .cindex "SMTP" "syntax errors; logging"
37275 .cindex "SMTP" "unknown command; logging"
37276 .cindex "log" "unknown SMTP command"
37277 .cindex "log" "SMTP syntax error"
37278 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
37279 encountered. An unrecognized command is treated as a syntax error. For an
37280 external connection, the host identity is given; for an internal connection
37281 using &%-bs%& the sender identification (normally the calling user) is given.
37283 .cindex "log" "subject"
37284 .cindex "subject, logging"
37285 &%subject%&: The subject of the message is added to the arrival log line,
37286 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
37287 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
37288 specifies whether characters with values greater than 127 should be logged
37289 unchanged, or whether they should be rendered as escape sequences.
37291 .cindex "log" "certificate verification"
37293 .cindex DANE logging
37294 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
37295 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
37297 using a CA trust anchor,
37298 &`CA=dane`& if using a DNS trust anchor,
37299 and &`CV=no`& if not.
37301 .cindex "log" "TLS cipher"
37302 .cindex "TLS" "logging cipher"
37303 &%tls_cipher%&: When a message is sent or received over an encrypted
37304 connection, the cipher suite used is added to the log line, preceded by X=.
37306 .cindex "log" "TLS peer DN"
37307 .cindex "TLS" "logging peer DN"
37308 &%tls_peerdn%&: When a message is sent or received over an encrypted
37309 connection, and a certificate is supplied by the remote host, the peer DN is
37310 added to the log line, preceded by DN=.
37312 .cindex "log" "TLS SNI"
37313 .cindex "TLS" "logging SNI"
37314 &%tls_sni%&: When a message is received over an encrypted connection, and
37315 the remote host provided the Server Name Indication extension, the SNI is
37316 added to the log line, preceded by SNI=.
37318 .cindex "log" "DNS failure in list"
37319 &%unknown_in_list%&: This setting causes a log entry to be written when the
37320 result of a list match is failure because a DNS lookup failed.
37324 .section "Message log" "SECID260"
37325 .cindex "message" "log file for"
37326 .cindex "log" "message log; description of"
37327 .cindex "&_msglog_& directory"
37328 .oindex "&%preserve_message_logs%&"
37329 In addition to the general log files, Exim writes a log file for each message
37330 that it handles. The names of these per-message logs are the message ids, and
37331 they are kept in the &_msglog_& sub-directory of the spool directory. Each
37332 message log contains copies of the log lines that apply to the message. This
37333 makes it easier to inspect the status of an individual message without having
37334 to search the main log. A message log is deleted when processing of the message
37335 is complete, unless &%preserve_message_logs%& is set, but this should be used
37336 only with great care because they can fill up your disk very quickly.
37338 On a heavily loaded system, it may be desirable to disable the use of
37339 per-message logs, in order to reduce disk I/O. This can be done by setting the
37340 &%message_logs%& option false.
37346 . ////////////////////////////////////////////////////////////////////////////
37347 . ////////////////////////////////////////////////////////////////////////////
37349 .chapter "Exim utilities" "CHAPutils"
37350 .scindex IIDutils "utilities"
37351 A number of utility scripts and programs are supplied with Exim and are
37352 described in this chapter. There is also the Exim Monitor, which is covered in
37353 the next chapter. The utilities described here are:
37355 .itable none 0 0 3 7* left 15* left 40* left
37356 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
37357 "list what Exim processes are doing"
37358 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
37359 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
37360 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
37361 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
37363 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
37364 .irow &<<SECTmailstat>>& &'eximstats'& &&&
37365 "extract statistics from the log"
37366 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
37367 "check address acceptance from given IP"
37368 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
37369 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
37370 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
37371 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
37372 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
37373 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
37376 Another utility that might be of use to sites with many MTAs is Tom Kistner's
37377 &'exilog'&. It provides log visualizations across multiple Exim servers. See
37378 &url(https://duncanthrax.net/exilog/) for details.
37383 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
37384 .cindex "&'exiwhat'&"
37385 .cindex "process, querying"
37387 On operating systems that can restart a system call after receiving a signal
37388 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
37389 a line describing what it is doing to the file &_exim-process.info_& in the
37390 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
37391 processes it can find, having first emptied the file. It then waits for one
37392 second to allow the Exim processes to react before displaying the results. In
37393 order to run &'exiwhat'& successfully you have to have sufficient privilege to
37394 send the signal to the Exim processes, so it is normally run as root.
37396 &*Warning*&: This is not an efficient process. It is intended for occasional
37397 use by system administrators. It is not sensible, for example, to set up a
37398 script that sends SIGUSR1 signals to Exim processes at short intervals.
37401 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
37402 varies in different operating systems. Not only are different options used,
37403 but the format of the output is different. For this reason, there are some
37404 system configuration options that configure exactly how &'exiwhat'& works. If
37405 it doesn't seem to be working for you, check the following compile-time
37408 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
37409 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
37410 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
37411 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
37413 An example of typical output from &'exiwhat'& is
37415 164 daemon: -q1h, listening on port 25
37416 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
37417 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
37418 [10.19.42.42] (editor@ref.example)
37419 10592 handling incoming call from [192.168.243.242]
37420 10628 accepting a local non-SMTP message
37422 The first number in the output line is the process number. The third line has
37423 been split here, in order to fit it on the page.
37427 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
37428 .cindex "&'exiqgrep'&"
37429 .cindex "queue" "grepping"
37430 This utility is a Perl script contributed by Matt Hubbard. It runs
37434 or (in case &*-a*& switch is specified)
37438 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
37439 contain alternate exim configuration the queue management might be using.
37441 to obtain a queue listing, and then greps the output to select messages
37442 that match given criteria. The following selection options are available:
37445 .vitem &*-f*&&~<&'regex'&>
37446 Match the sender address using a case-insensitive search. The field that is
37447 tested is enclosed in angle brackets, so you can test for bounce messages with
37451 .vitem &*-r*&&~<&'regex'&>
37452 Match a recipient address using a case-insensitive search. The field that is
37453 tested is not enclosed in angle brackets.
37455 .vitem &*-s*&&~<&'regex'&>
37456 Match against the size field.
37458 .vitem &*-y*&&~<&'seconds'&>
37459 Match messages that are younger than the given time.
37461 .vitem &*-o*&&~<&'seconds'&>
37462 Match messages that are older than the given time.
37465 Match only frozen messages.
37468 Match only non-frozen messages.
37471 The following options control the format of the output:
37475 Display only the count of matching messages.
37478 Long format &-- display the full message information as output by Exim. This is
37482 Display message ids only.
37485 Brief format &-- one line per message.
37488 Display messages in reverse order.
37491 Include delivered recipients in queue listing.
37494 There is one more option, &%-h%&, which outputs a list of options.
37498 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
37499 .cindex "&'exiqsumm'&"
37500 .cindex "queue" "summary"
37501 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
37502 -bp`& and produces a summary of the messages in the queue. Thus, you use it by
37503 running a command such as
37505 exim -bp | exiqsumm
37507 The output consists of one line for each domain that has messages waiting for
37508 it, as in the following example:
37510 3 2322 74m 66m msn.com.example
37512 Each line lists the number of pending deliveries for a domain, their total
37513 volume, and the length of time that the oldest and the newest messages have
37514 been waiting. Note that the number of pending deliveries is greater than the
37515 number of messages when messages have more than one recipient.
37517 A summary line is output at the end. By default the output is sorted on the
37518 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
37519 the output to be sorted by oldest message and by count of messages,
37520 respectively. There are also three options that split the messages for each
37521 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
37522 separates frozen messages, and &%-s%& separates messages according to their
37525 The output of &'exim -bp'& contains the original addresses in the message, so
37526 this also applies to the output from &'exiqsumm'&. No domains from addresses
37527 generated by aliasing or forwarding are included (unless the &%one_time%&
37528 option of the &(redirect)& router has been used to convert them into &"top
37529 level"& addresses).
37534 .section "Extracting specific information from the log (exigrep)" &&&
37536 .cindex "&'exigrep'&"
37537 .cindex "log" "extracts; grepping for"
37538 The &'exigrep'& utility is a Perl script that searches one or more main log
37539 files for entries that match a given pattern. When it finds a match, it
37540 extracts all the log entries for the relevant message, not just those that
37541 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
37542 given message, or all mail for a given user, or for a given host, for example.
37543 The input files can be in Exim log format or syslog format.
37544 If a matching log line is not associated with a specific message, it is
37545 included in &'exigrep'&'s output without any additional lines. The usage is:
37547 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
37549 If no log filenames are given on the command line, the standard input is read.
37551 The &%-t%& argument specifies a number of seconds. It adds an additional
37552 condition for message selection. Messages that are complete are shown only if
37553 they spent more than <&'n'&> seconds in the queue.
37555 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
37556 makes it case-sensitive. This may give a performance improvement when searching
37557 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
37558 option; with &%-I%& they do not. In both cases it is possible to change the
37559 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
37561 The &%-l%& option means &"literal"&, that is, treat all characters in the
37562 pattern as standing for themselves. Otherwise the pattern must be a Perl
37563 regular expression.
37565 The &%-v%& option inverts the matching condition. That is, a line is selected
37566 if it does &'not'& match the pattern.
37568 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
37569 that are generated as a result/response to a message that &'exigrep'& matched
37573 user_a sends a message to user_b, which generates a bounce back to user_b. If
37574 &'exigrep'& is used to search for &"user_a"&, only the first message will be
37575 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
37576 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
37577 when searching for &"user_a"& will show both messages since the bounce is
37578 &"related"& to or a &"result"& of the first message that was found by the
37581 If the location of a &'zcat'& command is known from the definition of
37582 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
37583 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
37584 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
37585 autodetection of some well known compression extensions.
37588 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
37589 .cindex "&'exipick'&"
37590 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
37591 lists messages from the queue according to a variety of criteria. For details
37592 of &'exipick'&'s facilities, run &'exipick'& with
37593 the &%--help%& option.
37596 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
37597 .cindex "log" "cycling local files"
37598 .cindex "cycling logs"
37599 .cindex "&'exicyclog'&"
37600 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
37601 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
37602 you are using log files with datestamps in their names (see section
37603 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
37604 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
37605 There are two command line options for &'exicyclog'&:
37607 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
37608 default that is set when Exim is built. The default default is 10.
37610 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
37611 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
37612 overriding the script's default, which is to find the setting from Exim's
37616 Each time &'exicyclog'& is run the filenames get &"shuffled down"& by one. If
37617 the main log filename is &_mainlog_& (the default) then when &'exicyclog'& is
37618 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
37619 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
37620 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
37621 logs are handled similarly.
37623 If the limit is greater than 99, the script uses 3-digit numbers such as
37624 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
37625 to one that is greater, or &'vice versa'&, you will have to fix the names of
37626 any existing log files.
37628 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
37629 the end are deleted. All files with numbers greater than 01 are compressed,
37630 using a compression command which is configured by the COMPRESS_COMMAND
37631 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
37632 root &%crontab%& entry of the form
37634 1 0 * * * su exim -c /usr/exim/bin/exicyclog
37636 assuming you have used the name &"exim"& for the Exim user. You can run
37637 &'exicyclog'& as root if you wish, but there is no need.
37641 .section "Mail statistics (eximstats)" "SECTmailstat"
37642 .cindex "statistics"
37643 .cindex "&'eximstats'&"
37644 A Perl script called &'eximstats'& is provided for extracting statistical
37645 information from log files. The output is either plain text, or HTML.
37646 . --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan
37647 . --- 404 error and everything else points to that.
37649 The &'eximstats'& script has been hacked about quite a bit over time. The
37650 latest version is the result of some extensive revision by Steve Campbell. A
37651 lot of information is given by default, but there are options for suppressing
37652 various parts of it. Following any options, the arguments to the script are a
37653 list of files, which should be main log files. For example:
37655 eximstats -nr /var/spool/exim/log/mainlog.01
37657 By default, &'eximstats'& extracts information about the number and volume of
37658 messages received from or delivered to various hosts. The information is sorted
37659 both by message count and by volume, and the top fifty hosts in each category
37660 are listed on the standard output. Similar information, based on email
37661 addresses or domains instead of hosts can be requested by means of various
37662 options. For messages delivered and received locally, similar statistics are
37663 also produced per user.
37665 The output also includes total counts and statistics about delivery errors, and
37666 histograms showing the number of messages received and deliveries made in each
37667 hour of the day. A delivery with more than one address in its envelope (for
37668 example, an SMTP transaction with more than one RCPT command) is counted
37669 as a single delivery by &'eximstats'&.
37671 Though normally more deliveries than receipts are reported (as messages may
37672 have multiple recipients), it is possible for &'eximstats'& to report more
37673 messages received than delivered, even though the queue is empty at the start
37674 and end of the period in question. If an incoming message contains no valid
37675 recipients, no deliveries are recorded for it. A bounce message is handled as
37676 an entirely separate message.
37678 &'eximstats'& always outputs a grand total summary giving the volume and number
37679 of messages received and deliveries made, and the number of hosts involved in
37680 each case. It also outputs the number of messages that were delayed (that is,
37681 not completely delivered at the first attempt), and the number that had at
37682 least one address that failed.
37684 The remainder of the output is in sections that can be independently disabled
37685 or modified by various options. It consists of a summary of deliveries by
37686 transport, histograms of messages received and delivered per time interval
37687 (default per hour), information about the time messages spent in the queue,
37688 a list of relayed messages, lists of the top fifty sending hosts, local
37689 senders, destination hosts, and destination local users by count and by volume,
37690 and a list of delivery errors that occurred.
37692 The relay information lists messages that were actually relayed, that is, they
37693 came from a remote host and were directly delivered to some other remote host,
37694 without being processed (for example, for aliasing or forwarding) locally.
37696 There are quite a few options for &'eximstats'& to control exactly what it
37697 outputs. These are documented in the Perl script itself, and can be extracted
37698 by running the command &(perldoc)& on the script. For example:
37700 perldoc /usr/exim/bin/eximstats
37703 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
37704 .cindex "&'exim_checkaccess'&"
37705 .cindex "policy control" "checking access"
37706 .cindex "checking access"
37707 The &%-bh%& command line argument allows you to run a fake SMTP session with
37708 debugging output, in order to check what Exim is doing when it is applying
37709 policy controls to incoming SMTP mail. However, not everybody is sufficiently
37710 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
37711 sometimes you just want to answer the question &"Does this address have
37712 access?"& without bothering with any further details.
37714 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
37715 two arguments, an IP address and an email address:
37717 exim_checkaccess 10.9.8.7 A.User@a.domain.example
37719 The utility runs a call to Exim with the &%-bh%& option, to test whether the
37720 given email address would be accepted in a RCPT command in a TCP/IP
37721 connection from the host with the given IP address. The output of the utility
37722 is either the word &"accepted"&, or the SMTP error response, for example:
37725 550 Relay not permitted
37727 When running this test, the utility uses &`<>`& as the envelope sender address
37728 for the MAIL command, but you can change this by providing additional
37729 options. These are passed directly to the Exim command. For example, to specify
37730 that the test is to be run with the sender address &'himself@there.example'&
37733 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
37734 -f himself@there.example
37736 Note that these additional Exim command line items must be given after the two
37737 mandatory arguments.
37739 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
37740 while running its checks. You can run checks that include callouts by using
37741 &%-bhc%&, but this is not yet available in a &"packaged"& form.
37745 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
37746 .cindex "DBM" "building dbm files"
37747 .cindex "building DBM files"
37748 .cindex "&'exim_dbmbuild'&"
37749 .cindex "lower casing"
37750 .cindex "binary zero" "in lookup key"
37751 The &'exim_dbmbuild'& program reads an input file containing keys and data in
37752 the format used by the &(lsearch)& lookup (see section
37753 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
37754 names as keys and the remainder of the information as data. The lower-casing
37755 can be prevented by calling the program with the &%-nolc%& option.
37757 A terminating zero is included as part of the key string. This is expected by
37758 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
37759 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
37760 strings or the data strings. The &(dbmnz)& lookup type can be used with such
37763 The program requires two arguments: the name of the input file (which can be a
37764 single hyphen to indicate the standard input), and the name of the output file.
37765 It creates the output under a temporary name, and then renames it if all went
37769 If the native DB interface is in use (USE_DB is set in a compile-time
37770 configuration file &-- this is common in free versions of Unix) the two
37771 filenames must be different, because in this mode the Berkeley DB functions
37772 create a single output file using exactly the name given. For example,
37774 exim_dbmbuild /etc/aliases /etc/aliases.db
37776 reads the system alias file and creates a DBM version of it in
37777 &_/etc/aliases.db_&.
37779 In systems that use the &'ndbm'& routines (mostly proprietary versions of
37780 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
37781 environment, the suffixes are added to the second argument of
37782 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
37783 when the Berkeley functions are used in compatibility mode (though this is not
37784 recommended), because in that case it adds a &_.db_& suffix to the filename.
37786 If a duplicate key is encountered, the program outputs a warning, and when it
37787 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
37788 option is used. By default, only the first of a set of duplicates is used &--
37789 this makes it compatible with &(lsearch)& lookups. There is an option
37790 &%-lastdup%& which causes it to use the data for the last duplicate instead.
37791 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
37792 &%stderr%&. For other errors, where it doesn't actually make a new file, the
37798 .section "Finding individual retry times (exinext)" "SECTfinindret"
37799 .cindex "retry" "times"
37800 .cindex "&'exinext'&"
37801 A utility called &'exinext'& (mostly a Perl script) provides the ability to
37802 fish specific information out of the retry database. Given a mail domain (or a
37803 complete address), it looks up the hosts for that domain, and outputs any retry
37804 information for the hosts or for the domain. At present, the retry information
37805 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
37806 output. For example:
37808 $ exinext piglet@milne.fict.example
37809 kanga.milne.example:192.168.8.1 error 146: Connection refused
37810 first failed: 21-Feb-1996 14:57:34
37811 last tried: 21-Feb-1996 14:57:34
37812 next try at: 21-Feb-1996 15:02:34
37813 roo.milne.example:192.168.8.3 error 146: Connection refused
37814 first failed: 20-Jan-1996 13:12:08
37815 last tried: 21-Feb-1996 11:42:03
37816 next try at: 21-Feb-1996 19:42:03
37817 past final cutoff time
37819 You can also give &'exinext'& a local part, without a domain, and it
37820 will give any retry information for that local part in your default domain.
37821 A message id can be used to obtain retry information pertaining to a specific
37822 message. This exists only when an attempt to deliver a message to a remote host
37823 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
37824 &'exinext'& is not particularly efficient, but then it is not expected to be
37827 The &'exinext'& utility calls Exim to find out information such as the location
37828 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
37829 passed on to the &'exim'& commands. The first specifies an alternate Exim
37830 configuration file, and the second sets macros for use within the configuration
37831 file. These features are mainly to help in testing, but might also be useful in
37832 environments where more than one configuration file is in use.
37836 .section "Hints database maintenance" "SECThindatmai"
37837 .cindex "hints database" "maintenance"
37838 .cindex "maintaining Exim's hints database"
37839 Three utility programs are provided for maintaining the DBM files that Exim
37840 uses to contain its delivery hint information. Each program requires two
37841 arguments. The first specifies the name of Exim's spool directory, and the
37842 second is the name of the database it is to operate on. These are as follows:
37845 &'retry'&: the database of retry information
37847 &'wait-'&<&'transport name'&>: databases of information about messages waiting
37850 &'callout'&: the callout cache
37852 &'ratelimit'&: the data for implementing the ratelimit ACL condition
37854 &'misc'&: other hints data
37857 The &'misc'& database is used for
37860 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
37862 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
37863 &(smtp)& transport)
37865 Limiting the concurrency of specific transports (when &%max_parallel%& is set
37871 .section "exim_dumpdb" "SECID261"
37872 .cindex "&'exim_dumpdb'&"
37873 The entire contents of a database are written to the standard output by the
37874 &'exim_dumpdb'& program, which has no options or arguments other than the
37875 spool and database names. For example, to dump the retry database:
37877 exim_dumpdb /var/spool/exim retry
37879 Two lines of output are produced for each entry:
37881 T:mail.ref.example:192.168.242.242 146 77 Connection refused
37882 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
37884 The first item on the first line is the key of the record. It starts with one
37885 of the letters R, or T, depending on whether it refers to a routing or
37886 transport retry. For a local delivery, the next part is the local address; for
37887 a remote delivery it is the name of the remote host, followed by its failing IP
37888 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
37889 transport). If the remote port is not the standard one (port 25), it is added
37890 to the IP address. Then there follows an error code, an additional error code,
37891 and a textual description of the error.
37893 The three times on the second line are the time of first failure, the time of
37894 the last delivery attempt, and the computed time for the next attempt. The line
37895 ends with an asterisk if the cutoff time for the last retry rule has been
37898 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
37899 consists of a host name followed by a list of ids for messages that are or were
37900 waiting to be delivered to that host. If there are a very large number for any
37901 one host, continuation records, with a sequence number added to the host name,
37902 may be seen. The data in these records is often out of date, because a message
37903 may be routed to several alternative hosts, and Exim makes no effort to keep
37908 .section "exim_tidydb" "SECID262"
37909 .cindex "&'exim_tidydb'&"
37910 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
37911 database. If run with no options, it removes all records that are more than 30
37912 days old. The age is calculated from the date and time that the record was last
37913 updated. Note that, in the case of the retry database, it is &'not'& the time
37914 since the first delivery failure. Information about a host that has been down
37915 for more than 30 days will remain in the database, provided that the record is
37916 updated sufficiently often.
37918 The cutoff date can be altered by means of the &%-t%& option, which must be
37919 followed by a time. For example, to remove all records older than a week from
37920 the retry database:
37922 exim_tidydb -t 7d /var/spool/exim retry
37924 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
37925 message ids. In the former these appear as data in records keyed by host &--
37926 they were messages that were waiting for that host &-- and in the latter they
37927 are the keys for retry information for messages that have suffered certain
37928 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
37929 message ids in database records are those of messages that are still on the
37930 queue. Message ids for messages that no longer exist are removed from
37931 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
37932 For the &'retry'& database, records whose keys are non-existent message ids are
37933 removed. The &'exim_tidydb'& utility outputs comments on the standard output
37934 whenever it removes information from the database.
37936 Certain records are automatically removed by Exim when they are no longer
37937 needed, but others are not. For example, if all the MX hosts for a domain are
37938 down, a retry record is created for each one. If the primary MX host comes back
37939 first, its record is removed when Exim successfully delivers to it, but the
37940 records for the others remain because Exim has not tried to use those hosts.
37942 It is important, therefore, to run &'exim_tidydb'& periodically on all the
37943 hints databases. You should do this at a quiet time of day, because it requires
37944 a database to be locked (and therefore inaccessible to Exim) while it does its
37945 work. Removing records from a DBM file does not normally make the file smaller,
37946 but all the common DBM libraries are able to re-use the space that is released.
37947 After an initial phase of increasing in size, the databases normally reach a
37948 point at which they no longer get any bigger, as long as they are regularly
37951 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
37952 databases is likely to keep on increasing.
37957 .section "exim_fixdb" "SECID263"
37958 .cindex "&'exim_fixdb'&"
37959 The &'exim_fixdb'& program is a utility for interactively modifying databases.
37960 Its main use is for testing Exim, but it might also be occasionally useful for
37961 getting round problems in a live system. It has no options, and its interface
37962 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
37963 key of a database record can then be entered, and the data for that record is
37966 If &"d"& is typed at the next prompt, the entire record is deleted. For all
37967 except the &'retry'& database, that is the only operation that can be carried
37968 out. For the &'retry'& database, each field is output preceded by a number, and
37969 data for individual fields can be changed by typing the field number followed
37970 by new data, for example:
37974 resets the time of the next delivery attempt. Time values are given as a
37975 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
37976 used as optional separators.
37981 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
37982 .cindex "mailbox" "maintenance"
37983 .cindex "&'exim_lock'&"
37984 .cindex "locking mailboxes"
37985 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
37986 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
37987 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
37988 a user agent while investigating a problem. The utility requires the name of
37989 the file as its first argument. If the locking is successful, the second
37990 argument is run as a command (using C's &[system()]& function); if there is no
37991 second argument, the value of the SHELL environment variable is used; if this
37992 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
37993 is unlocked and the utility ends. The following options are available:
37997 Use &[fcntl()]& locking on the open mailbox.
38000 Use &[flock()]& locking on the open mailbox, provided the operating system
38003 .vitem &%-interval%&
38004 This must be followed by a number, which is a number of seconds; it sets the
38005 interval to sleep between retries (default 3).
38007 .vitem &%-lockfile%&
38008 Create a lock file before opening the mailbox.
38011 Lock the mailbox using MBX rules.
38014 Suppress verification output.
38016 .vitem &%-retries%&
38017 This must be followed by a number; it sets the number of times to try to get
38018 the lock (default 10).
38020 .vitem &%-restore_time%&
38021 This option causes &%exim_lock%& to restore the modified and read times to the
38022 locked file before exiting. This allows you to access a locked mailbox (for
38023 example, to take a backup copy) without disturbing the times that the user
38026 .vitem &%-timeout%&
38027 This must be followed by a number, which is a number of seconds; it sets a
38028 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
38029 default), a non-blocking call is used.
38032 Generate verbose output.
38035 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
38036 default is to create a lock file and also to use &[fcntl()]& locking on the
38037 mailbox, which is the same as Exim's default. The use of &%-flock%& or
38038 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
38039 requires that the directory containing the file be writeable. Locking by lock
38040 file does not last forever; Exim assumes that a lock file is expired if it is
38041 more than 30 minutes old.
38043 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
38044 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
38045 to be taken out on the open mailbox, and an exclusive lock on the file
38046 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
38047 number of the mailbox file. When the locking is released, if an exclusive lock
38048 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
38050 The default output contains verification of the locking that takes place. The
38051 &%-v%& option causes some additional information to be given. The &%-q%& option
38052 suppresses all output except error messages.
38056 exim_lock /var/spool/mail/spqr
38058 runs an interactive shell while the file is locked, whereas
38060 &`exim_lock -q /var/spool/mail/spqr <<End`&
38061 <&'some commands'&>
38064 runs a specific non-interactive sequence of commands while the file is locked,
38065 suppressing all verification output. A single command can be run by a command
38068 exim_lock -q /var/spool/mail/spqr \
38069 "cp /var/spool/mail/spqr /some/where"
38071 Note that if a command is supplied, it must be entirely contained within the
38072 second argument &-- hence the quotes.
38076 . ////////////////////////////////////////////////////////////////////////////
38077 . ////////////////////////////////////////////////////////////////////////////
38079 .chapter "The Exim monitor" "CHAPeximon"
38080 .scindex IIDeximon "Exim monitor" "description"
38081 .cindex "X-windows"
38082 .cindex "&'eximon'&"
38083 .cindex "Local/eximon.conf"
38084 .cindex "&_exim_monitor/EDITME_&"
38085 The Exim monitor is an application which displays in an X window information
38086 about the state of Exim's queue and what Exim is doing. An admin user can
38087 perform certain operations on messages from this GUI interface; however all
38088 such facilities are also available from the command line, and indeed, the
38089 monitor itself makes use of the command line to perform any actions requested.
38093 .section "Running the monitor" "SECID264"
38094 The monitor is started by running the script called &'eximon'&. This is a shell
38095 script that sets up a number of environment variables, and then runs the
38096 binary called &_eximon.bin_&. The default appearance of the monitor window can
38097 be changed by editing the &_Local/eximon.conf_& file created by editing
38098 &_exim_monitor/EDITME_&. Comments in that file describe what the various
38099 parameters are for.
38101 The parameters that get built into the &'eximon'& script can be overridden for
38102 a particular invocation by setting up environment variables of the same names,
38103 preceded by &`EXIMON_`&. For example, a shell command such as
38105 EXIMON_LOG_DEPTH=400 eximon
38107 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
38108 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
38109 overrides the Exim log file configuration. This makes it possible to have
38110 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
38111 syslog messages are routed to a file on the local host.
38113 X resources can be used to change the appearance of the window in the normal
38114 way. For example, a resource setting of the form
38116 Eximon*background: gray94
38118 changes the colour of the background to light grey rather than white. The
38119 stripcharts are drawn with both the data lines and the reference lines in
38120 black. This means that the reference lines are not visible when on top of the
38121 data. However, their colour can be changed by setting a resource called
38122 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
38123 For example, if your X server is running Unix, you could set up lighter
38124 reference lines in the stripcharts by obeying
38127 Eximon*highlight: gray
38130 .cindex "admin user"
38131 In order to see the contents of messages in the queue, and to operate on them,
38132 &'eximon'& must either be run as root or by an admin user.
38134 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
38135 contain X11 resource parameters interpreted by the X11 library. In addition,
38136 if the first parameter starts with the string "gdb" then it is removed and the
38137 binary is invoked under gdb (the parameter is used as the gdb command-name, so
38138 versioned variants of gdb can be invoked).
38140 The monitor's window is divided into three parts. The first contains one or
38141 more stripcharts and two action buttons, the second contains a &"tail"& of the
38142 main log file, and the third is a display of the queue of messages awaiting
38143 delivery, with two more action buttons. The following sections describe these
38144 different parts of the display.
38149 .section "The stripcharts" "SECID265"
38150 .cindex "stripchart"
38151 The first stripchart is always a count of messages in the queue. Its name can
38152 be configured by setting QUEUE_STRIPCHART_NAME in the
38153 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
38154 configuration script by regular expression matches on log file entries, making
38155 it possible to display, for example, counts of messages delivered to certain
38156 hosts or using certain transports. The supplied defaults display counts of
38157 received and delivered messages, and of local and SMTP deliveries. The default
38158 period between stripchart updates is one minute; this can be adjusted by a
38159 parameter in the &_Local/eximon.conf_& file.
38161 The stripchart displays rescale themselves automatically as the value they are
38162 displaying changes. There are always 10 horizontal lines in each chart; the
38163 title string indicates the value of each division when it is greater than one.
38164 For example, &"x2"& means that each division represents a value of 2.
38166 It is also possible to have a stripchart which shows the percentage fullness of
38167 a particular disk partition, which is useful when local deliveries are confined
38168 to a single partition.
38170 .cindex "&%statvfs%& function"
38171 This relies on the availability of the &[statvfs()]& function or equivalent in
38172 the operating system. Most, but not all versions of Unix that support Exim have
38173 this. For this particular stripchart, the top of the chart always represents
38174 100%, and the scale is given as &"x10%"&. This chart is configured by setting
38175 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
38176 &_Local/eximon.conf_& file.
38181 .section "Main action buttons" "SECID266"
38182 .cindex "size" "of monitor window"
38183 .cindex "Exim monitor" "window size"
38184 .cindex "window size"
38185 Below the stripcharts there is an action button for quitting the monitor. Next
38186 to this is another button marked &"Size"&. They are placed here so that
38187 shrinking the window to its default minimum size leaves just the queue count
38188 stripchart and these two buttons visible. Pressing the &"Size"& button causes
38189 the window to expand to its maximum size, unless it is already at the maximum,
38190 in which case it is reduced to its minimum.
38192 When expanding to the maximum, if the window cannot be fully seen where it
38193 currently is, it is moved back to where it was the last time it was at full
38194 size. When it is expanding from its minimum size, the old position is
38195 remembered, and next time it is reduced to the minimum it is moved back there.
38197 The idea is that you can keep a reduced window just showing one or two
38198 stripcharts at a convenient place on your screen, easily expand it to show
38199 the full window when required, and just as easily put it back to what it was.
38200 The idea is copied from what the &'twm'& window manager does for its
38201 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
38202 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
38204 Normally, the monitor starts up with the window at its full size, but it can be
38205 built so that it starts up with the window at its smallest size, by setting
38206 START_SMALL=yes in &_Local/eximon.conf_&.
38210 .section "The log display" "SECID267"
38211 .cindex "log" "tail of; in monitor"
38212 The second section of the window is an area in which a display of the tail of
38213 the main log is maintained.
38214 To save space on the screen, the timestamp on each log line is shortened by
38215 removing the date and, if &%log_timezone%& is set, the timezone.
38216 The log tail is not available when the only destination for logging data is
38217 syslog, unless the syslog lines are routed to a local file whose name is passed
38218 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
38220 The log sub-window has a scroll bar at its lefthand side which can be used to
38221 move back to look at earlier text, and the up and down arrow keys also have a
38222 scrolling effect. The amount of log that is kept depends on the setting of
38223 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
38224 to use. When this is full, the earlier 50% of data is discarded &-- this is
38225 much more efficient than throwing it away line by line. The sub-window also has
38226 a horizontal scroll bar for accessing the ends of long log lines. This is the
38227 only means of horizontal scrolling; the right and left arrow keys are not
38228 available. Text can be cut from this part of the window using the mouse in the
38229 normal way. The size of this subwindow is controlled by parameters in the
38230 configuration file &_Local/eximon.conf_&.
38232 Searches of the text in the log window can be carried out by means of the ^R
38233 and ^S keystrokes, which default to a reverse and a forward search,
38234 respectively. The search covers only the text that is displayed in the window.
38235 It cannot go further back up the log.
38237 The point from which the search starts is indicated by a caret marker. This is
38238 normally at the end of the text in the window, but can be positioned explicitly
38239 by pointing and clicking with the left mouse button, and is moved automatically
38240 by a successful search. If new text arrives in the window when it is scrolled
38241 back, the caret remains where it is, but if the window is not scrolled back,
38242 the caret is moved to the end of the new text.
38244 Pressing ^R or ^S pops up a window into which the search text can be typed.
38245 There are buttons for selecting forward or reverse searching, for carrying out
38246 the search, and for cancelling. If the &"Search"& button is pressed, the search
38247 happens and the window remains so that further searches can be done. If the
38248 &"Return"& key is pressed, a single search is done and the window is closed. If
38249 ^C is typed the search is cancelled.
38251 The searching facility is implemented using the facilities of the Athena text
38252 widget. By default this pops up a window containing both &"search"& and
38253 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
38254 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
38255 However, the linkers in BSDI and HP-UX seem unable to handle an externally
38256 provided version of &%TextPop%& when the remaining parts of the text widget
38257 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
38258 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
38259 on these systems, at the expense of having unwanted items in the search popup
38264 .section "The queue display" "SECID268"
38265 .cindex "queue" "display in monitor"
38266 The bottom section of the monitor window contains a list of all messages that
38267 are in the queue, which includes those currently being received or delivered,
38268 as well as those awaiting delivery. The size of this subwindow is controlled by
38269 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
38270 at which it is updated is controlled by another parameter in the same file &--
38271 the default is 5 minutes, since queue scans can be quite expensive. However,
38272 there is an &"Update"& action button just above the display which can be used
38273 to force an update of the queue display at any time.
38275 When a host is down for some time, a lot of pending mail can build up for it,
38276 and this can make it hard to deal with other messages in the queue. To help
38277 with this situation there is a button next to &"Update"& called &"Hide"&. If
38278 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
38279 type anything in here and press &"Return"&, the text is added to a chain of
38280 such texts, and if every undelivered address in a message matches at least one
38281 of the texts, the message is not displayed.
38283 If there is an address that does not match any of the texts, all the addresses
38284 are displayed as normal. The matching happens on the ends of addresses so, for
38285 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
38286 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
38287 has been set up, a button called &"Unhide"& is displayed. If pressed, it
38288 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
38289 a hide request is automatically cancelled after one hour.
38291 While the dialogue box is displayed, you can't press any buttons or do anything
38292 else to the monitor window. For this reason, if you want to cut text from the
38293 queue display to use in the dialogue box, you have to do the cutting before
38294 pressing the &"Hide"& button.
38296 The queue display contains, for each unhidden queued message, the length of
38297 time it has been in the queue, the size of the message, the message id, the
38298 message sender, and the first undelivered recipient, all on one line. If it is
38299 a bounce message, the sender is shown as &"<>"&. If there is more than one
38300 recipient to which the message has not yet been delivered, subsequent ones are
38301 listed on additional lines, up to a maximum configured number, following which
38302 an ellipsis is displayed. Recipients that have already received the message are
38305 .cindex "frozen messages" "display"
38306 If a message is frozen, an asterisk is displayed at the left-hand side.
38308 The queue display has a vertical scroll bar, and can also be scrolled by means
38309 of the arrow keys. Text can be cut from it using the mouse in the normal way.
38310 The text searching facilities, as described above for the log window, are also
38311 available, but the caret is always moved to the end of the text when the queue
38312 display is updated.
38316 .section "The queue menu" "SECID269"
38317 .cindex "queue" "menu in monitor"
38318 If the &%shift%& key is held down and the left button is clicked when the mouse
38319 pointer is over the text for any message, an action menu pops up, and the first
38320 line of the queue display for the message is highlighted. This does not affect
38323 If you want to use some other event for popping up the menu, you can set the
38324 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
38325 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
38326 value set in this parameter is a standard X event description. For example, to
38327 run eximon using &%ctrl%& rather than &%shift%& you could use
38329 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
38331 The title of the menu is the message id, and it contains entries which act as
38335 &'message log'&: The contents of the message log for the message are displayed
38336 in a new text window.
38338 &'headers'&: Information from the spool file that contains the envelope
38339 information and headers is displayed in a new text window. See chapter
38340 &<<CHAPspool>>& for a description of the format of spool files.
38342 &'body'&: The contents of the spool file containing the body of the message are
38343 displayed in a new text window. There is a default limit of 20,000 bytes to the
38344 amount of data displayed. This can be changed by setting the BODY_MAX
38345 option at compile time, or the EXIMON_BODY_MAX option at runtime.
38347 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
38348 delivery of the message. This causes an automatic thaw if the message is
38349 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
38350 a new text window. The delivery is run in a separate process, to avoid holding
38351 up the monitor while the delivery proceeds.
38353 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
38354 that the message be frozen.
38356 .cindex "thawing messages"
38357 .cindex "unfreezing messages"
38358 .cindex "frozen messages" "thawing"
38359 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
38360 that the message be thawed.
38362 .cindex "delivery" "forcing failure"
38363 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
38364 that Exim gives up trying to deliver the message. A bounce message is generated
38365 for any remaining undelivered addresses.
38367 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
38368 that the message be deleted from the system without generating a bounce
38371 &'add recipient'&: A dialog box is displayed into which a recipient address can
38372 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
38373 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
38374 Otherwise it must be entered as a fully qualified address. Pressing RETURN
38375 causes a call to Exim to be made using the &%-Mar%& option to request that an
38376 additional recipient be added to the message, unless the entry box is empty, in
38377 which case no action is taken.
38379 &'mark delivered'&: A dialog box is displayed into which a recipient address
38380 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
38381 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
38382 Otherwise it must be entered as a fully qualified address. Pressing RETURN
38383 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
38384 recipient address as already delivered, unless the entry box is empty, in which
38385 case no action is taken.
38387 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
38388 mark all recipient addresses as already delivered.
38390 &'edit sender'&: A dialog box is displayed initialized with the current
38391 sender's address. Pressing RETURN causes a call to Exim to be made using the
38392 &%-Mes%& option to replace the sender address, unless the entry box is empty,
38393 in which case no action is taken. If you want to set an empty sender (as in
38394 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
38395 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
38396 the address is qualified with that domain.
38399 When a delivery is forced, a window showing the &%-v%& output is displayed. In
38400 other cases when a call to Exim is made, if there is any output from Exim (in
38401 particular, if the command fails) a window containing the command and the
38402 output is displayed. Otherwise, the results of the action are normally apparent
38403 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
38404 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
38405 if no output is generated.
38407 The queue display is automatically updated for actions such as freezing and
38408 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
38409 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
38410 force an update of the display after one of these actions.
38412 In any text window that is displayed as result of a menu action, the normal
38413 cut-and-paste facility is available, and searching can be carried out using ^R
38414 and ^S, as described above for the log tail window.
38421 . ////////////////////////////////////////////////////////////////////////////
38422 . ////////////////////////////////////////////////////////////////////////////
38424 .chapter "Security considerations" "CHAPsecurity"
38425 .scindex IIDsecurcon "security" "discussion of"
38426 This chapter discusses a number of issues concerned with security, some of
38427 which are also covered in other parts of this manual.
38429 For reasons that this author does not understand, some people have promoted
38430 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
38431 existence of this chapter in the documentation. However, the intent of the
38432 chapter is simply to describe the way Exim works in relation to certain
38433 security concerns, not to make any specific claims about the effectiveness of
38434 its security as compared with other MTAs.
38436 What follows is a description of the way Exim is supposed to be. Best efforts
38437 have been made to try to ensure that the code agrees with the theory, but an
38438 absence of bugs can never be guaranteed. Any that are reported will get fixed
38439 as soon as possible.
38442 .section "Building a more &""hardened""& Exim" "SECID286"
38443 .cindex "security" "build-time features"
38444 There are a number of build-time options that can be set in &_Local/Makefile_&
38445 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
38446 Exim administrator who does not have the root password, or by someone who has
38447 penetrated the Exim (but not the root) account. These options are as follows:
38450 ALT_CONFIG_PREFIX can be set to a string that is required to match the
38451 start of any filenames used with the &%-C%& option. When it is set, these
38452 filenames are also not allowed to contain the sequence &"/../"&. (However, if
38453 the value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
38454 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
38455 default setting for &%ALT_CONFIG_PREFIX%&.
38457 If the permitted configuration files are confined to a directory to
38458 which only root has access, this guards against someone who has broken
38459 into the Exim account from running a privileged Exim with an arbitrary
38460 configuration file, and using it to break into other accounts.
38463 If a non-trusted configuration file (i.e. not the default configuration file
38464 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
38465 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
38466 the next item), then root privilege is retained only if the caller of Exim is
38467 root. This locks out the possibility of testing a configuration using &%-C%&
38468 right through message reception and delivery, even if the caller is root. The
38469 reception works, but by that time, Exim is running as the Exim user, so when
38470 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
38471 privilege to be lost. However, root can test reception and delivery using two
38475 The WHITELIST_D_MACROS build option declares some macros to be safe to override
38476 with &%-D%& if the real uid is one of root, the Exim run-time user or the
38477 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
38478 requiring the run-time value supplied to &%-D%& to match a regex that errs on
38479 the restrictive side. Requiring build-time selection of safe macros is onerous
38480 but this option is intended solely as a transition mechanism to permit
38481 previously-working configurations to continue to work after release 4.73.
38483 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
38486 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
38487 never to be used for any deliveries. This is like the &%never_users%& runtime
38488 option, but it cannot be overridden; the runtime option adds additional users
38489 to the list. The default setting is &"root"&; this prevents a non-root user who
38490 is permitted to modify the runtime file from using Exim as a way to get root.
38495 .section "Root privilege" "SECID270"
38497 .cindex "root privilege"
38498 The Exim binary is normally setuid to root, which means that it gains root
38499 privilege (runs as root) when it starts execution. In some special cases (for
38500 example, when the daemon is not in use and there are no local deliveries), it
38501 may be possible to run Exim setuid to some user other than root. This is
38502 discussed in the next section. However, in most installations, root privilege
38503 is required for two things:
38506 To set up a socket connected to the standard SMTP port (25) when initialising
38507 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
38510 To be able to change uid and gid in order to read users' &_.forward_& files and
38511 perform local deliveries as the receiving user or as specified in the
38515 It is not necessary to be root to do any of the other things Exim does, such as
38516 receiving messages and delivering them externally over SMTP, and it is
38517 obviously more secure if Exim does not run as root except when necessary.
38518 For this reason, a user and group for Exim to use must be defined in
38519 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
38520 group"&. Their values can be changed by the runtime configuration, though this
38521 is not recommended. Often a user called &'exim'& is used, but some sites use
38522 &'mail'& or another user name altogether.
38524 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
38525 abdication; the process cannot regain root afterwards. Prior to release 4.00,
38526 &[seteuid()]& was used in some circumstances, but this is no longer the case.
38528 After a new Exim process has interpreted its command line options, it changes
38529 uid and gid in the following cases:
38534 If the &%-C%& option is used to specify an alternate configuration file, or if
38535 the &%-D%& option is used to define macro values for the configuration, and the
38536 calling process is not running as root, the uid and gid are changed to those of
38537 the calling process.
38538 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
38539 option may not be used at all.
38540 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
38541 can be supplied if the calling process is running as root, the Exim run-time
38542 user or CONFIGURE_OWNER, if defined.
38547 If the expansion test option (&%-be%&) or one of the filter testing options
38548 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
38551 If the process is not a daemon process or a queue runner process or a delivery
38552 process or a process for testing address routing (started with &%-bt%&), the
38553 uid and gid are changed to the Exim user and group. This means that Exim always
38554 runs under its own uid and gid when receiving messages. This also applies when
38555 testing address verification
38558 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
38561 For a daemon, queue runner, delivery, or address testing process, the uid
38562 remains as root at this stage, but the gid is changed to the Exim group.
38565 The processes that initially retain root privilege behave as follows:
38568 A daemon process changes the gid to the Exim group and the uid to the Exim
38569 user after setting up one or more listening sockets. The &[initgroups()]&
38570 function is called, so that if the Exim user is in any additional groups, they
38571 will be used during message reception.
38573 A queue runner process retains root privilege throughout its execution. Its
38574 job is to fork a controlled sequence of delivery processes.
38576 A delivery process retains root privilege throughout most of its execution,
38577 but any actual deliveries (that is, the transports themselves) are run in
38578 subprocesses which always change to a non-root uid and gid. For local
38579 deliveries this is typically the uid and gid of the owner of the mailbox; for
38580 remote deliveries, the Exim uid and gid are used. Once all the delivery
38581 subprocesses have been run, a delivery process changes to the Exim uid and gid
38582 while doing post-delivery tidying up such as updating the retry database and
38583 generating bounce and warning messages.
38585 While the recipient addresses in a message are being routed, the delivery
38586 process runs as root. However, if a user's filter file has to be processed,
38587 this is done in a subprocess that runs under the individual user's uid and
38588 gid. A system filter is run as root unless &%system_filter_user%& is set.
38590 A process that is testing addresses (the &%-bt%& option) runs as root so that
38591 the routing is done in the same environment as a message delivery.
38597 .section "Running Exim without privilege" "SECTrunexiwitpri"
38598 .cindex "privilege, running without"
38599 .cindex "unprivileged running"
38600 .cindex "root privilege" "running without"
38601 Some installations like to run Exim in an unprivileged state for more of its
38602 operation, for added security. Support for this mode of operation is provided
38603 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
38604 gid are changed to the Exim user and group at the start of a delivery process
38605 (and also queue runner and address testing processes). This means that address
38606 routing is no longer run as root, and the deliveries themselves cannot change
38610 .cindex "daemon" "restarting"
38611 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
38612 that the daemon can still be started in the usual way, and it can respond
38613 correctly to SIGHUP because the re-invocation regains root privilege.
38615 An alternative approach is to make Exim setuid to the Exim user and also setgid
38616 to the Exim group. If you do this, the daemon must be started from a root
38617 process. (Calling Exim from a root process makes it behave in the way it does
38618 when it is setuid root.) However, the daemon cannot restart itself after a
38619 SIGHUP signal because it cannot regain privilege.
38621 It is still useful to set &%deliver_drop_privilege%& in this case, because it
38622 stops Exim from trying to re-invoke itself to do a delivery after a message has
38623 been received. Such a re-invocation is a waste of resources because it has no
38626 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
38627 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
38628 to the Exim user seems a clean approach, but there is one complication:
38630 In this style of operation, Exim is running with the real uid and gid set to
38631 those of the calling process, and the effective uid/gid set to Exim's values.
38632 Ideally, any association with the calling process' uid/gid should be dropped,
38633 that is, the real uid/gid should be reset to the effective values so as to
38634 discard any privileges that the caller may have. While some operating systems
38635 have a function that permits this action for a non-root effective uid, quite a
38636 number of them do not. Because of this lack of standardization, Exim does not
38637 address this problem at this time.
38639 For this reason, the recommended approach for &"mostly unprivileged"& running
38640 is to keep the Exim binary setuid to root, and to set
38641 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
38642 be used in the most straightforward way.
38644 If you configure Exim not to run delivery processes as root, there are a
38645 number of restrictions on what you can do:
38648 You can deliver only as the Exim user/group. You should explicitly use the
38649 &%user%& and &%group%& options to override routers or local transports that
38650 normally deliver as the recipient. This makes sure that configurations that
38651 work in this mode function the same way in normal mode. Any implicit or
38652 explicit specification of another user causes an error.
38654 Use of &_.forward_& files is severely restricted, such that it is usually
38655 not worthwhile to include them in the configuration.
38657 Users who wish to use &_.forward_& would have to make their home directory and
38658 the file itself accessible to the Exim user. Pipe and append-to-file entries,
38659 and their equivalents in Exim filters, cannot be used. While they could be
38660 enabled in the Exim user's name, that would be insecure and not very useful.
38662 Unless the local user mailboxes are all owned by the Exim user (possible in
38663 some POP3 or IMAP-only environments):
38666 They must be owned by the Exim group and be writeable by that group. This
38667 implies you must set &%mode%& in the appendfile configuration, as well as the
38668 mode of the mailbox files themselves.
38670 You must set &%no_check_owner%&, since most or all of the files will not be
38671 owned by the Exim user.
38673 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
38674 on a newly created mailbox when unprivileged. This also implies that new
38675 mailboxes need to be created manually.
38680 These restrictions severely restrict what can be done in local deliveries.
38681 However, there are no restrictions on remote deliveries. If you are running a
38682 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
38683 gives more security at essentially no cost.
38685 If you are using the &%mua_wrapper%& facility (see chapter
38686 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
38691 .section "Delivering to local files" "SECID271"
38692 Full details of the checks applied by &(appendfile)& before it writes to a file
38693 are given in chapter &<<CHAPappendfile>>&.
38697 .section "Running local commands" "SECTsecconslocalcmds"
38698 .cindex "security" "local commands"
38699 .cindex "security" "command injection attacks"
38700 There are a number of ways in which an administrator can configure Exim to run
38701 commands based upon received, untrustworthy, data. Further, in some
38702 configurations a user who can control a &_.forward_& file can also arrange to
38703 run commands. Configuration to check includes, but is not limited to:
38706 Use of &%use_shell%& in the pipe transport: various forms of shell command
38707 injection may be possible with this option present. It is dangerous and should
38708 be used only with considerable caution. Consider constraints which whitelist
38709 allowed characters in a variable which is to be used in a pipe transport that
38710 has &%use_shell%& enabled.
38712 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
38713 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
38714 &_.forward_& files in a redirect router. If Exim is running on a central mail
38715 hub to which ordinary users do not have shell access, but home directories are
38716 NFS mounted (for instance) then administrators should review the list of these
38717 forbid options available, and should bear in mind that the options that may
38718 need forbidding can change as new features are added between releases.
38720 The &%${run...}%& expansion item does not use a shell by default, but
38721 administrators can configure use of &_/bin/sh_& as part of the command.
38722 Such invocations should be viewed with prejudicial suspicion.
38724 Administrators who use embedded Perl are advised to explore how Perl's
38725 taint checking might apply to their usage.
38727 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
38728 administrators are well advised to view its use with suspicion, in case (for
38729 instance) it allows a local-part to contain embedded Exim directives.
38731 Use of &%${match_local_part...}%& and friends becomes more dangerous if
38732 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
38733 each can reference arbitrary lists and files, rather than just being a list
38735 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
38736 real-world security vulnerabilities caused by its use with untrustworthy data
38737 injected in, for SQL injection attacks.
38738 Consider the use of the &%inlisti%& expansion condition instead.
38744 .section "Trust in configuration data" "SECTsecconfdata"
38745 .cindex "security" "data sources"
38746 .cindex "security" "regular expressions"
38747 .cindex "regular expressions" "security"
38748 .cindex "PCRE" "security"
38749 If configuration data for Exim can come from untrustworthy sources, there
38750 are some issues to be aware of:
38753 Use of &%${expand...}%& may provide a path for shell injection attacks.
38755 Letting untrusted data provide a regular expression is unwise.
38757 Using &%${match...}%& to apply a fixed regular expression against untrusted
38758 data may result in pathological behaviour within PCRE. Be aware of what
38759 "backtracking" means and consider options for being more strict with a regular
38760 expression. Avenues to explore include limiting what can match (avoiding &`.`&
38761 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
38762 possessive quantifiers or just not using regular expressions against untrusted
38765 It can be important to correctly use &%${quote:...}%&,
38766 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
38767 items to ensure that data is correctly constructed.
38769 Some lookups might return multiple results, even though normal usage is only
38770 expected to yield one result.
38776 .section "IPv4 source routing" "SECID272"
38777 .cindex "source routing" "in IP packets"
38778 .cindex "IP source routing"
38779 Many operating systems suppress IP source-routed packets in the kernel, but
38780 some cannot be made to do this, so Exim does its own check. It logs incoming
38781 IPv4 source-routed TCP calls, and then drops them. Things are all different in
38782 IPv6. No special checking is currently done.
38786 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
38787 Support for these SMTP commands is disabled by default. If required, they can
38788 be enabled by defining suitable ACLs.
38793 .section "Privileged users" "SECID274"
38794 .cindex "trusted users"
38795 .cindex "admin user"
38796 .cindex "privileged user"
38797 .cindex "user" "trusted"
38798 .cindex "user" "admin"
38799 Exim recognizes two sets of users with special privileges. Trusted users are
38800 able to submit new messages to Exim locally, but supply their own sender
38801 addresses and information about a sending host. For other users submitting
38802 local messages, Exim sets up the sender address from the uid, and doesn't
38803 permit a remote host to be specified.
38806 However, an untrusted user is permitted to use the &%-f%& command line option
38807 in the special form &%-f <>%& to indicate that a delivery failure for the
38808 message should not cause an error report. This affects the message's envelope,
38809 but it does not affect the &'Sender:'& header. Untrusted users may also be
38810 permitted to use specific forms of address with the &%-f%& option by setting
38811 the &%untrusted_set_sender%& option.
38813 Trusted users are used to run processes that receive mail messages from some
38814 other mail domain and pass them on to Exim for delivery either locally, or over
38815 the Internet. Exim trusts a caller that is running as root, as the Exim user,
38816 as any user listed in the &%trusted_users%& configuration option, or under any
38817 group listed in the &%trusted_groups%& option.
38819 Admin users are permitted to do things to the messages on Exim's queue. They
38820 can freeze or thaw messages, cause them to be returned to their senders, remove
38821 them entirely, or modify them in various ways. In addition, admin users can run
38822 the Exim monitor and see all the information it is capable of providing, which
38823 includes the contents of files on the spool.
38827 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
38828 delivery of messages on its queue is restricted to admin users. This
38829 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
38830 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
38831 queue is also restricted to admin users. This restriction can be relaxed by
38832 setting &%no_queue_list_requires_admin%&.
38834 Exim recognizes an admin user if the calling process is running as root or as
38835 the Exim user or if any of the groups associated with the calling process is
38836 the Exim group. It is not necessary actually to be running under the Exim
38837 group. However, if admin users who are not root or the Exim user are to access
38838 the contents of files on the spool via the Exim monitor (which runs
38839 unprivileged), Exim must be built to allow group read access to its spool
38842 By default, regular users are trusted to perform basic testing and
38843 introspection commands, as themselves. This setting can be tightened by
38844 setting the &%commandline_checks_require_admin%& option.
38845 This affects most of the checking options,
38846 such as &%-be%& and anything else &%-b*%&.
38849 .section "Spool files" "SECID275"
38850 .cindex "spool directory" "files"
38851 Exim's spool directory and everything it contains is owned by the Exim user and
38852 set to the Exim group. The mode for spool files is defined in the
38853 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
38854 any user who is a member of the Exim group can access these files.
38858 .section "Use of argv[0]" "SECID276"
38859 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
38860 of specific strings, Exim assumes certain options. For example, calling Exim
38861 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
38862 to calling it with the option &%-bS%&. There are no security implications in
38867 .section "Use of %f formatting" "SECID277"
38868 The only use made of &"%f"& by Exim is in formatting load average values. These
38869 are actually stored in integer variables as 1000 times the load average.
38870 Consequently, their range is limited and so therefore is the length of the
38875 .section "Embedded Exim path" "SECID278"
38876 Exim uses its own path name, which is embedded in the code, only when it needs
38877 to re-exec in order to regain root privilege. Therefore, it is not root when it
38878 does so. If some bug allowed the path to get overwritten, it would lead to an
38879 arbitrary program's being run as exim, not as root.
38883 .section "Dynamic module directory" "SECTdynmoddir"
38884 Any dynamically loadable modules must be installed into the directory
38885 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
38889 .section "Use of sprintf()" "SECID279"
38890 .cindex "&[sprintf()]&"
38891 A large number of occurrences of &"sprintf"& in the code are actually calls to
38892 &'string_sprintf()'&, a function that returns the result in malloc'd store.
38893 The intermediate formatting is done into a large fixed buffer by a function
38894 that runs through the format string itself, and checks the length of each
38895 conversion before performing it, thus preventing buffer overruns.
38897 The remaining uses of &[sprintf()]& happen in controlled circumstances where
38898 the output buffer is known to be sufficiently long to contain the converted
38903 .section "Use of debug_printf() and log_write()" "SECID280"
38904 Arbitrary strings are passed to both these functions, but they do their
38905 formatting by calling the function &'string_vformat()'&, which runs through
38906 the format string itself, and checks the length of each conversion.
38910 .section "Use of strcat() and strcpy()" "SECID281"
38911 These are used only in cases where the output buffer is known to be large
38912 enough to hold the result.
38913 .ecindex IIDsecurcon
38918 . ////////////////////////////////////////////////////////////////////////////
38919 . ////////////////////////////////////////////////////////////////////////////
38921 .chapter "Format of spool files" "CHAPspool"
38922 .scindex IIDforspo1 "format" "spool files"
38923 .scindex IIDforspo2 "spool directory" "format of files"
38924 .scindex IIDforspo3 "spool files" "format of"
38925 .cindex "spool files" "editing"
38926 A message on Exim's queue consists of two files, whose names are the message id
38927 followed by -D and -H, respectively. The data portion of the message is kept in
38928 the -D file on its own. The message's envelope, status, and headers are all
38929 kept in the -H file, whose format is described in this chapter. Each of these
38930 two files contains the final component of its own name as its first line. This
38931 is insurance against disk crashes where the directory is lost but the files
38932 themselves are recoverable.
38934 The file formats may be changed, or new formats added, at any release.
38935 Spool files are not intended as an interface to other programs
38936 and should not be used as such.
38938 Some people are tempted into editing -D files in order to modify messages. You
38939 need to be extremely careful if you do this; it is not recommended and you are
38940 on your own if you do it. Here are some of the pitfalls:
38943 You must ensure that Exim does not try to deliver the message while you are
38944 fiddling with it. The safest way is to take out a write lock on the -D file,
38945 which is what Exim itself does, using &[fcntl()]&. If you update the file in
38946 place, the lock will be retained. If you write a new file and rename it, the
38947 lock will be lost at the instant of rename.
38949 .vindex "&$body_linecount$&"
38950 If you change the number of lines in the file, the value of
38951 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
38952 cause incomplete transmission of messages or undeliverable messages.
38954 If the message is in MIME format, you must take care not to break it.
38956 If the message is cryptographically signed, any change will invalidate the
38959 All in all, modifying -D files is fraught with danger.
38961 Files whose names end with -J may also be seen in the &_input_& directory (or
38962 its subdirectories when &%split_spool_directory%& is set). These are journal
38963 files, used to record addresses to which the message has been delivered during
38964 the course of a delivery attempt. If there are still undelivered recipients at
38965 the end, the -H file is updated, and the -J file is deleted. If, however, there
38966 is some kind of crash (for example, a power outage) before this happens, the -J
38967 file remains in existence. When Exim next processes the message, it notices the
38968 -J file and uses it to update the -H file before starting the next delivery
38971 Files whose names end with -K or .eml may also be seen in the spool.
38972 These are temporaries used for DKIM or malware processing, when that is used.
38973 They should be tidied up by normal operations; any old ones are probably
38974 relics of crashes and can be removed.
38976 .section "Format of the -H file" "SECID282"
38977 .cindex "uid (user id)" "in spool file"
38978 .cindex "gid (group id)" "in spool file"
38979 The second line of the -H file contains the login name for the uid of the
38980 process that called Exim to read the message, followed by the numerical uid and
38981 gid. For a locally generated message, this is normally the user who sent the
38982 message. For a message received over TCP/IP via the daemon, it is
38983 normally the Exim user.
38985 The third line of the file contains the address of the message's sender as
38986 transmitted in the envelope, contained in angle brackets. The sender address is
38987 empty for bounce messages. For incoming SMTP mail, the sender address is given
38988 in the MAIL command. For locally generated mail, the sender address is
38989 created by Exim from the login name of the current user and the configured
38990 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
38991 leading &"From&~"& line if the caller is trusted, or if the supplied address is
38992 &"<>"& or an address that matches &%untrusted_set_senders%&.
38994 The fourth line contains two numbers. The first is the time that the message
38995 was received, in the conventional Unix form &-- the number of seconds since the
38996 start of the epoch. The second number is a count of the number of messages
38997 warning of delayed delivery that have been sent to the sender.
38999 There follow a number of lines starting with a hyphen. These can appear in any
39000 order, and are omitted when not relevant:
39003 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
39004 This item is obsolete, and is not generated from Exim release 4.61 onwards;
39005 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
39006 recognized, to provide backward compatibility. In the old format, a line of
39007 this form is present for every ACL variable that is not empty. The number
39008 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
39009 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
39010 the data string for the variable. The string itself starts at the beginning of
39011 the next line, and is followed by a newline character. It may contain internal
39014 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
39015 A line of this form is present for every ACL connection variable that is
39016 defined. Note that there is a space between &%-aclc%& and the rest of the name.
39017 The length is the length of the data string for the variable. The string itself
39018 starts at the beginning of the next line, and is followed by a newline
39019 character. It may contain internal newlines.
39021 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
39022 A line of this form is present for every ACL message variable that is defined.
39023 Note that there is a space between &%-aclm%& and the rest of the name. The
39024 length is the length of the data string for the variable. The string itself
39025 starts at the beginning of the next line, and is followed by a newline
39026 character. It may contain internal newlines.
39028 .vitem "&%-active_hostname%&&~<&'hostname'&>"
39029 This is present if, when the message was received over SMTP, the value of
39030 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
39032 .vitem &%-allow_unqualified_recipient%&
39033 This is present if unqualified recipient addresses are permitted in header
39034 lines (to stop such addresses from being qualified if rewriting occurs at
39035 transport time). Local messages that were input using &%-bnq%& and remote
39036 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
39038 .vitem &%-allow_unqualified_sender%&
39039 This is present if unqualified sender addresses are permitted in header lines
39040 (to stop such addresses from being qualified if rewriting occurs at transport
39041 time). Local messages that were input using &%-bnq%& and remote messages from
39042 hosts that match &%sender_unqualified_hosts%& set this flag.
39044 .vitem "&%-auth_id%&&~<&'text'&>"
39045 The id information for a message received on an authenticated SMTP connection
39046 &-- the value of the &$authenticated_id$& variable.
39048 .vitem "&%-auth_sender%&&~<&'address'&>"
39049 The address of an authenticated sender &-- the value of the
39050 &$authenticated_sender$& variable.
39052 .vitem "&%-body_linecount%&&~<&'number'&>"
39053 This records the number of lines in the body of the message, and is
39054 present unless &%-spool_file_wireformat%& is.
39056 .vitem "&%-body_zerocount%&&~<&'number'&>"
39057 This records the number of binary zero bytes in the body of the message, and is
39058 present if the number is greater than zero.
39060 .vitem &%-deliver_firsttime%&
39061 This is written when a new message is first added to the spool. When the spool
39062 file is updated after a deferral, it is omitted.
39064 .vitem "&%-frozen%&&~<&'time'&>"
39065 .cindex "frozen messages" "spool data"
39066 The message is frozen, and the freezing happened at <&'time'&>.
39068 .vitem "&%-helo_name%&&~<&'text'&>"
39069 This records the host name as specified by a remote host in a HELO or EHLO
39072 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
39073 This records the IP address of the host from which the message was received and
39074 the remote port number that was used. It is omitted for locally generated
39077 .vitem "&%-host_auth%&&~<&'text'&>"
39078 If the message was received on an authenticated SMTP connection, this records
39079 the name of the authenticator &-- the value of the
39080 &$sender_host_authenticated$& variable.
39082 .vitem &%-host_lookup_failed%&
39083 This is present if an attempt to look up the sending host's name from its IP
39084 address failed. It corresponds to the &$host_lookup_failed$& variable.
39086 .vitem "&%-host_name%&&~<&'text'&>"
39087 .cindex "reverse DNS lookup"
39088 .cindex "DNS" "reverse lookup"
39089 This records the name of the remote host from which the message was received,
39090 if the host name was looked up from the IP address when the message was being
39091 received. It is not present if no reverse lookup was done.
39093 .vitem "&%-ident%&&~<&'text'&>"
39094 For locally submitted messages, this records the login of the originating user,
39095 unless it was a trusted user and the &%-oMt%& option was used to specify an
39096 ident value. For messages received over TCP/IP, this records the ident string
39097 supplied by the remote host, if any.
39099 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
39100 This records the IP address of the local interface and the port number through
39101 which a message was received from a remote host. It is omitted for locally
39102 generated messages.
39105 The message is from a local sender.
39107 .vitem &%-localerror%&
39108 The message is a locally-generated bounce message.
39110 .vitem "&%-local_scan%&&~<&'string'&>"
39111 This records the data string that was returned by the &[local_scan()]& function
39112 when the message was received &-- the value of the &$local_scan_data$&
39113 variable. It is omitted if no data was returned.
39115 .vitem &%-manual_thaw%&
39116 The message was frozen but has been thawed manually, that is, by an explicit
39117 Exim command rather than via the auto-thaw process.
39120 A testing delivery process was started using the &%-N%& option to suppress any
39121 actual deliveries, but delivery was deferred. At any further delivery attempts,
39124 .vitem &%-received_protocol%&
39125 This records the value of the &$received_protocol$& variable, which contains
39126 the name of the protocol by which the message was received.
39128 .vitem &%-sender_set_untrusted%&
39129 The envelope sender of this message was set by an untrusted local caller (used
39130 to ensure that the caller is displayed in queue listings).
39132 .vitem "&%-spam_score_int%&&~<&'number'&>"
39133 If a message was scanned by SpamAssassin, this is present. It records the value
39134 of &$spam_score_int$&.
39136 .vitem &%-spool_file_wireformat%&
39137 The -D file for this message is in wire-format (for ESMTP CHUNKING)
39138 rather than Unix-format.
39139 The line-ending is CRLF rather than newline.
39140 There is still, however, no leading-dot-stuffing.
39142 .vitem &%-tls_certificate_verified%&
39143 A TLS certificate was received from the client that sent this message, and the
39144 certificate was verified by the server.
39146 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
39147 When the message was received over an encrypted connection, this records the
39148 name of the cipher suite that was used.
39150 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
39151 When the message was received over an encrypted connection, and a certificate
39152 was received from the client, this records the Distinguished Name from that
39156 Following the options there is a list of those addresses to which the message
39157 is not to be delivered. This set of addresses is initialized from the command
39158 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
39159 is set; otherwise it starts out empty. Whenever a successful delivery is made,
39160 the address is added to this set. The addresses are kept internally as a
39161 balanced binary tree, and it is a representation of that tree which is written
39162 to the spool file. If an address is expanded via an alias or forward file, the
39163 original address is added to the tree when deliveries to all its child
39164 addresses are complete.
39166 If the tree is empty, there is a single line in the spool file containing just
39167 the text &"XX"&. Otherwise, each line consists of two letters, which are either
39168 Y or N, followed by an address. The address is the value for the node of the
39169 tree, and the letters indicate whether the node has a left branch and/or a
39170 right branch attached to it, respectively. If branches exist, they immediately
39171 follow. Here is an example of a three-node tree:
39173 YY darcy@austen.fict.example
39174 NN alice@wonderland.fict.example
39175 NN editor@thesaurus.ref.example
39177 After the non-recipients tree, there is a list of the message's recipients.
39178 This is a simple list, preceded by a count. It includes all the original
39179 recipients of the message, including those to whom the message has already been
39180 delivered. In the simplest case, the list contains one address per line. For
39184 editor@thesaurus.ref.example
39185 darcy@austen.fict.example
39187 alice@wonderland.fict.example
39189 However, when a child address has been added to the top-level addresses as a
39190 result of the use of the &%one_time%& option on a &(redirect)& router, each
39191 line is of the following form:
39193 <&'top-level address'&> <&'errors_to address'&> &&&
39194 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
39196 The 01 flag bit indicates the presence of the three other fields that follow
39197 the top-level address. Other bits may be used in future to support additional
39198 fields. The <&'parent number'&> is the offset in the recipients list of the
39199 original parent of the &"one time"& address. The first two fields are the
39200 envelope sender that is associated with this address and its length. If the
39201 length is zero, there is no special envelope sender (there are then two space
39202 characters in the line). A non-empty field can arise from a &(redirect)& router
39203 that has an &%errors_to%& setting.
39206 A blank line separates the envelope and status information from the headers
39207 which follow. A header may occupy several lines of the file, and to save effort
39208 when reading it in, each header is preceded by a number and an identifying
39209 character. The number is the number of characters in the header, including any
39210 embedded newlines and the terminating newline. The character is one of the
39214 .row <&'blank'&> "header in which Exim has no special interest"
39215 .row &`B`& "&'Bcc:'& header"
39216 .row &`C`& "&'Cc:'& header"
39217 .row &`F`& "&'From:'& header"
39218 .row &`I`& "&'Message-id:'& header"
39219 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
39220 .row &`R`& "&'Reply-To:'& header"
39221 .row &`S`& "&'Sender:'& header"
39222 .row &`T`& "&'To:'& header"
39223 .row &`*`& "replaced or deleted header"
39226 Deleted or replaced (rewritten) headers remain in the spool file for debugging
39227 purposes. They are not transmitted when the message is delivered. Here is a
39228 typical set of headers:
39230 111P Received: by hobbit.fict.example with local (Exim 4.00)
39231 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
39232 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
39233 038* X-rewrote-sender: bb@hobbit.fict.example
39234 042* From: Bilbo Baggins <bb@hobbit.fict.example>
39235 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
39236 099* To: alice@wonderland.fict.example, rdo@foundation,
39237 darcy@austen.fict.example, editor@thesaurus.ref.example
39238 104T To: alice@wonderland.fict.example, rdo@foundation.example,
39239 darcy@austen.fict.example, editor@thesaurus.ref.example
39240 038 Date: Fri, 11 May 2001 10:28:59 +0100
39242 The asterisked headers indicate that the envelope sender, &'From:'& header, and
39243 &'To:'& header have been rewritten, the last one because routing expanded the
39244 unqualified domain &'foundation'&.
39245 .ecindex IIDforspo1
39246 .ecindex IIDforspo2
39247 .ecindex IIDforspo3
39249 .section "Format of the -D file" "SECID282a"
39250 The data file is traditionally in Unix-standard format: lines are ended with
39251 an ASCII newline character.
39252 However, when the &%spool_wireformat%& main option is used some -D files
39253 can have an alternate format.
39254 This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
39255 The -D file lines (not including the first name-component line) are
39256 suitable for direct copying to the wire when transmitting using the
39257 ESMTP CHUNKING option, meaning lower processing overhead.
39258 Lines are terminated with an ASCII CRLF pair.
39259 There is no dot-stuffing (and no dot-termination).
39261 . ////////////////////////////////////////////////////////////////////////////
39262 . ////////////////////////////////////////////////////////////////////////////
39264 .chapter "DKIM and SPF" "CHAPdkim" &&&
39265 "DKIM and SPF Support"
39268 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
39270 DKIM is a mechanism by which messages sent by some entity can be provably
39271 linked to a domain which that entity controls. It permits reputation to
39272 be tracked on a per-domain basis, rather than merely upon source IP address.
39273 DKIM is documented in RFC 6376.
39275 As DKIM relies on the message being unchanged in transit, messages handled
39276 by a mailing-list (which traditionally adds to the message) will not match
39277 any original DKIM signature.
39279 DKIM support is compiled into Exim by default if TLS support is present.
39280 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
39282 Exim's DKIM implementation allows for
39284 Signing outgoing messages: This function is implemented in the SMTP transport.
39285 It can co-exist with all other Exim features
39286 (including transport filters)
39287 except cutthrough delivery.
39289 Verifying signatures in incoming messages: This is implemented by an additional
39290 ACL (acl_smtp_dkim), which can be called several times per message, with
39291 different signature contexts.
39294 In typical Exim style, the verification implementation does not include any
39295 default "policy". Instead it enables you to build your own policy using
39296 Exim's standard controls.
39298 Please note that verification of DKIM signatures in incoming mail is turned
39299 on by default for logging (in the <= line) purposes.
39301 Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
39302 When set, for each signature in incoming email,
39303 exim will log a line displaying the most important signature details, and the
39304 signature status. Here is an example (with line-breaks added for clarity):
39306 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
39307 d=facebookmail.com s=q1-2009b
39308 c=relaxed/relaxed a=rsa-sha1
39309 i=@facebookmail.com t=1252484542 [verification succeeded]
39312 You might want to turn off DKIM verification processing entirely for internal
39313 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
39314 control modifier. This should typically be done in the RCPT ACL, at points
39315 where you accept mail from relay sources (internal hosts or authenticated
39319 .section "Signing outgoing messages" "SECDKIMSIGN"
39320 .cindex "DKIM" "signing"
39322 For signing to be usable you must have published a DKIM record in DNS.
39323 Note that RFC 8301 says:
39325 rsa-sha1 MUST NOT be used for signing or verifying.
39327 Signers MUST use RSA keys of at least 1024 bits for all keys.
39328 Signers SHOULD use RSA keys of at least 2048 bits.
39331 Note also that the key content (the 'p=' field)
39332 in the DNS record is different between RSA and EC keys;
39333 for the former it is the base64 of the ASN.1 for the RSA public key
39334 (equivalent to the private-key .pem with the header/trailer stripped)
39335 but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
39337 Signing is enabled by setting private options on the SMTP transport.
39338 These options take (expandable) strings as arguments.
39340 .option dkim_domain smtp string list&!! unset
39341 The domain(s) you want to sign with.
39342 After expansion, this can be a list.
39343 Each element in turn is put into the &%$dkim_domain%& expansion variable
39344 while expanding the remaining signing options.
39345 If it is empty after expansion, DKIM signing is not done,
39346 and no error will result even if &%dkim_strict%& is set.
39348 .option dkim_selector smtp string list&!! unset
39349 This sets the key selector string.
39350 After expansion, which can use &$dkim_domain$&, this can be a list.
39351 Each element in turn is put in the expansion
39352 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
39353 option along with &%$dkim_domain%&.
39354 If the option is empty after expansion, DKIM signing is not done for this domain,
39355 and no error will result even if &%dkim_strict%& is set.
39357 .option dkim_private_key smtp string&!! unset
39358 This sets the private key to use.
39359 You can use the &%$dkim_domain%& and
39360 &%$dkim_selector%& expansion variables to determine the private key to use.
39361 The result can either
39363 be a valid RSA private key in ASCII armor (.pem file), including line breaks
39365 with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
39366 be a valid Ed25519 private key (same format as above)
39368 start with a slash, in which case it is treated as a file that contains
39371 be "0", "false" or the empty string, in which case the message will not
39372 be signed. This case will not result in an error, even if &%dkim_strict%&
39376 To generate keys under OpenSSL:
39378 openssl genrsa -out dkim_rsa.private 2048
39379 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
39381 Take the base-64 lines from the output of the second command, concatenated,
39382 for the DNS TXT record.
39383 See section 3.6 of RFC6376 for the record specification.
39387 certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
39388 certtool --load-privkey=dkim_rsa.private --pubkey-info
39391 Note that RFC 8301 says:
39393 Signers MUST use RSA keys of at least 1024 bits for all keys.
39394 Signers SHOULD use RSA keys of at least 2048 bits.
39397 Support for EC keys is being developed under
39398 &url(https://datatracker.ietf.org/doc/draft-ietf-dcrup-dkim-crypto/).
39399 They are considerably smaller than RSA keys for equivalent protection.
39400 As they are a recent development, users should consider dual-signing
39401 (by setting a list of selectors, and an expansion for this option)
39402 for some transition period.
39403 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
39406 OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
39408 openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
39409 certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
39412 To produce the required public key value for a DNS record:
39414 openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
39415 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
39418 Note that the format
39419 of Ed25519 keys in DNS has not yet been decided; this release supports
39420 both of the leading candidates at this time, a future release will
39421 probably drop support for whichever proposal loses.
39423 .option dkim_hash smtp string&!! sha256
39424 Can be set to any one of the supported hash methods, which are:
39426 &`sha1`& &-- should not be used, is old and insecure
39428 &`sha256`& &-- the default
39430 &`sha512`& &-- possibly more secure but less well supported
39433 Note that RFC 8301 says:
39435 rsa-sha1 MUST NOT be used for signing or verifying.
39438 .option dkim_identity smtp string&!! unset
39439 If set after expansion, the value is used to set an "i=" tag in
39440 the signing header. The DKIM standards restrict the permissible
39441 syntax of this optional tag to a mail address, with possibly-empty
39442 local part, an @, and a domain identical to or subdomain of the "d="
39443 tag value. Note that Exim does not check the value.
39445 .option dkim_canon smtp string&!! unset
39446 This option sets the canonicalization method used when signing a message.
39447 The DKIM RFC currently supports two methods: "simple" and "relaxed".
39448 The option defaults to "relaxed" when unset. Note: the current implementation
39449 only supports signing with the same canonicalization method for both headers and body.
39451 .option dkim_strict smtp string&!! unset
39452 This option defines how Exim behaves when signing a message that
39453 should be signed fails for some reason. When the expansion evaluates to
39454 either "1" or "true", Exim will defer. Otherwise Exim will send the message
39455 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
39458 .option dkim_sign_headers smtp string&!! "see below"
39459 If set, this option must expand to a colon-separated
39460 list of header names.
39461 Headers with these names, or the absence or such a header, will be included
39462 in the message signature.
39463 When unspecified, the header names listed in RFC4871 will be used,
39464 whether or not each header is present in the message.
39465 The default list is available for the expansion in the macro
39466 "_DKIM_SIGN_HEADERS".
39468 If a name is repeated, multiple headers by that name (or the absence thereof)
39469 will be signed. The textually later headers in the headers part of the
39470 message are signed first, if there are multiples.
39472 A name can be prefixed with either an '=' or a '+' character.
39473 If an '=' prefix is used, all headers that are present with this name
39475 If a '+' prefix if used, all headers that are present with this name
39476 will be signed, and one signature added for a missing header with the
39477 name will be appended.
39479 .option dkim_timestamps smtp integer&!! unset
39480 This option controls the inclusion of timestamp information in the signature.
39481 If not set, no such information will be included.
39482 Otherwise, must be an unsigned number giving an offset in seconds from the current time
39484 (eg. 1209600 for two weeks);
39485 both creation (t=) and expiry (x=) tags will be included.
39487 RFC 6376 lists these tags as RECOMMENDED.
39490 .section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
39491 .cindex "DKIM" "verification"
39493 Verification of DKIM signatures in SMTP incoming email is done for all
39494 messages for which an ACL control &%dkim_disable_verify%& has not been set.
39495 .cindex authentication "expansion item"
39496 Performing verification sets up information used by the
39497 &$authresults$& expansion item.
39499 The results of that verification are then made available to the
39500 &%acl_smtp_dkim%& ACL, which can examine and modify them.
39501 By default, this ACL is called once for each
39502 syntactically(!) correct signature in the incoming message.
39503 A missing ACL definition defaults to accept.
39504 If any ACL call does not accept, the message is not accepted.
39505 If a cutthrough delivery was in progress for the message, that is
39506 summarily dropped (having wasted the transmission effort).
39508 To evaluate the verification result in the ACL
39509 a large number of expansion variables
39510 containing the signature status and its details are set up during the
39511 runtime of the ACL.
39513 Calling the ACL only for existing signatures is not sufficient to build
39514 more advanced policies. For that reason, the global option
39515 &%dkim_verify_signers%&, and a global expansion variable
39516 &%$dkim_signers%& exist.
39518 The global option &%dkim_verify_signers%& can be set to a colon-separated
39519 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
39520 called. It is expanded when the message has been received. At this point,
39521 the expansion variable &%$dkim_signers%& already contains a colon-separated
39522 list of signer domains and identities for the message. When
39523 &%dkim_verify_signers%& is not specified in the main configuration,
39526 dkim_verify_signers = $dkim_signers
39528 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
39529 DKIM signature in the message. Current DKIM verifiers may want to explicitly
39530 call the ACL for known domains or identities. This would be achieved as follows:
39532 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
39534 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
39535 and "ebay.com", plus all domains and identities that have signatures in the message.
39536 You can also be more creative in constructing your policy. For example:
39538 dkim_verify_signers = $sender_address_domain:$dkim_signers
39541 If a domain or identity is listed several times in the (expanded) value of
39542 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
39544 If multiple signatures match a domain (or identity), the ACL is called once
39545 for each matching signature.
39548 Inside the &%acl_smtp_dkim%&, the following expansion variables are
39549 available (from most to least important):
39553 .vitem &%$dkim_cur_signer%&
39554 The signer that is being evaluated in this ACL run. This can be a domain or
39555 an identity. This is one of the list items from the expanded main option
39556 &%dkim_verify_signers%& (see above).
39558 .vitem &%$dkim_verify_status%&
39559 Within the DKIM ACL,
39560 a string describing the general status of the signature. One of
39562 &%none%&: There is no signature in the message for the current domain or
39563 identity (as reflected by &%$dkim_cur_signer%&).
39565 &%invalid%&: The signature could not be verified due to a processing error.
39566 More detail is available in &%$dkim_verify_reason%&.
39568 &%fail%&: Verification of the signature failed. More detail is
39569 available in &%$dkim_verify_reason%&.
39571 &%pass%&: The signature passed verification. It is valid.
39574 This variable can be overwritten using an ACL 'set' modifier.
39575 This might, for instance, be done to enforce a policy restriction on
39576 hash-method or key-size:
39578 warn condition = ${if eq {$dkim_verify_status}{pass}}
39579 condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
39580 condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
39581 {< {$dkim_key_length}{1024}}}}
39582 logwrite = NOTE: forcing DKIM verify fail (was pass)
39583 set dkim_verify_status = fail
39584 set dkim_verify_reason = hash too weak or key too short
39587 So long as a DKIM ACL is defined (it need do no more than accept),
39588 after all the DKIM ACL runs have completed, the value becomes a
39589 colon-separated list of the values after each run.
39590 This is maintained for the mime, prdr and data ACLs.
39592 .vitem &%$dkim_verify_reason%&
39593 A string giving a little bit more detail when &%$dkim_verify_status%& is either
39594 "fail" or "invalid". One of
39596 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
39597 key for the domain could not be retrieved. This may be a temporary problem.
39599 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
39600 record for the domain is syntactically invalid.
39602 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
39603 body hash does not match the one specified in the signature header. This
39604 means that the message body was modified in transit.
39606 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
39607 could not be verified. This may mean that headers were modified,
39608 re-written or otherwise changed in a way which is incompatible with
39609 DKIM verification. It may of course also mean that the signature is forged.
39612 This variable can be overwritten, with any value, using an ACL 'set' modifier.
39614 .vitem &%$dkim_domain%&
39615 The signing domain. IMPORTANT: This variable is only populated if there is
39616 an actual signature in the message for the current domain or identity (as
39617 reflected by &%$dkim_cur_signer%&).
39619 .vitem &%$dkim_identity%&
39620 The signing identity, if present. IMPORTANT: This variable is only populated
39621 if there is an actual signature in the message for the current domain or
39622 identity (as reflected by &%$dkim_cur_signer%&).
39624 .vitem &%$dkim_selector%&
39625 The key record selector string.
39627 .vitem &%$dkim_algo%&
39628 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
39629 If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
39630 may also be 'ed25519-sha256'.
39631 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
39634 Note that RFC 8301 says:
39636 rsa-sha1 MUST NOT be used for signing or verifying.
39638 DKIM signatures identified as having been signed with historic
39639 algorithms (currently, rsa-sha1) have permanently failed evaluation
39642 To enforce this you must have a DKIM ACL which checks this variable
39643 and overwrites the &$dkim_verify_status$& variable as discussed above.
39645 .vitem &%$dkim_canon_body%&
39646 The body canonicalization method. One of 'relaxed' or 'simple'.
39648 .vitem &%$dkim_canon_headers%&
39649 The header canonicalization method. One of 'relaxed' or 'simple'.
39651 .vitem &%$dkim_copiedheaders%&
39652 A transcript of headers and their values which are included in the signature
39653 (copied from the 'z=' tag of the signature).
39654 Note that RFC6376 requires that verification fail if the From: header is
39655 not included in the signature. Exim does not enforce this; sites wishing
39656 strict enforcement should code the check explicitly.
39658 .vitem &%$dkim_bodylength%&
39659 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
39660 limit was set by the signer, "9999999999999" is returned. This makes sure
39661 that this variable always expands to an integer value.
39662 &*Note:*& The presence of the signature tag specifying a signing body length
39663 is one possible route to spoofing of valid DKIM signatures.
39664 A paranoid implementation might wish to regard signature where this variable
39665 shows less than the "no limit" return as being invalid.
39667 .vitem &%$dkim_created%&
39668 UNIX timestamp reflecting the date and time when the signature was created.
39669 When this was not specified by the signer, "0" is returned.
39671 .vitem &%$dkim_expires%&
39672 UNIX timestamp reflecting the date and time when the signer wants the
39673 signature to be treated as "expired". When this was not specified by the
39674 signer, "9999999999999" is returned. This makes it possible to do useful
39675 integer size comparisons against this value.
39676 Note that Exim does not check this value.
39678 .vitem &%$dkim_headernames%&
39679 A colon-separated list of names of headers included in the signature.
39681 .vitem &%$dkim_key_testing%&
39682 "1" if the key record has the "testing" flag set, "0" if not.
39684 .vitem &%$dkim_key_nosubdomains%&
39685 "1" if the key record forbids subdomaining, "0" otherwise.
39687 .vitem &%$dkim_key_srvtype%&
39688 Service type (tag s=) from the key record. Defaults to "*" if not specified
39691 .vitem &%$dkim_key_granularity%&
39692 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
39695 .vitem &%$dkim_key_notes%&
39696 Notes from the key record (tag n=).
39698 .vitem &%$dkim_key_length%&
39699 Number of bits in the key.
39701 Note that RFC 8301 says:
39703 Verifiers MUST NOT consider signatures using RSA keys of
39704 less than 1024 bits as valid signatures.
39707 To enforce this you must have a DKIM ACL which checks this variable
39708 and overwrites the &$dkim_verify_status$& variable as discussed above.
39709 As EC keys are much smaller, the check should only do this for RSA keys.
39713 In addition, two ACL conditions are provided:
39716 .vitem &%dkim_signers%&
39717 ACL condition that checks a colon-separated list of domains or identities
39718 for a match against the domain or identity that the ACL is currently verifying
39719 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
39720 verb to a group of domains or identities. For example:
39723 # Warn when Mail purportedly from GMail has no gmail signature
39724 warn log_message = GMail sender without gmail.com DKIM signature
39725 sender_domains = gmail.com
39726 dkim_signers = gmail.com
39730 Note that the above does not check for a total lack of DKIM signing;
39731 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
39733 .vitem &%dkim_status%&
39734 ACL condition that checks a colon-separated list of possible DKIM verification
39735 results against the actual result of verification. This is typically used
39736 to restrict an ACL verb to a list of verification outcomes, for example:
39739 deny message = Mail from Paypal with invalid/missing signature
39740 sender_domains = paypal.com:paypal.de
39741 dkim_signers = paypal.com:paypal.de
39742 dkim_status = none:invalid:fail
39745 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
39746 see the documentation of the &%$dkim_verify_status%& expansion variable above
39747 for more information of what they mean.
39753 .section "SPF (Sender Policy Framework)" SECSPF
39754 .cindex SPF verification
39756 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
39757 messages with its domain in the envelope from, documented by RFC 7208.
39758 For more information on SPF see &url(http://www.openspf.org).
39759 . --- 2018-09-07: still not https
39761 Messages sent by a system not authorised will fail checking of such assertions.
39762 This includes retransmissions done by traditional forwarders.
39764 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
39765 &_Local/Makefile_&. The support uses the &_libspf2_& library
39766 &url(https://www.libspf2.org/).
39767 There is no Exim involvement in the transmission of messages;
39768 publishing certain DNS records is all that is required.
39770 For verification, an ACL condition and an expansion lookup are provided.
39771 .cindex authentication "expansion item"
39772 Performing verification sets up information used by the
39773 &$authresults$& expansion item.
39776 .cindex SPF "ACL condition"
39777 .cindex ACL "spf condition"
39778 The ACL condition "spf" can be used at or after the MAIL ACL.
39779 It takes as an argument a list of strings giving the outcome of the SPF check,
39780 and will succeed for any matching outcome.
39784 The SPF check passed, the sending host is positively verified by SPF.
39787 The SPF check failed, the sending host is NOT allowed to send mail for the
39788 domain in the envelope-from address.
39790 .vitem &%softfail%&
39791 The SPF check failed, but the queried domain can't absolutely confirm that this
39795 The queried domain does not publish SPF records.
39798 The SPF check returned a "neutral" state. This means the queried domain has
39799 published a SPF record, but wants to allow outside servers to send mail under
39800 its domain as well. This should be treated like "none".
39802 .vitem &%permerror%&
39803 This indicates a syntax error in the SPF record of the queried domain.
39804 You may deny messages when this occurs.
39806 .vitem &%temperror%&
39807 This indicates a temporary error during all processing, including Exim's
39808 SPF processing. You may defer messages when this occurs.
39811 You can prefix each string with an exclamation mark to invert
39812 its meaning, for example "!fail" will match all results but
39813 "fail". The string list is evaluated left-to-right, in a
39814 short-circuit fashion.
39819 message = $sender_host_address is not allowed to send mail from \
39820 ${if def:sender_address_domain \
39821 {$sender_address_domain}{$sender_helo_name}}. \
39822 Please see http://www.openspf.org/Why?scope=\
39823 ${if def:sender_address_domain {mfrom}{helo}};\
39824 identity=${if def:sender_address_domain \
39825 {$sender_address}{$sender_helo_name}};\
39826 ip=$sender_host_address
39829 When the spf condition has run, it sets up several expansion
39832 .cindex SPF "verification variables"
39834 .vitem &$spf_header_comment$&
39835 .vindex &$spf_header_comment$&
39836 This contains a human-readable string describing the outcome
39837 of the SPF check. You can add it to a custom header or use
39838 it for logging purposes.
39840 .vitem &$spf_received$&
39841 .vindex &$spf_received$&
39842 This contains a complete Received-SPF: header that can be
39843 added to the message. Please note that according to the SPF
39844 draft, this header must be added at the top of the header
39845 list. Please see section 10 on how you can do this.
39847 Note: in case of "Best-guess" (see below), the convention is
39848 to put this string in a header called X-SPF-Guess: instead.
39850 .vitem &$spf_result$&
39851 .vindex &$spf_result$&
39852 This contains the outcome of the SPF check in string form,
39853 one of pass, fail, softfail, none, neutral, permerror or
39856 .vitem &$spf_result_guessed$&
39857 .vindex &$spf_result_guessed$&
39858 This boolean is true only if a best-guess operation was used
39859 and required in order to obtain a result.
39861 .vitem &$spf_smtp_comment$&
39862 .vindex &$spf_smtp_comment$&
39863 This contains a string that can be used in a SMTP response
39864 to the calling party. Useful for "fail".
39868 .cindex SPF "ACL condition"
39869 .cindex ACL "spf_guess condition"
39870 .cindex SPF "best guess"
39871 In addition to SPF, you can also perform checks for so-called
39872 "Best-guess". Strictly speaking, "Best-guess" is not standard
39873 SPF, but it is supported by the same framework that enables SPF
39875 Refer to &url(http://www.openspf.org/FAQ/Best_guess_record)
39876 for a description of what it means.
39877 . --- 2018-09-07: still not https:
39879 To access this feature, simply use the spf_guess condition in place
39880 of the spf one. For example:
39883 deny spf_guess = fail
39884 message = $sender_host_address doesn't look trustworthy to me
39887 In case you decide to reject messages based on this check, you
39888 should note that although it uses the same framework, "Best-guess"
39889 is not SPF, and therefore you should not mention SPF at all in your
39892 When the spf_guess condition has run, it sets up the same expansion
39893 variables as when spf condition is run, described above.
39895 Additionally, since Best-guess is not standardized, you may redefine
39896 what "Best-guess" means to you by redefining the main configuration
39897 &%spf_guess%& option.
39898 For example, the following:
39901 spf_guess = v=spf1 a/16 mx/16 ptr ?all
39904 would relax host matching rules to a broader network range.
39907 .cindex SPF "lookup expansion"
39909 A lookup expansion is also available. It takes an email
39910 address as the key and an IP address as the database:
39913 ${lookup {username@domain} spf {ip.ip.ip.ip}}
39916 The lookup will return the same result strings as can appear in
39917 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
39918 Currently, only IPv4 addresses are supported.
39923 . ////////////////////////////////////////////////////////////////////////////
39924 . ////////////////////////////////////////////////////////////////////////////
39926 .chapter "Proxies" "CHAPproxies" &&&
39928 .cindex "proxy support"
39929 .cindex "proxy" "access via"
39931 A proxy is an intermediate system through which communication is passed.
39932 Proxies may provide a security, availability or load-distribution function.
39935 .section "Inbound proxies" SECTproxyInbound
39936 .cindex proxy inbound
39937 .cindex proxy "server side"
39938 .cindex proxy "Proxy protocol"
39939 .cindex "Proxy protocol" proxy
39941 Exim has support for receiving inbound SMTP connections via a proxy
39942 that uses &"Proxy Protocol"& to speak to it.
39943 To include this support, include &"SUPPORT_PROXY=yes"&
39946 It was built on the HAProxy specification, found at
39947 &url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt).
39949 The purpose of this facility is so that an application load balancer,
39950 such as HAProxy, can sit in front of several Exim servers
39951 to distribute load.
39952 Exim uses the local protocol communication with the proxy to obtain
39953 the remote SMTP system IP address and port information.
39954 There is no logging if a host passes or
39955 fails Proxy Protocol negotiation, but it can easily be determined and
39956 recorded in an ACL (example is below).
39958 Use of a proxy is enabled by setting the &%hosts_proxy%&
39959 main configuration option to a hostlist; connections from these
39960 hosts will use Proxy Protocol.
39961 Exim supports both version 1 and version 2 of the Proxy Protocol and
39962 automatically determines which version is in use.
39964 The Proxy Protocol header is the first data received on a TCP connection
39965 and is inserted before any TLS-on-connect handshake from the client; Exim
39966 negotiates TLS between Exim-as-server and the remote client, not between
39967 Exim and the proxy server.
39969 The following expansion variables are usable
39970 (&"internal"& and &"external"& here refer to the interfaces
39973 &'proxy_external_address '& IP of host being proxied or IP of remote interface of proxy
39974 &'proxy_external_port '& Port of host being proxied or Port on remote interface of proxy
39975 &'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
39976 &'proxy_local_port '& Port of proxy server inbound or Port on local interface of proxy
39977 &'proxy_session '& boolean: SMTP connection via proxy
39979 If &$proxy_session$& is set but &$proxy_external_address$& is empty
39980 there was a protocol error.
39982 Since the real connections are all coming from the proxy, and the
39983 per host connection tracking is done before Proxy Protocol is
39984 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
39985 handle all of the parallel volume you expect per inbound proxy.
39986 With the option set so high, you lose the ability
39987 to protect your server from many connections from one IP.
39988 In order to prevent your server from overload, you
39989 need to add a per connection ratelimit to your connect ACL.
39990 A possible solution is:
39992 # Set max number of connections per host
39994 # Or do some kind of IP lookup in a flat file or database
39995 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
39997 defer message = Too many connections from this IP right now
39998 ratelimit = LIMIT / 5s / per_conn / strict
40003 .section "Outbound proxies" SECTproxySOCKS
40004 .cindex proxy outbound
40005 .cindex proxy "client side"
40006 .cindex proxy SOCKS
40007 .cindex SOCKS proxy
40008 Exim has support for sending outbound SMTP via a proxy
40009 using a protocol called SOCKS5 (defined by RFC1928).
40010 The support can be optionally included by defining SUPPORT_SOCKS=yes in
40013 Use of a proxy is enabled by setting the &%socks_proxy%& option
40014 on an smtp transport.
40015 The option value is expanded and should then be a list
40016 (colon-separated by default) of proxy specifiers.
40017 Each proxy specifier is a list
40018 (space-separated by default) where the initial element
40019 is an IP address and any subsequent elements are options.
40021 Options are a string <name>=<value>.
40022 The list of options is in the following table:
40024 &'auth '& authentication method
40025 &'name '& authentication username
40026 &'pass '& authentication password
40028 &'tmo '& connection timeout
40030 &'weight '& selection bias
40033 More details on each of these options follows:
40036 .cindex authentication "to proxy"
40037 .cindex proxy authentication
40038 &%auth%&: Either &"none"& (default) or &"name"&.
40039 Using &"name"& selects username/password authentication per RFC 1929
40040 for access to the proxy.
40041 Default is &"none"&.
40043 &%name%&: sets the username for the &"name"& authentication method.
40046 &%pass%&: sets the password for the &"name"& authentication method.
40049 &%port%&: the TCP port number to use for the connection to the proxy.
40052 &%tmo%&: sets a connection timeout in seconds for this proxy.
40055 &%pri%&: specifies a priority for the proxy within the list,
40056 higher values being tried first.
40057 The default priority is 1.
40059 &%weight%&: specifies a selection bias.
40060 Within a priority set servers are queried in a random fashion,
40061 weighted by this value.
40062 The default value for selection bias is 1.
40065 Proxies from the list are tried according to their priority
40066 and weight settings until one responds. The timeout for the
40067 overall connection applies to the set of proxied attempts.
40069 .section Logging SECTproxyLog
40070 To log the (local) IP of a proxy in the incoming or delivery logline,
40071 add &"+proxy"& to the &%log_selector%& option.
40072 This will add a component tagged with &"PRX="& to the line.
40074 . ////////////////////////////////////////////////////////////////////////////
40075 . ////////////////////////////////////////////////////////////////////////////
40077 .chapter "Internationalisation" "CHAPi18n" &&&
40078 "Internationalisation""
40079 .cindex internationalisation "email address"
40082 .cindex utf8 "mail name handling"
40084 Exim has support for Internationalised mail names.
40085 To include this it must be built with SUPPORT_I18N and the libidn library.
40086 Standards supported are RFCs 2060, 5890, 6530 and 6533.
40088 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
40089 instead of it) then IDNA2008 is supported; this adds an extra library
40090 requirement, upon libidn2.
40092 .section "MTA operations" SECTi18nMTA
40093 .cindex SMTPUTF8 "ESMTP option"
40094 The main configuration option &%smtputf8_advertise_hosts%& specifies
40095 a host list. If this matches the sending host and
40096 accept_8bitmime is true (the default) then the ESMTP option
40097 SMTPUTF8 will be advertised.
40099 If the sender specifies the SMTPUTF8 option on a MAIL command
40100 international handling for the message is enabled and
40101 the expansion variable &$message_smtputf8$& will have value TRUE.
40103 The option &%allow_utf8_domains%& is set to true for this
40104 message. All DNS lookups are converted to a-label form
40105 whatever the setting of &%allow_utf8_domains%&
40106 when Exim is built with SUPPORT_I18N.
40108 Both localparts and domain are maintained as the original
40109 UTF-8 form internally; any comparison or regular-expression use will
40110 require appropriate care. Filenames created, eg. by
40111 the appendfile transport, will have UTF-8 names.
40113 HELO names sent by the smtp transport will have any UTF-8
40114 components expanded to a-label form,
40115 and any certificate name checks will be done using the a-label
40118 .cindex log protocol
40119 .cindex SMTPUTF8 logging
40120 .cindex i18n logging
40121 Log lines and Received-by: header lines will acquire a "utf8"
40122 prefix on the protocol element, eg. utf8esmtp.
40124 The following expansion operators can be used:
40126 ${utf8_domain_to_alabel:str}
40127 ${utf8_domain_from_alabel:str}
40128 ${utf8_localpart_to_alabel:str}
40129 ${utf8_localpart_from_alabel:str}
40132 .cindex utf8 "address downconversion"
40133 .cindex i18n "utf8 address downconversion"
40135 may use the following modifier:
40137 control = utf8_downconvert
40138 control = utf8_downconvert/<value>
40140 This sets a flag requiring that addresses are converted to
40141 a-label form before smtp delivery, for use in a
40142 Message Submission Agent context.
40143 If a value is appended it may be:
40145 &`1 `& (default) mandatory downconversion
40146 &`0 `& no downconversion
40147 &`-1 `& if SMTPUTF8 not supported by destination host
40150 If mua_wrapper is set, the utf8_downconvert control
40151 is initially set to -1.
40153 The smtp transport has an option &%utf8_downconvert%&.
40154 If set it must expand to one of the three values described above,
40155 and it overrides any previously set value.
40158 There is no explicit support for VRFY and EXPN.
40159 Configurations supporting these should inspect
40160 &$smtp_command_argument$& for an SMTPUTF8 argument.
40162 There is no support for LMTP on Unix sockets.
40163 Using the "lmtp" protocol option on an smtp transport,
40164 for LMTP over TCP, should work as expected.
40166 There is no support for DSN unitext handling,
40167 and no provision for converting logging from or to UTF-8.
40171 .section "MDA operations" SECTi18nMDA
40172 To aid in constructing names suitable for IMAP folders
40173 the following expansion operator can be used:
40175 ${imapfolder {<string>} {<sep>} {<specials>}}
40178 The string is converted from the charset specified by
40179 the "headers charset" command (in a filter file)
40180 or &%headers_charset%& main configuration option (otherwise),
40182 modified UTF-7 encoding specified by RFC 2060,
40183 with the following exception: All occurrences of <sep>
40184 (which has to be a single character)
40185 are replaced with periods ("."), and all periods and slashes that are not
40186 <sep> and are not in the <specials> string are BASE64 encoded.
40188 The third argument can be omitted, defaulting to an empty string.
40189 The second argument can be omitted, defaulting to "/".
40191 This is the encoding used by Courier for Maildir names on disk, and followed
40192 by many other IMAP servers.
40196 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
40197 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
40198 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
40201 Note that the source charset setting is vital, and also that characters
40202 must be representable in UTF-16.
40205 . ////////////////////////////////////////////////////////////////////////////
40206 . ////////////////////////////////////////////////////////////////////////////
40208 .chapter "Events" "CHAPevents" &&&
40212 The events mechanism in Exim can be used to intercept processing at a number
40213 of points. It was originally invented to give a way to do customised logging
40214 actions (for example, to a database) but can also be used to modify some
40215 processing actions.
40217 Most installations will never need to use Events.
40218 The support can be left out of a build by defining DISABLE_EVENT=yes
40219 in &_Local/Makefile_&.
40221 There are two major classes of events: main and transport.
40222 The main configuration option &%event_action%& controls reception events;
40223 a transport option &%event_action%& controls delivery events.
40225 Both options are a string which is expanded when the event fires.
40226 An example might look like:
40227 .cindex logging custom
40229 event_action = ${if eq {msg:delivery}{$event_name} \
40230 {${lookup pgsql {SELECT * FROM record_Delivery( \
40231 '${quote_pgsql:$sender_address_domain}',\
40232 '${quote_pgsql:${lc:$sender_address_local_part}}', \
40233 '${quote_pgsql:$domain}', \
40234 '${quote_pgsql:${lc:$local_part}}', \
40235 '${quote_pgsql:$host_address}', \
40236 '${quote_pgsql:${lc:$host}}', \
40237 '${quote_pgsql:$message_exim_id}')}} \
40241 Events have names which correspond to the point in process at which they fire.
40242 The name is placed in the variable &$event_name$& and the event action
40243 expansion must check this, as it will be called for every possible event type.
40245 The current list of events is:
40247 &`dane:fail after transport `& per connection
40248 &`msg:complete after main `& per message
40249 &`msg:delivery after transport `& per recipient
40250 &`msg:rcpt:host:defer after transport `& per recipient per host
40251 &`msg:rcpt:defer after transport `& per recipient
40252 &`msg:host:defer after transport `& per attempt
40253 &`msg:fail:delivery after transport `& per recipient
40254 &`msg:fail:internal after main `& per recipient
40255 &`tcp:connect before transport `& per connection
40256 &`tcp:close after transport `& per connection
40257 &`tls:cert before both `& per certificate in verification chain
40258 &`smtp:connect after transport `& per connection
40260 New event types may be added in future.
40262 The event name is a colon-separated list, defining the type of
40263 event in a tree of possibilities. It may be used as a list
40264 or just matched on as a whole. There will be no spaces in the name.
40266 The second column in the table above describes whether the event fires
40267 before or after the action is associates with. Those which fire before
40268 can be used to affect that action (more on this below).
40270 The third column in the table above says what section of the configuration
40271 should define the event action.
40273 An additional variable, &$event_data$&, is filled with information varying
40274 with the event type:
40276 &`dane:fail `& failure reason
40277 &`msg:delivery `& smtp confirmation message
40278 &`msg:fail:internal `& failure reason
40279 &`msg:fail:delivery `& smtp error message
40280 &`msg:rcpt:host:defer `& error string
40281 &`msg:rcpt:defer `& error string
40282 &`msg:host:defer `& error string
40283 &`tls:cert `& verification chain depth
40284 &`smtp:connect `& smtp banner
40287 The :defer events populate one extra variable: &$event_defer_errno$&.
40289 For complex operations an ACL expansion can be used in &%event_action%&
40290 however due to the multiple contexts that Exim operates in during
40291 the course of its processing:
40293 variables set in transport events will not be visible outside that
40296 acl_m variables in a server context are lost on a new connection,
40297 and after smtp helo/ehlo/mail/starttls/rset commands
40299 Using an ACL expansion with the logwrite modifier can be
40300 a useful way of writing to the main log.
40302 The expansion of the event_action option should normally
40303 return an empty string. Should it return anything else the
40304 following will be forced:
40306 &`tcp:connect `& do not connect
40307 &`tls:cert `& refuse verification
40308 &`smtp:connect `& close connection
40310 All other message types ignore the result string, and
40311 no other use is made of it.
40313 For a tcp:connect event, if the connection is being made to a proxy
40314 then the address and port variables will be that of the proxy and not
40317 For tls:cert events, if GnuTLS is in use this will trigger only per
40318 chain element received on the connection.
40319 For OpenSSL it will trigger for every chain element including those
40322 . ////////////////////////////////////////////////////////////////////////////
40323 . ////////////////////////////////////////////////////////////////////////////
40325 .chapter "Adding new drivers or lookup types" "CHID13" &&&
40326 "Adding drivers or lookups"
40327 .cindex "adding drivers"
40328 .cindex "new drivers, adding"
40329 .cindex "drivers" "adding new"
40330 The following actions have to be taken in order to add a new router, transport,
40331 authenticator, or lookup type to Exim:
40334 Choose a name for the driver or lookup type that does not conflict with any
40335 existing name; I will use &"newdriver"& in what follows.
40337 Add to &_src/EDITME_& the line:
40339 <&'type'&>&`_NEWDRIVER=yes`&
40341 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
40342 code is not to be included in the binary by default, comment this line out. You
40343 should also add any relevant comments about the driver or lookup type.
40345 Add to &_src/config.h.defaults_& the line:
40347 #define <type>_NEWDRIVER
40350 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
40351 and create a table entry as is done for all the other drivers and lookup types.
40353 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
40354 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
40355 Add your &`NEWDRIVER`& to that list.
40356 As long as the dynamic module would be named &_newdriver.so_&, you can use the
40357 simple form that most lookups have.
40359 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
40360 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
40361 driver or lookup type and add it to the definition of OBJ.
40363 Edit &_OS/Makefile-Base_& adding a &_.o_& file for the predefined-macros, to the
40364 definition of OBJ_MACRO. Add a set of line to do the compile also.
40366 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
40369 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
40370 as for other drivers and lookups.
40373 Then all you need to do is write the code! A good way to start is to make a
40374 proforma by copying an existing module of the same type, globally changing all
40375 occurrences of the name, and cutting out most of the code. Note that any
40376 options you create must be listed in alphabetical order, because the tables are
40377 searched using a binary chop procedure.
40379 There is a &_README_& file in each of the sub-directories of &_src_& describing
40380 the interface that is expected.
40385 . ////////////////////////////////////////////////////////////////////////////
40386 . ////////////////////////////////////////////////////////////////////////////
40388 . /////////////////////////////////////////////////////////////////////////////
40389 . These lines are processing instructions for the Simple DocBook Processor that
40390 . Philip Hazel has developed as a less cumbersome way of making PostScript and
40391 . PDFs than using xmlto and fop. They will be ignored by all other XML
40393 . /////////////////////////////////////////////////////////////////////////////
40398 foot_right_recto="&chaptertitle;"
40399 foot_right_verso="&chaptertitle;"
40403 .makeindex "Options index" "option"
40404 .makeindex "Variables index" "variable"
40405 .makeindex "Concept index" "concept"
40408 . /////////////////////////////////////////////////////////////////////////////
40409 . /////////////////////////////////////////////////////////////////////////////