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).
1398 If the &%domains%& option is set, the domain of the address must be in the set
1399 of domains that it defines.
1401 .vindex "&$local_part_prefix$&"
1402 .vindex "&$local_part_prefix_v$&"
1403 .vindex "&$local_part$&"
1404 .vindex "&$local_part_suffix$&"
1405 .vindex "&$local_part_suffix_v$&"
1406 .cindex affix "router precondition"
1407 If the &%local_parts%& option is set, the local part of the address must be in
1408 the set of local parts that it defines. If &%local_part_prefix%& or
1409 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1410 part before this check. If you want to do precondition tests on local parts
1411 that include affixes, you can do so by using a &%condition%& option (see below)
1412 that uses the variables &$local_part$&, &$local_part_prefix$&,
1413 &$local_part_prefix_v$&, &$local_part_suffix$&
1414 and &$local_part_suffix_v$& as necessary.
1416 .vindex "&$local_user_uid$&"
1417 .vindex "&$local_user_gid$&"
1419 If the &%check_local_user%& option is set, the local part must be the name of
1420 an account on the local host. If this check succeeds, the uid and gid of the
1421 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1422 user's home directory is placed in &$home$&; these values can be used in the
1423 remaining preconditions.
1425 If the &%router_home_directory%& option is set, it is expanded at this point,
1426 because it overrides the value of &$home$&. If this expansion were left till
1427 later, the value of &$home$& as set by &%check_local_user%& would be used in
1428 subsequent tests. Having two different values of &$home$& in the same router
1429 could lead to confusion.
1431 If the &%senders%& option is set, the envelope sender address must be in the
1432 set of addresses that it defines.
1434 If the &%require_files%& option is set, the existence or non-existence of
1435 specified files is tested.
1437 .cindex "customizing" "precondition"
1438 If the &%condition%& option is set, it is evaluated and tested. This option
1439 uses an expanded string to allow you to set up your own custom preconditions.
1440 Expanded strings are described in chapter &<<CHAPexpand>>&.
1444 Note that &%require_files%& comes near the end of the list, so you cannot use
1445 it to check for the existence of a file in which to lookup up a domain, local
1446 part, or sender. However, as these options are all expanded, you can use the
1447 &%exists%& expansion condition to make such tests within each condition. The
1448 &%require_files%& option is intended for checking files that the router may be
1449 going to use internally, or which are needed by a specific transport (for
1450 example, &_.procmailrc_&).
1454 .section "Delivery in detail" "SECID18"
1455 .cindex "delivery" "in detail"
1456 When a message is to be delivered, the sequence of events is as follows:
1459 If a system-wide filter file is specified, the message is passed to it. The
1460 filter may add recipients to the message, replace the recipients, discard the
1461 message, cause a new message to be generated, or cause the message delivery to
1462 fail. The format of the system filter file is the same as for Exim user filter
1463 files, described in the separate document entitled &'Exim's interfaces to mail
1465 .cindex "Sieve filter" "not available for system filter"
1466 (&*Note*&: Sieve cannot be used for system filter files.)
1468 Some additional features are available in system filters &-- see chapter
1469 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1470 filter only once per delivery attempt, however many recipients it has. However,
1471 if there are several delivery attempts because one or more addresses could not
1472 be immediately delivered, the system filter is run each time. The filter
1473 condition &%first_delivery%& can be used to detect the first run of the system
1476 Each recipient address is offered to each configured router, in turn, subject to
1477 its preconditions, until one is able to handle it. If no router can handle the
1478 address, that is, if they all decline, the address is failed. Because routers
1479 can be targeted at particular domains, several locally handled domains can be
1480 processed entirely independently of each other.
1482 .cindex "routing" "loops in"
1483 .cindex "loop" "while routing"
1484 A router that accepts an address may assign it to a local or a remote
1485 transport. However, the transport is not run at this time. Instead, the address
1486 is placed on a list for the particular transport, which will be run later.
1487 Alternatively, the router may generate one or more new addresses (typically
1488 from alias, forward, or filter files). New addresses are fed back into this
1489 process from the top, but in order to avoid loops, a router ignores any address
1490 which has an identically-named ancestor that was processed by itself.
1492 When all the routing has been done, addresses that have been successfully
1493 handled are passed to their assigned transports. When local transports are
1494 doing real local deliveries, they handle only one address at a time, but if a
1495 local transport is being used as a pseudo-remote transport (for example, to
1496 collect batched SMTP messages for transmission by some other means) multiple
1497 addresses can be handled. Remote transports can always handle more than one
1498 address at a time, but can be configured not to do so, or to restrict multiple
1499 addresses to the same domain.
1501 Each local delivery to a file or a pipe runs in a separate process under a
1502 non-privileged uid, and these deliveries are run one at a time. Remote
1503 deliveries also run in separate processes, normally under a uid that is private
1504 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1505 run in parallel. The maximum number of simultaneous remote deliveries for any
1506 one message is set by the &%remote_max_parallel%& option.
1507 The order in which deliveries are done is not defined, except that all local
1508 deliveries happen before any remote deliveries.
1510 .cindex "queue runner"
1511 When it encounters a local delivery during a queue run, Exim checks its retry
1512 database to see if there has been a previous temporary delivery failure for the
1513 address before running the local transport. If there was a previous failure,
1514 Exim does not attempt a new delivery until the retry time for the address is
1515 reached. However, this happens only for delivery attempts that are part of a
1516 queue run. Local deliveries are always attempted when delivery immediately
1517 follows message reception, even if retry times are set for them. This makes for
1518 better behaviour if one particular message is causing problems (for example,
1519 causing quota overflow, or provoking an error in a filter file).
1521 .cindex "delivery" "retry in remote transports"
1522 Remote transports do their own retry handling, since an address may be
1523 deliverable to one of a number of hosts, each of which may have a different
1524 retry time. If there have been previous temporary failures and no host has
1525 reached its retry time, no delivery is attempted, whether in a queue run or
1526 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1528 If there were any permanent errors, a bounce message is returned to an
1529 appropriate address (the sender in the common case), with details of the error
1530 for each failing address. Exim can be configured to send copies of bounce
1531 messages to other addresses.
1533 .cindex "delivery" "deferral"
1534 If one or more addresses suffered a temporary failure, the message is left on
1535 the queue, to be tried again later. Delivery of these addresses is said to be
1538 When all the recipient addresses have either been delivered or bounced,
1539 handling of the message is complete. The spool files and message log are
1540 deleted, though the message log can optionally be preserved if required.
1546 .section "Retry mechanism" "SECID19"
1547 .cindex "delivery" "retry mechanism"
1548 .cindex "retry" "description of mechanism"
1549 .cindex "queue runner"
1550 Exim's mechanism for retrying messages that fail to get delivered at the first
1551 attempt is the queue runner process. You must either run an Exim daemon that
1552 uses the &%-q%& option with a time interval to start queue runners at regular
1553 intervals or use some other means (such as &'cron'&) to start them. If you do
1554 not arrange for queue runners to be run, messages that fail temporarily at the
1555 first attempt will remain in your queue forever. A queue runner process works
1556 its way through the queue, one message at a time, trying each delivery that has
1557 passed its retry time.
1558 You can run several queue runners at once.
1560 Exim uses a set of configured rules to determine when next to retry the failing
1561 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1562 should give up trying to deliver to the address, at which point it generates a
1563 bounce message. If no retry rules are set for a particular host, address, and
1564 error combination, no retries are attempted, and temporary errors are treated
1569 .section "Temporary delivery failure" "SECID20"
1570 .cindex "delivery" "temporary failure"
1571 There are many reasons why a message may not be immediately deliverable to a
1572 particular address. Failure to connect to a remote machine (because it, or the
1573 connection to it, is down) is one of the most common. Temporary failures may be
1574 detected during routing as well as during the transport stage of delivery.
1575 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1576 is on a file system where the user is over quota. Exim can be configured to
1577 impose its own quotas on local mailboxes; where system quotas are set they will
1580 If a host is unreachable for a period of time, a number of messages may be
1581 waiting for it by the time it recovers, and sending them in a single SMTP
1582 connection is clearly beneficial. Whenever a delivery to a remote host is
1584 .cindex "hints database" "deferred deliveries"
1585 Exim makes a note in its hints database, and whenever a successful
1586 SMTP delivery has happened, it looks to see if any other messages are waiting
1587 for the same host. If any are found, they are sent over the same SMTP
1588 connection, subject to a configuration limit as to the maximum number in any
1593 .section "Permanent delivery failure" "SECID21"
1594 .cindex "delivery" "permanent failure"
1595 .cindex "bounce message" "when generated"
1596 When a message cannot be delivered to some or all of its intended recipients, a
1597 bounce message is generated. Temporary delivery failures turn into permanent
1598 errors when their timeout expires. All the addresses that fail in a given
1599 delivery attempt are listed in a single message. If the original message has
1600 many recipients, it is possible for some addresses to fail in one delivery
1601 attempt and others to fail subsequently, giving rise to more than one bounce
1602 message. The wording of bounce messages can be customized by the administrator.
1603 See chapter &<<CHAPemsgcust>>& for details.
1605 .cindex "&'X-Failed-Recipients:'& header line"
1606 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1607 failed addresses, for the benefit of programs that try to analyse such messages
1610 .cindex "bounce message" "recipient of"
1611 A bounce message is normally sent to the sender of the original message, as
1612 obtained from the message's envelope. For incoming SMTP messages, this is the
1613 address given in the MAIL command. However, when an address is expanded via a
1614 forward or alias file, an alternative address can be specified for delivery
1615 failures of the generated addresses. For a mailing list expansion (see section
1616 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1621 .section "Failures to deliver bounce messages" "SECID22"
1622 .cindex "bounce message" "failure to deliver"
1623 If a bounce message (either locally generated or received from a remote host)
1624 itself suffers a permanent delivery failure, the message is left in the queue,
1625 but it is frozen, awaiting the attention of an administrator. There are options
1626 that can be used to make Exim discard such failed messages, or to keep them
1627 for only a short time (see &%timeout_frozen_after%& and
1628 &%ignore_bounce_errors_after%&).
1634 . ////////////////////////////////////////////////////////////////////////////
1635 . ////////////////////////////////////////////////////////////////////////////
1637 .chapter "Building and installing Exim" "CHID3"
1638 .scindex IIDbuex "building Exim"
1640 .section "Unpacking" "SECID23"
1641 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1642 creates a directory with the name of the current release (for example,
1643 &_exim-&version()_&) into which the following files are placed:
1646 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1647 .irow &_CHANGES_& "contains a reference to where changes are &&&
1649 .irow &_LICENCE_& "the GNU General Public Licence"
1650 .irow &_Makefile_& "top-level make file"
1651 .irow &_NOTICE_& "conditions for the use of Exim"
1652 .irow &_README_& "list of files, directories and simple build &&&
1656 Other files whose names begin with &_README_& may also be present. The
1657 following subdirectories are created:
1660 .irow &_Local_& "an empty directory for local configuration files"
1661 .irow &_OS_& "OS-specific files"
1662 .irow &_doc_& "documentation files"
1663 .irow &_exim_monitor_& "source files for the Exim monitor"
1664 .irow &_scripts_& "scripts used in the build process"
1665 .irow &_src_& "remaining source files"
1666 .irow &_util_& "independent utilities"
1669 The main utility programs are contained in the &_src_& directory and are built
1670 with the Exim binary. The &_util_& directory contains a few optional scripts
1671 that may be useful to some sites.
1674 .section "Multiple machine architectures and operating systems" "SECID24"
1675 .cindex "building Exim" "multiple OS/architectures"
1676 The building process for Exim is arranged to make it easy to build binaries for
1677 a number of different architectures and operating systems from the same set of
1678 source files. Compilation does not take place in the &_src_& directory.
1679 Instead, a &'build directory'& is created for each architecture and operating
1681 .cindex "symbolic link" "to build directory"
1682 Symbolic links to the sources are installed in this directory, which is where
1683 the actual building takes place. In most cases, Exim can discover the machine
1684 architecture and operating system for itself, but the defaults can be
1685 overridden if necessary.
1686 .cindex compiler requirements
1687 .cindex compiler version
1688 A C99-capable compiler will be required for the build.
1691 .section "PCRE library" "SECTpcre"
1692 .cindex "PCRE library"
1693 Exim no longer has an embedded PCRE library as the vast majority of
1694 modern systems include PCRE as a system library, although you may need to
1695 install the PCRE package or the PCRE development package for your operating
1696 system. If your system has a normal PCRE installation the Exim build
1697 process will need no further configuration. If the library or the
1698 headers are in an unusual location you will need to either set the PCRE_LIBS
1699 and INCLUDE directives appropriately,
1700 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1701 If your operating system has no
1702 PCRE support then you will need to obtain and build the current PCRE
1703 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1704 More information on PCRE is available at &url(https://www.pcre.org/).
1706 .section "DBM libraries" "SECTdb"
1707 .cindex "DBM libraries" "discussion of"
1708 .cindex "hints database" "DBM files used for"
1709 Even if you do not use any DBM files in your configuration, Exim still needs a
1710 DBM library in order to operate, because it uses indexed files for its hints
1711 databases. Unfortunately, there are a number of DBM libraries in existence, and
1712 different operating systems often have different ones installed.
1714 .cindex "Solaris" "DBM library for"
1715 .cindex "IRIX, DBM library for"
1716 .cindex "BSD, DBM library for"
1717 .cindex "Linux, DBM library for"
1718 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1719 Linux distribution, the DBM configuration should happen automatically, and you
1720 may be able to ignore this section. Otherwise, you may have to learn more than
1721 you would like about DBM libraries from what follows.
1723 .cindex "&'ndbm'& DBM library"
1724 Licensed versions of Unix normally contain a library of DBM functions operating
1725 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1726 versions of Unix seem to vary in what they contain as standard. In particular,
1727 some early versions of Linux have no default DBM library, and different
1728 distributors have chosen to bundle different libraries with their packaged
1729 versions. However, the more recent releases seem to have standardized on the
1730 Berkeley DB library.
1732 Different DBM libraries have different conventions for naming the files they
1733 use. When a program opens a file called &_dbmfile_&, there are several
1737 A traditional &'ndbm'& implementation, such as that supplied as part of
1738 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1740 .cindex "&'gdbm'& DBM library"
1741 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1742 compatibility interface it makes two different hard links to it with names
1743 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1744 filename is used unmodified.
1746 .cindex "Berkeley DB library"
1747 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1748 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1749 programmer exactly the same as the traditional &'ndbm'& implementation.
1751 If the Berkeley package is used in its native mode, it operates on a single
1752 file called &_dbmfile_&; the programmer's interface is somewhat different to
1753 the traditional &'ndbm'& interface.
1755 To complicate things further, there are several very different versions of the
1756 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1757 2.&'x'& and 3.&'x'& were current for a while, but the latest versions when Exim last revamped support were numbered 4.&'x'&.
1758 Maintenance of some of the earlier releases has ceased. All versions of
1759 Berkeley DB could be obtained from
1760 &url(http://www.sleepycat.com/), which is now a redirect to their new owner's
1761 page with far newer versions listed.
1762 It is probably wise to plan to move your storage configurations away from
1763 Berkeley DB format, as today there are smaller and simpler alternatives more
1764 suited to Exim's usage model.
1766 .cindex "&'tdb'& DBM library"
1767 Yet another DBM library, called &'tdb'&, is available from
1768 &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also
1769 operates on a single file.
1773 .cindex "DBM libraries" "configuration for building"
1774 Exim and its utilities can be compiled to use any of these interfaces. In order
1775 to use any version of the Berkeley DB package in native mode, you must set
1776 USE_DB in an appropriate configuration file (typically
1777 &_Local/Makefile_&). For example:
1781 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1782 error is diagnosed if you set more than one of these.
1784 At the lowest level, the build-time configuration sets none of these options,
1785 thereby assuming an interface of type (1). However, some operating system
1786 configuration files (for example, those for the BSD operating systems and
1787 Linux) assume type (4) by setting USE_DB as their default, and the
1788 configuration files for Cygwin set USE_GDBM. Anything you set in
1789 &_Local/Makefile_&, however, overrides these system defaults.
1791 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1792 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1793 in one of these lines:
1798 Settings like that will work if the DBM library is installed in the standard
1799 place. Sometimes it is not, and the library's header file may also not be in
1800 the default path. You may need to set INCLUDE to specify where the header
1801 file is, and to specify the path to the library more fully in DBMLIB, as in
1804 INCLUDE=-I/usr/local/include/db-4.1
1805 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1807 There is further detailed discussion about the various DBM libraries in the
1808 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1812 .section "Pre-building configuration" "SECID25"
1813 .cindex "building Exim" "pre-building configuration"
1814 .cindex "configuration for building Exim"
1815 .cindex "&_Local/Makefile_&"
1816 .cindex "&_src/EDITME_&"
1817 Before building Exim, a local configuration file that specifies options
1818 independent of any operating system has to be created with the name
1819 &_Local/Makefile_&. A template for this file is supplied as the file
1820 &_src/EDITME_&, and it contains full descriptions of all the option settings
1821 therein. These descriptions are therefore not repeated here. If you are
1822 building Exim for the first time, the simplest thing to do is to copy
1823 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1825 There are three settings that you must supply, because Exim will not build
1826 without them. They are the location of the runtime configuration file
1827 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1828 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1829 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1830 a colon-separated list of filenames; Exim uses the first of them that exists.
1832 There are a few other parameters that can be specified either at build time or
1833 at runtime, to enable the same binary to be used on a number of different
1834 machines. However, if the locations of Exim's spool directory and log file
1835 directory (if not within the spool directory) are fixed, it is recommended that
1836 you specify them in &_Local/Makefile_& instead of at runtime, so that errors
1837 detected early in Exim's execution (such as a malformed configuration file) can
1840 .cindex "content scanning" "specifying at build time"
1841 Exim's interfaces for calling virus and spam scanning software directly from
1842 access control lists are not compiled by default. If you want to include these
1843 facilities, you need to set
1845 WITH_CONTENT_SCAN=yes
1847 in your &_Local/Makefile_&. For details of the facilities themselves, see
1848 chapter &<<CHAPexiscan>>&.
1851 .cindex "&_Local/eximon.conf_&"
1852 .cindex "&_exim_monitor/EDITME_&"
1853 If you are going to build the Exim monitor, a similar configuration process is
1854 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1855 your installation and saved under the name &_Local/eximon.conf_&. If you are
1856 happy with the default settings described in &_exim_monitor/EDITME_&,
1857 &_Local/eximon.conf_& can be empty, but it must exist.
1859 This is all the configuration that is needed in straightforward cases for known
1860 operating systems. However, the building process is set up so that it is easy
1861 to override options that are set by default or by operating-system-specific
1862 configuration files, for example, to change the C compiler, which
1863 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1868 .section "Support for iconv()" "SECID26"
1869 .cindex "&[iconv()]& support"
1871 The contents of header lines in messages may be encoded according to the rules
1872 described RFC 2047. This makes it possible to transmit characters that are not
1873 in the ASCII character set, and to label them as being in a particular
1874 character set. When Exim is inspecting header lines by means of the &%$h_%&
1875 mechanism, it decodes them, and translates them into a specified character set
1876 (default is set at build time). The translation is possible only if the operating system
1877 supports the &[iconv()]& function.
1879 However, some of the operating systems that supply &[iconv()]& do not support
1880 very many conversions. The GNU &%libiconv%& library (available from
1881 &url(https://www.gnu.org/software/libiconv/)) can be installed on such
1882 systems to remedy this deficiency, as well as on systems that do not supply
1883 &[iconv()]& at all. After installing &%libiconv%&, you should add
1887 to your &_Local/Makefile_& and rebuild Exim.
1891 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1892 .cindex "TLS" "including support for TLS"
1893 .cindex "encryption" "including support for"
1894 .cindex "OpenSSL" "building Exim with"
1895 .cindex "GnuTLS" "building Exim with"
1896 Exim is usually built to support encrypted SMTP connections, using the STARTTLS
1897 command as per RFC 2487. It can also support clients that expect to
1898 start a TLS session immediately on connection to a non-standard port (see the
1899 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1902 If you want to build Exim with TLS support, you must first install either the
1903 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1906 If you do not want TLS support you should set
1910 in &_Local/Makefile_&.
1912 If OpenSSL is installed, you should set
1915 TLS_LIBS=-lssl -lcrypto
1917 in &_Local/Makefile_&. You may also need to specify the locations of the
1918 OpenSSL library and include files. For example:
1921 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1922 TLS_INCLUDE=-I/usr/local/openssl/include/
1924 .cindex "pkg-config" "OpenSSL"
1925 If you have &'pkg-config'& available, then instead you can just use:
1928 USE_OPENSSL_PC=openssl
1930 .cindex "USE_GNUTLS"
1931 If GnuTLS is installed, you should set
1934 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1936 in &_Local/Makefile_&, and again you may need to specify the locations of the
1937 library and include files. For example:
1940 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1941 TLS_INCLUDE=-I/usr/gnu/include
1943 .cindex "pkg-config" "GnuTLS"
1944 If you have &'pkg-config'& available, then instead you can just use:
1947 USE_GNUTLS_PC=gnutls
1950 You do not need to set TLS_INCLUDE if the relevant directory is already
1951 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1952 given in chapter &<<CHAPTLS>>&.
1957 .section "Use of tcpwrappers" "SECID27"
1959 .cindex "tcpwrappers, building Exim to support"
1960 .cindex "USE_TCP_WRAPPERS"
1961 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1962 .cindex "tcp_wrappers_daemon_name"
1963 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1964 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1965 alternative to Exim's own checking facilities for installations that are
1966 already making use of &'tcpwrappers'& for other purposes. To do this, you
1967 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1968 &_tcpd.h_& to be available at compile time, and also ensure that the library
1969 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1970 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1973 USE_TCP_WRAPPERS=yes
1974 CFLAGS=-O -I/usr/local/include
1975 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1977 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1978 files is &"exim"&. For example, the line
1980 exim : LOCAL 192.168.1. .friendly.domain.example
1982 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1983 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1984 All other connections are denied. The daemon name used by &'tcpwrappers'&
1985 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1986 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1987 configure file. Consult the &'tcpwrappers'& documentation for
1991 .section "Including support for IPv6" "SECID28"
1992 .cindex "IPv6" "including support for"
1993 Exim contains code for use on systems that have IPv6 support. Setting
1994 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1995 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1996 where the IPv6 support is not fully integrated into the normal include and
1999 Two different types of DNS record for handling IPv6 addresses have been
2000 defined. AAAA records (analogous to A records for IPv4) are in use, and are
2001 currently seen as the mainstream. Another record type called A6 was proposed
2002 as better than AAAA because it had more flexibility. However, it was felt to be
2003 over-complex, and its status was reduced to &"experimental"&.
2005 have a compile option for including A6 record support but this has now been
2010 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
2011 .cindex "lookup modules"
2012 .cindex "dynamic modules"
2013 .cindex ".so building"
2014 On some platforms, Exim supports not compiling all lookup types directly into
2015 the main binary, instead putting some into external modules which can be loaded
2017 This permits packagers to build Exim with support for lookups with extensive
2018 library dependencies without requiring all users to install all of those
2020 Most, but not all, lookup types can be built this way.
2022 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2023 installed; Exim will only load modules from that directory, as a security
2024 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2025 for your OS; see &_OS/Makefile-Linux_& for an example.
2026 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2027 see &_src/EDITME_& for details.
2029 Then, for each module to be loaded dynamically, define the relevant
2030 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2031 For example, this will build in lsearch but load sqlite and mysql support
2040 .section "The building process" "SECID29"
2041 .cindex "build directory"
2042 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2043 created, run &'make'& at the top level. It determines the architecture and
2044 operating system types, and creates a build directory if one does not exist.
2045 For example, on a Sun system running Solaris 8, the directory
2046 &_build-SunOS5-5.8-sparc_& is created.
2047 .cindex "symbolic link" "to source files"
2048 Symbolic links to relevant source files are installed in the build directory.
2050 If this is the first time &'make'& has been run, it calls a script that builds
2051 a make file inside the build directory, using the configuration files from the
2052 &_Local_& directory. The new make file is then passed to another instance of
2053 &'make'&. This does the real work, building a number of utility scripts, and
2054 then compiling and linking the binaries for the Exim monitor (if configured), a
2055 number of utility programs, and finally Exim itself. The command &`make
2056 makefile`& can be used to force a rebuild of the make file in the build
2057 directory, should this ever be necessary.
2059 If you have problems building Exim, check for any comments there may be in the
2060 &_README_& file concerning your operating system, and also take a look at the
2061 FAQ, where some common problems are covered.
2065 .section 'Output from &"make"&' "SECID283"
2066 The output produced by the &'make'& process for compile lines is often very
2067 unreadable, because these lines can be very long. For this reason, the normal
2068 output is suppressed by default, and instead output similar to that which
2069 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2070 each module that is being compiled or linked. However, it is still possible to
2071 get the full output, by calling &'make'& like this:
2075 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2076 command reflection in &'make'&. When you ask for the full output, it is
2077 given in addition to the short output.
2081 .section "Overriding build-time options for Exim" "SECToverride"
2082 .cindex "build-time options, overriding"
2083 The main make file that is created at the beginning of the building process
2084 consists of the concatenation of a number of files which set configuration
2085 values, followed by a fixed set of &'make'& instructions. If a value is set
2086 more than once, the last setting overrides any previous ones. This provides a
2087 convenient way of overriding defaults. The files that are concatenated are, in
2090 &_OS/Makefile-Default_&
2091 &_OS/Makefile-_&<&'ostype'&>
2093 &_Local/Makefile-_&<&'ostype'&>
2094 &_Local/Makefile-_&<&'archtype'&>
2095 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2096 &_OS/Makefile-Base_&
2098 .cindex "&_Local/Makefile_&"
2099 .cindex "building Exim" "operating system type"
2100 .cindex "building Exim" "architecture type"
2101 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2102 architecture type. &_Local/Makefile_& is required to exist, and the building
2103 process fails if it is absent. The other three &_Local_& files are optional,
2104 and are often not needed.
2106 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2107 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2108 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2109 values are used, thereby providing a means of forcing particular settings.
2110 Otherwise, the scripts try to get values from the &%uname%& command. If this
2111 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2112 of &'ad hoc'& transformations are then applied, to produce the standard names
2113 that Exim expects. You can run these scripts directly from the shell in order
2114 to find out what values are being used on your system.
2117 &_OS/Makefile-Default_& contains comments about the variables that are set
2118 therein. Some (but not all) are mentioned below. If there is something that
2119 needs changing, review the contents of this file and the contents of the make
2120 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2124 .cindex "building Exim" "overriding default settings"
2125 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2126 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2127 need to change the original files. Instead, you should make the changes by
2128 putting the new values in an appropriate &_Local_& file. For example,
2129 .cindex "Tru64-Unix build-time settings"
2130 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2131 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2132 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2133 called with the option &%-std1%&, to make it recognize some of the features of
2134 Standard C that Exim uses. (Most other compilers recognize Standard C by
2135 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2136 containing the lines
2141 If you are compiling for just one operating system, it may be easier to put
2142 these lines directly into &_Local/Makefile_&.
2144 Keeping all your local configuration settings separate from the distributed
2145 files makes it easy to transfer them to new versions of Exim simply by copying
2146 the contents of the &_Local_& directory.
2149 .cindex "NIS lookup type" "including support for"
2150 .cindex "NIS+ lookup type" "including support for"
2151 .cindex "LDAP" "including support for"
2152 .cindex "lookup" "inclusion in binary"
2153 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2154 lookup, but not all systems have these components installed, so the default is
2155 not to include the relevant code in the binary. All the different kinds of file
2156 and database lookup that Exim supports are implemented as separate code modules
2157 which are included only if the relevant compile-time options are set. In the
2158 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2164 and similar settings apply to the other lookup types. They are all listed in
2165 &_src/EDITME_&. In many cases the relevant include files and interface
2166 libraries need to be installed before compiling Exim.
2167 .cindex "cdb" "including support for"
2168 However, there are some optional lookup types (such as cdb) for which
2169 the code is entirely contained within Exim, and no external include
2170 files or libraries are required. When a lookup type is not included in the
2171 binary, attempts to configure Exim to use it cause runtime configuration
2174 .cindex "pkg-config" "lookups"
2175 .cindex "pkg-config" "authenticators"
2176 Many systems now use a tool called &'pkg-config'& to encapsulate information
2177 about how to compile against a library; Exim has some initial support for
2178 being able to use pkg-config for lookups and authenticators. For any given
2179 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2180 variable with the &`_PC`& suffix in the name and assign as the value the
2181 name of the package to be queried. The results of querying via the
2182 &'pkg-config'& command will be added to the appropriate Makefile variables
2183 with &`+=`& directives, so your version of &'make'& will need to support that
2184 syntax. For instance:
2187 LOOKUP_SQLITE_PC=sqlite3
2189 AUTH_GSASL_PC=libgsasl
2190 AUTH_HEIMDAL_GSSAPI=yes
2191 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2194 .cindex "Perl" "including support for"
2195 Exim can be linked with an embedded Perl interpreter, allowing Perl
2196 subroutines to be called during string expansion. To enable this facility,
2200 must be defined in &_Local/Makefile_&. Details of this facility are given in
2201 chapter &<<CHAPperl>>&.
2203 .cindex "X11 libraries, location of"
2204 The location of the X11 libraries is something that varies a lot between
2205 operating systems, and there may be different versions of X11 to cope
2206 with. Exim itself makes no use of X11, but if you are compiling the Exim
2207 monitor, the X11 libraries must be available.
2208 The following three variables are set in &_OS/Makefile-Default_&:
2211 XINCLUDE=-I$(X11)/include
2212 XLFLAGS=-L$(X11)/lib
2214 These are overridden in some of the operating-system configuration files. For
2215 example, in &_OS/Makefile-SunOS5_& there is
2218 XINCLUDE=-I$(X11)/include
2219 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2221 If you need to override the default setting for your operating system, place a
2222 definition of all three of these variables into your
2223 &_Local/Makefile-<ostype>_& file.
2226 If you need to add any extra libraries to the link steps, these can be put in a
2227 variable called EXTRALIBS, which appears in all the link commands, but by
2228 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2229 command for linking the main Exim binary, and not for any associated utilities.
2231 .cindex "DBM libraries" "configuration for building"
2232 There is also DBMLIB, which appears in the link commands for binaries that
2233 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2234 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2235 binary, and which can be used, for example, to include additional X11
2238 .cindex "configuration file" "editing"
2239 The make file copes with rebuilding Exim correctly if any of the configuration
2240 files are edited. However, if an optional configuration file is deleted, it is
2241 necessary to touch the associated non-optional file (that is,
2242 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2245 .section "OS-specific header files" "SECID30"
2247 .cindex "building Exim" "OS-specific C header files"
2248 The &_OS_& directory contains a number of files with names of the form
2249 &_os.h-<ostype>_&. These are system-specific C header files that should not
2250 normally need to be changed. There is a list of macro settings that are
2251 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2252 are porting Exim to a new operating system.
2256 .section "Overriding build-time options for the monitor" "SECID31"
2257 .cindex "building Eximon"
2258 A similar process is used for overriding things when building the Exim monitor,
2259 where the files that are involved are
2261 &_OS/eximon.conf-Default_&
2262 &_OS/eximon.conf-_&<&'ostype'&>
2263 &_Local/eximon.conf_&
2264 &_Local/eximon.conf-_&<&'ostype'&>
2265 &_Local/eximon.conf-_&<&'archtype'&>
2266 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2268 .cindex "&_Local/eximon.conf_&"
2269 As with Exim itself, the final three files need not exist, and in this case the
2270 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2271 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2272 variables of the same name, preceded by EXIMON_. For example, setting
2273 EXIMON_LOG_DEPTH in the environment overrides the value of
2274 LOG_DEPTH at runtime.
2278 .section "Installing Exim binaries and scripts" "SECID32"
2279 .cindex "installing Exim"
2280 .cindex "BIN_DIRECTORY"
2281 The command &`make install`& runs the &(exim_install)& script with no
2282 arguments. The script copies binaries and utility scripts into the directory
2283 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2284 .cindex "setuid" "installing Exim with"
2285 The install script copies files only if they are newer than the files they are
2286 going to replace. The Exim binary is required to be owned by root and have the
2287 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2288 install`& as root so that it can set up the Exim binary in this way. However, in
2289 some special situations (for example, if a host is doing no local deliveries)
2290 it may be possible to run Exim without making the binary setuid root (see
2291 chapter &<<CHAPsecurity>>& for details).
2293 .cindex "CONFIGURE_FILE"
2294 Exim's runtime configuration file is named by the CONFIGURE_FILE setting
2295 in &_Local/Makefile_&. If this names a single file, and the file does not
2296 exist, the default configuration file &_src/configure.default_& is copied there
2297 by the installation script. If a runtime configuration file already exists, it
2298 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2299 alternative files, no default is installed.
2301 .cindex "system aliases file"
2302 .cindex "&_/etc/aliases_&"
2303 One change is made to the default configuration file when it is installed: the
2304 default configuration contains a router that references a system aliases file.
2305 The path to this file is set to the value specified by
2306 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2307 If the system aliases file does not exist, the installation script creates it,
2308 and outputs a comment to the user.
2310 The created file contains no aliases, but it does contain comments about the
2311 aliases a site should normally have. Mail aliases have traditionally been
2312 kept in &_/etc/aliases_&. However, some operating systems are now using
2313 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2314 Exim's configuration if necessary.
2316 The default configuration uses the local host's name as the only local domain,
2317 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2318 running as the local user. System aliases and &_.forward_& files in users' home
2319 directories are supported, but no NIS or NIS+ support is configured. Domains
2320 other than the name of the local host are routed using the DNS, with delivery
2323 It is possible to install Exim for special purposes (such as building a binary
2324 distribution) in a private part of the file system. You can do this by a
2327 make DESTDIR=/some/directory/ install
2329 This has the effect of pre-pending the specified directory to all the file
2330 paths, except the name of the system aliases file that appears in the default
2331 configuration. (If a default alias file is created, its name &'is'& modified.)
2332 For backwards compatibility, ROOT is used if DESTDIR is not set,
2333 but this usage is deprecated.
2335 .cindex "installing Exim" "what is not installed"
2336 Running &'make install'& does not copy the Exim 4 conversion script
2337 &'convert4r4'&. You will probably run this only once if you are
2338 upgrading from Exim 3. None of the documentation files in the &_doc_&
2339 directory are copied, except for the info files when you have set
2340 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2342 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2343 to their names. The Exim binary itself, however, is handled differently. It is
2344 installed under a name that includes the version number and the compile number,
2345 for example, &_exim-&version()-1_&. The script then arranges for a symbolic link
2346 called &_exim_& to point to the binary. If you are updating a previous version
2347 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2348 from the directory (as seen by other processes).
2350 .cindex "installing Exim" "testing the script"
2351 If you want to see what the &'make install'& will do before running it for
2352 real, you can pass the &%-n%& option to the installation script by this
2355 make INSTALL_ARG=-n install
2357 The contents of the variable INSTALL_ARG are passed to the installation
2358 script. You do not need to be root to run this test. Alternatively, you can run
2359 the installation script directly, but this must be from within the build
2360 directory. For example, from the top-level Exim directory you could use this
2363 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2365 .cindex "installing Exim" "install script options"
2366 There are two other options that can be supplied to the installation script.
2369 &%-no_chown%& bypasses the call to change the owner of the installed binary
2370 to root, and the call to make it a setuid binary.
2372 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2376 INSTALL_ARG can be used to pass these options to the script. For example:
2378 make INSTALL_ARG=-no_symlink install
2380 The installation script can also be given arguments specifying which files are
2381 to be copied. For example, to install just the Exim binary, and nothing else,
2382 without creating the symbolic link, you could use:
2384 make INSTALL_ARG='-no_symlink exim' install
2389 .section "Installing info documentation" "SECTinsinfdoc"
2390 .cindex "installing Exim" "&'info'& documentation"
2391 Not all systems use the GNU &'info'& system for documentation, and for this
2392 reason, the Texinfo source of Exim's documentation is not included in the main
2393 distribution. Instead it is available separately from the FTP site (see section
2396 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2397 source of the documentation is found in the source tree, running &`make
2398 install`& automatically builds the info files and installs them.
2402 .section "Setting up the spool directory" "SECID33"
2403 .cindex "spool directory" "creating"
2404 When it starts up, Exim tries to create its spool directory if it does not
2405 exist. The Exim uid and gid are used for the owner and group of the spool
2406 directory. Sub-directories are automatically created in the spool directory as
2412 .section "Testing" "SECID34"
2413 .cindex "testing" "installation"
2414 Having installed Exim, you can check that the runtime configuration file is
2415 syntactically valid by running the following command, which assumes that the
2416 Exim binary directory is within your PATH environment variable:
2420 If there are any errors in the configuration file, Exim outputs error messages.
2421 Otherwise it outputs the version number and build date,
2422 the DBM library that is being used, and information about which drivers and
2423 other optional code modules are included in the binary.
2424 Some simple routing tests can be done by using the address testing option. For
2427 &`exim -bt`& <&'local username'&>
2429 should verify that it recognizes a local mailbox, and
2431 &`exim -bt`& <&'remote address'&>
2433 a remote one. Then try getting it to deliver mail, both locally and remotely.
2434 This can be done by passing messages directly to Exim, without going through a
2435 user agent. For example:
2437 exim -v postmaster@your.domain.example
2438 From: user@your.domain.example
2439 To: postmaster@your.domain.example
2440 Subject: Testing Exim
2442 This is a test message.
2445 The &%-v%& option causes Exim to output some verification of what it is doing.
2446 In this case you should see copies of three log lines, one for the message's
2447 arrival, one for its delivery, and one containing &"Completed"&.
2449 .cindex "delivery" "problems with"
2450 If you encounter problems, look at Exim's log files (&'mainlog'& and
2451 &'paniclog'&) to see if there is any relevant information there. Another source
2452 of information is running Exim with debugging turned on, by specifying the
2453 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2454 with debugging turned on by a command of the form
2456 &`exim -d -M`& <&'exim-message-id'&>
2458 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2459 produces rather a lot of output, but you can cut this down to specific areas.
2460 For example, if you use &%-d-all+route%& only the debugging information
2461 relevant to routing is included. (See the &%-d%& option in chapter
2462 &<<CHAPcommandline>>& for more details.)
2464 .cindex '&"sticky"& bit'
2465 .cindex "lock files"
2466 One specific problem that has shown up on some sites is the inability to do
2467 local deliveries into a shared mailbox directory, because it does not have the
2468 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2469 writing to a mailbox file, and if it cannot create the lock file, the delivery
2470 is deferred. You can get round this either by setting the &"sticky bit"& on the
2471 directory, or by setting a specific group for local deliveries and allowing
2472 that group to create files in the directory (see the comments above the
2473 &(local_delivery)& transport in the default configuration file). Another
2474 approach is to configure Exim not to use lock files, but just to rely on
2475 &[fcntl()]& locking instead. However, you should do this only if all user
2476 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2477 see chapter &<<CHAPappendfile>>&.
2479 One thing that cannot be tested on a system that is already running an MTA is
2480 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2481 &%-oX%& option can be used to run an Exim daemon that listens on some other
2482 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2483 &'exim_checkaccess'& utility can be used to check out policy controls on
2486 Testing a new version on a system that is already running Exim can most easily
2487 be done by building a binary with a different CONFIGURE_FILE setting. From
2488 within the runtime configuration, all other file and directory names
2489 that Exim uses can be altered, in order to keep it entirely clear of the
2493 .section "Replacing another MTA with Exim" "SECID35"
2494 .cindex "replacing another MTA"
2495 Building and installing Exim for the first time does not of itself put it in
2496 general use. The name by which the system's MTA is called by mail user agents
2497 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2498 operating system), and it is necessary to make this name point to the &'exim'&
2499 binary in order to get the user agents to pass messages to Exim. This is
2500 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2501 or &_/usr/lib/sendmail_&
2502 .cindex "symbolic link" "to &'exim'& binary"
2503 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2504 privilege and executable status from the old MTA. It is then necessary to stop
2505 and restart the mailer daemon, if one is running.
2507 .cindex "FreeBSD, MTA indirection"
2508 .cindex "&_/etc/mail/mailer.conf_&"
2509 Some operating systems have introduced alternative ways of switching MTAs. For
2510 example, if you are running FreeBSD, you need to edit the file
2511 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2512 described. A typical example of the contents of this file for running Exim is
2515 sendmail /usr/exim/bin/exim
2516 send-mail /usr/exim/bin/exim
2517 mailq /usr/exim/bin/exim -bp
2518 newaliases /usr/bin/true
2520 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2521 your Exim installation is &"live"&. Check it by sending a message from your
2522 favourite user agent.
2524 You should consider what to tell your users about the change of MTA. Exim may
2525 have different capabilities to what was previously running, and there are
2526 various operational differences such as the text of messages produced by
2527 command line options and in bounce messages. If you allow your users to make
2528 use of Exim's filtering capabilities, you should make the document entitled
2529 &'Exim's interface to mail filtering'& available to them.
2533 .section "Upgrading Exim" "SECID36"
2534 .cindex "upgrading Exim"
2535 If you are already running Exim on your host, building and installing a new
2536 version automatically makes it available to MUAs, or any other programs that
2537 call the MTA directly. However, if you are running an Exim daemon, you do need
2538 .cindex restart "on HUP signal"
2539 .cindex signal "HUP, to restart"
2540 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2541 new binary. You do not need to stop processing mail in order to install a new
2542 version of Exim. The install script does not modify an existing runtime
2548 .section "Stopping the Exim daemon on Solaris" "SECID37"
2549 .cindex "Solaris" "stopping Exim on"
2550 The standard command for stopping the mailer daemon on Solaris is
2552 /etc/init.d/sendmail stop
2554 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2555 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2556 for the text &"sendmail"&; this is not present because the actual program name
2557 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2558 solution is to replace the line that finds the process id with something like
2560 pid=`cat /var/spool/exim/exim-daemon.pid`
2562 to obtain the daemon's pid directly from the file that Exim saves it in.
2564 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2565 still be received from local processes, and if automatic delivery is configured
2566 (the normal case), deliveries will still occur.
2571 . ////////////////////////////////////////////////////////////////////////////
2572 . ////////////////////////////////////////////////////////////////////////////
2574 .chapter "The Exim command line" "CHAPcommandline"
2575 .scindex IIDclo1 "command line" "options"
2576 .scindex IIDclo2 "options" "command line"
2577 Exim's command line takes the standard Unix form of a sequence of options,
2578 each starting with a hyphen character, followed by a number of arguments. The
2579 options are compatible with the main options of Sendmail, and there are also
2580 some additional options, some of which are compatible with Smail 3. Certain
2581 combinations of options do not make sense, and provoke an error if used.
2582 The form of the arguments depends on which options are set.
2585 .section "Setting options by program name" "SECID38"
2587 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2588 were present before any other options.
2589 The &%-bp%& option requests a listing of the contents of the mail queue on the
2591 This feature is for compatibility with some systems that contain a command of
2592 that name in one of the standard libraries, symbolically linked to
2593 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2596 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2597 were present before any other options, for compatibility with Smail. The
2598 &%-bS%& option is used for reading in a number of messages in batched SMTP
2602 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2603 &%-oee%& options were present before any other options, for compatibility with
2604 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2607 .cindex "queue runner"
2608 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2609 were present before any other options, for compatibility with Smail. The &%-q%&
2610 option causes a single queue runner process to be started.
2612 .cindex "&'newaliases'&"
2613 .cindex "alias file" "building"
2614 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2615 If Exim is called under the name &'newaliases'& it behaves as if the option
2616 &%-bi%& were present before any other options, for compatibility with Sendmail.
2617 This option is used for rebuilding Sendmail's alias file. Exim does not have
2618 the concept of a single alias file, but can be configured to run a given
2619 command if called with the &%-bi%& option.
2622 .section "Trusted and admin users" "SECTtrustedadmin"
2623 Some Exim options are available only to &'trusted users'& and others are
2624 available only to &'admin users'&. In the description below, the phrases &"Exim
2625 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2626 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2627 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2630 .cindex "trusted users" "definition of"
2631 .cindex "user" "trusted definition of"
2632 The trusted users are root, the Exim user, any user listed in the
2633 &%trusted_users%& configuration option, and any user whose current group or any
2634 supplementary group is one of those listed in the &%trusted_groups%&
2635 configuration option. Note that the Exim group is not automatically trusted.
2637 .cindex '&"From"& line'
2638 .cindex "envelope from"
2639 .cindex "envelope sender"
2640 Trusted users are always permitted to use the &%-f%& option or a leading
2641 &"From&~"& line to specify the envelope sender of a message that is passed to
2642 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2643 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2644 users to set envelope senders.
2646 .cindex "&'From:'& header line"
2647 .cindex "&'Sender:'& header line"
2648 .cindex "header lines" "From:"
2649 .cindex "header lines" "Sender:"
2650 For a trusted user, there is never any check on the contents of the &'From:'&
2651 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2652 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2654 Trusted users may also specify a host name, host address, interface address,
2655 protocol name, ident value, and authentication data when submitting a message
2656 locally. Thus, they are able to insert messages into Exim's queue locally that
2657 have the characteristics of messages received from a remote host. Untrusted
2658 users may in some circumstances use &%-f%&, but can never set the other values
2659 that are available to trusted users.
2661 .cindex "user" "admin definition of"
2662 .cindex "admin user" "definition of"
2663 The admin users are root, the Exim user, and any user that is a member of the
2664 Exim group or of any group listed in the &%admin_groups%& configuration option.
2665 The current group does not have to be one of these groups.
2667 Admin users are permitted to list the queue, and to carry out certain
2668 operations on messages, for example, to force delivery failures. It is also
2669 necessary to be an admin user in order to see the full information provided by
2670 the Exim monitor, and full debugging output.
2672 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2673 Exim to attempt delivery of messages on its queue is restricted to admin users.
2674 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2675 option false (that is, specifying &%no_prod_requires_admin%&).
2677 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2678 is restricted to admin users unless &%queue_list_requires_admin%& is set
2683 &*Warning*&: If you configure your system so that admin users are able to
2684 edit Exim's configuration file, you are giving those users an easy way of
2685 getting root. There is further discussion of this issue at the start of chapter
2691 .section "Command line options" "SECID39"
2692 Exim's command line options are described in alphabetical order below. If none
2693 of the options that specifies a specific action (such as starting the daemon or
2694 a queue runner, or testing an address, or receiving a message in a specific
2695 format, or listing the queue) are present, and there is at least one argument
2696 on the command line, &%-bm%& (accept a local message on the standard input,
2697 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2698 outputs a brief message about itself and exits.
2700 . ////////////////////////////////////////////////////////////////////////////
2701 . Insert a stylized XML comment here, to identify the start of the command line
2702 . options. This is for the benefit of the Perl script that automatically
2703 . creates a man page for the options.
2704 . ////////////////////////////////////////////////////////////////////////////
2707 <!-- === Start of command line options === -->
2714 .cindex "options" "command line; terminating"
2715 This is a pseudo-option whose only purpose is to terminate the options and
2716 therefore to cause subsequent command line items to be treated as arguments
2717 rather than options, even if they begin with hyphens.
2720 .oindex "&%--help%&"
2721 This option causes Exim to output a few sentences stating what it is.
2722 The same output is generated if the Exim binary is called with no options and
2725 .vitem &%--version%&
2726 .oindex "&%--version%&"
2727 This option is an alias for &%-bV%& and causes version information to be
2734 These options are used by Sendmail for selecting configuration files and are
2737 .vitem &%-B%&<&'type'&>
2739 .cindex "8-bit characters"
2740 .cindex "Sendmail compatibility" "8-bit characters"
2741 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2742 clean; it ignores this option.
2747 .cindex "SMTP" "listener"
2748 .cindex "queue runner"
2749 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2750 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2751 that the daemon should also initiate periodic queue runs.
2753 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2754 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2755 disconnect from the controlling terminal. When running this way, it can be
2756 stopped by pressing ctrl-C.
2758 By default, Exim listens for incoming connections to the standard SMTP port on
2759 all the host's running interfaces. However, it is possible to listen on other
2760 ports, on multiple ports, and only on specific interfaces. Chapter
2761 &<<CHAPinterfaces>>& contains a description of the options that control this.
2763 When a listening daemon
2764 .cindex "daemon" "process id (pid)"
2765 .cindex "pid (process id)" "of daemon"
2766 is started without the use of &%-oX%& (that is, without overriding the normal
2767 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2768 in Exim's spool directory. This location can be overridden by setting
2769 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2772 When &%-oX%& is used on the command line to start a listening daemon, the
2773 process id is not written to the normal pid file path. However, &%-oP%& can be
2774 used to specify a path on the command line if a pid file is required.
2778 .cindex restart "on HUP signal"
2779 .cindex signal "HUP, to restart"
2780 .cindex "daemon" "restarting"
2781 .cindex signal "to reload configuration"
2782 .cindex daemon "reload configuration"
2783 .cindex reload configuration
2784 can be used to cause the daemon to re-execute itself. This should be done
2785 whenever Exim's configuration file, or any file that is incorporated into it by
2786 means of the &%.include%& facility, is changed, and also whenever a new version
2787 of Exim is installed. It is not necessary to do this when other files that are
2788 referenced from the configuration (for example, alias files) are changed,
2789 because these are reread each time they are used.
2793 This option has the same effect as &%-bd%& except that it never disconnects
2794 from the controlling terminal, even when no debugging is specified.
2798 .cindex "testing" "string expansion"
2799 .cindex "expansion" "testing"
2800 Run Exim in expansion testing mode. Exim discards its root privilege, to
2801 prevent ordinary users from using this mode to read otherwise inaccessible
2802 files. If no arguments are given, Exim runs interactively, prompting for lines
2803 of data. Otherwise, it processes each argument in turn.
2805 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2806 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2807 used without command line arguments. If successful, it uses the &[readline()]&
2808 function, which provides extensive line-editing facilities, for reading the
2809 test data. A line history is supported.
2811 Long expansion expressions can be split over several lines by using backslash
2812 continuations. As in Exim's runtime configuration, white space at the start of
2813 continuation lines is ignored. Each argument or data line is passed through the
2814 string expansion mechanism, and the result is output. Variable values from the
2815 configuration file (for example, &$qualify_domain$&) are available, but no
2816 message-specific values (such as &$message_exim_id$&) are set, because no message
2817 is being processed (but see &%-bem%& and &%-Mset%&).
2819 &*Note*&: If you use this mechanism to test lookups, and you change the data
2820 files or databases you are using, you must exit and restart Exim before trying
2821 the same lookup again. Otherwise, because each Exim process caches the results
2822 of lookups, you will just get the same result as before.
2824 Macro processing is done on lines before string-expansion: new macros can be
2825 defined and macros will be expanded.
2826 Because macros in the config file are often used for secrets, those are only
2827 available to admin users.
2829 .vitem &%-bem%&&~<&'filename'&>
2831 .cindex "testing" "string expansion"
2832 .cindex "expansion" "testing"
2833 This option operates like &%-be%& except that it must be followed by the name
2834 of a file. For example:
2836 exim -bem /tmp/testmessage
2838 The file is read as a message (as if receiving a locally-submitted non-SMTP
2839 message) before any of the test expansions are done. Thus, message-specific
2840 variables such as &$message_size$& and &$header_from:$& are available. However,
2841 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2842 recipients are read from the headers in the normal way, and are shown in the
2843 &$recipients$& variable. Note that recipients cannot be given on the command
2844 line, because further arguments are taken as strings to expand (just like
2847 .vitem &%-bF%&&~<&'filename'&>
2849 .cindex "system filter" "testing"
2850 .cindex "testing" "system filter"
2851 This option is the same as &%-bf%& except that it assumes that the filter being
2852 tested is a system filter. The additional commands that are available only in
2853 system filters are recognized.
2855 .vitem &%-bf%&&~<&'filename'&>
2857 .cindex "filter" "testing"
2858 .cindex "testing" "filter file"
2859 .cindex "forward file" "testing"
2860 .cindex "testing" "forward file"
2861 .cindex "Sieve filter" "testing"
2862 This option runs Exim in user filter testing mode; the file is the filter file
2863 to be tested, and a test message must be supplied on the standard input. If
2864 there are no message-dependent tests in the filter, an empty file can be
2867 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2868 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2869 filter and a user filter in the same run. For example:
2871 exim -bF /system/filter -bf /user/filter </test/message
2873 This is helpful when the system filter adds header lines or sets filter
2874 variables that are used by the user filter.
2876 If the test filter file does not begin with one of the special lines
2881 it is taken to be a normal &_.forward_& file, and is tested for validity under
2882 that interpretation. See sections &<<SECTitenonfilred>>& to
2883 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2886 The result of an Exim command that uses &%-bf%&, provided no errors are
2887 detected, is a list of the actions that Exim would try to take if presented
2888 with the message for real. More details of filter testing are given in the
2889 separate document entitled &'Exim's interfaces to mail filtering'&.
2891 When testing a filter file,
2892 .cindex "&""From""& line"
2893 .cindex "envelope from"
2894 .cindex "envelope sender"
2895 .oindex "&%-f%&" "for filter testing"
2896 the envelope sender can be set by the &%-f%& option,
2897 or by a &"From&~"& line at the start of the test message. Various parameters
2898 that would normally be taken from the envelope recipient address of the message
2899 can be set by means of additional command line options (see the next four
2902 .vitem &%-bfd%&&~<&'domain'&>
2904 .vindex "&$qualify_domain$&"
2905 This sets the domain of the recipient address when a filter file is being
2906 tested by means of the &%-bf%& option. The default is the value of
2909 .vitem &%-bfl%&&~<&'local&~part'&>
2911 This sets the local part of the recipient address when a filter file is being
2912 tested by means of the &%-bf%& option. The default is the username of the
2913 process that calls Exim. A local part should be specified with any prefix or
2914 suffix stripped, because that is how it appears to the filter when a message is
2915 actually being delivered.
2917 .vitem &%-bfp%&&~<&'prefix'&>
2919 .cindex affix "filter testing"
2920 This sets the prefix of the local part of the recipient address when a filter
2921 file is being tested by means of the &%-bf%& option. The default is an empty
2924 .vitem &%-bfs%&&~<&'suffix'&>
2926 .cindex affix "filter testing"
2927 This sets the suffix of the local part of the recipient address when a filter
2928 file is being tested by means of the &%-bf%& option. The default is an empty
2931 .vitem &%-bh%&&~<&'IP&~address'&>
2933 .cindex "testing" "incoming SMTP"
2934 .cindex "SMTP" "testing incoming"
2935 .cindex "testing" "relay control"
2936 .cindex "relaying" "testing configuration"
2937 .cindex "policy control" "testing"
2938 .cindex "debugging" "&%-bh%& option"
2939 This option runs a fake SMTP session as if from the given IP address, using the
2940 standard input and output. The IP address may include a port number at the end,
2941 after a full stop. For example:
2943 exim -bh 10.9.8.7.1234
2944 exim -bh fe80::a00:20ff:fe86:a061.5678
2946 When an IPv6 address is given, it is converted into canonical form. In the case
2947 of the second example above, the value of &$sender_host_address$& after
2948 conversion to the canonical form is
2949 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2951 Comments as to what is going on are written to the standard error file. These
2952 include lines beginning with &"LOG"& for anything that would have been logged.
2953 This facility is provided for testing configuration options for incoming
2954 messages, to make sure they implement the required policy. For example, you can
2955 test your relay controls using &%-bh%&.
2959 You can test features of the configuration that rely on ident (RFC 1413)
2960 information by using the &%-oMt%& option. However, Exim cannot actually perform
2961 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2964 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2965 are also skipped when testing using &%-bh%&. If you want these callouts to
2966 occur, use &%-bhc%& instead.
2968 Messages supplied during the testing session are discarded, and nothing is
2969 written to any of the real log files. There may be pauses when DNS (and other)
2970 lookups are taking place, and of course these may time out. The &%-oMi%& option
2971 can be used to specify a specific IP interface and port if this is important,
2972 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2973 session were authenticated.
2975 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2976 output just states whether a given recipient address from a given host is
2977 acceptable or not. See section &<<SECTcheckaccess>>&.
2979 Features such as authentication and encryption, where the client input is not
2980 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2981 specialized SMTP test program such as
2982 &url(https://www.jetmore.org/john/code/swaks/,swaks).
2984 .vitem &%-bhc%&&~<&'IP&~address'&>
2986 This option operates in the same way as &%-bh%&, except that address
2987 verification callouts are performed if required. This includes consulting and
2988 updating the callout cache database.
2992 .cindex "alias file" "building"
2993 .cindex "building alias file"
2994 .cindex "Sendmail compatibility" "&%-bi%& option"
2995 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2996 Exim does not have the concept of a single alias file, and so it cannot mimic
2997 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2998 tend to appear in various scripts such as NIS make files, so the option must be
3001 If &%-bi%& is encountered, the command specified by the &%bi_command%&
3002 configuration option is run, under the uid and gid of the caller of Exim. If
3003 the &%-oA%& option is used, its value is passed to the command as an argument.
3004 The command set by &%bi_command%& may not contain arguments. The command can
3005 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
3006 if this is required. If the &%bi_command%& option is not set, calling Exim with
3009 . // Keep :help first, then the rest in alphabetical order
3011 .oindex "&%-bI:help%&"
3012 .cindex "querying exim information"
3013 We shall provide various options starting &`-bI:`& for querying Exim for
3014 information. The output of many of these will be intended for machine
3015 consumption. This one is not. The &%-bI:help%& option asks Exim for a
3016 synopsis of supported options beginning &`-bI:`&. Use of any of these
3017 options shall cause Exim to exit after producing the requested output.
3020 .oindex "&%-bI:dscp%&"
3021 .cindex "DSCP" "values"
3022 This option causes Exim to emit an alphabetically sorted list of all
3023 recognised DSCP names.
3025 .vitem &%-bI:sieve%&
3026 .oindex "&%-bI:sieve%&"
3027 .cindex "Sieve filter" "capabilities"
3028 This option causes Exim to emit an alphabetically sorted list of all supported
3029 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3030 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3031 &`SIEVE`& capability response line. As the precise list may depend upon
3032 compile-time build options, which this option will adapt to, this is the only
3033 way to guarantee a correct response.
3037 .cindex "local message reception"
3038 This option runs an Exim receiving process that accepts an incoming,
3039 locally-generated message on the standard input. The recipients are given as the
3040 command arguments (except when &%-t%& is also present &-- see below). Each
3041 argument can be a comma-separated list of RFC 2822 addresses. This is the
3042 default option for selecting the overall action of an Exim call; it is assumed
3043 if no other conflicting option is present.
3045 If any addresses in the message are unqualified (have no domain), they are
3046 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3047 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3048 suppressing this for special cases.
3050 Policy checks on the contents of local messages can be enforced by means of
3051 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3053 .cindex "return code" "for &%-bm%&"
3054 The return code is zero if the message is successfully accepted. Otherwise, the
3055 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3058 .cindex "message" "format"
3059 .cindex "format" "message"
3060 .cindex "&""From""& line"
3061 .cindex "UUCP" "&""From""& line"
3062 .cindex "Sendmail compatibility" "&""From""& line"
3063 of the message must be as defined in RFC 2822, except that, for
3064 compatibility with Sendmail and Smail, a line in one of the forms
3066 From sender Fri Jan 5 12:55 GMT 1997
3067 From sender Fri, 5 Jan 97 12:55:01
3069 (with the weekday optional, and possibly with additional text after the date)
3070 is permitted to appear at the start of the message. There appears to be no
3071 authoritative specification of the format of this line. Exim recognizes it by
3072 matching against the regular expression defined by the &%uucp_from_pattern%&
3073 option, which can be changed if necessary.
3075 .oindex "&%-f%&" "overriding &""From""& line"
3076 The specified sender is treated as if it were given as the argument to the
3077 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3078 preference to the address taken from the message. The caller of Exim must be a
3079 trusted user for the sender of a message to be set in this way.
3081 .vitem &%-bmalware%&&~<&'filename'&>
3082 .oindex "&%-bmalware%&"
3083 .cindex "testing", "malware"
3084 .cindex "malware scan test"
3085 This debugging option causes Exim to scan the given file or directory
3086 (depending on the used scanner interface),
3087 using the malware scanning framework. The option of &%av_scanner%& influences
3088 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3089 the expansion should have defaults which apply to this invocation. ACLs are
3090 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3091 will never be populated and &%-bmalware%& will fail.
3093 Exim will have changed working directory before resolving the filename, so
3094 using fully qualified pathnames is advisable. Exim will be running as the Exim
3095 user when it tries to open the file, rather than as the invoking user.
3096 This option requires admin privileges.
3098 The &%-bmalware%& option will not be extended to be more generally useful,
3099 there are better tools for file-scanning. This option exists to help
3100 administrators verify their Exim and AV scanner configuration.
3104 .cindex "address qualification, suppressing"
3105 By default, Exim automatically qualifies unqualified addresses (those
3106 without domains) that appear in messages that are submitted locally (that
3107 is, not over TCP/IP). This qualification applies both to addresses in
3108 envelopes, and addresses in header lines. Sender addresses are qualified using
3109 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3110 defaults to the value of &%qualify_domain%&).
3112 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3113 being used to re-submit messages that originally came from remote hosts after
3114 content scanning, you probably do not want to qualify unqualified addresses in
3115 header lines. (Such lines will be present only if you have not enabled a header
3116 syntax check in the appropriate ACL.)
3118 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3119 messages that originate on the local host. When this is used, unqualified
3120 addresses in the envelope provoke errors (causing message rejection) and
3121 unqualified addresses in header lines are left alone.
3126 .cindex "configuration options" "extracting"
3127 .cindex "options" "configuration &-- extracting"
3128 If this option is given with no arguments, it causes the values of all Exim's
3129 main configuration options to be written to the standard output. The values
3130 of one or more specific options can be requested by giving their names as
3131 arguments, for example:
3133 exim -bP qualify_domain hold_domains
3135 .cindex "hiding configuration option values"
3136 .cindex "configuration options" "hiding value of"
3137 .cindex "options" "hiding value of"
3138 However, any option setting that is preceded by the word &"hide"& in the
3139 configuration file is not shown in full, except to an admin user. For other
3140 users, the output is as in this example:
3142 mysql_servers = <value not displayable>
3144 If &%config%& is given as an argument, the config is
3145 output, as it was parsed, any include file resolved, any comment removed.
3147 If &%config_file%& is given as an argument, the name of the runtime
3148 configuration file is output. (&%configure_file%& works too, for
3149 backward compatibility.)
3150 If a list of configuration files was supplied, the value that is output here
3151 is the name of the file that was actually used.
3153 .cindex "options" "hiding name of"
3154 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3155 name will not be output.
3157 .cindex "daemon" "process id (pid)"
3158 .cindex "pid (process id)" "of daemon"
3159 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3160 directories where log files and daemon pid files are written are output,
3161 respectively. If these values are unset, log files are written in a
3162 sub-directory of the spool directory called &%log%&, and the pid file is
3163 written directly into the spool directory.
3165 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3167 exim -bP +local_domains
3169 it searches for a matching named list of any type (domain, host, address, or
3170 local part) and outputs what it finds.
3172 .cindex "options" "router &-- extracting"
3173 .cindex "options" "transport &-- extracting"
3174 .cindex "options" "authenticator &-- extracting"
3175 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3176 followed by the name of an appropriate driver instance, the option settings for
3177 that driver are output. For example:
3179 exim -bP transport local_delivery
3181 The generic driver options are output first, followed by the driver's private
3182 options. A list of the names of drivers of a particular type can be obtained by
3183 using one of the words &%router_list%&, &%transport_list%&, or
3184 &%authenticator_list%&, and a complete list of all drivers with their option
3185 settings can be obtained by using &%routers%&, &%transports%&, or
3188 .cindex "environment"
3189 If &%environment%& is given as an argument, the set of environment
3190 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3193 .cindex "options" "macro &-- extracting"
3194 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3195 are available, similarly to the drivers. Because macros are sometimes used
3196 for storing passwords, this option is restricted.
3197 The output format is one item per line.
3198 For the "-bP macro <name>" form, if no such macro is found
3199 the exit status will be nonzero.
3203 .cindex "queue" "listing messages in"
3204 .cindex "listing" "messages in the queue"
3205 This option requests a listing of the contents of the mail queue on the
3206 standard output. If the &%-bp%& option is followed by a list of message ids,
3207 just those messages are listed. By default, this option can be used only by an
3208 admin user. However, the &%queue_list_requires_admin%& option can be set false
3209 to allow any user to see the queue.
3211 Each message in the queue is displayed as in the following example:
3213 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3214 red.king@looking-glass.fict.example
3217 .cindex "message" "size in queue listing"
3218 .cindex "size" "of message"
3219 The first line contains the length of time the message has been in the queue
3220 (in this case 25 minutes), the size of the message (2.9K), the unique local
3221 identifier for the message, and the message sender, as contained in the
3222 envelope. For bounce messages, the sender address is empty, and appears as
3223 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3224 the default sender address, the user's login name is shown in parentheses
3225 before the sender address.
3227 .cindex "frozen messages" "in queue listing"
3228 If the message is frozen (attempts to deliver it are suspended) then the text
3229 &"*** frozen ***"& is displayed at the end of this line.
3231 The recipients of the message (taken from the envelope, not the headers) are
3232 displayed on subsequent lines. Those addresses to which the message has already
3233 been delivered are marked with the letter D. If an original address gets
3234 expanded into several addresses via an alias or forward file, the original is
3235 displayed with a D only when deliveries for all of its child addresses are
3241 This option operates like &%-bp%&, but in addition it shows delivered addresses
3242 that were generated from the original top level address(es) in each message by
3243 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3249 .cindex "queue" "count of messages on"
3250 This option counts the number of messages in the queue, and writes the total
3251 to the standard output. It is restricted to admin users, unless
3252 &%queue_list_requires_admin%& is set false.
3257 This option operates like &%-bp%&, but the output is not sorted into
3258 chronological order of message arrival. This can speed it up when there are
3259 lots of messages in the queue, and is particularly useful if the output is
3260 going to be post-processed in a way that doesn't need the sorting.
3264 This option is a combination of &%-bpr%& and &%-bpa%&.
3268 This option is a combination of &%-bpr%& and &%-bpu%&.
3273 This option operates like &%-bp%& but shows only undelivered top-level
3274 addresses for each message displayed. Addresses generated by aliasing or
3275 forwarding are not shown, unless the message was deferred after processing by a
3276 router with the &%one_time%& option set.
3281 .cindex "testing" "retry configuration"
3282 .cindex "retry" "configuration testing"
3283 This option is for testing retry rules, and it must be followed by up to three
3284 arguments. It causes Exim to look for a retry rule that matches the values
3285 and to write it to the standard output. For example:
3287 exim -brt bach.comp.mus.example
3288 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3290 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3291 argument, which is required, can be a complete address in the form
3292 &'local_part@domain'&, or it can be just a domain name. If the second argument
3293 contains a dot, it is interpreted as an optional second domain name; if no
3294 retry rule is found for the first argument, the second is tried. This ties in
3295 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3296 rule is found that matches the host, one that matches the mail domain is
3297 sought. Finally, an argument that is the name of a specific delivery error, as
3298 used in setting up retry rules, can be given. For example:
3300 exim -brt haydn.comp.mus.example quota_3d
3301 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3306 .cindex "testing" "rewriting"
3307 .cindex "rewriting" "testing"
3308 This option is for testing address rewriting rules, and it must be followed by
3309 a single argument, consisting of either a local part without a domain, or a
3310 complete address with a fully qualified domain. Exim outputs how this address
3311 would be rewritten for each possible place it might appear. See chapter
3312 &<<CHAPrewrite>>& for further details.
3316 .cindex "SMTP" "batched incoming"
3317 .cindex "batched SMTP input"
3318 This option is used for batched SMTP input, which is an alternative interface
3319 for non-interactive local message submission. A number of messages can be
3320 submitted in a single run. However, despite its name, this is not really SMTP
3321 input. Exim reads each message's envelope from SMTP commands on the standard
3322 input, but generates no responses. If the caller is trusted, or
3323 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3324 believed; otherwise the sender is always the caller of Exim.
3326 The message itself is read from the standard input, in SMTP format (leading
3327 dots doubled), terminated by a line containing just a single dot. An error is
3328 provoked if the terminating dot is missing. A further message may then follow.
3330 As for other local message submissions, the contents of incoming batch SMTP
3331 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3332 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3333 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3335 Some other SMTP commands are recognized in the input. HELO and EHLO act
3336 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3337 QUIT quits, ignoring the rest of the standard input.
3339 .cindex "return code" "for &%-bS%&"
3340 If any error is encountered, reports are written to the standard output and
3341 error streams, and Exim gives up immediately. The return code is 0 if no error
3342 was detected; it is 1 if one or more messages were accepted before the error
3343 was detected; otherwise it is 2.
3345 More details of input using batched SMTP are given in section
3346 &<<SECTincomingbatchedSMTP>>&.
3350 .cindex "SMTP" "local input"
3351 .cindex "local SMTP input"
3352 This option causes Exim to accept one or more messages by reading SMTP commands
3353 on the standard input, and producing SMTP replies on the standard output. SMTP
3354 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3355 Some user agents use this interface as a way of passing locally-generated
3356 messages to the MTA.
3359 .cindex "sender" "source of"
3360 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3361 set, the senders of messages are taken from the SMTP MAIL commands.
3362 Otherwise the content of these commands is ignored and the sender is set up as
3363 the calling user. Unqualified addresses are automatically qualified using
3364 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3365 &%-bnq%& option is used.
3369 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3370 using a listening daemon. Exim can distinguish the two cases by checking
3371 whether the standard input is a TCP/IP socket. When Exim is called from
3372 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3373 above concerning senders and qualification do not apply. In this situation,
3374 Exim behaves in exactly the same way as it does when receiving a message via
3375 the listening daemon.
3379 .cindex "testing" "addresses"
3380 .cindex "address" "testing"
3381 This option runs Exim in address testing mode, in which each argument is taken
3382 as a recipient address to be tested for deliverability. The results are
3383 written to the standard output. If a test fails, and the caller is not an admin
3384 user, no details of the failure are output, because these might contain
3385 sensitive information such as usernames and passwords for database lookups.
3387 If no arguments are given, Exim runs in an interactive manner, prompting with a
3388 right angle bracket for addresses to be tested.
3390 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3391 &[readline()]& function, because it is running as &'root'& and there are
3394 Each address is handled as if it were the recipient address of a message
3395 (compare the &%-bv%& option). It is passed to the routers and the result is
3396 written to the standard output. However, any router that has
3397 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3398 genuine routing tests if your first router passes everything to a scanner
3401 .cindex "return code" "for &%-bt%&"
3402 The return code is 2 if any address failed outright; it is 1 if no address
3403 failed outright but at least one could not be resolved for some reason. Return
3404 code 0 is given only when all addresses succeed.
3406 .cindex "duplicate addresses"
3407 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3408 addresses after routing is complete, so that only one delivery takes place.
3409 This does not happen when testing with &%-bt%&; the full results of routing are
3412 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3413 routers in the configuration makes any tests on the sender address of a
3415 .oindex "&%-f%&" "for address testing"
3416 you can use the &%-f%& option to set an appropriate sender when running
3417 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3418 default qualifying domain. However, if you have set up (for example) routers
3419 whose behaviour depends on the contents of an incoming message, you cannot test
3420 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3425 .cindex "version number of Exim"
3426 This option causes Exim to write the current version number, compilation
3427 number, and compilation date of the &'exim'& binary to the standard output.
3428 It also lists the DBM library that is being used, the optional modules (such as
3429 specific lookup types), the drivers that are included in the binary, and the
3430 name of the runtime configuration file that is in use.
3432 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3433 configuration file. However, this is a static check only. It cannot check
3434 values that are to be expanded. For example, although a misspelt ACL verb is
3435 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3436 alone to discover (for example) all the typos in the configuration; some
3437 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3438 dynamic testing facilities.
3442 .cindex "verifying address" "using &%-bv%&"
3443 .cindex "address" "verification"
3444 This option runs Exim in address verification mode, in which each argument is
3445 taken as a recipient address to be verified by the routers. (This does
3446 not involve any verification callouts). During normal operation, verification
3447 happens mostly as a consequence processing a &%verify%& condition in an ACL
3448 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3449 including callouts, see the &%-bh%& and &%-bhc%& options.
3451 If verification fails, and the caller is not an admin user, no details of the
3452 failure are output, because these might contain sensitive information such as
3453 usernames and passwords for database lookups.
3455 If no arguments are given, Exim runs in an interactive manner, prompting with a
3456 right angle bracket for addresses to be verified.
3458 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3459 &[readline()]& function, because it is running as &'exim'& and there are
3462 Verification differs from address testing (the &%-bt%& option) in that routers
3463 that have &%no_verify%& set are skipped, and if the address is accepted by a
3464 router that has &%fail_verify%& set, verification fails. The address is
3465 verified as a recipient if &%-bv%& is used; to test verification for a sender
3466 address, &%-bvs%& should be used.
3468 If the &%-v%& option is not set, the output consists of a single line for each
3469 address, stating whether it was verified or not, and giving a reason in the
3470 latter case. Without &%-v%&, generating more than one address by redirection
3471 causes verification to end successfully, without considering the generated
3472 addresses. However, if just one address is generated, processing continues,
3473 and the generated address must verify successfully for the overall verification
3476 When &%-v%& is set, more details are given of how the address has been handled,
3477 and in the case of address redirection, all the generated addresses are also
3478 considered. Verification may succeed for some and fail for others.
3481 .cindex "return code" "for &%-bv%&"
3482 return code is 2 if any address failed outright; it is 1 if no address
3483 failed outright but at least one could not be resolved for some reason. Return
3484 code 0 is given only when all addresses succeed.
3486 If any of the routers in the configuration makes any tests on the sender
3487 address of a message, you should use the &%-f%& option to set an appropriate
3488 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3489 calling user at the default qualifying domain.
3493 This option acts like &%-bv%&, but verifies the address as a sender rather
3494 than a recipient address. This affects any rewriting and qualification that
3501 .cindex "inetd" "wait mode"
3502 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3503 similarly to the &%-bd%& option. All port specifications on the command-line
3504 and in the configuration file are ignored. Queue-running may not be specified.
3506 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3507 listening for connections. This permits the system to start up and have
3508 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3509 each port only when the first connection is received.
3511 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3512 which the daemon will exit, which should cause inetd to listen once more.
3514 .vitem &%-C%&&~<&'filelist'&>
3516 .cindex "configuration file" "alternate"
3517 .cindex "CONFIGURE_FILE"
3518 .cindex "alternate configuration file"
3519 This option causes Exim to find the runtime configuration file from the given
3520 list instead of from the list specified by the CONFIGURE_FILE
3521 compile-time setting. Usually, the list will consist of just a single filename,
3522 but it can be a colon-separated list of names. In this case, the first
3523 file that exists is used. Failure to open an existing file stops Exim from
3524 proceeding any further along the list, and an error is generated.
3526 When this option is used by a caller other than root, and the list is different
3527 from the compiled-in list, Exim gives up its root privilege immediately, and
3528 runs with the real and effective uid and gid set to those of the caller.
3529 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3530 file contains a list of full pathnames, one per line, for configuration files
3531 which are trusted. Root privilege is retained for any configuration file so
3532 listed, as long as the caller is the Exim user (or the user specified in the
3533 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3534 not writeable by inappropriate users or groups.
3536 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3537 configuration using &%-C%& right through message reception and delivery,
3538 even if the caller is root. The reception works, but by that time, Exim is
3539 running as the Exim user, so when it re-executes to regain privilege for the
3540 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3541 test reception and delivery using two separate commands (one to put a message
3542 in the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3544 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3545 prefix string with which any file named in a &%-C%& command line option
3546 must start. In addition, the filename must not contain the sequence &`/../`&.
3547 However, if the value of the &%-C%& option is identical to the value of
3548 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3549 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3550 unset, any filename can be used with &%-C%&.
3552 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3553 to a directory to which only root has access. This prevents someone who has
3554 broken into the Exim account from running a privileged Exim with an arbitrary
3557 The &%-C%& facility is useful for ensuring that configuration files are
3558 syntactically correct, but cannot be used for test deliveries, unless the
3559 caller is privileged, or unless it is an exotic configuration that does not
3560 require privilege. No check is made on the owner or group of the files
3561 specified by this option.
3564 .vitem &%-D%&<&'macro'&>=<&'value'&>
3566 .cindex "macro" "setting on command line"
3567 This option can be used to override macro definitions in the configuration file
3568 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3569 unprivileged caller, it causes Exim to give up its root privilege.
3570 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3571 completely disabled, and its use causes an immediate error exit.
3573 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3574 colon-separated list of macros which are considered safe and, if &%-D%& only
3575 supplies macros from this list, and the values are acceptable, then Exim will
3576 not give up root privilege if the caller is root, the Exim run-time user, or
3577 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3578 to be removed in the future. Acceptable values for the macros satisfy the
3579 regexp: &`^[A-Za-z0-9_/.-]*$`&
3581 The entire option (including equals sign if present) must all be within one
3582 command line item. &%-D%& can be used to set the value of a macro to the empty
3583 string, in which case the equals sign is optional. These two commands are
3589 To include spaces in a macro definition item, quotes must be used. If you use
3590 quotes, spaces are permitted around the macro name and the equals sign. For
3593 exim '-D ABC = something' ...
3595 &%-D%& may be repeated up to 10 times on a command line.
3596 Only macro names up to 22 letters long can be set.
3599 .vitem &%-d%&<&'debug&~options'&>
3601 .cindex "debugging" "list of selectors"
3602 .cindex "debugging" "&%-d%& option"
3603 This option causes debugging information to be written to the standard
3604 error stream. It is restricted to admin users because debugging output may show
3605 database queries that contain password information. Also, the details of users'
3606 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3607 writes an error message to the standard error stream and exits with a non-zero
3610 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3611 standard debugging data is output. This can be reduced, or increased to include
3612 some more rarely needed information, by directly following &%-d%& with a string
3613 made up of names preceded by plus or minus characters. These add or remove sets
3614 of debugging data, respectively. For example, &%-d+filter%& adds filter
3615 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3616 no spaces are allowed in the debug setting. The available debugging categories
3619 &`acl `& ACL interpretation
3620 &`auth `& authenticators
3621 &`deliver `& general delivery logic
3622 &`dns `& DNS lookups (see also resolver)
3623 &`dnsbl `& DNS black list (aka RBL) code
3624 &`exec `& arguments for &[execv()]& calls
3625 &`expand `& detailed debugging for string expansions
3626 &`filter `& filter handling
3627 &`hints_lookup `& hints data lookups
3628 &`host_lookup `& all types of name-to-IP address handling
3629 &`ident `& ident lookup
3630 &`interface `& lists of local interfaces
3631 &`lists `& matching things in lists
3632 &`load `& system load checks
3633 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3634 &<<CHAPlocalscan>>&)
3635 &`lookup `& general lookup code and all lookups
3636 &`memory `& memory handling
3637 &`noutf8 `& modifier: avoid UTF-8 line-drawing
3638 &`pid `& modifier: add pid to debug output lines
3639 &`process_info `& setting info for the process log
3640 &`queue_run `& queue runs
3641 &`receive `& general message reception logic
3642 &`resolver `& turn on the DNS resolver's debugging output
3643 &`retry `& retry handling
3644 &`rewrite `& address rewriting
3645 &`route `& address routing
3646 &`timestamp `& modifier: add timestamp to debug output lines
3648 &`transport `& transports
3649 &`uid `& changes of uid/gid and looking up uid/gid
3650 &`verify `& address verification logic
3651 &`all `& almost all of the above (see below), and also &%-v%&
3653 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3654 for &`-all`&. The reason for this is that &`+all`& is something that people
3655 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3656 is included, an awful lot of output that is very rarely of interest is
3657 generated, so it now has to be explicitly requested. However, &`-all`& does
3658 turn everything off.
3660 .cindex "resolver, debugging output"
3661 .cindex "DNS resolver, debugging output"
3662 The &`resolver`& option produces output only if the DNS resolver was compiled
3663 with DEBUG enabled. This is not the case in some operating systems. Also,
3664 unfortunately, debugging output from the DNS resolver is written to stdout
3667 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3668 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3669 However, the &`pid`& selector is forced when debugging is turned on for a
3670 daemon, which then passes it on to any re-executed Exims. Exim also
3671 automatically adds the pid to debug lines when several remote deliveries are
3674 The &`timestamp`& selector causes the current time to be inserted at the start
3675 of all debug output lines. This can be useful when trying to track down delays
3678 .cindex debugging "UTF-8 in"
3679 .cindex UTF-8 "in debug output"
3680 The &`noutf8`& selector disables the use of
3681 UTF-8 line-drawing characters to group related information.
3682 When disabled. ascii-art is used instead.
3683 Using the &`+all`& option does not set this modifier,
3685 If the &%debug_print%& option is set in any driver, it produces output whenever
3686 any debugging is selected, or if &%-v%& is used.
3688 .vitem &%-dd%&<&'debug&~options'&>
3690 This option behaves exactly like &%-d%& except when used on a command that
3691 starts a daemon process. In that case, debugging is turned off for the
3692 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3693 behaviour of the daemon without creating as much output as full debugging does.
3696 .oindex "&%-dropcr%&"
3697 This is an obsolete option that is now a no-op. It used to affect the way Exim
3698 handled CR and LF characters in incoming messages. What happens now is
3699 described in section &<<SECTlineendings>>&.
3703 .cindex "bounce message" "generating"
3704 This option specifies that an incoming message is a locally-generated delivery
3705 failure report. It is used internally by Exim when handling delivery failures
3706 and is not intended for external use. Its only effect is to stop Exim
3707 generating certain messages to the postmaster, as otherwise message cascades
3708 could occur in some situations. As part of the same option, a message id may
3709 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3710 new message contains the id, following &"R="&, as a cross-reference.
3713 .oindex "&%-e%&&'x'&"
3714 There are a number of Sendmail options starting with &%-oe%& which seem to be
3715 called by various programs without the leading &%o%& in the option. For
3716 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3717 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3719 .vitem &%-F%&&~<&'string'&>
3721 .cindex "sender" "name"
3722 .cindex "name" "of sender"
3723 This option sets the sender's full name for use when a locally-generated
3724 message is being accepted. In the absence of this option, the user's &'gecos'&
3725 entry from the password data is used. As users are generally permitted to alter
3726 their &'gecos'& entries, no security considerations are involved. White space
3727 between &%-F%& and the <&'string'&> is optional.
3729 .vitem &%-f%&&~<&'address'&>
3731 .cindex "sender" "address"
3732 .cindex "address" "sender"
3733 .cindex "trusted users"
3734 .cindex "envelope from"
3735 .cindex "envelope sender"
3736 .cindex "user" "trusted"
3737 This option sets the address of the envelope sender of a locally-generated
3738 message (also known as the return path). The option can normally be used only
3739 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3742 Processes running as root or the Exim user are always trusted. Other
3743 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3744 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3745 of a local message is set to the caller's login name at the default qualify
3748 There is one exception to the restriction on the use of &%-f%&: an empty sender
3749 can be specified by any user, trusted or not, to create a message that can
3750 never provoke a bounce. An empty sender can be specified either as an empty
3751 string, or as a pair of angle brackets with nothing between them, as in these
3752 examples of shell commands:
3754 exim -f '<>' user@domain
3755 exim -f "" user@domain
3757 In addition, the use of &%-f%& is not restricted when testing a filter file
3758 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3761 Allowing untrusted users to change the sender address does not of itself make
3762 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3763 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3764 though this can be overridden by setting &%no_local_from_check%&.
3767 .cindex "&""From""& line"
3768 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3769 given as two arguments or one combined argument). The sender of a
3770 locally-generated message can also be set (when permitted) by an initial
3771 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3772 if &%-f%& is also present, it overrides &"From&~"&.
3776 .cindex "submission fixups, suppressing (command-line)"
3777 This option is equivalent to an ACL applying:
3779 control = suppress_local_fixups
3781 for every message received. Note that Sendmail will complain about such
3782 bad formatting, where Exim silently just does not fix it up. This may change
3785 As this affects audit information, the caller must be a trusted user to use
3788 .vitem &%-h%&&~<&'number'&>
3790 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3791 This option is accepted for compatibility with Sendmail, but has no effect. (In
3792 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3797 .cindex "Solaris" "&'mail'& command"
3798 .cindex "dot" "in incoming non-SMTP message"
3799 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3800 line by itself should not terminate an incoming, non-SMTP message. I can find
3801 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3802 command in Solaris 2.4 uses it. See also &%-ti%&.
3804 .vitem &%-L%&&~<&'tag'&>
3806 .cindex "syslog" "process name; set with flag"
3807 This option is equivalent to setting &%syslog_processname%& in the config
3808 file and setting &%log_file_path%& to &`syslog`&.
3809 Its use is restricted to administrators. The configuration file has to be
3810 read and parsed, to determine access rights, before this is set and takes
3811 effect, so early configuration file errors will not honour this flag.
3813 The tag should not be longer than 32 characters.
3815 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3817 .cindex "forcing delivery"
3818 .cindex "delivery" "forcing attempt"
3819 .cindex "frozen messages" "forcing delivery"
3820 This option requests Exim to run a delivery attempt on each message in turn. If
3821 any of the messages are frozen, they are automatically thawed before the
3822 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3823 and &%hold_domains%& are ignored.
3826 .cindex "hints database" "overriding retry hints"
3827 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3828 the normal retry time has not yet been reached. This option requires the caller
3829 to be an admin user. However, there is an option called &%prod_requires_admin%&
3830 which can be set false to relax this restriction (and also the same requirement
3831 for the &%-q%&, &%-R%&, and &%-S%& options).
3833 The deliveries happen synchronously, that is, the original Exim process does
3834 not terminate until all the delivery attempts have finished. No output is
3835 produced unless there is a serious error. If you want to see what is happening,
3836 use the &%-v%& option as well, or inspect Exim's main log.
3838 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3840 .cindex "message" "adding recipients"
3841 .cindex "recipient" "adding"
3842 This option requests Exim to add the addresses to the list of recipients of the
3843 message (&"ar"& for &"add recipients"&). The first argument must be a message
3844 id, and the remaining ones must be email addresses. However, if the message is
3845 active (in the middle of a delivery attempt), it is not altered. This option
3846 can be used only by an admin user.
3848 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3849 &~<&'message&~id'&>"
3851 .cindex "SMTP" "passed connection"
3852 .cindex "SMTP" "multiple deliveries"
3853 .cindex "multiple SMTP deliveries"
3854 This option is not intended for use by external callers. It is used internally
3855 by Exim to invoke another instance of itself to deliver a waiting message using
3856 an existing SMTP connection, which is passed as the standard input. Details are
3857 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3858 must be root or the Exim user in order to use it.
3862 This option is not intended for use by external callers. It is used internally
3863 by Exim in conjunction with the &%-MC%& option. It signifies that the
3864 connection to the remote host has been authenticated.
3868 This option is not intended for use by external callers. It is used internally
3869 by Exim in conjunction with the &%-MC%& option. It signifies that the
3870 remote host supports the ESMTP &_DSN_& extension.
3874 This option is not intended for use by external callers. It is used internally
3875 by Exim in conjunction with the &%-d%& option
3876 to pass on an information string on the purpose of the process.
3878 .vitem &%-MCG%&&~<&'queue&~name'&>
3880 This option is not intended for use by external callers. It is used internally
3881 by Exim in conjunction with the &%-MC%& option. It signifies that an
3882 alternate queue is used, named by the following argument.
3886 This option is not intended for use by external callers. It is used internally
3887 by Exim in conjunction with the &%-MC%& option. It signifies that a
3888 remote host supports the ESMTP &_CHUNKING_& extension.
3892 This option is not intended for use by external callers. It is used internally
3893 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3894 which Exim is connected supports pipelining.
3896 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3898 This option is not intended for use by external callers. It is used internally
3899 by Exim in conjunction with the &%-MC%& option when the original delivery was
3900 started by a queue runner. It passes on the process id of the queue runner,
3901 together with the file descriptor number of an open pipe. Closure of the pipe
3902 signals the final completion of the sequence of processes that are passing
3903 messages through the same SMTP connection.
3906 .vitem &%-MCq%&&~<&'recipient&~address'&>&~<&'size'&>
3908 This option is not intended for use by external callers. It is used internally
3909 by Exim to implement quota checking for local users.
3914 This option is not intended for use by external callers. It is used internally
3915 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3916 ESMTP SIZE option should be used on messages delivered down the existing
3921 This option is not intended for use by external callers. It is used internally
3922 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3923 host to which Exim is connected supports TLS encryption.
3926 .vitem &%-MCr%&&~<&'SNI'&> &&&
3930 These options are not intended for use by external callers. It is used internally
3931 by Exim in conjunction with the &%-MCt%& option, and passes on the fact that
3932 a TLS Server Name Indication was sent as part of the channel establishment.
3933 The argument gives the SNI string.
3934 The "r" variant indicates a DANE-verified connection.
3937 .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
3939 This option is not intended for use by external callers. It is used internally
3940 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3941 connection is being proxied by a parent process for handling TLS encryption.
3942 The arguments give the local address and port being proxied, and the TLS cipher.
3944 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3946 .cindex "hints database" "not overridden by &%-Mc%&"
3947 .cindex "delivery" "manually started &-- not forced"
3948 This option requests Exim to run a delivery attempt on each message, in turn,
3949 but unlike the &%-M%& option, it does check for retry hints, and respects any
3950 that are found. This option is not very useful to external callers. It is
3951 provided mainly for internal use by Exim when it needs to re-invoke itself in
3952 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3953 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3954 respects retry times and other options such as &%hold_domains%& that are
3955 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3956 If you want to run a specific delivery as if in a queue run, you should use
3957 &%-q%& with a message id argument. A distinction between queue run deliveries
3958 and other deliveries is made in one or two places.
3960 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3962 .cindex "message" "changing sender"
3963 .cindex "sender" "changing"
3964 This option requests Exim to change the sender address in the message to the
3965 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3966 &"edit sender"&). There must be exactly two arguments. The first argument must
3967 be a message id, and the second one an email address. However, if the message
3968 is active (in the middle of a delivery attempt), its status is not altered.
3969 This option can be used only by an admin user.
3971 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3973 .cindex "freezing messages"
3974 .cindex "message" "manually freezing"
3975 This option requests Exim to mark each listed message as &"frozen"&. This
3976 prevents any delivery attempts taking place until the message is &"thawed"&,
3977 either manually or as a result of the &%auto_thaw%& configuration option.
3978 However, if any of the messages are active (in the middle of a delivery
3979 attempt), their status is not altered. This option can be used only by an admin
3982 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3984 .cindex "giving up on messages"
3985 .cindex "message" "abandoning delivery attempts"
3986 .cindex "delivery" "abandoning further attempts"
3987 This option requests Exim to give up trying to deliver the listed messages,
3988 including any that are frozen. However, if any of the messages are active,
3989 their status is not altered. For non-bounce messages, a delivery error message
3990 is sent to the sender, containing the text &"cancelled by administrator"&.
3991 Bounce messages are just discarded. This option can be used only by an admin
3994 .vitem &%-MG%&&~<&'queue&~name'&>&~<&'message&~id'&>&~<&'message&~id'&>&~...
3997 .cindex "named queues" "moving messages"
3998 .cindex "queue" "moving messages"
3999 This option requests that each listed message be moved from its current
4000 queue to the given named queue.
4001 The destination queue name argument is required, but can be an empty
4002 string to define the default queue.
4003 If the messages are not currently located in the default queue,
4004 a &%-qG<name>%& option will be required to define the source queue.
4006 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4008 .cindex "delivery" "cancelling all"
4009 This option requests Exim to mark all the recipient addresses in the messages
4010 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
4011 message is active (in the middle of a delivery attempt), its status is not
4012 altered. This option can be used only by an admin user.
4014 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
4016 .cindex "delivery" "cancelling by address"
4017 .cindex "recipient" "removing"
4018 .cindex "removing recipients"
4019 This option requests Exim to mark the given addresses as already delivered
4020 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
4021 the remaining ones must be email addresses. These are matched to recipient
4022 addresses in the message in a case-sensitive manner. If the message is active
4023 (in the middle of a delivery attempt), its status is not altered. This option
4024 can be used only by an admin user.
4026 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4028 .cindex "removing messages"
4029 .cindex "abandoning mail"
4030 .cindex "message" "manually discarding"
4031 This option requests Exim to remove the given messages from the queue. No
4032 bounce messages are sent; each message is simply forgotten. However, if any of
4033 the messages are active, their status is not altered. This option can be used
4034 only by an admin user or by the user who originally caused the message to be
4035 placed in the queue.
4040 . .cindex REQUIRETLS
4041 . This option is used to request REQUIRETLS processing on the message.
4042 . It is used internally by Exim in conjunction with -E when generating
4046 .vitem &%-Mset%&&~<&'message&~id'&>
4048 .cindex "testing" "string expansion"
4049 .cindex "expansion" "testing"
4050 This option is useful only in conjunction with &%-be%& (that is, when testing
4051 string expansions). Exim loads the given message from its spool before doing
4052 the test expansions, thus setting message-specific variables such as
4053 &$message_size$& and the header variables. The &$recipients$& variable is made
4054 available. This feature is provided to make it easier to test expansions that
4055 make use of these variables. However, this option can be used only by an admin
4056 user. See also &%-bem%&.
4058 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
4060 .cindex "thawing messages"
4061 .cindex "unfreezing messages"
4062 .cindex "frozen messages" "thawing"
4063 .cindex "message" "thawing frozen"
4064 This option requests Exim to &"thaw"& any of the listed messages that are
4065 &"frozen"&, so that delivery attempts can resume. However, if any of the
4066 messages are active, their status is not altered. This option can be used only
4069 .vitem &%-Mvb%&&~<&'message&~id'&>
4071 .cindex "listing" "message body"
4072 .cindex "message" "listing body of"
4073 This option causes the contents of the message body (-D) spool file to be
4074 written to the standard output. This option can be used only by an admin user.
4076 .vitem &%-Mvc%&&~<&'message&~id'&>
4078 .cindex "message" "listing in RFC 2822 format"
4079 .cindex "listing" "message in RFC 2822 format"
4080 This option causes a copy of the complete message (header lines plus body) to
4081 be written to the standard output in RFC 2822 format. This option can be used
4082 only by an admin user.
4084 .vitem &%-Mvh%&&~<&'message&~id'&>
4086 .cindex "listing" "message headers"
4087 .cindex "header lines" "listing"
4088 .cindex "message" "listing header lines"
4089 This option causes the contents of the message headers (-H) spool file to be
4090 written to the standard output. This option can be used only by an admin user.
4092 .vitem &%-Mvl%&&~<&'message&~id'&>
4094 .cindex "listing" "message log"
4095 .cindex "message" "listing message log"
4096 This option causes the contents of the message log spool file to be written to
4097 the standard output. This option can be used only by an admin user.
4101 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
4102 treats it that way too.
4106 .cindex "debugging" "&%-N%& option"
4107 .cindex "debugging" "suppressing delivery"
4108 This is a debugging option that inhibits delivery of a message at the transport
4109 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4110 it just doesn't actually transport the message, but instead behaves as if it
4111 had successfully done so. However, it does not make any updates to the retry
4112 database, and the log entries for deliveries are flagged with &"*>"& rather
4115 Because &%-N%& discards any message to which it applies, only root or the Exim
4116 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4117 words, an ordinary user can use it only when supplying an incoming message to
4118 which it will apply. Although transportation never fails when &%-N%& is set, an
4119 address may be deferred because of a configuration problem on a transport, or a
4120 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4121 the message, and applies to any subsequent delivery attempts that may happen
4126 This option is interpreted by Sendmail to mean &"no aliasing"&.
4127 For normal modes of operation, it is ignored by Exim.
4128 When combined with &%-bP%& it makes the output more terse (suppresses
4129 option names, environment values and config pretty printing).
4131 .vitem &%-O%&&~<&'data'&>
4133 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4136 .vitem &%-oA%&&~<&'file&~name'&>
4138 .cindex "Sendmail compatibility" "&%-oA%& option"
4139 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4140 alternative alias filename. Exim handles &%-bi%& differently; see the
4143 .vitem &%-oB%&&~<&'n'&>
4145 .cindex "SMTP" "passed connection"
4146 .cindex "SMTP" "multiple deliveries"
4147 .cindex "multiple SMTP deliveries"
4148 This is a debugging option which limits the maximum number of messages that can
4149 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4150 transport. If <&'n'&> is omitted, the limit is set to 1.
4154 .cindex "background delivery"
4155 .cindex "delivery" "in the background"
4156 This option applies to all modes in which Exim accepts incoming messages,
4157 including the listening daemon. It requests &"background"& delivery of such
4158 messages, which means that the accepting process automatically starts a
4159 delivery process for each message received, but does not wait for the delivery
4160 processes to finish.
4162 When all the messages have been received, the reception process exits,
4163 leaving the delivery processes to finish in their own time. The standard output
4164 and error streams are closed at the start of each delivery process.
4165 This is the default action if none of the &%-od%& options are present.
4167 If one of the queueing options in the configuration file
4168 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4169 overrides it if &%queue_only_override%& is set true, which is the default
4170 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4174 .cindex "foreground delivery"
4175 .cindex "delivery" "in the foreground"
4176 This option requests &"foreground"& (synchronous) delivery when Exim has
4177 accepted a locally-generated message. (For the daemon it is exactly the same as
4178 &%-odb%&.) A delivery process is automatically started to deliver the message,
4179 and Exim waits for it to complete before proceeding.
4181 The original Exim reception process does not finish until the delivery
4182 process for the final message has ended. The standard error stream is left open
4185 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4186 false and one of the queueing options in the configuration file is in effect.
4188 If there is a temporary delivery error during foreground delivery, the
4189 message is left in the queue for later delivery, and the original reception
4190 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4191 restricted configuration that never queues messages.
4196 This option is synonymous with &%-odf%&. It is provided for compatibility with
4201 .cindex "non-immediate delivery"
4202 .cindex "delivery" "suppressing immediate"
4203 .cindex "queueing incoming messages"
4204 This option applies to all modes in which Exim accepts incoming messages,
4205 including the listening daemon. It specifies that the accepting process should
4206 not automatically start a delivery process for each message received. Messages
4207 are placed in the queue, and remain there until a subsequent queue runner
4208 process encounters them. There are several configuration options (such as
4209 &%queue_only%&) that can be used to queue incoming messages under certain
4210 conditions. This option overrides all of them and also &%-odqs%&. It always
4215 .cindex "SMTP" "delaying delivery"
4216 .cindex "first pass routing"
4217 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4218 However, like &%-odb%& and &%-odi%&, this option has no effect if
4219 &%queue_only_override%& is false and one of the queueing options in the
4220 configuration file is in effect.
4222 When &%-odqs%& does operate, a delivery process is started for each incoming
4223 message, in the background by default, but in the foreground if &%-odi%& is
4224 also present. The recipient addresses are routed, and local deliveries are done
4225 in the normal way. However, if any SMTP deliveries are required, they are not
4226 done at this time, so the message remains in the queue until a subsequent queue
4227 runner process encounters it. Because routing was done, Exim knows which
4228 messages are waiting for which hosts, and so a number of messages for the same
4229 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4230 configuration option has the same effect for specific domains. See also the
4235 .cindex "error" "reporting"
4236 If an error is detected while a non-SMTP message is being received (for
4237 example, a malformed address), the error is reported to the sender in a mail
4240 .cindex "return code" "for &%-oee%&"
4242 this error message is successfully sent, the Exim receiving process
4243 exits with a return code of zero. If not, the return code is 2 if the problem
4244 is that the original message has no recipients, or 1 for any other error.
4245 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4249 .cindex "error" "reporting"
4250 .cindex "return code" "for &%-oem%&"
4251 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4252 return code, whether or not the error message was successfully sent.
4253 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4257 .cindex "error" "reporting"
4258 If an error is detected while a non-SMTP message is being received, the
4259 error is reported by writing a message to the standard error file (stderr).
4260 .cindex "return code" "for &%-oep%&"
4261 The return code is 1 for all errors.
4265 .cindex "error" "reporting"
4266 This option is supported for compatibility with Sendmail, but has the same
4271 .cindex "error" "reporting"
4272 This option is supported for compatibility with Sendmail, but has the same
4277 .cindex "dot" "in incoming non-SMTP message"
4278 This option, which has the same effect as &%-i%&, specifies that a dot on a
4279 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4280 single dot does terminate, though Exim does no special processing for other
4281 lines that start with a dot. This option is set by default if Exim is called as
4282 &'rmail'&. See also &%-ti%&.
4285 .oindex "&%-oitrue%&"
4286 This option is treated as synonymous with &%-oi%&.
4288 .vitem &%-oMa%&&~<&'host&~address'&>
4290 .cindex "sender" "host address, specifying for local message"
4291 A number of options starting with &%-oM%& can be used to set values associated
4292 with remote hosts on locally-submitted messages (that is, messages not received
4293 over TCP/IP). These options can be used by any caller in conjunction with the
4294 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4295 other circumstances, they are ignored unless the caller is trusted.
4297 The &%-oMa%& option sets the sender host address. This may include a port
4298 number at the end, after a full stop (period). For example:
4300 exim -bs -oMa 10.9.8.7.1234
4302 An alternative syntax is to enclose the IP address in square brackets,
4303 followed by a colon and the port number:
4305 exim -bs -oMa [10.9.8.7]:1234
4307 The IP address is placed in the &$sender_host_address$& variable, and the
4308 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4309 are present on the command line, the sender host IP address is taken from
4310 whichever one is last.
4312 .vitem &%-oMaa%&&~<&'name'&>
4314 .cindex "authentication" "name, specifying for local message"
4315 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4316 option sets the value of &$sender_host_authenticated$& (the authenticator
4317 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4318 This option can be used with &%-bh%& and &%-bs%& to set up an
4319 authenticated SMTP session without actually using the SMTP AUTH command.
4321 .vitem &%-oMai%&&~<&'string'&>
4323 .cindex "authentication" "id, specifying for local message"
4324 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4325 option sets the value of &$authenticated_id$& (the id that was authenticated).
4326 This overrides the default value (the caller's login id, except with &%-bh%&,
4327 where there is no default) for messages from local sources. See chapter
4328 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4330 .vitem &%-oMas%&&~<&'address'&>
4332 .cindex "authentication" "sender, specifying for local message"
4333 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4334 option sets the authenticated sender value in &$authenticated_sender$&. It
4335 overrides the sender address that is created from the caller's login id for
4336 messages from local sources, except when &%-bh%& is used, when there is no
4337 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4338 specified on a MAIL command overrides this value. See chapter
4339 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4341 .vitem &%-oMi%&&~<&'interface&~address'&>
4343 .cindex "interface" "address, specifying for local message"
4344 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4345 option sets the IP interface address value. A port number may be included,
4346 using the same syntax as for &%-oMa%&. The interface address is placed in
4347 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4349 .vitem &%-oMm%&&~<&'message&~reference'&>
4351 .cindex "message reference" "message reference, specifying for local message"
4352 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4353 option sets the message reference, e.g. message-id, and is logged during
4354 delivery. This is useful when some kind of audit trail is required to tie
4355 messages together. The format of the message reference is checked and will
4356 abort if the format is invalid. The option will only be accepted if exim is
4357 running in trusted mode, not as any regular user.
4359 The best example of a message reference is when Exim sends a bounce message.
4360 The message reference is the message-id of the original message for which Exim
4361 is sending the bounce.
4363 .vitem &%-oMr%&&~<&'protocol&~name'&>
4365 .cindex "protocol, specifying for local message"
4366 .vindex "&$received_protocol$&"
4367 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4368 option sets the received protocol value that is stored in
4369 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4370 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4371 SMTP protocol names (see the description of &$received_protocol$& in section
4372 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4373 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4374 be set by &%-oMr%&. Repeated use of this option is not supported.
4376 .vitem &%-oMs%&&~<&'host&~name'&>
4378 .cindex "sender" "host name, specifying for local message"
4379 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4380 option sets the sender host name in &$sender_host_name$&. When this option is
4381 present, Exim does not attempt to look up a host name from an IP address; it
4382 uses the name it is given.
4384 .vitem &%-oMt%&&~<&'ident&~string'&>
4386 .cindex "sender" "ident string, specifying for local message"
4387 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4388 option sets the sender ident value in &$sender_ident$&. The default setting for
4389 local callers is the login id of the calling process, except when &%-bh%& is
4390 used, when there is no default.
4394 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4395 In Sendmail, this option means &"me too"&, indicating that the sender of a
4396 message should receive a copy of the message if the sender appears in an alias
4397 expansion. Exim always does this, so the option does nothing.
4401 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4402 This option is ignored. In Sendmail it specifies &"old style headers"&,
4403 whatever that means.
4405 .vitem &%-oP%&&~<&'path'&>
4407 .cindex "pid (process id)" "of daemon"
4408 .cindex "daemon" "process id (pid)"
4409 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4410 value. The option specifies the file to which the process id of the daemon is
4411 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4412 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4413 because in those cases, the normal pid file is not used.
4417 .cindex "pid (process id)" "of daemon"
4418 .cindex "daemon" "process id (pid)"
4419 This option is not intended for general use.
4420 The daemon uses it when terminating due to a SIGTEM, possibly in
4421 combination with &%-oP%&&~<&'path'&>.
4422 It causes the pid file to be removed.
4424 .vitem &%-or%&&~<&'time'&>
4426 .cindex "timeout" "for non-SMTP input"
4427 This option sets a timeout value for incoming non-SMTP messages. If it is not
4428 set, Exim will wait forever for the standard input. The value can also be set
4429 by the &%receive_timeout%& option. The format used for specifying times is
4430 described in section &<<SECTtimeformat>>&.
4432 .vitem &%-os%&&~<&'time'&>
4434 .cindex "timeout" "for SMTP input"
4435 .cindex "SMTP" "input timeout"
4436 This option sets a timeout value for incoming SMTP messages. The timeout
4437 applies to each SMTP command and block of data. The value can also be set by
4438 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4439 for specifying times is described in section &<<SECTtimeformat>>&.
4443 This option has exactly the same effect as &%-v%&.
4445 .vitem &%-oX%&&~<&'number&~or&~string'&>
4447 .cindex "TCP/IP" "setting listening ports"
4448 .cindex "TCP/IP" "setting listening interfaces"
4449 .cindex "port" "receiving TCP/IP"
4450 This option is relevant only when the &%-bd%& (start listening daemon) option
4451 is also given. It controls which ports and interfaces the daemon uses. Details
4452 of the syntax, and how it interacts with configuration file options, are given
4453 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4454 file is written unless &%-oP%& is also present to specify a pid filename.
4459 .cindex "daemon notifier socket"
4460 This option controls the creation of an inter-process communications endpoint
4462 It is only relevant when the &%-bd%& (start listening daemon) option is also
4464 Normally the daemon creates this socket, unless a &%-oX%& and &*no*& &%-oP%&
4465 option is also present.
4466 If this option is given then the socket will not be created. This could be
4467 required if the system is running multiple daemons.
4469 The socket is currently used for
4471 fast ramp-up of queue runner processes
4473 obtaining a current queue size
4479 .cindex "Perl" "starting the interpreter"
4480 This option applies when an embedded Perl interpreter is linked with Exim (see
4481 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4482 option, forcing the starting of the interpreter to be delayed until it is
4487 .cindex "Perl" "starting the interpreter"
4488 This option applies when an embedded Perl interpreter is linked with Exim (see
4489 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4490 option, forcing the starting of the interpreter to occur as soon as Exim is
4493 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4495 For compatibility with Sendmail, this option is equivalent to
4497 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4499 It sets the incoming protocol and host name (for trusted callers). The
4500 host name and its colon can be omitted when only the protocol is to be set.
4501 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4502 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4503 or &`s`& using this option (but that does not seem a real limitation).
4504 Repeated use of this option is not supported.
4508 .cindex "queue runner" "starting manually"
4509 This option is normally restricted to admin users. However, there is a
4510 configuration option called &%prod_requires_admin%& which can be set false to
4511 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4512 and &%-S%& options).
4514 .cindex "queue runner" "description of operation"
4515 If other commandline options do not specify an action,
4516 the &%-q%& option starts one queue runner process. This scans the queue of
4517 waiting messages, and runs a delivery process for each one in turn. It waits
4518 for each delivery process to finish before starting the next one. A delivery
4519 process may not actually do any deliveries if the retry times for the addresses
4520 have not been reached. Use &%-qf%& (see below) if you want to override this.
4523 .cindex "SMTP" "passed connection"
4524 .cindex "SMTP" "multiple deliveries"
4525 .cindex "multiple SMTP deliveries"
4526 the delivery process spawns other processes to deliver other messages down
4527 passed SMTP connections, the queue runner waits for these to finish before
4530 When all the queued messages have been considered, the original queue runner
4531 process terminates. In other words, a single pass is made over the waiting
4532 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4533 this to be repeated periodically.
4535 Exim processes the waiting messages in an unpredictable order. It isn't very
4536 random, but it is likely to be different each time, which is all that matters.
4537 If one particular message screws up a remote MTA, other messages to the same
4538 MTA have a chance of getting through if they get tried first.
4540 It is possible to cause the messages to be processed in lexical message id
4541 order, which is essentially the order in which they arrived, by setting the
4542 &%queue_run_in_order%& option, but this is not recommended for normal use.
4544 .vitem &%-q%&<&'qflags'&>
4545 The &%-q%& option may be followed by one or more flag letters that change its
4546 behaviour. They are all optional, but if more than one is present, they must
4547 appear in the correct order. Each flag is described in a separate item below.
4551 .cindex "queue" "double scanning"
4552 .cindex "queue" "routing"
4553 .cindex "routing" "whole queue before delivery"
4554 .cindex "first pass routing"
4555 .cindex "queue runner" "two phase"
4556 An option starting with &%-qq%& requests a two-stage queue run. In the first
4557 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4558 every domain. Addresses are routed, local deliveries happen, but no remote
4561 Performance will be best if the &%queue_run_in_order%& option is false.
4562 If that is so and the &%queue_fast_ramp%& option is true then
4563 in the first phase of the run,
4564 once a threshold number of messages are routed for a given host,
4565 a delivery process is forked in parallel with the rest of the scan.
4567 .cindex "hints database" "remembering routing"
4568 The hints database that remembers which messages are waiting for specific hosts
4569 is updated, as if delivery to those hosts had been deferred. After this is
4570 complete, a second, normal queue scan happens, with routing and delivery taking
4571 place as normal. Messages that are routed to the same host should mostly be
4572 delivered down a single SMTP
4573 .cindex "SMTP" "passed connection"
4574 .cindex "SMTP" "multiple deliveries"
4575 .cindex "multiple SMTP deliveries"
4576 connection because of the hints that were set up during the first queue scan.
4577 This option may be useful for hosts that are connected to the Internet
4580 .vitem &%-q[q]i...%&
4582 .cindex "queue" "initial delivery"
4583 If the &'i'& flag is present, the queue runner runs delivery processes only for
4584 those messages that haven't previously been tried. (&'i'& stands for &"initial
4585 delivery"&.) This can be helpful if you are putting messages in the queue using
4586 &%-odq%& and want a queue runner just to process the new messages.
4588 .vitem &%-q[q][i]f...%&
4590 .cindex "queue" "forcing delivery"
4591 .cindex "delivery" "forcing in queue run"
4592 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4593 message, whereas without &'f'& only those non-frozen addresses that have passed
4594 their retry times are tried.
4596 .vitem &%-q[q][i]ff...%&
4598 .cindex "frozen messages" "forcing delivery"
4599 If &'ff'& is present, a delivery attempt is forced for every message, whether
4602 .vitem &%-q[q][i][f[f]]l%&
4604 .cindex "queue" "local deliveries only"
4605 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4606 be done. If a message requires any remote deliveries, it remains in the queue
4609 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4612 .cindex "named queues" "deliver from"
4613 .cindex "queue" "delivering specific messages"
4614 If the &'G'& flag and a name is present, the queue runner operates on the
4615 queue with the given name rather than the default queue.
4616 The name should not contain a &'/'& character.
4617 For a periodic queue run (see below)
4618 append to the name a slash and a time value.
4620 If other commandline options specify an action, a &'-qG<name>'& option
4621 will specify a queue to operate on.
4624 exim -bp -qGquarantine
4626 exim -qGoffpeak -Rf @special.domain.example
4629 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4630 When scanning the queue, Exim can be made to skip over messages whose ids are
4631 lexically less than a given value by following the &%-q%& option with a
4632 starting message id. For example:
4634 exim -q 0t5C6f-0000c8-00
4636 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4637 second message id is given, messages whose ids are lexically greater than it
4638 are also skipped. If the same id is given twice, for example,
4640 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4642 just one delivery process is started, for that message. This differs from
4643 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4644 that it counts as a delivery from a queue run. Note that the selection
4645 mechanism does not affect the order in which the messages are scanned. There
4646 are also other ways of selecting specific sets of messages for delivery in a
4647 queue run &-- see &%-R%& and &%-S%&.
4649 .vitem &%-q%&<&'qflags'&><&'time'&>
4650 .cindex "queue runner" "starting periodically"
4651 .cindex "periodic queue running"
4652 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4653 starting a queue runner process at intervals specified by the given time value
4654 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4655 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4656 single daemon process handles both functions. A common way of starting up a
4657 combined daemon at system boot time is to use a command such as
4659 /usr/exim/bin/exim -bd -q30m
4661 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4662 process every 30 minutes.
4664 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4665 pid file is written unless one is explicitly requested by the &%-oP%& option.
4667 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4669 This option is synonymous with &%-R%&. It is provided for Sendmail
4672 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4674 This option is synonymous with &%-S%&.
4676 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4678 .cindex "queue runner" "for specific recipients"
4679 .cindex "delivery" "to given domain"
4680 .cindex "domain" "delivery to"
4681 The <&'rsflags'&> may be empty, in which case the white space before the string
4682 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4683 which are the possible values for <&'rsflags'&>. White space is required if
4684 <&'rsflags'&> is not empty.
4686 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4687 perform a single queue run, except that, when scanning the messages on the
4688 queue, Exim processes only those that have at least one undelivered recipient
4689 address containing the given string, which is checked in a case-independent
4690 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4691 regular expression; otherwise it is a literal string.
4693 If you want to do periodic queue runs for messages with specific recipients,
4694 you can combine &%-R%& with &%-q%& and a time value. For example:
4696 exim -q25m -R @special.domain.example
4698 This example does a queue run for messages with recipients in the given domain
4699 every 25 minutes. Any additional flags that are specified with &%-q%& are
4700 applied to each queue run.
4702 Once a message is selected for delivery by this mechanism, all its addresses
4703 are processed. For the first selected message, Exim overrides any retry
4704 information and forces a delivery attempt for each undelivered address. This
4705 means that if delivery of any address in the first message is successful, any
4706 existing retry information is deleted, and so delivery attempts for that
4707 address in subsequently selected messages (which are processed without forcing)
4708 will run. However, if delivery of any address does not succeed, the retry
4709 information is updated, and in subsequently selected messages, the failing
4710 address will be skipped.
4712 .cindex "frozen messages" "forcing delivery"
4713 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4714 all selected messages, not just the first; frozen messages are included when
4717 The &%-R%& option makes it straightforward to initiate delivery of all messages
4718 to a given domain after a host has been down for some time. When the SMTP
4719 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4720 effect is to run Exim with the &%-R%& option, but it can be configured to run
4721 an arbitrary command instead.
4725 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4727 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4729 .cindex "delivery" "from given sender"
4730 .cindex "queue runner" "for specific senders"
4731 This option acts like &%-R%& except that it checks the string against each
4732 message's sender instead of against the recipients. If &%-R%& is also set, both
4733 conditions must be met for a message to be selected. If either of the options
4734 has &'f'& or &'ff'& in its flags, the associated action is taken.
4736 .vitem &%-Tqt%&&~<&'times'&>
4738 This is an option that is exclusively for use by the Exim testing suite. It is not
4739 recognized when Exim is run normally. It allows for the setting up of explicit
4740 &"queue times"& so that various warning/retry features can be tested.
4744 .cindex "recipient" "extracting from header lines"
4745 .cindex "&'Bcc:'& header line"
4746 .cindex "&'Cc:'& header line"
4747 .cindex "&'To:'& header line"
4748 When Exim is receiving a locally-generated, non-SMTP message on its standard
4749 input, the &%-t%& option causes the recipients of the message to be obtained
4750 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4751 from the command arguments. The addresses are extracted before any rewriting
4752 takes place and the &'Bcc:'& header line, if present, is then removed.
4754 .cindex "Sendmail compatibility" "&%-t%& option"
4755 If the command has any arguments, they specify addresses to which the message
4756 is &'not'& to be delivered. That is, the argument addresses are removed from
4757 the recipients list obtained from the headers. This is compatible with Smail 3
4758 and in accordance with the documented behaviour of several versions of
4759 Sendmail, as described in man pages on a number of operating systems (e.g.
4760 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4761 argument addresses to those obtained from the headers, and the O'Reilly
4762 Sendmail book documents it that way. Exim can be made to add argument addresses
4763 instead of subtracting them by setting the option
4764 &%extract_addresses_remove_arguments%& false.
4766 .cindex "&%Resent-%& header lines" "with &%-t%&"
4767 If there are any &%Resent-%& header lines in the message, Exim extracts
4768 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4769 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4770 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4771 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4773 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4774 message is resent several times). The RFC also specifies that they should be
4775 added at the front of the message, and separated by &'Received:'& lines. It is
4776 not at all clear how &%-t%& should operate in the present of multiple sets,
4777 nor indeed exactly what constitutes a &"set"&.
4778 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4779 are often added at the end of the header, and if a message is resent more than
4780 once, it is common for the original set of &%Resent-%& headers to be renamed as
4781 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4785 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4786 compatibility with Sendmail.
4788 .vitem &%-tls-on-connect%&
4789 .oindex "&%-tls-on-connect%&"
4790 .cindex "TLS" "use without STARTTLS"
4791 .cindex "TLS" "automatic start"
4792 This option is available when Exim is compiled with TLS support. It forces all
4793 incoming SMTP connections to behave as if the incoming port is listed in the
4794 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4795 &<<CHAPTLS>>& for further details.
4800 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4801 Sendmail uses this option for &"initial message submission"&, and its
4802 documentation states that in future releases, it may complain about
4803 syntactically invalid messages rather than fixing them when this flag is not
4804 set. Exim ignores this option.
4808 This option causes Exim to write information to the standard error stream,
4809 describing what it is doing. In particular, it shows the log lines for
4810 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4811 dialogue is shown. Some of the log lines shown may not actually be written to
4812 the log if the setting of &%log_selector%& discards them. Any relevant
4813 selectors are shown with each log line. If none are shown, the logging is
4818 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4819 National Language Support extended characters in the body of the mail item"&).
4820 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4823 .vitem &%-X%&&~<&'logfile'&>
4825 This option is interpreted by Sendmail to cause debug information to be sent
4826 to the named file. It is ignored by Exim.
4828 .vitem &%-z%&&~<&'log-line'&>
4830 This option writes its argument to Exim's logfile.
4831 Use is restricted to administrators; the intent is for operational notes.
4832 Quotes should be used to maintain a multi-word item as a single argument,
4840 . ////////////////////////////////////////////////////////////////////////////
4841 . Insert a stylized DocBook comment here, to identify the end of the command
4842 . line options. This is for the benefit of the Perl script that automatically
4843 . creates a man page for the options.
4844 . ////////////////////////////////////////////////////////////////////////////
4847 <!-- === End of command line options === -->
4854 . ////////////////////////////////////////////////////////////////////////////
4855 . ////////////////////////////////////////////////////////////////////////////
4858 .chapter "The Exim runtime configuration file" "CHAPconf" &&&
4859 "The runtime configuration file"
4861 .cindex "runtime configuration"
4862 .cindex "configuration file" "general description"
4863 .cindex "CONFIGURE_FILE"
4864 .cindex "configuration file" "errors in"
4865 .cindex "error" "in configuration file"
4866 .cindex "return code" "for bad configuration"
4867 Exim uses a single runtime configuration file that is read whenever an Exim
4868 binary is executed. Note that in normal operation, this happens frequently,
4869 because Exim is designed to operate in a distributed manner, without central
4872 If a syntax error is detected while reading the configuration file, Exim
4873 writes a message on the standard error, and exits with a non-zero return code.
4874 The message is also written to the panic log. &*Note*&: Only simple syntax
4875 errors can be detected at this time. The values of any expanded options are
4876 not checked until the expansion happens, even when the expansion does not
4877 actually alter the string.
4879 The name of the configuration file is compiled into the binary for security
4880 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4881 most configurations, this specifies a single file. However, it is permitted to
4882 give a colon-separated list of filenames, in which case Exim uses the first
4883 existing file in the list.
4886 .cindex "EXIM_GROUP"
4887 .cindex "CONFIGURE_OWNER"
4888 .cindex "CONFIGURE_GROUP"
4889 .cindex "configuration file" "ownership"
4890 .cindex "ownership" "configuration file"
4891 The runtime configuration file must be owned by root or by the user that is
4892 specified at compile time by the CONFIGURE_OWNER option (if set). The
4893 configuration file must not be world-writeable, or group-writeable unless its
4894 group is the root group or the one specified at compile time by the
4895 CONFIGURE_GROUP option.
4897 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4898 to root, anybody who is able to edit the runtime configuration file has an
4899 easy way to run commands as root. If you specify a user or group in the
4900 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4901 who are members of that group will trivially be able to obtain root privileges.
4903 Up to Exim version 4.72, the runtime configuration file was also permitted to
4904 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4905 since it offered a simple privilege escalation for any attacker who managed to
4906 compromise the Exim user account.
4908 A default configuration file, which will work correctly in simple situations,
4909 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4910 defines just one filename, the installation process copies the default
4911 configuration to a new file of that name if it did not previously exist. If
4912 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4913 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4918 .section "Using a different configuration file" "SECID40"
4919 .cindex "configuration file" "alternate"
4920 A one-off alternate configuration can be specified by the &%-C%& command line
4921 option, which may specify a single file or a list of files. However, when
4922 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4923 unless the argument for &%-C%& is identical to the built-in value from
4924 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4925 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4926 is useful mainly for checking the syntax of configuration files before
4927 installing them. No owner or group checks are done on a configuration file
4928 specified by &%-C%&, if root privilege has been dropped.
4930 Even the Exim user is not trusted to specify an arbitrary configuration file
4931 with the &%-C%& option to be used with root privileges, unless that file is
4932 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4933 testing a configuration using &%-C%& right through message reception and
4934 delivery, even if the caller is root. The reception works, but by that time,
4935 Exim is running as the Exim user, so when it re-execs to regain privilege for
4936 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4937 can test reception and delivery using two separate commands (one to put a
4938 message in the queue, using &%-odq%&, and another to do the delivery, using
4941 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4942 prefix string with which any file named in a &%-C%& command line option must
4943 start. In addition, the filename must not contain the sequence &"&`/../`&"&.
4944 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any
4945 filename can be used with &%-C%&.
4947 One-off changes to a configuration can be specified by the &%-D%& command line
4948 option, which defines and overrides values for macros used inside the
4949 configuration file. However, like &%-C%&, the use of this option by a
4950 non-privileged user causes Exim to discard its root privilege.
4951 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4952 completely disabled, and its use causes an immediate error exit.
4954 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4955 to declare certain macro names trusted, such that root privilege will not
4956 necessarily be discarded.
4957 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4958 considered safe and, if &%-D%& only supplies macros from this list, and the
4959 values are acceptable, then Exim will not give up root privilege if the caller
4960 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4961 transition mechanism and is expected to be removed in the future. Acceptable
4962 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4964 Some sites may wish to use the same Exim binary on different machines that
4965 share a file system, but to use different configuration files on each machine.
4966 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4967 looks for a file whose name is the configuration filename followed by a dot
4968 and the machine's node name, as obtained from the &[uname()]& function. If this
4969 file does not exist, the standard name is tried. This processing occurs for
4970 each filename in the list given by CONFIGURE_FILE or &%-C%&.
4972 In some esoteric situations different versions of Exim may be run under
4973 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4974 help with this. See the comments in &_src/EDITME_& for details.
4978 .section "Configuration file format" "SECTconffilfor"
4979 .cindex "configuration file" "format of"
4980 .cindex "format" "configuration file"
4981 Exim's configuration file is divided into a number of different parts. General
4982 option settings must always appear at the start of the file. The other parts
4983 are all optional, and may appear in any order. Each part other than the first
4984 is introduced by the word &"begin"& followed by at least one literal
4985 space, and the name of the part. The optional parts are:
4988 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4991 .cindex "AUTH" "configuration"
4992 &'authenticators'&: Configuration settings for the authenticator drivers. These
4993 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4995 &'routers'&: Configuration settings for the router drivers. Routers process
4996 addresses and determine how the message is to be delivered (see chapters
4997 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4999 &'transports'&: Configuration settings for the transport drivers. Transports
5000 define mechanisms for copying messages to destinations (see chapters
5001 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
5003 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
5004 If there is no retry section, or if it is empty (that is, no retry rules are
5005 defined), Exim will not retry deliveries. In this situation, temporary errors
5006 are treated the same as permanent errors. Retry rules are discussed in chapter
5009 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
5010 when new addresses are generated during delivery. Rewriting is discussed in
5011 chapter &<<CHAPrewrite>>&.
5013 &'local_scan'&: Private options for the &[local_scan()]& function. If you
5014 want to use this feature, you must set
5016 LOCAL_SCAN_HAS_OPTIONS=yes
5018 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
5019 facility are given in chapter &<<CHAPlocalscan>>&.
5022 .cindex "configuration file" "leading white space in"
5023 .cindex "configuration file" "trailing white space in"
5024 .cindex "white space" "in configuration file"
5025 Leading and trailing white space in configuration lines is always ignored.
5027 Blank lines in the file, and lines starting with a # character (ignoring
5028 leading white space) are treated as comments and are ignored. &*Note*&: A
5029 # character other than at the beginning of a line is not treated specially,
5030 and does not introduce a comment.
5032 Any non-comment line can be continued by ending it with a backslash. Note that
5033 the general rule for white space means that trailing white space after the
5034 backslash and leading white space at the start of continuation
5035 lines is ignored. Comment lines beginning with # (but not empty lines) may
5036 appear in the middle of a sequence of continuation lines.
5038 A convenient way to create a configuration file is to start from the
5039 default, which is supplied in &_src/configure.default_&, and add, delete, or
5040 change settings as required.
5042 The ACLs, retry rules, and rewriting rules have their own syntax which is
5043 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
5044 respectively. The other parts of the configuration file have some syntactic
5045 items in common, and these are described below, from section &<<SECTcos>>&
5046 onwards. Before that, the inclusion, macro, and conditional facilities are
5051 .section "File inclusions in the configuration file" "SECID41"
5052 .cindex "inclusions in configuration file"
5053 .cindex "configuration file" "including other files"
5054 .cindex "&`.include`& in configuration file"
5055 .cindex "&`.include_if_exists`& in configuration file"
5056 You can include other files inside Exim's runtime configuration file by
5059 &`.include`& <&'filename'&>
5060 &`.include_if_exists`& <&'filename'&>
5062 on a line by itself. Double quotes round the filename are optional. If you use
5063 the first form, a configuration error occurs if the file does not exist; the
5064 second form does nothing for non-existent files.
5065 The first form allows a relative name. It is resolved relative to
5066 the directory of the including file. For the second form an absolute filename
5069 Includes may be nested to any depth, but remember that Exim reads its
5070 configuration file often, so it is a good idea to keep them to a minimum.
5071 If you change the contents of an included file, you must HUP the daemon,
5072 because an included file is read only when the configuration itself is read.
5074 The processing of inclusions happens early, at a physical line level, so, like
5075 comment lines, an inclusion can be used in the middle of an option setting,
5078 hosts_lookup = a.b.c \
5081 Include processing happens after macro processing (see below). Its effect is to
5082 process the lines of the included file as if they occurred inline where the
5087 .section "Macros in the configuration file" "SECTmacrodefs"
5088 .cindex "macro" "description of"
5089 .cindex "configuration file" "macros"
5090 If a line in the main part of the configuration (that is, before the first
5091 &"begin"& line) begins with an upper case letter, it is taken as a macro
5092 definition, and must be of the form
5094 <&'name'&> = <&'rest of line'&>
5096 The name must consist of letters, digits, and underscores, and need not all be
5097 in upper case, though that is recommended. The rest of the line, including any
5098 continuations, is the replacement text, and has leading and trailing white
5099 space removed. Quotes are not removed. The replacement text can never end with
5100 a backslash character, but this doesn't seem to be a serious limitation.
5102 Macros may also be defined between router, transport, authenticator, or ACL
5103 definitions. They may not, however, be defined within an individual driver or
5104 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
5106 .section "Macro substitution" "SECID42"
5107 Once a macro is defined, all subsequent lines in the file (and any included
5108 files) are scanned for the macro name; if there are several macros, the line is
5109 scanned for each, in turn, in the order in which the macros are defined. The
5110 replacement text is not re-scanned for the current macro, though it is scanned
5111 for subsequently defined macros. For this reason, a macro name may not contain
5112 the name of a previously defined macro as a substring. You could, for example,
5115 &`ABCD_XYZ = `&<&'something'&>
5116 &`ABCD = `&<&'something else'&>
5118 but putting the definitions in the opposite order would provoke a configuration
5119 error. Macro expansion is applied to individual physical lines from the file,
5120 before checking for line continuation or file inclusion (see above). If a line
5121 consists solely of a macro name, and the expansion of the macro is empty, the
5122 line is ignored. A macro at the start of a line may turn the line into a
5123 comment line or a &`.include`& line.
5126 .section "Redefining macros" "SECID43"
5127 Once defined, the value of a macro can be redefined later in the configuration
5128 (or in an included file). Redefinition is specified by using &'=='& instead of
5133 MAC == updated value
5135 Redefinition does not alter the order in which the macros are applied to the
5136 subsequent lines of the configuration file. It is still the same order in which
5137 the macros were originally defined. All that changes is the macro's value.
5138 Redefinition makes it possible to accumulate values. For example:
5142 MAC == MAC and something added
5144 This can be helpful in situations where the configuration file is built
5145 from a number of other files.
5147 .section "Overriding macro values" "SECID44"
5148 The values set for macros in the configuration file can be overridden by the
5149 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5150 used, unless called by root or the Exim user. A definition on the command line
5151 using the &%-D%& option causes all definitions and redefinitions within the
5156 .section "Example of macro usage" "SECID45"
5157 As an example of macro usage, consider a configuration where aliases are looked
5158 up in a MySQL database. It helps to keep the file less cluttered if long
5159 strings such as SQL statements are defined separately as macros, for example:
5161 ALIAS_QUERY = select mailbox from user where \
5162 login='${quote_mysql:$local_part}';
5164 This can then be used in a &(redirect)& router setting like this:
5166 data = ${lookup mysql{ALIAS_QUERY}}
5168 In earlier versions of Exim macros were sometimes used for domain, host, or
5169 address lists. In Exim 4 these are handled better by named lists &-- see
5170 section &<<SECTnamedlists>>&.
5173 .section "Builtin macros" "SECTbuiltinmacros"
5174 Exim defines some macros depending on facilities available, which may
5175 differ due to build-time definitions and from one release to another.
5176 All of these macros start with an underscore.
5177 They can be used to conditionally include parts of a configuration
5180 The following classes of macros are defined:
5182 &` _HAVE_* `& build-time defines
5183 &` _DRIVER_ROUTER_* `& router drivers
5184 &` _DRIVER_TRANSPORT_* `& transport drivers
5185 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5186 &` _LOG_* `& log_selector values
5187 &` _OPT_MAIN_* `& main config options
5188 &` _OPT_ROUTERS_* `& generic router options
5189 &` _OPT_TRANSPORTS_* `& generic transport options
5190 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5191 &` _OPT_ROUTER_*_* `& private router options
5192 &` _OPT_TRANSPORT_*_* `& private transport options
5193 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5196 Use an &"exim -bP macros"& command to get the list of macros.
5199 .section "Conditional skips in the configuration file" "SECID46"
5200 .cindex "configuration file" "conditional skips"
5201 .cindex "&`.ifdef`&"
5202 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5203 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5204 portions of the configuration file. The processing happens whenever the file is
5205 read (that is, when an Exim binary starts to run).
5207 The implementation is very simple. Instances of the first four directives must
5208 be followed by text that includes the names of one or macros. The condition
5209 that is tested is whether or not any macro substitution has taken place in the
5213 message_size_limit = 50M
5215 message_size_limit = 100M
5218 sets a message size limit of 50M if the macro &`AAA`& is defined
5219 (or &`A`& or &`AA`&), and 100M
5220 otherwise. If there is more than one macro named on the line, the condition
5221 is true if any of them are defined. That is, it is an &"or"& condition. To
5222 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5224 Although you can use a macro expansion to generate one of these directives,
5225 it is not very useful, because the condition &"there was a macro substitution
5226 in this line"& will always be true.
5228 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5229 to clarify complicated nestings.
5233 .section "Common option syntax" "SECTcos"
5234 .cindex "common option syntax"
5235 .cindex "syntax of common options"
5236 .cindex "configuration file" "common option syntax"
5237 For the main set of options, driver options, and &[local_scan()]& options,
5238 each setting is on a line by itself, and starts with a name consisting of
5239 lower-case letters and underscores. Many options require a data value, and in
5240 these cases the name must be followed by an equals sign (with optional white
5241 space) and then the value. For example:
5243 qualify_domain = mydomain.example.com
5245 .cindex "hiding configuration option values"
5246 .cindex "configuration options" "hiding value of"
5247 .cindex "options" "hiding value of"
5248 Some option settings may contain sensitive data, for example, passwords for
5249 accessing databases. To stop non-admin users from using the &%-bP%& command
5250 line option to read these values, you can precede the option settings with the
5251 word &"hide"&. For example:
5253 hide mysql_servers = localhost/users/admin/secret-password
5255 For non-admin users, such options are displayed like this:
5257 mysql_servers = <value not displayable>
5259 If &"hide"& is used on a driver option, it hides the value of that option on
5260 all instances of the same driver.
5262 The following sections describe the syntax used for the different data types
5263 that are found in option settings.
5266 .section "Boolean options" "SECID47"
5267 .cindex "format" "boolean"
5268 .cindex "boolean configuration values"
5269 .oindex "&%no_%&&'xxx'&"
5270 .oindex "&%not_%&&'xxx'&"
5271 Options whose type is given as boolean are on/off switches. There are two
5272 different ways of specifying such options: with and without a data value. If
5273 the option name is specified on its own without data, the switch is turned on;
5274 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5275 boolean options may be followed by an equals sign and one of the words
5276 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5277 the following two settings have exactly the same effect:
5282 The following two lines also have the same (opposite) effect:
5287 You can use whichever syntax you prefer.
5292 .section "Integer values" "SECID48"
5293 .cindex "integer configuration values"
5294 .cindex "format" "integer"
5295 If an option's type is given as &"integer"&, the value can be given in decimal,
5296 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5297 number is assumed. Otherwise, it is treated as an octal number unless it starts
5298 with the characters &"0x"&, in which case the remainder is interpreted as a
5301 If an integer value is followed by the letter K, it is multiplied by 1024; if
5302 it is followed by the letter M, it is multiplied by 1024x1024;
5303 if by the letter G, 1024x1024x1024.
5305 of integer option settings are output, values which are an exact multiple of
5306 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5307 and M. The printing style is independent of the actual input format that was
5311 .section "Octal integer values" "SECID49"
5312 .cindex "integer format"
5313 .cindex "format" "octal integer"
5314 If an option's type is given as &"octal integer"&, its value is always
5315 interpreted as an octal number, whether or not it starts with the digit zero.
5316 Such options are always output in octal.
5319 .section "Fixed point numbers" "SECID50"
5320 .cindex "fixed point configuration values"
5321 .cindex "format" "fixed point"
5322 If an option's type is given as &"fixed-point"&, its value must be a decimal
5323 integer, optionally followed by a decimal point and up to three further digits.
5327 .section "Time intervals" "SECTtimeformat"
5328 .cindex "time interval" "specifying in configuration"
5329 .cindex "format" "time interval"
5330 A time interval is specified as a sequence of numbers, each followed by one of
5331 the following letters, with no intervening white space:
5341 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5342 intervals are output in the same format. Exim does not restrict the values; it
5343 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5347 .section "String values" "SECTstrings"
5348 .cindex "string" "format of configuration values"
5349 .cindex "format" "string"
5350 If an option's type is specified as &"string"&, the value can be specified with
5351 or without double-quotes. If it does not start with a double-quote, the value
5352 consists of the remainder of the line plus any continuation lines, starting at
5353 the first character after any leading white space, with trailing white space
5354 removed, and with no interpretation of the characters in the string. Because
5355 Exim removes comment lines (those beginning with #) at an early stage, they can
5356 appear in the middle of a multi-line string. The following two settings are
5357 therefore equivalent:
5359 trusted_users = uucp:mail
5360 trusted_users = uucp:\
5361 # This comment line is ignored
5364 .cindex "string" "quoted"
5365 .cindex "escape characters in quoted strings"
5366 If a string does start with a double-quote, it must end with a closing
5367 double-quote, and any backslash characters other than those used for line
5368 continuation are interpreted as escape characters, as follows:
5371 .irow &`\\`& "single backslash"
5372 .irow &`\n`& "newline"
5373 .irow &`\r`& "carriage return"
5375 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5376 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5380 If a backslash is followed by some other character, including a double-quote
5381 character, that character replaces the pair.
5383 Quoting is necessary only if you want to make use of the backslash escapes to
5384 insert special characters, or if you need to specify a value with leading or
5385 trailing spaces. These cases are rare, so quoting is almost never needed in
5386 current versions of Exim. In versions of Exim before 3.14, quoting was required
5387 in order to continue lines, so you may come across older configuration files
5388 and examples that apparently quote unnecessarily.
5391 .section "Expanded strings" "SECID51"
5392 .cindex "expansion" "definition of"
5393 Some strings in the configuration file are subjected to &'string expansion'&,
5394 by which means various parts of the string may be changed according to the
5395 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5396 is as just described; in particular, the handling of backslashes in quoted
5397 strings is done as part of the input process, before expansion takes place.
5398 However, backslash is also an escape character for the expander, so any
5399 backslashes that are required for that reason must be doubled if they are
5400 within a quoted configuration string.
5403 .section "User and group names" "SECID52"
5404 .cindex "user name" "format of"
5405 .cindex "format" "user name"
5406 .cindex "groups" "name format"
5407 .cindex "format" "group name"
5408 User and group names are specified as strings, using the syntax described
5409 above, but the strings are interpreted specially. A user or group name must
5410 either consist entirely of digits, or be a name that can be looked up using the
5411 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5414 .section "List construction" "SECTlistconstruct"
5415 .cindex "list" "syntax of in configuration"
5416 .cindex "format" "list item in configuration"
5417 .cindex "string" "list, definition of"
5418 The data for some configuration options is a list of items, with colon as the
5419 default separator. Many of these options are shown with type &"string list"& in
5420 the descriptions later in this document. Others are listed as &"domain list"&,
5421 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5422 are all the same; however, those other than &"string list"& are subject to
5423 particular kinds of interpretation, as described in chapter
5424 &<<CHAPdomhosaddlists>>&.
5426 In all these cases, the entire list is treated as a single string as far as the
5427 input syntax is concerned. The &%trusted_users%& setting in section
5428 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5429 in a list, it must be entered as two colons. Leading and trailing white space
5430 on each item in a list is ignored. This makes it possible to include items that
5431 start with a colon, and in particular, certain forms of IPv6 address. For
5434 local_interfaces = 127.0.0.1 : ::::1
5436 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5438 &*Note*&: Although leading and trailing white space is ignored in individual
5439 list items, it is not ignored when parsing the list. The space after the first
5440 colon in the example above is necessary. If it were not there, the list would
5441 be interpreted as the two items 127.0.0.1:: and 1.
5443 .section "Changing list separators" "SECTlistsepchange"
5444 .cindex "list separator" "changing"
5445 .cindex "IPv6" "addresses in lists"
5446 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5447 introduced to allow the separator character to be changed. If a list begins
5448 with a left angle bracket, followed by any punctuation character, that
5449 character is used instead of colon as the list separator. For example, the list
5450 above can be rewritten to use a semicolon separator like this:
5452 local_interfaces = <; 127.0.0.1 ; ::1
5454 This facility applies to all lists, with the exception of the list in
5455 &%log_file_path%&. It is recommended that the use of non-colon separators be
5456 confined to circumstances where they really are needed.
5458 .cindex "list separator" "newline as"
5459 .cindex "newline" "as list separator"
5460 It is also possible to use newline and other control characters (those with
5461 code values less than 32, plus DEL) as separators in lists. Such separators
5462 must be provided literally at the time the list is processed. For options that
5463 are string-expanded, you can write the separator using a normal escape
5464 sequence. This will be processed by the expander before the string is
5465 interpreted as a list. For example, if a newline-separated list of domains is
5466 generated by a lookup, you can process it directly by a line such as this:
5468 domains = <\n ${lookup mysql{.....}}
5470 This avoids having to change the list separator in such data. You are unlikely
5471 to want to use a control character as a separator in an option that is not
5472 expanded, because the value is literal text. However, it can be done by giving
5473 the value in quotes. For example:
5475 local_interfaces = "<\n 127.0.0.1 \n ::1"
5477 Unlike printing character separators, which can be included in list items by
5478 doubling, it is not possible to include a control character as data when it is
5479 set as the separator. Two such characters in succession are interpreted as
5480 enclosing an empty list item.
5484 .section "Empty items in lists" "SECTempitelis"
5485 .cindex "list" "empty item in"
5486 An empty item at the end of a list is always ignored. In other words, trailing
5487 separator characters are ignored. Thus, the list in
5489 senders = user@domain :
5491 contains only a single item. If you want to include an empty string as one item
5492 in a list, it must not be the last item. For example, this list contains three
5493 items, the second of which is empty:
5495 senders = user1@domain : : user2@domain
5497 &*Note*&: There must be white space between the two colons, as otherwise they
5498 are interpreted as representing a single colon data character (and the list
5499 would then contain just one item). If you want to specify a list that contains
5500 just one, empty item, you can do it as in this example:
5504 In this case, the first item is empty, and the second is discarded because it
5505 is at the end of the list.
5510 .section "Format of driver configurations" "SECTfordricon"
5511 .cindex "drivers" "configuration format"
5512 There are separate parts in the configuration for defining routers, transports,
5513 and authenticators. In each part, you are defining a number of driver
5514 instances, each with its own set of options. Each driver instance is defined by
5515 a sequence of lines like this:
5517 <&'instance name'&>:
5522 In the following example, the instance name is &(localuser)&, and it is
5523 followed by three options settings:
5528 transport = local_delivery
5530 For each driver instance, you specify which Exim code module it uses &-- by the
5531 setting of the &%driver%& option &-- and (optionally) some configuration
5532 settings. For example, in the case of transports, if you want a transport to
5533 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5534 a local file you would use the &(appendfile)& driver. Each of the drivers is
5535 described in detail in its own separate chapter later in this manual.
5537 You can have several routers, transports, or authenticators that are based on
5538 the same underlying driver (each must have a different instance name).
5540 The order in which routers are defined is important, because addresses are
5541 passed to individual routers one by one, in order. The order in which
5542 transports are defined does not matter at all. The order in which
5543 authenticators are defined is used only when Exim, as a client, is searching
5544 them to find one that matches an authentication mechanism offered by the
5547 .cindex "generic options"
5548 .cindex "options" "generic &-- definition of"
5549 Within a driver instance definition, there are two kinds of option: &'generic'&
5550 and &'private'&. The generic options are those that apply to all drivers of the
5551 same type (that is, all routers, all transports or all authenticators). The
5552 &%driver%& option is a generic option that must appear in every definition.
5553 .cindex "private options"
5554 The private options are special for each driver, and none need appear, because
5555 they all have default values.
5557 The options may appear in any order, except that the &%driver%& option must
5558 precede any private options, since these depend on the particular driver. For
5559 this reason, it is recommended that &%driver%& always be the first option.
5561 Driver instance names, which are used for reference in log entries and
5562 elsewhere, can be any sequence of letters, digits, and underscores (starting
5563 with a letter) and must be unique among drivers of the same type. A router and
5564 a transport (for example) can each have the same name, but no two router
5565 instances can have the same name. The name of a driver instance should not be
5566 confused with the name of the underlying driver module. For example, the
5567 configuration lines:
5572 create an instance of the &(smtp)& transport driver whose name is
5573 &(remote_smtp)&. The same driver code can be used more than once, with
5574 different instance names and different option settings each time. A second
5575 instance of the &(smtp)& transport, with different options, might be defined
5581 command_timeout = 10s
5583 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5584 these transport instances from routers, and these names would appear in log
5587 Comment lines may be present in the middle of driver specifications. The full
5588 list of option settings for any particular driver instance, including all the
5589 defaulted values, can be extracted by making use of the &%-bP%& command line
5597 . ////////////////////////////////////////////////////////////////////////////
5598 . ////////////////////////////////////////////////////////////////////////////
5600 .chapter "The default configuration file" "CHAPdefconfil"
5601 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5602 .cindex "default" "configuration file &""walk through""&"
5603 The default configuration file supplied with Exim as &_src/configure.default_&
5604 is sufficient for a host with simple mail requirements. As an introduction to
5605 the way Exim is configured, this chapter &"walks through"& the default
5606 configuration, giving brief explanations of the settings. Detailed descriptions
5607 of the options are given in subsequent chapters. The default configuration file
5608 itself contains extensive comments about ways you might want to modify the
5609 initial settings. However, note that there are many options that are not
5610 mentioned at all in the default configuration.
5614 .section "Macros" "SECTdefconfmacros"
5615 All macros should be defined before any options.
5617 One macro is specified, but commented out, in the default configuration:
5619 # ROUTER_SMARTHOST=MAIL.HOSTNAME.FOR.CENTRAL.SERVER.EXAMPLE
5621 If all off-site mail is expected to be delivered to a "smarthost", then set the
5622 hostname here and uncomment the macro. This will affect which router is used
5623 later on. If this is left commented out, then Exim will perform direct-to-MX
5624 deliveries using a &(dnslookup)& router.
5626 In addition to macros defined here, Exim includes a number of built-in macros
5627 to enable configuration to be guarded by a binary built with support for a
5628 given feature. See section &<<SECTbuiltinmacros>>& for more details.
5631 .section "Main configuration settings" "SECTdefconfmain"
5632 The main (global) configuration option settings section must always come first
5633 in the file, after the macros.
5634 The first thing you'll see in the file, after some initial comments, is the line
5636 # primary_hostname =
5638 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5639 to know the official, fully qualified name of your host, and this is where you
5640 can specify it. However, in most cases you do not need to set this option. When
5641 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5643 The first three non-comment configuration lines are as follows:
5645 domainlist local_domains = @
5646 domainlist relay_to_domains =
5647 hostlist relay_from_hosts = 127.0.0.1
5649 These are not, in fact, option settings. They are definitions of two named
5650 domain lists and one named host list. Exim allows you to give names to lists of
5651 domains, hosts, and email addresses, in order to make it easier to manage the
5652 configuration file (see section &<<SECTnamedlists>>&).
5654 The first line defines a domain list called &'local_domains'&; this is used
5655 later in the configuration to identify domains that are to be delivered
5658 .cindex "@ in a domain list"
5659 There is just one item in this list, the string &"@"&. This is a special form
5660 of entry which means &"the name of the local host"&. Thus, if the local host is
5661 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5662 be delivered locally. Because the local host's name is referenced indirectly,
5663 the same configuration file can be used on different hosts.
5665 The second line defines a domain list called &'relay_to_domains'&, but the
5666 list itself is empty. Later in the configuration we will come to the part that
5667 controls mail relaying through the local host; it allows relaying to any
5668 domains in this list. By default, therefore, no relaying on the basis of a mail
5669 domain is permitted.
5671 The third line defines a host list called &'relay_from_hosts'&. This list is
5672 used later in the configuration to permit relaying from any host or IP address
5673 that matches the list. The default contains just the IP address of the IPv4
5674 loopback interface, which means that processes on the local host are able to
5675 submit mail for relaying by sending it over TCP/IP to that interface. No other
5676 hosts are permitted to submit messages for relaying.
5678 Just to be sure there's no misunderstanding: at this point in the configuration
5679 we aren't actually setting up any controls. We are just defining some domains
5680 and hosts that will be used in the controls that are specified later.
5682 The next two configuration lines are genuine option settings:
5684 acl_smtp_rcpt = acl_check_rcpt
5685 acl_smtp_data = acl_check_data
5687 These options specify &'Access Control Lists'& (ACLs) that are to be used
5688 during an incoming SMTP session for every recipient of a message (every RCPT
5689 command), and after the contents of the message have been received,
5690 respectively. The names of the lists are &'acl_check_rcpt'& and
5691 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5692 section of the configuration. The RCPT ACL controls which recipients are
5693 accepted for an incoming message &-- if a configuration does not provide an ACL
5694 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5695 contents of a message to be checked.
5697 Two commented-out option settings are next:
5699 # av_scanner = clamd:/tmp/clamd
5700 # spamd_address = 127.0.0.1 783
5702 These are example settings that can be used when Exim is compiled with the
5703 content-scanning extension. The first specifies the interface to the virus
5704 scanner, and the second specifies the interface to SpamAssassin. Further
5705 details are given in chapter &<<CHAPexiscan>>&.
5707 Three more commented-out option settings follow:
5709 # tls_advertise_hosts = *
5710 # tls_certificate = /etc/ssl/exim.crt
5711 # tls_privatekey = /etc/ssl/exim.pem
5713 These are example settings that can be used when Exim is compiled with
5714 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5715 first one specifies the list of clients that are allowed to use TLS when
5716 connecting to this server; in this case, the wildcard means all clients. The
5717 other options specify where Exim should find its TLS certificate and private
5718 key, which together prove the server's identity to any clients that connect.
5719 More details are given in chapter &<<CHAPTLS>>&.
5721 Another two commented-out option settings follow:
5723 # daemon_smtp_ports = 25 : 465 : 587
5724 # tls_on_connect_ports = 465
5726 .cindex "port" "465 and 587"
5727 .cindex "port" "for message submission"
5728 .cindex "message" "submission, ports for"
5729 .cindex "submissions protocol"
5730 .cindex "smtps protocol"
5731 .cindex "ssmtp protocol"
5732 .cindex "SMTP" "submissions protocol"
5733 .cindex "SMTP" "ssmtp protocol"
5734 .cindex "SMTP" "smtps protocol"
5735 These options provide better support for roaming users who wish to use this
5736 server for message submission. They are not much use unless you have turned on
5737 TLS (as described in the previous paragraph) and authentication (about which
5738 more in section &<<SECTdefconfauth>>&).
5739 Mail submission from mail clients (MUAs) should be separate from inbound mail
5740 to your domain (MX delivery) for various good reasons (eg, ability to impose
5741 much saner TLS protocol and ciphersuite requirements without unintended
5743 RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
5744 which uses STARTTLS, so this is the &"submission"& port.
5745 RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
5746 which should be used in preference to 587.
5747 You should also consider deploying SRV records to help clients find
5749 Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
5751 Two more commented-out options settings follow:
5754 # qualify_recipient =
5756 The first of these specifies a domain that Exim uses when it constructs a
5757 complete email address from a local login name. This is often needed when Exim
5758 receives a message from a local process. If you do not set &%qualify_domain%&,
5759 the value of &%primary_hostname%& is used. If you set both of these options,
5760 you can have different qualification domains for sender and recipient
5761 addresses. If you set only the first one, its value is used in both cases.
5763 .cindex "domain literal" "recognizing format"
5764 The following line must be uncommented if you want Exim to recognize
5765 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5766 (an IP address within square brackets) instead of a named domain.
5768 # allow_domain_literals
5770 The RFCs still require this form, but many people think that in the modern
5771 Internet it makes little sense to permit mail to be sent to specific hosts by
5772 quoting their IP addresses. This ancient format has been used by people who
5773 try to abuse hosts by using them for unwanted relaying. However, some
5774 people believe there are circumstances (for example, messages addressed to
5775 &'postmaster'&) where domain literals are still useful.
5777 The next configuration line is a kind of trigger guard:
5781 It specifies that no delivery must ever be run as the root user. The normal
5782 convention is to set up &'root'& as an alias for the system administrator. This
5783 setting is a guard against slips in the configuration.
5784 The list of users specified by &%never_users%& is not, however, the complete
5785 list; the build-time configuration in &_Local/Makefile_& has an option called
5786 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5787 contents of &%never_users%& are added to this list. By default
5788 FIXED_NEVER_USERS also specifies root.
5790 When a remote host connects to Exim in order to send mail, the only information
5791 Exim has about the host's identity is its IP address. The next configuration
5796 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5797 in order to get a host name. This improves the quality of the logging
5798 information, but if you feel it is too expensive, you can remove it entirely,
5799 or restrict the lookup to hosts on &"nearby"& networks.
5800 Note that it is not always possible to find a host name from an IP address,
5801 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5804 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5805 1413 (hence their names):
5808 rfc1413_query_timeout = 0s
5810 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5811 Few hosts offer RFC1413 service these days; calls have to be
5812 terminated by a timeout and this needlessly delays the startup
5813 of an incoming SMTP connection.
5814 If you have hosts for which you trust RFC1413 and need this
5815 information, you can change this.
5817 This line enables an efficiency SMTP option. It is negotiated by clients
5818 and not expected to cause problems but can be disabled if needed.
5823 When Exim receives messages over SMTP connections, it expects all addresses to
5824 be fully qualified with a domain, as required by the SMTP definition. However,
5825 if you are running a server to which simple clients submit messages, you may
5826 find that they send unqualified addresses. The two commented-out options:
5828 # sender_unqualified_hosts =
5829 # recipient_unqualified_hosts =
5831 show how you can specify hosts that are permitted to send unqualified sender
5832 and recipient addresses, respectively.
5834 The &%log_selector%& option is used to increase the detail of logging
5837 log_selector = +smtp_protocol_error +smtp_syntax_error \
5838 +tls_certificate_verified
5841 The &%percent_hack_domains%& option is also commented out:
5843 # percent_hack_domains =
5845 It provides a list of domains for which the &"percent hack"& is to operate.
5846 This is an almost obsolete form of explicit email routing. If you do not know
5847 anything about it, you can safely ignore this topic.
5849 The next two settings in the main part of the default configuration are
5850 concerned with messages that have been &"frozen"& on Exim's queue. When a
5851 message is frozen, Exim no longer continues to try to deliver it. Freezing
5852 occurs when a bounce message encounters a permanent failure because the sender
5853 address of the original message that caused the bounce is invalid, so the
5854 bounce cannot be delivered. This is probably the most common case, but there
5855 are also other conditions that cause freezing, and frozen messages are not
5856 always bounce messages.
5858 ignore_bounce_errors_after = 2d
5859 timeout_frozen_after = 7d
5861 The first of these options specifies that failing bounce messages are to be
5862 discarded after 2 days in the queue. The second specifies that any frozen
5863 message (whether a bounce message or not) is to be timed out (and discarded)
5864 after a week. In this configuration, the first setting ensures that no failing
5865 bounce message ever lasts a week.
5867 Exim queues it's messages in a spool directory. If you expect to have
5868 large queues, you may consider using this option. It splits the spool
5869 directory into subdirectories to avoid file system degradation from
5870 many files in a single directory, resulting in better performance.
5871 Manual manipulation of queued messages becomes more complex (though fortunately
5874 # split_spool_directory = true
5877 In an ideal world everybody follows the standards. For non-ASCII
5878 messages RFC 2047 is a standard, allowing a maximum line length of 76
5879 characters. Exim adheres that standard and won't process messages which
5880 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5881 In particular, the Exim maintainers have had multiple reports of
5882 problems from Russian administrators of issues until they disable this
5883 check, because of some popular, yet buggy, mail composition software.
5885 # check_rfc2047_length = false
5888 If you need to be strictly RFC compliant you may wish to disable the
5889 8BITMIME advertisement. Use this, if you exchange mails with systems
5890 that are not 8-bit clean.
5892 # accept_8bitmime = false
5895 Libraries you use may depend on specific environment settings. This
5896 imposes a security risk (e.g. PATH). There are two lists:
5897 &%keep_environment%& for the variables to import as they are, and
5898 &%add_environment%& for variables we want to set to a fixed value.
5899 Note that TZ is handled separately, by the $%timezone%$ runtime
5900 option and by the TIMEZONE_DEFAULT buildtime option.
5902 # keep_environment = ^LDAP
5903 # add_environment = PATH=/usr/bin::/bin
5907 .section "ACL configuration" "SECID54"
5908 .cindex "default" "ACLs"
5909 .cindex "&ACL;" "default configuration"
5910 In the default configuration, the ACL section follows the main configuration.
5911 It starts with the line
5915 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5916 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5917 and &%acl_smtp_data%& above.
5919 .cindex "RCPT" "ACL for"
5920 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5921 RCPT command specifies one of the message's recipients. The ACL statements
5922 are considered in order, until the recipient address is either accepted or
5923 rejected. The RCPT command is then accepted or rejected, according to the
5924 result of the ACL processing.
5928 This line, consisting of a name terminated by a colon, marks the start of the
5933 This ACL statement accepts the recipient if the sending host matches the list.
5934 But what does that strange list mean? It doesn't actually contain any host
5935 names or IP addresses. The presence of the colon puts an empty item in the
5936 list; Exim matches this only if the incoming message did not come from a remote
5937 host, because in that case, the remote hostname is empty. The colon is
5938 important. Without it, the list itself is empty, and can never match anything.
5940 What this statement is doing is to accept unconditionally all recipients in
5941 messages that are submitted by SMTP from local processes using the standard
5942 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5945 deny domains = +local_domains
5946 local_parts = ^[.] : ^.*[@%!/|]
5947 message = Restricted characters in address
5949 deny domains = !+local_domains
5950 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5951 message = Restricted characters in address
5953 These statements are concerned with local parts that contain any of the
5954 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5955 Although these characters are entirely legal in local parts (in the case of
5956 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5957 in Internet mail addresses.
5959 The first three have in the past been associated with explicitly routed
5960 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5961 option). Addresses containing these characters are regularly tried by spammers
5962 in an attempt to bypass relaying restrictions, and also by open relay testing
5963 programs. Unless you really need them it is safest to reject these characters
5964 at this early stage. This configuration is heavy-handed in rejecting these
5965 characters for all messages it accepts from remote hosts. This is a deliberate
5966 policy of being as safe as possible.
5968 The first rule above is stricter, and is applied to messages that are addressed
5969 to one of the local domains handled by this host. This is implemented by the
5970 first condition, which restricts it to domains that are listed in the
5971 &'local_domains'& domain list. The &"+"& character is used to indicate a
5972 reference to a named list. In this configuration, there is just one domain in
5973 &'local_domains'&, but in general there may be many.
5975 The second condition on the first statement uses two regular expressions to
5976 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5977 or &"|"&. If you have local accounts that include these characters, you will
5978 have to modify this rule.
5980 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5981 allows them because they have been encountered in practice. (Consider the
5982 common convention of local parts constructed as
5983 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5984 the author of Exim, who has no second initial.) However, a local part starting
5985 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5986 filename (for example, for a mailing list). This is also true for local parts
5987 that contain slashes. A pipe symbol can also be troublesome if the local part
5988 is incorporated unthinkingly into a shell command line.
5990 The second rule above applies to all other domains, and is less strict. This
5991 allows your own users to send outgoing messages to sites that use slashes
5992 and vertical bars in their local parts. It blocks local parts that begin
5993 with a dot, slash, or vertical bar, but allows these characters within the
5994 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5995 and &"!"& is blocked, as before. The motivation here is to prevent your users
5996 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5998 accept local_parts = postmaster
5999 domains = +local_domains
6001 This statement, which has two conditions, accepts an incoming address if the
6002 local part is &'postmaster'& and the domain is one of those listed in the
6003 &'local_domains'& domain list. The &"+"& character is used to indicate a
6004 reference to a named list. In this configuration, there is just one domain in
6005 &'local_domains'&, but in general there may be many.
6007 The presence of this statement means that mail to postmaster is never blocked
6008 by any of the subsequent tests. This can be helpful while sorting out problems
6009 in cases where the subsequent tests are incorrectly denying access.
6011 require verify = sender
6013 This statement requires the sender address to be verified before any subsequent
6014 ACL statement can be used. If verification fails, the incoming recipient
6015 address is refused. Verification consists of trying to route the address, to
6016 see if a bounce message could be delivered to it. In the case of remote
6017 addresses, basic verification checks only the domain, but &'callouts'& can be
6018 used for more verification if required. Section &<<SECTaddressverification>>&
6019 discusses the details of address verification.
6021 accept hosts = +relay_from_hosts
6022 control = submission
6024 This statement accepts the address if the message is coming from one of the
6025 hosts that are defined as being allowed to relay through this host. Recipient
6026 verification is omitted here, because in many cases the clients are dumb MUAs
6027 that do not cope well with SMTP error responses. For the same reason, the
6028 second line specifies &"submission mode"& for messages that are accepted. This
6029 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
6030 messages that are deficient in some way, for example, because they lack a
6031 &'Date:'& header line. If you are actually relaying out from MTAs, you should
6032 probably add recipient verification here, and disable submission mode.
6034 accept authenticated = *
6035 control = submission
6037 This statement accepts the address if the client host has authenticated itself.
6038 Submission mode is again specified, on the grounds that such messages are most
6039 likely to come from MUAs. The default configuration does not define any
6040 authenticators, though it does include some nearly complete commented-out
6041 examples described in &<<SECTdefconfauth>>&. This means that no client can in
6042 fact authenticate until you complete the authenticator definitions.
6044 require message = relay not permitted
6045 domains = +local_domains : +relay_to_domains
6047 This statement rejects the address if its domain is neither a local domain nor
6048 one of the domains for which this host is a relay.
6050 require verify = recipient
6052 This statement requires the recipient address to be verified; if verification
6053 fails, the address is rejected.
6055 # deny dnslists = black.list.example
6056 # message = rejected because $sender_host_address \
6057 # is in a black list at $dnslist_domain\n\
6060 # warn dnslists = black.list.example
6061 # add_header = X-Warning: $sender_host_address is in \
6062 # a black list at $dnslist_domain
6063 # log_message = found in $dnslist_domain
6065 These commented-out lines are examples of how you could configure Exim to check
6066 sending hosts against a DNS black list. The first statement rejects messages
6067 from blacklisted hosts, whereas the second just inserts a warning header
6070 # require verify = csa
6072 This commented-out line is an example of how you could turn on client SMTP
6073 authorization (CSA) checking. Such checks do DNS lookups for special SRV
6078 The final statement in the first ACL unconditionally accepts any recipient
6079 address that has successfully passed all the previous tests.
6083 This line marks the start of the second ACL, and names it. Most of the contents
6084 of this ACL are commented out:
6087 # message = This message contains a virus \
6090 These lines are examples of how to arrange for messages to be scanned for
6091 viruses when Exim has been compiled with the content-scanning extension, and a
6092 suitable virus scanner is installed. If the message is found to contain a
6093 virus, it is rejected with the given custom error message.
6095 # warn spam = nobody
6096 # message = X-Spam_score: $spam_score\n\
6097 # X-Spam_score_int: $spam_score_int\n\
6098 # X-Spam_bar: $spam_bar\n\
6099 # X-Spam_report: $spam_report
6101 These lines are an example of how to arrange for messages to be scanned by
6102 SpamAssassin when Exim has been compiled with the content-scanning extension,
6103 and SpamAssassin has been installed. The SpamAssassin check is run with
6104 &`nobody`& as its user parameter, and the results are added to the message as a
6105 series of extra header line. In this case, the message is not rejected,
6106 whatever the spam score.
6110 This final line in the DATA ACL accepts the message unconditionally.
6113 .section "Router configuration" "SECID55"
6114 .cindex "default" "routers"
6115 .cindex "routers" "default"
6116 The router configuration comes next in the default configuration, introduced
6121 Routers are the modules in Exim that make decisions about where to send
6122 messages. An address is passed to each router, in turn, until it is either
6123 accepted, or failed. This means that the order in which you define the routers
6124 matters. Each router is fully described in its own chapter later in this
6125 manual. Here we give only brief overviews.
6128 # driver = ipliteral
6129 # domains = !+local_domains
6130 # transport = remote_smtp
6132 .cindex "domain literal" "default router"
6133 This router is commented out because the majority of sites do not want to
6134 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
6135 you uncomment this router, you also need to uncomment the setting of
6136 &%allow_domain_literals%& in the main part of the configuration.
6138 Which router is used next depends upon whether or not the ROUTER_SMARTHOST
6139 macro has been defined, per
6141 .ifdef ROUTER_SMARTHOST
6150 If ROUTER_SMARTHOST has been defined, either at the top of the file or on the
6151 command-line, then we route all non-local mail to that smarthost; otherwise, we'll
6152 perform DNS lookups for direct-to-MX lookup. Any mail which is to a local domain will
6153 skip these routers because of the &%domains%& option.
6157 driver = manualroute
6158 domains = ! +local_domains
6159 transport = smarthost_smtp
6160 route_data = ROUTER_SMARTHOST
6161 ignore_target_hosts = <; 0.0.0.0 ; 127.0.0.0/8 ; ::1
6164 This router only handles mail which is not to any local domains; this is
6165 specified by the line
6167 domains = ! +local_domains
6169 The &%domains%& option lists the domains to which this router applies, but the
6170 exclamation mark is a negation sign, so the router is used only for domains
6171 that are not in the domain list called &'local_domains'& (which was defined at
6172 the start of the configuration). The plus sign before &'local_domains'&
6173 indicates that it is referring to a named list. Addresses in other domains are
6174 passed on to the following routers.
6176 The name of the router driver is &(manualroute)& because we are manually
6177 specifying how mail should be routed onwards, instead of using DNS MX.
6178 While the name of this router instance is arbitrary, the &%driver%& option must
6179 be one of the driver modules that is in the Exim binary.
6181 With no pre-conditions other than &%domains%&, all mail for non-local domains
6182 will be handled by this router, and the &%no_more%& setting will ensure that no
6183 other routers will be used for messages matching the pre-conditions. See
6184 &<<SECTrouprecon>>& for more on how the pre-conditions apply. For messages which
6185 are handled by this router, we provide a hostname to deliver to in &%route_data%&
6186 and the macro supplies the value; the address is then queued for the
6187 &(smarthost_smtp)& transport.
6192 domains = ! +local_domains
6193 transport = remote_smtp
6194 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
6197 The &%domains%& option behaves as per smarthost, above.
6199 The name of the router driver is &(dnslookup)&,
6200 and is specified by the &%driver%& option. Do not be confused by the fact that
6201 the name of this router instance is the same as the name of the driver. The
6202 instance name is arbitrary, but the name set in the &%driver%& option must be
6203 one of the driver modules that is in the Exim binary.
6205 The &(dnslookup)& router routes addresses by looking up their domains in the
6206 DNS in order to obtain a list of hosts to which the address is routed. If the
6207 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6208 specified by the &%transport%& option. If the router does not find the domain
6209 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6210 the address fails and is bounced.
6212 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6213 be entirely ignored. This option is present because a number of cases have been
6214 encountered where MX records in the DNS point to host names
6215 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6216 Completely ignoring these IP addresses causes Exim to fail to route the
6217 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6218 continue to try to deliver the message periodically until the address timed
6225 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6227 file_transport = address_file
6228 pipe_transport = address_pipe
6230 Control reaches this and subsequent routers only for addresses in the local
6231 domains. This router checks to see whether the local part is defined as an
6232 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6233 data that it looks up from that file. If no data is found for the local part,
6234 the value of the &%data%& option is empty, causing the address to be passed to
6237 &_/etc/aliases_& is a conventional name for the system aliases file that is
6238 often used. That is why it is referenced by from the default configuration
6239 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6240 &_Local/Makefile_& before building Exim.
6245 # local_part_suffix = +* : -*
6246 # local_part_suffix_optional
6247 file = $home/.forward
6252 file_transport = address_file
6253 pipe_transport = address_pipe
6254 reply_transport = address_reply
6256 This is the most complicated router in the default configuration. It is another
6257 redirection router, but this time it is looking for forwarding data set up by
6258 individual users. The &%check_local_user%& setting specifies a check that the
6259 local part of the address is the login name of a local user. If it is not, the
6260 router is skipped. The two commented options that follow &%check_local_user%&,
6263 # local_part_suffix = +* : -*
6264 # local_part_suffix_optional
6266 .vindex "&$local_part_suffix$&"
6267 show how you can specify the recognition of local part suffixes. If the first
6268 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6269 by any sequence of characters, is removed from the local part and placed in the
6270 variable &$local_part_suffix$&. The second suffix option specifies that the
6271 presence of a suffix in the local part is optional. When a suffix is present,
6272 the check for a local login uses the local part with the suffix removed.
6274 When a local user account is found, the file called &_.forward_& in the user's
6275 home directory is consulted. If it does not exist, or is empty, the router
6276 declines. Otherwise, the contents of &_.forward_& are interpreted as
6277 redirection data (see chapter &<<CHAPredirect>>& for more details).
6279 .cindex "Sieve filter" "enabling in default router"
6280 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6281 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6282 is commented out by default), the contents of the file are interpreted as a set
6283 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6284 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6285 separate document entitled &'Exim's interfaces to mail filtering'&.
6287 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6288 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6289 There are two reasons for doing this:
6292 Whether or not a local user has a &_.forward_& file is not really relevant when
6293 checking an address for validity; it makes sense not to waste resources doing
6296 More importantly, when Exim is verifying addresses or handling an EXPN
6297 command during an SMTP session, it is running as the Exim user, not as root.
6298 The group is the Exim group, and no additional groups are set up.
6299 It may therefore not be possible for Exim to read users' &_.forward_& files at
6303 The setting of &%check_ancestor%& prevents the router from generating a new
6304 address that is the same as any previous address that was redirected. (This
6305 works round a problem concerning a bad interaction between aliasing and
6306 forwarding &-- see section &<<SECTredlocmai>>&).
6308 The final three option settings specify the transports that are to be used when
6309 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6310 auto-reply, respectively. For example, if a &_.forward_& file contains
6312 a.nother@elsewhere.example, /home/spqr/archive
6314 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6320 # local_part_suffix = +* : -*
6321 # local_part_suffix_optional
6322 transport = local_delivery
6324 The final router sets up delivery into local mailboxes, provided that the local
6325 part is the name of a local login, by accepting the address and assigning it to
6326 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6327 routers, so the address is bounced. The commented suffix settings fulfil the
6328 same purpose as they do for the &(userforward)& router.
6331 .section "Transport configuration" "SECID56"
6332 .cindex "default" "transports"
6333 .cindex "transports" "default"
6334 Transports define mechanisms for actually delivering messages. They operate
6335 only when referenced from routers, so the order in which they are defined does
6336 not matter. The transports section of the configuration starts with
6340 Two remote transports and four local transports are defined.
6344 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6349 This transport is used for delivering messages over SMTP connections.
6350 The list of remote hosts comes from the router.
6351 The &%message_size_limit%& usage is a hack to avoid sending on messages
6352 with over-long lines.
6354 The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is
6355 negotiated between client and server and not expected to cause problems
6356 but can be disabled if needed. The built-in macro _HAVE_PRDR guards the
6357 use of the &%hosts_try_prdr%& configuration option.
6359 The other remote transport is used when delivering to a specific smarthost
6360 with whom there must be some kind of existing relationship, instead of the
6361 usual federated system.
6366 message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
6370 # Comment out any of these which you have to, then file a Support
6371 # request with your smarthost provider to get things fixed:
6372 hosts_require_tls = *
6373 tls_verify_hosts = *
6374 # As long as tls_verify_hosts is enabled, this won't matter, but if you
6375 # have to comment it out then this will at least log whether you succeed
6377 tls_try_verify_hosts = *
6379 # The SNI name should match the name which we'll expect to verify;
6380 # many mail systems don't use SNI and this doesn't matter, but if it does,
6381 # we need to send a name which the remote site will recognize.
6382 # This _should_ be the name which the smarthost operators specified as
6383 # the hostname for sending your mail to.
6384 tls_sni = ROUTER_SMARTHOST
6386 .ifdef _HAVE_OPENSSL
6387 tls_require_ciphers = HIGH:!aNULL:@STRENGTH
6390 tls_require_ciphers = SECURE192:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1
6397 After the same &%message_size_limit%& hack, we then specify that this Transport
6398 can handle messages to multiple domains in one run. The assumption here is
6399 that you're routing all non-local mail to the same place and that place is
6400 happy to take all messages from you as quickly as possible.
6401 All other options depend upon built-in macros; if Exim was built without TLS support
6402 then no other options are defined.
6403 If TLS is available, then we configure "stronger than default" TLS ciphersuites
6404 and versions using the &%tls_require_ciphers%& option, where the value to be
6405 used depends upon the library providing TLS.
6406 Beyond that, the options adopt the stance that you should have TLS support available
6407 from your smarthost on today's Internet, so we turn on requiring TLS for the
6408 mail to be delivered, and requiring that the certificate be valid, and match
6409 the expected hostname. The &%tls_sni%& option can be used by service providers
6410 to select an appropriate certificate to present to you and here we re-use the
6411 ROUTER_SMARTHOST macro, because that is unaffected by CNAMEs present in DNS.
6412 You want to specify the hostname which you'll expect to validate for, and that
6413 should not be subject to insecure tampering via DNS results.
6415 For the &%hosts_try_prdr%& option see the previous transport.
6417 All other options are defaulted.
6421 file = /var/mail/$local_part_data
6428 This &(appendfile)& transport is used for local delivery to user mailboxes in
6429 traditional BSD mailbox format.
6431 We prefer to avoid using &$local_part$& directly to define the mailbox filename,
6432 as it is provided by a potential bad actor.
6433 Instead we use &$local_part_data$&,
6434 the result of looking up &$local_part$& in the user database
6435 (done by using &%check_local_user%& in the the router).
6437 By default &(appendfile)& runs under the uid and gid of the
6438 local user, which requires the sticky bit to be set on the &_/var/mail_&
6439 directory. Some systems use the alternative approach of running mail deliveries
6440 under a particular group instead of using the sticky bit. The commented options
6441 show how this can be done.
6443 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6444 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6445 similarly-named options above.
6451 This transport is used for handling deliveries to pipes that are generated by
6452 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6453 option specifies that any output on stdout or stderr generated by the pipe is to
6454 be returned to the sender.
6462 This transport is used for handling deliveries to files that are generated by
6463 redirection. The name of the file is not specified in this instance of
6464 &(appendfile)&, because it comes from the &(redirect)& router.
6469 This transport is used for handling automatic replies generated by users'
6474 .section "Default retry rule" "SECID57"
6475 .cindex "retry" "default rule"
6476 .cindex "default" "retry rule"
6477 The retry section of the configuration file contains rules which affect the way
6478 Exim retries deliveries that cannot be completed at the first attempt. It is
6479 introduced by the line
6483 In the default configuration, there is just one rule, which applies to all
6486 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6488 This causes any temporarily failing address to be retried every 15 minutes for
6489 2 hours, then at intervals starting at one hour and increasing by a factor of
6490 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6491 is not delivered after 4 days of temporary failure, it is bounced. The time is
6492 measured from first failure, not from the time the message was received.
6494 If the retry section is removed from the configuration, or is empty (that is,
6495 if no retry rules are defined), Exim will not retry deliveries. This turns
6496 temporary errors into permanent errors.
6499 .section "Rewriting configuration" "SECID58"
6500 The rewriting section of the configuration, introduced by
6504 contains rules for rewriting addresses in messages as they arrive. There are no
6505 rewriting rules in the default configuration file.
6509 .section "Authenticators configuration" "SECTdefconfauth"
6510 .cindex "AUTH" "configuration"
6511 The authenticators section of the configuration, introduced by
6513 begin authenticators
6515 defines mechanisms for the use of the SMTP AUTH command. The default
6516 configuration file contains two commented-out example authenticators
6517 which support plaintext username/password authentication using the
6518 standard PLAIN mechanism and the traditional but non-standard LOGIN
6519 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6520 to support most MUA software.
6522 The example PLAIN authenticator looks like this:
6525 # driver = plaintext
6526 # server_set_id = $auth2
6527 # server_prompts = :
6528 # server_condition = Authentication is not yet configured
6529 # server_advertise_condition = ${if def:tls_in_cipher }
6531 And the example LOGIN authenticator looks like this:
6534 # driver = plaintext
6535 # server_set_id = $auth1
6536 # server_prompts = <| Username: | Password:
6537 # server_condition = Authentication is not yet configured
6538 # server_advertise_condition = ${if def:tls_in_cipher }
6541 The &%server_set_id%& option makes Exim remember the authenticated username
6542 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6543 &%server_prompts%& option configures the &(plaintext)& authenticator so
6544 that it implements the details of the specific authentication mechanism,
6545 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6546 when Exim offers authentication to clients; in the examples, this is only
6547 when TLS or SSL has been started, so to enable the authenticators you also
6548 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6550 The &%server_condition%& setting defines how to verify that the username and
6551 password are correct. In the examples it just produces an error message.
6552 To make the authenticators work, you can use a string expansion
6553 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6555 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6556 usercode and password are in different positions.
6557 Chapter &<<CHAPplaintext>>& covers both.
6559 .ecindex IIDconfiwal
6563 . ////////////////////////////////////////////////////////////////////////////
6564 . ////////////////////////////////////////////////////////////////////////////
6566 .chapter "Regular expressions" "CHAPregexp"
6568 .cindex "regular expressions" "library"
6570 Exim supports the use of regular expressions in many of its options. It
6571 uses the PCRE regular expression library; this provides regular expression
6572 matching that is compatible with Perl 5. The syntax and semantics of
6573 regular expressions is discussed in
6574 online Perl manpages, in
6575 many Perl reference books, and also in
6576 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6577 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6578 . --- the http: URL here redirects to another page with the ISBN in the URL
6579 . --- where trying to use https: just redirects back to http:, so sticking
6580 . --- to the old URL for now. 2018-09-07.
6582 The documentation for the syntax and semantics of the regular expressions that
6583 are supported by PCRE is included in the PCRE distribution, and no further
6584 description is included here. The PCRE functions are called from Exim using
6585 the default option settings (that is, with no PCRE options set), except that
6586 the PCRE_CASELESS option is set when the matching is required to be
6589 In most cases, when a regular expression is required in an Exim configuration,
6590 it has to start with a circumflex, in order to distinguish it from plain text
6591 or an &"ends with"& wildcard. In this example of a configuration setting, the
6592 second item in the colon-separated list is a regular expression.
6594 domains = a.b.c : ^\\d{3} : *.y.z : ...
6596 The doubling of the backslash is required because of string expansion that
6597 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6598 of this issue, and a way of avoiding the need for doubling backslashes. The
6599 regular expression that is eventually used in this example contains just one
6600 backslash. The circumflex is included in the regular expression, and has the
6601 normal effect of &"anchoring"& it to the start of the string that is being
6604 There are, however, two cases where a circumflex is not required for the
6605 recognition of a regular expression: these are the &%match%& condition in a
6606 string expansion, and the &%matches%& condition in an Exim filter file. In
6607 these cases, the relevant string is always treated as a regular expression; if
6608 it does not start with a circumflex, the expression is not anchored, and can
6609 match anywhere in the subject string.
6611 In all cases, if you want a regular expression to match at the end of a string,
6612 you must code the $ metacharacter to indicate this. For example:
6614 domains = ^\\d{3}\\.example
6616 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6619 domains = ^\\d{3}\\.example\$
6621 if you want &'example'& to be the top-level domain. The backslash before the
6622 $ is needed because string expansion also interprets dollar characters.
6626 . ////////////////////////////////////////////////////////////////////////////
6627 . ////////////////////////////////////////////////////////////////////////////
6629 .chapter "File and database lookups" "CHAPfdlookup"
6630 .scindex IIDfidalo1 "file" "lookups"
6631 .scindex IIDfidalo2 "database" "lookups"
6632 .cindex "lookup" "description of"
6633 Exim can be configured to look up data in files or databases as it processes
6634 messages. Two different kinds of syntax are used:
6637 A string that is to be expanded may contain explicit lookup requests. These
6638 cause parts of the string to be replaced by data that is obtained from the
6639 lookup. Lookups of this type are conditional expansion items. Different results
6640 can be defined for the cases of lookup success and failure. See chapter
6641 &<<CHAPexpand>>&, where string expansions are described in detail.
6642 The key for the lookup is &*specified*& as part of the string expansion.
6644 Lists of domains, hosts, and email addresses can contain lookup requests as a
6645 way of avoiding excessively long linear lists. In this case, the data that is
6646 returned by the lookup is often (but not always) discarded; whether the lookup
6647 succeeds or fails is what really counts. These kinds of list are described in
6648 chapter &<<CHAPdomhosaddlists>>&.
6649 The key for the lookup is &*implicit*&,
6650 given by the context in which the list is expanded.
6653 String expansions, lists, and lookups interact with each other in such a way
6654 that there is no order in which to describe any one of them that does not
6655 involve references to the others. Each of these three chapters makes more sense
6656 if you have read the other two first. If you are reading this for the first
6657 time, be aware that some of it will make a lot more sense after you have read
6658 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6660 .section "Examples of different lookup syntax" "SECID60"
6661 It is easy to confuse the two different kinds of lookup, especially as the
6662 lists that may contain the second kind are always expanded before being
6663 processed as lists. Therefore, they may also contain lookups of the first kind.
6664 Be careful to distinguish between the following two examples:
6666 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6667 domains = lsearch;/some/file
6669 The first uses a string expansion, the result of which must be a domain list.
6670 No strings have been specified for a successful or a failing lookup; the
6671 defaults in this case are the looked-up data and an empty string, respectively.
6672 The expansion takes place before the string is processed as a list, and the
6673 file that is searched could contain lines like this:
6675 192.168.3.4: domain1:domain2:...
6676 192.168.1.9: domain3:domain4:...
6678 When the lookup succeeds, the result of the expansion is a list of domains (and
6679 possibly other types of item that are allowed in domain lists).
6680 .cindex "tainted data" "de-tainting"
6681 The result of the expansion is not tainted.
6683 In the second example, the lookup is a single item in a domain list. It causes
6684 Exim to use a lookup to see if the domain that is being processed can be found
6686 The file could contains lines like this:
6691 Any data that follows the keys is not relevant when checking that the domain
6692 matches the list item.
6694 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6695 Consider a file containing lines like this:
6697 192.168.5.6: lsearch;/another/file
6699 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6700 first &%domains%& setting above generates the second setting, which therefore
6701 causes a second lookup to occur.
6704 The lookup type may optionally be followed by a comma
6705 and a comma-separated list of options.
6706 Each option is a &"name=value"& pair.
6707 Whether an option is meaningful depends on the lookup type.
6709 All lookups support the option &"cache=no_rd"&.
6710 If this is given then the cache that Exim manages for lookup results
6711 is not checked before doing the lookup.
6712 The result of the lookup is still written to the cache.
6715 The rest of this chapter describes the different lookup types that are
6716 available. Any of them can be used in any part of the configuration where a
6717 lookup is permitted.
6720 .section "Lookup types" "SECID61"
6721 .cindex "lookup" "types of"
6722 .cindex "single-key lookup" "definition of"
6723 Two different types of data lookup are implemented:
6726 The &'single-key'& type requires the specification of a file in which to look,
6727 and a single key to search for. The key must be a non-empty string for the
6728 lookup to succeed. The lookup type determines how the file is searched.
6729 .cindex "tainted data" "single-key lookups"
6730 The file string may not be tainted
6732 .cindex "tainted data" "de-tainting"
6733 All single-key lookups support the option &"ret=key"&.
6734 If this is given and the lookup
6735 (either underlying implementation or cached value)
6736 returns data, the result is replaced with a non-tainted
6737 version of the lookup key.
6738 .cindex "tainted data" "de-tainting"
6740 .cindex "query-style lookup" "definition of"
6741 The &'query-style'& type accepts a generalized database query. No particular
6742 key value is assumed by Exim for query-style lookups. You can use whichever
6743 Exim variables you need to construct the database query.
6746 The code for each lookup type is in a separate source file that is included in
6747 the binary of Exim only if the corresponding compile-time option is set. The
6748 default settings in &_src/EDITME_& are:
6753 which means that only linear searching and DBM lookups are included by default.
6754 For some types of lookup (e.g. SQL databases), you need to install appropriate
6755 libraries and header files before building Exim.
6760 .section "Single-key lookup types" "SECTsinglekeylookups"
6761 .cindex "lookup" "single-key types"
6762 .cindex "single-key lookup" "list of types"
6763 The following single-key lookup types are implemented:
6766 .cindex "cdb" "description of"
6767 .cindex "lookup" "cdb"
6768 .cindex "binary zero" "in lookup key"
6769 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6770 string without a terminating binary zero. The cdb format is designed for
6771 indexed files that are read frequently and never updated, except by total
6772 re-creation. As such, it is particularly suitable for large files containing
6773 aliases or other indexed data referenced by an MTA. Information about cdb and
6774 tools for building the files can be found in several places:
6776 &url(https://cr.yp.to/cdb.html)
6777 &url(https://www.corpit.ru/mjt/tinycdb.html)
6778 &url(https://packages.debian.org/stable/utils/freecdb)
6779 &url(https://github.com/philpennock/cdbtools) (in Go)
6781 A cdb distribution is not needed in order to build Exim with cdb support,
6782 because the code for reading cdb files is included directly in Exim itself.
6783 However, no means of building or testing cdb files is provided with Exim, so
6784 you need to obtain a cdb distribution in order to do this.
6786 .cindex "DBM" "lookup type"
6787 .cindex "lookup" "dbm"
6788 .cindex "binary zero" "in lookup key"
6789 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6790 DBM file by looking up the record with the given key. A terminating binary
6791 zero is included in the key that is passed to the DBM library. See section
6792 &<<SECTdb>>& for a discussion of DBM libraries.
6794 .cindex "Berkeley DB library" "file format"
6795 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6796 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6797 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6798 the DB_UNKNOWN option. This enables it to handle any of the types of database
6799 that the library supports, and can be useful for accessing DBM files created by
6800 other applications. (For earlier DB versions, DB_HASH is always used.)
6802 .cindex "lookup" "dbmjz"
6803 .cindex "lookup" "dbm &-- embedded NULs"
6805 .cindex "dbmjz lookup type"
6806 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6807 interpreted as an Exim list; the elements of the list are joined together with
6808 ASCII NUL characters to form the lookup key. An example usage would be to
6809 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6810 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6811 &(cram_md5)& authenticator.
6813 .cindex "lookup" "dbmnz"
6814 .cindex "lookup" "dbm &-- terminating zero"
6815 .cindex "binary zero" "in lookup key"
6817 .cindex "&_/etc/userdbshadow.dat_&"
6818 .cindex "dbmnz lookup type"
6819 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6820 is not included in the key that is passed to the DBM library. You may need this
6821 if you want to look up data in files that are created by or shared with some
6822 other application that does not use terminating zeros. For example, you need to
6823 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6824 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6825 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6826 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6828 .cindex "lookup" "dsearch"
6829 .cindex "dsearch lookup type"
6830 &(dsearch)&: The given file must be an
6832 directory path; this is searched for an entry
6833 whose name is the key by calling the &[lstat()]& function.
6835 contain any forward slash characters.
6836 If &[lstat()]& succeeds then so does the lookup.
6837 .cindex "tainted data" "dsearch result"
6838 The result is regarded as untainted.
6840 Options for the lookup can be given by appending them after the word "dsearch",
6841 separated by a comma. Options, if present, are a comma-separated list having
6842 each element starting with a tag name and an equals.
6844 Two options are supported, for the return value and for filtering match
6846 The "ret" option requests an alternate result value of
6847 the entire path for the entry. Example:
6849 ${lookup {passwd} dsearch,ret=full {/etc}}
6851 The default result is just the requested entry.
6852 The "filter" option requests that only directory entries of a given type
6853 are matched. The match value is one of "file", "dir" or "subdir" (the latter
6854 not matching "." or ".."). Example:
6856 ${lookup {passwd} dsearch,filter=file {/etc}}
6858 The default matching is for any entry type, including directories
6861 An example of how this
6862 lookup can be used to support virtual domains is given in section
6863 &<<SECTvirtualdomains>>&.
6865 .cindex "lookup" "iplsearch"
6866 .cindex "iplsearch lookup type"
6867 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6868 terminated by a colon or white space or the end of the line. The keys in the
6869 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6870 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6871 being interpreted as a key terminator. For example:
6873 1.2.3.4: data for 1.2.3.4
6874 192.168.0.0/16: data for 192.168.0.0/16
6875 "abcd::cdab": data for abcd::cdab
6876 "abcd:abcd::/32" data for abcd:abcd::/32
6878 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6879 file is searched linearly, using the CIDR masks where present, until a matching
6880 key is found. The first key that matches is used; there is no attempt to find a
6881 &"best"& match. Apart from the way the keys are matched, the processing for
6882 &(iplsearch)& is the same as for &(lsearch)&.
6884 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6885 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6886 lookup types support only literal keys.
6888 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6889 the implicit key is the host's IP address rather than its name (see section
6890 &<<SECThoslispatsikey>>&).
6892 &*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
6893 IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
6894 notation before executing the lookup.)
6897 One option is supported, "ret=full", to request the return of the entire line
6898 rather than omitting the key porttion.
6899 Note however that the key portion will have been de-quoted.
6904 .cindex json "lookup type"
6905 .cindex JSON expansions
6906 &(json)&: The given file is a text file with a JSON structure.
6907 An element of the structure is extracted, defined by the search key.
6908 The key is a list of subelement selectors
6909 (colon-separated by default but changeable in the usual way)
6910 which are applied in turn to select smaller and smaller portions
6911 of the JSON structure.
6912 If a selector is numeric, it must apply to a JSON array; the (zero-based)
6913 nunbered array element is selected.
6914 Otherwise it must apply to a JSON object; the named element is selected.
6915 The final resulting element can be a simple JSON type or a JSON object
6916 or array; for the latter two a string-representation of the JSON
6918 For elements of type string, the returned value is de-quoted.
6925 .cindex database lmdb
6926 &(lmdb)&: The given file is an LMDB database.
6927 LMDB is a memory-mapped key-value store,
6928 with API modeled loosely on that of BerkeleyDB.
6929 See &url(https://symas.com/products/lightning-memory-mapped-database/)
6930 for the feature set and operation modes.
6932 Exim provides read-only access via the LMDB C library.
6933 The library can be obtained from &url(https://github.com/LMDB/lmdb)
6934 or your operating system package repository.
6935 To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&.
6937 You will need to separately create the LMDB database file,
6938 possibly using the &"mdb_load"& utility.
6943 .cindex "linear search"
6944 .cindex "lookup" "lsearch"
6945 .cindex "lsearch lookup type"
6946 .cindex "case sensitivity" "in lsearch lookup"
6947 &(lsearch)&: The given file is a text file that is searched linearly for a
6948 line beginning with the search key, terminated by a colon or white space or the
6949 end of the line. The search is case-insensitive; that is, upper and lower case
6950 letters are treated as the same. The first occurrence of the key that is found
6951 in the file is used.
6953 White space between the key and the colon is permitted. The remainder of the
6954 line, with leading and trailing white space removed, is the data. This can be
6955 continued onto subsequent lines by starting them with any amount of white
6956 space, but only a single space character is included in the data at such a
6957 junction. If the data begins with a colon, the key must be terminated by a
6962 Empty lines and lines beginning with # are ignored, even if they occur in the
6963 middle of an item. This is the traditional textual format of alias files. Note
6964 that the keys in an &(lsearch)& file are literal strings. There is no
6965 wildcarding of any kind.
6967 .cindex "lookup" "lsearch &-- colons in keys"
6968 .cindex "white space" "in lsearch key"
6969 In most &(lsearch)& files, keys are not required to contain colons or #
6970 characters, or white space. However, if you need this feature, it is available.
6971 If a key begins with a doublequote character, it is terminated only by a
6972 matching quote (or end of line), and the normal escaping rules apply to its
6973 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6974 quoted keys (exactly as for unquoted keys). There is no special handling of
6975 quotes for the data part of an &(lsearch)& line.
6978 .cindex "NIS lookup type"
6979 .cindex "lookup" "NIS"
6980 .cindex "binary zero" "in lookup key"
6981 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6982 the given key, without a terminating binary zero. There is a variant called
6983 &(nis0)& which does include the terminating binary zero in the key. This is
6984 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6985 aliases; the full map names must be used.
6988 .cindex "wildlsearch lookup type"
6989 .cindex "lookup" "wildlsearch"
6990 .cindex "nwildlsearch lookup type"
6991 .cindex "lookup" "nwildlsearch"
6992 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6993 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6994 the file may be wildcarded. The difference between these two lookup types is
6995 that for &(wildlsearch)&, each key in the file is string-expanded before being
6996 used, whereas for &(nwildlsearch)&, no expansion takes place.
6998 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6999 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
7000 file that are regular expressions can be made case-sensitive by the use of
7001 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
7003 . ==== As this is a nested list, any displays it contains must be indented
7004 . ==== as otherwise they are too far to the left.
7007 The string may begin with an asterisk to mean &"ends with"&. For example:
7009 *.a.b.c data for anything.a.b.c
7010 *fish data for anythingfish
7013 The string may begin with a circumflex to indicate a regular expression. For
7014 example, for &(wildlsearch)&:
7016 ^\N\d+\.a\.b\N data for <digits>.a.b
7018 Note the use of &`\N`& to disable expansion of the contents of the regular
7019 expression. If you are using &(nwildlsearch)&, where the keys are not
7020 string-expanded, the equivalent entry is:
7022 ^\d+\.a\.b data for <digits>.a.b
7024 The case-insensitive flag is set at the start of compiling the regular
7025 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
7026 For example, to make the entire pattern case-sensitive:
7028 ^(?-i)\d+\.a\.b data for <digits>.a.b
7031 If the regular expression contains white space or colon characters, you must
7032 either quote it (see &(lsearch)& above), or represent these characters in other
7033 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
7034 colon. This may be easier than quoting, because if you quote, you have to
7035 escape all the backslashes inside the quotes.
7037 &*Note*&: It is not possible to capture substrings in a regular expression
7038 match for later use, because the results of all lookups are cached. If a lookup
7039 is repeated, the result is taken from the cache, and no actual pattern matching
7040 takes place. The values of all the numeric variables are unset after a
7041 &((n)wildlsearch)& match.
7044 Although I cannot see it being of much use, the general matching function that
7045 is used to implement &((n)wildlsearch)& means that the string may begin with a
7046 lookup name terminated by a semicolon, and followed by lookup data. For
7049 cdb;/some/file data for keys that match the file
7051 The data that is obtained from the nested lookup is discarded.
7054 Keys that do not match any of these patterns are interpreted literally. The
7055 continuation rules for the data are the same as for &(lsearch)&, and keys may
7056 be followed by optional colons.
7058 &*Warning*&: Unlike most other single-key lookup types, a file of data for
7059 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
7060 lookup types support only literal keys.
7063 .cindex "spf lookup type"
7064 .cindex "lookup" "spf"
7065 &(spf)&: If Exim is built with SPF support, manual lookups can be done
7066 (as opposed to the standard ACL condition method).
7067 For details see section &<<SECSPF>>&.
7071 .section "Query-style lookup types" "SECTquerystylelookups"
7072 .cindex "lookup" "query-style types"
7073 .cindex "query-style lookup" "list of types"
7074 The supported query-style lookup types are listed below. Further details about
7075 many of them are given in later sections.
7078 .cindex "DNS" "as a lookup type"
7079 .cindex "lookup" "DNS"
7080 &(dnsdb)&: This does a DNS search for one or more records whose domain names
7081 are given in the supplied query. The resulting data is the contents of the
7082 records. See section &<<SECTdnsdb>>&.
7084 .cindex "InterBase lookup type"
7085 .cindex "lookup" "InterBase"
7086 &(ibase)&: This does a lookup in an InterBase database.
7088 .cindex "LDAP" "lookup type"
7089 .cindex "lookup" "LDAP"
7090 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
7091 returns attributes from a single entry. There is a variant called &(ldapm)&
7092 that permits values from multiple entries to be returned. A third variant
7093 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
7094 any attribute values. See section &<<SECTldap>>&.
7096 .cindex "MySQL" "lookup type"
7097 .cindex "lookup" "MySQL"
7098 &(mysql)&: The format of the query is an SQL statement that is passed to a
7099 MySQL database. See section &<<SECTsql>>&.
7101 .cindex "NIS+ lookup type"
7102 .cindex "lookup" "NIS+"
7103 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
7104 the field to be returned. See section &<<SECTnisplus>>&.
7106 .cindex "Oracle" "lookup type"
7107 .cindex "lookup" "Oracle"
7108 &(oracle)&: The format of the query is an SQL statement that is passed to an
7109 Oracle database. See section &<<SECTsql>>&.
7111 .cindex "lookup" "passwd"
7112 .cindex "passwd lookup type"
7113 .cindex "&_/etc/passwd_&"
7114 &(passwd)& is a query-style lookup with queries that are just user names. The
7115 lookup calls &[getpwnam()]& to interrogate the system password data, and on
7116 success, the result string is the same as you would get from an &(lsearch)&
7117 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
7118 password value. For example:
7120 *:42:42:King Rat:/home/kr:/bin/bash
7123 .cindex "PostgreSQL lookup type"
7124 .cindex "lookup" "PostgreSQL"
7125 &(pgsql)&: The format of the query is an SQL statement that is passed to a
7126 PostgreSQL database. See section &<<SECTsql>>&.
7129 .cindex "Redis lookup type"
7130 .cindex lookup Redis
7131 &(redis)&: The format of the query is either a simple get or simple set,
7132 passed to a Redis database. See section &<<SECTsql>>&.
7135 .cindex "sqlite lookup type"
7136 .cindex "lookup" "sqlite"
7137 &(sqlite)&: The format of the query is
7138 an SQL statement that is passed to an SQLite database. See section &<<SECTsqlite>>&.
7141 &(testdb)&: This is a lookup type that is used for testing Exim. It is
7142 not likely to be useful in normal operation.
7144 .cindex "whoson lookup type"
7145 .cindex "lookup" "whoson"
7146 . --- still http:-only, 2018-09-07
7147 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
7148 allows a server to check whether a particular (dynamically allocated) IP
7149 address is currently allocated to a known (trusted) user and, optionally, to
7150 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
7151 at one time for &"POP before SMTP"& authentication, but that approach has been
7152 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
7153 &"POP before SMTP"& checking using ACL statements such as
7155 require condition = \
7156 ${lookup whoson {$sender_host_address}{yes}{no}}
7158 The query consists of a single IP address. The value returned is the name of
7159 the authenticated user, which is stored in the variable &$value$&. However, in
7160 this example, the data in &$value$& is not used; the result of the lookup is
7161 one of the fixed strings &"yes"& or &"no"&.
7166 .section "Temporary errors in lookups" "SECID63"
7167 .cindex "lookup" "temporary error in"
7168 Lookup functions can return temporary error codes if the lookup cannot be
7169 completed. For example, an SQL or LDAP database might be unavailable. For this
7170 reason, it is not advisable to use a lookup that might do this for critical
7171 options such as a list of local domains.
7173 When a lookup cannot be completed in a router or transport, delivery
7174 of the message (to the relevant address) is deferred, as for any other
7175 temporary error. In other circumstances Exim may assume the lookup has failed,
7176 or may give up altogether.
7180 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
7181 .cindex "wildcard lookups"
7182 .cindex "lookup" "default values"
7183 .cindex "lookup" "wildcard"
7184 .cindex "lookup" "* added to type"
7185 .cindex "default" "in single-key lookups"
7186 In this context, a &"default value"& is a value specified by the administrator
7187 that is to be used if a lookup fails.
7189 &*Note:*& This section applies only to single-key lookups. For query-style
7190 lookups, the facilities of the query language must be used. An attempt to
7191 specify a default for a query-style lookup provokes an error.
7193 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
7194 and the initial lookup fails, the key &"*"& is looked up in the file to
7195 provide a default value. See also the section on partial matching below.
7197 .cindex "*@ with single-key lookup"
7198 .cindex "lookup" "*@ added to type"
7199 .cindex "alias file" "per-domain default"
7200 Alternatively, if &"*@"& is added to a single-key lookup type (for example
7201 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
7202 character, a second lookup is done with everything before the last @ replaced
7203 by *. This makes it possible to provide per-domain defaults in alias files
7204 that include the domains in the keys. If the second lookup fails (or doesn't
7205 take place because there is no @ in the key), &"*"& is looked up.
7206 For example, a &(redirect)& router might contain:
7208 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
7210 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
7211 looks up these keys, in this order:
7217 The data is taken from whichever key it finds first. &*Note*&: In an
7218 &(lsearch)& file, this does not mean the first of these keys in the file. A
7219 complete scan is done for each key, and only if it is not found at all does
7220 Exim move on to try the next key.
7224 .section "Partial matching in single-key lookups" "SECTpartiallookup"
7225 .cindex "partial matching"
7226 .cindex "wildcard lookups"
7227 .cindex "lookup" "partial matching"
7228 .cindex "lookup" "wildcard"
7229 .cindex "asterisk" "in search type"
7230 The normal operation of a single-key lookup is to search the file for an exact
7231 match with the given key. However, in a number of situations where domains are
7232 being looked up, it is useful to be able to do partial matching. In this case,
7233 information in the file that has a key starting with &"*."& is matched by any
7234 domain that ends with the components that follow the full stop. For example, if
7235 a key in a DBM file is
7237 *.dates.fict.example
7239 then when partial matching is enabled this is matched by (amongst others)
7240 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
7241 by &'dates.fict.example'&, if that does not appear as a separate key in the
7244 &*Note*&: Partial matching is not available for query-style lookups. It is
7245 also not available for any lookup items in address lists (see section
7246 &<<SECTaddresslist>>&).
7248 Partial matching is implemented by doing a series of separate lookups using
7249 keys constructed by modifying the original subject key. This means that it can
7250 be used with any of the single-key lookup types, provided that
7251 partial matching keys
7252 beginning with a special prefix (default &"*."&) are included in the data file.
7253 Keys in the file that do not begin with the prefix are matched only by
7254 unmodified subject keys when partial matching is in use.
7256 Partial matching is requested by adding the string &"partial-"& to the front of
7257 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
7258 is done, the subject key is first looked up unmodified; if that fails, &"*."&
7259 is added at the start of the subject key, and it is looked up again. If that
7260 fails, further lookups are tried with dot-separated components removed from the
7261 start of the subject key, one-by-one, and &"*."& added on the front of what
7264 A minimum number of two non-* components are required. This can be adjusted
7265 by including a number before the hyphen in the search type. For example,
7266 &%partial3-lsearch%& specifies a minimum of three non-* components in the
7267 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
7268 subject key is &'2250.dates.fict.example'& then the following keys are looked
7269 up when the minimum number of non-* components is two:
7271 2250.dates.fict.example
7272 *.2250.dates.fict.example
7273 *.dates.fict.example
7276 As soon as one key in the sequence is successfully looked up, the lookup
7279 .cindex "lookup" "partial matching &-- changing prefix"
7280 .cindex "prefix" "for partial matching"
7281 The use of &"*."& as the partial matching prefix is a default that can be
7282 changed. The motivation for this feature is to allow Exim to operate with file
7283 formats that are used by other MTAs. A different prefix can be supplied in
7284 parentheses instead of the hyphen after &"partial"&. For example:
7286 domains = partial(.)lsearch;/some/file
7288 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
7289 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
7290 components is unchanged). The prefix may consist of any punctuation characters
7291 other than a closing parenthesis. It may be empty, for example:
7293 domains = partial1()cdb;/some/file
7295 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
7296 &`a.b.c`&, &`b.c`&, and &`c`&.
7298 If &"partial0"& is specified, what happens at the end (when the lookup with
7299 just one non-wild component has failed, and the original key is shortened right
7300 down to the null string) depends on the prefix:
7303 If the prefix has zero length, the whole lookup fails.
7305 If the prefix has length 1, a lookup for just the prefix is done. For
7306 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
7308 Otherwise, if the prefix ends in a dot, the dot is removed, and the
7309 remainder is looked up. With the default prefix, therefore, the final lookup is
7310 for &"*"& on its own.
7312 Otherwise, the whole prefix is looked up.
7316 If the search type ends in &"*"& or &"*@"& (see section
7317 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
7318 this implies happens after all partial lookups have failed. If &"partial0"& is
7319 specified, adding &"*"& to the search type has no effect with the default
7320 prefix, because the &"*"& key is already included in the sequence of partial
7321 lookups. However, there might be a use for lookup types such as
7322 &"partial0(.)lsearch*"&.
7324 The use of &"*"& in lookup partial matching differs from its use as a wildcard
7325 in domain lists and the like. Partial matching works only in terms of
7326 dot-separated components; a key such as &`*fict.example`&
7327 in a database file is useless, because the asterisk in a partial matching
7328 subject key is always followed by a dot.
7333 .section "Lookup caching" "SECID64"
7334 .cindex "lookup" "caching"
7335 .cindex "caching" "lookup data"
7336 Exim caches all lookup results in order to avoid needless repetition of
7337 lookups. However, because (apart from the daemon) Exim operates as a collection
7338 of independent, short-lived processes, this caching applies only within a
7339 single Exim process. There is no inter-process lookup caching facility.
7341 For single-key lookups, Exim keeps the relevant files open in case there is
7342 another lookup that needs them. In some types of configuration this can lead to
7343 many files being kept open for messages with many recipients. To avoid hitting
7344 the operating system limit on the number of simultaneously open files, Exim
7345 closes the least recently used file when it needs to open more files than its
7346 own internal limit, which can be changed via the &%lookup_open_max%& option.
7348 The single-key lookup files are closed and the lookup caches are flushed at
7349 strategic points during delivery &-- for example, after all routing is
7355 .section "Quoting lookup data" "SECID65"
7356 .cindex "lookup" "quoting"
7357 .cindex "quoting" "in lookups"
7358 When data from an incoming message is included in a query-style lookup, there
7359 is the possibility of special characters in the data messing up the syntax of
7360 the query. For example, a NIS+ query that contains
7364 will be broken if the local part happens to contain a closing square bracket.
7365 For NIS+, data can be enclosed in double quotes like this:
7367 [name="$local_part"]
7369 but this still leaves the problem of a double quote in the data. The rule for
7370 NIS+ is that double quotes must be doubled. Other lookup types have different
7371 rules, and to cope with the differing requirements, an expansion operator
7372 of the following form is provided:
7374 ${quote_<lookup-type>:<string>}
7376 For example, the safest way to write the NIS+ query is
7378 [name="${quote_nisplus:$local_part}"]
7380 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
7381 operator can be used for all lookup types, but has no effect for single-key
7382 lookups, since no quoting is ever needed in their key strings.
7387 .section "More about dnsdb" "SECTdnsdb"
7388 .cindex "dnsdb lookup"
7389 .cindex "lookup" "dnsdb"
7390 .cindex "DNS" "as a lookup type"
7391 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7392 of a record type and a domain name, separated by an equals sign. For example,
7393 an expansion string could contain:
7395 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7397 If the lookup succeeds, the result is placed in &$value$&, which in this case
7398 is used on its own as the result. If the lookup does not succeed, the
7399 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7400 &<<SECTforexpfai>>& for an explanation of what this means.
7402 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7403 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7404 If no type is given, TXT is assumed.
7406 For any record type, if multiple records are found, the data is returned as a
7407 concatenation, with newline as the default separator. The order, of course,
7408 depends on the DNS resolver. You can specify a different separator character
7409 between multiple records by putting a right angle-bracket followed immediately
7410 by the new separator at the start of the query. For example:
7412 ${lookup dnsdb{>: a=host1.example}}
7414 It is permitted to specify a space as the separator character. Further
7415 white space is ignored.
7416 For lookup types that return multiple fields per record,
7417 an alternate field separator can be specified using a comma after the main
7418 separator character, followed immediately by the field separator.
7420 .cindex "PTR record" "in &(dnsdb)& lookup"
7421 When the type is PTR,
7422 the data can be an IP address, written as normal; inversion and the addition of
7423 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7425 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7427 If the data for a PTR record is not a syntactically valid IP address, it is not
7428 altered and nothing is added.
7430 .cindex "MX record" "in &(dnsdb)& lookup"
7431 .cindex "SRV record" "in &(dnsdb)& lookup"
7432 For an MX lookup, both the preference value and the host name are returned for
7433 each record, separated by a space. For an SRV lookup, the priority, weight,
7434 port, and host name are returned for each record, separated by spaces.
7435 The field separator can be modified as above.
7437 .cindex "TXT record" "in &(dnsdb)& lookup"
7438 .cindex "SPF record" "in &(dnsdb)& lookup"
7439 For TXT records with multiple items of data, only the first item is returned,
7440 unless a field separator is specified.
7441 To concatenate items without a separator, use a semicolon instead.
7443 default behaviour is to concatenate multiple items without using a separator.
7445 ${lookup dnsdb{>\n,: txt=a.b.example}}
7446 ${lookup dnsdb{>\n; txt=a.b.example}}
7447 ${lookup dnsdb{spf=example.org}}
7449 It is permitted to specify a space as the separator character. Further
7450 white space is ignored.
7452 .cindex "SOA record" "in &(dnsdb)& lookup"
7453 For an SOA lookup, while no result is obtained the lookup is redone with
7454 successively more leading components dropped from the given domain.
7455 Only the primary-nameserver field is returned unless a field separator is
7458 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7461 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7462 .cindex "dnsdb modifiers"
7463 .cindex "modifiers" "dnsdb"
7464 .cindex "options" "dnsdb"
7465 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7466 each followed by a comma,
7467 that may appear before the record type.
7469 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7470 temporary DNS error for any of them, the behaviour is controlled by
7471 a defer-option modifier.
7472 The possible keywords are
7473 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7474 With &"strict"& behaviour, any temporary DNS error causes the
7475 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7476 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7477 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7478 error causes the whole lookup to defer only if none of the other lookups
7479 succeed. The default is &"lax"&, so the following lookups are equivalent:
7481 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7482 ${lookup dnsdb{a=one.host.com:two.host.com}}
7484 Thus, in the default case, as long as at least one of the DNS lookups
7485 yields some data, the lookup succeeds.
7487 .cindex "DNSSEC" "dns lookup"
7488 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7489 The possible keywords are
7490 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7491 With &"strict"& or &"lax"& DNSSEC information is requested
7493 With &"strict"& a response from the DNS resolver that
7494 is not labelled as authenticated data
7495 is treated as equivalent to a temporary DNS error.
7496 The default is &"lax"&.
7498 See also the &$lookup_dnssec_authenticated$& variable.
7500 .cindex timeout "dns lookup"
7501 .cindex "DNS" timeout
7502 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7503 The form is &"retrans_VAL"& where VAL is an Exim time specification
7505 The default value is set by the main configuration option &%dns_retrans%&.
7507 Retries for the dnsdb lookup can be controlled by a retry modifier.
7508 The form if &"retry_VAL"& where VAL is an integer.
7509 The default count is set by the main configuration option &%dns_retry%&.
7511 .cindex caching "of dns lookup"
7512 .cindex TTL "of dns lookup"
7514 Dnsdb lookup results are cached within a single process (and its children).
7515 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7516 value of the set of returned DNS records.
7519 .section "Pseudo dnsdb record types" "SECID66"
7520 .cindex "MX record" "in &(dnsdb)& lookup"
7521 By default, both the preference value and the host name are returned for
7522 each MX record, separated by a space. If you want only host names, you can use
7523 the pseudo-type MXH:
7525 ${lookup dnsdb{mxh=a.b.example}}
7527 In this case, the preference values are omitted, and just the host names are
7530 .cindex "name server for enclosing domain"
7531 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7532 records on the given domain, but if none are found, it removes the first
7533 component of the domain name, and tries again. This process continues until NS
7534 records are found or there are no more components left (or there is a DNS
7535 error). In other words, it may return the name servers for a top-level domain,
7536 but it never returns the root name servers. If there are no NS records for the
7537 top-level domain, the lookup fails. Consider these examples:
7539 ${lookup dnsdb{zns=xxx.quercite.com}}
7540 ${lookup dnsdb{zns=xxx.edu}}
7542 Assuming that in each case there are no NS records for the full domain name,
7543 the first returns the name servers for &%quercite.com%&, and the second returns
7544 the name servers for &%edu%&.
7546 You should be careful about how you use this lookup because, unless the
7547 top-level domain does not exist, the lookup always returns some host names. The
7548 sort of use to which this might be put is for seeing if the name servers for a
7549 given domain are on a blacklist. You can probably assume that the name servers
7550 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7553 .cindex "CSA" "in &(dnsdb)& lookup"
7554 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7555 records according to the CSA rules, which are described in section
7556 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7557 not sufficient because of the extra parent domain search behaviour of CSA. The
7558 result of a successful lookup such as:
7560 ${lookup dnsdb {csa=$sender_helo_name}}
7562 has two space-separated fields: an authorization code and a target host name.
7563 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7564 authorization required but absent, or &"?"& for unknown.
7566 .cindex "A+" "in &(dnsdb)& lookup"
7567 The pseudo-type A+ performs an AAAA
7568 and then an A lookup. All results are returned; defer processing
7569 (see below) is handled separately for each lookup. Example:
7571 ${lookup dnsdb {>; a+=$sender_helo_name}}
7575 .section "Multiple dnsdb lookups" "SECID67"
7576 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7577 However, you can specify a list of domains or IP addresses in a single
7578 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7579 the default separator, but with the ability to change this. For example:
7581 ${lookup dnsdb{one.domain.com:two.domain.com}}
7582 ${lookup dnsdb{a=one.host.com:two.host.com}}
7583 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7585 In order to retain backwards compatibility, there is one special case: if
7586 the lookup type is PTR and no change of separator is specified, Exim looks
7587 to see if the rest of the string is precisely one IPv6 address. In this
7588 case, it does not treat it as a list.
7590 The data from each lookup is concatenated, with newline separators by default,
7591 in the same way that multiple DNS records for a single item are handled. A
7592 different separator can be specified, as described above.
7597 .section "More about LDAP" "SECTldap"
7598 .cindex "LDAP" "lookup, more about"
7599 .cindex "lookup" "LDAP"
7600 .cindex "Solaris" "LDAP"
7601 The original LDAP implementation came from the University of Michigan; this has
7602 become &"Open LDAP"&, and there are now two different releases. Another
7603 implementation comes from Netscape, and Solaris 7 and subsequent releases
7604 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7605 the lookup function level, their error handling is different. For this reason
7606 it is necessary to set a compile-time variable when building Exim with LDAP, to
7607 indicate which LDAP library is in use. One of the following should appear in
7608 your &_Local/Makefile_&:
7610 LDAP_LIB_TYPE=UMICHIGAN
7611 LDAP_LIB_TYPE=OPENLDAP1
7612 LDAP_LIB_TYPE=OPENLDAP2
7613 LDAP_LIB_TYPE=NETSCAPE
7614 LDAP_LIB_TYPE=SOLARIS
7616 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7617 same interface as the University of Michigan version.
7619 There are three LDAP lookup types in Exim. These behave slightly differently in
7620 the way they handle the results of a query:
7623 &(ldap)& requires the result to contain just one entry; if there are more, it
7626 &(ldapdn)& also requires the result to contain just one entry, but it is the
7627 Distinguished Name that is returned rather than any attribute values.
7629 &(ldapm)& permits the result to contain more than one entry; the attributes
7630 from all of them are returned.
7634 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7635 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7636 the data returned by a successful lookup is described in the next section.
7637 First we explain how LDAP queries are coded.
7640 .section "Format of LDAP queries" "SECTforldaque"
7641 .cindex "LDAP" "query format"
7642 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7643 the configuration of a &(redirect)& router one might have this setting:
7645 data = ${lookup ldap \
7646 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7647 c=UK?mailbox?base?}}
7649 .cindex "LDAP" "with TLS"
7650 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7651 secure (encrypted) LDAP connections. The second of these ensures that an
7652 encrypted TLS connection is used.
7654 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7655 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7656 See the &%ldap_start_tls%& option.
7658 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7659 controlled. Every part of the TLS configuration can be configured by settings in
7660 &_exim.conf_&. Depending on the version of the client libraries installed on
7661 your system, some of the initialization may have required setting options in
7662 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7663 certificates. This revealed a nuance where the current UID that exim was
7664 running as could affect which config files it read. With Exim 4.83, these
7665 methods become optional, only taking effect if not specifically set in
7669 .section "LDAP quoting" "SECID68"
7670 .cindex "LDAP" "quoting"
7671 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7672 and the second because the LDAP query is represented as a URL. Furthermore,
7673 within an LDAP query, two different kinds of quoting are required. For this
7674 reason, there are two different LDAP-specific quoting operators.
7676 The &%quote_ldap%& operator is designed for use on strings that are part of
7677 filter specifications. Conceptually, it first does the following conversions on
7685 in accordance with RFC 2254. The resulting string is then quoted according
7686 to the rules for URLs, that is, all non-alphanumeric characters except
7690 are converted to their hex values, preceded by a percent sign. For example:
7692 ${quote_ldap: a(bc)*, a<yz>; }
7696 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7698 Removing the URL quoting, this is (with a leading and a trailing space):
7700 a\28bc\29\2A, a<yz>;
7702 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7703 base DN specifications in queries. Conceptually, it first converts the string
7704 by inserting a backslash in front of any of the following characters:
7708 It also inserts a backslash before any leading spaces or # characters, and
7709 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7710 is then quoted according to the rules for URLs. For example:
7712 ${quote_ldap_dn: a(bc)*, a<yz>; }
7716 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7718 Removing the URL quoting, this is (with a trailing space):
7720 \ a(bc)*\, a\<yz\>\;\
7722 There are some further comments about quoting in the section on LDAP
7723 authentication below.
7726 .section "LDAP connections" "SECID69"
7727 .cindex "LDAP" "connections"
7728 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7729 is in use, via a Unix domain socket. The example given above does not specify
7730 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7733 ldap://<hostname>:<port>/...
7735 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7736 used. When no server is specified in a query, a list of default servers is
7737 taken from the &%ldap_default_servers%& configuration option. This supplies a
7738 colon-separated list of servers which are tried in turn until one successfully
7739 handles a query, or there is a serious error. Successful handling either
7740 returns the requested data, or indicates that it does not exist. Serious errors
7741 are syntactical, or multiple values when only a single value is expected.
7742 Errors which cause the next server to be tried are connection failures, bind
7743 failures, and timeouts.
7745 For each server name in the list, a port number can be given. The standard way
7746 of specifying a host and port is to use a colon separator (RFC 1738). Because
7747 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7748 doubled. For example
7750 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7752 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7753 to the LDAP library with no server name, and the library's default (normally
7754 the local host) is used.
7756 If you are using the OpenLDAP library, you can connect to an LDAP server using
7757 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7758 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7759 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7762 For this type of connection, instead of a host name for the server, a pathname
7763 for the socket is required, and the port number is not relevant. The pathname
7764 can be specified either as an item in &%ldap_default_servers%&, or inline in
7765 the query. In the former case, you can have settings such as
7767 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7769 When the pathname is given in the query, you have to escape the slashes as
7770 &`%2F`& to fit in with the LDAP URL syntax. For example:
7772 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7774 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7775 a pathname, it uses the Unix domain socket code, even if the query actually
7776 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7777 socket connection. This behaviour means that you can use a setting of
7778 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7779 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7780 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7783 If an explicit &`ldapi`& type is given in a query when a host name is
7784 specified, an error is diagnosed. However, if there are more items in
7785 &%ldap_default_servers%&, they are tried. In other words:
7788 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7791 Using &`ldapi`& with a host name causes an error.
7795 Using &`ldapi`& with no host or path in the query, and no setting of
7796 &%ldap_default_servers%&, does whatever the library does by default.
7800 .section "LDAP authentication and control information" "SECID70"
7801 .cindex "LDAP" "authentication"
7802 The LDAP URL syntax provides no way of passing authentication and other control
7803 information to the server. To make this possible, the URL in an LDAP query may
7804 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7805 spaces. If a value contains spaces it must be enclosed in double quotes, and
7806 when double quotes are used, backslash is interpreted in the usual way inside
7807 them. The following names are recognized:
7809 &`DEREFERENCE`& set the dereferencing parameter
7810 &`NETTIME `& set a timeout for a network operation
7811 &`USER `& set the DN, for authenticating the LDAP bind
7812 &`PASS `& set the password, likewise
7813 &`REFERRALS `& set the referrals parameter
7814 &`SERVERS `& set alternate server list for this query only
7815 &`SIZE `& set the limit for the number of entries returned
7816 &`TIME `& set the maximum waiting time for a query
7818 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7819 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7820 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7821 library from trying to follow referrals issued by the LDAP server.
7823 .cindex LDAP timeout
7824 .cindex timeout "LDAP lookup"
7825 The name CONNECT is an obsolete name for NETTIME, retained for
7826 backwards compatibility. This timeout (specified as a number of seconds) is
7827 enforced from the client end for operations that can be carried out over a
7828 network. Specifically, it applies to network connections and calls to the
7829 &'ldap_result()'& function. If the value is greater than zero, it is used if
7830 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7831 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7832 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7833 Netscape SDK; for OpenLDAP no action is taken.
7835 The TIME parameter (also a number of seconds) is passed to the server to
7836 set a server-side limit on the time taken to complete a search.
7838 The SERVERS parameter allows you to specify an alternate list of ldap servers
7839 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7840 default list of ldap servers, and a single lookup can specify a single ldap
7841 server to use. But when you need to do a lookup with a list of servers that is
7842 different than the default list (maybe different order, maybe a completely
7843 different set of servers), the SERVERS parameter allows you to specify this
7844 alternate list (colon-separated).
7846 Here is an example of an LDAP query in an Exim lookup that uses some of these
7847 values. This is a single line, folded to fit on the page:
7850 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7851 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7854 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7855 any of the auxiliary data. Exim configuration settings that include lookups
7856 which contain password information should be preceded by &"hide"& to prevent
7857 non-admin users from using the &%-bP%& option to see their values.
7859 The auxiliary data items may be given in any order. The default is no
7860 connection timeout (the system timeout is used), no user or password, no limit
7861 on the number of entries returned, and no time limit on queries.
7863 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7864 removes any URL quoting that it may contain before passing it LDAP. Apparently
7865 some libraries do this for themselves, but some do not. Removing the URL
7866 quoting has two advantages:
7869 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7870 DNs as with DNs inside actual queries.
7872 It permits spaces inside USER= DNs.
7875 For example, a setting such as
7877 USER=cn=${quote_ldap_dn:$1}
7879 should work even if &$1$& contains spaces.
7881 Expanded data for the PASS= value should be quoted using the &%quote%&
7882 expansion operator, rather than the LDAP quote operators. The only reason this
7883 field needs quoting is to ensure that it conforms to the Exim syntax, which
7884 does not allow unquoted spaces. For example:
7888 The LDAP authentication mechanism can be used to check passwords as part of
7889 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7894 .section "Format of data returned by LDAP" "SECID71"
7895 .cindex "LDAP" "returned data formats"
7896 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7897 as a sequence of values, for example
7899 cn=manager,o=University of Cambridge,c=UK
7901 The &(ldap)& lookup type generates an error if more than one entry matches the
7902 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7903 the result between the data from different entries. It is possible for multiple
7904 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7905 you know that whatever values are returned all came from a single entry in the
7908 In the common case where you specify a single attribute in your LDAP query, the
7909 result is not quoted, and does not contain the attribute name. If the attribute
7910 has multiple values, they are separated by commas. Any comma that is
7911 part of an attribute's value is doubled.
7913 If you specify multiple attributes, the result contains space-separated, quoted
7914 strings, each preceded by the attribute name and an equals sign. Within the
7915 quotes, the quote character, backslash, and newline are escaped with
7916 backslashes, and commas are used to separate multiple values for the attribute.
7917 Any commas in attribute values are doubled
7918 (permitting treatment of the values as a comma-separated list).
7919 Apart from the escaping, the string within quotes takes the same form as the
7920 output when a single attribute is requested. Specifying no attributes is the
7921 same as specifying all of an entry's attributes.
7923 Here are some examples of the output format. The first line of each pair is an
7924 LDAP query, and the second is the data that is returned. The attribute called
7925 &%attr1%& has two values, one of them with an embedded comma, whereas
7926 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7927 (they have SUP &%attr%& in their schema definitions).
7930 ldap:///o=base?attr1?sub?(uid=fred)
7933 ldap:///o=base?attr2?sub?(uid=fred)
7936 ldap:///o=base?attr?sub?(uid=fred)
7937 value1.1,value1,,2,value two
7939 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7940 attr1="value1.1,value1,,2" attr2="value two"
7942 ldap:///o=base??sub?(uid=fred)
7943 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7946 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7947 results of LDAP lookups.
7948 The &%extract%& operator in string expansions can be used to pick out
7949 individual fields from data that consists of &'key'&=&'value'& pairs.
7950 The &%listextract%& operator should be used to pick out individual values
7951 of attributes, even when only a single value is expected.
7952 The doubling of embedded commas allows you to use the returned data as a
7953 comma separated list (using the "<," syntax for changing the input list separator).
7958 .section "More about NIS+" "SECTnisplus"
7959 .cindex "NIS+ lookup type"
7960 .cindex "lookup" "NIS+"
7961 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7962 and field name. If this is given, the result of a successful query is the
7963 contents of the named field; otherwise the result consists of a concatenation
7964 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7965 values containing spaces are quoted. For example, the query
7967 [name=mg1456],passwd.org_dir
7969 might return the string
7971 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7972 home=/home/mg1456 shell=/bin/bash shadow=""
7974 (split over two lines here to fit on the page), whereas
7976 [name=mg1456],passwd.org_dir:gcos
7982 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7983 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7984 operator is to double any quote characters within the text.
7988 .section "SQL lookups" "SECTsql"
7989 .cindex "SQL lookup types"
7990 .cindex "MySQL" "lookup type"
7991 .cindex "PostgreSQL lookup type"
7992 .cindex "lookup" "MySQL"
7993 .cindex "lookup" "PostgreSQL"
7994 .cindex "Oracle" "lookup type"
7995 .cindex "lookup" "Oracle"
7996 .cindex "InterBase lookup type"
7997 .cindex "lookup" "InterBase"
7998 .cindex "Redis lookup type"
7999 .cindex lookup Redis
8000 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
8002 databases. Queries for these databases contain SQL statements, so an example
8005 ${lookup mysql{select mailbox from users where id='userx'}\
8008 If the result of the query contains more than one field, the data for each
8009 field in the row is returned, preceded by its name, so the result of
8011 ${lookup pgsql{select home,name from users where id='userx'}\
8016 home=/home/userx name="Mister X"
8018 Empty values and values containing spaces are double quoted, with embedded
8019 quotes escaped by a backslash. If the result of the query contains just one
8020 field, the value is passed back verbatim, without a field name, for example:
8024 If the result of the query yields more than one row, it is all concatenated,
8025 with a newline between the data for each row.
8028 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
8029 .cindex "MySQL" "lookup type"
8030 .cindex "PostgreSQL lookup type"
8031 .cindex "lookup" "MySQL"
8032 .cindex "lookup" "PostgreSQL"
8033 .cindex "Oracle" "lookup type"
8034 .cindex "lookup" "Oracle"
8035 .cindex "InterBase lookup type"
8036 .cindex "lookup" "InterBase"
8037 .cindex "Redis lookup type"
8038 .cindex lookup Redis
8039 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
8040 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
8041 or &%redis_servers%&
8042 option (as appropriate) must be set to a colon-separated list of server
8044 .oindex &%mysql_servers%&
8045 .oindex &%pgsql_servers%&
8046 .oindex &%oracle_servers%&
8047 .oindex &%ibase_servers%&
8048 .oindex &%redis_servers%&
8049 (For MySQL and PostgreSQL, the global option need not be set if all
8050 queries contain their own server information &-- see section
8051 &<<SECTspeserque>>&.)
8053 each item in the list is a slash-separated list of four
8054 items: host name, database name, user name, and password. In the case of
8055 Oracle, the host name field is used for the &"service name"&, and the database
8056 name field is not used and should be empty. For example:
8058 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
8060 Because password data is sensitive, you should always precede the setting with
8061 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
8062 option. Here is an example where two MySQL servers are listed:
8064 hide mysql_servers = localhost/users/root/secret:\
8065 otherhost/users/root/othersecret
8067 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
8068 because this is a colon-separated list, the colon has to be doubled. For each
8069 query, these parameter groups are tried in order until a connection is made and
8070 a query is successfully processed. The result of a query may be that no data is
8071 found, but that is still a successful query. In other words, the list of
8072 servers provides a backup facility, not a list of different places to look.
8074 For Redis the global option need not be specified if all queries contain their
8075 own server information &-- see section &<<SECTspeserque>>&.
8076 If specified, the option must be set to a colon-separated list of server
8078 Each item in the list is a slash-separated list of three items:
8079 host, database number, and password.
8081 The host is required and may be either an IPv4 address and optional
8082 port number (separated by a colon, which needs doubling due to the
8083 higher-level list), or a Unix socket pathname enclosed in parentheses
8085 The database number is optional; if present that number is selected in the backend
8087 The password is optional; if present it is used to authenticate to the backend
8090 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
8091 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
8092 respectively, and the characters single-quote, double-quote, and backslash
8093 itself are escaped with backslashes.
8095 The &%quote_redis%& expansion operator
8096 escapes whitespace and backslash characters with a backslash.
8098 .section "Specifying the server in the query" "SECTspeserque"
8099 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
8100 it is possible to specify a list of servers with an individual query. This is
8101 done by appending a comma-separated option to the query type:
8103 &`,servers=`&&'server1:server2:server3:...'&
8105 Each item in the list may take one of two forms:
8107 If it contains no slashes it is assumed to be just a host name. The appropriate
8108 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
8109 of the same name, and the remaining parameters (database, user, password) are
8112 If it contains any slashes, it is taken as a complete parameter set.
8114 The list of servers is used in exactly the same way as the global list.
8115 Once a connection to a server has happened and a query has been
8116 successfully executed, processing of the lookup ceases.
8118 This feature is intended for use in master/slave situations where updates
8119 are occurring and you want to update the master rather than a slave. If the
8120 master is in the list as a backup for reading, you might have a global setting
8123 mysql_servers = slave1/db/name/pw:\
8127 In an updating lookup, you could then write:
8129 ${lookup mysql,servers=master {UPDATE ...} }
8131 That query would then be sent only to the master server. If, on the other hand,
8132 the master is not to be used for reading, and so is not present in the global
8133 option, you can still update it by a query of this form:
8135 ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
8138 An older syntax places the servers specification before the query,
8139 semicolon separated:
8141 ${lookup mysql{servers=master; UPDATE ...} }
8143 The new version avoids potential issues with tainted
8144 arguments in the query, for explicit expansion.
8145 &*Note*&: server specifications in list-style lookups are still problematic.
8148 .section "Special MySQL features" "SECID73"
8149 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
8150 causes a connection to the server on the local host by means of a Unix domain
8151 socket. An alternate socket can be specified in parentheses.
8152 An option group name for MySQL option files can be specified in square brackets;
8153 the default value is &"exim"&.
8154 The full syntax of each item in &%mysql_servers%& is:
8156 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
8157 <&'database'&>/<&'user'&>/<&'password'&>
8159 Any of the four sub-parts of the first field can be omitted. For normal use on
8160 the local host it can be left blank or set to just &"localhost"&.
8162 No database need be supplied &-- but if it is absent here, it must be given in
8165 If a MySQL query is issued that does not request any data (an insert, update,
8166 or delete command), the result of the lookup is the number of rows affected.
8168 &*Warning*&: This can be misleading. If an update does not actually change
8169 anything (for example, setting a field to the value it already has), the result
8170 is zero because no rows are affected.
8173 .section "Special PostgreSQL features" "SECID74"
8174 PostgreSQL lookups can also use Unix domain socket connections to the database.
8175 This is usually faster and costs less CPU time than a TCP/IP connection.
8176 However it can be used only if the mail server runs on the same machine as the
8177 database server. A configuration line for PostgreSQL via Unix domain sockets
8180 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
8182 In other words, instead of supplying a host name, a path to the socket is
8183 given. The path name is enclosed in parentheses so that its slashes aren't
8184 visually confused with the delimiters for the other server parameters.
8186 If a PostgreSQL query is issued that does not request any data (an insert,
8187 update, or delete command), the result of the lookup is the number of rows
8190 .section "More about SQLite" "SECTsqlite"
8191 .cindex "lookup" "SQLite"
8192 .cindex "sqlite lookup type"
8193 SQLite is different to the other SQL lookups because a filename is required in
8194 addition to the SQL query. An SQLite database is a single file, and there is no
8195 daemon as in the other SQL databases.
8198 .oindex &%sqlite_dbfile%&
8199 There are two ways of
8200 specifying the file.
8201 The first is is by using the &%sqlite_dbfile%& main option.
8202 The second, which allows separate files for each query,
8203 is to use an option appended, comma-separated, to the &"sqlite"&
8204 lookup type word. The option is the word &"file"&, then an equals,
8206 The filename in this case cannot contain whitespace or open-brace charachters.
8209 A deprecated method is available, prefixing the query with the filename
8210 separated by white space.
8212 .cindex "tainted data" "sqlite file"
8213 the query cannot use any tainted values, as that taints
8214 the entire query including the filename - resulting in a refusal to open
8217 In all the above cases the filename must be an absolute path.
8219 Here is a lookup expansion example:
8221 sqlite_dbfile = /some/thing/sqlitedb
8223 ${lookup sqlite {select name from aliases where id='userx';}}
8225 In a list, the syntax is similar. For example:
8227 domainlist relay_to_domains = sqlite;\
8228 select * from relays where ip='$sender_host_address';
8230 The only character affected by the &%quote_sqlite%& operator is a single
8231 quote, which it doubles.
8233 .cindex timeout SQLite
8234 .cindex sqlite "lookup timeout"
8235 The SQLite library handles multiple simultaneous accesses to the database
8236 internally. Multiple readers are permitted, but only one process can
8237 update at once. Attempts to access the database while it is being updated
8238 are rejected after a timeout period, during which the SQLite library
8239 waits for the lock to be released. In Exim, the default timeout is set
8240 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
8243 .section "More about Redis" "SECTredis"
8244 .cindex "lookup" "Redis"
8245 .cindex "redis lookup type"
8246 Redis is a non-SQL database. Commands are simple get and set.
8249 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
8250 ${lookup redis{get keyname}}
8253 As of release 4.91, "lightweight" support for Redis Cluster is available.
8254 Requires &%redis_servers%& list to contain all the servers in the cluster, all
8255 of which must be reachable from the running exim instance. If the cluster has
8256 master/slave replication, the list must contain all the master and slave
8259 When the Redis Cluster returns a "MOVED" response to a query, Exim does not
8260 immediately follow the redirection but treats the response as a DEFER, moving on
8261 to the next server in the &%redis_servers%& list until the correct server is
8268 . ////////////////////////////////////////////////////////////////////////////
8269 . ////////////////////////////////////////////////////////////////////////////
8271 .chapter "Domain, host, address, and local part lists" &&&
8272 "CHAPdomhosaddlists" &&&
8273 "Domain, host, and address lists"
8274 .scindex IIDdohoadli "lists of domains; hosts; etc."
8275 A number of Exim configuration options contain lists of domains, hosts,
8276 email addresses, or local parts. For example, the &%hold_domains%& option
8277 contains a list of domains whose delivery is currently suspended. These lists
8278 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
8279 arguments to expansion conditions such as &%match_domain%&.
8281 Each item in one of these lists is a pattern to be matched against a domain,
8282 host, email address, or local part, respectively. In the sections below, the
8283 different types of pattern for each case are described, but first we cover some
8284 general facilities that apply to all four kinds of list.
8286 Note that other parts of Exim use a &'string list'& which does not
8287 support all the complexity available in
8288 domain, host, address and local part lists.
8292 .section "Expansion of lists" "SECTlistexpand"
8293 .cindex "expansion" "of lists"
8294 Each list is expanded as a single string before it is used.
8296 &'Exception: the router headers_remove option, where list-item
8297 splitting is done before string-expansion.'&
8300 expansion must be a list, possibly containing empty items, which is split up
8301 into separate items for matching. By default, colon is the separator character,
8302 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
8303 &<<SECTempitelis>>& for details of the list syntax; the second of these
8304 discusses the way to specify empty list items.
8307 If the string expansion is forced to fail, Exim behaves as if the item it is
8308 testing (domain, host, address, or local part) is not in the list. Other
8309 expansion failures cause temporary errors.
8311 If an item in a list is a regular expression, backslashes, dollars and possibly
8312 other special characters in the expression must be protected against
8313 misinterpretation by the string expander. The easiest way to do this is to use
8314 the &`\N`& expansion feature to indicate that the contents of the regular
8315 expression should not be expanded. For example, in an ACL you might have:
8317 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
8318 ${lookup{$domain}lsearch{/badsenders/bydomain}}
8320 The first item is a regular expression that is protected from expansion by
8321 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
8322 senders based on the receiving domain.
8327 .section "Negated items in lists" "SECID76"
8328 .cindex "list" "negation"
8329 .cindex "negation" "in lists"
8330 Items in a list may be positive or negative. Negative items are indicated by a
8331 leading exclamation mark, which may be followed by optional white space. A list
8332 defines a set of items (domains, etc). When Exim processes one of these lists,
8333 it is trying to find out whether a domain, host, address, or local part
8334 (respectively) is in the set that is defined by the list. It works like this:
8336 The list is scanned from left to right. If a positive item is matched, the
8337 subject that is being checked is in the set; if a negative item is matched, the
8338 subject is not in the set. If the end of the list is reached without the
8339 subject having matched any of the patterns, it is in the set if the last item
8340 was a negative one, but not if it was a positive one. For example, the list in
8342 domainlist relay_to_domains = !a.b.c : *.b.c
8344 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
8345 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
8346 list is positive. However, if the setting were
8348 domainlist relay_to_domains = !a.b.c
8350 then all domains other than &'a.b.c'& would match because the last item in the
8351 list is negative. In other words, a list that ends with a negative item behaves
8352 as if it had an extra item &`:*`& on the end.
8354 Another way of thinking about positive and negative items in lists is to read
8355 the connector as &"or"& after a positive item and as &"and"& after a negative
8360 .section "File names in lists" "SECTfilnamlis"
8361 .cindex "list" "filename in"
8362 If an item in a domain, host, address, or local part list is an absolute
8363 filename (beginning with a slash character), each line of the file is read and
8364 processed as if it were an independent item in the list, except that further
8365 filenames are not allowed,
8366 and no expansion of the data from the file takes place.
8367 Empty lines in the file are ignored, and the file may also contain comment
8371 For domain and host lists, if a # character appears anywhere in a line of the
8372 file, it and all following characters are ignored.
8374 Because local parts may legitimately contain # characters, a comment in an
8375 address list or local part list file is recognized only if # is preceded by
8376 white space or the start of the line. For example:
8378 not#comment@x.y.z # but this is a comment
8382 Putting a filename in a list has the same effect as inserting each line of the
8383 file as an item in the list (blank lines and comments excepted). However, there
8384 is one important difference: the file is read each time the list is processed,
8385 so if its contents vary over time, Exim's behaviour changes.
8387 If a filename is preceded by an exclamation mark, the sense of any match
8388 within the file is inverted. For example, if
8390 hold_domains = !/etc/nohold-domains
8392 and the file contains the lines
8397 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
8398 any domain matching &`*.b.c`& is not.
8402 .section "An lsearch file is not an out-of-line list" "SECID77"
8403 As will be described in the sections that follow, lookups can be used in lists
8404 to provide indexed methods of checking list membership. There has been some
8405 confusion about the way &(lsearch)& lookups work in lists. Because
8406 an &(lsearch)& file contains plain text and is scanned sequentially, it is
8407 sometimes thought that it is allowed to contain wild cards and other kinds of
8408 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
8409 always fixed strings, just as for any other single-key lookup type.
8411 If you want to use a file to contain wild-card patterns that form part of a
8412 list, just give the filename on its own, without a search type, as described
8413 in the previous section. You could also use the &(wildlsearch)& or
8414 &(nwildlsearch)&, but there is no advantage in doing this.
8419 .section "Results of list checking" SECTlistresults
8420 The primary result of doing a list check is a truth value.
8421 In some contexts additional information is stored
8422 about the list element that matched:
8425 A &%hosts%& ACL condition
8426 will store a result in the &$host_data$& variable.
8428 A &%local_parts%& router option or &%local_parts%& ACL condition
8429 will store a result in the &$local_part_data$& variable.
8431 A &%domains%& router option or &%domains%& ACL condition
8433 A &%senders%& router option or &%senders%& ACL condition
8434 will store a result in the &$sender_data$& variable.
8436 A &%recipients%& ACL condition
8437 will store a result in the &$recipient_data$& variable.
8440 The detail of the additional information depends on the
8441 type of match and is given below as the &*value*& information.
8446 .section "Named lists" "SECTnamedlists"
8447 .cindex "named lists"
8448 .cindex "list" "named"
8449 A list of domains, hosts, email addresses, or local parts can be given a name
8450 which is then used to refer to the list elsewhere in the configuration. This is
8451 particularly convenient if the same list is required in several different
8452 places. It also allows lists to be given meaningful names, which can improve
8453 the readability of the configuration. For example, it is conventional to define
8454 a domain list called &'local_domains'& for all the domains that are handled
8455 locally on a host, using a configuration line such as
8457 domainlist local_domains = localhost:my.dom.example
8459 Named lists are referenced by giving their name preceded by a plus sign, so,
8460 for example, a router that is intended to handle local domains would be
8461 configured with the line
8463 domains = +local_domains
8465 The first router in a configuration is often one that handles all domains
8466 except the local ones, using a configuration with a negated item like this:
8470 domains = ! +local_domains
8471 transport = remote_smtp
8474 The four kinds of named list are created by configuration lines starting with
8475 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8476 respectively. Then there follows the name that you are defining, followed by an
8477 equals sign and the list itself. For example:
8479 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8480 addresslist bad_senders = cdb;/etc/badsenders
8482 A named list may refer to other named lists:
8484 domainlist dom1 = first.example : second.example
8485 domainlist dom2 = +dom1 : third.example
8486 domainlist dom3 = fourth.example : +dom2 : fifth.example
8488 &*Warning*&: If the last item in a referenced list is a negative one, the
8489 effect may not be what you intended, because the negation does not propagate
8490 out to the higher level. For example, consider:
8492 domainlist dom1 = !a.b
8493 domainlist dom2 = +dom1 : *.b
8495 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8496 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8497 means it matches the second list as well. The effect is not the same as
8499 domainlist dom2 = !a.b : *.b
8501 where &'x.y'& does not match. It's best to avoid negation altogether in
8502 referenced lists if you can.
8504 .cindex "hiding named list values"
8505 .cindex "named lists" "hiding value of"
8506 Some named list definitions may contain sensitive data, for example, passwords for
8507 accessing databases. To stop non-admin users from using the &%-bP%& command
8508 line option to read these values, you can precede the definition with the
8509 word &"hide"&. For example:
8511 hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
8515 Named lists may have a performance advantage. When Exim is routing an
8516 address or checking an incoming message, it caches the result of tests on named
8517 lists. So, if you have a setting such as
8519 domains = +local_domains
8521 on several of your routers
8522 or in several ACL statements,
8523 the actual test is done only for the first one. However, the caching works only
8524 if there are no expansions within the list itself or any sublists that it
8525 references. In other words, caching happens only for lists that are known to be
8526 the same each time they are referenced.
8528 By default, there may be up to 16 named lists of each type. This limit can be
8529 extended by changing a compile-time variable. The use of domain and host lists
8530 is recommended for concepts such as local domains, relay domains, and relay
8531 hosts. The default configuration is set up like this.
8535 .section "Named lists compared with macros" "SECID78"
8536 .cindex "list" "named compared with macro"
8537 .cindex "macro" "compared with named list"
8538 At first sight, named lists might seem to be no different from macros in the
8539 configuration file. However, macros are just textual substitutions. If you
8542 ALIST = host1 : host2
8543 auth_advertise_hosts = !ALIST
8545 it probably won't do what you want, because that is exactly the same as
8547 auth_advertise_hosts = !host1 : host2
8549 Notice that the second host name is not negated. However, if you use a host
8552 hostlist alist = host1 : host2
8553 auth_advertise_hosts = ! +alist
8555 the negation applies to the whole list, and so that is equivalent to
8557 auth_advertise_hosts = !host1 : !host2
8561 .section "Named list caching" "SECID79"
8562 .cindex "list" "caching of named"
8563 .cindex "caching" "named lists"
8564 While processing a message, Exim caches the result of checking a named list if
8565 it is sure that the list is the same each time. In practice, this means that
8566 the cache operates only if the list contains no $ characters, which guarantees
8567 that it will not change when it is expanded. Sometimes, however, you may have
8568 an expanded list that you know will be the same each time within a given
8569 message. For example:
8571 domainlist special_domains = \
8572 ${lookup{$sender_host_address}cdb{/some/file}}
8574 This provides a list of domains that depends only on the sending host's IP
8575 address. If this domain list is referenced a number of times (for example,
8576 in several ACL lines, or in several routers) the result of the check is not
8577 cached by default, because Exim does not know that it is going to be the
8578 same list each time.
8580 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8581 cache the result anyway. For example:
8583 domainlist_cache special_domains = ${lookup{...
8585 If you do this, you should be absolutely sure that caching is going to do
8586 the right thing in all cases. When in doubt, leave it out.
8590 .section "Domain lists" "SECTdomainlist"
8591 .cindex "domain list" "patterns for"
8592 .cindex "list" "domain list"
8593 Domain lists contain patterns that are to be matched against a mail domain.
8594 The following types of item may appear in domain lists:
8597 .cindex "primary host name"
8598 .cindex "host name" "matched in domain list"
8599 .oindex "&%primary_hostname%&"
8600 .cindex "domain list" "matching primary host name"
8601 .cindex "@ in a domain list"
8602 If a pattern consists of a single @ character, it matches the local host name,
8603 as set by the &%primary_hostname%& option (or defaulted). This makes it
8604 possible to use the same configuration file on several different hosts that
8605 differ only in their names.
8607 The value for a match will be the primary host name.
8611 .cindex "@[] in a domain list"
8612 .cindex "domain list" "matching local IP interfaces"
8613 .cindex "domain literal"
8614 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8615 in square brackets (as in an email address that contains a domain literal), but
8616 only if that IP address is recognized as local for email routing purposes. The
8617 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8618 control which of a host's several IP addresses are treated as local.
8619 In today's Internet, the use of domain literals is controversial;
8620 see the &%allow_domain_literals%& main option.
8622 The value for a match will be the string &`@[]`&.
8627 .cindex "@mx_primary"
8628 .cindex "@mx_secondary"
8629 .cindex "domain list" "matching MX pointers to local host"
8630 If a pattern consists of the string &`@mx_any`& it matches any domain that
8631 has an MX record pointing to the local host or to any host that is listed in
8632 .oindex "&%hosts_treat_as_local%&"
8633 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8634 are similar, except that the first matches only when a primary MX target is the
8635 local host, and the second only when no primary MX target is the local host,
8636 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8637 preference value &-- there may of course be more than one of them.
8639 The MX lookup that takes place when matching a pattern of this type is
8640 performed with the resolver options for widening names turned off. Thus, for
8641 example, a single-component domain will &'not'& be expanded by adding the
8642 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8643 options of the &(dnslookup)& router for a discussion of domain widening.
8645 Sometimes you may want to ignore certain IP addresses when using one of these
8646 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8647 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8648 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8649 on a router). For example:
8651 domains = @mx_any/ignore=127.0.0.1
8653 This example matches any domain that has an MX record pointing to one of
8654 the local host's IP addresses other than 127.0.0.1.
8656 The list of IP addresses is in fact processed by the same code that processes
8657 host lists, so it may contain CIDR-coded network specifications and it may also
8658 contain negative items.
8660 Because the list of IP addresses is a sublist within a domain list, you have to
8661 be careful about delimiters if there is more than one address. Like any other
8662 list, the default delimiter can be changed. Thus, you might have:
8664 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8665 an.other.domain : ...
8667 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8668 involved, it is easiest to change the delimiter for the main list as well:
8670 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8671 an.other.domain ? ...
8673 The value for a match will be the list element string (starting &`@mx_`&).
8677 .cindex "asterisk" "in domain list"
8678 .cindex "domain list" "asterisk in"
8679 .cindex "domain list" "matching &""ends with""&"
8680 If a pattern starts with an asterisk, the remaining characters of the pattern
8681 are compared with the terminating characters of the domain. The use of &"*"& in
8682 domain lists differs from its use in partial matching lookups. In a domain
8683 list, the character following the asterisk need not be a dot, whereas partial
8684 matching works only in terms of dot-separated components. For example, a domain
8685 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8688 The value for a match will be the list element string (starting with the asterisk).
8689 Additionally, &$0$& will be set to the matched string
8690 and &$1$& to the variable portion which the asterisk matched.
8693 .cindex "regular expressions" "in domain list"
8694 .cindex "domain list" "matching regular expression"
8695 If a pattern starts with a circumflex character, it is treated as a regular
8696 expression, and matched against the domain using a regular expression matching
8697 function. The circumflex is treated as part of the regular expression.
8698 Email domains are case-independent, so this regular expression match is by
8699 default case-independent, but you can make it case-dependent by starting it
8700 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8701 are given in chapter &<<CHAPregexp>>&.
8703 &*Warning*&: Because domain lists are expanded before being processed, you
8704 must escape any backslash and dollar characters in the regular expression, or
8705 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8706 it is not to be expanded (unless you really do want to build a regular
8707 expression by expansion, of course).
8709 The value for a match will be the list element string (starting with the circumflex).
8710 Additionally, &$0$& will be set to the string matching the regular expression,
8711 and &$1$& (onwards) to any submatches identified by parentheses.
8716 .cindex "lookup" "in domain list"
8717 .cindex "domain list" "matching by lookup"
8718 If a pattern starts with the name of a single-key lookup type followed by a
8719 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8720 must be a filename in a suitable format for the lookup type. For example, for
8721 &"cdb;"& it must be an absolute path:
8723 domains = cdb;/etc/mail/local_domains.cdb
8725 The appropriate type of lookup is done on the file using the domain name as the
8726 key. In most cases, the value resulting from the lookup is not used; Exim is interested
8727 only in whether or not the key is present in the file. However, when a lookup
8728 is used for the &%domains%& option on a router
8729 or a &%domains%& condition in an ACL statement, the value is preserved in the
8730 &$domain_data$& variable and can be referred to in other router options or
8731 other statements in the same ACL.
8732 .cindex "tainted data" "de-tainting"
8733 The value will be untainted.
8737 Any of the single-key lookup type names may be preceded by
8738 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8740 domains = partial-dbm;/partial/domains
8742 This causes partial matching logic to be invoked; a description of how this
8743 works is given in section &<<SECTpartiallookup>>&.
8746 .cindex "asterisk" "in lookup type"
8747 Any of the single-key lookup types may be followed by an asterisk. This causes
8748 a default lookup for a key consisting of a single asterisk to be done if the
8749 original lookup fails. This is not a useful feature when using a domain list to
8750 select particular domains (because any domain would match), but it might have
8751 value if the result of the lookup is being used via the &$domain_data$&
8755 If the pattern starts with the name of a query-style lookup type followed by a
8756 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8757 pattern must be an appropriate query for the lookup type, as described in
8758 chapter &<<CHAPfdlookup>>&. For example:
8760 hold_domains = mysql;select domain from holdlist \
8761 where domain = '${quote_mysql:$domain}';
8763 In most cases, the value resulting from the lookup is not used (so for an SQL query, for
8764 example, it doesn't matter what field you select). Exim is interested only in
8765 whether or not the query succeeds. However, when a lookup is used for the
8766 &%domains%& option on a router, the value is preserved in the &$domain_data$&
8767 variable and can be referred to in other options.
8768 .cindex "tainted data" "de-tainting"
8769 The value will be untainted.
8772 If the pattern starts with the name of a lookup type
8773 of either kind (single-key or query-style) it may be
8774 followed by a comma and options,
8775 The options are lookup-type specific and consist of a comma-separated list.
8776 Each item starts with a tag and and equals "=".
8779 .cindex "domain list" "matching literal domain name"
8780 If none of the above cases apply, a caseless textual comparison is made
8781 between the pattern and the domain.
8783 The value for a match will be the list element string.
8784 .cindex "tainted data" "de-tainting"
8785 Note that this is commonly untainted
8786 (depending on the way the list was created).
8787 Specifically, explicit text in the configuration file in not tainted.
8788 This is a useful way of obtaining an untainted equivalent to
8789 the domain, for later operations.
8791 However if the list (including one-element lists)
8792 is created by expanding a variable containing tainted data,
8793 it is tainted and so will the match value be.
8797 Here is an example that uses several different kinds of pattern:
8799 domainlist funny_domains = \
8802 *.foundation.fict.example : \
8803 \N^[1-2]\d{3}\.fict\.example$\N : \
8804 partial-dbm;/opt/data/penguin/book : \
8805 nis;domains.byname : \
8806 nisplus;[name=$domain,status=local],domains.org_dir
8808 There are obvious processing trade-offs among the various matching modes. Using
8809 an asterisk is faster than a regular expression, and listing a few names
8810 explicitly probably is too. The use of a file or database lookup is expensive,
8811 but may be the only option if hundreds of names are required. Because the
8812 patterns are tested in order, it makes sense to put the most commonly matched
8817 .section "Host lists" "SECThostlist"
8818 .cindex "host list" "patterns in"
8819 .cindex "list" "host list"
8820 Host lists are used to control what remote hosts are allowed to do. For
8821 example, some hosts may be allowed to use the local host as a relay, and some
8822 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8823 two different ways, by name or by IP address. In a host list, some types of
8824 pattern are matched to a host name, and some are matched to an IP address.
8825 You need to be particularly careful with this when single-key lookups are
8826 involved, to ensure that the right value is being used as the key.
8829 .section "Special host list patterns" "SECID80"
8830 .cindex "empty item in hosts list"
8831 .cindex "host list" "empty string in"
8832 If a host list item is the empty string, it matches only when no remote host is
8833 involved. This is the case when a message is being received from a local
8834 process using SMTP on the standard input, that is, when a TCP/IP connection is
8837 .cindex "asterisk" "in host list"
8838 The special pattern &"*"& in a host list matches any host or no host. Neither
8839 the IP address nor the name is actually inspected.
8843 .section "Host list patterns that match by IP address" "SECThoslispatip"
8844 .cindex "host list" "matching IP addresses"
8845 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8846 the incoming address actually appears in the IPv6 host as
8847 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8848 list, it is converted into a traditional IPv4 address first. (Not all operating
8849 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8852 The following types of pattern in a host list check the remote host by
8853 inspecting its IP address:
8856 If the pattern is a plain domain name (not a regular expression, not starting
8857 with *, not a lookup of any kind), Exim calls the operating system function
8858 to find the associated IP address(es). Exim uses the newer
8859 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8860 This typically causes a forward DNS lookup of the name. The result is compared
8861 with the IP address of the subject host.
8863 If there is a temporary problem (such as a DNS timeout) with the host name
8864 lookup, a temporary error occurs. For example, if the list is being used in an
8865 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8866 temporary SMTP error code. If no IP address can be found for the host name,
8867 what happens is described in section &<<SECTbehipnot>>& below.
8870 .cindex "@ in a host list"
8871 If the pattern is &"@"&, the primary host name is substituted and used as a
8872 domain name, as just described.
8875 If the pattern is an IP address, it is matched against the IP address of the
8876 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8877 IPv6 addresses can be given in colon-separated format, but the colons have to
8878 be doubled so as not to be taken as item separators when the default list
8879 separator is used. IPv6 addresses are recognized even when Exim is compiled
8880 without IPv6 support. This means that if they appear in a host list on an
8881 IPv4-only host, Exim will not treat them as host names. They are just addresses
8882 that can never match a client host.
8885 .cindex "@[] in a host list"
8886 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8887 the local host. For example, if the local host is an IPv4 host with one
8888 interface address 10.45.23.56, these two ACL statements have the same effect:
8890 accept hosts = 127.0.0.1 : 10.45.23.56
8894 .cindex "CIDR notation"
8895 If the pattern is an IP address followed by a slash and a mask length (for
8896 example 10.11.42.0/24), it is matched against the IP address of the subject
8897 host under the given mask. This allows, an entire network of hosts to be
8898 included (or excluded) by a single item. The mask uses CIDR notation; it
8899 specifies the number of address bits that must match, starting from the most
8900 significant end of the address.
8902 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8903 of a range of addresses. It is the number of bits in the network portion of the
8904 address. The above example specifies a 24-bit netmask, so it matches all 256
8905 addresses in the 10.11.42.0 network. An item such as
8909 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8910 32 for an IPv4 address is the same as no mask at all; just a single address
8913 Here is another example which shows an IPv4 and an IPv6 network:
8915 recipient_unqualified_hosts = 192.168.0.0/16: \
8916 3ffe::ffff::836f::::/48
8918 The doubling of list separator characters applies only when these items
8919 appear inline in a host list. It is not required when indirecting via a file.
8922 recipient_unqualified_hosts = /opt/exim/unqualnets
8924 could make use of a file containing
8929 to have exactly the same effect as the previous example. When listing IPv6
8930 addresses inline, it is usually more convenient to use the facility for
8931 changing separator characters. This list contains the same two networks:
8933 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8936 The separator is changed to semicolon by the leading &"<;"& at the start of the
8942 .section "Host list patterns for single-key lookups by host address" &&&
8943 "SECThoslispatsikey"
8944 .cindex "host list" "lookup of IP address"
8945 When a host is to be identified by a single-key lookup of its complete IP
8946 address, the pattern takes this form:
8948 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8952 hosts_lookup = net-cdb;/hosts-by-ip.db
8954 The text form of the IP address of the subject host is used as the lookup key.
8955 IPv6 addresses are converted to an unabbreviated form, using lower case
8956 letters, with dots as separators because colon is the key terminator in
8957 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8958 quoting the keys, but this is a facility that was added later.] The data
8959 returned by the lookup is not used.
8961 .cindex "IP address" "masking"
8962 .cindex "host list" "masked IP address"
8963 Single-key lookups can also be performed using masked IP addresses, using
8964 patterns of this form:
8966 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8970 net24-dbm;/networks.db
8972 The IP address of the subject host is masked using <&'number'&> as the mask
8973 length. A textual string is constructed from the masked value, followed by the
8974 mask, and this is used as the lookup key. For example, if the host's IP address
8975 is 192.168.34.6, the key that is looked up for the above example is
8976 &"192.168.34.0/24"&.
8978 When an IPv6 address is converted to a string, dots are normally used instead
8979 of colons, so that keys in &(lsearch)& files need not contain colons (which
8980 terminate &(lsearch)& keys). This was implemented some time before the ability
8981 to quote keys was made available in &(lsearch)& files. However, the more
8982 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8983 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8984 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8985 converted using colons and not dots.
8986 In all cases except IPv4-mapped IPv6, full, unabbreviated IPv6
8987 addresses are always used.
8988 The latter are converted to IPv4 addresses, in dotted-quad form.
8990 Ideally, it would be nice to tidy up this anomalous situation by changing to
8991 colons in all cases, given that quoting is now available for &(lsearch)&.
8992 However, this would be an incompatible change that might break some existing
8995 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8996 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8997 the former case the key strings include the mask value, whereas in the latter
8998 case the IP address is used on its own.
9002 .section "Host list patterns that match by host name" "SECThoslispatnam"
9003 .cindex "host" "lookup failures"
9004 .cindex "unknown host name"
9005 .cindex "host list" "matching host name"
9006 There are several types of pattern that require Exim to know the name of the
9007 remote host. These are either wildcard patterns or lookups by name. (If a
9008 complete hostname is given without any wildcarding, it is used to find an IP
9009 address to match against, as described in section &<<SECThoslispatip>>&
9012 If the remote host name is not already known when Exim encounters one of these
9013 patterns, it has to be found from the IP address.
9014 Although many sites on the Internet are conscientious about maintaining reverse
9015 DNS data for their hosts, there are also many that do not do this.
9016 Consequently, a name cannot always be found, and this may lead to unwanted
9017 effects. Take care when configuring host lists with wildcarded name patterns.
9018 Consider what will happen if a name cannot be found.
9020 Because of the problems of determining host names from IP addresses, matching
9021 against host names is not as common as matching against IP addresses.
9023 By default, in order to find a host name, Exim first does a reverse DNS lookup;
9024 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
9025 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
9026 are done can be changed by setting the &%host_lookup_order%& option. For
9027 security, once Exim has found one or more names, it looks up the IP addresses
9028 for these names and compares them with the IP address that it started with.
9029 Only those names whose IP addresses match are accepted. Any other names are
9030 discarded. If no names are left, Exim behaves as if the host name cannot be
9031 found. In the most common case there is only one name and one IP address.
9033 There are some options that control what happens if a host name cannot be
9034 found. These are described in section &<<SECTbehipnot>>& below.
9036 .cindex "host" "alias for"
9037 .cindex "alias for host"
9038 As a result of aliasing, hosts may have more than one name. When processing any
9039 of the following types of pattern, all the host's names are checked:
9042 .cindex "asterisk" "in host list"
9043 If a pattern starts with &"*"& the remainder of the item must match the end of
9044 the host name. For example, &`*.b.c`& matches all hosts whose names end in
9045 &'.b.c'&. This special simple form is provided because this is a very common
9046 requirement. Other kinds of wildcarding require the use of a regular
9049 .cindex "regular expressions" "in host list"
9050 .cindex "host list" "regular expression in"
9051 If the item starts with &"^"& it is taken to be a regular expression which is
9052 matched against the host name. Host names are case-independent, so this regular
9053 expression match is by default case-independent, but you can make it
9054 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
9055 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
9060 is a regular expression that matches either of the two hosts &'a.c.d'& or
9061 &'b.c.d'&. When a regular expression is used in a host list, you must take care
9062 that backslash and dollar characters are not misinterpreted as part of the
9063 string expansion. The simplest way to do this is to use &`\N`& to mark that
9064 part of the string as non-expandable. For example:
9066 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
9068 &*Warning*&: If you want to match a complete host name, you must include the
9069 &`$`& terminating metacharacter in the regular expression, as in the above
9070 example. Without it, a match at the start of the host name is all that is
9077 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
9078 .cindex "host" "lookup failures, permanent"
9079 While processing a host list, Exim may need to look up an IP address from a
9080 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
9081 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
9082 behaviour when it fails to find the information it is seeking is the same.
9084 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
9085 apply to temporary DNS errors, whose handling is described in the next section.
9087 .cindex "&`+include_unknown`&"
9088 .cindex "&`+ignore_unknown`&"
9089 Exim parses a host list from left to right. If it encounters a permanent
9090 lookup failure in any item in the host list before it has found a match,
9091 Exim treats it as a failure and the default behavior is as if the host
9092 does not match the list. This may not always be what you want to happen.
9093 To change Exim's behaviour, the special items &`+include_unknown`& or
9094 &`+ignore_unknown`& may appear in the list (at top level &-- they are
9095 not recognized in an indirected file).
9098 If any item that follows &`+include_unknown`& requires information that
9099 cannot found, Exim behaves as if the host does match the list. For example,
9101 host_reject_connection = +include_unknown:*.enemy.ex
9103 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
9104 any hosts whose name it cannot find.
9107 If any item that follows &`+ignore_unknown`& requires information that cannot
9108 be found, Exim ignores that item and proceeds to the rest of the list. For
9111 accept hosts = +ignore_unknown : friend.example : \
9114 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
9115 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
9116 name can be found for 192.168.4.5, it is rejected.
9119 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
9120 list. The effect of each one lasts until the next, or until the end of the
9123 .section "Mixing wildcarded host names and addresses in host lists" &&&
9125 .cindex "host list" "mixing names and addresses in"
9127 This section explains the host/ip processing logic with the same concepts
9128 as the previous section, but specifically addresses what happens when a
9129 wildcarded hostname is one of the items in the hostlist.
9132 If you have name lookups or wildcarded host names and
9133 IP addresses in the same host list, you should normally put the IP
9134 addresses first. For example, in an ACL you could have:
9136 accept hosts = 10.9.8.7 : *.friend.example
9138 The reason you normally would order it this way lies in the
9139 left-to-right way that Exim processes lists. It can test IP addresses
9140 without doing any DNS lookups, but when it reaches an item that requires
9141 a host name, it fails if it cannot find a host name to compare with the
9142 pattern. If the above list is given in the opposite order, the
9143 &%accept%& statement fails for a host whose name cannot be found, even
9144 if its IP address is 10.9.8.7.
9147 If you really do want to do the name check first, and still recognize the IP
9148 address, you can rewrite the ACL like this:
9150 accept hosts = *.friend.example
9151 accept hosts = 10.9.8.7
9153 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
9154 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
9155 &`+ignore_unknown`&, which was discussed in depth in the first example in
9160 .section "Temporary DNS errors when looking up host information" &&&
9162 .cindex "host" "lookup failures, temporary"
9163 .cindex "&`+include_defer`&"
9164 .cindex "&`+ignore_defer`&"
9165 A temporary DNS lookup failure normally causes a defer action (except when
9166 &%dns_again_means_nonexist%& converts it into a permanent error). However,
9167 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
9168 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
9169 section. These options should be used with care, probably only in non-critical
9170 host lists such as whitelists.
9174 .section "Host list patterns for single-key lookups by host name" &&&
9175 "SECThoslispatnamsk"
9176 .cindex "unknown host name"
9177 .cindex "host list" "matching host name"
9178 If a pattern is of the form
9180 <&'single-key-search-type'&>;<&'search-data'&>
9184 dbm;/host/accept/list
9186 a single-key lookup is performed, using the host name as its key. If the
9187 lookup succeeds, the host matches the item. The actual data that is looked up
9190 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
9191 keys in the file, not IP addresses. If you want to do lookups based on IP
9192 addresses, you must precede the search type with &"net-"& (see section
9193 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
9194 two items in the same list, one doing an address lookup and one doing a name
9195 lookup, both using the same file.
9199 .section "Host list patterns for query-style lookups" "SECID81"
9200 If a pattern is of the form
9202 <&'query-style-search-type'&>;<&'query'&>
9204 the query is obeyed, and if it succeeds, the host matches the item. The actual
9205 data that is looked up is not used. The variables &$sender_host_address$& and
9206 &$sender_host_name$& can be used in the query. For example:
9208 hosts_lookup = pgsql;\
9209 select ip from hostlist where ip='$sender_host_address'
9211 The value of &$sender_host_address$& for an IPv6 address contains colons. You
9212 can use the &%sg%& expansion item to change this if you need to. If you want to
9213 use masked IP addresses in database queries, you can use the &%mask%& expansion
9216 If the query contains a reference to &$sender_host_name$&, Exim automatically
9217 looks up the host name if it has not already done so. (See section
9218 &<<SECThoslispatnam>>& for comments on finding host names.)
9220 Historical note: prior to release 4.30, Exim would always attempt to find a
9221 host name before running the query, unless the search type was preceded by
9222 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
9223 still recognized for query-style lookups, but its presence or absence has no
9224 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
9225 See section &<<SECThoslispatsikey>>&.)
9231 .section "Address lists" "SECTaddresslist"
9232 .cindex "list" "address list"
9233 .cindex "address list" "empty item"
9234 .cindex "address list" "patterns"
9235 Address lists contain patterns that are matched against mail addresses. There
9236 is one special case to be considered: the sender address of a bounce message is
9237 always empty. You can test for this by providing an empty item in an address
9238 list. For example, you can set up a router to process bounce messages by
9239 using this option setting:
9243 The presence of the colon creates an empty item. If you do not provide any
9244 data, the list is empty and matches nothing. The empty sender can also be
9245 detected by a regular expression that matches an empty string,
9246 and by a query-style lookup that succeeds when &$sender_address$& is empty.
9248 Non-empty items in an address list can be straightforward email addresses. For
9251 senders = jbc@askone.example : hs@anacreon.example
9253 A certain amount of wildcarding is permitted. If a pattern contains an @
9254 character, but is not a regular expression and does not begin with a
9255 semicolon-terminated lookup type (described below), the local part of the
9256 subject address is compared with the local part of the pattern, which may start
9257 with an asterisk. If the local parts match, the domain is checked in exactly
9258 the same way as for a pattern in a domain list. For example, the domain can be
9259 wildcarded, refer to a named list, or be a lookup:
9261 deny senders = *@*.spamming.site:\
9262 *@+hostile_domains:\
9263 bozo@partial-lsearch;/list/of/dodgy/sites:\
9264 *@dbm;/bad/domains.db
9266 .cindex "local part" "starting with !"
9267 .cindex "address list" "local part starting with !"
9268 If a local part that begins with an exclamation mark is required, it has to be
9269 specified using a regular expression, because otherwise the exclamation mark is
9270 treated as a sign of negation, as is standard in lists.
9272 If a non-empty pattern that is not a regular expression or a lookup does not
9273 contain an @ character, it is matched against the domain part of the subject
9274 address. The only two formats that are recognized this way are a literal
9275 domain, or a domain pattern that starts with *. In both these cases, the effect
9276 is the same as if &`*@`& preceded the pattern. For example:
9278 deny senders = enemy.domain : *.enemy.domain
9281 The following kinds of more complicated address list pattern can match any
9282 address, including the empty address that is characteristic of bounce message
9286 .cindex "regular expressions" "in address list"
9287 .cindex "address list" "regular expression in"
9288 If (after expansion) a pattern starts with &"^"&, a regular expression match is
9289 done against the complete address, with the pattern as the regular expression.
9290 You must take care that backslash and dollar characters are not misinterpreted
9291 as part of the string expansion. The simplest way to do this is to use &`\N`&
9292 to mark that part of the string as non-expandable. For example:
9294 deny senders = \N^.*this.*@example\.com$\N : \
9295 \N^\d{8}.+@spamhaus.example$\N : ...
9297 The &`\N`& sequences are removed by the expansion, so these items do indeed
9298 start with &"^"& by the time they are being interpreted as address patterns.
9301 .cindex "address list" "lookup for complete address"
9302 Complete addresses can be looked up by using a pattern that starts with a
9303 lookup type terminated by a semicolon, followed by the data for the lookup. For
9306 deny senders = cdb;/etc/blocked.senders : \
9307 mysql;select address from blocked where \
9308 address='${quote_mysql:$sender_address}'
9310 Both query-style and single-key lookup types can be used. For a single-key
9311 lookup type, Exim uses the complete address as the key. However, empty keys are
9312 not supported for single-key lookups, so a match against the empty address
9313 always fails. This restriction does not apply to query-style lookups.
9315 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
9316 cannot be used, and is ignored if specified, with an entry being written to the
9318 .cindex "*@ with single-key lookup"
9319 However, you can configure lookup defaults, as described in section
9320 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
9321 default. For example, with this lookup:
9323 accept senders = lsearch*@;/some/file
9325 the file could contains lines like this:
9327 user1@domain1.example
9330 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
9333 nimrod@jaeger.example
9337 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
9338 would mean that every address matches, thus rendering the test useless.
9340 &*Warning 2*&: Do not confuse these two kinds of item:
9342 deny recipients = dbm*@;/some/file
9343 deny recipients = *@dbm;/some/file
9345 The first does a whole address lookup, with defaulting, as just described,
9346 because it starts with a lookup type. The second matches the local part and
9347 domain independently, as described in a bullet point below.
9351 The following kinds of address list pattern can match only non-empty addresses.
9352 If the subject address is empty, a match against any of these pattern types
9357 .cindex "@@ with single-key lookup"
9358 .cindex "address list" "@@ lookup type"
9359 .cindex "address list" "split local part and domain"
9360 If a pattern starts with &"@@"& followed by a single-key lookup item
9361 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
9362 split into a local part and a domain. The domain is looked up in the file. If
9363 it is not found, there is no match. If it is found, the data that is looked up
9364 from the file is treated as a colon-separated list of local part patterns, each
9365 of which is matched against the subject local part in turn.
9367 .cindex "asterisk" "in address list"
9368 The lookup may be a partial one, and/or one involving a search for a default
9369 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
9370 patterns that are looked up can be regular expressions or begin with &"*"&, or
9371 even be further lookups. They may also be independently negated. For example,
9374 deny senders = @@dbm;/etc/reject-by-domain
9376 the data from which the DBM file is built could contain lines like
9378 baddomain.com: !postmaster : *
9380 to reject all senders except &%postmaster%& from that domain.
9382 .cindex "local part" "starting with !"
9383 If a local part that actually begins with an exclamation mark is required, it
9384 has to be specified using a regular expression. In &(lsearch)& files, an entry
9385 may be split over several lines by indenting the second and subsequent lines,
9386 but the separating colon must still be included at line breaks. White space
9387 surrounding the colons is ignored. For example:
9389 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
9392 As in all colon-separated lists in Exim, a colon can be included in an item by
9395 If the last item in the list starts with a right angle-bracket, the remainder
9396 of the item is taken as a new key to look up in order to obtain a continuation
9397 list of local parts. The new key can be any sequence of characters. Thus one
9398 might have entries like
9400 aol.com: spammer1 : spammer 2 : >*
9401 xyz.com: spammer3 : >*
9404 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
9405 local parts for all domains, in addition to the specific local parts listed for
9406 each domain. Of course, using this feature costs another lookup each time a
9407 chain is followed, but the effort needed to maintain the data is reduced.
9409 .cindex "loop" "in lookups"
9410 It is possible to construct loops using this facility, and in order to catch
9411 them, the chains may be no more than fifty items long.
9414 The @@<&'lookup'&> style of item can also be used with a query-style
9415 lookup, but in this case, the chaining facility is not available. The lookup
9416 can only return a single list of local parts.
9419 &*Warning*&: There is an important difference between the address list items
9420 in these two examples:
9423 senders = *@+my_list
9425 In the first one, &`my_list`& is a named address list, whereas in the second
9426 example it is a named domain list.
9431 .section "Case of letters in address lists" "SECTcasletadd"
9432 .cindex "case of local parts"
9433 .cindex "address list" "case forcing"
9434 .cindex "case forcing in address lists"
9435 Domains in email addresses are always handled caselessly, but for local parts
9436 case may be significant on some systems (see &%caseful_local_part%& for how
9437 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
9438 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
9439 blocking lists should be done in a case-independent manner. Since most address
9440 lists in Exim are used for this kind of control, Exim attempts to do this by
9443 The domain portion of an address is always lowercased before matching it to an
9444 address list. The local part is lowercased by default, and any string
9445 comparisons that take place are done caselessly. This means that the data in
9446 the address list itself, in files included as plain filenames, and in any file
9447 that is looked up using the &"@@"& mechanism, can be in any case. However, the
9448 keys in files that are looked up by a search type other than &(lsearch)& (which
9449 works caselessly) must be in lower case, because these lookups are not
9452 .cindex "&`+caseful`&"
9453 To allow for the possibility of caseful address list matching, if an item in
9454 an address list is the string &"+caseful"&, the original case of the local
9455 part is restored for any comparisons that follow, and string comparisons are no
9456 longer case-independent. This does not affect the domain, which remains in
9457 lower case. However, although independent matches on the domain alone are still
9458 performed caselessly, regular expressions that match against an entire address
9459 become case-sensitive after &"+caseful"& has been seen.
9463 .section "Local part lists" "SECTlocparlis"
9464 .cindex "list" "local part list"
9465 .cindex "local part" "list"
9466 These behave in the same way as domain and host lists, with the following
9469 Case-sensitivity in local part lists is handled in the same way as for address
9470 lists, as just described. The &"+caseful"& item can be used if required. In a
9471 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
9472 set false, the subject is lowercased and the matching is initially
9473 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
9474 matching in the local part list, but not elsewhere in the router. If
9475 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
9476 option is case-sensitive from the start.
9478 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
9479 comments are handled in the same way as address lists &-- they are recognized
9480 only if the # is preceded by white space or the start of the line.
9481 Otherwise, local part lists are matched in the same way as domain lists, except
9482 that the special items that refer to the local host (&`@`&, &`@[]`&,
9483 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
9484 Refer to section &<<SECTdomainlist>>& for details of the other available item
9486 .ecindex IIDdohoadli
9491 . ////////////////////////////////////////////////////////////////////////////
9492 . ////////////////////////////////////////////////////////////////////////////
9494 .chapter "String expansions" "CHAPexpand"
9495 .scindex IIDstrexp "expansion" "of strings"
9496 Many strings in Exim's runtime configuration are expanded before use. Some of
9497 them are expanded every time they are used; others are expanded only once.
9499 When a string is being expanded it is copied verbatim from left to right except
9500 .cindex expansion "string concatenation"
9501 when a dollar or backslash character is encountered. A dollar specifies the
9502 start of a portion of the string that is interpreted and replaced as described
9503 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
9504 escape character, as described in the following section.
9506 Whether a string is expanded depends upon the context. Usually this is solely
9507 dependent upon the option for which a value is sought; in this documentation,
9508 options for which string expansion is performed are marked with † after
9509 the data type. ACL rules always expand strings. A couple of expansion
9510 conditions do not expand some of the brace-delimited branches, for security
9512 .cindex "tainted data" expansion
9513 .cindex "tainted data" definition
9514 .cindex expansion "tainted data"
9515 and expansion of data deriving from the sender (&"tainted data"&)
9519 Common ways of obtaining untainted equivalents of variables with
9521 .cindex "tainted data" "de-tainting"
9522 come down to using the tainted value as a lookup key in a trusted database.
9523 This database could be the filesystem structure,
9524 or the password file,
9525 or accessed via a DBMS.
9526 Specific methods are indexed under &"de-tainting"&.
9531 .section "Literal text in expanded strings" "SECTlittext"
9532 .cindex "expansion" "including literal text"
9533 An uninterpreted dollar can be included in an expanded string by putting a
9534 backslash in front of it. A backslash can be used to prevent any special
9535 character being treated specially in an expansion, including backslash itself.
9536 If the string appears in quotes in the configuration file, two backslashes are
9537 required because the quotes themselves cause interpretation of backslashes when
9538 the string is read in (see section &<<SECTstrings>>&).
9540 .cindex "expansion" "non-expandable substrings"
9541 A portion of the string can specified as non-expandable by placing it between
9542 two occurrences of &`\N`&. This is particularly useful for protecting regular
9543 expressions, which often contain backslashes and dollar signs. For example:
9545 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
9547 On encountering the first &`\N`&, the expander copies subsequent characters
9548 without interpretation until it reaches the next &`\N`& or the end of the
9553 .section "Character escape sequences in expanded strings" "SECID82"
9554 .cindex "expansion" "escape sequences"
9555 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9556 expanded string is recognized as an escape sequence for the character newline,
9557 carriage return, or tab, respectively. A backslash followed by up to three
9558 octal digits is recognized as an octal encoding for a single character, and a
9559 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9562 These escape sequences are also recognized in quoted strings when they are read
9563 in. Their interpretation in expansions as well is useful for unquoted strings,
9564 and for other cases such as looked-up strings that are then expanded.
9567 .section "Testing string expansions" "SECID83"
9568 .cindex "expansion" "testing"
9569 .cindex "testing" "string expansion"
9571 Many expansions can be tested by calling Exim with the &%-be%& option. This
9572 takes the command arguments, or lines from the standard input if there are no
9573 arguments, runs them through the string expansion code, and writes the results
9574 to the standard output. Variables based on configuration values are set up, but
9575 since no message is being processed, variables such as &$local_part$& have no
9576 value. Nevertheless the &%-be%& option can be useful for checking out file and
9577 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9580 Exim gives up its root privilege when it is called with the &%-be%& option, and
9581 instead runs under the uid and gid it was called with, to prevent users from
9582 using &%-be%& for reading files to which they do not have access.
9585 If you want to test expansions that include variables whose values are taken
9586 from a message, there are two other options that can be used. The &%-bem%&
9587 option is like &%-be%& except that it is followed by a filename. The file is
9588 read as a message before doing the test expansions. For example:
9590 exim -bem /tmp/test.message '$h_subject:'
9592 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9593 Exim message identifier. For example:
9595 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9597 This loads the message from Exim's spool before doing the test expansions, and
9598 is therefore restricted to admin users.
9601 .section "Forced expansion failure" "SECTforexpfai"
9602 .cindex "expansion" "forced failure"
9603 A number of expansions that are described in the following section have
9604 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9605 (which are sometimes called &"curly brackets"&). Which of the two strings is
9606 used depends on some condition that is evaluated as part of the expansion. If,
9607 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9608 the entire string expansion fails in a way that can be detected by the code
9609 that requested the expansion. This is called &"forced expansion failure"&, and
9610 its consequences depend on the circumstances. In some cases it is no different
9611 from any other expansion failure, but in others a different action may be
9612 taken. Such variations are mentioned in the documentation of the option that is
9618 .section "Expansion items" "SECTexpansionitems"
9619 The following items are recognized in expanded strings. White space may be used
9620 between sub-items that are keywords or substrings enclosed in braces inside an
9621 outer set of braces, to improve readability. &*Warning*&: Within braces,
9622 white space is significant.
9625 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9626 .cindex "expansion" "variables"
9627 Substitute the contents of the named variable, for example:
9632 The second form can be used to separate the name from subsequent alphanumeric
9633 characters. This form (using braces) is available only for variables; it does
9634 &'not'& apply to message headers. The names of the variables are given in
9635 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9636 given, the expansion fails.
9638 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9639 .cindex "expansion" "operators"
9640 The string is first itself expanded, and then the operation specified by
9641 <&'op'&> is applied to it. For example:
9645 The string starts with the first character after the colon, which may be
9646 leading white space. A list of operators is given in section &<<SECTexpop>>&
9647 below. The operator notation is used for simple expansion items that have just
9648 one argument, because it reduces the number of braces and therefore makes the
9649 string easier to understand.
9651 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9652 This item inserts &"basic"& header lines. It is described with the &%header%&
9653 expansion item below.
9656 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9657 .cindex "expansion" "calling an acl"
9658 .cindex "&%acl%&" "call from expansion"
9659 The name and zero to nine argument strings are first expanded separately. The expanded
9660 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9661 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9662 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9663 and may use the variables; if another acl expansion is used the values
9664 are restored after it returns. If the ACL sets
9665 a value using a "message =" modifier and returns accept or deny, the value becomes
9666 the result of the expansion.
9667 If no message is set and the ACL returns accept or deny
9668 the expansion result is an empty string.
9669 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9672 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
9673 .cindex authentication "results header"
9674 .cindex headers "authentication-results:"
9675 .cindex authentication "expansion item"
9676 This item returns a string suitable for insertion as an
9677 &'Authentication-Results:'&
9679 The given <&'authserv-id'&> is included in the result; typically this
9680 will be a domain name identifying the system performing the authentications.
9681 Methods that might be present in the result include:
9690 Example use (as an ACL modifier):
9692 add_header = :at_start:${authresults {$primary_hostname}}
9694 This is safe even if no authentication results are available.
9697 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9698 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9699 .cindex "expansion" "extracting certificate fields"
9700 .cindex "&%certextract%&" "certificate fields"
9701 .cindex "certificate" "extracting fields"
9702 The <&'certificate'&> must be a variable of type certificate.
9703 The field name is expanded and used to retrieve the relevant field from
9704 the certificate. Supported fields are:
9708 &`subject `& RFC4514 DN
9709 &`issuer `& RFC4514 DN
9714 &`subj_altname `& tagged list
9718 If the field is found,
9719 <&'string2'&> is expanded, and replaces the whole item;
9720 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9721 variable &$value$& contains the value that has been extracted. Afterwards, it
9722 is restored to any previous value it might have had.
9724 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9725 key is not found. If {<&'string2'&>} is also omitted, the value that was
9728 Some field names take optional modifiers, appended and separated by commas.
9730 The field selectors marked as "RFC4514" above
9731 output a Distinguished Name string which is
9733 parseable by Exim as a comma-separated tagged list
9734 (the exceptions being elements containing commas).
9735 RDN elements of a single type may be selected by
9736 a modifier of the type label; if so the expansion
9737 result is a list (newline-separated by default).
9738 The separator may be changed by another modifier of
9739 a right angle-bracket followed immediately by the new separator.
9740 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9742 The field selectors marked as "time" above
9743 take an optional modifier of "int"
9744 for which the result is the number of seconds since epoch.
9745 Otherwise the result is a human-readable string
9746 in the timezone selected by the main "timezone" option.
9748 The field selectors marked as "list" above return a list,
9749 newline-separated by default,
9750 (embedded separator characters in elements are doubled).
9751 The separator may be changed by a modifier of
9752 a right angle-bracket followed immediately by the new separator.
9754 The field selectors marked as "tagged" above
9755 prefix each list element with a type string and an equals sign.
9756 Elements of only one type may be selected by a modifier
9757 which is one of "dns", "uri" or "mail";
9758 if so the element tags are omitted.
9760 If not otherwise noted field values are presented in human-readable form.
9762 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9763 {*&<&'arg'&>&*}...}*&"
9765 This expansion dynamically loads and then calls a locally-written C function.
9766 This functionality is available only if Exim is compiled with
9770 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9771 object so that it doesn't reload the same object file in the same Exim process
9772 (but of course Exim does start new processes frequently).
9774 There may be from zero to eight arguments to the function.
9777 a local function that is to be called in this way,
9778 first &_DLFUNC_IMPL_& should be defined,
9779 and second &_local_scan.h_& should be included.
9780 The Exim variables and functions that are defined by that API
9781 are also available for dynamically loaded functions. The function itself
9782 must have the following type:
9784 int dlfunction(uschar **yield, int argc, uschar *argv[])
9786 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9787 function should return one of the following values:
9789 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9790 into the expanded string that is being built.
9792 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9793 from &'yield'&, if it is set.
9795 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9796 taken from &'yield'& if it is set.
9798 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9800 When compiling a function that is to be used in this way with gcc,
9801 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9802 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9805 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9806 .cindex "expansion" "extracting value from environment"
9807 .cindex "environment" "values from"
9808 The key is first expanded separately, and leading and trailing white space
9810 This is then searched for as a name in the environment.
9811 If a variable is found then its value is placed in &$value$&
9812 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9814 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9815 appear, for example:
9817 ${env{USER}{$value} fail }
9819 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9820 {<&'string1'&>} must be present for &"fail"& to be recognized.
9822 If {<&'string2'&>} is omitted an empty string is substituted on
9824 If {<&'string1'&>} is omitted the search result is substituted on
9827 The environment is adjusted by the &%keep_environment%& and
9828 &%add_environment%& main section options.
9831 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9832 {*&<&'string3'&>&*}}*&"
9833 .cindex "expansion" "extracting substrings by key"
9834 .cindex "&%extract%&" "substrings by key"
9835 The key and <&'string1'&> are first expanded separately. Leading and trailing
9836 white space is removed from the key (but not from any of the strings). The key
9837 must not be empty and must not consist entirely of digits.
9838 The expanded <&'string1'&> must be of the form:
9840 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9843 where the equals signs and spaces (but not both) are optional. If any of the
9844 values contain white space, they must be enclosed in double quotes, and any
9845 values that are enclosed in double quotes are subject to escape processing as
9846 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9847 for the value that corresponds to the key. The search is case-insensitive. If
9848 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9849 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9850 variable &$value$& contains the value that has been extracted. Afterwards, it
9851 is restored to any previous value it might have had.
9853 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9854 key is not found. If {<&'string2'&>} is also omitted, the value that was
9855 extracted is used. Thus, for example, these two expansions are identical, and
9858 ${extract{gid}{uid=1984 gid=2001}}
9859 ${extract{gid}{uid=1984 gid=2001}{$value}}
9861 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9862 appear, for example:
9864 ${extract{Z}{A=... B=...}{$value} fail }
9866 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9867 {<&'string2'&>} must be present for &"fail"& to be recognized.
9869 .vitem "&*${extract json{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9870 {*&<&'string3'&>&*}}*&" &&&
9871 "&*${extract jsons{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9872 {*&<&'string3'&>&*}}*&"
9873 .cindex "expansion" "extracting from JSON object"
9874 .cindex JSON expansions
9875 The key and <&'string1'&> are first expanded separately. Leading and trailing
9876 white space is removed from the key (but not from any of the strings). The key
9877 must not be empty and must not consist entirely of digits.
9878 The expanded <&'string1'&> must be of the form:
9880 { <&'"key1"'&> : <&'value1'&> , <&'"key2"'&> , <&'value2'&> ... }
9883 The braces, commas and colons, and the quoting of the member name are required;
9884 the spaces are optional.
9885 Matching of the key against the member names is done case-sensitively.
9886 For the &"json"& variant,
9887 if a returned value is a JSON string, it retains its leading and
9889 For the &"jsons"& variant, which is intended for use with JSON strings, the
9890 leading and trailing quotes are removed from the returned value.
9891 . XXX should be a UTF-8 compare
9893 The results of matching are handled as above.
9896 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9897 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9898 .cindex "expansion" "extracting substrings by number"
9899 .cindex "&%extract%&" "substrings by number"
9900 The <&'number'&> argument must consist entirely of decimal digits,
9901 apart from leading and trailing white space, which is ignored.
9902 This is what distinguishes this form of &%extract%& from the previous kind. It
9903 behaves in the same way, except that, instead of extracting a named field, it
9904 extracts from <&'string1'&> the field whose number is given as the first
9905 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9906 <&'string3'&> as before.
9908 The fields in the string are separated by any one of the characters in the
9909 separator string. These may include space or tab characters.
9910 The first field is numbered one. If the number is negative, the fields are
9911 counted from the end of the string, with the rightmost one numbered -1. If the
9912 number given is zero, the entire string is returned. If the modulus of the
9913 number is greater than the number of fields in the string, the result is the
9914 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9915 provided. For example:
9917 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9921 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9923 yields &"99"&. Two successive separators mean that the field between them is
9924 empty (for example, the fifth field above).
9927 .vitem "&*${extract json {*&<&'number'&>&*}}&&&
9928 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&" &&&
9929 "&*${extract jsons{*&<&'number'&>&*}}&&&
9930 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9931 .cindex "expansion" "extracting from JSON array"
9932 .cindex JSON expansions
9933 The <&'number'&> argument must consist entirely of decimal digits,
9934 apart from leading and trailing white space, which is ignored.
9936 Field selection and result handling is as above;
9937 there is no choice of field separator.
9938 For the &"json"& variant,
9939 if a returned value is a JSON string, it retains its leading and
9941 For the &"jsons"& variant, which is intended for use with JSON strings, the
9942 leading and trailing quotes are removed from the returned value.
9945 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9946 .cindex "list" "selecting by condition"
9947 .cindex "expansion" "selecting from list by condition"
9949 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9950 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
9952 in this list, its value is place in &$item$&, and then the condition is
9953 evaluated. If the condition is true, &$item$& is added to the output as an
9954 item in a new list; if the condition is false, the item is discarded. The
9955 separator used for the output list is the same as the one used for the
9956 input, but a separator setting is not included in the output. For example:
9958 ${filter{a:b:c}{!eq{$item}{b}}}
9960 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9961 to what it was before. See also the &%map%& and &%reduce%& expansion items.
9964 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9965 .cindex "hash function" "textual"
9966 .cindex "expansion" "textual hash"
9967 This is a textual hashing function, and was the first to be implemented in
9968 early versions of Exim. In current releases, there are other hashing functions
9969 (numeric, MD5, and SHA-1), which are described below.
9971 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9972 <&'n'&>. If you are using fixed values for these numbers, that is, if
9973 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9974 use the simpler operator notation that avoids some of the braces:
9976 ${hash_<n>_<m>:<string>}
9978 The second number is optional (in both notations). If <&'n'&> is greater than
9979 or equal to the length of the string, the expansion item returns the string.
9980 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9981 function to the string. The new string consists of characters taken from the
9982 first <&'m'&> characters of the string
9984 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9986 If <&'m'&> is not present the value 26 is used, so that only lower case
9987 letters appear. For example:
9989 &`$hash{3}{monty}} `& yields &`jmg`&
9990 &`$hash{5}{monty}} `& yields &`monty`&
9991 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9994 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9995 &*$h_*&<&'header&~name'&>&*:*&" &&&
9996 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9997 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9998 "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9999 &*$lh_*&<&'header&~name'&>&*:*&" &&&
10000 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
10001 &*$rh_*&<&'header&~name'&>&*:*&"
10002 .cindex "expansion" "header insertion"
10003 .vindex "&$header_$&"
10004 .vindex "&$bheader_$&"
10005 .vindex "&$lheader_$&"
10006 .vindex "&$rheader_$&"
10007 .cindex "header lines" "in expansion strings"
10008 .cindex "header lines" "character sets"
10009 .cindex "header lines" "decoding"
10010 Substitute the contents of the named message header line, for example
10014 The newline that terminates a header line is not included in the expansion, but
10015 internal newlines (caused by splitting the header line over several physical
10016 lines) may be present.
10018 The difference between the four pairs of expansions is in the way
10019 the data in the header line is interpreted.
10022 .cindex "white space" "in header lines"
10023 &%rheader%& gives the original &"raw"& content of the header line, with no
10024 processing at all, and without the removal of leading and trailing white space.
10027 .cindex "list" "of header lines"
10028 &%lheader%& gives a colon-separated list, one element per header when there
10029 are multiple headers with a given name.
10030 Any embedded colon characters within an element are doubled, so normal Exim
10031 list-processing facilities can be used.
10032 The terminating newline of each element is removed; in other respects
10033 the content is &"raw"&.
10036 .cindex "base64 encoding" "in header lines"
10037 &%bheader%& removes leading and trailing white space, and then decodes base64
10038 or quoted-printable MIME &"words"& within the header text, but does no
10039 character set translation. If decoding of what looks superficially like a MIME
10040 &"word"& fails, the raw string is returned. If decoding
10041 .cindex "binary zero" "in header line"
10042 produces a binary zero character, it is replaced by a question mark &-- this is
10043 what Exim does for binary zeros that are actually received in header lines.
10046 &%header%& tries to translate the string as decoded by &%bheader%& to a
10047 standard character set. This is an attempt to produce the same string as would
10048 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
10049 returned. Translation is attempted only on operating systems that support the
10050 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
10051 a system Makefile or in &_Local/Makefile_&.
10054 In a filter file, the target character set for &%header%& can be specified by a
10055 command of the following form:
10057 headers charset "UTF-8"
10059 This command affects all references to &$h_$& (or &$header_$&) expansions in
10060 subsequently obeyed filter commands. In the absence of this command, the target
10061 character set in a filter is taken from the setting of the &%headers_charset%&
10062 option in the runtime configuration. The value of this option defaults to the
10063 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
10066 Header names follow the syntax of RFC 2822, which states that they may contain
10067 any printing characters except space and colon. Consequently, curly brackets
10068 &'do not'& terminate header names, and should not be used to enclose them as
10069 if they were variables. Attempting to do so causes a syntax error.
10071 Only header lines that are common to all copies of a message are visible to
10072 this mechanism. These are the original header lines that are received with the
10073 message, and any that are added by an ACL statement or by a system
10074 filter. Header lines that are added to a particular copy of a message by a
10075 router or transport are not accessible.
10077 For incoming SMTP messages, no header lines are visible in
10078 ACLs that are obeyed before the data phase completes,
10079 because the header structure is not set up until the message is received.
10080 They are visible in DKIM, PRDR and DATA ACLs.
10081 Header lines that are added in a RCPT ACL (for example)
10082 are saved until the message's incoming header lines are available, at which
10083 point they are added.
10084 When any of the above ACLs ar
10085 running, however, header lines added by earlier ACLs are visible.
10087 Upper case and lower case letters are synonymous in header names. If the
10088 following character is white space, the terminating colon may be omitted, but
10089 this is not recommended, because you may then forget it when it is needed. When
10090 white space terminates the header name, this white space is included in the
10091 expanded string. If the message does not contain the given header, the
10092 expansion item is replaced by an empty string. (See the &%def%& condition in
10093 section &<<SECTexpcond>>& for a means of testing for the existence of a
10096 If there is more than one header with the same name, they are all concatenated
10097 to form the substitution string, up to a maximum length of 64K. Unless
10098 &%rheader%& is being used, leading and trailing white space is removed from
10099 each header before concatenation, and a completely empty header is ignored. A
10100 newline character is then inserted between non-empty headers, but there is no
10101 newline at the very end. For the &%header%& and &%bheader%& expansion, for
10102 those headers that contain lists of addresses, a comma is also inserted at the
10103 junctions between headers. This does not happen for the &%rheader%& expansion.
10105 .cindex "tainted data"
10106 When the headers are from an incoming message,
10107 the result of expanding any of these variables is tainted.
10110 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
10111 .cindex "expansion" "hmac hashing"
10113 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
10114 shared secret and some text into a message authentication code, as specified in
10115 RFC 2104. This differs from &`${md5:secret_text...}`& or
10116 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
10117 cryptographic hash, allowing for authentication that is not possible with MD5
10118 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
10119 present. For example:
10121 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
10123 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
10126 dd97e3ba5d1a61b5006108f8c8252953
10128 As an example of how this might be used, you might put in the main part of
10129 an Exim configuration:
10131 SPAMSCAN_SECRET=cohgheeLei2thahw
10133 In a router or a transport you could then have:
10136 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
10137 ${hmac{md5}{SPAMSCAN_SECRET}\
10138 {${primary_hostname},${message_exim_id},$h_message-id:}}
10140 Then given a message, you can check where it was scanned by looking at the
10141 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
10142 this header line is authentic by recomputing the authentication code from the
10143 host name, message ID and the &'Message-id:'& header line. This can be done
10144 using Exim's &%-be%& option, or by other means, for example, by using the
10145 &'hmac_md5_hex()'& function in Perl.
10148 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10149 .cindex "expansion" "conditional"
10150 .cindex "&%if%&, expansion item"
10151 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
10152 item; otherwise <&'string2'&> is used. The available conditions are described
10153 in section &<<SECTexpcond>>& below. For example:
10155 ${if eq {$local_part}{postmaster} {yes}{no} }
10157 The second string need not be present; if it is not and the condition is not
10158 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
10159 be present instead of the second string (without any curly brackets). In this
10160 case, the expansion is forced to fail if the condition is not true (see section
10161 &<<SECTforexpfai>>&).
10163 If both strings are omitted, the result is the string &`true`& if the condition
10164 is true, and the empty string if the condition is false. This makes it less
10165 cumbersome to write custom ACL and router conditions. For example, instead of
10167 condition = ${if >{$acl_m4}{3}{true}{false}}
10171 condition = ${if >{$acl_m4}{3}}
10176 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
10177 .cindex expansion "imap folder"
10178 .cindex "&%imapfolder%& expansion item"
10179 This item converts a (possibly multilevel, or with non-ASCII characters)
10180 folder specification to a Maildir name for filesystem use.
10181 For information on internationalisation support see &<<SECTi18nMDA>>&.
10185 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10186 .cindex "expansion" "string truncation"
10187 .cindex "&%length%& expansion item"
10188 The &%length%& item is used to extract the initial portion of a string. Both
10189 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
10190 you are using a fixed value for the number, that is, if <&'string1'&> does not
10191 change when expanded, you can use the simpler operator notation that avoids
10192 some of the braces:
10194 ${length_<n>:<string>}
10196 The result of this item is either the first <&'n'&> bytes or the whole
10197 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
10198 &%strlen%&, which gives the length of a string.
10199 All measurement is done in bytes and is not UTF-8 aware.
10202 .vitem "&*${listextract{*&<&'number'&>&*}&&&
10203 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
10204 .cindex "expansion" "extracting list elements by number"
10205 .cindex "&%listextract%&" "extract list elements by number"
10206 .cindex "list" "extracting elements by number"
10207 The <&'number'&> argument must consist entirely of decimal digits,
10208 apart from an optional leading minus,
10209 and leading and trailing white space (which is ignored).
10211 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10212 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10214 The first field of the list is numbered one.
10215 If the number is negative, the fields are
10216 counted from the end of the list, with the rightmost one numbered -1.
10217 The numbered element of the list is extracted and placed in &$value$&,
10218 then <&'string2'&> is expanded as the result.
10220 If the modulus of the
10221 number is zero or greater than the number of fields in the string,
10222 the result is the expansion of <&'string3'&>.
10226 ${listextract{2}{x:42:99}}
10230 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
10232 yields &"result: 42"&.
10234 If {<&'string3'&>} is omitted, an empty string is used for string3.
10235 If {<&'string2'&>} is also omitted, the value that was
10237 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
10241 .vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*&
10242 .cindex quoting "for list"
10243 .cindex list quoting
10244 This item doubles any occurrence of the separator character
10245 in the given string.
10246 An empty string is replaced with a single space.
10247 This converts the string into a safe form for use as a list element,
10248 in a list using the given separator.
10252 .vitem "&*${lookup&~{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
10253 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" &&&
10254 "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
10255 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
10256 .cindex "expansion" "lookup in"
10257 .cindex "file" "lookups"
10258 .cindex "lookup" "in expanded string"
10259 The two forms of lookup item specify data lookups in files and databases, as
10260 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
10261 lookups, and the second is used for query-style lookups. The <&'key'&>,
10262 <&'file'&>, and <&'query'&> strings are expanded before use.
10264 If there is any white space in a lookup item which is part of a filter command,
10265 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
10266 other place where white space is significant, the lookup item must be enclosed
10267 in double quotes. The use of data lookups in users' filter files may be locked
10268 out by the system administrator.
10270 .vindex "&$value$&"
10271 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
10272 During its expansion, the variable &$value$& contains the data returned by the
10273 lookup. Afterwards it reverts to the value it had previously (at the outer
10274 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
10275 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
10276 string on failure. If <&'string2'&> is provided, it can itself be a nested
10277 lookup, thus providing a mechanism for looking up a default value when the
10278 original lookup fails.
10280 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
10281 data for the outer lookup while the parameters of the second lookup are
10282 expanded, and also while <&'string2'&> of the second lookup is expanded, should
10283 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
10284 appear, and in this case, if the lookup fails, the entire expansion is forced
10285 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
10286 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
10287 successful lookup, and nothing in the case of failure.
10289 For single-key lookups, the string &"partial"& is permitted to precede the
10290 search type in order to do partial matching, and * or *@ may follow a search
10291 type to request default lookups if the key does not match (see sections
10292 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
10294 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
10295 If a partial search is used, the variables &$1$& and &$2$& contain the wild
10296 and non-wild parts of the key during the expansion of the replacement text.
10297 They return to their previous values at the end of the lookup item.
10299 This example looks up the postmaster alias in the conventional alias file:
10301 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
10303 This example uses NIS+ to look up the full name of the user corresponding to
10304 the local part of an address, forcing the expansion to fail if it is not found:
10306 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
10311 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
10312 .cindex "expansion" "list creation"
10314 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
10315 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10317 in this list, its value is place in &$item$&, and then <&'string2'&> is
10318 expanded and added to the output as an item in a new list. The separator used
10319 for the output list is the same as the one used for the input, but a separator
10320 setting is not included in the output. For example:
10322 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
10324 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
10325 value of &$item$& is restored to what it was before. See also the &%filter%&
10326 and &%reduce%& expansion items.
10328 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10329 .cindex "expansion" "numeric hash"
10330 .cindex "hash function" "numeric"
10331 The three strings are expanded; the first two must yield numbers. Call them
10332 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10333 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10334 can use the simpler operator notation that avoids some of the braces:
10336 ${nhash_<n>_<m>:<string>}
10338 The second number is optional (in both notations). If there is only one number,
10339 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
10340 processed by a div/mod hash function that returns two numbers, separated by a
10341 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
10344 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
10346 returns the string &"6/33"&.
10350 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
10351 .cindex "Perl" "use in expanded string"
10352 .cindex "expansion" "calling Perl from"
10353 This item is available only if Exim has been built to include an embedded Perl
10354 interpreter. The subroutine name and the arguments are first separately
10355 expanded, and then the Perl subroutine is called with those arguments. No
10356 additional arguments need be given; the maximum number permitted, including the
10357 name of the subroutine, is nine.
10359 The return value of the subroutine is inserted into the expanded string, unless
10360 the return value is &%undef%&. In that case, the expansion fails in the same
10361 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
10362 Whatever you return is evaluated in a scalar context. For example, if you
10363 return the name of a Perl vector, the return value is the size of the vector,
10366 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
10367 with the error message that was passed to &%die%&. More details of the embedded
10368 Perl facility are given in chapter &<<CHAPperl>>&.
10370 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
10371 out the use of this expansion item in filter files.
10374 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
10375 .cindex "&%prvs%& expansion item"
10376 The first argument is a complete email address and the second is secret
10377 keystring. The third argument, specifying a key number, is optional. If absent,
10378 it defaults to 0. The result of the expansion is a prvs-signed email address,
10379 to be typically used with the &%return_path%& option on an &(smtp)& transport
10380 as part of a bounce address tag validation (BATV) scheme. For more discussion
10381 and an example, see section &<<SECTverifyPRVS>>&.
10383 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
10384 {*&<&'string'&>&*}}*&"
10385 .cindex "&%prvscheck%& expansion item"
10386 This expansion item is the complement of the &%prvs%& item. It is used for
10387 checking prvs-signed addresses. If the expansion of the first argument does not
10388 yield a syntactically valid prvs-signed address, the whole item expands to the
10389 empty string. When the first argument does expand to a syntactically valid
10390 prvs-signed address, the second argument is expanded, with the prvs-decoded
10391 version of the address and the key number extracted from the address in the
10392 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
10394 These two variables can be used in the expansion of the second argument to
10395 retrieve the secret. The validity of the prvs-signed address is then checked
10396 against the secret. The result is stored in the variable &$prvscheck_result$&,
10397 which is empty for failure or &"1"& for success.
10399 The third argument is optional; if it is missing, it defaults to an empty
10400 string. This argument is now expanded. If the result is an empty string, the
10401 result of the expansion is the decoded version of the address. This is the case
10402 whether or not the signature was valid. Otherwise, the result of the expansion
10403 is the expansion of the third argument.
10405 All three variables can be used in the expansion of the third argument.
10406 However, once the expansion is complete, only &$prvscheck_result$& remains set.
10407 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
10409 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
10410 .cindex "expansion" "inserting an entire file"
10411 .cindex "file" "inserting into expansion"
10412 .cindex "&%readfile%& expansion item"
10413 The filename and end-of-line string are first expanded separately. The file is
10414 then read, and its contents replace the entire item. All newline characters in
10415 the file are replaced by the end-of-line string if it is present. Otherwise,
10416 newlines are left in the string.
10417 String expansion is not applied to the contents of the file. If you want this,
10418 you must wrap the item in an &%expand%& operator. If the file cannot be read,
10419 the string expansion fails.
10421 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
10422 locks out the use of this expansion item in filter files.
10426 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
10427 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
10428 .cindex "expansion" "inserting from a socket"
10429 .cindex "socket, use of in expansion"
10430 .cindex "&%readsocket%& expansion item"
10431 This item inserts data from a Unix domain or TCP socket into the expanded
10432 string. The minimal way of using it uses just two arguments, as in these
10435 ${readsocket{/socket/name}{request string}}
10436 ${readsocket{inet:some.host:1234}{request string}}
10438 For a Unix domain socket, the first substring must be the path to the socket.
10439 For an Internet socket, the first substring must contain &`inet:`& followed by
10440 a host name or IP address, followed by a colon and a port, which can be a
10441 number or the name of a TCP port in &_/etc/services_&. An IP address may
10442 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
10445 ${readsocket{inet:[::1]:1234}{request string}}
10447 Only a single host name may be given, but if looking it up yields more than
10448 one IP address, they are each tried in turn until a connection is made. For
10449 both kinds of socket, Exim makes a connection, writes the request string
10450 unless it is an empty string; and no terminating NUL is ever sent)
10451 and reads from the socket until an end-of-file
10452 is read. A timeout of 5 seconds is applied. Additional, optional arguments
10453 extend what can be done. Firstly, you can vary the timeout. For example:
10455 ${readsocket{/socket/name}{request string}{3s}}
10458 The third argument is a list of options, of which the first element is the timeout
10459 and must be present if any options are given.
10460 Further elements are options of form &'name=value'&.
10463 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
10466 The following option names are recognised:
10469 Defines if the result data can be cached for use by a later identical
10470 request in the same process.
10471 Values are &"yes"& or &"no"& (the default).
10472 If not, all cached results for this connection specification
10473 will be invalidated.
10477 Defines whether or not a write-shutdown is done on the connection after
10478 sending the request. Values are &"yes"& (the default) or &"no"&
10479 (preferred, eg. by some webservers).
10483 Controls the use of TLS on the connection.
10484 Values are &"yes"& or &"no"& (the default).
10485 If it is enabled, a shutdown as descripbed above is never done.
10489 A fourth argument allows you to change any newlines that are in the data
10490 that is read, in the same way as for &%readfile%& (see above). This example
10491 turns them into spaces:
10493 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
10495 As with all expansions, the substrings are expanded before the processing
10496 happens. Errors in these sub-expansions cause the expansion to fail. In
10497 addition, the following errors can occur:
10500 Failure to create a socket file descriptor;
10502 Failure to connect the socket;
10504 Failure to write the request string;
10506 Timeout on reading from the socket.
10509 By default, any of these errors causes the expansion to fail. However, if
10510 you supply a fifth substring, it is expanded and used when any of the above
10511 errors occurs. For example:
10513 ${readsocket{/socket/name}{request string}{3s}{\n}\
10516 You can test for the existence of a Unix domain socket by wrapping this
10517 expansion in &`${if exists`&, but there is a race condition between that test
10518 and the actual opening of the socket, so it is safer to use the fifth argument
10519 if you want to be absolutely sure of avoiding an expansion error for a
10520 non-existent Unix domain socket, or a failure to connect to an Internet socket.
10522 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
10523 locks out the use of this expansion item in filter files.
10526 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10527 .cindex "expansion" "reducing a list to a scalar"
10528 .cindex "list" "reducing to a scalar"
10529 .vindex "&$value$&"
10531 This operation reduces a list to a single, scalar string. After expansion,
10532 <&'string1'&> is interpreted as a list, colon-separated by default, but the
10533 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10534 Then <&'string2'&> is expanded and
10535 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
10536 list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
10537 them. The result of that expansion is assigned to &$value$& before the next
10538 iteration. When the end of the list is reached, the final value of &$value$& is
10539 added to the expansion output. The &%reduce%& expansion item can be used in a
10540 number of ways. For example, to add up a list of numbers:
10542 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
10544 The result of that expansion would be &`6`&. The maximum of a list of numbers
10547 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
10549 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
10550 restored to what they were before. See also the &%filter%& and &%map%&
10553 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
10554 This item inserts &"raw"& header lines. It is described with the &%header%&
10555 expansion item in section &<<SECTexpansionitems>>& above.
10557 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
10558 {*&<&'string2'&>&*}}*&"
10559 .cindex "expansion" "running a command"
10560 .cindex "&%run%& expansion item"
10561 The command and its arguments are first expanded as one string. The string is
10562 split apart into individual arguments by spaces, and then the command is run
10563 in a separate process, but under the same uid and gid. As in other command
10564 executions from Exim, a shell is not used by default. If the command requires
10565 a shell, you must explicitly code it.
10567 Since the arguments are split by spaces, when there is a variable expansion
10568 which has an empty result, it will cause the situation that the argument will
10569 simply be omitted when the program is actually executed by Exim. If the
10570 script/program requires a specific number of arguments and the expanded
10571 variable could possibly result in this empty expansion, the variable must be
10572 quoted. This is more difficult if the expanded variable itself could result
10573 in a string containing quotes, because it would interfere with the quotes
10574 around the command arguments. A possible guard against this is to wrap the
10575 variable in the &%sg%& operator to change any quote marks to some other
10578 The standard input for the command exists, but is empty. The standard output
10579 and standard error are set to the same file descriptor.
10580 .cindex "return code" "from &%run%& expansion"
10581 .vindex "&$value$&"
10582 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
10583 and replaces the entire item; during this expansion, the standard output/error
10584 from the command is in the variable &$value$&. If the command fails,
10585 <&'string2'&>, if present, is expanded and used. Once again, during the
10586 expansion, the standard output/error from the command is in the variable
10589 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
10590 can be the word &"fail"& (not in braces) to force expansion failure if the
10591 command does not succeed. If both strings are omitted, the result is contents
10592 of the standard output/error on success, and nothing on failure.
10594 .vindex "&$run_in_acl$&"
10595 The standard output/error of the command is put in the variable &$value$&.
10596 In this ACL example, the output of a command is logged for the admin to
10599 warn condition = ${run{/usr/bin/id}{yes}{no}}
10600 log_message = Output of id: $value
10602 If the command requires shell idioms, such as the > redirect operator, the
10603 shell must be invoked directly, such as with:
10605 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
10608 .vindex "&$runrc$&"
10609 The return code from the command is put in the variable &$runrc$&, and this
10610 remains set afterwards, so in a filter file you can do things like this:
10612 if "${run{x y z}{}}$runrc" is 1 then ...
10613 elif $runrc is 2 then ...
10617 If execution of the command fails (for example, the command does not exist),
10618 the return code is 127 &-- the same code that shells use for non-existent
10621 &*Warning*&: In a router or transport, you cannot assume the order in which
10622 option values are expanded, except for those preconditions whose order of
10623 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
10624 by the expansion of one option, and use it in another.
10626 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
10627 out the use of this expansion item in filter files.
10630 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
10631 .cindex "expansion" "string substitution"
10632 .cindex "&%sg%& expansion item"
10633 This item works like Perl's substitution operator (s) with the global (/g)
10634 option; hence its name. However, unlike the Perl equivalent, Exim does not
10635 modify the subject string; instead it returns the modified string for insertion
10636 into the overall expansion. The item takes three arguments: the subject string,
10637 a regular expression, and a substitution string. For example:
10639 ${sg{abcdefabcdef}{abc}{xyz}}
10641 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
10642 if any $, } or \ characters are required in the regular expression or in the
10643 substitution string, they have to be escaped. For example:
10645 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
10647 yields &"defabc"&, and
10649 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
10651 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
10652 the regular expression from string expansion.
10654 The regular expression is compiled in 8-bit mode, working against bytes
10655 rather than any Unicode-aware character handling.
10658 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
10659 .cindex sorting "a list"
10660 .cindex list sorting
10661 .cindex expansion "list sorting"
10662 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10663 default, but the separator can be changed in the usual way (&<<SECTlistsepchange>>&).
10664 The <&'comparator'&> argument is interpreted as the operator
10665 of a two-argument expansion condition.
10666 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
10667 The comparison should return true when applied to two values
10668 if the first value should sort before the second value.
10669 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
10670 the element being placed in &$item$&,
10671 to give values for comparison.
10673 The item result is a sorted list,
10674 with the original list separator,
10675 of the list elements (in full) of the original.
10679 ${sort{3:2:1:4}{<}{$item}}
10681 sorts a list of numbers, and
10683 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10685 will sort an MX lookup into priority order.
10690 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
10691 SRS encoding. See SECT &<<SECTSRS>>& for details.
10696 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10697 .cindex "&%substr%& expansion item"
10698 .cindex "substring extraction"
10699 .cindex "expansion" "substring extraction"
10700 The three strings are expanded; the first two must yield numbers. Call them
10701 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10702 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10703 can use the simpler operator notation that avoids some of the braces:
10705 ${substr_<n>_<m>:<string>}
10707 The second number is optional (in both notations).
10708 If it is absent in the simpler format, the preceding underscore must also be
10711 The &%substr%& item can be used to extract more general substrings than
10712 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10713 length required. For example
10715 ${substr{3}{2}{$local_part}}
10717 If the starting offset is greater than the string length the result is the
10718 null string; if the length plus starting offset is greater than the string
10719 length, the result is the right-hand part of the string, starting from the
10720 given offset. The first byte (character) in the string has offset zero.
10722 The &%substr%& expansion item can take negative offset values to count
10723 from the right-hand end of its operand. The last byte (character) is offset -1,
10724 the second-last is offset -2, and so on. Thus, for example,
10726 ${substr{-5}{2}{1234567}}
10728 yields &"34"&. If the absolute value of a negative offset is greater than the
10729 length of the string, the substring starts at the beginning of the string, and
10730 the length is reduced by the amount of overshoot. Thus, for example,
10732 ${substr{-5}{2}{12}}
10734 yields an empty string, but
10736 ${substr{-3}{2}{12}}
10740 When the second number is omitted from &%substr%&, the remainder of the string
10741 is taken if the offset is positive. If it is negative, all bytes (characters) in the
10742 string preceding the offset point are taken. For example, an offset of -1 and
10743 no length, as in these semantically identical examples:
10746 ${substr{-1}{abcde}}
10748 yields all but the last character of the string, that is, &"abcd"&.
10750 All measurement is done in bytes and is not UTF-8 aware.
10754 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10755 {*&<&'replacements'&>&*}}*&"
10756 .cindex "expansion" "character translation"
10757 .cindex "&%tr%& expansion item"
10758 This item does single-character (in bytes) translation on its subject string. The second
10759 argument is a list of characters to be translated in the subject string. Each
10760 matching character is replaced by the corresponding character from the
10761 replacement list. For example
10763 ${tr{abcdea}{ac}{13}}
10765 yields &`1b3de1`&. If there are duplicates in the second character string, the
10766 last occurrence is used. If the third string is shorter than the second, its
10767 last character is replicated. However, if it is empty, no translation takes
10770 All character handling is done in bytes and is not UTF-8 aware.
10776 .section "Expansion operators" "SECTexpop"
10777 .cindex "expansion" "operators"
10778 For expansion items that perform transformations on a single argument string,
10779 the &"operator"& notation is used because it is simpler and uses fewer braces.
10780 The substring is first expanded before the operation is applied to it. The
10781 following operations can be performed:
10784 .vitem &*${address:*&<&'string'&>&*}*&
10785 .cindex "expansion" "RFC 2822 address handling"
10786 .cindex "&%address%& expansion item"
10787 The string is interpreted as an RFC 2822 address, as it might appear in a
10788 header line, and the effective address is extracted from it. If the string does
10789 not parse successfully, the result is empty.
10791 The parsing correctly handles SMTPUTF8 Unicode in the string.
10794 .vitem &*${addresses:*&<&'string'&>&*}*&
10795 .cindex "expansion" "RFC 2822 address handling"
10796 .cindex "&%addresses%& expansion item"
10797 The string (after expansion) is interpreted as a list of addresses in RFC
10798 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10799 operative address (&'local-part@domain'&) is extracted from each item, and the
10800 result of the expansion is a colon-separated list, with appropriate
10801 doubling of colons should any happen to be present in the email addresses.
10802 Syntactically invalid RFC2822 address items are omitted from the output.
10804 It is possible to specify a character other than colon for the output
10805 separator by starting the string with > followed by the new separator
10806 character. For example:
10808 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10810 expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
10811 first, so if the expanded string starts with >, it may change the output
10812 separator unintentionally. This can be avoided by setting the output
10813 separator explicitly:
10815 ${addresses:>:$h_from:}
10818 Compare the &%address%& (singular)
10819 expansion item, which extracts the working address from a single RFC2822
10820 address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
10823 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10824 a strict interpretation of header line formatting. Exim parses the bare,
10825 unquoted portion of an email address and if it finds a comma, treats it as an
10826 email address separator. For the example header line:
10828 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10830 The first example below demonstrates that Q-encoded email addresses are parsed
10831 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10832 It does not see the comma because it's still encoded as "=2C". The second
10833 example below is passed the contents of &`$header_from:`&, meaning it gets
10834 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10835 The third example shows that the presence of a comma is skipped when it is
10836 quoted. The fourth example shows SMTPUTF8 handling.
10838 # exim -be '${addresses:From: \
10839 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10841 # exim -be '${addresses:From: Last, First <user@example.com>}'
10842 Last:user@example.com
10843 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10845 # exim -be '${addresses:フィル <フィリップ@example.jp>}'
10849 .vitem &*${base32:*&<&'digits'&>&*}*&
10850 .cindex "&%base32%& expansion item"
10851 .cindex "expansion" "conversion to base 32"
10852 The string must consist entirely of decimal digits. The number is converted to
10853 base 32 and output as a (empty, for zero) string of characters.
10854 Only lowercase letters are used.
10856 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10857 .cindex "&%base32d%& expansion item"
10858 .cindex "expansion" "conversion to base 32"
10859 The string must consist entirely of base-32 digits.
10860 The number is converted to decimal and output as a string.
10862 .vitem &*${base62:*&<&'digits'&>&*}*&
10863 .cindex "&%base62%& expansion item"
10864 .cindex "expansion" "conversion to base 62"
10865 The string must consist entirely of decimal digits. The number is converted to
10866 base 62 and output as a string of six characters, including leading zeros. In
10867 the few operating environments where Exim uses base 36 instead of base 62 for
10868 its message identifiers (because those systems do not have case-sensitive
10869 filenames), base 36 is used by this operator, despite its name. &*Note*&: Just
10870 to be absolutely clear: this is &'not'& base64 encoding.
10872 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10873 .cindex "&%base62d%& expansion item"
10874 .cindex "expansion" "conversion to base 62"
10875 The string must consist entirely of base-62 digits, or, in operating
10876 environments where Exim uses base 36 instead of base 62 for its message
10877 identifiers, base-36 digits. The number is converted to decimal and output as a
10880 .vitem &*${base64:*&<&'string'&>&*}*&
10881 .cindex "expansion" "base64 encoding"
10882 .cindex "base64 encoding" "in string expansion"
10883 .cindex "&%base64%& expansion item"
10884 .cindex certificate "base64 of DER"
10885 This operator converts a string into one that is base64 encoded.
10887 If the string is a single variable of type certificate,
10888 returns the base64 encoding of the DER form of the certificate.
10891 .vitem &*${base64d:*&<&'string'&>&*}*&
10892 .cindex "expansion" "base64 decoding"
10893 .cindex "base64 decoding" "in string expansion"
10894 .cindex "&%base64d%& expansion item"
10895 This operator converts a base64-encoded string into the un-coded form.
10898 .vitem &*${domain:*&<&'string'&>&*}*&
10899 .cindex "domain" "extraction"
10900 .cindex "expansion" "domain extraction"
10901 The string is interpreted as an RFC 2822 address and the domain is extracted
10902 from it. If the string does not parse successfully, the result is empty.
10905 .vitem &*${escape:*&<&'string'&>&*}*&
10906 .cindex "expansion" "escaping non-printing characters"
10907 .cindex "&%escape%& expansion item"
10908 If the string contains any non-printing characters, they are converted to
10909 escape sequences starting with a backslash. Whether characters with the most
10910 significant bit set (so-called &"8-bit characters"&) count as printing or not
10911 is controlled by the &%print_topbitchars%& option.
10913 .vitem &*${escape8bit:*&<&'string'&>&*}*&
10914 .cindex "expansion" "escaping 8-bit characters"
10915 .cindex "&%escape8bit%& expansion item"
10916 If the string contains and characters with the most significant bit set,
10917 they are converted to escape sequences starting with a backslash.
10918 Backslashes and DEL characters are also converted.
10921 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
10922 .cindex "expansion" "expression evaluation"
10923 .cindex "expansion" "arithmetic expression"
10924 .cindex "&%eval%& expansion item"
10925 These items supports simple arithmetic and bitwise logical operations in
10926 expansion strings. The string (after expansion) must be a conventional
10927 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
10928 logical operators, and parentheses. All operations are carried out using
10929 integer arithmetic. The operator priorities are as follows (the same as in the
10930 C programming language):
10932 .irow &'highest:'& "not (~), negate (-)"
10933 .irow "" "multiply (*), divide (/), remainder (%)"
10934 .irow "" "plus (+), minus (-)"
10935 .irow "" "shift-left (<<), shift-right (>>)"
10936 .irow "" "and (&&)"
10938 .irow &'lowest:'& "or (|)"
10940 Binary operators with the same priority are evaluated from left to right. White
10941 space is permitted before or after operators.
10943 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
10944 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
10945 decimal, even if they start with a leading zero; hexadecimal numbers are not
10946 permitted. This can be useful when processing numbers extracted from dates or
10947 times, which often do have leading zeros.
10949 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
10951 respectively. Negative numbers are supported. The result of the computation is
10952 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
10955 &`${eval:1+1} `& yields 2
10956 &`${eval:1+2*3} `& yields 7
10957 &`${eval:(1+2)*3} `& yields 9
10958 &`${eval:2+42%5} `& yields 4
10959 &`${eval:0xc&5} `& yields 4
10960 &`${eval:0xc|5} `& yields 13
10961 &`${eval:0xc^5} `& yields 9
10962 &`${eval:0xc>>1} `& yields 6
10963 &`${eval:0xc<<1} `& yields 24
10964 &`${eval:~255&0x1234} `& yields 4608
10965 &`${eval:-(~255&0x1234)} `& yields -4608
10968 As a more realistic example, in an ACL you might have
10972 {>{$rcpt_count}{10}} \
10975 {$recipients_count} \
10976 {${eval:$rcpt_count/2}} \
10979 message = Too many bad recipients
10981 The condition is true if there have been more than 10 RCPT commands and
10982 fewer than half of them have resulted in a valid recipient.
10985 .vitem &*${expand:*&<&'string'&>&*}*&
10986 .cindex "expansion" "re-expansion of substring"
10987 The &%expand%& operator causes a string to be expanded for a second time. For
10990 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
10992 first looks up a string in a file while expanding the operand for &%expand%&,
10993 and then re-expands what it has found.
10996 .vitem &*${from_utf8:*&<&'string'&>&*}*&
10998 .cindex "UTF-8" "conversion from"
10999 .cindex "expansion" "UTF-8 conversion"
11000 .cindex "&%from_utf8%& expansion item"
11001 The world is slowly moving towards Unicode, although there are no standards for
11002 email yet. However, other applications (including some databases) are starting
11003 to store data in Unicode, using UTF-8 encoding. This operator converts from a
11004 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
11005 converted to underscores. The input must be a valid UTF-8 string. If it is not,
11006 the result is an undefined sequence of bytes.
11008 Unicode code points with values less than 256 are compatible with ASCII and
11009 ISO-8859-1 (also known as Latin-1).
11010 For example, character 169 is the copyright symbol in both cases, though the
11011 way it is encoded is different. In UTF-8, more than one byte is needed for
11012 characters with code values greater than 127, whereas ISO-8859-1 is a
11013 single-byte encoding (but thereby limited to 256 characters). This makes
11014 translation from UTF-8 to ISO-8859-1 straightforward.
11017 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11018 .cindex "hash function" "textual"
11019 .cindex "expansion" "textual hash"
11020 The &%hash%& operator is a simpler interface to the hashing function that can
11021 be used when the two parameters are fixed numbers (as opposed to strings that
11022 change when expanded). The effect is the same as
11024 ${hash{<n>}{<m>}{<string>}}
11026 See the description of the general &%hash%& item above for details. The
11027 abbreviation &%h%& can be used when &%hash%& is used as an operator.
11031 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
11032 .cindex "base64 encoding" "conversion from hex"
11033 .cindex "expansion" "hex to base64"
11034 .cindex "&%hex2b64%& expansion item"
11035 This operator converts a hex string into one that is base64 encoded. This can
11036 be useful for processing the output of the various hashing functions.
11040 .vitem &*${hexquote:*&<&'string'&>&*}*&
11041 .cindex "quoting" "hex-encoded unprintable characters"
11042 .cindex "&%hexquote%& expansion item"
11043 This operator converts non-printable characters in a string into a hex
11044 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
11045 as is, and other byte values are converted to &`\xNN`&, for example, a
11046 byte value 127 is converted to &`\x7f`&.
11049 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
11050 .cindex "&%ipv6denorm%& expansion item"
11051 .cindex "IP address" normalisation
11052 This expands an IPv6 address to a full eight-element colon-separated set
11053 of hex digits including leading zeroes.
11054 A trailing ipv4-style dotted-decimal set is converted to hex.
11055 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11057 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
11058 .cindex "&%ipv6norm%& expansion item"
11059 .cindex "IP address" normalisation
11060 .cindex "IP address" "canonical form"
11061 This converts an IPv6 address to canonical form.
11062 Leading zeroes of groups are omitted, and the longest
11063 set of zero-valued groups is replaced with a double colon.
11064 A trailing ipv4-style dotted-decimal set is converted to hex.
11065 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
11068 .vitem &*${lc:*&<&'string'&>&*}*&
11069 .cindex "case forcing in strings"
11070 .cindex "string" "case forcing"
11071 .cindex "lower casing"
11072 .cindex "expansion" "case forcing"
11073 .cindex "&%lc%& expansion item"
11074 This forces the letters in the string into lower-case, for example:
11078 Case is defined per the system C locale.
11080 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
11081 .cindex "expansion" "string truncation"
11082 .cindex "&%length%& expansion item"
11083 The &%length%& operator is a simpler interface to the &%length%& function that
11084 can be used when the parameter is a fixed number (as opposed to a string that
11085 changes when expanded). The effect is the same as
11087 ${length{<number>}{<string>}}
11089 See the description of the general &%length%& item above for details. Note that
11090 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
11091 when &%length%& is used as an operator.
11092 All measurement is done in bytes and is not UTF-8 aware.
11095 .vitem &*${listcount:*&<&'string'&>&*}*&
11096 .cindex "expansion" "list item count"
11097 .cindex "list" "item count"
11098 .cindex "list" "count of items"
11099 .cindex "&%listcount%& expansion item"
11100 The string is interpreted as a list and the number of items is returned.
11103 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
11104 .cindex "expansion" "named list"
11105 .cindex "&%listnamed%& expansion item"
11106 The name is interpreted as a named list and the content of the list is returned,
11107 expanding any referenced lists, re-quoting as needed for colon-separation.
11108 If the optional type is given it must be one of "a", "d", "h" or "l"
11109 and selects address-, domain-, host- or localpart- lists to search among respectively.
11110 Otherwise all types are searched in an undefined order and the first
11111 matching list is returned.
11114 .vitem &*${local_part:*&<&'string'&>&*}*&
11115 .cindex "expansion" "local part extraction"
11116 .cindex "&%local_part%& expansion item"
11117 The string is interpreted as an RFC 2822 address and the local part is
11118 extracted from it. If the string does not parse successfully, the result is
11120 The parsing correctly handles SMTPUTF8 Unicode in the string.
11123 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
11124 .cindex "masked IP address"
11125 .cindex "IP address" "masking"
11126 .cindex "CIDR notation"
11127 .cindex "expansion" "IP address masking"
11128 .cindex "&%mask%& expansion item"
11129 If the form of the string to be operated on is not an IP address followed by a
11130 slash and an integer (that is, a network address in CIDR notation), the
11131 expansion fails. Otherwise, this operator converts the IP address to binary,
11132 masks off the least significant bits according to the bit count, and converts
11133 the result back to text, with mask appended. For example,
11135 ${mask:10.111.131.206/28}
11137 returns the string &"10.111.131.192/28"&. Since this operation is expected to
11138 be mostly used for looking up masked addresses in files, the result for an IPv6
11139 address uses dots to separate components instead of colons, because colon
11140 terminates a key string in lsearch files. So, for example,
11142 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
11146 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
11148 Letters in IPv6 addresses are always output in lower case.
11151 .vitem &*${md5:*&<&'string'&>&*}*&
11153 .cindex "expansion" "MD5 hash"
11154 .cindex certificate fingerprint
11155 .cindex "&%md5%& expansion item"
11156 The &%md5%& operator computes the MD5 hash value of the string, and returns it
11157 as a 32-digit hexadecimal number, in which any letters are in lower case.
11159 If the string is a single variable of type certificate,
11160 returns the MD5 hash fingerprint of the certificate.
11163 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
11164 .cindex "expansion" "numeric hash"
11165 .cindex "hash function" "numeric"
11166 The &%nhash%& operator is a simpler interface to the numeric hashing function
11167 that can be used when the two parameters are fixed numbers (as opposed to
11168 strings that change when expanded). The effect is the same as
11170 ${nhash{<n>}{<m>}{<string>}}
11172 See the description of the general &%nhash%& item above for details.
11175 .vitem &*${quote:*&<&'string'&>&*}*&
11176 .cindex "quoting" "in string expansions"
11177 .cindex "expansion" "quoting"
11178 .cindex "&%quote%& expansion item"
11179 The &%quote%& operator puts its argument into double quotes if it
11180 is an empty string or
11181 contains anything other than letters, digits, underscores, dots, and hyphens.
11182 Any occurrences of double quotes and backslashes are escaped with a backslash.
11183 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
11184 respectively For example,
11192 The place where this is useful is when the argument is a substitution from a
11193 variable or a message header.
11195 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
11196 .cindex "&%quote_local_part%& expansion item"
11197 This operator is like &%quote%&, except that it quotes the string only if
11198 required to do so by the rules of RFC 2822 for quoting local parts. For
11199 example, a plus sign would not cause quoting (but it would for &%quote%&).
11200 If you are creating a new email address from the contents of &$local_part$&
11201 (or any other unknown data), you should always use this operator.
11203 This quoting determination is not SMTPUTF8-aware, thus quoting non-ASCII data
11204 will likely use the quoting form.
11205 Thus &'${quote_local_part:フィル}'& will always become &'"フィル"'&.
11208 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
11209 .cindex "quoting" "lookup-specific"
11210 This operator applies lookup-specific quoting rules to the string. Each
11211 query-style lookup type has its own quoting rules which are described with
11212 the lookups in chapter &<<CHAPfdlookup>>&. For example,
11214 ${quote_ldap:two * two}
11220 For single-key lookup types, no quoting is ever necessary and this operator
11221 yields an unchanged string.
11224 .vitem &*${randint:*&<&'n'&>&*}*&
11225 .cindex "random number"
11226 This operator returns a somewhat random number which is less than the
11227 supplied number and is at least 0. The quality of this randomness depends
11228 on how Exim was built; the values are not suitable for keying material.
11229 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
11230 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
11231 for versions of GnuTLS with that function.
11232 Otherwise, the implementation may be arc4random(), random() seeded by
11233 srandomdev() or srandom(), or a custom implementation even weaker than
11237 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
11238 .cindex "expansion" "IP address"
11239 This operator reverses an IP address; for IPv4 addresses, the result is in
11240 dotted-quad decimal form, while for IPv6 addresses the result is in
11241 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
11242 for DNS. For example,
11244 ${reverse_ip:192.0.2.4}
11245 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
11250 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
11254 .vitem &*${rfc2047:*&<&'string'&>&*}*&
11255 .cindex "expansion" "RFC 2047"
11256 .cindex "RFC 2047" "expansion operator"
11257 .cindex "&%rfc2047%& expansion item"
11258 This operator encodes text according to the rules of RFC 2047. This is an
11259 encoding that is used in header lines to encode non-ASCII characters. It is
11260 assumed that the input string is in the encoding specified by the
11261 &%headers_charset%& option, which gets its default at build time. If the string
11262 contains only characters in the range 33&--126, and no instances of the
11265 ? = ( ) < > @ , ; : \ " . [ ] _
11267 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
11268 string, using as many &"encoded words"& as necessary to encode all the
11272 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
11273 .cindex "expansion" "RFC 2047"
11274 .cindex "RFC 2047" "decoding"
11275 .cindex "&%rfc2047d%& expansion item"
11276 This operator decodes strings that are encoded as per RFC 2047. Binary zero
11277 bytes are replaced by question marks. Characters are converted into the
11278 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
11279 not recognized unless &%check_rfc2047_length%& is set false.
11281 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
11282 access a header line, RFC 2047 decoding is done automatically. You do not need
11283 to use this operator as well.
11287 .vitem &*${rxquote:*&<&'string'&>&*}*&
11288 .cindex "quoting" "in regular expressions"
11289 .cindex "regular expressions" "quoting"
11290 .cindex "&%rxquote%& expansion item"
11291 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
11292 characters in its argument. This is useful when substituting the values of
11293 variables or headers inside regular expressions.
11296 .vitem &*${sha1:*&<&'string'&>&*}*&
11297 .cindex "SHA-1 hash"
11298 .cindex "expansion" "SHA-1 hashing"
11299 .cindex certificate fingerprint
11300 .cindex "&%sha1%& expansion item"
11301 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
11302 it as a 40-digit hexadecimal number, in which any letters are in upper case.
11304 If the string is a single variable of type certificate,
11305 returns the SHA-1 hash fingerprint of the certificate.
11308 .vitem &*${sha256:*&<&'string'&>&*}*& &&&
11309 &*${sha2:*&<&'string'&>&*}*& &&&
11310 &*${sha2_<n>:*&<&'string'&>&*}*&
11311 .cindex "SHA-256 hash"
11312 .cindex "SHA-2 hash"
11313 .cindex certificate fingerprint
11314 .cindex "expansion" "SHA-256 hashing"
11315 .cindex "&%sha256%& expansion item"
11316 .cindex "&%sha2%& expansion item"
11317 The &%sha256%& operator computes the SHA-256 hash value of the string
11319 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11321 If the string is a single variable of type certificate,
11322 returns the SHA-256 hash fingerprint of the certificate.
11324 The operator can also be spelled &%sha2%& and does the same as &%sha256%&
11325 (except for certificates, which are not supported).
11326 Finally, if an underbar
11327 and a number is appended it specifies the output length, selecting a
11328 member of the SHA-2 family of hash functions.
11329 Values of 256, 384 and 512 are accepted, with 256 being the default.
11332 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
11333 &*${sha3_<n>:*&<&'string'&>&*}*&
11334 .cindex "SHA3 hash"
11335 .cindex "expansion" "SHA3 hashing"
11336 .cindex "&%sha3%& expansion item"
11337 The &%sha3%& operator computes the SHA3-256 hash value of the string
11339 it as a 64-digit hexadecimal number, in which any letters are in upper case.
11341 If a number is appended, separated by an underbar, it specifies
11342 the output length. Values of 224, 256, 384 and 512 are accepted;
11343 with 256 being the default.
11345 The &%sha3%& expansion item is only supported if Exim has been
11346 compiled with GnuTLS 3.5.0 or later,
11347 or OpenSSL 1.1.1 or later.
11348 The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
11351 .vitem &*${stat:*&<&'string'&>&*}*&
11352 .cindex "expansion" "statting a file"
11353 .cindex "file" "extracting characteristics"
11354 .cindex "&%stat%& expansion item"
11355 The string, after expansion, must be a file path. A call to the &[stat()]&
11356 function is made for this path. If &[stat()]& fails, an error occurs and the
11357 expansion fails. If it succeeds, the data from the stat replaces the item, as a
11358 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
11359 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
11360 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
11361 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
11362 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
11363 can extract individual fields using the &%extract%& expansion item.
11365 The use of the &%stat%& expansion in users' filter files can be locked out by
11366 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
11367 systems for files larger than 2GB.
11369 .vitem &*${str2b64:*&<&'string'&>&*}*&
11370 .cindex "&%str2b64%& expansion item"
11371 Now deprecated, a synonym for the &%base64%& expansion operator.
11375 .vitem &*${strlen:*&<&'string'&>&*}*&
11376 .cindex "expansion" "string length"
11377 .cindex "string" "length in expansion"
11378 .cindex "&%strlen%& expansion item"
11379 The item is replace by the length of the expanded string, expressed as a
11380 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
11381 All measurement is done in bytes and is not UTF-8 aware.
11384 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
11385 .cindex "&%substr%& expansion item"
11386 .cindex "substring extraction"
11387 .cindex "expansion" "substring expansion"
11388 The &%substr%& operator is a simpler interface to the &%substr%& function that
11389 can be used when the two parameters are fixed numbers (as opposed to strings
11390 that change when expanded). The effect is the same as
11392 ${substr{<start>}{<length>}{<string>}}
11394 See the description of the general &%substr%& item above for details. The
11395 abbreviation &%s%& can be used when &%substr%& is used as an operator.
11396 All measurement is done in bytes and is not UTF-8 aware.
11398 .vitem &*${time_eval:*&<&'string'&>&*}*&
11399 .cindex "&%time_eval%& expansion item"
11400 .cindex "time interval" "decoding"
11401 This item converts an Exim time interval such as &`2d4h5m`& into a number of
11404 .vitem &*${time_interval:*&<&'string'&>&*}*&
11405 .cindex "&%time_interval%& expansion item"
11406 .cindex "time interval" "formatting"
11407 The argument (after sub-expansion) must be a sequence of decimal digits that
11408 represents an interval of time as a number of seconds. It is converted into a
11409 number of larger units and output in Exim's normal time format, for example,
11412 .vitem &*${uc:*&<&'string'&>&*}*&
11413 .cindex "case forcing in strings"
11414 .cindex "string" "case forcing"
11415 .cindex "upper casing"
11416 .cindex "expansion" "case forcing"
11417 .cindex "&%uc%& expansion item"
11418 This forces the letters in the string into upper-case.
11419 Case is defined per the system C locale.
11421 .vitem &*${utf8clean:*&<&'string'&>&*}*&
11422 .cindex "correction of invalid utf-8 sequences in strings"
11423 .cindex "utf-8" "utf-8 sequences"
11424 .cindex "incorrect utf-8"
11425 .cindex "expansion" "utf-8 forcing"
11426 .cindex "&%utf8clean%& expansion item"
11427 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
11428 In versions of Exim before 4.92, this did not correctly do so for a truncated
11429 final codepoint's encoding, and the character would be silently dropped.
11430 If you must handle detection of this scenario across both sets of Exim behavior,
11431 the complexity will depend upon the task.
11432 For instance, to detect if the first character is multibyte and a 1-byte
11433 extraction can be successfully used as a path component (as is common for
11434 dividing up delivery folders), you might use:
11436 condition = ${if inlist{${utf8clean:${length_1:$local_part}}}{:?}{yes}{no}}
11438 (which will false-positive if the first character of the local part is a
11439 literal question mark).
11441 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
11442 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
11443 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
11444 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
11445 .cindex expansion UTF-8
11446 .cindex UTF-8 expansion
11448 .cindex internationalisation
11449 .cindex "&%utf8_domain_to_alabel%& expansion item"
11450 .cindex "&%utf8_domain_from_alabel%& expansion item"
11451 .cindex "&%utf8_localpart_to_alabel%& expansion item"
11452 .cindex "&%utf8_localpart_from_alabel%& expansion item"
11453 These convert EAI mail name components between UTF-8 and a-label forms.
11454 For information on internationalisation support see &<<SECTi18nMTA>>&.
11462 .section "Expansion conditions" "SECTexpcond"
11463 .scindex IIDexpcond "expansion" "conditions"
11464 The following conditions are available for testing by the &%${if%& construct
11465 while expanding strings:
11468 .vitem &*!*&<&'condition'&>
11469 .cindex "expansion" "negating a condition"
11470 .cindex "negation" "in expansion condition"
11471 Preceding any condition with an exclamation mark negates the result of the
11474 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11475 .cindex "numeric comparison"
11476 .cindex "expansion" "numeric comparison"
11477 There are a number of symbolic operators for doing numeric comparisons. They
11483 &`>= `& greater or equal
11485 &`<= `& less or equal
11489 ${if >{$message_size}{10M} ...
11491 Note that the general negation operator provides for inequality testing. The
11492 two strings must take the form of optionally signed decimal integers,
11493 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
11494 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
11495 As a special case, the numerical value of an empty string is taken as
11498 In all cases, a relative comparator OP is testing if <&'string1'&> OP
11499 <&'string2'&>; the above example is checking if &$message_size$& is larger than
11500 10M, not if 10M is larger than &$message_size$&.
11503 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
11504 {*&<&'arg2'&>&*}...}*&
11505 .cindex "expansion" "calling an acl"
11506 .cindex "&%acl%&" "expansion condition"
11507 The name and zero to nine argument strings are first expanded separately. The expanded
11508 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
11509 Any unused are made empty. The variable &$acl_narg$& is set to the number of
11510 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
11511 and may use the variables; if another acl expansion is used the values
11512 are restored after it returns. If the ACL sets
11513 a value using a "message =" modifier the variable $value becomes
11514 the result of the expansion, otherwise it is empty.
11515 If the ACL returns accept the condition is true; if deny, false.
11516 If the ACL returns defer the result is a forced-fail.
11518 .vitem &*bool&~{*&<&'string'&>&*}*&
11519 .cindex "expansion" "boolean parsing"
11520 .cindex "&%bool%& expansion condition"
11521 This condition turns a string holding a true or false representation into
11522 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
11523 (case-insensitively); also integer numbers map to true if non-zero,
11525 An empty string is treated as false.
11526 Leading and trailing whitespace is ignored;
11527 thus a string consisting only of whitespace is false.
11528 All other string values will result in expansion failure.
11530 When combined with ACL variables, this expansion condition will let you
11531 make decisions in one place and act on those decisions in another place.
11534 ${if bool{$acl_m_privileged_sender} ...
11538 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
11539 .cindex "expansion" "boolean parsing"
11540 .cindex "&%bool_lax%& expansion condition"
11541 Like &%bool%&, this condition turns a string into a boolean state. But
11542 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
11543 loose definition that the Router &%condition%& option uses. The empty string
11544 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
11545 true. Leading and trailing whitespace is ignored.
11547 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
11549 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11550 .cindex "expansion" "encrypted comparison"
11551 .cindex "encrypted strings, comparing"
11552 .cindex "&%crypteq%& expansion condition"
11553 This condition is included in the Exim binary if it is built to support any
11554 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
11555 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
11556 included in the binary.
11558 The &%crypteq%& condition has two arguments. The first is encrypted and
11559 compared against the second, which is already encrypted. The second string may
11560 be in the LDAP form for storing encrypted strings, which starts with the
11561 encryption type in curly brackets, followed by the data. If the second string
11562 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
11563 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
11564 Typically this will be a field from a password file. An example of an encrypted
11565 string in LDAP form is:
11567 {md5}CY9rzUYh03PK3k6DJie09g==
11569 If such a string appears directly in an expansion, the curly brackets have to
11570 be quoted, because they are part of the expansion syntax. For example:
11572 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
11574 The following encryption types (whose names are matched case-independently) are
11579 .cindex "base64 encoding" "in encrypted password"
11580 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
11581 printable characters to compare with the remainder of the second string. If the
11582 length of the comparison string is 24, Exim assumes that it is base64 encoded
11583 (as in the above example). If the length is 32, Exim assumes that it is a
11584 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
11588 .cindex "SHA-1 hash"
11589 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
11590 printable characters to compare with the remainder of the second string. If the
11591 length of the comparison string is 28, Exim assumes that it is base64 encoded.
11592 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
11593 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
11596 .cindex "&[crypt()]&"
11597 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
11598 only the first eight characters of the password. However, in modern operating
11599 systems this is no longer true, and in many cases the entire password is used,
11600 whatever its length.
11603 .cindex "&[crypt16()]&"
11604 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
11605 use up to 16 characters of the password in some operating systems. Again, in
11606 modern operating systems, more characters may be used.
11608 Exim has its own version of &[crypt16()]&, which is just a double call to
11609 &[crypt()]&. For operating systems that have their own version, setting
11610 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
11611 operating system version instead of its own. This option is set by default in
11612 the OS-dependent &_Makefile_& for those operating systems that are known to
11613 support &[crypt16()]&.
11615 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
11616 it was not using the same algorithm as some operating systems' versions. It
11617 turns out that as well as &[crypt16()]& there is a function called
11618 &[bigcrypt()]& in some operating systems. This may or may not use the same
11619 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
11621 However, since there is now a move away from the traditional &[crypt()]&
11622 functions towards using SHA1 and other algorithms, tidying up this area of
11623 Exim is seen as very low priority.
11625 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
11626 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
11627 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
11628 default is &`{crypt}`&. Whatever the default, you can always use either
11629 function by specifying it explicitly in curly brackets.
11631 .vitem &*def:*&<&'variable&~name'&>
11632 .cindex "expansion" "checking for empty variable"
11633 .cindex "&%def%& expansion condition"
11634 The &%def%& condition must be followed by the name of one of the expansion
11635 variables defined in section &<<SECTexpvar>>&. The condition is true if the
11636 variable does not contain the empty string. For example:
11638 ${if def:sender_ident {from $sender_ident}}
11640 Note that the variable name is given without a leading &%$%& character. If the
11641 variable does not exist, the expansion fails.
11643 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
11644 &~&*def:h_*&<&'header&~name'&>&*:*&"
11645 .cindex "expansion" "checking header line existence"
11646 This condition is true if a message is being processed and the named header
11647 exists in the message. For example,
11649 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
11651 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
11652 the header name must be terminated by a colon if white space does not follow.
11654 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11655 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11656 .cindex "string" "comparison"
11657 .cindex "expansion" "string comparison"
11658 .cindex "&%eq%& expansion condition"
11659 .cindex "&%eqi%& expansion condition"
11660 The two substrings are first expanded. The condition is true if the two
11661 resulting strings are identical. For &%eq%& the comparison includes the case of
11662 letters, whereas for &%eqi%& the comparison is case-independent, where
11663 case is defined per the system C locale.
11665 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
11666 .cindex "expansion" "file existence test"
11667 .cindex "file" "existence test"
11668 .cindex "&%exists%&, expansion condition"
11669 The substring is first expanded and then interpreted as an absolute path. The
11670 condition is true if the named file (or directory) exists. The existence test
11671 is done by calling the &[stat()]& function. The use of the &%exists%& test in
11672 users' filter files may be locked out by the system administrator.
11675 &*Note:*& Testing a path using this condition is not a sufficient way of
11679 .vitem &*first_delivery*&
11680 .cindex "delivery" "first"
11681 .cindex "first delivery"
11682 .cindex "expansion" "first delivery test"
11683 .cindex "&%first_delivery%& expansion condition"
11684 This condition, which has no data, is true during a message's first delivery
11685 attempt. It is false during any subsequent delivery attempts.
11688 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
11689 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
11690 .cindex "list" "iterative conditions"
11691 .cindex "expansion" "&*forall*& condition"
11692 .cindex "expansion" "&*forany*& condition"
11694 These conditions iterate over a list. The first argument is expanded to form
11695 the list. By default, the list separator is a colon, but it can be changed by
11696 the normal method (&<<SECTlistsepchange>>&).
11697 The second argument is interpreted as a condition that is to
11698 be applied to each item in the list in turn. During the interpretation of the
11699 condition, the current list item is placed in a variable called &$item$&.
11701 For &*forany*&, interpretation stops if the condition is true for any item, and
11702 the result of the whole condition is true. If the condition is false for all
11703 items in the list, the overall condition is false.
11705 For &*forall*&, interpretation stops if the condition is false for any item,
11706 and the result of the whole condition is false. If the condition is true for
11707 all items in the list, the overall condition is true.
11709 Note that negation of &*forany*& means that the condition must be false for all
11710 items for the overall condition to succeed, and negation of &*forall*& means
11711 that the condition must be false for at least one item. In this example, the
11712 list separator is changed to a comma:
11714 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
11716 The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
11717 being processed, to enable these expansion items to be nested.
11719 To scan a named list, expand it with the &*listnamed*& operator.
11721 .vitem "&*forall_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11722 "&*forany_json{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11723 "&*forall_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&" &&&
11724 "&*forany_jsons{*&<&'a JSON array'&>&*}{*&<&'a condition'&>&*}*&"
11725 .cindex JSON "iterative conditions"
11726 .cindex JSON expansions
11727 .cindex expansion "&*forall_json*& condition"
11728 .cindex expansion "&*forany_json*& condition"
11729 .cindex expansion "&*forall_jsons*& condition"
11730 .cindex expansion "&*forany_jsons*& condition"
11731 As for the above, except that the first argument must, after expansion,
11733 The array separator is not changeable.
11734 For the &"jsons"& variants the elements are expected to be JSON strings
11735 and have their quotes removed before the evaluation of the condition.
11739 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11740 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11741 .cindex "string" "comparison"
11742 .cindex "expansion" "string comparison"
11743 .cindex "&%ge%& expansion condition"
11744 .cindex "&%gei%& expansion condition"
11745 The two substrings are first expanded. The condition is true if the first
11746 string is lexically greater than or equal to the second string. For &%ge%& the
11747 comparison includes the case of letters, whereas for &%gei%& the comparison is
11749 Case and collation order are defined per the system C locale.
11751 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11752 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11753 .cindex "string" "comparison"
11754 .cindex "expansion" "string comparison"
11755 .cindex "&%gt%& expansion condition"
11756 .cindex "&%gti%& expansion condition"
11757 The two substrings are first expanded. The condition is true if the first
11758 string is lexically greater than the second string. For &%gt%& the comparison
11759 includes the case of letters, whereas for &%gti%& the comparison is
11761 Case and collation order are defined per the system C locale.
11765 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
11766 SRS decode. See SECT &<<SECTSRS>>& for details.
11770 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11771 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11772 .cindex "string" "comparison"
11773 .cindex "list" "iterative conditions"
11774 Both strings are expanded; the second string is treated as a list of simple
11775 strings; if the first string is a member of the second, then the condition
11777 For the case-independent &%inlisti%& condition, case is defined per the system C locale.
11779 These are simpler to use versions of the more powerful &*forany*& condition.
11780 Examples, and the &*forany*& equivalents:
11782 ${if inlist{needle}{foo:needle:bar}}
11783 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11784 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11785 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11788 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11789 &*isip4&~{*&<&'string'&>&*}*& &&&
11790 &*isip6&~{*&<&'string'&>&*}*&
11791 .cindex "IP address" "testing string format"
11792 .cindex "string" "testing for IP address"
11793 .cindex "&%isip%& expansion condition"
11794 .cindex "&%isip4%& expansion condition"
11795 .cindex "&%isip6%& expansion condition"
11796 The substring is first expanded, and then tested to see if it has the form of
11797 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11798 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11800 For an IPv4 address, the test is for four dot-separated components, each of
11801 which consists of from one to three digits. For an IPv6 address, up to eight
11802 colon-separated components are permitted, each containing from one to four
11803 hexadecimal digits. There may be fewer than eight components if an empty
11804 component (adjacent colons) is present. Only one empty component is permitted.
11806 &*Note*&: The checks used to be just on the form of the address; actual numerical
11807 values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
11809 This is no longer the case.
11811 The main use of these tests is to distinguish between IP addresses and
11812 host names, or between IPv4 and IPv6 addresses. For example, you could use
11814 ${if isip4{$sender_host_address}...
11816 to test which IP version an incoming SMTP connection is using.
11818 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11819 .cindex "LDAP" "use for authentication"
11820 .cindex "expansion" "LDAP authentication test"
11821 .cindex "&%ldapauth%& expansion condition"
11822 This condition supports user authentication using LDAP. See section
11823 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11824 queries. For this use, the query must contain a user name and password. The
11825 query itself is not used, and can be empty. The condition is true if the
11826 password is not empty, and the user name and password are accepted by the LDAP
11827 server. An empty password is rejected without calling LDAP because LDAP binds
11828 with an empty password are considered anonymous regardless of the username, and
11829 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11830 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11834 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11835 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11836 .cindex "string" "comparison"
11837 .cindex "expansion" "string comparison"
11838 .cindex "&%le%& expansion condition"
11839 .cindex "&%lei%& expansion condition"
11840 The two substrings are first expanded. The condition is true if the first
11841 string is lexically less than or equal to the second string. For &%le%& the
11842 comparison includes the case of letters, whereas for &%lei%& the comparison is
11844 Case and collation order are defined per the system C locale.
11846 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11847 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11848 .cindex "string" "comparison"
11849 .cindex "expansion" "string comparison"
11850 .cindex "&%lt%& expansion condition"
11851 .cindex "&%lti%& expansion condition"
11852 The two substrings are first expanded. The condition is true if the first
11853 string is lexically less than the second string. For &%lt%& the comparison
11854 includes the case of letters, whereas for &%lti%& the comparison is
11856 Case and collation order are defined per the system C locale.
11859 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11860 .cindex "expansion" "regular expression comparison"
11861 .cindex "regular expressions" "match in expanded string"
11862 .cindex "&%match%& expansion condition"
11863 The two substrings are first expanded. The second is then treated as a regular
11864 expression and applied to the first. Because of the pre-expansion, if the
11865 regular expression contains dollar, or backslash characters, they must be
11866 escaped. Care must also be taken if the regular expression contains braces
11867 (curly brackets). A closing brace must be escaped so that it is not taken as a
11868 premature termination of <&'string2'&>. The easiest approach is to use the
11869 &`\N`& feature to disable expansion of the regular expression.
11872 ${if match {$local_part}{\N^\d{3}\N} ...
11874 If the whole expansion string is in double quotes, further escaping of
11875 backslashes is also required.
11877 The condition is true if the regular expression match succeeds.
11878 The regular expression is not required to begin with a circumflex
11879 metacharacter, but if there is no circumflex, the expression is not anchored,
11880 and it may match anywhere in the subject, not just at the start. If you want
11881 the pattern to match at the end of the subject, you must include the &`$`&
11882 metacharacter at an appropriate point.
11883 All character handling is done in bytes and is not UTF-8 aware,
11884 but we might change this in a future Exim release.
11886 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11887 At the start of an &%if%& expansion the values of the numeric variable
11888 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11889 succeeds causes them to be reset to the substrings of that condition and they
11890 will have these values during the expansion of the success string. At the end
11891 of the &%if%& expansion, the previous values are restored. After testing a
11892 combination of conditions using &%or%&, the subsequent values of the numeric
11893 variables are those of the condition that succeeded.
11895 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11896 .cindex "&%match_address%& expansion condition"
11897 See &*match_local_part*&.
11899 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11900 .cindex "&%match_domain%& expansion condition"
11901 See &*match_local_part*&.
11903 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11904 .cindex "&%match_ip%& expansion condition"
11905 This condition matches an IP address to a list of IP address patterns. It must
11906 be followed by two argument strings. The first (after expansion) must be an IP
11907 address or an empty string. The second (not expanded) is a restricted host
11908 list that can match only an IP address, not a host name. For example:
11910 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
11912 The specific types of host list item that are permitted in the list are:
11915 An IP address, optionally with a CIDR mask.
11917 A single asterisk, which matches any IP address.
11919 An empty item, which matches only if the IP address is empty. This could be
11920 useful for testing for a locally submitted message or one from specific hosts
11921 in a single test such as
11922 . ==== As this is a nested list, any displays it contains must be indented
11923 . ==== as otherwise they are too far to the left. This comment applies to
11924 . ==== the use of xmlto plus fop. There's no problem when formatting with
11925 . ==== sdop, with or without the extra indent.
11927 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
11929 where the first item in the list is the empty string.
11931 The item @[] matches any of the local host's interface addresses.
11933 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
11934 even if &`net-`& is not specified. There is never any attempt to turn the IP
11935 address into a host name. The most common type of linear search for
11936 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
11937 masks. For example:
11939 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
11941 It is of course possible to use other kinds of lookup, and in such a case, you
11942 do need to specify the &`net-`& prefix if you want to specify a specific
11943 address mask, for example:
11945 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
11947 However, unless you are combining a &%match_ip%& condition with others, it is
11948 just as easy to use the fact that a lookup is itself a condition, and write:
11950 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
11954 Note that <&'string2'&> is not itself subject to string expansion, unless
11955 Exim was built with the EXPAND_LISTMATCH_RHS option.
11957 Consult section &<<SECThoslispatip>>& for further details of these patterns.
11959 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11960 .cindex "domain list" "in expansion condition"
11961 .cindex "address list" "in expansion condition"
11962 .cindex "local part" "list, in expansion condition"
11963 .cindex "&%match_local_part%& expansion condition"
11964 This condition, together with &%match_address%& and &%match_domain%&, make it
11965 possible to test domain, address, and local part lists within expansions. Each
11966 condition requires two arguments: an item and a list to match. A trivial
11969 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
11971 In each case, the second argument may contain any of the allowable items for a
11972 list of the appropriate type. Also, because the second argument
11973 is a standard form of list, it is possible to refer to a named list.
11974 Thus, you can use conditions like this:
11976 ${if match_domain{$domain}{+local_domains}{...
11978 .cindex "&`+caseful`&"
11979 For address lists, the matching starts off caselessly, but the &`+caseful`&
11980 item can be used, as in all address lists, to cause subsequent items to
11981 have their local parts matched casefully. Domains are always matched
11984 Note that <&'string2'&> is not itself subject to string expansion, unless
11985 Exim was built with the EXPAND_LISTMATCH_RHS option.
11987 &*Note*&: Host lists are &'not'& supported in this way. This is because
11988 hosts have two identities: a name and an IP address, and it is not clear
11989 how to specify cleanly how such a test would work. However, IP addresses can be
11990 matched using &%match_ip%&.
11992 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
11993 .cindex "PAM authentication"
11994 .cindex "AUTH" "with PAM"
11995 .cindex "Solaris" "PAM support"
11996 .cindex "expansion" "PAM authentication test"
11997 .cindex "&%pam%& expansion condition"
11998 &'Pluggable Authentication Modules'&
11999 (&url(https://mirrors.edge.kernel.org/pub/linux/libs/pam/)) are a facility that is
12000 available in the latest releases of Solaris and in some GNU/Linux
12001 distributions. The Exim support, which is intended for use in conjunction with
12002 the SMTP AUTH command, is available only if Exim is compiled with
12006 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
12007 in some releases of GNU/Linux &%-ldl%& is also needed.
12009 The argument string is first expanded, and the result must be a
12010 colon-separated list of strings. Leading and trailing white space is ignored.
12011 The PAM module is initialized with the service name &"exim"& and the user name
12012 taken from the first item in the colon-separated data string (<&'string1'&>).
12013 The remaining items in the data string are passed over in response to requests
12014 from the authentication function. In the simple case there will only be one
12015 request, for a password, so the data consists of just two strings.
12017 There can be problems if any of the strings are permitted to contain colon
12018 characters. In the usual way, these have to be doubled to avoid being taken as
12020 The &%listquote%& expansion item can be used for this.
12021 For example, the configuration
12022 of a LOGIN authenticator might contain this setting:
12024 server_condition = ${if pam{$auth1:${listquote{:}{$auth2}}}}
12026 In some operating systems, PAM authentication can be done only from a process
12027 running as root. Since Exim is running as the Exim user when receiving
12028 messages, this means that PAM cannot be used directly in those systems.
12029 . --- 2018-09-07: the pam_exim modified variant has gone, removed claims re using Exim via that
12032 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
12033 .cindex "&'pwcheck'& daemon"
12035 .cindex "expansion" "&'pwcheck'& authentication test"
12036 .cindex "&%pwcheck%& expansion condition"
12037 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
12038 This is one way of making it possible for passwords to be checked by a process
12039 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
12040 deprecated. Its replacement is &'saslauthd'& (see below).
12042 The pwcheck support is not included in Exim by default. You need to specify
12043 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
12044 building Exim. For example:
12046 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
12048 You do not need to install the full Cyrus software suite in order to use
12049 the pwcheck daemon. You can compile and install just the daemon alone
12050 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
12051 access to the &_/var/pwcheck_& directory.
12053 The &%pwcheck%& condition takes one argument, which must be the user name and
12054 password, separated by a colon. For example, in a LOGIN authenticator
12055 configuration, you might have this:
12057 server_condition = ${if pwcheck{$auth1:$auth2}}
12059 Again, for a PLAIN authenticator configuration, this would be:
12061 server_condition = ${if pwcheck{$auth2:$auth3}}
12063 .vitem &*queue_running*&
12064 .cindex "queue runner" "detecting when delivering from"
12065 .cindex "expansion" "queue runner test"
12066 .cindex "&%queue_running%& expansion condition"
12067 This condition, which has no data, is true during delivery attempts that are
12068 initiated by queue runner processes, and false otherwise.
12071 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
12073 .cindex "expansion" "Radius authentication"
12074 .cindex "&%radius%& expansion condition"
12075 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
12076 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
12077 the Radius client configuration file in order to build Exim with Radius
12080 With just that one setting, Exim expects to be linked with the &%radiusclient%&
12081 library, using the original API. If you are using release 0.4.0 or later of
12082 this library, you need to set
12084 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
12086 in &_Local/Makefile_& when building Exim. You can also link Exim with the
12087 &%libradius%& library that comes with FreeBSD. To do this, set
12089 RADIUS_LIB_TYPE=RADLIB
12091 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
12092 You may also have to supply a suitable setting in EXTRALIBS so that the
12093 Radius library can be found when Exim is linked.
12095 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
12096 Radius client library, which calls the Radius server. The condition is true if
12097 the authentication is successful. For example:
12099 server_condition = ${if radius{<arguments>}}
12103 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
12104 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
12105 .cindex "&'saslauthd'& daemon"
12107 .cindex "expansion" "&'saslauthd'& authentication test"
12108 .cindex "&%saslauthd%& expansion condition"
12109 This condition supports user authentication using the Cyrus &'saslauthd'&
12110 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
12111 Using this daemon is one way of making it possible for passwords to be checked
12112 by a process that is not running as root.
12114 The saslauthd support is not included in Exim by default. You need to specify
12115 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
12116 building Exim. For example:
12118 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
12120 You do not need to install the full Cyrus software suite in order to use
12121 the saslauthd daemon. You can compile and install just the daemon alone
12122 from the Cyrus SASL library.
12124 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
12125 two are mandatory. For example:
12127 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
12129 The service and the realm are optional (which is why the arguments are enclosed
12130 in their own set of braces). For details of the meaning of the service and
12131 realm, and how to run the daemon, consult the Cyrus documentation.
12136 .section "Combining expansion conditions" "SECID84"
12137 .cindex "expansion" "combining conditions"
12138 Several conditions can be tested at once by combining them using the &%and%&
12139 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
12140 conditions on their own, and precede their lists of sub-conditions. Each
12141 sub-condition must be enclosed in braces within the overall braces that contain
12142 the list. No repetition of &%if%& is used.
12146 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12147 .cindex "&""or""& expansion condition"
12148 .cindex "expansion" "&""or""& of conditions"
12149 The sub-conditions are evaluated from left to right. The condition is true if
12150 any one of the sub-conditions is true.
12153 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
12155 When a true sub-condition is found, the following ones are parsed but not
12156 evaluated. If there are several &"match"& sub-conditions the values of the
12157 numeric variables afterwards are taken from the first one that succeeds.
12159 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
12160 .cindex "&""and""& expansion condition"
12161 .cindex "expansion" "&""and""& of conditions"
12162 The sub-conditions are evaluated from left to right. The condition is true if
12163 all of the sub-conditions are true. If there are several &"match"&
12164 sub-conditions, the values of the numeric variables afterwards are taken from
12165 the last one. When a false sub-condition is found, the following ones are
12166 parsed but not evaluated.
12168 .ecindex IIDexpcond
12173 .section "Expansion variables" "SECTexpvar"
12174 .cindex "expansion" "variables, list of"
12175 This section contains an alphabetical list of all the expansion variables. Some
12176 of them are available only when Exim is compiled with specific options such as
12177 support for TLS or the content scanning extension.
12180 .vitem "&$0$&, &$1$&, etc"
12181 .cindex "numerical variables (&$1$& &$2$& etc)"
12182 When a &%match%& expansion condition succeeds, these variables contain the
12183 captured substrings identified by the regular expression during subsequent
12184 processing of the success string of the containing &%if%& expansion item.
12185 In the expansion condition case
12186 they do not retain their values afterwards; in fact, their previous
12187 values are restored at the end of processing an &%if%& item. The numerical
12188 variables may also be set externally by some other matching process which
12189 precedes the expansion of the string. For example, the commands available in
12190 Exim filter files include an &%if%& command with its own regular expression
12191 matching condition.
12193 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
12194 Within an acl condition, expansion condition or expansion item
12195 any arguments are copied to these variables,
12196 any unused variables being made empty.
12198 .vitem "&$acl_c...$&"
12199 Values can be placed in these variables by the &%set%& modifier in an ACL. They
12200 can be given any name that starts with &$acl_c$& and is at least six characters
12201 long, but the sixth character must be either a digit or an underscore. For
12202 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
12203 variables persist throughout the lifetime of an SMTP connection. They can be
12204 used to pass information between ACLs and between different invocations of the
12205 same ACL. When a message is received, the values of these variables are saved
12206 with the message, and can be accessed by filters, routers, and transports
12207 during subsequent delivery.
12209 .vitem "&$acl_m...$&"
12210 These variables are like the &$acl_c...$& variables, except that their values
12211 are reset after a message has been received. Thus, if several messages are
12212 received in one SMTP connection, &$acl_m...$& values are not passed on from one
12213 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
12214 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
12215 message is received, the values of these variables are saved with the message,
12216 and can be accessed by filters, routers, and transports during subsequent
12219 .vitem &$acl_narg$&
12220 Within an acl condition, expansion condition or expansion item
12221 this variable has the number of arguments.
12223 .vitem &$acl_verify_message$&
12224 .vindex "&$acl_verify_message$&"
12225 After an address verification has failed, this variable contains the failure
12226 message. It retains its value for use in subsequent modifiers. The message can
12227 be preserved by coding like this:
12229 warn !verify = sender
12230 set acl_m0 = $acl_verify_message
12232 You can use &$acl_verify_message$& during the expansion of the &%message%& or
12233 &%log_message%& modifiers, to include information about the verification
12236 .vitem &$address_data$&
12237 .vindex "&$address_data$&"
12238 This variable is set by means of the &%address_data%& option in routers. The
12239 value then remains with the address while it is processed by subsequent routers
12240 and eventually a transport. If the transport is handling multiple addresses,
12241 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
12242 for more details. &*Note*&: The contents of &$address_data$& are visible in
12245 If &$address_data$& is set when the routers are called from an ACL to verify
12246 a recipient address, the final value is still in the variable for subsequent
12247 conditions and modifiers of the ACL statement. If routing the address caused it
12248 to be redirected to just one address, the child address is also routed as part
12249 of the verification, and in this case the final value of &$address_data$& is
12250 from the child's routing.
12252 If &$address_data$& is set when the routers are called from an ACL to verify a
12253 sender address, the final value is also preserved, but this time in
12254 &$sender_address_data$&, to distinguish it from data from a recipient
12257 In both cases (recipient and sender verification), the value does not persist
12258 after the end of the current ACL statement. If you want to preserve
12259 these values for longer, you can save them in ACL variables.
12261 .vitem &$address_file$&
12262 .vindex "&$address_file$&"
12263 When, as a result of aliasing, forwarding, or filtering, a message is directed
12264 to a specific file, this variable holds the name of the file when the transport
12265 is running. At other times, the variable is empty. For example, using the
12266 default configuration, if user &%r2d2%& has a &_.forward_& file containing
12268 /home/r2d2/savemail
12270 then when the &(address_file)& transport is running, &$address_file$&
12271 contains the text string &`/home/r2d2/savemail`&.
12272 .cindex "Sieve filter" "value of &$address_file$&"
12273 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
12274 then up to the transport configuration to generate an appropriate absolute path
12275 to the relevant file.
12277 .vitem &$address_pipe$&
12278 .vindex "&$address_pipe$&"
12279 When, as a result of aliasing or forwarding, a message is directed to a pipe,
12280 this variable holds the pipe command when the transport is running.
12282 .vitem "&$auth1$& &-- &$auth3$&"
12283 .vindex "&$auth1$&, &$auth2$&, etc"
12284 These variables are used in SMTP authenticators (see chapters
12285 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
12287 .vitem &$authenticated_id$&
12288 .cindex "authentication" "id"
12289 .vindex "&$authenticated_id$&"
12290 When a server successfully authenticates a client it may be configured to
12291 preserve some of the authentication information in the variable
12292 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
12293 user/password authenticator configuration might preserve the user name for use
12294 in the routers. Note that this is not the same information that is saved in
12295 &$sender_host_authenticated$&.
12297 When a message is submitted locally (that is, not over a TCP connection)
12298 the value of &$authenticated_id$& is normally the login name of the calling
12299 process. However, a trusted user can override this by means of the &%-oMai%&
12300 command line option.
12301 This second case also sets up information used by the
12302 &$authresults$& expansion item.
12304 .vitem &$authenticated_fail_id$&
12305 .cindex "authentication" "fail" "id"
12306 .vindex "&$authenticated_fail_id$&"
12307 When an authentication attempt fails, the variable &$authenticated_fail_id$&
12308 will contain the failed authentication id. If more than one authentication
12309 id is attempted, it will contain only the last one. The variable is
12310 available for processing in the ACL's, generally the quit or notquit ACL.
12311 A message to a local recipient could still be accepted without requiring
12312 authentication, which means this variable could also be visible in all of
12316 .vitem &$authenticated_sender$&
12317 .cindex "sender" "authenticated"
12318 .cindex "authentication" "sender"
12319 .cindex "AUTH" "on MAIL command"
12320 .vindex "&$authenticated_sender$&"
12321 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
12322 SMTP MAIL command if it believes the sender is sufficiently trusted, as
12323 described in section &<<SECTauthparamail>>&. Unless the data is the string
12324 &"<>"&, it is set as the authenticated sender of the message, and the value is
12325 available during delivery in the &$authenticated_sender$& variable. If the
12326 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
12328 .vindex "&$qualify_domain$&"
12329 When a message is submitted locally (that is, not over a TCP connection), the
12330 value of &$authenticated_sender$& is an address constructed from the login
12331 name of the calling process and &$qualify_domain$&, except that a trusted user
12332 can override this by means of the &%-oMas%& command line option.
12335 .vitem &$authentication_failed$&
12336 .cindex "authentication" "failure"
12337 .vindex "&$authentication_failed$&"
12338 This variable is set to &"1"& in an Exim server if a client issues an AUTH
12339 command that does not succeed. Otherwise it is set to &"0"&. This makes it
12340 possible to distinguish between &"did not try to authenticate"&
12341 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
12342 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
12343 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
12344 negative response to an AUTH command, including (for example) an attempt to use
12345 an undefined mechanism.
12347 .vitem &$av_failed$&
12348 .cindex "content scanning" "AV scanner failure"
12349 This variable is available when Exim is compiled with the content-scanning
12350 extension. It is set to &"0"& by default, but will be set to &"1"& if any
12351 problem occurs with the virus scanner (specified by &%av_scanner%&) during
12352 the ACL malware condition.
12354 .vitem &$body_linecount$&
12355 .cindex "message body" "line count"
12356 .cindex "body of message" "line count"
12357 .vindex "&$body_linecount$&"
12358 When a message is being received or delivered, this variable contains the
12359 number of lines in the message's body. See also &$message_linecount$&.
12361 .vitem &$body_zerocount$&
12362 .cindex "message body" "binary zero count"
12363 .cindex "body of message" "binary zero count"
12364 .cindex "binary zero" "in message body"
12365 .vindex "&$body_zerocount$&"
12366 When a message is being received or delivered, this variable contains the
12367 number of binary zero bytes (ASCII NULs) in the message's body.
12369 .vitem &$bounce_recipient$&
12370 .vindex "&$bounce_recipient$&"
12371 This is set to the recipient address of a bounce message while Exim is creating
12372 it. It is useful if a customized bounce message text file is in use (see
12373 chapter &<<CHAPemsgcust>>&).
12375 .vitem &$bounce_return_size_limit$&
12376 .vindex "&$bounce_return_size_limit$&"
12377 This contains the value set in the &%bounce_return_size_limit%& option, rounded
12378 up to a multiple of 1000. It is useful when a customized error message text
12379 file is in use (see chapter &<<CHAPemsgcust>>&).
12381 .vitem &$caller_gid$&
12382 .cindex "gid (group id)" "caller"
12383 .vindex "&$caller_gid$&"
12384 The real group id under which the process that called Exim was running. This is
12385 not the same as the group id of the originator of a message (see
12386 &$originator_gid$&). If Exim re-execs itself, this variable in the new
12387 incarnation normally contains the Exim gid.
12389 .vitem &$caller_uid$&
12390 .cindex "uid (user id)" "caller"
12391 .vindex "&$caller_uid$&"
12392 The real user id under which the process that called Exim was running. This is
12393 not the same as the user id of the originator of a message (see
12394 &$originator_uid$&). If Exim re-execs itself, this variable in the new
12395 incarnation normally contains the Exim uid.
12397 .vitem &$callout_address$&
12398 .vindex "&$callout_address$&"
12399 After a callout for verification, spamd or malware daemon service, the
12400 address that was connected to.
12402 .vitem &$compile_number$&
12403 .vindex "&$compile_number$&"
12404 The building process for Exim keeps a count of the number
12405 of times it has been compiled. This serves to distinguish different
12406 compilations of the same version of Exim.
12408 .vitem &$config_dir$&
12409 .vindex "&$config_dir$&"
12410 The directory name of the main configuration file. That is, the content of
12411 &$config_file$& with the last component stripped. The value does not
12412 contain the trailing slash. If &$config_file$& does not contain a slash,
12413 &$config_dir$& is ".".
12415 .vitem &$config_file$&
12416 .vindex "&$config_file$&"
12417 The name of the main configuration file Exim is using.
12419 .vitem &$dkim_verify_status$&
12420 Results of DKIM verification.
12421 For details see section &<<SECDKIMVFY>>&.
12423 .vitem &$dkim_cur_signer$& &&&
12424 &$dkim_verify_reason$& &&&
12425 &$dkim_domain$& &&&
12426 &$dkim_identity$& &&&
12427 &$dkim_selector$& &&&
12429 &$dkim_canon_body$& &&&
12430 &$dkim_canon_headers$& &&&
12431 &$dkim_copiedheaders$& &&&
12432 &$dkim_bodylength$& &&&
12433 &$dkim_created$& &&&
12434 &$dkim_expires$& &&&
12435 &$dkim_headernames$& &&&
12436 &$dkim_key_testing$& &&&
12437 &$dkim_key_nosubdomains$& &&&
12438 &$dkim_key_srvtype$& &&&
12439 &$dkim_key_granularity$& &&&
12440 &$dkim_key_notes$& &&&
12441 &$dkim_key_length$&
12442 These variables are only available within the DKIM ACL.
12443 For details see section &<<SECDKIMVFY>>&.
12445 .vitem &$dkim_signers$&
12446 .vindex &$dkim_signers$&
12447 When a message has been received this variable contains
12448 a colon-separated list of signer domains and identities for the message.
12449 For details see section &<<SECDKIMVFY>>&.
12451 .vitem &$dmarc_domain_policy$& &&&
12452 &$dmarc_status$& &&&
12453 &$dmarc_status_text$& &&&
12454 &$dmarc_used_domains$&
12455 Results of DMARC verification.
12456 For details see section &<<SECDMARC>>&.
12458 .vitem &$dnslist_domain$& &&&
12459 &$dnslist_matched$& &&&
12460 &$dnslist_text$& &&&
12462 .vindex "&$dnslist_domain$&"
12463 .vindex "&$dnslist_matched$&"
12464 .vindex "&$dnslist_text$&"
12465 .vindex "&$dnslist_value$&"
12466 .cindex "black list (DNS)"
12467 When a DNS (black) list lookup succeeds, these variables are set to contain
12468 the following data from the lookup: the list's domain name, the key that was
12469 looked up, the contents of any associated TXT record, and the value from the
12470 main A record. See section &<<SECID204>>& for more details.
12473 .vindex "&$domain$&"
12474 When an address is being routed, or delivered on its own, this variable
12475 contains the domain. Uppercase letters in the domain are converted into lower
12476 case for &$domain$&.
12478 Global address rewriting happens when a message is received, so the value of
12479 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
12480 is set during user filtering, but not during system filtering, because a
12481 message may have many recipients and the system filter is called just once.
12483 When more than one address is being delivered at once (for example, several
12484 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
12485 have the same domain. Transports can be restricted to handling only one domain
12486 at a time if the value of &$domain$& is required at transport time &-- this is
12487 the default for local transports. For further details of the environment in
12488 which local transports are run, see chapter &<<CHAPenvironment>>&.
12490 .oindex "&%delay_warning_condition%&"
12491 At the end of a delivery, if all deferred addresses have the same domain, it is
12492 set in &$domain$& during the expansion of &%delay_warning_condition%&.
12494 The &$domain$& variable is also used in some other circumstances:
12497 When an ACL is running for a RCPT command, &$domain$& contains the domain of
12498 the recipient address. The domain of the &'sender'& address is in
12499 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
12500 normally set during the running of the MAIL ACL. However, if the sender address
12501 is verified with a callout during the MAIL ACL, the sender domain is placed in
12502 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
12503 the &(smtp)& transport.
12506 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12507 &$domain$& contains the domain portion of the address that is being rewritten;
12508 it can be used in the expansion of the replacement address, for example, to
12509 rewrite domains by file lookup.
12512 With one important exception, whenever a domain list is being scanned,
12513 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
12514 a &%sender_domains%& condition in an ACL is being processed, the subject domain
12515 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
12516 that, in a RCPT ACL, the sender domain list can be dependent on the
12517 recipient domain (which is what is in &$domain$& at this time).
12520 .cindex "ETRN" "value of &$domain$&"
12521 .oindex "&%smtp_etrn_command%&"
12522 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
12523 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
12526 .cindex "tainted data"
12527 If the origin of the data is an incoming message,
12528 the result of expanding this variable is tainted and may not
12529 be further expanded or used as a filename.
12530 When an untainted version is needed, one should be obtained from
12531 looking up the value in a local (therefore trusted) database.
12532 Often &$domain_data$& is usable in this role.
12535 .vitem &$domain_data$&
12536 .vindex "&$domain_data$&"
12537 When the &%domains%& condition on a router
12541 against a list, the match value is copied to &$domain_data$&.
12542 This is an enhancement over previous versions of Exim, when it only
12543 applied to the data read by a lookup.
12544 For details on match values see section &<<SECTlistresults>>& et. al.
12547 If the router routes the
12548 address to a transport, the value is available in that transport. If the
12549 transport is handling multiple addresses, the value from the first address is
12552 &$domain_data$& set in an ACL is available during
12553 the rest of the ACL statement.
12555 .vitem &$exim_gid$&
12556 .vindex "&$exim_gid$&"
12557 This variable contains the numerical value of the Exim group id.
12559 .vitem &$exim_path$&
12560 .vindex "&$exim_path$&"
12561 This variable contains the path to the Exim binary.
12563 .vitem &$exim_uid$&
12564 .vindex "&$exim_uid$&"
12565 This variable contains the numerical value of the Exim user id.
12567 .vitem &$exim_version$&
12568 .vindex "&$exim_version$&"
12569 This variable contains the version string of the Exim build.
12570 The first character is a major version number, currently 4.
12571 Then after a dot, the next group of digits is a minor version number.
12572 There may be other characters following the minor version.
12573 This value may be overridden by the &%exim_version%& main config option.
12575 .vitem &$header_$&<&'name'&>
12576 This is not strictly an expansion variable. It is expansion syntax for
12577 inserting the message header line with the given name. Note that the name must
12578 be terminated by colon or white space, because it may contain a wide variety of
12579 characters. Note also that braces must &'not'& be used.
12580 See the full description in section &<<SECTexpansionitems>>& above.
12582 .vitem &$headers_added$&
12583 .vindex "&$headers_added$&"
12584 Within an ACL this variable contains the headers added so far by
12585 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
12586 The headers are a newline-separated list.
12590 When the &%check_local_user%& option is set for a router, the user's home
12591 directory is placed in &$home$& when the check succeeds. In particular, this
12592 means it is set during the running of users' filter files. A router may also
12593 explicitly set a home directory for use by a transport; this can be overridden
12594 by a setting on the transport itself.
12596 When running a filter test via the &%-bf%& option, &$home$& is set to the value
12597 of the environment variable HOME, which is subject to the
12598 &%keep_environment%& and &%add_environment%& main config options.
12602 If a router assigns an address to a transport (any transport), and passes a
12603 list of hosts with the address, the value of &$host$& when the transport starts
12604 to run is the name of the first host on the list. Note that this applies both
12605 to local and remote transports.
12607 .cindex "transport" "filter"
12608 .cindex "filter" "transport filter"
12609 For the &(smtp)& transport, if there is more than one host, the value of
12610 &$host$& changes as the transport works its way through the list. In
12611 particular, when the &(smtp)& transport is expanding its options for encryption
12612 using TLS, or for specifying a transport filter (see chapter
12613 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
12616 When used in the client part of an authenticator configuration (see chapter
12617 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
12618 client is connected.
12621 .vitem &$host_address$&
12622 .vindex "&$host_address$&"
12623 This variable is set to the remote host's IP address whenever &$host$& is set
12624 for a remote connection. It is also set to the IP address that is being checked
12625 when the &%ignore_target_hosts%& option is being processed.
12627 .vitem &$host_data$&
12628 .vindex "&$host_data$&"
12629 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
12630 result of the lookup is made available in the &$host_data$& variable. This
12631 allows you, for example, to do things like this:
12633 deny hosts = net-lsearch;/some/file
12634 message = $host_data
12636 .vitem &$host_lookup_deferred$&
12637 .cindex "host name" "lookup, failure of"
12638 .vindex "&$host_lookup_deferred$&"
12639 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
12640 message comes from a remote host and there is an attempt to look up the host's
12641 name from its IP address, and the attempt is not successful, one of these
12642 variables is set to &"1"&.
12645 If the lookup receives a definite negative response (for example, a DNS lookup
12646 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
12649 If there is any kind of problem during the lookup, such that Exim cannot
12650 tell whether or not the host name is defined (for example, a timeout for a DNS
12651 lookup), &$host_lookup_deferred$& is set to &"1"&.
12654 Looking up a host's name from its IP address consists of more than just a
12655 single reverse lookup. Exim checks that a forward lookup of at least one of the
12656 names it receives from a reverse lookup yields the original IP address. If this
12657 is not the case, Exim does not accept the looked up name(s), and
12658 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
12659 IP address (for example, the existence of a PTR record in the DNS) is not
12660 sufficient on its own for the success of a host name lookup. If the reverse
12661 lookup succeeds, but there is a lookup problem such as a timeout when checking
12662 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
12663 &"1"&. See also &$sender_host_name$&.
12665 .cindex authentication "expansion item"
12666 Performing these checks sets up information used by the
12667 &%authresults%& expansion item.
12670 .vitem &$host_lookup_failed$&
12671 .vindex "&$host_lookup_failed$&"
12672 See &$host_lookup_deferred$&.
12674 .vitem &$host_port$&
12675 .vindex "&$host_port$&"
12676 This variable is set to the remote host's TCP port whenever &$host$& is set
12677 for an outbound connection.
12679 .vitem &$initial_cwd$&
12680 .vindex "&$initial_cwd$&
12681 This variable contains the full path name of the initial working
12682 directory of the current Exim process. This may differ from the current
12683 working directory, as Exim changes this to "/" during early startup, and
12684 to &$spool_directory$& later.
12687 .vindex "&$inode$&"
12688 The only time this variable is set is while expanding the &%directory_file%&
12689 option in the &(appendfile)& transport. The variable contains the inode number
12690 of the temporary file which is about to be renamed. It can be used to construct
12691 a unique name for the file.
12693 .vitem &$interface_address$&
12694 .vindex "&$interface_address$&"
12695 This is an obsolete name for &$received_ip_address$&.
12697 .vitem &$interface_port$&
12698 .vindex "&$interface_port$&"
12699 This is an obsolete name for &$received_port$&.
12703 This variable is used during the expansion of &*forall*& and &*forany*&
12704 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
12705 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
12709 .vindex "&$ldap_dn$&"
12710 This variable, which is available only when Exim is compiled with LDAP support,
12711 contains the DN from the last entry in the most recently successful LDAP
12714 .vitem &$load_average$&
12715 .vindex "&$load_average$&"
12716 This variable contains the system load average, multiplied by 1000 so that it
12717 is an integer. For example, if the load average is 0.21, the value of the
12718 variable is 210. The value is recomputed every time the variable is referenced.
12720 .vitem &$local_part$&
12721 .vindex "&$local_part$&"
12722 When an address is being routed, or delivered on its own, this
12723 variable contains the local part. When a number of addresses are being
12724 delivered together (for example, multiple RCPT commands in an SMTP
12725 session), &$local_part$& is not set.
12727 Global address rewriting happens when a message is received, so the value of
12728 &$local_part$& during routing and delivery is the value after rewriting.
12729 &$local_part$& is set during user filtering, but not during system filtering,
12730 because a message may have many recipients and the system filter is called just
12733 .cindex "tainted data"
12734 If the origin of the data is an incoming message,
12735 the result of expanding this variable is tainted and
12736 may not be further expanded or used as a filename.
12738 &*Warning*&: the content of this variable is usually provided by a potential
12740 Consider carefully the implications of using it unvalidated as a name
12742 This presents issues for users' &_.forward_& and filter files.
12743 For traditional full user accounts, use &%check_local_users%& and the
12744 &$local_part_data$& variable rather than this one.
12745 For virtual users, store a suitable pathname component in the database
12746 which is used for account name validation, and use that retrieved value
12747 rather than this variable.
12748 Often &$local_part_data$& is usable in this role.
12749 If needed, use a router &%address_data%& or &%set%& option for
12750 the retrieved data.
12752 When a message is being delivered to a file, pipe, or autoreply transport as a
12753 result of aliasing or forwarding, &$local_part$& is set to the local part of
12754 the parent address, not to the filename or command (see &$address_file$& and
12757 When an ACL is running for a RCPT command, &$local_part$& contains the
12758 local part of the recipient address.
12760 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12761 &$local_part$& contains the local part of the address that is being rewritten;
12762 it can be used in the expansion of the replacement address, for example.
12764 In all cases, all quoting is removed from the local part. For example, for both
12767 "abc:xyz"@test.example
12768 abc\:xyz@test.example
12770 the value of &$local_part$& is
12774 If you use &$local_part$& to create another address, you should always wrap it
12775 inside a quoting operator. For example, in a &(redirect)& router you could
12778 data = ${quote_local_part:$local_part}@new.domain.example
12780 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
12781 to process local parts in a case-dependent manner in a router, you can set the
12782 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
12784 .vitem &$local_part_data$&
12785 .vindex "&$local_part_data$&"
12786 When the &%local_parts%& condition on a router or ACL
12787 matches a local part list
12789 the match value is copied to &$local_part_data$&.
12790 This is an enhancement over previous versions of Exim, when it only
12791 applied to the data read by a lookup.
12792 For details on match values see section &<<SECTlistresults>>& et. al.
12795 The &%check_local_user%& router option also sets this variable.
12797 .vindex &$local_part_prefix$& &&&
12798 &$local_part_prefix_v$& &&&
12799 &$local_part_suffix$& &&&
12800 &$local_part_suffix_v$&
12801 .cindex affix variables
12802 If a local part prefix or suffix has been recognized, it is not included in the
12803 value of &$local_part$& during routing and subsequent delivery. The values of
12804 any prefix or suffix are in &$local_part_prefix$& and
12805 &$local_part_suffix$&, respectively.
12806 .cindex "tainted data"
12807 If the specification did not include a wildcard then
12808 the affix variable value is not tainted.
12810 If the affix specification included a wildcard then the portion of
12811 the affix matched by the wildcard is in
12812 &$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate,
12813 and both the whole and varying values are tainted.
12815 .vitem &$local_scan_data$&
12816 .vindex "&$local_scan_data$&"
12817 This variable contains the text returned by the &[local_scan()]& function when
12818 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
12820 .vitem &$local_user_gid$&
12821 .vindex "&$local_user_gid$&"
12822 See &$local_user_uid$&.
12824 .vitem &$local_user_uid$&
12825 .vindex "&$local_user_uid$&"
12826 This variable and &$local_user_gid$& are set to the uid and gid after the
12827 &%check_local_user%& router precondition succeeds. This means that their values
12828 are available for the remaining preconditions (&%senders%&, &%require_files%&,
12829 and &%condition%&), for the &%address_data%& expansion, and for any
12830 router-specific expansions. At all other times, the values in these variables
12831 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
12833 .vitem &$localhost_number$&
12834 .vindex "&$localhost_number$&"
12835 This contains the expanded value of the
12836 &%localhost_number%& option. The expansion happens after the main options have
12839 .vitem &$log_inodes$&
12840 .vindex "&$log_inodes$&"
12841 The number of free inodes in the disk partition where Exim's
12842 log files are being written. The value is recalculated whenever the variable is
12843 referenced. If the relevant file system does not have the concept of inodes,
12844 the value of is -1. See also the &%check_log_inodes%& option.
12846 .vitem &$log_space$&
12847 .vindex "&$log_space$&"
12848 The amount of free space (as a number of kilobytes) in the disk
12849 partition where Exim's log files are being written. The value is recalculated
12850 whenever the variable is referenced. If the operating system does not have the
12851 ability to find the amount of free space (only true for experimental systems),
12852 the space value is -1. See also the &%check_log_space%& option.
12855 .vitem &$lookup_dnssec_authenticated$&
12856 .vindex "&$lookup_dnssec_authenticated$&"
12857 This variable is set after a DNS lookup done by
12858 a dnsdb lookup expansion, dnslookup router or smtp transport.
12859 .cindex "DNS" "DNSSEC"
12860 It will be empty if &(DNSSEC)& was not requested,
12861 &"no"& if the result was not labelled as authenticated data
12862 and &"yes"& if it was.
12863 Results that are labelled as authoritative answer that match
12864 the &%dns_trust_aa%& configuration variable count also
12865 as authenticated data.
12867 .vitem &$mailstore_basename$&
12868 .vindex "&$mailstore_basename$&"
12869 This variable is set only when doing deliveries in &"mailstore"& format in the
12870 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
12871 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
12872 contains the basename of the files that are being written, that is, the name
12873 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
12876 .vitem &$malware_name$&
12877 .vindex "&$malware_name$&"
12878 This variable is available when Exim is compiled with the
12879 content-scanning extension. It is set to the name of the virus that was found
12880 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12882 .vitem &$max_received_linelength$&
12883 .vindex "&$max_received_linelength$&"
12884 .cindex "maximum" "line length"
12885 .cindex "line length" "maximum"
12886 This variable contains the number of bytes in the longest line that was
12887 received as part of the message, not counting the line termination
12889 It is not valid if the &%spool_files_wireformat%& option is used.
12891 .vitem &$message_age$&
12892 .cindex "message" "age of"
12893 .vindex "&$message_age$&"
12894 This variable is set at the start of a delivery attempt to contain the number
12895 of seconds since the message was received. It does not change during a single
12898 .vitem &$message_body$&
12899 .cindex "body of message" "expansion variable"
12900 .cindex "message body" "in expansion"
12901 .cindex "binary zero" "in message body"
12902 .vindex "&$message_body$&"
12903 .oindex "&%message_body_visible%&"
12904 This variable contains the initial portion of a message's body while it is
12905 being delivered, and is intended mainly for use in filter files. The maximum
12906 number of characters of the body that are put into the variable is set by the
12907 &%message_body_visible%& configuration option; the default is 500.
12909 .oindex "&%message_body_newlines%&"
12910 By default, newlines are converted into spaces in &$message_body$&, to make it
12911 easier to search for phrases that might be split over a line break. However,
12912 this can be disabled by setting &%message_body_newlines%& to be true. Binary
12913 zeros are always converted into spaces.
12915 .vitem &$message_body_end$&
12916 .cindex "body of message" "expansion variable"
12917 .cindex "message body" "in expansion"
12918 .vindex "&$message_body_end$&"
12919 This variable contains the final portion of a message's
12920 body while it is being delivered. The format and maximum size are as for
12923 .vitem &$message_body_size$&
12924 .cindex "body of message" "size"
12925 .cindex "message body" "size"
12926 .vindex "&$message_body_size$&"
12927 When a message is being delivered, this variable contains the size of the body
12928 in bytes. The count starts from the character after the blank line that
12929 separates the body from the header. Newlines are included in the count. See
12930 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
12932 If the spool file is wireformat
12933 (see the &%spool_files_wireformat%& main option)
12934 the CRLF line-terminators are included in the count.
12936 .vitem &$message_exim_id$&
12937 .vindex "&$message_exim_id$&"
12938 When a message is being received or delivered, this variable contains the
12939 unique message id that is generated and used by Exim to identify the message.
12940 An id is not created for a message until after its header has been successfully
12941 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
12942 line; it is the local id that Exim assigns to the message, for example:
12943 &`1BXTIK-0001yO-VA`&.
12945 .vitem &$message_headers$&
12946 .vindex &$message_headers$&
12947 This variable contains a concatenation of all the header lines when a message
12948 is being processed, except for lines added by routers or transports. The header
12949 lines are separated by newline characters. Their contents are decoded in the
12950 same way as a header line that is inserted by &%bheader%&.
12952 .vitem &$message_headers_raw$&
12953 .vindex &$message_headers_raw$&
12954 This variable is like &$message_headers$& except that no processing of the
12955 contents of header lines is done.
12957 .vitem &$message_id$&
12958 This is an old name for &$message_exim_id$&. It is now deprecated.
12960 .vitem &$message_linecount$&
12961 .vindex "&$message_linecount$&"
12962 This variable contains the total number of lines in the header and body of the
12963 message. Compare &$body_linecount$&, which is the count for the body only.
12964 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
12965 number of lines received. Before delivery happens (that is, before filters,
12966 routers, and transports run) the count is increased to include the
12967 &'Received:'& header line that Exim standardly adds, and also any other header
12968 lines that are added by ACLs. The blank line that separates the message header
12969 from the body is not counted.
12971 As with the special case of &$message_size$&, during the expansion of the
12972 appendfile transport's maildir_tag option in maildir format, the value of
12973 &$message_linecount$& is the precise size of the number of newlines in the
12974 file that has been written (minus one for the blank line between the
12975 header and the body).
12977 Here is an example of the use of this variable in a DATA ACL:
12980 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
12981 message = Too many lines in message header
12983 In the MAIL and RCPT ACLs, the value is zero because at that stage the
12984 message has not yet been received.
12986 This variable is not valid if the &%spool_files_wireformat%& option is used.
12988 .vitem &$message_size$&
12989 .cindex "size" "of message"
12990 .cindex "message" "size"
12991 .vindex "&$message_size$&"
12992 When a message is being processed, this variable contains its size in bytes. In
12993 most cases, the size includes those headers that were received with the
12994 message, but not those (such as &'Envelope-to:'&) that are added to individual
12995 deliveries as they are written. However, there is one special case: during the
12996 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
12997 doing a delivery in maildir format, the value of &$message_size$& is the
12998 precise size of the file that has been written. See also
12999 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
13001 .cindex "RCPT" "value of &$message_size$&"
13002 While running a per message ACL (mail/rcpt/predata), &$message_size$&
13003 contains the size supplied on the MAIL command, or -1 if no size was given. The
13004 value may not, of course, be truthful.
13006 .vitem &$mime_$&&'xxx'&
13007 A number of variables whose names start with &$mime$& are
13008 available when Exim is compiled with the content-scanning extension. For
13009 details, see section &<<SECTscanmimepart>>&.
13011 .vitem "&$n0$& &-- &$n9$&"
13012 These variables are counters that can be incremented by means
13013 of the &%add%& command in filter files.
13015 .vitem &$original_domain$&
13016 .vindex "&$domain$&"
13017 .vindex "&$original_domain$&"
13018 When a top-level address is being processed for delivery, this contains the
13019 same value as &$domain$&. However, if a &"child"& address (for example,
13020 generated by an alias, forward, or filter file) is being processed, this
13021 variable contains the domain of the original address (lower cased). This
13022 differs from &$parent_domain$& only when there is more than one level of
13023 aliasing or forwarding. When more than one address is being delivered in a
13024 single transport run, &$original_domain$& is not set.
13026 If a new address is created by means of a &%deliver%& command in a system
13027 filter, it is set up with an artificial &"parent"& address. This has the local
13028 part &'system-filter'& and the default qualify domain.
13030 .vitem &$original_local_part$&
13031 .vindex "&$local_part$&"
13032 .vindex "&$original_local_part$&"
13033 When a top-level address is being processed for delivery, this contains the
13034 same value as &$local_part$&, unless a prefix or suffix was removed from the
13035 local part, because &$original_local_part$& always contains the full local
13036 part. When a &"child"& address (for example, generated by an alias, forward, or
13037 filter file) is being processed, this variable contains the full local part of
13038 the original address.
13040 If the router that did the redirection processed the local part
13041 case-insensitively, the value in &$original_local_part$& is in lower case.
13042 This variable differs from &$parent_local_part$& only when there is more than
13043 one level of aliasing or forwarding. When more than one address is being
13044 delivered in a single transport run, &$original_local_part$& is not set.
13046 If a new address is created by means of a &%deliver%& command in a system
13047 filter, it is set up with an artificial &"parent"& address. This has the local
13048 part &'system-filter'& and the default qualify domain.
13050 .vitem &$originator_gid$&
13051 .cindex "gid (group id)" "of originating user"
13052 .cindex "sender" "gid"
13053 .vindex "&$caller_gid$&"
13054 .vindex "&$originator_gid$&"
13055 This variable contains the value of &$caller_gid$& that was set when the
13056 message was received. For messages received via the command line, this is the
13057 gid of the sending user. For messages received by SMTP over TCP/IP, this is
13058 normally the gid of the Exim user.
13060 .vitem &$originator_uid$&
13061 .cindex "uid (user id)" "of originating user"
13062 .cindex "sender" "uid"
13063 .vindex "&$caller_uid$&"
13064 .vindex "&$originator_uid$&"
13065 The value of &$caller_uid$& that was set when the message was received. For
13066 messages received via the command line, this is the uid of the sending user.
13067 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
13070 .vitem &$parent_domain$&
13071 .vindex "&$parent_domain$&"
13072 This variable is similar to &$original_domain$& (see
13073 above), except that it refers to the immediately preceding parent address.
13075 .vitem &$parent_local_part$&
13076 .vindex "&$parent_local_part$&"
13077 This variable is similar to &$original_local_part$&
13078 (see above), except that it refers to the immediately preceding parent address.
13081 .cindex "pid (process id)" "of current process"
13083 This variable contains the current process id.
13085 .vitem &$pipe_addresses$&
13086 .cindex "filter" "transport filter"
13087 .cindex "transport" "filter"
13088 .vindex "&$pipe_addresses$&"
13089 This is not an expansion variable, but is mentioned here because the string
13090 &`$pipe_addresses`& is handled specially in the command specification for the
13091 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
13092 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
13093 It cannot be used in general expansion strings, and provokes an &"unknown
13094 variable"& error if encountered.
13096 .vitem &$primary_hostname$&
13097 .vindex "&$primary_hostname$&"
13098 This variable contains the value set by &%primary_hostname%& in the
13099 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
13100 a single-component name, Exim calls &[gethostbyname()]& (or
13101 &[getipnodebyname()]& where available) in an attempt to acquire a fully
13102 qualified host name. See also &$smtp_active_hostname$&.
13105 .vitem &$proxy_external_address$& &&&
13106 &$proxy_external_port$& &&&
13107 &$proxy_local_address$& &&&
13108 &$proxy_local_port$& &&&
13110 These variables are only available when built with Proxy Protocol
13112 For details see chapter &<<SECTproxyInbound>>&.
13114 .vitem &$prdr_requested$&
13115 .cindex "PRDR" "variable for"
13116 This variable is set to &"yes"& if PRDR was requested by the client for the
13117 current message, otherwise &"no"&.
13119 .vitem &$prvscheck_address$&
13120 This variable is used in conjunction with the &%prvscheck%& expansion item,
13121 which is described in sections &<<SECTexpansionitems>>& and
13122 &<<SECTverifyPRVS>>&.
13124 .vitem &$prvscheck_keynum$&
13125 This variable is used in conjunction with the &%prvscheck%& expansion item,
13126 which is described in sections &<<SECTexpansionitems>>& and
13127 &<<SECTverifyPRVS>>&.
13129 .vitem &$prvscheck_result$&
13130 This variable is used in conjunction with the &%prvscheck%& expansion item,
13131 which is described in sections &<<SECTexpansionitems>>& and
13132 &<<SECTverifyPRVS>>&.
13134 .vitem &$qualify_domain$&
13135 .vindex "&$qualify_domain$&"
13136 The value set for the &%qualify_domain%& option in the configuration file.
13138 .vitem &$qualify_recipient$&
13139 .vindex "&$qualify_recipient$&"
13140 The value set for the &%qualify_recipient%& option in the configuration file,
13141 or if not set, the value of &$qualify_domain$&.
13143 .vitem &$queue_name$&
13144 .vindex &$queue_name$&
13145 .cindex "named queues" variable
13146 .cindex queues named
13147 The name of the spool queue in use; empty for the default queue.
13149 .vitem &$queue_size$&
13150 .vindex "&$queue_size$&"
13151 .cindex "queue" "size of"
13152 .cindex "spool" "number of messages"
13153 This variable contains the number of messages queued.
13154 It is evaluated on demand, but no more often than once every minute.
13155 If there is no daemon notifier socket open, the value will be
13160 .cindex router variables
13161 Values can be placed in these variables by the &%set%& option of a router.
13162 They can be given any name that starts with &$r_$&.
13163 The values persist for the address being handled through subsequent routers
13164 and the eventual transport.
13166 .vitem &$rcpt_count$&
13167 .vindex "&$rcpt_count$&"
13168 When a message is being received by SMTP, this variable contains the number of
13169 RCPT commands received for the current message. If this variable is used in a
13170 RCPT ACL, its value includes the current command.
13172 .vitem &$rcpt_defer_count$&
13173 .vindex "&$rcpt_defer_count$&"
13174 .cindex "4&'xx'& responses" "count of"
13175 When a message is being received by SMTP, this variable contains the number of
13176 RCPT commands in the current message that have previously been rejected with a
13177 temporary (4&'xx'&) response.
13179 .vitem &$rcpt_fail_count$&
13180 .vindex "&$rcpt_fail_count$&"
13181 When a message is being received by SMTP, this variable contains the number of
13182 RCPT commands in the current message that have previously been rejected with a
13183 permanent (5&'xx'&) response.
13185 .vitem &$received_count$&
13186 .vindex "&$received_count$&"
13187 This variable contains the number of &'Received:'& header lines in the message,
13188 including the one added by Exim (so its value is always greater than zero). It
13189 is available in the DATA ACL, the non-SMTP ACL, and while routing and
13192 .vitem &$received_for$&
13193 .vindex "&$received_for$&"
13194 If there is only a single recipient address in an incoming message, this
13195 variable contains that address when the &'Received:'& header line is being
13196 built. The value is copied after recipient rewriting has happened, but before
13197 the &[local_scan()]& function is run.
13199 .vitem &$received_ip_address$&
13200 .vindex "&$received_ip_address$&"
13201 As soon as an Exim server starts processing an incoming TCP/IP connection, this
13202 variable is set to the address of the local IP interface, and &$received_port$&
13203 is set to the local port number. (The remote IP address and port are in
13204 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
13205 the port value is -1 unless it has been set using the &%-oMi%& command line
13208 As well as being useful in ACLs (including the &"connect"& ACL), these variable
13209 could be used, for example, to make the filename for a TLS certificate depend
13210 on which interface and/or port is being used for the incoming connection. The
13211 values of &$received_ip_address$& and &$received_port$& are saved with any
13212 messages that are received, thus making these variables available at delivery
13214 For outbound connections see &$sending_ip_address$&.
13216 .vitem &$received_port$&
13217 .vindex "&$received_port$&"
13218 See &$received_ip_address$&.
13220 .vitem &$received_protocol$&
13221 .vindex "&$received_protocol$&"
13222 When a message is being processed, this variable contains the name of the
13223 protocol by which it was received. Most of the names used by Exim are defined
13224 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
13225 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
13226 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
13227 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
13228 connection and the client was successfully authenticated.
13230 Exim uses the protocol name &"smtps"& for the case when encryption is
13231 automatically set up on connection without the use of STARTTLS (see
13232 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
13233 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
13234 where the client initially uses EHLO, sets up an encrypted connection using
13235 STARTTLS, and then uses HELO afterwards.
13237 The &%-oMr%& option provides a way of specifying a custom protocol name for
13238 messages that are injected locally by trusted callers. This is commonly used to
13239 identify messages that are being re-injected after some kind of scanning.
13241 .vitem &$received_time$&
13242 .vindex "&$received_time$&"
13243 This variable contains the date and time when the current message was received,
13244 as a number of seconds since the start of the Unix epoch.
13246 .vitem &$recipient_data$&
13247 .vindex "&$recipient_data$&"
13248 This variable is set after an indexing lookup success in an ACL &%recipients%&
13249 condition. It contains the data from the lookup, and the value remains set
13250 until the next &%recipients%& test. Thus, you can do things like this:
13252 &`require recipients = cdb*@;/some/file`&
13253 &`deny `&&'some further test involving'& &`$recipient_data`&
13255 &*Warning*&: This variable is set only when a lookup is used as an indexing
13256 method in the address list, using the semicolon syntax as in the example above.
13257 The variable is not set for a lookup that is used as part of the string
13258 expansion that all such lists undergo before being interpreted.
13260 .vitem &$recipient_verify_failure$&
13261 .vindex "&$recipient_verify_failure$&"
13262 In an ACL, when a recipient verification fails, this variable contains
13263 information about the failure. It is set to one of the following words:
13266 &"qualify"&: The address was unqualified (no domain), and the message
13267 was neither local nor came from an exempted host.
13270 &"route"&: Routing failed.
13273 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
13274 or before the MAIL command (that is, on initial connection, HELO, or
13278 &"recipient"&: The RCPT command in a callout was rejected.
13281 &"postmaster"&: The postmaster check in a callout was rejected.
13284 The main use of this variable is expected to be to distinguish between
13285 rejections of MAIL and rejections of RCPT.
13287 .vitem &$recipients$&
13288 .vindex "&$recipients$&"
13289 This variable contains a list of envelope recipients for a message. A comma and
13290 a space separate the addresses in the replacement text. However, the variable
13291 is not generally available, to prevent exposure of Bcc recipients in
13292 unprivileged users' filter files. You can use &$recipients$& only in these
13296 In a system filter file.
13298 In the ACLs associated with the DATA command and with non-SMTP messages, that
13299 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
13300 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
13301 &%acl_not_smtp_mime%&.
13303 From within a &[local_scan()]& function.
13307 .vitem &$recipients_count$&
13308 .vindex "&$recipients_count$&"
13309 When a message is being processed, this variable contains the number of
13310 envelope recipients that came with the message. Duplicates are not excluded
13311 from the count. While a message is being received over SMTP, the number
13312 increases for each accepted recipient. It can be referenced in an ACL.
13315 .vitem &$regex_match_string$&
13316 .vindex "&$regex_match_string$&"
13317 This variable is set to contain the matching regular expression after a
13318 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
13320 .vitem "&$regex1$&, &$regex2$&, etc"
13321 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
13322 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
13323 these variables contain the
13324 captured substrings identified by the regular expression.
13327 .vitem &$reply_address$&
13328 .vindex "&$reply_address$&"
13329 When a message is being processed, this variable contains the contents of the
13330 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
13331 contents of the &'From:'& header line. Apart from the removal of leading
13332 white space, the value is not processed in any way. In particular, no RFC 2047
13333 decoding or character code translation takes place.
13335 .vitem &$return_path$&
13336 .vindex "&$return_path$&"
13337 When a message is being delivered, this variable contains the return path &--
13338 the sender field that will be sent as part of the envelope. It is not enclosed
13339 in <> characters. At the start of routing an address, &$return_path$& has the
13340 same value as &$sender_address$&, but if, for example, an incoming message to a
13341 mailing list has been expanded by a router which specifies a different address
13342 for bounce messages, &$return_path$& subsequently contains the new bounce
13343 address, whereas &$sender_address$& always contains the original sender address
13344 that was received with the message. In other words, &$sender_address$& contains
13345 the incoming envelope sender, and &$return_path$& contains the outgoing
13348 .vitem &$return_size_limit$&
13349 .vindex "&$return_size_limit$&"
13350 This is an obsolete name for &$bounce_return_size_limit$&.
13352 .vitem &$router_name$&
13353 .cindex "router" "name"
13354 .cindex "name" "of router"
13355 .vindex "&$router_name$&"
13356 During the running of a router this variable contains its name.
13359 .cindex "return code" "from &%run%& expansion"
13360 .vindex "&$runrc$&"
13361 This variable contains the return code from a command that is run by the
13362 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
13363 assume the order in which option values are expanded, except for those
13364 preconditions whose order of testing is documented. Therefore, you cannot
13365 reliably expect to set &$runrc$& by the expansion of one option, and use it in
13368 .vitem &$self_hostname$&
13369 .oindex "&%self%&" "value of host name"
13370 .vindex "&$self_hostname$&"
13371 When an address is routed to a supposedly remote host that turns out to be the
13372 local host, what happens is controlled by the &%self%& generic router option.
13373 One of its values causes the address to be passed to another router. When this
13374 happens, &$self_hostname$& is set to the name of the local host that the
13375 original router encountered. In other circumstances its contents are null.
13377 .vitem &$sender_address$&
13378 .vindex "&$sender_address$&"
13379 When a message is being processed, this variable contains the sender's address
13380 that was received in the message's envelope. The case of letters in the address
13381 is retained, in both the local part and the domain. For bounce messages, the
13382 value of this variable is the empty string. See also &$return_path$&.
13384 .vitem &$sender_address_data$&
13385 .vindex "&$address_data$&"
13386 .vindex "&$sender_address_data$&"
13387 If &$address_data$& is set when the routers are called from an ACL to verify a
13388 sender address, the final value is preserved in &$sender_address_data$&, to
13389 distinguish it from data from a recipient address. The value does not persist
13390 after the end of the current ACL statement. If you want to preserve it for
13391 longer, you can save it in an ACL variable.
13393 .vitem &$sender_address_domain$&
13394 .vindex "&$sender_address_domain$&"
13395 The domain portion of &$sender_address$&.
13397 .vitem &$sender_address_local_part$&
13398 .vindex "&$sender_address_local_part$&"
13399 The local part portion of &$sender_address$&.
13401 .vitem &$sender_data$&
13402 .vindex "&$sender_data$&"
13403 This variable is set after a lookup success in an ACL &%senders%& condition or
13404 in a router &%senders%& option. It contains the data from the lookup, and the
13405 value remains set until the next &%senders%& test. Thus, you can do things like
13408 &`require senders = cdb*@;/some/file`&
13409 &`deny `&&'some further test involving'& &`$sender_data`&
13411 &*Warning*&: This variable is set only when a lookup is used as an indexing
13412 method in the address list, using the semicolon syntax as in the example above.
13413 The variable is not set for a lookup that is used as part of the string
13414 expansion that all such lists undergo before being interpreted.
13416 .vitem &$sender_fullhost$&
13417 .vindex "&$sender_fullhost$&"
13418 When a message is received from a remote host, this variable contains the host
13419 name and IP address in a single string. It ends with the IP address in square
13420 brackets, followed by a colon and a port number if the logging of ports is
13421 enabled. The format of the rest of the string depends on whether the host
13422 issued a HELO or EHLO SMTP command, and whether the host name was verified by
13423 looking up its IP address. (Looking up the IP address can be forced by the
13424 &%host_lookup%& option, independent of verification.) A plain host name at the
13425 start of the string is a verified host name; if this is not present,
13426 verification either failed or was not requested. A host name in parentheses is
13427 the argument of a HELO or EHLO command. This is omitted if it is identical to
13428 the verified host name or to the host's IP address in square brackets.
13430 .vitem &$sender_helo_dnssec$&
13431 .vindex "&$sender_helo_dnssec$&"
13432 This boolean variable is true if a successful HELO verification was
13433 .cindex "DNS" "DNSSEC"
13434 done using DNS information the resolver library stated was authenticated data.
13436 .vitem &$sender_helo_name$&
13437 .vindex "&$sender_helo_name$&"
13438 When a message is received from a remote host that has issued a HELO or EHLO
13439 command, the argument of that command is placed in this variable. It is also
13440 set if HELO or EHLO is used when a message is received using SMTP locally via
13441 the &%-bs%& or &%-bS%& options.
13443 .vitem &$sender_host_address$&
13444 .vindex "&$sender_host_address$&"
13445 When a message is received from a remote host using SMTP,
13446 this variable contains that
13447 host's IP address. For locally non-SMTP submitted messages, it is empty.
13449 .vitem &$sender_host_authenticated$&
13450 .vindex "&$sender_host_authenticated$&"
13451 This variable contains the name (not the public name) of the authenticator
13452 driver that successfully authenticated the client from which the message was
13453 received. It is empty if there was no successful authentication. See also
13454 &$authenticated_id$&.
13456 .vitem &$sender_host_dnssec$&
13457 .vindex "&$sender_host_dnssec$&"
13458 If an attempt to populate &$sender_host_name$& has been made
13459 (by reference, &%hosts_lookup%& or
13460 otherwise) then this boolean will have been set true if, and only if, the
13461 resolver library states that both
13462 the reverse and forward DNS were authenticated data. At all
13463 other times, this variable is false.
13465 .cindex "DNS" "DNSSEC"
13466 It is likely that you will need to coerce DNSSEC support on in the resolver
13467 library, by setting:
13472 In addition, on Linux with glibc 2.31 or newer the resolver library will
13473 default to stripping out a successful validation status.
13474 This will break a previously working Exim installation.
13475 Provided that you do trust the resolver (ie, is on localhost) you can tell
13476 glibc to pass through any successful validation with a new option in
13477 &_/etc/resolv.conf_&:
13482 Exim does not perform DNSSEC validation itself, instead leaving that to a
13483 validating resolver (e.g. unbound, or bind with suitable configuration).
13485 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
13486 mechanism in the list, then this variable will be false.
13488 This requires that your system resolver library support EDNS0 (and that
13489 DNSSEC flags exist in the system headers). If the resolver silently drops
13490 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
13491 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
13494 .vitem &$sender_host_name$&
13495 .vindex "&$sender_host_name$&"
13496 When a message is received from a remote host, this variable contains the
13497 host's name as obtained by looking up its IP address. For messages received by
13498 other means, this variable is empty.
13500 .vindex "&$host_lookup_failed$&"
13501 If the host name has not previously been looked up, a reference to
13502 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
13503 A looked up name is accepted only if it leads back to the original IP address
13504 via a forward lookup. If either the reverse or the forward lookup fails to find
13505 any data, or if the forward lookup does not yield the original IP address,
13506 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
13508 .vindex "&$host_lookup_deferred$&"
13509 However, if either of the lookups cannot be completed (for example, there is a
13510 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
13511 &$host_lookup_failed$& remains set to &"0"&.
13513 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
13514 host name again if there is a subsequent reference to &$sender_host_name$&
13515 in the same Exim process, but it does try again if &$host_lookup_deferred$&
13518 Exim does not automatically look up every calling host's name. If you want
13519 maximum efficiency, you should arrange your configuration so that it avoids
13520 these lookups altogether. The lookup happens only if one or more of the
13521 following are true:
13524 A string containing &$sender_host_name$& is expanded.
13526 The calling host matches the list in &%host_lookup%&. In the default
13527 configuration, this option is set to *, so it must be changed if lookups are
13528 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
13530 Exim needs the host name in order to test an item in a host list. The items
13531 that require this are described in sections &<<SECThoslispatnam>>& and
13532 &<<SECThoslispatnamsk>>&.
13534 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
13535 In this case, the host name is required to compare with the name quoted in any
13536 EHLO or HELO commands that the client issues.
13538 The remote host issues a EHLO or HELO command that quotes one of the
13539 domains in &%helo_lookup_domains%&. The default value of this option is
13540 . ==== As this is a nested list, any displays it contains must be indented
13541 . ==== as otherwise they are too far to the left.
13543 helo_lookup_domains = @ : @[]
13545 which causes a lookup if a remote host (incorrectly) gives the server's name or
13546 IP address in an EHLO or HELO command.
13550 .vitem &$sender_host_port$&
13551 .vindex "&$sender_host_port$&"
13552 When a message is received from a remote host, this variable contains the port
13553 number that was used on the remote host.
13555 .vitem &$sender_ident$&
13556 .vindex "&$sender_ident$&"
13557 When a message is received from a remote host, this variable contains the
13558 identification received in response to an RFC 1413 request. When a message has
13559 been received locally, this variable contains the login name of the user that
13562 .vitem &$sender_rate_$&&'xxx'&
13563 A number of variables whose names begin &$sender_rate_$& are set as part of the
13564 &%ratelimit%& ACL condition. Details are given in section
13565 &<<SECTratelimiting>>&.
13567 .vitem &$sender_rcvhost$&
13568 .cindex "DNS" "reverse lookup"
13569 .cindex "reverse DNS lookup"
13570 .vindex "&$sender_rcvhost$&"
13571 This is provided specifically for use in &'Received:'& headers. It starts with
13572 either the verified host name (as obtained from a reverse DNS lookup) or, if
13573 there is no verified host name, the IP address in square brackets. After that
13574 there may be text in parentheses. When the first item is a verified host name,
13575 the first thing in the parentheses is the IP address in square brackets,
13576 followed by a colon and a port number if port logging is enabled. When the
13577 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
13580 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
13581 was used and its argument was not identical to the real host name or IP
13582 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
13583 all three items are present in the parentheses, a newline and tab are inserted
13584 into the string, to improve the formatting of the &'Received:'& header.
13586 .vitem &$sender_verify_failure$&
13587 .vindex "&$sender_verify_failure$&"
13588 In an ACL, when a sender verification fails, this variable contains information
13589 about the failure. The details are the same as for
13590 &$recipient_verify_failure$&.
13592 .vitem &$sending_ip_address$&
13593 .vindex "&$sending_ip_address$&"
13594 This variable is set whenever an outgoing SMTP connection to another host has
13595 been set up. It contains the IP address of the local interface that is being
13596 used. This is useful if a host that has more than one IP address wants to take
13597 on different personalities depending on which one is being used. For incoming
13598 connections, see &$received_ip_address$&.
13600 .vitem &$sending_port$&
13601 .vindex "&$sending_port$&"
13602 This variable is set whenever an outgoing SMTP connection to another host has
13603 been set up. It contains the local port that is being used. For incoming
13604 connections, see &$received_port$&.
13606 .vitem &$smtp_active_hostname$&
13607 .vindex "&$smtp_active_hostname$&"
13608 During an incoming SMTP session, this variable contains the value of the active
13609 host name, as specified by the &%smtp_active_hostname%& option. The value of
13610 &$smtp_active_hostname$& is saved with any message that is received, so its
13611 value can be consulted during routing and delivery.
13613 .vitem &$smtp_command$&
13614 .vindex "&$smtp_command$&"
13615 During the processing of an incoming SMTP command, this variable contains the
13616 entire command. This makes it possible to distinguish between HELO and EHLO in
13617 the HELO ACL, and also to distinguish between commands such as these:
13622 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
13623 command, the address in &$smtp_command$& is the original address before any
13624 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
13625 the address after SMTP-time rewriting.
13627 .vitem &$smtp_command_argument$&
13628 .cindex "SMTP" "command, argument for"
13629 .vindex "&$smtp_command_argument$&"
13630 While an ACL is running to check an SMTP command, this variable contains the
13631 argument, that is, the text that follows the command name, with leading white
13632 space removed. Following the introduction of &$smtp_command$&, this variable is
13633 somewhat redundant, but is retained for backwards compatibility.
13635 .vitem &$smtp_command_history$&
13636 .cindex SMTP "command history"
13637 .vindex "&$smtp_command_history$&"
13638 A comma-separated list (with no whitespace) of the most-recent SMTP commands
13639 received, in time-order left to right. Only a limited number of commands
13642 .vitem &$smtp_count_at_connection_start$&
13643 .vindex "&$smtp_count_at_connection_start$&"
13644 This variable is set greater than zero only in processes spawned by the Exim
13645 daemon for handling incoming SMTP connections. The name is deliberately long,
13646 in order to emphasize what the contents are. When the daemon accepts a new
13647 connection, it increments this variable. A copy of the variable is passed to
13648 the child process that handles the connection, but its value is fixed, and
13649 never changes. It is only an approximation of how many incoming connections
13650 there actually are, because many other connections may come and go while a
13651 single connection is being processed. When a child process terminates, the
13652 daemon decrements its copy of the variable.
13654 .vitem "&$sn0$& &-- &$sn9$&"
13655 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
13656 that were current at the end of the system filter file. This allows a system
13657 filter file to set values that can be tested in users' filter files. For
13658 example, a system filter could set a value indicating how likely it is that a
13659 message is junk mail.
13661 .vitem &$spam_$&&'xxx'&
13662 A number of variables whose names start with &$spam$& are available when Exim
13663 is compiled with the content-scanning extension. For details, see section
13664 &<<SECTscanspamass>>&.
13666 .vitem &$spf_header_comment$& &&&
13667 &$spf_received$& &&&
13669 &$spf_result_guessed$& &&&
13670 &$spf_smtp_comment$&
13671 These variables are only available if Exim is built with SPF support.
13672 For details see section &<<SECSPF>>&.
13674 .vitem &$spool_directory$&
13675 .vindex "&$spool_directory$&"
13676 The name of Exim's spool directory.
13678 .vitem &$spool_inodes$&
13679 .vindex "&$spool_inodes$&"
13680 The number of free inodes in the disk partition where Exim's spool files are
13681 being written. The value is recalculated whenever the variable is referenced.
13682 If the relevant file system does not have the concept of inodes, the value of
13683 is -1. See also the &%check_spool_inodes%& option.
13685 .vitem &$spool_space$&
13686 .vindex "&$spool_space$&"
13687 The amount of free space (as a number of kilobytes) in the disk partition where
13688 Exim's spool files are being written. The value is recalculated whenever the
13689 variable is referenced. If the operating system does not have the ability to
13690 find the amount of free space (only true for experimental systems), the space
13691 value is -1. For example, to check in an ACL that there is at least 50
13692 megabytes free on the spool, you could write:
13694 condition = ${if > {$spool_space}{50000}}
13696 See also the &%check_spool_space%& option.
13699 .vitem &$thisaddress$&
13700 .vindex "&$thisaddress$&"
13701 This variable is set only during the processing of the &%foranyaddress%&
13702 command in a filter file. Its use is explained in the description of that
13703 command, which can be found in the separate document entitled &'Exim's
13704 interfaces to mail filtering'&.
13706 .vitem &$tls_in_bits$&
13707 .vindex "&$tls_in_bits$&"
13708 Contains an approximation of the TLS cipher's bit-strength
13709 on the inbound connection; the meaning of
13710 this depends upon the TLS implementation used.
13711 If TLS has not been negotiated, the value will be 0.
13712 The value of this is automatically fed into the Cyrus SASL authenticator
13713 when acting as a server, to specify the "external SSF" (a SASL term).
13715 The deprecated &$tls_bits$& variable refers to the inbound side
13716 except when used in the context of an outbound SMTP delivery, when it refers to
13719 .vitem &$tls_out_bits$&
13720 .vindex "&$tls_out_bits$&"
13721 Contains an approximation of the TLS cipher's bit-strength
13722 on an outbound SMTP connection; the meaning of
13723 this depends upon the TLS implementation used.
13724 If TLS has not been negotiated, the value will be 0.
13726 .vitem &$tls_in_ourcert$&
13727 .vindex "&$tls_in_ourcert$&"
13728 .cindex certificate variables
13729 This variable refers to the certificate presented to the peer of an
13730 inbound connection when the message was received.
13731 It is only useful as the argument of a
13732 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13733 or a &%def%& condition.
13735 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
13736 when a list of more than one
13737 file is used for &%tls_certificate%&, this variable is not reliable.
13738 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
13740 .vitem &$tls_in_peercert$&
13741 .vindex "&$tls_in_peercert$&"
13742 This variable refers to the certificate presented by the peer of an
13743 inbound connection when the message was received.
13744 It is only useful as the argument of a
13745 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13746 or a &%def%& condition.
13747 If certificate verification fails it may refer to a failing chain element
13748 which is not the leaf.
13750 .vitem &$tls_out_ourcert$&
13751 .vindex "&$tls_out_ourcert$&"
13752 This variable refers to the certificate presented to the peer of an
13753 outbound connection. It is only useful as the argument of a
13754 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13755 or a &%def%& condition.
13757 .vitem &$tls_out_peercert$&
13758 .vindex "&$tls_out_peercert$&"
13759 This variable refers to the certificate presented by the peer of an
13760 outbound connection. It is only useful as the argument of a
13761 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13762 or a &%def%& condition.
13763 If certificate verification fails it may refer to a failing chain element
13764 which is not the leaf.
13766 .vitem &$tls_in_certificate_verified$&
13767 .vindex "&$tls_in_certificate_verified$&"
13768 This variable is set to &"1"& if a TLS certificate was verified when the
13769 message was received, and &"0"& otherwise.
13771 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
13772 except when used in the context of an outbound SMTP delivery, when it refers to
13775 .vitem &$tls_out_certificate_verified$&
13776 .vindex "&$tls_out_certificate_verified$&"
13777 This variable is set to &"1"& if a TLS certificate was verified when an
13778 outbound SMTP connection was made,
13779 and &"0"& otherwise.
13781 .vitem &$tls_in_cipher$&
13782 .vindex "&$tls_in_cipher$&"
13783 .vindex "&$tls_cipher$&"
13784 When a message is received from a remote host over an encrypted SMTP
13785 connection, this variable is set to the cipher suite that was negotiated, for
13786 example DES-CBC3-SHA. In other circumstances, in particular, for message
13787 received over unencrypted connections, the variable is empty. Testing
13788 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
13789 non-encrypted connections during ACL processing.
13791 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
13792 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
13793 becomes the same as &$tls_out_cipher$&.
13795 .vitem &$tls_in_cipher_std$&
13796 .vindex "&$tls_in_cipher_std$&"
13797 As above, but returning the RFC standard name for the cipher suite.
13799 .vitem &$tls_out_cipher$&
13800 .vindex "&$tls_out_cipher$&"
13802 cleared before any outgoing SMTP connection is made,
13803 and then set to the outgoing cipher suite if one is negotiated. See chapter
13804 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
13805 details of the &(smtp)& transport.
13807 .vitem &$tls_out_cipher_std$&
13808 .vindex "&$tls_out_cipher_std$&"
13809 As above, but returning the RFC standard name for the cipher suite.
13811 .vitem &$tls_out_dane$&
13812 .vindex &$tls_out_dane$&
13813 DANE active status. See section &<<SECDANE>>&.
13815 .vitem &$tls_in_ocsp$&
13816 .vindex "&$tls_in_ocsp$&"
13817 When a message is received from a remote client connection
13818 the result of any OCSP request from the client is encoded in this variable:
13820 0 OCSP proof was not requested (default value)
13821 1 No response to request
13822 2 Response not verified
13823 3 Verification failed
13824 4 Verification succeeded
13827 .vitem &$tls_out_ocsp$&
13828 .vindex "&$tls_out_ocsp$&"
13829 When a message is sent to a remote host connection
13830 the result of any OCSP request made is encoded in this variable.
13831 See &$tls_in_ocsp$& for values.
13833 .vitem &$tls_in_peerdn$&
13834 .vindex "&$tls_in_peerdn$&"
13835 .vindex "&$tls_peerdn$&"
13836 .cindex certificate "extracting fields"
13837 When a message is received from a remote host over an encrypted SMTP
13838 connection, and Exim is configured to request a certificate from the client,
13839 the value of the Distinguished Name of the certificate is made available in the
13840 &$tls_in_peerdn$& during subsequent processing.
13841 If certificate verification fails it may refer to a failing chain element
13842 which is not the leaf.
13844 The deprecated &$tls_peerdn$& variable refers to the inbound side
13845 except when used in the context of an outbound SMTP delivery, when it refers to
13848 .vitem &$tls_out_peerdn$&
13849 .vindex "&$tls_out_peerdn$&"
13850 When a message is being delivered to a remote host over an encrypted SMTP
13851 connection, and Exim is configured to request a certificate from the server,
13852 the value of the Distinguished Name of the certificate is made available in the
13853 &$tls_out_peerdn$& during subsequent processing.
13854 If certificate verification fails it may refer to a failing chain element
13855 which is not the leaf.
13859 .vitem &$tls_in_resumption$& &&&
13860 &$tls_out_resumption$&
13861 .vindex &$tls_in_resumption$&
13862 .vindex &$tls_out_resumption$&
13863 .cindex TLS resumption
13864 Observability for TLS session resumption. See &<<SECTresumption>>& for details.
13868 .vitem &$tls_in_sni$&
13869 .vindex "&$tls_in_sni$&"
13870 .vindex "&$tls_sni$&"
13871 .cindex "TLS" "Server Name Indication"
13873 .cindex SNI "observability on server"
13874 When a TLS session is being established, if the client sends the Server
13875 Name Indication extension, the value will be placed in this variable.
13876 If the variable appears in &%tls_certificate%& then this option and
13877 some others, described in &<<SECTtlssni>>&,
13878 will be re-expanded early in the TLS session, to permit
13879 a different certificate to be presented (and optionally a different key to be
13880 used) to the client, based upon the value of the SNI extension.
13882 The deprecated &$tls_sni$& variable refers to the inbound side
13883 except when used in the context of an outbound SMTP delivery, when it refers to
13886 .vitem &$tls_out_sni$&
13887 .vindex "&$tls_out_sni$&"
13888 .cindex "TLS" "Server Name Indication"
13890 .cindex SNI "observability in client"
13892 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
13895 .vitem &$tls_out_tlsa_usage$&
13896 .vindex &$tls_out_tlsa_usage$&
13897 Bitfield of TLSA record types found. See section &<<SECDANE>>&.
13899 .vitem &$tls_in_ver$&
13900 .vindex "&$tls_in_ver$&"
13901 When a message is received from a remote host over an encrypted SMTP connection
13902 this variable is set to the protocol version, eg &'TLS1.2'&.
13904 .vitem &$tls_out_ver$&
13905 .vindex "&$tls_out_ver$&"
13906 When a message is being delivered to a remote host over an encrypted SMTP connection
13907 this variable is set to the protocol version.
13910 .vitem &$tod_bsdinbox$&
13911 .vindex "&$tod_bsdinbox$&"
13912 The time of day and the date, in the format required for BSD-style mailbox
13913 files, for example: Thu Oct 17 17:14:09 1995.
13915 .vitem &$tod_epoch$&
13916 .vindex "&$tod_epoch$&"
13917 The time and date as a number of seconds since the start of the Unix epoch.
13919 .vitem &$tod_epoch_l$&
13920 .vindex "&$tod_epoch_l$&"
13921 The time and date as a number of microseconds since the start of the Unix epoch.
13923 .vitem &$tod_full$&
13924 .vindex "&$tod_full$&"
13925 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
13926 +0100. The timezone is always given as a numerical offset from UTC, with
13927 positive values used for timezones that are ahead (east) of UTC, and negative
13928 values for those that are behind (west).
13931 .vindex "&$tod_log$&"
13932 The time and date in the format used for writing Exim's log files, for example:
13933 1995-10-12 15:32:29, but without a timezone.
13935 .vitem &$tod_logfile$&
13936 .vindex "&$tod_logfile$&"
13937 This variable contains the date in the format yyyymmdd. This is the format that
13938 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
13941 .vitem &$tod_zone$&
13942 .vindex "&$tod_zone$&"
13943 This variable contains the numerical value of the local timezone, for example:
13946 .vitem &$tod_zulu$&
13947 .vindex "&$tod_zulu$&"
13948 This variable contains the UTC date and time in &"Zulu"& format, as specified
13949 by ISO 8601, for example: 20030221154023Z.
13951 .vitem &$transport_name$&
13952 .cindex "transport" "name"
13953 .cindex "name" "of transport"
13954 .vindex "&$transport_name$&"
13955 During the running of a transport, this variable contains its name.
13958 .vindex "&$value$&"
13959 This variable contains the result of an expansion lookup, extraction operation,
13960 or external command, as described above. It is also used during a
13961 &*reduce*& expansion.
13963 .vitem &$verify_mode$&
13964 .vindex "&$verify_mode$&"
13965 While a router or transport is being run in verify mode or for cutthrough delivery,
13966 contains "S" for sender-verification or "R" for recipient-verification.
13969 .vitem &$version_number$&
13970 .vindex "&$version_number$&"
13971 The version number of Exim. Same as &$exim_version$&, may be overridden
13972 by the &%exim_version%& main config option.
13974 .vitem &$warn_message_delay$&
13975 .vindex "&$warn_message_delay$&"
13976 This variable is set only during the creation of a message warning about a
13977 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13979 .vitem &$warn_message_recipients$&
13980 .vindex "&$warn_message_recipients$&"
13981 This variable is set only during the creation of a message warning about a
13982 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13988 . ////////////////////////////////////////////////////////////////////////////
13989 . ////////////////////////////////////////////////////////////////////////////
13991 .chapter "Embedded Perl" "CHAPperl"
13992 .scindex IIDperl "Perl" "calling from Exim"
13993 Exim can be built to include an embedded Perl interpreter. When this is done,
13994 Perl subroutines can be called as part of the string expansion process. To make
13995 use of the Perl support, you need version 5.004 or later of Perl installed on
13996 your system. To include the embedded interpreter in the Exim binary, include
14001 in your &_Local/Makefile_& and then build Exim in the normal way.
14004 .section "Setting up so Perl can be used" "SECID85"
14005 .oindex "&%perl_startup%&"
14006 Access to Perl subroutines is via a global configuration option called
14007 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
14008 no &%perl_startup%& option in the Exim configuration file then no Perl
14009 interpreter is started and there is almost no overhead for Exim (since none of
14010 the Perl library will be paged in unless used). If there is a &%perl_startup%&
14011 option then the associated value is taken to be Perl code which is executed in
14012 a newly created Perl interpreter.
14014 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
14015 need backslashes before any characters to escape special meanings. The option
14016 should usually be something like
14018 perl_startup = do '/etc/exim.pl'
14020 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
14021 use from Exim. Exim can be configured either to start up a Perl interpreter as
14022 soon as it is entered, or to wait until the first time it is needed. Starting
14023 the interpreter at the beginning ensures that it is done while Exim still has
14024 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
14025 fact used in a particular run. Also, note that this does not mean that Exim is
14026 necessarily running as root when Perl is called at a later time. By default,
14027 the interpreter is started only when it is needed, but this can be changed in
14031 .oindex "&%perl_at_start%&"
14032 Setting &%perl_at_start%& (a boolean option) in the configuration requests
14033 a startup when Exim is entered.
14035 The command line option &%-ps%& also requests a startup when Exim is entered,
14036 overriding the setting of &%perl_at_start%&.
14039 There is also a command line option &%-pd%& (for delay) which suppresses the
14040 initial startup, even if &%perl_at_start%& is set.
14043 .oindex "&%perl_taintmode%&"
14044 .cindex "Perl" "taintmode"
14045 To provide more security executing Perl code via the embedded Perl
14046 interpreter, the &%perl_taintmode%& option can be set. This enables the
14047 taint mode of the Perl interpreter. You are encouraged to set this
14048 option to a true value. To avoid breaking existing installations, it
14052 .section "Calling Perl subroutines" "SECID86"
14053 When the configuration file includes a &%perl_startup%& option you can make use
14054 of the string expansion item to call the Perl subroutines that are defined
14055 by the &%perl_startup%& code. The operator is used in any of the following
14059 ${perl{foo}{argument}}
14060 ${perl{foo}{argument1}{argument2} ... }
14062 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
14063 arguments may be passed. Passing more than this results in an expansion failure
14064 with an error message of the form
14066 Too many arguments passed to Perl subroutine "foo" (max is 8)
14068 The return value of the Perl subroutine is evaluated in a scalar context before
14069 it is passed back to Exim to be inserted into the expanded string. If the
14070 return value is &'undef'&, the expansion is forced to fail in the same way as
14071 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
14072 by obeying Perl's &%die%& function, the expansion fails with the error message
14073 that was passed to &%die%&.
14076 .section "Calling Exim functions from Perl" "SECID87"
14077 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
14078 is available to call back into Exim's string expansion function. For example,
14081 my $lp = Exim::expand_string('$local_part');
14083 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
14084 Note those are single quotes and not double quotes to protect against
14085 &$local_part$& being interpolated as a Perl variable.
14087 If the string expansion is forced to fail by a &"fail"& item, the result of
14088 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
14089 expansion string, the Perl call from the original expansion string fails with
14090 an appropriate error message, in the same way as if &%die%& were used.
14092 .cindex "debugging" "from embedded Perl"
14093 .cindex "log" "writing from embedded Perl"
14094 Two other Exim functions are available for use from within Perl code.
14095 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
14096 debugging is enabled. If you want a newline at the end, you must supply it.
14097 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
14098 timestamp. In this case, you should not supply a terminating newline.
14101 .section "Use of standard output and error by Perl" "SECID88"
14102 .cindex "Perl" "standard output and error"
14103 You should not write to the standard error or output streams from within your
14104 Perl code, as it is not defined how these are set up. In versions of Exim
14105 before 4.50, it is possible for the standard output or error to refer to the
14106 SMTP connection during message reception via the daemon. Writing to this stream
14107 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
14108 error streams are connected to &_/dev/null_& in the daemon. The chaos is
14109 avoided, but the output is lost.
14111 .cindex "Perl" "use of &%warn%&"
14112 The Perl &%warn%& statement writes to the standard error stream by default.
14113 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
14114 you have no control. When Exim starts up the Perl interpreter, it arranges for
14115 output from the &%warn%& statement to be written to the Exim main log. You can
14116 change this by including appropriate Perl magic somewhere in your Perl code.
14117 For example, to discard &%warn%& output completely, you need this:
14119 $SIG{__WARN__} = sub { };
14121 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
14122 example, the code for the subroutine is empty, so it does nothing, but you can
14123 include any Perl code that you like. The text of the &%warn%& message is passed
14124 as the first subroutine argument.
14128 . ////////////////////////////////////////////////////////////////////////////
14129 . ////////////////////////////////////////////////////////////////////////////
14131 .chapter "Starting the daemon and the use of network interfaces" &&&
14132 "CHAPinterfaces" &&&
14133 "Starting the daemon"
14134 .cindex "daemon" "starting"
14135 .cindex "interface" "listening"
14136 .cindex "network interface"
14137 .cindex "interface" "network"
14138 .cindex "IP address" "for listening"
14139 .cindex "daemon" "listening IP addresses"
14140 .cindex "TCP/IP" "setting listening interfaces"
14141 .cindex "TCP/IP" "setting listening ports"
14142 A host that is connected to a TCP/IP network may have one or more physical
14143 hardware network interfaces. Each of these interfaces may be configured as one
14144 or more &"logical"& interfaces, which are the entities that a program actually
14145 works with. Each of these logical interfaces is associated with an IP address.
14146 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
14147 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
14148 knowledge about the host's interfaces for use in three different circumstances:
14151 When a listening daemon is started, Exim needs to know which interfaces
14152 and ports to listen on.
14154 When Exim is routing an address, it needs to know which IP addresses
14155 are associated with local interfaces. This is required for the correct
14156 processing of MX lists by removing the local host and others with the
14157 same or higher priority values. Also, Exim needs to detect cases
14158 when an address is routed to an IP address that in fact belongs to the
14159 local host. Unless the &%self%& router option or the &%allow_localhost%&
14160 option of the smtp transport is set (as appropriate), this is treated
14161 as an error situation.
14163 When Exim connects to a remote host, it may need to know which interface to use
14164 for the outgoing connection.
14168 Exim's default behaviour is likely to be appropriate in the vast majority
14169 of cases. If your host has only one interface, and you want all its IP
14170 addresses to be treated in the same way, and you are using only the
14171 standard SMTP port, you should not need to take any special action. The
14172 rest of this chapter does not apply to you.
14174 In a more complicated situation you may want to listen only on certain
14175 interfaces, or on different ports, and for this reason there are a number of
14176 options that can be used to influence Exim's behaviour. The rest of this
14177 chapter describes how they operate.
14179 When a message is received over TCP/IP, the interface and port that were
14180 actually used are set in &$received_ip_address$& and &$received_port$&.
14184 .section "Starting a listening daemon" "SECID89"
14185 When a listening daemon is started (by means of the &%-bd%& command line
14186 option), the interfaces and ports on which it listens are controlled by the
14190 &%daemon_smtp_ports%& contains a list of default ports
14192 (For backward compatibility, this option can also be specified in the singular.)
14194 &%local_interfaces%& contains list of interface IP addresses on which to
14195 listen. Each item may optionally also specify a port.
14198 The default list separator in both cases is a colon, but this can be changed as
14199 described in section &<<SECTlistsepchange>>&. When IPv6 addresses are involved,
14200 it is usually best to change the separator to avoid having to double all the
14201 colons. For example:
14203 local_interfaces = <; 127.0.0.1 ; \
14206 3ffe:ffff:836f::fe86:a061
14208 There are two different formats for specifying a port along with an IP address
14209 in &%local_interfaces%&:
14212 The port is added onto the address with a dot separator. For example, to listen
14213 on port 1234 on two different IP addresses:
14215 local_interfaces = <; 192.168.23.65.1234 ; \
14216 3ffe:ffff:836f::fe86:a061.1234
14219 The IP address is enclosed in square brackets, and the port is added
14220 with a colon separator, for example:
14222 local_interfaces = <; [192.168.23.65]:1234 ; \
14223 [3ffe:ffff:836f::fe86:a061]:1234
14227 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
14228 default setting contains just one port:
14230 daemon_smtp_ports = smtp
14232 If more than one port is listed, each interface that does not have its own port
14233 specified listens on all of them. Ports that are listed in
14234 &%daemon_smtp_ports%& can be identified either by name (defined in
14235 &_/etc/services_&) or by number. However, when ports are given with individual
14236 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
14240 .section "Special IP listening addresses" "SECID90"
14241 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
14242 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
14243 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
14244 instead of setting up separate listening sockets for each interface. The
14245 default value of &%local_interfaces%& is
14247 local_interfaces = 0.0.0.0
14249 when Exim is built without IPv6 support; otherwise it is:
14251 local_interfaces = <; ::0 ; 0.0.0.0
14253 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
14257 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
14258 The &%-oX%& command line option can be used to override the values of
14259 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
14260 instance. Another way of doing this would be to use macros and the &%-D%&
14261 option. However, &%-oX%& can be used by any admin user, whereas modification of
14262 the runtime configuration by &%-D%& is allowed only when the caller is root or
14265 The value of &%-oX%& is a list of items. The default colon separator can be
14266 changed in the usual way (&<<SECTlistsepchange>>&) if required.
14267 If there are any items that do not
14268 contain dots or colons (that is, are not IP addresses), the value of
14269 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
14270 items that do contain dots or colons, the value of &%local_interfaces%& is
14271 replaced by those items. Thus, for example,
14275 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
14278 -oX 192.168.34.5.1125
14280 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
14281 (However, since &%local_interfaces%& now contains no items without ports, the
14282 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
14286 .section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
14287 .cindex "submissions protocol"
14288 .cindex "ssmtp protocol"
14289 .cindex "smtps protocol"
14290 .cindex "SMTP" "ssmtp protocol"
14291 .cindex "SMTP" "smtps protocol"
14292 Exim supports the use of TLS-on-connect, used by mail clients in the
14293 &"submissions"& protocol, historically also known as SMTPS or SSMTP.
14294 For some years, IETF Standards Track documents only blessed the
14295 STARTTLS-based Submission service (port 587) while common practice was to support
14296 the same feature set on port 465, but using TLS-on-connect.
14297 If your installation needs to provide service to mail clients
14298 (Mail User Agents, MUAs) then you should provide service on both the 587 and
14301 If the &%tls_on_connect_ports%& option is set to a list of port numbers or
14302 service names, connections to those ports must first establish TLS, before
14303 proceeding to the application layer use of the SMTP protocol.
14305 The common use of this option is expected to be
14307 tls_on_connect_ports = 465
14310 There is also a command line option &%-tls-on-connect%&, which forces all ports
14311 to behave in this way when a daemon is started.
14313 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
14314 daemon to listen on those ports. You must still specify them in
14315 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
14316 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
14317 connections via the daemon.)
14322 .section "IPv6 address scopes" "SECID92"
14323 .cindex "IPv6" "address scopes"
14324 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
14325 can, in principle, have the same link-local IPv6 address on different
14326 interfaces. Thus, additional information is needed, over and above the IP
14327 address, to distinguish individual interfaces. A convention of using a
14328 percent sign followed by something (often the interface name) has been
14329 adopted in some cases, leading to addresses like this:
14331 fe80::202:b3ff:fe03:45c1%eth0
14333 To accommodate this usage, a percent sign followed by an arbitrary string is
14334 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
14335 to convert a textual IPv6 address for actual use. This function recognizes the
14336 percent convention in operating systems that support it, and it processes the
14337 address appropriately. Unfortunately, some older libraries have problems with
14338 &[getaddrinfo()]&. If
14340 IPV6_USE_INET_PTON=yes
14342 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
14343 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
14344 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
14345 function.) Of course, this means that the additional functionality of
14346 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
14348 .section "Disabling IPv6" "SECID93"
14349 .cindex "IPv6" "disabling"
14350 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
14351 run on a host whose kernel does not support IPv6. The binary will fall back to
14352 using IPv4, but it may waste resources looking up AAAA records, and trying to
14353 connect to IPv6 addresses, causing delays to mail delivery. If you set the
14354 .oindex "&%disable_ipv6%&"
14355 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
14356 activities take place. AAAA records are never looked up, and any IPv6 addresses
14357 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
14358 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14359 to handle IPv6 literal addresses.
14361 On the other hand, when IPv6 is in use, there may be times when you want to
14362 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
14363 option to globally suppress the lookup of AAAA records for specified domains,
14364 and you can use the &%ignore_target_hosts%& generic router option to ignore
14365 IPv6 addresses in an individual router.
14369 .section "Examples of starting a listening daemon" "SECID94"
14370 The default case in an IPv6 environment is
14372 daemon_smtp_ports = smtp
14373 local_interfaces = <; ::0 ; 0.0.0.0
14375 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
14376 Either one or two sockets may be used, depending on the characteristics of
14377 the TCP/IP stack. (This is complicated and messy; for more information,
14378 read the comments in the &_daemon.c_& source file.)
14380 To specify listening on ports 25 and 26 on all interfaces:
14382 daemon_smtp_ports = 25 : 26
14384 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
14386 local_interfaces = <; ::0.25 ; ::0.26 \
14387 0.0.0.0.25 ; 0.0.0.0.26
14389 To listen on the default port on all IPv4 interfaces, and on port 26 on the
14390 IPv4 loopback address only:
14392 local_interfaces = 0.0.0.0 : 127.0.0.1.26
14394 To specify listening on the default port on specific interfaces only:
14396 local_interfaces = 10.0.0.67 : 192.168.34.67
14398 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
14402 .section "Recognizing the local host" "SECTreclocipadd"
14403 The &%local_interfaces%& option is also used when Exim needs to determine
14404 whether or not an IP address refers to the local host. That is, the IP
14405 addresses of all the interfaces on which a daemon is listening are always
14408 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
14409 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
14410 available interfaces from the operating system, and extracts the relevant
14411 (that is, IPv4 or IPv6) addresses to use for checking.
14413 Some systems set up large numbers of virtual interfaces in order to provide
14414 many virtual web servers. In this situation, you may want to listen for
14415 email on only a few of the available interfaces, but nevertheless treat all
14416 interfaces as local when routing. You can do this by setting
14417 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
14418 &"all"& wildcard values. These addresses are recognized as local, but are not
14419 used for listening. Consider this example:
14421 local_interfaces = <; 127.0.0.1 ; ::1 ; \
14423 3ffe:2101:12:1:a00:20ff:fe86:a061
14425 extra_local_interfaces = <; ::0 ; 0.0.0.0
14427 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
14428 address, but all available interface addresses are treated as local when
14431 In some environments the local host name may be in an MX list, but with an IP
14432 address that is not assigned to any local interface. In other cases it may be
14433 desirable to treat other host names as if they referred to the local host. Both
14434 these cases can be handled by setting the &%hosts_treat_as_local%& option.
14435 This contains host names rather than IP addresses. When a host is referenced
14436 during routing, either via an MX record or directly, it is treated as the local
14437 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
14438 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
14442 .section "Delivering to a remote host" "SECID95"
14443 Delivery to a remote host is handled by the smtp transport. By default, it
14444 allows the system's TCP/IP functions to choose which interface to use (if
14445 there is more than one) when connecting to a remote host. However, the
14446 &%interface%& option can be set to specify which interface is used. See the
14447 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
14453 . ////////////////////////////////////////////////////////////////////////////
14454 . ////////////////////////////////////////////////////////////////////////////
14456 .chapter "Main configuration" "CHAPmainconfig"
14457 .scindex IIDconfima "configuration file" "main section"
14458 .scindex IIDmaiconf "main configuration"
14459 The first part of the runtime configuration file contains three types of item:
14462 Macro definitions: These lines start with an upper case letter. See section
14463 &<<SECTmacrodefs>>& for details of macro processing.
14465 Named list definitions: These lines start with one of the words &"domainlist"&,
14466 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
14467 section &<<SECTnamedlists>>&.
14469 Main configuration settings: Each setting occupies one line of the file
14470 (with possible continuations). If any setting is preceded by the word
14471 &"hide"&, the &%-bP%& command line option displays its value to admin users
14472 only. See section &<<SECTcos>>& for a description of the syntax of these option
14476 This chapter specifies all the main configuration options, along with their
14477 types and default values. For ease of finding a particular option, they appear
14478 in alphabetical order in section &<<SECTalomo>>& below. However, because there
14479 are now so many options, they are first listed briefly in functional groups, as
14480 an aid to finding the name of the option you are looking for. Some options are
14481 listed in more than one group.
14483 .section "Miscellaneous" "SECID96"
14485 .row &%bi_command%& "to run for &%-bi%& command line option"
14486 .row &%debug_store%& "do extra internal checks"
14487 .row &%disable_ipv6%& "do no IPv6 processing"
14488 .row &%keep_malformed%& "for broken files &-- should not happen"
14489 .row &%localhost_number%& "for unique message ids in clusters"
14490 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
14491 .row &%message_body_visible%& "how much to show in &$message_body$&"
14492 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
14493 .row &%print_topbitchars%& "top-bit characters are printing"
14494 .row &%spool_wireformat%& "use wire-format spool data files when possible"
14495 .row &%timezone%& "force time zone"
14499 .section "Exim parameters" "SECID97"
14501 .row &%exim_group%& "override compiled-in value"
14502 .row &%exim_path%& "override compiled-in value"
14503 .row &%exim_user%& "override compiled-in value"
14504 .row &%primary_hostname%& "default from &[uname()]&"
14505 .row &%split_spool_directory%& "use multiple directories"
14506 .row &%spool_directory%& "override compiled-in value"
14511 .section "Privilege controls" "SECID98"
14513 .row &%admin_groups%& "groups that are Exim admin users"
14514 .row &%commandline_checks_require_admin%& "require admin for various checks"
14515 .row &%deliver_drop_privilege%& "drop root for delivery processes"
14516 .row &%local_from_check%& "insert &'Sender:'& if necessary"
14517 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
14518 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
14519 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
14520 .row &%never_users%& "do not run deliveries as these"
14521 .row &%prod_requires_admin%& "forced delivery requires admin user"
14522 .row &%queue_list_requires_admin%& "queue listing requires admin user"
14523 .row &%trusted_groups%& "groups that are trusted"
14524 .row &%trusted_users%& "users that are trusted"
14529 .section "Logging" "SECID99"
14531 .row &%event_action%& "custom logging"
14532 .row &%hosts_connection_nolog%& "exemption from connect logging"
14533 .row &%log_file_path%& "override compiled-in value"
14534 .row &%log_selector%& "set/unset optional logging"
14535 .row &%log_timezone%& "add timezone to log lines"
14536 .row &%message_logs%& "create per-message logs"
14537 .row &%preserve_message_logs%& "after message completion"
14538 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
14539 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
14540 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
14541 .row &%syslog_facility%& "set syslog &""facility""& field"
14542 .row &%syslog_pid%& "pid in syslog lines"
14543 .row &%syslog_processname%& "set syslog &""ident""& field"
14544 .row &%syslog_timestamp%& "timestamp syslog lines"
14545 .row &%write_rejectlog%& "control use of message log"
14550 .section "Frozen messages" "SECID100"
14552 .row &%auto_thaw%& "sets time for retrying frozen messages"
14553 .row &%freeze_tell%& "send message when freezing"
14554 .row &%move_frozen_messages%& "to another directory"
14555 .row &%timeout_frozen_after%& "keep frozen messages only so long"
14560 .section "Data lookups" "SECID101"
14562 .row &%ibase_servers%& "InterBase servers"
14563 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
14564 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
14565 .row &%ldap_cert_file%& "client cert file for LDAP"
14566 .row &%ldap_cert_key%& "client key file for LDAP"
14567 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
14568 .row &%ldap_default_servers%& "used if no server in query"
14569 .row &%ldap_require_cert%& "action to take without LDAP server cert"
14570 .row &%ldap_start_tls%& "require TLS within LDAP"
14571 .row &%ldap_version%& "set protocol version"
14572 .row &%lookup_open_max%& "lookup files held open"
14573 .row &%mysql_servers%& "default MySQL servers"
14574 .row &%oracle_servers%& "Oracle servers"
14575 .row &%pgsql_servers%& "default PostgreSQL servers"
14576 .row &%sqlite_lock_timeout%& "as it says"
14581 .section "Message ids" "SECID102"
14583 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
14584 .row &%message_id_header_text%& "ditto"
14589 .section "Embedded Perl Startup" "SECID103"
14591 .row &%perl_at_start%& "always start the interpreter"
14592 .row &%perl_startup%& "code to obey when starting Perl"
14593 .row &%perl_taintmode%& "enable taint mode in Perl"
14598 .section "Daemon" "SECID104"
14600 .row &%daemon_smtp_ports%& "default ports"
14601 .row &%daemon_startup_retries%& "number of times to retry"
14602 .row &%daemon_startup_sleep%& "time to sleep between tries"
14603 .row &%extra_local_interfaces%& "not necessarily listened on"
14604 .row &%local_interfaces%& "on which to listen, with optional ports"
14605 .row &%notifier_socket%& "override compiled-in value"
14606 .row &%pid_file_path%& "override compiled-in value"
14607 .row &%queue_run_max%& "maximum simultaneous queue runners"
14612 .section "Resource control" "SECID105"
14614 .row &%check_log_inodes%& "before accepting a message"
14615 .row &%check_log_space%& "before accepting a message"
14616 .row &%check_spool_inodes%& "before accepting a message"
14617 .row &%check_spool_space%& "before accepting a message"
14618 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
14619 .row &%queue_only_load%& "queue incoming if load high"
14620 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14621 .row &%queue_run_max%& "maximum simultaneous queue runners"
14622 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14623 .row &%smtp_accept_max%& "simultaneous incoming connections"
14624 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14625 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14626 .row &%smtp_accept_max_per_connection%& "messages per connection"
14627 .row &%smtp_accept_max_per_host%& "connections from one host"
14628 .row &%smtp_accept_queue%& "queue mail if more connections"
14629 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14631 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14632 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14633 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14634 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
14635 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14640 .section "Policy controls" "SECID106"
14642 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
14643 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
14644 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
14645 .row &%acl_smtp_auth%& "ACL for AUTH"
14646 .row &%acl_smtp_connect%& "ACL for connection"
14647 .row &%acl_smtp_data%& "ACL for DATA"
14648 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
14649 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
14650 .row &%acl_smtp_etrn%& "ACL for ETRN"
14651 .row &%acl_smtp_expn%& "ACL for EXPN"
14652 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
14653 .row &%acl_smtp_mail%& "ACL for MAIL"
14654 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
14655 .row &%acl_smtp_mime%& "ACL for MIME parts"
14656 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
14657 .row &%acl_smtp_predata%& "ACL for start of data"
14658 .row &%acl_smtp_quit%& "ACL for QUIT"
14659 .row &%acl_smtp_rcpt%& "ACL for RCPT"
14660 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
14661 .row &%acl_smtp_vrfy%& "ACL for VRFY"
14662 .row &%av_scanner%& "specify virus scanner"
14663 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14665 .row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
14666 .row &%dns_csa_search_limit%& "control CSA parent search depth"
14667 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
14668 .row &%header_maxsize%& "total size of message header"
14669 .row &%header_line_maxsize%& "individual header line limit"
14670 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
14671 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
14672 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
14673 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
14674 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
14675 .row &%host_lookup%& "host name looked up for these hosts"
14676 .row &%host_lookup_order%& "order of DNS and local name lookups"
14677 .row &%hosts_proxy%& "use proxy protocol for these hosts"
14678 .row &%host_reject_connection%& "reject connection from these hosts"
14679 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
14680 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
14681 .row &%message_size_limit%& "for all messages"
14682 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14683 .row &%spamd_address%& "set interface to SpamAssassin"
14684 .row &%strict_acl_vars%& "object to unset ACL variables"
14685 .row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&"
14690 .section "Callout cache" "SECID107"
14692 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
14694 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
14696 .row &%callout_negative_expire%& "timeout for negative address cache item"
14697 .row &%callout_positive_expire%& "timeout for positive address cache item"
14698 .row &%callout_random_local_part%& "string to use for &""random""& testing"
14703 .section "TLS" "SECID108"
14705 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
14706 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
14707 .row &%openssl_options%& "adjust OpenSSL compatibility options"
14708 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14709 .row &%tls_certificate%& "location of server certificate"
14710 .row &%tls_crl%& "certificate revocation list"
14711 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
14712 .row &%tls_dhparam%& "DH parameters for server"
14713 .row &%tls_eccurve%& "EC curve selection for server"
14714 .row &%tls_ocsp_file%& "location of server certificate status proof"
14715 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
14716 .row &%tls_privatekey%& "location of server private key"
14717 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
14718 .row &%tls_require_ciphers%& "specify acceptable ciphers"
14719 .row &%tls_try_verify_hosts%& "try to verify client certificate"
14720 .row &%tls_verify_certificates%& "expected client certificates"
14721 .row &%tls_verify_hosts%& "insist on client certificate verify"
14726 .section "Local user handling" "SECID109"
14728 .row &%finduser_retries%& "useful in NIS environments"
14729 .row &%gecos_name%& "used when creating &'Sender:'&"
14730 .row &%gecos_pattern%& "ditto"
14731 .row &%max_username_length%& "for systems that truncate"
14732 .row &%unknown_login%& "used when no login name found"
14733 .row &%unknown_username%& "ditto"
14734 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
14735 .row &%uucp_from_sender%& "ditto"
14740 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
14742 .row &%header_maxsize%& "total size of message header"
14743 .row &%header_line_maxsize%& "individual header line limit"
14744 .row &%message_size_limit%& "applies to all messages"
14745 .row &%percent_hack_domains%& "recognize %-hack for these domains"
14746 .row &%received_header_text%& "expanded to make &'Received:'&"
14747 .row &%received_headers_max%& "for mail loop detection"
14748 .row &%recipients_max%& "limit per message"
14749 .row &%recipients_max_reject%& "permanently reject excess recipients"
14755 .section "Non-SMTP incoming messages" "SECID111"
14757 .row &%receive_timeout%& "for non-SMTP messages"
14764 .section "Incoming SMTP messages" "SECID112"
14765 See also the &'Policy controls'& section above.
14768 .row &%dkim_verify_hashes%& "DKIM hash methods accepted for signatures"
14769 .row &%dkim_verify_keytypes%& "DKIM key types accepted for signatures"
14770 .row &%dkim_verify_min_keysizes%& "DKIM key sizes accepted for signatures"
14771 .row &%dkim_verify_signers%& "DKIM domains for which DKIM ACL is run"
14772 .row &%dmarc_forensic_sender%& "DMARC sender for report messages"
14773 .row &%dmarc_history_file%& "DMARC results log"
14774 .row &%dmarc_tld_file%& "DMARC toplevel domains file"
14775 .row &%host_lookup%& "host name looked up for these hosts"
14776 .row &%host_lookup_order%& "order of DNS and local name lookups"
14777 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
14778 .row &%rfc1413_hosts%& "make ident calls to these hosts"
14779 .row &%rfc1413_query_timeout%& "zero disables ident calls"
14780 .row &%sender_unqualified_hosts%& "may send unqualified senders"
14781 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
14782 .row &%smtp_accept_max%& "simultaneous incoming connections"
14783 .row &%smtp_accept_max_nonmail%& "non-mail commands"
14784 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14785 .row &%smtp_accept_max_per_connection%& "messages per connection"
14786 .row &%smtp_accept_max_per_host%& "connections from one host"
14787 .row &%smtp_accept_queue%& "queue mail if more connections"
14788 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14790 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14791 .row &%smtp_active_hostname%& "host name to use in messages"
14792 .row &%smtp_banner%& "text for welcome banner"
14793 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14794 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14795 .row &%smtp_enforce_sync%& "of SMTP command/responses"
14796 .row &%smtp_etrn_command%& "what to run for ETRN"
14797 .row &%smtp_etrn_serialize%& "only one at once"
14798 .row &%smtp_load_reserve%& "only reserve hosts if this load"
14799 .row &%smtp_max_unknown_commands%& "before dropping connection"
14800 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
14801 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
14802 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
14803 .row &%smtp_receive_timeout%& "per command or data line"
14804 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14805 .row &%smtp_return_error_details%& "give detail on rejections"
14810 .section "SMTP extensions" "SECID113"
14812 .row &%accept_8bitmime%& "advertise 8BITMIME"
14813 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
14814 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
14815 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
14816 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
14817 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
14818 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
14819 .row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts"
14820 .row &%prdr_enable%& "advertise PRDR to all hosts"
14821 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
14822 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14827 .section "Processing messages" "SECID114"
14829 .row &%allow_domain_literals%& "recognize domain literal syntax"
14830 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
14831 .row &%allow_utf8_domains%& "in addresses"
14832 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14834 .row &%delivery_date_remove%& "from incoming messages"
14835 .row &%envelope_to_remove%& "from incoming messages"
14836 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
14837 .row &%headers_charset%& "default for translations"
14838 .row &%qualify_domain%& "default for senders"
14839 .row &%qualify_recipient%& "default for recipients"
14840 .row &%return_path_remove%& "from incoming messages"
14841 .row &%strip_excess_angle_brackets%& "in addresses"
14842 .row &%strip_trailing_dot%& "at end of addresses"
14843 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
14848 .section "System filter" "SECID115"
14850 .row &%system_filter%& "locate system filter"
14851 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
14853 .row &%system_filter_file_transport%& "transport for delivery to a file"
14854 .row &%system_filter_group%& "group for filter running"
14855 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
14856 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
14857 .row &%system_filter_user%& "user for filter running"
14862 .section "Routing and delivery" "SECID116"
14864 .row &%disable_ipv6%& "do no IPv6 processing"
14865 .row &%dns_again_means_nonexist%& "for broken domains"
14866 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
14867 .row &%dns_dnssec_ok%& "parameter for resolver"
14868 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
14869 .row &%dns_retrans%& "parameter for resolver"
14870 .row &%dns_retry%& "parameter for resolver"
14871 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
14872 .row &%dns_use_edns0%& "parameter for resolver"
14873 .row &%hold_domains%& "hold delivery for these domains"
14874 .row &%local_interfaces%& "for routing checks"
14875 .row &%queue_domains%& "no immediate delivery for these"
14876 .row &%queue_fast_ramp%& "parallel delivery with 2-phase queue run"
14877 .row &%queue_only%& "no immediate delivery at all"
14878 .row &%queue_only_file%& "no immediate delivery if file exists"
14879 .row &%queue_only_load%& "no immediate delivery if load is high"
14880 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14881 .row &%queue_only_override%& "allow command line to override"
14882 .row &%queue_run_in_order%& "order of arrival"
14883 .row &%queue_run_max%& "of simultaneous queue runners"
14884 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
14885 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14886 .row &%remote_sort_domains%& "order of remote deliveries"
14887 .row &%retry_data_expire%& "timeout for retry data"
14888 .row &%retry_interval_max%& "safety net for retry rules"
14893 .section "Bounce and warning messages" "SECID117"
14895 .row &%bounce_message_file%& "content of bounce"
14896 .row &%bounce_message_text%& "content of bounce"
14897 .row &%bounce_return_body%& "include body if returning message"
14898 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
14899 .row &%bounce_return_message%& "include original message in bounce"
14900 .row &%bounce_return_size_limit%& "limit on returned message"
14901 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
14902 .row &%dsn_from%& "set &'From:'& contents in bounces"
14903 .row &%errors_copy%& "copy bounce messages"
14904 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
14905 .row &%delay_warning%& "time schedule"
14906 .row &%delay_warning_condition%& "condition for warning messages"
14907 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
14908 .row &%smtp_return_error_details%& "give detail on rejections"
14909 .row &%warn_message_file%& "content of warning message"
14914 .section "Alphabetical list of main options" "SECTalomo"
14915 Those options that undergo string expansion before use are marked with
14918 .option accept_8bitmime main boolean true
14920 .cindex "8-bit characters"
14921 .cindex "log" "selectors"
14922 .cindex "log" "8BITMIME"
14923 .cindex "ESMTP extensions" 8BITMIME
14924 This option causes Exim to send 8BITMIME in its response to an SMTP
14925 EHLO command, and to accept the BODY= parameter on MAIL commands.
14926 However, though Exim is 8-bit clean, it is not a protocol converter, and it
14927 takes no steps to do anything special with messages received by this route.
14929 Historically Exim kept this option off by default, but the maintainers
14930 feel that in today's Internet, this causes more problems than it solves.
14931 It now defaults to true.
14932 A more detailed analysis of the issues is provided by Dan Bernstein:
14934 &url(https://cr.yp.to/smtp/8bitmime.html)
14937 To log received 8BITMIME status use
14939 log_selector = +8bitmime
14942 .option acl_not_smtp main string&!! unset
14943 .cindex "&ACL;" "for non-SMTP messages"
14944 .cindex "non-SMTP messages" "ACLs for"
14945 This option defines the ACL that is run when a non-SMTP message has been
14946 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
14949 .option acl_not_smtp_mime main string&!! unset
14950 This option defines the ACL that is run for individual MIME parts of non-SMTP
14951 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
14954 .option acl_not_smtp_start main string&!! unset
14955 .cindex "&ACL;" "at start of non-SMTP message"
14956 .cindex "non-SMTP messages" "ACLs for"
14957 This option defines the ACL that is run before Exim starts reading a
14958 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
14960 .option acl_smtp_auth main string&!! unset
14961 .cindex "&ACL;" "setting up for SMTP commands"
14962 .cindex "AUTH" "ACL for"
14963 This option defines the ACL that is run when an SMTP AUTH command is
14964 received. See chapter &<<CHAPACL>>& for further details.
14966 .option acl_smtp_connect main string&!! unset
14967 .cindex "&ACL;" "on SMTP connection"
14968 This option defines the ACL that is run when an SMTP connection is received.
14969 See chapter &<<CHAPACL>>& for further details.
14971 .option acl_smtp_data main string&!! unset
14972 .cindex "DATA" "ACL for"
14973 This option defines the ACL that is run after an SMTP DATA command has been
14974 processed and the message itself has been received, but before the final
14975 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
14977 .option acl_smtp_data_prdr main string&!! accept
14978 .cindex "PRDR" "ACL for"
14979 .cindex "DATA" "PRDR ACL for"
14980 .cindex "&ACL;" "PRDR-related"
14981 .cindex "&ACL;" "per-user data processing"
14982 This option defines the ACL that,
14983 if the PRDR feature has been negotiated,
14984 is run for each recipient after an SMTP DATA command has been
14985 processed and the message itself has been received, but before the
14986 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
14988 .option acl_smtp_dkim main string&!! unset
14989 .cindex DKIM "ACL for"
14990 This option defines the ACL that is run for each DKIM signature
14991 (by default, or as specified in the dkim_verify_signers option)
14992 of a received message.
14993 See section &<<SECDKIMVFY>>& for further details.
14995 .option acl_smtp_etrn main string&!! unset
14996 .cindex "ETRN" "ACL for"
14997 This option defines the ACL that is run when an SMTP ETRN command is
14998 received. See chapter &<<CHAPACL>>& for further details.
15000 .option acl_smtp_expn main string&!! unset
15001 .cindex "EXPN" "ACL for"
15002 This option defines the ACL that is run when an SMTP EXPN command is
15003 received. See chapter &<<CHAPACL>>& for further details.
15005 .option acl_smtp_helo main string&!! unset
15006 .cindex "EHLO" "ACL for"
15007 .cindex "HELO" "ACL for"
15008 This option defines the ACL that is run when an SMTP EHLO or HELO
15009 command is received. See chapter &<<CHAPACL>>& for further details.
15012 .option acl_smtp_mail main string&!! unset
15013 .cindex "MAIL" "ACL for"
15014 This option defines the ACL that is run when an SMTP MAIL command is
15015 received. See chapter &<<CHAPACL>>& for further details.
15017 .option acl_smtp_mailauth main string&!! unset
15018 .cindex "AUTH" "on MAIL command"
15019 This option defines the ACL that is run when there is an AUTH parameter on
15020 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
15021 &<<CHAPSMTPAUTH>>& for details of authentication.
15023 .option acl_smtp_mime main string&!! unset
15024 .cindex "MIME content scanning" "ACL for"
15025 This option is available when Exim is built with the content-scanning
15026 extension. It defines the ACL that is run for each MIME part in a message. See
15027 section &<<SECTscanmimepart>>& for details.
15029 .option acl_smtp_notquit main string&!! unset
15030 .cindex "not-QUIT, ACL for"
15031 This option defines the ACL that is run when an SMTP session
15032 ends without a QUIT command being received.
15033 See chapter &<<CHAPACL>>& for further details.
15035 .option acl_smtp_predata main string&!! unset
15036 This option defines the ACL that is run when an SMTP DATA command is
15037 received, before the message itself is received. See chapter &<<CHAPACL>>& for
15040 .option acl_smtp_quit main string&!! unset
15041 .cindex "QUIT, ACL for"
15042 This option defines the ACL that is run when an SMTP QUIT command is
15043 received. See chapter &<<CHAPACL>>& for further details.
15045 .option acl_smtp_rcpt main string&!! unset
15046 .cindex "RCPT" "ACL for"
15047 This option defines the ACL that is run when an SMTP RCPT command is
15048 received. See chapter &<<CHAPACL>>& for further details.
15050 .option acl_smtp_starttls main string&!! unset
15051 .cindex "STARTTLS, ACL for"
15052 This option defines the ACL that is run when an SMTP STARTTLS command is
15053 received. See chapter &<<CHAPACL>>& for further details.
15055 .option acl_smtp_vrfy main string&!! unset
15056 .cindex "VRFY" "ACL for"
15057 This option defines the ACL that is run when an SMTP VRFY command is
15058 received. See chapter &<<CHAPACL>>& for further details.
15060 .option add_environment main "string list" empty
15061 .cindex "environment" "set values"
15062 This option adds individual environment variables that the
15063 currently linked libraries and programs in child processes may use.
15064 Each list element should be of the form &"name=value"&.
15066 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
15068 .option admin_groups main "string list&!!" unset
15069 .cindex "admin user"
15070 This option is expanded just once, at the start of Exim's processing. If the
15071 current group or any of the supplementary groups of an Exim caller is in this
15072 colon-separated list, the caller has admin privileges. If all your system
15073 programmers are in a specific group, for example, you can give them all Exim
15074 admin privileges by putting that group in &%admin_groups%&. However, this does
15075 not permit them to read Exim's spool files (whose group owner is the Exim gid).
15076 To permit this, you have to add individuals to the Exim group.
15078 .option allow_domain_literals main boolean false
15079 .cindex "domain literal"
15080 If this option is set, the RFC 2822 domain literal format is permitted in
15081 email addresses. The option is not set by default, because the domain literal
15082 format is not normally required these days, and few people know about it. It
15083 has, however, been exploited by mail abusers.
15085 Unfortunately, it seems that some DNS black list maintainers are using this
15086 format to report black listing to postmasters. If you want to accept messages
15087 addressed to your hosts by IP address, you need to set
15088 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
15089 domains (defined in the named domain list &%local_domains%& in the default
15090 configuration). This &"magic string"& matches the domain literal form of all
15091 the local host's IP addresses.
15094 .option allow_mx_to_ip main boolean false
15095 .cindex "MX record" "pointing to IP address"
15096 It appears that more and more DNS zone administrators are breaking the rules
15097 and putting domain names that look like IP addresses on the right hand side of
15098 MX records. Exim follows the rules and rejects this, giving an error message
15099 that explains the misconfiguration. However, some other MTAs support this
15100 practice, so to avoid &"Why can't Exim do this?"& complaints,
15101 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
15102 recommended, except when you have no other choice.
15104 .option allow_utf8_domains main boolean false
15105 .cindex "domain" "UTF-8 characters in"
15106 .cindex "UTF-8" "in domain name"
15107 Lots of discussion is going on about internationalized domain names. One
15108 camp is strongly in favour of just using UTF-8 characters, and it seems
15109 that at least two other MTAs permit this.
15110 This option allows Exim users to experiment if they wish.
15112 If it is set true, Exim's domain parsing function allows valid
15113 UTF-8 multicharacters to appear in domain name components, in addition to
15114 letters, digits, and hyphens.
15116 If Exim is built with internationalization support
15117 and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
15118 this option can be left as default.
15120 if you want to look up such domain names in the DNS, you must also
15121 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
15122 suitable setting is:
15124 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
15125 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
15127 Alternatively, you can just disable this feature by setting
15129 dns_check_names_pattern =
15131 That is, set the option to an empty string so that no check is done.
15134 .option auth_advertise_hosts main "host list&!!" *
15135 .cindex "authentication" "advertising"
15136 .cindex "AUTH" "advertising"
15137 .cindex "ESMTP extensions" AUTH
15138 If any server authentication mechanisms are configured, Exim advertises them in
15139 response to an EHLO command only if the calling host matches this list.
15140 Otherwise, Exim does not advertise AUTH.
15141 Exim does not accept AUTH commands from clients to which it has not
15142 advertised the availability of AUTH. The advertising of individual
15143 authentication mechanisms can be controlled by the use of the
15144 &%server_advertise_condition%& generic authenticator option on the individual
15145 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
15147 Certain mail clients (for example, Netscape) require the user to provide a name
15148 and password for authentication if AUTH is advertised, even though it may
15149 not be needed (the host may accept messages from hosts on its local LAN without
15150 authentication, for example). The &%auth_advertise_hosts%& option can be used
15151 to make these clients more friendly by excluding them from the set of hosts to
15152 which Exim advertises AUTH.
15154 .cindex "AUTH" "advertising when encrypted"
15155 If you want to advertise the availability of AUTH only when the connection
15156 is encrypted using TLS, you can make use of the fact that the value of this
15157 option is expanded, with a setting like this:
15159 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
15161 .vindex "&$tls_in_cipher$&"
15162 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
15163 the expansion is empty, thus matching no hosts. Otherwise, the result of the
15164 expansion is *, which matches all hosts.
15167 .option auto_thaw main time 0s
15168 .cindex "thawing messages"
15169 .cindex "unfreezing messages"
15170 If this option is set to a time greater than zero, a queue runner will try a
15171 new delivery attempt on any frozen message, other than a bounce message, if
15172 this much time has passed since it was frozen. This may result in the message
15173 being re-frozen if nothing has changed since the last attempt. It is a way of
15174 saying &"keep on trying, even though there are big problems"&.
15176 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
15177 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
15178 thought to be very useful any more, and its use should probably be avoided.
15181 .option av_scanner main string "see below"
15182 This option is available if Exim is built with the content-scanning extension.
15183 It specifies which anti-virus scanner to use. The default value is:
15185 sophie:/var/run/sophie
15187 If the value of &%av_scanner%& starts with a dollar character, it is expanded
15188 before use. See section &<<SECTscanvirus>>& for further details.
15191 .option bi_command main string unset
15193 This option supplies the name of a command that is run when Exim is called with
15194 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
15195 just the command name, it is not a complete command line. If an argument is
15196 required, it must come from the &%-oA%& command line option.
15199 .option bounce_message_file main string&!! unset
15200 .cindex "bounce message" "customizing"
15201 .cindex "customizing" "bounce message"
15202 This option defines a template file containing paragraphs of text to be used
15203 for constructing bounce messages. Details of the file's contents are given in
15204 chapter &<<CHAPemsgcust>>&.
15205 .cindex bounce_message_file "tainted data"
15206 The option is expanded to give the file path, which must be
15207 absolute and untainted.
15208 See also &%warn_message_file%&.
15211 .option bounce_message_text main string unset
15212 When this option is set, its contents are included in the default bounce
15213 message immediately after &"This message was created automatically by mail
15214 delivery software."& It is not used if &%bounce_message_file%& is set.
15216 .option bounce_return_body main boolean true
15217 .cindex "bounce message" "including body"
15218 This option controls whether the body of an incoming message is included in a
15219 bounce message when &%bounce_return_message%& is true. The default setting
15220 causes the entire message, both header and body, to be returned (subject to the
15221 value of &%bounce_return_size_limit%&). If this option is false, only the
15222 message header is included. In the case of a non-SMTP message containing an
15223 error that is detected during reception, only those header lines preceding the
15224 point at which the error was detected are returned.
15225 .cindex "bounce message" "including original"
15227 .option bounce_return_linesize_limit main integer 998
15228 .cindex "size" "of bounce lines, limit"
15229 .cindex "bounce message" "line length limit"
15230 .cindex "limit" "bounce message line length"
15231 This option sets a limit in bytes on the line length of messages
15232 that are returned to senders due to delivery problems,
15233 when &%bounce_return_message%& is true.
15234 The default value corresponds to RFC limits.
15235 If the message being returned has lines longer than this value it is
15236 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
15238 The option also applies to bounces returned when an error is detected
15239 during reception of a message.
15240 In this case lines from the original are truncated.
15242 The option does not apply to messages generated by an &(autoreply)& transport.
15245 .option bounce_return_message main boolean true
15246 If this option is set false, none of the original message is included in
15247 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
15248 &%bounce_return_body%&.
15251 .option bounce_return_size_limit main integer 100K
15252 .cindex "size" "of bounce, limit"
15253 .cindex "bounce message" "size limit"
15254 .cindex "limit" "bounce message size"
15255 This option sets a limit in bytes on the size of messages that are returned to
15256 senders as part of bounce messages when &%bounce_return_message%& is true. The
15257 limit should be less than the value of the global &%message_size_limit%& and of
15258 any &%message_size_limit%& settings on transports, to allow for the bounce text
15259 that Exim generates. If this option is set to zero there is no limit.
15261 When the body of any message that is to be included in a bounce message is
15262 greater than the limit, it is truncated, and a comment pointing this out is
15263 added at the top. The actual cutoff may be greater than the value given, owing
15264 to the use of buffering for transferring the message in chunks (typically 8K in
15265 size). The idea is to save bandwidth on those undeliverable 15-megabyte
15268 .option bounce_sender_authentication main string unset
15269 .cindex "bounce message" "sender authentication"
15270 .cindex "authentication" "bounce message"
15271 .cindex "AUTH" "on bounce message"
15272 This option provides an authenticated sender address that is sent with any
15273 bounce messages generated by Exim that are sent over an authenticated SMTP
15274 connection. A typical setting might be:
15276 bounce_sender_authentication = mailer-daemon@my.domain.example
15278 which would cause bounce messages to be sent using the SMTP command:
15280 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
15282 The value of &%bounce_sender_authentication%& must always be a complete email
15285 .option callout_domain_negative_expire main time 3h
15286 .cindex "caching" "callout timeouts"
15287 .cindex "callout" "caching timeouts"
15288 This option specifies the expiry time for negative callout cache data for a
15289 domain. See section &<<SECTcallver>>& for details of callout verification, and
15290 section &<<SECTcallvercache>>& for details of the caching.
15293 .option callout_domain_positive_expire main time 7d
15294 This option specifies the expiry time for positive callout cache data for a
15295 domain. See section &<<SECTcallver>>& for details of callout verification, and
15296 section &<<SECTcallvercache>>& for details of the caching.
15299 .option callout_negative_expire main time 2h
15300 This option specifies the expiry time for negative callout cache data for an
15301 address. See section &<<SECTcallver>>& for details of callout verification, and
15302 section &<<SECTcallvercache>>& for details of the caching.
15305 .option callout_positive_expire main time 24h
15306 This option specifies the expiry time for positive callout cache data for an
15307 address. See section &<<SECTcallver>>& for details of callout verification, and
15308 section &<<SECTcallvercache>>& for details of the caching.
15311 .option callout_random_local_part main string&!! "see below"
15312 This option defines the &"random"& local part that can be used as part of
15313 callout verification. The default value is
15315 $primary_hostname-$tod_epoch-testing
15317 See section &<<CALLaddparcall>>& for details of how this value is used.
15320 .option check_log_inodes main integer 100
15321 See &%check_spool_space%& below.
15324 .option check_log_space main integer 10M
15325 See &%check_spool_space%& below.
15327 .oindex "&%check_rfc2047_length%&"
15328 .cindex "RFC 2047" "disabling length check"
15329 .option check_rfc2047_length main boolean true
15330 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
15331 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
15332 word; strings to be encoded that exceed this length are supposed to use
15333 multiple encoded words. By default, Exim does not recognize encoded words that
15334 exceed the maximum length. However, it seems that some software, in violation
15335 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
15336 set false, Exim recognizes encoded words of any length.
15339 .option check_spool_inodes main integer 100
15340 See &%check_spool_space%& below.
15343 .option check_spool_space main integer 10M
15344 .cindex "checking disk space"
15345 .cindex "disk space, checking"
15346 .cindex "spool directory" "checking space"
15347 The four &%check_...%& options allow for checking of disk resources before a
15348 message is accepted.
15350 .vindex "&$log_inodes$&"
15351 .vindex "&$log_space$&"
15352 .vindex "&$spool_inodes$&"
15353 .vindex "&$spool_space$&"
15354 When any of these options are nonzero, they apply to all incoming messages. If you
15355 want to apply different checks to different kinds of message, you can do so by
15356 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
15357 &$spool_space$& in an ACL with appropriate additional conditions.
15360 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
15361 either value is greater than zero, for example:
15363 check_spool_space = 100M
15364 check_spool_inodes = 100
15366 The spool partition is the one that contains the directory defined by
15367 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
15370 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
15371 files are written if either is greater than zero. These should be set only if
15372 &%log_file_path%& and &%spool_directory%& refer to different partitions.
15374 If there is less space or fewer inodes than requested, Exim refuses to accept
15375 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
15376 error response to the MAIL command. If ESMTP is in use and there was a
15377 SIZE parameter on the MAIL command, its value is added to the
15378 &%check_spool_space%& value, and the check is performed even if
15379 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
15381 The values for &%check_spool_space%& and &%check_log_space%& are held as a
15382 number of kilobytes (though specified in bytes).
15383 If a non-multiple of 1024 is specified, it is rounded up.
15385 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
15386 failure a message is written to stderr and Exim exits with a non-zero code, as
15387 it obviously cannot send an error message of any kind.
15389 There is a slight performance penalty for these checks.
15390 Versions of Exim preceding 4.88 had these disabled by default;
15391 high-rate installations confident they will never run out of resources
15392 may wish to deliberately disable them.
15394 .option chunking_advertise_hosts main "host list&!!" *
15395 .cindex CHUNKING advertisement
15396 .cindex "RFC 3030" "CHUNKING"
15397 .cindex "ESMTP extensions" CHUNKING
15398 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
15400 Hosts may use the BDAT command as an alternate to DATA.
15402 .option commandline_checks_require_admin main boolean &`false`&
15403 .cindex "restricting access to features"
15404 This option restricts various basic checking features to require an
15405 administrative user.
15406 This affects most of the &%-b*%& options, such as &%-be%&.
15408 .option debug_store main boolean &`false`&
15409 .cindex debugging "memory corruption"
15410 .cindex memory debugging
15411 This option, when true, enables extra checking in Exim's internal memory
15412 management. For use when a memory corruption issue is being investigated,
15413 it should normally be left as default.
15415 .option daemon_smtp_ports main string &`smtp`&
15416 .cindex "port" "for daemon"
15417 .cindex "TCP/IP" "setting listening ports"
15418 This option specifies one or more default SMTP ports on which the Exim daemon
15419 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
15420 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
15422 .option daemon_startup_retries main integer 9
15423 .cindex "daemon startup, retrying"
15424 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
15425 the daemon at startup when it cannot immediately bind a listening socket
15426 (typically because the socket is already in use): &%daemon_startup_retries%&
15427 defines the number of retries after the first failure, and
15428 &%daemon_startup_sleep%& defines the length of time to wait between retries.
15430 .option daemon_startup_sleep main time 30s
15431 See &%daemon_startup_retries%&.
15433 .option delay_warning main "time list" 24h
15434 .cindex "warning of delay"
15435 .cindex "delay warning, specifying"
15436 .cindex "queue" "delay warning"
15437 When a message is delayed, Exim sends a warning message to the sender at
15438 intervals specified by this option. The data is a colon-separated list of times
15439 after which to send warning messages. If the value of the option is an empty
15440 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
15441 message has been in the queue for longer than the last time, the last interval
15442 between the times is used to compute subsequent warning times. For example,
15445 delay_warning = 4h:8h:24h
15447 the first message is sent after 4 hours, the second after 8 hours, and
15448 the third one after 24 hours. After that, messages are sent every 16 hours,
15449 because that is the interval between the last two times on the list. If you set
15450 just one time, it specifies the repeat interval. For example, with:
15454 messages are repeated every six hours. To stop warnings after a given time, set
15455 a very large time at the end of the list. For example:
15457 delay_warning = 2h:12h:99d
15459 Note that the option is only evaluated at the time a delivery attempt fails,
15460 which depends on retry and queue-runner configuration.
15461 Typically retries will be configured more frequently than warning messages.
15463 .option delay_warning_condition main string&!! "see below"
15464 .vindex "&$domain$&"
15465 The string is expanded at the time a warning message might be sent. If all the
15466 deferred addresses have the same domain, it is set in &$domain$& during the
15467 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
15468 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
15469 &"false"& (the comparison being done caselessly) then the warning message is
15470 not sent. The default is:
15472 delay_warning_condition = ${if or {\
15473 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
15474 { match{$h_precedence:}{(?i)bulk|list|junk} }\
15475 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
15478 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
15479 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
15480 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
15481 &"auto-replied"& in an &'Auto-Submitted:'& header.
15483 .option deliver_drop_privilege main boolean false
15484 .cindex "unprivileged delivery"
15485 .cindex "delivery" "unprivileged"
15486 If this option is set true, Exim drops its root privilege at the start of a
15487 delivery process, and runs as the Exim user throughout. This severely restricts
15488 the kinds of local delivery that are possible, but is viable in certain types
15489 of configuration. There is a discussion about the use of root privilege in
15490 chapter &<<CHAPsecurity>>&.
15492 .option deliver_queue_load_max main fixed-point unset
15493 .cindex "load average"
15494 .cindex "queue runner" "abandoning"
15495 When this option is set, a queue run is abandoned if the system load average
15496 becomes greater than the value of the option. The option has no effect on
15497 ancient operating systems on which Exim cannot determine the load average.
15498 See also &%queue_only_load%& and &%smtp_load_reserve%&.
15501 .option delivery_date_remove main boolean true
15502 .cindex "&'Delivery-date:'& header line"
15503 Exim's transports have an option for adding a &'Delivery-date:'& header to a
15504 message when it is delivered, in exactly the same way as &'Return-path:'& is
15505 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
15506 should not be present in incoming messages, and this option causes them to be
15507 removed at the time the message is received, to avoid any problems that might
15508 occur when a delivered message is subsequently sent on to some other recipient.
15510 .option disable_fsync main boolean false
15511 .cindex "&[fsync()]&, disabling"
15512 This option is available only if Exim was built with the compile-time option
15513 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
15514 a runtime configuration generates an &"unknown option"& error. You should not
15515 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
15516 really, really, really understand what you are doing. &'No pre-compiled
15517 distributions of Exim should ever make this option available.'&
15519 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
15520 updated files' data to be written to disc before continuing. Unexpected events
15521 such as crashes and power outages may cause data to be lost or scrambled.
15522 Here be Dragons. &*Beware.*&
15525 .option disable_ipv6 main boolean false
15526 .cindex "IPv6" "disabling"
15527 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
15528 activities take place. AAAA records are never looked up, and any IPv6 addresses
15529 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
15530 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
15531 to handle IPv6 literal addresses.
15534 .option dkim_verify_hashes main "string list" "sha256 : sha512"
15535 .cindex DKIM "selecting signature algorithms"
15536 This option gives a list of hash types which are acceptable in signatures,
15537 and an order of processing.
15538 Signatures with algorithms not in the list will be ignored.
15540 Acceptable values include:
15547 Note that the acceptance of sha1 violates RFC 8301.
15549 .option dkim_verify_keytypes main "string list" "ed25519 : rsa"
15550 This option gives a list of key types which are acceptable in signatures,
15551 and an order of processing.
15552 Signatures with algorithms not in the list will be ignored.
15555 .option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250"
15556 This option gives a list of key sizes which are acceptable in signatures.
15557 The list is keyed by the algorithm type for the key; the values are in bits.
15558 Signatures with keys smaller than given by this option will fail verification.
15560 The default enforces the RFC 8301 minimum key size for RSA signatures.
15562 .option dkim_verify_minimal main boolean false
15563 If set to true, verification of signatures will terminate after the
15566 .option dkim_verify_signers main "domain list&!!" $dkim_signers
15567 .cindex DKIM "controlling calls to the ACL"
15568 This option gives a list of DKIM domains for which the DKIM ACL is run.
15569 It is expanded after the message is received; by default it runs
15570 the ACL once for each signature in the message.
15571 See section &<<SECDKIMVFY>>&.
15574 .option dmarc_forensic_sender main string&!! unset
15575 .option dmarc_history_file main string unset
15576 .option dmarc_tld_file main string unset
15577 .cindex DMARC "main section options"
15578 These options control DMARC processing.
15579 See section &<<SECDMARC>>& for details.
15582 .option dns_again_means_nonexist main "domain list&!!" unset
15583 .cindex "DNS" "&""try again""& response; overriding"
15584 DNS lookups give a &"try again"& response for the DNS errors
15585 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
15586 keep trying to deliver a message, or to give repeated temporary errors to
15587 incoming mail. Sometimes the effect is caused by a badly set up name server and
15588 may persist for a long time. If a domain which exhibits this problem matches
15589 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
15590 This option should be used with care. You can make it apply to reverse lookups
15591 by a setting such as this:
15593 dns_again_means_nonexist = *.in-addr.arpa
15595 This option applies to all DNS lookups that Exim does. It also applies when the
15596 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
15597 since these are most likely to be caused by DNS lookup problems. The
15598 &(dnslookup)& router has some options of its own for controlling what happens
15599 when lookups for MX or SRV records give temporary errors. These more specific
15600 options are applied after this global option.
15602 .option dns_check_names_pattern main string "see below"
15603 .cindex "DNS" "pre-check of name syntax"
15604 When this option is set to a non-empty string, it causes Exim to check domain
15605 names for characters that are not allowed in host names before handing them to
15606 the DNS resolver, because some resolvers give temporary errors for names that
15607 contain unusual characters. If a domain name contains any unwanted characters,
15608 a &"not found"& result is forced, and the resolver is not called. The check is
15609 done by matching the domain name against a regular expression, which is the
15610 value of this option. The default pattern is
15612 dns_check_names_pattern = \
15613 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
15615 which permits only letters, digits, slashes, and hyphens in components, but
15616 they must start and end with a letter or digit. Slashes are not, in fact,
15617 permitted in host names, but they are found in certain NS records (which can be
15618 accessed in Exim by using a &%dnsdb%& lookup). If you set
15619 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
15622 .option dns_csa_search_limit main integer 5
15623 This option controls the depth of parental searching for CSA SRV records in the
15624 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
15626 .option dns_csa_use_reverse main boolean true
15627 This option controls whether or not an IP address, given as a CSA domain, is
15628 reversed and looked up in the reverse DNS, as described in more detail in
15629 section &<<SECTverifyCSA>>&.
15631 .option dns_cname_loops main integer 1
15632 .cindex DNS "CNAME following"
15633 This option controls the following of CNAME chains, needed if the resolver does
15634 not do it internally.
15635 As of 2018 most should, and the default can be left.
15636 If you have an ancient one, a value of 10 is likely needed.
15638 The default value of one CNAME-follow is needed
15639 thanks to the observed return for an MX request,
15640 given no MX presence but a CNAME to an A, of the CNAME.
15643 .option dns_dnssec_ok main integer -1
15644 .cindex "DNS" "resolver options"
15645 .cindex "DNS" "DNSSEC"
15646 If this option is set to a non-negative number then Exim will initialise the
15647 DNS resolver library to either use or not use DNSSEC, overriding the system
15648 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
15650 If the resolver library does not support DNSSEC then this option has no effect.
15652 On Linux with glibc 2.31 or newer this is insufficient, the resolver library
15653 will default to stripping out a successful validation status.
15654 This will break a previously working Exim installation.
15655 Provided that you do trust the resolver (ie, is on localhost) you can tell
15656 glibc to pass through any successful validation with a new option in
15657 &_/etc/resolv.conf_&:
15663 .option dns_ipv4_lookup main "domain list&!!" unset
15664 .cindex "IPv6" "DNS lookup for AAAA records"
15665 .cindex "DNS" "IPv6 lookup for AAAA records"
15666 .cindex DNS "IPv6 disabling"
15667 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
15668 looks for IPv6 address records (AAAA records) as well as IPv4 address records
15669 (A records) when trying to find IP addresses for hosts, unless the host's
15670 domain matches this list.
15672 This is a fudge to help with name servers that give big delays or otherwise do
15673 not work for the AAAA record type. In due course, when the world's name
15674 servers have all been upgraded, there should be no need for this option.
15675 Note that all lookups, including those done for verification, are affected;
15676 this will result in verify failure for IPv6 connections or ones using names
15677 only valid for IPv6 addresses.
15680 .option dns_retrans main time 0s
15681 .cindex "DNS" "resolver options"
15682 .cindex timeout "dns lookup"
15683 .cindex "DNS" timeout
15684 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
15685 retransmission and retry parameters for DNS lookups. Values of zero (the
15686 defaults) leave the system default settings unchanged. The first value is the
15687 time between retries, and the second is the number of retries. It isn't
15688 totally clear exactly how these settings affect the total time a DNS lookup may
15689 take. I haven't found any documentation about timeouts on DNS lookups; these
15690 parameter values are available in the external resolver interface structure,
15691 but nowhere does it seem to describe how they are used or what you might want
15693 See also the &%slow_lookup_log%& option.
15696 .option dns_retry main integer 0
15697 See &%dns_retrans%& above.
15700 .option dns_trust_aa main "domain list&!!" unset
15701 .cindex "DNS" "resolver options"
15702 .cindex "DNS" "DNSSEC"
15703 If this option is set then lookup results marked with the AA bit
15704 (Authoritative Answer) are trusted the same way as if they were
15705 DNSSEC-verified. The authority section's name of the answer must
15706 match with this expanded domain list.
15708 Use this option only if you talk directly to a resolver that is
15709 authoritative for some zones and does not set the AD (Authentic Data)
15710 bit in the answer. Some DNS servers may have an configuration option to
15711 mark the answers from their own zones as verified (they set the AD bit).
15712 Others do not have this option. It is considered as poor practice using
15713 a resolver that is an authoritative server for some zones.
15715 Use this option only if you really have to (e.g. if you want
15716 to use DANE for remote delivery to a server that is listed in the DNS
15717 zones that your resolver is authoritative for).
15719 If the DNS answer packet has the AA bit set and contains resource record
15720 in the answer section, the name of the first NS record appearing in the
15721 authority section is compared against the list. If the answer packet is
15722 authoritative but the answer section is empty, the name of the first SOA
15723 record in the authoritative section is used instead.
15725 .cindex "DNS" "resolver options"
15726 .option dns_use_edns0 main integer -1
15727 .cindex "DNS" "resolver options"
15728 .cindex "DNS" "EDNS0"
15729 .cindex "DNS" "OpenBSD
15730 If this option is set to a non-negative number then Exim will initialise the
15731 DNS resolver library to either use or not use EDNS0 extensions, overriding
15732 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
15735 If the resolver library does not support EDNS0 then this option has no effect.
15737 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
15738 means that DNSSEC will not work with Exim on that platform either, unless Exim
15739 is linked against an alternative DNS client library.
15742 .option drop_cr main boolean false
15743 This is an obsolete option that is now a no-op. It used to affect the way Exim
15744 handled CR and LF characters in incoming messages. What happens now is
15745 described in section &<<SECTlineendings>>&.
15747 .option dsn_advertise_hosts main "host list&!!" unset
15748 .cindex "bounce messages" "success"
15749 .cindex "DSN" "success"
15750 .cindex "Delivery Status Notification" "success"
15751 .cindex "ESMTP extensions" DSN
15752 DSN extensions (RFC3461) will be advertised in the EHLO message to,
15753 and accepted from, these hosts.
15754 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
15755 and RET and ORCPT options on MAIL FROM commands.
15756 A NOTIFY=SUCCESS option requests success-DSN messages.
15757 A NOTIFY= option with no argument requests that no delay or failure DSNs
15759 &*Note*&: Supplying success-DSN messages has been criticised
15760 on privacy grounds; it can leak details of internal forwarding.
15762 .option dsn_from main "string&!!" "see below"
15763 .cindex "&'From:'& header line" "in bounces"
15764 .cindex "bounce messages" "&'From:'& line, specifying"
15765 This option can be used to vary the contents of &'From:'& header lines in
15766 bounces and other automatically generated messages (&"Delivery Status
15767 Notifications"& &-- hence the name of the option). The default setting is:
15769 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
15771 The value is expanded every time it is needed. If the expansion fails, a
15772 panic is logged, and the default value is used.
15774 .option envelope_to_remove main boolean true
15775 .cindex "&'Envelope-to:'& header line"
15776 Exim's transports have an option for adding an &'Envelope-to:'& header to a
15777 message when it is delivered, in exactly the same way as &'Return-path:'& is
15778 handled. &'Envelope-to:'& records the original recipient address from the
15779 message's envelope that caused the delivery to happen. Such headers should not
15780 be present in incoming messages, and this option causes them to be removed at
15781 the time the message is received, to avoid any problems that might occur when a
15782 delivered message is subsequently sent on to some other recipient.
15785 .option errors_copy main "string list&!!" unset
15786 .cindex "bounce message" "copy to other address"
15787 .cindex "copy of bounce message"
15788 Setting this option causes Exim to send bcc copies of bounce messages that it
15789 generates to other addresses. &*Note*&: This does not apply to bounce messages
15790 coming from elsewhere. The value of the option is a colon-separated list of
15791 items. Each item consists of a pattern, terminated by white space, followed by
15792 a comma-separated list of email addresses. If a pattern contains spaces, it
15793 must be enclosed in double quotes.
15795 Each pattern is processed in the same way as a single item in an address list
15796 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
15797 the bounce message, the message is copied to the addresses on the list. The
15798 items are scanned in order, and once a matching one is found, no further items
15799 are examined. For example:
15801 errors_copy = spqr@mydomain postmaster@mydomain.example :\
15802 rqps@mydomain hostmaster@mydomain.example,\
15803 postmaster@mydomain.example
15805 .vindex "&$domain$&"
15806 .vindex "&$local_part$&"
15807 The address list is expanded before use. The expansion variables &$local_part$&
15808 and &$domain$& are set from the original recipient of the error message, and if
15809 there was any wildcard matching in the pattern, the expansion
15810 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
15811 variables &$0$&, &$1$&, etc. are set in the normal way.
15814 .option errors_reply_to main string unset
15815 .cindex "bounce message" "&'Reply-to:'& in"
15816 By default, Exim's bounce and delivery warning messages contain the header line
15818 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
15820 .oindex &%quota_warn_message%&
15821 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
15822 A warning message that is generated by the &%quota_warn_message%& option in an
15823 &(appendfile)& transport may contain its own &'From:'& header line that
15824 overrides the default.
15826 Experience shows that people reply to bounce messages. If the
15827 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
15828 and warning messages. For example:
15830 errors_reply_to = postmaster@my.domain.example
15832 The value of the option is not expanded. It must specify a valid RFC 2822
15833 address. However, if a warning message that is generated by the
15834 &%quota_warn_message%& option in an &(appendfile)& transport contain its
15835 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
15839 .option event_action main string&!! unset
15841 This option declares a string to be expanded for Exim's events mechanism.
15842 For details see chapter &<<CHAPevents>>&.
15845 .option exim_group main string "compile-time configured"
15846 .cindex "gid (group id)" "Exim's own"
15847 .cindex "Exim group"
15848 This option changes the gid under which Exim runs when it gives up root
15849 privilege. The default value is compiled into the binary. The value of this
15850 option is used only when &%exim_user%& is also set. Unless it consists entirely
15851 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
15852 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
15856 .option exim_path main string "see below"
15857 .cindex "Exim binary, path name"
15858 This option specifies the path name of the Exim binary, which is used when Exim
15859 needs to re-exec itself. The default is set up to point to the file &'exim'& in
15860 the directory configured at compile time by the BIN_DIRECTORY setting. It
15861 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
15863 &*Warning*&: Do not use a macro to define the value of this option, because
15864 you will break those Exim utilities that scan the configuration file to find
15865 where the binary is. (They then use the &%-bP%& option to extract option
15866 settings such as the value of &%spool_directory%&.)
15869 .option exim_user main string "compile-time configured"
15870 .cindex "uid (user id)" "Exim's own"
15871 .cindex "Exim user"
15872 This option changes the uid under which Exim runs when it gives up root
15873 privilege. The default value is compiled into the binary. Ownership of the run
15874 time configuration file and the use of the &%-C%& and &%-D%& command line
15875 options is checked against the values in the binary, not what is set here.
15877 Unless it consists entirely of digits, the string is looked up using
15878 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
15879 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
15880 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
15883 .option exim_version main string "current version"
15884 .cindex "Exim version"
15885 .cindex customizing "version number"
15886 .cindex "version number of Exim" override
15887 This option overrides the &$version_number$&/&$exim_version$& that Exim reports in
15888 various places. Use with care; this may fool stupid security scanners.
15891 .option extra_local_interfaces main "string list" unset
15892 This option defines network interfaces that are to be considered local when
15893 routing, but which are not used for listening by the daemon. See section
15894 &<<SECTreclocipadd>>& for details.
15897 . Allow this long option name to split; give it unsplit as a fifth argument
15898 . for the automatic .oindex that is generated by .option.
15900 .option "extract_addresses_remove_arguments" main boolean true &&&
15901 extract_addresses_remove_arguments
15903 .cindex "command line" "addresses with &%-t%&"
15904 .cindex "Sendmail compatibility" "&%-t%& option"
15905 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
15906 are present on the command line when the &%-t%& option is used to build an
15907 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
15908 line addresses are removed from the recipients list. This is also how Smail
15909 behaves. However, other Sendmail documentation (the O'Reilly book) states that
15910 command line addresses are added to those obtained from the header lines. When
15911 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
15912 argument headers. If it is set false, Exim adds rather than removes argument
15916 .option finduser_retries main integer 0
15917 .cindex "NIS, retrying user lookups"
15918 On systems running NIS or other schemes in which user and group information is
15919 distributed from a remote system, there can be times when &[getpwnam()]& and
15920 related functions fail, even when given valid data, because things time out.
15921 Unfortunately these failures cannot be distinguished from genuine &"not found"&
15922 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
15923 many extra times to find a user or a group, waiting for one second between
15926 .cindex "&_/etc/passwd_&" "multiple reading of"
15927 You should not set this option greater than zero if your user information is in
15928 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
15929 search the file multiple times for non-existent users, and also cause delay.
15933 .option freeze_tell main "string list, comma separated" unset
15934 .cindex "freezing messages" "sending a message when freezing"
15935 On encountering certain errors, or when configured to do so in a system filter,
15936 ACL, or special router, Exim freezes a message. This means that no further
15937 delivery attempts take place until an administrator thaws the message, or the
15938 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
15939 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
15940 warning message whenever it freezes something, unless the message it is
15941 freezing is a locally-generated bounce message. (Without this exception there
15942 is the possibility of looping.) The warning message is sent to the addresses
15943 supplied as the comma-separated value of this option. If several of the
15944 message's addresses cause freezing, only a single message is sent. If the
15945 freezing was automatic, the reason(s) for freezing can be found in the message
15946 log. If you configure freezing in a filter or ACL, you must arrange for any
15947 logging that you require.
15950 .option gecos_name main string&!! unset
15952 .cindex "&""gecos""& field, parsing"
15953 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
15954 password file to hold other information in addition to users' real names. Exim
15955 looks up this field for use when it is creating &'Sender:'& or &'From:'&
15956 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
15957 of the field are used unchanged, except that, if an ampersand is encountered,
15958 it is replaced by the user's login name with the first character forced to
15959 upper case, since this is a convention that is observed on many systems.
15961 When these options are set, &%gecos_pattern%& is treated as a regular
15962 expression that is to be applied to the field (again with && replaced by the
15963 login name), and if it matches, &%gecos_name%& is expanded and used as the
15966 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
15967 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
15968 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
15969 name terminates at the first comma, the following can be used:
15971 gecos_pattern = ([^,]*)
15975 .option gecos_pattern main string unset
15976 See &%gecos_name%& above.
15979 .option gnutls_compat_mode main boolean unset
15980 This option controls whether GnuTLS is used in compatibility mode in an Exim
15981 server. This reduces security slightly, but improves interworking with older
15982 implementations of TLS.
15985 .option gnutls_allow_auto_pkcs11 main boolean unset
15986 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
15987 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
15990 &url(https://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
15995 .option headers_charset main string "see below"
15996 This option sets a default character set for translating from encoded MIME
15997 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
15998 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
15999 ultimate default is ISO-8859-1. For more details see the description of header
16000 insertions in section &<<SECTexpansionitems>>&.
16004 .option header_maxsize main integer "see below"
16005 .cindex "header section" "maximum size of"
16006 .cindex "limit" "size of message header section"
16007 This option controls the overall maximum size of a message's header
16008 section. The default is the value of HEADER_MAXSIZE in
16009 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
16010 sections are rejected.
16013 .option header_line_maxsize main integer 0
16014 .cindex "header lines" "maximum size of"
16015 .cindex "limit" "size of one header line"
16016 This option limits the length of any individual header line in a message, after
16017 all the continuations have been joined together. Messages with individual
16018 header lines that are longer than the limit are rejected. The default value of
16019 zero means &"no limit"&.
16024 .option helo_accept_junk_hosts main "host list&!!" unset
16025 .cindex "HELO" "accepting junk data"
16026 .cindex "EHLO" "accepting junk data"
16027 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
16028 mail, and gives an error response for invalid data. Unfortunately, there are
16029 some SMTP clients that send syntactic junk. They can be accommodated by setting
16030 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
16031 if you want to do semantic checking.
16032 See also &%helo_allow_chars%& for a way of extending the permitted character
16036 .option helo_allow_chars main string unset
16037 .cindex "HELO" "underscores in"
16038 .cindex "EHLO" "underscores in"
16039 .cindex "underscore in EHLO/HELO"
16040 This option can be set to a string of rogue characters that are permitted in
16041 all EHLO and HELO names in addition to the standard letters, digits,
16042 hyphens, and dots. If you really must allow underscores, you can set
16044 helo_allow_chars = _
16046 Note that the value is one string, not a list.
16049 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
16050 .cindex "HELO" "forcing reverse lookup"
16051 .cindex "EHLO" "forcing reverse lookup"
16052 If the domain given by a client in a HELO or EHLO command matches this
16053 list, a reverse lookup is done in order to establish the host's true name. The
16054 default forces a lookup if the client host gives the server's name or any of
16055 its IP addresses (in brackets), something that broken clients have been seen to
16059 .option helo_try_verify_hosts main "host list&!!" unset
16060 .cindex "HELO verifying" "optional"
16061 .cindex "EHLO" "verifying, optional"
16062 By default, Exim just checks the syntax of HELO and EHLO commands (see
16063 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
16064 to do more extensive checking of the data supplied by these commands. The ACL
16065 condition &`verify = helo`& is provided to make this possible.
16066 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
16067 to force the check to occur. From release 4.53 onwards, this is no longer
16068 necessary. If the check has not been done before &`verify = helo`& is
16069 encountered, it is done at that time. Consequently, this option is obsolete.
16070 Its specification is retained here for backwards compatibility.
16072 When an EHLO or HELO command is received, if the calling host matches
16073 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
16074 EHLO command either:
16077 is an IP literal matching the calling address of the host, or
16079 .cindex "DNS" "reverse lookup"
16080 .cindex "reverse DNS lookup"
16081 matches the host name that Exim obtains by doing a reverse lookup of the
16082 calling host address, or
16084 when looked up in DNS yields the calling host address.
16087 However, the EHLO or HELO command is not rejected if any of the checks
16088 fail. Processing continues, but the result of the check is remembered, and can
16089 be detected later in an ACL by the &`verify = helo`& condition.
16091 If DNS was used for successful verification, the variable
16092 .cindex "DNS" "DNSSEC"
16093 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
16095 .option helo_verify_hosts main "host list&!!" unset
16096 .cindex "HELO verifying" "mandatory"
16097 .cindex "EHLO" "verifying, mandatory"
16098 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
16099 backwards compatibility. For hosts that match this option, Exim checks the host
16100 name given in the HELO or EHLO in the same way as for
16101 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
16102 rejected with a 550 error, and entries are written to the main and reject logs.
16103 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
16106 .option hold_domains main "domain list&!!" unset
16107 .cindex "domain" "delaying delivery"
16108 .cindex "delivery" "delaying certain domains"
16109 This option allows mail for particular domains to be held in the queue
16110 manually. The option is overridden if a message delivery is forced with the
16111 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
16112 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
16113 item in &%hold_domains%&, no routing or delivery for that address is done, and
16114 it is deferred every time the message is looked at.
16116 This option is intended as a temporary operational measure for delaying the
16117 delivery of mail while some problem is being sorted out, or some new
16118 configuration tested. If you just want to delay the processing of some
16119 domains until a queue run occurs, you should use &%queue_domains%& or
16120 &%queue_smtp_domains%&, not &%hold_domains%&.
16122 A setting of &%hold_domains%& does not override Exim's code for removing
16123 messages from the queue if they have been there longer than the longest retry
16124 time in any retry rule. If you want to hold messages for longer than the normal
16125 retry times, insert a dummy retry rule with a long retry time.
16128 .option host_lookup main "host list&!!" unset
16129 .cindex "host name" "lookup, forcing"
16130 Exim does not look up the name of a calling host from its IP address unless it
16131 is required to compare against some host list, or the host matches
16132 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
16133 option (which normally contains IP addresses rather than host names). The
16134 default configuration file contains
16138 which causes a lookup to happen for all hosts. If the expense of these lookups
16139 is felt to be too great, the setting can be changed or removed.
16141 After a successful reverse lookup, Exim does a forward lookup on the name it
16142 has obtained, to verify that it yields the IP address that it started with. If
16143 this check fails, Exim behaves as if the name lookup failed.
16145 .vindex "&$host_lookup_failed$&"
16146 .vindex "&$sender_host_name$&"
16147 After any kind of failure, the host name (in &$sender_host_name$&) remains
16148 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
16149 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
16150 &`verify = reverse_host_lookup`& in ACLs.
16153 .option host_lookup_order main "string list" &`bydns:byaddr`&
16154 This option specifies the order of different lookup methods when Exim is trying
16155 to find a host name from an IP address. The default is to do a DNS lookup
16156 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
16157 if that fails. You can change the order of these lookups, or omit one entirely,
16160 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
16161 multiple PTR records in the DNS and the IP address is not listed in
16162 &_/etc/hosts_&. Different operating systems give different results in this
16163 case. That is why the default tries a DNS lookup first.
16167 .option host_reject_connection main "host list&!!" unset
16168 .cindex "host" "rejecting connections from"
16169 If this option is set, incoming SMTP calls from the hosts listed are rejected
16170 as soon as the connection is made.
16171 This option is obsolete, and retained only for backward compatibility, because
16172 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
16173 connections immediately.
16175 The ability to give an immediate rejection (either by this option or using an
16176 ACL) is provided for use in unusual cases. Many hosts will just try again,
16177 sometimes without much delay. Normally, it is better to use an ACL to reject
16178 incoming messages at a later stage, such as after RCPT commands. See
16179 chapter &<<CHAPACL>>&.
16182 .option hosts_connection_nolog main "host list&!!" unset
16183 .cindex "host" "not logging connections from"
16184 This option defines a list of hosts for which connection logging does not
16185 happen, even though the &%smtp_connection%& log selector is set. For example,
16186 you might want not to log SMTP connections from local processes, or from
16187 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
16188 the daemon; you should therefore strive to restrict its value to a short inline
16189 list of IP addresses and networks. To disable logging SMTP connections from
16190 local processes, you must create a host list with an empty item. For example:
16192 hosts_connection_nolog = :
16194 If the &%smtp_connection%& log selector is not set, this option has no effect.
16198 .option hosts_proxy main "host list&!!" unset
16199 .cindex proxy "proxy protocol"
16200 This option enables use of Proxy Protocol proxies for incoming
16201 connections. For details see section &<<SECTproxyInbound>>&.
16204 .option hosts_treat_as_local main "domain list&!!" unset
16205 .cindex "local host" "domains treated as"
16206 .cindex "host" "treated as local"
16207 If this option is set, any host names that match the domain list are treated as
16208 if they were the local host when Exim is scanning host lists obtained from MX
16210 or other sources. Note that the value of this option is a domain list, not a
16211 host list, because it is always used to check host names, not IP addresses.
16213 This option also applies when Exim is matching the special items
16214 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
16215 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
16216 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
16217 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
16218 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
16219 interfaces and recognizing the local host.
16222 .option ibase_servers main "string list" unset
16223 .cindex "InterBase" "server list"
16224 This option provides a list of InterBase servers and associated connection data,
16225 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
16226 The option is available only if Exim has been built with InterBase support.
16230 .option ignore_bounce_errors_after main time 10w
16231 .cindex "bounce message" "discarding"
16232 .cindex "discarding bounce message"
16233 This option affects the processing of bounce messages that cannot be delivered,
16234 that is, those that suffer a permanent delivery failure. (Bounce messages that
16235 suffer temporary delivery failures are of course retried in the usual way.)
16237 After a permanent delivery failure, bounce messages are frozen,
16238 because there is no sender to whom they can be returned. When a frozen bounce
16239 message has been in the queue for more than the given time, it is unfrozen at
16240 the next queue run, and a further delivery is attempted. If delivery fails
16241 again, the bounce message is discarded. This makes it possible to keep failed
16242 bounce messages around for a shorter time than the normal maximum retry time
16243 for frozen messages. For example,
16245 ignore_bounce_errors_after = 12h
16247 retries failed bounce message deliveries after 12 hours, discarding any further
16248 failures. If the value of this option is set to a zero time period, bounce
16249 failures are discarded immediately. Setting a very long time (as in the default
16250 value) has the effect of disabling this option. For ways of automatically
16251 dealing with other kinds of frozen message, see &%auto_thaw%& and
16252 &%timeout_frozen_after%&.
16255 .option ignore_fromline_hosts main "host list&!!" unset
16256 .cindex "&""From""& line"
16257 .cindex "UUCP" "&""From""& line"
16258 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
16259 the headers of a message. By default this is treated as the start of the
16260 message's body, which means that any following headers are not recognized as
16261 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
16262 match those hosts that insist on sending it. If the sender is actually a local
16263 process rather than a remote host, and is using &%-bs%& to inject the messages,
16264 &%ignore_fromline_local%& must be set to achieve this effect.
16267 .option ignore_fromline_local main boolean false
16268 See &%ignore_fromline_hosts%& above.
16270 .option keep_environment main "string list" unset
16271 .cindex "environment" "values from"
16272 This option contains a string list of environment variables to keep.
16273 You have to trust these variables or you have to be sure that
16274 these variables do not impose any security risk. Keep in mind that
16275 during the startup phase Exim is running with an effective UID 0 in most
16276 installations. As the default value is an empty list, the default
16277 environment for using libraries, running embedded Perl code, or running
16278 external binaries is empty, and does not not even contain PATH or HOME.
16280 Actually the list is interpreted as a list of patterns
16281 (&<<SECTlistexpand>>&), except that it is not expanded first.
16283 WARNING: Macro substitution is still done first, so having a macro
16284 FOO and having FOO_HOME in your &%keep_environment%& option may have
16285 unexpected results. You may work around this using a regular expression
16286 that does not match the macro name: ^[F]OO_HOME$.
16288 Current versions of Exim issue a warning during startup if you do not mention
16289 &%keep_environment%& in your runtime configuration file and if your
16290 current environment is not empty. Future versions may not issue that warning
16293 See the &%add_environment%& main config option for a way to set
16294 environment variables to a fixed value. The environment for &(pipe)&
16295 transports is handled separately, see section &<<SECTpipeenv>>& for
16299 .option keep_malformed main time 4d
16300 This option specifies the length of time to keep messages whose spool files
16301 have been corrupted in some way. This should, of course, never happen. At the
16302 next attempt to deliver such a message, it gets removed. The incident is
16306 .option ldap_ca_cert_dir main string unset
16307 .cindex "LDAP", "TLS CA certificate directory"
16308 .cindex certificate "directory for LDAP"
16309 This option indicates which directory contains CA certificates for verifying
16310 a TLS certificate presented by an LDAP server.
16311 While Exim does not provide a default value, your SSL library may.
16312 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16313 and constrained to be a directory.
16316 .option ldap_ca_cert_file main string unset
16317 .cindex "LDAP", "TLS CA certificate file"
16318 .cindex certificate "file for LDAP"
16319 This option indicates which file contains CA certificates for verifying
16320 a TLS certificate presented by an LDAP server.
16321 While Exim does not provide a default value, your SSL library may.
16322 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
16323 and constrained to be a file.
16326 .option ldap_cert_file main string unset
16327 .cindex "LDAP" "TLS client certificate file"
16328 .cindex certificate "file for LDAP"
16329 This option indicates which file contains an TLS client certificate which
16330 Exim should present to the LDAP server during TLS negotiation.
16331 Should be used together with &%ldap_cert_key%&.
16334 .option ldap_cert_key main string unset
16335 .cindex "LDAP" "TLS client key file"
16336 .cindex certificate "key for LDAP"
16337 This option indicates which file contains the secret/private key to use
16338 to prove identity to the LDAP server during TLS negotiation.
16339 Should be used together with &%ldap_cert_file%&, which contains the
16340 identity to be proven.
16343 .option ldap_cipher_suite main string unset
16344 .cindex "LDAP" "TLS cipher suite"
16345 This controls the TLS cipher-suite negotiation during TLS negotiation with
16346 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
16347 cipher-suite options with OpenSSL (as used by LDAP client libraries).
16350 .option ldap_default_servers main "string list" unset
16351 .cindex "LDAP" "default servers"
16352 This option provides a list of LDAP servers which are tried in turn when an
16353 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
16354 details of LDAP queries. This option is available only when Exim has been built
16358 .option ldap_require_cert main string unset.
16359 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
16360 This should be one of the values "hard", "demand", "allow", "try" or "never".
16361 A value other than one of these is interpreted as "never".
16362 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
16363 Although Exim does not set a default, the LDAP library probably defaults
16367 .option ldap_start_tls main boolean false
16368 .cindex "LDAP" "whether or not to negotiate TLS"
16369 If set, Exim will attempt to negotiate TLS with the LDAP server when
16370 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
16371 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
16373 In the event of failure to negotiate TLS, the action taken is controlled
16374 by &%ldap_require_cert%&.
16375 This option is ignored for &`ldapi`& connections.
16378 .option ldap_version main integer unset
16379 .cindex "LDAP" "protocol version, forcing"
16380 This option can be used to force Exim to set a specific protocol version for
16381 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
16382 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
16383 the LDAP headers; otherwise it is 2. This option is available only when Exim
16384 has been built with LDAP support.
16388 .option local_from_check main boolean true
16389 .cindex "&'Sender:'& header line" "disabling addition of"
16390 .cindex "&'From:'& header line" "disabling checking of"
16391 When a message is submitted locally (that is, not over a TCP/IP connection) by
16392 an untrusted user, Exim removes any existing &'Sender:'& header line, and
16393 checks that the &'From:'& header line matches the login of the calling user and
16394 the domain specified by &%qualify_domain%&.
16396 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
16397 locally submitted message is automatically qualified by Exim, unless the
16398 &%-bnq%& command line option is used.
16400 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
16401 on the local part. If the &'From:'& header line does not match, Exim adds a
16402 &'Sender:'& header with an address constructed from the calling user's login
16403 and the default qualify domain.
16405 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
16406 and no &'Sender:'& header is ever added. If, in addition, you want to retain
16407 &'Sender:'& header lines supplied by untrusted users, you must also set
16408 &%local_sender_retain%& to be true.
16410 .cindex "envelope from"
16411 .cindex "envelope sender"
16412 These options affect only the header lines in the message. The envelope sender
16413 is still forced to be the login id at the qualify domain unless
16414 &%untrusted_set_sender%& permits the user to supply an envelope sender.
16416 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
16417 request similar header line checking. See section &<<SECTthesenhea>>&, which
16418 has more details about &'Sender:'& processing.
16423 .option local_from_prefix main string unset
16424 When Exim checks the &'From:'& header line of locally submitted messages for
16425 matching the login id (see &%local_from_check%& above), it can be configured to
16426 ignore certain prefixes and suffixes in the local part of the address. This is
16427 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
16428 appropriate lists, in the same form as the &%local_part_prefix%& and
16429 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
16432 local_from_prefix = *-
16434 is set, a &'From:'& line containing
16436 From: anything-user@your.domain.example
16438 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
16439 matches the actual sender address that is constructed from the login name and
16443 .option local_from_suffix main string unset
16444 See &%local_from_prefix%& above.
16447 .option local_interfaces main "string list" "see below"
16448 This option controls which network interfaces are used by the daemon for
16449 listening; they are also used to identify the local host when routing. Chapter
16450 &<<CHAPinterfaces>>& contains a full description of this option and the related
16451 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
16452 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
16453 &%local_interfaces%& is
16455 local_interfaces = 0.0.0.0
16457 when Exim is built without IPv6 support; otherwise it is
16459 local_interfaces = <; ::0 ; 0.0.0.0
16462 .option local_scan_timeout main time 5m
16463 .cindex "timeout" "for &[local_scan()]& function"
16464 .cindex "&[local_scan()]& function" "timeout"
16465 This timeout applies to the &[local_scan()]& function (see chapter
16466 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
16467 the incoming message is rejected with a temporary error if it is an SMTP
16468 message. For a non-SMTP message, the message is dropped and Exim ends with a
16469 non-zero code. The incident is logged on the main and reject logs.
16473 .option local_sender_retain main boolean false
16474 .cindex "&'Sender:'& header line" "retaining from local submission"
16475 When a message is submitted locally (that is, not over a TCP/IP connection) by
16476 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
16477 do not want this to happen, you must set &%local_sender_retain%&, and you must
16478 also set &%local_from_check%& to be false (Exim will complain if you do not).
16479 See also the ACL modifier &`control = suppress_local_fixups`&. Section
16480 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
16485 .option localhost_number main string&!! unset
16486 .cindex "host" "locally unique number for"
16487 .cindex "message ids" "with multiple hosts"
16488 .vindex "&$localhost_number$&"
16489 Exim's message ids are normally unique only within the local host. If
16490 uniqueness among a set of hosts is required, each host must set a different
16491 value for the &%localhost_number%& option. The string is expanded immediately
16492 after reading the configuration file (so that a number can be computed from the
16493 host name, for example) and the result of the expansion must be a number in the
16494 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
16495 systems). This is available in subsequent string expansions via the variable
16496 &$localhost_number$&. When &%localhost_number is set%&, the final two
16497 characters of the message id, instead of just being a fractional part of the
16498 time, are computed from the time and the local host number as described in
16499 section &<<SECTmessiden>>&.
16503 .option log_file_path main "string list&!!" "set at compile time"
16504 .cindex "log" "file path for"
16505 This option sets the path which is used to determine the names of Exim's log
16506 files, or indicates that logging is to be to syslog, or both. It is expanded
16507 when Exim is entered, so it can, for example, contain a reference to the host
16508 name. If no specific path is set for the log files at compile or runtime,
16509 or if the option is unset at runtime (i.e. &`log_file_path = `&)
16510 they are written in a sub-directory called &_log_& in Exim's spool directory.
16511 A path must start with a slash.
16512 To send to syslog, use the word &"syslog"&.
16513 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
16514 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
16515 used. If this string is fixed at your installation (contains no expansion
16516 variables) it is recommended that you do not set this option in the
16517 configuration file, but instead supply the path using LOG_FILE_PATH in
16518 &_Local/Makefile_& so that it is available to Exim for logging errors detected
16519 early on &-- in particular, failure to read the configuration file.
16522 .option log_selector main string unset
16523 .cindex "log" "selectors"
16524 This option can be used to reduce or increase the number of things that Exim
16525 writes to its log files. Its argument is made up of names preceded by plus or
16526 minus characters. For example:
16528 log_selector = +arguments -retry_defer
16530 A list of possible names and what they control is given in the chapter on
16531 logging, in section &<<SECTlogselector>>&.
16534 .option log_timezone main boolean false
16535 .cindex "log" "timezone for entries"
16536 .vindex "&$tod_log$&"
16537 .vindex "&$tod_zone$&"
16538 By default, the timestamps on log lines are in local time without the
16539 timezone. This means that if your timezone changes twice a year, the timestamps
16540 in log lines are ambiguous for an hour when the clocks go back. One way of
16541 avoiding this problem is to set the timezone to UTC. An alternative is to set
16542 &%log_timezone%& true. This turns on the addition of the timezone offset to
16543 timestamps in log lines. Turning on this option can add quite a lot to the size
16544 of log files because each line is extended by 6 characters. Note that the
16545 &$tod_log$& variable contains the log timestamp without the zone, but there is
16546 another variable called &$tod_zone$& that contains just the timezone offset.
16549 .option lookup_open_max main integer 25
16550 .cindex "too many open files"
16551 .cindex "open files, too many"
16552 .cindex "file" "too many open"
16553 .cindex "lookup" "maximum open files"
16554 .cindex "limit" "open files for lookups"
16555 This option limits the number of simultaneously open files for single-key
16556 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
16557 Exim normally keeps these files open during routing, because often the same
16558 file is required several times. If the limit is reached, Exim closes the least
16559 recently used file. Note that if you are using the &'ndbm'& library, it
16560 actually opens two files for each logical DBM database, though it still counts
16561 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
16562 open files"& errors with NDBM, you need to reduce the value of
16563 &%lookup_open_max%&.
16566 .option max_username_length main integer 0
16567 .cindex "length of login name"
16568 .cindex "user name" "maximum length"
16569 .cindex "limit" "user name length"
16570 Some operating systems are broken in that they truncate long arguments to
16571 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
16572 this option is set greater than zero, any attempt to call &[getpwnam()]& with
16573 an argument that is longer behaves as if &[getpwnam()]& failed.
16576 .option message_body_newlines main bool false
16577 .cindex "message body" "newlines in variables"
16578 .cindex "newline" "in message body variables"
16579 .vindex "&$message_body$&"
16580 .vindex "&$message_body_end$&"
16581 By default, newlines in the message body are replaced by spaces when setting
16582 the &$message_body$& and &$message_body_end$& expansion variables. If this
16583 option is set true, this no longer happens.
16586 .option message_body_visible main integer 500
16587 .cindex "body of message" "visible size"
16588 .cindex "message body" "visible size"
16589 .vindex "&$message_body$&"
16590 .vindex "&$message_body_end$&"
16591 This option specifies how much of a message's body is to be included in the
16592 &$message_body$& and &$message_body_end$& expansion variables.
16595 .option message_id_header_domain main string&!! unset
16596 .cindex "&'Message-ID:'& header line"
16597 If this option is set, the string is expanded and used as the right hand side
16598 (domain) of the &'Message-ID:'& header that Exim creates if a
16599 locally-originated incoming message does not have one. &"Locally-originated"&
16600 means &"not received over TCP/IP."&
16601 Otherwise, the primary host name is used.
16602 Only letters, digits, dot and hyphen are accepted; any other characters are
16603 replaced by hyphens. If the expansion is forced to fail, or if the result is an
16604 empty string, the option is ignored.
16607 .option message_id_header_text main string&!! unset
16608 If this variable is set, the string is expanded and used to augment the text of
16609 the &'Message-id:'& header that Exim creates if a locally-originated incoming
16610 message does not have one. The text of this header is required by RFC 2822 to
16611 take the form of an address. By default, Exim uses its internal message id as
16612 the local part, and the primary host name as the domain. If this option is set,
16613 it is expanded, and provided the expansion is not forced to fail, and does not
16614 yield an empty string, the result is inserted into the header immediately
16615 before the @, separated from the internal message id by a dot. Any characters
16616 that are illegal in an address are automatically converted into hyphens. This
16617 means that variables such as &$tod_log$& can be used, because the spaces and
16618 colons will become hyphens.
16621 .option message_logs main boolean true
16622 .cindex "message logs" "disabling"
16623 .cindex "log" "message log; disabling"
16624 If this option is turned off, per-message log files are not created in the
16625 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
16626 Exim, by reducing the number of files involved in handling a message from a
16627 minimum of four (header spool file, body spool file, delivery journal, and
16628 per-message log) to three. The other major I/O activity is Exim's main log,
16629 which is not affected by this option.
16632 .option message_size_limit main string&!! 50M
16633 .cindex "message" "size limit"
16634 .cindex "limit" "message size"
16635 .cindex "size" "of message, limit"
16636 This option limits the maximum size of message that Exim will process. The
16637 value is expanded for each incoming connection so, for example, it can be made
16638 to depend on the IP address of the remote host for messages arriving via
16639 TCP/IP. After expansion, the value must be a sequence of decimal digits,
16640 optionally followed by K or M.
16642 .cindex "SIZE" "ESMTP extension, advertising"
16643 .cindex "ESMTP extensions" SIZE
16644 If nonzero the value will be advertised as a parameter to the ESMTP SIZE
16645 service extension keyword.
16647 &*Note*&: This limit cannot be made to depend on a message's sender or any
16648 other properties of an individual message, because it has to be advertised in
16649 the server's response to EHLO. String expansion failure causes a temporary
16650 error. A value of zero means no limit, but its use is not recommended. See also
16651 &%bounce_return_size_limit%&.
16653 Incoming SMTP messages are failed with a 552 error if the limit is
16654 exceeded; locally-generated messages either get a stderr message or a delivery
16655 failure message to the sender, depending on the &%-oe%& setting. Rejection of
16656 an oversized message is logged in both the main and the reject logs. See also
16657 the generic transport option &%message_size_limit%&, which limits the size of
16658 message that an individual transport can process.
16660 If you use a virus-scanner and set this option to to a value larger than the
16661 maximum size that your virus-scanner is configured to support, you may get
16662 failures triggered by large mails. The right size to configure for the
16663 virus-scanner depends upon what data is passed and the options in use but it's
16664 probably safest to just set it to a little larger than this value. E.g., with a
16665 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
16666 some problems may result.
16668 A value of 0 will disable size limit checking; Exim will still advertise the
16669 SIZE extension in an EHLO response, but without a limit, so as to permit
16670 SMTP clients to still indicate the message size along with the MAIL verb.
16673 .option move_frozen_messages main boolean false
16674 .cindex "frozen messages" "moving"
16675 This option, which is available only if Exim has been built with the setting
16677 SUPPORT_MOVE_FROZEN_MESSAGES=yes
16679 in &_Local/Makefile_&, causes frozen messages and their message logs to be
16680 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
16681 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
16682 standard utilities for handling such moved messages, and they do not show up in
16683 lists generated by &%-bp%& or by the Exim monitor.
16686 .option mua_wrapper main boolean false
16687 Setting this option true causes Exim to run in a very restrictive mode in which
16688 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
16689 contains a full description of this facility.
16693 .option mysql_servers main "string list" unset
16694 .cindex "MySQL" "server list"
16695 This option provides a list of MySQL servers and associated connection data, to
16696 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
16697 option is available only if Exim has been built with MySQL support.
16700 .option never_users main "string list&!!" unset
16701 This option is expanded just once, at the start of Exim's processing. Local
16702 message deliveries are normally run in processes that are setuid to the
16703 recipient, and remote deliveries are normally run under Exim's own uid and gid.
16704 It is usually desirable to prevent any deliveries from running as root, as a
16707 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
16708 list of users that must not be used for local deliveries. This list is fixed in
16709 the binary and cannot be overridden by the configuration file. By default, it
16710 contains just the single user name &"root"&. The &%never_users%& runtime option
16711 can be used to add more users to the fixed list.
16713 If a message is to be delivered as one of the users on the fixed list or the
16714 &%never_users%& list, an error occurs, and delivery is deferred. A common
16717 never_users = root:daemon:bin
16719 Including root is redundant if it is also on the fixed list, but it does no
16720 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
16724 .option notifier_socket main string "$spool_directory/exim_daemon_notify"
16725 This option gives the name for a unix-domain socket on which the daemon
16726 listens for work and information-requests.
16727 Only installations running multiple daemons sharing a spool directory
16728 should need to modify the default.
16730 The option is expanded before use.
16731 If the platform supports Linux-style abstract socket names, the result
16732 is used with a nul byte prefixed.
16734 .new "if nonempty,"
16735 it should be a full path name and use a directory accessible
16739 If this option is set as empty,
16740 or the command line &%-oY%& option is used, or
16742 the command line uses a &%-oX%& option and does not use &%-oP%&,
16743 then a notifier socket is not created.
16746 .option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation"
16747 .cindex "OpenSSL "compatibility options"
16748 This option allows an administrator to adjust the SSL options applied
16749 by OpenSSL to connections. It is given as a space-separated list of items,
16750 each one to be +added or -subtracted from the current value.
16752 This option is only available if Exim is built against OpenSSL. The values
16753 available for this option vary according to the age of your OpenSSL install.
16754 The &"all"& value controls a subset of flags which are available, typically
16755 the bug workaround options. The &'SSL_CTX_set_options'& man page will
16756 list the values known on your system and Exim should support all the
16757 &"bug workaround"& options and many of the &"modifying"& options. The Exim
16758 names lose the leading &"SSL_OP_"& and are lower-cased.
16760 Note that adjusting the options can have severe impact upon the security of
16761 SSL as used by Exim. It is possible to disable safety checks and shoot
16762 yourself in the foot in various unpleasant ways. This option should not be
16763 adjusted lightly. An unrecognised item will be detected at startup, by
16764 invoking Exim with the &%-bV%& flag.
16766 The option affects Exim operating both as a server and as a client.
16768 Historical note: prior to release 4.80, Exim defaulted this value to
16769 "+dont_insert_empty_fragments", which may still be needed for compatibility
16770 with some clients, but which lowers security by increasing exposure to
16771 some now infamous attacks.
16775 # Make both old MS and old Eudora happy:
16776 openssl_options = -all +microsoft_big_sslv3_buffer \
16777 +dont_insert_empty_fragments
16779 # Disable older protocol versions:
16780 openssl_options = +no_sslv2 +no_sslv3
16783 Possible options may include:
16787 &`allow_unsafe_legacy_renegotiation`&
16789 &`cipher_server_preference`&
16791 &`dont_insert_empty_fragments`&
16795 &`legacy_server_connect`&
16797 &`microsoft_big_sslv3_buffer`&
16799 &`microsoft_sess_id_bug`&
16801 &`msie_sslv2_rsa_padding`&
16803 &`netscape_challenge_bug`&
16805 &`netscape_reuse_cipher_change_bug`&
16809 &`no_session_resumption_on_renegotiation`&
16823 &`safari_ecdhe_ecdsa_bug`&
16827 &`single_ecdh_use`&
16829 &`ssleay_080_client_dh_bug`&
16831 &`sslref2_reuse_cert_type_bug`&
16833 &`tls_block_padding_bug`&
16837 &`tls_rollback_bug`&
16840 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
16841 all clients connecting using the MacOS SecureTransport TLS facility prior
16842 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
16843 to negotiate TLS then this option value might help, provided that your OpenSSL
16844 release is new enough to contain this work-around. This may be a situation
16845 where you have to upgrade OpenSSL to get buggy clients working.
16848 .option oracle_servers main "string list" unset
16849 .cindex "Oracle" "server list"
16850 This option provides a list of Oracle servers and associated connection data,
16851 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
16852 The option is available only if Exim has been built with Oracle support.
16855 .option percent_hack_domains main "domain list&!!" unset
16856 .cindex "&""percent hack""&"
16857 .cindex "source routing" "in email address"
16858 .cindex "address" "source-routed"
16859 The &"percent hack"& is the convention whereby a local part containing a
16860 percent sign is re-interpreted as a new email address, with the percent
16861 replaced by @. This is sometimes called &"source routing"&, though that term is
16862 also applied to RFC 2822 addresses that begin with an @ character. If this
16863 option is set, Exim implements the percent facility for those domains listed,
16864 but no others. This happens before an incoming SMTP address is tested against
16867 &*Warning*&: The &"percent hack"& has often been abused by people who are
16868 trying to get round relaying restrictions. For this reason, it is best avoided
16869 if at all possible. Unfortunately, a number of less security-conscious MTAs
16870 implement it unconditionally. If you are running Exim on a gateway host, and
16871 routing mail through to internal MTAs without processing the local parts, it is
16872 a good idea to reject recipient addresses with percent characters in their
16873 local parts. Exim's default configuration does this.
16876 .option perl_at_start main boolean false
16878 This option is available only when Exim is built with an embedded Perl
16879 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16882 .option perl_startup main string unset
16884 This option is available only when Exim is built with an embedded Perl
16885 interpreter. See chapter &<<CHAPperl>>& for details of its use.
16887 .option perl_taintmode main boolean false
16889 This option enables the taint mode of the embedded Perl interpreter.
16892 .option pgsql_servers main "string list" unset
16893 .cindex "PostgreSQL lookup type" "server list"
16894 This option provides a list of PostgreSQL servers and associated connection
16895 data, to be used in conjunction with &(pgsql)& lookups (see section
16896 &<<SECID72>>&). The option is available only if Exim has been built with
16897 PostgreSQL support.
16900 .option pid_file_path main string&!! "set at compile time"
16901 .cindex "daemon" "pid file path"
16902 .cindex "pid file, path for"
16903 This option sets the name of the file to which the Exim daemon writes its
16904 process id. The string is expanded, so it can contain, for example, references
16907 pid_file_path = /var/log/$primary_hostname/exim.pid
16909 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
16911 The value set by the option can be overridden by the &%-oP%& command line
16912 option. A pid file is not written if a &"non-standard"& daemon is run by means
16913 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
16916 .option pipelining_advertise_hosts main "host list&!!" *
16917 .cindex "PIPELINING" "suppressing advertising"
16918 .cindex "ESMTP extensions" PIPELINING
16919 This option can be used to suppress the advertisement of the SMTP
16920 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
16921 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
16922 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
16923 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
16924 that clients will use it; &"out of order"& commands that are &"expected"& do
16925 not count as protocol errors (see &%smtp_max_synprot_errors%&).
16927 .option pipelining_connect_advertise_hosts main "host list&!!" *
16928 .cindex "pipelining" "early connection"
16929 .cindex "pipelining" PIPE_CONNECT
16930 .cindex "ESMTP extensions" X_PIPE_CONNECT
16931 If Exim is built with the SUPPORT_PIPE_CONNECT build option
16932 this option controls which hosts the facility is advertised to
16933 and from which pipeline early-connection (before MAIL) SMTP
16934 commands are acceptable.
16935 When used, the pipelining saves on roundtrip times.
16937 See also the &%hosts_pipe_connect%& smtp transport option.
16939 Currently the option name &"X_PIPE_CONNECT"& is used.
16942 .option prdr_enable main boolean false
16943 .cindex "PRDR" "enabling on server"
16944 .cindex "ESMTP extensions" PRDR
16945 This option can be used to enable the Per-Recipient Data Response extension
16946 to SMTP, defined by Eric Hall.
16947 If the option is set, PRDR is advertised by Exim when operating as a server.
16948 If the client requests PRDR, and more than one recipient, for a message
16949 an additional ACL is called for each recipient after the message content
16950 is received. See section &<<SECTPRDRACL>>&.
16952 .option preserve_message_logs main boolean false
16953 .cindex "message logs" "preserving"
16954 If this option is set, message log files are not deleted when messages are
16955 completed. Instead, they are moved to a sub-directory of the spool directory
16956 called &_msglog.OLD_&, where they remain available for statistical or debugging
16957 purposes. This is a dangerous option to set on systems with any appreciable
16958 volume of mail. Use with care!
16961 .option primary_hostname main string "see below"
16962 .cindex "name" "of local host"
16963 .cindex "host" "name of local"
16964 .cindex "local host" "name of"
16965 .vindex "&$primary_hostname$&"
16966 This specifies the name of the current host. It is used in the default EHLO or
16967 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
16968 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
16969 The value is also used by default in some SMTP response messages from an Exim
16970 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
16972 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
16973 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
16974 contains only one component, Exim passes it to &[gethostbyname()]& (or
16975 &[getipnodebyname()]& when available) in order to obtain the fully qualified
16976 version. The variable &$primary_hostname$& contains the host name, whether set
16977 explicitly by this option, or defaulted.
16980 .option print_topbitchars main boolean false
16981 .cindex "printing characters"
16982 .cindex "8-bit characters"
16983 By default, Exim considers only those characters whose codes lie in the range
16984 32&--126 to be printing characters. In a number of circumstances (for example,
16985 when writing log entries) non-printing characters are converted into escape
16986 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
16987 is set, code values of 128 and above are also considered to be printing
16990 This option also affects the header syntax checks performed by the
16991 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
16992 the user's full name when constructing From: and Sender: addresses (as
16993 described in section &<<SECTconstr>>&). Setting this option can cause
16994 Exim to generate eight bit message headers that do not conform to the
16998 .option process_log_path main string unset
16999 .cindex "process log path"
17000 .cindex "log" "process log"
17001 .cindex "&'exiwhat'&"
17002 This option sets the name of the file to which an Exim process writes its
17003 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
17004 utility script. If this option is unset, the file called &_exim-process.info_&
17005 in Exim's spool directory is used. The ability to specify the name explicitly
17006 can be useful in environments where two different Exims are running, using
17007 different spool directories.
17010 .option prod_requires_admin main boolean true
17011 .cindex "restricting access to features"
17015 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
17016 admin user unless &%prod_requires_admin%& is set false. See also
17017 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
17020 .option qualify_domain main string "see below"
17021 .cindex "domain" "for qualifying addresses"
17022 .cindex "address" "qualification"
17023 This option specifies the domain name that is added to any envelope sender
17024 addresses that do not have a domain qualification. It also applies to
17025 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
17026 are accepted by default only for locally-generated messages. Qualification is
17027 also applied to addresses in header lines such as &'From:'& and &'To:'& for
17028 locally-generated messages, unless the &%-bnq%& command line option is used.
17030 Messages from external sources must always contain fully qualified addresses,
17031 unless the sending host matches &%sender_unqualified_hosts%& or
17032 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
17033 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
17034 necessary. Internally, Exim always works with fully qualified envelope
17035 addresses. If &%qualify_domain%& is not set, it defaults to the
17036 &%primary_hostname%& value.
17039 .option qualify_recipient main string "see below"
17040 This option allows you to specify a different domain for qualifying recipient
17041 addresses to the one that is used for senders. See &%qualify_domain%& above.
17045 .option queue_domains main "domain list&!!" unset
17046 .cindex "domain" "specifying non-immediate delivery"
17047 .cindex "queueing incoming messages"
17048 .cindex "message" "queueing certain domains"
17049 This option lists domains for which immediate delivery is not required.
17050 A delivery process is started whenever a message is received, but only those
17051 domains that do not match are processed. All other deliveries wait until the
17052 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
17056 .option queue_fast_ramp main boolean false
17057 .cindex "queue runner" "two phase"
17058 .cindex "queue" "double scanning"
17059 If set to true, two-phase queue runs, initiated using &%-qq%& on the
17060 command line, may start parallel delivery processes during their first
17061 phase. This will be done when a threshold number of messages have been
17062 routed for a single host.
17066 .option queue_list_requires_admin main boolean true
17067 .cindex "restricting access to features"
17069 The &%-bp%& command-line option, which lists the messages that are on the
17070 queue, requires the caller to be an admin user unless
17071 &%queue_list_requires_admin%& is set false.
17072 See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
17075 .option queue_only main boolean false
17076 .cindex "queueing incoming messages"
17077 .cindex "message" "queueing unconditionally"
17078 If &%queue_only%& is set, a delivery process is not automatically started
17079 whenever a message is received. Instead, the message waits in the queue for the
17080 next queue run. Even if &%queue_only%& is false, incoming messages may not get
17081 delivered immediately when certain conditions (such as heavy load) occur.
17083 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
17084 and &%-odi%& command line options override &%queue_only%& unless
17085 &%queue_only_override%& is set false. See also &%queue_only_file%&,
17086 &%queue_only_load%&, and &%smtp_accept_queue%&.
17089 .option queue_only_file main string unset
17090 .cindex "queueing incoming messages"
17091 .cindex "message" "queueing by file existence"
17092 This option can be set to a colon-separated list of absolute path names, each
17093 one optionally preceded by &"smtp"&. When Exim is receiving a message,
17094 it tests for the existence of each listed path using a call to &[stat()]&. For
17095 each path that exists, the corresponding queueing option is set.
17096 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
17097 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
17099 queue_only_file = smtp/some/file
17101 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
17102 &_/some/file_& exists.
17105 .option queue_only_load main fixed-point unset
17106 .cindex "load average"
17107 .cindex "queueing incoming messages"
17108 .cindex "message" "queueing by load"
17109 If the system load average is higher than this value, incoming messages from
17110 all sources are queued, and no automatic deliveries are started. If this
17111 happens during local or remote SMTP input, all subsequent messages received on
17112 the same SMTP connection are queued by default, whatever happens to the load in
17113 the meantime, but this can be changed by setting &%queue_only_load_latch%&
17116 Deliveries will subsequently be performed by queue runner processes. This
17117 option has no effect on ancient operating systems on which Exim cannot
17118 determine the load average. See also &%deliver_queue_load_max%& and
17119 &%smtp_load_reserve%&.
17122 .option queue_only_load_latch main boolean true
17123 .cindex "load average" "re-evaluating per message"
17124 When this option is true (the default), once one message has been queued
17125 because the load average is higher than the value set by &%queue_only_load%&,
17126 all subsequent messages received on the same SMTP connection are also queued.
17127 This is a deliberate choice; even though the load average may fall below the
17128 threshold, it doesn't seem right to deliver later messages on the same
17129 connection when not delivering earlier ones. However, there are special
17130 circumstances such as very long-lived connections from scanning appliances
17131 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
17132 should be set false. This causes the value of the load average to be
17133 re-evaluated for each message.
17136 .option queue_only_override main boolean true
17137 .cindex "queueing incoming messages"
17138 When this option is true, the &%-od%&&'x'& command line options override the
17139 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
17140 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
17141 to override; they are accepted, but ignored.
17144 .option queue_run_in_order main boolean false
17145 .cindex "queue runner" "processing messages in order"
17146 If this option is set, queue runs happen in order of message arrival instead of
17147 in an arbitrary order. For this to happen, a complete list of the entire queue
17148 must be set up before the deliveries start. When the queue is all held in a
17149 single directory (the default), a single list is created for both the ordered
17150 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
17151 single list is not created when &%queue_run_in_order%& is false. In this case,
17152 the sub-directories are processed one at a time (in a random order), and this
17153 avoids setting up one huge list for the whole queue. Thus, setting
17154 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
17155 when the queue is large, because of the extra work in setting up the single,
17156 large list. In most situations, &%queue_run_in_order%& should not be set.
17160 .option queue_run_max main integer&!! 5
17161 .cindex "queue runner" "maximum number of"
17162 This controls the maximum number of queue runner processes that an Exim daemon
17163 can run simultaneously. This does not mean that it starts them all at once,
17164 but rather that if the maximum number are still running when the time comes to
17165 start another one, it refrains from starting another one. This can happen with
17166 very large queues and/or very sluggish deliveries. This option does not,
17167 however, interlock with other processes, so additional queue runners can be
17168 started by other means, or by killing and restarting the daemon.
17170 Setting this option to zero does not suppress queue runs; rather, it disables
17171 the limit, allowing any number of simultaneous queue runner processes to be
17172 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
17173 the daemon's command line.
17175 .cindex queues named
17176 .cindex "named queues" "resource limit"
17177 To set limits for different named queues use
17178 an expansion depending on the &$queue_name$& variable.
17180 .option queue_smtp_domains main "domain list&!!" unset
17181 .cindex "queueing incoming messages"
17182 .cindex "message" "queueing remote deliveries"
17183 .cindex "first pass routing"
17184 When this option is set, a delivery process is started whenever a message is
17185 received, routing is performed, and local deliveries take place.
17186 However, if any SMTP deliveries are required for domains that match
17187 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
17188 message waits in the queue for the next queue run. Since routing of the message
17189 has taken place, Exim knows to which remote hosts it must be delivered, and so
17190 when the queue run happens, multiple messages for the same host are delivered
17191 over a single SMTP connection. The &%-odqs%& command line option causes all
17192 SMTP deliveries to be queued in this way, and is equivalent to setting
17193 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
17197 .option receive_timeout main time 0s
17198 .cindex "timeout" "for non-SMTP input"
17199 This option sets the timeout for accepting a non-SMTP message, that is, the
17200 maximum time that Exim waits when reading a message on the standard input. If
17201 the value is zero, it will wait forever. This setting is overridden by the
17202 &%-or%& command line option. The timeout for incoming SMTP messages is
17203 controlled by &%smtp_receive_timeout%&.
17205 .option received_header_text main string&!! "see below"
17206 .cindex "customizing" "&'Received:'& header"
17207 .cindex "&'Received:'& header line" "customizing"
17208 This string defines the contents of the &'Received:'& message header that is
17209 added to each message, except for the timestamp, which is automatically added
17210 on at the end (preceded by a semicolon). The string is expanded each time it is
17211 used. If the expansion yields an empty string, no &'Received:'& header line is
17212 added to the message. Otherwise, the string should start with the text
17213 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
17215 The default setting is:
17218 received_header_text = Received: \
17219 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
17220 {${if def:sender_ident \
17221 {from ${quote_local_part:$sender_ident} }}\
17222 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
17223 by $primary_hostname \
17224 ${if def:received_protocol {with $received_protocol }}\
17225 ${if def:tls_in_ver { ($tls_in_ver)}}\
17226 ${if def:tls_in_cipher_std { tls $tls_in_cipher_std\n\t}}\
17227 (Exim $version_number)\n\t\
17228 ${if def:sender_address \
17229 {(envelope-from <$sender_address>)\n\t}}\
17230 id $message_exim_id\
17231 ${if def:received_for {\n\tfor $received_for}}
17234 The references to the TLS version and cipher are
17235 omitted when Exim is built without TLS
17236 support. The use of conditional expansions ensures that this works for both
17237 locally generated messages and messages received from remote hosts, giving
17238 header lines such as the following:
17240 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
17241 by marley.carol.example with esmtp (Exim 4.00)
17242 (envelope-from <bob@carol.example>)
17243 id 16IOWa-00019l-00
17244 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
17245 Received: by scrooge.carol.example with local (Exim 4.00)
17246 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
17248 Until the body of the message has been received, the timestamp is the time when
17249 the message started to be received. Once the body has arrived, and all policy
17250 checks have taken place, the timestamp is updated to the time at which the
17251 message was accepted.
17254 .option received_headers_max main integer 30
17255 .cindex "loop" "prevention"
17256 .cindex "mail loop prevention"
17257 .cindex "&'Received:'& header line" "counting"
17258 When a message is to be delivered, the number of &'Received:'& headers is
17259 counted, and if it is greater than this parameter, a mail loop is assumed to
17260 have occurred, the delivery is abandoned, and an error message is generated.
17261 This applies to both local and remote deliveries.
17264 .option recipient_unqualified_hosts main "host list&!!" unset
17265 .cindex "unqualified addresses"
17266 .cindex "host" "unqualified addresses from"
17267 This option lists those hosts from which Exim is prepared to accept unqualified
17268 recipient addresses in message envelopes. The addresses are made fully
17269 qualified by the addition of the &%qualify_recipient%& value. This option also
17270 affects message header lines. Exim does not reject unqualified recipient
17271 addresses in headers, but it qualifies them only if the message came from a
17272 host that matches &%recipient_unqualified_hosts%&,
17273 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
17274 option was not set.
17277 .option recipients_max main integer 0
17278 .cindex "limit" "number of recipients"
17279 .cindex "recipient" "maximum number"
17280 If this option is set greater than zero, it specifies the maximum number of
17281 original recipients for any message. Additional recipients that are generated
17282 by aliasing or forwarding do not count. SMTP messages get a 452 response for
17283 all recipients over the limit; earlier recipients are delivered as normal.
17284 Non-SMTP messages with too many recipients are failed, and no deliveries are
17287 .cindex "RCPT" "maximum number of incoming"
17288 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
17289 RCPT commands in a single message.
17292 .option recipients_max_reject main boolean false
17293 If this option is set true, Exim rejects SMTP messages containing too many
17294 recipients by giving 552 errors to the surplus RCPT commands, and a 554
17295 error to the eventual DATA command. Otherwise (the default) it gives a 452
17296 error to the surplus RCPT commands and accepts the message on behalf of the
17297 initial set of recipients. The remote server should then re-send the message
17298 for the remaining recipients at a later time.
17301 .option remote_max_parallel main integer 2
17302 .cindex "delivery" "parallelism for remote"
17303 This option controls parallel delivery of one message to a number of remote
17304 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
17305 does all the remote deliveries for a message one by one. Otherwise, if a single
17306 message has to be delivered to more than one remote host, or if several copies
17307 have to be sent to the same remote host, up to &%remote_max_parallel%&
17308 deliveries are done simultaneously. If more than &%remote_max_parallel%&
17309 deliveries are required, the maximum number of processes are started, and as
17310 each one finishes, another is begun. The order of starting processes is the
17311 same as if sequential delivery were being done, and can be controlled by the
17312 &%remote_sort_domains%& option. If parallel delivery takes place while running
17313 with debugging turned on, the debugging output from each delivery process is
17314 tagged with its process id.
17316 This option controls only the maximum number of parallel deliveries for one
17317 message in one Exim delivery process. Because Exim has no central queue
17318 manager, there is no way of controlling the total number of simultaneous
17319 deliveries if the configuration allows a delivery attempt as soon as a message
17322 See also the &%max_parallel%& generic transport option,
17323 and the &%serialize_hosts%& smtp transport option.
17325 .cindex "number of deliveries"
17326 .cindex "delivery" "maximum number of"
17327 If you want to control the total number of deliveries on the system, you
17328 need to set the &%queue_only%& option. This ensures that all incoming messages
17329 are added to the queue without starting a delivery process. Then set up an Exim
17330 daemon to start queue runner processes at appropriate intervals (probably
17331 fairly often, for example, every minute), and limit the total number of queue
17332 runners by setting the &%queue_run_max%& parameter. Because each queue runner
17333 delivers only one message at a time, the maximum number of deliveries that can
17334 then take place at once is &%queue_run_max%& multiplied by
17335 &%remote_max_parallel%&.
17337 If it is purely remote deliveries you want to control, use
17338 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
17339 doing the SMTP routing before queueing, so that several messages for the same
17340 host will eventually get delivered down the same connection.
17343 .option remote_sort_domains main "domain list&!!" unset
17344 .cindex "sorting remote deliveries"
17345 .cindex "delivery" "sorting remote"
17346 When there are a number of remote deliveries for a message, they are sorted by
17347 domain into the order given by this list. For example,
17349 remote_sort_domains = *.cam.ac.uk:*.uk
17351 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
17352 then to those in the &%uk%& domain, then to any others.
17355 .option retry_data_expire main time 7d
17356 .cindex "hints database" "data expiry"
17357 This option sets a &"use before"& time on retry information in Exim's hints
17358 database. Any older retry data is ignored. This means that, for example, once a
17359 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
17363 .option retry_interval_max main time 24h
17364 .cindex "retry" "limit on interval"
17365 .cindex "limit" "on retry interval"
17366 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
17367 intervals between delivery attempts for messages that cannot be delivered
17368 straight away. This option sets an overall limit to the length of time between
17369 retries. It cannot be set greater than 24 hours; any attempt to do so forces
17373 .option return_path_remove main boolean true
17374 .cindex "&'Return-path:'& header line" "removing"
17375 RFC 2821, section 4.4, states that an SMTP server must insert a
17376 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
17377 The &'Return-path:'& header preserves the sender address as received in the
17378 MAIL command. This description implies that this header should not be present
17379 in an incoming message. If &%return_path_remove%& is true, any existing
17380 &'Return-path:'& headers are removed from messages at the time they are
17381 received. Exim's transports have options for adding &'Return-path:'& headers at
17382 the time of delivery. They are normally used only for final local deliveries.
17385 .option return_size_limit main integer 100K
17386 This option is an obsolete synonym for &%bounce_return_size_limit%&.
17389 .option rfc1413_hosts main "host list&!!" @[]
17391 .cindex "host" "for RFC 1413 calls"
17392 RFC 1413 identification calls are made to any client host which matches
17393 an item in the list.
17394 The default value specifies just this host, being any local interface
17397 .option rfc1413_query_timeout main time 0s
17398 .cindex "RFC 1413" "query timeout"
17399 .cindex "timeout" "for RFC 1413 call"
17400 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
17401 no RFC 1413 calls are ever made.
17404 .option sender_unqualified_hosts main "host list&!!" unset
17405 .cindex "unqualified addresses"
17406 .cindex "host" "unqualified addresses from"
17407 This option lists those hosts from which Exim is prepared to accept unqualified
17408 sender addresses. The addresses are made fully qualified by the addition of
17409 &%qualify_domain%&. This option also affects message header lines. Exim does
17410 not reject unqualified addresses in headers that contain sender addresses, but
17411 it qualifies them only if the message came from a host that matches
17412 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
17413 using TCP/IP), and the &%-bnq%& option was not set.
17416 .option slow_lookup_log main integer 0
17417 .cindex "logging" "slow lookups"
17418 .cindex "dns" "logging slow lookups"
17419 This option controls logging of slow lookups.
17420 If the value is nonzero it is taken as a number of milliseconds
17421 and lookups taking longer than this are logged.
17422 Currently this applies only to DNS lookups.
17426 .option smtp_accept_keepalive main boolean true
17427 .cindex "keepalive" "on incoming connection"
17428 This option controls the setting of the SO_KEEPALIVE option on incoming
17429 TCP/IP socket connections. When set, it causes the kernel to probe idle
17430 connections periodically, by sending packets with &"old"& sequence numbers. The
17431 other end of the connection should send an acknowledgment if the connection is
17432 still okay or a reset if the connection has been aborted. The reason for doing
17433 this is that it has the beneficial effect of freeing up certain types of
17434 connection that can get stuck when the remote host is disconnected without
17435 tidying up the TCP/IP call properly. The keepalive mechanism takes several
17436 hours to detect unreachable hosts.
17440 .option smtp_accept_max main integer 20
17441 .cindex "limit" "incoming SMTP connections"
17442 .cindex "SMTP" "incoming connection count"
17444 This option specifies the maximum number of simultaneous incoming SMTP calls
17445 that Exim will accept. It applies only to the listening daemon; there is no
17446 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
17447 value is set to zero, no limit is applied. However, it is required to be
17448 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
17449 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
17451 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
17452 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
17453 that limit has not been reached for the client host, &%smtp_accept_reserve%&
17454 and &%smtp_load_reserve%& are then checked before accepting the connection.
17457 .option smtp_accept_max_nonmail main integer 10
17458 .cindex "limit" "non-mail SMTP commands"
17459 .cindex "SMTP" "limiting non-mail commands"
17460 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
17461 the connection if there are too many. This option defines &"too many"&. The
17462 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
17463 client looping sending EHLO, for example. The check is applied only if the
17464 client host matches &%smtp_accept_max_nonmail_hosts%&.
17466 When a new message is expected, one occurrence of RSET is not counted. This
17467 allows a client to send one RSET between messages (this is not necessary,
17468 but some clients do it). Exim also allows one uncounted occurrence of HELO
17469 or EHLO, and one occurrence of STARTTLS between messages. After
17470 starting up a TLS session, another EHLO is expected, and so it too is not
17471 counted. The first occurrence of AUTH in a connection, or immediately
17472 following STARTTLS is not counted. Otherwise, all commands other than
17473 MAIL, RCPT, DATA, and QUIT are counted.
17476 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
17477 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
17478 check by setting this option. The default value makes it apply to all hosts. By
17479 changing the value, you can exclude any badly-behaved hosts that you have to
17483 . Allow this long option name to split; give it unsplit as a fifth argument
17484 . for the automatic .oindex that is generated by .option.
17485 . We insert " &~&~" which is both pretty nasty visually and results in
17486 . non-searchable text. HowItWorks.txt mentions an option for inserting
17487 . zero-width-space, which would be nicer visually and results in (at least)
17488 . html that Firefox will split on when it's forced to reflow (rather than
17489 . inserting a horizontal scrollbar). However, the text is still not
17490 . searchable. NM changed this occurrence for bug 1197 to no longer allow
17491 . the option name to split.
17493 .option "smtp_accept_max_per_connection" main integer 1000 &&&
17494 smtp_accept_max_per_connection
17495 .cindex "SMTP" "limiting incoming message count"
17496 .cindex "limit" "messages per SMTP connection"
17497 The value of this option limits the number of MAIL commands that Exim is
17498 prepared to accept over a single SMTP connection, whether or not each command
17499 results in the transfer of a message. After the limit is reached, a 421
17500 response is given to subsequent MAIL commands. This limit is a safety
17501 precaution against a client that goes mad (incidents of this type have been
17505 .option smtp_accept_max_per_host main string&!! unset
17506 .cindex "limit" "SMTP connections from one host"
17507 .cindex "host" "limiting SMTP connections from"
17508 This option restricts the number of simultaneous IP connections from a single
17509 host (strictly, from a single IP address) to the Exim daemon. The option is
17510 expanded, to enable different limits to be applied to different hosts by
17511 reference to &$sender_host_address$&. Once the limit is reached, additional
17512 connection attempts from the same host are rejected with error code 421. This
17513 is entirely independent of &%smtp_accept_reserve%&. The option's default value
17514 of zero imposes no limit. If this option is set greater than zero, it is
17515 required that &%smtp_accept_max%& be non-zero.
17517 &*Warning*&: When setting this option you should not use any expansion
17518 constructions that take an appreciable amount of time. The expansion and test
17519 happen in the main daemon loop, in order to reject additional connections
17520 without forking additional processes (otherwise a denial-of-service attack
17521 could cause a vast number or processes to be created). While the daemon is
17522 doing this processing, it cannot accept any other incoming connections.
17526 .option smtp_accept_queue main integer 0
17527 .cindex "SMTP" "incoming connection count"
17528 .cindex "queueing incoming messages"
17529 .cindex "message" "queueing by SMTP connection count"
17530 If the number of simultaneous incoming SMTP connections being handled via the
17531 listening daemon exceeds this value, messages received by SMTP are just placed
17532 in the queue; no delivery processes are started automatically. The count is
17533 fixed at the start of an SMTP connection. It cannot be updated in the
17534 subprocess that receives messages, and so the queueing or not queueing applies
17535 to all messages received in the same connection.
17537 A value of zero implies no limit, and clearly any non-zero value is useful only
17538 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
17539 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
17540 various &%-od%&&'x'& command line options.
17543 . See the comment on smtp_accept_max_per_connection
17545 .option "smtp_accept_queue_per_connection" main integer 10 &&&
17546 smtp_accept_queue_per_connection
17547 .cindex "queueing incoming messages"
17548 .cindex "message" "queueing by message count"
17549 This option limits the number of delivery processes that Exim starts
17550 automatically when receiving messages via SMTP, whether via the daemon or by
17551 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
17552 and the number of messages received in a single SMTP session exceeds this
17553 number, subsequent messages are placed in the queue, but no delivery processes
17554 are started. This helps to limit the number of Exim processes when a server
17555 restarts after downtime and there is a lot of mail waiting for it on other
17556 systems. On large systems, the default should probably be increased, and on
17557 dial-in client systems it should probably be set to zero (that is, disabled).
17560 .option smtp_accept_reserve main integer 0
17561 .cindex "SMTP" "incoming call count"
17562 .cindex "host" "reserved"
17563 When &%smtp_accept_max%& is set greater than zero, this option specifies a
17564 number of SMTP connections that are reserved for connections from the hosts
17565 that are specified in &%smtp_reserve_hosts%&. The value set in
17566 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
17567 restricted to this number of connections; the option specifies a minimum number
17568 of connection slots for them, not a maximum. It is a guarantee that this group
17569 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
17570 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
17573 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
17574 set to 5, once there are 45 active connections (from any hosts), new
17575 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
17576 provided the other criteria for acceptance are met.
17579 .option smtp_active_hostname main string&!! unset
17580 .cindex "host" "name in SMTP responses"
17581 .cindex "SMTP" "host name in responses"
17582 .vindex "&$primary_hostname$&"
17583 This option is provided for multi-homed servers that want to masquerade as
17584 several different hosts. At the start of an incoming SMTP connection, its value
17585 is expanded and used instead of the value of &$primary_hostname$& in SMTP
17586 responses. For example, it is used as domain name in the response to an
17587 incoming HELO or EHLO command.
17589 .vindex "&$smtp_active_hostname$&"
17590 The active hostname is placed in the &$smtp_active_hostname$& variable, which
17591 is saved with any messages that are received. It is therefore available for use
17592 in routers and transports when the message is later delivered.
17594 If this option is unset, or if its expansion is forced to fail, or if the
17595 expansion results in an empty string, the value of &$primary_hostname$& is
17596 used. Other expansion failures cause a message to be written to the main and
17597 panic logs, and the SMTP command receives a temporary error. Typically, the
17598 value of &%smtp_active_hostname%& depends on the incoming interface address.
17601 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
17602 {cox.mydomain}{box.mydomain}}
17605 Although &$smtp_active_hostname$& is primarily concerned with incoming
17606 messages, it is also used as the default for HELO commands in callout
17607 verification if there is no remote transport from which to obtain a
17608 &%helo_data%& value.
17610 .option smtp_banner main string&!! "see below"
17611 .cindex "SMTP" "welcome banner"
17612 .cindex "banner for SMTP"
17613 .cindex "welcome banner for SMTP"
17614 .cindex "customizing" "SMTP banner"
17615 This string, which is expanded every time it is used, is output as the initial
17616 positive response to an SMTP connection. The default setting is:
17618 smtp_banner = $smtp_active_hostname ESMTP Exim \
17619 $version_number $tod_full
17621 Failure to expand the string causes a panic error. If you want to create a
17622 multiline response to the initial SMTP connection, use &"\n"& in the string at
17623 appropriate points, but not at the end. Note that the 220 code is not included
17624 in this string. Exim adds it automatically (several times in the case of a
17625 multiline response).
17628 .option smtp_check_spool_space main boolean true
17629 .cindex "checking disk space"
17630 .cindex "disk space, checking"
17631 .cindex "spool directory" "checking space"
17632 When this option is set, if an incoming SMTP session encounters the SIZE
17633 option on a MAIL command, it checks that there is enough space in the
17634 spool directory's partition to accept a message of that size, while still
17635 leaving free the amount specified by &%check_spool_space%& (even if that value
17636 is zero). If there isn't enough space, a temporary error code is returned.
17639 .option smtp_connect_backlog main integer 20
17640 .cindex "connection backlog"
17641 .cindex "SMTP" "connection backlog"
17642 .cindex "backlog of connections"
17643 This option specifies a maximum number of waiting SMTP connections. Exim passes
17644 this value to the TCP/IP system when it sets up its listener. Once this number
17645 of connections are waiting for the daemon's attention, subsequent connection
17646 attempts are refused at the TCP/IP level. At least, that is what the manuals
17647 say; in some circumstances such connection attempts have been observed to time
17648 out instead. For large systems it is probably a good idea to increase the
17649 value (to 50, say). It also gives some protection against denial-of-service
17650 attacks by SYN flooding.
17653 .option smtp_enforce_sync main boolean true
17654 .cindex "SMTP" "synchronization checking"
17655 .cindex "synchronization checking in SMTP"
17656 The SMTP protocol specification requires the client to wait for a response from
17657 the server at certain points in the dialogue. Without PIPELINING these
17658 synchronization points are after every command; with PIPELINING they are
17659 fewer, but they still exist.
17661 Some spamming sites send out a complete set of SMTP commands without waiting
17662 for any response. Exim protects against this by rejecting a message if the
17663 client has sent further input when it should not have. The error response &"554
17664 SMTP synchronization error"& is sent, and the connection is dropped. Testing
17665 for this error cannot be perfect because of transmission delays (unexpected
17666 input may be on its way but not yet received when Exim checks). However, it
17667 does detect many instances.
17669 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
17670 If you want to disable the check selectively (for example, only for certain
17671 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
17672 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
17676 .option smtp_etrn_command main string&!! unset
17677 .cindex "ETRN" "command to be run"
17678 .cindex "ESMTP extensions" ETRN
17679 .vindex "&$domain$&"
17680 If this option is set, the given command is run whenever an SMTP ETRN
17681 command is received from a host that is permitted to issue such commands (see
17682 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
17683 are independently expanded. The expansion variable &$domain$& is set to the
17684 argument of the ETRN command, and no syntax checking is done on it. For
17687 smtp_etrn_command = /etc/etrn_command $domain \
17688 $sender_host_address
17690 If the option is not set, the argument for the ETRN command must
17691 be a &'#'& followed by an address string.
17692 In this case an &'exim -R <string>'& command is used;
17693 if the ETRN ACL has set up a named-queue then &'-MCG <queue>'& is appended.
17695 A new process is created to run the command, but Exim does not wait for it to
17696 complete. Consequently, its status cannot be checked. If the command cannot be
17697 run, a line is written to the panic log, but the ETRN caller still receives
17698 a 250 success response. Exim is normally running under its own uid when
17699 receiving SMTP, so it is not possible for it to change the uid before running
17703 .option smtp_etrn_serialize main boolean true
17704 .cindex "ETRN" "serializing"
17705 When this option is set, it prevents the simultaneous execution of more than
17706 one identical command as a result of ETRN in an SMTP connection. See
17707 section &<<SECTETRN>>& for details.
17710 .option smtp_load_reserve main fixed-point unset
17711 .cindex "load average"
17712 If the system load average ever gets higher than this, incoming SMTP calls are
17713 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
17714 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
17715 the load is over the limit. The option has no effect on ancient operating
17716 systems on which Exim cannot determine the load average. See also
17717 &%deliver_queue_load_max%& and &%queue_only_load%&.
17721 .option smtp_max_synprot_errors main integer 3
17722 .cindex "SMTP" "limiting syntax and protocol errors"
17723 .cindex "limit" "SMTP syntax and protocol errors"
17724 Exim rejects SMTP commands that contain syntax or protocol errors. In
17725 particular, a syntactically invalid email address, as in this command:
17727 RCPT TO:<abc xyz@a.b.c>
17729 causes immediate rejection of the command, before any other tests are done.
17730 (The ACL cannot be run if there is no valid address to set up for it.) An
17731 example of a protocol error is receiving RCPT before MAIL. If there are
17732 too many syntax or protocol errors in one SMTP session, the connection is
17733 dropped. The limit is set by this option.
17735 .cindex "PIPELINING" "expected errors"
17736 When the PIPELINING extension to SMTP is in use, some protocol errors are
17737 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
17738 Exim assumes that PIPELINING will be used if it advertises it (see
17739 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
17740 not count towards the limit.
17744 .option smtp_max_unknown_commands main integer 3
17745 .cindex "SMTP" "limiting unknown commands"
17746 .cindex "limit" "unknown SMTP commands"
17747 If there are too many unrecognized commands in an incoming SMTP session, an
17748 Exim server drops the connection. This is a defence against some kinds of abuse
17751 into making connections to SMTP ports; in these circumstances, a number of
17752 non-SMTP command lines are sent first.
17756 .option smtp_ratelimit_hosts main "host list&!!" unset
17757 .cindex "SMTP" "rate limiting"
17758 .cindex "limit" "rate of message arrival"
17759 .cindex "RCPT" "rate limiting"
17760 Some sites find it helpful to be able to limit the rate at which certain hosts
17761 can send them messages, and the rate at which an individual message can specify
17764 Exim has two rate-limiting facilities. This section describes the older
17765 facility, which can limit rates within a single connection. The newer
17766 &%ratelimit%& ACL condition can limit rates across all connections. See section
17767 &<<SECTratelimiting>>& for details of the newer facility.
17769 When a host matches &%smtp_ratelimit_hosts%&, the values of
17770 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
17771 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
17772 respectively. Each option, if set, must contain a set of four comma-separated
17776 A threshold, before which there is no rate limiting.
17778 An initial time delay. Unlike other times in Exim, numbers with decimal
17779 fractional parts are allowed here.
17781 A factor by which to increase the delay each time.
17783 A maximum value for the delay. This should normally be less than 5 minutes,
17784 because after that time, the client is liable to timeout the SMTP command.
17787 For example, these settings have been used successfully at the site which
17788 first suggested this feature, for controlling mail from their customers:
17790 smtp_ratelimit_mail = 2,0.5s,1.05,4m
17791 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
17793 The first setting specifies delays that are applied to MAIL commands after
17794 two have been received over a single connection. The initial delay is 0.5
17795 seconds, increasing by a factor of 1.05 each time. The second setting applies
17796 delays to RCPT commands when more than four occur in a single message.
17799 .option smtp_ratelimit_mail main string unset
17800 See &%smtp_ratelimit_hosts%& above.
17803 .option smtp_ratelimit_rcpt main string unset
17804 See &%smtp_ratelimit_hosts%& above.
17807 .option smtp_receive_timeout main time&!! 5m
17808 .cindex "timeout" "for SMTP input"
17809 .cindex "SMTP" "input timeout"
17810 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
17811 input, including batch SMTP. If a line of input (either an SMTP command or a
17812 data line) is not received within this time, the SMTP connection is dropped and
17813 the message is abandoned.
17814 A line is written to the log containing one of the following messages:
17816 SMTP command timeout on connection from...
17817 SMTP data timeout on connection from...
17819 The former means that Exim was expecting to read an SMTP command; the latter
17820 means that it was in the DATA phase, reading the contents of a message.
17822 If the first character of the option is a &"$"& the option is
17823 expanded before use and may depend on
17824 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
17828 The value set by this option can be overridden by the
17829 &%-os%& command-line option. A setting of zero time disables the timeout, but
17830 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
17831 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
17832 timeout is controlled by &%receive_timeout%& and &%-or%&.
17835 .option smtp_reserve_hosts main "host list&!!" unset
17836 This option defines hosts for which SMTP connections are reserved; see
17837 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
17840 .option smtp_return_error_details main boolean false
17841 .cindex "SMTP" "details policy failures"
17842 .cindex "policy control" "rejection, returning details"
17843 In the default state, Exim uses bland messages such as
17844 &"Administrative prohibition"& when it rejects SMTP commands for policy
17845 reasons. Many sysadmins like this because it gives away little information
17846 to spammers. However, some other sysadmins who are applying strict checking
17847 policies want to give out much fuller information about failures. Setting
17848 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
17849 example, instead of &"Administrative prohibition"&, it might give:
17851 550-Rejected after DATA: '>' missing at end of address:
17852 550 failing address in "From" header is: <user@dom.ain
17856 .option smtputf8_advertise_hosts main "host list&!!" *
17857 .cindex "SMTPUTF8" "ESMTP extension, advertising"
17858 .cindex "ESMTP extensions" SMTPUTF8
17859 When Exim is built with support for internationalised mail names,
17860 the availability thereof is advertised in
17861 response to EHLO only to those client hosts that match this option. See
17862 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
17865 .option spamd_address main string "127.0.0.1 783"
17866 This option is available when Exim is compiled with the content-scanning
17867 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
17868 See section &<<SECTscanspamass>>& for more details.
17872 .option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
17873 This option is available when Exim is compiled with SPF support.
17874 See section &<<SECSPF>>& for more details.
17876 .option spf_smtp_comment_template main string&!! "Please%_see%_http://www.open-spf.org/Why"
17877 This option is available when Exim is compiled with SPF support. It
17878 allows the customisation of the SMTP comment that the SPF library
17879 generates. You are strongly encouraged to link to your own explanative
17880 site. The template must not contain spaces. If you need spaces in the
17881 output, use the proper placeholder. If libspf2 can not parse the
17882 template, it uses a built-in default broken link. The following placeholders
17883 (along with Exim variables (but see below)) are allowed in the template:
17887 &*%{L}*&: Envelope sender's local part.
17889 &*%{S}*&: Envelope sender.
17891 &*%{O}*&: Envelope sender's domain.
17893 &*%{D}*&: Current(?) domain.
17895 &*%{I}*&: SMTP client Ip.
17897 &*%{C}*&: SMTP client pretty IP.
17899 &*%{T}*&: Epoch time (UTC).
17901 &*%{P}*&: SMTP client domain name.
17903 &*%{V}*&: IP version.
17905 &*%{H}*&: EHLO/HELO domain.
17907 &*%{R}*&: Receiving domain.
17909 The capitalized placeholders do proper URL encoding, if you use them
17910 lowercased, no encoding takes place. This list was compiled from the
17913 A note on using Exim variables: As
17914 currently the SPF library is initialized before the SMTP EHLO phase,
17915 the variables useful for expansion are quite limited.
17918 .option split_spool_directory main boolean false
17919 .cindex "multiple spool directories"
17920 .cindex "spool directory" "split"
17921 .cindex "directories, multiple"
17922 If this option is set, it causes Exim to split its input directory into 62
17923 subdirectories, each with a single alphanumeric character as its name. The
17924 sixth character of the message id is used to allocate messages to
17925 subdirectories; this is the least significant base-62 digit of the time of
17926 arrival of the message.
17928 Splitting up the spool in this way may provide better performance on systems
17929 where there are long mail queues, by reducing the number of files in any one
17930 directory. The msglog directory is also split up in a similar way to the input
17931 directory; however, if &%preserve_message_logs%& is set, all old msglog files
17932 are still placed in the single directory &_msglog.OLD_&.
17934 It is not necessary to take any special action for existing messages when
17935 changing &%split_spool_directory%&. Exim notices messages that are in the
17936 &"wrong"& place, and continues to process them. If the option is turned off
17937 after a period of being on, the subdirectories will eventually empty and be
17938 automatically deleted.
17940 When &%split_spool_directory%& is set, the behaviour of queue runner processes
17941 changes. Instead of creating a list of all messages in the queue, and then
17942 trying to deliver each one, in turn, it constructs a list of those in one
17943 sub-directory and tries to deliver them, before moving on to the next
17944 sub-directory. The sub-directories are processed in a random order. This
17945 spreads out the scanning of the input directories, and uses less memory. It is
17946 particularly beneficial when there are lots of messages in the queue. However,
17947 if &%queue_run_in_order%& is set, none of this new processing happens. The
17948 entire queue has to be scanned and sorted before any deliveries can start.
17951 .option spool_directory main string&!! "set at compile time"
17952 .cindex "spool directory" "path to"
17953 This defines the directory in which Exim keeps its spool, that is, the messages
17954 it is waiting to deliver. The default value is taken from the compile-time
17955 configuration setting, if there is one. If not, this option must be set. The
17956 string is expanded, so it can contain, for example, a reference to
17957 &$primary_hostname$&.
17959 If the spool directory name is fixed on your installation, it is recommended
17960 that you set it at build time rather than from this option, particularly if the
17961 log files are being written to the spool directory (see &%log_file_path%&).
17962 Otherwise log files cannot be used for errors that are detected early on, such
17963 as failures in the configuration file.
17965 By using this option to override the compiled-in path, it is possible to run
17966 tests of Exim without using the standard spool.
17968 .option spool_wireformat main boolean false
17969 .cindex "spool directory" "file formats"
17970 If this option is set, Exim may for some messages use an alternative format
17971 for data-files in the spool which matches the wire format.
17972 Doing this permits more efficient message reception and transmission.
17973 Currently it is only done for messages received using the ESMTP CHUNKING
17976 The following variables will not have useful values:
17978 $max_received_linelength
17983 Users of the local_scan() API (see &<<CHAPlocalscan>>&),
17984 and any external programs which are passed a reference to a message data file
17985 (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
17986 will need to be aware of the different formats potentially available.
17988 Using any of the ACL conditions noted will negate the reception benefit
17989 (as a Unix-mbox-format file is constructed for them).
17990 The transmission benefit is maintained.
17992 .option sqlite_lock_timeout main time 5s
17993 .cindex "sqlite lookup type" "lock timeout"
17994 This option controls the timeout that the &(sqlite)& lookup uses when trying to
17995 access an SQLite database. See section &<<SECTsqlite>>& for more details.
17997 .option strict_acl_vars main boolean false
17998 .cindex "&ACL;" "variables, handling unset"
17999 This option controls what happens if a syntactically valid but undefined ACL
18000 variable is referenced. If it is false (the default), an empty string
18001 is substituted; if it is true, an error is generated. See section
18002 &<<SECTaclvariables>>& for details of ACL variables.
18004 .option strip_excess_angle_brackets main boolean false
18005 .cindex "angle brackets, excess"
18006 If this option is set, redundant pairs of angle brackets round &"route-addr"&
18007 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
18008 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
18009 passed on to another MTA, the excess angle brackets are not passed on. If this
18010 option is not set, multiple pairs of angle brackets cause a syntax error.
18013 .option strip_trailing_dot main boolean false
18014 .cindex "trailing dot on domain"
18015 .cindex "dot" "trailing on domain"
18016 If this option is set, a trailing dot at the end of a domain in an address is
18017 ignored. If this is in the envelope and the message is passed on to another
18018 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
18019 domain causes a syntax error.
18020 However, addresses in header lines are checked only when an ACL requests header
18024 .option syslog_duplication main boolean true
18025 .cindex "syslog" "duplicate log lines; suppressing"
18026 When Exim is logging to syslog, it writes the log lines for its three
18027 separate logs at different syslog priorities so that they can in principle
18028 be separated on the logging hosts. Some installations do not require this
18029 separation, and in those cases, the duplication of certain log lines is a
18030 nuisance. If &%syslog_duplication%& is set false, only one copy of any
18031 particular log line is written to syslog. For lines that normally go to
18032 both the main log and the reject log, the reject log version (possibly
18033 containing message header lines) is written, at LOG_NOTICE priority.
18034 Lines that normally go to both the main and the panic log are written at
18035 the LOG_ALERT priority.
18038 .option syslog_facility main string unset
18039 .cindex "syslog" "facility; setting"
18040 This option sets the syslog &"facility"& name, used when Exim is logging to
18041 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
18042 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
18043 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
18044 details of Exim's logging.
18047 .option syslog_pid main boolean true
18048 .cindex "syslog" "pid"
18049 If &%syslog_pid%& is set false, the PID on Exim's log lines are
18050 omitted when these lines are sent to syslog. (Syslog normally prefixes
18051 the log lines with the PID of the logging process automatically.) You need
18052 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
18053 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
18057 .option syslog_processname main string &`exim`&
18058 .cindex "syslog" "process name; setting"
18059 This option sets the syslog &"ident"& name, used when Exim is logging to
18060 syslog. The value must be no longer than 32 characters. See chapter
18061 &<<CHAPlog>>& for details of Exim's logging.
18065 .option syslog_timestamp main boolean true
18066 .cindex "syslog" "timestamps"
18067 .cindex timestamps syslog
18068 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
18069 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
18070 details of Exim's logging.
18073 .option system_filter main string&!! unset
18074 .cindex "filter" "system filter"
18075 .cindex "system filter" "specifying"
18076 .cindex "Sieve filter" "not available for system filter"
18077 This option specifies an Exim filter file that is applied to all messages at
18078 the start of each delivery attempt, before any routing is done. System filters
18079 must be Exim filters; they cannot be Sieve filters. If the system filter
18080 generates any deliveries to files or pipes, or any new mail messages, the
18081 appropriate &%system_filter_..._transport%& option(s) must be set, to define
18082 which transports are to be used. Details of this facility are given in chapter
18083 &<<CHAPsystemfilter>>&.
18084 A forced expansion failure results in no filter operation.
18087 .option system_filter_directory_transport main string&!! unset
18088 .vindex "&$address_file$&"
18089 This sets the name of the transport driver that is to be used when the
18090 &%save%& command in a system message filter specifies a path ending in &"/"&,
18091 implying delivery of each message into a separate file in some directory.
18092 During the delivery, the variable &$address_file$& contains the path name.
18095 .option system_filter_file_transport main string&!! unset
18096 .cindex "file" "transport for system filter"
18097 This sets the name of the transport driver that is to be used when the &%save%&
18098 command in a system message filter specifies a path not ending in &"/"&. During
18099 the delivery, the variable &$address_file$& contains the path name.
18101 .option system_filter_group main string unset
18102 .cindex "gid (group id)" "system filter"
18103 This option is used only when &%system_filter_user%& is also set. It sets the
18104 gid under which the system filter is run, overriding any gid that is associated
18105 with the user. The value may be numerical or symbolic.
18107 .option system_filter_pipe_transport main string&!! unset
18108 .cindex "&(pipe)& transport" "for system filter"
18109 .vindex "&$address_pipe$&"
18110 This specifies the transport driver that is to be used when a &%pipe%& command
18111 is used in a system filter. During the delivery, the variable &$address_pipe$&
18112 contains the pipe command.
18115 .option system_filter_reply_transport main string&!! unset
18116 .cindex "&(autoreply)& transport" "for system filter"
18117 This specifies the transport driver that is to be used when a &%mail%& command
18118 is used in a system filter.
18121 .option system_filter_user main string unset
18122 .cindex "uid (user id)" "system filter"
18123 If this option is set to root, the system filter is run in the main Exim
18124 delivery process, as root. Otherwise, the system filter runs in a separate
18125 process, as the given user, defaulting to the Exim run-time user.
18126 Unless the string consists entirely of digits, it
18127 is looked up in the password data. Failure to find the named user causes a
18128 configuration error. The gid is either taken from the password data, or
18129 specified by &%system_filter_group%&. When the uid is specified numerically,
18130 &%system_filter_group%& is required to be set.
18132 If the system filter generates any pipe, file, or reply deliveries, the uid
18133 under which the filter is run is used when transporting them, unless a
18134 transport option overrides.
18137 .option tcp_nodelay main boolean true
18138 .cindex "daemon" "TCP_NODELAY on sockets"
18139 .cindex "Nagle algorithm"
18140 .cindex "TCP_NODELAY on listening sockets"
18141 If this option is set false, it stops the Exim daemon setting the
18142 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
18143 turns off the &"Nagle algorithm"&, which is a way of improving network
18144 performance in interactive (character-by-character) situations. Turning it off
18145 should improve Exim's performance a bit, so that is what happens by default.
18146 However, it appears that some broken clients cannot cope, and time out. Hence
18147 this option. It affects only those sockets that are set up for listening by the
18148 daemon. Sockets created by the smtp transport for delivering mail always set
18152 .option timeout_frozen_after main time 0s
18153 .cindex "frozen messages" "timing out"
18154 .cindex "timeout" "frozen messages"
18155 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
18156 message of any kind that has been in the queue for longer than the given time
18157 is automatically cancelled at the next queue run. If the frozen message is a
18158 bounce message, it is just discarded; otherwise, a bounce is sent to the
18159 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
18160 If you want to timeout frozen bounce messages earlier than other kinds of
18161 frozen message, see &%ignore_bounce_errors_after%&.
18163 &*Note:*& the default value of zero means no timeouts; with this setting,
18164 frozen messages remain in the queue forever (except for any frozen bounce
18165 messages that are released by &%ignore_bounce_errors_after%&).
18168 .option timezone main string unset
18169 .cindex "timezone, setting"
18170 .cindex "environment" "values from"
18171 The value of &%timezone%& is used to set the environment variable TZ while
18172 running Exim (if it is different on entry). This ensures that all timestamps
18173 created by Exim are in the required timezone. If you want all your timestamps
18174 to be in UTC (aka GMT) you should set
18178 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
18179 or, if that is not set, from the value of the TZ environment variable when Exim
18180 is built. If &%timezone%& is set to the empty string, either at build or run
18181 time, any existing TZ variable is removed from the environment when Exim
18182 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
18183 unfortunately not all, operating systems.
18186 .option tls_advertise_hosts main "host list&!!" *
18187 .cindex "TLS" "advertising"
18188 .cindex "encryption" "on SMTP connection"
18189 .cindex "SMTP" "encrypted connection"
18190 .cindex "ESMTP extensions" STARTTLS
18191 When Exim is built with support for TLS encrypted connections, the availability
18192 of the STARTTLS command to set up an encrypted session is advertised in
18193 response to EHLO only to those client hosts that match this option. See
18194 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
18195 Note that the default value requires that a certificate be supplied
18196 using the &%tls_certificate%& option. If TLS support for incoming connections
18197 is not required the &%tls_advertise_hosts%& option should be set empty.
18200 .option tls_certificate main string list&!! unset
18201 .cindex "TLS" "server certificate; location of"
18202 .cindex "certificate" "server, location of"
18203 The value of this option is expanded, and must then be a list of absolute paths to
18204 files which contain the server's certificates (in PEM format).
18205 Commonly only one file is needed.
18206 The server's private key is also
18207 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
18208 &<<CHAPTLS>>& for further details.
18210 &*Note*&: The certificates defined by this option are used only when Exim is
18211 receiving incoming messages as a server. If you want to supply certificates for
18212 use when sending messages as a client, you must set the &%tls_certificate%&
18213 option in the relevant &(smtp)& transport.
18215 &*Note*&: If you use filenames based on IP addresses, change the list
18216 separator in the usual way (&<<SECTlistsepchange>>&) to avoid confusion under IPv6.
18218 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
18219 when a list of more than one
18220 file is used, the &$tls_in_ourcert$& variable is unreliable.
18221 The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
18223 .cindex SNI "selecting server certificate based on"
18224 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
18225 if the OpenSSL build supports TLS extensions and the TLS client sends the
18226 Server Name Indication extension, then this option and others documented in
18227 &<<SECTtlssni>>& will be re-expanded.
18229 If this option is unset or empty a fresh self-signed certificate will be
18230 generated for every connection.
18232 .option tls_crl main string&!! unset
18233 .cindex "TLS" "server certificate revocation list"
18234 .cindex "certificate" "revocation list for server"
18235 This option specifies a certificate revocation list. The expanded value must
18236 be the name of a file that contains CRLs in PEM format.
18238 Under OpenSSL the option can specify a directory with CRL files.
18240 &*Note:*& Under OpenSSL the option must, if given, supply a CRL
18241 for each signing element of the certificate chain (i.e. all but the leaf).
18242 For the file variant this can be multiple PEM blocks in the one file.
18244 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18247 .option tls_dh_max_bits main integer 2236
18248 .cindex "TLS" "D-H bit count"
18249 The number of bits used for Diffie-Hellman key-exchange may be suggested by
18250 the chosen TLS library. That value might prove to be too high for
18251 interoperability. This option provides a maximum clamp on the value
18252 suggested, trading off security for interoperability.
18254 The value must be at least 1024.
18256 The value 2236 was chosen because, at time of adding the option, it was the
18257 hard-coded maximum value supported by the NSS cryptographic library, as used
18258 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
18260 If you prefer more security and are willing to break some clients, raise this
18263 Note that the value passed to GnuTLS for *generating* a new prime may be a
18264 little less than this figure, because GnuTLS is inexact and may produce a
18265 larger prime than requested.
18268 .option tls_dhparam main string&!! unset
18269 .cindex "TLS" "D-H parameters for server"
18270 The value of this option is expanded and indicates the source of DH parameters
18271 to be used by Exim.
18273 This option is ignored for GnuTLS version 3.6.0 and later.
18274 The library manages parameter negotiation internally.
18276 &*Note: The Exim Maintainers strongly recommend,
18277 for other TLS library versions,
18278 using a filename with site-generated
18279 local DH parameters*&, which has been supported across all versions of Exim. The
18280 other specific constants available are a fallback so that even when
18281 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
18283 If &%tls_dhparam%& is a filename starting with a &`/`&,
18284 then it names a file from which DH
18285 parameters should be loaded. If the file exists, it should hold a PEM-encoded
18286 PKCS#3 representation of the DH prime. If the file does not exist, for
18287 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
18288 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
18289 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
18290 and treated as though the &%tls_dhparam%& were set to "none".
18292 If this option expands to the string "none", then no DH parameters will be
18295 If this option expands to the string "historic" and Exim is using GnuTLS, then
18296 Exim will attempt to load a file from inside the spool directory. If the file
18297 does not exist, Exim will attempt to create it.
18298 See section &<<SECTgnutlsparam>>& for further details.
18300 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
18301 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
18303 In older versions of Exim the default was the 2048 bit prime described in section
18304 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
18305 in IKE is assigned number 23.
18307 Otherwise, the option must expand to the name used by Exim for any of a number
18308 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
18309 sources. As names, Exim uses a standard specified name, else "ike" followed by
18310 the number used by IKE, or "default" which corresponds to
18311 &`exim.dev.20160529.3`&.
18313 The available standard primes are:
18314 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
18315 &`ike1`&, &`ike2`&, &`ike5`&,
18316 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
18317 &`ike22`&, &`ike23`& and &`ike24`&.
18319 The available additional primes are:
18320 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
18322 Some of these will be too small to be accepted by clients.
18323 Some may be too large to be accepted by clients.
18324 The open cryptographic community has suspicions about the integrity of some
18325 of the later IKE values, which led into RFC7919 providing new fixed constants
18326 (the "ffdhe" identifiers).
18328 At this point, all of the "ike" values should be considered obsolete;
18329 they're still in Exim to avoid breaking unusual configurations, but are
18330 candidates for removal the next time we have backwards-incompatible changes.
18332 The TLS protocol does not negotiate an acceptable size for this; clients tend
18333 to hard-drop connections if what is offered by the server is unacceptable,
18334 whether too large or too small, and there's no provision for the client to
18335 tell the server what these constraints are. Thus, as a server operator, you
18336 need to make an educated guess as to what is most likely to work for your
18339 Some known size constraints suggest that a bit-size in the range 2048 to 2236
18340 is most likely to maximise interoperability. The upper bound comes from
18341 applications using the Mozilla Network Security Services (NSS) library, which
18342 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
18343 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
18344 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
18345 acceptable bound from 1024 to 2048.
18348 .option tls_eccurve main string&!! &`auto`&
18349 .cindex TLS "EC cryptography"
18350 This option selects a EC curve for use by Exim when used with OpenSSL.
18351 It has no effect when Exim is used with GnuTLS.
18353 After expansion it must contain a valid EC curve parameter, such as
18354 &`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
18355 for valid selections.
18357 For OpenSSL versions before (and not including) 1.0.2, the string
18358 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
18359 &`auto`& tells the library to choose.
18361 If the option expands to an empty string, no EC curves will be enabled.
18364 .option tls_ocsp_file main string&!! unset
18365 .cindex TLS "certificate status"
18366 .cindex TLS "OCSP proof file"
18368 must if set expand to the absolute path to a file which contains a current
18369 status proof for the server's certificate, as obtained from the
18370 Certificate Authority.
18372 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
18373 The macro "_HAVE_TLS_OCSP" will be defined for those versions.
18375 For OpenSSL 1.1.0 or later, and
18376 for GnuTLS 3.5.6 or later the expanded value of this option can be a list
18377 of files, to match a list given for the &%tls_certificate%& option.
18378 The ordering of the two lists must match.
18379 The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
18381 The file(s) should be in DER format,
18382 except for GnuTLS 3.6.3 or later
18384 when an optional filetype prefix can be used.
18385 The prefix must be one of "DER" or "PEM", followed by
18386 a single space. If one is used it sets the format for subsequent
18387 files in the list; the initial format is DER.
18388 If multiple proofs are wanted, for multiple chain elements
18389 (this only works under TLS1.3)
18390 they must be coded as a combined OCSP response.
18392 Although GnuTLS will accept PEM files with multiple separate
18393 PEM blobs (ie. separate OCSP responses), it sends them in the
18394 TLS Certificate record interleaved with the certificates of the chain;
18395 although a GnuTLS client is happy with that, an OpenSSL client is not.
18397 .option tls_on_connect_ports main "string list" unset
18400 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
18401 operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
18402 set up without waiting for the client to issue a STARTTLS command. For
18403 further details, see section &<<SECTsupobssmt>>&.
18407 .option tls_privatekey main string list&!! unset
18408 .cindex "TLS" "server private key; location of"
18409 The value of this option is expanded, and must then be a list of absolute paths to
18410 files which contains the server's private keys.
18411 If this option is unset, or if
18412 the expansion is forced to fail, or the result is an empty string, the private
18413 key is assumed to be in the same file as the server's certificates. See chapter
18414 &<<CHAPTLS>>& for further details.
18416 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18419 .option tls_remember_esmtp main boolean false
18420 .cindex "TLS" "esmtp state; remembering"
18421 .cindex "TLS" "broken clients"
18422 If this option is set true, Exim violates the RFCs by remembering that it is in
18423 &"esmtp"& state after successfully negotiating a TLS session. This provides
18424 support for broken clients that fail to send a new EHLO after starting a
18428 .option tls_require_ciphers main string&!! unset
18429 .cindex "TLS" "requiring specific ciphers"
18430 .cindex "cipher" "requiring specific"
18431 This option controls which ciphers can be used for incoming TLS connections.
18432 The &(smtp)& transport has an option of the same name for controlling outgoing
18433 connections. This option is expanded for each connection, so can be varied for
18434 different clients if required. The value of this option must be a list of
18435 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
18436 in somewhat different ways. If GnuTLS is being used, the client controls the
18437 preference order of the available ciphers. Details are given in sections
18438 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
18442 .option tls_resumption_hosts main "host list&!!" unset
18443 .cindex TLS resumption
18444 This option controls which connections to offer the TLS resumption feature.
18445 See &<<SECTresumption>>& for details.
18449 .option tls_try_verify_hosts main "host list&!!" unset
18450 .cindex "TLS" "client certificate verification"
18451 .cindex "certificate" "verification of client"
18452 See &%tls_verify_hosts%& below.
18455 .option tls_verify_certificates main string&!! system
18456 .cindex "TLS" "client certificate verification"
18457 .cindex "certificate" "verification of client"
18458 The value of this option is expanded, and must then be either the
18460 or the absolute path to
18461 a file or directory containing permitted certificates for clients that
18462 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
18464 The "system" value for the option will use a
18465 system default location compiled into the SSL library.
18466 This is not available for GnuTLS versions preceding 3.0.20,
18467 and will be taken as empty; an explicit location
18470 The use of a directory for the option value is not available for GnuTLS versions
18471 preceding 3.3.6 and a single file must be used.
18473 With OpenSSL the certificates specified
18475 either by file or directory
18476 are added to those given by the system default location.
18478 These certificates should be for the certificate authorities trusted, rather
18479 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
18480 the value is a file then the certificates are sent by Exim as a server to
18481 connecting clients, defining the list of accepted certificate authorities.
18482 Thus the values defined should be considered public data. To avoid this,
18483 use the explicit directory version.
18485 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
18487 A forced expansion failure or setting to an empty string is equivalent to
18491 .option tls_verify_hosts main "host list&!!" unset
18492 .cindex "TLS" "client certificate verification"
18493 .cindex "certificate" "verification of client"
18494 This option, along with &%tls_try_verify_hosts%&, controls the checking of
18495 certificates from clients. The expected certificates are defined by
18496 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
18497 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
18498 &%tls_verify_certificates%& is not set.
18500 Any client that matches &%tls_verify_hosts%& is constrained by
18501 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
18502 present one of the listed certificates. If it does not, the connection is
18503 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
18504 the host to use TLS. It can still send SMTP commands through unencrypted
18505 connections. Forcing a client to use TLS has to be done separately using an
18506 ACL to reject inappropriate commands when the connection is not encrypted.
18508 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
18509 matches this option (but not &%tls_verify_hosts%&), Exim requests a
18510 certificate and checks it against &%tls_verify_certificates%&, but does not
18511 abort the connection if there is no certificate or if it does not match. This
18512 state can be detected in an ACL, which makes it possible to implement policies
18513 such as &"accept for relay only if a verified certificate has been received,
18514 but accept for local delivery if encrypted, even without a verified
18517 Client hosts that match neither of these lists are not asked to present
18521 .option trusted_groups main "string list&!!" unset
18522 .cindex "trusted groups"
18523 .cindex "groups" "trusted"
18524 This option is expanded just once, at the start of Exim's processing. If this
18525 option is set, any process that is running in one of the listed groups, or
18526 which has one of them as a supplementary group, is trusted. The groups can be
18527 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
18528 details of what trusted callers are permitted to do. If neither
18529 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
18532 .option trusted_users main "string list&!!" unset
18533 .cindex "trusted users"
18534 .cindex "user" "trusted"
18535 This option is expanded just once, at the start of Exim's processing. If this
18536 option is set, any process that is running as one of the listed users is
18537 trusted. The users can be specified numerically or by name. See section
18538 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
18539 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
18540 Exim user are trusted.
18542 .option unknown_login main string&!! unset
18543 .cindex "uid (user id)" "unknown caller"
18544 .vindex "&$caller_uid$&"
18545 This is a specialized feature for use in unusual configurations. By default, if
18546 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
18547 gives up. The &%unknown_login%& option can be used to set a login name to be
18548 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
18549 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
18550 is used for the user's real name (gecos field), unless this has been set by the
18553 .option unknown_username main string unset
18554 See &%unknown_login%&.
18556 .option untrusted_set_sender main "address list&!!" unset
18557 .cindex "trusted users"
18558 .cindex "sender" "setting by untrusted user"
18559 .cindex "untrusted user setting sender"
18560 .cindex "user" "untrusted setting sender"
18561 .cindex "envelope from"
18562 .cindex "envelope sender"
18563 When an untrusted user submits a message to Exim using the standard input, Exim
18564 normally creates an envelope sender address from the user's login and the
18565 default qualification domain. Data from the &%-f%& option (for setting envelope
18566 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
18567 is used) is ignored.
18569 However, untrusted users are permitted to set an empty envelope sender address,
18570 to declare that a message should never generate any bounces. For example:
18572 exim -f '<>' user@domain.example
18574 .vindex "&$sender_ident$&"
18575 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
18576 other envelope sender addresses in a controlled way. When it is set, untrusted
18577 users are allowed to set envelope sender addresses that match any of the
18578 patterns in the list. Like all address lists, the string is expanded. The
18579 identity of the user is in &$sender_ident$&, so you can, for example, restrict
18580 users to setting senders that start with their login ids
18581 followed by a hyphen
18582 by a setting like this:
18584 untrusted_set_sender = ^$sender_ident-
18586 If you want to allow untrusted users to set envelope sender addresses without
18587 restriction, you can use
18589 untrusted_set_sender = *
18591 The &%untrusted_set_sender%& option applies to all forms of local input, but
18592 only to the setting of the envelope sender. It does not permit untrusted users
18593 to use the other options which trusted user can use to override message
18594 parameters. Furthermore, it does not stop Exim from removing an existing
18595 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
18596 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
18597 overriding these actions. The handling of the &'Sender:'& header is also
18598 described in section &<<SECTthesenhea>>&.
18600 The log line for a message's arrival shows the envelope sender following
18601 &"<="&. For local messages, the user's login always follows, after &"U="&. In
18602 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
18603 envelope sender address, the user's login is shown in parentheses after the
18607 .option uucp_from_pattern main string "see below"
18608 .cindex "&""From""& line"
18609 .cindex "UUCP" "&""From""& line"
18610 Some applications that pass messages to an MTA via a command line interface use
18611 an initial line starting with &"From&~"& to pass the envelope sender. In
18612 particular, this is used by UUCP software. Exim recognizes such a line by means
18613 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
18614 matches, the sender address is constructed by expanding the contents of
18615 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
18616 default pattern recognizes lines in the following two forms:
18618 From ph10 Fri Jan 5 12:35 GMT 1996
18619 From ph10 Fri, 7 Jan 97 14:00:00 GMT
18621 The pattern can be seen by running
18623 exim -bP uucp_from_pattern
18625 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
18626 year in the second case. The first word after &"From&~"& is matched in the
18627 regular expression by a parenthesized subpattern. The default value for
18628 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
18629 (&"ph10"& in the example above) as the message's sender. See also
18630 &%ignore_fromline_hosts%&.
18633 .option uucp_from_sender main string&!! &`$1`&
18634 See &%uucp_from_pattern%& above.
18637 .option warn_message_file main string&!! unset
18638 .cindex "warning of delay" "customizing the message"
18639 .cindex "customizing" "warning message"
18640 This option defines a template file containing paragraphs of text to be used
18641 for constructing the warning message which is sent by Exim when a message has
18642 been in the queue for a specified amount of time, as specified by
18643 &%delay_warning%&. Details of the file's contents are given in chapter
18644 &<<CHAPemsgcust>>&.
18645 .cindex warn_message_file "tainted data"
18646 The option is expanded to give the file path, which must be
18647 absolute and untainted.
18648 See also &%bounce_message_file%&.
18651 .option write_rejectlog main boolean true
18652 .cindex "reject log" "disabling"
18653 If this option is set false, Exim no longer writes anything to the reject log.
18654 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
18655 .ecindex IIDconfima
18656 .ecindex IIDmaiconf
18661 . ////////////////////////////////////////////////////////////////////////////
18662 . ////////////////////////////////////////////////////////////////////////////
18664 .chapter "Generic options for routers" "CHAProutergeneric"
18665 .scindex IIDgenoprou1 "options" "generic; for routers"
18666 .scindex IIDgenoprou2 "generic options" "router"
18667 This chapter describes the generic options that apply to all routers.
18668 Those that are preconditions are marked with ‡ in the &"use"& field.
18670 For a general description of how a router operates, see sections
18671 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
18672 which the preconditions are tested. The order of expansion of the options that
18673 provide data for a transport is: &%errors_to%&, &%headers_add%&,
18674 &%headers_remove%&, &%transport%&.
18678 .option address_data routers string&!! unset
18679 .cindex "router" "data attached to address"
18680 The string is expanded just before the router is run, that is, after all the
18681 precondition tests have succeeded. If the expansion is forced to fail, the
18682 router declines, the value of &%address_data%& remains unchanged, and the
18683 &%more%& option controls what happens next. Other expansion failures cause
18684 delivery of the address to be deferred.
18686 .vindex "&$address_data$&"
18687 When the expansion succeeds, the value is retained with the address, and can be
18688 accessed using the variable &$address_data$& in the current router, subsequent
18689 routers, and the eventual transport.
18691 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
18692 that runs a user's filter file, the contents of &$address_data$& are accessible
18693 in the filter. This is not normally a problem, because such data is usually
18694 either not confidential or it &"belongs"& to the current user, but if you do
18695 put confidential data into &$address_data$& you need to remember this point.
18697 Even if the router declines or passes, the value of &$address_data$& remains
18698 with the address, though it can be changed by another &%address_data%& setting
18699 on a subsequent router. If a router generates child addresses, the value of
18700 &$address_data$& propagates to them. This also applies to the special kind of
18701 &"child"& that is generated by a router with the &%unseen%& option.
18703 The idea of &%address_data%& is that you can use it to look up a lot of data
18704 for the address once, and then pick out parts of the data later. For example,
18705 you could use a single LDAP lookup to return a string of the form
18707 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
18709 In the transport you could pick out the mailbox by a setting such as
18711 file = ${extract{mailbox}{$address_data}}
18713 This makes the configuration file less messy, and also reduces the number of
18714 lookups (though Exim does cache lookups).
18716 See also the &%set%& option below.
18718 .vindex "&$sender_address_data$&"
18719 .vindex "&$address_data$&"
18720 The &%address_data%& facility is also useful as a means of passing information
18721 from one router to another, and from a router to a transport. In addition, if
18722 &$address_data$& is set by a router when verifying a recipient address from an
18723 ACL, it remains available for use in the rest of the ACL statement. After
18724 verifying a sender, the value is transferred to &$sender_address_data$&.
18728 .option address_test routers&!? boolean true
18730 .cindex "router" "skipping when address testing"
18731 If this option is set false, the router is skipped when routing is being tested
18732 by means of the &%-bt%& command line option. This can be a convenience when
18733 your first router sends messages to an external scanner, because it saves you
18734 having to set the &"already scanned"& indicator when testing real address
18739 .option cannot_route_message routers string&!! unset
18740 .cindex "router" "customizing &""cannot route""& message"
18741 .cindex "customizing" "&""cannot route""& message"
18742 This option specifies a text message that is used when an address cannot be
18743 routed because Exim has run out of routers. The default message is
18744 &"Unrouteable address"&. This option is useful only on routers that have
18745 &%more%& set false, or on the very last router in a configuration, because the
18746 value that is used is taken from the last router that is considered. This
18747 includes a router that is skipped because its preconditions are not met, as
18748 well as a router that declines. For example, using the default configuration,
18751 cannot_route_message = Remote domain not found in DNS
18753 on the first router, which is a &(dnslookup)& router with &%more%& set false,
18756 cannot_route_message = Unknown local user
18758 on the final router that checks for local users. If string expansion fails for
18759 this option, the default message is used. Unless the expansion failure was
18760 explicitly forced, a message about the failure is written to the main and panic
18761 logs, in addition to the normal message about the routing failure.
18764 .option caseful_local_part routers boolean false
18765 .cindex "case of local parts"
18766 .cindex "router" "case of local parts"
18767 By default, routers handle the local parts of addresses in a case-insensitive
18768 manner, though the actual case is preserved for transmission with the message.
18769 If you want the case of letters to be significant in a router, you must set
18770 this option true. For individual router options that contain address or local
18771 part lists (for example, &%local_parts%&), case-sensitive matching can be
18772 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
18775 .vindex "&$local_part$&"
18776 .vindex "&$original_local_part$&"
18777 .vindex "&$parent_local_part$&"
18778 The value of the &$local_part$& variable is forced to lower case while a
18779 router is running unless &%caseful_local_part%& is set. When a router assigns
18780 an address to a transport, the value of &$local_part$& when the transport runs
18781 is the same as it was in the router. Similarly, when a router generates child
18782 addresses by aliasing or forwarding, the values of &$original_local_part$&
18783 and &$parent_local_part$& are those that were used by the redirecting router.
18785 This option applies to the processing of an address by a router. When a
18786 recipient address is being processed in an ACL, there is a separate &%control%&
18787 modifier that can be used to specify case-sensitive processing within the ACL
18788 (see section &<<SECTcontrols>>&).
18792 .option check_local_user routers&!? boolean false
18793 .cindex "local user, checking in router"
18794 .cindex "router" "checking for local user"
18795 .cindex "&_/etc/passwd_&"
18797 When this option is true, Exim checks that the local part of the recipient
18798 address (with affixes removed if relevant) is the name of an account on the
18799 local system. The check is done by calling the &[getpwnam()]& function rather
18800 than trying to read &_/etc/passwd_& directly. This means that other methods of
18801 holding password data (such as NIS) are supported. If the local part is a local
18802 user, &$home$& is set from the password data, and can be tested in other
18803 preconditions that are evaluated after this one (the order of evaluation is
18804 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
18805 overridden by &%router_home_directory%&. If the local part is not a local user,
18806 the router is skipped.
18808 If you want to check that the local part is either the name of a local user
18809 or matches something else, you cannot combine &%check_local_user%& with a
18810 setting of &%local_parts%&, because that specifies the logical &'and'& of the
18811 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
18812 setting to achieve this. For example:
18814 local_parts = passwd;$local_part : lsearch;/etc/other/users
18816 Note, however, that the side effects of &%check_local_user%& (such as setting
18817 up a home directory) do not occur when a &(passwd)& lookup is used in a
18818 &%local_parts%& (or any other) precondition.
18822 .option condition routers&!? string&!! unset
18823 .cindex "router" "customized precondition"
18824 This option specifies a general precondition test that has to succeed for the
18825 router to be called. The &%condition%& option is the last precondition to be
18826 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
18827 result is a forced failure, or an empty string, or one of the strings &"0"& or
18828 &"no"& or &"false"& (checked without regard to the case of the letters), the
18829 router is skipped, and the address is offered to the next one.
18831 If the result is any other value, the router is run (as this is the last
18832 precondition to be evaluated, all the other preconditions must be true).
18834 This option is unusual in that multiple &%condition%& options may be present.
18835 All &%condition%& options must succeed.
18837 The &%condition%& option provides a means of applying custom conditions to the
18838 running of routers. Note that in the case of a simple conditional expansion,
18839 the default expansion values are exactly what is wanted. For example:
18841 condition = ${if >{$message_age}{600}}
18843 Because of the default behaviour of the string expansion, this is equivalent to
18845 condition = ${if >{$message_age}{600}{true}{}}
18848 A multiple condition example, which succeeds:
18850 condition = ${if >{$message_age}{600}}
18851 condition = ${if !eq{${lc:$local_part}}{postmaster}}
18855 If the expansion fails (other than forced failure) delivery is deferred. Some
18856 of the other precondition options are common special cases that could in fact
18857 be specified using &%condition%&.
18859 Historical note: We have &%condition%& on ACLs and on Routers. Routers
18860 are far older, and use one set of semantics. ACLs are newer and when
18861 they were created, the ACL &%condition%& process was given far stricter
18862 parse semantics. The &%bool{}%& expansion condition uses the same rules as
18863 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
18864 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
18865 Router rules processing behavior.
18867 This is best illustrated in an example:
18869 # If used in an ACL condition will fail with a syntax error, but
18870 # in a router condition any extra characters are treated as a string
18872 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
18875 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
18878 In each example above, the &%if%& statement actually ends after
18879 &"{google.com}}"&. Since no true or false braces were defined, the
18880 default &%if%& behavior is to return a boolean true or a null answer
18881 (which evaluates to false). The rest of the line is then treated as a
18882 string. So the first example resulted in the boolean answer &"true"&
18883 with the string &" {yes} {no}}"& appended to it. The second example
18884 resulted in the null output (indicating false) with the string
18885 &" {yes} {no}}"& appended to it.
18887 In fact you can put excess forward braces in too. In the router
18888 &%condition%&, Exim's parser only looks for &"{"& symbols when they
18889 mean something, like after a &"$"& or when required as part of a
18890 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
18893 Thus, in a Router, the above expansion strings will both always evaluate
18894 true, as the result of expansion is a non-empty string which doesn't
18895 match an explicit false value. This can be tricky to debug. By
18896 contrast, in an ACL either of those strings will always result in an
18897 expansion error because the result doesn't look sufficiently boolean.
18900 .option debug_print routers string&!! unset
18901 .cindex "testing" "variables in drivers"
18902 If this option is set and debugging is enabled (see the &%-d%& command line
18903 option) or in address-testing mode (see the &%-bt%& command line option),
18904 the string is expanded and included in the debugging output.
18905 If expansion of the string fails, the error message is written to the debugging
18906 output, and Exim carries on processing.
18907 This option is provided to help with checking out the values of variables and
18908 so on when debugging router configurations. For example, if a &%condition%&
18909 option appears not to be working, &%debug_print%& can be used to output the
18910 variables it references. The output happens after checks for &%domains%&,
18911 &%local_parts%&, and &%check_local_user%& but before any other preconditions
18912 are tested. A newline is added to the text if it does not end with one.
18913 The variable &$router_name$& contains the name of the router.
18917 .option disable_logging routers boolean false
18918 If this option is set true, nothing is logged for any routing errors
18919 or for any deliveries caused by this router. You should not set this option
18920 unless you really, really know what you are doing. See also the generic
18921 transport option of the same name.
18923 .option dnssec_request_domains routers "domain list&!!" *
18924 .cindex "MX record" "security"
18925 .cindex "DNSSEC" "MX lookup"
18926 .cindex "security" "MX lookup"
18927 .cindex "DNS" "DNSSEC"
18928 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
18929 the dnssec request bit set.
18930 This applies to all of the SRV, MX, AAAA, A lookup sequence.
18932 .option dnssec_require_domains routers "domain list&!!" unset
18933 .cindex "MX record" "security"
18934 .cindex "DNSSEC" "MX lookup"
18935 .cindex "security" "MX lookup"
18936 .cindex "DNS" "DNSSEC"
18937 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
18938 the dnssec request bit set. Any returns not having the Authenticated Data bit
18939 (AD bit) set will be ignored and logged as a host-lookup failure.
18940 This applies to all of the SRV, MX, AAAA, A lookup sequence.
18943 .option domains routers&!? "domain list&!!" unset
18944 .cindex "router" "restricting to specific domains"
18945 .vindex "&$domain_data$&"
18946 If this option is set, the router is skipped unless the current domain matches
18947 the list. If the match is achieved by means of a file lookup, the data that the
18948 lookup returned for the domain is placed in &$domain_data$& for use in string
18949 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
18950 a list of the order in which preconditions are evaluated.
18954 .option driver routers string unset
18955 This option must always be set. It specifies which of the available routers is
18959 .option dsn_lasthop routers boolean false
18960 .cindex "DSN" "success"
18961 .cindex "Delivery Status Notification" "success"
18962 If this option is set true, and extended DSN (RFC3461) processing is in effect,
18963 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
18964 instead send a success DSN as if the next hop does not support DSN.
18965 Not effective on redirect routers.
18969 .option errors_to routers string&!! unset
18970 .cindex "envelope from"
18971 .cindex "envelope sender"
18972 .cindex "router" "changing address for errors"
18973 If a router successfully handles an address, it may assign the address to a
18974 transport for delivery or it may generate child addresses. In both cases, if
18975 there is a delivery problem during later processing, the resulting bounce
18976 message is sent to the address that results from expanding this string,
18977 provided that the address verifies successfully. The &%errors_to%& option is
18978 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
18980 The &%errors_to%& setting associated with an address can be overridden if it
18981 subsequently passes through other routers that have their own &%errors_to%&
18982 settings, or if the message is delivered by a transport with a &%return_path%&
18985 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
18986 the expansion fails to verify, the errors address associated with the incoming
18987 address is used. At top level, this is the envelope sender. A non-forced
18988 expansion failure causes delivery to be deferred.
18990 If an address for which &%errors_to%& has been set ends up being delivered over
18991 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
18992 any bounces that are generated by other MTAs on the delivery route are also
18993 sent there. You can set &%errors_to%& to the empty string by either of these
18999 An expansion item that yields an empty string has the same effect. If you do
19000 this, a locally detected delivery error for addresses processed by this router
19001 no longer gives rise to a bounce message; the error is discarded. If the
19002 address is delivered to a remote host, the return path is set to &`<>`&, unless
19003 overridden by the &%return_path%& option on the transport.
19005 .vindex "&$address_data$&"
19006 If for some reason you want to discard local errors, but use a non-empty
19007 MAIL command for remote delivery, you can preserve the original return
19008 path in &$address_data$& in the router, and reinstate it in the transport by
19009 setting &%return_path%&.
19011 The most common use of &%errors_to%& is to direct mailing list bounces to the
19012 manager of the list, as described in section &<<SECTmailinglists>>&, or to
19013 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
19017 .option expn routers&!? boolean true
19018 .cindex "address" "testing"
19019 .cindex "testing" "addresses"
19020 .cindex "EXPN" "router skipping"
19021 .cindex "router" "skipping for EXPN"
19022 If this option is turned off, the router is skipped when testing an address
19023 as a result of processing an SMTP EXPN command. You might, for example,
19024 want to turn it off on a router for users' &_.forward_& files, while leaving it
19025 on for the system alias file.
19026 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19029 The use of the SMTP EXPN command is controlled by an ACL (see chapter
19030 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
19031 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
19035 .option fail_verify routers boolean false
19036 .cindex "router" "forcing verification failure"
19037 Setting this option has the effect of setting both &%fail_verify_sender%& and
19038 &%fail_verify_recipient%& to the same value.
19042 .option fail_verify_recipient routers boolean false
19043 If this option is true and an address is accepted by this router when
19044 verifying a recipient, verification fails.
19048 .option fail_verify_sender routers boolean false
19049 If this option is true and an address is accepted by this router when
19050 verifying a sender, verification fails.
19054 .option fallback_hosts routers "string list" unset
19055 .cindex "router" "fallback hosts"
19056 .cindex "fallback" "hosts specified on router"
19057 String expansion is not applied to this option. The argument must be a
19058 colon-separated list of host names or IP addresses. The list separator can be
19059 changed (see section &<<SECTlistsepchange>>&), and a port can be specified with
19060 each name or address. In fact, the format of each item is exactly the same as
19061 defined for the list of hosts in a &(manualroute)& router (see section
19062 &<<SECTformatonehostitem>>&).
19064 If a router queues an address for a remote transport, this host list is
19065 associated with the address, and used instead of the transport's fallback host
19066 list. If &%hosts_randomize%& is set on the transport, the order of the list is
19067 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
19068 transport for further details.
19071 .option group routers string&!! "see below"
19072 .cindex "gid (group id)" "local delivery"
19073 .cindex "local transports" "uid and gid"
19074 .cindex "transport" "local"
19075 .cindex "router" "setting group"
19076 When a router queues an address for a transport, and the transport does not
19077 specify a group, the group given here is used when running the delivery
19079 The group may be specified numerically or by name. If expansion fails, the
19080 error is logged and delivery is deferred.
19081 The default is unset, unless &%check_local_user%& is set, when the default
19082 is taken from the password information. See also &%initgroups%& and &%user%&
19083 and the discussion in chapter &<<CHAPenvironment>>&.
19087 .option headers_add routers list&!! unset
19088 .cindex "header lines" "adding"
19089 .cindex "router" "adding header lines"
19090 This option specifies a list of text headers,
19091 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19092 that is associated with any addresses that are accepted by the router.
19093 Each item is separately expanded, at routing time. However, this
19094 option has no effect when an address is just being verified. The way in which
19095 the text is used to add header lines at transport time is described in section
19096 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
19097 message is in the process of being transported. This means that references to
19098 header lines in string expansions in the transport's configuration do not
19099 &"see"& the added header lines.
19101 The &%headers_add%& option is expanded after &%errors_to%&, but before
19102 &%headers_remove%& and &%transport%&. If an item is empty, or if
19103 an item expansion is forced to fail, the item has no effect. Other expansion
19104 failures are treated as configuration errors.
19106 Unlike most options, &%headers_add%& can be specified multiple times
19107 for a router; all listed headers are added.
19109 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
19110 router that has the &%one_time%& option set.
19112 .cindex "duplicate addresses"
19113 .oindex "&%unseen%&"
19114 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19115 additions are deleted when the address is passed on to subsequent routers.
19116 For a &%redirect%& router, if a generated address is the same as the incoming
19117 address, this can lead to duplicate addresses with different header
19118 modifications. Exim does not do duplicate deliveries (except, in certain
19119 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
19120 which of the duplicates is discarded, so this ambiguous situation should be
19121 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
19125 .option headers_remove routers list&!! unset
19126 .cindex "header lines" "removing"
19127 .cindex "router" "removing header lines"
19128 This option specifies a list of text headers,
19129 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
19130 that is associated with any addresses that are accepted by the router.
19131 However, the option has no effect when an address is just being verified.
19132 Each list item is separately expanded, at transport time.
19133 If an item ends in *, it will match any header with the given prefix.
19135 the text is used to remove header lines at transport time is described in
19136 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
19137 the message is in the process of being transported. This means that references
19138 to header lines in string expansions in the transport's configuration still
19139 &"see"& the original header lines.
19141 The &%headers_remove%& option is handled after &%errors_to%& and
19142 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
19143 the item has no effect. Other expansion failures are treated as configuration
19146 Unlike most options, &%headers_remove%& can be specified multiple times
19147 for a router; all listed headers are removed.
19149 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
19150 router that has the &%one_time%& option set.
19152 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
19153 removal requests are deleted when the address is passed on to subsequent
19154 routers, and this can lead to problems with duplicates -- see the similar
19155 warning for &%headers_add%& above.
19157 &*Warning 3*&: Because of the separate expansion of the list items,
19158 items that contain a list separator must have it doubled.
19159 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
19163 .option ignore_target_hosts routers "host list&!!" unset
19164 .cindex "IP address" "discarding"
19165 .cindex "router" "discarding IP addresses"
19166 Although this option is a host list, it should normally contain IP address
19167 entries rather than names. If any host that is looked up by the router has an
19168 IP address that matches an item in this list, Exim behaves as if that IP
19169 address did not exist. This option allows you to cope with rogue DNS entries
19172 remote.domain.example. A 127.0.0.1
19176 ignore_target_hosts = 127.0.0.1
19178 on the relevant router. If all the hosts found by a &(dnslookup)& router are
19179 discarded in this way, the router declines. In a conventional configuration, an
19180 attempt to mail to such a domain would normally provoke the &"unrouteable
19181 domain"& error, and an attempt to verify an address in the domain would fail.
19182 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
19183 router declines if presented with one of the listed addresses.
19185 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
19186 means of the first or the second of the following settings, respectively:
19188 ignore_target_hosts = 0.0.0.0/0
19189 ignore_target_hosts = <; 0::0/0
19191 The pattern in the first line matches all IPv4 addresses, whereas the pattern
19192 in the second line matches all IPv6 addresses.
19194 This option may also be useful for ignoring link-local and site-local IPv6
19195 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
19196 is expanded before use as a list, it is possible to make it dependent on the
19197 domain that is being routed.
19199 .vindex "&$host_address$&"
19200 During its expansion, &$host_address$& is set to the IP address that is being
19203 .option initgroups routers boolean false
19204 .cindex "additional groups"
19205 .cindex "groups" "additional"
19206 .cindex "local transports" "uid and gid"
19207 .cindex "transport" "local"
19208 If the router queues an address for a transport, and this option is true, and
19209 the uid supplied by the router is not overridden by the transport, the
19210 &[initgroups()]& function is called when running the transport to ensure that
19211 any additional groups associated with the uid are set up. See also &%group%&
19212 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
19216 .option local_part_prefix routers&!? "string list" unset
19217 .cindex affix "router precondition"
19218 .cindex "router" "prefix for local part"
19219 .cindex "prefix" "for local part, used in router"
19220 If this option is set, the router is skipped unless the local part starts with
19221 one of the given strings, or &%local_part_prefix_optional%& is true. See
19222 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
19225 The list is scanned from left to right, and the first prefix that matches is
19226 used. A limited form of wildcard is available; if the prefix begins with an
19227 asterisk, it matches the longest possible sequence of arbitrary characters at
19228 the start of the local part. An asterisk should therefore always be followed by
19229 some character that does not occur in normal local parts.
19230 .cindex "multiple mailboxes"
19231 .cindex "mailbox" "multiple"
19232 Wildcarding can be used to set up multiple user mailboxes, as described in
19233 section &<<SECTmulbox>>&.
19235 .vindex "&$local_part$&"
19236 .vindex "&$local_part_prefix$&"
19237 During the testing of the &%local_parts%& option, and while the router is
19238 running, the prefix is removed from the local part, and is available in the
19239 expansion variable &$local_part_prefix$&. When a message is being delivered, if
19240 the router accepts the address, this remains true during subsequent delivery by
19241 a transport. In particular, the local part that is transmitted in the RCPT
19242 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
19243 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
19244 the relevant transport.
19246 .vindex &$local_part_prefix_v$&
19247 If wildcarding (above) was used then the part of the prefix matching the
19248 wildcard is available in &$local_part_prefix_v$&.
19250 When an address is being verified, &%local_part_prefix%& affects only the
19251 behaviour of the router. If the callout feature of verification is in use, this
19252 means that the full address, including the prefix, will be used during the
19255 The prefix facility is commonly used to handle local parts of the form
19256 &%owner-something%&. Another common use is to support local parts of the form
19257 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
19258 to tell a user their forwarding is broken &-- by placing a router like this one
19259 immediately before the router that handles &_.forward_& files:
19263 local_part_prefix = real-
19265 transport = local_delivery
19267 For security, it would probably be a good idea to restrict the use of this
19268 router to locally-generated messages, using a condition such as this:
19270 condition = ${if match {$sender_host_address}\
19271 {\N^(|127\.0\.0\.1)$\N}}
19274 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
19275 both conditions must be met if not optional. Care must be taken if wildcards
19276 are used in both a prefix and a suffix on the same router. Different
19277 separator characters must be used to avoid ambiguity.
19280 .option local_part_prefix_optional routers boolean false
19281 See &%local_part_prefix%& above.
19285 .option local_part_suffix routers&!? "string list" unset
19286 .cindex "router" "suffix for local part"
19287 .cindex "suffix for local part" "used in router"
19288 This option operates in the same way as &%local_part_prefix%&, except that the
19289 local part must end (rather than start) with the given string, the
19290 &%local_part_suffix_optional%& option determines whether the suffix is
19291 mandatory, and the wildcard * character, if present, must be the last
19292 character of the suffix. This option facility is commonly used to handle local
19293 parts of the form &%something-request%& and multiple user mailboxes of the form
19297 .option local_part_suffix_optional routers boolean false
19298 See &%local_part_suffix%& above.
19302 .option local_parts routers&!? "local part list&!!" unset
19303 .cindex "router" "restricting to specific local parts"
19304 .cindex "local part" "checking in router"
19305 The router is run only if the local part of the address matches the list.
19306 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19308 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
19309 string is expanded, it is possible to make it depend on the domain, for
19312 local_parts = dbm;/usr/local/specials/$domain
19314 .vindex "&$local_part_data$&"
19315 If the match is achieved by a lookup, the data that the lookup returned
19316 for the local part is placed in the variable &$local_part_data$& for use in
19317 expansions of the router's private options. You might use this option, for
19318 example, if you have a large number of local virtual domains, and you want to
19319 send all postmaster mail to the same place without having to set up an alias in
19320 each virtual domain:
19324 local_parts = postmaster
19325 data = postmaster@real.domain.example
19329 .option log_as_local routers boolean "see below"
19330 .cindex "log" "delivery line"
19331 .cindex "delivery" "log line format"
19332 Exim has two logging styles for delivery, the idea being to make local
19333 deliveries stand out more visibly from remote ones. In the &"local"& style, the
19334 recipient address is given just as the local part, without a domain. The use of
19335 this style is controlled by this option. It defaults to true for the &(accept)&
19336 router, and false for all the others. This option applies only when a
19337 router assigns an address to a transport. It has no effect on routers that
19338 redirect addresses.
19342 .option more routers boolean&!! true
19343 The result of string expansion for this option must be a valid boolean value,
19344 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19345 result causes an error, and delivery is deferred. If the expansion is forced to
19346 fail, the default value for the option (true) is used. Other failures cause
19347 delivery to be deferred.
19349 If this option is set false, and the router declines to handle the address, no
19350 further routers are tried, routing fails, and the address is bounced.
19352 However, if the router explicitly passes an address to the following router by
19353 means of the setting
19357 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
19358 does not affect the behaviour if one of the precondition tests fails. In that
19359 case, the address is always passed to the next router.
19361 Note that &%address_data%& is not considered to be a precondition. If its
19362 expansion is forced to fail, the router declines, and the value of &%more%&
19363 controls what happens next.
19366 .option pass_on_timeout routers boolean false
19367 .cindex "timeout" "of router"
19368 .cindex "router" "timeout"
19369 If a router times out during a host lookup, it normally causes deferral of the
19370 address. If &%pass_on_timeout%& is set, the address is passed on to the next
19371 router, overriding &%no_more%&. This may be helpful for systems that are
19372 intermittently connected to the Internet, or those that want to pass to a smart
19373 host any messages that cannot immediately be delivered.
19375 There are occasional other temporary errors that can occur while doing DNS
19376 lookups. They are treated in the same way as a timeout, and this option
19377 applies to all of them.
19381 .option pass_router routers string unset
19382 .cindex "router" "go to after &""pass""&"
19383 Routers that recognize the generic &%self%& option (&(dnslookup)&,
19384 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
19385 routing to continue, and overriding a false setting of &%more%&. When one of
19386 these routers returns &"pass"&, the address is normally handed on to the next
19387 router in sequence. This can be changed by setting &%pass_router%& to the name
19388 of another router. However (unlike &%redirect_router%&) the named router must
19389 be below the current router, to avoid loops. Note that this option applies only
19390 to the special case of &"pass"&. It does not apply when a router returns
19391 &"decline"& because it cannot handle an address.
19395 .option redirect_router routers string unset
19396 .cindex "router" "start at after redirection"
19397 Sometimes an administrator knows that it is pointless to reprocess addresses
19398 generated from alias or forward files with the same router again. For
19399 example, if an alias file translates real names into login ids there is no
19400 point searching the alias file a second time, especially if it is a large file.
19402 The &%redirect_router%& option can be set to the name of any router instance.
19403 It causes the routing of any generated addresses to start at the named router
19404 instead of at the first router. This option has no effect if the router in
19405 which it is set does not generate new addresses.
19409 .option require_files routers&!? "string list&!!" unset
19410 .cindex "file" "requiring for router"
19411 .cindex "router" "requiring file existence"
19412 This option provides a general mechanism for predicating the running of a
19413 router on the existence or non-existence of certain files or directories.
19414 Before running a router, as one of its precondition tests, Exim works its way
19415 through the &%require_files%& list, expanding each item separately.
19417 Because the list is split before expansion, any colons in expansion items must
19418 be doubled, or the facility for using a different list separator must be used
19419 (&<<SECTlistsepchange>>&).
19420 If any expansion is forced to fail, the item is ignored. Other expansion
19421 failures cause routing of the address to be deferred.
19423 If any expanded string is empty, it is ignored. Otherwise, except as described
19424 below, each string must be a fully qualified file path, optionally preceded by
19425 &"!"&. The paths are passed to the &[stat()]& function to test for the
19426 existence of the files or directories. The router is skipped if any paths not
19427 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
19430 If &[stat()]& cannot determine whether a file exists or not, delivery of
19431 the message is deferred. This can happen when NFS-mounted filesystems are
19434 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
19435 options, so you cannot use it to check for the existence of a file in which to
19436 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
19437 full list of the order in which preconditions are evaluated.) However, as
19438 these options are all expanded, you can use the &%exists%& expansion condition
19439 to make such tests. The &%require_files%& option is intended for checking files
19440 that the router may be going to use internally, or which are needed by a
19441 transport (e.g., &_.procmailrc_&).
19443 During delivery, the &[stat()]& function is run as root, but there is a
19444 facility for some checking of the accessibility of a file by another user.
19445 This is not a proper permissions check, but just a &"rough"& check that
19446 operates as follows:
19448 If an item in a &%require_files%& list does not contain any forward slash
19449 characters, it is taken to be the user (and optional group, separated by a
19450 comma) to be checked for subsequent files in the list. If no group is specified
19451 but the user is specified symbolically, the gid associated with the uid is
19454 require_files = mail:/some/file
19455 require_files = $local_part_data:$home/.procmailrc
19457 If a user or group name in a &%require_files%& list does not exist, the
19458 &%require_files%& condition fails.
19460 Exim performs the check by scanning along the components of the file path, and
19461 checking the access for the given uid and gid. It checks for &"x"& access on
19462 directories, and &"r"& access on the final file. Note that this means that file
19463 access control lists, if the operating system has them, are ignored.
19465 &*Warning 1*&: When the router is being run to verify addresses for an
19466 incoming SMTP message, Exim is not running as root, but under its own uid. This
19467 may affect the result of a &%require_files%& check. In particular, &[stat()]&
19468 may yield the error EACCES (&"Permission denied"&). This means that the Exim
19469 user is not permitted to read one of the directories on the file's path.
19471 &*Warning 2*&: Even when Exim is running as root while delivering a message,
19472 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
19473 without root access. In this case, if a check for access by a particular user
19474 is requested, Exim creates a subprocess that runs as that user, and tries the
19475 check again in that process.
19477 The default action for handling an unresolved EACCES is to consider it to
19478 be caused by a configuration error, and routing is deferred because the
19479 existence or non-existence of the file cannot be determined. However, in some
19480 circumstances it may be desirable to treat this condition as if the file did
19481 not exist. If the filename (or the exclamation mark that precedes the filename
19482 for non-existence) is preceded by a plus sign, the EACCES error is treated
19483 as if the file did not exist. For example:
19485 require_files = +/some/file
19487 If the router is not an essential part of verification (for example, it
19488 handles users' &_.forward_& files), another solution is to set the &%verify%&
19489 option false so that the router is skipped when verifying.
19493 .option retry_use_local_part routers boolean "see below"
19494 .cindex "hints database" "retry keys"
19495 .cindex "local part" "in retry keys"
19496 When a delivery suffers a temporary routing failure, a retry record is created
19497 in Exim's hints database. For addresses whose routing depends only on the
19498 domain, the key for the retry record should not involve the local part, but for
19499 other addresses, both the domain and the local part should be included.
19500 Usually, remote routing is of the former kind, and local routing is of the
19503 This option controls whether the local part is used to form the key for retry
19504 hints for addresses that suffer temporary errors while being handled by this
19505 router. The default value is true for any router that has any of
19506 &%check_local_user%&,
19509 &%local_part_prefix%&,
19510 &%local_part_suffix%&,
19513 set, and false otherwise. Note that this option does not apply to hints keys
19514 for transport delays; they are controlled by a generic transport option of the
19517 Failing to set this option when it is needed
19518 (because a remote router handles only some of the local-parts for a domain)
19519 can result in incorrect error messages being generated.
19521 The setting of &%retry_use_local_part%& applies only to the router on which it
19522 appears. If the router generates child addresses, they are routed
19523 independently; this setting does not become attached to them.
19527 .option router_home_directory routers string&!! unset
19528 .cindex "router" "home directory for"
19529 .cindex "home directory" "for router"
19531 This option sets a home directory for use while the router is running. (Compare
19532 &%transport_home_directory%&, which sets a home directory for later
19533 transporting.) In particular, if used on a &(redirect)& router, this option
19534 sets a value for &$home$& while a filter is running. The value is expanded;
19535 forced expansion failure causes the option to be ignored &-- other failures
19536 cause the router to defer.
19538 Expansion of &%router_home_directory%& happens immediately after the
19539 &%check_local_user%& test (if configured), before any further expansions take
19541 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19543 While the router is running, &%router_home_directory%& overrides the value of
19544 &$home$& that came from &%check_local_user%&.
19546 When a router accepts an address and assigns it to a local transport (including
19547 the cases when a &(redirect)& router generates a pipe, file, or autoreply
19548 delivery), the home directory setting for the transport is taken from the first
19549 of these values that is set:
19552 The &%home_directory%& option on the transport;
19554 The &%transport_home_directory%& option on the router;
19556 The password data if &%check_local_user%& is set on the router;
19558 The &%router_home_directory%& option on the router.
19561 In other words, &%router_home_directory%& overrides the password data for the
19562 router, but not for the transport.
19566 .option self routers string freeze
19567 .cindex "MX record" "pointing to local host"
19568 .cindex "local host" "MX pointing to"
19569 This option applies to those routers that use a recipient address to find a
19570 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
19571 and &(manualroute)& routers.
19572 Certain configurations of the &(queryprogram)& router can also specify a list
19574 Usually such routers are configured to send the message to a remote host via an
19575 &(smtp)& transport. The &%self%& option specifies what happens when the first
19576 host on the list turns out to be the local host.
19577 The way in which Exim checks for the local host is described in section
19578 &<<SECTreclocipadd>>&.
19580 Normally this situation indicates either an error in Exim's configuration (for
19581 example, the router should be configured not to process this domain), or an
19582 error in the DNS (for example, the MX should not point to this host). For this
19583 reason, the default action is to log the incident, defer the address, and
19584 freeze the message. The following alternatives are provided for use in special
19589 Delivery of the message is tried again later, but the message is not frozen.
19591 .vitem "&%reroute%&: <&'domain'&>"
19592 The domain is changed to the given domain, and the address is passed back to
19593 be reprocessed by the routers. No rewriting of headers takes place. This
19594 behaviour is essentially a redirection.
19596 .vitem "&%reroute: rewrite:%& <&'domain'&>"
19597 The domain is changed to the given domain, and the address is passed back to be
19598 reprocessed by the routers. Any headers that contain the original domain are
19603 .vindex "&$self_hostname$&"
19604 The router passes the address to the next router, or to the router named in the
19605 &%pass_router%& option if it is set. This overrides &%no_more%&. During
19606 subsequent routing and delivery, the variable &$self_hostname$& contains the
19607 name of the local host that the router encountered. This can be used to
19608 distinguish between different cases for hosts with multiple names. The
19614 ensures that only those addresses that routed to the local host are passed on.
19615 Without &%no_more%&, addresses that were declined for other reasons would also
19616 be passed to the next router.
19619 Delivery fails and an error report is generated.
19622 .cindex "local host" "sending to"
19623 The anomaly is ignored and the address is queued for the transport. This
19624 setting should be used with extreme caution. For an &(smtp)& transport, it
19625 makes sense only in cases where the program that is listening on the SMTP port
19626 is not this version of Exim. That is, it must be some other MTA, or Exim with a
19627 different configuration file that handles the domain in another way.
19632 .option senders routers&!? "address list&!!" unset
19633 .cindex "router" "checking senders"
19634 If this option is set, the router is skipped unless the message's sender
19635 address matches something on the list.
19636 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19639 There are issues concerning verification when the running of routers is
19640 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
19641 setting, it sets the sender to the null string. When using the &%-bt%& option
19642 to check a configuration file, it is necessary also to use the &%-f%& option to
19643 set an appropriate sender. For incoming mail, the sender is unset when
19644 verifying the sender, but is available when verifying any recipients. If the
19645 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
19649 .option set routers "string list" unset
19650 .cindex router variables
19651 This option may be used multiple times on a router;
19652 because of this the list aspect is mostly irrelevant.
19653 The list separator is a semicolon but can be changed in the
19656 Each list-element given must be of the form &"name = value"&
19657 and the names used must start with the string &"r_"&.
19658 Values containing a list-separator should have them doubled.
19659 When a router runs, the strings are evaluated in order,
19660 to create variables which are added to the set associated with
19662 The variable is set with the expansion of the value.
19663 The variables can be used by the router options
19664 (not including any preconditions)
19665 and by the transport.
19666 Later definitions of a given named variable will override former ones.
19667 Variable use is via the usual &$r_...$& syntax.
19669 This is similar to the &%address_data%& option, except that
19670 many independent variables can be used, with choice of naming.
19673 .option translate_ip_address routers string&!! unset
19674 .cindex "IP address" "translating"
19675 .cindex "packet radio"
19676 .cindex "router" "IP address translation"
19677 There exist some rare networking situations (for example, packet radio) where
19678 it is helpful to be able to translate IP addresses generated by normal routing
19679 mechanisms into other IP addresses, thus performing a kind of manual IP
19680 routing. This should be done only if the normal IP routing of the TCP/IP stack
19681 is inadequate or broken. Because this is an extremely uncommon requirement, the
19682 code to support this option is not included in the Exim binary unless
19683 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
19685 .vindex "&$host_address$&"
19686 The &%translate_ip_address%& string is expanded for every IP address generated
19687 by the router, with the generated address set in &$host_address$&. If the
19688 expansion is forced to fail, no action is taken.
19689 For any other expansion error, delivery of the message is deferred.
19690 If the result of the expansion is an IP address, that replaces the original
19691 address; otherwise the result is assumed to be a host name &-- this is looked
19692 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
19693 produce one or more replacement IP addresses. For example, to subvert all IP
19694 addresses in some specific networks, this could be added to a router:
19696 translate_ip_address = \
19697 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
19700 The file would contain lines like
19702 10.2.3.128/26 some.host
19703 10.8.4.34/26 10.44.8.15
19705 You should not make use of this facility unless you really understand what you
19710 .option transport routers string&!! unset
19711 This option specifies the transport to be used when a router accepts an address
19712 and sets it up for delivery. A transport is never needed if a router is used
19713 only for verification. The value of the option is expanded at routing time,
19714 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
19715 and result must be the name of one of the configured transports. If it is not,
19716 delivery is deferred.
19718 The &%transport%& option is not used by the &(redirect)& router, but it does
19719 have some private options that set up transports for pipe and file deliveries
19720 (see chapter &<<CHAPredirect>>&).
19724 .option transport_current_directory routers string&!! unset
19725 .cindex "current directory for local transport"
19726 This option associates a current directory with any address that is routed
19727 to a local transport. This can happen either because a transport is
19728 explicitly configured for the router, or because it generates a delivery to a
19729 file or a pipe. During the delivery process (that is, at transport time), this
19730 option string is expanded and is set as the current directory, unless
19731 overridden by a setting on the transport.
19732 If the expansion fails for any reason, including forced failure, an error is
19733 logged, and delivery is deferred.
19734 See chapter &<<CHAPenvironment>>& for details of the local delivery
19740 .option transport_home_directory routers string&!! "see below"
19741 .cindex "home directory" "for local transport"
19742 This option associates a home directory with any address that is routed to a
19743 local transport. This can happen either because a transport is explicitly
19744 configured for the router, or because it generates a delivery to a file or a
19745 pipe. During the delivery process (that is, at transport time), the option
19746 string is expanded and is set as the home directory, unless overridden by a
19747 setting of &%home_directory%& on the transport.
19748 If the expansion fails for any reason, including forced failure, an error is
19749 logged, and delivery is deferred.
19751 If the transport does not specify a home directory, and
19752 &%transport_home_directory%& is not set for the router, the home directory for
19753 the transport is taken from the password data if &%check_local_user%& is set for
19754 the router. Otherwise it is taken from &%router_home_directory%& if that option
19755 is set; if not, no home directory is set for the transport.
19757 See chapter &<<CHAPenvironment>>& for further details of the local delivery
19763 .option unseen routers boolean&!! false
19764 .cindex "router" "carrying on after success"
19765 The result of string expansion for this option must be a valid boolean value,
19766 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
19767 result causes an error, and delivery is deferred. If the expansion is forced to
19768 fail, the default value for the option (false) is used. Other failures cause
19769 delivery to be deferred.
19771 When this option is set true, routing does not cease if the router accepts the
19772 address. Instead, a copy of the incoming address is passed to the next router,
19773 overriding a false setting of &%more%&. There is little point in setting
19774 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
19775 the value of &%unseen%& contains expansion items (and therefore, presumably, is
19776 sometimes true and sometimes false).
19778 .cindex "copy of message (&%unseen%& option)"
19779 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
19780 qualifier in filter files. It can be used to cause copies of messages to be
19781 delivered to some other destination, while also carrying out a normal delivery.
19782 In effect, the current address is made into a &"parent"& that has two children
19783 &-- one that is delivered as specified by this router, and a clone that goes on
19784 to be routed further. For this reason, &%unseen%& may not be combined with the
19785 &%one_time%& option in a &(redirect)& router.
19787 &*Warning*&: Header lines added to the address (or specified for removal) by
19788 this router or by previous routers affect the &"unseen"& copy of the message
19789 only. The clone that continues to be processed by further routers starts with
19790 no added headers and none specified for removal. For a &%redirect%& router, if
19791 a generated address is the same as the incoming address, this can lead to
19792 duplicate addresses with different header modifications. Exim does not do
19793 duplicate deliveries (except, in certain circumstances, to pipes -- see section
19794 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
19795 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
19796 &%redirect%& router may be of help.
19798 Unlike the handling of header modifications, any data that was set by the
19799 &%address_data%& option in the current or previous routers &'is'& passed on to
19800 subsequent routers.
19803 .option user routers string&!! "see below"
19804 .cindex "uid (user id)" "local delivery"
19805 .cindex "local transports" "uid and gid"
19806 .cindex "transport" "local"
19807 .cindex "router" "user for filter processing"
19808 .cindex "filter" "user for processing"
19809 When a router queues an address for a transport, and the transport does not
19810 specify a user, the user given here is used when running the delivery process.
19811 The user may be specified numerically or by name. If expansion fails, the
19812 error is logged and delivery is deferred.
19813 This user is also used by the &(redirect)& router when running a filter file.
19814 The default is unset, except when &%check_local_user%& is set. In this case,
19815 the default is taken from the password information. If the user is specified as
19816 a name, and &%group%& is not set, the group associated with the user is used.
19817 See also &%initgroups%& and &%group%& and the discussion in chapter
19818 &<<CHAPenvironment>>&.
19822 .option verify routers&!? boolean true
19823 Setting this option has the effect of setting &%verify_sender%& and
19824 &%verify_recipient%& to the same value.
19827 .option verify_only routers&!? boolean false
19828 .cindex "EXPN" "with &%verify_only%&"
19830 .cindex "router" "used only when verifying"
19831 If this option is set, the router is used only when verifying an address,
19832 delivering in cutthrough mode or
19833 testing with the &%-bv%& option, not when actually doing a delivery, testing
19834 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
19835 restricted to verifying only senders or recipients by means of
19836 &%verify_sender%& and &%verify_recipient%&.
19838 &*Warning*&: When the router is being run to verify addresses for an incoming
19839 SMTP message, Exim is not running as root, but under its own uid. If the router
19840 accesses any files, you need to make sure that they are accessible to the Exim
19844 .option verify_recipient routers&!? boolean true
19845 If this option is false, the router is skipped when verifying recipient
19847 delivering in cutthrough mode
19848 or testing recipient verification using &%-bv%&.
19849 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19851 See also the &$verify_mode$& variable.
19854 .option verify_sender routers&!? boolean true
19855 If this option is false, the router is skipped when verifying sender addresses
19856 or testing sender verification using &%-bvs%&.
19857 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
19859 See also the &$verify_mode$& variable.
19860 .ecindex IIDgenoprou1
19861 .ecindex IIDgenoprou2
19868 . ////////////////////////////////////////////////////////////////////////////
19869 . ////////////////////////////////////////////////////////////////////////////
19871 .chapter "The accept router" "CHID4"
19872 .cindex "&(accept)& router"
19873 .cindex "routers" "&(accept)&"
19874 The &(accept)& router has no private options of its own. Unless it is being
19875 used purely for verification (see &%verify_only%&) a transport is required to
19876 be defined by the generic &%transport%& option. If the preconditions that are
19877 specified by generic options are met, the router accepts the address and queues
19878 it for the given transport. The most common use of this router is for setting
19879 up deliveries to local mailboxes. For example:
19883 domains = mydomain.example
19885 transport = local_delivery
19887 The &%domains%& condition in this example checks the domain of the address, and
19888 &%check_local_user%& checks that the local part is the login of a local user.
19889 When both preconditions are met, the &(accept)& router runs, and queues the
19890 address for the &(local_delivery)& transport.
19897 . ////////////////////////////////////////////////////////////////////////////
19898 . ////////////////////////////////////////////////////////////////////////////
19900 .chapter "The dnslookup router" "CHAPdnslookup"
19901 .scindex IIDdnsrou1 "&(dnslookup)& router"
19902 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
19903 The &(dnslookup)& router looks up the hosts that handle mail for the
19904 recipient's domain in the DNS. A transport must always be set for this router,
19905 unless &%verify_only%& is set.
19907 If SRV support is configured (see &%check_srv%& below), Exim first searches for
19908 SRV records. If none are found, or if SRV support is not configured,
19909 MX records are looked up. If no MX records exist, address records are sought.
19910 However, &%mx_domains%& can be set to disable the direct use of address
19913 MX records of equal priority are sorted by Exim into a random order. Exim then
19914 looks for address records for the host names obtained from MX or SRV records.
19915 When a host has more than one IP address, they are sorted into a random order,
19916 except that IPv6 addresses are sorted before IPv4 addresses. If all the
19917 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
19918 generic option, the router declines.
19920 Unless they have the highest priority (lowest MX value), MX records that point
19921 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
19922 are discarded, together with any other MX records of equal or lower priority.
19924 .cindex "MX record" "pointing to local host"
19925 .cindex "local host" "MX pointing to"
19926 .oindex "&%self%&" "in &(dnslookup)& router"
19927 If the host pointed to by the highest priority MX record, or looked up as an
19928 address record, is the local host, or matches &%hosts_treat_as_local%&, what
19929 happens is controlled by the generic &%self%& option.
19932 .section "Problems with DNS lookups" "SECTprowitdnsloo"
19933 There have been problems with DNS servers when SRV records are looked up.
19934 Some misbehaving servers return a DNS error or timeout when a non-existent
19935 SRV record is sought. Similar problems have in the past been reported for
19936 MX records. The global &%dns_again_means_nonexist%& option can help with this
19937 problem, but it is heavy-handed because it is a global option.
19939 For this reason, there are two options, &%srv_fail_domains%& and
19940 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
19941 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
19942 an attempt to look up an SRV or MX record causes one of these results, and the
19943 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
19944 such record"&. In the case of an SRV lookup, this means that the router
19945 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
19946 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
19947 case routing fails.
19950 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
19951 .cindex "&(dnslookup)& router" "declines"
19952 There are a few cases where a &(dnslookup)& router will decline to accept
19953 an address; if such a router is expected to handle "all remaining non-local
19954 domains", then it is important to set &%no_more%&.
19956 The router will defer rather than decline if the domain
19957 is found in the &%fail_defer_domains%& router option.
19959 Reasons for a &(dnslookup)& router to decline currently include:
19961 The domain does not exist in DNS
19963 The domain exists but the MX record's host part is just "."; this is a common
19964 convention (borrowed from SRV) used to indicate that there is no such service
19965 for this domain and to not fall back to trying A/AAAA records.
19967 Ditto, but for SRV records, when &%check_srv%& is set on this router.
19969 MX record points to a non-existent host.
19971 MX record points to an IP address and the main section option
19972 &%allow_mx_to_ip%& is not set.
19974 MX records exist and point to valid hosts, but all hosts resolve only to
19975 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
19977 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
19978 &%dns_check_names_pattern%& for handling one variant of this)
19980 &%check_secondary_mx%& is set on this router but the local host can
19981 not be found in the MX records (see below)
19987 .section "Private options for dnslookup" "SECID118"
19988 .cindex "options" "&(dnslookup)& router"
19989 The private options for the &(dnslookup)& router are as follows:
19991 .option check_secondary_mx dnslookup boolean false
19992 .cindex "MX record" "checking for secondary"
19993 If this option is set, the router declines unless the local host is found in
19994 (and removed from) the list of hosts obtained by MX lookup. This can be used to
19995 process domains for which the local host is a secondary mail exchanger
19996 differently to other domains. The way in which Exim decides whether a host is
19997 the local host is described in section &<<SECTreclocipadd>>&.
20000 .option check_srv dnslookup string&!! unset
20001 .cindex "SRV record" "enabling use of"
20002 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
20003 addition to MX and address records. The support is disabled by default. To
20004 enable SRV support, set the &%check_srv%& option to the name of the service
20005 required. For example,
20009 looks for SRV records that refer to the normal smtp service. The option is
20010 expanded, so the service name can vary from message to message or address
20011 to address. This might be helpful if SRV records are being used for a
20012 submission service. If the expansion is forced to fail, the &%check_srv%&
20013 option is ignored, and the router proceeds to look for MX records in the
20016 When the expansion succeeds, the router searches first for SRV records for
20017 the given service (it assumes TCP protocol). A single SRV record with a
20018 host name that consists of just a single dot indicates &"no such service for
20019 this domain"&; if this is encountered, the router declines. If other kinds of
20020 SRV record are found, they are used to construct a host list for delivery
20021 according to the rules of RFC 2782. MX records are not sought in this case.
20023 When no SRV records are found, MX records (and address records) are sought in
20024 the traditional way. In other words, SRV records take precedence over MX
20025 records, just as MX records take precedence over address records. Note that
20026 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
20027 defined it. It is apparently believed that MX records are sufficient for email
20028 and that SRV records should not be used for this purpose. However, SRV records
20029 have an additional &"weight"& feature which some people might find useful when
20030 trying to split an SMTP load between hosts of different power.
20032 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
20033 when there is a DNS lookup error.
20038 .option fail_defer_domains dnslookup "domain list&!!" unset
20039 .cindex "MX record" "not found"
20040 DNS lookups for domains matching &%fail_defer_domains%&
20041 which find no matching record will cause the router to defer
20042 rather than the default behaviour of decline.
20043 This maybe be useful for queueing messages for a newly created
20044 domain while the DNS configuration is not ready.
20045 However, it will result in any message with mistyped domains
20049 .option ipv4_only "string&!!" unset
20050 .cindex IPv6 disabling
20051 .cindex DNS "IPv6 disabling"
20052 The string is expanded, and if the result is anything but a forced failure,
20053 or an empty string, or one of the strings “0” or “no” or “false”
20054 (checked without regard to the case of the letters),
20055 only A records are used.
20057 .option ipv4_prefer "string&!!" unset
20058 .cindex IPv4 preference
20059 .cindex DNS "IPv4 preference"
20060 The string is expanded, and if the result is anything but a forced failure,
20061 or an empty string, or one of the strings “0” or “no” or “false”
20062 (checked without regard to the case of the letters),
20063 A records are sorted before AAAA records (inverting the default).
20065 .option mx_domains dnslookup "domain list&!!" unset
20066 .cindex "MX record" "required to exist"
20067 .cindex "SRV record" "required to exist"
20068 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
20069 record in order to be recognized. (The name of this option could be improved.)
20070 For example, if all the mail hosts in &'fict.example'& are known to have MX
20071 records, except for those in &'discworld.fict.example'&, you could use this
20074 mx_domains = ! *.discworld.fict.example : *.fict.example
20076 This specifies that messages addressed to a domain that matches the list but
20077 has no MX record should be bounced immediately instead of being routed using
20078 the address record.
20081 .option mx_fail_domains dnslookup "domain list&!!" unset
20082 If the DNS lookup for MX records for one of the domains in this list causes a
20083 DNS lookup error, Exim behaves as if no MX records were found. See section
20084 &<<SECTprowitdnsloo>>& for more discussion.
20089 .option qualify_single dnslookup boolean true
20090 .cindex "DNS" "resolver options"
20091 .cindex "DNS" "qualifying single-component names"
20092 When this option is true, the resolver option RES_DEFNAMES is set for DNS
20093 lookups. Typically, but not standardly, this causes the resolver to qualify
20094 single-component names with the default domain. For example, on a machine
20095 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
20096 &'thesaurus.ref.example'& inside the resolver. For details of what your
20097 resolver actually does, consult your man pages for &'resolver'& and
20102 .option rewrite_headers dnslookup boolean true
20103 .cindex "rewriting" "header lines"
20104 .cindex "header lines" "rewriting"
20105 If the domain name in the address that is being processed is not fully
20106 qualified, it may be expanded to its full form by a DNS lookup. For example, if
20107 an address is specified as &'dormouse@teaparty'&, the domain might be
20108 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
20109 occur as a result of setting the &%widen_domains%& option. If
20110 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
20111 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
20112 header lines of the message are rewritten with the full domain name.
20114 This option should be turned off only when it is known that no message is
20115 ever going to be sent outside an environment where the abbreviation makes
20118 When an MX record is looked up in the DNS and matches a wildcard record, name
20119 servers normally return a record containing the name that has been looked up,
20120 making it impossible to detect whether a wildcard was present or not. However,
20121 some name servers have recently been seen to return the wildcard entry. If the
20122 name returned by a DNS lookup begins with an asterisk, it is not used for
20126 .option same_domain_copy_routing dnslookup boolean false
20127 .cindex "address" "copying routing"
20128 Addresses with the same domain are normally routed by the &(dnslookup)& router
20129 to the same list of hosts. However, this cannot be presumed, because the router
20130 options and preconditions may refer to the local part of the address. By
20131 default, therefore, Exim routes each address in a message independently. DNS
20132 servers run caches, so repeated DNS lookups are not normally expensive, and in
20133 any case, personal messages rarely have more than a few recipients.
20135 If you are running mailing lists with large numbers of subscribers at the same
20136 domain, and you are using a &(dnslookup)& router which is independent of the
20137 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20138 lookups for identical domains in one message. In this case, when &(dnslookup)&
20139 routes an address to a remote transport, any other unrouted addresses in the
20140 message that have the same domain are automatically given the same routing
20141 without processing them independently,
20142 provided the following conditions are met:
20145 No router that processed the address specified &%headers_add%& or
20146 &%headers_remove%&.
20148 The router did not change the address in any way, for example, by &"widening"&
20155 .option search_parents dnslookup boolean false
20156 .cindex "DNS" "resolver options"
20157 When this option is true, the resolver option RES_DNSRCH is set for DNS
20158 lookups. This is different from the &%qualify_single%& option in that it
20159 applies to domains containing dots. Typically, but not standardly, it causes
20160 the resolver to search for the name in the current domain and in parent
20161 domains. For example, on a machine in the &'fict.example'& domain, if looking
20162 up &'teaparty.wonderland'& failed, the resolver would try
20163 &'teaparty.wonderland.fict.example'&. For details of what your resolver
20164 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
20166 Setting this option true can cause problems in domains that have a wildcard MX
20167 record, because any domain that does not have its own MX record matches the
20172 .option srv_fail_domains dnslookup "domain list&!!" unset
20173 If the DNS lookup for SRV records for one of the domains in this list causes a
20174 DNS lookup error, Exim behaves as if no SRV records were found. See section
20175 &<<SECTprowitdnsloo>>& for more discussion.
20180 .option widen_domains dnslookup "string list" unset
20181 .cindex "domain" "partial; widening"
20182 If a DNS lookup fails and this option is set, each of its strings in turn is
20183 added onto the end of the domain, and the lookup is tried again. For example,
20186 widen_domains = fict.example:ref.example
20188 is set and a lookup of &'klingon.dictionary'& fails,
20189 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
20190 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
20191 and &%search_parents%& options can cause some widening to be undertaken inside
20192 the DNS resolver. &%widen_domains%& is not applied to sender addresses
20193 when verifying, unless &%rewrite_headers%& is false (not the default).
20196 .section "Effect of qualify_single and search_parents" "SECID119"
20197 When a domain from an envelope recipient is changed by the resolver as a result
20198 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
20199 corresponding address in the message's header lines unless &%rewrite_headers%&
20200 is set false. Exim then re-routes the address, using the full domain.
20202 These two options affect only the DNS lookup that takes place inside the router
20203 for the domain of the address that is being routed. They do not affect lookups
20204 such as that implied by
20208 that may happen while processing a router precondition before the router is
20209 entered. No widening ever takes place for these lookups.
20210 .ecindex IIDdnsrou1
20211 .ecindex IIDdnsrou2
20221 . ////////////////////////////////////////////////////////////////////////////
20222 . ////////////////////////////////////////////////////////////////////////////
20224 .chapter "The ipliteral router" "CHID5"
20225 .cindex "&(ipliteral)& router"
20226 .cindex "domain literal" "routing"
20227 .cindex "routers" "&(ipliteral)&"
20228 This router has no private options. Unless it is being used purely for
20229 verification (see &%verify_only%&) a transport is required to be defined by the
20230 generic &%transport%& option. The router accepts the address if its domain part
20231 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
20232 router handles the address
20236 by setting up delivery to the host with that IP address. IPv4 domain literals
20237 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
20238 are similar, but the address is preceded by &`ipv6:`&. For example:
20240 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
20242 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
20243 grounds that sooner or later somebody will try it.
20245 .oindex "&%self%&" "in &(ipliteral)& router"
20246 If the IP address matches something in &%ignore_target_hosts%&, the router
20247 declines. If an IP literal turns out to refer to the local host, the generic
20248 &%self%& option determines what happens.
20250 The RFCs require support for domain literals; however, their use is
20251 controversial in today's Internet. If you want to use this router, you must
20252 also set the main configuration option &%allow_domain_literals%&. Otherwise,
20253 Exim will not recognize the domain literal syntax in addresses.
20257 . ////////////////////////////////////////////////////////////////////////////
20258 . ////////////////////////////////////////////////////////////////////////////
20260 .chapter "The iplookup router" "CHID6"
20261 .cindex "&(iplookup)& router"
20262 .cindex "routers" "&(iplookup)&"
20263 The &(iplookup)& router was written to fulfil a specific requirement in
20264 Cambridge University (which in fact no longer exists). For this reason, it is
20265 not included in the binary of Exim by default. If you want to include it, you
20268 ROUTER_IPLOOKUP=yes
20270 in your &_Local/Makefile_& configuration file.
20272 The &(iplookup)& router routes an address by sending it over a TCP or UDP
20273 connection to one or more specific hosts. The host can then return the same or
20274 a different address &-- in effect rewriting the recipient address in the
20275 message's envelope. The new address is then passed on to subsequent routers. If
20276 this process fails, the address can be passed on to other routers, or delivery
20277 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
20278 must not be specified for it.
20280 .cindex "options" "&(iplookup)& router"
20281 .option hosts iplookup string unset
20282 This option must be supplied. Its value is a colon-separated list of host
20283 names. The hosts are looked up using &[gethostbyname()]&
20284 (or &[getipnodebyname()]& when available)
20285 and are tried in order until one responds to the query. If none respond, what
20286 happens is controlled by &%optional%&.
20289 .option optional iplookup boolean false
20290 If &%optional%& is true, if no response is obtained from any host, the address
20291 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
20292 delivery to the address is deferred.
20295 .option port iplookup integer 0
20296 .cindex "port" "&(iplookup)& router"
20297 This option must be supplied. It specifies the port number for the TCP or UDP
20301 .option protocol iplookup string udp
20302 This option can be set to &"udp"& or &"tcp"& to specify which of the two
20303 protocols is to be used.
20306 .option query iplookup string&!! "see below"
20307 This defines the content of the query that is sent to the remote hosts. The
20310 $local_part@$domain $local_part@$domain
20312 The repetition serves as a way of checking that a response is to the correct
20313 query in the default case (see &%response_pattern%& below).
20316 .option reroute iplookup string&!! unset
20317 If this option is not set, the rerouted address is precisely the byte string
20318 returned by the remote host, up to the first white space, if any. If set, the
20319 string is expanded to form the rerouted address. It can include parts matched
20320 in the response by &%response_pattern%& by means of numeric variables such as
20321 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
20322 whether or not a pattern is in use. In all cases, the rerouted address must end
20323 up in the form &'local_part@domain'&.
20326 .option response_pattern iplookup string unset
20327 This option can be set to a regular expression that is applied to the string
20328 returned from the remote host. If the pattern does not match the response, the
20329 router declines. If &%response_pattern%& is not set, no checking of the
20330 response is done, unless the query was defaulted, in which case there is a
20331 check that the text returned after the first white space is the original
20332 address. This checks that the answer that has been received is in response to
20333 the correct question. For example, if the response is just a new domain, the
20334 following could be used:
20336 response_pattern = ^([^@]+)$
20337 reroute = $local_part@$1
20340 .option timeout iplookup time 5s
20341 This specifies the amount of time to wait for a response from the remote
20342 machine. The same timeout is used for the &[connect()]& function for a TCP
20343 call. It does not apply to UDP.
20348 . ////////////////////////////////////////////////////////////////////////////
20349 . ////////////////////////////////////////////////////////////////////////////
20351 .chapter "The manualroute router" "CHID7"
20352 .scindex IIDmanrou1 "&(manualroute)& router"
20353 .scindex IIDmanrou2 "routers" "&(manualroute)&"
20354 .cindex "domain" "manually routing"
20355 The &(manualroute)& router is so-called because it provides a way of manually
20356 routing an address according to its domain. It is mainly used when you want to
20357 route addresses to remote hosts according to your own rules, bypassing the
20358 normal DNS routing that looks up MX records. However, &(manualroute)& can also
20359 route to local transports, a facility that may be useful if you want to save
20360 messages for dial-in hosts in local files.
20362 The &(manualroute)& router compares a list of domain patterns with the domain
20363 it is trying to route. If there is no match, the router declines. Each pattern
20364 has associated with it a list of hosts and some other optional data, which may
20365 include a transport. The combination of a pattern and its data is called a
20366 &"routing rule"&. For patterns that do not have an associated transport, the
20367 generic &%transport%& option must specify a transport, unless the router is
20368 being used purely for verification (see &%verify_only%&).
20371 In the case of verification, matching the domain pattern is sufficient for the
20372 router to accept the address. When actually routing an address for delivery,
20373 an address that matches a domain pattern is queued for the associated
20374 transport. If the transport is not a local one, a host list must be associated
20375 with the pattern; IP addresses are looked up for the hosts, and these are
20376 passed to the transport along with the mail address. For local transports, a
20377 host list is optional. If it is present, it is passed in &$host$& as a single
20380 The list of routing rules can be provided as an inline string in
20381 &%route_list%&, or the data can be obtained by looking up the domain in a file
20382 or database by setting &%route_data%&. Only one of these settings may appear in
20383 any one instance of &(manualroute)&. The format of routing rules is described
20384 below, following the list of private options.
20387 .section "Private options for manualroute" "SECTprioptman"
20389 .cindex "options" "&(manualroute)& router"
20390 The private options for the &(manualroute)& router are as follows:
20392 .option host_all_ignored manualroute string defer
20393 See &%host_find_failed%&.
20395 .option host_find_failed manualroute string freeze
20396 This option controls what happens when &(manualroute)& tries to find an IP
20397 address for a host, and the host does not exist. The option can be set to one
20398 of the following values:
20407 The default (&"freeze"&) assumes that this state is a serious configuration
20408 error. The difference between &"pass"& and &"decline"& is that the former
20409 forces the address to be passed to the next router (or the router defined by
20412 overriding &%no_more%&, whereas the latter passes the address to the next
20413 router only if &%more%& is true.
20415 The value &"ignore"& causes Exim to completely ignore a host whose IP address
20416 cannot be found. If all the hosts in the list are ignored, the behaviour is
20417 controlled by the &%host_all_ignored%& option. This takes the same values
20418 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
20420 The &%host_find_failed%& option applies only to a definite &"does not exist"&
20421 state; if a host lookup gets a temporary error, delivery is deferred unless the
20422 generic &%pass_on_timeout%& option is set.
20425 .option hosts_randomize manualroute boolean false
20426 .cindex "randomized host list"
20427 .cindex "host" "list of; randomized"
20428 If this option is set, the order of the items in a host list in a routing rule
20429 is randomized each time the list is used, unless an option in the routing rule
20430 overrides (see below). Randomizing the order of a host list can be used to do
20431 crude load sharing. However, if more than one mail address is routed by the
20432 same router to the same host list, the host lists are considered to be the same
20433 (even though they may be randomized into different orders) for the purpose of
20434 deciding whether to batch the deliveries into a single SMTP transaction.
20436 When &%hosts_randomize%& is true, a host list may be split
20437 into groups whose order is separately randomized. This makes it possible to
20438 set up MX-like behaviour. The boundaries between groups are indicated by an
20439 item that is just &`+`& in the host list. For example:
20441 route_list = * host1:host2:host3:+:host4:host5
20443 The order of the first three hosts and the order of the last two hosts is
20444 randomized for each use, but the first three always end up before the last two.
20445 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
20446 randomized host list is passed to an &(smtp)& transport that also has
20447 &%hosts_randomize set%&, the list is not re-randomized.
20450 .option route_data manualroute string&!! unset
20451 If this option is set, it must expand to yield the data part of a routing rule.
20452 Typically, the expansion string includes a lookup based on the domain. For
20455 route_data = ${lookup{$domain}dbm{/etc/routes}}
20457 If the expansion is forced to fail, or the result is an empty string, the
20458 router declines. Other kinds of expansion failure cause delivery to be
20462 .option route_list manualroute "string list" unset
20463 This string is a list of routing rules, in the form defined below. Note that,
20464 unlike most string lists, the items are separated by semicolons. This is so
20465 that they may contain colon-separated host lists.
20468 .option same_domain_copy_routing manualroute boolean false
20469 .cindex "address" "copying routing"
20470 Addresses with the same domain are normally routed by the &(manualroute)&
20471 router to the same list of hosts. However, this cannot be presumed, because the
20472 router options and preconditions may refer to the local part of the address. By
20473 default, therefore, Exim routes each address in a message independently. DNS
20474 servers run caches, so repeated DNS lookups are not normally expensive, and in
20475 any case, personal messages rarely have more than a few recipients.
20477 If you are running mailing lists with large numbers of subscribers at the same
20478 domain, and you are using a &(manualroute)& router which is independent of the
20479 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
20480 lookups for identical domains in one message. In this case, when
20481 &(manualroute)& routes an address to a remote transport, any other unrouted
20482 addresses in the message that have the same domain are automatically given the
20483 same routing without processing them independently. However, this is only done
20484 if &%headers_add%& and &%headers_remove%& are unset.
20489 .section "Routing rules in route_list" "SECID120"
20490 The value of &%route_list%& is a string consisting of a sequence of routing
20491 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
20492 entered as two semicolons. Alternatively, the list separator can be changed as
20493 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
20494 Empty rules are ignored. The format of each rule is
20496 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
20498 The following example contains two rules, each with a simple domain pattern and
20502 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
20503 thes.ref.example mail-3.ref.example:mail-4.ref.example
20505 The three parts of a rule are separated by white space. The pattern and the
20506 list of hosts can be enclosed in quotes if necessary, and if they are, the
20507 usual quoting rules apply. Each rule in a &%route_list%& must start with a
20508 single domain pattern, which is the only mandatory item in the rule. The
20509 pattern is in the same format as one item in a domain list (see section
20510 &<<SECTdomainlist>>&),
20511 except that it may not be the name of an interpolated file.
20512 That is, it may be wildcarded, or a regular expression, or a file or database
20513 lookup (with semicolons doubled, because of the use of semicolon as a separator
20514 in a &%route_list%&).
20516 The rules in &%route_list%& are searched in order until one of the patterns
20517 matches the domain that is being routed. The list of hosts and then options are
20518 then used as described below. If there is no match, the router declines. When
20519 &%route_list%& is set, &%route_data%& must not be set.
20523 .section "Routing rules in route_data" "SECID121"
20524 The use of &%route_list%& is convenient when there are only a small number of
20525 routing rules. For larger numbers, it is easier to use a file or database to
20526 hold the routing information, and use the &%route_data%& option instead.
20527 The value of &%route_data%& is a list of hosts, followed by (optional) options.
20528 Most commonly, &%route_data%& is set as a string that contains an
20529 expansion lookup. For example, suppose we place two routing rules in a file
20532 dict.ref.example: mail-1.ref.example:mail-2.ref.example
20533 thes.ref.example: mail-3.ref.example:mail-4.ref.example
20535 This data can be accessed by setting
20537 route_data = ${lookup{$domain}lsearch{/the/file/name}}
20539 Failure of the lookup results in an empty string, causing the router to
20540 decline. However, you do not have to use a lookup in &%route_data%&. The only
20541 requirement is that the result of expanding the string is a list of hosts,
20542 possibly followed by options, separated by white space. The list of hosts must
20543 be enclosed in quotes if it contains white space.
20548 .section "Format of the list of hosts" "SECID122"
20549 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
20550 always separately expanded before use. If the expansion fails, the router
20551 declines. The result of the expansion must be a colon-separated list of names
20552 and/or IP addresses, optionally also including ports.
20553 If the list is written with spaces, it must be protected with quotes.
20554 The format of each item
20555 in the list is described in the next section. The list separator can be changed
20556 as described in section &<<SECTlistsepchange>>&.
20558 If the list of hosts was obtained from a &%route_list%& item, the following
20559 variables are set during its expansion:
20562 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
20563 If the domain was matched against a regular expression, the numeric variables
20564 &$1$&, &$2$&, etc. may be set. For example:
20566 route_list = ^domain(\d+) host-$1.text.example
20569 &$0$& is always set to the entire domain.
20571 &$1$& is also set when partial matching is done in a file lookup.
20574 .vindex "&$value$&"
20575 If the pattern that matched the domain was a lookup item, the data that was
20576 looked up is available in the expansion variable &$value$&. For example:
20578 route_list = lsearch;;/some/file.routes $value
20582 Note the doubling of the semicolon in the pattern that is necessary because
20583 semicolon is the default route list separator.
20587 .section "Format of one host item" "SECTformatonehostitem"
20588 Each item in the list of hosts can be either a host name or an IP address,
20589 optionally with an attached port number, or it can be a single "+"
20590 (see &%hosts_randomize%&).
20591 When no port is given, an IP address
20592 is not enclosed in brackets. When a port is specified, it overrides the port
20593 specification on the transport. The port is separated from the name or address
20594 by a colon. This leads to some complications:
20597 Because colon is the default separator for the list of hosts, either
20598 the colon that specifies a port must be doubled, or the list separator must
20599 be changed. The following two examples have the same effect:
20601 route_list = * "host1.tld::1225 : host2.tld::1226"
20602 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
20605 When IPv6 addresses are involved, it gets worse, because they contain
20606 colons of their own. To make this case easier, it is permitted to
20607 enclose an IP address (either v4 or v6) in square brackets if a port
20608 number follows. For example:
20610 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
20614 .section "How the list of hosts is used" "SECThostshowused"
20615 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
20616 the hosts is tried, in the order specified, when carrying out the SMTP
20617 delivery. However, the order can be changed by setting the &%hosts_randomize%&
20618 option, either on the router (see section &<<SECTprioptman>>& above), or on the
20621 Hosts may be listed by name or by IP address. An unadorned name in the list of
20622 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
20623 interpreted as an indirection to a sublist of hosts obtained by looking up MX
20624 records in the DNS. For example:
20626 route_list = * x.y.z:p.q.r/MX:e.f.g
20628 If this feature is used with a port specifier, the port must come last. For
20631 route_list = * dom1.tld/mx::1225
20633 If the &%hosts_randomize%& option is set, the order of the items in the list is
20634 randomized before any lookups are done. Exim then scans the list; for any name
20635 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
20636 be an interface on the local host and the item is not the first in the list,
20637 Exim discards it and any subsequent items. If it is the first item, what
20638 happens is controlled by the
20639 .oindex "&%self%&" "in &(manualroute)& router"
20640 &%self%& option of the router.
20642 A name on the list that is followed by &`/MX`& is replaced with the list of
20643 hosts obtained by looking up MX records for the name. This is always a DNS
20644 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
20645 below) are not relevant here. The order of these hosts is determined by the
20646 preference values in the MX records, according to the usual rules. Because
20647 randomizing happens before the MX lookup, it does not affect the order that is
20648 defined by MX preferences.
20650 If the local host is present in the sublist obtained from MX records, but is
20651 not the most preferred host in that list, it and any equally or less
20652 preferred hosts are removed before the sublist is inserted into the main list.
20654 If the local host is the most preferred host in the MX list, what happens
20655 depends on where in the original list of hosts the &`/MX`& item appears. If it
20656 is not the first item (that is, there are previous hosts in the main list),
20657 Exim discards this name and any subsequent items in the main list.
20659 If the MX item is first in the list of hosts, and the local host is the
20660 most preferred host, what happens is controlled by the &%self%& option of the
20663 DNS failures when lookup up the MX records are treated in the same way as DNS
20664 failures when looking up IP addresses: &%pass_on_timeout%& and
20665 &%host_find_failed%& are used when relevant.
20667 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
20668 whether obtained from an MX lookup or not.
20672 .section "How the options are used" "SECThowoptused"
20673 The options are a sequence of words, space-separated.
20674 One of the words can be the name of a transport; this overrides the
20675 &%transport%& option on the router for this particular routing rule only. The
20676 other words (if present) control randomization of the list of hosts on a
20677 per-rule basis, and how the IP addresses of the hosts are to be found when
20678 routing to a remote transport. These options are as follows:
20681 &%randomize%&: randomize the order of the hosts in this list, overriding the
20682 setting of &%hosts_randomize%& for this routing rule only.
20684 &%no_randomize%&: do not randomize the order of the hosts in this list,
20685 overriding the setting of &%hosts_randomize%& for this routing rule only.
20687 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
20688 find IP addresses. This function may ultimately cause a DNS lookup, but it may
20689 also look in &_/etc/hosts_& or other sources of information.
20691 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
20692 no address records are found. If there is a temporary DNS error (such as a
20693 timeout), delivery is deferred.
20695 &%ipv4_only%&: in direct DNS lookups, look up only A records.
20697 &%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
20702 route_list = domain1 host1:host2:host3 randomize bydns;\
20703 domain2 host4:host5
20705 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
20706 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
20707 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
20708 or &[gethostbyname()]&, and the result of the lookup is the result of that
20711 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
20712 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
20713 instead of TRY_AGAIN. That is why the default action is to try a DNS
20714 lookup first. Only if that gives a definite &"no such host"& is the local
20717 &*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
20718 inadvertent constraint that a transport name as an option had to be the last
20723 If no IP address for a host can be found, what happens is controlled by the
20724 &%host_find_failed%& option.
20727 When an address is routed to a local transport, IP addresses are not looked up.
20728 The host list is passed to the transport in the &$host$& variable.
20732 .section "Manualroute examples" "SECID123"
20733 In some of the examples that follow, the presence of the &%remote_smtp%&
20734 transport, as defined in the default configuration file, is assumed:
20737 .cindex "smart host" "example router"
20738 The &(manualroute)& router can be used to forward all external mail to a
20739 &'smart host'&. If you have set up, in the main part of the configuration, a
20740 named domain list that contains your local domains, for example:
20742 domainlist local_domains = my.domain.example
20744 You can arrange for all other domains to be routed to a smart host by making
20745 your first router something like this:
20748 driver = manualroute
20749 domains = !+local_domains
20750 transport = remote_smtp
20751 route_list = * smarthost.ref.example
20753 This causes all non-local addresses to be sent to the single host
20754 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
20755 they are tried in order
20756 (but you can use &%hosts_randomize%& to vary the order each time).
20757 Another way of configuring the same thing is this:
20760 driver = manualroute
20761 transport = remote_smtp
20762 route_list = !+local_domains smarthost.ref.example
20764 There is no difference in behaviour between these two routers as they stand.
20765 However, they behave differently if &%no_more%& is added to them. In the first
20766 example, the router is skipped if the domain does not match the &%domains%&
20767 precondition; the following router is always tried. If the router runs, it
20768 always matches the domain and so can never decline. Therefore, &%no_more%&
20769 would have no effect. In the second case, the router is never skipped; it
20770 always runs. However, if it doesn't match the domain, it declines. In this case
20771 &%no_more%& would prevent subsequent routers from running.
20774 .cindex "mail hub example"
20775 A &'mail hub'& is a host which receives mail for a number of domains via MX
20776 records in the DNS and delivers it via its own private routing mechanism. Often
20777 the final destinations are behind a firewall, with the mail hub being the one
20778 machine that can connect to machines both inside and outside the firewall. The
20779 &(manualroute)& router is usually used on a mail hub to route incoming messages
20780 to the correct hosts. For a small number of domains, the routing can be inline,
20781 using the &%route_list%& option, but for a larger number a file or database
20782 lookup is easier to manage.
20784 If the domain names are in fact the names of the machines to which the mail is
20785 to be sent by the mail hub, the configuration can be quite simple. For
20789 driver = manualroute
20790 transport = remote_smtp
20791 route_list = *.rhodes.tvs.example $domain
20793 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
20794 whose names are the same as the mail domains. A similar approach can be taken
20795 if the host name can be obtained from the domain name by a string manipulation
20796 that the expansion facilities can handle. Otherwise, a lookup based on the
20797 domain can be used to find the host:
20800 driver = manualroute
20801 transport = remote_smtp
20802 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
20804 The result of the lookup must be the name or IP address of the host (or
20805 hosts) to which the address is to be routed. If the lookup fails, the route
20806 data is empty, causing the router to decline. The address then passes to the
20810 .cindex "batched SMTP output example"
20811 .cindex "SMTP" "batched outgoing; example"
20812 You can use &(manualroute)& to deliver messages to pipes or files in batched
20813 SMTP format for onward transportation by some other means. This is one way of
20814 storing mail for a dial-up host when it is not connected. The route list entry
20815 can be as simple as a single domain name in a configuration like this:
20818 driver = manualroute
20819 transport = batchsmtp_appendfile
20820 route_list = saved.domain.example
20822 though often a pattern is used to pick up more than one domain. If there are
20823 several domains or groups of domains with different transport requirements,
20824 different transports can be listed in the routing information:
20827 driver = manualroute
20829 *.saved.domain1.example $domain batch_appendfile; \
20830 *.saved.domain2.example \
20831 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
20834 .vindex "&$domain$&"
20836 The first of these just passes the domain in the &$host$& variable, which
20837 doesn't achieve much (since it is also in &$domain$&), but the second does a
20838 file lookup to find a value to pass, causing the router to decline to handle
20839 the address if the lookup fails.
20842 .cindex "UUCP" "example of router for"
20843 Routing mail directly to UUCP software is a specific case of the use of
20844 &(manualroute)& in a gateway to another mail environment. This is an example of
20845 one way it can be done:
20851 command = /usr/local/bin/uux -r - \
20852 ${substr_-5:$host}!rmail ${local_part}
20853 return_fail_output = true
20858 driver = manualroute
20860 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
20862 The file &_/usr/local/exim/uucphosts_& contains entries like
20864 darksite.ethereal.example: darksite.UUCP
20866 It can be set up more simply without adding and removing &".UUCP"& but this way
20867 makes clear the distinction between the domain name
20868 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
20870 .ecindex IIDmanrou1
20871 .ecindex IIDmanrou2
20880 . ////////////////////////////////////////////////////////////////////////////
20881 . ////////////////////////////////////////////////////////////////////////////
20883 .chapter "The queryprogram router" "CHAPdriverlast"
20884 .scindex IIDquerou1 "&(queryprogram)& router"
20885 .scindex IIDquerou2 "routers" "&(queryprogram)&"
20886 .cindex "routing" "by external program"
20887 The &(queryprogram)& router routes an address by running an external command
20888 and acting on its output. This is an expensive way to route, and is intended
20889 mainly for use in lightly-loaded systems, or for performing experiments.
20890 However, if it is possible to use the precondition options (&%domains%&,
20891 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
20892 be used in special cases, even on a busy host. There are the following private
20894 .cindex "options" "&(queryprogram)& router"
20896 .option command queryprogram string&!! unset
20897 This option must be set. It specifies the command that is to be run. The
20898 command is split up into a command name and arguments, and then each is
20899 expanded separately (exactly as for a &(pipe)& transport, described in chapter
20900 &<<CHAPpipetransport>>&).
20903 .option command_group queryprogram string unset
20904 .cindex "gid (group id)" "in &(queryprogram)& router"
20905 This option specifies a gid to be set when running the command while routing an
20906 address for deliver. It must be set if &%command_user%& specifies a numerical
20907 uid. If it begins with a digit, it is interpreted as the numerical value of the
20908 gid. Otherwise it is looked up using &[getgrnam()]&.
20911 .option command_user queryprogram string unset
20912 .cindex "uid (user id)" "for &(queryprogram)&"
20913 This option must be set. It specifies the uid which is set when running the
20914 command while routing an address for delivery. If the value begins with a digit,
20915 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
20916 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
20917 not set, a value for the gid also.
20919 &*Warning:*& Changing uid and gid is possible only when Exim is running as
20920 root, which it does during a normal delivery in a conventional configuration.
20921 However, when an address is being verified during message reception, Exim is
20922 usually running as the Exim user, not as root. If the &(queryprogram)& router
20923 is called from a non-root process, Exim cannot change uid or gid before running
20924 the command. In this circumstance the command runs under the current uid and
20928 .option current_directory queryprogram string /
20929 This option specifies an absolute path which is made the current directory
20930 before running the command.
20933 .option timeout queryprogram time 1h
20934 If the command does not complete within the timeout period, its process group
20935 is killed and the message is frozen. A value of zero time specifies no
20939 The standard output of the command is connected to a pipe, which is read when
20940 the command terminates. It should consist of a single line of output,
20941 containing up to five fields, separated by white space. The maximum length of
20942 the line is 1023 characters. Longer lines are silently truncated. The first
20943 field is one of the following words (case-insensitive):
20946 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
20949 &'Decline'&: the router declines; pass the address to the next router, unless
20950 &%no_more%& is set.
20952 &'Fail'&: routing failed; do not pass the address to any more routers. Any
20953 subsequent text on the line is an error message. If the router is run as part
20954 of address verification during an incoming SMTP message, the message is
20955 included in the SMTP response.
20957 &'Defer'&: routing could not be completed at this time; try again later. Any
20958 subsequent text on the line is an error message which is logged. It is not
20959 included in any SMTP response.
20961 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
20963 &'Pass'&: pass the address to the next router (or the router specified by
20964 &%pass_router%&), overriding &%no_more%&.
20966 &'Redirect'&: the message is redirected. The remainder of the line is a list of
20967 new addresses, which are routed independently, starting with the first router,
20968 or the router specified by &%redirect_router%&, if set.
20971 When the first word is &'accept'&, the remainder of the line consists of a
20972 number of keyed data values, as follows (split into two lines here, to fit on
20975 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
20976 LOOKUP=byname|bydns DATA=<text>
20978 The data items can be given in any order, and all are optional. If no transport
20979 is included, the transport specified by the generic &%transport%& option is
20980 used. The list of hosts and the lookup type are needed only if the transport is
20981 an &(smtp)& transport that does not itself supply a list of hosts.
20983 The format of the list of hosts is the same as for the &(manualroute)& router.
20984 As well as host names and IP addresses with optional port numbers, as described
20985 in section &<<SECTformatonehostitem>>&, it may contain names followed by
20986 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
20987 (see section &<<SECThostshowused>>&).
20989 If the lookup type is not specified, Exim behaves as follows when trying to
20990 find an IP address for each host: First, a DNS lookup is done. If this yields
20991 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
20992 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
20993 result of the lookup is the result of that call.
20995 .vindex "&$address_data$&"
20996 If the DATA field is set, its value is placed in the &$address_data$&
20997 variable. For example, this return line
20999 accept hosts=x1.y.example:x2.y.example data="rule1"
21001 routes the address to the default transport, passing a list of two hosts. When
21002 the transport runs, the string &"rule1"& is in &$address_data$&.
21003 .ecindex IIDquerou1
21004 .ecindex IIDquerou2
21009 . ////////////////////////////////////////////////////////////////////////////
21010 . ////////////////////////////////////////////////////////////////////////////
21012 .chapter "The redirect router" "CHAPredirect"
21013 .scindex IIDredrou1 "&(redirect)& router"
21014 .scindex IIDredrou2 "routers" "&(redirect)&"
21015 .cindex "alias file" "in a &(redirect)& router"
21016 .cindex "address redirection" "&(redirect)& router"
21017 The &(redirect)& router handles several kinds of address redirection. Its most
21018 common uses are for resolving local part aliases from a central alias file
21019 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
21020 files, but it has many other potential uses. The incoming address can be
21021 redirected in several different ways:
21024 It can be replaced by one or more new addresses which are themselves routed
21027 It can be routed to be delivered to a given file or directory.
21029 It can be routed to be delivered to a specified pipe command.
21031 It can cause an automatic reply to be generated.
21033 It can be forced to fail, optionally with a custom error message.
21035 It can be temporarily deferred, optionally with a custom message.
21037 It can be discarded.
21040 The generic &%transport%& option must not be set for &(redirect)& routers.
21041 However, there are some private options which define transports for delivery to
21042 files and pipes, and for generating autoreplies. See the &%file_transport%&,
21043 &%pipe_transport%& and &%reply_transport%& descriptions below.
21045 If success DSNs have been requested
21046 .cindex "DSN" "success"
21047 .cindex "Delivery Status Notification" "success"
21048 redirection triggers one and the DSN options are not passed any further.
21052 .section "Redirection data" "SECID124"
21053 The router operates by interpreting a text string which it obtains either by
21054 expanding the contents of the &%data%& option, or by reading the entire
21055 contents of a file whose name is given in the &%file%& option. These two
21056 options are mutually exclusive. The first is commonly used for handling system
21057 aliases, in a configuration like this:
21061 data = ${lookup{$local_part}lsearch{/etc/aliases}}
21063 If the lookup fails, the expanded string in this example is empty. When the
21064 expansion of &%data%& results in an empty string, the router declines. A forced
21065 expansion failure also causes the router to decline; other expansion failures
21066 cause delivery to be deferred.
21068 A configuration using &%file%& is commonly used for handling users'
21069 &_.forward_& files, like this:
21074 file = $home/.forward
21077 If the file does not exist, or causes no action to be taken (for example, it is
21078 empty or consists only of comments), the router declines. &*Warning*&: This
21079 is not the case when the file contains syntactically valid items that happen to
21080 yield empty addresses, for example, items containing only RFC 2822 address
21083 .cindex "tainted data" "in filenames"
21084 .cindex redirect "tainted data"
21085 Tainted data may not be used for a filename.
21087 &*Warning*&: It is unwise to use &$local_part$& or &$domain$&
21088 directly for redirection,
21089 as they are provided by a potential attacker.
21090 In the examples above, &$local_part$& is used for looking up data held locally
21091 on the system, and not used directly (the second example derives &$home$& via
21092 the passsword file or database, using &$local_part$&).
21096 .section "Forward files and address verification" "SECID125"
21097 .cindex "address redirection" "while verifying"
21098 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
21099 &_.forward_& files, as in the example above. There are two reasons for this:
21102 When Exim is receiving an incoming SMTP message from a remote host, it is
21103 running under the Exim uid, not as root. Exim is unable to change uid to read
21104 the file as the user, and it may not be able to read it as the Exim user. So in
21105 practice the router may not be able to operate.
21107 However, even when the router can operate, the existence of a &_.forward_& file
21108 is unimportant when verifying an address. What should be checked is whether the
21109 local part is a valid user name or not. Cutting out the redirection processing
21110 saves some resources.
21118 .section "Interpreting redirection data" "SECID126"
21119 .cindex "Sieve filter" "specifying in redirection data"
21120 .cindex "filter" "specifying in redirection data"
21121 The contents of the data string, whether obtained from &%data%& or &%file%&,
21122 can be interpreted in two different ways:
21125 If the &%allow_filter%& option is set true, and the data begins with the text
21126 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
21127 &'filtering'& instructions in the form of an Exim or Sieve filter file,
21128 respectively. Details of the syntax and semantics of filter files are described
21129 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
21130 document is intended for use by end users.
21132 Otherwise, the data must be a comma-separated list of redirection items, as
21133 described in the next section.
21136 When a message is redirected to a file (a &"mail folder"&), the filename given
21137 in a non-filter redirection list must always be an absolute path. A filter may
21138 generate a relative path &-- how this is handled depends on the transport's
21139 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
21140 for the &(appendfile)& transport.
21144 .section "Items in a non-filter redirection list" "SECTitenonfilred"
21145 .cindex "address redirection" "non-filter list items"
21146 When the redirection data is not an Exim or Sieve filter, for example, if it
21147 comes from a conventional alias or forward file, it consists of a list of
21148 addresses, filenames, pipe commands, or certain special items (see section
21149 &<<SECTspecitredli>>& below). The special items can be individually enabled or
21150 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
21151 depending on their default values. The items in the list are separated by
21152 commas or newlines.
21153 If a comma is required in an item, the entire item must be enclosed in double
21156 Lines starting with a # character are comments, and are ignored, and # may
21157 also appear following a comma, in which case everything between the # and the
21158 next newline character is ignored.
21160 If an item is entirely enclosed in double quotes, these are removed. Otherwise
21161 double quotes are retained because some forms of mail address require their use
21162 (but never to enclose the entire address). In the following description,
21163 &"item"& refers to what remains after any surrounding double quotes have been
21166 .vindex "&$local_part$&"
21167 &*Warning*&: If you use an Exim expansion to construct a redirection address,
21168 and the expansion contains a reference to &$local_part$&, you should make use
21169 of the &%quote_local_part%& expansion operator, in case the local part contains
21170 special characters. For example, to redirect all mail for the domain
21171 &'obsolete.example'&, retaining the existing local part, you could use this
21174 data = ${quote_local_part:$local_part}@newdomain.example
21178 .section "Redirecting to a local mailbox" "SECTredlocmai"
21179 .cindex "routing" "loops in"
21180 .cindex "loop" "while routing, avoidance of"
21181 .cindex "address redirection" "to local mailbox"
21182 A redirection item may safely be the same as the address currently under
21183 consideration. This does not cause a routing loop, because a router is
21184 automatically skipped if any ancestor of the address that is being processed
21185 is the same as the current address and was processed by the current router.
21186 Such an address is therefore passed to the following routers, so it is handled
21187 as if there were no redirection. When making this loop-avoidance test, the
21188 complete local part, including any prefix or suffix, is used.
21190 .cindex "address redirection" "local part without domain"
21191 Specifying the same local part without a domain is a common usage in personal
21192 filter files when the user wants to have messages delivered to the local
21193 mailbox and also forwarded elsewhere. For example, the user whose login is
21194 &'cleo'& might have a &_.forward_& file containing this:
21196 cleo, cleopatra@egypt.example
21198 .cindex "backslash in alias file"
21199 .cindex "alias file" "backslash in"
21200 For compatibility with other MTAs, such unqualified local parts may be
21201 preceded by &"\"&, but this is not a requirement for loop prevention. However,
21202 it does make a difference if more than one domain is being handled
21205 If an item begins with &"\"& and the rest of the item parses as a valid RFC
21206 2822 address that does not include a domain, the item is qualified using the
21207 domain of the incoming address. In the absence of a leading &"\"&, unqualified
21208 addresses are qualified using the value in &%qualify_recipient%&, but you can
21209 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
21211 Care must be taken if there are alias names for local users.
21212 Consider an MTA handling a single local domain where the system alias file
21217 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
21218 messages in the local mailbox, and also forward copies elsewhere. He creates
21221 Sam.Reman, spqr@reme.elsewhere.example
21223 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
21224 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
21225 second time round, because it has previously routed it,
21226 and the following routers presumably cannot handle the alias. The forward file
21227 should really contain
21229 spqr, spqr@reme.elsewhere.example
21231 but because this is such a common error, the &%check_ancestor%& option (see
21232 below) exists to provide a way to get round it. This is normally set on a
21233 &(redirect)& router that is handling users' &_.forward_& files.
21237 .section "Special items in redirection lists" "SECTspecitredli"
21238 In addition to addresses, the following types of item may appear in redirection
21239 lists (that is, in non-filter redirection data):
21242 .cindex "pipe" "in redirection list"
21243 .cindex "address redirection" "to pipe"
21244 An item is treated as a pipe command if it begins with &"|"& and does not parse
21245 as a valid RFC 2822 address that includes a domain. A transport for running the
21246 command must be specified by the &%pipe_transport%& option.
21247 Normally, either the router or the transport specifies a user and a group under
21248 which to run the delivery. The default is to use the Exim user and group.
21250 Single or double quotes can be used for enclosing the individual arguments of
21251 the pipe command; no interpretation of escapes is done for single quotes. If
21252 the command contains a comma character, it is necessary to put the whole item
21253 in double quotes, for example:
21255 "|/some/command ready,steady,go"
21257 since items in redirection lists are terminated by commas. Do not, however,
21258 quote just the command. An item such as
21260 |"/some/command ready,steady,go"
21262 is interpreted as a pipe with a rather strange command name, and no arguments.
21264 Note that the above example assumes that the text comes from a lookup source
21265 of some sort, so that the quotes are part of the data. If composing a
21266 redirect router with a &%data%& option directly specifying this command, the
21267 quotes will be used by the configuration parser to define the extent of one
21268 string, but will not be passed down into the redirect router itself. There
21269 are two main approaches to get around this: escape quotes to be part of the
21270 data itself, or avoid using this mechanism and instead create a custom
21271 transport with the &%command%& option set and reference that transport from
21272 an &%accept%& router.
21275 .cindex "file" "in redirection list"
21276 .cindex "address redirection" "to file"
21277 An item is interpreted as a path name if it begins with &"/"& and does not
21278 parse as a valid RFC 2822 address that includes a domain. For example,
21280 /home/world/minbari
21282 is treated as a filename, but
21284 /s=molari/o=babylon/@x400gate.way
21286 is treated as an address. For a filename, a transport must be specified using
21287 the &%file_transport%& option. However, if the generated path name ends with a
21288 forward slash character, it is interpreted as a directory name rather than a
21289 filename, and &%directory_transport%& is used instead.
21291 Normally, either the router or the transport specifies a user and a group under
21292 which to run the delivery. The default is to use the Exim user and group.
21294 .cindex "&_/dev/null_&"
21295 However, if a redirection item is the path &_/dev/null_&, delivery to it is
21296 bypassed at a high level, and the log entry shows &"**bypassed**"&
21297 instead of a transport name. In this case the user and group are not used.
21300 .cindex "included address list"
21301 .cindex "address redirection" "included external list"
21302 If an item is of the form
21304 :include:<path name>
21306 a list of further items is taken from the given file and included at that
21307 point. &*Note*&: Such a file can not be a filter file; it is just an
21308 out-of-line addition to the list. The items in the included list are separated
21309 by commas or newlines and are not subject to expansion. If this is the first
21310 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
21311 the alias name. This example is incorrect:
21313 list1 :include:/opt/lists/list1
21315 It must be given as
21317 list1: :include:/opt/lists/list1
21319 .cindex "tainted data" "in filenames"
21320 .cindex redirect "tainted data"
21321 Tainted data may not be used for a filename.
21323 .cindex "address redirection" "to black hole"
21324 .cindex "delivery" "discard"
21325 .cindex "delivery" "blackhole"
21326 .cindex "black hole"
21327 .cindex "abandoning mail"
21328 Sometimes you want to throw away mail to a particular local part. Making the
21329 &%data%& option expand to an empty string does not work, because that causes
21330 the router to decline. Instead, the alias item
21334 can be used. It does what its name implies. No delivery is
21335 done, and no error message is generated. This has the same effect as specifying
21336 &_/dev/null_& as a destination, but it can be independently disabled.
21338 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
21339 delivery is done for the original local part, even if other redirection items
21340 are present. If you are generating a multi-item list (for example, by reading a
21341 database) and need the ability to provide a no-op item, you must use
21345 .cindex "delivery" "forcing failure"
21346 .cindex "delivery" "forcing deferral"
21347 .cindex "failing delivery" "forcing"
21348 .cindex "deferred delivery, forcing"
21349 .cindex "customizing" "failure message"
21350 An attempt to deliver a particular address can be deferred or forced to fail by
21351 redirection items of the form
21356 respectively. When a redirection list contains such an item, it applies
21357 to the entire redirection; any other items in the list are ignored. Any
21358 text following &':fail:'& or &':defer:'& is placed in the error text
21359 associated with the failure. For example, an alias file might contain:
21361 X.Employee: :fail: Gone away, no forwarding address
21363 In the case of an address that is being verified from an ACL or as the subject
21365 .cindex "VRFY" "error text, display of"
21366 VRFY command, the text is included in the SMTP error response by
21368 .cindex "EXPN" "error text, display of"
21369 The text is not included in the response to an EXPN command. In non-SMTP cases
21370 the text is included in the error message that Exim generates.
21372 .cindex "SMTP" "error codes"
21373 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
21374 &':fail:'&. However, if the message starts with three digits followed by a
21375 space, optionally followed by an extended code of the form &'n.n.n'&, also
21376 followed by a space, and the very first digit is the same as the default error
21377 code, the code from the message is used instead. If the very first digit is
21378 incorrect, a panic error is logged, and the default code is used. You can
21379 suppress the use of the supplied code in a redirect router by setting the
21380 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
21383 .vindex "&$acl_verify_message$&"
21384 In an ACL, an explicitly provided message overrides the default, but the
21385 default message is available in the variable &$acl_verify_message$& and can
21386 therefore be included in a custom message if this is desired.
21388 Normally the error text is the rest of the redirection list &-- a comma does
21389 not terminate it &-- but a newline does act as a terminator. Newlines are not
21390 normally present in alias expansions. In &(lsearch)& lookups they are removed
21391 as part of the continuation process, but they may exist in other kinds of
21392 lookup and in &':include:'& files.
21394 During routing for message delivery (as opposed to verification), a redirection
21395 containing &':fail:'& causes an immediate failure of the incoming address,
21396 whereas &':defer:'& causes the message to remain in the queue so that a
21397 subsequent delivery attempt can happen at a later time. If an address is
21398 deferred for too long, it will ultimately fail, because the normal retry
21402 .cindex "alias file" "exception to default"
21403 Sometimes it is useful to use a single-key search type with a default (see
21404 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
21405 for exceptions to the default. These can be handled by aliasing them to
21406 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
21407 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
21408 results in an empty redirection list has the same effect.
21412 .section "Duplicate addresses" "SECTdupaddr"
21413 .cindex "duplicate addresses"
21414 .cindex "address duplicate, discarding"
21415 .cindex "pipe" "duplicated"
21416 Exim removes duplicate addresses from the list to which it is delivering, so as
21417 to deliver just one copy to each address. This does not apply to deliveries
21418 routed to pipes by different immediate parent addresses, but an indirect
21419 aliasing scheme of the type
21421 pipe: |/some/command $local_part
21425 does not work with a message that is addressed to both local parts, because
21426 when the second is aliased to the intermediate local part &"pipe"& it gets
21427 discarded as being the same as a previously handled address. However, a scheme
21430 localpart1: |/some/command $local_part
21431 localpart2: |/some/command $local_part
21433 does result in two different pipe deliveries, because the immediate parents of
21434 the pipes are distinct.
21438 .section "Repeated redirection expansion" "SECID128"
21439 .cindex "repeated redirection expansion"
21440 .cindex "address redirection" "repeated for each delivery attempt"
21441 When a message cannot be delivered to all of its recipients immediately,
21442 leading to two or more delivery attempts, redirection expansion is carried out
21443 afresh each time for those addresses whose children were not all previously
21444 delivered. If redirection is being used as a mailing list, this can lead to new
21445 members of the list receiving copies of old messages. The &%one_time%& option
21446 can be used to avoid this.
21449 .section "Errors in redirection lists" "SECID129"
21450 .cindex "address redirection" "errors"
21451 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
21452 error is skipped, and an entry is written to the main log. This may be useful
21453 for mailing lists that are automatically managed. Otherwise, if an error is
21454 detected while generating the list of new addresses, the original address is
21455 deferred. See also &%syntax_errors_to%&.
21459 .section "Private options for the redirect router" "SECID130"
21461 .cindex "options" "&(redirect)& router"
21462 The private options for the &(redirect)& router are as follows:
21465 .option allow_defer redirect boolean false
21466 Setting this option allows the use of &':defer:'& in non-filter redirection
21467 data, or the &%defer%& command in an Exim filter file.
21470 .option allow_fail redirect boolean false
21471 .cindex "failing delivery" "from filter"
21472 If this option is true, the &':fail:'& item can be used in a redirection list,
21473 and the &%fail%& command may be used in an Exim filter file.
21476 .option allow_filter redirect boolean false
21477 .cindex "filter" "enabling use of"
21478 .cindex "Sieve filter" "enabling use of"
21479 Setting this option allows Exim to interpret redirection data that starts with
21480 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
21481 are some features of Exim filter files that some administrators may wish to
21482 lock out; see the &%forbid_filter_%&&'xxx'& options below.
21484 It is also possible to lock out Exim filters or Sieve filters while allowing
21485 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
21488 The filter is run using the uid and gid set by the generic &%user%& and
21489 &%group%& options. These take their defaults from the password data if
21490 &%check_local_user%& is set, so in the normal case of users' personal filter
21491 files, the filter is run as the relevant user. When &%allow_filter%& is set
21492 true, Exim insists that either &%check_local_user%& or &%user%& is set.
21496 .option allow_freeze redirect boolean false
21497 .cindex "freezing messages" "allowing in filter"
21498 Setting this option allows the use of the &%freeze%& command in an Exim filter.
21499 This command is more normally encountered in system filters, and is disabled by
21500 default for redirection filters because it isn't something you usually want to
21501 let ordinary users do.
21505 .option check_ancestor redirect boolean false
21506 This option is concerned with handling generated addresses that are the same
21507 as some address in the list of redirection ancestors of the current address.
21508 Although it is turned off by default in the code, it is set in the default
21509 configuration file for handling users' &_.forward_& files. It is recommended
21510 for this use of the &(redirect)& router.
21512 When &%check_ancestor%& is set, if a generated address (including the domain)
21513 is the same as any ancestor of the current address, it is replaced by a copy of
21514 the current address. This helps in the case where local part A is aliased to B,
21515 and B has a &_.forward_& file pointing back to A. For example, within a single
21516 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
21517 &_&~jb/.forward_& contains:
21519 \Joe.Bloggs, <other item(s)>
21521 Without the &%check_ancestor%& setting, either local part (&"jb"& or
21522 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
21523 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
21524 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
21525 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
21526 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
21527 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
21528 original address. See also the &%repeat_use%& option below.
21531 .option check_group redirect boolean "see below"
21532 When the &%file%& option is used, the group owner of the file is checked only
21533 when this option is set. The permitted groups are those listed in the
21534 &%owngroups%& option, together with the user's default group if
21535 &%check_local_user%& is set. If the file has the wrong group, routing is
21536 deferred. The default setting for this option is true if &%check_local_user%&
21537 is set and the &%modemask%& option permits the group write bit, or if the
21538 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
21542 .option check_owner redirect boolean "see below"
21543 When the &%file%& option is used, the owner of the file is checked only when
21544 this option is set. If &%check_local_user%& is set, the local user is
21545 permitted; otherwise the owner must be one of those listed in the &%owners%&
21546 option. The default value for this option is true if &%check_local_user%& or
21547 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
21550 .option data redirect string&!! unset
21551 This option is mutually exclusive with &%file%&. One or other of them must be
21552 set, but not both. The contents of &%data%& are expanded, and then used as the
21553 list of forwarding items, or as a set of filtering instructions. If the
21554 expansion is forced to fail, or the result is an empty string or a string that
21555 has no effect (consists entirely of comments), the router declines.
21557 When filtering instructions are used, the string must begin with &"#Exim
21558 filter"&, and all comments in the string, including this initial one, must be
21559 terminated with newline characters. For example:
21561 data = #Exim filter\n\
21562 if $h_to: contains Exim then save $home/mail/exim endif
21564 If you are reading the data from a database where newlines cannot be included,
21565 you can use the &${sg}$& expansion item to turn the escape string of your
21566 choice into a newline.
21569 .option directory_transport redirect string&!! unset
21570 A &(redirect)& router sets up a direct delivery to a directory when a path name
21571 ending with a slash is specified as a new &"address"&. The transport used is
21572 specified by this option, which, after expansion, must be the name of a
21573 configured transport. This should normally be an &(appendfile)& transport.
21576 .option file redirect string&!! unset
21577 This option specifies the name of a file that contains the redirection data. It
21578 is mutually exclusive with the &%data%& option. The string is expanded before
21579 use; if the expansion is forced to fail, the router declines. Other expansion
21580 failures cause delivery to be deferred. The result of a successful expansion
21581 must be an absolute path. The entire file is read and used as the redirection
21582 data. If the data is an empty string or a string that has no effect (consists
21583 entirely of comments), the router declines.
21585 .cindex "NFS" "checking for file existence"
21586 If the attempt to open the file fails with a &"does not exist"& error, Exim
21587 runs a check on the containing directory,
21588 unless &%ignore_enotdir%& is true (see below).
21589 If the directory does not appear to exist, delivery is deferred. This can
21590 happen when users' &_.forward_& files are in NFS-mounted directories, and there
21591 is a mount problem. If the containing directory does exist, but the file does
21592 not, the router declines.
21595 .option file_transport redirect string&!! unset
21596 .vindex "&$address_file$&"
21597 A &(redirect)& router sets up a direct delivery to a file when a path name not
21598 ending in a slash is specified as a new &"address"&. The transport used is
21599 specified by this option, which, after expansion, must be the name of a
21600 configured transport. This should normally be an &(appendfile)& transport. When
21601 it is running, the filename is in &$address_file$&.
21604 .option filter_prepend_home redirect boolean true
21605 When this option is true, if a &(save)& command in an Exim filter specifies a
21606 relative path, and &$home$& is defined, it is automatically prepended to the
21607 relative path. If this option is set false, this action does not happen. The
21608 relative path is then passed to the transport unmodified.
21611 .option forbid_blackhole redirect boolean false
21612 .cindex "restricting access to features"
21613 .cindex "filter" "locking out certain features"
21614 If this option is true, the &':blackhole:'& item may not appear in a
21618 .option forbid_exim_filter redirect boolean false
21619 .cindex "restricting access to features"
21620 .cindex "filter" "locking out certain features"
21621 If this option is set true, only Sieve filters are permitted when
21622 &%allow_filter%& is true.
21627 .option forbid_file redirect boolean false
21628 .cindex "restricting access to features"
21629 .cindex "delivery" "to file; forbidding"
21630 .cindex "filter" "locking out certain features"
21631 .cindex "Sieve filter" "forbidding delivery to a file"
21632 .cindex "Sieve filter" "&""keep""& facility; disabling"
21633 If this option is true, this router may not generate a new address that
21634 specifies delivery to a local file or directory, either from a filter or from a
21635 conventional forward file. This option is forced to be true if &%one_time%& is
21636 set. It applies to Sieve filters as well as to Exim filters, but if true, it
21637 locks out the Sieve's &"keep"& facility.
21640 .option forbid_filter_dlfunc redirect boolean false
21641 .cindex "restricting access to features"
21642 .cindex "filter" "locking out certain features"
21643 If this option is true, string expansions in Exim filters are not allowed to
21644 make use of the &%dlfunc%& expansion facility to run dynamically loaded
21647 .option forbid_filter_existstest redirect boolean false
21648 .cindex "restricting access to features"
21649 .cindex "filter" "locking out certain features"
21650 .cindex "expansion" "statting a file"
21651 If this option is true, string expansions in Exim filters are not allowed to
21652 make use of the &%exists%& condition or the &%stat%& expansion item.
21654 .option forbid_filter_logwrite redirect boolean false
21655 .cindex "restricting access to features"
21656 .cindex "filter" "locking out certain features"
21657 If this option is true, use of the logging facility in Exim filters is not
21658 permitted. Logging is in any case available only if the filter is being run
21659 under some unprivileged uid (which is normally the case for ordinary users'
21660 &_.forward_& files).
21663 .option forbid_filter_lookup redirect boolean false
21664 .cindex "restricting access to features"
21665 .cindex "filter" "locking out certain features"
21666 If this option is true, string expansions in Exim filter files are not allowed
21667 to make use of &%lookup%& items.
21670 .option forbid_filter_perl redirect boolean false
21671 .cindex "restricting access to features"
21672 .cindex "filter" "locking out certain features"
21673 This option has an effect only if Exim is built with embedded Perl support. If
21674 it is true, string expansions in Exim filter files are not allowed to make use
21675 of the embedded Perl support.
21678 .option forbid_filter_readfile redirect boolean false
21679 .cindex "restricting access to features"
21680 .cindex "filter" "locking out certain features"
21681 If this option is true, string expansions in Exim filter files are not allowed
21682 to make use of &%readfile%& items.
21685 .option forbid_filter_readsocket redirect boolean false
21686 .cindex "restricting access to features"
21687 .cindex "filter" "locking out certain features"
21688 If this option is true, string expansions in Exim filter files are not allowed
21689 to make use of &%readsocket%& items.
21692 .option forbid_filter_reply redirect boolean false
21693 .cindex "restricting access to features"
21694 .cindex "filter" "locking out certain features"
21695 If this option is true, this router may not generate an automatic reply
21696 message. Automatic replies can be generated only from Exim or Sieve filter
21697 files, not from traditional forward files. This option is forced to be true if
21698 &%one_time%& is set.
21701 .option forbid_filter_run redirect boolean false
21702 .cindex "restricting access to features"
21703 .cindex "filter" "locking out certain features"
21704 If this option is true, string expansions in Exim filter files are not allowed
21705 to make use of &%run%& items.
21708 .option forbid_include redirect boolean false
21709 .cindex "restricting access to features"
21710 .cindex "filter" "locking out certain features"
21711 If this option is true, items of the form
21713 :include:<path name>
21715 are not permitted in non-filter redirection lists.
21718 .option forbid_pipe redirect boolean false
21719 .cindex "restricting access to features"
21720 .cindex "filter" "locking out certain features"
21721 .cindex "delivery" "to pipe; forbidding"
21722 If this option is true, this router may not generate a new address which
21723 specifies delivery to a pipe, either from an Exim filter or from a conventional
21724 forward file. This option is forced to be true if &%one_time%& is set.
21727 .option forbid_sieve_filter redirect boolean false
21728 .cindex "restricting access to features"
21729 .cindex "filter" "locking out certain features"
21730 If this option is set true, only Exim filters are permitted when
21731 &%allow_filter%& is true.
21734 .cindex "SMTP" "error codes"
21735 .option forbid_smtp_code redirect boolean false
21736 If this option is set true, any SMTP error codes that are present at the start
21737 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
21738 the default codes (451 and 550, respectively) are always used.
21743 .option hide_child_in_errmsg redirect boolean false
21744 .cindex "bounce message" "redirection details; suppressing"
21745 If this option is true, it prevents Exim from quoting a child address if it
21746 generates a bounce or delay message for it. Instead it says &"an address
21747 generated from <&'the top level address'&>"&. Of course, this applies only to
21748 bounces generated locally. If a message is forwarded to another host, &'its'&
21749 bounce may well quote the generated address.
21752 .option ignore_eacces redirect boolean false
21754 If this option is set and an attempt to open a redirection file yields the
21755 EACCES error (permission denied), the &(redirect)& router behaves as if the
21756 file did not exist.
21759 .option ignore_enotdir redirect boolean false
21761 If this option is set and an attempt to open a redirection file yields the
21762 ENOTDIR error (something on the path is not a directory), the &(redirect)&
21763 router behaves as if the file did not exist.
21765 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
21766 router that has the &%file%& option set discovers that the file does not exist
21767 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
21768 against unmounted NFS directories. If the parent can not be statted, delivery
21769 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
21770 is set, because that option tells Exim to ignore &"something on the path is not
21771 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
21772 that some operating systems give ENOENT where others give ENOTDIR.
21776 .option include_directory redirect string unset
21777 If this option is set, the path names of any &':include:'& items in a
21778 redirection list must start with this directory.
21781 .option modemask redirect "octal integer" 022
21782 This specifies mode bits which must not be set for a file specified by the
21783 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
21786 .option one_time redirect boolean false
21787 .cindex "one-time aliasing/forwarding expansion"
21788 .cindex "alias file" "one-time expansion"
21789 .cindex "forward file" "one-time expansion"
21790 .cindex "mailing lists" "one-time expansion"
21791 .cindex "address redirection" "one-time expansion"
21792 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
21793 files each time it tries to deliver a message causes a problem when one or more
21794 of the generated addresses fails be delivered at the first attempt. The problem
21795 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
21796 but of what happens when the redirection list changes during the time that the
21797 message is on Exim's queue. This is particularly true in the case of mailing
21798 lists, where new subscribers might receive copies of messages that were posted
21799 before they subscribed.
21801 If &%one_time%& is set and any addresses generated by the router fail to
21802 deliver at the first attempt, the failing addresses are added to the message as
21803 &"top level"& addresses, and the parent address that generated them is marked
21804 &"delivered"&. Thus, redirection does not happen again at the next delivery
21807 &*Warning 1*&: Any header line addition or removal that is specified by this
21808 router would be lost if delivery did not succeed at the first attempt. For this
21809 reason, the &%headers_add%& and &%headers_remove%& generic options are not
21810 permitted when &%one_time%& is set.
21812 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
21813 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
21814 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
21816 &*Warning 3*&: The &%unseen%& generic router option may not be set with
21819 The original top-level address is remembered with each of the generated
21820 addresses, and is output in any log messages. However, any intermediate parent
21821 addresses are not recorded. This makes a difference to the log only if
21822 &%all_parents%& log selector is set. It is expected that &%one_time%& will
21823 typically be used for mailing lists, where there is normally just one level of
21827 .option owners redirect "string list" unset
21828 .cindex "ownership" "alias file"
21829 .cindex "ownership" "forward file"
21830 .cindex "alias file" "ownership"
21831 .cindex "forward file" "ownership"
21832 This specifies a list of permitted owners for the file specified by &%file%&.
21833 This list is in addition to the local user when &%check_local_user%& is set.
21834 See &%check_owner%& above.
21837 .option owngroups redirect "string list" unset
21838 This specifies a list of permitted groups for the file specified by &%file%&.
21839 The list is in addition to the local user's primary group when
21840 &%check_local_user%& is set. See &%check_group%& above.
21843 .option pipe_transport redirect string&!! unset
21844 .vindex "&$address_pipe$&"
21845 A &(redirect)& router sets up a direct delivery to a pipe when a string
21846 starting with a vertical bar character is specified as a new &"address"&. The
21847 transport used is specified by this option, which, after expansion, must be the
21848 name of a configured transport. This should normally be a &(pipe)& transport.
21849 When the transport is run, the pipe command is in &$address_pipe$&.
21852 .option qualify_domain redirect string&!! unset
21853 .vindex "&$qualify_recipient$&"
21854 If this option is set, and an unqualified address (one without a domain) is
21855 generated, and that address would normally be qualified by the global setting
21856 in &%qualify_recipient%&, it is instead qualified with the domain specified by
21857 expanding this string. If the expansion fails, the router declines. If you want
21858 to revert to the default, you can have the expansion generate
21859 &$qualify_recipient$&.
21861 This option applies to all unqualified addresses generated by Exim filters,
21862 but for traditional &_.forward_& files, it applies only to addresses that are
21863 not preceded by a backslash. Sieve filters cannot generate unqualified
21866 .option qualify_preserve_domain redirect boolean false
21867 .cindex "domain" "in redirection; preserving"
21868 .cindex "preserving domain in redirection"
21869 .cindex "address redirection" "domain; preserving"
21870 If this option is set, the router's local &%qualify_domain%& option must not be
21871 set (a configuration error occurs if it is). If an unqualified address (one
21872 without a domain) is generated, it is qualified with the domain of the parent
21873 address (the immediately preceding ancestor) instead of the global
21874 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
21875 this applies whether or not the address is preceded by a backslash.
21878 .option repeat_use redirect boolean true
21879 If this option is set false, the router is skipped for a child address that has
21880 any ancestor that was routed by this router. This test happens before any of
21881 the other preconditions are tested. Exim's default anti-looping rules skip
21882 only when the ancestor is the same as the current address. See also
21883 &%check_ancestor%& above and the generic &%redirect_router%& option.
21886 .option reply_transport redirect string&!! unset
21887 A &(redirect)& router sets up an automatic reply when a &%mail%& or
21888 &%vacation%& command is used in a filter file. The transport used is specified
21889 by this option, which, after expansion, must be the name of a configured
21890 transport. This should normally be an &(autoreply)& transport. Other transports
21891 are unlikely to do anything sensible or useful.
21894 .option rewrite redirect boolean true
21895 .cindex "address redirection" "disabling rewriting"
21896 If this option is set false, addresses generated by the router are not
21897 subject to address rewriting. Otherwise, they are treated like new addresses
21898 and are rewritten according to the global rewriting rules.
21901 .option sieve_subaddress redirect string&!! unset
21902 The value of this option is passed to a Sieve filter to specify the
21903 :subaddress part of an address.
21905 .option sieve_useraddress redirect string&!! unset
21906 The value of this option is passed to a Sieve filter to specify the :user part
21907 of an address. However, if it is unset, the entire original local part
21908 (including any prefix or suffix) is used for :user.
21911 .option sieve_vacation_directory redirect string&!! unset
21912 .cindex "Sieve filter" "vacation directory"
21913 To enable the &"vacation"& extension for Sieve filters, you must set
21914 &%sieve_vacation_directory%& to the directory where vacation databases are held
21915 (do not put anything else in that directory), and ensure that the
21916 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
21917 needs their own directory; Exim will create it if necessary.
21921 .option skip_syntax_errors redirect boolean false
21922 .cindex "forward file" "broken"
21923 .cindex "address redirection" "broken files"
21924 .cindex "alias file" "broken"
21925 .cindex "broken alias or forward files"
21926 .cindex "ignoring faulty addresses"
21927 .cindex "skipping faulty addresses"
21928 .cindex "error" "skipping bad syntax"
21929 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
21930 non-filter redirection data are skipped, and each failing address is logged. If
21931 &%syntax_errors_to%& is set, a message is sent to the address it defines,
21932 giving details of the failures. If &%syntax_errors_text%& is set, its contents
21933 are expanded and placed at the head of the error message generated by
21934 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
21935 be the same address as the generic &%errors_to%& option. The
21936 &%skip_syntax_errors%& option is often used when handling mailing lists.
21938 If all the addresses in a redirection list are skipped because of syntax
21939 errors, the router declines to handle the original address, and it is passed to
21940 the following routers.
21942 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
21943 error in the filter causes filtering to be abandoned without any action being
21944 taken. The incident is logged, and the router declines to handle the address,
21945 so it is passed to the following routers.
21947 .cindex "Sieve filter" "syntax errors in"
21948 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
21949 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
21950 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
21952 &%skip_syntax_errors%& can be used to specify that errors in users' forward
21953 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
21954 option, used with an address that does not get redirected, can be used to
21955 notify users of these errors, by means of a router like this:
21961 file = $home/.forward
21962 file_transport = address_file
21963 pipe_transport = address_pipe
21964 reply_transport = address_reply
21967 syntax_errors_to = real-$local_part@$domain
21968 syntax_errors_text = \
21969 This is an automatically generated message. An error has\n\
21970 been found in your .forward file. Details of the error are\n\
21971 reported below. While this error persists, you will receive\n\
21972 a copy of this message for every message that is addressed\n\
21973 to you. If your .forward file is a filter file, or if it is\n\
21974 a non-filter file containing no valid forwarding addresses,\n\
21975 a copy of each incoming message will be put in your normal\n\
21976 mailbox. If a non-filter file contains at least one valid\n\
21977 forwarding address, forwarding to the valid addresses will\n\
21978 happen, and those will be the only deliveries that occur.
21980 You also need a router to ensure that local addresses that are prefixed by
21981 &`real-`& are recognized, but not forwarded or filtered. For example, you could
21982 put this immediately before the &(userforward)& router:
21987 local_part_prefix = real-
21988 transport = local_delivery
21990 For security, it would probably be a good idea to restrict the use of this
21991 router to locally-generated messages, using a condition such as this:
21993 condition = ${if match {$sender_host_address}\
21994 {\N^(|127\.0\.0\.1)$\N}}
21998 .option syntax_errors_text redirect string&!! unset
21999 See &%skip_syntax_errors%& above.
22002 .option syntax_errors_to redirect string unset
22003 See &%skip_syntax_errors%& above.
22004 .ecindex IIDredrou1
22005 .ecindex IIDredrou2
22012 . ////////////////////////////////////////////////////////////////////////////
22013 . ////////////////////////////////////////////////////////////////////////////
22015 .chapter "Environment for running local transports" "CHAPenvironment" &&&
22016 "Environment for local transports"
22017 .scindex IIDenvlotra1 "local transports" "environment for"
22018 .scindex IIDenvlotra2 "environment" "local transports"
22019 .scindex IIDenvlotra3 "transport" "local; environment for"
22020 Local transports handle deliveries to files and pipes. (The &(autoreply)&
22021 transport can be thought of as similar to a pipe.) Exim always runs transports
22022 in subprocesses, under specified uids and gids. Typical deliveries to local
22023 mailboxes run under the uid and gid of the local user.
22025 Exim also sets a specific current directory while running the transport; for
22026 some transports a home directory setting is also relevant. The &(pipe)&
22027 transport is the only one that sets up environment variables; see section
22028 &<<SECTpipeenv>>& for details.
22030 The values used for the uid, gid, and the directories may come from several
22031 different places. In many cases, the router that handles the address associates
22032 settings with that address as a result of its &%check_local_user%&, &%group%&,
22033 or &%user%& options. However, values may also be given in the transport's own
22034 configuration, and these override anything that comes from the router.
22038 .section "Concurrent deliveries" "SECID131"
22039 .cindex "concurrent deliveries"
22040 .cindex "simultaneous deliveries"
22041 If two different messages for the same local recipient arrive more or less
22042 simultaneously, the two delivery processes are likely to run concurrently. When
22043 the &(appendfile)& transport is used to write to a file, Exim applies locking
22044 rules to stop concurrent processes from writing to the same file at the same
22047 However, when you use a &(pipe)& transport, it is up to you to arrange any
22048 locking that is needed. Here is a silly example:
22052 command = /bin/sh -c 'cat >>/some/file'
22054 This is supposed to write the message at the end of the file. However, if two
22055 messages arrive at the same time, the file will be scrambled. You can use the
22056 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
22057 file using the same algorithm that Exim itself uses.
22062 .section "Uids and gids" "SECTenvuidgid"
22063 .cindex "local transports" "uid and gid"
22064 .cindex "transport" "local; uid and gid"
22065 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
22066 overrides any group that the router set in the address, even if &%user%& is not
22067 set for the transport. This makes it possible, for example, to run local mail
22068 delivery under the uid of the recipient (set by the router), but in a special
22069 group (set by the transport). For example:
22072 # User/group are set by check_local_user in this router
22076 transport = group_delivery
22079 # This transport overrides the group
22081 driver = appendfile
22082 file = /var/spool/mail/$local_part_data
22085 If &%user%& is set for a transport, its value overrides what is set in the
22086 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
22087 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
22090 .oindex "&%initgroups%&"
22091 When the uid is taken from the transport's configuration, the &[initgroups()]&
22092 function is called for the groups associated with that uid if the
22093 &%initgroups%& option is set for the transport. When the uid is not specified
22094 by the transport, but is associated with the address by a router, the option
22095 for calling &[initgroups()]& is taken from the router configuration.
22097 .cindex "&(pipe)& transport" "uid for"
22098 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
22099 is set and &%user%& is not set, the uid of the process that called Exim to
22100 receive the message is used, and if &%group%& is not set, the corresponding
22101 original gid is also used.
22103 This is the detailed preference order for obtaining a gid; the first of the
22104 following that is set is used:
22107 A &%group%& setting of the transport;
22109 A &%group%& setting of the router;
22111 A gid associated with a user setting of the router, either as a result of
22112 &%check_local_user%& or an explicit non-numeric &%user%& setting;
22114 The group associated with a non-numeric &%user%& setting of the transport;
22116 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
22117 the uid is the creator's uid;
22119 The Exim gid if the Exim uid is being used as a default.
22122 If, for example, the user is specified numerically on the router and there are
22123 no group settings, no gid is available. In this situation, an error occurs.
22124 This is different for the uid, for which there always is an ultimate default.
22125 The first of the following that is set is used:
22128 A &%user%& setting of the transport;
22130 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
22132 A &%user%& setting of the router;
22134 A &%check_local_user%& setting of the router;
22139 Of course, an error will still occur if the uid that is chosen is on the
22140 &%never_users%& list.
22146 .section "Current and home directories" "SECID132"
22147 .cindex "current directory for local transport"
22148 .cindex "home directory" "for local transport"
22149 .cindex "transport" "local; home directory for"
22150 .cindex "transport" "local; current directory for"
22151 Routers may set current and home directories for local transports by means of
22152 the &%transport_current_directory%& and &%transport_home_directory%& options.
22153 However, if the transport's &%current_directory%& or &%home_directory%& options
22154 are set, they override the router's values. In detail, the home directory
22155 for a local transport is taken from the first of these values that is set:
22158 The &%home_directory%& option on the transport;
22160 The &%transport_home_directory%& option on the router;
22162 The password data if &%check_local_user%& is set on the router;
22164 The &%router_home_directory%& option on the router.
22167 The current directory is taken from the first of these values that is set:
22170 The &%current_directory%& option on the transport;
22172 The &%transport_current_directory%& option on the router.
22176 If neither the router nor the transport sets a current directory, Exim uses the
22177 value of the home directory, if it is set. Otherwise it sets the current
22178 directory to &_/_& before running a local transport.
22182 .section "Expansion variables derived from the address" "SECID133"
22183 .vindex "&$domain$&"
22184 .vindex "&$local_part$&"
22185 .vindex "&$original_domain$&"
22186 Normally a local delivery is handling a single address, and in that case the
22187 variables such as &$domain$& and &$local_part$& are set during local
22188 deliveries. However, in some circumstances more than one address may be handled
22189 at once (for example, while writing batch SMTP for onward transmission by some
22190 other means). In this case, the variables associated with the local part are
22191 never set, &$domain$& is set only if all the addresses have the same domain,
22192 and &$original_domain$& is never set.
22193 .ecindex IIDenvlotra1
22194 .ecindex IIDenvlotra2
22195 .ecindex IIDenvlotra3
22203 . ////////////////////////////////////////////////////////////////////////////
22204 . ////////////////////////////////////////////////////////////////////////////
22206 .chapter "Generic options for transports" "CHAPtransportgeneric"
22207 .scindex IIDgenoptra1 "generic options" "transport"
22208 .scindex IIDgenoptra2 "options" "generic; for transports"
22209 .scindex IIDgenoptra3 "transport" "generic options for"
22210 The following generic options apply to all transports:
22213 .option body_only transports boolean false
22214 .cindex "transport" "body only"
22215 .cindex "message" "transporting body only"
22216 .cindex "body of message" "transporting"
22217 If this option is set, the message's headers are not transported. It is
22218 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
22219 or &(pipe)& transports, the settings of &%message_prefix%& and
22220 &%message_suffix%& should be checked, because this option does not
22221 automatically suppress them.
22224 .option current_directory transports string&!! unset
22225 .cindex "transport" "current directory for"
22226 This specifies the current directory that is to be set while running the
22227 transport, overriding any value that may have been set by the router.
22228 If the expansion fails for any reason, including forced failure, an error is
22229 logged, and delivery is deferred.
22232 .option disable_logging transports boolean false
22233 If this option is set true, nothing is logged for any
22234 deliveries by the transport or for any
22235 transport errors. You should not set this option unless you really, really know
22236 what you are doing.
22239 .option debug_print transports string&!! unset
22240 .cindex "testing" "variables in drivers"
22241 If this option is set and debugging is enabled (see the &%-d%& command line
22242 option), the string is expanded and included in the debugging output when the
22244 If expansion of the string fails, the error message is written to the debugging
22245 output, and Exim carries on processing.
22246 This facility is provided to help with checking out the values of variables and
22247 so on when debugging driver configurations. For example, if a &%headers_add%&
22248 option is not working properly, &%debug_print%& could be used to output the
22249 variables it references. A newline is added to the text if it does not end with
22251 The variables &$transport_name$& and &$router_name$& contain the name of the
22252 transport and the router that called it.
22254 .option delivery_date_add transports boolean false
22255 .cindex "&'Delivery-date:'& header line"
22256 If this option is true, a &'Delivery-date:'& header is added to the message.
22257 This gives the actual time the delivery was made. As this is not a standard
22258 header, Exim has a configuration option (&%delivery_date_remove%&) which
22259 requests its removal from incoming messages, so that delivered messages can
22260 safely be resent to other recipients.
22263 .option driver transports string unset
22264 This specifies which of the available transport drivers is to be used.
22265 There is no default, and this option must be set for every transport.
22268 .option envelope_to_add transports boolean false
22269 .cindex "&'Envelope-to:'& header line"
22270 If this option is true, an &'Envelope-to:'& header is added to the message.
22271 This gives the original address(es) in the incoming envelope that caused this
22272 delivery to happen. More than one address may be present if the transport is
22273 configured to handle several addresses at once, or if more than one original
22274 address was redirected to the same final address. As this is not a standard
22275 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
22276 its removal from incoming messages, so that delivered messages can safely be
22277 resent to other recipients.
22280 .option event_action transports string&!! unset
22282 This option declares a string to be expanded for Exim's events mechanism.
22283 For details see chapter &<<CHAPevents>>&.
22286 .option group transports string&!! "Exim group"
22287 .cindex "transport" "group; specifying"
22288 This option specifies a gid for running the transport process, overriding any
22289 value that the router supplies, and also overriding any value associated with
22290 &%user%& (see below).
22293 .option headers_add transports list&!! unset
22294 .cindex "header lines" "adding in transport"
22295 .cindex "transport" "header lines; adding"
22296 This option specifies a list of text headers,
22297 newline-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22298 which are (separately) expanded and added to the header
22299 portion of a message as it is transported, as described in section
22300 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
22301 routers. If the result of the expansion is an empty string, or if the expansion
22302 is forced to fail, no action is taken. Other expansion failures are treated as
22303 errors and cause the delivery to be deferred.
22305 Unlike most options, &%headers_add%& can be specified multiple times
22306 for a transport; all listed headers are added.
22309 .option headers_only transports boolean false
22310 .cindex "transport" "header lines only"
22311 .cindex "message" "transporting headers only"
22312 .cindex "header lines" "transporting"
22313 If this option is set, the message's body is not transported. It is mutually
22314 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
22315 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
22316 checked, since this option does not automatically suppress them.
22319 .option headers_remove transports list&!! unset
22320 .cindex "header lines" "removing"
22321 .cindex "transport" "header lines; removing"
22322 This option specifies a list of text headers,
22323 colon-separated (by default, changeable in the usual way &<<SECTlistsepchange>>&),
22324 to be removed from the message.
22325 However, the option has no effect when an address is just being verified.
22326 Each list item is separately expanded.
22327 If the result of the expansion is an empty string, or if the expansion
22328 is forced to fail, no action is taken. Other expansion failures are treated as
22329 errors and cause the delivery to be deferred.
22330 If an item ends in *, it will match any header with the given prefix.
22332 Matching headers are omitted from the message as it is transported, as described
22333 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
22336 Unlike most options, &%headers_remove%& can be specified multiple times
22337 for a transport; all listed headers are removed.
22339 &*Warning*&: Because of the separate expansion of the list items,
22340 items that contain a list separator must have it doubled.
22341 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
22345 .option headers_rewrite transports string unset
22346 .cindex "transport" "header lines; rewriting"
22347 .cindex "rewriting" "at transport time"
22348 This option allows addresses in header lines to be rewritten at transport time,
22349 that is, as the message is being copied to its destination. The contents of the
22350 option are a colon-separated list of rewriting rules. Each rule is in exactly
22351 the same form as one of the general rewriting rules that are applied when a
22352 message is received. These are described in chapter &<<CHAPrewrite>>&. For
22355 headers_rewrite = a@b c@d f : \
22358 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
22359 &'w@z'& in all address-bearing header lines. The rules are applied to the
22360 header lines just before they are written out at transport time, so they affect
22361 only those copies of the message that pass through the transport. However, only
22362 the message's original header lines, and any that were added by a system
22363 filter, are rewritten. If a router or transport adds header lines, they are not
22364 affected by this option. These rewriting rules are &'not'& applied to the
22365 envelope. You can change the return path using &%return_path%&, but you cannot
22366 change envelope recipients at this time.
22369 .option home_directory transports string&!! unset
22370 .cindex "transport" "home directory for"
22372 This option specifies a home directory setting for a local transport,
22373 overriding any value that may be set by the router. The home directory is
22374 placed in &$home$& while expanding the transport's private options. It is also
22375 used as the current directory if no current directory is set by the
22376 &%current_directory%& option on the transport or the
22377 &%transport_current_directory%& option on the router. If the expansion fails
22378 for any reason, including forced failure, an error is logged, and delivery is
22382 .option initgroups transports boolean false
22383 .cindex "additional groups"
22384 .cindex "groups" "additional"
22385 .cindex "transport" "group; additional"
22386 If this option is true and the uid for the delivery process is provided by the
22387 transport, the &[initgroups()]& function is called when running the transport
22388 to ensure that any additional groups associated with the uid are set up.
22391 .option max_parallel transports integer&!! unset
22392 .cindex limit "transport parallelism"
22393 .cindex transport "parallel processes"
22394 .cindex transport "concurrency limit"
22395 .cindex "delivery" "parallelism for transport"
22396 If this option is set and expands to an integer greater than zero
22397 it limits the number of concurrent runs of the transport.
22398 The control does not apply to shadow transports.
22400 .cindex "hints database" "transport concurrency control"
22401 Exim implements this control by means of a hints database in which a record is
22402 incremented whenever a transport process is being created. The record
22403 is decremented and possibly removed when the process terminates.
22404 Obviously there is scope for
22405 records to get left lying around if there is a system or program crash. To
22406 guard against this, Exim ignores any records that are more than six hours old.
22408 If you use this option, you should also arrange to delete the
22409 relevant hints database whenever your system reboots. The names of the files
22410 start with &_misc_& and they are kept in the &_spool/db_& directory. There
22411 may be one or two files, depending on the type of DBM in use. The same files
22412 are used for ETRN and smtp transport serialization.
22415 .option message_size_limit transports string&!! 0
22416 .cindex "limit" "message size per transport"
22417 .cindex "size" "of message, limit"
22418 .cindex "transport" "message size; limiting"
22419 This option controls the size of messages passed through the transport. It is
22420 expanded before use; the result of the expansion must be a sequence of decimal
22421 digits, optionally followed by K or M. If the expansion fails for any reason,
22422 including forced failure, or if the result is not of the required form,
22423 delivery is deferred. If the value is greater than zero and the size of a
22424 message exceeds this limit, the address is failed. If there is any chance that
22425 the resulting bounce message could be routed to the same transport, you should
22426 ensure that &%return_size_limit%& is less than the transport's
22427 &%message_size_limit%&, as otherwise the bounce message will fail to get
22432 .option rcpt_include_affixes transports boolean false
22433 .cindex "prefix" "for local part, including in envelope"
22434 .cindex "suffix for local part" "including in envelope"
22435 .cindex "local part" "prefix"
22436 .cindex "local part" "suffix"
22437 When this option is false (the default), and an address that has had any
22438 affixes (prefixes or suffixes) removed from the local part is delivered by any
22439 form of SMTP or LMTP, the affixes are not included. For example, if a router
22442 local_part_prefix = *-
22444 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
22447 RCPT TO:<xyz@some.domain>
22449 This is also the case when an ACL-time callout is being used to verify a
22450 recipient address. However, if &%rcpt_include_affixes%& is set true, the
22451 whole local part is included in the RCPT command. This option applies to BSMTP
22452 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
22453 &(lmtp)& and &(smtp)& transports.
22456 .option retry_use_local_part transports boolean "see below"
22457 .cindex "hints database" "retry keys"
22458 When a delivery suffers a temporary failure, a retry record is created
22459 in Exim's hints database. For remote deliveries, the key for the retry record
22460 is based on the name and/or IP address of the failing remote host. For local
22461 deliveries, the key is normally the entire address, including both the local
22462 part and the domain. This is suitable for most common cases of local delivery
22463 temporary failure &-- for example, exceeding a mailbox quota should delay only
22464 deliveries to that mailbox, not to the whole domain.
22466 However, in some special cases you may want to treat a temporary local delivery
22467 as a failure associated with the domain, and not with a particular local part.
22468 (For example, if you are storing all mail for some domain in files.) You can do
22469 this by setting &%retry_use_local_part%& false.
22471 For all the local transports, its default value is true. For remote transports,
22472 the default value is false for tidiness, but changing the value has no effect
22473 on a remote transport in the current implementation.
22476 .option return_path transports string&!! unset
22477 .cindex "envelope sender"
22478 .cindex "envelope from"
22479 .cindex "transport" "return path; changing"
22480 .cindex "return path" "changing in transport"
22481 If this option is set, the string is expanded at transport time and replaces
22482 the existing return path (envelope sender) value in the copy of the message
22483 that is being delivered. An empty return path is permitted. This feature is
22484 designed for remote deliveries, where the value of this option is used in the
22485 SMTP MAIL command. If you set &%return_path%& for a local transport, the
22486 only effect is to change the address that is placed in the &'Return-path:'&
22487 header line, if one is added to the message (see the next option).
22489 &*Note:*& A changed return path is not logged unless you add
22490 &%return_path_on_delivery%& to the log selector.
22492 .vindex "&$return_path$&"
22493 The expansion can refer to the existing value via &$return_path$&. This is
22494 either the message's envelope sender, or an address set by the
22495 &%errors_to%& option on a router. If the expansion is forced to fail, no
22496 replacement occurs; if it fails for another reason, delivery is deferred. This
22497 option can be used to support VERP (Variable Envelope Return Paths) &-- see
22498 section &<<SECTverp>>&.
22500 &*Note*&: If a delivery error is detected locally, including the case when a
22501 remote server rejects a message at SMTP time, the bounce message is not sent to
22502 the value of this option. It is sent to the previously set errors address.
22503 This defaults to the incoming sender address, but can be changed by setting
22504 &%errors_to%& in a router.
22508 .option return_path_add transports boolean false
22509 .cindex "&'Return-path:'& header line"
22510 If this option is true, a &'Return-path:'& header is added to the message.
22511 Although the return path is normally available in the prefix line of BSD
22512 mailboxes, this is commonly not displayed by MUAs, and so the user does not
22513 have easy access to it.
22515 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
22516 the delivery SMTP server makes the final delivery"&. This implies that this
22517 header should not be present in incoming messages. Exim has a configuration
22518 option, &%return_path_remove%&, which requests removal of this header from
22519 incoming messages, so that delivered messages can safely be resent to other
22523 .option shadow_condition transports string&!! unset
22524 See &%shadow_transport%& below.
22527 .option shadow_transport transports string unset
22528 .cindex "shadow transport"
22529 .cindex "transport" "shadow"
22530 A local transport may set the &%shadow_transport%& option to the name of
22531 another local transport. Shadow remote transports are not supported.
22533 Whenever a delivery to the main transport succeeds, and either
22534 &%shadow_condition%& is unset, or its expansion does not result in the empty
22535 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
22536 passed to the shadow transport, with the same delivery address or addresses. If
22537 expansion fails, no action is taken except that non-forced expansion failures
22538 cause a log line to be written.
22540 The result of the shadow transport is discarded and does not affect the
22541 subsequent processing of the message. Only a single level of shadowing is
22542 provided; the &%shadow_transport%& option is ignored on any transport when it
22543 is running as a shadow. Options concerned with output from pipes are also
22544 ignored. The log line for the successful delivery has an item added on the end,
22547 ST=<shadow transport name>
22549 If the shadow transport did not succeed, the error message is put in
22550 parentheses afterwards. Shadow transports can be used for a number of different
22551 purposes, including keeping more detailed log information than Exim normally
22552 provides, and implementing automatic acknowledgment policies based on message
22553 headers that some sites insist on.
22556 .option transport_filter transports string&!! unset
22557 .cindex "transport" "filter"
22558 .cindex "filter" "transport filter"
22559 This option sets up a filtering (in the Unix shell sense) process for messages
22560 at transport time. It should not be confused with mail filtering as set up by
22561 individual users or via a system filter.
22562 If unset, or expanding to an empty string, no filtering is done.
22564 When the message is about to be written out, the command specified by
22565 &%transport_filter%& is started up in a separate, parallel process, and
22566 the entire message, including the header lines, is passed to it on its standard
22567 input (this in fact is done from a third process, to avoid deadlock). The
22568 command must be specified as an absolute path.
22570 The lines of the message that are written to the transport filter are
22571 terminated by newline (&"\n"&). The message is passed to the filter before any
22572 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
22573 lines beginning with a dot, and also before any processing implied by the
22574 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
22575 &(pipe)& transports.
22577 The standard error for the filter process is set to the same destination as its
22578 standard output; this is read and written to the message's ultimate
22579 destination. The process that writes the message to the filter, the
22580 filter itself, and the original process that reads the result and delivers it
22581 are all run in parallel, like a shell pipeline.
22583 The filter can perform any transformations it likes, but of course should take
22584 care not to break RFC 2822 syntax. Exim does not check the result, except to
22585 test for a final newline when SMTP is in use. All messages transmitted over
22586 SMTP must end with a newline, so Exim supplies one if it is missing.
22588 .cindex "content scanning" "per user"
22589 A transport filter can be used to provide content-scanning on a per-user basis
22590 at delivery time if the only required effect of the scan is to modify the
22591 message. For example, a content scan could insert a new header line containing
22592 a spam score. This could be interpreted by a filter in the user's MUA. It is
22593 not possible to discard a message at this stage.
22595 .cindex "SIZE" "ESMTP extension"
22596 A problem might arise if the filter increases the size of a message that is
22597 being sent down an SMTP connection. If the receiving SMTP server has indicated
22598 support for the SIZE parameter, Exim will have sent the size of the message
22599 at the start of the SMTP session. If what is actually sent is substantially
22600 more, the server might reject the message. This can be worked round by setting
22601 the &%size_addition%& option on the &(smtp)& transport, either to allow for
22602 additions to the message, or to disable the use of SIZE altogether.
22604 .vindex "&$pipe_addresses$&"
22605 The value of the &%transport_filter%& option is the command string for starting
22606 the filter, which is run directly from Exim, not under a shell. The string is
22607 parsed by Exim in the same way as a command string for the &(pipe)& transport:
22608 Exim breaks it up into arguments and then expands each argument separately (see
22609 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
22610 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
22611 of arguments, one for each address that applies to this delivery. (This isn't
22612 an ideal name for this feature here, but as it was already implemented for the
22613 &(pipe)& transport, it seemed sensible not to change it.)
22616 .vindex "&$host_address$&"
22617 The expansion variables &$host$& and &$host_address$& are available when the
22618 transport is a remote one. They contain the name and IP address of the host to
22619 which the message is being sent. For example:
22621 transport_filter = /some/directory/transport-filter.pl \
22622 $host $host_address $sender_address $pipe_addresses
22625 Two problems arise if you want to use more complicated expansion items to
22626 generate transport filter commands, both of which due to the fact that the
22627 command is split up &'before'& expansion.
22629 If an expansion item contains white space, you must quote it, so that it is all
22630 part of the same command item. If the entire option setting is one such
22631 expansion item, you have to take care what kind of quoting you use. For
22634 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
22636 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
22637 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
22638 stripped by Exim when it read the option's value. When the value is used, if
22639 the single quotes were missing, the line would be split into two items,
22640 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
22641 Exim tried to expand the first one.
22643 Except for the special case of &$pipe_addresses$& that is mentioned above, an
22644 expansion cannot generate multiple arguments, or a command name followed by
22645 arguments. Consider this example:
22647 transport_filter = ${lookup{$host}lsearch{/a/file}\
22648 {$value}{/bin/cat}}
22650 The result of the lookup is interpreted as the name of the command, even
22651 if it contains white space. The simplest way round this is to use a shell:
22653 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
22654 {$value}{/bin/cat}}
22658 The filter process is run under the same uid and gid as the normal delivery.
22659 For remote deliveries this is the Exim uid/gid by default. The command should
22660 normally yield a zero return code. Transport filters are not supposed to fail.
22661 A non-zero code is taken to mean that the transport filter encountered some
22662 serious problem. Delivery of the message is deferred; the message remains on
22663 the queue and is tried again later. It is not possible to cause a message to be
22664 bounced from a transport filter.
22666 If a transport filter is set on an autoreply transport, the original message is
22667 passed through the filter as it is being copied into the newly generated
22668 message, which happens if the &%return_message%& option is set.
22671 .option transport_filter_timeout transports time 5m
22672 .cindex "transport" "filter, timeout"
22673 When Exim is reading the output of a transport filter, it applies a timeout
22674 that can be set by this option. Exceeding the timeout is normally treated as a
22675 temporary delivery failure. However, if a transport filter is used with a
22676 &(pipe)& transport, a timeout in the transport filter is treated in the same
22677 way as a timeout in the pipe command itself. By default, a timeout is a hard
22678 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
22679 becomes a temporary error.
22682 .option user transports string&!! "Exim user"
22683 .cindex "uid (user id)" "local delivery"
22684 .cindex "transport" "user, specifying"
22685 This option specifies the user under whose uid the delivery process is to be
22686 run, overriding any uid that may have been set by the router. If the user is
22687 given as a name, the uid is looked up from the password data, and the
22688 associated group is taken as the value of the gid to be used if the &%group%&
22691 For deliveries that use local transports, a user and group are normally
22692 specified explicitly or implicitly (for example, as a result of
22693 &%check_local_user%&) by the router or transport.
22695 .cindex "hints database" "access by remote transport"
22696 For remote transports, you should leave this option unset unless you really are
22697 sure you know what you are doing. When a remote transport is running, it needs
22698 to be able to access Exim's hints databases, because each host may have its own
22700 .ecindex IIDgenoptra1
22701 .ecindex IIDgenoptra2
22702 .ecindex IIDgenoptra3
22709 . ////////////////////////////////////////////////////////////////////////////
22710 . ////////////////////////////////////////////////////////////////////////////
22712 .chapter "Address batching in local transports" "CHAPbatching" &&&
22714 .cindex "transport" "local; address batching in"
22715 The only remote transport (&(smtp)&) is normally configured to handle more than
22716 one address at a time, so that when several addresses are routed to the same
22717 remote host, just one copy of the message is sent. Local transports, however,
22718 normally handle one address at a time. That is, a separate instance of the
22719 transport is run for each address that is routed to the transport. A separate
22720 copy of the message is delivered each time.
22722 .cindex "batched local delivery"
22723 .oindex "&%batch_max%&"
22724 .oindex "&%batch_id%&"
22725 In special cases, it may be desirable to handle several addresses at once in a
22726 local transport, for example:
22729 In an &(appendfile)& transport, when storing messages in files for later
22730 delivery by some other means, a single copy of the message with multiple
22731 recipients saves space.
22733 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
22734 a single copy saves time, and is the normal way LMTP is expected to work.
22736 In a &(pipe)& transport, when passing the message
22737 to a scanner program or
22738 to some other delivery mechanism such as UUCP, multiple recipients may be
22742 These three local transports all have the same options for controlling multiple
22743 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
22744 repeating the information for each transport, these options are described here.
22746 The &%batch_max%& option specifies the maximum number of addresses that can be
22747 delivered together in a single run of the transport. Its default value is one
22748 (no batching). When more than one address is routed to a transport that has a
22749 &%batch_max%& value greater than one, the addresses are delivered in a batch
22750 (that is, in a single run of the transport with multiple recipients), subject
22751 to certain conditions:
22754 .vindex "&$local_part$&"
22755 If any of the transport's options contain a reference to &$local_part$&, no
22756 batching is possible.
22758 .vindex "&$domain$&"
22759 If any of the transport's options contain a reference to &$domain$&, only
22760 addresses with the same domain are batched.
22762 .cindex "customizing" "batching condition"
22763 If &%batch_id%& is set, it is expanded for each address, and only those
22764 addresses with the same expanded value are batched. This allows you to specify
22765 customized batching conditions. Failure of the expansion for any reason,
22766 including forced failure, disables batching, but it does not stop the delivery
22769 Batched addresses must also have the same errors address (where to send
22770 delivery errors), the same header additions and removals, the same user and
22771 group for the transport, and if a host list is present, the first host must
22775 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
22776 both when the file or pipe command is specified in the transport, and when it
22777 is specified by a &(redirect)& router, but all the batched addresses must of
22778 course be routed to the same file or pipe command. These two transports have an
22779 option called &%use_bsmtp%&, which causes them to deliver the message in
22780 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
22781 &%check_string%& and &%escape_string%& options are forced to the values
22784 escape_string = ".."
22786 when batched SMTP is in use. A full description of the batch SMTP mechanism is
22787 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
22788 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
22790 .cindex "&'Envelope-to:'& header line"
22791 If the generic &%envelope_to_add%& option is set for a batching transport, the
22792 &'Envelope-to:'& header that is added to the message contains all the addresses
22793 that are being processed together. If you are using a batching &(appendfile)&
22794 transport without &%use_bsmtp%&, the only way to preserve the recipient
22795 addresses is to set the &%envelope_to_add%& option.
22797 .cindex "&(pipe)& transport" "with multiple addresses"
22798 .vindex "&$pipe_addresses$&"
22799 If you are using a &(pipe)& transport without BSMTP, and setting the
22800 transport's &%command%& option, you can include &$pipe_addresses$& as part of
22801 the command. This is not a true variable; it is a bit of magic that causes each
22802 of the recipient addresses to be inserted into the command as a separate
22803 argument. This provides a way of accessing all the addresses that are being
22804 delivered in the batch. &*Note:*& This is not possible for pipe commands that
22805 are specified by a &(redirect)& router.
22810 . ////////////////////////////////////////////////////////////////////////////
22811 . ////////////////////////////////////////////////////////////////////////////
22813 .chapter "The appendfile transport" "CHAPappendfile"
22814 .scindex IIDapptra1 "&(appendfile)& transport"
22815 .scindex IIDapptra2 "transports" "&(appendfile)&"
22816 .cindex "directory creation"
22817 .cindex "creating directories"
22818 The &(appendfile)& transport delivers a message by appending it to an existing
22819 file, or by creating an entirely new file in a specified directory. Single
22820 files to which messages are appended can be in the traditional Unix mailbox
22821 format, or optionally in the MBX format supported by the Pine MUA and
22822 University of Washington IMAP daemon, &'inter alia'&. When each message is
22823 being delivered as a separate file, &"maildir"& format can optionally be used
22824 to give added protection against failures that happen part-way through the
22825 delivery. A third form of separate-file delivery known as &"mailstore"& is also
22826 supported. For all file formats, Exim attempts to create as many levels of
22827 directory as necessary, provided that &%create_directory%& is set.
22829 The code for the optional formats is not included in the Exim binary by
22830 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
22831 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
22834 .cindex "quota" "system"
22835 Exim recognizes system quota errors, and generates an appropriate message. Exim
22836 also supports its own quota control within the transport, for use when the
22837 system facility is unavailable or cannot be used for some reason.
22839 If there is an error while appending to a file (for example, quota exceeded or
22840 partition filled), Exim attempts to reset the file's length and last
22841 modification time back to what they were before. If there is an error while
22842 creating an entirely new file, the new file is removed.
22844 Before appending to a file, a number of security checks are made, and the
22845 file is locked. A detailed description is given below, after the list of
22848 The &(appendfile)& transport is most commonly used for local deliveries to
22849 users' mailboxes. However, it can also be used as a pseudo-remote transport for
22850 putting messages into files for remote delivery by some means other than Exim.
22851 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
22856 .section "The file and directory options" "SECTfildiropt"
22857 The &%file%& option specifies a single file, to which the message is appended;
22858 the &%directory%& option specifies a directory, in which a new file containing
22859 the message is created. Only one of these two options can be set, and for
22860 normal deliveries to mailboxes, one of them &'must'& be set.
22862 .vindex "&$address_file$&"
22863 .vindex "&$local_part$&"
22864 However, &(appendfile)& is also used for delivering messages to files or
22865 directories whose names (or parts of names) are obtained from alias,
22866 forwarding, or filtering operations (for example, a &%save%& command in a
22867 user's Exim filter). When such a transport is running, &$local_part$& contains
22868 the local part that was aliased or forwarded, and &$address_file$& contains the
22869 name (or partial name) of the file or directory generated by the redirection
22870 operation. There are two cases:
22873 If neither &%file%& nor &%directory%& is set, the redirection operation
22874 must specify an absolute path (one that begins with &`/`&). This is the most
22875 common case when users with local accounts use filtering to sort mail into
22876 different folders. See for example, the &(address_file)& transport in the
22877 default configuration. If the path ends with a slash, it is assumed to be the
22878 name of a directory. A delivery to a directory can also be forced by setting
22879 &%maildir_format%& or &%mailstore_format%&.
22881 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
22882 used to determine the file or directory name for the delivery. Normally, the
22883 contents of &$address_file$& are used in some way in the string expansion.
22885 .cindex "tainted data" "in filenames"
22886 .cindex appendfile "tainted data"
22887 Tainted data may not be used for a file or directory name.
22888 This means that, for instance, &$local_part$& cannot be used directly
22889 as a component of a path. It can however be used as the key for a lookup
22890 which returns a path (or component).
22893 .cindex "Sieve filter" "configuring &(appendfile)&"
22894 .cindex "Sieve filter" "relative mailbox path handling"
22895 As an example of the second case, consider an environment where users do not
22896 have home directories. They may be permitted to use Exim filter commands of the
22901 or Sieve filter commands of the form:
22903 require "fileinto";
22904 fileinto "folder23";
22906 In this situation, the expansion of &%file%& or &%directory%& in the transport
22907 must transform the relative path into an appropriate absolute filename. In the
22908 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
22909 is used as a result of a &"keep"& action in the filter. This example shows one
22910 way of handling this requirement:
22912 file = ${if eq{$address_file}{inbox} \
22913 {/var/mail/$local_part_data} \
22914 {${if eq{${substr_0_1:$address_file}}{/} \
22916 {$home/mail/$address_file} \
22920 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
22921 location, absolute paths are used without change, and other folders are in the
22922 &_mail_& directory within the home directory.
22924 &*Note 1*&: While processing an Exim filter, a relative path such as
22925 &_folder23_& is turned into an absolute path if a home directory is known to
22926 the router. In particular, this is the case if &%check_local_user%& is set. If
22927 you want to prevent this happening at routing time, you can set
22928 &%router_home_directory%& empty. This forces the router to pass the relative
22929 path to the transport.
22931 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
22932 the &%file%& or &%directory%& option is still used if it is set.
22937 .section "Private options for appendfile" "SECID134"
22938 .cindex "options" "&(appendfile)& transport"
22942 .option allow_fifo appendfile boolean false
22943 .cindex "fifo (named pipe)"
22944 .cindex "named pipe (fifo)"
22945 .cindex "pipe" "named (fifo)"
22946 Setting this option permits delivery to named pipes (FIFOs) as well as to
22947 regular files. If no process is reading the named pipe at delivery time, the
22948 delivery is deferred.
22951 .option allow_symlink appendfile boolean false
22952 .cindex "symbolic link" "to mailbox"
22953 .cindex "mailbox" "symbolic link"
22954 By default, &(appendfile)& will not deliver if the path name for the file is
22955 that of a symbolic link. Setting this option relaxes that constraint, but there
22956 are security issues involved in the use of symbolic links. Be sure you know
22957 what you are doing if you set this. Details of exactly what this option affects
22958 are included in the discussion which follows this list of options.
22961 .option batch_id appendfile string&!! unset
22962 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22963 However, batching is automatically disabled for &(appendfile)& deliveries that
22964 happen as a result of forwarding or aliasing or other redirection directly to a
22968 .option batch_max appendfile integer 1
22969 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22972 .option check_group appendfile boolean false
22973 When this option is set, the group owner of the file defined by the &%file%&
22974 option is checked to see that it is the same as the group under which the
22975 delivery process is running. The default setting is false because the default
22976 file mode is 0600, which means that the group is irrelevant.
22979 .option check_owner appendfile boolean true
22980 When this option is set, the owner of the file defined by the &%file%& option
22981 is checked to ensure that it is the same as the user under which the delivery
22982 process is running.
22985 .option check_string appendfile string "see below"
22986 .cindex "&""From""& line"
22987 As &(appendfile)& writes the message, the start of each line is tested for
22988 matching &%check_string%&, and if it does, the initial matching characters are
22989 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
22990 a literal string, not a regular expression, and the case of any letters it
22991 contains is significant.
22993 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
22994 are forced to &"."& and &".."& respectively, and any settings in the
22995 configuration are ignored. Otherwise, they default to &"From&~"& and
22996 &">From&~"& when the &%file%& option is set, and unset when any of the
22997 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
22999 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
23000 suitable for traditional &"BSD"& mailboxes, where a line beginning with
23001 &"From&~"& indicates the start of a new message. All four options need changing
23002 if another format is used. For example, to deliver to mailboxes in MMDF format:
23003 .cindex "MMDF format mailbox"
23004 .cindex "mailbox" "MMDF format"
23006 check_string = "\1\1\1\1\n"
23007 escape_string = "\1\1\1\1 \n"
23008 message_prefix = "\1\1\1\1\n"
23009 message_suffix = "\1\1\1\1\n"
23011 .option create_directory appendfile boolean true
23012 .cindex "directory creation"
23013 When this option is true, Exim attempts to create any missing superior
23014 directories for the file that it is about to write. A created directory's mode
23015 is given by the &%directory_mode%& option.
23017 The group ownership of a newly created directory is highly dependent on the
23018 operating system (and possibly the file system) that is being used. For
23019 example, in Solaris, if the parent directory has the setgid bit set, its group
23020 is propagated to the child; if not, the currently set group is used. However,
23021 in FreeBSD, the parent's group is always used.
23025 .option create_file appendfile string anywhere
23026 This option constrains the location of files and directories that are created
23027 by this transport. It applies to files defined by the &%file%& option and
23028 directories defined by the &%directory%& option. In the case of maildir
23029 delivery, it applies to the top level directory, not the maildir directories
23032 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
23033 &"belowhome"&. In the second and third cases, a home directory must have been
23034 set for the transport. This option is not useful when an explicit filename is
23035 given for normal mailbox deliveries. It is intended for the case when filenames
23036 are generated from users' &_.forward_& files. These are usually handled
23037 by an &(appendfile)& transport called &%address_file%&. See also
23038 &%file_must_exist%&.
23041 .option directory appendfile string&!! unset
23042 This option is mutually exclusive with the &%file%& option, but one of &%file%&
23043 or &%directory%& must be set, unless the delivery is the direct result of a
23044 redirection (see section &<<SECTfildiropt>>&).
23046 When &%directory%& is set, the string is expanded, and the message is delivered
23047 into a new file or files in or below the given directory, instead of being
23048 appended to a single mailbox file. A number of different formats are provided
23049 (see &%maildir_format%& and &%mailstore_format%&), and see section
23050 &<<SECTopdir>>& for further details of this form of delivery.
23053 .option directory_file appendfile string&!! "see below"
23055 .vindex "&$inode$&"
23056 When &%directory%& is set, but neither &%maildir_format%& nor
23057 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
23058 whose name is obtained by expanding this string. The default value is:
23060 q${base62:$tod_epoch}-$inode
23062 This generates a unique name from the current time, in base 62 form, and the
23063 inode of the file. The variable &$inode$& is available only when expanding this
23067 .option directory_mode appendfile "octal integer" 0700
23068 If &(appendfile)& creates any directories as a result of the
23069 &%create_directory%& option, their mode is specified by this option.
23072 .option escape_string appendfile string "see description"
23073 See &%check_string%& above.
23076 .option file appendfile string&!! unset
23077 This option is mutually exclusive with the &%directory%& option, but one of
23078 &%file%& or &%directory%& must be set, unless the delivery is the direct result
23079 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
23080 specifies a single file, to which the message is appended. One or more of
23081 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
23084 .cindex "NFS" "lock file"
23085 .cindex "locking files"
23086 .cindex "lock files"
23087 If you are using more than one host to deliver over NFS into the same
23088 mailboxes, you should always use lock files.
23090 The string value is expanded for each delivery, and must yield an absolute
23091 path. The most common settings of this option are variations on one of these
23094 file = /var/spool/mail/$local_part_data
23095 file = /home/$local_part_data/inbox
23098 .cindex "&""sticky""& bit"
23099 In the first example, all deliveries are done into the same directory. If Exim
23100 is configured to use lock files (see &%use_lockfile%& below) it must be able to
23101 create a file in the directory, so the &"sticky"& bit must be turned on for
23102 deliveries to be possible, or alternatively the &%group%& option can be used to
23103 run the delivery under a group id which has write access to the directory.
23107 .option file_format appendfile string unset
23108 .cindex "file" "mailbox; checking existing format"
23109 This option requests the transport to check the format of an existing file
23110 before adding to it. The check consists of matching a specific string at the
23111 start of the file. The value of the option consists of an even number of
23112 colon-separated strings. The first of each pair is the test string, and the
23113 second is the name of a transport. If the transport associated with a matched
23114 string is not the current transport, control is passed over to the other
23115 transport. For example, suppose the standard &(local_delivery)& transport has
23118 file_format = "From : local_delivery :\
23119 \1\1\1\1\n : local_mmdf_delivery"
23121 Mailboxes that begin with &"From"& are still handled by this transport, but if
23122 a mailbox begins with four binary ones followed by a newline, control is passed
23123 to a transport called &%local_mmdf_delivery%&, which presumably is configured
23124 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
23125 is assumed to match the current transport. If the start of a mailbox doesn't
23126 match any string, or if the transport named for a given string is not defined,
23127 delivery is deferred.
23130 .option file_must_exist appendfile boolean false
23131 If this option is true, the file specified by the &%file%& option must exist.
23132 A temporary error occurs if it does not, causing delivery to be deferred.
23133 If this option is false, the file is created if it does not exist.
23136 .option lock_fcntl_timeout appendfile time 0s
23137 .cindex "timeout" "mailbox locking"
23138 .cindex "mailbox" "locking, blocking and non-blocking"
23139 .cindex "locking files"
23140 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
23141 when locking an open mailbox file. If the call fails, the delivery process
23142 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
23143 Non-blocking calls are used so that the file is not kept open during the wait
23144 for the lock; the reason for this is to make it as safe as possible for
23145 deliveries over NFS in the case when processes might be accessing an NFS
23146 mailbox without using a lock file. This should not be done, but
23147 misunderstandings and hence misconfigurations are not unknown.
23149 On a busy system, however, the performance of a non-blocking lock approach is
23150 not as good as using a blocking lock with a timeout. In this case, the waiting
23151 is done inside the system call, and Exim's delivery process acquires the lock
23152 and can proceed as soon as the previous lock holder releases it.
23154 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
23155 timeout, are used. There may still be some retrying: the maximum number of
23158 (lock_retries * lock_interval) / lock_fcntl_timeout
23160 rounded up to the next whole number. In other words, the total time during
23161 which &(appendfile)& is trying to get a lock is roughly the same, unless
23162 &%lock_fcntl_timeout%& is set very large.
23164 You should consider setting this option if you are getting a lot of delayed
23165 local deliveries because of errors of the form
23167 failed to lock mailbox /some/file (fcntl)
23170 .option lock_flock_timeout appendfile time 0s
23171 This timeout applies to file locking when using &[flock()]& (see
23172 &%use_flock%&); the timeout operates in a similar manner to
23173 &%lock_fcntl_timeout%&.
23176 .option lock_interval appendfile time 3s
23177 This specifies the time to wait between attempts to lock the file. See below
23178 for details of locking.
23181 .option lock_retries appendfile integer 10
23182 This specifies the maximum number of attempts to lock the file. A value of zero
23183 is treated as 1. See below for details of locking.
23186 .option lockfile_mode appendfile "octal integer" 0600
23187 This specifies the mode of the created lock file, when a lock file is being
23188 used (see &%use_lockfile%& and &%use_mbx_lock%&).
23191 .option lockfile_timeout appendfile time 30m
23192 .cindex "timeout" "mailbox locking"
23193 When a lock file is being used (see &%use_lockfile%&), if a lock file already
23194 exists and is older than this value, it is assumed to have been left behind by
23195 accident, and Exim attempts to remove it.
23198 .option mailbox_filecount appendfile string&!! unset
23199 .cindex "mailbox" "specifying size of"
23200 .cindex "size" "of mailbox"
23201 If this option is set, it is expanded, and the result is taken as the current
23202 number of files in the mailbox. It must be a decimal number, optionally
23203 followed by K or M. This provides a way of obtaining this information from an
23204 external source that maintains the data.
23207 .option mailbox_size appendfile string&!! unset
23208 .cindex "mailbox" "specifying size of"
23209 .cindex "size" "of mailbox"
23210 If this option is set, it is expanded, and the result is taken as the current
23211 size the mailbox. It must be a decimal number, optionally followed by K or M.
23212 This provides a way of obtaining this information from an external source that
23213 maintains the data. This is likely to be helpful for maildir deliveries where
23214 it is computationally expensive to compute the size of a mailbox.
23218 .option maildir_format appendfile boolean false
23219 .cindex "maildir format" "specifying"
23220 If this option is set with the &%directory%& option, the delivery is into a new
23221 file, in the &"maildir"& format that is used by other mail software. When the
23222 transport is activated directly from a &(redirect)& router (for example, the
23223 &(address_file)& transport in the default configuration), setting
23224 &%maildir_format%& causes the path received from the router to be treated as a
23225 directory, whether or not it ends with &`/`&. This option is available only if
23226 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
23227 &<<SECTmaildirdelivery>>& below for further details.
23230 .option maildir_quota_directory_regex appendfile string "See below"
23231 .cindex "maildir format" "quota; directories included in"
23232 .cindex "quota" "maildir; directories included in"
23233 This option is relevant only when &%maildir_use_size_file%& is set. It defines
23234 a regular expression for specifying directories, relative to the quota
23235 directory (see &%quota_directory%&), that should be included in the quota
23236 calculation. The default value is:
23238 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
23240 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
23241 (directories whose names begin with a dot). If you want to exclude the
23243 folder from the count (as some sites do), you need to change this setting to
23245 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
23247 This uses a negative lookahead in the regular expression to exclude the
23248 directory whose name is &_.Trash_&. When a directory is excluded from quota
23249 calculations, quota processing is bypassed for any messages that are delivered
23250 directly into that directory.
23253 .option maildir_retries appendfile integer 10
23254 This option specifies the number of times to retry when writing a file in
23255 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
23258 .option maildir_tag appendfile string&!! unset
23259 This option applies only to deliveries in maildir format, and is described in
23260 section &<<SECTmaildirdelivery>>& below.
23263 .option maildir_use_size_file appendfile&!! boolean false
23264 .cindex "maildir format" "&_maildirsize_& file"
23265 The result of string expansion for this option must be a valid boolean value.
23266 If it is true, it enables support for &_maildirsize_& files. Exim
23267 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
23268 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
23269 value is zero. See &%maildir_quota_directory_regex%& above and section
23270 &<<SECTmaildirdelivery>>& below for further details.
23272 .option maildirfolder_create_regex appendfile string unset
23273 .cindex "maildir format" "&_maildirfolder_& file"
23274 .cindex "&_maildirfolder_&, creating"
23275 The value of this option is a regular expression. If it is unset, it has no
23276 effect. Otherwise, before a maildir delivery takes place, the pattern is
23277 matched against the name of the maildir directory, that is, the directory
23278 containing the &_new_& and &_tmp_& subdirectories that will be used for the
23279 delivery. If there is a match, Exim checks for the existence of a file called
23280 &_maildirfolder_& in the directory, and creates it if it does not exist.
23281 See section &<<SECTmaildirdelivery>>& for more details.
23284 .option mailstore_format appendfile boolean false
23285 .cindex "mailstore format" "specifying"
23286 If this option is set with the &%directory%& option, the delivery is into two
23287 new files in &"mailstore"& format. The option is available only if
23288 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
23289 below for further details.
23292 .option mailstore_prefix appendfile string&!! unset
23293 This option applies only to deliveries in mailstore format, and is described in
23294 section &<<SECTopdir>>& below.
23297 .option mailstore_suffix appendfile string&!! unset
23298 This option applies only to deliveries in mailstore format, and is described in
23299 section &<<SECTopdir>>& below.
23302 .option mbx_format appendfile boolean false
23303 .cindex "locking files"
23304 .cindex "file" "locking"
23305 .cindex "file" "MBX format"
23306 .cindex "MBX format, specifying"
23307 This option is available only if Exim has been compiled with SUPPORT_MBX
23308 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
23309 the message is appended to the mailbox file in MBX format instead of
23310 traditional Unix format. This format is supported by Pine4 and its associated
23311 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
23313 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
23314 automatically changed by the use of &%mbx_format%&. They should normally be set
23315 empty when using MBX format, so this option almost always appears in this
23322 If none of the locking options are mentioned in the configuration,
23323 &%use_mbx_lock%& is assumed and the other locking options default to false. It
23324 is possible to specify the other kinds of locking with &%mbx_format%&, but
23325 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
23326 interworks with &'c-client'&, providing for shared access to the mailbox. It
23327 should not be used if any program that does not use this form of locking is
23328 going to access the mailbox, nor should it be used if the mailbox file is NFS
23329 mounted, because it works only when the mailbox is accessed from a single host.
23331 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
23332 the standard version of &'c-client'&, because as long as it has a mailbox open
23333 (this means for the whole of a Pine or IMAP session), Exim will not be able to
23334 append messages to it.
23337 .option message_prefix appendfile string&!! "see below"
23338 .cindex "&""From""& line"
23339 The string specified here is expanded and output at the start of every message.
23340 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23341 in which case it is:
23343 message_prefix = "From ${if def:return_path{$return_path}\
23344 {MAILER-DAEMON}} $tod_bsdinbox\n"
23346 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23347 &`\n`& to &`\r\n`& in &%message_prefix%&.
23349 .option message_suffix appendfile string&!! "see below"
23350 The string specified here is expanded and output at the end of every message.
23351 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
23352 in which case it is a single newline character. The suffix can be suppressed by
23357 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23358 &`\n`& to &`\r\n`& in &%message_suffix%&.
23360 .option mode appendfile "octal integer" 0600
23361 If the output file is created, it is given this mode. If it already exists and
23362 has wider permissions, they are reduced to this mode. If it has narrower
23363 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
23364 if the delivery is the result of a &%save%& command in a filter file specifying
23365 a particular mode, the mode of the output file is always forced to take that
23366 value, and this option is ignored.
23369 .option mode_fail_narrower appendfile boolean true
23370 This option applies in the case when an existing mailbox file has a narrower
23371 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
23372 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
23373 continues with the delivery attempt, using the existing mode of the file.
23376 .option notify_comsat appendfile boolean false
23377 If this option is true, the &'comsat'& daemon is notified after every
23378 successful delivery to a user mailbox. This is the daemon that notifies logged
23379 on users about incoming mail.
23382 .option quota appendfile string&!! unset
23383 .cindex "quota" "imposed by Exim"
23384 This option imposes a limit on the size of the file to which Exim is appending,
23385 or to the total space used in the directory tree when the &%directory%& option
23386 is set. In the latter case, computation of the space used is expensive, because
23387 all the files in the directory (and any sub-directories) have to be
23388 individually inspected and their sizes summed. (See &%quota_size_regex%& and
23389 &%maildir_use_size_file%& for ways to avoid this in environments where users
23390 have no shell access to their mailboxes).
23392 As there is no interlock against two simultaneous deliveries into a
23393 multi-file mailbox, it is possible for the quota to be overrun in this case.
23394 For single-file mailboxes, of course, an interlock is a necessity.
23396 A file's size is taken as its &'used'& value. Because of blocking effects, this
23397 may be a lot less than the actual amount of disk space allocated to the file.
23398 If the sizes of a number of files are being added up, the rounding effect can
23399 become quite noticeable, especially on systems that have large block sizes.
23400 Nevertheless, it seems best to stick to the &'used'& figure, because this is
23401 the obvious value which users understand most easily.
23403 The value of the option is expanded, and must then be a numerical value
23404 (decimal point allowed), optionally followed by one of the letters K, M, or G,
23405 for kilobytes, megabytes, or gigabytes, optionally followed by a slash
23406 and further option modifiers. If Exim is running on a system with
23407 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
23410 The option modifier &%no_check%& can be used to force delivery even if the over
23411 quota condition is met. The quota gets updated as usual.
23413 &*Note*&: A value of zero is interpreted as &"no quota"&.
23415 The expansion happens while Exim is running as root, before it changes uid for
23416 the delivery. This means that files that are inaccessible to the end user can
23417 be used to hold quota values that are looked up in the expansion. When delivery
23418 fails because this quota is exceeded, the handling of the error is as for
23419 system quota failures.
23421 By default, Exim's quota checking mimics system quotas, and restricts the
23422 mailbox to the specified maximum size, though the value is not accurate to the
23423 last byte, owing to separator lines and additional headers that may get added
23424 during message delivery. When a mailbox is nearly full, large messages may get
23425 refused even though small ones are accepted, because the size of the current
23426 message is added to the quota when the check is made. This behaviour can be
23427 changed by setting &%quota_is_inclusive%& false. When this is done, the check
23428 for exceeding the quota does not include the current message. Thus, deliveries
23429 continue until the quota has been exceeded; thereafter, no further messages are
23430 delivered. See also &%quota_warn_threshold%&.
23433 .option quota_directory appendfile string&!! unset
23434 This option defines the directory to check for quota purposes when delivering
23435 into individual files. The default is the delivery directory, or, if a file
23436 called &_maildirfolder_& exists in a maildir directory, the parent of the
23437 delivery directory.
23440 .option quota_filecount appendfile string&!! 0
23441 This option applies when the &%directory%& option is set. It limits the total
23442 number of files in the directory (compare the inode limit in system quotas). It
23443 can only be used if &%quota%& is also set. The value is expanded; an expansion
23444 failure causes delivery to be deferred. A value of zero is interpreted as
23447 The option modifier &%no_check%& can be used to force delivery even if the over
23448 quota condition is met. The quota gets updated as usual.
23450 .option quota_is_inclusive appendfile boolean true
23451 See &%quota%& above.
23454 .option quota_size_regex appendfile string unset
23455 This option applies when one of the delivery modes that writes a separate file
23456 for each message is being used. When Exim wants to find the size of one of
23457 these files in order to test the quota, it first checks &%quota_size_regex%&.
23458 If this is set to a regular expression that matches the filename, and it
23459 captures one string, that string is interpreted as a representation of the
23460 file's size. The value of &%quota_size_regex%& is not expanded.
23462 This feature is useful only when users have no shell access to their mailboxes
23463 &-- otherwise they could defeat the quota simply by renaming the files. This
23464 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
23465 the file length to the filename. For example:
23467 maildir_tag = ,S=$message_size
23468 quota_size_regex = ,S=(\d+)
23470 An alternative to &$message_size$& is &$message_linecount$&, which contains the
23471 number of lines in the message.
23473 The regular expression should not assume that the length is at the end of the
23474 filename (even though &%maildir_tag%& puts it there) because maildir MUAs
23475 sometimes add other information onto the ends of message filenames.
23477 Section &<<SECID136>>& contains further information.
23479 This option should not be used when other message-handling software
23480 may duplicate messages by making hardlinks to the files. When that is done Exim
23481 will count the message size once for each filename, in contrast with the actual
23482 disk usage. When the option is not set, calculating total usage requires
23483 a system-call per file to get the size; the number of links is then available also
23484 as is used to adjust the effective size.
23487 .option quota_warn_message appendfile string&!! "see below"
23488 See below for the use of this option. If it is not set when
23489 &%quota_warn_threshold%& is set, it defaults to
23491 quota_warn_message = "\
23492 To: $local_part@$domain\n\
23493 Subject: Your mailbox\n\n\
23494 This message is automatically created \
23495 by mail delivery software.\n\n\
23496 The size of your mailbox has exceeded \
23497 a warning threshold that is\n\
23498 set by the system administrator.\n"
23502 .option quota_warn_threshold appendfile string&!! 0
23503 .cindex "quota" "warning threshold"
23504 .cindex "mailbox" "size warning"
23505 .cindex "size" "of mailbox"
23506 This option is expanded in the same way as &%quota%& (see above). If the
23507 resulting value is greater than zero, and delivery of the message causes the
23508 size of the file or total space in the directory tree to cross the given
23509 threshold, a warning message is sent. If &%quota%& is also set, the threshold
23510 may be specified as a percentage of it by following the value with a percent
23514 quota_warn_threshold = 75%
23516 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
23517 percent sign is ignored.
23519 The warning message itself is specified by the &%quota_warn_message%& option,
23520 and it must start with a &'To:'& header line containing the recipient(s) of the
23521 warning message. These do not necessarily have to include the recipient(s) of
23522 the original message. A &'Subject:'& line should also normally be supplied. You
23523 can include any other header lines that you want. If you do not include a
23524 &'From:'& line, the default is:
23526 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
23528 .oindex &%errors_reply_to%&
23529 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
23532 The &%quota%& option does not have to be set in order to use this option; they
23533 are independent of one another except when the threshold is specified as a
23537 .option use_bsmtp appendfile boolean false
23538 .cindex "envelope from"
23539 .cindex "envelope sender"
23540 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
23541 format, with the envelope sender and recipient(s) included as SMTP commands. If
23542 you want to include a leading HELO command with such messages, you can do
23543 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
23544 for details of batch SMTP.
23547 .option use_crlf appendfile boolean false
23548 .cindex "carriage return"
23550 This option causes lines to be terminated with the two-character CRLF sequence
23551 (carriage return, linefeed) instead of just a linefeed character. In the case
23552 of batched SMTP, the byte sequence written to the file is then an exact image
23553 of what would be sent down a real SMTP connection.
23555 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
23556 (which are used to supply the traditional &"From&~"& and blank line separators
23557 in Berkeley-style mailboxes) are written verbatim, so must contain their own
23558 carriage return characters if these are needed. In cases where these options
23559 have non-empty defaults, the values end with a single linefeed, so they must be
23560 changed to end with &`\r\n`& if &%use_crlf%& is set.
23563 .option use_fcntl_lock appendfile boolean "see below"
23564 This option controls the use of the &[fcntl()]& function to lock a file for
23565 exclusive use when a message is being appended. It is set by default unless
23566 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
23567 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
23568 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
23571 .option use_flock_lock appendfile boolean false
23572 This option is provided to support the use of &[flock()]& for file locking, for
23573 the few situations where it is needed. Most modern operating systems support
23574 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
23575 each other. Exim uses &[fcntl()]& locking by default.
23577 This option is required only if you are using an operating system where
23578 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
23579 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
23580 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
23582 .cindex "Solaris" "&[flock()]& support"
23583 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
23584 have it (and some, I think, provide a not quite right version built on top of
23585 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
23586 the ability to use it, and any attempt to do so will cause a configuration
23589 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
23590 is just being mapped onto &[fcntl()]& by the OS).
23593 .option use_lockfile appendfile boolean "see below"
23594 If this option is turned off, Exim does not attempt to create a lock file when
23595 appending to a mailbox file. In this situation, the only locking is by
23596 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
23597 sure that every MUA that is ever going to look at your users' mailboxes uses
23598 &[fcntl()]& rather than a lock file, and even then only when you are not
23599 delivering over NFS from more than one host.
23601 .cindex "NFS" "lock file"
23602 In order to append to an NFS file safely from more than one host, it is
23603 necessary to take out a lock &'before'& opening the file, and the lock file
23604 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
23607 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
23608 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
23609 except when &%mbx_format%& is set.
23612 .option use_mbx_lock appendfile boolean "see below"
23613 This option is available only if Exim has been compiled with SUPPORT_MBX
23614 set in &_Local/Makefile_&. Setting the option specifies that special MBX
23615 locking rules be used. It is set by default if &%mbx_format%& is set and none
23616 of the locking options are mentioned in the configuration. The locking rules
23617 are the same as are used by the &'c-client'& library that underlies Pine and
23618 the IMAP4 and POP daemons that come with it (see the discussion below). The
23619 rules allow for shared access to the mailbox. However, this kind of locking
23620 does not work when the mailbox is NFS mounted.
23622 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
23623 &%use_flock_lock%& to control what kind of locking is used in implementing the
23624 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
23625 without &%use_fcntl_lock%& or &%use_flock_lock%&.
23630 .section "Operational details for appending" "SECTopappend"
23631 .cindex "appending to a file"
23632 .cindex "file" "appending"
23633 Before appending to a file, the following preparations are made:
23636 If the name of the file is &_/dev/null_&, no action is taken, and a success
23640 .cindex "directory creation"
23641 If any directories on the file's path are missing, Exim creates them if the
23642 &%create_directory%& option is set. A created directory's mode is given by the
23643 &%directory_mode%& option.
23646 If &%file_format%& is set, the format of an existing file is checked. If this
23647 indicates that a different transport should be used, control is passed to that
23651 .cindex "file" "locking"
23652 .cindex "locking files"
23653 .cindex "NFS" "lock file"
23654 If &%use_lockfile%& is set, a lock file is built in a way that will work
23655 reliably over NFS, as follows:
23658 Create a &"hitching post"& file whose name is that of the lock file with the
23659 current time, primary host name, and process id added, by opening for writing
23660 as a new file. If this fails with an access error, delivery is deferred.
23662 Close the hitching post file, and hard link it to the lock filename.
23664 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
23665 Unlink the hitching post name.
23667 Otherwise, use &[stat()]& to get information about the hitching post file, and
23668 then unlink hitching post name. If the number of links is exactly two, creation
23669 of the lock file succeeded but something (for example, an NFS server crash and
23670 restart) caused this fact not to be communicated to the &[link()]& call.
23672 If creation of the lock file failed, wait for &%lock_interval%& and try again,
23673 up to &%lock_retries%& times. However, since any program that writes to a
23674 mailbox should complete its task very quickly, it is reasonable to time out old
23675 lock files that are normally the result of user agent and system crashes. If an
23676 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
23677 it before trying again.
23681 A call is made to &[lstat()]& to discover whether the main file exists, and if
23682 so, what its characteristics are. If &[lstat()]& fails for any reason other
23683 than non-existence, delivery is deferred.
23686 .cindex "symbolic link" "to mailbox"
23687 .cindex "mailbox" "symbolic link"
23688 If the file does exist and is a symbolic link, delivery is deferred, unless the
23689 &%allow_symlink%& option is set, in which case the ownership of the link is
23690 checked, and then &[stat()]& is called to find out about the real file, which
23691 is then subjected to the checks below. The check on the top-level link
23692 ownership prevents one user creating a link for another's mailbox in a sticky
23693 directory, though allowing symbolic links in this case is definitely not a good
23694 idea. If there is a chain of symbolic links, the intermediate ones are not
23698 If the file already exists but is not a regular file, or if the file's owner
23699 and group (if the group is being checked &-- see &%check_group%& above) are
23700 different from the user and group under which the delivery is running,
23701 delivery is deferred.
23704 If the file's permissions are more generous than specified, they are reduced.
23705 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
23706 is set false, in which case the delivery is tried using the existing
23710 The file's inode number is saved, and the file is then opened for appending.
23711 If this fails because the file has vanished, &(appendfile)& behaves as if it
23712 hadn't existed (see below). For any other failures, delivery is deferred.
23715 If the file is opened successfully, check that the inode number hasn't
23716 changed, that it is still a regular file, and that the owner and permissions
23717 have not changed. If anything is wrong, defer delivery and freeze the message.
23720 If the file did not exist originally, defer delivery if the &%file_must_exist%&
23721 option is set. Otherwise, check that the file is being created in a permitted
23722 directory if the &%create_file%& option is set (deferring on failure), and then
23723 open for writing as a new file, with the O_EXCL and O_CREAT options,
23724 except when dealing with a symbolic link (the &%allow_symlink%& option must be
23725 set). In this case, which can happen if the link points to a non-existent file,
23726 the file is opened for writing using O_CREAT but not O_EXCL, because
23727 that prevents link following.
23730 .cindex "loop" "while file testing"
23731 If opening fails because the file exists, obey the tests given above for
23732 existing files. However, to avoid looping in a situation where the file is
23733 being continuously created and destroyed, the exists/not-exists loop is broken
23734 after 10 repetitions, and the message is then frozen.
23737 If opening fails with any other error, defer delivery.
23740 .cindex "file" "locking"
23741 .cindex "locking files"
23742 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
23743 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
23744 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
23745 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
23746 file, and an exclusive lock on the file whose name is
23748 /tmp/.<device-number>.<inode-number>
23750 using the device and inode numbers of the open mailbox file, in accordance with
23751 the MBX locking rules. This file is created with a mode that is specified by
23752 the &%lockfile_mode%& option.
23754 If Exim fails to lock the file, there are two possible courses of action,
23755 depending on the value of the locking timeout. This is obtained from
23756 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
23758 If the timeout value is zero, the file is closed, Exim waits for
23759 &%lock_interval%&, and then goes back and re-opens the file as above and tries
23760 to lock it again. This happens up to &%lock_retries%& times, after which the
23761 delivery is deferred.
23763 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
23764 &[flock()]& are used (with the given timeout), so there has already been some
23765 waiting involved by the time locking fails. Nevertheless, Exim does not give up
23766 immediately. It retries up to
23768 (lock_retries * lock_interval) / <timeout>
23770 times (rounded up).
23773 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
23774 and/or &[flock()]& locks) and then deletes the lock file if one was created.
23777 .section "Operational details for delivery to a new file" "SECTopdir"
23778 .cindex "delivery" "to single file"
23779 .cindex "&""From""& line"
23780 When the &%directory%& option is set instead of &%file%&, each message is
23781 delivered into a newly-created file or set of files. When &(appendfile)& is
23782 activated directly from a &(redirect)& router, neither &%file%& nor
23783 &%directory%& is normally set, because the path for delivery is supplied by the
23784 router. (See for example, the &(address_file)& transport in the default
23785 configuration.) In this case, delivery is to a new file if either the path name
23786 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
23788 No locking is required while writing the message to a new file, so the various
23789 locking options of the transport are ignored. The &"From"& line that by default
23790 separates messages in a single file is not normally needed, nor is the escaping
23791 of message lines that start with &"From"&, and there is no need to ensure a
23792 newline at the end of each message. Consequently, the default values for
23793 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
23794 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
23796 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
23797 the files in the delivery directory by default. However, you can specify a
23798 different directory by setting &%quota_directory%&. Also, for maildir
23799 deliveries (see below) the &_maildirfolder_& convention is honoured.
23802 .cindex "maildir format"
23803 .cindex "mailstore format"
23804 There are three different ways in which delivery to individual files can be
23805 done, controlled by the settings of the &%maildir_format%& and
23806 &%mailstore_format%& options. Note that code to support maildir or mailstore
23807 formats is not included in the binary unless SUPPORT_MAILDIR or
23808 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
23810 .cindex "directory creation"
23811 In all three cases an attempt is made to create the directory and any necessary
23812 sub-directories if they do not exist, provided that the &%create_directory%&
23813 option is set (the default). The location of a created directory can be
23814 constrained by setting &%create_file%&. A created directory's mode is given by
23815 the &%directory_mode%& option. If creation fails, or if the
23816 &%create_directory%& option is not set when creation is required, delivery is
23821 .section "Maildir delivery" "SECTmaildirdelivery"
23822 .cindex "maildir format" "description of"
23823 If the &%maildir_format%& option is true, Exim delivers each message by writing
23824 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
23825 directory that is defined by the &%directory%& option (the &"delivery
23826 directory"&). If the delivery is successful, the file is renamed into the
23827 &_new_& subdirectory.
23829 In the filename, <&'stime'&> is the current time of day in seconds, and
23830 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
23831 Exim checks that the time-of-day clock has moved on by at least one microsecond
23832 before terminating the delivery process. This guarantees uniqueness for the
23833 filename. However, as a precaution, Exim calls &[stat()]& for the file before
23834 opening it. If any response other than ENOENT (does not exist) is given,
23835 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
23837 Before Exim carries out a maildir delivery, it ensures that subdirectories
23838 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
23839 do not exist, Exim tries to create them and any superior directories in their
23840 path, subject to the &%create_directory%& and &%create_file%& options. If the
23841 &%maildirfolder_create_regex%& option is set, and the regular expression it
23842 contains matches the delivery directory, Exim also ensures that a file called
23843 &_maildirfolder_& exists in the delivery directory. If a missing directory or
23844 &_maildirfolder_& file cannot be created, delivery is deferred.
23846 These features make it possible to use Exim to create all the necessary files
23847 and directories in a maildir mailbox, including subdirectories for maildir++
23848 folders. Consider this example:
23850 maildir_format = true
23851 directory = /var/mail/$local_part_data\
23852 ${if eq{$local_part_suffix}{}{}\
23853 {/.${substr_1:$local_part_suffix}}}
23854 maildirfolder_create_regex = /\.[^/]+$
23856 If &$local_part_suffix$& is empty (there was no suffix for the local part),
23857 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
23858 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
23859 not match this name, so Exim will not look for or create the file
23860 &_/var/mail/pimbo/maildirfolder_&, though it will create
23861 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
23863 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
23864 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
23865 does match &%maildirfolder_create_regex%&. In this case, Exim will create
23866 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
23867 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
23869 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
23870 not inadvertently match the toplevel maildir directory, because a
23871 &_maildirfolder_& file at top level would completely break quota calculations.
23873 .cindex "quota" "in maildir delivery"
23874 .cindex "maildir++"
23875 If Exim is required to check a &%quota%& setting before a maildir delivery, and
23876 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
23877 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
23878 Exim assumes the directory is a maildir++ folder directory, which is one level
23879 down from the user's top level mailbox directory. This causes it to start at
23880 the parent directory instead of the current directory when calculating the
23881 amount of space used.
23883 One problem with delivering into a multi-file mailbox is that it is
23884 computationally expensive to compute the size of the mailbox for quota
23885 checking. Various approaches have been taken to reduce the amount of work
23886 needed. The next two sections describe two of them. A third alternative is to
23887 use some external process for maintaining the size data, and use the expansion
23888 of the &%mailbox_size%& option as a way of importing it into Exim.
23893 .section "Using tags to record message sizes" "SECID135"
23894 If &%maildir_tag%& is set, the string is expanded for each delivery.
23895 When the maildir file is renamed into the &_new_& sub-directory, the
23896 tag is added to its name. However, if adding the tag takes the length of the
23897 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
23898 the tag is dropped and the maildir file is created with no tag.
23901 .vindex "&$message_size$&"
23902 Tags can be used to encode the size of files in their names; see
23903 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
23904 happens after the message has been written. The value of the &$message_size$&
23905 variable is set to the number of bytes actually written. If the expansion is
23906 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
23907 be deferred. The expanded tag may contain any printing characters except &"/"&.
23908 Non-printing characters in the string are ignored; if the resulting string is
23909 empty, it is ignored. If it starts with an alphanumeric character, a leading
23910 colon is inserted; this default has not proven to be the path that popular
23911 maildir implementations have chosen (but changing it in Exim would break
23912 backwards compatibility).
23914 For one common implementation, you might set:
23916 maildir_tag = ,S=${message_size}
23918 but you should check the documentation of the other software to be sure.
23920 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
23921 as this allows Exim to extract the size from your tag, instead of having to
23922 &[stat()]& each message file.
23925 .section "Using a maildirsize file" "SECID136"
23926 .cindex "quota" "in maildir delivery"
23927 .cindex "maildir format" "&_maildirsize_& file"
23928 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
23929 storing quota and message size information in a file called &_maildirsize_&
23930 within the toplevel maildir directory. If this file does not exist, Exim
23931 creates it, setting the quota from the &%quota%& option of the transport. If
23932 the maildir directory itself does not exist, it is created before any attempt
23933 to write a &_maildirsize_& file.
23935 The &_maildirsize_& file is used to hold information about the sizes of
23936 messages in the maildir, thus speeding up quota calculations. The quota value
23937 in the file is just a cache; if the quota is changed in the transport, the new
23938 value overrides the cached value when the next message is delivered. The cache
23939 is maintained for the benefit of other programs that access the maildir and
23940 need to know the quota.
23942 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
23943 file is maintained (with a zero quota setting), but no quota is imposed.
23945 A regular expression is available for controlling which directories in the
23946 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
23947 See the description of the &%maildir_quota_directory_regex%& option above for
23951 .section "Mailstore delivery" "SECID137"
23952 .cindex "mailstore format" "description of"
23953 If the &%mailstore_format%& option is true, each message is written as two
23954 files in the given directory. A unique base name is constructed from the
23955 message id and the current delivery process, and the files that are written use
23956 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
23957 contains the message's envelope, and the &_.msg_& file contains the message
23958 itself. The base name is placed in the variable &$mailstore_basename$&.
23960 During delivery, the envelope is first written to a file with the suffix
23961 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
23962 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
23963 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
23964 file before accessing either of them. An alternative approach is to wait for
23965 the absence of a &_.tmp_& file.
23967 The envelope file starts with any text defined by the &%mailstore_prefix%&
23968 option, expanded and terminated by a newline if there isn't one. Then follows
23969 the sender address on one line, then all the recipient addresses, one per line.
23970 There can be more than one recipient only if the &%batch_max%& option is set
23971 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
23972 appended to the file, followed by a newline if it does not end with one.
23974 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
23975 failure, it is ignored. Other expansion errors are treated as serious
23976 configuration errors, and delivery is deferred. The variable
23977 &$mailstore_basename$& is available for use during these expansions.
23980 .section "Non-special new file delivery" "SECID138"
23981 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
23982 file is created directly in the named directory. For example, when delivering
23983 messages into files in batched SMTP format for later delivery to some host (see
23984 section &<<SECTbatchSMTP>>&), a setting such as
23986 directory = /var/bsmtp/$host
23988 might be used. A message is written to a file with a temporary name, which is
23989 then renamed when the delivery is complete. The final name is obtained by
23990 expanding the contents of the &%directory_file%& option.
23991 .ecindex IIDapptra1
23992 .ecindex IIDapptra2
23999 . ////////////////////////////////////////////////////////////////////////////
24000 . ////////////////////////////////////////////////////////////////////////////
24002 .chapter "The autoreply transport" "CHID8"
24003 .scindex IIDauttra1 "transports" "&(autoreply)&"
24004 .scindex IIDauttra2 "&(autoreply)& transport"
24005 The &(autoreply)& transport is not a true transport in that it does not cause
24006 the message to be transmitted. Instead, it generates a new mail message as an
24007 automatic reply to the incoming message. &'References:'& and
24008 &'Auto-Submitted:'& header lines are included. These are constructed according
24009 to the rules in RFCs 2822 and 3834, respectively.
24011 If the router that passes the message to this transport does not have the
24012 &%unseen%& option set, the original message (for the current recipient) is not
24013 delivered anywhere. However, when the &%unseen%& option is set on the router
24014 that passes the message to this transport, routing of the address continues, so
24015 another router can set up a normal message delivery.
24018 The &(autoreply)& transport is usually run as the result of mail filtering, a
24019 &"vacation"& message being the standard example. However, it can also be run
24020 directly from a router like any other transport. To reduce the possibility of
24021 message cascades, messages created by the &(autoreply)& transport always have
24022 empty envelope sender addresses, like bounce messages.
24024 The parameters of the message to be sent can be specified in the configuration
24025 by options described below. However, these are used only when the address
24026 passed to the transport does not contain its own reply information. When the
24027 transport is run as a consequence of a
24029 or &%vacation%& command in a filter file, the parameters of the message are
24030 supplied by the filter, and passed with the address. The transport's options
24031 that define the message are then ignored (so they are not usually set in this
24032 case). The message is specified entirely by the filter or by the transport; it
24033 is never built from a mixture of options. However, the &%file_optional%&,
24034 &%mode%&, and &%return_message%& options apply in all cases.
24036 &(Autoreply)& is implemented as a local transport. When used as a result of a
24037 command in a user's filter file, &(autoreply)& normally runs under the uid and
24038 gid of the user, and with appropriate current and home directories (see chapter
24039 &<<CHAPenvironment>>&).
24041 There is a subtle difference between routing a message to a &(pipe)& transport
24042 that generates some text to be returned to the sender, and routing it to an
24043 &(autoreply)& transport. This difference is noticeable only if more than one
24044 address from the same message is so handled. In the case of a pipe, the
24045 separate outputs from the different addresses are gathered up and returned to
24046 the sender in a single message, whereas if &(autoreply)& is used, a separate
24047 message is generated for each address that is passed to it.
24049 Non-printing characters are not permitted in the header lines generated for the
24050 message that &(autoreply)& creates, with the exception of newlines that are
24051 immediately followed by white space. If any non-printing characters are found,
24052 the transport defers.
24053 Whether characters with the top bit set count as printing characters or not is
24054 controlled by the &%print_topbitchars%& global option.
24056 If any of the generic options for manipulating headers (for example,
24057 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
24058 of the original message that is included in the generated message when
24059 &%return_message%& is set. They do not apply to the generated message itself.
24061 .vindex "&$sender_address$&"
24062 If the &(autoreply)& transport receives return code 2 from Exim when it submits
24063 the message, indicating that there were no recipients, it does not treat this
24064 as an error. This means that autoreplies sent to &$sender_address$& when this
24065 is empty (because the incoming message is a bounce message) do not cause
24066 problems. They are just discarded.
24070 .section "Private options for autoreply" "SECID139"
24071 .cindex "options" "&(autoreply)& transport"
24073 .option bcc autoreply string&!! unset
24074 This specifies the addresses that are to receive &"blind carbon copies"& of the
24075 message when the message is specified by the transport.
24078 .option cc autoreply string&!! unset
24079 This specifies recipients of the message and the contents of the &'Cc:'& header
24080 when the message is specified by the transport.
24083 .option file autoreply string&!! unset
24084 The contents of the file are sent as the body of the message when the message
24085 is specified by the transport. If both &%file%& and &%text%& are set, the text
24086 string comes first.
24089 .option file_expand autoreply boolean false
24090 If this is set, the contents of the file named by the &%file%& option are
24091 subjected to string expansion as they are added to the message.
24094 .option file_optional autoreply boolean false
24095 If this option is true, no error is generated if the file named by the &%file%&
24096 option or passed with the address does not exist or cannot be read.
24099 .option from autoreply string&!! unset
24100 This specifies the contents of the &'From:'& header when the message is
24101 specified by the transport.
24104 .option headers autoreply string&!! unset
24105 This specifies additional RFC 2822 headers that are to be added to the message
24106 when the message is specified by the transport. Several can be given by using
24107 &"\n"& to separate them. There is no check on the format.
24110 .option log autoreply string&!! unset
24111 This option names a file in which a record of every message sent is logged when
24112 the message is specified by the transport.
24115 .option mode autoreply "octal integer" 0600
24116 If either the log file or the &"once"& file has to be created, this mode is
24120 .option never_mail autoreply "address list&!!" unset
24121 If any run of the transport creates a message with a recipient that matches any
24122 item in the list, that recipient is quietly discarded. If all recipients are
24123 discarded, no message is created. This applies both when the recipients are
24124 generated by a filter and when they are specified in the transport.
24128 .option once autoreply string&!! unset
24129 This option names a file or DBM database in which a record of each &'To:'&
24130 recipient is kept when the message is specified by the transport. &*Note*&:
24131 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
24133 If &%once%& is unset, or is set to an empty string, the message is always sent.
24134 By default, if &%once%& is set to a non-empty filename, the message
24135 is not sent if a potential recipient is already listed in the database.
24136 However, if the &%once_repeat%& option specifies a time greater than zero, the
24137 message is sent if that much time has elapsed since a message was last sent to
24138 this recipient. A setting of zero time for &%once_repeat%& (the default)
24139 prevents a message from being sent a second time &-- in this case, zero means
24142 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
24143 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
24144 greater than zero, it changes the way Exim implements the &%once%& option.
24145 Instead of using a DBM file to record every recipient it sends to, it uses a
24146 regular file, whose size will never get larger than the given value.
24148 In the file, Exim keeps a linear list of recipient addresses and the times at
24149 which they were sent messages. If the file is full when a new address needs to
24150 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
24151 means that a given recipient may receive multiple messages, but at
24152 unpredictable intervals that depend on the rate of turnover of addresses in the
24153 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
24156 .option once_file_size autoreply integer 0
24157 See &%once%& above.
24160 .option once_repeat autoreply time&!! 0s
24161 See &%once%& above.
24162 After expansion, the value of this option must be a valid time value.
24165 .option reply_to autoreply string&!! unset
24166 This specifies the contents of the &'Reply-To:'& header when the message is
24167 specified by the transport.
24170 .option return_message autoreply boolean false
24171 If this is set, a copy of the original message is returned with the new
24172 message, subject to the maximum size set in the &%return_size_limit%& global
24173 configuration option.
24176 .option subject autoreply string&!! unset
24177 This specifies the contents of the &'Subject:'& header when the message is
24178 specified by the transport. It is tempting to quote the original subject in
24179 automatic responses. For example:
24181 subject = Re: $h_subject:
24183 There is a danger in doing this, however. It may allow a third party to
24184 subscribe your users to an opt-in mailing list, provided that the list accepts
24185 bounce messages as subscription confirmations. Well-managed lists require a
24186 non-bounce message to confirm a subscription, so the danger is relatively
24191 .option text autoreply string&!! unset
24192 This specifies a single string to be used as the body of the message when the
24193 message is specified by the transport. If both &%text%& and &%file%& are set,
24194 the text comes first.
24197 .option to autoreply string&!! unset
24198 This specifies recipients of the message and the contents of the &'To:'& header
24199 when the message is specified by the transport.
24200 .ecindex IIDauttra1
24201 .ecindex IIDauttra2
24206 . ////////////////////////////////////////////////////////////////////////////
24207 . ////////////////////////////////////////////////////////////////////////////
24209 .chapter "The lmtp transport" "CHAPLMTP"
24210 .cindex "transports" "&(lmtp)&"
24211 .cindex "&(lmtp)& transport"
24212 .cindex "LMTP" "over a pipe"
24213 .cindex "LMTP" "over a socket"
24214 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
24216 or by interacting with a Unix domain socket.
24217 This transport is something of a cross between the &(pipe)& and &(smtp)&
24218 transports. Exim also has support for using LMTP over TCP/IP; this is
24219 implemented as an option for the &(smtp)& transport. Because LMTP is expected
24220 to be of minority interest, the default build-time configure in &_src/EDITME_&
24221 has it commented out. You need to ensure that
24225 .cindex "options" "&(lmtp)& transport"
24226 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
24227 included in the Exim binary. The private options of the &(lmtp)& transport are
24230 .option batch_id lmtp string&!! unset
24231 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24234 .option batch_max lmtp integer 1
24235 This limits the number of addresses that can be handled in a single delivery.
24236 Most LMTP servers can handle several addresses at once, so it is normally a
24237 good idea to increase this value. See the description of local delivery
24238 batching in chapter &<<CHAPbatching>>&.
24241 .option command lmtp string&!! unset
24242 This option must be set if &%socket%& is not set. The string is a command which
24243 is run in a separate process. It is split up into a command name and list of
24244 arguments, each of which is separately expanded (so expansion cannot change the
24245 number of arguments). The command is run directly, not via a shell. The message
24246 is passed to the new process using the standard input and output to operate the
24249 .option ignore_quota lmtp boolean false
24250 .cindex "LMTP" "ignoring quota errors"
24251 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
24252 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
24253 in its response to the LHLO command.
24255 .option socket lmtp string&!! unset
24256 This option must be set if &%command%& is not set. The result of expansion must
24257 be the name of a Unix domain socket. The transport connects to the socket and
24258 delivers the message to it using the LMTP protocol.
24261 .option timeout lmtp time 5m
24262 The transport is aborted if the created process or Unix domain socket does not
24263 respond to LMTP commands or message input within this timeout. Delivery
24264 is deferred, and will be tried again later. Here is an example of a typical
24269 command = /some/local/lmtp/delivery/program
24273 This delivers up to 20 addresses at a time, in a mixture of domains if
24274 necessary, running as the user &'exim'&.
24278 . ////////////////////////////////////////////////////////////////////////////
24279 . ////////////////////////////////////////////////////////////////////////////
24281 .chapter "The pipe transport" "CHAPpipetransport"
24282 .scindex IIDpiptra1 "transports" "&(pipe)&"
24283 .scindex IIDpiptra2 "&(pipe)& transport"
24284 The &(pipe)& transport is used to deliver messages via a pipe to a command
24285 running in another process. One example is the use of &(pipe)& as a
24286 pseudo-remote transport for passing messages to some other delivery mechanism
24287 (such as UUCP). Another is the use by individual users to automatically process
24288 their incoming messages. The &(pipe)& transport can be used in one of the
24292 .vindex "&$local_part$&"
24293 A router routes one address to a transport in the normal way, and the
24294 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
24295 contains the local part of the address (as usual), and the command that is run
24296 is specified by the &%command%& option on the transport.
24298 .vindex "&$pipe_addresses$&"
24299 If the &%batch_max%& option is set greater than 1 (the default is 1), the
24300 transport can handle more than one address in a single run. In this case, when
24301 more than one address is routed to the transport, &$local_part$& is not set
24302 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
24303 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
24304 that are routed to the transport.
24306 .vindex "&$address_pipe$&"
24307 A router redirects an address directly to a pipe command (for example, from an
24308 alias or forward file). In this case, &$address_pipe$& contains the text of the
24309 pipe command, and the &%command%& option on the transport is ignored unless
24310 &%force_command%& is set. If only one address is being transported
24311 (&%batch_max%& is not greater than one, or only one address was redirected to
24312 this pipe command), &$local_part$& contains the local part that was redirected.
24316 The &(pipe)& transport is a non-interactive delivery method. Exim can also
24317 deliver messages over pipes using the LMTP interactive protocol. This is
24318 implemented by the &(lmtp)& transport.
24320 In the case when &(pipe)& is run as a consequence of an entry in a local user's
24321 &_.forward_& file, the command runs under the uid and gid of that user. In
24322 other cases, the uid and gid have to be specified explicitly, either on the
24323 transport or on the router that handles the address. Current and &"home"&
24324 directories are also controllable. See chapter &<<CHAPenvironment>>& for
24325 details of the local delivery environment and chapter &<<CHAPbatching>>&
24326 for a discussion of local delivery batching.
24328 .cindex "tainted data" "in pipe command"
24329 .cindex pipe "tainted data"
24330 Tainted data may not be used for the command name.
24333 .section "Concurrent delivery" "SECID140"
24334 If two messages arrive at almost the same time, and both are routed to a pipe
24335 delivery, the two pipe transports may be run concurrently. You must ensure that
24336 any pipe commands you set up are robust against this happening. If the commands
24337 write to a file, the &%exim_lock%& utility might be of use.
24338 Alternatively the &%max_parallel%& option could be used with a value
24339 of "1" to enforce serialization.
24344 .section "Returned status and data" "SECID141"
24345 .cindex "&(pipe)& transport" "returned data"
24346 If the command exits with a non-zero return code, the delivery is deemed to
24347 have failed, unless either the &%ignore_status%& option is set (in which case
24348 the return code is treated as zero), or the return code is one of those listed
24349 in the &%temp_errors%& option, which are interpreted as meaning &"try again
24350 later"&. In this case, delivery is deferred. Details of a permanent failure are
24351 logged, but are not included in the bounce message, which merely contains
24352 &"local delivery failed"&.
24354 If the command exits on a signal and the &%freeze_signal%& option is set then
24355 the message will be frozen in the queue. If that option is not set, a bounce
24356 will be sent as normal.
24358 If the return code is greater than 128 and the command being run is a shell
24359 script, it normally means that the script was terminated by a signal whose
24360 value is the return code minus 128. The &%freeze_signal%& option does not
24361 apply in this case.
24363 If Exim is unable to run the command (that is, if &[execve()]& fails), the
24364 return code is set to 127. This is the value that a shell returns if it is
24365 asked to run a non-existent command. The wording for the log line suggests that
24366 a non-existent command may be the problem.
24368 The &%return_output%& option can affect the result of a pipe delivery. If it is
24369 set and the command produces any output on its standard output or standard
24370 error streams, the command is considered to have failed, even if it gave a zero
24371 return code or if &%ignore_status%& is set. The output from the command is
24372 included as part of the bounce message. The &%return_fail_output%& option is
24373 similar, except that output is returned only when the command exits with a
24374 failure return code, that is, a value other than zero or a code that matches
24379 .section "How the command is run" "SECThowcommandrun"
24380 .cindex "&(pipe)& transport" "path for command"
24381 The command line is (by default) broken down into a command name and arguments
24382 by the &(pipe)& transport itself. The &%allow_commands%& and
24383 &%restrict_to_path%& options can be used to restrict the commands that may be
24386 .cindex "quoting" "in pipe command"
24387 Unquoted arguments are delimited by white space. If an argument appears in
24388 double quotes, backslash is interpreted as an escape character in the usual
24389 way. If an argument appears in single quotes, no escaping is done.
24391 String expansion is applied to the command line except when it comes from a
24392 traditional &_.forward_& file (commands from a filter file are expanded). The
24393 expansion is applied to each argument in turn rather than to the whole line.
24394 For this reason, any string expansion item that contains white space must be
24395 quoted so as to be contained within a single argument. A setting such as
24397 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
24399 will not work, because the expansion item gets split between several
24400 arguments. You have to write
24402 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
24404 to ensure that it is all in one argument. The expansion is done in this way,
24405 argument by argument, so that the number of arguments cannot be changed as a
24406 result of expansion, and quotes or backslashes in inserted variables do not
24407 interact with external quoting. However, this leads to problems if you want to
24408 generate multiple arguments (or the command name plus arguments) from a single
24409 expansion. In this situation, the simplest solution is to use a shell. For
24412 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
24415 .cindex "transport" "filter"
24416 .cindex "filter" "transport filter"
24417 .vindex "&$pipe_addresses$&"
24418 Special handling takes place when an argument consists of precisely the text
24419 &`$pipe_addresses`& (no quotes).
24420 This is not a general expansion variable; the only
24421 place this string is recognized is when it appears as an argument for a pipe or
24422 transport filter command. It causes each address that is being handled to be
24423 inserted in the argument list at that point &'as a separate argument'&. This
24424 avoids any problems with spaces or shell metacharacters, and is of use when a
24425 &(pipe)& transport is handling groups of addresses in a batch.
24427 If &%force_command%& is enabled on the transport, special handling takes place
24428 for an argument that consists of precisely the text &`$address_pipe`&. It
24429 is handled similarly to &$pipe_addresses$& above. It is expanded and each
24430 argument is inserted in the argument list at that point
24431 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
24432 the only item in the argument; in fact, if it were then &%force_command%&
24433 should behave as a no-op. Rather, it should be used to adjust the command
24434 run while preserving the argument vector separation.
24436 After splitting up into arguments and expansion, the resulting command is run
24437 in a subprocess directly from the transport, &'not'& under a shell. The
24438 message that is being delivered is supplied on the standard input, and the
24439 standard output and standard error are both connected to a single pipe that is
24440 read by Exim. The &%max_output%& option controls how much output the command
24441 may produce, and the &%return_output%& and &%return_fail_output%& options
24442 control what is done with it.
24444 Not running the command under a shell (by default) lessens the security risks
24445 in cases when a command from a user's filter file is built out of data that was
24446 taken from an incoming message. If a shell is required, it can of course be
24447 explicitly specified as the command to be run. However, there are circumstances
24448 where existing commands (for example, in &_.forward_& files) expect to be run
24449 under a shell and cannot easily be modified. To allow for these cases, there is
24450 an option called &%use_shell%&, which changes the way the &(pipe)& transport
24451 works. Instead of breaking up the command line as just described, it expands it
24452 as a single string and passes the result to &_/bin/sh_&. The
24453 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
24454 with &%use_shell%&, and the whole mechanism is inherently less secure.
24458 .section "Environment variables" "SECTpipeenv"
24459 .cindex "&(pipe)& transport" "environment for command"
24460 .cindex "environment" "&(pipe)& transport"
24461 The environment variables listed below are set up when the command is invoked.
24462 This list is a compromise for maximum compatibility with other MTAs. Note that
24463 the &%environment%& option can be used to add additional variables to this
24464 environment. The environment for the &(pipe)& transport is not subject
24465 to the &%add_environment%& and &%keep_environment%& main config options.
24467 &`DOMAIN `& the domain of the address
24468 &`HOME `& the home directory, if set
24469 &`HOST `& the host name when called from a router (see below)
24470 &`LOCAL_PART `& see below
24471 &`LOCAL_PART_PREFIX `& see below
24472 &`LOCAL_PART_SUFFIX `& see below
24473 &`LOGNAME `& see below
24474 &`MESSAGE_ID `& Exim's local ID for the message
24475 &`PATH `& as specified by the &%path%& option below
24476 &`QUALIFY_DOMAIN `& the sender qualification domain
24477 &`RECIPIENT `& the complete recipient address
24478 &`SENDER `& the sender of the message (empty if a bounce)
24479 &`SHELL `& &`/bin/sh`&
24480 &`TZ `& the value of the &%timezone%& option, if set
24481 &`USER `& see below
24483 When a &(pipe)& transport is called directly from (for example) an &(accept)&
24484 router, LOCAL_PART is set to the local part of the address. When it is
24485 called as a result of a forward or alias expansion, LOCAL_PART is set to
24486 the local part of the address that was expanded. In both cases, any affixes are
24487 removed from the local part, and made available in LOCAL_PART_PREFIX and
24488 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
24489 same value as LOCAL_PART for compatibility with other MTAs.
24492 HOST is set only when a &(pipe)& transport is called from a router that
24493 associates hosts with an address, typically when using &(pipe)& as a
24494 pseudo-remote transport. HOST is set to the first host name specified by
24498 If the transport's generic &%home_directory%& option is set, its value is used
24499 for the HOME environment variable. Otherwise, a home directory may be set
24500 by the router's &%transport_home_directory%& option, which defaults to the
24501 user's home directory if &%check_local_user%& is set.
24504 .section "Private options for pipe" "SECID142"
24505 .cindex "options" "&(pipe)& transport"
24509 .option allow_commands pipe "string list&!!" unset
24510 .cindex "&(pipe)& transport" "permitted commands"
24511 The string is expanded, and is then interpreted as a colon-separated list of
24512 permitted commands. If &%restrict_to_path%& is not set, the only commands
24513 permitted are those in the &%allow_commands%& list. They need not be absolute
24514 paths; the &%path%& option is still used for relative paths. If
24515 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
24516 in the &%allow_commands%& list, or a name without any slashes that is found on
24517 the path. In other words, if neither &%allow_commands%& nor
24518 &%restrict_to_path%& is set, there is no restriction on the command, but
24519 otherwise only commands that are permitted by one or the other are allowed. For
24522 allow_commands = /usr/bin/vacation
24524 and &%restrict_to_path%& is not set, the only permitted command is
24525 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
24526 &%use_shell%& is set.
24529 .option batch_id pipe string&!! unset
24530 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24533 .option batch_max pipe integer 1
24534 This limits the number of addresses that can be handled in a single delivery.
24535 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
24538 .option check_string pipe string unset
24539 As &(pipe)& writes the message, the start of each line is tested for matching
24540 &%check_string%&, and if it does, the initial matching characters are replaced
24541 by the contents of &%escape_string%&, provided both are set. The value of
24542 &%check_string%& is a literal string, not a regular expression, and the case of
24543 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
24544 of &%check_string%& and &%escape_string%& are forced to values that implement
24545 the SMTP escaping protocol. Any settings made in the configuration file are
24549 .option command pipe string&!! unset
24550 This option need not be set when &(pipe)& is being used to deliver to pipes
24551 obtained directly from address redirections. In other cases, the option must be
24552 set, to provide a command to be run. It need not yield an absolute path (see
24553 the &%path%& option below). The command is split up into separate arguments by
24554 Exim, and each argument is separately expanded, as described in section
24555 &<<SECThowcommandrun>>& above.
24558 .option environment pipe string&!! unset
24559 .cindex "&(pipe)& transport" "environment for command"
24560 .cindex "environment" "&(pipe)& transport"
24561 This option is used to add additional variables to the environment in which the
24562 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
24563 a string which is expanded, and then interpreted as a colon-separated list of
24564 environment settings of the form <&'name'&>=<&'value'&>.
24567 .option escape_string pipe string unset
24568 See &%check_string%& above.
24571 .option freeze_exec_fail pipe boolean false
24572 .cindex "exec failure"
24573 .cindex "failure of exec"
24574 .cindex "&(pipe)& transport" "failure of exec"
24575 Failure to exec the command in a pipe transport is by default treated like
24576 any other failure while running the command. However, if &%freeze_exec_fail%&
24577 is set, failure to exec is treated specially, and causes the message to be
24578 frozen, whatever the setting of &%ignore_status%&.
24581 .option freeze_signal pipe boolean false
24582 .cindex "signal exit"
24583 .cindex "&(pipe)& transport", "signal exit"
24584 Normally if the process run by a command in a pipe transport exits on a signal,
24585 a bounce message is sent. If &%freeze_signal%& is set, the message will be
24586 frozen in Exim's queue instead.
24589 .option force_command pipe boolean false
24590 .cindex "force command"
24591 .cindex "&(pipe)& transport", "force command"
24592 Normally when a router redirects an address directly to a pipe command
24593 the &%command%& option on the transport is ignored. If &%force_command%&
24594 is set, the &%command%& option will used. This is especially
24595 useful for forcing a wrapper or additional argument to be added to the
24596 command. For example:
24598 command = /usr/bin/remote_exec myhost -- $address_pipe
24602 Note that &$address_pipe$& is handled specially in &%command%& when
24603 &%force_command%& is set, expanding out to the original argument vector as
24604 separate items, similarly to a Unix shell &`"$@"`& construct.
24607 .option ignore_status pipe boolean false
24608 If this option is true, the status returned by the subprocess that is set up to
24609 run the command is ignored, and Exim behaves as if zero had been returned.
24610 Otherwise, a non-zero status or termination by signal causes an error return
24611 from the transport unless the status value is one of those listed in
24612 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
24614 &*Note*&: This option does not apply to timeouts, which do not return a status.
24615 See the &%timeout_defer%& option for how timeouts are handled.
24618 .option log_defer_output pipe boolean false
24619 .cindex "&(pipe)& transport" "logging output"
24620 If this option is set, and the status returned by the command is
24621 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
24622 and any output was produced on stdout or stderr, the first line of it is
24623 written to the main log.
24626 .option log_fail_output pipe boolean false
24627 If this option is set, and the command returns any output on stdout or
24628 stderr, and also ends with a return code that is neither zero nor one of
24629 the return codes listed in &%temp_errors%& (that is, the delivery
24630 failed), the first line of output is written to the main log. This
24631 option and &%log_output%& are mutually exclusive. Only one of them may
24635 .option log_output pipe boolean false
24636 If this option is set and the command returns any output on stdout or
24637 stderr, the first line of output is written to the main log, whatever
24638 the return code. This option and &%log_fail_output%& are mutually
24639 exclusive. Only one of them may be set.
24642 .option max_output pipe integer 20K
24643 This specifies the maximum amount of output that the command may produce on its
24644 standard output and standard error file combined. If the limit is exceeded, the
24645 process running the command is killed. This is intended as a safety measure to
24646 catch runaway processes. The limit is applied independently of the settings of
24647 the options that control what is done with such output (for example,
24648 &%return_output%&). Because of buffering effects, the amount of output may
24649 exceed the limit by a small amount before Exim notices.
24652 .option message_prefix pipe string&!! "see below"
24653 The string specified here is expanded and output at the start of every message.
24654 The default is unset if &%use_bsmtp%& is set. Otherwise it is
24657 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
24661 .cindex "&%tmail%&"
24662 .cindex "&""From""& line"
24663 This is required by the commonly used &_/usr/bin/vacation_& program.
24664 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
24665 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
24670 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24671 &`\n`& to &`\r\n`& in &%message_prefix%&.
24674 .option message_suffix pipe string&!! "see below"
24675 The string specified here is expanded and output at the end of every message.
24676 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
24677 The suffix can be suppressed by setting
24681 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
24682 &`\n`& to &`\r\n`& in &%message_suffix%&.
24685 .option path pipe string&!! "/bin:/usr/bin"
24686 This option is expanded and
24687 specifies the string that is set up in the PATH environment
24688 variable of the subprocess.
24689 If the &%command%& option does not yield an absolute path name, the command is
24690 sought in the PATH directories, in the usual way. &*Warning*&: This does not
24691 apply to a command specified as a transport filter.
24694 .option permit_coredump pipe boolean false
24695 Normally Exim inhibits core-dumps during delivery. If you have a need to get
24696 a core-dump of a pipe command, enable this command. This enables core-dumps
24697 during delivery and affects both the Exim binary and the pipe command run.
24698 It is recommended that this option remain off unless and until you have a need
24699 for it and that this only be enabled when needed, as the risk of excessive
24700 resource consumption can be quite high. Note also that Exim is typically
24701 installed as a setuid binary and most operating systems will inhibit coredumps
24702 of these by default, so further OS-specific action may be required.
24705 .option pipe_as_creator pipe boolean false
24706 .cindex "uid (user id)" "local delivery"
24707 If the generic &%user%& option is not set and this option is true, the delivery
24708 process is run under the uid that was in force when Exim was originally called
24709 to accept the message. If the group id is not otherwise set (via the generic
24710 &%group%& option), the gid that was in force when Exim was originally called to
24711 accept the message is used.
24714 .option restrict_to_path pipe boolean false
24715 When this option is set, any command name not listed in &%allow_commands%& must
24716 contain no slashes. The command is searched for only in the directories listed
24717 in the &%path%& option. This option is intended for use in the case when a pipe
24718 command has been generated from a user's &_.forward_& file. This is usually
24719 handled by a &(pipe)& transport called &%address_pipe%&.
24722 .option return_fail_output pipe boolean false
24723 If this option is true, and the command produced any output and ended with a
24724 return code other than zero or one of the codes listed in &%temp_errors%& (that
24725 is, the delivery failed), the output is returned in the bounce message.
24726 However, if the message has a null sender (that is, it is itself a bounce
24727 message), output from the command is discarded. This option and
24728 &%return_output%& are mutually exclusive. Only one of them may be set.
24732 .option return_output pipe boolean false
24733 If this option is true, and the command produced any output, the delivery is
24734 deemed to have failed whatever the return code from the command, and the output
24735 is returned in the bounce message. Otherwise, the output is just discarded.
24736 However, if the message has a null sender (that is, it is a bounce message),
24737 output from the command is always discarded, whatever the setting of this
24738 option. This option and &%return_fail_output%& are mutually exclusive. Only one
24739 of them may be set.
24743 .option temp_errors pipe "string list" "see below"
24744 .cindex "&(pipe)& transport" "temporary failure"
24745 This option contains either a colon-separated list of numbers, or a single
24746 asterisk. If &%ignore_status%& is false
24747 and &%return_output%& is not set,
24748 and the command exits with a non-zero return code, the failure is treated as
24749 temporary and the delivery is deferred if the return code matches one of the
24750 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
24751 codes are treated as permanent errors. The default setting contains the codes
24752 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
24753 compiled on a system that does not define these macros, it assumes values of 75
24754 and 73, respectively.
24757 .option timeout pipe time 1h
24758 If the command fails to complete within this time, it is killed. This normally
24759 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
24760 specifies no timeout. In order to ensure that any subprocesses created by the
24761 command are also killed, Exim makes the initial process a process group leader,
24762 and kills the whole process group on a timeout. However, this can be defeated
24763 if one of the processes starts a new process group.
24765 .option timeout_defer pipe boolean false
24766 A timeout in a &(pipe)& transport, either in the command that the transport
24767 runs, or in a transport filter that is associated with it, is by default
24768 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
24769 is set true, both kinds of timeout become temporary errors, causing the
24770 delivery to be deferred.
24772 .option umask pipe "octal integer" 022
24773 This specifies the umask setting for the subprocess that runs the command.
24776 .option use_bsmtp pipe boolean false
24777 .cindex "envelope sender"
24778 If this option is set true, the &(pipe)& transport writes messages in &"batch
24779 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
24780 commands. If you want to include a leading HELO command with such messages,
24781 you can do so by setting the &%message_prefix%& option. See section
24782 &<<SECTbatchSMTP>>& for details of batch SMTP.
24784 .option use_classresources pipe boolean false
24785 .cindex "class resources (BSD)"
24786 This option is available only when Exim is running on FreeBSD, NetBSD, or
24787 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
24788 resource limits when a &(pipe)& transport is run to perform a delivery. The
24789 limits for the uid under which the pipe is to run are obtained from the login
24793 .option use_crlf pipe boolean false
24794 .cindex "carriage return"
24796 This option causes lines to be terminated with the two-character CRLF sequence
24797 (carriage return, linefeed) instead of just a linefeed character. In the case
24798 of batched SMTP, the byte sequence written to the pipe is then an exact image
24799 of what would be sent down a real SMTP connection.
24801 The contents of the &%message_prefix%& and &%message_suffix%& options are
24802 written verbatim, so must contain their own carriage return characters if these
24803 are needed. When &%use_bsmtp%& is not set, the default values for both
24804 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
24805 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
24808 .option use_shell pipe boolean false
24809 .vindex "&$pipe_addresses$&"
24810 If this option is set, it causes the command to be passed to &_/bin/sh_&
24811 instead of being run directly from the transport, as described in section
24812 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
24813 where the command is expected to be run under a shell and cannot easily be
24814 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
24815 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
24816 command is expanded as a single string, and handed to &_/bin/sh_& as data for
24821 .section "Using an external local delivery agent" "SECID143"
24822 .cindex "local delivery" "using an external agent"
24823 .cindex "&'procmail'&"
24824 .cindex "external local delivery"
24825 .cindex "delivery" "&'procmail'&"
24826 .cindex "delivery" "by external agent"
24827 The &(pipe)& transport can be used to pass all messages that require local
24828 delivery to a separate local delivery agent such as &%procmail%&. When doing
24829 this, care must be taken to ensure that the pipe is run under an appropriate
24830 uid and gid. In some configurations one wants this to be a uid that is trusted
24831 by the delivery agent to supply the correct sender of the message. It may be
24832 necessary to recompile or reconfigure the delivery agent so that it trusts an
24833 appropriate user. The following is an example transport and router
24834 configuration for &%procmail%&:
24839 command = /usr/local/bin/procmail -d $local_part_data
24843 check_string = "From "
24844 escape_string = ">From "
24846 user = $local_part_data
24853 transport = procmail_pipe
24855 In this example, the pipe is run as the local user, but with the group set to
24856 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
24857 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
24858 user to supply a correct sender address. If you do not specify either a
24859 &%group%& or a &%user%& option, the pipe command is run as the local user. The
24860 home directory is the user's home directory by default.
24862 &*Note*&: The command that the pipe transport runs does &'not'& begin with
24866 as shown in some &%procmail%& documentation, because Exim does not by default
24867 use a shell to run pipe commands.
24870 The next example shows a transport and a router for a system where local
24871 deliveries are handled by the Cyrus IMAP server.
24874 local_delivery_cyrus:
24876 command = /usr/cyrus/bin/deliver \
24877 -m ${substr_1:$local_part_suffix} -- $local_part
24889 local_part_suffix = .*
24890 transport = local_delivery_cyrus
24892 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
24893 &%return_output%& to cause any text written by Cyrus to be returned to the
24895 .ecindex IIDpiptra1
24896 .ecindex IIDpiptra2
24899 . ////////////////////////////////////////////////////////////////////////////
24900 . ////////////////////////////////////////////////////////////////////////////
24902 .chapter "The smtp transport" "CHAPsmtptrans"
24903 .scindex IIDsmttra1 "transports" "&(smtp)&"
24904 .scindex IIDsmttra2 "&(smtp)& transport"
24905 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
24906 or LMTP protocol. The list of hosts to try can either be taken from the address
24907 that is being processed (having been set up by the router), or specified
24908 explicitly for the transport. Timeout and retry processing (see chapter
24909 &<<CHAPretry>>&) is applied to each IP address independently.
24912 .section "Multiple messages on a single connection" "SECID144"
24913 The sending of multiple messages over a single TCP/IP connection can arise in
24917 If a message contains more than &%max_rcpt%& (see below) addresses that are
24918 routed to the same host, more than one copy of the message has to be sent to
24919 that host. In this situation, multiple copies may be sent in a single run of
24920 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
24921 does when it has too many addresses to send in one message also depends on the
24922 value of the global &%remote_max_parallel%& option. Details are given in
24923 section &<<SECToutSMTPTCP>>&.)
24925 .cindex "hints database" "remembering routing"
24926 When a message has been successfully delivered over a TCP/IP connection, Exim
24927 looks in its hints database to see if there are any other messages awaiting a
24928 connection to the same host. If there are, a new delivery process is started
24929 for one of them, and the current TCP/IP connection is passed on to it. The new
24930 process may in turn send multiple copies and possibly create yet another
24935 For each copy sent over the same TCP/IP connection, a sequence counter is
24936 incremented, and if it ever gets to the value of &%connection_max_messages%&,
24937 no further messages are sent over that connection.
24941 .section "Use of the $host and $host_address variables" "SECID145"
24943 .vindex "&$host_address$&"
24944 At the start of a run of the &(smtp)& transport, the values of &$host$& and
24945 &$host_address$& are the name and IP address of the first host on the host list
24946 passed by the router. However, when the transport is about to connect to a
24947 specific host, and while it is connected to that host, &$host$& and
24948 &$host_address$& are set to the values for that host. These are the values
24949 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
24950 &%serialize_hosts%&, and the various TLS options are expanded.
24953 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
24954 .vindex &$tls_bits$&
24955 .vindex &$tls_cipher$&
24956 .vindex &$tls_peerdn$&
24957 .vindex &$tls_sni$&
24958 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
24959 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
24960 are the values that were set when the message was received.
24961 These are the values that are used for options that are expanded before any
24962 SMTP connections are made. Just before each connection is made, these four
24963 variables are emptied. If TLS is subsequently started, they are set to the
24964 appropriate values for the outgoing connection, and these are the values that
24965 are in force when any authenticators are run and when the
24966 &%authenticated_sender%& option is expanded.
24968 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
24969 and will be removed in a future release.
24972 .section "Private options for smtp" "SECID146"
24973 .cindex "options" "&(smtp)& transport"
24974 The private options of the &(smtp)& transport are as follows:
24977 .option address_retry_include_sender smtp boolean true
24978 .cindex "4&'xx'& responses" "retrying after"
24979 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
24980 is the combination of sender and recipient that is delayed in subsequent queue
24981 runs until the retry time is reached. You can delay the recipient without
24982 reference to the sender (which is what earlier versions of Exim did), by
24983 setting &%address_retry_include_sender%& false. However, this can lead to
24984 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
24986 .option allow_localhost smtp boolean false
24987 .cindex "local host" "sending to"
24988 .cindex "fallback" "hosts specified on transport"
24989 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
24990 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
24991 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
24992 the delivery anyway. This should be used only in special cases when the
24993 configuration ensures that no looping will result (for example, a differently
24994 configured Exim is listening on the port to which the message is sent).
24997 .option authenticated_sender smtp string&!! unset
24999 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
25000 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
25001 overriding any existing authenticated sender value. If the string expansion is
25002 forced to fail, the option is ignored. Other expansion failures cause delivery
25003 to be deferred. If the result of expansion is an empty string, that is also
25006 The expansion happens after the outgoing connection has been made and TLS
25007 started, if required. This means that the &$host$&, &$host_address$&,
25008 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
25009 particular connection.
25011 If the SMTP session is not authenticated, the expansion of
25012 &%authenticated_sender%& still happens (and can cause the delivery to be
25013 deferred if it fails), but no AUTH= item is added to MAIL commands
25014 unless &%authenticated_sender_force%& is true.
25016 This option allows you to use the &(smtp)& transport in LMTP mode to
25017 deliver mail to Cyrus IMAP and provide the proper local part as the
25018 &"authenticated sender"&, via a setting such as:
25020 authenticated_sender = $local_part
25022 This removes the need for IMAP subfolders to be assigned special ACLs to
25023 allow direct delivery to those subfolders.
25025 Because of expected uses such as that just described for Cyrus (when no
25026 domain is involved), there is no checking on the syntax of the provided
25030 .option authenticated_sender_force smtp boolean false
25031 If this option is set true, the &%authenticated_sender%& option's value
25032 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
25033 authenticated as a client.
25036 .option command_timeout smtp time 5m
25037 This sets a timeout for receiving a response to an SMTP command that has been
25038 sent out. It is also used when waiting for the initial banner line from the
25039 remote host. Its value must not be zero.
25042 .option connect_timeout smtp time 5m
25043 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
25044 to a remote host. A setting of zero allows the system timeout (typically
25045 several minutes) to act. To have any effect, the value of this option must be
25046 less than the system timeout. However, it has been observed that on some
25047 systems there is no system timeout, which is why the default value for this
25048 option is 5 minutes, a value recommended by RFC 1123.
25051 .option connection_max_messages smtp integer 500
25052 .cindex "SMTP" "passed connection"
25053 .cindex "SMTP" "multiple deliveries"
25054 .cindex "multiple SMTP deliveries"
25055 This controls the maximum number of separate message deliveries that are sent
25056 over a single TCP/IP connection. If the value is zero, there is no limit.
25057 For testing purposes, this value can be overridden by the &%-oB%& command line
25061 .option dane_require_tls_ciphers smtp string&!! unset
25062 .cindex "TLS" "requiring specific ciphers for DANE"
25063 .cindex "cipher" "requiring specific"
25064 .cindex DANE "TLS ciphers"
25065 This option may be used to override &%tls_require_ciphers%& for connections
25066 where DANE has been determined to be in effect.
25067 If not set, then &%tls_require_ciphers%& will be used.
25068 Normal SMTP delivery is not able to make strong demands of TLS cipher
25069 configuration, because delivery will fall back to plaintext. Once DANE has
25070 been determined to be in effect, there is no plaintext fallback and making the
25071 TLS cipherlist configuration stronger will increase security, rather than
25072 counter-intuitively decreasing it.
25073 If the option expands to be empty or is forced to fail, then it will
25074 be treated as unset and &%tls_require_ciphers%& will be used instead.
25077 .option data_timeout smtp time 5m
25078 This sets a timeout for the transmission of each block in the data portion of
25079 the message. As a result, the overall timeout for a message depends on the size
25080 of the message. Its value must not be zero. See also &%final_timeout%&.
25083 .option dkim_canon smtp string&!! unset
25084 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25085 .option dkim_domain smtp string list&!! unset
25086 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25087 .option dkim_hash smtp string&!! sha256
25088 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25089 .option dkim_identity smtp string&!! unset
25090 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25091 .option dkim_private_key smtp string&!! unset
25092 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25093 .option dkim_selector smtp string&!! unset
25094 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25095 .option dkim_strict smtp string&!! unset
25096 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25097 .option dkim_sign_headers smtp string&!! "per RFC"
25098 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25099 .option dkim_timestamps smtp string&!! unset
25100 DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
25103 .option delay_after_cutoff smtp boolean true
25104 .cindex "final cutoff" "retries, controlling"
25105 .cindex retry "final cutoff"
25106 This option controls what happens when all remote IP addresses for a given
25107 domain have been inaccessible for so long that they have passed their retry
25110 In the default state, if the next retry time has not been reached for any of
25111 them, the address is bounced without trying any deliveries. In other words,
25112 Exim delays retrying an IP address after the final cutoff time until a new
25113 retry time is reached, and can therefore bounce an address without ever trying
25114 a delivery, when machines have been down for a long time. Some people are
25115 unhappy at this prospect, so...
25117 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25118 addresses are past their final cutoff time, Exim tries to deliver to those
25119 IP addresses that have not been tried since the message arrived. If there are
25120 none, of if they all fail, the address is bounced. In other words, it does not
25121 delay when a new message arrives, but immediately tries those expired IP
25122 addresses that haven't been tried since the message arrived. If there is a
25123 continuous stream of messages for the dead hosts, unsetting
25124 &%delay_after_cutoff%& means that there will be many more attempts to deliver
25128 .option dns_qualify_single smtp boolean true
25129 If the &%hosts%& or &%fallback_hosts%& option is being used,
25130 and the &%gethostbyname%& option is false,
25131 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
25132 in chapter &<<CHAPdnslookup>>& for more details.
25135 .option dns_search_parents smtp boolean false
25136 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
25137 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
25138 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
25142 .option dnssec_request_domains smtp "domain list&!!" *
25143 .cindex "MX record" "security"
25144 .cindex "DNSSEC" "MX lookup"
25145 .cindex "security" "MX lookup"
25146 .cindex "DNS" "DNSSEC"
25147 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
25148 the dnssec request bit set. Setting this transport option is only useful if the
25149 transport overrides or sets the host names. See the &%dnssec_request_domains%&
25154 .option dnssec_require_domains smtp "domain list&!!" unset
25155 .cindex "MX record" "security"
25156 .cindex "DNSSEC" "MX lookup"
25157 .cindex "security" "MX lookup"
25158 .cindex "DNS" "DNSSEC"
25159 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
25160 the dnssec request bit set. Setting this transport option is only
25161 useful if the transport overrides or sets the host names. See the
25162 &%dnssec_require_domains%& router option.
25166 .option dscp smtp string&!! unset
25167 .cindex "DCSP" "outbound"
25168 This option causes the DSCP value associated with a socket to be set to one
25169 of a number of fixed strings or to numeric value.
25170 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
25171 Common values include &`throughput`&, &`mincost`&, and on newer systems
25172 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
25174 The outbound packets from Exim will be marked with this value in the header
25175 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
25176 that these values will have any effect, not be stripped by networking
25177 equipment, or do much of anything without cooperation with your Network
25178 Engineer and those of all network operators between the source and destination.
25181 .option fallback_hosts smtp "string list" unset
25182 .cindex "fallback" "hosts specified on transport"
25183 String expansion is not applied to this option. The argument must be a
25184 colon-separated list of host names or IP addresses, optionally also including
25185 port numbers, though the separator can be changed, as described in section
25186 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25187 item in a &%route_list%& setting for the &(manualroute)& router, as described
25188 in section &<<SECTformatonehostitem>>&.
25190 Fallback hosts can also be specified on routers, which associate them with the
25191 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
25192 &%fallback_hosts%& specified on the transport is used only if the address does
25193 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
25194 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
25195 However, &%hosts_randomize%& does apply to fallback host lists.
25197 If Exim is unable to deliver to any of the hosts for a particular address, and
25198 the errors are not permanent rejections, the address is put on a separate
25199 transport queue with its host list replaced by the fallback hosts, unless the
25200 address was routed via MX records and the current host was in the original MX
25201 list. In that situation, the fallback host list is not used.
25203 Once normal deliveries are complete, the fallback queue is delivered by
25204 re-running the same transports with the new host lists. If several failing
25205 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
25206 copy of the message is sent.
25208 The resolution of the host names on the fallback list is controlled by the
25209 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
25210 both to cases when the host list comes with the address and when it is taken
25211 from &%hosts%&. This option provides a &"use a smart host only if delivery
25215 .option final_timeout smtp time 10m
25216 This is the timeout that applies while waiting for the response to the final
25217 line containing just &"."& that terminates a message. Its value must not be
25220 .option gethostbyname smtp boolean false
25221 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
25222 being used, names are looked up using &[gethostbyname()]&
25223 (or &[getipnodebyname()]& when available)
25224 instead of using the DNS. Of course, that function may in fact use the DNS, but
25225 it may also consult other sources of information such as &_/etc/hosts_&.
25227 .option gnutls_compat_mode smtp boolean unset
25228 This option controls whether GnuTLS is used in compatibility mode in an Exim
25229 server. This reduces security slightly, but improves interworking with older
25230 implementations of TLS.
25232 .option helo_data smtp string&!! "see below"
25233 .cindex "HELO" "argument, setting"
25234 .cindex "EHLO" "argument, setting"
25235 .cindex "LHLO argument setting"
25236 The value of this option is expanded after a connection to a another host has
25237 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
25238 command that starts the outgoing SMTP or LMTP session. The default value of the
25243 During the expansion, the variables &$host$& and &$host_address$& are set to
25244 the identity of the remote host, and the variables &$sending_ip_address$& and
25245 &$sending_port$& are set to the local IP address and port number that are being
25246 used. These variables can be used to generate different values for different
25247 servers or different local IP addresses. For example, if you want the string
25248 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
25249 interface address, you could use this:
25251 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
25252 {$primary_hostname}}
25254 The use of &%helo_data%& applies both to sending messages and when doing
25257 .option hosts smtp "string list&!!" unset
25258 Hosts are associated with an address by a router such as &(dnslookup)&, which
25259 finds the hosts by looking up the address domain in the DNS, or by
25260 &(manualroute)&, which has lists of hosts in its configuration. However,
25261 email addresses can be passed to the &(smtp)& transport by any router, and not
25262 all of them can provide an associated list of hosts.
25264 The &%hosts%& option specifies a list of hosts to be used if the address being
25265 processed does not have any hosts associated with it. The hosts specified by
25266 &%hosts%& are also used, whether or not the address has its own hosts, if
25267 &%hosts_override%& is set.
25269 The string is first expanded, before being interpreted as a colon-separated
25270 list of host names or IP addresses, possibly including port numbers. The
25271 separator may be changed to something other than colon, as described in section
25272 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
25273 item in a &%route_list%& setting for the &(manualroute)& router, as described
25274 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
25275 of the &(manualroute)& router is not available here.
25277 If the expansion fails, delivery is deferred. Unless the failure was caused by
25278 the inability to complete a lookup, the error is logged to the panic log as
25279 well as the main log. Host names are looked up either by searching directly for
25280 address records in the DNS or by calling &[gethostbyname()]& (or
25281 &[getipnodebyname()]& when available), depending on the setting of the
25282 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
25283 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
25286 During delivery, the hosts are tried in order, subject to their retry status,
25287 unless &%hosts_randomize%& is set.
25290 .option hosts_avoid_esmtp smtp "host list&!!" unset
25291 .cindex "ESMTP, avoiding use of"
25292 .cindex "HELO" "forcing use of"
25293 .cindex "EHLO" "avoiding use of"
25294 .cindex "PIPELINING" "avoiding the use of"
25295 This option is for use with broken hosts that announce ESMTP facilities (for
25296 example, PIPELINING) and then fail to implement them properly. When a host
25297 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
25298 start of the SMTP session. This means that it cannot use any of the ESMTP
25299 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
25302 .option hosts_avoid_pipelining smtp "host list&!!" unset
25303 .cindex "PIPELINING" "avoiding the use of"
25304 .cindex "ESMTP extensions" PIPELINING
25305 Exim will not use the ESMTP PIPELINING extension when delivering to any host
25306 that matches this list, even if the server host advertises PIPELINING support.
25308 .option hosts_pipe_connect smtp "host list&!!" unset
25309 .cindex "pipelining" "early connection"
25310 .cindex "pipelining" PIPE_CONNECT
25311 If Exim is built with the SUPPORT_PIPE_CONNECT build option
25312 this option controls which to hosts the facility watched for
25313 and recorded, and used for subsequent connections.
25315 The retry hints database is used for the record,
25316 and records are subject to the &%retry_data_expire%& option.
25317 When used, the pipelining saves on roundtrip times.
25318 It also turns SMTP into a client-first protocol
25319 so combines well with TCP Fast Open.
25321 See also the &%pipelining_connect_advertise_hosts%& main option.
25324 When the facility is used, the transport &%helo_data%& option
25325 will be expanded before the &$sending_ip_address$& variable
25327 A check is made for the use of that variable, without the
25328 presence of a &"def:"& test on it, but suitably complex coding
25329 can avoid the check and produce unexpected results.
25330 You have been warned.
25333 .option hosts_avoid_tls smtp "host list&!!" unset
25334 .cindex "TLS" "avoiding for certain hosts"
25335 Exim will not try to start a TLS session when delivering to any host that
25336 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25338 .option hosts_verify_avoid_tls smtp "host list&!!" unset
25339 .cindex "TLS" "avoiding for certain hosts"
25340 Exim will not try to start a TLS session for a verify callout,
25341 or when delivering in cutthrough mode,
25342 to any host that matches this list.
25345 .option hosts_max_try smtp integer 5
25346 .cindex "host" "maximum number to try"
25347 .cindex "limit" "number of hosts tried"
25348 .cindex "limit" "number of MX tried"
25349 .cindex "MX record" "maximum tried"
25350 This option limits the number of IP addresses that are tried for any one
25351 delivery in cases where there are temporary delivery errors. Section
25352 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
25355 .option hosts_max_try_hardlimit smtp integer 50
25356 This is an additional check on the maximum number of IP addresses that Exim
25357 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
25362 .option hosts_nopass_tls smtp "host list&!!" unset
25363 .cindex "TLS" "passing connection"
25364 .cindex "multiple SMTP deliveries"
25365 .cindex "TLS" "multiple message deliveries"
25366 For any host that matches this list, a connection on which a TLS session has
25367 been started will not be passed to a new delivery process for sending another
25368 message on the same connection. See section &<<SECTmulmessam>>& for an
25369 explanation of when this might be needed.
25371 .option hosts_noproxy_tls smtp "host list&!!" unset
25372 .cindex "TLS" "passing connection"
25373 .cindex "multiple SMTP deliveries"
25374 .cindex "TLS" "multiple message deliveries"
25375 For any host that matches this list, a TLS session which has
25376 been started will not be passed to a new delivery process for sending another
25377 message on the same session.
25379 The traditional implementation closes down TLS and re-starts it in the new
25380 process, on the same open TCP connection, for each successive message
25381 sent. If permitted by this option a pipe to to the new process is set up
25382 instead, and the original process maintains the TLS connection and proxies
25383 the SMTP connection from and to the new process and any subsequents.
25384 The new process has no access to TLS information, so cannot include it in
25389 .option hosts_override smtp boolean false
25390 If this option is set and the &%hosts%& option is also set, any hosts that are
25391 attached to the address are ignored, and instead the hosts specified by the
25392 &%hosts%& option are always used. This option does not apply to
25393 &%fallback_hosts%&.
25396 .option hosts_randomize smtp boolean false
25397 .cindex "randomized host list"
25398 .cindex "host" "list of; randomized"
25399 .cindex "fallback" "randomized hosts"
25400 If this option is set, and either the list of hosts is taken from the
25401 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
25402 were not obtained from MX records (this includes fallback hosts from the
25403 router), and were not randomized by the router, the order of trying the hosts
25404 is randomized each time the transport runs. Randomizing the order of a host
25405 list can be used to do crude load sharing.
25407 When &%hosts_randomize%& is true, a host list may be split into groups whose
25408 order is separately randomized. This makes it possible to set up MX-like
25409 behaviour. The boundaries between groups are indicated by an item that is just
25410 &`+`& in the host list. For example:
25412 hosts = host1:host2:host3:+:host4:host5
25414 The order of the first three hosts and the order of the last two hosts is
25415 randomized for each use, but the first three always end up before the last two.
25416 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
25418 .option hosts_require_auth smtp "host list&!!" unset
25419 .cindex "authentication" "required by client"
25420 This option provides a list of servers for which authentication must succeed
25421 before Exim will try to transfer a message. If authentication fails for
25422 servers which are not in this list, Exim tries to send unauthenticated. If
25423 authentication fails for one of these servers, delivery is deferred. This
25424 temporary error is detectable in the retry rules, so it can be turned into a
25425 hard failure if required. See also &%hosts_try_auth%&, and chapter
25426 &<<CHAPSMTPAUTH>>& for details of authentication.
25429 .option hosts_request_ocsp smtp "host list&!!" *
25430 .cindex "TLS" "requiring for certain servers"
25431 Exim will request a Certificate Status on a
25432 TLS session for any host that matches this list.
25433 &%tls_verify_certificates%& should also be set for the transport.
25435 .option hosts_require_dane smtp "host list&!!" unset
25436 .cindex DANE "transport options"
25437 .cindex DANE "requiring for certain servers"
25438 If built with DANE support, Exim will require that a DNSSEC-validated
25439 TLSA record is present for any host matching the list,
25440 and that a DANE-verified TLS connection is made. See
25441 the &%dnssec_request_domains%& router and transport options.
25442 There will be no fallback to in-clear communication.
25443 See section &<<SECDANE>>&.
25445 .option hosts_require_ocsp smtp "host list&!!" unset
25446 .cindex "TLS" "requiring for certain servers"
25447 Exim will request, and check for a valid Certificate Status being given, on a
25448 TLS session for any host that matches this list.
25449 &%tls_verify_certificates%& should also be set for the transport.
25451 .option hosts_require_tls smtp "host list&!!" unset
25452 .cindex "TLS" "requiring for certain servers"
25453 Exim will insist on using a TLS session when delivering to any host that
25454 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
25455 &*Note*&: This option affects outgoing mail only. To insist on TLS for
25456 incoming messages, use an appropriate ACL.
25458 .option hosts_try_auth smtp "host list&!!" unset
25459 .cindex "authentication" "optional in client"
25460 This option provides a list of servers to which, provided they announce
25461 authentication support, Exim will attempt to authenticate as a client when it
25462 connects. If authentication fails, Exim will try to transfer the message
25463 unauthenticated. See also &%hosts_require_auth%&, and chapter
25464 &<<CHAPSMTPAUTH>>& for details of authentication.
25466 .option hosts_try_chunking smtp "host list&!!" *
25467 .cindex CHUNKING "enabling, in client"
25468 .cindex BDAT "SMTP command"
25469 .cindex "RFC 3030" "CHUNKING"
25470 This option provides a list of servers to which, provided they announce
25471 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
25472 Unless DKIM signing is being done,
25473 BDAT will not be used in conjunction with a transport filter.
25475 .option hosts_try_dane smtp "host list&!!" *
25476 .cindex DANE "transport options"
25477 .cindex DANE "attempting for certain servers"
25478 If built with DANE support, Exim will require that a DNSSEC-validated
25479 TLSA record is present for any host matching the list,
25480 and that a DANE-verified TLS connection is made. See
25481 the &%dnssec_request_domains%& router and transport options.
25482 There will be no fallback to in-clear communication.
25483 See section &<<SECDANE>>&.
25485 .option hosts_try_fastopen smtp "host list&!!" *
25486 .cindex "fast open, TCP" "enabling, in client"
25487 .cindex "TCP Fast Open" "enabling, in client"
25488 .cindex "RFC 7413" "TCP Fast Open"
25489 This option provides a list of servers to which, provided
25490 the facility is supported by this system, Exim will attempt to
25491 perform a TCP Fast Open.
25492 No data is sent on the SYN segment but, if the remote server also
25493 supports the facility, it can send its SMTP banner immediately after
25494 the SYN,ACK segment. This can save up to one round-trip time.
25496 The facility is only active for previously-contacted servers,
25497 as the initiator must present a cookie in the SYN segment.
25499 On (at least some) current Linux distributions the facility must be enabled
25500 in the kernel by the sysadmin before the support is usable.
25501 There is no option for control of the server side; if the system supports
25502 it it is always enabled. Note that lengthy operations in the connect ACL,
25503 such as DNSBL lookups, will still delay the emission of the SMTP banner.
25505 .option hosts_try_prdr smtp "host list&!!" *
25506 .cindex "PRDR" "enabling, optional in client"
25507 .cindex "ESMTP extensions" PRDR
25508 This option provides a list of servers to which, provided they announce
25509 PRDR support, Exim will attempt to negotiate PRDR
25510 for multi-recipient messages.
25511 The option can usually be left as default.
25513 .option interface smtp "string list&!!" unset
25514 .cindex "bind IP address"
25515 .cindex "IP address" "binding"
25517 .vindex "&$host_address$&"
25518 This option specifies which interface to bind to when making an outgoing SMTP
25519 call. The value is an IP address, not an interface name such as
25520 &`eth0`&. Do not confuse this with the interface address that was used when a
25521 message was received, which is in &$received_ip_address$&, formerly known as
25522 &$interface_address$&. The name was changed to minimize confusion with the
25523 outgoing interface address. There is no variable that contains an outgoing
25524 interface address because, unless it is set by this option, its value is
25527 During the expansion of the &%interface%& option the variables &$host$& and
25528 &$host_address$& refer to the host to which a connection is about to be made
25529 during the expansion of the string. Forced expansion failure, or an empty
25530 string result causes the option to be ignored. Otherwise, after expansion, the
25531 string must be a list of IP addresses, colon-separated by default, but the
25532 separator can be changed in the usual way (&<<SECTlistsepchange>>&).
25535 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
25537 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
25538 connection. If none of them are the correct type, the option is ignored. If
25539 &%interface%& is not set, or is ignored, the system's IP functions choose which
25540 interface to use if the host has more than one.
25543 .option keepalive smtp boolean true
25544 .cindex "keepalive" "on outgoing connection"
25545 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
25546 connections. When set, it causes the kernel to probe idle connections
25547 periodically, by sending packets with &"old"& sequence numbers. The other end
25548 of the connection should send a acknowledgment if the connection is still okay
25549 or a reset if the connection has been aborted. The reason for doing this is
25550 that it has the beneficial effect of freeing up certain types of connection
25551 that can get stuck when the remote host is disconnected without tidying up the
25552 TCP/IP call properly. The keepalive mechanism takes several hours to detect
25556 .option lmtp_ignore_quota smtp boolean false
25557 .cindex "LMTP" "ignoring quota errors"
25558 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
25559 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
25560 has advertised support for IGNOREQUOTA in its response to the LHLO command.
25562 .option max_rcpt smtp integer 100
25563 .cindex "RCPT" "maximum number of outgoing"
25564 This option limits the number of RCPT commands that are sent in a single
25565 SMTP message transaction. Each set of addresses is treated independently, and
25566 so can cause parallel connections to the same host if &%remote_max_parallel%&
25571 .option message_linelength_limit smtp integer 998
25572 .cindex "line length" limit
25573 This option sets the maximum line length, in bytes, that the transport
25574 will send. Any messages with lines exceeding the given value
25575 will fail and a failure-DSN ("bounce") message will if possible be returned
25577 The default value is that defined by the SMTP standards.
25579 It is generally wise to also check in the data ACL so that messages
25580 received via SMTP can be refused without producing a bounce.
25584 .option multi_domain smtp boolean&!! true
25585 .vindex "&$domain$&"
25586 When this option is set, the &(smtp)& transport can handle a number of
25587 addresses containing a mixture of different domains provided they all resolve
25588 to the same list of hosts. Turning the option off restricts the transport to
25589 handling only one domain at a time. This is useful if you want to use
25590 &$domain$& in an expansion for the transport, because it is set only when there
25591 is a single domain involved in a remote delivery.
25593 It is expanded per-address and can depend on any of
25594 &$address_data$&, &$domain_data$&, &$local_part_data$&,
25595 &$host$&, &$host_address$& and &$host_port$&.
25597 .option port smtp string&!! "see below"
25598 .cindex "port" "sending TCP/IP"
25599 .cindex "TCP/IP" "setting outgoing port"
25600 This option specifies the TCP/IP port on the server to which Exim connects.
25601 &*Note:*& Do not confuse this with the port that was used when a message was
25602 received, which is in &$received_port$&, formerly known as &$interface_port$&.
25603 The name was changed to minimize confusion with the outgoing port. There is no
25604 variable that contains an outgoing port.
25606 If the value of this option begins with a digit it is taken as a port number;
25607 otherwise it is looked up using &[getservbyname()]&. The default value is
25609 but if &%protocol%& is set to &"lmtp"& the default is &"lmtp"&
25610 and if &%protocol%& is set to &"smtps"& the default is &"smtps"&.
25611 If the expansion fails, or if a port number cannot be found, delivery
25614 Note that at least one Linux distribution has been seen failing
25615 to put &"smtps"& in its &"/etc/services"& file, resulting is such deferrals.
25619 .option protocol smtp string smtp
25620 .cindex "LMTP" "over TCP/IP"
25621 .cindex "ssmtp protocol" "outbound"
25622 .cindex "TLS" "SSL-on-connect outbound"
25624 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
25625 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
25626 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
25627 deliveries into closed message stores. Exim also has support for running LMTP
25628 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
25630 If this option is set to &"smtps"&, the default value for the &%port%& option
25631 changes to &"smtps"&, and the transport initiates TLS immediately after
25632 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
25633 The Internet standards bodies used to strongly discourage use of this mode,
25634 but as of RFC 8314 it is perferred over STARTTLS for message submission
25635 (as distinct from MTA-MTA communication).
25638 .option retry_include_ip_address smtp boolean&!! true
25639 Exim normally includes both the host name and the IP address in the key it
25640 constructs for indexing retry data after a temporary delivery failure. This
25641 means that when one of several IP addresses for a host is failing, it gets
25642 tried periodically (controlled by the retry rules), but use of the other IP
25643 addresses is not affected.
25645 However, in some dialup environments hosts are assigned a different IP address
25646 each time they connect. In this situation the use of the IP address as part of
25647 the retry key leads to undesirable behaviour. Setting this option false causes
25648 Exim to use only the host name.
25649 Since it is expanded it can be made to depend on the host or domain.
25652 .option serialize_hosts smtp "host list&!!" unset
25653 .cindex "serializing connections"
25654 .cindex "host" "serializing connections"
25655 Because Exim operates in a distributed manner, if several messages for the same
25656 host arrive at around the same time, more than one simultaneous connection to
25657 the remote host can occur. This is not usually a problem except when there is a
25658 slow link between the hosts. In that situation it may be helpful to restrict
25659 Exim to one connection at a time. This can be done by setting
25660 &%serialize_hosts%& to match the relevant hosts.
25662 .cindex "hints database" "serializing deliveries to a host"
25663 Exim implements serialization by means of a hints database in which a record is
25664 written whenever a process connects to one of the restricted hosts. The record
25665 is deleted when the connection is completed. Obviously there is scope for
25666 records to get left lying around if there is a system or program crash. To
25667 guard against this, Exim ignores any records that are more than six hours old.
25669 If you set up this kind of serialization, you should also arrange to delete the
25670 relevant hints database whenever your system reboots. The names of the files
25671 start with &_misc_& and they are kept in the &_spool/db_& directory. There
25672 may be one or two files, depending on the type of DBM in use. The same files
25673 are used for ETRN serialization.
25675 See also the &%max_parallel%& generic transport option.
25678 .option size_addition smtp integer 1024
25679 .cindex "SIZE" "ESMTP extension"
25680 .cindex "message" "size issue for transport filter"
25681 .cindex "size" "of message"
25682 .cindex "transport" "filter"
25683 .cindex "filter" "transport filter"
25684 If a remote SMTP server indicates that it supports the SIZE option of the
25685 MAIL command, Exim uses this to pass over the message size at the start of
25686 an SMTP transaction. It adds the value of &%size_addition%& to the value it
25687 sends, to allow for headers and other text that may be added during delivery by
25688 configuration options or in a transport filter. It may be necessary to increase
25689 this if a lot of text is added to messages.
25691 Alternatively, if the value of &%size_addition%& is set negative, it disables
25692 the use of the SIZE option altogether.
25695 .option socks_proxy smtp string&!! unset
25696 .cindex proxy SOCKS
25697 This option enables use of SOCKS proxies for connections made by the
25698 transport. For details see section &<<SECTproxySOCKS>>&.
25701 .option tls_certificate smtp string&!! unset
25702 .cindex "TLS" "client certificate, location of"
25703 .cindex "certificate" "client, location of"
25705 .vindex "&$host_address$&"
25706 The value of this option must be the absolute path to a file which contains the
25707 client's certificate, for possible use when sending a message over an encrypted
25708 connection. The values of &$host$& and &$host_address$& are set to the name and
25709 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
25712 &*Note*&: This option must be set if you want Exim to be able to use a TLS
25713 certificate when sending messages as a client. The global option of the same
25714 name specifies the certificate for Exim as a server; it is not automatically
25715 assumed that the same certificate should be used when Exim is operating as a
25719 .option tls_crl smtp string&!! unset
25720 .cindex "TLS" "client certificate revocation list"
25721 .cindex "certificate" "revocation list for client"
25722 This option specifies a certificate revocation list. The expanded value must
25723 be the name of a file that contains a CRL in PEM format.
25726 .option tls_dh_min_bits smtp integer 1024
25727 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
25728 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
25729 key agreement is negotiated, the server will provide a large prime number
25730 for use. This option establishes the minimum acceptable size of that number.
25731 If the parameter offered by the server is too small, then the TLS handshake
25734 Only supported when using GnuTLS.
25737 .option tls_privatekey smtp string&!! unset
25738 .cindex "TLS" "client private key, location of"
25740 .vindex "&$host_address$&"
25741 The value of this option must be the absolute path to a file which contains the
25742 client's private key. This is used when sending a message over an encrypted
25743 connection using a client certificate. The values of &$host$& and
25744 &$host_address$& are set to the name and address of the server during the
25745 expansion. If this option is unset, or the expansion is forced to fail, or the
25746 result is an empty string, the private key is assumed to be in the same file as
25747 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
25750 .option tls_require_ciphers smtp string&!! unset
25751 .cindex "TLS" "requiring specific ciphers"
25752 .cindex "cipher" "requiring specific"
25754 .vindex "&$host_address$&"
25755 The value of this option must be a list of permitted cipher suites, for use
25756 when setting up an outgoing encrypted connection. (There is a global option of
25757 the same name for controlling incoming connections.) The values of &$host$& and
25758 &$host_address$& are set to the name and address of the server during the
25759 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
25760 is used in different ways by OpenSSL and GnuTLS (see sections
25761 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
25762 ciphers is a preference order.
25766 .option tls_resumption_hosts smtp "host list&!!" unset
25767 .cindex TLS resumption
25768 This option controls which connections to use the TLS resumption feature.
25769 See &<<SECTresumption>>& for details.
25774 .option tls_sni smtp string&!! unset
25775 .cindex "TLS" "Server Name Indication"
25777 .cindex SNI "setting in client"
25778 .vindex "&$tls_sni$&"
25779 If this option is set
25781 and the connection is not DANE-validated
25783 then it sets the $tls_out_sni variable and causes any
25784 TLS session to pass this value as the Server Name Indication extension to
25785 the remote side, which can be used by the remote side to select an appropriate
25786 certificate and private key for the session.
25788 See &<<SECTtlssni>>& for more information.
25790 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
25796 .option tls_tempfail_tryclear smtp boolean true
25797 .cindex "4&'xx'& responses" "to STARTTLS"
25798 When the server host is not in &%hosts_require_tls%&, and there is a problem in
25799 setting up a TLS session, this option determines whether or not Exim should try
25800 to deliver the message unencrypted. If it is set false, delivery to the
25801 current host is deferred; if there are other hosts, they are tried. If this
25802 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
25803 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
25804 TLS negotiation fails, Exim closes the current connection (because it is in an
25805 unknown state), opens a new one to the same host, and then tries the delivery
25809 .option tls_try_verify_hosts smtp "host list&!!" *
25810 .cindex "TLS" "server certificate verification"
25811 .cindex "certificate" "verification of server"
25812 This option gives a list of hosts for which, on encrypted connections,
25813 certificate verification will be tried but need not succeed.
25814 The &%tls_verify_certificates%& option must also be set.
25815 Note that unless the host is in this list
25816 TLS connections will be denied to hosts using self-signed certificates
25817 when &%tls_verify_certificates%& is matched.
25818 The &$tls_out_certificate_verified$& variable is set when
25819 certificate verification succeeds.
25822 .option tls_verify_cert_hostnames smtp "host list&!!" *
25823 .cindex "TLS" "server certificate hostname verification"
25824 .cindex "certificate" "verification of server"
25825 This option give a list of hosts for which,
25826 while verifying the server certificate,
25827 checks will be included on the host name
25828 (note that this will generally be the result of a DNS MX lookup)
25829 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
25830 limited to being the initial component of a 3-or-more component FQDN.
25832 There is no equivalent checking on client certificates.
25835 .option tls_verify_certificates smtp string&!! system
25836 .cindex "TLS" "server certificate verification"
25837 .cindex "certificate" "verification of server"
25839 .vindex "&$host_address$&"
25840 The value of this option must be either the
25842 or the absolute path to
25843 a file or directory containing permitted certificates for servers,
25844 for use when setting up an encrypted connection.
25846 The "system" value for the option will use a location compiled into the SSL library.
25847 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
25848 is taken as empty and an explicit location
25851 The use of a directory for the option value is not available for GnuTLS versions
25852 preceding 3.3.6 and a single file must be used.
25854 With OpenSSL the certificates specified
25856 either by file or directory
25857 are added to those given by the system default location.
25859 The values of &$host$& and
25860 &$host_address$& are set to the name and address of the server during the
25861 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
25863 For back-compatibility,
25864 if neither tls_verify_hosts nor tls_try_verify_hosts are set
25865 (a single-colon empty list counts as being set)
25866 and certificate verification fails the TLS connection is closed.
25869 .option tls_verify_hosts smtp "host list&!!" unset
25870 .cindex "TLS" "server certificate verification"
25871 .cindex "certificate" "verification of server"
25872 This option gives a list of hosts for which, on encrypted connections,
25873 certificate verification must succeed.
25874 The &%tls_verify_certificates%& option must also be set.
25875 If both this option and &%tls_try_verify_hosts%& are unset
25876 operation is as if this option selected all hosts.
25878 .option utf8_downconvert smtp integer&!! -1
25879 .cindex utf8 "address downconversion"
25880 .cindex i18n "utf8 address downconversion"
25881 If built with internationalization support,
25882 this option controls conversion of UTF-8 in message envelope addresses
25884 If, after expansion, the value is 1, 0, or -1 then this value overrides
25885 any value previously set for the message. Otherwise, any previously
25886 set value is used. To permit use of a previous value,
25887 set this option to an empty string.
25888 For details on the values see section &<<SECTi18nMTA>>&.
25893 .section "How the limits for the number of hosts to try are used" &&&
25895 .cindex "host" "maximum number to try"
25896 .cindex "limit" "hosts; maximum number tried"
25897 There are two options that are concerned with the number of hosts that are
25898 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
25899 &%hosts_max_try_hardlimit%&.
25902 The &%hosts_max_try%& option limits the number of hosts that are tried
25903 for a single delivery. However, despite the term &"host"& in its name, the
25904 option actually applies to each IP address independently. In other words, a
25905 multihomed host is treated as several independent hosts, just as it is for
25908 Many of the larger ISPs have multiple MX records which often point to
25909 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
25910 created as a result of routing one of these domains.
25912 Trying every single IP address on such a long list does not seem sensible; if
25913 several at the top of the list fail, it is reasonable to assume there is some
25914 problem that is likely to affect all of them. Roughly speaking, the value of
25915 &%hosts_max_try%& is the maximum number that are tried before deferring the
25916 delivery. However, the logic cannot be quite that simple.
25918 Firstly, IP addresses that are skipped because their retry times have not
25919 arrived do not count, and in addition, addresses that are past their retry
25920 limits are also not counted, even when they are tried. This means that when
25921 some IP addresses are past their retry limits, more than the value of
25922 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
25923 that all IP addresses are considered before timing out an email address (but
25924 see below for an exception).
25926 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
25927 list to see if there is a subsequent host with a different (higher valued) MX.
25928 If there is, that host is considered next, and the current IP address is used
25929 but not counted. This behaviour helps in the case of a domain with a retry rule
25930 that hardly ever delays any hosts, as is now explained:
25932 Consider the case of a long list of hosts with one MX value, and a few with a
25933 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
25934 hosts at the top of the list are tried at first. With the default retry rule,
25935 which specifies increasing retry times, the higher MX hosts are eventually
25936 tried when those at the top of the list are skipped because they have not
25937 reached their retry times.
25939 However, it is common practice to put a fixed short retry time on domains for
25940 large ISPs, on the grounds that their servers are rarely down for very long.
25941 Unfortunately, these are exactly the domains that tend to resolve to long lists
25942 of hosts. The short retry time means that the lowest MX hosts are tried every
25943 time. The attempts may be in a different order because of random sorting, but
25944 without the special MX check, the higher MX hosts would never be tried until
25945 all the lower MX hosts had timed out (which might be several days), because
25946 there are always some lower MX hosts that have reached their retry times. With
25947 the special check, Exim considers at least one IP address from each MX value at
25948 every delivery attempt, even if the &%hosts_max_try%& limit has already been
25951 The above logic means that &%hosts_max_try%& is not a hard limit, and in
25952 particular, Exim normally eventually tries all the IP addresses before timing
25953 out an email address. When &%hosts_max_try%& was implemented, this seemed a
25954 reasonable thing to do. Recently, however, some lunatic DNS configurations have
25955 been set up with hundreds of IP addresses for some domains. It can
25956 take a very long time indeed for an address to time out in these cases.
25958 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
25959 Exim never tries more than this number of IP addresses; if it hits this limit
25960 and they are all timed out, the email address is bounced, even though not all
25961 possible IP addresses have been tried.
25962 .ecindex IIDsmttra1
25963 .ecindex IIDsmttra2
25969 . ////////////////////////////////////////////////////////////////////////////
25970 . ////////////////////////////////////////////////////////////////////////////
25972 .chapter "Address rewriting" "CHAPrewrite"
25973 .scindex IIDaddrew "rewriting" "addresses"
25974 There are some circumstances in which Exim automatically rewrites domains in
25975 addresses. The two most common are when an address is given without a domain
25976 (referred to as an &"unqualified address"&) or when an address contains an
25977 abbreviated domain that is expanded by DNS lookup.
25979 Unqualified envelope addresses are accepted only for locally submitted
25980 messages, or for messages that are received from hosts matching
25981 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
25982 appropriate. Unqualified addresses in header lines are qualified if they are in
25983 locally submitted messages, or messages from hosts that are permitted to send
25984 unqualified envelope addresses. Otherwise, unqualified addresses in header
25985 lines are neither qualified nor rewritten.
25987 One situation in which Exim does &'not'& automatically rewrite a domain is
25988 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
25989 such a domain should be rewritten using the &"canonical"& name, and some MTAs
25990 do this. The new RFCs do not contain this suggestion.
25993 .section "Explicitly configured address rewriting" "SECID147"
25994 This chapter describes the rewriting rules that can be used in the
25995 main rewrite section of the configuration file, and also in the generic
25996 &%headers_rewrite%& option that can be set on any transport.
25998 Some people believe that configured address rewriting is a Mortal Sin.
25999 Others believe that life is not possible without it. Exim provides the
26000 facility; you do not have to use it.
26002 The main rewriting rules that appear in the &"rewrite"& section of the
26003 configuration file are applied to addresses in incoming messages, both envelope
26004 addresses and addresses in header lines. Each rule specifies the types of
26005 address to which it applies.
26007 Whether or not addresses in header lines are rewritten depends on the origin of
26008 the headers and the type of rewriting. Global rewriting, that is, rewriting
26009 rules from the rewrite section of the configuration file, is applied only to
26010 those headers that were received with the message. Header lines that are added
26011 by ACLs or by a system filter or by individual routers or transports (which
26012 are specific to individual recipient addresses) are not rewritten by the global
26015 Rewriting at transport time, by means of the &%headers_rewrite%& option,
26016 applies all headers except those added by routers and transports. That is, as
26017 well as the headers that were received with the message, it also applies to
26018 headers that were added by an ACL or a system filter.
26021 In general, rewriting addresses from your own system or domain has some
26022 legitimacy. Rewriting other addresses should be done only with great care and
26023 in special circumstances. The author of Exim believes that rewriting should be
26024 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
26025 Although it can sometimes be used as a routing tool, this is very strongly
26028 There are two commonly encountered circumstances where rewriting is used, as
26029 illustrated by these examples:
26032 The company whose domain is &'hitch.fict.example'& has a number of hosts that
26033 exchange mail with each other behind a firewall, but there is only a single
26034 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
26035 &'hitch.fict.example'& when sending mail off-site.
26037 A host rewrites the local parts of its own users so that, for example,
26038 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
26043 .section "When does rewriting happen?" "SECID148"
26044 .cindex "rewriting" "timing of"
26045 .cindex "&ACL;" "rewriting addresses in"
26046 Configured address rewriting can take place at several different stages of a
26047 message's processing.
26049 .vindex "&$sender_address$&"
26050 At the start of an ACL for MAIL, the sender address may have been rewritten
26051 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
26052 ordinary rewrite rules have yet been applied. If, however, the sender address
26053 is verified in the ACL, it is rewritten before verification, and remains
26054 rewritten thereafter. The subsequent value of &$sender_address$& is the
26055 rewritten address. This also applies if sender verification happens in a
26056 RCPT ACL. Otherwise, when the sender address is not verified, it is
26057 rewritten as soon as a message's header lines have been received.
26059 .vindex "&$domain$&"
26060 .vindex "&$local_part$&"
26061 Similarly, at the start of an ACL for RCPT, the current recipient's address
26062 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
26063 rewrite rules have yet been applied to it. However, the behaviour is different
26064 from the sender address when a recipient is verified. The address is rewritten
26065 for the verification, but the rewriting is not remembered at this stage. The
26066 value of &$local_part$& and &$domain$& after verification are always the same
26067 as they were before (that is, they contain the unrewritten &-- except for
26068 SMTP-time rewriting &-- address).
26070 As soon as a message's header lines have been received, all the envelope
26071 recipient addresses are permanently rewritten, and rewriting is also applied to
26072 the addresses in the header lines (if configured). This happens before adding
26073 any header lines that were specified in MAIL or RCPT ACLs, and
26074 .cindex "&[local_scan()]& function" "address rewriting; timing of"
26075 before the DATA ACL and &[local_scan()]& functions are run.
26077 When an address is being routed, either for delivery or for verification,
26078 rewriting is applied immediately to child addresses that are generated by
26079 redirection, unless &%no_rewrite%& is set on the router.
26081 .cindex "envelope from"
26082 .cindex "envelope sender" "rewriting at transport time"
26083 .cindex "rewriting" "at transport time"
26084 .cindex "header lines" "rewriting at transport time"
26085 At transport time, additional rewriting of addresses in header lines can be
26086 specified by setting the generic &%headers_rewrite%& option on a transport.
26087 This option contains rules that are identical in form to those in the rewrite
26088 section of the configuration file. They are applied to the original message
26089 header lines and any that were added by ACLs or a system filter. They are not
26090 applied to header lines that are added by routers or the transport.
26092 The outgoing envelope sender can be rewritten by means of the &%return_path%&
26093 transport option. However, it is not possible to rewrite envelope recipients at
26099 .section "Testing the rewriting rules that apply on input" "SECID149"
26100 .cindex "rewriting" "testing"
26101 .cindex "testing" "rewriting"
26102 Exim's input rewriting configuration appears in a part of the runtime
26103 configuration file headed by &"begin rewrite"&. It can be tested by the
26104 &%-brw%& command line option. This takes an address (which can be a full RFC
26105 2822 address) as its argument. The output is a list of how the address would be
26106 transformed by the rewriting rules for each of the different places it might
26107 appear in an incoming message, that is, for each different header and for the
26108 envelope sender and recipient fields. For example,
26110 exim -brw ph10@exim.workshop.example
26112 might produce the output
26114 sender: Philip.Hazel@exim.workshop.example
26115 from: Philip.Hazel@exim.workshop.example
26116 to: ph10@exim.workshop.example
26117 cc: ph10@exim.workshop.example
26118 bcc: ph10@exim.workshop.example
26119 reply-to: Philip.Hazel@exim.workshop.example
26120 env-from: Philip.Hazel@exim.workshop.example
26121 env-to: ph10@exim.workshop.example
26123 which shows that rewriting has been set up for that address when used in any of
26124 the source fields, but not when it appears as a recipient address. At the
26125 present time, there is no equivalent way of testing rewriting rules that are
26126 set for a particular transport.
26129 .section "Rewriting rules" "SECID150"
26130 .cindex "rewriting" "rules"
26131 The rewrite section of the configuration file consists of lines of rewriting
26134 <&'source pattern'&> <&'replacement'&> <&'flags'&>
26136 Rewriting rules that are specified for the &%headers_rewrite%& generic
26137 transport option are given as a colon-separated list. Each item in the list
26138 takes the same form as a line in the main rewriting configuration (except that
26139 any colons must be doubled, of course).
26141 The formats of source patterns and replacement strings are described below.
26142 Each is terminated by white space, unless enclosed in double quotes, in which
26143 case normal quoting conventions apply inside the quotes. The flags are single
26144 characters which may appear in any order. Spaces and tabs between them are
26147 For each address that could potentially be rewritten, the rules are scanned in
26148 order, and replacements for the address from earlier rules can themselves be
26149 replaced by later rules (but see the &"q"& and &"R"& flags).
26151 The order in which addresses are rewritten is undefined, may change between
26152 releases, and must not be relied on, with one exception: when a message is
26153 received, the envelope sender is always rewritten first, before any header
26154 lines are rewritten. For example, the replacement string for a rewrite of an
26155 address in &'To:'& must not assume that the message's address in &'From:'& has
26156 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
26157 that the envelope sender has already been rewritten.
26159 .vindex "&$domain$&"
26160 .vindex "&$local_part$&"
26161 The variables &$local_part$& and &$domain$& can be used in the replacement
26162 string to refer to the address that is being rewritten. Note that lookup-driven
26163 rewriting can be done by a rule of the form
26167 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
26168 refer to the address that is being rewritten.
26171 .section "Rewriting patterns" "SECID151"
26172 .cindex "rewriting" "patterns"
26173 .cindex "address list" "in a rewriting pattern"
26174 The source pattern in a rewriting rule is any item which may appear in an
26175 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
26176 single-item address list, which means that it is expanded before being tested
26177 against the address. As always, if you use a regular expression as a pattern,
26178 you must take care to escape dollar and backslash characters, or use the &`\N`&
26179 facility to suppress string expansion within the regular expression.
26181 Domains in patterns should be given in lower case. Local parts in patterns are
26182 case-sensitive. If you want to do case-insensitive matching of local parts, you
26183 can use a regular expression that starts with &`^(?i)`&.
26185 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
26186 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
26187 depending on the type of match which occurred. These can be used in the
26188 replacement string to insert portions of the incoming address. &$0$& always
26189 refers to the complete incoming address. When a regular expression is used, the
26190 numerical variables are set from its capturing subexpressions. For other types
26191 of pattern they are set as follows:
26194 If a local part or domain starts with an asterisk, the numerical variables
26195 refer to the character strings matched by asterisks, with &$1$& associated with
26196 the first asterisk, and &$2$& with the second, if present. For example, if the
26199 *queen@*.fict.example
26201 is matched against the address &'hearts-queen@wonderland.fict.example'& then
26203 $0 = hearts-queen@wonderland.fict.example
26207 Note that if the local part does not start with an asterisk, but the domain
26208 does, it is &$1$& that contains the wild part of the domain.
26211 If the domain part of the pattern is a partial lookup, the wild and fixed parts
26212 of the domain are placed in the next available numerical variables. Suppose,
26213 for example, that the address &'foo@bar.baz.example'& is processed by a
26214 rewriting rule of the form
26216 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
26218 and the key in the file that matches the domain is &`*.baz.example`&. Then
26224 If the address &'foo@baz.example'& is looked up, this matches the same
26225 wildcard file entry, and in this case &$2$& is set to the empty string, but
26226 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
26227 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
26228 whole domain. For non-partial domain lookups, no numerical variables are set.
26232 .section "Rewriting replacements" "SECID152"
26233 .cindex "rewriting" "replacements"
26234 If the replacement string for a rule is a single asterisk, addresses that
26235 match the pattern and the flags are &'not'& rewritten, and no subsequent
26236 rewriting rules are scanned. For example,
26238 hatta@lookingglass.fict.example * f
26240 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
26243 .vindex "&$domain$&"
26244 .vindex "&$local_part$&"
26245 If the replacement string is not a single asterisk, it is expanded, and must
26246 yield a fully qualified address. Within the expansion, the variables
26247 &$local_part$& and &$domain$& refer to the address that is being rewritten.
26248 Any letters they contain retain their original case &-- they are not lower
26249 cased. The numerical variables are set up according to the type of pattern that
26250 matched the address, as described above. If the expansion is forced to fail by
26251 the presence of &"fail"& in a conditional or lookup item, rewriting by the
26252 current rule is abandoned, but subsequent rules may take effect. Any other
26253 expansion failure causes the entire rewriting operation to be abandoned, and an
26254 entry written to the panic log.
26258 .section "Rewriting flags" "SECID153"
26259 There are three different kinds of flag that may appear on rewriting rules:
26262 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
26265 A flag that specifies rewriting at SMTP time: S.
26267 Flags that control the rewriting process: Q, q, R, w.
26270 For rules that are part of the &%headers_rewrite%& generic transport option,
26271 E, F, T, and S are not permitted.
26275 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
26277 .cindex "rewriting" "flags"
26278 If none of the following flag letters, nor the &"S"& flag (see section
26279 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
26280 and to both the sender and recipient fields of the envelope, whereas a
26281 transport-time rewriting rule just applies to all headers. Otherwise, the
26282 rewriting rule is skipped unless the relevant addresses are being processed.
26284 &`E`& rewrite all envelope fields
26285 &`F`& rewrite the envelope From field
26286 &`T`& rewrite the envelope To field
26287 &`b`& rewrite the &'Bcc:'& header
26288 &`c`& rewrite the &'Cc:'& header
26289 &`f`& rewrite the &'From:'& header
26290 &`h`& rewrite all headers
26291 &`r`& rewrite the &'Reply-To:'& header
26292 &`s`& rewrite the &'Sender:'& header
26293 &`t`& rewrite the &'To:'& header
26295 "All headers" means all of the headers listed above that can be selected
26296 individually, plus their &'Resent-'& versions. It does not include
26297 other headers such as &'Subject:'& etc.
26299 You should be particularly careful about rewriting &'Sender:'& headers, and
26300 restrict this to special known cases in your own domains.
26303 .section "The SMTP-time rewriting flag" "SECTrewriteS"
26304 .cindex "SMTP" "rewriting malformed addresses"
26305 .cindex "RCPT" "rewriting argument of"
26306 .cindex "MAIL" "rewriting argument of"
26307 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
26308 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
26309 before any other processing; even before syntax checking. The pattern is
26310 required to be a regular expression, and it is matched against the whole of the
26311 data for the command, including any surrounding angle brackets.
26313 .vindex "&$domain$&"
26314 .vindex "&$local_part$&"
26315 This form of rewrite rule allows for the handling of addresses that are not
26316 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
26317 input). Because the input is not required to be a syntactically valid address,
26318 the variables &$local_part$& and &$domain$& are not available during the
26319 expansion of the replacement string. The result of rewriting replaces the
26320 original address in the MAIL or RCPT command.
26323 .section "Flags controlling the rewriting process" "SECID155"
26324 There are four flags which control the way the rewriting process works. These
26325 take effect only when a rule is invoked, that is, when the address is of the
26326 correct type (matches the flags) and matches the pattern:
26329 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
26330 unqualified local part. It is qualified with &%qualify_recipient%&. In the
26331 absence of &"Q"& the rewritten address must always include a domain.
26333 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
26334 even if no rewriting actually takes place because of a &"fail"& in the
26335 expansion. The &"q"& flag is not effective if the address is of the wrong type
26336 (does not match the flags) or does not match the pattern.
26338 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
26339 address, up to ten times. It can be combined with the &"q"& flag, to stop
26340 rewriting once it fails to match (after at least one successful rewrite).
26342 .cindex "rewriting" "whole addresses"
26343 When an address in a header is rewritten, the rewriting normally applies only
26344 to the working part of the address, with any comments and RFC 2822 &"phrase"&
26345 left unchanged. For example, rewriting might change
26347 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
26351 From: Ford Prefect <prefectf@hitch.fict.example>
26354 Sometimes there is a need to replace the whole address item, and this can be
26355 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
26356 causes an address in a header line to be rewritten, the entire address is
26357 replaced, not just the working part. The replacement must be a complete RFC
26358 2822 address, including the angle brackets if necessary. If text outside angle
26359 brackets contains a character whose value is greater than 126 or less than 32
26360 (except for tab), the text is encoded according to RFC 2047. The character set
26361 is taken from &%headers_charset%&, which gets its default at build time.
26363 When the &"w"& flag is set on a rule that causes an envelope address to be
26364 rewritten, all but the working part of the replacement address is discarded.
26368 .section "Rewriting examples" "SECID156"
26369 Here is an example of the two common rewriting paradigms:
26371 *@*.hitch.fict.example $1@hitch.fict.example
26372 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
26373 {$value}fail}@hitch.fict.example bctfrF
26375 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
26376 the string expansion to fail if the lookup does not succeed. In this context it
26377 has the effect of leaving the original address unchanged, but Exim goes on to
26378 consider subsequent rewriting rules, if any, because the &"q"& flag is not
26379 present in that rule. An alternative to &"fail"& would be to supply &$1$&
26380 explicitly, which would cause the rewritten address to be the same as before,
26381 at the cost of a small bit of processing. Not supplying either of these is an
26382 error, since the rewritten address would then contain no local part.
26384 The first example above replaces the domain with a superior, more general
26385 domain. This may not be desirable for certain local parts. If the rule
26387 root@*.hitch.fict.example *
26389 were inserted before the first rule, rewriting would be suppressed for the
26390 local part &'root'& at any domain ending in &'hitch.fict.example'&.
26392 Rewriting can be made conditional on a number of tests, by making use of
26393 &${if$& in the expansion item. For example, to apply a rewriting rule only to
26394 messages that originate outside the local host:
26396 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
26397 {$1@hitch.fict.example}fail}"
26399 The replacement string is quoted in this example because it contains white
26402 .cindex "rewriting" "bang paths"
26403 .cindex "bang paths" "rewriting"
26404 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
26405 an address it treats it as an unqualified local part which it qualifies with
26406 the local qualification domain (if the source of the message is local or if the
26407 remote host is permitted to send unqualified addresses). Rewriting can
26408 sometimes be used to handle simple bang paths with a fixed number of
26409 components. For example, the rule
26411 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
26413 rewrites a two-component bang path &'host.name!user'& as the domain address
26414 &'user@host.name'&. However, there is a security implication in using this as
26415 a global rewriting rule for envelope addresses. It can provide a backdoor
26416 method for using your system as a relay, because the incoming addresses appear
26417 to be local. If the bang path addresses are received via SMTP, it is safer to
26418 use the &"S"& flag to rewrite them as they are received, so that relay checking
26419 can be done on the rewritten addresses.
26426 . ////////////////////////////////////////////////////////////////////////////
26427 . ////////////////////////////////////////////////////////////////////////////
26429 .chapter "Retry configuration" "CHAPretry"
26430 .scindex IIDretconf1 "retry" "configuration, description of"
26431 .scindex IIDregconf2 "configuration file" "retry section"
26432 The &"retry"& section of the runtime configuration file contains a list of
26433 retry rules that control how often Exim tries to deliver messages that cannot
26434 be delivered at the first attempt. If there are no retry rules (the section is
26435 empty or not present), there are no retries. In this situation, temporary
26436 errors are treated as permanent. The default configuration contains a single,
26437 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
26438 line option can be used to test which retry rule will be used for a given
26439 address, domain and error.
26441 The most common cause of retries is temporary failure to deliver to a remote
26442 host because the host is down, or inaccessible because of a network problem.
26443 Exim's retry processing in this case is applied on a per-host (strictly, per IP
26444 address) basis, not on a per-message basis. Thus, if one message has recently
26445 been delayed, delivery of a new message to the same host is not immediately
26446 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
26447 log selector is set, the message
26448 .cindex "retry" "time not reached"
26449 &"retry time not reached"& is written to the main log whenever a delivery is
26450 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
26451 the handling of errors during remote deliveries.
26453 Retry processing applies to routing as well as to delivering, except as covered
26454 in the next paragraph. The retry rules do not distinguish between these
26455 actions. It is not possible, for example, to specify different behaviour for
26456 failures to route the domain &'snark.fict.example'& and failures to deliver to
26457 the host &'snark.fict.example'&. I didn't think anyone would ever need this
26458 added complication, so did not implement it. However, although they share the
26459 same retry rule, the actual retry times for routing and transporting a given
26460 domain are maintained independently.
26462 When a delivery is not part of a queue run (typically an immediate delivery on
26463 receipt of a message), the routers are always run, and local deliveries are
26464 always attempted, even if retry times are set for them. This makes for better
26465 behaviour if one particular message is causing problems (for example, causing
26466 quota overflow, or provoking an error in a filter file). If such a delivery
26467 suffers a temporary failure, the retry data is updated as normal, and
26468 subsequent delivery attempts from queue runs occur only when the retry time for
26469 the local address is reached.
26471 .section "Changing retry rules" "SECID157"
26472 If you change the retry rules in your configuration, you should consider
26473 whether or not to delete the retry data that is stored in Exim's spool area in
26474 files with names like &_db/retry_&. Deleting any of Exim's hints files is
26475 always safe; that is why they are called &"hints"&.
26477 The hints retry data contains suggested retry times based on the previous
26478 rules. In the case of a long-running problem with a remote host, it might
26479 record the fact that the host has timed out. If your new rules increase the
26480 timeout time for such a host, you should definitely remove the old retry data
26481 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
26482 messages that it should now be retaining.
26486 .section "Format of retry rules" "SECID158"
26487 .cindex "retry" "rules"
26488 Each retry rule occupies one line and consists of three or four parts,
26489 separated by white space: a pattern, an error name, an optional list of sender
26490 addresses, and a list of retry parameters. The pattern and sender lists must be
26491 enclosed in double quotes if they contain white space. The rules are searched
26492 in order until one is found where the pattern, error name, and sender list (if
26493 present) match the failing host or address, the error that occurred, and the
26494 message's sender, respectively.
26497 The pattern is any single item that may appear in an address list (see section
26498 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
26499 which means that it is expanded before being tested against the address that
26500 has been delayed. A negated address list item is permitted. Address
26501 list processing treats a plain domain name as if it were preceded by &"*@"&,
26502 which makes it possible for many retry rules to start with just a domain. For
26505 lookingglass.fict.example * F,24h,30m;
26507 provides a rule for any address in the &'lookingglass.fict.example'& domain,
26510 alice@lookingglass.fict.example * F,24h,30m;
26512 applies only to temporary failures involving the local part &%alice%&.
26513 In practice, almost all rules start with a domain name pattern without a local
26516 .cindex "regular expressions" "in retry rules"
26517 &*Warning*&: If you use a regular expression in a retry rule pattern, it
26518 must match a complete address, not just a domain, because that is how regular
26519 expressions work in address lists.
26521 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
26522 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
26526 .section "Choosing which retry rule to use for address errors" "SECID159"
26527 When Exim is looking for a retry rule after a routing attempt has failed (for
26528 example, after a DNS timeout), each line in the retry configuration is tested
26529 against the complete address only if &%retry_use_local_part%& is set for the
26530 router. Otherwise, only the domain is used, except when matching against a
26531 regular expression, when the local part of the address is replaced with &"*"&.
26532 A domain on its own can match a domain pattern, or a pattern that starts with
26533 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
26534 &%check_local_user%& is true, and false for other routers.
26536 Similarly, when Exim is looking for a retry rule after a local delivery has
26537 failed (for example, after a mailbox full error), each line in the retry
26538 configuration is tested against the complete address only if
26539 &%retry_use_local_part%& is set for the transport (it defaults true for all
26542 .cindex "4&'xx'& responses" "retry rules for"
26543 However, when Exim is looking for a retry rule after a remote delivery attempt
26544 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
26545 whole address is always used as the key when searching the retry rules. The
26546 rule that is found is used to create a retry time for the combination of the
26547 failing address and the message's sender. It is the combination of sender and
26548 recipient that is delayed in subsequent queue runs until its retry time is
26549 reached. You can delay the recipient without regard to the sender by setting
26550 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
26551 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
26556 .section "Choosing which retry rule to use for host and message errors" &&&
26558 For a temporary error that is not related to an individual address (for
26559 example, a connection timeout), each line in the retry configuration is checked
26560 twice. First, the name of the remote host is used as a domain name (preceded by
26561 &"*@"& when matching a regular expression). If this does not match the line,
26562 the domain from the email address is tried in a similar fashion. For example,
26563 suppose the MX records for &'a.b.c.example'& are
26565 a.b.c.example MX 5 x.y.z.example
26569 and the retry rules are
26571 p.q.r.example * F,24h,30m;
26572 a.b.c.example * F,4d,45m;
26574 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
26575 first rule matches neither the host nor the domain, so Exim looks at the second
26576 rule. This does not match the host, but it does match the domain, so it is used
26577 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
26578 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
26579 first retry rule is used, because it matches the host.
26581 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
26582 first rule to determine retry times, but for all the other hosts for the domain
26583 &'a.b.c.example'&, the second rule is used. The second rule is also used if
26584 routing to &'a.b.c.example'& suffers a temporary failure.
26586 &*Note*&: The host name is used when matching the patterns, not its IP address.
26587 However, if a message is routed directly to an IP address without the use of a
26588 host name, for example, if a &(manualroute)& router contains a setting such as:
26590 route_list = *.a.example 192.168.34.23
26592 then the &"host name"& that is used when searching for a retry rule is the
26593 textual form of the IP address.
26595 .section "Retry rules for specific errors" "SECID161"
26596 .cindex "retry" "specific errors; specifying"
26597 The second field in a retry rule is the name of a particular error, or an
26598 asterisk, which matches any error. The errors that can be tested for are:
26601 .vitem &%auth_failed%&
26602 Authentication failed when trying to send to a host in the
26603 &%hosts_require_auth%& list in an &(smtp)& transport.
26605 .vitem &%data_4xx%&
26606 A 4&'xx'& error was received for an outgoing DATA command, either immediately
26607 after the command, or after sending the message's data.
26609 .vitem &%mail_4xx%&
26610 A 4&'xx'& error was received for an outgoing MAIL command.
26612 .vitem &%rcpt_4xx%&
26613 A 4&'xx'& error was received for an outgoing RCPT command.
26616 For the three 4&'xx'& errors, either the first or both of the x's can be given
26617 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
26618 recognize 452 errors given to RCPT commands for addresses in a certain domain,
26619 and have retries every ten minutes with a one-hour timeout, you could set up a
26620 retry rule of this form:
26622 the.domain.name rcpt_452 F,1h,10m
26624 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
26625 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
26628 .vitem &%lost_connection%&
26629 A server unexpectedly closed the SMTP connection. There may, of course,
26630 legitimate reasons for this (host died, network died), but if it repeats a lot
26631 for the same host, it indicates something odd.
26634 A DNS lookup for a host failed.
26635 Note that a &%dnslookup%& router will need to have matched
26636 its &%fail_defer_domains%& option for this retry type to be usable.
26637 Also note that a &%manualroute%& router will probably need
26638 its &%host_find_failed%& option set to &%defer%&.
26640 .vitem &%refused_MX%&
26641 A connection to a host obtained from an MX record was refused.
26643 .vitem &%refused_A%&
26644 A connection to a host not obtained from an MX record was refused.
26647 A connection was refused.
26649 .vitem &%timeout_connect_MX%&
26650 A connection attempt to a host obtained from an MX record timed out.
26652 .vitem &%timeout_connect_A%&
26653 A connection attempt to a host not obtained from an MX record timed out.
26655 .vitem &%timeout_connect%&
26656 A connection attempt timed out.
26658 .vitem &%timeout_MX%&
26659 There was a timeout while connecting or during an SMTP session with a host
26660 obtained from an MX record.
26662 .vitem &%timeout_A%&
26663 There was a timeout while connecting or during an SMTP session with a host not
26664 obtained from an MX record.
26667 There was a timeout while connecting or during an SMTP session.
26669 .vitem &%tls_required%&
26670 The server was required to use TLS (it matched &%hosts_require_tls%& in the
26671 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
26672 to STARTTLS, or there was a problem setting up the TLS connection.
26675 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26678 .vitem &%quota_%&<&'time'&>
26679 .cindex "quota" "error testing in retry rule"
26680 .cindex "retry" "quota error testing"
26681 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
26682 transport, and the mailbox has not been accessed for <&'time'&>. For example,
26683 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
26687 .cindex "mailbox" "time of last read"
26688 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
26689 timeouts when the mailbox is full and is not being read by its owner. Ideally,
26690 it should be based on the last time that the user accessed the mailbox.
26691 However, it is not always possible to determine this. Exim uses the following
26695 If the mailbox is a single file, the time of last access (the &"atime"&) is
26696 used. As no new messages are being delivered (because the mailbox is over
26697 quota), Exim does not access the file, so this is the time of last user access.
26699 .cindex "maildir format" "time of last read"
26700 For a maildir delivery, the time of last modification of the &_new_&
26701 subdirectory is used. As the mailbox is over quota, no new files are created in
26702 the &_new_& subdirectory, because no new messages are being delivered. Any
26703 change to the &_new_& subdirectory is therefore assumed to be the result of an
26704 MUA moving a new message to the &_cur_& directory when it is first read. The
26705 time that is used is therefore the last time that the user read a new message.
26707 For other kinds of multi-file mailbox, the time of last access cannot be
26708 obtained, so a retry rule that uses this type of error field is never matched.
26711 The quota errors apply both to system-enforced quotas and to Exim's own quota
26712 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
26713 when a local delivery is deferred because a partition is full (the ENOSPC
26718 .section "Retry rules for specified senders" "SECID162"
26719 .cindex "retry" "rules; sender-specific"
26720 You can specify retry rules that apply only when the failing message has a
26721 specific sender. In particular, this can be used to define retry rules that
26722 apply only to bounce messages. The third item in a retry rule can be of this
26725 &`senders=`&<&'address list'&>
26727 The retry timings themselves are then the fourth item. For example:
26729 * rcpt_4xx senders=: F,1h,30m
26731 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
26732 host. If the address list contains white space, it must be enclosed in quotes.
26735 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
26737 &*Warning*&: This facility can be unhelpful if it is used for host errors
26738 (which do not depend on the recipient). The reason is that the sender is used
26739 only to match the retry rule. Once the rule has been found for a host error,
26740 its contents are used to set a retry time for the host, and this will apply to
26741 all messages, not just those with specific senders.
26743 When testing retry rules using &%-brt%&, you can supply a sender using the
26744 &%-f%& command line option, like this:
26746 exim -f "" -brt user@dom.ain
26748 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
26749 list is never matched.
26755 .section "Retry parameters" "SECID163"
26756 .cindex "retry" "parameters in rules"
26757 The third (or fourth, if a senders list is present) field in a retry rule is a
26758 sequence of retry parameter sets, separated by semicolons. Each set consists of
26760 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
26762 The letter identifies the algorithm for computing a new retry time; the cutoff
26763 time is the time beyond which this algorithm no longer applies, and the
26764 arguments vary the algorithm's action. The cutoff time is measured from the
26765 time that the first failure for the domain (combined with the local part if
26766 relevant) was detected, not from the time the message was received.
26768 .cindex "retry" "algorithms"
26769 .cindex "retry" "fixed intervals"
26770 .cindex "retry" "increasing intervals"
26771 .cindex "retry" "random intervals"
26772 The available algorithms are:
26775 &'F'&: retry at fixed intervals. There is a single time parameter specifying
26778 &'G'&: retry at geometrically increasing intervals. The first argument
26779 specifies a starting value for the interval, and the second a multiplier, which
26780 is used to increase the size of the interval at each retry.
26782 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
26783 retry, the previous interval is multiplied by the factor in order to get a
26784 maximum for the next interval. The minimum interval is the first argument of
26785 the parameter, and an actual interval is chosen randomly between them. Such a
26786 rule has been found to be helpful in cluster configurations when all the
26787 members of the cluster restart at once, and may therefore synchronize their
26788 queue processing times.
26791 When computing the next retry time, the algorithm definitions are scanned in
26792 order until one whose cutoff time has not yet passed is reached. This is then
26793 used to compute a new retry time that is later than the current time. In the
26794 case of fixed interval retries, this simply means adding the interval to the
26795 current time. For geometrically increasing intervals, retry intervals are
26796 computed from the rule's parameters until one that is greater than the previous
26797 interval is found. The main configuration variable
26798 .cindex "limit" "retry interval"
26799 .cindex "retry" "interval, maximum"
26800 .oindex "&%retry_interval_max%&"
26801 &%retry_interval_max%& limits the maximum interval between retries. It
26802 cannot be set greater than &`24h`&, which is its default value.
26804 A single remote domain may have a number of hosts associated with it, and each
26805 host may have more than one IP address. Retry algorithms are selected on the
26806 basis of the domain name, but are applied to each IP address independently. If,
26807 for example, a host has two IP addresses and one is unusable, Exim will
26808 generate retry times for it and will not try to use it until its next retry
26809 time comes. Thus the good IP address is likely to be tried first most of the
26812 .cindex "hints database" "use for retrying"
26813 Retry times are hints rather than promises. Exim does not make any attempt to
26814 run deliveries exactly at the computed times. Instead, a queue runner process
26815 starts delivery processes for delayed messages periodically, and these attempt
26816 new deliveries only for those addresses that have passed their next retry time.
26817 If a new message arrives for a deferred address, an immediate delivery attempt
26818 occurs only if the address has passed its retry time. In the absence of new
26819 messages, the minimum time between retries is the interval between queue runner
26820 processes. There is not much point in setting retry times of five minutes if
26821 your queue runners happen only once an hour, unless there are a significant
26822 number of incoming messages (which might be the case on a system that is
26823 sending everything to a smart host, for example).
26825 The data in the retry hints database can be inspected by using the
26826 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
26827 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
26828 &'exinext'& utility script can be used to find out what the next retry times
26829 are for the hosts associated with a particular mail domain, and also for local
26830 deliveries that have been deferred.
26833 .section "Retry rule examples" "SECID164"
26834 Here are some example retry rules:
26836 alice@wonderland.fict.example quota_5d F,7d,3h
26837 wonderland.fict.example quota_5d
26838 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
26839 lookingglass.fict.example * F,24h,30m;
26840 * refused_A F,2h,20m;
26841 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
26843 The first rule sets up special handling for mail to
26844 &'alice@wonderland.fict.example'& when there is an over-quota error and the
26845 mailbox has not been read for at least 5 days. Retries continue every three
26846 hours for 7 days. The second rule handles over-quota errors for all other local
26847 parts at &'wonderland.fict.example'&; the absence of a local part has the same
26848 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
26849 fail are bounced immediately if the mailbox has not been read for at least 5
26852 The third rule handles all other errors at &'wonderland.fict.example'&; retries
26853 happen every 15 minutes for an hour, then with geometrically increasing
26854 intervals until two days have passed since a delivery first failed. After the
26855 first hour there is a delay of one hour, then two hours, then four hours, and
26856 so on (this is a rather extreme example).
26858 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
26859 They happen every 30 minutes for 24 hours only. The remaining two rules handle
26860 all other domains, with special action for connection refusal from hosts that
26861 were not obtained from an MX record.
26863 The final rule in a retry configuration should always have asterisks in the
26864 first two fields so as to provide a general catch-all for any addresses that do
26865 not have their own special handling. This example tries every 15 minutes for 2
26866 hours, then with intervals starting at one hour and increasing by a factor of
26867 1.5 up to 16 hours, then every 8 hours up to 5 days.
26871 .section "Timeout of retry data" "SECID165"
26872 .cindex "timeout" "of retry data"
26873 .oindex "&%retry_data_expire%&"
26874 .cindex "hints database" "data expiry"
26875 .cindex "retry" "timeout of data"
26876 Exim timestamps the data that it writes to its retry hints database. When it
26877 consults the data during a delivery it ignores any that is older than the value
26878 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
26879 been tried for 7 days, Exim will try to deliver to it immediately a message
26880 arrives, and if that fails, it will calculate a retry time as if it were
26881 failing for the first time.
26883 This improves the behaviour for messages routed to rarely-used hosts such as MX
26884 backups. If such a host was down at one time, and happens to be down again when
26885 Exim tries a month later, using the old retry data would imply that it had been
26886 down all the time, which is not a justified assumption.
26888 If a host really is permanently dead, this behaviour causes a burst of retries
26889 every now and again, but only if messages routed to it are rare. If there is a
26890 message at least once every 7 days the retry data never expires.
26895 .section "Long-term failures" "SECID166"
26896 .cindex "delivery failure, long-term"
26897 .cindex "retry" "after long-term failure"
26898 Special processing happens when an email address has been failing for so long
26899 that the cutoff time for the last algorithm is reached. For example, using the
26900 default retry rule:
26902 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
26904 the cutoff time is four days. Reaching the retry cutoff is independent of how
26905 long any specific message has been failing; it is the length of continuous
26906 failure for the recipient address that counts.
26908 When the cutoff time is reached for a local delivery, or for all the IP
26909 addresses associated with a remote delivery, a subsequent delivery failure
26910 causes Exim to give up on the address, and a bounce message is generated.
26911 In order to cater for new messages that use the failing address, a next retry
26912 time is still computed from the final algorithm, and is used as follows:
26914 For local deliveries, one delivery attempt is always made for any subsequent
26915 messages. If this delivery fails, the address fails immediately. The
26916 post-cutoff retry time is not used.
26918 .cindex "final cutoff" "retries, controlling"
26919 .cindex retry "final cutoff"
26920 If the delivery is remote, there are two possibilities, controlled by the
26921 .oindex "&%delay_after_cutoff%&"
26922 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
26923 default. Until the post-cutoff retry time for one of the IP addresses,
26924 as set by the &%retry_data_expire%& option, is
26925 reached, the failing email address is bounced immediately, without a delivery
26926 attempt taking place. After that time, one new delivery attempt is made to
26927 those IP addresses that are past their retry times, and if that still fails,
26928 the address is bounced and new retry times are computed.
26930 In other words, when all the hosts for a given email address have been failing
26931 for a long time, Exim bounces rather then defers until one of the hosts' retry
26932 times is reached. Then it tries once, and bounces if that attempt fails. This
26933 behaviour ensures that few resources are wasted in repeatedly trying to deliver
26934 to a broken destination, but if the host does recover, Exim will eventually
26937 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
26938 addresses are past their final cutoff time, Exim tries to deliver to those IP
26939 addresses that have not been tried since the message arrived. If there are
26940 no suitable IP addresses, or if they all fail, the address is bounced. In other
26941 words, it does not delay when a new message arrives, but tries the expired
26942 addresses immediately, unless they have been tried since the message arrived.
26943 If there is a continuous stream of messages for the failing domains, setting
26944 &%delay_after_cutoff%& false means that there will be many more attempts to
26945 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
26948 .section "Deliveries that work intermittently" "SECID167"
26949 .cindex "retry" "intermittently working deliveries"
26950 Some additional logic is needed to cope with cases where a host is
26951 intermittently available, or when a message has some attribute that prevents
26952 its delivery when others to the same address get through. In this situation,
26953 because some messages are successfully delivered, the &"retry clock"& for the
26954 host or address keeps getting reset by the successful deliveries, and so
26955 failing messages remain in the queue for ever because the cutoff time is never
26958 Two exceptional actions are applied to prevent this happening. The first
26959 applies to errors that are related to a message rather than a remote host.
26960 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
26961 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
26962 commands, and quota failures. For this type of error, if a message's arrival
26963 time is earlier than the &"first failed"& time for the error, the earlier time
26964 is used when scanning the retry rules to decide when to try next and when to
26965 time out the address.
26967 The exceptional second action applies in all cases. If a message has been on
26968 the queue for longer than the cutoff time of any applicable retry rule for a
26969 given address, a delivery is attempted for that address, even if it is not yet
26970 time, and if this delivery fails, the address is timed out. A new retry time is
26971 not computed in this case, so that other messages for the same address are
26972 considered immediately.
26973 .ecindex IIDretconf1
26974 .ecindex IIDregconf2
26981 . ////////////////////////////////////////////////////////////////////////////
26982 . ////////////////////////////////////////////////////////////////////////////
26984 .chapter "SMTP authentication" "CHAPSMTPAUTH"
26985 .scindex IIDauthconf1 "SMTP" "authentication configuration"
26986 .scindex IIDauthconf2 "authentication"
26987 The &"authenticators"& section of Exim's runtime configuration is concerned
26988 with SMTP authentication. This facility is an extension to the SMTP protocol,
26989 described in RFC 2554, which allows a client SMTP host to authenticate itself
26990 to a server. This is a common way for a server to recognize clients that are
26991 permitted to use it as a relay. SMTP authentication is not of relevance to the
26992 transfer of mail between servers that have no managerial connection with each
26995 .cindex "AUTH" "description of"
26996 .cindex "ESMTP extensions" AUTH
26997 Very briefly, the way SMTP authentication works is as follows:
27000 The server advertises a number of authentication &'mechanisms'& in response to
27001 the client's EHLO command.
27003 The client issues an AUTH command, naming a specific mechanism. The command
27004 may, optionally, contain some authentication data.
27006 The server may issue one or more &'challenges'&, to which the client must send
27007 appropriate responses. In simple authentication mechanisms, the challenges are
27008 just prompts for user names and passwords. The server does not have to issue
27009 any challenges &-- in some mechanisms the relevant data may all be transmitted
27010 with the AUTH command.
27012 The server either accepts or denies authentication.
27014 If authentication succeeds, the client may optionally make use of the AUTH
27015 option on the MAIL command to pass an authenticated sender in subsequent
27016 mail transactions. Authentication lasts for the remainder of the SMTP
27019 If authentication fails, the client may give up, or it may try a different
27020 authentication mechanism, or it may try transferring mail over the
27021 unauthenticated connection.
27024 If you are setting up a client, and want to know which authentication
27025 mechanisms the server supports, you can use Telnet to connect to port 25 (the
27026 SMTP port) on the server, and issue an EHLO command. The response to this
27027 includes the list of supported mechanisms. For example:
27029 &`$ `&&*&`telnet server.example 25`&*&
27030 &`Trying 192.168.34.25...`&
27031 &`Connected to server.example.`&
27032 &`Escape character is '^]'.`&
27033 &`220 server.example ESMTP Exim 4.20 ...`&
27034 &*&`ehlo client.example`&*&
27035 &`250-server.example Hello client.example [10.8.4.5]`&
27036 &`250-SIZE 52428800`&
27041 The second-last line of this example output shows that the server supports
27042 authentication using the PLAIN mechanism. In Exim, the different authentication
27043 mechanisms are configured by specifying &'authenticator'& drivers. Like the
27044 routers and transports, which authenticators are included in the binary is
27045 controlled by build-time definitions. The following are currently available,
27046 included by setting
27049 AUTH_CYRUS_SASL=yes
27053 AUTH_HEIMDAL_GSSAPI=yes
27058 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
27059 authentication mechanism (RFC 2195), and the second provides an interface to
27060 the Cyrus SASL authentication library.
27061 The third is an interface to Dovecot's authentication system, delegating the
27062 work via a socket interface.
27063 The fourth provides for negotiation of authentication done via non-SMTP means,
27064 as defined by RFC 4422 Appendix A.
27065 The fifth provides an interface to the GNU SASL authentication library, which
27066 provides mechanisms but typically not data sources.
27067 The sixth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
27068 supporting setting a server keytab.
27069 The seventh can be configured to support
27070 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
27071 not formally documented, but used by several MUAs.
27072 The eighth authenticator
27073 supports Microsoft's &'Secure Password Authentication'& mechanism.
27074 The last is an Exim authenticator but not an SMTP one;
27075 instead it can use information from a TLS negotiation.
27077 The authenticators are configured using the same syntax as other drivers (see
27078 section &<<SECTfordricon>>&). If no authenticators are required, no
27079 authentication section need be present in the configuration file. Each
27080 authenticator can in principle have both server and client functions. When Exim
27081 is receiving SMTP mail, it is acting as a server; when it is sending out
27082 messages over SMTP, it is acting as a client. Authenticator configuration
27083 options are provided for use in both these circumstances.
27085 To make it clear which options apply to which situation, the prefixes
27086 &%server_%& and &%client_%& are used on option names that are specific to
27087 either the server or the client function, respectively. Server and client
27088 functions are disabled if none of their options are set. If an authenticator is
27089 to be used for both server and client functions, a single definition, using
27090 both sets of options, is required. For example:
27094 public_name = CRAM-MD5
27095 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
27097 client_secret = secret2
27099 The &%server_%& option is used when Exim is acting as a server, and the
27100 &%client_%& options when it is acting as a client.
27102 Descriptions of the individual authenticators are given in subsequent chapters.
27103 The remainder of this chapter covers the generic options for the
27104 authenticators, followed by general discussion of the way authentication works
27107 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
27108 per-mechanism basis. Please read carefully to determine which variables hold
27109 account labels such as usercodes and which hold passwords or other
27110 authenticating data.
27112 Note that some mechanisms support two different identifiers for accounts: the
27113 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
27114 and &'authz'& are commonly encountered. The American spelling is standard here.
27115 Conceptually, authentication data such as passwords are tied to the identifier
27116 used to authenticate; servers may have rules to permit one user to act as a
27117 second user, so that after login the session is treated as though that second
27118 user had logged in. That second user is the &'authorization id'&. A robust
27119 configuration might confirm that the &'authz'& field is empty or matches the
27120 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
27121 as verified data, the &'authz'& as an unverified request which the server might
27124 A &'realm'& is a text string, typically a domain name, presented by a server
27125 to a client to help it select an account and credentials to use. In some
27126 mechanisms, the client and server provably agree on the realm, but clients
27127 typically can not treat the realm as secure data to be blindly trusted.
27131 .section "Generic options for authenticators" "SECID168"
27132 .cindex "authentication" "generic options"
27133 .cindex "options" "generic; for authenticators"
27135 .option client_condition authenticators string&!! unset
27136 When Exim is authenticating as a client, it skips any authenticator whose
27137 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
27138 used, for example, to skip plain text authenticators when the connection is not
27139 encrypted by a setting such as:
27141 client_condition = ${if !eq{$tls_out_cipher}{}}
27145 .option client_set_id authenticators string&!! unset
27146 When client authentication succeeds, this condition is expanded; the
27147 result is used in the log lines for outbound messages.
27148 Typically it will be the user name used for authentication.
27151 .option driver authenticators string unset
27152 This option must always be set. It specifies which of the available
27153 authenticators is to be used.
27156 .option public_name authenticators string unset
27157 This option specifies the name of the authentication mechanism that the driver
27158 implements, and by which it is known to the outside world. These names should
27159 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
27160 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
27161 defaults to the driver's instance name.
27164 .option server_advertise_condition authenticators string&!! unset
27165 When a server is about to advertise an authentication mechanism, the condition
27166 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
27167 mechanism is not advertised.
27168 If the expansion fails, the mechanism is not advertised. If the failure was not
27169 forced, and was not caused by a lookup defer, the incident is logged.
27170 See section &<<SECTauthexiser>>& below for further discussion.
27173 .option server_condition authenticators string&!! unset
27174 This option must be set for a &%plaintext%& server authenticator, where it
27175 is used directly to control authentication. See section &<<SECTplainserver>>&
27178 For the &(gsasl)& authenticator, this option is required for various
27179 mechanisms; see chapter &<<CHAPgsasl>>& for details.
27181 For the other authenticators, &%server_condition%& can be used as an additional
27182 authentication or authorization mechanism that is applied after the other
27183 authenticator conditions succeed. If it is set, it is expanded when the
27184 authenticator would otherwise return a success code. If the expansion is forced
27185 to fail, authentication fails. Any other expansion failure causes a temporary
27186 error code to be returned. If the result of a successful expansion is an empty
27187 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27188 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
27189 other result, a temporary error code is returned, with the expanded string as
27193 .option server_debug_print authenticators string&!! unset
27194 If this option is set and authentication debugging is enabled (see the &%-d%&
27195 command line option), the string is expanded and included in the debugging
27196 output when the authenticator is run as a server. This can help with checking
27197 out the values of variables.
27198 If expansion of the string fails, the error message is written to the debugging
27199 output, and Exim carries on processing.
27202 .option server_set_id authenticators string&!! unset
27203 .vindex "&$authenticated_id$&"
27204 .vindex "&$authenticated_fail_id$&"
27205 When an Exim server successfully authenticates a client, this string is
27206 expanded using data from the authentication, and preserved for any incoming
27207 messages in the variable &$authenticated_id$&. It is also included in the log
27208 lines for incoming messages. For example, a user/password authenticator
27209 configuration might preserve the user name that was used to authenticate, and
27210 refer to it subsequently during delivery of the message.
27211 On a failing authentication the expansion result is instead saved in
27212 the &$authenticated_fail_id$& variable.
27213 If expansion fails, the option is ignored.
27216 .option server_mail_auth_condition authenticators string&!! unset
27217 This option allows a server to discard authenticated sender addresses supplied
27218 as part of MAIL commands in SMTP connections that are authenticated by the
27219 driver on which &%server_mail_auth_condition%& is set. The option is not used
27220 as part of the authentication process; instead its (unexpanded) value is
27221 remembered for later use.
27222 How it is used is described in the following section.
27228 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
27229 .cindex "authentication" "sender; authenticated"
27230 .cindex "AUTH" "on MAIL command"
27231 When a client supplied an AUTH= item on a MAIL command, Exim applies
27232 the following checks before accepting it as the authenticated sender of the
27236 If the connection is not using extended SMTP (that is, HELO was used rather
27237 than EHLO), the use of AUTH= is a syntax error.
27239 If the value of the AUTH= parameter is &"<>"&, it is ignored.
27241 .vindex "&$authenticated_sender$&"
27242 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
27243 running, the value of &$authenticated_sender$& is set to the value obtained
27244 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
27245 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
27246 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
27247 given for the MAIL command.
27249 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
27250 is accepted and placed in &$authenticated_sender$& only if the client has
27253 If the AUTH= value was accepted by either of the two previous rules, and
27254 the client has authenticated, and the authenticator has a setting for the
27255 &%server_mail_auth_condition%&, the condition is checked at this point. The
27256 valued that was saved from the authenticator is expanded. If the expansion
27257 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
27258 &$authenticated_sender$& is deleted. If the expansion yields any other value,
27259 the value of &$authenticated_sender$& is retained and passed on with the
27264 When &$authenticated_sender$& is set for a message, it is passed on to other
27265 hosts to which Exim authenticates as a client. Do not confuse this value with
27266 &$authenticated_id$&, which is a string obtained from the authentication
27267 process, and which is not usually a complete email address.
27269 .vindex "&$sender_address$&"
27270 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
27271 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
27272 therefore make use of &$authenticated_sender$&. The converse is not true: the
27273 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
27278 .section "Authentication on an Exim server" "SECTauthexiser"
27279 .cindex "authentication" "on an Exim server"
27280 When Exim receives an EHLO command, it advertises the public names of those
27281 authenticators that are configured as servers, subject to the following
27285 The client host must match &%auth_advertise_hosts%& (default *).
27287 It the &%server_advertise_condition%& option is set, its expansion must not
27288 yield the empty string, &"0"&, &"no"&, or &"false"&.
27291 The order in which the authenticators are defined controls the order in which
27292 the mechanisms are advertised.
27294 Some mail clients (for example, some versions of Netscape) require the user to
27295 provide a name and password for authentication whenever AUTH is advertised,
27296 even though authentication may not in fact be needed (for example, Exim may be
27297 set up to allow unconditional relaying from the client by an IP address check).
27298 You can make such clients more friendly by not advertising AUTH to them.
27299 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
27300 that runs for RCPT) to relay without authentication, you should set
27302 auth_advertise_hosts = ! 10.9.8.0/24
27304 so that no authentication mechanisms are advertised to them.
27306 The &%server_advertise_condition%& controls the advertisement of individual
27307 authentication mechanisms. For example, it can be used to restrict the
27308 advertisement of a particular mechanism to encrypted connections, by a setting
27311 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
27313 .vindex "&$tls_in_cipher$&"
27314 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
27315 yields &"yes"&, which allows the advertisement to happen.
27317 When an Exim server receives an AUTH command from a client, it rejects it
27318 immediately if AUTH was not advertised in response to an earlier EHLO
27319 command. This is the case if
27322 The client host does not match &%auth_advertise_hosts%&; or
27324 No authenticators are configured with server options; or
27326 Expansion of &%server_advertise_condition%& blocked the advertising of all the
27327 server authenticators.
27331 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
27332 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
27333 AUTH is accepted from any client host.
27335 If AUTH is not rejected by the ACL, Exim searches its configuration for a
27336 server authentication mechanism that was advertised in response to EHLO and
27337 that matches the one named in the AUTH command. If it finds one, it runs
27338 the appropriate authentication protocol, and authentication either succeeds or
27339 fails. If there is no matching advertised mechanism, the AUTH command is
27340 rejected with a 504 error.
27342 .vindex "&$received_protocol$&"
27343 .vindex "&$sender_host_authenticated$&"
27344 When a message is received from an authenticated host, the value of
27345 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
27346 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
27347 public name) of the authenticator driver that successfully authenticated the
27348 client from which the message was received. This variable is empty if there was
27349 no successful authentication.
27351 .cindex authentication "expansion item"
27352 Successful authentication sets up information used by the
27353 &%authresults%& expansion item.
27358 .section "Testing server authentication" "SECID169"
27359 .cindex "authentication" "testing a server"
27360 .cindex "AUTH" "testing a server"
27361 .cindex "base64 encoding" "creating authentication test data"
27362 Exim's &%-bh%& option can be useful for testing server authentication
27363 configurations. The data for the AUTH command has to be sent using base64
27364 encoding. A quick way to produce such data for testing is the following Perl
27368 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
27370 .cindex "binary zero" "in authentication data"
27371 This interprets its argument as a Perl string, and then encodes it. The
27372 interpretation as a Perl string allows binary zeros, which are required for
27373 some kinds of authentication, to be included in the data. For example, a
27374 command line to run this script on such data might be
27376 encode '\0user\0password'
27378 Note the use of single quotes to prevent the shell interpreting the
27379 backslashes, so that they can be interpreted by Perl to specify characters
27380 whose code value is zero.
27382 &*Warning 1*&: If either of the user or password strings starts with an octal
27383 digit, you must use three zeros instead of one after the leading backslash. If
27384 you do not, the octal digit that starts your string will be incorrectly
27385 interpreted as part of the code for the first character.
27387 &*Warning 2*&: If there are characters in the strings that Perl interprets
27388 specially, you must use a Perl escape to prevent them being misinterpreted. For
27389 example, a command such as
27391 encode '\0user@domain.com\0pas$$word'
27393 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
27395 If you have the &%mimencode%& command installed, another way to do produce
27396 base64-encoded strings is to run the command
27398 echo -e -n `\0user\0password' | mimencode
27400 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
27401 in the argument, and the &%-n%& option specifies no newline at the end of its
27402 output. However, not all versions of &%echo%& recognize these options, so you
27403 should check your version before relying on this suggestion.
27407 .section "Authentication by an Exim client" "SECID170"
27408 .cindex "authentication" "on an Exim client"
27409 The &(smtp)& transport has two options called &%hosts_require_auth%& and
27410 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
27411 announces support for authentication, and the host matches an entry in either
27412 of these options, Exim (as a client) tries to authenticate as follows:
27415 For each authenticator that is configured as a client, in the order in which
27416 they are defined in the configuration, it searches the authentication
27417 mechanisms announced by the server for one whose name matches the public name
27418 of the authenticator.
27421 .vindex "&$host_address$&"
27422 When it finds one that matches, it runs the authenticator's client code. The
27423 variables &$host$& and &$host_address$& are available for any string expansions
27424 that the client might do. They are set to the server's name and IP address. If
27425 any expansion is forced to fail, the authentication attempt is abandoned, and
27426 Exim moves on to the next authenticator. Otherwise an expansion failure causes
27427 delivery to be deferred.
27429 If the result of the authentication attempt is a temporary error or a timeout,
27430 Exim abandons trying to send the message to the host for the moment. It will
27431 try again later. If there are any backup hosts available, they are tried in the
27434 If the response to authentication is a permanent error (5&'xx'& code), Exim
27435 carries on searching the list of authenticators and tries another one if
27436 possible. If all authentication attempts give permanent errors, or if there are
27437 no attempts because no mechanisms match (or option expansions force failure),
27438 what happens depends on whether the host matches &%hosts_require_auth%& or
27439 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
27440 delivery is deferred. The error can be detected in the retry rules, and thereby
27441 turned into a permanent error if you wish. In the second case, Exim tries to
27442 deliver the message unauthenticated.
27445 Note that the hostlist test for whether to do authentication can be
27446 confused if name-IP lookups change between the time the peer is decided
27447 upon and the time that the transport runs. For example, with a manualroute
27448 router given a host name, and with DNS "round-robin" used by that name: if
27449 the local resolver cache times out between the router and the transport
27450 running, the transport may get an IP for the name for its authentication
27451 check which does not match the connection peer IP.
27452 No authentication will then be done, despite the names being identical.
27454 For such cases use a separate transport which always authenticates.
27456 .cindex "AUTH" "on MAIL command"
27457 When Exim has authenticated itself to a remote server, it adds the AUTH
27458 parameter to the MAIL commands it sends, if it has an authenticated sender for
27459 the message. If the message came from a remote host, the authenticated sender
27460 is the one that was receiving on an incoming MAIL command, provided that the
27461 incoming connection was authenticated and the &%server_mail_auth%& condition
27462 allowed the authenticated sender to be retained. If a local process calls Exim
27463 to send a message, the sender address that is built from the login name and
27464 &%qualify_domain%& is treated as authenticated. However, if the
27465 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
27466 the authenticated sender that was received with the message.
27467 .ecindex IIDauthconf1
27468 .ecindex IIDauthconf2
27475 . ////////////////////////////////////////////////////////////////////////////
27476 . ////////////////////////////////////////////////////////////////////////////
27478 .chapter "The plaintext authenticator" "CHAPplaintext"
27479 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
27480 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
27481 The &(plaintext)& authenticator can be configured to support the PLAIN and
27482 LOGIN authentication mechanisms, both of which transfer authentication data as
27483 plain (unencrypted) text (though base64 encoded). The use of plain text is a
27484 security risk; you are strongly advised to insist on the use of SMTP encryption
27485 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
27486 use unencrypted plain text, you should not use the same passwords for SMTP
27487 connections as you do for login accounts.
27489 .section "Avoiding cleartext use" "SECTplain_TLS"
27490 The following generic option settings will disable &(plaintext)& authenticators when
27491 TLS is not being used:
27493 server_advertise_condition = ${if def:tls_in_cipher }
27494 client_condition = ${if def:tls_out_cipher}
27497 &*Note*&: a plaintext SMTP AUTH done inside TLS is not vulnerable to casual snooping,
27498 but is still vulnerable to a Man In The Middle attack unless certificates
27499 (including their names) have been properly verified.
27501 .section "Plaintext server options" "SECID171"
27502 .cindex "options" "&(plaintext)& authenticator (server)"
27503 When configured as a server, &(plaintext)& uses the following options:
27505 .option server_condition authenticators string&!! unset
27506 This is actually a global authentication option, but it must be set in order to
27507 configure the &(plaintext)& driver as a server. Its use is described below.
27509 .option server_prompts plaintext "string list&!!" unset
27510 The contents of this option, after expansion, must be a colon-separated list of
27511 prompt strings. If expansion fails, a temporary authentication rejection is
27514 .section "Using plaintext in a server" "SECTplainserver"
27515 .cindex "AUTH" "in &(plaintext)& authenticator"
27516 .cindex "binary zero" "in &(plaintext)& authenticator"
27517 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
27518 "in &(plaintext)& authenticator"
27519 .vindex "&$auth1$&, &$auth2$&, etc"
27520 .cindex "base64 encoding" "in &(plaintext)& authenticator"
27522 When running as a server, &(plaintext)& performs the authentication test by
27523 expanding a string. The data sent by the client with the AUTH command, or in
27524 response to subsequent prompts, is base64 encoded, and so may contain any byte
27525 values when decoded. If any data is supplied with the command, it is treated as
27526 a list of strings, separated by NULs (binary zeros), the first three of which
27527 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
27528 (neither LOGIN nor PLAIN uses more than three strings).
27530 For compatibility with previous releases of Exim, the values are also placed in
27531 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
27532 variables for this purpose is now deprecated, as it can lead to confusion in
27533 string expansions that also use them for other things.
27535 If there are more strings in &%server_prompts%& than the number of strings
27536 supplied with the AUTH command, the remaining prompts are used to obtain more
27537 data. Each response from the client may be a list of NUL-separated strings.
27539 .vindex "&$authenticated_id$&"
27540 Once a sufficient number of data strings have been received,
27541 &%server_condition%& is expanded. If the expansion is forced to fail,
27542 authentication fails. Any other expansion failure causes a temporary error code
27543 to be returned. If the result of a successful expansion is an empty string,
27544 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
27545 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
27546 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
27547 For any other result, a temporary error code is returned, with the expanded
27548 string as the error text.
27550 &*Warning*&: If you use a lookup in the expansion to find the user's
27551 password, be sure to make the authentication fail if the user is unknown.
27552 There are good and bad examples at the end of the next section.
27556 .section "The PLAIN authentication mechanism" "SECID172"
27557 .cindex "PLAIN authentication mechanism"
27558 .cindex authentication PLAIN
27559 .cindex "binary zero" "in &(plaintext)& authenticator"
27560 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
27561 sent as one item of data (that is, one combined string containing two NUL
27562 separators). The data is sent either as part of the AUTH command, or
27563 subsequently in response to an empty prompt from the server.
27565 The second and third strings are a user name and a corresponding password.
27566 Using a single fixed user name and password as an example, this could be
27567 configured as follows:
27571 public_name = PLAIN
27573 server_condition = \
27574 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
27575 server_set_id = $auth2
27577 Note that the default result strings from &%if%& (&"true"& or an empty string)
27578 are exactly what we want here, so they need not be specified. Obviously, if the
27579 password contains expansion-significant characters such as dollar, backslash,
27580 or closing brace, they have to be escaped.
27582 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
27583 the end of a string list are ignored). If all the data comes as part of the
27584 AUTH command, as is commonly the case, the prompt is not used. This
27585 authenticator is advertised in the response to EHLO as
27589 and a client host can authenticate itself by sending the command
27591 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
27593 As this contains three strings (more than the number of prompts), no further
27594 data is required from the client. Alternatively, the client may just send
27598 to initiate authentication, in which case the server replies with an empty
27599 prompt. The client must respond with the combined data string.
27601 The data string is base64 encoded, as required by the RFC. This example,
27602 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
27603 represents a zero byte. This is split up into three strings, the first of which
27604 is empty. The &%server_condition%& option in the authenticator checks that the
27605 second two are &`username`& and &`mysecret`& respectively.
27607 Having just one fixed user name and password, as in this example, is not very
27608 realistic, though for a small organization with only a handful of
27609 authenticating clients it could make sense.
27611 A more sophisticated instance of this authenticator could use the user name in
27612 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
27613 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
27614 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
27615 This is an incorrect example:
27617 server_condition = \
27618 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
27620 The expansion uses the user name (&$auth2$&) as the key to look up a password,
27621 which it then compares to the supplied password (&$auth3$&). Why is this example
27622 incorrect? It works fine for existing users, but consider what happens if a
27623 non-existent user name is given. The lookup fails, but as no success/failure
27624 strings are given for the lookup, it yields an empty string. Thus, to defeat
27625 the authentication, all a client has to do is to supply a non-existent user
27626 name and an empty password. The correct way of writing this test is:
27628 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
27629 {${if eq{$value}{$auth3}}} {false}}
27631 In this case, if the lookup succeeds, the result is checked; if the lookup
27632 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
27633 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
27634 always fails if its second argument is empty. However, the second way of
27635 writing the test makes the logic clearer.
27638 .section "The LOGIN authentication mechanism" "SECID173"
27639 .cindex "LOGIN authentication mechanism"
27640 .cindex authentication LOGIN
27641 The LOGIN authentication mechanism is not documented in any RFC, but is in use
27642 in a number of programs. No data is sent with the AUTH command. Instead, a
27643 user name and password are supplied separately, in response to prompts. The
27644 plaintext authenticator can be configured to support this as in this example:
27648 public_name = LOGIN
27649 server_prompts = User Name : Password
27650 server_condition = \
27651 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
27652 server_set_id = $auth1
27654 Because of the way plaintext operates, this authenticator accepts data supplied
27655 with the AUTH command (in contravention of the specification of LOGIN), but
27656 if the client does not supply it (as is the case for LOGIN clients), the prompt
27657 strings are used to obtain two data items.
27659 Some clients are very particular about the precise text of the prompts. For
27660 example, Outlook Express is reported to recognize only &"Username:"& and
27661 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
27662 strings. It uses the &%ldapauth%& expansion condition to check the user
27663 name and password by binding to an LDAP server:
27667 public_name = LOGIN
27668 server_prompts = Username:: : Password::
27669 server_condition = ${if and{{ \
27672 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
27673 pass=${quote:$auth2} \
27674 ldap://ldap.example.org/} }} }
27675 server_set_id = uid=$auth1,ou=people,o=example.org
27677 We have to check that the username is not empty before using it, because LDAP
27678 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
27679 operator to correctly quote the DN for authentication. However, the basic
27680 &%quote%& operator, rather than any of the LDAP quoting operators, is the
27681 correct one to use for the password, because quoting is needed only to make
27682 the password conform to the Exim syntax. At the LDAP level, the password is an
27683 uninterpreted string.
27686 .section "Support for different kinds of authentication" "SECID174"
27687 A number of string expansion features are provided for the purpose of
27688 interfacing to different ways of user authentication. These include checking
27689 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
27690 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
27696 .section "Using plaintext in a client" "SECID175"
27697 .cindex "options" "&(plaintext)& authenticator (client)"
27698 The &(plaintext)& authenticator has two client options:
27700 .option client_ignore_invalid_base64 plaintext boolean false
27701 If the client receives a server prompt that is not a valid base64 string,
27702 authentication is abandoned by default. However, if this option is set true,
27703 the error in the challenge is ignored and the client sends the response as
27706 .option client_send plaintext string&!! unset
27707 The string is a colon-separated list of authentication data strings. Each
27708 string is independently expanded before being sent to the server. The first
27709 string is sent with the AUTH command; any more strings are sent in response
27710 to prompts from the server. Before each string is expanded, the value of the
27711 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
27712 with &$auth1$& for the first prompt. Up to three prompts are stored in this
27713 way. Thus, the prompt that is received in response to sending the first string
27714 (with the AUTH command) can be used in the expansion of the second string, and
27715 so on. If an invalid base64 string is received when
27716 &%client_ignore_invalid_base64%& is set, an empty string is put in the
27717 &$auth$&<&'n'&> variable.
27719 &*Note*&: You cannot use expansion to create multiple strings, because
27720 splitting takes priority and happens first.
27722 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
27723 the data, further processing is applied to each string before it is sent. If
27724 there are any single circumflex characters in the string, they are converted to
27725 NULs. Should an actual circumflex be required as data, it must be doubled in
27728 This is an example of a client configuration that implements the PLAIN
27729 authentication mechanism with a fixed user name and password:
27733 public_name = PLAIN
27734 client_send = ^username^mysecret
27736 The lack of colons means that the entire text is sent with the AUTH
27737 command, with the circumflex characters converted to NULs. A similar example
27738 that uses the LOGIN mechanism is:
27742 public_name = LOGIN
27743 client_send = : username : mysecret
27745 The initial colon means that the first string is empty, so no data is sent with
27746 the AUTH command itself. The remaining strings are sent in response to
27748 .ecindex IIDplaiauth1
27749 .ecindex IIDplaiauth2
27754 . ////////////////////////////////////////////////////////////////////////////
27755 . ////////////////////////////////////////////////////////////////////////////
27757 .chapter "The cram_md5 authenticator" "CHID9"
27758 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
27759 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
27760 .cindex "CRAM-MD5 authentication mechanism"
27761 .cindex authentication CRAM-MD5
27762 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
27763 sends a challenge string to the client, and the response consists of a user
27764 name and the CRAM-MD5 digest of the challenge string combined with a secret
27765 string (password) which is known to both server and client. Thus, the secret
27766 is not sent over the network as plain text, which makes this authenticator more
27767 secure than &(plaintext)&. However, the downside is that the secret has to be
27768 available in plain text at either end.
27771 .section "Using cram_md5 as a server" "SECID176"
27772 .cindex "options" "&(cram_md5)& authenticator (server)"
27773 This authenticator has one server option, which must be set to configure the
27774 authenticator as a server:
27776 .option server_secret cram_md5 string&!! unset
27777 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
27778 When the server receives the client's response, the user name is placed in
27779 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
27780 obtain the password for that user. The server then computes the CRAM-MD5 digest
27781 that the client should have sent, and checks that it received the correct
27782 string. If the expansion of &%server_secret%& is forced to fail, authentication
27783 fails. If the expansion fails for some other reason, a temporary error code is
27784 returned to the client.
27786 For compatibility with previous releases of Exim, the user name is also placed
27787 in &$1$&. However, the use of this variables for this purpose is now
27788 deprecated, as it can lead to confusion in string expansions that also use
27789 numeric variables for other things.
27791 For example, the following authenticator checks that the user name given by the
27792 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
27793 user name, authentication fails.
27797 public_name = CRAM-MD5
27798 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
27799 server_set_id = $auth1
27801 .vindex "&$authenticated_id$&"
27802 If authentication succeeds, the setting of &%server_set_id%& preserves the user
27803 name in &$authenticated_id$&. A more typical configuration might look up the
27804 secret string in a file, using the user name as the key. For example:
27808 public_name = CRAM-MD5
27809 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
27811 server_set_id = $auth1
27813 Note that this expansion explicitly forces failure if the lookup fails
27814 because &$auth1$& contains an unknown user name.
27816 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
27817 using the relevant libraries, you need to know the realm to specify in the
27818 lookup and then ask for the &"userPassword"& attribute for that user in that
27823 public_name = CRAM-MD5
27824 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
27825 dbmjz{/etc/sasldb2}{$value}fail}
27826 server_set_id = $auth1
27829 .section "Using cram_md5 as a client" "SECID177"
27830 .cindex "options" "&(cram_md5)& authenticator (client)"
27831 When used as a client, the &(cram_md5)& authenticator has two options:
27835 .option client_name cram_md5 string&!! "the primary host name"
27836 This string is expanded, and the result used as the user name data when
27837 computing the response to the server's challenge.
27840 .option client_secret cram_md5 string&!! unset
27841 This option must be set for the authenticator to work as a client. Its value is
27842 expanded and the result used as the secret string when computing the response.
27846 .vindex "&$host_address$&"
27847 Different user names and secrets can be used for different servers by referring
27848 to &$host$& or &$host_address$& in the options. Forced failure of either
27849 expansion string is treated as an indication that this authenticator is not
27850 prepared to handle this case. Exim moves on to the next configured client
27851 authenticator. Any other expansion failure causes Exim to give up trying to
27852 send the message to the current server.
27854 A simple example configuration of a &(cram_md5)& authenticator, using fixed
27859 public_name = CRAM-MD5
27861 client_secret = secret
27863 .ecindex IIDcramauth1
27864 .ecindex IIDcramauth2
27868 . ////////////////////////////////////////////////////////////////////////////
27869 . ////////////////////////////////////////////////////////////////////////////
27871 .chapter "The cyrus_sasl authenticator" "CHID10"
27872 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
27873 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
27874 .cindex "Cyrus" "SASL library"
27876 The code for this authenticator was provided by Matthew Byng-Maddick while
27877 at A L Digital Ltd.
27879 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
27880 library implementation of the RFC 2222 (&"Simple Authentication and Security
27881 Layer"&). This library supports a number of authentication mechanisms,
27882 including PLAIN and LOGIN, but also several others that Exim does not support
27883 directly. In particular, there is support for Kerberos authentication.
27885 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
27886 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
27887 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
27888 name of the driver to determine which mechanism to support.
27890 Where access to some kind of secret file is required, for example, in GSSAPI
27891 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
27892 user, and that the Cyrus SASL library has no way of escalating privileges
27893 by default. You may also find you need to set environment variables,
27894 depending on the driver you are using.
27896 The application name provided by Exim is &"exim"&, so various SASL options may
27897 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
27898 Kerberos, note that because of limitations in the GSSAPI interface,
27899 changing the server keytab might need to be communicated down to the Kerberos
27900 layer independently. The mechanism for doing so is dependent upon the Kerberos
27903 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
27904 may be set to point to an alternative keytab file. Exim will pass this
27905 variable through from its own inherited environment when started as root or the
27906 Exim user. The keytab file needs to be readable by the Exim user.
27907 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
27908 environment variable. In practice, for those releases, the Cyrus authenticator
27909 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
27910 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
27913 .section "Using cyrus_sasl as a server" "SECID178"
27914 The &(cyrus_sasl)& authenticator has four private options. It puts the username
27915 (on a successful authentication) into &$auth1$&. For compatibility with
27916 previous releases of Exim, the username is also placed in &$1$&. However, the
27917 use of this variable for this purpose is now deprecated, as it can lead to
27918 confusion in string expansions that also use numeric variables for other
27922 .option server_hostname cyrus_sasl string&!! "see below"
27923 This option selects the hostname that is used when communicating with the
27924 library. The default value is &`$primary_hostname`&. It is up to the underlying
27925 SASL plug-in what it does with this data.
27928 .option server_mech cyrus_sasl string "see below"
27929 This option selects the authentication mechanism this driver should use. The
27930 default is the value of the generic &%public_name%& option. This option allows
27931 you to use a different underlying mechanism from the advertised name. For
27935 driver = cyrus_sasl
27936 public_name = X-ANYTHING
27937 server_mech = CRAM-MD5
27938 server_set_id = $auth1
27941 .option server_realm cyrus_sasl string&!! unset
27942 This specifies the SASL realm that the server claims to be in.
27945 .option server_service cyrus_sasl string &`smtp`&
27946 This is the SASL service that the server claims to implement.
27949 For straightforward cases, you do not need to set any of the authenticator's
27950 private options. All you need to do is to specify an appropriate mechanism as
27951 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
27952 PLAIN, you could have two authenticators as follows:
27955 driver = cyrus_sasl
27956 public_name = CRAM-MD5
27957 server_set_id = $auth1
27960 driver = cyrus_sasl
27961 public_name = PLAIN
27962 server_set_id = $auth2
27964 Cyrus SASL does implement the LOGIN authentication method, even though it is
27965 not a standard method. It is disabled by default in the source distribution,
27966 but it is present in many binary distributions.
27967 .ecindex IIDcyrauth1
27968 .ecindex IIDcyrauth2
27973 . ////////////////////////////////////////////////////////////////////////////
27974 . ////////////////////////////////////////////////////////////////////////////
27975 .chapter "The dovecot authenticator" "CHAPdovecot"
27976 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
27977 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
27978 This authenticator is an interface to the authentication facility of the
27979 Dovecot 2 POP/IMAP server, which can support a number of authentication methods.
27980 Note that Dovecot must be configured to use auth-client not auth-userdb.
27981 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
27982 to use the same mechanisms for SMTP authentication. This is a server
27983 authenticator only. There is only one option:
27985 .option server_socket dovecot string unset
27987 This option must specify the UNIX socket that is the interface to Dovecot
27988 authentication. The &%public_name%& option must specify an authentication
27989 mechanism that Dovecot is configured to support. You can have several
27990 authenticators for different mechanisms. For example:
27994 public_name = PLAIN
27995 server_socket = /var/run/dovecot/auth-client
27996 server_set_id = $auth1
28001 server_socket = /var/run/dovecot/auth-client
28002 server_set_id = $auth1
28004 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
28005 &$received_ip_address$& (that is, the connection is local), the &"secured"&
28006 option is passed in the Dovecot authentication command. If, for a TLS
28007 connection, a client certificate has been verified, the &"valid-client-cert"&
28008 option is passed. When authentication succeeds, the identity of the user
28009 who authenticated is placed in &$auth1$&.
28011 The Dovecot configuration to match the above wil look
28014 conf.d/10-master.conf :-
28019 unix_listener auth-client {
28026 conf.d/10-auth.conf :-
28028 auth_mechanisms = plain login ntlm
28031 .ecindex IIDdcotauth1
28032 .ecindex IIDdcotauth2
28035 . ////////////////////////////////////////////////////////////////////////////
28036 . ////////////////////////////////////////////////////////////////////////////
28037 .chapter "The gsasl authenticator" "CHAPgsasl"
28038 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
28039 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
28040 .cindex "authentication" "GNU SASL"
28041 .cindex "authentication" "SASL"
28042 .cindex "authentication" "EXTERNAL"
28043 .cindex "authentication" "ANONYMOUS"
28044 .cindex "authentication" "PLAIN"
28045 .cindex "authentication" "LOGIN"
28046 .cindex "authentication" "DIGEST-MD5"
28047 .cindex "authentication" "CRAM-MD5"
28048 .cindex "authentication" "SCRAM family"
28049 The &(gsasl)& authenticator provides integration for the GNU SASL
28050 library and the mechanisms it provides. This is new as of the 4.80 release
28051 and there are a few areas where the library does not let Exim smoothly
28052 scale to handle future authentication mechanisms, so no guarantee can be
28053 made that any particular new authentication mechanism will be supported
28054 without code changes in Exim.
28056 The library is expected to add support in an upcoming
28057 realease for the SCRAM-SHA-256 method.
28058 The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
28062 .option client_authz gsasl string&!! unset
28063 This option can be used to supply an &'authorization id'&
28064 which is different to the &'authentication_id'& provided
28065 by &%client_username%& option.
28066 If unset or (after expansion) empty it is not used,
28067 which is the common case.
28069 .option client_channelbinding gsasl boolean false
28070 See &%server_channelbinding%& below.
28072 .option client_password gsasl string&!! unset
28073 This option is exapanded before use, and should result in
28074 the password to be used, in clear.
28076 .option client_username gsasl string&!! unset
28077 This option is exapanded before use, and should result in
28078 the account name to be used.
28080 .option client_spassword gsasl string&!! unset
28081 If a SCRAM mechanism is being used and this option is set
28082 it is used in preference to &%client_password%&.
28083 The value after expansion should be
28084 a 40 (for SHA-1) or 64 (for SHA-256) character string
28085 with the PBKDF2-prepared password, hex-encoded.
28086 Note that this value will depend on the salt and iteration-count
28087 supplied by the server.
28091 .option server_channelbinding gsasl boolean false
28092 Do not set this true and rely on the properties
28093 without consulting a cryptographic engineer.
28095 Some authentication mechanisms are able to use external context at both ends
28096 of the session to bind the authentication to that context, and fail the
28097 authentication process if that context differs. Specifically, some TLS
28098 ciphersuites can provide identifying information about the cryptographic
28101 This should have meant that certificate identity and verification becomes a
28102 non-issue, as a man-in-the-middle attack will cause the correct client and
28103 server to see different identifiers and authentication will fail.
28106 only usable by mechanisms which support "channel binding"; at time of
28107 writing, that's the SCRAM family.
28108 When using this feature the "-PLUS" variants of the method names need to be used.
28110 This defaults off to ensure smooth upgrade across Exim releases, in case
28111 this option causes some clients to start failing. Some future release
28112 of Exim might have switched the default to be true.
28114 However, Channel Binding in TLS has proven to be vulnerable in current versions.
28115 Do not plan to rely upon this feature for security, ever, without consulting
28116 with a subject matter expert (a cryptographic engineer).
28119 .option server_hostname gsasl string&!! "see below"
28120 This option selects the hostname that is used when communicating with the
28121 library. The default value is &`$primary_hostname`&.
28122 Some mechanisms will use this data.
28125 .option server_mech gsasl string "see below"
28126 This option selects the authentication mechanism this driver should use. The
28127 default is the value of the generic &%public_name%& option. This option allows
28128 you to use a different underlying mechanism from the advertised name. For
28133 public_name = X-ANYTHING
28134 server_mech = CRAM-MD5
28135 server_set_id = $auth1
28139 .option server_password gsasl string&!! unset
28140 Various mechanisms need access to the cleartext password on the server, so
28141 that proof-of-possession can be demonstrated on the wire, without sending
28142 the password itself.
28144 The data available for lookup varies per mechanism.
28145 In all cases, &$auth1$& is set to the &'authentication id'&.
28146 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
28147 if available, else the empty string.
28148 The &$auth3$& variable will always be the &'realm'& if available,
28149 else the empty string.
28151 A forced failure will cause authentication to defer.
28153 If using this option, it may make sense to set the &%server_condition%&
28154 option to be simply "true".
28157 .option server_realm gsasl string&!! unset
28158 This specifies the SASL realm that the server claims to be in.
28159 Some mechanisms will use this data.
28162 .option server_scram_iter gsasl string&!! 4096
28163 This option provides data for the SCRAM family of mechanisms.
28164 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28165 when this option is expanded.
28167 The result of expansion should be a decimal number,
28168 and represents both a lower-bound on the security, and
28169 a compute cost factor imposed on the client
28170 (if it does not cache results, or the server changes
28171 either the iteration count or the salt).
28172 A minimum value of 4096 is required by the standards
28173 for all current SCRAM mechanism variants.
28175 .option server_scram_salt gsasl string&!! unset
28176 This option provides data for the SCRAM family of mechanisms.
28177 The &$auth1$&, &$auth2$& and &$auth3$& variables are available
28178 when this option is expanded.
28179 The value should be a base64-encoded string,
28180 of random data typically 4-to-16 bytes long.
28181 If unset or empty after expansion the library will provides a value for the
28182 protocol conversation.
28185 .option server_key gsasl string&!! unset
28186 .option server_skey gsasl string&!! unset
28187 These options can be used for the SCRAM family of mechanisms
28188 to provide stored information related to a password,
28189 the storage of which is preferable to plaintext.
28191 &%server_key%& is the value defined in the SCRAM standards as ServerKey;
28192 &%server_skey%& is StoredKey.
28194 They are only available for version 1.9.0 (or later) of the gsasl library.
28195 When this is so, the macros
28196 _OPT_AUTHENTICATOR_GSASL_SERVER_KEY
28197 and _HAVE_AUTH_GSASL_SCRAM_S_KEY
28200 The &$authN$& variables are available when these options are expanded.
28202 If set, the results of expansion should for each
28203 should be a 28 (for SHA-1) or 44 (for SHA-256) character string
28204 of base64-coded data, and will be used in preference to the
28205 &%server_password%& option.
28206 If unset or not of the right length, &%server_password%& will be used.
28208 The libgsasl library release includes a utility &'gsasl'& which can be used
28209 to generate these values.
28212 .option server_service gsasl string &`smtp`&
28213 This is the SASL service that the server claims to implement.
28214 Some mechanisms will use this data.
28217 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
28218 .vindex "&$auth1$&, &$auth2$&, etc"
28219 These may be set when evaluating specific options, as detailed above.
28220 They will also be set when evaluating &%server_condition%&.
28222 Unless otherwise stated below, the &(gsasl)& integration will use the following
28223 meanings for these variables:
28226 .vindex "&$auth1$&"
28227 &$auth1$&: the &'authentication id'&
28229 .vindex "&$auth2$&"
28230 &$auth2$&: the &'authorization id'&
28232 .vindex "&$auth3$&"
28233 &$auth3$&: the &'realm'&
28236 On a per-mechanism basis:
28239 .cindex "authentication" "EXTERNAL"
28240 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
28241 the &%server_condition%& option must be present.
28243 .cindex "authentication" "ANONYMOUS"
28244 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
28245 the &%server_condition%& option must be present.
28247 .cindex "authentication" "GSSAPI"
28248 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
28249 &$auth2$& will be set to the &'authorization id'&,
28250 the &%server_condition%& option must be present.
28253 An &'anonymous token'& is something passed along as an unauthenticated
28254 identifier; this is analogous to FTP anonymous authentication passing an
28255 email address, or software-identifier@, as the "password".
28258 An example showing the password having the realm specified in the callback
28259 and demonstrating a Cyrus SASL to GSASL migration approach is:
28261 gsasl_cyrusless_crammd5:
28263 public_name = CRAM-MD5
28264 server_realm = imap.example.org
28265 server_password = ${lookup{$auth1:$auth3:userPassword}\
28266 dbmjz{/etc/sasldb2}{$value}fail}
28267 server_set_id = ${quote:$auth1}
28268 server_condition = yes
28272 . ////////////////////////////////////////////////////////////////////////////
28273 . ////////////////////////////////////////////////////////////////////////////
28275 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
28276 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
28277 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
28278 .cindex "authentication" "GSSAPI"
28279 .cindex "authentication" "Kerberos"
28280 The &(heimdal_gssapi)& authenticator provides server integration for the
28281 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
28284 .option server_hostname heimdal_gssapi string&!! "see below"
28285 This option selects the hostname that is used, with &%server_service%&,
28286 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
28287 identifier. The default value is &`$primary_hostname`&.
28289 .option server_keytab heimdal_gssapi string&!! unset
28290 If set, then Heimdal will not use the system default keytab (typically
28291 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
28292 The value should be a pathname, with no &"file:"& prefix.
28294 .option server_service heimdal_gssapi string&!! "smtp"
28295 This option specifies the service identifier used, in conjunction with
28296 &%server_hostname%&, for building the identifier for finding credentials
28300 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
28301 Beware that these variables will typically include a realm, thus will appear
28302 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
28303 not verified, so a malicious client can set it to anything.
28305 The &$auth1$& field should be safely trustable as a value from the Key
28306 Distribution Center. Note that these are not quite email addresses.
28307 Each identifier is for a role, and so the left-hand-side may include a
28308 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
28310 .vindex "&$auth1$&, &$auth2$&, etc"
28312 .vindex "&$auth1$&"
28313 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
28315 .vindex "&$auth2$&"
28316 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
28317 authentication. If that was empty, this will also be set to the
28322 . ////////////////////////////////////////////////////////////////////////////
28323 . ////////////////////////////////////////////////////////////////////////////
28325 .chapter "The spa authenticator" "CHAPspa"
28326 .scindex IIDspaauth1 "&(spa)& authenticator"
28327 .scindex IIDspaauth2 "authenticators" "&(spa)&"
28328 .cindex "authentication" "Microsoft Secure Password"
28329 .cindex "authentication" "NTLM"
28330 .cindex "Microsoft Secure Password Authentication"
28331 .cindex "NTLM authentication"
28332 The &(spa)& authenticator provides client support for Microsoft's &'Secure
28333 Password Authentication'& mechanism,
28334 which is also sometimes known as NTLM (NT LanMan). The code for client side of
28335 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
28336 taken from the Samba project (&url(https://www.samba.org/)). The code for the
28337 server side was subsequently contributed by Tom Kistner. The mechanism works as
28341 After the AUTH command has been accepted, the client sends an SPA
28342 authentication request based on the user name and optional domain.
28344 The server sends back a challenge.
28346 The client builds a challenge response which makes use of the user's password
28347 and sends it to the server, which then accepts or rejects it.
28350 Encryption is used to protect the password in transit.
28354 .section "Using spa as a server" "SECID179"
28355 .cindex "options" "&(spa)& authenticator (server)"
28356 The &(spa)& authenticator has just one server option:
28358 .option server_password spa string&!! unset
28359 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
28360 This option is expanded, and the result must be the cleartext password for the
28361 authenticating user, whose name is at this point in &$auth1$&. For
28362 compatibility with previous releases of Exim, the user name is also placed in
28363 &$1$&. However, the use of this variable for this purpose is now deprecated, as
28364 it can lead to confusion in string expansions that also use numeric variables
28365 for other things. For example:
28370 server_password = \
28371 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
28373 If the expansion is forced to fail, authentication fails. Any other expansion
28374 failure causes a temporary error code to be returned.
28380 .section "Using spa as a client" "SECID180"
28381 .cindex "options" "&(spa)& authenticator (client)"
28382 The &(spa)& authenticator has the following client options:
28386 .option client_domain spa string&!! unset
28387 This option specifies an optional domain for the authentication.
28390 .option client_password spa string&!! unset
28391 This option specifies the user's password, and must be set.
28394 .option client_username spa string&!! unset
28395 This option specifies the user name, and must be set. Here is an example of a
28396 configuration of this authenticator for use with the mail servers at
28402 client_username = msn/msn_username
28403 client_password = msn_plaintext_password
28404 client_domain = DOMAIN_OR_UNSET
28406 .ecindex IIDspaauth1
28407 .ecindex IIDspaauth2
28413 . ////////////////////////////////////////////////////////////////////////////
28414 . ////////////////////////////////////////////////////////////////////////////
28416 .chapter "The external authenticator" "CHAPexternauth"
28417 .scindex IIDexternauth1 "&(external)& authenticator"
28418 .scindex IIDexternauth2 "authenticators" "&(external)&"
28419 .cindex "authentication" "Client Certificate"
28420 .cindex "authentication" "X509"
28421 .cindex "Certificate-based authentication"
28422 The &(external)& authenticator provides support for
28423 authentication based on non-SMTP information.
28424 The specification is in RFC 4422 Appendix A
28425 (&url(https://tools.ietf.org/html/rfc4422)).
28426 It is only a transport and negotiation mechanism;
28427 the process of authentication is entirely controlled
28428 by the server configuration.
28430 The client presents an identity in-clear.
28431 It is probably wise for a server to only advertise,
28432 and for clients to only attempt,
28433 this authentication method on a secure (eg. under TLS) connection.
28435 One possible use, compatible with the
28436 K-9 Mail Andoid client (&url(https://k9mail.github.io/)),
28437 is for using X509 client certificates.
28439 It thus overlaps in function with the TLS authenticator
28440 (see &<<CHAPtlsauth>>&)
28441 but is a full SMTP SASL authenticator
28442 rather than being implicit for TLS-connection carried
28443 client certificates only.
28445 The examples and discussion in this chapter assume that
28446 client-certificate authentication is being done.
28448 The client must present a certificate,
28449 for which it must have been requested via the
28450 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28451 (see &<<CHAPTLS>>&).
28452 For authentication to be effective the certificate should be
28453 verifiable against a trust-anchor certificate known to the server.
28455 .section "External options" "SECTexternsoptions"
28456 .cindex "options" "&(external)& authenticator (server)"
28457 The &(external)& authenticator has two server options:
28459 .option server_param2 external string&!! unset
28460 .option server_param3 external string&!! unset
28461 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(external)& authenticator"
28462 These options are expanded before the &%server_condition%& option
28463 and the result are placed in &$auth2$& and &$auth3$& resectively.
28464 If the expansion is forced to fail, authentication fails. Any other expansion
28465 failure causes a temporary error code to be returned.
28467 They can be used to clarify the coding of a complex &%server_condition%&.
28469 .section "Using external in a server" "SECTexternserver"
28470 .cindex "AUTH" "in &(external)& authenticator"
28471 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
28472 "in &(external)& authenticator"
28473 .vindex "&$auth1$&, &$auth2$&, etc"
28474 .cindex "base64 encoding" "in &(external)& authenticator"
28476 When running as a server, &(external)& performs the authentication test by
28477 expanding a string. The data sent by the client with the AUTH command, or in
28478 response to subsequent prompts, is base64 encoded, and so may contain any byte
28479 values when decoded. The decoded value is treated as
28480 an identity for authentication and
28481 placed in the expansion variable &$auth1$&.
28483 For compatibility with previous releases of Exim, the value is also placed in
28484 the expansion variable &$1$&. However, the use of this
28485 variable for this purpose is now deprecated, as it can lead to confusion in
28486 string expansions that also use them for other things.
28488 .vindex "&$authenticated_id$&"
28489 Once an identity has been received,
28490 &%server_condition%& is expanded. If the expansion is forced to fail,
28491 authentication fails. Any other expansion failure causes a temporary error code
28492 to be returned. If the result of a successful expansion is an empty string,
28493 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
28494 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
28495 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
28496 For any other result, a temporary error code is returned, with the expanded
28497 string as the error text.
28501 ext_ccert_san_mail:
28503 public_name = EXTERNAL
28505 server_advertise_condition = $tls_in_certificate_verified
28506 server_param2 = ${certextract {subj_altname,mail,>:} \
28507 {$tls_in_peercert}}
28508 server_condition = ${if forany {$auth2} \
28509 {eq {$item}{$auth1}}}
28510 server_set_id = $auth1
28512 This accepts a client certificate that is verifiable against any
28513 of your configured trust-anchors
28514 (which usually means the full set of public CAs)
28515 and which has a mail-SAN matching the claimed identity sent by the client.
28517 &*Note*&: up to TLS1.2, the client cert is on the wire in-clear, including the SAN.
28518 The account name is therefore guessable by an opponent.
28519 TLS 1.3 protects both server and client certificates, and is not vulnerable
28523 .section "Using external in a client" "SECTexternclient"
28524 .cindex "options" "&(external)& authenticator (client)"
28525 The &(external)& authenticator has one client option:
28527 .option client_send external string&!! unset
28528 This option is expanded and sent with the AUTH command as the
28529 identity being asserted.
28535 public_name = EXTERNAL
28537 client_condition = ${if !eq{$tls_out_cipher}{}}
28538 client_send = myaccount@smarthost.example.net
28542 .ecindex IIDexternauth1
28543 .ecindex IIDexternauth2
28549 . ////////////////////////////////////////////////////////////////////////////
28550 . ////////////////////////////////////////////////////////////////////////////
28552 .chapter "The tls authenticator" "CHAPtlsauth"
28553 .scindex IIDtlsauth1 "&(tls)& authenticator"
28554 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
28555 .cindex "authentication" "Client Certificate"
28556 .cindex "authentication" "X509"
28557 .cindex "Certificate-based authentication"
28558 The &(tls)& authenticator provides server support for
28559 authentication based on client certificates.
28561 It is not an SMTP authentication mechanism and is not
28562 advertised by the server as part of the SMTP EHLO response.
28563 It is an Exim authenticator in the sense that it affects
28564 the protocol element of the log line, can be tested for
28565 by the &%authenticated%& ACL condition, and can set
28566 the &$authenticated_id$& variable.
28568 The client must present a verifiable certificate,
28569 for which it must have been requested via the
28570 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
28571 (see &<<CHAPTLS>>&).
28573 If an authenticator of this type is configured it is
28574 run before any SMTP-level communication is done,
28575 and can authenticate the connection.
28576 If it does, SMTP authentication is not offered.
28578 A maximum of one authenticator of this type may be present.
28581 .cindex "options" "&(tls)& authenticator (server)"
28582 The &(tls)& authenticator has three server options:
28584 .option server_param1 tls string&!! unset
28585 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
28586 This option is expanded after the TLS negotiation and
28587 the result is placed in &$auth1$&.
28588 If the expansion is forced to fail, authentication fails. Any other expansion
28589 failure causes a temporary error code to be returned.
28591 .option server_param2 tls string&!! unset
28592 .option server_param3 tls string&!! unset
28593 As above, for &$auth2$& and &$auth3$&.
28595 &%server_param1%& may also be spelled &%server_param%&.
28602 server_param1 = ${certextract {subj_altname,mail,>:} \
28603 {$tls_in_peercert}}
28604 server_condition = ${if and { {eq{$tls_in_certificate_verified}{1}} \
28607 {${lookup ldap{ldap:///\
28608 mailname=${quote_ldap_dn:${lc:$item}},\
28609 ou=users,LDAP_DC?mailid} {$value}{0} \
28611 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
28613 This accepts a client certificate that is verifiable against any
28614 of your configured trust-anchors
28615 (which usually means the full set of public CAs)
28616 and which has a SAN with a good account name.
28618 Note that, up to TLS1.2, the client cert is on the wire in-clear, including the SAN,
28619 The account name is therefore guessable by an opponent.
28620 TLS 1.3 protects both server and client certificates, and is not vulnerable
28622 Likewise, a traditional plaintext SMTP AUTH done inside TLS is not.
28624 . An alternative might use
28626 . server_param1 = ${sha256:$tls_in_peercert}
28628 . to require one of a set of specific certs that define a given account
28629 . (the verification is still required, but mostly irrelevant).
28630 . This would help for per-device use.
28632 . However, for the future we really need support for checking a
28633 . user cert in LDAP - which probably wants a base-64 DER.
28635 .ecindex IIDtlsauth1
28636 .ecindex IIDtlsauth2
28639 Note that because authentication is traditionally an SMTP operation,
28640 the &%authenticated%& ACL condition cannot be used in
28641 a connect- or helo-ACL.
28645 . ////////////////////////////////////////////////////////////////////////////
28646 . ////////////////////////////////////////////////////////////////////////////
28648 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
28649 "Encrypted SMTP connections"
28650 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
28651 .scindex IIDencsmtp2 "SMTP" "encryption"
28652 .cindex "TLS" "on SMTP connection"
28655 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
28656 Sockets Layer), is implemented by making use of the OpenSSL library or the
28657 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
28658 cryptographic code in the Exim distribution itself for implementing TLS. In
28659 order to use this feature you must install OpenSSL or GnuTLS, and then build a
28660 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
28661 You also need to understand the basic concepts of encryption at a managerial
28662 level, and in particular, the way that public keys, private keys, and
28663 certificates are used.
28665 RFC 3207 defines how SMTP connections can make use of encryption. Once a
28666 connection is established, the client issues a STARTTLS command. If the
28667 server accepts this, the client and the server negotiate an encryption
28668 mechanism. If the negotiation succeeds, the data that subsequently passes
28669 between them is encrypted.
28671 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
28672 and if so, what cipher suite is in use, whether the client supplied a
28673 certificate, and whether or not that certificate was verified. This makes it
28674 possible for an Exim server to deny or accept certain commands based on the
28677 &*Warning*&: Certain types of firewall and certain anti-virus products can
28678 disrupt TLS connections. You need to turn off SMTP scanning for these products
28679 in order to get TLS to work.
28683 .section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
28685 .cindex "submissions protocol"
28686 .cindex "ssmtp protocol"
28687 .cindex "smtps protocol"
28688 .cindex "SMTP" "submissions protocol"
28689 .cindex "SMTP" "ssmtp protocol"
28690 .cindex "SMTP" "smtps protocol"
28691 The history of port numbers for TLS in SMTP is a little messy and has been
28692 contentious. As of RFC 8314, the common practice of using the historically
28693 allocated port 465 for "email submission but with TLS immediately upon connect
28694 instead of using STARTTLS" is officially blessed by the IETF, and recommended
28695 by them in preference to STARTTLS.
28697 The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
28698 clarity emerged over the dual roles of SMTP, for MX delivery and Email
28699 Submission, nomenclature has shifted. The modern name is now &"submissions"&.
28701 This approach was, for a while, officially abandoned when encrypted SMTP was
28702 standardized, but many clients kept using it, even as the TCP port number was
28703 reassigned for other use.
28704 Thus you may encounter guidance claiming that you shouldn't enable use of
28706 In practice, a number of mail-clients have only ever supported submissions,
28707 not submission with STARTTLS upgrade.
28708 Ideally, offer both submission (587) and submissions (465) service.
28710 Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
28711 global option. Its value must be a list of port numbers;
28712 the most common use is expected to be:
28714 tls_on_connect_ports = 465
28716 The port numbers specified by this option apply to all SMTP connections, both
28717 via the daemon and via &'inetd'&. You still need to specify all the ports that
28718 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
28719 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
28720 an extra port &-- rather, it specifies different behaviour on a port that is
28723 There is also a &%-tls-on-connect%& command line option. This overrides
28724 &%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
28731 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
28732 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
28733 TLS is supported in Exim using either the OpenSSL or GnuTLS library.
28734 To build Exim to use OpenSSL you need to set
28740 To build Exim to use GnuTLS, you need to set
28746 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
28747 include files and libraries for GnuTLS can be found.
28749 There are some differences in usage when using GnuTLS instead of OpenSSL:
28752 The &%tls_verify_certificates%& option
28753 cannot be the path of a directory
28754 for GnuTLS versions before 3.3.6
28755 (for later versions, or OpenSSL, it can be either).
28757 The default value for &%tls_dhparam%& differs for historical reasons.
28759 .vindex "&$tls_in_peerdn$&"
28760 .vindex "&$tls_out_peerdn$&"
28761 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
28762 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
28763 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
28765 OpenSSL identifies cipher suites using hyphens as separators, for example:
28766 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
28767 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
28768 in a cipher list. To make life simpler, Exim changes underscores to hyphens
28769 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
28770 to handle its own older variants) when processing lists of cipher suites in the
28771 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
28774 The &%tls_require_ciphers%& options operate differently, as described in the
28775 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
28777 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
28778 When using OpenSSL, this option is ignored.
28779 (If an API is found to let OpenSSL be configured in this way,
28780 let the Exim Maintainers know and we'll likely use it).
28782 With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
28783 main option, it must be ordered to match the &%tls_certificate%& list.
28785 Some other recently added features may only be available in one or the other.
28786 This should be documented with the feature. If the documentation does not
28787 explicitly state that the feature is infeasible in the other TLS
28788 implementation, then patches are welcome.
28791 The output from "exim -bV" will show which (if any) support was included
28793 Also, the macro "_HAVE_OPENSSL" or "_HAVE_GNUTLS" will be defined.
28798 .section "GnuTLS parameter computation" "SECTgnutlsparam"
28799 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
28800 an explicit path; if the latter, then the text about generation still applies,
28801 but not the chosen filename.
28802 By default, as of Exim 4.80 a hard-coded D-H prime is used.
28803 See the documentation of &%tls_dhparam%& for more information.
28805 GnuTLS uses D-H parameters that may take a substantial amount of time
28806 to compute. It is unreasonable to re-compute them for every TLS session.
28807 Therefore, Exim keeps this data in a file in its spool directory, called
28808 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
28810 The file is owned by the Exim user and is readable only by
28811 its owner. Every Exim process that start up GnuTLS reads the D-H
28812 parameters from this file. If the file does not exist, the first Exim process
28813 that needs it computes the data and writes it to a temporary file which is
28814 renamed once it is complete. It does not matter if several Exim processes do
28815 this simultaneously (apart from wasting a few resources). Once a file is in
28816 place, new Exim processes immediately start using it.
28818 For maximum security, the parameters that are stored in this file should be
28819 recalculated periodically, the frequency depending on your paranoia level.
28820 If you are avoiding using the fixed D-H primes published in RFCs, then you
28821 are concerned about some advanced attacks and will wish to do this; if you do
28822 not regenerate then you might as well stick to the standard primes.
28824 Arranging this is easy in principle; just delete the file when you want new
28825 values to be computed. However, there may be a problem. The calculation of new
28826 parameters needs random numbers, and these are obtained from &_/dev/random_&.
28827 If the system is not very active, &_/dev/random_& may delay returning data
28828 until enough randomness (entropy) is available. This may cause Exim to hang for
28829 a substantial amount of time, causing timeouts on incoming connections.
28831 The solution is to generate the parameters externally to Exim. They are stored
28832 in &_gnutls-params-N_& in PEM format, which means that they can be
28833 generated externally using the &(certtool)& command that is part of GnuTLS.
28835 To replace the parameters with new ones, instead of deleting the file
28836 and letting Exim re-create it, you can generate new parameters using
28837 &(certtool)& and, when this has been done, replace Exim's cache file by
28838 renaming. The relevant commands are something like this:
28841 [ look for file; assume gnutls-params-2236 is the most recent ]
28844 # chown exim:exim new-params
28845 # chmod 0600 new-params
28846 # certtool --generate-dh-params --bits 2236 >>new-params
28847 # openssl dhparam -noout -text -in new-params | head
28848 [ check the first line, make sure it's not more than 2236;
28849 if it is, then go back to the start ("rm") and repeat
28850 until the size generated is at most the size requested ]
28851 # chmod 0400 new-params
28852 # mv new-params gnutls-params-2236
28854 If Exim never has to generate the parameters itself, the possibility of
28855 stalling is removed.
28857 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
28858 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
28859 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
28860 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
28861 and Exim does so. This attempt to remove Exim from TLS policy decisions
28862 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
28863 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
28864 which applies to all D-H usage, client or server. If the value returned by
28865 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
28866 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
28867 limit, which is still much higher than Exim historically used.
28869 The filename and bits used will change as the GnuTLS maintainers change the
28870 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
28871 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
28872 2432 bits, while NSS is limited to 2236 bits.
28874 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
28875 increase the chance of the generated prime actually being within acceptable
28876 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
28877 procedure above. There is no sane procedure available to Exim to double-check
28878 the size of the generated prime, so it might still be too large.
28881 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
28882 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
28883 .oindex "&%tls_require_ciphers%&" "OpenSSL"
28884 There is a function in the OpenSSL library that can be passed a list of cipher
28885 suites before the cipher negotiation takes place. This specifies which ciphers
28886 are acceptable for TLS versions prior to 1.3.
28887 The list is colon separated and may contain names like
28888 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
28889 directly to this function call.
28890 Many systems will install the OpenSSL manual-pages, so you may have
28891 &'ciphers(1)'& available to you.
28892 The following quotation from the OpenSSL
28893 documentation specifies what forms of item are allowed in the cipher string:
28896 It can consist of a single cipher suite such as RC4-SHA.
28898 It can represent a list of cipher suites containing a certain algorithm,
28899 or cipher suites of a certain type. For example SHA1 represents all
28900 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
28903 Lists of cipher suites can be combined in a single cipher string using
28904 the + character. This is used as a logical and operation. For example
28905 SHA1+DES represents all cipher suites containing the SHA1 and the DES
28909 Each cipher string can be optionally preceded by one of the characters &`!`&,
28912 If &`!`& is used, the ciphers are permanently deleted from the list. The
28913 ciphers deleted can never reappear in the list even if they are explicitly
28916 If &`-`& is used, the ciphers are deleted from the list, but some or all
28917 of the ciphers can be added again by later options.
28919 If &`+`& is used, the ciphers are moved to the end of the list. This
28920 option does not add any new ciphers; it just moves matching existing ones.
28923 If none of these characters is present, the string is interpreted as
28924 a list of ciphers to be appended to the current preference list. If the list
28925 includes any ciphers already present they will be ignored: that is, they will
28926 not be moved to the end of the list.
28929 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
28932 # note single-quotes to get ! past any shell history expansion
28933 $ openssl ciphers 'HIGH:!MD5:!SHA1'
28936 This example will let the library defaults be permitted on the MX port, where
28937 there's probably no identity verification anyway, but ups the ante on the
28938 submission ports where the administrator might have some influence on the
28939 choice of clients used:
28941 # OpenSSL variant; see man ciphers(1)
28942 tls_require_ciphers = ${if =={$received_port}{25}\
28947 This example will prefer ECDSA-authenticated ciphers over RSA ones:
28949 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
28952 For TLS version 1.3 the control available is less fine-grained
28953 and Exim does not provide access to it at present.
28954 The value of the &%tls_require_ciphers%& option is ignored when
28955 TLS version 1.3 is negotiated.
28957 As of writing the library default cipher suite list for TLSv1.3 is
28959 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
28963 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
28965 .cindex "GnuTLS" "specifying parameters for"
28966 .cindex "TLS" "specifying ciphers (GnuTLS)"
28967 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
28968 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
28969 .cindex "TLS" "specifying protocols (GnuTLS)"
28970 .cindex "TLS" "specifying priority string (GnuTLS)"
28971 .oindex "&%tls_require_ciphers%&" "GnuTLS"
28972 The GnuTLS library allows the caller to provide a "priority string", documented
28973 as part of the &[gnutls_priority_init]& function. This is very similar to the
28974 ciphersuite specification in OpenSSL.
28976 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
28977 and controls both protocols and ciphers.
28979 The &%tls_require_ciphers%& option is available both as an global option,
28980 controlling how Exim behaves as a server, and also as an option of the
28981 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
28982 the value is string expanded. The resulting string is not an Exim list and
28983 the string is given to the GnuTLS library, so that Exim does not need to be
28984 aware of future feature enhancements of GnuTLS.
28986 Documentation of the strings accepted may be found in the GnuTLS manual, under
28987 "Priority strings". This is online as
28988 &url(https://www.gnutls.org/manual/html_node/Priority-Strings.html),
28989 but beware that this relates to GnuTLS 3, which may be newer than the version
28990 installed on your system. If you are using GnuTLS 3,
28991 then the example code
28992 &url(https://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
28993 on that site can be used to test a given string.
28997 # Disable older versions of protocols
28998 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
29001 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
29002 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
29003 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
29005 This example will let the library defaults be permitted on the MX port, where
29006 there's probably no identity verification anyway, and lowers security further
29007 by increasing compatibility; but this ups the ante on the submission ports
29008 where the administrator might have some influence on the choice of clients
29012 tls_require_ciphers = ${if =={$received_port}{25}\
29018 .section "Configuring an Exim server to use TLS" "SECID182"
29019 .cindex "TLS" "configuring an Exim server"
29020 .cindex "ESMTP extensions" STARTTLS
29021 When Exim has been built with TLS support, it advertises the availability of
29022 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
29023 but not to any others. The default value of this option is *, which means
29024 that STARTTLS is always advertised. Set it to blank to never advertise;
29025 this is reasonable for systems that want to use TLS only as a client.
29027 If STARTTLS is to be used you
29028 need to set some other options in order to make TLS available.
29030 If a client issues a STARTTLS command and there is some configuration
29031 problem in the server, the command is rejected with a 454 error. If the client
29032 persists in trying to issue SMTP commands, all except QUIT are rejected
29035 554 Security failure
29037 If a STARTTLS command is issued within an existing TLS session, it is
29038 rejected with a 554 error code.
29040 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
29041 must be set to match some hosts. The default is * which matches all hosts.
29043 If this is all you do, TLS encryption will be enabled but not authentication -
29044 meaning that the peer has no assurance it is actually you he is talking to.
29045 You gain protection from a passive sniffer listening on the wire but not
29046 from someone able to intercept the communication.
29048 Further protection requires some further configuration at the server end.
29050 To make TLS work you need to set, in the server,
29052 tls_certificate = /some/file/name
29053 tls_privatekey = /some/file/name
29055 These options are, in fact, expanded strings, so you can make them depend on
29056 the identity of the client that is connected if you wish. The first file
29057 contains the server's X509 certificate, and the second contains the private key
29058 that goes with it. These files need to be
29059 PEM format and readable by the Exim user, and must
29060 always be given as full path names.
29061 The key must not be password-protected.
29062 They can be the same file if both the
29063 certificate and the key are contained within it. If &%tls_privatekey%& is not
29064 set, or if its expansion is forced to fail or results in an empty string, this
29065 is assumed to be the case. The certificate file may also contain intermediate
29066 certificates that need to be sent to the client to enable it to authenticate
29067 the server's certificate.
29069 For dual-stack (eg. RSA and ECDSA) configurations, these options can be
29070 colon-separated lists of file paths. Ciphers using given authentication
29071 algorithms require the presence of a suitable certificate to supply the
29072 public-key. The server selects among the certificates to present to the
29073 client depending on the selected cipher, hence the priority ordering for
29074 ciphers will affect which certificate is used.
29076 If you do not understand about certificates and keys, please try to find a
29077 source of this background information, which is not Exim-specific. (There are a
29078 few comments below in section &<<SECTcerandall>>&.)
29080 &*Note*&: These options do not apply when Exim is operating as a client &--
29081 they apply only in the case of a server. If you need to use a certificate in an
29082 Exim client, you must set the options of the same names in an &(smtp)&
29085 With just these options, an Exim server will be able to use TLS. It does not
29086 require the client to have a certificate (but see below for how to insist on
29087 this). There is one other option that may be needed in other situations. If
29089 tls_dhparam = /some/file/name
29091 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
29092 with the parameters contained in the file.
29093 Set this to &`none`& to disable use of DH entirely, by making no prime
29098 This may also be set to a string identifying a standard prime to be used for
29099 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
29100 used is &`ike23`&. There are a few standard primes available, see the
29101 documentation for &%tls_dhparam%& for the complete list.
29107 for a way of generating file data.
29109 The strings supplied for these three options are expanded every time a client
29110 host connects. It is therefore possible to use different certificates and keys
29111 for different hosts, if you so wish, by making use of the client's IP address
29112 in &$sender_host_address$& to control the expansion. If a string expansion is
29113 forced to fail, Exim behaves as if the option is not set.
29115 .cindex "cipher" "logging"
29116 .cindex "log" "TLS cipher"
29117 .vindex "&$tls_in_cipher$&"
29118 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
29119 an incoming TLS connection. It is included in the &'Received:'& header of an
29120 incoming message (by default &-- you can, of course, change this), and it is
29121 also included in the log line that records a message's arrival, keyed by
29122 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
29123 condition can be used to test for specific cipher suites in ACLs.
29125 Once TLS has been established, the ACLs that run for subsequent SMTP commands
29126 can check the name of the cipher suite and vary their actions accordingly. The
29127 cipher suite names vary, depending on which TLS library is being used. For
29128 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
29129 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
29130 documentation for more details.
29132 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
29133 (again depending on the &%tls_cipher%& log selector).
29136 .section "Requesting and verifying client certificates" "SECID183"
29137 .cindex "certificate" "verification of client"
29138 .cindex "TLS" "client certificate verification"
29139 If you want an Exim server to request a certificate when negotiating a TLS
29140 session with a client, you must set either &%tls_verify_hosts%& or
29141 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
29142 apply to all TLS connections. For any host that matches one of these options,
29143 Exim requests a certificate as part of the setup of the TLS session. The
29144 contents of the certificate are verified by comparing it with a list of
29145 expected trust-anchors or certificates.
29146 These may be the system default set (depending on library version),
29147 an explicit file or,
29148 depending on library version, a directory, identified by
29149 &%tls_verify_certificates%&.
29151 A file can contain multiple certificates, concatenated end to end. If a
29154 each certificate must be in a separate file, with a name (or a symbolic link)
29155 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
29156 certificate. You can compute the relevant hash by running the command
29158 openssl x509 -hash -noout -in /cert/file
29160 where &_/cert/file_& contains a single certificate.
29162 There is no checking of names of the client against the certificate
29163 Subject Name or Subject Alternate Names.
29165 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
29166 what happens if the client does not supply a certificate, or if the certificate
29167 does not match any of the certificates in the collection named by
29168 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
29169 attempt to set up a TLS session is aborted, and the incoming connection is
29170 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
29171 session continues. ACLs that run for subsequent SMTP commands can detect the
29172 fact that no certificate was verified, and vary their actions accordingly. For
29173 example, you can insist on a certificate before accepting a message for
29174 relaying, but not when the message is destined for local delivery.
29176 .vindex "&$tls_in_peerdn$&"
29177 When a client supplies a certificate (whether it verifies or not), the value of
29178 the Distinguished Name of the certificate is made available in the variable
29179 &$tls_in_peerdn$& during subsequent processing of the message.
29181 .cindex "log" "distinguished name"
29182 Because it is often a long text string, it is not included in the log line or
29183 &'Received:'& header by default. You can arrange for it to be logged, keyed by
29184 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
29185 &%received_header_text%& to change the &'Received:'& header. When no
29186 certificate is supplied, &$tls_in_peerdn$& is empty.
29189 .section "Revoked certificates" "SECID184"
29190 .cindex "TLS" "revoked certificates"
29191 .cindex "revocation list"
29192 .cindex "certificate" "revocation list"
29193 .cindex "OCSP" "stapling"
29194 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
29195 certificates are revoked. If you have such a list, you can pass it to an Exim
29196 server using the global option called &%tls_crl%& and to an Exim client using
29197 an identically named option for the &(smtp)& transport. In each case, the value
29198 of the option is expanded and must then be the name of a file that contains a
29200 The downside is that clients have to periodically re-download a potentially huge
29201 file from every certificate authority they know of.
29203 The way with most moving parts at query time is Online Certificate
29204 Status Protocol (OCSP), where the client verifies the certificate
29205 against an OCSP server run by the CA. This lets the CA track all
29206 usage of the certs. It requires running software with access to the
29207 private key of the CA, to sign the responses to the OCSP queries. OCSP
29208 is based on HTTP and can be proxied accordingly.
29210 The only widespread OCSP server implementation (known to this writer)
29211 comes as part of OpenSSL and aborts on an invalid request, such as
29212 connecting to the port and then disconnecting. This requires
29213 re-entering the passphrase each time some random client does this.
29215 The third way is OCSP Stapling; in this, the server using a certificate
29216 issued by the CA periodically requests an OCSP proof of validity from
29217 the OCSP server, then serves it up inline as part of the TLS
29218 negotiation. This approach adds no extra round trips, does not let the
29219 CA track users, scales well with number of certs issued by the CA and is
29220 resilient to temporary OCSP server failures, as long as the server
29221 starts retrying to fetch an OCSP proof some time before its current
29222 proof expires. The downside is that it requires server support.
29224 Unless Exim is built with the support disabled,
29225 or with GnuTLS earlier than version 3.3.16 / 3.4.8
29226 support for OCSP stapling is included.
29228 There is a global option called &%tls_ocsp_file%&.
29229 The file specified therein is expected to be in DER format, and contain
29230 an OCSP proof. Exim will serve it as part of the TLS handshake. This
29231 option will be re-expanded for SNI, if the &%tls_certificate%& option
29232 contains &`tls_in_sni`&, as per other TLS options.
29234 Exim does not at this time implement any support for fetching a new OCSP
29235 proof. The burden is on the administrator to handle this, outside of
29236 Exim. The file specified should be replaced atomically, so that the
29237 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
29238 on each connection, so a new file will be handled transparently on the
29241 When built with OpenSSL Exim will check for a valid next update timestamp
29242 in the OCSP proof; if not present, or if the proof has expired, it will be
29245 For the client to be able to verify the stapled OCSP the server must
29246 also supply, in its stapled information, any intermediate
29247 certificates for the chain leading to the OCSP proof from the signer
29248 of the server certificate. There may be zero or one such. These
29249 intermediate certificates should be added to the server OCSP stapling
29250 file named by &%tls_ocsp_file%&.
29252 Note that the proof only covers the terminal server certificate,
29253 not any of the chain from CA to it.
29255 There is no current way to staple a proof for a client certificate.
29258 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
29259 OCSP server is supplied. The server URL may be included in the
29260 server certificate, if the CA is helpful.
29262 One failure mode seen was the OCSP Signer cert expiring before the end
29263 of validity of the OCSP proof. The checking done by Exim/OpenSSL
29264 noted this as invalid overall, but the re-fetch script did not.
29270 .section "Configuring an Exim client to use TLS" "SECTclientTLS"
29271 .cindex "cipher" "logging"
29272 .cindex "log" "TLS cipher"
29273 .cindex "log" "distinguished name"
29274 .cindex "TLS" "configuring an Exim client"
29275 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
29276 deliveries as well as to incoming, the latter one causing logging of the
29277 server certificate's DN. The remaining client configuration for TLS is all
29278 within the &(smtp)& transport.
29280 .cindex "ESMTP extensions" STARTTLS
29281 It is not necessary to set any options to have TLS work in the &(smtp)&
29282 transport. If Exim is built with TLS support, and TLS is advertised by a
29283 server, the &(smtp)& transport always tries to start a TLS session. However,
29284 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
29285 transport) to a list of server hosts for which TLS should not be used.
29287 If you do not want Exim to attempt to send messages unencrypted when an attempt
29288 to set up an encrypted connection fails in any way, you can set
29289 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
29290 those hosts, delivery is always deferred if an encrypted connection cannot be
29291 set up. If there are any other hosts for the address, they are tried in the
29294 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
29295 the message unencrypted. It always does this if the response to STARTTLS is
29296 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
29297 session after a success response code, what happens is controlled by the
29298 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
29299 delivery to this host is deferred, and other hosts (if available) are tried. If
29300 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
29301 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
29302 negotiation fails, Exim closes the current connection (because it is in an
29303 unknown state), opens a new one to the same host, and then tries the delivery
29306 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
29307 transport provide the client with a certificate, which is passed to the server
29308 if it requests it. If the server is Exim, it will request a certificate only if
29309 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
29311 &*Note*&: Do not use a certificate which has the OCSP-must-staple extension,
29312 for client use (they are usable for server use).
29313 As the TLS protocol has no means for the client to staple before TLS 1.3 it will result
29314 in failed connections.
29316 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
29317 specifies a collection of expected server certificates.
29319 the system default set (depending on library version),
29321 or (depending on library version) a directory.
29322 The client verifies the server's certificate
29323 against this collection, taking into account any revoked certificates that are
29324 in the list defined by &%tls_crl%&.
29325 Failure to verify fails the TLS connection unless either of the
29326 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
29328 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
29329 certificate verification to the listed servers. Verification either must
29330 or need not succeed respectively.
29332 The &%tls_verify_cert_hostnames%& option lists hosts for which additional
29333 name checks are made on the server certificate.
29335 The match against this list is, as per other Exim usage, the
29336 IP for the host. That is most closely associated with the
29337 name on the DNS A (or AAAA) record for the host.
29338 However, the name that needs to be in the certificate
29339 is the one at the head of any CNAME chain leading to the A record.
29341 The option defaults to always checking.
29343 The &(smtp)& transport has two OCSP-related options:
29344 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
29345 is requested and required for the connection to proceed. The default
29347 &%hosts_request_ocsp%&; a host-list for which (additionally)
29348 a Certificate Status is requested (but not necessarily verified). The default
29349 value is "*" meaning that requests are made unless configured
29352 The host(s) should also be in &%hosts_require_tls%&, and
29353 &%tls_verify_certificates%& configured for the transport,
29354 for OCSP to be relevant.
29357 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
29358 list of permitted cipher suites. If either of these checks fails, delivery to
29359 the current host is abandoned, and the &(smtp)& transport tries to deliver to
29360 alternative hosts, if any.
29363 These options must be set in the &(smtp)& transport for Exim to use TLS when it
29364 is operating as a client. Exim does not assume that a server certificate (set
29365 by the global options of the same name) should also be used when operating as a
29369 .vindex "&$host_address$&"
29370 All the TLS options in the &(smtp)& transport are expanded before use, with
29371 &$host$& and &$host_address$& containing the name and address of the server to
29372 which the client is connected. Forced failure of an expansion causes Exim to
29373 behave as if the relevant option were unset.
29375 .vindex &$tls_out_bits$&
29376 .vindex &$tls_out_cipher$&
29377 .vindex &$tls_out_peerdn$&
29378 .vindex &$tls_out_sni$&
29379 Before an SMTP connection is established, the
29380 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
29381 variables are emptied. (Until the first connection, they contain the values
29382 that were set when the message was received.) If STARTTLS is subsequently
29383 successfully obeyed, these variables are set to the relevant values for the
29384 outgoing connection.
29388 .section "Use of TLS Server Name Indication" "SECTtlssni"
29389 .cindex "TLS" "Server Name Indication"
29392 .vindex "&$tls_in_sni$&"
29393 .oindex "&%tls_in_sni%&"
29394 With TLS1.0 or above, there is an extension mechanism by which extra
29395 information can be included at various points in the protocol. One of these
29396 extensions, documented in RFC 6066 (and before that RFC 4366) is
29397 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
29398 client in the initial handshake, so that the server can examine the servername
29399 within and possibly choose to use different certificates and keys (and more)
29402 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
29403 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
29406 With SMTP to MX, there are the same problems here as in choosing the identity
29407 against which to validate a certificate: you can't rely on insecure DNS to
29408 provide the identity which you then cryptographically verify. So this will
29409 be of limited use in that environment.
29411 With SMTP to Submission, there is a well-defined hostname which clients are
29412 connecting to and can validate certificates against. Thus clients &*can*&
29413 choose to include this information in the TLS negotiation. If this becomes
29414 wide-spread, then hosters can choose to present different certificates to
29415 different clients. Or even negotiate different cipher suites.
29417 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
29418 if not empty, will be sent on a TLS session as part of the handshake. There's
29419 nothing more to it. Choosing a sensible value not derived insecurely is the
29420 only point of caution. The &$tls_out_sni$& variable will be set to this string
29421 for the lifetime of the client connection (including during authentication).
29424 If DANE validated the connection attempt then the value of the &%tls_sni%& option
29425 is forced to the domain part of the recipient address.
29428 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
29429 received from a client.
29430 It can be logged with the &%log_selector%& item &`+tls_sni`&.
29432 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
29433 option (prior to expansion) then the following options will be re-expanded
29434 during TLS session handshake, to permit alternative values to be chosen:
29437 &%tls_certificate%&
29443 &%tls_verify_certificates%&
29448 Great care should be taken to deal with matters of case, various injection
29449 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
29450 can always be referenced; it is important to remember that &$tls_in_sni$& is
29451 arbitrary unverified data provided prior to authentication.
29452 Further, the initial certificate is loaded before SNI has arrived, so
29453 an expansion for &%tls_certificate%& must have a default which is used
29454 when &$tls_in_sni$& is empty.
29456 The Exim developers are proceeding cautiously and so far no other TLS options
29459 When Exim is built against OpenSSL, OpenSSL must have been built with support
29460 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
29461 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
29462 see &`-servername`& in the output, then OpenSSL has support.
29464 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
29465 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
29466 built, then you have SNI support).
29470 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
29472 .cindex "multiple SMTP deliveries with TLS"
29473 .cindex "TLS" "multiple message deliveries"
29474 Exim sends multiple messages down the same TCP/IP connection by starting up
29475 an entirely new delivery process for each message, passing the socket from
29476 one process to the next. This implementation does not fit well with the use
29477 of TLS, because there is quite a lot of state information associated with a TLS
29478 connection, not just a socket identification. Passing all the state information
29479 to a new process is not feasible. Consequently, for sending using TLS Exim
29480 starts an additional proxy process for handling the encryption, piping the
29481 unencrypted data stream from and to the delivery processes.
29483 An older mode of operation can be enabled on a per-host basis by the
29484 &%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
29485 this list the proxy process described above is not used; instead Exim
29486 shuts down an existing TLS session being run by the delivery process
29487 before passing the socket to a new process. The new process may then
29488 try to start a new TLS session, and if successful, may try to re-authenticate
29489 if AUTH is in use, before sending the next message.
29491 The RFC is not clear as to whether or not an SMTP session continues in clear
29492 after TLS has been shut down, or whether TLS may be restarted again later, as
29493 just described. However, if the server is Exim, this shutdown and
29494 reinitialization works. It is not known which (if any) other servers operate
29495 successfully if the client closes a TLS session and continues with unencrypted
29496 SMTP, but there are certainly some that do not work. For such servers, Exim
29497 should not pass the socket to another process, because the failure of the
29498 subsequent attempt to use it would cause Exim to record a temporary host error,
29499 and delay other deliveries to that host.
29501 To test for this case, Exim sends an EHLO command to the server after
29502 closing down the TLS session. If this fails in any way, the connection is
29503 closed instead of being passed to a new delivery process, but no retry
29504 information is recorded.
29506 There is also a manual override; you can set &%hosts_nopass_tls%& on the
29507 &(smtp)& transport to match those hosts for which Exim should not pass
29508 connections to new processes if TLS has been used.
29513 .section "Certificates and all that" "SECTcerandall"
29514 .cindex "certificate" "references to discussion"
29515 In order to understand fully how TLS works, you need to know about
29516 certificates, certificate signing, and certificate authorities.
29517 This is a large topic and an introductory guide is unsuitable for the Exim
29518 reference manual, so instead we provide pointers to existing documentation.
29520 The Apache web-server was for a long time the canonical guide, so their
29521 documentation is a good place to start; their SSL module's Introduction
29522 document is currently at
29524 &url(https://httpd.apache.org/docs/current/ssl/ssl_intro.html)
29526 and their FAQ is at
29528 &url(https://httpd.apache.org/docs/current/ssl/ssl_faq.html)
29531 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
29532 0-201-61598-3) in 2001, contains both introductory and more in-depth
29534 More recently Ivan Ristić's book &'Bulletproof SSL and TLS'&,
29535 published by Feisty Duck (ISBN 978-1907117046) in 2013 is good.
29536 Ivan is the author of the popular TLS testing tools at
29537 &url(https://www.ssllabs.com/).
29540 .section "Certificate chains" "SECID186"
29541 The file named by &%tls_certificate%& may contain more than one
29542 certificate. This is useful in the case where the certificate that is being
29543 sent is validated by an intermediate certificate which the other end does
29544 not have. Multiple certificates must be in the correct order in the file.
29545 First the host's certificate itself, then the first intermediate
29546 certificate to validate the issuer of the host certificate, then the next
29547 intermediate certificate to validate the issuer of the first intermediate
29548 certificate, and so on, until finally (optionally) the root certificate.
29549 The root certificate must already be trusted by the recipient for
29550 validation to succeed, of course, but if it's not preinstalled, sending the
29551 root certificate along with the rest makes it available for the user to
29552 install if the receiving end is a client MUA that can interact with a user.
29554 Note that certificates using MD5 are unlikely to work on today's Internet;
29555 even if your libraries allow loading them for use in Exim when acting as a
29556 server, increasingly clients will not accept such certificates. The error
29557 diagnostics in such a case can be frustratingly vague.
29561 .section "Self-signed certificates" "SECID187"
29562 .cindex "certificate" "self-signed"
29563 You can create a self-signed certificate using the &'req'& command provided
29564 with OpenSSL, like this:
29565 . ==== Do not shorten the duration here without reading and considering
29566 . ==== the text below. Please leave it at 9999 days.
29568 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
29571 &_file1_& and &_file2_& can be the same file; the key and the certificate are
29572 delimited and so can be identified independently. The &%-days%& option
29573 specifies a period for which the certificate is valid. The &%-nodes%& option is
29574 important: if you do not set it, the key is encrypted with a passphrase
29575 that you are prompted for, and any use that is made of the key causes more
29576 prompting for the passphrase. This is not helpful if you are going to use
29577 this certificate and key in an MTA, where prompting is not possible.
29579 . ==== I expect to still be working 26 years from now. The less technical
29580 . ==== debt I create, in terms of storing up trouble for my later years, the
29581 . ==== happier I will be then. We really have reached the point where we
29582 . ==== should start, at the very least, provoking thought and making folks
29583 . ==== pause before proceeding, instead of leaving all the fixes until two
29584 . ==== years before 2^31 seconds after the 1970 Unix epoch.
29586 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
29587 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
29588 the above command might produce a date in the past. Think carefully about
29589 the lifetime of the systems you're deploying, and either reduce the duration
29590 of the certificate or reconsider your platform deployment. (At time of
29591 writing, reducing the duration is the most likely choice, but the inexorable
29592 progression of time takes us steadily towards an era where this will not
29593 be a sensible resolution).
29595 A self-signed certificate made in this way is sufficient for testing, and
29596 may be adequate for all your requirements if you are mainly interested in
29597 encrypting transfers, and not in secure identification.
29599 However, many clients require that the certificate presented by the server be a
29600 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
29601 certificate. In this situation, the self-signed certificate described above
29602 must be installed on the client host as a trusted root &'certification
29603 authority'& (CA), and the certificate used by Exim must be a user certificate
29604 signed with that self-signed certificate.
29606 For information on creating self-signed CA certificates and using them to sign
29607 user certificates, see the &'General implementation overview'& chapter of the
29608 Open-source PKI book, available online at
29609 &url(https://sourceforge.net/projects/ospkibook/).
29610 .ecindex IIDencsmtp1
29611 .ecindex IIDencsmtp2
29615 .section "TLS Resumption" "SECTresumption"
29616 .cindex TLS resumption
29617 TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
29618 in RFC 5077 for 1.2). The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1
29621 Session resumption (this is the "stateless" variant) involves the server sending
29622 a "session ticket" to the client on one connection, which can be stored by the
29623 client and used for a later session. The ticket contains sufficient state for
29624 the server to reconstruct the TLS session, avoiding some expensive crypto
29625 calculation and (on TLS1.2) one full packet roundtrip time.
29628 Operational cost/benefit:
29630 The extra data being transmitted costs a minor amount, and the client has
29631 extra costs in storing and retrieving the data.
29633 In the Exim/Gnutls implementation the extra cost on an initial connection
29634 which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware.
29635 The saved cost on a subsequent connection is about 4ms; three or more
29636 connections become a net win. On longer network paths, two or more
29637 connections will have an average lower startup time thanks to the one
29638 saved packet roundtrip. TLS1.3 will save the crypto cpu costs but not any
29641 .cindex "hints database" tls
29642 Since a new hints DB is used on the TLS client,
29643 the hints DB maintenance should be updated to additionally handle "tls".
29648 The session ticket is encrypted, but is obviously an additional security
29649 vulnarability surface. An attacker able to decrypt it would have access
29650 all connections using the resumed session.
29651 The session ticket encryption key is not committed to storage by the server
29652 and is rotated regularly (OpenSSL: 1hr, and one previous key is used for
29653 overlap; GnuTLS 6hr but does not specify any overlap).
29654 Tickets have limited lifetime (2hr, and new ones issued after 1hr under
29655 OpenSSL. GnuTLS 2hr, appears to not do overlap).
29657 There is a question-mark over the security of the Diffie-Helman parameters
29658 used for session negotiation.
29663 The &%log_selector%& "tls_resumption" appends an asterisk to the tls_cipher "X="
29666 The variables &$tls_in_resumption$& and &$tls_out_resumption$&
29667 have bits 0-4 indicating respectively
29668 support built, client requested ticket, client offered session,
29669 server issued ticket, resume used. A suitable decode list is provided
29670 in the builtin macro _RESUME_DECODE for in &%listextract%& expansions.
29675 The &%tls_resumption_hosts%& main option specifies a hostlist for which
29676 exim, operating as a server, will offer resumption to clients.
29677 Current best practice is to not offer the feature to MUA connection.
29678 Commonly this can be done like this:
29680 tls_resumption_hosts = ${if inlist {$received_port}{587:465} {:}{*}}
29682 If the peer host matches the list after expansion then resumption
29683 is offered and/or accepted.
29685 The &%tls_resumption_hosts%& smtp transport option performs the
29686 equivalent function for operation as a client.
29687 If the peer host matches the list after expansion then resumption
29688 is attempted (if a stored session is available) or the information
29689 stored (if supplied by the peer).
29695 In a resumed session:
29697 The variables &$tls_{in,out}_cipher$& will have values different
29698 to the original (under GnuTLS).
29700 The variables &$tls_{in,out}_ocsp$& will be "not requested" or "no response",
29701 and the &%hosts_require_ocsp%& smtp trasnport option will fail.
29702 . XXX need to do something with that hosts_require_ocsp
29709 .section DANE "SECDANE"
29711 DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
29712 it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
29713 operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
29714 you and the server still think you have an encrypted connection) and, if one of the "well known" set of
29715 Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
29716 certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
29718 What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
29719 that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
29720 by (a) is thought to be smaller than that of the set of root CAs.
29722 It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
29723 fail to pass on a server's STARTTLS.
29725 DANE scales better than having to maintain (and communicate via side-channel) copies of server certificates
29726 for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
29727 client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
29729 DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
29730 that DNS lookups they do for the server have not been tampered with. The domain MX record applying
29731 to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
29733 2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
29734 3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
29736 There are no changes to Exim specific to server-side operation of DANE.
29737 Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
29738 in &_Local/Makefile_&.
29739 If it has been included, the macro "_HAVE_DANE" will be defined.
29741 A TLSA record consist of 4 fields, the "Certificate Usage", the
29742 "Selector", the "Matching type", and the "Certificate Association Data".
29743 For a detailed description of the TLSA record see
29744 &url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671).
29746 The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3).
29747 These are the "Trust Anchor" and "End Entity" variants.
29748 The latter specifies the End Entity directly, i.e. the certificate involved is that of the server
29749 (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake);
29750 this is appropriate for a single system, using a self-signed certificate.
29751 DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
29753 A private CA at simplest is just a self-signed certificate (with certain
29754 attributes) which is used to sign server certificates, but running one securely
29755 does require careful arrangement.
29756 With DANE-TA, as implemented in Exim and commonly in other MTAs,
29757 the server TLS handshake must transmit the entire certificate chain from CA to server-certificate.
29758 DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
29759 all of which point to a single TLSA record.
29760 DANE-TA and DANE-EE can both be used together.
29762 Our recommendation is to use DANE with a certificate from a public CA,
29763 because this enables a variety of strategies for remote clients to verify
29765 You can then publish information both via DANE and another technology,
29766 "MTA-STS", described below.
29768 When you use DANE-TA to publish trust anchor information, you ask entities
29769 outside your administrative control to trust the Certificate Authority for
29770 connections to you.
29771 If using a private CA then you should expect others to still apply the
29772 technical criteria they'd use for a public CA to your certificates.
29773 In particular, you should probably try to follow current best practices for CA
29774 operation around hash algorithms and key sizes.
29775 Do not expect other organizations to lower their security expectations just
29776 because a particular profile might be reasonable for your own internal use.
29778 When this text was last updated, this in practice means to avoid use of SHA-1
29779 and MD5; if using RSA to use key sizes of at least 2048 bits (and no larger
29780 than 4096, for interoperability); to use keyUsage fields correctly; to use
29781 random serial numbers.
29782 The list of requirements is subject to change as best practices evolve.
29783 If you're not already using a private CA, or it doesn't meet these
29784 requirements, then we encourage you to avoid all these issues and use a public
29785 CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead.
29787 The TLSA record should have a "Selector" (2nd) field of SPKI(1) and
29788 a "Matching Type" (3rd) field of SHA2-512(2).
29790 For the "Certificate Authority Data" (4th) field, commands like
29793 openssl x509 -pubkey -noout <certificate.pem \
29794 | openssl rsa -outform der -pubin 2>/dev/null \
29799 are workable to create a hash of the certificate's public key.
29801 An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like
29804 _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E...
29807 At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
29808 is useful for quickly generating TLSA records.
29811 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
29813 The Certificate issued by the CA published in the DANE-TA model should be
29814 issued using a strong hash algorithm.
29815 Exim, and importantly various other MTAs sending to you, will not
29816 re-enable hash algorithms which have been disabled by default in TLS
29818 This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable
29819 interoperability (and probably the maximum too, in 2018).
29821 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
29822 be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
29823 default of requesting OCSP for all hosts is modified iff DANE is in use, to:
29826 hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
29827 {= {4}{$tls_out_tlsa_usage}} } \
29831 The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
29832 The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
29833 found. If the definition of &%hosts_request_ocsp%& includes the
29834 string "tls_out_tlsa_usage", they are re-expanded in time to
29835 control the OCSP request.
29837 This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
29838 those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
29841 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
29842 and &%dane_require_tls_ciphers%&.
29843 The &"require"& variant will result in failure if the target host is not
29844 DNSSEC-secured. To get DNSSEC-secured hostname resolution, use
29845 the &%dnssec_request_domains%& router or transport option.
29847 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
29849 A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using dnssec.
29850 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
29851 will be required for the host. If it does not, the host will not
29852 be used; there is no fallback to non-DANE or non-TLS.
29854 If DANE is requested and usable, then the TLS cipher list configuration
29855 prefers to use the option &%dane_require_tls_ciphers%& and falls
29856 back to &%tls_require_ciphers%& only if that is unset.
29857 This lets you configure "decent crypto" for DANE and "better than nothing
29858 crypto" as the default. Note though that while GnuTLS lets the string control
29859 which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
29860 limited to ciphersuite constraints.
29862 If DANE is requested and useable (see above) the following transport options are ignored:
29866 tls_try_verify_hosts
29867 tls_verify_certificates
29869 tls_verify_cert_hostnames
29873 If DANE is not usable, whether requested or not, and CA-anchored
29874 verification evaluation is wanted, the above variables should be set appropriately.
29876 The router and transport option &%dnssec_request_domains%& must not be
29877 set to &"never"&, and &%dnssec_require_domains%& is ignored.
29879 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
29881 There is a new variable &$tls_out_dane$& which will have "yes" if
29882 verification succeeded using DANE and "no" otherwise (only useful
29883 in combination with events; see &<<CHAPevents>>&),
29884 and a new variable &$tls_out_tlsa_usage$& (detailed above).
29886 .cindex DANE reporting
29887 An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
29888 to achieve DANE-verified connection, if one was either requested and offered, or
29889 required. This is intended to support TLS-reporting as defined in
29890 &url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
29891 The &$event_data$& will be one of the Result Types defined in
29892 Section 4.3 of that document.
29894 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
29896 DANE is specified in published RFCs and decouples certificate authority trust
29897 selection from a "race to the bottom" of "you must trust everything for mail
29898 to get through". There is an alternative technology called MTA-STS, which
29899 instead publishes MX trust anchor information on an HTTPS website. At the
29900 time this text was last updated, MTA-STS was still a draft, not yet an RFC.
29901 Exim has no support for MTA-STS as a client, but Exim mail server operators
29902 can choose to publish information describing their TLS configuration using
29903 MTA-STS to let those clients who do use that protocol derive trust
29906 The MTA-STS design requires a certificate from a public Certificate Authority
29907 which is recognized by clients sending to you.
29908 That selection of which CAs are trusted by others is outside your control.
29910 The most interoperable course of action is probably to use
29911 &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
29912 renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
29913 records for DANE clients (such as Exim and Postfix) and to publish anchor
29914 information for MTA-STS as well. This is what is done for the &'exim.org'&
29915 domain itself (with caveats around occasionally broken MTA-STS because of
29916 incompatible specification changes prior to reaching RFC status).
29920 . ////////////////////////////////////////////////////////////////////////////
29921 . ////////////////////////////////////////////////////////////////////////////
29923 .chapter "Access control lists" "CHAPACL"
29924 .scindex IIDacl "&ACL;" "description"
29925 .cindex "control of incoming mail"
29926 .cindex "message" "controlling incoming"
29927 .cindex "policy control" "access control lists"
29928 Access Control Lists (ACLs) are defined in a separate section of the runtime
29929 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
29930 name, terminated by a colon. Here is a complete ACL section that contains just
29931 one very small ACL:
29935 accept hosts = one.host.only
29937 You can have as many lists as you like in the ACL section, and the order in
29938 which they appear does not matter. The lists are self-terminating.
29940 The majority of ACLs are used to control Exim's behaviour when it receives
29941 certain SMTP commands. This applies both to incoming TCP/IP connections, and
29942 when a local process submits a message using SMTP by specifying the &%-bs%&
29943 option. The most common use is for controlling which recipients are accepted
29944 in incoming messages. In addition, you can define an ACL that is used to check
29945 local non-SMTP messages. The default configuration file contains an example of
29946 a realistic ACL for checking RCPT commands. This is discussed in chapter
29947 &<<CHAPdefconfil>>&.
29950 .section "Testing ACLs" "SECID188"
29951 The &%-bh%& command line option provides a way of testing your ACL
29952 configuration locally by running a fake SMTP session with which you interact.
29955 .section "Specifying when ACLs are used" "SECID189"
29956 .cindex "&ACL;" "options for specifying"
29957 In order to cause an ACL to be used, you have to name it in one of the relevant
29958 options in the main part of the configuration. These options are:
29959 .cindex "AUTH" "ACL for"
29960 .cindex "DATA" "ACLs for"
29961 .cindex "ETRN" "ACL for"
29962 .cindex "EXPN" "ACL for"
29963 .cindex "HELO" "ACL for"
29964 .cindex "EHLO" "ACL for"
29965 .cindex "DKIM" "ACL for"
29966 .cindex "MAIL" "ACL for"
29967 .cindex "QUIT, ACL for"
29968 .cindex "RCPT" "ACL for"
29969 .cindex "STARTTLS, ACL for"
29970 .cindex "VRFY" "ACL for"
29971 .cindex "SMTP" "connection, ACL for"
29972 .cindex "non-SMTP messages" "ACLs for"
29973 .cindex "MIME content scanning" "ACL for"
29974 .cindex "PRDR" "ACL for"
29977 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
29978 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
29979 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
29980 .irow &%acl_smtp_auth%& "ACL for AUTH"
29981 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
29982 .irow &%acl_smtp_data%& "ACL after DATA is complete"
29983 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
29984 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
29985 .irow &%acl_smtp_etrn%& "ACL for ETRN"
29986 .irow &%acl_smtp_expn%& "ACL for EXPN"
29987 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
29988 .irow &%acl_smtp_mail%& "ACL for MAIL"
29989 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
29990 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
29991 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
29992 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
29993 .irow &%acl_smtp_quit%& "ACL for QUIT"
29994 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
29995 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
29996 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
29999 For example, if you set
30001 acl_smtp_rcpt = small_acl
30003 the little ACL defined above is used whenever Exim receives a RCPT command
30004 in an SMTP dialogue. The majority of policy tests on incoming messages can be
30005 done when RCPT commands arrive. A rejection of RCPT should cause the
30006 sending MTA to give up on the recipient address contained in the RCPT
30007 command, whereas rejection at other times may cause the client MTA to keep on
30008 trying to deliver the message. It is therefore recommended that you do as much
30009 testing as possible at RCPT time.
30012 .section "The non-SMTP ACLs" "SECID190"
30013 .cindex "non-SMTP messages" "ACLs for"
30014 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
30015 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
30016 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
30017 the state of the SMTP connection such as encryption and authentication) are not
30018 relevant and are forbidden in these ACLs. However, the sender and recipients
30019 are known, so the &%senders%& and &%sender_domains%& conditions and the
30020 &$sender_address$& and &$recipients$& variables can be used. Variables such as
30021 &$authenticated_sender$& are also available. You can specify added header lines
30022 in any of these ACLs.
30024 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
30025 non-SMTP message, before any of the message has been read. (This is the
30026 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
30027 batched SMTP input, it runs after the DATA command has been reached. The
30028 result of this ACL is ignored; it cannot be used to reject a message. If you
30029 really need to, you could set a value in an ACL variable here and reject based
30030 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
30031 controls, and in particular, it can be used to set
30033 control = suppress_local_fixups
30035 This cannot be used in the other non-SMTP ACLs because by the time they are
30036 run, it is too late.
30038 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
30039 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30041 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
30042 kind of rejection is treated as permanent, because there is no way of sending a
30043 temporary error for these kinds of message.
30046 .section "The SMTP connect ACL" "SECID191"
30047 .cindex "SMTP" "connection, ACL for"
30048 .oindex &%smtp_banner%&
30049 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
30050 session, after the test specified by &%host_reject_connection%& (which is now
30051 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
30052 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
30053 the message override the banner message that is otherwise specified by the
30054 &%smtp_banner%& option.
30057 .section "The EHLO/HELO ACL" "SECID192"
30058 .cindex "EHLO" "ACL for"
30059 .cindex "HELO" "ACL for"
30060 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
30061 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
30062 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
30063 Note that a client may issue more than one EHLO or HELO command in an SMTP
30064 session, and indeed is required to issue a new EHLO or HELO after successfully
30065 setting up encryption following a STARTTLS command.
30067 Note also that a deny neither forces the client to go away nor means that
30068 mail will be refused on the connection. Consider checking for
30069 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
30071 If the command is accepted by an &%accept%& verb that has a &%message%&
30072 modifier, the message may not contain more than one line (it will be truncated
30073 at the first newline and a panic logged if it does). Such a message cannot
30074 affect the EHLO options that are listed on the second and subsequent lines of
30078 .section "The DATA ACLs" "SECID193"
30079 .cindex "DATA" "ACLs for"
30080 Two ACLs are associated with the DATA command, because it is two-stage
30081 command, with two responses being sent to the client.
30082 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
30083 is obeyed. This gives you control after all the RCPT commands, but before
30084 the message itself is received. It offers the opportunity to give a negative
30085 response to the DATA command before the data is transmitted. Header lines
30086 added by MAIL or RCPT ACLs are not visible at this time, but any that
30087 are defined here are visible when the &%acl_smtp_data%& ACL is run.
30089 You cannot test the contents of the message, for example, to verify addresses
30090 in the headers, at RCPT time or when the DATA command is received. Such
30091 tests have to appear in the ACL that is run after the message itself has been
30092 received, before the final response to the DATA command is sent. This is
30093 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
30094 associated with the DATA command.
30096 .cindex CHUNKING "BDAT command"
30097 .cindex BDAT "SMTP command"
30098 .cindex "RFC 3030" CHUNKING
30099 If CHUNKING was advertised and a BDAT command sequence is received,
30100 the &%acl_smtp_predata%& ACL is not run.
30101 . XXX why not? It should be possible, for the first BDAT.
30102 The &%acl_smtp_data%& is run after the last BDAT command and all of
30103 the data specified is received.
30105 For both of these ACLs, it is not possible to reject individual recipients. An
30106 error response rejects the entire message. Unfortunately, it is known that some
30107 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
30108 before or after the data) correctly &-- they keep the message on their queues
30109 and try again later, but that is their problem, though it does waste some of
30112 The &%acl_smtp_data%& ACL is run after
30113 the &%acl_smtp_data_prdr%&,
30114 the &%acl_smtp_dkim%&
30115 and the &%acl_smtp_mime%& ACLs.
30117 .section "The SMTP DKIM ACL" "SECTDKIMACL"
30118 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
30119 enabled (which is the default).
30121 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
30122 received, and is executed for each DKIM signature found in a message. If not
30123 otherwise specified, the default action is to accept.
30125 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
30127 For details on the operation of DKIM, see section &<<SECDKIM>>&.
30130 .section "The SMTP MIME ACL" "SECID194"
30131 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
30132 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
30134 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30137 .section "The SMTP PRDR ACL" "SECTPRDRACL"
30138 .cindex "PRDR" "ACL for"
30139 .oindex "&%prdr_enable%&"
30140 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
30141 with PRDR support enabled (which is the default).
30142 It becomes active only when the PRDR feature is negotiated between
30143 client and server for a message, and more than one recipient
30146 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
30147 has been received, and is executed once for each recipient of the message
30148 with &$local_part$& and &$domain$& valid.
30149 The test may accept, defer or deny for individual recipients.
30150 The &%acl_smtp_data%& will still be called after this ACL and
30151 can reject the message overall, even if this ACL has accepted it
30152 for some or all recipients.
30154 PRDR may be used to support per-user content filtering. Without it
30155 one must defer any recipient after the first that has a different
30156 content-filter configuration. With PRDR, the RCPT-time check
30157 .cindex "PRDR" "variable for"
30158 for this can be disabled when the variable &$prdr_requested$&
30160 Any required difference in behaviour of the main DATA-time
30161 ACL should however depend on the PRDR-time ACL having run, as Exim
30162 will avoid doing so in some situations (e.g. single-recipient mails).
30164 See also the &%prdr_enable%& global option
30165 and the &%hosts_try_prdr%& smtp transport option.
30167 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
30168 If the ACL is not defined, processing completes as if
30169 the feature was not requested by the client.
30171 .section "The QUIT ACL" "SECTQUITACL"
30172 .cindex "QUIT, ACL for"
30173 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
30174 does not affect the response code to QUIT, which is always 221. Thus, the ACL
30175 does not in fact control any access.
30176 For this reason, it may only accept
30177 or warn as its final result.
30179 This ACL can be used for tasks such as custom logging at the end of an SMTP
30180 session. For example, you can use ACL variables in other ACLs to count
30181 messages, recipients, etc., and log the totals at QUIT time using one or
30182 more &%logwrite%& modifiers on a &%warn%& verb.
30184 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
30185 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
30187 You do not need to have a final &%accept%&, but if you do, you can use a
30188 &%message%& modifier to specify custom text that is sent as part of the 221
30191 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
30192 failure (for example, failure to open a log file, or when Exim is bombing out
30193 because it has detected an unrecoverable error), all SMTP commands from the
30194 client are given temporary error responses until QUIT is received or the
30195 connection is closed. In these special cases, the QUIT ACL does not run.
30198 .section "The not-QUIT ACL" "SECTNOTQUITACL"
30199 .vindex &$acl_smtp_notquit$&
30200 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
30201 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
30202 trouble, such as being unable to write to its log files, this ACL is not run,
30203 because it might try to do things (such as write to log files) that make the
30204 situation even worse.
30206 Like the QUIT ACL, this ACL is provided to make it possible to do customized
30207 logging or to gather statistics, and its outcome is ignored. The &%delay%&
30208 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
30211 .vindex &$smtp_notquit_reason$&
30212 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
30213 to a string that indicates the reason for the termination of the SMTP
30214 connection. The possible values are:
30216 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
30217 .irow &`bad-commands`& "Too many unknown or non-mail commands"
30218 .irow &`command-timeout`& "Timeout while reading SMTP commands"
30219 .irow &`connection-lost`& "The SMTP connection has been lost"
30220 .irow &`data-timeout`& "Timeout while reading message data"
30221 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
30222 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
30223 .irow &`signal-exit`& "SIGTERM or SIGINT"
30224 .irow &`synchronization-error`& "SMTP synchronization error"
30225 .irow &`tls-failed`& "TLS failed to start"
30227 In most cases when an SMTP connection is closed without having received QUIT,
30228 Exim sends an SMTP response message before actually closing the connection.
30229 With the exception of the &`acl-drop`& case, the default message can be
30230 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
30231 &%drop%& verb in another ACL, it is the message from the other ACL that is
30235 .section "Finding an ACL to use" "SECID195"
30236 .cindex "&ACL;" "finding which to use"
30237 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
30238 you can use different ACLs in different circumstances. For example,
30240 acl_smtp_rcpt = ${if ={25}{$interface_port} \
30241 {acl_check_rcpt} {acl_check_rcpt_submit} }
30243 In the default configuration file there are some example settings for
30244 providing an RFC 4409 message &"submission"& service on port 587 and
30245 an RFC 8314 &"submissions"& service on port 465. You can use a string
30246 expansion like this to choose an ACL for MUAs on these ports which is
30247 more appropriate for this purpose than the default ACL on port 25.
30249 The expanded string does not have to be the name of an ACL in the
30250 configuration file; there are other possibilities. Having expanded the
30251 string, Exim searches for an ACL as follows:
30254 If the string begins with a slash, Exim uses it as a filename, and reads its
30255 contents as an ACL. The lines are processed in the same way as lines in the
30256 Exim configuration file. In particular, continuation lines are supported, blank
30257 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
30258 If the file does not exist or cannot be read, an error occurs (typically
30259 causing a temporary failure of whatever caused the ACL to be run). For example:
30261 acl_smtp_data = /etc/acls/\
30262 ${lookup{$sender_host_address}lsearch\
30263 {/etc/acllist}{$value}{default}}
30265 This looks up an ACL file to use on the basis of the host's IP address, falling
30266 back to a default if the lookup fails. If an ACL is successfully read from a
30267 file, it is retained in memory for the duration of the Exim process, so that it
30268 can be re-used without having to re-read the file.
30270 If the string does not start with a slash, and does not contain any spaces,
30271 Exim searches the ACL section of the configuration for an ACL whose name
30272 matches the string.
30274 If no named ACL is found, or if the string contains spaces, Exim parses
30275 the string as an inline ACL. This can save typing in cases where you just
30276 want to have something like
30278 acl_smtp_vrfy = accept
30280 in order to allow free use of the VRFY command. Such a string may contain
30281 newlines; it is processed in the same way as an ACL that is read from a file.
30287 .section "ACL return codes" "SECID196"
30288 .cindex "&ACL;" "return codes"
30289 Except for the QUIT ACL, which does not affect the SMTP return code (see
30290 section &<<SECTQUITACL>>& above), the result of running an ACL is either
30291 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
30292 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
30293 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
30294 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
30295 This also causes a 4&'xx'& return code.
30297 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
30298 &"deny"&, because there is no mechanism for passing temporary errors to the
30299 submitters of non-SMTP messages.
30302 ACLs that are relevant to message reception may also return &"discard"&. This
30303 has the effect of &"accept"&, but causes either the entire message or an
30304 individual recipient address to be discarded. In other words, it is a
30305 blackholing facility. Use it with care.
30307 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
30308 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
30309 RCPT ACL is to discard just the one recipient address. If there are no
30310 recipients left when the message's data is received, the DATA ACL is not
30311 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
30312 remaining recipients. The &"discard"& return is not permitted for the
30313 &%acl_smtp_predata%& ACL.
30315 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
30316 is done on the address and the result determines the SMTP response.
30319 .cindex "&[local_scan()]& function" "when all recipients discarded"
30320 The &[local_scan()]& function is always run, even if there are no remaining
30321 recipients; it may create new recipients.
30325 .section "Unset ACL options" "SECID197"
30326 .cindex "&ACL;" "unset options"
30327 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
30328 all the same. &*Note*&: These defaults apply only when the relevant ACL is
30329 not defined at all. For any defined ACL, the default action when control
30330 reaches the end of the ACL statements is &"deny"&.
30332 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
30333 these two are ACLs that are used only for their side effects. They cannot be
30334 used to accept or reject anything.
30336 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
30337 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
30338 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
30339 when the ACL is not defined is &"accept"&.
30341 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
30342 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
30343 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
30344 messages over an SMTP connection. For an example, see the ACL in the default
30345 configuration file.
30350 .section "Data for message ACLs" "SECID198"
30351 .cindex "&ACL;" "data for message ACL"
30353 .vindex &$local_part$&
30354 .vindex &$sender_address$&
30355 .vindex &$sender_host_address$&
30356 .vindex &$smtp_command$&
30357 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
30358 that contain information about the host and the message's sender (for example,
30359 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
30360 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
30361 &$local_part$& are set from the argument address. The entire SMTP command
30362 is available in &$smtp_command$&.
30364 When an ACL for the AUTH parameter of MAIL is running, the variables that
30365 contain information about the host are set, but &$sender_address$& is not yet
30366 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
30369 .vindex "&$message_size$&"
30370 The &$message_size$& variable is set to the value of the SIZE parameter on
30371 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
30372 that parameter is not given. The value is updated to the true message size by
30373 the time the final DATA ACL is run (after the message data has been
30376 .vindex "&$rcpt_count$&"
30377 .vindex "&$recipients_count$&"
30378 The &$rcpt_count$& variable increases by one for each RCPT command received.
30379 The &$recipients_count$& variable increases by one each time a RCPT command is
30380 accepted, so while an ACL for RCPT is being processed, it contains the number
30381 of previously accepted recipients. At DATA time (for both the DATA ACLs),
30382 &$rcpt_count$& contains the total number of RCPT commands, and
30383 &$recipients_count$& contains the total number of accepted recipients.
30389 .section "Data for non-message ACLs" "SECTdatfornon"
30390 .cindex "&ACL;" "data for non-message ACL"
30391 .vindex &$smtp_command_argument$&
30392 .vindex &$smtp_command$&
30393 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
30394 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
30395 and the entire SMTP command is available in &$smtp_command$&.
30396 These variables can be tested using a &%condition%& condition. For example,
30397 here is an ACL for use with AUTH, which insists that either the session is
30398 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
30399 does not permit authentication methods that use cleartext passwords on
30400 unencrypted connections.
30403 accept encrypted = *
30404 accept condition = ${if eq{${uc:$smtp_command_argument}}\
30406 deny message = TLS encryption or CRAM-MD5 required
30408 (Another way of applying this restriction is to arrange for the authenticators
30409 that use cleartext passwords not to be advertised when the connection is not
30410 encrypted. You can use the generic &%server_advertise_condition%& authenticator
30411 option to do this.)
30415 .section "Format of an ACL" "SECID199"
30416 .cindex "&ACL;" "format of"
30417 .cindex "&ACL;" "verbs, definition of"
30418 An individual ACL consists of a number of statements. Each statement starts
30419 with a verb, optionally followed by a number of conditions and &"modifiers"&.
30420 Modifiers can change the way the verb operates, define error and log messages,
30421 set variables, insert delays, and vary the processing of accepted messages.
30423 If all the conditions are met, the verb is obeyed. The same condition may be
30424 used (with different arguments) more than once in the same statement. This
30425 provides a means of specifying an &"and"& conjunction between conditions. For
30428 deny dnslists = list1.example
30429 dnslists = list2.example
30431 If there are no conditions, the verb is always obeyed. Exim stops evaluating
30432 the conditions and modifiers when it reaches a condition that fails. What
30433 happens then depends on the verb (and in one case, on a special modifier). Not
30434 all the conditions make sense at every testing point. For example, you cannot
30435 test a sender address in the ACL that is run for a VRFY command.
30438 .section "ACL verbs" "SECID200"
30439 The ACL verbs are as follows:
30442 .cindex "&%accept%& ACL verb"
30443 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
30444 of the conditions are not met, what happens depends on whether &%endpass%&
30445 appears among the conditions (for syntax see below). If the failing condition
30446 is before &%endpass%&, control is passed to the next ACL statement; if it is
30447 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
30448 check a RCPT command:
30450 accept domains = +local_domains
30454 If the recipient domain does not match the &%domains%& condition, control
30455 passes to the next statement. If it does match, the recipient is verified, and
30456 the command is accepted if verification succeeds. However, if verification
30457 fails, the ACL yields &"deny"&, because the failing condition is after
30460 The &%endpass%& feature has turned out to be confusing to many people, so its
30461 use is not recommended nowadays. It is always possible to rewrite an ACL so
30462 that &%endpass%& is not needed, and it is no longer used in the default
30465 .cindex "&%message%& ACL modifier" "with &%accept%&"
30466 If a &%message%& modifier appears on an &%accept%& statement, its action
30467 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
30468 (when an &%accept%& verb either accepts or passes control to the next
30469 statement), &%message%& can be used to vary the message that is sent when an
30470 SMTP command is accepted. For example, in a RCPT ACL you could have:
30472 &`accept `&<&'some conditions'&>
30473 &` message = OK, I will allow you through today`&
30475 You can specify an SMTP response code, optionally followed by an &"extended
30476 response code"& at the start of the message, but the first digit must be the
30477 same as would be sent by default, which is 2 for an &%accept%& verb.
30479 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
30480 an error message that is used when access is denied. This behaviour is retained
30481 for backward compatibility, but current &"best practice"& is to avoid the use
30486 .cindex "&%defer%& ACL verb"
30487 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
30488 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
30489 &%defer%& is the same as &%deny%&, because there is no way of sending a
30490 temporary error. For a RCPT command, &%defer%& is much the same as using a
30491 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
30492 be used in any ACL, and even for a recipient it might be a simpler approach.
30496 .cindex "&%deny%& ACL verb"
30497 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
30498 the conditions are not met, control is passed to the next ACL statement. For
30501 deny dnslists = blackholes.mail-abuse.org
30503 rejects commands from hosts that are on a DNS black list.
30507 .cindex "&%discard%& ACL verb"
30508 &%discard%&: This verb behaves like &%accept%&, except that it returns
30509 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
30510 that are concerned with receiving messages. When all the conditions are true,
30511 the sending entity receives a &"success"& response. However, &%discard%& causes
30512 recipients to be discarded. If it is used in an ACL for RCPT, just the one
30513 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
30514 message's recipients are discarded. Recipients that are discarded before DATA
30515 do not appear in the log line when the &%received_recipients%& log selector is set.
30517 If the &%log_message%& modifier is set when &%discard%& operates,
30518 its contents are added to the line that is automatically written to the log.
30519 The &%message%& modifier operates exactly as it does for &%accept%&.
30523 .cindex "&%drop%& ACL verb"
30524 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
30525 forcibly closed after the 5&'xx'& error message has been sent. For example:
30527 drop condition = ${if > {$rcpt_count}{20}}
30528 message = I don't take more than 20 RCPTs
30530 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
30531 The connection is always dropped after sending a 550 response.
30534 .cindex "&%require%& ACL verb"
30535 &%require%&: If all the conditions are met, control is passed to the next ACL
30536 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
30537 example, when checking a RCPT command,
30539 require message = Sender did not verify
30542 passes control to subsequent statements only if the message's sender can be
30543 verified. Otherwise, it rejects the command. Note the positioning of the
30544 &%message%& modifier, before the &%verify%& condition. The reason for this is
30545 discussed in section &<<SECTcondmodproc>>&.
30548 .cindex "&%warn%& ACL verb"
30549 &%warn%&: If all the conditions are true, a line specified by the
30550 &%log_message%& modifier is written to Exim's main log. Control always passes
30551 to the next ACL statement. If any condition is false, the log line is not
30552 written. If an identical log line is requested several times in the same
30553 message, only one copy is actually written to the log. If you want to force
30554 duplicates to be written, use the &%logwrite%& modifier instead.
30556 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
30557 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
30558 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
30559 first failing condition. There is more about adding header lines in section
30560 &<<SECTaddheadacl>>&.
30562 If any condition on a &%warn%& statement cannot be completed (that is, there is
30563 some sort of defer), the log line specified by &%log_message%& is not written.
30564 This does not include the case of a forced failure from a lookup, which
30565 is considered to be a successful completion. After a defer, no further
30566 conditions or modifiers in the &%warn%& statement are processed. The incident
30567 is logged, and the ACL continues to be processed, from the next statement
30571 .vindex "&$acl_verify_message$&"
30572 When one of the &%warn%& conditions is an address verification that fails, the
30573 text of the verification failure message is in &$acl_verify_message$&. If you
30574 want this logged, you must set it up explicitly. For example:
30576 warn !verify = sender
30577 log_message = sender verify failed: $acl_verify_message
30581 At the end of each ACL there is an implicit unconditional &%deny%&.
30583 As you can see from the examples above, the conditions and modifiers are
30584 written one to a line, with the first one on the same line as the verb, and
30585 subsequent ones on following lines. If you have a very long condition, you can
30586 continue it onto several physical lines by the usual backslash continuation
30587 mechanism. It is conventional to align the conditions vertically.
30591 .section "ACL variables" "SECTaclvariables"
30592 .cindex "&ACL;" "variables"
30593 There are some special variables that can be set during ACL processing. They
30594 can be used to pass information between different ACLs, different invocations
30595 of the same ACL in the same SMTP connection, and between ACLs and the routers,
30596 transports, and filters that are used to deliver a message. The names of these
30597 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
30598 an underscore, but the remainder of the name can be any sequence of
30599 alphanumeric characters and underscores that you choose. There is no limit on
30600 the number of ACL variables. The two sets act as follows:
30602 The values of those variables whose names begin with &$acl_c$& persist
30603 throughout an SMTP connection. They are never reset. Thus, a value that is set
30604 while receiving one message is still available when receiving the next message
30605 on the same SMTP connection.
30607 The values of those variables whose names begin with &$acl_m$& persist only
30608 while a message is being received. They are reset afterwards. They are also
30609 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
30612 When a message is accepted, the current values of all the ACL variables are
30613 preserved with the message and are subsequently made available at delivery
30614 time. The ACL variables are set by a modifier called &%set%&. For example:
30616 accept hosts = whatever
30617 set acl_m4 = some value
30618 accept authenticated = *
30619 set acl_c_auth = yes
30621 &*Note*&: A leading dollar sign is not used when naming a variable that is to
30622 be set. If you want to set a variable without taking any action, you can use a
30623 &%warn%& verb without any other modifiers or conditions.
30625 .oindex &%strict_acl_vars%&
30626 What happens if a syntactically valid but undefined ACL variable is
30627 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
30628 false (the default), an empty string is substituted; if it is true, an
30629 error is generated.
30631 Versions of Exim before 4.64 have a limited set of numbered variables, but
30632 their names are compatible, so there is no problem with upgrading.
30635 .section "Condition and modifier processing" "SECTcondmodproc"
30636 .cindex "&ACL;" "conditions; processing"
30637 .cindex "&ACL;" "modifiers; processing"
30638 An exclamation mark preceding a condition negates its result. For example:
30640 deny domains = *.dom.example
30641 !verify = recipient
30643 causes the ACL to return &"deny"& if the recipient domain ends in
30644 &'dom.example'& and the recipient address cannot be verified. Sometimes
30645 negation can be used on the right-hand side of a condition. For example, these
30646 two statements are equivalent:
30648 deny hosts = !192.168.3.4
30649 deny !hosts = 192.168.3.4
30651 However, for many conditions (&%verify%& being a good example), only left-hand
30652 side negation of the whole condition is possible.
30654 The arguments of conditions and modifiers are expanded. A forced failure
30655 of an expansion causes a condition to be ignored, that is, it behaves as if the
30656 condition is true. Consider these two statements:
30658 accept senders = ${lookup{$host_name}lsearch\
30659 {/some/file}{$value}fail}
30660 accept senders = ${lookup{$host_name}lsearch\
30661 {/some/file}{$value}{}}
30663 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
30664 the returned list is searched, but if the lookup fails the behaviour is
30665 different in the two cases. The &%fail%& in the first statement causes the
30666 condition to be ignored, leaving no further conditions. The &%accept%& verb
30667 therefore succeeds. The second statement, however, generates an empty list when
30668 the lookup fails. No sender can match an empty list, so the condition fails,
30669 and therefore the &%accept%& also fails.
30671 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
30672 specify actions that are taken as the conditions for a statement are checked;
30673 others specify text for messages that are used when access is denied or a
30674 warning is generated. The &%control%& modifier affects the way an incoming
30675 message is handled.
30677 The positioning of the modifiers in an ACL statement is important, because the
30678 processing of a verb ceases as soon as its outcome is known. Only those
30679 modifiers that have already been encountered will take effect. For example,
30680 consider this use of the &%message%& modifier:
30682 require message = Can't verify sender
30684 message = Can't verify recipient
30686 message = This message cannot be used
30688 If sender verification fails, Exim knows that the result of the statement is
30689 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
30690 so its text is used as the error message. If sender verification succeeds, but
30691 recipient verification fails, the second message is used. If recipient
30692 verification succeeds, the third message becomes &"current"&, but is never used
30693 because there are no more conditions to cause failure.
30695 For the &%deny%& verb, on the other hand, it is always the last &%message%&
30696 modifier that is used, because all the conditions must be true for rejection to
30697 happen. Specifying more than one &%message%& modifier does not make sense, and
30698 the message can even be specified after all the conditions. For example:
30701 !senders = *@my.domain.example
30702 message = Invalid sender from client host
30704 The &"deny"& result does not happen until the end of the statement is reached,
30705 by which time Exim has set up the message.
30709 .section "ACL modifiers" "SECTACLmodi"
30710 .cindex "&ACL;" "modifiers; list of"
30711 The ACL modifiers are as follows:
30714 .vitem &*add_header*&&~=&~<&'text'&>
30715 This modifier specifies one or more header lines that are to be added to an
30716 incoming message, assuming, of course, that the message is ultimately
30717 accepted. For details, see section &<<SECTaddheadacl>>&.
30719 .vitem &*continue*&&~=&~<&'text'&>
30720 .cindex "&%continue%& ACL modifier"
30721 .cindex "database" "updating in ACL"
30722 This modifier does nothing of itself, and processing of the ACL always
30723 continues with the next condition or modifier. The value of &%continue%& is in
30724 the side effects of expanding its argument. Typically this could be used to
30725 update a database. It is really just a syntactic tidiness, to avoid having to
30726 write rather ugly lines like this:
30728 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
30730 Instead, all you need is
30732 &`continue = `&<&'some expansion'&>
30735 .vitem &*control*&&~=&~<&'text'&>
30736 .cindex "&%control%& ACL modifier"
30737 This modifier affects the subsequent processing of the SMTP connection or of an
30738 incoming message that is accepted. The effect of the first type of control
30739 lasts for the duration of the connection, whereas the effect of the second type
30740 lasts only until the current message has been received. The message-specific
30741 controls always apply to the whole message, not to individual recipients,
30742 even if the &%control%& modifier appears in a RCPT ACL.
30744 As there are now quite a few controls that can be applied, they are described
30745 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
30746 in several different ways. For example:
30748 . ==== As this is a nested list, any displays it contains must be indented
30749 . ==== as otherwise they are too far to the left. That comment applies only
30750 . ==== when xmlto and fop are used; formatting with sdop gets it right either
30754 It can be at the end of an &%accept%& statement:
30756 accept ...some conditions
30759 In this case, the control is applied when this statement yields &"accept"&, in
30760 other words, when the conditions are all true.
30763 It can be in the middle of an &%accept%& statement:
30765 accept ...some conditions...
30767 ...some more conditions...
30769 If the first set of conditions are true, the control is applied, even if the
30770 statement does not accept because one of the second set of conditions is false.
30771 In this case, some subsequent statement must yield &"accept"& for the control
30775 It can be used with &%warn%& to apply the control, leaving the
30776 decision about accepting or denying to a subsequent verb. For
30779 warn ...some conditions...
30783 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
30784 &%logwrite%&, so it does not add anything to the message and does not write a
30788 If you want to apply a control unconditionally, you can use it with a
30789 &%require%& verb. For example:
30791 require control = no_multiline_responses
30795 .vitem &*delay*&&~=&~<&'time'&>
30796 .cindex "&%delay%& ACL modifier"
30798 This modifier may appear in any ACL except notquit. It causes Exim to wait for
30799 the time interval before proceeding. However, when testing Exim using the
30800 &%-bh%& option, the delay is not actually imposed (an appropriate message is
30801 output instead). The time is given in the usual Exim notation, and the delay
30802 happens as soon as the modifier is processed. In an SMTP session, pending
30803 output is flushed before the delay is imposed.
30805 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
30808 deny ...some conditions...
30811 The delay happens if all the conditions are true, before the statement returns
30812 &"deny"&. Compare this with:
30815 ...some conditions...
30817 which waits for 30s before processing the conditions. The &%delay%& modifier
30818 can also be used with &%warn%& and together with &%control%&:
30820 warn ...some conditions...
30826 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
30827 responses to several commands are no longer buffered and sent in one packet (as
30828 they would normally be) because all output is flushed before imposing the
30829 delay. This optimization is disabled so that a number of small delays do not
30830 appear to the client as one large aggregated delay that might provoke an
30831 unwanted timeout. You can, however, disable output flushing for &%delay%& by
30832 using a &%control%& modifier to set &%no_delay_flush%&.
30836 .cindex "&%endpass%& ACL modifier"
30837 This modifier, which has no argument, is recognized only in &%accept%& and
30838 &%discard%& statements. It marks the boundary between the conditions whose
30839 failure causes control to pass to the next statement, and the conditions whose
30840 failure causes the ACL to return &"deny"&. This concept has proved to be
30841 confusing to some people, so the use of &%endpass%& is no longer recommended as
30842 &"best practice"&. See the description of &%accept%& above for more details.
30845 .vitem &*log_message*&&~=&~<&'text'&>
30846 .cindex "&%log_message%& ACL modifier"
30847 This modifier sets up a message that is used as part of the log message if the
30848 ACL denies access or a &%warn%& statement's conditions are true. For example:
30850 require log_message = wrong cipher suite $tls_in_cipher
30851 encrypted = DES-CBC3-SHA
30853 &%log_message%& is also used when recipients are discarded by &%discard%&. For
30856 &`discard `&<&'some conditions'&>
30857 &` log_message = Discarded $local_part@$domain because...`&
30859 When access is denied, &%log_message%& adds to any underlying error message
30860 that may exist because of a condition failure. For example, while verifying a
30861 recipient address, a &':fail:'& redirection might have already set up a
30864 The message may be defined before the conditions to which it applies, because
30865 the string expansion does not happen until Exim decides that access is to be
30866 denied. This means that any variables that are set by the condition are
30867 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
30868 variables are set after a DNS black list lookup succeeds. If the expansion of
30869 &%log_message%& fails, or if the result is an empty string, the modifier is
30872 .vindex "&$acl_verify_message$&"
30873 If you want to use a &%warn%& statement to log the result of an address
30874 verification, you can use &$acl_verify_message$& to include the verification
30877 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
30878 the start of the logged message. If the same warning log message is requested
30879 more than once while receiving a single email message, only one copy is
30880 actually logged. If you want to log multiple copies, use &%logwrite%& instead
30881 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
30882 is logged for a successful &%warn%& statement.
30884 If &%log_message%& is not present and there is no underlying error message (for
30885 example, from the failure of address verification), but &%message%& is present,
30886 the &%message%& text is used for logging rejections. However, if any text for
30887 logging contains newlines, only the first line is logged. In the absence of
30888 both &%log_message%& and &%message%&, a default built-in message is used for
30889 logging rejections.
30892 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
30893 .cindex "&%log_reject_target%& ACL modifier"
30894 .cindex "logging in ACL" "specifying which log"
30895 This modifier makes it possible to specify which logs are used for messages
30896 about ACL rejections. Its argument is a colon-separated list of words that can
30897 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
30898 may be empty, in which case a rejection is not logged at all. For example, this
30899 ACL fragment writes no logging information when access is denied:
30901 &`deny `&<&'some conditions'&>
30902 &` log_reject_target =`&
30904 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
30905 permanent and temporary rejections. Its effect lasts for the rest of the
30909 .vitem &*logwrite*&&~=&~<&'text'&>
30910 .cindex "&%logwrite%& ACL modifier"
30911 .cindex "logging in ACL" "immediate"
30912 This modifier writes a message to a log file as soon as it is encountered when
30913 processing an ACL. (Compare &%log_message%&, which, except in the case of
30914 &%warn%& and &%discard%&, is used only if the ACL statement denies
30915 access.) The &%logwrite%& modifier can be used to log special incidents in
30918 &`accept `&<&'some special conditions'&>
30919 &` control = freeze`&
30920 &` logwrite = froze message because ...`&
30922 By default, the message is written to the main log. However, it may begin
30923 with a colon, followed by a comma-separated list of log names, and then
30924 another colon, to specify exactly which logs are to be written. For
30927 logwrite = :main,reject: text for main and reject logs
30928 logwrite = :panic: text for panic log only
30932 .vitem &*message*&&~=&~<&'text'&>
30933 .cindex "&%message%& ACL modifier"
30934 This modifier sets up a text string that is expanded and used as a response
30935 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
30936 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
30937 there is some complication if &%endpass%& is involved; see the description of
30938 &%accept%& for details.)
30940 The expansion of the message happens at the time Exim decides that the ACL is
30941 to end, not at the time it processes &%message%&. If the expansion fails, or
30942 generates an empty string, the modifier is ignored. Here is an example where
30943 &%message%& must be specified first, because the ACL ends with a rejection if
30944 the &%hosts%& condition fails:
30946 require message = Host not recognized
30949 (Once a condition has failed, no further conditions or modifiers are
30952 .cindex "SMTP" "error codes"
30953 .oindex "&%smtp_banner%&
30954 For ACLs that are triggered by SMTP commands, the message is returned as part
30955 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
30956 is meaningful only for SMTP, as no message is returned when a non-SMTP message
30957 is accepted. In the case of the connect ACL, accepting with a message modifier
30958 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
30959 accept message may not contain more than one line (otherwise it will be
30960 truncated at the first newline and a panic logged), and it cannot affect the
30963 When SMTP is involved, the message may begin with an overriding response code,
30964 consisting of three digits optionally followed by an &"extended response code"&
30965 of the form &'n.n.n'&, each code being followed by a space. For example:
30967 deny message = 599 1.2.3 Host not welcome
30968 hosts = 192.168.34.0/24
30970 The first digit of the supplied response code must be the same as would be sent
30971 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
30972 access, but for the predata ACL, note that the default success code is 354, not
30975 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
30976 the message modifier cannot override the 221 response code.
30978 The text in a &%message%& modifier is literal; any quotes are taken as
30979 literals, but because the string is expanded, backslash escapes are processed
30980 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
30983 .vindex "&$acl_verify_message$&"
30984 For ACLs that are called by an &%acl =%& ACL condition, the message is
30985 stored in &$acl_verify_message$&, from which the calling ACL may use it.
30987 If &%message%& is used on a statement that verifies an address, the message
30988 specified overrides any message that is generated by the verification process.
30989 However, the original message is available in the variable
30990 &$acl_verify_message$&, so you can incorporate it into your message if you
30991 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
30992 routers to be passed back as part of the SMTP response, you should either not
30993 use a &%message%& modifier, or make use of &$acl_verify_message$&.
30995 For compatibility with previous releases of Exim, a &%message%& modifier that
30996 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
30997 modifier, but this usage is now deprecated. However, &%message%& acts only when
30998 all the conditions are true, wherever it appears in an ACL command, whereas
30999 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
31000 &%warn%& in an ACL that is not concerned with receiving a message, it has no
31004 .vitem &*queue*&&~=&~<&'text'&>
31005 .cindex "&%queue%& ACL modifier"
31006 .cindex "named queues" "selecting in ACL"
31007 This modifier specifies the use of a named queue for spool files
31009 It can only be used before the message is received (i.e. not in
31011 This could be used, for example, for known high-volume burst sources
31012 of traffic, or for quarantine of messages.
31013 Separate queue-runner processes will be needed for named queues.
31014 If the text after expansion is empty, the default queue is used.
31017 .vitem &*remove_header*&&~=&~<&'text'&>
31018 This modifier specifies one or more header names in a colon-separated list
31019 that are to be removed from an incoming message, assuming, of course, that
31020 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
31023 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
31024 .cindex "&%set%& ACL modifier"
31025 This modifier puts a value into one of the ACL variables (see section
31026 &<<SECTaclvariables>>&).
31029 .vitem &*udpsend*&&~=&~<&'parameters'&>
31030 .cindex "UDP communications"
31031 This modifier sends a UDP packet, for purposes such as statistics
31032 collection or behaviour monitoring. The parameters are expanded, and
31033 the result of the expansion must be a colon-separated list consisting
31034 of a destination server, port number, and the packet contents. The
31035 server can be specified as a host name or IPv4 or IPv6 address. The
31036 separator can be changed with the usual angle bracket syntax. For
31037 example, you might want to collect information on which hosts connect
31040 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
31041 $tod_zulu $sender_host_address
31048 .section "Use of the control modifier" "SECTcontrols"
31049 .cindex "&%control%& ACL modifier"
31050 The &%control%& modifier supports the following settings:
31053 .vitem &*control&~=&~allow_auth_unadvertised*&
31054 This modifier allows a client host to use the SMTP AUTH command even when it
31055 has not been advertised in response to EHLO. Furthermore, because there are
31056 apparently some really broken clients that do this, Exim will accept AUTH after
31057 HELO (rather than EHLO) when this control is set. It should be used only if you
31058 really need it, and you should limit its use to those broken clients that do
31059 not work without it. For example:
31061 warn hosts = 192.168.34.25
31062 control = allow_auth_unadvertised
31064 Normally, when an Exim server receives an AUTH command, it checks the name of
31065 the authentication mechanism that is given in the command to ensure that it
31066 matches an advertised mechanism. When this control is set, the check that a
31067 mechanism has been advertised is bypassed. Any configured mechanism can be used
31068 by the client. This control is permitted only in the connection and HELO ACLs.
31071 .vitem &*control&~=&~caseful_local_part*& &&&
31072 &*control&~=&~caselower_local_part*&
31073 .cindex "&ACL;" "case of local part in"
31074 .cindex "case of local parts"
31075 .vindex "&$local_part$&"
31076 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
31077 (that is, during RCPT processing). By default, the contents of &$local_part$&
31078 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
31079 any uppercase letters in the original local part are restored in &$local_part$&
31080 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
31083 These controls affect only the current recipient. Moreover, they apply only to
31084 local part handling that takes place directly in the ACL (for example, as a key
31085 in lookups). If a test to verify the recipient is obeyed, the case-related
31086 handling of the local part during the verification is controlled by the router
31087 configuration (see the &%caseful_local_part%& generic router option).
31089 This facility could be used, for example, to add a spam score to local parts
31090 containing upper case letters. For example, using &$acl_m4$& to accumulate the
31093 warn control = caseful_local_part
31094 set acl_m4 = ${eval:\
31096 ${if match{$local_part}{[A-Z]}{1}{0}}\
31098 control = caselower_local_part
31100 Notice that we put back the lower cased version afterwards, assuming that
31101 is what is wanted for subsequent tests.
31104 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
31105 .cindex "&ACL;" "cutthrough routing"
31106 .cindex "cutthrough" "requesting"
31107 This option requests delivery be attempted while the item is being received.
31109 The option is usable in the RCPT ACL.
31110 If enabled for a message received via smtp and routed to an smtp transport,
31111 and only one transport, interface, destination host and port combination
31112 is used for all recipients of the message,
31113 then the delivery connection is made while the receiving connection is open
31114 and data is copied from one to the other.
31116 An attempt to set this option for any recipient but the first
31117 for a mail will be quietly ignored.
31118 If a recipient-verify callout
31120 connection is subsequently
31121 requested in the same ACL it is held open and used for
31122 any subsequent recipients and the data,
31123 otherwise one is made after the initial RCPT ACL completes.
31125 Note that routers are used in verify mode,
31126 and cannot depend on content of received headers.
31127 Note also that headers cannot be
31128 modified by any of the post-data ACLs (DATA, MIME and DKIM).
31129 Headers may be modified by routers (subject to the above) and transports.
31130 The &'Received-By:'& header is generated as soon as the body reception starts,
31131 rather than the traditional time after the full message is received;
31132 this will affect the timestamp.
31134 All the usual ACLs are called; if one results in the message being
31135 rejected, all effort spent in delivery (including the costs on
31136 the ultimate destination) will be wasted.
31137 Note that in the case of data-time ACLs this includes the entire
31140 Cutthrough delivery is not supported via transport-filters or when DKIM signing
31141 of outgoing messages is done, because it sends data to the ultimate destination
31142 before the entire message has been received from the source.
31143 It is not supported for messages received with the SMTP PRDR
31147 Should the ultimate destination system positively accept or reject the mail,
31148 a corresponding indication is given to the source system and nothing is queued.
31149 If the item is successfully delivered in cutthrough mode
31150 the delivery log lines are tagged with ">>" rather than "=>" and appear
31151 before the acceptance "<=" line.
31153 If there is a temporary error the item is queued for later delivery in the
31155 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
31156 to the control; the default value is &"spool"& and the alternate value
31157 &"pass"& copies an SMTP defer response from the target back to the initiator
31158 and does not queue the message.
31159 Note that this is independent of any recipient verify conditions in the ACL.
31161 Delivery in this mode avoids the generation of a bounce mail to a
31163 sender when the destination system is doing content-scan based rejection.
31166 .vitem &*control&~=&~debug/*&<&'options'&>
31167 .cindex "&ACL;" "enabling debug logging"
31168 .cindex "debugging" "enabling from an ACL"
31169 This control turns on debug logging, almost as though Exim had been invoked
31170 with &`-d`&, with the output going to a new logfile in the usual logs directory,
31171 by default called &'debuglog'&.
31172 The filename can be adjusted with the &'tag'& option, which
31173 may access any variables already defined. The logging may be adjusted with
31174 the &'opts'& option, which takes the same values as the &`-d`& command-line
31176 Logging started this way may be stopped, and the file removed,
31177 with the &'kill'& option.
31178 Some examples (which depend on variables that don't exist in all
31182 control = debug/tag=.$sender_host_address
31183 control = debug/opts=+expand+acl
31184 control = debug/tag=.$message_exim_id/opts=+expand
31185 control = debug/kill
31189 .vitem &*control&~=&~dkim_disable_verify*&
31190 .cindex "disable DKIM verify"
31191 .cindex "DKIM" "disable verify"
31192 This control turns off DKIM verification processing entirely. For details on
31193 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
31196 .vitem &*control&~=&~dmarc_disable_verify*&
31197 .cindex "disable DMARC verify"
31198 .cindex "DMARC" "disable verify"
31199 This control turns off DMARC verification processing entirely. For details on
31200 the operation and configuration of DMARC, see section &<<SECDMARC>>&.
31203 .vitem &*control&~=&~dscp/*&<&'value'&>
31204 .cindex "&ACL;" "setting DSCP value"
31205 .cindex "DSCP" "inbound"
31206 This option causes the DSCP value associated with the socket for the inbound
31207 connection to be adjusted to a given value, given as one of a number of fixed
31208 strings or to numeric value.
31209 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
31210 Common values include &`throughput`&, &`mincost`&, and on newer systems
31211 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
31213 The outbound packets from Exim will be marked with this value in the header
31214 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
31215 that these values will have any effect, not be stripped by networking
31216 equipment, or do much of anything without cooperation with your Network
31217 Engineer and those of all network operators between the source and destination.
31220 .vitem &*control&~=&~enforce_sync*& &&&
31221 &*control&~=&~no_enforce_sync*&
31222 .cindex "SMTP" "synchronization checking"
31223 .cindex "synchronization checking in SMTP"
31224 These controls make it possible to be selective about when SMTP synchronization
31225 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
31226 state of the switch (it is true by default). See the description of this option
31227 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
31229 The effect of these two controls lasts for the remainder of the SMTP
31230 connection. They can appear in any ACL except the one for the non-SMTP
31231 messages. The most straightforward place to put them is in the ACL defined by
31232 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
31233 before the first synchronization check. The expected use is to turn off the
31234 synchronization checks for badly-behaved hosts that you nevertheless need to
31238 .vitem &*control&~=&~fakedefer/*&<&'message'&>
31239 .cindex "fake defer"
31240 .cindex "defer, fake"
31241 This control works in exactly the same way as &%fakereject%& (described below)
31242 except that it causes an SMTP 450 response after the message data instead of a
31243 550 response. You must take care when using &%fakedefer%& because it causes the
31244 messages to be duplicated when the sender retries. Therefore, you should not
31245 use &%fakedefer%& if the message is to be delivered normally.
31247 .vitem &*control&~=&~fakereject/*&<&'message'&>
31248 .cindex "fake rejection"
31249 .cindex "rejection, fake"
31250 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
31251 words, only when an SMTP message is being received. If Exim accepts the
31252 message, instead the final 250 response, a 550 rejection message is sent.
31253 However, Exim proceeds to deliver the message as normal. The control applies
31254 only to the current message, not to any subsequent ones that may be received in
31255 the same SMTP connection.
31257 The text for the 550 response is taken from the &%control%& modifier. If no
31258 message is supplied, the following is used:
31260 550-Your message has been rejected but is being
31261 550-kept for evaluation.
31262 550-If it was a legitimate message, it may still be
31263 550 delivered to the target recipient(s).
31265 This facility should be used with extreme caution.
31267 .vitem &*control&~=&~freeze*&
31268 .cindex "frozen messages" "forcing in ACL"
31269 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31270 other words, only when a message is being received. If the message is accepted,
31271 it is placed on Exim's queue and frozen. The control applies only to the
31272 current message, not to any subsequent ones that may be received in the same
31275 This modifier can optionally be followed by &`/no_tell`&. If the global option
31276 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
31277 is told about the freezing), provided all the &*control=freeze*& modifiers that
31278 are obeyed for the current message have the &`/no_tell`& option.
31280 .vitem &*control&~=&~no_delay_flush*&
31281 .cindex "SMTP" "output flushing, disabling for delay"
31282 Exim normally flushes SMTP output before implementing a delay in an ACL, to
31283 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31284 use. This control, as long as it is encountered before the &%delay%& modifier,
31285 disables such output flushing.
31287 .vitem &*control&~=&~no_callout_flush*&
31288 .cindex "SMTP" "output flushing, disabling for callout"
31289 Exim normally flushes SMTP output before performing a callout in an ACL, to
31290 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
31291 use. This control, as long as it is encountered before the &%verify%& condition
31292 that causes the callout, disables such output flushing.
31294 .vitem &*control&~=&~no_mbox_unspool*&
31295 This control is available when Exim is compiled with the content scanning
31296 extension. Content scanning may require a copy of the current message, or parts
31297 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
31298 or spam scanner. Normally, such copies are deleted when they are no longer
31299 needed. If this control is set, the copies are not deleted. The control applies
31300 only to the current message, not to any subsequent ones that may be received in
31301 the same SMTP connection. It is provided for debugging purposes and is unlikely
31302 to be useful in production.
31304 .vitem &*control&~=&~no_multiline_responses*&
31305 .cindex "multiline responses, suppressing"
31306 This control is permitted for any ACL except the one for non-SMTP messages.
31307 It seems that there are broken clients in use that cannot handle multiline
31308 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
31310 If this control is set, multiline SMTP responses from ACL rejections are
31311 suppressed. One way of doing this would have been to put out these responses as
31312 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
31313 (&"use multiline responses for more"& it says &-- ha!), and some of the
31314 responses might get close to that. So this facility, which is after all only a
31315 sop to broken clients, is implemented by doing two very easy things:
31318 Extra information that is normally output as part of a rejection caused by
31319 sender verification failure is omitted. Only the final line (typically &"sender
31320 verification failed"&) is sent.
31322 If a &%message%& modifier supplies a multiline response, only the first
31326 The setting of the switch can, of course, be made conditional on the
31327 calling host. Its effect lasts until the end of the SMTP connection.
31329 .vitem &*control&~=&~no_pipelining*&
31330 .cindex "PIPELINING" "suppressing advertising"
31331 .cindex "ESMTP extensions" PIPELINING
31332 This control turns off the advertising of the PIPELINING extension to SMTP in
31333 the current session. To be useful, it must be obeyed before Exim sends its
31334 response to an EHLO command. Therefore, it should normally appear in an ACL
31335 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
31336 &%pipelining_advertise_hosts%&.
31338 .vitem &*control&~=&~queue/*&<&'options'&>* &&&
31339 &*control&~=&~queue_only*&
31340 .oindex "&%queue%&"
31341 .oindex "&%queue_only%&"
31342 .cindex "queueing incoming messages"
31343 .cindex queueing "forcing in ACL"
31344 .cindex "first pass routing"
31345 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
31346 other words, only when a message is being received. If the message is accepted,
31347 it is placed on Exim's queue and left there for delivery by a subsequent queue
31349 If used with no options set,
31350 no immediate delivery process is started. In other words, it has the
31351 effect as the &%queue_only%& global option or &'-odq'& command-line option.
31353 If the &'first_pass_route'& option is given then
31354 the behaviour is like the command-line &'-oqds'& option;
31355 a delivery process is started which stops short of making
31356 any SMTP delivery. The benefit is that the hints database will be updated for
31357 the message being waiting for a specific host, and a later queue run will be
31358 able to send all such messages on a single connection.
31360 The control only applies to the current message, not to any subsequent ones that
31361 may be received in the same SMTP connection.
31363 .vitem &*control&~=&~submission/*&<&'options'&>
31364 .cindex "message" "submission"
31365 .cindex "submission mode"
31366 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
31367 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
31368 the current message is a submission from a local MUA. In this case, Exim
31369 operates in &"submission mode"&, and applies certain fixups to the message if
31370 necessary. For example, it adds a &'Date:'& header line if one is not present.
31371 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
31372 late (the message has already been created).
31374 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
31375 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
31376 submission mode; the available options for this control are described there.
31377 The control applies only to the current message, not to any subsequent ones
31378 that may be received in the same SMTP connection.
31380 .vitem &*control&~=&~suppress_local_fixups*&
31381 .cindex "submission fixups, suppressing"
31382 This control applies to locally submitted (non TCP/IP) messages, and is the
31383 complement of &`control = submission`&. It disables the fixups that are
31384 normally applied to locally-submitted messages. Specifically:
31387 Any &'Sender:'& header line is left alone (in this respect, it is a
31388 dynamic version of &%local_sender_retain%&).
31390 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
31392 There is no check that &'From:'& corresponds to the actual sender.
31395 This control may be useful when a remotely-originated message is accepted,
31396 passed to some scanning program, and then re-submitted for delivery. It can be
31397 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
31398 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
31401 &*Note:*& This control applies only to the current message, not to any others
31402 that are being submitted at the same time using &%-bs%& or &%-bS%&.
31404 .vitem &*control&~=&~utf8_downconvert*&
31405 This control enables conversion of UTF-8 in message envelope addresses
31407 For details see section &<<SECTi18nMTA>>&.
31411 .section "Summary of message fixup control" "SECTsummesfix"
31412 All four possibilities for message fixups can be specified:
31415 Locally submitted, fixups applied: the default.
31417 Locally submitted, no fixups applied: use
31418 &`control = suppress_local_fixups`&.
31420 Remotely submitted, no fixups applied: the default.
31422 Remotely submitted, fixups applied: use &`control = submission`&.
31427 .section "Adding header lines in ACLs" "SECTaddheadacl"
31428 .cindex "header lines" "adding in an ACL"
31429 .cindex "header lines" "position of added lines"
31430 .cindex "&%add_header%& ACL modifier"
31431 The &%add_header%& modifier can be used to add one or more extra header lines
31432 to an incoming message, as in this example:
31434 warn dnslists = sbl.spamhaus.org : \
31435 dialup.mail-abuse.org
31436 add_header = X-blacklisted-at: $dnslist_domain
31438 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31439 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31440 receiving a message). The message must ultimately be accepted for
31441 &%add_header%& to have any significant effect. You can use &%add_header%& with
31442 any ACL verb, including &%deny%& (though this is potentially useful only in a
31445 Headers will not be added to the message if the modifier is used in
31446 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31448 Leading and trailing newlines are removed from
31449 the data for the &%add_header%& modifier; if it then
31450 contains one or more newlines that
31451 are not followed by a space or a tab, it is assumed to contain multiple header
31452 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
31453 front of any line that is not a valid header line.
31455 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
31456 They are added to the message before processing the DATA and MIME ACLs.
31457 However, if an identical header line is requested more than once, only one copy
31458 is actually added to the message. Further header lines may be accumulated
31459 during the DATA and MIME ACLs, after which they are added to the message, again
31460 with duplicates suppressed. Thus, it is possible to add two identical header
31461 lines to an SMTP message, but only if one is added before DATA and one after.
31462 In the case of non-SMTP messages, new headers are accumulated during the
31463 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
31464 message is rejected after DATA or by the non-SMTP ACL, all added header lines
31465 are included in the entry that is written to the reject log.
31467 .cindex "header lines" "added; visibility of"
31468 Header lines are not visible in string expansions
31470 until they are added to the
31471 message. It follows that header lines defined in the MAIL, RCPT, and predata
31472 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
31473 header lines that are added by the DATA or MIME ACLs are not visible in those
31474 ACLs. Because of this restriction, you cannot use header lines as a way of
31475 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
31476 this, you can use ACL variables, as described in section
31477 &<<SECTaclvariables>>&.
31479 The list of headers yet to be added is given by the &%$headers_added%& variable.
31481 The &%add_header%& modifier acts immediately as it is encountered during the
31482 processing of an ACL. Notice the difference between these two cases:
31484 &`accept add_header = ADDED: some text`&
31485 &` `&<&'some condition'&>
31487 &`accept `&<&'some condition'&>
31488 &` add_header = ADDED: some text`&
31490 In the first case, the header line is always added, whether or not the
31491 condition is true. In the second case, the header line is added only if the
31492 condition is true. Multiple occurrences of &%add_header%& may occur in the same
31493 ACL statement. All those that are encountered before a condition fails are
31496 .cindex "&%warn%& ACL verb"
31497 For compatibility with previous versions of Exim, a &%message%& modifier for a
31498 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
31499 effect only if all the conditions are true, even if it appears before some of
31500 them. Furthermore, only the last occurrence of &%message%& is honoured. This
31501 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
31502 are present on a &%warn%& verb, both are processed according to their
31505 By default, new header lines are added to a message at the end of the existing
31506 header lines. However, you can specify that any particular header line should
31507 be added right at the start (before all the &'Received:'& lines), immediately
31508 after the first block of &'Received:'& lines, or immediately before any line
31509 that is not a &'Received:'& or &'Resent-something:'& header.
31511 This is done by specifying &":at_start:"&, &":after_received:"&, or
31512 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
31513 header line, respectively. (Header text cannot start with a colon, as there has
31514 to be a header name first.) For example:
31516 warn add_header = \
31517 :after_received:X-My-Header: something or other...
31519 If more than one header line is supplied in a single &%add_header%& modifier,
31520 each one is treated independently and can therefore be placed differently. If
31521 you add more than one line at the start, or after the Received: block, they end
31522 up in reverse order.
31524 &*Warning*&: This facility currently applies only to header lines that are
31525 added in an ACL. It does NOT work for header lines that are added in a
31526 system filter or in a router or transport.
31530 .section "Removing header lines in ACLs" "SECTremoveheadacl"
31531 .cindex "header lines" "removing in an ACL"
31532 .cindex "header lines" "position of removed lines"
31533 .cindex "&%remove_header%& ACL modifier"
31534 The &%remove_header%& modifier can be used to remove one or more header lines
31535 from an incoming message, as in this example:
31537 warn message = Remove internal headers
31538 remove_header = x-route-mail1 : x-route-mail2
31540 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
31541 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
31542 receiving a message). The message must ultimately be accepted for
31543 &%remove_header%& to have any significant effect. You can use &%remove_header%&
31544 with any ACL verb, including &%deny%&, though this is really not useful for
31545 any verb that doesn't result in a delivered message.
31547 Headers will not be removed from the message if the modifier is used in
31548 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
31550 More than one header can be removed at the same time by using a colon separated
31551 list of header names. The header matching is case insensitive. Wildcards are
31552 not permitted, nor is list expansion performed, so you cannot use hostlists to
31553 create a list of headers, however both connection and message variable expansion
31554 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
31556 warn hosts = +internal_hosts
31557 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
31558 warn message = Remove internal headers
31559 remove_header = $acl_c_ihdrs
31561 Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
31562 Matching header lines are removed from the message before processing the DATA and MIME ACLs.
31563 If multiple header lines match, all are removed.
31564 There is no harm in attempting to remove the same header twice nor in removing
31565 a non-existent header. Further header lines to be removed may be accumulated
31566 during the DATA and MIME ACLs, after which they are removed from the message,
31567 if present. In the case of non-SMTP messages, headers to be removed are
31568 accumulated during the non-SMTP ACLs, and are removed from the message after
31569 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
31570 ACL, there really is no effect because there is no logging of what headers
31571 would have been removed.
31573 .cindex "header lines" "removed; visibility of"
31574 Header lines are not visible in string expansions until the DATA phase when it
31575 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
31576 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
31577 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
31578 this restriction, you cannot use header lines as a way of controlling data
31579 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
31580 you should instead use ACL variables, as described in section
31581 &<<SECTaclvariables>>&.
31583 The &%remove_header%& modifier acts immediately as it is encountered during the
31584 processing of an ACL. Notice the difference between these two cases:
31586 &`accept remove_header = X-Internal`&
31587 &` `&<&'some condition'&>
31589 &`accept `&<&'some condition'&>
31590 &` remove_header = X-Internal`&
31592 In the first case, the header line is always removed, whether or not the
31593 condition is true. In the second case, the header line is removed only if the
31594 condition is true. Multiple occurrences of &%remove_header%& may occur in the
31595 same ACL statement. All those that are encountered before a condition fails
31598 &*Warning*&: This facility currently applies only to header lines that are
31599 present during ACL processing. It does NOT remove header lines that are added
31600 in a system filter or in a router or transport.
31605 .section "ACL conditions" "SECTaclconditions"
31606 .cindex "&ACL;" "conditions; list of"
31607 Some of the conditions listed in this section are available only when Exim is
31608 compiled with the content-scanning extension. They are included here briefly
31609 for completeness. More detailed descriptions can be found in the discussion on
31610 content scanning in chapter &<<CHAPexiscan>>&.
31612 Not all conditions are relevant in all circumstances. For example, testing
31613 senders and recipients does not make sense in an ACL that is being run as the
31614 result of the arrival of an ETRN command, and checks on message headers can be
31615 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
31616 can use the same condition (with different parameters) more than once in the
31617 same ACL statement. This provides a way of specifying an &"and"& conjunction.
31618 The conditions are as follows:
31622 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
31623 .cindex "&ACL;" "nested"
31624 .cindex "&ACL;" "indirect"
31625 .cindex "&ACL;" "arguments"
31626 .cindex "&%acl%& ACL condition"
31627 The possible values of the argument are the same as for the
31628 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
31629 &"accept"& the condition is true; if it returns &"deny"& the condition is
31630 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
31631 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
31632 condition false. This means that further processing of the &%warn%& verb
31633 ceases, but processing of the ACL continues.
31635 If the argument is a named ACL, up to nine space-separated optional values
31636 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
31637 and $acl_narg is set to the count of values.
31638 Previous values of these variables are restored after the call returns.
31639 The name and values are expanded separately.
31640 Note that spaces in complex expansions which are used as arguments
31641 will act as argument separators.
31643 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
31644 the connection is dropped. If it returns &"discard"&, the verb must be
31645 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
31646 conditions are tested.
31648 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
31649 loops. This condition allows you to use different ACLs in different
31650 circumstances. For example, different ACLs can be used to handle RCPT commands
31651 for different local users or different local domains.
31653 .vitem &*authenticated&~=&~*&<&'string&~list'&>
31654 .cindex "&%authenticated%& ACL condition"
31655 .cindex "authentication" "ACL checking"
31656 .cindex "&ACL;" "testing for authentication"
31657 If the SMTP connection is not authenticated, the condition is false. Otherwise,
31658 the name of the authenticator is tested against the list. To test for
31659 authentication by any authenticator, you can set
31664 .vitem &*condition&~=&~*&<&'string'&>
31665 .cindex "&%condition%& ACL condition"
31666 .cindex "customizing" "ACL condition"
31667 .cindex "&ACL;" "customized test"
31668 .cindex "&ACL;" "testing, customized"
31669 This feature allows you to make up custom conditions. If the result of
31670 expanding the string is an empty string, the number zero, or one of the strings
31671 &"no"& or &"false"&, the condition is false. If the result is any non-zero
31672 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
31673 any other value, some error is assumed to have occurred, and the ACL returns
31674 &"defer"&. However, if the expansion is forced to fail, the condition is
31675 ignored. The effect is to treat it as true, whether it is positive or
31678 .vitem &*decode&~=&~*&<&'location'&>
31679 .cindex "&%decode%& ACL condition"
31680 This condition is available only when Exim is compiled with the
31681 content-scanning extension, and it is allowed only in the ACL defined by
31682 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
31683 If all goes well, the condition is true. It is false only if there are
31684 problems such as a syntax error or a memory shortage. For more details, see
31685 chapter &<<CHAPexiscan>>&.
31687 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
31688 .cindex "&%dnslists%& ACL condition"
31689 .cindex "DNS list" "in ACL"
31690 .cindex "black list (DNS)"
31691 .cindex "&ACL;" "testing a DNS list"
31692 This condition checks for entries in DNS black lists. These are also known as
31693 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
31694 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
31695 different variants of this condition to describe briefly here. See sections
31696 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
31698 .vitem &*domains&~=&~*&<&'domain&~list'&>
31699 .cindex "&%domains%& ACL condition"
31700 .cindex "domain" "ACL checking"
31701 .cindex "&ACL;" "testing a recipient domain"
31702 .vindex "&$domain_data$&"
31703 This condition is relevant only after a RCPT command. It checks that the domain
31704 of the recipient address is in the domain list. If percent-hack processing is
31705 enabled, it is done before this test is done. If the check succeeds with a
31706 lookup, the result of the lookup is placed in &$domain_data$& until the next
31709 &*Note carefully*& (because many people seem to fall foul of this): you cannot
31710 use &%domains%& in a DATA ACL.
31713 .vitem &*encrypted&~=&~*&<&'string&~list'&>
31714 .cindex "&%encrypted%& ACL condition"
31715 .cindex "encryption" "checking in an ACL"
31716 .cindex "&ACL;" "testing for encryption"
31717 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
31718 name of the cipher suite in use is tested against the list. To test for
31719 encryption without testing for any specific cipher suite(s), set
31725 .vitem &*hosts&~=&~*&<&'host&~list'&>
31726 .cindex "&%hosts%& ACL condition"
31727 .cindex "host" "ACL checking"
31728 .cindex "&ACL;" "testing the client host"
31729 This condition tests that the calling host matches the host list. If you have
31730 name lookups or wildcarded host names and IP addresses in the same host list,
31731 you should normally put the IP addresses first. For example, you could have:
31733 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
31735 The lookup in this example uses the host name for its key. This is implied by
31736 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
31737 and it wouldn't matter which way round you had these two items.)
31739 The reason for the problem with host names lies in the left-to-right way that
31740 Exim processes lists. It can test IP addresses without doing any DNS lookups,
31741 but when it reaches an item that requires a host name, it fails if it cannot
31742 find a host name to compare with the pattern. If the above list is given in the
31743 opposite order, the &%accept%& statement fails for a host whose name cannot be
31744 found, even if its IP address is 10.9.8.7.
31746 If you really do want to do the name check first, and still recognize the IP
31747 address even if the name lookup fails, you can rewrite the ACL like this:
31749 accept hosts = dbm;/etc/friendly/hosts
31750 accept hosts = 10.9.8.7
31752 The default action on failing to find the host name is to assume that the host
31753 is not in the list, so the first &%accept%& statement fails. The second
31754 statement can then check the IP address.
31756 .vindex "&$host_data$&"
31757 If a &%hosts%& condition is satisfied by means of a lookup, the result
31758 of the lookup is made available in the &$host_data$& variable. This
31759 allows you, for example, to set up a statement like this:
31761 deny hosts = net-lsearch;/some/file
31762 message = $host_data
31764 which gives a custom error message for each denied host.
31766 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
31767 .cindex "&%local_parts%& ACL condition"
31768 .cindex "local part" "ACL checking"
31769 .cindex "&ACL;" "testing a local part"
31770 .vindex "&$local_part_data$&"
31771 This condition is relevant only after a RCPT command. It checks that the local
31772 part of the recipient address is in the list. If percent-hack processing is
31773 enabled, it is done before this test. If the check succeeds with a lookup, the
31774 result of the lookup is placed in &$local_part_data$&, which remains set until
31775 the next &%local_parts%& test.
31777 .vitem &*malware&~=&~*&<&'option'&>
31778 .cindex "&%malware%& ACL condition"
31779 .cindex "&ACL;" "virus scanning"
31780 .cindex "&ACL;" "scanning for viruses"
31781 This condition is available only when Exim is compiled with the
31782 content-scanning extension
31783 and only after a DATA command.
31784 It causes the incoming message to be scanned for
31785 viruses. For details, see chapter &<<CHAPexiscan>>&.
31787 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
31788 .cindex "&%mime_regex%& ACL condition"
31789 .cindex "&ACL;" "testing by regex matching"
31790 This condition is available only when Exim is compiled with the
31791 content-scanning extension, and it is allowed only in the ACL defined by
31792 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
31793 with any of the regular expressions. For details, see chapter
31796 .vitem &*ratelimit&~=&~*&<&'parameters'&>
31797 .cindex "rate limiting"
31798 This condition can be used to limit the rate at which a user or host submits
31799 messages. Details are given in section &<<SECTratelimiting>>&.
31801 .vitem &*recipients&~=&~*&<&'address&~list'&>
31802 .cindex "&%recipients%& ACL condition"
31803 .cindex "recipient" "ACL checking"
31804 .cindex "&ACL;" "testing a recipient"
31805 This condition is relevant only after a RCPT command. It checks the entire
31806 recipient address against a list of recipients.
31808 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
31809 .cindex "&%regex%& ACL condition"
31810 .cindex "&ACL;" "testing by regex matching"
31811 This condition is available only when Exim is compiled with the
31812 content-scanning extension, and is available only in the DATA, MIME, and
31813 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
31814 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
31816 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
31817 .cindex "&%sender_domains%& ACL condition"
31818 .cindex "sender" "ACL checking"
31819 .cindex "&ACL;" "testing a sender domain"
31820 .vindex "&$domain$&"
31821 .vindex "&$sender_address_domain$&"
31822 This condition tests the domain of the sender of the message against the given
31823 domain list. &*Note*&: The domain of the sender address is in
31824 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
31825 of this condition. This is an exception to the general rule for testing domain
31826 lists. It is done this way so that, if this condition is used in an ACL for a
31827 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
31828 influence the sender checking.
31830 &*Warning*&: It is a bad idea to use this condition on its own as a control on
31831 relaying, because sender addresses are easily, and commonly, forged.
31833 .vitem &*senders&~=&~*&<&'address&~list'&>
31834 .cindex "&%senders%& ACL condition"
31835 .cindex "sender" "ACL checking"
31836 .cindex "&ACL;" "testing a sender"
31837 This condition tests the sender of the message against the given list. To test
31838 for a bounce message, which has an empty sender, set
31842 &*Warning*&: It is a bad idea to use this condition on its own as a control on
31843 relaying, because sender addresses are easily, and commonly, forged.
31845 .vitem &*spam&~=&~*&<&'username'&>
31846 .cindex "&%spam%& ACL condition"
31847 .cindex "&ACL;" "scanning for spam"
31848 This condition is available only when Exim is compiled with the
31849 content-scanning extension. It causes the incoming message to be scanned by
31850 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
31852 .vitem &*verify&~=&~certificate*&
31853 .cindex "&%verify%& ACL condition"
31854 .cindex "TLS" "client certificate verification"
31855 .cindex "certificate" "verification of client"
31856 .cindex "&ACL;" "certificate verification"
31857 .cindex "&ACL;" "testing a TLS certificate"
31858 This condition is true in an SMTP session if the session is encrypted, and a
31859 certificate was received from the client, and the certificate was verified. The
31860 server requests a certificate only if the client matches &%tls_verify_hosts%&
31861 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
31863 .vitem &*verify&~=&~csa*&
31864 .cindex "CSA verification"
31865 This condition checks whether the sending host (the client) is authorized to
31866 send email. Details of how this works are given in section
31867 &<<SECTverifyCSA>>&.
31869 .vitem &*verify&~=&~header_names_ascii*&
31870 .cindex "&%verify%& ACL condition"
31871 .cindex "&ACL;" "verifying header names only ASCII"
31872 .cindex "header lines" "verifying header names only ASCII"
31873 .cindex "verifying" "header names only ASCII"
31874 This condition is relevant only in an ACL that is run after a message has been
31876 This usually means an ACL specified by &%acl_smtp_data%& or &%acl_not_smtp%&.
31877 It checks all header names (not the content) to make sure
31878 there are no non-ASCII characters, also excluding control characters. The
31879 allowable characters are decimal ASCII values 33 through 126.
31881 Exim itself will handle headers with non-ASCII characters, but it can cause
31882 problems for downstream applications, so this option will allow their
31883 detection and rejection in the DATA ACL's.
31885 .vitem &*verify&~=&~header_sender/*&<&'options'&>
31886 .cindex "&%verify%& ACL condition"
31887 .cindex "&ACL;" "verifying sender in the header"
31888 .cindex "header lines" "verifying the sender in"
31889 .cindex "sender" "verifying in header"
31890 .cindex "verifying" "sender in header"
31891 This condition is relevant only in an ACL that is run after a message has been
31892 received, that is, in an ACL specified by &%acl_smtp_data%& or
31893 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
31894 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
31895 is loosely thought of as a &"sender"& address (hence the name of the test).
31896 However, an address that appears in one of these headers need not be an address
31897 that accepts bounce messages; only sender addresses in envelopes are required
31898 to accept bounces. Therefore, if you use the callout option on this check, you
31899 might want to arrange for a non-empty address in the MAIL command.
31901 Details of address verification and the options are given later, starting at
31902 section &<<SECTaddressverification>>& (callouts are described in section
31903 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
31904 condition to restrict it to bounce messages only:
31907 !verify = header_sender
31908 message = A valid sender header is required for bounces
31911 .vitem &*verify&~=&~header_syntax*&
31912 .cindex "&%verify%& ACL condition"
31913 .cindex "&ACL;" "verifying header syntax"
31914 .cindex "header lines" "verifying syntax"
31915 .cindex "verifying" "header syntax"
31916 This condition is relevant only in an ACL that is run after a message has been
31917 received, that is, in an ACL specified by &%acl_smtp_data%& or
31918 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
31919 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
31920 and &'Bcc:'&), returning true if there are no problems.
31921 Unqualified addresses (local parts without domains) are
31922 permitted only in locally generated messages and from hosts that match
31923 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
31926 Note that this condition is a syntax check only. However, a common spamming
31927 ploy used to be to send syntactically invalid headers such as
31931 and this condition can be used to reject such messages, though they are not as
31932 common as they used to be.
31934 .vitem &*verify&~=&~helo*&
31935 .cindex "&%verify%& ACL condition"
31936 .cindex "&ACL;" "verifying HELO/EHLO"
31937 .cindex "HELO" "verifying"
31938 .cindex "EHLO" "verifying"
31939 .cindex "verifying" "EHLO"
31940 .cindex "verifying" "HELO"
31941 This condition is true if a HELO or EHLO command has been received from the
31942 client host, and its contents have been verified. If there has been no previous
31943 attempt to verify the HELO/EHLO contents, it is carried out when this
31944 condition is encountered. See the description of the &%helo_verify_hosts%& and
31945 &%helo_try_verify_hosts%& options for details of how to request verification
31946 independently of this condition, and for detail of the verification.
31948 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
31949 option), this condition is always true.
31952 .vitem &*verify&~=&~not_blind/*&<&'options'&>
31953 .cindex "verifying" "not blind"
31954 .cindex "bcc recipients, verifying none"
31955 This condition checks that there are no blind (bcc) recipients in the message.
31956 Every envelope recipient must appear either in a &'To:'& header line or in a
31957 &'Cc:'& header line for this condition to be true. Local parts are checked
31958 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
31959 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
31960 used only in a DATA or non-SMTP ACL.
31962 There is one possible option, &`case_insensitive`&. If this is present then
31963 local parts are checked case-insensitively.
31965 There are, of course, many legitimate messages that make use of blind (bcc)
31966 recipients. This check should not be used on its own for blocking messages.
31969 .vitem &*verify&~=&~recipient/*&<&'options'&>
31970 .cindex "&%verify%& ACL condition"
31971 .cindex "&ACL;" "verifying recipient"
31972 .cindex "recipient" "verifying"
31973 .cindex "verifying" "recipient"
31974 .vindex "&$address_data$&"
31975 This condition is relevant only after a RCPT command. It verifies the current
31976 recipient. Details of address verification are given later, starting at section
31977 &<<SECTaddressverification>>&. After a recipient has been verified, the value
31978 of &$address_data$& is the last value that was set while routing the address.
31979 This applies even if the verification fails. When an address that is being
31980 verified is redirected to a single address, verification continues with the new
31981 address, and in that case, the subsequent value of &$address_data$& is the
31982 value for the child address.
31984 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
31985 .cindex "&%verify%& ACL condition"
31986 .cindex "&ACL;" "verifying host reverse lookup"
31987 .cindex "host" "verifying reverse lookup"
31988 This condition ensures that a verified host name has been looked up from the IP
31989 address of the client host. (This may have happened already if the host name
31990 was needed for checking a host list, or if the host matched &%host_lookup%&.)
31991 Verification ensures that the host name obtained from a reverse DNS lookup, or
31992 one of its aliases, does, when it is itself looked up in the DNS, yield the
31993 original IP address.
31995 There is one possible option, &`defer_ok`&. If this is present and a
31996 DNS operation returns a temporary error, the verify condition succeeds.
31998 If this condition is used for a locally generated message (that is, when there
31999 is no client host involved), it always succeeds.
32001 .vitem &*verify&~=&~sender/*&<&'options'&>
32002 .cindex "&%verify%& ACL condition"
32003 .cindex "&ACL;" "verifying sender"
32004 .cindex "sender" "verifying"
32005 .cindex "verifying" "sender"
32006 This condition is relevant only after a MAIL or RCPT command, or after a
32007 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
32008 the message's sender is empty (that is, this is a bounce message), the
32009 condition is true. Otherwise, the sender address is verified.
32011 .vindex "&$address_data$&"
32012 .vindex "&$sender_address_data$&"
32013 If there is data in the &$address_data$& variable at the end of routing, its
32014 value is placed in &$sender_address_data$& at the end of verification. This
32015 value can be used in subsequent conditions and modifiers in the same ACL
32016 statement. It does not persist after the end of the current statement. If you
32017 want to preserve the value for longer, you can save it in an ACL variable.
32019 Details of verification are given later, starting at section
32020 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
32021 to avoid doing it more than once per message.
32023 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
32024 .cindex "&%verify%& ACL condition"
32025 This is a variation of the previous option, in which a modified address is
32026 verified as a sender.
32028 Note that '/' is legal in local-parts; if the address may have such
32029 (eg. is generated from the received message)
32030 they must be protected from the options parsing by doubling:
32032 verify = sender=${listquote{/}{${address:$h_sender:}}}
32038 .section "Using DNS lists" "SECTmorednslists"
32039 .cindex "DNS list" "in ACL"
32040 .cindex "black list (DNS)"
32041 .cindex "&ACL;" "testing a DNS list"
32042 In its simplest form, the &%dnslists%& condition tests whether the calling host
32043 is on at least one of a number of DNS lists by looking up the inverted IP
32044 address in one or more DNS domains. (Note that DNS list domains are not mail
32045 domains, so the &`+`& syntax for named lists doesn't work - it is used for
32046 special options instead.) For example, if the calling host's IP
32047 address is 192.168.62.43, and the ACL statement is
32049 deny dnslists = blackholes.mail-abuse.org : \
32050 dialups.mail-abuse.org
32052 the following records are looked up:
32054 43.62.168.192.blackholes.mail-abuse.org
32055 43.62.168.192.dialups.mail-abuse.org
32057 As soon as Exim finds an existing DNS record, processing of the list stops.
32058 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
32059 to test that a host is on more than one list (an &"and"& conjunction), you can
32060 use two separate conditions:
32062 deny dnslists = blackholes.mail-abuse.org
32063 dnslists = dialups.mail-abuse.org
32065 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
32066 behaves as if the host does not match the list item, that is, as if the DNS
32067 record does not exist. If there are further items in the DNS list, they are
32070 This is usually the required action when &%dnslists%& is used with &%deny%&
32071 (which is the most common usage), because it prevents a DNS failure from
32072 blocking mail. However, you can change this behaviour by putting one of the
32073 following special items in the list:
32075 &`+include_unknown `& behave as if the item is on the list
32076 &`+exclude_unknown `& behave as if the item is not on the list (default)
32077 &`+defer_unknown `& give a temporary error
32079 .cindex "&`+include_unknown`&"
32080 .cindex "&`+exclude_unknown`&"
32081 .cindex "&`+defer_unknown`&"
32082 Each of these applies to any subsequent items on the list. For example:
32084 deny dnslists = +defer_unknown : foo.bar.example
32086 Testing the list of domains stops as soon as a match is found. If you want to
32087 warn for one list and block for another, you can use two different statements:
32089 deny dnslists = blackholes.mail-abuse.org
32090 warn dnslists = dialups.mail-abuse.org
32091 message = X-Warn: sending host is on dialups list
32093 .cindex caching "of dns lookup"
32095 DNS list lookups are cached by Exim for the duration of the SMTP session
32096 (but limited by the DNS return TTL value),
32097 so a lookup based on the IP address is done at most once for any incoming
32098 connection (assuming long-enough TTL).
32099 Exim does not share information between multiple incoming
32100 connections (but your local name server cache should be active).
32102 There are a number of DNS lists to choose from, some commercial, some free,
32103 or free for small deployments. An overview can be found at
32104 &url(https://en.wikipedia.org/wiki/Comparison_of_DNS_blacklists).
32108 .section "Specifying the IP address for a DNS list lookup" "SECID201"
32109 .cindex "DNS list" "keyed by explicit IP address"
32110 By default, the IP address that is used in a DNS list lookup is the IP address
32111 of the calling host. However, you can specify another IP address by listing it
32112 after the domain name, introduced by a slash. For example:
32114 deny dnslists = black.list.tld/192.168.1.2
32116 This feature is not very helpful with explicit IP addresses; it is intended for
32117 use with IP addresses that are looked up, for example, the IP addresses of the
32118 MX hosts or nameservers of an email sender address. For an example, see section
32119 &<<SECTmulkeyfor>>& below.
32124 .section "DNS lists keyed on domain names" "SECID202"
32125 .cindex "DNS list" "keyed by domain name"
32126 There are some lists that are keyed on domain names rather than inverted IP
32127 addresses (see, e.g., the &'domain based zones'& link at
32128 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
32129 with these lists. You can change the name that is looked up in a DNS list by
32130 listing it after the domain name, introduced by a slash. For example,
32132 deny dnslists = dsn.rfc-ignorant.org/$sender_address_domain
32133 message = Sender's domain is listed at $dnslist_domain
32135 This particular example is useful only in ACLs that are obeyed after the
32136 RCPT or DATA commands, when a sender address is available. If (for
32137 example) the message's sender is &'user@tld.example'& the name that is looked
32138 up by this example is
32140 tld.example.dsn.rfc-ignorant.org
32142 A single &%dnslists%& condition can contain entries for both names and IP
32143 addresses. For example:
32145 deny dnslists = sbl.spamhaus.org : \
32146 dsn.rfc-ignorant.org/$sender_address_domain
32148 The first item checks the sending host's IP address; the second checks a domain
32149 name. The whole condition is true if either of the DNS lookups succeeds.
32154 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
32155 .cindex "DNS list" "multiple keys for"
32156 The syntax described above for looking up explicitly-defined values (either
32157 names or IP addresses) in a DNS blacklist is a simplification. After the domain
32158 name for the DNS list, what follows the slash can in fact be a list of items.
32159 As with all lists in Exim, the default separator is a colon. However, because
32160 this is a sublist within the list of DNS blacklist domains, it is necessary
32161 either to double the separators like this:
32163 dnslists = black.list.tld/name.1::name.2
32165 or to change the separator character, like this:
32167 dnslists = black.list.tld/<;name.1;name.2
32169 If an item in the list is an IP address, it is inverted before the DNS
32170 blacklist domain is appended. If it is not an IP address, no inversion
32171 occurs. Consider this condition:
32173 dnslists = black.list.tld/<;192.168.1.2;a.domain
32175 The DNS lookups that occur are:
32177 2.1.168.192.black.list.tld
32178 a.domain.black.list.tld
32180 Once a DNS record has been found (that matches a specific IP return
32181 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
32182 are done. If there is a temporary DNS error, the rest of the sublist of domains
32183 or IP addresses is tried. A temporary error for the whole dnslists item occurs
32184 only if no other DNS lookup in this sublist succeeds. In other words, a
32185 successful lookup for any of the items in the sublist overrides a temporary
32186 error for a previous item.
32188 The ability to supply a list of items after the slash is in some sense just a
32189 syntactic convenience. These two examples have the same effect:
32191 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
32192 dnslists = black.list.tld/a.domain::b.domain
32194 However, when the data for the list is obtained from a lookup, the second form
32195 is usually much more convenient. Consider this example:
32197 deny dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
32198 ${lookup dnsdb {>|mxh=\
32199 $sender_address_domain} }} }
32200 message = The mail servers for the domain \
32201 $sender_address_domain \
32202 are listed at $dnslist_domain ($dnslist_value); \
32205 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
32206 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
32207 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
32208 of expanding the condition might be something like this:
32210 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
32212 Thus, this example checks whether or not the IP addresses of the sender
32213 domain's mail servers are on the Spamhaus black list.
32215 The key that was used for a successful DNS list lookup is put into the variable
32216 &$dnslist_matched$& (see section &<<SECID204>>&).
32221 .section "Data returned by DNS lists" "SECID203"
32222 .cindex "DNS list" "data returned from"
32223 DNS lists are constructed using address records in the DNS. The original RBL
32224 just used the address 127.0.0.1 on the right hand side of each record, but the
32225 RBL+ list and some other lists use a number of values with different meanings.
32226 The values used on the RBL+ list are:
32230 127.1.0.3 DUL and RBL
32232 127.1.0.5 RSS and RBL
32233 127.1.0.6 RSS and DUL
32234 127.1.0.7 RSS and DUL and RBL
32236 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
32237 different values. Some DNS lists may return more than one address record;
32238 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
32241 .section "Variables set from DNS lists" "SECID204"
32242 .cindex "expansion" "variables, set from DNS list"
32243 .cindex "DNS list" "variables set from"
32244 .vindex "&$dnslist_domain$&"
32245 .vindex "&$dnslist_matched$&"
32246 .vindex "&$dnslist_text$&"
32247 .vindex "&$dnslist_value$&"
32248 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
32249 the name of the overall domain that matched (for example,
32250 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
32251 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
32252 the DNS record. When the key is an IP address, it is not reversed in
32253 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
32254 cases, for example:
32256 deny dnslists = spamhaus.example
32258 the key is also available in another variable (in this case,
32259 &$sender_host_address$&). In more complicated cases, however, this is not true.
32260 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
32261 might generate a dnslists lookup like this:
32263 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
32265 If this condition succeeds, the value in &$dnslist_matched$& might be
32266 &`192.168.6.7`& (for example).
32268 If more than one address record is returned by the DNS lookup, all the IP
32269 addresses are included in &$dnslist_value$&, separated by commas and spaces.
32270 The variable &$dnslist_text$& contains the contents of any associated TXT
32271 record. For lists such as RBL+ the TXT record for a merged entry is often not
32272 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
32275 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
32276 &-- even if these appear before the condition in the ACL, they are not
32277 expanded until after it has failed. For example:
32279 deny hosts = !+local_networks
32280 message = $sender_host_address is listed \
32282 dnslists = rbl-plus.mail-abuse.example
32287 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
32288 .cindex "DNS list" "matching specific returned data"
32289 You can add an equals sign and an IP address after a &%dnslists%& domain name
32290 in order to restrict its action to DNS records with a matching right hand side.
32293 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
32295 rejects only those hosts that yield 127.0.0.2. Without this additional data,
32296 any address record is considered to be a match. For the moment, we assume
32297 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
32298 describes how multiple records are handled.
32300 More than one IP address may be given for checking, using a comma as a
32301 separator. These are alternatives &-- if any one of them matches, the
32302 &%dnslists%& condition is true. For example:
32304 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32306 If you want to specify a constraining address list and also specify names or IP
32307 addresses to be looked up, the constraining address list must be specified
32308 first. For example:
32310 deny dnslists = dsn.rfc-ignorant.org\
32311 =127.0.0.2/$sender_address_domain
32314 If the character &`&&`& is used instead of &`=`&, the comparison for each
32315 listed IP address is done by a bitwise &"and"& instead of by an equality test.
32316 In other words, the listed addresses are used as bit masks. The comparison is
32317 true if all the bits in the mask are present in the address that is being
32318 tested. For example:
32320 dnslists = a.b.c&0.0.0.3
32322 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
32323 want to test whether one bit or another bit is present (as opposed to both
32324 being present), you must use multiple values. For example:
32326 dnslists = a.b.c&0.0.0.1,0.0.0.2
32328 matches if the final component of the address is an odd number or two times
32333 .section "Negated DNS matching conditions" "SECID205"
32334 You can supply a negative list of IP addresses as part of a &%dnslists%&
32337 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
32339 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32340 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
32342 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
32344 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
32345 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
32346 words, the result of the test is inverted if an exclamation mark appears before
32347 the &`=`& (or the &`&&`&) sign.
32349 &*Note*&: This kind of negation is not the same as negation in a domain,
32350 host, or address list (which is why the syntax is different).
32352 If you are using just one list, the negation syntax does not gain you much. The
32353 previous example is precisely equivalent to
32355 deny dnslists = a.b.c
32356 !dnslists = a.b.c=127.0.0.2,127.0.0.3
32358 However, if you are using multiple lists, the negation syntax is clearer.
32359 Consider this example:
32361 deny dnslists = sbl.spamhaus.org : \
32363 dnsbl.njabl.org!=127.0.0.3 : \
32366 Using only positive lists, this would have to be:
32368 deny dnslists = sbl.spamhaus.org : \
32370 deny dnslists = dnsbl.njabl.org
32371 !dnslists = dnsbl.njabl.org=127.0.0.3
32372 deny dnslists = relays.ordb.org
32374 which is less clear, and harder to maintain.
32379 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
32380 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
32381 thereby providing more than one IP address. When an item in a &%dnslists%& list
32382 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
32383 the match to specific results from the DNS lookup, there are two ways in which
32384 the checking can be handled. For example, consider the condition:
32386 dnslists = a.b.c=127.0.0.1
32388 What happens if the DNS lookup for the incoming IP address yields both
32389 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
32390 condition true because at least one given value was found, or is it false
32391 because at least one of the found values was not listed? And how does this
32392 affect negated conditions? Both possibilities are provided for with the help of
32393 additional separators &`==`& and &`=&&`&.
32396 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
32397 IP addresses matches one of the listed addresses. For the example above, the
32398 condition is true because 127.0.0.1 matches.
32400 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
32401 looked up IP addresses matches one of the listed addresses. If the condition is
32404 dnslists = a.b.c==127.0.0.1
32406 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32407 false because 127.0.0.2 is not listed. You would need to have:
32409 dnslists = a.b.c==127.0.0.1,127.0.0.2
32411 for the condition to be true.
32414 When &`!`& is used to negate IP address matching, it inverts the result, giving
32415 the precise opposite of the behaviour above. Thus:
32417 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
32418 addresses matches one of the listed addresses. Consider:
32420 dnslists = a.b.c!&0.0.0.1
32422 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32423 false because 127.0.0.1 matches.
32425 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
32426 looked up IP address that does not match. Consider:
32428 dnslists = a.b.c!=&0.0.0.1
32430 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
32431 true, because 127.0.0.2 does not match. You would need to have:
32433 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
32435 for the condition to be false.
32437 When the DNS lookup yields only a single IP address, there is no difference
32438 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
32443 .section "Detailed information from merged DNS lists" "SECTmordetinf"
32444 .cindex "DNS list" "information from merged"
32445 When the facility for restricting the matching IP values in a DNS list is used,
32446 the text from the TXT record that is set in &$dnslist_text$& may not reflect
32447 the true reason for rejection. This happens when lists are merged and the IP
32448 address in the A record is used to distinguish them; unfortunately there is
32449 only one TXT record. One way round this is not to use merged lists, but that
32450 can be inefficient because it requires multiple DNS lookups where one would do
32451 in the vast majority of cases when the host of interest is not on any of the
32454 A less inefficient way of solving this problem is available. If
32455 two domain names, comma-separated, are given, the second is used first to
32456 do an initial check, making use of any IP value restrictions that are set.
32457 If there is a match, the first domain is used, without any IP value
32458 restrictions, to get the TXT record. As a byproduct of this, there is also
32459 a check that the IP being tested is indeed on the first list. The first
32460 domain is the one that is put in &$dnslist_domain$&. For example:
32463 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
32464 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32466 rejected because $sender_host_address is blacklisted \
32467 at $dnslist_domain\n$dnslist_text
32469 For the first blacklist item, this starts by doing a lookup in
32470 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
32471 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
32472 value, and as long as something is found, it looks for the corresponding TXT
32473 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
32474 The second blacklist item is processed similarly.
32476 If you are interested in more than one merged list, the same list must be
32477 given several times, but because the results of the DNS lookups are cached,
32478 the DNS calls themselves are not repeated. For example:
32481 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
32482 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
32483 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
32484 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
32486 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
32487 values matches (or if no record is found), this is the only lookup that is
32488 done. Only if there is a match is one of the more specific lists consulted.
32492 .section "DNS lists and IPv6" "SECTmorednslistslast"
32493 .cindex "IPv6" "DNS black lists"
32494 .cindex "DNS list" "IPv6 usage"
32495 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
32496 nibble by nibble. For example, if the calling host's IP address is
32497 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
32499 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
32500 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
32502 (split over two lines here to fit on the page). Unfortunately, some of the DNS
32503 lists contain wildcard records, intended for IPv4, that interact badly with
32504 IPv6. For example, the DNS entry
32506 *.3.some.list.example. A 127.0.0.1
32508 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
32509 Unfortunately, it also matches the entire 3::/4 IPv6 network.
32511 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
32512 &%condition%& condition, as in this example:
32514 deny condition = ${if isip4{$sender_host_address}}
32515 dnslists = some.list.example
32518 If an explicit key is being used for a DNS lookup and it may be an IPv6
32519 address you should specify alternate list separators for both the outer
32520 (DNS list name) list and inner (lookup keys) list:
32522 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
32525 .section "Rate limiting incoming messages" "SECTratelimiting"
32526 .cindex "rate limiting" "client sending"
32527 .cindex "limiting client sending rates"
32528 .oindex "&%smtp_ratelimit_*%&"
32529 The &%ratelimit%& ACL condition can be used to measure and control the rate at
32530 which clients can send email. This is more powerful than the
32531 &%smtp_ratelimit_*%& options, because those options control the rate of
32532 commands in a single SMTP session only, whereas the &%ratelimit%& condition
32533 works across all connections (concurrent and sequential) from the same client
32534 host. The syntax of the &%ratelimit%& condition is:
32536 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
32538 If the average client sending rate is less than &'m'& messages per time
32539 period &'p'& then the condition is false; otherwise it is true.
32541 As a side-effect, the &%ratelimit%& condition sets the expansion variable
32542 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
32543 configured value of &'m'&, and &$sender_rate_period$& to the configured value
32546 The parameter &'p'& is the smoothing time constant, in the form of an Exim
32547 time interval, for example, &`8h`& for eight hours. A larger time constant
32548 means that it takes Exim longer to forget a client's past behaviour. The
32549 parameter &'m'& is the maximum number of messages that a client is permitted to
32550 send in each time interval. It also specifies the number of messages permitted
32551 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
32552 constant, you can allow a client to send more messages in a burst without
32553 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
32554 both small, messages must be sent at an even rate.
32556 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
32557 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
32558 when deploying the &%ratelimit%& ACL condition. The script prints usage
32559 instructions when it is run with no arguments.
32561 The key is used to look up the data for calculating the client's average
32562 sending rate. This data is stored in Exim's spool directory, alongside the
32563 retry and other hints databases. The default key is &$sender_host_address$&,
32564 which means Exim computes the sending rate of each client host IP address.
32565 By changing the key you can change how Exim identifies clients for the purpose
32566 of ratelimiting. For example, to limit the sending rate of each authenticated
32567 user, independent of the computer they are sending from, set the key to
32568 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
32569 example, &$authenticated_id$& is only meaningful if the client has
32570 authenticated (which you can check with the &%authenticated%& ACL condition).
32572 The lookup key does not have to identify clients: If you want to limit the
32573 rate at which a recipient receives messages, you can use the key
32574 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
32577 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
32578 specifies what Exim measures the rate of, for example, messages or recipients
32579 or bytes. You can adjust the measurement using the &%unique=%& and/or
32580 &%count=%& options. You can also control when Exim updates the recorded rate
32581 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
32582 separated by a slash, like the other parameters. They may appear in any order.
32584 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
32585 any options that alter the meaning of the stored data. The limit &'m'& is not
32586 stored, so you can alter the configured maximum rate and Exim will still
32587 remember clients' past behaviour. If you change the &%per_*%& mode or add or
32588 remove the &%unique=%& option, the lookup key changes so Exim will forget past
32589 behaviour. The lookup key is not affected by changes to the update mode and
32590 the &%count=%& option.
32593 .section "Ratelimit options for what is being measured" "ratoptmea"
32594 .cindex "rate limiting" "per_* options"
32595 The &%per_conn%& option limits the client's connection rate. It is not
32596 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
32597 &%acl_not_smtp_start%& ACLs.
32599 The &%per_mail%& option limits the client's rate of sending messages. This is
32600 the default if none of the &%per_*%& options is specified. It can be used in
32601 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
32602 &%acl_smtp_data%&, or &%acl_not_smtp%&.
32604 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
32605 the same ACLs as the &%per_mail%& option, though it is best to use this option
32606 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
32607 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
32608 in its MAIL command, which may be inaccurate or completely missing. You can
32609 follow the limit &'m'& in the configuration with K, M, or G to specify limits
32610 in kilobytes, megabytes, or gigabytes, respectively.
32612 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
32613 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
32614 &%acl_smtp_mime%&, or &%acl_smtp_data%& ACLs. In
32615 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
32616 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
32617 in either case the rate limiting engine will see a message with many
32618 recipients as a large high-speed burst.
32620 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
32621 number of different recipients that the client has sent messages to in the
32622 last time period. That is, if the client repeatedly sends messages to the same
32623 recipient, its measured rate is not increased. This option can only be used in
32626 The &%per_cmd%& option causes Exim to recompute the rate every time the
32627 condition is processed. This can be used to limit the rate of any SMTP
32628 command. If it is used in multiple ACLs it can limit the aggregate rate of
32629 multiple different commands.
32631 The &%count=%& option can be used to alter how much Exim adds to the client's
32632 measured rate. For example, the &%per_byte%& option is equivalent to
32633 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
32634 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
32635 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
32637 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
32640 .section "Ratelimit update modes" "ratoptupd"
32641 .cindex "rate limiting" "reading data without updating"
32642 You can specify one of three options with the &%ratelimit%& condition to
32643 control when its database is updated. This section describes the &%readonly%&
32644 mode, and the next section describes the &%strict%& and &%leaky%& modes.
32646 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
32647 previously-computed rate to check against the limit.
32649 For example, you can test the client's sending rate and deny it access (when
32650 it is too fast) in the connect ACL. If the client passes this check then it
32651 can go on to send a message, in which case its recorded rate will be updated
32652 in the MAIL ACL. Subsequent connections from the same client will check this
32656 deny ratelimit = 100 / 5m / readonly
32657 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
32658 (max $sender_rate_limit)
32661 warn ratelimit = 100 / 5m / strict
32662 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
32663 (max $sender_rate_limit)
32666 If Exim encounters multiple &%ratelimit%& conditions with the same key when
32667 processing a message then it may increase the client's measured rate more than
32668 it should. For example, this will happen if you check the &%per_rcpt%& option
32669 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
32670 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
32671 multiple update problems by using the &%readonly%& option on later ratelimit
32674 The &%per_*%& options described above do not make sense in some ACLs. If you
32675 use a &%per_*%& option in an ACL where it is not normally permitted then the
32676 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
32677 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
32678 next section) so you must specify the &%readonly%& option explicitly.
32681 .section "Ratelimit options for handling fast clients" "ratoptfast"
32682 .cindex "rate limiting" "strict and leaky modes"
32683 If a client's average rate is greater than the maximum, the rate limiting
32684 engine can react in two possible ways, depending on the presence of the
32685 &%strict%& or &%leaky%& update modes. This is independent of the other
32686 counter-measures (such as rejecting the message) that may be specified by the
32689 The &%leaky%& (default) option means that the client's recorded rate is not
32690 updated if it is above the limit. The effect of this is that Exim measures the
32691 client's average rate of successfully sent email,
32692 up to the given limit.
32693 This is appropriate if the countermeasure when the condition is true
32694 consists of refusing the message, and
32695 is generally the better choice if you have clients that retry automatically.
32696 If the action when true is anything more complex then this option is
32697 likely not what is wanted.
32699 The &%strict%& option means that the client's recorded rate is always
32700 updated. The effect of this is that Exim measures the client's average rate
32701 of attempts to send email, which can be much higher than the maximum it is
32702 actually allowed. If the client is over the limit it may be subjected to
32703 counter-measures by the ACL. It must slow down and allow sufficient time to
32704 pass that its computed rate falls below the maximum before it can send email
32705 again. The time (the number of smoothing periods) it must wait and not
32706 attempt to send mail can be calculated with this formula:
32708 ln(peakrate/maxrate)
32712 .section "Limiting the rate of different events" "ratoptuniq"
32713 .cindex "rate limiting" "counting unique events"
32714 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
32715 rate of different events. For example, the &%per_addr%& option uses this
32716 mechanism to count the number of different recipients that the client has
32717 sent messages to in the last time period; it is equivalent to
32718 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
32719 measure the rate that a client uses different sender addresses with the
32720 options &`per_mail/unique=$sender_address`&.
32722 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
32723 has seen for that key. The whole set is thrown away when it is older than the
32724 rate smoothing period &'p'&, so each different event is counted at most once
32725 per period. In the &%leaky%& update mode, an event that causes the client to
32726 go over the limit is not added to the set, in the same way that the client's
32727 recorded rate is not updated in the same situation.
32729 When you combine the &%unique=%& and &%readonly%& options, the specific
32730 &%unique=%& value is ignored, and Exim just retrieves the client's stored
32733 The &%unique=%& mechanism needs more space in the ratelimit database than the
32734 other &%ratelimit%& options in order to store the event set. The number of
32735 unique values is potentially as large as the rate limit, so the extra space
32736 required increases with larger limits.
32738 The uniqueification is not perfect: there is a small probability that Exim
32739 will think a new event has happened before. If the sender's rate is less than
32740 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
32741 the measured rate can go above the limit, in which case Exim may under-count
32742 events by a significant margin. Fortunately, if the rate is high enough (2.7
32743 times the limit) that the false positive rate goes above 9%, then Exim will
32744 throw away the over-full event set before the measured rate falls below the
32745 limit. Therefore the only harm should be that exceptionally high sending rates
32746 are logged incorrectly; any countermeasures you configure will be as effective
32750 .section "Using rate limiting" "useratlim"
32751 Exim's other ACL facilities are used to define what counter-measures are taken
32752 when the rate limit is exceeded. This might be anything from logging a warning
32753 (for example, while measuring existing sending rates in order to define
32754 policy), through time delays to slow down fast senders, up to rejecting the
32755 message. For example:
32757 # Log all senders' rates
32758 warn ratelimit = 0 / 1h / strict
32759 log_message = Sender rate $sender_rate / $sender_rate_period
32761 # Slow down fast senders; note the need to truncate $sender_rate
32762 # at the decimal point.
32763 warn ratelimit = 100 / 1h / per_rcpt / strict
32764 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
32765 $sender_rate_limit }s
32767 # Keep authenticated users under control
32768 deny authenticated = *
32769 ratelimit = 100 / 1d / strict / $authenticated_id
32771 # System-wide rate limit
32772 defer ratelimit = 10 / 1s / $primary_hostname
32773 message = Sorry, too busy. Try again later.
32775 # Restrict incoming rate from each host, with a default
32776 # set using a macro and special cases looked up in a table.
32777 defer ratelimit = ${lookup {$sender_host_address} \
32778 cdb {DB/ratelimits.cdb} \
32779 {$value} {RATELIMIT} }
32780 message = Sender rate exceeds $sender_rate_limit \
32781 messages per $sender_rate_period
32783 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
32784 especially with the &%per_rcpt%& option, you may suffer from a performance
32785 bottleneck caused by locking on the ratelimit hints database. Apart from
32786 making your ACLs less complicated, you can reduce the problem by using a
32787 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
32788 this means that Exim will lose its hints data after a reboot (including retry
32789 hints, the callout cache, and ratelimit data).
32793 .section "Address verification" "SECTaddressverification"
32794 .cindex "verifying address" "options for"
32795 .cindex "policy control" "address verification"
32796 Several of the &%verify%& conditions described in section
32797 &<<SECTaclconditions>>& cause addresses to be verified. Section
32798 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
32799 The verification conditions can be followed by options that modify the
32800 verification process. The options are separated from the keyword and from each
32801 other by slashes, and some of them contain parameters. For example:
32803 verify = sender/callout
32804 verify = recipient/defer_ok/callout=10s,defer_ok
32806 The first stage of address verification, which always happens, is to run the
32807 address through the routers, in &"verify mode"&. Routers can detect the
32808 difference between verification and routing for delivery, and their actions can
32809 be varied by a number of generic options such as &%verify%& and &%verify_only%&
32810 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
32811 The available options are as follows:
32814 If the &%callout%& option is specified, successful routing to one or more
32815 remote hosts is followed by a &"callout"& to those hosts as an additional
32816 check. Callouts and their sub-options are discussed in the next section.
32818 If there is a defer error while doing verification routing, the ACL
32819 normally returns &"defer"&. However, if you include &%defer_ok%& in the
32820 options, the condition is forced to be true instead. Note that this is a main
32821 verification option as well as a suboption for callouts.
32823 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
32824 discusses the reporting of sender address verification failures.
32826 The &%success_on_redirect%& option causes verification always to succeed
32827 immediately after a successful redirection. By default, if a redirection
32828 generates just one address, that address is also verified. See further
32829 discussion in section &<<SECTredirwhilveri>>&.
32832 If the &%quota%& option is specified for recipient verify,
32833 successful routing to an appendfile transport is followed by a call into
32834 the transport to evaluate the quota status for the recipient.
32835 No actual delivery is done, but verification will succeed if the quota
32836 is sufficient for the message (if the sender gave a message size) or
32837 not already exceeded (otherwise).
32841 .cindex "verifying address" "differentiating failures"
32842 .vindex "&$recipient_verify_failure$&"
32843 .vindex "&$sender_verify_failure$&"
32844 .vindex "&$acl_verify_message$&"
32845 After an address verification failure, &$acl_verify_message$& contains the
32846 error message that is associated with the failure. It can be preserved by
32849 warn !verify = sender
32850 set acl_m0 = $acl_verify_message
32852 If you are writing your own custom rejection message or log message when
32853 denying access, you can use this variable to include information about the
32854 verification failure.
32856 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
32857 appropriate) contains one of the following words:
32860 &%qualify%&: The address was unqualified (no domain), and the message
32861 was neither local nor came from an exempted host.
32863 &%route%&: Routing failed.
32865 &%mail%&: Routing succeeded, and a callout was attempted; rejection
32866 occurred at or before the MAIL command (that is, on initial
32867 connection, HELO, or MAIL).
32869 &%recipient%&: The RCPT command in a callout was rejected.
32871 &%postmaster%&: The postmaster check in a callout was rejected.
32874 &%quota%&: The quota check for a local recipient did non pass.
32877 The main use of these variables is expected to be to distinguish between
32878 rejections of MAIL and rejections of RCPT in callouts.
32880 The above variables may also be set after a &*successful*&
32881 address verification to:
32884 &%random%&: A random local-part callout succeeded
32890 .section "Callout verification" "SECTcallver"
32891 .cindex "verifying address" "by callout"
32892 .cindex "callout" "verification"
32893 .cindex "SMTP" "callout verification"
32894 For non-local addresses, routing verifies the domain, but is unable to do any
32895 checking of the local part. There are situations where some means of verifying
32896 the local part is desirable. One way this can be done is to make an SMTP
32897 &'callback'& to a delivery host for the sender address or a &'callforward'& to
32898 a subsequent host for a recipient address, to see if the host accepts the
32899 address. We use the term &'callout'& to cover both cases. Note that for a
32900 sender address, the callback is not to the client host that is trying to
32901 deliver the message, but to one of the hosts that accepts incoming mail for the
32904 Exim does not do callouts by default. If you want them to happen, you must
32905 request them by setting appropriate options on the &%verify%& condition, as
32906 described below. This facility should be used with care, because it can add a
32907 lot of resource usage to the cost of verifying an address. However, Exim does
32908 cache the results of callouts, which helps to reduce the cost. Details of
32909 caching are in section &<<SECTcallvercache>>&.
32911 Recipient callouts are usually used only between hosts that are controlled by
32912 the same administration. For example, a corporate gateway host could use
32913 callouts to check for valid recipients on an internal mailserver. A successful
32914 callout does not guarantee that a real delivery to the address would succeed;
32915 on the other hand, a failing callout does guarantee that a delivery would fail.
32917 If the &%callout%& option is present on a condition that verifies an address, a
32918 second stage of verification occurs if the address is successfully routed to
32919 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
32920 &(manualroute)& router, where the router specifies the hosts. However, if a
32921 router that does not set up hosts routes to an &(smtp)& transport with a
32922 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
32923 &%hosts_override%& set, its hosts are always used, whether or not the router
32924 supplies a host list.
32925 Callouts are only supported on &(smtp)& transports.
32927 The port that is used is taken from the transport, if it is specified and is a
32928 remote transport. (For routers that do verification only, no transport need be
32929 specified.) Otherwise, the default SMTP port is used. If a remote transport
32930 specifies an outgoing interface, this is used; otherwise the interface is not
32931 specified. Likewise, the text that is used for the HELO command is taken from
32932 the transport's &%helo_data%& option; if there is no transport, the value of
32933 &$smtp_active_hostname$& is used.
32935 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
32936 test whether a bounce message could be delivered to the sender address. The
32937 following SMTP commands are sent:
32939 &`HELO `&<&'local host name'&>
32941 &`RCPT TO:`&<&'the address to be tested'&>
32944 LHLO is used instead of HELO if the transport's &%protocol%& option is
32947 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
32950 A recipient callout check is similar. By default, it also uses an empty address
32951 for the sender. This default is chosen because most hosts do not make use of
32952 the sender address when verifying a recipient. Using the same address means
32953 that a single cache entry can be used for each recipient. Some sites, however,
32954 do make use of the sender address when verifying. These are catered for by the
32955 &%use_sender%& and &%use_postmaster%& options, described in the next section.
32957 If the response to the RCPT command is a 2&'xx'& code, the verification
32958 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
32959 Exim tries the next host, if any. If there is a problem with all the remote
32960 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
32961 &%callout%& option is given, in which case the condition is forced to succeed.
32963 .cindex "SMTP" "output flushing, disabling for callout"
32964 A callout may take a little time. For this reason, Exim normally flushes SMTP
32965 output before performing a callout in an ACL, to avoid unexpected timeouts in
32966 clients when the SMTP PIPELINING extension is in use. The flushing can be
32967 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
32972 .section "Additional parameters for callouts" "CALLaddparcall"
32973 .cindex "callout" "additional parameters for"
32974 The &%callout%& option can be followed by an equals sign and a number of
32975 optional parameters, separated by commas. For example:
32977 verify = recipient/callout=10s,defer_ok
32979 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
32980 separate verify options, is retained for backwards compatibility, but is now
32981 deprecated. The additional parameters for &%callout%& are as follows:
32985 .vitem <&'a&~time&~interval'&>
32986 .cindex "callout" "timeout, specifying"
32987 This specifies the timeout that applies for the callout attempt to each host.
32990 verify = sender/callout=5s
32992 The default is 30 seconds. The timeout is used for each response from the
32993 remote host. It is also used for the initial connection, unless overridden by
32994 the &%connect%& parameter.
32997 .vitem &*connect&~=&~*&<&'time&~interval'&>
32998 .cindex "callout" "connection timeout, specifying"
32999 This parameter makes it possible to set a different (usually smaller) timeout
33000 for making the SMTP connection. For example:
33002 verify = sender/callout=5s,connect=1s
33004 If not specified, this timeout defaults to the general timeout value.
33006 .vitem &*defer_ok*&
33007 .cindex "callout" "defer, action on"
33008 When this parameter is present, failure to contact any host, or any other kind
33009 of temporary error, is treated as success by the ACL. However, the cache is not
33010 updated in this circumstance.
33012 .vitem &*fullpostmaster*&
33013 .cindex "callout" "full postmaster check"
33014 This operates like the &%postmaster%& option (see below), but if the check for
33015 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
33016 accordance with the specification in RFC 2821. The RFC states that the
33017 unqualified address &'postmaster'& should be accepted.
33020 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
33021 .cindex "callout" "sender when verifying header"
33022 When verifying addresses in header lines using the &%header_sender%&
33023 verification option, Exim behaves by default as if the addresses are envelope
33024 sender addresses from a message. Callout verification therefore tests to see
33025 whether a bounce message could be delivered, by using an empty address in the
33026 MAIL command. However, it is arguable that these addresses might never be used
33027 as envelope senders, and could therefore justifiably reject bounce messages
33028 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
33029 address to use in the MAIL command. For example:
33031 require verify = header_sender/callout=mailfrom=abcd@x.y.z
33033 This parameter is available only for the &%header_sender%& verification option.
33036 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
33037 .cindex "callout" "overall timeout, specifying"
33038 This parameter sets an overall timeout for performing a callout verification.
33041 verify = sender/callout=5s,maxwait=30s
33043 This timeout defaults to four times the callout timeout for individual SMTP
33044 commands. The overall timeout applies when there is more than one host that can
33045 be tried. The timeout is checked before trying the next host. This prevents
33046 very long delays if there are a large number of hosts and all are timing out
33047 (for example, when network connections are timing out).
33050 .vitem &*no_cache*&
33051 .cindex "callout" "cache, suppressing"
33052 .cindex "caching callout, suppressing"
33053 When this parameter is given, the callout cache is neither read nor updated.
33055 .vitem &*postmaster*&
33056 .cindex "callout" "postmaster; checking"
33057 When this parameter is set, a successful callout check is followed by a similar
33058 check for the local part &'postmaster'& at the same domain. If this address is
33059 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
33060 the postmaster check is recorded in a cache record; if it is a failure, this is
33061 used to fail subsequent callouts for the domain without a connection being
33062 made, until the cache record expires.
33064 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
33065 The postmaster check uses an empty sender in the MAIL command by default.
33066 You can use this parameter to do a postmaster check using a different address.
33069 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
33071 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
33072 one overrides. The &%postmaster%& parameter is equivalent to this example:
33074 require verify = sender/callout=postmaster_mailfrom=
33076 &*Warning*&: The caching arrangements for postmaster checking do not take
33077 account of the sender address. It is assumed that either the empty address or
33078 a fixed non-empty address will be used. All that Exim remembers is that the
33079 postmaster check for the domain succeeded or failed.
33083 .cindex "callout" "&""random""& check"
33084 When this parameter is set, before doing the normal callout check, Exim does a
33085 check for a &"random"& local part at the same domain. The local part is not
33086 really random &-- it is defined by the expansion of the option
33087 &%callout_random_local_part%&, which defaults to
33089 $primary_hostname-$tod_epoch-testing
33091 The idea here is to try to determine whether the remote host accepts all local
33092 parts without checking. If it does, there is no point in doing callouts for
33093 specific local parts. If the &"random"& check succeeds, the result is saved in
33094 a cache record, and used to force the current and subsequent callout checks to
33095 succeed without a connection being made, until the cache record expires.
33097 .vitem &*use_postmaster*&
33098 .cindex "callout" "sender for recipient check"
33099 This parameter applies to recipient callouts only. For example:
33101 deny !verify = recipient/callout=use_postmaster
33103 .vindex "&$qualify_domain$&"
33104 It causes a non-empty postmaster address to be used in the MAIL command when
33105 performing the callout for the recipient, and also for a &"random"& check if
33106 that is configured. The local part of the address is &`postmaster`& and the
33107 domain is the contents of &$qualify_domain$&.
33109 .vitem &*use_sender*&
33110 This option applies to recipient callouts only. For example:
33112 require verify = recipient/callout=use_sender
33114 It causes the message's actual sender address to be used in the MAIL
33115 command when performing the callout, instead of an empty address. There is no
33116 need to use this option unless you know that the called hosts make use of the
33117 sender when checking recipients. If used indiscriminately, it reduces the
33118 usefulness of callout caching.
33121 This option applies to recipient callouts only. For example:
33123 require verify = recipient/callout=use_sender,hold
33125 It causes the connection to be held open and used for any further recipients
33126 and for eventual delivery (should that be done quickly).
33127 Doing this saves on TCP and SMTP startup costs, and TLS costs also
33128 when that is used for the connections.
33129 The advantage is only gained if there are no callout cache hits
33130 (which could be enforced by the no_cache option),
33131 if the use_sender option is used,
33132 if neither the random nor the use_postmaster option is used,
33133 and if no other callouts intervene.
33136 If you use any of the parameters that set a non-empty sender for the MAIL
33137 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
33138 &%use_sender%&), you should think about possible loops. Recipient checking is
33139 usually done between two hosts that are under the same management, and the host
33140 that receives the callouts is not normally configured to do callouts itself.
33141 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
33142 these circumstances.
33144 However, if you use a non-empty sender address for a callout to an arbitrary
33145 host, there is the likelihood that the remote host will itself initiate a
33146 callout check back to your host. As it is checking what appears to be a message
33147 sender, it is likely to use an empty address in MAIL, thus avoiding a
33148 callout loop. However, to be on the safe side it would be best to set up your
33149 own ACLs so that they do not do sender verification checks when the recipient
33150 is the address you use for header sender or postmaster callout checking.
33152 Another issue to think about when using non-empty senders for callouts is
33153 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
33154 by the sender/recipient combination; thus, for any given recipient, many more
33155 actual callouts are performed than when an empty sender or postmaster is used.
33160 .section "Callout caching" "SECTcallvercache"
33161 .cindex "hints database" "callout cache"
33162 .cindex "callout" "cache, description of"
33163 .cindex "caching" "callout"
33164 Exim caches the results of callouts in order to reduce the amount of resources
33165 used, unless you specify the &%no_cache%& parameter with the &%callout%&
33166 option. A hints database called &"callout"& is used for the cache. Two
33167 different record types are used: one records the result of a callout check for
33168 a specific address, and the other records information that applies to the
33169 entire domain (for example, that it accepts the local part &'postmaster'&).
33171 When an original callout fails, a detailed SMTP error message is given about
33172 the failure. However, for subsequent failures use the cache data, this message
33175 The expiry times for negative and positive address cache records are
33176 independent, and can be set by the global options &%callout_negative_expire%&
33177 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
33179 If a host gives a negative response to an SMTP connection, or rejects any
33180 commands up to and including
33184 (but not including the MAIL command with a non-empty address),
33185 any callout attempt is bound to fail. Exim remembers such failures in a
33186 domain cache record, which it uses to fail callouts for the domain without
33187 making new connections, until the domain record times out. There are two
33188 separate expiry times for domain cache records:
33189 &%callout_domain_negative_expire%& (default 3h) and
33190 &%callout_domain_positive_expire%& (default 7d).
33192 Domain records expire when the negative expiry time is reached if callouts
33193 cannot be made for the domain, or if the postmaster check failed.
33194 Otherwise, they expire when the positive expiry time is reached. This
33195 ensures that, for example, a host that stops accepting &"random"& local parts
33196 will eventually be noticed.
33198 The callout caching mechanism is based on the domain of the address that is
33199 being tested. If the domain routes to several hosts, it is assumed that their
33200 behaviour will be the same.
33205 .section "Quota caching" "SECTquotacache"
33206 .cindex "hints database" "quota cache"
33207 .cindex "quota" "cache, description of"
33208 .cindex "caching" "quota"
33209 Exim caches the results of quota verification
33210 in order to reduce the amount of resources used.
33211 The &"callout"& hints database is used.
33213 The default cache periods are five minutes for a positive (good) result
33214 and one hour for a negative result.
33215 To change the periods the &%quota%& option can be followed by an equals sign
33216 and a number of optional paramemters, separated by commas.
33219 verify = recipient/quota=cachepos=1h,cacheneg=1d
33221 Possible parameters are:
33223 .vitem &*cachepos&~=&~*&<&'time&~interval'&>
33224 .cindex "quota cache" "positive entry expiry, specifying"
33225 Set the lifetime for a positive cache entry.
33226 A value of zero seconds is legitimate.
33228 .vitem &*cacheneg&~=&~*&<&'time&~interval'&>
33229 .cindex "quota cache" "negative entry expiry, specifying"
33230 As above, for a negative entry.
33232 .vitem &*no_cache*&
33233 Set both positive and negative lifetimes to zero.
33236 .section "Sender address verification reporting" "SECTsenaddver"
33237 .cindex "verifying" "suppressing error details"
33238 See section &<<SECTaddressverification>>& for a general discussion of
33239 verification. When sender verification fails in an ACL, the details of the
33240 failure are given as additional output lines before the 550 response to the
33241 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
33244 MAIL FROM:<xyz@abc.example>
33246 RCPT TO:<pqr@def.example>
33247 550-Verification failed for <xyz@abc.example>
33248 550-Called: 192.168.34.43
33249 550-Sent: RCPT TO:<xyz@abc.example>
33250 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
33251 550 Sender verification failed
33253 If more than one RCPT command fails in the same way, the details are given
33254 only for the first of them. However, some administrators do not want to send
33255 out this much information. You can suppress the details by adding
33256 &`/no_details`& to the ACL statement that requests sender verification. For
33259 verify = sender/no_details
33262 .section "Redirection while verifying" "SECTredirwhilveri"
33263 .cindex "verifying" "redirection while"
33264 .cindex "address redirection" "while verifying"
33265 A dilemma arises when a local address is redirected by aliasing or forwarding
33266 during verification: should the generated addresses themselves be verified,
33267 or should the successful expansion of the original address be enough to verify
33268 it? By default, Exim takes the following pragmatic approach:
33271 When an incoming address is redirected to just one child address, verification
33272 continues with the child address, and if that fails to verify, the original
33273 verification also fails.
33275 When an incoming address is redirected to more than one child address,
33276 verification does not continue. A success result is returned.
33279 This seems the most reasonable behaviour for the common use of aliasing as a
33280 way of redirecting different local parts to the same mailbox. It means, for
33281 example, that a pair of alias entries of the form
33284 aw123: :fail: Gone away, no forwarding address
33286 work as expected, with both local parts causing verification failure. When a
33287 redirection generates more than one address, the behaviour is more like a
33288 mailing list, where the existence of the alias itself is sufficient for
33289 verification to succeed.
33291 It is possible, however, to change the default behaviour so that all successful
33292 redirections count as successful verifications, however many new addresses are
33293 generated. This is specified by the &%success_on_redirect%& verification
33294 option. For example:
33296 require verify = recipient/success_on_redirect/callout=10s
33298 In this example, verification succeeds if a router generates a new address, and
33299 the callout does not occur, because no address was routed to a remote host.
33301 When verification is being tested via the &%-bv%& option, the treatment of
33302 redirections is as just described, unless the &%-v%& or any debugging option is
33303 also specified. In that case, full verification is done for every generated
33304 address and a report is output for each of them.
33308 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
33309 .cindex "CSA" "verifying"
33310 Client SMTP Authorization is a system that allows a site to advertise
33311 which machines are and are not permitted to send email. This is done by placing
33312 special SRV records in the DNS; these are looked up using the client's HELO
33313 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
33314 Authorization checks in Exim are performed by the ACL condition:
33318 This fails if the client is not authorized. If there is a DNS problem, or if no
33319 valid CSA SRV record is found, or if the client is authorized, the condition
33320 succeeds. These three cases can be distinguished using the expansion variable
33321 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
33322 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
33323 be likely to cause problems for legitimate email.
33325 The error messages produced by the CSA code include slightly more
33326 detail. If &$csa_status$& is &"defer"&, this may be because of problems
33327 looking up the CSA SRV record, or problems looking up the CSA target
33328 address record. There are four reasons for &$csa_status$& being &"fail"&:
33331 The client's host name is explicitly not authorized.
33333 The client's IP address does not match any of the CSA target IP addresses.
33335 The client's host name is authorized but it has no valid target IP addresses
33336 (for example, the target's addresses are IPv6 and the client is using IPv4).
33338 The client's host name has no CSA SRV record but a parent domain has asserted
33339 that all subdomains must be explicitly authorized.
33342 The &%csa%& verification condition can take an argument which is the domain to
33343 use for the DNS query. The default is:
33345 verify = csa/$sender_helo_name
33347 This implementation includes an extension to CSA. If the query domain
33348 is an address literal such as [192.0.2.95], or if it is a bare IP
33349 address, Exim searches for CSA SRV records in the reverse DNS as if
33350 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
33353 verify = csa/$sender_host_address
33355 In fact, this is the check that Exim performs if the client does not say HELO.
33356 This extension can be turned off by setting the main configuration option
33357 &%dns_csa_use_reverse%& to be false.
33359 If a CSA SRV record is not found for the domain itself, a search
33360 is performed through its parent domains for a record which might be
33361 making assertions about subdomains. The maximum depth of this search is limited
33362 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
33363 default. Exim does not look for CSA SRV records in a top level domain, so the
33364 default settings handle HELO domains as long as seven
33365 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
33366 of legitimate HELO domains.
33368 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
33369 direct SRV lookups, this is not sufficient because of the extra parent domain
33370 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
33371 addresses into lookups in the reverse DNS space. The result of a successful
33374 ${lookup dnsdb {csa=$sender_helo_name}}
33376 has two space-separated fields: an authorization code and a target host name.
33377 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
33378 authorization required but absent, or &"?"& for unknown.
33383 .section "Bounce address tag validation" "SECTverifyPRVS"
33384 .cindex "BATV, verifying"
33385 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
33386 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
33387 Genuine incoming bounce messages should therefore always be addressed to
33388 recipients that have a valid tag. This scheme is a way of detecting unwanted
33389 bounce messages caused by sender address forgeries (often called &"collateral
33390 spam"&), because the recipients of such messages do not include valid tags.
33392 There are two expansion items to help with the implementation of the BATV
33393 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
33394 the original envelope sender address by using a simple key to add a hash of the
33395 address and some time-based randomizing information. The &%prvs%& expansion
33396 item creates a signed address, and the &%prvscheck%& expansion item checks one.
33397 The syntax of these expansion items is described in section
33398 &<<SECTexpansionitems>>&.
33399 The validity period on signed addresses is seven days.
33401 As an example, suppose the secret per-address keys are stored in an MySQL
33402 database. A query to look up the key for an address could be defined as a macro
33405 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
33406 WHERE sender='${quote_mysql:$prvscheck_address}'\
33409 Suppose also that the senders who make use of BATV are defined by an address
33410 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
33413 # Bounces: drop unsigned addresses for BATV senders
33415 recipients = +batv_senders
33416 message = This address does not send an unsigned reverse path
33418 # Bounces: In case of prvs-signed address, check signature.
33420 condition = ${prvscheck {$local_part@$domain}\
33421 {PRVSCHECK_SQL}{1}}
33422 !condition = $prvscheck_result
33423 message = Invalid reverse path signature.
33425 The first statement rejects recipients for bounce messages that are addressed
33426 to plain BATV sender addresses, because it is known that BATV senders do not
33427 send out messages with plain sender addresses. The second statement rejects
33428 recipients that are prvs-signed, but with invalid signatures (either because
33429 the key is wrong, or the signature has timed out).
33431 A non-prvs-signed address is not rejected by the second statement, because the
33432 &%prvscheck%& expansion yields an empty string if its first argument is not a
33433 prvs-signed address, thus causing the &%condition%& condition to be false. If
33434 the first argument is a syntactically valid prvs-signed address, the yield is
33435 the third string (in this case &"1"&), whether or not the cryptographic and
33436 timeout checks succeed. The &$prvscheck_result$& variable contains the result
33437 of the checks (empty for failure, &"1"& for success).
33439 There is one more issue you must consider when implementing prvs-signing:
33440 you have to ensure that the routers accept prvs-signed addresses and
33441 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
33442 router to remove the signature with a configuration along these lines:
33446 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
33448 This works because, if the third argument of &%prvscheck%& is empty, the result
33449 of the expansion of a prvs-signed address is the decoded value of the original
33450 address. This router should probably be the first of your routers that handles
33453 To create BATV-signed addresses in the first place, a transport of this form
33456 external_smtp_batv:
33458 return_path = ${prvs {$return_path} \
33459 {${lookup mysql{SELECT \
33460 secret FROM batv_prvs WHERE \
33461 sender='${quote_mysql:$sender_address}'} \
33464 If no key can be found for the existing return path, no signing takes place.
33468 .section "Using an ACL to control relaying" "SECTrelaycontrol"
33469 .cindex "&ACL;" "relay control"
33470 .cindex "relaying" "control by ACL"
33471 .cindex "policy control" "relay control"
33472 An MTA is said to &'relay'& a message if it receives it from some host and
33473 delivers it directly to another host as a result of a remote address contained
33474 within it. Redirecting a local address via an alias or forward file and then
33475 passing the message on to another host is not relaying,
33476 .cindex "&""percent hack""&"
33477 but a redirection as a result of the &"percent hack"& is.
33479 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
33480 A host which is acting as a gateway or an MX backup is concerned with incoming
33481 relaying from arbitrary hosts to a specific set of domains. On the other hand,
33482 a host which is acting as a smart host for a number of clients is concerned
33483 with outgoing relaying from those clients to the Internet at large. Often the
33484 same host is fulfilling both functions,
33486 . as illustrated in the diagram below,
33488 but in principle these two kinds of relaying are entirely independent. What is
33489 not wanted is the transmission of mail from arbitrary remote hosts through your
33490 system to arbitrary domains.
33493 You can implement relay control by means of suitable statements in the ACL that
33494 runs for each RCPT command. For convenience, it is often easiest to use
33495 Exim's named list facility to define the domains and hosts involved. For
33496 example, suppose you want to do the following:
33499 Deliver a number of domains to mailboxes on the local host (or process them
33500 locally in some other way). Let's say these are &'my.dom1.example'& and
33501 &'my.dom2.example'&.
33503 Relay mail for a number of other domains for which you are the secondary MX.
33504 These might be &'friend1.example'& and &'friend2.example'&.
33506 Relay mail from the hosts on your local LAN, to whatever domains are involved.
33507 Suppose your LAN is 192.168.45.0/24.
33511 In the main part of the configuration, you put the following definitions:
33513 domainlist local_domains = my.dom1.example : my.dom2.example
33514 domainlist relay_to_domains = friend1.example : friend2.example
33515 hostlist relay_from_hosts = 192.168.45.0/24
33517 Now you can use these definitions in the ACL that is run for every RCPT
33521 accept domains = +local_domains : +relay_to_domains
33522 accept hosts = +relay_from_hosts
33524 The first statement accepts any RCPT command that contains an address in
33525 the local or relay domains. For any other domain, control passes to the second
33526 statement, which accepts the command only if it comes from one of the relay
33527 hosts. In practice, you will probably want to make your ACL more sophisticated
33528 than this, for example, by including sender and recipient verification. The
33529 default configuration includes a more comprehensive example, which is described
33530 in chapter &<<CHAPdefconfil>>&.
33534 .section "Checking a relay configuration" "SECTcheralcon"
33535 .cindex "relaying" "checking control of"
33536 You can check the relay characteristics of your configuration in the same way
33537 that you can test any ACL behaviour for an incoming SMTP connection, by using
33538 the &%-bh%& option to run a fake SMTP session with which you interact.
33543 . ////////////////////////////////////////////////////////////////////////////
33544 . ////////////////////////////////////////////////////////////////////////////
33546 .chapter "Content scanning at ACL time" "CHAPexiscan"
33547 .scindex IIDcosca "content scanning" "at ACL time"
33548 The extension of Exim to include content scanning at ACL time, formerly known
33549 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
33550 was integrated into the main source for Exim release 4.50, and Tom continues to
33551 maintain it. Most of the wording of this chapter is taken from Tom's
33554 It is also possible to scan the content of messages at other times. The
33555 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
33556 scanning after all the ACLs have run. A transport filter can be used to scan
33557 messages at delivery time (see the &%transport_filter%& option, described in
33558 chapter &<<CHAPtransportgeneric>>&).
33560 If you want to include the ACL-time content-scanning features when you compile
33561 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
33562 &_Local/Makefile_&. When you do that, the Exim binary is built with:
33565 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
33566 for all MIME parts for SMTP and non-SMTP messages, respectively.
33568 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
33569 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
33570 run at the end of message reception (the &%acl_smtp_data%& ACL).
33572 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
33573 of messages, or parts of messages, for debugging purposes.
33575 Additional expansion variables that are set in the new ACL and by the new
33578 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
33581 Content-scanning is continually evolving, and new features are still being
33582 added. While such features are still unstable and liable to incompatible
33583 changes, they are made available in Exim by setting options whose names begin
33584 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
33585 this manual. You can find out about them by reading the file called
33586 &_doc/experimental.txt_&.
33588 All the content-scanning facilities work on a MBOX copy of the message that is
33589 temporarily created in a file called:
33591 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
33593 The &_.eml_& extension is a friendly hint to virus scanners that they can
33594 expect an MBOX-like structure inside that file. The file is created when the
33595 first content scanning facility is called. Subsequent calls to content
33596 scanning conditions open the same file again. The directory is recursively
33597 removed when the &%acl_smtp_data%& ACL has finished running, unless
33599 control = no_mbox_unspool
33601 has been encountered. When the MIME ACL decodes files, they are put into the
33602 same directory by default.
33606 .section "Scanning for viruses" "SECTscanvirus"
33607 .cindex "virus scanning"
33608 .cindex "content scanning" "for viruses"
33609 .cindex "content scanning" "the &%malware%& condition"
33610 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
33611 It supports a &"generic"& interface to scanners called via the shell, and
33612 specialized interfaces for &"daemon"& type virus scanners, which are resident
33613 in memory and thus are much faster.
33615 Since message data needs to have arrived,
33616 the condition may be only called in ACL defined by
33618 &%acl_smtp_data_prdr%&,
33619 &%acl_smtp_mime%& or
33622 A timeout of 2 minutes is applied to a scanner call (by default);
33623 if it expires then a defer action is taken.
33625 .oindex "&%av_scanner%&"
33626 You can set the &%av_scanner%& option in the main part of the configuration
33627 to specify which scanner to use, together with any additional options that
33628 are needed. The basic syntax is as follows:
33630 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
33632 If you do not set &%av_scanner%&, it defaults to
33634 av_scanner = sophie:/var/run/sophie
33636 If the value of &%av_scanner%& starts with a dollar character, it is expanded
33638 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
33639 The following scanner types are supported in this release,
33640 though individual ones can be included or not at build time:
33644 .cindex "virus scanners" "avast"
33645 This is the scanner daemon of Avast. It has been tested with Avast Core
33646 Security (currently at version 2.2.0).
33647 You can get a trial version at &url(https://www.avast.com) or for Linux
33648 at &url(https://www.avast.com/linux-server-antivirus).
33649 This scanner type takes one option,
33650 which can be either a full path to a UNIX socket,
33651 or host and port specifiers separated by white space.
33652 The host may be a name or an IP address; the port is either a
33653 single number or a pair of numbers with a dash between.
33654 A list of options may follow. These options are interpreted on the
33655 Exim's side of the malware scanner, or are given on separate lines to
33656 the daemon as options before the main scan command.
33658 .cindex &`pass_unscanned`& "avast"
33659 If &`pass_unscanned`&
33660 is set, any files the Avast scanner can't scan (e.g.
33661 decompression bombs, or invalid archives) are considered clean. Use with
33666 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
33667 av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
33668 av_scanner = avast:192.168.2.22 5036
33670 If you omit the argument, the default path
33671 &_/var/run/avast/scan.sock_&
33673 If you use a remote host,
33674 you need to make Exim's spool directory available to it,
33675 as the scanner is passed a file path, not file contents.
33676 For information about available commands and their options you may use
33678 $ socat UNIX:/var/run/avast/scan.sock STDIO:
33684 If the scanner returns a temporary failure (e.g. license issues, or
33685 permission problems), the message is deferred and a paniclog entry is
33686 written. The usual &`defer_ok`& option is available.
33688 .vitem &%aveserver%&
33689 .cindex "virus scanners" "Kaspersky"
33690 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
33691 at &url(https://www.kaspersky.com/). This scanner type takes one option,
33692 which is the path to the daemon's UNIX socket. The default is shown in this
33695 av_scanner = aveserver:/var/run/aveserver
33700 .cindex "virus scanners" "clamd"
33701 This daemon-type scanner is GPL and free. You can get it at
33702 &url(https://www.clamav.net/). Some older versions of clamd do not seem to
33703 unpack MIME containers, so it used to be recommended to unpack MIME attachments
33704 in the MIME ACL. This is no longer believed to be necessary.
33706 The options are a list of server specifiers, which may be
33707 a UNIX socket specification,
33708 a TCP socket specification,
33709 or a (global) option.
33711 A socket specification consists of a space-separated list.
33712 For a Unix socket the first element is a full path for the socket,
33713 for a TCP socket the first element is the IP address
33714 and the second a port number,
33715 Any further elements are per-server (non-global) options.
33716 These per-server options are supported:
33718 retry=<timespec> Retry on connect fail
33721 The &`retry`& option specifies a time after which a single retry for
33722 a failed connect is made. The default is to not retry.
33724 If a Unix socket file is specified, only one server is supported.
33728 av_scanner = clamd:/opt/clamd/socket
33729 av_scanner = clamd:192.0.2.3 1234
33730 av_scanner = clamd:192.0.2.3 1234:local
33731 av_scanner = clamd:192.0.2.3 1234 retry=10s
33732 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
33734 If the value of av_scanner points to a UNIX socket file or contains the
33736 option, then the ClamAV interface will pass a filename containing the data
33737 to be scanned, which should normally result in less I/O happening and be
33738 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
33739 Exim does not assume that there is a common filesystem with the remote host.
33741 The final example shows that multiple TCP targets can be specified. Exim will
33742 randomly use one for each incoming email (i.e. it load balances them). Note
33743 that only TCP targets may be used if specifying a list of scanners; a UNIX
33744 socket cannot be mixed in with TCP targets. If one of the servers becomes
33745 unavailable, Exim will try the remaining one(s) until it finds one that works.
33746 When a clamd server becomes unreachable, Exim will log a message. Exim does
33747 not keep track of scanner state between multiple messages, and the scanner
33748 selection is random, so the message will get logged in the mainlog for each
33749 email that the down scanner gets chosen first (message wrapped to be readable):
33751 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
33752 clamd: connection to localhost, port 3310 failed
33753 (Connection refused)
33756 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
33757 contributing the code for this scanner.
33760 .cindex "virus scanners" "command line interface"
33761 This is the keyword for the generic command line scanner interface. It can be
33762 used to attach virus scanners that are invoked from the shell. This scanner
33763 type takes 3 mandatory options:
33766 The full path and name of the scanner binary, with all command line options,
33767 and a placeholder (&`%s`&) for the directory to scan.
33770 A regular expression to match against the STDOUT and STDERR output of the
33771 virus scanner. If the expression matches, a virus was found. You must make
33772 absolutely sure that this expression matches on &"virus found"&. This is called
33773 the &"trigger"& expression.
33776 Another regular expression, containing exactly one pair of parentheses, to
33777 match the name of the virus found in the scanners output. This is called the
33778 &"name"& expression.
33781 For example, Sophos Sweep reports a virus on a line like this:
33783 Virus 'W32/Magistr-B' found in file ./those.bat
33785 For the trigger expression, we can match the phrase &"found in file"&. For the
33786 name expression, we want to extract the W32/Magistr-B string, so we can match
33787 for the single quotes left and right of it. Altogether, this makes the
33788 configuration setting:
33790 av_scanner = cmdline:\
33791 /path/to/sweep -ss -all -rec -archive %s:\
33792 found in file:'(.+)'
33795 .cindex "virus scanners" "DrWeb"
33796 The DrWeb daemon scanner (&url(https://www.sald.ru/)) interface
33798 either a full path to a UNIX socket,
33799 or host and port specifiers separated by white space.
33800 The host may be a name or an IP address; the port is either a
33801 single number or a pair of numbers with a dash between.
33804 av_scanner = drweb:/var/run/drwebd.sock
33805 av_scanner = drweb:192.168.2.20 31337
33807 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
33808 is used. Thanks to Alex Miller for contributing the code for this scanner.
33811 .cindex "virus scanners" "f-protd"
33812 The f-protd scanner is accessed via HTTP over TCP.
33813 One argument is taken, being a space-separated hostname and port number
33817 av_scanner = f-protd:localhost 10200-10204
33819 If you omit the argument, the default values shown above are used.
33821 .vitem &%f-prot6d%&
33822 .cindex "virus scanners" "f-prot6d"
33823 The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
33824 One argument is taken, being a space-separated hostname and port number.
33827 av_scanner = f-prot6d:localhost 10200
33829 If you omit the argument, the default values show above are used.
33832 .cindex "virus scanners" "F-Secure"
33833 The F-Secure daemon scanner (&url(https://www.f-secure.com/)) takes one
33834 argument which is the path to a UNIX socket. For example:
33836 av_scanner = fsecure:/path/to/.fsav
33838 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
33839 Thelmen for contributing the code for this scanner.
33841 .vitem &%kavdaemon%&
33842 .cindex "virus scanners" "Kaspersky"
33843 This is the scanner daemon of Kaspersky Version 4. This version of the
33844 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
33845 scanner type takes one option, which is the path to the daemon's UNIX socket.
33848 av_scanner = kavdaemon:/opt/AVP/AvpCtl
33850 The default path is &_/var/run/AvpCtl_&.
33853 .cindex "virus scanners" "mksd"
33854 This was a daemon type scanner that is aimed mainly at Polish users,
33855 though some documentation was available in English.
33856 The history can be shown at &url(https://en.wikipedia.org/wiki/Mks_vir)
33857 and this appears to be a candidate for removal from Exim, unless
33858 we are informed of other virus scanners which use the same protocol
33860 The only option for this scanner type is
33861 the maximum number of processes used simultaneously to scan the attachments,
33862 provided that mksd has
33863 been run with at least the same number of child processes. For example:
33865 av_scanner = mksd:2
33867 You can safely omit this option (the default value is 1).
33870 .cindex "virus scanners" "simple socket-connected"
33871 This is a general-purpose way of talking to simple scanner daemons
33872 running on the local machine.
33873 There are four options:
33874 an address (which may be an IP address and port, or the path of a Unix socket),
33875 a commandline to send (may include a single %s which will be replaced with
33876 the path to the mail file to be scanned),
33877 an RE to trigger on from the returned data,
33878 and an RE to extract malware_name from the returned data.
33881 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
33883 Note that surrounding whitespace is stripped from each option, meaning
33884 there is no way to specify a trailing newline.
33885 The socket specifier and both regular-expressions are required.
33886 Default for the commandline is &_%s\n_& (note this does have a trailing newline);
33887 specify an empty element to get this.
33890 .cindex "virus scanners" "Sophos and Sophie"
33891 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
33892 You can get Sophie at &url(http://sophie.sourceforge.net/). The only option
33893 for this scanner type is the path to the UNIX socket that Sophie uses for
33894 client communication. For example:
33896 av_scanner = sophie:/tmp/sophie
33898 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
33902 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
33903 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
33906 The &%av_scanner%& option is expanded each time &%malware%& is called. This
33907 makes it possible to use different scanners. See further below for an example.
33908 The &%malware%& condition caches its results, so when you use it multiple times
33909 for the same message, the actual scanning process is only carried out once.
33910 However, using expandable items in &%av_scanner%& disables this caching, in
33911 which case each use of the &%malware%& condition causes a new scan of the
33914 The &%malware%& condition takes a right-hand argument that is expanded before
33915 use and taken as a list, slash-separated by default.
33916 The first element can then be one of
33919 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
33920 The condition succeeds if a virus was found, and fail otherwise. This is the
33923 &"false"& or &"0"& or an empty string, in which case no scanning is done and
33924 the condition fails immediately.
33926 A regular expression, in which case the message is scanned for viruses. The
33927 condition succeeds if a virus is found and its name matches the regular
33928 expression. This allows you to take special actions on certain types of virus.
33929 Note that &"/"& characters in the RE must be doubled due to the list-processing,
33930 unless the separator is changed (in the usual way &<<SECTlistsepchange>>&).
33933 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
33934 messages even if there is a problem with the virus scanner.
33935 Otherwise, such a problem causes the ACL to defer.
33937 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
33938 specify a non-default timeout. The default is two minutes.
33941 malware = * / defer_ok / tmo=10s
33943 A timeout causes the ACL to defer.
33945 .vindex "&$callout_address$&"
33946 When a connection is made to the scanner the expansion variable &$callout_address$&
33947 is set to record the actual address used.
33949 .vindex "&$malware_name$&"
33950 When a virus is found, the condition sets up an expansion variable called
33951 &$malware_name$& that contains the name of the virus. You can use it in a
33952 &%message%& modifier that specifies the error returned to the sender, and/or in
33955 Beware the interaction of Exim's &%message_size_limit%& with any size limits
33956 imposed by your anti-virus scanner.
33958 Here is a very simple scanning example:
33961 message = This message contains malware ($malware_name)
33963 The next example accepts messages when there is a problem with the scanner:
33965 deny malware = */defer_ok
33966 message = This message contains malware ($malware_name)
33968 The next example shows how to use an ACL variable to scan with both sophie and
33969 aveserver. It assumes you have set:
33971 av_scanner = $acl_m0
33973 in the main Exim configuration.
33975 deny set acl_m0 = sophie
33977 message = This message contains malware ($malware_name)
33979 deny set acl_m0 = aveserver
33981 message = This message contains malware ($malware_name)
33985 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
33986 .cindex "content scanning" "for spam"
33987 .cindex "spam scanning"
33988 .cindex "SpamAssassin"
33990 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
33991 score and a report for the message.
33992 Support is also provided for Rspamd.
33994 For more information about installation and configuration of SpamAssassin or
33995 Rspamd refer to their respective websites at
33996 &url(https://spamassassin.apache.org/) and &url(https://www.rspamd.com/)
33998 SpamAssassin can be installed with CPAN by running:
34000 perl -MCPAN -e 'install Mail::SpamAssassin'
34002 SpamAssassin has its own set of configuration files. Please review its
34003 documentation to see how you can tweak it. The default installation should work
34006 .oindex "&%spamd_address%&"
34007 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
34008 intend to use an instance running on the local host you do not need to set
34009 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
34010 you must set the &%spamd_address%& option in the global part of the Exim
34011 configuration as follows (example):
34013 spamd_address = 192.168.99.45 783
34015 The SpamAssassin protocol relies on a TCP half-close from the client.
34016 If your SpamAssassin client side is running a Linux system with an
34017 iptables firewall, consider setting
34018 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
34019 timeout, Exim uses when waiting for a response from the SpamAssassin
34020 server (currently defaulting to 120s). With a lower value the Linux
34021 connection tracking may consider your half-closed connection as dead too
34025 To use Rspamd (which by default listens on all local addresses
34027 you should add &%variant=rspamd%& after the address/port pair, for example:
34029 spamd_address = 127.0.0.1 11333 variant=rspamd
34032 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
34033 sockets. If you want to us these, supply &%spamd_address%& with an absolute
34034 filename instead of an address/port pair:
34036 spamd_address = /var/run/spamd_socket
34038 You can have multiple &%spamd%& servers to improve scalability. These can
34039 reside on other hardware reachable over the network. To specify multiple
34040 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
34041 option, separated with colons (the separator can be changed in the usual way &<<SECTlistsepchange>>&):
34043 spamd_address = 192.168.2.10 783 : \
34044 192.168.2.11 783 : \
34047 Up to 32 &%spamd%& servers are supported.
34048 When a server fails to respond to the connection attempt, all other
34049 servers are tried until one succeeds. If no server responds, the &%spam%&
34052 Unix and TCP socket specifications may be mixed in any order.
34053 Each element of the list is a list itself, space-separated by default
34054 and changeable in the usual way (&<<SECTlistsepchange>>&);
34055 take care to not double the separator.
34057 For TCP socket specifications a host name or IP (v4 or v6, but
34058 subject to list-separator quoting rules) address can be used,
34059 and the port can be one or a dash-separated pair.
34060 In the latter case, the range is tried in strict order.
34062 Elements after the first for Unix sockets, or second for TCP socket,
34064 The supported options are:
34066 pri=<priority> Selection priority
34067 weight=<value> Selection bias
34068 time=<start>-<end> Use only between these times of day
34069 retry=<timespec> Retry on connect fail
34070 tmo=<timespec> Connection time limit
34071 variant=rspamd Use Rspamd rather than SpamAssassin protocol
34074 The &`pri`& option specifies a priority for the server within the list,
34075 higher values being tried first.
34076 The default priority is 1.
34078 The &`weight`& option specifies a selection bias.
34079 Within a priority set
34080 servers are queried in a random fashion, weighted by this value.
34081 The default value for selection bias is 1.
34083 Time specifications for the &`time`& option are <hour>.<minute>.<second>
34084 in the local time zone; each element being one or more digits.
34085 Either the seconds or both minutes and seconds, plus the leading &`.`&
34086 characters, may be omitted and will be taken as zero.
34088 Timeout specifications for the &`retry`& and &`tmo`& options
34089 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
34091 The &`tmo`& option specifies an overall timeout for communication.
34092 The default value is two minutes.
34094 The &`retry`& option specifies a time after which a single retry for
34095 a failed connect is made.
34096 The default is to not retry.
34098 The &%spamd_address%& variable is expanded before use if it starts with
34099 a dollar sign. In this case, the expansion may return a string that is
34100 used as the list so that multiple spamd servers can be the result of an
34103 .vindex "&$callout_address$&"
34104 When a connection is made to the server the expansion variable &$callout_address$&
34105 is set to record the actual address used.
34107 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
34108 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
34111 message = This message was classified as SPAM
34113 The right-hand side of the &%spam%& condition specifies a name. This is
34114 relevant if you have set up multiple SpamAssassin profiles. If you do not want
34115 to scan using a specific profile, but rather use the SpamAssassin system-wide
34116 default profile, you can scan for an unknown name, or simply use &"nobody"&.
34117 Rspamd does not use this setting. However, you must put something on the
34120 The name allows you to use per-domain or per-user antispam profiles in
34121 principle, but this is not straightforward in practice, because a message may
34122 have multiple recipients, not necessarily all in the same domain. Because the
34123 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
34124 read the contents of the message, the variables &$local_part$& and &$domain$&
34126 Careful enforcement of single-recipient messages
34127 (e.g. by responding with defer in the recipient ACL for all recipients
34129 or the use of PRDR,
34130 .cindex "PRDR" "use for per-user SpamAssassin profiles"
34131 are needed to use this feature.
34133 The right-hand side of the &%spam%& condition is expanded before being used, so
34134 you can put lookups or conditions there. When the right-hand side evaluates to
34135 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
34138 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
34139 large ones may cause significant performance degradation. As most spam messages
34140 are quite small, it is recommended that you do not scan the big ones. For
34143 deny condition = ${if < {$message_size}{10K}}
34145 message = This message was classified as SPAM
34148 The &%spam%& condition returns true if the threshold specified in the user's
34149 SpamAssassin profile has been matched or exceeded. If you want to use the
34150 &%spam%& condition for its side effects (see the variables below), you can make
34151 it always return &"true"& by appending &`:true`& to the username.
34153 .cindex "spam scanning" "returned variables"
34154 When the &%spam%& condition is run, it sets up a number of expansion
34156 Except for &$spam_report$&,
34157 these variables are saved with the received message so are
34158 available for use at delivery time.
34161 .vitem &$spam_score$&
34162 The spam score of the message, for example, &"3.4"& or &"30.5"&. This is useful
34163 for inclusion in log or reject messages.
34165 .vitem &$spam_score_int$&
34166 The spam score of the message, multiplied by ten, as an integer value. For
34167 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
34168 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
34169 The integer value is useful for numeric comparisons in conditions.
34171 .vitem &$spam_bar$&
34172 A string consisting of a number of &"+"& or &"-"& characters, representing the
34173 integer part of the spam score value. A spam score of 4.4 would have a
34174 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
34175 headers, since MUAs can match on such strings. The maximum length of the
34176 spam bar is 50 characters.
34178 .vitem &$spam_report$&
34179 A multiline text table, containing the full SpamAssassin report for the
34180 message. Useful for inclusion in headers or reject messages.
34181 This variable is only usable in a DATA-time ACL.
34182 Beware that SpamAssassin may return non-ASCII characters, especially
34183 when running in country-specific locales, which are not legal
34184 unencoded in headers.
34186 .vitem &$spam_action$&
34187 For SpamAssassin either 'reject' or 'no action' depending on the
34188 spam score versus threshold.
34189 For Rspamd, the recommended action.
34193 The &%spam%& condition caches its results unless expansion in
34194 spamd_address was used. If you call it again with the same user name, it
34195 does not scan again, but rather returns the same values as before.
34197 The &%spam%& condition returns DEFER if there is any error while running
34198 the message through SpamAssassin or if the expansion of spamd_address
34199 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
34200 statement block), append &`/defer_ok`& to the right-hand side of the
34201 spam condition, like this:
34203 deny spam = joe/defer_ok
34204 message = This message was classified as SPAM
34206 This causes messages to be accepted even if there is a problem with &%spamd%&.
34208 Here is a longer, commented example of the use of the &%spam%&
34211 # put headers in all messages (no matter if spam or not)
34212 warn spam = nobody:true
34213 add_header = X-Spam-Score: $spam_score ($spam_bar)
34214 add_header = X-Spam-Report: $spam_report
34216 # add second subject line with *SPAM* marker when message
34217 # is over threshold
34219 add_header = Subject: *SPAM* $h_Subject:
34221 # reject spam at high scores (> 12)
34222 deny spam = nobody:true
34223 condition = ${if >{$spam_score_int}{120}{1}{0}}
34224 message = This message scored $spam_score spam points.
34229 .section "Scanning MIME parts" "SECTscanmimepart"
34230 .cindex "content scanning" "MIME parts"
34231 .cindex "MIME content scanning"
34232 .oindex "&%acl_smtp_mime%&"
34233 .oindex "&%acl_not_smtp_mime%&"
34234 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
34235 each MIME part of an SMTP message, including multipart types, in the sequence
34236 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
34237 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
34238 options may both refer to the same ACL if you want the same processing in both
34241 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
34242 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
34243 the case of a non-SMTP message. However, a MIME ACL is called only if the
34244 message contains a &'Content-Type:'& header line. When a call to a MIME
34245 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
34246 result code is sent to the client. In the case of an SMTP message, the
34247 &%acl_smtp_data%& ACL is not called when this happens.
34249 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
34250 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
34251 condition to match against the raw MIME part. You can also use the
34252 &%mime_regex%& condition to match against the decoded MIME part (see section
34253 &<<SECTscanregex>>&).
34255 At the start of a MIME ACL, a number of variables are set from the header
34256 information for the relevant MIME part. These are described below. The contents
34257 of the MIME part are not by default decoded into a disk file except for MIME
34258 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
34259 part into a disk file, you can use the &%decode%& condition. The general
34262 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
34264 The right hand side is expanded before use. After expansion,
34268 &"0"& or &"false"&, in which case no decoding is done.
34270 The string &"default"&. In that case, the file is put in the temporary
34271 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
34272 a sequential filename consisting of the message id and a sequence number. The
34273 full path and name is available in &$mime_decoded_filename$& after decoding.
34275 A full path name starting with a slash. If the full name is an existing
34276 directory, it is used as a replacement for the default directory. The filename
34277 is then sequentially assigned. If the path does not exist, it is used as
34278 the full path and filename.
34280 If the string does not start with a slash, it is used as the
34281 filename, and the default path is then used.
34283 The &%decode%& condition normally succeeds. It is only false for syntax
34284 errors or unusual circumstances such as memory shortages. You can easily decode
34285 a file with its original, proposed filename using
34287 decode = $mime_filename
34289 However, you should keep in mind that &$mime_filename$& might contain
34290 anything. If you place files outside of the default path, they are not
34291 automatically unlinked.
34293 For RFC822 attachments (these are messages attached to messages, with a
34294 content-type of &"message/rfc822"&), the ACL is called again in the same manner
34295 as for the primary message, only that the &$mime_is_rfc822$& expansion
34296 variable is set (see below). Attached messages are always decoded to disk
34297 before being checked, and the files are unlinked once the check is done.
34299 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
34300 used to match regular expressions against raw and decoded MIME parts,
34301 respectively. They are described in section &<<SECTscanregex>>&.
34303 .cindex "MIME content scanning" "returned variables"
34304 The following list describes all expansion variables that are
34305 available in the MIME ACL:
34308 .vitem &$mime_anomaly_level$& &&&
34309 &$mime_anomaly_text$&
34310 .vindex &$mime_anomaly_level$&
34311 .vindex &$mime_anomaly_text$&
34312 If there are problems decoding, these variables contain information on
34313 the detected issue.
34315 .vitem &$mime_boundary$&
34316 .vindex &$mime_boundary$&
34317 If the current part is a multipart (see &$mime_is_multipart$& below), it should
34318 have a boundary string, which is stored in this variable. If the current part
34319 has no boundary parameter in the &'Content-Type:'& header, this variable
34320 contains the empty string.
34322 .vitem &$mime_charset$&
34323 .vindex &$mime_charset$&
34324 This variable contains the character set identifier, if one was found in the
34325 &'Content-Type:'& header. Examples for charset identifiers are:
34331 Please note that this value is not normalized, so you should do matches
34332 case-insensitively.
34334 .vitem &$mime_content_description$&
34335 .vindex &$mime_content_description$&
34336 This variable contains the normalized content of the &'Content-Description:'&
34337 header. It can contain a human-readable description of the parts content. Some
34338 implementations repeat the filename for attachments here, but they are usually
34339 only used for display purposes.
34341 .vitem &$mime_content_disposition$&
34342 .vindex &$mime_content_disposition$&
34343 This variable contains the normalized content of the &'Content-Disposition:'&
34344 header. You can expect strings like &"attachment"& or &"inline"& here.
34346 .vitem &$mime_content_id$&
34347 .vindex &$mime_content_id$&
34348 This variable contains the normalized content of the &'Content-ID:'& header.
34349 This is a unique ID that can be used to reference a part from another part.
34351 .vitem &$mime_content_size$&
34352 .vindex &$mime_content_size$&
34353 This variable is set only after the &%decode%& modifier (see above) has been
34354 successfully run. It contains the size of the decoded part in kilobytes. The
34355 size is always rounded up to full kilobytes, so only a completely empty part
34356 has a &$mime_content_size$& of zero.
34358 .vitem &$mime_content_transfer_encoding$&
34359 .vindex &$mime_content_transfer_encoding$&
34360 This variable contains the normalized content of the
34361 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
34362 type. Typical values are &"base64"& and &"quoted-printable"&.
34364 .vitem &$mime_content_type$&
34365 .vindex &$mime_content_type$&
34366 If the MIME part has a &'Content-Type:'& header, this variable contains its
34367 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
34368 are some examples of popular MIME types, as they may appear in this variable:
34372 application/octet-stream
34376 If the MIME part has no &'Content-Type:'& header, this variable contains the
34379 .vitem &$mime_decoded_filename$&
34380 .vindex &$mime_decoded_filename$&
34381 This variable is set only after the &%decode%& modifier (see above) has been
34382 successfully run. It contains the full path and filename of the file
34383 containing the decoded data.
34388 .vitem &$mime_filename$&
34389 .vindex &$mime_filename$&
34390 This is perhaps the most important of the MIME variables. It contains a
34391 proposed filename for an attachment, if one was found in either the
34392 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
34395 decoded, but no additional sanity checks are done.
34397 found, this variable contains the empty string.
34399 .vitem &$mime_is_coverletter$&
34400 .vindex &$mime_is_coverletter$&
34401 This variable attempts to differentiate the &"cover letter"& of an e-mail from
34402 attached data. It can be used to clamp down on flashy or unnecessarily encoded
34403 content in the cover letter, while not restricting attachments at all.
34405 The variable contains 1 (true) for a MIME part believed to be part of the
34406 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
34410 The outermost MIME part of a message is always a cover letter.
34413 If a multipart/alternative or multipart/related MIME part is a cover letter,
34414 so are all MIME subparts within that multipart.
34417 If any other multipart is a cover letter, the first subpart is a cover letter,
34418 and the rest are attachments.
34421 All parts contained within an attachment multipart are attachments.
34424 As an example, the following will ban &"HTML mail"& (including that sent with
34425 alternative plain text), while allowing HTML files to be attached. HTML
34426 coverletter mail attached to non-HTML coverletter mail will also be allowed:
34428 deny !condition = $mime_is_rfc822
34429 condition = $mime_is_coverletter
34430 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
34431 message = HTML mail is not accepted here
34434 .vitem &$mime_is_multipart$&
34435 .vindex &$mime_is_multipart$&
34436 This variable has the value 1 (true) when the current part has the main type
34437 &"multipart"&, for example, &"multipart/alternative"& or &"multipart/mixed"&.
34438 Since multipart entities only serve as containers for other parts, you may not
34439 want to carry out specific actions on them.
34441 .vitem &$mime_is_rfc822$&
34442 .vindex &$mime_is_rfc822$&
34443 This variable has the value 1 (true) if the current part is not a part of the
34444 checked message itself, but part of an attached message. Attached message
34445 decoding is fully recursive.
34447 .vitem &$mime_part_count$&
34448 .vindex &$mime_part_count$&
34449 This variable is a counter that is raised for each processed MIME part. It
34450 starts at zero for the very first part (which is usually a multipart). The
34451 counter is per-message, so it is reset when processing RFC822 attachments (see
34452 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
34453 complete, so you can use it in the DATA ACL to determine the number of MIME
34454 parts of a message. For non-MIME messages, this variable contains the value -1.
34459 .section "Scanning with regular expressions" "SECTscanregex"
34460 .cindex "content scanning" "with regular expressions"
34461 .cindex "regular expressions" "content scanning with"
34462 You can specify your own custom regular expression matches on the full body of
34463 the message, or on individual MIME parts.
34465 The &%regex%& condition takes one or more regular expressions as arguments and
34466 matches them against the full message (when called in the DATA ACL) or a raw
34467 MIME part (when called in the MIME ACL). The &%regex%& condition matches
34468 linewise, with a maximum line length of 32K characters. That means you cannot
34469 have multiline matches with the &%regex%& condition.
34471 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
34472 to 32K of decoded content (the whole content at once, not linewise). If the
34473 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
34474 is decoded automatically when &%mime_regex%& is executed (using default path
34475 and filename values). If the decoded data is larger than 32K, only the first
34476 32K characters are checked.
34478 The regular expressions are passed as a colon-separated list. To include a
34479 literal colon, you must double it. Since the whole right-hand side string is
34480 expanded before being used, you must also escape dollar signs and backslashes
34481 with more backslashes, or use the &`\N`& facility to disable expansion.
34482 Here is a simple example that contains two regular expressions:
34484 deny regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
34485 message = contains blacklisted regex ($regex_match_string)
34487 The conditions returns true if any one of the regular expressions matches. The
34488 &$regex_match_string$& expansion variable is then set up and contains the
34489 matching regular expression.
34490 The expansion variables &$regex1$& &$regex2$& etc
34491 are set to any substrings captured by the regular expression.
34493 &*Warning*&: With large messages, these conditions can be fairly
34501 . ////////////////////////////////////////////////////////////////////////////
34502 . ////////////////////////////////////////////////////////////////////////////
34504 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
34505 "Local scan function"
34506 .scindex IIDlosca "&[local_scan()]& function" "description of"
34507 .cindex "customizing" "input scan using C function"
34508 .cindex "policy control" "by local scan function"
34509 In these days of email worms, viruses, and ever-increasing spam, some sites
34510 want to apply a lot of checking to messages before accepting them.
34512 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
34513 passing messages to external virus and spam scanning software. You can also do
34514 a certain amount in Exim itself through string expansions and the &%condition%&
34515 condition in the ACL that runs after the SMTP DATA command or the ACL for
34516 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
34518 To allow for further customization to a site's own requirements, there is the
34519 possibility of linking Exim with a private message scanning function, written
34520 in C. If you want to run code that is written in something other than C, you
34521 can of course use a little C stub to call it.
34523 The local scan function is run once for every incoming message, at the point
34524 when Exim is just about to accept the message.
34525 It can therefore be used to control non-SMTP messages from local processes as
34526 well as messages arriving via SMTP.
34528 Exim applies a timeout to calls of the local scan function, and there is an
34529 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
34530 Zero means &"no timeout"&.
34531 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
34532 before calling the local scan function, so that the most common types of crash
34533 are caught. If the timeout is exceeded or one of those signals is caught, the
34534 incoming message is rejected with a temporary error if it is an SMTP message.
34535 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
34536 code. The incident is logged on the main and reject logs.
34540 .section "Building Exim to use a local scan function" "SECID207"
34541 .cindex "&[local_scan()]& function" "building Exim to use"
34542 To make use of the local scan function feature, you must tell Exim where your
34543 function is before building Exim, by setting
34544 both HAVE_LOCAL_SCAN and
34545 LOCAL_SCAN_SOURCE in your
34546 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
34547 directory, so you might set
34549 HAVE_LOCAL_SCAN=yes
34550 LOCAL_SCAN_SOURCE=Local/local_scan.c
34552 for example. The function must be called &[local_scan()]&;
34553 the source file(s) for it should first #define LOCAL_SCAN
34554 and then #include "local_scan.h".
34556 Exim after it has received a message, when the success return code is about to
34557 be sent. This is after all the ACLs have been run. The return code from your
34558 function controls whether the message is actually accepted or not. There is a
34559 commented template function (that just accepts the message) in the file
34560 _src/local_scan.c_.
34562 If you want to make use of Exim's runtime configuration file to set options
34563 for your &[local_scan()]& function, you must also set
34565 LOCAL_SCAN_HAS_OPTIONS=yes
34567 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
34572 .section "API for local_scan()" "SECTapiforloc"
34573 .cindex "&[local_scan()]& function" "API description"
34574 .cindex &%dlfunc%& "API description"
34575 You must include this line near the start of your code:
34578 #include "local_scan.h"
34580 This header file defines a number of variables and other values, and the
34581 prototype for the function itself. Exim is coded to use unsigned char values
34582 almost exclusively, and one of the things this header defines is a shorthand
34583 for &`unsigned char`& called &`uschar`&.
34584 It also makes available the following macro definitions, to simplify casting character
34585 strings and pointers to character strings:
34587 #define CS (char *)
34588 #define CCS (const char *)
34589 #define CSS (char **)
34590 #define US (unsigned char *)
34591 #define CUS (const unsigned char *)
34592 #define USS (unsigned char **)
34594 The function prototype for &[local_scan()]& is:
34596 extern int local_scan(int fd, uschar **return_text);
34598 The arguments are as follows:
34601 &%fd%& is a file descriptor for the file that contains the body of the message
34602 (the -D file). The file is open for reading and writing, but updating it is not
34603 recommended. &*Warning*&: You must &'not'& close this file descriptor.
34605 The descriptor is positioned at character 19 of the file, which is the first
34606 character of the body itself, because the first 19 characters are the message
34607 id followed by &`-D`& and a newline. If you rewind the file, you should use the
34608 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
34609 case this changes in some future version.
34611 &%return_text%& is an address which you can use to return a pointer to a text
34612 string at the end of the function. The value it points to on entry is NULL.
34615 The function must return an &%int%& value which is one of the following macros:
34618 .vitem &`LOCAL_SCAN_ACCEPT`&
34619 .vindex "&$local_scan_data$&"
34620 The message is accepted. If you pass back a string of text, it is saved with
34621 the message, and made available in the variable &$local_scan_data$&. No
34622 newlines are permitted (if there are any, they are turned into spaces) and the
34623 maximum length of text is 1000 characters.
34625 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
34626 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
34627 queued without immediate delivery, and is frozen.
34629 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
34630 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
34631 queued without immediate delivery.
34633 .vitem &`LOCAL_SCAN_REJECT`&
34634 The message is rejected; the returned text is used as an error message which is
34635 passed back to the sender and which is also logged. Newlines are permitted &--
34636 they cause a multiline response for SMTP rejections, but are converted to
34637 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
34640 .vitem &`LOCAL_SCAN_TEMPREJECT`&
34641 The message is temporarily rejected; the returned text is used as an error
34642 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
34645 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
34646 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
34647 message is not written to the reject log. It has the effect of unsetting the
34648 &%rejected_header%& log selector for just this rejection. If
34649 &%rejected_header%& is already unset (see the discussion of the
34650 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
34651 same as LOCAL_SCAN_REJECT.
34653 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
34654 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
34655 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
34658 If the message is not being received by interactive SMTP, rejections are
34659 reported by writing to &%stderr%& or by sending an email, as configured by the
34660 &%-oe%& command line options.
34664 .section "Configuration options for local_scan()" "SECTconoptloc"
34665 .cindex "&[local_scan()]& function" "configuration options"
34666 It is possible to have option settings in the main configuration file
34667 that set values in static variables in the &[local_scan()]& module. If you
34668 want to do this, you must have the line
34670 LOCAL_SCAN_HAS_OPTIONS=yes
34672 in your &_Local/Makefile_& when you build Exim. (This line is in
34673 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
34674 file, you must define static variables to hold the option values, and a table
34677 The table must be a vector called &%local_scan_options%&, of type
34678 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
34679 and a pointer to the variable that holds the value. The entries must appear in
34680 alphabetical order. Following &%local_scan_options%& you must also define a
34681 variable called &%local_scan_options_count%& that contains the number of
34682 entries in the table. Here is a short example, showing two kinds of option:
34684 static int my_integer_option = 42;
34685 static uschar *my_string_option = US"a default string";
34687 optionlist local_scan_options[] = {
34688 { "my_integer", opt_int, &my_integer_option },
34689 { "my_string", opt_stringptr, &my_string_option }
34692 int local_scan_options_count =
34693 sizeof(local_scan_options)/sizeof(optionlist);
34695 The values of the variables can now be changed from Exim's runtime
34696 configuration file by including a local scan section as in this example:
34700 my_string = some string of text...
34702 The available types of option data are as follows:
34705 .vitem &*opt_bool*&
34706 This specifies a boolean (true/false) option. The address should point to a
34707 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
34708 that are defined as &"1"& and &"0"&, respectively. If you want to detect
34709 whether such a variable has been set at all, you can initialize it to
34710 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
34713 .vitem &*opt_fixed*&
34714 This specifies a fixed point number, such as is used for load averages.
34715 The address should point to a variable of type &`int`&. The value is stored
34716 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
34719 This specifies an integer; the address should point to a variable of type
34720 &`int`&. The value may be specified in any of the integer formats accepted by
34723 .vitem &*opt_mkint*&
34724 This is the same as &%opt_int%&, except that when such a value is output in a
34725 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
34726 printed with the suffix K or M.
34728 .vitem &*opt_octint*&
34729 This also specifies an integer, but the value is always interpreted as an
34730 octal integer, whether or not it starts with the digit zero, and it is
34731 always output in octal.
34733 .vitem &*opt_stringptr*&
34734 This specifies a string value; the address must be a pointer to a
34735 variable that points to a string (for example, of type &`uschar *`&).
34737 .vitem &*opt_time*&
34738 This specifies a time interval value. The address must point to a variable of
34739 type &`int`&. The value that is placed there is a number of seconds.
34742 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
34743 out the values of all the &[local_scan()]& options.
34747 .section "Available Exim variables" "SECID208"
34748 .cindex "&[local_scan()]& function" "available Exim variables"
34749 The header &_local_scan.h_& gives you access to a number of C variables. These
34750 are the only ones that are guaranteed to be maintained from release to release.
34751 Note, however, that you can obtain the value of any Exim expansion variable,
34752 including &$recipients$&, by calling &'expand_string()'&. The exported
34753 C variables are as follows:
34756 .vitem &*int&~body_linecount*&
34757 This variable contains the number of lines in the message's body.
34758 It is not valid if the &%spool_files_wireformat%& option is used.
34760 .vitem &*int&~body_zerocount*&
34761 This variable contains the number of binary zero bytes in the message's body.
34762 It is not valid if the &%spool_files_wireformat%& option is used.
34764 .vitem &*unsigned&~int&~debug_selector*&
34765 This variable is set to zero when no debugging is taking place. Otherwise, it
34766 is a bitmap of debugging selectors. Two bits are identified for use in
34767 &[local_scan()]&; they are defined as macros:
34770 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
34771 testing option that is not privileged &-- any caller may set it. All the
34772 other selector bits can be set only by admin users.
34775 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
34776 by the &`+local_scan`& debug selector. It is not included in the default set
34780 Thus, to write to the debugging output only when &`+local_scan`& has been
34781 selected, you should use code like this:
34783 if ((debug_selector & D_local_scan) != 0)
34784 debug_printf("xxx", ...);
34786 .vitem &*uschar&~*expand_string_message*&
34787 After a failing call to &'expand_string()'& (returned value NULL), the
34788 variable &%expand_string_message%& contains the error message, zero-terminated.
34790 .vitem &*header_line&~*header_list*&
34791 A pointer to a chain of header lines. The &%header_line%& structure is
34794 .vitem &*header_line&~*header_last*&
34795 A pointer to the last of the header lines.
34797 .vitem &*uschar&~*headers_charset*&
34798 The value of the &%headers_charset%& configuration option.
34800 .vitem &*BOOL&~host_checking*&
34801 This variable is TRUE during a host checking session that is initiated by the
34802 &%-bh%& command line option.
34804 .vitem &*uschar&~*interface_address*&
34805 The IP address of the interface that received the message, as a string. This
34806 is NULL for locally submitted messages.
34808 .vitem &*int&~interface_port*&
34809 The port on which this message was received. When testing with the &%-bh%&
34810 command line option, the value of this variable is -1 unless a port has been
34811 specified via the &%-oMi%& option.
34813 .vitem &*uschar&~*message_id*&
34814 This variable contains Exim's message id for the incoming message (the value of
34815 &$message_exim_id$&) as a zero-terminated string.
34817 .vitem &*uschar&~*received_protocol*&
34818 The name of the protocol by which the message was received.
34820 .vitem &*int&~recipients_count*&
34821 The number of accepted recipients.
34823 .vitem &*recipient_item&~*recipients_list*&
34824 .cindex "recipient" "adding in local scan"
34825 .cindex "recipient" "removing in local scan"
34826 The list of accepted recipients, held in a vector of length
34827 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
34828 can add additional recipients by calling &'receive_add_recipient()'& (see
34829 below). You can delete recipients by removing them from the vector and
34830 adjusting the value in &%recipients_count%&. In particular, by setting
34831 &%recipients_count%& to zero you remove all recipients. If you then return the
34832 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
34833 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
34834 and then call &'receive_add_recipient()'& as often as needed.
34836 .vitem &*uschar&~*sender_address*&
34837 The envelope sender address. For bounce messages this is the empty string.
34839 .vitem &*uschar&~*sender_host_address*&
34840 The IP address of the sending host, as a string. This is NULL for
34841 locally-submitted messages.
34843 .vitem &*uschar&~*sender_host_authenticated*&
34844 The name of the authentication mechanism that was used, or NULL if the message
34845 was not received over an authenticated SMTP connection.
34847 .vitem &*uschar&~*sender_host_name*&
34848 The name of the sending host, if known.
34850 .vitem &*int&~sender_host_port*&
34851 The port on the sending host.
34853 .vitem &*BOOL&~smtp_input*&
34854 This variable is TRUE for all SMTP input, including BSMTP.
34856 .vitem &*BOOL&~smtp_batched_input*&
34857 This variable is TRUE for BSMTP input.
34859 .vitem &*int&~store_pool*&
34860 The contents of this variable control which pool of memory is used for new
34861 requests. See section &<<SECTmemhanloc>>& for details.
34865 .section "Structure of header lines" "SECID209"
34866 The &%header_line%& structure contains the members listed below.
34867 You can add additional header lines by calling the &'header_add()'& function
34868 (see below). You can cause header lines to be ignored (deleted) by setting
34873 .vitem &*struct&~header_line&~*next*&
34874 A pointer to the next header line, or NULL for the last line.
34876 .vitem &*int&~type*&
34877 A code identifying certain headers that Exim recognizes. The codes are printing
34878 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
34879 Notice in particular that any header line whose type is * is not transmitted
34880 with the message. This flagging is used for header lines that have been
34881 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
34882 lines.) Effectively, * means &"deleted"&.
34884 .vitem &*int&~slen*&
34885 The number of characters in the header line, including the terminating and any
34888 .vitem &*uschar&~*text*&
34889 A pointer to the text of the header. It always ends with a newline, followed by
34890 a zero byte. Internal newlines are preserved.
34895 .section "Structure of recipient items" "SECID210"
34896 The &%recipient_item%& structure contains these members:
34899 .vitem &*uschar&~*address*&
34900 This is a pointer to the recipient address as it was received.
34902 .vitem &*int&~pno*&
34903 This is used in later Exim processing when top level addresses are created by
34904 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
34905 and must always contain -1 at this stage.
34907 .vitem &*uschar&~*errors_to*&
34908 If this value is not NULL, bounce messages caused by failing to deliver to the
34909 recipient are sent to the address it contains. In other words, it overrides the
34910 envelope sender for this one recipient. (Compare the &%errors_to%& generic
34911 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
34912 an unqualified address, Exim qualifies it using the domain from
34913 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
34914 is NULL for all recipients.
34919 .section "Available Exim functions" "SECID211"
34920 .cindex "&[local_scan()]& function" "available Exim functions"
34921 The header &_local_scan.h_& gives you access to a number of Exim functions.
34922 These are the only ones that are guaranteed to be maintained from release to
34926 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
34927 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
34929 This function creates a child process that runs the command specified by
34930 &%argv%&. The environment for the process is specified by &%envp%&, which can
34931 be NULL if no environment variables are to be passed. A new umask is supplied
34932 for the process in &%newumask%&.
34934 Pipes to the standard input and output of the new process are set up
34935 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
34936 standard error is cloned to the standard output. If there are any file
34937 descriptors &"in the way"& in the new process, they are closed. If the final
34938 argument is TRUE, the new process is made into a process group leader.
34940 The function returns the pid of the new process, or -1 if things go wrong.
34942 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
34943 This function waits for a child process to terminate, or for a timeout (in
34944 seconds) to expire. A timeout value of zero means wait as long as it takes. The
34945 return value is as follows:
34950 The process terminated by a normal exit and the value is the process
34956 The process was terminated by a signal and the value is the negation of the
34962 The process timed out.
34966 The was some other error in wait(); &%errno%& is still set.
34969 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
34970 This function provide you with a means of submitting a new message to
34971 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
34972 want, but this packages it all up for you.) The function creates a pipe,
34973 forks a subprocess that is running
34975 exim -t -oem -oi -f <>
34977 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
34978 that is connected to the standard input. The yield of the function is the PID
34979 of the subprocess. You can then write a message to the file descriptor, with
34980 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
34982 When you have finished, call &'child_close()'& to wait for the process to
34983 finish and to collect its ending status. A timeout value of zero is usually
34984 fine in this circumstance. Unless you have made a mistake with the recipient
34985 addresses, you should get a return code of zero.
34988 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
34989 *sender_authentication)*&
34990 This function is a more sophisticated version of &'child_open()'&. The command
34993 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
34995 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
34998 .vitem &*void&~debug_printf(char&~*,&~...)*&
34999 This is Exim's debugging function, with arguments as for &'(printf()'&. The
35000 output is written to the standard error stream. If no debugging is selected,
35001 calls to &'debug_printf()'& have no effect. Normally, you should make calls
35002 conditional on the &`local_scan`& debug selector by coding like this:
35004 if ((debug_selector & D_local_scan) != 0)
35005 debug_printf("xxx", ...);
35008 .vitem &*uschar&~*expand_string(uschar&~*string)*&
35009 This is an interface to Exim's string expansion code. The return value is the
35010 expanded string, or NULL if there was an expansion failure.
35011 The C variable &%expand_string_message%& contains an error message after an
35012 expansion failure. If expansion does not change the string, the return value is
35013 the pointer to the input string. Otherwise, the return value points to a new
35014 block of memory that was obtained by a call to &'store_get()'&. See section
35015 &<<SECTmemhanloc>>& below for a discussion of memory handling.
35017 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
35018 This function allows you to an add additional header line at the end of the
35019 existing ones. The first argument is the type, and should normally be a space
35020 character. The second argument is a format string and any number of
35021 substitution arguments as for &[sprintf()]&. You may include internal newlines
35022 if you want, and you must ensure that the string ends with a newline.
35024 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
35025 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
35026 This function adds a new header line at a specified point in the header
35027 chain. The header itself is specified as for &'header_add()'&.
35029 If &%name%& is NULL, the new header is added at the end of the chain if
35030 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
35031 NULL, the header lines are searched for the first non-deleted header that
35032 matches the name. If one is found, the new header is added before it if
35033 &%after%& is false. If &%after%& is true, the new header is added after the
35034 found header and any adjacent subsequent ones with the same name (even if
35035 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
35036 option controls where the header is added. If it is true, addition is at the
35037 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
35038 headers, or at the top if there are no &'Received:'& headers, you could use
35040 header_add_at_position(TRUE, US"Received", TRUE,
35041 ' ', "X-xxx: ...");
35043 Normally, there is always at least one non-deleted &'Received:'& header, but
35044 there may not be if &%received_header_text%& expands to an empty string.
35047 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
35048 This function removes header lines. If &%occurrence%& is zero or negative, all
35049 occurrences of the header are removed. If occurrence is greater than zero, that
35050 particular instance of the header is removed. If no header(s) can be found that
35051 match the specification, the function does nothing.
35054 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
35055 int&~length,&~BOOL&~notdel)*&"
35056 This function tests whether the given header has the given name. It is not just
35057 a string comparison, because white space is permitted between the name and the
35058 colon. If the &%notdel%& argument is true, a false return is forced for all
35059 &"deleted"& headers; otherwise they are not treated specially. For example:
35061 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
35063 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
35064 .cindex "base64 encoding" "functions for &[local_scan()]& use"
35065 This function base64-encodes a string, which is passed by address and length.
35066 The text may contain bytes of any value, including zero. The result is passed
35067 back in dynamic memory that is obtained by calling &'store_get()'&. It is
35070 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
35071 This function decodes a base64-encoded string. Its arguments are a
35072 zero-terminated base64-encoded string and the address of a variable that is set
35073 to point to the result, which is in dynamic memory. The length of the decoded
35074 string is the yield of the function. If the input is invalid base64 data, the
35075 yield is -1. A zero byte is added to the end of the output string to make it
35076 easy to interpret as a C string (assuming it contains no zeros of its own). The
35077 added zero byte is not included in the returned count.
35079 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
35080 This function checks for a match in a domain list. Domains are always
35081 matched caselessly. The return value is one of the following:
35083 &`OK `& match succeeded
35084 &`FAIL `& match failed
35085 &`DEFER `& match deferred
35087 DEFER is usually caused by some kind of lookup defer, such as the
35088 inability to contact a database.
35090 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
35092 This function checks for a match in a local part list. The third argument
35093 controls case-sensitivity. The return values are as for
35094 &'lss_match_domain()'&.
35096 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
35098 This function checks for a match in an address list. The third argument
35099 controls the case-sensitivity of the local part match. The domain is always
35100 matched caselessly. The return values are as for &'lss_match_domain()'&.
35102 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
35104 This function checks for a match in a host list. The most common usage is
35107 lss_match_host(sender_host_name, sender_host_address, ...)
35109 .vindex "&$sender_host_address$&"
35110 An empty address field matches an empty item in the host list. If the host name
35111 is NULL, the name corresponding to &$sender_host_address$& is automatically
35112 looked up if a host name is required to match an item in the list. The return
35113 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
35114 returns ERROR in the case when it had to look up a host name, but the lookup
35117 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
35119 This function writes to Exim's log files. The first argument should be zero (it
35120 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
35121 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
35122 them. It specifies to which log or logs the message is written. The remaining
35123 arguments are a format and relevant insertion arguments. The string should not
35124 contain any newlines, not even at the end.
35127 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
35128 This function adds an additional recipient to the message. The first argument
35129 is the recipient address. If it is unqualified (has no domain), it is qualified
35130 with the &%qualify_recipient%& domain. The second argument must always be -1.
35132 This function does not allow you to specify a private &%errors_to%& address (as
35133 described with the structure of &%recipient_item%& above), because it pre-dates
35134 the addition of that field to the structure. However, it is easy to add such a
35135 value afterwards. For example:
35137 receive_add_recipient(US"monitor@mydom.example", -1);
35138 recipients_list[recipients_count-1].errors_to =
35139 US"postmaster@mydom.example";
35142 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
35143 This is a convenience function to remove a named recipient from the list of
35144 recipients. It returns true if a recipient was removed, and false if no
35145 matching recipient could be found. The argument must be a complete email
35152 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
35153 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
35154 This function decodes strings that are encoded according to RFC 2047. Typically
35155 these are the contents of header lines. First, each &"encoded word"& is decoded
35156 from the Q or B encoding into a byte-string. Then, if provided with the name of
35157 a charset encoding, and if the &[iconv()]& function is available, an attempt is
35158 made to translate the result to the named character set. If this fails, the
35159 binary string is returned with an error message.
35161 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
35162 maximum MIME word length is enforced. The third argument is the target
35163 encoding, or NULL if no translation is wanted.
35165 .cindex "binary zero" "in RFC 2047 decoding"
35166 .cindex "RFC 2047" "binary zero in"
35167 If a binary zero is encountered in the decoded string, it is replaced by the
35168 contents of the &%zeroval%& argument. For use with Exim headers, the value must
35169 not be 0 because header lines are handled as zero-terminated strings.
35171 The function returns the result of processing the string, zero-terminated; if
35172 &%lenptr%& is not NULL, the length of the result is set in the variable to
35173 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
35175 If an error is encountered, the function returns NULL and uses the &%error%&
35176 argument to return an error message. The variable pointed to by &%error%& is
35177 set to NULL if there is no error; it may be set non-NULL even when the function
35178 returns a non-NULL value if decoding was successful, but there was a problem
35182 .vitem &*int&~smtp_fflush(void)*&
35183 This function is used in conjunction with &'smtp_printf()'&, as described
35186 .vitem &*void&~smtp_printf(char&~*,BOOL,&~...)*&
35187 The arguments of this function are almost like &[printf()]&; it writes to the SMTP
35188 output stream. You should use this function only when there is an SMTP output
35189 stream, that is, when the incoming message is being received via interactive
35190 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
35191 is FALSE. If you want to test for an incoming message from another host (as
35192 opposed to a local process that used the &%-bs%& command line option), you can
35193 test the value of &%sender_host_address%&, which is non-NULL when a remote host
35196 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
35197 output function, so it can be used for all forms of SMTP connection.
35199 The second argument is used to request that the data be buffered
35200 (when TRUE) or flushed (along with any previously buffered, when FALSE).
35201 This is advisory only, but likely to save on system-calls and packets
35202 sent when a sequence of calls to the function are made.
35204 The argument was added in Exim version 4.90 - changing the API/ABI.
35205 Nobody noticed until 4.93 was imminent, at which point the
35206 ABI version number was incremented.
35208 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
35209 must start with an appropriate response code: 550 if you are going to return
35210 LOCAL_SCAN_REJECT, 451 if you are going to return
35211 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
35212 initial lines of a multi-line response, the code must be followed by a hyphen
35213 to indicate that the line is not the final response line. You must also ensure
35214 that the lines you write terminate with CRLF. For example:
35216 smtp_printf("550-this is some extra info\r\n");
35217 return LOCAL_SCAN_REJECT;
35219 Note that you can also create multi-line responses by including newlines in
35220 the data returned via the &%return_text%& argument. The added value of using
35221 &'smtp_printf()'& is that, for instance, you could introduce delays between
35222 multiple output lines.
35224 The &'smtp_printf()'& function does not return any error indication, because it
35226 guarantee a flush of
35227 pending output, and therefore does not test
35228 the state of the stream. (In the main code of Exim, flushing and error
35229 detection is done when Exim is ready for the next SMTP input command.) If
35230 you want to flush the output and check for an error (for example, the
35231 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
35232 arguments. It flushes the output stream, and returns a non-zero value if there
35235 .vitem &*void&~*store_get(int,BOOL)*&
35236 This function accesses Exim's internal store (memory) manager. It gets a new
35237 chunk of memory whose size is given by the first argument.
35238 The second argument should be given as TRUE if the memory will be used for
35239 data possibly coming from an attacker (eg. the message content),
35240 FALSE if it is locally-sourced.
35241 Exim bombs out if it ever
35242 runs out of memory. See the next section for a discussion of memory handling.
35244 .vitem &*void&~*store_get_perm(int,BOOL)*&
35245 This function is like &'store_get()'&, but it always gets memory from the
35246 permanent pool. See the next section for a discussion of memory handling.
35248 .vitem &*uschar&~*string_copy(uschar&~*string)*&
35251 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
35254 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
35255 These three functions create strings using Exim's dynamic memory facilities.
35256 The first makes a copy of an entire string. The second copies up to a maximum
35257 number of characters, indicated by the second argument. The third uses a format
35258 and insertion arguments to create a new string. In each case, the result is a
35259 pointer to a new string in the current memory pool. See the next section for
35265 .section "More about Exim's memory handling" "SECTmemhanloc"
35266 .cindex "&[local_scan()]& function" "memory handling"
35267 No function is provided for freeing memory, because that is never needed.
35268 The dynamic memory that Exim uses when receiving a message is automatically
35269 recycled if another message is received by the same process (this applies only
35270 to incoming SMTP connections &-- other input methods can supply only one
35271 message at a time). After receiving the last message, a reception process
35274 Because it is recycled, the normal dynamic memory cannot be used for holding
35275 data that must be preserved over a number of incoming messages on the same SMTP
35276 connection. However, Exim in fact uses two pools of dynamic memory; the second
35277 one is not recycled, and can be used for this purpose.
35279 If you want to allocate memory that remains available for subsequent messages
35280 in the same SMTP connection, you should set
35282 store_pool = POOL_PERM
35284 before calling the function that does the allocation. There is no need to
35285 restore the value if you do not need to; however, if you do want to revert to
35286 the normal pool, you can either restore the previous value of &%store_pool%& or
35287 set it explicitly to POOL_MAIN.
35289 The pool setting applies to all functions that get dynamic memory, including
35290 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
35291 There is also a convenience function called &'store_get_perm()'& that gets a
35292 block of memory from the permanent pool while preserving the value of
35299 . ////////////////////////////////////////////////////////////////////////////
35300 . ////////////////////////////////////////////////////////////////////////////
35302 .chapter "System-wide message filtering" "CHAPsystemfilter"
35303 .scindex IIDsysfil1 "filter" "system filter"
35304 .scindex IIDsysfil2 "filtering all mail"
35305 .scindex IIDsysfil3 "system filter"
35306 The previous chapters (on ACLs and the local scan function) describe checks
35307 that can be applied to messages before they are accepted by a host. There is
35308 also a mechanism for checking messages once they have been received, but before
35309 they are delivered. This is called the &'system filter'&.
35311 The system filter operates in a similar manner to users' filter files, but it
35312 is run just once per message (however many recipients the message has).
35313 It should not normally be used as a substitute for routing, because &%deliver%&
35314 commands in a system router provide new envelope recipient addresses.
35315 The system filter must be an Exim filter. It cannot be a Sieve filter.
35317 The system filter is run at the start of a delivery attempt, before any routing
35318 is done. If a message fails to be completely delivered at the first attempt,
35319 the system filter is run again at the start of every retry.
35320 If you want your filter to do something only once per message, you can make use
35321 of the &%first_delivery%& condition in an &%if%& command in the filter to
35322 prevent it happening on retries.
35324 .vindex "&$domain$&"
35325 .vindex "&$local_part$&"
35326 &*Warning*&: Because the system filter runs just once, variables that are
35327 specific to individual recipient addresses, such as &$local_part$& and
35328 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
35329 you want to run a centrally-specified filter for each recipient address
35330 independently, you can do so by setting up a suitable &(redirect)& router, as
35331 described in section &<<SECTperaddfil>>& below.
35334 .section "Specifying a system filter" "SECID212"
35335 .cindex "uid (user id)" "system filter"
35336 .cindex "gid (group id)" "system filter"
35337 The name of the file that contains the system filter must be specified by
35338 setting &%system_filter%&. If you want the filter to run under a uid and gid
35339 other than root, you must also set &%system_filter_user%& and
35340 &%system_filter_group%& as appropriate. For example:
35342 system_filter = /etc/mail/exim.filter
35343 system_filter_user = exim
35345 If a system filter generates any deliveries directly to files or pipes (via the
35346 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
35347 specified by setting &%system_filter_file_transport%& and
35348 &%system_filter_pipe_transport%&, respectively. Similarly,
35349 &%system_filter_reply_transport%& must be set to handle any messages generated
35350 by the &%reply%& command.
35353 .section "Testing a system filter" "SECID213"
35354 You can run simple tests of a system filter in the same way as for a user
35355 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
35356 are permitted only in system filters are recognized.
35358 If you want to test the combined effect of a system filter and a user filter,
35359 you can use both &%-bF%& and &%-bf%& on the same command line.
35363 .section "Contents of a system filter" "SECID214"
35364 The language used to specify system filters is the same as for users' filter
35365 files. It is described in the separate end-user document &'Exim's interface to
35366 mail filtering'&. However, there are some additional features that are
35367 available only in system filters; these are described in subsequent sections.
35368 If they are encountered in a user's filter file or when testing with &%-bf%&,
35371 .cindex "frozen messages" "manual thaw; testing in filter"
35372 There are two special conditions which, though available in users' filter
35373 files, are designed for use in system filters. The condition &%first_delivery%&
35374 is true only for the first attempt at delivering a message, and
35375 &%manually_thawed%& is true only if the message has been frozen, and
35376 subsequently thawed by an admin user. An explicit forced delivery counts as a
35377 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
35379 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
35380 specify an &"unseen"& (non-significant) delivery, and that delivery does not
35381 succeed, it will not be tried again.
35382 If you want Exim to retry an unseen delivery until it succeeds, you should
35383 arrange to set it up every time the filter runs.
35385 When a system filter finishes running, the values of the variables &$n0$& &--
35386 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
35387 users' filter files. Thus a system filter can, for example, set up &"scores"&
35388 to which users' filter files can refer.
35392 .section "Additional variable for system filters" "SECID215"
35393 .vindex "&$recipients$&"
35394 The expansion variable &$recipients$&, containing a list of all the recipients
35395 of the message (separated by commas and white space), is available in system
35396 filters. It is not available in users' filters for privacy reasons.
35400 .section "Defer, freeze, and fail commands for system filters" "SECID216"
35401 .cindex "freezing messages"
35402 .cindex "message" "freezing"
35403 .cindex "message" "forced failure"
35404 .cindex "&%fail%&" "in system filter"
35405 .cindex "&%freeze%& in system filter"
35406 .cindex "&%defer%& in system filter"
35407 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
35408 always available in system filters, but are not normally enabled in users'
35409 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
35410 for the &(redirect)& router.) These commands can optionally be followed by the
35411 word &%text%& and a string containing an error message, for example:
35413 fail text "this message looks like spam to me"
35415 The keyword &%text%& is optional if the next character is a double quote.
35417 The &%defer%& command defers delivery of the original recipients of the
35418 message. The &%fail%& command causes all the original recipients to be failed,
35419 and a bounce message to be created. The &%freeze%& command suspends all
35420 delivery attempts for the original recipients. In all cases, any new deliveries
35421 that are specified by the filter are attempted as normal after the filter has
35424 The &%freeze%& command is ignored if the message has been manually unfrozen and
35425 not manually frozen since. This means that automatic freezing by a system
35426 filter can be used as a way of checking out suspicious messages. If a message
35427 is found to be all right, manually unfreezing it allows it to be delivered.
35429 .cindex "log" "&%fail%& command log line"
35430 .cindex "&%fail%&" "log line; reducing"
35431 The text given with a fail command is used as part of the bounce message as
35432 well as being written to the log. If the message is quite long, this can fill
35433 up a lot of log space when such failures are common. To reduce the size of the
35434 log message, Exim interprets the text in a special way if it starts with the
35435 two characters &`<<`& and contains &`>>`& later. The text between these two
35436 strings is written to the log, and the rest of the text is used in the bounce
35437 message. For example:
35439 fail "<<filter test 1>>Your message is rejected \
35440 because it contains attachments that we are \
35441 not prepared to receive."
35444 .cindex "loop" "caused by &%fail%&"
35445 Take great care with the &%fail%& command when basing the decision to fail on
35446 the contents of the message, because the bounce message will of course include
35447 the contents of the original message and will therefore trigger the &%fail%&
35448 command again (causing a mail loop) unless steps are taken to prevent this.
35449 Testing the &%error_message%& condition is one way to prevent this. You could
35452 if $message_body contains "this is spam" and not error_message
35453 then fail text "spam is not wanted here" endif
35455 though of course that might let through unwanted bounce messages. The
35456 alternative is clever checking of the body and/or headers to detect bounces
35457 generated by the filter.
35459 The interpretation of a system filter file ceases after a
35461 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
35462 set up earlier in the filter file are honoured, so you can use a sequence such
35468 to send a specified message when the system filter is freezing (or deferring or
35469 failing) a message. The normal deliveries for the message do not, of course,
35474 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
35475 .cindex "header lines" "adding; in system filter"
35476 .cindex "header lines" "removing; in system filter"
35477 .cindex "filter" "header lines; adding/removing"
35478 Two filter commands that are available only in system filters are:
35480 headers add <string>
35481 headers remove <string>
35483 The argument for the &%headers add%& is a string that is expanded and then
35484 added to the end of the message's headers. It is the responsibility of the
35485 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
35486 space is ignored, and if the string is otherwise empty, or if the expansion is
35487 forced to fail, the command has no effect.
35489 You can use &"\n"& within the string, followed by white space, to specify
35490 continued header lines. More than one header may be added in one command by
35491 including &"\n"& within the string without any following white space. For
35494 headers add "X-header-1: ....\n \
35495 continuation of X-header-1 ...\n\
35498 Note that the header line continuation white space after the first newline must
35499 be placed before the backslash that continues the input string, because white
35500 space after input continuations is ignored.
35502 The argument for &%headers remove%& is a colon-separated list of header names.
35503 This command applies only to those headers that are stored with the message;
35504 those that are added at delivery time (such as &'Envelope-To:'& and
35505 &'Return-Path:'&) cannot be removed by this means. If there is more than one
35506 header with the same name, they are all removed.
35508 The &%headers%& command in a system filter makes an immediate change to the set
35509 of header lines that was received with the message (with possible additions
35510 from ACL processing). Subsequent commands in the system filter operate on the
35511 modified set, which also forms the basis for subsequent message delivery.
35512 Unless further modified during routing or transporting, this set of headers is
35513 used for all recipients of the message.
35515 During routing and transporting, the variables that refer to the contents of
35516 header lines refer only to those lines that are in this set. Thus, header lines
35517 that are added by a system filter are visible to users' filter files and to all
35518 routers and transports. This contrasts with the manipulation of header lines by
35519 routers and transports, which is not immediate, but which instead is saved up
35520 until the message is actually being written (see section
35521 &<<SECTheadersaddrem>>&).
35523 If the message is not delivered at the first attempt, header lines that were
35524 added by the system filter are stored with the message, and so are still
35525 present at the next delivery attempt. Header lines that were removed are still
35526 present, but marked &"deleted"& so that they are not transported with the
35527 message. For this reason, it is usual to make the &%headers%& command
35528 conditional on &%first_delivery%& so that the set of header lines is not
35529 modified more than once.
35531 Because header modification in a system filter acts immediately, you have to
35532 use an indirect approach if you want to modify the contents of a header line.
35535 headers add "Old-Subject: $h_subject:"
35536 headers remove "Subject"
35537 headers add "Subject: new subject (was: $h_old-subject:)"
35538 headers remove "Old-Subject"
35543 .section "Setting an errors address in a system filter" "SECID217"
35544 .cindex "envelope from"
35545 .cindex "envelope sender"
35546 In a system filter, if a &%deliver%& command is followed by
35548 errors_to <some address>
35550 in order to change the envelope sender (and hence the error reporting) for that
35551 delivery, any address may be specified. (In a user filter, only the current
35552 user's address can be set.) For example, if some mail is being monitored, you
35555 unseen deliver monitor@spying.example errors_to root@local.example
35557 to take a copy which would not be sent back to the normal error reporting
35558 address if its delivery failed.
35562 .section "Per-address filtering" "SECTperaddfil"
35563 .vindex "&$domain_data$&"
35564 .vindex "&$local_part_data$&"
35565 In contrast to the system filter, which is run just once per message for each
35566 delivery attempt, it is also possible to set up a system-wide filtering
35567 operation that runs once for each recipient address. In this case, variables
35568 such as &$local_part_data$& and &$domain_data$& can be used,
35569 and indeed, the choice of filter file could be made dependent on them.
35570 This is an example of a router which implements such a filter:
35575 domains = +local_domains
35576 file = /central/filters/$local_part_data
35581 The filter is run in a separate process under its own uid. Therefore, either
35582 &%check_local_user%& must be set (as above), in which case the filter is run as
35583 the local user, or the &%user%& option must be used to specify which user to
35584 use. If both are set, &%user%& overrides.
35586 Care should be taken to ensure that none of the commands in the filter file
35587 specify a significant delivery if the message is to go on to be delivered to
35588 its intended recipient. The router will not then claim to have dealt with the
35589 address, so it will be passed on to subsequent routers to be delivered in the
35591 .ecindex IIDsysfil1
35592 .ecindex IIDsysfil2
35593 .ecindex IIDsysfil3
35600 . ////////////////////////////////////////////////////////////////////////////
35601 . ////////////////////////////////////////////////////////////////////////////
35603 .chapter "Message processing" "CHAPmsgproc"
35604 .scindex IIDmesproc "message" "general processing"
35605 Exim performs various transformations on the sender and recipient addresses of
35606 all messages that it handles, and also on the messages' header lines. Some of
35607 these are optional and configurable, while others always take place. All of
35608 this processing, except rewriting as a result of routing, and the addition or
35609 removal of header lines while delivering, happens when a message is received,
35610 before it is placed on Exim's queue.
35612 Some of the automatic processing takes place by default only for
35613 &"locally-originated"& messages. This adjective is used to describe messages
35614 that are not received over TCP/IP, but instead are passed to an Exim process on
35615 its standard input. This includes the interactive &"local SMTP"& case that is
35616 set up by the &%-bs%& command line option.
35618 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
35619 or ::1) are not considered to be locally-originated. Exim does not treat the
35620 loopback interface specially in any way.
35622 If you want the loopback interface to be treated specially, you must ensure
35623 that there are appropriate entries in your ACLs.
35628 .section "Submission mode for non-local messages" "SECTsubmodnon"
35629 .cindex "message" "submission"
35630 .cindex "submission mode"
35631 Processing that happens automatically for locally-originated messages (unless
35632 &%suppress_local_fixups%& is set) can also be requested for messages that are
35633 received over TCP/IP. The term &"submission mode"& is used to describe this
35634 state. Submission mode is set by the modifier
35636 control = submission
35638 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
35639 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
35640 a local submission, and is normally used when the source of the message is
35641 known to be an MUA running on a client host (as opposed to an MTA). For
35642 example, to set submission mode for messages originating on the IPv4 loopback
35643 interface, you could include the following in the MAIL ACL:
35645 warn hosts = 127.0.0.1
35646 control = submission
35648 .cindex "&%sender_retain%& submission option"
35649 There are some options that can be used when setting submission mode. A slash
35650 is used to separate options. For example:
35652 control = submission/sender_retain
35654 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
35655 true and &%local_from_check%& false for the current incoming message. The first
35656 of these allows an existing &'Sender:'& header in the message to remain, and
35657 the second suppresses the check to ensure that &'From:'& matches the
35658 authenticated sender. With this setting, Exim still fixes up messages by adding
35659 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
35660 attempt to check sender authenticity in header lines.
35662 When &%sender_retain%& is not set, a submission mode setting may specify a
35663 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
35666 control = submission/domain=some.domain
35668 The domain may be empty. How this value is used is described in sections
35669 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
35670 that allows you to specify the user's full name for inclusion in a created
35671 &'Sender:'& or &'From:'& header line. For example:
35673 accept authenticated = *
35674 control = submission/domain=wonderland.example/\
35675 name=${lookup {$authenticated_id} \
35676 lsearch {/etc/exim/namelist}}
35678 Because the name may contain any characters, including slashes, the &%name%&
35679 option must be given last. The remainder of the string is used as the name. For
35680 the example above, if &_/etc/exim/namelist_& contains:
35682 bigegg: Humpty Dumpty
35684 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
35687 Sender: Humpty Dumpty <bigegg@wonderland.example>
35689 .cindex "return path" "in submission mode"
35690 By default, submission mode forces the return path to the same address as is
35691 used to create the &'Sender:'& header. However, if &%sender_retain%& is
35692 specified, the return path is also left unchanged.
35694 &*Note*&: The changes caused by submission mode take effect after the predata
35695 ACL. This means that any sender checks performed before the fix-ups use the
35696 untrusted sender address specified by the user, not the trusted sender address
35697 specified by submission mode. Although this might be slightly unexpected, it
35698 does mean that you can configure ACL checks to spot that a user is trying to
35699 spoof another's address.
35701 .section "Line endings" "SECTlineendings"
35702 .cindex "line endings"
35703 .cindex "carriage return"
35705 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
35706 linefeed) is the line ending for messages transmitted over the Internet using
35707 SMTP over TCP/IP. However, within individual operating systems, different
35708 conventions are used. For example, Unix-like systems use just LF, but others
35709 use CRLF or just CR.
35711 Exim was designed for Unix-like systems, and internally, it stores messages
35712 using the system's convention of a single LF as a line terminator. When
35713 receiving a message, all line endings are translated to this standard format.
35714 Originally, it was thought that programs that passed messages directly to an
35715 MTA within an operating system would use that system's convention. Experience
35716 has shown that this is not the case; for example, there are Unix applications
35717 that use CRLF in this circumstance. For this reason, and for compatibility with
35718 other MTAs, the way Exim handles line endings for all messages is now as
35722 LF not preceded by CR is treated as a line ending.
35724 CR is treated as a line ending; if it is immediately followed by LF, the LF
35727 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
35728 nor a local message in the state where a line containing only a dot is a
35731 If a bare CR is encountered within a header line, an extra space is added after
35732 the line terminator so as not to end the header line. The reasoning behind this
35733 is that bare CRs in header lines are most likely either to be mistakes, or
35734 people trying to play silly games.
35736 If the first header line received in a message ends with CRLF, a subsequent
35737 bare LF in a header line is treated in the same way as a bare CR in a header
35745 .section "Unqualified addresses" "SECID218"
35746 .cindex "unqualified addresses"
35747 .cindex "address" "qualification"
35748 By default, Exim expects every envelope address it receives from an external
35749 host to be fully qualified. Unqualified addresses cause negative responses to
35750 SMTP commands. However, because SMTP is used as a means of transporting
35751 messages from MUAs running on personal workstations, there is sometimes a
35752 requirement to accept unqualified addresses from specific hosts or IP networks.
35754 Exim has two options that separately control which hosts may send unqualified
35755 sender or recipient addresses in SMTP commands, namely
35756 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
35757 cases, if an unqualified address is accepted, it is qualified by adding the
35758 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
35760 .oindex "&%qualify_domain%&"
35761 .oindex "&%qualify_recipient%&"
35762 Unqualified addresses in header lines are automatically qualified for messages
35763 that are locally originated, unless the &%-bnq%& option is given on the command
35764 line. For messages received over SMTP, unqualified addresses in header lines
35765 are qualified only if unqualified addresses are permitted in SMTP commands. In
35766 other words, such qualification is also controlled by
35767 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
35772 .section "The UUCP From line" "SECID219"
35773 .cindex "&""From""& line"
35774 .cindex "UUCP" "&""From""& line"
35775 .cindex "sender" "address"
35776 .oindex "&%uucp_from_pattern%&"
35777 .oindex "&%uucp_from_sender%&"
35778 .cindex "envelope from"
35779 .cindex "envelope sender"
35780 .cindex "Sendmail compatibility" "&""From""& line"
35781 Messages that have come from UUCP (and some other applications) often begin
35782 with a line containing the envelope sender and a timestamp, following the word
35783 &"From"&. Examples of two common formats are:
35785 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
35786 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
35788 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
35789 Exim recognizes such lines at the start of messages that are submitted to it
35790 via the command line (that is, on the standard input). It does not recognize
35791 such lines in incoming SMTP messages, unless the sending host matches
35792 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
35793 and &%ignore_fromline_local%& is set. The recognition is controlled by a
35794 regular expression that is defined by the &%uucp_from_pattern%& option, whose
35795 default value matches the two common cases shown above and puts the address
35796 that follows &"From"& into &$1$&.
35798 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
35799 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
35800 a trusted user, the message's sender address is constructed by expanding the
35801 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
35802 then parsed as an RFC 2822 address. If there is no domain, the local part is
35803 qualified with &%qualify_domain%& unless it is the empty string. However, if
35804 the command line &%-f%& option is used, it overrides the &"From"& line.
35806 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
35807 sender address is not changed. This is also the case for incoming SMTP messages
35808 that are permitted to contain &"From"& lines.
35810 Only one &"From"& line is recognized. If there is more than one, the second is
35811 treated as a data line that starts the body of the message, as it is not valid
35812 as a header line. This also happens if a &"From"& line is present in an
35813 incoming SMTP message from a source that is not permitted to send them.
35817 .section "Resent- header lines" "SECID220"
35818 .cindex "&%Resent-%& header lines"
35819 .cindex "header lines" "Resent-"
35820 RFC 2822 makes provision for sets of header lines starting with the string
35821 &`Resent-`& to be added to a message when it is resent by the original
35822 recipient to somebody else. These headers are &'Resent-Date:'&,
35823 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
35824 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
35827 &'Resent fields are strictly informational. They MUST NOT be used in the normal
35828 processing of replies or other such automatic actions on messages.'&
35831 This leaves things a bit vague as far as other processing actions such as
35832 address rewriting are concerned. Exim treats &%Resent-%& header lines as
35836 A &'Resent-From:'& line that just contains the login id of the submitting user
35837 is automatically rewritten in the same way as &'From:'& (see below).
35839 If there's a rewriting rule for a particular header line, it is also applied to
35840 &%Resent-%& header lines of the same type. For example, a rule that rewrites
35841 &'From:'& also rewrites &'Resent-From:'&.
35843 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
35846 For a locally-submitted message,
35847 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
35848 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
35849 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
35850 included in log lines in this case.
35852 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
35853 &%Resent-%& header lines are present.
35859 .section "The Auto-Submitted: header line" "SECID221"
35860 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
35861 includes the header line:
35863 Auto-Submitted: auto-replied
35866 .section "The Bcc: header line" "SECID222"
35867 .cindex "&'Bcc:'& header line"
35868 If Exim is called with the &%-t%& option, to take recipient addresses from a
35869 message's header, it removes any &'Bcc:'& header line that may exist (after
35870 extracting its addresses). If &%-t%& is not present on the command line, any
35871 existing &'Bcc:'& is not removed.
35874 .section "The Date: header line" "SECID223"
35875 .cindex "&'Date:'& header line"
35876 .cindex "header lines" "Date:"
35877 If a locally-generated or submission-mode message has no &'Date:'& header line,
35878 Exim adds one, using the current date and time, unless the
35879 &%suppress_local_fixups%& control has been specified.
35881 .section "The Delivery-date: header line" "SECID224"
35882 .cindex "&'Delivery-date:'& header line"
35883 .oindex "&%delivery_date_remove%&"
35884 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
35885 set. Exim can be configured to add them to the final delivery of messages. (See
35886 the generic &%delivery_date_add%& transport option.) They should not be present
35887 in messages in transit. If the &%delivery_date_remove%& configuration option is
35888 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
35892 .section "The Envelope-to: header line" "SECID225"
35893 .cindex "&'Envelope-to:'& header line"
35894 .cindex "header lines" "Envelope-to:"
35895 .oindex "&%envelope_to_remove%&"
35896 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
35897 Exim can be configured to add them to the final delivery of messages. (See the
35898 generic &%envelope_to_add%& transport option.) They should not be present in
35899 messages in transit. If the &%envelope_to_remove%& configuration option is set
35900 (the default), Exim removes &'Envelope-to:'& header lines from incoming
35904 .section "The From: header line" "SECTthefrohea"
35905 .cindex "&'From:'& header line"
35906 .cindex "header lines" "From:"
35907 .cindex "Sendmail compatibility" "&""From""& line"
35908 .cindex "message" "submission"
35909 .cindex "submission mode"
35910 If a submission-mode message does not contain a &'From:'& header line, Exim
35911 adds one if either of the following conditions is true:
35914 The envelope sender address is not empty (that is, this is not a bounce
35915 message). The added header line copies the envelope sender address.
35917 .vindex "&$authenticated_id$&"
35918 The SMTP session is authenticated and &$authenticated_id$& is not empty.
35920 .vindex "&$qualify_domain$&"
35921 If no domain is specified by the submission control, the local part is
35922 &$authenticated_id$& and the domain is &$qualify_domain$&.
35924 If a non-empty domain is specified by the submission control, the local
35925 part is &$authenticated_id$&, and the domain is the specified domain.
35927 If an empty domain is specified by the submission control,
35928 &$authenticated_id$& is assumed to be the complete address.
35932 A non-empty envelope sender takes precedence.
35934 If a locally-generated incoming message does not contain a &'From:'& header
35935 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
35936 containing the sender's address. The calling user's login name and full name
35937 are used to construct the address, as described in section &<<SECTconstr>>&.
35938 They are obtained from the password data by calling &[getpwuid()]& (but see the
35939 &%unknown_login%& configuration option). The address is qualified with
35940 &%qualify_domain%&.
35942 For compatibility with Sendmail, if an incoming, non-SMTP message has a
35943 &'From:'& header line containing just the unqualified login name of the calling
35944 user, this is replaced by an address containing the user's login name and full
35945 name as described in section &<<SECTconstr>>&.
35948 .section "The Message-ID: header line" "SECID226"
35949 .cindex "&'Message-ID:'& header line"
35950 .cindex "header lines" "Message-ID:"
35951 .cindex "message" "submission"
35952 .oindex "&%message_id_header_text%&"
35953 If a locally-generated or submission-mode incoming message does not contain a
35954 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
35955 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
35956 to the message. If there are any &'Resent-:'& headers in the message, it
35957 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
35958 message id, preceded by the letter E to ensure it starts with a letter, and
35959 followed by @ and the primary host name. Additional information can be included
35960 in this header line by setting the &%message_id_header_text%& and/or
35961 &%message_id_header_domain%& options.
35964 .section "The Received: header line" "SECID227"
35965 .cindex "&'Received:'& header line"
35966 .cindex "header lines" "Received:"
35967 A &'Received:'& header line is added at the start of every message. The
35968 contents are defined by the &%received_header_text%& configuration option, and
35969 Exim automatically adds a semicolon and a timestamp to the configured string.
35971 The &'Received:'& header is generated as soon as the message's header lines
35972 have been received. At this stage, the timestamp in the &'Received:'& header
35973 line is the time that the message started to be received. This is the value
35974 that is seen by the DATA ACL and by the &[local_scan()]& function.
35976 Once a message is accepted, the timestamp in the &'Received:'& header line is
35977 changed to the time of acceptance, which is (apart from a small delay while the
35978 -H spool file is written) the earliest time at which delivery could start.
35981 .section "The References: header line" "SECID228"
35982 .cindex "&'References:'& header line"
35983 .cindex "header lines" "References:"
35984 Messages created by the &(autoreply)& transport include a &'References:'&
35985 header line. This is constructed according to the rules that are described in
35986 section 3.64 of RFC 2822 (which states that replies should contain such a
35987 header line), and section 3.14 of RFC 3834 (which states that automatic
35988 responses are not different in this respect). However, because some mail
35989 processing software does not cope well with very long header lines, no more
35990 than 12 message IDs are copied from the &'References:'& header line in the
35991 incoming message. If there are more than 12, the first one and then the final
35992 11 are copied, before adding the message ID of the incoming message.
35996 .section "The Return-path: header line" "SECID229"
35997 .cindex "&'Return-path:'& header line"
35998 .cindex "header lines" "Return-path:"
35999 .oindex "&%return_path_remove%&"
36000 &'Return-path:'& header lines are defined as something an MTA may insert when
36001 it does the final delivery of messages. (See the generic &%return_path_add%&
36002 transport option.) Therefore, they should not be present in messages in
36003 transit. If the &%return_path_remove%& configuration option is set (the
36004 default), Exim removes &'Return-path:'& header lines from incoming messages.
36008 .section "The Sender: header line" "SECTthesenhea"
36009 .cindex "&'Sender:'& header line"
36010 .cindex "message" "submission"
36011 .cindex "header lines" "Sender:"
36012 For a locally-originated message from an untrusted user, Exim may remove an
36013 existing &'Sender:'& header line, and it may add a new one. You can modify
36014 these actions by setting the &%local_sender_retain%& option true, the
36015 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
36018 When a local message is received from an untrusted user and
36019 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
36020 control has not been set, a check is made to see if the address given in the
36021 &'From:'& header line is the correct (local) sender of the message. The address
36022 that is expected has the login name as the local part and the value of
36023 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
36024 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
36025 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
36026 line is added to the message.
36028 If you set &%local_from_check%& false, this checking does not occur. However,
36029 the removal of an existing &'Sender:'& line still happens, unless you also set
36030 &%local_sender_retain%& to be true. It is not possible to set both of these
36031 options true at the same time.
36033 .cindex "submission mode"
36034 By default, no processing of &'Sender:'& header lines is done for messages
36035 received over TCP/IP or for messages submitted by trusted users. However, when
36036 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
36037 not specified on the submission control, the following processing takes place:
36039 .vindex "&$authenticated_id$&"
36040 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
36041 authenticated, and &$authenticated_id$& is not empty, a sender address is
36042 created as follows:
36045 .vindex "&$qualify_domain$&"
36046 If no domain is specified by the submission control, the local part is
36047 &$authenticated_id$& and the domain is &$qualify_domain$&.
36049 If a non-empty domain is specified by the submission control, the local part
36050 is &$authenticated_id$&, and the domain is the specified domain.
36052 If an empty domain is specified by the submission control,
36053 &$authenticated_id$& is assumed to be the complete address.
36056 This address is compared with the address in the &'From:'& header line. If they
36057 are different, a &'Sender:'& header line containing the created address is
36058 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
36059 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
36061 .cindex "return path" "created from &'Sender:'&"
36062 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
36063 the message (the envelope sender address) is changed to be the same address,
36064 except in the case of submission mode when &%sender_retain%& is specified.
36068 .section "Adding and removing header lines in routers and transports" &&&
36069 "SECTheadersaddrem"
36070 .cindex "header lines" "adding; in router or transport"
36071 .cindex "header lines" "removing; in router or transport"
36072 When a message is delivered, the addition and removal of header lines can be
36073 specified in a system filter, or on any of the routers and transports that
36074 process the message. Section &<<SECTaddremheasys>>& contains details about
36075 modifying headers in a system filter. Header lines can also be added in an ACL
36076 as a message is received (see section &<<SECTaddheadacl>>&).
36078 In contrast to what happens in a system filter, header modifications that are
36079 specified on routers and transports apply only to the particular recipient
36080 addresses that are being processed by those routers and transports. These
36081 changes do not actually take place until a copy of the message is being
36082 transported. Therefore, they do not affect the basic set of header lines, and
36083 they do not affect the values of the variables that refer to header lines.
36085 &*Note*&: In particular, this means that any expansions in the configuration of
36086 the transport cannot refer to the modified header lines, because such
36087 expansions all occur before the message is actually transported.
36089 For both routers and transports, the argument of a &%headers_add%&
36090 option must be in the form of one or more RFC 2822 header lines, separated by
36091 newlines (coded as &"\n"&). For example:
36093 headers_add = X-added-header: added by $primary_hostname\n\
36094 X-added-second: another added header line
36096 Exim does not check the syntax of these added header lines.
36098 Multiple &%headers_add%& options for a single router or transport can be
36099 specified; the values will append to a single list of header lines.
36100 Each header-line is separately expanded.
36102 The argument of a &%headers_remove%& option must consist of a colon-separated
36103 list of header names. This is confusing, because header names themselves are
36104 often terminated by colons. In this case, the colons are the list separators,
36105 not part of the names. For example:
36107 headers_remove = return-receipt-to:acknowledge-to
36110 Multiple &%headers_remove%& options for a single router or transport can be
36111 specified; the arguments will append to a single header-names list.
36112 Each item is separately expanded.
36113 Note that colons in complex expansions which are used to
36114 form all or part of a &%headers_remove%& list
36115 will act as list separators.
36117 When &%headers_add%& or &%headers_remove%& is specified on a router,
36118 items are expanded at routing time,
36119 and then associated with all addresses that are
36120 accepted by that router, and also with any new addresses that it generates. If
36121 an address passes through several routers as a result of aliasing or
36122 forwarding, the changes are cumulative.
36124 .oindex "&%unseen%&"
36125 However, this does not apply to multiple routers that result from the use of
36126 the &%unseen%& option. Any header modifications that were specified by the
36127 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
36129 Addresses that end up with different &%headers_add%& or &%headers_remove%&
36130 settings cannot be delivered together in a batch, so a transport is always
36131 dealing with a set of addresses that have the same header-processing
36134 The transport starts by writing the original set of header lines that arrived
36135 with the message, possibly modified by the system filter. As it writes out
36136 these lines, it consults the list of header names that were attached to the
36137 recipient address(es) by &%headers_remove%& options in routers, and it also
36138 consults the transport's own &%headers_remove%& option. Header lines whose
36139 names are on either of these lists are not written out. If there are multiple
36140 instances of any listed header, they are all skipped.
36142 After the remaining original header lines have been written, new header
36143 lines that were specified by routers' &%headers_add%& options are written, in
36144 the order in which they were attached to the address. These are followed by any
36145 header lines specified by the transport's &%headers_add%& option.
36147 This way of handling header line modifications in routers and transports has
36148 the following consequences:
36151 The original set of header lines, possibly modified by the system filter,
36152 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
36153 to it, at all times.
36155 Header lines that are added by a router's
36156 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
36157 expansion syntax in subsequent routers or the transport.
36159 Conversely, header lines that are specified for removal by &%headers_remove%&
36160 in a router remain visible to subsequent routers and the transport.
36162 Headers added to an address by &%headers_add%& in a router cannot be removed by
36163 a later router or by a transport.
36165 An added header can refer to the contents of an original header that is to be
36166 removed, even it has the same name as the added header. For example:
36168 headers_remove = subject
36169 headers_add = Subject: new subject (was: $h_subject:)
36173 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
36174 for a &(redirect)& router that has the &%one_time%& option set.
36180 .section "Constructed addresses" "SECTconstr"
36181 .cindex "address" "constructed"
36182 .cindex "constructed address"
36183 When Exim constructs a sender address for a locally-generated message, it uses
36186 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
36190 Zaphod Beeblebrox <zaphod@end.univ.example>
36192 The user name is obtained from the &%-F%& command line option if set, or
36193 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
36194 &"gecos"& field from the password entry. If the &"gecos"& field contains an
36195 ampersand character, this is replaced by the login name with the first letter
36196 upper cased, as is conventional in a number of operating systems. See the
36197 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
36198 The &%unknown_username%& option can be used to specify user names in cases when
36199 there is no password file entry.
36202 In all cases, the user name is made to conform to RFC 2822 by quoting all or
36203 parts of it if necessary. In addition, if it contains any non-printing
36204 characters, it is encoded as described in RFC 2047, which defines a way of
36205 including non-ASCII characters in header lines. The value of the
36206 &%headers_charset%& option specifies the name of the encoding that is used (the
36207 characters are assumed to be in this encoding). The setting of
36208 &%print_topbitchars%& controls whether characters with the top bit set (that
36209 is, with codes greater than 127) count as printing characters or not.
36213 .section "Case of local parts" "SECID230"
36214 .cindex "case of local parts"
36215 .cindex "local part" "case of"
36216 RFC 2822 states that the case of letters in the local parts of addresses cannot
36217 be assumed to be non-significant. Exim preserves the case of local parts of
36218 addresses, but by default it uses a lower-cased form when it is routing,
36219 because on most Unix systems, usernames are in lower case and case-insensitive
36220 routing is required. However, any particular router can be made to use the
36221 original case for local parts by setting the &%caseful_local_part%& generic
36224 .cindex "mixed-case login names"
36225 If you must have mixed-case user names on your system, the best way to proceed,
36226 assuming you want case-independent handling of incoming email, is to set up
36227 your first router to convert incoming local parts in your domains to the
36228 correct case by means of a file lookup. For example:
36232 domains = +local_domains
36233 data = ${lookup{$local_part}cdb\
36234 {/etc/usercased.cdb}{$value}fail}\
36237 For this router, the local part is forced to lower case by the default action
36238 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
36239 up a new local part in the correct case. If you then set &%caseful_local_part%&
36240 on any subsequent routers which process your domains, they will operate on
36241 local parts with the correct case in a case-sensitive manner.
36245 .section "Dots in local parts" "SECID231"
36246 .cindex "dot" "in local part"
36247 .cindex "local part" "dots in"
36248 RFC 2822 forbids empty components in local parts. That is, an unquoted local
36249 part may not begin or end with a dot, nor have two consecutive dots in the
36250 middle. However, it seems that many MTAs do not enforce this, so Exim permits
36251 empty components for compatibility.
36255 .section "Rewriting addresses" "SECID232"
36256 .cindex "rewriting" "addresses"
36257 Rewriting of sender and recipient addresses, and addresses in headers, can
36258 happen automatically, or as the result of configuration options, as described
36259 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
36260 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
36262 Automatic rewriting includes qualification, as mentioned above. The other case
36263 in which it can happen is when an incomplete non-local domain is given. The
36264 routing process may cause this to be expanded into the full domain name. For
36265 example, a header such as
36269 might get rewritten as
36271 To: hare@teaparty.wonderland.fict.example
36273 Rewriting as a result of routing is the one kind of message processing that
36274 does not happen at input time, as it cannot be done until the address has
36277 Strictly, one should not do &'any'& deliveries of a message until all its
36278 addresses have been routed, in case any of the headers get changed as a
36279 result of routing. However, doing this in practice would hold up many
36280 deliveries for unreasonable amounts of time, just because one address could not
36281 immediately be routed. Exim therefore does not delay other deliveries when
36282 routing of one or more addresses is deferred.
36283 .ecindex IIDmesproc
36287 . ////////////////////////////////////////////////////////////////////////////
36288 . ////////////////////////////////////////////////////////////////////////////
36290 .chapter "SMTP processing" "CHAPSMTP"
36291 .scindex IIDsmtpproc1 "SMTP" "processing details"
36292 .scindex IIDsmtpproc2 "LMTP" "processing details"
36293 Exim supports a number of different ways of using the SMTP protocol, and its
36294 LMTP variant, which is an interactive protocol for transferring messages into a
36295 closed mail store application. This chapter contains details of how SMTP is
36296 processed. For incoming mail, the following are available:
36299 SMTP over TCP/IP (Exim daemon or &'inetd'&);
36301 SMTP over the standard input and output (the &%-bs%& option);
36303 Batched SMTP on the standard input (the &%-bS%& option).
36306 For mail delivery, the following are available:
36309 SMTP over TCP/IP (the &(smtp)& transport);
36311 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
36314 LMTP over a pipe to a process running in the local host (the &(lmtp)&
36317 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
36318 the &%use_bsmtp%& option set).
36321 &'Batched SMTP'& is the name for a process in which batches of messages are
36322 stored in or read from files (or pipes), in a format in which SMTP commands are
36323 used to contain the envelope information.
36327 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
36328 .cindex "SMTP" "outgoing over TCP/IP"
36329 .cindex "outgoing SMTP over TCP/IP"
36330 .cindex "LMTP" "over TCP/IP"
36331 .cindex "outgoing LMTP over TCP/IP"
36334 .cindex "SIZE" "option on MAIL command"
36335 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
36336 The &%protocol%& option selects which protocol is to be used, but the actual
36337 processing is the same in both cases.
36339 .cindex "ESMTP extensions" SIZE
36340 If, in response to its EHLO command, Exim is told that the SIZE
36341 extension is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
36342 command. The value of <&'n'&> is the message size plus the value of the
36343 &%size_addition%& option (default 1024) to allow for additions to the message
36344 such as per-transport header lines, or changes made in a
36345 .cindex "transport" "filter"
36346 .cindex "filter" "transport filter"
36347 transport filter. If &%size_addition%& is set negative, the use of SIZE is
36350 If the remote server advertises support for PIPELINING, Exim uses the
36351 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
36352 required for the transaction.
36354 If the remote server advertises support for the STARTTLS command, and Exim
36355 was built to support TLS encryption, it tries to start a TLS session unless the
36356 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
36357 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
36358 is called for verification.
36360 If the remote server advertises support for the AUTH command, Exim scans
36361 the authenticators configuration for any suitable client settings, as described
36362 in chapter &<<CHAPSMTPAUTH>>&.
36364 .cindex "carriage return"
36366 Responses from the remote host are supposed to be terminated by CR followed by
36367 LF. However, there are known to be hosts that do not send CR characters, so in
36368 order to be able to interwork with such hosts, Exim treats LF on its own as a
36371 If a message contains a number of different addresses, all those with the same
36372 characteristics (for example, the same envelope sender) that resolve to the
36373 same set of hosts, in the same order, are sent in a single SMTP transaction,
36374 even if they are for different domains, unless there are more than the setting
36375 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
36376 they are split into groups containing no more than &%max_rcpt%&s addresses
36377 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
36378 in parallel sessions. The order of hosts with identical MX values is not
36379 significant when checking whether addresses can be batched in this way.
36381 When the &(smtp)& transport suffers a temporary failure that is not
36382 message-related, Exim updates its transport-specific database, which contains
36383 records indexed by host name that remember which messages are waiting for each
36384 particular host. It also updates the retry database with new retry times.
36386 .cindex "hints database" "retry keys"
36387 Exim's retry hints are based on host name plus IP address, so if one address of
36388 a multi-homed host is broken, it will soon be skipped most of the time.
36389 See the next section for more detail about error handling.
36391 .cindex "SMTP" "passed connection"
36392 .cindex "SMTP" "batching over TCP/IP"
36393 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
36394 looks in the hints database for the transport to see if there are any queued
36395 messages waiting for the host to which it is connected. If it finds one, it
36396 creates a new Exim process using the &%-MC%& option (which can only be used by
36397 a process running as root or the Exim user) and passes the TCP/IP socket to it
36398 so that it can deliver another message using the same socket. The new process
36399 does only those deliveries that are routed to the connected host, and may in
36400 turn pass the socket on to a third process, and so on.
36402 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
36403 limit the number of messages sent down a single TCP/IP connection.
36405 .cindex "asterisk" "after IP address"
36406 The second and subsequent messages delivered down an existing connection are
36407 identified in the main log by the addition of an asterisk after the closing
36408 square bracket of the IP address.
36413 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
36414 .cindex "error" "in outgoing SMTP"
36415 .cindex "SMTP" "errors in outgoing"
36416 .cindex "host" "error"
36417 Three different kinds of error are recognized for outgoing SMTP: host errors,
36418 message errors, and recipient errors.
36421 .vitem "&*Host errors*&"
36422 A host error is not associated with a particular message or with a
36423 particular recipient of a message. The host errors are:
36426 Connection refused or timed out,
36428 Any error response code on connection,
36430 Any error response code to EHLO or HELO,
36432 Loss of connection at any time, except after &"."&,
36434 I/O errors at any time,
36436 Timeouts during the session, other than in response to MAIL, RCPT or
36437 the &"."& at the end of the data.
36440 For a host error, a permanent error response on connection, or in response to
36441 EHLO, causes all addresses routed to the host to be failed. Any other host
36442 error causes all addresses to be deferred, and retry data to be created for the
36443 host. It is not tried again, for any message, until its retry time arrives. If
36444 the current set of addresses are not all delivered in this run (to some
36445 alternative host), the message is added to the list of those waiting for this
36446 host, so if it is still undelivered when a subsequent successful delivery is
36447 made to the host, it will be sent down the same SMTP connection.
36449 .vitem "&*Message errors*&"
36450 .cindex "message" "error"
36451 A message error is associated with a particular message when sent to a
36452 particular host, but not with a particular recipient of the message. The
36453 message errors are:
36456 Any error response code to MAIL, DATA, or the &"."& that terminates
36459 Timeout after MAIL,
36461 Timeout or loss of connection after the &"."& that terminates the data. A
36462 timeout after the DATA command itself is treated as a host error, as is loss of
36463 connection at any other time.
36466 For a message error, a permanent error response (5&'xx'&) causes all addresses
36467 to be failed, and a delivery error report to be returned to the sender. A
36468 temporary error response (4&'xx'&), or one of the timeouts, causes all
36469 addresses to be deferred. Retry data is not created for the host, but instead,
36470 a retry record for the combination of host plus message id is created. The
36471 message is not added to the list of those waiting for this host. This ensures
36472 that the failing message will not be sent to this host again until the retry
36473 time arrives. However, other messages that are routed to the host are not
36474 affected, so if it is some property of the message that is causing the error,
36475 it will not stop the delivery of other mail.
36477 If the remote host specified support for the SIZE parameter in its response
36478 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
36479 over-large message will cause a message error because the error arrives as a
36482 .vitem "&*Recipient errors*&"
36483 .cindex "recipient" "error"
36484 A recipient error is associated with a particular recipient of a message. The
36485 recipient errors are:
36488 Any error response to RCPT,
36490 Timeout after RCPT.
36493 For a recipient error, a permanent error response (5&'xx'&) causes the
36494 recipient address to be failed, and a bounce message to be returned to the
36495 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
36496 address to be deferred, and routing retry data to be created for it. This is
36497 used to delay processing of the address in subsequent queue runs, until its
36498 routing retry time arrives. This applies to all messages, but because it
36499 operates only in queue runs, one attempt will be made to deliver a new message
36500 to the failing address before the delay starts to operate. This ensures that,
36501 if the failure is really related to the message rather than the recipient
36502 (&"message too big for this recipient"& is a possible example), other messages
36503 have a chance of getting delivered. If a delivery to the address does succeed,
36504 the retry information gets cleared, so all stuck messages get tried again, and
36505 the retry clock is reset.
36507 The message is not added to the list of those waiting for this host. Use of the
36508 host for other messages is unaffected, and except in the case of a timeout,
36509 other recipients are processed independently, and may be successfully delivered
36510 in the current SMTP session. After a timeout it is of course impossible to
36511 proceed with the session, so all addresses get deferred. However, those other
36512 than the one that failed do not suffer any subsequent retry delays. Therefore,
36513 if one recipient is causing trouble, the others have a chance of getting
36514 through when a subsequent delivery attempt occurs before the failing
36515 recipient's retry time.
36518 In all cases, if there are other hosts (or IP addresses) available for the
36519 current set of addresses (for example, from multiple MX records), they are
36520 tried in this run for any undelivered addresses, subject of course to their
36521 own retry data. In other words, recipient error retry data does not take effect
36522 until the next delivery attempt.
36524 Some hosts have been observed to give temporary error responses to every
36525 MAIL command at certain times (&"insufficient space"& has been seen). It
36526 would be nice if such circumstances could be recognized, and defer data for the
36527 host itself created, but this is not possible within the current Exim design.
36528 What actually happens is that retry data for every (host, message) combination
36531 The reason that timeouts after MAIL and RCPT are treated specially is that
36532 these can sometimes arise as a result of the remote host's verification
36533 procedures. Exim makes this assumption, and treats them as if a temporary error
36534 response had been received. A timeout after &"."& is treated specially because
36535 it is known that some broken implementations fail to recognize the end of the
36536 message if the last character of the last line is a binary zero. Thus, it is
36537 helpful to treat this case as a message error.
36539 Timeouts at other times are treated as host errors, assuming a problem with the
36540 host, or the connection to it. If a timeout after MAIL, RCPT,
36541 or &"."& is really a connection problem, the assumption is that at the next try
36542 the timeout is likely to occur at some other point in the dialogue, causing it
36543 then to be treated as a host error.
36545 There is experimental evidence that some MTAs drop the connection after the
36546 terminating &"."& if they do not like the contents of the message for some
36547 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
36548 should be given. That is why Exim treats this case as a message rather than a
36549 host error, in order not to delay other messages to the same host.
36554 .section "Incoming SMTP messages over TCP/IP" "SECID233"
36555 .cindex "SMTP" "incoming over TCP/IP"
36556 .cindex "incoming SMTP over TCP/IP"
36559 Incoming SMTP messages can be accepted in one of two ways: by running a
36560 listening daemon, or by using &'inetd'&. In the latter case, the entry in
36561 &_/etc/inetd.conf_& should be like this:
36563 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
36565 Exim distinguishes between this case and the case of a locally running user
36566 agent using the &%-bs%& option by checking whether or not the standard input is
36567 a socket. When it is, either the port must be privileged (less than 1024), or
36568 the caller must be root or the Exim user. If any other user passes a socket
36569 with an unprivileged port number, Exim prints a message on the standard error
36570 stream and exits with an error code.
36572 By default, Exim does not make a log entry when a remote host connects or
36573 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
36574 unexpected. It can be made to write such log entries by setting the
36575 &%smtp_connection%& log selector.
36577 .cindex "carriage return"
36579 Commands from the remote host are supposed to be terminated by CR followed by
36580 LF. However, there are known to be hosts that do not send CR characters. In
36581 order to be able to interwork with such hosts, Exim treats LF on its own as a
36583 Furthermore, because common code is used for receiving messages from all
36584 sources, a CR on its own is also interpreted as a line terminator. However, the
36585 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
36587 .cindex "EHLO" "invalid data"
36588 .cindex "HELO" "invalid data"
36589 One area that sometimes gives rise to problems concerns the EHLO or
36590 HELO commands. Some clients send syntactically invalid versions of these
36591 commands, which Exim rejects by default. (This is nothing to do with verifying
36592 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
36593 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
36594 match the broken hosts that send invalid commands.
36596 .cindex "SIZE option on MAIL command"
36597 .cindex "MAIL" "SIZE option"
36598 The amount of disk space available is checked whenever SIZE is received on
36599 a MAIL command, independently of whether &%message_size_limit%& or
36600 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
36601 false. A temporary error is given if there is not enough space. If
36602 &%check_spool_space%& is set, the check is for that amount of space plus the
36603 value given with SIZE, that is, it checks that the addition of the incoming
36604 message will not reduce the space below the threshold.
36606 When a message is successfully received, Exim includes the local message id in
36607 its response to the final &"."& that terminates the data. If the remote host
36608 logs this text it can help with tracing what has happened to a message.
36610 The Exim daemon can limit the number of simultaneous incoming connections it is
36611 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
36612 number of simultaneous incoming connections from a single remote host (see the
36613 &%smtp_accept_max_per_host%& option). Additional connection attempts are
36614 rejected using the SMTP temporary error code 421.
36616 The Exim daemon does not rely on the SIGCHLD signal to detect when a
36617 subprocess has finished, as this can get lost at busy times. Instead, it looks
36618 for completed subprocesses every time it wakes up. Provided there are other
36619 things happening (new incoming calls, starts of queue runs), completed
36620 processes will be noticed and tidied away. On very quiet systems you may
36621 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
36622 it will be noticed when the daemon next wakes up.
36624 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
36625 and can also be set up to reject SMTP calls from non-reserved hosts at times of
36626 high system load &-- for details see the &%smtp_accept_reserve%&,
36627 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
36628 applies in both the daemon and &'inetd'& cases.
36630 Exim normally starts a delivery process for each message received, though this
36631 can be varied by means of the &%-odq%& command line option and the
36632 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
36633 number of simultaneously running delivery processes started in this way from
36634 SMTP input can be limited by the &%smtp_accept_queue%& and
36635 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
36636 subsequently received messages are just put on the input queue without starting
36637 a delivery process.
36639 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
36640 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
36641 started up from the &'inetd'& daemon, because in that case each connection is
36642 handled by an entirely independent Exim process. Control by load average is,
36643 however, available with &'inetd'&.
36645 Exim can be configured to verify addresses in incoming SMTP commands as they
36646 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
36647 to rewrite addresses at this time &-- before any syntax checking is done. See
36648 section &<<SECTrewriteS>>&.
36650 Exim can also be configured to limit the rate at which a client host submits
36651 MAIL and RCPT commands in a single SMTP session. See the
36652 &%smtp_ratelimit_hosts%& option.
36656 .section "Unrecognized SMTP commands" "SECID234"
36657 .cindex "SMTP" "unrecognized commands"
36658 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
36659 commands during a single SMTP connection, it drops the connection after sending
36660 the error response to the last command. The default value for
36661 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
36662 abuse that subvert web servers into making connections to SMTP ports; in these
36663 circumstances, a number of non-SMTP lines are sent first.
36666 .section "Syntax and protocol errors in SMTP commands" "SECID235"
36667 .cindex "SMTP" "syntax errors"
36668 .cindex "SMTP" "protocol errors"
36669 A syntax error is detected if an SMTP command is recognized, but there is
36670 something syntactically wrong with its data, for example, a malformed email
36671 address in a RCPT command. Protocol errors include invalid command
36672 sequencing such as RCPT before MAIL. If Exim receives more than
36673 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
36674 drops the connection after sending the error response to the last command. The
36675 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
36676 broken clients that loop sending bad commands (yes, it has been seen).
36680 .section "Use of non-mail SMTP commands" "SECID236"
36681 .cindex "SMTP" "non-mail commands"
36682 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
36683 DATA. Exim counts such commands, and drops the connection if there are too
36684 many of them in a single SMTP session. This action catches some
36685 denial-of-service attempts and things like repeated failing AUTHs, or a mad
36686 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
36687 defines what &"too many"& means. Its default value is 10.
36689 When a new message is expected, one occurrence of RSET is not counted. This
36690 allows a client to send one RSET between messages (this is not necessary,
36691 but some clients do it). Exim also allows one uncounted occurrence of HELO
36692 or EHLO, and one occurrence of STARTTLS between messages. After
36693 starting up a TLS session, another EHLO is expected, and so it too is not
36696 The first occurrence of AUTH in a connection, or immediately following
36697 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
36698 RCPT, DATA, and QUIT are counted.
36700 You can control which hosts are subject to the limit set by
36701 &%smtp_accept_max_nonmail%& by setting
36702 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
36703 the limit apply to all hosts. This option means that you can exclude any
36704 specific badly-behaved hosts that you have to live with.
36709 .section "The VRFY and EXPN commands" "SECID237"
36710 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
36711 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
36712 appropriate) in order to decide whether the command should be accepted or not.
36714 .cindex "VRFY" "processing"
36715 When no ACL is defined for VRFY, or if it rejects without
36716 setting an explicit response code, the command is accepted
36717 (with a 252 SMTP response code)
36718 in order to support awkward clients that do a VRFY before every RCPT.
36719 When VRFY is accepted, it runs exactly the same code as when Exim is
36720 called with the &%-bv%& option, and returns 250/451/550
36721 SMTP response codes.
36723 .cindex "EXPN" "processing"
36724 If no ACL for EXPN is defined, the command is rejected.
36725 When EXPN is accepted, a single-level expansion of the address is done.
36726 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
36727 than a verification (the &%-bv%& option). If an unqualified local part is given
36728 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
36729 of VRFY and EXPN commands are logged on the main and reject logs, and
36730 VRFY verification failures are logged on the main log for consistency with
36735 .section "The ETRN command" "SECTETRN"
36736 .cindex "ETRN" "processing"
36737 .cindex "ESMTP extensions" ETRN
36738 RFC 1985 describes an ESMTP command called ETRN that is designed to
36739 overcome the security problems of the TURN command (which has fallen into
36740 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
36741 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
36742 should be accepted or not. If no ACL is defined, the command is rejected.
36744 The ETRN command is concerned with &"releasing"& messages that are awaiting
36745 delivery to certain hosts. As Exim does not organize its message queue by host,
36746 the only form of ETRN that is supported by default is the one where the
36747 text starts with the &"#"& prefix, in which case the remainder of the text is
36748 specific to the SMTP server. A valid ETRN command causes a run of Exim with
36749 the &%-R%& option to happen, with the remainder of the ETRN text as its
36750 argument. For example,
36758 which causes a delivery attempt on all messages with undelivered addresses
36759 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
36760 default), Exim prevents the simultaneous execution of more than one queue run
36761 for the same argument string as a result of an ETRN command. This stops
36762 a misbehaving client from starting more than one queue runner at once.
36764 .cindex "hints database" "ETRN serialization"
36765 Exim implements the serialization by means of a hints database in which a
36766 record is written whenever a process is started by ETRN, and deleted when
36767 the process completes. However, Exim does not keep the SMTP session waiting for
36768 the ETRN process to complete. Once ETRN is accepted, the client is sent
36769 a &"success"& return code. Obviously there is scope for hints records to get
36770 left lying around if there is a system or program crash. To guard against this,
36771 Exim ignores any records that are more than six hours old.
36773 .oindex "&%smtp_etrn_command%&"
36774 For more control over what ETRN does, the &%smtp_etrn_command%& option can
36775 used. This specifies a command that is run whenever ETRN is received,
36776 whatever the form of its argument. For
36779 smtp_etrn_command = /etc/etrn_command $domain \
36780 $sender_host_address
36782 .vindex "&$domain$&"
36783 The string is split up into arguments which are independently expanded. The
36784 expansion variable &$domain$& is set to the argument of the ETRN command,
36785 and no syntax checking is done on the contents of this argument. Exim does not
36786 wait for the command to complete, so its status code is not checked. Exim runs
36787 under its own uid and gid when receiving incoming SMTP, so it is not possible
36788 for it to change them before running the command.
36792 .section "Incoming local SMTP" "SECID238"
36793 .cindex "SMTP" "local incoming"
36794 Some user agents use SMTP to pass messages to their local MTA using the
36795 standard input and output, as opposed to passing the envelope on the command
36796 line and writing the message to the standard input. This is supported by the
36797 &%-bs%& option. This form of SMTP is handled in the same way as incoming
36798 messages over TCP/IP (including the use of ACLs), except that the envelope
36799 sender given in a MAIL command is ignored unless the caller is trusted. In
36800 an ACL you can detect this form of SMTP input by testing for an empty host
36801 identification. It is common to have this as the first line in the ACL that
36802 runs for RCPT commands:
36806 This accepts SMTP messages from local processes without doing any other tests.
36810 .section "Outgoing batched SMTP" "SECTbatchSMTP"
36811 .cindex "SMTP" "batched outgoing"
36812 .cindex "batched SMTP output"
36813 Both the &(appendfile)& and &(pipe)& transports can be used for handling
36814 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
36815 be output in BSMTP format. No SMTP responses are possible for this form of
36816 delivery. All it is doing is using SMTP commands as a way of transmitting the
36817 envelope along with the message.
36819 The message is written to the file or pipe preceded by the SMTP commands
36820 MAIL and RCPT, and followed by a line containing a single dot. Lines in
36821 the message that start with a dot have an extra dot added. The SMTP command
36822 HELO is not normally used. If it is required, the &%message_prefix%& option
36823 can be used to specify it.
36825 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
36826 one recipient address at a time by default. However, you can arrange for them
36827 to handle several addresses at once by setting the &%batch_max%& option. When
36828 this is done for BSMTP, messages may contain multiple RCPT commands. See
36829 chapter &<<CHAPbatching>>& for more details.
36832 When one or more addresses are routed to a BSMTP transport by a router that
36833 sets up a host list, the name of the first host on the list is available to the
36834 transport in the variable &$host$&. Here is an example of such a transport and
36839 driver = manualroute
36840 transport = smtp_appendfile
36841 route_list = domain.example batch.host.example
36845 driver = appendfile
36846 directory = /var/bsmtp/$host
36851 This causes messages addressed to &'domain.example'& to be written in BSMTP
36852 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
36853 message (unless there are more than 1000 recipients).
36857 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
36858 .cindex "SMTP" "batched incoming"
36859 .cindex "batched SMTP input"
36860 The &%-bS%& command line option causes Exim to accept one or more messages by
36861 reading SMTP on the standard input, but to generate no responses. If the caller
36862 is trusted, the senders in the MAIL commands are believed; otherwise the
36863 sender is always the caller of Exim. Unqualified senders and receivers are not
36864 rejected (there seems little point) but instead just get qualified. HELO
36865 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
36866 as NOOP; QUIT quits.
36868 Minimal policy checking is done for BSMTP input. Only the non-SMTP
36869 ACL is run in the same way as for non-SMTP local input.
36871 If an error is detected while reading a message, including a missing &"."& at
36872 the end, Exim gives up immediately. It writes details of the error to the
36873 standard output in a stylized way that the calling program should be able to
36874 make some use of automatically, for example:
36876 554 Unexpected end of file
36877 Transaction started in line 10
36878 Error detected in line 14
36880 It writes a more verbose version, for human consumption, to the standard error
36883 An error was detected while processing a file of BSMTP input.
36884 The error message was:
36886 501 '>' missing at end of address
36888 The SMTP transaction started in line 10.
36889 The error was detected in line 12.
36890 The SMTP command at fault was:
36892 rcpt to:<malformed@in.com.plete
36894 1 previous message was successfully processed.
36895 The rest of the batch was abandoned.
36897 The return code from Exim is zero only if there were no errors. It is 1 if some
36898 messages were accepted before an error was detected, and 2 if no messages were
36900 .ecindex IIDsmtpproc1
36901 .ecindex IIDsmtpproc2
36905 . ////////////////////////////////////////////////////////////////////////////
36906 . ////////////////////////////////////////////////////////////////////////////
36908 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
36909 "Customizing messages"
36910 When a message fails to be delivered, or remains in the queue for more than a
36911 configured amount of time, Exim sends a message to the original sender, or
36912 to an alternative configured address. The text of these messages is built into
36913 the code of Exim, but it is possible to change it, either by adding a single
36914 string, or by replacing each of the paragraphs by text supplied in a file.
36916 The &'From:'& and &'To:'& header lines are automatically generated; you can
36917 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
36918 option. Exim also adds the line
36920 Auto-Submitted: auto-generated
36922 to all warning and bounce messages,
36925 .section "Customizing bounce messages" "SECID239"
36926 .cindex "customizing" "bounce message"
36927 .cindex "bounce message" "customizing"
36928 If &%bounce_message_text%& is set, its contents are included in the default
36929 message immediately after &"This message was created automatically by mail
36930 delivery software."& The string is not expanded. It is not used if
36931 &%bounce_message_file%& is set.
36933 When &%bounce_message_file%& is set, it must point to a template file for
36934 constructing error messages. The file consists of a series of text items,
36935 separated by lines consisting of exactly four asterisks. If the file cannot be
36936 opened, default text is used and a message is written to the main and panic
36937 logs. If any text item in the file is empty, default text is used for that
36940 .vindex "&$bounce_recipient$&"
36941 .vindex "&$bounce_return_size_limit$&"
36942 Each item of text that is read from the file is expanded, and there are two
36943 expansion variables which can be of use here: &$bounce_recipient$& is set to
36944 the recipient of an error message while it is being created, and
36945 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
36946 option, rounded to a whole number.
36948 The items must appear in the file in the following order:
36951 The first item is included in the headers, and should include at least a
36952 &'Subject:'& header. Exim does not check the syntax of these headers.
36954 The second item forms the start of the error message. After it, Exim lists the
36955 failing addresses with their error messages.
36957 The third item is used to introduce any text from pipe transports that is to be
36958 returned to the sender. It is omitted if there is no such text.
36960 The fourth, fifth and sixth items will be ignored and may be empty.
36961 The fields exist for back-compatibility
36964 The default state (&%bounce_message_file%& unset) is equivalent to the
36965 following file, in which the sixth item is empty. The &'Subject:'& and some
36966 other lines have been split in order to fit them on the page:
36968 Subject: Mail delivery failed
36969 ${if eq{$sender_address}{$bounce_recipient}
36970 {: returning message to sender}}
36972 This message was created automatically by mail delivery software.
36974 A message ${if eq{$sender_address}{$bounce_recipient}
36975 {that you sent }{sent by
36979 }}could not be delivered to all of its recipients.
36980 This is a permanent error. The following address(es) failed:
36982 The following text was generated during the delivery attempt(s):
36984 ------ This is a copy of the message, including all the headers.
36987 ------ The body of the message is $message_size characters long;
36989 ------ $bounce_return_size_limit or so are included here.
36992 .section "Customizing warning messages" "SECTcustwarn"
36993 .cindex "customizing" "warning message"
36994 .cindex "warning of delay" "customizing the message"
36995 The option &%warn_message_file%& can be pointed at a template file for use when
36996 warnings about message delays are created. In this case there are only three
37000 The first item is included in the headers, and should include at least a
37001 &'Subject:'& header. Exim does not check the syntax of these headers.
37003 The second item forms the start of the warning message. After it, Exim lists
37004 the delayed addresses.
37006 The third item then ends the message.
37009 The default state is equivalent to the following file, except that some lines
37010 have been split here, in order to fit them on the page:
37012 Subject: Warning: message $message_exim_id delayed
37013 $warn_message_delay
37015 This message was created automatically by mail delivery software.
37017 A message ${if eq{$sender_address}{$warn_message_recipients}
37018 {that you sent }{sent by
37022 }}has not been delivered to all of its recipients after
37023 more than $warn_message_delay in the queue on $primary_hostname.
37025 The message identifier is: $message_exim_id
37026 The subject of the message is: $h_subject
37027 The date of the message is: $h_date
37029 The following address(es) have not yet been delivered:
37031 No action is required on your part. Delivery attempts will
37032 continue for some time, and this warning may be repeated at
37033 intervals if the message remains undelivered. Eventually the
37034 mail delivery software will give up, and when that happens,
37035 the message will be returned to you.
37037 .vindex "&$warn_message_delay$&"
37038 .vindex "&$warn_message_recipients$&"
37039 However, in the default state the subject and date lines are omitted if no
37040 appropriate headers exist. During the expansion of this file,
37041 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
37042 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
37043 of recipients for the warning message. There may be more than one if there are
37044 multiple addresses with different &%errors_to%& settings on the routers that
37050 . ////////////////////////////////////////////////////////////////////////////
37051 . ////////////////////////////////////////////////////////////////////////////
37053 .chapter "Some common configuration settings" "CHAPcomconreq"
37054 This chapter discusses some configuration settings that seem to be fairly
37055 common. More examples and discussion can be found in the Exim book.
37059 .section "Sending mail to a smart host" "SECID240"
37060 .cindex "smart host" "example router"
37061 If you want to send all mail for non-local domains to a &"smart host"&, you
37062 should replace the default &(dnslookup)& router with a router which does the
37063 routing explicitly:
37065 send_to_smart_host:
37066 driver = manualroute
37067 route_list = !+local_domains smart.host.name
37068 transport = remote_smtp
37070 You can use the smart host's IP address instead of the name if you wish.
37071 If you are using Exim only to submit messages to a smart host, and not for
37072 receiving incoming messages, you can arrange for it to do the submission
37073 synchronously by setting the &%mua_wrapper%& option (see chapter
37074 &<<CHAPnonqueueing>>&).
37079 .section "Using Exim to handle mailing lists" "SECTmailinglists"
37080 .cindex "mailing lists"
37081 Exim can be used to run simple mailing lists, but for large and/or complicated
37082 requirements, the use of additional specialized mailing list software such as
37083 Majordomo or Mailman is recommended.
37085 The &(redirect)& router can be used to handle mailing lists where each list
37086 is maintained in a separate file, which can therefore be managed by an
37087 independent manager. The &%domains%& router option can be used to run these
37088 lists in a separate domain from normal mail. For example:
37092 domains = lists.example
37093 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37096 errors_to = ${quote_local_part:$local_part-request}@lists.example
37099 This router is skipped for domains other than &'lists.example'&. For addresses
37100 in that domain, it looks for a file that matches the local part. If there is no
37101 such file, the router declines, but because &%no_more%& is set, no subsequent
37102 routers are tried, and so the whole delivery fails.
37104 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
37105 expanded into a filename or a pipe delivery, which is usually inappropriate in
37108 .oindex "&%errors_to%&"
37109 The &%errors_to%& option specifies that any delivery errors caused by addresses
37110 taken from a mailing list are to be sent to the given address rather than the
37111 original sender of the message. However, before acting on this, Exim verifies
37112 the error address, and ignores it if verification fails.
37114 For example, using the configuration above, mail sent to
37115 &'dicts@lists.example'& is passed on to those addresses contained in
37116 &_/usr/lists/dicts_&, with error reports directed to
37117 &'dicts-request@lists.example'&, provided that this address can be verified.
37118 There could be a file called &_/usr/lists/dicts-request_& containing
37119 the address(es) of this particular list's manager(s), but other approaches,
37120 such as setting up an earlier router (possibly using the &%local_part_prefix%&
37121 or &%local_part_suffix%& options) to handle addresses of the form
37122 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
37126 .section "Syntax errors in mailing lists" "SECID241"
37127 .cindex "mailing lists" "syntax errors in"
37128 If an entry in redirection data contains a syntax error, Exim normally defers
37129 delivery of the original address. That means that a syntax error in a mailing
37130 list holds up all deliveries to the list. This may not be appropriate when a
37131 list is being maintained automatically from data supplied by users, and the
37132 addresses are not rigorously checked.
37134 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
37135 entries that fail to parse, noting the incident in the log. If in addition
37136 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
37137 whenever a broken address is skipped. It is usually appropriate to set
37138 &%syntax_errors_to%& to the same address as &%errors_to%&.
37142 .section "Re-expansion of mailing lists" "SECID242"
37143 .cindex "mailing lists" "re-expansion of"
37144 Exim remembers every individual address to which a message has been delivered,
37145 in order to avoid duplication, but it normally stores only the original
37146 recipient addresses with a message. If all the deliveries to a mailing list
37147 cannot be done at the first attempt, the mailing list is re-expanded when the
37148 delivery is next tried. This means that alterations to the list are taken into
37149 account at each delivery attempt, so addresses that have been added to
37150 the list since the message arrived will therefore receive a copy of the
37151 message, even though it pre-dates their subscription.
37153 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
37154 on the &(redirect)& router. If this is done, any addresses generated by the
37155 router that fail to deliver at the first attempt are added to the message as
37156 &"top level"& addresses, and the parent address that generated them is marked
37157 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
37158 subsequent delivery attempts. The disadvantage of this is that if any of the
37159 failing addresses are incorrect, correcting them in the file has no effect on
37160 pre-existing messages.
37162 The original top-level address is remembered with each of the generated
37163 addresses, and is output in any log messages. However, any intermediate parent
37164 addresses are not recorded. This makes a difference to the log only if the
37165 &%all_parents%& selector is set, but for mailing lists there is normally only
37166 one level of expansion anyway.
37170 .section "Closed mailing lists" "SECID243"
37171 .cindex "mailing lists" "closed"
37172 The examples so far have assumed open mailing lists, to which anybody may
37173 send mail. It is also possible to set up closed lists, where mail is accepted
37174 from specified senders only. This is done by making use of the generic
37175 &%senders%& option to restrict the router that handles the list.
37177 The following example uses the same file as a list of recipients and as a list
37178 of permitted senders. It requires three routers:
37182 domains = lists.example
37183 local_part_suffix = -request
37184 local_parts = ${lookup {$local_part} dsearch,filter=file {/usr/lists}}
37185 file = /usr/lists/${local_part_data}-request
37190 domains = lists.example
37191 senders = ${if exists {/usr/lists/$local_part}\
37192 {lsearch;/usr/lists/$local_part}{*}}
37193 file = ${lookup {$local_part} dsearch,ret=full {/usr/lists}}
37196 errors_to = ${quote_local_part:$local_part-request}@lists.example
37201 domains = lists.example
37203 data = :fail: $local_part@lists.example is a closed mailing list
37205 All three routers have the same &%domains%& setting, so for any other domains,
37206 they are all skipped. The first router runs only if the local part ends in
37207 &%-request%&. It handles messages to the list manager(s) by means of an open
37210 The second router runs only if the &%senders%& precondition is satisfied. It
37211 checks for the existence of a list that corresponds to the local part, and then
37212 checks that the sender is on the list by means of a linear search. It is
37213 necessary to check for the existence of the file before trying to search it,
37214 because otherwise Exim thinks there is a configuration error. If the file does
37215 not exist, the expansion of &%senders%& is *, which matches all senders. This
37216 means that the router runs, but because there is no list, declines, and
37217 &%no_more%& ensures that no further routers are run. The address fails with an
37218 &"unrouteable address"& error.
37220 The third router runs only if the second router is skipped, which happens when
37221 a mailing list exists, but the sender is not on it. This router forcibly fails
37222 the address, giving a suitable error message.
37227 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
37229 .cindex "Variable Envelope Return Paths"
37230 .cindex "envelope from"
37231 .cindex "envelope sender"
37232 Variable Envelope Return Paths &-- see &url(https://cr.yp.to/proto/verp.txt) &--
37233 are a way of helping mailing list administrators discover which subscription
37234 address is the cause of a particular delivery failure. The idea is to encode
37235 the original recipient address in the outgoing envelope sender address, so that
37236 if the message is forwarded by another host and then subsequently bounces, the
37237 original recipient can be extracted from the recipient address of the bounce.
37239 .oindex &%errors_to%&
37240 .oindex &%return_path%&
37241 Envelope sender addresses can be modified by Exim using two different
37242 facilities: the &%errors_to%& option on a router (as shown in previous mailing
37243 list examples), or the &%return_path%& option on a transport. The second of
37244 these is effective only if the message is successfully delivered to another
37245 host; it is not used for errors detected on the local host (see the description
37246 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
37247 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
37253 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37254 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37256 This has the effect of rewriting the return path (envelope sender) on outgoing
37257 SMTP messages, if the local part of the original return path ends in
37258 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
37259 local part and domain of the recipient into the return path. Suppose, for
37260 example, that a message whose return path has been set to
37261 &'somelist-request@your.dom.example'& is sent to
37262 &'subscriber@other.dom.example'&. In the transport, the return path is
37265 somelist-request+subscriber=other.dom.example@your.dom.example
37267 .vindex "&$local_part$&"
37268 For this to work, you must tell Exim to send multiple copies of messages that
37269 have more than one recipient, so that each copy has just one recipient. This is
37270 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
37271 might be sent to several different recipients in the same domain, in which case
37272 &$local_part$& is not available in the transport, because it is not unique.
37274 Unless your host is doing nothing but mailing list deliveries, you should
37275 probably use a separate transport for the VERP deliveries, so as not to use
37276 extra resources in making one-per-recipient copies for other deliveries. This
37277 can easily be done by expanding the &%transport%& option in the router:
37281 domains = ! +local_domains
37283 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
37284 {verp_smtp}{remote_smtp}}
37287 If you want to change the return path using &%errors_to%& in a router instead
37288 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
37289 routers that handle mailing list addresses. This will ensure that all delivery
37290 errors, including those detected on the local host, are sent to the VERP
37293 On a host that does no local deliveries and has no manual routing, only the
37294 &(dnslookup)& router needs to be changed. A special transport is not needed for
37295 SMTP deliveries. Every mailing list recipient has its own return path value,
37296 and so Exim must hand them to the transport one at a time. Here is an example
37297 of a &(dnslookup)& router that implements VERP:
37301 domains = ! +local_domains
37302 transport = remote_smtp
37304 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
37305 {${quote_local_part:$1-request+$local_part=$domain}@your.dom.example}fail}
37308 Before you start sending out messages with VERPed return paths, you must also
37309 configure Exim to accept the bounce messages that come back to those paths.
37310 Typically this is done by setting a &%local_part_suffix%& option for a
37311 router, and using this to route the messages to wherever you want to handle
37314 The overhead incurred in using VERP depends very much on the size of the
37315 message, the number of recipient addresses that resolve to the same remote
37316 host, and the speed of the connection over which the message is being sent. If
37317 a lot of addresses resolve to the same host and the connection is slow, sending
37318 a separate copy of the message for each address may take substantially longer
37319 than sending a single copy with many recipients (for which VERP cannot be
37327 .section "Virtual domains" "SECTvirtualdomains"
37328 .cindex "virtual domains"
37329 .cindex "domain" "virtual"
37330 The phrase &'virtual domain'& is unfortunately used with two rather different
37334 A domain for which there are no real mailboxes; all valid local parts are
37335 aliases for other email addresses. Common examples are organizational
37336 top-level domains and &"vanity"& domains.
37338 One of a number of independent domains that are all handled by the same host,
37339 with mailboxes on that host, but where the mailbox owners do not necessarily
37340 have login accounts on that host.
37343 The first usage is probably more common, and does seem more &"virtual"& than
37344 the second. This kind of domain can be handled in Exim with a straightforward
37345 aliasing router. One approach is to create a separate alias file for each
37346 virtual domain. Exim can test for the existence of the alias file to determine
37347 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
37348 to a router of this form:
37352 domains = dsearch;/etc/mail/virtual
37353 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
37356 The &%domains%& option specifies that the router is to be skipped, unless there
37357 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
37358 domain that is being processed.
37359 The &(dsearch)& lookup used results in an untainted version of &$domain$&
37360 being placed into the &$domain_data$& variable.
37362 When the router runs, it looks up the local
37363 part in the file to find a new address (or list of addresses). The &%no_more%&
37364 setting ensures that if the lookup fails (leading to &%data%& being an empty
37365 string), Exim gives up on the address without trying any subsequent routers.
37367 This one router can handle all the virtual domains because the alias filenames
37368 follow a fixed pattern. Permissions can be arranged so that appropriate people
37369 can edit the different alias files. A successful aliasing operation results in
37370 a new envelope recipient address, which is then routed from scratch.
37372 The other kind of &"virtual"& domain can also be handled in a straightforward
37373 way. One approach is to create a file for each domain containing a list of
37374 valid local parts, and use it in a router like this:
37378 domains = dsearch;/etc/mail/domains
37379 local_parts = lsearch;/etc/mail/domains/$domain
37380 transport = my_mailboxes
37382 The address is accepted if there is a file for the domain, and the local part
37383 can be found in the file. The &%domains%& option is used to check for the
37384 file's existence because &%domains%& is tested before the &%local_parts%&
37385 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
37386 because that option is tested after &%local_parts%&. The transport is as
37390 driver = appendfile
37391 file = /var/mail/$domain_data/$local_part_data
37394 This uses a directory of mailboxes for each domain. The &%user%& setting is
37395 required, to specify which uid is to be used for writing to the mailboxes.
37397 The configuration shown here is just one example of how you might support this
37398 requirement. There are many other ways this kind of configuration can be set
37399 up, for example, by using a database instead of separate files to hold all the
37400 information about the domains.
37404 .section "Multiple user mailboxes" "SECTmulbox"
37405 .cindex "multiple mailboxes"
37406 .cindex "mailbox" "multiple"
37407 .cindex "local part" "prefix"
37408 .cindex "local part" "suffix"
37409 Heavy email users often want to operate with multiple mailboxes, into which
37410 incoming mail is automatically sorted. A popular way of handling this is to
37411 allow users to use multiple sender addresses, so that replies can easily be
37412 identified. Users are permitted to add prefixes or suffixes to their local
37413 parts for this purpose. The wildcard facility of the generic router options
37414 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
37415 example, consider this router:
37420 file = $home/.forward
37421 local_part_suffix = -*
37422 local_part_suffix_optional
37425 .vindex "&$local_part_suffix$&"
37426 It runs a user's &_.forward_& file for all local parts of the form
37427 &'username-*'&. Within the filter file the user can distinguish different
37428 cases by testing the variable &$local_part_suffix$&. For example:
37430 if $local_part_suffix contains -special then
37431 save /home/$local_part_data/Mail/special
37434 If the filter file does not exist, or does not deal with such addresses, they
37435 fall through to subsequent routers, and, assuming no subsequent use of the
37436 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
37437 control over which suffixes are valid.
37439 Alternatively, a suffix can be used to trigger the use of a different
37440 &_.forward_& file &-- which is the way a similar facility is implemented in
37446 local_part_suffix = -*
37447 local_part_suffix_optional
37448 file = ${lookup {.forward$local_part_suffix} dsearch,ret=full {$home} {$value}fail}
37451 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
37452 example, &_.forward-special_& is used. Once again, if the appropriate file
37453 does not exist, or does not deal with the address, it is passed on to
37454 subsequent routers, which could, if required, look for an unqualified
37455 &_.forward_& file to use as a default.
37459 .section "Simplified vacation processing" "SECID244"
37460 .cindex "vacation processing"
37461 The traditional way of running the &'vacation'& program is for a user to set up
37462 a pipe command in a &_.forward_& file
37463 (see section &<<SECTspecitredli>>& for syntax details).
37464 This is prone to error by inexperienced users. There are two features of Exim
37465 that can be used to make this process simpler for users:
37468 A local part prefix such as &"vacation-"& can be specified on a router which
37469 can cause the message to be delivered directly to the &'vacation'& program, or
37470 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
37471 &_.forward_& file are then much simpler. For example:
37473 spqr, vacation-spqr
37476 The &%require_files%& generic router option can be used to trigger a
37477 vacation delivery by checking for the existence of a certain file in the
37478 user's home directory. The &%unseen%& generic option should also be used, to
37479 ensure that the original delivery also proceeds. In this case, all the user has
37480 to do is to create a file called, say, &_.vacation_&, containing a vacation
37484 Another advantage of both these methods is that they both work even when the
37485 use of arbitrary pipes by users is locked out.
37489 .section "Taking copies of mail" "SECID245"
37490 .cindex "message" "copying every"
37491 Some installations have policies that require archive copies of all messages to
37492 be made. A single copy of each message can easily be taken by an appropriate
37493 command in a system filter, which could, for example, use a different file for
37494 each day's messages.
37496 There is also a shadow transport mechanism that can be used to take copies of
37497 messages that are successfully delivered by local transports, one copy per
37498 delivery. This could be used, &'inter alia'&, to implement automatic
37499 notification of delivery by sites that insist on doing such things.
37503 .section "Intermittently connected hosts" "SECID246"
37504 .cindex "intermittently connected hosts"
37505 It has become quite common (because it is cheaper) for hosts to connect to the
37506 Internet periodically rather than remain connected all the time. The normal
37507 arrangement is that mail for such hosts accumulates on a system that is
37508 permanently connected.
37510 Exim was designed for use on permanently connected hosts, and so it is not
37511 particularly well-suited to use in an intermittently connected environment.
37512 Nevertheless there are some features that can be used.
37515 .section "Exim on the upstream server host" "SECID247"
37516 It is tempting to arrange for incoming mail for the intermittently connected
37517 host to remain in Exim's queue until the client connects. However, this
37518 approach does not scale very well. Two different kinds of waiting message are
37519 being mixed up in the same queue &-- those that cannot be delivered because of
37520 some temporary problem, and those that are waiting for their destination host
37521 to connect. This makes it hard to manage the queue, as well as wasting
37522 resources, because each queue runner scans the entire queue.
37524 A better approach is to separate off those messages that are waiting for an
37525 intermittently connected host. This can be done by delivering these messages
37526 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
37527 format, from where they are transmitted by other software when their
37528 destination connects. This makes it easy to collect all the mail for one host
37529 in a single directory, and to apply local timeout rules on a per-message basis
37532 On a very small scale, leaving the mail on Exim's queue can be made to work. If
37533 you are doing this, you should configure Exim with a long retry period for the
37534 intermittent host. For example:
37536 cheshire.wonderland.fict.example * F,5d,24h
37538 This stops a lot of failed delivery attempts from occurring, but Exim remembers
37539 which messages it has queued up for that host. Once the intermittent host comes
37540 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
37541 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
37542 causes all the queued up messages to be delivered, often down a single SMTP
37543 connection. While the host remains connected, any new messages get delivered
37546 If the connecting hosts do not have fixed IP addresses, that is, if a host is
37547 issued with a different IP address each time it connects, Exim's retry
37548 mechanisms on the holding host get confused, because the IP address is normally
37549 used as part of the key string for holding retry information. This can be
37550 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
37551 Since this has disadvantages for permanently connected hosts, it is best to
37552 arrange a separate transport for the intermittently connected ones.
37556 .section "Exim on the intermittently connected client host" "SECID248"
37557 The value of &%smtp_accept_queue_per_connection%& should probably be
37558 increased, or even set to zero (that is, disabled) on the intermittently
37559 connected host, so that all incoming messages down a single connection get
37560 delivered immediately.
37562 .cindex "SMTP" "passed connection"
37563 .cindex "SMTP" "multiple deliveries"
37564 .cindex "multiple SMTP deliveries"
37565 .cindex "first pass routing"
37566 Mail waiting to be sent from an intermittently connected host will probably
37567 not have been routed, because without a connection DNS lookups are not
37568 possible. This means that if a normal queue run is done at connection time,
37569 each message is likely to be sent in a separate SMTP session. This can be
37570 avoided by starting the queue run with a command line option beginning with
37571 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
37572 first pass, routing is done but no deliveries take place. The second pass is a
37573 normal queue run; since all the messages have been previously routed, those
37574 destined for the same host are likely to get sent as multiple deliveries in a
37575 single SMTP connection.
37579 . ////////////////////////////////////////////////////////////////////////////
37580 . ////////////////////////////////////////////////////////////////////////////
37582 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
37583 "Exim as a non-queueing client"
37584 .cindex "client, non-queueing"
37585 .cindex "smart host" "suppressing queueing"
37586 On a personal computer, it is a common requirement for all
37587 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
37588 configured to operate that way, for all the popular operating systems.
37589 However, there are some MUAs for Unix-like systems that cannot be so
37590 configured: they submit messages using the command line interface of
37591 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
37594 If the personal computer runs continuously, there is no problem, because it can
37595 run a conventional MTA that handles delivery to the smart host, and deal with
37596 any delays via its queueing mechanism. However, if the computer does not run
37597 continuously or runs different operating systems at different times, queueing
37598 email is not desirable.
37600 There is therefore a requirement for something that can provide the
37601 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
37602 any queueing or retrying facilities. Furthermore, the delivery to the smart
37603 host should be synchronous, so that if it fails, the sending MUA is immediately
37604 informed. In other words, we want something that extends an MUA that submits
37605 to a local MTA via the command line so that it behaves like one that submits
37606 to a remote smart host using TCP/SMTP.
37608 There are a number of applications (for example, there is one called &'ssmtp'&)
37609 that do this job. However, people have found them to be lacking in various
37610 ways. For instance, you might want to allow aliasing and forwarding to be done
37611 before sending a message to the smart host.
37613 Exim already had the necessary infrastructure for doing this job. Just a few
37614 tweaks were needed to make it behave as required, though it is somewhat of an
37615 overkill to use a fully-featured MTA for this purpose.
37617 .oindex "&%mua_wrapper%&"
37618 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
37619 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
37620 assumes that it is being used to &"wrap"& a command-line MUA in the manner
37621 just described. As well as setting &%mua_wrapper%&, you also need to provide a
37622 compatible router and transport configuration. Typically there will be just one
37623 router and one transport, sending everything to a smart host.
37625 When run in MUA wrapping mode, the behaviour of Exim changes in the
37629 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
37630 In other words, the only way to submit messages is via the command line.
37632 Each message is synchronously delivered as soon as it is received (&%-odi%& is
37633 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
37634 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
37635 does not finish until the delivery attempt is complete. If the delivery is
37636 successful, a zero return code is given.
37638 Address redirection is permitted, but the final routing for all addresses must
37639 be to the same remote transport, and to the same list of hosts. Furthermore,
37640 the return address (envelope sender) must be the same for all recipients, as
37641 must any added or deleted header lines. In other words, it must be possible to
37642 deliver the message in a single SMTP transaction, however many recipients there
37645 If these conditions are not met, or if routing any address results in a
37646 failure or defer status, or if Exim is unable to deliver all the recipients
37647 successfully to one of the smart hosts, delivery of the entire message fails.
37649 Because no queueing is allowed, all failures are treated as permanent; there
37650 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
37651 smart host. Furthermore, because only a single yes/no response can be given to
37652 the caller, it is not possible to deliver to some recipients and not others. If
37653 there is an error (temporary or permanent) for any recipient, all are failed.
37655 If more than one smart host is listed, Exim will try another host after a
37656 connection failure or a timeout, in the normal way. However, if this kind of
37657 failure happens for all the hosts, the delivery fails.
37659 When delivery fails, an error message is written to the standard error stream
37660 (as well as to Exim's log), and Exim exits to the caller with a return code
37661 value 1. The message is expunged from Exim's spool files. No bounce messages
37662 are ever generated.
37664 No retry data is maintained, and any retry rules are ignored.
37666 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
37667 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
37668 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
37671 The overall effect is that Exim makes a single synchronous attempt to deliver
37672 the message, failing if there is any kind of problem. Because no local
37673 deliveries are done and no daemon can be run, Exim does not need root
37674 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
37675 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
37676 the advantages and disadvantages of running without root privilege.
37681 . ////////////////////////////////////////////////////////////////////////////
37682 . ////////////////////////////////////////////////////////////////////////////
37684 .chapter "Log files" "CHAPlog"
37685 .scindex IIDloggen "log" "general description"
37686 .cindex "log" "types of"
37687 Exim writes three different logs, referred to as the main log, the reject log,
37692 The main log records the arrival of each message and each delivery in a single
37693 line in each case. The format is as compact as possible, in an attempt to keep
37694 down the size of log files. Two-character flag sequences make it easy to pick
37695 out these lines. A number of other events are recorded in the main log. Some of
37696 them are optional, in which case the &%log_selector%& option controls whether
37697 they are included or not. A Perl script called &'eximstats'&, which does simple
37698 analysis of main log files, is provided in the Exim distribution (see section
37699 &<<SECTmailstat>>&).
37701 .cindex "reject log"
37702 The reject log records information from messages that are rejected as a result
37703 of a configuration option (that is, for policy reasons).
37704 The first line of each rejection is a copy of the line that is also written to
37705 the main log. Then, if the message's header has been read at the time the log
37706 is written, its contents are written to this log. Only the original header
37707 lines are available; header lines added by ACLs are not logged. You can use the
37708 reject log to check that your policy controls are working correctly; on a busy
37709 host this may be easier than scanning the main log for rejection messages. You
37710 can suppress the writing of the reject log by setting &%write_rejectlog%&
37713 .cindex "panic log"
37714 .cindex "system log"
37715 When certain serious errors occur, Exim writes entries to its panic log. If the
37716 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
37717 are usually written to the main log as well, but can get lost amid the mass of
37718 other entries. The panic log should be empty under normal circumstances. It is
37719 therefore a good idea to check it (or to have a &'cron'& script check it)
37720 regularly, in order to become aware of any problems. When Exim cannot open its
37721 panic log, it tries as a last resort to write to the system log (syslog). This
37722 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
37723 message itself is written at priority LOG_CRIT.
37726 Every log line starts with a timestamp, in the format shown in the following
37727 example. Note that many of the examples shown in this chapter are line-wrapped.
37728 In the log file, this would be all on one line:
37730 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
37733 By default, the timestamps are in the local timezone. There are two
37734 ways of changing this:
37737 You can set the &%timezone%& option to a different time zone; in particular, if
37742 the timestamps will be in UTC (aka GMT).
37744 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
37747 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
37751 .cindex "log" "process ids in"
37752 .cindex "pid (process id)" "in log lines"
37753 Exim does not include its process id in log lines by default, but you can
37754 request that it does so by specifying the &`pid`& log selector (see section
37755 &<<SECTlogselector>>&). When this is set, the process id is output, in square
37756 brackets, immediately after the time and date.
37761 .section "Where the logs are written" "SECTwhelogwri"
37762 .cindex "log" "destination"
37763 .cindex "log" "to file"
37764 .cindex "log" "to syslog"
37766 The logs may be written to local files, or to syslog, or both. However, it
37767 should be noted that many syslog implementations use UDP as a transport, and
37768 are therefore unreliable in the sense that messages are not guaranteed to
37769 arrive at the loghost, nor is the ordering of messages necessarily maintained.
37770 It has also been reported that on large log files (tens of megabytes) you may
37771 need to tweak syslog to prevent it syncing the file with each write &-- on
37772 Linux this has been seen to make syslog take 90% plus of CPU time.
37774 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
37775 &_Local/Makefile_& or by setting &%log_file_path%& in the runtime
37776 configuration. This latter string is expanded, so it can contain, for example,
37777 references to the host name:
37779 log_file_path = /var/log/$primary_hostname/exim_%slog
37781 It is generally advisable, however, to set the string in &_Local/Makefile_&
37782 rather than at runtime, because then the setting is available right from the
37783 start of Exim's execution. Otherwise, if there's something it wants to log
37784 before it has read the configuration file (for example, an error in the
37785 configuration file) it will not use the path you want, and may not be able to
37788 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
37789 list, currently limited to at most two items. This is one option where the
37790 facility for changing a list separator may not be used. The list must always be
37791 colon-separated. If an item in the list is &"syslog"& then syslog is used;
37792 otherwise the item must either be an absolute path, containing &`%s`& at the
37793 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
37794 implying the use of a default path.
37796 When Exim encounters an empty item in the list, it searches the list defined by
37797 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
37798 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
37799 mean &"use the path specified at build time"&. It no such item exists, log
37800 files are written in the &_log_& subdirectory of the spool directory. This is
37801 equivalent to the setting:
37803 log_file_path = $spool_directory/log/%slog
37805 If you do not specify anything at build time or runtime,
37806 or if you unset the option at runtime (i.e. &`log_file_path = `&),
37807 that is where the logs are written.
37809 A log file path may also contain &`%D`& or &`%M`& if datestamped log filenames
37810 are in use &-- see section &<<SECTdatlogfil>>& below.
37812 Here are some examples of possible settings:
37814 &`LOG_FILE_PATH=syslog `& syslog only
37815 &`LOG_FILE_PATH=:syslog `& syslog and default path
37816 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
37817 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
37819 If there are more than two paths in the list, the first is used and a panic
37824 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
37825 .cindex "log" "cycling local files"
37826 .cindex "cycling logs"
37827 .cindex "&'exicyclog'&"
37828 .cindex "log" "local files; writing to"
37829 Some operating systems provide centralized and standardized methods for cycling
37830 log files. For those that do not, a utility script called &'exicyclog'& is
37831 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
37832 main and reject logs each time it is called. The maximum number of old logs to
37833 keep can be set. It is suggested this script is run as a daily &'cron'& job.
37835 An Exim delivery process opens the main log when it first needs to write to it,
37836 and it keeps the file open in case subsequent entries are required &-- for
37837 example, if a number of different deliveries are being done for the same
37838 message. However, remote SMTP deliveries can take a long time, and this means
37839 that the file may be kept open long after it is renamed if &'exicyclog'& or
37840 something similar is being used to rename log files on a regular basis. To
37841 ensure that a switch of log files is noticed as soon as possible, Exim calls
37842 &[stat()]& on the main log's name before reusing an open file, and if the file
37843 does not exist, or its inode has changed, the old file is closed and Exim
37844 tries to open the main log from scratch. Thus, an old log file may remain open
37845 for quite some time, but no Exim processes should write to it once it has been
37850 .section "Datestamped log files" "SECTdatlogfil"
37851 .cindex "log" "datestamped files"
37852 Instead of cycling the main and reject log files by renaming them
37853 periodically, some sites like to use files whose names contain a datestamp,
37854 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
37855 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
37856 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
37857 point where the datestamp is required. For example:
37859 log_file_path = /var/spool/exim/log/%slog-%D
37860 log_file_path = /var/log/exim-%s-%D.log
37861 log_file_path = /var/spool/exim/log/%D-%slog
37862 log_file_path = /var/log/exim/%s.%M
37864 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
37865 examples of names generated by the above examples:
37867 /var/spool/exim/log/mainlog-20021225
37868 /var/log/exim-reject-20021225.log
37869 /var/spool/exim/log/20021225-mainlog
37870 /var/log/exim/main.200212
37872 When this form of log file is specified, Exim automatically switches to new
37873 files at midnight. It does not make any attempt to compress old logs; you
37874 will need to write your own script if you require this. You should not
37875 run &'exicyclog'& with this form of logging.
37877 The location of the panic log is also determined by &%log_file_path%&, but it
37878 is not datestamped, because rotation of the panic log does not make sense.
37879 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
37880 the string. In addition, if it immediately follows a slash, a following
37881 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
37882 character is removed. Thus, the four examples above would give these panic
37885 /var/spool/exim/log/paniclog
37886 /var/log/exim-panic.log
37887 /var/spool/exim/log/paniclog
37888 /var/log/exim/panic
37892 .section "Logging to syslog" "SECID249"
37893 .cindex "log" "syslog; writing to"
37894 The use of syslog does not change what Exim logs or the format of its messages,
37895 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
37896 Exim's log lines are omitted when these lines are sent to syslog. Apart from
37897 that, the same strings are written to syslog as to log files. The syslog
37898 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
37899 by default, but you can change these by setting the &%syslog_facility%& and
37900 &%syslog_processname%& options, respectively. If Exim was compiled with
37901 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
37902 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
37903 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
37904 the time and host name to each line.
37905 The three log streams are mapped onto syslog priorities as follows:
37908 &'mainlog'& is mapped to LOG_INFO
37910 &'rejectlog'& is mapped to LOG_NOTICE
37912 &'paniclog'& is mapped to LOG_ALERT
37915 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
37916 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
37917 these are routed by syslog to the same place. You can suppress this duplication
37918 by setting &%syslog_duplication%& false.
37920 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
37921 entries contain multiple lines when headers are included. To cope with both
37922 these cases, entries written to syslog are split into separate &[syslog()]&
37923 calls at each internal newline, and also after a maximum of
37924 870 data characters. (This allows for a total syslog line length of 1024, when
37925 additions such as timestamps are added.) If you are running a syslog
37926 replacement that can handle lines longer than the 1024 characters allowed by
37927 RFC 3164, you should set
37929 SYSLOG_LONG_LINES=yes
37931 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
37932 lines, but it still splits at internal newlines in &'reject'& log entries.
37934 To make it easy to re-assemble split lines later, each component of a split
37935 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
37936 where <&'n'&> is the component number and <&'m'&> is the total number of
37937 components in the entry. The / delimiter is used when the line was split
37938 because it was too long; if it was split because of an internal newline, the \
37939 delimiter is used. For example, supposing the length limit to be 50 instead of
37940 870, the following would be the result of a typical rejection message to
37941 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
37942 name, and pid as added by syslog:
37944 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
37945 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
37946 [3/5] when scanning for sender: missing or malformed lo
37947 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
37950 The same error might cause the following lines to be written to &"rejectlog"&
37953 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
37954 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
37955 [3/18] er when scanning for sender: missing or malformed
37956 [4/18] local part in "<>" (envelope sender is <ph10@cam
37958 [6\18] Recipients: ph10@some.domain.cam.example
37959 [7\18] P Received: from [127.0.0.1] (ident=ph10)
37960 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
37961 [9\18] id 16RdAL-0006pc-00
37962 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
37963 [11\18] 09:43 +0100
37965 [13\18] Subject: this is a test header
37966 [18\18] X-something: this is another header
37967 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
37970 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
37972 Log lines that are neither too long nor contain newlines are written to syslog
37973 without modification.
37975 If only syslog is being used, the Exim monitor is unable to provide a log tail
37976 display, unless syslog is routing &'mainlog'& to a file on the local host and
37977 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
37982 .section "Log line flags" "SECID250"
37983 One line is written to the main log for each message received, and for each
37984 successful, unsuccessful, and delayed delivery. These lines can readily be
37985 picked out by the distinctive two-character flags that immediately follow the
37986 timestamp. The flags are:
37988 &`<=`& message arrival
37989 &`(=`& message fakereject
37990 &`=>`& normal message delivery
37991 &`->`& additional address in same delivery
37992 &`>>`& cutthrough message delivery
37993 &`*>`& delivery suppressed by &%-N%&
37994 &`**`& delivery failed; address bounced
37995 &`==`& delivery deferred; temporary problem
37999 .section "Logging message reception" "SECID251"
38000 .cindex "log" "reception line"
38001 The format of the single-line entry in the main log that is written for every
38002 message received is shown in the basic example below, which is split over
38003 several lines in order to fit it on the page:
38005 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
38006 H=mailer.fict.example [192.168.123.123] U=exim
38007 P=smtp S=5678 id=<incoming message id>
38009 The address immediately following &"<="& is the envelope sender address. A
38010 bounce message is shown with the sender address &"<>"&, and if it is locally
38011 generated, this is followed by an item of the form
38015 which is a reference to the message that caused the bounce to be sent.
38019 For messages from other hosts, the H and U fields identify the remote host and
38020 record the RFC 1413 identity of the user that sent the message, if one was
38021 received. The number given in square brackets is the IP address of the sending
38022 host. If there is a single, unparenthesized host name in the H field, as
38023 above, it has been verified to correspond to the IP address (see the
38024 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
38025 by the remote host in the SMTP HELO or EHLO command, and has not been
38026 verified. If verification yields a different name to that given for HELO or
38027 EHLO, the verified name appears first, followed by the HELO or EHLO
38028 name in parentheses.
38030 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
38031 without brackets, in the HELO or EHLO command, leading to entries in
38032 the log containing text like these examples:
38034 H=(10.21.32.43) [192.168.8.34]
38035 H=([10.21.32.43]) [192.168.8.34]
38037 This can be confusing. Only the final address in square brackets can be relied
38040 For locally generated messages (that is, messages not received over TCP/IP),
38041 the H field is omitted, and the U field contains the login name of the caller
38044 .cindex "authentication" "logging"
38045 .cindex "AUTH" "logging"
38046 For all messages, the P field specifies the protocol used to receive the
38047 message. This is the value that is stored in &$received_protocol$&. In the case
38048 of incoming SMTP messages, the value indicates whether or not any SMTP
38049 extensions (ESMTP), encryption, or authentication were used. If the SMTP
38050 session was encrypted, there is an additional X field that records the cipher
38051 suite that was used.
38053 .cindex log protocol
38054 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
38055 hosts that have authenticated themselves using the SMTP AUTH command. The first
38056 value is used when the SMTP connection was encrypted (&"secure"&). In this case
38057 there is an additional item A= followed by the name of the authenticator that
38058 was used. If an authenticated identification was set up by the authenticator's
38059 &%server_set_id%& option, this is logged too, separated by a colon from the
38060 authenticator name.
38062 .cindex "size" "of message"
38063 The id field records the existing message id, if present. The size of the
38064 received message is given by the S field. When the message is delivered,
38065 headers may be removed or added, so that the size of delivered copies of the
38066 message may not correspond with this value (and indeed may be different to each
38069 The &%log_selector%& option can be used to request the logging of additional
38070 data when a message is received. See section &<<SECTlogselector>>& below.
38074 .section "Logging deliveries" "SECID252"
38075 .cindex "log" "delivery line"
38076 The format of the single-line entry in the main log that is written for every
38077 delivery is shown in one of the examples below, for local and remote
38078 deliveries, respectively. Each example has been split into multiple lines in order
38079 to fit it on the page:
38081 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
38082 <marv@hitch.fict.example> R=localuser T=local_delivery
38083 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
38084 monk@holistic.fict.example R=dnslookup T=remote_smtp
38085 H=holistic.fict.example [192.168.234.234]
38087 For ordinary local deliveries, the original address is given in angle brackets
38088 after the final delivery address, which might be a pipe or a file. If
38089 intermediate address(es) exist between the original and the final address, the
38090 last of these is given in parentheses after the final address. The R and T
38091 fields record the router and transport that were used to process the address.
38093 If SMTP AUTH was used for the delivery there is an additional item A=
38094 followed by the name of the authenticator that was used.
38095 If an authenticated identification was set up by the authenticator's &%client_set_id%&
38096 option, this is logged too, as a second colon-separated list item.
38097 Optionally (see the &%smtp_mailauth%& &%log_selector%&) there may be a third list item.
38099 If a shadow transport was run after a successful local delivery, the log line
38100 for the successful delivery has an item added on the end, of the form
38102 &`ST=<`&&'shadow transport name'&&`>`&
38104 If the shadow transport did not succeed, the error message is put in
38105 parentheses afterwards.
38107 .cindex "asterisk" "after IP address"
38108 When more than one address is included in a single delivery (for example, two
38109 SMTP RCPT commands in one transaction) the second and subsequent addresses are
38110 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
38111 down a single SMTP connection, an asterisk follows the IP address in the log
38112 lines for the second and subsequent messages.
38113 When two or more messages are delivered down a single TLS connection, the
38114 DNS and some TLS-related information logged for the first message delivered
38115 will not be present in the log lines for the second and subsequent messages.
38116 TLS cipher information is still available.
38118 .cindex "delivery" "cutthrough; logging"
38119 .cindex "cutthrough" "logging"
38120 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
38121 line precedes the reception line, since cutthrough waits for a possible
38122 rejection from the destination in case it can reject the sourced item.
38124 The generation of a reply message by a filter file gets logged as a
38125 &"delivery"& to the addressee, preceded by &">"&.
38127 The &%log_selector%& option can be used to request the logging of additional
38128 data when a message is delivered. See section &<<SECTlogselector>>& below.
38131 .section "Discarded deliveries" "SECID253"
38132 .cindex "discarded messages"
38133 .cindex "message" "discarded"
38134 .cindex "delivery" "discarded; logging"
38135 When a message is discarded as a result of the command &"seen finish"& being
38136 obeyed in a filter file which generates no deliveries, a log entry of the form
38138 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
38139 <low.club@bridge.example> R=userforward
38141 is written, to record why no deliveries are logged. When a message is discarded
38142 because it is aliased to &":blackhole:"& the log line is like this:
38144 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
38145 <hole@nowhere.example> R=blackhole_router
38149 .section "Deferred deliveries" "SECID254"
38150 When a delivery is deferred, a line of the following form is logged:
38152 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
38153 R=dnslookup T=smtp defer (146): Connection refused
38155 In the case of remote deliveries, the error is the one that was given for the
38156 last IP address that was tried. Details of individual SMTP failures are also
38157 written to the log, so the above line would be preceded by something like
38159 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
38160 mail1.endrest.example [192.168.239.239]: Connection refused
38162 When a deferred address is skipped because its retry time has not been reached,
38163 a message is written to the log, but this can be suppressed by setting an
38164 appropriate value in &%log_selector%&.
38168 .section "Delivery failures" "SECID255"
38169 .cindex "delivery" "failure; logging"
38170 If a delivery fails because an address cannot be routed, a line of the
38171 following form is logged:
38173 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
38174 <jim@trek99.example>: unknown mail domain
38176 If a delivery fails at transport time, the router and transport are shown, and
38177 the response from the remote host is included, as in this example:
38179 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
38180 R=dnslookup T=remote_smtp: SMTP error from remote mailer
38181 after pipelined RCPT TO:<ace400@pb.example>: host
38182 pbmail3.py.example [192.168.63.111]: 553 5.3.0
38183 <ace400@pb.example>...Addressee unknown
38185 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
38186 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
38187 disabling PIPELINING. The log lines for all forms of delivery failure are
38188 flagged with &`**`&.
38192 .section "Fake deliveries" "SECID256"
38193 .cindex "delivery" "fake; logging"
38194 If a delivery does not actually take place because the &%-N%& option has been
38195 used to suppress it, a normal delivery line is written to the log, except that
38196 &"=>"& is replaced by &"*>"&.
38200 .section "Completion" "SECID257"
38203 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
38205 is written to the main log when a message is about to be removed from the spool
38206 at the end of its processing.
38211 .section "Summary of Fields in Log Lines" "SECID258"
38212 .cindex "log" "summary of fields"
38213 A summary of the field identifiers that are used in log lines is shown in
38214 the following table:
38216 &`A `& authenticator name (and optional id and sender)
38217 &`C `& SMTP confirmation on delivery
38218 &` `& command list for &"no mail in SMTP session"&
38219 &`CV `& certificate verification status
38220 &`D `& duration of &"no mail in SMTP session"&
38221 &`DKIM`& domain verified in incoming message
38222 &`DN `& distinguished name from peer certificate
38223 &`DS `& DNSSEC secured lookups
38224 &`DT `& on &`=>`&, &'=='& and &'**'& lines: time taken for, or to attempt, a delivery
38225 &`F `& sender address (on delivery lines)
38226 &`H `& host name and IP address
38227 &`I `& local interface used
38228 &`id `& message id (from header) for incoming message
38229 &`K `& CHUNKING extension used
38230 &`L `& on &`<=`& and &`=>`& lines: PIPELINING extension used
38231 &`M8S `& 8BITMIME status for incoming message
38232 &`P `& on &`<=`& lines: protocol used
38233 &` `& on &`=>`& and &`**`& lines: return path
38234 &`PRDR`& PRDR extension used
38235 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
38236 &`Q `& alternate queue name
38237 &`QT `& on &`=>`& lines: time spent on queue so far
38238 &` `& on &"Completed"& lines: time spent on queue
38239 &`R `& on &`<=`& lines: reference for local bounce
38240 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
38241 &`RT `& on &`<=`& lines: time taken for reception
38242 &`S `& size of message in bytes
38243 &`SNI `& server name indication from TLS client hello
38244 &`ST `& shadow transport name
38245 &`T `& on &`<=`& lines: message subject (topic)
38246 &`TFO `& connection took advantage of TCP Fast Open
38247 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
38248 &`U `& local user or RFC 1413 identity
38249 &`X `& TLS cipher suite
38253 .section "Other log entries" "SECID259"
38254 Various other types of log entry are written from time to time. Most should be
38255 self-explanatory. Among the more common are:
38258 .cindex "retry" "time not reached"
38259 &'retry time not reached'&&~&~An address previously suffered a temporary error
38260 during routing or local delivery, and the time to retry has not yet arrived.
38261 This message is not written to an individual message log file unless it happens
38262 during the first delivery attempt.
38264 &'retry time not reached for any host'&&~&~An address previously suffered
38265 temporary errors during remote delivery, and the retry time has not yet arrived
38266 for any of the hosts to which it is routed.
38268 .cindex "spool directory" "file locked"
38269 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
38270 some other Exim process is already working on the message. This can be quite
38271 common if queue running processes are started at frequent intervals. The
38272 &'exiwhat'& utility script can be used to find out what Exim processes are
38275 .cindex "error" "ignored"
38276 &'error ignored'&&~&~There are several circumstances that give rise to this
38279 Exim failed to deliver a bounce message whose age was greater than
38280 &%ignore_bounce_errors_after%&. The bounce was discarded.
38282 A filter file set up a delivery using the &"noerror"& option, and the delivery
38283 failed. The delivery was discarded.
38285 A delivery set up by a router configured with
38286 . ==== As this is a nested list, any displays it contains must be indented
38287 . ==== as otherwise they are too far to the left.
38291 failed. The delivery was discarded.
38294 .cindex DKIM "log line"
38295 &'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
38296 logging and the message has a DKIM signature header.
38303 .section "Reducing or increasing what is logged" "SECTlogselector"
38304 .cindex "log" "selectors"
38305 By setting the &%log_selector%& global option, you can disable some of Exim's
38306 default logging, or you can request additional logging. The value of
38307 &%log_selector%& is made up of names preceded by plus or minus characters. For
38310 log_selector = +arguments -retry_defer
38312 The list of optional log items is in the following table, with the default
38313 selection marked by asterisks:
38315 &` 8bitmime `& received 8BITMIME status
38316 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
38317 &` address_rewrite `& address rewriting
38318 &` all_parents `& all parents in => lines
38319 &` arguments `& command line arguments
38320 &`*connection_reject `& connection rejections
38321 &`*delay_delivery `& immediate delivery delayed
38322 &` deliver_time `& time taken to attempt delivery
38323 &` delivery_size `& add &`S=`&&'nnn'& to => lines
38324 &`*dkim `& DKIM verified domain on <= lines
38325 &` dkim_verbose `& separate full DKIM verification result line, per signature
38326 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
38327 &` dnssec `& DNSSEC secured lookups
38328 &`*etrn `& ETRN commands
38329 &`*host_lookup_failed `& as it says
38330 &` ident_timeout `& timeout for ident connection
38331 &` incoming_interface `& local interface on <= and => lines
38332 &` incoming_port `& remote port on <= lines
38333 &`*lost_incoming_connection `& as it says (includes timeouts)
38334 &` millisec `& millisecond timestamps and RT,QT,DT,D times
38335 &`*msg_id `& on <= lines, Message-ID: header value
38336 &` msg_id_created `& on <= lines, Message-ID: header value when one had to be added
38337 &` outgoing_interface `& local interface on => lines
38338 &` outgoing_port `& add remote port to => lines
38339 &`*queue_run `& start and end queue runs
38340 &` queue_time `& time on queue for one recipient
38341 &` queue_time_overall `& time on queue for whole message
38342 &` pid `& Exim process id
38343 &` pipelining `& PIPELINING use, on <= and => lines
38344 &` proxy `& proxy address on <= and => lines
38345 &` receive_time `& time taken to receive message
38346 &` received_recipients `& recipients on <= lines
38347 &` received_sender `& sender on <= lines
38348 &`*rejected_header `& header contents on reject log
38349 &`*retry_defer `& &"retry time not reached"&
38350 &` return_path_on_delivery `& put return path on => and ** lines
38351 &` sender_on_delivery `& add sender to => lines
38352 &`*sender_verify_fail `& sender verification failures
38353 &`*size_reject `& rejection because too big
38354 &`*skip_delivery `& delivery skipped in a queue run
38355 &`*smtp_confirmation `& SMTP confirmation on => lines
38356 &` smtp_connection `& incoming SMTP connections
38357 &` smtp_incomplete_transaction`& incomplete SMTP transactions
38358 &` smtp_mailauth `& AUTH argument to MAIL commands
38359 &` smtp_no_mail `& session with no MAIL commands
38360 &` smtp_protocol_error `& SMTP protocol errors
38361 &` smtp_syntax_error `& SMTP syntax errors
38362 &` subject `& contents of &'Subject:'& on <= lines
38363 &`*tls_certificate_verified `& certificate verification status
38364 &`*tls_cipher `& TLS cipher suite on <= and => lines
38365 &` tls_peerdn `& TLS peer DN on <= and => lines
38366 &` tls_resumption `& append * to cipher field
38367 &` tls_sni `& TLS SNI on <= lines
38368 &` unknown_in_list `& DNS lookup failed in list match
38370 &` all `& all of the above
38372 See also the &%slow_lookup_log%& main configuration option,
38373 section &<<SECID99>>&
38375 More details on each of these items follows:
38379 .cindex "log" "8BITMIME"
38380 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
38381 which may help in tracking down interoperability issues with ancient MTAs
38382 that are not 8bit clean. This is added to the &"<="& line, tagged with
38383 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
38384 &`7BIT`& and &`8BITMIME`& respectively.
38386 .cindex "&%warn%& ACL verb" "log when skipping"
38387 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
38388 its conditions cannot be evaluated, a log line to this effect is written if
38389 this log selector is set.
38391 .cindex "log" "rewriting"
38392 .cindex "rewriting" "logging"
38393 &%address_rewrite%&: This applies both to global rewrites and per-transport
38394 rewrites, but not to rewrites in filters run as an unprivileged user (because
38395 such users cannot access the log).
38397 .cindex "log" "full parentage"
38398 &%all_parents%&: Normally only the original and final addresses are logged on
38399 delivery lines; with this selector, intermediate parents are given in
38400 parentheses between them.
38402 .cindex "log" "Exim arguments"
38403 .cindex "Exim arguments, logging"
38404 &%arguments%&: This causes Exim to write the arguments with which it was called
38405 to the main log, preceded by the current working directory. This is a debugging
38406 feature, added to make it easier to find out how certain MUAs call
38407 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
38408 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
38409 that are empty or that contain white space are quoted. Non-printing characters
38410 are shown as escape sequences. This facility cannot log unrecognized arguments,
38411 because the arguments are checked before the configuration file is read. The
38412 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
38413 between the caller and Exim.
38415 .cindex "log" "connection rejections"
38416 &%connection_reject%&: A log entry is written whenever an incoming SMTP
38417 connection is rejected, for whatever reason.
38419 .cindex "log" "delayed delivery"
38420 .cindex "delayed delivery, logging"
38421 &%delay_delivery%&: A log entry is written whenever a delivery process is not
38422 started for an incoming message because the load is too high or too many
38423 messages were received on one connection. Logging does not occur if no delivery
38424 process is started because &%queue_only%& is set or &%-odq%& was used.
38426 .cindex "log" "delivery duration"
38427 &%deliver_time%&: For each delivery, the amount of real time it has taken to
38428 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
38429 If millisecond logging is enabled, short times will be shown with greater
38430 precision, eg. &`DT=0.304s`&.
38432 .cindex "log" "message size on delivery"
38433 .cindex "size" "of message"
38434 &%delivery_size%&: For each delivery, the size of message delivered is added to
38435 the &"=>"& line, tagged with S=.
38437 .cindex log "DKIM verification"
38438 .cindex DKIM "verification logging"
38439 &%dkim%&: For message acceptance log lines, when an DKIM signature in the header
38440 verifies successfully a tag of DKIM is added, with one of the verified domains.
38442 .cindex log "DKIM verification"
38443 .cindex DKIM "verification logging"
38444 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
38446 .cindex "log" "dnslist defer"
38447 .cindex "DNS list" "logging defer"
38448 .cindex "black list (DNS)"
38449 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
38450 DNS black list suffers a temporary error.
38453 .cindex dnssec logging
38454 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
38455 dns lookups gave secure results a tag of DS is added.
38456 For acceptance this covers the reverse and forward lookups for host name verification.
38457 It does not cover helo-name verification.
38458 For delivery this covers the SRV, MX, A and/or AAAA lookups.
38460 .cindex "log" "ETRN commands"
38461 .cindex "ETRN" "logging"
38462 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
38463 is run to determine whether or not it is actually accepted. An invalid ETRN
38464 command, or one received within a message transaction is not logged by this
38465 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
38467 .cindex "log" "host lookup failure"
38468 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
38469 any addresses, or when a lookup of an IP address fails to find a host name, a
38470 log line is written. This logging does not apply to direct DNS lookups when
38471 routing email addresses, but it does apply to &"byname"& lookups.
38473 .cindex "log" "ident timeout"
38474 .cindex "RFC 1413" "logging timeout"
38475 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
38476 client's ident port times out.
38478 .cindex "log" "incoming interface"
38479 .cindex "log" "local interface"
38480 .cindex "log" "local address and port"
38481 .cindex "TCP/IP" "logging local address and port"
38482 .cindex "interface" "logging"
38483 &%incoming_interface%&: The interface on which a message was received is added
38484 to the &"<="& line as an IP address in square brackets, tagged by I= and
38485 followed by a colon and the port number. The local interface and port are also
38486 added to other SMTP log lines, for example, &"SMTP connection from"&, to
38487 rejection lines, and (despite the name) to outgoing &"=>"& and &"->"& lines.
38488 The latter can be disabled by turning off the &%outgoing_interface%& option.
38490 .cindex log "incoming proxy address"
38491 .cindex proxy "logging proxy address"
38492 .cindex "TCP/IP" "logging proxy address"
38493 &%proxy%&: The internal (closest to the system running Exim) IP address
38494 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
38495 on a proxied connection
38496 or the &"=>"& line for a message delivered on a proxied connection.
38497 See &<<SECTproxyInbound>>& for more information.
38499 .cindex "log" "incoming remote port"
38500 .cindex "port" "logging remote"
38501 .cindex "TCP/IP" "logging incoming remote port"
38502 .vindex "&$sender_fullhost$&"
38503 .vindex "&$sender_rcvhost$&"
38504 &%incoming_port%&: The remote port number from which a message was received is
38505 added to log entries and &'Received:'& header lines, following the IP address
38506 in square brackets, and separated from it by a colon. This is implemented by
38507 changing the value that is put in the &$sender_fullhost$& and
38508 &$sender_rcvhost$& variables. Recording the remote port number has become more
38509 important with the widening use of NAT (see RFC 2505).
38511 .cindex "log" "dropped connection"
38512 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
38513 connection is unexpectedly dropped.
38515 .cindex "log" "millisecond timestamps"
38516 .cindex millisecond logging
38517 .cindex timestamps "millisecond, in logs"
38518 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
38519 appended to the seconds value.
38521 .cindex "log" "message id"
38522 &%msg_id%&: The value of the Message-ID: header.
38524 &%msg_id_created%&: The value of the Message-ID: header, when one had to be created.
38525 This will be either because the message is a bounce, or was submitted locally
38526 (submission mode) without one.
38527 The field identifier will have an asterix appended: &"id*="&.
38529 .cindex "log" "outgoing interface"
38530 .cindex "log" "local interface"
38531 .cindex "log" "local address and port"
38532 .cindex "TCP/IP" "logging local address and port"
38533 .cindex "interface" "logging"
38534 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
38535 interface on which a message was sent is added to delivery lines as an I= tag
38536 followed by IP address in square brackets. You can disable this by turning
38537 off the &%outgoing_interface%& option.
38539 .cindex "log" "outgoing remote port"
38540 .cindex "port" "logging outgoing remote"
38541 .cindex "TCP/IP" "logging outgoing remote port"
38542 &%outgoing_port%&: The remote port number is added to delivery log lines (those
38543 containing => tags) following the IP address.
38544 The local port is also added if &%incoming_interface%& and
38545 &%outgoing_interface%& are both enabled.
38546 This option is not included in the default setting, because for most ordinary
38547 configurations, the remote port number is always 25 (the SMTP port), and the
38548 local port is a random ephemeral port.
38550 .cindex "log" "process ids in"
38551 .cindex "pid (process id)" "in log lines"
38552 &%pid%&: The current process id is added to every log line, in square brackets,
38553 immediately after the time and date.
38555 .cindex log pipelining
38556 .cindex pipelining "logging outgoing"
38557 &%pipelining%&: A field is added to delivery and accept
38558 log lines when the ESMTP PIPELINING extension was used.
38559 The field is a single "L".
38561 On accept lines, where PIPELINING was offered but not used by the client,
38562 the field has a minus appended.
38564 .cindex "pipelining" "early connection"
38565 If Exim is built with the SUPPORT_PIPE_CONNECT build option
38566 accept "L" fields have a period appended if the feature was
38567 offered but not used, or an asterisk appended if used.
38568 Delivery "L" fields have an asterisk appended if used.
38571 .cindex "log" "queue run"
38572 .cindex "queue runner" "logging"
38573 &%queue_run%&: The start and end of every queue run are logged.
38575 .cindex "log" "queue time"
38576 &%queue_time%&: The amount of time the message has been in the queue on the
38577 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
38578 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
38579 includes reception time as well as the delivery time for the current address.
38580 This means that it may be longer than the difference between the arrival and
38581 delivery log line times, because the arrival log line is not written until the
38582 message has been successfully received.
38583 If millisecond logging is enabled, short times will be shown with greater
38584 precision, eg. &`QT=1.578s`&.
38586 &%queue_time_overall%&: The amount of time the message has been in the queue on
38587 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
38588 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
38589 message, so it includes reception time as well as the total delivery time.
38591 .cindex "log" "receive duration"
38592 &%receive_time%&: For each message, the amount of real time it has taken to
38593 perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
38594 If millisecond logging is enabled, short times will be shown with greater
38595 precision, eg. &`RT=0.204s`&.
38597 .cindex "log" "recipients"
38598 &%received_recipients%&: The recipients of a message are listed in the main log
38599 as soon as the message is received. The list appears at the end of the log line
38600 that is written when a message is received, preceded by the word &"for"&. The
38601 addresses are listed after they have been qualified, but before any rewriting
38603 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
38606 .cindex "log" "sender reception"
38607 &%received_sender%&: The unrewritten original sender of a message is added to
38608 the end of the log line that records the message's arrival, after the word
38609 &"from"& (before the recipients if &%received_recipients%& is also set).
38611 .cindex "log" "header lines for rejection"
38612 &%rejected_header%&: If a message's header has been received at the time a
38613 rejection is written to the reject log, the complete header is added to the
38614 log. Header logging can be turned off individually for messages that are
38615 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
38617 .cindex "log" "retry defer"
38618 &%retry_defer%&: A log line is written if a delivery is deferred because a
38619 retry time has not yet been reached. However, this &"retry time not reached"&
38620 message is always omitted from individual message logs after the first delivery
38623 .cindex "log" "return path"
38624 &%return_path_on_delivery%&: The return path that is being transmitted with
38625 the message is included in delivery and bounce lines, using the tag P=.
38626 This is omitted if no delivery actually happens, for example, if routing fails,
38627 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
38629 .cindex "log" "sender on delivery"
38630 &%sender_on_delivery%&: The message's sender address is added to every delivery
38631 and bounce line, tagged by F= (for &"from"&).
38632 This is the original sender that was received with the message; it is not
38633 necessarily the same as the outgoing return path.
38635 .cindex "log" "sender verify failure"
38636 &%sender_verify_fail%&: If this selector is unset, the separate log line that
38637 gives details of a sender verification failure is not written. Log lines for
38638 the rejection of SMTP commands contain just &"sender verify failed"&, so some
38641 .cindex "log" "size rejection"
38642 &%size_reject%&: A log line is written whenever a message is rejected because
38645 .cindex "log" "frozen messages; skipped"
38646 .cindex "frozen messages" "logging skipping"
38647 &%skip_delivery%&: A log line is written whenever a message is skipped during a
38648 queue run because it is frozen or because another process is already delivering
38650 .cindex "&""spool file is locked""&"
38651 The message that is written is &"spool file is locked"&.
38653 .cindex "log" "smtp confirmation"
38654 .cindex "SMTP" "logging confirmation"
38655 .cindex "LMTP" "logging confirmation"
38656 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
38657 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
38658 A number of MTAs (including Exim) return an identifying string in this
38661 .cindex "log" "SMTP connections"
38662 .cindex "SMTP" "logging connections"
38663 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
38664 established or closed, unless the connection is from a host that matches
38665 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
38666 only when the closure is unexpected.) This applies to connections from local
38667 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
38668 dropped in the middle of a message, a log line is always written, whether or
38669 not this selector is set, but otherwise nothing is written at the start and end
38670 of connections unless this selector is enabled.
38672 For TCP/IP connections to an Exim daemon, the current number of connections is
38673 included in the log message for each new connection, but note that the count is
38674 reset if the daemon is restarted.
38675 Also, because connections are closed (and the closure is logged) in
38676 subprocesses, the count may not include connections that have been closed but
38677 whose termination the daemon has not yet noticed. Thus, while it is possible to
38678 match up the opening and closing of connections in the log, the value of the
38679 logged counts may not be entirely accurate.
38681 .cindex "log" "SMTP transaction; incomplete"
38682 .cindex "SMTP" "logging incomplete transactions"
38683 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
38684 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
38685 and the message sender plus any accepted recipients are included in the log
38686 line. This can provide evidence of dictionary attacks.
38688 .cindex "log" "non-MAIL SMTP sessions"
38689 .cindex "MAIL" "logging session without"
38690 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
38691 connection terminates without having issued a MAIL command. This includes both
38692 the case when the connection is dropped, and the case when QUIT is used. It
38693 does not include cases where the connection is rejected right at the start (by
38694 an ACL, or because there are too many connections, or whatever). These cases
38695 already have their own log lines.
38697 The log line that is written contains the identity of the client in the usual
38698 way, followed by D= and a time, which records the duration of the connection.
38699 If the connection was authenticated, this fact is logged exactly as it is for
38700 an incoming message, with an A= item. If the connection was encrypted, CV=,
38701 DN=, and X= items may appear as they do for an incoming message, controlled by
38702 the same logging options.
38704 Finally, if any SMTP commands were issued during the connection, a C= item
38705 is added to the line, listing the commands that were used. For example,
38709 shows that the client issued QUIT straight after EHLO. If there were fewer
38710 than 20 commands, they are all listed. If there were more than 20 commands,
38711 the last 20 are listed, preceded by &"..."&. However, with the default
38712 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
38713 have been aborted before 20 non-mail commands are processed.
38715 &%smtp_mailauth%&: A third subfield with the authenticated sender,
38716 colon-separated, is appended to the A= item for a message arrival or delivery
38717 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
38718 was accepted or used.
38720 .cindex "log" "SMTP protocol error"
38721 .cindex "SMTP" "logging protocol error"
38722 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
38723 encountered. Exim does not have perfect detection of all protocol errors
38724 because of transmission delays and the use of pipelining. If PIPELINING has
38725 been advertised to a client, an Exim server assumes that the client will use
38726 it, and therefore it does not count &"expected"& errors (for example, RCPT
38727 received after rejecting MAIL) as protocol errors.
38729 .cindex "SMTP" "logging syntax errors"
38730 .cindex "SMTP" "syntax errors; logging"
38731 .cindex "SMTP" "unknown command; logging"
38732 .cindex "log" "unknown SMTP command"
38733 .cindex "log" "SMTP syntax error"
38734 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
38735 encountered. An unrecognized command is treated as a syntax error. For an
38736 external connection, the host identity is given; for an internal connection
38737 using &%-bs%& the sender identification (normally the calling user) is given.
38739 .cindex "log" "subject"
38740 .cindex "subject, logging"
38741 &%subject%&: The subject of the message is added to the arrival log line,
38742 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
38743 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
38744 specifies whether characters with values greater than 127 should be logged
38745 unchanged, or whether they should be rendered as escape sequences.
38747 .cindex "log" "certificate verification"
38749 .cindex DANE logging
38750 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
38751 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
38753 using a CA trust anchor,
38754 &`CA=dane`& if using a DNS trust anchor,
38755 and &`CV=no`& if not.
38757 .cindex "log" "TLS cipher"
38758 .cindex "TLS" "logging cipher"
38759 &%tls_cipher%&: When a message is sent or received over an encrypted
38760 connection, the cipher suite used is added to the log line, preceded by X=.
38762 .cindex "log" "TLS peer DN"
38763 .cindex "TLS" "logging peer DN"
38764 &%tls_peerdn%&: When a message is sent or received over an encrypted
38765 connection, and a certificate is supplied by the remote host, the peer DN is
38766 added to the log line, preceded by DN=.
38768 .cindex "log" "TLS resumption"
38769 .cindex "TLS" "logging session resumption"
38771 &%tls_resumption%&: When a message is sent or received over an encrypted
38772 connection and the TLS session resumed one used on a previous TCP connection,
38773 an asterisk is appended to the X= cipher field in the log line.
38776 .cindex "log" "TLS SNI"
38777 .cindex "TLS" "logging SNI"
38778 .cindex SNI logging
38779 &%tls_sni%&: When a message is received over an encrypted connection, and
38780 the remote host provided the Server Name Indication extension, the SNI is
38781 added to the log line, preceded by SNI=.
38783 .cindex "log" "DNS failure in list"
38784 &%unknown_in_list%&: This setting causes a log entry to be written when the
38785 result of a list match is failure because a DNS lookup failed.
38789 .section "Message log" "SECID260"
38790 .cindex "message" "log file for"
38791 .cindex "log" "message log; description of"
38792 .cindex "&_msglog_& directory"
38793 .oindex "&%preserve_message_logs%&"
38794 In addition to the general log files, Exim writes a log file for each message
38795 that it handles. The names of these per-message logs are the message ids, and
38796 they are kept in the &_msglog_& sub-directory of the spool directory. Each
38797 message log contains copies of the log lines that apply to the message. This
38798 makes it easier to inspect the status of an individual message without having
38799 to search the main log. A message log is deleted when processing of the message
38800 is complete, unless &%preserve_message_logs%& is set, but this should be used
38801 only with great care because they can fill up your disk very quickly.
38803 On a heavily loaded system, it may be desirable to disable the use of
38804 per-message logs, in order to reduce disk I/O. This can be done by setting the
38805 &%message_logs%& option false.
38811 . ////////////////////////////////////////////////////////////////////////////
38812 . ////////////////////////////////////////////////////////////////////////////
38814 .chapter "Exim utilities" "CHAPutils"
38815 .scindex IIDutils "utilities"
38816 A number of utility scripts and programs are supplied with Exim and are
38817 described in this chapter. There is also the Exim Monitor, which is covered in
38818 the next chapter. The utilities described here are:
38820 .itable none 0 0 3 7* left 15* left 40* left
38821 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
38822 "list what Exim processes are doing"
38823 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
38824 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
38825 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
38826 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
38828 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
38829 .irow &<<SECTmailstat>>& &'eximstats'& &&&
38830 "extract statistics from the log"
38831 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
38832 "check address acceptance from given IP"
38833 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
38834 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
38835 .irow &<<SECTdumpdb>>& &'exim_dumpdb'& "dump a hints database"
38836 .irow &<<SECTtidydb>>& &'exim_tidydb'& "clean up a hints database"
38837 .irow &<<SECTfixdb>>& &'exim_fixdb'& "patch a hints database"
38838 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
38841 Another utility that might be of use to sites with many MTAs is Tom Kistner's
38842 &'exilog'&. It provides log visualizations across multiple Exim servers. See
38843 &url(https://duncanthrax.net/exilog/) for details.
38848 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
38849 .cindex "&'exiwhat'&"
38850 .cindex "process, querying"
38852 On operating systems that can restart a system call after receiving a signal
38853 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
38854 a line describing what it is doing to the file &_exim-process.info_& in the
38855 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
38856 processes it can find, having first emptied the file. It then waits for one
38857 second to allow the Exim processes to react before displaying the results. In
38858 order to run &'exiwhat'& successfully you have to have sufficient privilege to
38859 send the signal to the Exim processes, so it is normally run as root.
38861 &*Warning*&: This is not an efficient process. It is intended for occasional
38862 use by system administrators. It is not sensible, for example, to set up a
38863 script that sends SIGUSR1 signals to Exim processes at short intervals.
38866 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
38867 varies in different operating systems. Not only are different options used,
38868 but the format of the output is different. For this reason, there are some
38869 system configuration options that configure exactly how &'exiwhat'& works. If
38870 it doesn't seem to be working for you, check the following compile-time
38873 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
38874 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
38875 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
38876 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
38878 An example of typical output from &'exiwhat'& is
38880 164 daemon: -q1h, listening on port 25
38881 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
38882 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
38883 [10.19.42.42] (editor@ref.example)
38884 10592 handling incoming call from [192.168.243.242]
38885 10628 accepting a local non-SMTP message
38887 The first number in the output line is the process number. The third line has
38888 been split here, in order to fit it on the page.
38892 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
38893 .cindex "&'exiqgrep'&"
38894 .cindex "queue" "grepping"
38895 This utility is a Perl script contributed by Matt Hubbard. It runs
38899 or (in case &*-a*& switch is specified)
38903 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
38904 contain alternate exim configuration the queue management might be using.
38906 to obtain a queue listing, and then greps the output to select messages
38907 that match given criteria. The following selection options are available:
38910 .vitem &*-f*&&~<&'regex'&>
38911 Match the sender address using a case-insensitive search. The field that is
38912 tested is enclosed in angle brackets, so you can test for bounce messages with
38916 .vitem &*-r*&&~<&'regex'&>
38917 Match a recipient address using a case-insensitive search. The field that is
38918 tested is not enclosed in angle brackets.
38920 .vitem &*-s*&&~<&'regex'&>
38921 Match against the size field.
38923 .vitem &*-y*&&~<&'seconds'&>
38924 Match messages that are younger than the given time.
38926 .vitem &*-o*&&~<&'seconds'&>
38927 Match messages that are older than the given time.
38930 Match only frozen messages.
38933 Match only non-frozen messages.
38935 .vitem &*-G*&&~<&'queuename'&>
38936 Match only messages in the given queue. Without this, the default queue is searched.
38939 The following options control the format of the output:
38943 Display only the count of matching messages.
38946 Long format &-- display the full message information as output by Exim. This is
38950 Display message ids only.
38953 Brief format &-- one line per message.
38956 Display messages in reverse order.
38959 Include delivered recipients in queue listing.
38962 There is one more option, &%-h%&, which outputs a list of options.
38966 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
38967 .cindex "&'exiqsumm'&"
38968 .cindex "queue" "summary"
38969 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
38970 -bp`& and produces a summary of the messages in the queue. Thus, you use it by
38971 running a command such as
38973 exim -bp | exiqsumm
38975 The output consists of one line for each domain that has messages waiting for
38976 it, as in the following example:
38978 3 2322 74m 66m msn.com.example
38980 Each line lists the number of pending deliveries for a domain, their total
38981 volume, and the length of time that the oldest and the newest messages have
38982 been waiting. Note that the number of pending deliveries is greater than the
38983 number of messages when messages have more than one recipient.
38985 A summary line is output at the end. By default the output is sorted on the
38986 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
38987 the output to be sorted by oldest message and by count of messages,
38988 respectively. There are also three options that split the messages for each
38989 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
38990 separates frozen messages, and &%-s%& separates messages according to their
38993 The output of &'exim -bp'& contains the original addresses in the message, so
38994 this also applies to the output from &'exiqsumm'&. No domains from addresses
38995 generated by aliasing or forwarding are included (unless the &%one_time%&
38996 option of the &(redirect)& router has been used to convert them into &"top
38997 level"& addresses).
39002 .section "Extracting specific information from the log (exigrep)" &&&
39004 .cindex "&'exigrep'&"
39005 .cindex "log" "extracts; grepping for"
39006 The &'exigrep'& utility is a Perl script that searches one or more main log
39007 files for entries that match a given pattern. When it finds a match, it
39008 extracts all the log entries for the relevant message, not just those that
39009 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
39010 given message, or all mail for a given user, or for a given host, for example.
39011 The input files can be in Exim log format or syslog format.
39012 If a matching log line is not associated with a specific message, it is
39013 included in &'exigrep'&'s output without any additional lines. The usage is:
39015 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
39017 If no log filenames are given on the command line, the standard input is read.
39019 The &%-t%& argument specifies a number of seconds. It adds an additional
39020 condition for message selection. Messages that are complete are shown only if
39021 they spent more than <&'n'&> seconds in the queue.
39023 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
39024 makes it case-sensitive. This may give a performance improvement when searching
39025 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
39026 option; with &%-I%& they do not. In both cases it is possible to change the
39027 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
39029 The &%-l%& option means &"literal"&, that is, treat all characters in the
39030 pattern as standing for themselves. Otherwise the pattern must be a Perl
39031 regular expression.
39033 The &%-v%& option inverts the matching condition. That is, a line is selected
39034 if it does &'not'& match the pattern.
39036 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
39037 that are generated as a result/response to a message that &'exigrep'& matched
39041 user_a sends a message to user_b, which generates a bounce back to user_b. If
39042 &'exigrep'& is used to search for &"user_a"&, only the first message will be
39043 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
39044 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
39045 when searching for &"user_a"& will show both messages since the bounce is
39046 &"related"& to or a &"result"& of the first message that was found by the
39049 If the location of a &'zcat'& command is known from the definition of
39050 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
39051 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
39052 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
39053 autodetection of some well known compression extensions.
39056 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
39057 .cindex "&'exipick'&"
39058 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
39059 lists messages from the queue according to a variety of criteria. For details
39060 of &'exipick'&'s facilities, run &'exipick'& with
39061 the &%--help%& option.
39064 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
39065 .cindex "log" "cycling local files"
39066 .cindex "cycling logs"
39067 .cindex "&'exicyclog'&"
39068 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
39069 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
39070 you are using log files with datestamps in their names (see section
39071 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
39072 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
39073 There are two command line options for &'exicyclog'&:
39075 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
39076 default that is set when Exim is built. The default default is 10.
39078 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
39079 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
39080 overriding the script's default, which is to find the setting from Exim's
39084 Each time &'exicyclog'& is run the filenames get &"shuffled down"& by one. If
39085 the main log filename is &_mainlog_& (the default) then when &'exicyclog'& is
39086 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
39087 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
39088 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
39089 logs are handled similarly.
39091 If the limit is greater than 99, the script uses 3-digit numbers such as
39092 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
39093 to one that is greater, or &'vice versa'&, you will have to fix the names of
39094 any existing log files.
39096 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
39097 the end are deleted. All files with numbers greater than 01 are compressed,
39098 using a compression command which is configured by the COMPRESS_COMMAND
39099 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
39100 root &%crontab%& entry of the form
39102 1 0 * * * su exim -c /usr/exim/bin/exicyclog
39104 assuming you have used the name &"exim"& for the Exim user. You can run
39105 &'exicyclog'& as root if you wish, but there is no need.
39109 .section "Mail statistics (eximstats)" "SECTmailstat"
39110 .cindex "statistics"
39111 .cindex "&'eximstats'&"
39112 A Perl script called &'eximstats'& is provided for extracting statistical
39113 information from log files. The output is either plain text, or HTML.
39114 . --- 2018-09-07: LogReport's Lire appears to be dead; website is a Yahoo Japan
39115 . --- 404 error and everything else points to that.
39117 The &'eximstats'& script has been hacked about quite a bit over time. The
39118 latest version is the result of some extensive revision by Steve Campbell. A
39119 lot of information is given by default, but there are options for suppressing
39120 various parts of it. Following any options, the arguments to the script are a
39121 list of files, which should be main log files. For example:
39123 eximstats -nr /var/spool/exim/log/mainlog.01
39125 By default, &'eximstats'& extracts information about the number and volume of
39126 messages received from or delivered to various hosts. The information is sorted
39127 both by message count and by volume, and the top fifty hosts in each category
39128 are listed on the standard output. Similar information, based on email
39129 addresses or domains instead of hosts can be requested by means of various
39130 options. For messages delivered and received locally, similar statistics are
39131 also produced per user.
39133 The output also includes total counts and statistics about delivery errors, and
39134 histograms showing the number of messages received and deliveries made in each
39135 hour of the day. A delivery with more than one address in its envelope (for
39136 example, an SMTP transaction with more than one RCPT command) is counted
39137 as a single delivery by &'eximstats'&.
39139 Though normally more deliveries than receipts are reported (as messages may
39140 have multiple recipients), it is possible for &'eximstats'& to report more
39141 messages received than delivered, even though the queue is empty at the start
39142 and end of the period in question. If an incoming message contains no valid
39143 recipients, no deliveries are recorded for it. A bounce message is handled as
39144 an entirely separate message.
39146 &'eximstats'& always outputs a grand total summary giving the volume and number
39147 of messages received and deliveries made, and the number of hosts involved in
39148 each case. It also outputs the number of messages that were delayed (that is,
39149 not completely delivered at the first attempt), and the number that had at
39150 least one address that failed.
39152 The remainder of the output is in sections that can be independently disabled
39153 or modified by various options. It consists of a summary of deliveries by
39154 transport, histograms of messages received and delivered per time interval
39155 (default per hour), information about the time messages spent in the queue,
39156 a list of relayed messages, lists of the top fifty sending hosts, local
39157 senders, destination hosts, and destination local users by count and by volume,
39158 and a list of delivery errors that occurred.
39160 The relay information lists messages that were actually relayed, that is, they
39161 came from a remote host and were directly delivered to some other remote host,
39162 without being processed (for example, for aliasing or forwarding) locally.
39164 There are quite a few options for &'eximstats'& to control exactly what it
39165 outputs. These are documented in the Perl script itself, and can be extracted
39166 by running the command &(perldoc)& on the script. For example:
39168 perldoc /usr/exim/bin/eximstats
39171 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
39172 .cindex "&'exim_checkaccess'&"
39173 .cindex "policy control" "checking access"
39174 .cindex "checking access"
39175 The &%-bh%& command line argument allows you to run a fake SMTP session with
39176 debugging output, in order to check what Exim is doing when it is applying
39177 policy controls to incoming SMTP mail. However, not everybody is sufficiently
39178 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
39179 sometimes you just want to answer the question &"Does this address have
39180 access?"& without bothering with any further details.
39182 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
39183 two arguments, an IP address and an email address:
39185 exim_checkaccess 10.9.8.7 A.User@a.domain.example
39187 The utility runs a call to Exim with the &%-bh%& option, to test whether the
39188 given email address would be accepted in a RCPT command in a TCP/IP
39189 connection from the host with the given IP address. The output of the utility
39190 is either the word &"accepted"&, or the SMTP error response, for example:
39193 550 Relay not permitted
39195 When running this test, the utility uses &`<>`& as the envelope sender address
39196 for the MAIL command, but you can change this by providing additional
39197 options. These are passed directly to the Exim command. For example, to specify
39198 that the test is to be run with the sender address &'himself@there.example'&
39201 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
39202 -f himself@there.example
39204 Note that these additional Exim command line items must be given after the two
39205 mandatory arguments.
39207 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
39208 while running its checks. You can run checks that include callouts by using
39209 &%-bhc%&, but this is not yet available in a &"packaged"& form.
39213 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
39214 .cindex "DBM" "building dbm files"
39215 .cindex "building DBM files"
39216 .cindex "&'exim_dbmbuild'&"
39217 .cindex "lower casing"
39218 .cindex "binary zero" "in lookup key"
39219 The &'exim_dbmbuild'& program reads an input file containing keys and data in
39220 the format used by the &(lsearch)& lookup (see section
39221 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
39222 names as keys and the remainder of the information as data. The lower-casing
39223 can be prevented by calling the program with the &%-nolc%& option.
39225 A terminating zero is included as part of the key string. This is expected by
39226 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
39227 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
39228 strings or the data strings. The &(dbmnz)& lookup type can be used with such
39231 The program requires two arguments: the name of the input file (which can be a
39232 single hyphen to indicate the standard input), and the name of the output file.
39233 It creates the output under a temporary name, and then renames it if all went
39237 If the native DB interface is in use (USE_DB is set in a compile-time
39238 configuration file &-- this is common in free versions of Unix) the two
39239 filenames must be different, because in this mode the Berkeley DB functions
39240 create a single output file using exactly the name given. For example,
39242 exim_dbmbuild /etc/aliases /etc/aliases.db
39244 reads the system alias file and creates a DBM version of it in
39245 &_/etc/aliases.db_&.
39247 In systems that use the &'ndbm'& routines (mostly proprietary versions of
39248 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
39249 environment, the suffixes are added to the second argument of
39250 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
39251 when the Berkeley functions are used in compatibility mode (though this is not
39252 recommended), because in that case it adds a &_.db_& suffix to the filename.
39254 If a duplicate key is encountered, the program outputs a warning, and when it
39255 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
39256 option is used. By default, only the first of a set of duplicates is used &--
39257 this makes it compatible with &(lsearch)& lookups. There is an option
39258 &%-lastdup%& which causes it to use the data for the last duplicate instead.
39259 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
39260 &%stderr%&. For other errors, where it doesn't actually make a new file, the
39266 .section "Finding individual retry times (exinext)" "SECTfinindret"
39267 .cindex "retry" "times"
39268 .cindex "&'exinext'&"
39269 A utility called &'exinext'& (mostly a Perl script) provides the ability to
39270 fish specific information out of the retry database. Given a mail domain (or a
39271 complete address), it looks up the hosts for that domain, and outputs any retry
39272 information for the hosts or for the domain. At present, the retry information
39273 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
39274 output. For example:
39276 $ exinext piglet@milne.fict.example
39277 kanga.milne.example:192.168.8.1 error 146: Connection refused
39278 first failed: 21-Feb-1996 14:57:34
39279 last tried: 21-Feb-1996 14:57:34
39280 next try at: 21-Feb-1996 15:02:34
39281 roo.milne.example:192.168.8.3 error 146: Connection refused
39282 first failed: 20-Jan-1996 13:12:08
39283 last tried: 21-Feb-1996 11:42:03
39284 next try at: 21-Feb-1996 19:42:03
39285 past final cutoff time
39287 You can also give &'exinext'& a local part, without a domain, and it
39288 will give any retry information for that local part in your default domain.
39289 A message id can be used to obtain retry information pertaining to a specific
39290 message. This exists only when an attempt to deliver a message to a remote host
39291 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
39292 &'exinext'& is not particularly efficient, but then it is not expected to be
39295 The &'exinext'& utility calls Exim to find out information such as the location
39296 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
39297 passed on to the &'exim'& commands. The first specifies an alternate Exim
39298 configuration file, and the second sets macros for use within the configuration
39299 file. These features are mainly to help in testing, but might also be useful in
39300 environments where more than one configuration file is in use.
39304 .section "Hints database maintenance" "SECThindatmai"
39305 .cindex "hints database" "maintenance"
39306 .cindex "maintaining Exim's hints database"
39307 Three utility programs are provided for maintaining the DBM files that Exim
39308 uses to contain its delivery hint information. Each program requires two
39309 arguments. The first specifies the name of Exim's spool directory, and the
39310 second is the name of the database it is to operate on. These are as follows:
39313 &'retry'&: the database of retry information
39315 &'wait-'&<&'transport name'&>: databases of information about messages waiting
39318 &'callout'&: the callout cache
39320 &'ratelimit'&: the data for implementing the ratelimit ACL condition
39323 &'tls'&: TLS session resumption data
39326 &'misc'&: other hints data
39329 The &'misc'& database is used for
39332 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
39334 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
39335 &(smtp)& transport)
39337 Limiting the concurrency of specific transports (when &%max_parallel%& is set
39343 .section "exim_dumpdb" "SECTdumpdb"
39344 .cindex "&'exim_dumpdb'&"
39345 The entire contents of a database are written to the standard output by the
39346 &'exim_dumpdb'& program, which has no options or arguments other than the
39347 spool and database names. For example, to dump the retry database:
39349 exim_dumpdb /var/spool/exim retry
39351 Two lines of output are produced for each entry:
39353 T:mail.ref.example:192.168.242.242 146 77 Connection refused
39354 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
39356 The first item on the first line is the key of the record. It starts with one
39357 of the letters R, or T, depending on whether it refers to a routing or
39358 transport retry. For a local delivery, the next part is the local address; for
39359 a remote delivery it is the name of the remote host, followed by its failing IP
39360 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
39361 transport). If the remote port is not the standard one (port 25), it is added
39362 to the IP address. Then there follows an error code, an additional error code,
39363 and a textual description of the error.
39365 The three times on the second line are the time of first failure, the time of
39366 the last delivery attempt, and the computed time for the next attempt. The line
39367 ends with an asterisk if the cutoff time for the last retry rule has been
39370 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
39371 consists of a host name followed by a list of ids for messages that are or were
39372 waiting to be delivered to that host. If there are a very large number for any
39373 one host, continuation records, with a sequence number added to the host name,
39374 may be seen. The data in these records is often out of date, because a message
39375 may be routed to several alternative hosts, and Exim makes no effort to keep
39380 .section "exim_tidydb" "SECTtidydb"
39381 .cindex "&'exim_tidydb'&"
39382 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
39383 database. If run with no options, it removes all records that are more than 30
39384 days old. The age is calculated from the date and time that the record was last
39385 updated. Note that, in the case of the retry database, it is &'not'& the time
39386 since the first delivery failure. Information about a host that has been down
39387 for more than 30 days will remain in the database, provided that the record is
39388 updated sufficiently often.
39390 The cutoff date can be altered by means of the &%-t%& option, which must be
39391 followed by a time. For example, to remove all records older than a week from
39392 the retry database:
39394 exim_tidydb -t 7d /var/spool/exim retry
39396 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
39397 message ids. In the former these appear as data in records keyed by host &--
39398 they were messages that were waiting for that host &-- and in the latter they
39399 are the keys for retry information for messages that have suffered certain
39400 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
39401 message ids in database records are those of messages that are still on the
39402 queue. Message ids for messages that no longer exist are removed from
39403 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
39404 For the &'retry'& database, records whose keys are non-existent message ids are
39405 removed. The &'exim_tidydb'& utility outputs comments on the standard output
39406 whenever it removes information from the database.
39408 Certain records are automatically removed by Exim when they are no longer
39409 needed, but others are not. For example, if all the MX hosts for a domain are
39410 down, a retry record is created for each one. If the primary MX host comes back
39411 first, its record is removed when Exim successfully delivers to it, but the
39412 records for the others remain because Exim has not tried to use those hosts.
39414 It is important, therefore, to run &'exim_tidydb'& periodically on all the
39415 hints databases. You should do this at a quiet time of day, because it requires
39416 a database to be locked (and therefore inaccessible to Exim) while it does its
39417 work. Removing records from a DBM file does not normally make the file smaller,
39418 but all the common DBM libraries are able to re-use the space that is released.
39419 After an initial phase of increasing in size, the databases normally reach a
39420 point at which they no longer get any bigger, as long as they are regularly
39423 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
39424 databases is likely to keep on increasing.
39429 .section "exim_fixdb" "SECTfixdb"
39430 .cindex "&'exim_fixdb'&"
39431 The &'exim_fixdb'& program is a utility for interactively modifying databases.
39432 Its main use is for testing Exim, but it might also be occasionally useful for
39433 getting round problems in a live system. It has no options, and its interface
39434 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
39435 key of a database record can then be entered, and the data for that record is
39438 If &"d"& is typed at the next prompt, the entire record is deleted. For all
39439 except the &'retry'& database, that is the only operation that can be carried
39440 out. For the &'retry'& database, each field is output preceded by a number, and
39441 data for individual fields can be changed by typing the field number followed
39442 by new data, for example:
39446 resets the time of the next delivery attempt. Time values are given as a
39447 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
39448 used as optional separators.
39453 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
39454 .cindex "mailbox" "maintenance"
39455 .cindex "&'exim_lock'&"
39456 .cindex "locking mailboxes"
39457 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
39458 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
39459 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
39460 a user agent while investigating a problem. The utility requires the name of
39461 the file as its first argument. If the locking is successful, the second
39462 argument is run as a command (using C's &[system()]& function); if there is no
39463 second argument, the value of the SHELL environment variable is used; if this
39464 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
39465 is unlocked and the utility ends. The following options are available:
39469 Use &[fcntl()]& locking on the open mailbox.
39472 Use &[flock()]& locking on the open mailbox, provided the operating system
39475 .vitem &%-interval%&
39476 This must be followed by a number, which is a number of seconds; it sets the
39477 interval to sleep between retries (default 3).
39479 .vitem &%-lockfile%&
39480 Create a lock file before opening the mailbox.
39483 Lock the mailbox using MBX rules.
39486 Suppress verification output.
39488 .vitem &%-retries%&
39489 This must be followed by a number; it sets the number of times to try to get
39490 the lock (default 10).
39492 .vitem &%-restore_time%&
39493 This option causes &%exim_lock%& to restore the modified and read times to the
39494 locked file before exiting. This allows you to access a locked mailbox (for
39495 example, to take a backup copy) without disturbing the times that the user
39498 .vitem &%-timeout%&
39499 This must be followed by a number, which is a number of seconds; it sets a
39500 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
39501 default), a non-blocking call is used.
39504 Generate verbose output.
39507 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
39508 default is to create a lock file and also to use &[fcntl()]& locking on the
39509 mailbox, which is the same as Exim's default. The use of &%-flock%& or
39510 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
39511 requires that the directory containing the file be writeable. Locking by lock
39512 file does not last forever; Exim assumes that a lock file is expired if it is
39513 more than 30 minutes old.
39515 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
39516 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
39517 to be taken out on the open mailbox, and an exclusive lock on the file
39518 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
39519 number of the mailbox file. When the locking is released, if an exclusive lock
39520 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
39522 The default output contains verification of the locking that takes place. The
39523 &%-v%& option causes some additional information to be given. The &%-q%& option
39524 suppresses all output except error messages.
39528 exim_lock /var/spool/mail/spqr
39530 runs an interactive shell while the file is locked, whereas
39532 &`exim_lock -q /var/spool/mail/spqr <<End`&
39533 <&'some commands'&>
39536 runs a specific non-interactive sequence of commands while the file is locked,
39537 suppressing all verification output. A single command can be run by a command
39540 exim_lock -q /var/spool/mail/spqr \
39541 "cp /var/spool/mail/spqr /some/where"
39543 Note that if a command is supplied, it must be entirely contained within the
39544 second argument &-- hence the quotes.
39548 . ////////////////////////////////////////////////////////////////////////////
39549 . ////////////////////////////////////////////////////////////////////////////
39551 .chapter "The Exim monitor" "CHAPeximon"
39552 .scindex IIDeximon "Exim monitor" "description"
39553 .cindex "X-windows"
39554 .cindex "&'eximon'&"
39555 .cindex "Local/eximon.conf"
39556 .cindex "&_exim_monitor/EDITME_&"
39557 The Exim monitor is an application which displays in an X window information
39558 about the state of Exim's queue and what Exim is doing. An admin user can
39559 perform certain operations on messages from this GUI interface; however all
39560 such facilities are also available from the command line, and indeed, the
39561 monitor itself makes use of the command line to perform any actions requested.
39565 .section "Running the monitor" "SECID264"
39566 The monitor is started by running the script called &'eximon'&. This is a shell
39567 script that sets up a number of environment variables, and then runs the
39568 binary called &_eximon.bin_&. The default appearance of the monitor window can
39569 be changed by editing the &_Local/eximon.conf_& file created by editing
39570 &_exim_monitor/EDITME_&. Comments in that file describe what the various
39571 parameters are for.
39573 The parameters that get built into the &'eximon'& script can be overridden for
39574 a particular invocation by setting up environment variables of the same names,
39575 preceded by &`EXIMON_`&. For example, a shell command such as
39577 EXIMON_LOG_DEPTH=400 eximon
39579 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
39580 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
39581 overrides the Exim log file configuration. This makes it possible to have
39582 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
39583 syslog messages are routed to a file on the local host.
39585 X resources can be used to change the appearance of the window in the normal
39586 way. For example, a resource setting of the form
39588 Eximon*background: gray94
39590 changes the colour of the background to light grey rather than white. The
39591 stripcharts are drawn with both the data lines and the reference lines in
39592 black. This means that the reference lines are not visible when on top of the
39593 data. However, their colour can be changed by setting a resource called
39594 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
39595 For example, if your X server is running Unix, you could set up lighter
39596 reference lines in the stripcharts by obeying
39599 Eximon*highlight: gray
39602 .cindex "admin user"
39603 In order to see the contents of messages in the queue, and to operate on them,
39604 &'eximon'& must either be run as root or by an admin user.
39606 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
39607 contain X11 resource parameters interpreted by the X11 library. In addition,
39608 if the first parameter starts with the string "gdb" then it is removed and the
39609 binary is invoked under gdb (the parameter is used as the gdb command-name, so
39610 versioned variants of gdb can be invoked).
39612 The monitor's window is divided into three parts. The first contains one or
39613 more stripcharts and two action buttons, the second contains a &"tail"& of the
39614 main log file, and the third is a display of the queue of messages awaiting
39615 delivery, with two more action buttons. The following sections describe these
39616 different parts of the display.
39621 .section "The stripcharts" "SECID265"
39622 .cindex "stripchart"
39623 The first stripchart is always a count of messages in the queue. Its name can
39624 be configured by setting QUEUE_STRIPCHART_NAME in the
39625 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
39626 configuration script by regular expression matches on log file entries, making
39627 it possible to display, for example, counts of messages delivered to certain
39628 hosts or using certain transports. The supplied defaults display counts of
39629 received and delivered messages, and of local and SMTP deliveries. The default
39630 period between stripchart updates is one minute; this can be adjusted by a
39631 parameter in the &_Local/eximon.conf_& file.
39633 The stripchart displays rescale themselves automatically as the value they are
39634 displaying changes. There are always 10 horizontal lines in each chart; the
39635 title string indicates the value of each division when it is greater than one.
39636 For example, &"x2"& means that each division represents a value of 2.
39638 It is also possible to have a stripchart which shows the percentage fullness of
39639 a particular disk partition, which is useful when local deliveries are confined
39640 to a single partition.
39642 .cindex "&%statvfs%& function"
39643 This relies on the availability of the &[statvfs()]& function or equivalent in
39644 the operating system. Most, but not all versions of Unix that support Exim have
39645 this. For this particular stripchart, the top of the chart always represents
39646 100%, and the scale is given as &"x10%"&. This chart is configured by setting
39647 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
39648 &_Local/eximon.conf_& file.
39653 .section "Main action buttons" "SECID266"
39654 .cindex "size" "of monitor window"
39655 .cindex "Exim monitor" "window size"
39656 .cindex "window size"
39657 Below the stripcharts there is an action button for quitting the monitor. Next
39658 to this is another button marked &"Size"&. They are placed here so that
39659 shrinking the window to its default minimum size leaves just the queue count
39660 stripchart and these two buttons visible. Pressing the &"Size"& button causes
39661 the window to expand to its maximum size, unless it is already at the maximum,
39662 in which case it is reduced to its minimum.
39664 When expanding to the maximum, if the window cannot be fully seen where it
39665 currently is, it is moved back to where it was the last time it was at full
39666 size. When it is expanding from its minimum size, the old position is
39667 remembered, and next time it is reduced to the minimum it is moved back there.
39669 The idea is that you can keep a reduced window just showing one or two
39670 stripcharts at a convenient place on your screen, easily expand it to show
39671 the full window when required, and just as easily put it back to what it was.
39672 The idea is copied from what the &'twm'& window manager does for its
39673 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
39674 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
39676 Normally, the monitor starts up with the window at its full size, but it can be
39677 built so that it starts up with the window at its smallest size, by setting
39678 START_SMALL=yes in &_Local/eximon.conf_&.
39682 .section "The log display" "SECID267"
39683 .cindex "log" "tail of; in monitor"
39684 The second section of the window is an area in which a display of the tail of
39685 the main log is maintained.
39686 To save space on the screen, the timestamp on each log line is shortened by
39687 removing the date and, if &%log_timezone%& is set, the timezone.
39688 The log tail is not available when the only destination for logging data is
39689 syslog, unless the syslog lines are routed to a local file whose name is passed
39690 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
39692 The log sub-window has a scroll bar at its lefthand side which can be used to
39693 move back to look at earlier text, and the up and down arrow keys also have a
39694 scrolling effect. The amount of log that is kept depends on the setting of
39695 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
39696 to use. When this is full, the earlier 50% of data is discarded &-- this is
39697 much more efficient than throwing it away line by line. The sub-window also has
39698 a horizontal scroll bar for accessing the ends of long log lines. This is the
39699 only means of horizontal scrolling; the right and left arrow keys are not
39700 available. Text can be cut from this part of the window using the mouse in the
39701 normal way. The size of this subwindow is controlled by parameters in the
39702 configuration file &_Local/eximon.conf_&.
39704 Searches of the text in the log window can be carried out by means of the ^R
39705 and ^S keystrokes, which default to a reverse and a forward search,
39706 respectively. The search covers only the text that is displayed in the window.
39707 It cannot go further back up the log.
39709 The point from which the search starts is indicated by a caret marker. This is
39710 normally at the end of the text in the window, but can be positioned explicitly
39711 by pointing and clicking with the left mouse button, and is moved automatically
39712 by a successful search. If new text arrives in the window when it is scrolled
39713 back, the caret remains where it is, but if the window is not scrolled back,
39714 the caret is moved to the end of the new text.
39716 Pressing ^R or ^S pops up a window into which the search text can be typed.
39717 There are buttons for selecting forward or reverse searching, for carrying out
39718 the search, and for cancelling. If the &"Search"& button is pressed, the search
39719 happens and the window remains so that further searches can be done. If the
39720 &"Return"& key is pressed, a single search is done and the window is closed. If
39721 ^C is typed the search is cancelled.
39723 The searching facility is implemented using the facilities of the Athena text
39724 widget. By default this pops up a window containing both &"search"& and
39725 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
39726 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
39727 However, the linkers in BSDI and HP-UX seem unable to handle an externally
39728 provided version of &%TextPop%& when the remaining parts of the text widget
39729 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
39730 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
39731 on these systems, at the expense of having unwanted items in the search popup
39736 .section "The queue display" "SECID268"
39737 .cindex "queue" "display in monitor"
39738 The bottom section of the monitor window contains a list of all messages that
39739 are in the queue, which includes those currently being received or delivered,
39740 as well as those awaiting delivery. The size of this subwindow is controlled by
39741 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
39742 at which it is updated is controlled by another parameter in the same file &--
39743 the default is 5 minutes, since queue scans can be quite expensive. However,
39744 there is an &"Update"& action button just above the display which can be used
39745 to force an update of the queue display at any time.
39747 When a host is down for some time, a lot of pending mail can build up for it,
39748 and this can make it hard to deal with other messages in the queue. To help
39749 with this situation there is a button next to &"Update"& called &"Hide"&. If
39750 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
39751 type anything in here and press &"Return"&, the text is added to a chain of
39752 such texts, and if every undelivered address in a message matches at least one
39753 of the texts, the message is not displayed.
39755 If there is an address that does not match any of the texts, all the addresses
39756 are displayed as normal. The matching happens on the ends of addresses so, for
39757 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
39758 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
39759 has been set up, a button called &"Unhide"& is displayed. If pressed, it
39760 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
39761 a hide request is automatically cancelled after one hour.
39763 While the dialogue box is displayed, you can't press any buttons or do anything
39764 else to the monitor window. For this reason, if you want to cut text from the
39765 queue display to use in the dialogue box, you have to do the cutting before
39766 pressing the &"Hide"& button.
39768 The queue display contains, for each unhidden queued message, the length of
39769 time it has been in the queue, the size of the message, the message id, the
39770 message sender, and the first undelivered recipient, all on one line. If it is
39771 a bounce message, the sender is shown as &"<>"&. If there is more than one
39772 recipient to which the message has not yet been delivered, subsequent ones are
39773 listed on additional lines, up to a maximum configured number, following which
39774 an ellipsis is displayed. Recipients that have already received the message are
39777 .cindex "frozen messages" "display"
39778 If a message is frozen, an asterisk is displayed at the left-hand side.
39780 The queue display has a vertical scroll bar, and can also be scrolled by means
39781 of the arrow keys. Text can be cut from it using the mouse in the normal way.
39782 The text searching facilities, as described above for the log window, are also
39783 available, but the caret is always moved to the end of the text when the queue
39784 display is updated.
39788 .section "The queue menu" "SECID269"
39789 .cindex "queue" "menu in monitor"
39790 If the &%shift%& key is held down and the left button is clicked when the mouse
39791 pointer is over the text for any message, an action menu pops up, and the first
39792 line of the queue display for the message is highlighted. This does not affect
39795 If you want to use some other event for popping up the menu, you can set the
39796 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
39797 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
39798 value set in this parameter is a standard X event description. For example, to
39799 run eximon using &%ctrl%& rather than &%shift%& you could use
39801 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
39803 The title of the menu is the message id, and it contains entries which act as
39807 &'message log'&: The contents of the message log for the message are displayed
39808 in a new text window.
39810 &'headers'&: Information from the spool file that contains the envelope
39811 information and headers is displayed in a new text window. See chapter
39812 &<<CHAPspool>>& for a description of the format of spool files.
39814 &'body'&: The contents of the spool file containing the body of the message are
39815 displayed in a new text window. There is a default limit of 20,000 bytes to the
39816 amount of data displayed. This can be changed by setting the BODY_MAX
39817 option at compile time, or the EXIMON_BODY_MAX option at runtime.
39819 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
39820 delivery of the message. This causes an automatic thaw if the message is
39821 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
39822 a new text window. The delivery is run in a separate process, to avoid holding
39823 up the monitor while the delivery proceeds.
39825 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
39826 that the message be frozen.
39828 .cindex "thawing messages"
39829 .cindex "unfreezing messages"
39830 .cindex "frozen messages" "thawing"
39831 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
39832 that the message be thawed.
39834 .cindex "delivery" "forcing failure"
39835 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
39836 that Exim gives up trying to deliver the message. A bounce message is generated
39837 for any remaining undelivered addresses.
39839 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
39840 that the message be deleted from the system without generating a bounce
39843 &'add recipient'&: A dialog box is displayed into which a recipient address can
39844 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
39845 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
39846 Otherwise it must be entered as a fully qualified address. Pressing RETURN
39847 causes a call to Exim to be made using the &%-Mar%& option to request that an
39848 additional recipient be added to the message, unless the entry box is empty, in
39849 which case no action is taken.
39851 &'mark delivered'&: A dialog box is displayed into which a recipient address
39852 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
39853 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
39854 Otherwise it must be entered as a fully qualified address. Pressing RETURN
39855 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
39856 recipient address as already delivered, unless the entry box is empty, in which
39857 case no action is taken.
39859 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
39860 mark all recipient addresses as already delivered.
39862 &'edit sender'&: A dialog box is displayed initialized with the current
39863 sender's address. Pressing RETURN causes a call to Exim to be made using the
39864 &%-Mes%& option to replace the sender address, unless the entry box is empty,
39865 in which case no action is taken. If you want to set an empty sender (as in
39866 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
39867 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
39868 the address is qualified with that domain.
39871 When a delivery is forced, a window showing the &%-v%& output is displayed. In
39872 other cases when a call to Exim is made, if there is any output from Exim (in
39873 particular, if the command fails) a window containing the command and the
39874 output is displayed. Otherwise, the results of the action are normally apparent
39875 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
39876 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
39877 if no output is generated.
39879 The queue display is automatically updated for actions such as freezing and
39880 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
39881 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
39882 force an update of the display after one of these actions.
39884 In any text window that is displayed as result of a menu action, the normal
39885 cut-and-paste facility is available, and searching can be carried out using ^R
39886 and ^S, as described above for the log tail window.
39893 . ////////////////////////////////////////////////////////////////////////////
39894 . ////////////////////////////////////////////////////////////////////////////
39896 .chapter "Security considerations" "CHAPsecurity"
39897 .scindex IIDsecurcon "security" "discussion of"
39898 This chapter discusses a number of issues concerned with security, some of
39899 which are also covered in other parts of this manual.
39901 For reasons that this author does not understand, some people have promoted
39902 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
39903 existence of this chapter in the documentation. However, the intent of the
39904 chapter is simply to describe the way Exim works in relation to certain
39905 security concerns, not to make any specific claims about the effectiveness of
39906 its security as compared with other MTAs.
39908 What follows is a description of the way Exim is supposed to be. Best efforts
39909 have been made to try to ensure that the code agrees with the theory, but an
39910 absence of bugs can never be guaranteed. Any that are reported will get fixed
39911 as soon as possible.
39914 .section "Building a more &""hardened""& Exim" "SECID286"
39915 .cindex "security" "build-time features"
39916 There are a number of build-time options that can be set in &_Local/Makefile_&
39917 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
39918 Exim administrator who does not have the root password, or by someone who has
39919 penetrated the Exim (but not the root) account. These options are as follows:
39922 ALT_CONFIG_PREFIX can be set to a string that is required to match the
39923 start of any filenames used with the &%-C%& option. When it is set, these
39924 filenames are also not allowed to contain the sequence &"/../"&. (However, if
39925 the value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
39926 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
39927 default setting for &%ALT_CONFIG_PREFIX%&.
39929 If the permitted configuration files are confined to a directory to
39930 which only root has access, this guards against someone who has broken
39931 into the Exim account from running a privileged Exim with an arbitrary
39932 configuration file, and using it to break into other accounts.
39935 If a non-trusted configuration file (i.e. not the default configuration file
39936 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
39937 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
39938 the next item), then root privilege is retained only if the caller of Exim is
39939 root. This locks out the possibility of testing a configuration using &%-C%&
39940 right through message reception and delivery, even if the caller is root. The
39941 reception works, but by that time, Exim is running as the Exim user, so when
39942 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
39943 privilege to be lost. However, root can test reception and delivery using two
39947 The WHITELIST_D_MACROS build option declares some macros to be safe to override
39948 with &%-D%& if the real uid is one of root, the Exim run-time user or the
39949 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
39950 requiring the run-time value supplied to &%-D%& to match a regex that errs on
39951 the restrictive side. Requiring build-time selection of safe macros is onerous
39952 but this option is intended solely as a transition mechanism to permit
39953 previously-working configurations to continue to work after release 4.73.
39955 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
39958 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
39959 never to be used for any deliveries. This is like the &%never_users%& runtime
39960 option, but it cannot be overridden; the runtime option adds additional users
39961 to the list. The default setting is &"root"&; this prevents a non-root user who
39962 is permitted to modify the runtime file from using Exim as a way to get root.
39967 .section "Root privilege" "SECID270"
39969 .cindex "root privilege"
39970 The Exim binary is normally setuid to root, which means that it gains root
39971 privilege (runs as root) when it starts execution. In some special cases (for
39972 example, when the daemon is not in use and there are no local deliveries), it
39973 may be possible to run Exim setuid to some user other than root. This is
39974 discussed in the next section. However, in most installations, root privilege
39975 is required for two things:
39978 To set up a socket connected to the standard SMTP port (25) when initialising
39979 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
39982 To be able to change uid and gid in order to read users' &_.forward_& files and
39983 perform local deliveries as the receiving user or as specified in the
39987 It is not necessary to be root to do any of the other things Exim does, such as
39988 receiving messages and delivering them externally over SMTP, and it is
39989 obviously more secure if Exim does not run as root except when necessary.
39990 For this reason, a user and group for Exim to use must be defined in
39991 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
39992 group"&. Their values can be changed by the runtime configuration, though this
39993 is not recommended. Often a user called &'exim'& is used, but some sites use
39994 &'mail'& or another user name altogether.
39996 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
39997 abdication; the process cannot regain root afterwards. Prior to release 4.00,
39998 &[seteuid()]& was used in some circumstances, but this is no longer the case.
40000 After a new Exim process has interpreted its command line options, it changes
40001 uid and gid in the following cases:
40006 If the &%-C%& option is used to specify an alternate configuration file, or if
40007 the &%-D%& option is used to define macro values for the configuration, and the
40008 calling process is not running as root, the uid and gid are changed to those of
40009 the calling process.
40010 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
40011 option may not be used at all.
40012 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
40013 can be supplied if the calling process is running as root, the Exim run-time
40014 user or CONFIGURE_OWNER, if defined.
40019 If the expansion test option (&%-be%&) or one of the filter testing options
40020 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
40023 If the process is not a daemon process or a queue runner process or a delivery
40024 process or a process for testing address routing (started with &%-bt%&), the
40025 uid and gid are changed to the Exim user and group. This means that Exim always
40026 runs under its own uid and gid when receiving messages. This also applies when
40027 testing address verification
40030 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
40033 For a daemon, queue runner, delivery, or address testing process, the uid
40034 remains as root at this stage, but the gid is changed to the Exim group.
40037 The processes that initially retain root privilege behave as follows:
40040 A daemon process changes the gid to the Exim group and the uid to the Exim
40041 user after setting up one or more listening sockets. The &[initgroups()]&
40042 function is called, so that if the Exim user is in any additional groups, they
40043 will be used during message reception.
40045 A queue runner process retains root privilege throughout its execution. Its
40046 job is to fork a controlled sequence of delivery processes.
40048 A delivery process retains root privilege throughout most of its execution,
40049 but any actual deliveries (that is, the transports themselves) are run in
40050 subprocesses which always change to a non-root uid and gid. For local
40051 deliveries this is typically the uid and gid of the owner of the mailbox; for
40052 remote deliveries, the Exim uid and gid are used. Once all the delivery
40053 subprocesses have been run, a delivery process changes to the Exim uid and gid
40054 while doing post-delivery tidying up such as updating the retry database and
40055 generating bounce and warning messages.
40057 While the recipient addresses in a message are being routed, the delivery
40058 process runs as root. However, if a user's filter file has to be processed,
40059 this is done in a subprocess that runs under the individual user's uid and
40060 gid. A system filter is run as root unless &%system_filter_user%& is set.
40062 A process that is testing addresses (the &%-bt%& option) runs as root so that
40063 the routing is done in the same environment as a message delivery.
40069 .section "Running Exim without privilege" "SECTrunexiwitpri"
40070 .cindex "privilege, running without"
40071 .cindex "unprivileged running"
40072 .cindex "root privilege" "running without"
40073 Some installations like to run Exim in an unprivileged state for more of its
40074 operation, for added security. Support for this mode of operation is provided
40075 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
40076 gid are changed to the Exim user and group at the start of a delivery process
40077 (and also queue runner and address testing processes). This means that address
40078 routing is no longer run as root, and the deliveries themselves cannot change
40082 .cindex "daemon" "restarting"
40083 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
40084 that the daemon can still be started in the usual way, and it can respond
40085 correctly to SIGHUP because the re-invocation regains root privilege.
40087 An alternative approach is to make Exim setuid to the Exim user and also setgid
40088 to the Exim group. If you do this, the daemon must be started from a root
40089 process. (Calling Exim from a root process makes it behave in the way it does
40090 when it is setuid root.) However, the daemon cannot restart itself after a
40091 SIGHUP signal because it cannot regain privilege.
40093 It is still useful to set &%deliver_drop_privilege%& in this case, because it
40094 stops Exim from trying to re-invoke itself to do a delivery after a message has
40095 been received. Such a re-invocation is a waste of resources because it has no
40098 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
40099 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
40100 to the Exim user seems a clean approach, but there is one complication:
40102 In this style of operation, Exim is running with the real uid and gid set to
40103 those of the calling process, and the effective uid/gid set to Exim's values.
40104 Ideally, any association with the calling process' uid/gid should be dropped,
40105 that is, the real uid/gid should be reset to the effective values so as to
40106 discard any privileges that the caller may have. While some operating systems
40107 have a function that permits this action for a non-root effective uid, quite a
40108 number of them do not. Because of this lack of standardization, Exim does not
40109 address this problem at this time.
40111 For this reason, the recommended approach for &"mostly unprivileged"& running
40112 is to keep the Exim binary setuid to root, and to set
40113 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
40114 be used in the most straightforward way.
40116 If you configure Exim not to run delivery processes as root, there are a
40117 number of restrictions on what you can do:
40120 You can deliver only as the Exim user/group. You should explicitly use the
40121 &%user%& and &%group%& options to override routers or local transports that
40122 normally deliver as the recipient. This makes sure that configurations that
40123 work in this mode function the same way in normal mode. Any implicit or
40124 explicit specification of another user causes an error.
40126 Use of &_.forward_& files is severely restricted, such that it is usually
40127 not worthwhile to include them in the configuration.
40129 Users who wish to use &_.forward_& would have to make their home directory and
40130 the file itself accessible to the Exim user. Pipe and append-to-file entries,
40131 and their equivalents in Exim filters, cannot be used. While they could be
40132 enabled in the Exim user's name, that would be insecure and not very useful.
40134 Unless the local user mailboxes are all owned by the Exim user (possible in
40135 some POP3 or IMAP-only environments):
40138 They must be owned by the Exim group and be writeable by that group. This
40139 implies you must set &%mode%& in the appendfile configuration, as well as the
40140 mode of the mailbox files themselves.
40142 You must set &%no_check_owner%&, since most or all of the files will not be
40143 owned by the Exim user.
40145 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
40146 on a newly created mailbox when unprivileged. This also implies that new
40147 mailboxes need to be created manually.
40152 These restrictions severely restrict what can be done in local deliveries.
40153 However, there are no restrictions on remote deliveries. If you are running a
40154 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
40155 gives more security at essentially no cost.
40157 If you are using the &%mua_wrapper%& facility (see chapter
40158 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
40163 .section "Delivering to local files" "SECID271"
40164 Full details of the checks applied by &(appendfile)& before it writes to a file
40165 are given in chapter &<<CHAPappendfile>>&.
40169 .section "Running local commands" "SECTsecconslocalcmds"
40170 .cindex "security" "local commands"
40171 .cindex "security" "command injection attacks"
40172 There are a number of ways in which an administrator can configure Exim to run
40173 commands based upon received, untrustworthy, data. Further, in some
40174 configurations a user who can control a &_.forward_& file can also arrange to
40175 run commands. Configuration to check includes, but is not limited to:
40178 Use of &%use_shell%& in the pipe transport: various forms of shell command
40179 injection may be possible with this option present. It is dangerous and should
40180 be used only with considerable caution. Consider constraints which whitelist
40181 allowed characters in a variable which is to be used in a pipe transport that
40182 has &%use_shell%& enabled.
40184 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
40185 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
40186 &_.forward_& files in a redirect router. If Exim is running on a central mail
40187 hub to which ordinary users do not have shell access, but home directories are
40188 NFS mounted (for instance) then administrators should review the list of these
40189 forbid options available, and should bear in mind that the options that may
40190 need forbidding can change as new features are added between releases.
40192 The &%${run...}%& expansion item does not use a shell by default, but
40193 administrators can configure use of &_/bin/sh_& as part of the command.
40194 Such invocations should be viewed with prejudicial suspicion.
40196 Administrators who use embedded Perl are advised to explore how Perl's
40197 taint checking might apply to their usage.
40199 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
40200 administrators are well advised to view its use with suspicion, in case (for
40201 instance) it allows a local-part to contain embedded Exim directives.
40203 Use of &%${match_local_part...}%& and friends becomes more dangerous if
40204 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
40205 each can reference arbitrary lists and files, rather than just being a list
40207 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
40208 real-world security vulnerabilities caused by its use with untrustworthy data
40209 injected in, for SQL injection attacks.
40210 Consider the use of the &%inlisti%& expansion condition instead.
40216 .section "Trust in configuration data" "SECTsecconfdata"
40217 .cindex "security" "data sources"
40218 .cindex "security" "regular expressions"
40219 .cindex "regular expressions" "security"
40220 .cindex "PCRE" "security"
40221 If configuration data for Exim can come from untrustworthy sources, there
40222 are some issues to be aware of:
40225 Use of &%${expand...}%& may provide a path for shell injection attacks.
40227 Letting untrusted data provide a regular expression is unwise.
40229 Using &%${match...}%& to apply a fixed regular expression against untrusted
40230 data may result in pathological behaviour within PCRE. Be aware of what
40231 "backtracking" means and consider options for being more strict with a regular
40232 expression. Avenues to explore include limiting what can match (avoiding &`.`&
40233 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
40234 possessive quantifiers or just not using regular expressions against untrusted
40237 It can be important to correctly use &%${quote:...}%&,
40238 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
40239 items to ensure that data is correctly constructed.
40241 Some lookups might return multiple results, even though normal usage is only
40242 expected to yield one result.
40248 .section "IPv4 source routing" "SECID272"
40249 .cindex "source routing" "in IP packets"
40250 .cindex "IP source routing"
40251 Many operating systems suppress IP source-routed packets in the kernel, but
40252 some cannot be made to do this, so Exim does its own check. It logs incoming
40253 IPv4 source-routed TCP calls, and then drops them. Things are all different in
40254 IPv6. No special checking is currently done.
40258 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
40259 Support for these SMTP commands is disabled by default. If required, they can
40260 be enabled by defining suitable ACLs.
40265 .section "Privileged users" "SECID274"
40266 .cindex "trusted users"
40267 .cindex "admin user"
40268 .cindex "privileged user"
40269 .cindex "user" "trusted"
40270 .cindex "user" "admin"
40271 Exim recognizes two sets of users with special privileges. Trusted users are
40272 able to submit new messages to Exim locally, but supply their own sender
40273 addresses and information about a sending host. For other users submitting
40274 local messages, Exim sets up the sender address from the uid, and doesn't
40275 permit a remote host to be specified.
40278 However, an untrusted user is permitted to use the &%-f%& command line option
40279 in the special form &%-f <>%& to indicate that a delivery failure for the
40280 message should not cause an error report. This affects the message's envelope,
40281 but it does not affect the &'Sender:'& header. Untrusted users may also be
40282 permitted to use specific forms of address with the &%-f%& option by setting
40283 the &%untrusted_set_sender%& option.
40285 Trusted users are used to run processes that receive mail messages from some
40286 other mail domain and pass them on to Exim for delivery either locally, or over
40287 the Internet. Exim trusts a caller that is running as root, as the Exim user,
40288 as any user listed in the &%trusted_users%& configuration option, or under any
40289 group listed in the &%trusted_groups%& option.
40291 Admin users are permitted to do things to the messages on Exim's queue. They
40292 can freeze or thaw messages, cause them to be returned to their senders, remove
40293 them entirely, or modify them in various ways. In addition, admin users can run
40294 the Exim monitor and see all the information it is capable of providing, which
40295 includes the contents of files on the spool.
40299 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
40300 delivery of messages on its queue is restricted to admin users. This
40301 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
40302 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
40303 queue is also restricted to admin users. This restriction can be relaxed by
40304 setting &%no_queue_list_requires_admin%&.
40306 Exim recognizes an admin user if the calling process is running as root or as
40307 the Exim user or if any of the groups associated with the calling process is
40308 the Exim group. It is not necessary actually to be running under the Exim
40309 group. However, if admin users who are not root or the Exim user are to access
40310 the contents of files on the spool via the Exim monitor (which runs
40311 unprivileged), Exim must be built to allow group read access to its spool
40314 By default, regular users are trusted to perform basic testing and
40315 introspection commands, as themselves. This setting can be tightened by
40316 setting the &%commandline_checks_require_admin%& option.
40317 This affects most of the checking options,
40318 such as &%-be%& and anything else &%-b*%&.
40321 .section "Spool files" "SECID275"
40322 .cindex "spool directory" "files"
40323 Exim's spool directory and everything it contains is owned by the Exim user and
40324 set to the Exim group. The mode for spool files is defined in the
40325 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
40326 any user who is a member of the Exim group can access these files.
40330 .section "Use of argv[0]" "SECID276"
40331 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
40332 of specific strings, Exim assumes certain options. For example, calling Exim
40333 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
40334 to calling it with the option &%-bS%&. There are no security implications in
40339 .section "Use of %f formatting" "SECID277"
40340 The only use made of &"%f"& by Exim is in formatting load average values. These
40341 are actually stored in integer variables as 1000 times the load average.
40342 Consequently, their range is limited and so therefore is the length of the
40347 .section "Embedded Exim path" "SECID278"
40348 Exim uses its own path name, which is embedded in the code, only when it needs
40349 to re-exec in order to regain root privilege. Therefore, it is not root when it
40350 does so. If some bug allowed the path to get overwritten, it would lead to an
40351 arbitrary program's being run as exim, not as root.
40355 .section "Dynamic module directory" "SECTdynmoddir"
40356 Any dynamically loadable modules must be installed into the directory
40357 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
40361 .section "Use of sprintf()" "SECID279"
40362 .cindex "&[sprintf()]&"
40363 A large number of occurrences of &"sprintf"& in the code are actually calls to
40364 &'string_sprintf()'&, a function that returns the result in malloc'd store.
40365 The intermediate formatting is done into a large fixed buffer by a function
40366 that runs through the format string itself, and checks the length of each
40367 conversion before performing it, thus preventing buffer overruns.
40369 The remaining uses of &[sprintf()]& happen in controlled circumstances where
40370 the output buffer is known to be sufficiently long to contain the converted
40375 .section "Use of debug_printf() and log_write()" "SECID280"
40376 Arbitrary strings are passed to both these functions, but they do their
40377 formatting by calling the function &'string_vformat()'&, which runs through
40378 the format string itself, and checks the length of each conversion.
40382 .section "Use of strcat() and strcpy()" "SECID281"
40383 These are used only in cases where the output buffer is known to be large
40384 enough to hold the result.
40385 .ecindex IIDsecurcon
40390 . ////////////////////////////////////////////////////////////////////////////
40391 . ////////////////////////////////////////////////////////////////////////////
40393 .chapter "Format of spool files" "CHAPspool"
40394 .scindex IIDforspo1 "format" "spool files"
40395 .scindex IIDforspo2 "spool directory" "format of files"
40396 .scindex IIDforspo3 "spool files" "format of"
40397 .cindex "spool files" "editing"
40398 A message on Exim's queue consists of two files, whose names are the message id
40399 followed by -D and -H, respectively. The data portion of the message is kept in
40400 the -D file on its own. The message's envelope, status, and headers are all
40401 kept in the -H file, whose format is described in this chapter. Each of these
40402 two files contains the final component of its own name as its first line. This
40403 is insurance against disk crashes where the directory is lost but the files
40404 themselves are recoverable.
40406 The file formats may be changed, or new formats added, at any release.
40407 Spool files are not intended as an interface to other programs
40408 and should not be used as such.
40410 Some people are tempted into editing -D files in order to modify messages. You
40411 need to be extremely careful if you do this; it is not recommended and you are
40412 on your own if you do it. Here are some of the pitfalls:
40415 You must ensure that Exim does not try to deliver the message while you are
40416 fiddling with it. The safest way is to take out a write lock on the -D file,
40417 which is what Exim itself does, using &[fcntl()]&. If you update the file in
40418 place, the lock will be retained. If you write a new file and rename it, the
40419 lock will be lost at the instant of rename.
40421 .vindex "&$body_linecount$&"
40422 If you change the number of lines in the file, the value of
40423 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
40424 cause incomplete transmission of messages or undeliverable messages.
40426 If the message is in MIME format, you must take care not to break it.
40428 If the message is cryptographically signed, any change will invalidate the
40431 All in all, modifying -D files is fraught with danger.
40433 Files whose names end with -J may also be seen in the &_input_& directory (or
40434 its subdirectories when &%split_spool_directory%& is set). These are journal
40435 files, used to record addresses to which the message has been delivered during
40436 the course of a delivery attempt. If there are still undelivered recipients at
40437 the end, the -H file is updated, and the -J file is deleted. If, however, there
40438 is some kind of crash (for example, a power outage) before this happens, the -J
40439 file remains in existence. When Exim next processes the message, it notices the
40440 -J file and uses it to update the -H file before starting the next delivery
40443 Files whose names end with -K or .eml may also be seen in the spool.
40444 These are temporaries used for DKIM or malware processing, when that is used.
40445 They should be tidied up by normal operations; any old ones are probably
40446 relics of crashes and can be removed.
40448 .section "Format of the -H file" "SECID282"
40449 .cindex "uid (user id)" "in spool file"
40450 .cindex "gid (group id)" "in spool file"
40451 The second line of the -H file contains the login name for the uid of the
40452 process that called Exim to read the message, followed by the numerical uid and
40453 gid. For a locally generated message, this is normally the user who sent the
40454 message. For a message received over TCP/IP via the daemon, it is
40455 normally the Exim user.
40457 The third line of the file contains the address of the message's sender as
40458 transmitted in the envelope, contained in angle brackets. The sender address is
40459 empty for bounce messages. For incoming SMTP mail, the sender address is given
40460 in the MAIL command. For locally generated mail, the sender address is
40461 created by Exim from the login name of the current user and the configured
40462 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
40463 leading &"From&~"& line if the caller is trusted, or if the supplied address is
40464 &"<>"& or an address that matches &%untrusted_set_senders%&.
40466 The fourth line contains two numbers. The first is the time that the message
40467 was received, in the conventional Unix form &-- the number of seconds since the
40468 start of the epoch. The second number is a count of the number of messages
40469 warning of delayed delivery that have been sent to the sender.
40471 There follow a number of lines starting with a hyphen. These can appear in any
40472 order, and are omitted when not relevant:
40475 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
40476 This item is obsolete, and is not generated from Exim release 4.61 onwards;
40477 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
40478 recognized, to provide backward compatibility. In the old format, a line of
40479 this form is present for every ACL variable that is not empty. The number
40480 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
40481 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
40482 the data string for the variable. The string itself starts at the beginning of
40483 the next line, and is followed by a newline character. It may contain internal
40486 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
40487 A line of this form is present for every ACL connection variable that is
40488 defined. Note that there is a space between &%-aclc%& and the rest of the name.
40489 The length is the length of the data string for the variable. The string itself
40490 starts at the beginning of the next line, and is followed by a newline
40491 character. It may contain internal newlines.
40493 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
40494 A line of this form is present for every ACL message variable that is defined.
40495 Note that there is a space between &%-aclm%& and the rest of the name. The
40496 length is the length of the data string for the variable. The string itself
40497 starts at the beginning of the next line, and is followed by a newline
40498 character. It may contain internal newlines.
40500 .vitem "&%-active_hostname%&&~<&'hostname'&>"
40501 This is present if, when the message was received over SMTP, the value of
40502 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
40504 .vitem &%-allow_unqualified_recipient%&
40505 This is present if unqualified recipient addresses are permitted in header
40506 lines (to stop such addresses from being qualified if rewriting occurs at
40507 transport time). Local messages that were input using &%-bnq%& and remote
40508 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
40510 .vitem &%-allow_unqualified_sender%&
40511 This is present if unqualified sender addresses are permitted in header lines
40512 (to stop such addresses from being qualified if rewriting occurs at transport
40513 time). Local messages that were input using &%-bnq%& and remote messages from
40514 hosts that match &%sender_unqualified_hosts%& set this flag.
40516 .vitem "&%-auth_id%&&~<&'text'&>"
40517 The id information for a message received on an authenticated SMTP connection
40518 &-- the value of the &$authenticated_id$& variable.
40520 .vitem "&%-auth_sender%&&~<&'address'&>"
40521 The address of an authenticated sender &-- the value of the
40522 &$authenticated_sender$& variable.
40524 .vitem "&%-body_linecount%&&~<&'number'&>"
40525 This records the number of lines in the body of the message, and is
40526 present unless &%-spool_file_wireformat%& is.
40528 .vitem "&%-body_zerocount%&&~<&'number'&>"
40529 This records the number of binary zero bytes in the body of the message, and is
40530 present if the number is greater than zero.
40532 .vitem &%-deliver_firsttime%&
40533 This is written when a new message is first added to the spool. When the spool
40534 file is updated after a deferral, it is omitted.
40536 .vitem "&%-frozen%&&~<&'time'&>"
40537 .cindex "frozen messages" "spool data"
40538 The message is frozen, and the freezing happened at <&'time'&>.
40540 .vitem "&%-helo_name%&&~<&'text'&>"
40541 This records the host name as specified by a remote host in a HELO or EHLO
40544 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
40545 This records the IP address of the host from which the message was received and
40546 the remote port number that was used. It is omitted for locally generated
40549 .vitem "&%-host_auth%&&~<&'text'&>"
40550 If the message was received on an authenticated SMTP connection, this records
40551 the name of the authenticator &-- the value of the
40552 &$sender_host_authenticated$& variable.
40554 .vitem &%-host_lookup_failed%&
40555 This is present if an attempt to look up the sending host's name from its IP
40556 address failed. It corresponds to the &$host_lookup_failed$& variable.
40558 .vitem "&%-host_name%&&~<&'text'&>"
40559 .cindex "reverse DNS lookup"
40560 .cindex "DNS" "reverse lookup"
40561 This records the name of the remote host from which the message was received,
40562 if the host name was looked up from the IP address when the message was being
40563 received. It is not present if no reverse lookup was done.
40565 .vitem "&%-ident%&&~<&'text'&>"
40566 For locally submitted messages, this records the login of the originating user,
40567 unless it was a trusted user and the &%-oMt%& option was used to specify an
40568 ident value. For messages received over TCP/IP, this records the ident string
40569 supplied by the remote host, if any.
40571 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
40572 This records the IP address of the local interface and the port number through
40573 which a message was received from a remote host. It is omitted for locally
40574 generated messages.
40577 The message is from a local sender.
40579 .vitem &%-localerror%&
40580 The message is a locally-generated bounce message.
40582 .vitem "&%-local_scan%&&~<&'string'&>"
40583 This records the data string that was returned by the &[local_scan()]& function
40584 when the message was received &-- the value of the &$local_scan_data$&
40585 variable. It is omitted if no data was returned.
40587 .vitem &%-manual_thaw%&
40588 The message was frozen but has been thawed manually, that is, by an explicit
40589 Exim command rather than via the auto-thaw process.
40592 A testing delivery process was started using the &%-N%& option to suppress any
40593 actual deliveries, but delivery was deferred. At any further delivery attempts,
40596 .vitem &%-received_protocol%&
40597 This records the value of the &$received_protocol$& variable, which contains
40598 the name of the protocol by which the message was received.
40600 .vitem &%-sender_set_untrusted%&
40601 The envelope sender of this message was set by an untrusted local caller (used
40602 to ensure that the caller is displayed in queue listings).
40604 .vitem "&%-spam_score_int%&&~<&'number'&>"
40605 If a message was scanned by SpamAssassin, this is present. It records the value
40606 of &$spam_score_int$&.
40608 .vitem &%-spool_file_wireformat%&
40609 The -D file for this message is in wire-format (for ESMTP CHUNKING)
40610 rather than Unix-format.
40611 The line-ending is CRLF rather than newline.
40612 There is still, however, no leading-dot-stuffing.
40614 .vitem &%-tls_certificate_verified%&
40615 A TLS certificate was received from the client that sent this message, and the
40616 certificate was verified by the server.
40618 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
40619 When the message was received over an encrypted connection, this records the
40620 name of the cipher suite that was used.
40622 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
40623 When the message was received over an encrypted connection, and a certificate
40624 was received from the client, this records the Distinguished Name from that
40628 Any of the above may have an extra hyphen prepended, to indicate the the
40629 corresponding data is untrusted.
40631 Following the options there is a list of those addresses to which the message
40632 is not to be delivered. This set of addresses is initialized from the command
40633 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
40634 is set; otherwise it starts out empty. Whenever a successful delivery is made,
40635 the address is added to this set. The addresses are kept internally as a
40636 balanced binary tree, and it is a representation of that tree which is written
40637 to the spool file. If an address is expanded via an alias or forward file, the
40638 original address is added to the tree when deliveries to all its child
40639 addresses are complete.
40641 If the tree is empty, there is a single line in the spool file containing just
40642 the text &"XX"&. Otherwise, each line consists of two letters, which are either
40643 Y or N, followed by an address. The address is the value for the node of the
40644 tree, and the letters indicate whether the node has a left branch and/or a
40645 right branch attached to it, respectively. If branches exist, they immediately
40646 follow. Here is an example of a three-node tree:
40648 YY darcy@austen.fict.example
40649 NN alice@wonderland.fict.example
40650 NN editor@thesaurus.ref.example
40652 After the non-recipients tree, there is a list of the message's recipients.
40653 This is a simple list, preceded by a count. It includes all the original
40654 recipients of the message, including those to whom the message has already been
40655 delivered. In the simplest case, the list contains one address per line. For
40659 editor@thesaurus.ref.example
40660 darcy@austen.fict.example
40662 alice@wonderland.fict.example
40664 However, when a child address has been added to the top-level addresses as a
40665 result of the use of the &%one_time%& option on a &(redirect)& router, each
40666 line is of the following form:
40668 <&'top-level address'&> <&'errors_to address'&> &&&
40669 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
40671 The 01 flag bit indicates the presence of the three other fields that follow
40672 the top-level address. Other bits may be used in future to support additional
40673 fields. The <&'parent number'&> is the offset in the recipients list of the
40674 original parent of the &"one time"& address. The first two fields are the
40675 envelope sender that is associated with this address and its length. If the
40676 length is zero, there is no special envelope sender (there are then two space
40677 characters in the line). A non-empty field can arise from a &(redirect)& router
40678 that has an &%errors_to%& setting.
40681 A blank line separates the envelope and status information from the headers
40682 which follow. A header may occupy several lines of the file, and to save effort
40683 when reading it in, each header is preceded by a number and an identifying
40684 character. The number is the number of characters in the header, including any
40685 embedded newlines and the terminating newline. The character is one of the
40689 .row <&'blank'&> "header in which Exim has no special interest"
40690 .row &`B`& "&'Bcc:'& header"
40691 .row &`C`& "&'Cc:'& header"
40692 .row &`F`& "&'From:'& header"
40693 .row &`I`& "&'Message-id:'& header"
40694 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
40695 .row &`R`& "&'Reply-To:'& header"
40696 .row &`S`& "&'Sender:'& header"
40697 .row &`T`& "&'To:'& header"
40698 .row &`*`& "replaced or deleted header"
40701 Deleted or replaced (rewritten) headers remain in the spool file for debugging
40702 purposes. They are not transmitted when the message is delivered. Here is a
40703 typical set of headers:
40705 111P Received: by hobbit.fict.example with local (Exim 4.00)
40706 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
40707 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
40708 038* X-rewrote-sender: bb@hobbit.fict.example
40709 042* From: Bilbo Baggins <bb@hobbit.fict.example>
40710 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
40711 099* To: alice@wonderland.fict.example, rdo@foundation,
40712 darcy@austen.fict.example, editor@thesaurus.ref.example
40713 104T To: alice@wonderland.fict.example, rdo@foundation.example,
40714 darcy@austen.fict.example, editor@thesaurus.ref.example
40715 038 Date: Fri, 11 May 2001 10:28:59 +0100
40717 The asterisked headers indicate that the envelope sender, &'From:'& header, and
40718 &'To:'& header have been rewritten, the last one because routing expanded the
40719 unqualified domain &'foundation'&.
40720 .ecindex IIDforspo1
40721 .ecindex IIDforspo2
40722 .ecindex IIDforspo3
40724 .section "Format of the -D file" "SECID282a"
40725 The data file is traditionally in Unix-standard format: lines are ended with
40726 an ASCII newline character.
40727 However, when the &%spool_wireformat%& main option is used some -D files
40728 can have an alternate format.
40729 This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
40730 The -D file lines (not including the first name-component line) are
40731 suitable for direct copying to the wire when transmitting using the
40732 ESMTP CHUNKING option, meaning lower processing overhead.
40733 Lines are terminated with an ASCII CRLF pair.
40734 There is no dot-stuffing (and no dot-termination).
40736 . ////////////////////////////////////////////////////////////////////////////
40737 . ////////////////////////////////////////////////////////////////////////////
40739 .chapter "DKIM, SPF, SRS and DMARC" "CHAPdkim" &&&
40740 "DKIM, SPF, SRS and DMARC Support"
40742 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
40745 DKIM is a mechanism by which messages sent by some entity can be provably
40746 linked to a domain which that entity controls. It permits reputation to
40747 be tracked on a per-domain basis, rather than merely upon source IP address.
40748 DKIM is documented in RFC 6376.
40750 As DKIM relies on the message being unchanged in transit, messages handled
40751 by a mailing-list (which traditionally adds to the message) will not match
40752 any original DKIM signature.
40754 DKIM support is compiled into Exim by default if TLS support is present.
40755 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
40757 Exim's DKIM implementation allows for
40759 Signing outgoing messages: This function is implemented in the SMTP transport.
40760 It can co-exist with all other Exim features
40761 (including transport filters)
40762 except cutthrough delivery.
40764 Verifying signatures in incoming messages: This is implemented by an additional
40765 ACL (acl_smtp_dkim), which can be called several times per message, with
40766 different signature contexts.
40769 In typical Exim style, the verification implementation does not include any
40770 default "policy". Instead it enables you to build your own policy using
40771 Exim's standard controls.
40773 Please note that verification of DKIM signatures in incoming mail is turned
40774 on by default for logging (in the <= line) purposes.
40776 Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
40777 When set, for each signature in incoming email,
40778 exim will log a line displaying the most important signature details, and the
40779 signature status. Here is an example (with line-breaks added for clarity):
40781 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
40782 d=facebookmail.com s=q1-2009b
40783 c=relaxed/relaxed a=rsa-sha1
40784 i=@facebookmail.com t=1252484542 [verification succeeded]
40787 You might want to turn off DKIM verification processing entirely for internal
40788 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
40789 control modifier. This should typically be done in the RCPT ACL, at points
40790 where you accept mail from relay sources (internal hosts or authenticated
40794 .section "Signing outgoing messages" "SECDKIMSIGN"
40795 .cindex "DKIM" "signing"
40797 For signing to be usable you must have published a DKIM record in DNS.
40798 Note that RFC 8301 (which does not cover EC keys) says:
40800 rsa-sha1 MUST NOT be used for signing or verifying.
40802 Signers MUST use RSA keys of at least 1024 bits for all keys.
40803 Signers SHOULD use RSA keys of at least 2048 bits.
40806 Note also that the key content (the 'p=' field)
40807 in the DNS record is different between RSA and EC keys;
40808 for the former it is the base64 of the ASN.1 for the RSA public key
40809 (equivalent to the private-key .pem with the header/trailer stripped)
40810 but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
40812 Signing is enabled by setting private options on the SMTP transport.
40813 These options take (expandable) strings as arguments.
40815 .option dkim_domain smtp string list&!! unset
40816 The domain(s) you want to sign with.
40817 After expansion, this can be a list.
40818 Each element in turn,
40820 is put into the &%$dkim_domain%& expansion variable
40821 while expanding the remaining signing options.
40822 If it is empty after expansion, DKIM signing is not done,
40823 and no error will result even if &%dkim_strict%& is set.
40825 .option dkim_selector smtp string list&!! unset
40826 This sets the key selector string.
40827 After expansion, which can use &$dkim_domain$&, this can be a list.
40828 Each element in turn is put in the expansion
40829 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
40830 option along with &%$dkim_domain%&.
40831 If the option is empty after expansion, DKIM signing is not done for this domain,
40832 and no error will result even if &%dkim_strict%& is set.
40834 .option dkim_private_key smtp string&!! unset
40835 This sets the private key to use.
40836 You can use the &%$dkim_domain%& and
40837 &%$dkim_selector%& expansion variables to determine the private key to use.
40838 The result can either
40840 be a valid RSA private key in ASCII armor (.pem file), including line breaks
40842 with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
40843 be a valid Ed25519 private key (same format as above)
40845 start with a slash, in which case it is treated as a file that contains
40848 be "0", "false" or the empty string, in which case the message will not
40849 be signed. This case will not result in an error, even if &%dkim_strict%&
40853 To generate keys under OpenSSL:
40855 openssl genrsa -out dkim_rsa.private 2048
40856 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
40858 The result file from the first command should be retained, and
40859 this option set to use it.
40860 Take the base-64 lines from the output of the second command, concatenated,
40861 for the DNS TXT record.
40862 See section 3.6 of RFC6376 for the record specification.
40866 certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
40867 certtool --load-privkey=dkim_rsa.private --pubkey-info
40870 Note that RFC 8301 says:
40872 Signers MUST use RSA keys of at least 1024 bits for all keys.
40873 Signers SHOULD use RSA keys of at least 2048 bits.
40876 EC keys for DKIM are defined by RFC 8463.
40877 They are considerably smaller than RSA keys for equivalent protection.
40878 As they are a recent development, users should consider dual-signing
40879 (by setting a list of selectors, and an expansion for this option)
40880 for some transition period.
40881 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
40884 OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
40886 openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
40887 certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
40890 To produce the required public key value for a DNS record:
40892 openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
40893 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
40896 Exim also supports an alternate format
40897 of Ed25519 keys in DNS which was a candidate during development
40898 of the standard, but not adopted.
40899 A future release will probably drop that support.
40901 .option dkim_hash smtp string&!! sha256
40902 Can be set to any one of the supported hash methods, which are:
40904 &`sha1`& &-- should not be used, is old and insecure
40906 &`sha256`& &-- the default
40908 &`sha512`& &-- possibly more secure but less well supported
40911 Note that RFC 8301 says:
40913 rsa-sha1 MUST NOT be used for signing or verifying.
40916 .option dkim_identity smtp string&!! unset
40917 If set after expansion, the value is used to set an "i=" tag in
40918 the signing header. The DKIM standards restrict the permissible
40919 syntax of this optional tag to a mail address, with possibly-empty
40920 local part, an @, and a domain identical to or subdomain of the "d="
40921 tag value. Note that Exim does not check the value.
40923 .option dkim_canon smtp string&!! unset
40924 This option sets the canonicalization method used when signing a message.
40925 The DKIM RFC currently supports two methods: "simple" and "relaxed".
40926 The option defaults to "relaxed" when unset. Note: the current implementation
40927 only supports signing with the same canonicalization method for both headers and body.
40929 .option dkim_strict smtp string&!! unset
40930 This option defines how Exim behaves when signing a message that
40931 should be signed fails for some reason. When the expansion evaluates to
40932 either &"1"& or &"true"&, Exim will defer. Otherwise Exim will send the message
40933 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
40936 .option dkim_sign_headers smtp string&!! "see below"
40937 If set, this option must expand to a colon-separated
40938 list of header names.
40939 Headers with these names, or the absence or such a header, will be included
40940 in the message signature.
40941 When unspecified, the header names listed in RFC4871 will be used,
40942 whether or not each header is present in the message.
40943 The default list is available for the expansion in the macro
40944 &"_DKIM_SIGN_HEADERS"&
40945 and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
40947 If a name is repeated, multiple headers by that name (or the absence thereof)
40948 will be signed. The textually later headers in the headers part of the
40949 message are signed first, if there are multiples.
40951 A name can be prefixed with either an &"="& or a &"+"& character.
40952 If an &"="& prefix is used, all headers that are present with this name
40954 If a &"+"& prefix if used, all headers that are present with this name
40955 will be signed, and one signature added for a missing header with the
40956 name will be appended.
40958 .option dkim_timestamps smtp integer&!! unset
40959 This option controls the inclusion of timestamp information in the signature.
40960 If not set, no such information will be included.
40961 Otherwise, must be an unsigned number giving an offset in seconds from the current time
40963 (eg. 1209600 for two weeks);
40964 both creation (t=) and expiry (x=) tags will be included.
40966 RFC 6376 lists these tags as RECOMMENDED.
40969 .section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
40970 .cindex "DKIM" "verification"
40972 Verification of DKIM signatures in SMTP incoming email is done for all
40973 messages for which an ACL control &%dkim_disable_verify%& has not been set.
40974 .cindex DKIM "selecting signature algorithms"
40975 Individual classes of signature algorithm can be ignored by changing
40976 the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&.
40977 The &%dkim_verify_minimal%& option can be set to cease verification
40978 processing for a message once the first passing signature is found.
40980 .cindex authentication "expansion item"
40981 Performing verification sets up information used by the
40982 &%authresults%& expansion item.
40984 For most purposes the default option settings suffice and the remainder
40985 of this section can be ignored.
40987 The results of verification are made available to the
40988 &%acl_smtp_dkim%& ACL, which can examine and modify them.
40989 A missing ACL definition defaults to accept.
40990 By default, the ACL is called once for each
40991 syntactically(!) correct signature in the incoming message.
40992 If any ACL call does not accept, the message is not accepted.
40993 If a cutthrough delivery was in progress for the message, that is
40994 summarily dropped (having wasted the transmission effort).
40996 To evaluate the verification result in the ACL
40997 a large number of expansion variables
40998 containing the signature status and its details are set up during the
40999 runtime of the ACL.
41001 Calling the ACL only for existing signatures is not sufficient to build
41002 more advanced policies. For that reason, the main option
41003 &%dkim_verify_signers%&, and an expansion variable
41004 &%$dkim_signers%& exist.
41006 The main option &%dkim_verify_signers%& can be set to a colon-separated
41007 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
41008 called. It is expanded when the message has been received. At this point,
41009 the expansion variable &%$dkim_signers%& already contains a colon-separated
41010 list of signer domains and identities for the message. When
41011 &%dkim_verify_signers%& is not specified in the main configuration,
41014 dkim_verify_signers = $dkim_signers
41016 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
41017 DKIM signature in the message. Current DKIM verifiers may want to explicitly
41018 call the ACL for known domains or identities. This would be achieved as follows:
41020 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
41022 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
41023 and "ebay.com", plus all domains and identities that have signatures in the message.
41024 You can also be more creative in constructing your policy. For example:
41026 dkim_verify_signers = $sender_address_domain:$dkim_signers
41029 If a domain or identity is listed several times in the (expanded) value of
41030 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
41032 Note that if the option is set using untrustworthy data
41033 (such as the From: header)
41034 care should be taken to force lowercase for domains
41035 and for the domain part if identities.
41036 The default setting can be regarded as trustworthy in this respect.
41038 If multiple signatures match a domain (or identity), the ACL is called once
41039 for each matching signature.
41042 Inside the DKIM ACL, the following expansion variables are
41043 available (from most to least important):
41047 .vitem &%$dkim_cur_signer%&
41048 The signer that is being evaluated in this ACL run. This can be a domain or
41049 an identity. This is one of the list items from the expanded main option
41050 &%dkim_verify_signers%& (see above).
41052 .vitem &%$dkim_verify_status%&
41053 Within the DKIM ACL,
41054 a string describing the general status of the signature. One of
41056 &%none%&: There is no signature in the message for the current domain or
41057 identity (as reflected by &%$dkim_cur_signer%&).
41059 &%invalid%&: The signature could not be verified due to a processing error.
41060 More detail is available in &%$dkim_verify_reason%&.
41062 &%fail%&: Verification of the signature failed. More detail is
41063 available in &%$dkim_verify_reason%&.
41065 &%pass%&: The signature passed verification. It is valid.
41068 This variable can be overwritten using an ACL 'set' modifier.
41069 This might, for instance, be done to enforce a policy restriction on
41070 hash-method or key-size:
41072 warn condition = ${if eq {$dkim_verify_status}{pass}}
41073 condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
41074 condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
41075 {< {$dkim_key_length}{1024}}}}
41076 logwrite = NOTE: forcing DKIM verify fail (was pass)
41077 set dkim_verify_status = fail
41078 set dkim_verify_reason = hash too weak or key too short
41081 So long as a DKIM ACL is defined (it need do no more than accept),
41082 after all the DKIM ACL runs have completed, the value becomes a
41083 colon-separated list of the values after each run.
41084 This is maintained for the mime, prdr and data ACLs.
41086 .vitem &%$dkim_verify_reason%&
41087 A string giving a little bit more detail when &%$dkim_verify_status%& is either
41088 "fail" or "invalid". One of
41090 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
41091 key for the domain could not be retrieved. This may be a temporary problem.
41093 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
41094 record for the domain is syntactically invalid.
41096 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
41097 body hash does not match the one specified in the signature header. This
41098 means that the message body was modified in transit.
41100 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
41101 could not be verified. This may mean that headers were modified,
41102 re-written or otherwise changed in a way which is incompatible with
41103 DKIM verification. It may of course also mean that the signature is forged.
41106 This variable can be overwritten, with any value, using an ACL 'set' modifier.
41108 .vitem &%$dkim_domain%&
41109 The signing domain. IMPORTANT: This variable is only populated if there is
41110 an actual signature in the message for the current domain or identity (as
41111 reflected by &%$dkim_cur_signer%&).
41113 .vitem &%$dkim_identity%&
41114 The signing identity, if present. IMPORTANT: This variable is only populated
41115 if there is an actual signature in the message for the current domain or
41116 identity (as reflected by &%$dkim_cur_signer%&).
41118 .vitem &%$dkim_selector%&
41119 The key record selector string.
41121 .vitem &%$dkim_algo%&
41122 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
41123 If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
41124 may also be 'ed25519-sha256'.
41125 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
41128 Note that RFC 8301 says:
41130 rsa-sha1 MUST NOT be used for signing or verifying.
41132 DKIM signatures identified as having been signed with historic
41133 algorithms (currently, rsa-sha1) have permanently failed evaluation
41136 To enforce this you must either have a DKIM ACL which checks this variable
41137 and overwrites the &$dkim_verify_status$& variable as discussed above,
41138 or have set the main option &%dkim_verify_hashes%& to exclude
41139 processing of such signatures.
41141 .vitem &%$dkim_canon_body%&
41142 The body canonicalization method. One of 'relaxed' or 'simple'.
41144 .vitem &%$dkim_canon_headers%&
41145 The header canonicalization method. One of 'relaxed' or 'simple'.
41147 .vitem &%$dkim_copiedheaders%&
41148 A transcript of headers and their values which are included in the signature
41149 (copied from the 'z=' tag of the signature).
41150 Note that RFC6376 requires that verification fail if the From: header is
41151 not included in the signature. Exim does not enforce this; sites wishing
41152 strict enforcement should code the check explicitly.
41154 .vitem &%$dkim_bodylength%&
41155 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
41156 limit was set by the signer, "9999999999999" is returned. This makes sure
41157 that this variable always expands to an integer value.
41158 &*Note:*& The presence of the signature tag specifying a signing body length
41159 is one possible route to spoofing of valid DKIM signatures.
41160 A paranoid implementation might wish to regard signature where this variable
41161 shows less than the "no limit" return as being invalid.
41163 .vitem &%$dkim_created%&
41164 UNIX timestamp reflecting the date and time when the signature was created.
41165 When this was not specified by the signer, "0" is returned.
41167 .vitem &%$dkim_expires%&
41168 UNIX timestamp reflecting the date and time when the signer wants the
41169 signature to be treated as "expired". When this was not specified by the
41170 signer, "9999999999999" is returned. This makes it possible to do useful
41171 integer size comparisons against this value.
41172 Note that Exim does not check this value.
41174 .vitem &%$dkim_headernames%&
41175 A colon-separated list of names of headers included in the signature.
41177 .vitem &%$dkim_key_testing%&
41178 "1" if the key record has the "testing" flag set, "0" if not.
41180 .vitem &%$dkim_key_nosubdomains%&
41181 "1" if the key record forbids subdomaining, "0" otherwise.
41183 .vitem &%$dkim_key_srvtype%&
41184 Service type (tag s=) from the key record. Defaults to "*" if not specified
41187 .vitem &%$dkim_key_granularity%&
41188 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
41191 .vitem &%$dkim_key_notes%&
41192 Notes from the key record (tag n=).
41194 .vitem &%$dkim_key_length%&
41195 Number of bits in the key.
41196 Valid only once the key is loaded, which is at the time the header signature
41197 is verified, which is after the body hash is.
41199 Note that RFC 8301 says:
41201 Verifiers MUST NOT consider signatures using RSA keys of
41202 less than 1024 bits as valid signatures.
41205 This is enforced by the default setting for the &%dkim_verify_min_keysizes%&
41210 In addition, two ACL conditions are provided:
41213 .vitem &%dkim_signers%&
41214 ACL condition that checks a colon-separated list of domains or identities
41215 for a match against the domain or identity that the ACL is currently verifying
41216 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
41217 verb to a group of domains or identities. For example:
41220 # Warn when Mail purportedly from GMail has no gmail signature
41221 warn sender_domains = gmail.com
41222 dkim_signers = gmail.com
41224 log_message = GMail sender without gmail.com DKIM signature
41227 Note that the above does not check for a total lack of DKIM signing;
41228 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
41230 .vitem &%dkim_status%&
41231 ACL condition that checks a colon-separated list of possible DKIM verification
41232 results against the actual result of verification. This is typically used
41233 to restrict an ACL verb to a list of verification outcomes, for example:
41236 deny sender_domains = paypal.com:paypal.de
41237 dkim_signers = paypal.com:paypal.de
41238 dkim_status = none:invalid:fail
41239 message = Mail from Paypal with invalid/missing signature
41242 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
41243 see the documentation of the &%$dkim_verify_status%& expansion variable above
41244 for more information of what they mean.
41250 .section "SPF (Sender Policy Framework)" SECSPF
41251 .cindex SPF verification
41253 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
41254 messages with its domain in the envelope from, documented by RFC 7208.
41255 For more information on SPF see &url(http://www.open-spf.org), a static copy of
41256 the &url(http://openspf.org).
41257 . --- 2019-10-28: still not https, open-spf.org is told to be a
41258 . --- web-archive copy of the now dead openspf.org site
41259 . --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a
41262 Messages sent by a system not authorised will fail checking of such assertions.
41263 This includes retransmissions done by traditional forwarders.
41265 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
41266 &_Local/Makefile_&. The support uses the &_libspf2_& library
41267 &url(https://www.libspf2.org/).
41268 There is no Exim involvement in the transmission of messages;
41269 publishing certain DNS records is all that is required.
41271 For verification, an ACL condition and an expansion lookup are provided.
41272 .cindex authentication "expansion item"
41273 Performing verification sets up information used by the
41274 &%authresults%& expansion item.
41277 .cindex SPF "ACL condition"
41278 .cindex ACL "spf condition"
41279 The ACL condition "spf" can be used at or after the MAIL ACL.
41280 It takes as an argument a list of strings giving the outcome of the SPF check,
41281 and will succeed for any matching outcome.
41285 The SPF check passed, the sending host is positively verified by SPF.
41288 The SPF check failed, the sending host is NOT allowed to send mail for the
41289 domain in the envelope-from address.
41291 .vitem &%softfail%&
41292 The SPF check failed, but the queried domain can't absolutely confirm that this
41296 The queried domain does not publish SPF records.
41299 The SPF check returned a "neutral" state. This means the queried domain has
41300 published a SPF record, but wants to allow outside servers to send mail under
41301 its domain as well. This should be treated like "none".
41303 .vitem &%permerror%&
41304 This indicates a syntax error in the SPF record of the queried domain.
41305 You may deny messages when this occurs.
41307 .vitem &%temperror%&
41308 This indicates a temporary error during all processing, including Exim's
41309 SPF processing. You may defer messages when this occurs.
41312 You can prefix each string with an exclamation mark to invert
41313 its meaning, for example "!fail" will match all results but
41314 "fail". The string list is evaluated left-to-right, in a
41315 short-circuit fashion.
41320 message = $sender_host_address is not allowed to send mail from \
41321 ${if def:sender_address_domain \
41322 {$sender_address_domain}{$sender_helo_name}}. \
41323 Please see http://www.open-spf.org/Why;\
41324 identity=${if def:sender_address_domain \
41325 {$sender_address}{$sender_helo_name}};\
41326 ip=$sender_host_address
41329 Note: The above mentioned URL may not be as helpful as expected. You are
41330 encouraged to replace the link with a link to a site with more
41333 When the spf condition has run, it sets up several expansion
41336 .cindex SPF "verification variables"
41338 .vitem &$spf_header_comment$&
41339 .vindex &$spf_header_comment$&
41340 This contains a human-readable string describing the outcome
41341 of the SPF check. You can add it to a custom header or use
41342 it for logging purposes.
41344 .vitem &$spf_received$&
41345 .vindex &$spf_received$&
41346 This contains a complete Received-SPF: header that can be
41347 added to the message. Please note that according to the SPF
41348 draft, this header must be added at the top of the header
41349 list. Please see section 10 on how you can do this.
41351 Note: in case of "Best-guess" (see below), the convention is
41352 to put this string in a header called X-SPF-Guess: instead.
41354 .vitem &$spf_result$&
41355 .vindex &$spf_result$&
41356 This contains the outcome of the SPF check in string form,
41357 one of pass, fail, softfail, none, neutral, permerror or
41360 .vitem &$spf_result_guessed$&
41361 .vindex &$spf_result_guessed$&
41362 This boolean is true only if a best-guess operation was used
41363 and required in order to obtain a result.
41365 .vitem &$spf_smtp_comment$&
41366 .vindex &$spf_smtp_comment$&
41367 .vindex &%spf_smtp_comment_template%&
41368 This contains a string that can be used in a SMTP response
41369 to the calling party. Useful for "fail".
41370 The string is generated by the SPF library from the template configured in the main config
41371 option &%spf_smtp_comment_template%&.
41375 .cindex SPF "ACL condition"
41376 .cindex ACL "spf_guess condition"
41377 .cindex SPF "best guess"
41378 In addition to SPF, you can also perform checks for so-called
41379 "Best-guess". Strictly speaking, "Best-guess" is not standard
41380 SPF, but it is supported by the same framework that enables SPF
41382 Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record)
41383 for a description of what it means.
41384 . --- 2019-10-28: still not https:
41386 To access this feature, simply use the spf_guess condition in place
41387 of the spf one. For example:
41390 deny spf_guess = fail
41391 message = $sender_host_address doesn't look trustworthy to me
41394 In case you decide to reject messages based on this check, you
41395 should note that although it uses the same framework, "Best-guess"
41396 is not SPF, and therefore you should not mention SPF at all in your
41399 When the spf_guess condition has run, it sets up the same expansion
41400 variables as when spf condition is run, described above.
41402 Additionally, since Best-guess is not standardized, you may redefine
41403 what "Best-guess" means to you by redefining the main configuration
41404 &%spf_guess%& option.
41405 For example, the following:
41408 spf_guess = v=spf1 a/16 mx/16 ptr ?all
41411 would relax host matching rules to a broader network range.
41414 .cindex SPF "lookup expansion"
41416 A lookup expansion is also available. It takes an email
41417 address as the key and an IP address
41422 ${lookup {username@domain} spf {ip.ip.ip.ip}}
41425 The lookup will return the same result strings as can appear in
41426 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
41432 .section "SRS (Sender Rewriting Scheme)" SECTSRS
41433 .cindex SRS "sender rewriting scheme"
41436 SRS can be used to modify sender addresses when forwarding so that
41437 SPF verification does not object to them.
41438 It operates by encoding the original envelope sender in a new
41439 sender local part and using a domain run by the forwarding site
41440 as the new domain for the sender. Any DSN message should be returned
41441 to this new sender at the forwarding site, which can extract the
41442 original sender from the coded local part and forward the DSN to
41445 This is a way of avoiding the breakage that SPF does to forwarding.
41446 The constructed local-part will be longer than the original,
41447 leading to possible problems with very long addresses.
41448 The changing of the sender address also hinders the tracing of mail
41451 Exim can be built to include native SRS support. To do this
41452 SUPPORT_SRS=yes must be defined in &_Local/Makefile_&.
41453 If this has been done, the macros _HAVE_SRS and _HAVE_NATIVE_SRS
41455 The support is limited to SRS0-encoding; SRS1 is not supported.
41457 .cindex SRS excoding
41458 To encode an address use this expansion item:
41460 .vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
41461 .cindex "&%srs_encode%& expansion item"
41462 .cindex SRS "expansion item"
41463 The first argument should be a secret known and used by all systems
41464 handling the recipient domain for the original message.
41465 There is no need to periodically change this key; a timestamp is also
41467 The second argument should be given as the envelope sender address before this
41468 encoding operation.
41469 The third argument should be the recipient domain of the message when
41470 it arrived at this system.
41473 .cindex SRS decoding
41474 To decode an address use this expansion condition:
41476 .vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
41477 The first argument should be the recipient local prt as is was received.
41478 The second argument is the site secret.
41480 If the messages is not for an SRS-encoded recipient the condition will
41481 return false. If it is, the condition will return true and the variable
41482 &$srs_recipient$& will be set to the decoded (original) value.
41488 SRS_SECRET = <pick something unique for your site for this. Use on all MXs.>
41494 # if outbound, and forwarding has been done, use an alternate transport
41495 domains = ! +my_domains
41496 transport = ${if eq {$local_part@$domain} \
41497 {$original_local_part@$original_domain} \
41498 {remote_smtp} {remote_forwarded_smtp}}
41503 domains = +my_domains
41504 # detect inbound bounces which are SRS'd, and decode them
41505 condition = ${if inbound_srs {$local_part} {SRS_SECRET}}
41506 data = $srs_recipient
41508 inbound_srs_failure:
41511 domains = +my_domains
41512 # detect inbound bounces which look SRS'd but are invalid
41513 condition = ${if inbound_srs {$local_part} {}}
41515 data = :fail: Invalid SRS recipient address
41517 #... further routers here
41520 # transport; should look like the non-forward outbound
41521 # one, plus the max_rcpt and return_path options
41522 remote_forwarded_smtp:
41524 # modify the envelope from, for mails that we forward
41526 return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}}
41534 .section DMARC SECDMARC
41535 .cindex DMARC verification
41537 DMARC combines feedback from SPF, DKIM, and header From: in order
41538 to attempt to provide better indicators of the authenticity of an
41539 email. This document does not explain the fundamentals; you
41540 should read and understand how it works by visiting the website at
41541 &url(http://www.dmarc.org/).
41543 If Exim is built with DMARC support,
41544 the libopendmarc library is used.
41546 For building Exim yourself, obtain the library from
41547 &url(http://sourceforge.net/projects/opendmarc/)
41548 to obtain a copy, or find it in your favorite package
41549 repository. You will need to attend to the local/Makefile feature
41550 SUPPORT_DMARC and the associated LDFLAGS addition.
41551 This description assumes
41552 that headers will be in /usr/local/include, and that the libraries
41553 are in /usr/local/lib.
41557 There are three main-configuration options:
41558 .cindex DMARC "configuration options"
41560 The &%dmarc_tld_file%& option
41561 .oindex &%dmarc_tld_file%&
41562 defines the location of a text file of valid
41563 top level domains the opendmarc library uses
41564 during domain parsing. Maintained by Mozilla,
41565 the most current version can be downloaded
41566 from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat).
41567 See also the util/renew-opendmarc-tlds.sh script.
41568 The default for the option is unset.
41569 If not set, DMARC processing is disabled.
41572 The &%dmarc_history_file%& option, if set
41573 .oindex &%dmarc_history_file%&
41574 defines the location of a file to log results
41575 of dmarc verification on inbound emails. The
41576 contents are importable by the opendmarc tools
41577 which will manage the data, send out DMARC
41578 reports, and expire the data. Make sure the
41579 directory of this file is writable by the user
41581 The default is unset.
41583 The &%dmarc_forensic_sender%& option
41584 .oindex &%dmarc_forensic_sender%&
41585 defines an alternate email address to use when sending a
41586 forensic report detailing alignment failures
41587 if a sender domain's dmarc record specifies it
41588 and you have configured Exim to send them.
41589 If set, this is expanded and used for the
41590 From: header line; the address is extracted
41591 from it and used for the envelope from.
41592 If not set (the default), the From: header is expanded from
41593 the dsn_from option, and <> is used for the
41596 . I wish we had subsections...
41598 .cindex DMARC controls
41599 By default, the DMARC processing will run for any remote,
41600 non-authenticated user. It makes sense to only verify DMARC
41601 status of messages coming from remote, untrusted sources. You can
41602 use standard conditions such as hosts, senders, etc, to decide that
41603 DMARC verification should *not* be performed for them and disable
41604 DMARC with an ACL control modifier:
41606 control = dmarc_disable_verify
41608 A DMARC record can also specify a "forensic address", which gives
41609 exim an email address to submit reports about failed alignment.
41610 Exim does not do this by default because in certain conditions it
41611 results in unintended information leakage (what lists a user might
41612 be subscribed to, etc). You must configure exim to submit forensic
41613 reports to the owner of the domain. If the DMARC record contains a
41614 forensic address and you specify the control statement below, then
41615 exim will send these forensic emails. It is also advised that you
41616 configure a &%dmarc_forensic_sender%& because the default sender address
41617 construction might be inadequate.
41619 control = dmarc_enable_forensic
41621 (AGAIN: You can choose not to send these forensic reports by simply
41622 not putting the dmarc_enable_forensic control line at any point in
41623 your exim config. If you don't tell exim to send them, it will not
41626 There are no options to either control. Both must appear before
41631 DMARC checks cam be run on incoming SMTP messages by using the
41632 &"dmarc_status"& ACL condition in the DATA ACL. You are required to
41633 call the &"spf"& condition first in the ACLs, then the &"dmarc_status"&
41634 condition. Putting this condition in the ACLs is required in order
41635 for a DMARC check to actually occur. All of the variables are set
41636 up before the DATA ACL, but there is no actual DMARC check that
41637 occurs until a &"dmarc_status"& condition is encountered in the ACLs.
41639 The &"dmarc_status"& condition takes a list of strings on its
41640 right-hand side. These strings describe recommended action based
41641 on the DMARC check. To understand what the policy recommendations
41642 mean, refer to the DMARC website above. Valid strings are:
41644 &'accept '& The DMARC check passed and the library recommends accepting the email.
41645 &'reject '& The DMARC check failed and the library recommends rejecting the email.
41646 &'quarantine '& The DMARC check failed and the library recommends keeping it for further inspection.
41647 &'none '& The DMARC check passed and the library recommends no specific action, neutral.
41648 &'norecord '& No policy section in the DMARC record for this RFC5322.From field
41649 &'nofrom '& Unable to determine the domain of the sender.
41650 &'temperror '& Library error or dns error.
41651 &'off '& The DMARC check was disabled for this email.
41653 You can prefix each string with an exclamation mark to invert its
41654 meaning, for example "!accept" will match all results but
41655 "accept". The string list is evaluated left-to-right in a
41656 short-circuit fashion. When a string matches the outcome of the
41657 DMARC check, the condition succeeds. If none of the listed
41658 strings matches the outcome of the DMARC check, the condition
41661 Of course, you can also use any other lookup method that Exim
41662 supports, including LDAP, Postgres, MySQL, etc, as long as the
41663 result is a list of colon-separated strings.
41665 Performing the check sets up information used by the
41666 &%authresults%& expansion item.
41668 Several expansion variables are set before the DATA ACL is
41669 processed, and you can use them in this ACL. The following
41670 expansion variables are available:
41673 .vitem &$dmarc_status$&
41674 .vindex &$dmarc_status$&
41675 .cindex DMARC result
41676 A one word status indicating what the DMARC library
41677 thinks of the email. It is a combination of the results of
41678 DMARC record lookup and the SPF/DKIM/DMARC processing results
41679 (if a DMARC record was found). The actual policy declared
41680 in the DMARC record is in a separate expansion variable.
41682 .vitem &$dmarc_status_text$&
41683 .vindex &$dmarc_status_text$&
41684 Slightly longer, human readable status.
41686 .vitem &$dmarc_used_domain$&
41687 .vindex &$dmarc_used_domain$&
41688 The domain which DMARC used to look up the DMARC policy record.
41690 .vitem &$dmarc_domain_policy$&
41691 .vindex &$dmarc_domain_policy$&
41692 The policy declared in the DMARC record. Valid values
41693 are "none", "reject" and "quarantine". It is blank when there
41694 is any error, including no DMARC record.
41699 By default, Exim's DMARC configuration is intended to be
41700 non-intrusive and conservative. To facilitate this, Exim will not
41701 create any type of logging files without explicit configuration by
41702 you, the admin. Nor will Exim send out any emails/reports about
41703 DMARC issues without explicit configuration by you, the admin (other
41704 than typical bounce messages that may come about due to ACL
41705 processing or failure delivery issues).
41707 In order to log statistics suitable to be imported by the opendmarc
41708 tools, you need to:
41710 Configure the global option &%dmarc_history_file%&
41712 Configure cron jobs to call the appropriate opendmarc history
41713 import scripts and truncating the dmarc_history_file
41716 In order to send forensic reports, you need to:
41718 Configure the global option &%dmarc_forensic_sender%&
41720 Configure, somewhere before the DATA ACL, the control option to
41721 enable sending DMARC forensic reports
41729 warn domains = +local_domains
41730 hosts = +local_hosts
41731 control = dmarc_disable_verify
41733 warn !domains = +screwed_up_dmarc_records
41734 control = dmarc_enable_forensic
41736 warn condition = (lookup if destined to mailing list)
41737 set acl_m_mailing_list = 1
41740 warn dmarc_status = accept : none : off
41742 log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
41744 warn dmarc_status = !accept
41746 log_message = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
41748 warn dmarc_status = quarantine
41750 set $acl_m_quarantine = 1
41751 # Do something in a transport with this flag variable
41753 deny condition = ${if eq{$dmarc_domain_policy}{reject}}
41754 condition = ${if eq{$acl_m_mailing_list}{1}}
41755 message = Messages from $dmarc_used_domain break mailing lists
41757 deny dmarc_status = reject
41759 message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
41761 warn add_header = :at_start:${authresults {$primary_hostname}}
41768 . ////////////////////////////////////////////////////////////////////////////
41769 . ////////////////////////////////////////////////////////////////////////////
41771 .chapter "Proxies" "CHAPproxies" &&&
41773 .cindex "proxy support"
41774 .cindex "proxy" "access via"
41776 A proxy is an intermediate system through which communication is passed.
41777 Proxies may provide a security, availability or load-distribution function.
41780 .section "Inbound proxies" SECTproxyInbound
41781 .cindex proxy inbound
41782 .cindex proxy "server side"
41783 .cindex proxy "Proxy protocol"
41784 .cindex "Proxy protocol" proxy
41786 Exim has support for receiving inbound SMTP connections via a proxy
41787 that uses &"Proxy Protocol"& to speak to it.
41788 To include this support, include &"SUPPORT_PROXY=yes"&
41791 It was built on the HAProxy specification, found at
41792 &url(https://www.haproxy.org/download/1.8/doc/proxy-protocol.txt).
41794 The purpose of this facility is so that an application load balancer,
41795 such as HAProxy, can sit in front of several Exim servers
41796 to distribute load.
41797 Exim uses the local protocol communication with the proxy to obtain
41798 the remote SMTP system IP address and port information.
41799 There is no logging if a host passes or
41800 fails Proxy Protocol negotiation, but it can easily be determined and
41801 recorded in an ACL (example is below).
41803 Use of a proxy is enabled by setting the &%hosts_proxy%&
41804 main configuration option to a hostlist; connections from these
41805 hosts will use Proxy Protocol.
41806 Exim supports both version 1 and version 2 of the Proxy Protocol and
41807 automatically determines which version is in use.
41809 The Proxy Protocol header is the first data received on a TCP connection
41810 and is inserted before any TLS-on-connect handshake from the client; Exim
41811 negotiates TLS between Exim-as-server and the remote client, not between
41812 Exim and the proxy server.
41814 The following expansion variables are usable
41815 (&"internal"& and &"external"& here refer to the interfaces
41818 &'proxy_external_address '& IP of host being proxied or IP of remote interface of proxy
41819 &'proxy_external_port '& Port of host being proxied or Port on remote interface of proxy
41820 &'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
41821 &'proxy_local_port '& Port of proxy server inbound or Port on local interface of proxy
41822 &'proxy_session '& boolean: SMTP connection via proxy
41824 If &$proxy_session$& is set but &$proxy_external_address$& is empty
41825 there was a protocol error.
41826 The variables &$sender_host_address$& and &$sender_host_port$&
41827 will have values for the actual client system, not the proxy.
41829 Since the real connections are all coming from the proxy, and the
41830 per host connection tracking is done before Proxy Protocol is
41831 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
41832 handle all of the parallel volume you expect per inbound proxy.
41833 With the option set so high, you lose the ability
41834 to protect your server from many connections from one IP.
41835 In order to prevent your server from overload, you
41836 need to add a per connection ratelimit to your connect ACL.
41837 A possible solution is:
41839 # Set max number of connections per host
41841 # Or do some kind of IP lookup in a flat file or database
41842 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
41844 defer ratelimit = LIMIT / 5s / per_conn / strict
41845 message = Too many connections from this IP right now
41850 .section "Outbound proxies" SECTproxySOCKS
41851 .cindex proxy outbound
41852 .cindex proxy "client side"
41853 .cindex proxy SOCKS
41854 .cindex SOCKS proxy
41855 Exim has support for sending outbound SMTP via a proxy
41856 using a protocol called SOCKS5 (defined by RFC1928).
41857 The support can be optionally included by defining SUPPORT_SOCKS=yes in
41860 Use of a proxy is enabled by setting the &%socks_proxy%& option
41861 on an smtp transport.
41862 The option value is expanded and should then be a list
41863 (colon-separated by default) of proxy specifiers.
41864 Each proxy specifier is a list
41865 (space-separated by default) where the initial element
41866 is an IP address and any subsequent elements are options.
41868 Options are a string <name>=<value>.
41869 The list of options is in the following table:
41871 &'auth '& authentication method
41872 &'name '& authentication username
41873 &'pass '& authentication password
41875 &'tmo '& connection timeout
41877 &'weight '& selection bias
41880 More details on each of these options follows:
41883 .cindex authentication "to proxy"
41884 .cindex proxy authentication
41885 &%auth%&: Either &"none"& (default) or &"name"&.
41886 Using &"name"& selects username/password authentication per RFC 1929
41887 for access to the proxy.
41888 Default is &"none"&.
41890 &%name%&: sets the username for the &"name"& authentication method.
41893 &%pass%&: sets the password for the &"name"& authentication method.
41896 &%port%&: the TCP port number to use for the connection to the proxy.
41899 &%tmo%&: sets a connection timeout in seconds for this proxy.
41902 &%pri%&: specifies a priority for the proxy within the list,
41903 higher values being tried first.
41904 The default priority is 1.
41906 &%weight%&: specifies a selection bias.
41907 Within a priority set servers are queried in a random fashion,
41908 weighted by this value.
41909 The default value for selection bias is 1.
41912 Proxies from the list are tried according to their priority
41913 and weight settings until one responds. The timeout for the
41914 overall connection applies to the set of proxied attempts.
41916 .section Logging SECTproxyLog
41917 To log the (local) IP of a proxy in the incoming or delivery logline,
41918 add &"+proxy"& to the &%log_selector%& option.
41919 This will add a component tagged with &"PRX="& to the line.
41921 . ////////////////////////////////////////////////////////////////////////////
41922 . ////////////////////////////////////////////////////////////////////////////
41924 .chapter "Internationalisation" "CHAPi18n" &&&
41925 "Internationalisation""
41926 .cindex internationalisation "email address"
41929 .cindex utf8 "mail name handling"
41931 Exim has support for Internationalised mail names.
41932 To include this it must be built with SUPPORT_I18N and the libidn library.
41933 Standards supported are RFCs 2060, 5890, 6530 and 6533.
41935 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
41936 instead of it) then IDNA2008 is supported; this adds an extra library
41937 requirement, upon libidn2.
41939 .section "MTA operations" SECTi18nMTA
41940 .cindex SMTPUTF8 "ESMTP option"
41941 .cindex "ESMTP extensions" SMTPUTF8
41942 The main configuration option &%smtputf8_advertise_hosts%& specifies
41943 a host list. If this matches the sending host and
41944 accept_8bitmime is true (the default) then the ESMTP option
41945 SMTPUTF8 will be advertised.
41947 If the sender specifies the SMTPUTF8 option on a MAIL command
41948 international handling for the message is enabled and
41949 the expansion variable &$message_smtputf8$& will have value TRUE.
41951 The option &%allow_utf8_domains%& is set to true for this
41952 message. All DNS lookups are converted to a-label form
41953 whatever the setting of &%allow_utf8_domains%&
41954 when Exim is built with SUPPORT_I18N.
41956 Both localparts and domain are maintained as the original
41957 UTF-8 form internally; any comparison or regular-expression use will
41958 require appropriate care. Filenames created, eg. by
41959 the appendfile transport, will have UTF-8 names.
41961 HELO names sent by the smtp transport will have any UTF-8
41962 components expanded to a-label form,
41963 and any certificate name checks will be done using the a-label
41966 .cindex log protocol
41967 .cindex SMTPUTF8 logging
41968 .cindex i18n logging
41969 Log lines and Received-by: header lines will acquire a "utf8"
41970 prefix on the protocol element, eg. utf8esmtp.
41972 The following expansion operators can be used:
41974 ${utf8_domain_to_alabel:str}
41975 ${utf8_domain_from_alabel:str}
41976 ${utf8_localpart_to_alabel:str}
41977 ${utf8_localpart_from_alabel:str}
41980 .cindex utf8 "address downconversion"
41981 .cindex i18n "utf8 address downconversion"
41983 may use the following modifier:
41985 control = utf8_downconvert
41986 control = utf8_downconvert/<value>
41988 This sets a flag requiring that envelope addresses are converted to
41989 a-label form before smtp delivery.
41990 This is usually for use in a Message Submission Agent context,
41991 but could be used for any message.
41993 If a value is appended it may be:
41995 &`1 `& mandatory downconversion
41996 &`0 `& no downconversion
41997 &`-1 `& if SMTPUTF8 not supported by destination host
41999 If no value is given, 1 is used.
42001 If mua_wrapper is set, the utf8_downconvert control
42002 is initially set to -1.
42004 The smtp transport has an option &%utf8_downconvert%&.
42005 If set it must expand to one of the three values described above,
42006 or an empty string.
42007 If non-empty it overrides value previously set
42008 (due to mua_wrapper or by an ACL control).
42011 There is no explicit support for VRFY and EXPN.
42012 Configurations supporting these should inspect
42013 &$smtp_command_argument$& for an SMTPUTF8 argument.
42015 There is no support for LMTP on Unix sockets.
42016 Using the "lmtp" protocol option on an smtp transport,
42017 for LMTP over TCP, should work as expected.
42019 There is no support for DSN unitext handling,
42020 and no provision for converting logging from or to UTF-8.
42024 .section "MDA operations" SECTi18nMDA
42025 To aid in constructing names suitable for IMAP folders
42026 the following expansion operator can be used:
42028 ${imapfolder {<string>} {<sep>} {<specials>}}
42031 The string is converted from the charset specified by
42032 the "headers charset" command (in a filter file)
42033 or &%headers_charset%& main configuration option (otherwise),
42035 modified UTF-7 encoding specified by RFC 2060,
42036 with the following exception: All occurrences of <sep>
42037 (which has to be a single character)
42038 are replaced with periods ("."), and all periods and slashes that are not
42039 <sep> and are not in the <specials> string are BASE64 encoded.
42041 The third argument can be omitted, defaulting to an empty string.
42042 The second argument can be omitted, defaulting to "/".
42044 This is the encoding used by Courier for Maildir names on disk, and followed
42045 by many other IMAP servers.
42049 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
42050 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
42051 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
42054 Note that the source charset setting is vital, and also that characters
42055 must be representable in UTF-16.
42058 . ////////////////////////////////////////////////////////////////////////////
42059 . ////////////////////////////////////////////////////////////////////////////
42061 .chapter "Events" "CHAPevents" &&&
42065 The events mechanism in Exim can be used to intercept processing at a number
42066 of points. It was originally invented to give a way to do customised logging
42067 actions (for example, to a database) but can also be used to modify some
42068 processing actions.
42070 Most installations will never need to use Events.
42071 The support can be left out of a build by defining DISABLE_EVENT=yes
42072 in &_Local/Makefile_&.
42074 There are two major classes of events: main and transport.
42075 The main configuration option &%event_action%& controls reception events;
42076 a transport option &%event_action%& controls delivery events.
42078 Both options are a string which is expanded when the event fires.
42079 An example might look like:
42080 .cindex logging custom
42082 event_action = ${if eq {msg:delivery}{$event_name} \
42083 {${lookup pgsql {SELECT * FROM record_Delivery( \
42084 '${quote_pgsql:$sender_address_domain}',\
42085 '${quote_pgsql:${lc:$sender_address_local_part}}', \
42086 '${quote_pgsql:$domain}', \
42087 '${quote_pgsql:${lc:$local_part}}', \
42088 '${quote_pgsql:$host_address}', \
42089 '${quote_pgsql:${lc:$host}}', \
42090 '${quote_pgsql:$message_exim_id}')}} \
42094 Events have names which correspond to the point in process at which they fire.
42095 The name is placed in the variable &$event_name$& and the event action
42096 expansion must check this, as it will be called for every possible event type.
42098 The current list of events is:
42100 &`dane:fail after transport `& per connection
42101 &`msg:complete after main `& per message
42102 &`msg:defer after transport `& per message per delivery try
42103 &`msg:delivery after transport `& per recipient
42104 &`msg:rcpt:host:defer after transport `& per recipient per host
42105 &`msg:rcpt:defer after transport `& per recipient
42106 &`msg:host:defer after transport `& per host per delivery try; host errors
42107 &`msg:fail:delivery after transport `& per recipient
42108 &`msg:fail:internal after main `& per recipient
42109 &`tcp:connect before transport `& per connection
42110 &`tcp:close after transport `& per connection
42111 &`tls:cert before both `& per certificate in verification chain
42112 &`smtp:connect after transport `& per connection
42113 &`smtp:ehlo after transport `& per connection
42115 New event types may be added in future.
42117 The event name is a colon-separated list, defining the type of
42118 event in a tree of possibilities. It may be used as a list
42119 or just matched on as a whole. There will be no spaces in the name.
42121 The second column in the table above describes whether the event fires
42122 before or after the action is associates with. Those which fire before
42123 can be used to affect that action (more on this below).
42125 The third column in the table above says what section of the configuration
42126 should define the event action.
42128 An additional variable, &$event_data$&, is filled with information varying
42129 with the event type:
42131 &`dane:fail `& failure reason
42132 &`msg:defer `& error string
42133 &`msg:delivery `& smtp confirmation message
42134 &`msg:fail:internal `& failure reason
42135 &`msg:fail:delivery `& smtp error message
42136 &`msg:host:defer `& error string
42137 &`msg:rcpt:host:defer `& error string
42138 &`msg:rcpt:defer `& error string
42139 &`tls:cert `& verification chain depth
42140 &`smtp:connect `& smtp banner
42141 &`smtp:ehlo `& smtp ehlo response
42144 The :defer events populate one extra variable: &$event_defer_errno$&.
42146 For complex operations an ACL expansion can be used in &%event_action%&
42147 however due to the multiple contexts that Exim operates in during
42148 the course of its processing:
42150 variables set in transport events will not be visible outside that
42153 acl_m variables in a server context are lost on a new connection,
42154 and after smtp helo/ehlo/mail/starttls/rset commands
42156 Using an ACL expansion with the logwrite modifier can be
42157 a useful way of writing to the main log.
42159 The expansion of the event_action option should normally
42160 return an empty string. Should it return anything else the
42161 following will be forced:
42163 &`tcp:connect `& do not connect
42164 &`tls:cert `& refuse verification
42165 &`smtp:connect `& close connection
42167 All other message types ignore the result string, and
42168 no other use is made of it.
42170 For a tcp:connect event, if the connection is being made to a proxy
42171 then the address and port variables will be that of the proxy and not
42174 For tls:cert events, if GnuTLS is in use this will trigger only per
42175 chain element received on the connection.
42176 For OpenSSL it will trigger for every chain element including those
42179 . ////////////////////////////////////////////////////////////////////////////
42180 . ////////////////////////////////////////////////////////////////////////////
42182 .chapter "Adding new drivers or lookup types" "CHID13" &&&
42183 "Adding drivers or lookups"
42184 .cindex "adding drivers"
42185 .cindex "new drivers, adding"
42186 .cindex "drivers" "adding new"
42187 The following actions have to be taken in order to add a new router, transport,
42188 authenticator, or lookup type to Exim:
42191 Choose a name for the driver or lookup type that does not conflict with any
42192 existing name; I will use &"newdriver"& in what follows.
42194 Add to &_src/EDITME_& the line:
42196 <&'type'&>&`_NEWDRIVER=yes`&
42198 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
42199 code is not to be included in the binary by default, comment this line out. You
42200 should also add any relevant comments about the driver or lookup type.
42202 Add to &_src/config.h.defaults_& the line:
42204 #define <type>_NEWDRIVER
42207 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
42208 and create a table entry as is done for all the other drivers and lookup types.
42210 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
42211 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
42212 Add your &`NEWDRIVER`& to that list.
42213 As long as the dynamic module would be named &_newdriver.so_&, you can use the
42214 simple form that most lookups have.
42216 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
42217 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
42218 driver or lookup type and add it to the definition of OBJ.
42220 Edit &_OS/Makefile-Base_& adding a &_.o_& file for the predefined-macros, to the
42221 definition of OBJ_MACRO. Add a set of line to do the compile also.
42223 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
42226 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
42227 as for other drivers and lookups.
42230 Then all you need to do is write the code! A good way to start is to make a
42231 proforma by copying an existing module of the same type, globally changing all
42232 occurrences of the name, and cutting out most of the code. Note that any
42233 options you create must be listed in alphabetical order, because the tables are
42234 searched using a binary chop procedure.
42236 There is a &_README_& file in each of the sub-directories of &_src_& describing
42237 the interface that is expected.
42242 . ////////////////////////////////////////////////////////////////////////////
42243 . ////////////////////////////////////////////////////////////////////////////
42245 . /////////////////////////////////////////////////////////////////////////////
42246 . These lines are processing instructions for the Simple DocBook Processor that
42247 . Philip Hazel has developed as a less cumbersome way of making PostScript and
42248 . PDFs than using xmlto and fop. They will be ignored by all other XML
42250 . /////////////////////////////////////////////////////////////////////////////
42255 foot_right_recto="&chaptertitle;"
42256 foot_right_verso="&chaptertitle;"
42260 .makeindex "Options index" "option"
42261 .makeindex "Variables index" "variable"
42262 .makeindex "Concept index" "concept"
42265 . /////////////////////////////////////////////////////////////////////////////
42266 . /////////////////////////////////////////////////////////////////////////////