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 "4.94"
49 .include ./local_params
51 .set ACL "access control lists (ACLs)"
52 .set I " "
58 . /////////////////////////////////////////////////////////////////////////////
59 . Additional xfpt markup used by this document, over and above the default
60 . provided in the xfpt library.
61 . /////////////////////////////////////////////////////////////////////////////
63 . --- Override the &$ flag to automatically insert a $ with the variable name.
65 .flag &$ $& "<varname>$" "</varname>"
67 . --- Short flags for daggers in option headings. They will always be inside
68 . --- an italic string, but we want the daggers to be in Roman.
70 .flag &!! "</emphasis>†<emphasis>"
71 .flag &!? "</emphasis>‡<emphasis>"
73 . --- A macro for an Exim option definition heading, generating a one-line
74 . --- table with four columns. For cases when the option name is given with
75 . --- a space, so that it can be split, a fifth argument is used for the
85 .itable all 0 0 4 8* left 6* center 6* center 6* right
86 .row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&"
90 . --- A macro for the common 2-column tables. The width of the first column
91 . --- is suitable for the many tables at the start of the main options chapter;
92 . --- a small number of other 2-column tables override it.
94 .macro table2 196pt 254pt
95 .itable none 0 0 2 $1 left $2 left
98 . --- A macro that generates .row, but puts &I; at the start of the first
99 . --- argument, thus indenting it. Assume a minimum of two arguments, and
100 . --- allow up to four arguments, which is as many as we'll ever need.
104 .row "&I;$1" "$2" "$3" "$4"
108 .row "&I;$1" "$2" "$3"
116 . --- Macros for option, variable, and concept index entries. For a "range"
117 . --- style of entry, use .scindex for the start and .ecindex for the end. The
118 . --- first argument of .scindex and the only argument of .ecindex must be the
119 . --- ID that ties them together.
122 &<indexterm role="concept">&
123 &<primary>&$1&</primary>&
125 &<secondary>&$2&</secondary>&
131 &<indexterm role="concept" id="$1" class="startofrange">&
132 &<primary>&$2&</primary>&
134 &<secondary>&$3&</secondary>&
140 &<indexterm role="concept" startref="$1" class="endofrange"/>&
144 &<indexterm role="option">&
145 &<primary>&$1&</primary>&
147 &<secondary>&$2&</secondary>&
153 &<indexterm role="variable">&
154 &<primary>&$1&</primary>&
156 &<secondary>&$2&</secondary>&
162 .echo "** Don't use .index; use .cindex or .oindex or .vindex"
164 . ////////////////////////////////////////////////////////////////////////////
167 . ////////////////////////////////////////////////////////////////////////////
168 . The <bookinfo> element is removed from the XML before processing for ASCII
170 . ////////////////////////////////////////////////////////////////////////////
174 <title>Specification of the Exim Mail Transfer Agent</title>
175 <titleabbrev>The Exim MTA</titleabbrev>
179 <author><firstname>Exim</firstname><surname>Maintainers</surname></author>
180 <authorinitials>EM</authorinitials>
181 <revhistory><revision>
183 <authorinitials>EM</authorinitials>
184 </revision></revhistory>
187 </year><holder>University of Cambridge</holder></copyright>
192 . /////////////////////////////////////////////////////////////////////////////
193 . This chunk of literal XML implements index entries of the form "x, see y" and
194 . "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
195 . at the top level, so we have to put the .chapter directive first.
196 . /////////////////////////////////////////////////////////////////////////////
198 .chapter "Introduction" "CHID1"
201 <indexterm role="variable">
202 <primary>$1, $2, etc.</primary>
203 <see><emphasis>numerical variables</emphasis></see>
205 <indexterm role="concept">
206 <primary>address</primary>
207 <secondary>rewriting</secondary>
208 <see><emphasis>rewriting</emphasis></see>
210 <indexterm role="concept">
211 <primary>Bounce Address Tag Validation</primary>
212 <see><emphasis>BATV</emphasis></see>
214 <indexterm role="concept">
215 <primary>Client SMTP Authorization</primary>
216 <see><emphasis>CSA</emphasis></see>
218 <indexterm role="concept">
219 <primary>CR character</primary>
220 <see><emphasis>carriage return</emphasis></see>
222 <indexterm role="concept">
223 <primary>CRL</primary>
224 <see><emphasis>certificate revocation list</emphasis></see>
226 <indexterm role="concept">
227 <primary>delivery</primary>
228 <secondary>failure report</secondary>
229 <see><emphasis>bounce message</emphasis></see>
231 <indexterm role="concept">
232 <primary>dialup</primary>
233 <see><emphasis>intermittently connected hosts</emphasis></see>
235 <indexterm role="concept">
236 <primary>exiscan</primary>
237 <see><emphasis>content scanning</emphasis></see>
239 <indexterm role="concept">
240 <primary>failover</primary>
241 <see><emphasis>fallback</emphasis></see>
243 <indexterm role="concept">
244 <primary>fallover</primary>
245 <see><emphasis>fallback</emphasis></see>
247 <indexterm role="concept">
248 <primary>filter</primary>
249 <secondary>Sieve</secondary>
250 <see><emphasis>Sieve filter</emphasis></see>
252 <indexterm role="concept">
253 <primary>ident</primary>
254 <see><emphasis>RFC 1413</emphasis></see>
256 <indexterm role="concept">
257 <primary>LF character</primary>
258 <see><emphasis>linefeed</emphasis></see>
260 <indexterm role="concept">
261 <primary>maximum</primary>
262 <seealso><emphasis>limit</emphasis></seealso>
264 <indexterm role="concept">
265 <primary>monitor</primary>
266 <see><emphasis>Exim monitor</emphasis></see>
268 <indexterm role="concept">
269 <primary>no_<emphasis>xxx</emphasis></primary>
270 <see>entry for xxx</see>
272 <indexterm role="concept">
273 <primary>NUL</primary>
274 <see><emphasis>binary zero</emphasis></see>
276 <indexterm role="concept">
277 <primary>passwd file</primary>
278 <see><emphasis>/etc/passwd</emphasis></see>
280 <indexterm role="concept">
281 <primary>process id</primary>
282 <see><emphasis>pid</emphasis></see>
284 <indexterm role="concept">
285 <primary>RBL</primary>
286 <see><emphasis>DNS list</emphasis></see>
288 <indexterm role="concept">
289 <primary>redirection</primary>
290 <see><emphasis>address redirection</emphasis></see>
292 <indexterm role="concept">
293 <primary>return path</primary>
294 <seealso><emphasis>envelope sender</emphasis></seealso>
296 <indexterm role="concept">
297 <primary>scanning</primary>
298 <see><emphasis>content scanning</emphasis></see>
300 <indexterm role="concept">
301 <primary>SSL</primary>
302 <see><emphasis>TLS</emphasis></see>
304 <indexterm role="concept">
305 <primary>string</primary>
306 <secondary>expansion</secondary>
307 <see><emphasis>expansion</emphasis></see>
309 <indexterm role="concept">
310 <primary>top bit</primary>
311 <see><emphasis>8-bit characters</emphasis></see>
313 <indexterm role="concept">
314 <primary>variables</primary>
315 <see><emphasis>expansion, variables</emphasis></see>
317 <indexterm role="concept">
318 <primary>zero, binary</primary>
319 <see><emphasis>binary zero</emphasis></see>
325 . /////////////////////////////////////////////////////////////////////////////
326 . This is the real start of the first chapter. See the comment above as to why
327 . we can't have the .chapter line here.
328 . chapter "Introduction"
329 . /////////////////////////////////////////////////////////////////////////////
331 Exim is a mail transfer agent (MTA) for hosts that are running Unix or
332 Unix-like operating systems. It was designed on the assumption that it would be
333 run on hosts that are permanently connected to the Internet. However, it can be
334 used on intermittently connected hosts with suitable configuration adjustments.
336 Configuration files currently exist for the following operating systems: AIX,
337 BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, Dragonfly, FreeBSD, GNU/Hurd,
338 GNU/Linux, HI-OSF (Hitachi), HI-UX, HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD,
339 OpenUNIX, QNX, SCO, SCO SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4,
340 Tru64-Unix (formerly Digital UNIX, formerly DEC-OSF1), Ultrix, and UnixWare.
341 Some of these operating systems are no longer current and cannot easily be
342 tested, so the configuration files may no longer work in practice.
344 There are also configuration files for compiling Exim in the Cygwin environment
345 that can be installed on systems running Windows. However, this document does
346 not contain any information about running Exim in the Cygwin environment.
348 The terms and conditions for the use and distribution of Exim are contained in
349 the file &_NOTICE_&. Exim is distributed under the terms of the GNU General
350 Public Licence, a copy of which may be found in the file &_LICENCE_&.
352 The use, supply, or promotion of Exim for the purpose of sending bulk,
353 unsolicited electronic mail is incompatible with the basic aims of Exim,
354 which revolve around the free provision of a service that enhances the quality
355 of personal communications. The author of Exim regards indiscriminate
356 mass-mailing as an antisocial, irresponsible abuse of the Internet.
358 Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
359 experience of running and working on the Smail 3 code, I could never have
360 contemplated starting to write a new MTA. Many of the ideas and user interfaces
361 were originally taken from Smail 3, though the actual code of Exim is entirely
362 new, and has developed far beyond the initial concept.
364 Many people, both in Cambridge and around the world, have contributed to the
365 development and the testing of Exim, and to porting it to various operating
366 systems. I am grateful to them all. The distribution now contains a file called
367 &_ACKNOWLEDGMENTS_&, in which I have started recording the names of
371 .section "Exim documentation" "SECID1"
372 . Keep this example change bar when updating the documentation!
375 .cindex "documentation"
376 This edition of the Exim specification applies to version &version() of Exim.
377 Substantive changes from the &previousversion; edition are marked in some
378 renditions of this document; this paragraph is so marked if the rendition is
379 capable of showing a change indicator.
382 This document is very much a reference manual; it is not a tutorial. The reader
383 is expected to have some familiarity with the SMTP mail transfer protocol and
384 with general Unix system administration. Although there are some discussions
385 and examples in places, the information is mostly organized in a way that makes
386 it easy to look up, rather than in a natural order for sequential reading.
387 Furthermore, this manual aims to cover every aspect of Exim in detail, including
388 a number of rarely-used, special-purpose features that are unlikely to be of
391 .cindex "books about Exim"
392 An &"easier"& discussion of Exim which provides more in-depth explanatory,
393 introductory, and tutorial material can be found in a book entitled &'The Exim
394 SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge
395 (&url(https://www.uit.co.uk/exim-book/)).
397 The book also contains a chapter that gives a general introduction to SMTP and
398 Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
399 with the latest release of Exim. (Note that the earlier book about Exim,
400 published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)
402 .cindex "Debian" "information sources"
403 If you are using a Debian distribution of Exim, you will find information about
404 Debian-specific features in the file
405 &_/usr/share/doc/exim4-base/README.Debian_&.
406 The command &(man update-exim.conf)& is another source of Debian-specific
409 .cindex "&_doc/NewStuff_&"
410 .cindex "&_doc/ChangeLog_&"
412 As Exim develops, there may be features in newer versions that have not
413 yet made it into this document, which is updated only when the most significant
414 digit of the fractional part of the version number changes. Specifications of
415 new features that are not yet in this manual are placed in the file
416 &_doc/NewStuff_& in the Exim distribution.
418 Some features may be classified as &"experimental"&. These may change
419 incompatibly while they are developing, or even be withdrawn. For this reason,
420 they are not documented in this manual. Information about experimental features
421 can be found in the file &_doc/experimental.txt_&.
423 All changes to Exim (whether new features, bug fixes, or other kinds of
424 change) are noted briefly in the file called &_doc/ChangeLog_&.
426 .cindex "&_doc/spec.txt_&"
427 This specification itself is available as an ASCII file in &_doc/spec.txt_& so
428 that it can easily be searched with a text editor. Other files in the &_doc_&
432 .row &_OptionLists.txt_& "list of all options in alphabetical order"
433 .row &_dbm.discuss.txt_& "discussion about DBM libraries"
434 .row &_exim.8_& "a man page of Exim's command line options"
435 .row &_experimental.txt_& "documentation of experimental features"
436 .row &_filter.txt_& "specification of the filter language"
437 .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3"
438 .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4"
439 .row &_openssl.txt_& "installing a current OpenSSL release"
442 The main specification and the specification of the filtering language are also
443 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
444 &<<SECTavail>>& below tells you how to get hold of these.
448 .section "FTP site and websites" "SECID2"
451 The primary site for Exim source distributions is the &%exim.org%& FTP site,
452 available over HTTPS, HTTP and FTP. These services, and the &%exim.org%&
453 website, are hosted at the University of Cambridge.
457 As well as Exim distribution tar files, the Exim website contains a number of
458 differently formatted versions of the documentation. A recent addition to the
459 online information is the Exim wiki (&url(https://wiki.exim.org)),
460 which contains what used to be a separate FAQ, as well as various other
461 examples, tips, and know-how that have been contributed by Exim users.
462 The wiki site should always redirect to the correct place, which is currently
463 provided by GitHub, and is open to editing by anyone with a GitHub account.
466 An Exim Bugzilla exists at &url(https://bugs.exim.org). You can use
467 this to report bugs, and also to add items to the wish list. Please search
468 first to check that you are not duplicating a previous entry.
469 Please do not ask for configuration help in the bug-tracker.
472 .section "Mailing lists" "SECID3"
473 .cindex "mailing lists" "for Exim users"
474 The following Exim mailing lists exist:
477 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
478 .row &'exim-users@exim.org'& "General discussion list"
479 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
480 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
483 You can subscribe to these lists, change your existing subscriptions, and view
484 or search the archives via the mailing lists link on the Exim home page.
485 .cindex "Debian" "mailing list for"
486 If you are using a Debian distribution of Exim, you may wish to subscribe to
487 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
490 &url(https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/pkg-exim4-users)
492 Please ask Debian-specific questions on that list and not on the general Exim
495 .section "Bug reports" "SECID5"
496 .cindex "bug reports"
497 .cindex "reporting bugs"
498 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
499 via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
500 whether some behaviour is a bug or not, the best thing to do is to post a
501 message to the &'exim-dev'& mailing list and have it discussed.
505 .section "Where to find the Exim distribution" "SECTavail"
507 .cindex "HTTPS download site"
508 .cindex "distribution" "FTP site"
509 .cindex "distribution" "https site"
510 The master distribution site for the Exim distribution is
512 &url(https://downloads.exim.org/)
514 The service is available over HTTPS, HTTP and FTP.
515 We encourage people to migrate to HTTPS.
517 The content served at &url(https://downloads.exim.org/) is identical to the
518 content served at &url(https://ftp.exim.org/pub/exim) and
519 &url(ftp://ftp.exim.org/pub/exim).
521 If accessing via a hostname containing &'ftp'&, then the file references that
522 follow are relative to the &_exim_& directories at these sites.
523 If accessing via the hostname &'downloads'& then the subdirectories described
524 here are top-level directories.
526 There are now quite a number of independent mirror sites around
527 the world. Those that I know about are listed in the file called &_Mirrors_&.
529 Within the top exim directory there are subdirectories called &_exim3_& (for
530 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
531 distributions), and &_Testing_& for testing versions. In the &_exim4_&
532 subdirectory, the current release can always be found in files called
536 &_exim-n.nn.tar.bz2_&
538 where &'n.nn'& is the highest such version number in the directory. The three
539 files contain identical data; the only difference is the type of compression.
540 The &_.xz_& file is usually the smallest, while the &_.gz_& file is the
541 most portable to old systems.
543 .cindex "distribution" "signing details"
544 .cindex "distribution" "public key"
545 .cindex "public key for signed distribution"
546 The distributions will be PGP signed by an individual key of the Release
547 Coordinator. This key will have a uid containing an email address in the
548 &'exim.org'& domain and will have signatures from other people, including
549 other Exim maintainers. We expect that the key will be in the "strong set" of
550 PGP keys. There should be a trust path to that key from the Exim Maintainer's
551 PGP keys, a version of which can be found in the release directory in the file
552 &_Exim-Maintainers-Keyring.asc_&. All keys used will be available in public keyserver pools,
553 such as &'pool.sks-keyservers.net'&.
555 At the time of the last update, releases were being made by Jeremy Harris and signed
556 with key &'0xBCE58C8CE41F32DF'&. Other recent keys used for signing are those
557 of Heiko Schlittermann, &'0x26101B62F69376CE'&,
558 and of Phil Pennock, &'0x4D1E900E14C1CC04'&.
560 The signatures for the tar bundles are in:
562 &_exim-n.nn.tar.xz.asc_&
563 &_exim-n.nn.tar.gz.asc_&
564 &_exim-n.nn.tar.bz2.asc_&
566 For each released version, the log of changes is made available in a
567 separate file in the directory &_ChangeLogs_& so that it is possible to
568 find out what has changed without having to download the entire distribution.
570 .cindex "documentation" "available formats"
571 The main distribution contains ASCII versions of this specification and other
572 documentation; other formats of the documents are available in separate files
573 inside the &_exim4_& directory of the FTP site:
575 &_exim-html-n.nn.tar.gz_&
576 &_exim-pdf-n.nn.tar.gz_&
577 &_exim-postscript-n.nn.tar.gz_&
578 &_exim-texinfo-n.nn.tar.gz_&
580 These tar files contain only the &_doc_& directory, not the complete
581 distribution, and are also available in &_.bz2_& and &_.xz_& forms.
584 .section "Limitations" "SECID6"
586 .cindex "limitations of Exim"
587 .cindex "bang paths" "not handled by Exim"
588 Exim is designed for use as an Internet MTA, and therefore handles addresses in
589 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
590 simple two-component bang paths can be converted by a straightforward rewriting
591 configuration. This restriction does not prevent Exim from being interfaced to
592 UUCP as a transport mechanism, provided that domain addresses are used.
594 .cindex "domainless addresses"
595 .cindex "address" "without domain"
596 Exim insists that every address it handles has a domain attached. For incoming
597 local messages, domainless addresses are automatically qualified with a
598 configured domain value. Configuration options specify from which remote
599 systems unqualified addresses are acceptable. These are then qualified on
602 .cindex "transport" "external"
603 .cindex "external transports"
604 The only external transport mechanisms that are currently implemented are SMTP
605 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
606 transport is available, and there are facilities for writing messages to files
607 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
608 to send messages to other transport mechanisms such as UUCP, provided they can
609 handle domain-style addresses. Batched SMTP input is also catered for.
611 Exim is not designed for storing mail for dial-in hosts. When the volumes of
612 such mail are large, it is better to get the messages &"delivered"& into files
613 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
616 Although Exim does have basic facilities for scanning incoming messages, these
617 are not comprehensive enough to do full virus or spam scanning. Such operations
618 are best carried out using additional specialized software packages. If you
619 compile Exim with the content-scanning extension, straightforward interfaces to
620 a number of common scanners are provided.
624 .section "Runtime configuration" "SECID7"
625 Exim's runtime configuration is held in a single text file that is divided
626 into a number of sections. The entries in this file consist of keywords and
627 values, in the style of Smail 3 configuration files. A default configuration
628 file which is suitable for simple online installations is provided in the
629 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
632 .section "Calling interface" "SECID8"
633 .cindex "Sendmail compatibility" "command line interface"
634 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
635 can be a straight replacement for &_/usr/lib/sendmail_& or
636 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
637 about Sendmail in order to run Exim. For actions other than sending messages,
638 Sendmail-compatible options also exist, but those that produce output (for
639 example, &%-bp%&, which lists the messages in the queue) do so in Exim's own
640 format. There are also some additional options that are compatible with Smail
641 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
642 documents all Exim's command line options. This information is automatically
643 made into the man page that forms part of the Exim distribution.
645 Control of messages in the queue can be done via certain privileged command
646 line options. There is also an optional monitor program called &'eximon'&,
647 which displays current information in an X window, and which contains a menu
648 interface to Exim's command line administration options.
652 .section "Terminology" "SECID9"
653 .cindex "terminology definitions"
654 .cindex "body of message" "definition of"
655 The &'body'& of a message is the actual data that the sender wants to transmit.
656 It is the last part of a message and is separated from the &'header'& (see
657 below) by a blank line.
659 .cindex "bounce message" "definition of"
660 When a message cannot be delivered, it is normally returned to the sender in a
661 delivery failure message or a &"non-delivery report"& (NDR). The term
662 &'bounce'& is commonly used for this action, and the error reports are often
663 called &'bounce messages'&. This is a convenient shorthand for &"delivery
664 failure error report"&. Such messages have an empty sender address in the
665 message's &'envelope'& (see below) to ensure that they cannot themselves give
666 rise to further bounce messages.
668 The term &'default'& appears frequently in this manual. It is used to qualify a
669 value which is used in the absence of any setting in the configuration. It may
670 also qualify an action which is taken unless a configuration setting specifies
673 The term &'defer'& is used when the delivery of a message to a specific
674 destination cannot immediately take place for some reason (a remote host may be
675 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
678 The word &'domain'& is sometimes used to mean all but the first component of a
679 host's name. It is &'not'& used in that sense here, where it normally refers to
680 the part of an email address following the @ sign.
682 .cindex "envelope, definition of"
683 .cindex "sender" "definition of"
684 A message in transit has an associated &'envelope'&, as well as a header and a
685 body. The envelope contains a sender address (to which bounce messages should
686 be delivered), and any number of recipient addresses. References to the
687 sender or the recipients of a message usually mean the addresses in the
688 envelope. An MTA uses these addresses for delivery, and for returning bounce
689 messages, not the addresses that appear in the header lines.
691 .cindex "message" "header, definition of"
692 .cindex "header section" "definition of"
693 The &'header'& of a message is the first part of a message's text, consisting
694 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
695 &'Subject:'&, etc. Long header lines can be split over several text lines by
696 indenting the continuations. The header is separated from the body by a blank
699 .cindex "local part" "definition of"
700 .cindex "domain" "definition of"
701 The term &'local part'&, which is taken from RFC 2822, is used to refer to the
702 part of an email address that precedes the @ sign. The part that follows the
703 @ sign is called the &'domain'& or &'mail domain'&.
705 .cindex "local delivery" "definition of"
706 .cindex "remote delivery, definition of"
707 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
708 delivery to a file or a pipe on the local host from delivery by SMTP over
709 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
710 host it is running on are &'remote'&.
712 .cindex "return path" "definition of"
713 &'Return path'& is another name that is used for the sender address in a
716 .cindex "queue" "definition of"
717 The term &'queue'& is used to refer to the set of messages awaiting delivery
718 because this term is in widespread use in the context of MTAs. However, in
719 Exim's case, the reality is more like a pool than a queue, because there is
720 normally no ordering of waiting messages.
722 .cindex "queue runner" "definition of"
723 The term &'queue runner'& is used to describe a process that scans the queue
724 and attempts to deliver those messages whose retry times have come. This term
725 is used by other MTAs and also relates to the command &%runq%&, but in Exim
726 the waiting messages are normally processed in an unpredictable order.
728 .cindex "spool directory" "definition of"
729 The term &'spool directory'& is used for a directory in which Exim keeps the
730 messages in its queue &-- that is, those that it is in the process of
731 delivering. This should not be confused with the directory in which local
732 mailboxes are stored, which is called a &"spool directory"& by some people. In
733 the Exim documentation, &"spool"& is always used in the first sense.
740 . ////////////////////////////////////////////////////////////////////////////
741 . ////////////////////////////////////////////////////////////////////////////
743 .chapter "Incorporated code" "CHID2"
744 .cindex "incorporated code"
745 .cindex "regular expressions" "library"
748 A number of pieces of external code are included in the Exim distribution.
751 Regular expressions are supported in the main Exim program and in the
752 Exim monitor using the freely-distributable PCRE library, copyright
753 © University of Cambridge. The source to PCRE is no longer shipped with
754 Exim, so you will need to use the version of PCRE shipped with your system,
755 or obtain and install the full version of the library from
756 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
758 .cindex "cdb" "acknowledgment"
759 Support for the cdb (Constant DataBase) lookup method is provided by code
760 contributed by Nigel Metheringham of (at the time he contributed it) Planet
761 Online Ltd. The implementation is completely contained within the code of Exim.
762 It does not link against an external cdb library. The code contains the
763 following statements:
766 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
768 This program is free software; you can redistribute it and/or modify it under
769 the terms of the GNU General Public License as published by the Free Software
770 Foundation; either version 2 of the License, or (at your option) any later
772 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
773 the spec and sample code for cdb can be obtained from
774 &url(https://cr.yp.to/cdb.html). This implementation borrows
775 some code from Dan Bernstein's implementation (which has no license
776 restrictions applied to it).
779 .cindex "SPA authentication"
780 .cindex "Samba project"
781 .cindex "Microsoft Secure Password Authentication"
782 Client support for Microsoft's &'Secure Password Authentication'& is provided
783 by code contributed by Marc Prud'hommeaux. Server support was contributed by
784 Tom Kistner. This includes code taken from the Samba project, which is released
788 .cindex "&'pwcheck'& daemon"
789 .cindex "&'pwauthd'& daemon"
790 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
791 by code taken from the Cyrus-SASL library and adapted by Alexander S.
792 Sabourenkov. The permission notice appears below, in accordance with the
793 conditions expressed therein.
796 Copyright © 2001 Carnegie Mellon University. All rights reserved.
798 Redistribution and use in source and binary forms, with or without
799 modification, are permitted provided that the following conditions
803 Redistributions of source code must retain the above copyright
804 notice, this list of conditions and the following disclaimer.
806 Redistributions in binary form must reproduce the above copyright
807 notice, this list of conditions and the following disclaimer in
808 the documentation and/or other materials provided with the
811 The name &"Carnegie Mellon University"& must not be used to
812 endorse or promote products derived from this software without
813 prior written permission. For permission or any other legal
814 details, please contact
816 Office of Technology Transfer
817 Carnegie Mellon University
819 Pittsburgh, PA 15213-3890
820 (412) 268-4387, fax: (412) 268-7395
821 tech-transfer@andrew.cmu.edu
824 Redistributions of any form whatsoever must retain the following
827 &"This product includes software developed by Computing Services
828 at Carnegie Mellon University (&url(https://www.cmu.edu/computing/)."&
830 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
831 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
832 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
833 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
834 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
835 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
836 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
841 .cindex "Exim monitor" "acknowledgment"
844 The Exim Monitor program, which is an X-Window application, includes
845 modified versions of the Athena StripChart and TextPop widgets.
846 This code is copyright by DEC and MIT, and their permission notice appears
847 below, in accordance with the conditions expressed therein.
850 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
851 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
855 Permission to use, copy, modify, and distribute this software and its
856 documentation for any purpose and without fee is hereby granted,
857 provided that the above copyright notice appear in all copies and that
858 both that copyright notice and this permission notice appear in
859 supporting documentation, and that the names of Digital or MIT not be
860 used in advertising or publicity pertaining to distribution of the
861 software without specific, written prior permission.
863 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
864 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
865 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
866 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
867 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
868 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
873 .cindex "opendmarc" "acknowledgment"
874 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
875 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
876 derived code are indicated in the respective source files. The full OpenDMARC
877 license is provided in the LICENSE.opendmarc file contained in the distributed
881 Many people have contributed code fragments, some large, some small, that were
882 not covered by any specific license requirements. It is assumed that the
883 contributors are happy to see their code incorporated into Exim under the GPL.
890 . ////////////////////////////////////////////////////////////////////////////
891 . ////////////////////////////////////////////////////////////////////////////
893 .chapter "How Exim receives and delivers mail" "CHID11" &&&
894 "Receiving and delivering mail"
897 .section "Overall philosophy" "SECID10"
898 .cindex "design philosophy"
899 Exim is designed to work efficiently on systems that are permanently connected
900 to the Internet and are handling a general mix of mail. In such circumstances,
901 most messages can be delivered immediately. Consequently, Exim does not
902 maintain independent queues of messages for specific domains or hosts, though
903 it does try to send several messages in a single SMTP connection after a host
904 has been down, and it also maintains per-host retry information.
907 .section "Policy control" "SECID11"
908 .cindex "policy control" "overview"
909 Policy controls are now an important feature of MTAs that are connected to the
910 Internet. Perhaps their most important job is to stop MTAs from being abused as
911 &"open relays"& by misguided individuals who send out vast amounts of
912 unsolicited junk and want to disguise its source. Exim provides flexible
913 facilities for specifying policy controls on incoming mail:
916 .cindex "&ACL;" "introduction"
917 Exim 4 (unlike previous versions of Exim) implements policy controls on
918 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
919 series of statements that may either grant or deny access. ACLs can be used at
920 several places in the SMTP dialogue while receiving a message from a remote
921 host. However, the most common places are after each RCPT command, and at the
922 very end of the message. The sysadmin can specify conditions for accepting or
923 rejecting individual recipients or the entire message, respectively, at these
924 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
927 An ACL is also available for locally generated, non-SMTP messages. In this
928 case, the only available actions are to accept or deny the entire message.
930 When Exim is compiled with the content-scanning extension, facilities are
931 provided in the ACL mechanism for passing the message to external virus and/or
932 spam scanning software. The result of such a scan is passed back to the ACL,
933 which can then use it to decide what to do with the message.
935 When a message has been received, either from a remote host or from the local
936 host, but before the final acknowledgment has been sent, a locally supplied C
937 function called &[local_scan()]& can be run to inspect the message and decide
938 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
939 is accepted, the list of recipients can be modified by the function.
941 Using the &[local_scan()]& mechanism is another way of calling external scanner
942 software. The &%SA-Exim%& add-on package works this way. It does not require
943 Exim to be compiled with the content-scanning extension.
945 After a message has been accepted, a further checking mechanism is available in
946 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
947 runs at the start of every delivery process.
952 .section "User filters" "SECID12"
953 .cindex "filter" "introduction"
954 .cindex "Sieve filter"
955 In a conventional Exim configuration, users are able to run private filters by
956 setting up appropriate &_.forward_& files in their home directories. See
957 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
958 configuration needed to support this, and the separate document entitled
959 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
960 of filtering are available:
963 Sieve filters are written in the standard filtering language that is defined
966 Exim filters are written in a syntax that is unique to Exim, but which is more
967 powerful than Sieve, which it pre-dates.
970 User filters are run as part of the routing process, described below.
974 .section "Message identification" "SECTmessiden"
975 .cindex "message ids" "details of format"
976 .cindex "format" "of message id"
977 .cindex "id of message"
982 Every message handled by Exim is given a &'message id'& which is sixteen
983 characters long. It is divided into three parts, separated by hyphens, for
984 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
985 normally encoding numbers in base 62. However, in the Darwin operating
986 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
987 (avoiding the use of lower case letters) is used instead, because the message
988 id is used to construct filenames, and the names of files in those systems are
989 not always case-sensitive.
991 .cindex "pid (process id)" "re-use of"
992 The detail of the contents of the message id have changed as Exim has evolved.
993 Earlier versions relied on the operating system not re-using a process id (pid)
994 within one second. On modern operating systems, this assumption can no longer
995 be made, so the algorithm had to be changed. To retain backward compatibility,
996 the format of the message id was retained, which is why the following rules are
1000 The first six characters of the message id are the time at which the message
1001 started to be received, to a granularity of one second. That is, this field
1002 contains the number of seconds since the start of the epoch (the normal Unix
1003 way of representing the date and time of day).
1005 After the first hyphen, the next six characters are the id of the process that
1006 received the message.
1008 There are two different possibilities for the final two characters:
1010 .oindex "&%localhost_number%&"
1011 If &%localhost_number%& is not set, this value is the fractional part of the
1012 time of reception, normally in units of 1/2000 of a second, but for systems
1013 that must use base 36 instead of base 62 (because of case-insensitive file
1014 systems), the units are 1/1000 of a second.
1016 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1017 the fractional part of the time, which in this case is in units of 1/200
1018 (1/100) of a second.
1022 After a message has been received, Exim waits for the clock to tick at the
1023 appropriate resolution before proceeding, so that if another message is
1024 received by the same process, or by another process with the same (re-used)
1025 pid, it is guaranteed that the time will be different. In most cases, the clock
1026 will already have ticked while the message was being received.
1029 .section "Receiving mail" "SECID13"
1030 .cindex "receiving mail"
1031 .cindex "message" "reception"
1032 The only way Exim can receive mail from another host is using SMTP over
1033 TCP/IP, in which case the sender and recipient addresses are transferred using
1034 SMTP commands. However, from a locally running process (such as a user's MUA),
1035 there are several possibilities:
1038 If the process runs Exim with the &%-bm%& option, the message is read
1039 non-interactively (usually via a pipe), with the recipients taken from the
1040 command line, or from the body of the message if &%-t%& is also used.
1042 If the process runs Exim with the &%-bS%& option, the message is also read
1043 non-interactively, but in this case the recipients are listed at the start of
1044 the message in a series of SMTP RCPT commands, terminated by a DATA
1045 command. This is called &"batch SMTP"& format,
1046 but it isn't really SMTP. The SMTP commands are just another way of passing
1047 envelope addresses in a non-interactive submission.
1049 If the process runs Exim with the &%-bs%& option, the message is read
1050 interactively, using the SMTP protocol. A two-way pipe is normally used for
1051 passing data between the local process and the Exim process.
1052 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1053 example, the ACLs for SMTP commands are used for this form of submission.
1055 A local process may also make a TCP/IP call to the host's loopback address
1056 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1057 does not treat the loopback address specially. It treats all such connections
1058 in the same way as connections from other hosts.
1062 .cindex "message sender, constructed by Exim"
1063 .cindex "sender" "constructed by Exim"
1064 In the three cases that do not involve TCP/IP, the sender address is
1065 constructed from the login name of the user that called Exim and a default
1066 qualification domain (which can be set by the &%qualify_domain%& configuration
1067 option). For local or batch SMTP, a sender address that is passed using the
1068 SMTP MAIL command is ignored. However, the system administrator may allow
1069 certain users (&"trusted users"&) to specify a different sender addresses
1070 unconditionally, or all users to specify certain forms of different sender
1071 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1072 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1073 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1074 users to change sender addresses.
1076 Messages received by either of the non-interactive mechanisms are subject to
1077 checking by the non-SMTP ACL if one is defined. Messages received using SMTP
1078 (either over TCP/IP or interacting with a local process) can be checked by a
1079 number of ACLs that operate at different times during the SMTP session. Either
1080 individual recipients or the entire message can be rejected if local policy
1081 requirements are not met. The &[local_scan()]& function (see chapter
1082 &<<CHAPlocalscan>>&) is run for all incoming messages.
1084 Exim can be configured not to start a delivery process when a message is
1085 received; this can be unconditional, or depend on the number of incoming SMTP
1086 connections or the system load. In these situations, new messages wait on the
1087 queue until a queue runner process picks them up. However, in standard
1088 configurations under normal conditions, delivery is started as soon as a
1089 message is received.
1095 .section "Handling an incoming message" "SECID14"
1096 .cindex "spool directory" "files that hold a message"
1097 .cindex "file" "how a message is held"
1098 When Exim accepts a message, it writes two files in its spool directory. The
1099 first contains the envelope information, the current status of the message, and
1100 the header lines, and the second contains the body of the message. The names of
1101 the two spool files consist of the message id, followed by &`-H`& for the
1102 file containing the envelope and header, and &`-D`& for the data file.
1104 .cindex "spool directory" "&_input_& sub-directory"
1105 By default, all these message files are held in a single directory called
1106 &_input_& inside the general Exim spool directory. Some operating systems do
1107 not perform very well if the number of files in a directory gets large; to
1108 improve performance in such cases, the &%split_spool_directory%& option can be
1109 used. This causes Exim to split up the input files into 62 sub-directories
1110 whose names are single letters or digits. When this is done, the queue is
1111 processed one sub-directory at a time instead of all at once, which can improve
1112 overall performance even when there are not enough files in each directory to
1113 affect file system performance.
1115 The envelope information consists of the address of the message's sender and
1116 the addresses of the recipients. This information is entirely separate from
1117 any addresses contained in the header lines. The status of the message includes
1118 a list of recipients who have already received the message. The format of the
1119 first spool file is described in chapter &<<CHAPspool>>&.
1121 .cindex "rewriting" "addresses"
1122 Address rewriting that is specified in the rewrite section of the configuration
1123 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1124 both in the header lines and the envelope, at the time the message is accepted.
1125 If during the course of delivery additional addresses are generated (for
1126 example, via aliasing), these new addresses are rewritten as soon as they are
1127 generated. At the time a message is actually delivered (transported) further
1128 rewriting can take place; because this is a transport option, it can be
1129 different for different forms of delivery. It is also possible to specify the
1130 addition or removal of certain header lines at the time the message is
1131 delivered (see chapters &<<CHAProutergeneric>>& and
1132 &<<CHAPtransportgeneric>>&).
1136 .section "Life of a message" "SECID15"
1137 .cindex "message" "life of"
1138 .cindex "message" "frozen"
1139 A message remains in the spool directory until it is completely delivered to
1140 its recipients or to an error address, or until it is deleted by an
1141 administrator or by the user who originally created it. In cases when delivery
1142 cannot proceed &-- for example when a message can neither be delivered to its
1143 recipients nor returned to its sender, the message is marked &"frozen"& on the
1144 spool, and no more deliveries are attempted.
1146 .cindex "frozen messages" "thawing"
1147 .cindex "message" "thawing frozen"
1148 An administrator can &"thaw"& such messages when the problem has been
1149 corrected, and can also freeze individual messages by hand if necessary. In
1150 addition, an administrator can force a delivery error, causing a bounce message
1153 .oindex "&%timeout_frozen_after%&"
1154 .oindex "&%ignore_bounce_errors_after%&"
1155 There are options called &%ignore_bounce_errors_after%& and
1156 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1157 The first applies only to frozen bounces, the second to all frozen messages.
1159 .cindex "message" "log file for"
1160 .cindex "log" "file for each message"
1161 While Exim is working on a message, it writes information about each delivery
1162 attempt to its main log file. This includes successful, unsuccessful, and
1163 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1164 lines are also written to a separate &'message log'& file for each message.
1165 These logs are solely for the benefit of the administrator and are normally
1166 deleted along with the spool files when processing of a message is complete.
1167 The use of individual message logs can be disabled by setting
1168 &%no_message_logs%&; this might give an improvement in performance on very busy
1171 .cindex "journal file"
1172 .cindex "file" "journal"
1173 All the information Exim itself needs to set up a delivery is kept in the first
1174 spool file, along with the header lines. When a successful delivery occurs, the
1175 address is immediately written at the end of a journal file, whose name is the
1176 message id followed by &`-J`&. At the end of a delivery run, if there are some
1177 addresses left to be tried again later, the first spool file (the &`-H`& file)
1178 is updated to indicate which these are, and the journal file is then deleted.
1179 Updating the spool file is done by writing a new file and renaming it, to
1180 minimize the possibility of data loss.
1182 Should the system or Exim crash after a successful delivery but before
1183 the spool file has been updated, the journal is left lying around. The next
1184 time Exim attempts to deliver the message, it reads the journal file and
1185 updates the spool file before proceeding. This minimizes the chances of double
1186 deliveries caused by crashes.
1190 .section "Processing an address for delivery" "SECTprocaddress"
1191 .cindex "drivers" "definition of"
1192 .cindex "router" "definition of"
1193 .cindex "transport" "definition of"
1194 The main delivery processing elements of Exim are called &'routers'& and
1195 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1196 number of them is provided in the source distribution, and compile-time options
1197 specify which ones are included in the binary. Runtime options specify which
1198 ones are actually used for delivering messages.
1200 .cindex "drivers" "instance definition"
1201 Each driver that is specified in the runtime configuration is an &'instance'&
1202 of that particular driver type. Multiple instances are allowed; for example,
1203 you can set up several different &(smtp)& transports, each with different
1204 option values that might specify different ports or different timeouts. Each
1205 instance has its own identifying name. In what follows we will normally use the
1206 instance name when discussing one particular instance (that is, one specific
1207 configuration of the driver), and the generic driver name when discussing
1208 the driver's features in general.
1210 A &'router'& is a driver that operates on an address, either determining how
1211 its delivery should happen, by assigning it to a specific transport, or
1212 converting the address into one or more new addresses (for example, via an
1213 alias file). A router may also explicitly choose to fail an address, causing it
1216 A &'transport'& is a driver that transmits a copy of the message from Exim's
1217 spool to some destination. There are two kinds of transport: for a &'local'&
1218 transport, the destination is a file or a pipe on the local host, whereas for a
1219 &'remote'& transport the destination is some other host. A message is passed
1220 to a specific transport as a result of successful routing. If a message has
1221 several recipients, it may be passed to a number of different transports.
1223 .cindex "preconditions" "definition of"
1224 An address is processed by passing it to each configured router instance in
1225 turn, subject to certain preconditions, until a router accepts the address or
1226 specifies that it should be bounced. We will describe this process in more
1227 detail shortly. First, as a simple example, we consider how each recipient
1228 address in a message is processed in a small configuration of three routers.
1230 To make this a more concrete example, it is described in terms of some actual
1231 routers, but remember, this is only an example. You can configure Exim's
1232 routers in many different ways, and there may be any number of routers in a
1235 The first router that is specified in a configuration is often one that handles
1236 addresses in domains that are not recognized specifically by the local host.
1237 Typically these are addresses for arbitrary domains on the Internet. A precondition
1238 is set up which looks for the special domains known to the host (for example,
1239 its own domain name), and the router is run for addresses that do &'not'&
1240 match. Typically, this is a router that looks up domains in the DNS in order to
1241 find the hosts to which this address routes. If it succeeds, the address is
1242 assigned to a suitable SMTP transport; if it does not succeed, the router is
1243 configured to fail the address.
1245 The second router is reached only when the domain is recognized as one that
1246 &"belongs"& to the local host. This router does redirection &-- also known as
1247 aliasing and forwarding. When it generates one or more new addresses from the
1248 original, each of them is routed independently from the start. Otherwise, the
1249 router may cause an address to fail, or it may simply decline to handle the
1250 address, in which case the address is passed to the next router.
1252 The final router in many configurations is one that checks to see if the
1253 address belongs to a local mailbox. The precondition may involve a check to
1254 see if the local part is the name of a login account, or it may look up the
1255 local part in a file or a database. If its preconditions are not met, or if
1256 the router declines, we have reached the end of the routers. When this happens,
1257 the address is bounced.
1261 .section "Processing an address for verification" "SECID16"
1262 .cindex "router" "for verification"
1263 .cindex "verifying address" "overview"
1264 As well as being used to decide how to deliver to an address, Exim's routers
1265 are also used for &'address verification'&. Verification can be requested as
1266 one of the checks to be performed in an ACL for incoming messages, on both
1267 sender and recipient addresses, and it can be tested using the &%-bv%& and
1268 &%-bvs%& command line options.
1270 When an address is being verified, the routers are run in &"verify mode"&. This
1271 does not affect the way the routers work, but it is a state that can be
1272 detected. By this means, a router can be skipped or made to behave differently
1273 when verifying. A common example is a configuration in which the first router
1274 sends all messages to a message-scanning program unless they have been
1275 previously scanned. Thus, the first router accepts all addresses without any
1276 checking, making it useless for verifying. Normally, the &%no_verify%& option
1277 would be set for such a router, causing it to be skipped in verify mode.
1282 .section "Running an individual router" "SECTrunindrou"
1283 .cindex "router" "running details"
1284 .cindex "preconditions" "checking"
1285 .cindex "router" "result of running"
1286 As explained in the example above, a number of preconditions are checked before
1287 running a router. If any are not met, the router is skipped, and the address is
1288 passed to the next router. When all the preconditions on a router &'are'& met,
1289 the router is run. What happens next depends on the outcome, which is one of
1293 &'accept'&: The router accepts the address, and either assigns it to a
1294 transport or generates one or more &"child"& addresses. Processing the
1295 original address ceases
1296 .oindex "&%unseen%&"
1297 unless the &%unseen%& option is set on the router. This option
1298 can be used to set up multiple deliveries with different routing (for example,
1299 for keeping archive copies of messages). When &%unseen%& is set, the address is
1300 passed to the next router. Normally, however, an &'accept'& return marks the
1303 Any child addresses generated by the router are processed independently,
1304 starting with the first router by default. It is possible to change this by
1305 setting the &%redirect_router%& option to specify which router to start at for
1306 child addresses. Unlike &%pass_router%& (see below) the router specified by
1307 &%redirect_router%& may be anywhere in the router configuration.
1309 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1310 requests that the address be passed to another router. By default, the address
1311 is passed to the next router, but this can be changed by setting the
1312 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1313 must be below the current router (to avoid loops).
1315 &'decline'&: The router declines to accept the address because it does not
1316 recognize it at all. By default, the address is passed to the next router, but
1317 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1318 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1319 &'decline'& into &'fail'&.
1321 &'fail'&: The router determines that the address should fail, and queues it for
1322 the generation of a bounce message. There is no further processing of the
1323 original address unless &%unseen%& is set on the router.
1325 &'defer'&: The router cannot handle the address at the present time. (A
1326 database may be offline, or a DNS lookup may have timed out.) No further
1327 processing of the address happens in this delivery attempt. It is tried again
1328 next time the message is considered for delivery.
1330 &'error'&: There is some error in the router (for example, a syntax error in
1331 its configuration). The action is as for defer.
1334 If an address reaches the end of the routers without having been accepted by
1335 any of them, it is bounced as unrouteable. The default error message in this
1336 situation is &"unrouteable address"&, but you can set your own message by
1337 making use of the &%cannot_route_message%& option. This can be set for any
1338 router; the value from the last router that &"saw"& the address is used.
1340 Sometimes while routing you want to fail a delivery when some conditions are
1341 met but others are not, instead of passing the address on for further routing.
1342 You can do this by having a second router that explicitly fails the delivery
1343 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1344 facility for this purpose.
1347 .section "Duplicate addresses" "SECID17"
1348 .cindex "case of local parts"
1349 .cindex "address duplicate, discarding"
1350 .cindex "duplicate addresses"
1351 Once routing is complete, Exim scans the addresses that are assigned to local
1352 and remote transports and discards any duplicates that it finds. During this
1353 check, local parts are treated case-sensitively. This happens only when
1354 actually delivering a message; when testing routers with &%-bt%&, all the
1355 routed addresses are shown.
1359 .section "Router preconditions" "SECTrouprecon"
1360 .cindex "router" "preconditions, order of processing"
1361 .cindex "preconditions" "order of processing"
1362 The preconditions that are tested for each router are listed below, in the
1363 order in which they are tested. The individual configuration options are
1364 described in more detail in chapter &<<CHAProutergeneric>>&.
1367 .cindex affix "router precondition"
1368 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1369 the local parts handled by the router may or must have certain prefixes and/or
1370 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1371 skipped. These conditions are tested first. When an affix is present, it is
1372 removed from the local part before further processing, including the evaluation
1373 of any other conditions.
1375 Routers can be designated for use only when not verifying an address, that is,
1376 only when routing it for delivery (or testing its delivery routing). If the
1377 &%verify%& option is set false, the router is skipped when Exim is verifying an
1379 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1380 &%verify_recipient%&, which independently control the use of the router for
1381 sender and recipient verification. You can set these options directly if
1382 you want a router to be used for only one type of verification.
1383 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1385 If the &%address_test%& option is set false, the router is skipped when Exim is
1386 run with the &%-bt%& option to test an address routing. This can be helpful
1387 when the first router sends all new messages to a scanner of some sort; it
1388 makes it possible to use &%-bt%& to test subsequent delivery routing without
1389 having to simulate the effect of the scanner.
1391 Routers can be designated for use only when verifying an address, as
1392 opposed to routing it for delivery. The &%verify_only%& option controls this.
1393 Again, cutthrough delivery counts as a verification.
1395 Individual routers can be explicitly skipped when running the routers to
1396 check an address given in the SMTP EXPN command (see the &%expn%& option).
1399 If the &%domains%& option is set, the domain of the address must be in the set
1400 of domains that it defines.
1402 .cindex "tainted data" "de-tainting"
1403 A match verifies the variable &$domain$& (which carries tainted data)
1404 and assigns an untainted value to the &$domain_data$& variable.
1405 Such an untainted value is often needed in the transport.
1406 For specifics of the matching operation and the resulting untainted value,
1407 refer to section &<<SECTdomainlist>>&.
1409 When an untainted value is wanted, use this option
1410 rather than the generic &%condition%& option.
1414 .vindex "&$local_part_prefix$&"
1415 .vindex "&$local_part_prefix_v$&"
1416 .vindex "&$local_part$&"
1417 .vindex "&$local_part_suffix$&"
1418 .vindex "&$local_part_suffix_v$&"
1419 .cindex affix "router precondition"
1420 If the &%local_parts%& option is set, the local part of the address must be in
1421 the set of local parts that it defines.
1423 A match verifies the variable &$local_part$& (which carries tainted data)
1424 and assigns an untainted value to the &$local_part_data$& variable.
1425 Such an untainted value is often needed in the transport.
1426 For specifics of the matching operation and the resulting untainted value,
1427 refer to section &<<SECTlocparlis>>&.
1429 When an untainted value is wanted, use this option
1430 rather than the generic &%condition%& option.
1433 If &%local_part_prefix%& or
1434 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1435 part before this check. If you want to do precondition tests on local parts
1436 that include affixes, you can do so by using a &%condition%& option (see below)
1437 that uses the variables &$local_part$&, &$local_part_prefix$&,
1438 &$local_part_prefix_v$&, &$local_part_suffix$&
1439 and &$local_part_suffix_v$& as necessary.
1442 .vindex "&$local_user_uid$&"
1443 .vindex "&$local_user_gid$&"
1445 If the &%check_local_user%& option is set, the local part must be the name of
1446 an account on the local host. If this check succeeds, the uid and gid of the
1447 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1448 user's home directory is placed in &$home$&; these values can be used in the
1449 remaining preconditions.
1452 If the &%router_home_directory%& option is set, it is expanded at this point,
1453 because it overrides the value of &$home$&. If this expansion were left till
1454 later, the value of &$home$& as set by &%check_local_user%& would be used in
1455 subsequent tests. Having two different values of &$home$& in the same router
1456 could lead to confusion.
1459 If the &%senders%& option is set, the envelope sender address must be in the
1460 set of addresses that it defines.
1463 If the &%require_files%& option is set, the existence or non-existence of
1464 specified files is tested.
1467 .cindex "customizing" "precondition"
1468 If the &%condition%& option is set, it is evaluated and tested. This option
1469 uses an expanded string to allow you to set up your own custom preconditions.
1470 Expanded strings are described in chapter &<<CHAPexpand>>&.
1473 Note that while using
1474 this option for address matching technically works,
1475 it does not set any de-tainted values.
1476 Such values are often needed, either for router-specific options or
1477 for transport options.
1478 Using the &%domains%& and &%local_parts%& options is usually the most
1479 convenient way to obtain them.
1484 Note that &%require_files%& comes near the end of the list, so you cannot use
1485 it to check for the existence of a file in which to lookup up a domain, local
1486 part, or sender. However, as these options are all expanded, you can use the
1487 &%exists%& expansion condition to make such tests within each condition. The
1488 &%require_files%& option is intended for checking files that the router may be
1489 going to use internally, or which are needed by a specific transport (for
1490 example, &_.procmailrc_&).
1494 .section "Delivery in detail" "SECID18"
1495 .cindex "delivery" "in detail"
1496 When a message is to be delivered, the sequence of events is as follows:
1499 If a system-wide filter file is specified, the message is passed to it. The
1500 filter may add recipients to the message, replace the recipients, discard the
1501 message, cause a new message to be generated, or cause the message delivery to
1502 fail. The format of the system filter file is the same as for Exim user filter
1503 files, described in the separate document entitled &'Exim's interfaces to mail
1505 .cindex "Sieve filter" "not available for system filter"
1506 (&*Note*&: Sieve cannot be used for system filter files.)
1508 Some additional features are available in system filters &-- see chapter
1509 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1510 filter only once per delivery attempt, however many recipients it has. However,
1511 if there are several delivery attempts because one or more addresses could not
1512 be immediately delivered, the system filter is run each time. The filter
1513 condition &%first_delivery%& can be used to detect the first run of the system
1516 Each recipient address is offered to each configured router, in turn, subject to
1517 its preconditions, until one is able to handle it. If no router can handle the
1518 address, that is, if they all decline, the address is failed. Because routers
1519 can be targeted at particular domains, several locally handled domains can be
1520 processed entirely independently of each other.
1522 .cindex "routing" "loops in"
1523 .cindex "loop" "while routing"
1524 A router that accepts an address may assign it to a local or a remote
1525 transport. However, the transport is not run at this time. Instead, the address
1526 is placed on a list for the particular transport, which will be run later.
1527 Alternatively, the router may generate one or more new addresses (typically
1528 from alias, forward, or filter files). New addresses are fed back into this
1529 process from the top, but in order to avoid loops, a router ignores any address
1530 which has an identically-named ancestor that was processed by itself.
1532 When all the routing has been done, addresses that have been successfully
1533 handled are passed to their assigned transports. When local transports are
1534 doing real local deliveries, they handle only one address at a time, but if a
1535 local transport is being used as a pseudo-remote transport (for example, to
1536 collect batched SMTP messages for transmission by some other means) multiple
1537 addresses can be handled. Remote transports can always handle more than one
1538 address at a time, but can be configured not to do so, or to restrict multiple
1539 addresses to the same domain.
1541 Each local delivery to a file or a pipe runs in a separate process under a
1542 non-privileged uid, and these deliveries are run one at a time. Remote
1543 deliveries also run in separate processes, normally under a uid that is private
1544 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1545 run in parallel. The maximum number of simultaneous remote deliveries for any
1546 one message is set by the &%remote_max_parallel%& option.
1547 The order in which deliveries are done is not defined, except that all local
1548 deliveries happen before any remote deliveries.
1550 .cindex "queue runner"
1551 When it encounters a local delivery during a queue run, Exim checks its retry
1552 database to see if there has been a previous temporary delivery failure for the
1553 address before running the local transport. If there was a previous failure,
1554 Exim does not attempt a new delivery until the retry time for the address is
1555 reached. However, this happens only for delivery attempts that are part of a
1556 queue run. Local deliveries are always attempted when delivery immediately
1557 follows message reception, even if retry times are set for them. This makes for
1558 better behaviour if one particular message is causing problems (for example,
1559 causing quota overflow, or provoking an error in a filter file).
1561 .cindex "delivery" "retry in remote transports"
1562 Remote transports do their own retry handling, since an address may be
1563 deliverable to one of a number of hosts, each of which may have a different
1564 retry time. If there have been previous temporary failures and no host has
1565 reached its retry time, no delivery is attempted, whether in a queue run or
1566 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1568 If there were any permanent errors, a bounce message is returned to an
1569 appropriate address (the sender in the common case), with details of the error
1570 for each failing address. Exim can be configured to send copies of bounce
1571 messages to other addresses.
1573 .cindex "delivery" "deferral"
1574 If one or more addresses suffered a temporary failure, the message is left on
1575 the queue, to be tried again later. Delivery of these addresses is said to be
1578 When all the recipient addresses have either been delivered or bounced,
1579 handling of the message is complete. The spool files and message log are
1580 deleted, though the message log can optionally be preserved if required.
1586 .section "Retry mechanism" "SECID19"
1587 .cindex "delivery" "retry mechanism"
1588 .cindex "retry" "description of mechanism"
1589 .cindex "queue runner"
1590 Exim's mechanism for retrying messages that fail to get delivered at the first
1591 attempt is the queue runner process. You must either run an Exim daemon that
1592 uses the &%-q%& option with a time interval to start queue runners at regular
1593 intervals or use some other means (such as &'cron'&) to start them. If you do
1594 not arrange for queue runners to be run, messages that fail temporarily at the
1595 first attempt will remain in your queue forever. A queue runner process works
1596 its way through the queue, one message at a time, trying each delivery that has
1597 passed its retry time.
1598 You can run several queue runners at once.
1600 Exim uses a set of configured rules to determine when next to retry the failing
1601 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1602 should give up trying to deliver to the address, at which point it generates a
1603 bounce message. If no retry rules are set for a particular host, address, and
1604 error combination, no retries are attempted, and temporary errors are treated
1609 .section "Temporary delivery failure" "SECID20"
1610 .cindex "delivery" "temporary failure"
1611 There are many reasons why a message may not be immediately deliverable to a
1612 particular address. Failure to connect to a remote machine (because it, or the
1613 connection to it, is down) is one of the most common. Temporary failures may be
1614 detected during routing as well as during the transport stage of delivery.
1615 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1616 is on a file system where the user is over quota. Exim can be configured to
1617 impose its own quotas on local mailboxes; where system quotas are set they will
1620 If a host is unreachable for a period of time, a number of messages may be
1621 waiting for it by the time it recovers, and sending them in a single SMTP
1622 connection is clearly beneficial. Whenever a delivery to a remote host is
1624 .cindex "hints database" "deferred deliveries"
1625 Exim makes a note in its hints database, and whenever a successful
1626 SMTP delivery has happened, it looks to see if any other messages are waiting
1627 for the same host. If any are found, they are sent over the same SMTP
1628 connection, subject to a configuration limit as to the maximum number in any
1633 .section "Permanent delivery failure" "SECID21"
1634 .cindex "delivery" "permanent failure"
1635 .cindex "bounce message" "when generated"
1636 When a message cannot be delivered to some or all of its intended recipients, a
1637 bounce message is generated. Temporary delivery failures turn into permanent
1638 errors when their timeout expires. All the addresses that fail in a given
1639 delivery attempt are listed in a single message. If the original message has
1640 many recipients, it is possible for some addresses to fail in one delivery
1641 attempt and others to fail subsequently, giving rise to more than one bounce
1642 message. The wording of bounce messages can be customized by the administrator.
1643 See chapter &<<CHAPemsgcust>>& for details.
1645 .cindex "&'X-Failed-Recipients:'& header line"
1646 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1647 failed addresses, for the benefit of programs that try to analyse such messages
1650 .cindex "bounce message" "recipient of"
1651 A bounce message is normally sent to the sender of the original message, as
1652 obtained from the message's envelope. For incoming SMTP messages, this is the
1653 address given in the MAIL command. However, when an address is expanded via a
1654 forward or alias file, an alternative address can be specified for delivery
1655 failures of the generated addresses. For a mailing list expansion (see section
1656 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1661 .section "Failures to deliver bounce messages" "SECID22"
1662 .cindex "bounce message" "failure to deliver"
1663 If a bounce message (either locally generated or received from a remote host)
1664 itself suffers a permanent delivery failure, the message is left in the queue,
1665 but it is frozen, awaiting the attention of an administrator. There are options
1666 that can be used to make Exim discard such failed messages, or to keep them
1667 for only a short time (see &%timeout_frozen_after%& and
1668 &%ignore_bounce_errors_after%&).
1674 . ////////////////////////////////////////////////////////////////////////////
1675 . ////////////////////////////////////////////////////////////////////////////
1677 .chapter "Building and installing Exim" "CHID3"
1678 .scindex IIDbuex "building Exim"
1680 .section "Unpacking" "SECID23"
1681 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1682 creates a directory with the name of the current release (for example,
1683 &_exim-&version()_&) into which the following files are placed:
1686 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1687 .irow &_CHANGES_& "contains a reference to where changes are &&&
1689 .irow &_LICENCE_& "the GNU General Public Licence"
1690 .irow &_Makefile_& "top-level make file"
1691 .irow &_NOTICE_& "conditions for the use of Exim"
1692 .irow &_README_& "list of files, directories and simple build &&&
1696 Other files whose names begin with &_README_& may also be present. The
1697 following subdirectories are created:
1700 .irow &_Local_& "an empty directory for local configuration files"
1701 .irow &_OS_& "OS-specific files"
1702 .irow &_doc_& "documentation files"
1703 .irow &_exim_monitor_& "source files for the Exim monitor"
1704 .irow &_scripts_& "scripts used in the build process"
1705 .irow &_src_& "remaining source files"
1706 .irow &_util_& "independent utilities"
1709 The main utility programs are contained in the &_src_& directory and are built
1710 with the Exim binary. The &_util_& directory contains a few optional scripts
1711 that may be useful to some sites.
1714 .section "Multiple machine architectures and operating systems" "SECID24"
1715 .cindex "building Exim" "multiple OS/architectures"
1716 The building process for Exim is arranged to make it easy to build binaries for
1717 a number of different architectures and operating systems from the same set of
1718 source files. Compilation does not take place in the &_src_& directory.
1719 Instead, a &'build directory'& is created for each architecture and operating
1721 .cindex "symbolic link" "to build directory"
1722 Symbolic links to the sources are installed in this directory, which is where
1723 the actual building takes place. In most cases, Exim can discover the machine
1724 architecture and operating system for itself, but the defaults can be
1725 overridden if necessary.
1726 .cindex compiler requirements
1727 .cindex compiler version
1728 A C99-capable compiler will be required for the build.
1731 .section "PCRE library" "SECTpcre"
1732 .cindex "PCRE library"
1733 Exim no longer has an embedded PCRE library as the vast majority of
1734 modern systems include PCRE as a system library, although you may need to
1735 install the PCRE package or the PCRE development package for your operating
1736 system. If your system has a normal PCRE installation the Exim build
1737 process will need no further configuration. If the library or the
1738 headers are in an unusual location you will need to either set the PCRE_LIBS
1739 and INCLUDE directives appropriately,
1740 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1741 If your operating system has no
1742 PCRE support then you will need to obtain and build the current PCRE
1743 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1744 More information on PCRE is available at &url(https://www.pcre.org/).
1746 .section "DBM libraries" "SECTdb"
1747 .cindex "DBM libraries" "discussion of"
1748 .cindex "hints database" "DBM files used for"
1749 Even if you do not use any DBM files in your configuration, Exim still needs a
1750 DBM library in order to operate, because it uses indexed files for its hints
1751 databases. Unfortunately, there are a number of DBM libraries in existence, and
1752 different operating systems often have different ones installed.
1754 .cindex "Solaris" "DBM library for"
1755 .cindex "IRIX, DBM library for"
1756 .cindex "BSD, DBM library for"
1757 .cindex "Linux, DBM library for"
1758 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1759 Linux distribution, the DBM configuration should happen automatically, and you
1760 may be able to ignore this section. Otherwise, you may have to learn more than
1761 you would like about DBM libraries from what follows.
1763 .cindex "&'ndbm'& DBM library"
1764 Licensed versions of Unix normally contain a library of DBM functions operating
1765 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1766 versions of Unix seem to vary in what they contain as standard. In particular,
1767 some early versions of Linux have no default DBM library, and different
1768 distributors have chosen to bundle different libraries with their packaged
1769 versions. However, the more recent releases seem to have standardized on the
1770 Berkeley DB library.
1772 Different DBM libraries have different conventions for naming the files they
1773 use. When a program opens a file called &_dbmfile_&, there are several
1777 A traditional &'ndbm'& implementation, such as that supplied as part of
1778 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1780 .cindex "&'gdbm'& DBM library"
1781 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1782 compatibility interface it makes two different hard links to it with names
1783 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1784 filename is used unmodified.
1786 .cindex "Berkeley DB library"
1787 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1788 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1789 programmer exactly the same as the traditional &'ndbm'& implementation.
1791 If the Berkeley package is used in its native mode, it operates on a single
1792 file called &_dbmfile_&; the programmer's interface is somewhat different to
1793 the traditional &'ndbm'& interface.
1795 To complicate things further, there are several very different versions of the
1796 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1797 2.&'x'& and 3.&'x'& were current for a while, but the latest versions when Exim last revamped support were numbered 4.&'x'&.
1798 Maintenance of some of the earlier releases has ceased. All versions of
1799 Berkeley DB could be obtained from
1800 &url(http://www.sleepycat.com/), which is now a redirect to their new owner's
1801 page with far newer versions listed.
1802 It is probably wise to plan to move your storage configurations away from
1803 Berkeley DB format, as today there are smaller and simpler alternatives more
1804 suited to Exim's usage model.
1806 .cindex "&'tdb'& DBM library"
1807 Yet another DBM library, called &'tdb'&, is available from
1808 &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
1809 operates on a single file.
1813 .cindex "DBM libraries" "configuration for building"
1814 Exim and its utilities can be compiled to use any of these interfaces. In order
1815 to use any version of the Berkeley DB package in native mode, you must set
1816 USE_DB in an appropriate configuration file (typically
1817 &_Local/Makefile_&). For example:
1821 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1822 error is diagnosed if you set more than one of these.
1824 At the lowest level, the build-time configuration sets none of these options,
1825 thereby assuming an interface of type (1). However, some operating system
1826 configuration files (for example, those for the BSD operating systems and
1827 Linux) assume type (4) by setting USE_DB as their default, and the
1828 configuration files for Cygwin set USE_GDBM. Anything you set in
1829 &_Local/Makefile_&, however, overrides these system defaults.
1831 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1832 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1833 in one of these lines:
1838 Settings like that will work if the DBM library is installed in the standard
1839 place. Sometimes it is not, and the library's header file may also not be in
1840 the default path. You may need to set INCLUDE to specify where the header
1841 file is, and to specify the path to the library more fully in DBMLIB, as in
1844 INCLUDE=-I/usr/local/include/db-4.1
1845 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1847 There is further detailed discussion about the various DBM libraries in the
1848 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1852 .section "Pre-building configuration" "SECID25"
1853 .cindex "building Exim" "pre-building configuration"
1854 .cindex "configuration for building Exim"
1855 .cindex "&_Local/Makefile_&"
1856 .cindex "&_src/EDITME_&"
1857 Before building Exim, a local configuration file that specifies options
1858 independent of any operating system has to be created with the name
1859 &_Local/Makefile_&. A template for this file is supplied as the file
1860 &_src/EDITME_&, and it contains full descriptions of all the option settings
1861 therein. These descriptions are therefore not repeated here. If you are
1862 building Exim for the first time, the simplest thing to do is to copy
1863 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1865 There are three settings that you must supply, because Exim will not build
1866 without them. They are the location of the runtime configuration file
1867 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1868 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1869 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1870 a colon-separated list of filenames; Exim uses the first of them that exists.
1872 There are a few other parameters that can be specified either at build time or
1873 at runtime, to enable the same binary to be used on a number of different
1874 machines. However, if the locations of Exim's spool directory and log file
1875 directory (if not within the spool directory) are fixed, it is recommended that
1876 you specify them in &_Local/Makefile_& instead of at runtime, so that errors
1877 detected early in Exim's execution (such as a malformed configuration file) can
1880 .cindex "content scanning" "specifying at build time"
1881 Exim's interfaces for calling virus and spam scanning software directly from
1882 access control lists are not compiled by default. If you want to include these
1883 facilities, you need to set
1885 WITH_CONTENT_SCAN=yes
1887 in your &_Local/Makefile_&. For details of the facilities themselves, see
1888 chapter &<<CHAPexiscan>>&.
1891 .cindex "&_Local/eximon.conf_&"
1892 .cindex "&_exim_monitor/EDITME_&"
1893 If you are going to build the Exim monitor, a similar configuration process is
1894 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1895 your installation and saved under the name &_Local/eximon.conf_&. If you are
1896 happy with the default settings described in &_exim_monitor/EDITME_&,
1897 &_Local/eximon.conf_& can be empty, but it must exist.
1899 This is all the configuration that is needed in straightforward cases for known
1900 operating systems. However, the building process is set up so that it is easy
1901 to override options that are set by default or by operating-system-specific
1902 configuration files, for example, to change the C compiler, which
1903 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1908 .section "Support for iconv()" "SECID26"
1909 .cindex "&[iconv()]& support"
1911 The contents of header lines in messages may be encoded according to the rules
1912 described RFC 2047. This makes it possible to transmit characters that are not
1913 in the ASCII character set, and to label them as being in a particular
1914 character set. When Exim is inspecting header lines by means of the &%$h_%&
1915 mechanism, it decodes them, and translates them into a specified character set
1916 (default is set at build time). The translation is possible only if the operating system
1917 supports the &[iconv()]& function.
1919 However, some of the operating systems that supply &[iconv()]& do not support
1920 very many conversions. The GNU &%libiconv%& library (available from
1921 &url(https://www.gnu.org/software/libiconv/)) can be installed on such
1922 systems to remedy this deficiency, as well as on systems that do not supply
1923 &[iconv()]& at all. After installing &%libiconv%&, you should add
1927 to your &_Local/Makefile_& and rebuild Exim.
1931 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1932 .cindex "TLS" "including support for TLS"
1933 .cindex "encryption" "including support for"
1934 .cindex "OpenSSL" "building Exim with"
1935 .cindex "GnuTLS" "building Exim with"
1936 Exim is usually built to support encrypted SMTP connections, using the STARTTLS
1937 command as per RFC 2487. It can also support clients that expect to
1938 start a TLS session immediately on connection to a non-standard port (see the
1939 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1942 If you want to build Exim with TLS support, you must first install either the
1943 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1946 If you do not want TLS support you should set
1950 in &_Local/Makefile_&.
1952 If OpenSSL is installed, you should set
1955 TLS_LIBS=-lssl -lcrypto
1957 in &_Local/Makefile_&. You may also need to specify the locations of the
1958 OpenSSL library and include files. For example:
1961 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1962 TLS_INCLUDE=-I/usr/local/openssl/include/
1964 .cindex "pkg-config" "OpenSSL"
1965 If you have &'pkg-config'& available, then instead you can just use:
1968 USE_OPENSSL_PC=openssl
1970 .cindex "USE_GNUTLS"
1971 If GnuTLS is installed, you should set
1974 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1976 in &_Local/Makefile_&, and again you may need to specify the locations of the
1977 library and include files. For example:
1980 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1981 TLS_INCLUDE=-I/usr/gnu/include
1983 .cindex "pkg-config" "GnuTLS"
1984 If you have &'pkg-config'& available, then instead you can just use:
1987 USE_GNUTLS_PC=gnutls
1990 You do not need to set TLS_INCLUDE if the relevant directory is already
1991 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1992 given in chapter &<<CHAPTLS>>&.
1997 .section "Use of tcpwrappers" "SECID27"
1999 .cindex "tcpwrappers, building Exim to support"
2000 .cindex "USE_TCP_WRAPPERS"
2001 .cindex "TCP_WRAPPERS_DAEMON_NAME"
2002 .cindex "tcp_wrappers_daemon_name"
2003 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
2004 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
2005 alternative to Exim's own checking facilities for installations that are
2006 already making use of &'tcpwrappers'& for other purposes. To do this, you
2007 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
2008 &_tcpd.h_& to be available at compile time, and also ensure that the library
2009 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
2010 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
2013 USE_TCP_WRAPPERS=yes
2014 CFLAGS=-O -I/usr/local/include
2015 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
2017 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
2018 files is &"exim"&. For example, the line
2020 exim : LOCAL 192.168.1. .friendly.domain.example
2022 in your &_/etc/hosts.allow_& file allows connections from the local host, from
2023 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
2024 All other connections are denied. The daemon name used by &'tcpwrappers'&
2025 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
2026 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
2027 configure file. Consult the &'tcpwrappers'& documentation for
2031 .section "Including support for IPv6" "SECID28"
2032 .cindex "IPv6" "including support for"
2033 Exim contains code for use on systems that have IPv6 support. Setting
2034 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
2035 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
2036 where the IPv6 support is not fully integrated into the normal include and
2039 Two different types of DNS record for handling IPv6 addresses have been
2040 defined. AAAA records (analogous to A records for IPv4) are in use, and are
2041 currently seen as the mainstream. Another record type called A6 was proposed
2042 as better than AAAA because it had more flexibility. However, it was felt to be
2043 over-complex, and its status was reduced to &"experimental"&.
2045 have a compile option for including A6 record support but this has now been
2050 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
2051 .cindex "lookup modules"
2052 .cindex "dynamic modules"
2053 .cindex ".so building"
2054 On some platforms, Exim supports not compiling all lookup types directly into
2055 the main binary, instead putting some into external modules which can be loaded
2057 This permits packagers to build Exim with support for lookups with extensive
2058 library dependencies without requiring all users to install all of those
2060 Most, but not all, lookup types can be built this way.
2062 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2063 installed; Exim will only load modules from that directory, as a security
2064 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2065 for your OS; see &_OS/Makefile-Linux_& for an example.
2066 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2067 see &_src/EDITME_& for details.
2069 Then, for each module to be loaded dynamically, define the relevant
2070 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2071 For example, this will build in lsearch but load sqlite and mysql support
2080 .section "The building process" "SECID29"
2081 .cindex "build directory"
2082 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2083 created, run &'make'& at the top level. It determines the architecture and
2084 operating system types, and creates a build directory if one does not exist.
2085 For example, on a Sun system running Solaris 8, the directory
2086 &_build-SunOS5-5.8-sparc_& is created.
2087 .cindex "symbolic link" "to source files"
2088 Symbolic links to relevant source files are installed in the build directory.
2090 If this is the first time &'make'& has been run, it calls a script that builds
2091 a make file inside the build directory, using the configuration files from the
2092 &_Local_& directory. The new make file is then passed to another instance of
2093 &'make'&. This does the real work, building a number of utility scripts, and
2094 then compiling and linking the binaries for the Exim monitor (if configured), a
2095 number of utility programs, and finally Exim itself. The command &`make
2096 makefile`& can be used to force a rebuild of the make file in the build
2097 directory, should this ever be necessary.
2099 If you have problems building Exim, check for any comments there may be in the
2100 &_README_& file concerning your operating system, and also take a look at the
2101 FAQ, where some common problems are covered.
2105 .section 'Output from &"make"&' "SECID283"
2106 The output produced by the &'make'& process for compile lines is often very
2107 unreadable, because these lines can be very long. For this reason, the normal
2108 output is suppressed by default, and instead output similar to that which
2109 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2110 each module that is being compiled or linked. However, it is still possible to
2111 get the full output, by calling &'make'& like this:
2115 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2116 command reflection in &'make'&. When you ask for the full output, it is
2117 given in addition to the short output.
2121 .section "Overriding build-time options for Exim" "SECToverride"
2122 .cindex "build-time options, overriding"
2123 The main make file that is created at the beginning of the building process
2124 consists of the concatenation of a number of files which set configuration
2125 values, followed by a fixed set of &'make'& instructions. If a value is set
2126 more than once, the last setting overrides any previous ones. This provides a
2127 convenient way of overriding defaults. The files that are concatenated are, in
2130 &_OS/Makefile-Default_&
2131 &_OS/Makefile-_&<&'ostype'&>
2133 &_Local/Makefile-_&<&'ostype'&>
2134 &_Local/Makefile-_&<&'archtype'&>
2135 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2136 &_OS/Makefile-Base_&
2138 .cindex "&_Local/Makefile_&"
2139 .cindex "building Exim" "operating system type"
2140 .cindex "building Exim" "architecture type"
2141 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2142 architecture type. &_Local/Makefile_& is required to exist, and the building
2143 process fails if it is absent. The other three &_Local_& files are optional,
2144 and are often not needed.
2146 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2147 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2148 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2149 values are used, thereby providing a means of forcing particular settings.
2150 Otherwise, the scripts try to get values from the &%uname%& command. If this
2151 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2152 of &'ad hoc'& transformations are then applied, to produce the standard names
2153 that Exim expects. You can run these scripts directly from the shell in order
2154 to find out what values are being used on your system.
2157 &_OS/Makefile-Default_& contains comments about the variables that are set
2158 therein. Some (but not all) are mentioned below. If there is something that
2159 needs changing, review the contents of this file and the contents of the make
2160 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2164 .cindex "building Exim" "overriding default settings"
2165 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2166 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2167 need to change the original files. Instead, you should make the changes by
2168 putting the new values in an appropriate &_Local_& file. For example,
2169 .cindex "Tru64-Unix build-time settings"
2170 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2171 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2172 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2173 called with the option &%-std1%&, to make it recognize some of the features of
2174 Standard C that Exim uses. (Most other compilers recognize Standard C by
2175 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2176 containing the lines
2181 If you are compiling for just one operating system, it may be easier to put
2182 these lines directly into &_Local/Makefile_&.
2184 Keeping all your local configuration settings separate from the distributed
2185 files makes it easy to transfer them to new versions of Exim simply by copying
2186 the contents of the &_Local_& directory.
2189 .cindex "NIS lookup type" "including support for"
2190 .cindex "NIS+ lookup type" "including support for"
2191 .cindex "LDAP" "including support for"
2192 .cindex "lookup" "inclusion in binary"
2193 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2194 lookup, but not all systems have these components installed, so the default is
2195 not to include the relevant code in the binary. All the different kinds of file
2196 and database lookup that Exim supports are implemented as separate code modules
2197 which are included only if the relevant compile-time options are set. In the
2198 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2204 and similar settings apply to the other lookup types. They are all listed in
2205 &_src/EDITME_&. In many cases the relevant include files and interface
2206 libraries need to be installed before compiling Exim.
2207 .cindex "cdb" "including support for"
2208 However, there are some optional lookup types (such as cdb) for which
2209 the code is entirely contained within Exim, and no external include
2210 files or libraries are required. When a lookup type is not included in the
2211 binary, attempts to configure Exim to use it cause runtime configuration
2214 .cindex "pkg-config" "lookups"
2215 .cindex "pkg-config" "authenticators"
2216 Many systems now use a tool called &'pkg-config'& to encapsulate information
2217 about how to compile against a library; Exim has some initial support for
2218 being able to use pkg-config for lookups and authenticators. For any given
2219 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2220 variable with the &`_PC`& suffix in the name and assign as the value the
2221 name of the package to be queried. The results of querying via the
2222 &'pkg-config'& command will be added to the appropriate Makefile variables
2223 with &`+=`& directives, so your version of &'make'& will need to support that
2224 syntax. For instance:
2227 LOOKUP_SQLITE_PC=sqlite3
2229 AUTH_GSASL_PC=libgsasl
2230 AUTH_HEIMDAL_GSSAPI=yes
2231 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2234 .cindex "Perl" "including support for"
2235 Exim can be linked with an embedded Perl interpreter, allowing Perl
2236 subroutines to be called during string expansion. To enable this facility,
2240 must be defined in &_Local/Makefile_&. Details of this facility are given in
2241 chapter &<<CHAPperl>>&.
2243 .cindex "X11 libraries, location of"
2244 The location of the X11 libraries is something that varies a lot between
2245 operating systems, and there may be different versions of X11 to cope
2246 with. Exim itself makes no use of X11, but if you are compiling the Exim
2247 monitor, the X11 libraries must be available.
2248 The following three variables are set in &_OS/Makefile-Default_&:
2251 XINCLUDE=-I$(X11)/include
2252 XLFLAGS=-L$(X11)/lib
2254 These are overridden in some of the operating-system configuration files. For
2255 example, in &_OS/Makefile-SunOS5_& there is
2258 XINCLUDE=-I$(X11)/include
2259 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2261 If you need to override the default setting for your operating system, place a
2262 definition of all three of these variables into your
2263 &_Local/Makefile-<ostype>_& file.
2266 If you need to add any extra libraries to the link steps, these can be put in a
2267 variable called EXTRALIBS, which appears in all the link commands, but by
2268 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2269 command for linking the main Exim binary, and not for any associated utilities.
2271 .cindex "DBM libraries" "configuration for building"
2272 There is also DBMLIB, which appears in the link commands for binaries that
2273 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2274 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2275 binary, and which can be used, for example, to include additional X11
2278 .cindex "configuration file" "editing"
2279 The make file copes with rebuilding Exim correctly if any of the configuration
2280 files are edited. However, if an optional configuration file is deleted, it is
2281 necessary to touch the associated non-optional file (that is,
2282 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2285 .section "OS-specific header files" "SECID30"
2287 .cindex "building Exim" "OS-specific C header files"
2288 The &_OS_& directory contains a number of files with names of the form
2289 &_os.h-<ostype>_&. These are system-specific C header files that should not
2290 normally need to be changed. There is a list of macro settings that are
2291 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2292 are porting Exim to a new operating system.
2296 .section "Overriding build-time options for the monitor" "SECID31"
2297 .cindex "building Eximon"
2298 A similar process is used for overriding things when building the Exim monitor,
2299 where the files that are involved are
2301 &_OS/eximon.conf-Default_&
2302 &_OS/eximon.conf-_&<&'ostype'&>
2303 &_Local/eximon.conf_&
2304 &_Local/eximon.conf-_&<&'ostype'&>
2305 &_Local/eximon.conf-_&<&'archtype'&>
2306 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2308 .cindex "&_Local/eximon.conf_&"
2309 As with Exim itself, the final three files need not exist, and in this case the
2310 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2311 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2312 variables of the same name, preceded by EXIMON_. For example, setting
2313 EXIMON_LOG_DEPTH in the environment overrides the value of
2314 LOG_DEPTH at runtime.
2318 .section "Installing Exim binaries and scripts" "SECID32"
2319 .cindex "installing Exim"
2320 .cindex "BIN_DIRECTORY"
2321 The command &`make install`& runs the &(exim_install)& script with no
2322 arguments. The script copies binaries and utility scripts into the directory
2323 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2324 .cindex "setuid" "installing Exim with"
2325 The install script copies files only if they are newer than the files they are
2326 going to replace. The Exim binary is required to be owned by root and have the
2327 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2328 install`& as root so that it can set up the Exim binary in this way. However, in
2329 some special situations (for example, if a host is doing no local deliveries)
2330 it may be possible to run Exim without making the binary setuid root (see
2331 chapter &<<CHAPsecurity>>& for details).
2333 .cindex "CONFIGURE_FILE"
2334 Exim's runtime configuration file is named by the CONFIGURE_FILE setting
2335 in &_Local/Makefile_&. If this names a single file, and the file does not
2336 exist, the default configuration file &_src/configure.default_& is copied there
2337 by the installation script. If a runtime configuration file already exists, it
2338 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2339 alternative files, no default is installed.
2341 .cindex "system aliases file"
2342 .cindex "&_/etc/aliases_&"
2343 One change is made to the default configuration file when it is installed: the
2344 default configuration contains a router that references a system aliases file.
2345 The path to this file is set to the value specified by
2346 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2347 If the system aliases file does not exist, the installation script creates it,
2348 and outputs a comment to the user.
2350 The created file contains no aliases, but it does contain comments about the
2351 aliases a site should normally have. Mail aliases have traditionally been
2352 kept in &_/etc/aliases_&. However, some operating systems are now using
2353 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2354 Exim's configuration if necessary.
2356 The default configuration uses the local host's name as the only local domain,
2357 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2358 running as the local user. System aliases and &_.forward_& files in users' home
2359 directories are supported, but no NIS or NIS+ support is configured. Domains
2360 other than the name of the local host are routed using the DNS, with delivery
2363 It is possible to install Exim for special purposes (such as building a binary
2364 distribution) in a private part of the file system. You can do this by a
2367 make DESTDIR=/some/directory/ install
2369 This has the effect of pre-pending the specified directory to all the file
2370 paths, except the name of the system aliases file that appears in the default
2371 configuration. (If a default alias file is created, its name &'is'& modified.)
2372 For backwards compatibility, ROOT is used if DESTDIR is not set,
2373 but this usage is deprecated.
2375 .cindex "installing Exim" "what is not installed"
2376 Running &'make install'& does not copy the Exim 4 conversion script
2377 &'convert4r4'&. You will probably run this only once if you are
2378 upgrading from Exim 3. None of the documentation files in the &_doc_&
2379 directory are copied, except for the info files when you have set
2380 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2382 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2383 to their names. The Exim binary itself, however, is handled differently. It is
2384 installed under a name that includes the version number and the compile number,
2385 for example, &_exim-&version()-1_&. The script then arranges for a symbolic link
2386 called &_exim_& to point to the binary. If you are updating a previous version
2387 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2388 from the directory (as seen by other processes).
2390 .cindex "installing Exim" "testing the script"
2391 If you want to see what the &'make install'& will do before running it for
2392 real, you can pass the &%-n%& option to the installation script by this
2395 make INSTALL_ARG=-n install
2397 The contents of the variable INSTALL_ARG are passed to the installation
2398 script. You do not need to be root to run this test. Alternatively, you can run
2399 the installation script directly, but this must be from within the build
2400 directory. For example, from the top-level Exim directory you could use this
2403 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2405 .cindex "installing Exim" "install script options"
2406 There are two other options that can be supplied to the installation script.
2409 &%-no_chown%& bypasses the call to change the owner of the installed binary
2410 to root, and the call to make it a setuid binary.
2412 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2416 INSTALL_ARG can be used to pass these options to the script. For example:
2418 make INSTALL_ARG=-no_symlink install
2420 The installation script can also be given arguments specifying which files are
2421 to be copied. For example, to install just the Exim binary, and nothing else,
2422 without creating the symbolic link, you could use:
2424 make INSTALL_ARG='-no_symlink exim' install
2429 .section "Installing info documentation" "SECTinsinfdoc"
2430 .cindex "installing Exim" "&'info'& documentation"
2431 Not all systems use the GNU &'info'& system for documentation, and for this
2432 reason, the Texinfo source of Exim's documentation is not included in the main
2433 distribution. Instead it is available separately from the FTP site (see section
2436 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2437 source of the documentation is found in the source tree, running &`make
2438 install`& automatically builds the info files and installs them.
2442 .section "Setting up the spool directory" "SECID33"
2443 .cindex "spool directory" "creating"
2444 When it starts up, Exim tries to create its spool directory if it does not
2445 exist. The Exim uid and gid are used for the owner and group of the spool
2446 directory. Sub-directories are automatically created in the spool directory as
2452 .section "Testing" "SECID34"
2453 .cindex "testing" "installation"
2454 Having installed Exim, you can check that the runtime configuration file is
2455 syntactically valid by running the following command, which assumes that the
2456 Exim binary directory is within your PATH environment variable:
2460 If there are any errors in the configuration file, Exim outputs error messages.
2461 Otherwise it outputs the version number and build date,
2462 the DBM library that is being used, and information about which drivers and
2463 other optional code modules are included in the binary.
2464 Some simple routing tests can be done by using the address testing option. For
2467 &`exim -bt`& <&'local username'&>
2469 should verify that it recognizes a local mailbox, and
2471 &`exim -bt`& <&'remote address'&>
2473 a remote one. Then try getting it to deliver mail, both locally and remotely.
2474 This can be done by passing messages directly to Exim, without going through a
2475 user agent. For example:
2477 exim -v postmaster@your.domain.example
2478 From: user@your.domain.example
2479 To: postmaster@your.domain.example
2480 Subject: Testing Exim
2482 This is a test message.
2485 The &%-v%& option causes Exim to output some verification of what it is doing.
2486 In this case you should see copies of three log lines, one for the message's
2487 arrival, one for its delivery, and one containing &"Completed"&.
2489 .cindex "delivery" "problems with"
2490 If you encounter problems, look at Exim's log files (&'mainlog'& and
2491 &'paniclog'&) to see if there is any relevant information there. Another source
2492 of information is running Exim with debugging turned on, by specifying the
2493 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2494 with debugging turned on by a command of the form
2496 &`exim -d -M`& <&'exim-message-id'&>
2498 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2499 produces rather a lot of output, but you can cut this down to specific areas.
2500 For example, if you use &%-d-all+route%& only the debugging information
2501 relevant to routing is included. (See the &%-d%& option in chapter
2502 &<<CHAPcommandline>>& for more details.)
2504 .cindex '&"sticky"& bit'
2505 .cindex "lock files"
2506 One specific problem that has shown up on some sites is the inability to do
2507 local deliveries into a shared mailbox directory, because it does not have the
2508 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2509 writing to a mailbox file, and if it cannot create the lock file, the delivery
2510 is deferred. You can get round this either by setting the &"sticky bit"& on the
2511 directory, or by setting a specific group for local deliveries and allowing
2512 that group to create files in the directory (see the comments above the
2513 &(local_delivery)& transport in the default configuration file). Another
2514 approach is to configure Exim not to use lock files, but just to rely on
2515 &[fcntl()]& locking instead. However, you should do this only if all user
2516 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2517 see chapter &<<CHAPappendfile>>&.
2519 One thing that cannot be tested on a system that is already running an MTA is
2520 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2521 &%-oX%& option can be used to run an Exim daemon that listens on some other
2522 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2523 &'exim_checkaccess'& utility can be used to check out policy controls on
2526 Testing a new version on a system that is already running Exim can most easily
2527 be done by building a binary with a different CONFIGURE_FILE setting. From
2528 within the runtime configuration, all other file and directory names
2529 that Exim uses can be altered, in order to keep it entirely clear of the
2533 .section "Replacing another MTA with Exim" "SECID35"
2534 .cindex "replacing another MTA"
2535 Building and installing Exim for the first time does not of itself put it in
2536 general use. The name by which the system's MTA is called by mail user agents
2537 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2538 operating system), and it is necessary to make this name point to the &'exim'&
2539 binary in order to get the user agents to pass messages to Exim. This is
2540 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2541 or &_/usr/lib/sendmail_&
2542 .cindex "symbolic link" "to &'exim'& binary"
2543 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2544 privilege and executable status from the old MTA. It is then necessary to stop
2545 and restart the mailer daemon, if one is running.
2547 .cindex "FreeBSD, MTA indirection"
2548 .cindex "&_/etc/mail/mailer.conf_&"
2549 Some operating systems have introduced alternative ways of switching MTAs. For
2550 example, if you are running FreeBSD, you need to edit the file
2551 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2552 described. A typical example of the contents of this file for running Exim is
2555 sendmail /usr/exim/bin/exim
2556 send-mail /usr/exim/bin/exim
2557 mailq /usr/exim/bin/exim -bp
2558 newaliases /usr/bin/true
2560 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2561 your Exim installation is &"live"&. Check it by sending a message from your
2562 favourite user agent.
2564 You should consider what to tell your users about the change of MTA. Exim may
2565 have different capabilities to what was previously running, and there are
2566 various operational differences such as the text of messages produced by
2567 command line options and in bounce messages. If you allow your users to make
2568 use of Exim's filtering capabilities, you should make the document entitled
2569 &'Exim's interface to mail filtering'& available to them.
2573 .section "Upgrading Exim" "SECID36"
2574 .cindex "upgrading Exim"
2575 If you are already running Exim on your host, building and installing a new
2576 version automatically makes it available to MUAs, or any other programs that
2577 call the MTA directly. However, if you are running an Exim daemon, you do need
2578 .cindex restart "on HUP signal"
2579 .cindex signal "HUP, to restart"
2580 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2581 new binary. You do not need to stop processing mail in order to install a new
2582 version of Exim. The install script does not modify an existing runtime
2588 .section "Stopping the Exim daemon on Solaris" "SECID37"
2589 .cindex "Solaris" "stopping Exim on"
2590 The standard command for stopping the mailer daemon on Solaris is
2592 /etc/init.d/sendmail stop
2594 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2595 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2596 for the text &"sendmail"&; this is not present because the actual program name
2597 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2598 solution is to replace the line that finds the process id with something like
2600 pid=`cat /var/spool/exim/exim-daemon.pid`
2602 to obtain the daemon's pid directly from the file that Exim saves it in.
2604 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2605 still be received from local processes, and if automatic delivery is configured
2606 (the normal case), deliveries will still occur.
2611 . ////////////////////////////////////////////////////////////////////////////
2612 . ////////////////////////////////////////////////////////////////////////////
2614 .chapter "The Exim command line" "CHAPcommandline"
2615 .scindex IIDclo1 "command line" "options"
2616 .scindex IIDclo2 "options" "command line"
2617 Exim's command line takes the standard Unix form of a sequence of options,
2618 each starting with a hyphen character, followed by a number of arguments. The
2619 options are compatible with the main options of Sendmail, and there are also
2620 some additional options, some of which are compatible with Smail 3. Certain
2621 combinations of options do not make sense, and provoke an error if used.
2622 The form of the arguments depends on which options are set.
2625 .section "Setting options by program name" "SECID38"
2627 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2628 were present before any other options.
2629 The &%-bp%& option requests a listing of the contents of the mail queue on the
2631 This feature is for compatibility with some systems that contain a command of
2632 that name in one of the standard libraries, symbolically linked to
2633 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2636 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2637 were present before any other options, for compatibility with Smail. The
2638 &%-bS%& option is used for reading in a number of messages in batched SMTP
2642 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2643 &%-oee%& options were present before any other options, for compatibility with
2644 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2647 .cindex "queue runner"
2648 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2649 were present before any other options, for compatibility with Smail. The &%-q%&
2650 option causes a single queue runner process to be started.
2652 .cindex "&'newaliases'&"
2653 .cindex "alias file" "building"
2654 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2655 If Exim is called under the name &'newaliases'& it behaves as if the option
2656 &%-bi%& were present before any other options, for compatibility with Sendmail.
2657 This option is used for rebuilding Sendmail's alias file. Exim does not have
2658 the concept of a single alias file, but can be configured to run a given
2659 command if called with the &%-bi%& option.
2662 .section "Trusted and admin users" "SECTtrustedadmin"
2663 Some Exim options are available only to &'trusted users'& and others are
2664 available only to &'admin users'&. In the description below, the phrases &"Exim
2665 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2666 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2667 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2670 .cindex "trusted users" "definition of"
2671 .cindex "user" "trusted definition of"
2672 The trusted users are root, the Exim user, any user listed in the
2673 &%trusted_users%& configuration option, and any user whose current group or any
2674 supplementary group is one of those listed in the &%trusted_groups%&
2675 configuration option. Note that the Exim group is not automatically trusted.
2677 .cindex '&"From"& line'
2678 .cindex "envelope from"
2679 .cindex "envelope sender"
2680 Trusted users are always permitted to use the &%-f%& option or a leading
2681 &"From&~"& line to specify the envelope sender of a message that is passed to
2682 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2683 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2684 users to set envelope senders.
2686 .cindex "&'From:'& header line"
2687 .cindex "&'Sender:'& header line"
2688 .cindex "header lines" "From:"
2689 .cindex "header lines" "Sender:"
2690 For a trusted user, there is never any check on the contents of the &'From:'&
2691 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2692 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2694 Trusted users may also specify a host name, host address, interface address,
2695 protocol name, ident value, and authentication data when submitting a message
2696 locally. Thus, they are able to insert messages into Exim's queue locally that
2697 have the characteristics of messages received from a remote host. Untrusted
2698 users may in some circumstances use &%-f%&, but can never set the other values
2699 that are available to trusted users.
2701 .cindex "user" "admin definition of"
2702 .cindex "admin user" "definition of"
2703 The admin users are root, the Exim user, and any user that is a member of the
2704 Exim group or of any group listed in the &%admin_groups%& configuration option.
2705 The current group does not have to be one of these groups.
2707 Admin users are permitted to list the queue, and to carry out certain
2708 operations on messages, for example, to force delivery failures. It is also
2709 necessary to be an admin user in order to see the full information provided by
2710 the Exim monitor, and full debugging output.
2712 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2713 Exim to attempt delivery of messages on its queue is restricted to admin users.
2714 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2715 option false (that is, specifying &%no_prod_requires_admin%&).
2717 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2718 is restricted to admin users unless &%queue_list_requires_admin%& is set
2723 &*Warning*&: If you configure your system so that admin users are able to
2724 edit Exim's configuration file, you are giving those users an easy way of
2725 getting root. There is further discussion of this issue at the start of chapter
2731 .section "Command line options" "SECID39"
2732 Exim's command line options are described in alphabetical order below. If none
2733 of the options that specifies a specific action (such as starting the daemon or
2734 a queue runner, or testing an address, or receiving a message in a specific
2735 format, or listing the queue) are present, and there is at least one argument
2736 on the command line, &%-bm%& (accept a local message on the standard input,
2737 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2738 outputs a brief message about itself and exits.
2740 . ////////////////////////////////////////////////////////////////////////////
2741 . Insert a stylized XML comment here, to identify the start of the command line
2742 . options. This is for the benefit of the Perl script that automatically
2743 . creates a man page for the options.
2744 . ////////////////////////////////////////////////////////////////////////////
2747 <!-- === Start of command line options === -->
2754 .cindex "options" "command line; terminating"
2755 This is a pseudo-option whose only purpose is to terminate the options and
2756 therefore to cause subsequent command line items to be treated as arguments
2757 rather than options, even if they begin with hyphens.
2760 .oindex "&%--help%&"
2761 This option causes Exim to output a few sentences stating what it is.
2762 The same output is generated if the Exim binary is called with no options and
2765 .vitem &%--version%&
2766 .oindex "&%--version%&"
2767 This option is an alias for &%-bV%& and causes version information to be
2774 These options are used by Sendmail for selecting configuration files and are
2777 .vitem &%-B%&<&'type'&>
2779 .cindex "8-bit characters"
2780 .cindex "Sendmail compatibility" "8-bit characters"
2781 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2782 clean; it ignores this option.
2787 .cindex "SMTP" "listener"
2788 .cindex "queue runner"
2789 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2790 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2791 that the daemon should also initiate periodic queue runs.
2793 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2794 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2795 disconnect from the controlling terminal. When running this way, it can be
2796 stopped by pressing ctrl-C.
2798 By default, Exim listens for incoming connections to the standard SMTP port on
2799 all the host's running interfaces. However, it is possible to listen on other
2800 ports, on multiple ports, and only on specific interfaces. Chapter
2801 &<<CHAPinterfaces>>& contains a description of the options that control this.
2803 When a listening daemon
2804 .cindex "daemon" "process id (pid)"
2805 .cindex "pid (process id)" "of daemon"
2806 is started without the use of &%-oX%& (that is, without overriding the normal
2807 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2808 in Exim's spool directory. This location can be overridden by setting
2809 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2812 When &%-oX%& is used on the command line to start a listening daemon, the
2813 process id is not written to the normal pid file path. However, &%-oP%& can be
2814 used to specify a path on the command line if a pid file is required.
2818 .cindex restart "on HUP signal"
2819 .cindex signal "HUP, to restart"
2820 .cindex "daemon" "restarting"
2821 .cindex signal "to reload configuration"
2822 .cindex daemon "reload configuration"
2823 .cindex reload configuration
2824 can be used to cause the daemon to re-execute itself. This should be done
2825 whenever Exim's configuration file, or any file that is incorporated into it by
2826 means of the &%.include%& facility, is changed, and also whenever a new version
2827 of Exim is installed. It is not necessary to do this when other files that are
2828 referenced from the configuration (for example, alias files) are changed,
2829 because these are reread each time they are used.
2833 This option has the same effect as &%-bd%& except that it never disconnects
2834 from the controlling terminal, even when no debugging is specified.
2838 .cindex "testing" "string expansion"
2839 .cindex "expansion" "testing"
2840 Run Exim in expansion testing mode. Exim discards its root privilege, to
2841 prevent ordinary users from using this mode to read otherwise inaccessible
2842 files. If no arguments are given, Exim runs interactively, prompting for lines
2843 of data. Otherwise, it processes each argument in turn.
2845 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2846 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2847 used without command line arguments. If successful, it uses the &[readline()]&
2848 function, which provides extensive line-editing facilities, for reading the
2849 test data. A line history is supported.
2851 Long expansion expressions can be split over several lines by using backslash
2852 continuations. As in Exim's runtime configuration, white space at the start of
2853 continuation lines is ignored. Each argument or data line is passed through the
2854 string expansion mechanism, and the result is output. Variable values from the
2855 configuration file (for example, &$qualify_domain$&) are available, but no
2856 message-specific values (such as &$message_exim_id$&) are set, because no message
2857 is being processed (but see &%-bem%& and &%-Mset%&).
2859 &*Note*&: If you use this mechanism to test lookups, and you change the data
2860 files or databases you are using, you must exit and restart Exim before trying
2861 the same lookup again. Otherwise, because each Exim process caches the results
2862 of lookups, you will just get the same result as before.
2864 Macro processing is done on lines before string-expansion: new macros can be
2865 defined and macros will be expanded.
2866 Because macros in the config file are often used for secrets, those are only
2867 available to admin users.
2869 .vitem &%-bem%&&~<&'filename'&>
2871 .cindex "testing" "string expansion"
2872 .cindex "expansion" "testing"
2873 This option operates like &%-be%& except that it must be followed by the name
2874 of a file. For example:
2876 exim -bem /tmp/testmessage
2878 The file is read as a message (as if receiving a locally-submitted non-SMTP
2879 message) before any of the test expansions are done. Thus, message-specific
2880 variables such as &$message_size$& and &$header_from:$& are available. However,
2881 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2882 recipients are read from the headers in the normal way, and are shown in the
2883 &$recipients$& variable. Note that recipients cannot be given on the command
2884 line, because further arguments are taken as strings to expand (just like
2887 .vitem &%-bF%&&~<&'filename'&>
2889 .cindex "system filter" "testing"
2890 .cindex "testing" "system filter"
2891 This option is the same as &%-bf%& except that it assumes that the filter being
2892 tested is a system filter. The additional commands that are available only in
2893 system filters are recognized.
2895 .vitem &%-bf%&&~<&'filename'&>
2897 .cindex "filter" "testing"
2898 .cindex "testing" "filter file"
2899 .cindex "forward file" "testing"
2900 .cindex "testing" "forward file"
2901 .cindex "Sieve filter" "testing"
2902 This option runs Exim in user filter testing mode; the file is the filter file
2903 to be tested, and a test message must be supplied on the standard input. If
2904 there are no message-dependent tests in the filter, an empty file can be
2907 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2908 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2909 filter and a user filter in the same run. For example:
2911 exim -bF /system/filter -bf /user/filter </test/message
2913 This is helpful when the system filter adds header lines or sets filter
2914 variables that are used by the user filter.
2916 If the test filter file does not begin with one of the special lines
2921 it is taken to be a normal &_.forward_& file, and is tested for validity under
2922 that interpretation. See sections &<<SECTitenonfilred>>& to
2923 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2926 The result of an Exim command that uses &%-bf%&, provided no errors are
2927 detected, is a list of the actions that Exim would try to take if presented
2928 with the message for real. More details of filter testing are given in the
2929 separate document entitled &'Exim's interfaces to mail filtering'&.
2931 When testing a filter file,
2932 .cindex "&""From""& line"
2933 .cindex "envelope from"
2934 .cindex "envelope sender"
2935 .oindex "&%-f%&" "for filter testing"
2936 the envelope sender can be set by the &%-f%& option,
2937 or by a &"From&~"& line at the start of the test message. Various parameters
2938 that would normally be taken from the envelope recipient address of the message
2939 can be set by means of additional command line options (see the next four
2942 .vitem &%-bfd%&&~<&'domain'&>
2944 .vindex "&$qualify_domain$&"
2945 This sets the domain of the recipient address when a filter file is being
2946 tested by means of the &%-bf%& option. The default is the value of
2949 .vitem &%-bfl%&&~<&'local&~part'&>
2951 This sets the local part of the recipient address when a filter file is being
2952 tested by means of the &%-bf%& option. The default is the username of the
2953 process that calls Exim. A local part should be specified with any prefix or
2954 suffix stripped, because that is how it appears to the filter when a message is
2955 actually being delivered.
2957 .vitem &%-bfp%&&~<&'prefix'&>
2959 .cindex affix "filter testing"
2960 This sets the prefix of the local part of the recipient address when a filter
2961 file is being tested by means of the &%-bf%& option. The default is an empty
2964 .vitem &%-bfs%&&~<&'suffix'&>
2966 .cindex affix "filter testing"
2967 This sets the suffix of the local part of the recipient address when a filter
2968 file is being tested by means of the &%-bf%& option. The default is an empty
2971 .vitem &%-bh%&&~<&'IP&~address'&>
2973 .cindex "testing" "incoming SMTP"
2974 .cindex "SMTP" "testing incoming"
2975 .cindex "testing" "relay control"
2976 .cindex "relaying" "testing configuration"
2977 .cindex "policy control" "testing"
2978 .cindex "debugging" "&%-bh%& option"
2979 This option runs a fake SMTP session as if from the given IP address, using the
2980 standard input and output. The IP address may include a port number at the end,
2981 after a full stop. For example:
2983 exim -bh 10.9.8.7.1234
2984 exim -bh fe80::a00:20ff:fe86:a061.5678
2986 When an IPv6 address is given, it is converted into canonical form. In the case
2987 of the second example above, the value of &$sender_host_address$& after
2988 conversion to the canonical form is
2989 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2991 Comments as to what is going on are written to the standard error file. These
2992 include lines beginning with &"LOG"& for anything that would have been logged.
2993 This facility is provided for testing configuration options for incoming
2994 messages, to make sure they implement the required policy. For example, you can
2995 test your relay controls using &%-bh%&.
2999 You can test features of the configuration that rely on ident (RFC 1413)
3000 information by using the &%-oMt%& option. However, Exim cannot actually perform
3001 an ident callout when testing using &%-bh%& because there is no incoming SMTP
3004 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
3005 are also skipped when testing using &%-bh%&. If you want these callouts to
3006 occur, use &%-bhc%& instead.
3008 Messages supplied during the testing session are discarded, and nothing is
3009 written to any of the real log files. There may be pauses when DNS (and other)
3010 lookups are taking place, and of course these may time out. The &%-oMi%& option
3011 can be used to specify a specific IP interface and port if this is important,
3012 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
3013 session were authenticated.
3015 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
3016 output just states whether a given recipient address from a given host is
3017 acceptable or not. See section &<<SECTcheckaccess>>&.
3019 Features such as authentication and encryption, where the client input is not
3020 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
3021 specialized SMTP test program such as
3022 &url(https://www.jetmore.org/john/code/swaks/,swaks).
3024 .vitem &%-bhc%&&~<&'IP&~address'&>
3026 This option operates in the same way as &%-bh%&, except that address
3027 verification callouts are performed if required. This includes consulting and
3028 updating the callout cache database.
3032 .cindex "alias file" "building"
3033 .cindex "building alias file"
3034 .cindex "Sendmail compatibility" "&%-bi%& option"
3035 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
3036 Exim does not have the concept of a single alias file, and so it cannot mimic
3037 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
3038 tend to appear in various scripts such as NIS make files, so the option must be
3041 If &%-bi%& is encountered, the command specified by the &%bi_command%&
3042 configuration option is run, under the uid and gid of the caller of Exim. If
3043 the &%-oA%& option is used, its value is passed to the command as an argument.
3044 The command set by &%bi_command%& may not contain arguments. The command can
3045 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
3046 if this is required. If the &%bi_command%& option is not set, calling Exim with
3049 . // Keep :help first, then the rest in alphabetical order
3051 .oindex "&%-bI:help%&"
3052 .cindex "querying exim information"
3053 We shall provide various options starting &`-bI:`& for querying Exim for
3054 information. The output of many of these will be intended for machine
3055 consumption. This one is not. The &%-bI:help%& option asks Exim for a
3056 synopsis of supported options beginning &`-bI:`&. Use of any of these
3057 options shall cause Exim to exit after producing the requested output.
3060 .oindex "&%-bI:dscp%&"
3061 .cindex "DSCP" "values"
3062 This option causes Exim to emit an alphabetically sorted list of all
3063 recognised DSCP names.
3065 .vitem &%-bI:sieve%&
3066 .oindex "&%-bI:sieve%&"
3067 .cindex "Sieve filter" "capabilities"
3068 This option causes Exim to emit an alphabetically sorted list of all supported
3069 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3070 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3071 &`SIEVE`& capability response line. As the precise list may depend upon
3072 compile-time build options, which this option will adapt to, this is the only
3073 way to guarantee a correct response.
3077 .cindex "local message reception"
3078 This option runs an Exim receiving process that accepts an incoming,
3079 locally-generated message on the standard input. The recipients are given as the
3080 command arguments (except when &%-t%& is also present &-- see below). Each
3081 argument can be a comma-separated list of RFC 2822 addresses. This is the
3082 default option for selecting the overall action of an Exim call; it is assumed
3083 if no other conflicting option is present.
3085 If any addresses in the message are unqualified (have no domain), they are
3086 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3087 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3088 suppressing this for special cases.
3090 Policy checks on the contents of local messages can be enforced by means of
3091 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3093 .cindex "return code" "for &%-bm%&"
3094 The return code is zero if the message is successfully accepted. Otherwise, the
3095 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3098 .cindex "message" "format"
3099 .cindex "format" "message"
3100 .cindex "&""From""& line"
3101 .cindex "UUCP" "&""From""& line"
3102 .cindex "Sendmail compatibility" "&""From""& line"
3103 of the message must be as defined in RFC 2822, except that, for
3104 compatibility with Sendmail and Smail, a line in one of the forms
3106 From sender Fri Jan 5 12:55 GMT 1997
3107 From sender Fri, 5 Jan 97 12:55:01
3109 (with the weekday optional, and possibly with additional text after the date)
3110 is permitted to appear at the start of the message. There appears to be no
3111 authoritative specification of the format of this line. Exim recognizes it by
3112 matching against the regular expression defined by the &%uucp_from_pattern%&
3113 option, which can be changed if necessary.
3115 .oindex "&%-f%&" "overriding &""From""& line"
3116 The specified sender is treated as if it were given as the argument to the
3117 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3118 preference to the address taken from the message. The caller of Exim must be a
3119 trusted user for the sender of a message to be set in this way.
3121 .vitem &%-bmalware%&&~<&'filename'&>
3122 .oindex "&%-bmalware%&"
3123 .cindex "testing", "malware"
3124 .cindex "malware scan test"
3125 This debugging option causes Exim to scan the given file or directory
3126 (depending on the used scanner interface),
3127 using the malware scanning framework. The option of &%av_scanner%& influences
3128 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3129 the expansion should have defaults which apply to this invocation. ACLs are
3130 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3131 will never be populated and &%-bmalware%& will fail.
3133 Exim will have changed working directory before resolving the filename, so
3134 using fully qualified pathnames is advisable. Exim will be running as the Exim
3135 user when it tries to open the file, rather than as the invoking user.
3136 This option requires admin privileges.
3138 The &%-bmalware%& option will not be extended to be more generally useful,
3139 there are better tools for file-scanning. This option exists to help
3140 administrators verify their Exim and AV scanner configuration.
3144 .cindex "address qualification, suppressing"
3145 By default, Exim automatically qualifies unqualified addresses (those
3146 without domains) that appear in messages that are submitted locally (that
3147 is, not over TCP/IP). This qualification applies both to addresses in
3148 envelopes, and addresses in header lines. Sender addresses are qualified using
3149 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3150 defaults to the value of &%qualify_domain%&).
3152 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3153 being used to re-submit messages that originally came from remote hosts after
3154 content scanning, you probably do not want to qualify unqualified addresses in
3155 header lines. (Such lines will be present only if you have not enabled a header
3156 syntax check in the appropriate ACL.)
3158 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3159 messages that originate on the local host. When this is used, unqualified
3160 addresses in the envelope provoke errors (causing message rejection) and
3161 unqualified addresses in header lines are left alone.
3166 .cindex "configuration options" "extracting"
3167 .cindex "options" "configuration &-- extracting"
3168 If this option is given with no arguments, it causes the values of all Exim's
3169 main configuration options to be written to the standard output. The values
3170 of one or more specific options can be requested by giving their names as
3171 arguments, for example:
3173 exim -bP qualify_domain hold_domains
3175 .cindex "hiding configuration option values"
3176 .cindex "configuration options" "hiding value of"
3177 .cindex "options" "hiding value of"
3178 However, any option setting that is preceded by the word &"hide"& in the
3179 configuration file is not shown in full, except to an admin user. For other
3180 users, the output is as in this example:
3182 mysql_servers = <value not displayable>
3184 If &%config%& is given as an argument, the config is
3185 output, as it was parsed, any include file resolved, any comment removed.
3187 If &%config_file%& is given as an argument, the name of the runtime
3188 configuration file is output. (&%configure_file%& works too, for
3189 backward compatibility.)
3190 If a list of configuration files was supplied, the value that is output here
3191 is the name of the file that was actually used.
3193 .cindex "options" "hiding name of"
3194 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3195 name will not be output.
3197 .cindex "daemon" "process id (pid)"
3198 .cindex "pid (process id)" "of daemon"
3199 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3200 directories where log files and daemon pid files are written are output,
3201 respectively. If these values are unset, log files are written in a
3202 sub-directory of the spool directory called &%log%&, and the pid file is
3203 written directly into the spool directory.
3205 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3207 exim -bP +local_domains
3209 it searches for a matching named list of any type (domain, host, address, or
3210 local part) and outputs what it finds.
3212 .cindex "options" "router &-- extracting"
3213 .cindex "options" "transport &-- extracting"
3214 .cindex "options" "authenticator &-- extracting"
3215 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3216 followed by the name of an appropriate driver instance, the option settings for
3217 that driver are output. For example:
3219 exim -bP transport local_delivery
3221 The generic driver options are output first, followed by the driver's private
3222 options. A list of the names of drivers of a particular type can be obtained by
3223 using one of the words &%router_list%&, &%transport_list%&, or
3224 &%authenticator_list%&, and a complete list of all drivers with their option
3225 settings can be obtained by using &%routers%&, &%transports%&, or
3228 .cindex "environment"
3229 If &%environment%& is given as an argument, the set of environment
3230 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3233 .cindex "options" "macro &-- extracting"
3234 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3235 are available, similarly to the drivers. Because macros are sometimes used
3236 for storing passwords, this option is restricted.
3237 The output format is one item per line.
3238 For the "-bP macro <name>" form, if no such macro is found
3239 the exit status will be nonzero.
3243 .cindex "queue" "listing messages in"
3244 .cindex "listing" "messages in the queue"
3245 This option requests a listing of the contents of the mail queue on the
3246 standard output. If the &%-bp%& option is followed by a list of message ids,
3247 just those messages are listed. By default, this option can be used only by an
3248 admin user. However, the &%queue_list_requires_admin%& option can be set false
3249 to allow any user to see the queue.
3251 Each message in the queue is displayed as in the following example:
3253 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3254 red.king@looking-glass.fict.example
3257 .cindex "message" "size in queue listing"
3258 .cindex "size" "of message"
3259 The first line contains the length of time the message has been in the queue
3260 (in this case 25 minutes), the size of the message (2.9K), the unique local
3261 identifier for the message, and the message sender, as contained in the
3262 envelope. For bounce messages, the sender address is empty, and appears as
3263 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3264 the default sender address, the user's login name is shown in parentheses
3265 before the sender address.
3267 .cindex "frozen messages" "in queue listing"
3268 If the message is frozen (attempts to deliver it are suspended) then the text
3269 &"*** frozen ***"& is displayed at the end of this line.
3271 The recipients of the message (taken from the envelope, not the headers) are
3272 displayed on subsequent lines. Those addresses to which the message has already
3273 been delivered are marked with the letter D. If an original address gets
3274 expanded into several addresses via an alias or forward file, the original is
3275 displayed with a D only when deliveries for all of its child addresses are
3281 This option operates like &%-bp%&, but in addition it shows delivered addresses
3282 that were generated from the original top level address(es) in each message by
3283 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3289 .cindex "queue" "count of messages on"
3290 This option counts the number of messages in the queue, and writes the total
3291 to the standard output. It is restricted to admin users, unless
3292 &%queue_list_requires_admin%& is set false.
3297 This option operates like &%-bp%&, but the output is not sorted into
3298 chronological order of message arrival. This can speed it up when there are
3299 lots of messages in the queue, and is particularly useful if the output is
3300 going to be post-processed in a way that doesn't need the sorting.
3304 This option is a combination of &%-bpr%& and &%-bpa%&.
3308 This option is a combination of &%-bpr%& and &%-bpu%&.
3313 This option operates like &%-bp%& but shows only undelivered top-level
3314 addresses for each message displayed. Addresses generated by aliasing or
3315 forwarding are not shown, unless the message was deferred after processing by a
3316 router with the &%one_time%& option set.
3321 .cindex "testing" "retry configuration"
3322 .cindex "retry" "configuration testing"
3323 This option is for testing retry rules, and it must be followed by up to three
3324 arguments. It causes Exim to look for a retry rule that matches the values
3325 and to write it to the standard output. For example:
3327 exim -brt bach.comp.mus.example
3328 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3330 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3331 argument, which is required, can be a complete address in the form
3332 &'local_part@domain'&, or it can be just a domain name. If the second argument
3333 contains a dot, it is interpreted as an optional second domain name; if no
3334 retry rule is found for the first argument, the second is tried. This ties in
3335 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3336 rule is found that matches the host, one that matches the mail domain is
3337 sought. Finally, an argument that is the name of a specific delivery error, as
3338 used in setting up retry rules, can be given. For example:
3340 exim -brt haydn.comp.mus.example quota_3d
3341 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3346 .cindex "testing" "rewriting"
3347 .cindex "rewriting" "testing"
3348 This option is for testing address rewriting rules, and it must be followed by
3349 a single argument, consisting of either a local part without a domain, or a
3350 complete address with a fully qualified domain. Exim outputs how this address
3351 would be rewritten for each possible place it might appear. See chapter
3352 &<<CHAPrewrite>>& for further details.
3356 .cindex "SMTP" "batched incoming"
3357 .cindex "batched SMTP input"
3358 This option is used for batched SMTP input, which is an alternative interface
3359 for non-interactive local message submission. A number of messages can be
3360 submitted in a single run. However, despite its name, this is not really SMTP
3361 input. Exim reads each message's envelope from SMTP commands on the standard
3362 input, but generates no responses. If the caller is trusted, or
3363 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3364 believed; otherwise the sender is always the caller of Exim.
3366 The message itself is read from the standard input, in SMTP format (leading
3367 dots doubled), terminated by a line containing just a single dot. An error is
3368 provoked if the terminating dot is missing. A further message may then follow.
3370 As for other local message submissions, the contents of incoming batch SMTP
3371 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3372 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3373 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3375 Some other SMTP commands are recognized in the input. HELO and EHLO act
3376 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3377 QUIT quits, ignoring the rest of the standard input.
3379 .cindex "return code" "for &%-bS%&"
3380 If any error is encountered, reports are written to the standard output and
3381 error streams, and Exim gives up immediately. The return code is 0 if no error
3382 was detected; it is 1 if one or more messages were accepted before the error
3383 was detected; otherwise it is 2.
3385 More details of input using batched SMTP are given in section
3386 &<<SECTincomingbatchedSMTP>>&.
3390 .cindex "SMTP" "local input"
3391 .cindex "local SMTP input"
3392 This option causes Exim to accept one or more messages by reading SMTP commands
3393 on the standard input, and producing SMTP replies on the standard output. SMTP
3394 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3395 Some user agents use this interface as a way of passing locally-generated
3396 messages to the MTA.
3399 .cindex "sender" "source of"
3400 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3401 set, the senders of messages are taken from the SMTP MAIL commands.
3402 Otherwise the content of these commands is ignored and the sender is set up as
3403 the calling user. Unqualified addresses are automatically qualified using
3404 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3405 &%-bnq%& option is used.
3409 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3410 using a listening daemon. Exim can distinguish the two cases by checking
3411 whether the standard input is a TCP/IP socket. When Exim is called from
3412 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3413 above concerning senders and qualification do not apply. In this situation,
3414 Exim behaves in exactly the same way as it does when receiving a message via
3415 the listening daemon.
3419 .cindex "testing" "addresses"
3420 .cindex "address" "testing"
3421 This option runs Exim in address testing mode, in which each argument is taken
3422 as a recipient address to be tested for deliverability. The results are
3423 written to the standard output. If a test fails, and the caller is not an admin
3424 user, no details of the failure are output, because these might contain
3425 sensitive information such as usernames and passwords for database lookups.
3427 If no arguments are given, Exim runs in an interactive manner, prompting with a
3428 right angle bracket for addresses to be tested.
3430 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3431 &[readline()]& function, because it is running as &'root'& and there are
3434 Each address is handled as if it were the recipient address of a message
3435 (compare the &%-bv%& option). It is passed to the routers and the result is
3436 written to the standard output. However, any router that has
3437 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3438 genuine routing tests if your first router passes everything to a scanner
3441 .cindex "return code" "for &%-bt%&"
3442 The return code is 2 if any address failed outright; it is 1 if no address
3443 failed outright but at least one could not be resolved for some reason. Return
3444 code 0 is given only when all addresses succeed.
3446 .cindex "duplicate addresses"
3447 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3448 addresses after routing is complete, so that only one delivery takes place.
3449 This does not happen when testing with &%-bt%&; the full results of routing are
3452 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3453 routers in the configuration makes any tests on the sender address of a
3455 .oindex "&%-f%&" "for address testing"
3456 you can use the &%-f%& option to set an appropriate sender when running
3457 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3458 default qualifying domain. However, if you have set up (for example) routers
3459 whose behaviour depends on the contents of an incoming message, you cannot test
3460 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3465 .cindex "version number of Exim"
3466 This option causes Exim to write the current version number, compilation
3467 number, and compilation date of the &'exim'& binary to the standard output.
3468 It also lists the DBM library that is being used, the optional modules (such as
3469 specific lookup types), the drivers that are included in the binary, and the
3470 name of the runtime configuration file that is in use.
3472 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3473 configuration file. However, this is a static check only. It cannot check
3474 values that are to be expanded. For example, although a misspelt ACL verb is
3475 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3476 alone to discover (for example) all the typos in the configuration; some
3477 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3478 dynamic testing facilities.
3482 .cindex "verifying address" "using &%-bv%&"
3483 .cindex "address" "verification"
3484 This option runs Exim in address verification mode, in which each argument is
3485 taken as a recipient address to be verified by the routers. (This does
3486 not involve any verification callouts). During normal operation, verification
3487 happens mostly as a consequence processing a &%verify%& condition in an ACL
3488 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3489 including callouts, see the &%-bh%& and &%-bhc%& options.
3491 If verification fails, and the caller is not an admin user, no details of the
3492 failure are output, because these might contain sensitive information such as
3493 usernames and passwords for database lookups.
3495 If no arguments are given, Exim runs in an interactive manner, prompting with a
3496 right angle bracket for addresses to be verified.
3498 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3499 &[readline()]& function, because it is running as &'exim'& and there are
3502 Verification differs from address testing (the &%-bt%& option) in that routers
3503 that have &%no_verify%& set are skipped, and if the address is accepted by a
3504 router that has &%fail_verify%& set, verification fails. The address is
3505 verified as a recipient if &%-bv%& is used; to test verification for a sender
3506 address, &%-bvs%& should be used.
3508 If the &%-v%& option is not set, the output consists of a single line for each
3509 address, stating whether it was verified or not, and giving a reason in the
3510 latter case. Without &%-v%&, generating more than one address by redirection
3511 causes verification to end successfully, without considering the generated
3512 addresses. However, if just one address is generated, processing continues,
3513 and the generated address must verify successfully for the overall verification
3516 When &%-v%& is set, more details are given of how the address has been handled,
3517 and in the case of address redirection, all the generated addresses are also
3518 considered. Verification may succeed for some and fail for others.
3521 .cindex "return code" "for &%-bv%&"
3522 return code is 2 if any address failed outright; it is 1 if no address
3523 failed outright but at least one could not be resolved for some reason. Return
3524 code 0 is given only when all addresses succeed.
3526 If any of the routers in the configuration makes any tests on the sender
3527 address of a message, you should use the &%-f%& option to set an appropriate
3528 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3529 calling user at the default qualifying domain.
3533 This option acts like &%-bv%&, but verifies the address as a sender rather
3534 than a recipient address. This affects any rewriting and qualification that
3541 .cindex "inetd" "wait mode"
3542 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3543 similarly to the &%-bd%& option. All port specifications on the command-line
3544 and in the configuration file are ignored. Queue-running may not be specified.
3546 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3547 listening for connections. This permits the system to start up and have
3548 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3549 each port only when the first connection is received.
3551 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3552 which the daemon will exit, which should cause inetd to listen once more.
3554 .vitem &%-C%&&~<&'filelist'&>
3556 .cindex "configuration file" "alternate"
3557 .cindex "CONFIGURE_FILE"
3558 .cindex "alternate configuration file"
3559 This option causes Exim to find the runtime configuration file from the given
3560 list instead of from the list specified by the CONFIGURE_FILE
3561 compile-time setting. Usually, the list will consist of just a single filename,
3562 but it can be a colon-separated list of names. In this case, the first
3563 file that exists is used. Failure to open an existing file stops Exim from
3564 proceeding any further along the list, and an error is generated.
3566 When this option is used by a caller other than root, and the list is different
3567 from the compiled-in list, Exim gives up its root privilege immediately, and
3568 runs with the real and effective uid and gid set to those of the caller.
3569 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3570 file contains a list of full pathnames, one per line, for configuration files
3571 which are trusted. Root privilege is retained for any configuration file so
3572 listed, as long as the caller is the Exim user (or the user specified in the
3573 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3574 not writeable by inappropriate users or groups.
3576 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3577 configuration using &%-C%& right through message reception and delivery,
3578 even if the caller is root. The reception works, but by that time, Exim is
3579 running as the Exim user, so when it re-executes to regain privilege for the
3580 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3581 test reception and delivery using two separate commands (one to put a message
3582 in the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3584 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3585 prefix string with which any file named in a &%-C%& command line option
3586 must start. In addition, the filename must not contain the sequence &`/../`&.
3587 However, if the value of the &%-C%& option is identical to the value of
3588 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3589 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3590 unset, any filename can be used with &%-C%&.
3592 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3593 to a directory to which only root has access. This prevents someone who has
3594 broken into the Exim account from running a privileged Exim with an arbitrary
3597 The &%-C%& facility is useful for ensuring that configuration files are
3598 syntactically correct, but cannot be used for test deliveries, unless the
3599 caller is privileged, or unless it is an exotic configuration that does not
3600 require privilege. No check is made on the owner or group of the files
3601 specified by this option.
3604 .vitem &%-D%&<&'macro'&>=<&'value'&>
3606 .cindex "macro" "setting on command line"
3607 This option can be used to override macro definitions in the configuration file
3608 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3609 unprivileged caller, it causes Exim to give up its root privilege.
3610 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3611 completely disabled, and its use causes an immediate error exit.
3613 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3614 colon-separated list of macros which are considered safe and, if &%-D%& only
3615 supplies macros from this list, and the values are acceptable, then Exim will
3616 not give up root privilege if the caller is root, the Exim run-time user, or
3617 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3618 to be removed in the future. Acceptable values for the macros satisfy the
3619 regexp: &`^[A-Za-z0-9_/.-]*$`&
3621 The entire option (including equals sign if present) must all be within one
3622 command line item. &%-D%& can be used to set the value of a macro to the empty
3623 string, in which case the equals sign is optional. These two commands are
3629 To include spaces in a macro definition item, quotes must be used. If you use
3630 quotes, spaces are permitted around the macro name and the equals sign. For
3633 exim '-D ABC = something' ...
3635 &%-D%& may be repeated up to 10 times on a command line.
3636 Only macro names up to 22 letters long can be set.
3639 .vitem &%-d%&<&'debug&~options'&>
3641 .cindex "debugging" "list of selectors"
3642 .cindex "debugging" "&%-d%& option"
3643 This option causes debugging information to be written to the standard
3644 error stream. It is restricted to admin users because debugging output may show
3645 database queries that contain password information. Also, the details of users'
3646 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3647 writes an error message to the standard error stream and exits with a non-zero
3650 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3651 standard debugging data is output. This can be reduced, or increased to include
3652 some more rarely needed information, by directly following &%-d%& with a string
3653 made up of names preceded by plus or minus characters. These add or remove sets
3654 of debugging data, respectively. For example, &%-d+filter%& adds filter
3655 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3656 no spaces are allowed in the debug setting. The available debugging categories
3659 &`acl `& ACL interpretation
3660 &`auth `& authenticators
3661 &`deliver `& general delivery logic
3662 &`dns `& DNS lookups (see also resolver)
3663 &`dnsbl `& DNS black list (aka RBL) code
3664 &`exec `& arguments for &[execv()]& calls
3665 &`expand `& detailed debugging for string expansions
3666 &`filter `& filter handling
3667 &`hints_lookup `& hints data lookups
3668 &`host_lookup `& all types of name-to-IP address handling
3669 &`ident `& ident lookup
3670 &`interface `& lists of local interfaces
3671 &`lists `& matching things in lists
3672 &`load `& system load checks
3673 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3674 &<<CHAPlocalscan>>&)
3675 &`lookup `& general lookup code and all lookups
3676 &`memory `& memory handling
3677 &`noutf8 `& modifier: avoid UTF-8 line-drawing
3678 &`pid `& modifier: add pid to debug output lines
3679 &`process_info `& setting info for the process log
3680 &`queue_run `& queue runs
3681 &`receive `& general message reception logic
3682 &`resolver `& turn on the DNS resolver's debugging output
3683 &`retry `& retry handling
3684 &`rewrite `& address rewriting
3685 &`route `& address routing
3686 &`timestamp `& modifier: add timestamp to debug output lines
3688 &`transport `& transports
3689 &`uid `& changes of uid/gid and looking up uid/gid
3690 &`verify `& address verification logic
3691 &`all `& almost all of the above (see below), and also &%-v%&
3693 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3694 for &`-all`&. The reason for this is that &`+all`& is something that people
3695 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3696 is included, an awful lot of output that is very rarely of interest is
3697 generated, so it now has to be explicitly requested. However, &`-all`& does
3698 turn everything off.
3700 .cindex "resolver, debugging output"
3701 .cindex "DNS resolver, debugging output"
3702 The &`resolver`& option produces output only if the DNS resolver was compiled
3703 with DEBUG enabled. This is not the case in some operating systems. Also,
3704 unfortunately, debugging output from the DNS resolver is written to stdout
3707 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3708 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3709 However, the &`pid`& selector is forced when debugging is turned on for a
3710 daemon, which then passes it on to any re-executed Exims. Exim also
3711 automatically adds the pid to debug lines when several remote deliveries are
3714 The &`timestamp`& selector causes the current time to be inserted at the start
3715 of all debug output lines. This can be useful when trying to track down delays
3718 .cindex debugging "UTF-8 in"
3719 .cindex UTF-8 "in debug output"
3720 The &`noutf8`& selector disables the use of
3721 UTF-8 line-drawing characters to group related information.
3722 When disabled. ascii-art is used instead.
3723 Using the &`+all`& option does not set this modifier,
3725 If the &%debug_print%& option is set in any driver, it produces output whenever
3726 any debugging is selected, or if &%-v%& is used.
3728 .vitem &%-dd%&<&'debug&~options'&>
3730 This option behaves exactly like &%-d%& except when used on a command that
3731 starts a daemon process. In that case, debugging is turned off for the
3732 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3733 behaviour of the daemon without creating as much output as full debugging does.
3736 .oindex "&%-dropcr%&"
3737 This is an obsolete option that is now a no-op. It used to affect the way Exim
3738 handled CR and LF characters in incoming messages. What happens now is
3739 described in section &<<SECTlineendings>>&.
3743 .cindex "bounce message" "generating"
3744 This option specifies that an incoming message is a locally-generated delivery
3745 failure report. It is used internally by Exim when handling delivery failures
3746 and is not intended for external use. Its only effect is to stop Exim
3747 generating certain messages to the postmaster, as otherwise message cascades
3748 could occur in some situations. As part of the same option, a message id may
3749 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3750 new message contains the id, following &"R="&, as a cross-reference.
3753 .oindex "&%-e%&&'x'&"
3754 There are a number of Sendmail options starting with &%-oe%& which seem to be
3755 called by various programs without the leading &%o%& in the option. For
3756 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3757 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3759 .vitem &%-F%&&~<&'string'&>
3761 .cindex "sender" "name"
3762 .cindex "name" "of sender"
3763 This option sets the sender's full name for use when a locally-generated
3764 message is being accepted. In the absence of this option, the user's &'gecos'&
3765 entry from the password data is used. As users are generally permitted to alter
3766 their &'gecos'& entries, no security considerations are involved. White space
3767 between &%-F%& and the <&'string'&> is optional.
3769 .vitem &%-f%&&~<&'address'&>
3771 .cindex "sender" "address"
3772 .cindex "address" "sender"
3773 .cindex "trusted users"
3774 .cindex "envelope from"
3775 .cindex "envelope sender"
3776 .cindex "user" "trusted"
3777 This option sets the address of the envelope sender of a locally-generated
3778 message (also known as the return path). The option can normally be used only
3779 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3782 Processes running as root or the Exim user are always trusted. Other
3783 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3784 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3785 of a local message is set to the caller's login name at the default qualify
3788 There is one exception to the restriction on the use of &%-f%&: an empty sender
3789 can be specified by any user, trusted or not, to create a message that can
3790 never provoke a bounce. An empty sender can be specified either as an empty
3791 string, or as a pair of angle brackets with nothing between them, as in these
3792 examples of shell commands:
3794 exim -f '<>' user@domain
3795 exim -f "" user@domain
3797 In addition, the use of &%-f%& is not restricted when testing a filter file
3798 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3801 Allowing untrusted users to change the sender address does not of itself make
3802 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3803 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3804 though this can be overridden by setting &%no_local_from_check%&.
3807 .cindex "&""From""& line"
3808 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3809 given as two arguments or one combined argument). The sender of a
3810 locally-generated message can also be set (when permitted) by an initial
3811 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3812 if &%-f%& is also present, it overrides &"From&~"&.
3816 .cindex "submission fixups, suppressing (command-line)"
3817 This option is equivalent to an ACL applying:
3819 control = suppress_local_fixups
3821 for every message received. Note that Sendmail will complain about such
3822 bad formatting, where Exim silently just does not fix it up. This may change
3825 As this affects audit information, the caller must be a trusted user to use
3828 .vitem &%-h%&&~<&'number'&>
3830 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3831 This option is accepted for compatibility with Sendmail, but has no effect. (In
3832 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3837 .cindex "Solaris" "&'mail'& command"
3838 .cindex "dot" "in incoming non-SMTP message"
3839 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3840 line by itself should not terminate an incoming, non-SMTP message. I can find
3841 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3842 command in Solaris 2.4 uses it. See also &%-ti%&.
3844 .vitem &%-L%&&~<&'tag'&>
3846 .cindex "syslog" "process name; set with flag"
3847 This option is equivalent to setting &%syslog_processname%& in the config
3848 file and setting &%log_file_path%& to &`syslog`&.
3849 Its use is restricted to administrators. The configuration file has to be
3850 read and parsed, to determine access rights, before this is set and takes
3851 effect, so early configuration file errors will not honour this flag.
3853 The tag should not be longer than 32 characters.
3855 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3857 .cindex "forcing delivery"
3858 .cindex "delivery" "forcing attempt"
3859 .cindex "frozen messages" "forcing delivery"
3860 This option requests Exim to run a delivery attempt on each message in turn. If
3861 any of the messages are frozen, they are automatically thawed before the
3862 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3863 and &%hold_domains%& are ignored.
3866 .cindex "hints database" "overriding retry hints"
3867 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3868 the normal retry time has not yet been reached. This option requires the caller
3869 to be an admin user. However, there is an option called &%prod_requires_admin%&
3870 which can be set false to relax this restriction (and also the same requirement
3871 for the &%-q%&, &%-R%&, and &%-S%& options).
3873 The deliveries happen synchronously, that is, the original Exim process does
3874 not terminate until all the delivery attempts have finished. No output is
3875 produced unless there is a serious error. If you want to see what is happening,
3876 use the &%-v%& option as well, or inspect Exim's main log.
3878 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3880 .cindex "message" "adding recipients"
3881 .cindex "recipient" "adding"
3882 This option requests Exim to add the addresses to the list of recipients of the
3883 message (&"ar"& for &"add recipients"&). The first argument must be a message
3884 id, and the remaining ones must be email addresses. However, if the message is
3885 active (in the middle of a delivery attempt), it is not altered. This option
3886 can be used only by an admin user.
3888 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3889 &~<&'message&~id'&>"
3891 .cindex "SMTP" "passed connection"
3892 .cindex "SMTP" "multiple deliveries"
3893 .cindex "multiple SMTP deliveries"
3894 This option is not intended for use by external callers. It is used internally
3895 by Exim to invoke another instance of itself to deliver a waiting message using
3896 an existing SMTP connection, which is passed as the standard input. Details are
3897 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3898 must be root or the Exim user in order to use it.
3902 This option is not intended for use by external callers. It is used internally
3903 by Exim in conjunction with the &%-MC%& option. It signifies that the
3904 connection to the remote host has been authenticated.
3908 This option is not intended for use by external callers. It is used internally
3909 by Exim in conjunction with the &%-MC%& option. It signifies that the
3910 remote host supports the ESMTP &_DSN_& extension.
3914 This option is not intended for use by external callers. It is used internally
3915 by Exim in conjunction with the &%-d%& option
3916 to pass on an information string on the purpose of the process.
3918 .vitem &%-MCG%&&~<&'queue&~name'&>
3920 This option is not intended for use by external callers. It is used internally
3921 by Exim in conjunction with the &%-MC%& option. It signifies that an
3922 alternate queue is used, named by the following argument.
3926 This option is not intended for use by external callers. It is used internally
3927 by Exim in conjunction with the &%-MC%& option. It signifies that a
3928 remote host supports the ESMTP &_CHUNKING_& extension.
3932 This option is not intended for use by external callers. It is used internally
3933 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3934 which Exim is connected supports pipelining.
3936 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3938 This option is not intended for use by external callers. It is used internally
3939 by Exim in conjunction with the &%-MC%& option when the original delivery was
3940 started by a queue runner. It passes on the process id of the queue runner,
3941 together with the file descriptor number of an open pipe. Closure of the pipe
3942 signals the final completion of the sequence of processes that are passing
3943 messages through the same SMTP connection.
3946 .vitem &%-MCq%&&~<&'recipient&~address'&>&~<&'size'&>
3948 This option is not intended for use by external callers. It is used internally
3949 by Exim to implement quota checking for local users.
3954 This option is not intended for use by external callers. It is used internally
3955 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3956 ESMTP SIZE option should be used on messages delivered down the existing
3961 This option is not intended for use by external callers. It is used internally
3962 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3963 host to which Exim is connected supports TLS encryption.
3966 .vitem &%-MCr%&&~<&'SNI'&> &&&
3970 These options are not intended for use by external callers. It is used internally
3971 by Exim in conjunction with the &%-MCt%& option, and passes on the fact that
3972 a TLS Server Name Indication was sent as part of the channel establishment.
3973 The argument gives the SNI string.
3974 The "r" variant indicates a DANE-verified connection.
3977 .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
3979 This option is not intended for use by external callers. It is used internally
3980 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3981 connection is being proxied by a parent process for handling TLS encryption.
3982 The arguments give the local address and port being proxied, and the TLS cipher.
3984 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3986 .cindex "hints database" "not overridden by &%-Mc%&"
3987 .cindex "delivery" "manually started &-- not forced"
3988 This option requests Exim to run a delivery attempt on each message, in turn,
3989 but unlike the &%-M%& option, it does check for retry hints, and respects any
3990 that are found. This option is not very useful to external callers. It is
3991 provided mainly for internal use by Exim when it needs to re-invoke itself in
3992 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3993 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3994 respects retry times and other options such as &%hold_domains%& that are
3995 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3996 If you want to run a specific delivery as if in a queue run, you should use
3997 &%-q%& with a message id argument. A distinction between queue run deliveries
3998 and other deliveries is made in one or two places.
4000 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
4002 .cindex "message" "changing sender"
4003 .cindex "sender" "changing"
4004 This option requests Exim to change the sender address in the message to the
4005 given address, which must be a fully qualified address or &"<>"& (&"es"& for
4006 &"edit sender"&). There must be exactly two arguments. The first argument must
4007 be a message id, and the second one an email address. However, if the message
4008 is active (in the middle of a delivery attempt), its status is not altered.
4009 This option can be used only by an admin user.
4011 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4013 .cindex "freezing messages"
4014 .cindex "message" "manually freezing"
4015 This option requests Exim to mark each listed message as &"frozen"&. This
4016 prevents any delivery attempts taking place until the message is &"thawed"&,
4017 either manually or as a result of the &%auto_thaw%& configuration option.
4018 However, if any of the messages are active (in the middle of a delivery
4019 attempt), their status is not altered. This option can be used only by an admin
4022 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4024 .cindex "giving up on messages"
4025 .cindex "message" "abandoning delivery attempts"
4026 .cindex "delivery" "abandoning further attempts"
4027 This option requests Exim to give up trying to deliver the listed messages,
4028 including any that are frozen. However, if any of the messages are active,
4029 their status is not altered. For non-bounce messages, a delivery error message
4030 is sent to the sender, containing the text &"cancelled by administrator"&.
4031 Bounce messages are just discarded. This option can be used only by an admin
4034 .vitem &%-MG%&&~<&'queue&~name'&>&~<&'message&~id'&>&~<&'message&~id'&>&~...
4037 .cindex "named queues" "moving messages"
4038 .cindex "queue" "moving messages"
4039 This option requests that each listed message be moved from its current
4040 queue to the given named queue.
4041 The destination queue name argument is required, but can be an empty
4042 string to define the default queue.
4043 If the messages are not currently located in the default queue,
4044 a &%-qG<name>%& option will be required to define the source queue.
4046 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4048 .cindex "delivery" "cancelling all"
4049 This option requests Exim to mark all the recipient addresses in the messages
4050 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
4051 message is active (in the middle of a delivery attempt), its status is not
4052 altered. This option can be used only by an admin user.
4054 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
4056 .cindex "delivery" "cancelling by address"
4057 .cindex "recipient" "removing"
4058 .cindex "removing recipients"
4059 This option requests Exim to mark the given addresses as already delivered
4060 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
4061 the remaining ones must be email addresses. These are matched to recipient
4062 addresses in the message in a case-sensitive manner. If the message is active
4063 (in the middle of a delivery attempt), its status is not altered. This option
4064 can be used only by an admin user.
4066 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4068 .cindex "removing messages"
4069 .cindex "abandoning mail"
4070 .cindex "message" "manually discarding"
4071 This option requests Exim to remove the given messages from the queue. No
4072 bounce messages are sent; each message is simply forgotten. However, if any of
4073 the messages are active, their status is not altered. This option can be used
4074 only by an admin user or by the user who originally caused the message to be
4075 placed in the queue.
4080 . .cindex REQUIRETLS
4081 . This option is used to request REQUIRETLS processing on the message.
4082 . It is used internally by Exim in conjunction with -E when generating
4086 .vitem &%-Mset%&&~<&'message&~id'&>
4088 .cindex "testing" "string expansion"
4089 .cindex "expansion" "testing"
4090 This option is useful only in conjunction with &%-be%& (that is, when testing
4091 string expansions). Exim loads the given message from its spool before doing
4092 the test expansions, thus setting message-specific variables such as
4093 &$message_size$& and the header variables. The &$recipients$& variable is made
4094 available. This feature is provided to make it easier to test expansions that
4095 make use of these variables. However, this option can be used only by an admin
4096 user. See also &%-bem%&.
4098 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4100 .cindex "thawing messages"
4101 .cindex "unfreezing messages"
4102 .cindex "frozen messages" "thawing"
4103 .cindex "message" "thawing frozen"
4104 This option requests Exim to &"thaw"& any of the listed messages that are
4105 &"frozen"&, so that delivery attempts can resume. However, if any of the
4106 messages are active, their status is not altered. This option can be used only
4109 .vitem &%-Mvb%&&~<&'message&~id'&>
4111 .cindex "listing" "message body"
4112 .cindex "message" "listing body of"
4113 This option causes the contents of the message body (-D) spool file to be
4114 written to the standard output. This option can be used only by an admin user.
4116 .vitem &%-Mvc%&&~<&'message&~id'&>
4118 .cindex "message" "listing in RFC 2822 format"
4119 .cindex "listing" "message in RFC 2822 format"
4120 This option causes a copy of the complete message (header lines plus body) to
4121 be written to the standard output in RFC 2822 format. This option can be used
4122 only by an admin user.
4124 .vitem &%-Mvh%&&~<&'message&~id'&>
4126 .cindex "listing" "message headers"
4127 .cindex "header lines" "listing"
4128 .cindex "message" "listing header lines"
4129 This option causes the contents of the message headers (-H) spool file to be
4130 written to the standard output. This option can be used only by an admin user.
4132 .vitem &%-Mvl%&&~<&'message&~id'&>
4134 .cindex "listing" "message log"
4135 .cindex "message" "listing message log"
4136 This option causes the contents of the message log spool file to be written to
4137 the standard output. This option can be used only by an admin user.
4141 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
4142 treats it that way too.
4146 .cindex "debugging" "&%-N%& option"
4147 .cindex "debugging" "suppressing delivery"
4148 This is a debugging option that inhibits delivery of a message at the transport
4149 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4150 it just doesn't actually transport the message, but instead behaves as if it
4151 had successfully done so. However, it does not make any updates to the retry
4152 database, and the log entries for deliveries are flagged with &"*>"& rather
4155 Because &%-N%& discards any message to which it applies, only root or the Exim
4156 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4157 words, an ordinary user can use it only when supplying an incoming message to
4158 which it will apply. Although transportation never fails when &%-N%& is set, an
4159 address may be deferred because of a configuration problem on a transport, or a
4160 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4161 the message, and applies to any subsequent delivery attempts that may happen
4166 This option is interpreted by Sendmail to mean &"no aliasing"&.
4167 For normal modes of operation, it is ignored by Exim.
4168 When combined with &%-bP%& it makes the output more terse (suppresses
4169 option names, environment values and config pretty printing).
4171 .vitem &%-O%&&~<&'data'&>
4173 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4176 .vitem &%-oA%&&~<&'file&~name'&>
4178 .cindex "Sendmail compatibility" "&%-oA%& option"
4179 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4180 alternative alias filename. Exim handles &%-bi%& differently; see the
4183 .vitem &%-oB%&&~<&'n'&>
4185 .cindex "SMTP" "passed connection"
4186 .cindex "SMTP" "multiple deliveries"
4187 .cindex "multiple SMTP deliveries"
4188 This is a debugging option which limits the maximum number of messages that can
4189 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4190 transport. If <&'n'&> is omitted, the limit is set to 1.
4194 .cindex "background delivery"
4195 .cindex "delivery" "in the background"
4196 This option applies to all modes in which Exim accepts incoming messages,
4197 including the listening daemon. It requests &"background"& delivery of such
4198 messages, which means that the accepting process automatically starts a
4199 delivery process for each message received, but does not wait for the delivery
4200 processes to finish.
4202 When all the messages have been received, the reception process exits,
4203 leaving the delivery processes to finish in their own time. The standard output
4204 and error streams are closed at the start of each delivery process.
4205 This is the default action if none of the &%-od%& options are present.
4207 If one of the queueing options in the configuration file
4208 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4209 overrides it if &%queue_only_override%& is set true, which is the default
4210 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4214 .cindex "foreground delivery"
4215 .cindex "delivery" "in the foreground"
4216 This option requests &"foreground"& (synchronous) delivery when Exim has
4217 accepted a locally-generated message. (For the daemon it is exactly the same as
4218 &%-odb%&.) A delivery process is automatically started to deliver the message,
4219 and Exim waits for it to complete before proceeding.
4221 The original Exim reception process does not finish until the delivery
4222 process for the final message has ended. The standard error stream is left open
4225 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4226 false and one of the queueing options in the configuration file is in effect.
4228 If there is a temporary delivery error during foreground delivery, the
4229 message is left in the queue for later delivery, and the original reception
4230 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4231 restricted configuration that never queues messages.
4236 This option is synonymous with &%-odf%&. It is provided for compatibility with
4241 .cindex "non-immediate delivery"
4242 .cindex "delivery" "suppressing immediate"
4243 .cindex "queueing incoming messages"
4244 This option applies to all modes in which Exim accepts incoming messages,
4245 including the listening daemon. It specifies that the accepting process should
4246 not automatically start a delivery process for each message received. Messages
4247 are placed in the queue, and remain there until a subsequent queue runner
4248 process encounters them. There are several configuration options (such as
4249 &%queue_only%&) that can be used to queue incoming messages under certain
4250 conditions. This option overrides all of them and also &%-odqs%&. It always
4255 .cindex "SMTP" "delaying delivery"
4256 .cindex "first pass routing"
4257 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4258 However, like &%-odb%& and &%-odi%&, this option has no effect if
4259 &%queue_only_override%& is false and one of the queueing options in the
4260 configuration file is in effect.
4262 When &%-odqs%& does operate, a delivery process is started for each incoming
4263 message, in the background by default, but in the foreground if &%-odi%& is
4264 also present. The recipient addresses are routed, and local deliveries are done
4265 in the normal way. However, if any SMTP deliveries are required, they are not
4266 done at this time, so the message remains in the queue until a subsequent queue
4267 runner process encounters it. Because routing was done, Exim knows which
4268 messages are waiting for which hosts, and so a number of messages for the same
4269 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4270 configuration option has the same effect for specific domains. See also the
4275 .cindex "error" "reporting"
4276 If an error is detected while a non-SMTP message is being received (for
4277 example, a malformed address), the error is reported to the sender in a mail
4280 .cindex "return code" "for &%-oee%&"
4282 this error message is successfully sent, the Exim receiving process
4283 exits with a return code of zero. If not, the return code is 2 if the problem
4284 is that the original message has no recipients, or 1 for any other error.
4285 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4289 .cindex "error" "reporting"
4290 .cindex "return code" "for &%-oem%&"
4291 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4292 return code, whether or not the error message was successfully sent.
4293 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4297 .cindex "error" "reporting"
4298 If an error is detected while a non-SMTP message is being received, the
4299 error is reported by writing a message to the standard error file (stderr).
4300 .cindex "return code" "for &%-oep%&"
4301 The return code is 1 for all errors.
4305 .cindex "error" "reporting"
4306 This option is supported for compatibility with Sendmail, but has the same
4311 .cindex "error" "reporting"
4312 This option is supported for compatibility with Sendmail, but has the same
4317 .cindex "dot" "in incoming non-SMTP message"
4318 This option, which has the same effect as &%-i%&, specifies that a dot on a
4319 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4320 single dot does terminate, though Exim does no special processing for other
4321 lines that start with a dot. This option is set by default if Exim is called as
4322 &'rmail'&. See also &%-ti%&.
4325 .oindex "&%-oitrue%&"
4326 This option is treated as synonymous with &%-oi%&.
4328 .vitem &%-oMa%&&~<&'host&~address'&>
4330 .cindex "sender" "host address, specifying for local message"
4331 A number of options starting with &%-oM%& can be used to set values associated
4332 with remote hosts on locally-submitted messages (that is, messages not received
4333 over TCP/IP). These options can be used by any caller in conjunction with the
4334 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4335 other circumstances, they are ignored unless the caller is trusted.
4337 The &%-oMa%& option sets the sender host address. This may include a port
4338 number at the end, after a full stop (period). For example:
4340 exim -bs -oMa 10.9.8.7.1234
4342 An alternative syntax is to enclose the IP address in square brackets,
4343 followed by a colon and the port number:
4345 exim -bs -oMa [10.9.8.7]:1234
4347 The IP address is placed in the &$sender_host_address$& variable, and the
4348 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4349 are present on the command line, the sender host IP address is taken from
4350 whichever one is last.
4352 .vitem &%-oMaa%&&~<&'name'&>
4354 .cindex "authentication" "name, specifying for local message"
4355 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4356 option sets the value of &$sender_host_authenticated$& (the authenticator
4357 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4358 This option can be used with &%-bh%& and &%-bs%& to set up an
4359 authenticated SMTP session without actually using the SMTP AUTH command.
4361 .vitem &%-oMai%&&~<&'string'&>
4363 .cindex "authentication" "id, specifying for local message"
4364 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4365 option sets the value of &$authenticated_id$& (the id that was authenticated).
4366 This overrides the default value (the caller's login id, except with &%-bh%&,
4367 where there is no default) for messages from local sources. See chapter
4368 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4370 .vitem &%-oMas%&&~<&'address'&>
4372 .cindex "authentication" "sender, specifying for local message"
4373 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4374 option sets the authenticated sender value in &$authenticated_sender$&. It
4375 overrides the sender address that is created from the caller's login id for
4376 messages from local sources, except when &%-bh%& is used, when there is no
4377 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4378 specified on a MAIL command overrides this value. See chapter
4379 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4381 .vitem &%-oMi%&&~<&'interface&~address'&>
4383 .cindex "interface" "address, specifying for local message"
4384 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4385 option sets the IP interface address value. A port number may be included,
4386 using the same syntax as for &%-oMa%&. The interface address is placed in
4387 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4389 .vitem &%-oMm%&&~<&'message&~reference'&>
4391 .cindex "message reference" "message reference, specifying for local message"
4392 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4393 option sets the message reference, e.g. message-id, and is logged during
4394 delivery. This is useful when some kind of audit trail is required to tie
4395 messages together. The format of the message reference is checked and will
4396 abort if the format is invalid. The option will only be accepted if exim is
4397 running in trusted mode, not as any regular user.
4399 The best example of a message reference is when Exim sends a bounce message.
4400 The message reference is the message-id of the original message for which Exim
4401 is sending the bounce.
4403 .vitem &%-oMr%&&~<&'protocol&~name'&>
4405 .cindex "protocol, specifying for local message"
4406 .vindex "&$received_protocol$&"
4407 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4408 option sets the received protocol value that is stored in
4409 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4410 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4411 SMTP protocol names (see the description of &$received_protocol$& in section
4412 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4413 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4414 be set by &%-oMr%&. Repeated use of this option is not supported.
4416 .vitem &%-oMs%&&~<&'host&~name'&>
4418 .cindex "sender" "host name, specifying for local message"
4419 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4420 option sets the sender host name in &$sender_host_name$&. When this option is
4421 present, Exim does not attempt to look up a host name from an IP address; it
4422 uses the name it is given.
4424 .vitem &%-oMt%&&~<&'ident&~string'&>
4426 .cindex "sender" "ident string, specifying for local message"
4427 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4428 option sets the sender ident value in &$sender_ident$&. The default setting for
4429 local callers is the login id of the calling process, except when &%-bh%& is
4430 used, when there is no default.
4434 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4435 In Sendmail, this option means &"me too"&, indicating that the sender of a
4436 message should receive a copy of the message if the sender appears in an alias
4437 expansion. Exim always does this, so the option does nothing.
4441 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4442 This option is ignored. In Sendmail it specifies &"old style headers"&,
4443 whatever that means.
4445 .vitem &%-oP%&&~<&'path'&>
4447 .cindex "pid (process id)" "of daemon"
4448 .cindex "daemon" "process id (pid)"
4449 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4450 value. The option specifies the file to which the process id of the daemon is
4451 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4452 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4453 because in those cases, the normal pid file is not used.
4457 .cindex "pid (process id)" "of daemon"
4458 .cindex "daemon" "process id (pid)"
4459 This option is not intended for general use.
4460 The daemon uses it when terminating due to a SIGTEM, possibly in
4461 combination with &%-oP%&&~<&'path'&>.
4462 It causes the pid file to be removed.
4464 .vitem &%-or%&&~<&'time'&>
4466 .cindex "timeout" "for non-SMTP input"
4467 This option sets a timeout value for incoming non-SMTP messages. If it is not
4468 set, Exim will wait forever for the standard input. The value can also be set
4469 by the &%receive_timeout%& option. The format used for specifying times is
4470 described in section &<<SECTtimeformat>>&.
4472 .vitem &%-os%&&~<&'time'&>
4474 .cindex "timeout" "for SMTP input"
4475 .cindex "SMTP" "input timeout"
4476 This option sets a timeout value for incoming SMTP messages. The timeout
4477 applies to each SMTP command and block of data. The value can also be set by
4478 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4479 for specifying times is described in section &<<SECTtimeformat>>&.
4483 This option has exactly the same effect as &%-v%&.
4485 .vitem &%-oX%&&~<&'number&~or&~string'&>
4487 .cindex "TCP/IP" "setting listening ports"
4488 .cindex "TCP/IP" "setting listening interfaces"
4489 .cindex "port" "receiving TCP/IP"
4490 This option is relevant only when the &%-bd%& (start listening daemon) option
4491 is also given. It controls which ports and interfaces the daemon uses. Details
4492 of the syntax, and how it interacts with configuration file options, are given
4493 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4494 file is written unless &%-oP%& is also present to specify a pid filename.
4499 .cindex "daemon notifier socket"
4500 This option controls the creation of an inter-process communications endpoint
4502 It is only relevant when the &%-bd%& (start listening daemon) option is also
4504 Normally the daemon creates this socket, unless a &%-oX%& and &*no*& &%-oP%&
4505 option is also present.
4506 If this option is given then the socket will not be created. This could be
4507 required if the system is running multiple daemons.
4509 The socket is currently used for
4511 fast ramp-up of queue runner processes
4513 obtaining a current queue size
4519 .cindex "Perl" "starting the interpreter"
4520 This option applies when an embedded Perl interpreter is linked with Exim (see
4521 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4522 option, forcing the starting of the interpreter to be delayed until it is
4527 .cindex "Perl" "starting the interpreter"
4528 This option applies when an embedded Perl interpreter is linked with Exim (see
4529 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4530 option, forcing the starting of the interpreter to occur as soon as Exim is
4533 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4535 For compatibility with Sendmail, this option is equivalent to
4537 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4539 It sets the incoming protocol and host name (for trusted callers). The
4540 host name and its colon can be omitted when only the protocol is to be set.
4541 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4542 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4543 or &`s`& using this option (but that does not seem a real limitation).
4544 Repeated use of this option is not supported.
4548 .cindex "queue runner" "starting manually"
4549 This option is normally restricted to admin users. However, there is a
4550 configuration option called &%prod_requires_admin%& which can be set false to
4551 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4552 and &%-S%& options).
4554 .cindex "queue runner" "description of operation"
4555 If other commandline options do not specify an action,
4556 the &%-q%& option starts one queue runner process. This scans the queue of
4557 waiting messages, and runs a delivery process for each one in turn. It waits
4558 for each delivery process to finish before starting the next one. A delivery
4559 process may not actually do any deliveries if the retry times for the addresses
4560 have not been reached. Use &%-qf%& (see below) if you want to override this.
4563 .cindex "SMTP" "passed connection"
4564 .cindex "SMTP" "multiple deliveries"
4565 .cindex "multiple SMTP deliveries"
4566 the delivery process spawns other processes to deliver other messages down
4567 passed SMTP connections, the queue runner waits for these to finish before
4570 When all the queued messages have been considered, the original queue runner
4571 process terminates. In other words, a single pass is made over the waiting
4572 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4573 this to be repeated periodically.
4575 Exim processes the waiting messages in an unpredictable order. It isn't very
4576 random, but it is likely to be different each time, which is all that matters.
4577 If one particular message screws up a remote MTA, other messages to the same
4578 MTA have a chance of getting through if they get tried first.
4580 It is possible to cause the messages to be processed in lexical message id
4581 order, which is essentially the order in which they arrived, by setting the
4582 &%queue_run_in_order%& option, but this is not recommended for normal use.
4584 .vitem &%-q%&<&'qflags'&>
4585 The &%-q%& option may be followed by one or more flag letters that change its
4586 behaviour. They are all optional, but if more than one is present, they must
4587 appear in the correct order. Each flag is described in a separate item below.
4591 .cindex "queue" "double scanning"
4592 .cindex "queue" "routing"
4593 .cindex "routing" "whole queue before delivery"
4594 .cindex "first pass routing"
4595 .cindex "queue runner" "two phase"
4596 An option starting with &%-qq%& requests a two-stage queue run. In the first
4597 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4598 every domain. Addresses are routed, local deliveries happen, but no remote
4601 Performance will be best if the &%queue_run_in_order%& option is false.
4602 If that is so and the &%queue_fast_ramp%& option is true then
4603 in the first phase of the run,
4604 once a threshold number of messages are routed for a given host,
4605 a delivery process is forked in parallel with the rest of the scan.
4607 .cindex "hints database" "remembering routing"
4608 The hints database that remembers which messages are waiting for specific hosts
4609 is updated, as if delivery to those hosts had been deferred. After this is
4610 complete, a second, normal queue scan happens, with routing and delivery taking
4611 place as normal. Messages that are routed to the same host should mostly be
4612 delivered down a single SMTP
4613 .cindex "SMTP" "passed connection"
4614 .cindex "SMTP" "multiple deliveries"
4615 .cindex "multiple SMTP deliveries"
4616 connection because of the hints that were set up during the first queue scan.
4617 This option may be useful for hosts that are connected to the Internet
4620 .vitem &%-q[q]i...%&
4622 .cindex "queue" "initial delivery"
4623 If the &'i'& flag is present, the queue runner runs delivery processes only for
4624 those messages that haven't previously been tried. (&'i'& stands for &"initial
4625 delivery"&.) This can be helpful if you are putting messages in the queue using
4626 &%-odq%& and want a queue runner just to process the new messages.
4628 .vitem &%-q[q][i]f...%&
4630 .cindex "queue" "forcing delivery"
4631 .cindex "delivery" "forcing in queue run"
4632 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4633 message, whereas without &'f'& only those non-frozen addresses that have passed
4634 their retry times are tried.
4636 .vitem &%-q[q][i]ff...%&
4638 .cindex "frozen messages" "forcing delivery"
4639 If &'ff'& is present, a delivery attempt is forced for every message, whether
4642 .vitem &%-q[q][i][f[f]]l%&
4644 .cindex "queue" "local deliveries only"
4645 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4646 be done. If a message requires any remote deliveries, it remains in the queue
4649 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4652 .cindex "named queues" "deliver from"
4653 .cindex "queue" "delivering specific messages"
4654 If the &'G'& flag and a name is present, the queue runner operates on the
4655 queue with the given name rather than the default queue.
4656 The name should not contain a &'/'& character.
4657 For a periodic queue run (see below)
4658 append to the name a slash and a time value.
4660 If other commandline options specify an action, a &'-qG<name>'& option
4661 will specify a queue to operate on.
4664 exim -bp -qGquarantine
4666 exim -qGoffpeak -Rf @special.domain.example
4669 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4670 When scanning the queue, Exim can be made to skip over messages whose ids are
4671 lexically less than a given value by following the &%-q%& option with a
4672 starting message id. For example:
4674 exim -q 0t5C6f-0000c8-00
4676 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4677 second message id is given, messages whose ids are lexically greater than it
4678 are also skipped. If the same id is given twice, for example,
4680 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4682 just one delivery process is started, for that message. This differs from
4683 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4684 that it counts as a delivery from a queue run. Note that the selection
4685 mechanism does not affect the order in which the messages are scanned. There
4686 are also other ways of selecting specific sets of messages for delivery in a
4687 queue run &-- see &%-R%& and &%-S%&.
4689 .vitem &%-q%&<&'qflags'&><&'time'&>
4690 .cindex "queue runner" "starting periodically"
4691 .cindex "periodic queue running"
4692 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4693 starting a queue runner process at intervals specified by the given time value
4694 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4695 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4696 single daemon process handles both functions. A common way of starting up a
4697 combined daemon at system boot time is to use a command such as
4699 /usr/exim/bin/exim -bd -q30m
4701 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4702 process every 30 minutes.
4704 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4705 pid file is written unless one is explicitly requested by the &%-oP%& option.
4707 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4709 This option is synonymous with &%-R%&. It is provided for Sendmail
4712 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4714 This option is synonymous with &%-S%&.
4716 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4718 .cindex "queue runner" "for specific recipients"
4719 .cindex "delivery" "to given domain"
4720 .cindex "domain" "delivery to"
4721 The <&'rsflags'&> may be empty, in which case the white space before the string
4722 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4723 which are the possible values for <&'rsflags'&>. White space is required if
4724 <&'rsflags'&> is not empty.
4726 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4727 perform a single queue run, except that, when scanning the messages on the
4728 queue, Exim processes only those that have at least one undelivered recipient
4729 address containing the given string, which is checked in a case-independent
4730 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4731 regular expression; otherwise it is a literal string.
4733 If you want to do periodic queue runs for messages with specific recipients,
4734 you can combine &%-R%& with &%-q%& and a time value. For example:
4736 exim -q25m -R @special.domain.example
4738 This example does a queue run for messages with recipients in the given domain
4739 every 25 minutes. Any additional flags that are specified with &%-q%& are
4740 applied to each queue run.
4742 Once a message is selected for delivery by this mechanism, all its addresses
4743 are processed. For the first selected message, Exim overrides any retry
4744 information and forces a delivery attempt for each undelivered address. This
4745 means that if delivery of any address in the first message is successful, any
4746 existing retry information is deleted, and so delivery attempts for that
4747 address in subsequently selected messages (which are processed without forcing)
4748 will run. However, if delivery of any address does not succeed, the retry
4749 information is updated, and in subsequently selected messages, the failing
4750 address will be skipped.
4752 .cindex "frozen messages" "forcing delivery"
4753 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4754 all selected messages, not just the first; frozen messages are included when
4757 The &%-R%& option makes it straightforward to initiate delivery of all messages
4758 to a given domain after a host has been down for some time. When the SMTP
4759 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4760 effect is to run Exim with the &%-R%& option, but it can be configured to run
4761 an arbitrary command instead.
4765 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4767 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4769 .cindex "delivery" "from given sender"
4770 .cindex "queue runner" "for specific senders"
4771 This option acts like &%-R%& except that it checks the string against each
4772 message's sender instead of against the recipients. If &%-R%& is also set, both
4773 conditions must be met for a message to be selected. If either of the options
4774 has &'f'& or &'ff'& in its flags, the associated action is taken.
4776 .vitem &%-Tqt%&&~<&'times'&>
4778 This is an option that is exclusively for use by the Exim testing suite. It is not
4779 recognized when Exim is run normally. It allows for the setting up of explicit
4780 &"queue times"& so that various warning/retry features can be tested.
4784 .cindex "recipient" "extracting from header lines"
4785 .cindex "&'Bcc:'& header line"
4786 .cindex "&'Cc:'& header line"
4787 .cindex "&'To:'& header line"
4788 When Exim is receiving a locally-generated, non-SMTP message on its standard
4789 input, the &%-t%& option causes the recipients of the message to be obtained
4790 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4791 from the command arguments. The addresses are extracted before any rewriting
4792 takes place and the &'Bcc:'& header line, if present, is then removed.
4794 .cindex "Sendmail compatibility" "&%-t%& option"
4795 If the command has any arguments, they specify addresses to which the message
4796 is &'not'& to be delivered. That is, the argument addresses are removed from
4797 the recipients list obtained from the headers. This is compatible with Smail 3
4798 and in accordance with the documented behaviour of several versions of
4799 Sendmail, as described in man pages on a number of operating systems (e.g.
4800 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4801 argument addresses to those obtained from the headers, and the O'Reilly
4802 Sendmail book documents it that way. Exim can be made to add argument addresses
4803 instead of subtracting them by setting the option
4804 &%extract_addresses_remove_arguments%& false.
4806 .cindex "&%Resent-%& header lines" "with &%-t%&"
4807 If there are any &%Resent-%& header lines in the message, Exim extracts
4808 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4809 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4810 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4811 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4813 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4814 message is resent several times). The RFC also specifies that they should be
4815 added at the front of the message, and separated by &'Received:'& lines. It is
4816 not at all clear how &%-t%& should operate in the present of multiple sets,
4817 nor indeed exactly what constitutes a &"set"&.
4818 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4819 are often added at the end of the header, and if a message is resent more than
4820 once, it is common for the original set of &%Resent-%& headers to be renamed as
4821 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4825 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4826 compatibility with Sendmail.
4828 .vitem &%-tls-on-connect%&
4829 .oindex "&%-tls-on-connect%&"
4830 .cindex "TLS" "use without STARTTLS"
4831 .cindex "TLS" "automatic start"
4832 This option is available when Exim is compiled with TLS support. It forces all
4833 incoming SMTP connections to behave as if the incoming port is listed in the
4834 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4835 &<<CHAPTLS>>& for further details.
4840 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4841 Sendmail uses this option for &"initial message submission"&, and its
4842 documentation states that in future releases, it may complain about
4843 syntactically invalid messages rather than fixing them when this flag is not
4844 set. Exim ignores this option.
4848 This option causes Exim to write information to the standard error stream,
4849 describing what it is doing. In particular, it shows the log lines for
4850 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4851 dialogue is shown. Some of the log lines shown may not actually be written to
4852 the log if the setting of &%log_selector%& discards them. Any relevant
4853 selectors are shown with each log line. If none are shown, the logging is
4858 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4859 National Language Support extended characters in the body of the mail item"&).
4860 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4863 .vitem &%-X%&&~<&'logfile'&>
4865 This option is interpreted by Sendmail to cause debug information to be sent
4866 to the named file. It is ignored by Exim.
4868 .vitem &%-z%&&~<&'log-line'&>
4870 This option writes its argument to Exim's logfile.
4871 Use is restricted to administrators; the intent is for operational notes.
4872 Quotes should be used to maintain a multi-word item as a single argument,
4880 . ////////////////////////////////////////////////////////////////////////////
4881 . Insert a stylized DocBook comment here, to identify the end of the command
4882 . line options. This is for the benefit of the Perl script that automatically
4883 . creates a man page for the options.
4884 . ////////////////////////////////////////////////////////////////////////////
4887 <!-- === End of command line options === -->
4894 . ////////////////////////////////////////////////////////////////////////////
4895 . ////////////////////////////////////////////////////////////////////////////
4898 .chapter "The Exim runtime configuration file" "CHAPconf" &&&
4899 "The runtime configuration file"
4901 .cindex "runtime configuration"
4902 .cindex "configuration file" "general description"
4903 .cindex "CONFIGURE_FILE"
4904 .cindex "configuration file" "errors in"
4905 .cindex "error" "in configuration file"
4906 .cindex "return code" "for bad configuration"
4907 Exim uses a single runtime configuration file that is read whenever an Exim
4908 binary is executed. Note that in normal operation, this happens frequently,
4909 because Exim is designed to operate in a distributed manner, without central
4912 If a syntax error is detected while reading the configuration file, Exim
4913 writes a message on the standard error, and exits with a non-zero return code.
4914 The message is also written to the panic log. &*Note*&: Only simple syntax
4915 errors can be detected at this time. The values of any expanded options are
4916 not checked until the expansion happens, even when the expansion does not
4917 actually alter the string.
4919 The name of the configuration file is compiled into the binary for security
4920 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4921 most configurations, this specifies a single file. However, it is permitted to
4922 give a colon-separated list of filenames, in which case Exim uses the first
4923 existing file in the list.
4926 .cindex "EXIM_GROUP"
4927 .cindex "CONFIGURE_OWNER"
4928 .cindex "CONFIGURE_GROUP"
4929 .cindex "configuration file" "ownership"
4930 .cindex "ownership" "configuration file"
4931 The runtime configuration file must be owned by root or by the user that is
4932 specified at compile time by the CONFIGURE_OWNER option (if set). The
4933 configuration file must not be world-writeable, or group-writeable unless its
4934 group is the root group or the one specified at compile time by the
4935 CONFIGURE_GROUP option.
4937 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4938 to root, anybody who is able to edit the runtime configuration file has an
4939 easy way to run commands as root. If you specify a user or group in the
4940 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4941 who are members of that group will trivially be able to obtain root privileges.
4943 Up to Exim version 4.72, the runtime configuration file was also permitted to
4944 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4945 since it offered a simple privilege escalation for any attacker who managed to
4946 compromise the Exim user account.
4948 A default configuration file, which will work correctly in simple situations,
4949 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4950 defines just one filename, the installation process copies the default
4951 configuration to a new file of that name if it did not previously exist. If
4952 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4953 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4958 .section "Using a different configuration file" "SECID40"
4959 .cindex "configuration file" "alternate"
4960 A one-off alternate configuration can be specified by the &%-C%& command line
4961 option, which may specify a single file or a list of files. However, when
4962 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4963 unless the argument for &%-C%& is identical to the built-in value from
4964 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4965 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4966 is useful mainly for checking the syntax of configuration files before
4967 installing them. No owner or group checks are done on a configuration file
4968 specified by &%-C%&, if root privilege has been dropped.
4970 Even the Exim user is not trusted to specify an arbitrary configuration file
4971 with the &%-C%& option to be used with root privileges, unless that file is
4972 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4973 testing a configuration using &%-C%& right through message reception and
4974 delivery, even if the caller is root. The reception works, but by that time,
4975 Exim is running as the Exim user, so when it re-execs to regain privilege for
4976 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4977 can test reception and delivery using two separate commands (one to put a
4978 message in the queue, using &%-odq%&, and another to do the delivery, using
4981 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4982 prefix string with which any file named in a &%-C%& command line option must
4983 start. In addition, the filename must not contain the sequence &"&`/../`&"&.
4984 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any
4985 filename can be used with &%-C%&.
4987 One-off changes to a configuration can be specified by the &%-D%& command line
4988 option, which defines and overrides values for macros used inside the
4989 configuration file. However, like &%-C%&, the use of this option by a
4990 non-privileged user causes Exim to discard its root privilege.
4991 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4992 completely disabled, and its use causes an immediate error exit.
4994 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4995 to declare certain macro names trusted, such that root privilege will not
4996 necessarily be discarded.
4997 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4998 considered safe and, if &%-D%& only supplies macros from this list, and the
4999 values are acceptable, then Exim will not give up root privilege if the caller
5000 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
5001 transition mechanism and is expected to be removed in the future. Acceptable
5002 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
5004 Some sites may wish to use the same Exim binary on different machines that
5005 share a file system, but to use different configuration files on each machine.
5006 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
5007 looks for a file whose name is the configuration filename followed by a dot
5008 and the machine's node name, as obtained from the &[uname()]& function. If this
5009 file does not exist, the standard name is tried. This processing occurs for
5010 each filename in the list given by CONFIGURE_FILE or &%-C%&.
5012 In some esoteric situations different versions of Exim may be run under
5013 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
5014 help with this. See the comments in &_src/EDITME_& for details.
5018 .section "Configuration file format" "SECTconffilfor"
5019 .cindex "configuration file" "format of"
5020 .cindex "format" "configuration file"
5021 Exim's configuration file is divided into a number of different parts. General
5022 option settings must always appear at the start of the file. The other parts
5023 are all optional, and may appear in any order. Each part other than the first
5024 is introduced by the word &"begin"& followed by at least one literal
5025 space, and the name of the part. The optional parts are:
5028 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
5031 .cindex "AUTH" "configuration"
5032 &'authenticators'&: Configuration settings for the authenticator drivers. These
5033 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
5035 &'routers'&: Configuration settings for the router drivers. Routers process
5036 addresses and determine how the message is to be delivered (see chapters
5037 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
5039 &'transports'&: Configuration settings for the transport drivers. Transports
5040 define mechanisms for copying messages to destinations (see chapters
5041 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
5043 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
5044 If there is no retry section, or if it is empty (that is, no retry rules are
5045 defined), Exim will not retry deliveries. In this situation, temporary errors
5046 are treated the same as permanent errors. Retry rules are discussed in chapter
5049 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
5050 when new addresses are generated during delivery. Rewriting is discussed in
5051 chapter &<<CHAPrewrite>>&.
5053 &'local_scan'&: Private options for the &[local_scan()]& function. If you
5054 want to use this feature, you must set
5056 LOCAL_SCAN_HAS_OPTIONS=yes
5058 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
5059 facility are given in chapter &<<CHAPlocalscan>>&.
5062 .cindex "configuration file" "leading white space in"
5063 .cindex "configuration file" "trailing white space in"
5064 .cindex "white space" "in configuration file"
5065 Leading and trailing white space in configuration lines is always ignored.
5067 Blank lines in the file, and lines starting with a # character (ignoring
5068 leading white space) are treated as comments and are ignored. &*Note*&: A
5069 # character other than at the beginning of a line is not treated specially,
5070 and does not introduce a comment.
5072 Any non-comment line can be continued by ending it with a backslash. Note that
5073 the general rule for white space means that trailing white space after the
5074 backslash and leading white space at the start of continuation
5075 lines is ignored. Comment lines beginning with # (but not empty lines) may
5076 appear in the middle of a sequence of continuation lines.
5078 A convenient way to create a configuration file is to start from the
5079 default, which is supplied in &_src/configure.default_&, and add, delete, or
5080 change settings as required.
5082 The ACLs, retry rules, and rewriting rules have their own syntax which is
5083 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
5084 respectively. The other parts of the configuration file have some syntactic
5085 items in common, and these are described below, from section &<<SECTcos>>&
5086 onwards. Before that, the inclusion, macro, and conditional facilities are
5091 .section "File inclusions in the configuration file" "SECID41"
5092 .cindex "inclusions in configuration file"
5093 .cindex "configuration file" "including other files"
5094 .cindex "&`.include`& in configuration file"
5095 .cindex "&`.include_if_exists`& in configuration file"
5096 You can include other files inside Exim's runtime configuration file by
5099 &`.include`& <&'filename'&>
5100 &`.include_if_exists`& <&'filename'&>
5102 on a line by itself. Double quotes round the filename are optional. If you use
5103 the first form, a configuration error occurs if the file does not exist; the
5104 second form does nothing for non-existent files.
5105 The first form allows a relative name. It is resolved relative to
5106 the directory of the including file. For the second form an absolute filename
5109 Includes may be nested to any depth, but remember that Exim reads its
5110 configuration file often, so it is a good idea to keep them to a minimum.
5111 If you change the contents of an included file, you must HUP the daemon,
5112 because an included file is read only when the configuration itself is read.
5114 The processing of inclusions happens early, at a physical line level, so, like
5115 comment lines, an inclusion can be used in the middle of an option setting,
5118 hosts_lookup = a.b.c \
5121 Include processing happens after macro processing (see below). Its effect is to
5122 process the lines of the included file as if they occurred inline where the
5127 .section "Macros in the configuration file" "SECTmacrodefs"
5128 .cindex "macro" "description of"
5129 .cindex "configuration file" "macros"
5130 If a line in the main part of the configuration (that is, before the first
5131 &"begin"& line) begins with an upper case letter, it is taken as a macro
5132 definition, and must be of the form
5134 <&'name'&> = <&'rest of line'&>
5136 The name must consist of letters, digits, and underscores, and need not all be
5137 in upper case, though that is recommended. The rest of the line, including any
5138 continuations, is the replacement text, and has leading and trailing white
5139 space removed. Quotes are not removed. The replacement text can never end with
5140 a backslash character, but this doesn't seem to be a serious limitation.
5142 Macros may also be defined between router, transport, authenticator, or ACL
5143 definitions. They may not, however, be defined within an individual driver or
5144 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
5146 .section "Macro substitution" "SECID42"
5147 Once a macro is defined, all subsequent lines in the file (and any included
5148 files) are scanned for the macro name; if there are several macros, the line is
5149 scanned for each, in turn, in the order in which the macros are defined. The
5150 replacement text is not re-scanned for the current macro, though it is scanned
5151 for subsequently defined macros. For this reason, a macro name may not contain
5152 the name of a previously defined macro as a substring. You could, for example,
5155 &`ABCD_XYZ = `&<&'something'&>
5156 &`ABCD = `&<&'something else'&>
5158 but putting the definitions in the opposite order would provoke a configuration
5159 error. Macro expansion is applied to individual physical lines from the file,
5160 before checking for line continuation or file inclusion (see above). If a line
5161 consists solely of a macro name, and the expansion of the macro is empty, the
5162 line is ignored. A macro at the start of a line may turn the line into a
5163 comment line or a &`.include`& line.
5166 .section "Redefining macros" "SECID43"
5167 Once defined, the value of a macro can be redefined later in the configuration
5168 (or in an included file). Redefinition is specified by using &'=='& instead of
5173 MAC == updated value
5175 Redefinition does not alter the order in which the macros are applied to the
5176 subsequent lines of the configuration file. It is still the same order in which
5177 the macros were originally defined. All that changes is the macro's value.
5178 Redefinition makes it possible to accumulate values. For example:
5182 MAC == MAC and something added
5184 This can be helpful in situations where the configuration file is built
5185 from a number of other files.
5187 .section "Overriding macro values" "SECID44"
5188 The values set for macros in the configuration file can be overridden by the
5189 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5190 used, unless called by root or the Exim user. A definition on the command line
5191 using the &%-D%& option causes all definitions and redefinitions within the
5196 .section "Example of macro usage" "SECID45"
5197 As an example of macro usage, consider a configuration where aliases are looked
5198 up in a MySQL database. It helps to keep the file less cluttered if long
5199 strings such as SQL statements are defined separately as macros, for example:
5201 ALIAS_QUERY = select mailbox from user where \
5202 login='${quote_mysql:$local_part}';
5204 This can then be used in a &(redirect)& router setting like this:
5206 data = ${lookup mysql{ALIAS_QUERY}}
5208 In earlier versions of Exim macros were sometimes used for domain, host, or
5209 address lists. In Exim 4 these are handled better by named lists &-- see
5210 section &<<SECTnamedlists>>&.
5213 .section "Builtin macros" "SECTbuiltinmacros"
5214 Exim defines some macros depending on facilities available, which may
5215 differ due to build-time definitions and from one release to another.
5216 All of these macros start with an underscore.
5217 They can be used to conditionally include parts of a configuration
5220 The following classes of macros are defined:
5222 &` _HAVE_* `& build-time defines
5223 &` _DRIVER_ROUTER_* `& router drivers
5224 &` _DRIVER_TRANSPORT_* `& transport drivers
5225 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5226 &` _LOG_* `& log_selector values
5227 &` _OPT_MAIN_* `& main config options
5228 &` _OPT_ROUTERS_* `& generic router options
5229 &` _OPT_TRANSPORTS_* `& generic transport options
5230 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5231 &` _OPT_ROUTER_*_* `& private router options
5232 &` _OPT_TRANSPORT_*_* `& private transport options
5233 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5236 Use an &"exim -bP macros"& command to get the list of macros.
5239 .section "Conditional skips in the configuration file" "SECID46"
5240 .cindex "configuration file" "conditional skips"
5241 .cindex "&`.ifdef`&"
5242 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5243 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5244 portions of the configuration file. The processing happens whenever the file is
5245 read (that is, when an Exim binary starts to run).
5247 The implementation is very simple. Instances of the first four directives must
5248 be followed by text that includes the names of one or macros. The condition
5249 that is tested is whether or not any macro substitution has taken place in the
5253 message_size_limit = 50M
5255 message_size_limit = 100M
5258 sets a message size limit of 50M if the macro &`AAA`& is defined
5259 (or &`A`& or &`AA`&), and 100M
5260 otherwise. If there is more than one macro named on the line, the condition
5261 is true if any of them are defined. That is, it is an &"or"& condition. To
5262 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5264 Although you can use a macro expansion to generate one of these directives,
5265 it is not very useful, because the condition &"there was a macro substitution
5266 in this line"& will always be true.
5268 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5269 to clarify complicated nestings.
5273 .section "Common option syntax" "SECTcos"
5274 .cindex "common option syntax"
5275 .cindex "syntax of common options"
5276 .cindex "configuration file" "common option syntax"
5277 For the main set of options, driver options, and &[local_scan()]& options,
5278 each setting is on a line by itself, and starts with a name consisting of
5279 lower-case letters and underscores. Many options require a data value, and in
5280 these cases the name must be followed by an equals sign (with optional white
5281 space) and then the value. For example:
5283 qualify_domain = mydomain.example.com
5285 .cindex "hiding configuration option values"
5286 .cindex "configuration options" "hiding value of"
5287 .cindex "options" "hiding value of"
5288 Some option settings may contain sensitive data, for example, passwords for
5289 accessing databases. To stop non-admin users from using the &%-bP%& command
5290 line option to read these values, you can precede the option settings with the
5291 word &"hide"&. For example:
5293 hide mysql_servers = localhost/users/admin/secret-password
5295 For non-admin users, such options are displayed like this:
5297 mysql_servers = <value not displayable>
5299 If &"hide"& is used on a driver option, it hides the value of that option on
5300 all instances of the same driver.
5302 The following sections describe the syntax used for the different data types
5303 that are found in option settings.
5306 .section "Boolean options" "SECID47"
5307 .cindex "format" "boolean"
5308 .cindex "boolean configuration values"
5309 .oindex "&%no_%&&'xxx'&"
5310 .oindex "&%not_%&&'xxx'&"
5311 Options whose type is given as boolean are on/off switches. There are two
5312 different ways of specifying such options: with and without a data value. If
5313 the option name is specified on its own without data, the switch is turned on;
5314 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5315 boolean options may be followed by an equals sign and one of the words
5316 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5317 the following two settings have exactly the same effect:
5322 The following two lines also have the same (opposite) effect:
5327 You can use whichever syntax you prefer.
5332 .section "Integer values" "SECID48"
5333 .cindex "integer configuration values"
5334 .cindex "format" "integer"
5335 If an option's type is given as &"integer"&, the value can be given in decimal,
5336 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5337 number is assumed. Otherwise, it is treated as an octal number unless it starts
5338 with the characters &"0x"&, in which case the remainder is interpreted as a
5341 If an integer value is followed by the letter K, it is multiplied by 1024; if
5342 it is followed by the letter M, it is multiplied by 1024x1024;
5343 if by the letter G, 1024x1024x1024.
5345 of integer option settings are output, values which are an exact multiple of
5346 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5347 and M. The printing style is independent of the actual input format that was
5351 .section "Octal integer values" "SECID49"
5352 .cindex "integer format"
5353 .cindex "format" "octal integer"
5354 If an option's type is given as &"octal integer"&, its value is always
5355 interpreted as an octal number, whether or not it starts with the digit zero.
5356 Such options are always output in octal.
5359 .section "Fixed point numbers" "SECID50"
5360 .cindex "fixed point configuration values"
5361 .cindex "format" "fixed point"
5362 If an option's type is given as &"fixed-point"&, its value must be a decimal
5363 integer, optionally followed by a decimal point and up to three further digits.
5367 .section "Time intervals" "SECTtimeformat"
5368 .cindex "time interval" "specifying in configuration"
5369 .cindex "format" "time interval"
5370 A time interval is specified as a sequence of numbers, each followed by one of
5371 the following letters, with no intervening white space:
5381 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5382 intervals are output in the same format. Exim does not restrict the values; it
5383 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5387 .section "String values" "SECTstrings"
5388 .cindex "string" "format of configuration values"
5389 .cindex "format" "string"
5390 If an option's type is specified as &"string"&, the value can be specified with
5391 or without double-quotes. If it does not start with a double-quote, the value
5392 consists of the remainder of the line plus any continuation lines, starting at
5393 the first character after any leading white space, with trailing white space
5394 removed, and with no interpretation of the characters in the string. Because
5395 Exim removes comment lines (those beginning with #) at an early stage, they can
5396 appear in the middle of a multi-line string. The following two settings are
5397 therefore equivalent:
5399 trusted_users = uucp:mail
5400 trusted_users = uucp:\
5401 # This comment line is ignored
5404 .cindex "string" "quoted"
5405 .cindex "escape characters in quoted strings"
5406 If a string does start with a double-quote, it must end with a closing
5407 double-quote, and any backslash characters other than those used for line
5408 continuation are interpreted as escape characters, as follows:
5411 .irow &`\\`& "single backslash"
5412 .irow &`\n`& "newline"
5413 .irow &`\r`& "carriage return"
5415 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5416 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5420 If a backslash is followed by some other character, including a double-quote
5421 character, that character replaces the pair.
5423 Quoting is necessary only if you want to make use of the backslash escapes to
5424 insert special characters, or if you need to specify a value with leading or
5425 trailing spaces. These cases are rare, so quoting is almost never needed in
5426 current versions of Exim. In versions of Exim before 3.14, quoting was required
5427 in order to continue lines, so you may come across older configuration files
5428 and examples that apparently quote unnecessarily.
5431 .section "Expanded strings" "SECID51"
5432 .cindex "expansion" "definition of"
5433 Some strings in the configuration file are subjected to &'string expansion'&,
5434 by which means various parts of the string may be changed according to the
5435 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5436 is as just described; in particular, the handling of backslashes in quoted
5437 strings is done as part of the input process, before expansion takes place.
5438 However, backslash is also an escape character for the expander, so any
5439 backslashes that are required for that reason must be doubled if they are
5440 within a quoted configuration string.
5443 .section "User and group names" "SECID52"
5444 .cindex "user name" "format of"
5445 .cindex "format" "user name"
5446 .cindex "groups" "name format"
5447 .cindex "format" "group name"
5448 User and group names are specified as strings, using the syntax described
5449 above, but the strings are interpreted specially. A user or group name must
5450 either consist entirely of digits, or be a name that can be looked up using the
5451 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5454 .section "List construction" "SECTlistconstruct"
5455 .cindex "list" "syntax of in configuration"
5456 .cindex "format" "list item in configuration"
5457 .cindex "string" "list, definition of"
5458 The data for some configuration options is a list of items, with colon as the
5459 default separator. Many of these options are shown with type &"string list"& in
5460 the descriptions later in this document. Others are listed as &"domain list"&,
5461 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5462 are all the same; however, those other than &"string list"& are subject to
5463 particular kinds of interpretation, as described in chapter
5464 &<<CHAPdomhosaddlists>>&.
5466 In all these cases, the entire list is treated as a single string as far as the
5467 input syntax is concerned. The &%trusted_users%& setting in section
5468 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5469 in a list, it must be entered as two colons. Leading and trailing white space
5470 on each item in a list is ignored. This makes it possible to include items that
5471 start with a colon, and in particular, certain forms of IPv6 address. For
5474 local_interfaces = 127.0.0.1 : ::::1
5476 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5478 &*Note*&: Although leading and trailing white space is ignored in individual
5479 list items, it is not ignored when parsing the list. The space after the first
5480 colon in the example above is necessary. If it were not there, the list would
5481 be interpreted as the two items 127.0.0.1:: and 1.
5483 .section "Changing list separators" "SECTlistsepchange"
5484 .cindex "list separator" "changing"
5485 .cindex "IPv6" "addresses in lists"
5486 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5487 introduced to allow the separator character to be changed. If a list begins
5488 with a left angle bracket, followed by any punctuation character, that
5489 character is used instead of colon as the list separator. For example, the list
5490 above can be rewritten to use a semicolon separator like this:
5492 local_interfaces = <; 127.0.0.1 ; ::1
5494 This facility applies to all lists, with the exception of the list in
5495 &%log_file_path%&. It is recommended that the use of non-colon separators be
5496 confined to circumstances where they really are needed.
5498 .cindex "list separator" "newline as"
5499 .cindex "newline" "as list separator"
5500 It is also possible to use newline and other control characters (those with
5501 code values less than 32, plus DEL) as separators in lists. Such separators
5502 must be provided literally at the time the list is processed. For options that
5503 are string-expanded, you can write the separator using a normal escape
5504 sequence. This will be processed by the expander before the string is
5505 interpreted as a list. For example, if a newline-separated list of domains is
5506 generated by a lookup, you can process it directly by a line such as this:
5508 domains = <\n ${lookup mysql{.....}}
5510 This avoids having to change the list separator in such data. You are unlikely
5511 to want to use a control character as a separator in an option that is not
5512 expanded, because the value is literal text. However, it can be done by giving
5513 the value in quotes. For example:
5515 local_interfaces = "<\n 127.0.0.1 \n ::1"
5517 Unlike printing character separators, which can be included in list items by
5518 doubling, it is not possible to include a control character as data when it is
5519 set as the separator. Two such characters in succession are interpreted as
5520 enclosing an empty list item.
5524 .section "Empty items in lists" "SECTempitelis"
5525 .cindex "list" "empty item in"
5526 An empty item at the end of a list is always ignored. In other words, trailing
5527 separator characters are ignored. Thus, the list in
5529 senders = user@domain :
5531 contains only a single item. If you want to include an empty string as one item
5532 in a list, it must not be the last item. For example, this list contains three
5533 items, the second of which is empty:
5535 senders = user1@domain : : user2@domain
5537 &*Note*&: There must be white space between the two colons, as otherwise they
5538 are interpreted as representing a single colon data character (and the list
5539 would then contain just one item). If you want to specify a list that contains
5540 just one, empty item, you can do it as in this example:
5544 In this case, the first item is empty, and the second is discarded because it
5545 is at the end of the list.
5550 .section "Format of driver configurations" "SECTfordricon"
5551 .cindex "drivers" "configuration format"
5552 There are separate parts in the configuration for defining routers, transports,
5553 and authenticators. In each part, you are defining a number of driver
5554 instances, each with its own set of options. Each driver instance is defined by
5555 a sequence of lines like this:
5557 <&'instance name'&>:
5562 In the following example, the instance name is &(localuser)&, and it is
5563 followed by three options settings:
5568 transport = local_delivery
5570 For each driver instance, you specify which Exim code module it uses &-- by the
5571 setting of the &%driver%& option &-- and (optionally) some configuration
5572 settings. For example, in the case of transports, if you want a transport to
5573 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5574 a local file you would use the &(appendfile)& driver. Each of the drivers is
5575 described in detail in its own separate chapter later in this manual.
5577 You can have several routers, transports, or authenticators that are based on
5578 the same underlying driver (each must have a different instance name).
5580 The order in which routers are defined is important, because addresses are
5581 passed to individual routers one by one, in order. The order in which
5582 transports are defined does not matter at all. The order in which
5583 authenticators are defined is used only when Exim, as a client, is searching
5584 them to find one that matches an authentication mechanism offered by the
5587 .cindex "generic options"
5588 .cindex "options" "generic &-- definition of"
5589 Within a driver instance definition, there are two kinds of option: &'generic'&
5590 and &'private'&. The generic options are those that apply to all drivers of the
5591 same type (that is, all routers, all transports or all authenticators). The
5592 &%driver%& option is a generic option that must appear in every definition.
5593 .cindex "private options"
5594 The private options are special for each driver, and none need appear, because
5595 they all have default values.
5597 The options may appear in any order, except that the &%driver%& option must
5598 precede any private options, since these depend on the particular driver. For
5599 this reason, it is recommended that &%driver%& always be the first option.
5601 Driver instance names, which are used for reference in log entries and
5602 elsewhere, can be any sequence of letters, digits, and underscores (starting
5603 with a letter) and must be unique among drivers of the same type. A router and
5604 a transport (for example) can each have the same name, but no two router
5605 instances can have the same name. The name of a driver instance should not be
5606 confused with the name of the underlying driver module. For example, the
5607 configuration lines:
5612 create an instance of the &(smtp)& transport driver whose name is
5613 &(remote_smtp)&. The same driver code can be used more than once, with
5614 different instance names and different option settings each time. A second
5615 instance of the &(smtp)& transport, with different options, might be defined
5621 command_timeout = 10s
5623 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5624 these transport instances from routers, and these names would appear in log
5627 Comment lines may be present in the middle of driver specifications. The full
5628 list of option settings for any particular driver instance, including all the
5629 defaulted values, can be extracted by making use of the &%-bP%& command line
5637 . ////////////////////////////////////////////////////////////////////////////
5638 . ////////////////////////////////////////////////////////////////////////////
5640 .chapter "The default configuration file" "CHAPdefconfil"
5641 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5642 .cindex "default" "configuration file &""walk through""&"
5643 The default configuration file supplied with Exim as &_src/configure.default_&
5644 is sufficient for a host with simple mail requirements. As an introduction to
5645 the way Exim is configured, this chapter &"walks through"& the default
5646 configuration, giving brief explanations of the settings. Detailed descriptions
5647 of the options are given in subsequent chapters. The default configuration file
5648 itself contains extensive comments about ways you might want to modify the
5649 initial settings. However, note that there are many options that are not
5650 mentioned at all in the default configuration.
5654 .section "Macros" "SECTdefconfmacros"
5655 All macros should be defined before any options.
5657 One macro is specified, but commented out, in the default configuration:
5659 # ROUTER_SMARTHOST=MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
5661 If all off-site mail is expected to be delivered to a "smarthost", then set the
5662 hostname here and uncomment the macro. This will affect which router is used
5663 later on. If this is left commented out, then Exim will perform direct-to-MX
5664 deliveries using a &(dnslookup)& router.
5666 In addition to macros defined here, Exim includes a number of built-in macros
5667 to enable configuration to be guarded by a binary built with support for a
5668 given feature. See section &<<SECTbuiltinmacros>>& for more details.
5671 .section "Main configuration settings" "SECTdefconfmain"
5672 The main (global) configuration option settings section must always come first
5673 in the file, after the macros.
5674 The first thing you'll see in the file, after some initial comments, is the line
5676 # primary_hostname =
5678 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5679 to know the official, fully qualified name of your host, and this is where you
5680 can specify it. However, in most cases you do not need to set this option. When
5681 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5683 The first three non-comment configuration lines are as follows:
5685 domainlist local_domains = @
5686 domainlist relay_to_domains =
5687 hostlist relay_from_hosts = 127.0.0.1
5689 These are not, in fact, option settings. They are definitions of two named
5690 domain lists and one named host list. Exim allows you to give names to lists of
5691 domains, hosts, and email addresses, in order to make it easier to manage the
5692 configuration file (see section &<<SECTnamedlists>>&).
5694 The first line defines a domain list called &'local_domains'&; this is used
5695 later in the configuration to identify domains that are to be delivered
5698 .cindex "@ in a domain list"
5699 There is just one item in this list, the string &"@"&. This is a special form
5700 of entry which means &"the name of the local host"&. Thus, if the local host is
5701 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5702 be delivered locally. Because the local host's name is referenced indirectly,
5703 the same configuration file can be used on different hosts.
5705 The second line defines a domain list called &'relay_to_domains'&, but the
5706 list itself is empty. Later in the configuration we will come to the part that
5707 controls mail relaying through the local host; it allows relaying to any
5708 domains in this list. By default, therefore, no relaying on the basis of a mail
5709 domain is permitted.
5711 The third line defines a host list called &'relay_from_hosts'&. This list is
5712 used later in the configuration to permit relaying from any host or IP address
5713 that matches the list. The default contains just the IP address of the IPv4
5714 loopback interface, which means that processes on the local host are able to
5715 submit mail for relaying by sending it over TCP/IP to that interface. No other
5716 hosts are permitted to submit messages for relaying.
5718 Just to be sure there's no misunderstanding: at this point in the configuration
5719 we aren't actually setting up any controls. We are just defining some domains
5720 and hosts that will be used in the controls that are specified later.
5722 The next two configuration lines are genuine option settings:
5724 acl_smtp_rcpt = acl_check_rcpt
5725 acl_smtp_data = acl_check_data
5727 These options specify &'Access Control Lists'& (ACLs) that are to be used
5728 during an incoming SMTP session for every recipient of a message (every RCPT
5729 command), and after the contents of the message have been received,
5730 respectively. The names of the lists are &'acl_check_rcpt'& and
5731 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5732 section of the configuration. The RCPT ACL controls which recipients are
5733 accepted for an incoming message &-- if a configuration does not provide an ACL
5734 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5735 contents of a message to be checked.
5737 Two commented-out option settings are next:
5739 # av_scanner = clamd:/tmp/clamd
5740 # spamd_address = 127.0.0.1 783
5742 These are example settings that can be used when Exim is compiled with the
5743 content-scanning extension. The first specifies the interface to the virus
5744 scanner, and the second specifies the interface to SpamAssassin. Further
5745 details are given in chapter &<<CHAPexiscan>>&.
5747 Three more commented-out option settings follow:
5749 # tls_advertise_hosts = *
5750 # tls_certificate = /etc/ssl/exim.crt
5751 # tls_privatekey = /etc/ssl/exim.pem
5753 These are example settings that can be used when Exim is compiled with
5754 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5755 first one specifies the list of clients that are allowed to use TLS when
5756 connecting to this server; in this case, the wildcard means all clients. The
5757 other options specify where Exim should find its TLS certificate and private
5758 key, which together prove the server's identity to any clients that connect.
5759 More details are given in chapter &<<CHAPTLS>>&.
5761 Another two commented-out option settings follow:
5763 # daemon_smtp_ports = 25 : 465 : 587
5764 # tls_on_connect_ports = 465
5766 .cindex "port" "465 and 587"
5767 .cindex "port" "for message submission"
5768 .cindex "message" "submission, ports for"
5769 .cindex "submissions protocol"
5770 .cindex "smtps protocol"
5771 .cindex "ssmtp protocol"
5772 .cindex "SMTP" "submissions protocol"
5773 .cindex "SMTP" "ssmtp protocol"
5774 .cindex "SMTP" "smtps protocol"
5775 These options provide better support for roaming users who wish to use this
5776 server for message submission. They are not much use unless you have turned on
5777 TLS (as described in the previous paragraph) and authentication (about which
5778 more in section &<<SECTdefconfauth>>&).
5779 Mail submission from mail clients (MUAs) should be separate from inbound mail
5780 to your domain (MX delivery) for various good reasons (eg, ability to impose
5781 much saner TLS protocol and ciphersuite requirements without unintended
5783 RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
5784 which uses STARTTLS, so this is the &"submission"& port.
5785 RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
5786 which should be used in preference to 587.
5787 You should also consider deploying SRV records to help clients find
5789 Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
5791 Two more commented-out options settings follow:
5794 # qualify_recipient =
5796 The first of these specifies a domain that Exim uses when it constructs a
5797 complete email address from a local login name. This is often needed when Exim
5798 receives a message from a local process. If you do not set &%qualify_domain%&,
5799 the value of &%primary_hostname%& is used. If you set both of these options,
5800 you can have different qualification domains for sender and recipient
5801 addresses. If you set only the first one, its value is used in both cases.
5803 .cindex "domain literal" "recognizing format"
5804 The following line must be uncommented if you want Exim to recognize
5805 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5806 (an IP address within square brackets) instead of a named domain.
5808 # allow_domain_literals
5810 The RFCs still require this form, but many people think that in the modern
5811 Internet it makes little sense to permit mail to be sent to specific hosts by
5812 quoting their IP addresses. This ancient format has been used by people who
5813 try to abuse hosts by using them for unwanted relaying. However, some
5814 people believe there are circumstances (for example, messages addressed to
5815 &'postmaster'&) where domain literals are still useful.
5817 The next configuration line is a kind of trigger guard:
5821 It specifies that no delivery must ever be run as the root user. The normal
5822 convention is to set up &'root'& as an alias for the system administrator. This
5823 setting is a guard against slips in the configuration.
5824 The list of users specified by &%never_users%& is not, however, the complete
5825 list; the build-time configuration in &_Local/Makefile_& has an option called
5826 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5827 contents of &%never_users%& are added to this list. By default
5828 FIXED_NEVER_USERS also specifies root.
5830 When a remote host connects to Exim in order to send mail, the only information
5831 Exim has about the host's identity is its IP address. The next configuration
5836 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5837 in order to get a host name. This improves the quality of the logging
5838 information, but if you feel it is too expensive, you can remove it entirely,
5839 or restrict the lookup to hosts on &"nearby"& networks.
5840 Note that it is not always possible to find a host name from an IP address,
5841 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5844 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5845 1413 (hence their names):
5848 rfc1413_query_timeout = 0s
5850 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5851 Few hosts offer RFC1413 service these days; calls have to be
5852 terminated by a timeout and this needlessly delays the startup
5853 of an incoming SMTP connection.
5854 If you have hosts for which you trust RFC1413 and need this
5855 information, you can change this.
5857 This line enables an efficiency SMTP option. It is negotiated by clients
5858 and not expected to cause problems but can be disabled if needed.
5863 When Exim receives messages over SMTP connections, it expects all addresses to
5864 be fully qualified with a domain, as required by the SMTP definition. However,
5865 if you are running a server to which simple clients submit messages, you may
5866 find that they send unqualified addresses. The two commented-out options:
5868 # sender_unqualified_hosts =
5869 # recipient_unqualified_hosts =
5871 show how you can specify hosts that are permitted to send unqualified sender
5872 and recipient addresses, respectively.
5874 The &%log_selector%& option is used to increase the detail of logging
5877 log_selector = +smtp_protocol_error +smtp_syntax_error \
5878 +tls_certificate_verified
5881 The &%percent_hack_domains%& option is also commented out:
5883 # percent_hack_domains =
5885 It provides a list of domains for which the &"percent hack"& is to operate.
5886 This is an almost obsolete form of explicit email routing. If you do not know
5887 anything about it, you can safely ignore this topic.
5889 The next two settings in the main part of the default configuration are
5890 concerned with messages that have been &"frozen"& on Exim's queue. When a
5891 message is frozen, Exim no longer continues to try to deliver it. Freezing
5892 occurs when a bounce message encounters a permanent failure because the sender
5893 address of the original message that caused the bounce is invalid, so the
5894 bounce cannot be delivered. This is probably the most common case, but there
5895 are also other conditions that cause freezing, and frozen messages are not
5896 always bounce messages.
5898 ignore_bounce_errors_after = 2d
5899 timeout_frozen_after = 7d
5901 The first of these options specifies that failing bounce messages are to be
5902 discarded after 2 days in the queue. The second specifies that any frozen
5903 message (whether a bounce message or not) is to be timed out (and discarded)
5904 after a week. In this configuration, the first setting ensures that no failing
5905 bounce message ever lasts a week.
5907 Exim queues it's messages in a spool directory. If you expect to have
5908 large queues, you may consider using this option. It splits the spool
5909 directory into subdirectories to avoid file system degradation from
5910 many files in a single directory, resulting in better performance.
5911 Manual manipulation of queued messages becomes more complex (though fortunately
5914 # split_spool_directory = true
5917 In an ideal world everybody follows the standards. For non-ASCII
5918 messages RFC 2047 is a standard, allowing a maximum line length of 76
5919 characters. Exim adheres that standard and won't process messages which
5920 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5921 In particular, the Exim maintainers have had multiple reports of
5922 problems from Russian administrators of issues until they disable this
5923 check, because of some popular, yet buggy, mail composition software.
5925 # check_rfc2047_length = false
5928 If you need to be strictly RFC compliant you may wish to disable the
5929 8BITMIME advertisement. Use this, if you exchange mails with systems
5930 that are not 8-bit clean.
5932 # accept_8bitmime = false
5935 Libraries you use may depend on specific environment settings. This
5936 imposes a security risk (e.g. PATH). There are two lists:
5937 &%keep_environment%& for the variables to import as they are, and
5938 &%add_environment%& for variables we want to set to a fixed value.
5939 Note that TZ is handled separately, by the $%timezone%$ runtime
5940 option and by the TIMEZONE_DEFAULT buildtime option.
5942 # keep_environment = ^LDAP
5943 # add_environment = PATH=/usr/bin::/bin
5947 .section "ACL configuration" "SECID54"
5948 .cindex "default" "ACLs"
5949 .cindex "&ACL;" "default configuration"
5950 In the default configuration, the ACL section follows the main configuration.
5951 It starts with the line
5955 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5956 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5957 and &%acl_smtp_data%& above.
5959 .cindex "RCPT" "ACL for"
5960 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5961 RCPT command specifies one of the message's recipients. The ACL statements
5962 are considered in order, until the recipient address is either accepted or
5963 rejected. The RCPT command is then accepted or rejected, according to the
5964 result of the ACL processing.
5968 This line, consisting of a name terminated by a colon, marks the start of the
5973 This ACL statement accepts the recipient if the sending host matches the list.
5974 But what does that strange list mean? It doesn't actually contain any host
5975 names or IP addresses. The presence of the colon puts an empty item in the
5976 list; Exim matches this only if the incoming message did not come from a remote
5977 host, because in that case, the remote hostname is empty. The colon is
5978 important. Without it, the list itself is empty, and can never match anything.
5980 What this statement is doing is to accept unconditionally all recipients in
5981 messages that are submitted by SMTP from local processes using the standard
5982 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5985 deny domains = +local_domains
5986 local_parts = ^[.] : ^.*[@%!/|]
5987 message = Restricted characters in address
5989 deny domains = !+local_domains
5990 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5991 message = Restricted characters in address
5993 These statements are concerned with local parts that contain any of the
5994 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5995 Although these characters are entirely legal in local parts (in the case of
5996 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5997 in Internet mail addresses.
5999 The first three have in the past been associated with explicitly routed
6000 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
6001 option). Addresses containing these characters are regularly tried by spammers
6002 in an attempt to bypass relaying restrictions, and also by open relay testing
6003 programs. Unless you really need them it is safest to reject these characters
6004 at this early stage. This configuration is heavy-handed in rejecting these
6005 characters for all messages it accepts from remote hosts. This is a deliberate
6006 policy of being as safe as possible.
6008 The first rule above is stricter, and is applied to messages that are addressed
6009 to one of the local domains handled by this host. This is implemented by the
6010 first condition, which restricts it to domains that are listed in the
6011 &'local_domains'& domain list. The &"+"& character is used to indicate a
6012 reference to a named list. In this configuration, there is just one domain in
6013 &'local_domains'&, but in general there may be many.
6015 The second condition on the first statement uses two regular expressions to
6016 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
6017 or &"|"&. If you have local accounts that include these characters, you will
6018 have to modify this rule.
6020 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
6021 allows them because they have been encountered in practice. (Consider the
6022 common convention of local parts constructed as
6023 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
6024 the author of Exim, who has no second initial.) However, a local part starting
6025 with a dot or containing &"/../"& can cause trouble if it is used as part of a
6026 filename (for example, for a mailing list). This is also true for local parts
6027 that contain slashes. A pipe symbol can also be troublesome if the local part
6028 is incorporated unthinkingly into a shell command line.
6030 The second rule above applies to all other domains, and is less strict. This
6031 allows your own users to send outgoing messages to sites that use slashes
6032 and vertical bars in their local parts. It blocks local parts that begin
6033 with a dot, slash, or vertical bar, but allows these characters within the
6034 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
6035 and &"!"& is blocked, as before. The motivation here is to prevent your users
6036 (or your users' viruses) from mounting certain kinds of attack on remote sites.
6038 accept local_parts = postmaster
6039 domains = +local_domains
6041 This statement, which has two conditions, accepts an incoming address if the
6042 local part is &'postmaster'& and the domain is one of those listed in the
6043 &'local_domains'& domain list. The &"+"& character is used to indicate a
6044 reference to a named list. In this configuration, there is just one domain in
6045 &'local_domains'&, but in general there may be many.
6047 The presence of this statement means that mail to postmaster is never blocked
6048 by any of the subsequent tests. This can be helpful while sorting out problems
6049 in cases where the subsequent tests are incorrectly denying access.
6051 require verify = sender
6053 This statement requires the sender address to be verified before any subsequent
6054 ACL statement can be used. If verification fails, the incoming recipient
6055 address is refused. Verification consists of trying to route the address, to
6056 see if a bounce message could be delivered to it. In the case of remote
6057 addresses, basic verification checks only the domain, but &'callouts'& can be
6058 used for more verification if required. Section &<<SECTaddressverification>>&
6059 discusses the details of address verification.
6061 accept hosts = +relay_from_hosts
6062 control = submission
6064 This statement accepts the address if the message is coming from one of the
6065 hosts that are defined as being allowed to relay through this host. Recipient
6066 verification is omitted here, because in many cases the clients are dumb MUAs
6067 that do not cope well with SMTP error responses. For the same reason, the
6068 second line specifies &"submission mode"& for messages that are accepted. This
6069 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
6070 messages that are deficient in some way, for example, because they lack a
6071 &'Date:'& header line. If you are actually relaying out from MTAs, you should
6072 probably add recipient verification here, and disable submission mode.
6074 accept authenticated = *
6075 control = submission
6077 This statement accepts the address if the client host has authenticated itself.
6078 Submission mode is again specified, on the grounds that such messages are most
6079 likely to come from MUAs. The default configuration does not define any
6080 authenticators, though it does include some nearly complete commented-out
6081 examples described in &<<SECTdefconfauth>>&. This means that no client can in
6082 fact authenticate until you complete the authenticator definitions.
6084 require message = relay not permitted
6085 domains = +local_domains : +relay_to_domains
6087 This statement rejects the address if its domain is neither a local domain nor
6088 one of the domains for which this host is a relay.
6090 require verify = recipient
6092 This statement requires the recipient address to be verified; if verification
6093 fails, the address is rejected.
6095 # deny dnslists = black.list.example
6096 # message = rejected because $sender_host_address \
6097 # is in a black list at $dnslist_domain\n\
6100 # warn dnslists = black.list.example
6101 # add_header = X-Warning: $sender_host_address is in \
6102 # a black list at $dnslist_domain
6103 # log_message = found in $dnslist_domain
6105 These commented-out lines are examples of how you could configure Exim to check
6106 sending hosts against a DNS black list. The first statement rejects messages
6107 from blacklisted hosts, whereas the second just inserts a warning header
6110 # require verify = csa
6112 This commented-out line is an example of how you could turn on client SMTP
6113 authorization (CSA) checking. Such checks do DNS lookups for special SRV
6118 The final statement in the first ACL unconditionally accepts any recipient
6119 address that has successfully passed all the previous tests.
6123 This line marks the start of the second ACL, and names it. Most of the contents
6124 of this ACL are commented out:
6127 # message = This message contains a virus \
6130 These lines are examples of how to arrange for messages to be scanned for
6131 viruses when Exim has been compiled with the content-scanning extension, and a
6132 suitable virus scanner is installed. If the message is found to contain a
6133 virus, it is rejected with the given custom error message.
6135 # warn spam = nobody
6136 # message = X-Spam_score: $spam_score\n\
6137 # X-Spam_score_int: $spam_score_int\n\
6138 # X-Spam_bar: $spam_bar\n\
6139 # X-Spam_report: $spam_report
6141 These lines are an example of how to arrange for messages to be scanned by
6142 SpamAssassin when Exim has been compiled with the content-scanning extension,
6143 and SpamAssassin has been installed. The SpamAssassin check is run with
6144 &`nobody`& as its user parameter, and the results are added to the message as a
6145 series of extra header line. In this case, the message is not rejected,
6146 whatever the spam score.
6150 This final line in the DATA ACL accepts the message unconditionally.
6153 .section "Router configuration" "SECID55"
6154 .cindex "default" "routers"
6155 .cindex "routers" "default"
6156 The router configuration comes next in the default configuration, introduced
6161 Routers are the modules in Exim that make decisions about where to send
6162 messages. An address is passed to each router, in turn, until it is either
6163 accepted, or failed. This means that the order in which you define the routers
6164 matters. Each router is fully described in its own chapter later in this
6165 manual. Here we give only brief overviews.
6168 # driver = ipliteral
6169 # domains = !+local_domains
6170 # transport = remote_smtp
6172 .cindex "domain literal" "default router"
6173 This router is commented out because the majority of sites do not want to
6174 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
6175 you uncomment this router, you also need to uncomment the setting of
6176 &%allow_domain_literals%& in the main part of the configuration.
6178 Which router is used next depends upon whether or not the ROUTER_SMARTHOST
6179 macro has been defined, per
6181 .ifdef ROUTER_SMARTHOST
6190 If ROUTER_SMARTHOST has been defined, either at the top of the file or on the
6191 command-line, then we route all non-local mail to that smarthost; otherwise, we'll
6192 perform DNS lookups for direct-to-MX lookup. Any mail which is to a local domain will
6193 skip these routers because of the &%domains%& option.
6197 driver = manualroute
6198 domains = ! +local_domains
6199 transport = smarthost_smtp
6200 route_data = ROUTER_SMARTHOST
6201 ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
6204 This router only handles mail which is not to any local domains; this is
6205 specified by the line
6207 domains = ! +local_domains
6209 The &%domains%& option lists the domains to which this router applies, but the
6210 exclamation mark is a negation sign, so the router is used only for domains
6211 that are not in the domain list called &'local_domains'& (which was defined at
6212 the start of the configuration). The plus sign before &'local_domains'&
6213 indicates that it is referring to a named list. Addresses in other domains are
6214 passed on to the following routers.
6216 The name of the router driver is &(manualroute)& because we are manually
6217 specifying how mail should be routed onwards, instead of using DNS MX.
6218 While the name of this router instance is arbitrary, the &%driver%& option must
6219 be one of the driver modules that is in the Exim binary.
6221 With no pre-conditions other than &%domains%&, all mail for non-local domains
6222 will be handled by this router, and the &%no_more%& setting will ensure that no
6223 other routers will be used for messages matching the pre-conditions. See
6224 &<<SECTrouprecon>>& for more on how the pre-conditions apply. For messages which
6225 are handled by this router, we provide a hostname to deliver to in &%route_data%&
6226 and the macro supplies the value; the address is then queued for the
6227 &(smarthost_smtp)& transport.
6232 domains = ! +local_domains
6233 transport = remote_smtp
6234 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
6237 The &%domains%& option behaves as per smarthost, above.
6239 The name of the router driver is &(dnslookup)&,
6240 and is specified by the &%driver%& option. Do not be confused by the fact that
6241 the name of this router instance is the same as the name of the driver. The
6242 instance name is arbitrary, but the name set in the &%driver%& option must be
6243 one of the driver modules that is in the Exim binary.
6245 The &(dnslookup)& router routes addresses by looking up their domains in the
6246 DNS in order to obtain a list of hosts to which the address is routed. If the
6247 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6248 specified by the &%transport%& option. If the router does not find the domain
6249 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6250 the address fails and is bounced.
6252 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6253 be entirely ignored. This option is present because a number of cases have been
6254 encountered where MX records in the DNS point to host names
6255 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6256 Completely ignoring these IP addresses causes Exim to fail to route the
6257 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6258 continue to try to deliver the message periodically until the address timed
6265 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6267 file_transport = address_file
6268 pipe_transport = address_pipe
6270 Control reaches this and subsequent routers only for addresses in the local
6271 domains. This router checks to see whether the local part is defined as an
6272 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6273 data that it looks up from that file. If no data is found for the local part,
6274 the value of the &%data%& option is empty, causing the address to be passed to
6277 &_/etc/aliases_& is a conventional name for the system aliases file that is
6278 often used. That is why it is referenced by from the default configuration
6279 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6280 &_Local/Makefile_& before building Exim.
6285 # local_part_suffix = +* : -*
6286 # local_part_suffix_optional
6287 file = $home/.forward
6292 file_transport = address_file
6293 pipe_transport = address_pipe
6294 reply_transport = address_reply
6296 This is the most complicated router in the default configuration. It is another
6297 redirection router, but this time it is looking for forwarding data set up by
6298 individual users. The &%check_local_user%& setting specifies a check that the
6299 local part of the address is the login name of a local user. If it is not, the
6300 router is skipped. The two commented options that follow &%check_local_user%&,
6303 # local_part_suffix = +* : -*
6304 # local_part_suffix_optional
6306 .vindex "&$local_part_suffix$&"
6307 show how you can specify the recognition of local part suffixes. If the first
6308 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6309 by any sequence of characters, is removed from the local part and placed in the
6310 variable &$local_part_suffix$&. The second suffix option specifies that the
6311 presence of a suffix in the local part is optional. When a suffix is present,
6312 the check for a local login uses the local part with the suffix removed.
6314 When a local user account is found, the file called &_.forward_& in the user's
6315 home directory is consulted. If it does not exist, or is empty, the router
6316 declines. Otherwise, the contents of &_.forward_& are interpreted as
6317 redirection data (see chapter &<<CHAPredirect>>& for more details).
6319 .cindex "Sieve filter" "enabling in default router"
6320 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6321 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6322 is commented out by default), the contents of the file are interpreted as a set
6323 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6324 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6325 separate document entitled &'Exim's interfaces to mail filtering'&.
6327 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6328 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6329 There are two reasons for doing this:
6332 Whether or not a local user has a &_.forward_& file is not really relevant when
6333 checking an address for validity; it makes sense not to waste resources doing
6336 More importantly, when Exim is verifying addresses or handling an EXPN
6337 command during an SMTP session, it is running as the Exim user, not as root.
6338 The group is the Exim group, and no additional groups are set up.
6339 It may therefore not be possible for Exim to read users' &_.forward_& files at
6343 The setting of &%check_ancestor%& prevents the router from generating a new
6344 address that is the same as any previous address that was redirected. (This
6345 works round a problem concerning a bad interaction between aliasing and
6346 forwarding &-- see section &<<SECTredlocmai>>&).
6348 The final three option settings specify the transports that are to be used when
6349 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6350 auto-reply, respectively. For example, if a &_.forward_& file contains
6352 a.nother@elsewhere.example, /home/spqr/archive
6354 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6360 # local_part_suffix = +* : -*
6361 # local_part_suffix_optional
6362 transport = local_delivery
6364 The final router sets up delivery into local mailboxes, provided that the local
6365 part is the name of a local login, by accepting the address and assigning it to
6366 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6367 routers, so the address is bounced. The commented suffix settings fulfil the
6368 same purpose as they do for the &(userforward)& router.
6371 .section "Transport configuration" "SECID56"
6372 .cindex "default" "transports"
6373 .cindex "transports" "default"
6374 Transports define mechanisms for actually delivering messages. They operate
6375 only when referenced from routers, so the order in which they are defined does
6376 not matter. The transports section of the configuration starts with
6380 Two remote transports and four local transports are defined.
6384 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6389 This transport is used for delivering messages over SMTP connections.
6390 The list of remote hosts comes from the router.
6391 The &%message_size_limit%& usage is a hack to avoid sending on messages
6392 with over-long lines.
6394 The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
6395 negotiated between client and server and not expected to cause problems
6396 but can be disabled if needed. The built-in macro _HAVE_PRDR guards the
6397 use of the &%hosts_try_prdr%& configuration option.
6399 The other remote transport is used when delivering to a specific smarthost
6400 with whom there must be some kind of existing relationship, instead of the
6401 usual federated system.
6406 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6410 # Comment out any of these which you have to, then file a Support
6411 # request with your smarthost provider to get things fixed:
6412 hosts_require_tls = *
6413 tls_verify_hosts = *
6414 # As long as tls_verify_hosts is enabled, this won't matter, but if you
6415 # have to comment it out then this will at least log whether you succeed
6417 tls_try_verify_hosts = *
6419 # The SNI name should match the name which we'll expect to verify;
6420 # many mail systems don't use SNI and this doesn't matter, but if it does,
6421 # we need to send a name which the remote site will recognize.
6422 # This _should_ be the name which the smarthost operators specified as
6423 # the hostname for sending your mail to.
6424 tls_sni = ROUTER_SMARTHOST
6426 .ifdef _HAVE_OPENSSL
6427 tls_require_ciphers = HIGH:!aNULL:@STRENGTH
6430 tls_require_ciphers = SECURE192:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1
6437 After the same &%message_size_limit%& hack, we then specify that this Transport
6438 can handle messages to multiple domains in one run. The assumption here is
6439 that you're routing all non-local mail to the same place and that place is
6440 happy to take all messages from you as quickly as possible.
6441 All other options depend upon built-in macros; if Exim was built without TLS support
6442 then no other options are defined.
6443 If TLS is available, then we configure "stronger than default" TLS ciphersuites
6444 and versions using the &%tls_require_ciphers%& option, where the value to be
6445 used depends upon the library providing TLS.
6446 Beyond that, the options adopt the stance that you should have TLS support available
6447 from your smarthost on today's Internet, so we turn on requiring TLS for the
6448 mail to be delivered, and requiring that the certificate be valid, and match
6449 the expected hostname. The &%tls_sni%& option can be used by service providers
6450 to select an appropriate certificate to present to you and here we re-use the
6451 ROUTER_SMARTHOST macro, because that is unaffected by CNAMEs present in DNS.
6452 You want to specify the hostname which you'll expect to validate for, and that
6453 should not be subject to insecure tampering via DNS results.
6455 For the &%hosts_try_prdr%& option see the previous transport.
6457 All other options are defaulted.
6461 file = /var/mail/$local_part_data
6468 This &(appendfile)& transport is used for local delivery to user mailboxes in
6469 traditional BSD mailbox format.
6471 We prefer to avoid using &$local_part$& directly to define the mailbox filename,
6472 as it is provided by a potential bad actor.
6473 Instead we use &$local_part_data$&,
6474 the result of looking up &$local_part$& in the user database
6475 (done by using &%check_local_user%& in the the router).
6477 By default &(appendfile)& runs under the uid and gid of the
6478 local user, which requires the sticky bit to be set on the &_/var/mail_&
6479 directory. Some systems use the alternative approach of running mail deliveries
6480 under a particular group instead of using the sticky bit. The commented options
6481 show how this can be done.
6483 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6484 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6485 similarly-named options above.
6491 This transport is used for handling deliveries to pipes that are generated by
6492 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6493 option specifies that any output on stdout or stderr generated by the pipe is to
6494 be returned to the sender.
6502 This transport is used for handling deliveries to files that are generated by
6503 redirection. The name of the file is not specified in this instance of
6504 &(appendfile)&, because it comes from the &(redirect)& router.
6509 This transport is used for handling automatic replies generated by users'
6514 .section "Default retry rule" "SECID57"
6515 .cindex "retry" "default rule"
6516 .cindex "default" "retry rule"
6517 The retry section of the configuration file contains rules which affect the way
6518 Exim retries deliveries that cannot be completed at the first attempt. It is
6519 introduced by the line
6523 In the default configuration, there is just one rule, which applies to all
6526 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6528 This causes any temporarily failing address to be retried every 15 minutes for
6529 2 hours, then at intervals starting at one hour and increasing by a factor of
6530 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6531 is not delivered after 4 days of temporary failure, it is bounced. The time is
6532 measured from first failure, not from the time the message was received.
6534 If the retry section is removed from the configuration, or is empty (that is,
6535 if no retry rules are defined), Exim will not retry deliveries. This turns
6536 temporary errors into permanent errors.
6539 .section "Rewriting configuration" "SECID58"
6540 The rewriting section of the configuration, introduced by
6544 contains rules for rewriting addresses in messages as they arrive. There are no
6545 rewriting rules in the default configuration file.
6549 .section "Authenticators configuration" "SECTdefconfauth"
6550 .cindex "AUTH" "configuration"
6551 The authenticators section of the configuration, introduced by
6553 begin authenticators
6555 defines mechanisms for the use of the SMTP AUTH command. The default
6556 configuration file contains two commented-out example authenticators
6557 which support plaintext username/password authentication using the
6558 standard PLAIN mechanism and the traditional but non-standard LOGIN
6559 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6560 to support most MUA software.
6562 The example PLAIN authenticator looks like this:
6565 # driver = plaintext
6566 # server_set_id = $auth2
6567 # server_prompts = :
6568 # server_condition = Authentication is not yet configured
6569 # server_advertise_condition = ${if def:tls_in_cipher }
6571 And the example LOGIN authenticator looks like this:
6574 # driver = plaintext
6575 # server_set_id = $auth1
6576 # server_prompts = <| Username: | Password:
6577 # server_condition = Authentication is not yet configured
6578 # server_advertise_condition = ${if def:tls_in_cipher }
6581 The &%server_set_id%& option makes Exim remember the authenticated username
6582 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6583 &%server_prompts%& option configures the &(plaintext)& authenticator so
6584 that it implements the details of the specific authentication mechanism,
6585 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6586 when Exim offers authentication to clients; in the examples, this is only
6587 when TLS or SSL has been started, so to enable the authenticators you also
6588 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6590 The &%server_condition%& setting defines how to verify that the username and
6591 password are correct. In the examples it just produces an error message.
6592 To make the authenticators work, you can use a string expansion
6593 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6595 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6596 usercode and password are in different positions.
6597 Chapter &<<CHAPplaintext>>& covers both.
6599 .ecindex IIDconfiwal
6603 . ////////////////////////////////////////////////////////////////////////////
6604 . ////////////////////////////////////////////////////////////////////////////
6606 .chapter "Regular expressions" "CHAPregexp"
6608 .cindex "regular expressions" "library"
6610 Exim supports the use of regular expressions in many of its options. It
6611 uses the PCRE regular expression library; this provides regular expression
6612 matching that is compatible with Perl 5. The syntax and semantics of
6613 regular expressions is discussed in
6614 online Perl manpages, in
6615 many Perl reference books, and also in
6616 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6617 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6618 . --- the http: URL here redirects to another page with the ISBN in the URL
6619 . --- where trying to use https: just redirects back to http:, so sticking
6620 . --- to the old URL for now. 2018-09-07.
6622 The documentation for the syntax and semantics of the regular expressions that
6623 are supported by PCRE is included in the PCRE distribution, and no further
6624 description is included here. The PCRE functions are called from Exim using
6625 the default option settings (that is, with no PCRE options set), except that
6626 the PCRE_CASELESS option is set when the matching is required to be
6629 In most cases, when a regular expression is required in an Exim configuration,
6630 it has to start with a circumflex, in order to distinguish it from plain text
6631 or an &"ends with"& wildcard. In this example of a configuration setting, the
6632 second item in the colon-separated list is a regular expression.
6634 domains = a.b.c : ^\\d{3} : *.y.z : ...
6636 The doubling of the backslash is required because of string expansion that
6637 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6638 of this issue, and a way of avoiding the need for doubling backslashes. The
6639 regular expression that is eventually used in this example contains just one
6640 backslash. The circumflex is included in the regular expression, and has the
6641 normal effect of &"anchoring"& it to the start of the string that is being
6644 There are, however, two cases where a circumflex is not required for the
6645 recognition of a regular expression: these are the &%match%& condition in a
6646 string expansion, and the &%matches%& condition in an Exim filter file. In
6647 these cases, the relevant string is always treated as a regular expression; if
6648 it does not start with a circumflex, the expression is not anchored, and can
6649 match anywhere in the subject string.
6651 In all cases, if you want a regular expression to match at the end of a string,
6652 you must code the $ metacharacter to indicate this. For example:
6654 domains = ^\\d{3}\\.example
6656 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6659 domains = ^\\d{3}\\.example\$
6661 if you want &'example'& to be the top-level domain. The backslash before the
6662 $ is needed because string expansion also interprets dollar characters.
6666 . ////////////////////////////////////////////////////////////////////////////
6667 . ////////////////////////////////////////////////////////////////////////////
6669 .chapter "File and database lookups" "CHAPfdlookup"
6670 .scindex IIDfidalo1 "file" "lookups"
6671 .scindex IIDfidalo2 "database" "lookups"
6672 .cindex "lookup" "description of"
6673 Exim can be configured to look up data in files or databases as it processes
6674 messages. Two different kinds of syntax are used:
6677 A string that is to be expanded may contain explicit lookup requests. These
6678 cause parts of the string to be replaced by data that is obtained from the
6679 lookup. Lookups of this type are conditional expansion items. Different results
6680 can be defined for the cases of lookup success and failure. See chapter
6681 &<<CHAPexpand>>&, where string expansions are described in detail.
6682 The key for the lookup is &*specified*& as part of the string expansion.
6684 Lists of domains, hosts, and email addresses can contain lookup requests as a
6685 way of avoiding excessively long linear lists. In this case, the data that is
6686 returned by the lookup is often (but not always) discarded; whether the lookup
6687 succeeds or fails is what really counts. These kinds of list are described in
6688 chapter &<<CHAPdomhosaddlists>>&.
6689 The key for the lookup is &*implicit*&,
6690 given by the context in which the list is expanded.
6693 String expansions, lists, and lookups interact with each other in such a way
6694 that there is no order in which to describe any one of them that does not
6695 involve references to the others. Each of these three chapters makes more sense
6696 if you have read the other two first. If you are reading this for the first
6697 time, be aware that some of it will make a lot more sense after you have read
6698 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6700 .section "Examples of different lookup syntax" "SECID60"
6701 It is easy to confuse the two different kinds of lookup, especially as the
6702 lists that may contain the second kind are always expanded before being
6703 processed as lists. Therefore, they may also contain lookups of the first kind.
6704 Be careful to distinguish between the following two examples:
6706 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6707 domains = lsearch;/some/file
6709 The first uses a string expansion, the result of which must be a domain list.
6710 No strings have been specified for a successful or a failing lookup; the
6711 defaults in this case are the looked-up data and an empty string, respectively.
6712 The expansion takes place before the string is processed as a list, and the
6713 file that is searched could contain lines like this:
6715 192.168.3.4: domain1:domain2:...
6716 192.168.1.9: domain3:domain4:...
6718 When the lookup succeeds, the result of the expansion is a list of domains (and
6719 possibly other types of item that are allowed in domain lists).
6720 .cindex "tainted data" "de-tainting"
6721 The result of the expansion is not tainted.
6723 In the second example, the lookup is a single item in a domain list. It causes
6724 Exim to use a lookup to see if the domain that is being processed can be found
6726 The file could contains lines like this:
6731 Any data that follows the keys is not relevant when checking that the domain
6732 matches the list item.
6734 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6735 Consider a file containing lines like this:
6737 192.168.5.6: lsearch;/another/file
6739 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6740 first &%domains%& setting above generates the second setting, which therefore
6741 causes a second lookup to occur.
6744 The lookup type may optionally be followed by a comma
6745 and a comma-separated list of options.
6746 Each option is a &"name=value"& pair.
6747 Whether an option is meaningful depends on the lookup type.
6749 All lookups support the option &"cache=no_rd"&.
6750 If this is given then the cache that Exim manages for lookup results
6751 is not checked before doing the lookup.
6752 The result of the lookup is still written to the cache.
6755 The rest of this chapter describes the different lookup types that are
6756 available. Any of them can be used in any part of the configuration where a
6757 lookup is permitted.
6760 .section "Lookup types" "SECID61"
6761 .cindex "lookup" "types of"
6762 .cindex "single-key lookup" "definition of"
6763 Two different types of data lookup are implemented:
6766 The &'single-key'& type requires the specification of a file in which to look,
6767 and a single key to search for. The key must be a non-empty string for the
6768 lookup to succeed. The lookup type determines how the file is searched.
6769 .cindex "tainted data" "single-key lookups"
6770 The file string may not be tainted
6772 .cindex "tainted data" "de-tainting"
6773 All single-key lookups support the option &"ret=key"&.
6774 If this is given and the lookup
6775 (either underlying implementation or cached value)
6776 returns data, the result is replaced with a non-tainted
6777 version of the lookup key.
6778 .cindex "tainted data" "de-tainting"
6780 .cindex "query-style lookup" "definition of"
6781 The &'query-style'& type accepts a generalized database query. No particular
6782 key value is assumed by Exim for query-style lookups. You can use whichever
6783 Exim variables you need to construct the database query.
6786 The code for each lookup type is in a separate source file that is included in
6787 the binary of Exim only if the corresponding compile-time option is set. The
6788 default settings in &_src/EDITME_& are:
6793 which means that only linear searching and DBM lookups are included by default.
6794 For some types of lookup (e.g. SQL databases), you need to install appropriate
6795 libraries and header files before building Exim.
6800 .section "Single-key lookup types" "SECTsinglekeylookups"
6801 .cindex "lookup" "single-key types"
6802 .cindex "single-key lookup" "list of types"
6803 The following single-key lookup types are implemented:
6806 .cindex "cdb" "description of"
6807 .cindex "lookup" "cdb"
6808 .cindex "binary zero" "in lookup key"
6809 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6810 string without a terminating binary zero. The cdb format is designed for
6811 indexed files that are read frequently and never updated, except by total
6812 re-creation. As such, it is particularly suitable for large files containing
6813 aliases or other indexed data referenced by an MTA. Information about cdb and
6814 tools for building the files can be found in several places:
6816 &url(https://cr.yp.to/cdb.html)
6817 &url(https://www.corpit.ru/mjt/tinycdb.html)
6818 &url(https://packages.debian.org/stable/utils/freecdb)
6819 &url(https://github.com/philpennock/cdbtools) (in Go)
6821 A cdb distribution is not needed in order to build Exim with cdb support,
6822 because the code for reading cdb files is included directly in Exim itself.
6823 However, no means of building or testing cdb files is provided with Exim, so
6824 you need to obtain a cdb distribution in order to do this.
6826 .cindex "DBM" "lookup type"
6827 .cindex "lookup" "dbm"
6828 .cindex "binary zero" "in lookup key"
6829 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6830 DBM file by looking up the record with the given key. A terminating binary
6831 zero is included in the key that is passed to the DBM library. See section
6832 &<<SECTdb>>& for a discussion of DBM libraries.
6834 .cindex "Berkeley DB library" "file format"
6835 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6836 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6837 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6838 the DB_UNKNOWN option. This enables it to handle any of the types of database
6839 that the library supports, and can be useful for accessing DBM files created by
6840 other applications. (For earlier DB versions, DB_HASH is always used.)
6842 .cindex "lookup" "dbmjz"
6843 .cindex "lookup" "dbm &-- embedded NULs"
6845 .cindex "dbmjz lookup type"
6846 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6847 interpreted as an Exim list; the elements of the list are joined together with
6848 ASCII NUL characters to form the lookup key. An example usage would be to
6849 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6850 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6851 &(cram_md5)& authenticator.
6853 .cindex "lookup" "dbmnz"
6854 .cindex "lookup" "dbm &-- terminating zero"
6855 .cindex "binary zero" "in lookup key"
6857 .cindex "&_/etc/userdbshadow.dat_&"
6858 .cindex "dbmnz lookup type"
6859 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6860 is not included in the key that is passed to the DBM library. You may need this
6861 if you want to look up data in files that are created by or shared with some
6862 other application that does not use terminating zeros. For example, you need to
6863 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6864 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6865 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6866 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6868 .cindex "lookup" "dsearch"
6869 .cindex "dsearch lookup type"
6870 &(dsearch)&: The given file must be an
6872 directory path; this is searched for an entry
6873 whose name is the key by calling the &[lstat()]& function.
6875 contain any forward slash characters.
6876 If &[lstat()]& succeeds then so does the lookup.
6877 .cindex "tainted data" "dsearch result"
6878 The result is regarded as untainted.
6880 Options for the lookup can be given by appending them after the word "dsearch",
6881 separated by a comma. Options, if present, are a comma-separated list having
6882 each element starting with a tag name and an equals.
6884 Two options are supported, for the return value and for filtering match
6886 The "ret" option requests an alternate result value of
6887 the entire path for the entry. Example:
6889 ${lookup {passwd} dsearch,ret=full {/etc}}
6891 The default result is just the requested entry.
6892 The "filter" option requests that only directory entries of a given type
6893 are matched. The match value is one of "file", "dir" or "subdir" (the latter
6894 not matching "." or ".."). Example:
6896 ${lookup {passwd} dsearch,filter=file {/etc}}
6898 The default matching is for any entry type, including directories
6901 An example of how this
6902 lookup can be used to support virtual domains is given in section
6903 &<<SECTvirtualdomains>>&.
6905 .cindex "lookup" "iplsearch"
6906 .cindex "iplsearch lookup type"
6907 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6908 terminated by a colon or white space or the end of the line. The keys in the
6909 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6910 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6911 being interpreted as a key terminator. For example:
6913 1.2.3.4: data for 1.2.3.4
6914 192.168.0.0/16: data for 192.168.0.0/16
6915 "abcd::cdab": data for abcd::cdab
6916 "abcd:abcd::/32" data for abcd:abcd::/32
6918 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6919 file is searched linearly, using the CIDR masks where present, until a matching
6920 key is found. The first key that matches is used; there is no attempt to find a
6921 &"best"& match. Apart from the way the keys are matched, the processing for
6922 &(iplsearch)& is the same as for &(lsearch)&.
6924 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6925 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6926 lookup types support only literal keys.
6928 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6929 the implicit key is the host's IP address rather than its name (see section
6930 &<<SECThoslispatsikey>>&).
6932 &*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
6933 IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
6934 notation before executing the lookup.)
6937 One option is supported, "ret=full", to request the return of the entire line
6938 rather than omitting the key porttion.
6939 Note however that the key portion will have been de-quoted.
6944 .cindex json "lookup type"
6945 .cindex JSON expansions
6946 &(json)&: The given file is a text file with a JSON structure.
6947 An element of the structure is extracted, defined by the search key.
6948 The key is a list of subelement selectors
6949 (colon-separated by default but changeable in the usual way)
6950 which are applied in turn to select smaller and smaller portions
6951 of the JSON structure.
6952 If a selector is numeric, it must apply to a JSON array; the (zero-based)
6953 nunbered array element is selected.
6954 Otherwise it must apply to a JSON object; the named element is selected.
6955 The final resulting element can be a simple JSON type or a JSON object
6956 or array; for the latter two a string-representation of the JSON
6958 For elements of type string, the returned value is de-quoted.
6965 .cindex database lmdb
6966 &(lmdb)&: The given file is an LMDB database.
6967 LMDB is a memory-mapped key-value store,
6968 with API modeled loosely on that of BerkeleyDB.
6969 See &url(https://symas.com/products/lightning-memory-mapped-database/)
6970 for the feature set and operation modes.
6972 Exim provides read-only access via the LMDB C library.
6973 The library can be obtained from &url(https://github.com/LMDB/lmdb)
6974 or your operating system package repository.
6975 To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&.
6977 You will need to separately create the LMDB database file,
6978 possibly using the &"mdb_load"& utility.
6983 .cindex "linear search"
6984 .cindex "lookup" "lsearch"
6985 .cindex "lsearch lookup type"
6986 .cindex "case sensitivity" "in lsearch lookup"
6987 &(lsearch)&: The given file is a text file that is searched linearly for a
6988 line beginning with the search key, terminated by a colon or white space or the
6989 end of the line. The search is case-insensitive; that is, upper and lower case
6990 letters are treated as the same. The first occurrence of the key that is found
6991 in the file is used.
6993 White space between the key and the colon is permitted. The remainder of the
6994 line, with leading and trailing white space removed, is the data. This can be
6995 continued onto subsequent lines by starting them with any amount of white
6996 space, but only a single space character is included in the data at such a
6997 junction. If the data begins with a colon, the key must be terminated by a
7002 Empty lines and lines beginning with # are ignored, even if they occur in the
7003 middle of an item. This is the traditional textual format of alias files. Note
7004 that the keys in an &(lsearch)& file are literal strings. There is no
7005 wildcarding of any kind.
7007 .cindex "lookup" "lsearch &-- colons in keys"
7008 .cindex "white space" "in lsearch key"
7009 In most &(lsearch)& files, keys are not required to contain colons or #
7010 characters, or white space. However, if you need this feature, it is available.
7011 If a key begins with a doublequote character, it is terminated only by a
7012 matching quote (or end of line), and the normal escaping rules apply to its
7013 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
7014 quoted keys (exactly as for unquoted keys). There is no special handling of
7015 quotes for the data part of an &(lsearch)& line.
7018 .cindex "NIS lookup type"
7019 .cindex "lookup" "NIS"
7020 .cindex "binary zero" "in lookup key"
7021 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
7022 the given key, without a terminating binary zero. There is a variant called
7023 &(nis0)& which does include the terminating binary zero in the key. This is
7024 reportedly needed for Sun-style alias files. Exim does not recognize NIS
7025 aliases; the full map names must be used.
7028 .cindex "wildlsearch lookup type"
7029 .cindex "lookup" "wildlsearch"
7030 .cindex "nwildlsearch lookup type"
7031 .cindex "lookup" "nwildlsearch"
7032 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
7033 &(lsearch)&, but instead of being interpreted as a literal string, each key in
7034 the file may be wildcarded. The difference between these two lookup types is
7035 that for &(wildlsearch)&, each key in the file is string-expanded before being
7036 used, whereas for &(nwildlsearch)&, no expansion takes place.
7038 .cindex "case sensitivity" "in (n)wildlsearch lookup"
7039 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
7040 file that are regular expressions can be made case-sensitive by the use of
7041 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
7043 . ==== As this is a nested list, any displays it contains must be indented
7044 . ==== as otherwise they are too far to the left.
7047 The string may begin with an asterisk to mean &"ends with"&. For example:
7049 *.a.b.c data for anything.a.b.c
7050 *fish data for anythingfish
7053 The string may begin with a circumflex to indicate a regular expression. For
7054 example, for &(wildlsearch)&:
7056 ^\N\d+\.a\.b\N data for <digits>.a.b
7058 Note the use of &`\N`& to disable expansion of the contents of the regular
7059 expression. If you are using &(nwildlsearch)&, where the keys are not
7060 string-expanded, the equivalent entry is:
7062 ^\d+\.a\.b data for <digits>.a.b
7064 The case-insensitive flag is set at the start of compiling the regular
7065 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
7066 For example, to make the entire pattern case-sensitive:
7068 ^(?-i)\d+\.a\.b data for <digits>.a.b
7071 If the regular expression contains white space or colon characters, you must
7072 either quote it (see &(lsearch)& above), or represent these characters in other
7073 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
7074 colon. This may be easier than quoting, because if you quote, you have to
7075 escape all the backslashes inside the quotes.
7077 &*Note*&: It is not possible to capture substrings in a regular expression
7078 match for later use, because the results of all lookups are cached. If a lookup
7079 is repeated, the result is taken from the cache, and no actual pattern matching
7080 takes place. The values of all the numeric variables are unset after a
7081 &((n)wildlsearch)& match.
7084 Although I cannot see it being of much use, the general matching function that
7085 is used to implement &((n)wildlsearch)& means that the string may begin with a
7086 lookup name terminated by a semicolon, and followed by lookup data. For
7089 cdb;/some/file data for keys that match the file
7091 The data that is obtained from the nested lookup is discarded.
7094 Keys that do not match any of these patterns are interpreted literally. The
7095 continuation rules for the data are the same as for &(lsearch)&, and keys may
7096 be followed by optional colons.
7098 &*Warning*&: Unlike most other single-key lookup types, a file of data for
7099 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
7100 lookup types support only literal keys.
7103 .cindex "spf lookup type"
7104 .cindex "lookup" "spf"
7105 &(spf)&: If Exim is built with SPF support, manual lookups can be done
7106 (as opposed to the standard ACL condition method).
7107 For details see section &<<SECSPF>>&.
7111 .section "Query-style lookup types" "SECTquerystylelookups"
7112 .cindex "lookup" "query-style types"
7113 .cindex "query-style lookup" "list of types"
7114 The supported query-style lookup types are listed below. Further details about
7115 many of them are given in later sections.
7118 .cindex "DNS" "as a lookup type"
7119 .cindex "lookup" "DNS"
7120 &(dnsdb)&: This does a DNS search for one or more records whose domain names
7121 are given in the supplied query. The resulting data is the contents of the
7122 records. See section &<<SECTdnsdb>>&.
7124 .cindex "InterBase lookup type"
7125 .cindex "lookup" "InterBase"
7126 &(ibase)&: This does a lookup in an InterBase database.
7128 .cindex "LDAP" "lookup type"
7129 .cindex "lookup" "LDAP"
7130 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
7131 returns attributes from a single entry. There is a variant called &(ldapm)&
7132 that permits values from multiple entries to be returned. A third variant
7133 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
7134 any attribute values. See section &<<SECTldap>>&.
7136 .cindex "MySQL" "lookup type"
7137 .cindex "lookup" "MySQL"
7138 &(mysql)&: The format of the query is an SQL statement that is passed to a
7139 MySQL database. See section &<<SECTsql>>&.
7141 .cindex "NIS+ lookup type"
7142 .cindex "lookup" "NIS+"
7143 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
7144 the field to be returned. See section &<<SECTnisplus>>&.
7146 .cindex "Oracle" "lookup type"
7147 .cindex "lookup" "Oracle"
7148 &(oracle)&: The format of the query is an SQL statement that is passed to an
7149 Oracle database. See section &<<SECTsql>>&.
7151 .cindex "lookup" "passwd"
7152 .cindex "passwd lookup type"
7153 .cindex "&_/etc/passwd_&"
7154 &(passwd)& is a query-style lookup with queries that are just user names. The
7155 lookup calls &[getpwnam()]& to interrogate the system password data, and on
7156 success, the result string is the same as you would get from an &(lsearch)&
7157 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
7158 password value. For example:
7160 *:42:42:King Rat:/home/kr:/bin/bash
7163 .cindex "PostgreSQL lookup type"
7164 .cindex "lookup" "PostgreSQL"
7165 &(pgsql)&: The format of the query is an SQL statement that is passed to a
7166 PostgreSQL database. See section &<<SECTsql>>&.
7169 .cindex "Redis lookup type"
7170 .cindex lookup Redis
7171 &(redis)&: The format of the query is either a simple get or simple set,
7172 passed to a Redis database. See section &<<SECTsql>>&.
7175 .cindex "sqlite lookup type"
7176 .cindex "lookup" "sqlite"
7177 &(sqlite)&: The format of the query is
7178 an SQL statement that is passed to an SQLite database. See section &<<SECTsqlite>>&.
7181 &(testdb)&: This is a lookup type that is used for testing Exim. It is
7182 not likely to be useful in normal operation.
7184 .cindex "whoson lookup type"
7185 .cindex "lookup" "whoson"
7186 . --- still http:-only, 2018-09-07
7187 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
7188 allows a server to check whether a particular (dynamically allocated) IP
7189 address is currently allocated to a known (trusted) user and, optionally, to
7190 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
7191 at one time for &"POP before SMTP"& authentication, but that approach has been
7192 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
7193 &"POP before SMTP"& checking using ACL statements such as
7195 require condition = \
7196 ${lookup whoson {$sender_host_address}{yes}{no}}
7198 The query consists of a single IP address. The value returned is the name of
7199 the authenticated user, which is stored in the variable &$value$&. However, in
7200 this example, the data in &$value$& is not used; the result of the lookup is
7201 one of the fixed strings &"yes"& or &"no"&.
7206 .section "Temporary errors in lookups" "SECID63"
7207 .cindex "lookup" "temporary error in"
7208 Lookup functions can return temporary error codes if the lookup cannot be
7209 completed. For example, an SQL or LDAP database might be unavailable. For this
7210 reason, it is not advisable to use a lookup that might do this for critical
7211 options such as a list of local domains.
7213 When a lookup cannot be completed in a router or transport, delivery
7214 of the message (to the relevant address) is deferred, as for any other
7215 temporary error. In other circumstances Exim may assume the lookup has failed,
7216 or may give up altogether.
7220 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
7221 .cindex "wildcard lookups"
7222 .cindex "lookup" "default values"
7223 .cindex "lookup" "wildcard"
7224 .cindex "lookup" "* added to type"
7225 .cindex "default" "in single-key lookups"
7226 In this context, a &"default value"& is a value specified by the administrator
7227 that is to be used if a lookup fails.
7229 &*Note:*& This section applies only to single-key lookups. For query-style
7230 lookups, the facilities of the query language must be used. An attempt to
7231 specify a default for a query-style lookup provokes an error.
7233 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
7234 and the initial lookup fails, the key &"*"& is looked up in the file to
7235 provide a default value. See also the section on partial matching below.
7237 .cindex "*@ with single-key lookup"
7238 .cindex "lookup" "*@ added to type"
7239 .cindex "alias file" "per-domain default"
7240 Alternatively, if &"*@"& is added to a single-key lookup type (for example
7241 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
7242 character, a second lookup is done with everything before the last @ replaced
7243 by *. This makes it possible to provide per-domain defaults in alias files
7244 that include the domains in the keys. If the second lookup fails (or doesn't
7245 take place because there is no @ in the key), &"*"& is looked up.
7246 For example, a &(redirect)& router might contain:
7248 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
7250 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
7251 looks up these keys, in this order:
7257 The data is taken from whichever key it finds first. &*Note*&: In an
7258 &(lsearch)& file, this does not mean the first of these keys in the file. A
7259 complete scan is done for each key, and only if it is not found at all does
7260 Exim move on to try the next key.
7264 .section "Partial matching in single-key lookups" "SECTpartiallookup"
7265 .cindex "partial matching"
7266 .cindex "wildcard lookups"
7267 .cindex "lookup" "partial matching"
7268 .cindex "lookup" "wildcard"
7269 .cindex "asterisk" "in search type"
7270 The normal operation of a single-key lookup is to search the file for an exact
7271 match with the given key. However, in a number of situations where domains are
7272 being looked up, it is useful to be able to do partial matching. In this case,
7273 information in the file that has a key starting with &"*."& is matched by any
7274 domain that ends with the components that follow the full stop. For example, if
7275 a key in a DBM file is
7277 *.dates.fict.example
7279 then when partial matching is enabled this is matched by (amongst others)
7280 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
7281 by &'dates.fict.example'&, if that does not appear as a separate key in the
7284 &*Note*&: Partial matching is not available for query-style lookups. It is
7285 also not available for any lookup items in address lists (see section
7286 &<<SECTaddresslist>>&).
7288 Partial matching is implemented by doing a series of separate lookups using
7289 keys constructed by modifying the original subject key. This means that it can
7290 be used with any of the single-key lookup types, provided that
7291 partial matching keys
7292 beginning with a special prefix (default &"*."&) are included in the data file.
7293 Keys in the file that do not begin with the prefix are matched only by
7294 unmodified subject keys when partial matching is in use.
7296 Partial matching is requested by adding the string &"partial-"& to the front of
7297 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
7298 is done, the subject key is first looked up unmodified; if that fails, &"*."&
7299 is added at the start of the subject key, and it is looked up again. If that
7300 fails, further lookups are tried with dot-separated components removed from the
7301 start of the subject key, one-by-one, and &"*."& added on the front of what
7304 A minimum number of two non-* components are required. This can be adjusted
7305 by including a number before the hyphen in the search type. For example,
7306 &%partial3-lsearch%& specifies a minimum of three non-* components in the
7307 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
7308 subject key is &'2250.dates.fict.example'& then the following keys are looked
7309 up when the minimum number of non-* components is two:
7311 2250.dates.fict.example
7312 *.2250.dates.fict.example
7313 *.dates.fict.example
7316 As soon as one key in the sequence is successfully looked up, the lookup
7319 .cindex "lookup" "partial matching &-- changing prefix"
7320 .cindex "prefix" "for partial matching"
7321 The use of &"*."& as the partial matching prefix is a default that can be
7322 changed. The motivation for this feature is to allow Exim to operate with file
7323 formats that are used by other MTAs. A different prefix can be supplied in
7324 parentheses instead of the hyphen after &"partial"&. For example:
7326 domains = partial(.)lsearch;/some/file
7328 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
7329 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
7330 components is unchanged). The prefix may consist of any punctuation characters
7331 other than a closing parenthesis. It may be empty, for example:
7333 domains = partial1()cdb;/some/file
7335 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
7336 &`a.b.c`&, &`b.c`&, and &`c`&.
7338 If &"partial0"& is specified, what happens at the end (when the lookup with
7339 just one non-wild component has failed, and the original key is shortened right
7340 down to the null string) depends on the prefix:
7343 If the prefix has zero length, the whole lookup fails.
7345 If the prefix has length 1, a lookup for just the prefix is done. For
7346 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
7348 Otherwise, if the prefix ends in a dot, the dot is removed, and the
7349 remainder is looked up. With the default prefix, therefore, the final lookup is
7350 for &"*"& on its own.
7352 Otherwise, the whole prefix is looked up.
7356 If the search type ends in &"*"& or &"*@"& (see section
7357 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
7358 this implies happens after all partial lookups have failed. If &"partial0"& is
7359 specified, adding &"*"& to the search type has no effect with the default
7360 prefix, because the &"*"& key is already included in the sequence of partial
7361 lookups. However, there might be a use for lookup types such as
7362 &"partial0(.)lsearch*"&.
7364 The use of &"*"& in lookup partial matching differs from its use as a wildcard
7365 in domain lists and the like. Partial matching works only in terms of
7366 dot-separated components; a key such as &`*fict.example`&
7367 in a database file is useless, because the asterisk in a partial matching
7368 subject key is always followed by a dot.
7373 .section "Lookup caching" "SECID64"
7374 .cindex "lookup" "caching"
7375 .cindex "caching" "lookup data"
7376 Exim caches all lookup results in order to avoid needless repetition of
7377 lookups. However, because (apart from the daemon) Exim operates as a collection
7378 of independent, short-lived processes, this caching applies only within a
7379 single Exim process. There is no inter-process lookup caching facility.
7381 For single-key lookups, Exim keeps the relevant files open in case there is
7382 another lookup that needs them. In some types of configuration this can lead to
7383 many files being kept open for messages with many recipients. To avoid hitting
7384 the operating system limit on the number of simultaneously open files, Exim
7385 closes the least recently used file when it needs to open more files than its
7386 own internal limit, which can be changed via the &%lookup_open_max%& option.
7388 The single-key lookup files are closed and the lookup caches are flushed at
7389 strategic points during delivery &-- for example, after all routing is
7395 .section "Quoting lookup data" "SECID65"
7396 .cindex "lookup" "quoting"
7397 .cindex "quoting" "in lookups"
7398 When data from an incoming message is included in a query-style lookup, there
7399 is the possibility of special characters in the data messing up the syntax of
7400 the query. For example, a NIS+ query that contains
7404 will be broken if the local part happens to contain a closing square bracket.
7405 For NIS+, data can be enclosed in double quotes like this:
7407 [name="$local_part"]
7409 but this still leaves the problem of a double quote in the data. The rule for
7410 NIS+ is that double quotes must be doubled. Other lookup types have different
7411 rules, and to cope with the differing requirements, an expansion operator
7412 of the following form is provided:
7414 ${quote_<lookup-type>:<string>}
7416 For example, the safest way to write the NIS+ query is
7418 [name="${quote_nisplus:$local_part}"]
7420 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
7421 operator can be used for all lookup types, but has no effect for single-key
7422 lookups, since no quoting is ever needed in their key strings.
7427 .section "More about dnsdb" "SECTdnsdb"
7428 .cindex "dnsdb lookup"
7429 .cindex "lookup" "dnsdb"
7430 .cindex "DNS" "as a lookup type"
7431 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7432 of a record type and a domain name, separated by an equals sign. For example,
7433 an expansion string could contain:
7435 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7437 If the lookup succeeds, the result is placed in &$value$&, which in this case
7438 is used on its own as the result. If the lookup does not succeed, the
7439 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7440 &<<SECTforexpfai>>& for an explanation of what this means.
7442 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7443 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7444 If no type is given, TXT is assumed.
7446 For any record type, if multiple records are found, the data is returned as a
7447 concatenation, with newline as the default separator. The order, of course,
7448 depends on the DNS resolver. You can specify a different separator character
7449 between multiple records by putting a right angle-bracket followed immediately
7450 by the new separator at the start of the query. For example:
7452 ${lookup dnsdb{>: a=host1.example}}
7454 It is permitted to specify a space as the separator character. Further
7455 white space is ignored.
7456 For lookup types that return multiple fields per record,
7457 an alternate field separator can be specified using a comma after the main
7458 separator character, followed immediately by the field separator.
7460 .cindex "PTR record" "in &(dnsdb)& lookup"
7461 When the type is PTR,
7462 the data can be an IP address, written as normal; inversion and the addition of
7463 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7465 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7467 If the data for a PTR record is not a syntactically valid IP address, it is not
7468 altered and nothing is added.
7470 .cindex "MX record" "in &(dnsdb)& lookup"
7471 .cindex "SRV record" "in &(dnsdb)& lookup"
7472 For an MX lookup, both the preference value and the host name are returned for
7473 each record, separated by a space. For an SRV lookup, the priority, weight,
7474 port, and host name are returned for each record, separated by spaces.
7475 The field separator can be modified as above.
7477 .cindex "TXT record" "in &(dnsdb)& lookup"
7478 .cindex "SPF record" "in &(dnsdb)& lookup"
7479 For TXT records with multiple items of data, only the first item is returned,
7480 unless a field separator is specified.
7481 To concatenate items without a separator, use a semicolon instead.
7483 default behaviour is to concatenate multiple items without using a separator.
7485 ${lookup dnsdb{>\n,: txt=a.b.example}}
7486 ${lookup dnsdb{>\n; txt=a.b.example}}
7487 ${lookup dnsdb{spf=example.org}}
7489 It is permitted to specify a space as the separator character. Further
7490 white space is ignored.
7492 .cindex "SOA record" "in &(dnsdb)& lookup"
7493 For an SOA lookup, while no result is obtained the lookup is redone with
7494 successively more leading components dropped from the given domain.
7495 Only the primary-nameserver field is returned unless a field separator is
7498 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7501 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7502 .cindex "dnsdb modifiers"
7503 .cindex "modifiers" "dnsdb"
7504 .cindex "options" "dnsdb"
7505 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7506 each followed by a comma,
7507 that may appear before the record type.
7509 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7510 temporary DNS error for any of them, the behaviour is controlled by
7511 a defer-option modifier.
7512 The possible keywords are
7513 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7514 With &"strict"& behaviour, any temporary DNS error causes the
7515 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7516 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7517 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7518 error causes the whole lookup to defer only if none of the other lookups
7519 succeed. The default is &"lax"&, so the following lookups are equivalent:
7521 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7522 ${lookup dnsdb{a=one.host.com:two.host.com}}
7524 Thus, in the default case, as long as at least one of the DNS lookups
7525 yields some data, the lookup succeeds.
7527 .cindex "DNSSEC" "dns lookup"
7528 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7529 The possible keywords are
7530 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7531 With &"strict"& or &"lax"& DNSSEC information is requested
7533 With &"strict"& a response from the DNS resolver that
7534 is not labelled as authenticated data
7535 is treated as equivalent to a temporary DNS error.
7536 The default is &"lax"&.
7538 See also the &$lookup_dnssec_authenticated$& variable.
7540 .cindex timeout "dns lookup"
7541 .cindex "DNS" timeout
7542 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7543 The form is &"retrans_VAL"& where VAL is an Exim time specification
7545 The default value is set by the main configuration option &%dns_retrans%&.
7547 Retries for the dnsdb lookup can be controlled by a retry modifier.
7548 The form if &"retry_VAL"& where VAL is an integer.
7549 The default count is set by the main configuration option &%dns_retry%&.
7551 .cindex caching "of dns lookup"
7552 .cindex TTL "of dns lookup"
7554 Dnsdb lookup results are cached within a single process (and its children).
7555 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7556 value of the set of returned DNS records.
7559 .section "Pseudo dnsdb record types" "SECID66"
7560 .cindex "MX record" "in &(dnsdb)& lookup"
7561 By default, both the preference value and the host name are returned for
7562 each MX record, separated by a space. If you want only host names, you can use
7563 the pseudo-type MXH:
7565 ${lookup dnsdb{mxh=a.b.example}}
7567 In this case, the preference values are omitted, and just the host names are
7570 .cindex "name server for enclosing domain"
7571 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7572 records on the given domain, but if none are found, it removes the first
7573 component of the domain name, and tries again. This process continues until NS
7574 records are found or there are no more components left (or there is a DNS
7575 error). In other words, it may return the name servers for a top-level domain,
7576 but it never returns the root name servers. If there are no NS records for the
7577 top-level domain, the lookup fails. Consider these examples:
7579 ${lookup dnsdb{zns=xxx.quercite.com}}
7580 ${lookup dnsdb{zns=xxx.edu}}
7582 Assuming that in each case there are no NS records for the full domain name,
7583 the first returns the name servers for &%quercite.com%&, and the second returns
7584 the name servers for &%edu%&.
7586 You should be careful about how you use this lookup because, unless the
7587 top-level domain does not exist, the lookup always returns some host names. The
7588 sort of use to which this might be put is for seeing if the name servers for a
7589 given domain are on a blacklist. You can probably assume that the name servers
7590 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7593 .cindex "CSA" "in &(dnsdb)& lookup"
7594 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7595 records according to the CSA rules, which are described in section
7596 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7597 not sufficient because of the extra parent domain search behaviour of CSA. The
7598 result of a successful lookup such as:
7600 ${lookup dnsdb {csa=$sender_helo_name}}
7602 has two space-separated fields: an authorization code and a target host name.
7603 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7604 authorization required but absent, or &"?"& for unknown.
7606 .cindex "A+" "in &(dnsdb)& lookup"
7607 The pseudo-type A+ performs an AAAA
7608 and then an A lookup. All results are returned; defer processing
7609 (see below) is handled separately for each lookup. Example:
7611 ${lookup dnsdb {>; a+=$sender_helo_name}}
7615 .section "Multiple dnsdb lookups" "SECID67"
7616 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7617 However, you can specify a list of domains or IP addresses in a single
7618 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7619 the default separator, but with the ability to change this. For example:
7621 ${lookup dnsdb{one.domain.com:two.domain.com}}
7622 ${lookup dnsdb{a=one.host.com:two.host.com}}
7623 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7625 In order to retain backwards compatibility, there is one special case: if
7626 the lookup type is PTR and no change of separator is specified, Exim looks
7627 to see if the rest of the string is precisely one IPv6 address. In this
7628 case, it does not treat it as a list.
7630 The data from each lookup is concatenated, with newline separators by default,
7631 in the same way that multiple DNS records for a single item are handled. A
7632 different separator can be specified, as described above.
7637 .section "More about LDAP" "SECTldap"
7638 .cindex "LDAP" "lookup, more about"
7639 .cindex "lookup" "LDAP"
7640 .cindex "Solaris" "LDAP"
7641 The original LDAP implementation came from the University of Michigan; this has
7642 become &"Open LDAP"&, and there are now two different releases. Another
7643 implementation comes from Netscape, and Solaris 7 and subsequent releases
7644 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7645 the lookup function level, their error handling is different. For this reason
7646 it is necessary to set a compile-time variable when building Exim with LDAP, to
7647 indicate which LDAP library is in use. One of the following should appear in
7648 your &_Local/Makefile_&:
7650 LDAP_LIB_TYPE=UMICHIGAN
7651 LDAP_LIB_TYPE=OPENLDAP1
7652 LDAP_LIB_TYPE=OPENLDAP2
7653 LDAP_LIB_TYPE=NETSCAPE
7654 LDAP_LIB_TYPE=SOLARIS
7656 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7657 same interface as the University of Michigan version.
7659 There are three LDAP lookup types in Exim. These behave slightly differently in
7660 the way they handle the results of a query:
7663 &(ldap)& requires the result to contain just one entry; if there are more, it
7666 &(ldapdn)& also requires the result to contain just one entry, but it is the
7667 Distinguished Name that is returned rather than any attribute values.
7669 &(ldapm)& permits the result to contain more than one entry; the attributes
7670 from all of them are returned.
7674 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7675 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7676 the data returned by a successful lookup is described in the next section.
7677 First we explain how LDAP queries are coded.
7680 .section "Format of LDAP queries" "SECTforldaque"
7681 .cindex "LDAP" "query format"
7682 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7683 the configuration of a &(redirect)& router one might have this setting:
7685 data = ${lookup ldap \
7686 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7687 c=UK?mailbox?base?}}
7689 .cindex "LDAP" "with TLS"
7690 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7691 secure (encrypted) LDAP connections. The second of these ensures that an
7692 encrypted TLS connection is used.
7694 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7695 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7696 See the &%ldap_start_tls%& option.
7698 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7699 controlled. Every part of the TLS configuration can be configured by settings in
7700 &_exim.conf_&. Depending on the version of the client libraries installed on
7701 your system, some of the initialization may have required setting options in
7702 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7703 certificates. This revealed a nuance where the current UID that exim was
7704 running as could affect which config files it read. With Exim 4.83, these
7705 methods become optional, only taking effect if not specifically set in
7709 .section "LDAP quoting" "SECID68"
7710 .cindex "LDAP" "quoting"
7711 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7712 and the second because the LDAP query is represented as a URL. Furthermore,
7713 within an LDAP query, two different kinds of quoting are required. For this
7714 reason, there are two different LDAP-specific quoting operators.
7716 The &%quote_ldap%& operator is designed for use on strings that are part of
7717 filter specifications. Conceptually, it first does the following conversions on
7725 in accordance with RFC 2254. The resulting string is then quoted according
7726 to the rules for URLs, that is, all non-alphanumeric characters except
7730 are converted to their hex values, preceded by a percent sign. For example:
7732 ${quote_ldap: a(bc)*, a<yz>; }
7736 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7738 Removing the URL quoting, this is (with a leading and a trailing space):
7740 a\28bc\29\2A, a<yz>;
7742 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7743 base DN specifications in queries. Conceptually, it first converts the string
7744 by inserting a backslash in front of any of the following characters:
7748 It also inserts a backslash before any leading spaces or # characters, and
7749 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7750 is then quoted according to the rules for URLs. For example:
7752 ${quote_ldap_dn: a(bc)*, a<yz>; }
7756 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7758 Removing the URL quoting, this is (with a trailing space):
7760 \ a(bc)*\, a\<yz\>\;\
7762 There are some further comments about quoting in the section on LDAP
7763 authentication below.
7766 .section "LDAP connections" "SECID69"
7767 .cindex "LDAP" "connections"
7768 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7769 is in use, via a Unix domain socket. The example given above does not specify
7770 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7773 ldap://<hostname>:<port>/...
7775 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7776 used. When no server is specified in a query, a list of default servers is
7777 taken from the &%ldap_default_servers%& configuration option. This supplies a
7778 colon-separated list of servers which are tried in turn until one successfully
7779 handles a query, or there is a serious error. Successful handling either
7780 returns the requested data, or indicates that it does not exist. Serious errors
7781 are syntactical, or multiple values when only a single value is expected.
7782 Errors which cause the next server to be tried are connection failures, bind
7783 failures, and timeouts.
7785 For each server name in the list, a port number can be given. The standard way
7786 of specifying a host and port is to use a colon separator (RFC 1738). Because
7787 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7788 doubled. For example
7790 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7792 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7793 to the LDAP library with no server name, and the library's default (normally
7794 the local host) is used.
7796 If you are using the OpenLDAP library, you can connect to an LDAP server using
7797 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7798 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7799 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7802 For this type of connection, instead of a host name for the server, a pathname
7803 for the socket is required, and the port number is not relevant. The pathname
7804 can be specified either as an item in &%ldap_default_servers%&, or inline in
7805 the query. In the former case, you can have settings such as
7807 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7809 When the pathname is given in the query, you have to escape the slashes as
7810 &`%2F`& to fit in with the LDAP URL syntax. For example:
7812 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7814 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7815 a pathname, it uses the Unix domain socket code, even if the query actually
7816 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7817 socket connection. This behaviour means that you can use a setting of
7818 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7819 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7820 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7823 If an explicit &`ldapi`& type is given in a query when a host name is
7824 specified, an error is diagnosed. However, if there are more items in
7825 &%ldap_default_servers%&, they are tried. In other words:
7828 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7831 Using &`ldapi`& with a host name causes an error.
7835 Using &`ldapi`& with no host or path in the query, and no setting of
7836 &%ldap_default_servers%&, does whatever the library does by default.
7840 .section "LDAP authentication and control information" "SECID70"
7841 .cindex "LDAP" "authentication"
7842 The LDAP URL syntax provides no way of passing authentication and other control
7843 information to the server. To make this possible, the URL in an LDAP query may
7844 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7845 spaces. If a value contains spaces it must be enclosed in double quotes, and
7846 when double quotes are used, backslash is interpreted in the usual way inside
7847 them. The following names are recognized:
7849 &`DEREFERENCE`& set the dereferencing parameter
7850 &`NETTIME `& set a timeout for a network operation
7851 &`USER `& set the DN, for authenticating the LDAP bind
7852 &`PASS `& set the password, likewise
7853 &`REFERRALS `& set the referrals parameter
7854 &`SERVERS `& set alternate server list for this query only
7855 &`SIZE `& set the limit for the number of entries returned
7856 &`TIME `& set the maximum waiting time for a query
7858 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7859 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7860 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7861 library from trying to follow referrals issued by the LDAP server.
7863 .cindex LDAP timeout
7864 .cindex timeout "LDAP lookup"
7865 The name CONNECT is an obsolete name for NETTIME, retained for
7866 backwards compatibility. This timeout (specified as a number of seconds) is
7867 enforced from the client end for operations that can be carried out over a
7868 network. Specifically, it applies to network connections and calls to the
7869 &'ldap_result()'& function. If the value is greater than zero, it is used if
7870 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7871 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7872 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7873 Netscape SDK; for OpenLDAP no action is taken.
7875 The TIME parameter (also a number of seconds) is passed to the server to
7876 set a server-side limit on the time taken to complete a search.
7878 The SERVERS parameter allows you to specify an alternate list of ldap servers
7879 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7880 default list of ldap servers, and a single lookup can specify a single ldap
7881 server to use. But when you need to do a lookup with a list of servers that is
7882 different than the default list (maybe different order, maybe a completely
7883 different set of servers), the SERVERS parameter allows you to specify this
7884 alternate list (colon-separated).
7886 Here is an example of an LDAP query in an Exim lookup that uses some of these
7887 values. This is a single line, folded to fit on the page:
7890 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7891 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7894 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7895 any of the auxiliary data. Exim configuration settings that include lookups
7896 which contain password information should be preceded by &"hide"& to prevent
7897 non-admin users from using the &%-bP%& option to see their values.
7899 The auxiliary data items may be given in any order. The default is no
7900 connection timeout (the system timeout is used), no user or password, no limit
7901 on the number of entries returned, and no time limit on queries.
7903 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7904 removes any URL quoting that it may contain before passing it LDAP. Apparently
7905 some libraries do this for themselves, but some do not. Removing the URL
7906 quoting has two advantages:
7909 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7910 DNs as with DNs inside actual queries.
7912 It permits spaces inside USER= DNs.
7915 For example, a setting such as
7917 USER=cn=${quote_ldap_dn:$1}
7919 should work even if &$1$& contains spaces.
7921 Expanded data for the PASS= value should be quoted using the &%quote%&
7922 expansion operator, rather than the LDAP quote operators. The only reason this
7923 field needs quoting is to ensure that it conforms to the Exim syntax, which
7924 does not allow unquoted spaces. For example:
7928 The LDAP authentication mechanism can be used to check passwords as part of
7929 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7934 .section "Format of data returned by LDAP" "SECID71"
7935 .cindex "LDAP" "returned data formats"
7936 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7937 as a sequence of values, for example
7939 cn=manager,o=University of Cambridge,c=UK
7941 The &(ldap)& lookup type generates an error if more than one entry matches the
7942 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7943 the result between the data from different entries. It is possible for multiple
7944 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7945 you know that whatever values are returned all came from a single entry in the
7948 In the common case where you specify a single attribute in your LDAP query, the
7949 result is not quoted, and does not contain the attribute name. If the attribute
7950 has multiple values, they are separated by commas. Any comma that is
7951 part of an attribute's value is doubled.
7953 If you specify multiple attributes, the result contains space-separated, quoted
7954 strings, each preceded by the attribute name and an equals sign. Within the
7955 quotes, the quote character, backslash, and newline are escaped with
7956 backslashes, and commas are used to separate multiple values for the attribute.
7957 Any commas in attribute values are doubled
7958 (permitting treatment of the values as a comma-separated list).
7959 Apart from the escaping, the string within quotes takes the same form as the
7960 output when a single attribute is requested. Specifying no attributes is the
7961 same as specifying all of an entry's attributes.
7963 Here are some examples of the output format. The first line of each pair is an
7964 LDAP query, and the second is the data that is returned. The attribute called
7965 &%attr1%& has two values, one of them with an embedded comma, whereas
7966 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7967 (they have SUP &%attr%& in their schema definitions).
7970 ldap:///o=base?attr1?sub?(uid=fred)
7973 ldap:///o=base?attr2?sub?(uid=fred)
7976 ldap:///o=base?attr?sub?(uid=fred)
7977 value1.1,value1,,2,value two
7979 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7980 attr1="value1.1,value1,,2" attr2="value two"
7982 ldap:///o=base??sub?(uid=fred)
7983 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7986 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7987 results of LDAP lookups.
7988 The &%extract%& operator in string expansions can be used to pick out
7989 individual fields from data that consists of &'key'&=&'value'& pairs.
7990 The &%listextract%& operator should be used to pick out individual values
7991 of attributes, even when only a single value is expected.
7992 The doubling of embedded commas allows you to use the returned data as a
7993 comma separated list (using the "<," syntax for changing the input list separator).
7998 .section "More about NIS+" "SECTnisplus"
7999 .cindex "NIS+ lookup type"
8000 .cindex "lookup" "NIS+"
8001 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
8002 and field name. If this is given, the result of a successful query is the
8003 contents of the named field; otherwise the result consists of a concatenation
8004 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
8005 values containing spaces are quoted. For example, the query
8007 [name=mg1456],passwd.org_dir
8009 might return the string
8011 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
8012 home=/home/mg1456 shell=/bin/bash shadow=""
8014 (split over two lines here to fit on the page), whereas
8016 [name=mg1456],passwd.org_dir:gcos
8022 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
8023 for the given indexed key. The effect of the &%quote_nisplus%& expansion
8024 operator is to double any quote characters within the text.
8028 .section "SQL lookups" "SECTsql"
8029 .cindex "SQL lookup types"
8030 .cindex "MySQL" "lookup type"
8031 .cindex "PostgreSQL lookup type"
8032 .cindex "lookup" "MySQL"
8033 .cindex "lookup" "PostgreSQL"
8034 .cindex "Oracle" "lookup type"
8035 .cindex "lookup" "Oracle"
8036 .cindex "InterBase lookup type"
8037 .cindex "lookup" "InterBase"
8038 .cindex "Redis lookup type"
8039 .cindex lookup Redis
8040 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
8042 databases. Queries for these databases contain SQL statements, so an example
8045 ${lookup mysql{select mailbox from users where id='userx'}\
8048 If the result of the query contains more than one field, the data for each
8049 field in the row is returned, preceded by its name, so the result of
8051 ${lookup pgsql{select home,name from users where id='userx'}\
8056 home=/home/userx name="Mister X"
8058 Empty values and values containing spaces are double quoted, with embedded
8059 quotes escaped by a backslash. If the result of the query contains just one
8060 field, the value is passed back verbatim, without a field name, for example:
8064 If the result of the query yields more than one row, it is all concatenated,
8065 with a newline between the data for each row.
8068 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
8069 .cindex "MySQL" "lookup type"
8070 .cindex "PostgreSQL lookup type"
8071 .cindex "lookup" "MySQL"
8072 .cindex "lookup" "PostgreSQL"
8073 .cindex "Oracle" "lookup type"
8074 .cindex "lookup" "Oracle"
8075 .cindex "InterBase lookup type"
8076 .cindex "lookup" "InterBase"
8077 .cindex "Redis lookup type"
8078 .cindex lookup Redis
8079 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
8080 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
8081 or &%redis_servers%&
8082 option (as appropriate) must be set to a colon-separated list of server
8084 .oindex &%mysql_servers%&
8085 .oindex &%pgsql_servers%&
8086 .oindex &%oracle_servers%&
8087 .oindex &%ibase_servers%&
8088 .oindex &%redis_servers%&
8089 (For MySQL and PostgreSQL, the global option need not be set if all
8090 queries contain their own server information &-- see section
8091 &<<SECTspeserque>>&.)
8093 each item in the list is a slash-separated list of four
8094 items: host name, database name, user name, and password. In the case of
8095 Oracle, the host name field is used for the &"service name"&, and the database
8096 name field is not used and should be empty. For example:
8098 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
8100 Because password data is sensitive, you should always precede the setting with
8101 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
8102 option. Here is an example where two MySQL servers are listed:
8104 hide mysql_servers = localhost/users/root/secret:\
8105 otherhost/users/root/othersecret
8107 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
8108 because this is a colon-separated list, the colon has to be doubled. For each
8109 query, these parameter groups are tried in order until a connection is made and
8110 a query is successfully processed. The result of a query may be that no data is
8111 found, but that is still a successful query. In other words, the list of
8112 servers provides a backup facility, not a list of different places to look.
8114 For Redis the global option need not be specified if all queries contain their
8115 own server information &-- see section &<<SECTspeserque>>&.
8116 If specified, the option must be set to a colon-separated list of server
8118 Each item in the list is a slash-separated list of three items:
8119 host, database number, and password.
8121 The host is required and may be either an IPv4 address and optional
8122 port number (separated by a colon, which needs doubling due to the
8123 higher-level list), or a Unix socket pathname enclosed in parentheses
8125 The database number is optional; if present that number is selected in the backend
8127 The password is optional; if present it is used to authenticate to the backend
8130 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
8131 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
8132 respectively, and the characters single-quote, double-quote, and backslash
8133 itself are escaped with backslashes.
8135 The &%quote_redis%& expansion operator
8136 escapes whitespace and backslash characters with a backslash.
8138 .section "Specifying the server in the query" "SECTspeserque"
8139 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
8140 it is possible to specify a list of servers with an individual query. This is
8141 done by appending a comma-separated option to the query type:
8143 &`,servers=`&&'server1:server2:server3:...'&
8145 Each item in the list may take one of two forms:
8147 If it contains no slashes it is assumed to be just a host name. The appropriate
8148 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
8149 of the same name, and the remaining parameters (database, user, password) are
8152 If it contains any slashes, it is taken as a complete parameter set.
8154 The list of servers is used in exactly the same way as the global list.
8155 Once a connection to a server has happened and a query has been
8156 successfully executed, processing of the lookup ceases.
8158 This feature is intended for use in master/slave situations where updates
8159 are occurring and you want to update the master rather than a slave. If the
8160 master is in the list as a backup for reading, you might have a global setting
8163 mysql_servers = slave1/db/name/pw:\
8167 In an updating lookup, you could then write:
8169 ${lookup mysql,servers=master {UPDATE ...} }
8171 That query would then be sent only to the master server. If, on the other hand,
8172 the master is not to be used for reading, and so is not present in the global
8173 option, you can still update it by a query of this form:
8175 ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
8178 An older syntax places the servers specification before the query,
8179 semicolon separated:
8181 ${lookup mysql{servers=master; UPDATE ...} }
8183 The new version avoids potential issues with tainted
8184 arguments in the query, for explicit expansion.
8185 &*Note*&: server specifications in list-style lookups are still problematic.
8188 .section "Special MySQL features" "SECID73"
8189 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
8190 causes a connection to the server on the local host by means of a Unix domain
8191 socket. An alternate socket can be specified in parentheses.
8192 An option group name for MySQL option files can be specified in square brackets;
8193 the default value is &"exim"&.
8194 The full syntax of each item in &%mysql_servers%& is:
8196 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
8197 <&'database'&>/<&'user'&>/<&'password'&>
8199 Any of the four sub-parts of the first field can be omitted. For normal use on
8200 the local host it can be left blank or set to just &"localhost"&.
8202 No database need be supplied &-- but if it is absent here, it must be given in
8205 If a MySQL query is issued that does not request any data (an insert, update,
8206 or delete command), the result of the lookup is the number of rows affected.
8208 &*Warning*&: This can be misleading. If an update does not actually change
8209 anything (for example, setting a field to the value it already has), the result
8210 is zero because no rows are affected.
8213 .section "Special PostgreSQL features" "SECID74"
8214 PostgreSQL lookups can also use Unix domain socket connections to the database.
8215 This is usually faster and costs less CPU time than a TCP/IP connection.
8216 However it can be used only if the mail server runs on the same machine as the
8217 database server. A configuration line for PostgreSQL via Unix domain sockets
8220 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
8222 In other words, instead of supplying a host name, a path to the socket is
8223 given. The path name is enclosed in parentheses so that its slashes aren't
8224 visually confused with the delimiters for the other server parameters.
8226 If a PostgreSQL query is issued that does not request any data (an insert,
8227 update, or delete command), the result of the lookup is the number of rows
8230 .section "More about SQLite" "SECTsqlite"
8231 .cindex "lookup" "SQLite"
8232 .cindex "sqlite lookup type"
8233 SQLite is different to the other SQL lookups because a filename is required in
8234 addition to the SQL query. An SQLite database is a single file, and there is no
8235 daemon as in the other SQL databases.
8238 .oindex &%sqlite_dbfile%&
8239 There are two ways of
8240 specifying the file.
8241 The first is is by using the &%sqlite_dbfile%& main option.
8242 The second, which allows separate files for each query,
8243 is to use an option appended, comma-separated, to the &"sqlite"&
8244 lookup type word. The option is the word &"file"&, then an equals,
8246 The filename in this case cannot contain whitespace or open-brace charachters.
8249 A deprecated method is available, prefixing the query with the filename
8250 separated by white space.
8252 .cindex "tainted data" "sqlite file"
8253 the query cannot use any tainted values, as that taints
8254 the entire query including the filename - resulting in a refusal to open
8257 In all the above cases the filename must be an absolute path.
8259 Here is a lookup expansion example:
8261 sqlite_dbfile = /some/thing/sqlitedb
8263 ${lookup sqlite {select name from aliases where id='userx';}}
8265 In a list, the syntax is similar. For example:
8267 domainlist relay_to_domains = sqlite;\
8268 select * from relays where ip='$sender_host_address';
8270 The only character affected by the &%quote_sqlite%& operator is a single
8271 quote, which it doubles.
8273 .cindex timeout SQLite
8274 .cindex sqlite "lookup timeout"
8275 The SQLite library handles multiple simultaneous accesses to the database
8276 internally. Multiple readers are permitted, but only one process can
8277 update at once. Attempts to access the database while it is being updated
8278 are rejected after a timeout period, during which the SQLite library
8279 waits for the lock to be released. In Exim, the default timeout is set
8280 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
8283 .section "More about Redis" "SECTredis"
8284 .cindex "lookup" "Redis"
8285 .cindex "redis lookup type"
8286 Redis is a non-SQL database. Commands are simple get and set.
8289 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
8290 ${lookup redis{get keyname}}
8293 As of release 4.91, "lightweight" support for Redis Cluster is available.
8294 Requires &%redis_servers%& list to contain all the servers in the cluster, all
8295 of which must be reachable from the running exim instance. If the cluster has
8296 master/slave replication, the list must contain all the master and slave
8299 When the Redis Cluster returns a "MOVED" response to a query, Exim does not
8300 immediately follow the redirection but treats the response as a DEFER, moving on
8301 to the next server in the &%redis_servers%& list until the correct server is
8308 . ////////////////////////////////////////////////////////////////////////////
8309 . ////////////////////////////////////////////////////////////////////////////
8311 .chapter "Domain, host, address, and local part lists" &&&
8312 "CHAPdomhosaddlists" &&&
8313 "Domain, host, and address lists"
8314 .scindex IIDdohoadli "lists of domains; hosts; etc."
8315 A number of Exim configuration options contain lists of domains, hosts,
8316 email addresses, or local parts. For example, the &%hold_domains%& option
8317 contains a list of domains whose delivery is currently suspended. These lists
8318 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
8319 arguments to expansion conditions such as &%match_domain%&.
8321 Each item in one of these lists is a pattern to be matched against a domain,
8322 host, email address, or local part, respectively. In the sections below, the
8323 different types of pattern for each case are described, but first we cover some
8324 general facilities that apply to all four kinds of list.
8326 Note that other parts of Exim use a &'string list'& which does not
8327 support all the complexity available in
8328 domain, host, address and local part lists.
8332 .section "Expansion of lists" "SECTlistexpand"
8333 .cindex "expansion" "of lists"
8334 Each list is expanded as a single string before it is used.
8336 &'Exception: the router headers_remove option, where list-item
8337 splitting is done before string-expansion.'&
8340 expansion must be a list, possibly containing empty items, which is split up
8341 into separate items for matching. By default, colon is the separator character,
8342 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
8343 &<<SECTempitelis>>& for details of the list syntax; the second of these
8344 discusses the way to specify empty list items.
8347 If the string expansion is forced to fail, Exim behaves as if the item it is
8348 testing (domain, host, address, or local part) is not in the list. Other
8349 expansion failures cause temporary errors.
8351 If an item in a list is a regular expression, backslashes, dollars and possibly
8352 other special characters in the expression must be protected against
8353 misinterpretation by the string expander. The easiest way to do this is to use
8354 the &`\N`& expansion feature to indicate that the contents of the regular
8355 expression should not be expanded. For example, in an ACL you might have:
8357 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
8358 ${lookup{$domain}lsearch{/badsenders/bydomain}}
8360 The first item is a regular expression that is protected from expansion by
8361 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
8362 senders based on the receiving domain.
8367 .section "Negated items in lists" "SECID76"
8368 .cindex "list" "negation"
8369 .cindex "negation" "in lists"
8370 Items in a list may be positive or negative. Negative items are indicated by a
8371 leading exclamation mark, which may be followed by optional white space. A list
8372 defines a set of items (domains, etc). When Exim processes one of these lists,
8373 it is trying to find out whether a domain, host, address, or local part
8374 (respectively) is in the set that is defined by the list. It works like this:
8376 The list is scanned from left to right. If a positive item is matched, the
8377 subject that is being checked is in the set; if a negative item is matched, the
8378 subject is not in the set. If the end of the list is reached without the
8379 subject having matched any of the patterns, it is in the set if the last item
8380 was a negative one, but not if it was a positive one. For example, the list in
8382 domainlist relay_to_domains = !a.b.c : *.b.c
8384 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
8385 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
8386 list is positive. However, if the setting were
8388 domainlist relay_to_domains = !a.b.c
8390 then all domains other than &'a.b.c'& would match because the last item in the
8391 list is negative. In other words, a list that ends with a negative item behaves
8392 as if it had an extra item &`:*`& on the end.
8394 Another way of thinking about positive and negative items in lists is to read
8395 the connector as &"or"& after a positive item and as &"and"& after a negative
8400 .section "File names in lists" "SECTfilnamlis"
8401 .cindex "list" "filename in"
8402 If an item in a domain, host, address, or local part list is an absolute
8403 filename (beginning with a slash character), each line of the file is read and
8404 processed as if it were an independent item in the list, except that further
8405 filenames are not allowed,
8406 and no expansion of the data from the file takes place.
8407 Empty lines in the file are ignored, and the file may also contain comment
8411 For domain and host lists, if a # character appears anywhere in a line of the
8412 file, it and all following characters are ignored.
8414 Because local parts may legitimately contain # characters, a comment in an
8415 address list or local part list file is recognized only if # is preceded by
8416 white space or the start of the line. For example:
8418 not#comment@x.y.z # but this is a comment
8422 Putting a filename in a list has the same effect as inserting each line of the
8423 file as an item in the list (blank lines and comments excepted). However, there
8424 is one important difference: the file is read each time the list is processed,
8425 so if its contents vary over time, Exim's behaviour changes.
8427 If a filename is preceded by an exclamation mark, the sense of any match
8428 within the file is inverted. For example, if
8430 hold_domains = !/etc/nohold-domains
8432 and the file contains the lines
8437 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
8438 any domain matching &`*.b.c`& is not.
8442 .section "An lsearch file is not an out-of-line list" "SECID77"
8443 As will be described in the sections that follow, lookups can be used in lists
8444 to provide indexed methods of checking list membership. There has been some
8445 confusion about the way &(lsearch)& lookups work in lists. Because
8446 an &(lsearch)& file contains plain text and is scanned sequentially, it is
8447 sometimes thought that it is allowed to contain wild cards and other kinds of
8448 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
8449 always fixed strings, just as for any other single-key lookup type.
8451 If you want to use a file to contain wild-card patterns that form part of a
8452 list, just give the filename on its own, without a search type, as described
8453 in the previous section. You could also use the &(wildlsearch)& or
8454 &(nwildlsearch)&, but there is no advantage in doing this.
8459 .section "Results of list checking" SECTlistresults
8460 The primary result of doing a list check is a truth value.
8461 In some contexts additional information is stored
8462 about the list element that matched:
8465 A &%hosts%& ACL condition
8466 will store a result in the &$host_data$& variable.
8468 A &%local_parts%& router option or &%local_parts%& ACL condition
8469 will store a result in the &$local_part_data$& variable.
8472 A &%domains%& router option or &%domains%& ACL condition
8473 will store a result in the &$domain_data$& variable
8476 A &%senders%& router option or &%senders%& ACL condition
8477 will store a result in the &$sender_data$& variable.
8479 A &%recipients%& ACL condition
8480 will store a result in the &$recipient_data$& variable.
8483 The detail of the additional information depends on the
8484 type of match and is given below as the &*value*& information.
8489 .section "Named lists" "SECTnamedlists"
8490 .cindex "named lists"
8491 .cindex "list" "named"
8492 A list of domains, hosts, email addresses, or local parts can be given a name
8493 which is then used to refer to the list elsewhere in the configuration. This is
8494 particularly convenient if the same list is required in several different
8495 places. It also allows lists to be given meaningful names, which can improve
8496 the readability of the configuration. For example, it is conventional to define
8497 a domain list called &'local_domains'& for all the domains that are handled
8498 locally on a host, using a configuration line such as
8500 domainlist local_domains = localhost:my.dom.example
8502 Named lists are referenced by giving their name preceded by a plus sign, so,
8503 for example, a router that is intended to handle local domains would be
8504 configured with the line
8506 domains = +local_domains
8508 The first router in a configuration is often one that handles all domains
8509 except the local ones, using a configuration with a negated item like this:
8513 domains = ! +local_domains
8514 transport = remote_smtp
8517 The four kinds of named list are created by configuration lines starting with
8518 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8519 respectively. Then there follows the name that you are defining, followed by an
8520 equals sign and the list itself. For example:
8522 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8523 addresslist bad_senders = cdb;/etc/badsenders
8525 A named list may refer to other named lists:
8527 domainlist dom1 = first.example : second.example
8528 domainlist dom2 = +dom1 : third.example
8529 domainlist dom3 = fourth.example : +dom2 : fifth.example
8531 &*Warning*&: If the last item in a referenced list is a negative one, the
8532 effect may not be what you intended, because the negation does not propagate
8533 out to the higher level. For example, consider:
8535 domainlist dom1 = !a.b
8536 domainlist dom2 = +dom1 : *.b
8538 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8539 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8540 means it matches the second list as well. The effect is not the same as
8542 domainlist dom2 = !a.b : *.b
8544 where &'x.y'& does not match. It's best to avoid negation altogether in
8545 referenced lists if you can.
8547 .cindex "hiding named list values"
8548 .cindex "named lists" "hiding value of"
8549 Some named list definitions may contain sensitive data, for example, passwords for
8550 accessing databases. To stop non-admin users from using the &%-bP%& command
8551 line option to read these values, you can precede the definition with the
8552 word &"hide"&. For example:
8554 hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
8558 Named lists may have a performance advantage. When Exim is routing an
8559 address or checking an incoming message, it caches the result of tests on named
8560 lists. So, if you have a setting such as
8562 domains = +local_domains
8564 on several of your routers
8565 or in several ACL statements,
8566 the actual test is done only for the first one. However, the caching works only
8567 if there are no expansions within the list itself or any sublists that it
8568 references. In other words, caching happens only for lists that are known to be
8569 the same each time they are referenced.
8571 By default, there may be up to 16 named lists of each type. This limit can be
8572 extended by changing a compile-time variable. The use of domain and host lists
8573 is recommended for concepts such as local domains, relay domains, and relay
8574 hosts. The default configuration is set up like this.
8578 .section "Named lists compared with macros" "SECID78"
8579 .cindex "list" "named compared with macro"
8580 .cindex "macro" "compared with named list"
8581 At first sight, named lists might seem to be no different from macros in the
8582 configuration file. However, macros are just textual substitutions. If you
8585 ALIST = host1 : host2
8586 auth_advertise_hosts = !ALIST
8588 it probably won't do what you want, because that is exactly the same as
8590 auth_advertise_hosts = !host1 : host2
8592 Notice that the second host name is not negated. However, if you use a host
8595 hostlist alist = host1 : host2
8596 auth_advertise_hosts = ! +alist
8598 the negation applies to the whole list, and so that is equivalent to
8600 auth_advertise_hosts = !host1 : !host2
8604 .section "Named list caching" "SECID79"
8605 .cindex "list" "caching of named"
8606 .cindex "caching" "named lists"
8607 While processing a message, Exim caches the result of checking a named list if
8608 it is sure that the list is the same each time. In practice, this means that
8609 the cache operates only if the list contains no $ characters, which guarantees
8610 that it will not change when it is expanded. Sometimes, however, you may have
8611 an expanded list that you know will be the same each time within a given
8612 message. For example:
8614 domainlist special_domains = \
8615 ${lookup{$sender_host_address}cdb{/some/file}}
8617 This provides a list of domains that depends only on the sending host's IP
8618 address. If this domain list is referenced a number of times (for example,
8619 in several ACL lines, or in several routers) the result of the check is not
8620 cached by default, because Exim does not know that it is going to be the
8621 same list each time.
8623 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8624 cache the result anyway. For example:
8626 domainlist_cache special_domains = ${lookup{...
8628 If you do this, you should be absolutely sure that caching is going to do
8629 the right thing in all cases. When in doubt, leave it out.
8633 .section "Domain lists" "SECTdomainlist"
8634 .cindex "domain list" "patterns for"
8635 .cindex "list" "domain list"
8636 Domain lists contain patterns that are to be matched against a mail domain.
8637 The following types of item may appear in domain lists:
8640 .cindex "primary host name"
8641 .cindex "host name" "matched in domain list"
8642 .oindex "&%primary_hostname%&"
8643 .cindex "domain list" "matching primary host name"
8644 .cindex "@ in a domain list"
8645 If a pattern consists of a single @ character, it matches the local host name,
8646 as set by the &%primary_hostname%& option (or defaulted). This makes it
8647 possible to use the same configuration file on several different hosts that
8648 differ only in their names.
8650 The value for a match will be the primary host name.
8654 .cindex "@[] in a domain list"
8655 .cindex "domain list" "matching local IP interfaces"
8656 .cindex "domain literal"
8657 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8658 in square brackets (as in an email address that contains a domain literal), but
8659 only if that IP address is recognized as local for email routing purposes. The
8660 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8661 control which of a host's several IP addresses are treated as local.
8662 In today's Internet, the use of domain literals is controversial;
8663 see the &%allow_domain_literals%& main option.
8665 The value for a match will be the string &`@[]`&.
8670 .cindex "@mx_primary"
8671 .cindex "@mx_secondary"
8672 .cindex "domain list" "matching MX pointers to local host"
8673 If a pattern consists of the string &`@mx_any`& it matches any domain that
8674 has an MX record pointing to the local host or to any host that is listed in
8675 .oindex "&%hosts_treat_as_local%&"
8676 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8677 are similar, except that the first matches only when a primary MX target is the
8678 local host, and the second only when no primary MX target is the local host,
8679 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8680 preference value &-- there may of course be more than one of them.
8682 The MX lookup that takes place when matching a pattern of this type is
8683 performed with the resolver options for widening names turned off. Thus, for
8684 example, a single-component domain will &'not'& be expanded by adding the
8685 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8686 options of the &(dnslookup)& router for a discussion of domain widening.
8688 Sometimes you may want to ignore certain IP addresses when using one of these
8689 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8690 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8691 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8692 on a router). For example:
8694 domains = @mx_any/ignore=127.0.0.1
8696 This example matches any domain that has an MX record pointing to one of
8697 the local host's IP addresses other than 127.0.0.1.
8699 The list of IP addresses is in fact processed by the same code that processes
8700 host lists, so it may contain CIDR-coded network specifications and it may also
8701 contain negative items.
8703 Because the list of IP addresses is a sublist within a domain list, you have to
8704 be careful about delimiters if there is more than one address. Like any other
8705 list, the default delimiter can be changed. Thus, you might have:
8707 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8708 an.other.domain : ...
8710 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8711 involved, it is easiest to change the delimiter for the main list as well:
8713 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8714 an.other.domain ? ...
8716 The value for a match will be the list element string (starting &`@mx_`&).
8720 .cindex "asterisk" "in domain list"
8721 .cindex "domain list" "asterisk in"
8722 .cindex "domain list" "matching &""ends with""&"
8723 If a pattern starts with an asterisk, the remaining characters of the pattern
8724 are compared with the terminating characters of the domain. The use of &"*"& in
8725 domain lists differs from its use in partial matching lookups. In a domain
8726 list, the character following the asterisk need not be a dot, whereas partial
8727 matching works only in terms of dot-separated components. For example, a domain
8728 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8731 The value for a match will be the list element string (starting with the asterisk).
8732 Additionally, &$0$& will be set to the matched string
8733 and &$1$& to the variable portion which the asterisk matched.
8736 .cindex "regular expressions" "in domain list"
8737 .cindex "domain list" "matching regular expression"
8738 If a pattern starts with a circumflex character, it is treated as a regular
8739 expression, and matched against the domain using a regular expression matching
8740 function. The circumflex is treated as part of the regular expression.
8741 Email domains are case-independent, so this regular expression match is by
8742 default case-independent, but you can make it case-dependent by starting it
8743 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8744 are given in chapter &<<CHAPregexp>>&.
8746 &*Warning*&: Because domain lists are expanded before being processed, you
8747 must escape any backslash and dollar characters in the regular expression, or
8748 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8749 it is not to be expanded (unless you really do want to build a regular
8750 expression by expansion, of course).
8752 The value for a match will be the list element string (starting with the circumflex).
8753 Additionally, &$0$& will be set to the string matching the regular expression,
8754 and &$1$& (onwards) to any submatches identified by parentheses.
8759 .cindex "lookup" "in domain list"
8760 .cindex "domain list" "matching by lookup"
8761 If a pattern starts with the name of a single-key lookup type followed by a
8762 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8763 must be a filename in a suitable format for the lookup type. For example, for
8764 &"cdb;"& it must be an absolute path:
8766 domains = cdb;/etc/mail/local_domains.cdb
8768 The appropriate type of lookup is done on the file using the domain name as the
8769 key. In most cases, the value resulting from the lookup is not used; Exim is interested
8770 only in whether or not the key is present in the file. However, when a lookup
8771 is used for the &%domains%& option on a router
8772 or a &%domains%& condition in an ACL statement, the value is preserved in the
8773 &$domain_data$& variable and can be referred to in other router options or
8774 other statements in the same ACL.
8775 .cindex "tainted data" "de-tainting"
8776 The value will be untainted.
8780 Any of the single-key lookup type names may be preceded by
8781 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8783 domains = partial-dbm;/partial/domains
8785 This causes partial matching logic to be invoked; a description of how this
8786 works is given in section &<<SECTpartiallookup>>&.
8789 .cindex "asterisk" "in lookup type"
8790 Any of the single-key lookup types may be followed by an asterisk. This causes
8791 a default lookup for a key consisting of a single asterisk to be done if the
8792 original lookup fails. This is not a useful feature when using a domain list to
8793 select particular domains (because any domain would match), but it might have
8794 value if the result of the lookup is being used via the &$domain_data$&
8798 If the pattern starts with the name of a query-style lookup type followed by a
8799 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8800 pattern must be an appropriate query for the lookup type, as described in
8801 chapter &<<CHAPfdlookup>>&. For example:
8803 hold_domains = mysql;select domain from holdlist \
8804 where domain = '${quote_mysql:$domain}';
8806 In most cases, the value resulting from the lookup is not used (so for an SQL query, for
8807 example, it doesn't matter what field you select). Exim is interested only in
8808 whether or not the query succeeds. However, when a lookup is used for the
8809 &%domains%& option on a router, the value is preserved in the &$domain_data$&
8810 variable and can be referred to in other options.
8811 .cindex "tainted data" "de-tainting"
8812 The value will be untainted.
8815 If the pattern starts with the name of a lookup type
8816 of either kind (single-key or query-style) it may be
8817 followed by a comma and options,
8818 The options are lookup-type specific and consist of a comma-separated list.
8819 Each item starts with a tag and and equals "=".
8822 .cindex "domain list" "matching literal domain name"
8823 If none of the above cases apply, a caseless textual comparison is made
8824 between the pattern and the domain.
8826 The value for a match will be the list element string.
8827 .cindex "tainted data" "de-tainting"
8828 Note that this is commonly untainted
8829 (depending on the way the list was created).
8830 Specifically, explicit text in the configuration file in not tainted.
8831 This is a useful way of obtaining an untainted equivalent to
8832 the domain, for later operations.
8834 However if the list (including one-element lists)
8835 is created by expanding a variable containing tainted data,
8836 it is tainted and so will the match value be.
8840 Here is an example that uses several different kinds of pattern:
8842 domainlist funny_domains = \
8845 *.foundation.fict.example : \
8846 \N^[1-2]\d{3}\.fict\.example$\N : \
8847 partial-dbm;/opt/data/penguin/book : \
8848 nis;domains.byname : \
8849 nisplus;[name=$domain,status=local],domains.org_dir
8851 There are obvious processing trade-offs among the various matching modes. Using
8852 an asterisk is faster than a regular expression, and listing a few names
8853 explicitly probably is too. The use of a file or database lookup is expensive,
8854 but may be the only option if hundreds of names are required. Because the
8855 patterns are tested in order, it makes sense to put the most commonly matched
8860 .section "Host lists" "SECThostlist"
8861 .cindex "host list" "patterns in"
8862 .cindex "list" "host list"
8863 Host lists are used to control what remote hosts are allowed to do. For
8864 example, some hosts may be allowed to use the local host as a relay, and some
8865 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8866 two different ways, by name or by IP address. In a host list, some types of
8867 pattern are matched to a host name, and some are matched to an IP address.
8868 You need to be particularly careful with this when single-key lookups are
8869 involved, to ensure that the right value is being used as the key.
8872 .section "Special host list patterns" "SECID80"
8873 .cindex "empty item in hosts list"
8874 .cindex "host list" "empty string in"
8875 If a host list item is the empty string, it matches only when no remote host is
8876 involved. This is the case when a message is being received from a local
8877 process using SMTP on the standard input, that is, when a TCP/IP connection is
8880 .cindex "asterisk" "in host list"
8881 The special pattern &"*"& in a host list matches any host or no host. Neither
8882 the IP address nor the name is actually inspected.
8886 .section "Host list patterns that match by IP address" "SECThoslispatip"
8887 .cindex "host list" "matching IP addresses"
8888 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8889 the incoming address actually appears in the IPv6 host as
8890 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8891 list, it is converted into a traditional IPv4 address first. (Not all operating
8892 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8895 The following types of pattern in a host list check the remote host by
8896 inspecting its IP address:
8899 If the pattern is a plain domain name (not a regular expression, not starting
8900 with *, not a lookup of any kind), Exim calls the operating system function
8901 to find the associated IP address(es). Exim uses the newer
8902 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8903 This typically causes a forward DNS lookup of the name. The result is compared
8904 with the IP address of the subject host.
8906 If there is a temporary problem (such as a DNS timeout) with the host name
8907 lookup, a temporary error occurs. For example, if the list is being used in an
8908 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8909 temporary SMTP error code. If no IP address can be found for the host name,
8910 what happens is described in section &<<SECTbehipnot>>& below.
8913 .cindex "@ in a host list"
8914 If the pattern is &"@"&, the primary host name is substituted and used as a
8915 domain name, as just described.
8918 If the pattern is an IP address, it is matched against the IP address of the
8919 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8920 IPv6 addresses can be given in colon-separated format, but the colons have to
8921 be doubled so as not to be taken as item separators when the default list
8922 separator is used. IPv6 addresses are recognized even when Exim is compiled
8923 without IPv6 support. This means that if they appear in a host list on an
8924 IPv4-only host, Exim will not treat them as host names. They are just addresses
8925 that can never match a client host.
8928 .cindex "@[] in a host list"
8929 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8930 the local host. For example, if the local host is an IPv4 host with one
8931 interface address 10.45.23.56, these two ACL statements have the same effect:
8933 accept hosts = 127.0.0.1 : 10.45.23.56
8937 .cindex "CIDR notation"
8938 If the pattern is an IP address followed by a slash and a mask length (for
8939 example 10.11.42.0/24), it is matched against the IP address of the subject
8940 host under the given mask. This allows, an entire network of hosts to be
8941 included (or excluded) by a single item. The mask uses CIDR notation; it
8942 specifies the number of address bits that must match, starting from the most
8943 significant end of the address.
8945 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8946 of a range of addresses. It is the number of bits in the network portion of the
8947 address. The above example specifies a 24-bit netmask, so it matches all 256
8948 addresses in the 10.11.42.0 network. An item such as
8952 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8953 32 for an IPv4 address is the same as no mask at all; just a single address
8956 Here is another example which shows an IPv4 and an IPv6 network:
8958 recipient_unqualified_hosts = 192.168.0.0/16: \
8959 3ffe::ffff::836f::::/48
8961 The doubling of list separator characters applies only when these items
8962 appear inline in a host list. It is not required when indirecting via a file.
8965 recipient_unqualified_hosts = /opt/exim/unqualnets
8967 could make use of a file containing
8972 to have exactly the same effect as the previous example. When listing IPv6
8973 addresses inline, it is usually more convenient to use the facility for
8974 changing separator characters. This list contains the same two networks:
8976 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8979 The separator is changed to semicolon by the leading &"<;"& at the start of the
8985 .section "Host list patterns for single-key lookups by host address" &&&
8986 "SECThoslispatsikey"
8987 .cindex "host list" "lookup of IP address"
8988 When a host is to be identified by a single-key lookup of its complete IP
8989 address, the pattern takes this form:
8991 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8995 hosts_lookup = net-cdb;/hosts-by-ip.db
8997 The text form of the IP address of the subject host is used as the lookup key.
8998 IPv6 addresses are converted to an unabbreviated form, using lower case
8999 letters, with dots as separators because colon is the key terminator in
9000 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
9001 quoting the keys, but this is a facility that was added later.] The data
9002 returned by the lookup is not used.
9004 .cindex "IP address" "masking"
9005 .cindex "host list" "masked IP address"
9006 Single-key lookups can also be performed using masked IP addresses, using
9007 patterns of this form:
9009 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
9013 net24-dbm;/networks.db
9015 The IP address of the subject host is masked using <&'number'&> as the mask
9016 length. A textual string is constructed from the masked value, followed by the
9017 mask, and this is used as the lookup key. For example, if the host's IP address
9018 is 192.168.34.6, the key that is looked up for the above example is
9019 &"192.168.34.0/24"&.
9021 When an IPv6 address is converted to a string, dots are normally used instead
9022 of colons, so that keys in &(lsearch)& files need not contain colons (which
9023 terminate &(lsearch)& keys). This was implemented some time before the ability
9024 to quote keys was made available in &(lsearch)& files. However, the more
9025 recently implemented &(iplsearch)& files do require colons in IPv6 keys
9026 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
9027 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
9028 converted using colons and not dots.
9029 In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
9030 addresses are always used.
9031 The latter are converted to IPv4 addresses, in dotted-quad form.
9033 Ideally, it would be nice to tidy up this anomalous situation by changing to
9034 colons in all cases, given that quoting is now available for &(lsearch)&.
9035 However, this would be an incompatible change that might break some existing
9038 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
9039 IPv6 address) is not the same as specifying just &%net-%& without a number. In
9040 the former case the key strings include the mask value, whereas in the latter
9041 case the IP address is used on its own.
9045 .section "Host list patterns that match by host name" "SECThoslispatnam"
9046 .cindex "host" "lookup failures"
9047 .cindex "unknown host name"
9048 .cindex "host list" "matching host name"
9049 There are several types of pattern that require Exim to know the name of the
9050 remote host. These are either wildcard patterns or lookups by name. (If a
9051 complete hostname is given without any wildcarding, it is used to find an IP
9052 address to match against, as described in section &<<SECThoslispatip>>&
9055 If the remote host name is not already known when Exim encounters one of these
9056 patterns, it has to be found from the IP address.
9057 Although many sites on the Internet are conscientious about maintaining reverse
9058 DNS data for their hosts, there are also many that do not do this.
9059 Consequently, a name cannot always be found, and this may lead to unwanted
9060 effects. Take care when configuring host lists with wildcarded name patterns.
9061 Consider what will happen if a name cannot be found.
9063 Because of the problems of determining host names from IP addresses, matching
9064 against host names is not as common as matching against IP addresses.
9066 By default, in order to find a host name, Exim first does a reverse DNS lookup;
9067 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
9068 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
9069 are done can be changed by setting the &%host_lookup_order%& option. For
9070 security, once Exim has found one or more names, it looks up the IP addresses
9071 for these names and compares them with the IP address that it started with.
9072 Only those names whose IP addresses match are accepted. Any other names are
9073 discarded. If no names are left, Exim behaves as if the host name cannot be
9074 found. In the most common case there is only one name and one IP address.
9076 There are some options that control what happens if a host name cannot be
9077 found. These are described in section &<<SECTbehipnot>>& below.
9079 .cindex "host" "alias for"
9080 .cindex "alias for host"
9081 As a result of aliasing, hosts may have more than one name. When processing any
9082 of the following types of pattern, all the host's names are checked:
9085 .cindex "asterisk" "in host list"
9086 If a pattern starts with &"*"& the remainder of the item must match the end of
9087 the host name. For example, &`*.b.c`& matches all hosts whose names end in
9088 &'.b.c'&. This special simple form is provided because this is a very common
9089 requirement. Other kinds of wildcarding require the use of a regular
9092 .cindex "regular expressions" "in host list"
9093 .cindex "host list" "regular expression in"
9094 If the item starts with &"^"& it is taken to be a regular expression which is
9095 matched against the host name. Host names are case-independent, so this regular
9096 expression match is by default case-independent, but you can make it
9097 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
9098 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
9103 is a regular expression that matches either of the two hosts &'a.c.d'& or
9104 &'b.c.d'&. When a regular expression is used in a host list, you must take care
9105 that backslash and dollar characters are not misinterpreted as part of the
9106 string expansion. The simplest way to do this is to use &`\N`& to mark that
9107 part of the string as non-expandable. For example:
9109 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
9111 &*Warning*&: If you want to match a complete host name, you must include the
9112 &`$`& terminating metacharacter in the regular expression, as in the above
9113 example. Without it, a match at the start of the host name is all that is
9120 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
9121 .cindex "host" "lookup failures, permanent"
9122 While processing a host list, Exim may need to look up an IP address from a
9123 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
9124 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
9125 behaviour when it fails to find the information it is seeking is the same.
9127 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
9128 apply to temporary DNS errors, whose handling is described in the next section.
9130 .cindex "&`+include_unknown`&"
9131 .cindex "&`+ignore_unknown`&"
9132 Exim parses a host list from left to right. If it encounters a permanent
9133 lookup failure in any item in the host list before it has found a match,
9134 Exim treats it as a failure and the default behavior is as if the host
9135 does not match the list. This may not always be what you want to happen.
9136 To change Exim's behaviour, the special items &`+include_unknown`& or
9137 &`+ignore_unknown`& may appear in the list (at top level &-- they are
9138 not recognized in an indirected file).
9141 If any item that follows &`+include_unknown`& requires information that
9142 cannot found, Exim behaves as if the host does match the list. For example,
9144 host_reject_connection = +include_unknown:*.enemy.ex
9146 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
9147 any hosts whose name it cannot find.
9150 If any item that follows &`+ignore_unknown`& requires information that cannot
9151 be found, Exim ignores that item and proceeds to the rest of the list. For
9154 accept hosts = +ignore_unknown : friend.example : \
9157 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
9158 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
9159 name can be found for 192.168.4.5, it is rejected.
9162 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
9163 list. The effect of each one lasts until the next, or until the end of the
9166 .section "Mixing wildcarded host names and addresses in host lists" &&&
9168 .cindex "host list" "mixing names and addresses in"
9170 This section explains the host/ip processing logic with the same concepts
9171 as the previous section, but specifically addresses what happens when a
9172 wildcarded hostname is one of the items in the hostlist.
9175 If you have name lookups or wildcarded host names and
9176 IP addresses in the same host list, you should normally put the IP
9177 addresses first. For example, in an ACL you could have:
9179 accept hosts = 10.9.8.7 : *.friend.example
9181 The reason you normally would order it this way lies in the
9182 left-to-right way that Exim processes lists. It can test IP addresses
9183 without doing any DNS lookups, but when it reaches an item that requires
9184 a host name, it fails if it cannot find a host name to compare with the
9185 pattern. If the above list is given in the opposite order, the
9186 &%accept%& statement fails for a host whose name cannot be found, even
9187 if its IP address is 10.9.8.7.
9190 If you really do want to do the name check first, and still recognize the IP
9191 address, you can rewrite the ACL like this:
9193 accept hosts = *.friend.example
9194 accept hosts = 10.9.8.7
9196 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
9197 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
9198 &`+ignore_unknown`&, which was discussed in depth in the first example in
9203 .section "Temporary DNS errors when looking up host information" &&&
9205 .cindex "host" "lookup failures, temporary"
9206 .cindex "&`+include_defer`&"
9207 .cindex "&`+ignore_defer`&"
9208 A temporary DNS lookup failure normally causes a defer action (except when
9209 &%dns_again_means_nonexist%& converts it into a permanent error). However,
9210 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
9211 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
9212 section. These options should be used with care, probably only in non-critical
9213 host lists such as whitelists.
9217 .section "Host list patterns for single-key lookups by host name" &&&
9218 "SECThoslispatnamsk"
9219 .cindex "unknown host name"
9220 .cindex "host list" "matching host name"
9221 If a pattern is of the form
9223 <&'single-key-search-type'&>;<&'search-data'&>
9227 dbm;/host/accept/list
9229 a single-key lookup is performed, using the host name as its key. If the
9230 lookup succeeds, the host matches the item. The actual data that is looked up
9233 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
9234 keys in the file, not IP addresses. If you want to do lookups based on IP
9235 addresses, you must precede the search type with &"net-"& (see section
9236 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
9237 two items in the same list, one doing an address lookup and one doing a name
9238 lookup, both using the same file.
9242 .section "Host list patterns for query-style lookups" "SECID81"
9243 If a pattern is of the form
9245 <&'query-style-search-type'&>;<&'query'&>
9247 the query is obeyed, and if it succeeds, the host matches the item. The actual
9248 data that is looked up is not used. The variables &$sender_host_address$& and
9249 &$sender_host_name$& can be used in the query. For example:
9251 hosts_lookup = pgsql;\
9252 select ip from hostlist where ip='$sender_host_address'
9254 The value of &$sender_host_address$& for an IPv6 address contains colons. You
9255 can use the &%sg%& expansion item to change this if you need to. If you want to
9256 use masked IP addresses in database queries, you can use the &%mask%& expansion
9259 If the query contains a reference to &$sender_host_name$&, Exim automatically
9260 looks up the host name if it has not already done so. (See section
9261 &<<SECThoslispatnam>>& for comments on finding host names.)
9263 Historical note: prior to release 4.30, Exim would always attempt to find a
9264 host name before running the query, unless the search type was preceded by
9265 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
9266 still recognized for query-style lookups, but its presence or absence has no
9267 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
9268 See section &<<SECThoslispatsikey>>&.)
9274 .section "Address lists" "SECTaddresslist"
9275 .cindex "list" "address list"
9276 .cindex "address list" "empty item"
9277 .cindex "address list" "patterns"
9278 Address lists contain patterns that are matched against mail addresses. There
9279 is one special case to be considered: the sender address of a bounce message is
9280 always empty. You can test for this by providing an empty item in an address
9281 list. For example, you can set up a router to process bounce messages by
9282 using this option setting:
9286 The presence of the colon creates an empty item. If you do not provide any
9287 data, the list is empty and matches nothing. The empty sender can also be
9288 detected by a regular expression that matches an empty string,
9289 and by a query-style lookup that succeeds when &$sender_address$& is empty.
9291 Non-empty items in an address list can be straightforward email addresses. For
9294 senders = jbc@askone.example : hs@anacreon.example
9296 A certain amount of wildcarding is permitted. If a pattern contains an @
9297 character, but is not a regular expression and does not begin with a
9298 semicolon-terminated lookup type (described below), the local part of the
9299 subject address is compared with the local part of the pattern, which may start
9300 with an asterisk. If the local parts match, the domain is checked in exactly
9301 the same way as for a pattern in a domain list. For example, the domain can be
9302 wildcarded, refer to a named list, or be a lookup:
9304 deny senders = *@*.spamming.site:\
9305 *@+hostile_domains:\
9306 bozo@partial-lsearch;/list/of/dodgy/sites:\
9307 *@dbm;/bad/domains.db
9309 .cindex "local part" "starting with !"
9310 .cindex "address list" "local part starting with !"
9311 If a local part that begins with an exclamation mark is required, it has to be
9312 specified using a regular expression, because otherwise the exclamation mark is
9313 treated as a sign of negation, as is standard in lists.
9315 If a non-empty pattern that is not a regular expression or a lookup does not
9316 contain an @ character, it is matched against the domain part of the subject
9317 address. The only two formats that are recognized this way are a literal
9318 domain, or a domain pattern that starts with *. In both these cases, the effect
9319 is the same as if &`*@`& preceded the pattern. For example:
9321 deny senders = enemy.domain : *.enemy.domain
9324 The following kinds of more complicated address list pattern can match any
9325 address, including the empty address that is characteristic of bounce message
9329 .cindex "regular expressions" "in address list"
9330 .cindex "address list" "regular expression in"
9331 If (after expansion) a pattern starts with &"^"&, a regular expression match is
9332 done against the complete address, with the pattern as the regular expression.
9333 You must take care that backslash and dollar characters are not misinterpreted
9334 as part of the string expansion. The simplest way to do this is to use &`\N`&
9335 to mark that part of the string as non-expandable. For example:
9337 deny senders = \N^.*this.*@example\.com$\N : \
9338 \N^\d{8}.+@spamhaus.example$\N : ...
9340 The &`\N`& sequences are removed by the expansion, so these items do indeed
9341 start with &"^"& by the time they are being interpreted as address patterns.
9344 .cindex "address list" "lookup for complete address"
9345 Complete addresses can be looked up by using a pattern that starts with a
9346 lookup type terminated by a semicolon, followed by the data for the lookup. For
9349 deny senders = cdb;/etc/blocked.senders : \
9350 mysql;select address from blocked where \
9351 address='${quote_mysql:$sender_address}'
9353 Both query-style and single-key lookup types can be used. For a single-key
9354 lookup type, Exim uses the complete address as the key. However, empty keys are
9355 not supported for single-key lookups, so a match against the empty address
9356 always fails. This restriction does not apply to query-style lookups.
9358 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
9359 cannot be used, and is ignored if specified, with an entry being written to the
9361 .cindex "*@ with single-key lookup"
9362 However, you can configure lookup defaults, as described in section
9363 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
9364 default. For example, with this lookup:
9366 accept senders = lsearch*@;/some/file
9368 the file could contains lines like this:
9370 user1@domain1.example
9373 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
9376 nimrod@jaeger.example
9380 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
9381 would mean that every address matches, thus rendering the test useless.
9383 &*Warning 2*&: Do not confuse these two kinds of item:
9385 deny recipients = dbm*@;/some/file
9386 deny recipients = *@dbm;/some/file
9388 The first does a whole address lookup, with defaulting, as just described,
9389 because it starts with a lookup type. The second matches the local part and
9390 domain independently, as described in a bullet point below.
9394 The following kinds of address list pattern can match only non-empty addresses.
9395 If the subject address is empty, a match against any of these pattern types
9400 .cindex "@@ with single-key lookup"
9401 .cindex "address list" "@@ lookup type"
9402 .cindex "address list" "split local part and domain"
9403 If a pattern starts with &"@@"& followed by a single-key lookup item
9404 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
9405 split into a local part and a domain. The domain is looked up in the file. If
9406 it is not found, there is no match. If it is found, the data that is looked up
9407 from the file is treated as a colon-separated list of local part patterns, each
9408 of which is matched against the subject local part in turn.
9410 .cindex "asterisk" "in address list"
9411 The lookup may be a partial one, and/or one involving a search for a default
9412 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
9413 patterns that are looked up can be regular expressions or begin with &"*"&, or
9414 even be further lookups. They may also be independently negated. For example,
9417 deny senders = @@dbm;/etc/reject-by-domain
9419 the data from which the DBM file is built could contain lines like
9421 baddomain.com: !postmaster : *
9423 to reject all senders except &%postmaster%& from that domain.
9425 .cindex "local part" "starting with !"
9426 If a local part that actually begins with an exclamation mark is required, it
9427 has to be specified using a regular expression. In &(lsearch)& files, an entry
9428 may be split over several lines by indenting the second and subsequent lines,
9429 but the separating colon must still be included at line breaks. White space
9430 surrounding the colons is ignored. For example:
9432 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
9435 As in all colon-separated lists in Exim, a colon can be included in an item by
9438 If the last item in the list starts with a right angle-bracket, the remainder
9439 of the item is taken as a new key to look up in order to obtain a continuation
9440 list of local parts. The new key can be any sequence of characters. Thus one
9441 might have entries like
9443 aol.com: spammer1 : spammer 2 : >*
9444 xyz.com: spammer3 : >*
9447 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
9448 local parts for all domains, in addition to the specific local parts listed for
9449 each domain. Of course, using this feature costs another lookup each time a
9450 chain is followed, but the effort needed to maintain the data is reduced.
9452 .cindex "loop" "in lookups"
9453 It is possible to construct loops using this facility, and in order to catch
9454 them, the chains may be no more than fifty items long.
9457 The @@<&'lookup'&> style of item can also be used with a query-style
9458 lookup, but in this case, the chaining facility is not available. The lookup
9459 can only return a single list of local parts.
9462 &*Warning*&: There is an important difference between the address list items
9463 in these two examples:
9466 senders = *@+my_list
9468 In the first one, &`my_list`& is a named address list, whereas in the second
9469 example it is a named domain list.
9474 .section "Case of letters in address lists" "SECTcasletadd"
9475 .cindex "case of local parts"
9476 .cindex "address list" "case forcing"
9477 .cindex "case forcing in address lists"
9478 Domains in email addresses are always handled caselessly, but for local parts
9479 case may be significant on some systems (see &%caseful_local_part%& for how
9480 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
9481 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
9482 blocking lists should be done in a case-independent manner. Since most address
9483 lists in Exim are used for this kind of control, Exim attempts to do this by
9486 The domain portion of an address is always lowercased before matching it to an
9487 address list. The local part is lowercased by default, and any string
9488 comparisons that take place are done caselessly. This means that the data in
9489 the address list itself, in files included as plain filenames, and in any file
9490 that is looked up using the &"@@"& mechanism, can be in any case. However, the
9491 keys in files that are looked up by a search type other than &(lsearch)& (which
9492 works caselessly) must be in lower case, because these lookups are not
9495 .cindex "&`+caseful`&"
9496 To allow for the possibility of caseful address list matching, if an item in
9497 an address list is the string &"+caseful"&, the original case of the local
9498 part is restored for any comparisons that follow, and string comparisons are no
9499 longer case-independent. This does not affect the domain, which remains in
9500 lower case. However, although independent matches on the domain alone are still
9501 performed caselessly, regular expressions that match against an entire address
9502 become case-sensitive after &"+caseful"& has been seen.
9506 .section "Local part lists" "SECTlocparlis"
9507 .cindex "list" "local part list"
9508 .cindex "local part" "list"
9509 These behave in the same way as domain and host lists, with the following
9512 Case-sensitivity in local part lists is handled in the same way as for address
9513 lists, as just described. The &"+caseful"& item can be used if required. In a
9514 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
9515 set false, the subject is lowercased and the matching is initially
9516 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
9517 matching in the local part list, but not elsewhere in the router. If
9518 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
9519 option is case-sensitive from the start.
9521 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
9522 comments are handled in the same way as address lists &-- they are recognized
9523 only if the # is preceded by white space or the start of the line.
9524 Otherwise, local part lists are matched in the same way as domain lists, except
9525 that the special items that refer to the local host (&`@`&, &`@[]`&,
9526 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
9527 Refer to section &<<SECTdomainlist>>& for details of the other available item
9529 .ecindex IIDdohoadli
9534 . ////////////////////////////////////////////////////////////////////////////
9535 . ////////////////////////////////////////////////////////////////////////////
9537 .chapter "String expansions" "CHAPexpand"
9538 .scindex IIDstrexp "expansion" "of strings"
9539 Many strings in Exim's runtime configuration are expanded before use. Some of
9540 them are expanded every time they are used; others are expanded only once.
9542 When a string is being expanded it is copied verbatim from left to right except
9543 .cindex expansion "string concatenation"
9544 when a dollar or backslash character is encountered. A dollar specifies the
9545 start of a portion of the string that is interpreted and replaced as described
9546 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
9547 escape character, as described in the following section.
9549 Whether a string is expanded depends upon the context. Usually this is solely
9550 dependent upon the option for which a value is sought; in this documentation,
9551 options for which string expansion is performed are marked with † after
9552 the data type. ACL rules always expand strings. A couple of expansion
9553 conditions do not expand some of the brace-delimited branches, for security
9555 .cindex "tainted data" expansion
9556 .cindex "tainted data" definition
9557 .cindex expansion "tainted data"
9558 and expansion of data deriving from the sender (&"tainted data"&)
9560 is not permitted (including acessing a file using a tainted name).
9564 Common ways of obtaining untainted equivalents of variables with
9566 .cindex "tainted data" "de-tainting"
9567 come down to using the tainted value as a lookup key in a trusted database.
9568 This database could be the filesystem structure,
9569 or the password file,
9570 or accessed via a DBMS.
9571 Specific methods are indexed under &"de-tainting"&.
9576 .section "Literal text in expanded strings" "SECTlittext"
9577 .cindex "expansion" "including literal text"
9578 An uninterpreted dollar can be included in an expanded string by putting a
9579 backslash in front of it. A backslash can be used to prevent any special
9580 character being treated specially in an expansion, including backslash itself.
9581 If the string appears in quotes in the configuration file, two backslashes are
9582 required because the quotes themselves cause interpretation of backslashes when
9583 the string is read in (see section &<<SECTstrings>>&).
9585 .cindex "expansion" "non-expandable substrings"
9586 A portion of the string can specified as non-expandable by placing it between
9587 two occurrences of &`\N`&. This is particularly useful for protecting regular
9588 expressions, which often contain backslashes and dollar signs. For example:
9590 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
9592 On encountering the first &`\N`&, the expander copies subsequent characters
9593 without interpretation until it reaches the next &`\N`& or the end of the
9598 .section "Character escape sequences in expanded strings" "SECID82"
9599 .cindex "expansion" "escape sequences"
9600 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9601 expanded string is recognized as an escape sequence for the character newline,
9602 carriage return, or tab, respectively. A backslash followed by up to three
9603 octal digits is recognized as an octal encoding for a single character, and a
9604 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9607 These escape sequences are also recognized in quoted strings when they are read
9608 in. Their interpretation in expansions as well is useful for unquoted strings,
9609 and for other cases such as looked-up strings that are then expanded.
9612 .section "Testing string expansions" "SECID83"
9613 .cindex "expansion" "testing"
9614 .cindex "testing" "string expansion"
9616 Many expansions can be tested by calling Exim with the &%-be%& option. This
9617 takes the command arguments, or lines from the standard input if there are no
9618 arguments, runs them through the string expansion code, and writes the results
9619 to the standard output. Variables based on configuration values are set up, but
9620 since no message is being processed, variables such as &$local_part$& have no
9621 value. Nevertheless the &%-be%& option can be useful for checking out file and
9622 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9625 Exim gives up its root privilege when it is called with the &%-be%& option, and
9626 instead runs under the uid and gid it was called with, to prevent users from
9627 using &%-be%& for reading files to which they do not have access.
9630 If you want to test expansions that include variables whose values are taken
9631 from a message, there are two other options that can be used. The &%-bem%&
9632 option is like &%-be%& except that it is followed by a filename. The file is
9633 read as a message before doing the test expansions. For example:
9635 exim -bem /tmp/test.message '$h_subject:'
9637 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9638 Exim message identifier. For example:
9640 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9642 This loads the message from Exim's spool before doing the test expansions, and
9643 is therefore restricted to admin users.
9646 .section "Forced expansion failure" "SECTforexpfai"
9647 .cindex "expansion" "forced failure"
9648 A number of expansions that are described in the following section have
9649 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9650 (which are sometimes called &"curly brackets"&). Which of the two strings is
9651 used depends on some condition that is evaluated as part of the expansion. If,
9652 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9653 the entire string expansion fails in a way that can be detected by the code
9654 that requested the expansion. This is called &"forced expansion failure"&, and
9655 its consequences depend on the circumstances. In some cases it is no different
9656 from any other expansion failure, but in others a different action may be
9657 taken. Such variations are mentioned in the documentation of the option that is
9663 .section "Expansion items" "SECTexpansionitems"
9664 The following items are recognized in expanded strings. White space may be used
9665 between sub-items that are keywords or substrings enclosed in braces inside an
9666 outer set of braces, to improve readability. &*Warning*&: Within braces,
9667 white space is significant.
9670 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9671 .cindex "expansion" "variables"
9672 Substitute the contents of the named variable, for example:
9677 The second form can be used to separate the name from subsequent alphanumeric
9678 characters. This form (using braces) is available only for variables; it does
9679 &'not'& apply to message headers. The names of the variables are given in
9680 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9681 given, the expansion fails.
9683 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9684 .cindex "expansion" "operators"
9685 The string is first itself expanded, and then the operation specified by
9686 <&'op'&> is applied to it. For example:
9690 The string starts with the first character after the colon, which may be
9691 leading white space. A list of operators is given in section &<<SECTexpop>>&
9692 below. The operator notation is used for simple expansion items that have just
9693 one argument, because it reduces the number of braces and therefore makes the
9694 string easier to understand.
9696 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9697 This item inserts &"basic"& header lines. It is described with the &%header%&
9698 expansion item below.
9701 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9702 .cindex "expansion" "calling an acl"
9703 .cindex "&%acl%&" "call from expansion"
9704 The name and zero to nine argument strings are first expanded separately. The expanded
9705 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9706 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9707 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9708 and may use the variables; if another acl expansion is used the values
9709 are restored after it returns. If the ACL sets
9710 a value using a "message =" modifier and returns accept or deny, the value becomes
9711 the result of the expansion.
9712 If no message is set and the ACL returns accept or deny
9713 the expansion result is an empty string.
9714 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9717 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
9718 .cindex authentication "results header"
9719 .cindex headers "authentication-results:"
9720 .cindex authentication "expansion item"
9721 This item returns a string suitable for insertion as an
9722 &'Authentication-Results:'&
9724 The given <&'authserv-id'&> is included in the result; typically this
9725 will be a domain name identifying the system performing the authentications.
9726 Methods that might be present in the result include:
9735 Example use (as an ACL modifier):
9737 add_header = :at_start:${authresults {$primary_hostname}}
9739 This is safe even if no authentication results are available.
9742 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9743 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9744 .cindex "expansion" "extracting certificate fields"
9745 .cindex "&%certextract%&" "certificate fields"
9746 .cindex "certificate" "extracting fields"
9747 The <&'certificate'&> must be a variable of type certificate.
9748 The field name is expanded and used to retrieve the relevant field from
9749 the certificate. Supported fields are:
9753 &`subject `& RFC4514 DN
9754 &`issuer `& RFC4514 DN
9759 &`subj_altname `& tagged list
9763 If the field is found,
9764 <&'string2'&> is expanded, and replaces the whole item;
9765 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9766 variable &$value$& contains the value that has been extracted. Afterwards, it
9767 is restored to any previous value it might have had.
9769 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9770 key is not found. If {<&'string2'&>} is also omitted, the value that was
9773 Some field names take optional modifiers, appended and separated by commas.
9775 The field selectors marked as "RFC4514" above
9776 output a Distinguished Name string which is
9778 parseable by Exim as a comma-separated tagged list
9779 (the exceptions being elements containing commas).
9780 RDN elements of a single type may be selected by
9781 a modifier of the type label; if so the expansion
9782 result is a list (newline-separated by default).
9783 The separator may be changed by another modifier of
9784 a right angle-bracket followed immediately by the new separator.
9785 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9787 The field selectors marked as "time" above
9788 take an optional modifier of "int"
9789 for which the result is the number of seconds since epoch.
9790 Otherwise the result is a human-readable string
9791 in the timezone selected by the main "timezone" option.
9793 The field selectors marked as "list" above return a list,
9794 newline-separated by default,
9795 (embedded separator characters in elements are doubled).
9796 The separator may be changed by a modifier of
9797 a right angle-bracket followed immediately by the new separator.
9799 The field selectors marked as "tagged" above
9800 prefix each list element with a type string and an equals sign.
9801 Elements of only one type may be selected by a modifier
9802 which is one of "dns", "uri" or "mail";
9803 if so the element tags are omitted.
9805 If not otherwise noted field values are presented in human-readable form.
9807 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9808 {*&<&'arg'&>&*}...}*&"
9810 This expansion dynamically loads and then calls a locally-written C function.
9811 This functionality is available only if Exim is compiled with
9815 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9816 object so that it doesn't reload the same object file in the same Exim process
9817 (but of course Exim does start new processes frequently).
9819 There may be from zero to eight arguments to the function.
9822 a local function that is to be called in this way,
9823 first &_DLFUNC_IMPL_& should be defined,
9824 and second &_local_scan.h_& should be included.
9825 The Exim variables and functions that are defined by that API
9826 are also available for dynamically loaded functions. The function itself
9827 must have the following type:
9829 int dlfunction(uschar **yield, int argc, uschar *argv[])
9831 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9832 function should return one of the following values:
9834 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9835 into the expanded string that is being built.
9837 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9838 from &'yield'&, if it is set.
9840 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9841 taken from &'yield'& if it is set.
9843 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9845 When compiling a function that is to be used in this way with gcc,
9846 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9847 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9850 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9851 .cindex "expansion" "extracting value from environment"
9852 .cindex "environment" "values from"
9853 The key is first expanded separately, and leading and trailing white space
9855 This is then searched for as a name in the environment.
9856 If a variable is found then its value is placed in &$value$&
9857 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9859 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9860 appear, for example:
9862 ${env{USER}{$value} fail }
9864 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9865 {<&'string1'&>} must be present for &"fail"& to be recognized.
9867 If {<&'string2'&>} is omitted an empty string is substituted on
9869 If {<&'string1'&>} is omitted the search result is substituted on
9872 The environment is adjusted by the &%keep_environment%& and
9873 &%add_environment%& main section options.
9876 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9877 {*&<&'string3'&>&*}}*&"
9878 .cindex "expansion" "extracting substrings by key"
9879 .cindex "&%extract%&" "substrings by key"
9880 The key and <&'string1'&> are first expanded separately. Leading and trailing
9881 white space is removed from the key (but not from any of the strings). The key
9882 must not be empty and must not consist entirely of digits.
9883 The expanded <&'string1'&> must be of the form:
9885 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9888 where the equals signs and spaces (but not both) are optional. If any of the
9889 values contain white space, they must be enclosed in double quotes, and any
9890 values that are enclosed in double quotes are subject to escape processing as
9891 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9892 for the value that corresponds to the key. The search is case-insensitive. If
9893 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9894 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9895 variable &$value$& contains the value that has been extracted. Afterwards, it
9896 is restored to any previous value it might have had.
9898 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9899 key is not found. If {<&'string2'&>} is also omitted, the value that was
9900 extracted is used. Thus, for example, these two expansions are identical, and
9903 ${extract{gid}{uid=1984 gid=2001}}
9904 ${extract{gid}{uid=1984 gid=2001}{$value}}
9906 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9907 appear, for example:
9909 ${extract{Z}{A=... B=...}{$value} fail }
9911 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9912 {<&'string2'&>} must be present for &"fail"& to be recognized.
9914 .vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9915 {*&<&'string3'&>&*}}*&" &&&
9916 "&*${extract jsons{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9917 {*&<&'string3'&>&*}}*&"
9918 .cindex "expansion" "extracting from JSON object"
9919 .cindex JSON expansions
9920 The key and <&'string1'&> are first expanded separately. Leading and trailing
9921 white space is removed from the key (but not from any of the strings). The key
9922 must not be empty and must not consist entirely of digits.
9923 The expanded <&'string1'&> must be of the form:
9925 { <&'"key1"'&> : <&'value1'&> , <&'"key2"'&> , <&'value2'&> ... }
9928 The braces, commas and colons, and the quoting of the member name are required;
9929 the spaces are optional.
9930 Matching of the key against the member names is done case-sensitively.
9931 For the &"json"& variant,
9932 if a returned value is a JSON string, it retains its leading and
9934 For the &"jsons"& variant, which is intended for use with JSON strings, the
9935 leading and trailing quotes are removed from the returned value.
9936 . XXX should be a UTF-8 compare
9938 The results of matching are handled as above.
9941 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9942 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9943 .cindex "expansion" "extracting substrings by number"
9944 .cindex "&%extract%&" "substrings by number"
9945 The <&'number'&> argument must consist entirely of decimal digits,
9946 apart from leading and trailing white space, which is ignored.
9947 This is what distinguishes this form of &%extract%& from the previous kind. It
9948 behaves in the same way, except that, instead of extracting a named field, it
9949 extracts from <&'string1'&> the field whose number is given as the first
9950 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9951 <&'string3'&> as before.
9953 The fields in the string are separated by any one of the characters in the
9954 separator string. These may include space or tab characters.
9955 The first field is numbered one. If the number is negative, the fields are
9956 counted from the end of the string, with the rightmost one numbered -1. If the
9957 number given is zero, the entire string is returned. If the modulus of the
9958 number is greater than the number of fields in the string, the result is the
9959 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9960 provided. For example:
9962 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9966 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9968 yields &"99"&. Two successive separators mean that the field between them is
9969 empty (for example, the fifth field above).
9972 .vitem "&*${extract json {*&<&'number'&>&*}}&&&
9973 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" &&&
9974 "&*${extract jsons{*&<&'number'&>&*}}&&&
9975 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9976 .cindex "expansion" "extracting from JSON array"
9977 .cindex JSON expansions
9978 The <&'number'&> argument must consist entirely of decimal digits,
9979 apart from leading and trailing white space, which is ignored.
9981 Field selection and result handling is as above;
9982 there is no choice of field separator.
9983 For the &"json"& variant,
9984 if a returned value is a JSON string, it retains its leading and
9986 For the &"jsons"& variant, which is intended for use with JSON strings, the
9987 leading and trailing quotes are removed from the returned value.
9990 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9991 .cindex "list" "selecting by condition"
9992 .cindex "expansion" "selecting from list by condition"
9994 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9995 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
9997 in this list, its value is place in &$item$&, and then the condition is
9998 evaluated. If the condition is true, &$item$& is added to the output as an
9999 item in a new list; if the condition is false, the item is discarded. The
10000 separator used for the output list is the same as the one used for the
10001 input, but a separator setting is not included in the output. For example:
10003 ${filter{a:b:c}{!eq{$item}{b}}}
10005 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
10006 to what it was before. See also the &%map%& and &%reduce%& expansion items.
10009 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10010 .cindex "hash function" "textual"
10011 .cindex "expansion" "textual hash"
10012 This is a textual hashing function, and was the first to be implemented in
10013 early versions of Exim. In current releases, there are other hashing functions
10014 (numeric, MD5, and SHA-1), which are described below.
10016 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
10017 <&'n'&>. If you are using fixed values for these numbers, that is, if
10018 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
10019 use the simpler operator notation that avoids some of the braces:
10021 ${hash_<n>_<m>:<string>}
10023 The second number is optional (in both notations). If <&'n'&> is greater than
10024 or equal to the length of the string, the expansion item returns the string.
10025 Otherwise it computes a new string of length <&'n'&> by applying a hashing
10026 function to the string. The new string consists of characters taken from the
10027 first <&'m'&> characters of the string
10029 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
10031 If <&'m'&> is not present the value 26 is used, so that only lower case
10032 letters appear. For example:
10034 &`$hash{3}{monty}} `& yields &`jmg`&
10035 &`$hash{5}{monty}} `& yields &`monty`&
10036 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
10039 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
10040 &*$h_*&<&'header&~name'&>&*:*&" &&&
10041 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10042 &*$bh_*&<&'header&~name'&>&*:*&" &&&
10043 "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10044 &*$lh_*&<&'header&~name'&>&*:*&" &&&
10045 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10046 &*$rh_*&<&'header&~name'&>&*:*&"
10047 .cindex "expansion" "header insertion"
10048 .vindex "&$header_$&"
10049 .vindex "&$bheader_$&"
10050 .vindex "&$lheader_$&"
10051 .vindex "&$rheader_$&"
10052 .cindex "header lines" "in expansion strings"
10053 .cindex "header lines" "character sets"
10054 .cindex "header lines" "decoding"
10055 Substitute the contents of the named message header line, for example
10059 The newline that terminates a header line is not included in the expansion, but
10060 internal newlines (caused by splitting the header line over several physical
10061 lines) may be present.
10063 The difference between the four pairs of expansions is in the way
10064 the data in the header line is interpreted.
10067 .cindex "white space" "in header lines"
10068 &%rheader%& gives the original &"raw"& content of the header line, with no
10069 processing at all, and without the removal of leading and trailing white space.
10072 .cindex "list" "of header lines"
10073 &%lheader%& gives a colon-separated list, one element per header when there
10074 are multiple headers with a given name.
10075 Any embedded colon characters within an element are doubled, so normal Exim
10076 list-processing facilities can be used.
10077 The terminating newline of each element is removed; in other respects
10078 the content is &"raw"&.
10081 .cindex "base64 encoding" "in header lines"
10082 &%bheader%& removes leading and trailing white space, and then decodes base64
10083 or quoted-printable MIME &"words"& within the header text, but does no
10084 character set translation. If decoding of what looks superficially like a MIME
10085 &"word"& fails, the raw string is returned. If decoding
10086 .cindex "binary zero" "in header line"
10087 produces a binary zero character, it is replaced by a question mark &-- this is
10088 what Exim does for binary zeros that are actually received in header lines.
10091 &%header%& tries to translate the string as decoded by &%bheader%& to a
10092 standard character set. This is an attempt to produce the same string as would
10093 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
10094 returned. Translation is attempted only on operating systems that support the
10095 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
10096 a system Makefile or in &_Local/Makefile_&.
10099 In a filter file, the target character set for &%header%& can be specified by a
10100 command of the following form:
10102 headers charset "UTF-8"
10104 This command affects all references to &$h_$& (or &$header_$&) expansions in
10105 subsequently obeyed filter commands. In the absence of this command, the target
10106 character set in a filter is taken from the setting of the &%headers_charset%&
10107 option in the runtime configuration. The value of this option defaults to the
10108 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
10111 Header names follow the syntax of RFC 2822, which states that they may contain
10112 any printing characters except space and colon. Consequently, curly brackets
10113 &'do not'& terminate header names, and should not be used to enclose them as
10114 if they were variables. Attempting to do so causes a syntax error.
10116 Only header lines that are common to all copies of a message are visible to
10117 this mechanism. These are the original header lines that are received with the
10118 message, and any that are added by an ACL statement or by a system
10119 filter. Header lines that are added to a particular copy of a message by a
10120 router or transport are not accessible.
10122 For incoming SMTP messages, no header lines are visible in
10123 ACLs that are obeyed before the data phase completes,
10124 because the header structure is not set up until the message is received.
10125 They are visible in DKIM, PRDR and DATA ACLs.
10126 Header lines that are added in a RCPT ACL (for example)
10127 are saved until the message's incoming header lines are available, at which
10128 point they are added.
10129 When any of the above ACLs ar
10130 running, however, header lines added by earlier ACLs are visible.
10132 Upper case and lower case letters are synonymous in header names. If the
10133 following character is white space, the terminating colon may be omitted, but
10134 this is not recommended, because you may then forget it when it is needed. When
10135 white space terminates the header name, this white space is included in the
10136 expanded string. If the message does not contain the given header, the
10137 expansion item is replaced by an empty string. (See the &%def%& condition in
10138 section &<<SECTexpcond>>& for a means of testing for the existence of a
10141 If there is more than one header with the same name, they are all concatenated
10142 to form the substitution string, up to a maximum length of 64K. Unless
10143 &%rheader%& is being used, leading and trailing white space is removed from
10144 each header before concatenation, and a completely empty header is ignored. A
10145 newline character is then inserted between non-empty headers, but there is no
10146 newline at the very end. For the &%header%& and &%bheader%& expansion, for
10147 those headers that contain lists of addresses, a comma is also inserted at the
10148 junctions between headers. This does not happen for the &%rheader%& expansion.
10150 .cindex "tainted data" "message headers"
10151 When the headers are from an incoming message,
10152 the result of expanding any of these variables is tainted.
10155 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
10156 .cindex "expansion" "hmac hashing"
10158 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
10159 shared secret and some text into a message authentication code, as specified in
10160 RFC 2104. This differs from &`${md5:secret_text...}`& or
10161 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
10162 cryptographic hash, allowing for authentication that is not possible with MD5
10163 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
10164 present. For example:
10166 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
10168 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
10171 dd97e3ba5d1a61b5006108f8c8252953
10173 As an example of how this might be used, you might put in the main part of
10174 an Exim configuration:
10176 SPAMSCAN_SECRET=cohgheeLei2thahw
10178 In a router or a transport you could then have:
10181 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
10182 ${hmac{md5}{SPAMSCAN_SECRET}\
10183 {${primary_hostname},${message_exim_id},$h_message-id:}}
10185 Then given a message, you can check where it was scanned by looking at the
10186 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
10187 this header line is authentic by recomputing the authentication code from the
10188 host name, message ID and the &'Message-id:'& header line. This can be done
10189 using Exim's &%-be%& option, or by other means, for example, by using the
10190 &'hmac_md5_hex()'& function in Perl.
10193 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10194 .cindex "expansion" "conditional"
10195 .cindex "&%if%&, expansion item"
10196 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
10197 item; otherwise <&'string2'&> is used. The available conditions are described
10198 in section &<<SECTexpcond>>& below. For example:
10200 ${if eq {$local_part}{postmaster} {yes}{no} }
10202 The second string need not be present; if it is not and the condition is not
10203 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
10204 be present instead of the second string (without any curly brackets). In this
10205 case, the expansion is forced to fail if the condition is not true (see section
10206 &<<SECTforexpfai>>&).
10208 If both strings are omitted, the result is the string &`true`& if the condition
10209 is true, and the empty string if the condition is false. This makes it less
10210 cumbersome to write custom ACL and router conditions. For example, instead of
10212 condition = ${if >{$acl_m4}{3}{true}{false}}
10216 condition = ${if >{$acl_m4}{3}}
10221 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
10222 .cindex expansion "imap folder"
10223 .cindex "&%imapfolder%& expansion item"
10224 This item converts a (possibly multilevel, or with non-ASCII characters)
10225 folder specification to a Maildir name for filesystem use.
10226 For information on internationalisation support see &<<SECTi18nMDA>>&.
10230 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10231 .cindex "expansion" "string truncation"
10232 .cindex "&%length%& expansion item"
10233 The &%length%& item is used to extract the initial portion of a string. Both
10234 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
10235 you are using a fixed value for the number, that is, if <&'string1'&> does not
10236 change when expanded, you can use the simpler operator notation that avoids
10237 some of the braces:
10239 ${length_<n>:<string>}
10241 The result of this item is either the first <&'n'&> bytes or the whole
10242 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
10243 &%strlen%&, which gives the length of a string.
10244 All measurement is done in bytes and is not UTF-8 aware.
10247 .vitem "&*${listextract{*&<&'number'&>&*}&&&
10248 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10249 .cindex "expansion" "extracting list elements by number"
10250 .cindex "&%listextract%&" "extract list elements by number"
10251 .cindex "list" "extracting elements by number"
10252 The <&'number'&> argument must consist entirely of decimal digits,
10253 apart from an optional leading minus,
10254 and leading and trailing white space (which is ignored).
10256 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10257 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10259 The first field of the list is numbered one.
10260 If the number is negative, the fields are
10261 counted from the end of the list, with the rightmost one numbered -1.
10262 The numbered element of the list is extracted and placed in &$value$&,
10263 then <&'string2'&> is expanded as the result.
10265 If the modulus of the
10266 number is zero or greater than the number of fields in the string,
10267 the result is the expansion of <&'string3'&>.
10271 ${listextract{2}{x:42:99}}
10275 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
10277 yields &"result: 42"&.
10279 If {<&'string3'&>} is omitted, an empty string is used for string3.
10280 If {<&'string2'&>} is also omitted, the value that was
10282 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
10286 .vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*&
10287 .cindex quoting "for list"
10288 .cindex list quoting
10289 This item doubles any occurrence of the separator character
10290 in the given string.
10291 An empty string is replaced with a single space.
10292 This converts the string into a safe form for use as a list element,
10293 in a list using the given separator.
10297 .vitem "&*${lookup&~{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
10298 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" &&&
10299 "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
10300 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
10301 .cindex "expansion" "lookup in"
10302 .cindex "file" "lookups"
10303 .cindex "lookup" "in expanded string"
10304 The two forms of lookup item specify data lookups in files and databases, as
10305 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
10306 lookups, and the second is used for query-style lookups. The <&'key'&>,
10307 <&'file'&>, and <&'query'&> strings are expanded before use.
10309 If there is any white space in a lookup item which is part of a filter command,
10310 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
10311 other place where white space is significant, the lookup item must be enclosed
10312 in double quotes. The use of data lookups in users' filter files may be locked
10313 out by the system administrator.
10315 .vindex "&$value$&"
10316 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
10317 During its expansion, the variable &$value$& contains the data returned by the
10318 lookup. Afterwards it reverts to the value it had previously (at the outer
10319 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
10320 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
10321 string on failure. If <&'string2'&> is provided, it can itself be a nested
10322 lookup, thus providing a mechanism for looking up a default value when the
10323 original lookup fails.
10325 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
10326 data for the outer lookup while the parameters of the second lookup are
10327 expanded, and also while <&'string2'&> of the second lookup is expanded, should
10328 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
10329 appear, and in this case, if the lookup fails, the entire expansion is forced
10330 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
10331 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
10332 successful lookup, and nothing in the case of failure.
10334 For single-key lookups, the string &"partial"& is permitted to precede the
10335 search type in order to do partial matching, and * or *@ may follow a search
10336 type to request default lookups if the key does not match (see sections
10337 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
10339 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
10340 If a partial search is used, the variables &$1$& and &$2$& contain the wild
10341 and non-wild parts of the key during the expansion of the replacement text.
10342 They return to their previous values at the end of the lookup item.
10344 This example looks up the postmaster alias in the conventional alias file:
10346 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
10348 This example uses NIS+ to look up the full name of the user corresponding to
10349 the local part of an address, forcing the expansion to fail if it is not found:
10351 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
10356 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10357 .cindex "expansion" "list creation"
10359 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10360 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10362 in this list, its value is place in &$item$&, and then <&'string2'&> is
10363 expanded and added to the output as an item in a new list. The separator used
10364 for the output list is the same as the one used for the input, but a separator
10365 setting is not included in the output. For example:
10367 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
10369 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
10370 value of &$item$& is restored to what it was before. See also the &%filter%&
10371 and &%reduce%& expansion items.
10373 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10374 .cindex "expansion" "numeric hash"
10375 .cindex "hash function" "numeric"
10376 The three strings are expanded; the first two must yield numbers. Call them
10377 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10378 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10379 can use the simpler operator notation that avoids some of the braces:
10381 ${nhash_<n>_<m>:<string>}
10383 The second number is optional (in both notations). If there is only one number,
10384 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
10385 processed by a div/mod hash function that returns two numbers, separated by a
10386 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
10389 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
10391 returns the string &"6/33"&.
10395 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
10396 .cindex "Perl" "use in expanded string"
10397 .cindex "expansion" "calling Perl from"
10398 This item is available only if Exim has been built to include an embedded Perl
10399 interpreter. The subroutine name and the arguments are first separately
10400 expanded, and then the Perl subroutine is called with those arguments. No
10401 additional arguments need be given; the maximum number permitted, including the
10402 name of the subroutine, is nine.
10404 The return value of the subroutine is inserted into the expanded string, unless
10405 the return value is &%undef%&. In that case, the expansion fails in the same
10406 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
10407 Whatever you return is evaluated in a scalar context. For example, if you
10408 return the name of a Perl vector, the return value is the size of the vector,
10411 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
10412 with the error message that was passed to &%die%&. More details of the embedded
10413 Perl facility are given in chapter &<<CHAPperl>>&.
10415 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
10416 out the use of this expansion item in filter files.
10419 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
10420 .cindex "&%prvs%& expansion item"
10421 The first argument is a complete email address and the second is secret
10422 keystring. The third argument, specifying a key number, is optional. If absent,
10423 it defaults to 0. The result of the expansion is a prvs-signed email address,
10424 to be typically used with the &%return_path%& option on an &(smtp)& transport
10425 as part of a bounce address tag validation (BATV) scheme. For more discussion
10426 and an example, see section &<<SECTverifyPRVS>>&.
10428 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
10429 {*&<&'string'&>&*}}*&"
10430 .cindex "&%prvscheck%& expansion item"
10431 This expansion item is the complement of the &%prvs%& item. It is used for
10432 checking prvs-signed addresses. If the expansion of the first argument does not
10433 yield a syntactically valid prvs-signed address, the whole item expands to the
10434 empty string. When the first argument does expand to a syntactically valid
10435 prvs-signed address, the second argument is expanded, with the prvs-decoded
10436 version of the address and the key number extracted from the address in the
10437 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
10439 These two variables can be used in the expansion of the second argument to
10440 retrieve the secret. The validity of the prvs-signed address is then checked
10441 against the secret. The result is stored in the variable &$prvscheck_result$&,
10442 which is empty for failure or &"1"& for success.
10444 The third argument is optional; if it is missing, it defaults to an empty
10445 string. This argument is now expanded. If the result is an empty string, the
10446 result of the expansion is the decoded version of the address. This is the case
10447 whether or not the signature was valid. Otherwise, the result of the expansion
10448 is the expansion of the third argument.
10450 All three variables can be used in the expansion of the third argument.
10451 However, once the expansion is complete, only &$prvscheck_result$& remains set.
10452 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
10454 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
10455 .cindex "expansion" "inserting an entire file"
10456 .cindex "file" "inserting into expansion"
10457 .cindex "&%readfile%& expansion item"
10458 The filename and end-of-line string are first expanded separately. The file is
10459 then read, and its contents replace the entire item. All newline characters in
10460 the file are replaced by the end-of-line string if it is present. Otherwise,
10461 newlines are left in the string.
10462 String expansion is not applied to the contents of the file. If you want this,
10463 you must wrap the item in an &%expand%& operator. If the file cannot be read,
10464 the string expansion fails.
10466 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
10467 locks out the use of this expansion item in filter files.
10471 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
10472 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
10473 .cindex "expansion" "inserting from a socket"
10474 .cindex "socket, use of in expansion"
10475 .cindex "&%readsocket%& expansion item"
10476 This item inserts data from a Unix domain or TCP socket into the expanded
10477 string. The minimal way of using it uses just two arguments, as in these
10480 ${readsocket{/socket/name}{request string}}
10481 ${readsocket{inet:some.host:1234}{request string}}
10483 For a Unix domain socket, the first substring must be the path to the socket.
10484 For an Internet socket, the first substring must contain &`inet:`& followed by
10485 a host name or IP address, followed by a colon and a port, which can be a
10486 number or the name of a TCP port in &_/etc/services_&. An IP address may
10487 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
10490 ${readsocket{inet:[::1]:1234}{request string}}
10492 Only a single host name may be given, but if looking it up yields more than
10493 one IP address, they are each tried in turn until a connection is made. For
10494 both kinds of socket, Exim makes a connection, writes the request string
10495 unless it is an empty string; and no terminating NUL is ever sent)
10496 and reads from the socket until an end-of-file
10497 is read. A timeout of 5 seconds is applied. Additional, optional arguments
10498 extend what can be done. Firstly, you can vary the timeout. For example:
10500 ${readsocket{/socket/name}{request string}{3s}}
10503 The third argument is a list of options, of which the first element is the timeout
10504 and must be present if any options are given.
10505 Further elements are options of form &'name=value'&.
10508 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
10511 The following option names are recognised:
10514 Defines if the result data can be cached for use by a later identical
10515 request in the same process.
10516 Values are &"yes"& or &"no"& (the default).
10517 If not, all cached results for this connection specification
10518 will be invalidated.
10522 Defines whether or not a write-shutdown is done on the connection after
10523 sending the request. Values are &"yes"& (the default) or &"no"&
10524 (preferred, eg. by some webservers).
10528 Controls the use of TLS on the connection.
10529 Values are &"yes"& or &"no"& (the default).
10530 If it is enabled, a shutdown as descripbed above is never done.
10534 A fourth argument allows you to change any newlines that are in the data
10535 that is read, in the same way as for &%readfile%& (see above). This example
10536 turns them into spaces:
10538 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
10540 As with all expansions, the substrings are expanded before the processing
10541 happens. Errors in these sub-expansions cause the expansion to fail. In
10542 addition, the following errors can occur:
10545 Failure to create a socket file descriptor;
10547 Failure to connect the socket;
10549 Failure to write the request string;
10551 Timeout on reading from the socket.
10554 By default, any of these errors causes the expansion to fail. However, if
10555 you supply a fifth substring, it is expanded and used when any of the above
10556 errors occurs. For example:
10558 ${readsocket{/socket/name}{request string}{3s}{\n}\
10561 You can test for the existence of a Unix domain socket by wrapping this
10562 expansion in &`${if exists`&, but there is a race condition between that test
10563 and the actual opening of the socket, so it is safer to use the fifth argument
10564 if you want to be absolutely sure of avoiding an expansion error for a
10565 non-existent Unix domain socket, or a failure to connect to an Internet socket.
10567 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
10568 locks out the use of this expansion item in filter files.
10571 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10572 .cindex "expansion" "reducing a list to a scalar"
10573 .cindex "list" "reducing to a scalar"
10574 .vindex "&$value$&"
10576 This operation reduces a list to a single, scalar string. After expansion,
10577 <&'string1'&> is interpreted as a list, colon-separated by default, but the
10578 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10579 Then <&'string2'&> is expanded and
10580 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
10581 list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
10582 them. The result of that expansion is assigned to &$value$& before the next
10583 iteration. When the end of the list is reached, the final value of &$value$& is
10584 added to the expansion output. The &%reduce%& expansion item can be used in a
10585 number of ways. For example, to add up a list of numbers:
10587 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
10589 The result of that expansion would be &`6`&. The maximum of a list of numbers
10592 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
10594 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
10595 restored to what they were before. See also the &%filter%& and &%map%&
10598 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
10599 This item inserts &"raw"& header lines. It is described with the &%header%&
10600 expansion item in section &<<SECTexpansionitems>>& above.
10602 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
10603 {*&<&'string2'&>&*}}*&"
10604 .cindex "expansion" "running a command"
10605 .cindex "&%run%& expansion item"
10606 The command and its arguments are first expanded as one string. The string is
10607 split apart into individual arguments by spaces, and then the command is run
10608 in a separate process, but under the same uid and gid. As in other command
10609 executions from Exim, a shell is not used by default. If the command requires
10610 a shell, you must explicitly code it.
10612 Since the arguments are split by spaces, when there is a variable expansion
10613 which has an empty result, it will cause the situation that the argument will
10614 simply be omitted when the program is actually executed by Exim. If the
10615 script/program requires a specific number of arguments and the expanded
10616 variable could possibly result in this empty expansion, the variable must be
10617 quoted. This is more difficult if the expanded variable itself could result
10618 in a string containing quotes, because it would interfere with the quotes
10619 around the command arguments. A possible guard against this is to wrap the
10620 variable in the &%sg%& operator to change any quote marks to some other
10623 The standard input for the command exists, but is empty. The standard output
10624 and standard error are set to the same file descriptor.
10625 .cindex "return code" "from &%run%& expansion"
10626 .vindex "&$value$&"
10627 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
10628 and replaces the entire item; during this expansion, the standard output/error
10629 from the command is in the variable &$value$&. If the command fails,
10630 <&'string2'&>, if present, is expanded and used. Once again, during the
10631 expansion, the standard output/error from the command is in the variable
10634 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
10635 can be the word &"fail"& (not in braces) to force expansion failure if the
10636 command does not succeed. If both strings are omitted, the result is contents
10637 of the standard output/error on success, and nothing on failure.
10639 .vindex "&$run_in_acl$&"
10640 The standard output/error of the command is put in the variable &$value$&.
10641 In this ACL example, the output of a command is logged for the admin to
10644 warn condition = ${run{/usr/bin/id}{yes}{no}}
10645 log_message = Output of id: $value
10647 If the command requires shell idioms, such as the > redirect operator, the
10648 shell must be invoked directly, such as with:
10650 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
10653 .vindex "&$runrc$&"
10654 The return code from the command is put in the variable &$runrc$&, and this
10655 remains set afterwards, so in a filter file you can do things like this:
10657 if "${run{x y z}{}}$runrc" is 1 then ...
10658 elif $runrc is 2 then ...
10662 If execution of the command fails (for example, the command does not exist),
10663 the return code is 127 &-- the same code that shells use for non-existent
10666 &*Warning*&: In a router or transport, you cannot assume the order in which
10667 option values are expanded, except for those preconditions whose order of
10668 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
10669 by the expansion of one option, and use it in another.
10671 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
10672 out the use of this expansion item in filter files.
10675 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
10676 .cindex "expansion" "string substitution"
10677 .cindex "&%sg%& expansion item"
10678 This item works like Perl's substitution operator (s) with the global (/g)
10679 option; hence its name. However, unlike the Perl equivalent, Exim does not
10680 modify the subject string; instead it returns the modified string for insertion
10681 into the overall expansion. The item takes three arguments: the subject string,
10682 a regular expression, and a substitution string. For example:
10684 ${sg{abcdefabcdef}{abc}{xyz}}
10686 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
10687 if any $, } or \ characters are required in the regular expression or in the
10688 substitution string, they have to be escaped. For example:
10690 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
10692 yields &"defabc"&, and
10694 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
10696 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
10697 the regular expression from string expansion.
10699 The regular expression is compiled in 8-bit mode, working against bytes
10700 rather than any Unicode-aware character handling.
10703 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
10704 .cindex sorting "a list"
10705 .cindex list sorting
10706 .cindex expansion "list sorting"
10707 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10708 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10709 The <&'comparator'&> argument is interpreted as the operator
10710 of a two-argument expansion condition.
10711 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
10712 The comparison should return true when applied to two values
10713 if the first value should sort before the second value.
10714 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
10715 the element being placed in &$item$&,
10716 to give values for comparison.
10718 The item result is a sorted list,
10719 with the original list separator,
10720 of the list elements (in full) of the original.
10724 ${sort{3:2:1:4}{<}{$item}}
10726 sorts a list of numbers, and
10728 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10730 will sort an MX lookup into priority order.
10735 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
10736 SRS encoding. See SECT &<<SECTSRS>>& for details.
10741 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10742 .cindex "&%substr%& expansion item"
10743 .cindex "substring extraction"
10744 .cindex "expansion" "substring extraction"
10745 The three strings are expanded; the first two must yield numbers. Call them
10746 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10747 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10748 can use the simpler operator notation that avoids some of the braces:
10750 ${substr_<n>_<m>:<string>}
10752 The second number is optional (in both notations).
10753 If it is absent in the simpler format, the preceding underscore must also be
10756 The &%substr%& item can be used to extract more general substrings than
10757 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10758 length required. For example
10760 ${substr{3}{2}{$local_part}}
10762 If the starting offset is greater than the string length the result is the
10763 null string; if the length plus starting offset is greater than the string
10764 length, the result is the right-hand part of the string, starting from the
10765 given offset. The first byte (character) in the string has offset zero.
10767 The &%substr%& expansion item can take negative offset values to count
10768 from the right-hand end of its operand. The last byte (character) is offset -1,
10769 the second-last is offset -2, and so on. Thus, for example,
10771 ${substr{-5}{2}{1234567}}
10773 yields &"34"&. If the absolute value of a negative offset is greater than the
10774 length of the string, the substring starts at the beginning of the string, and
10775 the length is reduced by the amount of overshoot. Thus, for example,
10777 ${substr{-5}{2}{12}}
10779 yields an empty string, but
10781 ${substr{-3}{2}{12}}
10785 When the second number is omitted from &%substr%&, the remainder of the string
10786 is taken if the offset is positive. If it is negative, all bytes (characters) in the
10787 string preceding the offset point are taken. For example, an offset of -1 and
10788 no length, as in these semantically identical examples:
10791 ${substr{-1}{abcde}}
10793 yields all but the last character of the string, that is, &"abcd"&.
10795 All measurement is done in bytes and is not UTF-8 aware.
10799 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10800 {*&<&'replacements'&>&*}}*&"
10801 .cindex "expansion" "character translation"
10802 .cindex "&%tr%& expansion item"
10803 This item does single-character (in bytes) translation on its subject string. The second
10804 argument is a list of characters to be translated in the subject string. Each
10805 matching character is replaced by the corresponding character from the
10806 replacement list. For example
10808 ${tr{abcdea}{ac}{13}}
10810 yields &`1b3de1`&. If there are duplicates in the second character string, the
10811 last occurrence is used. If the third string is shorter than the second, its
10812 last character is replicated. However, if it is empty, no translation takes
10815 All character handling is done in bytes and is not UTF-8 aware.
10821 .section "Expansion operators" "SECTexpop"
10822 .cindex "expansion" "operators"
10823 For expansion items that perform transformations on a single argument string,
10824 the &"operator"& notation is used because it is simpler and uses fewer braces.
10825 The substring is first expanded before the operation is applied to it. The
10826 following operations can be performed:
10829 .vitem &*${address:*&<&'string'&>&*}*&
10830 .cindex "expansion" "RFC 2822 address handling"
10831 .cindex "&%address%& expansion item"
10832 The string is interpreted as an RFC 2822 address, as it might appear in a
10833 header line, and the effective address is extracted from it. If the string does
10834 not parse successfully, the result is empty.
10836 The parsing correctly handles SMTPUTF8 Unicode in the string.
10839 .vitem &*${addresses:*&<&'string'&>&*}*&
10840 .cindex "expansion" "RFC 2822 address handling"
10841 .cindex "&%addresses%& expansion item"
10842 The string (after expansion) is interpreted as a list of addresses in RFC
10843 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10844 operative address (&'local-part@domain'&) is extracted from each item, and the
10845 result of the expansion is a colon-separated list, with appropriate
10846 doubling of colons should any happen to be present in the email addresses.
10847 Syntactically invalid RFC2822 address items are omitted from the output.
10849 It is possible to specify a character other than colon for the output
10850 separator by starting the string with > followed by the new separator
10851 character. For example:
10853 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10855 expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
10856 first, so if the expanded string starts with >, it may change the output
10857 separator unintentionally. This can be avoided by setting the output
10858 separator explicitly:
10860 ${addresses:>:$h_from:}
10863 Compare the &%address%& (singular)
10864 expansion item, which extracts the working address from a single RFC2822
10865 address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
10868 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10869 a strict interpretation of header line formatting. Exim parses the bare,
10870 unquoted portion of an email address and if it finds a comma, treats it as an
10871 email address separator. For the example header line:
10873 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10875 The first example below demonstrates that Q-encoded email addresses are parsed
10876 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10877 It does not see the comma because it's still encoded as "=2C". The second
10878 example below is passed the contents of &`$header_from:`&, meaning it gets
10879 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10880 The third example shows that the presence of a comma is skipped when it is
10881 quoted. The fourth example shows SMTPUTF8 handling.
10883 # exim -be '${addresses:From: \
10884 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10886 # exim -be '${addresses:From: Last, First <user@example.com>}'
10887 Last:user@example.com
10888 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10890 # exim -be '${addresses:フィル <フィリップ@example.jp>}'
10894 .vitem &*${base32:*&<&'digits'&>&*}*&
10895 .cindex "&%base32%& expansion item"
10896 .cindex "expansion" "conversion to base 32"
10897 The string must consist entirely of decimal digits. The number is converted to
10898 base 32 and output as a (empty, for zero) string of characters.
10899 Only lowercase letters are used.
10901 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10902 .cindex "&%base32d%& expansion item"
10903 .cindex "expansion" "conversion to base 32"
10904 The string must consist entirely of base-32 digits.
10905 The number is converted to decimal and output as a string.
10907 .vitem &*${base62:*&<&'digits'&>&*}*&
10908 .cindex "&%base62%& expansion item"
10909 .cindex "expansion" "conversion to base 62"
10910 The string must consist entirely of decimal digits. The number is converted to
10911 base 62 and output as a string of six characters, including leading zeros. In
10912 the few operating environments where Exim uses base 36 instead of base 62 for
10913 its message identifiers (because those systems do not have case-sensitive
10914 filenames), base 36 is used by this operator, despite its name. &*Note*&: Just
10915 to be absolutely clear: this is &'not'& base64 encoding.
10917 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10918 .cindex "&%base62d%& expansion item"
10919 .cindex "expansion" "conversion to base 62"
10920 The string must consist entirely of base-62 digits, or, in operating
10921 environments where Exim uses base 36 instead of base 62 for its message
10922 identifiers, base-36 digits. The number is converted to decimal and output as a
10925 .vitem &*${base64:*&<&'string'&>&*}*&
10926 .cindex "expansion" "base64 encoding"
10927 .cindex "base64 encoding" "in string expansion"
10928 .cindex "&%base64%& expansion item"
10929 .cindex certificate "base64 of DER"
10930 This operator converts a string into one that is base64 encoded.
10932 If the string is a single variable of type certificate,
10933 returns the base64 encoding of the DER form of the certificate.
10936 .vitem &*${base64d:*&<&'string'&>&*}*&
10937 .cindex "expansion" "base64 decoding"
10938 .cindex "base64 decoding" "in string expansion"
10939 .cindex "&%base64d%& expansion item"
10940 This operator converts a base64-encoded string into the un-coded form.
10943 .vitem &*${domain:*&<&'string'&>&*}*&
10944 .cindex "domain" "extraction"
10945 .cindex "expansion" "domain extraction"
10946 The string is interpreted as an RFC 2822 address and the domain is extracted
10947 from it. If the string does not parse successfully, the result is empty.
10950 .vitem &*${escape:*&<&'string'&>&*}*&
10951 .cindex "expansion" "escaping non-printing characters"
10952 .cindex "&%escape%& expansion item"
10953 If the string contains any non-printing characters, they are converted to
10954 escape sequences starting with a backslash. Whether characters with the most
10955 significant bit set (so-called &"8-bit characters"&) count as printing or not
10956 is controlled by the &%print_topbitchars%& option.
10958 .vitem &*${escape8bit:*&<&'string'&>&*}*&
10959 .cindex "expansion" "escaping 8-bit characters"
10960 .cindex "&%escape8bit%& expansion item"
10961 If the string contains and characters with the most significant bit set,
10962 they are converted to escape sequences starting with a backslash.
10963 Backslashes and DEL characters are also converted.
10966 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
10967 .cindex "expansion" "expression evaluation"
10968 .cindex "expansion" "arithmetic expression"
10969 .cindex "&%eval%& expansion item"
10970 These items supports simple arithmetic and bitwise logical operations in
10971 expansion strings. The string (after expansion) must be a conventional
10972 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
10973 logical operators, and parentheses. All operations are carried out using
10974 integer arithmetic. The operator priorities are as follows (the same as in the
10975 C programming language):
10977 .irow &'highest:'& "not (~), negate (-)"
10978 .irow "" "multiply (*), divide (/), remainder (%)"
10979 .irow "" "plus (+), minus (-)"
10980 .irow "" "shift-left (<<), shift-right (>>)"
10981 .irow "" "and (&&)"
10983 .irow &'lowest:'& "or (|)"
10985 Binary operators with the same priority are evaluated from left to right. White
10986 space is permitted before or after operators.
10988 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
10989 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
10990 decimal, even if they start with a leading zero; hexadecimal numbers are not
10991 permitted. This can be useful when processing numbers extracted from dates or
10992 times, which often do have leading zeros.
10994 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
10996 respectively. Negative numbers are supported. The result of the computation is
10997 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
11000 &`${eval:1+1} `& yields 2
11001 &`${eval:1+2*3} `& yields 7
11002 &`${eval:(1+2)*3} `& yields 9
11003 &`${eval:2+42%5} `& yields 4
11004 &`${eval:0xc&5} `& yields 4
11005 &`${eval:0xc|5} `& yields 13
11006 &`${eval:0xc^5} `& yields 9
11007 &`${eval:0xc>>1} `& yields 6
11008 &`${eval:0xc<<1} `& yields 24
11009 &`${eval:~255&0x1234} `& yields 4608
11010 &`${eval:-(~255&0x1234)} `& yields -4608
11013 As a more realistic example, in an ACL you might have
11017 {>{$rcpt_count}{10}} \
11020 {$recipients_count} \
11021 {${eval:$rcpt_count/2}} \
11024 message = Too many bad recipients
11026 The condition is true if there have been more than 10 RCPT commands and
11027 fewer than half of them have resulted in a valid recipient.
11030 .vitem &*${expand:*&<&'string'&>&*}*&
11031 .cindex "expansion" "re-expansion of substring"
11032 The &%expand%& operator causes a string to be expanded for a second time. For
11035 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
11037 first looks up a string in a file while expanding the operand for &%expand%&,
11038 and then re-expands what it has found.
11041 .vitem &*${from_utf8:*&<&'string'&>&*}*&
11043 .cindex "UTF-8" "conversion from"
11044 .cindex "expansion" "UTF-8 conversion"
11045 .cindex "&%from_utf8%& expansion item"
11046 The world is slowly moving towards Unicode, although there are no standards for
11047 email yet. However, other applications (including some databases) are starting
11048 to store data in Unicode, using UTF-8 encoding. This operator converts from a
11049 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
11050 converted to underscores. The input must be a valid UTF-8 string. If it is not,
11051 the result is an undefined sequence of bytes.
11053 Unicode code points with values less than 256 are compatible with ASCII and
11054 ISO-8859-1 (also known as Latin-1).
11055 For example, character 169 is the copyright symbol in both cases, though the
11056 way it is encoded is different. In UTF-8, more than one byte is needed for
11057 characters with code values greater than 127, whereas ISO-8859-1 is a
11058 single-byte encoding (but thereby limited to 256 characters). This makes
11059 translation from UTF-8 to ISO-8859-1 straightforward.
11062 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11063 .cindex "hash function" "textual"
11064 .cindex "expansion" "textual hash"
11065 The &%hash%& operator is a simpler interface to the hashing function that can
11066 be used when the two parameters are fixed numbers (as opposed to strings that
11067 change when expanded). The effect is the same as
11069 ${hash{<n>}{<m>}{<string>}}
11071 See the description of the general &%hash%& item above for details. The
11072 abbreviation &%h%& can be used when &%hash%& is used as an operator.
11076 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
11077 .cindex "base64 encoding" "conversion from hex"
11078 .cindex "expansion" "hex to base64"
11079 .cindex "&%hex2b64%& expansion item"
11080 This operator converts a hex string into one that is base64 encoded. This can
11081 be useful for processing the output of the various hashing functions.
11085 .vitem &*${hexquote:*&<&'string'&>&*}*&
11086 .cindex "quoting" "hex-encoded unprintable characters"
11087 .cindex "&%hexquote%& expansion item"
11088 This operator converts non-printable characters in a string into a hex
11089 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
11090 as is, and other byte values are converted to &`\xNN`&, for example, a
11091 byte value 127 is converted to &`\x7f`&.
11094 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
11095 .cindex "&%ipv6denorm%& expansion item"
11096 .cindex "IP address" normalisation
11097 This expands an IPv6 address to a full eight-element colon-separated set
11098 of hex digits including leading zeroes.
11099 A trailing ipv4-style dotted-decimal set is converted to hex.
11100 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11102 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
11103 .cindex "&%ipv6norm%& expansion item"
11104 .cindex "IP address" normalisation
11105 .cindex "IP address" "canonical form"
11106 This converts an IPv6 address to canonical form.
11107 Leading zeroes of groups are omitted, and the longest
11108 set of zero-valued groups is replaced with a double colon.
11109 A trailing ipv4-style dotted-decimal set is converted to hex.
11110 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11113 .vitem &*${lc:*&<&'string'&>&*}*&
11114 .cindex "case forcing in strings"
11115 .cindex "string" "case forcing"
11116 .cindex "lower casing"
11117 .cindex "expansion" "case forcing"
11118 .cindex "&%lc%& expansion item"
11119 This forces the letters in the string into lower-case, for example:
11123 Case is defined per the system C locale.
11125 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
11126 .cindex "expansion" "string truncation"
11127 .cindex "&%length%& expansion item"
11128 The &%length%& operator is a simpler interface to the &%length%& function that
11129 can be used when the parameter is a fixed number (as opposed to a string that
11130 changes when expanded). The effect is the same as
11132 ${length{<number>}{<string>}}
11134 See the description of the general &%length%& item above for details. Note that
11135 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
11136 when &%length%& is used as an operator.
11137 All measurement is done in bytes and is not UTF-8 aware.
11140 .vitem &*${listcount:*&<&'string'&>&*}*&
11141 .cindex "expansion" "list item count"
11142 .cindex "list" "item count"
11143 .cindex "list" "count of items"
11144 .cindex "&%listcount%& expansion item"
11145 The string is interpreted as a list and the number of items is returned.
11148 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
11149 .cindex "expansion" "named list"
11150 .cindex "&%listnamed%& expansion item"
11151 The name is interpreted as a named list and the content of the list is returned,
11152 expanding any referenced lists, re-quoting as needed for colon-separation.
11153 If the optional type is given it must be one of "a", "d", "h" or "l"
11154 and selects address-, domain-, host- or localpart- lists to search among respectively.
11155 Otherwise all types are searched in an undefined order and the first
11156 matching list is returned.
11159 .vitem &*${local_part:*&<&'string'&>&*}*&
11160 .cindex "expansion" "local part extraction"
11161 .cindex "&%local_part%& expansion item"
11162 The string is interpreted as an RFC 2822 address and the local part is
11163 extracted from it. If the string does not parse successfully, the result is
11165 The parsing correctly handles SMTPUTF8 Unicode in the string.
11168 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
11169 .cindex "masked IP address"
11170 .cindex "IP address" "masking"
11171 .cindex "CIDR notation"
11172 .cindex "expansion" "IP address masking"
11173 .cindex "&%mask%& expansion item"
11174 If the form of the string to be operated on is not an IP address followed by a
11175 slash and an integer (that is, a network address in CIDR notation), the
11176 expansion fails. Otherwise, this operator converts the IP address to binary,
11177 masks off the least significant bits according to the bit count, and converts
11178 the result back to text, with mask appended. For example,
11180 ${mask:10.111.131.206/28}
11182 returns the string &"10.111.131.192/28"&. Since this operation is expected to
11183 be mostly used for looking up masked addresses in files, the result for an IPv6
11184 address uses dots to separate components instead of colons, because colon
11185 terminates a key string in lsearch files. So, for example,
11187 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
11191 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
11193 Letters in IPv6 addresses are always output in lower case.
11196 .vitem &*${md5:*&<&'string'&>&*}*&
11198 .cindex "expansion" "MD5 hash"
11199 .cindex certificate fingerprint
11200 .cindex "&%md5%& expansion item"
11201 The &%md5%& operator computes the MD5 hash value of the string, and returns it
11202 as a 32-digit hexadecimal number, in which any letters are in lower case.
11204 If the string is a single variable of type certificate,
11205 returns the MD5 hash fingerprint of the certificate.
11208 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11209 .cindex "expansion" "numeric hash"
11210 .cindex "hash function" "numeric"
11211 The &%nhash%& operator is a simpler interface to the numeric hashing function
11212 that can be used when the two parameters are fixed numbers (as opposed to
11213 strings that change when expanded). The effect is the same as
11215 ${nhash{<n>}{<m>}{<string>}}
11217 See the description of the general &%nhash%& item above for details.
11220 .vitem &*${quote:*&<&'string'&>&*}*&
11221 .cindex "quoting" "in string expansions"
11222 .cindex "expansion" "quoting"
11223 .cindex "&%quote%& expansion item"
11224 The &%quote%& operator puts its argument into double quotes if it
11225 is an empty string or
11226 contains anything other than letters, digits, underscores, dots, and hyphens.
11227 Any occurrences of double quotes and backslashes are escaped with a backslash.
11228 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
11229 respectively For example,
11237 The place where this is useful is when the argument is a substitution from a
11238 variable or a message header.
11240 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
11241 .cindex "&%quote_local_part%& expansion item"
11242 This operator is like &%quote%&, except that it quotes the string only if
11243 required to do so by the rules of RFC 2822 for quoting local parts. For
11244 example, a plus sign would not cause quoting (but it would for &%quote%&).
11245 If you are creating a new email address from the contents of &$local_part$&
11246 (or any other unknown data), you should always use this operator.
11248 This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
11249 will likely use the quoting form.
11250 Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
11253 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
11254 .cindex "quoting" "lookup-specific"
11255 This operator applies lookup-specific quoting rules to the string. Each
11256 query-style lookup type has its own quoting rules which are described with
11257 the lookups in chapter &<<CHAPfdlookup>>&. For example,
11259 ${quote_ldap:two * two}
11265 For single-key lookup types, no quoting is ever necessary and this operator
11266 yields an unchanged string.
11269 .vitem &*${randint:*&<&'n'&>&*}*&
11270 .cindex "random number"
11271 This operator returns a somewhat random number which is less than the
11272 supplied number and is at least 0. The quality of this randomness depends
11273 on how Exim was built; the values are not suitable for keying material.
11274 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
11275 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
11276 for versions of GnuTLS with that function.
11277 Otherwise, the implementation may be arc4random(), random() seeded by
11278 srandomdev() or srandom(), or a custom implementation even weaker than
11282 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
11283 .cindex "expansion" "IP address"
11284 This operator reverses an IP address; for IPv4 addresses, the result is in
11285 dotted-quad decimal form, while for IPv6 addresses the result is in
11286 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
11287 for DNS. For example,
11289 ${reverse_ip:192.0.2.4}
11290 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
11295 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
11299 .vitem &*${rfc2047:*&<&'string'&>&*}*&
11300 .cindex "expansion" "RFC 2047"
11301 .cindex "RFC 2047" "expansion operator"
11302 .cindex "&%rfc2047%& expansion item"
11303 This operator encodes text according to the rules of RFC 2047. This is an
11304 encoding that is used in header lines to encode non-ASCII characters. It is
11305 assumed that the input string is in the encoding specified by the
11306 &%headers_charset%& option, which gets its default at build time. If the string
11307 contains only characters in the range 33&--126, and no instances of the
11310 ? = ( ) < > @ , ; : \ " . [ ] _
11312 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
11313 string, using as many &"encoded words"& as necessary to encode all the
11317 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
11318 .cindex "expansion" "RFC 2047"
11319 .cindex "RFC 2047" "decoding"
11320 .cindex "&%rfc2047d%& expansion item"
11321 This operator decodes strings that are encoded as per RFC 2047. Binary zero
11322 bytes are replaced by question marks. Characters are converted into the
11323 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
11324 not recognized unless &%check_rfc2047_length%& is set false.
11326 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
11327 access a header line, RFC 2047 decoding is done automatically. You do not need
11328 to use this operator as well.
11332 .vitem &*${rxquote:*&<&'string'&>&*}*&
11333 .cindex "quoting" "in regular expressions"
11334 .cindex "regular expressions" "quoting"
11335 .cindex "&%rxquote%& expansion item"
11336 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
11337 characters in its argument. This is useful when substituting the values of
11338 variables or headers inside regular expressions.
11341 .vitem &*${sha1:*&<&'string'&>&*}*&
11342 .cindex "SHA-1 hash"
11343 .cindex "expansion" "SHA-1 hashing"
11344 .cindex certificate fingerprint
11345 .cindex "&%sha1%& expansion item"
11346 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
11347 it as a 40-digit hexadecimal number, in which any letters are in upper case.
11349 If the string is a single variable of type certificate,
11350 returns the SHA-1 hash fingerprint of the certificate.
11353 .vitem &*${sha256:*&<&'string'&>&*}*& &&&
11354 &*${sha2:*&<&'string'&>&*}*& &&&
11355 &*${sha2_<n>:*&<&'string'&>&*}*&
11356 .cindex "SHA-256 hash"
11357 .cindex "SHA-2 hash"
11358 .cindex certificate fingerprint
11359 .cindex "expansion" "SHA-256 hashing"
11360 .cindex "&%sha256%& expansion item"
11361 .cindex "&%sha2%& expansion item"
11362 The &%sha256%& operator computes the SHA-256 hash value of the string
11364 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11366 If the string is a single variable of type certificate,
11367 returns the SHA-256 hash fingerprint of the certificate.
11369 The operator can also be spelled &%sha2%& and does the same as &%sha256%&
11370 (except for certificates, which are not supported).
11371 Finally, if an underbar
11372 and a number is appended it specifies the output length, selecting a
11373 member of the SHA-2 family of hash functions.
11374 Values of 256, 384 and 512 are accepted, with 256 being the default.
11377 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
11378 &*${sha3_<n>:*&<&'string'&>&*}*&
11379 .cindex "SHA3 hash"
11380 .cindex "expansion" "SHA3 hashing"
11381 .cindex "&%sha3%& expansion item"
11382 The &%sha3%& operator computes the SHA3-256 hash value of the string
11384 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11386 If a number is appended, separated by an underbar, it specifies
11387 the output length. Values of 224, 256, 384 and 512 are accepted;
11388 with 256 being the default.
11390 The &%sha3%& expansion item is only supported if Exim has been
11391 compiled with GnuTLS 3.5.0 or later,
11392 or OpenSSL 1.1.1 or later.
11393 The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
11396 .vitem &*${stat:*&<&'string'&>&*}*&
11397 .cindex "expansion" "statting a file"
11398 .cindex "file" "extracting characteristics"
11399 .cindex "&%stat%& expansion item"
11400 The string, after expansion, must be a file path. A call to the &[stat()]&
11401 function is made for this path. If &[stat()]& fails, an error occurs and the
11402 expansion fails. If it succeeds, the data from the stat replaces the item, as a
11403 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
11404 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
11405 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
11406 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
11407 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
11408 can extract individual fields using the &%extract%& expansion item.
11410 The use of the &%stat%& expansion in users' filter files can be locked out by
11411 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
11412 systems for files larger than 2GB.
11414 .vitem &*${str2b64:*&<&'string'&>&*}*&
11415 .cindex "&%str2b64%& expansion item"
11416 Now deprecated, a synonym for the &%base64%& expansion operator.
11420 .vitem &*${strlen:*&<&'string'&>&*}*&
11421 .cindex "expansion" "string length"
11422 .cindex "string" "length in expansion"
11423 .cindex "&%strlen%& expansion item"
11424 The item is replace by the length of the expanded string, expressed as a
11425 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
11426 All measurement is done in bytes and is not UTF-8 aware.
11429 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
11430 .cindex "&%substr%& expansion item"
11431 .cindex "substring extraction"
11432 .cindex "expansion" "substring expansion"
11433 The &%substr%& operator is a simpler interface to the &%substr%& function that
11434 can be used when the two parameters are fixed numbers (as opposed to strings
11435 that change when expanded). The effect is the same as
11437 ${substr{<start>}{<length>}{<string>}}
11439 See the description of the general &%substr%& item above for details. The
11440 abbreviation &%s%& can be used when &%substr%& is used as an operator.
11441 All measurement is done in bytes and is not UTF-8 aware.
11443 .vitem &*${time_eval:*&<&'string'&>&*}*&
11444 .cindex "&%time_eval%& expansion item"
11445 .cindex "time interval" "decoding"
11446 This item converts an Exim time interval such as &`2d4h5m`& into a number of
11449 .vitem &*${time_interval:*&<&'string'&>&*}*&
11450 .cindex "&%time_interval%& expansion item"
11451 .cindex "time interval" "formatting"
11452 The argument (after sub-expansion) must be a sequence of decimal digits that
11453 represents an interval of time as a number of seconds. It is converted into a
11454 number of larger units and output in Exim's normal time format, for example,
11457 .vitem &*${uc:*&<&'string'&>&*}*&
11458 .cindex "case forcing in strings"
11459 .cindex "string" "case forcing"
11460 .cindex "upper casing"
11461 .cindex "expansion" "case forcing"
11462 .cindex "&%uc%& expansion item"
11463 This forces the letters in the string into upper-case.
11464 Case is defined per the system C locale.
11466 .vitem &*${utf8clean:*&<&'string'&>&*}*&
11467 .cindex "correction of invalid utf-8 sequences in strings"
11468 .cindex "utf-8" "utf-8 sequences"
11469 .cindex "incorrect utf-8"
11470 .cindex "expansion" "utf-8 forcing"
11471 .cindex "&%utf8clean%& expansion item"
11472 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
11473 In versions of Exim before 4.92, this did not correctly do so for a truncated
11474 final codepoint's encoding, and the character would be silently dropped.
11475 If you must handle detection of this scenario across both sets of Exim behavior,
11476 the complexity will depend upon the task.
11477 For instance, to detect if the first character is multibyte and a 1-byte
11478 extraction can be successfully used as a path component (as is common for
11479 dividing up delivery folders), you might use:
11481 condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
11483 (which will false-positive if the first character of the local part is a
11484 literal question mark).
11486 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
11487 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
11488 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
11489 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
11490 .cindex expansion UTF-8
11491 .cindex UTF-8 expansion
11493 .cindex internationalisation
11494 .cindex "&%utf8_domain_to_alabel%& expansion item"
11495 .cindex "&%utf8_domain_from_alabel%& expansion item"
11496 .cindex "&%utf8_localpart_to_alabel%& expansion item"
11497 .cindex "&%utf8_localpart_from_alabel%& expansion item"
11498 These convert EAI mail name components between UTF-8 and a-label forms.
11499 For information on internationalisation support see &<<SECTi18nMTA>>&.
11507 .section "Expansion conditions" "SECTexpcond"
11508 .scindex IIDexpcond "expansion" "conditions"
11509 The following conditions are available for testing by the &%${if%& construct
11510 while expanding strings:
11513 .vitem &*!*&<&'condition'&>
11514 .cindex "expansion" "negating a condition"
11515 .cindex "negation" "in expansion condition"
11516 Preceding any condition with an exclamation mark negates the result of the
11519 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11520 .cindex "numeric comparison"
11521 .cindex "expansion" "numeric comparison"
11522 There are a number of symbolic operators for doing numeric comparisons. They
11528 &`>= `& greater or equal
11530 &`<= `& less or equal
11534 ${if >{$message_size}{10M} ...
11536 Note that the general negation operator provides for inequality testing. The
11537 two strings must take the form of optionally signed decimal integers,
11538 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
11539 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
11540 As a special case, the numerical value of an empty string is taken as
11543 In all cases, a relative comparator OP is testing if <&'string1'&> OP
11544 <&'string2'&>; the above example is checking if &$message_size$& is larger than
11545 10M, not if 10M is larger than &$message_size$&.
11548 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
11549 {*&<&'arg2'&>&*}...}*&
11550 .cindex "expansion" "calling an acl"
11551 .cindex "&%acl%&" "expansion condition"
11552 The name and zero to nine argument strings are first expanded separately. The expanded
11553 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
11554 Any unused are made empty. The variable &$acl_narg$& is set to the number of
11555 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
11556 and may use the variables; if another acl expansion is used the values
11557 are restored after it returns. If the ACL sets
11558 a value using a "message =" modifier the variable $value becomes
11559 the result of the expansion, otherwise it is empty.
11560 If the ACL returns accept the condition is true; if deny, false.
11561 If the ACL returns defer the result is a forced-fail.
11563 .vitem &*bool&~{*&<&'string'&>&*}*&
11564 .cindex "expansion" "boolean parsing"
11565 .cindex "&%bool%& expansion condition"
11566 This condition turns a string holding a true or false representation into
11567 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
11568 (case-insensitively); also integer numbers map to true if non-zero,
11570 An empty string is treated as false.
11571 Leading and trailing whitespace is ignored;
11572 thus a string consisting only of whitespace is false.
11573 All other string values will result in expansion failure.
11575 When combined with ACL variables, this expansion condition will let you
11576 make decisions in one place and act on those decisions in another place.
11579 ${if bool{$acl_m_privileged_sender} ...
11583 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
11584 .cindex "expansion" "boolean parsing"
11585 .cindex "&%bool_lax%& expansion condition"
11586 Like &%bool%&, this condition turns a string into a boolean state. But
11587 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
11588 loose definition that the Router &%condition%& option uses. The empty string
11589 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
11590 true. Leading and trailing whitespace is ignored.
11592 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
11594 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11595 .cindex "expansion" "encrypted comparison"
11596 .cindex "encrypted strings, comparing"
11597 .cindex "&%crypteq%& expansion condition"
11598 This condition is included in the Exim binary if it is built to support any
11599 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
11600 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
11601 included in the binary.
11603 The &%crypteq%& condition has two arguments. The first is encrypted and
11604 compared against the second, which is already encrypted. The second string may
11605 be in the LDAP form for storing encrypted strings, which starts with the
11606 encryption type in curly brackets, followed by the data. If the second string
11607 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
11608 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
11609 Typically this will be a field from a password file. An example of an encrypted
11610 string in LDAP form is:
11612 {md5}CY9rzUYh03PK3k6DJie09g==
11614 If such a string appears directly in an expansion, the curly brackets have to
11615 be quoted, because they are part of the expansion syntax. For example:
11617 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
11619 The following encryption types (whose names are matched case-independently) are
11624 .cindex "base64 encoding" "in encrypted password"
11625 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
11626 printable characters to compare with the remainder of the second string. If the
11627 length of the comparison string is 24, Exim assumes that it is base64 encoded
11628 (as in the above example). If the length is 32, Exim assumes that it is a
11629 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
11633 .cindex "SHA-1 hash"
11634 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
11635 printable characters to compare with the remainder of the second string. If the
11636 length of the comparison string is 28, Exim assumes that it is base64 encoded.
11637 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
11638 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
11641 .cindex "&[crypt()]&"
11642 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
11643 only the first eight characters of the password. However, in modern operating
11644 systems this is no longer true, and in many cases the entire password is used,
11645 whatever its length.
11648 .cindex "&[crypt16()]&"
11649 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
11650 use up to 16 characters of the password in some operating systems. Again, in
11651 modern operating systems, more characters may be used.
11653 Exim has its own version of &[crypt16()]&, which is just a double call to
11654 &[crypt()]&. For operating systems that have their own version, setting
11655 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
11656 operating system version instead of its own. This option is set by default in
11657 the OS-dependent &_Makefile_& for those operating systems that are known to
11658 support &[crypt16()]&.
11660 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
11661 it was not using the same algorithm as some operating systems' versions. It
11662 turns out that as well as &[crypt16()]& there is a function called
11663 &[bigcrypt()]& in some operating systems. This may or may not use the same
11664 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
11666 However, since there is now a move away from the traditional &[crypt()]&
11667 functions towards using SHA1 and other algorithms, tidying up this area of
11668 Exim is seen as very low priority.
11670 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
11671 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
11672 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
11673 default is &`{crypt}`&. Whatever the default, you can always use either
11674 function by specifying it explicitly in curly brackets.
11676 .vitem &*def:*&<&'variable&~name'&>
11677 .cindex "expansion" "checking for empty variable"
11678 .cindex "&%def%& expansion condition"
11679 The &%def%& condition must be followed by the name of one of the expansion
11680 variables defined in section &<<SECTexpvar>>&. The condition is true if the
11681 variable does not contain the empty string. For example:
11683 ${if def:sender_ident {from $sender_ident}}
11685 Note that the variable name is given without a leading &%$%& character. If the
11686 variable does not exist, the expansion fails.
11688 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
11689 &~&*def:h_*&<&'header&~name'&>&*:*&"
11690 .cindex "expansion" "checking header line existence"
11691 This condition is true if a message is being processed and the named header
11692 exists in the message. For example,
11694 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
11696 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
11697 the header name must be terminated by a colon if white space does not follow.
11699 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11700 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11701 .cindex "string" "comparison"
11702 .cindex "expansion" "string comparison"
11703 .cindex "&%eq%& expansion condition"
11704 .cindex "&%eqi%& expansion condition"
11705 The two substrings are first expanded. The condition is true if the two
11706 resulting strings are identical. For &%eq%& the comparison includes the case of
11707 letters, whereas for &%eqi%& the comparison is case-independent, where
11708 case is defined per the system C locale.
11710 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
11711 .cindex "expansion" "file existence test"
11712 .cindex "file" "existence test"
11713 .cindex "&%exists%&, expansion condition"
11714 The substring is first expanded and then interpreted as an absolute path. The
11715 condition is true if the named file (or directory) exists. The existence test
11716 is done by calling the &[stat()]& function. The use of the &%exists%& test in
11717 users' filter files may be locked out by the system administrator.
11720 &*Note:*& Testing a path using this condition is not a sufficient way of
11724 .vitem &*first_delivery*&
11725 .cindex "delivery" "first"
11726 .cindex "first delivery"
11727 .cindex "expansion" "first delivery test"
11728 .cindex "&%first_delivery%& expansion condition"
11729 This condition, which has no data, is true during a message's first delivery
11730 attempt. It is false during any subsequent delivery attempts.
11733 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
11734 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
11735 .cindex "list" "iterative conditions"
11736 .cindex "expansion" "&*forall*& condition"
11737 .cindex "expansion" "&*forany*& condition"
11739 These conditions iterate over a list. The first argument is expanded to form
11740 the list. By default, the list separator is a colon, but it can be changed by
11741 the normal method (&<<SECTlistsepchange>>&).
11742 The second argument is interpreted as a condition that is to
11743 be applied to each item in the list in turn. During the interpretation of the
11744 condition, the current list item is placed in a variable called &$item$&.
11746 For &*forany*&, interpretation stops if the condition is true for any item, and
11747 the result of the whole condition is true. If the condition is false for all
11748 items in the list, the overall condition is false.
11750 For &*forall*&, interpretation stops if the condition is false for any item,
11751 and the result of the whole condition is false. If the condition is true for
11752 all items in the list, the overall condition is true.
11754 Note that negation of &*forany*& means that the condition must be false for all
11755 items for the overall condition to succeed, and negation of &*forall*& means
11756 that the condition must be false for at least one item. In this example, the
11757 list separator is changed to a comma:
11759 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
11761 The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
11762 being processed, to enable these expansion items to be nested.
11764 To scan a named list, expand it with the &*listnamed*& operator.
11766 .vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11767 "&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11768 "&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11769 "&*forany_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&"
11770 .cindex JSON "iterative conditions"
11771 .cindex JSON expansions
11772 .cindex expansion "&*forall_json*& condition"
11773 .cindex expansion "&*forany_json*& condition"
11774 .cindex expansion "&*forall_jsons*& condition"
11775 .cindex expansion "&*forany_jsons*& condition"
11776 As for the above, except that the first argument must, after expansion,
11778 The array separator is not changeable.
11779 For the &"jsons"& variants the elements are expected to be JSON strings
11780 and have their quotes removed before the evaluation of the condition.
11784 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11785 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11786 .cindex "string" "comparison"
11787 .cindex "expansion" "string comparison"
11788 .cindex "&%ge%& expansion condition"
11789 .cindex "&%gei%& expansion condition"
11790 The two substrings are first expanded. The condition is true if the first
11791 string is lexically greater than or equal to the second string. For &%ge%& the
11792 comparison includes the case of letters, whereas for &%gei%& the comparison is
11794 Case and collation order are defined per the system C locale.
11796 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11797 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11798 .cindex "string" "comparison"
11799 .cindex "expansion" "string comparison"
11800 .cindex "&%gt%& expansion condition"
11801 .cindex "&%gti%& expansion condition"
11802 The two substrings are first expanded. The condition is true if the first
11803 string is lexically greater than the second string. For &%gt%& the comparison
11804 includes the case of letters, whereas for &%gti%& the comparison is
11806 Case and collation order are defined per the system C locale.
11810 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
11811 SRS decode. See SECT &<<SECTSRS>>& for details.
11815 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11816 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11817 .cindex "string" "comparison"
11818 .cindex "list" "iterative conditions"
11819 Both strings are expanded; the second string is treated as a list of simple
11820 strings; if the first string is a member of the second, then the condition
11822 For the case-independent &%inlisti%& condition, case is defined per the system C locale.
11824 These are simpler to use versions of the more powerful &*forany*& condition.
11825 Examples, and the &*forany*& equivalents:
11827 ${if inlist{needle}{foo:needle:bar}}
11828 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11829 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11830 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11833 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11834 &*isip4&~{*&<&'string'&>&*}*& &&&
11835 &*isip6&~{*&<&'string'&>&*}*&
11836 .cindex "IP address" "testing string format"
11837 .cindex "string" "testing for IP address"
11838 .cindex "&%isip%& expansion condition"
11839 .cindex "&%isip4%& expansion condition"
11840 .cindex "&%isip6%& expansion condition"
11841 The substring is first expanded, and then tested to see if it has the form of
11842 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11843 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11845 For an IPv4 address, the test is for four dot-separated components, each of
11846 which consists of from one to three digits. For an IPv6 address, up to eight
11847 colon-separated components are permitted, each containing from one to four
11848 hexadecimal digits. There may be fewer than eight components if an empty
11849 component (adjacent colons) is present. Only one empty component is permitted.
11851 &*Note*&: The checks used to be just on the form of the address; actual numerical
11852 values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
11854 This is no longer the case.
11856 The main use of these tests is to distinguish between IP addresses and
11857 host names, or between IPv4 and IPv6 addresses. For example, you could use
11859 ${if isip4{$sender_host_address}...
11861 to test which IP version an incoming SMTP connection is using.
11863 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11864 .cindex "LDAP" "use for authentication"
11865 .cindex "expansion" "LDAP authentication test"
11866 .cindex "&%ldapauth%& expansion condition"
11867 This condition supports user authentication using LDAP. See section
11868 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11869 queries. For this use, the query must contain a user name and password. The
11870 query itself is not used, and can be empty. The condition is true if the
11871 password is not empty, and the user name and password are accepted by the LDAP
11872 server. An empty password is rejected without calling LDAP because LDAP binds
11873 with an empty password are considered anonymous regardless of the username, and
11874 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11875 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11879 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11880 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11881 .cindex "string" "comparison"
11882 .cindex "expansion" "string comparison"
11883 .cindex "&%le%& expansion condition"
11884 .cindex "&%lei%& expansion condition"
11885 The two substrings are first expanded. The condition is true if the first
11886 string is lexically less than or equal to the second string. For &%le%& the
11887 comparison includes the case of letters, whereas for &%lei%& the comparison is
11889 Case and collation order are defined per the system C locale.
11891 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11892 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11893 .cindex "string" "comparison"
11894 .cindex "expansion" "string comparison"
11895 .cindex "&%lt%& expansion condition"
11896 .cindex "&%lti%& expansion condition"
11897 The two substrings are first expanded. The condition is true if the first
11898 string is lexically less than the second string. For &%lt%& the comparison
11899 includes the case of letters, whereas for &%lti%& the comparison is
11901 Case and collation order are defined per the system C locale.
11904 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11905 .cindex "expansion" "regular expression comparison"
11906 .cindex "regular expressions" "match in expanded string"
11907 .cindex "&%match%& expansion condition"
11908 The two substrings are first expanded. The second is then treated as a regular
11909 expression and applied to the first. Because of the pre-expansion, if the
11910 regular expression contains dollar, or backslash characters, they must be
11911 escaped. Care must also be taken if the regular expression contains braces
11912 (curly brackets). A closing brace must be escaped so that it is not taken as a
11913 premature termination of <&'string2'&>. The easiest approach is to use the
11914 &`\N`& feature to disable expansion of the regular expression.
11917 ${if match {$local_part}{\N^\d{3}\N} ...
11919 If the whole expansion string is in double quotes, further escaping of
11920 backslashes is also required.
11922 The condition is true if the regular expression match succeeds.
11923 The regular expression is not required to begin with a circumflex
11924 metacharacter, but if there is no circumflex, the expression is not anchored,
11925 and it may match anywhere in the subject, not just at the start. If you want
11926 the pattern to match at the end of the subject, you must include the &`$`&
11927 metacharacter at an appropriate point.
11928 All character handling is done in bytes and is not UTF-8 aware,
11929 but we might change this in a future Exim release.
11931 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11932 At the start of an &%if%& expansion the values of the numeric variable
11933 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11934 succeeds causes them to be reset to the substrings of that condition and they
11935 will have these values during the expansion of the success string. At the end
11936 of the &%if%& expansion, the previous values are restored. After testing a
11937 combination of conditions using &%or%&, the subsequent values of the numeric
11938 variables are those of the condition that succeeded.
11940 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11941 .cindex "&%match_address%& expansion condition"
11942 See &*match_local_part*&.
11944 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11945 .cindex "&%match_domain%& expansion condition"
11946 See &*match_local_part*&.
11948 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11949 .cindex "&%match_ip%& expansion condition"
11950 This condition matches an IP address to a list of IP address patterns. It must
11951 be followed by two argument strings. The first (after expansion) must be an IP
11952 address or an empty string. The second (not expanded) is a restricted host
11953 list that can match only an IP address, not a host name. For example:
11955 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
11957 The specific types of host list item that are permitted in the list are:
11960 An IP address, optionally with a CIDR mask.
11962 A single asterisk, which matches any IP address.
11964 An empty item, which matches only if the IP address is empty. This could be
11965 useful for testing for a locally submitted message or one from specific hosts
11966 in a single test such as
11967 . ==== As this is a nested list, any displays it contains must be indented
11968 . ==== as otherwise they are too far to the left. This comment applies to
11969 . ==== the use of xmlto plus fop. There's no problem when formatting with
11970 . ==== sdop, with or without the extra indent.
11972 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
11974 where the first item in the list is the empty string.
11976 The item @[] matches any of the local host's interface addresses.
11978 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
11979 even if &`net-`& is not specified. There is never any attempt to turn the IP
11980 address into a host name. The most common type of linear search for
11981 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
11982 masks. For example:
11984 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
11986 It is of course possible to use other kinds of lookup, and in such a case, you
11987 do need to specify the &`net-`& prefix if you want to specify a specific
11988 address mask, for example:
11990 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
11992 However, unless you are combining a &%match_ip%& condition with others, it is
11993 just as easy to use the fact that a lookup is itself a condition, and write:
11995 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
11999 Note that <&'string2'&> is not itself subject to string expansion, unless
12000 Exim was built with the EXPAND_LISTMATCH_RHS option.
12002 Consult section &<<SECThoslispatip>>& for further details of these patterns.
12004 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
12005 .cindex "domain list" "in expansion condition"
12006 .cindex "address list" "in expansion condition"
12007 .cindex "local part" "list, in expansion condition"
12008 .cindex "&%match_local_part%& expansion condition"
12009 This condition, together with &%match_address%& and &%match_domain%&, make it
12010 possible to test domain, address, and local part lists within expansions. Each
12011 condition requires two arguments: an item and a list to match. A trivial
12014 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
12016 In each case, the second argument may contain any of the allowable items for a
12017 list of the appropriate type. Also, because the second argument
12018 is a standard form of list, it is possible to refer to a named list.
12019 Thus, you can use conditions like this:
12021 ${if match_domain{$domain}{+local_domains}{...
12023 .cindex "&`+caseful`&"
12024 For address lists, the matching starts off caselessly, but the &`+caseful`&
12025 item can be used, as in all address lists, to cause subsequent items to
12026 have their local parts matched casefully. Domains are always matched
12029 Note that <&'string2'&> is not itself subject to string expansion, unless
12030 Exim was built with the EXPAND_LISTMATCH_RHS option.
12032 &*Note*&: Host lists are &'not'& supported in this way. This is because
12033 hosts have two identities: a name and an IP address, and it is not clear
12034 how to specify cleanly how such a test would work. However, IP addresses can be
12035 matched using &%match_ip%&.
12037 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
12038 .cindex "PAM authentication"
12039 .cindex "AUTH" "with PAM"
12040 .cindex "Solaris" "PAM support"
12041 .cindex "expansion" "PAM authentication test"
12042 .cindex "&%pam%& expansion condition"
12043 &'Pluggable Authentication Modules'&
12044 (&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
12045 available in the latest releases of Solaris and in some GNU/Linux
12046 distributions. The Exim support, which is intended for use in conjunction with
12047 the SMTP AUTH command, is available only if Exim is compiled with
12051 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
12052 in some releases of GNU/Linux &%-ldl%& is also needed.
12054 The argument string is first expanded, and the result must be a
12055 colon-separated list of strings. Leading and trailing white space is ignored.
12056 The PAM module is initialized with the service name &"exim"& and the user name
12057 taken from the first item in the colon-separated data string (<&'string1'&>).
12058 The remaining items in the data string are passed over in response to requests
12059 from the authentication function. In the simple case there will only be one
12060 request, for a password, so the data consists of just two strings.
12062 There can be problems if any of the strings are permitted to contain colon
12063 characters. In the usual way, these have to be doubled to avoid being taken as
12065 The &%listquote%& expansion item can be used for this.
12066 For example, the configuration
12067 of a LOGIN authenticator might contain this setting:
12069 server_condition = ${if pam{$auth1:${listquote{:}{$auth2}}}}
12071 In some operating systems, PAM authentication can be done only from a process
12072 running as root. Since Exim is running as the Exim user when receiving
12073 messages, this means that PAM cannot be used directly in those systems.
12074 . --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that
12077 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
12078 .cindex "&'pwcheck'& daemon"
12080 .cindex "expansion" "&'pwcheck'& authentication test"
12081 .cindex "&%pwcheck%& expansion condition"
12082 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
12083 This is one way of making it possible for passwords to be checked by a process
12084 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
12085 deprecated. Its replacement is &'saslauthd'& (see below).
12087 The pwcheck support is not included in Exim by default. You need to specify
12088 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
12089 building Exim. For example:
12091 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
12093 You do not need to install the full Cyrus software suite in order to use
12094 the pwcheck daemon. You can compile and install just the daemon alone
12095 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
12096 access to the &_/var/pwcheck_& directory.
12098 The &%pwcheck%& condition takes one argument, which must be the user name and
12099 password, separated by a colon. For example, in a LOGIN authenticator
12100 configuration, you might have this:
12102 server_condition = ${if pwcheck{$auth1:$auth2}}
12104 Again, for a PLAIN authenticator configuration, this would be:
12106 server_condition = ${if pwcheck{$auth2:$auth3}}
12108 .vitem &*queue_running*&
12109 .cindex "queue runner" "detecting when delivering from"
12110 .cindex "expansion" "queue runner test"
12111 .cindex "&%queue_running%& expansion condition"
12112 This condition, which has no data, is true during delivery attempts that are
12113 initiated by queue runner processes, and false otherwise.
12116 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
12118 .cindex "expansion" "Radius authentication"
12119 .cindex "&%radius%& expansion condition"
12120 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
12121 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
12122 the Radius client configuration file in order to build Exim with Radius
12125 With just that one setting, Exim expects to be linked with the &%radiusclient%&
12126 library, using the original API. If you are using release 0.4.0 or later of
12127 this library, you need to set
12129 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
12131 in &_Local/Makefile_& when building Exim. You can also link Exim with the
12132 &%libradius%& library that comes with FreeBSD. To do this, set
12134 RADIUS_LIB_TYPE=RADLIB
12136 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
12137 You may also have to supply a suitable setting in EXTRALIBS so that the
12138 Radius library can be found when Exim is linked.
12140 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
12141 Radius client library, which calls the Radius server. The condition is true if
12142 the authentication is successful. For example:
12144 server_condition = ${if radius{<arguments>}}
12148 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
12149 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
12150 .cindex "&'saslauthd'& daemon"
12152 .cindex "expansion" "&'saslauthd'& authentication test"
12153 .cindex "&%saslauthd%& expansion condition"
12154 This condition supports user authentication using the Cyrus &'saslauthd'&
12155 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
12156 Using this daemon is one way of making it possible for passwords to be checked
12157 by a process that is not running as root.
12159 The saslauthd support is not included in Exim by default. You need to specify
12160 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
12161 building Exim. For example:
12163 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
12165 You do not need to install the full Cyrus software suite in order to use
12166 the saslauthd daemon. You can compile and install just the daemon alone
12167 from the Cyrus SASL library.
12169 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
12170 two are mandatory. For example:
12172 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
12174 The service and the realm are optional (which is why the arguments are enclosed
12175 in their own set of braces). For details of the meaning of the service and
12176 realm, and how to run the daemon, consult the Cyrus documentation.
12181 .section "Combining expansion conditions" "SECID84"
12182 .cindex "expansion" "combining conditions"
12183 Several conditions can be tested at once by combining them using the &%and%&
12184 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
12185 conditions on their own, and precede their lists of sub-conditions. Each
12186 sub-condition must be enclosed in braces within the overall braces that contain
12187 the list. No repetition of &%if%& is used.
12191 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12192 .cindex "&""or""& expansion condition"
12193 .cindex "expansion" "&""or""& of conditions"
12194 The sub-conditions are evaluated from left to right. The condition is true if
12195 any one of the sub-conditions is true.
12198 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
12200 When a true sub-condition is found, the following ones are parsed but not
12201 evaluated. If there are several &"match"& sub-conditions the values of the
12202 numeric variables afterwards are taken from the first one that succeeds.
12204 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12205 .cindex "&""and""& expansion condition"
12206 .cindex "expansion" "&""and""& of conditions"
12207 The sub-conditions are evaluated from left to right. The condition is true if
12208 all of the sub-conditions are true. If there are several &"match"&
12209 sub-conditions, the values of the numeric variables afterwards are taken from
12210 the last one. When a false sub-condition is found, the following ones are
12211 parsed but not evaluated.
12213 .ecindex IIDexpcond
12218 .section "Expansion variables" "SECTexpvar"
12219 .cindex "expansion" "variables, list of"
12220 This section contains an alphabetical list of all the expansion variables. Some
12221 of them are available only when Exim is compiled with specific options such as
12222 support for TLS or the content scanning extension.
12225 .vitem "&$0$&, &$1$&, etc"
12226 .cindex "numerical variables (&$1$& &$2$& etc)"
12227 When a &%match%& expansion condition succeeds, these variables contain the
12228 captured substrings identified by the regular expression during subsequent
12229 processing of the success string of the containing &%if%& expansion item.
12230 In the expansion condition case
12231 they do not retain their values afterwards; in fact, their previous
12232 values are restored at the end of processing an &%if%& item. The numerical
12233 variables may also be set externally by some other matching process which
12234 precedes the expansion of the string. For example, the commands available in
12235 Exim filter files include an &%if%& command with its own regular expression
12236 matching condition.
12238 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
12239 Within an acl condition, expansion condition or expansion item
12240 any arguments are copied to these variables,
12241 any unused variables being made empty.
12243 .vitem "&$acl_c...$&"
12244 Values can be placed in these variables by the &%set%& modifier in an ACL. They
12245 can be given any name that starts with &$acl_c$& and is at least six characters
12246 long, but the sixth character must be either a digit or an underscore. For
12247 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
12248 variables persist throughout the lifetime of an SMTP connection. They can be
12249 used to pass information between ACLs and between different invocations of the
12250 same ACL. When a message is received, the values of these variables are saved
12251 with the message, and can be accessed by filters, routers, and transports
12252 during subsequent delivery.
12254 .vitem "&$acl_m...$&"
12255 These variables are like the &$acl_c...$& variables, except that their values
12256 are reset after a message has been received. Thus, if several messages are
12257 received in one SMTP connection, &$acl_m...$& values are not passed on from one
12258 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
12259 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
12260 message is received, the values of these variables are saved with the message,
12261 and can be accessed by filters, routers, and transports during subsequent
12264 .vitem &$acl_narg$&
12265 Within an acl condition, expansion condition or expansion item
12266 this variable has the number of arguments.
12268 .vitem &$acl_verify_message$&
12269 .vindex "&$acl_verify_message$&"
12270 After an address verification has failed, this variable contains the failure
12271 message. It retains its value for use in subsequent modifiers. The message can
12272 be preserved by coding like this:
12274 warn !verify = sender
12275 set acl_m0 = $acl_verify_message
12277 You can use &$acl_verify_message$& during the expansion of the &%message%& or
12278 &%log_message%& modifiers, to include information about the verification
12281 .vitem &$address_data$&
12282 .vindex "&$address_data$&"
12283 This variable is set by means of the &%address_data%& option in routers. The
12284 value then remains with the address while it is processed by subsequent routers
12285 and eventually a transport. If the transport is handling multiple addresses,
12286 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
12287 for more details. &*Note*&: The contents of &$address_data$& are visible in
12290 If &$address_data$& is set when the routers are called from an ACL to verify
12291 a recipient address, the final value is still in the variable for subsequent
12292 conditions and modifiers of the ACL statement. If routing the address caused it
12293 to be redirected to just one address, the child address is also routed as part
12294 of the verification, and in this case the final value of &$address_data$& is
12295 from the child's routing.
12297 If &$address_data$& is set when the routers are called from an ACL to verify a
12298 sender address, the final value is also preserved, but this time in
12299 &$sender_address_data$&, to distinguish it from data from a recipient
12302 In both cases (recipient and sender verification), the value does not persist
12303 after the end of the current ACL statement. If you want to preserve
12304 these values for longer, you can save them in ACL variables.
12306 .vitem &$address_file$&
12307 .vindex "&$address_file$&"
12308 When, as a result of aliasing, forwarding, or filtering, a message is directed
12309 to a specific file, this variable holds the name of the file when the transport
12310 is running. At other times, the variable is empty. For example, using the
12311 default configuration, if user &%r2d2%& has a &_.forward_& file containing
12313 /home/r2d2/savemail
12315 then when the &(address_file)& transport is running, &$address_file$&
12316 contains the text string &`/home/r2d2/savemail`&.
12317 .cindex "Sieve filter" "value of &$address_file$&"
12318 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
12319 then up to the transport configuration to generate an appropriate absolute path
12320 to the relevant file.
12322 .vitem &$address_pipe$&
12323 .vindex "&$address_pipe$&"
12324 When, as a result of aliasing or forwarding, a message is directed to a pipe,
12325 this variable holds the pipe command when the transport is running.
12327 .vitem "&$auth1$& &-- &$auth3$&"
12328 .vindex "&$auth1$&, &$auth2$&, etc"
12329 These variables are used in SMTP authenticators (see chapters
12330 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
12332 .vitem &$authenticated_id$&
12333 .cindex "authentication" "id"
12334 .vindex "&$authenticated_id$&"
12335 When a server successfully authenticates a client it may be configured to
12336 preserve some of the authentication information in the variable
12337 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
12338 user/password authenticator configuration might preserve the user name for use
12339 in the routers. Note that this is not the same information that is saved in
12340 &$sender_host_authenticated$&.
12342 When a message is submitted locally (that is, not over a TCP connection)
12343 the value of &$authenticated_id$& is normally the login name of the calling
12344 process. However, a trusted user can override this by means of the &%-oMai%&
12345 command line option.
12346 This second case also sets up information used by the
12347 &$authresults$& expansion item.
12349 .vitem &$authenticated_fail_id$&
12350 .cindex "authentication" "fail" "id"
12351 .vindex "&$authenticated_fail_id$&"
12352 When an authentication attempt fails, the variable &$authenticated_fail_id$&
12353 will contain the failed authentication id. If more than one authentication
12354 id is attempted, it will contain only the last one. The variable is
12355 available for processing in the ACL's, generally the quit or notquit ACL.
12356 A message to a local recipient could still be accepted without requiring
12357 authentication, which means this variable could also be visible in all of
12361 .vitem &$authenticated_sender$&
12362 .cindex "sender" "authenticated"
12363 .cindex "authentication" "sender"
12364 .cindex "AUTH" "on MAIL command"
12365 .vindex "&$authenticated_sender$&"
12366 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
12367 SMTP MAIL command if it believes the sender is sufficiently trusted, as
12368 described in section &<<SECTauthparamail>>&. Unless the data is the string
12369 &"<>"&, it is set as the authenticated sender of the message, and the value is
12370 available during delivery in the &$authenticated_sender$& variable. If the
12371 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
12373 .vindex "&$qualify_domain$&"
12374 When a message is submitted locally (that is, not over a TCP connection), the
12375 value of &$authenticated_sender$& is an address constructed from the login
12376 name of the calling process and &$qualify_domain$&, except that a trusted user
12377 can override this by means of the &%-oMas%& command line option.
12380 .vitem &$authentication_failed$&
12381 .cindex "authentication" "failure"
12382 .vindex "&$authentication_failed$&"
12383 This variable is set to &"1"& in an Exim server if a client issues an AUTH
12384 command that does not succeed. Otherwise it is set to &"0"&. This makes it
12385 possible to distinguish between &"did not try to authenticate"&
12386 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
12387 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
12388 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
12389 negative response to an AUTH command, including (for example) an attempt to use
12390 an undefined mechanism.
12392 .vitem &$av_failed$&
12393 .cindex "content scanning" "AV scanner failure"
12394 This variable is available when Exim is compiled with the content-scanning
12395 extension. It is set to &"0"& by default, but will be set to &"1"& if any
12396 problem occurs with the virus scanner (specified by &%av_scanner%&) during
12397 the ACL malware condition.
12399 .vitem &$body_linecount$&
12400 .cindex "message body" "line count"
12401 .cindex "body of message" "line count"
12402 .vindex "&$body_linecount$&"
12403 When a message is being received or delivered, this variable contains the
12404 number of lines in the message's body. See also &$message_linecount$&.
12406 .vitem &$body_zerocount$&
12407 .cindex "message body" "binary zero count"
12408 .cindex "body of message" "binary zero count"
12409 .cindex "binary zero" "in message body"
12410 .vindex "&$body_zerocount$&"
12411 When a message is being received or delivered, this variable contains the
12412 number of binary zero bytes (ASCII NULs) in the message's body.
12414 .vitem &$bounce_recipient$&
12415 .vindex "&$bounce_recipient$&"
12416 This is set to the recipient address of a bounce message while Exim is creating
12417 it. It is useful if a customized bounce message text file is in use (see
12418 chapter &<<CHAPemsgcust>>&).
12420 .vitem &$bounce_return_size_limit$&
12421 .vindex "&$bounce_return_size_limit$&"
12422 This contains the value set in the &%bounce_return_size_limit%& option, rounded
12423 up to a multiple of 1000. It is useful when a customized error message text
12424 file is in use (see chapter &<<CHAPemsgcust>>&).
12426 .vitem &$caller_gid$&
12427 .cindex "gid (group id)" "caller"
12428 .vindex "&$caller_gid$&"
12429 The real group id under which the process that called Exim was running. This is
12430 not the same as the group id of the originator of a message (see
12431 &$originator_gid$&). If Exim re-execs itself, this variable in the new
12432 incarnation normally contains the Exim gid.
12434 .vitem &$caller_uid$&
12435 .cindex "uid (user id)" "caller"
12436 .vindex "&$caller_uid$&"
12437 The real user id under which the process that called Exim was running. This is
12438 not the same as the user id of the originator of a message (see
12439 &$originator_uid$&). If Exim re-execs itself, this variable in the new
12440 incarnation normally contains the Exim uid.
12442 .vitem &$callout_address$&
12443 .vindex "&$callout_address$&"
12444 After a callout for verification, spamd or malware daemon service, the
12445 address that was connected to.
12447 .vitem &$compile_number$&
12448 .vindex "&$compile_number$&"
12449 The building process for Exim keeps a count of the number
12450 of times it has been compiled. This serves to distinguish different
12451 compilations of the same version of Exim.
12453 .vitem &$config_dir$&
12454 .vindex "&$config_dir$&"
12455 The directory name of the main configuration file. That is, the content of
12456 &$config_file$& with the last component stripped. The value does not
12457 contain the trailing slash. If &$config_file$& does not contain a slash,
12458 &$config_dir$& is ".".
12460 .vitem &$config_file$&
12461 .vindex "&$config_file$&"
12462 The name of the main configuration file Exim is using.
12464 .vitem &$dkim_verify_status$&
12465 Results of DKIM verification.
12466 For details see section &<<SECDKIMVFY>>&.
12468 .vitem &$dkim_cur_signer$& &&&
12469 &$dkim_verify_reason$& &&&
12470 &$dkim_domain$& &&&
12471 &$dkim_identity$& &&&
12472 &$dkim_selector$& &&&
12474 &$dkim_canon_body$& &&&
12475 &$dkim_canon_headers$& &&&
12476 &$dkim_copiedheaders$& &&&
12477 &$dkim_bodylength$& &&&
12478 &$dkim_created$& &&&
12479 &$dkim_expires$& &&&
12480 &$dkim_headernames$& &&&
12481 &$dkim_key_testing$& &&&
12482 &$dkim_key_nosubdomains$& &&&
12483 &$dkim_key_srvtype$& &&&
12484 &$dkim_key_granularity$& &&&
12485 &$dkim_key_notes$& &&&
12486 &$dkim_key_length$&
12487 These variables are only available within the DKIM ACL.
12488 For details see section &<<SECDKIMVFY>>&.
12490 .vitem &$dkim_signers$&
12491 .vindex &$dkim_signers$&
12492 When a message has been received this variable contains
12493 a colon-separated list of signer domains and identities for the message.
12494 For details see section &<<SECDKIMVFY>>&.
12496 .vitem &$dmarc_domain_policy$& &&&
12497 &$dmarc_status$& &&&
12498 &$dmarc_status_text$& &&&
12499 &$dmarc_used_domains$&
12500 Results of DMARC verification.
12501 For details see section &<<SECDMARC>>&.
12503 .vitem &$dnslist_domain$& &&&
12504 &$dnslist_matched$& &&&
12505 &$dnslist_text$& &&&
12507 .vindex "&$dnslist_domain$&"
12508 .vindex "&$dnslist_matched$&"
12509 .vindex "&$dnslist_text$&"
12510 .vindex "&$dnslist_value$&"
12511 .cindex "black list (DNS)"
12512 When a DNS (black) list lookup succeeds, these variables are set to contain
12513 the following data from the lookup: the list's domain name, the key that was
12514 looked up, the contents of any associated TXT record, and the value from the
12515 main A record. See section &<<SECID204>>& for more details.
12518 .vindex "&$domain$&"
12519 When an address is being routed, or delivered on its own, this variable
12520 contains the domain. Uppercase letters in the domain are converted into lower
12521 case for &$domain$&.
12523 Global address rewriting happens when a message is received, so the value of
12524 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
12525 is set during user filtering, but not during system filtering, because a
12526 message may have many recipients and the system filter is called just once.
12528 When more than one address is being delivered at once (for example, several
12529 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
12530 have the same domain. Transports can be restricted to handling only one domain
12531 at a time if the value of &$domain$& is required at transport time &-- this is
12532 the default for local transports. For further details of the environment in
12533 which local transports are run, see chapter &<<CHAPenvironment>>&.
12535 .oindex "&%delay_warning_condition%&"
12536 At the end of a delivery, if all deferred addresses have the same domain, it is
12537 set in &$domain$& during the expansion of &%delay_warning_condition%&.
12539 The &$domain$& variable is also used in some other circumstances:
12542 When an ACL is running for a RCPT command, &$domain$& contains the domain of
12543 the recipient address. The domain of the &'sender'& address is in
12544 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
12545 normally set during the running of the MAIL ACL. However, if the sender address
12546 is verified with a callout during the MAIL ACL, the sender domain is placed in
12547 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
12548 the &(smtp)& transport.
12551 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12552 &$domain$& contains the domain portion of the address that is being rewritten;
12553 it can be used in the expansion of the replacement address, for example, to
12554 rewrite domains by file lookup.
12557 With one important exception, whenever a domain list is being scanned,
12558 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
12559 a &%sender_domains%& condition in an ACL is being processed, the subject domain
12560 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
12561 that, in a RCPT ACL, the sender domain list can be dependent on the
12562 recipient domain (which is what is in &$domain$& at this time).
12565 .cindex "ETRN" "value of &$domain$&"
12566 .oindex "&%smtp_etrn_command%&"
12567 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
12568 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
12571 .cindex "tainted data"
12572 If the origin of the data is an incoming message,
12573 the result of expanding this variable is tainted and may not
12574 be further expanded or used as a filename.
12575 When an untainted version is needed, one should be obtained from
12576 looking up the value in a local (therefore trusted) database.
12577 Often &$domain_data$& is usable in this role.
12580 .vitem &$domain_data$&
12581 .vindex "&$domain_data$&"
12582 When the &%domains%& condition on a router
12586 against a list, the match value is copied to &$domain_data$&.
12587 This is an enhancement over previous versions of Exim, when it only
12588 applied to the data read by a lookup.
12589 For details on match values see section &<<SECTlistresults>>& et. al.
12592 If the router routes the
12593 address to a transport, the value is available in that transport. If the
12594 transport is handling multiple addresses, the value from the first address is
12597 &$domain_data$& set in an ACL is available during
12598 the rest of the ACL statement.
12600 .vitem &$exim_gid$&
12601 .vindex "&$exim_gid$&"
12602 This variable contains the numerical value of the Exim group id.
12604 .vitem &$exim_path$&
12605 .vindex "&$exim_path$&"
12606 This variable contains the path to the Exim binary.
12608 .vitem &$exim_uid$&
12609 .vindex "&$exim_uid$&"
12610 This variable contains the numerical value of the Exim user id.
12612 .vitem &$exim_version$&
12613 .vindex "&$exim_version$&"
12614 This variable contains the version string of the Exim build.
12615 The first character is a major version number, currently 4.
12616 Then after a dot, the next group of digits is a minor version number.
12617 There may be other characters following the minor version.
12618 This value may be overridden by the &%exim_version%& main config option.
12620 .vitem &$header_$&<&'name'&>
12621 This is not strictly an expansion variable. It is expansion syntax for
12622 inserting the message header line with the given name. Note that the name must
12623 be terminated by colon or white space, because it may contain a wide variety of
12624 characters. Note also that braces must &'not'& be used.
12625 See the full description in section &<<SECTexpansionitems>>& above.
12627 .vitem &$headers_added$&
12628 .vindex "&$headers_added$&"
12629 Within an ACL this variable contains the headers added so far by
12630 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
12631 The headers are a newline-separated list.
12635 When the &%check_local_user%& option is set for a router, the user's home
12636 directory is placed in &$home$& when the check succeeds. In particular, this
12637 means it is set during the running of users' filter files. A router may also
12638 explicitly set a home directory for use by a transport; this can be overridden
12639 by a setting on the transport itself.
12641 When running a filter test via the &%-bf%& option, &$home$& is set to the value
12642 of the environment variable HOME, which is subject to the
12643 &%keep_environment%& and &%add_environment%& main config options.
12647 If a router assigns an address to a transport (any transport), and passes a
12648 list of hosts with the address, the value of &$host$& when the transport starts
12649 to run is the name of the first host on the list. Note that this applies both
12650 to local and remote transports.
12652 .cindex "transport" "filter"
12653 .cindex "filter" "transport filter"
12654 For the &(smtp)& transport, if there is more than one host, the value of
12655 &$host$& changes as the transport works its way through the list. In
12656 particular, when the &(smtp)& transport is expanding its options for encryption
12657 using TLS, or for specifying a transport filter (see chapter
12658 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
12661 When used in the client part of an authenticator configuration (see chapter
12662 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
12663 client is connected.
12666 .vitem &$host_address$&
12667 .vindex "&$host_address$&"
12668 This variable is set to the remote host's IP address whenever &$host$& is set
12669 for a remote connection. It is also set to the IP address that is being checked
12670 when the &%ignore_target_hosts%& option is being processed.
12672 .vitem &$host_data$&
12673 .vindex "&$host_data$&"
12674 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
12675 result of the lookup is made available in the &$host_data$& variable. This
12676 allows you, for example, to do things like this:
12678 deny hosts = net-lsearch;/some/file
12679 message = $host_data
12681 .vitem &$host_lookup_deferred$&
12682 .cindex "host name" "lookup, failure of"
12683 .vindex "&$host_lookup_deferred$&"
12684 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
12685 message comes from a remote host and there is an attempt to look up the host's
12686 name from its IP address, and the attempt is not successful, one of these
12687 variables is set to &"1"&.
12690 If the lookup receives a definite negative response (for example, a DNS lookup
12691 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
12694 If there is any kind of problem during the lookup, such that Exim cannot
12695 tell whether or not the host name is defined (for example, a timeout for a DNS
12696 lookup), &$host_lookup_deferred$& is set to &"1"&.
12699 Looking up a host's name from its IP address consists of more than just a
12700 single reverse lookup. Exim checks that a forward lookup of at least one of the
12701 names it receives from a reverse lookup yields the original IP address. If this
12702 is not the case, Exim does not accept the looked up name(s), and
12703 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
12704 IP address (for example, the existence of a PTR record in the DNS) is not
12705 sufficient on its own for the success of a host name lookup. If the reverse
12706 lookup succeeds, but there is a lookup problem such as a timeout when checking
12707 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
12708 &"1"&. See also &$sender_host_name$&.
12710 .cindex authentication "expansion item"
12711 Performing these checks sets up information used by the
12712 &%authresults%& expansion item.
12715 .vitem &$host_lookup_failed$&
12716 .vindex "&$host_lookup_failed$&"
12717 See &$host_lookup_deferred$&.
12719 .vitem &$host_port$&
12720 .vindex "&$host_port$&"
12721 This variable is set to the remote host's TCP port whenever &$host$& is set
12722 for an outbound connection.
12724 .vitem &$initial_cwd$&
12725 .vindex "&$initial_cwd$&
12726 This variable contains the full path name of the initial working
12727 directory of the current Exim process. This may differ from the current
12728 working directory, as Exim changes this to "/" during early startup, and
12729 to &$spool_directory$& later.
12732 .vindex "&$inode$&"
12733 The only time this variable is set is while expanding the &%directory_file%&
12734 option in the &(appendfile)& transport. The variable contains the inode number
12735 of the temporary file which is about to be renamed. It can be used to construct
12736 a unique name for the file.
12738 .vitem &$interface_address$&
12739 .vindex "&$interface_address$&"
12740 This is an obsolete name for &$received_ip_address$&.
12742 .vitem &$interface_port$&
12743 .vindex "&$interface_port$&"
12744 This is an obsolete name for &$received_port$&.
12748 This variable is used during the expansion of &*forall*& and &*forany*&
12749 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
12750 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
12754 .vindex "&$ldap_dn$&"
12755 This variable, which is available only when Exim is compiled with LDAP support,
12756 contains the DN from the last entry in the most recently successful LDAP
12759 .vitem &$load_average$&
12760 .vindex "&$load_average$&"
12761 This variable contains the system load average, multiplied by 1000 so that it
12762 is an integer. For example, if the load average is 0.21, the value of the
12763 variable is 210. The value is recomputed every time the variable is referenced.
12765 .vitem &$local_part$&
12766 .vindex "&$local_part$&"
12767 When an address is being routed, or delivered on its own, this
12768 variable contains the local part. When a number of addresses are being
12769 delivered together (for example, multiple RCPT commands in an SMTP
12770 session), &$local_part$& is not set.
12772 Global address rewriting happens when a message is received, so the value of
12773 &$local_part$& during routing and delivery is the value after rewriting.
12774 &$local_part$& is set during user filtering, but not during system filtering,
12775 because a message may have many recipients and the system filter is called just
12778 .cindex "tainted data"
12779 If the origin of the data is an incoming message,
12780 the result of expanding this variable is tainted and
12781 may not be further expanded or used as a filename.
12783 &*Warning*&: the content of this variable is usually provided by a potential
12785 Consider carefully the implications of using it unvalidated as a name
12787 This presents issues for users' &_.forward_& and filter files.
12788 For traditional full user accounts, use &%check_local_users%& and the
12789 &$local_part_data$& variable rather than this one.
12790 For virtual users, store a suitable pathname component in the database
12791 which is used for account name validation, and use that retrieved value
12792 rather than this variable.
12793 Often &$local_part_data$& is usable in this role.
12794 If needed, use a router &%address_data%& or &%set%& option for
12795 the retrieved data.
12797 When a message is being delivered to a file, pipe, or autoreply transport as a
12798 result of aliasing or forwarding, &$local_part$& is set to the local part of
12799 the parent address, not to the filename or command (see &$address_file$& and
12802 When an ACL is running for a RCPT command, &$local_part$& contains the
12803 local part of the recipient address.
12805 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12806 &$local_part$& contains the local part of the address that is being rewritten;
12807 it can be used in the expansion of the replacement address, for example.
12809 In all cases, all quoting is removed from the local part. For example, for both
12812 "abc:xyz"@test.example
12813 abc\:xyz@test.example
12815 the value of &$local_part$& is
12819 If you use &$local_part$& to create another address, you should always wrap it
12820 inside a quoting operator. For example, in a &(redirect)& router you could
12823 data = ${quote_local_part:$local_part}@new.domain.example
12825 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
12826 to process local parts in a case-dependent manner in a router, you can set the
12827 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
12829 .vitem &$local_part_data$&
12830 .vindex "&$local_part_data$&"
12831 When the &%local_parts%& condition on a router or ACL
12832 matches a local part list
12834 the match value is copied to &$local_part_data$&.
12835 This is an enhancement over previous versions of Exim, when it only
12836 applied to the data read by a lookup.
12837 For details on match values see section &<<SECTlistresults>>& et. al.
12840 The &%check_local_user%& router option also sets this variable.
12842 .vindex &$local_part_prefix$& &&&
12843 &$local_part_prefix_v$& &&&
12844 &$local_part_suffix$& &&&
12845 &$local_part_suffix_v$&
12846 .cindex affix variables
12847 If a local part prefix or suffix has been recognized, it is not included in the
12848 value of &$local_part$& during routing and subsequent delivery. The values of
12849 any prefix or suffix are in &$local_part_prefix$& and
12850 &$local_part_suffix$&, respectively.
12851 .cindex "tainted data"
12852 If the specification did not include a wildcard then
12853 the affix variable value is not tainted.
12855 If the affix specification included a wildcard then the portion of
12856 the affix matched by the wildcard is in
12857 &$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate,
12858 and both the whole and varying values are tainted.
12860 .vitem &$local_scan_data$&
12861 .vindex "&$local_scan_data$&"
12862 This variable contains the text returned by the &[local_scan()]& function when
12863 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
12865 .vitem &$local_user_gid$&
12866 .vindex "&$local_user_gid$&"
12867 See &$local_user_uid$&.
12869 .vitem &$local_user_uid$&
12870 .vindex "&$local_user_uid$&"
12871 This variable and &$local_user_gid$& are set to the uid and gid after the
12872 &%check_local_user%& router precondition succeeds. This means that their values
12873 are available for the remaining preconditions (&%senders%&, &%require_files%&,
12874 and &%condition%&), for the &%address_data%& expansion, and for any
12875 router-specific expansions. At all other times, the values in these variables
12876 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
12878 .vitem &$localhost_number$&
12879 .vindex "&$localhost_number$&"
12880 This contains the expanded value of the
12881 &%localhost_number%& option. The expansion happens after the main options have
12884 .vitem &$log_inodes$&
12885 .vindex "&$log_inodes$&"
12886 The number of free inodes in the disk partition where Exim's
12887 log files are being written. The value is recalculated whenever the variable is
12888 referenced. If the relevant file system does not have the concept of inodes,
12889 the value of is -1. See also the &%check_log_inodes%& option.
12891 .vitem &$log_space$&
12892 .vindex "&$log_space$&"
12893 The amount of free space (as a number of kilobytes) in the disk
12894 partition where Exim's log files are being written. The value is recalculated
12895 whenever the variable is referenced. If the operating system does not have the
12896 ability to find the amount of free space (only true for experimental systems),
12897 the space value is -1. See also the &%check_log_space%& option.
12900 .vitem &$lookup_dnssec_authenticated$&
12901 .vindex "&$lookup_dnssec_authenticated$&"
12902 This variable is set after a DNS lookup done by
12903 a dnsdb lookup expansion, dnslookup router or smtp transport.
12904 .cindex "DNS" "DNSSEC"
12905 It will be empty if &(DNSSEC)& was not requested,
12906 &"no"& if the result was not labelled as authenticated data
12907 and &"yes"& if it was.
12908 Results that are labelled as authoritative answer that match
12909 the &%dns_trust_aa%& configuration variable count also
12910 as authenticated data.
12912 .vitem &$mailstore_basename$&
12913 .vindex "&$mailstore_basename$&"
12914 This variable is set only when doing deliveries in &"mailstore"& format in the
12915 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
12916 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
12917 contains the basename of the files that are being written, that is, the name
12918 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
12921 .vitem &$malware_name$&
12922 .vindex "&$malware_name$&"
12923 This variable is available when Exim is compiled with the
12924 content-scanning extension. It is set to the name of the virus that was found
12925 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12927 .vitem &$max_received_linelength$&
12928 .vindex "&$max_received_linelength$&"
12929 .cindex "maximum" "line length"
12930 .cindex "line length" "maximum"
12931 This variable contains the number of bytes in the longest line that was
12932 received as part of the message, not counting the line termination
12934 It is not valid if the &%spool_files_wireformat%& option is used.
12936 .vitem &$message_age$&
12937 .cindex "message" "age of"
12938 .vindex "&$message_age$&"
12939 This variable is set at the start of a delivery attempt to contain the number
12940 of seconds since the message was received. It does not change during a single
12943 .vitem &$message_body$&
12944 .cindex "body of message" "expansion variable"
12945 .cindex "message body" "in expansion"
12946 .cindex "binary zero" "in message body"
12947 .vindex "&$message_body$&"
12948 .oindex "&%message_body_visible%&"
12949 This variable contains the initial portion of a message's body while it is
12950 being delivered, and is intended mainly for use in filter files. The maximum
12951 number of characters of the body that are put into the variable is set by the
12952 &%message_body_visible%& configuration option; the default is 500.
12954 .oindex "&%message_body_newlines%&"
12955 By default, newlines are converted into spaces in &$message_body$&, to make it
12956 easier to search for phrases that might be split over a line break. However,
12957 this can be disabled by setting &%message_body_newlines%& to be true. Binary
12958 zeros are always converted into spaces.
12960 .vitem &$message_body_end$&
12961 .cindex "body of message" "expansion variable"
12962 .cindex "message body" "in expansion"
12963 .vindex "&$message_body_end$&"
12964 This variable contains the final portion of a message's
12965 body while it is being delivered. The format and maximum size are as for
12968 .vitem &$message_body_size$&
12969 .cindex "body of message" "size"
12970 .cindex "message body" "size"
12971 .vindex "&$message_body_size$&"
12972 When a message is being delivered, this variable contains the size of the body
12973 in bytes. The count starts from the character after the blank line that
12974 separates the body from the header. Newlines are included in the count. See
12975 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
12977 If the spool file is wireformat
12978 (see the &%spool_files_wireformat%& main option)
12979 the CRLF line-terminators are included in the count.
12981 .vitem &$message_exim_id$&
12982 .vindex "&$message_exim_id$&"
12983 When a message is being received or delivered, this variable contains the
12984 unique message id that is generated and used by Exim to identify the message.
12985 An id is not created for a message until after its header has been successfully
12986 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
12987 line; it is the local id that Exim assigns to the message, for example:
12988 &`1BXTIK-0001yO-VA`&.
12990 .vitem &$message_headers$&
12991 .vindex &$message_headers$&
12992 This variable contains a concatenation of all the header lines when a message
12993 is being processed, except for lines added by routers or transports. The header
12994 lines are separated by newline characters. Their contents are decoded in the
12995 same way as a header line that is inserted by &%bheader%&.
12997 .vitem &$message_headers_raw$&
12998 .vindex &$message_headers_raw$&
12999 This variable is like &$message_headers$& except that no processing of the
13000 contents of header lines is done.
13002 .vitem &$message_id$&
13003 This is an old name for &$message_exim_id$&. It is now deprecated.
13005 .vitem &$message_linecount$&
13006 .vindex "&$message_linecount$&"
13007 This variable contains the total number of lines in the header and body of the
13008 message. Compare &$body_linecount$&, which is the count for the body only.
13009 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
13010 number of lines received. Before delivery happens (that is, before filters,
13011 routers, and transports run) the count is increased to include the
13012 &'Received:'& header line that Exim standardly adds, and also any other header
13013 lines that are added by ACLs. The blank line that separates the message header
13014 from the body is not counted.
13016 As with the special case of &$message_size$&, during the expansion of the
13017 appendfile transport's maildir_tag option in maildir format, the value of
13018 &$message_linecount$& is the precise size of the number of newlines in the
13019 file that has been written (minus one for the blank line between the
13020 header and the body).
13022 Here is an example of the use of this variable in a DATA ACL:
13025 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
13026 message = Too many lines in message header
13028 In the MAIL and RCPT ACLs, the value is zero because at that stage the
13029 message has not yet been received.
13031 This variable is not valid if the &%spool_files_wireformat%& option is used.
13033 .vitem &$message_size$&
13034 .cindex "size" "of message"
13035 .cindex "message" "size"
13036 .vindex "&$message_size$&"
13037 When a message is being processed, this variable contains its size in bytes. In
13038 most cases, the size includes those headers that were received with the
13039 message, but not those (such as &'Envelope-to:'&) that are added to individual
13040 deliveries as they are written. However, there is one special case: during the
13041 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
13042 doing a delivery in maildir format, the value of &$message_size$& is the
13043 precise size of the file that has been written. See also
13044 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
13046 .cindex "RCPT" "value of &$message_size$&"
13047 While running a per message ACL (mail/rcpt/predata), &$message_size$&
13048 contains the size supplied on the MAIL command, or -1 if no size was given. The
13049 value may not, of course, be truthful.
13051 .vitem &$mime_$&&'xxx'&
13052 A number of variables whose names start with &$mime$& are
13053 available when Exim is compiled with the content-scanning extension. For
13054 details, see section &<<SECTscanmimepart>>&.
13056 .vitem "&$n0$& &-- &$n9$&"
13057 These variables are counters that can be incremented by means
13058 of the &%add%& command in filter files.
13060 .vitem &$original_domain$&
13061 .vindex "&$domain$&"
13062 .vindex "&$original_domain$&"
13063 When a top-level address is being processed for delivery, this contains the
13064 same value as &$domain$&. However, if a &"child"& address (for example,
13065 generated by an alias, forward, or filter file) is being processed, this
13066 variable contains the domain of the original address (lower cased). This
13067 differs from &$parent_domain$& only when there is more than one level of
13068 aliasing or forwarding. When more than one address is being delivered in a
13069 single transport run, &$original_domain$& is not set.
13071 If a new address is created by means of a &%deliver%& command in a system
13072 filter, it is set up with an artificial &"parent"& address. This has the local
13073 part &'system-filter'& and the default qualify domain.
13075 .vitem &$original_local_part$&
13076 .vindex "&$local_part$&"
13077 .vindex "&$original_local_part$&"
13078 When a top-level address is being processed for delivery, this contains the
13079 same value as &$local_part$&, unless a prefix or suffix was removed from the
13080 local part, because &$original_local_part$& always contains the full local
13081 part. When a &"child"& address (for example, generated by an alias, forward, or
13082 filter file) is being processed, this variable contains the full local part of
13083 the original address.
13085 If the router that did the redirection processed the local part
13086 case-insensitively, the value in &$original_local_part$& is in lower case.
13087 This variable differs from &$parent_local_part$& only when there is more than
13088 one level of aliasing or forwarding. When more than one address is being
13089 delivered in a single transport run, &$original_local_part$& is not set.
13091 If a new address is created by means of a &%deliver%& command in a system
13092 filter, it is set up with an artificial &"parent"& address. This has the local
13093 part &'system-filter'& and the default qualify domain.
13095 .vitem &$originator_gid$&
13096 .cindex "gid (group id)" "of originating user"
13097 .cindex "sender" "gid"
13098 .vindex "&$caller_gid$&"
13099 .vindex "&$originator_gid$&"
13100 This variable contains the value of &$caller_gid$& that was set when the
13101 message was received. For messages received via the command line, this is the
13102 gid of the sending user. For messages received by SMTP over TCP/IP, this is
13103 normally the gid of the Exim user.
13105 .vitem &$originator_uid$&
13106 .cindex "uid (user id)" "of originating user"
13107 .cindex "sender" "uid"
13108 .vindex "&$caller_uid$&"
13109 .vindex "&$originator_uid$&"
13110 The value of &$caller_uid$& that was set when the message was received. For
13111 messages received via the command line, this is the uid of the sending user.
13112 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
13115 .vitem &$parent_domain$&
13116 .vindex "&$parent_domain$&"
13117 This variable is similar to &$original_domain$& (see
13118 above), except that it refers to the immediately preceding parent address.
13120 .vitem &$parent_local_part$&
13121 .vindex "&$parent_local_part$&"
13122 This variable is similar to &$original_local_part$&
13123 (see above), except that it refers to the immediately preceding parent address.
13126 .cindex "pid (process id)" "of current process"
13128 This variable contains the current process id.
13130 .vitem &$pipe_addresses$&
13131 .cindex "filter" "transport filter"
13132 .cindex "transport" "filter"
13133 .vindex "&$pipe_addresses$&"
13134 This is not an expansion variable, but is mentioned here because the string
13135 &`$pipe_addresses`& is handled specially in the command specification for the
13136 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
13137 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
13138 It cannot be used in general expansion strings, and provokes an &"unknown
13139 variable"& error if encountered.
13141 .vitem &$primary_hostname$&
13142 .vindex "&$primary_hostname$&"
13143 This variable contains the value set by &%primary_hostname%& in the
13144 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
13145 a single-component name, Exim calls &[gethostbyname()]& (or
13146 &[getipnodebyname()]& where available) in an attempt to acquire a fully
13147 qualified host name. See also &$smtp_active_hostname$&.
13150 .vitem &$proxy_external_address$& &&&
13151 &$proxy_external_port$& &&&
13152 &$proxy_local_address$& &&&
13153 &$proxy_local_port$& &&&
13155 These variables are only available when built with Proxy Protocol
13157 For details see chapter &<<SECTproxyInbound>>&.
13159 .vitem &$prdr_requested$&
13160 .cindex "PRDR" "variable for"
13161 This variable is set to &"yes"& if PRDR was requested by the client for the
13162 current message, otherwise &"no"&.
13164 .vitem &$prvscheck_address$&
13165 This variable is used in conjunction with the &%prvscheck%& expansion item,
13166 which is described in sections &<<SECTexpansionitems>>& and
13167 &<<SECTverifyPRVS>>&.
13169 .vitem &$prvscheck_keynum$&
13170 This variable is used in conjunction with the &%prvscheck%& expansion item,
13171 which is described in sections &<<SECTexpansionitems>>& and
13172 &<<SECTverifyPRVS>>&.
13174 .vitem &$prvscheck_result$&
13175 This variable is used in conjunction with the &%prvscheck%& expansion item,
13176 which is described in sections &<<SECTexpansionitems>>& and
13177 &<<SECTverifyPRVS>>&.
13179 .vitem &$qualify_domain$&
13180 .vindex "&$qualify_domain$&"
13181 The value set for the &%qualify_domain%& option in the configuration file.
13183 .vitem &$qualify_recipient$&
13184 .vindex "&$qualify_recipient$&"
13185 The value set for the &%qualify_recipient%& option in the configuration file,
13186 or if not set, the value of &$qualify_domain$&.
13188 .vitem &$queue_name$&
13189 .vindex &$queue_name$&
13190 .cindex "named queues" variable
13191 .cindex queues named
13192 The name of the spool queue in use; empty for the default queue.
13194 .vitem &$queue_size$&
13195 .vindex "&$queue_size$&"
13196 .cindex "queue" "size of"
13197 .cindex "spool" "number of messages"
13198 This variable contains the number of messages queued.
13199 It is evaluated on demand, but no more often than once every minute.
13200 If there is no daemon notifier socket open, the value will be
13205 .cindex router variables
13206 Values can be placed in these variables by the &%set%& option of a router.
13207 They can be given any name that starts with &$r_$&.
13208 The values persist for the address being handled through subsequent routers
13209 and the eventual transport.
13211 .vitem &$rcpt_count$&
13212 .vindex "&$rcpt_count$&"
13213 When a message is being received by SMTP, this variable contains the number of
13214 RCPT commands received for the current message. If this variable is used in a
13215 RCPT ACL, its value includes the current command.
13217 .vitem &$rcpt_defer_count$&
13218 .vindex "&$rcpt_defer_count$&"
13219 .cindex "4&'xx'& responses" "count of"
13220 When a message is being received by SMTP, this variable contains the number of
13221 RCPT commands in the current message that have previously been rejected with a
13222 temporary (4&'xx'&) response.
13224 .vitem &$rcpt_fail_count$&
13225 .vindex "&$rcpt_fail_count$&"
13226 When a message is being received by SMTP, this variable contains the number of
13227 RCPT commands in the current message that have previously been rejected with a
13228 permanent (5&'xx'&) response.
13230 .vitem &$received_count$&
13231 .vindex "&$received_count$&"
13232 This variable contains the number of &'Received:'& header lines in the message,
13233 including the one added by Exim (so its value is always greater than zero). It
13234 is available in the DATA ACL, the non-SMTP ACL, and while routing and
13237 .vitem &$received_for$&
13238 .vindex "&$received_for$&"
13239 If there is only a single recipient address in an incoming message, this
13240 variable contains that address when the &'Received:'& header line is being
13241 built. The value is copied after recipient rewriting has happened, but before
13242 the &[local_scan()]& function is run.
13244 .vitem &$received_ip_address$&
13245 .vindex "&$received_ip_address$&"
13246 As soon as an Exim server starts processing an incoming TCP/IP connection, this
13247 variable is set to the address of the local IP interface, and &$received_port$&
13248 is set to the local port number. (The remote IP address and port are in
13249 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
13250 the port value is -1 unless it has been set using the &%-oMi%& command line
13253 As well as being useful in ACLs (including the &"connect"& ACL), these variable
13254 could be used, for example, to make the filename for a TLS certificate depend
13255 on which interface and/or port is being used for the incoming connection. The
13256 values of &$received_ip_address$& and &$received_port$& are saved with any
13257 messages that are received, thus making these variables available at delivery
13259 For outbound connections see &$sending_ip_address$&.
13261 .vitem &$received_port$&
13262 .vindex "&$received_port$&"
13263 See &$received_ip_address$&.
13265 .vitem &$received_protocol$&
13266 .vindex "&$received_protocol$&"
13267 When a message is being processed, this variable contains the name of the
13268 protocol by which it was received. Most of the names used by Exim are defined
13269 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
13270 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
13271 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
13272 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
13273 connection and the client was successfully authenticated.
13275 Exim uses the protocol name &"smtps"& for the case when encryption is
13276 automatically set up on connection without the use of STARTTLS (see
13277 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
13278 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
13279 where the client initially uses EHLO, sets up an encrypted connection using
13280 STARTTLS, and then uses HELO afterwards.
13282 The &%-oMr%& option provides a way of specifying a custom protocol name for
13283 messages that are injected locally by trusted callers. This is commonly used to
13284 identify messages that are being re-injected after some kind of scanning.
13286 .vitem &$received_time$&
13287 .vindex "&$received_time$&"
13288 This variable contains the date and time when the current message was received,
13289 as a number of seconds since the start of the Unix epoch.
13291 .vitem &$recipient_data$&
13292 .vindex "&$recipient_data$&"
13293 This variable is set after an indexing lookup success in an ACL &%recipients%&
13294 condition. It contains the data from the lookup, and the value remains set
13295 until the next &%recipients%& test. Thus, you can do things like this:
13297 &`require recipients = cdb*@;/some/file`&
13298 &`deny `&&'some further test involving'& &`$recipient_data`&
13300 &*Warning*&: This variable is set only when a lookup is used as an indexing
13301 method in the address list, using the semicolon syntax as in the example above.
13302 The variable is not set for a lookup that is used as part of the string
13303 expansion that all such lists undergo before being interpreted.
13305 .vitem &$recipient_verify_failure$&
13306 .vindex "&$recipient_verify_failure$&"
13307 In an ACL, when a recipient verification fails, this variable contains
13308 information about the failure. It is set to one of the following words:
13311 &"qualify"&: The address was unqualified (no domain), and the message
13312 was neither local nor came from an exempted host.
13315 &"route"&: Routing failed.
13318 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
13319 or before the MAIL command (that is, on initial connection, HELO, or
13323 &"recipient"&: The RCPT command in a callout was rejected.
13326 &"postmaster"&: The postmaster check in a callout was rejected.
13329 The main use of this variable is expected to be to distinguish between
13330 rejections of MAIL and rejections of RCPT.
13332 .vitem &$recipients$&
13333 .vindex "&$recipients$&"
13334 This variable contains a list of envelope recipients for a message. A comma and
13335 a space separate the addresses in the replacement text. However, the variable
13336 is not generally available, to prevent exposure of Bcc recipients in
13337 unprivileged users' filter files. You can use &$recipients$& only in these
13341 In a system filter file.
13343 In the ACLs associated with the DATA command and with non-SMTP messages, that
13344 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
13345 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
13346 &%acl_not_smtp_mime%&.
13348 From within a &[local_scan()]& function.
13352 .vitem &$recipients_count$&
13353 .vindex "&$recipients_count$&"
13354 When a message is being processed, this variable contains the number of
13355 envelope recipients that came with the message. Duplicates are not excluded
13356 from the count. While a message is being received over SMTP, the number
13357 increases for each accepted recipient. It can be referenced in an ACL.
13360 .vitem &$regex_match_string$&
13361 .vindex "&$regex_match_string$&"
13362 This variable is set to contain the matching regular expression after a
13363 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
13365 .vitem "&$regex1$&, &$regex2$&, etc"
13366 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
13367 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
13368 these variables contain the
13369 captured substrings identified by the regular expression.
13372 .vitem &$reply_address$&
13373 .vindex "&$reply_address$&"
13374 When a message is being processed, this variable contains the contents of the
13375 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
13376 contents of the &'From:'& header line. Apart from the removal of leading
13377 white space, the value is not processed in any way. In particular, no RFC 2047
13378 decoding or character code translation takes place.
13380 .vitem &$return_path$&
13381 .vindex "&$return_path$&"
13382 When a message is being delivered, this variable contains the return path &--
13383 the sender field that will be sent as part of the envelope. It is not enclosed
13384 in <> characters. At the start of routing an address, &$return_path$& has the
13385 same value as &$sender_address$&, but if, for example, an incoming message to a
13386 mailing list has been expanded by a router which specifies a different address
13387 for bounce messages, &$return_path$& subsequently contains the new bounce
13388 address, whereas &$sender_address$& always contains the original sender address
13389 that was received with the message. In other words, &$sender_address$& contains
13390 the incoming envelope sender, and &$return_path$& contains the outgoing
13393 .vitem &$return_size_limit$&
13394 .vindex "&$return_size_limit$&"
13395 This is an obsolete name for &$bounce_return_size_limit$&.
13397 .vitem &$router_name$&
13398 .cindex "router" "name"
13399 .cindex "name" "of router"
13400 .vindex "&$router_name$&"
13401 During the running of a router this variable contains its name.
13404 .cindex "return code" "from &%run%& expansion"
13405 .vindex "&$runrc$&"
13406 This variable contains the return code from a command that is run by the
13407 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
13408 assume the order in which option values are expanded, except for those
13409 preconditions whose order of testing is documented. Therefore, you cannot
13410 reliably expect to set &$runrc$& by the expansion of one option, and use it in
13413 .vitem &$self_hostname$&
13414 .oindex "&%self%&" "value of host name"
13415 .vindex "&$self_hostname$&"
13416 When an address is routed to a supposedly remote host that turns out to be the
13417 local host, what happens is controlled by the &%self%& generic router option.
13418 One of its values causes the address to be passed to another router. When this
13419 happens, &$self_hostname$& is set to the name of the local host that the
13420 original router encountered. In other circumstances its contents are null.
13422 .vitem &$sender_address$&
13423 .vindex "&$sender_address$&"
13424 When a message is being processed, this variable contains the sender's address
13425 that was received in the message's envelope. The case of letters in the address
13426 is retained, in both the local part and the domain. For bounce messages, the
13427 value of this variable is the empty string. See also &$return_path$&.
13429 .vitem &$sender_address_data$&
13430 .vindex "&$address_data$&"
13431 .vindex "&$sender_address_data$&"
13432 If &$address_data$& is set when the routers are called from an ACL to verify a
13433 sender address, the final value is preserved in &$sender_address_data$&, to
13434 distinguish it from data from a recipient address. The value does not persist
13435 after the end of the current ACL statement. If you want to preserve it for
13436 longer, you can save it in an ACL variable.
13438 .vitem &$sender_address_domain$&
13439 .vindex "&$sender_address_domain$&"
13440 The domain portion of &$sender_address$&.
13442 .vitem &$sender_address_local_part$&
13443 .vindex "&$sender_address_local_part$&"
13444 The local part portion of &$sender_address$&.
13446 .vitem &$sender_data$&
13447 .vindex "&$sender_data$&"
13448 This variable is set after a lookup success in an ACL &%senders%& condition or
13449 in a router &%senders%& option. It contains the data from the lookup, and the
13450 value remains set until the next &%senders%& test. Thus, you can do things like
13453 &`require senders = cdb*@;/some/file`&
13454 &`deny `&&'some further test involving'& &`$sender_data`&
13456 &*Warning*&: This variable is set only when a lookup is used as an indexing
13457 method in the address list, using the semicolon syntax as in the example above.
13458 The variable is not set for a lookup that is used as part of the string
13459 expansion that all such lists undergo before being interpreted.
13461 .vitem &$sender_fullhost$&
13462 .vindex "&$sender_fullhost$&"
13463 When a message is received from a remote host, this variable contains the host
13464 name and IP address in a single string. It ends with the IP address in square
13465 brackets, followed by a colon and a port number if the logging of ports is
13466 enabled. The format of the rest of the string depends on whether the host
13467 issued a HELO or EHLO SMTP command, and whether the host name was verified by
13468 looking up its IP address. (Looking up the IP address can be forced by the
13469 &%host_lookup%& option, independent of verification.) A plain host name at the
13470 start of the string is a verified host name; if this is not present,
13471 verification either failed or was not requested. A host name in parentheses is
13472 the argument of a HELO or EHLO command. This is omitted if it is identical to
13473 the verified host name or to the host's IP address in square brackets.
13475 .vitem &$sender_helo_dnssec$&
13476 .vindex "&$sender_helo_dnssec$&"
13477 This boolean variable is true if a successful HELO verification was
13478 .cindex "DNS" "DNSSEC"
13479 done using DNS information the resolver library stated was authenticated data.
13481 .vitem &$sender_helo_name$&
13482 .vindex "&$sender_helo_name$&"
13483 When a message is received from a remote host that has issued a HELO or EHLO
13484 command, the argument of that command is placed in this variable. It is also
13485 set if HELO or EHLO is used when a message is received using SMTP locally via
13486 the &%-bs%& or &%-bS%& options.
13488 .vitem &$sender_host_address$&
13489 .vindex "&$sender_host_address$&"
13490 When a message is received from a remote host using SMTP,
13491 this variable contains that
13492 host's IP address. For locally non-SMTP submitted messages, it is empty.
13494 .vitem &$sender_host_authenticated$&
13495 .vindex "&$sender_host_authenticated$&"
13496 This variable contains the name (not the public name) of the authenticator
13497 driver that successfully authenticated the client from which the message was
13498 received. It is empty if there was no successful authentication. See also
13499 &$authenticated_id$&.
13501 .vitem &$sender_host_dnssec$&
13502 .vindex "&$sender_host_dnssec$&"
13503 If an attempt to populate &$sender_host_name$& has been made
13504 (by reference, &%hosts_lookup%& or
13505 otherwise) then this boolean will have been set true if, and only if, the
13506 resolver library states that both
13507 the reverse and forward DNS were authenticated data. At all
13508 other times, this variable is false.
13510 .cindex "DNS" "DNSSEC"
13511 It is likely that you will need to coerce DNSSEC support on in the resolver
13512 library, by setting:
13517 In addition, on Linux with glibc 2.31 or newer the resolver library will
13518 default to stripping out a successful validation status.
13519 This will break a previously working Exim installation.
13520 Provided that you do trust the resolver (ie, is on localhost) you can tell
13521 glibc to pass through any successful validation with a new option in
13522 &_/etc/resolv.conf_&:
13527 Exim does not perform DNSSEC validation itself, instead leaving that to a
13528 validating resolver (e.g. unbound, or bind with suitable configuration).
13530 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
13531 mechanism in the list, then this variable will be false.
13533 This requires that your system resolver library support EDNS0 (and that
13534 DNSSEC flags exist in the system headers). If the resolver silently drops
13535 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
13536 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
13539 .vitem &$sender_host_name$&
13540 .vindex "&$sender_host_name$&"
13541 When a message is received from a remote host, this variable contains the
13542 host's name as obtained by looking up its IP address. For messages received by
13543 other means, this variable is empty.
13545 .vindex "&$host_lookup_failed$&"
13546 If the host name has not previously been looked up, a reference to
13547 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
13548 A looked up name is accepted only if it leads back to the original IP address
13549 via a forward lookup. If either the reverse or the forward lookup fails to find
13550 any data, or if the forward lookup does not yield the original IP address,
13551 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
13553 .vindex "&$host_lookup_deferred$&"
13554 However, if either of the lookups cannot be completed (for example, there is a
13555 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
13556 &$host_lookup_failed$& remains set to &"0"&.
13558 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
13559 host name again if there is a subsequent reference to &$sender_host_name$&
13560 in the same Exim process, but it does try again if &$host_lookup_deferred$&
13563 Exim does not automatically look up every calling host's name. If you want
13564 maximum efficiency, you should arrange your configuration so that it avoids
13565 these lookups altogether. The lookup happens only if one or more of the
13566 following are true:
13569 A string containing &$sender_host_name$& is expanded.
13571 The calling host matches the list in &%host_lookup%&. In the default
13572 configuration, this option is set to *, so it must be changed if lookups are
13573 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
13575 Exim needs the host name in order to test an item in a host list. The items
13576 that require this are described in sections &<<SECThoslispatnam>>& and
13577 &<<SECThoslispatnamsk>>&.
13579 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
13580 In this case, the host name is required to compare with the name quoted in any
13581 EHLO or HELO commands that the client issues.
13583 The remote host issues a EHLO or HELO command that quotes one of the
13584 domains in &%helo_lookup_domains%&. The default value of this option is
13585 . ==== As this is a nested list, any displays it contains must be indented
13586 . ==== as otherwise they are too far to the left.
13588 helo_lookup_domains = @ : @[]
13590 which causes a lookup if a remote host (incorrectly) gives the server's name or
13591 IP address in an EHLO or HELO command.
13595 .vitem &$sender_host_port$&
13596 .vindex "&$sender_host_port$&"
13597 When a message is received from a remote host, this variable contains the port
13598 number that was used on the remote host.
13600 .vitem &$sender_ident$&
13601 .vindex "&$sender_ident$&"
13602 When a message is received from a remote host, this variable contains the
13603 identification received in response to an RFC 1413 request. When a message has
13604 been received locally, this variable contains the login name of the user that
13607 .vitem &$sender_rate_$&&'xxx'&
13608 A number of variables whose names begin &$sender_rate_$& are set as part of the
13609 &%ratelimit%& ACL condition. Details are given in section
13610 &<<SECTratelimiting>>&.
13612 .vitem &$sender_rcvhost$&
13613 .cindex "DNS" "reverse lookup"
13614 .cindex "reverse DNS lookup"
13615 .vindex "&$sender_rcvhost$&"
13616 This is provided specifically for use in &'Received:'& headers. It starts with
13617 either the verified host name (as obtained from a reverse DNS lookup) or, if
13618 there is no verified host name, the IP address in square brackets. After that
13619 there may be text in parentheses. When the first item is a verified host name,
13620 the first thing in the parentheses is the IP address in square brackets,
13621 followed by a colon and a port number if port logging is enabled. When the
13622 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
13625 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
13626 was used and its argument was not identical to the real host name or IP
13627 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
13628 all three items are present in the parentheses, a newline and tab are inserted
13629 into the string, to improve the formatting of the &'Received:'& header.
13631 .vitem &$sender_verify_failure$&
13632 .vindex "&$sender_verify_failure$&"
13633 In an ACL, when a sender verification fails, this variable contains information
13634 about the failure. The details are the same as for
13635 &$recipient_verify_failure$&.
13637 .vitem &$sending_ip_address$&
13638 .vindex "&$sending_ip_address$&"
13639 This variable is set whenever an outgoing SMTP connection to another host has
13640 been set up. It contains the IP address of the local interface that is being
13641 used. This is useful if a host that has more than one IP address wants to take
13642 on different personalities depending on which one is being used. For incoming
13643 connections, see &$received_ip_address$&.
13645 .vitem &$sending_port$&
13646 .vindex "&$sending_port$&"
13647 This variable is set whenever an outgoing SMTP connection to another host has
13648 been set up. It contains the local port that is being used. For incoming
13649 connections, see &$received_port$&.
13651 .vitem &$smtp_active_hostname$&
13652 .vindex "&$smtp_active_hostname$&"
13653 During an incoming SMTP session, this variable contains the value of the active
13654 host name, as specified by the &%smtp_active_hostname%& option. The value of
13655 &$smtp_active_hostname$& is saved with any message that is received, so its
13656 value can be consulted during routing and delivery.
13658 .vitem &$smtp_command$&
13659 .vindex "&$smtp_command$&"
13660 During the processing of an incoming SMTP command, this variable contains the
13661 entire command. This makes it possible to distinguish between HELO and EHLO in
13662 the HELO ACL, and also to distinguish between commands such as these:
13667 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
13668 command, the address in &$smtp_command$& is the original address before any
13669 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
13670 the address after SMTP-time rewriting.
13672 .vitem &$smtp_command_argument$&
13673 .cindex "SMTP" "command, argument for"
13674 .vindex "&$smtp_command_argument$&"
13675 While an ACL is running to check an SMTP command, this variable contains the
13676 argument, that is, the text that follows the command name, with leading white
13677 space removed. Following the introduction of &$smtp_command$&, this variable is
13678 somewhat redundant, but is retained for backwards compatibility.
13680 .vitem &$smtp_command_history$&
13681 .cindex SMTP "command history"
13682 .vindex "&$smtp_command_history$&"
13683 A comma-separated list (with no whitespace) of the most-recent SMTP commands
13684 received, in time-order left to right. Only a limited number of commands
13687 .vitem &$smtp_count_at_connection_start$&
13688 .vindex "&$smtp_count_at_connection_start$&"
13689 This variable is set greater than zero only in processes spawned by the Exim
13690 daemon for handling incoming SMTP connections. The name is deliberately long,
13691 in order to emphasize what the contents are. When the daemon accepts a new
13692 connection, it increments this variable. A copy of the variable is passed to
13693 the child process that handles the connection, but its value is fixed, and
13694 never changes. It is only an approximation of how many incoming connections
13695 there actually are, because many other connections may come and go while a
13696 single connection is being processed. When a child process terminates, the
13697 daemon decrements its copy of the variable.
13699 .vitem "&$sn0$& &-- &$sn9$&"
13700 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
13701 that were current at the end of the system filter file. This allows a system
13702 filter file to set values that can be tested in users' filter files. For
13703 example, a system filter could set a value indicating how likely it is that a
13704 message is junk mail.
13706 .vitem &$spam_score$& &&&
13707 &$spam_score_int$& &&&
13709 &$spam_report$& &&&
13711 A number of variables whose names start with &$spam$& are available when Exim
13712 is compiled with the content-scanning extension. For details, see section
13713 &<<SECTscanspamass>>&.
13715 .vitem &$spf_header_comment$& &&&
13716 &$spf_received$& &&&
13718 &$spf_result_guessed$& &&&
13719 &$spf_smtp_comment$&
13720 These variables are only available if Exim is built with SPF support.
13721 For details see section &<<SECSPF>>&.
13723 .vitem &$spool_directory$&
13724 .vindex "&$spool_directory$&"
13725 The name of Exim's spool directory.
13727 .vitem &$spool_inodes$&
13728 .vindex "&$spool_inodes$&"
13729 The number of free inodes in the disk partition where Exim's spool files are
13730 being written. The value is recalculated whenever the variable is referenced.
13731 If the relevant file system does not have the concept of inodes, the value of
13732 is -1. See also the &%check_spool_inodes%& option.
13734 .vitem &$spool_space$&
13735 .vindex "&$spool_space$&"
13736 The amount of free space (as a number of kilobytes) in the disk partition where
13737 Exim's spool files are being written. The value is recalculated whenever the
13738 variable is referenced. If the operating system does not have the ability to
13739 find the amount of free space (only true for experimental systems), the space
13740 value is -1. For example, to check in an ACL that there is at least 50
13741 megabytes free on the spool, you could write:
13743 condition = ${if > {$spool_space}{50000}}
13745 See also the &%check_spool_space%& option.
13748 .vitem &$thisaddress$&
13749 .vindex "&$thisaddress$&"
13750 This variable is set only during the processing of the &%foranyaddress%&
13751 command in a filter file. Its use is explained in the description of that
13752 command, which can be found in the separate document entitled &'Exim's
13753 interfaces to mail filtering'&.
13755 .vitem &$tls_in_bits$&
13756 .vindex "&$tls_in_bits$&"
13757 Contains an approximation of the TLS cipher's bit-strength
13758 on the inbound connection; the meaning of
13759 this depends upon the TLS implementation used.
13760 If TLS has not been negotiated, the value will be 0.
13761 The value of this is automatically fed into the Cyrus SASL authenticator
13762 when acting as a server, to specify the "external SSF" (a SASL term).
13764 The deprecated &$tls_bits$& variable refers to the inbound side
13765 except when used in the context of an outbound SMTP delivery, when it refers to
13768 .vitem &$tls_out_bits$&
13769 .vindex "&$tls_out_bits$&"
13770 Contains an approximation of the TLS cipher's bit-strength
13771 on an outbound SMTP connection; the meaning of
13772 this depends upon the TLS implementation used.
13773 If TLS has not been negotiated, the value will be 0.
13775 .vitem &$tls_in_ourcert$&
13776 .vindex "&$tls_in_ourcert$&"
13777 .cindex certificate variables
13778 This variable refers to the certificate presented to the peer of an
13779 inbound connection when the message was received.
13780 It is only useful as the argument of a
13781 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13782 or a &%def%& condition.
13784 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
13785 when a list of more than one
13786 file is used for &%tls_certificate%&, this variable is not reliable.
13787 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
13789 .vitem &$tls_in_peercert$&
13790 .vindex "&$tls_in_peercert$&"
13791 This variable refers to the certificate presented by the peer of an
13792 inbound connection when the message was received.
13793 It is only useful as the argument of a
13794 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13795 or a &%def%& condition.
13796 If certificate verification fails it may refer to a failing chain element
13797 which is not the leaf.
13799 .vitem &$tls_out_ourcert$&
13800 .vindex "&$tls_out_ourcert$&"
13801 This variable refers to the certificate presented to the peer of an
13802 outbound connection. It is only useful as the argument of a
13803 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13804 or a &%def%& condition.
13806 .vitem &$tls_out_peercert$&
13807 .vindex "&$tls_out_peercert$&"
13808 This variable refers to the certificate presented by the peer of an
13809 outbound connection. It is only useful as the argument of a
13810 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13811 or a &%def%& condition.
13812 If certificate verification fails it may refer to a failing chain element
13813 which is not the leaf.
13815 .vitem &$tls_in_certificate_verified$&
13816 .vindex "&$tls_in_certificate_verified$&"
13817 This variable is set to &"1"& if a TLS certificate was verified when the
13818 message was received, and &"0"& otherwise.
13820 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
13821 except when used in the context of an outbound SMTP delivery, when it refers to
13824 .vitem &$tls_out_certificate_verified$&
13825 .vindex "&$tls_out_certificate_verified$&"
13826 This variable is set to &"1"& if a TLS certificate was verified when an
13827 outbound SMTP connection was made,
13828 and &"0"& otherwise.
13830 .vitem &$tls_in_cipher$&
13831 .vindex "&$tls_in_cipher$&"
13832 .vindex "&$tls_cipher$&"
13833 When a message is received from a remote host over an encrypted SMTP
13834 connection, this variable is set to the cipher suite that was negotiated, for
13835 example DES-CBC3-SHA. In other circumstances, in particular, for message
13836 received over unencrypted connections, the variable is empty. Testing
13837 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
13838 non-encrypted connections during ACL processing.
13840 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
13841 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
13842 becomes the same as &$tls_out_cipher$&.
13844 .vitem &$tls_in_cipher_std$&
13845 .vindex "&$tls_in_cipher_std$&"
13846 As above, but returning the RFC standard name for the cipher suite.
13848 .vitem &$tls_out_cipher$&
13849 .vindex "&$tls_out_cipher$&"
13851 cleared before any outgoing SMTP connection is made,
13852 and then set to the outgoing cipher suite if one is negotiated. See chapter
13853 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
13854 details of the &(smtp)& transport.
13856 .vitem &$tls_out_cipher_std$&
13857 .vindex "&$tls_out_cipher_std$&"
13858 As above, but returning the RFC standard name for the cipher suite.
13860 .vitem &$tls_out_dane$&
13861 .vindex &$tls_out_dane$&
13862 DANE active status. See section &<<SECDANE>>&.
13864 .vitem &$tls_in_ocsp$&
13865 .vindex "&$tls_in_ocsp$&"
13866 When a message is received from a remote client connection
13867 the result of any OCSP request from the client is encoded in this variable:
13869 0 OCSP proof was not requested (default value)
13870 1 No response to request
13871 2 Response not verified
13872 3 Verification failed
13873 4 Verification succeeded
13876 .vitem &$tls_out_ocsp$&
13877 .vindex "&$tls_out_ocsp$&"
13878 When a message is sent to a remote host connection
13879 the result of any OCSP request made is encoded in this variable.
13880 See &$tls_in_ocsp$& for values.
13882 .vitem &$tls_in_peerdn$&
13883 .vindex "&$tls_in_peerdn$&"
13884 .vindex "&$tls_peerdn$&"
13885 .cindex certificate "extracting fields"
13886 When a message is received from a remote host over an encrypted SMTP
13887 connection, and Exim is configured to request a certificate from the client,
13888 the value of the Distinguished Name of the certificate is made available in the
13889 &$tls_in_peerdn$& during subsequent processing.
13890 If certificate verification fails it may refer to a failing chain element
13891 which is not the leaf.
13893 The deprecated &$tls_peerdn$& variable refers to the inbound side
13894 except when used in the context of an outbound SMTP delivery, when it refers to
13897 .vitem &$tls_out_peerdn$&
13898 .vindex "&$tls_out_peerdn$&"
13899 When a message is being delivered to a remote host over an encrypted SMTP
13900 connection, and Exim is configured to request a certificate from the server,
13901 the value of the Distinguished Name of the certificate is made available in the
13902 &$tls_out_peerdn$& during subsequent processing.
13903 If certificate verification fails it may refer to a failing chain element
13904 which is not the leaf.
13908 .vitem &$tls_in_resumption$& &&&
13909 &$tls_out_resumption$&
13910 .vindex &$tls_in_resumption$&
13911 .vindex &$tls_out_resumption$&
13912 .cindex TLS resumption
13913 Observability for TLS session resumption. See &<<SECTresumption>>& for details.
13917 .vitem &$tls_in_sni$&
13918 .vindex "&$tls_in_sni$&"
13919 .vindex "&$tls_sni$&"
13920 .cindex "TLS" "Server Name Indication"
13922 .cindex SNI "observability on server"
13923 When a TLS session is being established, if the client sends the Server
13924 Name Indication extension, the value will be placed in this variable.
13925 If the variable appears in &%tls_certificate%& then this option and
13926 some others, described in &<<SECTtlssni>>&,
13927 will be re-expanded early in the TLS session, to permit
13928 a different certificate to be presented (and optionally a different key to be
13929 used) to the client, based upon the value of the SNI extension.
13931 The deprecated &$tls_sni$& variable refers to the inbound side
13932 except when used in the context of an outbound SMTP delivery, when it refers to
13935 .vitem &$tls_out_sni$&
13936 .vindex "&$tls_out_sni$&"
13937 .cindex "TLS" "Server Name Indication"
13939 .cindex SNI "observability in client"
13941 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
13944 .vitem &$tls_out_tlsa_usage$&
13945 .vindex &$tls_out_tlsa_usage$&
13946 Bitfield of TLSA record types found. See section &<<SECDANE>>&.
13948 .vitem &$tls_in_ver$&
13949 .vindex "&$tls_in_ver$&"
13950 When a message is received from a remote host over an encrypted SMTP connection
13951 this variable is set to the protocol version, eg &'TLS1.2'&.
13953 .vitem &$tls_out_ver$&
13954 .vindex "&$tls_out_ver$&"
13955 When a message is being delivered to a remote host over an encrypted SMTP connection
13956 this variable is set to the protocol version.
13959 .vitem &$tod_bsdinbox$&
13960 .vindex "&$tod_bsdinbox$&"
13961 The time of day and the date, in the format required for BSD-style mailbox
13962 files, for example: Thu Oct 17 17:14:09 1995.
13964 .vitem &$tod_epoch$&
13965 .vindex "&$tod_epoch$&"
13966 The time and date as a number of seconds since the start of the Unix epoch.
13968 .vitem &$tod_epoch_l$&
13969 .vindex "&$tod_epoch_l$&"
13970 The time and date as a number of microseconds since the start of the Unix epoch.
13972 .vitem &$tod_full$&
13973 .vindex "&$tod_full$&"
13974 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
13975 +0100. The timezone is always given as a numerical offset from UTC, with
13976 positive values used for timezones that are ahead (east) of UTC, and negative
13977 values for those that are behind (west).
13980 .vindex "&$tod_log$&"
13981 The time and date in the format used for writing Exim's log files, for example:
13982 1995-10-12 15:32:29, but without a timezone.
13984 .vitem &$tod_logfile$&
13985 .vindex "&$tod_logfile$&"
13986 This variable contains the date in the format yyyymmdd. This is the format that
13987 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
13990 .vitem &$tod_zone$&
13991 .vindex "&$tod_zone$&"
13992 This variable contains the numerical value of the local timezone, for example:
13995 .vitem &$tod_zulu$&
13996 .vindex "&$tod_zulu$&"
13997 This variable contains the UTC date and time in &"Zulu"& format, as specified
13998 by ISO 8601, for example: 20030221154023Z.
14000 .vitem &$transport_name$&
14001 .cindex "transport" "name"
14002 .cindex "name" "of transport"
14003 .vindex "&$transport_name$&"
14004 During the running of a transport, this variable contains its name.
14007 .vindex "&$value$&"
14008 This variable contains the result of an expansion lookup, extraction operation,
14009 or external command, as described above. It is also used during a
14010 &*reduce*& expansion.
14012 .vitem &$verify_mode$&
14013 .vindex "&$verify_mode$&"
14014 While a router or transport is being run in verify mode or for cutthrough delivery,
14015 contains "S" for sender-verification or "R" for recipient-verification.
14018 .vitem &$version_number$&
14019 .vindex "&$version_number$&"
14020 The version number of Exim. Same as &$exim_version$&, may be overridden
14021 by the &%exim_version%& main config option.
14023 .vitem &$warn_message_delay$&
14024 .vindex "&$warn_message_delay$&"
14025 This variable is set only during the creation of a message warning about a
14026 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14028 .vitem &$warn_message_recipients$&
14029 .vindex "&$warn_message_recipients$&"
14030 This variable is set only during the creation of a message warning about a
14031 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
14037 . ////////////////////////////////////////////////////////////////////////////
14038 . ////////////////////////////////////////////////////////////////////////////
14040 .chapter "Embedded Perl" "CHAPperl"
14041 .scindex IIDperl "Perl" "calling from Exim"
14042 Exim can be built to include an embedded Perl interpreter. When this is done,
14043 Perl subroutines can be called as part of the string expansion process. To make
14044 use of the Perl support, you need version 5.004 or later of Perl installed on
14045 your system. To include the embedded interpreter in the Exim binary, include
14050 in your &_Local/Makefile_& and then build Exim in the normal way.
14053 .section "Setting up so Perl can be used" "SECID85"
14054 .oindex "&%perl_startup%&"
14055 Access to Perl subroutines is via a global configuration option called
14056 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
14057 no &%perl_startup%& option in the Exim configuration file then no Perl
14058 interpreter is started and there is almost no overhead for Exim (since none of
14059 the Perl library will be paged in unless used). If there is a &%perl_startup%&
14060 option then the associated value is taken to be Perl code which is executed in
14061 a newly created Perl interpreter.
14063 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
14064 need backslashes before any characters to escape special meanings. The option
14065 should usually be something like
14067 perl_startup = do '/etc/exim.pl'
14069 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
14070 use from Exim. Exim can be configured either to start up a Perl interpreter as
14071 soon as it is entered, or to wait until the first time it is needed. Starting
14072 the interpreter at the beginning ensures that it is done while Exim still has
14073 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
14074 fact used in a particular run. Also, note that this does not mean that Exim is
14075 necessarily running as root when Perl is called at a later time. By default,
14076 the interpreter is started only when it is needed, but this can be changed in
14080 .oindex "&%perl_at_start%&"
14081 Setting &%perl_at_start%& (a boolean option) in the configuration requests
14082 a startup when Exim is entered.
14084 The command line option &%-ps%& also requests a startup when Exim is entered,
14085 overriding the setting of &%perl_at_start%&.
14088 There is also a command line option &%-pd%& (for delay) which suppresses the
14089 initial startup, even if &%perl_at_start%& is set.
14092 .oindex "&%perl_taintmode%&"
14093 .cindex "Perl" "taintmode"
14094 To provide more security executing Perl code via the embedded Perl
14095 interpreter, the &%perl_taintmode%& option can be set. This enables the
14096 taint mode of the Perl interpreter. You are encouraged to set this
14097 option to a true value. To avoid breaking existing installations, it
14101 &*Note*&: This is entirely separate from Exim's tainted-data tracking.
14105 .section "Calling Perl subroutines" "SECID86"
14106 When the configuration file includes a &%perl_startup%& option you can make use
14107 of the string expansion item to call the Perl subroutines that are defined
14108 by the &%perl_startup%& code. The operator is used in any of the following
14112 ${perl{foo}{argument}}
14113 ${perl{foo}{argument1}{argument2} ... }
14115 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
14116 arguments may be passed. Passing more than this results in an expansion failure
14117 with an error message of the form
14119 Too many arguments passed to Perl subroutine "foo" (max is 8)
14121 The return value of the Perl subroutine is evaluated in a scalar context before
14122 it is passed back to Exim to be inserted into the expanded string. If the
14123 return value is &'undef'&, the expansion is forced to fail in the same way as
14124 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
14125 by obeying Perl's &%die%& function, the expansion fails with the error message
14126 that was passed to &%die%&.
14129 .section "Calling Exim functions from Perl" "SECID87"
14130 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
14131 is available to call back into Exim's string expansion function. For example,
14134 my $lp = Exim::expand_string('$local_part');
14136 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
14137 Note those are single quotes and not double quotes to protect against
14138 &$local_part$& being interpolated as a Perl variable.
14140 If the string expansion is forced to fail by a &"fail"& item, the result of
14141 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
14142 expansion string, the Perl call from the original expansion string fails with
14143 an appropriate error message, in the same way as if &%die%& were used.
14145 .cindex "debugging" "from embedded Perl"
14146 .cindex "log" "writing from embedded Perl"
14147 Two other Exim functions are available for use from within Perl code.
14148 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
14149 debugging is enabled. If you want a newline at the end, you must supply it.
14150 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
14151 timestamp. In this case, you should not supply a terminating newline.
14154 .section "Use of standard output and error by Perl" "SECID88"
14155 .cindex "Perl" "standard output and error"
14156 You should not write to the standard error or output streams from within your
14157 Perl code, as it is not defined how these are set up. In versions of Exim
14158 before 4.50, it is possible for the standard output or error to refer to the
14159 SMTP connection during message reception via the daemon. Writing to this stream
14160 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
14161 error streams are connected to &_/dev/null_& in the daemon. The chaos is
14162 avoided, but the output is lost.
14164 .cindex "Perl" "use of &%warn%&"
14165 The Perl &%warn%& statement writes to the standard error stream by default.
14166 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
14167 you have no control. When Exim starts up the Perl interpreter, it arranges for
14168 output from the &%warn%& statement to be written to the Exim main log. You can
14169 change this by including appropriate Perl magic somewhere in your Perl code.
14170 For example, to discard &%warn%& output completely, you need this:
14172 $SIG{__WARN__} = sub { };
14174 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
14175 example, the code for the subroutine is empty, so it does nothing, but you can
14176 include any Perl code that you like. The text of the &%warn%& message is passed
14177 as the first subroutine argument.
14181 . ////////////////////////////////////////////////////////////////////////////
14182 . ////////////////////////////////////////////////////////////////////////////
14184 .chapter "Starting the daemon and the use of network interfaces" &&&
14185 "CHAPinterfaces" &&&
14186 "Starting the daemon"
14187 .cindex "daemon" "starting"
14188 .cindex "interface" "listening"
14189 .cindex "network interface"
14190 .cindex "interface" "network"
14191 .cindex "IP address" "for listening"
14192 .cindex "daemon" "listening IP addresses"
14193 .cindex "TCP/IP" "setting listening interfaces"
14194 .cindex "TCP/IP" "setting listening ports"
14195 A host that is connected to a TCP/IP network may have one or more physical
14196 hardware network interfaces. Each of these interfaces may be configured as one
14197 or more &"logical"& interfaces, which are the entities that a program actually
14198 works with. Each of these logical interfaces is associated with an IP address.
14199 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
14200 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
14201 knowledge about the host's interfaces for use in three different circumstances:
14204 When a listening daemon is started, Exim needs to know which interfaces
14205 and ports to listen on.
14207 When Exim is routing an address, it needs to know which IP addresses
14208 are associated with local interfaces. This is required for the correct
14209 processing of MX lists by removing the local host and others with the
14210 same or higher priority values. Also, Exim needs to detect cases
14211 when an address is routed to an IP address that in fact belongs to the
14212 local host. Unless the &%self%& router option or the &%allow_localhost%&
14213 option of the smtp transport is set (as appropriate), this is treated
14214 as an error situation.
14216 When Exim connects to a remote host, it may need to know which interface to use
14217 for the outgoing connection.
14221 Exim's default behaviour is likely to be appropriate in the vast majority
14222 of cases. If your host has only one interface, and you want all its IP
14223 addresses to be treated in the same way, and you are using only the
14224 standard SMTP port, you should not need to take any special action. The
14225 rest of this chapter does not apply to you.
14227 In a more complicated situation you may want to listen only on certain
14228 interfaces, or on different ports, and for this reason there are a number of
14229 options that can be used to influence Exim's behaviour. The rest of this
14230 chapter describes how they operate.
14232 When a message is received over TCP/IP, the interface and port that were
14233 actually used are set in &$received_ip_address$& and &$received_port$&.
14237 .section "Starting a listening daemon" "SECID89"
14238 When a listening daemon is started (by means of the &%-bd%& command line
14239 option), the interfaces and ports on which it listens are controlled by the
14243 &%daemon_smtp_ports%& contains a list of default ports
14245 (For backward compatibility, this option can also be specified in the singular.)
14247 &%local_interfaces%& contains list of interface IP addresses on which to
14248 listen. Each item may optionally also specify a port.
14251 The default list separator in both cases is a colon, but this can be changed as
14252 described in section &<<SECTlistsepchange>>&. When IPv6 addresses are involved,
14253 it is usually best to change the separator to avoid having to double all the
14254 colons. For example:
14256 local_interfaces = <; 127.0.0.1 ; \
14259 3ffe:ffff:836f::fe86:a061
14261 There are two different formats for specifying a port along with an IP address
14262 in &%local_interfaces%&:
14265 The port is added onto the address with a dot separator. For example, to listen
14266 on port 1234 on two different IP addresses:
14268 local_interfaces = <; 192.168.23.65.1234 ; \
14269 3ffe:ffff:836f::fe86:a061.1234
14272 The IP address is enclosed in square brackets, and the port is added
14273 with a colon separator, for example:
14275 local_interfaces = <; [192.168.23.65]:1234 ; \
14276 [3ffe:ffff:836f::fe86:a061]:1234
14280 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
14281 default setting contains just one port:
14283 daemon_smtp_ports = smtp
14285 If more than one port is listed, each interface that does not have its own port
14286 specified listens on all of them. Ports that are listed in
14287 &%daemon_smtp_ports%& can be identified either by name (defined in
14288 &_/etc/services_&) or by number. However, when ports are given with individual
14289 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
14293 .section "Special IP listening addresses" "SECID90"
14294 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
14295 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
14296 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
14297 instead of setting up separate listening sockets for each interface. The
14298 default value of &%local_interfaces%& is
14300 local_interfaces = 0.0.0.0
14302 when Exim is built without IPv6 support; otherwise it is:
14304 local_interfaces = <; ::0 ; 0.0.0.0
14306 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
14310 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
14311 The &%-oX%& command line option can be used to override the values of
14312 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
14313 instance. Another way of doing this would be to use macros and the &%-D%&
14314 option. However, &%-oX%& can be used by any admin user, whereas modification of
14315 the runtime configuration by &%-D%& is allowed only when the caller is root or
14318 The value of &%-oX%& is a list of items. The default colon separator can be
14319 changed in the usual way (&<<SECTlistsepchange>>&) if required.
14320 If there are any items that do not
14321 contain dots or colons (that is, are not IP addresses), the value of
14322 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
14323 items that do contain dots or colons, the value of &%local_interfaces%& is
14324 replaced by those items. Thus, for example,
14328 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
14331 -oX 192.168.34.5.1125
14333 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
14334 (However, since &%local_interfaces%& now contains no items without ports, the
14335 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
14339 .section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
14340 .cindex "submissions protocol"
14341 .cindex "ssmtp protocol"
14342 .cindex "smtps protocol"
14343 .cindex "SMTP" "ssmtp protocol"
14344 .cindex "SMTP" "smtps protocol"
14345 Exim supports the use of TLS-on-connect, used by mail clients in the
14346 &"submissions"& protocol, historically also known as SMTPS or SSMTP.
14347 For some years, IETF Standards Track documents only blessed the
14348 STARTTLS-based Submission service (port 587) while common practice was to support
14349 the same feature set on port 465, but using TLS-on-connect.
14350 If your installation needs to provide service to mail clients
14351 (Mail User Agents, MUAs) then you should provide service on both the 587 and
14354 If the &%tls_on_connect_ports%& option is set to a list of port numbers or
14355 service names, connections to those ports must first establish TLS, before
14356 proceeding to the application layer use of the SMTP protocol.
14358 The common use of this option is expected to be
14360 tls_on_connect_ports = 465
14363 There is also a command line option &%-tls-on-connect%&, which forces all ports
14364 to behave in this way when a daemon is started.
14366 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
14367 daemon to listen on those ports. You must still specify them in
14368 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
14369 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
14370 connections via the daemon.)
14375 .section "IPv6 address scopes" "SECID92"
14376 .cindex "IPv6" "address scopes"
14377 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
14378 can, in principle, have the same link-local IPv6 address on different
14379 interfaces. Thus, additional information is needed, over and above the IP
14380 address, to distinguish individual interfaces. A convention of using a
14381 percent sign followed by something (often the interface name) has been
14382 adopted in some cases, leading to addresses like this:
14384 fe80::202:b3ff:fe03:45c1%eth0
14386 To accommodate this usage, a percent sign followed by an arbitrary string is
14387 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
14388 to convert a textual IPv6 address for actual use. This function recognizes the
14389 percent convention in operating systems that support it, and it processes the
14390 address appropriately. Unfortunately, some older libraries have problems with
14391 &[getaddrinfo()]&. If
14393 IPV6_USE_INET_PTON=yes
14395 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
14396 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
14397 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
14398 function.) Of course, this means that the additional functionality of
14399 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
14401 .section "Disabling IPv6" "SECID93"
14402 .cindex "IPv6" "disabling"
14403 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
14404 run on a host whose kernel does not support IPv6. The binary will fall back to
14405 using IPv4, but it may waste resources looking up AAAA records, and trying to
14406 connect to IPv6 addresses, causing delays to mail delivery. If you set the
14407 .oindex "&%disable_ipv6%&"
14408 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
14409 activities take place. AAAA records are never looked up, and any IPv6 addresses
14410 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
14411 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14412 to handle IPv6 literal addresses.
14414 On the other hand, when IPv6 is in use, there may be times when you want to
14415 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
14416 option to globally suppress the lookup of AAAA records for specified domains,
14417 and you can use the &%ignore_target_hosts%& generic router option to ignore
14418 IPv6 addresses in an individual router.
14422 .section "Examples of starting a listening daemon" "SECID94"
14423 The default case in an IPv6 environment is
14425 daemon_smtp_ports = smtp
14426 local_interfaces = <; ::0 ; 0.0.0.0
14428 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
14429 Either one or two sockets may be used, depending on the characteristics of
14430 the TCP/IP stack. (This is complicated and messy; for more information,
14431 read the comments in the &_daemon.c_& source file.)
14433 To specify listening on ports 25 and 26 on all interfaces:
14435 daemon_smtp_ports = 25 : 26
14437 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
14439 local_interfaces = <; ::0.25 ; ::0.26 \
14440 0.0.0.0.25 ; 0.0.0.0.26
14442 To listen on the default port on all IPv4 interfaces, and on port 26 on the
14443 IPv4 loopback address only:
14445 local_interfaces = 0.0.0.0 : 127.0.0.1.26
14447 To specify listening on the default port on specific interfaces only:
14449 local_interfaces = 10.0.0.67 : 192.168.34.67
14451 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
14455 .section "Recognizing the local host" "SECTreclocipadd"
14456 The &%local_interfaces%& option is also used when Exim needs to determine
14457 whether or not an IP address refers to the local host. That is, the IP
14458 addresses of all the interfaces on which a daemon is listening are always
14461 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
14462 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
14463 available interfaces from the operating system, and extracts the relevant
14464 (that is, IPv4 or IPv6) addresses to use for checking.
14466 Some systems set up large numbers of virtual interfaces in order to provide
14467 many virtual web servers. In this situation, you may want to listen for
14468 email on only a few of the available interfaces, but nevertheless treat all
14469 interfaces as local when routing. You can do this by setting
14470 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
14471 &"all"& wildcard values. These addresses are recognized as local, but are not
14472 used for listening. Consider this example:
14474 local_interfaces = <; 127.0.0.1 ; ::1 ; \
14476 3ffe:2101:12:1:a00:20ff:fe86:a061
14478 extra_local_interfaces = <; ::0 ; 0.0.0.0
14480 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
14481 address, but all available interface addresses are treated as local when
14484 In some environments the local host name may be in an MX list, but with an IP
14485 address that is not assigned to any local interface. In other cases it may be
14486 desirable to treat other host names as if they referred to the local host. Both
14487 these cases can be handled by setting the &%hosts_treat_as_local%& option.
14488 This contains host names rather than IP addresses. When a host is referenced
14489 during routing, either via an MX record or directly, it is treated as the local
14490 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
14491 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
14495 .section "Delivering to a remote host" "SECID95"
14496 Delivery to a remote host is handled by the smtp transport. By default, it
14497 allows the system's TCP/IP functions to choose which interface to use (if
14498 there is more than one) when connecting to a remote host. However, the
14499 &%interface%& option can be set to specify which interface is used. See the
14500 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
14506 . ////////////////////////////////////////////////////////////////////////////
14507 . ////////////////////////////////////////////////////////////////////////////
14509 .chapter "Main configuration" "CHAPmainconfig"
14510 .scindex IIDconfima "configuration file" "main section"
14511 .scindex IIDmaiconf "main configuration"
14512 The first part of the runtime configuration file contains three types of item:
14515 Macro definitions: These lines start with an upper case letter. See section
14516 &<<SECTmacrodefs>>& for details of macro processing.
14518 Named list definitions: These lines start with one of the words &"domainlist"&,
14519 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
14520 section &<<SECTnamedlists>>&.
14522 Main configuration settings: Each setting occupies one line of the file
14523 (with possible continuations). If any setting is preceded by the word
14524 &"hide"&, the &%-bP%& command line option displays its value to admin users
14525 only. See section &<<SECTcos>>& for a description of the syntax of these option
14529 This chapter specifies all the main configuration options, along with their
14530 types and default values. For ease of finding a particular option, they appear
14531 in alphabetical order in section &<<SECTalomo>>& below. However, because there
14532 are now so many options, they are first listed briefly in functional groups, as
14533 an aid to finding the name of the option you are looking for. Some options are
14534 listed in more than one group.
14536 .section "Miscellaneous" "SECID96"
14538 .row &%bi_command%& "to run for &%-bi%& command line option"
14539 .row &%debug_store%& "do extra internal checks"
14540 .row &%disable_ipv6%& "do no IPv6 processing"
14541 .row &%keep_malformed%& "for broken files &-- should not happen"
14542 .row &%localhost_number%& "for unique message ids in clusters"
14543 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
14544 .row &%message_body_visible%& "how much to show in &$message_body$&"
14545 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
14546 .row &%print_topbitchars%& "top-bit characters are printing"
14547 .row &%spool_wireformat%& "use wire-format spool data files when possible"
14548 .row &%timezone%& "force time zone"
14552 .section "Exim parameters" "SECID97"
14554 .row &%exim_group%& "override compiled-in value"
14555 .row &%exim_path%& "override compiled-in value"
14556 .row &%exim_user%& "override compiled-in value"
14557 .row &%primary_hostname%& "default from &[uname()]&"
14558 .row &%split_spool_directory%& "use multiple directories"
14559 .row &%spool_directory%& "override compiled-in value"
14564 .section "Privilege controls" "SECID98"
14566 .row &%admin_groups%& "groups that are Exim admin users"
14567 .row &%commandline_checks_require_admin%& "require admin for various checks"
14568 .row &%deliver_drop_privilege%& "drop root for delivery processes"
14569 .row &%local_from_check%& "insert &'Sender:'& if necessary"
14570 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
14571 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
14572 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
14573 .row &%never_users%& "do not run deliveries as these"
14574 .row &%prod_requires_admin%& "forced delivery requires admin user"
14575 .row &%queue_list_requires_admin%& "queue listing requires admin user"
14576 .row &%trusted_groups%& "groups that are trusted"
14577 .row &%trusted_users%& "users that are trusted"
14582 .section "Logging" "SECID99"
14584 .row &%event_action%& "custom logging"
14585 .row &%hosts_connection_nolog%& "exemption from connect logging"
14586 .row &%log_file_path%& "override compiled-in value"
14587 .row &%log_selector%& "set/unset optional logging"
14588 .row &%log_timezone%& "add timezone to log lines"
14589 .row &%message_logs%& "create per-message logs"
14590 .row &%preserve_message_logs%& "after message completion"
14591 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
14592 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
14593 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
14594 .row &%syslog_facility%& "set syslog &""facility""& field"
14595 .row &%syslog_pid%& "pid in syslog lines"
14596 .row &%syslog_processname%& "set syslog &""ident""& field"
14597 .row &%syslog_timestamp%& "timestamp syslog lines"
14598 .row &%write_rejectlog%& "control use of message log"
14603 .section "Frozen messages" "SECID100"
14605 .row &%auto_thaw%& "sets time for retrying frozen messages"
14606 .row &%freeze_tell%& "send message when freezing"
14607 .row &%move_frozen_messages%& "to another directory"
14608 .row &%timeout_frozen_after%& "keep frozen messages only so long"
14613 .section "Data lookups" "SECID101"
14615 .row &%ibase_servers%& "InterBase servers"
14616 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
14617 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
14618 .row &%ldap_cert_file%& "client cert file for LDAP"
14619 .row &%ldap_cert_key%& "client key file for LDAP"
14620 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
14621 .row &%ldap_default_servers%& "used if no server in query"
14622 .row &%ldap_require_cert%& "action to take without LDAP server cert"
14623 .row &%ldap_start_tls%& "require TLS within LDAP"
14624 .row &%ldap_version%& "set protocol version"
14625 .row &%lookup_open_max%& "lookup files held open"
14626 .row &%mysql_servers%& "default MySQL servers"
14627 .row &%oracle_servers%& "Oracle servers"
14628 .row &%pgsql_servers%& "default PostgreSQL servers"
14629 .row &%sqlite_lock_timeout%& "as it says"
14634 .section "Message ids" "SECID102"
14636 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
14637 .row &%message_id_header_text%& "ditto"
14642 .section "Embedded Perl Startup" "SECID103"
14644 .row &%perl_at_start%& "always start the interpreter"
14645 .row &%perl_startup%& "code to obey when starting Perl"
14646 .row &%perl_taintmode%& "enable taint mode in Perl"
14651 .section "Daemon" "SECID104"
14653 .row &%daemon_smtp_ports%& "default ports"
14654 .row &%daemon_startup_retries%& "number of times to retry"
14655 .row &%daemon_startup_sleep%& "time to sleep between tries"
14656 .row &%extra_local_interfaces%& "not necessarily listened on"
14657 .row &%local_interfaces%& "on which to listen, with optional ports"
14658 .row &%notifier_socket%& "override compiled-in value"
14659 .row &%pid_file_path%& "override compiled-in value"
14660 .row &%queue_run_max%& "maximum simultaneous queue runners"
14665 .section "Resource control" "SECID105"
14667 .row &%check_log_inodes%& "before accepting a message"
14668 .row &%check_log_space%& "before accepting a message"
14669 .row &%check_spool_inodes%& "before accepting a message"
14670 .row &%check_spool_space%& "before accepting a message"
14671 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
14672 .row &%queue_only_load%& "queue incoming if load high"
14673 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14674 .row &%queue_run_max%& "maximum simultaneous queue runners"
14675 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14676 .row &%smtp_accept_max%& "simultaneous incoming connections"
14677 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14678 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14679 .row &%smtp_accept_max_per_connection%& "messages per connection"
14680 .row &%smtp_accept_max_per_host%& "connections from one host"
14681 .row &%smtp_accept_queue%& "queue mail if more connections"
14682 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14684 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14685 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14686 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14687 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
14688 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14693 .section "Policy controls" "SECID106"
14695 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
14696 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
14697 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
14698 .row &%acl_smtp_auth%& "ACL for AUTH"
14699 .row &%acl_smtp_connect%& "ACL for connection"
14700 .row &%acl_smtp_data%& "ACL for DATA"
14701 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
14702 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
14703 .row &%acl_smtp_etrn%& "ACL for ETRN"
14704 .row &%acl_smtp_expn%& "ACL for EXPN"
14705 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
14706 .row &%acl_smtp_mail%& "ACL for MAIL"
14707 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
14708 .row &%acl_smtp_mime%& "ACL for MIME parts"
14709 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
14710 .row &%acl_smtp_predata%& "ACL for start of data"
14711 .row &%acl_smtp_quit%& "ACL for QUIT"
14712 .row &%acl_smtp_rcpt%& "ACL for RCPT"
14713 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
14714 .row &%acl_smtp_vrfy%& "ACL for VRFY"
14715 .row &%av_scanner%& "specify virus scanner"
14716 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14718 .row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
14719 .row &%dns_csa_search_limit%& "control CSA parent search depth"
14720 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
14721 .row &%header_maxsize%& "total size of message header"
14722 .row &%header_line_maxsize%& "individual header line limit"
14723 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
14724 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
14725 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
14726 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
14727 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
14728 .row &%host_lookup%& "host name looked up for these hosts"
14729 .row &%host_lookup_order%& "order of DNS and local name lookups"
14730 .row &%hosts_proxy%& "use proxy protocol for these hosts"
14731 .row &%host_reject_connection%& "reject connection from these hosts"
14732 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
14733 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
14734 .row &%message_size_limit%& "for all messages"
14735 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14736 .row &%proxy_protocol_timeout%& "timeout for proxy protocol negotiation"
14737 .row &%spamd_address%& "set interface to SpamAssassin"
14738 .row &%strict_acl_vars%& "object to unset ACL variables"
14739 .row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&"
14744 .section "Callout cache" "SECID107"
14746 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
14748 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
14750 .row &%callout_negative_expire%& "timeout for negative address cache item"
14751 .row &%callout_positive_expire%& "timeout for positive address cache item"
14752 .row &%callout_random_local_part%& "string to use for &""random""& testing"
14757 .section "TLS" "SECID108"
14759 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
14760 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
14761 .row &%openssl_options%& "adjust OpenSSL compatibility options"
14762 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14763 .row &%tls_certificate%& "location of server certificate"
14764 .row &%tls_crl%& "certificate revocation list"
14765 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
14766 .row &%tls_dhparam%& "DH parameters for server"
14767 .row &%tls_eccurve%& "EC curve selection for server"
14768 .row &%tls_ocsp_file%& "location of server certificate status proof"
14769 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
14770 .row &%tls_privatekey%& "location of server private key"
14771 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
14772 .row &%tls_require_ciphers%& "specify acceptable ciphers"
14773 .row &%tls_try_verify_hosts%& "try to verify client certificate"
14774 .row &%tls_verify_certificates%& "expected client certificates"
14775 .row &%tls_verify_hosts%& "insist on client certificate verify"
14780 .section "Local user handling" "SECID109"
14782 .row &%finduser_retries%& "useful in NIS environments"
14783 .row &%gecos_name%& "used when creating &'Sender:'&"
14784 .row &%gecos_pattern%& "ditto"
14785 .row &%max_username_length%& "for systems that truncate"
14786 .row &%unknown_login%& "used when no login name found"
14787 .row &%unknown_username%& "ditto"
14788 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
14789 .row &%uucp_from_sender%& "ditto"
14794 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
14796 .row &%header_maxsize%& "total size of message header"
14797 .row &%header_line_maxsize%& "individual header line limit"
14798 .row &%message_size_limit%& "applies to all messages"
14799 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14800 .row &%received_header_text%& "expanded to make &'Received:'&"
14801 .row &%received_headers_max%& "for mail loop detection"
14802 .row &%recipients_max%& "limit per message"
14803 .row &%recipients_max_reject%& "permanently reject excess recipients"
14809 .section "Non-SMTP incoming messages" "SECID111"
14811 .row &%receive_timeout%& "for non-SMTP messages"
14818 .section "Incoming SMTP messages" "SECID112"
14819 See also the &'Policy controls'& section above.
14822 .row &%dkim_verify_hashes%& "DKIM hash methods accepted for signatures"
14823 .row &%dkim_verify_keytypes%& "DKIM key types accepted for signatures"
14824 .row &%dkim_verify_min_keysizes%& "DKIM key sizes accepted for signatures"
14825 .row &%dkim_verify_signers%& "DKIM domains for which DKIM ACL is run"
14826 .row &%dmarc_forensic_sender%& "DMARC sender for report messages"
14827 .row &%dmarc_history_file%& "DMARC results log"
14828 .row &%dmarc_tld_file%& "DMARC toplevel domains file"
14829 .row &%host_lookup%& "host name looked up for these hosts"
14830 .row &%host_lookup_order%& "order of DNS and local name lookups"
14831 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
14832 .row &%rfc1413_hosts%& "make ident calls to these hosts"
14833 .row &%rfc1413_query_timeout%& "zero disables ident calls"
14834 .row &%sender_unqualified_hosts%& "may send unqualified senders"
14835 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
14836 .row &%smtp_accept_max%& "simultaneous incoming connections"
14837 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14838 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14839 .row &%smtp_accept_max_per_connection%& "messages per connection"
14840 .row &%smtp_accept_max_per_host%& "connections from one host"
14841 .row &%smtp_accept_queue%& "queue mail if more connections"
14842 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14844 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14845 .row &%smtp_active_hostname%& "host name to use in messages"
14846 .row &%smtp_banner%& "text for welcome banner"
14847 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14848 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14849 .row &%smtp_enforce_sync%& "of SMTP command/responses"
14850 .row &%smtp_etrn_command%& "what to run for ETRN"
14851 .row &%smtp_etrn_serialize%& "only one at once"
14852 .row &%smtp_load_reserve%& "only reserve hosts if this load"
14853 .row &%smtp_max_unknown_commands%& "before dropping connection"
14854 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
14855 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
14856 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
14857 .row &%smtp_receive_timeout%& "per command or data line"
14858 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14859 .row &%smtp_return_error_details%& "give detail on rejections"
14864 .section "SMTP extensions" "SECID113"
14866 .row &%accept_8bitmime%& "advertise 8BITMIME"
14867 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
14868 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
14869 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
14870 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
14871 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
14872 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
14873 .row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts"
14874 .row &%prdr_enable%& "advertise PRDR to all hosts"
14875 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
14876 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14881 .section "Processing messages" "SECID114"
14883 .row &%allow_domain_literals%& "recognize domain literal syntax"
14884 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
14885 .row &%allow_utf8_domains%& "in addresses"
14886 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14888 .row &%delivery_date_remove%& "from incoming messages"
14889 .row &%envelope_to_remove%& "from incoming messages"
14890 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
14891 .row &%headers_charset%& "default for translations"
14892 .row &%qualify_domain%& "default for senders"
14893 .row &%qualify_recipient%& "default for recipients"
14894 .row &%return_path_remove%& "from incoming messages"
14895 .row &%strip_excess_angle_brackets%& "in addresses"
14896 .row &%strip_trailing_dot%& "at end of addresses"
14897 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
14902 .section "System filter" "SECID115"
14904 .row &%system_filter%& "locate system filter"
14905 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
14907 .row &%system_filter_file_transport%& "transport for delivery to a file"
14908 .row &%system_filter_group%& "group for filter running"
14909 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
14910 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
14911 .row &%system_filter_user%& "user for filter running"
14916 .section "Routing and delivery" "SECID116"
14918 .row &%disable_ipv6%& "do no IPv6 processing"
14919 .row &%dns_again_means_nonexist%& "for broken domains"
14920 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
14921 .row &%dns_dnssec_ok%& "parameter for resolver"
14922 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
14923 .row &%dns_retrans%& "parameter for resolver"
14924 .row &%dns_retry%& "parameter for resolver"
14925 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
14926 .row &%dns_use_edns0%& "parameter for resolver"
14927 .row &%hold_domains%& "hold delivery for these domains"
14928 .row &%local_interfaces%& "for routing checks"
14929 .row &%queue_domains%& "no immediate delivery for these"
14930 .row &%queue_fast_ramp%& "parallel delivery with 2-phase queue run"
14931 .row &%queue_only%& "no immediate delivery at all"
14932 .row &%queue_only_file%& "no immediate delivery if file exists"
14933 .row &%queue_only_load%& "no immediate delivery if load is high"
14934 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14935 .row &%queue_only_override%& "allow command line to override"
14936 .row &%queue_run_in_order%& "order of arrival"
14937 .row &%queue_run_max%& "of simultaneous queue runners"
14938 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
14939 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14940 .row &%remote_sort_domains%& "order of remote deliveries"
14941 .row &%retry_data_expire%& "timeout for retry data"
14942 .row &%retry_interval_max%& "safety net for retry rules"
14947 .section "Bounce and warning messages" "SECID117"
14949 .row &%bounce_message_file%& "content of bounce"
14950 .row &%bounce_message_text%& "content of bounce"
14951 .row &%bounce_return_body%& "include body if returning message"
14952 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
14953 .row &%bounce_return_message%& "include original message in bounce"
14954 .row &%bounce_return_size_limit%& "limit on returned message"
14955 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
14956 .row &%dsn_from%& "set &'From:'& contents in bounces"
14957 .row &%errors_copy%& "copy bounce messages"
14958 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
14959 .row &%delay_warning%& "time schedule"
14960 .row &%delay_warning_condition%& "condition for warning messages"
14961 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
14962 .row &%smtp_return_error_details%& "give detail on rejections"
14963 .row &%warn_message_file%& "content of warning message"
14968 .section "Alphabetical list of main options" "SECTalomo"
14969 Those options that undergo string expansion before use are marked with
14972 .option accept_8bitmime main boolean true
14974 .cindex "8-bit characters"
14975 .cindex "log" "selectors"
14976 .cindex "log" "8BITMIME"
14977 .cindex "ESMTP extensions" 8BITMIME
14978 This option causes Exim to send 8BITMIME in its response to an SMTP
14979 EHLO command, and to accept the BODY= parameter on MAIL commands.
14980 However, though Exim is 8-bit clean, it is not a protocol converter, and it
14981 takes no steps to do anything special with messages received by this route.
14983 Historically Exim kept this option off by default, but the maintainers
14984 feel that in today's Internet, this causes more problems than it solves.
14985 It now defaults to true.
14986 A more detailed analysis of the issues is provided by Dan Bernstein:
14988 &url(https://cr.yp.to/smtp/8bitmime.html)
14991 To log received 8BITMIME status use
14993 log_selector = +8bitmime
14996 .option acl_not_smtp main string&!! unset
14997 .cindex "&ACL;" "for non-SMTP messages"
14998 .cindex "non-SMTP messages" "ACLs for"
14999 This option defines the ACL that is run when a non-SMTP message has been
15000 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
15003 .option acl_not_smtp_mime main string&!! unset
15004 This option defines the ACL that is run for individual MIME parts of non-SMTP
15005 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
15008 .option acl_not_smtp_start main string&!! unset
15009 .cindex "&ACL;" "at start of non-SMTP message"
15010 .cindex "non-SMTP messages" "ACLs for"
15011 This option defines the ACL that is run before Exim starts reading a
15012 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
15014 .option acl_smtp_auth main string&!! unset
15015 .cindex "&ACL;" "setting up for SMTP commands"
15016 .cindex "AUTH" "ACL for"
15017 This option defines the ACL that is run when an SMTP AUTH command is
15018 received. See chapter &<<CHAPACL>>& for further details.
15020 .option acl_smtp_connect main string&!! unset
15021 .cindex "&ACL;" "on SMTP connection"
15022 This option defines the ACL that is run when an SMTP connection is received.
15023 See chapter &<<CHAPACL>>& for further details.
15025 .option acl_smtp_data main string&!! unset
15026 .cindex "DATA" "ACL for"
15027 This option defines the ACL that is run after an SMTP DATA command has been
15028 processed and the message itself has been received, but before the final
15029 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15031 .option acl_smtp_data_prdr main string&!! accept
15032 .cindex "PRDR" "ACL for"
15033 .cindex "DATA" "PRDR ACL for"
15034 .cindex "&ACL;" "PRDR-related"
15035 .cindex "&ACL;" "per-user data processing"
15036 This option defines the ACL that,
15037 if the PRDR feature has been negotiated,
15038 is run for each recipient after an SMTP DATA command has been
15039 processed and the message itself has been received, but before the
15040 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
15042 .option acl_smtp_dkim main string&!! unset
15043 .cindex DKIM "ACL for"
15044 This option defines the ACL that is run for each DKIM signature
15045 (by default, or as specified in the dkim_verify_signers option)
15046 of a received message.
15047 See section &<<SECDKIMVFY>>& for further details.
15049 .option acl_smtp_etrn main string&!! unset
15050 .cindex "ETRN" "ACL for"
15051 This option defines the ACL that is run when an SMTP ETRN command is
15052 received. See chapter &<<CHAPACL>>& for further details.
15054 .option acl_smtp_expn main string&!! unset
15055 .cindex "EXPN" "ACL for"
15056 This option defines the ACL that is run when an SMTP EXPN command is
15057 received. See chapter &<<CHAPACL>>& for further details.
15059 .option acl_smtp_helo main string&!! unset
15060 .cindex "EHLO" "ACL for"
15061 .cindex "HELO" "ACL for"
15062 This option defines the ACL that is run when an SMTP EHLO or HELO
15063 command is received. See chapter &<<CHAPACL>>& for further details.
15066 .option acl_smtp_mail main string&!! unset
15067 .cindex "MAIL" "ACL for"
15068 This option defines the ACL that is run when an SMTP MAIL command is
15069 received. See chapter &<<CHAPACL>>& for further details.
15071 .option acl_smtp_mailauth main string&!! unset
15072 .cindex "AUTH" "on MAIL command"
15073 This option defines the ACL that is run when there is an AUTH parameter on
15074 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
15075 &<<CHAPSMTPAUTH>>& for details of authentication.
15077 .option acl_smtp_mime main string&!! unset
15078 .cindex "MIME content scanning" "ACL for"
15079 This option is available when Exim is built with the content-scanning
15080 extension. It defines the ACL that is run for each MIME part in a message. See
15081 section &<<SECTscanmimepart>>& for details.
15083 .option acl_smtp_notquit main string&!! unset
15084 .cindex "not-QUIT, ACL for"
15085 This option defines the ACL that is run when an SMTP session
15086 ends without a QUIT command being received.
15087 See chapter &<<CHAPACL>>& for further details.
15089 .option acl_smtp_predata main string&!! unset
15090 This option defines the ACL that is run when an SMTP DATA command is
15091 received, before the message itself is received. See chapter &<<CHAPACL>>& for
15094 .option acl_smtp_quit main string&!! unset
15095 .cindex "QUIT, ACL for"
15096 This option defines the ACL that is run when an SMTP QUIT command is
15097 received. See chapter &<<CHAPACL>>& for further details.
15099 .option acl_smtp_rcpt main string&!! unset
15100 .cindex "RCPT" "ACL for"
15101 This option defines the ACL that is run when an SMTP RCPT command is
15102 received. See chapter &<<CHAPACL>>& for further details.
15104 .option acl_smtp_starttls main string&!! unset
15105 .cindex "STARTTLS, ACL for"
15106 This option defines the ACL that is run when an SMTP STARTTLS command is
15107 received. See chapter &<<CHAPACL>>& for further details.
15109 .option acl_smtp_vrfy main string&!! unset
15110 .cindex "VRFY" "ACL for"
15111 This option defines the ACL that is run when an SMTP VRFY command is
15112 received. See chapter &<<CHAPACL>>& for further details.
15114 .option add_environment main "string list" empty
15115 .cindex "environment" "set values"
15116 This option adds individual environment variables that the
15117 currently linked libraries and programs in child processes may use.
15118 Each list element should be of the form &"name=value"&.
15120 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
15122 .option admin_groups main "string list&!!" unset
15123 .cindex "admin user"
15124 This option is expanded just once, at the start of Exim's processing. If the
15125 current group or any of the supplementary groups of an Exim caller is in this
15126 colon-separated list, the caller has admin privileges. If all your system
15127 programmers are in a specific group, for example, you can give them all Exim
15128 admin privileges by putting that group in &%admin_groups%&. However, this does
15129 not permit them to read Exim's spool files (whose group owner is the Exim gid).
15130 To permit this, you have to add individuals to the Exim group.
15132 .option allow_domain_literals main boolean false
15133 .cindex "domain literal"
15134 If this option is set, the RFC 2822 domain literal format is permitted in
15135 email addresses. The option is not set by default, because the domain literal
15136 format is not normally required these days, and few people know about it. It
15137 has, however, been exploited by mail abusers.
15139 Unfortunately, it seems that some DNS black list maintainers are using this
15140 format to report black listing to postmasters. If you want to accept messages
15141 addressed to your hosts by IP address, you need to set
15142 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
15143 domains (defined in the named domain list &%local_domains%& in the default
15144 configuration). This &"magic string"& matches the domain literal form of all
15145 the local host's IP addresses.
15148 .option allow_mx_to_ip main boolean false
15149 .cindex "MX record" "pointing to IP address"
15150 It appears that more and more DNS zone administrators are breaking the rules
15151 and putting domain names that look like IP addresses on the right hand side of
15152 MX records. Exim follows the rules and rejects this, giving an error message
15153 that explains the misconfiguration. However, some other MTAs support this
15154 practice, so to avoid &"Why can't Exim do this?"& complaints,
15155 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
15156 recommended, except when you have no other choice.
15158 .option allow_utf8_domains main boolean false
15159 .cindex "domain" "UTF-8 characters in"
15160 .cindex "UTF-8" "in domain name"
15161 Lots of discussion is going on about internationalized domain names. One
15162 camp is strongly in favour of just using UTF-8 characters, and it seems
15163 that at least two other MTAs permit this.
15164 This option allows Exim users to experiment if they wish.
15166 If it is set true, Exim's domain parsing function allows valid
15167 UTF-8 multicharacters to appear in domain name components, in addition to
15168 letters, digits, and hyphens.
15170 If Exim is built with internationalization support
15171 and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
15172 this option can be left as default.
15174 if you want to look up such domain names in the DNS, you must also
15175 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
15176 suitable setting is:
15178 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
15179 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
15181 Alternatively, you can just disable this feature by setting
15183 dns_check_names_pattern =
15185 That is, set the option to an empty string so that no check is done.
15188 .option auth_advertise_hosts main "host list&!!" *
15189 .cindex "authentication" "advertising"
15190 .cindex "AUTH" "advertising"
15191 .cindex "ESMTP extensions" AUTH
15192 If any server authentication mechanisms are configured, Exim advertises them in
15193 response to an EHLO command only if the calling host matches this list.
15194 Otherwise, Exim does not advertise AUTH.
15195 Exim does not accept AUTH commands from clients to which it has not
15196 advertised the availability of AUTH. The advertising of individual
15197 authentication mechanisms can be controlled by the use of the
15198 &%server_advertise_condition%& generic authenticator option on the individual
15199 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
15201 Certain mail clients (for example, Netscape) require the user to provide a name
15202 and password for authentication if AUTH is advertised, even though it may
15203 not be needed (the host may accept messages from hosts on its local LAN without
15204 authentication, for example). The &%auth_advertise_hosts%& option can be used
15205 to make these clients more friendly by excluding them from the set of hosts to
15206 which Exim advertises AUTH.
15208 .cindex "AUTH" "advertising when encrypted"
15209 If you want to advertise the availability of AUTH only when the connection
15210 is encrypted using TLS, you can make use of the fact that the value of this
15211 option is expanded, with a setting like this:
15213 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
15215 .vindex "&$tls_in_cipher$&"
15216 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
15217 the expansion is empty, thus matching no hosts. Otherwise, the result of the
15218 expansion is *, which matches all hosts.
15221 .option auto_thaw main time 0s
15222 .cindex "thawing messages"
15223 .cindex "unfreezing messages"
15224 If this option is set to a time greater than zero, a queue runner will try a
15225 new delivery attempt on any frozen message, other than a bounce message, if
15226 this much time has passed since it was frozen. This may result in the message
15227 being re-frozen if nothing has changed since the last attempt. It is a way of
15228 saying &"keep on trying, even though there are big problems"&.
15230 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
15231 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
15232 thought to be very useful any more, and its use should probably be avoided.
15235 .option av_scanner main string "see below"
15236 This option is available if Exim is built with the content-scanning extension.
15237 It specifies which anti-virus scanner to use. The default value is:
15239 sophie:/var/run/sophie
15241 If the value of &%av_scanner%& starts with a dollar character, it is expanded
15242 before use. See section &<<SECTscanvirus>>& for further details.
15245 .option bi_command main string unset
15247 This option supplies the name of a command that is run when Exim is called with
15248 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
15249 just the command name, it is not a complete command line. If an argument is
15250 required, it must come from the &%-oA%& command line option.
15253 .option bounce_message_file main string&!! unset
15254 .cindex "bounce message" "customizing"
15255 .cindex "customizing" "bounce message"
15256 This option defines a template file containing paragraphs of text to be used
15257 for constructing bounce messages. Details of the file's contents are given in
15258 chapter &<<CHAPemsgcust>>&.
15259 .cindex bounce_message_file "tainted data"
15260 The option is expanded to give the file path, which must be
15261 absolute and untainted.
15262 See also &%warn_message_file%&.
15265 .option bounce_message_text main string unset
15266 When this option is set, its contents are included in the default bounce
15267 message immediately after &"This message was created automatically by mail
15268 delivery software."& It is not used if &%bounce_message_file%& is set.
15270 .option bounce_return_body main boolean true
15271 .cindex "bounce message" "including body"
15272 This option controls whether the body of an incoming message is included in a
15273 bounce message when &%bounce_return_message%& is true. The default setting
15274 causes the entire message, both header and body, to be returned (subject to the
15275 value of &%bounce_return_size_limit%&). If this option is false, only the
15276 message header is included. In the case of a non-SMTP message containing an
15277 error that is detected during reception, only those header lines preceding the
15278 point at which the error was detected are returned.
15279 .cindex "bounce message" "including original"
15281 .option bounce_return_linesize_limit main integer 998
15282 .cindex "size" "of bounce lines, limit"
15283 .cindex "bounce message" "line length limit"
15284 .cindex "limit" "bounce message line length"
15285 This option sets a limit in bytes on the line length of messages
15286 that are returned to senders due to delivery problems,
15287 when &%bounce_return_message%& is true.
15288 The default value corresponds to RFC limits.
15289 If the message being returned has lines longer than this value it is
15290 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
15292 The option also applies to bounces returned when an error is detected
15293 during reception of a message.
15294 In this case lines from the original are truncated.
15296 The option does not apply to messages generated by an &(autoreply)& transport.
15299 .option bounce_return_message main boolean true
15300 If this option is set false, none of the original message is included in
15301 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
15302 &%bounce_return_body%&.
15305 .option bounce_return_size_limit main integer 100K
15306 .cindex "size" "of bounce, limit"
15307 .cindex "bounce message" "size limit"
15308 .cindex "limit" "bounce message size"
15309 This option sets a limit in bytes on the size of messages that are returned to
15310 senders as part of bounce messages when &%bounce_return_message%& is true. The
15311 limit should be less than the value of the global &%message_size_limit%& and of
15312 any &%message_size_limit%& settings on transports, to allow for the bounce text
15313 that Exim generates. If this option is set to zero there is no limit.
15315 When the body of any message that is to be included in a bounce message is
15316 greater than the limit, it is truncated, and a comment pointing this out is
15317 added at the top. The actual cutoff may be greater than the value given, owing
15318 to the use of buffering for transferring the message in chunks (typically 8K in
15319 size). The idea is to save bandwidth on those undeliverable 15-megabyte
15322 .option bounce_sender_authentication main string unset
15323 .cindex "bounce message" "sender authentication"
15324 .cindex "authentication" "bounce message"
15325 .cindex "AUTH" "on bounce message"
15326 This option provides an authenticated sender address that is sent with any
15327 bounce messages generated by Exim that are sent over an authenticated SMTP
15328 connection. A typical setting might be:
15330 bounce_sender_authentication = mailer-daemon@my.domain.example
15332 which would cause bounce messages to be sent using the SMTP command:
15334 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
15336 The value of &%bounce_sender_authentication%& must always be a complete email
15339 .option callout_domain_negative_expire main time 3h
15340 .cindex "caching" "callout timeouts"
15341 .cindex "callout" "caching timeouts"
15342 This option specifies the expiry time for negative callout cache data for a
15343 domain. See section &<<SECTcallver>>& for details of callout verification, and
15344 section &<<SECTcallvercache>>& for details of the caching.
15347 .option callout_domain_positive_expire main time 7d
15348 This option specifies the expiry time for positive callout cache data for a
15349 domain. See section &<<SECTcallver>>& for details of callout verification, and
15350 section &<<SECTcallvercache>>& for details of the caching.
15353 .option callout_negative_expire main time 2h
15354 This option specifies the expiry time for negative callout cache data for an
15355 address. See section &<<SECTcallver>>& for details of callout verification, and
15356 section &<<SECTcallvercache>>& for details of the caching.
15359 .option callout_positive_expire main time 24h
15360 This option specifies the expiry time for positive callout cache data for an
15361 address. See section &<<SECTcallver>>& for details of callout verification, and
15362 section &<<SECTcallvercache>>& for details of the caching.
15365 .option callout_random_local_part main string&!! "see below"
15366 This option defines the &"random"& local part that can be used as part of
15367 callout verification. The default value is
15369 $primary_hostname-$tod_epoch-testing
15371 See section &<<CALLaddparcall>>& for details of how this value is used.
15374 .option check_log_inodes main integer 100
15375 See &%check_spool_space%& below.
15378 .option check_log_space main integer 10M
15379 See &%check_spool_space%& below.
15381 .oindex "&%check_rfc2047_length%&"
15382 .cindex "RFC 2047" "disabling length check"
15383 .option check_rfc2047_length main boolean true
15384 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
15385 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
15386 word; strings to be encoded that exceed this length are supposed to use
15387 multiple encoded words. By default, Exim does not recognize encoded words that
15388 exceed the maximum length. However, it seems that some software, in violation
15389 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
15390 set false, Exim recognizes encoded words of any length.
15393 .option check_spool_inodes main integer 100
15394 See &%check_spool_space%& below.
15397 .option check_spool_space main integer 10M
15398 .cindex "checking disk space"
15399 .cindex "disk space, checking"
15400 .cindex "spool directory" "checking space"
15401 The four &%check_...%& options allow for checking of disk resources before a
15402 message is accepted.
15404 .vindex "&$log_inodes$&"
15405 .vindex "&$log_space$&"
15406 .vindex "&$spool_inodes$&"
15407 .vindex "&$spool_space$&"
15408 When any of these options are nonzero, they apply to all incoming messages. If you
15409 want to apply different checks to different kinds of message, you can do so by
15410 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
15411 &$spool_space$& in an ACL with appropriate additional conditions.
15414 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
15415 either value is greater than zero, for example:
15417 check_spool_space = 100M
15418 check_spool_inodes = 100
15420 The spool partition is the one that contains the directory defined by
15421 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
15424 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
15425 files are written if either is greater than zero. These should be set only if
15426 &%log_file_path%& and &%spool_directory%& refer to different partitions.
15428 If there is less space or fewer inodes than requested, Exim refuses to accept
15429 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
15430 error response to the MAIL command. If ESMTP is in use and there was a
15431 SIZE parameter on the MAIL command, its value is added to the
15432 &%check_spool_space%& value, and the check is performed even if
15433 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
15435 The values for &%check_spool_space%& and &%check_log_space%& are held as a
15436 number of kilobytes (though specified in bytes).
15437 If a non-multiple of 1024 is specified, it is rounded up.
15439 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
15440 failure a message is written to stderr and Exim exits with a non-zero code, as
15441 it obviously cannot send an error message of any kind.
15443 There is a slight performance penalty for these checks.
15444 Versions of Exim preceding 4.88 had these disabled by default;
15445 high-rate installations confident they will never run out of resources
15446 may wish to deliberately disable them.
15448 .option chunking_advertise_hosts main "host list&!!" *
15449 .cindex CHUNKING advertisement
15450 .cindex "RFC 3030" "CHUNKING"
15451 .cindex "ESMTP extensions" CHUNKING
15452 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
15454 Hosts may use the BDAT command as an alternate to DATA.
15456 .option commandline_checks_require_admin main boolean &`false`&
15457 .cindex "restricting access to features"
15458 This option restricts various basic checking features to require an
15459 administrative user.
15460 This affects most of the &%-b*%& options, such as &%-be%&.
15462 .option debug_store main boolean &`false`&
15463 .cindex debugging "memory corruption"
15464 .cindex memory debugging
15465 This option, when true, enables extra checking in Exim's internal memory
15466 management. For use when a memory corruption issue is being investigated,
15467 it should normally be left as default.
15469 .option daemon_smtp_ports main string &`smtp`&
15470 .cindex "port" "for daemon"
15471 .cindex "TCP/IP" "setting listening ports"
15472 This option specifies one or more default SMTP ports on which the Exim daemon
15473 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
15474 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
15476 .option daemon_startup_retries main integer 9
15477 .cindex "daemon startup, retrying"
15478 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
15479 the daemon at startup when it cannot immediately bind a listening socket
15480 (typically because the socket is already in use): &%daemon_startup_retries%&
15481 defines the number of retries after the first failure, and
15482 &%daemon_startup_sleep%& defines the length of time to wait between retries.
15484 .option daemon_startup_sleep main time 30s
15485 See &%daemon_startup_retries%&.
15487 .option delay_warning main "time list" 24h
15488 .cindex "warning of delay"
15489 .cindex "delay warning, specifying"
15490 .cindex "queue" "delay warning"
15491 When a message is delayed, Exim sends a warning message to the sender at
15492 intervals specified by this option. The data is a colon-separated list of times
15493 after which to send warning messages. If the value of the option is an empty
15494 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
15495 message has been in the queue for longer than the last time, the last interval
15496 between the times is used to compute subsequent warning times. For example,
15499 delay_warning = 4h:8h:24h
15501 the first message is sent after 4 hours, the second after 8 hours, and
15502 the third one after 24 hours. After that, messages are sent every 16 hours,
15503 because that is the interval between the last two times on the list. If you set
15504 just one time, it specifies the repeat interval. For example, with:
15508 messages are repeated every six hours. To stop warnings after a given time, set
15509 a very large time at the end of the list. For example:
15511 delay_warning = 2h:12h:99d
15513 Note that the option is only evaluated at the time a delivery attempt fails,
15514 which depends on retry and queue-runner configuration.
15515 Typically retries will be configured more frequently than warning messages.
15517 .option delay_warning_condition main string&!! "see below"
15518 .vindex "&$domain$&"
15519 The string is expanded at the time a warning message might be sent. If all the
15520 deferred addresses have the same domain, it is set in &$domain$& during the
15521 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
15522 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
15523 &"false"& (the comparison being done caselessly) then the warning message is
15524 not sent. The default is:
15526 delay_warning_condition = ${if or {\
15527 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
15528 { match{$h_precedence:}{(?i)bulk|list|junk} }\
15529 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
15532 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
15533 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
15534 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
15535 &"auto-replied"& in an &'Auto-Submitted:'& header.
15537 .option deliver_drop_privilege main boolean false
15538 .cindex "unprivileged delivery"
15539 .cindex "delivery" "unprivileged"
15540 If this option is set true, Exim drops its root privilege at the start of a
15541 delivery process, and runs as the Exim user throughout. This severely restricts
15542 the kinds of local delivery that are possible, but is viable in certain types
15543 of configuration. There is a discussion about the use of root privilege in
15544 chapter &<<CHAPsecurity>>&.
15546 .option deliver_queue_load_max main fixed-point unset
15547 .cindex "load average"
15548 .cindex "queue runner" "abandoning"
15549 When this option is set, a queue run is abandoned if the system load average
15550 becomes greater than the value of the option. The option has no effect on
15551 ancient operating systems on which Exim cannot determine the load average.
15552 See also &%queue_only_load%& and &%smtp_load_reserve%&.
15555 .option delivery_date_remove main boolean true
15556 .cindex "&'Delivery-date:'& header line"
15557 Exim's transports have an option for adding a &'Delivery-date:'& header to a
15558 message when it is delivered, in exactly the same way as &'Return-path:'& is
15559 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
15560 should not be present in incoming messages, and this option causes them to be
15561 removed at the time the message is received, to avoid any problems that might
15562 occur when a delivered message is subsequently sent on to some other recipient.
15564 .option disable_fsync main boolean false
15565 .cindex "&[fsync()]&, disabling"
15566 This option is available only if Exim was built with the compile-time option
15567 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
15568 a runtime configuration generates an &"unknown option"& error. You should not
15569 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
15570 really, really, really understand what you are doing. &'No pre-compiled
15571 distributions of Exim should ever make this option available.'&
15573 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
15574 updated files' data to be written to disc before continuing. Unexpected events
15575 such as crashes and power outages may cause data to be lost or scrambled.
15576 Here be Dragons. &*Beware.*&
15579 .option disable_ipv6 main boolean false
15580 .cindex "IPv6" "disabling"
15581 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
15582 activities take place. AAAA records are never looked up, and any IPv6 addresses
15583 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
15584 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
15585 to handle IPv6 literal addresses.
15588 .option dkim_verify_hashes main "string list" "sha256 : sha512"
15589 .cindex DKIM "selecting signature algorithms"
15590 This option gives a list of hash types which are acceptable in signatures,
15591 and an order of processing.
15592 Signatures with algorithms not in the list will be ignored.
15594 Acceptable values include:
15601 Note that the acceptance of sha1 violates RFC 8301.
15603 .option dkim_verify_keytypes main "string list" "ed25519 : rsa"
15604 This option gives a list of key types which are acceptable in signatures,
15605 and an order of processing.
15606 Signatures with algorithms not in the list will be ignored.
15609 .option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250"
15610 This option gives a list of key sizes which are acceptable in signatures.
15611 The list is keyed by the algorithm type for the key; the values are in bits.
15612 Signatures with keys smaller than given by this option will fail verification.
15614 The default enforces the RFC 8301 minimum key size for RSA signatures.
15616 .option dkim_verify_minimal main boolean false
15617 If set to true, verification of signatures will terminate after the
15620 .option dkim_verify_signers main "domain list&!!" $dkim_signers
15621 .cindex DKIM "controlling calls to the ACL"
15622 This option gives a list of DKIM domains for which the DKIM ACL is run.
15623 It is expanded after the message is received; by default it runs
15624 the ACL once for each signature in the message.
15625 See section &<<SECDKIMVFY>>&.
15628 .option dmarc_forensic_sender main string&!! unset
15629 .option dmarc_history_file main string unset
15630 .option dmarc_tld_file main string unset
15631 .cindex DMARC "main section options"
15632 These options control DMARC processing.
15633 See section &<<SECDMARC>>& for details.
15636 .option dns_again_means_nonexist main "domain list&!!" unset
15637 .cindex "DNS" "&""try again""& response; overriding"
15638 DNS lookups give a &"try again"& response for the DNS errors
15639 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
15640 keep trying to deliver a message, or to give repeated temporary errors to
15641 incoming mail. Sometimes the effect is caused by a badly set up name server and
15642 may persist for a long time. If a domain which exhibits this problem matches
15643 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
15644 This option should be used with care. You can make it apply to reverse lookups
15645 by a setting such as this:
15647 dns_again_means_nonexist = *.in-addr.arpa
15649 This option applies to all DNS lookups that Exim does. It also applies when the
15650 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
15651 since these are most likely to be caused by DNS lookup problems. The
15652 &(dnslookup)& router has some options of its own for controlling what happens
15653 when lookups for MX or SRV records give temporary errors. These more specific
15654 options are applied after this global option.
15656 .option dns_check_names_pattern main string "see below"
15657 .cindex "DNS" "pre-check of name syntax"
15658 When this option is set to a non-empty string, it causes Exim to check domain
15659 names for characters that are not allowed in host names before handing them to
15660 the DNS resolver, because some resolvers give temporary errors for names that
15661 contain unusual characters. If a domain name contains any unwanted characters,
15662 a &"not found"& result is forced, and the resolver is not called. The check is
15663 done by matching the domain name against a regular expression, which is the
15664 value of this option. The default pattern is
15666 dns_check_names_pattern = \
15667 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
15669 which permits only letters, digits, slashes, and hyphens in components, but
15670 they must start and end with a letter or digit. Slashes are not, in fact,
15671 permitted in host names, but they are found in certain NS records (which can be
15672 accessed in Exim by using a &%dnsdb%& lookup). If you set
15673 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
15676 .option dns_csa_search_limit main integer 5
15677 This option controls the depth of parental searching for CSA SRV records in the
15678 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
15680 .option dns_csa_use_reverse main boolean true
15681 This option controls whether or not an IP address, given as a CSA domain, is
15682 reversed and looked up in the reverse DNS, as described in more detail in
15683 section &<<SECTverifyCSA>>&.
15685 .option dns_cname_loops main integer 1
15686 .cindex DNS "CNAME following"
15687 This option controls the following of CNAME chains, needed if the resolver does
15688 not do it internally.
15689 As of 2018 most should, and the default can be left.
15690 If you have an ancient one, a value of 10 is likely needed.
15692 The default value of one CNAME-follow is needed
15693 thanks to the observed return for an MX request,
15694 given no MX presence but a CNAME to an A, of the CNAME.
15697 .option dns_dnssec_ok main integer -1
15698 .cindex "DNS" "resolver options"
15699 .cindex "DNS" "DNSSEC"
15700 If this option is set to a non-negative number then Exim will initialise the
15701 DNS resolver library to either use or not use DNSSEC, overriding the system
15702 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
15704 If the resolver library does not support DNSSEC then this option has no effect.
15706 On Linux with glibc 2.31 or newer this is insufficient, the resolver library
15707 will default to stripping out a successful validation status.
15708 This will break a previously working Exim installation.
15709 Provided that you do trust the resolver (ie, is on localhost) you can tell
15710 glibc to pass through any successful validation with a new option in
15711 &_/etc/resolv.conf_&:
15717 .option dns_ipv4_lookup main "domain list&!!" unset
15718 .cindex "IPv6" "DNS lookup for AAAA records"
15719 .cindex "DNS" "IPv6 lookup for AAAA records"
15720 .cindex DNS "IPv6 disabling"
15721 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
15722 looks for IPv6 address records (AAAA records) as well as IPv4 address records
15723 (A records) when trying to find IP addresses for hosts, unless the host's
15724 domain matches this list.
15726 This is a fudge to help with name servers that give big delays or otherwise do
15727 not work for the AAAA record type. In due course, when the world's name
15728 servers have all been upgraded, there should be no need for this option.
15729 Note that all lookups, including those done for verification, are affected;
15730 this will result in verify failure for IPv6 connections or ones using names
15731 only valid for IPv6 addresses.
15734 .option dns_retrans main time 0s
15735 .cindex "DNS" "resolver options"
15736 .cindex timeout "dns lookup"
15737 .cindex "DNS" timeout
15738 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
15739 retransmission and retry parameters for DNS lookups. Values of zero (the
15740 defaults) leave the system default settings unchanged. The first value is the
15741 time between retries, and the second is the number of retries. It isn't
15742 totally clear exactly how these settings affect the total time a DNS lookup may
15743 take. I haven't found any documentation about timeouts on DNS lookups; these
15744 parameter values are available in the external resolver interface structure,
15745 but nowhere does it seem to describe how they are used or what you might want
15747 See also the &%slow_lookup_log%& option.
15750 .option dns_retry main integer 0
15751 See &%dns_retrans%& above.
15754 .option dns_trust_aa main "domain list&!!" unset
15755 .cindex "DNS" "resolver options"
15756 .cindex "DNS" "DNSSEC"
15757 If this option is set then lookup results marked with the AA bit
15758 (Authoritative Answer) are trusted the same way as if they were
15759 DNSSEC-verified. The authority section's name of the answer must
15760 match with this expanded domain list.
15762 Use this option only if you talk directly to a resolver that is
15763 authoritative for some zones and does not set the AD (Authentic Data)
15764 bit in the answer. Some DNS servers may have an configuration option to
15765 mark the answers from their own zones as verified (they set the AD bit).
15766 Others do not have this option. It is considered as poor practice using
15767 a resolver that is an authoritative server for some zones.
15769 Use this option only if you really have to (e.g. if you want
15770 to use DANE for remote delivery to a server that is listed in the DNS
15771 zones that your resolver is authoritative for).
15773 If the DNS answer packet has the AA bit set and contains resource record
15774 in the answer section, the name of the first NS record appearing in the
15775 authority section is compared against the list. If the answer packet is
15776 authoritative but the answer section is empty, the name of the first SOA
15777 record in the authoritative section is used instead.
15779 .cindex "DNS" "resolver options"
15780 .option dns_use_edns0 main integer -1
15781 .cindex "DNS" "resolver options"
15782 .cindex "DNS" "EDNS0"
15783 .cindex "DNS" "OpenBSD
15784 If this option is set to a non-negative number then Exim will initialise the
15785 DNS resolver library to either use or not use EDNS0 extensions, overriding
15786 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
15789 If the resolver library does not support EDNS0 then this option has no effect.
15791 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
15792 means that DNSSEC will not work with Exim on that platform either, unless Exim
15793 is linked against an alternative DNS client library.
15796 .option drop_cr main boolean false
15797 This is an obsolete option that is now a no-op. It used to affect the way Exim
15798 handled CR and LF characters in incoming messages. What happens now is
15799 described in section &<<SECTlineendings>>&.
15801 .option dsn_advertise_hosts main "host list&!!" unset
15802 .cindex "bounce messages" "success"
15803 .cindex "DSN" "success"
15804 .cindex "Delivery Status Notification" "success"
15805 .cindex "ESMTP extensions" DSN
15806 DSN extensions (RFC3461) will be advertised in the EHLO message to,
15807 and accepted from, these hosts.
15808 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
15809 and RET and ORCPT options on MAIL FROM commands.
15810 A NOTIFY=SUCCESS option requests success-DSN messages.
15811 A NOTIFY= option with no argument requests that no delay or failure DSNs
15813 &*Note*&: Supplying success-DSN messages has been criticised
15814 on privacy grounds; it can leak details of internal forwarding.
15816 .option dsn_from main "string&!!" "see below"
15817 .cindex "&'From:'& header line" "in bounces"
15818 .cindex "bounce messages" "&'From:'& line, specifying"
15819 This option can be used to vary the contents of &'From:'& header lines in
15820 bounces and other automatically generated messages (&"Delivery Status
15821 Notifications"& &-- hence the name of the option). The default setting is:
15823 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
15825 The value is expanded every time it is needed. If the expansion fails, a
15826 panic is logged, and the default value is used.
15828 .option envelope_to_remove main boolean true
15829 .cindex "&'Envelope-to:'& header line"
15830 Exim's transports have an option for adding an &'Envelope-to:'& header to a
15831 message when it is delivered, in exactly the same way as &'Return-path:'& is
15832 handled. &'Envelope-to:'& records the original recipient address from the
15833 message's envelope that caused the delivery to happen. Such headers should not
15834 be present in incoming messages, and this option causes them to be removed at
15835 the time the message is received, to avoid any problems that might occur when a
15836 delivered message is subsequently sent on to some other recipient.
15839 .option errors_copy main "string list&!!" unset
15840 .cindex "bounce message" "copy to other address"
15841 .cindex "copy of bounce message"
15842 Setting this option causes Exim to send bcc copies of bounce messages that it
15843 generates to other addresses. &*Note*&: This does not apply to bounce messages
15844 coming from elsewhere. The value of the option is a colon-separated list of
15845 items. Each item consists of a pattern, terminated by white space, followed by
15846 a comma-separated list of email addresses. If a pattern contains spaces, it
15847 must be enclosed in double quotes.
15849 Each pattern is processed in the same way as a single item in an address list
15850 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
15851 the bounce message, the message is copied to the addresses on the list. The
15852 items are scanned in order, and once a matching one is found, no further items
15853 are examined. For example:
15855 errors_copy = spqr@mydomain postmaster@mydomain.example :\
15856 rqps@mydomain hostmaster@mydomain.example,\
15857 postmaster@mydomain.example
15859 .vindex "&$domain$&"
15860 .vindex "&$local_part$&"
15861 The address list is expanded before use. The expansion variables &$local_part$&
15862 and &$domain$& are set from the original recipient of the error message, and if
15863 there was any wildcard matching in the pattern, the expansion
15864 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
15865 variables &$0$&, &$1$&, etc. are set in the normal way.
15868 .option errors_reply_to main string unset
15869 .cindex "bounce message" "&'Reply-to:'& in"
15870 By default, Exim's bounce and delivery warning messages contain the header line
15872 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
15874 .oindex &%quota_warn_message%&
15875 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
15876 A warning message that is generated by the &%quota_warn_message%& option in an
15877 &(appendfile)& transport may contain its own &'From:'& header line that
15878 overrides the default.
15880 Experience shows that people reply to bounce messages. If the
15881 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
15882 and warning messages. For example:
15884 errors_reply_to = postmaster@my.domain.example
15886 The value of the option is not expanded. It must specify a valid RFC 2822
15887 address. However, if a warning message that is generated by the
15888 &%quota_warn_message%& option in an &(appendfile)& transport contain its
15889 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
15893 .option event_action main string&!! unset
15895 This option declares a string to be expanded for Exim's events mechanism.
15896 For details see chapter &<<CHAPevents>>&.
15899 .option exim_group main string "compile-time configured"
15900 .cindex "gid (group id)" "Exim's own"
15901 .cindex "Exim group"
15902 This option changes the gid under which Exim runs when it gives up root
15903 privilege. The default value is compiled into the binary. The value of this
15904 option is used only when &%exim_user%& is also set. Unless it consists entirely
15905 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
15906 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
15910 .option exim_path main string "see below"
15911 .cindex "Exim binary, path name"
15912 This option specifies the path name of the Exim binary, which is used when Exim
15913 needs to re-exec itself. The default is set up to point to the file &'exim'& in
15914 the directory configured at compile time by the BIN_DIRECTORY setting. It
15915 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
15917 &*Warning*&: Do not use a macro to define the value of this option, because
15918 you will break those Exim utilities that scan the configuration file to find
15919 where the binary is. (They then use the &%-bP%& option to extract option
15920 settings such as the value of &%spool_directory%&.)
15923 .option exim_user main string "compile-time configured"
15924 .cindex "uid (user id)" "Exim's own"
15925 .cindex "Exim user"
15926 This option changes the uid under which Exim runs when it gives up root
15927 privilege. The default value is compiled into the binary. Ownership of the run
15928 time configuration file and the use of the &%-C%& and &%-D%& command line
15929 options is checked against the values in the binary, not what is set here.
15931 Unless it consists entirely of digits, the string is looked up using
15932 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
15933 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
15934 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
15937 .option exim_version main string "current version"
15938 .cindex "Exim version"
15939 .cindex customizing "version number"
15940 .cindex "version number of Exim" override
15941 This option overrides the &$version_number$&/&$exim_version$& that Exim reports in
15942 various places. Use with care; this may fool stupid security scanners.
15945 .option extra_local_interfaces main "string list" unset
15946 This option defines network interfaces that are to be considered local when
15947 routing, but which are not used for listening by the daemon. See section
15948 &<<SECTreclocipadd>>& for details.
15951 . Allow this long option name to split; give it unsplit as a fifth argument
15952 . for the automatic .oindex that is generated by .option.
15954 .option "extract_addresses_remove_arguments" main boolean true &&&
15955 extract_addresses_remove_arguments
15957 .cindex "command line" "addresses with &%-t%&"
15958 .cindex "Sendmail compatibility" "&%-t%& option"
15959 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
15960 are present on the command line when the &%-t%& option is used to build an
15961 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
15962 line addresses are removed from the recipients list. This is also how Smail
15963 behaves. However, other Sendmail documentation (the O'Reilly book) states that
15964 command line addresses are added to those obtained from the header lines. When
15965 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
15966 argument headers. If it is set false, Exim adds rather than removes argument
15970 .option finduser_retries main integer 0
15971 .cindex "NIS, retrying user lookups"
15972 On systems running NIS or other schemes in which user and group information is
15973 distributed from a remote system, there can be times when &[getpwnam()]& and
15974 related functions fail, even when given valid data, because things time out.
15975 Unfortunately these failures cannot be distinguished from genuine &"not found"&
15976 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
15977 many extra times to find a user or a group, waiting for one second between
15980 .cindex "&_/etc/passwd_&" "multiple reading of"
15981 You should not set this option greater than zero if your user information is in
15982 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
15983 search the file multiple times for non-existent users, and also cause delay.
15987 .option freeze_tell main "string list, comma separated" unset
15988 .cindex "freezing messages" "sending a message when freezing"
15989 On encountering certain errors, or when configured to do so in a system filter,
15990 ACL, or special router, Exim freezes a message. This means that no further
15991 delivery attempts take place until an administrator thaws the message, or the
15992 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
15993 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
15994 warning message whenever it freezes something, unless the message it is
15995 freezing is a locally-generated bounce message. (Without this exception there
15996 is the possibility of looping.) The warning message is sent to the addresses
15997 supplied as the comma-separated value of this option. If several of the
15998 message's addresses cause freezing, only a single message is sent. If the
15999 freezing was automatic, the reason(s) for freezing can be found in the message
16000 log. If you configure freezing in a filter or ACL, you must arrange for any
16001 logging that you require.
16004 .option gecos_name main string&!! unset
16006 .cindex "&""gecos""& field, parsing"
16007 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
16008 password file to hold other information in addition to users' real names. Exim
16009 looks up this field for use when it is creating &'Sender:'& or &'From:'&
16010 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
16011 of the field are used unchanged, except that, if an ampersand is encountered,
16012 it is replaced by the user's login name with the first character forced to
16013 upper case, since this is a convention that is observed on many systems.
16015 When these options are set, &%gecos_pattern%& is treated as a regular
16016 expression that is to be applied to the field (again with && replaced by the
16017 login name), and if it matches, &%gecos_name%& is expanded and used as the
16020 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
16021 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
16022 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
16023 name terminates at the first comma, the following can be used:
16025 gecos_pattern = ([^,]*)
16029 .option gecos_pattern main string unset
16030 See &%gecos_name%& above.
16033 .option gnutls_compat_mode main boolean unset
16034 This option controls whether GnuTLS is used in compatibility mode in an Exim
16035 server. This reduces security slightly, but improves interworking with older
16036 implementations of TLS.
16039 .option gnutls_allow_auto_pkcs11 main boolean unset
16040 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
16041 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
16044 &url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
16049 .option headers_charset main string "see below"
16050 This option sets a default character set for translating from encoded MIME
16051 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
16052 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
16053 ultimate default is ISO-8859-1. For more details see the description of header
16054 insertions in section &<<SECTexpansionitems>>&.
16058 .option header_maxsize main integer "see below"
16059 .cindex "header section" "maximum size of"
16060 .cindex "limit" "size of message header section"
16061 This option controls the overall maximum size of a message's header
16062 section. The default is the value of HEADER_MAXSIZE in
16063 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
16064 sections are rejected.
16067 .option header_line_maxsize main integer 0
16068 .cindex "header lines" "maximum size of"
16069 .cindex "limit" "size of one header line"
16070 This option limits the length of any individual header line in a message, after
16071 all the continuations have been joined together. Messages with individual
16072 header lines that are longer than the limit are rejected. The default value of
16073 zero means &"no limit"&.
16078 .option helo_accept_junk_hosts main "host list&!!" unset
16079 .cindex "HELO" "accepting junk data"
16080 .cindex "EHLO" "accepting junk data"
16081 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
16082 mail, and gives an error response for invalid data. Unfortunately, there are
16083 some SMTP clients that send syntactic junk. They can be accommodated by setting
16084 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
16085 if you want to do semantic checking.
16086 See also &%helo_allow_chars%& for a way of extending the permitted character
16090 .option helo_allow_chars main string unset
16091 .cindex "HELO" "underscores in"
16092 .cindex "EHLO" "underscores in"
16093 .cindex "underscore in EHLO/HELO"
16094 This option can be set to a string of rogue characters that are permitted in
16095 all EHLO and HELO names in addition to the standard letters, digits,
16096 hyphens, and dots. If you really must allow underscores, you can set
16098 helo_allow_chars = _
16100 Note that the value is one string, not a list.
16103 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
16104 .cindex "HELO" "forcing reverse lookup"
16105 .cindex "EHLO" "forcing reverse lookup"
16106 If the domain given by a client in a HELO or EHLO command matches this
16107 list, a reverse lookup is done in order to establish the host's true name. The
16108 default forces a lookup if the client host gives the server's name or any of
16109 its IP addresses (in brackets), something that broken clients have been seen to
16113 .option helo_try_verify_hosts main "host list&!!" unset
16114 .cindex "HELO verifying" "optional"
16115 .cindex "EHLO" "verifying, optional"
16116 By default, Exim just checks the syntax of HELO and EHLO commands (see
16117 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
16118 to do more extensive checking of the data supplied by these commands. The ACL
16119 condition &`verify = helo`& is provided to make this possible.
16120 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
16121 to force the check to occur. From release 4.53 onwards, this is no longer
16122 necessary. If the check has not been done before &`verify = helo`& is
16123 encountered, it is done at that time. Consequently, this option is obsolete.
16124 Its specification is retained here for backwards compatibility.
16126 When an EHLO or HELO command is received, if the calling host matches
16127 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
16128 EHLO command either:
16131 is an IP literal matching the calling address of the host, or
16133 .cindex "DNS" "reverse lookup"
16134 .cindex "reverse DNS lookup"
16135 matches the host name that Exim obtains by doing a reverse lookup of the
16136 calling host address, or
16138 when looked up in DNS yields the calling host address.
16141 However, the EHLO or HELO command is not rejected if any of the checks
16142 fail. Processing continues, but the result of the check is remembered, and can
16143 be detected later in an ACL by the &`verify = helo`& condition.
16145 If DNS was used for successful verification, the variable
16146 .cindex "DNS" "DNSSEC"
16147 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
16149 .option helo_verify_hosts main "host list&!!" unset
16150 .cindex "HELO verifying" "mandatory"
16151 .cindex "EHLO" "verifying, mandatory"
16152 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
16153 backwards compatibility. For hosts that match this option, Exim checks the host
16154 name given in the HELO or EHLO in the same way as for
16155 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
16156 rejected with a 550 error, and entries are written to the main and reject logs.
16157 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
16160 .option hold_domains main "domain list&!!" unset
16161 .cindex "domain" "delaying delivery"
16162 .cindex "delivery" "delaying certain domains"
16163 This option allows mail for particular domains to be held in the queue
16164 manually. The option is overridden if a message delivery is forced with the
16165 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
16166 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
16167 item in &%hold_domains%&, no routing or delivery for that address is done, and
16168 it is deferred every time the message is looked at.
16170 This option is intended as a temporary operational measure for delaying the
16171 delivery of mail while some problem is being sorted out, or some new
16172 configuration tested. If you just want to delay the processing of some
16173 domains until a queue run occurs, you should use &%queue_domains%& or
16174 &%queue_smtp_domains%&, not &%hold_domains%&.
16176 A setting of &%hold_domains%& does not override Exim's code for removing
16177 messages from the queue if they have been there longer than the longest retry
16178 time in any retry rule. If you want to hold messages for longer than the normal
16179 retry times, insert a dummy retry rule with a long retry time.
16182 .option host_lookup main "host list&!!" unset
16183 .cindex "host name" "lookup, forcing"
16184 Exim does not look up the name of a calling host from its IP address unless it
16185 is required to compare against some host list, or the host matches
16186 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
16187 option (which normally contains IP addresses rather than host names). The
16188 default configuration file contains
16192 which causes a lookup to happen for all hosts. If the expense of these lookups
16193 is felt to be too great, the setting can be changed or removed.
16195 After a successful reverse lookup, Exim does a forward lookup on the name it
16196 has obtained, to verify that it yields the IP address that it started with. If
16197 this check fails, Exim behaves as if the name lookup failed.
16199 .vindex "&$host_lookup_failed$&"
16200 .vindex "&$sender_host_name$&"
16201 After any kind of failure, the host name (in &$sender_host_name$&) remains
16202 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
16203 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
16204 &`verify = reverse_host_lookup`& in ACLs.
16207 .option host_lookup_order main "string list" &`bydns:byaddr`&
16208 This option specifies the order of different lookup methods when Exim is trying
16209 to find a host name from an IP address. The default is to do a DNS lookup
16210 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
16211 if that fails. You can change the order of these lookups, or omit one entirely,
16214 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
16215 multiple PTR records in the DNS and the IP address is not listed in
16216 &_/etc/hosts_&. Different operating systems give different results in this
16217 case. That is why the default tries a DNS lookup first.
16221 .option host_reject_connection main "host list&!!" unset
16222 .cindex "host" "rejecting connections from"
16223 If this option is set, incoming SMTP calls from the hosts listed are rejected
16224 as soon as the connection is made.
16225 This option is obsolete, and retained only for backward compatibility, because
16226 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
16227 connections immediately.
16229 The ability to give an immediate rejection (either by this option or using an
16230 ACL) is provided for use in unusual cases. Many hosts will just try again,
16231 sometimes without much delay. Normally, it is better to use an ACL to reject
16232 incoming messages at a later stage, such as after RCPT commands. See
16233 chapter &<<CHAPACL>>&.
16236 .option hosts_connection_nolog main "host list&!!" unset
16237 .cindex "host" "not logging connections from"
16238 This option defines a list of hosts for which connection logging does not
16239 happen, even though the &%smtp_connection%& log selector is set. For example,
16240 you might want not to log SMTP connections from local processes, or from
16241 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
16242 the daemon; you should therefore strive to restrict its value to a short inline
16243 list of IP addresses and networks. To disable logging SMTP connections from
16244 local processes, you must create a host list with an empty item. For example:
16246 hosts_connection_nolog = :
16248 If the &%smtp_connection%& log selector is not set, this option has no effect.
16252 .option hosts_proxy main "host list&!!" unset
16253 .cindex proxy "proxy protocol"
16254 This option enables use of Proxy Protocol proxies for incoming
16255 connections. For details see section &<<SECTproxyInbound>>&.
16258 .option hosts_treat_as_local main "domain list&!!" unset
16259 .cindex "local host" "domains treated as"
16260 .cindex "host" "treated as local"
16261 If this option is set, any host names that match the domain list are treated as
16262 if they were the local host when Exim is scanning host lists obtained from MX
16264 or other sources. Note that the value of this option is a domain list, not a
16265 host list, because it is always used to check host names, not IP addresses.
16267 This option also applies when Exim is matching the special items
16268 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
16269 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
16270 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
16271 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
16272 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
16273 interfaces and recognizing the local host.
16276 .option ibase_servers main "string list" unset
16277 .cindex "InterBase" "server list"
16278 This option provides a list of InterBase servers and associated connection data,
16279 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
16280 The option is available only if Exim has been built with InterBase support.
16284 .option ignore_bounce_errors_after main time 10w
16285 .cindex "bounce message" "discarding"
16286 .cindex "discarding bounce message"
16287 This option affects the processing of bounce messages that cannot be delivered,
16288 that is, those that suffer a permanent delivery failure. (Bounce messages that
16289 suffer temporary delivery failures are of course retried in the usual way.)
16291 After a permanent delivery failure, bounce messages are frozen,
16292 because there is no sender to whom they can be returned. When a frozen bounce
16293 message has been in the queue for more than the given time, it is unfrozen at
16294 the next queue run, and a further delivery is attempted. If delivery fails
16295 again, the bounce message is discarded. This makes it possible to keep failed
16296 bounce messages around for a shorter time than the normal maximum retry time
16297 for frozen messages. For example,
16299 ignore_bounce_errors_after = 12h
16301 retries failed bounce message deliveries after 12 hours, discarding any further
16302 failures. If the value of this option is set to a zero time period, bounce
16303 failures are discarded immediately. Setting a very long time (as in the default
16304 value) has the effect of disabling this option. For ways of automatically
16305 dealing with other kinds of frozen message, see &%auto_thaw%& and
16306 &%timeout_frozen_after%&.
16309 .option ignore_fromline_hosts main "host list&!!" unset
16310 .cindex "&""From""& line"
16311 .cindex "UUCP" "&""From""& line"
16312 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
16313 the headers of a message. By default this is treated as the start of the
16314 message's body, which means that any following headers are not recognized as
16315 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
16316 match those hosts that insist on sending it. If the sender is actually a local
16317 process rather than a remote host, and is using &%-bs%& to inject the messages,
16318 &%ignore_fromline_local%& must be set to achieve this effect.
16321 .option ignore_fromline_local main boolean false
16322 See &%ignore_fromline_hosts%& above.
16324 .option keep_environment main "string list" unset
16325 .cindex "environment" "values from"
16326 This option contains a string list of environment variables to keep.
16327 You have to trust these variables or you have to be sure that
16328 these variables do not impose any security risk. Keep in mind that
16329 during the startup phase Exim is running with an effective UID 0 in most
16330 installations. As the default value is an empty list, the default
16331 environment for using libraries, running embedded Perl code, or running
16332 external binaries is empty, and does not not even contain PATH or HOME.
16334 Actually the list is interpreted as a list of patterns
16335 (&<<SECTlistexpand>>&), except that it is not expanded first.
16337 WARNING: Macro substitution is still done first, so having a macro
16338 FOO and having FOO_HOME in your &%keep_environment%& option may have
16339 unexpected results. You may work around this using a regular expression
16340 that does not match the macro name: ^[F]OO_HOME$.
16342 Current versions of Exim issue a warning during startup if you do not mention
16343 &%keep_environment%& in your runtime configuration file and if your
16344 current environment is not empty. Future versions may not issue that warning
16347 See the &%add_environment%& main config option for a way to set
16348 environment variables to a fixed value. The environment for &(pipe)&
16349 transports is handled separately, see section &<<SECTpipeenv>>& for
16353 .option keep_malformed main time 4d
16354 This option specifies the length of time to keep messages whose spool files
16355 have been corrupted in some way. This should, of course, never happen. At the
16356 next attempt to deliver such a message, it gets removed. The incident is
16360 .option ldap_ca_cert_dir main string unset
16361 .cindex "LDAP", "TLS CA certificate directory"
16362 .cindex certificate "directory for LDAP"
16363 This option indicates which directory contains CA certificates for verifying
16364 a TLS certificate presented by an LDAP server.
16365 While Exim does not provide a default value, your SSL library may.
16366 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16367 and constrained to be a directory.
16370 .option ldap_ca_cert_file main string unset
16371 .cindex "LDAP", "TLS CA certificate file"
16372 .cindex certificate "file for LDAP"
16373 This option indicates which file contains CA certificates for verifying
16374 a TLS certificate presented by an LDAP server.
16375 While Exim does not provide a default value, your SSL library may.
16376 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16377 and constrained to be a file.
16380 .option ldap_cert_file main string unset
16381 .cindex "LDAP" "TLS client certificate file"
16382 .cindex certificate "file for LDAP"
16383 This option indicates which file contains an TLS client certificate which
16384 Exim should present to the LDAP server during TLS negotiation.
16385 Should be used together with &%ldap_cert_key%&.
16388 .option ldap_cert_key main string unset
16389 .cindex "LDAP" "TLS client key file"
16390 .cindex certificate "key for LDAP"
16391 This option indicates which file contains the secret/private key to use
16392 to prove identity to the LDAP server during TLS negotiation.
16393 Should be used together with &%ldap_cert_file%&, which contains the
16394 identity to be proven.
16397 .option ldap_cipher_suite main string unset
16398 .cindex "LDAP" "TLS cipher suite"
16399 This controls the TLS cipher-suite negotiation during TLS negotiation with
16400 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
16401 cipher-suite options with OpenSSL (as used by LDAP client libraries).
16404 .option ldap_default_servers main "string list" unset
16405 .cindex "LDAP" "default servers"
16406 This option provides a list of LDAP servers which are tried in turn when an
16407 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
16408 details of LDAP queries. This option is available only when Exim has been built
16412 .option ldap_require_cert main string unset.
16413 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
16414 This should be one of the values "hard", "demand", "allow", "try" or "never".
16415 A value other than one of these is interpreted as "never".
16416 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
16417 Although Exim does not set a default, the LDAP library probably defaults
16421 .option ldap_start_tls main boolean false
16422 .cindex "LDAP" "whether or not to negotiate TLS"
16423 If set, Exim will attempt to negotiate TLS with the LDAP server when
16424 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
16425 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
16427 In the event of failure to negotiate TLS, the action taken is controlled
16428 by &%ldap_require_cert%&.
16429 This option is ignored for &`ldapi`& connections.
16432 .option ldap_version main integer unset
16433 .cindex "LDAP" "protocol version, forcing"
16434 This option can be used to force Exim to set a specific protocol version for
16435 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
16436 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
16437 the LDAP headers; otherwise it is 2. This option is available only when Exim
16438 has been built with LDAP support.
16442 .option local_from_check main boolean true
16443 .cindex "&'Sender:'& header line" "disabling addition of"
16444 .cindex "&'From:'& header line" "disabling checking of"
16445 When a message is submitted locally (that is, not over a TCP/IP connection) by
16446 an untrusted user, Exim removes any existing &'Sender:'& header line, and
16447 checks that the &'From:'& header line matches the login of the calling user and
16448 the domain specified by &%qualify_domain%&.
16450 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
16451 locally submitted message is automatically qualified by Exim, unless the
16452 &%-bnq%& command line option is used.
16454 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
16455 on the local part. If the &'From:'& header line does not match, Exim adds a
16456 &'Sender:'& header with an address constructed from the calling user's login
16457 and the default qualify domain.
16459 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
16460 and no &'Sender:'& header is ever added. If, in addition, you want to retain
16461 &'Sender:'& header lines supplied by untrusted users, you must also set
16462 &%local_sender_retain%& to be true.
16464 .cindex "envelope from"
16465 .cindex "envelope sender"
16466 These options affect only the header lines in the message. The envelope sender
16467 is still forced to be the login id at the qualify domain unless
16468 &%untrusted_set_sender%& permits the user to supply an envelope sender.
16470 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
16471 request similar header line checking. See section &<<SECTthesenhea>>&, which
16472 has more details about &'Sender:'& processing.
16477 .option local_from_prefix main string unset
16478 When Exim checks the &'From:'& header line of locally submitted messages for
16479 matching the login id (see &%local_from_check%& above), it can be configured to
16480 ignore certain prefixes and suffixes in the local part of the address. This is
16481 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
16482 appropriate lists, in the same form as the &%local_part_prefix%& and
16483 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
16486 local_from_prefix = *-
16488 is set, a &'From:'& line containing
16490 From: anything-user@your.domain.example
16492 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
16493 matches the actual sender address that is constructed from the login name and
16497 .option local_from_suffix main string unset
16498 See &%local_from_prefix%& above.
16501 .option local_interfaces main "string list" "see below"
16502 This option controls which network interfaces are used by the daemon for
16503 listening; they are also used to identify the local host when routing. Chapter
16504 &<<CHAPinterfaces>>& contains a full description of this option and the related
16505 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
16506 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
16507 &%local_interfaces%& is
16509 local_interfaces = 0.0.0.0
16511 when Exim is built without IPv6 support; otherwise it is
16513 local_interfaces = <; ::0 ; 0.0.0.0
16516 .option local_scan_timeout main time 5m
16517 .cindex "timeout" "for &[local_scan()]& function"
16518 .cindex "&[local_scan()]& function" "timeout"
16519 This timeout applies to the &[local_scan()]& function (see chapter
16520 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
16521 the incoming message is rejected with a temporary error if it is an SMTP
16522 message. For a non-SMTP message, the message is dropped and Exim ends with a
16523 non-zero code. The incident is logged on the main and reject logs.
16527 .option local_sender_retain main boolean false
16528 .cindex "&'Sender:'& header line" "retaining from local submission"
16529 When a message is submitted locally (that is, not over a TCP/IP connection) by
16530 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
16531 do not want this to happen, you must set &%local_sender_retain%&, and you must
16532 also set &%local_from_check%& to be false (Exim will complain if you do not).
16533 See also the ACL modifier &`control = suppress_local_fixups`&. Section
16534 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
16539 .option localhost_number main string&!! unset
16540 .cindex "host" "locally unique number for"
16541 .cindex "message ids" "with multiple hosts"
16542 .vindex "&$localhost_number$&"
16543 Exim's message ids are normally unique only within the local host. If
16544 uniqueness among a set of hosts is required, each host must set a different
16545 value for the &%localhost_number%& option. The string is expanded immediately
16546 after reading the configuration file (so that a number can be computed from the
16547 host name, for example) and the result of the expansion must be a number in the
16548 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
16549 systems). This is available in subsequent string expansions via the variable
16550 &$localhost_number$&. When &%localhost_number is set%&, the final two
16551 characters of the message id, instead of just being a fractional part of the
16552 time, are computed from the time and the local host number as described in
16553 section &<<SECTmessiden>>&.
16557 .option log_file_path main "string list&!!" "set at compile time"
16558 .cindex "log" "file path for"
16559 This option sets the path which is used to determine the names of Exim's log
16560 files, or indicates that logging is to be to syslog, or both. It is expanded
16561 when Exim is entered, so it can, for example, contain a reference to the host
16562 name. If no specific path is set for the log files at compile or runtime,
16563 or if the option is unset at runtime (i.e. &`log_file_path = `&)
16564 they are written in a sub-directory called &_log_& in Exim's spool directory.
16565 A path must start with a slash.
16566 To send to syslog, use the word &"syslog"&.
16567 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
16568 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
16569 used. If this string is fixed at your installation (contains no expansion
16570 variables) it is recommended that you do not set this option in the
16571 configuration file, but instead supply the path using LOG_FILE_PATH in
16572 &_Local/Makefile_& so that it is available to Exim for logging errors detected
16573 early on &-- in particular, failure to read the configuration file.
16576 .option log_selector main string unset
16577 .cindex "log" "selectors"
16578 This option can be used to reduce or increase the number of things that Exim
16579 writes to its log files. Its argument is made up of names preceded by plus or
16580 minus characters. For example:
16582 log_selector = +arguments -retry_defer
16584 A list of possible names and what they control is given in the chapter on
16585 logging, in section &<<SECTlogselector>>&.
16588 .option log_timezone main boolean false
16589 .cindex "log" "timezone for entries"
16590 .vindex "&$tod_log$&"
16591 .vindex "&$tod_zone$&"
16592 By default, the timestamps on log lines are in local time without the
16593 timezone. This means that if your timezone changes twice a year, the timestamps
16594 in log lines are ambiguous for an hour when the clocks go back. One way of
16595 avoiding this problem is to set the timezone to UTC. An alternative is to set
16596 &%log_timezone%& true. This turns on the addition of the timezone offset to
16597 timestamps in log lines. Turning on this option can add quite a lot to the size
16598 of log files because each line is extended by 6 characters. Note that the
16599 &$tod_log$& variable contains the log timestamp without the zone, but there is
16600 another variable called &$tod_zone$& that contains just the timezone offset.
16603 .option lookup_open_max main integer 25
16604 .cindex "too many open files"
16605 .cindex "open files, too many"
16606 .cindex "file" "too many open"
16607 .cindex "lookup" "maximum open files"
16608 .cindex "limit" "open files for lookups"
16609 This option limits the number of simultaneously open files for single-key
16610 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
16611 Exim normally keeps these files open during routing, because often the same
16612 file is required several times. If the limit is reached, Exim closes the least
16613 recently used file. Note that if you are using the &'ndbm'& library, it
16614 actually opens two files for each logical DBM database, though it still counts
16615 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
16616 open files"& errors with NDBM, you need to reduce the value of
16617 &%lookup_open_max%&.
16620 .option max_username_length main integer 0
16621 .cindex "length of login name"
16622 .cindex "user name" "maximum length"
16623 .cindex "limit" "user name length"
16624 Some operating systems are broken in that they truncate long arguments to
16625 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
16626 this option is set greater than zero, any attempt to call &[getpwnam()]& with
16627 an argument that is longer behaves as if &[getpwnam()]& failed.
16630 .option message_body_newlines main bool false
16631 .cindex "message body" "newlines in variables"
16632 .cindex "newline" "in message body variables"
16633 .vindex "&$message_body$&"
16634 .vindex "&$message_body_end$&"
16635 By default, newlines in the message body are replaced by spaces when setting
16636 the &$message_body$& and &$message_body_end$& expansion variables. If this
16637 option is set true, this no longer happens.
16640 .option message_body_visible main integer 500
16641 .cindex "body of message" "visible size"
16642 .cindex "message body" "visible size"
16643 .vindex "&$message_body$&"
16644 .vindex "&$message_body_end$&"
16645 This option specifies how much of a message's body is to be included in the
16646 &$message_body$& and &$message_body_end$& expansion variables.
16649 .option message_id_header_domain main string&!! unset
16650 .cindex "&'Message-ID:'& header line"
16651 If this option is set, the string is expanded and used as the right hand side
16652 (domain) of the &'Message-ID:'& header that Exim creates if a
16653 locally-originated incoming message does not have one. &"Locally-originated"&
16654 means &"not received over TCP/IP."&
16655 Otherwise, the primary host name is used.
16656 Only letters, digits, dot and hyphen are accepted; any other characters are
16657 replaced by hyphens. If the expansion is forced to fail, or if the result is an
16658 empty string, the option is ignored.
16661 .option message_id_header_text main string&!! unset
16662 If this variable is set, the string is expanded and used to augment the text of
16663 the &'Message-id:'& header that Exim creates if a locally-originated incoming
16664 message does not have one. The text of this header is required by RFC 2822 to
16665 take the form of an address. By default, Exim uses its internal message id as
16666 the local part, and the primary host name as the domain. If this option is set,
16667 it is expanded, and provided the expansion is not forced to fail, and does not
16668 yield an empty string, the result is inserted into the header immediately
16669 before the @, separated from the internal message id by a dot. Any characters
16670 that are illegal in an address are automatically converted into hyphens. This
16671 means that variables such as &$tod_log$& can be used, because the spaces and
16672 colons will become hyphens.
16675 .option message_logs main boolean true
16676 .cindex "message logs" "disabling"
16677 .cindex "log" "message log; disabling"
16678 If this option is turned off, per-message log files are not created in the
16679 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
16680 Exim, by reducing the number of files involved in handling a message from a
16681 minimum of four (header spool file, body spool file, delivery journal, and
16682 per-message log) to three. The other major I/O activity is Exim's main log,
16683 which is not affected by this option.
16686 .option message_size_limit main string&!! 50M
16687 .cindex "message" "size limit"
16688 .cindex "limit" "message size"
16689 .cindex "size" "of message, limit"
16690 This option limits the maximum size of message that Exim will process. The
16691 value is expanded for each incoming connection so, for example, it can be made
16692 to depend on the IP address of the remote host for messages arriving via
16693 TCP/IP. After expansion, the value must be a sequence of decimal digits,
16694 optionally followed by K or M.
16696 .cindex "SIZE" "ESMTP extension, advertising"
16697 .cindex "ESMTP extensions" SIZE
16698 If nonzero the value will be advertised as a parameter to the ESMTP SIZE
16699 service extension keyword.
16701 &*Note*&: This limit cannot be made to depend on a message's sender or any
16702 other properties of an individual message, because it has to be advertised in
16703 the server's response to EHLO. String expansion failure causes a temporary
16704 error. A value of zero means no limit, but its use is not recommended. See also
16705 &%bounce_return_size_limit%&.
16707 Incoming SMTP messages are failed with a 552 error if the limit is
16708 exceeded; locally-generated messages either get a stderr message or a delivery
16709 failure message to the sender, depending on the &%-oe%& setting. Rejection of
16710 an oversized message is logged in both the main and the reject logs. See also
16711 the generic transport option &%message_size_limit%&, which limits the size of
16712 message that an individual transport can process.
16714 If you use a virus-scanner and set this option to to a value larger than the
16715 maximum size that your virus-scanner is configured to support, you may get
16716 failures triggered by large mails. The right size to configure for the
16717 virus-scanner depends upon what data is passed and the options in use but it's
16718 probably safest to just set it to a little larger than this value. E.g., with a
16719 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
16720 some problems may result.
16722 A value of 0 will disable size limit checking; Exim will still advertise the
16723 SIZE extension in an EHLO response, but without a limit, so as to permit
16724 SMTP clients to still indicate the message size along with the MAIL verb.
16727 .option move_frozen_messages main boolean false
16728 .cindex "frozen messages" "moving"
16729 This option, which is available only if Exim has been built with the setting
16731 SUPPORT_MOVE_FROZEN_MESSAGES=yes
16733 in &_Local/Makefile_&, causes frozen messages and their message logs to be
16734 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
16735 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
16736 standard utilities for handling such moved messages, and they do not show up in
16737 lists generated by &%-bp%& or by the Exim monitor.
16740 .option mua_wrapper main boolean false
16741 Setting this option true causes Exim to run in a very restrictive mode in which
16742 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
16743 contains a full description of this facility.
16747 .option mysql_servers main "string list" unset
16748 .cindex "MySQL" "server list"
16749 This option provides a list of MySQL servers and associated connection data, to
16750 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
16751 option is available only if Exim has been built with MySQL support.
16754 .option never_users main "string list&!!" unset
16755 This option is expanded just once, at the start of Exim's processing. Local
16756 message deliveries are normally run in processes that are setuid to the
16757 recipient, and remote deliveries are normally run under Exim's own uid and gid.
16758 It is usually desirable to prevent any deliveries from running as root, as a
16761 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
16762 list of users that must not be used for local deliveries. This list is fixed in
16763 the binary and cannot be overridden by the configuration file. By default, it
16764 contains just the single user name &"root"&. The &%never_users%& runtime option
16765 can be used to add more users to the fixed list.
16767 If a message is to be delivered as one of the users on the fixed list or the
16768 &%never_users%& list, an error occurs, and delivery is deferred. A common
16771 never_users = root:daemon:bin
16773 Including root is redundant if it is also on the fixed list, but it does no
16774 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
16778 .option notifier_socket main string "$spool_directory/exim_daemon_notify"
16779 This option gives the name for a unix-domain socket on which the daemon
16780 listens for work and information-requests.
16781 Only installations running multiple daemons sharing a spool directory
16782 should need to modify the default.
16784 The option is expanded before use.
16785 If the platform supports Linux-style abstract socket names, the result
16786 is used with a nul byte prefixed.
16788 .new "if nonempty,"
16789 it should be a full path name and use a directory accessible
16793 If this option is set as empty,
16794 or the command line &%-oY%& option is used, or
16796 the command line uses a &%-oX%& option and does not use &%-oP%&,
16797 then a notifier socket is not created.
16800 .option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation"
16801 .cindex "OpenSSL "compatibility options"
16802 This option allows an administrator to adjust the SSL options applied
16803 by OpenSSL to connections. It is given as a space-separated list of items,
16804 each one to be +added or -subtracted from the current value.
16806 This option is only available if Exim is built against OpenSSL. The values
16807 available for this option vary according to the age of your OpenSSL install.
16808 The &"all"& value controls a subset of flags which are available, typically
16809 the bug workaround options. The &'SSL_CTX_set_options'& man page will
16810 list the values known on your system and Exim should support all the
16811 &"bug workaround"& options and many of the &"modifying"& options. The Exim
16812 names lose the leading &"SSL_OP_"& and are lower-cased.
16814 Note that adjusting the options can have severe impact upon the security of
16815 SSL as used by Exim. It is possible to disable safety checks and shoot
16816 yourself in the foot in various unpleasant ways. This option should not be
16817 adjusted lightly. An unrecognised item will be detected at startup, by
16818 invoking Exim with the &%-bV%& flag.
16820 The option affects Exim operating both as a server and as a client.
16822 Historical note: prior to release 4.80, Exim defaulted this value to
16823 "+dont_insert_empty_fragments", which may still be needed for compatibility
16824 with some clients, but which lowers security by increasing exposure to
16825 some now infamous attacks.
16829 # Make both old MS and old Eudora happy:
16830 openssl_options = -all +microsoft_big_sslv3_buffer \
16831 +dont_insert_empty_fragments
16833 # Disable older protocol versions:
16834 openssl_options = +no_sslv2 +no_sslv3
16837 Possible options may include:
16841 &`allow_unsafe_legacy_renegotiation`&
16843 &`cipher_server_preference`&
16845 &`dont_insert_empty_fragments`&
16849 &`legacy_server_connect`&
16851 &`microsoft_big_sslv3_buffer`&
16853 &`microsoft_sess_id_bug`&
16855 &`msie_sslv2_rsa_padding`&
16857 &`netscape_challenge_bug`&
16859 &`netscape_reuse_cipher_change_bug`&
16863 &`no_session_resumption_on_renegotiation`&
16877 &`safari_ecdhe_ecdsa_bug`&
16881 &`single_ecdh_use`&
16883 &`ssleay_080_client_dh_bug`&
16885 &`sslref2_reuse_cert_type_bug`&
16887 &`tls_block_padding_bug`&
16891 &`tls_rollback_bug`&
16894 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
16895 all clients connecting using the MacOS SecureTransport TLS facility prior
16896 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
16897 to negotiate TLS then this option value might help, provided that your OpenSSL
16898 release is new enough to contain this work-around. This may be a situation
16899 where you have to upgrade OpenSSL to get buggy clients working.
16902 .option oracle_servers main "string list" unset
16903 .cindex "Oracle" "server list"
16904 This option provides a list of Oracle servers and associated connection data,
16905 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
16906 The option is available only if Exim has been built with Oracle support.
16909 .option percent_hack_domains main "domain list&!!" unset
16910 .cindex "&""percent hack""&"
16911 .cindex "source routing" "in email address"
16912 .cindex "address" "source-routed"
16913 The &"percent hack"& is the convention whereby a local part containing a
16914 percent sign is re-interpreted as a new email address, with the percent
16915 replaced by @. This is sometimes called &"source routing"&, though that term is
16916 also applied to RFC 2822 addresses that begin with an @ character. If this
16917 option is set, Exim implements the percent facility for those domains listed,
16918 but no others. This happens before an incoming SMTP address is tested against
16921 &*Warning*&: The &"percent hack"& has often been abused by people who are
16922 trying to get round relaying restrictions. For this reason, it is best avoided
16923 if at all possible. Unfortunately, a number of less security-conscious MTAs
16924 implement it unconditionally. If you are running Exim on a gateway host, and
16925 routing mail through to internal MTAs without processing the local parts, it is
16926 a good idea to reject recipient addresses with percent characters in their
16927 local parts. Exim's default configuration does this.
16930 .option perl_at_start main boolean false
16932 This option is available only when Exim is built with an embedded Perl
16933 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16936 .option perl_startup main string unset
16938 This option is available only when Exim is built with an embedded Perl
16939 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16941 .option perl_taintmode main boolean false
16943 This option enables the taint mode of the embedded Perl interpreter.
16946 .option pgsql_servers main "string list" unset
16947 .cindex "PostgreSQL lookup type" "server list"
16948 This option provides a list of PostgreSQL servers and associated connection
16949 data, to be used in conjunction with &(pgsql)& lookups (see section
16950 &<<SECID72>>&). The option is available only if Exim has been built with
16951 PostgreSQL support.
16954 .option pid_file_path main string&!! "set at compile time"
16955 .cindex "daemon" "pid file path"
16956 .cindex "pid file, path for"
16957 This option sets the name of the file to which the Exim daemon writes its
16958 process id. The string is expanded, so it can contain, for example, references
16961 pid_file_path = /var/log/$primary_hostname/exim.pid
16963 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
16965 The value set by the option can be overridden by the &%-oP%& command line
16966 option. A pid file is not written if a &"non-standard"& daemon is run by means
16967 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
16970 .option pipelining_advertise_hosts main "host list&!!" *
16971 .cindex "PIPELINING" "suppressing advertising"
16972 .cindex "ESMTP extensions" PIPELINING
16973 This option can be used to suppress the advertisement of the SMTP
16974 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
16975 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
16976 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
16977 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
16978 that clients will use it; &"out of order"& commands that are &"expected"& do
16979 not count as protocol errors (see &%smtp_max_synprot_errors%&).
16981 .option pipelining_connect_advertise_hosts main "host list&!!" *
16982 .cindex "pipelining" "early connection"
16983 .cindex "pipelining" PIPE_CONNECT
16984 .cindex "ESMTP extensions" X_PIPE_CONNECT
16985 If Exim is built with the SUPPORT_PIPE_CONNECT build option
16986 this option controls which hosts the facility is advertised to
16987 and from which pipeline early-connection (before MAIL) SMTP
16988 commands are acceptable.
16989 When used, the pipelining saves on roundtrip times.
16991 See also the &%hosts_pipe_connect%& smtp transport option.
16993 Currently the option name &"X_PIPE_CONNECT"& is used.
16996 .option prdr_enable main boolean false
16997 .cindex "PRDR" "enabling on server"
16998 .cindex "ESMTP extensions" PRDR
16999 This option can be used to enable the Per-Recipient Data Response extension
17000 to SMTP, defined by Eric Hall.
17001 If the option is set, PRDR is advertised by Exim when operating as a server.
17002 If the client requests PRDR, and more than one recipient, for a message
17003 an additional ACL is called for each recipient after the message content
17004 is received. See section &<<SECTPRDRACL>>&.
17006 .option preserve_message_logs main boolean false
17007 .cindex "message logs" "preserving"
17008 If this option is set, message log files are not deleted when messages are
17009 completed. Instead, they are moved to a sub-directory of the spool directory
17010 called &_msglog.OLD_&, where they remain available for statistical or debugging
17011 purposes. This is a dangerous option to set on systems with any appreciable
17012 volume of mail. Use with care!
17015 .option primary_hostname main string "see below"
17016 .cindex "name" "of local host"
17017 .cindex "host" "name of local"
17018 .cindex "local host" "name of"
17019 .vindex "&$primary_hostname$&"
17020 This specifies the name of the current host. It is used in the default EHLO or
17021 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
17022 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
17023 The value is also used by default in some SMTP response messages from an Exim
17024 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
17026 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
17027 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
17028 contains only one component, Exim passes it to &[gethostbyname()]& (or
17029 &[getipnodebyname()]& when available) in order to obtain the fully qualified
17030 version. The variable &$primary_hostname$& contains the host name, whether set
17031 explicitly by this option, or defaulted.
17034 .option print_topbitchars main boolean false
17035 .cindex "printing characters"
17036 .cindex "8-bit characters"
17037 By default, Exim considers only those characters whose codes lie in the range
17038 32&--126 to be printing characters. In a number of circumstances (for example,
17039 when writing log entries) non-printing characters are converted into escape
17040 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
17041 is set, code values of 128 and above are also considered to be printing
17044 This option also affects the header syntax checks performed by the
17045 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
17046 the user's full name when constructing From: and Sender: addresses (as
17047 described in section &<<SECTconstr>>&). Setting this option can cause
17048 Exim to generate eight bit message headers that do not conform to the
17052 .option process_log_path main string unset
17053 .cindex "process log path"
17054 .cindex "log" "process log"
17055 .cindex "&'exiwhat'&"
17056 This option sets the name of the file to which an Exim process writes its
17057 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
17058 utility script. If this option is unset, the file called &_exim-process.info_&
17059 in Exim's spool directory is used. The ability to specify the name explicitly
17060 can be useful in environments where two different Exims are running, using
17061 different spool directories.
17064 .option prod_requires_admin main boolean true
17065 .cindex "restricting access to features"
17069 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
17070 admin user unless &%prod_requires_admin%& is set false. See also
17071 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
17075 .option proxy_protocol_timeout main time 3s
17076 .cindex proxy "proxy protocol"
17077 This option sets the timeout for proxy protocol negotiation.
17078 For details see section &<<SECTproxyInbound>>&.
17082 .option qualify_domain main string "see below"
17083 .cindex "domain" "for qualifying addresses"
17084 .cindex "address" "qualification"
17085 This option specifies the domain name that is added to any envelope sender
17086 addresses that do not have a domain qualification. It also applies to
17087 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
17088 are accepted by default only for locally-generated messages. Qualification is
17089 also applied to addresses in header lines such as &'From:'& and &'To:'& for
17090 locally-generated messages, unless the &%-bnq%& command line option is used.
17092 Messages from external sources must always contain fully qualified addresses,
17093 unless the sending host matches &%sender_unqualified_hosts%& or
17094 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
17095 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
17096 necessary. Internally, Exim always works with fully qualified envelope
17097 addresses. If &%qualify_domain%& is not set, it defaults to the
17098 &%primary_hostname%& value.
17101 .option qualify_recipient main string "see below"
17102 This option allows you to specify a different domain for qualifying recipient
17103 addresses to the one that is used for senders. See &%qualify_domain%& above.
17107 .option queue_domains main "domain list&!!" unset
17108 .cindex "domain" "specifying non-immediate delivery"
17109 .cindex "queueing incoming messages"
17110 .cindex "message" "queueing certain domains"
17111 This option lists domains for which immediate delivery is not required.
17112 A delivery process is started whenever a message is received, but only those
17113 domains that do not match are processed. All other deliveries wait until the
17114 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
17118 .option queue_fast_ramp main boolean false
17119 .cindex "queue runner" "two phase"
17120 .cindex "queue" "double scanning"
17121 If set to true, two-phase queue runs, initiated using &%-qq%& on the
17122 command line, may start parallel delivery processes during their first
17123 phase. This will be done when a threshold number of messages have been
17124 routed for a single host.
17128 .option queue_list_requires_admin main boolean true
17129 .cindex "restricting access to features"
17131 The &%-bp%& command-line option, which lists the messages that are on the
17132 queue, requires the caller to be an admin user unless
17133 &%queue_list_requires_admin%& is set false.
17134 See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
17137 .option queue_only main boolean false
17138 .cindex "queueing incoming messages"
17139 .cindex "message" "queueing unconditionally"
17140 If &%queue_only%& is set, a delivery process is not automatically started
17141 whenever a message is received. Instead, the message waits in the queue for the
17142 next queue run. Even if &%queue_only%& is false, incoming messages may not get
17143 delivered immediately when certain conditions (such as heavy load) occur.
17145 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
17146 and &%-odi%& command line options override &%queue_only%& unless
17147 &%queue_only_override%& is set false. See also &%queue_only_file%&,
17148 &%queue_only_load%&, and &%smtp_accept_queue%&.
17151 .option queue_only_file main string unset
17152 .cindex "queueing incoming messages"
17153 .cindex "message" "queueing by file existence"
17154 This option can be set to a colon-separated list of absolute path names, each
17155 one optionally preceded by &"smtp"&. When Exim is receiving a message,
17156 it tests for the existence of each listed path using a call to &[stat()]&. For
17157 each path that exists, the corresponding queueing option is set.
17158 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
17159 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
17161 queue_only_file = smtp/some/file
17163 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
17164 &_/some/file_& exists.
17167 .option queue_only_load main fixed-point unset
17168 .cindex "load average"
17169 .cindex "queueing incoming messages"
17170 .cindex "message" "queueing by load"
17171 If the system load average is higher than this value, incoming messages from
17172 all sources are queued, and no automatic deliveries are started. If this
17173 happens during local or remote SMTP input, all subsequent messages received on
17174 the same SMTP connection are queued by default, whatever happens to the load in
17175 the meantime, but this can be changed by setting &%queue_only_load_latch%&
17178 Deliveries will subsequently be performed by queue runner processes. This
17179 option has no effect on ancient operating systems on which Exim cannot
17180 determine the load average. See also &%deliver_queue_load_max%& and
17181 &%smtp_load_reserve%&.
17184 .option queue_only_load_latch main boolean true
17185 .cindex "load average" "re-evaluating per message"
17186 When this option is true (the default), once one message has been queued
17187 because the load average is higher than the value set by &%queue_only_load%&,
17188 all subsequent messages received on the same SMTP connection are also queued.
17189 This is a deliberate choice; even though the load average may fall below the
17190 threshold, it doesn't seem right to deliver later messages on the same
17191 connection when not delivering earlier ones. However, there are special
17192 circumstances such as very long-lived connections from scanning appliances
17193 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
17194 should be set false. This causes the value of the load average to be
17195 re-evaluated for each message.
17198 .option queue_only_override main boolean true
17199 .cindex "queueing incoming messages"
17200 When this option is true, the &%-od%&&'x'& command line options override the
17201 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
17202 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
17203 to override; they are accepted, but ignored.
17206 .option queue_run_in_order main boolean false
17207 .cindex "queue runner" "processing messages in order"
17208 If this option is set, queue runs happen in order of message arrival instead of
17209 in an arbitrary order. For this to happen, a complete list of the entire queue
17210 must be set up before the deliveries start. When the queue is all held in a
17211 single directory (the default), a single list is created for both the ordered
17212 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
17213 single list is not created when &%queue_run_in_order%& is false. In this case,
17214 the sub-directories are processed one at a time (in a random order), and this
17215 avoids setting up one huge list for the whole queue. Thus, setting
17216 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
17217 when the queue is large, because of the extra work in setting up the single,
17218 large list. In most situations, &%queue_run_in_order%& should not be set.
17222 .option queue_run_max main integer&!! 5
17223 .cindex "queue runner" "maximum number of"
17224 This controls the maximum number of queue runner processes that an Exim daemon
17225 can run simultaneously. This does not mean that it starts them all at once,
17226 but rather that if the maximum number are still running when the time comes to
17227 start another one, it refrains from starting another one. This can happen with
17228 very large queues and/or very sluggish deliveries. This option does not,
17229 however, interlock with other processes, so additional queue runners can be
17230 started by other means, or by killing and restarting the daemon.
17232 Setting this option to zero does not suppress queue runs; rather, it disables
17233 the limit, allowing any number of simultaneous queue runner processes to be
17234 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
17235 the daemon's command line.
17237 .cindex queues named
17238 .cindex "named queues" "resource limit"
17239 To set limits for different named queues use
17240 an expansion depending on the &$queue_name$& variable.
17242 .option queue_smtp_domains main "domain list&!!" unset
17243 .cindex "queueing incoming messages"
17244 .cindex "message" "queueing remote deliveries"
17245 .cindex "first pass routing"
17246 When this option is set, a delivery process is started whenever a message is
17247 received, routing is performed, and local deliveries take place.
17248 However, if any SMTP deliveries are required for domains that match
17249 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
17250 message waits in the queue for the next queue run. Since routing of the message
17251 has taken place, Exim knows to which remote hosts it must be delivered, and so
17252 when the queue run happens, multiple messages for the same host are delivered
17253 over a single SMTP connection. The &%-odqs%& command line option causes all
17254 SMTP deliveries to be queued in this way, and is equivalent to setting
17255 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
17259 .option receive_timeout main time 0s
17260 .cindex "timeout" "for non-SMTP input"
17261 This option sets the timeout for accepting a non-SMTP message, that is, the
17262 maximum time that Exim waits when reading a message on the standard input. If
17263 the value is zero, it will wait forever. This setting is overridden by the
17264 &%-or%& command line option. The timeout for incoming SMTP messages is
17265 controlled by &%smtp_receive_timeout%&.
17267 .option received_header_text main string&!! "see below"
17268 .cindex "customizing" "&'Received:'& header"
17269 .cindex "&'Received:'& header line" "customizing"
17270 This string defines the contents of the &'Received:'& message header that is
17271 added to each message, except for the timestamp, which is automatically added
17272 on at the end (preceded by a semicolon). The string is expanded each time it is
17273 used. If the expansion yields an empty string, no &'Received:'& header line is
17274 added to the message. Otherwise, the string should start with the text
17275 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
17277 The default setting is:
17280 received_header_text = Received: \
17281 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
17282 {${if def:sender_ident \
17283 {from ${quote_local_part:$sender_ident} }}\
17284 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
17285 by $primary_hostname \
17286 ${if def:received_protocol {with $received_protocol }}\
17287 ${if def:tls_in_ver { ($tls_in_ver)}}\
17288 ${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\
17289 (Exim $version_number)\n\t\
17290 ${if def:sender_address \
17291 {(envelope-from <$sender_address>)\n\t}}\
17292 id $message_exim_id\
17293 ${if def:received_for {\n\tfor $received_for}}
17296 The references to the TLS version and cipher are
17297 omitted when Exim is built without TLS
17298 support. The use of conditional expansions ensures that this works for both
17299 locally generated messages and messages received from remote hosts, giving
17300 header lines such as the following:
17302 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
17303 by marley.carol.example with esmtp (Exim 4.00)
17304 (envelope-from <bob@carol.example>)
17305 id 16IOWa-00019l-00
17306 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
17307 Received: by scrooge.carol.example with local (Exim 4.00)
17308 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
17310 Until the body of the message has been received, the timestamp is the time when
17311 the message started to be received. Once the body has arrived, and all policy
17312 checks have taken place, the timestamp is updated to the time at which the
17313 message was accepted.
17316 .option received_headers_max main integer 30
17317 .cindex "loop" "prevention"
17318 .cindex "mail loop prevention"
17319 .cindex "&'Received:'& header line" "counting"
17320 When a message is to be delivered, the number of &'Received:'& headers is
17321 counted, and if it is greater than this parameter, a mail loop is assumed to
17322 have occurred, the delivery is abandoned, and an error message is generated.
17323 This applies to both local and remote deliveries.
17326 .option recipient_unqualified_hosts main "host list&!!" unset
17327 .cindex "unqualified addresses"
17328 .cindex "host" "unqualified addresses from"
17329 This option lists those hosts from which Exim is prepared to accept unqualified
17330 recipient addresses in message envelopes. The addresses are made fully
17331 qualified by the addition of the &%qualify_recipient%& value. This option also
17332 affects message header lines. Exim does not reject unqualified recipient
17333 addresses in headers, but it qualifies them only if the message came from a
17334 host that matches &%recipient_unqualified_hosts%&,
17335 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
17336 option was not set.
17339 .option recipients_max main integer 0
17340 .cindex "limit" "number of recipients"
17341 .cindex "recipient" "maximum number"
17342 If this option is set greater than zero, it specifies the maximum number of
17343 original recipients for any message. Additional recipients that are generated
17344 by aliasing or forwarding do not count. SMTP messages get a 452 response for
17345 all recipients over the limit; earlier recipients are delivered as normal.
17346 Non-SMTP messages with too many recipients are failed, and no deliveries are
17349 .cindex "RCPT" "maximum number of incoming"
17350 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
17351 RCPT commands in a single message.
17354 .option recipients_max_reject main boolean false
17355 If this option is set true, Exim rejects SMTP messages containing too many
17356 recipients by giving 552 errors to the surplus RCPT commands, and a 554
17357 error to the eventual DATA command. Otherwise (the default) it gives a 452
17358 error to the surplus RCPT commands and accepts the message on behalf of the
17359 initial set of recipients. The remote server should then re-send the message
17360 for the remaining recipients at a later time.
17363 .option remote_max_parallel main integer 2
17364 .cindex "delivery" "parallelism for remote"
17365 This option controls parallel delivery of one message to a number of remote
17366 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
17367 does all the remote deliveries for a message one by one. Otherwise, if a single
17368 message has to be delivered to more than one remote host, or if several copies
17369 have to be sent to the same remote host, up to &%remote_max_parallel%&
17370 deliveries are done simultaneously. If more than &%remote_max_parallel%&
17371 deliveries are required, the maximum number of processes are started, and as
17372 each one finishes, another is begun. The order of starting processes is the
17373 same as if sequential delivery were being done, and can be controlled by the
17374 &%remote_sort_domains%& option. If parallel delivery takes place while running
17375 with debugging turned on, the debugging output from each delivery process is
17376 tagged with its process id.
17378 This option controls only the maximum number of parallel deliveries for one
17379 message in one Exim delivery process. Because Exim has no central queue
17380 manager, there is no way of controlling the total number of simultaneous
17381 deliveries if the configuration allows a delivery attempt as soon as a message
17384 See also the &%max_parallel%& generic transport option,
17385 and the &%serialize_hosts%& smtp transport option.
17387 .cindex "number of deliveries"
17388 .cindex "delivery" "maximum number of"
17389 If you want to control the total number of deliveries on the system, you
17390 need to set the &%queue_only%& option. This ensures that all incoming messages
17391 are added to the queue without starting a delivery process. Then set up an Exim
17392 daemon to start queue runner processes at appropriate intervals (probably
17393 fairly often, for example, every minute), and limit the total number of queue
17394 runners by setting the &%queue_run_max%& parameter. Because each queue runner
17395 delivers only one message at a time, the maximum number of deliveries that can
17396 then take place at once is &%queue_run_max%& multiplied by
17397 &%remote_max_parallel%&.
17399 If it is purely remote deliveries you want to control, use
17400 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
17401 doing the SMTP routing before queueing, so that several messages for the same
17402 host will eventually get delivered down the same connection.
17405 .option remote_sort_domains main "domain list&!!" unset
17406 .cindex "sorting remote deliveries"
17407 .cindex "delivery" "sorting remote"
17408 When there are a number of remote deliveries for a message, they are sorted by
17409 domain into the order given by this list. For example,
17411 remote_sort_domains = *.cam.ac.uk:*.uk
17413 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
17414 then to those in the &%uk%& domain, then to any others.
17417 .option retry_data_expire main time 7d
17418 .cindex "hints database" "data expiry"
17419 This option sets a &"use before"& time on retry information in Exim's hints
17420 database. Any older retry data is ignored. This means that, for example, once a
17421 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
17425 .option retry_interval_max main time 24h
17426 .cindex "retry" "limit on interval"
17427 .cindex "limit" "on retry interval"
17428 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
17429 intervals between delivery attempts for messages that cannot be delivered
17430 straight away. This option sets an overall limit to the length of time between
17431 retries. It cannot be set greater than 24 hours; any attempt to do so forces
17435 .option return_path_remove main boolean true
17436 .cindex "&'Return-path:'& header line" "removing"
17437 RFC 2821, section 4.4, states that an SMTP server must insert a
17438 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
17439 The &'Return-path:'& header preserves the sender address as received in the
17440 MAIL command. This description implies that this header should not be present
17441 in an incoming message. If &%return_path_remove%& is true, any existing
17442 &'Return-path:'& headers are removed from messages at the time they are
17443 received. Exim's transports have options for adding &'Return-path:'& headers at
17444 the time of delivery. They are normally used only for final local deliveries.
17447 .option return_size_limit main integer 100K
17448 This option is an obsolete synonym for &%bounce_return_size_limit%&.
17451 .option rfc1413_hosts main "host list&!!" @[]
17453 .cindex "host" "for RFC 1413 calls"
17454 RFC 1413 identification calls are made to any client host which matches
17455 an item in the list.
17456 The default value specifies just this host, being any local interface
17459 .option rfc1413_query_timeout main time 0s
17460 .cindex "RFC 1413" "query timeout"
17461 .cindex "timeout" "for RFC 1413 call"
17462 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
17463 no RFC 1413 calls are ever made.
17466 .option sender_unqualified_hosts main "host list&!!" unset
17467 .cindex "unqualified addresses"
17468 .cindex "host" "unqualified addresses from"
17469 This option lists those hosts from which Exim is prepared to accept unqualified
17470 sender addresses. The addresses are made fully qualified by the addition of
17471 &%qualify_domain%&. This option also affects message header lines. Exim does
17472 not reject unqualified addresses in headers that contain sender addresses, but
17473 it qualifies them only if the message came from a host that matches
17474 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
17475 using TCP/IP), and the &%-bnq%& option was not set.
17478 .option slow_lookup_log main integer 0
17479 .cindex "logging" "slow lookups"
17480 .cindex "dns" "logging slow lookups"
17481 This option controls logging of slow lookups.
17482 If the value is nonzero it is taken as a number of milliseconds
17483 and lookups taking longer than this are logged.
17484 Currently this applies only to DNS lookups.
17488 .option smtp_accept_keepalive main boolean true
17489 .cindex "keepalive" "on incoming connection"
17490 This option controls the setting of the SO_KEEPALIVE option on incoming
17491 TCP/IP socket connections. When set, it causes the kernel to probe idle
17492 connections periodically, by sending packets with &"old"& sequence numbers. The
17493 other end of the connection should send an acknowledgment if the connection is
17494 still okay or a reset if the connection has been aborted. The reason for doing
17495 this is that it has the beneficial effect of freeing up certain types of
17496 connection that can get stuck when the remote host is disconnected without
17497 tidying up the TCP/IP call properly. The keepalive mechanism takes several
17498 hours to detect unreachable hosts.
17502 .option smtp_accept_max main integer 20
17503 .cindex "limit" "incoming SMTP connections"
17504 .cindex "SMTP" "incoming connection count"
17506 This option specifies the maximum number of simultaneous incoming SMTP calls
17507 that Exim will accept. It applies only to the listening daemon; there is no
17508 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
17509 value is set to zero, no limit is applied. However, it is required to be
17510 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
17511 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
17513 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
17514 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
17515 that limit has not been reached for the client host, &%smtp_accept_reserve%&
17516 and &%smtp_load_reserve%& are then checked before accepting the connection.
17519 .option smtp_accept_max_nonmail main integer 10
17520 .cindex "limit" "non-mail SMTP commands"
17521 .cindex "SMTP" "limiting non-mail commands"
17522 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
17523 the connection if there are too many. This option defines &"too many"&. The
17524 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
17525 client looping sending EHLO, for example. The check is applied only if the
17526 client host matches &%smtp_accept_max_nonmail_hosts%&.
17528 When a new message is expected, one occurrence of RSET is not counted. This
17529 allows a client to send one RSET between messages (this is not necessary,
17530 but some clients do it). Exim also allows one uncounted occurrence of HELO
17531 or EHLO, and one occurrence of STARTTLS between messages. After
17532 starting up a TLS session, another EHLO is expected, and so it too is not
17533 counted. The first occurrence of AUTH in a connection, or immediately
17534 following STARTTLS is not counted. Otherwise, all commands other than
17535 MAIL, RCPT, DATA, and QUIT are counted.
17538 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
17539 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
17540 check by setting this option. The default value makes it apply to all hosts. By
17541 changing the value, you can exclude any badly-behaved hosts that you have to
17545 . Allow this long option name to split; give it unsplit as a fifth argument
17546 . for the automatic .oindex that is generated by .option.
17547 . We insert " &~&~" which is both pretty nasty visually and results in
17548 . non-searchable text. HowItWorks.txt mentions an option for inserting
17549 . zero-width-space, which would be nicer visually and results in (at least)
17550 . html that Firefox will split on when it's forced to reflow (rather than
17551 . inserting a horizontal scrollbar). However, the text is still not
17552 . searchable. NM changed this occurrence for bug 1197 to no longer allow
17553 . the option name to split.
17555 .option "smtp_accept_max_per_connection" main integer 1000 &&&
17556 smtp_accept_max_per_connection
17557 .cindex "SMTP" "limiting incoming message count"
17558 .cindex "limit" "messages per SMTP connection"
17559 The value of this option limits the number of MAIL commands that Exim is
17560 prepared to accept over a single SMTP connection, whether or not each command
17561 results in the transfer of a message. After the limit is reached, a 421
17562 response is given to subsequent MAIL commands. This limit is a safety
17563 precaution against a client that goes mad (incidents of this type have been
17567 .option smtp_accept_max_per_host main string&!! unset
17568 .cindex "limit" "SMTP connections from one host"
17569 .cindex "host" "limiting SMTP connections from"
17570 This option restricts the number of simultaneous IP connections from a single
17571 host (strictly, from a single IP address) to the Exim daemon. The option is
17572 expanded, to enable different limits to be applied to different hosts by
17573 reference to &$sender_host_address$&. Once the limit is reached, additional
17574 connection attempts from the same host are rejected with error code 421. This
17575 is entirely independent of &%smtp_accept_reserve%&. The option's default value
17576 of zero imposes no limit. If this option is set greater than zero, it is
17577 required that &%smtp_accept_max%& be non-zero.
17579 &*Warning*&: When setting this option you should not use any expansion
17580 constructions that take an appreciable amount of time. The expansion and test
17581 happen in the main daemon loop, in order to reject additional connections
17582 without forking additional processes (otherwise a denial-of-service attack
17583 could cause a vast number or processes to be created). While the daemon is
17584 doing this processing, it cannot accept any other incoming connections.
17588 .option smtp_accept_queue main integer 0
17589 .cindex "SMTP" "incoming connection count"
17590 .cindex "queueing incoming messages"
17591 .cindex "message" "queueing by SMTP connection count"
17592 If the number of simultaneous incoming SMTP connections being handled via the
17593 listening daemon exceeds this value, messages received by SMTP are just placed
17594 in the queue; no delivery processes are started automatically. The count is
17595 fixed at the start of an SMTP connection. It cannot be updated in the
17596 subprocess that receives messages, and so the queueing or not queueing applies
17597 to all messages received in the same connection.
17599 A value of zero implies no limit, and clearly any non-zero value is useful only
17600 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
17601 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
17602 various &%-od%&&'x'& command line options.
17605 . See the comment on smtp_accept_max_per_connection
17607 .option "smtp_accept_queue_per_connection" main integer 10 &&&
17608 smtp_accept_queue_per_connection
17609 .cindex "queueing incoming messages"
17610 .cindex "message" "queueing by message count"
17611 This option limits the number of delivery processes that Exim starts
17612 automatically when receiving messages via SMTP, whether via the daemon or by
17613 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
17614 and the number of messages received in a single SMTP session exceeds this
17615 number, subsequent messages are placed in the queue, but no delivery processes
17616 are started. This helps to limit the number of Exim processes when a server
17617 restarts after downtime and there is a lot of mail waiting for it on other
17618 systems. On large systems, the default should probably be increased, and on
17619 dial-in client systems it should probably be set to zero (that is, disabled).
17622 .option smtp_accept_reserve main integer 0
17623 .cindex "SMTP" "incoming call count"
17624 .cindex "host" "reserved"
17625 When &%smtp_accept_max%& is set greater than zero, this option specifies a
17626 number of SMTP connections that are reserved for connections from the hosts
17627 that are specified in &%smtp_reserve_hosts%&. The value set in
17628 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
17629 restricted to this number of connections; the option specifies a minimum number
17630 of connection slots for them, not a maximum. It is a guarantee that this group
17631 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
17632 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
17635 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
17636 set to 5, once there are 45 active connections (from any hosts), new
17637 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
17638 provided the other criteria for acceptance are met.
17641 .option smtp_active_hostname main string&!! unset
17642 .cindex "host" "name in SMTP responses"
17643 .cindex "SMTP" "host name in responses"
17644 .vindex "&$primary_hostname$&"
17645 This option is provided for multi-homed servers that want to masquerade as
17646 several different hosts. At the start of an incoming SMTP connection, its value
17647 is expanded and used instead of the value of &$primary_hostname$& in SMTP
17648 responses. For example, it is used as domain name in the response to an
17649 incoming HELO or EHLO command.
17651 .vindex "&$smtp_active_hostname$&"
17652 The active hostname is placed in the &$smtp_active_hostname$& variable, which
17653 is saved with any messages that are received. It is therefore available for use
17654 in routers and transports when the message is later delivered.
17656 If this option is unset, or if its expansion is forced to fail, or if the
17657 expansion results in an empty string, the value of &$primary_hostname$& is
17658 used. Other expansion failures cause a message to be written to the main and
17659 panic logs, and the SMTP command receives a temporary error. Typically, the
17660 value of &%smtp_active_hostname%& depends on the incoming interface address.
17663 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
17664 {cox.mydomain}{box.mydomain}}
17667 Although &$smtp_active_hostname$& is primarily concerned with incoming
17668 messages, it is also used as the default for HELO commands in callout
17669 verification if there is no remote transport from which to obtain a
17670 &%helo_data%& value.
17672 .option smtp_banner main string&!! "see below"
17673 .cindex "SMTP" "welcome banner"
17674 .cindex "banner for SMTP"
17675 .cindex "welcome banner for SMTP"
17676 .cindex "customizing" "SMTP banner"
17677 This string, which is expanded every time it is used, is output as the initial
17678 positive response to an SMTP connection. The default setting is:
17680 smtp_banner = $smtp_active_hostname ESMTP Exim \
17681 $version_number $tod_full
17683 Failure to expand the string causes a panic error. If you want to create a
17684 multiline response to the initial SMTP connection, use &"\n"& in the string at
17685 appropriate points, but not at the end. Note that the 220 code is not included
17686 in this string. Exim adds it automatically (several times in the case of a
17687 multiline response).
17690 .option smtp_check_spool_space main boolean true
17691 .cindex "checking disk space"
17692 .cindex "disk space, checking"
17693 .cindex "spool directory" "checking space"
17694 When this option is set, if an incoming SMTP session encounters the SIZE
17695 option on a MAIL command, it checks that there is enough space in the
17696 spool directory's partition to accept a message of that size, while still
17697 leaving free the amount specified by &%check_spool_space%& (even if that value
17698 is zero). If there isn't enough space, a temporary error code is returned.
17701 .option smtp_connect_backlog main integer 20
17702 .cindex "connection backlog"
17703 .cindex "SMTP" "connection backlog"
17704 .cindex "backlog of connections"
17705 This option specifies a maximum number of waiting SMTP connections. Exim passes
17706 this value to the TCP/IP system when it sets up its listener. Once this number
17707 of connections are waiting for the daemon's attention, subsequent connection
17708 attempts are refused at the TCP/IP level. At least, that is what the manuals
17709 say; in some circumstances such connection attempts have been observed to time
17710 out instead. For large systems it is probably a good idea to increase the
17711 value (to 50, say). It also gives some protection against denial-of-service
17712 attacks by SYN flooding.
17715 .option smtp_enforce_sync main boolean true
17716 .cindex "SMTP" "synchronization checking"
17717 .cindex "synchronization checking in SMTP"
17718 The SMTP protocol specification requires the client to wait for a response from
17719 the server at certain points in the dialogue. Without PIPELINING these
17720 synchronization points are after every command; with PIPELINING they are
17721 fewer, but they still exist.
17723 Some spamming sites send out a complete set of SMTP commands without waiting
17724 for any response. Exim protects against this by rejecting a message if the
17725 client has sent further input when it should not have. The error response &"554
17726 SMTP synchronization error"& is sent, and the connection is dropped. Testing
17727 for this error cannot be perfect because of transmission delays (unexpected
17728 input may be on its way but not yet received when Exim checks). However, it
17729 does detect many instances.
17731 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
17732 If you want to disable the check selectively (for example, only for certain
17733 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
17734 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
17738 .option smtp_etrn_command main string&!! unset
17739 .cindex "ETRN" "command to be run"
17740 .cindex "ESMTP extensions" ETRN
17741 .vindex "&$domain$&"
17742 If this option is set, the given command is run whenever an SMTP ETRN
17743 command is received from a host that is permitted to issue such commands (see
17744 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
17745 are independently expanded. The expansion variable &$domain$& is set to the
17746 argument of the ETRN command, and no syntax checking is done on it. For
17749 smtp_etrn_command = /etc/etrn_command $domain \
17750 $sender_host_address
17752 If the option is not set, the argument for the ETRN command must
17753 be a &'#'& followed by an address string.
17754 In this case an &'exim -R <string>'& command is used;
17755 if the ETRN ACL has set up a named-queue then &'-MCG <queue>'& is appended.
17757 A new process is created to run the command, but Exim does not wait for it to
17758 complete. Consequently, its status cannot be checked. If the command cannot be
17759 run, a line is written to the panic log, but the ETRN caller still receives
17760 a 250 success response. Exim is normally running under its own uid when
17761 receiving SMTP, so it is not possible for it to change the uid before running
17765 .option smtp_etrn_serialize main boolean true
17766 .cindex "ETRN" "serializing"
17767 When this option is set, it prevents the simultaneous execution of more than
17768 one identical command as a result of ETRN in an SMTP connection. See
17769 section &<<SECTETRN>>& for details.
17772 .option smtp_load_reserve main fixed-point unset
17773 .cindex "load average"
17774 If the system load average ever gets higher than this, incoming SMTP calls are
17775 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
17776 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
17777 the load is over the limit. The option has no effect on ancient operating
17778 systems on which Exim cannot determine the load average. See also
17779 &%deliver_queue_load_max%& and &%queue_only_load%&.
17783 .option smtp_max_synprot_errors main integer 3
17784 .cindex "SMTP" "limiting syntax and protocol errors"
17785 .cindex "limit" "SMTP syntax and protocol errors"
17786 Exim rejects SMTP commands that contain syntax or protocol errors. In
17787 particular, a syntactically invalid email address, as in this command:
17789 RCPT TO:<abc xyz@a.b.c>
17791 causes immediate rejection of the command, before any other tests are done.
17792 (The ACL cannot be run if there is no valid address to set up for it.) An
17793 example of a protocol error is receiving RCPT before MAIL. If there are
17794 too many syntax or protocol errors in one SMTP session, the connection is
17795 dropped. The limit is set by this option.
17797 .cindex "PIPELINING" "expected errors"
17798 When the PIPELINING extension to SMTP is in use, some protocol errors are
17799 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
17800 Exim assumes that PIPELINING will be used if it advertises it (see
17801 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
17802 not count towards the limit.
17806 .option smtp_max_unknown_commands main integer 3
17807 .cindex "SMTP" "limiting unknown commands"
17808 .cindex "limit" "unknown SMTP commands"
17809 If there are too many unrecognized commands in an incoming SMTP session, an
17810 Exim server drops the connection. This is a defence against some kinds of abuse
17813 into making connections to SMTP ports; in these circumstances, a number of
17814 non-SMTP command lines are sent first.
17818 .option smtp_ratelimit_hosts main "host list&!!" unset
17819 .cindex "SMTP" "rate limiting"
17820 .cindex "limit" "rate of message arrival"
17821 .cindex "RCPT" "rate limiting"
17822 Some sites find it helpful to be able to limit the rate at which certain hosts
17823 can send them messages, and the rate at which an individual message can specify
17826 Exim has two rate-limiting facilities. This section describes the older
17827 facility, which can limit rates within a single connection. The newer
17828 &%ratelimit%& ACL condition can limit rates across all connections. See section
17829 &<<SECTratelimiting>>& for details of the newer facility.
17831 When a host matches &%smtp_ratelimit_hosts%&, the values of
17832 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
17833 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
17834 respectively. Each option, if set, must contain a set of four comma-separated
17838 A threshold, before which there is no rate limiting.
17840 An initial time delay. Unlike other times in Exim, numbers with decimal
17841 fractional parts are allowed here.
17843 A factor by which to increase the delay each time.
17845 A maximum value for the delay. This should normally be less than 5 minutes,
17846 because after that time, the client is liable to timeout the SMTP command.
17849 For example, these settings have been used successfully at the site which
17850 first suggested this feature, for controlling mail from their customers:
17852 smtp_ratelimit_mail = 2,0.5s,1.05,4m
17853 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
17855 The first setting specifies delays that are applied to MAIL commands after
17856 two have been received over a single connection. The initial delay is 0.5
17857 seconds, increasing by a factor of 1.05 each time. The second setting applies
17858 delays to RCPT commands when more than four occur in a single message.
17861 .option smtp_ratelimit_mail main string unset
17862 See &%smtp_ratelimit_hosts%& above.
17865 .option smtp_ratelimit_rcpt main string unset
17866 See &%smtp_ratelimit_hosts%& above.
17869 .option smtp_receive_timeout main time&!! 5m
17870 .cindex "timeout" "for SMTP input"
17871 .cindex "SMTP" "input timeout"
17872 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
17873 input, including batch SMTP. If a line of input (either an SMTP command or a
17874 data line) is not received within this time, the SMTP connection is dropped and
17875 the message is abandoned.
17876 A line is written to the log containing one of the following messages:
17878 SMTP command timeout on connection from...
17879 SMTP data timeout on connection from...
17881 The former means that Exim was expecting to read an SMTP command; the latter
17882 means that it was in the DATA phase, reading the contents of a message.
17884 If the first character of the option is a &"$"& the option is
17885 expanded before use and may depend on
17886 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
17890 The value set by this option can be overridden by the
17891 &%-os%& command-line option. A setting of zero time disables the timeout, but
17892 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
17893 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
17894 timeout is controlled by &%receive_timeout%& and &%-or%&.
17897 .option smtp_reserve_hosts main "host list&!!" unset
17898 This option defines hosts for which SMTP connections are reserved; see
17899 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
17902 .option smtp_return_error_details main boolean false
17903 .cindex "SMTP" "details policy failures"
17904 .cindex "policy control" "rejection, returning details"
17905 In the default state, Exim uses bland messages such as
17906 &"Administrative prohibition"& when it rejects SMTP commands for policy
17907 reasons. Many sysadmins like this because it gives away little information
17908 to spammers. However, some other sysadmins who are applying strict checking
17909 policies want to give out much fuller information about failures. Setting
17910 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
17911 example, instead of &"Administrative prohibition"&, it might give:
17913 550-Rejected after DATA: '>' missing at end of address:
17914 550 failing address in "From" header is: <user@dom.ain
17918 .option smtputf8_advertise_hosts main "host list&!!" *
17919 .cindex "SMTPUTF8" "ESMTP extension, advertising"
17920 .cindex "ESMTP extensions" SMTPUTF8
17921 When Exim is built with support for internationalised mail names,
17922 the availability thereof is advertised in
17923 response to EHLO only to those client hosts that match this option. See
17924 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
17927 .option spamd_address main string "127.0.0.1 783"
17928 This option is available when Exim is compiled with the content-scanning
17929 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
17930 See section &<<SECTscanspamass>>& for more details.
17934 .option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
17935 This option is available when Exim is compiled with SPF support.
17936 See section &<<SECSPF>>& for more details.
17938 .option spf_smtp_comment_template main string&!! "Please%_see%_http://www.open-spf.org/Why"
17939 This option is available when Exim is compiled with SPF support. It
17940 allows the customisation of the SMTP comment that the SPF library
17941 generates. You are strongly encouraged to link to your own explanative
17942 site. The template must not contain spaces. If you need spaces in the
17943 output, use the proper placeholder. If libspf2 can not parse the
17944 template, it uses a built-in default broken link. The following placeholders
17945 (along with Exim variables (but see below)) are allowed in the template:
17949 &*%{L}*&: Envelope sender's local part.
17951 &*%{S}*&: Envelope sender.
17953 &*%{O}*&: Envelope sender's domain.
17955 &*%{D}*&: Current(?) domain.
17957 &*%{I}*&: SMTP client Ip.
17959 &*%{C}*&: SMTP client pretty IP.
17961 &*%{T}*&: Epoch time (UTC).
17963 &*%{P}*&: SMTP client domain name.
17965 &*%{V}*&: IP version.
17967 &*%{H}*&: EHLO/HELO domain.
17969 &*%{R}*&: Receiving domain.
17971 The capitalized placeholders do proper URL encoding, if you use them
17972 lowercased, no encoding takes place. This list was compiled from the
17975 A note on using Exim variables: As
17976 currently the SPF library is initialized before the SMTP EHLO phase,
17977 the variables useful for expansion are quite limited.
17980 .option split_spool_directory main boolean false
17981 .cindex "multiple spool directories"
17982 .cindex "spool directory" "split"
17983 .cindex "directories, multiple"
17984 If this option is set, it causes Exim to split its input directory into 62
17985 subdirectories, each with a single alphanumeric character as its name. The
17986 sixth character of the message id is used to allocate messages to
17987 subdirectories; this is the least significant base-62 digit of the time of
17988 arrival of the message.
17990 Splitting up the spool in this way may provide better performance on systems
17991 where there are long mail queues, by reducing the number of files in any one
17992 directory. The msglog directory is also split up in a similar way to the input
17993 directory; however, if &%preserve_message_logs%& is set, all old msglog files
17994 are still placed in the single directory &_msglog.OLD_&.
17996 It is not necessary to take any special action for existing messages when
17997 changing &%split_spool_directory%&. Exim notices messages that are in the
17998 &"wrong"& place, and continues to process them. If the option is turned off
17999 after a period of being on, the subdirectories will eventually empty and be
18000 automatically deleted.
18002 When &%split_spool_directory%& is set, the behaviour of queue runner processes
18003 changes. Instead of creating a list of all messages in the queue, and then
18004 trying to deliver each one, in turn, it constructs a list of those in one
18005 sub-directory and tries to deliver them, before moving on to the next
18006 sub-directory. The sub-directories are processed in a random order. This
18007 spreads out the scanning of the input directories, and uses less memory. It is
18008 particularly beneficial when there are lots of messages in the queue. However,
18009 if &%queue_run_in_order%& is set, none of this new processing happens. The
18010 entire queue has to be scanned and sorted before any deliveries can start.
18013 .option spool_directory main string&!! "set at compile time"
18014 .cindex "spool directory" "path to"
18015 This defines the directory in which Exim keeps its spool, that is, the messages
18016 it is waiting to deliver. The default value is taken from the compile-time
18017 configuration setting, if there is one. If not, this option must be set. The
18018 string is expanded, so it can contain, for example, a reference to
18019 &$primary_hostname$&.
18021 If the spool directory name is fixed on your installation, it is recommended
18022 that you set it at build time rather than from this option, particularly if the
18023 log files are being written to the spool directory (see &%log_file_path%&).
18024 Otherwise log files cannot be used for errors that are detected early on, such
18025 as failures in the configuration file.
18027 By using this option to override the compiled-in path, it is possible to run
18028 tests of Exim without using the standard spool.
18030 .option spool_wireformat main boolean false
18031 .cindex "spool directory" "file formats"
18032 If this option is set, Exim may for some messages use an alternative format
18033 for data-files in the spool which matches the wire format.
18034 Doing this permits more efficient message reception and transmission.
18035 Currently it is only done for messages received using the ESMTP CHUNKING
18038 The following variables will not have useful values:
18040 $max_received_linelength
18045 Users of the local_scan() API (see &<<CHAPlocalscan>>&),
18046 and any external programs which are passed a reference to a message data file
18047 (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
18048 will need to be aware of the different formats potentially available.
18050 Using any of the ACL conditions noted will negate the reception benefit
18051 (as a Unix-mbox-format file is constructed for them).
18052 The transmission benefit is maintained.
18054 .option sqlite_lock_timeout main time 5s
18055 .cindex "sqlite lookup type" "lock timeout"
18056 This option controls the timeout that the &(sqlite)& lookup uses when trying to
18057 access an SQLite database. See section &<<SECTsqlite>>& for more details.
18059 .option strict_acl_vars main boolean false
18060 .cindex "&ACL;" "variables, handling unset"
18061 This option controls what happens if a syntactically valid but undefined ACL
18062 variable is referenced. If it is false (the default), an empty string
18063 is substituted; if it is true, an error is generated. See section
18064 &<<SECTaclvariables>>& for details of ACL variables.
18066 .option strip_excess_angle_brackets main boolean false
18067 .cindex "angle brackets, excess"
18068 If this option is set, redundant pairs of angle brackets round &"route-addr"&
18069 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
18070 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
18071 passed on to another MTA, the excess angle brackets are not passed on. If this
18072 option is not set, multiple pairs of angle brackets cause a syntax error.
18075 .option strip_trailing_dot main boolean false
18076 .cindex "trailing dot on domain"
18077 .cindex "dot" "trailing on domain"
18078 If this option is set, a trailing dot at the end of a domain in an address is
18079 ignored. If this is in the envelope and the message is passed on to another
18080 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
18081 domain causes a syntax error.
18082 However, addresses in header lines are checked only when an ACL requests header
18086 .option syslog_duplication main boolean true
18087 .cindex "syslog" "duplicate log lines; suppressing"
18088 When Exim is logging to syslog, it writes the log lines for its three
18089 separate logs at different syslog priorities so that they can in principle
18090 be separated on the logging hosts. Some installations do not require this
18091 separation, and in those cases, the duplication of certain log lines is a
18092 nuisance. If &%syslog_duplication%& is set false, only one copy of any
18093 particular log line is written to syslog. For lines that normally go to
18094 both the main log and the reject log, the reject log version (possibly
18095 containing message header lines) is written, at LOG_NOTICE priority.
18096 Lines that normally go to both the main and the panic log are written at
18097 the LOG_ALERT priority.
18100 .option syslog_facility main string unset
18101 .cindex "syslog" "facility; setting"
18102 This option sets the syslog &"facility"& name, used when Exim is logging to
18103 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
18104 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
18105 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
18106 details of Exim's logging.
18109 .option syslog_pid main boolean true
18110 .cindex "syslog" "pid"
18111 If &%syslog_pid%& is set false, the PID on Exim's log lines are
18112 omitted when these lines are sent to syslog. (Syslog normally prefixes
18113 the log lines with the PID of the logging process automatically.) You need
18114 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
18115 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
18119 .option syslog_processname main string &`exim`&
18120 .cindex "syslog" "process name; setting"
18121 This option sets the syslog &"ident"& name, used when Exim is logging to
18122 syslog. The value must be no longer than 32 characters. See chapter
18123 &<<CHAPlog>>& for details of Exim's logging.
18127 .option syslog_timestamp main boolean true
18128 .cindex "syslog" "timestamps"
18129 .cindex timestamps syslog
18130 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
18131 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
18132 details of Exim's logging.
18135 .option system_filter main string&!! unset
18136 .cindex "filter" "system filter"
18137 .cindex "system filter" "specifying"
18138 .cindex "Sieve filter" "not available for system filter"
18139 This option specifies an Exim filter file that is applied to all messages at
18140 the start of each delivery attempt, before any routing is done. System filters
18141 must be Exim filters; they cannot be Sieve filters. If the system filter
18142 generates any deliveries to files or pipes, or any new mail messages, the
18143 appropriate &%system_filter_..._transport%& option(s) must be set, to define
18144 which transports are to be used. Details of this facility are given in chapter
18145 &<<CHAPsystemfilter>>&.
18146 A forced expansion failure results in no filter operation.
18149 .option system_filter_directory_transport main string&!! unset
18150 .vindex "&$address_file$&"
18151 This sets the name of the transport driver that is to be used when the
18152 &%save%& command in a system message filter specifies a path ending in &"/"&,
18153 implying delivery of each message into a separate file in some directory.
18154 During the delivery, the variable &$address_file$& contains the path name.
18157 .option system_filter_file_transport main string&!! unset
18158 .cindex "file" "transport for system filter"
18159 This sets the name of the transport driver that is to be used when the &%save%&
18160 command in a system message filter specifies a path not ending in &"/"&. During
18161 the delivery, the variable &$address_file$& contains the path name.
18163 .option system_filter_group main string unset
18164 .cindex "gid (group id)" "system filter"
18165 This option is used only when &%system_filter_user%& is also set. It sets the
18166 gid under which the system filter is run, overriding any gid that is associated
18167 with the user. The value may be numerical or symbolic.
18169 .option system_filter_pipe_transport main string&!! unset
18170 .cindex "&(pipe)& transport" "for system filter"
18171 .vindex "&$address_pipe$&"
18172 This specifies the transport driver that is to be used when a &%pipe%& command
18173 is used in a system filter. During the delivery, the variable &$address_pipe$&
18174 contains the pipe command.
18177 .option system_filter_reply_transport main string&!! unset
18178 .cindex "&(autoreply)& transport" "for system filter"
18179 This specifies the transport driver that is to be used when a &%mail%& command
18180 is used in a system filter.
18183 .option system_filter_user main string unset
18184 .cindex "uid (user id)" "system filter"
18185 If this option is set to root, the system filter is run in the main Exim
18186 delivery process, as root. Otherwise, the system filter runs in a separate
18187 process, as the given user, defaulting to the Exim run-time user.
18188 Unless the string consists entirely of digits, it
18189 is looked up in the password data. Failure to find the named user causes a
18190 configuration error. The gid is either taken from the password data, or
18191 specified by &%system_filter_group%&. When the uid is specified numerically,
18192 &%system_filter_group%& is required to be set.
18194 If the system filter generates any pipe, file, or reply deliveries, the uid
18195 under which the filter is run is used when transporting them, unless a
18196 transport option overrides.
18199 .option tcp_nodelay main boolean true
18200 .cindex "daemon" "TCP_NODELAY on sockets"
18201 .cindex "Nagle algorithm"
18202 .cindex "TCP_NODELAY on listening sockets"
18203 If this option is set false, it stops the Exim daemon setting the
18204 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
18205 turns off the &"Nagle algorithm"&, which is a way of improving network
18206 performance in interactive (character-by-character) situations. Turning it off
18207 should improve Exim's performance a bit, so that is what happens by default.
18208 However, it appears that some broken clients cannot cope, and time out. Hence
18209 this option. It affects only those sockets that are set up for listening by the
18210 daemon. Sockets created by the smtp transport for delivering mail always set
18214 .option timeout_frozen_after main time 0s
18215 .cindex "frozen messages" "timing out"
18216 .cindex "timeout" "frozen messages"
18217 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
18218 message of any kind that has been in the queue for longer than the given time
18219 is automatically cancelled at the next queue run. If the frozen message is a
18220 bounce message, it is just discarded; otherwise, a bounce is sent to the
18221 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
18222 If you want to timeout frozen bounce messages earlier than other kinds of
18223 frozen message, see &%ignore_bounce_errors_after%&.
18225 &*Note:*& the default value of zero means no timeouts; with this setting,
18226 frozen messages remain in the queue forever (except for any frozen bounce
18227 messages that are released by &%ignore_bounce_errors_after%&).
18230 .option timezone main string unset
18231 .cindex "timezone, setting"
18232 .cindex "environment" "values from"
18233 The value of &%timezone%& is used to set the environment variable TZ while
18234 running Exim (if it is different on entry). This ensures that all timestamps
18235 created by Exim are in the required timezone. If you want all your timestamps
18236 to be in UTC (aka GMT) you should set
18240 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
18241 or, if that is not set, from the value of the TZ environment variable when Exim
18242 is built. If &%timezone%& is set to the empty string, either at build or run
18243 time, any existing TZ variable is removed from the environment when Exim
18244 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
18245 unfortunately not all, operating systems.
18248 .option tls_advertise_hosts main "host list&!!" *
18249 .cindex "TLS" "advertising"
18250 .cindex "encryption" "on SMTP connection"
18251 .cindex "SMTP" "encrypted connection"
18252 .cindex "ESMTP extensions" STARTTLS
18253 When Exim is built with support for TLS encrypted connections, the availability
18254 of the STARTTLS command to set up an encrypted session is advertised in
18255 response to EHLO only to those client hosts that match this option. See
18256 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
18257 Note that the default value requires that a certificate be supplied
18258 using the &%tls_certificate%& option. If TLS support for incoming connections
18259 is not required the &%tls_advertise_hosts%& option should be set empty.
18262 .option tls_certificate main string list&!! unset
18263 .cindex "TLS" "server certificate; location of"
18264 .cindex "certificate" "server, location of"
18265 The value of this option is expanded, and must then be a list of absolute paths to
18266 files which contain the server's certificates (in PEM format).
18267 Commonly only one file is needed.
18268 The server's private key is also
18269 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
18270 &<<CHAPTLS>>& for further details.
18272 &*Note*&: The certificates defined by this option are used only when Exim is
18273 receiving incoming messages as a server. If you want to supply certificates for
18274 use when sending messages as a client, you must set the &%tls_certificate%&
18275 option in the relevant &(smtp)& transport.
18277 &*Note*&: If you use filenames based on IP addresses, change the list
18278 separator in the usual way (&<<SECTlistsepchange>>&) to avoid confusion under IPv6.
18280 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
18281 when a list of more than one
18282 file is used, the &$tls_in_ourcert$& variable is unreliable.
18283 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
18285 .cindex SNI "selecting server certificate based on"
18286 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
18287 if the OpenSSL build supports TLS extensions and the TLS client sends the
18288 Server Name Indication extension, then this option and others documented in
18289 &<<SECTtlssni>>& will be re-expanded.
18291 If this option is unset or empty a fresh self-signed certificate will be
18292 generated for every connection.
18294 .option tls_crl main string&!! unset
18295 .cindex "TLS" "server certificate revocation list"
18296 .cindex "certificate" "revocation list for server"
18297 This option specifies a certificate revocation list. The expanded value must
18298 be the name of a file that contains CRLs in PEM format.
18300 Under OpenSSL the option can specify a directory with CRL files.
18302 &*Note:*& Under OpenSSL the option must, if given, supply a CRL
18303 for each signing element of the certificate chain (i.e. all but the leaf).
18304 For the file variant this can be multiple PEM blocks in the one file.
18306 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18309 .option tls_dh_max_bits main integer 2236
18310 .cindex "TLS" "D-H bit count"
18311 The number of bits used for Diffie-Hellman key-exchange may be suggested by
18312 the chosen TLS library. That value might prove to be too high for
18313 interoperability. This option provides a maximum clamp on the value
18314 suggested, trading off security for interoperability.
18316 The value must be at least 1024.
18318 The value 2236 was chosen because, at time of adding the option, it was the
18319 hard-coded maximum value supported by the NSS cryptographic library, as used
18320 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
18322 If you prefer more security and are willing to break some clients, raise this
18325 Note that the value passed to GnuTLS for *generating* a new prime may be a
18326 little less than this figure, because GnuTLS is inexact and may produce a
18327 larger prime than requested.
18330 .option tls_dhparam main string&!! unset
18331 .cindex "TLS" "D-H parameters for server"
18332 The value of this option is expanded and indicates the source of DH parameters
18333 to be used by Exim.
18335 This option is ignored for GnuTLS version 3.6.0 and later.
18336 The library manages parameter negotiation internally.
18338 &*Note: The Exim Maintainers strongly recommend,
18339 for other TLS library versions,
18340 using a filename with site-generated
18341 local DH parameters*&, which has been supported across all versions of Exim. The
18342 other specific constants available are a fallback so that even when
18343 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
18345 If &%tls_dhparam%& is a filename starting with a &`/`&,
18346 then it names a file from which DH
18347 parameters should be loaded. If the file exists, it should hold a PEM-encoded
18348 PKCS#3 representation of the DH prime. If the file does not exist, for
18349 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
18350 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
18351 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
18352 and treated as though the &%tls_dhparam%& were set to "none".
18354 If this option expands to the string "none", then no DH parameters will be
18357 If this option expands to the string "historic" and Exim is using GnuTLS, then
18358 Exim will attempt to load a file from inside the spool directory. If the file
18359 does not exist, Exim will attempt to create it.
18360 See section &<<SECTgnutlsparam>>& for further details.
18362 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
18363 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
18365 In older versions of Exim the default was the 2048 bit prime described in section
18366 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
18367 in IKE is assigned number 23.
18369 Otherwise, the option must expand to the name used by Exim for any of a number
18370 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
18371 sources. As names, Exim uses a standard specified name, else "ike" followed by
18372 the number used by IKE, or "default" which corresponds to
18373 &`exim.dev.20160529.3`&.
18375 The available standard primes are:
18376 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
18377 &`ike1`&, &`ike2`&, &`ike5`&,
18378 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
18379 &`ike22`&, &`ike23`& and &`ike24`&.
18381 The available additional primes are:
18382 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
18384 Some of these will be too small to be accepted by clients.
18385 Some may be too large to be accepted by clients.
18386 The open cryptographic community has suspicions about the integrity of some
18387 of the later IKE values, which led into RFC7919 providing new fixed constants
18388 (the "ffdhe" identifiers).
18390 At this point, all of the "ike" values should be considered obsolete;
18391 they're still in Exim to avoid breaking unusual configurations, but are
18392 candidates for removal the next time we have backwards-incompatible changes.
18394 The TLS protocol does not negotiate an acceptable size for this; clients tend
18395 to hard-drop connections if what is offered by the server is unacceptable,
18396 whether too large or too small, and there's no provision for the client to
18397 tell the server what these constraints are. Thus, as a server operator, you
18398 need to make an educated guess as to what is most likely to work for your
18401 Some known size constraints suggest that a bit-size in the range 2048 to 2236
18402 is most likely to maximise interoperability. The upper bound comes from
18403 applications using the Mozilla Network Security Services (NSS) library, which
18404 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
18405 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
18406 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
18407 acceptable bound from 1024 to 2048.
18410 .option tls_eccurve main string&!! &`auto`&
18411 .cindex TLS "EC cryptography"
18412 This option selects a EC curve for use by Exim when used with OpenSSL.
18413 It has no effect when Exim is used with GnuTLS.
18415 After expansion it must contain a valid EC curve parameter, such as
18416 &`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
18417 for valid selections.
18419 For OpenSSL versions before (and not including) 1.0.2, the string
18420 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
18421 &`auto`& tells the library to choose.
18423 If the option expands to an empty string, no EC curves will be enabled.
18426 .option tls_ocsp_file main string&!! unset
18427 .cindex TLS "certificate status"
18428 .cindex TLS "OCSP proof file"
18430 must if set expand to the absolute path to a file which contains a current
18431 status proof for the server's certificate, as obtained from the
18432 Certificate Authority.
18434 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
18435 The macro "_HAVE_TLS_OCSP" will be defined for those versions.
18437 For OpenSSL 1.1.0 or later, and
18438 for GnuTLS 3.5.6 or later the expanded value of this option can be a list
18439 of files, to match a list given for the &%tls_certificate%& option.
18440 The ordering of the two lists must match.
18441 The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
18443 The file(s) should be in DER format,
18444 except for GnuTLS 3.6.3 or later
18446 when an optional filetype prefix can be used.
18447 The prefix must be one of "DER" or "PEM", followed by
18448 a single space. If one is used it sets the format for subsequent
18449 files in the list; the initial format is DER.
18450 If multiple proofs are wanted, for multiple chain elements
18451 (this only works under TLS1.3)
18452 they must be coded as a combined OCSP response.
18454 Although GnuTLS will accept PEM files with multiple separate
18455 PEM blobs (ie. separate OCSP responses), it sends them in the
18456 TLS Certificate record interleaved with the certificates of the chain;
18457 although a GnuTLS client is happy with that, an OpenSSL client is not.
18459 .option tls_on_connect_ports main "string list" unset
18462 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
18463 operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
18464 set up without waiting for the client to issue a STARTTLS command. For
18465 further details, see section &<<SECTsupobssmt>>&.
18469 .option tls_privatekey main string list&!! unset
18470 .cindex "TLS" "server private key; location of"
18471 The value of this option is expanded, and must then be a list of absolute paths to
18472 files which contains the server's private keys.
18473 If this option is unset, or if
18474 the expansion is forced to fail, or the result is an empty string, the private
18475 key is assumed to be in the same file as the server's certificates. See chapter
18476 &<<CHAPTLS>>& for further details.
18478 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18481 .option tls_remember_esmtp main boolean false
18482 .cindex "TLS" "esmtp state; remembering"
18483 .cindex "TLS" "broken clients"
18484 If this option is set true, Exim violates the RFCs by remembering that it is in
18485 &"esmtp"& state after successfully negotiating a TLS session. This provides
18486 support for broken clients that fail to send a new EHLO after starting a
18490 .option tls_require_ciphers main string&!! unset
18491 .cindex "TLS" "requiring specific ciphers"
18492 .cindex "cipher" "requiring specific"
18493 This option controls which ciphers can be used for incoming TLS connections.
18494 The &(smtp)& transport has an option of the same name for controlling outgoing
18495 connections. This option is expanded for each connection, so can be varied for
18496 different clients if required. The value of this option must be a list of
18497 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
18498 in somewhat different ways. If GnuTLS is being used, the client controls the
18499 preference order of the available ciphers. Details are given in sections
18500 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
18504 .option tls_resumption_hosts main "host list&!!" unset
18505 .cindex TLS resumption
18506 This option controls which connections to offer the TLS resumption feature.
18507 See &<<SECTresumption>>& for details.
18511 .option tls_try_verify_hosts main "host list&!!" unset
18512 .cindex "TLS" "client certificate verification"
18513 .cindex "certificate" "verification of client"
18514 See &%tls_verify_hosts%& below.
18517 .option tls_verify_certificates main string&!! system
18518 .cindex "TLS" "client certificate verification"
18519 .cindex "certificate" "verification of client"
18520 The value of this option is expanded, and must then be either the
18522 or the absolute path to
18523 a file or directory containing permitted certificates for clients that
18524 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
18526 The "system" value for the option will use a
18527 system default location compiled into the SSL library.
18528 This is not available for GnuTLS versions preceding 3.0.20,
18529 and will be taken as empty; an explicit location
18532 The use of a directory for the option value is not available for GnuTLS versions
18533 preceding 3.3.6 and a single file must be used.
18535 With OpenSSL the certificates specified
18537 either by file or directory
18538 are added to those given by the system default location.
18540 These certificates should be for the certificate authorities trusted, rather
18541 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
18542 the value is a file then the certificates are sent by Exim as a server to
18543 connecting clients, defining the list of accepted certificate authorities.
18544 Thus the values defined should be considered public data. To avoid this,
18545 use the explicit directory version. (If your peer is Exim up to 4.85,
18546 using GnuTLS, you may need to send the CAs (thus using the file
18547 variant). Otherwise the peer doesn't send its certificate.)
18549 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18551 A forced expansion failure or setting to an empty string is equivalent to
18555 .option tls_verify_hosts main "host list&!!" unset
18556 .cindex "TLS" "client certificate verification"
18557 .cindex "certificate" "verification of client"
18558 This option, along with &%tls_try_verify_hosts%&, controls the checking of
18559 certificates from clients. The expected certificates are defined by
18560 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
18561 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
18562 &%tls_verify_certificates%& is not set.
18564 Any client that matches &%tls_verify_hosts%& is constrained by
18565 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
18566 present one of the listed certificates. If it does not, the connection is
18567 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
18568 the host to use TLS. It can still send SMTP commands through unencrypted
18569 connections. Forcing a client to use TLS has to be done separately using an
18570 ACL to reject inappropriate commands when the connection is not encrypted.
18572 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
18573 matches this option (but not &%tls_verify_hosts%&), Exim requests a
18574 certificate and checks it against &%tls_verify_certificates%&, but does not
18575 abort the connection if there is no certificate or if it does not match. This
18576 state can be detected in an ACL, which makes it possible to implement policies
18577 such as &"accept for relay only if a verified certificate has been received,
18578 but accept for local delivery if encrypted, even without a verified
18581 Client hosts that match neither of these lists are not asked to present
18585 .option trusted_groups main "string list&!!" unset
18586 .cindex "trusted groups"
18587 .cindex "groups" "trusted"
18588 This option is expanded just once, at the start of Exim's processing. If this
18589 option is set, any process that is running in one of the listed groups, or
18590 which has one of them as a supplementary group, is trusted. The groups can be
18591 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
18592 details of what trusted callers are permitted to do. If neither
18593 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
18596 .option trusted_users main "string list&!!" unset
18597 .cindex "trusted users"
18598 .cindex "user" "trusted"
18599 This option is expanded just once, at the start of Exim's processing. If this
18600 option is set, any process that is running as one of the listed users is
18601 trusted. The users can be specified numerically or by name. See section
18602 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
18603 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
18604 Exim user are trusted.
18606 .option unknown_login main string&!! unset
18607 .cindex "uid (user id)" "unknown caller"
18608 .vindex "&$caller_uid$&"
18609 This is a specialized feature for use in unusual configurations. By default, if
18610 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
18611 gives up. The &%unknown_login%& option can be used to set a login name to be
18612 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
18613 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
18614 is used for the user's real name (gecos field), unless this has been set by the
18617 .option unknown_username main string unset
18618 See &%unknown_login%&.
18620 .option untrusted_set_sender main "address list&!!" unset
18621 .cindex "trusted users"
18622 .cindex "sender" "setting by untrusted user"
18623 .cindex "untrusted user setting sender"
18624 .cindex "user" "untrusted setting sender"
18625 .cindex "envelope from"
18626 .cindex "envelope sender"
18627 When an untrusted user submits a message to Exim using the standard input, Exim
18628 normally creates an envelope sender address from the user's login and the
18629 default qualification domain. Data from the &%-f%& option (for setting envelope
18630 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
18631 is used) is ignored.
18633 However, untrusted users are permitted to set an empty envelope sender address,
18634 to declare that a message should never generate any bounces. For example:
18636 exim -f '<>' user@domain.example
18638 .vindex "&$sender_ident$&"
18639 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
18640 other envelope sender addresses in a controlled way. When it is set, untrusted
18641 users are allowed to set envelope sender addresses that match any of the
18642 patterns in the list. Like all address lists, the string is expanded. The
18643 identity of the user is in &$sender_ident$&, so you can, for example, restrict
18644 users to setting senders that start with their login ids
18645 followed by a hyphen
18646 by a setting like this:
18648 untrusted_set_sender = ^$sender_ident-
18650 If you want to allow untrusted users to set envelope sender addresses without
18651 restriction, you can use
18653 untrusted_set_sender = *
18655 The &%untrusted_set_sender%& option applies to all forms of local input, but
18656 only to the setting of the envelope sender. It does not permit untrusted users
18657 to use the other options which trusted user can use to override message
18658 parameters. Furthermore, it does not stop Exim from removing an existing
18659 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
18660 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
18661 overriding these actions. The handling of the &'Sender:'& header is also
18662 described in section &<<SECTthesenhea>>&.
18664 The log line for a message's arrival shows the envelope sender following
18665 &"<="&. For local messages, the user's login always follows, after &"U="&. In
18666 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
18667 envelope sender address, the user's login is shown in parentheses after the
18671 .option uucp_from_pattern main string "see below"
18672 .cindex "&""From""& line"
18673 .cindex "UUCP" "&""From""& line"
18674 Some applications that pass messages to an MTA via a command line interface use
18675 an initial line starting with &"From&~"& to pass the envelope sender. In
18676 particular, this is used by UUCP software. Exim recognizes such a line by means
18677 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
18678 matches, the sender address is constructed by expanding the contents of
18679 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
18680 default pattern recognizes lines in the following two forms:
18682 From ph10 Fri Jan 5 12:35 GMT 1996
18683 From ph10 Fri, 7 Jan 97 14:00:00 GMT
18685 The pattern can be seen by running
18687 exim -bP uucp_from_pattern
18689 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
18690 year in the second case. The first word after &"From&~"& is matched in the
18691 regular expression by a parenthesized subpattern. The default value for
18692 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
18693 (&"ph10"& in the example above) as the message's sender. See also
18694 &%ignore_fromline_hosts%&.
18697 .option uucp_from_sender main string&!! &`$1`&
18698 See &%uucp_from_pattern%& above.
18701 .option warn_message_file main string&!! unset
18702 .cindex "warning of delay" "customizing the message"
18703 .cindex "customizing" "warning message"
18704 This option defines a template file containing paragraphs of text to be used
18705 for constructing the warning message which is sent by Exim when a message has
18706 been in the queue for a specified amount of time, as specified by
18707 &%delay_warning%&. Details of the file's contents are given in chapter
18708 &<<CHAPemsgcust>>&.
18709 .cindex warn_message_file "tainted data"
18710 The option is expanded to give the file path, which must be
18711 absolute and untainted.
18712 See also &%bounce_message_file%&.
18715 .option write_rejectlog main boolean true
18716 .cindex "reject log" "disabling"
18717 If this option is set false, Exim no longer writes anything to the reject log.
18718 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
18719 .ecindex IIDconfima
18720 .ecindex IIDmaiconf
18725 . ////////////////////////////////////////////////////////////////////////////
18726 . ////////////////////////////////////////////////////////////////////////////
18728 .chapter "Generic options for routers" "CHAProutergeneric"
18729 .scindex IIDgenoprou1 "options" "generic; for routers"
18730 .scindex IIDgenoprou2 "generic options" "router"
18731 This chapter describes the generic options that apply to all routers.
18732 Those that are preconditions are marked with ‡ in the &"use"& field.
18734 For a general description of how a router operates, see sections
18735 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
18736 which the preconditions are tested. The order of expansion of the options that
18737 provide data for a transport is: &%errors_to%&, &%headers_add%&,
18738 &%headers_remove%&, &%transport%&.
18742 .option address_data routers string&!! unset
18743 .cindex "router" "data attached to address"
18744 The string is expanded just before the router is run, that is, after all the
18745 precondition tests have succeeded. If the expansion is forced to fail, the
18746 router declines, the value of &%address_data%& remains unchanged, and the
18747 &%more%& option controls what happens next. Other expansion failures cause
18748 delivery of the address to be deferred.
18750 .vindex "&$address_data$&"
18751 When the expansion succeeds, the value is retained with the address, and can be
18752 accessed using the variable &$address_data$& in the current router, subsequent
18753 routers, and the eventual transport.
18755 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
18756 that runs a user's filter file, the contents of &$address_data$& are accessible
18757 in the filter. This is not normally a problem, because such data is usually
18758 either not confidential or it &"belongs"& to the current user, but if you do
18759 put confidential data into &$address_data$& you need to remember this point.
18761 Even if the router declines or passes, the value of &$address_data$& remains
18762 with the address, though it can be changed by another &%address_data%& setting
18763 on a subsequent router. If a router generates child addresses, the value of
18764 &$address_data$& propagates to them. This also applies to the special kind of
18765 &"child"& that is generated by a router with the &%unseen%& option.
18767 The idea of &%address_data%& is that you can use it to look up a lot of data
18768 for the address once, and then pick out parts of the data later. For example,
18769 you could use a single LDAP lookup to return a string of the form
18771 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
18773 In the transport you could pick out the mailbox by a setting such as
18775 file = ${extract{mailbox}{$address_data}}
18777 This makes the configuration file less messy, and also reduces the number of
18778 lookups (though Exim does cache lookups).
18780 See also the &%set%& option below.
18782 .vindex "&$sender_address_data$&"
18783 .vindex "&$address_data$&"
18784 The &%address_data%& facility is also useful as a means of passing information
18785 from one router to another, and from a router to a transport. In addition, if
18786 &$address_data$& is set by a router when verifying a recipient address from an
18787 ACL, it remains available for use in the rest of the ACL statement. After
18788 verifying a sender, the value is transferred to &$sender_address_data$&.
18792 .option address_test routers&!? boolean true
18794 .cindex "router" "skipping when address testing"
18795 If this option is set false, the router is skipped when routing is being tested
18796 by means of the &%-bt%& command line option. This can be a convenience when
18797 your first router sends messages to an external scanner, because it saves you
18798 having to set the &"already scanned"& indicator when testing real address
18803 .option cannot_route_message routers string&!! unset
18804 .cindex "router" "customizing &""cannot route""& message"
18805 .cindex "customizing" "&""cannot route""& message"
18806 This option specifies a text message that is used when an address cannot be
18807 routed because Exim has run out of routers. The default message is
18808 &"Unrouteable address"&. This option is useful only on routers that have
18809 &%more%& set false, or on the very last router in a configuration, because the
18810 value that is used is taken from the last router that is considered. This
18811 includes a router that is skipped because its preconditions are not met, as
18812 well as a router that declines. For example, using the default configuration,
18815 cannot_route_message = Remote domain not found in DNS
18817 on the first router, which is a &(dnslookup)& router with &%more%& set false,
18820 cannot_route_message = Unknown local user
18822 on the final router that checks for local users. If string expansion fails for
18823 this option, the default message is used. Unless the expansion failure was
18824 explicitly forced, a message about the failure is written to the main and panic
18825 logs, in addition to the normal message about the routing failure.
18828 .option caseful_local_part routers boolean false
18829 .cindex "case of local parts"
18830 .cindex "router" "case of local parts"
18831 By default, routers handle the local parts of addresses in a case-insensitive
18832 manner, though the actual case is preserved for transmission with the message.
18833 If you want the case of letters to be significant in a router, you must set
18834 this option true. For individual router options that contain address or local
18835 part lists (for example, &%local_parts%&), case-sensitive matching can be
18836 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
18839 .vindex "&$local_part$&"
18840 .vindex "&$original_local_part$&"
18841 .vindex "&$parent_local_part$&"
18842 The value of the &$local_part$& variable is forced to lower case while a
18843 router is running unless &%caseful_local_part%& is set. When a router assigns
18844 an address to a transport, the value of &$local_part$& when the transport runs
18845 is the same as it was in the router. Similarly, when a router generates child
18846 addresses by aliasing or forwarding, the values of &$original_local_part$&
18847 and &$parent_local_part$& are those that were used by the redirecting router.
18849 This option applies to the processing of an address by a router. When a
18850 recipient address is being processed in an ACL, there is a separate &%control%&
18851 modifier that can be used to specify case-sensitive processing within the ACL
18852 (see section &<<SECTcontrols>>&).
18856 .option check_local_user routers&!? boolean false
18857 .cindex "local user, checking in router"
18858 .cindex "router" "checking for local user"
18859 .cindex "&_/etc/passwd_&"
18861 When this option is true, Exim checks that the local part of the recipient
18862 address (with affixes removed if relevant) is the name of an account on the
18863 local system. The check is done by calling the &[getpwnam()]& function rather
18864 than trying to read &_/etc/passwd_& directly. This means that other methods of
18865 holding password data (such as NIS) are supported. If the local part is a local
18867 .cindex "tainted data" "de-tainting"
18868 &$local_part_data$& is set to an untainted version of the local part and
18869 &$home$& is set from the password data. The latter can be tested in other
18870 preconditions that are evaluated after this one (the order of evaluation is
18871 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
18872 overridden by &%router_home_directory%&. If the local part is not a local user,
18873 the router is skipped.
18875 If you want to check that the local part is either the name of a local user
18876 or matches something else, you cannot combine &%check_local_user%& with a
18877 setting of &%local_parts%&, because that specifies the logical &'and'& of the
18878 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
18879 setting to achieve this. For example:
18881 local_parts = passwd;$local_part : lsearch;/etc/other/users
18883 Note, however, that the side effects of &%check_local_user%& (such as setting
18884 up a home directory) do not occur when a &(passwd)& lookup is used in a
18885 &%local_parts%& (or any other) precondition.
18889 .option condition routers&!? string&!! unset
18890 .cindex "router" "customized precondition"
18891 This option specifies a general precondition test that has to succeed for the
18892 router to be called. The &%condition%& option is the last precondition to be
18893 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
18894 result is a forced failure, or an empty string, or one of the strings &"0"& or
18895 &"no"& or &"false"& (checked without regard to the case of the letters), the
18896 router is skipped, and the address is offered to the next one.
18898 If the result is any other value, the router is run (as this is the last
18899 precondition to be evaluated, all the other preconditions must be true).
18901 This option is unusual in that multiple &%condition%& options may be present.
18902 All &%condition%& options must succeed.
18904 The &%condition%& option provides a means of applying custom conditions to the
18905 running of routers. Note that in the case of a simple conditional expansion,
18906 the default expansion values are exactly what is wanted. For example:
18908 condition = ${if >{$message_age}{600}}
18910 Because of the default behaviour of the string expansion, this is equivalent to
18912 condition = ${if >{$message_age}{600}{true}{}}
18915 A multiple condition example, which succeeds:
18917 condition = ${if >{$message_age}{600}}
18918 condition = ${if !eq{${lc:$local_part}}{postmaster}}
18922 If the expansion fails (other than forced failure) delivery is deferred. Some
18923 of the other precondition options are common special cases that could in fact
18924 be specified using &%condition%&.
18926 Historical note: We have &%condition%& on ACLs and on Routers. Routers
18927 are far older, and use one set of semantics. ACLs are newer and when
18928 they were created, the ACL &%condition%& process was given far stricter
18929 parse semantics. The &%bool{}%& expansion condition uses the same rules as
18930 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
18931 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
18932 Router rules processing behavior.
18934 This is best illustrated in an example:
18936 # If used in an ACL condition will fail with a syntax error, but
18937 # in a router condition any extra characters are treated as a string
18939 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
18942 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
18945 In each example above, the &%if%& statement actually ends after
18946 &"{google.com}}"&. Since no true or false braces were defined, the
18947 default &%if%& behavior is to return a boolean true or a null answer
18948 (which evaluates to false). The rest of the line is then treated as a
18949 string. So the first example resulted in the boolean answer &"true"&
18950 with the string &" {yes} {no}}"& appended to it. The second example
18951 resulted in the null output (indicating false) with the string
18952 &" {yes} {no}}"& appended to it.
18954 In fact you can put excess forward braces in too. In the router
18955 &%condition%&, Exim's parser only looks for &"{"& symbols when they
18956 mean something, like after a &"$"& or when required as part of a
18957 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
18960 Thus, in a Router, the above expansion strings will both always evaluate
18961 true, as the result of expansion is a non-empty string which doesn't
18962 match an explicit false value. This can be tricky to debug. By
18963 contrast, in an ACL either of those strings will always result in an
18964 expansion error because the result doesn't look sufficiently boolean.
18967 .option debug_print routers string&!! unset
18968 .cindex "testing" "variables in drivers"
18969 If this option is set and debugging is enabled (see the &%-d%& command line
18970 option) or in address-testing mode (see the &%-bt%& command line option),
18971 the string is expanded and included in the debugging output.
18972 If expansion of the string fails, the error message is written to the debugging
18973 output, and Exim carries on processing.
18974 This option is provided to help with checking out the values of variables and
18975 so on when debugging router configurations. For example, if a &%condition%&
18976 option appears not to be working, &%debug_print%& can be used to output the
18977 variables it references. The output happens after checks for &%domains%&,
18978 &%local_parts%&, and &%check_local_user%& but before any other preconditions
18979 are tested. A newline is added to the text if it does not end with one.
18980 The variable &$router_name$& contains the name of the router.
18984 .option disable_logging routers boolean false
18985 If this option is set true, nothing is logged for any routing errors
18986 or for any deliveries caused by this router. You should not set this option
18987 unless you really, really know what you are doing. See also the generic
18988 transport option of the same name.
18990 .option dnssec_request_domains routers "domain list&!!" *
18991 .cindex "MX record" "security"
18992 .cindex "DNSSEC" "MX lookup"
18993 .cindex "security" "MX lookup"
18994 .cindex "DNS" "DNSSEC"
18995 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
18996 the dnssec request bit set.
18997 This applies to all of the SRV, MX, AAAA, A lookup sequence.
18999 .option dnssec_require_domains routers "domain list&!!" unset
19000 .cindex "MX record" "security"
19001 .cindex "DNSSEC" "MX lookup"
19002 .cindex "security" "MX lookup"
19003 .cindex "DNS" "DNSSEC"
19004 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
19005 the dnssec request bit set. Any returns not having the Authenticated Data bit
19006 (AD bit) set will be ignored and logged as a host-lookup failure.
19007 This applies to all of the SRV, MX, AAAA, A lookup sequence.
19010 .option domains routers&!? "domain list&!!" unset
19011 .cindex "router" "restricting to specific domains"
19012 .vindex "&$domain_data$&"
19013 If this option is set, the router is skipped unless the current domain matches
19014 the list. If the match is achieved by means of a file lookup, the data that the
19015 lookup returned for the domain is placed in &$domain_data$& for use in string
19016 expansions of the driver's private options and in the transport.
19017 See section &<<SECTrouprecon>>& for
19018 a list of the order in which preconditions are evaluated.
19022 .option driver routers string unset
19023 This option must always be set. It specifies which of the available routers is
19027 .option dsn_lasthop routers boolean false
19028 .cindex "DSN" "success"
19029 .cindex "Delivery Status Notification" "success"
19030 If this option is set true, and extended DSN (RFC3461) processing is in effect,
19031 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
19032 instead send a success DSN as if the next hop does not support DSN.
19033 Not effective on redirect routers.
19037 .option errors_to routers string&!! unset
19038 .cindex "envelope from"
19039 .cindex "envelope sender"
19040 .cindex "router" "changing address for errors"
19041 If a router successfully handles an address, it may assign the address to a
19042 transport for delivery or it may generate child addresses. In both cases, if
19043 there is a delivery problem during later processing, the resulting bounce
19044 message is sent to the address that results from expanding this string,
19045 provided that the address verifies successfully. The &%errors_to%& option is
19046 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
19048 The &%errors_to%& setting associated with an address can be overridden if it
19049 subsequently passes through other routers that have their own &%errors_to%&
19050 settings, or if the message is delivered by a transport with a &%return_path%&
19053 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
19054 the expansion fails to verify, the errors address associated with the incoming
19055 address is used. At top level, this is the envelope sender. A non-forced
19056 expansion failure causes delivery to be deferred.
19058 If an address for which &%errors_to%& has been set ends up being delivered over
19059 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
19060 any bounces that are generated by other MTAs on the delivery route are also
19061 sent there. You can set &%errors_to%& to the empty string by either of these
19067 An expansion item that yields an empty string has the same effect. If you do
19068 this, a locally detected delivery error for addresses processed by this router
19069 no longer gives rise to a bounce message; the error is discarded. If the
19070 address is delivered to a remote host, the return path is set to &`<>`&, unless
19071 overridden by the &%return_path%& option on the transport.
19073 .vindex "&$address_data$&"
19074 If for some reason you want to discard local errors, but use a non-empty
19075 MAIL command for remote delivery, you can preserve the original return
19076 path in &$address_data$& in the router, and reinstate it in the transport by
19077 setting &%return_path%&.
19079 The most common use of &%errors_to%& is to direct mailing list bounces to the
19080 manager of the list, as described in section &<<SECTmailinglists>>&, or to
19081 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
19085 .option expn routers&!? boolean true
19086 .cindex "address" "testing"
19087 .cindex "testing" "addresses"
19088 .cindex "EXPN" "router skipping"
19089 .cindex "router" "skipping for EXPN"
19090 If this option is turned off, the router is skipped when testing an address
19091 as a result of processing an SMTP EXPN command. You might, for example,
19092 want to turn it off on a router for users' &_.forward_& files, while leaving it
19093 on for the system alias file.
19094 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19097 The use of the SMTP EXPN command is controlled by an ACL (see chapter
19098 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
19099 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
19103 .option fail_verify routers boolean false
19104 .cindex "router" "forcing verification failure"
19105 Setting this option has the effect of setting both &%fail_verify_sender%& and
19106 &%fail_verify_recipient%& to the same value.
19110 .option fail_verify_recipient routers boolean false
19111 If this option is true and an address is accepted by this router when
19112 verifying a recipient, verification fails.
19116 .option fail_verify_sender routers boolean false
19117 If this option is true and an address is accepted by this router when
19118 verifying a sender, verification fails.
19122 .option fallback_hosts routers "string list" unset
19123 .cindex "router" "fallback hosts"
19124 .cindex "fallback" "hosts specified on router"
19125 String expansion is not applied to this option. The argument must be a
19126 colon-separated list of host names or IP addresses. The list separator can be
19127 changed (see section &<<SECTlistsepchange>>&), and a port can be specified with
19128 each name or address. In fact, the format of each item is exactly the same as
19129 defined for the list of hosts in a &(manualroute)& router (see section
19130 &<<SECTformatonehostitem>>&).
19132 If a router queues an address for a remote transport, this host list is
19133 associated with the address, and used instead of the transport's fallback host
19134 list. If &%hosts_randomize%& is set on the transport, the order of the list is
19135 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
19136 transport for further details.
19139 .option group routers string&!! "see below"
19140 .cindex "gid (group id)" "local delivery"
19141 .cindex "local transports" "uid and gid"
19142 .cindex "transport" "local"
19143 .cindex "router" "setting group"
19144 When a router queues an address for a transport, and the transport does not
19145 specify a group, the group given here is used when running the delivery
19147 The group may be specified numerically or by name. If expansion fails, the
19148 error is logged and delivery is deferred.
19149 The default is unset, unless &%check_local_user%& is set, when the default
19150 is taken from the password information. See also &%initgroups%& and &%user%&
19151 and the discussion in chapter &<<CHAPenvironment>>&.
19155 .option headers_add routers list&!! unset
19156 .cindex "header lines" "adding"
19157 .cindex "router" "adding header lines"
19158 This option specifies a list of text headers,
19159 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19160 that is associated with any addresses that are accepted by the router.
19161 Each item is separately expanded, at routing time. However, this
19162 option has no effect when an address is just being verified. The way in which
19163 the text is used to add header lines at transport time is described in section
19164 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
19165 message is in the process of being transported. This means that references to
19166 header lines in string expansions in the transport's configuration do not
19167 &"see"& the added header lines.
19169 The &%headers_add%& option is expanded after &%errors_to%&, but before
19170 &%headers_remove%& and &%transport%&. If an item is empty, or if
19171 an item expansion is forced to fail, the item has no effect. Other expansion
19172 failures are treated as configuration errors.
19174 Unlike most options, &%headers_add%& can be specified multiple times
19175 for a router; all listed headers are added.
19177 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
19178 router that has the &%one_time%& option set.
19180 .cindex "duplicate addresses"
19181 .oindex "&%unseen%&"
19182 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19183 additions are deleted when the address is passed on to subsequent routers.
19184 For a &%redirect%& router, if a generated address is the same as the incoming
19185 address, this can lead to duplicate addresses with different header
19186 modifications. Exim does not do duplicate deliveries (except, in certain
19187 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
19188 which of the duplicates is discarded, so this ambiguous situation should be
19189 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
19193 .option headers_remove routers list&!! unset
19194 .cindex "header lines" "removing"
19195 .cindex "router" "removing header lines"
19196 This option specifies a list of text headers,
19197 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19198 that is associated with any addresses that are accepted by the router.
19199 However, the option has no effect when an address is just being verified.
19200 Each list item is separately expanded, at transport time.
19201 If an item ends in *, it will match any header with the given prefix.
19203 the text is used to remove header lines at transport time is described in
19204 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
19205 the message is in the process of being transported. This means that references
19206 to header lines in string expansions in the transport's configuration still
19207 &"see"& the original header lines.
19209 The &%headers_remove%& option is handled after &%errors_to%& and
19210 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
19211 the item has no effect. Other expansion failures are treated as configuration
19214 Unlike most options, &%headers_remove%& can be specified multiple times
19215 for a router; all listed headers are removed.
19217 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
19218 router that has the &%one_time%& option set.
19220 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19221 removal requests are deleted when the address is passed on to subsequent
19222 routers, and this can lead to problems with duplicates -- see the similar
19223 warning for &%headers_add%& above.
19225 &*Warning 3*&: Because of the separate expansion of the list items,
19226 items that contain a list separator must have it doubled.
19227 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
19231 .option ignore_target_hosts routers "host list&!!" unset
19232 .cindex "IP address" "discarding"
19233 .cindex "router" "discarding IP addresses"
19234 Although this option is a host list, it should normally contain IP address
19235 entries rather than names. If any host that is looked up by the router has an
19236 IP address that matches an item in this list, Exim behaves as if that IP
19237 address did not exist. This option allows you to cope with rogue DNS entries
19240 remote.domain.example. A 127.0.0.1
19244 ignore_target_hosts = 127.0.0.1
19246 on the relevant router. If all the hosts found by a &(dnslookup)& router are
19247 discarded in this way, the router declines. In a conventional configuration, an
19248 attempt to mail to such a domain would normally provoke the &"unrouteable
19249 domain"& error, and an attempt to verify an address in the domain would fail.
19250 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
19251 router declines if presented with one of the listed addresses.
19253 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
19254 means of the first or the second of the following settings, respectively:
19256 ignore_target_hosts = 0.0.0.0/0
19257 ignore_target_hosts = <; 0::0/0
19259 The pattern in the first line matches all IPv4 addresses, whereas the pattern
19260 in the second line matches all IPv6 addresses.
19262 This option may also be useful for ignoring link-local and site-local IPv6
19263 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
19264 is expanded before use as a list, it is possible to make it dependent on the
19265 domain that is being routed.
19267 .vindex "&$host_address$&"
19268 During its expansion, &$host_address$& is set to the IP address that is being
19271 .option initgroups routers boolean false
19272 .cindex "additional groups"
19273 .cindex "groups" "additional"
19274 .cindex "local transports" "uid and gid"
19275 .cindex "transport" "local"
19276 If the router queues an address for a transport, and this option is true, and
19277 the uid supplied by the router is not overridden by the transport, the
19278 &[initgroups()]& function is called when running the transport to ensure that
19279 any additional groups associated with the uid are set up. See also &%group%&
19280 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
19284 .option local_part_prefix routers&!? "string list" unset
19285 .cindex affix "router precondition"
19286 .cindex "router" "prefix for local part"
19287 .cindex "prefix" "for local part, used in router"
19288 If this option is set, the router is skipped unless the local part starts with
19289 one of the given strings, or &%local_part_prefix_optional%& is true. See
19290 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
19293 The list is scanned from left to right, and the first prefix that matches is
19294 used. A limited form of wildcard is available; if the prefix begins with an
19295 asterisk, it matches the longest possible sequence of arbitrary characters at
19296 the start of the local part. An asterisk should therefore always be followed by
19297 some character that does not occur in normal local parts.
19298 .cindex "multiple mailboxes"
19299 .cindex "mailbox" "multiple"
19300 Wildcarding can be used to set up multiple user mailboxes, as described in
19301 section &<<SECTmulbox>>&.
19303 .vindex "&$local_part$&"
19304 .vindex "&$local_part_prefix$&"
19305 During the testing of the &%local_parts%& option, and while the router is
19306 running, the prefix is removed from the local part, and is available in the
19307 expansion variable &$local_part_prefix$&. When a message is being delivered, if
19308 the router accepts the address, this remains true during subsequent delivery by
19309 a transport. In particular, the local part that is transmitted in the RCPT
19310 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
19311 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
19312 the relevant transport.
19314 .vindex &$local_part_prefix_v$&
19315 If wildcarding (above) was used then the part of the prefix matching the
19316 wildcard is available in &$local_part_prefix_v$&.
19318 When an address is being verified, &%local_part_prefix%& affects only the
19319 behaviour of the router. If the callout feature of verification is in use, this
19320 means that the full address, including the prefix, will be used during the
19323 The prefix facility is commonly used to handle local parts of the form
19324 &%owner-something%&. Another common use is to support local parts of the form
19325 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
19326 to tell a user their forwarding is broken &-- by placing a router like this one
19327 immediately before the router that handles &_.forward_& files:
19331 local_part_prefix = real-
19333 transport = local_delivery
19335 For security, it would probably be a good idea to restrict the use of this
19336 router to locally-generated messages, using a condition such as this:
19338 condition = ${if match {$sender_host_address}\
19339 {\N^(|127\.0\.0\.1)$\N}}
19342 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
19343 both conditions must be met if not optional. Care must be taken if wildcards
19344 are used in both a prefix and a suffix on the same router. Different
19345 separator characters must be used to avoid ambiguity.
19348 .option local_part_prefix_optional routers boolean false
19349 See &%local_part_prefix%& above.
19353 .option local_part_suffix routers&!? "string list" unset
19354 .cindex "router" "suffix for local part"
19355 .cindex "suffix for local part" "used in router"
19356 This option operates in the same way as &%local_part_prefix%&, except that the
19357 local part must end (rather than start) with the given string, the
19358 &%local_part_suffix_optional%& option determines whether the suffix is
19359 mandatory, and the wildcard * character, if present, must be the last
19360 character of the suffix. This option facility is commonly used to handle local
19361 parts of the form &%something-request%& and multiple user mailboxes of the form
19365 .option local_part_suffix_optional routers boolean false
19366 See &%local_part_suffix%& above.
19370 .option local_parts routers&!? "local part list&!!" unset
19371 .cindex "router" "restricting to specific local parts"
19372 .cindex "local part" "checking in router"
19373 The router is run only if the local part of the address matches the list.
19374 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19376 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
19377 string is expanded, it is possible to make it depend on the domain, for
19380 local_parts = dbm;/usr/local/specials/$domain_data
19382 .vindex "&$local_part_data$&"
19383 If the match is achieved by a lookup, the data that the lookup returned
19384 for the local part is placed in the variable &$local_part_data$& for use in
19385 expansions of the router's private options or in the transport.
19386 You might use this option, for
19387 example, if you have a large number of local virtual domains, and you want to
19388 send all postmaster mail to the same place without having to set up an alias in
19389 each virtual domain:
19393 local_parts = postmaster
19394 data = postmaster@real.domain.example
19398 .option log_as_local routers boolean "see below"
19399 .cindex "log" "delivery line"
19400 .cindex "delivery" "log line format"
19401 Exim has two logging styles for delivery, the idea being to make local
19402 deliveries stand out more visibly from remote ones. In the &"local"& style, the
19403 recipient address is given just as the local part, without a domain. The use of
19404 this style is controlled by this option. It defaults to true for the &(accept)&
19405 router, and false for all the others. This option applies only when a
19406 router assigns an address to a transport. It has no effect on routers that
19407 redirect addresses.
19411 .option more routers boolean&!! true
19412 The result of string expansion for this option must be a valid boolean value,
19413 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19414 result causes an error, and delivery is deferred. If the expansion is forced to
19415 fail, the default value for the option (true) is used. Other failures cause
19416 delivery to be deferred.
19418 If this option is set false, and the router declines to handle the address, no
19419 further routers are tried, routing fails, and the address is bounced.
19421 However, if the router explicitly passes an address to the following router by
19422 means of the setting
19426 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
19427 does not affect the behaviour if one of the precondition tests fails. In that
19428 case, the address is always passed to the next router.
19430 Note that &%address_data%& is not considered to be a precondition. If its
19431 expansion is forced to fail, the router declines, and the value of &%more%&
19432 controls what happens next.
19435 .option pass_on_timeout routers boolean false
19436 .cindex "timeout" "of router"
19437 .cindex "router" "timeout"
19438 If a router times out during a host lookup, it normally causes deferral of the
19439 address. If &%pass_on_timeout%& is set, the address is passed on to the next
19440 router, overriding &%no_more%&. This may be helpful for systems that are
19441 intermittently connected to the Internet, or those that want to pass to a smart
19442 host any messages that cannot immediately be delivered.
19444 There are occasional other temporary errors that can occur while doing DNS
19445 lookups. They are treated in the same way as a timeout, and this option
19446 applies to all of them.
19450 .option pass_router routers string unset
19451 .cindex "router" "go to after &""pass""&"
19452 Routers that recognize the generic &%self%& option (&(dnslookup)&,
19453 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
19454 routing to continue, and overriding a false setting of &%more%&. When one of
19455 these routers returns &"pass"&, the address is normally handed on to the next
19456 router in sequence. This can be changed by setting &%pass_router%& to the name
19457 of another router. However (unlike &%redirect_router%&) the named router must
19458 be below the current router, to avoid loops. Note that this option applies only
19459 to the special case of &"pass"&. It does not apply when a router returns
19460 &"decline"& because it cannot handle an address.
19464 .option redirect_router routers string unset
19465 .cindex "router" "start at after redirection"
19466 Sometimes an administrator knows that it is pointless to reprocess addresses
19467 generated from alias or forward files with the same router again. For
19468 example, if an alias file translates real names into login ids there is no
19469 point searching the alias file a second time, especially if it is a large file.
19471 The &%redirect_router%& option can be set to the name of any router instance.
19472 It causes the routing of any generated addresses to start at the named router
19473 instead of at the first router. This option has no effect if the router in
19474 which it is set does not generate new addresses.
19478 .option require_files routers&!? "string list&!!" unset
19479 .cindex "file" "requiring for router"
19480 .cindex "router" "requiring file existence"
19481 This option provides a general mechanism for predicating the running of a
19482 router on the existence or non-existence of certain files or directories.
19483 Before running a router, as one of its precondition tests, Exim works its way
19484 through the &%require_files%& list, expanding each item separately.
19486 Because the list is split before expansion, any colons in expansion items must
19487 be doubled, or the facility for using a different list separator must be used
19488 (&<<SECTlistsepchange>>&).
19489 If any expansion is forced to fail, the item is ignored. Other expansion
19490 failures cause routing of the address to be deferred.
19492 If any expanded string is empty, it is ignored. Otherwise, except as described
19493 below, each string must be a fully qualified file path, optionally preceded by
19494 &"!"&. The paths are passed to the &[stat()]& function to test for the
19495 existence of the files or directories. The router is skipped if any paths not
19496 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
19499 If &[stat()]& cannot determine whether a file exists or not, delivery of
19500 the message is deferred. This can happen when NFS-mounted filesystems are
19503 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
19504 options, so you cannot use it to check for the existence of a file in which to
19505 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
19506 full list of the order in which preconditions are evaluated.) However, as
19507 these options are all expanded, you can use the &%exists%& expansion condition
19508 to make such tests. The &%require_files%& option is intended for checking files
19509 that the router may be going to use internally, or which are needed by a
19510 transport (e.g., &_.procmailrc_&).
19512 During delivery, the &[stat()]& function is run as root, but there is a
19513 facility for some checking of the accessibility of a file by another user.
19514 This is not a proper permissions check, but just a &"rough"& check that
19515 operates as follows:
19517 If an item in a &%require_files%& list does not contain any forward slash
19518 characters, it is taken to be the user (and optional group, separated by a
19519 comma) to be checked for subsequent files in the list. If no group is specified
19520 but the user is specified symbolically, the gid associated with the uid is
19523 require_files = mail:/some/file
19524 require_files = $local_part_data:$home/.procmailrc
19526 If a user or group name in a &%require_files%& list does not exist, the
19527 &%require_files%& condition fails.
19529 Exim performs the check by scanning along the components of the file path, and
19530 checking the access for the given uid and gid. It checks for &"x"& access on
19531 directories, and &"r"& access on the final file. Note that this means that file
19532 access control lists, if the operating system has them, are ignored.
19534 &*Warning 1*&: When the router is being run to verify addresses for an
19535 incoming SMTP message, Exim is not running as root, but under its own uid. This
19536 may affect the result of a &%require_files%& check. In particular, &[stat()]&
19537 may yield the error EACCES (&"Permission denied"&). This means that the Exim
19538 user is not permitted to read one of the directories on the file's path.
19540 &*Warning 2*&: Even when Exim is running as root while delivering a message,
19541 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
19542 without root access. In this case, if a check for access by a particular user
19543 is requested, Exim creates a subprocess that runs as that user, and tries the
19544 check again in that process.
19546 The default action for handling an unresolved EACCES is to consider it to
19547 be caused by a configuration error, and routing is deferred because the
19548 existence or non-existence of the file cannot be determined. However, in some
19549 circumstances it may be desirable to treat this condition as if the file did
19550 not exist. If the filename (or the exclamation mark that precedes the filename
19551 for non-existence) is preceded by a plus sign, the EACCES error is treated
19552 as if the file did not exist. For example:
19554 require_files = +/some/file
19556 If the router is not an essential part of verification (for example, it
19557 handles users' &_.forward_& files), another solution is to set the &%verify%&
19558 option false so that the router is skipped when verifying.
19562 .option retry_use_local_part routers boolean "see below"
19563 .cindex "hints database" "retry keys"
19564 .cindex "local part" "in retry keys"
19565 When a delivery suffers a temporary routing failure, a retry record is created
19566 in Exim's hints database. For addresses whose routing depends only on the
19567 domain, the key for the retry record should not involve the local part, but for
19568 other addresses, both the domain and the local part should be included.
19569 Usually, remote routing is of the former kind, and local routing is of the
19572 This option controls whether the local part is used to form the key for retry
19573 hints for addresses that suffer temporary errors while being handled by this
19574 router. The default value is true for any router that has any of
19575 &%check_local_user%&,
19578 &%local_part_prefix%&,
19579 &%local_part_suffix%&,
19582 set, and false otherwise. Note that this option does not apply to hints keys
19583 for transport delays; they are controlled by a generic transport option of the
19586 Failing to set this option when it is needed
19587 (because a remote router handles only some of the local-parts for a domain)
19588 can result in incorrect error messages being generated.
19590 The setting of &%retry_use_local_part%& applies only to the router on which it
19591 appears. If the router generates child addresses, they are routed
19592 independently; this setting does not become attached to them.
19596 .option router_home_directory routers string&!! unset
19597 .cindex "router" "home directory for"
19598 .cindex "home directory" "for router"
19600 This option sets a home directory for use while the router is running. (Compare
19601 &%transport_home_directory%&, which sets a home directory for later
19602 transporting.) In particular, if used on a &(redirect)& router, this option
19603 sets a value for &$home$& while a filter is running. The value is expanded;
19604 forced expansion failure causes the option to be ignored &-- other failures
19605 cause the router to defer.
19607 Expansion of &%router_home_directory%& happens immediately after the
19608 &%check_local_user%& test (if configured), before any further expansions take
19610 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19612 While the router is running, &%router_home_directory%& overrides the value of
19613 &$home$& that came from &%check_local_user%&.
19615 When a router accepts an address and assigns it to a local transport (including
19616 the cases when a &(redirect)& router generates a pipe, file, or autoreply
19617 delivery), the home directory setting for the transport is taken from the first
19618 of these values that is set:
19621 The &%home_directory%& option on the transport;
19623 The &%transport_home_directory%& option on the router;
19625 The password data if &%check_local_user%& is set on the router;
19627 The &%router_home_directory%& option on the router.
19630 In other words, &%router_home_directory%& overrides the password data for the
19631 router, but not for the transport.
19635 .option self routers string freeze
19636 .cindex "MX record" "pointing to local host"
19637 .cindex "local host" "MX pointing to"
19638 This option applies to those routers that use a recipient address to find a
19639 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
19640 and &(manualroute)& routers.
19641 Certain configurations of the &(queryprogram)& router can also specify a list
19643 Usually such routers are configured to send the message to a remote host via an
19644 &(smtp)& transport. The &%self%& option specifies what happens when the first
19645 host on the list turns out to be the local host.
19646 The way in which Exim checks for the local host is described in section
19647 &<<SECTreclocipadd>>&.
19649 Normally this situation indicates either an error in Exim's configuration (for
19650 example, the router should be configured not to process this domain), or an
19651 error in the DNS (for example, the MX should not point to this host). For this
19652 reason, the default action is to log the incident, defer the address, and
19653 freeze the message. The following alternatives are provided for use in special
19658 Delivery of the message is tried again later, but the message is not frozen.
19660 .vitem "&%reroute%&: <&'domain'&>"
19661 The domain is changed to the given domain, and the address is passed back to
19662 be reprocessed by the routers. No rewriting of headers takes place. This
19663 behaviour is essentially a redirection.
19665 .vitem "&%reroute: rewrite:%& <&'domain'&>"
19666 The domain is changed to the given domain, and the address is passed back to be
19667 reprocessed by the routers. Any headers that contain the original domain are
19672 .vindex "&$self_hostname$&"
19673 The router passes the address to the next router, or to the router named in the
19674 &%pass_router%& option if it is set. This overrides &%no_more%&. During
19675 subsequent routing and delivery, the variable &$self_hostname$& contains the
19676 name of the local host that the router encountered. This can be used to
19677 distinguish between different cases for hosts with multiple names. The
19683 ensures that only those addresses that routed to the local host are passed on.
19684 Without &%no_more%&, addresses that were declined for other reasons would also
19685 be passed to the next router.
19688 Delivery fails and an error report is generated.
19691 .cindex "local host" "sending to"
19692 The anomaly is ignored and the address is queued for the transport. This
19693 setting should be used with extreme caution. For an &(smtp)& transport, it
19694 makes sense only in cases where the program that is listening on the SMTP port
19695 is not this version of Exim. That is, it must be some other MTA, or Exim with a
19696 different configuration file that handles the domain in another way.
19701 .option senders routers&!? "address list&!!" unset
19702 .cindex "router" "checking senders"
19703 If this option is set, the router is skipped unless the message's sender
19704 address matches something on the list.
19705 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19708 There are issues concerning verification when the running of routers is
19709 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
19710 setting, it sets the sender to the null string. When using the &%-bt%& option
19711 to check a configuration file, it is necessary also to use the &%-f%& option to
19712 set an appropriate sender. For incoming mail, the sender is unset when
19713 verifying the sender, but is available when verifying any recipients. If the
19714 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
19718 .option set routers "string list" unset
19719 .cindex router variables
19720 This option may be used multiple times on a router;
19721 because of this the list aspect is mostly irrelevant.
19722 The list separator is a semicolon but can be changed in the
19725 Each list-element given must be of the form &"name = value"&
19726 and the names used must start with the string &"r_"&.
19727 Values containing a list-separator should have them doubled.
19728 When a router runs, the strings are evaluated in order,
19729 to create variables which are added to the set associated with
19731 The variable is set with the expansion of the value.
19732 The variables can be used by the router options
19733 (not including any preconditions)
19734 and by the transport.
19735 Later definitions of a given named variable will override former ones.
19736 Variable use is via the usual &$r_...$& syntax.
19738 This is similar to the &%address_data%& option, except that
19739 many independent variables can be used, with choice of naming.
19742 .option translate_ip_address routers string&!! unset
19743 .cindex "IP address" "translating"
19744 .cindex "packet radio"
19745 .cindex "router" "IP address translation"
19746 There exist some rare networking situations (for example, packet radio) where
19747 it is helpful to be able to translate IP addresses generated by normal routing
19748 mechanisms into other IP addresses, thus performing a kind of manual IP
19749 routing. This should be done only if the normal IP routing of the TCP/IP stack
19750 is inadequate or broken. Because this is an extremely uncommon requirement, the
19751 code to support this option is not included in the Exim binary unless
19752 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
19754 .vindex "&$host_address$&"
19755 The &%translate_ip_address%& string is expanded for every IP address generated
19756 by the router, with the generated address set in &$host_address$&. If the
19757 expansion is forced to fail, no action is taken.
19758 For any other expansion error, delivery of the message is deferred.
19759 If the result of the expansion is an IP address, that replaces the original
19760 address; otherwise the result is assumed to be a host name &-- this is looked
19761 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
19762 produce one or more replacement IP addresses. For example, to subvert all IP
19763 addresses in some specific networks, this could be added to a router:
19765 translate_ip_address = \
19766 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
19769 The file would contain lines like
19771 10.2.3.128/26 some.host
19772 10.8.4.34/26 10.44.8.15
19774 You should not make use of this facility unless you really understand what you
19779 .option transport routers string&!! unset
19780 This option specifies the transport to be used when a router accepts an address
19781 and sets it up for delivery. A transport is never needed if a router is used
19782 only for verification. The value of the option is expanded at routing time,
19783 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
19784 and result must be the name of one of the configured transports. If it is not,
19785 delivery is deferred.
19787 The &%transport%& option is not used by the &(redirect)& router, but it does
19788 have some private options that set up transports for pipe and file deliveries
19789 (see chapter &<<CHAPredirect>>&).
19793 .option transport_current_directory routers string&!! unset
19794 .cindex "current directory for local transport"
19795 This option associates a current directory with any address that is routed
19796 to a local transport. This can happen either because a transport is
19797 explicitly configured for the router, or because it generates a delivery to a
19798 file or a pipe. During the delivery process (that is, at transport time), this
19799 option string is expanded and is set as the current directory, unless
19800 overridden by a setting on the transport.
19801 If the expansion fails for any reason, including forced failure, an error is
19802 logged, and delivery is deferred.
19803 See chapter &<<CHAPenvironment>>& for details of the local delivery
19809 .option transport_home_directory routers string&!! "see below"
19810 .cindex "home directory" "for local transport"
19811 This option associates a home directory with any address that is routed to a
19812 local transport. This can happen either because a transport is explicitly
19813 configured for the router, or because it generates a delivery to a file or a
19814 pipe. During the delivery process (that is, at transport time), the option
19815 string is expanded and is set as the home directory, unless overridden by a
19816 setting of &%home_directory%& on the transport.
19817 If the expansion fails for any reason, including forced failure, an error is
19818 logged, and delivery is deferred.
19820 If the transport does not specify a home directory, and
19821 &%transport_home_directory%& is not set for the router, the home directory for
19822 the transport is taken from the password data if &%check_local_user%& is set for
19823 the router. Otherwise it is taken from &%router_home_directory%& if that option
19824 is set; if not, no home directory is set for the transport.
19826 See chapter &<<CHAPenvironment>>& for further details of the local delivery
19832 .option unseen routers boolean&!! false
19833 .cindex "router" "carrying on after success"
19834 The result of string expansion for this option must be a valid boolean value,
19835 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19836 result causes an error, and delivery is deferred. If the expansion is forced to
19837 fail, the default value for the option (false) is used. Other failures cause
19838 delivery to be deferred.
19840 When this option is set true, routing does not cease if the router accepts the
19841 address. Instead, a copy of the incoming address is passed to the next router,
19842 overriding a false setting of &%more%&. There is little point in setting
19843 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
19844 the value of &%unseen%& contains expansion items (and therefore, presumably, is
19845 sometimes true and sometimes false).
19847 .cindex "copy of message (&%unseen%& option)"
19848 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
19849 qualifier in filter files. It can be used to cause copies of messages to be
19850 delivered to some other destination, while also carrying out a normal delivery.
19851 In effect, the current address is made into a &"parent"& that has two children
19852 &-- one that is delivered as specified by this router, and a clone that goes on
19853 to be routed further. For this reason, &%unseen%& may not be combined with the
19854 &%one_time%& option in a &(redirect)& router.
19856 &*Warning*&: Header lines added to the address (or specified for removal) by
19857 this router or by previous routers affect the &"unseen"& copy of the message
19858 only. The clone that continues to be processed by further routers starts with
19859 no added headers and none specified for removal. For a &%redirect%& router, if
19860 a generated address is the same as the incoming address, this can lead to
19861 duplicate addresses with different header modifications. Exim does not do
19862 duplicate deliveries (except, in certain circumstances, to pipes -- see section
19863 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
19864 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
19865 &%redirect%& router may be of help.
19867 Unlike the handling of header modifications, any data that was set by the
19868 &%address_data%& option in the current or previous routers &'is'& passed on to
19869 subsequent routers.
19872 .option user routers string&!! "see below"
19873 .cindex "uid (user id)" "local delivery"
19874 .cindex "local transports" "uid and gid"
19875 .cindex "transport" "local"
19876 .cindex "router" "user for filter processing"
19877 .cindex "filter" "user for processing"
19878 When a router queues an address for a transport, and the transport does not
19879 specify a user, the user given here is used when running the delivery process.
19880 The user may be specified numerically or by name. If expansion fails, the
19881 error is logged and delivery is deferred.
19882 This user is also used by the &(redirect)& router when running a filter file.
19883 The default is unset, except when &%check_local_user%& is set. In this case,
19884 the default is taken from the password information. If the user is specified as
19885 a name, and &%group%& is not set, the group associated with the user is used.
19886 See also &%initgroups%& and &%group%& and the discussion in chapter
19887 &<<CHAPenvironment>>&.
19891 .option verify routers&!? boolean true
19892 Setting this option has the effect of setting &%verify_sender%& and
19893 &%verify_recipient%& to the same value.
19896 .option verify_only routers&!? boolean false
19897 .cindex "EXPN" "with &%verify_only%&"
19899 .cindex "router" "used only when verifying"
19900 If this option is set, the router is used only when verifying an address,
19901 delivering in cutthrough mode or
19902 testing with the &%-bv%& option, not when actually doing a delivery, testing
19903 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
19904 restricted to verifying only senders or recipients by means of
19905 &%verify_sender%& and &%verify_recipient%&.
19907 &*Warning*&: When the router is being run to verify addresses for an incoming
19908 SMTP message, Exim is not running as root, but under its own uid. If the router
19909 accesses any files, you need to make sure that they are accessible to the Exim
19913 .option verify_recipient routers&!? boolean true
19914 If this option is false, the router is skipped when verifying recipient
19916 delivering in cutthrough mode
19917 or testing recipient verification using &%-bv%&.
19918 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19920 See also the &$verify_mode$& variable.
19923 .option verify_sender routers&!? boolean true
19924 If this option is false, the router is skipped when verifying sender addresses
19925 or testing sender verification using &%-bvs%&.
19926 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19928 See also the &$verify_mode$& variable.
19929 .ecindex IIDgenoprou1
19930 .ecindex IIDgenoprou2
19937 . ////////////////////////////////////////////////////////////////////////////
19938 . ////////////////////////////////////////////////////////////////////////////
19940 .chapter "The accept router" "CHID4"
19941 .cindex "&(accept)& router"
19942 .cindex "routers" "&(accept)&"
19943 The &(accept)& router has no private options of its own. Unless it is being
19944 used purely for verification (see &%verify_only%&) a transport is required to
19945 be defined by the generic &%transport%& option. If the preconditions that are
19946 specified by generic options are met, the router accepts the address and queues
19947 it for the given transport. The most common use of this router is for setting
19948 up deliveries to local mailboxes. For example:
19952 domains = mydomain.example
19954 transport = local_delivery
19956 The &%domains%& condition in this example checks the domain of the address, and
19957 &%check_local_user%& checks that the local part is the login of a local user.
19958 When both preconditions are met, the &(accept)& router runs, and queues the
19959 address for the &(local_delivery)& transport.
19966 . ////////////////////////////////////////////////////////////////////////////
19967 . ////////////////////////////////////////////////////////////////////////////
19969 .chapter "The dnslookup router" "CHAPdnslookup"
19970 .scindex IIDdnsrou1 "&(dnslookup)& router"
19971 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
19972 The &(dnslookup)& router looks up the hosts that handle mail for the
19973 recipient's domain in the DNS. A transport must always be set for this router,
19974 unless &%verify_only%& is set.
19976 If SRV support is configured (see &%check_srv%& below), Exim first searches for
19977 SRV records. If none are found, or if SRV support is not configured,
19978 MX records are looked up. If no MX records exist, address records are sought.
19979 However, &%mx_domains%& can be set to disable the direct use of address
19982 MX records of equal priority are sorted by Exim into a random order. Exim then
19983 looks for address records for the host names obtained from MX or SRV records.
19984 When a host has more than one IP address, they are sorted into a random order,
19985 except that IPv6 addresses are sorted before IPv4 addresses. If all the
19986 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
19987 generic option, the router declines.
19989 Unless they have the highest priority (lowest MX value), MX records that point
19990 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
19991 are discarded, together with any other MX records of equal or lower priority.
19993 .cindex "MX record" "pointing to local host"
19994 .cindex "local host" "MX pointing to"
19995 .oindex "&%self%&" "in &(dnslookup)& router"
19996 If the host pointed to by the highest priority MX record, or looked up as an
19997 address record, is the local host, or matches &%hosts_treat_as_local%&, what
19998 happens is controlled by the generic &%self%& option.
20001 .section "Problems with DNS lookups" "SECTprowitdnsloo"
20002 There have been problems with DNS servers when SRV records are looked up.
20003 Some misbehaving servers return a DNS error or timeout when a non-existent
20004 SRV record is sought. Similar problems have in the past been reported for
20005 MX records. The global &%dns_again_means_nonexist%& option can help with this
20006 problem, but it is heavy-handed because it is a global option.
20008 For this reason, there are two options, &%srv_fail_domains%& and
20009 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
20010 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
20011 an attempt to look up an SRV or MX record causes one of these results, and the
20012 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
20013 such record"&. In the case of an SRV lookup, this means that the router
20014 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
20015 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
20016 case routing fails.
20019 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
20020 .cindex "&(dnslookup)& router" "declines"
20021 There are a few cases where a &(dnslookup)& router will decline to accept
20022 an address; if such a router is expected to handle "all remaining non-local
20023 domains", then it is important to set &%no_more%&.
20025 The router will defer rather than decline if the domain
20026 is found in the &%fail_defer_domains%& router option.
20028 Reasons for a &(dnslookup)& router to decline currently include:
20030 The domain does not exist in DNS
20032 The domain exists but the MX record's host part is just "."; this is a common
20033 convention (borrowed from SRV) used to indicate that there is no such service
20034 for this domain and to not fall back to trying A/AAAA records.
20036 Ditto, but for SRV records, when &%check_srv%& is set on this router.
20038 MX record points to a non-existent host.
20040 MX record points to an IP address and the main section option
20041 &%allow_mx_to_ip%& is not set.
20043 MX records exist and point to valid hosts, but all hosts resolve only to
20044 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
20046 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
20047 &%dns_check_names_pattern%& for handling one variant of this)
20049 &%check_secondary_mx%& is set on this router but the local host can
20050 not be found in the MX records (see below)
20056 .section "Private options for dnslookup" "SECID118"
20057 .cindex "options" "&(dnslookup)& router"
20058 The private options for the &(dnslookup)& router are as follows:
20060 .option check_secondary_mx dnslookup boolean false
20061 .cindex "MX record" "checking for secondary"
20062 If this option is set, the router declines unless the local host is found in
20063 (and removed from) the list of hosts obtained by MX lookup. This can be used to
20064 process domains for which the local host is a secondary mail exchanger
20065 differently to other domains. The way in which Exim decides whether a host is
20066 the local host is described in section &<<SECTreclocipadd>>&.
20069 .option check_srv dnslookup string&!! unset
20070 .cindex "SRV record" "enabling use of"
20071 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
20072 addition to MX and address records. The support is disabled by default. To
20073 enable SRV support, set the &%check_srv%& option to the name of the service
20074 required. For example,
20078 looks for SRV records that refer to the normal smtp service. The option is
20079 expanded, so the service name can vary from message to message or address
20080 to address. This might be helpful if SRV records are being used for a
20081 submission service. If the expansion is forced to fail, the &%check_srv%&
20082 option is ignored, and the router proceeds to look for MX records in the
20085 When the expansion succeeds, the router searches first for SRV records for
20086 the given service (it assumes TCP protocol). A single SRV record with a
20087 host name that consists of just a single dot indicates &"no such service for
20088 this domain"&; if this is encountered, the router declines. If other kinds of
20089 SRV record are found, they are used to construct a host list for delivery
20090 according to the rules of RFC 2782. MX records are not sought in this case.
20092 When no SRV records are found, MX records (and address records) are sought in
20093 the traditional way. In other words, SRV records take precedence over MX
20094 records, just as MX records take precedence over address records. Note that
20095 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
20096 defined it. It is apparently believed that MX records are sufficient for email
20097 and that SRV records should not be used for this purpose. However, SRV records
20098 have an additional &"weight"& feature which some people might find useful when
20099 trying to split an SMTP load between hosts of different power.
20101 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
20102 when there is a DNS lookup error.
20107 .option fail_defer_domains dnslookup "domain list&!!" unset
20108 .cindex "MX record" "not found"
20109 DNS lookups for domains matching &%fail_defer_domains%&
20110 which find no matching record will cause the router to defer
20111 rather than the default behaviour of decline.
20112 This maybe be useful for queueing messages for a newly created
20113 domain while the DNS configuration is not ready.
20114 However, it will result in any message with mistyped domains
20118 .option ipv4_only "string&!!" unset
20119 .cindex IPv6 disabling
20120 .cindex DNS "IPv6 disabling"
20121 The string is expanded, and if the result is anything but a forced failure,
20122 or an empty string, or one of the strings “0” or “no” or “false”
20123 (checked without regard to the case of the letters),
20124 only A records are used.
20126 .option ipv4_prefer "string&!!" unset
20127 .cindex IPv4 preference
20128 .cindex DNS "IPv4 preference"
20129 The string is expanded, and if the result is anything but a forced failure,
20130 or an empty string, or one of the strings “0” or “no” or “false”
20131 (checked without regard to the case of the letters),
20132 A records are sorted before AAAA records (inverting the default).
20134 .option mx_domains dnslookup "domain list&!!" unset
20135 .cindex "MX record" "required to exist"
20136 .cindex "SRV record" "required to exist"
20137 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
20138 record in order to be recognized. (The name of this option could be improved.)
20139 For example, if all the mail hosts in &'fict.example'& are known to have MX
20140 records, except for those in &'discworld.fict.example'&, you could use this
20143 mx_domains = ! *.discworld.fict.example : *.fict.example
20145 This specifies that messages addressed to a domain that matches the list but
20146 has no MX record should be bounced immediately instead of being routed using
20147 the address record.
20150 .option mx_fail_domains dnslookup "domain list&!!" unset
20151 If the DNS lookup for MX records for one of the domains in this list causes a
20152 DNS lookup error, Exim behaves as if no MX records were found. See section
20153 &<<SECTprowitdnsloo>>& for more discussion.
20158 .option qualify_single dnslookup boolean true
20159 .cindex "DNS" "resolver options"
20160 .cindex "DNS" "qualifying single-component names"
20161 When this option is true, the resolver option RES_DEFNAMES is set for DNS
20162 lookups. Typically, but not standardly, this causes the resolver to qualify
20163 single-component names with the default domain. For example, on a machine
20164 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
20165 &'thesaurus.ref.example'& inside the resolver. For details of what your
20166 resolver actually does, consult your man pages for &'resolver'& and
20171 .option rewrite_headers dnslookup boolean true
20172 .cindex "rewriting" "header lines"
20173 .cindex "header lines" "rewriting"
20174 If the domain name in the address that is being processed is not fully
20175 qualified, it may be expanded to its full form by a DNS lookup. For example, if
20176 an address is specified as &'dormouse@teaparty'&, the domain might be
20177 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
20178 occur as a result of setting the &%widen_domains%& option. If
20179 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
20180 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
20181 header lines of the message are rewritten with the full domain name.
20183 This option should be turned off only when it is known that no message is
20184 ever going to be sent outside an environment where the abbreviation makes
20187 When an MX record is looked up in the DNS and matches a wildcard record, name
20188 servers normally return a record containing the name that has been looked up,
20189 making it impossible to detect whether a wildcard was present or not. However,
20190 some name servers have recently been seen to return the wildcard entry. If the
20191 name returned by a DNS lookup begins with an asterisk, it is not used for
20195 .option same_domain_copy_routing dnslookup boolean false
20196 .cindex "address" "copying routing"
20197 Addresses with the same domain are normally routed by the &(dnslookup)& router
20198 to the same list of hosts. However, this cannot be presumed, because the router
20199 options and preconditions may refer to the local part of the address. By
20200 default, therefore, Exim routes each address in a message independently. DNS
20201 servers run caches, so repeated DNS lookups are not normally expensive, and in
20202 any case, personal messages rarely have more than a few recipients.
20204 If you are running mailing lists with large numbers of subscribers at the same
20205 domain, and you are using a &(dnslookup)& router which is independent of the
20206 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20207 lookups for identical domains in one message. In this case, when &(dnslookup)&
20208 routes an address to a remote transport, any other unrouted addresses in the
20209 message that have the same domain are automatically given the same routing
20210 without processing them independently,
20211 provided the following conditions are met:
20214 No router that processed the address specified &%headers_add%& or
20215 &%headers_remove%&.
20217 The router did not change the address in any way, for example, by &"widening"&
20224 .option search_parents dnslookup boolean false
20225 .cindex "DNS" "resolver options"
20226 When this option is true, the resolver option RES_DNSRCH is set for DNS
20227 lookups. This is different from the &%qualify_single%& option in that it
20228 applies to domains containing dots. Typically, but not standardly, it causes
20229 the resolver to search for the name in the current domain and in parent
20230 domains. For example, on a machine in the &'fict.example'& domain, if looking
20231 up &'teaparty.wonderland'& failed, the resolver would try
20232 &'teaparty.wonderland.fict.example'&. For details of what your resolver
20233 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
20235 Setting this option true can cause problems in domains that have a wildcard MX
20236 record, because any domain that does not have its own MX record matches the
20241 .option srv_fail_domains dnslookup "domain list&!!" unset
20242 If the DNS lookup for SRV records for one of the domains in this list causes a
20243 DNS lookup error, Exim behaves as if no SRV records were found. See section
20244 &<<SECTprowitdnsloo>>& for more discussion.
20249 .option widen_domains dnslookup "string list" unset
20250 .cindex "domain" "partial; widening"
20251 If a DNS lookup fails and this option is set, each of its strings in turn is
20252 added onto the end of the domain, and the lookup is tried again. For example,
20255 widen_domains = fict.example:ref.example
20257 is set and a lookup of &'klingon.dictionary'& fails,
20258 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
20259 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
20260 and &%search_parents%& options can cause some widening to be undertaken inside
20261 the DNS resolver. &%widen_domains%& is not applied to sender addresses
20262 when verifying, unless &%rewrite_headers%& is false (not the default).
20265 .section "Effect of qualify_single and search_parents" "SECID119"
20266 When a domain from an envelope recipient is changed by the resolver as a result
20267 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
20268 corresponding address in the message's header lines unless &%rewrite_headers%&
20269 is set false. Exim then re-routes the address, using the full domain.
20271 These two options affect only the DNS lookup that takes place inside the router
20272 for the domain of the address that is being routed. They do not affect lookups
20273 such as that implied by
20277 that may happen while processing a router precondition before the router is
20278 entered. No widening ever takes place for these lookups.
20279 .ecindex IIDdnsrou1
20280 .ecindex IIDdnsrou2
20290 . ////////////////////////////////////////////////////////////////////////////
20291 . ////////////////////////////////////////////////////////////////////////////
20293 .chapter "The ipliteral router" "CHID5"
20294 .cindex "&(ipliteral)& router"
20295 .cindex "domain literal" "routing"
20296 .cindex "routers" "&(ipliteral)&"
20297 This router has no private options. Unless it is being used purely for
20298 verification (see &%verify_only%&) a transport is required to be defined by the
20299 generic &%transport%& option. The router accepts the address if its domain part
20300 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
20301 router handles the address
20305 by setting up delivery to the host with that IP address. IPv4 domain literals
20306 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
20307 are similar, but the address is preceded by &`ipv6:`&. For example:
20309 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
20311 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
20312 grounds that sooner or later somebody will try it.
20314 .oindex "&%self%&" "in &(ipliteral)& router"
20315 If the IP address matches something in &%ignore_target_hosts%&, the router
20316 declines. If an IP literal turns out to refer to the local host, the generic
20317 &%self%& option determines what happens.
20319 The RFCs require support for domain literals; however, their use is
20320 controversial in today's Internet. If you want to use this router, you must
20321 also set the main configuration option &%allow_domain_literals%&. Otherwise,
20322 Exim will not recognize the domain literal syntax in addresses.
20326 . ////////////////////////////////////////////////////////////////////////////
20327 . ////////////////////////////////////////////////////////////////////////////
20329 .chapter "The iplookup router" "CHID6"
20330 .cindex "&(iplookup)& router"
20331 .cindex "routers" "&(iplookup)&"
20332 The &(iplookup)& router was written to fulfil a specific requirement in
20333 Cambridge University (which in fact no longer exists). For this reason, it is
20334 not included in the binary of Exim by default. If you want to include it, you
20337 ROUTER_IPLOOKUP=yes
20339 in your &_Local/Makefile_& configuration file.
20341 The &(iplookup)& router routes an address by sending it over a TCP or UDP
20342 connection to one or more specific hosts. The host can then return the same or
20343 a different address &-- in effect rewriting the recipient address in the
20344 message's envelope. The new address is then passed on to subsequent routers. If
20345 this process fails, the address can be passed on to other routers, or delivery
20346 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
20347 must not be specified for it.
20349 .cindex "options" "&(iplookup)& router"
20350 .option hosts iplookup string unset
20351 This option must be supplied. Its value is a colon-separated list of host
20352 names. The hosts are looked up using &[gethostbyname()]&
20353 (or &[getipnodebyname()]& when available)
20354 and are tried in order until one responds to the query. If none respond, what
20355 happens is controlled by &%optional%&.
20358 .option optional iplookup boolean false
20359 If &%optional%& is true, if no response is obtained from any host, the address
20360 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
20361 delivery to the address is deferred.
20364 .option port iplookup integer 0
20365 .cindex "port" "&(iplookup)& router"
20366 This option must be supplied. It specifies the port number for the TCP or UDP
20370 .option protocol iplookup string udp
20371 This option can be set to &"udp"& or &"tcp"& to specify which of the two
20372 protocols is to be used.
20375 .option query iplookup string&!! "see below"
20376 This defines the content of the query that is sent to the remote hosts. The
20379 $local_part@$domain $local_part@$domain
20381 The repetition serves as a way of checking that a response is to the correct
20382 query in the default case (see &%response_pattern%& below).
20385 .option reroute iplookup string&!! unset
20386 If this option is not set, the rerouted address is precisely the byte string
20387 returned by the remote host, up to the first white space, if any. If set, the
20388 string is expanded to form the rerouted address. It can include parts matched
20389 in the response by &%response_pattern%& by means of numeric variables such as
20390 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
20391 whether or not a pattern is in use. In all cases, the rerouted address must end
20392 up in the form &'local_part@domain'&.
20395 .option response_pattern iplookup string unset
20396 This option can be set to a regular expression that is applied to the string
20397 returned from the remote host. If the pattern does not match the response, the
20398 router declines. If &%response_pattern%& is not set, no checking of the
20399 response is done, unless the query was defaulted, in which case there is a
20400 check that the text returned after the first white space is the original
20401 address. This checks that the answer that has been received is in response to
20402 the correct question. For example, if the response is just a new domain, the
20403 following could be used:
20405 response_pattern = ^([^@]+)$
20406 reroute = $local_part@$1
20409 .option timeout iplookup time 5s
20410 This specifies the amount of time to wait for a response from the remote
20411 machine. The same timeout is used for the &[connect()]& function for a TCP
20412 call. It does not apply to UDP.
20417 . ////////////////////////////////////////////////////////////////////////////
20418 . ////////////////////////////////////////////////////////////////////////////
20420 .chapter "The manualroute router" "CHID7"
20421 .scindex IIDmanrou1 "&(manualroute)& router"
20422 .scindex IIDmanrou2 "routers" "&(manualroute)&"
20423 .cindex "domain" "manually routing"
20424 The &(manualroute)& router is so-called because it provides a way of manually
20425 routing an address according to its domain. It is mainly used when you want to
20426 route addresses to remote hosts according to your own rules, bypassing the
20427 normal DNS routing that looks up MX records. However, &(manualroute)& can also
20428 route to local transports, a facility that may be useful if you want to save
20429 messages for dial-in hosts in local files.
20431 The &(manualroute)& router compares a list of domain patterns with the domain
20432 it is trying to route. If there is no match, the router declines. Each pattern
20433 has associated with it a list of hosts and some other optional data, which may
20434 include a transport. The combination of a pattern and its data is called a
20435 &"routing rule"&. For patterns that do not have an associated transport, the
20436 generic &%transport%& option must specify a transport, unless the router is
20437 being used purely for verification (see &%verify_only%&).
20440 In the case of verification, matching the domain pattern is sufficient for the
20441 router to accept the address. When actually routing an address for delivery,
20442 an address that matches a domain pattern is queued for the associated
20443 transport. If the transport is not a local one, a host list must be associated
20444 with the pattern; IP addresses are looked up for the hosts, and these are
20445 passed to the transport along with the mail address. For local transports, a
20446 host list is optional. If it is present, it is passed in &$host$& as a single
20449 The list of routing rules can be provided as an inline string in
20450 &%route_list%&, or the data can be obtained by looking up the domain in a file
20451 or database by setting &%route_data%&. Only one of these settings may appear in
20452 any one instance of &(manualroute)&. The format of routing rules is described
20453 below, following the list of private options.
20456 .section "Private options for manualroute" "SECTprioptman"
20458 .cindex "options" "&(manualroute)& router"
20459 The private options for the &(manualroute)& router are as follows:
20461 .option host_all_ignored manualroute string defer
20462 See &%host_find_failed%&.
20464 .option host_find_failed manualroute string freeze
20465 This option controls what happens when &(manualroute)& tries to find an IP
20466 address for a host, and the host does not exist. The option can be set to one
20467 of the following values:
20476 The default (&"freeze"&) assumes that this state is a serious configuration
20477 error. The difference between &"pass"& and &"decline"& is that the former
20478 forces the address to be passed to the next router (or the router defined by
20481 overriding &%no_more%&, whereas the latter passes the address to the next
20482 router only if &%more%& is true.
20484 The value &"ignore"& causes Exim to completely ignore a host whose IP address
20485 cannot be found. If all the hosts in the list are ignored, the behaviour is
20486 controlled by the &%host_all_ignored%& option. This takes the same values
20487 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
20489 The &%host_find_failed%& option applies only to a definite &"does not exist"&
20490 state; if a host lookup gets a temporary error, delivery is deferred unless the
20491 generic &%pass_on_timeout%& option is set.
20494 .option hosts_randomize manualroute boolean false
20495 .cindex "randomized host list"
20496 .cindex "host" "list of; randomized"
20497 If this option is set, the order of the items in a host list in a routing rule
20498 is randomized each time the list is used, unless an option in the routing rule
20499 overrides (see below). Randomizing the order of a host list can be used to do
20500 crude load sharing. However, if more than one mail address is routed by the
20501 same router to the same host list, the host lists are considered to be the same
20502 (even though they may be randomized into different orders) for the purpose of
20503 deciding whether to batch the deliveries into a single SMTP transaction.
20505 When &%hosts_randomize%& is true, a host list may be split
20506 into groups whose order is separately randomized. This makes it possible to
20507 set up MX-like behaviour. The boundaries between groups are indicated by an
20508 item that is just &`+`& in the host list. For example:
20510 route_list = * host1:host2:host3:+:host4:host5
20512 The order of the first three hosts and the order of the last two hosts is
20513 randomized for each use, but the first three always end up before the last two.
20514 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
20515 randomized host list is passed to an &(smtp)& transport that also has
20516 &%hosts_randomize set%&, the list is not re-randomized.
20519 .option route_data manualroute string&!! unset
20520 If this option is set, it must expand to yield the data part of a routing rule.
20521 Typically, the expansion string includes a lookup based on the domain. For
20524 route_data = ${lookup{$domain}dbm{/etc/routes}}
20526 If the expansion is forced to fail, or the result is an empty string, the
20527 router declines. Other kinds of expansion failure cause delivery to be
20531 .option route_list manualroute "string list" unset
20532 This string is a list of routing rules, in the form defined below. Note that,
20533 unlike most string lists, the items are separated by semicolons. This is so
20534 that they may contain colon-separated host lists.
20537 .option same_domain_copy_routing manualroute boolean false
20538 .cindex "address" "copying routing"
20539 Addresses with the same domain are normally routed by the &(manualroute)&
20540 router to the same list of hosts. However, this cannot be presumed, because the
20541 router options and preconditions may refer to the local part of the address. By
20542 default, therefore, Exim routes each address in a message independently. DNS
20543 servers run caches, so repeated DNS lookups are not normally expensive, and in
20544 any case, personal messages rarely have more than a few recipients.
20546 If you are running mailing lists with large numbers of subscribers at the same
20547 domain, and you are using a &(manualroute)& router which is independent of the
20548 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20549 lookups for identical domains in one message. In this case, when
20550 &(manualroute)& routes an address to a remote transport, any other unrouted
20551 addresses in the message that have the same domain are automatically given the
20552 same routing without processing them independently. However, this is only done
20553 if &%headers_add%& and &%headers_remove%& are unset.
20558 .section "Routing rules in route_list" "SECID120"
20559 The value of &%route_list%& is a string consisting of a sequence of routing
20560 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
20561 entered as two semicolons. Alternatively, the list separator can be changed as
20562 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
20563 Empty rules are ignored. The format of each rule is
20565 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
20567 The following example contains two rules, each with a simple domain pattern and
20571 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
20572 thes.ref.example mail-3.ref.example:mail-4.ref.example
20574 The three parts of a rule are separated by white space. The pattern and the
20575 list of hosts can be enclosed in quotes if necessary, and if they are, the
20576 usual quoting rules apply. Each rule in a &%route_list%& must start with a
20577 single domain pattern, which is the only mandatory item in the rule. The
20578 pattern is in the same format as one item in a domain list (see section
20579 &<<SECTdomainlist>>&),
20580 except that it may not be the name of an interpolated file.
20581 That is, it may be wildcarded, or a regular expression, or a file or database
20582 lookup (with semicolons doubled, because of the use of semicolon as a separator
20583 in a &%route_list%&).
20585 The rules in &%route_list%& are searched in order until one of the patterns
20586 matches the domain that is being routed. The list of hosts and then options are
20587 then used as described below. If there is no match, the router declines. When
20588 &%route_list%& is set, &%route_data%& must not be set.
20592 .section "Routing rules in route_data" "SECID121"
20593 The use of &%route_list%& is convenient when there are only a small number of
20594 routing rules. For larger numbers, it is easier to use a file or database to
20595 hold the routing information, and use the &%route_data%& option instead.
20596 The value of &%route_data%& is a list of hosts, followed by (optional) options.
20597 Most commonly, &%route_data%& is set as a string that contains an
20598 expansion lookup. For example, suppose we place two routing rules in a file
20601 dict.ref.example: mail-1.ref.example:mail-2.ref.example
20602 thes.ref.example: mail-3.ref.example:mail-4.ref.example
20604 This data can be accessed by setting
20606 route_data = ${lookup{$domain}lsearch{/the/file/name}}
20608 Failure of the lookup results in an empty string, causing the router to
20609 decline. However, you do not have to use a lookup in &%route_data%&. The only
20610 requirement is that the result of expanding the string is a list of hosts,
20611 possibly followed by options, separated by white space. The list of hosts must
20612 be enclosed in quotes if it contains white space.
20617 .section "Format of the list of hosts" "SECID122"
20618 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
20619 always separately expanded before use. If the expansion fails, the router
20620 declines. The result of the expansion must be a colon-separated list of names
20621 and/or IP addresses, optionally also including ports.
20622 If the list is written with spaces, it must be protected with quotes.
20623 The format of each item
20624 in the list is described in the next section. The list separator can be changed
20625 as described in section &<<SECTlistsepchange>>&.
20627 If the list of hosts was obtained from a &%route_list%& item, the following
20628 variables are set during its expansion:
20631 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
20632 If the domain was matched against a regular expression, the numeric variables
20633 &$1$&, &$2$&, etc. may be set. For example:
20635 route_list = ^domain(\d+) host-$1.text.example
20638 &$0$& is always set to the entire domain.
20640 &$1$& is also set when partial matching is done in a file lookup.
20643 .vindex "&$value$&"
20644 If the pattern that matched the domain was a lookup item, the data that was
20645 looked up is available in the expansion variable &$value$&. For example:
20647 route_list = lsearch;;/some/file.routes $value
20651 Note the doubling of the semicolon in the pattern that is necessary because
20652 semicolon is the default route list separator.
20656 .section "Format of one host item" "SECTformatonehostitem"
20657 Each item in the list of hosts can be either a host name or an IP address,
20658 optionally with an attached port number, or it can be a single "+"
20659 (see &%hosts_randomize%&).
20660 When no port is given, an IP address
20661 is not enclosed in brackets. When a port is specified, it overrides the port
20662 specification on the transport. The port is separated from the name or address
20663 by a colon. This leads to some complications:
20666 Because colon is the default separator for the list of hosts, either
20667 the colon that specifies a port must be doubled, or the list separator must
20668 be changed. The following two examples have the same effect:
20670 route_list = * "host1.tld::1225 : host2.tld::1226"
20671 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
20674 When IPv6 addresses are involved, it gets worse, because they contain
20675 colons of their own. To make this case easier, it is permitted to
20676 enclose an IP address (either v4 or v6) in square brackets if a port
20677 number follows. For example:
20679 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
20683 .section "How the list of hosts is used" "SECThostshowused"
20684 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
20685 the hosts is tried, in the order specified, when carrying out the SMTP
20686 delivery. However, the order can be changed by setting the &%hosts_randomize%&
20687 option, either on the router (see section &<<SECTprioptman>>& above), or on the
20690 Hosts may be listed by name or by IP address. An unadorned name in the list of
20691 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
20692 interpreted as an indirection to a sublist of hosts obtained by looking up MX
20693 records in the DNS. For example:
20695 route_list = * x.y.z:p.q.r/MX:e.f.g
20697 If this feature is used with a port specifier, the port must come last. For
20700 route_list = * dom1.tld/mx::1225
20702 If the &%hosts_randomize%& option is set, the order of the items in the list is
20703 randomized before any lookups are done. Exim then scans the list; for any name
20704 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
20705 be an interface on the local host and the item is not the first in the list,
20706 Exim discards it and any subsequent items. If it is the first item, what
20707 happens is controlled by the
20708 .oindex "&%self%&" "in &(manualroute)& router"
20709 &%self%& option of the router.
20711 A name on the list that is followed by &`/MX`& is replaced with the list of
20712 hosts obtained by looking up MX records for the name. This is always a DNS
20713 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
20714 below) are not relevant here. The order of these hosts is determined by the
20715 preference values in the MX records, according to the usual rules. Because
20716 randomizing happens before the MX lookup, it does not affect the order that is
20717 defined by MX preferences.
20719 If the local host is present in the sublist obtained from MX records, but is
20720 not the most preferred host in that list, it and any equally or less
20721 preferred hosts are removed before the sublist is inserted into the main list.
20723 If the local host is the most preferred host in the MX list, what happens
20724 depends on where in the original list of hosts the &`/MX`& item appears. If it
20725 is not the first item (that is, there are previous hosts in the main list),
20726 Exim discards this name and any subsequent items in the main list.
20728 If the MX item is first in the list of hosts, and the local host is the
20729 most preferred host, what happens is controlled by the &%self%& option of the
20732 DNS failures when lookup up the MX records are treated in the same way as DNS
20733 failures when looking up IP addresses: &%pass_on_timeout%& and
20734 &%host_find_failed%& are used when relevant.
20736 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
20737 whether obtained from an MX lookup or not.
20741 .section "How the options are used" "SECThowoptused"
20742 The options are a sequence of words, space-separated.
20743 One of the words can be the name of a transport; this overrides the
20744 &%transport%& option on the router for this particular routing rule only. The
20745 other words (if present) control randomization of the list of hosts on a
20746 per-rule basis, and how the IP addresses of the hosts are to be found when
20747 routing to a remote transport. These options are as follows:
20750 &%randomize%&: randomize the order of the hosts in this list, overriding the
20751 setting of &%hosts_randomize%& for this routing rule only.
20753 &%no_randomize%&: do not randomize the order of the hosts in this list,
20754 overriding the setting of &%hosts_randomize%& for this routing rule only.
20756 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
20757 find IP addresses. This function may ultimately cause a DNS lookup, but it may
20758 also look in &_/etc/hosts_& or other sources of information.
20760 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
20761 no address records are found. If there is a temporary DNS error (such as a
20762 timeout), delivery is deferred.
20764 &%ipv4_only%&: in direct DNS lookups, look up only A records.
20766 &%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
20771 route_list = domain1 host1:host2:host3 randomize bydns;\
20772 domain2 host4:host5
20774 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
20775 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
20776 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
20777 or &[gethostbyname()]&, and the result of the lookup is the result of that
20780 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
20781 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
20782 instead of TRY_AGAIN. That is why the default action is to try a DNS
20783 lookup first. Only if that gives a definite &"no such host"& is the local
20786 &*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
20787 inadvertent constraint that a transport name as an option had to be the last
20792 If no IP address for a host can be found, what happens is controlled by the
20793 &%host_find_failed%& option.
20796 When an address is routed to a local transport, IP addresses are not looked up.
20797 The host list is passed to the transport in the &$host$& variable.
20801 .section "Manualroute examples" "SECID123"
20802 In some of the examples that follow, the presence of the &%remote_smtp%&
20803 transport, as defined in the default configuration file, is assumed:
20806 .cindex "smart host" "example router"
20807 The &(manualroute)& router can be used to forward all external mail to a
20808 &'smart host'&. If you have set up, in the main part of the configuration, a
20809 named domain list that contains your local domains, for example:
20811 domainlist local_domains = my.domain.example
20813 You can arrange for all other domains to be routed to a smart host by making
20814 your first router something like this:
20817 driver = manualroute
20818 domains = !+local_domains
20819 transport = remote_smtp
20820 route_list = * smarthost.ref.example
20822 This causes all non-local addresses to be sent to the single host
20823 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
20824 they are tried in order
20825 (but you can use &%hosts_randomize%& to vary the order each time).
20826 Another way of configuring the same thing is this:
20829 driver = manualroute
20830 transport = remote_smtp
20831 route_list = !+local_domains smarthost.ref.example
20833 There is no difference in behaviour between these two routers as they stand.
20834 However, they behave differently if &%no_more%& is added to them. In the first
20835 example, the router is skipped if the domain does not match the &%domains%&
20836 precondition; the following router is always tried. If the router runs, it
20837 always matches the domain and so can never decline. Therefore, &%no_more%&
20838 would have no effect. In the second case, the router is never skipped; it
20839 always runs. However, if it doesn't match the domain, it declines. In this case
20840 &%no_more%& would prevent subsequent routers from running.
20843 .cindex "mail hub example"
20844 A &'mail hub'& is a host which receives mail for a number of domains via MX
20845 records in the DNS and delivers it via its own private routing mechanism. Often
20846 the final destinations are behind a firewall, with the mail hub being the one
20847 machine that can connect to machines both inside and outside the firewall. The
20848 &(manualroute)& router is usually used on a mail hub to route incoming messages
20849 to the correct hosts. For a small number of domains, the routing can be inline,
20850 using the &%route_list%& option, but for a larger number a file or database
20851 lookup is easier to manage.
20853 If the domain names are in fact the names of the machines to which the mail is
20854 to be sent by the mail hub, the configuration can be quite simple. For
20858 driver = manualroute
20859 transport = remote_smtp
20860 route_list = *.rhodes.tvs.example $domain
20862 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
20863 whose names are the same as the mail domains. A similar approach can be taken
20864 if the host name can be obtained from the domain name by a string manipulation
20865 that the expansion facilities can handle. Otherwise, a lookup based on the
20866 domain can be used to find the host:
20869 driver = manualroute
20870 transport = remote_smtp
20871 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
20873 The result of the lookup must be the name or IP address of the host (or
20874 hosts) to which the address is to be routed. If the lookup fails, the route
20875 data is empty, causing the router to decline. The address then passes to the
20879 .cindex "batched SMTP output example"
20880 .cindex "SMTP" "batched outgoing; example"
20881 You can use &(manualroute)& to deliver messages to pipes or files in batched
20882 SMTP format for onward transportation by some other means. This is one way of
20883 storing mail for a dial-up host when it is not connected. The route list entry
20884 can be as simple as a single domain name in a configuration like this:
20887 driver = manualroute
20888 transport = batchsmtp_appendfile
20889 route_list = saved.domain.example
20891 though often a pattern is used to pick up more than one domain. If there are
20892 several domains or groups of domains with different transport requirements,
20893 different transports can be listed in the routing information:
20896 driver = manualroute
20898 *.saved.domain1.example $domain batch_appendfile; \
20899 *.saved.domain2.example \
20900 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
20903 .vindex "&$domain$&"
20905 The first of these just passes the domain in the &$host$& variable, which
20906 doesn't achieve much (since it is also in &$domain$&), but the second does a
20907 file lookup to find a value to pass, causing the router to decline to handle
20908 the address if the lookup fails.
20911 .cindex "UUCP" "example of router for"
20912 Routing mail directly to UUCP software is a specific case of the use of
20913 &(manualroute)& in a gateway to another mail environment. This is an example of
20914 one way it can be done:
20920 command = /usr/local/bin/uux -r - \
20921 ${substr_-5:$host}!rmail ${local_part}
20922 return_fail_output = true
20927 driver = manualroute
20929 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
20931 The file &_/usr/local/exim/uucphosts_& contains entries like
20933 darksite.ethereal.example: darksite.UUCP
20935 It can be set up more simply without adding and removing &".UUCP"& but this way
20936 makes clear the distinction between the domain name
20937 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
20939 .ecindex IIDmanrou1
20940 .ecindex IIDmanrou2
20949 . ////////////////////////////////////////////////////////////////////////////
20950 . ////////////////////////////////////////////////////////////////////////////
20952 .chapter "The queryprogram router" "CHAPdriverlast"
20953 .scindex IIDquerou1 "&(queryprogram)& router"
20954 .scindex IIDquerou2 "routers" "&(queryprogram)&"
20955 .cindex "routing" "by external program"
20956 The &(queryprogram)& router routes an address by running an external command
20957 and acting on its output. This is an expensive way to route, and is intended
20958 mainly for use in lightly-loaded systems, or for performing experiments.
20959 However, if it is possible to use the precondition options (&%domains%&,
20960 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
20961 be used in special cases, even on a busy host. There are the following private
20963 .cindex "options" "&(queryprogram)& router"
20965 .option command queryprogram string&!! unset
20966 This option must be set. It specifies the command that is to be run. The
20967 command is split up into a command name and arguments, and then each is
20968 expanded separately (exactly as for a &(pipe)& transport, described in chapter
20969 &<<CHAPpipetransport>>&).
20972 .option command_group queryprogram string unset
20973 .cindex "gid (group id)" "in &(queryprogram)& router"
20974 This option specifies a gid to be set when running the command while routing an
20975 address for deliver. It must be set if &%command_user%& specifies a numerical
20976 uid. If it begins with a digit, it is interpreted as the numerical value of the
20977 gid. Otherwise it is looked up using &[getgrnam()]&.
20980 .option command_user queryprogram string unset
20981 .cindex "uid (user id)" "for &(queryprogram)&"
20982 This option must be set. It specifies the uid which is set when running the
20983 command while routing an address for delivery. If the value begins with a digit,
20984 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
20985 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
20986 not set, a value for the gid also.
20988 &*Warning:*& Changing uid and gid is possible only when Exim is running as
20989 root, which it does during a normal delivery in a conventional configuration.
20990 However, when an address is being verified during message reception, Exim is
20991 usually running as the Exim user, not as root. If the &(queryprogram)& router
20992 is called from a non-root process, Exim cannot change uid or gid before running
20993 the command. In this circumstance the command runs under the current uid and
20997 .option current_directory queryprogram string /
20998 This option specifies an absolute path which is made the current directory
20999 before running the command.
21002 .option timeout queryprogram time 1h
21003 If the command does not complete within the timeout period, its process group
21004 is killed and the message is frozen. A value of zero time specifies no
21008 The standard output of the command is connected to a pipe, which is read when
21009 the command terminates. It should consist of a single line of output,
21010 containing up to five fields, separated by white space. The maximum length of
21011 the line is 1023 characters. Longer lines are silently truncated. The first
21012 field is one of the following words (case-insensitive):
21015 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
21018 &'Decline'&: the router declines; pass the address to the next router, unless
21019 &%no_more%& is set.
21021 &'Fail'&: routing failed; do not pass the address to any more routers. Any
21022 subsequent text on the line is an error message. If the router is run as part
21023 of address verification during an incoming SMTP message, the message is
21024 included in the SMTP response.
21026 &'Defer'&: routing could not be completed at this time; try again later. Any
21027 subsequent text on the line is an error message which is logged. It is not
21028 included in any SMTP response.
21030 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
21032 &'Pass'&: pass the address to the next router (or the router specified by
21033 &%pass_router%&), overriding &%no_more%&.
21035 &'Redirect'&: the message is redirected. The remainder of the line is a list of
21036 new addresses, which are routed independently, starting with the first router,
21037 or the router specified by &%redirect_router%&, if set.
21040 When the first word is &'accept'&, the remainder of the line consists of a
21041 number of keyed data values, as follows (split into two lines here, to fit on
21044 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
21045 LOOKUP=byname|bydns DATA=<text>
21047 The data items can be given in any order, and all are optional. If no transport
21048 is included, the transport specified by the generic &%transport%& option is
21049 used. The list of hosts and the lookup type are needed only if the transport is
21050 an &(smtp)& transport that does not itself supply a list of hosts.
21052 The format of the list of hosts is the same as for the &(manualroute)& router.
21053 As well as host names and IP addresses with optional port numbers, as described
21054 in section &<<SECTformatonehostitem>>&, it may contain names followed by
21055 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
21056 (see section &<<SECThostshowused>>&).
21058 If the lookup type is not specified, Exim behaves as follows when trying to
21059 find an IP address for each host: First, a DNS lookup is done. If this yields
21060 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
21061 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
21062 result of the lookup is the result of that call.
21064 .vindex "&$address_data$&"
21065 If the DATA field is set, its value is placed in the &$address_data$&
21066 variable. For example, this return line
21068 accept hosts=x1.y.example:x2.y.example data="rule1"
21070 routes the address to the default transport, passing a list of two hosts. When
21071 the transport runs, the string &"rule1"& is in &$address_data$&.
21072 .ecindex IIDquerou1
21073 .ecindex IIDquerou2
21078 . ////////////////////////////////////////////////////////////////////////////
21079 . ////////////////////////////////////////////////////////////////////////////
21081 .chapter "The redirect router" "CHAPredirect"
21082 .scindex IIDredrou1 "&(redirect)& router"
21083 .scindex IIDredrou2 "routers" "&(redirect)&"
21084 .cindex "alias file" "in a &(redirect)& router"
21085 .cindex "address redirection" "&(redirect)& router"
21086 The &(redirect)& router handles several kinds of address redirection. Its most
21087 common uses are for resolving local part aliases from a central alias file
21088 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
21089 files, but it has many other potential uses. The incoming address can be
21090 redirected in several different ways:
21093 It can be replaced by one or more new addresses which are themselves routed
21096 It can be routed to be delivered to a given file or directory.
21098 It can be routed to be delivered to a specified pipe command.
21100 It can cause an automatic reply to be generated.
21102 It can be forced to fail, optionally with a custom error message.
21104 It can be temporarily deferred, optionally with a custom message.
21106 It can be discarded.
21109 The generic &%transport%& option must not be set for &(redirect)& routers.
21110 However, there are some private options which define transports for delivery to
21111 files and pipes, and for generating autoreplies. See the &%file_transport%&,
21112 &%pipe_transport%& and &%reply_transport%& descriptions below.
21114 If success DSNs have been requested
21115 .cindex "DSN" "success"
21116 .cindex "Delivery Status Notification" "success"
21117 redirection triggers one and the DSN options are not passed any further.
21121 .section "Redirection data" "SECID124"
21122 The router operates by interpreting a text string which it obtains either by
21123 expanding the contents of the &%data%& option, or by reading the entire
21124 contents of a file whose name is given in the &%file%& option. These two
21125 options are mutually exclusive. The first is commonly used for handling system
21126 aliases, in a configuration like this:
21130 data = ${lookup{$local_part}lsearch{/etc/aliases}}
21132 If the lookup fails, the expanded string in this example is empty. When the
21133 expansion of &%data%& results in an empty string, the router declines. A forced
21134 expansion failure also causes the router to decline; other expansion failures
21135 cause delivery to be deferred.
21137 A configuration using &%file%& is commonly used for handling users'
21138 &_.forward_& files, like this:
21143 file = $home/.forward
21146 If the file does not exist, or causes no action to be taken (for example, it is
21147 empty or consists only of comments), the router declines. &*Warning*&: This
21148 is not the case when the file contains syntactically valid items that happen to
21149 yield empty addresses, for example, items containing only RFC 2822 address
21152 .cindex "tainted data" "in filenames"
21153 .cindex redirect "tainted data"
21154 Tainted data may not be used for a filename.
21156 &*Warning*&: It is unwise to use &$local_part$& or &$domain$&
21157 directly for redirection,
21158 as they are provided by a potential attacker.
21159 In the examples above, &$local_part$& is used for looking up data held locally
21160 on the system, and not used directly (the second example derives &$home$& via
21161 the passsword file or database, using &$local_part$&).
21165 .section "Forward files and address verification" "SECID125"
21166 .cindex "address redirection" "while verifying"
21167 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
21168 &_.forward_& files, as in the example above. There are two reasons for this:
21171 When Exim is receiving an incoming SMTP message from a remote host, it is
21172 running under the Exim uid, not as root. Exim is unable to change uid to read
21173 the file as the user, and it may not be able to read it as the Exim user. So in
21174 practice the router may not be able to operate.
21176 However, even when the router can operate, the existence of a &_.forward_& file
21177 is unimportant when verifying an address. What should be checked is whether the
21178 local part is a valid user name or not. Cutting out the redirection processing
21179 saves some resources.
21187 .section "Interpreting redirection data" "SECID126"
21188 .cindex "Sieve filter" "specifying in redirection data"
21189 .cindex "filter" "specifying in redirection data"
21190 The contents of the data string, whether obtained from &%data%& or &%file%&,
21191 can be interpreted in two different ways:
21194 If the &%allow_filter%& option is set true, and the data begins with the text
21195 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
21196 &'filtering'& instructions in the form of an Exim or Sieve filter file,
21197 respectively. Details of the syntax and semantics of filter files are described
21198 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
21199 document is intended for use by end users.
21201 Otherwise, the data must be a comma-separated list of redirection items, as
21202 described in the next section.
21205 When a message is redirected to a file (a &"mail folder"&), the filename given
21206 in a non-filter redirection list must always be an absolute path. A filter may
21207 generate a relative path &-- how this is handled depends on the transport's
21208 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
21209 for the &(appendfile)& transport.
21213 .section "Items in a non-filter redirection list" "SECTitenonfilred"
21214 .cindex "address redirection" "non-filter list items"
21215 When the redirection data is not an Exim or Sieve filter, for example, if it
21216 comes from a conventional alias or forward file, it consists of a list of
21217 addresses, filenames, pipe commands, or certain special items (see section
21218 &<<SECTspecitredli>>& below). The special items can be individually enabled or
21219 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
21220 depending on their default values. The items in the list are separated by
21221 commas or newlines.
21222 If a comma is required in an item, the entire item must be enclosed in double
21225 Lines starting with a # character are comments, and are ignored, and # may
21226 also appear following a comma, in which case everything between the # and the
21227 next newline character is ignored.
21229 If an item is entirely enclosed in double quotes, these are removed. Otherwise
21230 double quotes are retained because some forms of mail address require their use
21231 (but never to enclose the entire address). In the following description,
21232 &"item"& refers to what remains after any surrounding double quotes have been
21235 .vindex "&$local_part$&"
21236 &*Warning*&: If you use an Exim expansion to construct a redirection address,
21237 and the expansion contains a reference to &$local_part$&, you should make use
21238 of the &%quote_local_part%& expansion operator, in case the local part contains
21239 special characters. For example, to redirect all mail for the domain
21240 &'obsolete.example'&, retaining the existing local part, you could use this
21243 data = ${quote_local_part:$local_part}@newdomain.example
21247 .section "Redirecting to a local mailbox" "SECTredlocmai"
21248 .cindex "routing" "loops in"
21249 .cindex "loop" "while routing, avoidance of"
21250 .cindex "address redirection" "to local mailbox"
21251 A redirection item may safely be the same as the address currently under
21252 consideration. This does not cause a routing loop, because a router is
21253 automatically skipped if any ancestor of the address that is being processed
21254 is the same as the current address and was processed by the current router.
21255 Such an address is therefore passed to the following routers, so it is handled
21256 as if there were no redirection. When making this loop-avoidance test, the
21257 complete local part, including any prefix or suffix, is used.
21259 .cindex "address redirection" "local part without domain"
21260 Specifying the same local part without a domain is a common usage in personal
21261 filter files when the user wants to have messages delivered to the local
21262 mailbox and also forwarded elsewhere. For example, the user whose login is
21263 &'cleo'& might have a &_.forward_& file containing this:
21265 cleo, cleopatra@egypt.example
21267 .cindex "backslash in alias file"
21268 .cindex "alias file" "backslash in"
21269 For compatibility with other MTAs, such unqualified local parts may be
21270 preceded by &"\"&, but this is not a requirement for loop prevention. However,
21271 it does make a difference if more than one domain is being handled
21274 If an item begins with &"\"& and the rest of the item parses as a valid RFC
21275 2822 address that does not include a domain, the item is qualified using the
21276 domain of the incoming address. In the absence of a leading &"\"&, unqualified
21277 addresses are qualified using the value in &%qualify_recipient%&, but you can
21278 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
21280 Care must be taken if there are alias names for local users.
21281 Consider an MTA handling a single local domain where the system alias file
21286 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
21287 messages in the local mailbox, and also forward copies elsewhere. He creates
21290 Sam.Reman, spqr@reme.elsewhere.example
21292 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
21293 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
21294 second time round, because it has previously routed it,
21295 and the following routers presumably cannot handle the alias. The forward file
21296 should really contain
21298 spqr, spqr@reme.elsewhere.example
21300 but because this is such a common error, the &%check_ancestor%& option (see
21301 below) exists to provide a way to get round it. This is normally set on a
21302 &(redirect)& router that is handling users' &_.forward_& files.
21306 .section "Special items in redirection lists" "SECTspecitredli"
21307 In addition to addresses, the following types of item may appear in redirection
21308 lists (that is, in non-filter redirection data):
21311 .cindex "pipe" "in redirection list"
21312 .cindex "address redirection" "to pipe"
21313 An item is treated as a pipe command if it begins with &"|"& and does not parse
21314 as a valid RFC 2822 address that includes a domain. A transport for running the
21315 command must be specified by the &%pipe_transport%& option.
21316 Normally, either the router or the transport specifies a user and a group under
21317 which to run the delivery. The default is to use the Exim user and group.
21319 Single or double quotes can be used for enclosing the individual arguments of
21320 the pipe command; no interpretation of escapes is done for single quotes. If
21321 the command contains a comma character, it is necessary to put the whole item
21322 in double quotes, for example:
21324 "|/some/command ready,steady,go"
21326 since items in redirection lists are terminated by commas. Do not, however,
21327 quote just the command. An item such as
21329 |"/some/command ready,steady,go"
21331 is interpreted as a pipe with a rather strange command name, and no arguments.
21333 Note that the above example assumes that the text comes from a lookup source
21334 of some sort, so that the quotes are part of the data. If composing a
21335 redirect router with a &%data%& option directly specifying this command, the
21336 quotes will be used by the configuration parser to define the extent of one
21337 string, but will not be passed down into the redirect router itself. There
21338 are two main approaches to get around this: escape quotes to be part of the
21339 data itself, or avoid using this mechanism and instead create a custom
21340 transport with the &%command%& option set and reference that transport from
21341 an &%accept%& router.
21344 .cindex "file" "in redirection list"
21345 .cindex "address redirection" "to file"
21346 An item is interpreted as a path name if it begins with &"/"& and does not
21347 parse as a valid RFC 2822 address that includes a domain. For example,
21349 /home/world/minbari
21351 is treated as a filename, but
21353 /s=molari/o=babylon/@x400gate.way
21355 is treated as an address. For a filename, a transport must be specified using
21356 the &%file_transport%& option. However, if the generated path name ends with a
21357 forward slash character, it is interpreted as a directory name rather than a
21358 filename, and &%directory_transport%& is used instead.
21360 Normally, either the router or the transport specifies a user and a group under
21361 which to run the delivery. The default is to use the Exim user and group.
21363 .cindex "&_/dev/null_&"
21364 However, if a redirection item is the path &_/dev/null_&, delivery to it is
21365 bypassed at a high level, and the log entry shows &"**bypassed**"&
21366 instead of a transport name. In this case the user and group are not used.
21369 .cindex "included address list"
21370 .cindex "address redirection" "included external list"
21371 If an item is of the form
21373 :include:<path name>
21375 a list of further items is taken from the given file and included at that
21376 point. &*Note*&: Such a file can not be a filter file; it is just an
21377 out-of-line addition to the list. The items in the included list are separated
21378 by commas or newlines and are not subject to expansion. If this is the first
21379 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
21380 the alias name. This example is incorrect:
21382 list1 :include:/opt/lists/list1
21384 It must be given as
21386 list1: :include:/opt/lists/list1
21388 .cindex "tainted data" "in filenames"
21389 .cindex redirect "tainted data"
21390 Tainted data may not be used for a filename.
21392 .cindex "address redirection" "to black hole"
21393 .cindex "delivery" "discard"
21394 .cindex "delivery" "blackhole"
21395 .cindex "black hole"
21396 .cindex "abandoning mail"
21397 Sometimes you want to throw away mail to a particular local part. Making the
21398 &%data%& option expand to an empty string does not work, because that causes
21399 the router to decline. Instead, the alias item
21403 can be used. It does what its name implies. No delivery is
21404 done, and no error message is generated. This has the same effect as specifying
21405 &_/dev/null_& as a destination, but it can be independently disabled.
21407 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
21408 delivery is done for the original local part, even if other redirection items
21409 are present. If you are generating a multi-item list (for example, by reading a
21410 database) and need the ability to provide a no-op item, you must use
21414 .cindex "delivery" "forcing failure"
21415 .cindex "delivery" "forcing deferral"
21416 .cindex "failing delivery" "forcing"
21417 .cindex "deferred delivery, forcing"
21418 .cindex "customizing" "failure message"
21419 An attempt to deliver a particular address can be deferred or forced to fail by
21420 redirection items of the form
21425 respectively. When a redirection list contains such an item, it applies
21426 to the entire redirection; any other items in the list are ignored. Any
21427 text following &':fail:'& or &':defer:'& is placed in the error text
21428 associated with the failure. For example, an alias file might contain:
21430 X.Employee: :fail: Gone away, no forwarding address
21432 In the case of an address that is being verified from an ACL or as the subject
21434 .cindex "VRFY" "error text, display of"
21435 VRFY command, the text is included in the SMTP error response by
21437 .cindex "EXPN" "error text, display of"
21438 The text is not included in the response to an EXPN command. In non-SMTP cases
21439 the text is included in the error message that Exim generates.
21441 .cindex "SMTP" "error codes"
21442 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
21443 &':fail:'&. However, if the message starts with three digits followed by a
21444 space, optionally followed by an extended code of the form &'n.n.n'&, also
21445 followed by a space, and the very first digit is the same as the default error
21446 code, the code from the message is used instead. If the very first digit is
21447 incorrect, a panic error is logged, and the default code is used. You can
21448 suppress the use of the supplied code in a redirect router by setting the
21449 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
21452 .vindex "&$acl_verify_message$&"
21453 In an ACL, an explicitly provided message overrides the default, but the
21454 default message is available in the variable &$acl_verify_message$& and can
21455 therefore be included in a custom message if this is desired.
21457 Normally the error text is the rest of the redirection list &-- a comma does
21458 not terminate it &-- but a newline does act as a terminator. Newlines are not
21459 normally present in alias expansions. In &(lsearch)& lookups they are removed
21460 as part of the continuation process, but they may exist in other kinds of
21461 lookup and in &':include:'& files.
21463 During routing for message delivery (as opposed to verification), a redirection
21464 containing &':fail:'& causes an immediate failure of the incoming address,
21465 whereas &':defer:'& causes the message to remain in the queue so that a
21466 subsequent delivery attempt can happen at a later time. If an address is
21467 deferred for too long, it will ultimately fail, because the normal retry
21471 .cindex "alias file" "exception to default"
21472 Sometimes it is useful to use a single-key search type with a default (see
21473 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
21474 for exceptions to the default. These can be handled by aliasing them to
21475 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
21476 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
21477 results in an empty redirection list has the same effect.
21481 .section "Duplicate addresses" "SECTdupaddr"
21482 .cindex "duplicate addresses"
21483 .cindex "address duplicate, discarding"
21484 .cindex "pipe" "duplicated"
21485 Exim removes duplicate addresses from the list to which it is delivering, so as
21486 to deliver just one copy to each address. This does not apply to deliveries
21487 routed to pipes by different immediate parent addresses, but an indirect
21488 aliasing scheme of the type
21490 pipe: |/some/command $local_part
21494 does not work with a message that is addressed to both local parts, because
21495 when the second is aliased to the intermediate local part &"pipe"& it gets
21496 discarded as being the same as a previously handled address. However, a scheme
21499 localpart1: |/some/command $local_part
21500 localpart2: |/some/command $local_part
21502 does result in two different pipe deliveries, because the immediate parents of
21503 the pipes are distinct.
21507 .section "Repeated redirection expansion" "SECID128"
21508 .cindex "repeated redirection expansion"
21509 .cindex "address redirection" "repeated for each delivery attempt"
21510 When a message cannot be delivered to all of its recipients immediately,
21511 leading to two or more delivery attempts, redirection expansion is carried out
21512 afresh each time for those addresses whose children were not all previously
21513 delivered. If redirection is being used as a mailing list, this can lead to new
21514 members of the list receiving copies of old messages. The &%one_time%& option
21515 can be used to avoid this.
21518 .section "Errors in redirection lists" "SECID129"
21519 .cindex "address redirection" "errors"
21520 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
21521 error is skipped, and an entry is written to the main log. This may be useful
21522 for mailing lists that are automatically managed. Otherwise, if an error is
21523 detected while generating the list of new addresses, the original address is
21524 deferred. See also &%syntax_errors_to%&.
21528 .section "Private options for the redirect router" "SECID130"
21530 .cindex "options" "&(redirect)& router"
21531 The private options for the &(redirect)& router are as follows:
21534 .option allow_defer redirect boolean false
21535 Setting this option allows the use of &':defer:'& in non-filter redirection
21536 data, or the &%defer%& command in an Exim filter file.
21539 .option allow_fail redirect boolean false
21540 .cindex "failing delivery" "from filter"
21541 If this option is true, the &':fail:'& item can be used in a redirection list,
21542 and the &%fail%& command may be used in an Exim filter file.
21545 .option allow_filter redirect boolean false
21546 .cindex "filter" "enabling use of"
21547 .cindex "Sieve filter" "enabling use of"
21548 Setting this option allows Exim to interpret redirection data that starts with
21549 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
21550 are some features of Exim filter files that some administrators may wish to
21551 lock out; see the &%forbid_filter_%&&'xxx'& options below.
21553 It is also possible to lock out Exim filters or Sieve filters while allowing
21554 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
21557 The filter is run using the uid and gid set by the generic &%user%& and
21558 &%group%& options. These take their defaults from the password data if
21559 &%check_local_user%& is set, so in the normal case of users' personal filter
21560 files, the filter is run as the relevant user. When &%allow_filter%& is set
21561 true, Exim insists that either &%check_local_user%& or &%user%& is set.
21565 .option allow_freeze redirect boolean false
21566 .cindex "freezing messages" "allowing in filter"
21567 Setting this option allows the use of the &%freeze%& command in an Exim filter.
21568 This command is more normally encountered in system filters, and is disabled by
21569 default for redirection filters because it isn't something you usually want to
21570 let ordinary users do.
21574 .option check_ancestor redirect boolean false
21575 This option is concerned with handling generated addresses that are the same
21576 as some address in the list of redirection ancestors of the current address.
21577 Although it is turned off by default in the code, it is set in the default
21578 configuration file for handling users' &_.forward_& files. It is recommended
21579 for this use of the &(redirect)& router.
21581 When &%check_ancestor%& is set, if a generated address (including the domain)
21582 is the same as any ancestor of the current address, it is replaced by a copy of
21583 the current address. This helps in the case where local part A is aliased to B,
21584 and B has a &_.forward_& file pointing back to A. For example, within a single
21585 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
21586 &_&~jb/.forward_& contains:
21588 \Joe.Bloggs, <other item(s)>
21590 Without the &%check_ancestor%& setting, either local part (&"jb"& or
21591 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
21592 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
21593 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
21594 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
21595 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
21596 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
21597 original address. See also the &%repeat_use%& option below.
21600 .option check_group redirect boolean "see below"
21601 When the &%file%& option is used, the group owner of the file is checked only
21602 when this option is set. The permitted groups are those listed in the
21603 &%owngroups%& option, together with the user's default group if
21604 &%check_local_user%& is set. If the file has the wrong group, routing is
21605 deferred. The default setting for this option is true if &%check_local_user%&
21606 is set and the &%modemask%& option permits the group write bit, or if the
21607 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
21611 .option check_owner redirect boolean "see below"
21612 When the &%file%& option is used, the owner of the file is checked only when
21613 this option is set. If &%check_local_user%& is set, the local user is
21614 permitted; otherwise the owner must be one of those listed in the &%owners%&
21615 option. The default value for this option is true if &%check_local_user%& or
21616 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
21619 .option data redirect string&!! unset
21620 This option is mutually exclusive with &%file%&. One or other of them must be
21621 set, but not both. The contents of &%data%& are expanded, and then used as the
21622 list of forwarding items, or as a set of filtering instructions. If the
21623 expansion is forced to fail, or the result is an empty string or a string that
21624 has no effect (consists entirely of comments), the router declines.
21626 When filtering instructions are used, the string must begin with &"#Exim
21627 filter"&, and all comments in the string, including this initial one, must be
21628 terminated with newline characters. For example:
21630 data = #Exim filter\n\
21631 if $h_to: contains Exim then save $home/mail/exim endif
21633 If you are reading the data from a database where newlines cannot be included,
21634 you can use the &${sg}$& expansion item to turn the escape string of your
21635 choice into a newline.
21638 .option directory_transport redirect string&!! unset
21639 A &(redirect)& router sets up a direct delivery to a directory when a path name
21640 ending with a slash is specified as a new &"address"&. The transport used is
21641 specified by this option, which, after expansion, must be the name of a
21642 configured transport. This should normally be an &(appendfile)& transport.
21645 .option file redirect string&!! unset
21646 This option specifies the name of a file that contains the redirection data. It
21647 is mutually exclusive with the &%data%& option. The string is expanded before
21648 use; if the expansion is forced to fail, the router declines. Other expansion
21649 failures cause delivery to be deferred. The result of a successful expansion
21650 must be an absolute path. The entire file is read and used as the redirection
21651 data. If the data is an empty string or a string that has no effect (consists
21652 entirely of comments), the router declines.
21654 .cindex "NFS" "checking for file existence"
21655 If the attempt to open the file fails with a &"does not exist"& error, Exim
21656 runs a check on the containing directory,
21657 unless &%ignore_enotdir%& is true (see below).
21658 If the directory does not appear to exist, delivery is deferred. This can
21659 happen when users' &_.forward_& files are in NFS-mounted directories, and there
21660 is a mount problem. If the containing directory does exist, but the file does
21661 not, the router declines.
21664 .option file_transport redirect string&!! unset
21665 .vindex "&$address_file$&"
21666 A &(redirect)& router sets up a direct delivery to a file when a path name not
21667 ending in a slash is specified as a new &"address"&. The transport used is
21668 specified by this option, which, after expansion, must be the name of a
21669 configured transport. This should normally be an &(appendfile)& transport. When
21670 it is running, the filename is in &$address_file$&.
21673 .option filter_prepend_home redirect boolean true
21674 When this option is true, if a &(save)& command in an Exim filter specifies a
21675 relative path, and &$home$& is defined, it is automatically prepended to the
21676 relative path. If this option is set false, this action does not happen. The
21677 relative path is then passed to the transport unmodified.
21680 .option forbid_blackhole redirect boolean false
21681 .cindex "restricting access to features"
21682 .cindex "filter" "locking out certain features"
21683 If this option is true, the &':blackhole:'& item may not appear in a
21687 .option forbid_exim_filter redirect boolean false
21688 .cindex "restricting access to features"
21689 .cindex "filter" "locking out certain features"
21690 If this option is set true, only Sieve filters are permitted when
21691 &%allow_filter%& is true.
21696 .option forbid_file redirect boolean false
21697 .cindex "restricting access to features"
21698 .cindex "delivery" "to file; forbidding"
21699 .cindex "filter" "locking out certain features"
21700 .cindex "Sieve filter" "forbidding delivery to a file"
21701 .cindex "Sieve filter" "&""keep""& facility; disabling"
21702 If this option is true, this router may not generate a new address that
21703 specifies delivery to a local file or directory, either from a filter or from a
21704 conventional forward file. This option is forced to be true if &%one_time%& is
21705 set. It applies to Sieve filters as well as to Exim filters, but if true, it
21706 locks out the Sieve's &"keep"& facility.
21709 .option forbid_filter_dlfunc redirect boolean false
21710 .cindex "restricting access to features"
21711 .cindex "filter" "locking out certain features"
21712 If this option is true, string expansions in Exim filters are not allowed to
21713 make use of the &%dlfunc%& expansion facility to run dynamically loaded
21716 .option forbid_filter_existstest redirect boolean false
21717 .cindex "restricting access to features"
21718 .cindex "filter" "locking out certain features"
21719 .cindex "expansion" "statting a file"
21720 If this option is true, string expansions in Exim filters are not allowed to
21721 make use of the &%exists%& condition or the &%stat%& expansion item.
21723 .option forbid_filter_logwrite redirect boolean false
21724 .cindex "restricting access to features"
21725 .cindex "filter" "locking out certain features"
21726 If this option is true, use of the logging facility in Exim filters is not
21727 permitted. Logging is in any case available only if the filter is being run
21728 under some unprivileged uid (which is normally the case for ordinary users'
21729 &_.forward_& files).
21732 .option forbid_filter_lookup redirect boolean false
21733 .cindex "restricting access to features"
21734 .cindex "filter" "locking out certain features"
21735 If this option is true, string expansions in Exim filter files are not allowed
21736 to make use of &%lookup%& items.
21739 .option forbid_filter_perl redirect boolean false
21740 .cindex "restricting access to features"
21741 .cindex "filter" "locking out certain features"
21742 This option has an effect only if Exim is built with embedded Perl support. If
21743 it is true, string expansions in Exim filter files are not allowed to make use
21744 of the embedded Perl support.
21747 .option forbid_filter_readfile redirect boolean false
21748 .cindex "restricting access to features"
21749 .cindex "filter" "locking out certain features"
21750 If this option is true, string expansions in Exim filter files are not allowed
21751 to make use of &%readfile%& items.
21754 .option forbid_filter_readsocket redirect boolean false
21755 .cindex "restricting access to features"
21756 .cindex "filter" "locking out certain features"
21757 If this option is true, string expansions in Exim filter files are not allowed
21758 to make use of &%readsocket%& items.
21761 .option forbid_filter_reply redirect boolean false
21762 .cindex "restricting access to features"
21763 .cindex "filter" "locking out certain features"
21764 If this option is true, this router may not generate an automatic reply
21765 message. Automatic replies can be generated only from Exim or Sieve filter
21766 files, not from traditional forward files. This option is forced to be true if
21767 &%one_time%& is set.
21770 .option forbid_filter_run redirect boolean false
21771 .cindex "restricting access to features"
21772 .cindex "filter" "locking out certain features"
21773 If this option is true, string expansions in Exim filter files are not allowed
21774 to make use of &%run%& items.
21777 .option forbid_include redirect boolean false
21778 .cindex "restricting access to features"
21779 .cindex "filter" "locking out certain features"
21780 If this option is true, items of the form
21782 :include:<path name>
21784 are not permitted in non-filter redirection lists.
21787 .option forbid_pipe redirect boolean false
21788 .cindex "restricting access to features"
21789 .cindex "filter" "locking out certain features"
21790 .cindex "delivery" "to pipe; forbidding"
21791 If this option is true, this router may not generate a new address which
21792 specifies delivery to a pipe, either from an Exim filter or from a conventional
21793 forward file. This option is forced to be true if &%one_time%& is set.
21796 .option forbid_sieve_filter redirect boolean false
21797 .cindex "restricting access to features"
21798 .cindex "filter" "locking out certain features"
21799 If this option is set true, only Exim filters are permitted when
21800 &%allow_filter%& is true.
21803 .cindex "SMTP" "error codes"
21804 .option forbid_smtp_code redirect boolean false
21805 If this option is set true, any SMTP error codes that are present at the start
21806 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
21807 the default codes (451 and 550, respectively) are always used.
21812 .option hide_child_in_errmsg redirect boolean false
21813 .cindex "bounce message" "redirection details; suppressing"
21814 If this option is true, it prevents Exim from quoting a child address if it
21815 generates a bounce or delay message for it. Instead it says &"an address
21816 generated from <&'the top level address'&>"&. Of course, this applies only to
21817 bounces generated locally. If a message is forwarded to another host, &'its'&
21818 bounce may well quote the generated address.
21821 .option ignore_eacces redirect boolean false
21823 If this option is set and an attempt to open a redirection file yields the
21824 EACCES error (permission denied), the &(redirect)& router behaves as if the
21825 file did not exist.
21828 .option ignore_enotdir redirect boolean false
21830 If this option is set and an attempt to open a redirection file yields the
21831 ENOTDIR error (something on the path is not a directory), the &(redirect)&
21832 router behaves as if the file did not exist.
21834 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
21835 router that has the &%file%& option set discovers that the file does not exist
21836 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
21837 against unmounted NFS directories. If the parent can not be statted, delivery
21838 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
21839 is set, because that option tells Exim to ignore &"something on the path is not
21840 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
21841 that some operating systems give ENOENT where others give ENOTDIR.
21845 .option include_directory redirect string unset
21846 If this option is set, the path names of any &':include:'& items in a
21847 redirection list must start with this directory.
21850 .option modemask redirect "octal integer" 022
21851 This specifies mode bits which must not be set for a file specified by the
21852 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
21855 .option one_time redirect boolean false
21856 .cindex "one-time aliasing/forwarding expansion"
21857 .cindex "alias file" "one-time expansion"
21858 .cindex "forward file" "one-time expansion"
21859 .cindex "mailing lists" "one-time expansion"
21860 .cindex "address redirection" "one-time expansion"
21861 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
21862 files each time it tries to deliver a message causes a problem when one or more
21863 of the generated addresses fails be delivered at the first attempt. The problem
21864 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
21865 but of what happens when the redirection list changes during the time that the
21866 message is on Exim's queue. This is particularly true in the case of mailing
21867 lists, where new subscribers might receive copies of messages that were posted
21868 before they subscribed.
21870 If &%one_time%& is set and any addresses generated by the router fail to
21871 deliver at the first attempt, the failing addresses are added to the message as
21872 &"top level"& addresses, and the parent address that generated them is marked
21873 &"delivered"&. Thus, redirection does not happen again at the next delivery
21876 &*Warning 1*&: Any header line addition or removal that is specified by this
21877 router would be lost if delivery did not succeed at the first attempt. For this
21878 reason, the &%headers_add%& and &%headers_remove%& generic options are not
21879 permitted when &%one_time%& is set.
21881 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
21882 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
21883 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
21885 &*Warning 3*&: The &%unseen%& generic router option may not be set with
21888 The original top-level address is remembered with each of the generated
21889 addresses, and is output in any log messages. However, any intermediate parent
21890 addresses are not recorded. This makes a difference to the log only if
21891 &%all_parents%& log selector is set. It is expected that &%one_time%& will
21892 typically be used for mailing lists, where there is normally just one level of
21896 .option owners redirect "string list" unset
21897 .cindex "ownership" "alias file"
21898 .cindex "ownership" "forward file"
21899 .cindex "alias file" "ownership"
21900 .cindex "forward file" "ownership"
21901 This specifies a list of permitted owners for the file specified by &%file%&.
21902 This list is in addition to the local user when &%check_local_user%& is set.
21903 See &%check_owner%& above.
21906 .option owngroups redirect "string list" unset
21907 This specifies a list of permitted groups for the file specified by &%file%&.
21908 The list is in addition to the local user's primary group when
21909 &%check_local_user%& is set. See &%check_group%& above.
21912 .option pipe_transport redirect string&!! unset
21913 .vindex "&$address_pipe$&"
21914 A &(redirect)& router sets up a direct delivery to a pipe when a string
21915 starting with a vertical bar character is specified as a new &"address"&. The
21916 transport used is specified by this option, which, after expansion, must be the
21917 name of a configured transport. This should normally be a &(pipe)& transport.
21918 When the transport is run, the pipe command is in &$address_pipe$&.
21921 .option qualify_domain redirect string&!! unset
21922 .vindex "&$qualify_recipient$&"
21923 If this option is set, and an unqualified address (one without a domain) is
21924 generated, and that address would normally be qualified by the global setting
21925 in &%qualify_recipient%&, it is instead qualified with the domain specified by
21926 expanding this string. If the expansion fails, the router declines. If you want
21927 to revert to the default, you can have the expansion generate
21928 &$qualify_recipient$&.
21930 This option applies to all unqualified addresses generated by Exim filters,
21931 but for traditional &_.forward_& files, it applies only to addresses that are
21932 not preceded by a backslash. Sieve filters cannot generate unqualified
21935 .option qualify_preserve_domain redirect boolean false
21936 .cindex "domain" "in redirection; preserving"
21937 .cindex "preserving domain in redirection"
21938 .cindex "address redirection" "domain; preserving"
21939 If this option is set, the router's local &%qualify_domain%& option must not be
21940 set (a configuration error occurs if it is). If an unqualified address (one
21941 without a domain) is generated, it is qualified with the domain of the parent
21942 address (the immediately preceding ancestor) instead of the global
21943 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
21944 this applies whether or not the address is preceded by a backslash.
21947 .option repeat_use redirect boolean true
21948 If this option is set false, the router is skipped for a child address that has
21949 any ancestor that was routed by this router. This test happens before any of
21950 the other preconditions are tested. Exim's default anti-looping rules skip
21951 only when the ancestor is the same as the current address. See also
21952 &%check_ancestor%& above and the generic &%redirect_router%& option.
21955 .option reply_transport redirect string&!! unset
21956 A &(redirect)& router sets up an automatic reply when a &%mail%& or
21957 &%vacation%& command is used in a filter file. The transport used is specified
21958 by this option, which, after expansion, must be the name of a configured
21959 transport. This should normally be an &(autoreply)& transport. Other transports
21960 are unlikely to do anything sensible or useful.
21963 .option rewrite redirect boolean true
21964 .cindex "address redirection" "disabling rewriting"
21965 If this option is set false, addresses generated by the router are not
21966 subject to address rewriting. Otherwise, they are treated like new addresses
21967 and are rewritten according to the global rewriting rules.
21970 .option sieve_subaddress redirect string&!! unset
21971 The value of this option is passed to a Sieve filter to specify the
21972 :subaddress part of an address.
21974 .option sieve_useraddress redirect string&!! unset
21975 The value of this option is passed to a Sieve filter to specify the :user part
21976 of an address. However, if it is unset, the entire original local part
21977 (including any prefix or suffix) is used for :user.
21980 .option sieve_vacation_directory redirect string&!! unset
21981 .cindex "Sieve filter" "vacation directory"
21982 To enable the &"vacation"& extension for Sieve filters, you must set
21983 &%sieve_vacation_directory%& to the directory where vacation databases are held
21984 (do not put anything else in that directory), and ensure that the
21985 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
21986 needs their own directory; Exim will create it if necessary.
21990 .option skip_syntax_errors redirect boolean false
21991 .cindex "forward file" "broken"
21992 .cindex "address redirection" "broken files"
21993 .cindex "alias file" "broken"
21994 .cindex "broken alias or forward files"
21995 .cindex "ignoring faulty addresses"
21996 .cindex "skipping faulty addresses"
21997 .cindex "error" "skipping bad syntax"
21998 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
21999 non-filter redirection data are skipped, and each failing address is logged. If
22000 &%syntax_errors_to%& is set, a message is sent to the address it defines,
22001 giving details of the failures. If &%syntax_errors_text%& is set, its contents
22002 are expanded and placed at the head of the error message generated by
22003 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
22004 be the same address as the generic &%errors_to%& option. The
22005 &%skip_syntax_errors%& option is often used when handling mailing lists.
22007 If all the addresses in a redirection list are skipped because of syntax
22008 errors, the router declines to handle the original address, and it is passed to
22009 the following routers.
22011 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
22012 error in the filter causes filtering to be abandoned without any action being
22013 taken. The incident is logged, and the router declines to handle the address,
22014 so it is passed to the following routers.
22016 .cindex "Sieve filter" "syntax errors in"
22017 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
22018 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
22019 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
22021 &%skip_syntax_errors%& can be used to specify that errors in users' forward
22022 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
22023 option, used with an address that does not get redirected, can be used to
22024 notify users of these errors, by means of a router like this:
22030 file = $home/.forward
22031 file_transport = address_file
22032 pipe_transport = address_pipe
22033 reply_transport = address_reply
22036 syntax_errors_to = real-$local_part@$domain
22037 syntax_errors_text = \
22038 This is an automatically generated message. An error has\n\
22039 been found in your .forward file. Details of the error are\n\
22040 reported below. While this error persists, you will receive\n\
22041 a copy of this message for every message that is addressed\n\
22042 to you. If your .forward file is a filter file, or if it is\n\
22043 a non-filter file containing no valid forwarding addresses,\n\
22044 a copy of each incoming message will be put in your normal\n\
22045 mailbox. If a non-filter file contains at least one valid\n\
22046 forwarding address, forwarding to the valid addresses will\n\
22047 happen, and those will be the only deliveries that occur.
22049 You also need a router to ensure that local addresses that are prefixed by
22050 &`real-`& are recognized, but not forwarded or filtered. For example, you could
22051 put this immediately before the &(userforward)& router:
22056 local_part_prefix = real-
22057 transport = local_delivery
22059 For security, it would probably be a good idea to restrict the use of this
22060 router to locally-generated messages, using a condition such as this:
22062 condition = ${if match {$sender_host_address}\
22063 {\N^(|127\.0\.0\.1)$\N}}
22067 .option syntax_errors_text redirect string&!! unset
22068 See &%skip_syntax_errors%& above.
22071 .option syntax_errors_to redirect string unset
22072 See &%skip_syntax_errors%& above.
22073 .ecindex IIDredrou1
22074 .ecindex IIDredrou2
22081 . ////////////////////////////////////////////////////////////////////////////
22082 . ////////////////////////////////////////////////////////////////////////////
22084 .chapter "Environment for running local transports" "CHAPenvironment" &&&
22085 "Environment for local transports"
22086 .scindex IIDenvlotra1 "local transports" "environment for"
22087 .scindex IIDenvlotra2 "environment" "local transports"
22088 .scindex IIDenvlotra3 "transport" "local; environment for"
22089 Local transports handle deliveries to files and pipes. (The &(autoreply)&
22090 transport can be thought of as similar to a pipe.) Exim always runs transports
22091 in subprocesses, under specified uids and gids. Typical deliveries to local
22092 mailboxes run under the uid and gid of the local user.
22094 Exim also sets a specific current directory while running the transport; for
22095 some transports a home directory setting is also relevant. The &(pipe)&
22096 transport is the only one that sets up environment variables; see section
22097 &<<SECTpipeenv>>& for details.
22099 The values used for the uid, gid, and the directories may come from several
22100 different places. In many cases, the router that handles the address associates
22101 settings with that address as a result of its &%check_local_user%&, &%group%&,
22102 or &%user%& options. However, values may also be given in the transport's own
22103 configuration, and these override anything that comes from the router.
22107 .section "Concurrent deliveries" "SECID131"
22108 .cindex "concurrent deliveries"
22109 .cindex "simultaneous deliveries"
22110 If two different messages for the same local recipient arrive more or less
22111 simultaneously, the two delivery processes are likely to run concurrently. When
22112 the &(appendfile)& transport is used to write to a file, Exim applies locking
22113 rules to stop concurrent processes from writing to the same file at the same
22116 However, when you use a &(pipe)& transport, it is up to you to arrange any
22117 locking that is needed. Here is a silly example:
22121 command = /bin/sh -c 'cat >>/some/file'
22123 This is supposed to write the message at the end of the file. However, if two
22124 messages arrive at the same time, the file will be scrambled. You can use the
22125 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
22126 file using the same algorithm that Exim itself uses.
22131 .section "Uids and gids" "SECTenvuidgid"
22132 .cindex "local transports" "uid and gid"
22133 .cindex "transport" "local; uid and gid"
22134 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
22135 overrides any group that the router set in the address, even if &%user%& is not
22136 set for the transport. This makes it possible, for example, to run local mail
22137 delivery under the uid of the recipient (set by the router), but in a special
22138 group (set by the transport). For example:
22141 # User/group are set by check_local_user in this router
22145 transport = group_delivery
22148 # This transport overrides the group
22150 driver = appendfile
22151 file = /var/spool/mail/$local_part_data
22154 If &%user%& is set for a transport, its value overrides what is set in the
22155 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
22156 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
22159 .oindex "&%initgroups%&"
22160 When the uid is taken from the transport's configuration, the &[initgroups()]&
22161 function is called for the groups associated with that uid if the
22162 &%initgroups%& option is set for the transport. When the uid is not specified
22163 by the transport, but is associated with the address by a router, the option
22164 for calling &[initgroups()]& is taken from the router configuration.
22166 .cindex "&(pipe)& transport" "uid for"
22167 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
22168 is set and &%user%& is not set, the uid of the process that called Exim to
22169 receive the message is used, and if &%group%& is not set, the corresponding
22170 original gid is also used.
22172 This is the detailed preference order for obtaining a gid; the first of the
22173 following that is set is used:
22176 A &%group%& setting of the transport;
22178 A &%group%& setting of the router;
22180 A gid associated with a user setting of the router, either as a result of
22181 &%check_local_user%& or an explicit non-numeric &%user%& setting;
22183 The group associated with a non-numeric &%user%& setting of the transport;
22185 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
22186 the uid is the creator's uid;
22188 The Exim gid if the Exim uid is being used as a default.
22191 If, for example, the user is specified numerically on the router and there are
22192 no group settings, no gid is available. In this situation, an error occurs.
22193 This is different for the uid, for which there always is an ultimate default.
22194 The first of the following that is set is used:
22197 A &%user%& setting of the transport;
22199 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
22201 A &%user%& setting of the router;
22203 A &%check_local_user%& setting of the router;
22208 Of course, an error will still occur if the uid that is chosen is on the
22209 &%never_users%& list.
22215 .section "Current and home directories" "SECID132"
22216 .cindex "current directory for local transport"
22217 .cindex "home directory" "for local transport"
22218 .cindex "transport" "local; home directory for"
22219 .cindex "transport" "local; current directory for"
22220 Routers may set current and home directories for local transports by means of
22221 the &%transport_current_directory%& and &%transport_home_directory%& options.
22222 However, if the transport's &%current_directory%& or &%home_directory%& options
22223 are set, they override the router's values. In detail, the home directory
22224 for a local transport is taken from the first of these values that is set:
22227 The &%home_directory%& option on the transport;
22229 The &%transport_home_directory%& option on the router;
22231 The password data if &%check_local_user%& is set on the router;
22233 The &%router_home_directory%& option on the router.
22236 The current directory is taken from the first of these values that is set:
22239 The &%current_directory%& option on the transport;
22241 The &%transport_current_directory%& option on the router.
22245 If neither the router nor the transport sets a current directory, Exim uses the
22246 value of the home directory, if it is set. Otherwise it sets the current
22247 directory to &_/_& before running a local transport.
22251 .section "Expansion variables derived from the address" "SECID133"
22252 .vindex "&$domain$&"
22253 .vindex "&$local_part$&"
22254 .vindex "&$original_domain$&"
22255 Normally a local delivery is handling a single address, and in that case the
22256 variables such as &$domain$& and &$local_part$& are set during local
22257 deliveries. However, in some circumstances more than one address may be handled
22258 at once (for example, while writing batch SMTP for onward transmission by some
22259 other means). In this case, the variables associated with the local part are
22260 never set, &$domain$& is set only if all the addresses have the same domain,
22261 and &$original_domain$& is never set.
22262 .ecindex IIDenvlotra1
22263 .ecindex IIDenvlotra2
22264 .ecindex IIDenvlotra3
22272 . ////////////////////////////////////////////////////////////////////////////
22273 . ////////////////////////////////////////////////////////////////////////////
22275 .chapter "Generic options for transports" "CHAPtransportgeneric"
22276 .scindex IIDgenoptra1 "generic options" "transport"
22277 .scindex IIDgenoptra2 "options" "generic; for transports"
22278 .scindex IIDgenoptra3 "transport" "generic options for"
22279 The following generic options apply to all transports:
22282 .option body_only transports boolean false
22283 .cindex "transport" "body only"
22284 .cindex "message" "transporting body only"
22285 .cindex "body of message" "transporting"
22286 If this option is set, the message's headers are not transported. It is
22287 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
22288 or &(pipe)& transports, the settings of &%message_prefix%& and
22289 &%message_suffix%& should be checked, because this option does not
22290 automatically suppress them.
22293 .option current_directory transports string&!! unset
22294 .cindex "transport" "current directory for"
22295 This specifies the current directory that is to be set while running the
22296 transport, overriding any value that may have been set by the router.
22297 If the expansion fails for any reason, including forced failure, an error is
22298 logged, and delivery is deferred.
22301 .option disable_logging transports boolean false
22302 If this option is set true, nothing is logged for any
22303 deliveries by the transport or for any
22304 transport errors. You should not set this option unless you really, really know
22305 what you are doing.
22308 .option debug_print transports string&!! unset
22309 .cindex "testing" "variables in drivers"
22310 If this option is set and debugging is enabled (see the &%-d%& command line
22311 option), the string is expanded and included in the debugging output when the
22313 If expansion of the string fails, the error message is written to the debugging
22314 output, and Exim carries on processing.
22315 This facility is provided to help with checking out the values of variables and
22316 so on when debugging driver configurations. For example, if a &%headers_add%&
22317 option is not working properly, &%debug_print%& could be used to output the
22318 variables it references. A newline is added to the text if it does not end with
22320 The variables &$transport_name$& and &$router_name$& contain the name of the
22321 transport and the router that called it.
22323 .option delivery_date_add transports boolean false
22324 .cindex "&'Delivery-date:'& header line"
22325 If this option is true, a &'Delivery-date:'& header is added to the message.
22326 This gives the actual time the delivery was made. As this is not a standard
22327 header, Exim has a configuration option (&%delivery_date_remove%&) which
22328 requests its removal from incoming messages, so that delivered messages can
22329 safely be resent to other recipients.
22332 .option driver transports string unset
22333 This specifies which of the available transport drivers is to be used.
22334 There is no default, and this option must be set for every transport.
22337 .option envelope_to_add transports boolean false
22338 .cindex "&'Envelope-to:'& header line"
22339 If this option is true, an &'Envelope-to:'& header is added to the message.
22340 This gives the original address(es) in the incoming envelope that caused this
22341 delivery to happen. More than one address may be present if the transport is
22342 configured to handle several addresses at once, or if more than one original
22343 address was redirected to the same final address. As this is not a standard
22344 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
22345 its removal from incoming messages, so that delivered messages can safely be
22346 resent to other recipients.
22349 .option event_action transports string&!! unset
22351 This option declares a string to be expanded for Exim's events mechanism.
22352 For details see chapter &<<CHAPevents>>&.
22355 .option group transports string&!! "Exim group"
22356 .cindex "transport" "group; specifying"
22357 This option specifies a gid for running the transport process, overriding any
22358 value that the router supplies, and also overriding any value associated with
22359 &%user%& (see below).
22362 .option headers_add transports list&!! unset
22363 .cindex "header lines" "adding in transport"
22364 .cindex "transport" "header lines; adding"
22365 This option specifies a list of text headers,
22366 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22367 which are (separately) expanded and added to the header
22368 portion of a message as it is transported, as described in section
22369 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
22370 routers. If the result of the expansion is an empty string, or if the expansion
22371 is forced to fail, no action is taken. Other expansion failures are treated as
22372 errors and cause the delivery to be deferred.
22374 Unlike most options, &%headers_add%& can be specified multiple times
22375 for a transport; all listed headers are added.
22378 .option headers_only transports boolean false
22379 .cindex "transport" "header lines only"
22380 .cindex "message" "transporting headers only"
22381 .cindex "header lines" "transporting"
22382 If this option is set, the message's body is not transported. It is mutually
22383 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
22384 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
22385 checked, since this option does not automatically suppress them.
22388 .option headers_remove transports list&!! unset
22389 .cindex "header lines" "removing"
22390 .cindex "transport" "header lines; removing"
22391 This option specifies a list of text headers,
22392 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22393 to be removed from the message.
22394 However, the option has no effect when an address is just being verified.
22395 Each list item is separately expanded.
22396 If the result of the expansion is an empty string, or if the expansion
22397 is forced to fail, no action is taken. Other expansion failures are treated as
22398 errors and cause the delivery to be deferred.
22399 If an item ends in *, it will match any header with the given prefix.
22401 Matching headers are omitted from the message as it is transported, as described
22402 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
22405 Unlike most options, &%headers_remove%& can be specified multiple times
22406 for a transport; all listed headers are removed.
22408 &*Warning*&: Because of the separate expansion of the list items,
22409 items that contain a list separator must have it doubled.
22410 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
22414 .option headers_rewrite transports string unset
22415 .cindex "transport" "header lines; rewriting"
22416 .cindex "rewriting" "at transport time"
22417 This option allows addresses in header lines to be rewritten at transport time,
22418 that is, as the message is being copied to its destination. The contents of the
22419 option are a colon-separated list of rewriting rules. Each rule is in exactly
22420 the same form as one of the general rewriting rules that are applied when a
22421 message is received. These are described in chapter &<<CHAPrewrite>>&. For
22424 headers_rewrite = a@b c@d f : \
22427 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
22428 &'w@z'& in all address-bearing header lines. The rules are applied to the
22429 header lines just before they are written out at transport time, so they affect
22430 only those copies of the message that pass through the transport. However, only
22431 the message's original header lines, and any that were added by a system
22432 filter, are rewritten. If a router or transport adds header lines, they are not
22433 affected by this option. These rewriting rules are &'not'& applied to the
22434 envelope. You can change the return path using &%return_path%&, but you cannot
22435 change envelope recipients at this time.
22438 .option home_directory transports string&!! unset
22439 .cindex "transport" "home directory for"
22441 This option specifies a home directory setting for a local transport,
22442 overriding any value that may be set by the router. The home directory is
22443 placed in &$home$& while expanding the transport's private options. It is also
22444 used as the current directory if no current directory is set by the
22445 &%current_directory%& option on the transport or the
22446 &%transport_current_directory%& option on the router. If the expansion fails
22447 for any reason, including forced failure, an error is logged, and delivery is
22451 .option initgroups transports boolean false
22452 .cindex "additional groups"
22453 .cindex "groups" "additional"
22454 .cindex "transport" "group; additional"
22455 If this option is true and the uid for the delivery process is provided by the
22456 transport, the &[initgroups()]& function is called when running the transport
22457 to ensure that any additional groups associated with the uid are set up.
22460 .option max_parallel transports integer&!! unset
22461 .cindex limit "transport parallelism"
22462 .cindex transport "parallel processes"
22463 .cindex transport "concurrency limit"
22464 .cindex "delivery" "parallelism for transport"
22465 If this option is set and expands to an integer greater than zero
22466 it limits the number of concurrent runs of the transport.
22467 The control does not apply to shadow transports.
22469 .cindex "hints database" "transport concurrency control"
22470 Exim implements this control by means of a hints database in which a record is
22471 incremented whenever a transport process is being created. The record
22472 is decremented and possibly removed when the process terminates.
22473 Obviously there is scope for
22474 records to get left lying around if there is a system or program crash. To
22475 guard against this, Exim ignores any records that are more than six hours old.
22477 If you use this option, you should also arrange to delete the
22478 relevant hints database whenever your system reboots. The names of the files
22479 start with &_misc_& and they are kept in the &_spool/db_& directory. There
22480 may be one or two files, depending on the type of DBM in use. The same files
22481 are used for ETRN and smtp transport serialization.
22484 .option message_size_limit transports string&!! 0
22485 .cindex "limit" "message size per transport"
22486 .cindex "size" "of message, limit"
22487 .cindex "transport" "message size; limiting"
22488 This option controls the size of messages passed through the transport. It is
22489 expanded before use; the result of the expansion must be a sequence of decimal
22490 digits, optionally followed by K or M. If the expansion fails for any reason,
22491 including forced failure, or if the result is not of the required form,
22492 delivery is deferred. If the value is greater than zero and the size of a
22493 message exceeds this limit, the address is failed. If there is any chance that
22494 the resulting bounce message could be routed to the same transport, you should
22495 ensure that &%return_size_limit%& is less than the transport's
22496 &%message_size_limit%&, as otherwise the bounce message will fail to get
22501 .option rcpt_include_affixes transports boolean false
22502 .cindex "prefix" "for local part, including in envelope"
22503 .cindex "suffix for local part" "including in envelope"
22504 .cindex "local part" "prefix"
22505 .cindex "local part" "suffix"
22506 When this option is false (the default), and an address that has had any
22507 affixes (prefixes or suffixes) removed from the local part is delivered by any
22508 form of SMTP or LMTP, the affixes are not included. For example, if a router
22511 local_part_prefix = *-
22513 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
22516 RCPT TO:<xyz@some.domain>
22518 This is also the case when an ACL-time callout is being used to verify a
22519 recipient address. However, if &%rcpt_include_affixes%& is set true, the
22520 whole local part is included in the RCPT command. This option applies to BSMTP
22521 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
22522 &(lmtp)& and &(smtp)& transports.
22525 .option retry_use_local_part transports boolean "see below"
22526 .cindex "hints database" "retry keys"
22527 When a delivery suffers a temporary failure, a retry record is created
22528 in Exim's hints database. For remote deliveries, the key for the retry record
22529 is based on the name and/or IP address of the failing remote host. For local
22530 deliveries, the key is normally the entire address, including both the local
22531 part and the domain. This is suitable for most common cases of local delivery
22532 temporary failure &-- for example, exceeding a mailbox quota should delay only
22533 deliveries to that mailbox, not to the whole domain.
22535 However, in some special cases you may want to treat a temporary local delivery
22536 as a failure associated with the domain, and not with a particular local part.
22537 (For example, if you are storing all mail for some domain in files.) You can do
22538 this by setting &%retry_use_local_part%& false.
22540 For all the local transports, its default value is true. For remote transports,
22541 the default value is false for tidiness, but changing the value has no effect
22542 on a remote transport in the current implementation.
22545 .option return_path transports string&!! unset
22546 .cindex "envelope sender"
22547 .cindex "envelope from"
22548 .cindex "transport" "return path; changing"
22549 .cindex "return path" "changing in transport"
22550 If this option is set, the string is expanded at transport time and replaces
22551 the existing return path (envelope sender) value in the copy of the message
22552 that is being delivered. An empty return path is permitted. This feature is
22553 designed for remote deliveries, where the value of this option is used in the
22554 SMTP MAIL command. If you set &%return_path%& for a local transport, the
22555 only effect is to change the address that is placed in the &'Return-path:'&
22556 header line, if one is added to the message (see the next option).
22558 &*Note:*& A changed return path is not logged unless you add
22559 &%return_path_on_delivery%& to the log selector.
22561 .vindex "&$return_path$&"
22562 The expansion can refer to the existing value via &$return_path$&. This is
22563 either the message's envelope sender, or an address set by the
22564 &%errors_to%& option on a router. If the expansion is forced to fail, no
22565 replacement occurs; if it fails for another reason, delivery is deferred. This
22566 option can be used to support VERP (Variable Envelope Return Paths) &-- see
22567 section &<<SECTverp>>&.
22569 &*Note*&: If a delivery error is detected locally, including the case when a
22570 remote server rejects a message at SMTP time, the bounce message is not sent to
22571 the value of this option. It is sent to the previously set errors address.
22572 This defaults to the incoming sender address, but can be changed by setting
22573 &%errors_to%& in a router.
22577 .option return_path_add transports boolean false
22578 .cindex "&'Return-path:'& header line"
22579 If this option is true, a &'Return-path:'& header is added to the message.
22580 Although the return path is normally available in the prefix line of BSD
22581 mailboxes, this is commonly not displayed by MUAs, and so the user does not
22582 have easy access to it.
22584 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
22585 the delivery SMTP server makes the final delivery"&. This implies that this
22586 header should not be present in incoming messages. Exim has a configuration
22587 option, &%return_path_remove%&, which requests removal of this header from
22588 incoming messages, so that delivered messages can safely be resent to other
22592 .option shadow_condition transports string&!! unset
22593 See &%shadow_transport%& below.
22596 .option shadow_transport transports string unset
22597 .cindex "shadow transport"
22598 .cindex "transport" "shadow"
22599 A local transport may set the &%shadow_transport%& option to the name of
22600 another local transport. Shadow remote transports are not supported.
22602 Whenever a delivery to the main transport succeeds, and either
22603 &%shadow_condition%& is unset, or its expansion does not result in the empty
22604 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
22605 passed to the shadow transport, with the same delivery address or addresses. If
22606 expansion fails, no action is taken except that non-forced expansion failures
22607 cause a log line to be written.
22609 The result of the shadow transport is discarded and does not affect the
22610 subsequent processing of the message. Only a single level of shadowing is
22611 provided; the &%shadow_transport%& option is ignored on any transport when it
22612 is running as a shadow. Options concerned with output from pipes are also
22613 ignored. The log line for the successful delivery has an item added on the end,
22616 ST=<shadow transport name>
22618 If the shadow transport did not succeed, the error message is put in
22619 parentheses afterwards. Shadow transports can be used for a number of different
22620 purposes, including keeping more detailed log information than Exim normally
22621 provides, and implementing automatic acknowledgment policies based on message
22622 headers that some sites insist on.
22625 .option transport_filter transports string&!! unset
22626 .cindex "transport" "filter"
22627 .cindex "filter" "transport filter"
22628 This option sets up a filtering (in the Unix shell sense) process for messages
22629 at transport time. It should not be confused with mail filtering as set up by
22630 individual users or via a system filter.
22631 If unset, or expanding to an empty string, no filtering is done.
22633 When the message is about to be written out, the command specified by
22634 &%transport_filter%& is started up in a separate, parallel process, and
22635 the entire message, including the header lines, is passed to it on its standard
22636 input (this in fact is done from a third process, to avoid deadlock). The
22637 command must be specified as an absolute path.
22639 The lines of the message that are written to the transport filter are
22640 terminated by newline (&"\n"&). The message is passed to the filter before any
22641 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
22642 lines beginning with a dot, and also before any processing implied by the
22643 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
22644 &(pipe)& transports.
22646 The standard error for the filter process is set to the same destination as its
22647 standard output; this is read and written to the message's ultimate
22648 destination. The process that writes the message to the filter, the
22649 filter itself, and the original process that reads the result and delivers it
22650 are all run in parallel, like a shell pipeline.
22652 The filter can perform any transformations it likes, but of course should take
22653 care not to break RFC 2822 syntax. Exim does not check the result, except to
22654 test for a final newline when SMTP is in use. All messages transmitted over
22655 SMTP must end with a newline, so Exim supplies one if it is missing.
22657 .cindex "content scanning" "per user"
22658 A transport filter can be used to provide content-scanning on a per-user basis
22659 at delivery time if the only required effect of the scan is to modify the
22660 message. For example, a content scan could insert a new header line containing
22661 a spam score. This could be interpreted by a filter in the user's MUA. It is
22662 not possible to discard a message at this stage.
22664 .cindex "SIZE" "ESMTP extension"
22665 A problem might arise if the filter increases the size of a message that is
22666 being sent down an SMTP connection. If the receiving SMTP server has indicated
22667 support for the SIZE parameter, Exim will have sent the size of the message
22668 at the start of the SMTP session. If what is actually sent is substantially
22669 more, the server might reject the message. This can be worked round by setting
22670 the &%size_addition%& option on the &(smtp)& transport, either to allow for
22671 additions to the message, or to disable the use of SIZE altogether.
22673 .vindex "&$pipe_addresses$&"
22674 The value of the &%transport_filter%& option is the command string for starting
22675 the filter, which is run directly from Exim, not under a shell. The string is
22676 parsed by Exim in the same way as a command string for the &(pipe)& transport:
22677 Exim breaks it up into arguments and then expands each argument separately (see
22678 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
22679 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
22680 of arguments, one for each address that applies to this delivery. (This isn't
22681 an ideal name for this feature here, but as it was already implemented for the
22682 &(pipe)& transport, it seemed sensible not to change it.)
22685 .vindex "&$host_address$&"
22686 The expansion variables &$host$& and &$host_address$& are available when the
22687 transport is a remote one. They contain the name and IP address of the host to
22688 which the message is being sent. For example:
22690 transport_filter = /some/directory/transport-filter.pl \
22691 $host $host_address $sender_address $pipe_addresses
22694 Two problems arise if you want to use more complicated expansion items to
22695 generate transport filter commands, both of which due to the fact that the
22696 command is split up &'before'& expansion.
22698 If an expansion item contains white space, you must quote it, so that it is all
22699 part of the same command item. If the entire option setting is one such
22700 expansion item, you have to take care what kind of quoting you use. For
22703 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
22705 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
22706 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
22707 stripped by Exim when it read the option's value. When the value is used, if
22708 the single quotes were missing, the line would be split into two items,
22709 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
22710 Exim tried to expand the first one.
22712 Except for the special case of &$pipe_addresses$& that is mentioned above, an
22713 expansion cannot generate multiple arguments, or a command name followed by
22714 arguments. Consider this example:
22716 transport_filter = ${lookup{$host}lsearch{/a/file}\
22717 {$value}{/bin/cat}}
22719 The result of the lookup is interpreted as the name of the command, even
22720 if it contains white space. The simplest way round this is to use a shell:
22722 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
22723 {$value}{/bin/cat}}
22727 The filter process is run under the same uid and gid as the normal delivery.
22728 For remote deliveries this is the Exim uid/gid by default. The command should
22729 normally yield a zero return code. Transport filters are not supposed to fail.
22730 A non-zero code is taken to mean that the transport filter encountered some
22731 serious problem. Delivery of the message is deferred; the message remains on
22732 the queue and is tried again later. It is not possible to cause a message to be
22733 bounced from a transport filter.
22735 If a transport filter is set on an autoreply transport, the original message is
22736 passed through the filter as it is being copied into the newly generated
22737 message, which happens if the &%return_message%& option is set.
22740 .option transport_filter_timeout transports time 5m
22741 .cindex "transport" "filter, timeout"
22742 When Exim is reading the output of a transport filter, it applies a timeout
22743 that can be set by this option. Exceeding the timeout is normally treated as a
22744 temporary delivery failure. However, if a transport filter is used with a
22745 &(pipe)& transport, a timeout in the transport filter is treated in the same
22746 way as a timeout in the pipe command itself. By default, a timeout is a hard
22747 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
22748 becomes a temporary error.
22751 .option user transports string&!! "Exim user"
22752 .cindex "uid (user id)" "local delivery"
22753 .cindex "transport" "user, specifying"
22754 This option specifies the user under whose uid the delivery process is to be
22755 run, overriding any uid that may have been set by the router. If the user is
22756 given as a name, the uid is looked up from the password data, and the
22757 associated group is taken as the value of the gid to be used if the &%group%&
22760 For deliveries that use local transports, a user and group are normally
22761 specified explicitly or implicitly (for example, as a result of
22762 &%check_local_user%&) by the router or transport.
22764 .cindex "hints database" "access by remote transport"
22765 For remote transports, you should leave this option unset unless you really are
22766 sure you know what you are doing. When a remote transport is running, it needs
22767 to be able to access Exim's hints databases, because each host may have its own
22769 .ecindex IIDgenoptra1
22770 .ecindex IIDgenoptra2
22771 .ecindex IIDgenoptra3
22778 . ////////////////////////////////////////////////////////////////////////////
22779 . ////////////////////////////////////////////////////////////////////////////
22781 .chapter "Address batching in local transports" "CHAPbatching" &&&
22783 .cindex "transport" "local; address batching in"
22784 The only remote transport (&(smtp)&) is normally configured to handle more than
22785 one address at a time, so that when several addresses are routed to the same
22786 remote host, just one copy of the message is sent. Local transports, however,
22787 normally handle one address at a time. That is, a separate instance of the
22788 transport is run for each address that is routed to the transport. A separate
22789 copy of the message is delivered each time.
22791 .cindex "batched local delivery"
22792 .oindex "&%batch_max%&"
22793 .oindex "&%batch_id%&"
22794 In special cases, it may be desirable to handle several addresses at once in a
22795 local transport, for example:
22798 In an &(appendfile)& transport, when storing messages in files for later
22799 delivery by some other means, a single copy of the message with multiple
22800 recipients saves space.
22802 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
22803 a single copy saves time, and is the normal way LMTP is expected to work.
22805 In a &(pipe)& transport, when passing the message
22806 to a scanner program or
22807 to some other delivery mechanism such as UUCP, multiple recipients may be
22811 These three local transports all have the same options for controlling multiple
22812 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
22813 repeating the information for each transport, these options are described here.
22815 The &%batch_max%& option specifies the maximum number of addresses that can be
22816 delivered together in a single run of the transport. Its default value is one
22817 (no batching). When more than one address is routed to a transport that has a
22818 &%batch_max%& value greater than one, the addresses are delivered in a batch
22819 (that is, in a single run of the transport with multiple recipients), subject
22820 to certain conditions:
22823 .vindex "&$local_part$&"
22824 If any of the transport's options contain a reference to &$local_part$&, no
22825 batching is possible.
22827 .vindex "&$domain$&"
22828 If any of the transport's options contain a reference to &$domain$&, only
22829 addresses with the same domain are batched.
22831 .cindex "customizing" "batching condition"
22832 If &%batch_id%& is set, it is expanded for each address, and only those
22833 addresses with the same expanded value are batched. This allows you to specify
22834 customized batching conditions. Failure of the expansion for any reason,
22835 including forced failure, disables batching, but it does not stop the delivery
22838 Batched addresses must also have the same errors address (where to send
22839 delivery errors), the same header additions and removals, the same user and
22840 group for the transport, and if a host list is present, the first host must
22844 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
22845 both when the file or pipe command is specified in the transport, and when it
22846 is specified by a &(redirect)& router, but all the batched addresses must of
22847 course be routed to the same file or pipe command. These two transports have an
22848 option called &%use_bsmtp%&, which causes them to deliver the message in
22849 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
22850 &%check_string%& and &%escape_string%& options are forced to the values
22853 escape_string = ".."
22855 when batched SMTP is in use. A full description of the batch SMTP mechanism is
22856 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
22857 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
22859 .cindex "&'Envelope-to:'& header line"
22860 If the generic &%envelope_to_add%& option is set for a batching transport, the
22861 &'Envelope-to:'& header that is added to the message contains all the addresses
22862 that are being processed together. If you are using a batching &(appendfile)&
22863 transport without &%use_bsmtp%&, the only way to preserve the recipient
22864 addresses is to set the &%envelope_to_add%& option.
22866 .cindex "&(pipe)& transport" "with multiple addresses"
22867 .vindex "&$pipe_addresses$&"
22868 If you are using a &(pipe)& transport without BSMTP, and setting the
22869 transport's &%command%& option, you can include &$pipe_addresses$& as part of
22870 the command. This is not a true variable; it is a bit of magic that causes each
22871 of the recipient addresses to be inserted into the command as a separate
22872 argument. This provides a way of accessing all the addresses that are being
22873 delivered in the batch. &*Note:*& This is not possible for pipe commands that
22874 are specified by a &(redirect)& router.
22879 . ////////////////////////////////////////////////////////////////////////////
22880 . ////////////////////////////////////////////////////////////////////////////
22882 .chapter "The appendfile transport" "CHAPappendfile"
22883 .scindex IIDapptra1 "&(appendfile)& transport"
22884 .scindex IIDapptra2 "transports" "&(appendfile)&"
22885 .cindex "directory creation"
22886 .cindex "creating directories"
22887 The &(appendfile)& transport delivers a message by appending it to an existing
22888 file, or by creating an entirely new file in a specified directory. Single
22889 files to which messages are appended can be in the traditional Unix mailbox
22890 format, or optionally in the MBX format supported by the Pine MUA and
22891 University of Washington IMAP daemon, &'inter alia'&. When each message is
22892 being delivered as a separate file, &"maildir"& format can optionally be used
22893 to give added protection against failures that happen part-way through the
22894 delivery. A third form of separate-file delivery known as &"mailstore"& is also
22895 supported. For all file formats, Exim attempts to create as many levels of
22896 directory as necessary, provided that &%create_directory%& is set.
22898 The code for the optional formats is not included in the Exim binary by
22899 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
22900 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
22903 .cindex "quota" "system"
22904 Exim recognizes system quota errors, and generates an appropriate message. Exim
22905 also supports its own quota control within the transport, for use when the
22906 system facility is unavailable or cannot be used for some reason.
22908 If there is an error while appending to a file (for example, quota exceeded or
22909 partition filled), Exim attempts to reset the file's length and last
22910 modification time back to what they were before. If there is an error while
22911 creating an entirely new file, the new file is removed.
22913 Before appending to a file, a number of security checks are made, and the
22914 file is locked. A detailed description is given below, after the list of
22917 The &(appendfile)& transport is most commonly used for local deliveries to
22918 users' mailboxes. However, it can also be used as a pseudo-remote transport for
22919 putting messages into files for remote delivery by some means other than Exim.
22920 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
22925 .section "The file and directory options" "SECTfildiropt"
22926 The &%file%& option specifies a single file, to which the message is appended;
22927 the &%directory%& option specifies a directory, in which a new file containing
22928 the message is created. Only one of these two options can be set, and for
22929 normal deliveries to mailboxes, one of them &'must'& be set.
22931 .vindex "&$address_file$&"
22932 .vindex "&$local_part$&"
22933 However, &(appendfile)& is also used for delivering messages to files or
22934 directories whose names (or parts of names) are obtained from alias,
22935 forwarding, or filtering operations (for example, a &%save%& command in a
22936 user's Exim filter). When such a transport is running, &$local_part$& contains
22937 the local part that was aliased or forwarded, and &$address_file$& contains the
22938 name (or partial name) of the file or directory generated by the redirection
22939 operation. There are two cases:
22942 If neither &%file%& nor &%directory%& is set, the redirection operation
22943 must specify an absolute path (one that begins with &`/`&). This is the most
22944 common case when users with local accounts use filtering to sort mail into
22945 different folders. See for example, the &(address_file)& transport in the
22946 default configuration. If the path ends with a slash, it is assumed to be the
22947 name of a directory. A delivery to a directory can also be forced by setting
22948 &%maildir_format%& or &%mailstore_format%&.
22950 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
22951 used to determine the file or directory name for the delivery. Normally, the
22952 contents of &$address_file$& are used in some way in the string expansion.
22954 .cindex "tainted data" "in filenames"
22955 .cindex appendfile "tainted data"
22956 Tainted data may not be used for a file or directory name.
22957 This means that, for instance, &$local_part$& cannot be used directly
22958 as a component of a path. It can however be used as the key for a lookup
22959 which returns a path (or component).
22962 .cindex "Sieve filter" "configuring &(appendfile)&"
22963 .cindex "Sieve filter" "relative mailbox path handling"
22964 As an example of the second case, consider an environment where users do not
22965 have home directories. They may be permitted to use Exim filter commands of the
22970 or Sieve filter commands of the form:
22972 require "fileinto";
22973 fileinto "folder23";
22975 In this situation, the expansion of &%file%& or &%directory%& in the transport
22976 must transform the relative path into an appropriate absolute filename. In the
22977 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
22978 is used as a result of a &"keep"& action in the filter. This example shows one
22979 way of handling this requirement:
22981 file = ${if eq{$address_file}{inbox} \
22982 {/var/mail/$local_part_data} \
22983 {${if eq{${substr_0_1:$address_file}}{/} \
22985 {$home/mail/$address_file} \
22989 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
22990 location, absolute paths are used without change, and other folders are in the
22991 &_mail_& directory within the home directory.
22993 &*Note 1*&: While processing an Exim filter, a relative path such as
22994 &_folder23_& is turned into an absolute path if a home directory is known to
22995 the router. In particular, this is the case if &%check_local_user%& is set. If
22996 you want to prevent this happening at routing time, you can set
22997 &%router_home_directory%& empty. This forces the router to pass the relative
22998 path to the transport.
23000 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
23001 the &%file%& or &%directory%& option is still used if it is set.
23006 .section "Private options for appendfile" "SECID134"
23007 .cindex "options" "&(appendfile)& transport"
23011 .option allow_fifo appendfile boolean false
23012 .cindex "fifo (named pipe)"
23013 .cindex "named pipe (fifo)"
23014 .cindex "pipe" "named (fifo)"
23015 Setting this option permits delivery to named pipes (FIFOs) as well as to
23016 regular files. If no process is reading the named pipe at delivery time, the
23017 delivery is deferred.
23020 .option allow_symlink appendfile boolean false
23021 .cindex "symbolic link" "to mailbox"
23022 .cindex "mailbox" "symbolic link"
23023 By default, &(appendfile)& will not deliver if the path name for the file is
23024 that of a symbolic link. Setting this option relaxes that constraint, but there
23025 are security issues involved in the use of symbolic links. Be sure you know
23026 what you are doing if you set this. Details of exactly what this option affects
23027 are included in the discussion which follows this list of options.
23030 .option batch_id appendfile string&!! unset
23031 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23032 However, batching is automatically disabled for &(appendfile)& deliveries that
23033 happen as a result of forwarding or aliasing or other redirection directly to a
23037 .option batch_max appendfile integer 1
23038 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23041 .option check_group appendfile boolean false
23042 When this option is set, the group owner of the file defined by the &%file%&
23043 option is checked to see that it is the same as the group under which the
23044 delivery process is running. The default setting is false because the default
23045 file mode is 0600, which means that the group is irrelevant.
23048 .option check_owner appendfile boolean true
23049 When this option is set, the owner of the file defined by the &%file%& option
23050 is checked to ensure that it is the same as the user under which the delivery
23051 process is running.
23054 .option check_string appendfile string "see below"
23055 .cindex "&""From""& line"
23056 As &(appendfile)& writes the message, the start of each line is tested for
23057 matching &%check_string%&, and if it does, the initial matching characters are
23058 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
23059 a literal string, not a regular expression, and the case of any letters it
23060 contains is significant.
23062 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
23063 are forced to &"."& and &".."& respectively, and any settings in the
23064 configuration are ignored. Otherwise, they default to &"From&~"& and
23065 &">From&~"& when the &%file%& option is set, and unset when any of the
23066 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
23068 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
23069 suitable for traditional &"BSD"& mailboxes, where a line beginning with
23070 &"From&~"& indicates the start of a new message. All four options need changing
23071 if another format is used. For example, to deliver to mailboxes in MMDF format:
23072 .cindex "MMDF format mailbox"
23073 .cindex "mailbox" "MMDF format"
23075 check_string = "\1\1\1\1\n"
23076 escape_string = "\1\1\1\1 \n"
23077 message_prefix = "\1\1\1\1\n"
23078 message_suffix = "\1\1\1\1\n"
23080 .option create_directory appendfile boolean true
23081 .cindex "directory creation"
23082 When this option is true, Exim attempts to create any missing superior
23083 directories for the file that it is about to write. A created directory's mode
23084 is given by the &%directory_mode%& option.
23086 The group ownership of a newly created directory is highly dependent on the
23087 operating system (and possibly the file system) that is being used. For
23088 example, in Solaris, if the parent directory has the setgid bit set, its group
23089 is propagated to the child; if not, the currently set group is used. However,
23090 in FreeBSD, the parent's group is always used.
23094 .option create_file appendfile string anywhere
23095 This option constrains the location of files and directories that are created
23096 by this transport. It applies to files defined by the &%file%& option and
23097 directories defined by the &%directory%& option. In the case of maildir
23098 delivery, it applies to the top level directory, not the maildir directories
23101 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
23102 &"belowhome"&. In the second and third cases, a home directory must have been
23103 set for the transport. This option is not useful when an explicit filename is
23104 given for normal mailbox deliveries. It is intended for the case when filenames
23105 are generated from users' &_.forward_& files. These are usually handled
23106 by an &(appendfile)& transport called &%address_file%&. See also
23107 &%file_must_exist%&.
23110 .option directory appendfile string&!! unset
23111 This option is mutually exclusive with the &%file%& option, but one of &%file%&
23112 or &%directory%& must be set, unless the delivery is the direct result of a
23113 redirection (see section &<<SECTfildiropt>>&).
23115 When &%directory%& is set, the string is expanded, and the message is delivered
23116 into a new file or files in or below the given directory, instead of being
23117 appended to a single mailbox file. A number of different formats are provided
23118 (see &%maildir_format%& and &%mailstore_format%&), and see section
23119 &<<SECTopdir>>& for further details of this form of delivery.
23122 .option directory_file appendfile string&!! "see below"
23124 .vindex "&$inode$&"
23125 When &%directory%& is set, but neither &%maildir_format%& nor
23126 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
23127 whose name is obtained by expanding this string. The default value is:
23129 q${base62:$tod_epoch}-$inode
23131 This generates a unique name from the current time, in base 62 form, and the
23132 inode of the file. The variable &$inode$& is available only when expanding this
23136 .option directory_mode appendfile "octal integer" 0700
23137 If &(appendfile)& creates any directories as a result of the
23138 &%create_directory%& option, their mode is specified by this option.
23141 .option escape_string appendfile string "see description"
23142 See &%check_string%& above.
23145 .option file appendfile string&!! unset
23146 This option is mutually exclusive with the &%directory%& option, but one of
23147 &%file%& or &%directory%& must be set, unless the delivery is the direct result
23148 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
23149 specifies a single file, to which the message is appended. One or more of
23150 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
23153 .cindex "NFS" "lock file"
23154 .cindex "locking files"
23155 .cindex "lock files"
23156 If you are using more than one host to deliver over NFS into the same
23157 mailboxes, you should always use lock files.
23159 The string value is expanded for each delivery, and must yield an absolute
23160 path. The most common settings of this option are variations on one of these
23163 file = /var/spool/mail/$local_part_data
23164 file = /home/$local_part_data/inbox
23167 .cindex "&""sticky""& bit"
23168 In the first example, all deliveries are done into the same directory. If Exim
23169 is configured to use lock files (see &%use_lockfile%& below) it must be able to
23170 create a file in the directory, so the &"sticky"& bit must be turned on for
23171 deliveries to be possible, or alternatively the &%group%& option can be used to
23172 run the delivery under a group id which has write access to the directory.
23176 .option file_format appendfile string unset
23177 .cindex "file" "mailbox; checking existing format"
23178 This option requests the transport to check the format of an existing file
23179 before adding to it. The check consists of matching a specific string at the
23180 start of the file. The value of the option consists of an even number of
23181 colon-separated strings. The first of each pair is the test string, and the
23182 second is the name of a transport. If the transport associated with a matched
23183 string is not the current transport, control is passed over to the other
23184 transport. For example, suppose the standard &(local_delivery)& transport has
23187 file_format = "From : local_delivery :\
23188 \1\1\1\1\n : local_mmdf_delivery"
23190 Mailboxes that begin with &"From"& are still handled by this transport, but if
23191 a mailbox begins with four binary ones followed by a newline, control is passed
23192 to a transport called &%local_mmdf_delivery%&, which presumably is configured
23193 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
23194 is assumed to match the current transport. If the start of a mailbox doesn't
23195 match any string, or if the transport named for a given string is not defined,
23196 delivery is deferred.
23199 .option file_must_exist appendfile boolean false
23200 If this option is true, the file specified by the &%file%& option must exist.
23201 A temporary error occurs if it does not, causing delivery to be deferred.
23202 If this option is false, the file is created if it does not exist.
23205 .option lock_fcntl_timeout appendfile time 0s
23206 .cindex "timeout" "mailbox locking"
23207 .cindex "mailbox" "locking, blocking and non-blocking"
23208 .cindex "locking files"
23209 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
23210 when locking an open mailbox file. If the call fails, the delivery process
23211 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
23212 Non-blocking calls are used so that the file is not kept open during the wait
23213 for the lock; the reason for this is to make it as safe as possible for
23214 deliveries over NFS in the case when processes might be accessing an NFS
23215 mailbox without using a lock file. This should not be done, but
23216 misunderstandings and hence misconfigurations are not unknown.
23218 On a busy system, however, the performance of a non-blocking lock approach is
23219 not as good as using a blocking lock with a timeout. In this case, the waiting
23220 is done inside the system call, and Exim's delivery process acquires the lock
23221 and can proceed as soon as the previous lock holder releases it.
23223 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
23224 timeout, are used. There may still be some retrying: the maximum number of
23227 (lock_retries * lock_interval) / lock_fcntl_timeout
23229 rounded up to the next whole number. In other words, the total time during
23230 which &(appendfile)& is trying to get a lock is roughly the same, unless
23231 &%lock_fcntl_timeout%& is set very large.
23233 You should consider setting this option if you are getting a lot of delayed
23234 local deliveries because of errors of the form
23236 failed to lock mailbox /some/file (fcntl)
23239 .option lock_flock_timeout appendfile time 0s
23240 This timeout applies to file locking when using &[flock()]& (see
23241 &%use_flock%&); the timeout operates in a similar manner to
23242 &%lock_fcntl_timeout%&.
23245 .option lock_interval appendfile time 3s
23246 This specifies the time to wait between attempts to lock the file. See below
23247 for details of locking.
23250 .option lock_retries appendfile integer 10
23251 This specifies the maximum number of attempts to lock the file. A value of zero
23252 is treated as 1. See below for details of locking.
23255 .option lockfile_mode appendfile "octal integer" 0600
23256 This specifies the mode of the created lock file, when a lock file is being
23257 used (see &%use_lockfile%& and &%use_mbx_lock%&).
23260 .option lockfile_timeout appendfile time 30m
23261 .cindex "timeout" "mailbox locking"
23262 When a lock file is being used (see &%use_lockfile%&), if a lock file already
23263 exists and is older than this value, it is assumed to have been left behind by
23264 accident, and Exim attempts to remove it.
23267 .option mailbox_filecount appendfile string&!! unset
23268 .cindex "mailbox" "specifying size of"
23269 .cindex "size" "of mailbox"
23270 If this option is set, it is expanded, and the result is taken as the current
23271 number of files in the mailbox. It must be a decimal number, optionally
23272 followed by K or M. This provides a way of obtaining this information from an
23273 external source that maintains the data.
23276 .option mailbox_size appendfile string&!! unset
23277 .cindex "mailbox" "specifying size of"
23278 .cindex "size" "of mailbox"
23279 If this option is set, it is expanded, and the result is taken as the current
23280 size the mailbox. It must be a decimal number, optionally followed by K or M.
23281 This provides a way of obtaining this information from an external source that
23282 maintains the data. This is likely to be helpful for maildir deliveries where
23283 it is computationally expensive to compute the size of a mailbox.
23287 .option maildir_format appendfile boolean false
23288 .cindex "maildir format" "specifying"
23289 If this option is set with the &%directory%& option, the delivery is into a new
23290 file, in the &"maildir"& format that is used by other mail software. When the
23291 transport is activated directly from a &(redirect)& router (for example, the
23292 &(address_file)& transport in the default configuration), setting
23293 &%maildir_format%& causes the path received from the router to be treated as a
23294 directory, whether or not it ends with &`/`&. This option is available only if
23295 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
23296 &<<SECTmaildirdelivery>>& below for further details.
23299 .option maildir_quota_directory_regex appendfile string "See below"
23300 .cindex "maildir format" "quota; directories included in"
23301 .cindex "quota" "maildir; directories included in"
23302 This option is relevant only when &%maildir_use_size_file%& is set. It defines
23303 a regular expression for specifying directories, relative to the quota
23304 directory (see &%quota_directory%&), that should be included in the quota
23305 calculation. The default value is:
23307 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
23309 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
23310 (directories whose names begin with a dot). If you want to exclude the
23312 folder from the count (as some sites do), you need to change this setting to
23314 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
23316 This uses a negative lookahead in the regular expression to exclude the
23317 directory whose name is &_.Trash_&. When a directory is excluded from quota
23318 calculations, quota processing is bypassed for any messages that are delivered
23319 directly into that directory.
23322 .option maildir_retries appendfile integer 10
23323 This option specifies the number of times to retry when writing a file in
23324 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
23327 .option maildir_tag appendfile string&!! unset
23328 This option applies only to deliveries in maildir format, and is described in
23329 section &<<SECTmaildirdelivery>>& below.
23332 .option maildir_use_size_file appendfile&!! boolean false
23333 .cindex "maildir format" "&_maildirsize_& file"
23334 The result of string expansion for this option must be a valid boolean value.
23335 If it is true, it enables support for &_maildirsize_& files. Exim
23336 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
23337 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
23338 value is zero. See &%maildir_quota_directory_regex%& above and section
23339 &<<SECTmaildirdelivery>>& below for further details.
23341 .option maildirfolder_create_regex appendfile string unset
23342 .cindex "maildir format" "&_maildirfolder_& file"
23343 .cindex "&_maildirfolder_&, creating"
23344 The value of this option is a regular expression. If it is unset, it has no
23345 effect. Otherwise, before a maildir delivery takes place, the pattern is
23346 matched against the name of the maildir directory, that is, the directory
23347 containing the &_new_& and &_tmp_& subdirectories that will be used for the
23348 delivery. If there is a match, Exim checks for the existence of a file called
23349 &_maildirfolder_& in the directory, and creates it if it does not exist.
23350 See section &<<SECTmaildirdelivery>>& for more details.
23353 .option mailstore_format appendfile boolean false
23354 .cindex "mailstore format" "specifying"
23355 If this option is set with the &%directory%& option, the delivery is into two
23356 new files in &"mailstore"& format. The option is available only if
23357 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
23358 below for further details.
23361 .option mailstore_prefix appendfile string&!! unset
23362 This option applies only to deliveries in mailstore format, and is described in
23363 section &<<SECTopdir>>& below.
23366 .option mailstore_suffix appendfile string&!! unset
23367 This option applies only to deliveries in mailstore format, and is described in
23368 section &<<SECTopdir>>& below.
23371 .option mbx_format appendfile boolean false
23372 .cindex "locking files"
23373 .cindex "file" "locking"
23374 .cindex "file" "MBX format"
23375 .cindex "MBX format, specifying"
23376 This option is available only if Exim has been compiled with SUPPORT_MBX
23377 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
23378 the message is appended to the mailbox file in MBX format instead of
23379 traditional Unix format. This format is supported by Pine4 and its associated
23380 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
23382 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
23383 automatically changed by the use of &%mbx_format%&. They should normally be set
23384 empty when using MBX format, so this option almost always appears in this
23391 If none of the locking options are mentioned in the configuration,
23392 &%use_mbx_lock%& is assumed and the other locking options default to false. It
23393 is possible to specify the other kinds of locking with &%mbx_format%&, but
23394 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
23395 interworks with &'c-client'&, providing for shared access to the mailbox. It
23396 should not be used if any program that does not use this form of locking is
23397 going to access the mailbox, nor should it be used if the mailbox file is NFS
23398 mounted, because it works only when the mailbox is accessed from a single host.
23400 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
23401 the standard version of &'c-client'&, because as long as it has a mailbox open
23402 (this means for the whole of a Pine or IMAP session), Exim will not be able to
23403 append messages to it.
23406 .option message_prefix appendfile string&!! "see below"
23407 .cindex "&""From""& line"
23408 The string specified here is expanded and output at the start of every message.
23409 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23410 in which case it is:
23412 message_prefix = "From ${if def:return_path{$return_path}\
23413 {MAILER-DAEMON}} $tod_bsdinbox\n"
23415 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23416 &`\n`& to &`\r\n`& in &%message_prefix%&.
23418 .option message_suffix appendfile string&!! "see below"
23419 The string specified here is expanded and output at the end of every message.
23420 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23421 in which case it is a single newline character. The suffix can be suppressed by
23426 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23427 &`\n`& to &`\r\n`& in &%message_suffix%&.
23429 .option mode appendfile "octal integer" 0600
23430 If the output file is created, it is given this mode. If it already exists and
23431 has wider permissions, they are reduced to this mode. If it has narrower
23432 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
23433 if the delivery is the result of a &%save%& command in a filter file specifying
23434 a particular mode, the mode of the output file is always forced to take that
23435 value, and this option is ignored.
23438 .option mode_fail_narrower appendfile boolean true
23439 This option applies in the case when an existing mailbox file has a narrower
23440 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
23441 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
23442 continues with the delivery attempt, using the existing mode of the file.
23445 .option notify_comsat appendfile boolean false
23446 If this option is true, the &'comsat'& daemon is notified after every
23447 successful delivery to a user mailbox. This is the daemon that notifies logged
23448 on users about incoming mail.
23451 .option quota appendfile string&!! unset
23452 .cindex "quota" "imposed by Exim"
23453 This option imposes a limit on the size of the file to which Exim is appending,
23454 or to the total space used in the directory tree when the &%directory%& option
23455 is set. In the latter case, computation of the space used is expensive, because
23456 all the files in the directory (and any sub-directories) have to be
23457 individually inspected and their sizes summed. (See &%quota_size_regex%& and
23458 &%maildir_use_size_file%& for ways to avoid this in environments where users
23459 have no shell access to their mailboxes).
23461 As there is no interlock against two simultaneous deliveries into a
23462 multi-file mailbox, it is possible for the quota to be overrun in this case.
23463 For single-file mailboxes, of course, an interlock is a necessity.
23465 A file's size is taken as its &'used'& value. Because of blocking effects, this
23466 may be a lot less than the actual amount of disk space allocated to the file.
23467 If the sizes of a number of files are being added up, the rounding effect can
23468 become quite noticeable, especially on systems that have large block sizes.
23469 Nevertheless, it seems best to stick to the &'used'& figure, because this is
23470 the obvious value which users understand most easily.
23472 The value of the option is expanded, and must then be a numerical value
23473 (decimal point allowed), optionally followed by one of the letters K, M, or G,
23474 for kilobytes, megabytes, or gigabytes, optionally followed by a slash
23475 and further option modifiers. If Exim is running on a system with
23476 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
23479 The option modifier &%no_check%& can be used to force delivery even if the over
23480 quota condition is met. The quota gets updated as usual.
23482 &*Note*&: A value of zero is interpreted as &"no quota"&.
23484 The expansion happens while Exim is running as root, before it changes uid for
23485 the delivery. This means that files that are inaccessible to the end user can
23486 be used to hold quota values that are looked up in the expansion. When delivery
23487 fails because this quota is exceeded, the handling of the error is as for
23488 system quota failures.
23490 By default, Exim's quota checking mimics system quotas, and restricts the
23491 mailbox to the specified maximum size, though the value is not accurate to the
23492 last byte, owing to separator lines and additional headers that may get added
23493 during message delivery. When a mailbox is nearly full, large messages may get
23494 refused even though small ones are accepted, because the size of the current
23495 message is added to the quota when the check is made. This behaviour can be
23496 changed by setting &%quota_is_inclusive%& false. When this is done, the check
23497 for exceeding the quota does not include the current message. Thus, deliveries
23498 continue until the quota has been exceeded; thereafter, no further messages are
23499 delivered. See also &%quota_warn_threshold%&.
23502 .option quota_directory appendfile string&!! unset
23503 This option defines the directory to check for quota purposes when delivering
23504 into individual files. The default is the delivery directory, or, if a file
23505 called &_maildirfolder_& exists in a maildir directory, the parent of the
23506 delivery directory.
23509 .option quota_filecount appendfile string&!! 0
23510 This option applies when the &%directory%& option is set. It limits the total
23511 number of files in the directory (compare the inode limit in system quotas). It
23512 can only be used if &%quota%& is also set. The value is expanded; an expansion
23513 failure causes delivery to be deferred. A value of zero is interpreted as
23516 The option modifier &%no_check%& can be used to force delivery even if the over
23517 quota condition is met. The quota gets updated as usual.
23519 .option quota_is_inclusive appendfile boolean true
23520 See &%quota%& above.
23523 .option quota_size_regex appendfile string unset
23524 This option applies when one of the delivery modes that writes a separate file
23525 for each message is being used. When Exim wants to find the size of one of
23526 these files in order to test the quota, it first checks &%quota_size_regex%&.
23527 If this is set to a regular expression that matches the filename, and it
23528 captures one string, that string is interpreted as a representation of the
23529 file's size. The value of &%quota_size_regex%& is not expanded.
23531 This feature is useful only when users have no shell access to their mailboxes
23532 &-- otherwise they could defeat the quota simply by renaming the files. This
23533 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
23534 the file length to the filename. For example:
23536 maildir_tag = ,S=$message_size
23537 quota_size_regex = ,S=(\d+)
23539 An alternative to &$message_size$& is &$message_linecount$&, which contains the
23540 number of lines in the message.
23542 The regular expression should not assume that the length is at the end of the
23543 filename (even though &%maildir_tag%& puts it there) because maildir MUAs
23544 sometimes add other information onto the ends of message filenames.
23546 Section &<<SECID136>>& contains further information.
23548 This option should not be used when other message-handling software
23549 may duplicate messages by making hardlinks to the files. When that is done Exim
23550 will count the message size once for each filename, in contrast with the actual
23551 disk usage. When the option is not set, calculating total usage requires
23552 a system-call per file to get the size; the number of links is then available also
23553 as is used to adjust the effective size.
23556 .option quota_warn_message appendfile string&!! "see below"
23557 See below for the use of this option. If it is not set when
23558 &%quota_warn_threshold%& is set, it defaults to
23560 quota_warn_message = "\
23561 To: $local_part@$domain\n\
23562 Subject: Your mailbox\n\n\
23563 This message is automatically created \
23564 by mail delivery software.\n\n\
23565 The size of your mailbox has exceeded \
23566 a warning threshold that is\n\
23567 set by the system administrator.\n"
23571 .option quota_warn_threshold appendfile string&!! 0
23572 .cindex "quota" "warning threshold"
23573 .cindex "mailbox" "size warning"
23574 .cindex "size" "of mailbox"
23575 This option is expanded in the same way as &%quota%& (see above). If the
23576 resulting value is greater than zero, and delivery of the message causes the
23577 size of the file or total space in the directory tree to cross the given
23578 threshold, a warning message is sent. If &%quota%& is also set, the threshold
23579 may be specified as a percentage of it by following the value with a percent
23583 quota_warn_threshold = 75%
23585 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
23586 percent sign is ignored.
23588 The warning message itself is specified by the &%quota_warn_message%& option,
23589 and it must start with a &'To:'& header line containing the recipient(s) of the
23590 warning message. These do not necessarily have to include the recipient(s) of
23591 the original message. A &'Subject:'& line should also normally be supplied. You
23592 can include any other header lines that you want. If you do not include a
23593 &'From:'& line, the default is:
23595 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
23597 .oindex &%errors_reply_to%&
23598 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
23601 The &%quota%& option does not have to be set in order to use this option; they
23602 are independent of one another except when the threshold is specified as a
23606 .option use_bsmtp appendfile boolean false
23607 .cindex "envelope from"
23608 .cindex "envelope sender"
23609 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
23610 format, with the envelope sender and recipient(s) included as SMTP commands. If
23611 you want to include a leading HELO command with such messages, you can do
23612 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
23613 for details of batch SMTP.
23616 .option use_crlf appendfile boolean false
23617 .cindex "carriage return"
23619 This option causes lines to be terminated with the two-character CRLF sequence
23620 (carriage return, linefeed) instead of just a linefeed character. In the case
23621 of batched SMTP, the byte sequence written to the file is then an exact image
23622 of what would be sent down a real SMTP connection.
23624 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
23625 (which are used to supply the traditional &"From&~"& and blank line separators
23626 in Berkeley-style mailboxes) are written verbatim, so must contain their own
23627 carriage return characters if these are needed. In cases where these options
23628 have non-empty defaults, the values end with a single linefeed, so they must be
23629 changed to end with &`\r\n`& if &%use_crlf%& is set.
23632 .option use_fcntl_lock appendfile boolean "see below"
23633 This option controls the use of the &[fcntl()]& function to lock a file for
23634 exclusive use when a message is being appended. It is set by default unless
23635 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
23636 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
23637 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
23640 .option use_flock_lock appendfile boolean false
23641 This option is provided to support the use of &[flock()]& for file locking, for
23642 the few situations where it is needed. Most modern operating systems support
23643 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
23644 each other. Exim uses &[fcntl()]& locking by default.
23646 This option is required only if you are using an operating system where
23647 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
23648 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
23649 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
23651 .cindex "Solaris" "&[flock()]& support"
23652 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
23653 have it (and some, I think, provide a not quite right version built on top of
23654 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
23655 the ability to use it, and any attempt to do so will cause a configuration
23658 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
23659 is just being mapped onto &[fcntl()]& by the OS).
23662 .option use_lockfile appendfile boolean "see below"
23663 If this option is turned off, Exim does not attempt to create a lock file when
23664 appending to a mailbox file. In this situation, the only locking is by
23665 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
23666 sure that every MUA that is ever going to look at your users' mailboxes uses
23667 &[fcntl()]& rather than a lock file, and even then only when you are not
23668 delivering over NFS from more than one host.
23670 .cindex "NFS" "lock file"
23671 In order to append to an NFS file safely from more than one host, it is
23672 necessary to take out a lock &'before'& opening the file, and the lock file
23673 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
23676 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
23677 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
23678 except when &%mbx_format%& is set.
23681 .option use_mbx_lock appendfile boolean "see below"
23682 This option is available only if Exim has been compiled with SUPPORT_MBX
23683 set in &_Local/Makefile_&. Setting the option specifies that special MBX
23684 locking rules be used. It is set by default if &%mbx_format%& is set and none
23685 of the locking options are mentioned in the configuration. The locking rules
23686 are the same as are used by the &'c-client'& library that underlies Pine and
23687 the IMAP4 and POP daemons that come with it (see the discussion below). The
23688 rules allow for shared access to the mailbox. However, this kind of locking
23689 does not work when the mailbox is NFS mounted.
23691 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
23692 &%use_flock_lock%& to control what kind of locking is used in implementing the
23693 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
23694 without &%use_fcntl_lock%& or &%use_flock_lock%&.
23699 .section "Operational details for appending" "SECTopappend"
23700 .cindex "appending to a file"
23701 .cindex "file" "appending"
23702 Before appending to a file, the following preparations are made:
23705 If the name of the file is &_/dev/null_&, no action is taken, and a success
23709 .cindex "directory creation"
23710 If any directories on the file's path are missing, Exim creates them if the
23711 &%create_directory%& option is set. A created directory's mode is given by the
23712 &%directory_mode%& option.
23715 If &%file_format%& is set, the format of an existing file is checked. If this
23716 indicates that a different transport should be used, control is passed to that
23720 .cindex "file" "locking"
23721 .cindex "locking files"
23722 .cindex "NFS" "lock file"
23723 If &%use_lockfile%& is set, a lock file is built in a way that will work
23724 reliably over NFS, as follows:
23727 Create a &"hitching post"& file whose name is that of the lock file with the
23728 current time, primary host name, and process id added, by opening for writing
23729 as a new file. If this fails with an access error, delivery is deferred.
23731 Close the hitching post file, and hard link it to the lock filename.
23733 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
23734 Unlink the hitching post name.
23736 Otherwise, use &[stat()]& to get information about the hitching post file, and
23737 then unlink hitching post name. If the number of links is exactly two, creation
23738 of the lock file succeeded but something (for example, an NFS server crash and
23739 restart) caused this fact not to be communicated to the &[link()]& call.
23741 If creation of the lock file failed, wait for &%lock_interval%& and try again,
23742 up to &%lock_retries%& times. However, since any program that writes to a
23743 mailbox should complete its task very quickly, it is reasonable to time out old
23744 lock files that are normally the result of user agent and system crashes. If an
23745 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
23746 it before trying again.
23750 A call is made to &[lstat()]& to discover whether the main file exists, and if
23751 so, what its characteristics are. If &[lstat()]& fails for any reason other
23752 than non-existence, delivery is deferred.
23755 .cindex "symbolic link" "to mailbox"
23756 .cindex "mailbox" "symbolic link"
23757 If the file does exist and is a symbolic link, delivery is deferred, unless the
23758 &%allow_symlink%& option is set, in which case the ownership of the link is
23759 checked, and then &[stat()]& is called to find out about the real file, which
23760 is then subjected to the checks below. The check on the top-level link
23761 ownership prevents one user creating a link for another's mailbox in a sticky
23762 directory, though allowing symbolic links in this case is definitely not a good
23763 idea. If there is a chain of symbolic links, the intermediate ones are not
23767 If the file already exists but is not a regular file, or if the file's owner
23768 and group (if the group is being checked &-- see &%check_group%& above) are
23769 different from the user and group under which the delivery is running,
23770 delivery is deferred.
23773 If the file's permissions are more generous than specified, they are reduced.
23774 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
23775 is set false, in which case the delivery is tried using the existing
23779 The file's inode number is saved, and the file is then opened for appending.
23780 If this fails because the file has vanished, &(appendfile)& behaves as if it
23781 hadn't existed (see below). For any other failures, delivery is deferred.
23784 If the file is opened successfully, check that the inode number hasn't
23785 changed, that it is still a regular file, and that the owner and permissions
23786 have not changed. If anything is wrong, defer delivery and freeze the message.
23789 If the file did not exist originally, defer delivery if the &%file_must_exist%&
23790 option is set. Otherwise, check that the file is being created in a permitted
23791 directory if the &%create_file%& option is set (deferring on failure), and then
23792 open for writing as a new file, with the O_EXCL and O_CREAT options,
23793 except when dealing with a symbolic link (the &%allow_symlink%& option must be
23794 set). In this case, which can happen if the link points to a non-existent file,
23795 the file is opened for writing using O_CREAT but not O_EXCL, because
23796 that prevents link following.
23799 .cindex "loop" "while file testing"
23800 If opening fails because the file exists, obey the tests given above for
23801 existing files. However, to avoid looping in a situation where the file is
23802 being continuously created and destroyed, the exists/not-exists loop is broken
23803 after 10 repetitions, and the message is then frozen.
23806 If opening fails with any other error, defer delivery.
23809 .cindex "file" "locking"
23810 .cindex "locking files"
23811 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
23812 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
23813 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
23814 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
23815 file, and an exclusive lock on the file whose name is
23817 /tmp/.<device-number>.<inode-number>
23819 using the device and inode numbers of the open mailbox file, in accordance with
23820 the MBX locking rules. This file is created with a mode that is specified by
23821 the &%lockfile_mode%& option.
23823 If Exim fails to lock the file, there are two possible courses of action,
23824 depending on the value of the locking timeout. This is obtained from
23825 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
23827 If the timeout value is zero, the file is closed, Exim waits for
23828 &%lock_interval%&, and then goes back and re-opens the file as above and tries
23829 to lock it again. This happens up to &%lock_retries%& times, after which the
23830 delivery is deferred.
23832 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
23833 &[flock()]& are used (with the given timeout), so there has already been some
23834 waiting involved by the time locking fails. Nevertheless, Exim does not give up
23835 immediately. It retries up to
23837 (lock_retries * lock_interval) / <timeout>
23839 times (rounded up).
23842 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
23843 and/or &[flock()]& locks) and then deletes the lock file if one was created.
23846 .section "Operational details for delivery to a new file" "SECTopdir"
23847 .cindex "delivery" "to single file"
23848 .cindex "&""From""& line"
23849 When the &%directory%& option is set instead of &%file%&, each message is
23850 delivered into a newly-created file or set of files. When &(appendfile)& is
23851 activated directly from a &(redirect)& router, neither &%file%& nor
23852 &%directory%& is normally set, because the path for delivery is supplied by the
23853 router. (See for example, the &(address_file)& transport in the default
23854 configuration.) In this case, delivery is to a new file if either the path name
23855 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
23857 No locking is required while writing the message to a new file, so the various
23858 locking options of the transport are ignored. The &"From"& line that by default
23859 separates messages in a single file is not normally needed, nor is the escaping
23860 of message lines that start with &"From"&, and there is no need to ensure a
23861 newline at the end of each message. Consequently, the default values for
23862 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
23863 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
23865 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
23866 the files in the delivery directory by default. However, you can specify a
23867 different directory by setting &%quota_directory%&. Also, for maildir
23868 deliveries (see below) the &_maildirfolder_& convention is honoured.
23871 .cindex "maildir format"
23872 .cindex "mailstore format"
23873 There are three different ways in which delivery to individual files can be
23874 done, controlled by the settings of the &%maildir_format%& and
23875 &%mailstore_format%& options. Note that code to support maildir or mailstore
23876 formats is not included in the binary unless SUPPORT_MAILDIR or
23877 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
23879 .cindex "directory creation"
23880 In all three cases an attempt is made to create the directory and any necessary
23881 sub-directories if they do not exist, provided that the &%create_directory%&
23882 option is set (the default). The location of a created directory can be
23883 constrained by setting &%create_file%&. A created directory's mode is given by
23884 the &%directory_mode%& option. If creation fails, or if the
23885 &%create_directory%& option is not set when creation is required, delivery is
23890 .section "Maildir delivery" "SECTmaildirdelivery"
23891 .cindex "maildir format" "description of"
23892 If the &%maildir_format%& option is true, Exim delivers each message by writing
23893 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
23894 directory that is defined by the &%directory%& option (the &"delivery
23895 directory"&). If the delivery is successful, the file is renamed into the
23896 &_new_& subdirectory.
23898 In the filename, <&'stime'&> is the current time of day in seconds, and
23899 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
23900 Exim checks that the time-of-day clock has moved on by at least one microsecond
23901 before terminating the delivery process. This guarantees uniqueness for the
23902 filename. However, as a precaution, Exim calls &[stat()]& for the file before
23903 opening it. If any response other than ENOENT (does not exist) is given,
23904 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
23906 Before Exim carries out a maildir delivery, it ensures that subdirectories
23907 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
23908 do not exist, Exim tries to create them and any superior directories in their
23909 path, subject to the &%create_directory%& and &%create_file%& options. If the
23910 &%maildirfolder_create_regex%& option is set, and the regular expression it
23911 contains matches the delivery directory, Exim also ensures that a file called
23912 &_maildirfolder_& exists in the delivery directory. If a missing directory or
23913 &_maildirfolder_& file cannot be created, delivery is deferred.
23915 These features make it possible to use Exim to create all the necessary files
23916 and directories in a maildir mailbox, including subdirectories for maildir++
23917 folders. Consider this example:
23919 maildir_format = true
23920 directory = /var/mail/$local_part_data\
23921 ${if eq{$local_part_suffix}{}{}\
23922 {/.${substr_1:$local_part_suffix}}}
23923 maildirfolder_create_regex = /\.[^/]+$
23925 If &$local_part_suffix$& is empty (there was no suffix for the local part),
23926 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
23927 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
23928 not match this name, so Exim will not look for or create the file
23929 &_/var/mail/pimbo/maildirfolder_&, though it will create
23930 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
23932 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
23933 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
23934 does match &%maildirfolder_create_regex%&. In this case, Exim will create
23935 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
23936 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
23938 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
23939 not inadvertently match the toplevel maildir directory, because a
23940 &_maildirfolder_& file at top level would completely break quota calculations.
23942 .cindex "quota" "in maildir delivery"
23943 .cindex "maildir++"
23944 If Exim is required to check a &%quota%& setting before a maildir delivery, and
23945 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
23946 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
23947 Exim assumes the directory is a maildir++ folder directory, which is one level
23948 down from the user's top level mailbox directory. This causes it to start at
23949 the parent directory instead of the current directory when calculating the
23950 amount of space used.
23952 One problem with delivering into a multi-file mailbox is that it is
23953 computationally expensive to compute the size of the mailbox for quota
23954 checking. Various approaches have been taken to reduce the amount of work
23955 needed. The next two sections describe two of them. A third alternative is to
23956 use some external process for maintaining the size data, and use the expansion
23957 of the &%mailbox_size%& option as a way of importing it into Exim.
23962 .section "Using tags to record message sizes" "SECID135"
23963 If &%maildir_tag%& is set, the string is expanded for each delivery.
23964 When the maildir file is renamed into the &_new_& sub-directory, the
23965 tag is added to its name. However, if adding the tag takes the length of the
23966 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
23967 the tag is dropped and the maildir file is created with no tag.
23970 .vindex "&$message_size$&"
23971 Tags can be used to encode the size of files in their names; see
23972 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
23973 happens after the message has been written. The value of the &$message_size$&
23974 variable is set to the number of bytes actually written. If the expansion is
23975 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
23976 be deferred. The expanded tag may contain any printing characters except &"/"&.
23977 Non-printing characters in the string are ignored; if the resulting string is
23978 empty, it is ignored. If it starts with an alphanumeric character, a leading
23979 colon is inserted; this default has not proven to be the path that popular
23980 maildir implementations have chosen (but changing it in Exim would break
23981 backwards compatibility).
23983 For one common implementation, you might set:
23985 maildir_tag = ,S=${message_size}
23987 but you should check the documentation of the other software to be sure.
23989 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
23990 as this allows Exim to extract the size from your tag, instead of having to
23991 &[stat()]& each message file.
23994 .section "Using a maildirsize file" "SECID136"
23995 .cindex "quota" "in maildir delivery"
23996 .cindex "maildir format" "&_maildirsize_& file"
23997 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
23998 storing quota and message size information in a file called &_maildirsize_&
23999 within the toplevel maildir directory. If this file does not exist, Exim
24000 creates it, setting the quota from the &%quota%& option of the transport. If
24001 the maildir directory itself does not exist, it is created before any attempt
24002 to write a &_maildirsize_& file.
24004 The &_maildirsize_& file is used to hold information about the sizes of
24005 messages in the maildir, thus speeding up quota calculations. The quota value
24006 in the file is just a cache; if the quota is changed in the transport, the new
24007 value overrides the cached value when the next message is delivered. The cache
24008 is maintained for the benefit of other programs that access the maildir and
24009 need to know the quota.
24011 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
24012 file is maintained (with a zero quota setting), but no quota is imposed.
24014 A regular expression is available for controlling which directories in the
24015 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
24016 See the description of the &%maildir_quota_directory_regex%& option above for
24020 .section "Mailstore delivery" "SECID137"
24021 .cindex "mailstore format" "description of"
24022 If the &%mailstore_format%& option is true, each message is written as two
24023 files in the given directory. A unique base name is constructed from the
24024 message id and the current delivery process, and the files that are written use
24025 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
24026 contains the message's envelope, and the &_.msg_& file contains the message
24027 itself. The base name is placed in the variable &$mailstore_basename$&.
24029 During delivery, the envelope is first written to a file with the suffix
24030 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
24031 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
24032 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
24033 file before accessing either of them. An alternative approach is to wait for
24034 the absence of a &_.tmp_& file.
24036 The envelope file starts with any text defined by the &%mailstore_prefix%&
24037 option, expanded and terminated by a newline if there isn't one. Then follows
24038 the sender address on one line, then all the recipient addresses, one per line.
24039 There can be more than one recipient only if the &%batch_max%& option is set
24040 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
24041 appended to the file, followed by a newline if it does not end with one.
24043 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
24044 failure, it is ignored. Other expansion errors are treated as serious
24045 configuration errors, and delivery is deferred. The variable
24046 &$mailstore_basename$& is available for use during these expansions.
24049 .section "Non-special new file delivery" "SECID138"
24050 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
24051 file is created directly in the named directory. For example, when delivering
24052 messages into files in batched SMTP format for later delivery to some host (see
24053 section &<<SECTbatchSMTP>>&), a setting such as
24055 directory = /var/bsmtp/$host
24057 might be used. A message is written to a file with a temporary name, which is
24058 then renamed when the delivery is complete. The final name is obtained by
24059 expanding the contents of the &%directory_file%& option.
24060 .ecindex IIDapptra1
24061 .ecindex IIDapptra2
24068 . ////////////////////////////////////////////////////////////////////////////
24069 . ////////////////////////////////////////////////////////////////////////////
24071 .chapter "The autoreply transport" "CHID8"
24072 .scindex IIDauttra1 "transports" "&(autoreply)&"
24073 .scindex IIDauttra2 "&(autoreply)& transport"
24074 The &(autoreply)& transport is not a true transport in that it does not cause
24075 the message to be transmitted. Instead, it generates a new mail message as an
24076 automatic reply to the incoming message. &'References:'& and
24077 &'Auto-Submitted:'& header lines are included. These are constructed according
24078 to the rules in RFCs 2822 and 3834, respectively.
24080 If the router that passes the message to this transport does not have the
24081 &%unseen%& option set, the original message (for the current recipient) is not
24082 delivered anywhere. However, when the &%unseen%& option is set on the router
24083 that passes the message to this transport, routing of the address continues, so
24084 another router can set up a normal message delivery.
24087 The &(autoreply)& transport is usually run as the result of mail filtering, a
24088 &"vacation"& message being the standard example. However, it can also be run
24089 directly from a router like any other transport. To reduce the possibility of
24090 message cascades, messages created by the &(autoreply)& transport always have
24091 empty envelope sender addresses, like bounce messages.
24093 The parameters of the message to be sent can be specified in the configuration
24094 by options described below. However, these are used only when the address
24095 passed to the transport does not contain its own reply information. When the
24096 transport is run as a consequence of a
24098 or &%vacation%& command in a filter file, the parameters of the message are
24099 supplied by the filter, and passed with the address. The transport's options
24100 that define the message are then ignored (so they are not usually set in this
24101 case). The message is specified entirely by the filter or by the transport; it
24102 is never built from a mixture of options. However, the &%file_optional%&,
24103 &%mode%&, and &%return_message%& options apply in all cases.
24105 &(Autoreply)& is implemented as a local transport. When used as a result of a
24106 command in a user's filter file, &(autoreply)& normally runs under the uid and
24107 gid of the user, and with appropriate current and home directories (see chapter
24108 &<<CHAPenvironment>>&).
24110 There is a subtle difference between routing a message to a &(pipe)& transport
24111 that generates some text to be returned to the sender, and routing it to an
24112 &(autoreply)& transport. This difference is noticeable only if more than one
24113 address from the same message is so handled. In the case of a pipe, the
24114 separate outputs from the different addresses are gathered up and returned to
24115 the sender in a single message, whereas if &(autoreply)& is used, a separate
24116 message is generated for each address that is passed to it.
24118 Non-printing characters are not permitted in the header lines generated for the
24119 message that &(autoreply)& creates, with the exception of newlines that are
24120 immediately followed by white space. If any non-printing characters are found,
24121 the transport defers.
24122 Whether characters with the top bit set count as printing characters or not is
24123 controlled by the &%print_topbitchars%& global option.
24125 If any of the generic options for manipulating headers (for example,
24126 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
24127 of the original message that is included in the generated message when
24128 &%return_message%& is set. They do not apply to the generated message itself.
24130 .vindex "&$sender_address$&"
24131 If the &(autoreply)& transport receives return code 2 from Exim when it submits
24132 the message, indicating that there were no recipients, it does not treat this
24133 as an error. This means that autoreplies sent to &$sender_address$& when this
24134 is empty (because the incoming message is a bounce message) do not cause
24135 problems. They are just discarded.
24139 .section "Private options for autoreply" "SECID139"
24140 .cindex "options" "&(autoreply)& transport"
24142 .option bcc autoreply string&!! unset
24143 This specifies the addresses that are to receive &"blind carbon copies"& of the
24144 message when the message is specified by the transport.
24147 .option cc autoreply string&!! unset
24148 This specifies recipients of the message and the contents of the &'Cc:'& header
24149 when the message is specified by the transport.
24152 .option file autoreply string&!! unset
24153 The contents of the file are sent as the body of the message when the message
24154 is specified by the transport. If both &%file%& and &%text%& are set, the text
24155 string comes first.
24158 .option file_expand autoreply boolean false
24159 If this is set, the contents of the file named by the &%file%& option are
24160 subjected to string expansion as they are added to the message.
24163 .option file_optional autoreply boolean false
24164 If this option is true, no error is generated if the file named by the &%file%&
24165 option or passed with the address does not exist or cannot be read.
24168 .option from autoreply string&!! unset
24169 This specifies the contents of the &'From:'& header when the message is
24170 specified by the transport.
24173 .option headers autoreply string&!! unset
24174 This specifies additional RFC 2822 headers that are to be added to the message
24175 when the message is specified by the transport. Several can be given by using
24176 &"\n"& to separate them. There is no check on the format.
24179 .option log autoreply string&!! unset
24180 This option names a file in which a record of every message sent is logged when
24181 the message is specified by the transport.
24184 .option mode autoreply "octal integer" 0600
24185 If either the log file or the &"once"& file has to be created, this mode is
24189 .option never_mail autoreply "address list&!!" unset
24190 If any run of the transport creates a message with a recipient that matches any
24191 item in the list, that recipient is quietly discarded. If all recipients are
24192 discarded, no message is created. This applies both when the recipients are
24193 generated by a filter and when they are specified in the transport.
24197 .option once autoreply string&!! unset
24198 This option names a file or DBM database in which a record of each &'To:'&
24199 recipient is kept when the message is specified by the transport. &*Note*&:
24200 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
24202 If &%once%& is unset, or is set to an empty string, the message is always sent.
24203 By default, if &%once%& is set to a non-empty filename, the message
24204 is not sent if a potential recipient is already listed in the database.
24205 However, if the &%once_repeat%& option specifies a time greater than zero, the
24206 message is sent if that much time has elapsed since a message was last sent to
24207 this recipient. A setting of zero time for &%once_repeat%& (the default)
24208 prevents a message from being sent a second time &-- in this case, zero means
24211 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
24212 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
24213 greater than zero, it changes the way Exim implements the &%once%& option.
24214 Instead of using a DBM file to record every recipient it sends to, it uses a
24215 regular file, whose size will never get larger than the given value.
24217 In the file, Exim keeps a linear list of recipient addresses and the times at
24218 which they were sent messages. If the file is full when a new address needs to
24219 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
24220 means that a given recipient may receive multiple messages, but at
24221 unpredictable intervals that depend on the rate of turnover of addresses in the
24222 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
24225 .option once_file_size autoreply integer 0
24226 See &%once%& above.
24229 .option once_repeat autoreply time&!! 0s
24230 See &%once%& above.
24231 After expansion, the value of this option must be a valid time value.
24234 .option reply_to autoreply string&!! unset
24235 This specifies the contents of the &'Reply-To:'& header when the message is
24236 specified by the transport.
24239 .option return_message autoreply boolean false
24240 If this is set, a copy of the original message is returned with the new
24241 message, subject to the maximum size set in the &%return_size_limit%& global
24242 configuration option.
24245 .option subject autoreply string&!! unset
24246 This specifies the contents of the &'Subject:'& header when the message is
24247 specified by the transport. It is tempting to quote the original subject in
24248 automatic responses. For example:
24250 subject = Re: $h_subject:
24252 There is a danger in doing this, however. It may allow a third party to
24253 subscribe your users to an opt-in mailing list, provided that the list accepts
24254 bounce messages as subscription confirmations. Well-managed lists require a
24255 non-bounce message to confirm a subscription, so the danger is relatively
24260 .option text autoreply string&!! unset
24261 This specifies a single string to be used as the body of the message when the
24262 message is specified by the transport. If both &%text%& and &%file%& are set,
24263 the text comes first.
24266 .option to autoreply string&!! unset
24267 This specifies recipients of the message and the contents of the &'To:'& header
24268 when the message is specified by the transport.
24269 .ecindex IIDauttra1
24270 .ecindex IIDauttra2
24275 . ////////////////////////////////////////////////////////////////////////////
24276 . ////////////////////////////////////////////////////////////////////////////
24278 .chapter "The lmtp transport" "CHAPLMTP"
24279 .cindex "transports" "&(lmtp)&"
24280 .cindex "&(lmtp)& transport"
24281 .cindex "LMTP" "over a pipe"
24282 .cindex "LMTP" "over a socket"
24283 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
24285 or by interacting with a Unix domain socket.
24286 This transport is something of a cross between the &(pipe)& and &(smtp)&
24287 transports. Exim also has support for using LMTP over TCP/IP; this is
24288 implemented as an option for the &(smtp)& transport. Because LMTP is expected
24289 to be of minority interest, the default build-time configure in &_src/EDITME_&
24290 has it commented out. You need to ensure that
24294 .cindex "options" "&(lmtp)& transport"
24295 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
24296 included in the Exim binary. The private options of the &(lmtp)& transport are
24299 .option batch_id lmtp string&!! unset
24300 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24303 .option batch_max lmtp integer 1
24304 This limits the number of addresses that can be handled in a single delivery.
24305 Most LMTP servers can handle several addresses at once, so it is normally a
24306 good idea to increase this value. See the description of local delivery
24307 batching in chapter &<<CHAPbatching>>&.
24310 .option command lmtp string&!! unset
24311 This option must be set if &%socket%& is not set. The string is a command which
24312 is run in a separate process. It is split up into a command name and list of
24313 arguments, each of which is separately expanded (so expansion cannot change the
24314 number of arguments). The command is run directly, not via a shell. The message
24315 is passed to the new process using the standard input and output to operate the
24318 .option ignore_quota lmtp boolean false
24319 .cindex "LMTP" "ignoring quota errors"
24320 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
24321 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
24322 in its response to the LHLO command.
24324 .option socket lmtp string&!! unset
24325 This option must be set if &%command%& is not set. The result of expansion must
24326 be the name of a Unix domain socket. The transport connects to the socket and
24327 delivers the message to it using the LMTP protocol.
24330 .option timeout lmtp time 5m
24331 The transport is aborted if the created process or Unix domain socket does not
24332 respond to LMTP commands or message input within this timeout. Delivery
24333 is deferred, and will be tried again later. Here is an example of a typical
24338 command = /some/local/lmtp/delivery/program
24342 This delivers up to 20 addresses at a time, in a mixture of domains if
24343 necessary, running as the user &'exim'&.
24347 . ////////////////////////////////////////////////////////////////////////////
24348 . ////////////////////////////////////////////////////////////////////////////
24350 .chapter "The pipe transport" "CHAPpipetransport"
24351 .scindex IIDpiptra1 "transports" "&(pipe)&"
24352 .scindex IIDpiptra2 "&(pipe)& transport"
24353 The &(pipe)& transport is used to deliver messages via a pipe to a command
24354 running in another process. One example is the use of &(pipe)& as a
24355 pseudo-remote transport for passing messages to some other delivery mechanism
24356 (such as UUCP). Another is the use by individual users to automatically process
24357 their incoming messages. The &(pipe)& transport can be used in one of the
24361 .vindex "&$local_part$&"
24362 A router routes one address to a transport in the normal way, and the
24363 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
24364 contains the local part of the address (as usual), and the command that is run
24365 is specified by the &%command%& option on the transport.
24367 .vindex "&$pipe_addresses$&"
24368 If the &%batch_max%& option is set greater than 1 (the default is 1), the
24369 transport can handle more than one address in a single run. In this case, when
24370 more than one address is routed to the transport, &$local_part$& is not set
24371 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
24372 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
24373 that are routed to the transport.
24375 .vindex "&$address_pipe$&"
24376 A router redirects an address directly to a pipe command (for example, from an
24377 alias or forward file). In this case, &$address_pipe$& contains the text of the
24378 pipe command, and the &%command%& option on the transport is ignored unless
24379 &%force_command%& is set. If only one address is being transported
24380 (&%batch_max%& is not greater than one, or only one address was redirected to
24381 this pipe command), &$local_part$& contains the local part that was redirected.
24385 The &(pipe)& transport is a non-interactive delivery method. Exim can also
24386 deliver messages over pipes using the LMTP interactive protocol. This is
24387 implemented by the &(lmtp)& transport.
24389 In the case when &(pipe)& is run as a consequence of an entry in a local user's
24390 &_.forward_& file, the command runs under the uid and gid of that user. In
24391 other cases, the uid and gid have to be specified explicitly, either on the
24392 transport or on the router that handles the address. Current and &"home"&
24393 directories are also controllable. See chapter &<<CHAPenvironment>>& for
24394 details of the local delivery environment and chapter &<<CHAPbatching>>&
24395 for a discussion of local delivery batching.
24397 .cindex "tainted data" "in pipe command"
24398 .cindex pipe "tainted data"
24399 Tainted data may not be used for the command name.
24402 .section "Concurrent delivery" "SECID140"
24403 If two messages arrive at almost the same time, and both are routed to a pipe
24404 delivery, the two pipe transports may be run concurrently. You must ensure that
24405 any pipe commands you set up are robust against this happening. If the commands
24406 write to a file, the &%exim_lock%& utility might be of use.
24407 Alternatively the &%max_parallel%& option could be used with a value
24408 of "1" to enforce serialization.
24413 .section "Returned status and data" "SECID141"
24414 .cindex "&(pipe)& transport" "returned data"
24415 If the command exits with a non-zero return code, the delivery is deemed to
24416 have failed, unless either the &%ignore_status%& option is set (in which case
24417 the return code is treated as zero), or the return code is one of those listed
24418 in the &%temp_errors%& option, which are interpreted as meaning &"try again
24419 later"&. In this case, delivery is deferred. Details of a permanent failure are
24420 logged, but are not included in the bounce message, which merely contains
24421 &"local delivery failed"&.
24423 If the command exits on a signal and the &%freeze_signal%& option is set then
24424 the message will be frozen in the queue. If that option is not set, a bounce
24425 will be sent as normal.
24427 If the return code is greater than 128 and the command being run is a shell
24428 script, it normally means that the script was terminated by a signal whose
24429 value is the return code minus 128. The &%freeze_signal%& option does not
24430 apply in this case.
24432 If Exim is unable to run the command (that is, if &[execve()]& fails), the
24433 return code is set to 127. This is the value that a shell returns if it is
24434 asked to run a non-existent command. The wording for the log line suggests that
24435 a non-existent command may be the problem.
24437 The &%return_output%& option can affect the result of a pipe delivery. If it is
24438 set and the command produces any output on its standard output or standard
24439 error streams, the command is considered to have failed, even if it gave a zero
24440 return code or if &%ignore_status%& is set. The output from the command is
24441 included as part of the bounce message. The &%return_fail_output%& option is
24442 similar, except that output is returned only when the command exits with a
24443 failure return code, that is, a value other than zero or a code that matches
24448 .section "How the command is run" "SECThowcommandrun"
24449 .cindex "&(pipe)& transport" "path for command"
24450 The command line is (by default) broken down into a command name and arguments
24451 by the &(pipe)& transport itself. The &%allow_commands%& and
24452 &%restrict_to_path%& options can be used to restrict the commands that may be
24455 .cindex "quoting" "in pipe command"
24456 Unquoted arguments are delimited by white space. If an argument appears in
24457 double quotes, backslash is interpreted as an escape character in the usual
24458 way. If an argument appears in single quotes, no escaping is done.
24460 String expansion is applied to the command line except when it comes from a
24461 traditional &_.forward_& file (commands from a filter file are expanded). The
24462 expansion is applied to each argument in turn rather than to the whole line.
24463 For this reason, any string expansion item that contains white space must be
24464 quoted so as to be contained within a single argument. A setting such as
24466 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
24468 will not work, because the expansion item gets split between several
24469 arguments. You have to write
24471 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
24473 to ensure that it is all in one argument. The expansion is done in this way,
24474 argument by argument, so that the number of arguments cannot be changed as a
24475 result of expansion, and quotes or backslashes in inserted variables do not
24476 interact with external quoting. However, this leads to problems if you want to
24477 generate multiple arguments (or the command name plus arguments) from a single
24478 expansion. In this situation, the simplest solution is to use a shell. For
24481 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
24484 .cindex "transport" "filter"
24485 .cindex "filter" "transport filter"
24486 .vindex "&$pipe_addresses$&"
24487 Special handling takes place when an argument consists of precisely the text
24488 &`$pipe_addresses`& (no quotes).
24489 This is not a general expansion variable; the only
24490 place this string is recognized is when it appears as an argument for a pipe or
24491 transport filter command. It causes each address that is being handled to be
24492 inserted in the argument list at that point &'as a separate argument'&. This
24493 avoids any problems with spaces or shell metacharacters, and is of use when a
24494 &(pipe)& transport is handling groups of addresses in a batch.
24496 If &%force_command%& is enabled on the transport, special handling takes place
24497 for an argument that consists of precisely the text &`$address_pipe`&. It
24498 is handled similarly to &$pipe_addresses$& above. It is expanded and each
24499 argument is inserted in the argument list at that point
24500 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
24501 the only item in the argument; in fact, if it were then &%force_command%&
24502 should behave as a no-op. Rather, it should be used to adjust the command
24503 run while preserving the argument vector separation.
24505 After splitting up into arguments and expansion, the resulting command is run
24506 in a subprocess directly from the transport, &'not'& under a shell. The
24507 message that is being delivered is supplied on the standard input, and the
24508 standard output and standard error are both connected to a single pipe that is
24509 read by Exim. The &%max_output%& option controls how much output the command
24510 may produce, and the &%return_output%& and &%return_fail_output%& options
24511 control what is done with it.
24513 Not running the command under a shell (by default) lessens the security risks
24514 in cases when a command from a user's filter file is built out of data that was
24515 taken from an incoming message. If a shell is required, it can of course be
24516 explicitly specified as the command to be run. However, there are circumstances
24517 where existing commands (for example, in &_.forward_& files) expect to be run
24518 under a shell and cannot easily be modified. To allow for these cases, there is
24519 an option called &%use_shell%&, which changes the way the &(pipe)& transport
24520 works. Instead of breaking up the command line as just described, it expands it
24521 as a single string and passes the result to &_/bin/sh_&. The
24522 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
24523 with &%use_shell%&, and the whole mechanism is inherently less secure.
24527 .section "Environment variables" "SECTpipeenv"
24528 .cindex "&(pipe)& transport" "environment for command"
24529 .cindex "environment" "&(pipe)& transport"
24530 The environment variables listed below are set up when the command is invoked.
24531 This list is a compromise for maximum compatibility with other MTAs. Note that
24532 the &%environment%& option can be used to add additional variables to this
24533 environment. The environment for the &(pipe)& transport is not subject
24534 to the &%add_environment%& and &%keep_environment%& main config options.
24536 &`DOMAIN `& the domain of the address
24537 &`HOME `& the home directory, if set
24538 &`HOST `& the host name when called from a router (see below)
24539 &`LOCAL_PART `& see below
24540 &`LOCAL_PART_PREFIX `& see below
24541 &`LOCAL_PART_SUFFIX `& see below
24542 &`LOGNAME `& see below
24543 &`MESSAGE_ID `& Exim's local ID for the message
24544 &`PATH `& as specified by the &%path%& option below
24545 &`QUALIFY_DOMAIN `& the sender qualification domain
24546 &`RECIPIENT `& the complete recipient address
24547 &`SENDER `& the sender of the message (empty if a bounce)
24548 &`SHELL `& &`/bin/sh`&
24549 &`TZ `& the value of the &%timezone%& option, if set
24550 &`USER `& see below
24552 When a &(pipe)& transport is called directly from (for example) an &(accept)&
24553 router, LOCAL_PART is set to the local part of the address. When it is
24554 called as a result of a forward or alias expansion, LOCAL_PART is set to
24555 the local part of the address that was expanded. In both cases, any affixes are
24556 removed from the local part, and made available in LOCAL_PART_PREFIX and
24557 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
24558 same value as LOCAL_PART for compatibility with other MTAs.
24561 HOST is set only when a &(pipe)& transport is called from a router that
24562 associates hosts with an address, typically when using &(pipe)& as a
24563 pseudo-remote transport. HOST is set to the first host name specified by
24567 If the transport's generic &%home_directory%& option is set, its value is used
24568 for the HOME environment variable. Otherwise, a home directory may be set
24569 by the router's &%transport_home_directory%& option, which defaults to the
24570 user's home directory if &%check_local_user%& is set.
24573 .section "Private options for pipe" "SECID142"
24574 .cindex "options" "&(pipe)& transport"
24578 .option allow_commands pipe "string list&!!" unset
24579 .cindex "&(pipe)& transport" "permitted commands"
24580 The string is expanded, and is then interpreted as a colon-separated list of
24581 permitted commands. If &%restrict_to_path%& is not set, the only commands
24582 permitted are those in the &%allow_commands%& list. They need not be absolute
24583 paths; the &%path%& option is still used for relative paths. If
24584 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
24585 in the &%allow_commands%& list, or a name without any slashes that is found on
24586 the path. In other words, if neither &%allow_commands%& nor
24587 &%restrict_to_path%& is set, there is no restriction on the command, but
24588 otherwise only commands that are permitted by one or the other are allowed. For
24591 allow_commands = /usr/bin/vacation
24593 and &%restrict_to_path%& is not set, the only permitted command is
24594 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
24595 &%use_shell%& is set.
24598 .option batch_id pipe string&!! unset
24599 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24602 .option batch_max pipe integer 1
24603 This limits the number of addresses that can be handled in a single delivery.
24604 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24607 .option check_string pipe string unset
24608 As &(pipe)& writes the message, the start of each line is tested for matching
24609 &%check_string%&, and if it does, the initial matching characters are replaced
24610 by the contents of &%escape_string%&, provided both are set. The value of
24611 &%check_string%& is a literal string, not a regular expression, and the case of
24612 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
24613 of &%check_string%& and &%escape_string%& are forced to values that implement
24614 the SMTP escaping protocol. Any settings made in the configuration file are
24618 .option command pipe string&!! unset
24619 This option need not be set when &(pipe)& is being used to deliver to pipes
24620 obtained directly from address redirections. In other cases, the option must be
24621 set, to provide a command to be run. It need not yield an absolute path (see
24622 the &%path%& option below). The command is split up into separate arguments by
24623 Exim, and each argument is separately expanded, as described in section
24624 &<<SECThowcommandrun>>& above.
24627 .option environment pipe string&!! unset
24628 .cindex "&(pipe)& transport" "environment for command"
24629 .cindex "environment" "&(pipe)& transport"
24630 This option is used to add additional variables to the environment in which the
24631 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
24632 a string which is expanded, and then interpreted as a colon-separated list of
24633 environment settings of the form <&'name'&>=<&'value'&>.
24636 .option escape_string pipe string unset
24637 See &%check_string%& above.
24640 .option freeze_exec_fail pipe boolean false
24641 .cindex "exec failure"
24642 .cindex "failure of exec"
24643 .cindex "&(pipe)& transport" "failure of exec"
24644 Failure to exec the command in a pipe transport is by default treated like
24645 any other failure while running the command. However, if &%freeze_exec_fail%&
24646 is set, failure to exec is treated specially, and causes the message to be
24647 frozen, whatever the setting of &%ignore_status%&.
24650 .option freeze_signal pipe boolean false
24651 .cindex "signal exit"
24652 .cindex "&(pipe)& transport", "signal exit"
24653 Normally if the process run by a command in a pipe transport exits on a signal,
24654 a bounce message is sent. If &%freeze_signal%& is set, the message will be
24655 frozen in Exim's queue instead.
24658 .option force_command pipe boolean false
24659 .cindex "force command"
24660 .cindex "&(pipe)& transport", "force command"
24661 Normally when a router redirects an address directly to a pipe command
24662 the &%command%& option on the transport is ignored. If &%force_command%&
24663 is set, the &%command%& option will used. This is especially
24664 useful for forcing a wrapper or additional argument to be added to the
24665 command. For example:
24667 command = /usr/bin/remote_exec myhost -- $address_pipe
24671 Note that &$address_pipe$& is handled specially in &%command%& when
24672 &%force_command%& is set, expanding out to the original argument vector as
24673 separate items, similarly to a Unix shell &`"$@"`& construct.
24676 .option ignore_status pipe boolean false
24677 If this option is true, the status returned by the subprocess that is set up to
24678 run the command is ignored, and Exim behaves as if zero had been returned.
24679 Otherwise, a non-zero status or termination by signal causes an error return
24680 from the transport unless the status value is one of those listed in
24681 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
24683 &*Note*&: This option does not apply to timeouts, which do not return a status.
24684 See the &%timeout_defer%& option for how timeouts are handled.
24687 .option log_defer_output pipe boolean false
24688 .cindex "&(pipe)& transport" "logging output"
24689 If this option is set, and the status returned by the command is
24690 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
24691 and any output was produced on stdout or stderr, the first line of it is
24692 written to the main log.
24695 .option log_fail_output pipe boolean false
24696 If this option is set, and the command returns any output on stdout or
24697 stderr, and also ends with a return code that is neither zero nor one of
24698 the return codes listed in &%temp_errors%& (that is, the delivery
24699 failed), the first line of output is written to the main log. This
24700 option and &%log_output%& are mutually exclusive. Only one of them may
24704 .option log_output pipe boolean false
24705 If this option is set and the command returns any output on stdout or
24706 stderr, the first line of output is written to the main log, whatever
24707 the return code. This option and &%log_fail_output%& are mutually
24708 exclusive. Only one of them may be set.
24711 .option max_output pipe integer 20K
24712 This specifies the maximum amount of output that the command may produce on its
24713 standard output and standard error file combined. If the limit is exceeded, the
24714 process running the command is killed. This is intended as a safety measure to
24715 catch runaway processes. The limit is applied independently of the settings of
24716 the options that control what is done with such output (for example,
24717 &%return_output%&). Because of buffering effects, the amount of output may
24718 exceed the limit by a small amount before Exim notices.
24721 .option message_prefix pipe string&!! "see below"
24722 The string specified here is expanded and output at the start of every message.
24723 The default is unset if &%use_bsmtp%& is set. Otherwise it is
24726 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
24730 .cindex "&%tmail%&"
24731 .cindex "&""From""& line"
24732 This is required by the commonly used &_/usr/bin/vacation_& program.
24733 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
24734 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
24739 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24740 &`\n`& to &`\r\n`& in &%message_prefix%&.
24743 .option message_suffix pipe string&!! "see below"
24744 The string specified here is expanded and output at the end of every message.
24745 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
24746 The suffix can be suppressed by setting
24750 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24751 &`\n`& to &`\r\n`& in &%message_suffix%&.
24754 .option path pipe string&!! "/bin:/usr/bin"
24755 This option is expanded and
24756 specifies the string that is set up in the PATH environment
24757 variable of the subprocess.
24758 If the &%command%& option does not yield an absolute path name, the command is
24759 sought in the PATH directories, in the usual way. &*Warning*&: This does not
24760 apply to a command specified as a transport filter.
24763 .option permit_coredump pipe boolean false
24764 Normally Exim inhibits core-dumps during delivery. If you have a need to get
24765 a core-dump of a pipe command, enable this command. This enables core-dumps
24766 during delivery and affects both the Exim binary and the pipe command run.
24767 It is recommended that this option remain off unless and until you have a need
24768 for it and that this only be enabled when needed, as the risk of excessive
24769 resource consumption can be quite high. Note also that Exim is typically
24770 installed as a setuid binary and most operating systems will inhibit coredumps
24771 of these by default, so further OS-specific action may be required.
24774 .option pipe_as_creator pipe boolean false
24775 .cindex "uid (user id)" "local delivery"
24776 If the generic &%user%& option is not set and this option is true, the delivery
24777 process is run under the uid that was in force when Exim was originally called
24778 to accept the message. If the group id is not otherwise set (via the generic
24779 &%group%& option), the gid that was in force when Exim was originally called to
24780 accept the message is used.
24783 .option restrict_to_path pipe boolean false
24784 When this option is set, any command name not listed in &%allow_commands%& must
24785 contain no slashes. The command is searched for only in the directories listed
24786 in the &%path%& option. This option is intended for use in the case when a pipe
24787 command has been generated from a user's &_.forward_& file. This is usually
24788 handled by a &(pipe)& transport called &%address_pipe%&.
24791 .option return_fail_output pipe boolean false
24792 If this option is true, and the command produced any output and ended with a
24793 return code other than zero or one of the codes listed in &%temp_errors%& (that
24794 is, the delivery failed), the output is returned in the bounce message.
24795 However, if the message has a null sender (that is, it is itself a bounce
24796 message), output from the command is discarded. This option and
24797 &%return_output%& are mutually exclusive. Only one of them may be set.
24801 .option return_output pipe boolean false
24802 If this option is true, and the command produced any output, the delivery is
24803 deemed to have failed whatever the return code from the command, and the output
24804 is returned in the bounce message. Otherwise, the output is just discarded.
24805 However, if the message has a null sender (that is, it is a bounce message),
24806 output from the command is always discarded, whatever the setting of this
24807 option. This option and &%return_fail_output%& are mutually exclusive. Only one
24808 of them may be set.
24812 .option temp_errors pipe "string list" "see below"
24813 .cindex "&(pipe)& transport" "temporary failure"
24814 This option contains either a colon-separated list of numbers, or a single
24815 asterisk. If &%ignore_status%& is false
24816 and &%return_output%& is not set,
24817 and the command exits with a non-zero return code, the failure is treated as
24818 temporary and the delivery is deferred if the return code matches one of the
24819 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
24820 codes are treated as permanent errors. The default setting contains the codes
24821 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
24822 compiled on a system that does not define these macros, it assumes values of 75
24823 and 73, respectively.
24826 .option timeout pipe time 1h
24827 If the command fails to complete within this time, it is killed. This normally
24828 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
24829 specifies no timeout. In order to ensure that any subprocesses created by the
24830 command are also killed, Exim makes the initial process a process group leader,
24831 and kills the whole process group on a timeout. However, this can be defeated
24832 if one of the processes starts a new process group.
24834 .option timeout_defer pipe boolean false
24835 A timeout in a &(pipe)& transport, either in the command that the transport
24836 runs, or in a transport filter that is associated with it, is by default
24837 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
24838 is set true, both kinds of timeout become temporary errors, causing the
24839 delivery to be deferred.
24841 .option umask pipe "octal integer" 022
24842 This specifies the umask setting for the subprocess that runs the command.
24845 .option use_bsmtp pipe boolean false
24846 .cindex "envelope sender"
24847 If this option is set true, the &(pipe)& transport writes messages in &"batch
24848 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
24849 commands. If you want to include a leading HELO command with such messages,
24850 you can do so by setting the &%message_prefix%& option. See section
24851 &<<SECTbatchSMTP>>& for details of batch SMTP.
24853 .option use_classresources pipe boolean false
24854 .cindex "class resources (BSD)"
24855 This option is available only when Exim is running on FreeBSD, NetBSD, or
24856 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
24857 resource limits when a &(pipe)& transport is run to perform a delivery. The
24858 limits for the uid under which the pipe is to run are obtained from the login
24862 .option use_crlf pipe boolean false
24863 .cindex "carriage return"
24865 This option causes lines to be terminated with the two-character CRLF sequence
24866 (carriage return, linefeed) instead of just a linefeed character. In the case
24867 of batched SMTP, the byte sequence written to the pipe is then an exact image
24868 of what would be sent down a real SMTP connection.
24870 The contents of the &%message_prefix%& and &%message_suffix%& options are
24871 written verbatim, so must contain their own carriage return characters if these
24872 are needed. When &%use_bsmtp%& is not set, the default values for both
24873 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
24874 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
24877 .option use_shell pipe boolean false
24878 .vindex "&$pipe_addresses$&"
24879 If this option is set, it causes the command to be passed to &_/bin/sh_&
24880 instead of being run directly from the transport, as described in section
24881 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
24882 where the command is expected to be run under a shell and cannot easily be
24883 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
24884 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
24885 command is expanded as a single string, and handed to &_/bin/sh_& as data for
24890 .section "Using an external local delivery agent" "SECID143"
24891 .cindex "local delivery" "using an external agent"
24892 .cindex "&'procmail'&"
24893 .cindex "external local delivery"
24894 .cindex "delivery" "&'procmail'&"
24895 .cindex "delivery" "by external agent"
24896 The &(pipe)& transport can be used to pass all messages that require local
24897 delivery to a separate local delivery agent such as &%procmail%&. When doing
24898 this, care must be taken to ensure that the pipe is run under an appropriate
24899 uid and gid. In some configurations one wants this to be a uid that is trusted
24900 by the delivery agent to supply the correct sender of the message. It may be
24901 necessary to recompile or reconfigure the delivery agent so that it trusts an
24902 appropriate user. The following is an example transport and router
24903 configuration for &%procmail%&:
24908 command = /usr/local/bin/procmail -d $local_part_data
24912 check_string = "From "
24913 escape_string = ">From "
24915 user = $local_part_data
24922 transport = procmail_pipe
24924 In this example, the pipe is run as the local user, but with the group set to
24925 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
24926 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
24927 user to supply a correct sender address. If you do not specify either a
24928 &%group%& or a &%user%& option, the pipe command is run as the local user. The
24929 home directory is the user's home directory by default.
24931 &*Note*&: The command that the pipe transport runs does &'not'& begin with
24935 as shown in some &%procmail%& documentation, because Exim does not by default
24936 use a shell to run pipe commands.
24939 The next example shows a transport and a router for a system where local
24940 deliveries are handled by the Cyrus IMAP server.
24943 local_delivery_cyrus:
24945 command = /usr/cyrus/bin/deliver \
24946 -m ${substr_1:$local_part_suffix} -- $local_part
24958 local_part_suffix = .*
24959 transport = local_delivery_cyrus
24961 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
24962 &%return_output%& to cause any text written by Cyrus to be returned to the
24964 .ecindex IIDpiptra1
24965 .ecindex IIDpiptra2
24968 . ////////////////////////////////////////////////////////////////////////////
24969 . ////////////////////////////////////////////////////////////////////////////
24971 .chapter "The smtp transport" "CHAPsmtptrans"
24972 .scindex IIDsmttra1 "transports" "&(smtp)&"
24973 .scindex IIDsmttra2 "&(smtp)& transport"
24974 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
24975 or LMTP protocol. The list of hosts to try can either be taken from the address
24976 that is being processed (having been set up by the router), or specified
24977 explicitly for the transport. Timeout and retry processing (see chapter
24978 &<<CHAPretry>>&) is applied to each IP address independently.
24981 .section "Multiple messages on a single connection" "SECID144"
24982 The sending of multiple messages over a single TCP/IP connection can arise in
24986 If a message contains more than &%max_rcpt%& (see below) addresses that are
24987 routed to the same host, more than one copy of the message has to be sent to
24988 that host. In this situation, multiple copies may be sent in a single run of
24989 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
24990 does when it has too many addresses to send in one message also depends on the
24991 value of the global &%remote_max_parallel%& option. Details are given in
24992 section &<<SECToutSMTPTCP>>&.)
24994 .cindex "hints database" "remembering routing"
24995 When a message has been successfully delivered over a TCP/IP connection, Exim
24996 looks in its hints database to see if there are any other messages awaiting a
24997 connection to the same host. If there are, a new delivery process is started
24998 for one of them, and the current TCP/IP connection is passed on to it. The new
24999 process may in turn send multiple copies and possibly create yet another
25004 For each copy sent over the same TCP/IP connection, a sequence counter is
25005 incremented, and if it ever gets to the value of &%connection_max_messages%&,
25006 no further messages are sent over that connection.
25010 .section "Use of the $host and $host_address variables" "SECID145"
25012 .vindex "&$host_address$&"
25013 At the start of a run of the &(smtp)& transport, the values of &$host$& and
25014 &$host_address$& are the name and IP address of the first host on the host list
25015 passed by the router. However, when the transport is about to connect to a
25016 specific host, and while it is connected to that host, &$host$& and
25017 &$host_address$& are set to the values for that host. These are the values
25018 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
25019 &%serialize_hosts%&, and the various TLS options are expanded.
25022 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
25023 .vindex &$tls_bits$&
25024 .vindex &$tls_cipher$&
25025 .vindex &$tls_peerdn$&
25026 .vindex &$tls_sni$&
25027 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
25028 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
25029 are the values that were set when the message was received.
25030 These are the values that are used for options that are expanded before any
25031 SMTP connections are made. Just before each connection is made, these four
25032 variables are emptied. If TLS is subsequently started, they are set to the
25033 appropriate values for the outgoing connection, and these are the values that
25034 are in force when any authenticators are run and when the
25035 &%authenticated_sender%& option is expanded.
25037 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
25038 and will be removed in a future release.
25041 .section "Private options for smtp" "SECID146"
25042 .cindex "options" "&(smtp)& transport"
25043 The private options of the &(smtp)& transport are as follows:
25046 .option address_retry_include_sender smtp boolean true
25047 .cindex "4&'xx'& responses" "retrying after"
25048 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
25049 is the combination of sender and recipient that is delayed in subsequent queue
25050 runs until the retry time is reached. You can delay the recipient without
25051 reference to the sender (which is what earlier versions of Exim did), by
25052 setting &%address_retry_include_sender%& false. However, this can lead to
25053 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
25055 .option allow_localhost smtp boolean false
25056 .cindex "local host" "sending to"
25057 .cindex "fallback" "hosts specified on transport"
25058 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
25059 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
25060 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
25061 the delivery anyway. This should be used only in special cases when the
25062 configuration ensures that no looping will result (for example, a differently
25063 configured Exim is listening on the port to which the message is sent).
25066 .option authenticated_sender smtp string&!! unset
25068 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
25069 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
25070 overriding any existing authenticated sender value. If the string expansion is
25071 forced to fail, the option is ignored. Other expansion failures cause delivery
25072 to be deferred. If the result of expansion is an empty string, that is also
25075 The expansion happens after the outgoing connection has been made and TLS
25076 started, if required. This means that the &$host$&, &$host_address$&,
25077 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
25078 particular connection.
25080 If the SMTP session is not authenticated, the expansion of
25081 &%authenticated_sender%& still happens (and can cause the delivery to be
25082 deferred if it fails), but no AUTH= item is added to MAIL commands
25083 unless &%authenticated_sender_force%& is true.
25085 This option allows you to use the &(smtp)& transport in LMTP mode to
25086 deliver mail to Cyrus IMAP and provide the proper local part as the
25087 &"authenticated sender"&, via a setting such as:
25089 authenticated_sender = $local_part
25091 This removes the need for IMAP subfolders to be assigned special ACLs to
25092 allow direct delivery to those subfolders.
25094 Because of expected uses such as that just described for Cyrus (when no
25095 domain is involved), there is no checking on the syntax of the provided
25099 .option authenticated_sender_force smtp boolean false
25100 If this option is set true, the &%authenticated_sender%& option's value
25101 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
25102 authenticated as a client.
25105 .option command_timeout smtp time 5m
25106 .cindex timeout "smtp transport command"
25107 This sets a timeout for receiving a response to an SMTP command that has been
25108 sent out. It is also used when waiting for the initial banner line from the
25109 remote host. Its value must not be zero.
25112 .option connect_timeout smtp time 5m
25113 .cindex timeout "smtp transport connect"
25114 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
25115 to a remote host. A setting of zero allows the system timeout (typically
25116 several minutes) to act. To have any effect, the value of this option must be
25117 less than the system timeout. However, it has been observed that on some
25118 systems there is no system timeout, which is why the default value for this
25119 option is 5 minutes, a value recommended by RFC 1123.
25122 .option connection_max_messages smtp integer 500
25123 .cindex "SMTP" "passed connection"
25124 .cindex "SMTP" "multiple deliveries"
25125 .cindex "multiple SMTP deliveries"
25126 This controls the maximum number of separate message deliveries that are sent
25127 over a single TCP/IP connection. If the value is zero, there is no limit.
25128 For testing purposes, this value can be overridden by the &%-oB%& command line
25132 .option dane_require_tls_ciphers smtp string&!! unset
25133 .cindex "TLS" "requiring specific ciphers for DANE"
25134 .cindex "cipher" "requiring specific"
25135 .cindex DANE "TLS ciphers"
25136 This option may be used to override &%tls_require_ciphers%& for connections
25137 where DANE has been determined to be in effect.
25138 If not set, then &%tls_require_ciphers%& will be used.
25139 Normal SMTP delivery is not able to make strong demands of TLS cipher
25140 configuration, because delivery will fall back to plaintext. Once DANE has
25141 been determined to be in effect, there is no plaintext fallback and making the
25142 TLS cipherlist configuration stronger will increase security, rather than
25143 counter-intuitively decreasing it.
25144 If the option expands to be empty or is forced to fail, then it will
25145 be treated as unset and &%tls_require_ciphers%& will be used instead.
25148 .option data_timeout smtp time 5m
25149 .cindex timeout "for transmitted SMTP data blocks"
25150 This sets a timeout for the transmission of each block in the data portion of
25151 the message. As a result, the overall timeout for a message depends on the size
25152 of the message. Its value must not be zero. See also &%final_timeout%&.
25155 .option dkim_canon smtp string&!! unset
25156 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25157 .option dkim_domain smtp string list&!! unset
25158 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25159 .option dkim_hash smtp string&!! sha256
25160 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25161 .option dkim_identity smtp string&!! unset
25162 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25163 .option dkim_private_key smtp string&!! unset
25164 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25165 .option dkim_selector smtp string&!! unset
25166 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25167 .option dkim_strict smtp string&!! unset
25168 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25169 .option dkim_sign_headers smtp string&!! "per RFC"
25170 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25171 .option dkim_timestamps smtp string&!! unset
25172 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25175 .option delay_after_cutoff smtp boolean true
25176 .cindex "final cutoff" "retries, controlling"
25177 .cindex retry "final cutoff"
25178 This option controls what happens when all remote IP addresses for a given
25179 domain have been inaccessible for so long that they have passed their retry
25182 In the default state, if the next retry time has not been reached for any of
25183 them, the address is bounced without trying any deliveries. In other words,
25184 Exim delays retrying an IP address after the final cutoff time until a new
25185 retry time is reached, and can therefore bounce an address without ever trying
25186 a delivery, when machines have been down for a long time. Some people are
25187 unhappy at this prospect, so...
25189 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25190 addresses are past their final cutoff time, Exim tries to deliver to those
25191 IP addresses that have not been tried since the message arrived. If there are
25192 none, of if they all fail, the address is bounced. In other words, it does not
25193 delay when a new message arrives, but immediately tries those expired IP
25194 addresses that haven't been tried since the message arrived. If there is a
25195 continuous stream of messages for the dead hosts, unsetting
25196 &%delay_after_cutoff%& means that there will be many more attempts to deliver
25200 .option dns_qualify_single smtp boolean true
25201 If the &%hosts%& or &%fallback_hosts%& option is being used,
25202 and the &%gethostbyname%& option is false,
25203 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
25204 in chapter &<<CHAPdnslookup>>& for more details.
25207 .option dns_search_parents smtp boolean false
25208 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
25209 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
25210 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
25214 .option dnssec_request_domains smtp "domain list&!!" *
25215 .cindex "MX record" "security"
25216 .cindex "DNSSEC" "MX lookup"
25217 .cindex "security" "MX lookup"
25218 .cindex "DNS" "DNSSEC"
25219 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
25220 the dnssec request bit set. Setting this transport option is only useful if the
25221 transport overrides or sets the host names. See the &%dnssec_request_domains%&
25226 .option dnssec_require_domains smtp "domain list&!!" unset
25227 .cindex "MX record" "security"
25228 .cindex "DNSSEC" "MX lookup"
25229 .cindex "security" "MX lookup"
25230 .cindex "DNS" "DNSSEC"
25231 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
25232 the dnssec request bit set. Setting this transport option is only
25233 useful if the transport overrides or sets the host names. See the
25234 &%dnssec_require_domains%& router option.
25238 .option dscp smtp string&!! unset
25239 .cindex "DCSP" "outbound"
25240 This option causes the DSCP value associated with a socket to be set to one
25241 of a number of fixed strings or to numeric value.
25242 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
25243 Common values include &`throughput`&, &`mincost`&, and on newer systems
25244 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
25246 The outbound packets from Exim will be marked with this value in the header
25247 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
25248 that these values will have any effect, not be stripped by networking
25249 equipment, or do much of anything without cooperation with your Network
25250 Engineer and those of all network operators between the source and destination.
25253 .option fallback_hosts smtp "string list" unset
25254 .cindex "fallback" "hosts specified on transport"
25255 String expansion is not applied to this option. The argument must be a
25256 colon-separated list of host names or IP addresses, optionally also including
25257 port numbers, though the separator can be changed, as described in section
25258 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25259 item in a &%route_list%& setting for the &(manualroute)& router, as described
25260 in section &<<SECTformatonehostitem>>&.
25262 Fallback hosts can also be specified on routers, which associate them with the
25263 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
25264 &%fallback_hosts%& specified on the transport is used only if the address does
25265 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
25266 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
25267 However, &%hosts_randomize%& does apply to fallback host lists.
25269 If Exim is unable to deliver to any of the hosts for a particular address, and
25270 the errors are not permanent rejections, the address is put on a separate
25271 transport queue with its host list replaced by the fallback hosts, unless the
25272 address was routed via MX records and the current host was in the original MX
25273 list. In that situation, the fallback host list is not used.
25275 Once normal deliveries are complete, the fallback queue is delivered by
25276 re-running the same transports with the new host lists. If several failing
25277 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
25278 copy of the message is sent.
25280 The resolution of the host names on the fallback list is controlled by the
25281 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
25282 both to cases when the host list comes with the address and when it is taken
25283 from &%hosts%&. This option provides a &"use a smart host only if delivery
25287 .option final_timeout smtp time 10m
25288 .cindex timeout "for transmitted SMTP data accept"
25289 This is the timeout that applies while waiting for the response to the final
25290 line containing just &"."& that terminates a message. Its value must not be
25293 .option gethostbyname smtp boolean false
25294 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
25295 being used, names are looked up using &[gethostbyname()]&
25296 (or &[getipnodebyname()]& when available)
25297 instead of using the DNS. Of course, that function may in fact use the DNS, but
25298 it may also consult other sources of information such as &_/etc/hosts_&.
25300 .option gnutls_compat_mode smtp boolean unset
25301 This option controls whether GnuTLS is used in compatibility mode in an Exim
25302 server. This reduces security slightly, but improves interworking with older
25303 implementations of TLS.
25305 .option helo_data smtp string&!! "see below"
25306 .cindex "HELO" "argument, setting"
25307 .cindex "EHLO" "argument, setting"
25308 .cindex "LHLO argument setting"
25309 The value of this option is expanded after a connection to a another host has
25310 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
25311 command that starts the outgoing SMTP or LMTP session. The default value of the
25316 During the expansion, the variables &$host$& and &$host_address$& are set to
25317 the identity of the remote host, and the variables &$sending_ip_address$& and
25318 &$sending_port$& are set to the local IP address and port number that are being
25319 used. These variables can be used to generate different values for different
25320 servers or different local IP addresses. For example, if you want the string
25321 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
25322 interface address, you could use this:
25324 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
25325 {$primary_hostname}}
25327 The use of &%helo_data%& applies both to sending messages and when doing
25330 .option hosts smtp "string list&!!" unset
25331 Hosts are associated with an address by a router such as &(dnslookup)&, which
25332 finds the hosts by looking up the address domain in the DNS, or by
25333 &(manualroute)&, which has lists of hosts in its configuration. However,
25334 email addresses can be passed to the &(smtp)& transport by any router, and not
25335 all of them can provide an associated list of hosts.
25337 The &%hosts%& option specifies a list of hosts to be used if the address being
25338 processed does not have any hosts associated with it. The hosts specified by
25339 &%hosts%& are also used, whether or not the address has its own hosts, if
25340 &%hosts_override%& is set.
25342 The string is first expanded, before being interpreted as a colon-separated
25343 list of host names or IP addresses, possibly including port numbers. The
25344 separator may be changed to something other than colon, as described in section
25345 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25346 item in a &%route_list%& setting for the &(manualroute)& router, as described
25347 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
25348 of the &(manualroute)& router is not available here.
25350 If the expansion fails, delivery is deferred. Unless the failure was caused by
25351 the inability to complete a lookup, the error is logged to the panic log as
25352 well as the main log. Host names are looked up either by searching directly for
25353 address records in the DNS or by calling &[gethostbyname()]& (or
25354 &[getipnodebyname()]& when available), depending on the setting of the
25355 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
25356 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
25359 During delivery, the hosts are tried in order, subject to their retry status,
25360 unless &%hosts_randomize%& is set.
25363 .option hosts_avoid_esmtp smtp "host list&!!" unset
25364 .cindex "ESMTP, avoiding use of"
25365 .cindex "HELO" "forcing use of"
25366 .cindex "EHLO" "avoiding use of"
25367 .cindex "PIPELINING" "avoiding the use of"
25368 This option is for use with broken hosts that announce ESMTP facilities (for
25369 example, PIPELINING) and then fail to implement them properly. When a host
25370 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
25371 start of the SMTP session. This means that it cannot use any of the ESMTP
25372 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
25375 .option hosts_avoid_pipelining smtp "host list&!!" unset
25376 .cindex "PIPELINING" "avoiding the use of"
25377 .cindex "ESMTP extensions" PIPELINING
25378 Exim will not use the ESMTP PIPELINING extension when delivering to any host
25379 that matches this list, even if the server host advertises PIPELINING support.
25381 .option hosts_pipe_connect smtp "host list&!!" unset
25382 .cindex "pipelining" "early connection"
25383 .cindex "pipelining" PIPE_CONNECT
25384 If Exim is built with the SUPPORT_PIPE_CONNECT build option
25385 this option controls which to hosts the facility watched for
25386 and recorded, and used for subsequent connections.
25388 The retry hints database is used for the record,
25389 and records are subject to the &%retry_data_expire%& option.
25390 When used, the pipelining saves on roundtrip times.
25391 It also turns SMTP into a client-first protocol
25392 so combines well with TCP Fast Open.
25394 See also the &%pipelining_connect_advertise_hosts%& main option.
25397 When the facility is used, the transport &%helo_data%& option
25398 will be expanded before the &$sending_ip_address$& variable
25400 A check is made for the use of that variable, without the
25401 presence of a &"def:"& test on it, but suitably complex coding
25402 can avoid the check and produce unexpected results.
25403 You have been warned.
25406 .option hosts_avoid_tls smtp "host list&!!" unset
25407 .cindex "TLS" "avoiding for certain hosts"
25408 Exim will not try to start a TLS session when delivering to any host that
25409 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25411 .option hosts_verify_avoid_tls smtp "host list&!!" unset
25412 .cindex "TLS" "avoiding for certain hosts"
25413 Exim will not try to start a TLS session for a verify callout,
25414 or when delivering in cutthrough mode,
25415 to any host that matches this list.
25418 .option hosts_max_try smtp integer 5
25419 .cindex "host" "maximum number to try"
25420 .cindex "limit" "number of hosts tried"
25421 .cindex "limit" "number of MX tried"
25422 .cindex "MX record" "maximum tried"
25423 This option limits the number of IP addresses that are tried for any one
25424 delivery in cases where there are temporary delivery errors. Section
25425 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
25428 .option hosts_max_try_hardlimit smtp integer 50
25429 This is an additional check on the maximum number of IP addresses that Exim
25430 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
25435 .option hosts_nopass_tls smtp "host list&!!" unset
25436 .cindex "TLS" "passing connection"
25437 .cindex "multiple SMTP deliveries"
25438 .cindex "TLS" "multiple message deliveries"
25439 For any host that matches this list, a connection on which a TLS session has
25440 been started will not be passed to a new delivery process for sending another
25441 message on the same connection. See section &<<SECTmulmessam>>& for an
25442 explanation of when this might be needed.
25444 .option hosts_noproxy_tls smtp "host list&!!" unset
25445 .cindex "TLS" "passing connection"
25446 .cindex "multiple SMTP deliveries"
25447 .cindex "TLS" "multiple message deliveries"
25448 For any host that matches this list, a TLS session which has
25449 been started will not be passed to a new delivery process for sending another
25450 message on the same session.
25452 The traditional implementation closes down TLS and re-starts it in the new
25453 process, on the same open TCP connection, for each successive message
25454 sent. If permitted by this option a pipe to to the new process is set up
25455 instead, and the original process maintains the TLS connection and proxies
25456 the SMTP connection from and to the new process and any subsequents.
25457 The new process has no access to TLS information, so cannot include it in
25462 .option hosts_override smtp boolean false
25463 If this option is set and the &%hosts%& option is also set, any hosts that are
25464 attached to the address are ignored, and instead the hosts specified by the
25465 &%hosts%& option are always used. This option does not apply to
25466 &%fallback_hosts%&.
25469 .option hosts_randomize smtp boolean false
25470 .cindex "randomized host list"
25471 .cindex "host" "list of; randomized"
25472 .cindex "fallback" "randomized hosts"
25473 If this option is set, and either the list of hosts is taken from the
25474 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
25475 were not obtained from MX records (this includes fallback hosts from the
25476 router), and were not randomized by the router, the order of trying the hosts
25477 is randomized each time the transport runs. Randomizing the order of a host
25478 list can be used to do crude load sharing.
25480 When &%hosts_randomize%& is true, a host list may be split into groups whose
25481 order is separately randomized. This makes it possible to set up MX-like
25482 behaviour. The boundaries between groups are indicated by an item that is just
25483 &`+`& in the host list. For example:
25485 hosts = host1:host2:host3:+:host4:host5
25487 The order of the first three hosts and the order of the last two hosts is
25488 randomized for each use, but the first three always end up before the last two.
25489 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
25491 .option hosts_require_auth smtp "host list&!!" unset
25492 .cindex "authentication" "required by client"
25493 This option provides a list of servers for which authentication must succeed
25494 before Exim will try to transfer a message. If authentication fails for
25495 servers which are not in this list, Exim tries to send unauthenticated. If
25496 authentication fails for one of these servers, delivery is deferred. This
25497 temporary error is detectable in the retry rules, so it can be turned into a
25498 hard failure if required. See also &%hosts_try_auth%&, and chapter
25499 &<<CHAPSMTPAUTH>>& for details of authentication.
25502 .option hosts_request_ocsp smtp "host list&!!" *
25503 .cindex "TLS" "requiring for certain servers"
25504 Exim will request a Certificate Status on a
25505 TLS session for any host that matches this list.
25506 &%tls_verify_certificates%& should also be set for the transport.
25508 .option hosts_require_dane smtp "host list&!!" unset
25509 .cindex DANE "transport options"
25510 .cindex DANE "requiring for certain servers"
25511 If built with DANE support, Exim will require that a DNSSEC-validated
25512 TLSA record is present for any host matching the list,
25513 and that a DANE-verified TLS connection is made. See
25514 the &%dnssec_request_domains%& router and transport options.
25515 There will be no fallback to in-clear communication.
25516 See section &<<SECDANE>>&.
25518 .option hosts_require_ocsp smtp "host list&!!" unset
25519 .cindex "TLS" "requiring for certain servers"
25520 Exim will request, and check for a valid Certificate Status being given, on a
25521 TLS session for any host that matches this list.
25522 &%tls_verify_certificates%& should also be set for the transport.
25524 .option hosts_require_tls smtp "host list&!!" unset
25525 .cindex "TLS" "requiring for certain servers"
25526 Exim will insist on using a TLS session when delivering to any host that
25527 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25528 &*Note*&: This option affects outgoing mail only. To insist on TLS for
25529 incoming messages, use an appropriate ACL.
25531 .option hosts_try_auth smtp "host list&!!" unset
25532 .cindex "authentication" "optional in client"
25533 This option provides a list of servers to which, provided they announce
25534 authentication support, Exim will attempt to authenticate as a client when it
25535 connects. If authentication fails
25537 and &%hosts_require_auth%& permits,
25539 Exim will try to transfer the message unauthenticated.
25540 See also chapter &<<CHAPSMTPAUTH>>& for details of authentication.
25542 .option hosts_try_chunking smtp "host list&!!" *
25543 .cindex CHUNKING "enabling, in client"
25544 .cindex BDAT "SMTP command"
25545 .cindex "RFC 3030" "CHUNKING"
25546 This option provides a list of servers to which, provided they announce
25547 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
25548 Unless DKIM signing is being done,
25549 BDAT will not be used in conjunction with a transport filter.
25551 .option hosts_try_dane smtp "host list&!!" *
25552 .cindex DANE "transport options"
25553 .cindex DANE "attempting for certain servers"
25554 If built with DANE support, Exim will require that a DNSSEC-validated
25555 TLSA record is present for any host matching the list,
25556 and that a DANE-verified TLS connection is made. See
25557 the &%dnssec_request_domains%& router and transport options.
25558 There will be no fallback to in-clear communication.
25559 See section &<<SECDANE>>&.
25561 .option hosts_try_fastopen smtp "host list&!!" *
25562 .cindex "fast open, TCP" "enabling, in client"
25563 .cindex "TCP Fast Open" "enabling, in client"
25564 .cindex "RFC 7413" "TCP Fast Open"
25565 This option provides a list of servers to which, provided
25566 the facility is supported by this system, Exim will attempt to
25567 perform a TCP Fast Open.
25568 No data is sent on the SYN segment but, if the remote server also
25569 supports the facility, it can send its SMTP banner immediately after
25570 the SYN,ACK segment. This can save up to one round-trip time.
25572 The facility is only active for previously-contacted servers,
25573 as the initiator must present a cookie in the SYN segment.
25575 On (at least some) current Linux distributions the facility must be enabled
25576 in the kernel by the sysadmin before the support is usable.
25577 There is no option for control of the server side; if the system supports
25578 it it is always enabled. Note that lengthy operations in the connect ACL,
25579 such as DNSBL lookups, will still delay the emission of the SMTP banner.
25581 .option hosts_try_prdr smtp "host list&!!" *
25582 .cindex "PRDR" "enabling, optional in client"
25583 .cindex "ESMTP extensions" PRDR
25584 This option provides a list of servers to which, provided they announce
25585 PRDR support, Exim will attempt to negotiate PRDR
25586 for multi-recipient messages.
25587 The option can usually be left as default.
25589 .option interface smtp "string list&!!" unset
25590 .cindex "bind IP address"
25591 .cindex "IP address" "binding"
25593 .vindex "&$host_address$&"
25594 This option specifies which interface to bind to when making an outgoing SMTP
25595 call. The value is an IP address, not an interface name such as
25596 &`eth0`&. Do not confuse this with the interface address that was used when a
25597 message was received, which is in &$received_ip_address$&, formerly known as
25598 &$interface_address$&. The name was changed to minimize confusion with the
25599 outgoing interface address. There is no variable that contains an outgoing
25600 interface address because, unless it is set by this option, its value is
25603 During the expansion of the &%interface%& option the variables &$host$& and
25604 &$host_address$& refer to the host to which a connection is about to be made
25605 during the expansion of the string. Forced expansion failure, or an empty
25606 string result causes the option to be ignored. Otherwise, after expansion, the
25607 string must be a list of IP addresses, colon-separated by default, but the
25608 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
25611 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
25613 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
25614 connection. If none of them are the correct type, the option is ignored. If
25615 &%interface%& is not set, or is ignored, the system's IP functions choose which
25616 interface to use if the host has more than one.
25619 .option keepalive smtp boolean true
25620 .cindex "keepalive" "on outgoing connection"
25621 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
25622 connections. When set, it causes the kernel to probe idle connections
25623 periodically, by sending packets with &"old"& sequence numbers. The other end
25624 of the connection should send a acknowledgment if the connection is still okay
25625 or a reset if the connection has been aborted. The reason for doing this is
25626 that it has the beneficial effect of freeing up certain types of connection
25627 that can get stuck when the remote host is disconnected without tidying up the
25628 TCP/IP call properly. The keepalive mechanism takes several hours to detect
25632 .option lmtp_ignore_quota smtp boolean false
25633 .cindex "LMTP" "ignoring quota errors"
25634 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
25635 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
25636 has advertised support for IGNOREQUOTA in its response to the LHLO command.
25638 .option max_rcpt smtp integer 100
25639 .cindex "RCPT" "maximum number of outgoing"
25640 This option limits the number of RCPT commands that are sent in a single
25641 SMTP message transaction. Each set of addresses is treated independently, and
25642 so can cause parallel connections to the same host if &%remote_max_parallel%&
25647 .option message_linelength_limit smtp integer 998
25648 .cindex "line length" limit
25649 This option sets the maximum line length, in bytes, that the transport
25650 will send. Any messages with lines exceeding the given value
25651 will fail and a failure-DSN ("bounce") message will if possible be returned
25653 The default value is that defined by the SMTP standards.
25655 It is generally wise to also check in the data ACL so that messages
25656 received via SMTP can be refused without producing a bounce.
25660 .option multi_domain smtp boolean&!! true
25661 .vindex "&$domain$&"
25662 When this option is set, the &(smtp)& transport can handle a number of
25663 addresses containing a mixture of different domains provided they all resolve
25664 to the same list of hosts. Turning the option off restricts the transport to
25665 handling only one domain at a time. This is useful if you want to use
25666 &$domain$& in an expansion for the transport, because it is set only when there
25667 is a single domain involved in a remote delivery.
25669 It is expanded per-address and can depend on any of
25670 &$address_data$&, &$domain_data$&, &$local_part_data$&,
25671 &$host$&, &$host_address$& and &$host_port$&.
25674 If the connection is DANE-enabled then this option is ignored;
25675 only messages having the domain used for the DANE TLSA lookup are
25676 sent on the connection.
25679 .option port smtp string&!! "see below"
25680 .cindex "port" "sending TCP/IP"
25681 .cindex "TCP/IP" "setting outgoing port"
25682 This option specifies the TCP/IP port on the server to which Exim connects.
25683 &*Note:*& Do not confuse this with the port that was used when a message was
25684 received, which is in &$received_port$&, formerly known as &$interface_port$&.
25685 The name was changed to minimize confusion with the outgoing port. There is no
25686 variable that contains an outgoing port.
25688 If the value of this option begins with a digit it is taken as a port number;
25689 otherwise it is looked up using &[getservbyname()]&. The default value is
25691 but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"&
25692 and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
25693 If the expansion fails, or if a port number cannot be found, delivery
25696 Note that at least one Linux distribution has been seen failing
25697 to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
25701 .option protocol smtp string smtp
25702 .cindex "LMTP" "over TCP/IP"
25703 .cindex "ssmtp protocol" "outbound"
25704 .cindex "TLS" "SSL-on-connect outbound"
25706 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
25707 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
25708 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
25709 deliveries into closed message stores. Exim also has support for running LMTP
25710 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
25712 If this option is set to &"smtps"&, the default value for the &%port%& option
25713 changes to &"smtps"&, and the transport initiates TLS immediately after
25714 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
25715 The Internet standards bodies used to strongly discourage use of this mode,
25716 but as of RFC 8314 it is perferred over STARTTLS for message submission
25717 (as distinct from MTA-MTA communication).
25720 .option retry_include_ip_address smtp boolean&!! true
25721 Exim normally includes both the host name and the IP address in the key it
25722 constructs for indexing retry data after a temporary delivery failure. This
25723 means that when one of several IP addresses for a host is failing, it gets
25724 tried periodically (controlled by the retry rules), but use of the other IP
25725 addresses is not affected.
25727 However, in some dialup environments hosts are assigned a different IP address
25728 each time they connect. In this situation the use of the IP address as part of
25729 the retry key leads to undesirable behaviour. Setting this option false causes
25730 Exim to use only the host name.
25731 Since it is expanded it can be made to depend on the host or domain.
25734 .option serialize_hosts smtp "host list&!!" unset
25735 .cindex "serializing connections"
25736 .cindex "host" "serializing connections"
25737 Because Exim operates in a distributed manner, if several messages for the same
25738 host arrive at around the same time, more than one simultaneous connection to
25739 the remote host can occur. This is not usually a problem except when there is a
25740 slow link between the hosts. In that situation it may be helpful to restrict
25741 Exim to one connection at a time. This can be done by setting
25742 &%serialize_hosts%& to match the relevant hosts.
25744 .cindex "hints database" "serializing deliveries to a host"
25745 Exim implements serialization by means of a hints database in which a record is
25746 written whenever a process connects to one of the restricted hosts. The record
25747 is deleted when the connection is completed. Obviously there is scope for
25748 records to get left lying around if there is a system or program crash. To
25749 guard against this, Exim ignores any records that are more than six hours old.
25751 If you set up this kind of serialization, you should also arrange to delete the
25752 relevant hints database whenever your system reboots. The names of the files
25753 start with &_misc_& and they are kept in the &_spool/db_& directory. There
25754 may be one or two files, depending on the type of DBM in use. The same files
25755 are used for ETRN serialization.
25757 See also the &%max_parallel%& generic transport option.
25760 .option size_addition smtp integer 1024
25761 .cindex "SIZE" "ESMTP extension"
25762 .cindex "message" "size issue for transport filter"
25763 .cindex "size" "of message"
25764 .cindex "transport" "filter"
25765 .cindex "filter" "transport filter"
25766 If a remote SMTP server indicates that it supports the SIZE option of the
25767 MAIL command, Exim uses this to pass over the message size at the start of
25768 an SMTP transaction. It adds the value of &%size_addition%& to the value it
25769 sends, to allow for headers and other text that may be added during delivery by
25770 configuration options or in a transport filter. It may be necessary to increase
25771 this if a lot of text is added to messages.
25773 Alternatively, if the value of &%size_addition%& is set negative, it disables
25774 the use of the SIZE option altogether.
25777 .option socks_proxy smtp string&!! unset
25778 .cindex proxy SOCKS
25779 This option enables use of SOCKS proxies for connections made by the
25780 transport. For details see section &<<SECTproxySOCKS>>&.
25783 .option tls_certificate smtp string&!! unset
25784 .cindex "TLS" "client certificate, location of"
25785 .cindex "certificate" "client, location of"
25787 .vindex "&$host_address$&"
25788 The value of this option must be the absolute path to a file which contains the
25789 client's certificate, for possible use when sending a message over an encrypted
25790 connection. The values of &$host$& and &$host_address$& are set to the name and
25791 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
25794 &*Note*&: This option must be set if you want Exim to be able to use a TLS
25795 certificate when sending messages as a client. The global option of the same
25796 name specifies the certificate for Exim as a server; it is not automatically
25797 assumed that the same certificate should be used when Exim is operating as a
25801 .option tls_crl smtp string&!! unset
25802 .cindex "TLS" "client certificate revocation list"
25803 .cindex "certificate" "revocation list for client"
25804 This option specifies a certificate revocation list. The expanded value must
25805 be the name of a file that contains a CRL in PEM format.
25808 .option tls_dh_min_bits smtp integer 1024
25809 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
25810 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
25811 key agreement is negotiated, the server will provide a large prime number
25812 for use. This option establishes the minimum acceptable size of that number.
25813 If the parameter offered by the server is too small, then the TLS handshake
25816 Only supported when using GnuTLS.
25819 .option tls_privatekey smtp string&!! unset
25820 .cindex "TLS" "client private key, location of"
25822 .vindex "&$host_address$&"
25823 The value of this option must be the absolute path to a file which contains the
25824 client's private key. This is used when sending a message over an encrypted
25825 connection using a client certificate. The values of &$host$& and
25826 &$host_address$& are set to the name and address of the server during the
25827 expansion. If this option is unset, or the expansion is forced to fail, or the
25828 result is an empty string, the private key is assumed to be in the same file as
25829 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
25832 .option tls_require_ciphers smtp string&!! unset
25833 .cindex "TLS" "requiring specific ciphers"
25834 .cindex "cipher" "requiring specific"
25836 .vindex "&$host_address$&"
25837 The value of this option must be a list of permitted cipher suites, for use
25838 when setting up an outgoing encrypted connection. (There is a global option of
25839 the same name for controlling incoming connections.) The values of &$host$& and
25840 &$host_address$& are set to the name and address of the server during the
25841 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
25842 is used in different ways by OpenSSL and GnuTLS (see sections
25843 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
25844 ciphers is a preference order.
25848 .option tls_resumption_hosts smtp "host list&!!" unset
25849 .cindex TLS resumption
25850 This option controls which connections to use the TLS resumption feature.
25851 See &<<SECTresumption>>& for details.
25856 .option tls_sni smtp string&!! unset
25857 .cindex "TLS" "Server Name Indication"
25859 .cindex SNI "setting in client"
25860 .vindex "&$tls_sni$&"
25861 If this option is set
25863 and the connection is not DANE-validated
25865 then it sets the $tls_out_sni variable and causes any
25866 TLS session to pass this value as the Server Name Indication extension to
25867 the remote side, which can be used by the remote side to select an appropriate
25868 certificate and private key for the session.
25870 See &<<SECTtlssni>>& for more information.
25872 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
25878 .option tls_tempfail_tryclear smtp boolean true
25879 .cindex "4&'xx'& responses" "to STARTTLS"
25880 When the server host is not in &%hosts_require_tls%&, and there is a problem in
25881 setting up a TLS session, this option determines whether or not Exim should try
25882 to deliver the message unencrypted. If it is set false, delivery to the
25883 current host is deferred; if there are other hosts, they are tried. If this
25884 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
25885 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
25886 TLS negotiation fails, Exim closes the current connection (because it is in an
25887 unknown state), opens a new one to the same host, and then tries the delivery
25891 .option tls_try_verify_hosts smtp "host list&!!" *
25892 .cindex "TLS" "server certificate verification"
25893 .cindex "certificate" "verification of server"
25894 This option gives a list of hosts for which, on encrypted connections,
25895 certificate verification will be tried but need not succeed.
25896 The &%tls_verify_certificates%& option must also be set.
25897 Note that unless the host is in this list
25898 TLS connections will be denied to hosts using self-signed certificates
25899 when &%tls_verify_certificates%& is matched.
25900 The &$tls_out_certificate_verified$& variable is set when
25901 certificate verification succeeds.
25904 .option tls_verify_cert_hostnames smtp "host list&!!" *
25905 .cindex "TLS" "server certificate hostname verification"
25906 .cindex "certificate" "verification of server"
25907 This option give a list of hosts for which,
25908 while verifying the server certificate,
25909 checks will be included on the host name
25910 (note that this will generally be the result of a DNS MX lookup)
25911 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
25912 limited to being the initial component of a 3-or-more component FQDN.
25914 There is no equivalent checking on client certificates.
25917 .option tls_verify_certificates smtp string&!! system
25918 .cindex "TLS" "server certificate verification"
25919 .cindex "certificate" "verification of server"
25921 .vindex "&$host_address$&"
25922 The value of this option must be either the
25924 or the absolute path to
25925 a file or directory containing permitted certificates for servers,
25926 for use when setting up an encrypted connection.
25928 The "system" value for the option will use a location compiled into the SSL library.
25929 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
25930 is taken as empty and an explicit location
25933 The use of a directory for the option value is not available for GnuTLS versions
25934 preceding 3.3.6 and a single file must be used.
25936 With OpenSSL the certificates specified
25938 either by file or directory
25939 are added to those given by the system default location.
25941 The values of &$host$& and
25942 &$host_address$& are set to the name and address of the server during the
25943 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
25945 For back-compatibility,
25946 if neither tls_verify_hosts nor tls_try_verify_hosts are set
25947 (a single-colon empty list counts as being set)
25948 and certificate verification fails the TLS connection is closed.
25951 .option tls_verify_hosts smtp "host list&!!" unset
25952 .cindex "TLS" "server certificate verification"
25953 .cindex "certificate" "verification of server"
25954 This option gives a list of hosts for which, on encrypted connections,
25955 certificate verification must succeed.
25956 The &%tls_verify_certificates%& option must also be set.
25957 If both this option and &%tls_try_verify_hosts%& are unset
25958 operation is as if this option selected all hosts.
25960 .option utf8_downconvert smtp integer&!! -1
25961 .cindex utf8 "address downconversion"
25962 .cindex i18n "utf8 address downconversion"
25963 If built with internationalization support,
25964 this option controls conversion of UTF-8 in message envelope addresses
25966 If, after expansion, the value is 1, 0, or -1 then this value overrides
25967 any value previously set for the message. Otherwise, any previously
25968 set value is used. To permit use of a previous value,
25969 set this option to an empty string.
25970 For details on the values see section &<<SECTi18nMTA>>&.
25975 .section "How the limits for the number of hosts to try are used" &&&
25977 .cindex "host" "maximum number to try"
25978 .cindex "limit" "hosts; maximum number tried"
25979 There are two options that are concerned with the number of hosts that are
25980 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
25981 &%hosts_max_try_hardlimit%&.
25984 The &%hosts_max_try%& option limits the number of hosts that are tried
25985 for a single delivery. However, despite the term &"host"& in its name, the
25986 option actually applies to each IP address independently. In other words, a
25987 multihomed host is treated as several independent hosts, just as it is for
25990 Many of the larger ISPs have multiple MX records which often point to
25991 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
25992 created as a result of routing one of these domains.
25994 Trying every single IP address on such a long list does not seem sensible; if
25995 several at the top of the list fail, it is reasonable to assume there is some
25996 problem that is likely to affect all of them. Roughly speaking, the value of
25997 &%hosts_max_try%& is the maximum number that are tried before deferring the
25998 delivery. However, the logic cannot be quite that simple.
26000 Firstly, IP addresses that are skipped because their retry times have not
26001 arrived do not count, and in addition, addresses that are past their retry
26002 limits are also not counted, even when they are tried. This means that when
26003 some IP addresses are past their retry limits, more than the value of
26004 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
26005 that all IP addresses are considered before timing out an email address (but
26006 see below for an exception).
26008 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
26009 list to see if there is a subsequent host with a different (higher valued) MX.
26010 If there is, that host is considered next, and the current IP address is used
26011 but not counted. This behaviour helps in the case of a domain with a retry rule
26012 that hardly ever delays any hosts, as is now explained:
26014 Consider the case of a long list of hosts with one MX value, and a few with a
26015 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
26016 hosts at the top of the list are tried at first. With the default retry rule,
26017 which specifies increasing retry times, the higher MX hosts are eventually
26018 tried when those at the top of the list are skipped because they have not
26019 reached their retry times.
26021 However, it is common practice to put a fixed short retry time on domains for
26022 large ISPs, on the grounds that their servers are rarely down for very long.
26023 Unfortunately, these are exactly the domains that tend to resolve to long lists
26024 of hosts. The short retry time means that the lowest MX hosts are tried every
26025 time. The attempts may be in a different order because of random sorting, but
26026 without the special MX check, the higher MX hosts would never be tried until
26027 all the lower MX hosts had timed out (which might be several days), because
26028 there are always some lower MX hosts that have reached their retry times. With
26029 the special check, Exim considers at least one IP address from each MX value at
26030 every delivery attempt, even if the &%hosts_max_try%& limit has already been
26033 The above logic means that &%hosts_max_try%& is not a hard limit, and in
26034 particular, Exim normally eventually tries all the IP addresses before timing
26035 out an email address. When &%hosts_max_try%& was implemented, this seemed a
26036 reasonable thing to do. Recently, however, some lunatic DNS configurations have
26037 been set up with hundreds of IP addresses for some domains. It can
26038 take a very long time indeed for an address to time out in these cases.
26040 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
26041 Exim never tries more than this number of IP addresses; if it hits this limit
26042 and they are all timed out, the email address is bounced, even though not all
26043 possible IP addresses have been tried.
26044 .ecindex IIDsmttra1
26045 .ecindex IIDsmttra2
26051 . ////////////////////////////////////////////////////////////////////////////
26052 . ////////////////////////////////////////////////////////////////////////////
26054 .chapter "Address rewriting" "CHAPrewrite"
26055 .scindex IIDaddrew "rewriting" "addresses"
26056 There are some circumstances in which Exim automatically rewrites domains in
26057 addresses. The two most common are when an address is given without a domain
26058 (referred to as an &"unqualified address"&) or when an address contains an
26059 abbreviated domain that is expanded by DNS lookup.
26061 Unqualified envelope addresses are accepted only for locally submitted
26062 messages, or for messages that are received from hosts matching
26063 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
26064 appropriate. Unqualified addresses in header lines are qualified if they are in
26065 locally submitted messages, or messages from hosts that are permitted to send
26066 unqualified envelope addresses. Otherwise, unqualified addresses in header
26067 lines are neither qualified nor rewritten.
26069 One situation in which Exim does &'not'& automatically rewrite a domain is
26070 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
26071 such a domain should be rewritten using the &"canonical"& name, and some MTAs
26072 do this. The new RFCs do not contain this suggestion.
26075 .section "Explicitly configured address rewriting" "SECID147"
26076 This chapter describes the rewriting rules that can be used in the
26077 main rewrite section of the configuration file, and also in the generic
26078 &%headers_rewrite%& option that can be set on any transport.
26080 Some people believe that configured address rewriting is a Mortal Sin.
26081 Others believe that life is not possible without it. Exim provides the
26082 facility; you do not have to use it.
26084 The main rewriting rules that appear in the &"rewrite"& section of the
26085 configuration file are applied to addresses in incoming messages, both envelope
26086 addresses and addresses in header lines. Each rule specifies the types of
26087 address to which it applies.
26089 Whether or not addresses in header lines are rewritten depends on the origin of
26090 the headers and the type of rewriting. Global rewriting, that is, rewriting
26091 rules from the rewrite section of the configuration file, is applied only to
26092 those headers that were received with the message. Header lines that are added
26093 by ACLs or by a system filter or by individual routers or transports (which
26094 are specific to individual recipient addresses) are not rewritten by the global
26097 Rewriting at transport time, by means of the &%headers_rewrite%& option,
26098 applies all headers except those added by routers and transports. That is, as
26099 well as the headers that were received with the message, it also applies to
26100 headers that were added by an ACL or a system filter.
26103 In general, rewriting addresses from your own system or domain has some
26104 legitimacy. Rewriting other addresses should be done only with great care and
26105 in special circumstances. The author of Exim believes that rewriting should be
26106 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
26107 Although it can sometimes be used as a routing tool, this is very strongly
26110 There are two commonly encountered circumstances where rewriting is used, as
26111 illustrated by these examples:
26114 The company whose domain is &'hitch.fict.example'& has a number of hosts that
26115 exchange mail with each other behind a firewall, but there is only a single
26116 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
26117 &'hitch.fict.example'& when sending mail off-site.
26119 A host rewrites the local parts of its own users so that, for example,
26120 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
26125 .section "When does rewriting happen?" "SECID148"
26126 .cindex "rewriting" "timing of"
26127 .cindex "&ACL;" "rewriting addresses in"
26128 Configured address rewriting can take place at several different stages of a
26129 message's processing.
26131 .vindex "&$sender_address$&"
26132 At the start of an ACL for MAIL, the sender address may have been rewritten
26133 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
26134 ordinary rewrite rules have yet been applied. If, however, the sender address
26135 is verified in the ACL, it is rewritten before verification, and remains
26136 rewritten thereafter. The subsequent value of &$sender_address$& is the
26137 rewritten address. This also applies if sender verification happens in a
26138 RCPT ACL. Otherwise, when the sender address is not verified, it is
26139 rewritten as soon as a message's header lines have been received.
26141 .vindex "&$domain$&"
26142 .vindex "&$local_part$&"
26143 Similarly, at the start of an ACL for RCPT, the current recipient's address
26144 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
26145 rewrite rules have yet been applied to it. However, the behaviour is different
26146 from the sender address when a recipient is verified. The address is rewritten
26147 for the verification, but the rewriting is not remembered at this stage. The
26148 value of &$local_part$& and &$domain$& after verification are always the same
26149 as they were before (that is, they contain the unrewritten &-- except for
26150 SMTP-time rewriting &-- address).
26152 As soon as a message's header lines have been received, all the envelope
26153 recipient addresses are permanently rewritten, and rewriting is also applied to
26154 the addresses in the header lines (if configured). This happens before adding
26155 any header lines that were specified in MAIL or RCPT ACLs, and
26156 .cindex "&[local_scan()]& function" "address rewriting; timing of"
26157 before the DATA ACL and &[local_scan()]& functions are run.
26159 When an address is being routed, either for delivery or for verification,
26160 rewriting is applied immediately to child addresses that are generated by
26161 redirection, unless &%no_rewrite%& is set on the router.
26163 .cindex "envelope from"
26164 .cindex "envelope sender" "rewriting at transport time"
26165 .cindex "rewriting" "at transport time"
26166 .cindex "header lines" "rewriting at transport time"
26167 At transport time, additional rewriting of addresses in header lines can be
26168 specified by setting the generic &%headers_rewrite%& option on a transport.
26169 This option contains rules that are identical in form to those in the rewrite
26170 section of the configuration file. They are applied to the original message
26171 header lines and any that were added by ACLs or a system filter. They are not
26172 applied to header lines that are added by routers or the transport.
26174 The outgoing envelope sender can be rewritten by means of the &%return_path%&
26175 transport option. However, it is not possible to rewrite envelope recipients at
26181 .section "Testing the rewriting rules that apply on input" "SECID149"
26182 .cindex "rewriting" "testing"
26183 .cindex "testing" "rewriting"
26184 Exim's input rewriting configuration appears in a part of the runtime
26185 configuration file headed by &"begin rewrite"&. It can be tested by the
26186 &%-brw%& command line option. This takes an address (which can be a full RFC
26187 2822 address) as its argument. The output is a list of how the address would be
26188 transformed by the rewriting rules for each of the different places it might
26189 appear in an incoming message, that is, for each different header and for the
26190 envelope sender and recipient fields. For example,
26192 exim -brw ph10@exim.workshop.example
26194 might produce the output
26196 sender: Philip.Hazel@exim.workshop.example
26197 from: Philip.Hazel@exim.workshop.example
26198 to: ph10@exim.workshop.example
26199 cc: ph10@exim.workshop.example
26200 bcc: ph10@exim.workshop.example
26201 reply-to: Philip.Hazel@exim.workshop.example
26202 env-from: Philip.Hazel@exim.workshop.example
26203 env-to: ph10@exim.workshop.example
26205 which shows that rewriting has been set up for that address when used in any of
26206 the source fields, but not when it appears as a recipient address. At the
26207 present time, there is no equivalent way of testing rewriting rules that are
26208 set for a particular transport.
26211 .section "Rewriting rules" "SECID150"
26212 .cindex "rewriting" "rules"
26213 The rewrite section of the configuration file consists of lines of rewriting
26216 <&'source pattern'&> <&'replacement'&> <&'flags'&>
26218 Rewriting rules that are specified for the &%headers_rewrite%& generic
26219 transport option are given as a colon-separated list. Each item in the list
26220 takes the same form as a line in the main rewriting configuration (except that
26221 any colons must be doubled, of course).
26223 The formats of source patterns and replacement strings are described below.
26224 Each is terminated by white space, unless enclosed in double quotes, in which
26225 case normal quoting conventions apply inside the quotes. The flags are single
26226 characters which may appear in any order. Spaces and tabs between them are
26229 For each address that could potentially be rewritten, the rules are scanned in
26230 order, and replacements for the address from earlier rules can themselves be
26231 replaced by later rules (but see the &"q"& and &"R"& flags).
26233 The order in which addresses are rewritten is undefined, may change between
26234 releases, and must not be relied on, with one exception: when a message is
26235 received, the envelope sender is always rewritten first, before any header
26236 lines are rewritten. For example, the replacement string for a rewrite of an
26237 address in &'To:'& must not assume that the message's address in &'From:'& has
26238 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
26239 that the envelope sender has already been rewritten.
26241 .vindex "&$domain$&"
26242 .vindex "&$local_part$&"
26243 The variables &$local_part$& and &$domain$& can be used in the replacement
26244 string to refer to the address that is being rewritten. Note that lookup-driven
26245 rewriting can be done by a rule of the form
26249 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
26250 refer to the address that is being rewritten.
26253 .section "Rewriting patterns" "SECID151"
26254 .cindex "rewriting" "patterns"
26255 .cindex "address list" "in a rewriting pattern"
26256 The source pattern in a rewriting rule is any item which may appear in an
26257 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
26258 single-item address list, which means that it is expanded before being tested
26259 against the address. As always, if you use a regular expression as a pattern,
26260 you must take care to escape dollar and backslash characters, or use the &`\N`&
26261 facility to suppress string expansion within the regular expression.
26263 Domains in patterns should be given in lower case. Local parts in patterns are
26264 case-sensitive. If you want to do case-insensitive matching of local parts, you
26265 can use a regular expression that starts with &`^(?i)`&.
26267 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
26268 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
26269 depending on the type of match which occurred. These can be used in the
26270 replacement string to insert portions of the incoming address. &$0$& always
26271 refers to the complete incoming address. When a regular expression is used, the
26272 numerical variables are set from its capturing subexpressions. For other types
26273 of pattern they are set as follows:
26276 If a local part or domain starts with an asterisk, the numerical variables
26277 refer to the character strings matched by asterisks, with &$1$& associated with
26278 the first asterisk, and &$2$& with the second, if present. For example, if the
26281 *queen@*.fict.example
26283 is matched against the address &'hearts-queen@wonderland.fict.example'& then
26285 $0 = hearts-queen@wonderland.fict.example
26289 Note that if the local part does not start with an asterisk, but the domain
26290 does, it is &$1$& that contains the wild part of the domain.
26293 If the domain part of the pattern is a partial lookup, the wild and fixed parts
26294 of the domain are placed in the next available numerical variables. Suppose,
26295 for example, that the address &'foo@bar.baz.example'& is processed by a
26296 rewriting rule of the form
26298 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
26300 and the key in the file that matches the domain is &`*.baz.example`&. Then
26306 If the address &'foo@baz.example'& is looked up, this matches the same
26307 wildcard file entry, and in this case &$2$& is set to the empty string, but
26308 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
26309 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
26310 whole domain. For non-partial domain lookups, no numerical variables are set.
26314 .section "Rewriting replacements" "SECID152"
26315 .cindex "rewriting" "replacements"
26316 If the replacement string for a rule is a single asterisk, addresses that
26317 match the pattern and the flags are &'not'& rewritten, and no subsequent
26318 rewriting rules are scanned. For example,
26320 hatta@lookingglass.fict.example * f
26322 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
26325 .vindex "&$domain$&"
26326 .vindex "&$local_part$&"
26327 If the replacement string is not a single asterisk, it is expanded, and must
26328 yield a fully qualified address. Within the expansion, the variables
26329 &$local_part$& and &$domain$& refer to the address that is being rewritten.
26330 Any letters they contain retain their original case &-- they are not lower
26331 cased. The numerical variables are set up according to the type of pattern that
26332 matched the address, as described above. If the expansion is forced to fail by
26333 the presence of &"fail"& in a conditional or lookup item, rewriting by the
26334 current rule is abandoned, but subsequent rules may take effect. Any other
26335 expansion failure causes the entire rewriting operation to be abandoned, and an
26336 entry written to the panic log.
26340 .section "Rewriting flags" "SECID153"
26341 There are three different kinds of flag that may appear on rewriting rules:
26344 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
26347 A flag that specifies rewriting at SMTP time: S.
26349 Flags that control the rewriting process: Q, q, R, w.
26352 For rules that are part of the &%headers_rewrite%& generic transport option,
26353 E, F, T, and S are not permitted.
26357 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
26359 .cindex "rewriting" "flags"
26360 If none of the following flag letters, nor the &"S"& flag (see section
26361 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
26362 and to both the sender and recipient fields of the envelope, whereas a
26363 transport-time rewriting rule just applies to all headers. Otherwise, the
26364 rewriting rule is skipped unless the relevant addresses are being processed.
26366 &`E`& rewrite all envelope fields
26367 &`F`& rewrite the envelope From field
26368 &`T`& rewrite the envelope To field
26369 &`b`& rewrite the &'Bcc:'& header
26370 &`c`& rewrite the &'Cc:'& header
26371 &`f`& rewrite the &'From:'& header
26372 &`h`& rewrite all headers
26373 &`r`& rewrite the &'Reply-To:'& header
26374 &`s`& rewrite the &'Sender:'& header
26375 &`t`& rewrite the &'To:'& header
26377 "All headers" means all of the headers listed above that can be selected
26378 individually, plus their &'Resent-'& versions. It does not include
26379 other headers such as &'Subject:'& etc.
26381 You should be particularly careful about rewriting &'Sender:'& headers, and
26382 restrict this to special known cases in your own domains.
26385 .section "The SMTP-time rewriting flag" "SECTrewriteS"
26386 .cindex "SMTP" "rewriting malformed addresses"
26387 .cindex "RCPT" "rewriting argument of"
26388 .cindex "MAIL" "rewriting argument of"
26389 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
26390 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
26391 before any other processing; even before syntax checking. The pattern is
26392 required to be a regular expression, and it is matched against the whole of the
26393 data for the command, including any surrounding angle brackets.
26395 .vindex "&$domain$&"
26396 .vindex "&$local_part$&"
26397 This form of rewrite rule allows for the handling of addresses that are not
26398 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
26399 input). Because the input is not required to be a syntactically valid address,
26400 the variables &$local_part$& and &$domain$& are not available during the
26401 expansion of the replacement string. The result of rewriting replaces the
26402 original address in the MAIL or RCPT command.
26405 .section "Flags controlling the rewriting process" "SECID155"
26406 There are four flags which control the way the rewriting process works. These
26407 take effect only when a rule is invoked, that is, when the address is of the
26408 correct type (matches the flags) and matches the pattern:
26411 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
26412 unqualified local part. It is qualified with &%qualify_recipient%&. In the
26413 absence of &"Q"& the rewritten address must always include a domain.
26415 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
26416 even if no rewriting actually takes place because of a &"fail"& in the
26417 expansion. The &"q"& flag is not effective if the address is of the wrong type
26418 (does not match the flags) or does not match the pattern.
26420 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
26421 address, up to ten times. It can be combined with the &"q"& flag, to stop
26422 rewriting once it fails to match (after at least one successful rewrite).
26424 .cindex "rewriting" "whole addresses"
26425 When an address in a header is rewritten, the rewriting normally applies only
26426 to the working part of the address, with any comments and RFC 2822 &"phrase"&
26427 left unchanged. For example, rewriting might change
26429 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
26433 From: Ford Prefect <prefectf@hitch.fict.example>
26436 Sometimes there is a need to replace the whole address item, and this can be
26437 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
26438 causes an address in a header line to be rewritten, the entire address is
26439 replaced, not just the working part. The replacement must be a complete RFC
26440 2822 address, including the angle brackets if necessary. If text outside angle
26441 brackets contains a character whose value is greater than 126 or less than 32
26442 (except for tab), the text is encoded according to RFC 2047. The character set
26443 is taken from &%headers_charset%&, which gets its default at build time.
26445 When the &"w"& flag is set on a rule that causes an envelope address to be
26446 rewritten, all but the working part of the replacement address is discarded.
26450 .section "Rewriting examples" "SECID156"
26451 Here is an example of the two common rewriting paradigms:
26453 *@*.hitch.fict.example $1@hitch.fict.example
26454 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
26455 {$value}fail}@hitch.fict.example bctfrF
26457 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
26458 the string expansion to fail if the lookup does not succeed. In this context it
26459 has the effect of leaving the original address unchanged, but Exim goes on to
26460 consider subsequent rewriting rules, if any, because the &"q"& flag is not
26461 present in that rule. An alternative to &"fail"& would be to supply &$1$&
26462 explicitly, which would cause the rewritten address to be the same as before,
26463 at the cost of a small bit of processing. Not supplying either of these is an
26464 error, since the rewritten address would then contain no local part.
26466 The first example above replaces the domain with a superior, more general
26467 domain. This may not be desirable for certain local parts. If the rule
26469 root@*.hitch.fict.example *
26471 were inserted before the first rule, rewriting would be suppressed for the
26472 local part &'root'& at any domain ending in &'hitch.fict.example'&.
26474 Rewriting can be made conditional on a number of tests, by making use of
26475 &${if$& in the expansion item. For example, to apply a rewriting rule only to
26476 messages that originate outside the local host:
26478 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
26479 {$1@hitch.fict.example}fail}"
26481 The replacement string is quoted in this example because it contains white
26484 .cindex "rewriting" "bang paths"
26485 .cindex "bang paths" "rewriting"
26486 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
26487 an address it treats it as an unqualified local part which it qualifies with
26488 the local qualification domain (if the source of the message is local or if the
26489 remote host is permitted to send unqualified addresses). Rewriting can
26490 sometimes be used to handle simple bang paths with a fixed number of
26491 components. For example, the rule
26493 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
26495 rewrites a two-component bang path &'host.name!user'& as the domain address
26496 &'user@host.name'&. However, there is a security implication in using this as
26497 a global rewriting rule for envelope addresses. It can provide a backdoor
26498 method for using your system as a relay, because the incoming addresses appear
26499 to be local. If the bang path addresses are received via SMTP, it is safer to
26500 use the &"S"& flag to rewrite them as they are received, so that relay checking
26501 can be done on the rewritten addresses.
26508 . ////////////////////////////////////////////////////////////////////////////
26509 . ////////////////////////////////////////////////////////////////////////////
26511 .chapter "Retry configuration" "CHAPretry"
26512 .scindex IIDretconf1 "retry" "configuration, description of"
26513 .scindex IIDregconf2 "configuration file" "retry section"
26514 The &"retry"& section of the runtime configuration file contains a list of
26515 retry rules that control how often Exim tries to deliver messages that cannot
26516 be delivered at the first attempt. If there are no retry rules (the section is
26517 empty or not present), there are no retries. In this situation, temporary
26518 errors are treated as permanent. The default configuration contains a single,
26519 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
26520 line option can be used to test which retry rule will be used for a given
26521 address, domain and error.
26523 The most common cause of retries is temporary failure to deliver to a remote
26524 host because the host is down, or inaccessible because of a network problem.
26525 Exim's retry processing in this case is applied on a per-host (strictly, per IP
26526 address) basis, not on a per-message basis. Thus, if one message has recently
26527 been delayed, delivery of a new message to the same host is not immediately
26528 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
26529 log selector is set, the message
26530 .cindex "retry" "time not reached"
26531 &"retry time not reached"& is written to the main log whenever a delivery is
26532 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
26533 the handling of errors during remote deliveries.
26535 Retry processing applies to routing as well as to delivering, except as covered
26536 in the next paragraph. The retry rules do not distinguish between these
26537 actions. It is not possible, for example, to specify different behaviour for
26538 failures to route the domain &'snark.fict.example'& and failures to deliver to
26539 the host &'snark.fict.example'&. I didn't think anyone would ever need this
26540 added complication, so did not implement it. However, although they share the
26541 same retry rule, the actual retry times for routing and transporting a given
26542 domain are maintained independently.
26544 When a delivery is not part of a queue run (typically an immediate delivery on
26545 receipt of a message), the routers are always run, and local deliveries are
26546 always attempted, even if retry times are set for them. This makes for better
26547 behaviour if one particular message is causing problems (for example, causing
26548 quota overflow, or provoking an error in a filter file). If such a delivery
26549 suffers a temporary failure, the retry data is updated as normal, and
26550 subsequent delivery attempts from queue runs occur only when the retry time for
26551 the local address is reached.
26553 .section "Changing retry rules" "SECID157"
26554 If you change the retry rules in your configuration, you should consider
26555 whether or not to delete the retry data that is stored in Exim's spool area in
26556 files with names like &_db/retry_&. Deleting any of Exim's hints files is
26557 always safe; that is why they are called &"hints"&.
26559 The hints retry data contains suggested retry times based on the previous
26560 rules. In the case of a long-running problem with a remote host, it might
26561 record the fact that the host has timed out. If your new rules increase the
26562 timeout time for such a host, you should definitely remove the old retry data
26563 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
26564 messages that it should now be retaining.
26568 .section "Format of retry rules" "SECID158"
26569 .cindex "retry" "rules"
26570 Each retry rule occupies one line and consists of three or four parts,
26571 separated by white space: a pattern, an error name, an optional list of sender
26572 addresses, and a list of retry parameters. The pattern and sender lists must be
26573 enclosed in double quotes if they contain white space. The rules are searched
26574 in order until one is found where the pattern, error name, and sender list (if
26575 present) match the failing host or address, the error that occurred, and the
26576 message's sender, respectively.
26579 The pattern is any single item that may appear in an address list (see section
26580 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
26581 which means that it is expanded before being tested against the address that
26582 has been delayed. A negated address list item is permitted. Address
26583 list processing treats a plain domain name as if it were preceded by &"*@"&,
26584 which makes it possible for many retry rules to start with just a domain. For
26587 lookingglass.fict.example * F,24h,30m;
26589 provides a rule for any address in the &'lookingglass.fict.example'& domain,
26592 alice@lookingglass.fict.example * F,24h,30m;
26594 applies only to temporary failures involving the local part &%alice%&.
26595 In practice, almost all rules start with a domain name pattern without a local
26598 .cindex "regular expressions" "in retry rules"
26599 &*Warning*&: If you use a regular expression in a retry rule pattern, it
26600 must match a complete address, not just a domain, because that is how regular
26601 expressions work in address lists.
26603 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
26604 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
26608 .section "Choosing which retry rule to use for address errors" "SECID159"
26609 When Exim is looking for a retry rule after a routing attempt has failed (for
26610 example, after a DNS timeout), each line in the retry configuration is tested
26611 against the complete address only if &%retry_use_local_part%& is set for the
26612 router. Otherwise, only the domain is used, except when matching against a
26613 regular expression, when the local part of the address is replaced with &"*"&.
26614 A domain on its own can match a domain pattern, or a pattern that starts with
26615 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
26616 &%check_local_user%& is true, and false for other routers.
26618 Similarly, when Exim is looking for a retry rule after a local delivery has
26619 failed (for example, after a mailbox full error), each line in the retry
26620 configuration is tested against the complete address only if
26621 &%retry_use_local_part%& is set for the transport (it defaults true for all
26624 .cindex "4&'xx'& responses" "retry rules for"
26625 However, when Exim is looking for a retry rule after a remote delivery attempt
26626 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
26627 whole address is always used as the key when searching the retry rules. The
26628 rule that is found is used to create a retry time for the combination of the
26629 failing address and the message's sender. It is the combination of sender and
26630 recipient that is delayed in subsequent queue runs until its retry time is
26631 reached. You can delay the recipient without regard to the sender by setting
26632 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
26633 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
26638 .section "Choosing which retry rule to use for host and message errors" &&&
26640 For a temporary error that is not related to an individual address (for
26641 example, a connection timeout), each line in the retry configuration is checked
26642 twice. First, the name of the remote host is used as a domain name (preceded by
26643 &"*@"& when matching a regular expression). If this does not match the line,
26644 the domain from the email address is tried in a similar fashion. For example,
26645 suppose the MX records for &'a.b.c.example'& are
26647 a.b.c.example MX 5 x.y.z.example
26651 and the retry rules are
26653 p.q.r.example * F,24h,30m;
26654 a.b.c.example * F,4d,45m;
26656 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
26657 first rule matches neither the host nor the domain, so Exim looks at the second
26658 rule. This does not match the host, but it does match the domain, so it is used
26659 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
26660 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
26661 first retry rule is used, because it matches the host.
26663 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
26664 first rule to determine retry times, but for all the other hosts for the domain
26665 &'a.b.c.example'&, the second rule is used. The second rule is also used if
26666 routing to &'a.b.c.example'& suffers a temporary failure.
26668 &*Note*&: The host name is used when matching the patterns, not its IP address.
26669 However, if a message is routed directly to an IP address without the use of a
26670 host name, for example, if a &(manualroute)& router contains a setting such as:
26672 route_list = *.a.example 192.168.34.23
26674 then the &"host name"& that is used when searching for a retry rule is the
26675 textual form of the IP address.
26677 .section "Retry rules for specific errors" "SECID161"
26678 .cindex "retry" "specific errors; specifying"
26679 The second field in a retry rule is the name of a particular error, or an
26680 asterisk, which matches any error. The errors that can be tested for are:
26683 .vitem &%auth_failed%&
26684 Authentication failed when trying to send to a host in the
26685 &%hosts_require_auth%& list in an &(smtp)& transport.
26687 .vitem &%data_4xx%&
26688 A 4&'xx'& error was received for an outgoing DATA command, either immediately
26689 after the command, or after sending the message's data.
26691 .vitem &%mail_4xx%&
26692 A 4&'xx'& error was received for an outgoing MAIL command.
26694 .vitem &%rcpt_4xx%&
26695 A 4&'xx'& error was received for an outgoing RCPT command.
26698 For the three 4&'xx'& errors, either the first or both of the x's can be given
26699 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
26700 recognize 452 errors given to RCPT commands for addresses in a certain domain,
26701 and have retries every ten minutes with a one-hour timeout, you could set up a
26702 retry rule of this form:
26704 the.domain.name rcpt_452 F,1h,10m
26706 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
26707 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
26710 .vitem &%lost_connection%&
26711 A server unexpectedly closed the SMTP connection. There may, of course,
26712 legitimate reasons for this (host died, network died), but if it repeats a lot
26713 for the same host, it indicates something odd.
26716 A DNS lookup for a host failed.
26717 Note that a &%dnslookup%& router will need to have matched
26718 its &%fail_defer_domains%& option for this retry type to be usable.
26719 Also note that a &%manualroute%& router will probably need
26720 its &%host_find_failed%& option set to &%defer%&.
26722 .vitem &%refused_MX%&
26723 A connection to a host obtained from an MX record was refused.
26725 .vitem &%refused_A%&
26726 A connection to a host not obtained from an MX record was refused.
26729 A connection was refused.
26731 .vitem &%timeout_connect_MX%&
26732 A connection attempt to a host obtained from an MX record timed out.
26734 .vitem &%timeout_connect_A%&
26735 A connection attempt to a host not obtained from an MX record timed out.
26737 .vitem &%timeout_connect%&
26738 A connection attempt timed out.
26740 .vitem &%timeout_MX%&
26741 There was a timeout while connecting or during an SMTP session with a host
26742 obtained from an MX record.
26744 .vitem &%timeout_A%&
26745 There was a timeout while connecting or during an SMTP session with a host not
26746 obtained from an MX record.
26749 There was a timeout while connecting or during an SMTP session.
26751 .vitem &%tls_required%&
26752 The server was required to use TLS (it matched &%hosts_require_tls%& in the
26753 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
26754 to STARTTLS, or there was a problem setting up the TLS connection.
26757 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26760 .vitem &%quota_%&<&'time'&>
26761 .cindex "quota" "error testing in retry rule"
26762 .cindex "retry" "quota error testing"
26763 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26764 transport, and the mailbox has not been accessed for <&'time'&>. For example,
26765 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
26769 .cindex "mailbox" "time of last read"
26770 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
26771 timeouts when the mailbox is full and is not being read by its owner. Ideally,
26772 it should be based on the last time that the user accessed the mailbox.
26773 However, it is not always possible to determine this. Exim uses the following
26777 If the mailbox is a single file, the time of last access (the &"atime"&) is
26778 used. As no new messages are being delivered (because the mailbox is over
26779 quota), Exim does not access the file, so this is the time of last user access.
26781 .cindex "maildir format" "time of last read"
26782 For a maildir delivery, the time of last modification of the &_new_&
26783 subdirectory is used. As the mailbox is over quota, no new files are created in
26784 the &_new_& subdirectory, because no new messages are being delivered. Any
26785 change to the &_new_& subdirectory is therefore assumed to be the result of an
26786 MUA moving a new message to the &_cur_& directory when it is first read. The
26787 time that is used is therefore the last time that the user read a new message.
26789 For other kinds of multi-file mailbox, the time of last access cannot be
26790 obtained, so a retry rule that uses this type of error field is never matched.
26793 The quota errors apply both to system-enforced quotas and to Exim's own quota
26794 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
26795 when a local delivery is deferred because a partition is full (the ENOSPC
26800 .section "Retry rules for specified senders" "SECID162"
26801 .cindex "retry" "rules; sender-specific"
26802 You can specify retry rules that apply only when the failing message has a
26803 specific sender. In particular, this can be used to define retry rules that
26804 apply only to bounce messages. The third item in a retry rule can be of this
26807 &`senders=`&<&'address list'&>
26809 The retry timings themselves are then the fourth item. For example:
26811 * rcpt_4xx senders=: F,1h,30m
26813 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
26814 host. If the address list contains white space, it must be enclosed in quotes.
26817 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
26819 &*Warning*&: This facility can be unhelpful if it is used for host errors
26820 (which do not depend on the recipient). The reason is that the sender is used
26821 only to match the retry rule. Once the rule has been found for a host error,
26822 its contents are used to set a retry time for the host, and this will apply to
26823 all messages, not just those with specific senders.
26825 When testing retry rules using &%-brt%&, you can supply a sender using the
26826 &%-f%& command line option, like this:
26828 exim -f "" -brt user@dom.ain
26830 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
26831 list is never matched.
26837 .section "Retry parameters" "SECID163"
26838 .cindex "retry" "parameters in rules"
26839 The third (or fourth, if a senders list is present) field in a retry rule is a
26840 sequence of retry parameter sets, separated by semicolons. Each set consists of
26842 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
26844 The letter identifies the algorithm for computing a new retry time; the cutoff
26845 time is the time beyond which this algorithm no longer applies, and the
26846 arguments vary the algorithm's action. The cutoff time is measured from the
26847 time that the first failure for the domain (combined with the local part if
26848 relevant) was detected, not from the time the message was received.
26850 .cindex "retry" "algorithms"
26851 .cindex "retry" "fixed intervals"
26852 .cindex "retry" "increasing intervals"
26853 .cindex "retry" "random intervals"
26854 The available algorithms are:
26857 &'F'&: retry at fixed intervals. There is a single time parameter specifying
26860 &'G'&: retry at geometrically increasing intervals. The first argument
26861 specifies a starting value for the interval, and the second a multiplier, which
26862 is used to increase the size of the interval at each retry.
26864 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
26865 retry, the previous interval is multiplied by the factor in order to get a
26866 maximum for the next interval. The minimum interval is the first argument of
26867 the parameter, and an actual interval is chosen randomly between them. Such a
26868 rule has been found to be helpful in cluster configurations when all the
26869 members of the cluster restart at once, and may therefore synchronize their
26870 queue processing times.
26873 When computing the next retry time, the algorithm definitions are scanned in
26874 order until one whose cutoff time has not yet passed is reached. This is then
26875 used to compute a new retry time that is later than the current time. In the
26876 case of fixed interval retries, this simply means adding the interval to the
26877 current time. For geometrically increasing intervals, retry intervals are
26878 computed from the rule's parameters until one that is greater than the previous
26879 interval is found. The main configuration variable
26880 .cindex "limit" "retry interval"
26881 .cindex "retry" "interval, maximum"
26882 .oindex "&%retry_interval_max%&"
26883 &%retry_interval_max%& limits the maximum interval between retries. It
26884 cannot be set greater than &`24h`&, which is its default value.
26886 A single remote domain may have a number of hosts associated with it, and each
26887 host may have more than one IP address. Retry algorithms are selected on the
26888 basis of the domain name, but are applied to each IP address independently. If,
26889 for example, a host has two IP addresses and one is unusable, Exim will
26890 generate retry times for it and will not try to use it until its next retry
26891 time comes. Thus the good IP address is likely to be tried first most of the
26894 .cindex "hints database" "use for retrying"
26895 Retry times are hints rather than promises. Exim does not make any attempt to
26896 run deliveries exactly at the computed times. Instead, a queue runner process
26897 starts delivery processes for delayed messages periodically, and these attempt
26898 new deliveries only for those addresses that have passed their next retry time.
26899 If a new message arrives for a deferred address, an immediate delivery attempt
26900 occurs only if the address has passed its retry time. In the absence of new
26901 messages, the minimum time between retries is the interval between queue runner
26902 processes. There is not much point in setting retry times of five minutes if
26903 your queue runners happen only once an hour, unless there are a significant
26904 number of incoming messages (which might be the case on a system that is
26905 sending everything to a smart host, for example).
26907 The data in the retry hints database can be inspected by using the
26908 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
26909 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
26910 &'exinext'& utility script can be used to find out what the next retry times
26911 are for the hosts associated with a particular mail domain, and also for local
26912 deliveries that have been deferred.
26915 .section "Retry rule examples" "SECID164"
26916 Here are some example retry rules:
26918 alice@wonderland.fict.example quota_5d F,7d,3h
26919 wonderland.fict.example quota_5d
26920 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
26921 lookingglass.fict.example * F,24h,30m;
26922 * refused_A F,2h,20m;
26923 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
26925 The first rule sets up special handling for mail to
26926 &'alice@wonderland.fict.example'& when there is an over-quota error and the
26927 mailbox has not been read for at least 5 days. Retries continue every three
26928 hours for 7 days. The second rule handles over-quota errors for all other local
26929 parts at &'wonderland.fict.example'&; the absence of a local part has the same
26930 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
26931 fail are bounced immediately if the mailbox has not been read for at least 5
26934 The third rule handles all other errors at &'wonderland.fict.example'&; retries
26935 happen every 15 minutes for an hour, then with geometrically increasing
26936 intervals until two days have passed since a delivery first failed. After the
26937 first hour there is a delay of one hour, then two hours, then four hours, and
26938 so on (this is a rather extreme example).
26940 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
26941 They happen every 30 minutes for 24 hours only. The remaining two rules handle
26942 all other domains, with special action for connection refusal from hosts that
26943 were not obtained from an MX record.
26945 The final rule in a retry configuration should always have asterisks in the
26946 first two fields so as to provide a general catch-all for any addresses that do
26947 not have their own special handling. This example tries every 15 minutes for 2
26948 hours, then with intervals starting at one hour and increasing by a factor of
26949 1.5 up to 16 hours, then every 8 hours up to 5 days.
26953 .section "Timeout of retry data" "SECID165"
26954 .cindex "timeout" "of retry data"
26955 .oindex "&%retry_data_expire%&"
26956 .cindex "hints database" "data expiry"
26957 .cindex "retry" "timeout of data"
26958 Exim timestamps the data that it writes to its retry hints database. When it
26959 consults the data during a delivery it ignores any that is older than the value
26960 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
26961 been tried for 7 days, Exim will try to deliver to it immediately a message
26962 arrives, and if that fails, it will calculate a retry time as if it were
26963 failing for the first time.
26965 This improves the behaviour for messages routed to rarely-used hosts such as MX
26966 backups. If such a host was down at one time, and happens to be down again when
26967 Exim tries a month later, using the old retry data would imply that it had been
26968 down all the time, which is not a justified assumption.
26970 If a host really is permanently dead, this behaviour causes a burst of retries
26971 every now and again, but only if messages routed to it are rare. If there is a
26972 message at least once every 7 days the retry data never expires.
26977 .section "Long-term failures" "SECID166"
26978 .cindex "delivery failure, long-term"
26979 .cindex "retry" "after long-term failure"
26980 Special processing happens when an email address has been failing for so long
26981 that the cutoff time for the last algorithm is reached. For example, using the
26982 default retry rule:
26984 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
26986 the cutoff time is four days. Reaching the retry cutoff is independent of how
26987 long any specific message has been failing; it is the length of continuous
26988 failure for the recipient address that counts.
26990 When the cutoff time is reached for a local delivery, or for all the IP
26991 addresses associated with a remote delivery, a subsequent delivery failure
26992 causes Exim to give up on the address, and a bounce message is generated.
26993 In order to cater for new messages that use the failing address, a next retry
26994 time is still computed from the final algorithm, and is used as follows:
26996 For local deliveries, one delivery attempt is always made for any subsequent
26997 messages. If this delivery fails, the address fails immediately. The
26998 post-cutoff retry time is not used.
27000 .cindex "final cutoff" "retries, controlling"
27001 .cindex retry "final cutoff"
27002 If the delivery is remote, there are two possibilities, controlled by the
27003 .oindex "&%delay_after_cutoff%&"
27004 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
27005 default. Until the post-cutoff retry time for one of the IP addresses,
27006 as set by the &%retry_data_expire%& option, is
27007 reached, the failing email address is bounced immediately, without a delivery
27008 attempt taking place. After that time, one new delivery attempt is made to
27009 those IP addresses that are past their retry times, and if that still fails,
27010 the address is bounced and new retry times are computed.
27012 In other words, when all the hosts for a given email address have been failing
27013 for a long time, Exim bounces rather then defers until one of the hosts' retry
27014 times is reached. Then it tries once, and bounces if that attempt fails. This
27015 behaviour ensures that few resources are wasted in repeatedly trying to deliver
27016 to a broken destination, but if the host does recover, Exim will eventually
27019 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
27020 addresses are past their final cutoff time, Exim tries to deliver to those IP
27021 addresses that have not been tried since the message arrived. If there are
27022 no suitable IP addresses, or if they all fail, the address is bounced. In other
27023 words, it does not delay when a new message arrives, but tries the expired
27024 addresses immediately, unless they have been tried since the message arrived.
27025 If there is a continuous stream of messages for the failing domains, setting
27026 &%delay_after_cutoff%& false means that there will be many more attempts to
27027 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
27030 .section "Deliveries that work intermittently" "SECID167"
27031 .cindex "retry" "intermittently working deliveries"
27032 Some additional logic is needed to cope with cases where a host is
27033 intermittently available, or when a message has some attribute that prevents
27034 its delivery when others to the same address get through. In this situation,
27035 because some messages are successfully delivered, the &"retry clock"& for the
27036 host or address keeps getting reset by the successful deliveries, and so
27037 failing messages remain in the queue for ever because the cutoff time is never
27040 Two exceptional actions are applied to prevent this happening. The first
27041 applies to errors that are related to a message rather than a remote host.
27042 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
27043 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
27044 commands, and quota failures. For this type of error, if a message's arrival
27045 time is earlier than the &"first failed"& time for the error, the earlier time
27046 is used when scanning the retry rules to decide when to try next and when to
27047 time out the address.
27049 The exceptional second action applies in all cases. If a message has been on
27050 the queue for longer than the cutoff time of any applicable retry rule for a
27051 given address, a delivery is attempted for that address, even if it is not yet
27052 time, and if this delivery fails, the address is timed out. A new retry time is
27053 not computed in this case, so that other messages for the same address are
27054 considered immediately.
27055 .ecindex IIDretconf1
27056 .ecindex IIDregconf2
27063 . ////////////////////////////////////////////////////////////////////////////
27064 . ////////////////////////////////////////////////////////////////////////////
27066 .chapter "SMTP authentication" "CHAPSMTPAUTH"
27067 .scindex IIDauthconf1 "SMTP" "authentication configuration"
27068 .scindex IIDauthconf2 "authentication"
27069 The &"authenticators"& section of Exim's runtime configuration is concerned
27070 with SMTP authentication. This facility is an extension to the SMTP protocol,
27071 described in RFC 2554, which allows a client SMTP host to authenticate itself
27072 to a server. This is a common way for a server to recognize clients that are
27073 permitted to use it as a relay. SMTP authentication is not of relevance to the
27074 transfer of mail between servers that have no managerial connection with each
27077 .cindex "AUTH" "description of"
27078 .cindex "ESMTP extensions" AUTH
27079 Very briefly, the way SMTP authentication works is as follows:
27082 The server advertises a number of authentication &'mechanisms'& in response to
27083 the client's EHLO command.
27085 The client issues an AUTH command, naming a specific mechanism. The command
27086 may, optionally, contain some authentication data.
27088 The server may issue one or more &'challenges'&, to which the client must send
27089 appropriate responses. In simple authentication mechanisms, the challenges are
27090 just prompts for user names and passwords. The server does not have to issue
27091 any challenges &-- in some mechanisms the relevant data may all be transmitted
27092 with the AUTH command.
27094 The server either accepts or denies authentication.
27096 If authentication succeeds, the client may optionally make use of the AUTH
27097 option on the MAIL command to pass an authenticated sender in subsequent
27098 mail transactions. Authentication lasts for the remainder of the SMTP
27101 If authentication fails, the client may give up, or it may try a different
27102 authentication mechanism, or it may try transferring mail over the
27103 unauthenticated connection.
27106 If you are setting up a client, and want to know which authentication
27107 mechanisms the server supports, you can use Telnet to connect to port 25 (the
27108 SMTP port) on the server, and issue an EHLO command. The response to this
27109 includes the list of supported mechanisms. For example:
27111 &`$ `&&*&`telnet server.example 25`&*&
27112 &`Trying 192.168.34.25...`&
27113 &`Connected to server.example.`&
27114 &`Escape character is '^]'.`&
27115 &`220 server.example ESMTP Exim 4.20 ...`&
27116 &*&`ehlo client.example`&*&
27117 &`250-server.example Hello client.example [10.8.4.5]`&
27118 &`250-SIZE 52428800`&
27123 The second-last line of this example output shows that the server supports
27124 authentication using the PLAIN mechanism. In Exim, the different authentication
27125 mechanisms are configured by specifying &'authenticator'& drivers. Like the
27126 routers and transports, which authenticators are included in the binary is
27127 controlled by build-time definitions. The following are currently available,
27128 included by setting
27131 AUTH_CYRUS_SASL=yes
27135 AUTH_HEIMDAL_GSSAPI=yes
27140 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
27141 authentication mechanism (RFC 2195), and the second provides an interface to
27142 the Cyrus SASL authentication library.
27143 The third is an interface to Dovecot's authentication system, delegating the
27144 work via a socket interface.
27145 The fourth provides for negotiation of authentication done via non-SMTP means,
27146 as defined by RFC 4422 Appendix A.
27147 The fifth provides an interface to the GNU SASL authentication library, which
27148 provides mechanisms but typically not data sources.
27149 The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
27150 supporting setting a server keytab.
27151 The seventh can be configured to support
27152 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
27153 not formally documented, but used by several MUAs.
27154 The eighth authenticator
27155 supports Microsoft's &'Secure Password Authentication'& mechanism.
27156 The last is an Exim authenticator but not an SMTP one;
27157 instead it can use information from a TLS negotiation.
27159 The authenticators are configured using the same syntax as other drivers (see
27160 section &<<SECTfordricon>>&). If no authenticators are required, no
27161 authentication section need be present in the configuration file. Each
27162 authenticator can in principle have both server and client functions. When Exim
27163 is receiving SMTP mail, it is acting as a server; when it is sending out
27164 messages over SMTP, it is acting as a client. Authenticator configuration
27165 options are provided for use in both these circumstances.
27167 To make it clear which options apply to which situation, the prefixes
27168 &%server_%& and &%client_%& are used on option names that are specific to
27169 either the server or the client function, respectively. Server and client
27170 functions are disabled if none of their options are set. If an authenticator is
27171 to be used for both server and client functions, a single definition, using
27172 both sets of options, is required. For example:
27176 public_name = CRAM-MD5
27177 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
27179 client_secret = secret2
27181 The &%server_%& option is used when Exim is acting as a server, and the
27182 &%client_%& options when it is acting as a client.
27184 Descriptions of the individual authenticators are given in subsequent chapters.
27185 The remainder of this chapter covers the generic options for the
27186 authenticators, followed by general discussion of the way authentication works
27189 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
27190 per-mechanism basis. Please read carefully to determine which variables hold
27191 account labels such as usercodes and which hold passwords or other
27192 authenticating data.
27194 Note that some mechanisms support two different identifiers for accounts: the
27195 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
27196 and &'authz'& are commonly encountered. The American spelling is standard here.
27197 Conceptually, authentication data such as passwords are tied to the identifier
27198 used to authenticate; servers may have rules to permit one user to act as a
27199 second user, so that after login the session is treated as though that second
27200 user had logged in. That second user is the &'authorization id'&. A robust
27201 configuration might confirm that the &'authz'& field is empty or matches the
27202 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
27203 as verified data, the &'authz'& as an unverified request which the server might
27206 A &'realm'& is a text string, typically a domain name, presented by a server
27207 to a client to help it select an account and credentials to use. In some
27208 mechanisms, the client and server provably agree on the realm, but clients
27209 typically can not treat the realm as secure data to be blindly trusted.
27213 .section "Generic options for authenticators" "SECID168"
27214 .cindex "authentication" "generic options"
27215 .cindex "options" "generic; for authenticators"
27217 .option client_condition authenticators string&!! unset
27218 When Exim is authenticating as a client, it skips any authenticator whose
27219 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
27220 used, for example, to skip plain text authenticators when the connection is not
27221 encrypted by a setting such as:
27223 client_condition = ${if !eq{$tls_out_cipher}{}}
27227 .option client_set_id authenticators string&!! unset
27228 When client authentication succeeds, this condition is expanded; the
27229 result is used in the log lines for outbound messages.
27230 Typically it will be the user name used for authentication.
27233 .option driver authenticators string unset
27234 This option must always be set. It specifies which of the available
27235 authenticators is to be used.
27238 .option public_name authenticators string unset
27239 This option specifies the name of the authentication mechanism that the driver
27240 implements, and by which it is known to the outside world. These names should
27241 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
27242 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
27243 defaults to the driver's instance name.
27246 .option server_advertise_condition authenticators string&!! unset
27247 When a server is about to advertise an authentication mechanism, the condition
27248 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
27249 mechanism is not advertised.
27250 If the expansion fails, the mechanism is not advertised. If the failure was not
27251 forced, and was not caused by a lookup defer, the incident is logged.
27252 See section &<<SECTauthexiser>>& below for further discussion.
27255 .option server_condition authenticators string&!! unset
27256 This option must be set for a &%plaintext%& server authenticator, where it
27257 is used directly to control authentication. See section &<<SECTplainserver>>&
27260 For the &(gsasl)& authenticator, this option is required for various
27261 mechanisms; see chapter &<<CHAPgsasl>>& for details.
27263 For the other authenticators, &%server_condition%& can be used as an additional
27264 authentication or authorization mechanism that is applied after the other
27265 authenticator conditions succeed. If it is set, it is expanded when the
27266 authenticator would otherwise return a success code. If the expansion is forced
27267 to fail, authentication fails. Any other expansion failure causes a temporary
27268 error code to be returned. If the result of a successful expansion is an empty
27269 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27270 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
27271 other result, a temporary error code is returned, with the expanded string as
27275 .option server_debug_print authenticators string&!! unset
27276 If this option is set and authentication debugging is enabled (see the &%-d%&
27277 command line option), the string is expanded and included in the debugging
27278 output when the authenticator is run as a server. This can help with checking
27279 out the values of variables.
27280 If expansion of the string fails, the error message is written to the debugging
27281 output, and Exim carries on processing.
27284 .option server_set_id authenticators string&!! unset
27285 .vindex "&$authenticated_id$&"
27286 .vindex "&$authenticated_fail_id$&"
27287 When an Exim server successfully authenticates a client, this string is
27288 expanded using data from the authentication, and preserved for any incoming
27289 messages in the variable &$authenticated_id$&. It is also included in the log
27290 lines for incoming messages. For example, a user/password authenticator
27291 configuration might preserve the user name that was used to authenticate, and
27292 refer to it subsequently during delivery of the message.
27293 On a failing authentication the expansion result is instead saved in
27294 the &$authenticated_fail_id$& variable.
27295 If expansion fails, the option is ignored.
27298 .option server_mail_auth_condition authenticators string&!! unset
27299 This option allows a server to discard authenticated sender addresses supplied
27300 as part of MAIL commands in SMTP connections that are authenticated by the
27301 driver on which &%server_mail_auth_condition%& is set. The option is not used
27302 as part of the authentication process; instead its (unexpanded) value is
27303 remembered for later use.
27304 How it is used is described in the following section.
27310 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
27311 .cindex "authentication" "sender; authenticated"
27312 .cindex "AUTH" "on MAIL command"
27313 When a client supplied an AUTH= item on a MAIL command, Exim applies
27314 the following checks before accepting it as the authenticated sender of the
27318 If the connection is not using extended SMTP (that is, HELO was used rather
27319 than EHLO), the use of AUTH= is a syntax error.
27321 If the value of the AUTH= parameter is &"<>"&, it is ignored.
27323 .vindex "&$authenticated_sender$&"
27324 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
27325 running, the value of &$authenticated_sender$& is set to the value obtained
27326 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
27327 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
27328 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
27329 given for the MAIL command.
27331 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
27332 is accepted and placed in &$authenticated_sender$& only if the client has
27335 If the AUTH= value was accepted by either of the two previous rules, and
27336 the client has authenticated, and the authenticator has a setting for the
27337 &%server_mail_auth_condition%&, the condition is checked at this point. The
27338 valued that was saved from the authenticator is expanded. If the expansion
27339 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
27340 &$authenticated_sender$& is deleted. If the expansion yields any other value,
27341 the value of &$authenticated_sender$& is retained and passed on with the
27346 When &$authenticated_sender$& is set for a message, it is passed on to other
27347 hosts to which Exim authenticates as a client. Do not confuse this value with
27348 &$authenticated_id$&, which is a string obtained from the authentication
27349 process, and which is not usually a complete email address.
27351 .vindex "&$sender_address$&"
27352 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
27353 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
27354 therefore make use of &$authenticated_sender$&. The converse is not true: the
27355 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
27360 .section "Authentication on an Exim server" "SECTauthexiser"
27361 .cindex "authentication" "on an Exim server"
27362 When Exim receives an EHLO command, it advertises the public names of those
27363 authenticators that are configured as servers, subject to the following
27367 The client host must match &%auth_advertise_hosts%& (default *).
27369 It the &%server_advertise_condition%& option is set, its expansion must not
27370 yield the empty string, &"0"&, &"no"&, or &"false"&.
27373 The order in which the authenticators are defined controls the order in which
27374 the mechanisms are advertised.
27376 Some mail clients (for example, some versions of Netscape) require the user to
27377 provide a name and password for authentication whenever AUTH is advertised,
27378 even though authentication may not in fact be needed (for example, Exim may be
27379 set up to allow unconditional relaying from the client by an IP address check).
27380 You can make such clients more friendly by not advertising AUTH to them.
27381 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
27382 that runs for RCPT) to relay without authentication, you should set
27384 auth_advertise_hosts = ! 10.9.8.0/24
27386 so that no authentication mechanisms are advertised to them.
27388 The &%server_advertise_condition%& controls the advertisement of individual
27389 authentication mechanisms. For example, it can be used to restrict the
27390 advertisement of a particular mechanism to encrypted connections, by a setting
27393 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
27395 .vindex "&$tls_in_cipher$&"
27396 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
27397 yields &"yes"&, which allows the advertisement to happen.
27399 When an Exim server receives an AUTH command from a client, it rejects it
27400 immediately if AUTH was not advertised in response to an earlier EHLO
27401 command. This is the case if
27404 The client host does not match &%auth_advertise_hosts%&; or
27406 No authenticators are configured with server options; or
27408 Expansion of &%server_advertise_condition%& blocked the advertising of all the
27409 server authenticators.
27413 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
27414 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
27415 AUTH is accepted from any client host.
27417 If AUTH is not rejected by the ACL, Exim searches its configuration for a
27418 server authentication mechanism that was advertised in response to EHLO and
27419 that matches the one named in the AUTH command. If it finds one, it runs
27420 the appropriate authentication protocol, and authentication either succeeds or
27421 fails. If there is no matching advertised mechanism, the AUTH command is
27422 rejected with a 504 error.
27424 .vindex "&$received_protocol$&"
27425 .vindex "&$sender_host_authenticated$&"
27426 When a message is received from an authenticated host, the value of
27427 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
27428 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
27429 public name) of the authenticator driver that successfully authenticated the
27430 client from which the message was received. This variable is empty if there was
27431 no successful authentication.
27433 .cindex authentication "expansion item"
27434 Successful authentication sets up information used by the
27435 &%authresults%& expansion item.
27440 .section "Testing server authentication" "SECID169"
27441 .cindex "authentication" "testing a server"
27442 .cindex "AUTH" "testing a server"
27443 .cindex "base64 encoding" "creating authentication test data"
27444 Exim's &%-bh%& option can be useful for testing server authentication
27445 configurations. The data for the AUTH command has to be sent using base64
27446 encoding. A quick way to produce such data for testing is the following Perl
27450 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
27452 .cindex "binary zero" "in authentication data"
27453 This interprets its argument as a Perl string, and then encodes it. The
27454 interpretation as a Perl string allows binary zeros, which are required for
27455 some kinds of authentication, to be included in the data. For example, a
27456 command line to run this script on such data might be
27458 encode '\0user\0password'
27460 Note the use of single quotes to prevent the shell interpreting the
27461 backslashes, so that they can be interpreted by Perl to specify characters
27462 whose code value is zero.
27464 &*Warning 1*&: If either of the user or password strings starts with an octal
27465 digit, you must use three zeros instead of one after the leading backslash. If
27466 you do not, the octal digit that starts your string will be incorrectly
27467 interpreted as part of the code for the first character.
27469 &*Warning 2*&: If there are characters in the strings that Perl interprets
27470 specially, you must use a Perl escape to prevent them being misinterpreted. For
27471 example, a command such as
27473 encode '\0user@domain.com\0pas$$word'
27475 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
27477 If you have the &%mimencode%& command installed, another way to do produce
27478 base64-encoded strings is to run the command
27480 echo -e -n `\0user\0password' | mimencode
27482 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
27483 in the argument, and the &%-n%& option specifies no newline at the end of its
27484 output. However, not all versions of &%echo%& recognize these options, so you
27485 should check your version before relying on this suggestion.
27489 .section "Authentication by an Exim client" "SECID170"
27490 .cindex "authentication" "on an Exim client"
27491 The &(smtp)& transport has two options called &%hosts_require_auth%& and
27492 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
27493 announces support for authentication, and the host matches an entry in either
27494 of these options, Exim (as a client) tries to authenticate as follows:
27497 For each authenticator that is configured as a client, in the order in which
27498 they are defined in the configuration, it searches the authentication
27499 mechanisms announced by the server for one whose name matches the public name
27500 of the authenticator.
27503 .vindex "&$host_address$&"
27504 When it finds one that matches, it runs the authenticator's client code. The
27505 variables &$host$& and &$host_address$& are available for any string expansions
27506 that the client might do. They are set to the server's name and IP address. If
27507 any expansion is forced to fail, the authentication attempt is abandoned, and
27508 Exim moves on to the next authenticator. Otherwise an expansion failure causes
27509 delivery to be deferred.
27511 If the result of the authentication attempt is a temporary error or a timeout,
27512 Exim abandons trying to send the message to the host for the moment. It will
27513 try again later. If there are any backup hosts available, they are tried in the
27516 If the response to authentication is a permanent error (5&'xx'& code), Exim
27517 carries on searching the list of authenticators and tries another one if
27518 possible. If all authentication attempts give permanent errors, or if there are
27519 no attempts because no mechanisms match (or option expansions force failure),
27520 what happens depends on whether the host matches &%hosts_require_auth%& or
27521 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
27522 delivery is deferred. The error can be detected in the retry rules, and thereby
27523 turned into a permanent error if you wish. In the second case, Exim tries to
27524 deliver the message unauthenticated.
27527 Note that the hostlist test for whether to do authentication can be
27528 confused if name-IP lookups change between the time the peer is decided
27529 upon and the time that the transport runs. For example, with a manualroute
27530 router given a host name, and with DNS "round-robin" used by that name: if
27531 the local resolver cache times out between the router and the transport
27532 running, the transport may get an IP for the name for its authentication
27533 check which does not match the connection peer IP.
27534 No authentication will then be done, despite the names being identical.
27536 For such cases use a separate transport which always authenticates.
27538 .cindex "AUTH" "on MAIL command"
27539 When Exim has authenticated itself to a remote server, it adds the AUTH
27540 parameter to the MAIL commands it sends, if it has an authenticated sender for
27541 the message. If the message came from a remote host, the authenticated sender
27542 is the one that was receiving on an incoming MAIL command, provided that the
27543 incoming connection was authenticated and the &%server_mail_auth%& condition
27544 allowed the authenticated sender to be retained. If a local process calls Exim
27545 to send a message, the sender address that is built from the login name and
27546 &%qualify_domain%& is treated as authenticated. However, if the
27547 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
27548 the authenticated sender that was received with the message.
27549 .ecindex IIDauthconf1
27550 .ecindex IIDauthconf2
27557 . ////////////////////////////////////////////////////////////////////////////
27558 . ////////////////////////////////////////////////////////////////////////////
27560 .chapter "The plaintext authenticator" "CHAPplaintext"
27561 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
27562 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
27563 The &(plaintext)& authenticator can be configured to support the PLAIN and
27564 LOGIN authentication mechanisms, both of which transfer authentication data as
27565 plain (unencrypted) text (though base64 encoded). The use of plain text is a
27566 security risk; you are strongly advised to insist on the use of SMTP encryption
27567 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
27568 use unencrypted plain text, you should not use the same passwords for SMTP
27569 connections as you do for login accounts.
27571 .section "Avoiding cleartext use" "SECTplain_TLS"
27572 The following generic option settings will disable &(plaintext)& authenticators when
27573 TLS is not being used:
27575 server_advertise_condition = ${if def:tls_in_cipher }
27576 client_condition = ${if def:tls_out_cipher}
27579 &*Note*&: a plaintext SMTP AUTH done inside TLS is not vulnerable to casual snooping,
27580 but is still vulnerable to a Man In The Middle attack unless certificates
27581 (including their names) have been properly verified.
27583 .section "Plaintext server options" "SECID171"
27584 .cindex "options" "&(plaintext)& authenticator (server)"
27585 When configured as a server, &(plaintext)& uses the following options:
27587 .option server_condition authenticators string&!! unset
27588 This is actually a global authentication option, but it must be set in order to
27589 configure the &(plaintext)& driver as a server. Its use is described below.
27591 .option server_prompts plaintext "string list&!!" unset
27592 The contents of this option, after expansion, must be a colon-separated list of
27593 prompt strings. If expansion fails, a temporary authentication rejection is
27596 .section "Using plaintext in a server" "SECTplainserver"
27597 .cindex "AUTH" "in &(plaintext)& authenticator"
27598 .cindex "binary zero" "in &(plaintext)& authenticator"
27599 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
27600 "in &(plaintext)& authenticator"
27601 .vindex "&$auth1$&, &$auth2$&, etc"
27602 .cindex "base64 encoding" "in &(plaintext)& authenticator"
27604 When running as a server, &(plaintext)& performs the authentication test by
27605 expanding a string. The data sent by the client with the AUTH command, or in
27606 response to subsequent prompts, is base64 encoded, and so may contain any byte
27607 values when decoded. If any data is supplied with the command, it is treated as
27608 a list of strings, separated by NULs (binary zeros), the first three of which
27609 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
27610 (neither LOGIN nor PLAIN uses more than three strings).
27612 For compatibility with previous releases of Exim, the values are also placed in
27613 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
27614 variables for this purpose is now deprecated, as it can lead to confusion in
27615 string expansions that also use them for other things.
27617 If there are more strings in &%server_prompts%& than the number of strings
27618 supplied with the AUTH command, the remaining prompts are used to obtain more
27619 data. Each response from the client may be a list of NUL-separated strings.
27621 .vindex "&$authenticated_id$&"
27622 Once a sufficient number of data strings have been received,
27623 &%server_condition%& is expanded. If the expansion is forced to fail,
27624 authentication fails. Any other expansion failure causes a temporary error code
27625 to be returned. If the result of a successful expansion is an empty string,
27626 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27627 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
27628 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
27629 For any other result, a temporary error code is returned, with the expanded
27630 string as the error text.
27632 &*Warning*&: If you use a lookup in the expansion to find the user's
27633 password, be sure to make the authentication fail if the user is unknown.
27634 There are good and bad examples at the end of the next section.
27638 .section "The PLAIN authentication mechanism" "SECID172"
27639 .cindex "PLAIN authentication mechanism"
27640 .cindex authentication PLAIN
27641 .cindex "binary zero" "in &(plaintext)& authenticator"
27642 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
27643 sent as one item of data (that is, one combined string containing two NUL
27644 separators). The data is sent either as part of the AUTH command, or
27645 subsequently in response to an empty prompt from the server.
27647 The second and third strings are a user name and a corresponding password.
27648 Using a single fixed user name and password as an example, this could be
27649 configured as follows:
27653 public_name = PLAIN
27655 server_condition = \
27656 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
27657 server_set_id = $auth2
27659 Note that the default result strings from &%if%& (&"true"& or an empty string)
27660 are exactly what we want here, so they need not be specified. Obviously, if the
27661 password contains expansion-significant characters such as dollar, backslash,
27662 or closing brace, they have to be escaped.
27664 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
27665 the end of a string list are ignored). If all the data comes as part of the
27666 AUTH command, as is commonly the case, the prompt is not used. This
27667 authenticator is advertised in the response to EHLO as
27671 and a client host can authenticate itself by sending the command
27673 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
27675 As this contains three strings (more than the number of prompts), no further
27676 data is required from the client. Alternatively, the client may just send
27680 to initiate authentication, in which case the server replies with an empty
27681 prompt. The client must respond with the combined data string.
27683 The data string is base64 encoded, as required by the RFC. This example,
27684 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
27685 represents a zero byte. This is split up into three strings, the first of which
27686 is empty. The &%server_condition%& option in the authenticator checks that the
27687 second two are &`username`& and &`mysecret`& respectively.
27689 Having just one fixed user name and password, as in this example, is not very
27690 realistic, though for a small organization with only a handful of
27691 authenticating clients it could make sense.
27693 A more sophisticated instance of this authenticator could use the user name in
27694 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
27695 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
27696 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
27697 This is an incorrect example:
27699 server_condition = \
27700 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
27702 The expansion uses the user name (&$auth2$&) as the key to look up a password,
27703 which it then compares to the supplied password (&$auth3$&). Why is this example
27704 incorrect? It works fine for existing users, but consider what happens if a
27705 non-existent user name is given. The lookup fails, but as no success/failure
27706 strings are given for the lookup, it yields an empty string. Thus, to defeat
27707 the authentication, all a client has to do is to supply a non-existent user
27708 name and an empty password. The correct way of writing this test is:
27710 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
27711 {${if eq{$value}{$auth3}}} {false}}
27713 In this case, if the lookup succeeds, the result is checked; if the lookup
27714 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
27715 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
27716 always fails if its second argument is empty. However, the second way of
27717 writing the test makes the logic clearer.
27720 .section "The LOGIN authentication mechanism" "SECID173"
27721 .cindex "LOGIN authentication mechanism"
27722 .cindex authentication LOGIN
27723 The LOGIN authentication mechanism is not documented in any RFC, but is in use
27724 in a number of programs. No data is sent with the AUTH command. Instead, a
27725 user name and password are supplied separately, in response to prompts. The
27726 plaintext authenticator can be configured to support this as in this example:
27730 public_name = LOGIN
27731 server_prompts = User Name : Password
27732 server_condition = \
27733 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
27734 server_set_id = $auth1
27736 Because of the way plaintext operates, this authenticator accepts data supplied
27737 with the AUTH command (in contravention of the specification of LOGIN), but
27738 if the client does not supply it (as is the case for LOGIN clients), the prompt
27739 strings are used to obtain two data items.
27741 Some clients are very particular about the precise text of the prompts. For
27742 example, Outlook Express is reported to recognize only &"Username:"& and
27743 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
27744 strings. It uses the &%ldapauth%& expansion condition to check the user
27745 name and password by binding to an LDAP server:
27749 public_name = LOGIN
27750 server_prompts = Username:: : Password::
27751 server_condition = ${if and{{ \
27754 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
27755 pass=${quote:$auth2} \
27756 ldap://ldap.example.org/} }} }
27757 server_set_id = uid=$auth1,ou=people,o=example.org
27759 We have to check that the username is not empty before using it, because LDAP
27760 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
27761 operator to correctly quote the DN for authentication. However, the basic
27762 &%quote%& operator, rather than any of the LDAP quoting operators, is the
27763 correct one to use for the password, because quoting is needed only to make
27764 the password conform to the Exim syntax. At the LDAP level, the password is an
27765 uninterpreted string.
27768 .section "Support for different kinds of authentication" "SECID174"
27769 A number of string expansion features are provided for the purpose of
27770 interfacing to different ways of user authentication. These include checking
27771 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
27772 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
27778 .section "Using plaintext in a client" "SECID175"
27779 .cindex "options" "&(plaintext)& authenticator (client)"
27780 The &(plaintext)& authenticator has two client options:
27782 .option client_ignore_invalid_base64 plaintext boolean false
27783 If the client receives a server prompt that is not a valid base64 string,
27784 authentication is abandoned by default. However, if this option is set true,
27785 the error in the challenge is ignored and the client sends the response as
27788 .option client_send plaintext string&!! unset
27789 The string is a colon-separated list of authentication data strings. Each
27790 string is independently expanded before being sent to the server. The first
27791 string is sent with the AUTH command; any more strings are sent in response
27792 to prompts from the server. Before each string is expanded, the value of the
27793 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
27794 with &$auth1$& for the first prompt. Up to three prompts are stored in this
27795 way. Thus, the prompt that is received in response to sending the first string
27796 (with the AUTH command) can be used in the expansion of the second string, and
27797 so on. If an invalid base64 string is received when
27798 &%client_ignore_invalid_base64%& is set, an empty string is put in the
27799 &$auth$&<&'n'&> variable.
27801 &*Note*&: You cannot use expansion to create multiple strings, because
27802 splitting takes priority and happens first.
27804 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
27805 the data, further processing is applied to each string before it is sent. If
27806 there are any single circumflex characters in the string, they are converted to
27807 NULs. Should an actual circumflex be required as data, it must be doubled in
27810 This is an example of a client configuration that implements the PLAIN
27811 authentication mechanism with a fixed user name and password:
27815 public_name = PLAIN
27816 client_send = ^username^mysecret
27818 The lack of colons means that the entire text is sent with the AUTH
27819 command, with the circumflex characters converted to NULs. A similar example
27820 that uses the LOGIN mechanism is:
27824 public_name = LOGIN
27825 client_send = : username : mysecret
27827 The initial colon means that the first string is empty, so no data is sent with
27828 the AUTH command itself. The remaining strings are sent in response to
27830 .ecindex IIDplaiauth1
27831 .ecindex IIDplaiauth2
27836 . ////////////////////////////////////////////////////////////////////////////
27837 . ////////////////////////////////////////////////////////////////////////////
27839 .chapter "The cram_md5 authenticator" "CHID9"
27840 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
27841 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
27842 .cindex "CRAM-MD5 authentication mechanism"
27843 .cindex authentication CRAM-MD5
27844 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
27845 sends a challenge string to the client, and the response consists of a user
27846 name and the CRAM-MD5 digest of the challenge string combined with a secret
27847 string (password) which is known to both server and client. Thus, the secret
27848 is not sent over the network as plain text, which makes this authenticator more
27849 secure than &(plaintext)&. However, the downside is that the secret has to be
27850 available in plain text at either end.
27853 .section "Using cram_md5 as a server" "SECID176"
27854 .cindex "options" "&(cram_md5)& authenticator (server)"
27855 This authenticator has one server option, which must be set to configure the
27856 authenticator as a server:
27858 .option server_secret cram_md5 string&!! unset
27859 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
27860 When the server receives the client's response, the user name is placed in
27861 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
27862 obtain the password for that user. The server then computes the CRAM-MD5 digest
27863 that the client should have sent, and checks that it received the correct
27864 string. If the expansion of &%server_secret%& is forced to fail, authentication
27865 fails. If the expansion fails for some other reason, a temporary error code is
27866 returned to the client.
27868 For compatibility with previous releases of Exim, the user name is also placed
27869 in &$1$&. However, the use of this variables for this purpose is now
27870 deprecated, as it can lead to confusion in string expansions that also use
27871 numeric variables for other things.
27873 For example, the following authenticator checks that the user name given by the
27874 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
27875 user name, authentication fails.
27879 public_name = CRAM-MD5
27880 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
27881 server_set_id = $auth1
27883 .vindex "&$authenticated_id$&"
27884 If authentication succeeds, the setting of &%server_set_id%& preserves the user
27885 name in &$authenticated_id$&. A more typical configuration might look up the
27886 secret string in a file, using the user name as the key. For example:
27890 public_name = CRAM-MD5
27891 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
27893 server_set_id = $auth1
27895 Note that this expansion explicitly forces failure if the lookup fails
27896 because &$auth1$& contains an unknown user name.
27898 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
27899 using the relevant libraries, you need to know the realm to specify in the
27900 lookup and then ask for the &"userPassword"& attribute for that user in that
27905 public_name = CRAM-MD5
27906 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
27907 dbmjz{/etc/sasldb2}{$value}fail}
27908 server_set_id = $auth1
27911 .section "Using cram_md5 as a client" "SECID177"
27912 .cindex "options" "&(cram_md5)& authenticator (client)"
27913 When used as a client, the &(cram_md5)& authenticator has two options:
27917 .option client_name cram_md5 string&!! "the primary host name"
27918 This string is expanded, and the result used as the user name data when
27919 computing the response to the server's challenge.
27922 .option client_secret cram_md5 string&!! unset
27923 This option must be set for the authenticator to work as a client. Its value is
27924 expanded and the result used as the secret string when computing the response.
27928 .vindex "&$host_address$&"
27929 Different user names and secrets can be used for different servers by referring
27930 to &$host$& or &$host_address$& in the options. Forced failure of either
27931 expansion string is treated as an indication that this authenticator is not
27932 prepared to handle this case. Exim moves on to the next configured client
27933 authenticator. Any other expansion failure causes Exim to give up trying to
27934 send the message to the current server.
27936 A simple example configuration of a &(cram_md5)& authenticator, using fixed
27941 public_name = CRAM-MD5
27943 client_secret = secret
27945 .ecindex IIDcramauth1
27946 .ecindex IIDcramauth2
27950 . ////////////////////////////////////////////////////////////////////////////
27951 . ////////////////////////////////////////////////////////////////////////////
27953 .chapter "The cyrus_sasl authenticator" "CHID10"
27954 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
27955 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
27956 .cindex "Cyrus" "SASL library"
27958 The code for this authenticator was provided by Matthew Byng-Maddick while
27959 at A L Digital Ltd.
27961 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
27962 library implementation of the RFC 2222 (&"Simple Authentication and Security
27963 Layer"&). This library supports a number of authentication mechanisms,
27964 including PLAIN and LOGIN, but also several others that Exim does not support
27965 directly. In particular, there is support for Kerberos authentication.
27967 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
27968 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
27969 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
27970 name of the driver to determine which mechanism to support.
27972 Where access to some kind of secret file is required, for example, in GSSAPI
27973 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
27974 user, and that the Cyrus SASL library has no way of escalating privileges
27975 by default. You may also find you need to set environment variables,
27976 depending on the driver you are using.
27978 The application name provided by Exim is &"exim"&, so various SASL options may
27979 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
27980 Kerberos, note that because of limitations in the GSSAPI interface,
27981 changing the server keytab might need to be communicated down to the Kerberos
27982 layer independently. The mechanism for doing so is dependent upon the Kerberos
27985 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
27986 may be set to point to an alternative keytab file. Exim will pass this
27987 variable through from its own inherited environment when started as root or the
27988 Exim user. The keytab file needs to be readable by the Exim user.
27989 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
27990 environment variable. In practice, for those releases, the Cyrus authenticator
27991 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
27992 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
27995 .section "Using cyrus_sasl as a server" "SECID178"
27996 The &(cyrus_sasl)& authenticator has four private options. It puts the username
27997 (on a successful authentication) into &$auth1$&. For compatibility with
27998 previous releases of Exim, the username is also placed in &$1$&. However, the
27999 use of this variable for this purpose is now deprecated, as it can lead to
28000 confusion in string expansions that also use numeric variables for other
28004 .option server_hostname cyrus_sasl string&!! "see below"
28005 This option selects the hostname that is used when communicating with the
28006 library. The default value is &`$primary_hostname`&. It is up to the underlying
28007 SASL plug-in what it does with this data.
28010 .option server_mech cyrus_sasl string "see below"
28011 This option selects the authentication mechanism this driver should use. The
28012 default is the value of the generic &%public_name%& option. This option allows
28013 you to use a different underlying mechanism from the advertised name. For
28017 driver = cyrus_sasl
28018 public_name = X-ANYTHING
28019 server_mech = CRAM-MD5
28020 server_set_id = $auth1
28023 .option server_realm cyrus_sasl string&!! unset
28024 This specifies the SASL realm that the server claims to be in.
28027 .option server_service cyrus_sasl string &`smtp`&
28028 This is the SASL service that the server claims to implement.
28031 For straightforward cases, you do not need to set any of the authenticator's
28032 private options. All you need to do is to specify an appropriate mechanism as
28033 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
28034 PLAIN, you could have two authenticators as follows:
28037 driver = cyrus_sasl
28038 public_name = CRAM-MD5
28039 server_set_id = $auth1
28042 driver = cyrus_sasl
28043 public_name = PLAIN
28044 server_set_id = $auth2
28046 Cyrus SASL does implement the LOGIN authentication method, even though it is
28047 not a standard method. It is disabled by default in the source distribution,
28048 but it is present in many binary distributions.
28049 .ecindex IIDcyrauth1
28050 .ecindex IIDcyrauth2
28055 . ////////////////////////////////////////////////////////////////////////////
28056 . ////////////////////////////////////////////////////////////////////////////
28057 .chapter "The dovecot authenticator" "CHAPdovecot"
28058 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
28059 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
28060 This authenticator is an interface to the authentication facility of the
28061 Dovecot 2 POP/IMAP server, which can support a number of authentication methods.
28062 Note that Dovecot must be configured to use auth-client not auth-userdb.
28063 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
28064 to use the same mechanisms for SMTP authentication. This is a server
28065 authenticator only. There is only one option:
28067 .option server_socket dovecot string unset
28069 This option must specify the UNIX socket that is the interface to Dovecot
28070 authentication. The &%public_name%& option must specify an authentication
28071 mechanism that Dovecot is configured to support. You can have several
28072 authenticators for different mechanisms. For example:
28076 public_name = PLAIN
28077 server_socket = /var/run/dovecot/auth-client
28078 server_set_id = $auth1
28083 server_socket = /var/run/dovecot/auth-client
28084 server_set_id = $auth1
28086 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
28087 &$received_ip_address$& (that is, the connection is local), the &"secured"&
28088 option is passed in the Dovecot authentication command. If, for a TLS
28089 connection, a client certificate has been verified, the &"valid-client-cert"&
28090 option is passed. When authentication succeeds, the identity of the user
28091 who authenticated is placed in &$auth1$&.
28093 The Dovecot configuration to match the above wil look
28096 conf.d/10-master.conf :-
28101 unix_listener auth-client {
28108 conf.d/10-auth.conf :-
28110 auth_mechanisms = plain login ntlm
28113 .ecindex IIDdcotauth1
28114 .ecindex IIDdcotauth2
28117 . ////////////////////////////////////////////////////////////////////////////
28118 . ////////////////////////////////////////////////////////////////////////////
28119 .chapter "The gsasl authenticator" "CHAPgsasl"
28120 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
28121 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
28122 .cindex "authentication" "GNU SASL"
28123 .cindex "authentication" "SASL"
28124 .cindex "authentication" "EXTERNAL"
28125 .cindex "authentication" "ANONYMOUS"
28126 .cindex "authentication" "PLAIN"
28127 .cindex "authentication" "LOGIN"
28128 .cindex "authentication" "DIGEST-MD5"
28129 .cindex "authentication" "CRAM-MD5"
28130 .cindex "authentication" "SCRAM family"
28131 The &(gsasl)& authenticator provides integration for the GNU SASL
28132 library and the mechanisms it provides. This is new as of the 4.80 release
28133 and there are a few areas where the library does not let Exim smoothly
28134 scale to handle future authentication mechanisms, so no guarantee can be
28135 made that any particular new authentication mechanism will be supported
28136 without code changes in Exim.
28138 The library is expected to add support in an upcoming
28139 realease for the SCRAM-SHA-256 method.
28140 The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
28144 .option client_authz gsasl string&!! unset
28145 This option can be used to supply an &'authorization id'&
28146 which is different to the &'authentication_id'& provided
28147 by &%client_username%& option.
28148 If unset or (after expansion) empty it is not used,
28149 which is the common case.
28151 .option client_channelbinding gsasl boolean false
28152 See &%server_channelbinding%& below.
28154 .option client_password gsasl string&!! unset
28155 This option is exapanded before use, and should result in
28156 the password to be used, in clear.
28158 .option client_username gsasl string&!! unset
28159 This option is exapanded before use, and should result in
28160 the account name to be used.
28162 .option client_spassword gsasl string&!! unset
28163 If a SCRAM mechanism is being used and this option is set
28164 it is used in preference to &%client_password%&.
28165 The value after expansion should be
28166 a 40 (for SHA-1) or 64 (for SHA-256) character string
28167 with the PBKDF2-prepared password, hex-encoded.
28168 Note that this value will depend on the salt and iteration-count
28169 supplied by the server.
28173 .option server_channelbinding gsasl boolean false
28174 Do not set this true and rely on the properties
28175 without consulting a cryptographic engineer.
28177 Some authentication mechanisms are able to use external context at both ends
28178 of the session to bind the authentication to that context, and fail the
28179 authentication process if that context differs. Specifically, some TLS
28180 ciphersuites can provide identifying information about the cryptographic
28183 This should have meant that certificate identity and verification becomes a
28184 non-issue, as a man-in-the-middle attack will cause the correct client and
28185 server to see different identifiers and authentication will fail.
28188 only usable by mechanisms which support "channel binding"; at time of
28189 writing, that's the SCRAM family.
28190 When using this feature the "-PLUS" variants of the method names need to be used.
28192 This defaults off to ensure smooth upgrade across Exim releases, in case
28193 this option causes some clients to start failing. Some future release
28194 of Exim might have switched the default to be true.
28196 However, Channel Binding in TLS has proven to be vulnerable in current versions.
28197 Do not plan to rely upon this feature for security, ever, without consulting
28198 with a subject matter expert (a cryptographic engineer).
28201 .option server_hostname gsasl string&!! "see below"
28202 This option selects the hostname that is used when communicating with the
28203 library. The default value is &`$primary_hostname`&.
28204 Some mechanisms will use this data.
28207 .option server_mech gsasl string "see below"
28208 This option selects the authentication mechanism this driver should use. The
28209 default is the value of the generic &%public_name%& option. This option allows
28210 you to use a different underlying mechanism from the advertised name. For
28215 public_name = X-ANYTHING
28216 server_mech = CRAM-MD5
28217 server_set_id = $auth1
28221 .option server_password gsasl string&!! unset
28222 Various mechanisms need access to the cleartext password on the server, so
28223 that proof-of-possession can be demonstrated on the wire, without sending
28224 the password itself.
28226 The data available for lookup varies per mechanism.
28227 In all cases, &$auth1$& is set to the &'authentication id'&.
28228 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
28229 if available, else the empty string.
28230 The &$auth3$& variable will always be the &'realm'& if available,
28231 else the empty string.
28233 A forced failure will cause authentication to defer.
28235 If using this option, it may make sense to set the &%server_condition%&
28236 option to be simply "true".
28239 .option server_realm gsasl string&!! unset
28240 This specifies the SASL realm that the server claims to be in.
28241 Some mechanisms will use this data.
28244 .option server_scram_iter gsasl string&!! 4096
28245 This option provides data for the SCRAM family of mechanisms.
28246 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28247 when this option is expanded.
28249 The result of expansion should be a decimal number,
28250 and represents both a lower-bound on the security, and
28251 a compute cost factor imposed on the client
28252 (if it does not cache results, or the server changes
28253 either the iteration count or the salt).
28254 A minimum value of 4096 is required by the standards
28255 for all current SCRAM mechanism variants.
28257 .option server_scram_salt gsasl string&!! unset
28258 This option provides data for the SCRAM family of mechanisms.
28259 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28260 when this option is expanded.
28261 The value should be a base64-encoded string,
28262 of random data typically 4-to-16 bytes long.
28263 If unset or empty after expansion the library will provides a value for the
28264 protocol conversation.
28267 .option server_key gsasl string&!! unset
28268 .option server_skey gsasl string&!! unset
28269 These options can be used for the SCRAM family of mechanisms
28270 to provide stored information related to a password,
28271 the storage of which is preferable to plaintext.
28273 &%server_key%& is the value defined in the SCRAM standards as ServerKey;
28274 &%server_skey%& is StoredKey.
28276 They are only available for version 1.9.0 (or later) of the gsasl library.
28277 When this is so, the macros
28278 _OPT_AUTHENTICATOR_GSASL_SERVER_KEY
28279 and _HAVE_AUTH_GSASL_SCRAM_S_KEY
28282 The &$authN$& variables are available when these options are expanded.
28284 If set, the results of expansion should for each
28285 should be a 28 (for SHA-1) or 44 (for SHA-256) character string
28286 of base64-coded data, and will be used in preference to the
28287 &%server_password%& option.
28288 If unset or not of the right length, &%server_password%& will be used.
28290 The libgsasl library release includes a utility &'gsasl'& which can be used
28291 to generate these values.
28294 .option server_service gsasl string &`smtp`&
28295 This is the SASL service that the server claims to implement.
28296 Some mechanisms will use this data.
28299 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
28300 .vindex "&$auth1$&, &$auth2$&, etc"
28301 These may be set when evaluating specific options, as detailed above.
28302 They will also be set when evaluating &%server_condition%&.
28304 Unless otherwise stated below, the &(gsasl)& integration will use the following
28305 meanings for these variables:
28308 .vindex "&$auth1$&"
28309 &$auth1$&: the &'authentication id'&
28311 .vindex "&$auth2$&"
28312 &$auth2$&: the &'authorization id'&
28314 .vindex "&$auth3$&"
28315 &$auth3$&: the &'realm'&
28318 On a per-mechanism basis:
28321 .cindex "authentication" "EXTERNAL"
28322 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
28323 the &%server_condition%& option must be present.
28325 .cindex "authentication" "ANONYMOUS"
28326 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
28327 the &%server_condition%& option must be present.
28329 .cindex "authentication" "GSSAPI"
28330 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
28331 &$auth2$& will be set to the &'authorization id'&,
28332 the &%server_condition%& option must be present.
28335 An &'anonymous token'& is something passed along as an unauthenticated
28336 identifier; this is analogous to FTP anonymous authentication passing an
28337 email address, or software-identifier@, as the "password".
28340 An example showing the password having the realm specified in the callback
28341 and demonstrating a Cyrus SASL to GSASL migration approach is:
28343 gsasl_cyrusless_crammd5:
28345 public_name = CRAM-MD5
28346 server_realm = imap.example.org
28347 server_password = ${lookup{$auth1:$auth3:userPassword}\
28348 dbmjz{/etc/sasldb2}{$value}fail}
28349 server_set_id = ${quote:$auth1}
28350 server_condition = yes
28354 . ////////////////////////////////////////////////////////////////////////////
28355 . ////////////////////////////////////////////////////////////////////////////
28357 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
28358 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
28359 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
28360 .cindex "authentication" "GSSAPI"
28361 .cindex "authentication" "Kerberos"
28362 The &(heimdal_gssapi)& authenticator provides server integration for the
28363 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
28366 .option server_hostname heimdal_gssapi string&!! "see below"
28367 This option selects the hostname that is used, with &%server_service%&,
28368 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
28369 identifier. The default value is &`$primary_hostname`&.
28371 .option server_keytab heimdal_gssapi string&!! unset
28372 If set, then Heimdal will not use the system default keytab (typically
28373 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
28374 The value should be a pathname, with no &"file:"& prefix.
28376 .option server_service heimdal_gssapi string&!! "smtp"
28377 This option specifies the service identifier used, in conjunction with
28378 &%server_hostname%&, for building the identifier for finding credentials
28382 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
28383 Beware that these variables will typically include a realm, thus will appear
28384 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
28385 not verified, so a malicious client can set it to anything.
28387 The &$auth1$& field should be safely trustable as a value from the Key
28388 Distribution Center. Note that these are not quite email addresses.
28389 Each identifier is for a role, and so the left-hand-side may include a
28390 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
28392 .vindex "&$auth1$&, &$auth2$&, etc"
28394 .vindex "&$auth1$&"
28395 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
28397 .vindex "&$auth2$&"
28398 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
28399 authentication. If that was empty, this will also be set to the
28404 . ////////////////////////////////////////////////////////////////////////////
28405 . ////////////////////////////////////////////////////////////////////////////
28407 .chapter "The spa authenticator" "CHAPspa"
28408 .scindex IIDspaauth1 "&(spa)& authenticator"
28409 .scindex IIDspaauth2 "authenticators" "&(spa)&"
28410 .cindex "authentication" "Microsoft Secure Password"
28411 .cindex "authentication" "NTLM"
28412 .cindex "Microsoft Secure Password Authentication"
28413 .cindex "NTLM authentication"
28414 The &(spa)& authenticator provides client support for Microsoft's &'Secure
28415 Password Authentication'& mechanism,
28416 which is also sometimes known as NTLM (NT LanMan). The code for client side of
28417 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
28418 taken from the Samba project (&url(https://www.samba.org/)). The code for the
28419 server side was subsequently contributed by Tom Kistner. The mechanism works as
28423 After the AUTH command has been accepted, the client sends an SPA
28424 authentication request based on the user name and optional domain.
28426 The server sends back a challenge.
28428 The client builds a challenge response which makes use of the user's password
28429 and sends it to the server, which then accepts or rejects it.
28432 Encryption is used to protect the password in transit.
28436 .section "Using spa as a server" "SECID179"
28437 .cindex "options" "&(spa)& authenticator (server)"
28438 The &(spa)& authenticator has just one server option:
28440 .option server_password spa string&!! unset
28441 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
28442 This option is expanded, and the result must be the cleartext password for the
28443 authenticating user, whose name is at this point in &$auth1$&. For
28444 compatibility with previous releases of Exim, the user name is also placed in
28445 &$1$&. However, the use of this variable for this purpose is now deprecated, as
28446 it can lead to confusion in string expansions that also use numeric variables
28447 for other things. For example:
28452 server_password = \
28453 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
28455 If the expansion is forced to fail, authentication fails. Any other expansion
28456 failure causes a temporary error code to be returned.
28462 .section "Using spa as a client" "SECID180"
28463 .cindex "options" "&(spa)& authenticator (client)"
28464 The &(spa)& authenticator has the following client options:
28468 .option client_domain spa string&!! unset
28469 This option specifies an optional domain for the authentication.
28472 .option client_password spa string&!! unset
28473 This option specifies the user's password, and must be set.
28476 .option client_username spa string&!! unset
28477 This option specifies the user name, and must be set. Here is an example of a
28478 configuration of this authenticator for use with the mail servers at
28484 client_username = msn/msn_username
28485 client_password = msn_plaintext_password
28486 client_domain = DOMAIN_OR_UNSET
28488 .ecindex IIDspaauth1
28489 .ecindex IIDspaauth2
28495 . ////////////////////////////////////////////////////////////////////////////
28496 . ////////////////////////////////////////////////////////////////////////////
28498 .chapter "The external authenticator" "CHAPexternauth"
28499 .scindex IIDexternauth1 "&(external)& authenticator"
28500 .scindex IIDexternauth2 "authenticators" "&(external)&"
28501 .cindex "authentication" "Client Certificate"
28502 .cindex "authentication" "X509"
28503 .cindex "Certificate-based authentication"
28504 The &(external)& authenticator provides support for
28505 authentication based on non-SMTP information.
28506 The specification is in RFC 4422 Appendix A
28507 (&url(https://tools.ietf.org/html/rfc4422)).
28508 It is only a transport and negotiation mechanism;
28509 the process of authentication is entirely controlled
28510 by the server configuration.
28512 The client presents an identity in-clear.
28513 It is probably wise for a server to only advertise,
28514 and for clients to only attempt,
28515 this authentication method on a secure (eg. under TLS) connection.
28517 One possible use, compatible with the
28518 K-9 Mail Andoid client (&url(https://k9mail.github.io/)),
28519 is for using X509 client certificates.
28521 It thus overlaps in function with the TLS authenticator
28522 (see &<<CHAPtlsauth>>&)
28523 but is a full SMTP SASL authenticator
28524 rather than being implicit for TLS-connection carried
28525 client certificates only.
28527 The examples and discussion in this chapter assume that
28528 client-certificate authentication is being done.
28530 The client must present a certificate,
28531 for which it must have been requested via the
28532 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28533 (see &<<CHAPTLS>>&).
28534 For authentication to be effective the certificate should be
28535 verifiable against a trust-anchor certificate known to the server.
28537 .section "External options" "SECTexternsoptions"
28538 .cindex "options" "&(external)& authenticator (server)"
28539 The &(external)& authenticator has two server options:
28541 .option server_param2 external string&!! unset
28542 .option server_param3 external string&!! unset
28543 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(external)& authenticator"
28544 These options are expanded before the &%server_condition%& option
28545 and the result are placed in &$auth2$& and &$auth3$& resectively.
28546 If the expansion is forced to fail, authentication fails. Any other expansion
28547 failure causes a temporary error code to be returned.
28549 They can be used to clarify the coding of a complex &%server_condition%&.
28551 .section "Using external in a server" "SECTexternserver"
28552 .cindex "AUTH" "in &(external)& authenticator"
28553 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
28554 "in &(external)& authenticator"
28555 .vindex "&$auth1$&, &$auth2$&, etc"
28556 .cindex "base64 encoding" "in &(external)& authenticator"
28558 When running as a server, &(external)& performs the authentication test by
28559 expanding a string. The data sent by the client with the AUTH command, or in
28560 response to subsequent prompts, is base64 encoded, and so may contain any byte
28561 values when decoded. The decoded value is treated as
28562 an identity for authentication and
28563 placed in the expansion variable &$auth1$&.
28565 For compatibility with previous releases of Exim, the value is also placed in
28566 the expansion variable &$1$&. However, the use of this
28567 variable for this purpose is now deprecated, as it can lead to confusion in
28568 string expansions that also use them for other things.
28570 .vindex "&$authenticated_id$&"
28571 Once an identity has been received,
28572 &%server_condition%& is expanded. If the expansion is forced to fail,
28573 authentication fails. Any other expansion failure causes a temporary error code
28574 to be returned. If the result of a successful expansion is an empty string,
28575 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
28576 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
28577 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
28578 For any other result, a temporary error code is returned, with the expanded
28579 string as the error text.
28583 ext_ccert_san_mail:
28585 public_name = EXTERNAL
28587 server_advertise_condition = $tls_in_certificate_verified
28588 server_param2 = ${certextract {subj_altname,mail,>:} \
28589 {$tls_in_peercert}}
28590 server_condition = ${if forany {$auth2} \
28591 {eq {$item}{$auth1}}}
28592 server_set_id = $auth1
28594 This accepts a client certificate that is verifiable against any
28595 of your configured trust-anchors
28596 (which usually means the full set of public CAs)
28597 and which has a mail-SAN matching the claimed identity sent by the client.
28599 &*Note*&: up to TLS1.2, the client cert is on the wire in-clear, including the SAN.
28600 The account name is therefore guessable by an opponent.
28601 TLS 1.3 protects both server and client certificates, and is not vulnerable
28605 .section "Using external in a client" "SECTexternclient"
28606 .cindex "options" "&(external)& authenticator (client)"
28607 The &(external)& authenticator has one client option:
28609 .option client_send external string&!! unset
28610 This option is expanded and sent with the AUTH command as the
28611 identity being asserted.
28617 public_name = EXTERNAL
28619 client_condition = ${if !eq{$tls_out_cipher}{}}
28620 client_send = myaccount@smarthost.example.net
28624 .ecindex IIDexternauth1
28625 .ecindex IIDexternauth2
28631 . ////////////////////////////////////////////////////////////////////////////
28632 . ////////////////////////////////////////////////////////////////////////////
28634 .chapter "The tls authenticator" "CHAPtlsauth"
28635 .scindex IIDtlsauth1 "&(tls)& authenticator"
28636 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
28637 .cindex "authentication" "Client Certificate"
28638 .cindex "authentication" "X509"
28639 .cindex "Certificate-based authentication"
28640 The &(tls)& authenticator provides server support for
28641 authentication based on client certificates.
28643 It is not an SMTP authentication mechanism and is not
28644 advertised by the server as part of the SMTP EHLO response.
28645 It is an Exim authenticator in the sense that it affects
28646 the protocol element of the log line, can be tested for
28647 by the &%authenticated%& ACL condition, and can set
28648 the &$authenticated_id$& variable.
28650 The client must present a verifiable certificate,
28651 for which it must have been requested via the
28652 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28653 (see &<<CHAPTLS>>&).
28655 If an authenticator of this type is configured it is
28656 run before any SMTP-level communication is done,
28657 and can authenticate the connection.
28658 If it does, SMTP authentication is not offered.
28660 A maximum of one authenticator of this type may be present.
28663 .cindex "options" "&(tls)& authenticator (server)"
28664 The &(tls)& authenticator has three server options:
28666 .option server_param1 tls string&!! unset
28667 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
28668 This option is expanded after the TLS negotiation and
28669 the result is placed in &$auth1$&.
28670 If the expansion is forced to fail, authentication fails. Any other expansion
28671 failure causes a temporary error code to be returned.
28673 .option server_param2 tls string&!! unset
28674 .option server_param3 tls string&!! unset
28675 As above, for &$auth2$& and &$auth3$&.
28677 &%server_param1%& may also be spelled &%server_param%&.
28684 server_param1 = ${certextract {subj_altname,mail,>:} \
28685 {$tls_in_peercert}}
28686 server_condition = ${if and { {eq{$tls_in_certificate_verified}{1}} \
28689 {${lookup ldap{ldap:///\
28690 mailname=${quote_ldap_dn:${lc:$item}},\
28691 ou=users,LDAP_DC?mailid} {$value}{0} \
28693 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
28695 This accepts a client certificate that is verifiable against any
28696 of your configured trust-anchors
28697 (which usually means the full set of public CAs)
28698 and which has a SAN with a good account name.
28700 Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
28701 The account name is therefore guessable by an opponent.
28702 TLS 1.3 protects both server and client certificates, and is not vulnerable
28704 Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
28706 . An alternative might use
28708 . server_param1 = ${sha256:$tls_in_peercert}
28710 . to require one of a set of specific certs that define a given account
28711 . (the verification is still required, but mostly irrelevant).
28712 . This would help for per-device use.
28714 . However, for the future we really need support for checking a
28715 . user cert in LDAP - which probably wants a base-64 DER.
28717 .ecindex IIDtlsauth1
28718 .ecindex IIDtlsauth2
28721 Note that because authentication is traditionally an SMTP operation,
28722 the &%authenticated%& ACL condition cannot be used in
28723 a connect- or helo-ACL.
28727 . ////////////////////////////////////////////////////////////////////////////
28728 . ////////////////////////////////////////////////////////////////////////////
28730 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
28731 "Encrypted SMTP connections"
28732 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
28733 .scindex IIDencsmtp2 "SMTP" "encryption"
28734 .cindex "TLS" "on SMTP connection"
28737 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
28738 Sockets Layer), is implemented by making use of the OpenSSL library or the
28739 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
28740 cryptographic code in the Exim distribution itself for implementing TLS. In
28741 order to use this feature you must install OpenSSL or GnuTLS, and then build a
28742 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
28743 You also need to understand the basic concepts of encryption at a managerial
28744 level, and in particular, the way that public keys, private keys, and
28745 certificates are used.
28747 RFC 3207 defines how SMTP connections can make use of encryption. Once a
28748 connection is established, the client issues a STARTTLS command. If the
28749 server accepts this, the client and the server negotiate an encryption
28750 mechanism. If the negotiation succeeds, the data that subsequently passes
28751 between them is encrypted.
28753 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
28754 and if so, what cipher suite is in use, whether the client supplied a
28755 certificate, and whether or not that certificate was verified. This makes it
28756 possible for an Exim server to deny or accept certain commands based on the
28759 &*Warning*&: Certain types of firewall and certain anti-virus products can
28760 disrupt TLS connections. You need to turn off SMTP scanning for these products
28761 in order to get TLS to work.
28765 .section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
28767 .cindex "submissions protocol"
28768 .cindex "ssmtp protocol"
28769 .cindex "smtps protocol"
28770 .cindex "SMTP" "submissions protocol"
28771 .cindex "SMTP" "ssmtp protocol"
28772 .cindex "SMTP" "smtps protocol"
28773 The history of port numbers for TLS in SMTP is a little messy and has been
28774 contentious. As of RFC 8314, the common practice of using the historically
28775 allocated port 465 for "email submission but with TLS immediately upon connect
28776 instead of using STARTTLS" is officially blessed by the IETF, and recommended
28777 by them in preference to STARTTLS.
28779 The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
28780 clarity emerged over the dual roles of SMTP, for MX delivery and Email
28781 Submission, nomenclature has shifted. The modern name is now &"submissions"&.
28783 This approach was, for a while, officially abandoned when encrypted SMTP was
28784 standardized, but many clients kept using it, even as the TCP port number was
28785 reassigned for other use.
28786 Thus you may encounter guidance claiming that you shouldn't enable use of
28788 In practice, a number of mail-clients have only ever supported submissions,
28789 not submission with STARTTLS upgrade.
28790 Ideally, offer both submission (587) and submissions (465) service.
28792 Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
28793 global option. Its value must be a list of port numbers;
28794 the most common use is expected to be:
28796 tls_on_connect_ports = 465
28798 The port numbers specified by this option apply to all SMTP connections, both
28799 via the daemon and via &'inetd'&. You still need to specify all the ports that
28800 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
28801 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
28802 an extra port &-- rather, it specifies different behaviour on a port that is
28805 There is also a &%-tls-on-connect%& command line option. This overrides
28806 &%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
28813 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
28814 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
28815 TLS is supported in Exim using either the OpenSSL or GnuTLS library.
28816 To build Exim to use OpenSSL you need to set
28822 To build Exim to use GnuTLS, you need to set
28828 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
28829 include files and libraries for GnuTLS can be found.
28831 There are some differences in usage when using GnuTLS instead of OpenSSL:
28834 The &%tls_verify_certificates%& option
28835 cannot be the path of a directory
28836 for GnuTLS versions before 3.3.6
28837 (for later versions, or OpenSSL, it can be either).
28839 The default value for &%tls_dhparam%& differs for historical reasons.
28841 .vindex "&$tls_in_peerdn$&"
28842 .vindex "&$tls_out_peerdn$&"
28843 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
28844 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
28845 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
28847 OpenSSL identifies cipher suites using hyphens as separators, for example:
28848 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
28849 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
28850 in a cipher list. To make life simpler, Exim changes underscores to hyphens
28851 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
28852 to handle its own older variants) when processing lists of cipher suites in the
28853 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
28856 The &%tls_require_ciphers%& options operate differently, as described in the
28857 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
28859 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
28860 When using OpenSSL, this option is ignored.
28861 (If an API is found to let OpenSSL be configured in this way,
28862 let the Exim Maintainers know and we'll likely use it).
28864 With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
28865 main option, it must be ordered to match the &%tls_certificate%& list.
28867 Some other recently added features may only be available in one or the other.
28868 This should be documented with the feature. If the documentation does not
28869 explicitly state that the feature is infeasible in the other TLS
28870 implementation, then patches are welcome.
28873 The output from "exim -bV" will show which (if any) support was included
28875 Also, the macro "_HAVE_OPENSSL" or "_HAVE_GNUTLS" will be defined.
28880 .section "GnuTLS parameter computation" "SECTgnutlsparam"
28881 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
28882 an explicit path; if the latter, then the text about generation still applies,
28883 but not the chosen filename.
28884 By default, as of Exim 4.80 a hard-coded D-H prime is used.
28885 See the documentation of &%tls_dhparam%& for more information.
28887 GnuTLS uses D-H parameters that may take a substantial amount of time
28888 to compute. It is unreasonable to re-compute them for every TLS session.
28889 Therefore, Exim keeps this data in a file in its spool directory, called
28890 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
28892 The file is owned by the Exim user and is readable only by
28893 its owner. Every Exim process that start up GnuTLS reads the D-H
28894 parameters from this file. If the file does not exist, the first Exim process
28895 that needs it computes the data and writes it to a temporary file which is
28896 renamed once it is complete. It does not matter if several Exim processes do
28897 this simultaneously (apart from wasting a few resources). Once a file is in
28898 place, new Exim processes immediately start using it.
28900 For maximum security, the parameters that are stored in this file should be
28901 recalculated periodically, the frequency depending on your paranoia level.
28902 If you are avoiding using the fixed D-H primes published in RFCs, then you
28903 are concerned about some advanced attacks and will wish to do this; if you do
28904 not regenerate then you might as well stick to the standard primes.
28906 Arranging this is easy in principle; just delete the file when you want new
28907 values to be computed. However, there may be a problem. The calculation of new
28908 parameters needs random numbers, and these are obtained from &_/dev/random_&.
28909 If the system is not very active, &_/dev/random_& may delay returning data
28910 until enough randomness (entropy) is available. This may cause Exim to hang for
28911 a substantial amount of time, causing timeouts on incoming connections.
28913 The solution is to generate the parameters externally to Exim. They are stored
28914 in &_gnutls-params-N_& in PEM format, which means that they can be
28915 generated externally using the &(certtool)& command that is part of GnuTLS.
28917 To replace the parameters with new ones, instead of deleting the file
28918 and letting Exim re-create it, you can generate new parameters using
28919 &(certtool)& and, when this has been done, replace Exim's cache file by
28920 renaming. The relevant commands are something like this:
28923 [ look for file; assume gnutls-params-2236 is the most recent ]
28926 # chown exim:exim new-params
28927 # chmod 0600 new-params
28928 # certtool --generate-dh-params --bits 2236 >>new-params
28929 # openssl dhparam -noout -text -in new-params | head
28930 [ check the first line, make sure it's not more than 2236;
28931 if it is, then go back to the start ("rm") and repeat
28932 until the size generated is at most the size requested ]
28933 # chmod 0400 new-params
28934 # mv new-params gnutls-params-2236
28936 If Exim never has to generate the parameters itself, the possibility of
28937 stalling is removed.
28939 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
28940 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
28941 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
28942 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
28943 and Exim does so. This attempt to remove Exim from TLS policy decisions
28944 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
28945 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
28946 which applies to all D-H usage, client or server. If the value returned by
28947 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
28948 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
28949 limit, which is still much higher than Exim historically used.
28951 The filename and bits used will change as the GnuTLS maintainers change the
28952 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
28953 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
28954 2432 bits, while NSS is limited to 2236 bits.
28956 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
28957 increase the chance of the generated prime actually being within acceptable
28958 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
28959 procedure above. There is no sane procedure available to Exim to double-check
28960 the size of the generated prime, so it might still be too large.
28963 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
28964 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
28965 .oindex "&%tls_require_ciphers%&" "OpenSSL"
28966 There is a function in the OpenSSL library that can be passed a list of cipher
28967 suites before the cipher negotiation takes place. This specifies which ciphers
28968 are acceptable for TLS versions prior to 1.3.
28969 The list is colon separated and may contain names like
28970 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
28971 directly to this function call.
28972 Many systems will install the OpenSSL manual-pages, so you may have
28973 &'ciphers(1)'& available to you.
28974 The following quotation from the OpenSSL
28975 documentation specifies what forms of item are allowed in the cipher string:
28978 It can consist of a single cipher suite such as RC4-SHA.
28980 It can represent a list of cipher suites containing a certain algorithm,
28981 or cipher suites of a certain type. For example SHA1 represents all
28982 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
28985 Lists of cipher suites can be combined in a single cipher string using
28986 the + character. This is used as a logical and operation. For example
28987 SHA1+DES represents all cipher suites containing the SHA1 and the DES
28991 Each cipher string can be optionally preceded by one of the characters &`!`&,
28994 If &`!`& is used, the ciphers are permanently deleted from the list. The
28995 ciphers deleted can never reappear in the list even if they are explicitly
28998 If &`-`& is used, the ciphers are deleted from the list, but some or all
28999 of the ciphers can be added again by later options.
29001 If &`+`& is used, the ciphers are moved to the end of the list. This
29002 option does not add any new ciphers; it just moves matching existing ones.
29005 If none of these characters is present, the string is interpreted as
29006 a list of ciphers to be appended to the current preference list. If the list
29007 includes any ciphers already present they will be ignored: that is, they will
29008 not be moved to the end of the list.
29011 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
29014 # note single-quotes to get ! past any shell history expansion
29015 $ openssl ciphers 'HIGH:!MD5:!SHA1'
29018 This example will let the library defaults be permitted on the MX port, where
29019 there's probably no identity verification anyway, but ups the ante on the
29020 submission ports where the administrator might have some influence on the
29021 choice of clients used:
29023 # OpenSSL variant; see man ciphers(1)
29024 tls_require_ciphers = ${if =={$received_port}{25}\
29029 This example will prefer ECDSA-authenticated ciphers over RSA ones:
29031 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
29034 For TLS version 1.3 the control available is less fine-grained
29035 and Exim does not provide access to it at present.
29036 The value of the &%tls_require_ciphers%& option is ignored when
29037 TLS version 1.3 is negotiated.
29039 As of writing the library default cipher suite list for TLSv1.3 is
29041 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
29045 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
29047 .cindex "GnuTLS" "specifying parameters for"
29048 .cindex "TLS" "specifying ciphers (GnuTLS)"
29049 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
29050 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
29051 .cindex "TLS" "specifying protocols (GnuTLS)"
29052 .cindex "TLS" "specifying priority string (GnuTLS)"
29053 .oindex "&%tls_require_ciphers%&" "GnuTLS"
29054 The GnuTLS library allows the caller to provide a "priority string", documented
29055 as part of the &[gnutls_priority_init]& function. This is very similar to the
29056 ciphersuite specification in OpenSSL.
29058 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
29059 and controls both protocols and ciphers.
29061 The &%tls_require_ciphers%& option is available both as an global option,
29062 controlling how Exim behaves as a server, and also as an option of the
29063 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
29064 the value is string expanded. The resulting string is not an Exim list and
29065 the string is given to the GnuTLS library, so that Exim does not need to be
29066 aware of future feature enhancements of GnuTLS.
29068 Documentation of the strings accepted may be found in the GnuTLS manual, under
29069 "Priority strings". This is online as
29070 &url(https://www.gnutls.org/manual/html_node/Priority-Strings.html),
29071 but beware that this relates to GnuTLS 3, which may be newer than the version
29072 installed on your system. If you are using GnuTLS 3,
29073 then the example code
29074 &url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
29075 on that site can be used to test a given string.
29079 # Disable older versions of protocols
29080 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
29083 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
29084 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
29085 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
29087 This example will let the library defaults be permitted on the MX port, where
29088 there's probably no identity verification anyway, and lowers security further
29089 by increasing compatibility; but this ups the ante on the submission ports
29090 where the administrator might have some influence on the choice of clients
29094 tls_require_ciphers = ${if =={$received_port}{25}\
29100 .section "Configuring an Exim server to use TLS" "SECID182"
29101 .cindex "TLS" "configuring an Exim server"
29102 .cindex "ESMTP extensions" STARTTLS
29103 When Exim has been built with TLS support, it advertises the availability of
29104 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
29105 but not to any others. The default value of this option is *, which means
29106 that STARTTLS is always advertised. Set it to blank to never advertise;
29107 this is reasonable for systems that want to use TLS only as a client.
29109 If STARTTLS is to be used you
29110 need to set some other options in order to make TLS available.
29112 If a client issues a STARTTLS command and there is some configuration
29113 problem in the server, the command is rejected with a 454 error. If the client
29114 persists in trying to issue SMTP commands, all except QUIT are rejected
29117 554 Security failure
29119 If a STARTTLS command is issued within an existing TLS session, it is
29120 rejected with a 554 error code.
29122 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
29123 must be set to match some hosts. The default is * which matches all hosts.
29125 If this is all you do, TLS encryption will be enabled but not authentication -
29126 meaning that the peer has no assurance it is actually you he is talking to.
29127 You gain protection from a passive sniffer listening on the wire but not
29128 from someone able to intercept the communication.
29130 Further protection requires some further configuration at the server end.
29132 To make TLS work you need to set, in the server,
29134 tls_certificate = /some/file/name
29135 tls_privatekey = /some/file/name
29137 These options are, in fact, expanded strings, so you can make them depend on
29138 the identity of the client that is connected if you wish. The first file
29139 contains the server's X509 certificate, and the second contains the private key
29140 that goes with it. These files need to be
29141 PEM format and readable by the Exim user, and must
29142 always be given as full path names.
29143 The key must not be password-protected.
29144 They can be the same file if both the
29145 certificate and the key are contained within it. If &%tls_privatekey%& is not
29146 set, or if its expansion is forced to fail or results in an empty string, this
29147 is assumed to be the case. The certificate file may also contain intermediate
29148 certificates that need to be sent to the client to enable it to authenticate
29149 the server's certificate.
29151 For dual-stack (eg. RSA and ECDSA) configurations, these options can be
29152 colon-separated lists of file paths. Ciphers using given authentication
29153 algorithms require the presence of a suitable certificate to supply the
29154 public-key. The server selects among the certificates to present to the
29155 client depending on the selected cipher, hence the priority ordering for
29156 ciphers will affect which certificate is used.
29158 If you do not understand about certificates and keys, please try to find a
29159 source of this background information, which is not Exim-specific. (There are a
29160 few comments below in section &<<SECTcerandall>>&.)
29162 &*Note*&: These options do not apply when Exim is operating as a client &--
29163 they apply only in the case of a server. If you need to use a certificate in an
29164 Exim client, you must set the options of the same names in an &(smtp)&
29167 With just these options, an Exim server will be able to use TLS. It does not
29168 require the client to have a certificate (but see below for how to insist on
29169 this). There is one other option that may be needed in other situations. If
29171 tls_dhparam = /some/file/name
29173 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
29174 with the parameters contained in the file.
29175 Set this to &`none`& to disable use of DH entirely, by making no prime
29180 This may also be set to a string identifying a standard prime to be used for
29181 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
29182 used is &`ike23`&. There are a few standard primes available, see the
29183 documentation for &%tls_dhparam%& for the complete list.
29189 for a way of generating file data.
29191 The strings supplied for these three options are expanded every time a client
29192 host connects. It is therefore possible to use different certificates and keys
29193 for different hosts, if you so wish, by making use of the client's IP address
29194 in &$sender_host_address$& to control the expansion. If a string expansion is
29195 forced to fail, Exim behaves as if the option is not set.
29197 .cindex "cipher" "logging"
29198 .cindex "log" "TLS cipher"
29199 .vindex "&$tls_in_cipher$&"
29200 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
29201 an incoming TLS connection. It is included in the &'Received:'& header of an
29202 incoming message (by default &-- you can, of course, change this), and it is
29203 also included in the log line that records a message's arrival, keyed by
29204 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
29205 condition can be used to test for specific cipher suites in ACLs.
29207 Once TLS has been established, the ACLs that run for subsequent SMTP commands
29208 can check the name of the cipher suite and vary their actions accordingly. The
29209 cipher suite names vary, depending on which TLS library is being used. For
29210 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
29211 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
29212 documentation for more details.
29214 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
29215 (again depending on the &%tls_cipher%& log selector).
29218 .section "Requesting and verifying client certificates" "SECID183"
29219 .cindex "certificate" "verification of client"
29220 .cindex "TLS" "client certificate verification"
29221 If you want an Exim server to request a certificate when negotiating a TLS
29222 session with a client, you must set either &%tls_verify_hosts%& or
29223 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
29224 apply to all TLS connections. For any host that matches one of these options,
29225 Exim requests a certificate as part of the setup of the TLS session. The
29226 contents of the certificate are verified by comparing it with a list of
29227 expected trust-anchors or certificates.
29228 These may be the system default set (depending on library version),
29229 an explicit file or,
29230 depending on library version, a directory, identified by
29231 &%tls_verify_certificates%&.
29233 A file can contain multiple certificates, concatenated end to end. If a
29236 each certificate must be in a separate file, with a name (or a symbolic link)
29237 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
29238 certificate. You can compute the relevant hash by running the command
29240 openssl x509 -hash -noout -in /cert/file
29242 where &_/cert/file_& contains a single certificate.
29244 There is no checking of names of the client against the certificate
29245 Subject Name or Subject Alternate Names.
29247 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
29248 what happens if the client does not supply a certificate, or if the certificate
29249 does not match any of the certificates in the collection named by
29250 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
29251 attempt to set up a TLS session is aborted, and the incoming connection is
29252 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
29253 session continues. ACLs that run for subsequent SMTP commands can detect the
29254 fact that no certificate was verified, and vary their actions accordingly. For
29255 example, you can insist on a certificate before accepting a message for
29256 relaying, but not when the message is destined for local delivery.
29258 .vindex "&$tls_in_peerdn$&"
29259 When a client supplies a certificate (whether it verifies or not), the value of
29260 the Distinguished Name of the certificate is made available in the variable
29261 &$tls_in_peerdn$& during subsequent processing of the message.
29263 .cindex "log" "distinguished name"
29264 Because it is often a long text string, it is not included in the log line or
29265 &'Received:'& header by default. You can arrange for it to be logged, keyed by
29266 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
29267 &%received_header_text%& to change the &'Received:'& header. When no
29268 certificate is supplied, &$tls_in_peerdn$& is empty.
29271 .section "Revoked certificates" "SECID184"
29272 .cindex "TLS" "revoked certificates"
29273 .cindex "revocation list"
29274 .cindex "certificate" "revocation list"
29275 .cindex "OCSP" "stapling"
29276 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
29277 certificates are revoked. If you have such a list, you can pass it to an Exim
29278 server using the global option called &%tls_crl%& and to an Exim client using
29279 an identically named option for the &(smtp)& transport. In each case, the value
29280 of the option is expanded and must then be the name of a file that contains a
29282 The downside is that clients have to periodically re-download a potentially huge
29283 file from every certificate authority they know of.
29285 The way with most moving parts at query time is Online Certificate
29286 Status Protocol (OCSP), where the client verifies the certificate
29287 against an OCSP server run by the CA. This lets the CA track all
29288 usage of the certs. It requires running software with access to the
29289 private key of the CA, to sign the responses to the OCSP queries. OCSP
29290 is based on HTTP and can be proxied accordingly.
29292 The only widespread OCSP server implementation (known to this writer)
29293 comes as part of OpenSSL and aborts on an invalid request, such as
29294 connecting to the port and then disconnecting. This requires
29295 re-entering the passphrase each time some random client does this.
29297 The third way is OCSP Stapling; in this, the server using a certificate
29298 issued by the CA periodically requests an OCSP proof of validity from
29299 the OCSP server, then serves it up inline as part of the TLS
29300 negotiation. This approach adds no extra round trips, does not let the
29301 CA track users, scales well with number of certs issued by the CA and is
29302 resilient to temporary OCSP server failures, as long as the server
29303 starts retrying to fetch an OCSP proof some time before its current
29304 proof expires. The downside is that it requires server support.
29306 Unless Exim is built with the support disabled,
29307 or with GnuTLS earlier than version 3.3.16 / 3.4.8
29308 support for OCSP stapling is included.
29310 There is a global option called &%tls_ocsp_file%&.
29311 The file specified therein is expected to be in DER format, and contain
29312 an OCSP proof. Exim will serve it as part of the TLS handshake. This
29313 option will be re-expanded for SNI, if the &%tls_certificate%& option
29314 contains &`tls_in_sni`&, as per other TLS options.
29316 Exim does not at this time implement any support for fetching a new OCSP
29317 proof. The burden is on the administrator to handle this, outside of
29318 Exim. The file specified should be replaced atomically, so that the
29319 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
29320 on each connection, so a new file will be handled transparently on the
29323 When built with OpenSSL Exim will check for a valid next update timestamp
29324 in the OCSP proof; if not present, or if the proof has expired, it will be
29327 For the client to be able to verify the stapled OCSP the server must
29328 also supply, in its stapled information, any intermediate
29329 certificates for the chain leading to the OCSP proof from the signer
29330 of the server certificate. There may be zero or one such. These
29331 intermediate certificates should be added to the server OCSP stapling
29332 file named by &%tls_ocsp_file%&.
29334 Note that the proof only covers the terminal server certificate,
29335 not any of the chain from CA to it.
29337 There is no current way to staple a proof for a client certificate.
29340 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
29341 OCSP server is supplied. The server URL may be included in the
29342 server certificate, if the CA is helpful.
29344 One failure mode seen was the OCSP Signer cert expiring before the end
29345 of validity of the OCSP proof. The checking done by Exim/OpenSSL
29346 noted this as invalid overall, but the re-fetch script did not.
29351 .section "Caching of static server configuration items" "SECTserverTLScache"
29352 .cindex certificate caching
29353 .cindex privatekey caching
29354 .cindex crl caching
29355 .cindex ocsp caching
29356 .cindex ciphers caching
29357 .cindex "CA bundle" caching
29358 .cindex "certificate authorities" caching
29359 .cindex tls_certificate caching
29360 .cindex tls_privatekey caching
29361 .cindex tls_crl caching
29362 .cindex tls_ocsp_file caching
29363 .cindex tls_require_ciphers caching
29364 .cindex tls_verify_certificate caching
29365 .cindex caching certificate
29366 .cindex caching privatekey
29367 .cindex caching crl
29368 .cindex caching ocsp
29369 .cindex caching ciphers
29370 .cindex caching "certificate authorities
29371 If any of the main configuration options &%tls_certificate%&, &%tls_privatekey%&,
29372 &%tls_crl%& and &%tls_ocsp_file%& have values with no
29373 expandable elements,
29374 then the associated information is loaded at daemon startup.
29375 It is made available
29376 to child processes forked for handling received SMTP connections.
29378 This caching is currently only supported under Linux and FreeBSD.
29380 If caching is not possible, for example if an item has to be dependent
29381 on the peer host so contains a &$sender_host_name$& expansion, the load
29382 of the associated information is done at the startup of the TLS connection.
29384 The cache is invalidated and reloaded after any changes to the directories
29385 containing files specified by these options.
29387 The information specified by the main option &%tls_verify_certificates%&
29388 is similarly cached so long as it specifies files explicitly
29389 or (under GnuTLS) is the string &"system,cache"&.
29390 The latter case is not automatically invalidated;
29391 it is the operator's responsibility to arrange for a daemon restart
29392 any time the system certificate authority bundle is updated.
29393 A HUP signal is sufficient for this.
29394 The value &"system"& results in no caching under GnuTLS.
29396 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29397 is acceptable in configurations for the Exim executavble.
29399 Caching of the system Certificate Authorities bundle can
29400 save siginificant time and processing on every TLS connection
29407 .section "Configuring an Exim client to use TLS" "SECTclientTLS"
29408 .cindex "cipher" "logging"
29409 .cindex "log" "TLS cipher"
29410 .cindex "log" "distinguished name"
29411 .cindex "TLS" "configuring an Exim client"
29412 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
29413 deliveries as well as to incoming, the latter one causing logging of the
29414 server certificate's DN. The remaining client configuration for TLS is all
29415 within the &(smtp)& transport.
29417 .cindex "ESMTP extensions" STARTTLS
29418 It is not necessary to set any options to have TLS work in the &(smtp)&
29419 transport. If Exim is built with TLS support, and TLS is advertised by a
29420 server, the &(smtp)& transport always tries to start a TLS session. However,
29421 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
29422 transport) to a list of server hosts for which TLS should not be used.
29424 If you do not want Exim to attempt to send messages unencrypted when an attempt
29425 to set up an encrypted connection fails in any way, you can set
29426 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
29427 those hosts, delivery is always deferred if an encrypted connection cannot be
29428 set up. If there are any other hosts for the address, they are tried in the
29431 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
29432 the message unencrypted. It always does this if the response to STARTTLS is
29433 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
29434 session after a success response code, what happens is controlled by the
29435 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
29436 delivery to this host is deferred, and other hosts (if available) are tried. If
29437 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
29438 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
29439 negotiation fails, Exim closes the current connection (because it is in an
29440 unknown state), opens a new one to the same host, and then tries the delivery
29443 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
29444 transport provide the client with a certificate, which is passed to the server
29446 This is an optional thing for TLS connections, although either end
29448 If the server is Exim, it will request a certificate only if
29449 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
29451 &*Note*&: Do not use a certificate which has the OCSP-must-staple extension,
29452 for client use (they are usable for server use).
29453 As the TLS protocol has no means for the client to staple before TLS 1.3 it will result
29454 in failed connections.
29456 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
29457 specifies a collection of expected server certificates.
29459 the system default set (depending on library version),
29461 or (depending on library version) a directory.
29462 The client verifies the server's certificate
29463 against this collection, taking into account any revoked certificates that are
29464 in the list defined by &%tls_crl%&.
29465 Failure to verify fails the TLS connection unless either of the
29466 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
29468 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
29469 certificate verification to the listed servers. Verification either must
29470 or need not succeed respectively.
29472 The &%tls_verify_cert_hostnames%& option lists hosts for which additional
29473 name checks are made on the server certificate.
29475 The match against this list is, as per other Exim usage, the
29476 IP for the host. That is most closely associated with the
29477 name on the DNS A (or AAAA) record for the host.
29478 However, the name that needs to be in the certificate
29479 is the one at the head of any CNAME chain leading to the A record.
29481 The option defaults to always checking.
29483 The &(smtp)& transport has two OCSP-related options:
29484 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
29485 is requested and required for the connection to proceed. The default
29487 &%hosts_request_ocsp%&; a host-list for which (additionally)
29488 a Certificate Status is requested (but not necessarily verified). The default
29489 value is "*" meaning that requests are made unless configured
29492 The host(s) should also be in &%hosts_require_tls%&, and
29493 &%tls_verify_certificates%& configured for the transport,
29494 for OCSP to be relevant.
29497 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
29498 list of permitted cipher suites. If either of these checks fails, delivery to
29499 the current host is abandoned, and the &(smtp)& transport tries to deliver to
29500 alternative hosts, if any.
29503 These options must be set in the &(smtp)& transport for Exim to use TLS when it
29504 is operating as a client. Exim does not assume that a server certificate (set
29505 by the global options of the same name) should also be used when operating as a
29509 .vindex "&$host_address$&"
29510 All the TLS options in the &(smtp)& transport are expanded before use, with
29511 &$host$& and &$host_address$& containing the name and address of the server to
29512 which the client is connected. Forced failure of an expansion causes Exim to
29513 behave as if the relevant option were unset.
29515 .vindex &$tls_out_bits$&
29516 .vindex &$tls_out_cipher$&
29517 .vindex &$tls_out_peerdn$&
29518 .vindex &$tls_out_sni$&
29519 Before an SMTP connection is established, the
29520 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
29521 variables are emptied. (Until the first connection, they contain the values
29522 that were set when the message was received.) If STARTTLS is subsequently
29523 successfully obeyed, these variables are set to the relevant values for the
29524 outgoing connection.
29529 .section "Caching of static client configuration items" "SECTclientTLScache"
29530 .cindex certificate caching
29531 .cindex privatekey caching
29532 .cindex crl caching
29533 .cindex ciphers caching
29534 .cindex "CA bundle" caching
29535 .cindex "certificate authorities" caching
29536 .cindex tls_certificate caching
29537 .cindex tls_privatekey caching
29538 .cindex tls_crl caching
29539 .cindex tls_require_ciphers caching
29540 .cindex tls_verify_certificate caching
29541 .cindex caching certificate
29542 .cindex caching privatekey
29543 .cindex caching crl
29544 .cindex caching ciphers
29545 .cindex caching "certificate authorities
29546 If any of the transport configuration options &%tls_certificate%&, &%tls_privatekey%&
29547 and &%tls_crl%& have values with no
29548 expandable elements,
29549 then the associated information is loaded per smtp transport
29550 at daemon startup, at the start of a queue run, or on a
29551 command-line specified message delivery.
29552 It is made available
29553 to child processes forked for handling making SMTP connections.
29555 This caching is currently only supported under Linux.
29557 If caching is not possible, the load
29558 of the associated information is done at the startup of the TLS connection.
29560 The cache is invalidated in the daemon
29561 and reloaded after any changes to the directories
29562 containing files specified by these options.
29564 The information specified by the main option &%tls_verify_certificates%&
29565 is similarly cached so long as it specifies files explicitly
29566 or (under GnuTLS) is the string &"system,cache"&.
29567 The latter case is not automatically invaludated;
29568 it is the operator's responsibility to arrange for a daemon restart
29569 any time the system certificate authority bundle is updated.
29570 A HUP signal is sufficient for this.
29571 The value &"system"& results in no caching under GnuTLS.
29573 The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
29574 is acceptable in configurations for the Exim executavble.
29576 Caching of the system Certificate Authorities bundle can
29577 save siginificant time and processing on every TLS connection
29584 .section "Use of TLS Server Name Indication" "SECTtlssni"
29585 .cindex "TLS" "Server Name Indication"
29588 .vindex "&$tls_in_sni$&"
29589 .oindex "&%tls_in_sni%&"
29590 With TLS1.0 or above, there is an extension mechanism by which extra
29591 information can be included at various points in the protocol. One of these
29592 extensions, documented in RFC 6066 (and before that RFC 4366) is
29593 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
29594 client in the initial handshake, so that the server can examine the servername
29595 within and possibly choose to use different certificates and keys (and more)
29598 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
29599 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
29602 With SMTP to MX, there are the same problems here as in choosing the identity
29603 against which to validate a certificate: you can't rely on insecure DNS to
29604 provide the identity which you then cryptographically verify. So this will
29605 be of limited use in that environment.
29607 With SMTP to Submission, there is a well-defined hostname which clients are
29608 connecting to and can validate certificates against. Thus clients &*can*&
29609 choose to include this information in the TLS negotiation. If this becomes
29610 wide-spread, then hosters can choose to present different certificates to
29611 different clients. Or even negotiate different cipher suites.
29613 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
29614 if not empty, will be sent on a TLS session as part of the handshake. There's
29615 nothing more to it. Choosing a sensible value not derived insecurely is the
29616 only point of caution. The &$tls_out_sni$& variable will be set to this string
29617 for the lifetime of the client connection (including during authentication).
29620 If DANE validated the connection attempt then the value of the &%tls_sni%& option
29621 is forced to the domain part of the recipient address.
29624 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
29625 received from a client.
29626 It can be logged with the &%log_selector%& item &`+tls_sni`&.
29628 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
29629 option (prior to expansion) then the following options will be re-expanded
29630 during TLS session handshake, to permit alternative values to be chosen:
29633 &%tls_certificate%&
29639 &%tls_verify_certificates%&
29644 Great care should be taken to deal with matters of case, various injection
29645 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
29646 can always be referenced; it is important to remember that &$tls_in_sni$& is
29647 arbitrary unverified data provided prior to authentication.
29648 Further, the initial certificate is loaded before SNI has arrived, so
29649 an expansion for &%tls_certificate%& must have a default which is used
29650 when &$tls_in_sni$& is empty.
29652 The Exim developers are proceeding cautiously and so far no other TLS options
29655 When Exim is built against OpenSSL, OpenSSL must have been built with support
29656 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
29657 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
29658 see &`-servername`& in the output, then OpenSSL has support.
29660 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
29661 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
29662 built, then you have SNI support).
29666 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
29668 .cindex "multiple SMTP deliveries with TLS"
29669 .cindex "TLS" "multiple message deliveries"
29670 Exim sends multiple messages down the same TCP/IP connection by starting up
29671 an entirely new delivery process for each message, passing the socket from
29672 one process to the next. This implementation does not fit well with the use
29673 of TLS, because there is quite a lot of state information associated with a TLS
29674 connection, not just a socket identification. Passing all the state information
29675 to a new process is not feasible. Consequently, for sending using TLS Exim
29676 starts an additional proxy process for handling the encryption, piping the
29677 unencrypted data stream from and to the delivery processes.
29679 An older mode of operation can be enabled on a per-host basis by the
29680 &%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
29681 this list the proxy process described above is not used; instead Exim
29682 shuts down an existing TLS session being run by the delivery process
29683 before passing the socket to a new process. The new process may then
29684 try to start a new TLS session, and if successful, may try to re-authenticate
29685 if AUTH is in use, before sending the next message.
29687 The RFC is not clear as to whether or not an SMTP session continues in clear
29688 after TLS has been shut down, or whether TLS may be restarted again later, as
29689 just described. However, if the server is Exim, this shutdown and
29690 reinitialization works. It is not known which (if any) other servers operate
29691 successfully if the client closes a TLS session and continues with unencrypted
29692 SMTP, but there are certainly some that do not work. For such servers, Exim
29693 should not pass the socket to another process, because the failure of the
29694 subsequent attempt to use it would cause Exim to record a temporary host error,
29695 and delay other deliveries to that host.
29697 To test for this case, Exim sends an EHLO command to the server after
29698 closing down the TLS session. If this fails in any way, the connection is
29699 closed instead of being passed to a new delivery process, but no retry
29700 information is recorded.
29702 There is also a manual override; you can set &%hosts_nopass_tls%& on the
29703 &(smtp)& transport to match those hosts for which Exim should not pass
29704 connections to new processes if TLS has been used.
29709 .section "Certificates and all that" "SECTcerandall"
29710 .cindex "certificate" "references to discussion"
29711 In order to understand fully how TLS works, you need to know about
29712 certificates, certificate signing, and certificate authorities.
29713 This is a large topic and an introductory guide is unsuitable for the Exim
29714 reference manual, so instead we provide pointers to existing documentation.
29716 The Apache web-server was for a long time the canonical guide, so their
29717 documentation is a good place to start; their SSL module's Introduction
29718 document is currently at
29720 &url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html)
29722 and their FAQ is at
29724 &url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html)
29727 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
29728 0-201-61598-3) in 2001, contains both introductory and more in-depth
29730 More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&,
29731 published by Feisty Duck (ISBN 978-1907117046) in 2013 is good.
29732 Ivan is the author of the popular TLS testing tools at
29733 &url(https://www.ssllabs.com/).
29736 .section "Certificate chains" "SECID186"
29737 The file named by &%tls_certificate%& may contain more than one
29738 certificate. This is useful in the case where the certificate that is being
29739 sent is validated by an intermediate certificate which the other end does
29740 not have. Multiple certificates must be in the correct order in the file.
29741 First the host's certificate itself, then the first intermediate
29742 certificate to validate the issuer of the host certificate, then the next
29743 intermediate certificate to validate the issuer of the first intermediate
29744 certificate, and so on, until finally (optionally) the root certificate.
29745 The root certificate must already be trusted by the recipient for
29746 validation to succeed, of course, but if it's not preinstalled, sending the
29747 root certificate along with the rest makes it available for the user to
29748 install if the receiving end is a client MUA that can interact with a user.
29750 Note that certificates using MD5 are unlikely to work on today's Internet;
29751 even if your libraries allow loading them for use in Exim when acting as a
29752 server, increasingly clients will not accept such certificates. The error
29753 diagnostics in such a case can be frustratingly vague.
29757 .section "Self-signed certificates" "SECID187"
29758 .cindex "certificate" "self-signed"
29759 You can create a self-signed certificate using the &'req'& command provided
29760 with OpenSSL, like this:
29761 . ==== Do not shorten the duration here without reading and considering
29762 . ==== the text below. Please leave it at 9999 days.
29764 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
29767 &_file1_& and &_file2_& can be the same file; the key and the certificate are
29768 delimited and so can be identified independently. The &%-days%& option
29769 specifies a period for which the certificate is valid. The &%-nodes%& option is
29770 important: if you do not set it, the key is encrypted with a passphrase
29771 that you are prompted for, and any use that is made of the key causes more
29772 prompting for the passphrase. This is not helpful if you are going to use
29773 this certificate and key in an MTA, where prompting is not possible.
29775 . ==== I expect to still be working 26 years from now. The less technical
29776 . ==== debt I create, in terms of storing up trouble for my later years, the
29777 . ==== happier I will be then. We really have reached the point where we
29778 . ==== should start, at the very least, provoking thought and making folks
29779 . ==== pause before proceeding, instead of leaving all the fixes until two
29780 . ==== years before 2^31 seconds after the 1970 Unix epoch.
29782 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
29783 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
29784 the above command might produce a date in the past. Think carefully about
29785 the lifetime of the systems you're deploying, and either reduce the duration
29786 of the certificate or reconsider your platform deployment. (At time of
29787 writing, reducing the duration is the most likely choice, but the inexorable
29788 progression of time takes us steadily towards an era where this will not
29789 be a sensible resolution).
29791 A self-signed certificate made in this way is sufficient for testing, and
29792 may be adequate for all your requirements if you are mainly interested in
29793 encrypting transfers, and not in secure identification.
29795 However, many clients require that the certificate presented by the server be a
29796 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
29797 certificate. In this situation, the self-signed certificate described above
29798 must be installed on the client host as a trusted root &'certification
29799 authority'& (CA), and the certificate used by Exim must be a user certificate
29800 signed with that self-signed certificate.
29802 For information on creating self-signed CA certificates and using them to sign
29803 user certificates, see the &'General implementation overview'& chapter of the
29804 Open-source PKI book, available online at
29805 &url(https://sourceforge.net/projects/ospkibook/).
29806 .ecindex IIDencsmtp1
29807 .ecindex IIDencsmtp2
29811 .section "TLS Resumption" "SECTresumption"
29812 .cindex TLS resumption
29813 TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
29814 in RFC 5077 for 1.2). The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1
29817 Session resumption (this is the "stateless" variant) involves the server sending
29818 a "session ticket" to the client on one connection, which can be stored by the
29819 client and used for a later session. The ticket contains sufficient state for
29820 the server to reconstruct the TLS session, avoiding some expensive crypto
29821 calculation and (on TLS1.2) one full packet roundtrip time.
29824 Operational cost/benefit:
29826 The extra data being transmitted costs a minor amount, and the client has
29827 extra costs in storing and retrieving the data.
29829 In the Exim/Gnutls implementation the extra cost on an initial connection
29830 which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware.
29831 The saved cost on a subsequent connection is about 4ms; three or more
29832 connections become a net win. On longer network paths, two or more
29833 connections will have an average lower startup time thanks to the one
29834 saved packet roundtrip. TLS1.3 will save the crypto cpu costs but not any
29837 .cindex "hints database" tls
29838 Since a new hints DB is used on the TLS client,
29839 the hints DB maintenance should be updated to additionally handle "tls".
29844 The session ticket is encrypted, but is obviously an additional security
29845 vulnarability surface. An attacker able to decrypt it would have access
29846 all connections using the resumed session.
29847 The session ticket encryption key is not committed to storage by the server
29848 and is rotated regularly (OpenSSL: 1hr, and one previous key is used for
29849 overlap; GnuTLS 6hr but does not specify any overlap).
29850 Tickets have limited lifetime (2hr, and new ones issued after 1hr under
29851 OpenSSL. GnuTLS 2hr, appears to not do overlap).
29853 There is a question-mark over the security of the Diffie-Helman parameters
29854 used for session negotiation.
29859 The &%log_selector%& "tls_resumption" appends an asterisk to the tls_cipher "X="
29862 The variables &$tls_in_resumption$& and &$tls_out_resumption$&
29863 have bits 0-4 indicating respectively
29864 support built, client requested ticket, client offered session,
29865 server issued ticket, resume used. A suitable decode list is provided
29866 in the builtin macro _RESUME_DECODE for in &%listextract%& expansions.
29871 The &%tls_resumption_hosts%& main option specifies a hostlist for which
29872 exim, operating as a server, will offer resumption to clients.
29873 Current best practice is to not offer the feature to MUA connection.
29874 Commonly this can be done like this:
29876 tls_resumption_hosts = ${if inlist {$received_port}{587:465} {:}{*}}
29878 If the peer host matches the list after expansion then resumption
29879 is offered and/or accepted.
29881 The &%tls_resumption_hosts%& smtp transport option performs the
29882 equivalent function for operation as a client.
29883 If the peer host matches the list after expansion then resumption
29884 is attempted (if a stored session is available) or the information
29885 stored (if supplied by the peer).
29891 In a resumed session:
29893 The variables &$tls_{in,out}_cipher$& will have values different
29894 to the original (under GnuTLS).
29896 The variables &$tls_{in,out}_ocsp$& will be "not requested" or "no response",
29897 and the &%hosts_require_ocsp%& smtp trasnport option will fail.
29898 . XXX need to do something with that hosts_require_ocsp
29905 .section DANE "SECDANE"
29907 DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
29908 it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
29909 operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
29910 you and the server still think you have an encrypted connection) and, if one of the "well known" set of
29911 Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
29912 certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
29914 What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
29915 that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
29916 by (a) is thought to be smaller than that of the set of root CAs.
29918 It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
29919 fail to pass on a server's STARTTLS.
29921 DANE scales better than having to maintain (and communicate via side-channel) copies of server certificates
29922 for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
29923 client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
29925 DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
29926 that DNS lookups they do for the server have not been tampered with. The domain MX record applying
29927 to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
29929 2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
29930 3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
29932 There are no changes to Exim specific to server-side operation of DANE.
29933 Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
29934 in &_Local/Makefile_&.
29935 If it has been included, the macro "_HAVE_DANE" will be defined.
29937 A TLSA record consist of 4 fields, the "Certificate Usage", the
29938 "Selector", the "Matching type", and the "Certificate Association Data".
29939 For a detailed description of the TLSA record see
29940 &url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671).
29942 The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3).
29943 These are the "Trust Anchor" and "End Entity" variants.
29944 The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
29945 (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
29946 this is appropriate for a single system, using a self-signed certificate.
29947 DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
29949 A private CA at simplest is just a self-signed certificate (with certain
29950 attributes) which is used to sign server certificates, but running one securely
29951 does require careful arrangement.
29952 With DANE-TA, as implemented in Exim and commonly in other MTAs,
29953 the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
29954 DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
29955 all of which point to a single TLSA record.
29956 DANE-TA and DANE-EE can both be used together.
29958 Our recommendation is to use DANE with a certificate from a public CA,
29959 because this enables a variety of strategies for remote clients to verify
29961 You can then publish information both via DANE and another technology,
29962 "MTA-STS", described below.
29964 When you use DANE-TA to publish trust anchor information, you ask entities
29965 outside your administrative control to trust the Certificate Authority for
29966 connections to you.
29967 If using a private CA then you should expect others to still apply the
29968 technical criteria they'd use for a public CA to your certificates.
29969 In particular, you should probably try to follow current best practices for CA
29970 operation around hash algorithms and key sizes.
29971 Do not expect other organizations to lower their security expectations just
29972 because a particular profile might be reasonable for your own internal use.
29974 When this text was last updated, this in practice means to avoid use of SHA-1
29975 and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
29976 than 4096, for interoperability); to use keyUsage fields correctly; to use
29977 random serial numbers.
29978 The list of requirements is subject to change as best practices evolve.
29979 If you're not already using a private CA, or it doesn't meet these
29980 requirements, then we encourage you to avoid all these issues and use a public
29981 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
29983 The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
29984 a "Matching Type" (3rd) field of SHA2-512(2).
29986 For the "Certificate Authority Data" (4th) field, commands like
29989 openssl x509 -pubkey -noout <certificate.pem \
29990 | openssl rsa -outform der -pubin 2>/dev/null \
29995 are workable to create a hash of the certificate's public key.
29997 An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like
30000 _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E...
30003 At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
30004 is useful for quickly generating TLSA records.
30007 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
30009 The Certificate issued by the CA published in the DANE-TA model should be
30010 issued using a strong hash algorithm.
30011 Exim, and importantly various other MTAs sending to you, will not
30012 re-enable hash algorithms which have been disabled by default in TLS
30014 This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
30015 interoperability (and probably the maximum too, in 2018).
30017 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
30018 be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
30019 default of requesting OCSP for all hosts is modified iff DANE is in use, to:
30022 hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
30023 {= {4}{$tls_out_tlsa_usage}} } \
30027 The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
30028 The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
30029 found. If the definition of &%hosts_request_ocsp%& includes the
30030 string "tls_out_tlsa_usage", they are re-expanded in time to
30031 control the OCSP request.
30033 This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
30034 those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
30037 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
30038 and &%dane_require_tls_ciphers%&.
30039 The &"require"& variant will result in failure if the target host is not
30040 DNSSEC-secured. To get DNSSEC-secured hostname resolution, use
30041 the &%dnssec_request_domains%& router or transport option.
30043 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
30045 A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using dnssec.
30046 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
30047 will be required for the host. If it does not, the host will not
30048 be used; there is no fallback to non-DANE or non-TLS.
30050 If DANE is requested and usable, then the TLS cipher list configuration
30051 prefers to use the option &%dane_require_tls_ciphers%& and falls
30052 back to &%tls_require_ciphers%& only if that is unset.
30053 This lets you configure "decent crypto" for DANE and "better than nothing
30054 crypto" as the default. Note though that while GnuTLS lets the string control
30055 which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
30056 limited to ciphersuite constraints.
30058 If DANE is requested and useable (see above) the following transport options are ignored:
30062 tls_try_verify_hosts
30063 tls_verify_certificates
30065 tls_verify_cert_hostnames
30069 If DANE is not usable, whether requested or not, and CA-anchored
30070 verification evaluation is wanted, the above variables should be set appropriately.
30072 The router and transport option &%dnssec_request_domains%& must not be
30073 set to &"never"&, and &%dnssec_require_domains%& is ignored.
30075 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
30077 There is a new variable &$tls_out_dane$& which will have "yes" if
30078 verification succeeded using DANE and "no" otherwise (only useful
30079 in combination with events; see &<<CHAPevents>>&),
30080 and a new variable &$tls_out_tlsa_usage$& (detailed above).
30082 .cindex DANE reporting
30083 An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
30084 to achieve DANE-verified connection, if one was either requested and offered, or
30085 required. This is intended to support TLS-reporting as defined in
30086 &url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
30087 The &$event_data$& will be one of the Result Types defined in
30088 Section 4.3 of that document.
30090 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
30092 DANE is specified in published RFCs and decouples certificate authority trust
30093 selection from a "race to the bottom" of "you must trust everything for mail
30094 to get through". There is an alternative technology called MTA-STS, which
30095 instead publishes MX trust anchor information on an HTTPS website. At the
30096 time this text was last updated, MTA-STS was still a draft, not yet an RFC.
30097 Exim has no support for MTA-STS as a client, but Exim mail server operators
30098 can choose to publish information describing their TLS configuration using
30099 MTA-STS to let those clients who do use that protocol derive trust
30102 The MTA-STS design requires a certificate from a public Certificate Authority
30103 which is recognized by clients sending to you.
30104 That selection of which CAs are trusted by others is outside your control.
30106 The most interoperable course of action is probably to use
30107 &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
30108 renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
30109 records for DANE clients (such as Exim and Postfix) and to publish anchor
30110 information for MTA-STS as well. This is what is done for the &'exim.org'&
30111 domain itself (with caveats around occasionally broken MTA-STS because of
30112 incompatible specification changes prior to reaching RFC status).
30116 . ////////////////////////////////////////////////////////////////////////////
30117 . ////////////////////////////////////////////////////////////////////////////
30119 .chapter "Access control lists" "CHAPACL"
30120 .scindex IIDacl "&ACL;" "description"
30121 .cindex "control of incoming mail"
30122 .cindex "message" "controlling incoming"
30123 .cindex "policy control" "access control lists"
30124 Access Control Lists (ACLs) are defined in a separate section of the runtime
30125 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
30126 name, terminated by a colon. Here is a complete ACL section that contains just
30127 one very small ACL:
30131 accept hosts = one.host.only
30133 You can have as many lists as you like in the ACL section, and the order in
30134 which they appear does not matter. The lists are self-terminating.
30136 The majority of ACLs are used to control Exim's behaviour when it receives
30137 certain SMTP commands. This applies both to incoming TCP/IP connections, and
30138 when a local process submits a message using SMTP by specifying the &%-bs%&
30139 option. The most common use is for controlling which recipients are accepted
30140 in incoming messages. In addition, you can define an ACL that is used to check
30141 local non-SMTP messages. The default configuration file contains an example of
30142 a realistic ACL for checking RCPT commands. This is discussed in chapter
30143 &<<CHAPdefconfil>>&.
30146 .section "Testing ACLs" "SECID188"
30147 The &%-bh%& command line option provides a way of testing your ACL
30148 configuration locally by running a fake SMTP session with which you interact.
30151 .section "Specifying when ACLs are used" "SECID189"
30152 .cindex "&ACL;" "options for specifying"
30153 In order to cause an ACL to be used, you have to name it in one of the relevant
30154 options in the main part of the configuration. These options are:
30155 .cindex "AUTH" "ACL for"
30156 .cindex "DATA" "ACLs for"
30157 .cindex "ETRN" "ACL for"
30158 .cindex "EXPN" "ACL for"
30159 .cindex "HELO" "ACL for"
30160 .cindex "EHLO" "ACL for"
30161 .cindex "DKIM" "ACL for"
30162 .cindex "MAIL" "ACL for"
30163 .cindex "QUIT, ACL for"
30164 .cindex "RCPT" "ACL for"
30165 .cindex "STARTTLS, ACL for"
30166 .cindex "VRFY" "ACL for"
30167 .cindex "SMTP" "connection, ACL for"
30168 .cindex "non-SMTP messages" "ACLs for"
30169 .cindex "MIME content scanning" "ACL for"
30170 .cindex "PRDR" "ACL for"
30173 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
30174 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
30175 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
30176 .irow &%acl_smtp_auth%& "ACL for AUTH"
30177 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
30178 .irow &%acl_smtp_data%& "ACL after DATA is complete"
30179 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
30180 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
30181 .irow &%acl_smtp_etrn%& "ACL for ETRN"
30182 .irow &%acl_smtp_expn%& "ACL for EXPN"
30183 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
30184 .irow &%acl_smtp_mail%& "ACL for MAIL"
30185 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
30186 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
30187 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
30188 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
30189 .irow &%acl_smtp_quit%& "ACL for QUIT"
30190 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
30191 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
30192 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
30195 For example, if you set
30197 acl_smtp_rcpt = small_acl
30199 the little ACL defined above is used whenever Exim receives a RCPT command
30200 in an SMTP dialogue. The majority of policy tests on incoming messages can be
30201 done when RCPT commands arrive. A rejection of RCPT should cause the
30202 sending MTA to give up on the recipient address contained in the RCPT
30203 command, whereas rejection at other times may cause the client MTA to keep on
30204 trying to deliver the message. It is therefore recommended that you do as much
30205 testing as possible at RCPT time.
30208 .section "The non-SMTP ACLs" "SECID190"
30209 .cindex "non-SMTP messages" "ACLs for"
30210 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
30211 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
30212 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
30213 the state of the SMTP connection such as encryption and authentication) are not
30214 relevant and are forbidden in these ACLs. However, the sender and recipients
30215 are known, so the &%senders%& and &%sender_domains%& conditions and the
30216 &$sender_address$& and &$recipients$& variables can be used. Variables such as
30217 &$authenticated_sender$& are also available. You can specify added header lines
30218 in any of these ACLs.
30220 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
30221 non-SMTP message, before any of the message has been read. (This is the
30222 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
30223 batched SMTP input, it runs after the DATA command has been reached. The
30224 result of this ACL is ignored; it cannot be used to reject a message. If you
30225 really need to, you could set a value in an ACL variable here and reject based
30226 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
30227 controls, and in particular, it can be used to set
30229 control = suppress_local_fixups
30231 This cannot be used in the other non-SMTP ACLs because by the time they are
30232 run, it is too late.
30234 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
30235 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30237 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
30238 kind of rejection is treated as permanent, because there is no way of sending a
30239 temporary error for these kinds of message.
30242 .section "The SMTP connect ACL" "SECID191"
30243 .cindex "SMTP" "connection, ACL for"
30244 .oindex &%smtp_banner%&
30245 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
30246 session, after the test specified by &%host_reject_connection%& (which is now
30247 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
30248 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
30249 the message override the banner message that is otherwise specified by the
30250 &%smtp_banner%& option.
30253 .section "The EHLO/HELO ACL" "SECID192"
30254 .cindex "EHLO" "ACL for"
30255 .cindex "HELO" "ACL for"
30256 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
30257 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
30258 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
30259 Note that a client may issue more than one EHLO or HELO command in an SMTP
30260 session, and indeed is required to issue a new EHLO or HELO after successfully
30261 setting up encryption following a STARTTLS command.
30263 Note also that a deny neither forces the client to go away nor means that
30264 mail will be refused on the connection. Consider checking for
30265 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
30267 If the command is accepted by an &%accept%& verb that has a &%message%&
30268 modifier, the message may not contain more than one line (it will be truncated
30269 at the first newline and a panic logged if it does). Such a message cannot
30270 affect the EHLO options that are listed on the second and subsequent lines of
30274 .section "The DATA ACLs" "SECID193"
30275 .cindex "DATA" "ACLs for"
30276 Two ACLs are associated with the DATA command, because it is two-stage
30277 command, with two responses being sent to the client.
30278 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
30279 is obeyed. This gives you control after all the RCPT commands, but before
30280 the message itself is received. It offers the opportunity to give a negative
30281 response to the DATA command before the data is transmitted. Header lines
30282 added by MAIL or RCPT ACLs are not visible at this time, but any that
30283 are defined here are visible when the &%acl_smtp_data%& ACL is run.
30285 You cannot test the contents of the message, for example, to verify addresses
30286 in the headers, at RCPT time or when the DATA command is received. Such
30287 tests have to appear in the ACL that is run after the message itself has been
30288 received, before the final response to the DATA command is sent. This is
30289 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
30290 associated with the DATA command.
30292 .cindex CHUNKING "BDAT command"
30293 .cindex BDAT "SMTP command"
30294 .cindex "RFC 3030" CHUNKING
30295 If CHUNKING was advertised and a BDAT command sequence is received,
30296 the &%acl_smtp_predata%& ACL is not run.
30297 . XXX why not? It should be possible, for the first BDAT.
30298 The &%acl_smtp_data%& is run after the last BDAT command and all of
30299 the data specified is received.
30301 For both of these ACLs, it is not possible to reject individual recipients. An
30302 error response rejects the entire message. Unfortunately, it is known that some
30303 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
30304 before or after the data) correctly &-- they keep the message on their queues
30305 and try again later, but that is their problem, though it does waste some of
30308 The &%acl_smtp_data%& ACL is run after
30309 the &%acl_smtp_data_prdr%&,
30310 the &%acl_smtp_dkim%&
30311 and the &%acl_smtp_mime%& ACLs.
30313 .section "The SMTP DKIM ACL" "SECTDKIMACL"
30314 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
30315 enabled (which is the default).
30317 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
30318 received, and is executed for each DKIM signature found in a message. If not
30319 otherwise specified, the default action is to accept.
30321 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
30323 For details on the operation of DKIM, see section &<<SECDKIM>>&.
30326 .section "The SMTP MIME ACL" "SECID194"
30327 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
30328 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30330 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30333 .section "The SMTP PRDR ACL" "SECTPRDRACL"
30334 .cindex "PRDR" "ACL for"
30335 .oindex "&%prdr_enable%&"
30336 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
30337 with PRDR support enabled (which is the default).
30338 It becomes active only when the PRDR feature is negotiated between
30339 client and server for a message, and more than one recipient
30342 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
30343 has been received, and is executed once for each recipient of the message
30344 with &$local_part$& and &$domain$& valid.
30345 The test may accept, defer or deny for individual recipients.
30346 The &%acl_smtp_data%& will still be called after this ACL and
30347 can reject the message overall, even if this ACL has accepted it
30348 for some or all recipients.
30350 PRDR may be used to support per-user content filtering. Without it
30351 one must defer any recipient after the first that has a different
30352 content-filter configuration. With PRDR, the RCPT-time check
30353 .cindex "PRDR" "variable for"
30354 for this can be disabled when the variable &$prdr_requested$&
30356 Any required difference in behaviour of the main DATA-time
30357 ACL should however depend on the PRDR-time ACL having run, as Exim
30358 will avoid doing so in some situations (e.g. single-recipient mails).
30360 See also the &%prdr_enable%& global option
30361 and the &%hosts_try_prdr%& smtp transport option.
30363 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30364 If the ACL is not defined, processing completes as if
30365 the feature was not requested by the client.
30367 .section "The QUIT ACL" "SECTQUITACL"
30368 .cindex "QUIT, ACL for"
30369 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
30370 does not affect the response code to QUIT, which is always 221. Thus, the ACL
30371 does not in fact control any access.
30372 For this reason, it may only accept
30373 or warn as its final result.
30375 This ACL can be used for tasks such as custom logging at the end of an SMTP
30376 session. For example, you can use ACL variables in other ACLs to count
30377 messages, recipients, etc., and log the totals at QUIT time using one or
30378 more &%logwrite%& modifiers on a &%warn%& verb.
30380 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
30381 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
30383 You do not need to have a final &%accept%&, but if you do, you can use a
30384 &%message%& modifier to specify custom text that is sent as part of the 221
30387 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
30388 failure (for example, failure to open a log file, or when Exim is bombing out
30389 because it has detected an unrecoverable error), all SMTP commands from the
30390 client are given temporary error responses until QUIT is received or the
30391 connection is closed. In these special cases, the QUIT ACL does not run.
30394 .section "The not-QUIT ACL" "SECTNOTQUITACL"
30395 .vindex &$acl_smtp_notquit$&
30396 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
30397 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
30398 trouble, such as being unable to write to its log files, this ACL is not run,
30399 because it might try to do things (such as write to log files) that make the
30400 situation even worse.
30402 Like the QUIT ACL, this ACL is provided to make it possible to do customized
30403 logging or to gather statistics, and its outcome is ignored. The &%delay%&
30404 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
30407 .vindex &$smtp_notquit_reason$&
30408 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
30409 to a string that indicates the reason for the termination of the SMTP
30410 connection. The possible values are:
30412 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
30413 .irow &`bad-commands`& "Too many unknown or non-mail commands"
30414 .irow &`command-timeout`& "Timeout while reading SMTP commands"
30415 .irow &`connection-lost`& "The SMTP connection has been lost"
30416 .irow &`data-timeout`& "Timeout while reading message data"
30417 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
30418 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
30419 .irow &`signal-exit`& "SIGTERM or SIGINT"
30420 .irow &`synchronization-error`& "SMTP synchronization error"
30421 .irow &`tls-failed`& "TLS failed to start"
30423 In most cases when an SMTP connection is closed without having received QUIT,
30424 Exim sends an SMTP response message before actually closing the connection.
30425 With the exception of the &`acl-drop`& case, the default message can be
30426 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
30427 &%drop%& verb in another ACL, it is the message from the other ACL that is
30431 .section "Finding an ACL to use" "SECID195"
30432 .cindex "&ACL;" "finding which to use"
30433 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
30434 you can use different ACLs in different circumstances. For example,
30436 acl_smtp_rcpt = ${if ={25}{$interface_port} \
30437 {acl_check_rcpt} {acl_check_rcpt_submit} }
30439 In the default configuration file there are some example settings for
30440 providing an RFC 4409 message &"submission"& service on port 587 and
30441 an RFC 8314 &"submissions"& service on port 465. You can use a string
30442 expansion like this to choose an ACL for MUAs on these ports which is
30443 more appropriate for this purpose than the default ACL on port 25.
30445 The expanded string does not have to be the name of an ACL in the
30446 configuration file; there are other possibilities. Having expanded the
30447 string, Exim searches for an ACL as follows:
30450 If the string begins with a slash, Exim uses it as a filename, and reads its
30451 contents as an ACL. The lines are processed in the same way as lines in the
30452 Exim configuration file. In particular, continuation lines are supported, blank
30453 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
30454 If the file does not exist or cannot be read, an error occurs (typically
30455 causing a temporary failure of whatever caused the ACL to be run). For example:
30457 acl_smtp_data = /etc/acls/\
30458 ${lookup{$sender_host_address}lsearch\
30459 {/etc/acllist}{$value}{default}}
30461 This looks up an ACL file to use on the basis of the host's IP address, falling
30462 back to a default if the lookup fails. If an ACL is successfully read from a
30463 file, it is retained in memory for the duration of the Exim process, so that it
30464 can be re-used without having to re-read the file.
30466 If the string does not start with a slash, and does not contain any spaces,
30467 Exim searches the ACL section of the configuration for an ACL whose name
30468 matches the string.
30470 If no named ACL is found, or if the string contains spaces, Exim parses
30471 the string as an inline ACL. This can save typing in cases where you just
30472 want to have something like
30474 acl_smtp_vrfy = accept
30476 in order to allow free use of the VRFY command. Such a string may contain
30477 newlines; it is processed in the same way as an ACL that is read from a file.
30483 .section "ACL return codes" "SECID196"
30484 .cindex "&ACL;" "return codes"
30485 Except for the QUIT ACL, which does not affect the SMTP return code (see
30486 section &<<SECTQUITACL>>& above), the result of running an ACL is either
30487 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
30488 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
30489 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
30490 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
30491 This also causes a 4&'xx'& return code.
30493 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
30494 &"deny"&, because there is no mechanism for passing temporary errors to the
30495 submitters of non-SMTP messages.
30498 ACLs that are relevant to message reception may also return &"discard"&. This
30499 has the effect of &"accept"&, but causes either the entire message or an
30500 individual recipient address to be discarded. In other words, it is a
30501 blackholing facility. Use it with care.
30503 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
30504 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
30505 RCPT ACL is to discard just the one recipient address. If there are no
30506 recipients left when the message's data is received, the DATA ACL is not
30507 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
30508 remaining recipients. The &"discard"& return is not permitted for the
30509 &%acl_smtp_predata%& ACL.
30511 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
30512 is done on the address and the result determines the SMTP response.
30515 .cindex "&[local_scan()]& function" "when all recipients discarded"
30516 The &[local_scan()]& function is always run, even if there are no remaining
30517 recipients; it may create new recipients.
30521 .section "Unset ACL options" "SECID197"
30522 .cindex "&ACL;" "unset options"
30523 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
30524 all the same. &*Note*&: These defaults apply only when the relevant ACL is
30525 not defined at all. For any defined ACL, the default action when control
30526 reaches the end of the ACL statements is &"deny"&.
30528 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
30529 these two are ACLs that are used only for their side effects. They cannot be
30530 used to accept or reject anything.
30532 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
30533 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
30534 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
30535 when the ACL is not defined is &"accept"&.
30537 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
30538 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
30539 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
30540 messages over an SMTP connection. For an example, see the ACL in the default
30541 configuration file.
30546 .section "Data for message ACLs" "SECID198"
30547 .cindex "&ACL;" "data for message ACL"
30549 .vindex &$local_part$&
30550 .vindex &$sender_address$&
30551 .vindex &$sender_host_address$&
30552 .vindex &$smtp_command$&
30553 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
30554 that contain information about the host and the message's sender (for example,
30555 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
30556 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
30557 &$local_part$& are set from the argument address. The entire SMTP command
30558 is available in &$smtp_command$&.
30560 When an ACL for the AUTH parameter of MAIL is running, the variables that
30561 contain information about the host are set, but &$sender_address$& is not yet
30562 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
30565 .vindex "&$message_size$&"
30566 The &$message_size$& variable is set to the value of the SIZE parameter on
30567 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
30568 that parameter is not given. The value is updated to the true message size by
30569 the time the final DATA ACL is run (after the message data has been
30572 .vindex "&$rcpt_count$&"
30573 .vindex "&$recipients_count$&"
30574 The &$rcpt_count$& variable increases by one for each RCPT command received.
30575 The &$recipients_count$& variable increases by one each time a RCPT command is
30576 accepted, so while an ACL for RCPT is being processed, it contains the number
30577 of previously accepted recipients. At DATA time (for both the DATA ACLs),
30578 &$rcpt_count$& contains the total number of RCPT commands, and
30579 &$recipients_count$& contains the total number of accepted recipients.
30585 .section "Data for non-message ACLs" "SECTdatfornon"
30586 .cindex "&ACL;" "data for non-message ACL"
30587 .vindex &$smtp_command_argument$&
30588 .vindex &$smtp_command$&
30589 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
30590 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
30591 and the entire SMTP command is available in &$smtp_command$&.
30592 These variables can be tested using a &%condition%& condition. For example,
30593 here is an ACL for use with AUTH, which insists that either the session is
30594 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
30595 does not permit authentication methods that use cleartext passwords on
30596 unencrypted connections.
30599 accept encrypted = *
30600 accept condition = ${if eq{${uc:$smtp_command_argument}}\
30602 deny message = TLS encryption or CRAM-MD5 required
30604 (Another way of applying this restriction is to arrange for the authenticators
30605 that use cleartext passwords not to be advertised when the connection is not
30606 encrypted. You can use the generic &%server_advertise_condition%& authenticator
30607 option to do this.)
30611 .section "Format of an ACL" "SECID199"
30612 .cindex "&ACL;" "format of"
30613 .cindex "&ACL;" "verbs, definition of"
30614 An individual ACL consists of a number of statements. Each statement starts
30615 with a verb, optionally followed by a number of conditions and &"modifiers"&.
30616 Modifiers can change the way the verb operates, define error and log messages,
30617 set variables, insert delays, and vary the processing of accepted messages.
30619 If all the conditions are met, the verb is obeyed. The same condition may be
30620 used (with different arguments) more than once in the same statement. This
30621 provides a means of specifying an &"and"& conjunction between conditions. For
30624 deny dnslists = list1.example
30625 dnslists = list2.example
30627 If there are no conditions, the verb is always obeyed. Exim stops evaluating
30628 the conditions and modifiers when it reaches a condition that fails. What
30629 happens then depends on the verb (and in one case, on a special modifier). Not
30630 all the conditions make sense at every testing point. For example, you cannot
30631 test a sender address in the ACL that is run for a VRFY command.
30634 .section "ACL verbs" "SECID200"
30635 The ACL verbs are as follows:
30638 .cindex "&%accept%& ACL verb"
30639 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
30640 of the conditions are not met, what happens depends on whether &%endpass%&
30641 appears among the conditions (for syntax see below). If the failing condition
30642 is before &%endpass%&, control is passed to the next ACL statement; if it is
30643 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
30644 check a RCPT command:
30646 accept domains = +local_domains
30650 If the recipient domain does not match the &%domains%& condition, control
30651 passes to the next statement. If it does match, the recipient is verified, and
30652 the command is accepted if verification succeeds. However, if verification
30653 fails, the ACL yields &"deny"&, because the failing condition is after
30656 The &%endpass%& feature has turned out to be confusing to many people, so its
30657 use is not recommended nowadays. It is always possible to rewrite an ACL so
30658 that &%endpass%& is not needed, and it is no longer used in the default
30661 .cindex "&%message%& ACL modifier" "with &%accept%&"
30662 If a &%message%& modifier appears on an &%accept%& statement, its action
30663 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
30664 (when an &%accept%& verb either accepts or passes control to the next
30665 statement), &%message%& can be used to vary the message that is sent when an
30666 SMTP command is accepted. For example, in a RCPT ACL you could have:
30668 &`accept `&<&'some conditions'&>
30669 &` message = OK, I will allow you through today`&
30671 You can specify an SMTP response code, optionally followed by an &"extended
30672 response code"& at the start of the message, but the first digit must be the
30673 same as would be sent by default, which is 2 for an &%accept%& verb.
30675 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
30676 an error message that is used when access is denied. This behaviour is retained
30677 for backward compatibility, but current &"best practice"& is to avoid the use
30682 .cindex "&%defer%& ACL verb"
30683 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
30684 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
30685 &%defer%& is the same as &%deny%&, because there is no way of sending a
30686 temporary error. For a RCPT command, &%defer%& is much the same as using a
30687 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
30688 be used in any ACL, and even for a recipient it might be a simpler approach.
30692 .cindex "&%deny%& ACL verb"
30693 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
30694 the conditions are not met, control is passed to the next ACL statement. For
30697 deny dnslists = blackholes.mail-abuse.org
30699 rejects commands from hosts that are on a DNS black list.
30703 .cindex "&%discard%& ACL verb"
30704 &%discard%&: This verb behaves like &%accept%&, except that it returns
30705 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
30706 that are concerned with receiving messages. When all the conditions are true,
30707 the sending entity receives a &"success"& response. However, &%discard%& causes
30708 recipients to be discarded. If it is used in an ACL for RCPT, just the one
30709 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
30710 message's recipients are discarded. Recipients that are discarded before DATA
30711 do not appear in the log line when the &%received_recipients%& log selector is set.
30713 If the &%log_message%& modifier is set when &%discard%& operates,
30714 its contents are added to the line that is automatically written to the log.
30715 The &%message%& modifier operates exactly as it does for &%accept%&.
30719 .cindex "&%drop%& ACL verb"
30720 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
30721 forcibly closed after the 5&'xx'& error message has been sent. For example:
30723 drop condition = ${if > {$rcpt_count}{20}}
30724 message = I don't take more than 20 RCPTs
30726 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
30727 The connection is always dropped after sending a 550 response.
30730 .cindex "&%require%& ACL verb"
30731 &%require%&: If all the conditions are met, control is passed to the next ACL
30732 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
30733 example, when checking a RCPT command,
30735 require message = Sender did not verify
30738 passes control to subsequent statements only if the message's sender can be
30739 verified. Otherwise, it rejects the command. Note the positioning of the
30740 &%message%& modifier, before the &%verify%& condition. The reason for this is
30741 discussed in section &<<SECTcondmodproc>>&.
30744 .cindex "&%warn%& ACL verb"
30745 &%warn%&: If all the conditions are true, a line specified by the
30746 &%log_message%& modifier is written to Exim's main log. Control always passes
30747 to the next ACL statement. If any condition is false, the log line is not
30748 written. If an identical log line is requested several times in the same
30749 message, only one copy is actually written to the log. If you want to force
30750 duplicates to be written, use the &%logwrite%& modifier instead.
30752 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
30753 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
30754 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
30755 first failing condition. There is more about adding header lines in section
30756 &<<SECTaddheadacl>>&.
30758 If any condition on a &%warn%& statement cannot be completed (that is, there is
30759 some sort of defer), the log line specified by &%log_message%& is not written.
30760 This does not include the case of a forced failure from a lookup, which
30761 is considered to be a successful completion. After a defer, no further
30762 conditions or modifiers in the &%warn%& statement are processed. The incident
30763 is logged, and the ACL continues to be processed, from the next statement
30767 .vindex "&$acl_verify_message$&"
30768 When one of the &%warn%& conditions is an address verification that fails, the
30769 text of the verification failure message is in &$acl_verify_message$&. If you
30770 want this logged, you must set it up explicitly. For example:
30772 warn !verify = sender
30773 log_message = sender verify failed: $acl_verify_message
30777 At the end of each ACL there is an implicit unconditional &%deny%&.
30779 As you can see from the examples above, the conditions and modifiers are
30780 written one to a line, with the first one on the same line as the verb, and
30781 subsequent ones on following lines. If you have a very long condition, you can
30782 continue it onto several physical lines by the usual backslash continuation
30783 mechanism. It is conventional to align the conditions vertically.
30787 .section "ACL variables" "SECTaclvariables"
30788 .cindex "&ACL;" "variables"
30789 There are some special variables that can be set during ACL processing. They
30790 can be used to pass information between different ACLs, different invocations
30791 of the same ACL in the same SMTP connection, and between ACLs and the routers,
30792 transports, and filters that are used to deliver a message. The names of these
30793 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
30794 an underscore, but the remainder of the name can be any sequence of
30795 alphanumeric characters and underscores that you choose. There is no limit on
30796 the number of ACL variables. The two sets act as follows:
30798 The values of those variables whose names begin with &$acl_c$& persist
30799 throughout an SMTP connection. They are never reset. Thus, a value that is set
30800 while receiving one message is still available when receiving the next message
30801 on the same SMTP connection.
30803 The values of those variables whose names begin with &$acl_m$& persist only
30804 while a message is being received. They are reset afterwards. They are also
30805 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
30808 When a message is accepted, the current values of all the ACL variables are
30809 preserved with the message and are subsequently made available at delivery
30810 time. The ACL variables are set by a modifier called &%set%&. For example:
30812 accept hosts = whatever
30813 set acl_m4 = some value
30814 accept authenticated = *
30815 set acl_c_auth = yes
30817 &*Note*&: A leading dollar sign is not used when naming a variable that is to
30818 be set. If you want to set a variable without taking any action, you can use a
30819 &%warn%& verb without any other modifiers or conditions.
30821 .oindex &%strict_acl_vars%&
30822 What happens if a syntactically valid but undefined ACL variable is
30823 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
30824 false (the default), an empty string is substituted; if it is true, an
30825 error is generated.
30827 Versions of Exim before 4.64 have a limited set of numbered variables, but
30828 their names are compatible, so there is no problem with upgrading.
30831 .section "Condition and modifier processing" "SECTcondmodproc"
30832 .cindex "&ACL;" "conditions; processing"
30833 .cindex "&ACL;" "modifiers; processing"
30834 An exclamation mark preceding a condition negates its result. For example:
30836 deny domains = *.dom.example
30837 !verify = recipient
30839 causes the ACL to return &"deny"& if the recipient domain ends in
30840 &'dom.example'& and the recipient address cannot be verified. Sometimes
30841 negation can be used on the right-hand side of a condition. For example, these
30842 two statements are equivalent:
30844 deny hosts = !192.168.3.4
30845 deny !hosts = 192.168.3.4
30847 However, for many conditions (&%verify%& being a good example), only left-hand
30848 side negation of the whole condition is possible.
30850 The arguments of conditions and modifiers are expanded. A forced failure
30851 of an expansion causes a condition to be ignored, that is, it behaves as if the
30852 condition is true. Consider these two statements:
30854 accept senders = ${lookup{$host_name}lsearch\
30855 {/some/file}{$value}fail}
30856 accept senders = ${lookup{$host_name}lsearch\
30857 {/some/file}{$value}{}}
30859 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
30860 the returned list is searched, but if the lookup fails the behaviour is
30861 different in the two cases. The &%fail%& in the first statement causes the
30862 condition to be ignored, leaving no further conditions. The &%accept%& verb
30863 therefore succeeds. The second statement, however, generates an empty list when
30864 the lookup fails. No sender can match an empty list, so the condition fails,
30865 and therefore the &%accept%& also fails.
30867 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
30868 specify actions that are taken as the conditions for a statement are checked;
30869 others specify text for messages that are used when access is denied or a
30870 warning is generated. The &%control%& modifier affects the way an incoming
30871 message is handled.
30873 The positioning of the modifiers in an ACL statement is important, because the
30874 processing of a verb ceases as soon as its outcome is known. Only those
30875 modifiers that have already been encountered will take effect. For example,
30876 consider this use of the &%message%& modifier:
30878 require message = Can't verify sender
30880 message = Can't verify recipient
30882 message = This message cannot be used
30884 If sender verification fails, Exim knows that the result of the statement is
30885 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
30886 so its text is used as the error message. If sender verification succeeds, but
30887 recipient verification fails, the second message is used. If recipient
30888 verification succeeds, the third message becomes &"current"&, but is never used
30889 because there are no more conditions to cause failure.
30891 For the &%deny%& verb, on the other hand, it is always the last &%message%&
30892 modifier that is used, because all the conditions must be true for rejection to
30893 happen. Specifying more than one &%message%& modifier does not make sense, and
30894 the message can even be specified after all the conditions. For example:
30897 !senders = *@my.domain.example
30898 message = Invalid sender from client host
30900 The &"deny"& result does not happen until the end of the statement is reached,
30901 by which time Exim has set up the message.
30905 .section "ACL modifiers" "SECTACLmodi"
30906 .cindex "&ACL;" "modifiers; list of"
30907 The ACL modifiers are as follows:
30910 .vitem &*add_header*&&~=&~<&'text'&>
30911 This modifier specifies one or more header lines that are to be added to an
30912 incoming message, assuming, of course, that the message is ultimately
30913 accepted. For details, see section &<<SECTaddheadacl>>&.
30915 .vitem &*continue*&&~=&~<&'text'&>
30916 .cindex "&%continue%& ACL modifier"
30917 .cindex "database" "updating in ACL"
30918 This modifier does nothing of itself, and processing of the ACL always
30919 continues with the next condition or modifier. The value of &%continue%& is in
30920 the side effects of expanding its argument. Typically this could be used to
30921 update a database. It is really just a syntactic tidiness, to avoid having to
30922 write rather ugly lines like this:
30924 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
30926 Instead, all you need is
30928 &`continue = `&<&'some expansion'&>
30931 .vitem &*control*&&~=&~<&'text'&>
30932 .cindex "&%control%& ACL modifier"
30933 This modifier affects the subsequent processing of the SMTP connection or of an
30934 incoming message that is accepted. The effect of the first type of control
30935 lasts for the duration of the connection, whereas the effect of the second type
30936 lasts only until the current message has been received. The message-specific
30937 controls always apply to the whole message, not to individual recipients,
30938 even if the &%control%& modifier appears in a RCPT ACL.
30940 As there are now quite a few controls that can be applied, they are described
30941 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
30942 in several different ways. For example:
30944 . ==== As this is a nested list, any displays it contains must be indented
30945 . ==== as otherwise they are too far to the left. That comment applies only
30946 . ==== when xmlto and fop are used; formatting with sdop gets it right either
30950 It can be at the end of an &%accept%& statement:
30952 accept ...some conditions
30955 In this case, the control is applied when this statement yields &"accept"&, in
30956 other words, when the conditions are all true.
30959 It can be in the middle of an &%accept%& statement:
30961 accept ...some conditions...
30963 ...some more conditions...
30965 If the first set of conditions are true, the control is applied, even if the
30966 statement does not accept because one of the second set of conditions is false.
30967 In this case, some subsequent statement must yield &"accept"& for the control
30971 It can be used with &%warn%& to apply the control, leaving the
30972 decision about accepting or denying to a subsequent verb. For
30975 warn ...some conditions...
30979 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
30980 &%logwrite%&, so it does not add anything to the message and does not write a
30984 If you want to apply a control unconditionally, you can use it with a
30985 &%require%& verb. For example:
30987 require control = no_multiline_responses
30991 .vitem &*delay*&&~=&~<&'time'&>
30992 .cindex "&%delay%& ACL modifier"
30994 This modifier may appear in any ACL except notquit. It causes Exim to wait for
30995 the time interval before proceeding. However, when testing Exim using the
30996 &%-bh%& option, the delay is not actually imposed (an appropriate message is
30997 output instead). The time is given in the usual Exim notation, and the delay
30998 happens as soon as the modifier is processed. In an SMTP session, pending
30999 output is flushed before the delay is imposed.
31001 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
31004 deny ...some conditions...
31007 The delay happens if all the conditions are true, before the statement returns
31008 &"deny"&. Compare this with:
31011 ...some conditions...
31013 which waits for 30s before processing the conditions. The &%delay%& modifier
31014 can also be used with &%warn%& and together with &%control%&:
31016 warn ...some conditions...
31022 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
31023 responses to several commands are no longer buffered and sent in one packet (as
31024 they would normally be) because all output is flushed before imposing the
31025 delay. This optimization is disabled so that a number of small delays do not
31026 appear to the client as one large aggregated delay that might provoke an
31027 unwanted timeout. You can, however, disable output flushing for &%delay%& by
31028 using a &%control%& modifier to set &%no_delay_flush%&.
31032 .cindex "&%endpass%& ACL modifier"
31033 This modifier, which has no argument, is recognized only in &%accept%& and
31034 &%discard%& statements. It marks the boundary between the conditions whose
31035 failure causes control to pass to the next statement, and the conditions whose
31036 failure causes the ACL to return &"deny"&. This concept has proved to be
31037 confusing to some people, so the use of &%endpass%& is no longer recommended as
31038 &"best practice"&. See the description of &%accept%& above for more details.
31041 .vitem &*log_message*&&~=&~<&'text'&>
31042 .cindex "&%log_message%& ACL modifier"
31043 This modifier sets up a message that is used as part of the log message if the
31044 ACL denies access or a &%warn%& statement's conditions are true. For example:
31046 require log_message = wrong cipher suite $tls_in_cipher
31047 encrypted = DES-CBC3-SHA
31049 &%log_message%& is also used when recipients are discarded by &%discard%&. For
31052 &`discard `&<&'some conditions'&>
31053 &` log_message = Discarded $local_part@$domain because...`&
31055 When access is denied, &%log_message%& adds to any underlying error message
31056 that may exist because of a condition failure. For example, while verifying a
31057 recipient address, a &':fail:'& redirection might have already set up a
31060 The message may be defined before the conditions to which it applies, because
31061 the string expansion does not happen until Exim decides that access is to be
31062 denied. This means that any variables that are set by the condition are
31063 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
31064 variables are set after a DNS black list lookup succeeds. If the expansion of
31065 &%log_message%& fails, or if the result is an empty string, the modifier is
31068 .vindex "&$acl_verify_message$&"
31069 If you want to use a &%warn%& statement to log the result of an address
31070 verification, you can use &$acl_verify_message$& to include the verification
31073 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
31074 the start of the logged message. If the same warning log message is requested
31075 more than once while receiving a single email message, only one copy is
31076 actually logged. If you want to log multiple copies, use &%logwrite%& instead
31077 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
31078 is logged for a successful &%warn%& statement.
31080 If &%log_message%& is not present and there is no underlying error message (for
31081 example, from the failure of address verification), but &%message%& is present,
31082 the &%message%& text is used for logging rejections. However, if any text for
31083 logging contains newlines, only the first line is logged. In the absence of
31084 both &%log_message%& and &%message%&, a default built-in message is used for
31085 logging rejections.
31088 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
31089 .cindex "&%log_reject_target%& ACL modifier"
31090 .cindex "logging in ACL" "specifying which log"
31091 This modifier makes it possible to specify which logs are used for messages
31092 about ACL rejections. Its argument is a colon-separated list of words that can
31093 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
31094 may be empty, in which case a rejection is not logged at all. For example, this
31095 ACL fragment writes no logging information when access is denied:
31097 &`deny `&<&'some conditions'&>
31098 &` log_reject_target =`&
31100 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
31101 permanent and temporary rejections. Its effect lasts for the rest of the
31105 .vitem &*logwrite*&&~=&~<&'text'&>
31106 .cindex "&%logwrite%& ACL modifier"
31107 .cindex "logging in ACL" "immediate"
31108 This modifier writes a message to a log file as soon as it is encountered when
31109 processing an ACL. (Compare &%log_message%&, which, except in the case of
31110 &%warn%& and &%discard%&, is used only if the ACL statement denies
31111 access.) The &%logwrite%& modifier can be used to log special incidents in
31114 &`accept `&<&'some special conditions'&>
31115 &` control = freeze`&
31116 &` logwrite = froze message because ...`&
31118 By default, the message is written to the main log. However, it may begin
31119 with a colon, followed by a comma-separated list of log names, and then
31120 another colon, to specify exactly which logs are to be written. For
31123 logwrite = :main,reject: text for main and reject logs
31124 logwrite = :panic: text for panic log only
31128 .vitem &*message*&&~=&~<&'text'&>
31129 .cindex "&%message%& ACL modifier"
31130 This modifier sets up a text string that is expanded and used as a response
31131 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
31132 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
31133 there is some complication if &%endpass%& is involved; see the description of
31134 &%accept%& for details.)
31136 The expansion of the message happens at the time Exim decides that the ACL is
31137 to end, not at the time it processes &%message%&. If the expansion fails, or
31138 generates an empty string, the modifier is ignored. Here is an example where
31139 &%message%& must be specified first, because the ACL ends with a rejection if
31140 the &%hosts%& condition fails:
31142 require message = Host not recognized
31145 (Once a condition has failed, no further conditions or modifiers are
31148 .cindex "SMTP" "error codes"
31149 .oindex "&%smtp_banner%&
31150 For ACLs that are triggered by SMTP commands, the message is returned as part
31151 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
31152 is meaningful only for SMTP, as no message is returned when a non-SMTP message
31153 is accepted. In the case of the connect ACL, accepting with a message modifier
31154 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
31155 accept message may not contain more than one line (otherwise it will be
31156 truncated at the first newline and a panic logged), and it cannot affect the
31159 When SMTP is involved, the message may begin with an overriding response code,
31160 consisting of three digits optionally followed by an &"extended response code"&
31161 of the form &'n.n.n'&, each code being followed by a space. For example:
31163 deny message = 599 1.2.3 Host not welcome
31164 hosts = 192.168.34.0/24
31166 The first digit of the supplied response code must be the same as would be sent
31167 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
31168 access, but for the predata ACL, note that the default success code is 354, not
31171 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
31172 the message modifier cannot override the 221 response code.
31174 The text in a &%message%& modifier is literal; any quotes are taken as
31175 literals, but because the string is expanded, backslash escapes are processed
31176 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
31179 .vindex "&$acl_verify_message$&"
31180 For ACLs that are called by an &%acl =%& ACL condition, the message is
31181 stored in &$acl_verify_message$&, from which the calling ACL may use it.
31183 If &%message%& is used on a statement that verifies an address, the message
31184 specified overrides any message that is generated by the verification process.
31185 However, the original message is available in the variable
31186 &$acl_verify_message$&, so you can incorporate it into your message if you
31187 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
31188 routers to be passed back as part of the SMTP response, you should either not
31189 use a &%message%& modifier, or make use of &$acl_verify_message$&.
31191 For compatibility with previous releases of Exim, a &%message%& modifier that
31192 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
31193 modifier, but this usage is now deprecated. However, &%message%& acts only when
31194 all the conditions are true, wherever it appears in an ACL command, whereas
31195 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
31196 &%warn%& in an ACL that is not concerned with receiving a message, it has no
31200 .vitem &*queue*&&~=&~<&'text'&>
31201 .cindex "&%queue%& ACL modifier"
31202 .cindex "named queues" "selecting in ACL"
31203 This modifier specifies the use of a named queue for spool files
31205 It can only be used before the message is received (i.e. not in
31207 This could be used, for example, for known high-volume burst sources
31208 of traffic, or for quarantine of messages.
31209 Separate queue-runner processes will be needed for named queues.
31210 If the text after expansion is empty, the default queue is used.
31213 .vitem &*remove_header*&&~=&~<&'text'&>
31214 This modifier specifies one or more header names in a colon-separated list
31215 that are to be removed from an incoming message, assuming, of course, that
31216 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
31219 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
31220 .cindex "&%set%& ACL modifier"
31221 This modifier puts a value into one of the ACL variables (see section
31222 &<<SECTaclvariables>>&).
31225 .vitem &*udpsend*&&~=&~<&'parameters'&>
31226 .cindex "UDP communications"
31227 This modifier sends a UDP packet, for purposes such as statistics
31228 collection or behaviour monitoring. The parameters are expanded, and
31229 the result of the expansion must be a colon-separated list consisting
31230 of a destination server, port number, and the packet contents. The
31231 server can be specified as a host name or IPv4 or IPv6 address. The
31232 separator can be changed with the usual angle bracket syntax. For
31233 example, you might want to collect information on which hosts connect
31236 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
31237 $tod_zulu $sender_host_address
31244 .section "Use of the control modifier" "SECTcontrols"
31245 .cindex "&%control%& ACL modifier"
31246 The &%control%& modifier supports the following settings:
31249 .vitem &*control&~=&~allow_auth_unadvertised*&
31250 This modifier allows a client host to use the SMTP AUTH command even when it
31251 has not been advertised in response to EHLO. Furthermore, because there are
31252 apparently some really broken clients that do this, Exim will accept AUTH after
31253 HELO (rather than EHLO) when this control is set. It should be used only if you
31254 really need it, and you should limit its use to those broken clients that do
31255 not work without it. For example:
31257 warn hosts = 192.168.34.25
31258 control = allow_auth_unadvertised
31260 Normally, when an Exim server receives an AUTH command, it checks the name of
31261 the authentication mechanism that is given in the command to ensure that it
31262 matches an advertised mechanism. When this control is set, the check that a
31263 mechanism has been advertised is bypassed. Any configured mechanism can be used
31264 by the client. This control is permitted only in the connection and HELO ACLs.
31267 .vitem &*control&~=&~caseful_local_part*& &&&
31268 &*control&~=&~caselower_local_part*&
31269 .cindex "&ACL;" "case of local part in"
31270 .cindex "case of local parts"
31271 .vindex "&$local_part$&"
31272 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
31273 (that is, during RCPT processing). By default, the contents of &$local_part$&
31274 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
31275 any uppercase letters in the original local part are restored in &$local_part$&
31276 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
31279 These controls affect only the current recipient. Moreover, they apply only to
31280 local part handling that takes place directly in the ACL (for example, as a key
31281 in lookups). If a test to verify the recipient is obeyed, the case-related
31282 handling of the local part during the verification is controlled by the router
31283 configuration (see the &%caseful_local_part%& generic router option).
31285 This facility could be used, for example, to add a spam score to local parts
31286 containing upper case letters. For example, using &$acl_m4$& to accumulate the
31289 warn control = caseful_local_part
31290 set acl_m4 = ${eval:\
31292 ${if match{$local_part}{[A-Z]}{1}{0}}\
31294 control = caselower_local_part
31296 Notice that we put back the lower cased version afterwards, assuming that
31297 is what is wanted for subsequent tests.
31300 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
31301 .cindex "&ACL;" "cutthrough routing"
31302 .cindex "cutthrough" "requesting"
31303 This option requests delivery be attempted while the item is being received.
31305 The option is usable in the RCPT ACL.
31306 If enabled for a message received via smtp and routed to an smtp transport,
31307 and only one transport, interface, destination host and port combination
31308 is used for all recipients of the message,
31309 then the delivery connection is made while the receiving connection is open
31310 and data is copied from one to the other.
31312 An attempt to set this option for any recipient but the first
31313 for a mail will be quietly ignored.
31314 If a recipient-verify callout
31316 connection is subsequently
31317 requested in the same ACL it is held open and used for
31318 any subsequent recipients and the data,
31319 otherwise one is made after the initial RCPT ACL completes.
31321 Note that routers are used in verify mode,
31322 and cannot depend on content of received headers.
31323 Note also that headers cannot be
31324 modified by any of the post-data ACLs (DATA, MIME and DKIM).
31325 Headers may be modified by routers (subject to the above) and transports.
31326 The &'Received-By:'& header is generated as soon as the body reception starts,
31327 rather than the traditional time after the full message is received;
31328 this will affect the timestamp.
31330 All the usual ACLs are called; if one results in the message being
31331 rejected, all effort spent in delivery (including the costs on
31332 the ultimate destination) will be wasted.
31333 Note that in the case of data-time ACLs this includes the entire
31336 Cutthrough delivery is not supported via transport-filters or when DKIM signing
31337 of outgoing messages is done, because it sends data to the ultimate destination
31338 before the entire message has been received from the source.
31339 It is not supported for messages received with the SMTP PRDR
31343 Should the ultimate destination system positively accept or reject the mail,
31344 a corresponding indication is given to the source system and nothing is queued.
31345 If the item is successfully delivered in cutthrough mode
31346 the delivery log lines are tagged with ">>" rather than "=>" and appear
31347 before the acceptance "<=" line.
31349 If there is a temporary error the item is queued for later delivery in the
31351 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
31352 to the control; the default value is &"spool"& and the alternate value
31353 &"pass"& copies an SMTP defer response from the target back to the initiator
31354 and does not queue the message.
31355 Note that this is independent of any recipient verify conditions in the ACL.
31357 Delivery in this mode avoids the generation of a bounce mail to a
31359 sender when the destination system is doing content-scan based rejection.
31362 .vitem &*control&~=&~debug/*&<&'options'&>
31363 .cindex "&ACL;" "enabling debug logging"
31364 .cindex "debugging" "enabling from an ACL"
31365 This control turns on debug logging, almost as though Exim had been invoked
31366 with &`-d`&, with the output going to a new logfile in the usual logs directory,
31367 by default called &'debuglog'&.
31368 The filename can be adjusted with the &'tag'& option, which
31369 may access any variables already defined. The logging may be adjusted with
31370 the &'opts'& option, which takes the same values as the &`-d`& command-line
31372 Logging started this way may be stopped, and the file removed,
31373 with the &'kill'& option.
31374 Some examples (which depend on variables that don't exist in all
31378 control = debug/tag=.$sender_host_address
31379 control = debug/opts=+expand+acl
31380 control = debug/tag=.$message_exim_id/opts=+expand
31381 control = debug/kill
31385 .vitem &*control&~=&~dkim_disable_verify*&
31386 .cindex "disable DKIM verify"
31387 .cindex "DKIM" "disable verify"
31388 This control turns off DKIM verification processing entirely. For details on
31389 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
31392 .vitem &*control&~=&~dmarc_disable_verify*&
31393 .cindex "disable DMARC verify"
31394 .cindex "DMARC" "disable verify"
31395 This control turns off DMARC verification processing entirely. For details on
31396 the operation and configuration of DMARC, see section &<<SECDMARC>>&.
31399 .vitem &*control&~=&~dscp/*&<&'value'&>
31400 .cindex "&ACL;" "setting DSCP value"
31401 .cindex "DSCP" "inbound"
31402 This option causes the DSCP value associated with the socket for the inbound
31403 connection to be adjusted to a given value, given as one of a number of fixed
31404 strings or to numeric value.
31405 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
31406 Common values include &`throughput`&, &`mincost`&, and on newer systems
31407 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
31409 The outbound packets from Exim will be marked with this value in the header
31410 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
31411 that these values will have any effect, not be stripped by networking
31412 equipment, or do much of anything without cooperation with your Network
31413 Engineer and those of all network operators between the source and destination.
31416 .vitem &*control&~=&~enforce_sync*& &&&
31417 &*control&~=&~no_enforce_sync*&
31418 .cindex "SMTP" "synchronization checking"
31419 .cindex "synchronization checking in SMTP"
31420 These controls make it possible to be selective about when SMTP synchronization
31421 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
31422 state of the switch (it is true by default). See the description of this option
31423 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
31425 The effect of these two controls lasts for the remainder of the SMTP
31426 connection. They can appear in any ACL except the one for the non-SMTP
31427 messages. The most straightforward place to put them is in the ACL defined by
31428 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
31429 before the first synchronization check. The expected use is to turn off the
31430 synchronization checks for badly-behaved hosts that you nevertheless need to
31434 .vitem &*control&~=&~fakedefer/*&<&'message'&>
31435 .cindex "fake defer"
31436 .cindex "defer, fake"
31437 This control works in exactly the same way as &%fakereject%& (described below)
31438 except that it causes an SMTP 450 response after the message data instead of a
31439 550 response. You must take care when using &%fakedefer%& because it causes the
31440 messages to be duplicated when the sender retries. Therefore, you should not
31441 use &%fakedefer%& if the message is to be delivered normally.
31443 .vitem &*control&~=&~fakereject/*&<&'message'&>
31444 .cindex "fake rejection"
31445 .cindex "rejection, fake"
31446 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
31447 words, only when an SMTP message is being received. If Exim accepts the
31448 message, instead the final 250 response, a 550 rejection message is sent.
31449 However, Exim proceeds to deliver the message as normal. The control applies
31450 only to the current message, not to any subsequent ones that may be received in
31451 the same SMTP connection.
31453 The text for the 550 response is taken from the &%control%& modifier. If no
31454 message is supplied, the following is used:
31456 550-Your message has been rejected but is being
31457 550-kept for evaluation.
31458 550-If it was a legitimate message, it may still be
31459 550 delivered to the target recipient(s).
31461 This facility should be used with extreme caution.
31463 .vitem &*control&~=&~freeze*&
31464 .cindex "frozen messages" "forcing in ACL"
31465 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31466 other words, only when a message is being received. If the message is accepted,
31467 it is placed on Exim's queue and frozen. The control applies only to the
31468 current message, not to any subsequent ones that may be received in the same
31471 This modifier can optionally be followed by &`/no_tell`&. If the global option
31472 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
31473 is told about the freezing), provided all the &*control=freeze*& modifiers that
31474 are obeyed for the current message have the &`/no_tell`& option.
31476 .vitem &*control&~=&~no_delay_flush*&
31477 .cindex "SMTP" "output flushing, disabling for delay"
31478 Exim normally flushes SMTP output before implementing a delay in an ACL, to
31479 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31480 use. This control, as long as it is encountered before the &%delay%& modifier,
31481 disables such output flushing.
31483 .vitem &*control&~=&~no_callout_flush*&
31484 .cindex "SMTP" "output flushing, disabling for callout"
31485 Exim normally flushes SMTP output before performing a callout in an ACL, to
31486 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31487 use. This control, as long as it is encountered before the &%verify%& condition
31488 that causes the callout, disables such output flushing.
31490 .vitem &*control&~=&~no_mbox_unspool*&
31491 This control is available when Exim is compiled with the content scanning
31492 extension. Content scanning may require a copy of the current message, or parts
31493 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
31494 or spam scanner. Normally, such copies are deleted when they are no longer
31495 needed. If this control is set, the copies are not deleted. The control applies
31496 only to the current message, not to any subsequent ones that may be received in
31497 the same SMTP connection. It is provided for debugging purposes and is unlikely
31498 to be useful in production.
31500 .vitem &*control&~=&~no_multiline_responses*&
31501 .cindex "multiline responses, suppressing"
31502 This control is permitted for any ACL except the one for non-SMTP messages.
31503 It seems that there are broken clients in use that cannot handle multiline
31504 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
31506 If this control is set, multiline SMTP responses from ACL rejections are
31507 suppressed. One way of doing this would have been to put out these responses as
31508 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
31509 (&"use multiline responses for more"& it says &-- ha!), and some of the
31510 responses might get close to that. So this facility, which is after all only a
31511 sop to broken clients, is implemented by doing two very easy things:
31514 Extra information that is normally output as part of a rejection caused by
31515 sender verification failure is omitted. Only the final line (typically &"sender
31516 verification failed"&) is sent.
31518 If a &%message%& modifier supplies a multiline response, only the first
31522 The setting of the switch can, of course, be made conditional on the
31523 calling host. Its effect lasts until the end of the SMTP connection.
31525 .vitem &*control&~=&~no_pipelining*&
31526 .cindex "PIPELINING" "suppressing advertising"
31527 .cindex "ESMTP extensions" PIPELINING
31528 This control turns off the advertising of the PIPELINING extension to SMTP in
31529 the current session. To be useful, it must be obeyed before Exim sends its
31530 response to an EHLO command. Therefore, it should normally appear in an ACL
31531 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
31532 &%pipelining_advertise_hosts%&.
31534 .vitem &*control&~=&~queue/*&<&'options'&>* &&&
31535 &*control&~=&~queue_only*&
31536 .oindex "&%queue%&"
31537 .oindex "&%queue_only%&"
31538 .cindex "queueing incoming messages"
31539 .cindex queueing "forcing in ACL"
31540 .cindex "first pass routing"
31541 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31542 other words, only when a message is being received. If the message is accepted,
31543 it is placed on Exim's queue and left there for delivery by a subsequent queue
31545 If used with no options set,
31546 no immediate delivery process is started. In other words, it has the
31547 effect as the &%queue_only%& global option or &'-odq'& command-line option.
31549 If the &'first_pass_route'& option is given then
31550 the behaviour is like the command-line &'-oqds'& option;
31551 a delivery process is started which stops short of making
31552 any SMTP delivery. The benefit is that the hints database will be updated for
31553 the message being waiting for a specific host, and a later queue run will be
31554 able to send all such messages on a single connection.
31556 The control only applies to the current message, not to any subsequent ones that
31557 may be received in the same SMTP connection.
31559 .vitem &*control&~=&~submission/*&<&'options'&>
31560 .cindex "message" "submission"
31561 .cindex "submission mode"
31562 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
31563 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
31564 the current message is a submission from a local MUA. In this case, Exim
31565 operates in &"submission mode"&, and applies certain fixups to the message if
31566 necessary. For example, it adds a &'Date:'& header line if one is not present.
31567 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
31568 late (the message has already been created).
31570 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
31571 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
31572 submission mode; the available options for this control are described there.
31573 The control applies only to the current message, not to any subsequent ones
31574 that may be received in the same SMTP connection.
31576 .vitem &*control&~=&~suppress_local_fixups*&
31577 .cindex "submission fixups, suppressing"
31578 This control applies to locally submitted (non TCP/IP) messages, and is the
31579 complement of &`control = submission`&. It disables the fixups that are
31580 normally applied to locally-submitted messages. Specifically:
31583 Any &'Sender:'& header line is left alone (in this respect, it is a
31584 dynamic version of &%local_sender_retain%&).
31586 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
31588 There is no check that &'From:'& corresponds to the actual sender.
31591 This control may be useful when a remotely-originated message is accepted,
31592 passed to some scanning program, and then re-submitted for delivery. It can be
31593 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
31594 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
31597 &*Note:*& This control applies only to the current message, not to any others
31598 that are being submitted at the same time using &%-bs%& or &%-bS%&.
31600 .vitem &*control&~=&~utf8_downconvert*&
31601 This control enables conversion of UTF-8 in message envelope addresses
31603 For details see section &<<SECTi18nMTA>>&.
31607 .section "Summary of message fixup control" "SECTsummesfix"
31608 All four possibilities for message fixups can be specified:
31611 Locally submitted, fixups applied: the default.
31613 Locally submitted, no fixups applied: use
31614 &`control = suppress_local_fixups`&.
31616 Remotely submitted, no fixups applied: the default.
31618 Remotely submitted, fixups applied: use &`control = submission`&.
31623 .section "Adding header lines in ACLs" "SECTaddheadacl"
31624 .cindex "header lines" "adding in an ACL"
31625 .cindex "header lines" "position of added lines"
31626 .cindex "&%add_header%& ACL modifier"
31627 The &%add_header%& modifier can be used to add one or more extra header lines
31628 to an incoming message, as in this example:
31630 warn dnslists = sbl.spamhaus.org : \
31631 dialup.mail-abuse.org
31632 add_header = X-blacklisted-at: $dnslist_domain
31634 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31635 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31636 receiving a message). The message must ultimately be accepted for
31637 &%add_header%& to have any significant effect. You can use &%add_header%& with
31638 any ACL verb, including &%deny%& (though this is potentially useful only in a
31641 Headers will not be added to the message if the modifier is used in
31642 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31644 Leading and trailing newlines are removed from
31645 the data for the &%add_header%& modifier; if it then
31646 contains one or more newlines that
31647 are not followed by a space or a tab, it is assumed to contain multiple header
31648 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
31649 front of any line that is not a valid header line.
31651 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
31652 They are added to the message before processing the DATA and MIME ACLs.
31653 However, if an identical header line is requested more than once, only one copy
31654 is actually added to the message. Further header lines may be accumulated
31655 during the DATA and MIME ACLs, after which they are added to the message, again
31656 with duplicates suppressed. Thus, it is possible to add two identical header
31657 lines to an SMTP message, but only if one is added before DATA and one after.
31658 In the case of non-SMTP messages, new headers are accumulated during the
31659 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
31660 message is rejected after DATA or by the non-SMTP ACL, all added header lines
31661 are included in the entry that is written to the reject log.
31663 .cindex "header lines" "added; visibility of"
31664 Header lines are not visible in string expansions
31666 until they are added to the
31667 message. It follows that header lines defined in the MAIL, RCPT, and predata
31668 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
31669 header lines that are added by the DATA or MIME ACLs are not visible in those
31670 ACLs. Because of this restriction, you cannot use header lines as a way of
31671 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
31672 this, you can use ACL variables, as described in section
31673 &<<SECTaclvariables>>&.
31675 The list of headers yet to be added is given by the &%$headers_added%& variable.
31677 The &%add_header%& modifier acts immediately as it is encountered during the
31678 processing of an ACL. Notice the difference between these two cases:
31680 &`accept add_header = ADDED: some text`&
31681 &` `&<&'some condition'&>
31683 &`accept `&<&'some condition'&>
31684 &` add_header = ADDED: some text`&
31686 In the first case, the header line is always added, whether or not the
31687 condition is true. In the second case, the header line is added only if the
31688 condition is true. Multiple occurrences of &%add_header%& may occur in the same
31689 ACL statement. All those that are encountered before a condition fails are
31692 .cindex "&%warn%& ACL verb"
31693 For compatibility with previous versions of Exim, a &%message%& modifier for a
31694 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
31695 effect only if all the conditions are true, even if it appears before some of
31696 them. Furthermore, only the last occurrence of &%message%& is honoured. This
31697 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
31698 are present on a &%warn%& verb, both are processed according to their
31701 By default, new header lines are added to a message at the end of the existing
31702 header lines. However, you can specify that any particular header line should
31703 be added right at the start (before all the &'Received:'& lines), immediately
31704 after the first block of &'Received:'& lines, or immediately before any line
31705 that is not a &'Received:'& or &'Resent-something:'& header.
31707 This is done by specifying &":at_start:"&, &":after_received:"&, or
31708 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
31709 header line, respectively. (Header text cannot start with a colon, as there has
31710 to be a header name first.) For example:
31712 warn add_header = \
31713 :after_received:X-My-Header: something or other...
31715 If more than one header line is supplied in a single &%add_header%& modifier,
31716 each one is treated independently and can therefore be placed differently. If
31717 you add more than one line at the start, or after the Received: block, they end
31718 up in reverse order.
31720 &*Warning*&: This facility currently applies only to header lines that are
31721 added in an ACL. It does NOT work for header lines that are added in a
31722 system filter or in a router or transport.
31726 .section "Removing header lines in ACLs" "SECTremoveheadacl"
31727 .cindex "header lines" "removing in an ACL"
31728 .cindex "header lines" "position of removed lines"
31729 .cindex "&%remove_header%& ACL modifier"
31730 The &%remove_header%& modifier can be used to remove one or more header lines
31731 from an incoming message, as in this example:
31733 warn message = Remove internal headers
31734 remove_header = x-route-mail1 : x-route-mail2
31736 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31737 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31738 receiving a message). The message must ultimately be accepted for
31739 &%remove_header%& to have any significant effect. You can use &%remove_header%&
31740 with any ACL verb, including &%deny%&, though this is really not useful for
31741 any verb that doesn't result in a delivered message.
31743 Headers will not be removed from the message if the modifier is used in
31744 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31746 More than one header can be removed at the same time by using a colon separated
31747 list of header names. The header matching is case insensitive. Wildcards are
31748 not permitted, nor is list expansion performed, so you cannot use hostlists to
31749 create a list of headers, however both connection and message variable expansion
31750 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
31752 warn hosts = +internal_hosts
31753 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
31754 warn message = Remove internal headers
31755 remove_header = $acl_c_ihdrs
31757 Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
31758 Matching header lines are removed from the message before processing the DATA and MIME ACLs.
31759 If multiple header lines match, all are removed.
31760 There is no harm in attempting to remove the same header twice nor in removing
31761 a non-existent header. Further header lines to be removed may be accumulated
31762 during the DATA and MIME ACLs, after which they are removed from the message,
31763 if present. In the case of non-SMTP messages, headers to be removed are
31764 accumulated during the non-SMTP ACLs, and are removed from the message after
31765 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
31766 ACL, there really is no effect because there is no logging of what headers
31767 would have been removed.
31769 .cindex "header lines" "removed; visibility of"
31770 Header lines are not visible in string expansions until the DATA phase when it
31771 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
31772 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
31773 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
31774 this restriction, you cannot use header lines as a way of controlling data
31775 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
31776 you should instead use ACL variables, as described in section
31777 &<<SECTaclvariables>>&.
31779 The &%remove_header%& modifier acts immediately as it is encountered during the
31780 processing of an ACL. Notice the difference between these two cases:
31782 &`accept remove_header = X-Internal`&
31783 &` `&<&'some condition'&>
31785 &`accept `&<&'some condition'&>
31786 &` remove_header = X-Internal`&
31788 In the first case, the header line is always removed, whether or not the
31789 condition is true. In the second case, the header line is removed only if the
31790 condition is true. Multiple occurrences of &%remove_header%& may occur in the
31791 same ACL statement. All those that are encountered before a condition fails
31794 &*Warning*&: This facility currently applies only to header lines that are
31795 present during ACL processing. It does NOT remove header lines that are added
31796 in a system filter or in a router or transport.
31801 .section "ACL conditions" "SECTaclconditions"
31802 .cindex "&ACL;" "conditions; list of"
31803 Some of the conditions listed in this section are available only when Exim is
31804 compiled with the content-scanning extension. They are included here briefly
31805 for completeness. More detailed descriptions can be found in the discussion on
31806 content scanning in chapter &<<CHAPexiscan>>&.
31808 Not all conditions are relevant in all circumstances. For example, testing
31809 senders and recipients does not make sense in an ACL that is being run as the
31810 result of the arrival of an ETRN command, and checks on message headers can be
31811 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
31812 can use the same condition (with different parameters) more than once in the
31813 same ACL statement. This provides a way of specifying an &"and"& conjunction.
31814 The conditions are as follows:
31818 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
31819 .cindex "&ACL;" "nested"
31820 .cindex "&ACL;" "indirect"
31821 .cindex "&ACL;" "arguments"
31822 .cindex "&%acl%& ACL condition"
31823 The possible values of the argument are the same as for the
31824 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
31825 &"accept"& the condition is true; if it returns &"deny"& the condition is
31826 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
31827 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
31828 condition false. This means that further processing of the &%warn%& verb
31829 ceases, but processing of the ACL continues.
31831 If the argument is a named ACL, up to nine space-separated optional values
31832 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
31833 and $acl_narg is set to the count of values.
31834 Previous values of these variables are restored after the call returns.
31835 The name and values are expanded separately.
31836 Note that spaces in complex expansions which are used as arguments
31837 will act as argument separators.
31839 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
31840 the connection is dropped. If it returns &"discard"&, the verb must be
31841 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
31842 conditions are tested.
31844 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
31845 loops. This condition allows you to use different ACLs in different
31846 circumstances. For example, different ACLs can be used to handle RCPT commands
31847 for different local users or different local domains.
31849 .vitem &*authenticated&~=&~*&<&'string&~list'&>
31850 .cindex "&%authenticated%& ACL condition"
31851 .cindex "authentication" "ACL checking"
31852 .cindex "&ACL;" "testing for authentication"
31853 If the SMTP connection is not authenticated, the condition is false. Otherwise,
31854 the name of the authenticator is tested against the list. To test for
31855 authentication by any authenticator, you can set
31860 .vitem &*condition&~=&~*&<&'string'&>
31861 .cindex "&%condition%& ACL condition"
31862 .cindex "customizing" "ACL condition"
31863 .cindex "&ACL;" "customized test"
31864 .cindex "&ACL;" "testing, customized"
31865 This feature allows you to make up custom conditions. If the result of
31866 expanding the string is an empty string, the number zero, or one of the strings
31867 &"no"& or &"false"&, the condition is false. If the result is any non-zero
31868 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
31869 any other value, some error is assumed to have occurred, and the ACL returns
31870 &"defer"&. However, if the expansion is forced to fail, the condition is
31871 ignored. The effect is to treat it as true, whether it is positive or
31874 .vitem &*decode&~=&~*&<&'location'&>
31875 .cindex "&%decode%& ACL condition"
31876 This condition is available only when Exim is compiled with the
31877 content-scanning extension, and it is allowed only in the ACL defined by
31878 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
31879 If all goes well, the condition is true. It is false only if there are
31880 problems such as a syntax error or a memory shortage. For more details, see
31881 chapter &<<CHAPexiscan>>&.
31883 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
31884 .cindex "&%dnslists%& ACL condition"
31885 .cindex "DNS list" "in ACL"
31886 .cindex "black list (DNS)"
31887 .cindex "&ACL;" "testing a DNS list"
31888 This condition checks for entries in DNS black lists. These are also known as
31889 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
31890 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
31891 different variants of this condition to describe briefly here. See sections
31892 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
31894 .vitem &*domains&~=&~*&<&'domain&~list'&>
31895 .cindex "&%domains%& ACL condition"
31896 .cindex "domain" "ACL checking"
31897 .cindex "&ACL;" "testing a recipient domain"
31898 .vindex "&$domain_data$&"
31899 This condition is relevant only after a RCPT command. It checks that the domain
31900 of the recipient address is in the domain list. If percent-hack processing is
31901 enabled, it is done before this test is done. If the check succeeds with a
31902 lookup, the result of the lookup is placed in &$domain_data$& until the next
31905 &*Note carefully*& (because many people seem to fall foul of this): you cannot
31906 use &%domains%& in a DATA ACL.
31909 .vitem &*encrypted&~=&~*&<&'string&~list'&>
31910 .cindex "&%encrypted%& ACL condition"
31911 .cindex "encryption" "checking in an ACL"
31912 .cindex "&ACL;" "testing for encryption"
31913 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
31914 name of the cipher suite in use is tested against the list. To test for
31915 encryption without testing for any specific cipher suite(s), set
31921 .vitem &*hosts&~=&~*&<&'host&~list'&>
31922 .cindex "&%hosts%& ACL condition"
31923 .cindex "host" "ACL checking"
31924 .cindex "&ACL;" "testing the client host"
31925 This condition tests that the calling host matches the host list. If you have
31926 name lookups or wildcarded host names and IP addresses in the same host list,
31927 you should normally put the IP addresses first. For example, you could have:
31929 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
31931 The lookup in this example uses the host name for its key. This is implied by
31932 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
31933 and it wouldn't matter which way round you had these two items.)
31935 The reason for the problem with host names lies in the left-to-right way that
31936 Exim processes lists. It can test IP addresses without doing any DNS lookups,
31937 but when it reaches an item that requires a host name, it fails if it cannot
31938 find a host name to compare with the pattern. If the above list is given in the
31939 opposite order, the &%accept%& statement fails for a host whose name cannot be
31940 found, even if its IP address is 10.9.8.7.
31942 If you really do want to do the name check first, and still recognize the IP
31943 address even if the name lookup fails, you can rewrite the ACL like this:
31945 accept hosts = dbm;/etc/friendly/hosts
31946 accept hosts = 10.9.8.7
31948 The default action on failing to find the host name is to assume that the host
31949 is not in the list, so the first &%accept%& statement fails. The second
31950 statement can then check the IP address.
31952 .vindex "&$host_data$&"
31953 If a &%hosts%& condition is satisfied by means of a lookup, the result
31954 of the lookup is made available in the &$host_data$& variable. This
31955 allows you, for example, to set up a statement like this:
31957 deny hosts = net-lsearch;/some/file
31958 message = $host_data
31960 which gives a custom error message for each denied host.
31962 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
31963 .cindex "&%local_parts%& ACL condition"
31964 .cindex "local part" "ACL checking"
31965 .cindex "&ACL;" "testing a local part"
31966 .vindex "&$local_part_data$&"
31967 This condition is relevant only after a RCPT command. It checks that the local
31968 part of the recipient address is in the list. If percent-hack processing is
31969 enabled, it is done before this test. If the check succeeds with a lookup, the
31970 result of the lookup is placed in &$local_part_data$&, which remains set until
31971 the next &%local_parts%& test.
31973 .vitem &*malware&~=&~*&<&'option'&>
31974 .cindex "&%malware%& ACL condition"
31975 .cindex "&ACL;" "virus scanning"
31976 .cindex "&ACL;" "scanning for viruses"
31977 This condition is available only when Exim is compiled with the
31978 content-scanning extension
31979 and only after a DATA command.
31980 It causes the incoming message to be scanned for
31981 viruses. For details, see chapter &<<CHAPexiscan>>&.
31983 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
31984 .cindex "&%mime_regex%& ACL condition"
31985 .cindex "&ACL;" "testing by regex matching"
31986 This condition is available only when Exim is compiled with the
31987 content-scanning extension, and it is allowed only in the ACL defined by
31988 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
31989 with any of the regular expressions. For details, see chapter
31992 .vitem &*ratelimit&~=&~*&<&'parameters'&>
31993 .cindex "rate limiting"
31994 This condition can be used to limit the rate at which a user or host submits
31995 messages. Details are given in section &<<SECTratelimiting>>&.
31997 .vitem &*recipients&~=&~*&<&'address&~list'&>
31998 .cindex "&%recipients%& ACL condition"
31999 .cindex "recipient" "ACL checking"
32000 .cindex "&ACL;" "testing a recipient"
32001 This condition is relevant only after a RCPT command. It checks the entire
32002 recipient address against a list of recipients.
32004 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
32005 .cindex "&%regex%& ACL condition"
32006 .cindex "&ACL;" "testing by regex matching"
32007 This condition is available only when Exim is compiled with the
32008 content-scanning extension, and is available only in the DATA, MIME, and
32009 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
32010 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
32012 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
32013 .cindex "&%sender_domains%& ACL condition"
32014 .cindex "sender" "ACL checking"
32015 .cindex "&ACL;" "testing a sender domain"
32016 .vindex "&$domain$&"
32017 .vindex "&$sender_address_domain$&"
32018 This condition tests the domain of the sender of the message against the given
32019 domain list. &*Note*&: The domain of the sender address is in
32020 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
32021 of this condition. This is an exception to the general rule for testing domain
32022 lists. It is done this way so that, if this condition is used in an ACL for a
32023 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
32024 influence the sender checking.
32026 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32027 relaying, because sender addresses are easily, and commonly, forged.
32029 .vitem &*senders&~=&~*&<&'address&~list'&>
32030 .cindex "&%senders%& ACL condition"
32031 .cindex "sender" "ACL checking"
32032 .cindex "&ACL;" "testing a sender"
32033 This condition tests the sender of the message against the given list. To test
32034 for a bounce message, which has an empty sender, set
32038 &*Warning*&: It is a bad idea to use this condition on its own as a control on
32039 relaying, because sender addresses are easily, and commonly, forged.
32041 .vitem &*spam&~=&~*&<&'username'&>
32042 .cindex "&%spam%& ACL condition"
32043 .cindex "&ACL;" "scanning for spam"
32044 This condition is available only when Exim is compiled with the
32045 content-scanning extension. It causes the incoming message to be scanned by
32046 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
32048 .vitem &*verify&~=&~certificate*&
32049 .cindex "&%verify%& ACL condition"
32050 .cindex "TLS" "client certificate verification"
32051 .cindex "certificate" "verification of client"
32052 .cindex "&ACL;" "certificate verification"
32053 .cindex "&ACL;" "testing a TLS certificate"
32054 This condition is true in an SMTP session if the session is encrypted, and a
32055 certificate was received from the client, and the certificate was verified. The
32056 server requests a certificate only if the client matches &%tls_verify_hosts%&
32057 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
32059 .vitem &*verify&~=&~csa*&
32060 .cindex "CSA verification"
32061 This condition checks whether the sending host (the client) is authorized to
32062 send email. Details of how this works are given in section
32063 &<<SECTverifyCSA>>&.
32065 .vitem &*verify&~=&~header_names_ascii*&
32066 .cindex "&%verify%& ACL condition"
32067 .cindex "&ACL;" "verifying header names only ASCII"
32068 .cindex "header lines" "verifying header names only ASCII"
32069 .cindex "verifying" "header names only ASCII"
32070 This condition is relevant only in an ACL that is run after a message has been
32072 This usually means an ACL specified by &%acl_smtp_data%& or &%acl_not_smtp%&.
32073 It checks all header names (not the content) to make sure
32074 there are no non-ASCII characters, also excluding control characters. The
32075 allowable characters are decimal ASCII values 33 through 126.
32077 Exim itself will handle headers with non-ASCII characters, but it can cause
32078 problems for downstream applications, so this option will allow their
32079 detection and rejection in the DATA ACL's.
32081 .vitem &*verify&~=&~header_sender/*&<&'options'&>
32082 .cindex "&%verify%& ACL condition"
32083 .cindex "&ACL;" "verifying sender in the header"
32084 .cindex "header lines" "verifying the sender in"
32085 .cindex "sender" "verifying in header"
32086 .cindex "verifying" "sender in header"
32087 This condition is relevant only in an ACL that is run after a message has been
32088 received, that is, in an ACL specified by &%acl_smtp_data%& or
32089 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
32090 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
32091 is loosely thought of as a &"sender"& address (hence the name of the test).
32092 However, an address that appears in one of these headers need not be an address
32093 that accepts bounce messages; only sender addresses in envelopes are required
32094 to accept bounces. Therefore, if you use the callout option on this check, you
32095 might want to arrange for a non-empty address in the MAIL command.
32097 Details of address verification and the options are given later, starting at
32098 section &<<SECTaddressverification>>& (callouts are described in section
32099 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
32100 condition to restrict it to bounce messages only:
32103 !verify = header_sender
32104 message = A valid sender header is required for bounces
32107 .vitem &*verify&~=&~header_syntax*&
32108 .cindex "&%verify%& ACL condition"
32109 .cindex "&ACL;" "verifying header syntax"
32110 .cindex "header lines" "verifying syntax"
32111 .cindex "verifying" "header syntax"
32112 This condition is relevant only in an ACL that is run after a message has been
32113 received, that is, in an ACL specified by &%acl_smtp_data%& or
32114 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
32115 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
32116 and &'Bcc:'&), returning true if there are no problems.
32117 Unqualified addresses (local parts without domains) are
32118 permitted only in locally generated messages and from hosts that match
32119 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
32122 Note that this condition is a syntax check only. However, a common spamming
32123 ploy used to be to send syntactically invalid headers such as
32127 and this condition can be used to reject such messages, though they are not as
32128 common as they used to be.
32130 .vitem &*verify&~=&~helo*&
32131 .cindex "&%verify%& ACL condition"
32132 .cindex "&ACL;" "verifying HELO/EHLO"
32133 .cindex "HELO" "verifying"
32134 .cindex "EHLO" "verifying"
32135 .cindex "verifying" "EHLO"
32136 .cindex "verifying" "HELO"
32137 This condition is true if a HELO or EHLO command has been received from the
32138 client host, and its contents have been verified. If there has been no previous
32139 attempt to verify the HELO/EHLO contents, it is carried out when this
32140 condition is encountered. See the description of the &%helo_verify_hosts%& and
32141 &%helo_try_verify_hosts%& options for details of how to request verification
32142 independently of this condition, and for detail of the verification.
32144 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
32145 option), this condition is always true.
32148 .vitem &*verify&~=&~not_blind/*&<&'options'&>
32149 .cindex "verifying" "not blind"
32150 .cindex "bcc recipients, verifying none"
32151 This condition checks that there are no blind (bcc) recipients in the message.
32152 Every envelope recipient must appear either in a &'To:'& header line or in a
32153 &'Cc:'& header line for this condition to be true. Local parts are checked
32154 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
32155 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
32156 used only in a DATA or non-SMTP ACL.
32158 There is one possible option, &`case_insensitive`&. If this is present then
32159 local parts are checked case-insensitively.
32161 There are, of course, many legitimate messages that make use of blind (bcc)
32162 recipients. This check should not be used on its own for blocking messages.
32165 .vitem &*verify&~=&~recipient/*&<&'options'&>
32166 .cindex "&%verify%& ACL condition"
32167 .cindex "&ACL;" "verifying recipient"
32168 .cindex "recipient" "verifying"
32169 .cindex "verifying" "recipient"
32170 .vindex "&$address_data$&"
32171 This condition is relevant only after a RCPT command. It verifies the current
32172 recipient. Details of address verification are given later, starting at section
32173 &<<SECTaddressverification>>&. After a recipient has been verified, the value
32174 of &$address_data$& is the last value that was set while routing the address.
32175 This applies even if the verification fails. When an address that is being
32176 verified is redirected to a single address, verification continues with the new
32177 address, and in that case, the subsequent value of &$address_data$& is the
32178 value for the child address.
32180 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
32181 .cindex "&%verify%& ACL condition"
32182 .cindex "&ACL;" "verifying host reverse lookup"
32183 .cindex "host" "verifying reverse lookup"
32184 This condition ensures that a verified host name has been looked up from the IP
32185 address of the client host. (This may have happened already if the host name
32186 was needed for checking a host list, or if the host matched &%host_lookup%&.)
32187 Verification ensures that the host name obtained from a reverse DNS lookup, or
32188 one of its aliases, does, when it is itself looked up in the DNS, yield the
32189 original IP address.
32191 There is one possible option, &`defer_ok`&. If this is present and a
32192 DNS operation returns a temporary error, the verify condition succeeds.
32194 If this condition is used for a locally generated message (that is, when there
32195 is no client host involved), it always succeeds.
32197 .vitem &*verify&~=&~sender/*&<&'options'&>
32198 .cindex "&%verify%& ACL condition"
32199 .cindex "&ACL;" "verifying sender"
32200 .cindex "sender" "verifying"
32201 .cindex "verifying" "sender"
32202 This condition is relevant only after a MAIL or RCPT command, or after a
32203 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
32204 the message's sender is empty (that is, this is a bounce message), the
32205 condition is true. Otherwise, the sender address is verified.
32207 .vindex "&$address_data$&"
32208 .vindex "&$sender_address_data$&"
32209 If there is data in the &$address_data$& variable at the end of routing, its
32210 value is placed in &$sender_address_data$& at the end of verification. This
32211 value can be used in subsequent conditions and modifiers in the same ACL
32212 statement. It does not persist after the end of the current statement. If you
32213 want to preserve the value for longer, you can save it in an ACL variable.
32215 Details of verification are given later, starting at section
32216 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
32217 to avoid doing it more than once per message.
32219 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
32220 .cindex "&%verify%& ACL condition"
32221 This is a variation of the previous option, in which a modified address is
32222 verified as a sender.
32224 Note that '/' is legal in local-parts; if the address may have such
32225 (eg. is generated from the received message)
32226 they must be protected from the options parsing by doubling:
32228 verify = sender=${listquote{/}{${address:$h_sender:}}}
32234 .section "Using DNS lists" "SECTmorednslists"
32235 .cindex "DNS list" "in ACL"
32236 .cindex "black list (DNS)"
32237 .cindex "&ACL;" "testing a DNS list"
32238 In its simplest form, the &%dnslists%& condition tests whether the calling host
32239 is on at least one of a number of DNS lists by looking up the inverted IP
32240 address in one or more DNS domains. (Note that DNS list domains are not mail
32241 domains, so the &`+`& syntax for named lists doesn't work - it is used for
32242 special options instead.) For example, if the calling host's IP
32243 address is 192.168.62.43, and the ACL statement is
32245 deny dnslists = blackholes.mail-abuse.org : \
32246 dialups.mail-abuse.org
32248 the following records are looked up:
32250 43.62.168.192.blackholes.mail-abuse.org
32251 43.62.168.192.dialups.mail-abuse.org
32253 As soon as Exim finds an existing DNS record, processing of the list stops.
32254 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
32255 to test that a host is on more than one list (an &"and"& conjunction), you can
32256 use two separate conditions:
32258 deny dnslists = blackholes.mail-abuse.org
32259 dnslists = dialups.mail-abuse.org
32261 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
32262 behaves as if the host does not match the list item, that is, as if the DNS
32263 record does not exist. If there are further items in the DNS list, they are
32266 This is usually the required action when &%dnslists%& is used with &%deny%&
32267 (which is the most common usage), because it prevents a DNS failure from
32268 blocking mail. However, you can change this behaviour by putting one of the
32269 following special items in the list:
32271 &`+include_unknown `& behave as if the item is on the list
32272 &`+exclude_unknown `& behave as if the item is not on the list (default)
32273 &`+defer_unknown `& give a temporary error
32275 .cindex "&`+include_unknown`&"
32276 .cindex "&`+exclude_unknown`&"
32277 .cindex "&`+defer_unknown`&"
32278 Each of these applies to any subsequent items on the list. For example:
32280 deny dnslists = +defer_unknown : foo.bar.example
32282 Testing the list of domains stops as soon as a match is found. If you want to
32283 warn for one list and block for another, you can use two different statements:
32285 deny dnslists = blackholes.mail-abuse.org
32286 warn dnslists = dialups.mail-abuse.org
32287 message = X-Warn: sending host is on dialups list
32289 .cindex caching "of dns lookup"
32291 DNS list lookups are cached by Exim for the duration of the SMTP session
32292 (but limited by the DNS return TTL value),
32293 so a lookup based on the IP address is done at most once for any incoming
32294 connection (assuming long-enough TTL).
32295 Exim does not share information between multiple incoming
32296 connections (but your local name server cache should be active).
32298 There are a number of DNS lists to choose from, some commercial, some free,
32299 or free for small deployments. An overview can be found at
32300 &url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists).
32304 .section "Specifying the IP address for a DNS list lookup" "SECID201"
32305 .cindex "DNS list" "keyed by explicit IP address"
32306 By default, the IP address that is used in a DNS list lookup is the IP address
32307 of the calling host. However, you can specify another IP address by listing it
32308 after the domain name, introduced by a slash. For example:
32310 deny dnslists = black.list.tld/192.168.1.2
32312 This feature is not very helpful with explicit IP addresses; it is intended for
32313 use with IP addresses that are looked up, for example, the IP addresses of the
32314 MX hosts or nameservers of an email sender address. For an example, see section
32315 &<<SECTmulkeyfor>>& below.
32320 .section "DNS lists keyed on domain names" "SECID202"
32321 .cindex "DNS list" "keyed by domain name"
32322 There are some lists that are keyed on domain names rather than inverted IP
32323 addresses (see, e.g., the &'domain based zones'& link at
32324 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
32325 with these lists. You can change the name that is looked up in a DNS list by
32326 listing it after the domain name, introduced by a slash. For example,
32328 deny dnslists = dsn.rfc-ignorant.org/$sender_address_domain
32329 message = Sender's domain is listed at $dnslist_domain
32331 This particular example is useful only in ACLs that are obeyed after the
32332 RCPT or DATA commands, when a sender address is available. If (for
32333 example) the message's sender is &'user@tld.example'& the name that is looked
32334 up by this example is
32336 tld.example.dsn.rfc-ignorant.org
32338 A single &%dnslists%& condition can contain entries for both names and IP
32339 addresses. For example:
32341 deny dnslists = sbl.spamhaus.org : \
32342 dsn.rfc-ignorant.org/$sender_address_domain
32344 The first item checks the sending host's IP address; the second checks a domain
32345 name. The whole condition is true if either of the DNS lookups succeeds.
32350 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
32351 .cindex "DNS list" "multiple keys for"
32352 The syntax described above for looking up explicitly-defined values (either
32353 names or IP addresses) in a DNS blacklist is a simplification. After the domain
32354 name for the DNS list, what follows the slash can in fact be a list of items.
32355 As with all lists in Exim, the default separator is a colon. However, because
32356 this is a sublist within the list of DNS blacklist domains, it is necessary
32357 either to double the separators like this:
32359 dnslists = black.list.tld/name.1::name.2
32361 or to change the separator character, like this:
32363 dnslists = black.list.tld/<;name.1;name.2
32365 If an item in the list is an IP address, it is inverted before the DNS
32366 blacklist domain is appended. If it is not an IP address, no inversion
32367 occurs. Consider this condition:
32369 dnslists = black.list.tld/<;192.168.1.2;a.domain
32371 The DNS lookups that occur are:
32373 2.1.168.192.black.list.tld
32374 a.domain.black.list.tld
32376 Once a DNS record has been found (that matches a specific IP return
32377 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
32378 are done. If there is a temporary DNS error, the rest of the sublist of domains
32379 or IP addresses is tried. A temporary error for the whole dnslists item occurs
32380 only if no other DNS lookup in this sublist succeeds. In other words, a
32381 successful lookup for any of the items in the sublist overrides a temporary
32382 error for a previous item.
32384 The ability to supply a list of items after the slash is in some sense just a
32385 syntactic convenience. These two examples have the same effect:
32387 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
32388 dnslists = black.list.tld/a.domain::b.domain
32390 However, when the data for the list is obtained from a lookup, the second form
32391 is usually much more convenient. Consider this example:
32393 deny dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
32394 ${lookup dnsdb {>|mxh=\
32395 $sender_address_domain} }} }
32396 message = The mail servers for the domain \
32397 $sender_address_domain \
32398 are listed at $dnslist_domain ($dnslist_value); \
32401 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
32402 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
32403 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
32404 of expanding the condition might be something like this:
32406 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
32408 Thus, this example checks whether or not the IP addresses of the sender
32409 domain's mail servers are on the Spamhaus black list.
32411 The key that was used for a successful DNS list lookup is put into the variable
32412 &$dnslist_matched$& (see section &<<SECID204>>&).
32417 .section "Data returned by DNS lists" "SECID203"
32418 .cindex "DNS list" "data returned from"
32419 DNS lists are constructed using address records in the DNS. The original RBL
32420 just used the address 127.0.0.1 on the right hand side of each record, but the
32421 RBL+ list and some other lists use a number of values with different meanings.
32422 The values used on the RBL+ list are:
32426 127.1.0.3 DUL and RBL
32428 127.1.0.5 RSS and RBL
32429 127.1.0.6 RSS and DUL
32430 127.1.0.7 RSS and DUL and RBL
32432 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
32433 different values. Some DNS lists may return more than one address record;
32434 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
32437 .section "Variables set from DNS lists" "SECID204"
32438 .cindex "expansion" "variables, set from DNS list"
32439 .cindex "DNS list" "variables set from"
32440 .vindex "&$dnslist_domain$&"
32441 .vindex "&$dnslist_matched$&"
32442 .vindex "&$dnslist_text$&"
32443 .vindex "&$dnslist_value$&"
32444 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
32445 the name of the overall domain that matched (for example,
32446 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
32447 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
32448 the DNS record. When the key is an IP address, it is not reversed in
32449 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
32450 cases, for example:
32452 deny dnslists = spamhaus.example
32454 the key is also available in another variable (in this case,
32455 &$sender_host_address$&). In more complicated cases, however, this is not true.
32456 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
32457 might generate a dnslists lookup like this:
32459 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
32461 If this condition succeeds, the value in &$dnslist_matched$& might be
32462 &`192.168.6.7`& (for example).
32464 If more than one address record is returned by the DNS lookup, all the IP
32465 addresses are included in &$dnslist_value$&, separated by commas and spaces.
32466 The variable &$dnslist_text$& contains the contents of any associated TXT
32467 record. For lists such as RBL+ the TXT record for a merged entry is often not
32468 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
32471 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
32472 &-- even if these appear before the condition in the ACL, they are not
32473 expanded until after it has failed. For example:
32475 deny hosts = !+local_networks
32476 message = $sender_host_address is listed \
32478 dnslists = rbl-plus.mail-abuse.example
32483 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
32484 .cindex "DNS list" "matching specific returned data"
32485 You can add an equals sign and an IP address after a &%dnslists%& domain name
32486 in order to restrict its action to DNS records with a matching right hand side.
32489 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
32491 rejects only those hosts that yield 127.0.0.2. Without this additional data,
32492 any address record is considered to be a match. For the moment, we assume
32493 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
32494 describes how multiple records are handled.
32496 More than one IP address may be given for checking, using a comma as a
32497 separator. These are alternatives &-- if any one of them matches, the
32498 &%dnslists%& condition is true. For example:
32500 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32502 If you want to specify a constraining address list and also specify names or IP
32503 addresses to be looked up, the constraining address list must be specified
32504 first. For example:
32506 deny dnslists = dsn.rfc-ignorant.org\
32507 =127.0.0.2/$sender_address_domain
32510 If the character &`&&`& is used instead of &`=`&, the comparison for each
32511 listed IP address is done by a bitwise &"and"& instead of by an equality test.
32512 In other words, the listed addresses are used as bit masks. The comparison is
32513 true if all the bits in the mask are present in the address that is being
32514 tested. For example:
32516 dnslists = a.b.c&0.0.0.3
32518 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
32519 want to test whether one bit or another bit is present (as opposed to both
32520 being present), you must use multiple values. For example:
32522 dnslists = a.b.c&0.0.0.1,0.0.0.2
32524 matches if the final component of the address is an odd number or two times
32529 .section "Negated DNS matching conditions" "SECID205"
32530 You can supply a negative list of IP addresses as part of a &%dnslists%&
32533 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32535 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32536 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
32538 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
32540 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32541 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
32542 words, the result of the test is inverted if an exclamation mark appears before
32543 the &`=`& (or the &`&&`&) sign.
32545 &*Note*&: This kind of negation is not the same as negation in a domain,
32546 host, or address list (which is why the syntax is different).
32548 If you are using just one list, the negation syntax does not gain you much. The
32549 previous example is precisely equivalent to
32551 deny dnslists = a.b.c
32552 !dnslists = a.b.c=127.0.0.2,127.0.0.3
32554 However, if you are using multiple lists, the negation syntax is clearer.
32555 Consider this example:
32557 deny dnslists = sbl.spamhaus.org : \
32559 dnsbl.njabl.org!=127.0.0.3 : \
32562 Using only positive lists, this would have to be:
32564 deny dnslists = sbl.spamhaus.org : \
32566 deny dnslists = dnsbl.njabl.org
32567 !dnslists = dnsbl.njabl.org=127.0.0.3
32568 deny dnslists = relays.ordb.org
32570 which is less clear, and harder to maintain.
32575 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
32576 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
32577 thereby providing more than one IP address. When an item in a &%dnslists%& list
32578 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
32579 the match to specific results from the DNS lookup, there are two ways in which
32580 the checking can be handled. For example, consider the condition:
32582 dnslists = a.b.c=127.0.0.1
32584 What happens if the DNS lookup for the incoming IP address yields both
32585 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
32586 condition true because at least one given value was found, or is it false
32587 because at least one of the found values was not listed? And how does this
32588 affect negated conditions? Both possibilities are provided for with the help of
32589 additional separators &`==`& and &`=&&`&.
32592 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
32593 IP addresses matches one of the listed addresses. For the example above, the
32594 condition is true because 127.0.0.1 matches.
32596 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
32597 looked up IP addresses matches one of the listed addresses. If the condition is
32600 dnslists = a.b.c==127.0.0.1
32602 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32603 false because 127.0.0.2 is not listed. You would need to have:
32605 dnslists = a.b.c==127.0.0.1,127.0.0.2
32607 for the condition to be true.
32610 When &`!`& is used to negate IP address matching, it inverts the result, giving
32611 the precise opposite of the behaviour above. Thus:
32613 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
32614 addresses matches one of the listed addresses. Consider:
32616 dnslists = a.b.c!&0.0.0.1
32618 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32619 false because 127.0.0.1 matches.
32621 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
32622 looked up IP address that does not match. Consider:
32624 dnslists = a.b.c!=&0.0.0.1
32626 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32627 true, because 127.0.0.2 does not match. You would need to have:
32629 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
32631 for the condition to be false.
32633 When the DNS lookup yields only a single IP address, there is no difference
32634 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
32639 .section "Detailed information from merged DNS lists" "SECTmordetinf"
32640 .cindex "DNS list" "information from merged"
32641 When the facility for restricting the matching IP values in a DNS list is used,
32642 the text from the TXT record that is set in &$dnslist_text$& may not reflect
32643 the true reason for rejection. This happens when lists are merged and the IP
32644 address in the A record is used to distinguish them; unfortunately there is
32645 only one TXT record. One way round this is not to use merged lists, but that
32646 can be inefficient because it requires multiple DNS lookups where one would do
32647 in the vast majority of cases when the host of interest is not on any of the
32650 A less inefficient way of solving this problem is available. If
32651 two domain names, comma-separated, are given, the second is used first to
32652 do an initial check, making use of any IP value restrictions that are set.
32653 If there is a match, the first domain is used, without any IP value
32654 restrictions, to get the TXT record. As a byproduct of this, there is also
32655 a check that the IP being tested is indeed on the first list. The first
32656 domain is the one that is put in &$dnslist_domain$&. For example:
32659 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
32660 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32662 rejected because $sender_host_address is blacklisted \
32663 at $dnslist_domain\n$dnslist_text
32665 For the first blacklist item, this starts by doing a lookup in
32666 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
32667 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
32668 value, and as long as something is found, it looks for the corresponding TXT
32669 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
32670 The second blacklist item is processed similarly.
32672 If you are interested in more than one merged list, the same list must be
32673 given several times, but because the results of the DNS lookups are cached,
32674 the DNS calls themselves are not repeated. For example:
32677 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
32678 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
32679 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
32680 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32682 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
32683 values matches (or if no record is found), this is the only lookup that is
32684 done. Only if there is a match is one of the more specific lists consulted.
32688 .section "DNS lists and IPv6" "SECTmorednslistslast"
32689 .cindex "IPv6" "DNS black lists"
32690 .cindex "DNS list" "IPv6 usage"
32691 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
32692 nibble by nibble. For example, if the calling host's IP address is
32693 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
32695 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
32696 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
32698 (split over two lines here to fit on the page). Unfortunately, some of the DNS
32699 lists contain wildcard records, intended for IPv4, that interact badly with
32700 IPv6. For example, the DNS entry
32702 *.3.some.list.example. A 127.0.0.1
32704 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
32705 Unfortunately, it also matches the entire 3::/4 IPv6 network.
32707 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
32708 &%condition%& condition, as in this example:
32710 deny condition = ${if isip4{$sender_host_address}}
32711 dnslists = some.list.example
32714 If an explicit key is being used for a DNS lookup and it may be an IPv6
32715 address you should specify alternate list separators for both the outer
32716 (DNS list name) list and inner (lookup keys) list:
32718 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
32721 .section "Rate limiting incoming messages" "SECTratelimiting"
32722 .cindex "rate limiting" "client sending"
32723 .cindex "limiting client sending rates"
32724 .oindex "&%smtp_ratelimit_*%&"
32725 The &%ratelimit%& ACL condition can be used to measure and control the rate at
32726 which clients can send email. This is more powerful than the
32727 &%smtp_ratelimit_*%& options, because those options control the rate of
32728 commands in a single SMTP session only, whereas the &%ratelimit%& condition
32729 works across all connections (concurrent and sequential) from the same client
32730 host. The syntax of the &%ratelimit%& condition is:
32732 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
32734 If the average client sending rate is less than &'m'& messages per time
32735 period &'p'& then the condition is false; otherwise it is true.
32737 As a side-effect, the &%ratelimit%& condition sets the expansion variable
32738 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
32739 configured value of &'m'&, and &$sender_rate_period$& to the configured value
32742 The parameter &'p'& is the smoothing time constant, in the form of an Exim
32743 time interval, for example, &`8h`& for eight hours. A larger time constant
32744 means that it takes Exim longer to forget a client's past behaviour. The
32745 parameter &'m'& is the maximum number of messages that a client is permitted to
32746 send in each time interval. It also specifies the number of messages permitted
32747 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
32748 constant, you can allow a client to send more messages in a burst without
32749 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
32750 both small, messages must be sent at an even rate.
32752 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
32753 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
32754 when deploying the &%ratelimit%& ACL condition. The script prints usage
32755 instructions when it is run with no arguments.
32757 The key is used to look up the data for calculating the client's average
32758 sending rate. This data is stored in Exim's spool directory, alongside the
32759 retry and other hints databases. The default key is &$sender_host_address$&,
32760 which means Exim computes the sending rate of each client host IP address.
32761 By changing the key you can change how Exim identifies clients for the purpose
32762 of ratelimiting. For example, to limit the sending rate of each authenticated
32763 user, independent of the computer they are sending from, set the key to
32764 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
32765 example, &$authenticated_id$& is only meaningful if the client has
32766 authenticated (which you can check with the &%authenticated%& ACL condition).
32768 The lookup key does not have to identify clients: If you want to limit the
32769 rate at which a recipient receives messages, you can use the key
32770 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
32773 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
32774 specifies what Exim measures the rate of, for example, messages or recipients
32775 or bytes. You can adjust the measurement using the &%unique=%& and/or
32776 &%count=%& options. You can also control when Exim updates the recorded rate
32777 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
32778 separated by a slash, like the other parameters. They may appear in any order.
32780 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
32781 any options that alter the meaning of the stored data. The limit &'m'& is not
32782 stored, so you can alter the configured maximum rate and Exim will still
32783 remember clients' past behaviour. If you change the &%per_*%& mode or add or
32784 remove the &%unique=%& option, the lookup key changes so Exim will forget past
32785 behaviour. The lookup key is not affected by changes to the update mode and
32786 the &%count=%& option.
32789 .section "Ratelimit options for what is being measured" "ratoptmea"
32790 .cindex "rate limiting" "per_* options"
32791 The &%per_conn%& option limits the client's connection rate. It is not
32792 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
32793 &%acl_not_smtp_start%& ACLs.
32795 The &%per_mail%& option limits the client's rate of sending messages. This is
32796 the default if none of the &%per_*%& options is specified. It can be used in
32797 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
32798 &%acl_smtp_data%&, or &%acl_not_smtp%&.
32800 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
32801 the same ACLs as the &%per_mail%& option, though it is best to use this option
32802 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
32803 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
32804 in its MAIL command, which may be inaccurate or completely missing. You can
32805 follow the limit &'m'& in the configuration with K, M, or G to specify limits
32806 in kilobytes, megabytes, or gigabytes, respectively.
32808 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
32809 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
32810 &%acl_smtp_mime%&, or &%acl_smtp_data%& ACLs. In
32811 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
32812 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
32813 in either case the rate limiting engine will see a message with many
32814 recipients as a large high-speed burst.
32816 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
32817 number of different recipients that the client has sent messages to in the
32818 last time period. That is, if the client repeatedly sends messages to the same
32819 recipient, its measured rate is not increased. This option can only be used in
32822 The &%per_cmd%& option causes Exim to recompute the rate every time the
32823 condition is processed. This can be used to limit the rate of any SMTP
32824 command. If it is used in multiple ACLs it can limit the aggregate rate of
32825 multiple different commands.
32827 The &%count=%& option can be used to alter how much Exim adds to the client's
32828 measured rate. For example, the &%per_byte%& option is equivalent to
32829 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
32830 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
32831 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
32833 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
32836 .section "Ratelimit update modes" "ratoptupd"
32837 .cindex "rate limiting" "reading data without updating"
32838 You can specify one of three options with the &%ratelimit%& condition to
32839 control when its database is updated. This section describes the &%readonly%&
32840 mode, and the next section describes the &%strict%& and &%leaky%& modes.
32842 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
32843 previously-computed rate to check against the limit.
32845 For example, you can test the client's sending rate and deny it access (when
32846 it is too fast) in the connect ACL. If the client passes this check then it
32847 can go on to send a message, in which case its recorded rate will be updated
32848 in the MAIL ACL. Subsequent connections from the same client will check this
32852 deny ratelimit = 100 / 5m / readonly
32853 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
32854 (max $sender_rate_limit)
32857 warn ratelimit = 100 / 5m / strict
32858 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
32859 (max $sender_rate_limit)
32862 If Exim encounters multiple &%ratelimit%& conditions with the same key when
32863 processing a message then it may increase the client's measured rate more than
32864 it should. For example, this will happen if you check the &%per_rcpt%& option
32865 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
32866 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
32867 multiple update problems by using the &%readonly%& option on later ratelimit
32870 The &%per_*%& options described above do not make sense in some ACLs. If you
32871 use a &%per_*%& option in an ACL where it is not normally permitted then the
32872 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
32873 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
32874 next section) so you must specify the &%readonly%& option explicitly.
32877 .section "Ratelimit options for handling fast clients" "ratoptfast"
32878 .cindex "rate limiting" "strict and leaky modes"
32879 If a client's average rate is greater than the maximum, the rate limiting
32880 engine can react in two possible ways, depending on the presence of the
32881 &%strict%& or &%leaky%& update modes. This is independent of the other
32882 counter-measures (such as rejecting the message) that may be specified by the
32885 The &%leaky%& (default) option means that the client's recorded rate is not
32886 updated if it is above the limit. The effect of this is that Exim measures the
32887 client's average rate of successfully sent email,
32888 up to the given limit.
32889 This is appropriate if the countermeasure when the condition is true
32890 consists of refusing the message, and
32891 is generally the better choice if you have clients that retry automatically.
32892 If the action when true is anything more complex then this option is
32893 likely not what is wanted.
32895 The &%strict%& option means that the client's recorded rate is always
32896 updated. The effect of this is that Exim measures the client's average rate
32897 of attempts to send email, which can be much higher than the maximum it is
32898 actually allowed. If the client is over the limit it may be subjected to
32899 counter-measures by the ACL. It must slow down and allow sufficient time to
32900 pass that its computed rate falls below the maximum before it can send email
32901 again. The time (the number of smoothing periods) it must wait and not
32902 attempt to send mail can be calculated with this formula:
32904 ln(peakrate/maxrate)
32908 .section "Limiting the rate of different events" "ratoptuniq"
32909 .cindex "rate limiting" "counting unique events"
32910 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
32911 rate of different events. For example, the &%per_addr%& option uses this
32912 mechanism to count the number of different recipients that the client has
32913 sent messages to in the last time period; it is equivalent to
32914 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
32915 measure the rate that a client uses different sender addresses with the
32916 options &`per_mail/unique=$sender_address`&.
32918 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
32919 has seen for that key. The whole set is thrown away when it is older than the
32920 rate smoothing period &'p'&, so each different event is counted at most once
32921 per period. In the &%leaky%& update mode, an event that causes the client to
32922 go over the limit is not added to the set, in the same way that the client's
32923 recorded rate is not updated in the same situation.
32925 When you combine the &%unique=%& and &%readonly%& options, the specific
32926 &%unique=%& value is ignored, and Exim just retrieves the client's stored
32929 The &%unique=%& mechanism needs more space in the ratelimit database than the
32930 other &%ratelimit%& options in order to store the event set. The number of
32931 unique values is potentially as large as the rate limit, so the extra space
32932 required increases with larger limits.
32934 The uniqueification is not perfect: there is a small probability that Exim
32935 will think a new event has happened before. If the sender's rate is less than
32936 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
32937 the measured rate can go above the limit, in which case Exim may under-count
32938 events by a significant margin. Fortunately, if the rate is high enough (2.7
32939 times the limit) that the false positive rate goes above 9%, then Exim will
32940 throw away the over-full event set before the measured rate falls below the
32941 limit. Therefore the only harm should be that exceptionally high sending rates
32942 are logged incorrectly; any countermeasures you configure will be as effective
32946 .section "Using rate limiting" "useratlim"
32947 Exim's other ACL facilities are used to define what counter-measures are taken
32948 when the rate limit is exceeded. This might be anything from logging a warning
32949 (for example, while measuring existing sending rates in order to define
32950 policy), through time delays to slow down fast senders, up to rejecting the
32951 message. For example:
32953 # Log all senders' rates
32954 warn ratelimit = 0 / 1h / strict
32955 log_message = Sender rate $sender_rate / $sender_rate_period
32957 # Slow down fast senders; note the need to truncate $sender_rate
32958 # at the decimal point.
32959 warn ratelimit = 100 / 1h / per_rcpt / strict
32960 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
32961 $sender_rate_limit }s
32963 # Keep authenticated users under control
32964 deny authenticated = *
32965 ratelimit = 100 / 1d / strict / $authenticated_id
32967 # System-wide rate limit
32968 defer ratelimit = 10 / 1s / $primary_hostname
32969 message = Sorry, too busy. Try again later.
32971 # Restrict incoming rate from each host, with a default
32972 # set using a macro and special cases looked up in a table.
32973 defer ratelimit = ${lookup {$sender_host_address} \
32974 cdb {DB/ratelimits.cdb} \
32975 {$value} {RATELIMIT} }
32976 message = Sender rate exceeds $sender_rate_limit \
32977 messages per $sender_rate_period
32979 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
32980 especially with the &%per_rcpt%& option, you may suffer from a performance
32981 bottleneck caused by locking on the ratelimit hints database. Apart from
32982 making your ACLs less complicated, you can reduce the problem by using a
32983 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
32984 this means that Exim will lose its hints data after a reboot (including retry
32985 hints, the callout cache, and ratelimit data).
32989 .section "Address verification" "SECTaddressverification"
32990 .cindex "verifying address" "options for"
32991 .cindex "policy control" "address verification"
32992 Several of the &%verify%& conditions described in section
32993 &<<SECTaclconditions>>& cause addresses to be verified. Section
32994 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
32995 The verification conditions can be followed by options that modify the
32996 verification process. The options are separated from the keyword and from each
32997 other by slashes, and some of them contain parameters. For example:
32999 verify = sender/callout
33000 verify = recipient/defer_ok/callout=10s,defer_ok
33002 The first stage of address verification, which always happens, is to run the
33003 address through the routers, in &"verify mode"&. Routers can detect the
33004 difference between verification and routing for delivery, and their actions can
33005 be varied by a number of generic options such as &%verify%& and &%verify_only%&
33006 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
33007 The available options are as follows:
33010 If the &%callout%& option is specified, successful routing to one or more
33011 remote hosts is followed by a &"callout"& to those hosts as an additional
33012 check. Callouts and their sub-options are discussed in the next section.
33014 If there is a defer error while doing verification routing, the ACL
33015 normally returns &"defer"&. However, if you include &%defer_ok%& in the
33016 options, the condition is forced to be true instead. Note that this is a main
33017 verification option as well as a suboption for callouts.
33019 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
33020 discusses the reporting of sender address verification failures.
33022 The &%success_on_redirect%& option causes verification always to succeed
33023 immediately after a successful redirection. By default, if a redirection
33024 generates just one address, that address is also verified. See further
33025 discussion in section &<<SECTredirwhilveri>>&.
33028 If the &%quota%& option is specified for recipient verify,
33029 successful routing to an appendfile transport is followed by a call into
33030 the transport to evaluate the quota status for the recipient.
33031 No actual delivery is done, but verification will succeed if the quota
33032 is sufficient for the message (if the sender gave a message size) or
33033 not already exceeded (otherwise).
33037 .cindex "verifying address" "differentiating failures"
33038 .vindex "&$recipient_verify_failure$&"
33039 .vindex "&$sender_verify_failure$&"
33040 .vindex "&$acl_verify_message$&"
33041 After an address verification failure, &$acl_verify_message$& contains the
33042 error message that is associated with the failure. It can be preserved by
33045 warn !verify = sender
33046 set acl_m0 = $acl_verify_message
33048 If you are writing your own custom rejection message or log message when
33049 denying access, you can use this variable to include information about the
33050 verification failure.
33052 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
33053 appropriate) contains one of the following words:
33056 &%qualify%&: The address was unqualified (no domain), and the message
33057 was neither local nor came from an exempted host.
33059 &%route%&: Routing failed.
33061 &%mail%&: Routing succeeded, and a callout was attempted; rejection
33062 occurred at or before the MAIL command (that is, on initial
33063 connection, HELO, or MAIL).
33065 &%recipient%&: The RCPT command in a callout was rejected.
33067 &%postmaster%&: The postmaster check in a callout was rejected.
33070 &%quota%&: The quota check for a local recipient did non pass.
33073 The main use of these variables is expected to be to distinguish between
33074 rejections of MAIL and rejections of RCPT in callouts.
33076 The above variables may also be set after a &*successful*&
33077 address verification to:
33080 &%random%&: A random local-part callout succeeded
33086 .section "Callout verification" "SECTcallver"
33087 .cindex "verifying address" "by callout"
33088 .cindex "callout" "verification"
33089 .cindex "SMTP" "callout verification"
33090 For non-local addresses, routing verifies the domain, but is unable to do any
33091 checking of the local part. There are situations where some means of verifying
33092 the local part is desirable. One way this can be done is to make an SMTP
33093 &'callback'& to a delivery host for the sender address or a &'callforward'& to
33094 a subsequent host for a recipient address, to see if the host accepts the
33095 address. We use the term &'callout'& to cover both cases. Note that for a
33096 sender address, the callback is not to the client host that is trying to
33097 deliver the message, but to one of the hosts that accepts incoming mail for the
33100 Exim does not do callouts by default. If you want them to happen, you must
33101 request them by setting appropriate options on the &%verify%& condition, as
33102 described below. This facility should be used with care, because it can add a
33103 lot of resource usage to the cost of verifying an address. However, Exim does
33104 cache the results of callouts, which helps to reduce the cost. Details of
33105 caching are in section &<<SECTcallvercache>>&.
33107 Recipient callouts are usually used only between hosts that are controlled by
33108 the same administration. For example, a corporate gateway host could use
33109 callouts to check for valid recipients on an internal mailserver. A successful
33110 callout does not guarantee that a real delivery to the address would succeed;
33111 on the other hand, a failing callout does guarantee that a delivery would fail.
33113 If the &%callout%& option is present on a condition that verifies an address, a
33114 second stage of verification occurs if the address is successfully routed to
33115 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
33116 &(manualroute)& router, where the router specifies the hosts. However, if a
33117 router that does not set up hosts routes to an &(smtp)& transport with a
33118 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
33119 &%hosts_override%& set, its hosts are always used, whether or not the router
33120 supplies a host list.
33121 Callouts are only supported on &(smtp)& transports.
33123 The port that is used is taken from the transport, if it is specified and is a
33124 remote transport. (For routers that do verification only, no transport need be
33125 specified.) Otherwise, the default SMTP port is used. If a remote transport
33126 specifies an outgoing interface, this is used; otherwise the interface is not
33127 specified. Likewise, the text that is used for the HELO command is taken from
33128 the transport's &%helo_data%& option; if there is no transport, the value of
33129 &$smtp_active_hostname$& is used.
33131 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
33132 test whether a bounce message could be delivered to the sender address. The
33133 following SMTP commands are sent:
33135 &`HELO `&<&'local host name'&>
33137 &`RCPT TO:`&<&'the address to be tested'&>
33140 LHLO is used instead of HELO if the transport's &%protocol%& option is
33143 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
33146 A recipient callout check is similar. By default, it also uses an empty address
33147 for the sender. This default is chosen because most hosts do not make use of
33148 the sender address when verifying a recipient. Using the same address means
33149 that a single cache entry can be used for each recipient. Some sites, however,
33150 do make use of the sender address when verifying. These are catered for by the
33151 &%use_sender%& and &%use_postmaster%& options, described in the next section.
33153 If the response to the RCPT command is a 2&'xx'& code, the verification
33154 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
33155 Exim tries the next host, if any. If there is a problem with all the remote
33156 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
33157 &%callout%& option is given, in which case the condition is forced to succeed.
33159 .cindex "SMTP" "output flushing, disabling for callout"
33160 A callout may take a little time. For this reason, Exim normally flushes SMTP
33161 output before performing a callout in an ACL, to avoid unexpected timeouts in
33162 clients when the SMTP PIPELINING extension is in use. The flushing can be
33163 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
33168 .section "Additional parameters for callouts" "CALLaddparcall"
33169 .cindex "callout" "additional parameters for"
33170 The &%callout%& option can be followed by an equals sign and a number of
33171 optional parameters, separated by commas. For example:
33173 verify = recipient/callout=10s,defer_ok
33175 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
33176 separate verify options, is retained for backwards compatibility, but is now
33177 deprecated. The additional parameters for &%callout%& are as follows:
33181 .vitem <&'a&~time&~interval'&>
33182 .cindex "callout" "timeout, specifying"
33183 This specifies the timeout that applies for the callout attempt to each host.
33186 verify = sender/callout=5s
33188 The default is 30 seconds. The timeout is used for each response from the
33189 remote host. It is also used for the initial connection, unless overridden by
33190 the &%connect%& parameter.
33193 .vitem &*connect&~=&~*&<&'time&~interval'&>
33194 .cindex "callout" "connection timeout, specifying"
33195 This parameter makes it possible to set a different (usually smaller) timeout
33196 for making the SMTP connection. For example:
33198 verify = sender/callout=5s,connect=1s
33200 If not specified, this timeout defaults to the general timeout value.
33202 .vitem &*defer_ok*&
33203 .cindex "callout" "defer, action on"
33204 When this parameter is present, failure to contact any host, or any other kind
33205 of temporary error, is treated as success by the ACL. However, the cache is not
33206 updated in this circumstance.
33208 .vitem &*fullpostmaster*&
33209 .cindex "callout" "full postmaster check"
33210 This operates like the &%postmaster%& option (see below), but if the check for
33211 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
33212 accordance with the specification in RFC 2821. The RFC states that the
33213 unqualified address &'postmaster'& should be accepted.
33216 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
33217 .cindex "callout" "sender when verifying header"
33218 When verifying addresses in header lines using the &%header_sender%&
33219 verification option, Exim behaves by default as if the addresses are envelope
33220 sender addresses from a message. Callout verification therefore tests to see
33221 whether a bounce message could be delivered, by using an empty address in the
33222 MAIL command. However, it is arguable that these addresses might never be used
33223 as envelope senders, and could therefore justifiably reject bounce messages
33224 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
33225 address to use in the MAIL command. For example:
33227 require verify = header_sender/callout=mailfrom=abcd@x.y.z
33229 This parameter is available only for the &%header_sender%& verification option.
33232 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
33233 .cindex "callout" "overall timeout, specifying"
33234 This parameter sets an overall timeout for performing a callout verification.
33237 verify = sender/callout=5s,maxwait=30s
33239 This timeout defaults to four times the callout timeout for individual SMTP
33240 commands. The overall timeout applies when there is more than one host that can
33241 be tried. The timeout is checked before trying the next host. This prevents
33242 very long delays if there are a large number of hosts and all are timing out
33243 (for example, when network connections are timing out).
33246 .vitem &*no_cache*&
33247 .cindex "callout" "cache, suppressing"
33248 .cindex "caching callout, suppressing"
33249 When this parameter is given, the callout cache is neither read nor updated.
33251 .vitem &*postmaster*&
33252 .cindex "callout" "postmaster; checking"
33253 When this parameter is set, a successful callout check is followed by a similar
33254 check for the local part &'postmaster'& at the same domain. If this address is
33255 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
33256 the postmaster check is recorded in a cache record; if it is a failure, this is
33257 used to fail subsequent callouts for the domain without a connection being
33258 made, until the cache record expires.
33260 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
33261 The postmaster check uses an empty sender in the MAIL command by default.
33262 You can use this parameter to do a postmaster check using a different address.
33265 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
33267 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
33268 one overrides. The &%postmaster%& parameter is equivalent to this example:
33270 require verify = sender/callout=postmaster_mailfrom=
33272 &*Warning*&: The caching arrangements for postmaster checking do not take
33273 account of the sender address. It is assumed that either the empty address or
33274 a fixed non-empty address will be used. All that Exim remembers is that the
33275 postmaster check for the domain succeeded or failed.
33279 .cindex "callout" "&""random""& check"
33280 When this parameter is set, before doing the normal callout check, Exim does a
33281 check for a &"random"& local part at the same domain. The local part is not
33282 really random &-- it is defined by the expansion of the option
33283 &%callout_random_local_part%&, which defaults to
33285 $primary_hostname-$tod_epoch-testing
33287 The idea here is to try to determine whether the remote host accepts all local
33288 parts without checking. If it does, there is no point in doing callouts for
33289 specific local parts. If the &"random"& check succeeds, the result is saved in
33290 a cache record, and used to force the current and subsequent callout checks to
33291 succeed without a connection being made, until the cache record expires.
33293 .vitem &*use_postmaster*&
33294 .cindex "callout" "sender for recipient check"
33295 This parameter applies to recipient callouts only. For example:
33297 deny !verify = recipient/callout=use_postmaster
33299 .vindex "&$qualify_domain$&"
33300 It causes a non-empty postmaster address to be used in the MAIL command when
33301 performing the callout for the recipient, and also for a &"random"& check if
33302 that is configured. The local part of the address is &`postmaster`& and the
33303 domain is the contents of &$qualify_domain$&.
33305 .vitem &*use_sender*&
33306 This option applies to recipient callouts only. For example:
33308 require verify = recipient/callout=use_sender
33310 It causes the message's actual sender address to be used in the MAIL
33311 command when performing the callout, instead of an empty address. There is no
33312 need to use this option unless you know that the called hosts make use of the
33313 sender when checking recipients. If used indiscriminately, it reduces the
33314 usefulness of callout caching.
33317 This option applies to recipient callouts only. For example:
33319 require verify = recipient/callout=use_sender,hold
33321 It causes the connection to be held open and used for any further recipients
33322 and for eventual delivery (should that be done quickly).
33323 Doing this saves on TCP and SMTP startup costs, and TLS costs also
33324 when that is used for the connections.
33325 The advantage is only gained if there are no callout cache hits
33326 (which could be enforced by the no_cache option),
33327 if the use_sender option is used,
33328 if neither the random nor the use_postmaster option is used,
33329 and if no other callouts intervene.
33332 If you use any of the parameters that set a non-empty sender for the MAIL
33333 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
33334 &%use_sender%&), you should think about possible loops. Recipient checking is
33335 usually done between two hosts that are under the same management, and the host
33336 that receives the callouts is not normally configured to do callouts itself.
33337 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
33338 these circumstances.
33340 However, if you use a non-empty sender address for a callout to an arbitrary
33341 host, there is the likelihood that the remote host will itself initiate a
33342 callout check back to your host. As it is checking what appears to be a message
33343 sender, it is likely to use an empty address in MAIL, thus avoiding a
33344 callout loop. However, to be on the safe side it would be best to set up your
33345 own ACLs so that they do not do sender verification checks when the recipient
33346 is the address you use for header sender or postmaster callout checking.
33348 Another issue to think about when using non-empty senders for callouts is
33349 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
33350 by the sender/recipient combination; thus, for any given recipient, many more
33351 actual callouts are performed than when an empty sender or postmaster is used.
33356 .section "Callout caching" "SECTcallvercache"
33357 .cindex "hints database" "callout cache"
33358 .cindex "callout" "cache, description of"
33359 .cindex "caching" "callout"
33360 Exim caches the results of callouts in order to reduce the amount of resources
33361 used, unless you specify the &%no_cache%& parameter with the &%callout%&
33362 option. A hints database called &"callout"& is used for the cache. Two
33363 different record types are used: one records the result of a callout check for
33364 a specific address, and the other records information that applies to the
33365 entire domain (for example, that it accepts the local part &'postmaster'&).
33367 When an original callout fails, a detailed SMTP error message is given about
33368 the failure. However, for subsequent failures use the cache data, this message
33371 The expiry times for negative and positive address cache records are
33372 independent, and can be set by the global options &%callout_negative_expire%&
33373 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
33375 If a host gives a negative response to an SMTP connection, or rejects any
33376 commands up to and including
33380 (but not including the MAIL command with a non-empty address),
33381 any callout attempt is bound to fail. Exim remembers such failures in a
33382 domain cache record, which it uses to fail callouts for the domain without
33383 making new connections, until the domain record times out. There are two
33384 separate expiry times for domain cache records:
33385 &%callout_domain_negative_expire%& (default 3h) and
33386 &%callout_domain_positive_expire%& (default 7d).
33388 Domain records expire when the negative expiry time is reached if callouts
33389 cannot be made for the domain, or if the postmaster check failed.
33390 Otherwise, they expire when the positive expiry time is reached. This
33391 ensures that, for example, a host that stops accepting &"random"& local parts
33392 will eventually be noticed.
33394 The callout caching mechanism is based on the domain of the address that is
33395 being tested. If the domain routes to several hosts, it is assumed that their
33396 behaviour will be the same.
33401 .section "Quota caching" "SECTquotacache"
33402 .cindex "hints database" "quota cache"
33403 .cindex "quota" "cache, description of"
33404 .cindex "caching" "quota"
33405 Exim caches the results of quota verification
33406 in order to reduce the amount of resources used.
33407 The &"callout"& hints database is used.
33409 The default cache periods are five minutes for a positive (good) result
33410 and one hour for a negative result.
33411 To change the periods the &%quota%& option can be followed by an equals sign
33412 and a number of optional paramemters, separated by commas.
33415 verify = recipient/quota=cachepos=1h,cacheneg=1d
33417 Possible parameters are:
33419 .vitem &*cachepos&~=&~*&<&'time&~interval'&>
33420 .cindex "quota cache" "positive entry expiry, specifying"
33421 Set the lifetime for a positive cache entry.
33422 A value of zero seconds is legitimate.
33424 .vitem &*cacheneg&~=&~*&<&'time&~interval'&>
33425 .cindex "quota cache" "negative entry expiry, specifying"
33426 As above, for a negative entry.
33428 .vitem &*no_cache*&
33429 Set both positive and negative lifetimes to zero.
33432 .section "Sender address verification reporting" "SECTsenaddver"
33433 .cindex "verifying" "suppressing error details"
33434 See section &<<SECTaddressverification>>& for a general discussion of
33435 verification. When sender verification fails in an ACL, the details of the
33436 failure are given as additional output lines before the 550 response to the
33437 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
33440 MAIL FROM:<xyz@abc.example>
33442 RCPT TO:<pqr@def.example>
33443 550-Verification failed for <xyz@abc.example>
33444 550-Called: 192.168.34.43
33445 550-Sent: RCPT TO:<xyz@abc.example>
33446 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
33447 550 Sender verification failed
33449 If more than one RCPT command fails in the same way, the details are given
33450 only for the first of them. However, some administrators do not want to send
33451 out this much information. You can suppress the details by adding
33452 &`/no_details`& to the ACL statement that requests sender verification. For
33455 verify = sender/no_details
33458 .section "Redirection while verifying" "SECTredirwhilveri"
33459 .cindex "verifying" "redirection while"
33460 .cindex "address redirection" "while verifying"
33461 A dilemma arises when a local address is redirected by aliasing or forwarding
33462 during verification: should the generated addresses themselves be verified,
33463 or should the successful expansion of the original address be enough to verify
33464 it? By default, Exim takes the following pragmatic approach:
33467 When an incoming address is redirected to just one child address, verification
33468 continues with the child address, and if that fails to verify, the original
33469 verification also fails.
33471 When an incoming address is redirected to more than one child address,
33472 verification does not continue. A success result is returned.
33475 This seems the most reasonable behaviour for the common use of aliasing as a
33476 way of redirecting different local parts to the same mailbox. It means, for
33477 example, that a pair of alias entries of the form
33480 aw123: :fail: Gone away, no forwarding address
33482 work as expected, with both local parts causing verification failure. When a
33483 redirection generates more than one address, the behaviour is more like a
33484 mailing list, where the existence of the alias itself is sufficient for
33485 verification to succeed.
33487 It is possible, however, to change the default behaviour so that all successful
33488 redirections count as successful verifications, however many new addresses are
33489 generated. This is specified by the &%success_on_redirect%& verification
33490 option. For example:
33492 require verify = recipient/success_on_redirect/callout=10s
33494 In this example, verification succeeds if a router generates a new address, and
33495 the callout does not occur, because no address was routed to a remote host.
33497 When verification is being tested via the &%-bv%& option, the treatment of
33498 redirections is as just described, unless the &%-v%& or any debugging option is
33499 also specified. In that case, full verification is done for every generated
33500 address and a report is output for each of them.
33504 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
33505 .cindex "CSA" "verifying"
33506 Client SMTP Authorization is a system that allows a site to advertise
33507 which machines are and are not permitted to send email. This is done by placing
33508 special SRV records in the DNS; these are looked up using the client's HELO
33509 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
33510 Authorization checks in Exim are performed by the ACL condition:
33514 This fails if the client is not authorized. If there is a DNS problem, or if no
33515 valid CSA SRV record is found, or if the client is authorized, the condition
33516 succeeds. These three cases can be distinguished using the expansion variable
33517 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
33518 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
33519 be likely to cause problems for legitimate email.
33521 The error messages produced by the CSA code include slightly more
33522 detail. If &$csa_status$& is &"defer"&, this may be because of problems
33523 looking up the CSA SRV record, or problems looking up the CSA target
33524 address record. There are four reasons for &$csa_status$& being &"fail"&:
33527 The client's host name is explicitly not authorized.
33529 The client's IP address does not match any of the CSA target IP addresses.
33531 The client's host name is authorized but it has no valid target IP addresses
33532 (for example, the target's addresses are IPv6 and the client is using IPv4).
33534 The client's host name has no CSA SRV record but a parent domain has asserted
33535 that all subdomains must be explicitly authorized.
33538 The &%csa%& verification condition can take an argument which is the domain to
33539 use for the DNS query. The default is:
33541 verify = csa/$sender_helo_name
33543 This implementation includes an extension to CSA. If the query domain
33544 is an address literal such as [192.0.2.95], or if it is a bare IP
33545 address, Exim searches for CSA SRV records in the reverse DNS as if
33546 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
33549 verify = csa/$sender_host_address
33551 In fact, this is the check that Exim performs if the client does not say HELO.
33552 This extension can be turned off by setting the main configuration option
33553 &%dns_csa_use_reverse%& to be false.
33555 If a CSA SRV record is not found for the domain itself, a search
33556 is performed through its parent domains for a record which might be
33557 making assertions about subdomains. The maximum depth of this search is limited
33558 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
33559 default. Exim does not look for CSA SRV records in a top level domain, so the
33560 default settings handle HELO domains as long as seven
33561 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
33562 of legitimate HELO domains.
33564 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
33565 direct SRV lookups, this is not sufficient because of the extra parent domain
33566 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
33567 addresses into lookups in the reverse DNS space. The result of a successful
33570 ${lookup dnsdb {csa=$sender_helo_name}}
33572 has two space-separated fields: an authorization code and a target host name.
33573 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
33574 authorization required but absent, or &"?"& for unknown.
33579 .section "Bounce address tag validation" "SECTverifyPRVS"
33580 .cindex "BATV, verifying"
33581 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
33582 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
33583 Genuine incoming bounce messages should therefore always be addressed to
33584 recipients that have a valid tag. This scheme is a way of detecting unwanted
33585 bounce messages caused by sender address forgeries (often called &"collateral
33586 spam"&), because the recipients of such messages do not include valid tags.
33588 There are two expansion items to help with the implementation of the BATV
33589 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
33590 the original envelope sender address by using a simple key to add a hash of the
33591 address and some time-based randomizing information. The &%prvs%& expansion
33592 item creates a signed address, and the &%prvscheck%& expansion item checks one.
33593 The syntax of these expansion items is described in section
33594 &<<SECTexpansionitems>>&.
33595 The validity period on signed addresses is seven days.
33597 As an example, suppose the secret per-address keys are stored in an MySQL
33598 database. A query to look up the key for an address could be defined as a macro
33601 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
33602 WHERE sender='${quote_mysql:$prvscheck_address}'\
33605 Suppose also that the senders who make use of BATV are defined by an address
33606 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
33609 # Bounces: drop unsigned addresses for BATV senders
33611 recipients = +batv_senders
33612 message = This address does not send an unsigned reverse path
33614 # Bounces: In case of prvs-signed address, check signature.
33616 condition = ${prvscheck {$local_part@$domain}\
33617 {PRVSCHECK_SQL}{1}}
33618 !condition = $prvscheck_result
33619 message = Invalid reverse path signature.
33621 The first statement rejects recipients for bounce messages that are addressed
33622 to plain BATV sender addresses, because it is known that BATV senders do not
33623 send out messages with plain sender addresses. The second statement rejects
33624 recipients that are prvs-signed, but with invalid signatures (either because
33625 the key is wrong, or the signature has timed out).
33627 A non-prvs-signed address is not rejected by the second statement, because the
33628 &%prvscheck%& expansion yields an empty string if its first argument is not a
33629 prvs-signed address, thus causing the &%condition%& condition to be false. If
33630 the first argument is a syntactically valid prvs-signed address, the yield is
33631 the third string (in this case &"1"&), whether or not the cryptographic and
33632 timeout checks succeed. The &$prvscheck_result$& variable contains the result
33633 of the checks (empty for failure, &"1"& for success).
33635 There is one more issue you must consider when implementing prvs-signing:
33636 you have to ensure that the routers accept prvs-signed addresses and
33637 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
33638 router to remove the signature with a configuration along these lines:
33642 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
33644 This works because, if the third argument of &%prvscheck%& is empty, the result
33645 of the expansion of a prvs-signed address is the decoded value of the original
33646 address. This router should probably be the first of your routers that handles
33649 To create BATV-signed addresses in the first place, a transport of this form
33652 external_smtp_batv:
33654 return_path = ${prvs {$return_path} \
33655 {${lookup mysql{SELECT \
33656 secret FROM batv_prvs WHERE \
33657 sender='${quote_mysql:$sender_address}'} \
33660 If no key can be found for the existing return path, no signing takes place.
33664 .section "Using an ACL to control relaying" "SECTrelaycontrol"
33665 .cindex "&ACL;" "relay control"
33666 .cindex "relaying" "control by ACL"
33667 .cindex "policy control" "relay control"
33668 An MTA is said to &'relay'& a message if it receives it from some host and
33669 delivers it directly to another host as a result of a remote address contained
33670 within it. Redirecting a local address via an alias or forward file and then
33671 passing the message on to another host is not relaying,
33672 .cindex "&""percent hack""&"
33673 but a redirection as a result of the &"percent hack"& is.
33675 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
33676 A host which is acting as a gateway or an MX backup is concerned with incoming
33677 relaying from arbitrary hosts to a specific set of domains. On the other hand,
33678 a host which is acting as a smart host for a number of clients is concerned
33679 with outgoing relaying from those clients to the Internet at large. Often the
33680 same host is fulfilling both functions,
33682 . as illustrated in the diagram below,
33684 but in principle these two kinds of relaying are entirely independent. What is
33685 not wanted is the transmission of mail from arbitrary remote hosts through your
33686 system to arbitrary domains.
33689 You can implement relay control by means of suitable statements in the ACL that
33690 runs for each RCPT command. For convenience, it is often easiest to use
33691 Exim's named list facility to define the domains and hosts involved. For
33692 example, suppose you want to do the following:
33695 Deliver a number of domains to mailboxes on the local host (or process them
33696 locally in some other way). Let's say these are &'my.dom1.example'& and
33697 &'my.dom2.example'&.
33699 Relay mail for a number of other domains for which you are the secondary MX.
33700 These might be &'friend1.example'& and &'friend2.example'&.
33702 Relay mail from the hosts on your local LAN, to whatever domains are involved.
33703 Suppose your LAN is 192.168.45.0/24.
33707 In the main part of the configuration, you put the following definitions:
33709 domainlist local_domains = my.dom1.example : my.dom2.example
33710 domainlist relay_to_domains = friend1.example : friend2.example
33711 hostlist relay_from_hosts = 192.168.45.0/24
33713 Now you can use these definitions in the ACL that is run for every RCPT
33717 accept domains = +local_domains : +relay_to_domains
33718 accept hosts = +relay_from_hosts
33720 The first statement accepts any RCPT command that contains an address in
33721 the local or relay domains. For any other domain, control passes to the second
33722 statement, which accepts the command only if it comes from one of the relay
33723 hosts. In practice, you will probably want to make your ACL more sophisticated
33724 than this, for example, by including sender and recipient verification. The
33725 default configuration includes a more comprehensive example, which is described
33726 in chapter &<<CHAPdefconfil>>&.
33730 .section "Checking a relay configuration" "SECTcheralcon"
33731 .cindex "relaying" "checking control of"
33732 You can check the relay characteristics of your configuration in the same way
33733 that you can test any ACL behaviour for an incoming SMTP connection, by using
33734 the &%-bh%& option to run a fake SMTP session with which you interact.
33739 . ////////////////////////////////////////////////////////////////////////////
33740 . ////////////////////////////////////////////////////////////////////////////
33742 .chapter "Content scanning at ACL time" "CHAPexiscan"
33743 .scindex IIDcosca "content scanning" "at ACL time"
33744 The extension of Exim to include content scanning at ACL time, formerly known
33745 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
33746 was integrated into the main source for Exim release 4.50, and Tom continues to
33747 maintain it. Most of the wording of this chapter is taken from Tom's
33750 It is also possible to scan the content of messages at other times. The
33751 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
33752 scanning after all the ACLs have run. A transport filter can be used to scan
33753 messages at delivery time (see the &%transport_filter%& option, described in
33754 chapter &<<CHAPtransportgeneric>>&).
33756 If you want to include the ACL-time content-scanning features when you compile
33757 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
33758 &_Local/Makefile_&. When you do that, the Exim binary is built with:
33761 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
33762 for all MIME parts for SMTP and non-SMTP messages, respectively.
33764 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
33765 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
33766 run at the end of message reception (the &%acl_smtp_data%& ACL).
33768 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
33769 of messages, or parts of messages, for debugging purposes.
33771 Additional expansion variables that are set in the new ACL and by the new
33774 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
33777 Content-scanning is continually evolving, and new features are still being
33778 added. While such features are still unstable and liable to incompatible
33779 changes, they are made available in Exim by setting options whose names begin
33780 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
33781 this manual. You can find out about them by reading the file called
33782 &_doc/experimental.txt_&.
33784 All the content-scanning facilities work on a MBOX copy of the message that is
33785 temporarily created in a file called:
33787 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
33789 The &_.eml_& extension is a friendly hint to virus scanners that they can
33790 expect an MBOX-like structure inside that file. The file is created when the
33791 first content scanning facility is called. Subsequent calls to content
33792 scanning conditions open the same file again. The directory is recursively
33793 removed when the &%acl_smtp_data%& ACL has finished running, unless
33795 control = no_mbox_unspool
33797 has been encountered. When the MIME ACL decodes files, they are put into the
33798 same directory by default.
33802 .section "Scanning for viruses" "SECTscanvirus"
33803 .cindex "virus scanning"
33804 .cindex "content scanning" "for viruses"
33805 .cindex "content scanning" "the &%malware%& condition"
33806 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
33807 It supports a &"generic"& interface to scanners called via the shell, and
33808 specialized interfaces for &"daemon"& type virus scanners, which are resident
33809 in memory and thus are much faster.
33811 Since message data needs to have arrived,
33812 the condition may be only called in ACL defined by
33814 &%acl_smtp_data_prdr%&,
33815 &%acl_smtp_mime%& or
33818 A timeout of 2 minutes is applied to a scanner call (by default);
33819 if it expires then a defer action is taken.
33821 .oindex "&%av_scanner%&"
33822 You can set the &%av_scanner%& option in the main part of the configuration
33823 to specify which scanner to use, together with any additional options that
33824 are needed. The basic syntax is as follows:
33826 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
33828 If you do not set &%av_scanner%&, it defaults to
33830 av_scanner = sophie:/var/run/sophie
33832 If the value of &%av_scanner%& starts with a dollar character, it is expanded
33834 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
33835 The following scanner types are supported in this release,
33836 though individual ones can be included or not at build time:
33840 .cindex "virus scanners" "avast"
33841 This is the scanner daemon of Avast. It has been tested with Avast Core
33842 Security (currently at version 2.2.0).
33843 You can get a trial version at &url(https://www.avast.com) or for Linux
33844 at &url(https://www.avast.com/linux-server-antivirus).
33845 This scanner type takes one option,
33846 which can be either a full path to a UNIX socket,
33847 or host and port specifiers separated by white space.
33848 The host may be a name or an IP address; the port is either a
33849 single number or a pair of numbers with a dash between.
33850 A list of options may follow. These options are interpreted on the
33851 Exim's side of the malware scanner, or are given on separate lines to
33852 the daemon as options before the main scan command.
33854 .cindex &`pass_unscanned`& "avast"
33855 If &`pass_unscanned`&
33856 is set, any files the Avast scanner can't scan (e.g.
33857 decompression bombs, or invalid archives) are considered clean. Use with
33862 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
33863 av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
33864 av_scanner = avast:192.168.2.22 5036
33866 If you omit the argument, the default path
33867 &_/var/run/avast/scan.sock_&
33869 If you use a remote host,
33870 you need to make Exim's spool directory available to it,
33871 as the scanner is passed a file path, not file contents.
33872 For information about available commands and their options you may use
33874 $ socat UNIX:/var/run/avast/scan.sock STDIO:
33880 If the scanner returns a temporary failure (e.g. license issues, or
33881 permission problems), the message is deferred and a paniclog entry is
33882 written. The usual &`defer_ok`& option is available.
33884 .vitem &%aveserver%&
33885 .cindex "virus scanners" "Kaspersky"
33886 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
33887 at &url(https://www.kaspersky.com/). This scanner type takes one option,
33888 which is the path to the daemon's UNIX socket. The default is shown in this
33891 av_scanner = aveserver:/var/run/aveserver
33896 .cindex "virus scanners" "clamd"
33897 This daemon-type scanner is GPL and free. You can get it at
33898 &url(https://www.clamav.net/). Some older versions of clamd do not seem to
33899 unpack MIME containers, so it used to be recommended to unpack MIME attachments
33900 in the MIME ACL. This is no longer believed to be necessary.
33902 The options are a list of server specifiers, which may be
33903 a UNIX socket specification,
33904 a TCP socket specification,
33905 or a (global) option.
33907 A socket specification consists of a space-separated list.
33908 For a Unix socket the first element is a full path for the socket,
33909 for a TCP socket the first element is the IP address
33910 and the second a port number,
33911 Any further elements are per-server (non-global) options.
33912 These per-server options are supported:
33914 retry=<timespec> Retry on connect fail
33917 The &`retry`& option specifies a time after which a single retry for
33918 a failed connect is made. The default is to not retry.
33920 If a Unix socket file is specified, only one server is supported.
33924 av_scanner = clamd:/opt/clamd/socket
33925 av_scanner = clamd:192.0.2.3 1234
33926 av_scanner = clamd:192.0.2.3 1234:local
33927 av_scanner = clamd:192.0.2.3 1234 retry=10s
33928 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
33930 If the value of av_scanner points to a UNIX socket file or contains the
33932 option, then the ClamAV interface will pass a filename containing the data
33933 to be scanned, which should normally result in less I/O happening and be
33934 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
33935 Exim does not assume that there is a common filesystem with the remote host.
33937 The final example shows that multiple TCP targets can be specified. Exim will
33938 randomly use one for each incoming email (i.e. it load balances them). Note
33939 that only TCP targets may be used if specifying a list of scanners; a UNIX
33940 socket cannot be mixed in with TCP targets. If one of the servers becomes
33941 unavailable, Exim will try the remaining one(s) until it finds one that works.
33942 When a clamd server becomes unreachable, Exim will log a message. Exim does
33943 not keep track of scanner state between multiple messages, and the scanner
33944 selection is random, so the message will get logged in the mainlog for each
33945 email that the down scanner gets chosen first (message wrapped to be readable):
33947 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
33948 clamd: connection to localhost, port 3310 failed
33949 (Connection refused)
33952 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
33953 contributing the code for this scanner.
33956 .cindex "virus scanners" "command line interface"
33957 This is the keyword for the generic command line scanner interface. It can be
33958 used to attach virus scanners that are invoked from the shell. This scanner
33959 type takes 3 mandatory options:
33962 The full path and name of the scanner binary, with all command line options,
33963 and a placeholder (&`%s`&) for the directory to scan.
33966 A regular expression to match against the STDOUT and STDERR output of the
33967 virus scanner. If the expression matches, a virus was found. You must make
33968 absolutely sure that this expression matches on &"virus found"&. This is called
33969 the &"trigger"& expression.
33972 Another regular expression, containing exactly one pair of parentheses, to
33973 match the name of the virus found in the scanners output. This is called the
33974 &"name"& expression.
33977 For example, Sophos Sweep reports a virus on a line like this:
33979 Virus 'W32/Magistr-B' found in file ./those.bat
33981 For the trigger expression, we can match the phrase &"found in file"&. For the
33982 name expression, we want to extract the W32/Magistr-B string, so we can match
33983 for the single quotes left and right of it. Altogether, this makes the
33984 configuration setting:
33986 av_scanner = cmdline:\
33987 /path/to/sweep -ss -all -rec -archive %s:\
33988 found in file:'(.+)'
33991 .cindex "virus scanners" "DrWeb"
33992 The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface
33994 either a full path to a UNIX socket,
33995 or host and port specifiers separated by white space.
33996 The host may be a name or an IP address; the port is either a
33997 single number or a pair of numbers with a dash between.
34000 av_scanner = drweb:/var/run/drwebd.sock
34001 av_scanner = drweb:192.168.2.20 31337
34003 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
34004 is used. Thanks to Alex Miller for contributing the code for this scanner.
34007 .cindex "virus scanners" "f-protd"
34008 The f-protd scanner is accessed via HTTP over TCP.
34009 One argument is taken, being a space-separated hostname and port number
34013 av_scanner = f-protd:localhost 10200-10204
34015 If you omit the argument, the default values shown above are used.
34017 .vitem &%f-prot6d%&
34018 .cindex "virus scanners" "f-prot6d"
34019 The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
34020 One argument is taken, being a space-separated hostname and port number.
34023 av_scanner = f-prot6d:localhost 10200
34025 If you omit the argument, the default values show above are used.
34028 .cindex "virus scanners" "F-Secure"
34029 The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one
34030 argument which is the path to a UNIX socket. For example:
34032 av_scanner = fsecure:/path/to/.fsav
34034 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
34035 Thelmen for contributing the code for this scanner.
34037 .vitem &%kavdaemon%&
34038 .cindex "virus scanners" "Kaspersky"
34039 This is the scanner daemon of Kaspersky Version 4. This version of the
34040 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
34041 scanner type takes one option, which is the path to the daemon's UNIX socket.
34044 av_scanner = kavdaemon:/opt/AVP/AvpCtl
34046 The default path is &_/var/run/AvpCtl_&.
34049 .cindex "virus scanners" "mksd"
34050 This was a daemon type scanner that is aimed mainly at Polish users,
34051 though some documentation was available in English.
34052 The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir)
34053 and this appears to be a candidate for removal from Exim, unless
34054 we are informed of other virus scanners which use the same protocol
34056 The only option for this scanner type is
34057 the maximum number of processes used simultaneously to scan the attachments,
34058 provided that mksd has
34059 been run with at least the same number of child processes. For example:
34061 av_scanner = mksd:2
34063 You can safely omit this option (the default value is 1).
34066 .cindex "virus scanners" "simple socket-connected"
34067 This is a general-purpose way of talking to simple scanner daemons
34068 running on the local machine.
34069 There are four options:
34070 an address (which may be an IP address and port, or the path of a Unix socket),
34071 a commandline to send (may include a single %s which will be replaced with
34072 the path to the mail file to be scanned),
34073 an RE to trigger on from the returned data,
34074 and an RE to extract malware_name from the returned data.
34077 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
34079 Note that surrounding whitespace is stripped from each option, meaning
34080 there is no way to specify a trailing newline.
34081 The socket specifier and both regular-expressions are required.
34082 Default for the commandline is &_%s\n_& (note this does have a trailing newline);
34083 specify an empty element to get this.
34086 .cindex "virus scanners" "Sophos and Sophie"
34087 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
34088 You can get Sophie at &url(http://sophie.sourceforge.net/). The only option
34089 for this scanner type is the path to the UNIX socket that Sophie uses for
34090 client communication. For example:
34092 av_scanner = sophie:/tmp/sophie
34094 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
34098 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
34099 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
34102 The &%av_scanner%& option is expanded each time &%malware%& is called. This
34103 makes it possible to use different scanners. See further below for an example.
34104 The &%malware%& condition caches its results, so when you use it multiple times
34105 for the same message, the actual scanning process is only carried out once.
34106 However, using expandable items in &%av_scanner%& disables this caching, in
34107 which case each use of the &%malware%& condition causes a new scan of the
34110 The &%malware%& condition takes a right-hand argument that is expanded before
34111 use and taken as a list, slash-separated by default.
34112 The first element can then be one of
34115 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
34116 The condition succeeds if a virus was found, and fail otherwise. This is the
34119 &"false"& or &"0"& or an empty string, in which case no scanning is done and
34120 the condition fails immediately.
34122 A regular expression, in which case the message is scanned for viruses. The
34123 condition succeeds if a virus is found and its name matches the regular
34124 expression. This allows you to take special actions on certain types of virus.
34125 Note that &"/"& characters in the RE must be doubled due to the list-processing,
34126 unless the separator is changed (in the usual way &<<SECTlistsepchange>>&).
34129 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
34130 messages even if there is a problem with the virus scanner.
34131 Otherwise, such a problem causes the ACL to defer.
34133 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
34134 specify a non-default timeout. The default is two minutes.
34137 malware = * / defer_ok / tmo=10s
34139 A timeout causes the ACL to defer.
34141 .vindex "&$callout_address$&"
34142 When a connection is made to the scanner the expansion variable &$callout_address$&
34143 is set to record the actual address used.
34145 .vindex "&$malware_name$&"
34146 When a virus is found, the condition sets up an expansion variable called
34147 &$malware_name$& that contains the name of the virus. You can use it in a
34148 &%message%& modifier that specifies the error returned to the sender, and/or in
34151 Beware the interaction of Exim's &%message_size_limit%& with any size limits
34152 imposed by your anti-virus scanner.
34154 Here is a very simple scanning example:
34157 message = This message contains malware ($malware_name)
34159 The next example accepts messages when there is a problem with the scanner:
34161 deny malware = */defer_ok
34162 message = This message contains malware ($malware_name)
34164 The next example shows how to use an ACL variable to scan with both sophie and
34165 aveserver. It assumes you have set:
34167 av_scanner = $acl_m0
34169 in the main Exim configuration.
34171 deny set acl_m0 = sophie
34173 message = This message contains malware ($malware_name)
34175 deny set acl_m0 = aveserver
34177 message = This message contains malware ($malware_name)
34181 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
34182 .cindex "content scanning" "for spam"
34183 .cindex "spam scanning"
34184 .cindex "SpamAssassin"
34186 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
34187 score and a report for the message.
34188 Support is also provided for Rspamd.
34190 For more information about installation and configuration of SpamAssassin or
34191 Rspamd refer to their respective websites at
34192 &url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/)
34194 SpamAssassin can be installed with CPAN by running:
34196 perl -MCPAN -e 'install Mail::SpamAssassin'
34198 SpamAssassin has its own set of configuration files. Please review its
34199 documentation to see how you can tweak it. The default installation should work
34202 .oindex "&%spamd_address%&"
34203 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
34204 intend to use an instance running on the local host you do not need to set
34205 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
34206 you must set the &%spamd_address%& option in the global part of the Exim
34207 configuration as follows (example):
34209 spamd_address = 192.168.99.45 783
34211 The SpamAssassin protocol relies on a TCP half-close from the client.
34212 If your SpamAssassin client side is running a Linux system with an
34213 iptables firewall, consider setting
34214 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
34215 timeout, Exim uses when waiting for a response from the SpamAssassin
34216 server (currently defaulting to 120s). With a lower value the Linux
34217 connection tracking may consider your half-closed connection as dead too
34221 To use Rspamd (which by default listens on all local addresses
34223 you should add &%variant=rspamd%& after the address/port pair, for example:
34225 spamd_address = 127.0.0.1 11333 variant=rspamd
34228 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
34229 sockets. If you want to us these, supply &%spamd_address%& with an absolute
34230 filename instead of an address/port pair:
34232 spamd_address = /var/run/spamd_socket
34234 You can have multiple &%spamd%& servers to improve scalability. These can
34235 reside on other hardware reachable over the network. To specify multiple
34236 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
34237 option, separated with colons (the separator can be changed in the usual way &<<SECTlistsepchange>>&):
34239 spamd_address = 192.168.2.10 783 : \
34240 192.168.2.11 783 : \
34243 Up to 32 &%spamd%& servers are supported.
34244 When a server fails to respond to the connection attempt, all other
34245 servers are tried until one succeeds. If no server responds, the &%spam%&
34248 Unix and TCP socket specifications may be mixed in any order.
34249 Each element of the list is a list itself, space-separated by default
34250 and changeable in the usual way (&<<SECTlistsepchange>>&);
34251 take care to not double the separator.
34253 For TCP socket specifications a host name or IP (v4 or v6, but
34254 subject to list-separator quoting rules) address can be used,
34255 and the port can be one or a dash-separated pair.
34256 In the latter case, the range is tried in strict order.
34258 Elements after the first for Unix sockets, or second for TCP socket,
34260 The supported options are:
34262 pri=<priority> Selection priority
34263 weight=<value> Selection bias
34264 time=<start>-<end> Use only between these times of day
34265 retry=<timespec> Retry on connect fail
34266 tmo=<timespec> Connection time limit
34267 variant=rspamd Use Rspamd rather than SpamAssassin protocol
34270 The &`pri`& option specifies a priority for the server within the list,
34271 higher values being tried first.
34272 The default priority is 1.
34274 The &`weight`& option specifies a selection bias.
34275 Within a priority set
34276 servers are queried in a random fashion, weighted by this value.
34277 The default value for selection bias is 1.
34279 Time specifications for the &`time`& option are <hour>.<minute>.<second>
34280 in the local time zone; each element being one or more digits.
34281 Either the seconds or both minutes and seconds, plus the leading &`.`&
34282 characters, may be omitted and will be taken as zero.
34284 Timeout specifications for the &`retry`& and &`tmo`& options
34285 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
34287 The &`tmo`& option specifies an overall timeout for communication.
34288 The default value is two minutes.
34290 The &`retry`& option specifies a time after which a single retry for
34291 a failed connect is made.
34292 The default is to not retry.
34294 The &%spamd_address%& variable is expanded before use if it starts with
34295 a dollar sign. In this case, the expansion may return a string that is
34296 used as the list so that multiple spamd servers can be the result of an
34299 .vindex "&$callout_address$&"
34300 When a connection is made to the server the expansion variable &$callout_address$&
34301 is set to record the actual address used.
34303 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
34304 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
34307 message = This message was classified as SPAM
34309 The right-hand side of the &%spam%& condition specifies a name. This is
34310 relevant if you have set up multiple SpamAssassin profiles. If you do not want
34311 to scan using a specific profile, but rather use the SpamAssassin system-wide
34312 default profile, you can scan for an unknown name, or simply use &"nobody"&.
34313 Rspamd does not use this setting. However, you must put something on the
34316 The name allows you to use per-domain or per-user antispam profiles in
34317 principle, but this is not straightforward in practice, because a message may
34318 have multiple recipients, not necessarily all in the same domain. Because the
34319 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
34320 read the contents of the message, the variables &$local_part$& and &$domain$&
34322 Careful enforcement of single-recipient messages
34323 (e.g. by responding with defer in the recipient ACL for all recipients
34325 or the use of PRDR,
34326 .cindex "PRDR" "use for per-user SpamAssassin profiles"
34327 are needed to use this feature.
34329 The right-hand side of the &%spam%& condition is expanded before being used, so
34330 you can put lookups or conditions there. When the right-hand side evaluates to
34331 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
34334 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
34335 large ones may cause significant performance degradation. As most spam messages
34336 are quite small, it is recommended that you do not scan the big ones. For
34339 deny condition = ${if < {$message_size}{10K}}
34341 message = This message was classified as SPAM
34344 The &%spam%& condition returns true if the threshold specified in the user's
34345 SpamAssassin profile has been matched or exceeded. If you want to use the
34346 &%spam%& condition for its side effects (see the variables below), you can make
34347 it always return &"true"& by appending &`:true`& to the username.
34349 .cindex "spam scanning" "returned variables"
34350 When the &%spam%& condition is run, it sets up a number of expansion
34352 Except for &$spam_report$&,
34353 these variables are saved with the received message so are
34354 available for use at delivery time.
34357 .vitem &$spam_score$&
34358 The spam score of the message, for example, &"3.4"& or &"30.5"&. This is useful
34359 for inclusion in log or reject messages.
34361 .vitem &$spam_score_int$&
34362 The spam score of the message, multiplied by ten, as an integer value. For
34363 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
34364 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
34365 The integer value is useful for numeric comparisons in conditions.
34367 .vitem &$spam_bar$&
34368 A string consisting of a number of &"+"& or &"-"& characters, representing the
34369 integer part of the spam score value. A spam score of 4.4 would have a
34370 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
34371 headers, since MUAs can match on such strings. The maximum length of the
34372 spam bar is 50 characters.
34374 .vitem &$spam_report$&
34375 A multiline text table, containing the full SpamAssassin report for the
34376 message. Useful for inclusion in headers or reject messages.
34377 This variable is only usable in a DATA-time ACL.
34378 Beware that SpamAssassin may return non-ASCII characters, especially
34379 when running in country-specific locales, which are not legal
34380 unencoded in headers.
34382 .vitem &$spam_action$&
34383 For SpamAssassin either 'reject' or 'no action' depending on the
34384 spam score versus threshold.
34385 For Rspamd, the recommended action.
34389 The &%spam%& condition caches its results unless expansion in
34390 spamd_address was used. If you call it again with the same user name, it
34391 does not scan again, but rather returns the same values as before.
34393 The &%spam%& condition returns DEFER if there is any error while running
34394 the message through SpamAssassin or if the expansion of spamd_address
34395 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
34396 statement block), append &`/defer_ok`& to the right-hand side of the
34397 spam condition, like this:
34399 deny spam = joe/defer_ok
34400 message = This message was classified as SPAM
34402 This causes messages to be accepted even if there is a problem with &%spamd%&.
34404 Here is a longer, commented example of the use of the &%spam%&
34407 # put headers in all messages (no matter if spam or not)
34408 warn spam = nobody:true
34409 add_header = X-Spam-Score: $spam_score ($spam_bar)
34410 add_header = X-Spam-Report: $spam_report
34412 # add second subject line with *SPAM* marker when message
34413 # is over threshold
34415 add_header = Subject: *SPAM* $h_Subject:
34417 # reject spam at high scores (> 12)
34418 deny spam = nobody:true
34419 condition = ${if >{$spam_score_int}{120}{1}{0}}
34420 message = This message scored $spam_score spam points.
34425 .section "Scanning MIME parts" "SECTscanmimepart"
34426 .cindex "content scanning" "MIME parts"
34427 .cindex "MIME content scanning"
34428 .oindex "&%acl_smtp_mime%&"
34429 .oindex "&%acl_not_smtp_mime%&"
34430 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
34431 each MIME part of an SMTP message, including multipart types, in the sequence
34432 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
34433 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
34434 options may both refer to the same ACL if you want the same processing in both
34437 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
34438 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
34439 the case of a non-SMTP message. However, a MIME ACL is called only if the
34440 message contains a &'Content-Type:'& header line. When a call to a MIME
34441 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
34442 result code is sent to the client. In the case of an SMTP message, the
34443 &%acl_smtp_data%& ACL is not called when this happens.
34445 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
34446 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
34447 condition to match against the raw MIME part. You can also use the
34448 &%mime_regex%& condition to match against the decoded MIME part (see section
34449 &<<SECTscanregex>>&).
34451 At the start of a MIME ACL, a number of variables are set from the header
34452 information for the relevant MIME part. These are described below. The contents
34453 of the MIME part are not by default decoded into a disk file except for MIME
34454 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
34455 part into a disk file, you can use the &%decode%& condition. The general
34458 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
34460 The right hand side is expanded before use. After expansion,
34464 &"0"& or &"false"&, in which case no decoding is done.
34466 The string &"default"&. In that case, the file is put in the temporary
34467 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
34468 a sequential filename consisting of the message id and a sequence number. The
34469 full path and name is available in &$mime_decoded_filename$& after decoding.
34471 A full path name starting with a slash. If the full name is an existing
34472 directory, it is used as a replacement for the default directory. The filename
34473 is then sequentially assigned. If the path does not exist, it is used as
34474 the full path and filename.
34476 If the string does not start with a slash, it is used as the
34477 filename, and the default path is then used.
34479 The &%decode%& condition normally succeeds. It is only false for syntax
34480 errors or unusual circumstances such as memory shortages. You can easily decode
34481 a file with its original, proposed filename using
34483 decode = $mime_filename
34485 However, you should keep in mind that &$mime_filename$& might contain
34486 anything. If you place files outside of the default path, they are not
34487 automatically unlinked.
34489 For RFC822 attachments (these are messages attached to messages, with a
34490 content-type of &"message/rfc822"&), the ACL is called again in the same manner
34491 as for the primary message, only that the &$mime_is_rfc822$& expansion
34492 variable is set (see below). Attached messages are always decoded to disk
34493 before being checked, and the files are unlinked once the check is done.
34495 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
34496 used to match regular expressions against raw and decoded MIME parts,
34497 respectively. They are described in section &<<SECTscanregex>>&.
34499 .cindex "MIME content scanning" "returned variables"
34500 The following list describes all expansion variables that are
34501 available in the MIME ACL:
34504 .vitem &$mime_anomaly_level$& &&&
34505 &$mime_anomaly_text$&
34506 .vindex &$mime_anomaly_level$&
34507 .vindex &$mime_anomaly_text$&
34508 If there are problems decoding, these variables contain information on
34509 the detected issue.
34511 .vitem &$mime_boundary$&
34512 .vindex &$mime_boundary$&
34513 If the current part is a multipart (see &$mime_is_multipart$& below), it should
34514 have a boundary string, which is stored in this variable. If the current part
34515 has no boundary parameter in the &'Content-Type:'& header, this variable
34516 contains the empty string.
34518 .vitem &$mime_charset$&
34519 .vindex &$mime_charset$&
34520 This variable contains the character set identifier, if one was found in the
34521 &'Content-Type:'& header. Examples for charset identifiers are:
34527 Please note that this value is not normalized, so you should do matches
34528 case-insensitively.
34530 .vitem &$mime_content_description$&
34531 .vindex &$mime_content_description$&
34532 This variable contains the normalized content of the &'Content-Description:'&
34533 header. It can contain a human-readable description of the parts content. Some
34534 implementations repeat the filename for attachments here, but they are usually
34535 only used for display purposes.
34537 .vitem &$mime_content_disposition$&
34538 .vindex &$mime_content_disposition$&
34539 This variable contains the normalized content of the &'Content-Disposition:'&
34540 header. You can expect strings like &"attachment"& or &"inline"& here.
34542 .vitem &$mime_content_id$&
34543 .vindex &$mime_content_id$&
34544 This variable contains the normalized content of the &'Content-ID:'& header.
34545 This is a unique ID that can be used to reference a part from another part.
34547 .vitem &$mime_content_size$&
34548 .vindex &$mime_content_size$&
34549 This variable is set only after the &%decode%& modifier (see above) has been
34550 successfully run. It contains the size of the decoded part in kilobytes. The
34551 size is always rounded up to full kilobytes, so only a completely empty part
34552 has a &$mime_content_size$& of zero.
34554 .vitem &$mime_content_transfer_encoding$&
34555 .vindex &$mime_content_transfer_encoding$&
34556 This variable contains the normalized content of the
34557 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
34558 type. Typical values are &"base64"& and &"quoted-printable"&.
34560 .vitem &$mime_content_type$&
34561 .vindex &$mime_content_type$&
34562 If the MIME part has a &'Content-Type:'& header, this variable contains its
34563 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
34564 are some examples of popular MIME types, as they may appear in this variable:
34568 application/octet-stream
34572 If the MIME part has no &'Content-Type:'& header, this variable contains the
34575 .vitem &$mime_decoded_filename$&
34576 .vindex &$mime_decoded_filename$&
34577 This variable is set only after the &%decode%& modifier (see above) has been
34578 successfully run. It contains the full path and filename of the file
34579 containing the decoded data.
34584 .vitem &$mime_filename$&
34585 .vindex &$mime_filename$&
34586 This is perhaps the most important of the MIME variables. It contains a
34587 proposed filename for an attachment, if one was found in either the
34588 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
34591 decoded, but no additional sanity checks are done.
34593 found, this variable contains the empty string.
34595 .vitem &$mime_is_coverletter$&
34596 .vindex &$mime_is_coverletter$&
34597 This variable attempts to differentiate the &"cover letter"& of an e-mail from
34598 attached data. It can be used to clamp down on flashy or unnecessarily encoded
34599 content in the cover letter, while not restricting attachments at all.
34601 The variable contains 1 (true) for a MIME part believed to be part of the
34602 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
34606 The outermost MIME part of a message is always a cover letter.
34609 If a multipart/alternative or multipart/related MIME part is a cover letter,
34610 so are all MIME subparts within that multipart.
34613 If any other multipart is a cover letter, the first subpart is a cover letter,
34614 and the rest are attachments.
34617 All parts contained within an attachment multipart are attachments.
34620 As an example, the following will ban &"HTML mail"& (including that sent with
34621 alternative plain text), while allowing HTML files to be attached. HTML
34622 coverletter mail attached to non-HTML coverletter mail will also be allowed:
34624 deny !condition = $mime_is_rfc822
34625 condition = $mime_is_coverletter
34626 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
34627 message = HTML mail is not accepted here
34630 .vitem &$mime_is_multipart$&
34631 .vindex &$mime_is_multipart$&
34632 This variable has the value 1 (true) when the current part has the main type
34633 &"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
34634 Since multipart entities only serve as containers for other parts, you may not
34635 want to carry out specific actions on them.
34637 .vitem &$mime_is_rfc822$&
34638 .vindex &$mime_is_rfc822$&
34639 This variable has the value 1 (true) if the current part is not a part of the
34640 checked message itself, but part of an attached message. Attached message
34641 decoding is fully recursive.
34643 .vitem &$mime_part_count$&
34644 .vindex &$mime_part_count$&
34645 This variable is a counter that is raised for each processed MIME part. It
34646 starts at zero for the very first part (which is usually a multipart). The
34647 counter is per-message, so it is reset when processing RFC822 attachments (see
34648 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
34649 complete, so you can use it in the DATA ACL to determine the number of MIME
34650 parts of a message. For non-MIME messages, this variable contains the value -1.
34655 .section "Scanning with regular expressions" "SECTscanregex"
34656 .cindex "content scanning" "with regular expressions"
34657 .cindex "regular expressions" "content scanning with"
34658 You can specify your own custom regular expression matches on the full body of
34659 the message, or on individual MIME parts.
34661 The &%regex%& condition takes one or more regular expressions as arguments and
34662 matches them against the full message (when called in the DATA ACL) or a raw
34663 MIME part (when called in the MIME ACL). The &%regex%& condition matches
34664 linewise, with a maximum line length of 32K characters. That means you cannot
34665 have multiline matches with the &%regex%& condition.
34667 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
34668 to 32K of decoded content (the whole content at once, not linewise). If the
34669 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
34670 is decoded automatically when &%mime_regex%& is executed (using default path
34671 and filename values). If the decoded data is larger than 32K, only the first
34672 32K characters are checked.
34674 The regular expressions are passed as a colon-separated list. To include a
34675 literal colon, you must double it. Since the whole right-hand side string is
34676 expanded before being used, you must also escape dollar signs and backslashes
34677 with more backslashes, or use the &`\N`& facility to disable expansion.
34678 Here is a simple example that contains two regular expressions:
34680 deny regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
34681 message = contains blacklisted regex ($regex_match_string)
34683 The conditions returns true if any one of the regular expressions matches. The
34684 &$regex_match_string$& expansion variable is then set up and contains the
34685 matching regular expression.
34686 The expansion variables &$regex1$& &$regex2$& etc
34687 are set to any substrings captured by the regular expression.
34689 &*Warning*&: With large messages, these conditions can be fairly
34697 . ////////////////////////////////////////////////////////////////////////////
34698 . ////////////////////////////////////////////////////////////////////////////
34700 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
34701 "Local scan function"
34702 .scindex IIDlosca "&[local_scan()]& function" "description of"
34703 .cindex "customizing" "input scan using C function"
34704 .cindex "policy control" "by local scan function"
34705 In these days of email worms, viruses, and ever-increasing spam, some sites
34706 want to apply a lot of checking to messages before accepting them.
34708 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
34709 passing messages to external virus and spam scanning software. You can also do
34710 a certain amount in Exim itself through string expansions and the &%condition%&
34711 condition in the ACL that runs after the SMTP DATA command or the ACL for
34712 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
34714 To allow for further customization to a site's own requirements, there is the
34715 possibility of linking Exim with a private message scanning function, written
34716 in C. If you want to run code that is written in something other than C, you
34717 can of course use a little C stub to call it.
34719 The local scan function is run once for every incoming message, at the point
34720 when Exim is just about to accept the message.
34721 It can therefore be used to control non-SMTP messages from local processes as
34722 well as messages arriving via SMTP.
34724 Exim applies a timeout to calls of the local scan function, and there is an
34725 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
34726 Zero means &"no timeout"&.
34727 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
34728 before calling the local scan function, so that the most common types of crash
34729 are caught. If the timeout is exceeded or one of those signals is caught, the
34730 incoming message is rejected with a temporary error if it is an SMTP message.
34731 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
34732 code. The incident is logged on the main and reject logs.
34736 .section "Building Exim to use a local scan function" "SECID207"
34737 .cindex "&[local_scan()]& function" "building Exim to use"
34738 To make use of the local scan function feature, you must tell Exim where your
34739 function is before building Exim, by setting
34740 both HAVE_LOCAL_SCAN and
34741 LOCAL_SCAN_SOURCE in your
34742 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
34743 directory, so you might set
34745 HAVE_LOCAL_SCAN=yes
34746 LOCAL_SCAN_SOURCE=Local/local_scan.c
34748 for example. The function must be called &[local_scan()]&;
34749 the source file(s) for it should first #define LOCAL_SCAN
34750 and then #include "local_scan.h".
34752 Exim after it has received a message, when the success return code is about to
34753 be sent. This is after all the ACLs have been run. The return code from your
34754 function controls whether the message is actually accepted or not. There is a
34755 commented template function (that just accepts the message) in the file
34756 _src/local_scan.c_.
34758 If you want to make use of Exim's runtime configuration file to set options
34759 for your &[local_scan()]& function, you must also set
34761 LOCAL_SCAN_HAS_OPTIONS=yes
34763 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
34768 .section "API for local_scan()" "SECTapiforloc"
34769 .cindex "&[local_scan()]& function" "API description"
34770 .cindex &%dlfunc%& "API description"
34771 You must include this line near the start of your code:
34774 #include "local_scan.h"
34776 This header file defines a number of variables and other values, and the
34777 prototype for the function itself. Exim is coded to use unsigned char values
34778 almost exclusively, and one of the things this header defines is a shorthand
34779 for &`unsigned char`& called &`uschar`&.
34780 It also makes available the following macro definitions, to simplify casting character
34781 strings and pointers to character strings:
34783 #define CS (char *)
34784 #define CCS (const char *)
34785 #define CSS (char **)
34786 #define US (unsigned char *)
34787 #define CUS (const unsigned char *)
34788 #define USS (unsigned char **)
34790 The function prototype for &[local_scan()]& is:
34792 extern int local_scan(int fd, uschar **return_text);
34794 The arguments are as follows:
34797 &%fd%& is a file descriptor for the file that contains the body of the message
34798 (the -D file). The file is open for reading and writing, but updating it is not
34799 recommended. &*Warning*&: You must &'not'& close this file descriptor.
34801 The descriptor is positioned at character 19 of the file, which is the first
34802 character of the body itself, because the first 19 characters are the message
34803 id followed by &`-D`& and a newline. If you rewind the file, you should use the
34804 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
34805 case this changes in some future version.
34807 &%return_text%& is an address which you can use to return a pointer to a text
34808 string at the end of the function. The value it points to on entry is NULL.
34811 The function must return an &%int%& value which is one of the following macros:
34814 .vitem &`LOCAL_SCAN_ACCEPT`&
34815 .vindex "&$local_scan_data$&"
34816 The message is accepted. If you pass back a string of text, it is saved with
34817 the message, and made available in the variable &$local_scan_data$&. No
34818 newlines are permitted (if there are any, they are turned into spaces) and the
34819 maximum length of text is 1000 characters.
34821 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
34822 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
34823 queued without immediate delivery, and is frozen.
34825 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
34826 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
34827 queued without immediate delivery.
34829 .vitem &`LOCAL_SCAN_REJECT`&
34830 The message is rejected; the returned text is used as an error message which is
34831 passed back to the sender and which is also logged. Newlines are permitted &--
34832 they cause a multiline response for SMTP rejections, but are converted to
34833 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
34836 .vitem &`LOCAL_SCAN_TEMPREJECT`&
34837 The message is temporarily rejected; the returned text is used as an error
34838 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
34841 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
34842 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
34843 message is not written to the reject log. It has the effect of unsetting the
34844 &%rejected_header%& log selector for just this rejection. If
34845 &%rejected_header%& is already unset (see the discussion of the
34846 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
34847 same as LOCAL_SCAN_REJECT.
34849 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
34850 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
34851 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
34854 If the message is not being received by interactive SMTP, rejections are
34855 reported by writing to &%stderr%& or by sending an email, as configured by the
34856 &%-oe%& command line options.
34860 .section "Configuration options for local_scan()" "SECTconoptloc"
34861 .cindex "&[local_scan()]& function" "configuration options"
34862 It is possible to have option settings in the main configuration file
34863 that set values in static variables in the &[local_scan()]& module. If you
34864 want to do this, you must have the line
34866 LOCAL_SCAN_HAS_OPTIONS=yes
34868 in your &_Local/Makefile_& when you build Exim. (This line is in
34869 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
34870 file, you must define static variables to hold the option values, and a table
34873 The table must be a vector called &%local_scan_options%&, of type
34874 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
34875 and a pointer to the variable that holds the value. The entries must appear in
34876 alphabetical order. Following &%local_scan_options%& you must also define a
34877 variable called &%local_scan_options_count%& that contains the number of
34878 entries in the table. Here is a short example, showing two kinds of option:
34880 static int my_integer_option = 42;
34881 static uschar *my_string_option = US"a default string";
34883 optionlist local_scan_options[] = {
34884 { "my_integer", opt_int, &my_integer_option },
34885 { "my_string", opt_stringptr, &my_string_option }
34888 int local_scan_options_count =
34889 sizeof(local_scan_options)/sizeof(optionlist);
34891 The values of the variables can now be changed from Exim's runtime
34892 configuration file by including a local scan section as in this example:
34896 my_string = some string of text...
34898 The available types of option data are as follows:
34901 .vitem &*opt_bool*&
34902 This specifies a boolean (true/false) option. The address should point to a
34903 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
34904 that are defined as &"1"& and &"0"&, respectively. If you want to detect
34905 whether such a variable has been set at all, you can initialize it to
34906 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
34909 .vitem &*opt_fixed*&
34910 This specifies a fixed point number, such as is used for load averages.
34911 The address should point to a variable of type &`int`&. The value is stored
34912 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
34915 This specifies an integer; the address should point to a variable of type
34916 &`int`&. The value may be specified in any of the integer formats accepted by
34919 .vitem &*opt_mkint*&
34920 This is the same as &%opt_int%&, except that when such a value is output in a
34921 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
34922 printed with the suffix K or M.
34924 .vitem &*opt_octint*&
34925 This also specifies an integer, but the value is always interpreted as an
34926 octal integer, whether or not it starts with the digit zero, and it is
34927 always output in octal.
34929 .vitem &*opt_stringptr*&
34930 This specifies a string value; the address must be a pointer to a
34931 variable that points to a string (for example, of type &`uschar *`&).
34933 .vitem &*opt_time*&
34934 This specifies a time interval value. The address must point to a variable of
34935 type &`int`&. The value that is placed there is a number of seconds.
34938 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
34939 out the values of all the &[local_scan()]& options.
34943 .section "Available Exim variables" "SECID208"
34944 .cindex "&[local_scan()]& function" "available Exim variables"
34945 The header &_local_scan.h_& gives you access to a number of C variables. These
34946 are the only ones that are guaranteed to be maintained from release to release.
34947 Note, however, that you can obtain the value of any Exim expansion variable,
34948 including &$recipients$&, by calling &'expand_string()'&. The exported
34949 C variables are as follows:
34952 .vitem &*int&~body_linecount*&
34953 This variable contains the number of lines in the message's body.
34954 It is not valid if the &%spool_files_wireformat%& option is used.
34956 .vitem &*int&~body_zerocount*&
34957 This variable contains the number of binary zero bytes in the message's body.
34958 It is not valid if the &%spool_files_wireformat%& option is used.
34960 .vitem &*unsigned&~int&~debug_selector*&
34961 This variable is set to zero when no debugging is taking place. Otherwise, it
34962 is a bitmap of debugging selectors. Two bits are identified for use in
34963 &[local_scan()]&; they are defined as macros:
34966 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
34967 testing option that is not privileged &-- any caller may set it. All the
34968 other selector bits can be set only by admin users.
34971 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
34972 by the &`+local_scan`& debug selector. It is not included in the default set
34976 Thus, to write to the debugging output only when &`+local_scan`& has been
34977 selected, you should use code like this:
34979 if ((debug_selector & D_local_scan) != 0)
34980 debug_printf("xxx", ...);
34982 .vitem &*uschar&~*expand_string_message*&
34983 After a failing call to &'expand_string()'& (returned value NULL), the
34984 variable &%expand_string_message%& contains the error message, zero-terminated.
34986 .vitem &*header_line&~*header_list*&
34987 A pointer to a chain of header lines. The &%header_line%& structure is
34990 .vitem &*header_line&~*header_last*&
34991 A pointer to the last of the header lines.
34993 .vitem &*uschar&~*headers_charset*&
34994 The value of the &%headers_charset%& configuration option.
34996 .vitem &*BOOL&~host_checking*&
34997 This variable is TRUE during a host checking session that is initiated by the
34998 &%-bh%& command line option.
35000 .vitem &*uschar&~*interface_address*&
35001 The IP address of the interface that received the message, as a string. This
35002 is NULL for locally submitted messages.
35004 .vitem &*int&~interface_port*&
35005 The port on which this message was received. When testing with the &%-bh%&
35006 command line option, the value of this variable is -1 unless a port has been
35007 specified via the &%-oMi%& option.
35009 .vitem &*uschar&~*message_id*&
35010 This variable contains Exim's message id for the incoming message (the value of
35011 &$message_exim_id$&) as a zero-terminated string.
35013 .vitem &*uschar&~*received_protocol*&
35014 The name of the protocol by which the message was received.
35016 .vitem &*int&~recipients_count*&
35017 The number of accepted recipients.
35019 .vitem &*recipient_item&~*recipients_list*&
35020 .cindex "recipient" "adding in local scan"
35021 .cindex "recipient" "removing in local scan"
35022 The list of accepted recipients, held in a vector of length
35023 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
35024 can add additional recipients by calling &'receive_add_recipient()'& (see
35025 below). You can delete recipients by removing them from the vector and
35026 adjusting the value in &%recipients_count%&. In particular, by setting
35027 &%recipients_count%& to zero you remove all recipients. If you then return the
35028 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
35029 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
35030 and then call &'receive_add_recipient()'& as often as needed.
35032 .vitem &*uschar&~*sender_address*&
35033 The envelope sender address. For bounce messages this is the empty string.
35035 .vitem &*uschar&~*sender_host_address*&
35036 The IP address of the sending host, as a string. This is NULL for
35037 locally-submitted messages.
35039 .vitem &*uschar&~*sender_host_authenticated*&
35040 The name of the authentication mechanism that was used, or NULL if the message
35041 was not received over an authenticated SMTP connection.
35043 .vitem &*uschar&~*sender_host_name*&
35044 The name of the sending host, if known.
35046 .vitem &*int&~sender_host_port*&
35047 The port on the sending host.
35049 .vitem &*BOOL&~smtp_input*&
35050 This variable is TRUE for all SMTP input, including BSMTP.
35052 .vitem &*BOOL&~smtp_batched_input*&
35053 This variable is TRUE for BSMTP input.
35055 .vitem &*int&~store_pool*&
35056 The contents of this variable control which pool of memory is used for new
35057 requests. See section &<<SECTmemhanloc>>& for details.
35061 .section "Structure of header lines" "SECID209"
35062 The &%header_line%& structure contains the members listed below.
35063 You can add additional header lines by calling the &'header_add()'& function
35064 (see below). You can cause header lines to be ignored (deleted) by setting
35069 .vitem &*struct&~header_line&~*next*&
35070 A pointer to the next header line, or NULL for the last line.
35072 .vitem &*int&~type*&
35073 A code identifying certain headers that Exim recognizes. The codes are printing
35074 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
35075 Notice in particular that any header line whose type is * is not transmitted
35076 with the message. This flagging is used for header lines that have been
35077 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
35078 lines.) Effectively, * means &"deleted"&.
35080 .vitem &*int&~slen*&
35081 The number of characters in the header line, including the terminating and any
35084 .vitem &*uschar&~*text*&
35085 A pointer to the text of the header. It always ends with a newline, followed by
35086 a zero byte. Internal newlines are preserved.
35091 .section "Structure of recipient items" "SECID210"
35092 The &%recipient_item%& structure contains these members:
35095 .vitem &*uschar&~*address*&
35096 This is a pointer to the recipient address as it was received.
35098 .vitem &*int&~pno*&
35099 This is used in later Exim processing when top level addresses are created by
35100 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
35101 and must always contain -1 at this stage.
35103 .vitem &*uschar&~*errors_to*&
35104 If this value is not NULL, bounce messages caused by failing to deliver to the
35105 recipient are sent to the address it contains. In other words, it overrides the
35106 envelope sender for this one recipient. (Compare the &%errors_to%& generic
35107 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
35108 an unqualified address, Exim qualifies it using the domain from
35109 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
35110 is NULL for all recipients.
35115 .section "Available Exim functions" "SECID211"
35116 .cindex "&[local_scan()]& function" "available Exim functions"
35117 The header &_local_scan.h_& gives you access to a number of Exim functions.
35118 These are the only ones that are guaranteed to be maintained from release to
35122 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
35123 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
35125 This function creates a child process that runs the command specified by
35126 &%argv%&. The environment for the process is specified by &%envp%&, which can
35127 be NULL if no environment variables are to be passed. A new umask is supplied
35128 for the process in &%newumask%&.
35130 Pipes to the standard input and output of the new process are set up
35131 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
35132 standard error is cloned to the standard output. If there are any file
35133 descriptors &"in the way"& in the new process, they are closed. If the final
35134 argument is TRUE, the new process is made into a process group leader.
35136 The function returns the pid of the new process, or -1 if things go wrong.
35138 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
35139 This function waits for a child process to terminate, or for a timeout (in
35140 seconds) to expire. A timeout value of zero means wait as long as it takes. The
35141 return value is as follows:
35146 The process terminated by a normal exit and the value is the process
35152 The process was terminated by a signal and the value is the negation of the
35158 The process timed out.
35162 The was some other error in wait(); &%errno%& is still set.
35165 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
35166 This function provide you with a means of submitting a new message to
35167 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
35168 want, but this packages it all up for you.) The function creates a pipe,
35169 forks a subprocess that is running
35171 exim -t -oem -oi -f <>
35173 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
35174 that is connected to the standard input. The yield of the function is the PID
35175 of the subprocess. You can then write a message to the file descriptor, with
35176 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
35178 When you have finished, call &'child_close()'& to wait for the process to
35179 finish and to collect its ending status. A timeout value of zero is usually
35180 fine in this circumstance. Unless you have made a mistake with the recipient
35181 addresses, you should get a return code of zero.
35184 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
35185 *sender_authentication)*&
35186 This function is a more sophisticated version of &'child_open()'&. The command
35189 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
35191 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
35194 .vitem &*void&~debug_printf(char&~*,&~...)*&
35195 This is Exim's debugging function, with arguments as for &'(printf()'&. The
35196 output is written to the standard error stream. If no debugging is selected,
35197 calls to &'debug_printf()'& have no effect. Normally, you should make calls
35198 conditional on the &`local_scan`& debug selector by coding like this:
35200 if ((debug_selector & D_local_scan) != 0)
35201 debug_printf("xxx", ...);
35204 .vitem &*uschar&~*expand_string(uschar&~*string)*&
35205 This is an interface to Exim's string expansion code. The return value is the
35206 expanded string, or NULL if there was an expansion failure.
35207 The C variable &%expand_string_message%& contains an error message after an
35208 expansion failure. If expansion does not change the string, the return value is
35209 the pointer to the input string. Otherwise, the return value points to a new
35210 block of memory that was obtained by a call to &'store_get()'&. See section
35211 &<<SECTmemhanloc>>& below for a discussion of memory handling.
35213 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
35214 This function allows you to an add additional header line at the end of the
35215 existing ones. The first argument is the type, and should normally be a space
35216 character. The second argument is a format string and any number of
35217 substitution arguments as for &[sprintf()]&. You may include internal newlines
35218 if you want, and you must ensure that the string ends with a newline.
35220 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
35221 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
35222 This function adds a new header line at a specified point in the header
35223 chain. The header itself is specified as for &'header_add()'&.
35225 If &%name%& is NULL, the new header is added at the end of the chain if
35226 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
35227 NULL, the header lines are searched for the first non-deleted header that
35228 matches the name. If one is found, the new header is added before it if
35229 &%after%& is false. If &%after%& is true, the new header is added after the
35230 found header and any adjacent subsequent ones with the same name (even if
35231 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
35232 option controls where the header is added. If it is true, addition is at the
35233 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
35234 headers, or at the top if there are no &'Received:'& headers, you could use
35236 header_add_at_position(TRUE, US"Received", TRUE,
35237 ' ', "X-xxx: ...");
35239 Normally, there is always at least one non-deleted &'Received:'& header, but
35240 there may not be if &%received_header_text%& expands to an empty string.
35243 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
35244 This function removes header lines. If &%occurrence%& is zero or negative, all
35245 occurrences of the header are removed. If occurrence is greater than zero, that
35246 particular instance of the header is removed. If no header(s) can be found that
35247 match the specification, the function does nothing.
35250 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
35251 int&~length,&~BOOL&~notdel)*&"
35252 This function tests whether the given header has the given name. It is not just
35253 a string comparison, because white space is permitted between the name and the
35254 colon. If the &%notdel%& argument is true, a false return is forced for all
35255 &"deleted"& headers; otherwise they are not treated specially. For example:
35257 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
35259 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
35260 .cindex "base64 encoding" "functions for &[local_scan()]& use"
35261 This function base64-encodes a string, which is passed by address and length.
35262 The text may contain bytes of any value, including zero. The result is passed
35263 back in dynamic memory that is obtained by calling &'store_get()'&. It is
35266 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
35267 This function decodes a base64-encoded string. Its arguments are a
35268 zero-terminated base64-encoded string and the address of a variable that is set
35269 to point to the result, which is in dynamic memory. The length of the decoded
35270 string is the yield of the function. If the input is invalid base64 data, the
35271 yield is -1. A zero byte is added to the end of the output string to make it
35272 easy to interpret as a C string (assuming it contains no zeros of its own). The
35273 added zero byte is not included in the returned count.
35275 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
35276 This function checks for a match in a domain list. Domains are always
35277 matched caselessly. The return value is one of the following:
35279 &`OK `& match succeeded
35280 &`FAIL `& match failed
35281 &`DEFER `& match deferred
35283 DEFER is usually caused by some kind of lookup defer, such as the
35284 inability to contact a database.
35286 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
35288 This function checks for a match in a local part list. The third argument
35289 controls case-sensitivity. The return values are as for
35290 &'lss_match_domain()'&.
35292 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
35294 This function checks for a match in an address list. The third argument
35295 controls the case-sensitivity of the local part match. The domain is always
35296 matched caselessly. The return values are as for &'lss_match_domain()'&.
35298 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
35300 This function checks for a match in a host list. The most common usage is
35303 lss_match_host(sender_host_name, sender_host_address, ...)
35305 .vindex "&$sender_host_address$&"
35306 An empty address field matches an empty item in the host list. If the host name
35307 is NULL, the name corresponding to &$sender_host_address$& is automatically
35308 looked up if a host name is required to match an item in the list. The return
35309 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
35310 returns ERROR in the case when it had to look up a host name, but the lookup
35313 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
35315 This function writes to Exim's log files. The first argument should be zero (it
35316 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
35317 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
35318 them. It specifies to which log or logs the message is written. The remaining
35319 arguments are a format and relevant insertion arguments. The string should not
35320 contain any newlines, not even at the end.
35323 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
35324 This function adds an additional recipient to the message. The first argument
35325 is the recipient address. If it is unqualified (has no domain), it is qualified
35326 with the &%qualify_recipient%& domain. The second argument must always be -1.
35328 This function does not allow you to specify a private &%errors_to%& address (as
35329 described with the structure of &%recipient_item%& above), because it pre-dates
35330 the addition of that field to the structure. However, it is easy to add such a
35331 value afterwards. For example:
35333 receive_add_recipient(US"monitor@mydom.example", -1);
35334 recipients_list[recipients_count-1].errors_to =
35335 US"postmaster@mydom.example";
35338 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
35339 This is a convenience function to remove a named recipient from the list of
35340 recipients. It returns true if a recipient was removed, and false if no
35341 matching recipient could be found. The argument must be a complete email
35348 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
35349 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
35350 This function decodes strings that are encoded according to RFC 2047. Typically
35351 these are the contents of header lines. First, each &"encoded word"& is decoded
35352 from the Q or B encoding into a byte-string. Then, if provided with the name of
35353 a charset encoding, and if the &[iconv()]& function is available, an attempt is
35354 made to translate the result to the named character set. If this fails, the
35355 binary string is returned with an error message.
35357 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
35358 maximum MIME word length is enforced. The third argument is the target
35359 encoding, or NULL if no translation is wanted.
35361 .cindex "binary zero" "in RFC 2047 decoding"
35362 .cindex "RFC 2047" "binary zero in"
35363 If a binary zero is encountered in the decoded string, it is replaced by the
35364 contents of the &%zeroval%& argument. For use with Exim headers, the value must
35365 not be 0 because header lines are handled as zero-terminated strings.
35367 The function returns the result of processing the string, zero-terminated; if
35368 &%lenptr%& is not NULL, the length of the result is set in the variable to
35369 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
35371 If an error is encountered, the function returns NULL and uses the &%error%&
35372 argument to return an error message. The variable pointed to by &%error%& is
35373 set to NULL if there is no error; it may be set non-NULL even when the function
35374 returns a non-NULL value if decoding was successful, but there was a problem
35378 .vitem &*int&~smtp_fflush(void)*&
35379 This function is used in conjunction with &'smtp_printf()'&, as described
35382 .vitem &*void&~smtp_printf(char&~*,BOOL,&~...)*&
35383 The arguments of this function are almost like &[printf()]&; it writes to the SMTP
35384 output stream. You should use this function only when there is an SMTP output
35385 stream, that is, when the incoming message is being received via interactive
35386 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
35387 is FALSE. If you want to test for an incoming message from another host (as
35388 opposed to a local process that used the &%-bs%& command line option), you can
35389 test the value of &%sender_host_address%&, which is non-NULL when a remote host
35392 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
35393 output function, so it can be used for all forms of SMTP connection.
35395 The second argument is used to request that the data be buffered
35396 (when TRUE) or flushed (along with any previously buffered, when FALSE).
35397 This is advisory only, but likely to save on system-calls and packets
35398 sent when a sequence of calls to the function are made.
35400 The argument was added in Exim version 4.90 - changing the API/ABI.
35401 Nobody noticed until 4.93 was imminent, at which point the
35402 ABI version number was incremented.
35404 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
35405 must start with an appropriate response code: 550 if you are going to return
35406 LOCAL_SCAN_REJECT, 451 if you are going to return
35407 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
35408 initial lines of a multi-line response, the code must be followed by a hyphen
35409 to indicate that the line is not the final response line. You must also ensure
35410 that the lines you write terminate with CRLF. For example:
35412 smtp_printf("550-this is some extra info\r\n");
35413 return LOCAL_SCAN_REJECT;
35415 Note that you can also create multi-line responses by including newlines in
35416 the data returned via the &%return_text%& argument. The added value of using
35417 &'smtp_printf()'& is that, for instance, you could introduce delays between
35418 multiple output lines.
35420 The &'smtp_printf()'& function does not return any error indication, because it
35422 guarantee a flush of
35423 pending output, and therefore does not test
35424 the state of the stream. (In the main code of Exim, flushing and error
35425 detection is done when Exim is ready for the next SMTP input command.) If
35426 you want to flush the output and check for an error (for example, the
35427 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
35428 arguments. It flushes the output stream, and returns a non-zero value if there
35431 .vitem &*void&~*store_get(int,BOOL)*&
35432 This function accesses Exim's internal store (memory) manager. It gets a new
35433 chunk of memory whose size is given by the first argument.
35434 The second argument should be given as TRUE if the memory will be used for
35435 data possibly coming from an attacker (eg. the message content),
35436 FALSE if it is locally-sourced.
35437 Exim bombs out if it ever
35438 runs out of memory. See the next section for a discussion of memory handling.
35440 .vitem &*void&~*store_get_perm(int,BOOL)*&
35441 This function is like &'store_get()'&, but it always gets memory from the
35442 permanent pool. See the next section for a discussion of memory handling.
35444 .vitem &*uschar&~*string_copy(uschar&~*string)*&
35447 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
35450 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
35451 These three functions create strings using Exim's dynamic memory facilities.
35452 The first makes a copy of an entire string. The second copies up to a maximum
35453 number of characters, indicated by the second argument. The third uses a format
35454 and insertion arguments to create a new string. In each case, the result is a
35455 pointer to a new string in the current memory pool. See the next section for
35461 .section "More about Exim's memory handling" "SECTmemhanloc"
35462 .cindex "&[local_scan()]& function" "memory handling"
35463 No function is provided for freeing memory, because that is never needed.
35464 The dynamic memory that Exim uses when receiving a message is automatically
35465 recycled if another message is received by the same process (this applies only
35466 to incoming SMTP connections &-- other input methods can supply only one
35467 message at a time). After receiving the last message, a reception process
35470 Because it is recycled, the normal dynamic memory cannot be used for holding
35471 data that must be preserved over a number of incoming messages on the same SMTP
35472 connection. However, Exim in fact uses two pools of dynamic memory; the second
35473 one is not recycled, and can be used for this purpose.
35475 If you want to allocate memory that remains available for subsequent messages
35476 in the same SMTP connection, you should set
35478 store_pool = POOL_PERM
35480 before calling the function that does the allocation. There is no need to
35481 restore the value if you do not need to; however, if you do want to revert to
35482 the normal pool, you can either restore the previous value of &%store_pool%& or
35483 set it explicitly to POOL_MAIN.
35485 The pool setting applies to all functions that get dynamic memory, including
35486 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
35487 There is also a convenience function called &'store_get_perm()'& that gets a
35488 block of memory from the permanent pool while preserving the value of
35495 . ////////////////////////////////////////////////////////////////////////////
35496 . ////////////////////////////////////////////////////////////////////////////
35498 .chapter "System-wide message filtering" "CHAPsystemfilter"
35499 .scindex IIDsysfil1 "filter" "system filter"
35500 .scindex IIDsysfil2 "filtering all mail"
35501 .scindex IIDsysfil3 "system filter"
35502 The previous chapters (on ACLs and the local scan function) describe checks
35503 that can be applied to messages before they are accepted by a host. There is
35504 also a mechanism for checking messages once they have been received, but before
35505 they are delivered. This is called the &'system filter'&.
35507 The system filter operates in a similar manner to users' filter files, but it
35508 is run just once per message (however many recipients the message has).
35509 It should not normally be used as a substitute for routing, because &%deliver%&
35510 commands in a system router provide new envelope recipient addresses.
35511 The system filter must be an Exim filter. It cannot be a Sieve filter.
35513 The system filter is run at the start of a delivery attempt, before any routing
35514 is done. If a message fails to be completely delivered at the first attempt,
35515 the system filter is run again at the start of every retry.
35516 If you want your filter to do something only once per message, you can make use
35517 of the &%first_delivery%& condition in an &%if%& command in the filter to
35518 prevent it happening on retries.
35520 .vindex "&$domain$&"
35521 .vindex "&$local_part$&"
35522 &*Warning*&: Because the system filter runs just once, variables that are
35523 specific to individual recipient addresses, such as &$local_part$& and
35524 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
35525 you want to run a centrally-specified filter for each recipient address
35526 independently, you can do so by setting up a suitable &(redirect)& router, as
35527 described in section &<<SECTperaddfil>>& below.
35530 .section "Specifying a system filter" "SECID212"
35531 .cindex "uid (user id)" "system filter"
35532 .cindex "gid (group id)" "system filter"
35533 The name of the file that contains the system filter must be specified by
35534 setting &%system_filter%&. If you want the filter to run under a uid and gid
35535 other than root, you must also set &%system_filter_user%& and
35536 &%system_filter_group%& as appropriate. For example:
35538 system_filter = /etc/mail/exim.filter
35539 system_filter_user = exim
35541 If a system filter generates any deliveries directly to files or pipes (via the
35542 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
35543 specified by setting &%system_filter_file_transport%& and
35544 &%system_filter_pipe_transport%&, respectively. Similarly,
35545 &%system_filter_reply_transport%& must be set to handle any messages generated
35546 by the &%reply%& command.
35549 .section "Testing a system filter" "SECID213"
35550 You can run simple tests of a system filter in the same way as for a user
35551 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
35552 are permitted only in system filters are recognized.
35554 If you want to test the combined effect of a system filter and a user filter,
35555 you can use both &%-bF%& and &%-bf%& on the same command line.
35559 .section "Contents of a system filter" "SECID214"
35560 The language used to specify system filters is the same as for users' filter
35561 files. It is described in the separate end-user document &'Exim's interface to
35562 mail filtering'&. However, there are some additional features that are
35563 available only in system filters; these are described in subsequent sections.
35564 If they are encountered in a user's filter file or when testing with &%-bf%&,
35567 .cindex "frozen messages" "manual thaw; testing in filter"
35568 There are two special conditions which, though available in users' filter
35569 files, are designed for use in system filters. The condition &%first_delivery%&
35570 is true only for the first attempt at delivering a message, and
35571 &%manually_thawed%& is true only if the message has been frozen, and
35572 subsequently thawed by an admin user. An explicit forced delivery counts as a
35573 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
35575 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
35576 specify an &"unseen"& (non-significant) delivery, and that delivery does not
35577 succeed, it will not be tried again.
35578 If you want Exim to retry an unseen delivery until it succeeds, you should
35579 arrange to set it up every time the filter runs.
35581 When a system filter finishes running, the values of the variables &$n0$& &--
35582 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
35583 users' filter files. Thus a system filter can, for example, set up &"scores"&
35584 to which users' filter files can refer.
35588 .section "Additional variable for system filters" "SECID215"
35589 .vindex "&$recipients$&"
35590 The expansion variable &$recipients$&, containing a list of all the recipients
35591 of the message (separated by commas and white space), is available in system
35592 filters. It is not available in users' filters for privacy reasons.
35596 .section "Defer, freeze, and fail commands for system filters" "SECID216"
35597 .cindex "freezing messages"
35598 .cindex "message" "freezing"
35599 .cindex "message" "forced failure"
35600 .cindex "&%fail%&" "in system filter"
35601 .cindex "&%freeze%& in system filter"
35602 .cindex "&%defer%& in system filter"
35603 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
35604 always available in system filters, but are not normally enabled in users'
35605 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
35606 for the &(redirect)& router.) These commands can optionally be followed by the
35607 word &%text%& and a string containing an error message, for example:
35609 fail text "this message looks like spam to me"
35611 The keyword &%text%& is optional if the next character is a double quote.
35613 The &%defer%& command defers delivery of the original recipients of the
35614 message. The &%fail%& command causes all the original recipients to be failed,
35615 and a bounce message to be created. The &%freeze%& command suspends all
35616 delivery attempts for the original recipients. In all cases, any new deliveries
35617 that are specified by the filter are attempted as normal after the filter has
35620 The &%freeze%& command is ignored if the message has been manually unfrozen and
35621 not manually frozen since. This means that automatic freezing by a system
35622 filter can be used as a way of checking out suspicious messages. If a message
35623 is found to be all right, manually unfreezing it allows it to be delivered.
35625 .cindex "log" "&%fail%& command log line"
35626 .cindex "&%fail%&" "log line; reducing"
35627 The text given with a fail command is used as part of the bounce message as
35628 well as being written to the log. If the message is quite long, this can fill
35629 up a lot of log space when such failures are common. To reduce the size of the
35630 log message, Exim interprets the text in a special way if it starts with the
35631 two characters &`<<`& and contains &`>>`& later. The text between these two
35632 strings is written to the log, and the rest of the text is used in the bounce
35633 message. For example:
35635 fail "<<filter test 1>>Your message is rejected \
35636 because it contains attachments that we are \
35637 not prepared to receive."
35640 .cindex "loop" "caused by &%fail%&"
35641 Take great care with the &%fail%& command when basing the decision to fail on
35642 the contents of the message, because the bounce message will of course include
35643 the contents of the original message and will therefore trigger the &%fail%&
35644 command again (causing a mail loop) unless steps are taken to prevent this.
35645 Testing the &%error_message%& condition is one way to prevent this. You could
35648 if $message_body contains "this is spam" and not error_message
35649 then fail text "spam is not wanted here" endif
35651 though of course that might let through unwanted bounce messages. The
35652 alternative is clever checking of the body and/or headers to detect bounces
35653 generated by the filter.
35655 The interpretation of a system filter file ceases after a
35657 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
35658 set up earlier in the filter file are honoured, so you can use a sequence such
35664 to send a specified message when the system filter is freezing (or deferring or
35665 failing) a message. The normal deliveries for the message do not, of course,
35670 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
35671 .cindex "header lines" "adding; in system filter"
35672 .cindex "header lines" "removing; in system filter"
35673 .cindex "filter" "header lines; adding/removing"
35674 Two filter commands that are available only in system filters are:
35676 headers add <string>
35677 headers remove <string>
35679 The argument for the &%headers add%& is a string that is expanded and then
35680 added to the end of the message's headers. It is the responsibility of the
35681 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
35682 space is ignored, and if the string is otherwise empty, or if the expansion is
35683 forced to fail, the command has no effect.
35685 You can use &"\n"& within the string, followed by white space, to specify
35686 continued header lines. More than one header may be added in one command by
35687 including &"\n"& within the string without any following white space. For
35690 headers add "X-header-1: ....\n \
35691 continuation of X-header-1 ...\n\
35694 Note that the header line continuation white space after the first newline must
35695 be placed before the backslash that continues the input string, because white
35696 space after input continuations is ignored.
35698 The argument for &%headers remove%& is a colon-separated list of header names.
35699 This command applies only to those headers that are stored with the message;
35700 those that are added at delivery time (such as &'Envelope-To:'& and
35701 &'Return-Path:'&) cannot be removed by this means. If there is more than one
35702 header with the same name, they are all removed.
35704 The &%headers%& command in a system filter makes an immediate change to the set
35705 of header lines that was received with the message (with possible additions
35706 from ACL processing). Subsequent commands in the system filter operate on the
35707 modified set, which also forms the basis for subsequent message delivery.
35708 Unless further modified during routing or transporting, this set of headers is
35709 used for all recipients of the message.
35711 During routing and transporting, the variables that refer to the contents of
35712 header lines refer only to those lines that are in this set. Thus, header lines
35713 that are added by a system filter are visible to users' filter files and to all
35714 routers and transports. This contrasts with the manipulation of header lines by
35715 routers and transports, which is not immediate, but which instead is saved up
35716 until the message is actually being written (see section
35717 &<<SECTheadersaddrem>>&).
35719 If the message is not delivered at the first attempt, header lines that were
35720 added by the system filter are stored with the message, and so are still
35721 present at the next delivery attempt. Header lines that were removed are still
35722 present, but marked &"deleted"& so that they are not transported with the
35723 message. For this reason, it is usual to make the &%headers%& command
35724 conditional on &%first_delivery%& so that the set of header lines is not
35725 modified more than once.
35727 Because header modification in a system filter acts immediately, you have to
35728 use an indirect approach if you want to modify the contents of a header line.
35731 headers add "Old-Subject: $h_subject:"
35732 headers remove "Subject"
35733 headers add "Subject: new subject (was: $h_old-subject:)"
35734 headers remove "Old-Subject"
35739 .section "Setting an errors address in a system filter" "SECID217"
35740 .cindex "envelope from"
35741 .cindex "envelope sender"
35742 In a system filter, if a &%deliver%& command is followed by
35744 errors_to <some address>
35746 in order to change the envelope sender (and hence the error reporting) for that
35747 delivery, any address may be specified. (In a user filter, only the current
35748 user's address can be set.) For example, if some mail is being monitored, you
35751 unseen deliver monitor@spying.example errors_to root@local.example
35753 to take a copy which would not be sent back to the normal error reporting
35754 address if its delivery failed.
35758 .section "Per-address filtering" "SECTperaddfil"
35759 .vindex "&$domain_data$&"
35760 .vindex "&$local_part_data$&"
35761 In contrast to the system filter, which is run just once per message for each
35762 delivery attempt, it is also possible to set up a system-wide filtering
35763 operation that runs once for each recipient address. In this case, variables
35764 such as &$local_part_data$& and &$domain_data$& can be used,
35765 and indeed, the choice of filter file could be made dependent on them.
35766 This is an example of a router which implements such a filter:
35771 domains = +local_domains
35772 file = /central/filters/$local_part_data
35777 The filter is run in a separate process under its own uid. Therefore, either
35778 &%check_local_user%& must be set (as above), in which case the filter is run as
35779 the local user, or the &%user%& option must be used to specify which user to
35780 use. If both are set, &%user%& overrides.
35782 Care should be taken to ensure that none of the commands in the filter file
35783 specify a significant delivery if the message is to go on to be delivered to
35784 its intended recipient. The router will not then claim to have dealt with the
35785 address, so it will be passed on to subsequent routers to be delivered in the
35787 .ecindex IIDsysfil1
35788 .ecindex IIDsysfil2
35789 .ecindex IIDsysfil3
35796 . ////////////////////////////////////////////////////////////////////////////
35797 . ////////////////////////////////////////////////////////////////////////////
35799 .chapter "Message processing" "CHAPmsgproc"
35800 .scindex IIDmesproc "message" "general processing"
35801 Exim performs various transformations on the sender and recipient addresses of
35802 all messages that it handles, and also on the messages' header lines. Some of
35803 these are optional and configurable, while others always take place. All of
35804 this processing, except rewriting as a result of routing, and the addition or
35805 removal of header lines while delivering, happens when a message is received,
35806 before it is placed on Exim's queue.
35808 Some of the automatic processing takes place by default only for
35809 &"locally-originated"& messages. This adjective is used to describe messages
35810 that are not received over TCP/IP, but instead are passed to an Exim process on
35811 its standard input. This includes the interactive &"local SMTP"& case that is
35812 set up by the &%-bs%& command line option.
35814 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
35815 or ::1) are not considered to be locally-originated. Exim does not treat the
35816 loopback interface specially in any way.
35818 If you want the loopback interface to be treated specially, you must ensure
35819 that there are appropriate entries in your ACLs.
35824 .section "Submission mode for non-local messages" "SECTsubmodnon"
35825 .cindex "message" "submission"
35826 .cindex "submission mode"
35827 Processing that happens automatically for locally-originated messages (unless
35828 &%suppress_local_fixups%& is set) can also be requested for messages that are
35829 received over TCP/IP. The term &"submission mode"& is used to describe this
35830 state. Submission mode is set by the modifier
35832 control = submission
35834 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
35835 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
35836 a local submission, and is normally used when the source of the message is
35837 known to be an MUA running on a client host (as opposed to an MTA). For
35838 example, to set submission mode for messages originating on the IPv4 loopback
35839 interface, you could include the following in the MAIL ACL:
35841 warn hosts = 127.0.0.1
35842 control = submission
35844 .cindex "&%sender_retain%& submission option"
35845 There are some options that can be used when setting submission mode. A slash
35846 is used to separate options. For example:
35848 control = submission/sender_retain
35850 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
35851 true and &%local_from_check%& false for the current incoming message. The first
35852 of these allows an existing &'Sender:'& header in the message to remain, and
35853 the second suppresses the check to ensure that &'From:'& matches the
35854 authenticated sender. With this setting, Exim still fixes up messages by adding
35855 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
35856 attempt to check sender authenticity in header lines.
35858 When &%sender_retain%& is not set, a submission mode setting may specify a
35859 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
35862 control = submission/domain=some.domain
35864 The domain may be empty. How this value is used is described in sections
35865 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
35866 that allows you to specify the user's full name for inclusion in a created
35867 &'Sender:'& or &'From:'& header line. For example:
35869 accept authenticated = *
35870 control = submission/domain=wonderland.example/\
35871 name=${lookup {$authenticated_id} \
35872 lsearch {/etc/exim/namelist}}
35874 Because the name may contain any characters, including slashes, the &%name%&
35875 option must be given last. The remainder of the string is used as the name. For
35876 the example above, if &_/etc/exim/namelist_& contains:
35878 bigegg: Humpty Dumpty
35880 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
35883 Sender: Humpty Dumpty <bigegg@wonderland.example>
35885 .cindex "return path" "in submission mode"
35886 By default, submission mode forces the return path to the same address as is
35887 used to create the &'Sender:'& header. However, if &%sender_retain%& is
35888 specified, the return path is also left unchanged.
35890 &*Note*&: The changes caused by submission mode take effect after the predata
35891 ACL. This means that any sender checks performed before the fix-ups use the
35892 untrusted sender address specified by the user, not the trusted sender address
35893 specified by submission mode. Although this might be slightly unexpected, it
35894 does mean that you can configure ACL checks to spot that a user is trying to
35895 spoof another's address.
35897 .section "Line endings" "SECTlineendings"
35898 .cindex "line endings"
35899 .cindex "carriage return"
35901 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
35902 linefeed) is the line ending for messages transmitted over the Internet using
35903 SMTP over TCP/IP. However, within individual operating systems, different
35904 conventions are used. For example, Unix-like systems use just LF, but others
35905 use CRLF or just CR.
35907 Exim was designed for Unix-like systems, and internally, it stores messages
35908 using the system's convention of a single LF as a line terminator. When
35909 receiving a message, all line endings are translated to this standard format.
35910 Originally, it was thought that programs that passed messages directly to an
35911 MTA within an operating system would use that system's convention. Experience
35912 has shown that this is not the case; for example, there are Unix applications
35913 that use CRLF in this circumstance. For this reason, and for compatibility with
35914 other MTAs, the way Exim handles line endings for all messages is now as
35918 LF not preceded by CR is treated as a line ending.
35920 CR is treated as a line ending; if it is immediately followed by LF, the LF
35923 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
35924 nor a local message in the state where a line containing only a dot is a
35927 If a bare CR is encountered within a header line, an extra space is added after
35928 the line terminator so as not to end the header line. The reasoning behind this
35929 is that bare CRs in header lines are most likely either to be mistakes, or
35930 people trying to play silly games.
35932 If the first header line received in a message ends with CRLF, a subsequent
35933 bare LF in a header line is treated in the same way as a bare CR in a header
35941 .section "Unqualified addresses" "SECID218"
35942 .cindex "unqualified addresses"
35943 .cindex "address" "qualification"
35944 By default, Exim expects every envelope address it receives from an external
35945 host to be fully qualified. Unqualified addresses cause negative responses to
35946 SMTP commands. However, because SMTP is used as a means of transporting
35947 messages from MUAs running on personal workstations, there is sometimes a
35948 requirement to accept unqualified addresses from specific hosts or IP networks.
35950 Exim has two options that separately control which hosts may send unqualified
35951 sender or recipient addresses in SMTP commands, namely
35952 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
35953 cases, if an unqualified address is accepted, it is qualified by adding the
35954 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
35956 .oindex "&%qualify_domain%&"
35957 .oindex "&%qualify_recipient%&"
35958 Unqualified addresses in header lines are automatically qualified for messages
35959 that are locally originated, unless the &%-bnq%& option is given on the command
35960 line. For messages received over SMTP, unqualified addresses in header lines
35961 are qualified only if unqualified addresses are permitted in SMTP commands. In
35962 other words, such qualification is also controlled by
35963 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
35968 .section "The UUCP From line" "SECID219"
35969 .cindex "&""From""& line"
35970 .cindex "UUCP" "&""From""& line"
35971 .cindex "sender" "address"
35972 .oindex "&%uucp_from_pattern%&"
35973 .oindex "&%uucp_from_sender%&"
35974 .cindex "envelope from"
35975 .cindex "envelope sender"
35976 .cindex "Sendmail compatibility" "&""From""& line"
35977 Messages that have come from UUCP (and some other applications) often begin
35978 with a line containing the envelope sender and a timestamp, following the word
35979 &"From"&. Examples of two common formats are:
35981 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
35982 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
35984 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
35985 Exim recognizes such lines at the start of messages that are submitted to it
35986 via the command line (that is, on the standard input). It does not recognize
35987 such lines in incoming SMTP messages, unless the sending host matches
35988 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
35989 and &%ignore_fromline_local%& is set. The recognition is controlled by a
35990 regular expression that is defined by the &%uucp_from_pattern%& option, whose
35991 default value matches the two common cases shown above and puts the address
35992 that follows &"From"& into &$1$&.
35994 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
35995 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
35996 a trusted user, the message's sender address is constructed by expanding the
35997 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
35998 then parsed as an RFC 2822 address. If there is no domain, the local part is
35999 qualified with &%qualify_domain%& unless it is the empty string. However, if
36000 the command line &%-f%& option is used, it overrides the &"From"& line.
36002 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
36003 sender address is not changed. This is also the case for incoming SMTP messages
36004 that are permitted to contain &"From"& lines.
36006 Only one &"From"& line is recognized. If there is more than one, the second is
36007 treated as a data line that starts the body of the message, as it is not valid
36008 as a header line. This also happens if a &"From"& line is present in an
36009 incoming SMTP message from a source that is not permitted to send them.
36013 .section "Resent- header lines" "SECID220"
36014 .cindex "&%Resent-%& header lines"
36015 .cindex "header lines" "Resent-"
36016 RFC 2822 makes provision for sets of header lines starting with the string
36017 &`Resent-`& to be added to a message when it is resent by the original
36018 recipient to somebody else. These headers are &'Resent-Date:'&,
36019 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
36020 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
36023 &'Resent fields are strictly informational. They MUST NOT be used in the normal
36024 processing of replies or other such automatic actions on messages.'&
36027 This leaves things a bit vague as far as other processing actions such as
36028 address rewriting are concerned. Exim treats &%Resent-%& header lines as
36032 A &'Resent-From:'& line that just contains the login id of the submitting user
36033 is automatically rewritten in the same way as &'From:'& (see below).
36035 If there's a rewriting rule for a particular header line, it is also applied to
36036 &%Resent-%& header lines of the same type. For example, a rule that rewrites
36037 &'From:'& also rewrites &'Resent-From:'&.
36039 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
36042 For a locally-submitted message,
36043 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
36044 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
36045 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
36046 included in log lines in this case.
36048 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
36049 &%Resent-%& header lines are present.
36055 .section "The Auto-Submitted: header line" "SECID221"
36056 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
36057 includes the header line:
36059 Auto-Submitted: auto-replied
36062 .section "The Bcc: header line" "SECID222"
36063 .cindex "&'Bcc:'& header line"
36064 If Exim is called with the &%-t%& option, to take recipient addresses from a
36065 message's header, it removes any &'Bcc:'& header line that may exist (after
36066 extracting its addresses). If &%-t%& is not present on the command line, any
36067 existing &'Bcc:'& is not removed.
36070 .section "The Date: header line" "SECID223"
36071 .cindex "&'Date:'& header line"
36072 .cindex "header lines" "Date:"
36073 If a locally-generated or submission-mode message has no &'Date:'& header line,
36074 Exim adds one, using the current date and time, unless the
36075 &%suppress_local_fixups%& control has been specified.
36077 .section "The Delivery-date: header line" "SECID224"
36078 .cindex "&'Delivery-date:'& header line"
36079 .oindex "&%delivery_date_remove%&"
36080 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
36081 set. Exim can be configured to add them to the final delivery of messages. (See
36082 the generic &%delivery_date_add%& transport option.) They should not be present
36083 in messages in transit. If the &%delivery_date_remove%& configuration option is
36084 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
36088 .section "The Envelope-to: header line" "SECID225"
36089 .cindex "&'Envelope-to:'& header line"
36090 .cindex "header lines" "Envelope-to:"
36091 .oindex "&%envelope_to_remove%&"
36092 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
36093 Exim can be configured to add them to the final delivery of messages. (See the
36094 generic &%envelope_to_add%& transport option.) They should not be present in
36095 messages in transit. If the &%envelope_to_remove%& configuration option is set
36096 (the default), Exim removes &'Envelope-to:'& header lines from incoming
36100 .section "The From: header line" "SECTthefrohea"
36101 .cindex "&'From:'& header line"
36102 .cindex "header lines" "From:"
36103 .cindex "Sendmail compatibility" "&""From""& line"
36104 .cindex "message" "submission"
36105 .cindex "submission mode"
36106 If a submission-mode message does not contain a &'From:'& header line, Exim
36107 adds one if either of the following conditions is true:
36110 The envelope sender address is not empty (that is, this is not a bounce
36111 message). The added header line copies the envelope sender address.
36113 .vindex "&$authenticated_id$&"
36114 The SMTP session is authenticated and &$authenticated_id$& is not empty.
36116 .vindex "&$qualify_domain$&"
36117 If no domain is specified by the submission control, the local part is
36118 &$authenticated_id$& and the domain is &$qualify_domain$&.
36120 If a non-empty domain is specified by the submission control, the local
36121 part is &$authenticated_id$&, and the domain is the specified domain.
36123 If an empty domain is specified by the submission control,
36124 &$authenticated_id$& is assumed to be the complete address.
36128 A non-empty envelope sender takes precedence.
36130 If a locally-generated incoming message does not contain a &'From:'& header
36131 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
36132 containing the sender's address. The calling user's login name and full name
36133 are used to construct the address, as described in section &<<SECTconstr>>&.
36134 They are obtained from the password data by calling &[getpwuid()]& (but see the
36135 &%unknown_login%& configuration option). The address is qualified with
36136 &%qualify_domain%&.
36138 For compatibility with Sendmail, if an incoming, non-SMTP message has a
36139 &'From:'& header line containing just the unqualified login name of the calling
36140 user, this is replaced by an address containing the user's login name and full
36141 name as described in section &<<SECTconstr>>&.
36144 .section "The Message-ID: header line" "SECID226"
36145 .cindex "&'Message-ID:'& header line"
36146 .cindex "header lines" "Message-ID:"
36147 .cindex "message" "submission"
36148 .oindex "&%message_id_header_text%&"
36149 If a locally-generated or submission-mode incoming message does not contain a
36150 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
36151 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
36152 to the message. If there are any &'Resent-:'& headers in the message, it
36153 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
36154 message id, preceded by the letter E to ensure it starts with a letter, and
36155 followed by @ and the primary host name. Additional information can be included
36156 in this header line by setting the &%message_id_header_text%& and/or
36157 &%message_id_header_domain%& options.
36160 .section "The Received: header line" "SECID227"
36161 .cindex "&'Received:'& header line"
36162 .cindex "header lines" "Received:"
36163 A &'Received:'& header line is added at the start of every message. The
36164 contents are defined by the &%received_header_text%& configuration option, and
36165 Exim automatically adds a semicolon and a timestamp to the configured string.
36167 The &'Received:'& header is generated as soon as the message's header lines
36168 have been received. At this stage, the timestamp in the &'Received:'& header
36169 line is the time that the message started to be received. This is the value
36170 that is seen by the DATA ACL and by the &[local_scan()]& function.
36172 Once a message is accepted, the timestamp in the &'Received:'& header line is
36173 changed to the time of acceptance, which is (apart from a small delay while the
36174 -H spool file is written) the earliest time at which delivery could start.
36177 .section "The References: header line" "SECID228"
36178 .cindex "&'References:'& header line"
36179 .cindex "header lines" "References:"
36180 Messages created by the &(autoreply)& transport include a &'References:'&
36181 header line. This is constructed according to the rules that are described in
36182 section 3.64 of RFC 2822 (which states that replies should contain such a
36183 header line), and section 3.14 of RFC 3834 (which states that automatic
36184 responses are not different in this respect). However, because some mail
36185 processing software does not cope well with very long header lines, no more
36186 than 12 message IDs are copied from the &'References:'& header line in the
36187 incoming message. If there are more than 12, the first one and then the final
36188 11 are copied, before adding the message ID of the incoming message.
36192 .section "The Return-path: header line" "SECID229"
36193 .cindex "&'Return-path:'& header line"
36194 .cindex "header lines" "Return-path:"
36195 .oindex "&%return_path_remove%&"
36196 &'Return-path:'& header lines are defined as something an MTA may insert when
36197 it does the final delivery of messages. (See the generic &%return_path_add%&
36198 transport option.) Therefore, they should not be present in messages in
36199 transit. If the &%return_path_remove%& configuration option is set (the
36200 default), Exim removes &'Return-path:'& header lines from incoming messages.
36204 .section "The Sender: header line" "SECTthesenhea"
36205 .cindex "&'Sender:'& header line"
36206 .cindex "message" "submission"
36207 .cindex "header lines" "Sender:"
36208 For a locally-originated message from an untrusted user, Exim may remove an
36209 existing &'Sender:'& header line, and it may add a new one. You can modify
36210 these actions by setting the &%local_sender_retain%& option true, the
36211 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
36214 When a local message is received from an untrusted user and
36215 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
36216 control has not been set, a check is made to see if the address given in the
36217 &'From:'& header line is the correct (local) sender of the message. The address
36218 that is expected has the login name as the local part and the value of
36219 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
36220 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
36221 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
36222 line is added to the message.
36224 If you set &%local_from_check%& false, this checking does not occur. However,
36225 the removal of an existing &'Sender:'& line still happens, unless you also set
36226 &%local_sender_retain%& to be true. It is not possible to set both of these
36227 options true at the same time.
36229 .cindex "submission mode"
36230 By default, no processing of &'Sender:'& header lines is done for messages
36231 received over TCP/IP or for messages submitted by trusted users. However, when
36232 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
36233 not specified on the submission control, the following processing takes place:
36235 .vindex "&$authenticated_id$&"
36236 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
36237 authenticated, and &$authenticated_id$& is not empty, a sender address is
36238 created as follows:
36241 .vindex "&$qualify_domain$&"
36242 If no domain is specified by the submission control, the local part is
36243 &$authenticated_id$& and the domain is &$qualify_domain$&.
36245 If a non-empty domain is specified by the submission control, the local part
36246 is &$authenticated_id$&, and the domain is the specified domain.
36248 If an empty domain is specified by the submission control,
36249 &$authenticated_id$& is assumed to be the complete address.
36252 This address is compared with the address in the &'From:'& header line. If they
36253 are different, a &'Sender:'& header line containing the created address is
36254 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
36255 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
36257 .cindex "return path" "created from &'Sender:'&"
36258 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
36259 the message (the envelope sender address) is changed to be the same address,
36260 except in the case of submission mode when &%sender_retain%& is specified.
36264 .section "Adding and removing header lines in routers and transports" &&&
36265 "SECTheadersaddrem"
36266 .cindex "header lines" "adding; in router or transport"
36267 .cindex "header lines" "removing; in router or transport"
36268 When a message is delivered, the addition and removal of header lines can be
36269 specified in a system filter, or on any of the routers and transports that
36270 process the message. Section &<<SECTaddremheasys>>& contains details about
36271 modifying headers in a system filter. Header lines can also be added in an ACL
36272 as a message is received (see section &<<SECTaddheadacl>>&).
36274 In contrast to what happens in a system filter, header modifications that are
36275 specified on routers and transports apply only to the particular recipient
36276 addresses that are being processed by those routers and transports. These
36277 changes do not actually take place until a copy of the message is being
36278 transported. Therefore, they do not affect the basic set of header lines, and
36279 they do not affect the values of the variables that refer to header lines.
36281 &*Note*&: In particular, this means that any expansions in the configuration of
36282 the transport cannot refer to the modified header lines, because such
36283 expansions all occur before the message is actually transported.
36285 For both routers and transports, the argument of a &%headers_add%&
36286 option must be in the form of one or more RFC 2822 header lines, separated by
36287 newlines (coded as &"\n"&). For example:
36289 headers_add = X-added-header: added by $primary_hostname\n\
36290 X-added-second: another added header line
36292 Exim does not check the syntax of these added header lines.
36294 Multiple &%headers_add%& options for a single router or transport can be
36295 specified; the values will append to a single list of header lines.
36296 Each header-line is separately expanded.
36298 The argument of a &%headers_remove%& option must consist of a colon-separated
36299 list of header names. This is confusing, because header names themselves are
36300 often terminated by colons. In this case, the colons are the list separators,
36301 not part of the names. For example:
36303 headers_remove = return-receipt-to:acknowledge-to
36306 Multiple &%headers_remove%& options for a single router or transport can be
36307 specified; the arguments will append to a single header-names list.
36308 Each item is separately expanded.
36309 Note that colons in complex expansions which are used to
36310 form all or part of a &%headers_remove%& list
36311 will act as list separators.
36313 When &%headers_add%& or &%headers_remove%& is specified on a router,
36314 items are expanded at routing time,
36315 and then associated with all addresses that are
36316 accepted by that router, and also with any new addresses that it generates. If
36317 an address passes through several routers as a result of aliasing or
36318 forwarding, the changes are cumulative.
36320 .oindex "&%unseen%&"
36321 However, this does not apply to multiple routers that result from the use of
36322 the &%unseen%& option. Any header modifications that were specified by the
36323 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
36325 Addresses that end up with different &%headers_add%& or &%headers_remove%&
36326 settings cannot be delivered together in a batch, so a transport is always
36327 dealing with a set of addresses that have the same header-processing
36330 The transport starts by writing the original set of header lines that arrived
36331 with the message, possibly modified by the system filter. As it writes out
36332 these lines, it consults the list of header names that were attached to the
36333 recipient address(es) by &%headers_remove%& options in routers, and it also
36334 consults the transport's own &%headers_remove%& option. Header lines whose
36335 names are on either of these lists are not written out. If there are multiple
36336 instances of any listed header, they are all skipped.
36338 After the remaining original header lines have been written, new header
36339 lines that were specified by routers' &%headers_add%& options are written, in
36340 the order in which they were attached to the address. These are followed by any
36341 header lines specified by the transport's &%headers_add%& option.
36343 This way of handling header line modifications in routers and transports has
36344 the following consequences:
36347 The original set of header lines, possibly modified by the system filter,
36348 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
36349 to it, at all times.
36351 Header lines that are added by a router's
36352 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
36353 expansion syntax in subsequent routers or the transport.
36355 Conversely, header lines that are specified for removal by &%headers_remove%&
36356 in a router remain visible to subsequent routers and the transport.
36358 Headers added to an address by &%headers_add%& in a router cannot be removed by
36359 a later router or by a transport.
36361 An added header can refer to the contents of an original header that is to be
36362 removed, even it has the same name as the added header. For example:
36364 headers_remove = subject
36365 headers_add = Subject: new subject (was: $h_subject:)
36369 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
36370 for a &(redirect)& router that has the &%one_time%& option set.
36376 .section "Constructed addresses" "SECTconstr"
36377 .cindex "address" "constructed"
36378 .cindex "constructed address"
36379 When Exim constructs a sender address for a locally-generated message, it uses
36382 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
36386 Zaphod Beeblebrox <zaphod@end.univ.example>
36388 The user name is obtained from the &%-F%& command line option if set, or
36389 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
36390 &"gecos"& field from the password entry. If the &"gecos"& field contains an
36391 ampersand character, this is replaced by the login name with the first letter
36392 upper cased, as is conventional in a number of operating systems. See the
36393 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
36394 The &%unknown_username%& option can be used to specify user names in cases when
36395 there is no password file entry.
36398 In all cases, the user name is made to conform to RFC 2822 by quoting all or
36399 parts of it if necessary. In addition, if it contains any non-printing
36400 characters, it is encoded as described in RFC 2047, which defines a way of
36401 including non-ASCII characters in header lines. The value of the
36402 &%headers_charset%& option specifies the name of the encoding that is used (the
36403 characters are assumed to be in this encoding). The setting of
36404 &%print_topbitchars%& controls whether characters with the top bit set (that
36405 is, with codes greater than 127) count as printing characters or not.
36409 .section "Case of local parts" "SECID230"
36410 .cindex "case of local parts"
36411 .cindex "local part" "case of"
36412 RFC 2822 states that the case of letters in the local parts of addresses cannot
36413 be assumed to be non-significant. Exim preserves the case of local parts of
36414 addresses, but by default it uses a lower-cased form when it is routing,
36415 because on most Unix systems, usernames are in lower case and case-insensitive
36416 routing is required. However, any particular router can be made to use the
36417 original case for local parts by setting the &%caseful_local_part%& generic
36420 .cindex "mixed-case login names"
36421 If you must have mixed-case user names on your system, the best way to proceed,
36422 assuming you want case-independent handling of incoming email, is to set up
36423 your first router to convert incoming local parts in your domains to the
36424 correct case by means of a file lookup. For example:
36428 domains = +local_domains
36429 data = ${lookup{$local_part}cdb\
36430 {/etc/usercased.cdb}{$value}fail}\
36433 For this router, the local part is forced to lower case by the default action
36434 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
36435 up a new local part in the correct case. If you then set &%caseful_local_part%&
36436 on any subsequent routers which process your domains, they will operate on
36437 local parts with the correct case in a case-sensitive manner.
36441 .section "Dots in local parts" "SECID231"
36442 .cindex "dot" "in local part"
36443 .cindex "local part" "dots in"
36444 RFC 2822 forbids empty components in local parts. That is, an unquoted local
36445 part may not begin or end with a dot, nor have two consecutive dots in the
36446 middle. However, it seems that many MTAs do not enforce this, so Exim permits
36447 empty components for compatibility.
36451 .section "Rewriting addresses" "SECID232"
36452 .cindex "rewriting" "addresses"
36453 Rewriting of sender and recipient addresses, and addresses in headers, can
36454 happen automatically, or as the result of configuration options, as described
36455 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
36456 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
36458 Automatic rewriting includes qualification, as mentioned above. The other case
36459 in which it can happen is when an incomplete non-local domain is given. The
36460 routing process may cause this to be expanded into the full domain name. For
36461 example, a header such as
36465 might get rewritten as
36467 To: hare@teaparty.wonderland.fict.example
36469 Rewriting as a result of routing is the one kind of message processing that
36470 does not happen at input time, as it cannot be done until the address has
36473 Strictly, one should not do &'any'& deliveries of a message until all its
36474 addresses have been routed, in case any of the headers get changed as a
36475 result of routing. However, doing this in practice would hold up many
36476 deliveries for unreasonable amounts of time, just because one address could not
36477 immediately be routed. Exim therefore does not delay other deliveries when
36478 routing of one or more addresses is deferred.
36479 .ecindex IIDmesproc
36483 . ////////////////////////////////////////////////////////////////////////////
36484 . ////////////////////////////////////////////////////////////////////////////
36486 .chapter "SMTP processing" "CHAPSMTP"
36487 .scindex IIDsmtpproc1 "SMTP" "processing details"
36488 .scindex IIDsmtpproc2 "LMTP" "processing details"
36489 Exim supports a number of different ways of using the SMTP protocol, and its
36490 LMTP variant, which is an interactive protocol for transferring messages into a
36491 closed mail store application. This chapter contains details of how SMTP is
36492 processed. For incoming mail, the following are available:
36495 SMTP over TCP/IP (Exim daemon or &'inetd'&);
36497 SMTP over the standard input and output (the &%-bs%& option);
36499 Batched SMTP on the standard input (the &%-bS%& option).
36502 For mail delivery, the following are available:
36505 SMTP over TCP/IP (the &(smtp)& transport);
36507 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
36510 LMTP over a pipe to a process running in the local host (the &(lmtp)&
36513 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
36514 the &%use_bsmtp%& option set).
36517 &'Batched SMTP'& is the name for a process in which batches of messages are
36518 stored in or read from files (or pipes), in a format in which SMTP commands are
36519 used to contain the envelope information.
36523 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
36524 .cindex "SMTP" "outgoing over TCP/IP"
36525 .cindex "outgoing SMTP over TCP/IP"
36526 .cindex "LMTP" "over TCP/IP"
36527 .cindex "outgoing LMTP over TCP/IP"
36530 .cindex "SIZE" "option on MAIL command"
36531 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
36532 The &%protocol%& option selects which protocol is to be used, but the actual
36533 processing is the same in both cases.
36535 .cindex "ESMTP extensions" SIZE
36536 If, in response to its EHLO command, Exim is told that the SIZE
36537 extension is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
36538 command. The value of <&'n'&> is the message size plus the value of the
36539 &%size_addition%& option (default 1024) to allow for additions to the message
36540 such as per-transport header lines, or changes made in a
36541 .cindex "transport" "filter"
36542 .cindex "filter" "transport filter"
36543 transport filter. If &%size_addition%& is set negative, the use of SIZE is
36546 If the remote server advertises support for PIPELINING, Exim uses the
36547 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
36548 required for the transaction.
36550 If the remote server advertises support for the STARTTLS command, and Exim
36551 was built to support TLS encryption, it tries to start a TLS session unless the
36552 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
36553 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
36554 is called for verification.
36556 If the remote server advertises support for the AUTH command, Exim scans
36557 the authenticators configuration for any suitable client settings, as described
36558 in chapter &<<CHAPSMTPAUTH>>&.
36560 .cindex "carriage return"
36562 Responses from the remote host are supposed to be terminated by CR followed by
36563 LF. However, there are known to be hosts that do not send CR characters, so in
36564 order to be able to interwork with such hosts, Exim treats LF on its own as a
36567 If a message contains a number of different addresses, all those with the same
36568 characteristics (for example, the same envelope sender) that resolve to the
36569 same set of hosts, in the same order, are sent in a single SMTP transaction,
36570 even if they are for different domains, unless there are more than the setting
36571 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
36572 they are split into groups containing no more than &%max_rcpt%&s addresses
36573 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
36574 in parallel sessions. The order of hosts with identical MX values is not
36575 significant when checking whether addresses can be batched in this way.
36577 When the &(smtp)& transport suffers a temporary failure that is not
36578 message-related, Exim updates its transport-specific database, which contains
36579 records indexed by host name that remember which messages are waiting for each
36580 particular host. It also updates the retry database with new retry times.
36582 .cindex "hints database" "retry keys"
36583 Exim's retry hints are based on host name plus IP address, so if one address of
36584 a multi-homed host is broken, it will soon be skipped most of the time.
36585 See the next section for more detail about error handling.
36587 .cindex "SMTP" "passed connection"
36588 .cindex "SMTP" "batching over TCP/IP"
36589 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
36590 looks in the hints database for the transport to see if there are any queued
36591 messages waiting for the host to which it is connected. If it finds one, it
36592 creates a new Exim process using the &%-MC%& option (which can only be used by
36593 a process running as root or the Exim user) and passes the TCP/IP socket to it
36594 so that it can deliver another message using the same socket. The new process
36595 does only those deliveries that are routed to the connected host, and may in
36596 turn pass the socket on to a third process, and so on.
36598 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
36599 limit the number of messages sent down a single TCP/IP connection.
36601 .cindex "asterisk" "after IP address"
36602 The second and subsequent messages delivered down an existing connection are
36603 identified in the main log by the addition of an asterisk after the closing
36604 square bracket of the IP address.
36609 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
36610 .cindex "error" "in outgoing SMTP"
36611 .cindex "SMTP" "errors in outgoing"
36612 .cindex "host" "error"
36613 Three different kinds of error are recognized for outgoing SMTP: host errors,
36614 message errors, and recipient errors.
36617 .vitem "&*Host errors*&"
36618 A host error is not associated with a particular message or with a
36619 particular recipient of a message. The host errors are:
36622 Connection refused or timed out,
36624 Any error response code on connection,
36626 Any error response code to EHLO or HELO,
36628 Loss of connection at any time, except after &"."&,
36630 I/O errors at any time,
36632 Timeouts during the session, other than in response to MAIL, RCPT or
36633 the &"."& at the end of the data.
36636 For a host error, a permanent error response on connection, or in response to
36637 EHLO, causes all addresses routed to the host to be failed. Any other host
36638 error causes all addresses to be deferred, and retry data to be created for the
36639 host. It is not tried again, for any message, until its retry time arrives. If
36640 the current set of addresses are not all delivered in this run (to some
36641 alternative host), the message is added to the list of those waiting for this
36642 host, so if it is still undelivered when a subsequent successful delivery is
36643 made to the host, it will be sent down the same SMTP connection.
36645 .vitem "&*Message errors*&"
36646 .cindex "message" "error"
36647 A message error is associated with a particular message when sent to a
36648 particular host, but not with a particular recipient of the message. The
36649 message errors are:
36652 Any error response code to MAIL, DATA, or the &"."& that terminates
36655 Timeout after MAIL,
36657 Timeout or loss of connection after the &"."& that terminates the data. A
36658 timeout after the DATA command itself is treated as a host error, as is loss of
36659 connection at any other time.
36662 For a message error, a permanent error response (5&'xx'&) causes all addresses
36663 to be failed, and a delivery error report to be returned to the sender. A
36664 temporary error response (4&'xx'&), or one of the timeouts, causes all
36665 addresses to be deferred. Retry data is not created for the host, but instead,
36666 a retry record for the combination of host plus message id is created. The
36667 message is not added to the list of those waiting for this host. This ensures
36668 that the failing message will not be sent to this host again until the retry
36669 time arrives. However, other messages that are routed to the host are not
36670 affected, so if it is some property of the message that is causing the error,
36671 it will not stop the delivery of other mail.
36673 If the remote host specified support for the SIZE parameter in its response
36674 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
36675 over-large message will cause a message error because the error arrives as a
36678 .vitem "&*Recipient errors*&"
36679 .cindex "recipient" "error"
36680 A recipient error is associated with a particular recipient of a message. The
36681 recipient errors are:
36684 Any error response to RCPT,
36686 Timeout after RCPT.
36689 For a recipient error, a permanent error response (5&'xx'&) causes the
36690 recipient address to be failed, and a bounce message to be returned to the
36691 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
36692 address to be deferred, and routing retry data to be created for it. This is
36693 used to delay processing of the address in subsequent queue runs, until its
36694 routing retry time arrives. This applies to all messages, but because it
36695 operates only in queue runs, one attempt will be made to deliver a new message
36696 to the failing address before the delay starts to operate. This ensures that,
36697 if the failure is really related to the message rather than the recipient
36698 (&"message too big for this recipient"& is a possible example), other messages
36699 have a chance of getting delivered. If a delivery to the address does succeed,
36700 the retry information gets cleared, so all stuck messages get tried again, and
36701 the retry clock is reset.
36703 The message is not added to the list of those waiting for this host. Use of the
36704 host for other messages is unaffected, and except in the case of a timeout,
36705 other recipients are processed independently, and may be successfully delivered
36706 in the current SMTP session. After a timeout it is of course impossible to
36707 proceed with the session, so all addresses get deferred. However, those other
36708 than the one that failed do not suffer any subsequent retry delays. Therefore,
36709 if one recipient is causing trouble, the others have a chance of getting
36710 through when a subsequent delivery attempt occurs before the failing
36711 recipient's retry time.
36714 In all cases, if there are other hosts (or IP addresses) available for the
36715 current set of addresses (for example, from multiple MX records), they are
36716 tried in this run for any undelivered addresses, subject of course to their
36717 own retry data. In other words, recipient error retry data does not take effect
36718 until the next delivery attempt.
36720 Some hosts have been observed to give temporary error responses to every
36721 MAIL command at certain times (&"insufficient space"& has been seen). It
36722 would be nice if such circumstances could be recognized, and defer data for the
36723 host itself created, but this is not possible within the current Exim design.
36724 What actually happens is that retry data for every (host, message) combination
36727 The reason that timeouts after MAIL and RCPT are treated specially is that
36728 these can sometimes arise as a result of the remote host's verification
36729 procedures. Exim makes this assumption, and treats them as if a temporary error
36730 response had been received. A timeout after &"."& is treated specially because
36731 it is known that some broken implementations fail to recognize the end of the
36732 message if the last character of the last line is a binary zero. Thus, it is
36733 helpful to treat this case as a message error.
36735 Timeouts at other times are treated as host errors, assuming a problem with the
36736 host, or the connection to it. If a timeout after MAIL, RCPT,
36737 or &"."& is really a connection problem, the assumption is that at the next try
36738 the timeout is likely to occur at some other point in the dialogue, causing it
36739 then to be treated as a host error.
36741 There is experimental evidence that some MTAs drop the connection after the
36742 terminating &"."& if they do not like the contents of the message for some
36743 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
36744 should be given. That is why Exim treats this case as a message rather than a
36745 host error, in order not to delay other messages to the same host.
36750 .section "Incoming SMTP messages over TCP/IP" "SECID233"
36751 .cindex "SMTP" "incoming over TCP/IP"
36752 .cindex "incoming SMTP over TCP/IP"
36755 Incoming SMTP messages can be accepted in one of two ways: by running a
36756 listening daemon, or by using &'inetd'&. In the latter case, the entry in
36757 &_/etc/inetd.conf_& should be like this:
36759 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
36761 Exim distinguishes between this case and the case of a locally running user
36762 agent using the &%-bs%& option by checking whether or not the standard input is
36763 a socket. When it is, either the port must be privileged (less than 1024), or
36764 the caller must be root or the Exim user. If any other user passes a socket
36765 with an unprivileged port number, Exim prints a message on the standard error
36766 stream and exits with an error code.
36768 By default, Exim does not make a log entry when a remote host connects or
36769 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
36770 unexpected. It can be made to write such log entries by setting the
36771 &%smtp_connection%& log selector.
36773 .cindex "carriage return"
36775 Commands from the remote host are supposed to be terminated by CR followed by
36776 LF. However, there are known to be hosts that do not send CR characters. In
36777 order to be able to interwork with such hosts, Exim treats LF on its own as a
36779 Furthermore, because common code is used for receiving messages from all
36780 sources, a CR on its own is also interpreted as a line terminator. However, the
36781 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
36783 .cindex "EHLO" "invalid data"
36784 .cindex "HELO" "invalid data"
36785 One area that sometimes gives rise to problems concerns the EHLO or
36786 HELO commands. Some clients send syntactically invalid versions of these
36787 commands, which Exim rejects by default. (This is nothing to do with verifying
36788 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
36789 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
36790 match the broken hosts that send invalid commands.
36792 .cindex "SIZE option on MAIL command"
36793 .cindex "MAIL" "SIZE option"
36794 The amount of disk space available is checked whenever SIZE is received on
36795 a MAIL command, independently of whether &%message_size_limit%& or
36796 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
36797 false. A temporary error is given if there is not enough space. If
36798 &%check_spool_space%& is set, the check is for that amount of space plus the
36799 value given with SIZE, that is, it checks that the addition of the incoming
36800 message will not reduce the space below the threshold.
36802 When a message is successfully received, Exim includes the local message id in
36803 its response to the final &"."& that terminates the data. If the remote host
36804 logs this text it can help with tracing what has happened to a message.
36806 The Exim daemon can limit the number of simultaneous incoming connections it is
36807 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
36808 number of simultaneous incoming connections from a single remote host (see the
36809 &%smtp_accept_max_per_host%& option). Additional connection attempts are
36810 rejected using the SMTP temporary error code 421.
36812 The Exim daemon does not rely on the SIGCHLD signal to detect when a
36813 subprocess has finished, as this can get lost at busy times. Instead, it looks
36814 for completed subprocesses every time it wakes up. Provided there are other
36815 things happening (new incoming calls, starts of queue runs), completed
36816 processes will be noticed and tidied away. On very quiet systems you may
36817 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
36818 it will be noticed when the daemon next wakes up.
36820 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
36821 and can also be set up to reject SMTP calls from non-reserved hosts at times of
36822 high system load &-- for details see the &%smtp_accept_reserve%&,
36823 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
36824 applies in both the daemon and &'inetd'& cases.
36826 Exim normally starts a delivery process for each message received, though this
36827 can be varied by means of the &%-odq%& command line option and the
36828 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
36829 number of simultaneously running delivery processes started in this way from
36830 SMTP input can be limited by the &%smtp_accept_queue%& and
36831 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
36832 subsequently received messages are just put on the input queue without starting
36833 a delivery process.
36835 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
36836 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
36837 started up from the &'inetd'& daemon, because in that case each connection is
36838 handled by an entirely independent Exim process. Control by load average is,
36839 however, available with &'inetd'&.
36841 Exim can be configured to verify addresses in incoming SMTP commands as they
36842 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
36843 to rewrite addresses at this time &-- before any syntax checking is done. See
36844 section &<<SECTrewriteS>>&.
36846 Exim can also be configured to limit the rate at which a client host submits
36847 MAIL and RCPT commands in a single SMTP session. See the
36848 &%smtp_ratelimit_hosts%& option.
36852 .section "Unrecognized SMTP commands" "SECID234"
36853 .cindex "SMTP" "unrecognized commands"
36854 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
36855 commands during a single SMTP connection, it drops the connection after sending
36856 the error response to the last command. The default value for
36857 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
36858 abuse that subvert web servers into making connections to SMTP ports; in these
36859 circumstances, a number of non-SMTP lines are sent first.
36862 .section "Syntax and protocol errors in SMTP commands" "SECID235"
36863 .cindex "SMTP" "syntax errors"
36864 .cindex "SMTP" "protocol errors"
36865 A syntax error is detected if an SMTP command is recognized, but there is
36866 something syntactically wrong with its data, for example, a malformed email
36867 address in a RCPT command. Protocol errors include invalid command
36868 sequencing such as RCPT before MAIL. If Exim receives more than
36869 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
36870 drops the connection after sending the error response to the last command. The
36871 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
36872 broken clients that loop sending bad commands (yes, it has been seen).
36876 .section "Use of non-mail SMTP commands" "SECID236"
36877 .cindex "SMTP" "non-mail commands"
36878 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
36879 DATA. Exim counts such commands, and drops the connection if there are too
36880 many of them in a single SMTP session. This action catches some
36881 denial-of-service attempts and things like repeated failing AUTHs, or a mad
36882 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
36883 defines what &"too many"& means. Its default value is 10.
36885 When a new message is expected, one occurrence of RSET is not counted. This
36886 allows a client to send one RSET between messages (this is not necessary,
36887 but some clients do it). Exim also allows one uncounted occurrence of HELO
36888 or EHLO, and one occurrence of STARTTLS between messages. After
36889 starting up a TLS session, another EHLO is expected, and so it too is not
36892 The first occurrence of AUTH in a connection, or immediately following
36893 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
36894 RCPT, DATA, and QUIT are counted.
36896 You can control which hosts are subject to the limit set by
36897 &%smtp_accept_max_nonmail%& by setting
36898 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
36899 the limit apply to all hosts. This option means that you can exclude any
36900 specific badly-behaved hosts that you have to live with.
36905 .section "The VRFY and EXPN commands" "SECID237"
36906 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
36907 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
36908 appropriate) in order to decide whether the command should be accepted or not.
36910 .cindex "VRFY" "processing"
36911 When no ACL is defined for VRFY, or if it rejects without
36912 setting an explicit response code, the command is accepted
36913 (with a 252 SMTP response code)
36914 in order to support awkward clients that do a VRFY before every RCPT.
36915 When VRFY is accepted, it runs exactly the same code as when Exim is
36916 called with the &%-bv%& option, and returns 250/451/550
36917 SMTP response codes.
36919 .cindex "EXPN" "processing"
36920 If no ACL for EXPN is defined, the command is rejected.
36921 When EXPN is accepted, a single-level expansion of the address is done.
36922 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
36923 than a verification (the &%-bv%& option). If an unqualified local part is given
36924 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
36925 of VRFY and EXPN commands are logged on the main and reject logs, and
36926 VRFY verification failures are logged on the main log for consistency with
36931 .section "The ETRN command" "SECTETRN"
36932 .cindex "ETRN" "processing"
36933 .cindex "ESMTP extensions" ETRN
36934 RFC 1985 describes an ESMTP command called ETRN that is designed to
36935 overcome the security problems of the TURN command (which has fallen into
36936 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
36937 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
36938 should be accepted or not. If no ACL is defined, the command is rejected.
36940 The ETRN command is concerned with &"releasing"& messages that are awaiting
36941 delivery to certain hosts. As Exim does not organize its message queue by host,
36942 the only form of ETRN that is supported by default is the one where the
36943 text starts with the &"#"& prefix, in which case the remainder of the text is
36944 specific to the SMTP server. A valid ETRN command causes a run of Exim with
36945 the &%-R%& option to happen, with the remainder of the ETRN text as its
36946 argument. For example,
36954 which causes a delivery attempt on all messages with undelivered addresses
36955 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
36956 default), Exim prevents the simultaneous execution of more than one queue run
36957 for the same argument string as a result of an ETRN command. This stops
36958 a misbehaving client from starting more than one queue runner at once.
36960 .cindex "hints database" "ETRN serialization"
36961 Exim implements the serialization by means of a hints database in which a
36962 record is written whenever a process is started by ETRN, and deleted when
36963 the process completes. However, Exim does not keep the SMTP session waiting for
36964 the ETRN process to complete. Once ETRN is accepted, the client is sent
36965 a &"success"& return code. Obviously there is scope for hints records to get
36966 left lying around if there is a system or program crash. To guard against this,
36967 Exim ignores any records that are more than six hours old.
36969 .oindex "&%smtp_etrn_command%&"
36970 For more control over what ETRN does, the &%smtp_etrn_command%& option can
36971 used. This specifies a command that is run whenever ETRN is received,
36972 whatever the form of its argument. For
36975 smtp_etrn_command = /etc/etrn_command $domain \
36976 $sender_host_address
36978 .vindex "&$domain$&"
36979 The string is split up into arguments which are independently expanded. The
36980 expansion variable &$domain$& is set to the argument of the ETRN command,
36981 and no syntax checking is done on the contents of this argument. Exim does not
36982 wait for the command to complete, so its status code is not checked. Exim runs
36983 under its own uid and gid when receiving incoming SMTP, so it is not possible
36984 for it to change them before running the command.
36988 .section "Incoming local SMTP" "SECID238"
36989 .cindex "SMTP" "local incoming"
36990 Some user agents use SMTP to pass messages to their local MTA using the
36991 standard input and output, as opposed to passing the envelope on the command
36992 line and writing the message to the standard input. This is supported by the
36993 &%-bs%& option. This form of SMTP is handled in the same way as incoming
36994 messages over TCP/IP (including the use of ACLs), except that the envelope
36995 sender given in a MAIL command is ignored unless the caller is trusted. In
36996 an ACL you can detect this form of SMTP input by testing for an empty host
36997 identification. It is common to have this as the first line in the ACL that
36998 runs for RCPT commands:
37002 This accepts SMTP messages from local processes without doing any other tests.
37006 .section "Outgoing batched SMTP" "SECTbatchSMTP"
37007 .cindex "SMTP" "batched outgoing"
37008 .cindex "batched SMTP output"
37009 Both the &(appendfile)& and &(pipe)& transports can be used for handling
37010 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
37011 be output in BSMTP format. No SMTP responses are possible for this form of
37012 delivery. All it is doing is using SMTP commands as a way of transmitting the
37013 envelope along with the message.
37015 The message is written to the file or pipe preceded by the SMTP commands
37016 MAIL and RCPT, and followed by a line containing a single dot. Lines in
37017 the message that start with a dot have an extra dot added. The SMTP command
37018 HELO is not normally used. If it is required, the &%message_prefix%& option
37019 can be used to specify it.
37021 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
37022 one recipient address at a time by default. However, you can arrange for them
37023 to handle several addresses at once by setting the &%batch_max%& option. When
37024 this is done for BSMTP, messages may contain multiple RCPT commands. See
37025 chapter &<<CHAPbatching>>& for more details.
37028 When one or more addresses are routed to a BSMTP transport by a router that
37029 sets up a host list, the name of the first host on the list is available to the
37030 transport in the variable &$host$&. Here is an example of such a transport and
37035 driver = manualroute
37036 transport = smtp_appendfile
37037 route_list = domain.example batch.host.example
37041 driver = appendfile
37042 directory = /var/bsmtp/$host
37047 This causes messages addressed to &'domain.example'& to be written in BSMTP
37048 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
37049 message (unless there are more than 1000 recipients).
37053 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
37054 .cindex "SMTP" "batched incoming"
37055 .cindex "batched SMTP input"
37056 The &%-bS%& command line option causes Exim to accept one or more messages by
37057 reading SMTP on the standard input, but to generate no responses. If the caller
37058 is trusted, the senders in the MAIL commands are believed; otherwise the
37059 sender is always the caller of Exim. Unqualified senders and receivers are not
37060 rejected (there seems little point) but instead just get qualified. HELO
37061 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
37062 as NOOP; QUIT quits.
37064 Minimal policy checking is done for BSMTP input. Only the non-SMTP
37065 ACL is run in the same way as for non-SMTP local input.
37067 If an error is detected while reading a message, including a missing &"."& at
37068 the end, Exim gives up immediately. It writes details of the error to the
37069 standard output in a stylized way that the calling program should be able to
37070 make some use of automatically, for example:
37072 554 Unexpected end of file
37073 Transaction started in line 10
37074 Error detected in line 14
37076 It writes a more verbose version, for human consumption, to the standard error
37079 An error was detected while processing a file of BSMTP input.
37080 The error message was:
37082 501 '>' missing at end of address
37084 The SMTP transaction started in line 10.
37085 The error was detected in line 12.
37086 The SMTP command at fault was:
37088 rcpt to:<malformed@in.com.plete
37090 1 previous message was successfully processed.
37091 The rest of the batch was abandoned.
37093 The return code from Exim is zero only if there were no errors. It is 1 if some
37094 messages were accepted before an error was detected, and 2 if no messages were
37096 .ecindex IIDsmtpproc1
37097 .ecindex IIDsmtpproc2
37101 . ////////////////////////////////////////////////////////////////////////////
37102 . ////////////////////////////////////////////////////////////////////////////
37104 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
37105 "Customizing messages"
37106 When a message fails to be delivered, or remains in the queue for more than a
37107 configured amount of time, Exim sends a message to the original sender, or
37108 to an alternative configured address. The text of these messages is built into
37109 the code of Exim, but it is possible to change it, either by adding a single
37110 string, or by replacing each of the paragraphs by text supplied in a file.
37112 The &'From:'& and &'To:'& header lines are automatically generated; you can
37113 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
37114 option. Exim also adds the line
37116 Auto-Submitted: auto-generated
37118 to all warning and bounce messages,
37121 .section "Customizing bounce messages" "SECID239"
37122 .cindex "customizing" "bounce message"
37123 .cindex "bounce message" "customizing"
37124 If &%bounce_message_text%& is set, its contents are included in the default
37125 message immediately after &"This message was created automatically by mail
37126 delivery software."& The string is not expanded. It is not used if
37127 &%bounce_message_file%& is set.
37129 When &%bounce_message_file%& is set, it must point to a template file for
37130 constructing error messages. The file consists of a series of text items,
37131 separated by lines consisting of exactly four asterisks. If the file cannot be
37132 opened, default text is used and a message is written to the main and panic
37133 logs. If any text item in the file is empty, default text is used for that
37136 .vindex "&$bounce_recipient$&"
37137 .vindex "&$bounce_return_size_limit$&"
37138 Each item of text that is read from the file is expanded, and there are two
37139 expansion variables which can be of use here: &$bounce_recipient$& is set to
37140 the recipient of an error message while it is being created, and
37141 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
37142 option, rounded to a whole number.
37144 The items must appear in the file in the following order:
37147 The first item is included in the headers, and should include at least a
37148 &'Subject:'& header. Exim does not check the syntax of these headers.
37150 The second item forms the start of the error message. After it, Exim lists the
37151 failing addresses with their error messages.
37153 The third item is used to introduce any text from pipe transports that is to be
37154 returned to the sender. It is omitted if there is no such text.
37156 The fourth, fifth and sixth items will be ignored and may be empty.
37157 The fields exist for back-compatibility
37160 The default state (&%bounce_message_file%& unset) is equivalent to the
37161 following file, in which the sixth item is empty. The &'Subject:'& and some
37162 other lines have been split in order to fit them on the page:
37164 Subject: Mail delivery failed
37165 ${if eq{$sender_address}{$bounce_recipient}
37166 {: returning message to sender}}
37168 This message was created automatically by mail delivery software.
37170 A message ${if eq{$sender_address}{$bounce_recipient}
37171 {that you sent }{sent by
37175 }}could not be delivered to all of its recipients.
37176 This is a permanent error. The following address(es) failed:
37178 The following text was generated during the delivery attempt(s):
37180 ------ This is a copy of the message, including all the headers.
37183 ------ The body of the message is $message_size characters long;
37185 ------ $bounce_return_size_limit or so are included here.
37188 .section "Customizing warning messages" "SECTcustwarn"
37189 .cindex "customizing" "warning message"
37190 .cindex "warning of delay" "customizing the message"
37191 The option &%warn_message_file%& can be pointed at a template file for use when
37192 warnings about message delays are created. In this case there are only three
37196 The first item is included in the headers, and should include at least a
37197 &'Subject:'& header. Exim does not check the syntax of these headers.
37199 The second item forms the start of the warning message. After it, Exim lists
37200 the delayed addresses.
37202 The third item then ends the message.
37205 The default state is equivalent to the following file, except that some lines
37206 have been split here, in order to fit them on the page:
37208 Subject: Warning: message $message_exim_id delayed
37209 $warn_message_delay
37211 This message was created automatically by mail delivery software.
37213 A message ${if eq{$sender_address}{$warn_message_recipients}
37214 {that you sent }{sent by
37218 }}has not been delivered to all of its recipients after
37219 more than $warn_message_delay in the queue on $primary_hostname.
37221 The message identifier is: $message_exim_id
37222 The subject of the message is: $h_subject
37223 The date of the message is: $h_date
37225 The following address(es) have not yet been delivered:
37227 No action is required on your part. Delivery attempts will
37228 continue for some time, and this warning may be repeated at
37229 intervals if the message remains undelivered. Eventually the
37230 mail delivery software will give up, and when that happens,
37231 the message will be returned to you.
37233 .vindex "&$warn_message_delay$&"
37234 .vindex "&$warn_message_recipients$&"
37235 However, in the default state the subject and date lines are omitted if no
37236 appropriate headers exist. During the expansion of this file,
37237 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
37238 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
37239 of recipients for the warning message. There may be more than one if there are
37240 multiple addresses with different &%errors_to%& settings on the routers that
37246 . ////////////////////////////////////////////////////////////////////////////
37247 . ////////////////////////////////////////////////////////////////////////////
37249 .chapter "Some common configuration settings" "CHAPcomconreq"
37250 This chapter discusses some configuration settings that seem to be fairly
37251 common. More examples and discussion can be found in the Exim book.
37255 .section "Sending mail to a smart host" "SECID240"
37256 .cindex "smart host" "example router"
37257 If you want to send all mail for non-local domains to a &"smart host"&, you
37258 should replace the default &(dnslookup)& router with a router which does the
37259 routing explicitly:
37261 send_to_smart_host:
37262 driver = manualroute
37263 route_list = !+local_domains smart.host.name
37264 transport = remote_smtp
37266 You can use the smart host's IP address instead of the name if you wish.
37267 If you are using Exim only to submit messages to a smart host, and not for
37268 receiving incoming messages, you can arrange for it to do the submission
37269 synchronously by setting the &%mua_wrapper%& option (see chapter
37270 &<<CHAPnonqueueing>>&).
37275 .section "Using Exim to handle mailing lists" "SECTmailinglists"
37276 .cindex "mailing lists"
37277 Exim can be used to run simple mailing lists, but for large and/or complicated
37278 requirements, the use of additional specialized mailing list software such as
37279 Majordomo or Mailman is recommended.
37281 The &(redirect)& router can be used to handle mailing lists where each list
37282 is maintained in a separate file, which can therefore be managed by an
37283 independent manager. The &%domains%& router option can be used to run these
37284 lists in a separate domain from normal mail. For example:
37288 domains = lists.example
37289 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37292 errors_to = ${quote_local_part:$local_part-request}@lists.example
37295 This router is skipped for domains other than &'lists.example'&. For addresses
37296 in that domain, it looks for a file that matches the local part. If there is no
37297 such file, the router declines, but because &%no_more%& is set, no subsequent
37298 routers are tried, and so the whole delivery fails.
37300 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
37301 expanded into a filename or a pipe delivery, which is usually inappropriate in
37304 .oindex "&%errors_to%&"
37305 The &%errors_to%& option specifies that any delivery errors caused by addresses
37306 taken from a mailing list are to be sent to the given address rather than the
37307 original sender of the message. However, before acting on this, Exim verifies
37308 the error address, and ignores it if verification fails.
37310 For example, using the configuration above, mail sent to
37311 &'dicts@lists.example'& is passed on to those addresses contained in
37312 &_/usr/lists/dicts_&, with error reports directed to
37313 &'dicts-request@lists.example'&, provided that this address can be verified.
37314 There could be a file called &_/usr/lists/dicts-request_& containing
37315 the address(es) of this particular list's manager(s), but other approaches,
37316 such as setting up an earlier router (possibly using the &%local_part_prefix%&
37317 or &%local_part_suffix%& options) to handle addresses of the form
37318 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
37322 .section "Syntax errors in mailing lists" "SECID241"
37323 .cindex "mailing lists" "syntax errors in"
37324 If an entry in redirection data contains a syntax error, Exim normally defers
37325 delivery of the original address. That means that a syntax error in a mailing
37326 list holds up all deliveries to the list. This may not be appropriate when a
37327 list is being maintained automatically from data supplied by users, and the
37328 addresses are not rigorously checked.
37330 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
37331 entries that fail to parse, noting the incident in the log. If in addition
37332 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
37333 whenever a broken address is skipped. It is usually appropriate to set
37334 &%syntax_errors_to%& to the same address as &%errors_to%&.
37338 .section "Re-expansion of mailing lists" "SECID242"
37339 .cindex "mailing lists" "re-expansion of"
37340 Exim remembers every individual address to which a message has been delivered,
37341 in order to avoid duplication, but it normally stores only the original
37342 recipient addresses with a message. If all the deliveries to a mailing list
37343 cannot be done at the first attempt, the mailing list is re-expanded when the
37344 delivery is next tried. This means that alterations to the list are taken into
37345 account at each delivery attempt, so addresses that have been added to
37346 the list since the message arrived will therefore receive a copy of the
37347 message, even though it pre-dates their subscription.
37349 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
37350 on the &(redirect)& router. If this is done, any addresses generated by the
37351 router that fail to deliver at the first attempt are added to the message as
37352 &"top level"& addresses, and the parent address that generated them is marked
37353 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
37354 subsequent delivery attempts. The disadvantage of this is that if any of the
37355 failing addresses are incorrect, correcting them in the file has no effect on
37356 pre-existing messages.
37358 The original top-level address is remembered with each of the generated
37359 addresses, and is output in any log messages. However, any intermediate parent
37360 addresses are not recorded. This makes a difference to the log only if the
37361 &%all_parents%& selector is set, but for mailing lists there is normally only
37362 one level of expansion anyway.
37366 .section "Closed mailing lists" "SECID243"
37367 .cindex "mailing lists" "closed"
37368 The examples so far have assumed open mailing lists, to which anybody may
37369 send mail. It is also possible to set up closed lists, where mail is accepted
37370 from specified senders only. This is done by making use of the generic
37371 &%senders%& option to restrict the router that handles the list.
37373 The following example uses the same file as a list of recipients and as a list
37374 of permitted senders. It requires three routers:
37378 domains = lists.example
37379 local_part_suffix = -request
37380 local_parts = ${lookup {$local_part} dsearch,filter=file {/usr/lists}}
37381 file = /usr/lists/${local_part_data}-request
37386 domains = lists.example
37387 senders = ${if exists {/usr/lists/$local_part}\
37388 {lsearch;/usr/lists/$local_part}{*}}
37389 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37392 errors_to = ${quote_local_part:$local_part-request}@lists.example
37397 domains = lists.example
37399 data = :fail: $local_part@lists.example is a closed mailing list
37401 All three routers have the same &%domains%& setting, so for any other domains,
37402 they are all skipped. The first router runs only if the local part ends in
37403 &%-request%&. It handles messages to the list manager(s) by means of an open
37406 The second router runs only if the &%senders%& precondition is satisfied. It
37407 checks for the existence of a list that corresponds to the local part, and then
37408 checks that the sender is on the list by means of a linear search. It is
37409 necessary to check for the existence of the file before trying to search it,
37410 because otherwise Exim thinks there is a configuration error. If the file does
37411 not exist, the expansion of &%senders%& is *, which matches all senders. This
37412 means that the router runs, but because there is no list, declines, and
37413 &%no_more%& ensures that no further routers are run. The address fails with an
37414 &"unrouteable address"& error.
37416 The third router runs only if the second router is skipped, which happens when
37417 a mailing list exists, but the sender is not on it. This router forcibly fails
37418 the address, giving a suitable error message.
37423 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
37425 .cindex "Variable Envelope Return Paths"
37426 .cindex "envelope from"
37427 .cindex "envelope sender"
37428 Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
37429 are a way of helping mailing list administrators discover which subscription
37430 address is the cause of a particular delivery failure. The idea is to encode
37431 the original recipient address in the outgoing envelope sender address, so that
37432 if the message is forwarded by another host and then subsequently bounces, the
37433 original recipient can be extracted from the recipient address of the bounce.
37435 .oindex &%errors_to%&
37436 .oindex &%return_path%&
37437 Envelope sender addresses can be modified by Exim using two different
37438 facilities: the &%errors_to%& option on a router (as shown in previous mailing
37439 list examples), or the &%return_path%& option on a transport. The second of
37440 these is effective only if the message is successfully delivered to another
37441 host; it is not used for errors detected on the local host (see the description
37442 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
37443 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
37449 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37450 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37452 This has the effect of rewriting the return path (envelope sender) on outgoing
37453 SMTP messages, if the local part of the original return path ends in
37454 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
37455 local part and domain of the recipient into the return path. Suppose, for
37456 example, that a message whose return path has been set to
37457 &'somelist-request@your.dom.example'& is sent to
37458 &'subscriber@other.dom.example'&. In the transport, the return path is
37461 somelist-request+subscriber=other.dom.example@your.dom.example
37463 .vindex "&$local_part$&"
37464 For this to work, you must tell Exim to send multiple copies of messages that
37465 have more than one recipient, so that each copy has just one recipient. This is
37466 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
37467 might be sent to several different recipients in the same domain, in which case
37468 &$local_part$& is not available in the transport, because it is not unique.
37470 Unless your host is doing nothing but mailing list deliveries, you should
37471 probably use a separate transport for the VERP deliveries, so as not to use
37472 extra resources in making one-per-recipient copies for other deliveries. This
37473 can easily be done by expanding the &%transport%& option in the router:
37477 domains = ! +local_domains
37479 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37480 {verp_smtp}{remote_smtp}}
37483 If you want to change the return path using &%errors_to%& in a router instead
37484 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
37485 routers that handle mailing list addresses. This will ensure that all delivery
37486 errors, including those detected on the local host, are sent to the VERP
37489 On a host that does no local deliveries and has no manual routing, only the
37490 &(dnslookup)& router needs to be changed. A special transport is not needed for
37491 SMTP deliveries. Every mailing list recipient has its own return path value,
37492 and so Exim must hand them to the transport one at a time. Here is an example
37493 of a &(dnslookup)& router that implements VERP:
37497 domains = ! +local_domains
37498 transport = remote_smtp
37500 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
37501 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37504 Before you start sending out messages with VERPed return paths, you must also
37505 configure Exim to accept the bounce messages that come back to those paths.
37506 Typically this is done by setting a &%local_part_suffix%& option for a
37507 router, and using this to route the messages to wherever you want to handle
37510 The overhead incurred in using VERP depends very much on the size of the
37511 message, the number of recipient addresses that resolve to the same remote
37512 host, and the speed of the connection over which the message is being sent. If
37513 a lot of addresses resolve to the same host and the connection is slow, sending
37514 a separate copy of the message for each address may take substantially longer
37515 than sending a single copy with many recipients (for which VERP cannot be
37523 .section "Virtual domains" "SECTvirtualdomains"
37524 .cindex "virtual domains"
37525 .cindex "domain" "virtual"
37526 The phrase &'virtual domain'& is unfortunately used with two rather different
37530 A domain for which there are no real mailboxes; all valid local parts are
37531 aliases for other email addresses. Common examples are organizational
37532 top-level domains and &"vanity"& domains.
37534 One of a number of independent domains that are all handled by the same host,
37535 with mailboxes on that host, but where the mailbox owners do not necessarily
37536 have login accounts on that host.
37539 The first usage is probably more common, and does seem more &"virtual"& than
37540 the second. This kind of domain can be handled in Exim with a straightforward
37541 aliasing router. One approach is to create a separate alias file for each
37542 virtual domain. Exim can test for the existence of the alias file to determine
37543 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
37544 to a router of this form:
37548 domains = dsearch;/etc/mail/virtual
37549 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
37552 The &%domains%& option specifies that the router is to be skipped, unless there
37553 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
37554 domain that is being processed.
37555 The &(dsearch)& lookup used results in an untainted version of &$domain$&
37556 being placed into the &$domain_data$& variable.
37558 When the router runs, it looks up the local
37559 part in the file to find a new address (or list of addresses). The &%no_more%&
37560 setting ensures that if the lookup fails (leading to &%data%& being an empty
37561 string), Exim gives up on the address without trying any subsequent routers.
37563 This one router can handle all the virtual domains because the alias filenames
37564 follow a fixed pattern. Permissions can be arranged so that appropriate people
37565 can edit the different alias files. A successful aliasing operation results in
37566 a new envelope recipient address, which is then routed from scratch.
37568 The other kind of &"virtual"& domain can also be handled in a straightforward
37569 way. One approach is to create a file for each domain containing a list of
37570 valid local parts, and use it in a router like this:
37574 domains = dsearch;/etc/mail/domains
37575 local_parts = lsearch;/etc/mail/domains/$domain
37576 transport = my_mailboxes
37578 The address is accepted if there is a file for the domain, and the local part
37579 can be found in the file. The &%domains%& option is used to check for the
37580 file's existence because &%domains%& is tested before the &%local_parts%&
37581 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
37582 because that option is tested after &%local_parts%&. The transport is as
37586 driver = appendfile
37587 file = /var/mail/$domain_data/$local_part_data
37590 This uses a directory of mailboxes for each domain. The &%user%& setting is
37591 required, to specify which uid is to be used for writing to the mailboxes.
37593 The configuration shown here is just one example of how you might support this
37594 requirement. There are many other ways this kind of configuration can be set
37595 up, for example, by using a database instead of separate files to hold all the
37596 information about the domains.
37600 .section "Multiple user mailboxes" "SECTmulbox"
37601 .cindex "multiple mailboxes"
37602 .cindex "mailbox" "multiple"
37603 .cindex "local part" "prefix"
37604 .cindex "local part" "suffix"
37605 Heavy email users often want to operate with multiple mailboxes, into which
37606 incoming mail is automatically sorted. A popular way of handling this is to
37607 allow users to use multiple sender addresses, so that replies can easily be
37608 identified. Users are permitted to add prefixes or suffixes to their local
37609 parts for this purpose. The wildcard facility of the generic router options
37610 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
37611 example, consider this router:
37616 file = $home/.forward
37617 local_part_suffix = -*
37618 local_part_suffix_optional
37621 .vindex "&$local_part_suffix$&"
37622 It runs a user's &_.forward_& file for all local parts of the form
37623 &'username-*'&. Within the filter file the user can distinguish different
37624 cases by testing the variable &$local_part_suffix$&. For example:
37626 if $local_part_suffix contains -special then
37627 save /home/$local_part_data/Mail/special
37630 If the filter file does not exist, or does not deal with such addresses, they
37631 fall through to subsequent routers, and, assuming no subsequent use of the
37632 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
37633 control over which suffixes are valid.
37635 Alternatively, a suffix can be used to trigger the use of a different
37636 &_.forward_& file &-- which is the way a similar facility is implemented in
37642 local_part_suffix = -*
37643 local_part_suffix_optional
37644 file = ${lookup {.forward$local_part_suffix} dsearch,ret=full {$home} {$value}fail}
37647 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
37648 example, &_.forward-special_& is used. Once again, if the appropriate file
37649 does not exist, or does not deal with the address, it is passed on to
37650 subsequent routers, which could, if required, look for an unqualified
37651 &_.forward_& file to use as a default.
37655 .section "Simplified vacation processing" "SECID244"
37656 .cindex "vacation processing"
37657 The traditional way of running the &'vacation'& program is for a user to set up
37658 a pipe command in a &_.forward_& file
37659 (see section &<<SECTspecitredli>>& for syntax details).
37660 This is prone to error by inexperienced users. There are two features of Exim
37661 that can be used to make this process simpler for users:
37664 A local part prefix such as &"vacation-"& can be specified on a router which
37665 can cause the message to be delivered directly to the &'vacation'& program, or
37666 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
37667 &_.forward_& file are then much simpler. For example:
37669 spqr, vacation-spqr
37672 The &%require_files%& generic router option can be used to trigger a
37673 vacation delivery by checking for the existence of a certain file in the
37674 user's home directory. The &%unseen%& generic option should also be used, to
37675 ensure that the original delivery also proceeds. In this case, all the user has
37676 to do is to create a file called, say, &_.vacation_&, containing a vacation
37680 Another advantage of both these methods is that they both work even when the
37681 use of arbitrary pipes by users is locked out.
37685 .section "Taking copies of mail" "SECID245"
37686 .cindex "message" "copying every"
37687 Some installations have policies that require archive copies of all messages to
37688 be made. A single copy of each message can easily be taken by an appropriate
37689 command in a system filter, which could, for example, use a different file for
37690 each day's messages.
37692 There is also a shadow transport mechanism that can be used to take copies of
37693 messages that are successfully delivered by local transports, one copy per
37694 delivery. This could be used, &'inter alia'&, to implement automatic
37695 notification of delivery by sites that insist on doing such things.
37699 .section "Intermittently connected hosts" "SECID246"
37700 .cindex "intermittently connected hosts"
37701 It has become quite common (because it is cheaper) for hosts to connect to the
37702 Internet periodically rather than remain connected all the time. The normal
37703 arrangement is that mail for such hosts accumulates on a system that is
37704 permanently connected.
37706 Exim was designed for use on permanently connected hosts, and so it is not
37707 particularly well-suited to use in an intermittently connected environment.
37708 Nevertheless there are some features that can be used.
37711 .section "Exim on the upstream server host" "SECID247"
37712 It is tempting to arrange for incoming mail for the intermittently connected
37713 host to remain in Exim's queue until the client connects. However, this
37714 approach does not scale very well. Two different kinds of waiting message are
37715 being mixed up in the same queue &-- those that cannot be delivered because of
37716 some temporary problem, and those that are waiting for their destination host
37717 to connect. This makes it hard to manage the queue, as well as wasting
37718 resources, because each queue runner scans the entire queue.
37720 A better approach is to separate off those messages that are waiting for an
37721 intermittently connected host. This can be done by delivering these messages
37722 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
37723 format, from where they are transmitted by other software when their
37724 destination connects. This makes it easy to collect all the mail for one host
37725 in a single directory, and to apply local timeout rules on a per-message basis
37728 On a very small scale, leaving the mail on Exim's queue can be made to work. If
37729 you are doing this, you should configure Exim with a long retry period for the
37730 intermittent host. For example:
37732 cheshire.wonderland.fict.example * F,5d,24h
37734 This stops a lot of failed delivery attempts from occurring, but Exim remembers
37735 which messages it has queued up for that host. Once the intermittent host comes
37736 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
37737 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
37738 causes all the queued up messages to be delivered, often down a single SMTP
37739 connection. While the host remains connected, any new messages get delivered
37742 If the connecting hosts do not have fixed IP addresses, that is, if a host is
37743 issued with a different IP address each time it connects, Exim's retry
37744 mechanisms on the holding host get confused, because the IP address is normally
37745 used as part of the key string for holding retry information. This can be
37746 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
37747 Since this has disadvantages for permanently connected hosts, it is best to
37748 arrange a separate transport for the intermittently connected ones.
37752 .section "Exim on the intermittently connected client host" "SECID248"
37753 The value of &%smtp_accept_queue_per_connection%& should probably be
37754 increased, or even set to zero (that is, disabled) on the intermittently
37755 connected host, so that all incoming messages down a single connection get
37756 delivered immediately.
37758 .cindex "SMTP" "passed connection"
37759 .cindex "SMTP" "multiple deliveries"
37760 .cindex "multiple SMTP deliveries"
37761 .cindex "first pass routing"
37762 Mail waiting to be sent from an intermittently connected host will probably
37763 not have been routed, because without a connection DNS lookups are not
37764 possible. This means that if a normal queue run is done at connection time,
37765 each message is likely to be sent in a separate SMTP session. This can be
37766 avoided by starting the queue run with a command line option beginning with
37767 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
37768 first pass, routing is done but no deliveries take place. The second pass is a
37769 normal queue run; since all the messages have been previously routed, those
37770 destined for the same host are likely to get sent as multiple deliveries in a
37771 single SMTP connection.
37775 . ////////////////////////////////////////////////////////////////////////////
37776 . ////////////////////////////////////////////////////////////////////////////
37778 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
37779 "Exim as a non-queueing client"
37780 .cindex "client, non-queueing"
37781 .cindex "smart host" "suppressing queueing"
37782 On a personal computer, it is a common requirement for all
37783 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
37784 configured to operate that way, for all the popular operating systems.
37785 However, there are some MUAs for Unix-like systems that cannot be so
37786 configured: they submit messages using the command line interface of
37787 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
37790 If the personal computer runs continuously, there is no problem, because it can
37791 run a conventional MTA that handles delivery to the smart host, and deal with
37792 any delays via its queueing mechanism. However, if the computer does not run
37793 continuously or runs different operating systems at different times, queueing
37794 email is not desirable.
37796 There is therefore a requirement for something that can provide the
37797 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
37798 any queueing or retrying facilities. Furthermore, the delivery to the smart
37799 host should be synchronous, so that if it fails, the sending MUA is immediately
37800 informed. In other words, we want something that extends an MUA that submits
37801 to a local MTA via the command line so that it behaves like one that submits
37802 to a remote smart host using TCP/SMTP.
37804 There are a number of applications (for example, there is one called &'ssmtp'&)
37805 that do this job. However, people have found them to be lacking in various
37806 ways. For instance, you might want to allow aliasing and forwarding to be done
37807 before sending a message to the smart host.
37809 Exim already had the necessary infrastructure for doing this job. Just a few
37810 tweaks were needed to make it behave as required, though it is somewhat of an
37811 overkill to use a fully-featured MTA for this purpose.
37813 .oindex "&%mua_wrapper%&"
37814 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
37815 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
37816 assumes that it is being used to &"wrap"& a command-line MUA in the manner
37817 just described. As well as setting &%mua_wrapper%&, you also need to provide a
37818 compatible router and transport configuration. Typically there will be just one
37819 router and one transport, sending everything to a smart host.
37821 When run in MUA wrapping mode, the behaviour of Exim changes in the
37825 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
37826 In other words, the only way to submit messages is via the command line.
37828 Each message is synchronously delivered as soon as it is received (&%-odi%& is
37829 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
37830 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
37831 does not finish until the delivery attempt is complete. If the delivery is
37832 successful, a zero return code is given.
37834 Address redirection is permitted, but the final routing for all addresses must
37835 be to the same remote transport, and to the same list of hosts. Furthermore,
37836 the return address (envelope sender) must be the same for all recipients, as
37837 must any added or deleted header lines. In other words, it must be possible to
37838 deliver the message in a single SMTP transaction, however many recipients there
37841 If these conditions are not met, or if routing any address results in a
37842 failure or defer status, or if Exim is unable to deliver all the recipients
37843 successfully to one of the smart hosts, delivery of the entire message fails.
37845 Because no queueing is allowed, all failures are treated as permanent; there
37846 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
37847 smart host. Furthermore, because only a single yes/no response can be given to
37848 the caller, it is not possible to deliver to some recipients and not others. If
37849 there is an error (temporary or permanent) for any recipient, all are failed.
37851 If more than one smart host is listed, Exim will try another host after a
37852 connection failure or a timeout, in the normal way. However, if this kind of
37853 failure happens for all the hosts, the delivery fails.
37855 When delivery fails, an error message is written to the standard error stream
37856 (as well as to Exim's log), and Exim exits to the caller with a return code
37857 value 1. The message is expunged from Exim's spool files. No bounce messages
37858 are ever generated.
37860 No retry data is maintained, and any retry rules are ignored.
37862 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
37863 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
37864 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
37867 The overall effect is that Exim makes a single synchronous attempt to deliver
37868 the message, failing if there is any kind of problem. Because no local
37869 deliveries are done and no daemon can be run, Exim does not need root
37870 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
37871 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
37872 the advantages and disadvantages of running without root privilege.
37877 . ////////////////////////////////////////////////////////////////////////////
37878 . ////////////////////////////////////////////////////////////////////////////
37880 .chapter "Log files" "CHAPlog"
37881 .scindex IIDloggen "log" "general description"
37882 .cindex "log" "types of"
37883 Exim writes three different logs, referred to as the main log, the reject log,
37888 The main log records the arrival of each message and each delivery in a single
37889 line in each case. The format is as compact as possible, in an attempt to keep
37890 down the size of log files. Two-character flag sequences make it easy to pick
37891 out these lines. A number of other events are recorded in the main log. Some of
37892 them are optional, in which case the &%log_selector%& option controls whether
37893 they are included or not. A Perl script called &'eximstats'&, which does simple
37894 analysis of main log files, is provided in the Exim distribution (see section
37895 &<<SECTmailstat>>&).
37897 .cindex "reject log"
37898 The reject log records information from messages that are rejected as a result
37899 of a configuration option (that is, for policy reasons).
37900 The first line of each rejection is a copy of the line that is also written to
37901 the main log. Then, if the message's header has been read at the time the log
37902 is written, its contents are written to this log. Only the original header
37903 lines are available; header lines added by ACLs are not logged. You can use the
37904 reject log to check that your policy controls are working correctly; on a busy
37905 host this may be easier than scanning the main log for rejection messages. You
37906 can suppress the writing of the reject log by setting &%write_rejectlog%&
37909 .cindex "panic log"
37910 .cindex "system log"
37911 When certain serious errors occur, Exim writes entries to its panic log. If the
37912 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
37913 are usually written to the main log as well, but can get lost amid the mass of
37914 other entries. The panic log should be empty under normal circumstances. It is
37915 therefore a good idea to check it (or to have a &'cron'& script check it)
37916 regularly, in order to become aware of any problems. When Exim cannot open its
37917 panic log, it tries as a last resort to write to the system log (syslog). This
37918 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
37919 message itself is written at priority LOG_CRIT.
37922 Every log line starts with a timestamp, in the format shown in the following
37923 example. Note that many of the examples shown in this chapter are line-wrapped.
37924 In the log file, this would be all on one line:
37926 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
37929 By default, the timestamps are in the local timezone. There are two
37930 ways of changing this:
37933 You can set the &%timezone%& option to a different time zone; in particular, if
37938 the timestamps will be in UTC (aka GMT).
37940 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
37943 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
37947 .cindex "log" "process ids in"
37948 .cindex "pid (process id)" "in log lines"
37949 Exim does not include its process id in log lines by default, but you can
37950 request that it does so by specifying the &`pid`& log selector (see section
37951 &<<SECTlogselector>>&). When this is set, the process id is output, in square
37952 brackets, immediately after the time and date.
37957 .section "Where the logs are written" "SECTwhelogwri"
37958 .cindex "log" "destination"
37959 .cindex "log" "to file"
37960 .cindex "log" "to syslog"
37962 The logs may be written to local files, or to syslog, or both. However, it
37963 should be noted that many syslog implementations use UDP as a transport, and
37964 are therefore unreliable in the sense that messages are not guaranteed to
37965 arrive at the loghost, nor is the ordering of messages necessarily maintained.
37966 It has also been reported that on large log files (tens of megabytes) you may
37967 need to tweak syslog to prevent it syncing the file with each write &-- on
37968 Linux this has been seen to make syslog take 90% plus of CPU time.
37970 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
37971 &_Local/Makefile_& or by setting &%log_file_path%& in the runtime
37972 configuration. This latter string is expanded, so it can contain, for example,
37973 references to the host name:
37975 log_file_path = /var/log/$primary_hostname/exim_%slog
37977 It is generally advisable, however, to set the string in &_Local/Makefile_&
37978 rather than at runtime, because then the setting is available right from the
37979 start of Exim's execution. Otherwise, if there's something it wants to log
37980 before it has read the configuration file (for example, an error in the
37981 configuration file) it will not use the path you want, and may not be able to
37984 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
37985 list, currently limited to at most two items. This is one option where the
37986 facility for changing a list separator may not be used. The list must always be
37987 colon-separated. If an item in the list is &"syslog"& then syslog is used;
37988 otherwise the item must either be an absolute path, containing &`%s`& at the
37989 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
37990 implying the use of a default path.
37992 When Exim encounters an empty item in the list, it searches the list defined by
37993 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
37994 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
37995 mean &"use the path specified at build time"&. It no such item exists, log
37996 files are written in the &_log_& subdirectory of the spool directory. This is
37997 equivalent to the setting:
37999 log_file_path = $spool_directory/log/%slog
38001 If you do not specify anything at build time or runtime,
38002 or if you unset the option at runtime (i.e. &`log_file_path = `&),
38003 that is where the logs are written.
38005 A log file path may also contain &`%D`& or &`%M`& if datestamped log filenames
38006 are in use &-- see section &<<SECTdatlogfil>>& below.
38008 Here are some examples of possible settings:
38010 &`LOG_FILE_PATH=syslog `& syslog only
38011 &`LOG_FILE_PATH=:syslog `& syslog and default path
38012 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
38013 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
38015 If there are more than two paths in the list, the first is used and a panic
38020 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
38021 .cindex "log" "cycling local files"
38022 .cindex "cycling logs"
38023 .cindex "&'exicyclog'&"
38024 .cindex "log" "local files; writing to"
38025 Some operating systems provide centralized and standardized methods for cycling
38026 log files. For those that do not, a utility script called &'exicyclog'& is
38027 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
38028 main and reject logs each time it is called. The maximum number of old logs to
38029 keep can be set. It is suggested this script is run as a daily &'cron'& job.
38031 An Exim delivery process opens the main log when it first needs to write to it,
38032 and it keeps the file open in case subsequent entries are required &-- for
38033 example, if a number of different deliveries are being done for the same
38034 message. However, remote SMTP deliveries can take a long time, and this means
38035 that the file may be kept open long after it is renamed if &'exicyclog'& or
38036 something similar is being used to rename log files on a regular basis. To
38037 ensure that a switch of log files is noticed as soon as possible, Exim calls
38038 &[stat()]& on the main log's name before reusing an open file, and if the file
38039 does not exist, or its inode has changed, the old file is closed and Exim
38040 tries to open the main log from scratch. Thus, an old log file may remain open
38041 for quite some time, but no Exim processes should write to it once it has been
38046 .section "Datestamped log files" "SECTdatlogfil"
38047 .cindex "log" "datestamped files"
38048 Instead of cycling the main and reject log files by renaming them
38049 periodically, some sites like to use files whose names contain a datestamp,
38050 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
38051 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
38052 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
38053 point where the datestamp is required. For example:
38055 log_file_path = /var/spool/exim/log/%slog-%D
38056 log_file_path = /var/log/exim-%s-%D.log
38057 log_file_path = /var/spool/exim/log/%D-%slog
38058 log_file_path = /var/log/exim/%s.%M
38060 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
38061 examples of names generated by the above examples:
38063 /var/spool/exim/log/mainlog-20021225
38064 /var/log/exim-reject-20021225.log
38065 /var/spool/exim/log/20021225-mainlog
38066 /var/log/exim/main.200212
38068 When this form of log file is specified, Exim automatically switches to new
38069 files at midnight. It does not make any attempt to compress old logs; you
38070 will need to write your own script if you require this. You should not
38071 run &'exicyclog'& with this form of logging.
38073 The location of the panic log is also determined by &%log_file_path%&, but it
38074 is not datestamped, because rotation of the panic log does not make sense.
38075 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
38076 the string. In addition, if it immediately follows a slash, a following
38077 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
38078 character is removed. Thus, the four examples above would give these panic
38081 /var/spool/exim/log/paniclog
38082 /var/log/exim-panic.log
38083 /var/spool/exim/log/paniclog
38084 /var/log/exim/panic
38088 .section "Logging to syslog" "SECID249"
38089 .cindex "log" "syslog; writing to"
38090 The use of syslog does not change what Exim logs or the format of its messages,
38091 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
38092 Exim's log lines are omitted when these lines are sent to syslog. Apart from
38093 that, the same strings are written to syslog as to log files. The syslog
38094 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
38095 by default, but you can change these by setting the &%syslog_facility%& and
38096 &%syslog_processname%& options, respectively. If Exim was compiled with
38097 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
38098 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
38099 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
38100 the time and host name to each line.
38101 The three log streams are mapped onto syslog priorities as follows:
38104 &'mainlog'& is mapped to LOG_INFO
38106 &'rejectlog'& is mapped to LOG_NOTICE
38108 &'paniclog'& is mapped to LOG_ALERT
38111 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
38112 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
38113 these are routed by syslog to the same place. You can suppress this duplication
38114 by setting &%syslog_duplication%& false.
38116 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
38117 entries contain multiple lines when headers are included. To cope with both
38118 these cases, entries written to syslog are split into separate &[syslog()]&
38119 calls at each internal newline, and also after a maximum of
38120 870 data characters. (This allows for a total syslog line length of 1024, when
38121 additions such as timestamps are added.) If you are running a syslog
38122 replacement that can handle lines longer than the 1024 characters allowed by
38123 RFC 3164, you should set
38125 SYSLOG_LONG_LINES=yes
38127 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
38128 lines, but it still splits at internal newlines in &'reject'& log entries.
38130 To make it easy to re-assemble split lines later, each component of a split
38131 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
38132 where <&'n'&> is the component number and <&'m'&> is the total number of
38133 components in the entry. The / delimiter is used when the line was split
38134 because it was too long; if it was split because of an internal newline, the \
38135 delimiter is used. For example, supposing the length limit to be 50 instead of
38136 870, the following would be the result of a typical rejection message to
38137 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
38138 name, and pid as added by syslog:
38140 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
38141 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
38142 [3/5] when scanning for sender: missing or malformed lo
38143 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
38146 The same error might cause the following lines to be written to &"rejectlog"&
38149 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
38150 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
38151 [3/18] er when scanning for sender: missing or malformed
38152 [4/18] local part in "<>" (envelope sender is <ph10@cam
38154 [6\18] Recipients: ph10@some.domain.cam.example
38155 [7\18] P Received: from [127.0.0.1] (ident=ph10)
38156 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
38157 [9\18] id 16RdAL-0006pc-00
38158 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
38159 [11\18] 09:43 +0100
38161 [13\18] Subject: this is a test header
38162 [18\18] X-something: this is another header
38163 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
38166 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
38168 Log lines that are neither too long nor contain newlines are written to syslog
38169 without modification.
38171 If only syslog is being used, the Exim monitor is unable to provide a log tail
38172 display, unless syslog is routing &'mainlog'& to a file on the local host and
38173 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
38178 .section "Log line flags" "SECID250"
38179 One line is written to the main log for each message received, and for each
38180 successful, unsuccessful, and delayed delivery. These lines can readily be
38181 picked out by the distinctive two-character flags that immediately follow the
38182 timestamp. The flags are:
38184 &`<=`& message arrival
38185 &`(=`& message fakereject
38186 &`=>`& normal message delivery
38187 &`->`& additional address in same delivery
38188 &`>>`& cutthrough message delivery
38189 &`*>`& delivery suppressed by &%-N%&
38190 &`**`& delivery failed; address bounced
38191 &`==`& delivery deferred; temporary problem
38195 .section "Logging message reception" "SECID251"
38196 .cindex "log" "reception line"
38197 The format of the single-line entry in the main log that is written for every
38198 message received is shown in the basic example below, which is split over
38199 several lines in order to fit it on the page:
38201 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
38202 H=mailer.fict.example [192.168.123.123] U=exim
38203 P=smtp S=5678 id=<incoming message id>
38205 The address immediately following &"<="& is the envelope sender address. A
38206 bounce message is shown with the sender address &"<>"&, and if it is locally
38207 generated, this is followed by an item of the form
38211 which is a reference to the message that caused the bounce to be sent.
38215 For messages from other hosts, the H and U fields identify the remote host and
38216 record the RFC 1413 identity of the user that sent the message, if one was
38217 received. The number given in square brackets is the IP address of the sending
38218 host. If there is a single, unparenthesized host name in the H field, as
38219 above, it has been verified to correspond to the IP address (see the
38220 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
38221 by the remote host in the SMTP HELO or EHLO command, and has not been
38222 verified. If verification yields a different name to that given for HELO or
38223 EHLO, the verified name appears first, followed by the HELO or EHLO
38224 name in parentheses.
38226 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
38227 without brackets, in the HELO or EHLO command, leading to entries in
38228 the log containing text like these examples:
38230 H=(10.21.32.43) [192.168.8.34]
38231 H=([10.21.32.43]) [192.168.8.34]
38233 This can be confusing. Only the final address in square brackets can be relied
38236 For locally generated messages (that is, messages not received over TCP/IP),
38237 the H field is omitted, and the U field contains the login name of the caller
38240 .cindex "authentication" "logging"
38241 .cindex "AUTH" "logging"
38242 For all messages, the P field specifies the protocol used to receive the
38243 message. This is the value that is stored in &$received_protocol$&. In the case
38244 of incoming SMTP messages, the value indicates whether or not any SMTP
38245 extensions (ESMTP), encryption, or authentication were used. If the SMTP
38246 session was encrypted, there is an additional X field that records the cipher
38247 suite that was used.
38249 .cindex log protocol
38250 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
38251 hosts that have authenticated themselves using the SMTP AUTH command. The first
38252 value is used when the SMTP connection was encrypted (&"secure"&). In this case
38253 there is an additional item A= followed by the name of the authenticator that
38254 was used. If an authenticated identification was set up by the authenticator's
38255 &%server_set_id%& option, this is logged too, separated by a colon from the
38256 authenticator name.
38258 .cindex "size" "of message"
38259 The id field records the existing message id, if present. The size of the
38260 received message is given by the S field. When the message is delivered,
38261 headers may be removed or added, so that the size of delivered copies of the
38262 message may not correspond with this value (and indeed may be different to each
38265 The &%log_selector%& option can be used to request the logging of additional
38266 data when a message is received. See section &<<SECTlogselector>>& below.
38270 .section "Logging deliveries" "SECID252"
38271 .cindex "log" "delivery line"
38272 The format of the single-line entry in the main log that is written for every
38273 delivery is shown in one of the examples below, for local and remote
38274 deliveries, respectively. Each example has been split into multiple lines in order
38275 to fit it on the page:
38277 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
38278 <marv@hitch.fict.example> R=localuser T=local_delivery
38279 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
38280 monk@holistic.fict.example R=dnslookup T=remote_smtp
38281 H=holistic.fict.example [192.168.234.234]
38283 For ordinary local deliveries, the original address is given in angle brackets
38284 after the final delivery address, which might be a pipe or a file. If
38285 intermediate address(es) exist between the original and the final address, the
38286 last of these is given in parentheses after the final address. The R and T
38287 fields record the router and transport that were used to process the address.
38289 If SMTP AUTH was used for the delivery there is an additional item A=
38290 followed by the name of the authenticator that was used.
38291 If an authenticated identification was set up by the authenticator's &%client_set_id%&
38292 option, this is logged too, as a second colon-separated list item.
38293 Optionally (see the &%smtp_mailauth%& &%log_selector%&) there may be a third list item.
38295 If a shadow transport was run after a successful local delivery, the log line
38296 for the successful delivery has an item added on the end, of the form
38298 &`ST=<`&&'shadow transport name'&&`>`&
38300 If the shadow transport did not succeed, the error message is put in
38301 parentheses afterwards.
38303 .cindex "asterisk" "after IP address"
38304 When more than one address is included in a single delivery (for example, two
38305 SMTP RCPT commands in one transaction) the second and subsequent addresses are
38306 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
38307 down a single SMTP connection, an asterisk follows the IP address in the log
38308 lines for the second and subsequent messages.
38309 When two or more messages are delivered down a single TLS connection, the
38310 DNS and some TLS-related information logged for the first message delivered
38311 will not be present in the log lines for the second and subsequent messages.
38312 TLS cipher information is still available.
38314 .cindex "delivery" "cutthrough; logging"
38315 .cindex "cutthrough" "logging"
38316 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
38317 line precedes the reception line, since cutthrough waits for a possible
38318 rejection from the destination in case it can reject the sourced item.
38320 The generation of a reply message by a filter file gets logged as a
38321 &"delivery"& to the addressee, preceded by &">"&.
38323 The &%log_selector%& option can be used to request the logging of additional
38324 data when a message is delivered. See section &<<SECTlogselector>>& below.
38327 .section "Discarded deliveries" "SECID253"
38328 .cindex "discarded messages"
38329 .cindex "message" "discarded"
38330 .cindex "delivery" "discarded; logging"
38331 When a message is discarded as a result of the command &"seen finish"& being
38332 obeyed in a filter file which generates no deliveries, a log entry of the form
38334 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
38335 <low.club@bridge.example> R=userforward
38337 is written, to record why no deliveries are logged. When a message is discarded
38338 because it is aliased to &":blackhole:"& the log line is like this:
38340 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
38341 <hole@nowhere.example> R=blackhole_router
38345 .section "Deferred deliveries" "SECID254"
38346 When a delivery is deferred, a line of the following form is logged:
38348 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
38349 R=dnslookup T=smtp defer (146): Connection refused
38351 In the case of remote deliveries, the error is the one that was given for the
38352 last IP address that was tried. Details of individual SMTP failures are also
38353 written to the log, so the above line would be preceded by something like
38355 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
38356 mail1.endrest.example [192.168.239.239]: Connection refused
38358 When a deferred address is skipped because its retry time has not been reached,
38359 a message is written to the log, but this can be suppressed by setting an
38360 appropriate value in &%log_selector%&.
38364 .section "Delivery failures" "SECID255"
38365 .cindex "delivery" "failure; logging"
38366 If a delivery fails because an address cannot be routed, a line of the
38367 following form is logged:
38369 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
38370 <jim@trek99.example>: unknown mail domain
38372 If a delivery fails at transport time, the router and transport are shown, and
38373 the response from the remote host is included, as in this example:
38375 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
38376 R=dnslookup T=remote_smtp: SMTP error from remote mailer
38377 after pipelined RCPT TO:<ace400@pb.example>: host
38378 pbmail3.py.example [192.168.63.111]: 553 5.3.0
38379 <ace400@pb.example>...Addressee unknown
38381 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
38382 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
38383 disabling PIPELINING. The log lines for all forms of delivery failure are
38384 flagged with &`**`&.
38388 .section "Fake deliveries" "SECID256"
38389 .cindex "delivery" "fake; logging"
38390 If a delivery does not actually take place because the &%-N%& option has been
38391 used to suppress it, a normal delivery line is written to the log, except that
38392 &"=>"& is replaced by &"*>"&.
38396 .section "Completion" "SECID257"
38399 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
38401 is written to the main log when a message is about to be removed from the spool
38402 at the end of its processing.
38407 .section "Summary of Fields in Log Lines" "SECID258"
38408 .cindex "log" "summary of fields"
38409 A summary of the field identifiers that are used in log lines is shown in
38410 the following table:
38412 &`A `& authenticator name (and optional id and sender)
38413 &`C `& SMTP confirmation on delivery
38414 &` `& command list for &"no mail in SMTP session"&
38415 &`CV `& certificate verification status
38416 &`D `& duration of &"no mail in SMTP session"&
38417 &`DKIM`& domain verified in incoming message
38418 &`DN `& distinguished name from peer certificate
38419 &`DS `& DNSSEC secured lookups
38420 &`DT `& on &`=>`&, &'=='& and &'**'& lines: time taken for, or to attempt, a delivery
38421 &`F `& sender address (on delivery lines)
38422 &`H `& host name and IP address
38423 &`I `& local interface used
38424 &`id `& message id (from header) for incoming message
38425 &`K `& CHUNKING extension used
38426 &`L `& on &`<=`& and &`=>`& lines: PIPELINING extension used
38427 &`M8S `& 8BITMIME status for incoming message
38428 &`P `& on &`<=`& lines: protocol used
38429 &` `& on &`=>`& and &`**`& lines: return path
38430 &`PRDR`& PRDR extension used
38431 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
38432 &`Q `& alternate queue name
38433 &`QT `& on &`=>`& lines: time spent on queue so far
38434 &` `& on &"Completed"& lines: time spent on queue
38435 &`R `& on &`<=`& lines: reference for local bounce
38436 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
38437 &`RT `& on &`<=`& lines: time taken for reception
38438 &`S `& size of message in bytes
38439 &`SNI `& server name indication from TLS client hello
38440 &`ST `& shadow transport name
38441 &`T `& on &`<=`& lines: message subject (topic)
38442 &`TFO `& connection took advantage of TCP Fast Open
38443 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
38444 &`U `& local user or RFC 1413 identity
38445 &`X `& TLS cipher suite
38449 .section "Other log entries" "SECID259"
38450 Various other types of log entry are written from time to time. Most should be
38451 self-explanatory. Among the more common are:
38454 .cindex "retry" "time not reached"
38455 &'retry time not reached'&&~&~An address previously suffered a temporary error
38456 during routing or local delivery, and the time to retry has not yet arrived.
38457 This message is not written to an individual message log file unless it happens
38458 during the first delivery attempt.
38460 &'retry time not reached for any host'&&~&~An address previously suffered
38461 temporary errors during remote delivery, and the retry time has not yet arrived
38462 for any of the hosts to which it is routed.
38464 .cindex "spool directory" "file locked"
38465 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
38466 some other Exim process is already working on the message. This can be quite
38467 common if queue running processes are started at frequent intervals. The
38468 &'exiwhat'& utility script can be used to find out what Exim processes are
38471 .cindex "error" "ignored"
38472 &'error ignored'&&~&~There are several circumstances that give rise to this
38475 Exim failed to deliver a bounce message whose age was greater than
38476 &%ignore_bounce_errors_after%&. The bounce was discarded.
38478 A filter file set up a delivery using the &"noerror"& option, and the delivery
38479 failed. The delivery was discarded.
38481 A delivery set up by a router configured with
38482 . ==== As this is a nested list, any displays it contains must be indented
38483 . ==== as otherwise they are too far to the left.
38487 failed. The delivery was discarded.
38490 .cindex DKIM "log line"
38491 &'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
38492 logging and the message has a DKIM signature header.
38499 .section "Reducing or increasing what is logged" "SECTlogselector"
38500 .cindex "log" "selectors"
38501 By setting the &%log_selector%& global option, you can disable some of Exim's
38502 default logging, or you can request additional logging. The value of
38503 &%log_selector%& is made up of names preceded by plus or minus characters. For
38506 log_selector = +arguments -retry_defer
38508 The list of optional log items is in the following table, with the default
38509 selection marked by asterisks:
38511 &` 8bitmime `& received 8BITMIME status
38512 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
38513 &` address_rewrite `& address rewriting
38514 &` all_parents `& all parents in => lines
38515 &` arguments `& command line arguments
38516 &`*connection_reject `& connection rejections
38517 &`*delay_delivery `& immediate delivery delayed
38518 &` deliver_time `& time taken to attempt delivery
38519 &` delivery_size `& add &`S=`&&'nnn'& to => lines
38520 &`*dkim `& DKIM verified domain on <= lines
38521 &` dkim_verbose `& separate full DKIM verification result line, per signature
38522 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
38523 &` dnssec `& DNSSEC secured lookups
38524 &`*etrn `& ETRN commands
38525 &`*host_lookup_failed `& as it says
38526 &` ident_timeout `& timeout for ident connection
38527 &` incoming_interface `& local interface on <= and => lines
38528 &` incoming_port `& remote port on <= lines
38529 &`*lost_incoming_connection `& as it says (includes timeouts)
38530 &` millisec `& millisecond timestamps and RT,QT,DT,D times
38531 &`*msg_id `& on <= lines, Message-ID: header value
38532 &` msg_id_created `& on <= lines, Message-ID: header value when one had to be added
38533 &` outgoing_interface `& local interface on => lines
38534 &` outgoing_port `& add remote port to => lines
38535 &`*queue_run `& start and end queue runs
38536 &` queue_time `& time on queue for one recipient
38537 &` queue_time_overall `& time on queue for whole message
38538 &` pid `& Exim process id
38539 &` pipelining `& PIPELINING use, on <= and => lines
38540 &` proxy `& proxy address on <= and => lines
38541 &` receive_time `& time taken to receive message
38542 &` received_recipients `& recipients on <= lines
38543 &` received_sender `& sender on <= lines
38544 &`*rejected_header `& header contents on reject log
38545 &`*retry_defer `& &"retry time not reached"&
38546 &` return_path_on_delivery `& put return path on => and ** lines
38547 &` sender_on_delivery `& add sender to => lines
38548 &`*sender_verify_fail `& sender verification failures
38549 &`*size_reject `& rejection because too big
38550 &`*skip_delivery `& delivery skipped in a queue run
38551 &`*smtp_confirmation `& SMTP confirmation on => lines
38552 &` smtp_connection `& incoming SMTP connections
38553 &` smtp_incomplete_transaction`& incomplete SMTP transactions
38554 &` smtp_mailauth `& AUTH argument to MAIL commands
38555 &` smtp_no_mail `& session with no MAIL commands
38556 &` smtp_protocol_error `& SMTP protocol errors
38557 &` smtp_syntax_error `& SMTP syntax errors
38558 &` subject `& contents of &'Subject:'& on <= lines
38559 &`*tls_certificate_verified `& certificate verification status
38560 &`*tls_cipher `& TLS cipher suite on <= and => lines
38561 &` tls_peerdn `& TLS peer DN on <= and => lines
38562 &` tls_resumption `& append * to cipher field
38563 &` tls_sni `& TLS SNI on <= lines
38564 &` unknown_in_list `& DNS lookup failed in list match
38566 &` all `& all of the above
38568 See also the &%slow_lookup_log%& main configuration option,
38569 section &<<SECID99>>&
38571 More details on each of these items follows:
38575 .cindex "log" "8BITMIME"
38576 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
38577 which may help in tracking down interoperability issues with ancient MTAs
38578 that are not 8bit clean. This is added to the &"<="& line, tagged with
38579 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
38580 &`7BIT`& and &`8BITMIME`& respectively.
38582 .cindex "&%warn%& ACL verb" "log when skipping"
38583 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
38584 its conditions cannot be evaluated, a log line to this effect is written if
38585 this log selector is set.
38587 .cindex "log" "rewriting"
38588 .cindex "rewriting" "logging"
38589 &%address_rewrite%&: This applies both to global rewrites and per-transport
38590 rewrites, but not to rewrites in filters run as an unprivileged user (because
38591 such users cannot access the log).
38593 .cindex "log" "full parentage"
38594 &%all_parents%&: Normally only the original and final addresses are logged on
38595 delivery lines; with this selector, intermediate parents are given in
38596 parentheses between them.
38598 .cindex "log" "Exim arguments"
38599 .cindex "Exim arguments, logging"
38600 &%arguments%&: This causes Exim to write the arguments with which it was called
38601 to the main log, preceded by the current working directory. This is a debugging
38602 feature, added to make it easier to find out how certain MUAs call
38603 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
38604 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
38605 that are empty or that contain white space are quoted. Non-printing characters
38606 are shown as escape sequences. This facility cannot log unrecognized arguments,
38607 because the arguments are checked before the configuration file is read. The
38608 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
38609 between the caller and Exim.
38611 .cindex "log" "connection rejections"
38612 &%connection_reject%&: A log entry is written whenever an incoming SMTP
38613 connection is rejected, for whatever reason.
38615 .cindex "log" "delayed delivery"
38616 .cindex "delayed delivery, logging"
38617 &%delay_delivery%&: A log entry is written whenever a delivery process is not
38618 started for an incoming message because the load is too high or too many
38619 messages were received on one connection. Logging does not occur if no delivery
38620 process is started because &%queue_only%& is set or &%-odq%& was used.
38622 .cindex "log" "delivery duration"
38623 &%deliver_time%&: For each delivery, the amount of real time it has taken to
38624 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
38625 If millisecond logging is enabled, short times will be shown with greater
38626 precision, eg. &`DT=0.304s`&.
38628 .cindex "log" "message size on delivery"
38629 .cindex "size" "of message"
38630 &%delivery_size%&: For each delivery, the size of message delivered is added to
38631 the &"=>"& line, tagged with S=.
38633 .cindex log "DKIM verification"
38634 .cindex DKIM "verification logging"
38635 &%dkim%&: For message acceptance log lines, when an DKIM signature in the header
38636 verifies successfully a tag of DKIM is added, with one of the verified domains.
38638 .cindex log "DKIM verification"
38639 .cindex DKIM "verification logging"
38640 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
38642 .cindex "log" "dnslist defer"
38643 .cindex "DNS list" "logging defer"
38644 .cindex "black list (DNS)"
38645 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
38646 DNS black list suffers a temporary error.
38649 .cindex dnssec logging
38650 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
38651 dns lookups gave secure results a tag of DS is added.
38652 For acceptance this covers the reverse and forward lookups for host name verification.
38653 It does not cover helo-name verification.
38654 For delivery this covers the SRV, MX, A and/or AAAA lookups.
38656 .cindex "log" "ETRN commands"
38657 .cindex "ETRN" "logging"
38658 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
38659 is run to determine whether or not it is actually accepted. An invalid ETRN
38660 command, or one received within a message transaction is not logged by this
38661 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
38663 .cindex "log" "host lookup failure"
38664 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
38665 any addresses, or when a lookup of an IP address fails to find a host name, a
38666 log line is written. This logging does not apply to direct DNS lookups when
38667 routing email addresses, but it does apply to &"byname"& lookups.
38669 .cindex "log" "ident timeout"
38670 .cindex "RFC 1413" "logging timeout"
38671 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
38672 client's ident port times out.
38674 .cindex "log" "incoming interface"
38675 .cindex "log" "outgoing interface"
38676 .cindex "log" "local interface"
38677 .cindex "log" "local address and port"
38678 .cindex "TCP/IP" "logging local address and port"
38679 .cindex "interface" "logging"
38680 &%incoming_interface%&: The interface on which a message was received is added
38681 to the &"<="& line as an IP address in square brackets, tagged by I= and
38682 followed by a colon and the port number. The local interface and port are also
38683 added to other SMTP log lines, for example, &"SMTP connection from"&, to
38684 rejection lines, and (despite the name) to outgoing
38686 &"=>"&, &"->"&, &"=="& and &"**"& lines.
38688 The latter can be disabled by turning off the &%outgoing_interface%& option.
38690 .cindex log "incoming proxy address"
38691 .cindex proxy "logging proxy address"
38692 .cindex "TCP/IP" "logging proxy address"
38693 &%proxy%&: The internal (closest to the system running Exim) IP address
38694 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
38695 on a proxied connection
38696 or the &"=>"& line for a message delivered on a proxied connection.
38697 See &<<SECTproxyInbound>>& for more information.
38699 .cindex "log" "incoming remote port"
38700 .cindex "port" "logging remote"
38701 .cindex "TCP/IP" "logging incoming remote port"
38702 .vindex "&$sender_fullhost$&"
38703 .vindex "&$sender_rcvhost$&"
38704 &%incoming_port%&: The remote port number from which a message was received is
38705 added to log entries and &'Received:'& header lines, following the IP address
38706 in square brackets, and separated from it by a colon. This is implemented by
38707 changing the value that is put in the &$sender_fullhost$& and
38708 &$sender_rcvhost$& variables. Recording the remote port number has become more
38709 important with the widening use of NAT (see RFC 2505).
38711 .cindex "log" "dropped connection"
38712 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
38713 connection is unexpectedly dropped.
38715 .cindex "log" "millisecond timestamps"
38716 .cindex millisecond logging
38717 .cindex timestamps "millisecond, in logs"
38718 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
38719 appended to the seconds value.
38721 .cindex "log" "message id"
38722 &%msg_id%&: The value of the Message-ID: header.
38724 &%msg_id_created%&: The value of the Message-ID: header, when one had to be created.
38725 This will be either because the message is a bounce, or was submitted locally
38726 (submission mode) without one.
38727 The field identifier will have an asterix appended: &"id*="&.
38729 .cindex "log" "outgoing interface"
38730 .cindex "log" "local interface"
38731 .cindex "log" "local address and port"
38732 .cindex "TCP/IP" "logging local address and port"
38733 .cindex "interface" "logging"
38734 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
38735 interface on which a message was sent is added to delivery lines as an I= tag
38736 followed by IP address in square brackets. You can disable this by turning
38737 off the &%outgoing_interface%& option.
38739 .cindex "log" "outgoing remote port"
38740 .cindex "port" "logging outgoing remote"
38741 .cindex "TCP/IP" "logging outgoing remote port"
38742 &%outgoing_port%&: The remote port number is added to delivery log lines (those
38743 containing => tags) following the IP address.
38744 The local port is also added if &%incoming_interface%& and
38745 &%outgoing_interface%& are both enabled.
38746 This option is not included in the default setting, because for most ordinary
38747 configurations, the remote port number is always 25 (the SMTP port), and the
38748 local port is a random ephemeral port.
38750 .cindex "log" "process ids in"
38751 .cindex "pid (process id)" "in log lines"
38752 &%pid%&: The current process id is added to every log line, in square brackets,
38753 immediately after the time and date.
38755 .cindex log pipelining
38756 .cindex pipelining "logging outgoing"
38757 &%pipelining%&: A field is added to delivery and accept
38758 log lines when the ESMTP PIPELINING extension was used.
38759 The field is a single "L".
38761 On accept lines, where PIPELINING was offered but not used by the client,
38762 the field has a minus appended.
38764 .cindex "pipelining" "early connection"
38765 If Exim is built with the SUPPORT_PIPE_CONNECT build option
38766 accept "L" fields have a period appended if the feature was
38767 offered but not used, or an asterisk appended if used.
38768 Delivery "L" fields have an asterisk appended if used.
38771 .cindex "log" "queue run"
38772 .cindex "queue runner" "logging"
38773 &%queue_run%&: The start and end of every queue run are logged.
38775 .cindex "log" "queue time"
38776 &%queue_time%&: The amount of time the message has been in the queue on the
38777 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
38778 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
38779 includes reception time as well as the delivery time for the current address.
38780 This means that it may be longer than the difference between the arrival and
38781 delivery log line times, because the arrival log line is not written until the
38782 message has been successfully received.
38783 If millisecond logging is enabled, short times will be shown with greater
38784 precision, eg. &`QT=1.578s`&.
38786 &%queue_time_overall%&: The amount of time the message has been in the queue on
38787 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
38788 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
38789 message, so it includes reception time as well as the total delivery time.
38791 .cindex "log" "receive duration"
38792 &%receive_time%&: For each message, the amount of real time it has taken to
38793 perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
38794 If millisecond logging is enabled, short times will be shown with greater
38795 precision, eg. &`RT=0.204s`&.
38797 .cindex "log" "recipients"
38798 &%received_recipients%&: The recipients of a message are listed in the main log
38799 as soon as the message is received. The list appears at the end of the log line
38800 that is written when a message is received, preceded by the word &"for"&. The
38801 addresses are listed after they have been qualified, but before any rewriting
38803 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
38806 .cindex "log" "sender reception"
38807 &%received_sender%&: The unrewritten original sender of a message is added to
38808 the end of the log line that records the message's arrival, after the word
38809 &"from"& (before the recipients if &%received_recipients%& is also set).
38811 .cindex "log" "header lines for rejection"
38812 &%rejected_header%&: If a message's header has been received at the time a
38813 rejection is written to the reject log, the complete header is added to the
38814 log. Header logging can be turned off individually for messages that are
38815 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
38817 .cindex "log" "retry defer"
38818 &%retry_defer%&: A log line is written if a delivery is deferred because a
38819 retry time has not yet been reached. However, this &"retry time not reached"&
38820 message is always omitted from individual message logs after the first delivery
38823 .cindex "log" "return path"
38824 &%return_path_on_delivery%&: The return path that is being transmitted with
38825 the message is included in delivery and bounce lines, using the tag P=.
38826 This is omitted if no delivery actually happens, for example, if routing fails,
38827 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
38829 .cindex "log" "sender on delivery"
38830 &%sender_on_delivery%&: The message's sender address is added to every delivery
38831 and bounce line, tagged by F= (for &"from"&).
38832 This is the original sender that was received with the message; it is not
38833 necessarily the same as the outgoing return path.
38835 .cindex "log" "sender verify failure"
38836 &%sender_verify_fail%&: If this selector is unset, the separate log line that
38837 gives details of a sender verification failure is not written. Log lines for
38838 the rejection of SMTP commands contain just &"sender verify failed"&, so some
38841 .cindex "log" "size rejection"
38842 &%size_reject%&: A log line is written whenever a message is rejected because
38845 .cindex "log" "frozen messages; skipped"
38846 .cindex "frozen messages" "logging skipping"
38847 &%skip_delivery%&: A log line is written whenever a message is skipped during a
38848 queue run because it is frozen or because another process is already delivering
38850 .cindex "&""spool file is locked""&"
38851 The message that is written is &"spool file is locked"&.
38853 .cindex "log" "smtp confirmation"
38854 .cindex "SMTP" "logging confirmation"
38855 .cindex "LMTP" "logging confirmation"
38856 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
38857 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
38858 A number of MTAs (including Exim) return an identifying string in this
38861 .cindex "log" "SMTP connections"
38862 .cindex "SMTP" "logging connections"
38863 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
38864 established or closed, unless the connection is from a host that matches
38865 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
38866 only when the closure is unexpected.) This applies to connections from local
38867 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
38868 dropped in the middle of a message, a log line is always written, whether or
38869 not this selector is set, but otherwise nothing is written at the start and end
38870 of connections unless this selector is enabled.
38872 For TCP/IP connections to an Exim daemon, the current number of connections is
38873 included in the log message for each new connection, but note that the count is
38874 reset if the daemon is restarted.
38875 Also, because connections are closed (and the closure is logged) in
38876 subprocesses, the count may not include connections that have been closed but
38877 whose termination the daemon has not yet noticed. Thus, while it is possible to
38878 match up the opening and closing of connections in the log, the value of the
38879 logged counts may not be entirely accurate.
38881 .cindex "log" "SMTP transaction; incomplete"
38882 .cindex "SMTP" "logging incomplete transactions"
38883 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
38884 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
38885 and the message sender plus any accepted recipients are included in the log
38886 line. This can provide evidence of dictionary attacks.
38888 .cindex "log" "non-MAIL SMTP sessions"
38889 .cindex "MAIL" "logging session without"
38890 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
38891 connection terminates without having issued a MAIL command. This includes both
38892 the case when the connection is dropped, and the case when QUIT is used. It
38893 does not include cases where the connection is rejected right at the start (by
38894 an ACL, or because there are too many connections, or whatever). These cases
38895 already have their own log lines.
38897 The log line that is written contains the identity of the client in the usual
38898 way, followed by D= and a time, which records the duration of the connection.
38899 If the connection was authenticated, this fact is logged exactly as it is for
38900 an incoming message, with an A= item. If the connection was encrypted, CV=,
38901 DN=, and X= items may appear as they do for an incoming message, controlled by
38902 the same logging options.
38904 Finally, if any SMTP commands were issued during the connection, a C= item
38905 is added to the line, listing the commands that were used. For example,
38909 shows that the client issued QUIT straight after EHLO. If there were fewer
38910 than 20 commands, they are all listed. If there were more than 20 commands,
38911 the last 20 are listed, preceded by &"..."&. However, with the default
38912 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
38913 have been aborted before 20 non-mail commands are processed.
38915 &%smtp_mailauth%&: A third subfield with the authenticated sender,
38916 colon-separated, is appended to the A= item for a message arrival or delivery
38917 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
38918 was accepted or used.
38920 .cindex "log" "SMTP protocol error"
38921 .cindex "SMTP" "logging protocol error"
38922 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
38923 encountered. Exim does not have perfect detection of all protocol errors
38924 because of transmission delays and the use of pipelining. If PIPELINING has
38925 been advertised to a client, an Exim server assumes that the client will use
38926 it, and therefore it does not count &"expected"& errors (for example, RCPT
38927 received after rejecting MAIL) as protocol errors.
38929 .cindex "SMTP" "logging syntax errors"
38930 .cindex "SMTP" "syntax errors; logging"
38931 .cindex "SMTP" "unknown command; logging"
38932 .cindex "log" "unknown SMTP command"
38933 .cindex "log" "SMTP syntax error"
38934 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
38935 encountered. An unrecognized command is treated as a syntax error. For an
38936 external connection, the host identity is given; for an internal connection
38937 using &%-bs%& the sender identification (normally the calling user) is given.
38939 .cindex "log" "subject"
38940 .cindex "subject, logging"
38941 &%subject%&: The subject of the message is added to the arrival log line,
38942 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
38943 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
38944 specifies whether characters with values greater than 127 should be logged
38945 unchanged, or whether they should be rendered as escape sequences.
38947 .cindex "log" "certificate verification"
38949 .cindex DANE logging
38950 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
38951 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
38953 using a CA trust anchor,
38954 &`CA=dane`& if using a DNS trust anchor,
38955 and &`CV=no`& if not.
38957 .cindex "log" "TLS cipher"
38958 .cindex "TLS" "logging cipher"
38959 &%tls_cipher%&: When a message is sent or received over an encrypted
38960 connection, the cipher suite used is added to the log line, preceded by X=.
38962 .cindex "log" "TLS peer DN"
38963 .cindex "TLS" "logging peer DN"
38964 &%tls_peerdn%&: When a message is sent or received over an encrypted
38965 connection, and a certificate is supplied by the remote host, the peer DN is
38966 added to the log line, preceded by DN=.
38968 .cindex "log" "TLS resumption"
38969 .cindex "TLS" "logging session resumption"
38971 &%tls_resumption%&: When a message is sent or received over an encrypted
38972 connection and the TLS session resumed one used on a previous TCP connection,
38973 an asterisk is appended to the X= cipher field in the log line.
38976 .cindex "log" "TLS SNI"
38977 .cindex "TLS" "logging SNI"
38978 .cindex SNI logging
38979 &%tls_sni%&: When a message is received over an encrypted connection, and
38980 the remote host provided the Server Name Indication extension, the SNI is
38981 added to the log line, preceded by SNI=.
38983 .cindex "log" "DNS failure in list"
38984 &%unknown_in_list%&: This setting causes a log entry to be written when the
38985 result of a list match is failure because a DNS lookup failed.
38989 .section "Message log" "SECID260"
38990 .cindex "message" "log file for"
38991 .cindex "log" "message log; description of"
38992 .cindex "&_msglog_& directory"
38993 .oindex "&%preserve_message_logs%&"
38994 In addition to the general log files, Exim writes a log file for each message
38995 that it handles. The names of these per-message logs are the message ids, and
38996 they are kept in the &_msglog_& sub-directory of the spool directory. Each
38997 message log contains copies of the log lines that apply to the message. This
38998 makes it easier to inspect the status of an individual message without having
38999 to search the main log. A message log is deleted when processing of the message
39000 is complete, unless &%preserve_message_logs%& is set, but this should be used
39001 only with great care because they can fill up your disk very quickly.
39003 On a heavily loaded system, it may be desirable to disable the use of
39004 per-message logs, in order to reduce disk I/O. This can be done by setting the
39005 &%message_logs%& option false.
39011 . ////////////////////////////////////////////////////////////////////////////
39012 . ////////////////////////////////////////////////////////////////////////////
39014 .chapter "Exim utilities" "CHAPutils"
39015 .scindex IIDutils "utilities"
39016 A number of utility scripts and programs are supplied with Exim and are
39017 described in this chapter. There is also the Exim Monitor, which is covered in
39018 the next chapter. The utilities described here are:
39020 .itable none 0 0 3 7* left 15* left 40* left
39021 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
39022 "list what Exim processes are doing"
39023 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
39024 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
39025 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
39026 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
39028 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
39029 .irow &<<SECTmailstat>>& &'eximstats'& &&&
39030 "extract statistics from the log"
39031 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
39032 "check address acceptance from given IP"
39033 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
39034 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
39035 .irow &<<SECTdumpdb>>& &'exim_dumpdb'& "dump a hints database"
39036 .irow &<<SECTtidydb>>& &'exim_tidydb'& "clean up a hints database"
39037 .irow &<<SECTfixdb>>& &'exim_fixdb'& "patch a hints database"
39038 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
39041 Another utility that might be of use to sites with many MTAs is Tom Kistner's
39042 &'exilog'&. It provides log visualizations across multiple Exim servers. See
39043 &url(https://duncanthrax.net/exilog/) for details.
39048 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
39049 .cindex "&'exiwhat'&"
39050 .cindex "process, querying"
39052 On operating systems that can restart a system call after receiving a signal
39053 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
39054 a line describing what it is doing to the file &_exim-process.info_& in the
39055 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
39056 processes it can find, having first emptied the file. It then waits for one
39057 second to allow the Exim processes to react before displaying the results. In
39058 order to run &'exiwhat'& successfully you have to have sufficient privilege to
39059 send the signal to the Exim processes, so it is normally run as root.
39061 &*Warning*&: This is not an efficient process. It is intended for occasional
39062 use by system administrators. It is not sensible, for example, to set up a
39063 script that sends SIGUSR1 signals to Exim processes at short intervals.
39066 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
39067 varies in different operating systems. Not only are different options used,
39068 but the format of the output is different. For this reason, there are some
39069 system configuration options that configure exactly how &'exiwhat'& works. If
39070 it doesn't seem to be working for you, check the following compile-time
39073 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
39074 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
39075 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
39076 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
39078 An example of typical output from &'exiwhat'& is
39080 164 daemon: -q1h, listening on port 25
39081 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
39082 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
39083 [10.19.42.42] (editor@ref.example)
39084 10592 handling incoming call from [192.168.243.242]
39085 10628 accepting a local non-SMTP message
39087 The first number in the output line is the process number. The third line has
39088 been split here, in order to fit it on the page.
39092 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
39093 .cindex "&'exiqgrep'&"
39094 .cindex "queue" "grepping"
39095 This utility is a Perl script contributed by Matt Hubbard. It runs
39099 or (in case &*-a*& switch is specified)
39103 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
39104 contain alternate exim configuration the queue management might be using.
39106 to obtain a queue listing, and then greps the output to select messages
39107 that match given criteria. The following selection options are available:
39110 .vitem &*-f*&&~<&'regex'&>
39111 Match the sender address using a case-insensitive search. The field that is
39112 tested is enclosed in angle brackets, so you can test for bounce messages with
39116 .vitem &*-r*&&~<&'regex'&>
39117 Match a recipient address using a case-insensitive search. The field that is
39118 tested is not enclosed in angle brackets.
39120 .vitem &*-s*&&~<&'regex'&>
39121 Match against the size field.
39123 .vitem &*-y*&&~<&'seconds'&>
39124 Match messages that are younger than the given time.
39126 .vitem &*-o*&&~<&'seconds'&>
39127 Match messages that are older than the given time.
39130 Match only frozen messages.
39133 Match only non-frozen messages.
39135 .vitem &*-G*&&~<&'queuename'&>
39136 Match only messages in the given queue. Without this, the default queue is searched.
39139 The following options control the format of the output:
39143 Display only the count of matching messages.
39146 Long format &-- display the full message information as output by Exim. This is
39150 Display message ids only.
39153 Brief format &-- one line per message.
39156 Display messages in reverse order.
39159 Include delivered recipients in queue listing.
39162 There is one more option, &%-h%&, which outputs a list of options.
39166 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
39167 .cindex "&'exiqsumm'&"
39168 .cindex "queue" "summary"
39169 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
39170 -bp`& and produces a summary of the messages in the queue. Thus, you use it by
39171 running a command such as
39173 exim -bp | exiqsumm
39175 The output consists of one line for each domain that has messages waiting for
39176 it, as in the following example:
39178 3 2322 74m 66m msn.com.example
39180 Each line lists the number of pending deliveries for a domain, their total
39181 volume, and the length of time that the oldest and the newest messages have
39182 been waiting. Note that the number of pending deliveries is greater than the
39183 number of messages when messages have more than one recipient.
39185 A summary line is output at the end. By default the output is sorted on the
39186 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
39187 the output to be sorted by oldest message and by count of messages,
39188 respectively. There are also three options that split the messages for each
39189 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
39190 separates frozen messages, and &%-s%& separates messages according to their
39193 The output of &'exim -bp'& contains the original addresses in the message, so
39194 this also applies to the output from &'exiqsumm'&. No domains from addresses
39195 generated by aliasing or forwarding are included (unless the &%one_time%&
39196 option of the &(redirect)& router has been used to convert them into &"top
39197 level"& addresses).
39202 .section "Extracting specific information from the log (exigrep)" &&&
39204 .cindex "&'exigrep'&"
39205 .cindex "log" "extracts; grepping for"
39206 The &'exigrep'& utility is a Perl script that searches one or more main log
39207 files for entries that match a given pattern. When it finds a match, it
39208 extracts all the log entries for the relevant message, not just those that
39209 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
39210 given message, or all mail for a given user, or for a given host, for example.
39211 The input files can be in Exim log format or syslog format.
39212 If a matching log line is not associated with a specific message, it is
39213 included in &'exigrep'&'s output without any additional lines. The usage is:
39215 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
39217 If no log filenames are given on the command line, the standard input is read.
39219 The &%-t%& argument specifies a number of seconds. It adds an additional
39220 condition for message selection. Messages that are complete are shown only if
39221 they spent more than <&'n'&> seconds in the queue.
39223 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
39224 makes it case-sensitive. This may give a performance improvement when searching
39225 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
39226 option; with &%-I%& they do not. In both cases it is possible to change the
39227 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
39229 The &%-l%& option means &"literal"&, that is, treat all characters in the
39230 pattern as standing for themselves. Otherwise the pattern must be a Perl
39231 regular expression.
39233 The &%-v%& option inverts the matching condition. That is, a line is selected
39234 if it does &'not'& match the pattern.
39236 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
39237 that are generated as a result/response to a message that &'exigrep'& matched
39241 user_a sends a message to user_b, which generates a bounce back to user_b. If
39242 &'exigrep'& is used to search for &"user_a"&, only the first message will be
39243 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
39244 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
39245 when searching for &"user_a"& will show both messages since the bounce is
39246 &"related"& to or a &"result"& of the first message that was found by the
39249 If the location of a &'zcat'& command is known from the definition of
39250 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
39251 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
39252 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
39253 autodetection of some well known compression extensions.
39256 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
39257 .cindex "&'exipick'&"
39258 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
39259 lists messages from the queue according to a variety of criteria. For details
39260 of &'exipick'&'s facilities, run &'exipick'& with
39261 the &%--help%& option.
39264 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
39265 .cindex "log" "cycling local files"
39266 .cindex "cycling logs"
39267 .cindex "&'exicyclog'&"
39268 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
39269 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
39270 you are using log files with datestamps in their names (see section
39271 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
39272 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
39273 There are two command line options for &'exicyclog'&:
39275 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
39276 default that is set when Exim is built. The default default is 10.
39278 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
39279 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
39280 overriding the script's default, which is to find the setting from Exim's
39284 Each time &'exicyclog'& is run the filenames get &"shuffled down"& by one. If
39285 the main log filename is &_mainlog_& (the default) then when &'exicyclog'& is
39286 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
39287 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
39288 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
39289 logs are handled similarly.
39291 If the limit is greater than 99, the script uses 3-digit numbers such as
39292 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
39293 to one that is greater, or &'vice versa'&, you will have to fix the names of
39294 any existing log files.
39296 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
39297 the end are deleted. All files with numbers greater than 01 are compressed,
39298 using a compression command which is configured by the COMPRESS_COMMAND
39299 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
39300 root &%crontab%& entry of the form
39302 1 0 * * * su exim -c /usr/exim/bin/exicyclog
39304 assuming you have used the name &"exim"& for the Exim user. You can run
39305 &'exicyclog'& as root if you wish, but there is no need.
39309 .section "Mail statistics (eximstats)" "SECTmailstat"
39310 .cindex "statistics"
39311 .cindex "&'eximstats'&"
39312 A Perl script called &'eximstats'& is provided for extracting statistical
39313 information from log files. The output is either plain text, or HTML.
39314 . --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan
39315 . --- 404 error and everything else points to that.
39317 The &'eximstats'& script has been hacked about quite a bit over time. The
39318 latest version is the result of some extensive revision by Steve Campbell. A
39319 lot of information is given by default, but there are options for suppressing
39320 various parts of it. Following any options, the arguments to the script are a
39321 list of files, which should be main log files. For example:
39323 eximstats -nr /var/spool/exim/log/mainlog.01
39325 By default, &'eximstats'& extracts information about the number and volume of
39326 messages received from or delivered to various hosts. The information is sorted
39327 both by message count and by volume, and the top fifty hosts in each category
39328 are listed on the standard output. Similar information, based on email
39329 addresses or domains instead of hosts can be requested by means of various
39330 options. For messages delivered and received locally, similar statistics are
39331 also produced per user.
39333 The output also includes total counts and statistics about delivery errors, and
39334 histograms showing the number of messages received and deliveries made in each
39335 hour of the day. A delivery with more than one address in its envelope (for
39336 example, an SMTP transaction with more than one RCPT command) is counted
39337 as a single delivery by &'eximstats'&.
39339 Though normally more deliveries than receipts are reported (as messages may
39340 have multiple recipients), it is possible for &'eximstats'& to report more
39341 messages received than delivered, even though the queue is empty at the start
39342 and end of the period in question. If an incoming message contains no valid
39343 recipients, no deliveries are recorded for it. A bounce message is handled as
39344 an entirely separate message.
39346 &'eximstats'& always outputs a grand total summary giving the volume and number
39347 of messages received and deliveries made, and the number of hosts involved in
39348 each case. It also outputs the number of messages that were delayed (that is,
39349 not completely delivered at the first attempt), and the number that had at
39350 least one address that failed.
39352 The remainder of the output is in sections that can be independently disabled
39353 or modified by various options. It consists of a summary of deliveries by
39354 transport, histograms of messages received and delivered per time interval
39355 (default per hour), information about the time messages spent in the queue,
39356 a list of relayed messages, lists of the top fifty sending hosts, local
39357 senders, destination hosts, and destination local users by count and by volume,
39358 and a list of delivery errors that occurred.
39360 The relay information lists messages that were actually relayed, that is, they
39361 came from a remote host and were directly delivered to some other remote host,
39362 without being processed (for example, for aliasing or forwarding) locally.
39364 There are quite a few options for &'eximstats'& to control exactly what it
39365 outputs. These are documented in the Perl script itself, and can be extracted
39366 by running the command &(perldoc)& on the script. For example:
39368 perldoc /usr/exim/bin/eximstats
39371 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
39372 .cindex "&'exim_checkaccess'&"
39373 .cindex "policy control" "checking access"
39374 .cindex "checking access"
39375 The &%-bh%& command line argument allows you to run a fake SMTP session with
39376 debugging output, in order to check what Exim is doing when it is applying
39377 policy controls to incoming SMTP mail. However, not everybody is sufficiently
39378 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
39379 sometimes you just want to answer the question &"Does this address have
39380 access?"& without bothering with any further details.
39382 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
39383 two arguments, an IP address and an email address:
39385 exim_checkaccess 10.9.8.7 A.User@a.domain.example
39387 The utility runs a call to Exim with the &%-bh%& option, to test whether the
39388 given email address would be accepted in a RCPT command in a TCP/IP
39389 connection from the host with the given IP address. The output of the utility
39390 is either the word &"accepted"&, or the SMTP error response, for example:
39393 550 Relay not permitted
39395 When running this test, the utility uses &`<>`& as the envelope sender address
39396 for the MAIL command, but you can change this by providing additional
39397 options. These are passed directly to the Exim command. For example, to specify
39398 that the test is to be run with the sender address &'himself@there.example'&
39401 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
39402 -f himself@there.example
39404 Note that these additional Exim command line items must be given after the two
39405 mandatory arguments.
39407 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
39408 while running its checks. You can run checks that include callouts by using
39409 &%-bhc%&, but this is not yet available in a &"packaged"& form.
39413 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
39414 .cindex "DBM" "building dbm files"
39415 .cindex "building DBM files"
39416 .cindex "&'exim_dbmbuild'&"
39417 .cindex "lower casing"
39418 .cindex "binary zero" "in lookup key"
39419 The &'exim_dbmbuild'& program reads an input file containing keys and data in
39420 the format used by the &(lsearch)& lookup (see section
39421 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
39422 names as keys and the remainder of the information as data. The lower-casing
39423 can be prevented by calling the program with the &%-nolc%& option.
39425 A terminating zero is included as part of the key string. This is expected by
39426 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
39427 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
39428 strings or the data strings. The &(dbmnz)& lookup type can be used with such
39431 The program requires two arguments: the name of the input file (which can be a
39432 single hyphen to indicate the standard input), and the name of the output file.
39433 It creates the output under a temporary name, and then renames it if all went
39437 If the native DB interface is in use (USE_DB is set in a compile-time
39438 configuration file &-- this is common in free versions of Unix) the two
39439 filenames must be different, because in this mode the Berkeley DB functions
39440 create a single output file using exactly the name given. For example,
39442 exim_dbmbuild /etc/aliases /etc/aliases.db
39444 reads the system alias file and creates a DBM version of it in
39445 &_/etc/aliases.db_&.
39447 In systems that use the &'ndbm'& routines (mostly proprietary versions of
39448 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
39449 environment, the suffixes are added to the second argument of
39450 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
39451 when the Berkeley functions are used in compatibility mode (though this is not
39452 recommended), because in that case it adds a &_.db_& suffix to the filename.
39454 If a duplicate key is encountered, the program outputs a warning, and when it
39455 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
39456 option is used. By default, only the first of a set of duplicates is used &--
39457 this makes it compatible with &(lsearch)& lookups. There is an option
39458 &%-lastdup%& which causes it to use the data for the last duplicate instead.
39459 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
39460 &%stderr%&. For other errors, where it doesn't actually make a new file, the
39466 .section "Finding individual retry times (exinext)" "SECTfinindret"
39467 .cindex "retry" "times"
39468 .cindex "&'exinext'&"
39469 A utility called &'exinext'& (mostly a Perl script) provides the ability to
39470 fish specific information out of the retry database. Given a mail domain (or a
39471 complete address), it looks up the hosts for that domain, and outputs any retry
39472 information for the hosts or for the domain. At present, the retry information
39473 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
39474 output. For example:
39476 $ exinext piglet@milne.fict.example
39477 kanga.milne.example:192.168.8.1 error 146: Connection refused
39478 first failed: 21-Feb-1996 14:57:34
39479 last tried: 21-Feb-1996 14:57:34
39480 next try at: 21-Feb-1996 15:02:34
39481 roo.milne.example:192.168.8.3 error 146: Connection refused
39482 first failed: 20-Jan-1996 13:12:08
39483 last tried: 21-Feb-1996 11:42:03
39484 next try at: 21-Feb-1996 19:42:03
39485 past final cutoff time
39487 You can also give &'exinext'& a local part, without a domain, and it
39488 will give any retry information for that local part in your default domain.
39489 A message id can be used to obtain retry information pertaining to a specific
39490 message. This exists only when an attempt to deliver a message to a remote host
39491 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
39492 &'exinext'& is not particularly efficient, but then it is not expected to be
39495 The &'exinext'& utility calls Exim to find out information such as the location
39496 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
39497 passed on to the &'exim'& commands. The first specifies an alternate Exim
39498 configuration file, and the second sets macros for use within the configuration
39499 file. These features are mainly to help in testing, but might also be useful in
39500 environments where more than one configuration file is in use.
39504 .section "Hints database maintenance" "SECThindatmai"
39505 .cindex "hints database" "maintenance"
39506 .cindex "maintaining Exim's hints database"
39507 Three utility programs are provided for maintaining the DBM files that Exim
39508 uses to contain its delivery hint information. Each program requires two
39509 arguments. The first specifies the name of Exim's spool directory, and the
39510 second is the name of the database it is to operate on. These are as follows:
39513 &'retry'&: the database of retry information
39515 &'wait-'&<&'transport name'&>: databases of information about messages waiting
39518 &'callout'&: the callout cache
39520 &'ratelimit'&: the data for implementing the ratelimit ACL condition
39523 &'tls'&: TLS session resumption data
39526 &'misc'&: other hints data
39529 The &'misc'& database is used for
39532 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
39534 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
39535 &(smtp)& transport)
39537 Limiting the concurrency of specific transports (when &%max_parallel%& is set
39543 .section "exim_dumpdb" "SECTdumpdb"
39544 .cindex "&'exim_dumpdb'&"
39545 The entire contents of a database are written to the standard output by the
39546 &'exim_dumpdb'& program, which has no options or arguments other than the
39547 spool and database names. For example, to dump the retry database:
39549 exim_dumpdb /var/spool/exim retry
39551 Two lines of output are produced for each entry:
39553 T:mail.ref.example:192.168.242.242 146 77 Connection refused
39554 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
39556 The first item on the first line is the key of the record. It starts with one
39557 of the letters R, or T, depending on whether it refers to a routing or
39558 transport retry. For a local delivery, the next part is the local address; for
39559 a remote delivery it is the name of the remote host, followed by its failing IP
39560 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
39561 transport). If the remote port is not the standard one (port 25), it is added
39562 to the IP address. Then there follows an error code, an additional error code,
39563 and a textual description of the error.
39565 The three times on the second line are the time of first failure, the time of
39566 the last delivery attempt, and the computed time for the next attempt. The line
39567 ends with an asterisk if the cutoff time for the last retry rule has been
39570 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
39571 consists of a host name followed by a list of ids for messages that are or were
39572 waiting to be delivered to that host. If there are a very large number for any
39573 one host, continuation records, with a sequence number added to the host name,
39574 may be seen. The data in these records is often out of date, because a message
39575 may be routed to several alternative hosts, and Exim makes no effort to keep
39580 .section "exim_tidydb" "SECTtidydb"
39581 .cindex "&'exim_tidydb'&"
39582 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
39583 database. If run with no options, it removes all records that are more than 30
39584 days old. The age is calculated from the date and time that the record was last
39585 updated. Note that, in the case of the retry database, it is &'not'& the time
39586 since the first delivery failure. Information about a host that has been down
39587 for more than 30 days will remain in the database, provided that the record is
39588 updated sufficiently often.
39590 The cutoff date can be altered by means of the &%-t%& option, which must be
39591 followed by a time. For example, to remove all records older than a week from
39592 the retry database:
39594 exim_tidydb -t 7d /var/spool/exim retry
39596 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
39597 message ids. In the former these appear as data in records keyed by host &--
39598 they were messages that were waiting for that host &-- and in the latter they
39599 are the keys for retry information for messages that have suffered certain
39600 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
39601 message ids in database records are those of messages that are still on the
39602 queue. Message ids for messages that no longer exist are removed from
39603 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
39604 For the &'retry'& database, records whose keys are non-existent message ids are
39605 removed. The &'exim_tidydb'& utility outputs comments on the standard output
39606 whenever it removes information from the database.
39608 Certain records are automatically removed by Exim when they are no longer
39609 needed, but others are not. For example, if all the MX hosts for a domain are
39610 down, a retry record is created for each one. If the primary MX host comes back
39611 first, its record is removed when Exim successfully delivers to it, but the
39612 records for the others remain because Exim has not tried to use those hosts.
39614 It is important, therefore, to run &'exim_tidydb'& periodically on all the
39615 hints databases. You should do this at a quiet time of day, because it requires
39616 a database to be locked (and therefore inaccessible to Exim) while it does its
39617 work. Removing records from a DBM file does not normally make the file smaller,
39618 but all the common DBM libraries are able to re-use the space that is released.
39619 After an initial phase of increasing in size, the databases normally reach a
39620 point at which they no longer get any bigger, as long as they are regularly
39623 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
39624 databases is likely to keep on increasing.
39629 .section "exim_fixdb" "SECTfixdb"
39630 .cindex "&'exim_fixdb'&"
39631 The &'exim_fixdb'& program is a utility for interactively modifying databases.
39632 Its main use is for testing Exim, but it might also be occasionally useful for
39633 getting round problems in a live system. It has no options, and its interface
39634 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
39635 key of a database record can then be entered, and the data for that record is
39638 If &"d"& is typed at the next prompt, the entire record is deleted. For all
39639 except the &'retry'& database, that is the only operation that can be carried
39640 out. For the &'retry'& database, each field is output preceded by a number, and
39641 data for individual fields can be changed by typing the field number followed
39642 by new data, for example:
39646 resets the time of the next delivery attempt. Time values are given as a
39647 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
39648 used as optional separators.
39653 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
39654 .cindex "mailbox" "maintenance"
39655 .cindex "&'exim_lock'&"
39656 .cindex "locking mailboxes"
39657 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
39658 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
39659 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
39660 a user agent while investigating a problem. The utility requires the name of
39661 the file as its first argument. If the locking is successful, the second
39662 argument is run as a command (using C's &[system()]& function); if there is no
39663 second argument, the value of the SHELL environment variable is used; if this
39664 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
39665 is unlocked and the utility ends. The following options are available:
39669 Use &[fcntl()]& locking on the open mailbox.
39672 Use &[flock()]& locking on the open mailbox, provided the operating system
39675 .vitem &%-interval%&
39676 This must be followed by a number, which is a number of seconds; it sets the
39677 interval to sleep between retries (default 3).
39679 .vitem &%-lockfile%&
39680 Create a lock file before opening the mailbox.
39683 Lock the mailbox using MBX rules.
39686 Suppress verification output.
39688 .vitem &%-retries%&
39689 This must be followed by a number; it sets the number of times to try to get
39690 the lock (default 10).
39692 .vitem &%-restore_time%&
39693 This option causes &%exim_lock%& to restore the modified and read times to the
39694 locked file before exiting. This allows you to access a locked mailbox (for
39695 example, to take a backup copy) without disturbing the times that the user
39698 .vitem &%-timeout%&
39699 This must be followed by a number, which is a number of seconds; it sets a
39700 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
39701 default), a non-blocking call is used.
39704 Generate verbose output.
39707 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
39708 default is to create a lock file and also to use &[fcntl()]& locking on the
39709 mailbox, which is the same as Exim's default. The use of &%-flock%& or
39710 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
39711 requires that the directory containing the file be writeable. Locking by lock
39712 file does not last forever; Exim assumes that a lock file is expired if it is
39713 more than 30 minutes old.
39715 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
39716 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
39717 to be taken out on the open mailbox, and an exclusive lock on the file
39718 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
39719 number of the mailbox file. When the locking is released, if an exclusive lock
39720 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
39722 The default output contains verification of the locking that takes place. The
39723 &%-v%& option causes some additional information to be given. The &%-q%& option
39724 suppresses all output except error messages.
39728 exim_lock /var/spool/mail/spqr
39730 runs an interactive shell while the file is locked, whereas
39732 &`exim_lock -q /var/spool/mail/spqr <<End`&
39733 <&'some commands'&>
39736 runs a specific non-interactive sequence of commands while the file is locked,
39737 suppressing all verification output. A single command can be run by a command
39740 exim_lock -q /var/spool/mail/spqr \
39741 "cp /var/spool/mail/spqr /some/where"
39743 Note that if a command is supplied, it must be entirely contained within the
39744 second argument &-- hence the quotes.
39748 . ////////////////////////////////////////////////////////////////////////////
39749 . ////////////////////////////////////////////////////////////////////////////
39751 .chapter "The Exim monitor" "CHAPeximon"
39752 .scindex IIDeximon "Exim monitor" "description"
39753 .cindex "X-windows"
39754 .cindex "&'eximon'&"
39755 .cindex "Local/eximon.conf"
39756 .cindex "&_exim_monitor/EDITME_&"
39757 The Exim monitor is an application which displays in an X window information
39758 about the state of Exim's queue and what Exim is doing. An admin user can
39759 perform certain operations on messages from this GUI interface; however all
39760 such facilities are also available from the command line, and indeed, the
39761 monitor itself makes use of the command line to perform any actions requested.
39765 .section "Running the monitor" "SECID264"
39766 The monitor is started by running the script called &'eximon'&. This is a shell
39767 script that sets up a number of environment variables, and then runs the
39768 binary called &_eximon.bin_&. The default appearance of the monitor window can
39769 be changed by editing the &_Local/eximon.conf_& file created by editing
39770 &_exim_monitor/EDITME_&. Comments in that file describe what the various
39771 parameters are for.
39773 The parameters that get built into the &'eximon'& script can be overridden for
39774 a particular invocation by setting up environment variables of the same names,
39775 preceded by &`EXIMON_`&. For example, a shell command such as
39777 EXIMON_LOG_DEPTH=400 eximon
39779 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
39780 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
39781 overrides the Exim log file configuration. This makes it possible to have
39782 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
39783 syslog messages are routed to a file on the local host.
39785 X resources can be used to change the appearance of the window in the normal
39786 way. For example, a resource setting of the form
39788 Eximon*background: gray94
39790 changes the colour of the background to light grey rather than white. The
39791 stripcharts are drawn with both the data lines and the reference lines in
39792 black. This means that the reference lines are not visible when on top of the
39793 data. However, their colour can be changed by setting a resource called
39794 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
39795 For example, if your X server is running Unix, you could set up lighter
39796 reference lines in the stripcharts by obeying
39799 Eximon*highlight: gray
39802 .cindex "admin user"
39803 In order to see the contents of messages in the queue, and to operate on them,
39804 &'eximon'& must either be run as root or by an admin user.
39806 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
39807 contain X11 resource parameters interpreted by the X11 library. In addition,
39808 if the first parameter starts with the string "gdb" then it is removed and the
39809 binary is invoked under gdb (the parameter is used as the gdb command-name, so
39810 versioned variants of gdb can be invoked).
39812 The monitor's window is divided into three parts. The first contains one or
39813 more stripcharts and two action buttons, the second contains a &"tail"& of the
39814 main log file, and the third is a display of the queue of messages awaiting
39815 delivery, with two more action buttons. The following sections describe these
39816 different parts of the display.
39821 .section "The stripcharts" "SECID265"
39822 .cindex "stripchart"
39823 The first stripchart is always a count of messages in the queue. Its name can
39824 be configured by setting QUEUE_STRIPCHART_NAME in the
39825 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
39826 configuration script by regular expression matches on log file entries, making
39827 it possible to display, for example, counts of messages delivered to certain
39828 hosts or using certain transports. The supplied defaults display counts of
39829 received and delivered messages, and of local and SMTP deliveries. The default
39830 period between stripchart updates is one minute; this can be adjusted by a
39831 parameter in the &_Local/eximon.conf_& file.
39833 The stripchart displays rescale themselves automatically as the value they are
39834 displaying changes. There are always 10 horizontal lines in each chart; the
39835 title string indicates the value of each division when it is greater than one.
39836 For example, &"x2"& means that each division represents a value of 2.
39838 It is also possible to have a stripchart which shows the percentage fullness of
39839 a particular disk partition, which is useful when local deliveries are confined
39840 to a single partition.
39842 .cindex "&%statvfs%& function"
39843 This relies on the availability of the &[statvfs()]& function or equivalent in
39844 the operating system. Most, but not all versions of Unix that support Exim have
39845 this. For this particular stripchart, the top of the chart always represents
39846 100%, and the scale is given as &"x10%"&. This chart is configured by setting
39847 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
39848 &_Local/eximon.conf_& file.
39853 .section "Main action buttons" "SECID266"
39854 .cindex "size" "of monitor window"
39855 .cindex "Exim monitor" "window size"
39856 .cindex "window size"
39857 Below the stripcharts there is an action button for quitting the monitor. Next
39858 to this is another button marked &"Size"&. They are placed here so that
39859 shrinking the window to its default minimum size leaves just the queue count
39860 stripchart and these two buttons visible. Pressing the &"Size"& button causes
39861 the window to expand to its maximum size, unless it is already at the maximum,
39862 in which case it is reduced to its minimum.
39864 When expanding to the maximum, if the window cannot be fully seen where it
39865 currently is, it is moved back to where it was the last time it was at full
39866 size. When it is expanding from its minimum size, the old position is
39867 remembered, and next time it is reduced to the minimum it is moved back there.
39869 The idea is that you can keep a reduced window just showing one or two
39870 stripcharts at a convenient place on your screen, easily expand it to show
39871 the full window when required, and just as easily put it back to what it was.
39872 The idea is copied from what the &'twm'& window manager does for its
39873 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
39874 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
39876 Normally, the monitor starts up with the window at its full size, but it can be
39877 built so that it starts up with the window at its smallest size, by setting
39878 START_SMALL=yes in &_Local/eximon.conf_&.
39882 .section "The log display" "SECID267"
39883 .cindex "log" "tail of; in monitor"
39884 The second section of the window is an area in which a display of the tail of
39885 the main log is maintained.
39886 To save space on the screen, the timestamp on each log line is shortened by
39887 removing the date and, if &%log_timezone%& is set, the timezone.
39888 The log tail is not available when the only destination for logging data is
39889 syslog, unless the syslog lines are routed to a local file whose name is passed
39890 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
39892 The log sub-window has a scroll bar at its lefthand side which can be used to
39893 move back to look at earlier text, and the up and down arrow keys also have a
39894 scrolling effect. The amount of log that is kept depends on the setting of
39895 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
39896 to use. When this is full, the earlier 50% of data is discarded &-- this is
39897 much more efficient than throwing it away line by line. The sub-window also has
39898 a horizontal scroll bar for accessing the ends of long log lines. This is the
39899 only means of horizontal scrolling; the right and left arrow keys are not
39900 available. Text can be cut from this part of the window using the mouse in the
39901 normal way. The size of this subwindow is controlled by parameters in the
39902 configuration file &_Local/eximon.conf_&.
39904 Searches of the text in the log window can be carried out by means of the ^R
39905 and ^S keystrokes, which default to a reverse and a forward search,
39906 respectively. The search covers only the text that is displayed in the window.
39907 It cannot go further back up the log.
39909 The point from which the search starts is indicated by a caret marker. This is
39910 normally at the end of the text in the window, but can be positioned explicitly
39911 by pointing and clicking with the left mouse button, and is moved automatically
39912 by a successful search. If new text arrives in the window when it is scrolled
39913 back, the caret remains where it is, but if the window is not scrolled back,
39914 the caret is moved to the end of the new text.
39916 Pressing ^R or ^S pops up a window into which the search text can be typed.
39917 There are buttons for selecting forward or reverse searching, for carrying out
39918 the search, and for cancelling. If the &"Search"& button is pressed, the search
39919 happens and the window remains so that further searches can be done. If the
39920 &"Return"& key is pressed, a single search is done and the window is closed. If
39921 ^C is typed the search is cancelled.
39923 The searching facility is implemented using the facilities of the Athena text
39924 widget. By default this pops up a window containing both &"search"& and
39925 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
39926 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
39927 However, the linkers in BSDI and HP-UX seem unable to handle an externally
39928 provided version of &%TextPop%& when the remaining parts of the text widget
39929 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
39930 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
39931 on these systems, at the expense of having unwanted items in the search popup
39936 .section "The queue display" "SECID268"
39937 .cindex "queue" "display in monitor"
39938 The bottom section of the monitor window contains a list of all messages that
39939 are in the queue, which includes those currently being received or delivered,
39940 as well as those awaiting delivery. The size of this subwindow is controlled by
39941 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
39942 at which it is updated is controlled by another parameter in the same file &--
39943 the default is 5 minutes, since queue scans can be quite expensive. However,
39944 there is an &"Update"& action button just above the display which can be used
39945 to force an update of the queue display at any time.
39947 When a host is down for some time, a lot of pending mail can build up for it,
39948 and this can make it hard to deal with other messages in the queue. To help
39949 with this situation there is a button next to &"Update"& called &"Hide"&. If
39950 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
39951 type anything in here and press &"Return"&, the text is added to a chain of
39952 such texts, and if every undelivered address in a message matches at least one
39953 of the texts, the message is not displayed.
39955 If there is an address that does not match any of the texts, all the addresses
39956 are displayed as normal. The matching happens on the ends of addresses so, for
39957 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
39958 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
39959 has been set up, a button called &"Unhide"& is displayed. If pressed, it
39960 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
39961 a hide request is automatically cancelled after one hour.
39963 While the dialogue box is displayed, you can't press any buttons or do anything
39964 else to the monitor window. For this reason, if you want to cut text from the
39965 queue display to use in the dialogue box, you have to do the cutting before
39966 pressing the &"Hide"& button.
39968 The queue display contains, for each unhidden queued message, the length of
39969 time it has been in the queue, the size of the message, the message id, the
39970 message sender, and the first undelivered recipient, all on one line. If it is
39971 a bounce message, the sender is shown as &"<>"&. If there is more than one
39972 recipient to which the message has not yet been delivered, subsequent ones are
39973 listed on additional lines, up to a maximum configured number, following which
39974 an ellipsis is displayed. Recipients that have already received the message are
39977 .cindex "frozen messages" "display"
39978 If a message is frozen, an asterisk is displayed at the left-hand side.
39980 The queue display has a vertical scroll bar, and can also be scrolled by means
39981 of the arrow keys. Text can be cut from it using the mouse in the normal way.
39982 The text searching facilities, as described above for the log window, are also
39983 available, but the caret is always moved to the end of the text when the queue
39984 display is updated.
39988 .section "The queue menu" "SECID269"
39989 .cindex "queue" "menu in monitor"
39990 If the &%shift%& key is held down and the left button is clicked when the mouse
39991 pointer is over the text for any message, an action menu pops up, and the first
39992 line of the queue display for the message is highlighted. This does not affect
39995 If you want to use some other event for popping up the menu, you can set the
39996 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
39997 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
39998 value set in this parameter is a standard X event description. For example, to
39999 run eximon using &%ctrl%& rather than &%shift%& you could use
40001 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
40003 The title of the menu is the message id, and it contains entries which act as
40007 &'message log'&: The contents of the message log for the message are displayed
40008 in a new text window.
40010 &'headers'&: Information from the spool file that contains the envelope
40011 information and headers is displayed in a new text window. See chapter
40012 &<<CHAPspool>>& for a description of the format of spool files.
40014 &'body'&: The contents of the spool file containing the body of the message are
40015 displayed in a new text window. There is a default limit of 20,000 bytes to the
40016 amount of data displayed. This can be changed by setting the BODY_MAX
40017 option at compile time, or the EXIMON_BODY_MAX option at runtime.
40019 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
40020 delivery of the message. This causes an automatic thaw if the message is
40021 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
40022 a new text window. The delivery is run in a separate process, to avoid holding
40023 up the monitor while the delivery proceeds.
40025 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
40026 that the message be frozen.
40028 .cindex "thawing messages"
40029 .cindex "unfreezing messages"
40030 .cindex "frozen messages" "thawing"
40031 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
40032 that the message be thawed.
40034 .cindex "delivery" "forcing failure"
40035 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
40036 that Exim gives up trying to deliver the message. A bounce message is generated
40037 for any remaining undelivered addresses.
40039 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
40040 that the message be deleted from the system without generating a bounce
40043 &'add recipient'&: A dialog box is displayed into which a recipient address can
40044 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40045 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40046 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40047 causes a call to Exim to be made using the &%-Mar%& option to request that an
40048 additional recipient be added to the message, unless the entry box is empty, in
40049 which case no action is taken.
40051 &'mark delivered'&: A dialog box is displayed into which a recipient address
40052 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
40053 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
40054 Otherwise it must be entered as a fully qualified address. Pressing RETURN
40055 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
40056 recipient address as already delivered, unless the entry box is empty, in which
40057 case no action is taken.
40059 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
40060 mark all recipient addresses as already delivered.
40062 &'edit sender'&: A dialog box is displayed initialized with the current
40063 sender's address. Pressing RETURN causes a call to Exim to be made using the
40064 &%-Mes%& option to replace the sender address, unless the entry box is empty,
40065 in which case no action is taken. If you want to set an empty sender (as in
40066 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
40067 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
40068 the address is qualified with that domain.
40071 When a delivery is forced, a window showing the &%-v%& output is displayed. In
40072 other cases when a call to Exim is made, if there is any output from Exim (in
40073 particular, if the command fails) a window containing the command and the
40074 output is displayed. Otherwise, the results of the action are normally apparent
40075 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
40076 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
40077 if no output is generated.
40079 The queue display is automatically updated for actions such as freezing and
40080 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
40081 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
40082 force an update of the display after one of these actions.
40084 In any text window that is displayed as result of a menu action, the normal
40085 cut-and-paste facility is available, and searching can be carried out using ^R
40086 and ^S, as described above for the log tail window.
40093 . ////////////////////////////////////////////////////////////////////////////
40094 . ////////////////////////////////////////////////////////////////////////////
40096 .chapter "Security considerations" "CHAPsecurity"
40097 .scindex IIDsecurcon "security" "discussion of"
40098 This chapter discusses a number of issues concerned with security, some of
40099 which are also covered in other parts of this manual.
40101 For reasons that this author does not understand, some people have promoted
40102 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
40103 existence of this chapter in the documentation. However, the intent of the
40104 chapter is simply to describe the way Exim works in relation to certain
40105 security concerns, not to make any specific claims about the effectiveness of
40106 its security as compared with other MTAs.
40108 What follows is a description of the way Exim is supposed to be. Best efforts
40109 have been made to try to ensure that the code agrees with the theory, but an
40110 absence of bugs can never be guaranteed. Any that are reported will get fixed
40111 as soon as possible.
40114 .section "Building a more &""hardened""& Exim" "SECID286"
40115 .cindex "security" "build-time features"
40116 There are a number of build-time options that can be set in &_Local/Makefile_&
40117 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
40118 Exim administrator who does not have the root password, or by someone who has
40119 penetrated the Exim (but not the root) account. These options are as follows:
40122 ALT_CONFIG_PREFIX can be set to a string that is required to match the
40123 start of any filenames used with the &%-C%& option. When it is set, these
40124 filenames are also not allowed to contain the sequence &"/../"&. (However, if
40125 the value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
40126 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
40127 default setting for &%ALT_CONFIG_PREFIX%&.
40129 If the permitted configuration files are confined to a directory to
40130 which only root has access, this guards against someone who has broken
40131 into the Exim account from running a privileged Exim with an arbitrary
40132 configuration file, and using it to break into other accounts.
40135 If a non-trusted configuration file (i.e. not the default configuration file
40136 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
40137 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
40138 the next item), then root privilege is retained only if the caller of Exim is
40139 root. This locks out the possibility of testing a configuration using &%-C%&
40140 right through message reception and delivery, even if the caller is root. The
40141 reception works, but by that time, Exim is running as the Exim user, so when
40142 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
40143 privilege to be lost. However, root can test reception and delivery using two
40147 The WHITELIST_D_MACROS build option declares some macros to be safe to override
40148 with &%-D%& if the real uid is one of root, the Exim run-time user or the
40149 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
40150 requiring the run-time value supplied to &%-D%& to match a regex that errs on
40151 the restrictive side. Requiring build-time selection of safe macros is onerous
40152 but this option is intended solely as a transition mechanism to permit
40153 previously-working configurations to continue to work after release 4.73.
40155 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
40158 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
40159 never to be used for any deliveries. This is like the &%never_users%& runtime
40160 option, but it cannot be overridden; the runtime option adds additional users
40161 to the list. The default setting is &"root"&; this prevents a non-root user who
40162 is permitted to modify the runtime file from using Exim as a way to get root.
40167 .section "Root privilege" "SECID270"
40169 .cindex "root privilege"
40170 The Exim binary is normally setuid to root, which means that it gains root
40171 privilege (runs as root) when it starts execution. In some special cases (for
40172 example, when the daemon is not in use and there are no local deliveries), it
40173 may be possible to run Exim setuid to some user other than root. This is
40174 discussed in the next section. However, in most installations, root privilege
40175 is required for two things:
40178 To set up a socket connected to the standard SMTP port (25) when initialising
40179 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
40182 To be able to change uid and gid in order to read users' &_.forward_& files and
40183 perform local deliveries as the receiving user or as specified in the
40187 It is not necessary to be root to do any of the other things Exim does, such as
40188 receiving messages and delivering them externally over SMTP, and it is
40189 obviously more secure if Exim does not run as root except when necessary.
40190 For this reason, a user and group for Exim to use must be defined in
40191 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
40192 group"&. Their values can be changed by the runtime configuration, though this
40193 is not recommended. Often a user called &'exim'& is used, but some sites use
40194 &'mail'& or another user name altogether.
40196 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
40197 abdication; the process cannot regain root afterwards. Prior to release 4.00,
40198 &[seteuid()]& was used in some circumstances, but this is no longer the case.
40200 After a new Exim process has interpreted its command line options, it changes
40201 uid and gid in the following cases:
40206 If the &%-C%& option is used to specify an alternate configuration file, or if
40207 the &%-D%& option is used to define macro values for the configuration, and the
40208 calling process is not running as root, the uid and gid are changed to those of
40209 the calling process.
40210 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
40211 option may not be used at all.
40212 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
40213 can be supplied if the calling process is running as root, the Exim run-time
40214 user or CONFIGURE_OWNER, if defined.
40219 If the expansion test option (&%-be%&) or one of the filter testing options
40220 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
40223 If the process is not a daemon process or a queue runner process or a delivery
40224 process or a process for testing address routing (started with &%-bt%&), the
40225 uid and gid are changed to the Exim user and group. This means that Exim always
40226 runs under its own uid and gid when receiving messages. This also applies when
40227 testing address verification
40230 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
40233 For a daemon, queue runner, delivery, or address testing process, the uid
40234 remains as root at this stage, but the gid is changed to the Exim group.
40237 The processes that initially retain root privilege behave as follows:
40240 A daemon process changes the gid to the Exim group and the uid to the Exim
40241 user after setting up one or more listening sockets. The &[initgroups()]&
40242 function is called, so that if the Exim user is in any additional groups, they
40243 will be used during message reception.
40245 A queue runner process retains root privilege throughout its execution. Its
40246 job is to fork a controlled sequence of delivery processes.
40248 A delivery process retains root privilege throughout most of its execution,
40249 but any actual deliveries (that is, the transports themselves) are run in
40250 subprocesses which always change to a non-root uid and gid. For local
40251 deliveries this is typically the uid and gid of the owner of the mailbox; for
40252 remote deliveries, the Exim uid and gid are used. Once all the delivery
40253 subprocesses have been run, a delivery process changes to the Exim uid and gid
40254 while doing post-delivery tidying up such as updating the retry database and
40255 generating bounce and warning messages.
40257 While the recipient addresses in a message are being routed, the delivery
40258 process runs as root. However, if a user's filter file has to be processed,
40259 this is done in a subprocess that runs under the individual user's uid and
40260 gid. A system filter is run as root unless &%system_filter_user%& is set.
40262 A process that is testing addresses (the &%-bt%& option) runs as root so that
40263 the routing is done in the same environment as a message delivery.
40269 .section "Running Exim without privilege" "SECTrunexiwitpri"
40270 .cindex "privilege, running without"
40271 .cindex "unprivileged running"
40272 .cindex "root privilege" "running without"
40273 Some installations like to run Exim in an unprivileged state for more of its
40274 operation, for added security. Support for this mode of operation is provided
40275 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
40276 gid are changed to the Exim user and group at the start of a delivery process
40277 (and also queue runner and address testing processes). This means that address
40278 routing is no longer run as root, and the deliveries themselves cannot change
40282 .cindex "daemon" "restarting"
40283 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
40284 that the daemon can still be started in the usual way, and it can respond
40285 correctly to SIGHUP because the re-invocation regains root privilege.
40287 An alternative approach is to make Exim setuid to the Exim user and also setgid
40288 to the Exim group. If you do this, the daemon must be started from a root
40289 process. (Calling Exim from a root process makes it behave in the way it does
40290 when it is setuid root.) However, the daemon cannot restart itself after a
40291 SIGHUP signal because it cannot regain privilege.
40293 It is still useful to set &%deliver_drop_privilege%& in this case, because it
40294 stops Exim from trying to re-invoke itself to do a delivery after a message has
40295 been received. Such a re-invocation is a waste of resources because it has no
40298 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
40299 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
40300 to the Exim user seems a clean approach, but there is one complication:
40302 In this style of operation, Exim is running with the real uid and gid set to
40303 those of the calling process, and the effective uid/gid set to Exim's values.
40304 Ideally, any association with the calling process' uid/gid should be dropped,
40305 that is, the real uid/gid should be reset to the effective values so as to
40306 discard any privileges that the caller may have. While some operating systems
40307 have a function that permits this action for a non-root effective uid, quite a
40308 number of them do not. Because of this lack of standardization, Exim does not
40309 address this problem at this time.
40311 For this reason, the recommended approach for &"mostly unprivileged"& running
40312 is to keep the Exim binary setuid to root, and to set
40313 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
40314 be used in the most straightforward way.
40316 If you configure Exim not to run delivery processes as root, there are a
40317 number of restrictions on what you can do:
40320 You can deliver only as the Exim user/group. You should explicitly use the
40321 &%user%& and &%group%& options to override routers or local transports that
40322 normally deliver as the recipient. This makes sure that configurations that
40323 work in this mode function the same way in normal mode. Any implicit or
40324 explicit specification of another user causes an error.
40326 Use of &_.forward_& files is severely restricted, such that it is usually
40327 not worthwhile to include them in the configuration.
40329 Users who wish to use &_.forward_& would have to make their home directory and
40330 the file itself accessible to the Exim user. Pipe and append-to-file entries,
40331 and their equivalents in Exim filters, cannot be used. While they could be
40332 enabled in the Exim user's name, that would be insecure and not very useful.
40334 Unless the local user mailboxes are all owned by the Exim user (possible in
40335 some POP3 or IMAP-only environments):
40338 They must be owned by the Exim group and be writeable by that group. This
40339 implies you must set &%mode%& in the appendfile configuration, as well as the
40340 mode of the mailbox files themselves.
40342 You must set &%no_check_owner%&, since most or all of the files will not be
40343 owned by the Exim user.
40345 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
40346 on a newly created mailbox when unprivileged. This also implies that new
40347 mailboxes need to be created manually.
40352 These restrictions severely restrict what can be done in local deliveries.
40353 However, there are no restrictions on remote deliveries. If you are running a
40354 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
40355 gives more security at essentially no cost.
40357 If you are using the &%mua_wrapper%& facility (see chapter
40358 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
40363 .section "Delivering to local files" "SECID271"
40364 Full details of the checks applied by &(appendfile)& before it writes to a file
40365 are given in chapter &<<CHAPappendfile>>&.
40369 .section "Running local commands" "SECTsecconslocalcmds"
40370 .cindex "security" "local commands"
40371 .cindex "security" "command injection attacks"
40372 There are a number of ways in which an administrator can configure Exim to run
40373 commands based upon received, untrustworthy, data. Further, in some
40374 configurations a user who can control a &_.forward_& file can also arrange to
40375 run commands. Configuration to check includes, but is not limited to:
40378 Use of &%use_shell%& in the pipe transport: various forms of shell command
40379 injection may be possible with this option present. It is dangerous and should
40380 be used only with considerable caution. Consider constraints which whitelist
40381 allowed characters in a variable which is to be used in a pipe transport that
40382 has &%use_shell%& enabled.
40384 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
40385 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
40386 &_.forward_& files in a redirect router. If Exim is running on a central mail
40387 hub to which ordinary users do not have shell access, but home directories are
40388 NFS mounted (for instance) then administrators should review the list of these
40389 forbid options available, and should bear in mind that the options that may
40390 need forbidding can change as new features are added between releases.
40392 The &%${run...}%& expansion item does not use a shell by default, but
40393 administrators can configure use of &_/bin/sh_& as part of the command.
40394 Such invocations should be viewed with prejudicial suspicion.
40396 Administrators who use embedded Perl are advised to explore how Perl's
40397 taint checking might apply to their usage.
40399 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
40400 administrators are well advised to view its use with suspicion, in case (for
40401 instance) it allows a local-part to contain embedded Exim directives.
40403 Use of &%${match_local_part...}%& and friends becomes more dangerous if
40404 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
40405 each can reference arbitrary lists and files, rather than just being a list
40407 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
40408 real-world security vulnerabilities caused by its use with untrustworthy data
40409 injected in, for SQL injection attacks.
40410 Consider the use of the &%inlisti%& expansion condition instead.
40416 .section "Trust in configuration data" "SECTsecconfdata"
40417 .cindex "security" "data sources"
40418 .cindex "security" "regular expressions"
40419 .cindex "regular expressions" "security"
40420 .cindex "PCRE" "security"
40421 If configuration data for Exim can come from untrustworthy sources, there
40422 are some issues to be aware of:
40425 Use of &%${expand...}%& may provide a path for shell injection attacks.
40427 Letting untrusted data provide a regular expression is unwise.
40429 Using &%${match...}%& to apply a fixed regular expression against untrusted
40430 data may result in pathological behaviour within PCRE. Be aware of what
40431 "backtracking" means and consider options for being more strict with a regular
40432 expression. Avenues to explore include limiting what can match (avoiding &`.`&
40433 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
40434 possessive quantifiers or just not using regular expressions against untrusted
40437 It can be important to correctly use &%${quote:...}%&,
40438 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
40439 items to ensure that data is correctly constructed.
40441 Some lookups might return multiple results, even though normal usage is only
40442 expected to yield one result.
40448 .section "IPv4 source routing" "SECID272"
40449 .cindex "source routing" "in IP packets"
40450 .cindex "IP source routing"
40451 Many operating systems suppress IP source-routed packets in the kernel, but
40452 some cannot be made to do this, so Exim does its own check. It logs incoming
40453 IPv4 source-routed TCP calls, and then drops them. Things are all different in
40454 IPv6. No special checking is currently done.
40458 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
40459 Support for these SMTP commands is disabled by default. If required, they can
40460 be enabled by defining suitable ACLs.
40465 .section "Privileged users" "SECID274"
40466 .cindex "trusted users"
40467 .cindex "admin user"
40468 .cindex "privileged user"
40469 .cindex "user" "trusted"
40470 .cindex "user" "admin"
40471 Exim recognizes two sets of users with special privileges. Trusted users are
40472 able to submit new messages to Exim locally, but supply their own sender
40473 addresses and information about a sending host. For other users submitting
40474 local messages, Exim sets up the sender address from the uid, and doesn't
40475 permit a remote host to be specified.
40478 However, an untrusted user is permitted to use the &%-f%& command line option
40479 in the special form &%-f <>%& to indicate that a delivery failure for the
40480 message should not cause an error report. This affects the message's envelope,
40481 but it does not affect the &'Sender:'& header. Untrusted users may also be
40482 permitted to use specific forms of address with the &%-f%& option by setting
40483 the &%untrusted_set_sender%& option.
40485 Trusted users are used to run processes that receive mail messages from some
40486 other mail domain and pass them on to Exim for delivery either locally, or over
40487 the Internet. Exim trusts a caller that is running as root, as the Exim user,
40488 as any user listed in the &%trusted_users%& configuration option, or under any
40489 group listed in the &%trusted_groups%& option.
40491 Admin users are permitted to do things to the messages on Exim's queue. They
40492 can freeze or thaw messages, cause them to be returned to their senders, remove
40493 them entirely, or modify them in various ways. In addition, admin users can run
40494 the Exim monitor and see all the information it is capable of providing, which
40495 includes the contents of files on the spool.
40499 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
40500 delivery of messages on its queue is restricted to admin users. This
40501 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
40502 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
40503 queue is also restricted to admin users. This restriction can be relaxed by
40504 setting &%no_queue_list_requires_admin%&.
40506 Exim recognizes an admin user if the calling process is running as root or as
40507 the Exim user or if any of the groups associated with the calling process is
40508 the Exim group. It is not necessary actually to be running under the Exim
40509 group. However, if admin users who are not root or the Exim user are to access
40510 the contents of files on the spool via the Exim monitor (which runs
40511 unprivileged), Exim must be built to allow group read access to its spool
40514 By default, regular users are trusted to perform basic testing and
40515 introspection commands, as themselves. This setting can be tightened by
40516 setting the &%commandline_checks_require_admin%& option.
40517 This affects most of the checking options,
40518 such as &%-be%& and anything else &%-b*%&.
40521 .section "Spool files" "SECID275"
40522 .cindex "spool directory" "files"
40523 Exim's spool directory and everything it contains is owned by the Exim user and
40524 set to the Exim group. The mode for spool files is defined in the
40525 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
40526 any user who is a member of the Exim group can access these files.
40530 .section "Use of argv[0]" "SECID276"
40531 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
40532 of specific strings, Exim assumes certain options. For example, calling Exim
40533 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
40534 to calling it with the option &%-bS%&. There are no security implications in
40539 .section "Use of %f formatting" "SECID277"
40540 The only use made of &"%f"& by Exim is in formatting load average values. These
40541 are actually stored in integer variables as 1000 times the load average.
40542 Consequently, their range is limited and so therefore is the length of the
40547 .section "Embedded Exim path" "SECID278"
40548 Exim uses its own path name, which is embedded in the code, only when it needs
40549 to re-exec in order to regain root privilege. Therefore, it is not root when it
40550 does so. If some bug allowed the path to get overwritten, it would lead to an
40551 arbitrary program's being run as exim, not as root.
40555 .section "Dynamic module directory" "SECTdynmoddir"
40556 Any dynamically loadable modules must be installed into the directory
40557 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
40561 .section "Use of sprintf()" "SECID279"
40562 .cindex "&[sprintf()]&"
40563 A large number of occurrences of &"sprintf"& in the code are actually calls to
40564 &'string_sprintf()'&, a function that returns the result in malloc'd store.
40565 The intermediate formatting is done into a large fixed buffer by a function
40566 that runs through the format string itself, and checks the length of each
40567 conversion before performing it, thus preventing buffer overruns.
40569 The remaining uses of &[sprintf()]& happen in controlled circumstances where
40570 the output buffer is known to be sufficiently long to contain the converted
40575 .section "Use of debug_printf() and log_write()" "SECID280"
40576 Arbitrary strings are passed to both these functions, but they do their
40577 formatting by calling the function &'string_vformat()'&, which runs through
40578 the format string itself, and checks the length of each conversion.
40582 .section "Use of strcat() and strcpy()" "SECID281"
40583 These are used only in cases where the output buffer is known to be large
40584 enough to hold the result.
40585 .ecindex IIDsecurcon
40590 . ////////////////////////////////////////////////////////////////////////////
40591 . ////////////////////////////////////////////////////////////////////////////
40593 .chapter "Format of spool files" "CHAPspool"
40594 .scindex IIDforspo1 "format" "spool files"
40595 .scindex IIDforspo2 "spool directory" "format of files"
40596 .scindex IIDforspo3 "spool files" "format of"
40597 .cindex "spool files" "editing"
40598 A message on Exim's queue consists of two files, whose names are the message id
40599 followed by -D and -H, respectively. The data portion of the message is kept in
40600 the -D file on its own. The message's envelope, status, and headers are all
40601 kept in the -H file, whose format is described in this chapter. Each of these
40602 two files contains the final component of its own name as its first line. This
40603 is insurance against disk crashes where the directory is lost but the files
40604 themselves are recoverable.
40606 The file formats may be changed, or new formats added, at any release.
40607 Spool files are not intended as an interface to other programs
40608 and should not be used as such.
40610 Some people are tempted into editing -D files in order to modify messages. You
40611 need to be extremely careful if you do this; it is not recommended and you are
40612 on your own if you do it. Here are some of the pitfalls:
40615 You must ensure that Exim does not try to deliver the message while you are
40616 fiddling with it. The safest way is to take out a write lock on the -D file,
40617 which is what Exim itself does, using &[fcntl()]&. If you update the file in
40618 place, the lock will be retained. If you write a new file and rename it, the
40619 lock will be lost at the instant of rename.
40621 .vindex "&$body_linecount$&"
40622 If you change the number of lines in the file, the value of
40623 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
40624 cause incomplete transmission of messages or undeliverable messages.
40626 If the message is in MIME format, you must take care not to break it.
40628 If the message is cryptographically signed, any change will invalidate the
40631 All in all, modifying -D files is fraught with danger.
40633 Files whose names end with -J may also be seen in the &_input_& directory (or
40634 its subdirectories when &%split_spool_directory%& is set). These are journal
40635 files, used to record addresses to which the message has been delivered during
40636 the course of a delivery attempt. If there are still undelivered recipients at
40637 the end, the -H file is updated, and the -J file is deleted. If, however, there
40638 is some kind of crash (for example, a power outage) before this happens, the -J
40639 file remains in existence. When Exim next processes the message, it notices the
40640 -J file and uses it to update the -H file before starting the next delivery
40643 Files whose names end with -K or .eml may also be seen in the spool.
40644 These are temporaries used for DKIM or malware processing, when that is used.
40645 They should be tidied up by normal operations; any old ones are probably
40646 relics of crashes and can be removed.
40648 .section "Format of the -H file" "SECID282"
40649 .cindex "uid (user id)" "in spool file"
40650 .cindex "gid (group id)" "in spool file"
40651 The second line of the -H file contains the login name for the uid of the
40652 process that called Exim to read the message, followed by the numerical uid and
40653 gid. For a locally generated message, this is normally the user who sent the
40654 message. For a message received over TCP/IP via the daemon, it is
40655 normally the Exim user.
40657 The third line of the file contains the address of the message's sender as
40658 transmitted in the envelope, contained in angle brackets. The sender address is
40659 empty for bounce messages. For incoming SMTP mail, the sender address is given
40660 in the MAIL command. For locally generated mail, the sender address is
40661 created by Exim from the login name of the current user and the configured
40662 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
40663 leading &"From&~"& line if the caller is trusted, or if the supplied address is
40664 &"<>"& or an address that matches &%untrusted_set_senders%&.
40666 The fourth line contains two numbers. The first is the time that the message
40667 was received, in the conventional Unix form &-- the number of seconds since the
40668 start of the epoch. The second number is a count of the number of messages
40669 warning of delayed delivery that have been sent to the sender.
40671 There follow a number of lines starting with a hyphen. These can appear in any
40672 order, and are omitted when not relevant:
40675 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
40676 This item is obsolete, and is not generated from Exim release 4.61 onwards;
40677 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
40678 recognized, to provide backward compatibility. In the old format, a line of
40679 this form is present for every ACL variable that is not empty. The number
40680 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
40681 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
40682 the data string for the variable. The string itself starts at the beginning of
40683 the next line, and is followed by a newline character. It may contain internal
40686 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
40687 A line of this form is present for every ACL connection variable that is
40688 defined. Note that there is a space between &%-aclc%& and the rest of the name.
40689 The length is the length of the data string for the variable. The string itself
40690 starts at the beginning of the next line, and is followed by a newline
40691 character. It may contain internal newlines.
40693 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
40694 A line of this form is present for every ACL message variable that is defined.
40695 Note that there is a space between &%-aclm%& and the rest of the name. The
40696 length is the length of the data string for the variable. The string itself
40697 starts at the beginning of the next line, and is followed by a newline
40698 character. It may contain internal newlines.
40700 .vitem "&%-active_hostname%&&~<&'hostname'&>"
40701 This is present if, when the message was received over SMTP, the value of
40702 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
40704 .vitem &%-allow_unqualified_recipient%&
40705 This is present if unqualified recipient addresses are permitted in header
40706 lines (to stop such addresses from being qualified if rewriting occurs at
40707 transport time). Local messages that were input using &%-bnq%& and remote
40708 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
40710 .vitem &%-allow_unqualified_sender%&
40711 This is present if unqualified sender addresses are permitted in header lines
40712 (to stop such addresses from being qualified if rewriting occurs at transport
40713 time). Local messages that were input using &%-bnq%& and remote messages from
40714 hosts that match &%sender_unqualified_hosts%& set this flag.
40716 .vitem "&%-auth_id%&&~<&'text'&>"
40717 The id information for a message received on an authenticated SMTP connection
40718 &-- the value of the &$authenticated_id$& variable.
40720 .vitem "&%-auth_sender%&&~<&'address'&>"
40721 The address of an authenticated sender &-- the value of the
40722 &$authenticated_sender$& variable.
40724 .vitem "&%-body_linecount%&&~<&'number'&>"
40725 This records the number of lines in the body of the message, and is
40726 present unless &%-spool_file_wireformat%& is.
40728 .vitem "&%-body_zerocount%&&~<&'number'&>"
40729 This records the number of binary zero bytes in the body of the message, and is
40730 present if the number is greater than zero.
40732 .vitem &%-deliver_firsttime%&
40733 This is written when a new message is first added to the spool. When the spool
40734 file is updated after a deferral, it is omitted.
40736 .vitem "&%-frozen%&&~<&'time'&>"
40737 .cindex "frozen messages" "spool data"
40738 The message is frozen, and the freezing happened at <&'time'&>.
40740 .vitem "&%-helo_name%&&~<&'text'&>"
40741 This records the host name as specified by a remote host in a HELO or EHLO
40744 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
40745 This records the IP address of the host from which the message was received and
40746 the remote port number that was used. It is omitted for locally generated
40749 .vitem "&%-host_auth%&&~<&'text'&>"
40750 If the message was received on an authenticated SMTP connection, this records
40751 the name of the authenticator &-- the value of the
40752 &$sender_host_authenticated$& variable.
40754 .vitem &%-host_lookup_failed%&
40755 This is present if an attempt to look up the sending host's name from its IP
40756 address failed. It corresponds to the &$host_lookup_failed$& variable.
40758 .vitem "&%-host_name%&&~<&'text'&>"
40759 .cindex "reverse DNS lookup"
40760 .cindex "DNS" "reverse lookup"
40761 This records the name of the remote host from which the message was received,
40762 if the host name was looked up from the IP address when the message was being
40763 received. It is not present if no reverse lookup was done.
40765 .vitem "&%-ident%&&~<&'text'&>"
40766 For locally submitted messages, this records the login of the originating user,
40767 unless it was a trusted user and the &%-oMt%& option was used to specify an
40768 ident value. For messages received over TCP/IP, this records the ident string
40769 supplied by the remote host, if any.
40771 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
40772 This records the IP address of the local interface and the port number through
40773 which a message was received from a remote host. It is omitted for locally
40774 generated messages.
40777 The message is from a local sender.
40779 .vitem &%-localerror%&
40780 The message is a locally-generated bounce message.
40782 .vitem "&%-local_scan%&&~<&'string'&>"
40783 This records the data string that was returned by the &[local_scan()]& function
40784 when the message was received &-- the value of the &$local_scan_data$&
40785 variable. It is omitted if no data was returned.
40787 .vitem &%-manual_thaw%&
40788 The message was frozen but has been thawed manually, that is, by an explicit
40789 Exim command rather than via the auto-thaw process.
40792 A testing delivery process was started using the &%-N%& option to suppress any
40793 actual deliveries, but delivery was deferred. At any further delivery attempts,
40796 .vitem &%-received_protocol%&
40797 This records the value of the &$received_protocol$& variable, which contains
40798 the name of the protocol by which the message was received.
40800 .vitem &%-sender_set_untrusted%&
40801 The envelope sender of this message was set by an untrusted local caller (used
40802 to ensure that the caller is displayed in queue listings).
40804 .vitem "&%-spam_score_int%&&~<&'number'&>"
40805 If a message was scanned by SpamAssassin, this is present. It records the value
40806 of &$spam_score_int$&.
40808 .vitem &%-spool_file_wireformat%&
40809 The -D file for this message is in wire-format (for ESMTP CHUNKING)
40810 rather than Unix-format.
40811 The line-ending is CRLF rather than newline.
40812 There is still, however, no leading-dot-stuffing.
40814 .vitem &%-tls_certificate_verified%&
40815 A TLS certificate was received from the client that sent this message, and the
40816 certificate was verified by the server.
40818 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
40819 When the message was received over an encrypted connection, this records the
40820 name of the cipher suite that was used.
40822 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
40823 When the message was received over an encrypted connection, and a certificate
40824 was received from the client, this records the Distinguished Name from that
40828 Any of the above may have an extra hyphen prepended, to indicate the the
40829 corresponding data is untrusted.
40831 Following the options there is a list of those addresses to which the message
40832 is not to be delivered. This set of addresses is initialized from the command
40833 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
40834 is set; otherwise it starts out empty. Whenever a successful delivery is made,
40835 the address is added to this set. The addresses are kept internally as a
40836 balanced binary tree, and it is a representation of that tree which is written
40837 to the spool file. If an address is expanded via an alias or forward file, the
40838 original address is added to the tree when deliveries to all its child
40839 addresses are complete.
40841 If the tree is empty, there is a single line in the spool file containing just
40842 the text &"XX"&. Otherwise, each line consists of two letters, which are either
40843 Y or N, followed by an address. The address is the value for the node of the
40844 tree, and the letters indicate whether the node has a left branch and/or a
40845 right branch attached to it, respectively. If branches exist, they immediately
40846 follow. Here is an example of a three-node tree:
40848 YY darcy@austen.fict.example
40849 NN alice@wonderland.fict.example
40850 NN editor@thesaurus.ref.example
40852 After the non-recipients tree, there is a list of the message's recipients.
40853 This is a simple list, preceded by a count. It includes all the original
40854 recipients of the message, including those to whom the message has already been
40855 delivered. In the simplest case, the list contains one address per line. For
40859 editor@thesaurus.ref.example
40860 darcy@austen.fict.example
40862 alice@wonderland.fict.example
40864 However, when a child address has been added to the top-level addresses as a
40865 result of the use of the &%one_time%& option on a &(redirect)& router, each
40866 line is of the following form:
40868 <&'top-level address'&> <&'errors_to address'&> &&&
40869 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
40871 The 01 flag bit indicates the presence of the three other fields that follow
40872 the top-level address. Other bits may be used in future to support additional
40873 fields. The <&'parent number'&> is the offset in the recipients list of the
40874 original parent of the &"one time"& address. The first two fields are the
40875 envelope sender that is associated with this address and its length. If the
40876 length is zero, there is no special envelope sender (there are then two space
40877 characters in the line). A non-empty field can arise from a &(redirect)& router
40878 that has an &%errors_to%& setting.
40881 A blank line separates the envelope and status information from the headers
40882 which follow. A header may occupy several lines of the file, and to save effort
40883 when reading it in, each header is preceded by a number and an identifying
40884 character. The number is the number of characters in the header, including any
40885 embedded newlines and the terminating newline. The character is one of the
40889 .row <&'blank'&> "header in which Exim has no special interest"
40890 .row &`B`& "&'Bcc:'& header"
40891 .row &`C`& "&'Cc:'& header"
40892 .row &`F`& "&'From:'& header"
40893 .row &`I`& "&'Message-id:'& header"
40894 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
40895 .row &`R`& "&'Reply-To:'& header"
40896 .row &`S`& "&'Sender:'& header"
40897 .row &`T`& "&'To:'& header"
40898 .row &`*`& "replaced or deleted header"
40901 Deleted or replaced (rewritten) headers remain in the spool file for debugging
40902 purposes. They are not transmitted when the message is delivered. Here is a
40903 typical set of headers:
40905 111P Received: by hobbit.fict.example with local (Exim 4.00)
40906 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
40907 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
40908 038* X-rewrote-sender: bb@hobbit.fict.example
40909 042* From: Bilbo Baggins <bb@hobbit.fict.example>
40910 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
40911 099* To: alice@wonderland.fict.example, rdo@foundation,
40912 darcy@austen.fict.example, editor@thesaurus.ref.example
40913 104T To: alice@wonderland.fict.example, rdo@foundation.example,
40914 darcy@austen.fict.example, editor@thesaurus.ref.example
40915 038 Date: Fri, 11 May 2001 10:28:59 +0100
40917 The asterisked headers indicate that the envelope sender, &'From:'& header, and
40918 &'To:'& header have been rewritten, the last one because routing expanded the
40919 unqualified domain &'foundation'&.
40920 .ecindex IIDforspo1
40921 .ecindex IIDforspo2
40922 .ecindex IIDforspo3
40924 .section "Format of the -D file" "SECID282a"
40925 The data file is traditionally in Unix-standard format: lines are ended with
40926 an ASCII newline character.
40927 However, when the &%spool_wireformat%& main option is used some -D files
40928 can have an alternate format.
40929 This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
40930 The -D file lines (not including the first name-component line) are
40931 suitable for direct copying to the wire when transmitting using the
40932 ESMTP CHUNKING option, meaning lower processing overhead.
40933 Lines are terminated with an ASCII CRLF pair.
40934 There is no dot-stuffing (and no dot-termination).
40936 . ////////////////////////////////////////////////////////////////////////////
40937 . ////////////////////////////////////////////////////////////////////////////
40939 .chapter "DKIM, SPF, SRS and DMARC" "CHAPdkim" &&&
40940 "DKIM, SPF, SRS and DMARC Support"
40942 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
40945 DKIM is a mechanism by which messages sent by some entity can be provably
40946 linked to a domain which that entity controls. It permits reputation to
40947 be tracked on a per-domain basis, rather than merely upon source IP address.
40948 DKIM is documented in RFC 6376.
40950 As DKIM relies on the message being unchanged in transit, messages handled
40951 by a mailing-list (which traditionally adds to the message) will not match
40952 any original DKIM signature.
40954 DKIM support is compiled into Exim by default if TLS support is present.
40955 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
40957 Exim's DKIM implementation allows for
40959 Signing outgoing messages: This function is implemented in the SMTP transport.
40960 It can co-exist with all other Exim features
40961 (including transport filters)
40962 except cutthrough delivery.
40964 Verifying signatures in incoming messages: This is implemented by an additional
40965 ACL (acl_smtp_dkim), which can be called several times per message, with
40966 different signature contexts.
40969 In typical Exim style, the verification implementation does not include any
40970 default "policy". Instead it enables you to build your own policy using
40971 Exim's standard controls.
40973 Please note that verification of DKIM signatures in incoming mail is turned
40974 on by default for logging (in the <= line) purposes.
40976 Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
40977 When set, for each signature in incoming email,
40978 exim will log a line displaying the most important signature details, and the
40979 signature status. Here is an example (with line-breaks added for clarity):
40981 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
40982 d=facebookmail.com s=q1-2009b
40983 c=relaxed/relaxed a=rsa-sha1
40984 i=@facebookmail.com t=1252484542 [verification succeeded]
40987 You might want to turn off DKIM verification processing entirely for internal
40988 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
40989 control modifier. This should typically be done in the RCPT ACL, at points
40990 where you accept mail from relay sources (internal hosts or authenticated
40994 .section "Signing outgoing messages" "SECDKIMSIGN"
40995 .cindex "DKIM" "signing"
40997 For signing to be usable you must have published a DKIM record in DNS.
40998 Note that RFC 8301 (which does not cover EC keys) says:
41000 rsa-sha1 MUST NOT be used for signing or verifying.
41002 Signers MUST use RSA keys of at least 1024 bits for all keys.
41003 Signers SHOULD use RSA keys of at least 2048 bits.
41006 Note also that the key content (the 'p=' field)
41007 in the DNS record is different between RSA and EC keys;
41008 for the former it is the base64 of the ASN.1 for the RSA public key
41009 (equivalent to the private-key .pem with the header/trailer stripped)
41010 but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
41012 Signing is enabled by setting private options on the SMTP transport.
41013 These options take (expandable) strings as arguments.
41015 .option dkim_domain smtp "string list&!!" unset
41016 The domain(s) you want to sign with.
41017 After expansion, this can be a list.
41018 Each element in turn,
41020 is put into the &%$dkim_domain%& expansion variable
41021 while expanding the remaining signing options.
41022 If it is empty after expansion, DKIM signing is not done,
41023 and no error will result even if &%dkim_strict%& is set.
41025 .option dkim_selector smtp "string list&!!" unset
41026 This sets the key selector string.
41027 After expansion, which can use &$dkim_domain$&, this can be a list.
41028 Each element in turn is put in the expansion
41029 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
41030 option along with &%$dkim_domain%&.
41031 If the option is empty after expansion, DKIM signing is not done for this domain,
41032 and no error will result even if &%dkim_strict%& is set.
41034 .option dkim_private_key smtp string&!! unset
41035 This sets the private key to use.
41036 You can use the &%$dkim_domain%& and
41037 &%$dkim_selector%& expansion variables to determine the private key to use.
41038 The result can either
41040 be a valid RSA private key in ASCII armor (.pem file), including line breaks
41042 with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41043 be a valid Ed25519 private key (same format as above)
41045 start with a slash, in which case it is treated as a file that contains
41048 be "0", "false" or the empty string, in which case the message will not
41049 be signed. This case will not result in an error, even if &%dkim_strict%&
41053 To generate keys under OpenSSL:
41055 openssl genrsa -out dkim_rsa.private 2048
41056 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
41058 The result file from the first command should be retained, and
41059 this option set to use it.
41060 Take the base-64 lines from the output of the second command, concatenated,
41061 for the DNS TXT record.
41062 See section 3.6 of RFC6376 for the record specification.
41066 certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
41067 certtool --load-privkey=dkim_rsa.private --pubkey-info
41070 Note that RFC 8301 says:
41072 Signers MUST use RSA keys of at least 1024 bits for all keys.
41073 Signers SHOULD use RSA keys of at least 2048 bits.
41076 EC keys for DKIM are defined by RFC 8463.
41077 They are considerably smaller than RSA keys for equivalent protection.
41078 As they are a recent development, users should consider dual-signing
41079 (by setting a list of selectors, and an expansion for this option)
41080 for some transition period.
41081 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41084 OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
41086 openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
41087 certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
41090 To produce the required public key value for a DNS record:
41092 openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
41093 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
41096 Exim also supports an alternate format
41097 of Ed25519 keys in DNS which was a candidate during development
41098 of the standard, but not adopted.
41099 A future release will probably drop that support.
41101 .option dkim_hash smtp string&!! sha256
41102 Can be set to any one of the supported hash methods, which are:
41104 &`sha1`& &-- should not be used, is old and insecure
41106 &`sha256`& &-- the default
41108 &`sha512`& &-- possibly more secure but less well supported
41111 Note that RFC 8301 says:
41113 rsa-sha1 MUST NOT be used for signing or verifying.
41116 .option dkim_identity smtp string&!! unset
41117 If set after expansion, the value is used to set an "i=" tag in
41118 the signing header. The DKIM standards restrict the permissible
41119 syntax of this optional tag to a mail address, with possibly-empty
41120 local part, an @, and a domain identical to or subdomain of the "d="
41121 tag value. Note that Exim does not check the value.
41123 .option dkim_canon smtp string&!! unset
41124 This option sets the canonicalization method used when signing a message.
41125 The DKIM RFC currently supports two methods: "simple" and "relaxed".
41126 The option defaults to "relaxed" when unset. Note: the current implementation
41127 only supports signing with the same canonicalization method for both headers and body.
41129 .option dkim_strict smtp string&!! unset
41130 This option defines how Exim behaves when signing a message that
41131 should be signed fails for some reason. When the expansion evaluates to
41132 either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message
41133 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
41136 .option dkim_sign_headers smtp string&!! "see below"
41137 If set, this option must expand to a colon-separated
41138 list of header names.
41139 Headers with these names, or the absence or such a header, will be included
41140 in the message signature.
41141 When unspecified, the header names listed in RFC4871 will be used,
41142 whether or not each header is present in the message.
41143 The default list is available for the expansion in the macro
41144 &"_DKIM_SIGN_HEADERS"&
41145 and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
41147 If a name is repeated, multiple headers by that name (or the absence thereof)
41148 will be signed. The textually later headers in the headers part of the
41149 message are signed first, if there are multiples.
41151 A name can be prefixed with either an &"="& or a &"+"& character.
41152 If an &"="& prefix is used, all headers that are present with this name
41154 If a &"+"& prefix if used, all headers that are present with this name
41155 will be signed, and one signature added for a missing header with the
41156 name will be appended.
41158 .option dkim_timestamps smtp integer&!! unset
41159 This option controls the inclusion of timestamp information in the signature.
41160 If not set, no such information will be included.
41161 Otherwise, must be an unsigned number giving an offset in seconds from the current time
41163 (eg. 1209600 for two weeks);
41164 both creation (t=) and expiry (x=) tags will be included.
41166 RFC 6376 lists these tags as RECOMMENDED.
41169 .section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
41170 .cindex "DKIM" "verification"
41172 Verification of DKIM signatures in SMTP incoming email is done for all
41173 messages for which an ACL control &%dkim_disable_verify%& has not been set.
41174 .cindex DKIM "selecting signature algorithms"
41175 Individual classes of signature algorithm can be ignored by changing
41176 the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
41177 The &%dkim_verify_minimal%& option can be set to cease verification
41178 processing for a message once the first passing signature is found.
41180 .cindex authentication "expansion item"
41181 Performing verification sets up information used by the
41182 &%authresults%& expansion item.
41184 For most purposes the default option settings suffice and the remainder
41185 of this section can be ignored.
41187 The results of verification are made available to the
41188 &%acl_smtp_dkim%& ACL, which can examine and modify them.
41189 A missing ACL definition defaults to accept.
41190 By default, the ACL is called once for each
41191 syntactically(!) correct signature in the incoming message.
41192 If any ACL call does not accept, the message is not accepted.
41193 If a cutthrough delivery was in progress for the message, that is
41194 summarily dropped (having wasted the transmission effort).
41196 To evaluate the verification result in the ACL
41197 a large number of expansion variables
41198 containing the signature status and its details are set up during the
41199 runtime of the ACL.
41201 Calling the ACL only for existing signatures is not sufficient to build
41202 more advanced policies. For that reason, the main option
41203 &%dkim_verify_signers%&, and an expansion variable
41204 &%$dkim_signers%& exist.
41206 The main option &%dkim_verify_signers%& can be set to a colon-separated
41207 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
41208 called. It is expanded when the message has been received. At this point,
41209 the expansion variable &%$dkim_signers%& already contains a colon-separated
41210 list of signer domains and identities for the message. When
41211 &%dkim_verify_signers%& is not specified in the main configuration,
41214 dkim_verify_signers = $dkim_signers
41216 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
41217 DKIM signature in the message. Current DKIM verifiers may want to explicitly
41218 call the ACL for known domains or identities. This would be achieved as follows:
41220 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
41222 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
41223 and "ebay.com", plus all domains and identities that have signatures in the message.
41224 You can also be more creative in constructing your policy. For example:
41226 dkim_verify_signers = $sender_address_domain:$dkim_signers
41229 If a domain or identity is listed several times in the (expanded) value of
41230 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
41232 Note that if the option is set using untrustworthy data
41233 (such as the From: header)
41234 care should be taken to force lowercase for domains
41235 and for the domain part if identities.
41236 The default setting can be regarded as trustworthy in this respect.
41238 If multiple signatures match a domain (or identity), the ACL is called once
41239 for each matching signature.
41242 Inside the DKIM ACL, the following expansion variables are
41243 available (from most to least important):
41247 .vitem &%$dkim_cur_signer%&
41248 The signer that is being evaluated in this ACL run. This can be a domain or
41249 an identity. This is one of the list items from the expanded main option
41250 &%dkim_verify_signers%& (see above).
41252 .vitem &%$dkim_verify_status%&
41253 Within the DKIM ACL,
41254 a string describing the general status of the signature. One of
41256 &%none%&: There is no signature in the message for the current domain or
41257 identity (as reflected by &%$dkim_cur_signer%&).
41259 &%invalid%&: The signature could not be verified due to a processing error.
41260 More detail is available in &%$dkim_verify_reason%&.
41262 &%fail%&: Verification of the signature failed. More detail is
41263 available in &%$dkim_verify_reason%&.
41265 &%pass%&: The signature passed verification. It is valid.
41268 This variable can be overwritten using an ACL 'set' modifier.
41269 This might, for instance, be done to enforce a policy restriction on
41270 hash-method or key-size:
41272 warn condition = ${if eq {$dkim_verify_status}{pass}}
41273 condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
41274 condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
41275 {< {$dkim_key_length}{1024}}}}
41276 logwrite = NOTE: forcing DKIM verify fail (was pass)
41277 set dkim_verify_status = fail
41278 set dkim_verify_reason = hash too weak or key too short
41281 So long as a DKIM ACL is defined (it need do no more than accept),
41282 after all the DKIM ACL runs have completed, the value becomes a
41283 colon-separated list of the values after each run.
41284 This is maintained for the mime, prdr and data ACLs.
41286 .vitem &%$dkim_verify_reason%&
41287 A string giving a little bit more detail when &%$dkim_verify_status%& is either
41288 "fail" or "invalid". One of
41290 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
41291 key for the domain could not be retrieved. This may be a temporary problem.
41293 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
41294 record for the domain is syntactically invalid.
41296 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
41297 body hash does not match the one specified in the signature header. This
41298 means that the message body was modified in transit.
41300 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
41301 could not be verified. This may mean that headers were modified,
41302 re-written or otherwise changed in a way which is incompatible with
41303 DKIM verification. It may of course also mean that the signature is forged.
41306 This variable can be overwritten, with any value, using an ACL 'set' modifier.
41308 .vitem &%$dkim_domain%&
41309 The signing domain. IMPORTANT: This variable is only populated if there is
41310 an actual signature in the message for the current domain or identity (as
41311 reflected by &%$dkim_cur_signer%&).
41313 .vitem &%$dkim_identity%&
41314 The signing identity, if present. IMPORTANT: This variable is only populated
41315 if there is an actual signature in the message for the current domain or
41316 identity (as reflected by &%$dkim_cur_signer%&).
41318 .vitem &%$dkim_selector%&
41319 The key record selector string.
41321 .vitem &%$dkim_algo%&
41322 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
41323 If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41324 may also be 'ed25519-sha256'.
41325 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41328 Note that RFC 8301 says:
41330 rsa-sha1 MUST NOT be used for signing or verifying.
41332 DKIM signatures identified as having been signed with historic
41333 algorithms (currently, rsa-sha1) have permanently failed evaluation
41336 To enforce this you must either have a DKIM ACL which checks this variable
41337 and overwrites the &$dkim_verify_status$& variable as discussed above,
41338 or have set the main option &%dkim_verify_hashes%& to exclude
41339 processing of such signatures.
41341 .vitem &%$dkim_canon_body%&
41342 The body canonicalization method. One of 'relaxed' or 'simple'.
41344 .vitem &%$dkim_canon_headers%&
41345 The header canonicalization method. One of 'relaxed' or 'simple'.
41347 .vitem &%$dkim_copiedheaders%&
41348 A transcript of headers and their values which are included in the signature
41349 (copied from the 'z=' tag of the signature).
41350 Note that RFC6376 requires that verification fail if the From: header is
41351 not included in the signature. Exim does not enforce this; sites wishing
41352 strict enforcement should code the check explicitly.
41354 .vitem &%$dkim_bodylength%&
41355 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
41356 limit was set by the signer, "9999999999999" is returned. This makes sure
41357 that this variable always expands to an integer value.
41358 &*Note:*& The presence of the signature tag specifying a signing body length
41359 is one possible route to spoofing of valid DKIM signatures.
41360 A paranoid implementation might wish to regard signature where this variable
41361 shows less than the "no limit" return as being invalid.
41363 .vitem &%$dkim_created%&
41364 UNIX timestamp reflecting the date and time when the signature was created.
41365 When this was not specified by the signer, "0" is returned.
41367 .vitem &%$dkim_expires%&
41368 UNIX timestamp reflecting the date and time when the signer wants the
41369 signature to be treated as "expired". When this was not specified by the
41370 signer, "9999999999999" is returned. This makes it possible to do useful
41371 integer size comparisons against this value.
41372 Note that Exim does not check this value.
41374 .vitem &%$dkim_headernames%&
41375 A colon-separated list of names of headers included in the signature.
41377 .vitem &%$dkim_key_testing%&
41378 "1" if the key record has the "testing" flag set, "0" if not.
41380 .vitem &%$dkim_key_nosubdomains%&
41381 "1" if the key record forbids subdomaining, "0" otherwise.
41383 .vitem &%$dkim_key_srvtype%&
41384 Service type (tag s=) from the key record. Defaults to "*" if not specified
41387 .vitem &%$dkim_key_granularity%&
41388 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
41391 .vitem &%$dkim_key_notes%&
41392 Notes from the key record (tag n=).
41394 .vitem &%$dkim_key_length%&
41395 Number of bits in the key.
41396 Valid only once the key is loaded, which is at the time the header signature
41397 is verified, which is after the body hash is.
41399 Note that RFC 8301 says:
41401 Verifiers MUST NOT consider signatures using RSA keys of
41402 less than 1024 bits as valid signatures.
41405 This is enforced by the default setting for the &%dkim_verify_min_keysizes%&
41410 In addition, two ACL conditions are provided:
41413 .vitem &%dkim_signers%&
41414 ACL condition that checks a colon-separated list of domains or identities
41415 for a match against the domain or identity that the ACL is currently verifying
41416 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
41417 verb to a group of domains or identities. For example:
41420 # Warn when Mail purportedly from GMail has no gmail signature
41421 warn sender_domains = gmail.com
41422 dkim_signers = gmail.com
41424 log_message = GMail sender without gmail.com DKIM signature
41427 Note that the above does not check for a total lack of DKIM signing;
41428 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
41430 .vitem &%dkim_status%&
41431 ACL condition that checks a colon-separated list of possible DKIM verification
41432 results against the actual result of verification. This is typically used
41433 to restrict an ACL verb to a list of verification outcomes, for example:
41436 deny sender_domains = paypal.com:paypal.de
41437 dkim_signers = paypal.com:paypal.de
41438 dkim_status = none:invalid:fail
41439 message = Mail from Paypal with invalid/missing signature
41442 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
41443 see the documentation of the &%$dkim_verify_status%& expansion variable above
41444 for more information of what they mean.
41450 .section "SPF (Sender Policy Framework)" SECSPF
41451 .cindex SPF verification
41453 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
41454 messages with its domain in the envelope from, documented by RFC 7208.
41455 For more information on SPF see &url(http://www.open-spf.org), a static copy of
41456 the &url(http://openspf.org).
41457 . --- 2019-10-28: still not https, open-spf.org is told to be a
41458 . --- web-archive copy of the now dead openspf.org site
41459 . --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a
41462 Messages sent by a system not authorised will fail checking of such assertions.
41463 This includes retransmissions done by traditional forwarders.
41465 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
41466 &_Local/Makefile_&. The support uses the &_libspf2_& library
41467 &url(https://www.libspf2.org/).
41468 There is no Exim involvement in the transmission of messages;
41469 publishing certain DNS records is all that is required.
41471 For verification, an ACL condition and an expansion lookup are provided.
41472 .cindex authentication "expansion item"
41473 Performing verification sets up information used by the
41474 &%authresults%& expansion item.
41477 .cindex SPF "ACL condition"
41478 .cindex ACL "spf condition"
41479 The ACL condition "spf" can be used at or after the MAIL ACL.
41480 It takes as an argument a list of strings giving the outcome of the SPF check,
41481 and will succeed for any matching outcome.
41485 The SPF check passed, the sending host is positively verified by SPF.
41488 The SPF check failed, the sending host is NOT allowed to send mail for the
41489 domain in the envelope-from address.
41491 .vitem &%softfail%&
41492 The SPF check failed, but the queried domain can't absolutely confirm that this
41496 The queried domain does not publish SPF records.
41499 The SPF check returned a "neutral" state. This means the queried domain has
41500 published a SPF record, but wants to allow outside servers to send mail under
41501 its domain as well. This should be treated like "none".
41503 .vitem &%permerror%&
41504 This indicates a syntax error in the SPF record of the queried domain.
41505 You may deny messages when this occurs.
41507 .vitem &%temperror%&
41508 This indicates a temporary error during all processing, including Exim's
41509 SPF processing. You may defer messages when this occurs.
41512 You can prefix each string with an exclamation mark to invert
41513 its meaning, for example "!fail" will match all results but
41514 "fail". The string list is evaluated left-to-right, in a
41515 short-circuit fashion.
41520 message = $sender_host_address is not allowed to send mail from \
41521 ${if def:sender_address_domain \
41522 {$sender_address_domain}{$sender_helo_name}}. \
41523 Please see http://www.open-spf.org/Why;\
41524 identity=${if def:sender_address_domain \
41525 {$sender_address}{$sender_helo_name}};\
41526 ip=$sender_host_address
41529 Note: The above mentioned URL may not be as helpful as expected. You are
41530 encouraged to replace the link with a link to a site with more
41533 When the spf condition has run, it sets up several expansion
41536 .cindex SPF "verification variables"
41538 .vitem &$spf_header_comment$&
41539 .vindex &$spf_header_comment$&
41540 This contains a human-readable string describing the outcome
41541 of the SPF check. You can add it to a custom header or use
41542 it for logging purposes.
41544 .vitem &$spf_received$&
41545 .vindex &$spf_received$&
41546 This contains a complete Received-SPF: header that can be
41547 added to the message. Please note that according to the SPF
41548 draft, this header must be added at the top of the header
41549 list. Please see section 10 on how you can do this.
41551 Note: in case of "Best-guess" (see below), the convention is
41552 to put this string in a header called X-SPF-Guess: instead.
41554 .vitem &$spf_result$&
41555 .vindex &$spf_result$&
41556 This contains the outcome of the SPF check in string form,
41557 one of pass, fail, softfail, none, neutral, permerror or
41560 .vitem &$spf_result_guessed$&
41561 .vindex &$spf_result_guessed$&
41562 This boolean is true only if a best-guess operation was used
41563 and required in order to obtain a result.
41565 .vitem &$spf_smtp_comment$&
41566 .vindex &$spf_smtp_comment$&
41567 .vindex &%spf_smtp_comment_template%&
41568 This contains a string that can be used in a SMTP response
41569 to the calling party. Useful for "fail".
41570 The string is generated by the SPF library from the template configured in the main config
41571 option &%spf_smtp_comment_template%&.
41575 .cindex SPF "ACL condition"
41576 .cindex ACL "spf_guess condition"
41577 .cindex SPF "best guess"
41578 In addition to SPF, you can also perform checks for so-called
41579 "Best-guess". Strictly speaking, "Best-guess" is not standard
41580 SPF, but it is supported by the same framework that enables SPF
41582 Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record)
41583 for a description of what it means.
41584 . --- 2019-10-28: still not https:
41586 To access this feature, simply use the spf_guess condition in place
41587 of the spf one. For example:
41590 deny spf_guess = fail
41591 message = $sender_host_address doesn't look trustworthy to me
41594 In case you decide to reject messages based on this check, you
41595 should note that although it uses the same framework, "Best-guess"
41596 is not SPF, and therefore you should not mention SPF at all in your
41599 When the spf_guess condition has run, it sets up the same expansion
41600 variables as when spf condition is run, described above.
41602 Additionally, since Best-guess is not standardized, you may redefine
41603 what "Best-guess" means to you by redefining the main configuration
41604 &%spf_guess%& option.
41605 For example, the following:
41608 spf_guess = v=spf1 a/16 mx/16 ptr ?all
41611 would relax host matching rules to a broader network range.
41614 .cindex SPF "lookup expansion"
41616 A lookup expansion is also available. It takes an email
41617 address as the key and an IP address
41622 ${lookup {username@domain} spf {ip.ip.ip.ip}}
41625 The lookup will return the same result strings as can appear in
41626 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
41632 .section "SRS (Sender Rewriting Scheme)" SECTSRS
41633 .cindex SRS "sender rewriting scheme"
41636 SRS can be used to modify sender addresses when forwarding so that
41637 SPF verification does not object to them.
41638 It operates by encoding the original envelope sender in a new
41639 sender local part and using a domain run by the forwarding site
41640 as the new domain for the sender. Any DSN message should be returned
41641 to this new sender at the forwarding site, which can extract the
41642 original sender from the coded local part and forward the DSN to
41645 This is a way of avoiding the breakage that SPF does to forwarding.
41646 The constructed local-part will be longer than the original,
41647 leading to possible problems with very long addresses.
41648 The changing of the sender address also hinders the tracing of mail
41651 Exim can be built to include native SRS support. To do this
41652 SUPPORT_SRS=yes must be defined in &_Local/Makefile_&.
41653 If this has been done, the macros _HAVE_SRS and _HAVE_NATIVE_SRS
41655 The support is limited to SRS0-encoding; SRS1 is not supported.
41657 .cindex SRS excoding
41658 To encode an address use this expansion item:
41660 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
41661 .cindex "&%srs_encode%& expansion item"
41662 .cindex SRS "expansion item"
41663 The first argument should be a secret known and used by all systems
41664 handling the recipient domain for the original message.
41665 There is no need to periodically change this key; a timestamp is also
41667 The second argument should be given as the envelope sender address before this
41668 encoding operation.
41669 The third argument should be the recipient domain of the message when
41670 it arrived at this system.
41673 .cindex SRS decoding
41674 To decode an address use this expansion condition:
41676 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
41677 The first argument should be the recipient local prt as is was received.
41678 The second argument is the site secret.
41680 If the messages is not for an SRS-encoded recipient the condition will
41681 return false. If it is, the condition will return true and the variable
41682 &$srs_recipient$& will be set to the decoded (original) value.
41688 SRS_SECRET = <pick something unique for your site for this. Use on all MXs.>
41694 # if outbound, and forwarding has been done, use an alternate transport
41695 domains = ! +my_domains
41696 transport = ${if eq {$local_part@$domain} \
41697 {$original_local_part@$original_domain} \
41698 {remote_smtp} {remote_forwarded_smtp}}
41703 domains = +my_domains
41704 # detect inbound bounces which are SRS'd, and decode them
41705 condition = ${if inbound_srs {$local_part} {SRS_SECRET}}
41706 data = $srs_recipient
41708 inbound_srs_failure:
41711 domains = +my_domains
41712 # detect inbound bounces which look SRS'd but are invalid
41713 condition = ${if inbound_srs {$local_part} {}}
41715 data = :fail: Invalid SRS recipient address
41717 #... further routers here
41720 # transport; should look like the non-forward outbound
41721 # one, plus the max_rcpt and return_path options
41722 remote_forwarded_smtp:
41724 # modify the envelope from, for mails that we forward
41726 return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}}
41734 .section DMARC SECDMARC
41735 .cindex DMARC verification
41737 DMARC combines feedback from SPF, DKIM, and header From: in order
41738 to attempt to provide better indicators of the authenticity of an
41739 email. This document does not explain the fundamentals; you
41740 should read and understand how it works by visiting the website at
41741 &url(http://www.dmarc.org/).
41743 If Exim is built with DMARC support,
41744 the libopendmarc library is used.
41746 For building Exim yourself, obtain the library from
41747 &url(http://sourceforge.net/projects/opendmarc/)
41748 to obtain a copy, or find it in your favorite package
41749 repository. You will need to attend to the local/Makefile feature
41750 SUPPORT_DMARC and the associated LDFLAGS addition.
41751 This description assumes
41752 that headers will be in /usr/local/include, and that the libraries
41753 are in /usr/local/lib.
41757 There are three main-configuration options:
41758 .cindex DMARC "configuration options"
41760 The &%dmarc_tld_file%& option
41761 .oindex &%dmarc_tld_file%&
41762 defines the location of a text file of valid
41763 top level domains the opendmarc library uses
41764 during domain parsing. Maintained by Mozilla,
41765 the most current version can be downloaded
41766 from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat).
41767 See also the util/renew-opendmarc-tlds.sh script.
41768 The default for the option is unset.
41769 If not set, DMARC processing is disabled.
41772 The &%dmarc_history_file%& option, if set
41773 .oindex &%dmarc_history_file%&
41774 defines the location of a file to log results
41775 of dmarc verification on inbound emails. The
41776 contents are importable by the opendmarc tools
41777 which will manage the data, send out DMARC
41778 reports, and expire the data. Make sure the
41779 directory of this file is writable by the user
41781 The default is unset.
41783 The &%dmarc_forensic_sender%& option
41784 .oindex &%dmarc_forensic_sender%&
41785 defines an alternate email address to use when sending a
41786 forensic report detailing alignment failures
41787 if a sender domain's dmarc record specifies it
41788 and you have configured Exim to send them.
41789 If set, this is expanded and used for the
41790 From: header line; the address is extracted
41791 from it and used for the envelope from.
41792 If not set (the default), the From: header is expanded from
41793 the dsn_from option, and <> is used for the
41796 . I wish we had subsections...
41798 .cindex DMARC controls
41799 By default, the DMARC processing will run for any remote,
41800 non-authenticated user. It makes sense to only verify DMARC
41801 status of messages coming from remote, untrusted sources. You can
41802 use standard conditions such as hosts, senders, etc, to decide that
41803 DMARC verification should *not* be performed for them and disable
41804 DMARC with an ACL control modifier:
41806 control = dmarc_disable_verify
41808 A DMARC record can also specify a "forensic address", which gives
41809 exim an email address to submit reports about failed alignment.
41810 Exim does not do this by default because in certain conditions it
41811 results in unintended information leakage (what lists a user might
41812 be subscribed to, etc). You must configure exim to submit forensic
41813 reports to the owner of the domain. If the DMARC record contains a
41814 forensic address and you specify the control statement below, then
41815 exim will send these forensic emails. It is also advised that you
41816 configure a &%dmarc_forensic_sender%& because the default sender address
41817 construction might be inadequate.
41819 control = dmarc_enable_forensic
41821 (AGAIN: You can choose not to send these forensic reports by simply
41822 not putting the dmarc_enable_forensic control line at any point in
41823 your exim config. If you don't tell exim to send them, it will not
41826 There are no options to either control. Both must appear before
41831 DMARC checks cam be run on incoming SMTP messages by using the
41832 &"dmarc_status"& ACL condition in the DATA ACL. You are required to
41833 call the &"spf"& condition first in the ACLs, then the &"dmarc_status"&
41834 condition. Putting this condition in the ACLs is required in order
41835 for a DMARC check to actually occur. All of the variables are set
41836 up before the DATA ACL, but there is no actual DMARC check that
41837 occurs until a &"dmarc_status"& condition is encountered in the ACLs.
41839 The &"dmarc_status"& condition takes a list of strings on its
41840 right-hand side. These strings describe recommended action based
41841 on the DMARC check. To understand what the policy recommendations
41842 mean, refer to the DMARC website above. Valid strings are:
41844 &'accept '& The DMARC check passed and the library recommends accepting the email.
41845 &'reject '& The DMARC check failed and the library recommends rejecting the email.
41846 &'quarantine '& The DMARC check failed and the library recommends keeping it for further inspection.
41847 &'none '& The DMARC check passed and the library recommends no specific action, neutral.
41848 &'norecord '& No policy section in the DMARC record for this RFC5322.From field
41849 &'nofrom '& Unable to determine the domain of the sender.
41850 &'temperror '& Library error or dns error.
41851 &'off '& The DMARC check was disabled for this email.
41853 You can prefix each string with an exclamation mark to invert its
41854 meaning, for example "!accept" will match all results but
41855 "accept". The string list is evaluated left-to-right in a
41856 short-circuit fashion. When a string matches the outcome of the
41857 DMARC check, the condition succeeds. If none of the listed
41858 strings matches the outcome of the DMARC check, the condition
41861 Of course, you can also use any other lookup method that Exim
41862 supports, including LDAP, Postgres, MySQL, etc, as long as the
41863 result is a list of colon-separated strings.
41865 Performing the check sets up information used by the
41866 &%authresults%& expansion item.
41868 Several expansion variables are set before the DATA ACL is
41869 processed, and you can use them in this ACL. The following
41870 expansion variables are available:
41873 .vitem &$dmarc_status$&
41874 .vindex &$dmarc_status$&
41875 .cindex DMARC result
41876 A one word status indicating what the DMARC library
41877 thinks of the email. It is a combination of the results of
41878 DMARC record lookup and the SPF/DKIM/DMARC processing results
41879 (if a DMARC record was found). The actual policy declared
41880 in the DMARC record is in a separate expansion variable.
41882 .vitem &$dmarc_status_text$&
41883 .vindex &$dmarc_status_text$&
41884 Slightly longer, human readable status.
41886 .vitem &$dmarc_used_domain$&
41887 .vindex &$dmarc_used_domain$&
41888 The domain which DMARC used to look up the DMARC policy record.
41890 .vitem &$dmarc_domain_policy$&
41891 .vindex &$dmarc_domain_policy$&
41892 The policy declared in the DMARC record. Valid values
41893 are "none", "reject" and "quarantine". It is blank when there
41894 is any error, including no DMARC record.
41899 By default, Exim's DMARC configuration is intended to be
41900 non-intrusive and conservative. To facilitate this, Exim will not
41901 create any type of logging files without explicit configuration by
41902 you, the admin. Nor will Exim send out any emails/reports about
41903 DMARC issues without explicit configuration by you, the admin (other
41904 than typical bounce messages that may come about due to ACL
41905 processing or failure delivery issues).
41907 In order to log statistics suitable to be imported by the opendmarc
41908 tools, you need to:
41910 Configure the global option &%dmarc_history_file%&
41912 Configure cron jobs to call the appropriate opendmarc history
41913 import scripts and truncating the dmarc_history_file
41916 In order to send forensic reports, you need to:
41918 Configure the global option &%dmarc_forensic_sender%&
41920 Configure, somewhere before the DATA ACL, the control option to
41921 enable sending DMARC forensic reports
41929 warn domains = +local_domains
41930 hosts = +local_hosts
41931 control = dmarc_disable_verify
41933 warn !domains = +screwed_up_dmarc_records
41934 control = dmarc_enable_forensic
41936 warn condition = (lookup if destined to mailing list)
41937 set acl_m_mailing_list = 1
41940 warn dmarc_status = accept : none : off
41942 log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
41944 warn dmarc_status = !accept
41946 log_message = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
41948 warn dmarc_status = quarantine
41950 set $acl_m_quarantine = 1
41951 # Do something in a transport with this flag variable
41953 deny condition = ${if eq{$dmarc_domain_policy}{reject}}
41954 condition = ${if eq{$acl_m_mailing_list}{1}}
41955 message = Messages from $dmarc_used_domain break mailing lists
41957 deny dmarc_status = reject
41959 message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
41961 warn add_header = :at_start:${authresults {$primary_hostname}}
41968 . ////////////////////////////////////////////////////////////////////////////
41969 . ////////////////////////////////////////////////////////////////////////////
41971 .chapter "Proxies" "CHAPproxies" &&&
41973 .cindex "proxy support"
41974 .cindex "proxy" "access via"
41976 A proxy is an intermediate system through which communication is passed.
41977 Proxies may provide a security, availability or load-distribution function.
41980 .section "Inbound proxies" SECTproxyInbound
41981 .cindex proxy inbound
41982 .cindex proxy "server side"
41983 .cindex proxy "Proxy protocol"
41984 .cindex "Proxy protocol" proxy
41986 Exim has support for receiving inbound SMTP connections via a proxy
41987 that uses &"Proxy Protocol"& to speak to it.
41988 To include this support, include &"SUPPORT_PROXY=yes"&
41991 It was built on the HAProxy specification, found at
41992 &url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt).
41994 The purpose of this facility is so that an application load balancer,
41995 such as HAProxy, can sit in front of several Exim servers
41996 to distribute load.
41997 Exim uses the local protocol communication with the proxy to obtain
41998 the remote SMTP system IP address and port information.
41999 There is no logging if a host passes or
42000 fails Proxy Protocol negotiation, but it can easily be determined and
42001 recorded in an ACL (example is below).
42003 Use of a proxy is enabled by setting the &%hosts_proxy%&
42004 main configuration option to a hostlist; connections from these
42005 hosts will use Proxy Protocol.
42006 Exim supports both version 1 and version 2 of the Proxy Protocol and
42007 automatically determines which version is in use.
42009 The Proxy Protocol header is the first data received on a TCP connection
42010 and is inserted before any TLS-on-connect handshake from the client; Exim
42011 negotiates TLS between Exim-as-server and the remote client, not between
42012 Exim and the proxy server. The Proxy Protocol header must be received
42013 within &%proxy_protocol_timeout%&, which defaults to 3s.
42015 The following expansion variables are usable
42016 (&"internal"& and &"external"& here refer to the interfaces
42019 &'proxy_external_address '& IP of host being proxied or IP of remote interface of proxy
42020 &'proxy_external_port '& Port of host being proxied or Port on remote interface of proxy
42021 &'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
42022 &'proxy_local_port '& Port of proxy server inbound or Port on local interface of proxy
42023 &'proxy_session '& boolean: SMTP connection via proxy
42025 If &$proxy_session$& is set but &$proxy_external_address$& is empty
42026 there was a protocol error.
42027 The variables &$sender_host_address$& and &$sender_host_port$&
42028 will have values for the actual client system, not the proxy.
42030 Since the real connections are all coming from the proxy, and the
42031 per host connection tracking is done before Proxy Protocol is
42032 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
42033 handle all of the parallel volume you expect per inbound proxy.
42034 With the option set so high, you lose the ability
42035 to protect your server from many connections from one IP.
42036 In order to prevent your server from overload, you
42037 need to add a per connection ratelimit to your connect ACL.
42038 A possible solution is:
42040 # Set max number of connections per host
42042 # Or do some kind of IP lookup in a flat file or database
42043 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
42045 defer ratelimit = LIMIT / 5s / per_conn / strict
42046 message = Too many connections from this IP right now
42051 .section "Outbound proxies" SECTproxySOCKS
42052 .cindex proxy outbound
42053 .cindex proxy "client side"
42054 .cindex proxy SOCKS
42055 .cindex SOCKS proxy
42056 Exim has support for sending outbound SMTP via a proxy
42057 using a protocol called SOCKS5 (defined by RFC1928).
42058 The support can be optionally included by defining SUPPORT_SOCKS=yes in
42061 Use of a proxy is enabled by setting the &%socks_proxy%& option
42062 on an smtp transport.
42063 The option value is expanded and should then be a list
42064 (colon-separated by default) of proxy specifiers.
42065 Each proxy specifier is a list
42066 (space-separated by default) where the initial element
42067 is an IP address and any subsequent elements are options.
42069 Options are a string <name>=<value>.
42070 The list of options is in the following table:
42072 &'auth '& authentication method
42073 &'name '& authentication username
42074 &'pass '& authentication password
42076 &'tmo '& connection timeout
42078 &'weight '& selection bias
42081 More details on each of these options follows:
42084 .cindex authentication "to proxy"
42085 .cindex proxy authentication
42086 &%auth%&: Either &"none"& (default) or &"name"&.
42087 Using &"name"& selects username/password authentication per RFC 1929
42088 for access to the proxy.
42089 Default is &"none"&.
42091 &%name%&: sets the username for the &"name"& authentication method.
42094 &%pass%&: sets the password for the &"name"& authentication method.
42097 &%port%&: the TCP port number to use for the connection to the proxy.
42100 &%tmo%&: sets a connection timeout in seconds for this proxy.
42103 &%pri%&: specifies a priority for the proxy within the list,
42104 higher values being tried first.
42105 The default priority is 1.
42107 &%weight%&: specifies a selection bias.
42108 Within a priority set servers are queried in a random fashion,
42109 weighted by this value.
42110 The default value for selection bias is 1.
42113 Proxies from the list are tried according to their priority
42114 and weight settings until one responds. The timeout for the
42115 overall connection applies to the set of proxied attempts.
42117 .section Logging SECTproxyLog
42118 To log the (local) IP of a proxy in the incoming or delivery logline,
42119 add &"+proxy"& to the &%log_selector%& option.
42120 This will add a component tagged with &"PRX="& to the line.
42122 . ////////////////////////////////////////////////////////////////////////////
42123 . ////////////////////////////////////////////////////////////////////////////
42125 .chapter "Internationalisation" "CHAPi18n" &&&
42126 "Internationalisation""
42127 .cindex internationalisation "email address"
42130 .cindex utf8 "mail name handling"
42132 Exim has support for Internationalised mail names.
42133 To include this it must be built with SUPPORT_I18N and the libidn library.
42134 Standards supported are RFCs 2060, 5890, 6530 and 6533.
42136 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
42137 instead of it) then IDNA2008 is supported; this adds an extra library
42138 requirement, upon libidn2.
42140 .section "MTA operations" SECTi18nMTA
42141 .cindex SMTPUTF8 "ESMTP option"
42142 .cindex "ESMTP extensions" SMTPUTF8
42143 The main configuration option &%smtputf8_advertise_hosts%& specifies
42144 a host list. If this matches the sending host and
42145 accept_8bitmime is true (the default) then the ESMTP option
42146 SMTPUTF8 will be advertised.
42148 If the sender specifies the SMTPUTF8 option on a MAIL command
42149 international handling for the message is enabled and
42150 the expansion variable &$message_smtputf8$& will have value TRUE.
42152 The option &%allow_utf8_domains%& is set to true for this
42153 message. All DNS lookups are converted to a-label form
42154 whatever the setting of &%allow_utf8_domains%&
42155 when Exim is built with SUPPORT_I18N.
42157 Both localparts and domain are maintained as the original
42158 UTF-8 form internally; any comparison or regular-expression use will
42159 require appropriate care. Filenames created, eg. by
42160 the appendfile transport, will have UTF-8 names.
42162 HELO names sent by the smtp transport will have any UTF-8
42163 components expanded to a-label form,
42164 and any certificate name checks will be done using the a-label
42167 .cindex log protocol
42168 .cindex SMTPUTF8 logging
42169 .cindex i18n logging
42170 Log lines and Received-by: header lines will acquire a "utf8"
42171 prefix on the protocol element, eg. utf8esmtp.
42173 The following expansion operators can be used:
42175 ${utf8_domain_to_alabel:str}
42176 ${utf8_domain_from_alabel:str}
42177 ${utf8_localpart_to_alabel:str}
42178 ${utf8_localpart_from_alabel:str}
42181 .cindex utf8 "address downconversion"
42182 .cindex i18n "utf8 address downconversion"
42184 may use the following modifier:
42186 control = utf8_downconvert
42187 control = utf8_downconvert/<value>
42189 This sets a flag requiring that envelope addresses are converted to
42190 a-label form before smtp delivery.
42191 This is usually for use in a Message Submission Agent context,
42192 but could be used for any message.
42194 If a value is appended it may be:
42196 &`1 `& mandatory downconversion
42197 &`0 `& no downconversion
42198 &`-1 `& if SMTPUTF8 not supported by destination host
42200 If no value is given, 1 is used.
42202 If mua_wrapper is set, the utf8_downconvert control
42203 is initially set to -1.
42205 The smtp transport has an option &%utf8_downconvert%&.
42206 If set it must expand to one of the three values described above,
42207 or an empty string.
42208 If non-empty it overrides value previously set
42209 (due to mua_wrapper or by an ACL control).
42212 There is no explicit support for VRFY and EXPN.
42213 Configurations supporting these should inspect
42214 &$smtp_command_argument$& for an SMTPUTF8 argument.
42216 There is no support for LMTP on Unix sockets.
42217 Using the "lmtp" protocol option on an smtp transport,
42218 for LMTP over TCP, should work as expected.
42220 There is no support for DSN unitext handling,
42221 and no provision for converting logging from or to UTF-8.
42225 .section "MDA operations" SECTi18nMDA
42226 To aid in constructing names suitable for IMAP folders
42227 the following expansion operator can be used:
42229 ${imapfolder {<string>} {<sep>} {<specials>}}
42232 The string is converted from the charset specified by
42233 the "headers charset" command (in a filter file)
42234 or &%headers_charset%& main configuration option (otherwise),
42236 modified UTF-7 encoding specified by RFC 2060,
42237 with the following exception: All occurrences of <sep>
42238 (which has to be a single character)
42239 are replaced with periods ("."), and all periods and slashes that are not
42240 <sep> and are not in the <specials> string are BASE64 encoded.
42242 The third argument can be omitted, defaulting to an empty string.
42243 The second argument can be omitted, defaulting to "/".
42245 This is the encoding used by Courier for Maildir names on disk, and followed
42246 by many other IMAP servers.
42250 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
42251 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
42252 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
42255 Note that the source charset setting is vital, and also that characters
42256 must be representable in UTF-16.
42259 . ////////////////////////////////////////////////////////////////////////////
42260 . ////////////////////////////////////////////////////////////////////////////
42262 .chapter "Events" "CHAPevents" &&&
42266 The events mechanism in Exim can be used to intercept processing at a number
42267 of points. It was originally invented to give a way to do customised logging
42268 actions (for example, to a database) but can also be used to modify some
42269 processing actions.
42271 Most installations will never need to use Events.
42272 The support can be left out of a build by defining DISABLE_EVENT=yes
42273 in &_Local/Makefile_&.
42275 There are two major classes of events: main and transport.
42276 The main configuration option &%event_action%& controls reception events;
42277 a transport option &%event_action%& controls delivery events.
42279 Both options are a string which is expanded when the event fires.
42280 An example might look like:
42281 .cindex logging custom
42283 event_action = ${if eq {msg:delivery}{$event_name} \
42284 {${lookup pgsql {SELECT * FROM record_Delivery( \
42285 '${quote_pgsql:$sender_address_domain}',\
42286 '${quote_pgsql:${lc:$sender_address_local_part}}', \
42287 '${quote_pgsql:$domain}', \
42288 '${quote_pgsql:${lc:$local_part}}', \
42289 '${quote_pgsql:$host_address}', \
42290 '${quote_pgsql:${lc:$host}}', \
42291 '${quote_pgsql:$message_exim_id}')}} \
42295 Events have names which correspond to the point in process at which they fire.
42296 The name is placed in the variable &$event_name$& and the event action
42297 expansion must check this, as it will be called for every possible event type.
42299 The current list of events is:
42301 &`dane:fail after transport `& per connection
42302 &`msg:complete after main `& per message
42303 &`msg:defer after transport `& per message per delivery try
42304 &`msg:delivery after transport `& per recipient
42305 &`msg:rcpt:host:defer after transport `& per recipient per host
42306 &`msg:rcpt:defer after transport `& per recipient
42307 &`msg:host:defer after transport `& per host per delivery try; host errors
42308 &`msg:fail:delivery after transport `& per recipient
42309 &`msg:fail:internal after main `& per recipient
42310 &`tcp:connect before transport `& per connection
42311 &`tcp:close after transport `& per connection
42312 &`tls:cert before both `& per certificate in verification chain
42313 &`smtp:connect after transport `& per connection
42314 &`smtp:ehlo after transport `& per connection
42316 New event types may be added in future.
42318 The event name is a colon-separated list, defining the type of
42319 event in a tree of possibilities. It may be used as a list
42320 or just matched on as a whole. There will be no spaces in the name.
42322 The second column in the table above describes whether the event fires
42323 before or after the action is associates with. Those which fire before
42324 can be used to affect that action (more on this below).
42326 The third column in the table above says what section of the configuration
42327 should define the event action.
42329 An additional variable, &$event_data$&, is filled with information varying
42330 with the event type:
42332 &`dane:fail `& failure reason
42333 &`msg:defer `& error string
42334 &`msg:delivery `& smtp confirmation message
42335 &`msg:fail:internal `& failure reason
42336 &`msg:fail:delivery `& smtp error message
42337 &`msg:host:defer `& error string
42338 &`msg:rcpt:host:defer `& error string
42339 &`msg:rcpt:defer `& error string
42340 &`tls:cert `& verification chain depth
42341 &`smtp:connect `& smtp banner
42342 &`smtp:ehlo `& smtp ehlo response
42345 The :defer events populate one extra variable: &$event_defer_errno$&.
42347 For complex operations an ACL expansion can be used in &%event_action%&
42348 however due to the multiple contexts that Exim operates in during
42349 the course of its processing:
42351 variables set in transport events will not be visible outside that
42354 acl_m variables in a server context are lost on a new connection,
42355 and after smtp helo/ehlo/mail/starttls/rset commands
42357 Using an ACL expansion with the logwrite modifier can be
42358 a useful way of writing to the main log.
42360 The expansion of the event_action option should normally
42361 return an empty string. Should it return anything else the
42362 following will be forced:
42364 &`tcp:connect `& do not connect
42365 &`tls:cert `& refuse verification
42366 &`smtp:connect `& close connection
42368 All other message types ignore the result string, and
42369 no other use is made of it.
42371 For a tcp:connect event, if the connection is being made to a proxy
42372 then the address and port variables will be that of the proxy and not
42375 For tls:cert events, if GnuTLS is in use this will trigger only per
42376 chain element received on the connection.
42377 For OpenSSL it will trigger for every chain element including those
42380 . ////////////////////////////////////////////////////////////////////////////
42381 . ////////////////////////////////////////////////////////////////////////////
42383 .chapter "Adding new drivers or lookup types" "CHID13" &&&
42384 "Adding drivers or lookups"
42385 .cindex "adding drivers"
42386 .cindex "new drivers, adding"
42387 .cindex "drivers" "adding new"
42388 The following actions have to be taken in order to add a new router, transport,
42389 authenticator, or lookup type to Exim:
42392 Choose a name for the driver or lookup type that does not conflict with any
42393 existing name; I will use &"newdriver"& in what follows.
42395 Add to &_src/EDITME_& the line:
42397 <&'type'&>&`_NEWDRIVER=yes`&
42399 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
42400 code is not to be included in the binary by default, comment this line out. You
42401 should also add any relevant comments about the driver or lookup type.
42403 Add to &_src/config.h.defaults_& the line:
42405 #define <type>_NEWDRIVER
42408 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
42409 and create a table entry as is done for all the other drivers and lookup types.
42411 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
42412 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
42413 Add your &`NEWDRIVER`& to that list.
42414 As long as the dynamic module would be named &_newdriver.so_&, you can use the
42415 simple form that most lookups have.
42417 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
42418 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
42419 driver or lookup type and add it to the definition of OBJ.
42421 Edit &_OS/Makefile-Base_& adding a &_.o_& file for the predefined-macros, to the
42422 definition of OBJ_MACRO. Add a set of line to do the compile also.
42424 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
42427 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
42428 as for other drivers and lookups.
42431 Then all you need to do is write the code! A good way to start is to make a
42432 proforma by copying an existing module of the same type, globally changing all
42433 occurrences of the name, and cutting out most of the code. Note that any
42434 options you create must be listed in alphabetical order, because the tables are
42435 searched using a binary chop procedure.
42437 There is a &_README_& file in each of the sub-directories of &_src_& describing
42438 the interface that is expected.
42443 . ////////////////////////////////////////////////////////////////////////////
42444 . ////////////////////////////////////////////////////////////////////////////
42446 . /////////////////////////////////////////////////////////////////////////////
42447 . These lines are processing instructions for the Simple DocBook Processor that
42448 . Philip Hazel has developed as a less cumbersome way of making PostScript and
42449 . PDFs than using xmlto and fop. They will be ignored by all other XML
42451 . /////////////////////////////////////////////////////////////////////////////
42456 foot_right_recto="&chaptertitle;"
42457 foot_right_verso="&chaptertitle;"
42461 .makeindex "Options index" "option"
42462 .makeindex "Variables index" "variable"
42463 .makeindex "Concept index" "concept"
42466 . /////////////////////////////////////////////////////////////////////////////
42467 . /////////////////////////////////////////////////////////////////////////////